» wae º ，º → ...， ：w w ºwº • • • • • • • • • • • • » » »·
$i;„º.w №w » N • • • • • • • • • ► | ►-·
#:į šºs '， ： .× ： ， ، ، ، ، ، ، ، ، ، ، ، ، ، ، ، ، ،1.-··
• №fiº's （， ， ， ， ， ， ， ， ， ， , ， ， , ， ， ， ， ， ， , ， ， ，·-·· ·
^ ^ ' , ' « ' ■ .， ， , ， ， ，• №w №w （， ， \! \， （v） \，\！-- ----- ·■ ■ ■ ■ ■ ·|-
, , ; ， ; * * · * * *·º. - * * · * （ ` ） * \\•■ ■ ■ ■---- ·----. '·
· ·---- ·· ！
··* ， ,·~- -، ،
·-·º º|-- ······* … ， , ， ， , • • • • • •
، * * · · · · · ·-º ， ， ， ， ,··-- ··· ：■ ■ ■ ■ ■ ■ ' º.
' ！~：
…！ , ！
{{！!!
ſºț¢;;;;;;;;;;;
######if：:::：:：:::#ſpeſiſ，| + ' '~' ';
ſººſ º".}};"· * * *）§§· -D######
ſtrisytiviti iſk'，، ،∞ ·„ “, º ſº ：
§###########
§§§§
،， , ！
|-
∞d.},'º','!~
0 £º-º（ ， ，
*， ， ， ， și
' .'','','',§§iſ.!ſ''}} ''
Ķ Ķ ķ :;;，，,，.，:.，，,，,-,-，-）， ripºrärº , ！º ， •i º l'.«， ， , ， ，8. №
·* ：·…ſaef（）; **: expºs·· ---- ， ！· · · · ·* .
*）?\.\（'， ,'','','№ №w! №§§§§§ſºļºjºšºſiºſ:::ſſ，ºſºſaegſiſijº; igi;#：::’’’’， ， ， ， , ， ， ， ， , ， ，
įºw”， ºſ ºſ，ºſ ſºwº w №w ， ， ， ， , ， ， ， ， ，，，，,，，，-ſºſiae. №ſſºſițiſt#s ſiſ
\,^,\^_^x\,\!n.* * , w.º.，*,*\ſ*）*, '..?,?， º.º）（º）（º）（º）;*, ， ， ， ,'） ！！!, ºººkſ（№ſſºſ·#ffffff;&##
º ae ae·º _ （， ， ， ， ， ， ，， ！：
）„', ，'','','','º','º',''，'',·\，\,\,\，\，\!，-•,，，，，，，，--|-tv ： ， ， ， ， , ，
№• №w, ， ， , , ， ， ， ， ， ） »·•¿•)›, ， ， , ， ， ，k\！\， .- ·• ！ ' ： º. º.:·- ، ، ، ، ، ، ، ، ،e º „ “ （. ， ， ， ， ， ） »
º , ſ.ºw）'，'：'，'i', º. ſ. º ºſ v ºſſ （， ， s.ſ. ，ſ º（ ） w.« … », ， ， ， ，? !！ ） ■ ■ ■ ■ *-№ º， , ，ºſº:!ſ.-"A", "Mºſſº,º-…， ， ） » ' '）;'）, ）;
· º º, s.ſ. w. • +, −, ×， +， *） ≤ Y ≤ ∞ √° √∞ √° √°，，，，，，.，，，,，，，,，，-\，£） » «， ， , ， ， ， ， ，， , **··, ， ， , ， ,''.« *tº！·
§ ' ^ſ **. ：)A ： • •№. ！·ſ.&, # ', : v.v. º. º., v, ſ·• ſ） \， ， ， ， ） »ſ.-·：， ， ！、、 、 、、、 、、 、， ， ' +！
ſ ：·s.ſ..'ſ ºn №u）.'，aeſ º, º * （?） （… •.•·！\！\！\！\！\！\！\！\,， ºſſ！»•2 , ， ， , s.
·Œ œ№ºººººº !№， №. --★ → º, ſ.ſºſ.',''，''，''，'»', ，'']，į, 'nº'; 'º'，'!'），
*, ， , ºſN’s§©®°¶√≠√∞ √·（ſº）v（º）\，,，,，,，,，,，，,，,，|（9） * （ºr{， ， , ，
}-·· tºſº:§.N.）,\,\！"№ſſº;ſyſºſº,?,",º•,，„（...“， º.º.）**·º ： "…ſº ſºlº （.*?）:ºſº●'ſ
-----· * … ！·t. l.| º.º， ， \!Jº,}-ſiſſºlº, ºſ.º.º.º.1, ; ;:Ķ-·· - ·+ }*)?}}'，º ，ſºſ，
:,: （ ）ſae|-|-ſºſyº, “ſºſ”,ț¢”; “…', ，'$'}，·ºg №ſsº，ſººſ ºrºſ.',*!.
, ， , ， ， ，·|-·;º.º.º.,?,！?;:-
aſ w.º.， ， ， .į 4, 'ſ'）; },' ， , , ; , ）, º----· ·| * ''~
، ، ،№gºç， ，·-· ·----
** „H, , )º， ， ,·· ， ， , ; ，·*******·.ae ….……….……....
， ，|--* * · * *ſºyºtºff,ſyrſºr;
ſ'. … :}; ; ）
#*ºſſºſſº :
} + … ）
، ، ، ، ، ،�
. . . '---- ·.·-[ ºr·
ºſ º∞ſae - ， .·•！-----0•·· ·0 ···
ſººſſººſ！}ſºț¢;ſ.º.ſ.ºſº##'''№j''·¿:țir}wºlae” și--ſuae :', !B：-i.
،∞\， （\ſ*：',ſºſºïſſºſĶišķiği;;;;;;;ſ}،، ، ،
·، ،ſººſ №.Ķſtºſº,ț¢;łțy,$paſ
s） "* * · * * * ·ſ.º.º.“:”， ſºſº.
sº
º
------- -
[]
}}}
*, ， , ſ.tº，
§;.| 1
ºſi
};
*.*.*.*
*** *
• *
，
∞
:-）∞*•, , ）.№.; ： . ··ſı·*{·： · ·
ºyº, “...º.º. ºſºk, º• • • •º „ți）”， “№ºt: №ºt: „ ' , ， ， ,''[[',', ， , ， ).·--：0
º · .i * . ：:·; ºſ ſº ºſº ºſº, ºſſºſºiſſº， ºſſºſºſ·- ·, ， , º№ º
* … №ſ （ſººſ （ ， ， ， ; ：:"·- · -ſºſyº
ſw º w ~ ： »， ， ， ， ， ， ， ， ， ， ， ， ， ， ， ） »----
• • • • • • • • • • • ► ► ► ► ► ► ► ► ► ► ► ► ► ► ► ► ► ► ► ► ► ► ► ► ►ſ º-·-
ſºſ. №, ºſſº, ºſº ¿?. ?,'','','','','','','',''，'',）.Mae'，'º','！- -··№ſ， ºſ|-·：
، ، ،∞-·• … ►· · · · *■，···
ſººſ 'vºs'（）'， ，'']，-º， ， ， ， ， ， , ， ，· ·ſ（）'，''）;ſtºſ • № až 4%）,- ·ſ （ , !U
w * , ， ， ， , ， ， ， ， ， ， ） »·- ·ſ.， , ，}-，
- ■ -^·iſ 1， Nºvº „Ķwº：'，© -* , ， ， ） t.|-•};·is.sº
-• • • • w： i - ，----∞·* ：·：
• №w'ſ ' ， ， ， ， Yae·--■ ■ ■ ·：··ºſſº
ae, º.s'， ` ） ： ºxºſ. 'º' ſae;·· |- ·）-· ---------ſ º
Tºº„”,„№·， ， ， º· ：§§§···- ae ：
·-· |-ſ
|-ae ：· … º¿
-···， ， ， ， ）
¿?
Nº
[]
Nºſºs? º（º）（º）（ºsº，
Mſºſu i1. ' x ∈ , ºvºm i
!
∞ √° s. .a * ， ， ，
~ ~ ¡ ¿
：D
1.^ ^„ºg“ſae
·º ſe ººk
\,\,^,\º,w nºc, i.ſ M.
is.
º,ºn
B·
y '№yºſº. · №, º, 3, ſ.º.º.º., ~\~\}.
w l.
ſ º
}
x （）， ſº sº
º " ， ， ， ， ，
º » º v . s
! * ·
3 · 8ºs į
…iſ e ſae*）',''，''，'','',''.“, º.º.）.",!,：,
«! ！！ ！！ ！! !！ ！!× 1） ， ， ， ， ， ， ， ， , ，
！, s.ſ. •！ » （ ）„“， „“， „“º：
"… i ſ-
J
* （ ）
º , • , •|-· -
}}！s.
：w. • ? ： ;
！¿!}{ſ}\;
* „...º… º， ºſ.*\*,*\ſ*（.*
· · · · · ·
∞
tl ： * * · · · -
*, *ſ*...*..*..*º, º, º „º， , º
• • • b * * * * *ſº： ， ： * · * * *
lºgº,ººº,,ºyº，ſºy'u',''，''，، ، ، ، ،
w º ºs º, º i w= ' • • • • • • • • • • • • •
* w （ x *.* A * *, º*, *）*）*）\ſ*,*, *
' ： º.º）.vººº,）ſ ºs º T
},\*\* .*（f,ººº，w ºſ ſo ' º^ {
... :º*,*\ſ*)（.*）>）*,，，,%ſ',
· :º） º, º „ºſº, º<%
ſ ： » （* * p \, ： » :
، ، ، ،
... * * * *.
ķ- · ··T.·} （）:º， ，}}]！}）;+ ' }，）Ď
0t. ·******... * *, *） º., º „º. Brºſ.º ， ！
§№.----| . ' . .-*.* ‘.….' , ''）;}, º{i}',''）;};lº,
!D… * *· -·* .-|- -\, ， , ,
ſ ºk º！· ·|-·№.
At-
- cº, ºr
º
Nº
ſ
º
*:::::
*:::
' º ~ ' + w :-（
| * t）§§-
* , º sº
we see tº º
* -- * *
ºr ea •e wº
| + ' •
<！： ） * （g ）
（ºſſºſº,ſ） \,;
ſ.º.,！?;： }};{
ſuae
* º * * · · · *
RNÄS， ÄRR，·
§§$%;...… . . . .' . . .;·|-
§§ģĶķ·-----' .::: - ， ： ， :. . . . . . . . . . . .·
?§§·ſ.··'w ， ; * p * }----. . . . . ----, ， * * * * * * * * * * * · * * * * · *
ſººſ №ſſºſºſ- ------' .-·|- ſ +,'
ſſſſſſſſ: ºſſº| *'*********
$$$$$$$ s s ，
!1!！!！!
Œſº:}
sº ：|-
#########
ºſwael-----·ſuſț¢iºſiºſ . . . .|- -----~--~ -ſaeſ，-··|*****
§§ſae--|--§§§·…· · ·،- ' * , ！#, ! , :.:· -ſl... * , ！·· ' ’· · ' , '·------ }'.·}' , :. （ i ） : .-. . . , † ?.
%|ſae- |-·}}··|-ſae-ţ#####-;3&#####---- ·, ， ， º- ·- ·-· |--·, ，----:************¿¿.*
##3.· -Ķķiſ}}،|-$$$$ſſſſſ··· ·· ----| }-，-'-' : , ， , ' ，' , , ' ' , ' ' , ' ° ' ' : '.' ;
ſſſſſſſſſſþ###}&{};， *） ≤ v ≤ ≥ ± •* №i： ----· --------{!}}kºi::::::：:ſv:，
• • • • •|---- · · · · ·：ſºſ，·-:） ：）← → ·： ··####1[}; };ſºſ-. $ ſº ºº. :）
~-P*** ！！！~|--- - - - - -ff;{{};··-¿
-•Mae ſae ſae Rae ys. º. º.）- 3. ‘I （， ， , ºu :：šķī£;&######
|

~
ES
|
E.
J.
U.
i
t
§
§
AsíX2–
[[ITTTTTTTTV23 #ºsº
º
- - º `s ſº.
IIIIllllllllllº (nº :-
Y ARTES
LIBRARY
/ º
s ITY OF MIC
Nºnº's
Tv Er
sº of THE
§7 (J).
Y; ||||||||||||||||
ſºl\ 5– |
º
Eſſº
źllllllllllllllllllllllllll Tif
|E
t
=
º
illiºtt.
it! I'll li." || || || 1:
%
Ł
ºf
#
|
-
:
É
-
H
H




















L E C T U R E S
ON
A G R T C U L T U R A H, C H E MIS T R Y
AND
G E O L () G. Y.
ED INBURGH : PRINTED BY STARK AND COMPANY.
*
L E G T U R H S
ON
AGRICULTURAL CHEMISTRY
AND
G E O L 0 G Y
* \bi º BY
JAMES F. W. JOHNSTON, M.A., F. R. SS. L. & E.,
FELLOW OF THE GEOLOGICAL AND CHEMICAL SOCIETIES, Honor ARY MEMBER OF THE
ROYAL AGRICULTURAL SOCIETY, FOREIGN MEMBER OF THE ROYAL Swedish
ACADEMY OF AGRICULTURE, &c. &c., CHEMIST TO THE AGRICULTURAL
CHEMISTRY ASSOCIATION OF SCOTLAND, AND READER IN CHEMISTRY
AND MINERALOGY IN THE UNIVERSITY OF D URHAM.
SECOND EDITION.
W II, L I A M B L A C K W O O D AND SON S
ED IN B LJ R G H AND LONDON
MDCCCXLVII
*.Sº§
R
ss
ss
{
§
TO THE
WENERABLE CHARLES THORP, D.D., F.R.S., &c, &c.
ARCHDEACON OF DURHAM, AND WARDEN OF THE
UNIVERSITY OF DURHAM.
MY DEAR SIR,
I cannot more appropriately dedicate the following
Lectures than to the head of the University with which I
am officially connected, and within the walls of which the
earlier Lectures were first delivered.
In publishing this Volume I am only endeavouring to
follow out the enlightened intentions of yourself and the
other Founders of the University of Durham, who have
contributed so largely of their fortune and their influence
for the promotion and diffusion of sound and useful learn-
ing. That you have individually, so long and so success-
fully laboured to carry these intentions into effect, is an-
other reason why I desire to dedicate my work especially
to you.
*-
I need scarcely add how much pleasure it affords me to
embrace this public opportunity of testifying my own per-
sonal regard and esteem.
Believe me, my DEAR SIR,
With much respect,
Your obedient humble Servant,
JAMES F. W. JoHNSTON.
JDurham, 1st June 1844.
P. R. E. F. A. C. E.
THE first part of the following Lectures was addressed
to a Society of practical agriculturists, most of whom pos-
sessed no knowledge whatever of scientific Chemistry or
Geology. They commence, therefore, with the discussion
of those elementary principles which are necessary to a
proper understanding of each branch of the subject. Every-
thing in such Lectures which is not—or may not be—easily
understood by those to whom they are addressed is worse
than useless. It has been my wish, therefore, to employ
no scientific terms, and to refer to no philosophical prin-
ciples which I have not previously explained.
To many who may take up the latter portions of the
work, some points may appear obscure or difficult to be
fully understood ; such persons will, I hope, do me the
justice to begin at the beginning, and to blame the author
only when that which is necessary to the understanding of
the later is not to be found in the earlier Lectures.
For the sake of clearness, I have, in the following pages,
divided the subject into four parts, the study of each pre-
ceding part preparing the way for a complete understand-
ing of those which follow. Thus, the first part is devoted
viii PREFACE.
to the organic elements and parts of plants, the nature
and sources of these elements, and to an explanation of
the mode in which they become converted into the sub-
stance of plants;–the second to the inorganic elements
of plants, comprehending the study of the soils from which
these elements are derived, and the general relations of
geology to agriculture;—the third to the various methods,
mechanical and chemical, by which the soil may be improv-
ed, and especially to the nature of manures, by which
soils are made more productive, and the amount of vege-
table produce increased ; –and the fourth to the results
of vegetation, to the kind and value of the food produced
under different circumstances, and its relation to the
growth and feeding of cattle, and to the amount and qua-
lity of dairy produce.
By this method I have endeavoured to ascend from the
easy to the apparently difficult; and I trust that the will-
ing and attentive reader will find no difficulty in keeping
by my side during the entire ascent.
A D W E R T IS E M E N T
to the
S E C O N D E D I T I O N.
SINCE the completion of the former Edition of these
Lectures in June 1844, I have been almost incessantly em-
ployed in the prosecution of scientific agriculture by re.
searches in the laboratory and observations in the field.
That my own knowledge has been greatly enlarged dur-
ing this interval, and some of my former views corrected,
I am sufficiently sensible. I send forth the present Edi-
tion, therefore, in the belief that it is in many parts con-
siderably improved, and that it presents on the whole a
very correct view of the actual state of our knowledge in
regard to the subjects of which it treats. It is satisfactory
to me to think that, though I have made numerous addi-
tions, and have found occasion to introduce not a few al-
terations, in consequence of new researches, yet that I have
not found it necessary to alter a single important theo-
retical opinion which in the earlier edition I had ventured
to express, I trust that none of my readers will on this
account find occasion to cast upon me the reproach, that
a love of my own old opinions has influenced me more than
a love of the truth.
Edinburgh, March 1847.
C O N T E N T S.
PART I.
Lecture
I.
II.
Importance of Agriculture
Progress of Agriculture
Prospects of scientific agriculture e
Applications of Chemistry and Geology to Agriculture
Different kinds and states of matter - &
Carbon, its properties and relations to vegetable life
Oxygen,_its properties, &c.
Hydrogen,_its properties, &c.
Nitrogen,_its properties, &c.
Characteristic properties of organic substances g
Relative proportions in which the organic elements exist in the dried
parts of plants e & gº
Form or state in which the organic elements enter into and minister to
the growth of plants * e
The atmosphere, its constitution and relations to vegetable life
Nature and laws of chemical combination -
Of water and its relations to vegetable life te &
Of the cold produced by the evaporation of water in the soil, and its
influence on vegetation
III. Carbonic acid, its properties and relations to vegetable life
Oxalic acid, its properties and relations to vegetable life
Carbonic oxide, its constitution and properties e
Light carburetted hydrogen—the gas of marshes and of coal mines
Of the humic, ulmic, geic, crenic, apocrenic, and mudesous acids, and
of humin and ulmin * e ſe
General properties and mutual relations of the humic, ulmic, and geic
acids, and the purposes served by them in the soil
Ammonia, its properties and relations to vegetable life
Nitric acid, its constitution, properties, and production in nature
Source of the carbon of plants º
Form in which carbon enters into the circulation of plants
Source of the hydrogen of plants
Source of the oxygen of plants
Source of the nitrogen of plants tº tº t
Form in which the nitrogen enters into the circulation of plants
Absorption of ammonia by plants
Absorption of nitric acid by plants
36
39
40
42
47
59
62
66
68
69
75
78
87
90
• IV.
97
100
102
103
l()6
l 10
113
xii
CONTENTS.
Lecture
V.
General structure of plants, and of their several parts
The functions of the root
The course of the sap
Functions of the stem
Functions of the leaves
Functions of the bark * e tº
Circumstances by which the functions of the various parts of plants are
modified
Page
117
I 19
133 .
137
140
150
152
VI. The matter of wood–cellulose and incrusting substances—their compo-
VII.
VIII.
sition and properties te
Starch—its composition and properties º
Inuline and lichen starch—their composition and properties
Dextrin—its composition and properties
Gum—its composition and properties
Mucilage—its composition and properties º
Of sugar—its varieties and their chemical composition
Pectose, pectic acid, and parapectic acid
Mutual relations of cellulose, starch, gum, sugar, and pectic acid
Mutual transformations of cellular fibre, starch, gum, and sugar
Of the fermentation of starch and sugar—and of the relative circum-
stances under which cane and grape sugars generally occur in nature
Of the fatty substances of plants g *
Of elaine, margarine, and stcarine—their properties and composition
Composition of elaine, margarine, and stearine
Of wax—its composition and relation to the fats
Of resins and turpentine
Of the acid substances of plants
Of the acetic and lactic acids
Of tartaric, citric, and malic acids &
Of vegetable substances containing nitrogen. Animal and vegetable
albumen & &
Of gluten, glutin, gladiadin, and animal fibrin
Of animal and vegetable casein, emulsin, legumin, and avenin
Of protein, its properties and composition e
Composition of the several protein compounds found in plants
General properties and mutual relations of the above protein compounds
Of diastase—its properties and relations to vegetable life
Chemical changes which are observed during germination and during
the development of the first leaves and roots g
Explanation of the chemical changes which take place during germina-
tion e e ge
Of the chemical changes which take place between the formation of the
green leaf and the expansion of the flower g
On the production of oxalic acid in the leaves, stems, and sap of plants
Of the production of vegetable oils, fats, wax, and turpentine
Of the production of protein and its compounds
Of the chemical changes which take place between the opening of the
flower and the ripening of the fruit or seed
Of the ripening of the fruit
| 62
170
172
175
176
178
179
183
185
!87
191
194
195
] 96
199
201
202
203
206
209
21 1
212
215
216
217
219
225
228
232
238
241
242
2.46
2.49
CONTENTS.
Lecture
IX.
XI.
Of the chemical changes which take place after the ripening of the fruit
and seed e & º *
Of the rapidity with which these changes take place, and the circum-
stances by which they are promoted &
Of the proportion of their carbon which plants derive from the atmo-
sphere & & & e
Of the relation which the quantity of carbon extracted by plants from
the air, bears to the whole quantity contained in the atmosphere
How the supply of carbonic acid in the atmosphere is renewed and re-
gulated & e
Of the supply of ammonia to plants
Of the supply of nitric acid to plants * g
Theory of the respective action of nitric acid and of ammonia upon ve-
getation e © wº
Comparative influence of nitric acid and of ammonia in different cli-
mates e e
Supposed stimulating influence of these compounds ©
Concluding observations regarding the organic constituents of plant
PART II.
. Of the quanity of inorganic matter contained in different plants
Of the circumstances under which the proportion of ash left by vegeta-
ble substances varies * :
Of the kind or quality of the inorganic matter found in plants
Of the several elementary bodies usually met with in the ash of plants
Of chlorine, muriatic acid, and iodine * º
Of sulphur, sulphurous and Sulphuric acids, and sulphuretted hydrogen
Of potassium—potash—carbonate, sulphate, oxalate, tartrate, citrate
and Sulphate of potash—and chloride of potassium
Of sodium, soda, carbonate of Soda, sulphate of soda, phosphate of soda,
sulphurct of sodium, and chloride of sodium & †
Calcium, lime, carbonate of lime, sulphate of lime, nitrate of lime,
phosphates of lime, chloride of calcium, sulphuret of calcium
Of magnesium, magnesia, carbonate, sulphate, nitrate, and phosphate
of magnesia, and chloride of magnesium º
Aluminium, alumina, sulphate and phosphate of alumina—alum
Of silicon, silica, and the silicates of potash, soda, lime, magnesia, and
alumina *- e & *
Of iron—the oxides, Sulphurets, sulphates, and carbonate of iron
Of manganese—the oxides, chloride, carbonate, and sulphate of man-
gamese . * e g tº • N
Tabular view of the composition per cent of the compounds of the
inorganic elements above described
Of the ash of the grain and straw of wheat
Composition of the ash of barley and barley straw
Composition of the grain, straw, leaf, husk, and chaff of the oat
Of the ash of the grain and straw of rye
xiii
Page
253
254
258
261
262
274
281
289
293
294
297
303
307
312
314
316
3.18
340
346
349
356
360
YII.
36]
364
366
368
372
xiv
Lecture
XIII.
CONTENTS.
Composition of the ash of the grain and straw of Indian corn (Zea Mais)
Of the ash of rice º ->
Of the ash of the grain of buck-wheat and millet -
Of the ash of the grain and straw of the bean, the pea, the lentil, and
the vetch - e e
Composition of the ash of the seed and straw of the hemp and flax plants,
and of the seed of the gold of pleasure
Of the ash of the mustard, madia, and rye grass seeds -
Of the ash of the turnip, the beet, the Jerusalem artichoke, and the
potato . *
Of the ash of the cabbage
Of the ash of the grasses and clovers
Of the ash of the tobacco leaf
Of the ash of the coffee bean
Of the ash of the sugar cane
Of the ash of the twigs of the vine
Of the ash of the hop - • P º
Of the ash of the apple and cherry tree, and of the Chinese crab
Ash of the quince, lemon, and thorn-apple seeds e
Of the ash of the oak, elm, lime, and beech, and of the acorn, the beech
nut, and the chesnut e º * -
Ash of the wood of the larch and Scotch fir, and of the seeds of the
Scotch fir and pitch pine .
Ash of some common land weeds
Of the ash of some common parasitic plants
Of the ash of some common sea weeds º
To what extent do the crops most usually cultivated exhaust the soiſ of
inorganic food e e
What mineral substances are absolutely necessary to the existence of
plants of different kinds º *
Of the substances which occur in especial abundance in certain plants
or parts of plants e o e
Can any of these mineral ingredients take the place of each other with-
out injury to the growing plant
Influence of circumstances in modifying the relative proportions of the
inorganic constituents of plants sº
Is the inorganic matter all essential to, or a necessary part of the sub-
stance of the plant ſe e º º
Influence of steeping in water on the quantity and quality of the inor-
ganic matter in barley. Composition of the ash of barley steep-water
Influence of germination on the inorganic matter in barley—the ash of
barley sprouts and of malt & e
Of the inorganic substances dissolved out of the malt in the mash tub
—the ash of beer cztract and of brewer's draff
Effect of the growth of a plant towards maturity on the quantity and
quality of its inorganic constituents º
Composition of the ash of the leaves and straw of the oat at successive
periods of its growth
& *
Page
374
376
376
377
380
383
384
388
389
391
392
393
394
395
395
396
* 397
398
400
401
402
406
409
413
415
429
42
t}
43].
CONTENTS. , - XV
Lecture - Page
Composition of the ash of the leaves and stem of the potato at successive
stages of their growth, . g & 434
Of the value of our present analyses of the ashes of plants o 435
Must the inorganic food of plants exist in the soil in a peculiar state of
solubility or combination to suit each plant • g 437
XIV. Of the organic matter of the soil g ë 439
General composition of the earthy part of the soil © ſº 440
Of the classification of soils from their chemical constituents tº 443
Of the distinguishing characters of soils and subsoils & ſº 447
On the general origin of soils g e g . . 449
On the general structure of the earth's crust, and the general composi-
tion of rocks g & © 450
Relative positions and peculiar characters of the several strata . 454
Classification of the stratified rocks, their extent, and the agricultural
relations of the soils derived from them p 456
XV. Composition of the granitic rocks, and of the minerals of which they
consist & & g tº 483
Of the crumbling of the granitic rocks, and the theoretical character of
the soils formed from them e &
Extent of the granitic rocks in Great Britain and Ireland, and observed
qualities of their soils º & & e 490
Of the trap rocks, and the minerals of which they consist e 492
Extent of the trap rocks in the British Isles, and nature of the soils
formed from them º * & tº . 494
Of Superficial accumulations of foreign materials, and of the means by
which they have been transported • tº 498
Of the occurrence of such accumulations in Great Britain, and of their
influence in modifying the character of the soil & - 502
IIow far these accumulations of drift interfere with the general deduc-
tions of Agricultural Geology e & & 506
Of superficial accumulatious of peat g e & 510
XVI. Of the exact nature of the organic constituents of soils e 513
Of the mode of separating the organic constituents of the soil e 516
On the exact chemical constitution of the earthy part of the soil 518
Of the exact chemical composition of certain natural soils, and of the
results to be deduced from it e * tº g 519
Of the physical properties of soils e gº g 520
PART III.
XVII, On the connection between the kind of soil and the kind of plants
that grow upon it ë * 546
Of draining, its mode of action and its effects * * 550
Of the theory of springs e & & 558
Of ordinary ploughing . - gº e 567
Of subsoil ploughing and forking * tº 569
Of deep ploughing and trenching # w 5
Improvement of the soil by mixing
xvi.
Lecture
XVIII,
CONTENTS,
Of the carbonates of potash and soda, and the theory of their action
upon living plants sº iº •
Of the sulphates of potash, soda, magnesia, and lime, and the theory
of their action tº * gº
Of the nitrates of potash and soda, their observed effects upon diffe-
rent crops, and the theory of their action
Use of the chlorides of sodium (common salt) calcium, and magnesium
Use of the phosphates of lime, magnesia, potash, and soda, and the
theory of their action º • ë
Use of the silicates of potash, soda, and lime. Are they necessary to
the crop or to the land 2 *
Of the salts of ammonia and their special action on vegetation
Of mixed saline manures of vegetable origin—the ashes of wood, sea-
weeds, sugar cane, peat, and coal
Page
581
586
59]
605
610
XIX.
Mixed saline manures of mineral origin. Crushed granite, trap, and lava
Of artificial mixtures of saline manures, and their effects
Of the manufacture of mixed saline manures for different crops
Composition of special manures for wheat, barley, oats, rye, Indian
corn, rice, potatoes, turnips, cabbage, tobacco, the Sugar cane,
coffee, and flax e e * *
. Of the composition of common and magnesian lime-stones
Of the burning and slaking of lime—composition of the hydrates of
lime and magnesia {º we e
Changes which the hydrates of lime and magnesia undergo by pro-
longed exposure to the air
sº States of chemical combination in which lime may be applied to the
land * e ©
Of the various natural forms in which carbonate of lime is applied
to the land
Effects of marl and of the coral, shell, and lime-stone sands upon the soil
Of the use of chalk as a manure &
Is lime indispensable to the fertility of the soil P
State of combination in which lime exists in the soil
Of the quantity of lime which ought to be added to the soil
Ought lime to be applied in large doses at distant intervals, or in
Smaller quantities more frequently repeated e {e
Form and state of combination in which lime ought to be applied to
the land * > &
Of the use and advantage of the compost form
When ought lime to be applied ?
Of the effects produced by lime º
Circumstances by which the effects of lime are modified
Effects of an overdose of lime—overliming
Length of time during which lime acts
Of the sinking of lime into the soil
Why liming must be repeated © g
Theory of the action of lime
Of lime as a direct food of plants
613
615
619
632
634
637
639
649
652
654
656
658
666
G68
67]
673
676
683
686
687
689
693
697
699
700
702
704
705
Lecture
XXII.
CONTENTS,
The chemical action of lime is exerted chiefly upon the organie
matter of the soil & t tº
Of the forms in which organic matter usually exists in the soil, and
the circumstances under which its decomposition may take place
General action of alcaline substances upon organic matter
Special effects of caustic lime upon the several varieties of organic
matter in the soil º
Action of mild or carbonate of lime upon the vegetable matter of
the soil e &
Of the comparative utility of burned and unburned lime
Action of lime on organic substances which contain nitrogen
How these chemical changes directly benefit vegetation
Why lime must be kept near the surface . º
Action of lime upon the inorganic or mineral matter of the soil .
Of the exhausting effect of lime-Is exhaustion a necessary conse-
quence of the use of lime P e
Action of lime on animal and vegetable lif
Use of silicate of lime g
Of green manuring, or the application of vegetable matter in the
green state g *
Important practical results obtained by green manuring g
Of the plants which in different soils and climates are employed for
green manuring & ſº • g
Will green manuring alone prevent land from becoming exhausted P
Of the practice of green manuring §
Of natural manuring with recent vegetable matter
Improvement of the soil by laying down to grass
Improvement of the soil by eating off with sheep
Improvement of the soil by the planting of trees
Of the use of sea-weed as a manure
Of manuring with dry vegetable substances
Of the use of decayed vegetable matter as a manure
Use of charred vegetable matters as a manure •
Of the theoretical value of different vegetable substances as manures
Of flesh, blood, and skin
Wool, woollen-rags, hair, and horn
Of the composition of bones &
On what does the fertilizing action of bones depend ?
Of the application of bone-dust to pasture lands tº
Forms in which bones are applied to the land—dissolved bones
Of animal charcoal, the refuse of the sugar refineries, and animalised
carbon & • § . g
Of fish, fish refuse, shell fish, Sea blubber, whale blubber, and oil
Relative fertilizing values of the animal manures already described
Of the droppings of fowls—pigeons' dung, and guano .
Of liquid animal manures—general relations of the urine of man, of
the cow, the horse, the sheep, and the pig te
Composition of human urine. Of urea and the changes it undergoes
xvii.
Page
707
707
709
711
736
738
739
7.43
744
744
747
753
755
7.58
76]
766
768
772
776
779
78]
784
790 :
79]
Ö
794
796
798
800
807
808
xviii -
Lecture
2-
XXII.
/ Of the theory of fallows
/*
CONTENTS.
Composition of the urine of the cow, the horse, the sheep, the pig,
the goat, and the hare ſe
Composition of the drainings of dung heaps tº
Of the waste of human urine. Use of Sewer water as a manure.
Action of lime and gypsum upon urine—urate, sulphated urine
Waste of cow's urine—dilution with water—use of gypsum, and of
sulphate of iron tº - te •
Of solid animal manures—might soil, poudrette, taffo, the dung of the
cow, the horse, the sheep, and the pig . •
Of the quantity of manure produced from the same kinds of food by
the horse, the cow, and the sheep . .
Of the relative fertilizing values of different animal excretions
Influence of circumstances on the quality of animal manures
Of the changes which the food undergoes in passing through the
bodies of animals ſe *
Of farm-yard manure. Loss it undergoes by fermentation. State in
which it ought to be applied to the land
Of top-dressing with fermenting manures
Of the improvement of the soil by irrigation
* PART IV.
Of the maximum or greatest possible, and the average or actual, pro-
duce of the land º &
Of the circumstances, climate, season, soil, &c.—by which the pro-
duce of food is affected iº . *
Influence of the method of general culture, of the kind of manuring,
and of the rotation followed, upon the produce of food
Of the theory of the rotation of crops e •
Why land becomes tired of clover (clover sick)
Of the grain of wheat —relative proportions of bran and flour
Of the composition of bran
Of the composition of wheaten flour & g
Of the influence of soil and climate on the composition of wheaten
flour w ºp o &
Influence of variety of seed, of mode of culture, of time of cutting,
and of special manures on the composition of wheat
Of the effects of germination, and of baking, upon the flour of wheat
Of the supposed relation between the per-centage of gluten in flour,
and the weight of bread obtained from it g
Of the composition of barley, and the influence of different manures
upon the relative proportions of its several constituents
Effect of malting upon barley iº
Of the composition of the oat, and the effect of manures in modify-
ing that composition
Composition of rye
Page
8] 0
8ſ 1
813
816
83]
835
838
846
848
850
854
858
860
864
865
866
870
Composition of rice, maize or Indian corn, and buckwheat
X XIII. Composition of beans, peas, and vetches
873
875
88.1
883
884
889
89.1
Lecture
CONTENTs.
Effect of soils and manures upon the quality of peas and beans
. Of the composition of potatoes, and the effect of circumstances in
modifying their quality and composition &
Influence of soils and manures upon the quantity and quality of the
potato crop tº 4 ©
Composition of the yam and the sweet potato
Composition of the turnip gº fº *
Composition of mangold-wurtzel, and of the beet, carrot, parsnip,
and cabbage e º &
Relative nutritive properties of the potato, turnip, carrot, mangold-
wurtzel, and cabbage & - * ſº
Composition of the green stems of peas, vetches, clover, spurry, and
buck-wheat e
Composition of the grasses when made into hay
Composition of hemp, line, rape, and other oil bearing seeds
Composition of lintseed and gold of pleasure cakes
General differences in composition among the different kinds of ve-
getable food &
Composition of the mushroom and other fungi
Average composition and produce of nutritive matter per acre, by
each of the usually cultivated crops
Of the properties and composition of milk ... •
Of the circumstances by which the composition or quality of milk is
modified * e
Of the circumstances which affect the quantity of the milk
Of the mode of separating and estimating the several constituents of
milk tº e &
Of the Sugar of milk, and of the acid of milk or lactic acid
Of the mutual relations which exist between lactic acid and the cane,
grape, and milk sugars
Of the souring and preserving of milk º
Of the separation and measurement of cream, the galactometer, the
composition of cream, and the preparation of cream-cheese
Of the separation of butter by churning or otherwise
Of the composition of butter º *
Of the average quantity of butter yielded by milk and cream, and of
the yearly produce of a cow &
Of the circumstances which affect the quality of butter
Of the fatty substances of which butter consists, and of the acid of
butter (butyric acid.) and the capric and caproic acids
Of casein or the curd of milk and its properties
Of the relations of casein to the sugars and the fats
Of the rancidity and preservation of butter
xix
Page
896
899
906
90.9
9] ().
014
X
XIV.
XXV. Of the natural and artificial curdling of milk
Of the preparation of rennet
Theory of the action of rennet .. ſº
Of the circumstances by which the quality of cheese is affected
Circumstances under which cheese of different qualities may be ob-
tained from the same milk
9| 6
917
920
921
923
924
931
937
939
941
943
§ 46
96.3
970
973
978
980
§33
XX.
Lecture
XXVI.
CONTENTS.
Of the average quantity of cheese yielded by different varieties of
milk, and of the produce of a single cow
Of the average composition of cheese iº ſº
Profit of making butter and cheese compared with that of selling the
milk tº tº
Of the fermented liquor from milk, and of milk vinegar
Of the composition of the saline constituents of milk and cheese
Purposes served by milk in the animal economy e
Of the substances of which the parts of animals consist
Whence does the body obtain these substances? Are they contained
in the food P & • º
Of the respiration of animals, and of the purposes served by the
starch, gum, and Sugar contained in vegetable food
Of the origin and the purposes served by the fat of animals
Of the natural waste of the parts of the body in a full grown animal
Of the kind and quantity of food necessary to make up for the natu-
ral waste in the body of a full grown animal
The health of the animal can be sustained only by a mixed food
Of the kind and quantity of additional food required by the fattening
animal tº &
Kind and quantity of additional food required by a growing animal
Kind and quantity of additional food required by a pregnant animal
Kind and quantity of additional food required by a milking animal
Feeding a cow for dairy purposes tº
Influence of size, condition, warmth, exercise, and light on the quan-
tity of food necessary to make up for the natural waste
Influence of the form or state in which the food is given on the
quantity required by an animal
Use of malted or sprouted grain
Use of a mixture of malt and boiled potatoes &
Economical use of mixed and prepared food in feeding cattle
Can a substitute be recommended for oil-cake in the feeding of cattle
Of the supposed fattening property of common salt
Of the alleged unlike feeding qualities of green grass and dried hay
Can we correctly estimate the relative feeding properties of different
kinds of produce under all circumstances
Effect of different modes of feeding on the manure and on the soil
Summary of the views illustrated in the present lecture
Concluding Section
APPENDIX.
Of the examination and analysis of soils
Of the physical properties of the soil
Of the organic matter present in the soil *
Qualitative determination of the soluble saline matter in the soil
Determination of the quantities of the several constituents of the so-
luble saline matter ſº -
Of the insoluble earthy matter of the soil
Page
998
999
1004
1005
1006
l:008
1009
1014
1016
1021
1025
1027
1029
103.1
1032
1035
1036
1038
1040
1045
104.7
1050
1051
1053
1057
1059
106]
1064
1067
1070
1073
1073
1076
1080
1084
) 090
P A RT I.
ON THE ORGANIC ELEMENTS OF PLANTs.
ON THE
APPLICATIONS OF CHEMISTRY AND GEOLOGY
TO
A G. R. I O U L T U R E.
LECTURE I.
Importance of Agriculture. Relation of the growth of food in Great Britain to the
extent of its population. Recent progress and present prospects of English Agri-
culture. Agricultural instruction in schools and colleges. Application of Chemical
and Geological Science to the art of culture—to the improvement of soils—the ro-
tation of crops—the application of manures, &c. Outline of the Course of Lec-
tures. Different kinds and states of matter. Number and nature of the elemen-
tary bodies. Carbon, Hydrogen, Oxygen, and Nitrogen—the elements of which or-
ganic matter chiefly consists. Their properties and their relations to vegetable life.
WERE I about to address you in a single or detached Lecture
only, I should think it my duty to select some one branch of the
art of culture for special illustration, and without much introduc-
tory matter to proceed at once to the exposition of the principle or
principles on which it depended. As the present Lecture, how-
ever, is only the first of a Series which I hope to have the honour of
delivering to you, I may be permitted to introduce my subject with
a few prefatory remarks, which will here find their most appro-
priate place.
Of the importance of the art of Agriculture it may appear su-
perfluous in me to speak. That art on which a thousand mil-
lions of men are dependent for their very sustenance—in the
prosecution of which nine-tenths of the fixed capital of all civilized
nations is embarked—upon which probably two hundred millions
of men expend their daily toil—and which is, besides, the only
4. POPULATION AND GROWTH OF FOOD.
fired basis of national wealth and greatness—that art must con-
fessedly be the most important of all; the parent and precursor of
all other arts. In every country them, and at every period, the
investigation of the principles on which the rational practice of this
art is founded, ought to have commanded the principal attention
of the greatest minds. To what other object could they have been
more beneficially directed P
But there are periods in the history of every country when the
study of Agriculture becomes more urgent, and acquires a vastly tº
superior importance. When a tract of land is thinly peopled—
like the newly settled districts of North America, New Holland,
or New Zealand—a very defective system of culture will produce
food enough not only for the wants of the inhabitants, but for the
partial supply of other countries also. But when the population
becomes more dense, the same imperfect system will no longer suf-
fice. The land must be better tilled, its special qualities and defects
must be studied, and means must gradually be adopted for obtain-
ing from it the largest amount of food which, by greater knowledge,
skill, and industry, it can be made to yield.
The British islands are in this latter condition. Agriculture
now is of much greater importance to us as a nation, than it was
towards the close even of the last century. In 1780, the island of
Great Britain contained about 9 millions of inhabitants; it now
contains nearly 20. The land has not increased in quantity, but
the consumption of food has probably more than doubled. The
annual importation from abroad during the interval has not been
augmented in any very great degree ;—by improved management,
therefore, the same extent of land has been caused to yield a double
produce.
But the population will continue to increase. Can we expect
that the food raised from the land will continue to increase in the
same ratio 2 This is an important question, to which we can give
only an imperfect, though, upon the whole, not an unsatisfactory
3.I] SW62I’, -
The superficial area of Great Britain comprises about 57 mil-
lions of acres. Of these, 34 millions are in cultivation, about 10
millions are waste lands acknowledged to be susceptible of improve-
ment, while the remaining 13 millions are said to be incapable of
PROGRESS OF BRITISH AGRICULTURE. 5
culture. The present population, therefore, is supported by the
produce of 34 millions of acres, or every 34 acres raises food for
about 20 people. Suppose the 10 millions of acres which are sus-
ceptible of improvement to be brought into such a state of culture
as to maintain an equal proportion, they would raise food for an
additional population of about 6 millions, or would keep Great
Britain independent of any large and constant foreign supply till
the number of its inhabitants amounted to 26 millions. But at the
present rate of increase this will take place in about 16 years,” So
that by 1860, unless some general improvement take place in the agri-
culture of the country, the demands of the population will have com-
pletely overtaken the productive powers of the land.
It is satisfactory to know that such a general improvement is
possible. We cannot say exactly how far the general fertility of
the soil may be increased, or how long it may be able to keep
a-head of the growing numbers of the people; but we have our
own past experience, the example of other countries, and the indi-
cations of theory, all concurring to persuade us that the limit of
its productive powers can neither be predicted nor foreseen.
If we glance at the history of British agriculture during the last
half century—from the introduction of the green-crop system, or
the alternate husbandry, from Flanders into Norfolk, up to the
present time—we find the results of each successive improvement
more remarkable than the former. The use of lime, a more ge-
neral drainage of the soil, the invention of improved ploughs and
other agricultural implements, as well as the introduction of better
and more economical modes of using them, the application of bones
as a manure, more recently of thorough draining and subsoil
ploughing, and within the last three years of guano and numerous
artificial manures, have all tended not only to the raising of crops
at a less cost, but in far greater abundance, and on spots which
our forefathers considered wholly unfit for the growth of corn.
The result of each new improvement, I have said, has seemed
more astonishing than the former. For, after a waste piece of
land had been brought into an average state of productiveness, our
fathers were not prepared for any great improvement upon it by new
* For more precise data and calculations, see Porter's Progress of the Nation.
6 EXAMPLES OF CHINA AND SCOTLANI).
labours; nor could they anticipate that, half a century after such
land had been in culture, its produce or its value would at once be
doubled, by a better draining, by a deeper ploughing, by the ap-
plication of bones, or by sprinkling on its surface a small quantity
of a Saline or other substance imported from a foreign country.
When clover was first introduced into Germany to fill up the
year of naked fallow, in the triennial course of cropping, its effects
appeared so extraordinary, that it was pronounced to be the limit
of the art of culture, (Von Thaer.) It gave fodder for cattle dur-
ing the formerly naked year, it gave a better crop of corn in the
following season, and it was supposed to choke the weeds that in-
fested the fields of grain.
But the example of the Chinese shows us that the productive
powers of the soil are not to be easily estimated. Nothing repays
the labours of the husbandman more fully than the willing soil—
nothing is more grateful for his attention, or offers surer rewards
to patient industry, or to renewed attempts at improvement.
In China we see a people, whom we call semi-barbarians, multi-
plying within their own limits till their numbers are almost past
belief;-practising from the most remote ages, and in the most
skilful manner, various arts which the progress of modern science
has but recently introduced into civilized Europe;—cultivating
their soil with the most assiduous labour—stimulating its fertility
by means which we have hitherto neglected, despised, or been
wholly ignorant of, but which the discoveries of the present time
are pointing out as best fitted to secure the amplest harvests—and
thus compelling their limited territory to yield a sufficient suste-
mance for its almost unlimited population.* -
* The agricultural skill of the Chinese is questioned by recent writers on the cus-
toms of that country. This doubt is founded chiefly on the rudeness of their agricul-
tural implements and the scarcity of cattle, whether horses or cows, among them.
But in this densely peopled country, the hoe they employ serves the purpose of every
other implement, (Davis's China, ii. 282,) and, where the place of cattle is supplied
by an equivalent number of men, there can be no comparative want of valuable
manure. The population of China, however, is probably not so dense in all the pro-
vinces as it has hitherto been supposed. Many writers have estimated the entire po-
pulation at 300 millions, while recent statistics reduce it to 175 millions. Taking
even the higher estimate, the population, though excessively crowded in some pro-
vinces, is not on the whole more dense than in England and Holland—the area of
China Proper being 1,200,000 square miles, or eight times that of France. It is
PROSPECTS OF SCIENTIFIC AGRICULTURE. 7
If you have crossed the Bedford levels, or visited the Lincoln-
shire wolds, or made yourselves familiar with the agricultural history
of Norfolk—you are aware of what has already been done in some
parts of our country to subdue unproductive land to the growth of
corn for man. -
In the border country of England and Scotland also we have
a well ascertained and striking illustration of the power of human
industry and skill in developing the dormant energies of the soil,
and in compelling it to yield a richer produce:—and this not
merely where the sun was propitious, and “favouring breezes
blew,” but even where an ungenial climate seemed to forbid the
hope of a successful cultivation. *
How changed the present from the past condition of this ancient
debateable land of our two kingdoms | The agriculture of former
days crept timidly along the river sides, or summed herself in shel-
tered glades and nooks, and reaped her crops under the protection
of armed men;–now she boldly climbs the steepest mountain
sides, and on the tops of the highest hills exhibits the trophies of
her industry—her countless flocks of sheep and her sheaves of
golden corn.
But I would take you still further north, and in Ross-shire and
Sutherland I would ask you to look at the heavy wheat crops of
Easter Ross, and to the turnips and barley which flourish on the
coast line from Dornoch to Helmsdale, and thus to derive en-
couragement as to what man can do amid the vicissitudes even of
a northern climate. Even bleak Caithness and the maturally in-
hospitable Orkney are yielding to the continued application of
well-directed industry and skill, and waving fields of oats and
thriving plantations are gradually usurping the place of the bogs
and naked sheep-walks of a former generation. -
Experience and example, therefore, encourage us to look for-
ward to still further improvements in the art of culture, and, inde-
pendent of such as may be derived from purely mechanical prin-
ciples, theoretical chemistry seems to point out the direction in
considerably less dense, indeed, if we take into account the number of horses and
cattle which, in Europe, are reared and fed on the produce of the land. We may
hereafter expect more accurate information, however, especially regarding the interior
of this interesting country.
8 DIFFICULTY OF INTRODUCING NEW IMPROVEMENTS.
which important advances of another kind may reasonably be an-
ticipated. The Chinese are said to be not only familiar with the
relative value and efficiency of the various manures, but also to
understand how to prepare and apply without loss that which is
specially fitted to promote the growth of each kind of plant. How
far this statement is exaggerated we are unable at present to de-
termine, but it is in this direction among others that chemistry
appears likely to promote the advance of European agriculture.
The practical farmer already rejoices in having in one ton of bone
or rape dust, or in half that weight of Peruvian guano, the equivalent
of 40 tons of farm yard manure:–and it appears not unlikely that
methods will ere long be discovered for compressing into a still less
bulky form the substances especially required by all our cultivated
crops, and that extensive manufactories will by and bye be esta-
blished for the preparation of these condensed manures.
To what precise extent mechanical and chemical means toge-
ther may be expected to increase the total produce of our soil we
cannot say. I was myself formerly unwilling to adopt the opinion
of Mr Alison,”—“ that the husbandry of Flanders on our plains,
and that of Tuscany on our hill sides, would easily raise food
enough for the double of our present population;” or that of Mr
Smith of Deanston, “that by draining and subsoiling alone Great
Britain might, in the course of twenty years, become an exporting
°ountry.” The one an accomplished and eloquent writer, I
thought, might, on a subject. like this, indulge himself in a little
laxity of statement; while the other might be led, as I supposed,
into a little exaggeration by his enthusiasm in behalf of methods
of improvement which have mainly originated with himself.
I have, however, during the last three years travelled over a
large portion of Great Britain, and have examined the actual state
of its husbandry; and though I have found many spots on which it
is doubtful if the average produce can be very largely increased, yet
I am willing now to express it as my deliberate conviction, that as
a whole the island does not at present produce one-half the food
for man which it may be made to bear with profit to the farmer;
and which, by the time our population has doubled, I believe it
will be found readily to yield.
* Principles of Population, I. p. 216,
SCIENTIFIC AGRICULTURE NOT TAUGHT. 9
Thus much may be said in regard to the future hopes and pro-
spects of scientific agriculture, and in answer to the question—
Can the produce of the land be expected to keep pace with the
growth of the population ?
But how few practical men are acquainted with what is already
known of the principles of the important art by which they live—
of those principles by which this increased productiveness is to be
attained Trained up in ancient methods—attached generally to .
conservative ideas in every shape—the practical agriculturists, as
a body, have always been more opposed to change than any other
large class of the community. They have been slow to believe
in the superiority of any methods of culture which differed from
their own, from those of their fathers, or from those of the
districts in which they severally live; and, even when the superi-
ority could no longer be denied, they have been almost as slow
to adopt them.
But the awakening spirit of the time is making itself felt in theº
remotest agricultural districts, old prejudices are dying out, and
the cultivators of this most ancient, most important, and noblest of
all the arts, are becoming generally anxious for information, and
eager for improvement.
Two circumstances have contributed to retard the approach of
this better state of things. -
In the first place, the agricultural interest of England has hi-
therto expended its main strength in attempting to secure or main-
tain important political advantages in the state. The encourage-
ment of experimental agriculture has been in general neglected,
while the diffusion of practical knowledge, or of scientific know-
ledge having a practical bearing, has been either wholly over-
looked, or considered subordinate to other objects. No national
efforts have been made for the general improvement of the
methods of culture. While for the other important classes of the
community special Schools have been established, in which the ele-
ments of all the branches of knowledge most necessary for each class
have been more or less completely taught, and a more enlightened,
because better instructed, race of men gradually trained up ;-
scarcely any such schools have been founded for the special bene-
fit of the agriculturist. -
10 SCIENTIFIC AGRICULTURE NOT TAUGHT.
The tide, however, is now turning. The agricultural commu-
nity are becoming alive to their own wants and true interests, and
the importance of special agricultural schools is becoming gene-
rally recognised. The first of this class of schools as yet established
in England is the Royal Agricultural College at Cirencester,
which is now open for the reception of students. Another pro-
vincial institution with less pretensions, a Yeoman Agricultural
School, has been established at York, with much promise of suc-
cess, and it is probable that others will by and bye spring up in
different parts of the country. These institutions are signs of pro-
gress in the right direction, and will gradually remove one of
those obstacles to the advancement of agriculture, by which it has
hitherto been very much kept back.
But these institutions are intended for the sons of farmers only,
or for those who intend to become practical cultivators of the soil.
The higher class of proprietors is not to be taught in them, and
yet some instruction in this branch of knowledge is as necessary to
them as it is to the men by whom their land is farmed. In our uni-
versities, in which the owners of the land, those most interested in
its improvement, are nearly all educated, a lesson upon agriculture,
the right arm of the state, has hitherto scarcely ever been given.
Or if at Oxford or Durham an occasional course of lectures is an-
nounced, no sufficient encouragement is afforded either to the
teacher to continue his labours, or to the taught to enter upon the
study as an important branch of their academical business. I be-
lieve that a short annual course of twenty lectures on scientific
agriculture might be made very popular, very interesting, and very
useful, and that it might, without in any way interfering with the
usual university studies, be easily introduced into the ordinary
course of arts. The objections which have been urged against the
introduction of general chemistry and geology do not bear upon
this branch of applied science,—because it has a direct special
relation to the art by which the proprietors of the soil are main-
tained, and which is daily practised by those persons with whom
the clergy in the rural districts have the most frequent intercourse.
But there is a third class to whom neither the universities nor
the special agricultural colleges—because of the expense—can be
of any direct service. This class comprises the numerous body of
NEGLECT OF SCIENTIFIC AGRICULTURAL LITERATURE. 11
small farmers throughout the country, and the labouring popu-
lation, from among whom spring up the bailiffs and managers of
all our larger farms. The actual state of knowledge among this
class is of as much importance to the progress of agriculture as
among any other. They have much in their power either in the
way of promoting or of retarding any improvements which may be
suggested or actually commenced. It is of consequence, therefore,
that in the general movement this class should not be forgotten.
They are generally educated in the common elementary schools of
our rural districts. For their benefit, therefore, agricultural in-
struction of an elementary nature ought to be introduced into
these humbler schools. -
This view of the matter has been especially adopted in Scotland,
where the rural population is singularly intelligent, their children
apt to learn, and both old and young eager for information. The
parish and other schoolmasters have taken up the subject as a body,
and are now generally introducing into their schools a certain
amount of elementary instruction in chemical science as directly
applicable to the culture of the soil. In Ireland also the same
movement is in progress. The school of Templemoyle has long
been a source of good to the province in which it is situated; and
the Commissioners of National Education are anxious to introduce
agricultural instruction, such as that given in their school at Larne,
into all the national schools of the sister island.
The gradual introduction of this new branch into all our ele-
mentary schools will be greatly promoted by the special instruc-
tion in agricultural chemistry, which is now given to the rising
schoolmasters—in the training schools of York and Durham, in
the normal schools of Edinburgh and Glasgow, in the new train-
ing department at Templemoyle in the north of Ireland,-and at
the national model farm and training school of Glasnevin, near
Dublin.
In our colonies this diffusion of knowledge among the masses
is likewise recognised as a means of reviving the agricultural pro-
sperity—and in Jamaica the subject of agricultural instruction in
the common schools, has attracted nearly as much attention as
among ourselves.
The same is the case in the United States of America, the umi-
J2 GENERAL SCIENCE AND AGRICULTURE.
versities are there vying with each other in establishing chairs of
agricultural chemistry, -special agricultural colleges are in course
of erection in many places, and in thousands of their elementary
schools, the text-book compiled for the Scottish schools" is already
taught as a part of the weekly lessons.
When this combined system of instruction in the principles of scien-
tific agriculture shall have been introduced into our universities, spe-
cial colleges, and schools, we may hope to have our agricultural po-
pulation not only better instructed in their own art upon the whole,
but elevated also in intellectual rank by a knowledge of the prim-
ciples on which all their operations are based, and prepared both
to execute and to originate improvements, by which the soil they
till may be rendered more productive to the community and more
profitable to themselves.
And whereas hitherto scientific men have had no inducement to
devote their time and talents to the cause of agriculture, since it
held out to them no promise of reward, either in the shape of ac-
tual emolument or of honorary distinction,-the universities and
colleges will then hold out a promise of both, and thus, after an
outlet for the knowledge has been provided, new sources of it will
be opened up, from which much that is beneficial may be expected
to flow.
It is the want of this encouragement to scientific men on the
part of the agricultural community which has hitherto so much re-
tarded the application of science to the improvement of the art of
culture. Few men of science have cared to work for a class who
profess to hold all science in contempt; and who have hitherto
shown themselves so little grateful for any attempts to instruct
them. Little inducement also existed to the writing of books upon
scientific agriculture, when, instead of calmly considering any new
statements, or reasonably and patiently trying any new methods
which might be suggested and in the way recommended by their
author, ridicule has been unhesitatingly cast upon him as a mere
theorist, and his want of familiarity with a few of the manual ope-
rations of the farm, or of the terms by which they were denoted,
quoted as decisive proofs that he was ignorant of the whole sub-
ject, and that his opinions were unworthy of regard.
* CATECHISM of Agricultural Chemistry and Geology, 16th Ed. Blackwood, 1845,
GEOLOGY AND AGRICULTURE. 13
This mode of judging of science and of scientific books is now
happily dying away, and will altogether disappear with the present
generation; but to its existence is mainly, I believe, to be ascribed
the second of those circumstances by which the progress of agri-
culture has been retarded—the want, namely, of a scientific agri-
cultural literature.
With the exception of a small number of periodical publications,
none of these even too well supported, by which attempts have
been zealously made to diffuse important information among the
practical farmers—it cannot be denied that the press has not been
encouraged to do its utmost on behalf of agricultural knowledge
in general—while the single work of Sir Humphry Davy is nearly
all that chemical science has, in this country, been induced to con-
tribute to the advancement of agricultural theory during the first
forty years of the present century.*
Many of you have probably read this work of Sir H. Davy, and
are prepared to acknowledge its value. Yet how many things
does he pass over entirely, how many others leave unexplained
Since his time, not only have numerous practical observations and
discoveries been made, but the entire science of animal and vege-
table chemistry has been regenerated. We are not, therefore, to
expect in his work a view of the present state, either of our theo-
retical knowledge or of our practical agriculture. It belongs
rather to the history of the progress of knowledge, than to the
condition of existing information. Hence the merits of the agri-
cultural chemistry of Davy are not to be tried by its accordance
with actual knowledge, but with what was known in 1812, when
its distinguished author read his course of lectures for the last time
before the Board of Agriculture.
We may with certainty predict, however, that neither the prac-
tice nor the theory of agriculture will be permitted to experience
in future that want of general encouragement, under which during
the last half century they have in England been suffered to lan-
guish. The public mind has been awakened, and the establish-
ment of Agricultural Associations, provincial and local, in so many
parts—not only of the three kingdoms, but of our colonies also—
* The last edition of Lord Dundonald’s “Treatise on the intimate connection between
Chemistry and Agriculture,” which I have seen, is dated London, 1803.
14 AGRICULTURAL CHEMISTRY ASSOCIATIONS.
is a manifestation of the interest now felt upon the subject through-
out the whole of the British dominions. It requires only the con-
tinued exhibition of such an interest, and the adoption of some
general means of encouragement, to stimulate both practical in-
genuity and scientific zeal to expend themselves on this most va-
luable branch of national industry. -
Science is never unwilling to lend her hand to the practical arts;
on the contrary, she is ever forward to proffer her assistance, and
it is not till her advances have been rejected or frequently repulsed,
that she refrains from aiding in their advancement.
Need I advert, in proof of this, to the unwearied labours of the
vegetable physiologists—or to the many valuable observations and
experiments recorded in the memoirs of scientific chemists? In
these memoirs, or in professedly scientific works, such observations
have not unfrequently been permitted to rest;-the public mind
being unprepared either to appreciate their value or to encourage
the exertions of those who were willing to give them a practical
and popular for m. *>~ -
And how numerous are the branches of science connected with this
art! I need scarcely speak of botany, which is, as it were, the foun-
dation on which the first elements of agriculture rest; or of vege-
table physiology, to the indications of which it has hitherto almost
exclusively looked for improvement and increased success; or of
zoology, which alone can throw light on the nature of the nume-
rous insects that prey upon your crops, and so often ruin your
hopes, which can alone be reasonably expected to arm you
against their ravages, and instruct you to extirpate them? Me-
teorology among her other labours tabulates the highest, the mean,
and the lowest temperatures, as well as the quantity of rain which
falls during each day and each month of the year. Do you doubt
the importance of such knowledge to the proper cultivation of the
land? Consider the destructive effects of a late frost in spring, or
of a prolonged heat in summer, and your doubts will be shaken.
A wet season in our own climate brings with it many evils to the
practical agriculturist; but what effect must the rain have on the
soil, in countries where nearly as much falls in a month, as falls in
England during the course of a whole year;" where every thing
* At Canton, in the month of May, the fall of rain is often as much as 20 inches,
—Davis.
3
AGRICULTURAL CHEMISTRY ASSOCIATIONS. 15
soluble appears to be washed from the land, and nothing seems to
be left but a mixture of sand and gravel? It may indeed be said
with truth, that no department of natural science is incapable of
yielding instruction—that scarcely any knowledge is superfluous—
to the tiller of the soil.
It is thus that all branches of human knowledge are bound to-
gether, that all the arts of life, and all the cultivators of them, are
mutually dependent. And it is by lending each a helping hand
to the others, that the success of all is to be secured and hastened;
while with the general progress of the whole the advance of each
individual is made Sure.
The recent contributions and suggestions of geology afford a
striking proof of the readiness of the sciences of observation to give
their aid to the promotion especially of agricultural knowledge.
The geologist can best explain the immediate origin of your seve-
ral soils, the cause of the diversities which even in the same farm,
it may be in the same field, they not unfrequently exhibit;” the
nature of your subsoils, the nature and cause of their differences,
and the advantages you may expect from breaking them up or
from bringing them to the surface. -
Geology in its present state is essentially a popular science,
and the talents of its eminent English cultivators are admirably
fitted to make it still more so. Hence, a certain amount of know-
ledge of this science has been of late years very generally diffused,
and its relations to agriculture are in consequence becoming
every day better understood. The Highland Society of Scotland,
among its many other useful exertions, has done very much to
connect agriculture with geology in the minds of those who live
within the peculiar sphere of its own labours, while the Journal
and general proceedings of the Royal Agricultural Society of
England manifests a similar desire on the part of that numerous
and talented body, to illustrate the connection of agriculture with
geology and chemistry, in the southern division of the island.
But perhaps the most decided step yet taken in any country for
* I cannot refer to a plainer, more simple, or more beautiful illustration of this
fact than that which is presented in a short paper by Sir John Johnston, on the Ap-
plication of Geology to Agriculture, inserted in the Journal of the Royal Agricultural
Society, i. p. 271,
16 THE CHEMISTRY OF SOILS.
the purpose of more directly connecting science with agriculture,
is the recent establishment of the Agricultural Chemistry Associa-
tion of Scotland. Originating with the practical farmers, and sup-
ported by the Scottish proprietors, this association proposes to
diffuse elementary scientific knowledge among the agricultural
classes; to add to our knowledge by investigations in its laboratory;
to assist the farmer in improving his land, by analysing his soils
and the fertilizing substances he applies to it; and to defend the
purchaser of manufactured and other portable manures from im-
position by affording a ready and cheap means of analysing them,
and of thus ascertaining their real value. This association has now
been three years in operation, has performed upwards of 1500 ana-
lyses in its laboratory, and has sent out its officer to address agri-
cultural audiences in every part of Scotland. The result has
been, not only the diffusion of much knowledge, but an awak-
eming of the agricultural population to a degree of general mental
activity and zeal for improvement which has not been previously
witnessed by the present generation.
The example of this Association has already been followed in
Ireland by the establishment of the “Ulster Chemico-agricultural
Association,” having in view the same objects, with nearly the same
plan of operations—and in the United States by the American
Agricultural Society, which has its head-quarters in New York.
The new College of Chemistry in London proposes to attach to it-
self a special agricultural department, by which and by the labo-
ratory of the Museum of Economic Geology similar advantages
will be afforded to the agricultural population of the southern
counties. -
The time, therefore, appears to be peculiarly favourable for the
increase and diffusion of sound and useful agricultural knowledge
among practical men. The growth of our population requires it
—practical men are anxious to receive instruction—scientific men
are eager to impart what they know, and to make new researches
for the purpose of clearing up what is unknown—are we not jus-
tified, therefore, in anticipating hereafter a constant and general dif-
fusion of light, a steady progress of agricultural improvement?
Having thus glanced at the state and prospects of scientific
THE CHEMISTRY OF SOILS, 17
agriculture in general, and especially of the art of culture in Eng-
land, permit me to advert to a few of those questions of daily oc-
currence among you, to which chemistry alone can give satis-
factory answers. I shall not in this place allude to the subject of
manures—which form alone an entire department of most recom-
dite chemistry, and which I shall take up in its proper place,—but
I shall select rather a few isolated topics, the bearing of chemical
knowledge upon which is sufficiently striking.
1°. Some soils are maturally barren, but how few of our agricul-
turists are able, in regard to such soils generally, to say why; how
few who possess the knowledge requisite for discovering the cause !
Of these barren lands some may be improved so as amply to repay
the outlay; some, from their locality or from other causes, cannot
in the present state of our knowledge, be profitably reclaimed.
How important to be able to distinguish between these two cases 1
Again some apparently good soils are unproductive in a high
degree. In endeavouring to improve such soils, practical men
have no general rule—they can have none. They work in the
dark—like a man who makes experiments in a laboratory, without
a teacher or without a book, till, after many blunders and much
expense, he discovers some useful fact—which is new to himself
though long known to others, and which forms only one of many
analogous facts dependent upon a common, and probably well-un-
derstood, principle.
“The application of chemical tests to such a soil,” says Sir
Humphry Davy, “is obvious. It must contain some noxious prin-
ciple,” which may be easily discovered and probably easily destroy-
ed. Are any of the salts of iron present—they may be decomposed
by lime. Is there an excess of siliceous sand—the system of im-
provement must depend on the application of clay and calcareous
matters. Is there a defect of calcareous matter—the remedy is ob-
vious. Is an excess of vegetable matter indicated—it may be re-
moved by liming, paring, and burning. Is there a deficiency of
vegetable matter—it is to be supplied by manure.”—(Agricultural
Chemistry, Lecture I.) -
What was true in regard to the applications of chemistry in the
time of Sir Humphry Davy is more true in a high degree of the
* Or be deficient in some necessary element.—J.
B
I8 ROTATION OF CROPS —USE OF LIME AND GYPSU M .
chemistry of our time. Not only is the nature of soils better un-
derstood, but we know generally what a soil must contain be-
fore it will produce a given crop. Why do pine forests settle
themselves on the naked and apparently barren rocks of Scotland
and of Northern Europe, content if their young roots can find but
a crevice in the mountain to shelter them P Why does the beech
luxuriate in the alluvial soils of Southern Sweden, of Zealand, and
Continental Denmark? Why does the birch spring up from the
ashes of the pine forest, why the rapid rush of delicate grass from
the burned prairies of India and of Northern America? Whence
comes the thick and tender sward of the mountain limestone dis-
tricts—whence the gigantic wheat stalk of a virgin soil, or its rank
luxuriant clover ?—Why do the same forest trees propagate them-
selves for ages on the same spots without impoverishing the soil—
why do the matural grasses in many districts render the land more
fertile the longer they are undisturbed?
These one would think are scarcely chemical questions, and yet
to all of them, and to a thousand such, chemistry alone can and
will give a satisfactory answer.
2°. The rotation of crops is a practical rule, the benefit of which
has been proved by experience;—it becomes a true philosophical
principle of action, when we discover the causes from which this
benefit springs. Botany has thrown considerable light, and of an
interesting and important kind, upon this practice, but chemistry
has more fully cleared it up and in some degree established the
principle on which it depends.
3°. Sir Humphry Davy speaks of the use of lime. Can you ex-
plain the mysterious, and apparently fickle and diversified, agency
of this substance in reference to vegetation ? Are the advantages
so frequently attendant upon its use to be ascribed to the chemical
character of the soil to which it is applied, to the kind and quan-
tity of the vegetable matter it contains, to the kind of cropping or
other treatment to which it has been subjected, or to the geological
nature of the rocks on which it rests? Are they dependent upon
the drainage and exposure of the land—on the kind of crop to be
raised—on the general climate of the district—on the maxima and
minima of temperature—or on the quantity of rain which falls?
4°. So with gypsum. Why are its effects lauded in one district,
AGRICULTURE A CHEMICAL ART. 19
doubted in another, and decried in a third P Are no rules or
principles to be discovered, by which these diversified effects are to
be explained —none by which the true purpose and fit use of this
and other mineral substances is to be clearly pointed out? Such
principles are still to be sought for in regard to some substances;
but if sought by the way of well devised and accurately conducted
experiment—they are sure to be discovered.
5°. The land is exhausted by frequent cropping. What language
more familiar, what statement more true than this? Yet how few
understand what exhaustion implies; how few can explain either
how it takes place, by what means it can be remedied, or how, if the
land be laid down to rest, nature herself at length applies a remedy?
Have you any doubt in regard to the prevailing ignorance on
this subject P To be satisfied, you have only to look with an expe-
rienced eye on the agricultural practice of your own county of Dur-
ham. Are there not thousands of acres in the centre of this county
which exhibit a degree of unproductiveness not matural to the soil;
—which have been over-cropped, and worn out, and impoverished?
A soil comparatively fertile by nature has been rendered unfertile
by art. That which was naturally good has been rendered as un-
productive and unprofitable as that which was naturally bad. Has
this state of things arisen from ignorance, from design, from ne-
cessity, or merely from neglect? By whichever of these it has
been immediately caused, it is clear that the requisite degree of
knowledge on the part of the owners of the soil would haye retard-
ed if not wholly prevented it.
The same knowledge will enable them to reclaim these lands
again, and gradually restore them to a more fertile condition; for
the changes to the worse which the soil undergoes in such circum-
stances are nearly all chemical changes, either in the relative quan-
tities of the substances it contains, or in the state of combination in
which they exist.
6°. The art of culture indeed is almost entirely a chemical art,
since nearly all its processes are to be explained only on chemical
principles. If you add lime or gypsum to your land, you intro-
duce new chemical agents. If you irrigate your meadows, you
must demand a reason from the chemist for the abundant growth
of grass which follows. Do you find animal manures powerful in
20 THEORIETICAL KNOWLEDGE STILL VERY DEFECTIVE,
their action ?—is the effect of some permanent, while that of others
is speedily exhausted 2–does a mixture of animal and vegetable
manure prepare the land best for certain kinds of grain 2–do
you employ bones, or common salt, or saltpetre, or mitrate of
soda with advantage 2–do you find a mixture of these saline sub-
stances more useful than either of them applied singly?—in all these
cases you observe chemical results which you would be able to con-
trol and modify did you possess the requisite chemical knowledge.
It is not wonderful that even theoretical agriculturists should
be far behind in the knowledge of those principles on which their
most important operations depend. The greatest light has been
thrown upon the art of culture by the researches of organic che-
mistry, a branch which may be said to have started, if not into ex-
istence, at least into a new life, within the last ten years. Every
day too is adding to the number and value of its discoveries, and
the agriculturist may well be pardoned for not keeping pace with
the advances of a department of science, which even the professed
and devoted chemist can scarcely overtake.
7°. I might advert also to the mechanical operations of plough-
ing, whether common or subsoil, of fallowing, draining, weeding,
and many others, as being only so many methods by which chemical
action is induced or facilitated;—to the growth of plants, and even
to such observed differences as that of the relative quantity of leaves
and tubers in the potato, and of grain and straw in our corn-fields,
as interesting cases on which scientific chemistry throws a flood of
light. I might show how the rearing, feeding, and fattening of
your cattle, and the raising and management of dairy produce are
not beyond the province of chemistry, but that the only approach
to scientific principle yet made—even in these branches of hus-
bandry—is derived from the results of chemical research.
8°. And lastly, I might advert to the beautiful moral lessons which
this study is fitted to convey to the enquiring mind—showing how
the soil, the plant, and the animal are bound together by one com-
mon chain—are parts of the same system of things—of one single
conception as it were, the offspring of one mind—and how the ope-
rations they perform, and the changes they severally undergo, are
all so many beautiful provisions by which they mutually prepare
the food or anticipate the wants of each other. The subject is in-
deed full of beauty, wisdom, and goodness.
OUTLINE OF THE COURSE OF LECTURES. 2I
But I do not dwell on any of these points: they will all hereaf-
ter come under our review in their appropriate order, and will af-
ford me an opportunity of laying before you many important facts
as well as many practical deductions and observations, not less
valuable than the facts from which they are drawn.
While, however, I feel justified in saying thus much of the light
which existing chemical knowledge throws on the natural processes
of vegetation, and on the artificial methods of practical agriculture,
I would not lead you to suppose that our knowledge is by any
means complete, that there are not many points over which dark-
mess still rests—that some of the theoretical views now entertained
are not crude, adopted too hastily, and generalized too rapidly. But
a similar confession may be made in reference to all the modern
sciences of observation without diminishing their importance or de-
tracting from the value of the facts they embody. Human science
is progressive in all its branches, and to refuse to follow the indi-
cations of existing knowledge because it is to some extent uncer-
tain, would be as foolish as to refuse to avail ourselves of the morn
ing light, because it is not equal to that of the mid-day sun.
I advance, therefore, to the special object of these lectures, and I
shall first present you with an outline of the method which I intend
to follow. It is indispensable that this method should be simple, and
that every consecutive portion should be so fitted to clear the way for,
and to throw light upon, what is to follow, that we may be able
to advance from the first rudiments to the most difficult and ab-
struse parts of our subject, without any chance of the illustrations
being even difficult to comprehend. This end I do not hope per-
fectly to attain, but it will be my constant aim, and, with due at-
tention on your part, I do not fear that we shall fail in arriving at
a perfect understanding of the various points to which I shall have
occasion to direct your attention.
I propose, therefore, to bring before you—
I. The constitution of vegetable substances, with the properties
of the elementary and compound bodies which either form part of
the actual substance of living plants, or are believed to contribute
to their growth and nourishment.
22 ORGANIC AND IN ORGANIC MATTER.
II. The general structure and functions of the several parts of
plants, their mode of growth, the manner in which their food is
absorbed, the sources from which it is derived, the forms of chemi-
cal combination in which it enters into their circulation, and the
chemical changes it undergoes during its conversion into parts of
their substance.
III. The origin, nature, and principal chemical and mechanical
differences among soils—with the circumstances on which their re-
lative fertility depends, or under which it is modified.
VI. The nature and differences of manures, and their mode of
action—whether directly in supplying food to the plant, or indi-
rectly in hastening and increasing their growth.
V. The nature, the apparent diversities, and the chemical diffe-
rences which exist among the various kinds of vegetable food raised
as the result of culture—especially in reference to the way in which
they serve for food, and to their relative values in sustaining or
promoting the growth of animals.
Under this head the feeding of cattle and the variations in the
quantity and quality of dairy produce, will form subjects of con-
sideration.
These different branches, I believe, comprehend the whole sub-
ject of chemical agriculture. In regard to all of them we shall de-
rive either from chemistry or from geology much important infor-
mation.
§ 1. Of the different kinds and states of Matter.
1°. Organic and inorganic matter.—All the forms of matter
which present themselves to our view, whether in the solid crust
of the globe on which we live, in the air which forms the at-
mosphere by which we are surrounded, or in the bodies of
animals and plants—all are capable of being divided into the
two great groups of organic and inorganic matter. The solid
rocks, the incombustible part of soils, the atmosphere, the wa-
ters of the seas and oceans, everything which neither is nor has
been the seat of life, may generally be included under the head
of inorganic matter. The bodies of all living animals and
plants, and their dead carcases—consist of organic or organiz-
Ol{GANIC SUBSTANCES. 23
ed matter. These generally exhibit a kind of structure readily
visible by the eye, as in the pores of wood, and in the fibres of
hemp, or of the lean of beef,” and are thus readily distinguished
from inorganic matters, in which no such structure is observable.
But in many substances of organic origin also, no structure can
be observed. Thus, sugar, starch, and gum are formed in plants
in great abundance, and yet do not present any pores or fibres;
they have never been endowed with organs, yet being produced
by the agency of living organs, they are included under the gene
ral name of organic matter. So when animals and plants die,
their bodies undergo decay, but the substances of which they are
composed, or which are formed during their decay, are considered as
of organic origin, not only as long as any traces of structure are
observable, but even after all such traces have disappeared. Thus
coal is a substance of organic origin, though almost all traces of
the vegetable matter from which it has been derived have been
long ago obliterated.
Again heat chars and destroys wood, starch, and gum, forming
black substances totally unlike the original matter acted upon.
By distillation, wood yields tar and vinegar; and by fermentation,
sugar is converted first into alcohol, and then into vinegar. All
substances derived from vegetable or animal products by these and
similar processes are included under the general designation of
organic bodies.
2°. Simple and compound bodies.—Now if we take a portion of
almost any of those numerous forms of matter which we meet with
either in the in-organic or in the organic kingdoms, we find that, on
subjecting it to certain chemical processes, it is capable of being
resolved or separated into more than one substance. Thus coal
when put into a retort in our gas works is resolved into tar, coal-
gas, and certain other substances, leaving a portion of coke behind
—while wood, when treated in a similar way, yields pyroligneous
acid, tar, and water, and leaves behind a residue of charcoal.
But if we take the charcoal which is thus left and subject it to
the action of heat (not in the open air), or to any other process we
can devise, we can never separate any thing further from it. After
all our operations we obtain only charcoal.
* The pores of wood and fibres and minute vessels in animals being the organs or
instruments of life, the substances themselves are called organized or organic.
24 - NUMBER OF ELEMENTARY BODIES,
In like manner a piece of common lead ore, (galena,) when
heated will, if pure, give off sulphur only, and will leave the lead
behind, from which nothing but lead can afterwards be extracted.
Thus it is evident that coal, wood, and the ore of lead differ from
charcoal and metallic lead in this respect, that the former consist
of two or more kinds of matter, which can be separated from one
another, the latter of one kind of matter only. Hence charcoal and
lead are called simple or elementary bodies, while wood and all other
substances which are capable of being resolved into two or more
different kinds of matter are called compound bodies.
3°. Entire number of simple substances.—The diversified forms
of matter which present themselves to our motice in the mine-
ral crust of the globe, and in the organs and vessels of plants
and animals, are absolutely without number. We can no more
reckon them than we can the stars of heaven. Yet it is one of
those results of modern chemistry which to the mind not yet fa-
miliarized with chemical discoveries appears most wonderful,-
that these numberless forms of matter are capable of being resolv-
ed into, and therefore are composed or made up of, only 62* of
those substances, which are called simple or elementary. Oc-
casionally these elementary substances occur in mature in a sepa-
rate state, as in nativef gold and silver, but they are generally
found associated together, forming compound substances from
which two or more of these simple bodies may be extracted.
4°. Number of simple substances in the organic part of plants.—
All the material substances in nature consist of one or more of
these 62 elementary bodies. This as I have said is sufficiently
surprising, yet it is, if possible, still more remarkable that nearly
the entire mass of every vegetable substance may be resolved in-
to one or more of four only of these simple substances.
When a portion of animal or vegetable matter is burned, it
* The names of these elementary bodies are as follows:–Oxygen, hydrogen, nitro-
gen, sulphur, selenium, phosphorus, chlorine, bromine, iodine, fluorine, carbon, boron,
silicon, potassium, sodium, lithium, barium, strontium, calcium, magnesium, alumi-
nium, glucinium, yttrium, erbium, terbium, zirconium, norium, thorium, cerium, lan-
thanium, didymium, manganese, iron, cobalt, nickel, zinc, cadmium, lead, tin, bismuth,
copper, uranium, mercury, (quicksilver), silver, palladium, iridium, rhodium, ruthe-
mium, platinum, gold, osmium, titanium, tantalum, (columbium), niobium, pelopium,
tungsten, molybdenum, vanadium, chromium, antimony, tellurium, arsenic.
f So called when found in the malleable state.
ORGANIC CONSTITUTENTS OF PLANT$–CARBON. 25
either entirely disappears or leaves behind it only a small quantity
of ash. Animal and vegetable oils and fats, gum, sugar, and
starch, when burned, disappear entirely ; a piece of wood or of
lean meat leaves a small quantity of earthy (inorganic or mineral)
matter behind. -
Now all that disappears when any portion of vegetable matter,
of any kind, is burned, consists generally of three, and only in some
rare cases of more than four, of the elementary bodies. These
four are carbon, oxygen, hydrogen, and nitrogen. With the ex-
ception of the matter indestructible by fire (the ash), and a trace
of sulphur and phosphorus, chemical analysis" has hitherto failed to
detect the presence of more than these four elementary substances
in the principal parts of plants. The same remarks apply with al-
most equal truth to animal substances. The whole of that part of
animal bodies which is destroyed or dissipated by fire consists of the
same four elements with minute admixtures of phosphorus and
sulphur.
To the agriculturist, therefore, an acquaintance with these
four constituent parts of all that lives and grows on the face of the
globe is indispensable. It is impossible for him to comprehend
the laws by which the operations of nature in the vegetable king-
dom are conducted, nor the reason of the processes he himself
adopts in order to facilitate or to modify these operations, without
this previous knowledge of the nature of the elements—the raw
materials as it were-out of which all the products of vegetable
growth are elaborated.
I shall first, therefore, exhibit to you briefly the properties of
these constituents of the organic part of plants, in order that we may
be prepared for the further enquiries—by what means or in what
form they enter into the circulation of plants—and how, when they
have so entered, they are converted into those substances of which
the skeleton of the plant consists or which are produced in its se-
veral organs.
§ 2. Carbon—its properties and relations to vegetable life.
Carbon is the name given by chemists to the substance of wood
* Under the general name of chemical analysis are comprehended the various pro-
cesses by which natural forms of matter may be resolved or separated into the seve-
ral elements or simple substances of which they consist.
26 PROPERTIES OF CARBON.
charcoal in its purest form. When wood is distilled in close ves-
sels, or burned in heaps covered over so as to prevent the free ac-
cess of air, wood charcoal is left behind. When this process is
well performed, the charcoal consists of carbon with a small ad-
mixture of earthy and saline matters. From this mixture is de-
rived the small quantity of white ash which is left behind when
charcoal is burned in the air.
Charcoal burns in the air with little flame, and, with the ex-
ception of the ash which is left, entirely disappears. It is convert-
ed into a kind of air known among chemists by the name of car-
bonic acid, which ascends as it is formed and mingles with the
atmosphere.
Wood-charcoal is light and porous, and floats upon water, but
plumbago or black lead and the diamond, which are only other
forms of carbon, are heavy and dense. The former is 2%, and the
latter 3}, times heavier than water. The diamond is the purest
form of carbon, and at a high temperature it also burns in the air
or in oxygen gas, and, like charcoal, disappears in the state of car-
bonic acid gas. -
Of this carbon all vegetable substances contain a very large
proportion. All the parts of plants which are cultivated for the
food of animals or of man, after being dried by the heat of boiling
water, are found to contain from 40 to 50 per cent. of their weight
of this substance. In the economy of nature, therefore, it performs
a most important part.
The light porous charcoals obtained from animal substances,
such as horns, hoofs, wool, flesh, &c., and from certain kinds of
wood, such as the willow, the pime, and the box, possess several
interesting properties, which are of practical application in the art
of culture—thus, -
1°. They have the power of absorbing in large quantity into
their pores, the gaseous substances and vapours which exist in the
atmosphere. Thus of ammonia they absorb 95 times their own
bulk, of sulphuretted hydrogen 55 times, of oxygen 9 times, of
hydrogen nearly twice their bulk, and of watery vapour so much
as to increase their weight from 10 to 20 per cent. On this pro-
perty, as I shall explain hereafter, the use of charcoal powder as
a manure probably in some measure depends.
PROPERTIES OF CARBON. 27
3°. They also separate from water any decayed animal matters,
colouring substances, bitter extracts, &c. which it may hold in
solution; hence its use in filters for purifying and sweetening im-
pure river or spring waters, or for clarifying syrups and oils. This
action is so powerful that port wine is rendered perfectly colour-
less, and a decoction of hops becomes tasteless, when filtered through
a well prepared charcoal.
In or upon the soil charcoal will for a time act in the same
manner. From the air it will absorb moisture and gaseous sub-
stances, and from the rain and from flowing waters organized mat-
ters of various kinds, all of which it will yield up to the plants that
grow around it, when they are such as are likely to contribute to
their growth.
4°. They have the property also of absorbing disagreeable
odours in a very remarkable manner. Hence animal food keeps
longer sweet when placed in contact with charcoal—hence also
vegetable substances containing much water, such as potatoes, are
more completely preserved by the aid of a quantity of charcoal"—
and hence the refuse charcoal of the sugar refiners is found to de-
prive night soil of its disagreeable odour, and to convert it into a
dry and portable manure.
5°. They exhibit also the still more singular property of extract-
ing from water a portion of the Saline or mineral substances it may
happen to hold in solution, and thus of allowing it, when filtered
through them, to escape in a less impure form.
These two latter properties are possessed in the highest degree
by animal charcoal, such as is obtained by digesting ivory black in
weak muriatic acid, (spirit of salt) and are promoted by a moderate
heat. They are exhibited, however, to a certain extent, by nearly
all varieties of charcoal, and at all temperatures. The black ve-
getable matter of the soil also possesses them in a variable degree,
and upon this depend some of its many uses to vegetation. The
* Charcoal powder is said to have the property of preventing the sprouting of po-
tatoes in spring for a long period. At the approach of spring the potatoes should be
laid in thinnish layers, alternating with still thinner layers of dry charcoal in powder
or in small pieces. The charcoal, from its tendency to absorb moisture, is Supposed
to keep the potatoes always dry, and thus to prevent them from sprouting. Its ac-
tion, however, if the fact is to be depended upon, must be of a very different, and pro-
bably of a more purely chemical kind.
28 PROPERTIES OF OXY GEN.
decayed (half-carbonized) roots of grass, which have been long
subjected to irrigation, may also act in one or all of the above
ways on the more or less impure water by which they are irrigat-
ed, and may thus gradually arrest and collect from it the mate-
rials which are fitted to promote the growth of the coming crop.
§ 3. Oxygen—its properties and relations to vegetable life.
Oxygen is a substance with which we are acquainted only in
the state of gas or air. In this state it is readily obtained by heat-
ing in a glass retort the red oxide of mercury of the shops, or a
mixture of equal weights of chlorate of potash, and oxide of copper.
By the unaided senses this gas cannot be distinguished from com-
mon air, being void of colour, taste, and smell. But if a lighted
taper be plunged into it, the flame is wonderfully increased both in
size and brilliancy, and the taper burns away with great rapidity.
The effect of this gas upon animal life is of a similar kind.
When a living animal is introduced into a large vessel filled with
oxygen, the rapidity of the circulation is increased, all the vital
functions are stimulated and excited, a state of fever comes on, and
after a time the animal dies.
By these two characters, oxygen is distinguished from every
other elementary body. It exists in the atmosphere in a free or
uncombined state to the amount of about 21 per cent. of the bulk
of the air, and is necessary to the existence of animals and of
plants, and to the support of combustion on the face of the globe.
It exists also largely in water, not mixed with it, but as one of its
constituents—every nine pounds of this liquid containing eight
pounds of oxygen.
But the quantity of this substance which is stored up in the so-
lid rocks is still more remarkable. Nearly one-half of the weight
of the solid rocks which compose the crust of our globe—of every
solid substance we see around us—of the houses in which we live—
of the stones on which we tread—and of the soils which you daily
cultivate—and much more than one-half by weight of the bodies
of all living animals and plants, consists of this elementary body
oxygen, known to us, as I have already said, only in the state of a
gas. It may not appear surprising that any one elementary sub-
&B
stance should have been formed by the Creator in such abundance
PROPERTIES OF HYDROGEN. 29
as to constitute nearly one-half by weight of the entire crust of our
globe; but it must strike you as remarkable, that this should also
be the element on the presence of which all animal life depends—
and as nothing less than wonderful, that a substance which we
know only in the state of thin air, should, by some inconceivable
mechanism, in one form be bound up and imprisoned in such vast
stores in the solid mountains of the globe, in another be destined
to pervade and refresh all nature in the form of liquid water, and,
in a third, be seen to beautify and adorn the earth in the solid
parts of animals and plants. But mature is every where full of simi-
lar wonders, and in studying the principles of the art by which
you live, you will not fail at each step of your advance to mark
the united skill and bounty of the one great Contriver.
Oxygen gas is heavier than common air in the proportion of
about 11 to 10,—its specific gravity by experiment being 1.1057,
that of air being 1, (Dumas and Boussingault.) It is also capable
of being absorbed or dissolved by water to a certain extent. One
hundred measures of water dissolve 6% of the gas, according to De
Saussure, while according to Dr Henry, they absorb only 3% of
oxygen. Rain, spring, and river waters always contain a por-
tion of oxygen which they have derived from the atmosphere,
and this oxygen, as they trickle through the soil, ministers to the
growth and nourishment of plants in various ways. Some of these
will be explained in a subsequent lecture.
During the day time oxygen gas is given off-breathed out, as it
were, from the leaves and other green parts of plants. This may
be readily shown by introducing a green twig into an inverted tum-
bler full of water, and placing it in the sunshine. Bubbles of gas
speedily make their appearance on the surface of the leaves, and
gradually rise to the top of the tumbler. On examination these
bubbles are found to be oxygen gas nearly pure.
In an atmosphere of pure oxygen gas, plants refuse to vegetate
and speedily perish.
§ 4. Hydrogen—its properties and relations to vegetable life.
Hydrogen is also known to us only in the state of gas. It is
readily prepared by putting into water a few pieces of metallic iron
or zinc, and then adding a little sulphuric acid (oil of vitriol.) Bub-
30 PROPERTIES OF HYDROGEN.
bles of the gas immediately rise from the surface of the metal,
ascend through the water, and may be collected on the surface.
When perfectly pure, hydrogen agrees with oxygen and common
air in being without colour, taste, or smell. It is not known to
occur in nature in a free or simple state, nor does it exist so abun-
dantly as either carbon or oxygen. It forms a small per-centage
of the weight of all animal and vegetable substances, and consti-
tutes one-ninth of the weight of pure water, but with the exception
of coal, it does not enter as a constituent into any of the large
mineral masses that exist in the crust of the globe.
When a lighted taper is plunged into this gas it is immediately
extinguished, but if in contact with the air the gas itself takes fire
and burns with a pale yellow flame. If previously mixed with air
or with oxygen gas, it kindles and burns with a loud explosion.
During this combustion water is formed. (See Lecture II.)
Hydrogen is the lightest of all known substances, being about
14 times lighter than common air. Its specific gravity, by expe-
riment, is 0.0687, that of air being 1. Hence if the stopper
be removed from a bottle in which it is contained it almost imme-
diately escapes. Hence also it is capable of giving buoyancy to
balloons, and of raising heavy weights into the air. By this ex-
treme lightness and by its relations to flame it is readily distinguish-
ed from all other known substances. -
Water absorbs it only in very small quantity, 100 gallons tak-
ing up no more than about 1% gallons of hydrogen gas. But, as
already observed, this gas does not exist in nature in a free state—
is not necessary, therefore, to the growth of plants or animals in
this state—and hence its insolubility in water is in unison with the
general adaptation of every property of every body, to the health
and growth of the highest orders of living beings.
Hydrogen gas does not support either animal or vegetable life.
Animals cease to breathe when introduced into it, and plants gra-
dually wither and die.
It is sometimes given off from the leaves of plants in the day
time, especially in dull weather, forming with the oxygen given off
at the same time a mixture which explodes when a lighted taper is
introduced into it. (Schulze.) 3
PROPERTIES OF NITROGEN. 31
§ 5. Nitrogen, its properties and relations to vegetable life.
Nitrogen is also known to us only in the form of gas. It may
be prepared by mixing sal ammoniac with half its weight of nitre,
and heating the mixture in a retort over a lamp. The gas will
soon begin to be given off;
and may be collected over
water in the usual way.
It exists in the atmo-
sphere in large proportion,
forming about 79 per cent.
of its bulk. It may, there- arºse S&
fore, be obtained by burn- tºº-sºams=
ing phosphorus in a large bell glass over water. The phosphorus
as it burns takes up the oxygen, and on cooling, the air which
remains over the water is nearly pure nitrogen gas.
This gas is without colour, taste, or smell. Animals and plants
die, and a taper is instantly extinguished when introduced into it
—the gas itself undergoing no change. It is lighter than atmo-
spheric air, in the proportion of 974 to 100; its density being
0.976, that of air being 1.
Nitrogen is an essential constituent of the air we breathe, serv-
ing to temper the ardour with which combustion would proceed
and animals live in undiluted oxygen gas. It forms a part of very
many animal and of numerous vegetable substances, but it is not
known to enter into the composition of any of the great mineral mas-
ses of which the earth's crust is made up. In coal alone, which is of
vegetable origin, it has been detected to the amount of one or two
per cent. It is therefore much less abundant in nature than any
of the other so called organic elements—and it exhibits much less
decided properties than any of them ; yet we shall hereafter see
that it performs certain most important functions in reference both
to the growth of plants and to the nourishment of animals.
One hundred volumes of water, according to Henry, dissolve
about 1% volumes, according to De Saussure 4 volumes of this gas.
Spring and rain waters absorb it as they do oxygen, from the atmo-
spheric air, and bear it in solution to the roots of plants. It is not
unlikely that in this way a portion of their nitrogen finds its way into
the circulation of living plants.

32 REWARDS OF STUDY.
Nitrogen is not known to be absorbed directly from the air by
plants or animals—it is occasionally given off, however, in the day
time by the leaves and flowers of plants, though in uncertain pro-
portions.
Such are the several elementary bodies of which the organic or
destructible part of vegetable substances is almost entirely formed.
With one exception they are known to us only in the form of gas;
and yet out of these gases much of the solid parts of animals and of
plants is made up. When alone, at the ordinary temperature of
the atmosphere they form invisible kinds of air; when united, they
constitute those various forms of vegetable matter which it is the
aim and end of the art of culture to raise with rapidity, with cer-
tainty, and in abundance. How difficult to understand the intri-
cate processes by which nature works up these raw materials into
her many beautiful productions—yet how interesting it must be to
know her ways, how useful even partially to find them out!
Permit me, in conclusion, to submit to you one reflection. We
have seen that oxygen, hydrogen, and nitrogen, are all gaseous
substances, which when pure are destitute of colour, taste, and
smell. They cannot be distinguished by the aid of our senses.
Man in a state of nature—uneducated man—cannot discern that
they are different. Yet so simple an instrument as a lighted taper
at once shows them to be totally unlike each other. This simple
instrument, therefore, serves us instead of a new sense, and makes
us acquainted with properties the existence of which, without such
aid, we should not even have suspected. Has the Deity then been
unkind to man, or stinted in his benevolence in withholding the
gift of such a sense. On the contrary, he has given us an under-
standing which when cultivated is better than twenty new senses.
The chemist in his laboratory is better armed for the investigation
of nature, than if his organs of sense had been many times multi-
plied. He has many instruments at his command, each of which,
like the taper, tells him of properties which neither his senses nor
any other of his instruments can discover; and the further his re-
4
REWARDS OF STUDY. 33
searches are carried, the more willing does nature seem to reveal
her secrets to him, and the more rapidly do his chemical senses in-
crease. Do you think that the rewards of study and patient expe-
rimental research are confined to the laboratory of the chemist,
and that the Deity will prove less kind to you, whose daily toil is
in the great laboratory of nature ? As yet you see but faintly the
reason of many of your most common operations, and over their
results you have comparatively little control—but the light is ready
to spring up, the means are within your reach—you have only to
employ your minds as diligently as you labour with your hands,
and ultimate success is sure. -
LECTURE II.
Characteristic properties of organic substances. Proportion of water in our usually
cultivated crops. Relative proportions of the organic elements contained in the
dried parts of plants. Unlike proportions of the inorganic elements in different
species of plants. Form in which the organic elements are taken up by plants.
The atmosphere, its constitution and relations to vegetable life. Nature and laws
of chemical combination. Compounds of the organic elements which minister to
the growth of plants. Water and its relations to vegetable life. Adaptations vi-
sible in these relations. Cold produced by the evaporation of water in the soil, and
its influence on vegetation. Drainage of cold clay soils.
§ 1. Characteristic properties of organic substances.
Of the four elementary substances described in the former lec-
ture, the organic part of animal and vegetable substances almost
entirely consists. -
But organic substances possess certain characters by which they
are distinguished from the inorganic or dead matter of the globe,
and on which their connection with the principle of life, and with
the art of culture, entirely depends. These characteristic proper-
ties are chiefly the following:
1°. They are all easily decomposed or destroyed by a moderate-
ly high temperature. If wood or straw be heated in the air—over
a fire or in the flame of a candle—it becomes charred, kindles,
burns away, and is in a great measure dissipated. So sugar and
starch, when heated in the air, darken in colour, blacken, and take
fire. The same is true of all vegetable substances. But lime-
stone, clay, and other earthy or stony matters undergo no appa-
rent change in such circumstances—they are not decomposed.
2°. When exposed to the air, especially if it be warm and moist,
vegetable and animal substances putrefy and decay. They de-
compose of their own accord, and after a time almost entirely dis-
appear. Such is not the case with inorganic matters. If the rocks
PROPERTIES OF ORGANIC SUBSTANCES. 35
and stones crumble, their particles may be washed away by the
rains to a lower level, but they never putrefy or wholly disappear
from the earth's surface. .
3°. They consist almost entirely of two or more of the four or-
ganic elements only. The mineral substances we meet with on the
earth's surface, and collect for our cabinets, often contain portions
of many elementary bodies; but, with few exceptions, the organic
part of all plants, that which lives and grows, contains only the
four simple substances described in my former lecture, combined
in the case of some of them with minute quantities of sulphur and
phosphorus.
4°. They are distinguished also by this important character,
that they cannot be formed by human art. Many of the inorganic
compounds which occur in the mineral crust of the globe can be pro-
duced by the chemist in his laboratory, and were any corresponding
benefit likely to be derived from the expenditure of time and labour
it would require, there is reason to believe that, with a few excep-
tions, nature might be imitated in the formation of any of her mine-
ral productions. But in regard to organic substances, whether ani-
mal or vegetable, the chemist is perfectly at fault. He can form—
from their elements that is—neither the fibre of wood, nor sugar, mor
starch, nor gluten, nor muscular fibre, nor fat, nor any of those sub-
stances which constitute the chief bulk of animals and plants, and
which serve for the food of animated beings. This is an important
and striking, and is, I believe, likely to remain a permanent dis-
tinction between most substances of organic and inorganic origin.
Looking back at the vast strides which organic chemistry has
made within the last twenty years, and is still continuing to make,
and trusting to the continued progress of human discovery, some
sanguine chemists venture to anticipate the time when the art of
man shall not only acquire a dominion over that principle of life,
by the agency of which plants now grow and alone produce food
for man and beast,--but shall be able also, in many cases, to imi-
tate or dispense with the operations of that principle; and to pre-
dict that the time will come when man shall manufacture by art
those necessaries and luxuries for which he is now wholly depend-
ent on the vegetable kingdom.
And, having conquered the winds and the waves by the agency
36 PROSPECTS OF SCIENCE.
of steam, is man really destined to gain a victory over the uncer-
tain seasons too? Shall he come at last to tread the soil beneath
his feet as a really useless thing—to disregard the genial shower,
to despise the influence of the balmy dew—to be indifferent alike
to rain and drought, to cloud and to sunshine—to laugh at the
thousand cares of the husbandman—to pity the useless toil and the
sleepless anxieties of the ancient tillers of the soil 2 Is the order
of nature through all past time to be reversed ? Are the entire
constitution of society, and the habits and pursuits of the whole
human race, to be completely altered by the progress of scientific
knowledge? -
By placing before man so many incitements to the pursuit of
knowledge, the will of the Deity is—that out of this increase of
wisdom he should extract the means of increased happiness and
enjoyment also. But set man free from the necessity of tilling the
earth by the sweat of his brow, and you take from him at the same
time the calm and tranquil pleasures of a country life—the inno-
cent enjoyments of the returning seasons—the cheerful health and
happiness that wait upon labour in the free air and beneath the
bright sun of heaven. And for what?—only to imprison him in
manufactories, to condemn him to the fretful and feverish life of
crowded cities.
To such ends, I trust, science is not destined to lead; and he is
not only unreasonably, but thoughtlessly, Sanguine, who would
hope to derive from organic chemistry such power over dead mat-
ter as to be able to fashion it into food for living animals. With
such consequences before us it seems almost sinful to wish for it.
Yet, that this branch of chemical science will lead to great ame-
liorations in the art of culture, there is every reason to believe. It
will explain old methods,--it will clear up anomalies, will re-
concile contradictory results by explaining the principles from
which they flow, and will suggest new and cheaper methods by
which earlier, more abundant, or more certain harvests may be
reaped.
§ 2. Relative proportions in which the organic elements evist in the
dried parts of plants.
1°. The crops we cultivate, as they are gathered from the field,
RELATIVE PROPORTION OF THE ORGANIC ELEMENTS. 37
usually contain a large proportion of water. Thus, 100 lbs. of
each of the following crops, in the state in which they are given to
cattle or are laid up for preservation, lost by drying at 230° Fah-
renheit,
lbs. lbs.
Wheat e lost of water, 166 Aftermath Hay lost 136 to 140
Oats º - º l 51 Red Clover Hay — e 2] ()
Peas e *- e 86 Turnips º - e 925
Clover Seed . *- º ll 2 Potatoes º - º 722
Hay wº - * | 58 --
2°. The substance of plants thus dried consists chiefly of the
four so called organic elements, but these bodies enter into the
constitution of vegetable productions in very different proportions.
This fact has already been adverted to in a general manner:
it will appear more distinctly by the following statement of the
exact quantity of each element contained, according to the analyses
of Boussingault, in 100 lbs. by weight of some of the more im-
portant kinds of vegetable substances you are in the habit of cul-
tivating:—

d Yel- Clo- After- Red
Wheat. Oats. low ver: | Hay. |math clover Tur- |Pota-
Grain. Straw. Grainstraw Peas. seed. Hay. | Hay. nips. toes.
Carbon, 46.1 || 48.4 || 50.7 50.1 |46.5 49.4 45.8 |47.1 147.5 42.9 44.0
Hydrogen, 5.8 || 5.3 | 6.4 || 5.4 6.1 5.8 5.0 5.6 || 4.7 | 5.6 5.8
Oxygen, 43.4 |38.9%| 36.7 39.0 | 40.1 || 35.0 || 38.7 34.9 || 38.0 42.2 44.7
Nitrogen, 2.3 .3%| 2.2 .4 || 4.2 | 7.0 | 1.5 2.4 2.1 | 1.7 | 1.5
Ash, 2.4 || 7.0 || 4.0 | 5.1 | 3.1 | 2.8 9.0 | 10.0 7. 7.6 4.0
100° 100* |100° 100* |100* |100° 100t 100t 100- l 00* || 100
When artificially dried, the carbon approaches to one-half of
their weight, the oxygen to more than one-third, f the hydrogen
to little more than 5 per cent, and the nitrogen rarely to more
than 2% per cent. In the same kind of crop the above proportions
are variable, but they represent very nearly the relative weights in
which these elements enter into the constitution of those forms of
* Ammal. de Chim, et de Phys. February 1841, p. 234.
+ Ibid. June 1839, p. 113 to 136.
# This is no way inconsistent with the statement in the former Lecture, p. 28, that
oxygen constitutes one-half by weight of all living plants. Of the water driven off
in drying these plants, eight-ninths by weight consist of oxygen, and since 600 lbs.
of grass, for example, yield only from 80 to 100 lbs. of hay, it is obvious that in the
living undried plant, the oxygen must very greatly predominate,
38 - INORGANIC PORTION OF PLANTS.
vegetable matter, which are raised in the greatest quantity for the
Support of animal life.
From the above table you will observe that the different va-
rieties of straw contain a much smaller proportion of nitrogen
than the other kinds of vegetable produce raised for food. In this
respect they resemble the different kinds of wood, which usually
contain only a small proportion of mitrogen. This appears in the
following table:—
Composition of different kinds of dry wood, the ash being
deducted.

| Beech. Oak. Birch. | Aspen. Willow.
Sºm. Branch| Stem. Branch| Stem. Branch Stem. Branch|Stem. |Branch
0
Carbon, . 49.89 51-08 |50-64 50-89 50-61 || 51.93| 50-31|| 51,02 || 51.75 54:03
Hydrogen, 6-07 || 6’23 || 6-03 || 6′16 || 6’23 6-31 || 6′32 6-28 || 6’19| 6′56
Nitrogen, 0.93|| 1:08 || 1:28 || 1:01 || 1:12 || 1:07 || 0-98 l'05 || 0-98| 1:48
Oxygen, .. 43'll || 41-61 |42-05 || 41.94 || 42-04 || 40-69| 42:39, 41.65 41'08; 37.93
In all these dry woods the carbon forms half the weight, the
hydrogen about six, and the nitrogen about one per cent.
3°. Besides these organic elements, vegetable substances, as I
have already stated, contain an inorganic portion, which remains
behind in the form of ash when the plant is consumed by fire, or
of dust when it decomposes and disappears in consequence of na-
tural decay.
In the dried vegetable substances, of which the composition is
represented in the first of the above tables, we see that the
quantity of āsh obtained is different in each column. In oats it
is as small as 4 per cent, while in aftermath hay it amounts
to about 10 per cent, or onc-tenth of the whole. A similar
difference is observed generally to prevail throughout the ve-
getable kingdom. Each variety of plant, when burned, leaves
a weight of ash more or less peculiar to itself. Herbaceous plants
and grasses generally leave more than the wood of trees. Dif-
ferent parts of the same plant also yield unlike quantities of in-
organic matter. Thus in the turnip and potato a larger propor-
tion of ash is left by the leaves than by the tubers; in trees the
bark yields the most, then the leaves, and then the twigs, while
the stem yields the least." The absolute quantities vary, however,
b
O
*
* Thus of the oak, the dried bark left 60—the dried leaves 53—the dricd albur-
num 4—and the dried wood only 2 parts in a thousand of ash.—JDe Saussure.
INORGANIC PORTION OF PLANTS. 39
m some degree with the age of the plant, with the season, with the
manure, and with the soil in which it grows. These facts are of
great importance in the theory and in the enlightened practice of
agriculture. They will hereafter come under special and detailed
consideration, when we shall have examined the nature of the soils
in which plants grow, and shall be prepared to consider the che-
mical nature, the source, and the functions of the inorganic com-
pounds which exist in living animal and vegetable substances.
§ 3. Form or state in which the organic elements enter into and
minister to the growth of plants.
From the details already presented in the preceding Lecture,
in regard to the properties of carbon and hydrogen, and the cir-
cumstances under which they are met with in nature, it will
readily occur to you that neither of these elementary bodies is
likely to enter directly, or in a simple state, into the circulation of
plants. The former (carbon) being a solid substance, and inso-
luble in water, cannot obtain admission into the pores of the roots,
the only parts of plants with which, in nature, it can come in con-
tact. The latter (hydrogen) does not occur either in the atmo-
sphere or in the soil in any appreciable quantity, and hence, in its
simple state, is not known to form any part of the food of plants.
Oxygen and nitrogen, again, both exist in the atmosphere in the
gaseous state, and the former is inhaled, under certain conditions,
by the leaves of living plants. Nitrogen may also in like manner
be absorbed by them. It is believed to be so absorbed by certain
plants; but if so, it is in very small quantity, and the fact of
its being absorbed at all is still very uncertain. The two lat-
ter substances (oxygen and nitrogen) are also slightly soluble
in water, and, besides being inhaled by the leaves, may occasion-
ally be absorbed in minute quantity along with the water taken in
by the roots. But by far the largest proportion of these two ele-
mentary bodies, and the whole of the carbon and hydrogen which
find their way into the interior of plants, have previously entered
into a state of mutual combination—forming what are called dis-
tinct chemical compounds. Before describing the nature and con-
stitution of these compounds, it will be proper to explain, 1°. the
constitution of the atmosphere in which plants live, and 2°. the
40 CONSTITUTION OF THE ATMOSPHERE.
mature of chemical combination, and the laws by which it is regu-
lated. -
§4. The atmosphere—its constitution and relations to vegetable life.
The air we breathe, and in which plants live, is composed prin-
cipally of a mixture of oxygen and nitrogen gases, in the propor-
tion, by bulk, of about 21 of the former to 79 of the latter.
The most recent and probably the most accurate analysis yet
published—that of Dumas and Boussingault”—gives the following
as the relative proportions of these two gases in common air:-
Oxygen, . . 20.8 by volume, . . . 23 by weight.
Nitrogen, .. 79.2 . . . . . 77
100 100
The atmosphere contains, however, as a constituent necessary
to the very existence of vegetable life, a small per-centage of car-
bonic acid. On an average this carbonic acid amounts to about
gº oth partſ of the bulk of the air. On the shores of the sea, or
of great lakes, this quantity diminishes; and it becomes sensibly
less as we recede from the land. It is also less by day than by
night (as 3.38 to 4.32), and over a moist than over a dry soil.
The air of our atmosphere is also imbued with moisture. Wa-
tery vapour is every where diffused through it, but the quantity
varies with the season of the year, with the climate, with the na-
ture of the locality—its altitude, and its distance from the equator.
In temperate climates, it oscillates on the same spot between , and
14 per cent, of the weight of the air; being least in mid-winter,
and greatest in the hot months of summer. There are also mingled
with the atmosphere traces of the vast variety of substances, which
are capable of rising from the surface of the earth in the form of
vapour: such, for example, as the gases and odours which are
given off from the bodies of living animals, and from the leaves
and flowers of growing plants, such as escape from decaying ami-
mal or vegetable matter, such as are produced by disease in either
* Amn. de Chim. et de Phys, 3d Series, iii. p. 257.
+ 0.04 per cent. The mean of 104 experiments made by De Saussure at Geneva,
at all times of the year and of the day, gave 4.15 volumes in 10,000. The maxi-
mum was 5.74, and the minimum 3.15. The mean of 142 experiments at Paris gave
Boussingault 3.97 volumes in ten thousand.
USES OF THE AIR. 41
class of bodies—such as are evolved during the operations of nature
in the inorganic kingdom, or by the artificial processes of man.
Among these accidental vapours are to be included those mias-
mata, which, in certain parts of the world, render whole districts
unhealthy, as well as certain compounds of ammonia and of Sul-
phur, which are inferred to exist in the atmosphere, because they
are perceptibly given off by animal substances which decay in the
air, and because they can be detected in rain water, or in Snow
which has newly fallen.
In this constitution of the atmosphere we can discover many
beautiful adaptations to the wants and structure of animals and
plants. The exciting effect of pure oxygen on the animal eco-
nomy is lessened by its large admixture with nitrogen; while this
latter gas is not present in so large a proportion as to prevent the
oxygen from sustaining life and combustion.
The proportions of the two gases indeed are beautifully adjust-
ed to the existing condition of things. The oxygen in the atmo-
sphere, as above stated, forms something less than 21 per cent. of
its bulk. If this oxygen be diminished to 17 per cent. candles and
lamps go out, if it be lessened to 10 or 12 man instantly drops
in a state of helpless insensibility.” Thus the admixture of ni-
trogen is carried to the utmost limit which is consistent with the
main purposes which the oxygen is intended to serve.
The same is true of the other less abundant constituents of the
atmosphere. The quantity of carbonic acid present is sufficient to
supply food to the plant, while it is not so great as to prove inju-
rious to the animal;-and the watery vapours suffice to maintain
the requisite moisture and flexibility of the parts of both orders of
beings, without in general existing in such a proportion as to prove
hurtful to either.
The air also, by its subtlety, diffuses itself every where. Into
every pore of the soil it makes its way. When there, it yields its
oxygen or its carbonic acid to the dead vegetable matter or to the
living root. A shower of rain expels the half-corrupted air, to be
succeeded again by a purer portion as the water retires. The heat
of the sun warms the soil, and expands the imprisoned gases,
these partially escape, and are, as before, replaced by other air
when the rays of the sun are withdrawn.
* Leblanc, Am, de Chim, et de Phys, 3me series, xv, p. 495.
42 NATURE OF CHEMICAL COMBINATION.
By the action of these and other causes a constant circulation
is, to a certain extent, kept up between the atmosphere on the sur-
face, which plays among the leaves and stems of plants, and the
air which mingles with the soil and ministers to the roots beneath.
The precise effect and the importance of this provision will demand
our consideration in a future lecture.
§ 5. Nature and laws of chemical combination.
I. The terms combine and combination in chemical language
have a strict and precise application. If sand and saw-dust be
rubbed together in a mortar they may be intimately intermingled,
but by pouring water on the mass we can float off the particles of
wood and leave the samd unchanged behind. So if we stir oat-
meal and water together, we may cause them perfectly to mix to-
gether, but by the aid of a gentle heat we can expel the water and
obtain dry oatmeal in its original condition. Or, if salt be put into
water, it will dissolve and disappear, and form what is called a so-
lution, but if this solution be boiled down, as is done in our salt-
pans, the water may be entirely removed and the salt procured of
the weight originally employed, and possessed of its original pro-
perties. - - * - i
In mone of these cases has any chemical action taken place, or
any permanent change been produced upon any of the substances.
The two former were merely mixtures.
II. But in all cases of chemical action a permanent change takes
place in one or more of the substances employed; and this change
is the result either of a chemical combination, or of a chemical de-
composition. Thus,
a. When sulphur is burned in the air, it is converted into
white vapours possessed of a powerful and very unpleasant odour.
These vapours continue to be given off until the whole of the sul-
phur is dissipated. Here a solid substance is permanently changed
into noxious fumes which disappear in the air, and this change is
caused by the combination of the sulphur with the oxygen of the
atmosphere.
b. Again, when limestone is put into a kiln and strongly
heated or burned, it is changed or converted into quicklime—a
substance very different in its properties from the natural limestone
LAWS OF CHEMICAL COMBINATION. 43
employed. But this is a case of chemical decomposition. The
limestone consists of lime and carbonic acid. By the heat these
are separated, the latter is driven off and the former remains in
the kiln.
c. When a jet of hydrogen gas is kindled in the air or in
oxygen gas, it burns with a pale yellow flame. If a cold vessel be
held over this flame, it speedily becomes bedeved with moisture,
and drops of water collect upon it. Here the change is more re-
markable than in either of the other cases. The hydrogen during
this combustion unites with the oxygen of the atmosphere and forms
water. How different in its properties is this water from either
the oxygen or the hydrogen by the union of which it is produced
The former substance is a liquid, the latter substances are gases.
Water is an enemy to all combustion, while hydrogen burns rea-
dily itself, and oxygen is the very life and support of combustion
in all other bodies. It appears, therefore,
1°. That chemical combination or decomposition is always at-
tended by a permanent change. -
2°. That when combination takes place a new substance is form-
ed, differing in its properties from any of those from which it was
produced, or of which it consists.
When two or more elementary bodies thus unite together to
form a new substance, this new substance is called a chemical com-
pound. Thus water is a compound (not a mixture) of the two ele-
mentary bodies oxygen and hydrogen.
III. Now when such combination takes place, it is found to do
so always in accordance with certain fixed laws. Thus:
1°. Bodies unite together only in constant and definite proportions.
We can mic together oxygen and hydrogen gases, for example, in
any proportion,--a gallon of the one with any number of gallons
of the other, but if we burn two gallons of hydrogen gas in any
greater number of gallons of oxygen, they will only consume or
unite with one gallon of the oxygen, the rest of the gas re-
maining unchanged. A quantity of water will be formed by this
union, in which the whole of the hydrogen will be contained, com-
bined with all the oxygen that has disappeared. Under no circum-
stances can we burn hydrogen so as to cause it to consume more
oxygen, or from a given weight of hydrogen to produce more than
a known weight of water.
44 EQUIVALENT NUMBERS.
Oxygen is nearly sixteen times heavier than hydrogen, so that
one gallon of the former is about eight times heavier than two gal-
lons of the latter. When thus burned, therefore, these two gases
unite together by weight nearly in the proportion of 8 to 1,–one
pound of hydrogen forming nine pounds of water. -
Again, when pure carbon is burned in the air, it unites with a
fixed and constant weight of oxygen to form carbonic acid; it
never unites with more, and it does not form carbonic acid when
it unites with less.
Now this law of fixed and definite proportions is found to hold
in regard to all bodies, and in all cases of chemical combination.
Thus we have seen that by weight,
1 of hydrogen combines with 8 of oxygen to form water ; so
6 of carbon combine with 8 ............... carbonic oxide; and
14 of nitrogen .................. 8 ............... nitrous oxide.
Hence 1 of hydrogen, 6 of carbon, and 14 of nitrogen unite re-
spectively with the same weight (8) of oxygen. These several
numbers, therefore, are said to be equivalent to each other—they
are equivalent numbers. Or they represent the fixed and definite
proportions in which these several substances combine with oxygen
or with one another—they are definite proportionals. Some che-
mists consider these numbers to represent the relative weights of
the atoms or smallest particles of which the several substances are
made up, and hence not unfrequently speak of them as the atomic
weights of these substances, or more shortly their atoms.
For the sake of brevity, it is often useful to represent the simple
or elementary bodies by the initial letters of their names. Thus
hydrogen is represented by H, carbon by C, oxygen by O, and
nitrogen by N, and these letters are used to denote not only the
substances themselves, but that quantity of each which is recognised
as its equivalent, proportional, or atomic weight. Thus:
Equivalent or
Symbol. atomic weights. Name.
H ... denotes ... 1 ... by weight of ... hydrogen.
C ... ......... ... 6 ... ............... ... carbon.
O ... ......... ... 8 ... ............... ... Oxygen.
N ... ......... ... 14" ... ............... ... nitrogen.
* More correctly l, 6:04, 8:03 and 14-048.
ISOMERIC BODIES. 45
Chemical combination is expressed shortly by placing these let-
ters in juxtaposition, or sometimes in brackets, with the sign plus
(+) between them. Thus HO or (H+O) denotes the combination
of one atom or equivalent of hydrogen with one of oxygen, that
is water;-and at the same time a weight of water (9), equal to
the sum of the atomic weights (1+8) of hydrogen and oxygen.
A number prefixed or appended to a symbol denotes, that so
many equivalents of the substance represented by the symbol are
meant, as that number expresses. Thus 2HO, 3HO or 3 (H+O)
mean two or three equivalents of water, 3 H or H3 three equiva-
lents of hydrogen, 4C or C4 four of carbon, and 2N or N2 two
of nitrogen.
2°. Not only are the quantities of the substances which unite to-
gether definite and constant, but the properties or qualities of the
substances formed are in general equally so. The properties of
pure water or of carbonic acid are constant and invariable under
whatever circumstances they may be formed, and the elements of
which these substances consist, when they combine together in the
same proportions, are never known to form any other compounds
but water and carbonic acid.
This law, however, though generally, is not universally true.
Many substances are now known, which contain the same elements
united together in the same proportions, and which, nevertheless,
possess very different properties. Oil of turpentine and oil of le-
mons are in this condition. They both consist of the same ele-
ments, carbon and hydrogen, united together in the same propor-
tions, and yet their sensible properties as well as their chemical re-
lations” are very dissimilar. .
Cane sugar, starch and gum, all of them abundant products of
the vegetable kingdom, consist also of the same elements, carbon,
hydrogen, and oxygen,_united together in the same proportions,
and may even be represented by the same formula (Cia Hio O10);
and yet these substances are as unlike each other in their proper-
ties, as many other bodies are, of which the chemical composition
* By the chemical relations of a substance are meant the effects which are produced
upon it by contact with other chemical substances.
+ This formula means that starch, gum, and sugar, consist of 12 equivalents of car-
bon united to 10 of hygrogen and 10 of oxygen.
46 LAW OF MULTIPLE PROPORTIONS.
is very different. To compounds thus unlike in their properties,
and yet containing the same elements, in the same proportions,
chemists have given the name of Isomeric bodies. I shall have
occasion to make you more familiar with some of them here-
after.
3°. Another important law by which chemical combinations are
regulated, is known by the name of the law of multiple propor-
tions. Some substances are observed to be capable of uniting to-
gether in more than one proportion. Thus carbon unites with
oxygen in several proportions, forming carbonic oxide, oxalic
acid, carbonic acid, &c. Now when such is the case, it is found that
the quantity by weight of each substance which enters into the se-
veral compounds, if not actually represented by the equivalent
number or atomic weight, is represented by some simple multiple of
that number. Thus two equivalents of carbon (C) unite with 2, 3,
or 4 equivalents of oxygen (O), to form carbonic oxide, oxalic acid,
and carbonic acid respectively,–while one of nitrogen (N) unites
with 1, 2, 3, 4, or 5 of oxygen to form a series of compounds,
of which the last—(NO3) nitric acid, is the only one Ishall have
frequent occasion to speak of in the present lectures.
This law of multiple proportions, though of great importance in
chemical theory, I do not further illustrate, as we shall have very
little occasion to refer to it in the discussion of the several topics
which will hereafter come before us.
Having thus briefly explained the nature and laws of chemi-
cal combination, I proceed to make you acquainted with those com-
pounds of the organic elements, which are known, or supposed, to
minister to the growth of plants.
The number of compounds which the four so called organic ele-
ments form with each other is almost endless; but of this number
only a very few minister directly to the growth or nourishment of
plants. Of these, water, carbonic acid, the humic and other acids
contained in the soil, ammonia, and nitric acid are the most im-
portant; but it will be necessary shortly to advert to a few others,
RELATIONS OF WATER TO WIEGETABLE LIFE. 47
of the occurrence or production or action of which we may here-
after have occasion to speak.
§ 6. Of water and its relations to vegetable life.
Water is a compound of oxygen and hydrogen in the proportion,
as already stated, of 8 of the former to 1 of the latter by weight,
or of 1 of oxygen to 2 of hydrogen by volume.
It is more universally diffused throughout nature than any other
chemical compound with which we are acquainted, performs most
important functions in reference to animal and vegetable life, and
is endowed with properties by which it is wonderfully adapted to
the existing condition of things.
We are familiar with this chemical compound in three several
states of cohesion,-in the solid form as ice, in the fluid as water,
and in the gaseous as steam. At 32°F. and at lower tempera-
tures it continues solid, at higher temperatures it melts and
forms a liquid (water), which at 212°F. begins to boil and is con-
verted into steam. By this latter change from water to steam its
bulk is increased 1700 times, and it becomes nearly two-fifths
lighter than common air. The specific gravity of steam is 0.62,
that of common air being l;-it therefore readily rises into and
diffuses itself through the atmosphere.
I. There are only one or two circumstances under which this
compound when in the solid form materially affects or interferes
with the labours of the agriculturist. -
1°. During the frost of a severe winter, the soil contracts and
appears to shrink in. But the water contained in its pores freezes
and expands, and the minute crystals of ice thus formed being inter-
posed among the particles of the soil separate them from each other.
This expansion of the water may not be equal, in dry soils, to the
natural contraction of the soil itself, yet still it is sufficient to cause
a considerable separation of the earthy particles throughout the
whole frozen mass. When a milder temperature returns, and a
thaw commences, the soil expands and gradually returns to its
former bulk; but the outer layers thaw first, and the particles hav-
ing been previously separated by the crystals of ice, and being
now loosened by the thaw, fall off or crumble down, and thus the
soil becomes exposed to the mellowing action of the atmosphere,
48 ACTION OF SNOW ON WINTER, CROPS.
which is enabled everywhere to pervade it. On heavy clay land
this effect of the winter's frost not unfrequently proves very bene-
ficial.”
2°. In the form of snow it is often observed to be beneficial to
winter wheat and other crops. A heavy fall of snow shelters and
protects the soil and crop from the destructive effects of any severe
cold which may follow it. It forms a light porous covering by
which the escape of heat from the soil is almost entirely prevented.
It defends the young shoots also from those alternations of tem-
perature to which the periodical return of the sun's rays continually
exposes them;f and when a thaw arrives, by slowly melting, it al-
lows the tender herbage gradually to accustom itself to the milder
atmosphere.
In this manner a fall of snow may often be of great service to
the practical farmer. But some believe that winter wheat actu-
ally thrives under snow, that it is further advanced when the snow
disappears than it would have been had no snow lain upon the
ground. In regard to this fact, it is difficult to make accurate
observations, and were it even clearly established, it would be dif-
ficult to say how much of the observed effect was owing to the
mechanical covering above alluded to, and how much to supposed
chemical causes. I will here, however, mention two facts concern-
ing snow, which may possibly be connected with this supposed
nourishing quality.
a. In the first place, snow generally contains a certain quantity of
* This alternate contraction and expansion is often injurious to the practical
farmer in throwing out his winter wheat. Some varieties are more thrown out than
others, and this peculiarity is sometimes ascribed to the longer and stronger roots
which shoot from one variety than from another ; it is often, however, owing to the
different nature of the soils upon which the observations have been made, or when,
in the same soil, to the different states of dryness at different times.
+ The effects of such alternations are seen on the occurrence of a night's frost in
spring. If the sun's rays fall in the early morning on a frozen shoot, it droops, withers,
and blackens—it is destroyed by the frost. If the plant be in a shaded spot, where
the sun does not reach it till after the whole atmosphere has been gradually heated,
and the frozen tissue slowly thawed, its leaves sustain little injury, and the warmth of
the sun's rays, instead of injuring, cherish and invigorate it. -
A thick light covering of porous earth, not beaten down, preserves the potato pit
from the effects of the frost better than a solid compact coating of clay, in the same
way as snow protects the herbage better than a sheet of ice. When covered up, how-
ever, so as to prevent sudden alternations of temperature, potatoes, apples, and onions
may be frozen and thawed several times during winter without any serious injury.
PROPERTIES OF SNOW. 49
ammonia, or of animal matter which gives off ammonia during its
decomposition. This quantity is variable, and is occasionally so
small as to be very difficult of detection. Liebig found it in the
snow of the neighbourhood of Giessen, and I detected traces of it
in the snow which fell in Durham” during two separate storms in
1848. This ammonia is present in greater quantity in the first
portions that fall and lie nearest the plant. Hence if the plant
can grow beneath the snow, this ammonia may affect its growth,
or when the first thaw comes, it may descend to the root and be
there imbibed. Rain water also contains ammonia, but when rain
falls in large quantity it runs off the land, and may do less good
than the snow, which lies and melts gradually.
b. Another fact regarding snow was formerly considered very
singular. The air which is present in its pores usually contains
oxygen and nitrogen, in proportions very different from those in
which they exist in the atmosphere. The atmospheric air, as I
have already stated, contains about 21 per cent. of oxygen by
volume (or bulk), but air which is extracted from the pores of
melting snow has been found by various observers to contain a
much smaller quantity. Boussingaultſ filled a bottle with snow,
and then gently warmed it. The snow melted and left the bottle
partly filled with air and partly with water. The air he found to
contain 17 per cent. of oxygen only; and in a similar experiment
De Saussure found still less. - *
It was formerly supposed that this smaller proportion of oxygen
was owing to a peculiar property possessed by Snow as a porous
body, of absorbing the oxygen in smaller and the nitrogen in
larger proportion than they exist in the atmosphere; and that the
difficulty of breathing, which is felt on very high mountains, was
owing to the deficiency of oxygen in the air which is set free
from the snow when it is melted by the heat of the sun's rays.
The real cause, however, lies in a property possessed by liquid
water of absorbing oxygen and nitrogen in a different proportion
* By adding two drops of sulphuric acid to four pints of snow water, evaporating
to dryness, and then mixing the dry mass with quicklime or caustic potash. The
Saline matter left by the water contained a brown organic matter, mixed with sulphate
of ammonia and gypsum.
t Annalen der Physik (Poggendorf) xxxiv. p. 211.
D
50 WATER NECESSARY TO LIFE,
from that in which they exist in the air. In the air, as we have
seen, the oxygen is to the nitrogen as
Oxygen. Nitrogen.
21 to 79 by volume;
but in the air extracted from river, or rain water, or from melted
snow, the oxygen is to the nitrogen as -
Oxygen. Nitrogen.
* 35 to 79 by volume.
Hence when exposed to atmospheric air pure boiled water drinks
in more of its oxygen in proportion than it does of its nitrogen.
And hence when snow is melted in the presence of a limited quan-
tity of air—that which it retains in its pores—the water as it is
produced will absorb a certain quantity of the air, but more of its
oxygen in the proportion above stated. The air which remains
unabsorbed will therefore contain a less proportion of oxygen; and
hence the reason why Boussingault and De Saussure found less
oxygen in the air which escapes from melting snow. -
But the water formed during the melting of the snow upon our
fields enters the soil slowly, and carries with it this large propor-
tion of oxygen. We know that the admission of oxygen into the
soil is necessary to luxuriant vegetation. It is possible, therefore,
that the circumstances under which snow water enters the soil may
enable it in reality to hasten the growth of plants in a way which
cannot come into operation when no snow has fallen upon the
land.
II. In the fluid state, that of water, the agency of this compound
in reference to vegetable life, though occasionally obscure, is yet
every where discernible.
Pure water is a colourless transparent fluid, destitute of either
taste or smell. It enters largely into the constitution of all living
animals and plants, and forms upwards of one-half of the weight
of all the newly gathered vegetable substances we are in the habit.
of cultivating or collecting for the use of man (page 33).
Not only does it enter thus largely into the constitution of all
animals and plants, but, in the existing economy of nature, its
presence in large quantity is absolutely necessary to the continu-
ance of animal and vegetable life. In the midst of abundant
springs and showers, plants shoot forth with an amazing rapidity,
SOLVENT POWER OF WATER. - 5T
while they wither, droop, and die when water is withheld. How
much the manifestation of life is dependent upon its presence, is
beautifully illustrated by some of the humbler tribes of plants.
Certain mosses can be kept long in the herbarium, and yet will
revive again when the dried specimens are immersed in water.
At Manilla a species of Lycopodium grows upon the rocks, which,
though kept for years in a dried state, revives and expands its for
liage when placed in water.” Thus life lingers, as if unwilling to
depart—and rejoices to display itself again, when the moisture re-
turns.f -
There are, however, three special properties of water, which are
in a high degree interesting and important to the practical agri-
culturist, and to which I beg to direct your particular attention
These are,
1°. Its power of dissolving gases and solid substances.
2°. Its affinity for certain solid bodies; and
3°. The degree of affinity by which its own elements are held
together. -
1°. When pure boiled water is exposed to the air, it gradually
absorbs a quantity of the several gases of which the atmosphere is
composed, and acquires more or less of a sparkling appearance and
an agreeable taste. The air which is thus absorbed by pure water
varies from ºth to ºth of its own bulk. Sea water absorbs from
gºth to ºth of its bulk, and from both the air is entirely expelled .
by boiling. When thus expelled, this air, like that obtained from
* The Spaniards call it Triste de Corazon, Sorrow of the Heart.—Burnet's Wan-
derings, p. 72. - -
+ In some species of animals, life is in like manner suspended by the absence of
water. The inhabitants of some land and even marine shells may be dried and pre-
served for a long time in a state of torpor, and afterwards revived by immersion in
water. The Cerithium Armatum has been brought from the Mauritius in a dry state,
while snails are said to have been revived after being dried for 15 years. The vibrio
tritici (a species of worm, occurring in that form of blighted wheat known by the
name of the Ear-cockle, Purples, or Peppercorn—see Jour. of the Royal Agricult. So-
ciety, II. p. 19), was restored by Mr Bauer, after an apparent death of nearly 6 years,
by merely soaking it in water. The Furcularia Amastobea, a small microscopic animal,
may be made to undergo apparent death and resuscitation many times, by alternate
drying and moistening. According to Spallanzani, animalculi have been recovered
by moisture after a torpor of 27 years. These facts tend to lessen our surprise at the
alleged longevity of the seeds of plants.
52 ITS AFFINITY FOR SOLID SUBSTANCES.
melting snow, is found on examination to contain the oxygen, nitro-
gen, and carbonic acid in proportions very different from those in
which they exist in the atmosphere.
Thus the oxygen and carbonic acid are present in the atmo-
sphere and in air extracted from water in the following propor-
tions respectively by volume:
Oxygen. Carbonic acid.
In the atmosphere, • . 21 per cent. 0.04
In air extracted from water, 30 to 32* 0.11 to 0.60
—the oxygen being one-half greater, and the carbonic acid from 3
to 15 times greater in the air contained in water than in the air
of the atmosphere. -
In consequence of this property water performs important func-
tions in reference to vegetable life. As it falls in rain or trickles
along the surface of the land, it absorbs these gaseous substances
—and the oxygen and carbonic acid in large quantity—carries
them with it wherever it goes, conveys them to the roots and into
the circulation of plants, and thus, as we shall hereafter see, makes
them all minister to the growth and nourishment of living vege-
tables. -
Again, water possesses the power of dissolving many solid sub-
stances. If sugar or salt be mixed with water in certain quanti-
ties they speedily disappear. In like manner, many other bodies,
both simple and compound, are taken up by this liquid in greater
or less quantity, and can only be recovered by driving off the wa-
ter, through the aid of heat. -
Hence it is that in nature there is no such thing as pure water.
That of our springs and rivers always contains more or less common
salt, gypsum, carbonate of lime, carbonate of magnesia, and other
saline substances which water has the power of dissolving. Even
rain water, as it descends, washes and purifies the air, and brings
* The air extracted from stagnant water, in which green particles abound, contains
a larger proportion of oxygen the longer the Sun has been up. In the afternoon the
oxygen sometimes approaches to 60 per cent, of the entire bulk of the air. (Morren.)
In this case, however, it is the green matter which gives off oxygen under the influ-
ence of the sun's rays. The sea absorbs oxygen so largely from the atmosphere that
the layer of air nearest to its surface has been found to contain only 22:57 per cent.
of oxygen by weight (Levy), instead of 23 per cent, the proportion at every height
oyer the land. (An, de Chim. et de Phys. 3sieme serie, I. p. 456.)
MUTUAL AIFFINITY OF ITS ELEMENTS. 53
down portions of matter which had previously ascended in the form
of vapour, and thus reaches the earth in an impure state. And as
it afterwards flows along the surface or sinks through the soil, it
meets with and dissolves other solid or gaseous substances, and car-
ries them with it wherever it penetrates.
It is not without a purpose that all water we meet with is thus
impure. The fluids of the animal body contain nearly the same
saline substances as are present in the water we drink, and from
this source it is no doubt intended that a certain portion of those
saline substances should be obtained upon which the preservation
and health of our bodies depend. -
So the sap of plants, and even their solid parts, as we shall pre-
sently see, contain saline matter such as is present in the waters
that fall upon or rise through the soil; and it is certain that from
such watery solutions the roots of plants obtain their chief supply
of these saline or inorganic compounds.
Thus there is an obvious design and adaptation in the impurity
of our spring and river waters—for by that impurity they are better
fitted to minister to the wants of living beings.
The saline substances contained in water serve also another pur-
pose. They prevent animal and vegetable substances from too ra-
pidly decaying, whether in the soil or in the water, and they main-
tain in a wholesome condition the waters of the great oceans, in
which so vast an amount of animal and vegetable life is constantly
maintained.
This power of dissolving solid substances, whether organic or in-
organic, is in most cases increased by an elevation of temperature.
Warm water, for example, will dissolve Epsom salts or oxalic acid
in much larger quantity than cold water will, and the same is true
of nearly all solid substances which this fluid is capable of holding
in solution. To this increased solvent power of the water they ab-
sorb, is to be ascribed, among other causes, the peculiar character
and extraordinary luxuriance of the vegetable productions in many
tropical countries.
2°. But the affinity" which water exhibits for many solid sub-
stances is little less important and remarkable.
* By affinity is meant the tendency which bodies have to unite chemically and to
remain united or combined.
54 USEs of WATERY WAPOUR IN VEGETATION,
When water is thrown upon newly burned lime it is absorbed
by it in large proportion, while the lime heats, cracks, swells, and
finally falls to a white powder. When thus perfectly slaked, it is
found to be one-third heavier than before—every three tons hav-
ing absorbed one ton of water. This water is retained in a solid
form—more solid than water is when in the state of ice—and it can-
not be entirely separated from the lime without the application of
a red heat. When you lay upon your land, therefore, four tons
of slaked lime, you mix with your soil one ton of water, which the
lime afterwards gradually gives up, either in whole or in part, as .
it combines with other substances. To this fact we shall return
when we hereafter consider the various ways in which lime acts,
when it is employed by the farmer for the purpose of improving
his land.
For clay also, water has a considerable affinity, though by no
means equal to that which it displays for quicklime. Hence, in
well drained clay lands, the hottest summer does not entirely
rob the clay of its water. It cracks, contracts, and becomes hard,
yet still retains water enough to keep its wheat crops green and
flourishing, when the herbage on lighter soils of equal depth is
drooping or burned up. 8.
A similar affinity for water possessed by decaying vegetable
matter is one source of the advantages which are known to follow
from the admixture of a certain amount of such vegetable matter
with the soil; though, as in the case of charcoal, the porosity" of
this decomposing organic matter has some influence in retaining
moisture near the roots of plants. -
3°. The degree of affinity by which the elementary constituents
of water are held together, exercises a material influence on the
growth and production of all vegetable substances.
If I burn a jet of hydrogen gas in the air, water is formed by
the union of the hydrogen with the oxygen of the atmosphere, for
which it manifests on many occasions an apparently powerful affinity.
But if into a vessel of water I put a piece of iron or zinc and then
add sulphuric acid, the water is decomposed and the hydrogen set
* Affinity for water causes vegetable matter to combine chemically with it: poro-
sity causes it merely to drink in the water mechanically, and to retain it unchanged,
in its pores.
FORMATION OF CIOUDS AND RAIN. 55
free, while the metal combines with the oxygen. In the one case
the hydrogen unites with oxygen and forms water; in the other it
forsakes the oxygen of the water, yielding it to the zinc, and escapes
itself in the gaseous form.
So in the interior of plants and animals, water undergoes con-
tinual de-composition and re-composition. In its fluid state, it finds
its way and exists in every vessel and in every tissue. And so
slight, it would appear, in such situations, is the hold which its
elements have upon each other—or so strong their tendency to
combine with other substances, that they are ready to separate
from each other at every impulse—yielding now oxygen to one,
and now hydrogen to another, as the production of the several
compounds which each organ is destined to elaborate respectively
demands. Yet with the same readiness do they again re-attach
themselves and cling together, when new changes require it. It
is in the form of water, indeed, that nature introduces the greater
proportion of the oxygen and hydrogen which perform so important
a part, in the numerous and diversified changes that take place,
in the interior of plants and animals. Few things are really more
wonderful in chemical physiology, than the vast variety of trans-
mutations which are continually going on, through the agency of
the elements of water.
III. In the state of vapour water ministers most materially to
the life and growth of plants. It not only rises into the air at 212°
Fah, when it begins to boil, but it disappears or evaporates from
open vessels at almost every temperature, with a rapidity propor-
tioned to the previous dryness of the air, and to the velocity and
temperature of the wind that passes over it. Even ice and snow
are gradually dissipated in the coldest weather, and sometimes
with a degree of velocity which at first sight seems truly surprising."
It thus happens that the atmosphere is constantly impregnated
* Mr Howard states that a circular patch of snow 5 inches in diameter lost in the
month of January 150 grains of vapour between sunset and Sunrise, and 50 grains
more before the close of the day, when exposed to a smart breeze on a house-top.
From an acre of snow this would be equal to the evaporation of 1000 gallons of water
during the night only.—Proul's Bridgewater Treatise, p. 302.
In Von Wrangell's account of his visit to Siberia and the Polar sea, translated by
Major Sabine (p. 390), it is stated that, in the intense cold, not only living bodies--
but the very snow Smokes—and fills the air with vapour.
56 DESCENT OF DEW.
with watery vapour, which in this gaseous state accompanies the
air wherever it penetrates--permeates the soil--pervades the
leaves and pores of plants—and gains admission to the lungs and
general vascular system of animals. We cannot adequately ap-
preciate the influence which, in this highly comminuted form, wa-
ter exercises over the general economy of organic mature.
But it is chiefly when it assumes the form of rain and dew, and
re-descends to the earth, that the benefits arising from a previous
conversion of the water into vapour become distinctly appreciable.
The quantity of vapour which the air is capable of holding in sus-
pension is dependent upon its temperature. At high tempera-
tures, in warm climates, or in warm weather, it can sustain more—
at low temperatures or in cold weather less. Hence when a cur-
rent of comparatively warm air loaded with moisture, ascends to,
or comes in contact with, a cold mountain top, it is cooled down,
is rendered incapable of holding the whole of the vapour in suspen-
sion, and therefore leaves behind, in the form of a mist or cloud, a
portion of its watery burden. The aqueous particles which float in
this mist appear again on the plains below, in the form of streams
or springs, which bring nourishment” at once, and a grateful relief
to the thirsty soil.
So when two currents of air charged with moisture, but of un-
equal temperature, meet in the atmosphere, they mix, and the
mixture has the mean temperature of the two currents. But air
of this mean temperature is incapable of holding in suspension the
mean quantity of watery vapour contained in the two currents of
air; hence, as before, a cloud is formed, and the excess of moisture
falls to the earth in the form of rain.
In descending to refresh the earth, this rain discharges in its
progress another office. It washes the air as it passes through it
dissolving and carrying down those accidental vapours which,
though unwholesome to man, are yet fitted to assist the growth
of plants. It thus ministers in another, often unthought of man-
ner, to our health and comfort by maintaining the purity of the air
we breathe.
The dew, celebrated through all times and in every tongue for
* For the nature of this mourishment, see the Lectures in Part II., “On the inor-
ganic constituents of plants.”
UNIVERSAL BOUNTY DISPLAYED IN NATURE. 57
its sweet influences, presents the most beautiful and striking illus-
tration of the agency of water in the economy of nature, and ex-
hibits one of those wise and bountiful adaptations, by which the
whole system of things, animate and inanimate, is fitted and bound
together.
All bodies on the surface of the earth radiate, or throw out
rays of heat, in straight lines—every warmer body to every colder
—and the entire surface is itself continually sending rays upwards
through the clear air into free space. Thus on the earth's surface
all bodies strive, as it were, after an equal temperature (an equili-
brium of heat), while the surface as a whole tends gradually to-
wards a cooler state. But while the sun shines on any spot this
cooling will not there take place, for the surface then receives in
general more heat than it gives off; and if, when the sun goes
down, the clear sky be shut out by a canopy of clouds, these will
arrest and again throw back a portion of the heat which escapes by
radiation, and will thus prevent it from being so speedily dissipat-
ed. At night, them, when the Sun is absent, the earth will cool the
inost; on clear nights also more than when it is cloudy; and when
clouds only partially obscure the sky, those parts will become
coolest which look towards the clearest portions of the heavens.
Now when the surface cools, the air in contact with it must cool
also ; and, like the warm currents on the mountain side, must for-
sake a portion of the watery vapour it has hitherto retained. This
water, like the floating mist on the hills, descends in particles al-
most infinitely minute. These particles collect on every leaflet,
and suspend themselves from every blade of grass, in drops of
“ pearly dew.”
And mark here a beautiful adaptation. Different substances
are endowed with the property of radiating their heat, and of thus
becoming cool with different degrees of rapidity, and those sub-
stances which in the air become cool first, also attract first and most
abundantly, the particles of falling dew. Thus in the cool of a
summer's evening the grass plat is wet, while the gravel walk is
dry; and the thirsty pasture and every green leaf are drinking in
the descending moisture, while the naked land and the barren
highway are still unconscious of its fall.
IIow beautiful is the contrivance by which water is thus evapo-
58 COLD PRODUCED BY EVAPORATION.
rated or distilled as it were into the atmosphere—largely perhaps
from some particular spots, then diffused equably through the
wide and restless air, and afterwards precipitated again in refresh-
ing showers or in long mysterious dews!" But how much more
beautiful the contrivance, I might almost say the instinctive ten-
dency, by which the dew selects the objects on which it delights to
fall; descending first on every living plant, copiously ministering
to the wants of each, and expending its superfluity only on the un-
productive waste. *
And equally kind and bountiful, yet provident, is nature in all
her operations, and through all her works. Neither skill norma
terials are ever wasted; and yet she ungrudgingly dispenses her
favours, apparently without measure, and has subjected dead
matter to laws which compel it to minister, and yet with a most
ready willingness, to the wants and comforts of every living thing.
And how unceasingly does she press this her example, not only
of unbounded goodness, but of universal charity—above all other
men—on the attention of the tiller of the soil. Does the corn
spring more freshly when scattered by a Protestant hand?—are the
harvests more abundant on a Catholic soil 2–and does not the sun
shine alike, and the dew descend, on the domains of each political
party P
So science, from her daily converse with nature, fails not sooner
or later to take her hue and colour from the perception of this uni-
versal love and bounty. Party and sectarian differences dwindle
away and disappear from the eyes of him who is daily occupied in
the contemplation of the boundless munificence of the great Impar-
tial ; he sees himself standing in one common relation to all his
* The beauty of this arrangement appears more striking when we consider that the
whole of the watery vapour in the air, if it fell at once in the form of rain, would not
cover the whole surface of the globe to a depth of more than five inches. In Eng-
land the annual fall of rain varies from 22 inches (London, York, and Edinburgh) to
68 (Keswick), while in some few parts of the world (St Domingo) it amounts to as
much as 150 inches. At Bombay 80 inches fall—and on the Ghauts which separate
the Concan (the low land of the Malabar coast) from the high land of the Deccan, 240
inches—in the four rainy months from June to September. The mean annual fall of
rain over the whole earth is estimated at 32 to 33 inches; but if we suppose it to be
only 10 or 15 inches, the water which thus falls will require to be two or three times
re-distilled in the course of every year. This is exclusive of dew, which in many coun-
tries amounts to a very large quantity.—See Prout’s Bridgewater Treatise, p. 300,
WET AND COLD SOILS. 59
fellow-men, and feels himself to be most completely performing his
part in life, when he is able in any way or in any measure to con-
tribute to the general welfare of all. -
It is in this sense too that science, humbly tracing the footsteps
of the Deity in all his works, and from them deducing his intelli-
gence and his universal goodness—it is in this sense that science is
of no sect and of no party, but is equally the province, and the
property, and the friend of all.
§ 7. Of the cold produced by the evaporation of water in the soil,
and its influence on vegetation.
Beautiful, however, and beneficent as are the provisions by
which, in mature, watery vapour is made to serve so many useful
purposes, there are circumstances in which, and often through the
neglect of man, the presence of water becomes injurious to vege-
tation.
The ascent of water, in the form of vapour, permits the soil to
dry, and fits it for the labours of the husbandman; while its de-
scent in dew refreshes the plant, exhausted by the heat and excite-
ment of a long summer's day. But the same tendency to ascend
in vapour gives rise to the cold unproductive character of lands in
which water is present in great excess. This character you are
familiar with in what are called cold clay soils.
The epithet cold, applied to such soils, though derived probably
from no theoretical views, yet expresses very truly their actual
condition. The surface of the fields where such lands exist, is in
reality less warm, throughout the year, than that of fields of a
different quality, even in their immediate neighbourhood. This
is readily proved, by placing the bulb of a thermometer below the
surface of the soil in two such fields, when in the hottest day a
marked difference of temperature will in general be perceptible,
This difference is dependent upon the following principle:—
When an open pan of water is placed upon the fire, it continues
to acquire heat till it reaches the temperature of 212° F. It
then begins to boil, but ceases to become hotter. Steam, however,
passes off, and the water diminishes in quantity. But while the
vessel remains upon the fire the water continues to receive heat
from the burning fuel as it did before it began to boil. But since,
60 IMPROVED BY DRAINING,
as already stated, it becomes no hotter, the heat received from the
fire must be carried off by the steam.
Now this is universally true. Whenever water is converted into
steam, the ascending vapour carries off much heat along with it.
This heat is not missed, or its loss perceived, when the vapour or
steam is formed over a fire; but let water evaporate in the open air
from a stone, a leaf, or a field, and it must take heat with it from
these objects—the surface of the stone, the leaf, or the field must
become colder. That stone or leaf also must become coldest, from
which the largest quantity of vapour rises.
Now, let two adjoining fields be wet or moist in different de-
grees—that which is wettest will almost at all times give off
the largest quantity of vapour, and will, therefore, be the coldest.
Let spring arrive, and the genial sun will gently warm the earth
on the surface of the one, while the water in the other will swallow
up the heating rays, and cause them to re-ascend in the watery
vapour. Let summer come, and while the surface soil of the one
field rises at mid-day to perhaps 100°F, or upwards, that of the
other may, in ordinary seasons, rarely reach 80° or 90°–in wet
seasons may not even attain to this temperature—and only in long
droughts will derive the full benefit of the solar rays. I shall here-
after more particularly advert to the important influence which a
high temperature in the soil exercises over the growth of plants,
the functions of their several parts, and their power of ripening
seeds;–as well as to certain beautiful adaptations by which nature,
when left to herself, is continually imparting to the soil, especially in
northern latitudes, those qualities which fitit for deriving the greatest
possible benefit from the presence of the sun's rays. In the mean-
time you are willing to concede that warmth in the soil is favour-
able to the success of your agricultural pursuits. What, them, is
the cause of the coldness and poverty, the fickleness and uncer-
tainty of produce, in land of the kind now alluded to ? It is the
presence of too much water. What is the remedy ? . A removal
of the excess of water. And how 2 By effectual drainage.
There are other benefits to the land, which follow from this re-
moval of the excess of water by draining, of which it would here
be out of place to treat; but a knowledge of the above principle
shews you that the first effect upon the soil is the same as if you
WET AND COLD SOILS IMPROVED BY DRAINING, 6]
were to place it in a warmer climate, and under a milder sky—
where it could bring to maturity other fruits, and yield more cer-
tain crops.
The application of this merely rudimentary knowledge will ena-
ble you to remove from many improvable spots the stigma of being
poor and cold;...an appellation hitherto applied to them,-not be-
cause they are by nature unproductive, but because ignorance, or
indolence, or indifference has hitherto prevented their natural ca-
pabilities from being either appreciated or made available,
LEC TURE III.
Compounds of the organic elements which minister to the growth of plants. Carbonic
and oxalic acids, their properties and relations to vegetable life. Carbonic oxide
and light carburetted hydrogen, their properties and production in nature. Humic,
Ulmic, Geic, Crenic, Apocrenic and Mudesous Acids—their composition, mutual
relations, production in the soil, and uses to the plant. Ammonia, its properties and
relations to vegetable life. Supposed action of gypsum. Nitric acid, its prepara-
tion, properties, and production in nature.
THERE are three compounds of carbon with oxygen with which
it is necessary to make you acquainted. These are,
Carbon, Oxygen.
Carbonic acid, C O2, consisting of 27:37 72-63
Oxalic acid, C2O3, consisting of 33:44 66-56
Carbonic oxide, CO2, consisting of 42.98 57-12
I shall treat of these three compounds in the order in which I
have here placed them, which is that of their relative importance
in reference to the phenomena of vegetable life.
§ 1. Carbonic acid, its properties and relations to vegetable life.
When charcoal is burned in the air it combines slowly with the
oxygen of the atmosphere, and is transformed into carbonic acid
gas. In pure oxygen gas it burns more rapidly and vividly, pro-
ducing the same compound—the bulk of the new gas produced
being precisely equal to that of the oxygen employed.
This gas is colourless, like oxygen, hydrogen, and nitrogen, but
is readily distinguished from all these by its smell, its acid taste,
its solubility in water, its greater weight or density, and its property
of reddening vegetable blues.
Water at 60° F. and under the ordinary pressure of the atmo-
sphere, dissolves rather more than its own bulk of this gas (100
PROPERTIES OF CARBONIC ACID. 63
volumes dissolve 106), and, however the pressure may be increased,
it still dissolves the same bulk.
But all gases diminish in bulk uniformly as the pressure to which
they are subjected is increased. Thus under a pressure of two at-
mospheres they are reduced to one-half their bulk, of three atmo-
spheres to one-third, and so on. When water, therefore, is satu-
rated with carbonic acid under great pressure, as in the manufac-
ture of soda water, though it still dissolves only its own bulk, yet
it retains a weight of the gas which is in proportion to the pressure
applied. For the same reason also, when the pressure is removed,
—as in drawing the cork from a bottle of water so impregnated,—
the gas expands and escapes, causing a lively effervescence, and
the water retains only its own bulk at the existing pressure. This
solution in water has a slightly sour taste, and reddens vegetable
blues. These properties it owes to the presence of the gas, which
is therefore what chemists call an acid" body, and hence its name
of carbonic acid.
This gas is one-half heavier than atmospheric air, its density be-,
ing 1:524, and hence it may be poured through the air from one
vessel to another. Hence also, when it issues from crevices in the
earth—in caves, in wells, or in the soil—it diffuses itself through
the atmosphere and ascends into the air, much more slowly than
the gases described in the previous lecture. Where it issues from
the earth in large quantity, as in many volcanic districts, it flows
along the surface like water, enters into and fills up cracks and
hollows, and sometimes reaches to a considerable distance from its
source, before it is lost among the still air.
Burning bodies are extinguished by carbonic acid, and living
beings, plunged into it, instantly cease to breathe. When mixed
with one-ninth of its bulk of this gas, the atmospheric air is ren-
dered unfit for respiration. It is, however, an important food of
plants, being absorbed by their leaves, and probably by their roots
also, in large quantity. Hence the presence of carbonic acid in
the atmosphere is necessary to the growth of plants, and they have
been observed to thrive better when the usual quantity of this gas
* Acids have generally a sour taste, redden vegetable blues—such as the blue ex-
tracted from violets or from red cabbage by steeping them in water—or combine with
bases, such as lime, Soda, potash, &c., to form salts. -
64 EVIDENCE OF UNITY OF DESIGN.
in the air is considerably augmented. Common air, as has been
already stated, (p. 37,) does not contain on an average more than
gºath of its bulk of carbonic acid, but De Saussure found that
plants in the sunshine grew better when it was increased to ºth of
the bulk of the air. Beyond this quantity they were injured by
the gas, even when exposed to the sum. When the carbonic acid
amounted to one-half the plants died in seven days, when it reach-
ed two-thirds of the bulk of the air they ceased to grow altogether.
In the shade any increase of carbonic acid beyond that which natu-
rally exists in the atmosphere of our globe was found to be injurious.
These circumstances it is of importance to remember. Had the
sun been intended always to shine, on every part of the earth's sur-
face, the quantity of carbonic acid in the atmosphere might pro-
bably have been increased with advantage to vegetation. But every
such increase would have rendered the air less fit for the respira-
tion of existing races of animals. Thus we see that not only the
nature of living beings, both plants and animals, but also the pe-
riodical absence of the sun's rays have been taken into account in
the present arrangement of things.
Amid perpetual sunshine plants would flourish more luxuriantly
if the air contained more carbonic acid, but then they would droop
and die in any accidental shade. This is one of those proofs of
wnity of design which occasionally force themselves upon our atten-
tion in every department of mature, and compel us to recognise
the regulating superintendence of one mind. The same hand which
mingled the ingredients of the atmosphere, also set the sun to rule
the day only,–tempering the amount of carbonic acid to the length
of his periodical presence, as well as to the nature of animal and
vegetable life.
Carbonic acid consists of one equivalent of carbon (C) and two
of oxygen, (O2) and is therefore represented by CO2. It unites
with bases (potash, Soda, lime, &c.), and forms compounds known
by the name of carbonates. Thus pearlash is an impure carbonate
of potash,+the common soda of the shops, carbonate of soda,
and limestone or chalk, carbonate of lime. From these compounds
it may be readily disengaged by pouring upon them diluted muri-
atic or sulphuric acids, and in this way carbonic acid is usually pre-
pared. From limestone it is also readily expelled by heat, as in
CARBONIC ACID RENDERS LIME SOLUBLE, 65
the common lime-kilns. During this process the limestone loses
nearly 44 per cent. of its weight (43-7 when pure and dry), a loss
which represents the quantity of carbonic acid driven off.”
Common carbonate of lime, in its various forms of chalk, hard
limestone, or marble, is nearly insoluble in water, but it dissolves
readily in water containing carbonic acid. Thus, if a current of
this gas be passed through lime water, the liquid speedily becomes
milky from the formation and precipitation of carbonate of lime,
but the current of gas being continued, the cloudiness gradually
disappears, and the whole of the lime is re-dissolved. The appli-
cation of heat to this clear solution expels the excess of carbonic
acid, and causes the carbonate of lime again to fall.
When exposed to the air, pure water always absorbs a quantity
of carbonic acid from the atmosphere. As it afterwards trickles
through rocks or soils containing lime, it gradually dissolves a por-
tion of this substance, varying with the quantity of gas it holds in
solution, and thus reaches the surface impregnated with calcare-
ous matter. Or, as it flows beneath the surface of the soil, it car-
ries the lime to the roots of plants, by which its earthy contents are
made available, either directly or indirectly, to the promotion of
vegetable growth. To the lime thus held in solution, spring and
other waters owe their hardness. When such waters are boiled
the lime falls and forms a crust on the bottom of the boiler, be-
cause the heat drives off the excess of carbonic acid, and renders
the carbonate of lime insoluble.
I propose hereafter to consider, at some length, the action of lime
upon land, whenit is employed for agricultural purposes; but I may
here remark, that this property of dissolving lime which is possessed
by the carbonic acid contained in rain water is one of the principal
causes why lime is removed from your soils, and why fresh appli-
cations are necessary after a certain lapse of time. It is the cause
also of that deposit of calcareous matter at the mouths of drains,
which you not unfrequently see in places where lime has been laid
abundantly upon the land. The greater the quantity of rain,
therefore, which falls in a district, the less permanent will be the
effects of lime—the sooner will the land be robbed of this impor-
* Hence by burning limestone on the spot where it is quarried, nearly one-half of
the cost of transport is sayed.
- E
66 PROPERTIES OF OXALTC ACID,
tant element of a fertile soil. Still carbonic acid is only one of
several agents which act almost unceasingly in thus removing the
lime from your fields, a fact which I shall hereafter have occasion
more fully to explain.
In nature, carbonic acid is produced under a great variety of
circumstances. It is given off from the lungs of all animals dur-
ing respiration ; and from the leaves and green parts of plants
during the absence of the sun. It is formed during the progress
of fermentation,-fermented liquors owing their sparkling qualities
to the presence of this gas. During the decay of animal and ve-
getable substances in the air, in compost heaps, or in the soil, it is
evolved in great abundance. In certain volcanic countries it is-
sues in large quantity from springs and from cracks and fissures
in the surface of the earth ; while the vast amount of carbon con-
tained in the wood and coal daily consumed by burning, is carried
up into the atmosphere, chiefly in the form of carbonic acid. We
shall hereafter consider the relation which exists between these se-
veral sources of supply, and the proportion of carbonic acid per-
manently present in the air, and so necessary to the support of
vegetable life.
§ 2. Ovalic acid, its properties and relations to vegetable life.
Oxalic acid is another compound of carbon and oxygen, which,
though not known to minister either to their growth or nourish-
ment, is yet found largely in the interior of many varieties of
plants. In an uncombined state it exists in the hairs of the chick
pea. In combination with potash it is found in the wood sorrel
(Oxalis acetosella), in the common sorrel and other varieties of ru-
mew, causing the well known sourness of their leaves and stems. It
is also present in the roots of these plants, in the leaves and roots of
rhubarb, and in the roots of tormentilla, bistort, gentian, Saponaria,
and many other plants. It is this combination with potash, for-
merly extracted from wood-sorrel, which is known in commerce by
the name of salt of sorrel. In combination with lime it forms the
principal solid parts of many lichens, especially of the parmelia
and variolaria,” some of which contain as much oxalate of lime
* The Parmelia cruciata and Variolaria communis are mentioned as peculiarly rich
in this acid, which used to be extracted from them for sale. A species of parmelia,
g
PROPERTIES OF CARBONIC OXIDE. 67
as is equivalent to 15 or 20 parts of pure acid in 100 of the dried
plant. Oxalate of lime has also been observed in the state of
crystals in the interior of some plants, as in the Ficus Bengalensis,
in the Marantha zebrina (Unger), and in the tuber of the potato.
The oxalic acid of the shops forms transparent colourless crys-
tals, which have an intensely sour taste. These crystals dissolve
readily in twice their weight of cold water, and the solution, when
sufficiently dilute, is agreeably acid to the taste. This acid is ex-
ceedingly poisonous. Half an ounce of the crystals is sufficient
to destroy life in a very short time, and a quarter of an ounce
after the lapse of a few days. It consists solely of carbon and
oxygen in the proportion of two equivalents of the former to three
of the latter. Its symbol is C2O3. It combines with bases, and
forms salts which are known by the name of ovalates, and it is
characterised by the readiness with which it combines with lime to
form ovalate of lime. If a solution of the acid be poured into
lime water, the mixture immediately becomes milky from the forr
mation of this compound, which is insoluble in water.” It is this
oralate of lime which exists in the lichens, while ovalate of potash
exists in the Sorrels,
Oxalic acid is one of those compounds of organic origin, which
we cannot as yet form, as we can form carbonic acid, by the direct
union of its elements. In all our processes for preparing it artifi-
cially, we are obliged to have recourse to a substance previously or-
ganized in the living plant. It may be prepared from sugar, starch,
rosin, or even from wood, by various chemical processes. The usual
collected after the droughts on the sands of Persia and Georgia, contains 66 per cent.
of oxalate of lime, with about 23 per cent of a mucilaginous substance similar to that
obtained from Iceland moss. This lichen is used for food by the Kirghuis. A simi-
lar lichen is collected about Bagdad for the same purpose.
* Substances that are insoluble are generally without action on the animal eco-
nomy, and may be introduced into the stomach without producing any injurious ef.
fect. Hence this oxalate of lime, though it contains oxalic acid, is not poisonous.
Hence, also, if oxalic acid be present in the stomach, its poisonous action may be
taken away by causing lime water or milk of lime to be swallowed in sufficient quan-
tity. The acid combines with the lime, as in the experiment described in the text,
and forms insoluble oxalate of lime. The common magnesia of the shops will serve
the same purpose, forming an insoluble ocalate of magnesia. It is by performing
experiments under circumstances where the results are visible—as in glass vessels—
that we are enabled to predict the results in circumstances where the phenomena are
not visible, and to act with as much confidence as if we could really see them.
68 PROPERTIES OF CARBONIC OXII).E.
method is to mix potato starch with five times its weight of strong
nitric acid (aqua-fortis), and ten of water, to digest the mixture till
red fumes cease to be given off, and then to evaporate the solution.
The oxalic acid separates in crystals, or, as it is usually expressed,
crystallizes in the solution after it has been concentrated by evapo-
ration.
This acid is not known to exist in the soil or in the waters which
reach the roots of plants. Where it is found in living vegetables,
therefore, it must, like the other substances they contain, have been
for the most part formed in the interior of the plant itself. By
what very simple changes the production of this acid is, or may be,
effected we shall see in a subsequent lecture.
§ 3. Carbonic oxide, its constitution and properties.
When carbonic acid (CO2) is made to pass through a tube con-
taining red hot charcoal it undergoes a remarkable change. Its
form of gas remains unaltered, but it combines with a second equi-
valent of carbon—becoming C, Os. The new gas thus produced
is known by the name of carbonic oxide. It consists of one equi-
valent of carbon united to one of oxygen, and is represented by
C, O, or simply by CO. *
This gas is colourless, without taste or smell, lighter than com-
mon air, nearly insoluble in water, extinguishes flame, does not
support life, burns in the air or in oxygen gas with a blue flame,
and during this combustion combines with more oxygen and is
converted into carbonic acid. It is produced along with carbonic
acid during the imperfect combustion of coal in our fires and fur-
naces—is no doubt formed occasionally during the decay of vege-
table matter in our soils and compost heaps—but is not known to
occur in nature in any quantity, or to minister directly to the
growth of plants.
There exists a general relation among the three compounds of
carbon and oxygen above described, to which it may be interesting
to advert, in connection with the subject of vegetable physiology.
This relation appears when we compare together their chemical
constitution, as represented by their chemical formulae:—
LIGHT CARBURETTED HYDROGEN. 69.
Carbonic acid consists of one of carbon and two of oxygen, and
is represented by CO, ;
Carbonic ovide of one of carbon and one of oxygen, being re-
presented by CO;
So that if carbonic acid be present in a plant, and be there de-
prived of one equivalent of its oxygen, by any chemical or vital ac-
tion, it will be converted into carbonic oxide. -
Oxalic acid consists of two of carbon and three of oxygen, its
formula being C, Og. - *
If we add together the formulae for
Carbonic acid = CO, and
Carbonic oxide = CO we have
Oxalic acid = C, Os
Hence this acid may be formed in the interior of plants, either
by the direct union of carbonic oxide and carbonic acid, or by tak-
ing from
2 of carbonic acid = C, O,
1 of oxygen – O1 leaving
I of oxalic acid = C, Og
When in a subsequent lecture we shall have studied the structure
and functions of the leaves of plants, we shall see how very easy it
is to understand the process by which oxalic acid is in this way
formed from carbonic acid, and by which carbonic oxide also may
be, and probably is, produced in the interior of plants.
§ 4. Light carburetted hydrogen—the gas of marshes and of coal
mines.
During the decay of vegetable matter in moist places, or under
water, a light inflammable gas is not unfrequently given off, which
differs in its properties from any of those hitherto described. In
summer it may often be seen rising up in bubbles from the bottom
of stagnant pools and from marshy places, and in such cases may
readily be collected.
This gas is colourless, without taste or smell, and is little more
than half the weight of common air, its specific gravity being
0:5576, atmospheric air being 1. A lighted taper plunged into
70 HUMUS—THE DECAYING VEGETABLE MATTER IN THE SOIL.
it is immediately extinguished, while the gas takes fire and burns
with a pale yellow flame. It yields more light, however, than pure
hydrogen gas, which it in other respects resembles. Animals in-
troduced into it instantly cease to breathe. - .
It consists of 1 equivalent of carbon (C) united to 2 of hydrogen
(2H or H2) and is represented by CH3. When burned in the air
or in oxygen gas, the carbon it contains is converted into carbo-
nic acid (CO) and the hydrogen into water (HO). Thus,
One of marsh gas--4 oxygen = one of carbonic acid-i-2 of water.
CH, + 4 O = CO, + 2 HO.
Ilike oxalic acid this gas cannot, by any known process, be pro-
duced by the direct union of the carbon and hydrogen of which it
consists. It is readily obtained, however, by heating acetate" of
potash in a retort, with an equivalent proportion of caustic baryta.
In nature it is largely evolved in coal mines, and is the princi-
pal combustible ingredient in those explosive atmospheres, which
so frequently cause disastrous accidents in our mining districts.
This gas is also given off along with carbonic acid during the
fermentation of compost heaps, or of other large collections of ve-
getable matter, is said to be generally present in well-manured
soils,f-and is supposed by some to contribute in such cases to
the nourishment of plants. It is, however, very sparingly
soluble in water, so that in a state of solution, it cannot enter
largely into the pores of the roots, even though it be abundantly
present in the soil. How far it can with propriety be regarded as
a general source of food to plants, will be considered in the fol:
lowing lecture.
Being formed during the decay of vegetable matter on the earth's
surface, this light carburetted hydrogen is probably present in
ininute quantity in atmospheric air.
§ 5. Of the humic, ulmic, geic, crenic, apocrenic, and mudesous
acids, and of humin and ulmin.
Besides the three gaseous substances already described,—car-
bomic acid, carbonic oxide, and carburetted hydrogen,_there are
* Acetate of potash is prepared by pouring vinegar (acetic acid) on common pearl-
ash and evaporating the solution.
* PERSOz, Chimie Moleculaire, p. 549.
HUMIC ACIl) GROUP. 71.
formed from decaying vegetable substances in the soil numerous
solid compounds which are of much importance to the growth of
plants. -
Our cultivated soils are usually of a brown or black colour, more
or less dark, owing to an admixture of decaying animal and vege-
table matter with the earthy substances of which the soils princi-
pally consist. To this decaying brown or black organic matter
the name of humus has been given by agricultural writers.
But this humus consists of a number of different chemical com-
pounds. - .
, a. When the soil is boiled in water, a small portion of the or-
ganic matter along with other substances is dissolved. -
b. When the soil, after being thus treated with water, is di-
gested in a solution of caustic potash or of carbonate of soda, a
dark brown liquid is obtained, in which another portion of the or-
ganic matter is contained. -
c. But there remains still a large portion of the organic mat-
ter in the soil, which neither the water nor the alcaline solution
can extract.
Thus it is easily shown that there are at least three kinds of or-
ganic matter in the soil; one which is soluble in water, one in-
soluble in water but soluble in solutions of potash or soda, and one
which is insoluble in both.
But each of these three forms of organic matter are themselvés
mixtures of two or more different compounds. Hence the number
of solid organic substances contained in the soil is much greater
than you would suppose. As many as sixteen have been separated
by Hermann and distinguished by different names.* They are
mo doubt very numerous, and many compounds must be produced
in the soil with which we are as yet unacquainted, but all those
which have yet been extracted from it may be classed, under one
or other of three groups.
1°. The humic acid group.–The humic acids are all of a dark
brown or black colour. They are produced by the decay of vege-
table matter in the air or in the soil, by the action of sulphuric
acid upon sugar, of caustic potash upon wood, and even of heat
upon coal. Hence they exist abundantly in dark-coloured soils, in
* Erdmann and Marchand's Journal, 1841, I. and II. and 1842, I,
72 HUMIC AND ULMIC ACID GROUPS.
black peat and in soot, and may readily be obtained by boiling any
of these in a solution of carbonate of soda, and afterwards render-
ing the solution sour by the addition of muriatic acid. They then
fall in dark brown flocks.
The acids belonging to this group consist of carbon and water
only, and the several members of the group are distinguished by
containing a greater or less proportion of water combined with the
same quantity of carbon. Thus humic acids extracted from dif-
ferent substances by means of carbonate of soda, well washed and
then dried—all at the same temperature, —were found to consist of
Carbon -- Water C. H. O.
a. Humic acid from sugar, by } 40 + 12 or of 40 12 12
means of acids,
Carbon + Water C. H. O.
b. Humic acid from the soil of a
pasture field, } 40 + 14 or of 40 14 14
C from hard black } l 40 15 15
Dutch peat, + 15 =
d. from soot, 40 + 16 = 40 16 16
from rotten wood, 40 + 16 = 40 16 16
from an arable soil, 40 + 16 – 40 16 16
6. from another arable R
wº ..} 40 + 17 = 40 17 17
soil, ſ
f: — from a hard Scotch R .
g * 40 + 20 = 40 20 *20
peat, ſ
Besides these cight varieties of humic acid, there are probably
many more in which, while the carbon remains constant, the pro-
portion of water or its elements varies. They all resemble each
other, however, so much in their chemical properties, and in their
black shining coaly appearance when dry, that it is impossible to
distinguish them from each other except by an ultimate analysis.
2°. The ulmic acid group.–The ulmic acids are extracted from
soils and peats in the same way as the humic acids, with which
they occur mixed in nearly all soils. In the state of powder they
are generally of a lighter brown colour than the humic acids, as
* The last of these acids was analysed by myself, the others by Mulder. See his
Chemistry of Vegetable and Animal Physiology, p. 154.
4
GEIC, ACID GROUP. 73
they are supposed to be formed from vegetable matter in a less
advanced stage of decay than the humic acids. They can only be
distinguished from the humic acids, however, by analysis. They
consist of carbon and water with a variable excess of hydrogen.
Thus three varieties of ulmic acid have been found to consist of
Carbon + Water + Hydrogen C. H. O.
a. Ulmic acid from
sugar, by means 40 + 12 + 2 or of 40 14 12
of acids,
b. from
brown . Friesland g
turf by º 40 + 16 + 2 – 40 18 16
of soda,
Carbon + Water + Hydrogen C. H. O.
c. Ulmic acid from
black Scotch peat,
extracted by am- } + 9 + 5 or of 24 14 9
monia.
It will be seen that in these three acids the equivalents of hy-
drogen are always more numerous than those of the oxygen, and
such is the character of this group of acids. There are probably
many more of them formed in soils of different kinds, but we know
of no means by which they can be separated from each other, or
from the humic acid, with which they occur mixed in the soil.
3°. The geic acid group.–This group comprehends several acids
to which distinct names have been given. They all contain carbon
and water with an excess of oxygen, and are the result of a further
decay of the humic and ulmic acids under the influence of the oxy-
gen of the atmosphere. The acids belonging to this group which
have hitherto been detected in the soil are as follows:
• Carbon + Water + Oxygen C. H. O.
Geic acid from two kinds R 4.
of soil. ſ £0 15 + 2 or of 40 15 17
Cronic acid, 24 + 12 + 4 = 24 12 16.
Apocrenic acid, 48 + l2 + 12 = 48 12 24
Mudesous acid, 12 -- 5 + 3 = 12 5 S.
The number of equivalents of oxygen in all these acids is greater
than of hydrogen, and this is the chemical character of the group-
74. IIUMIN AND ULMIN.
a. The geic acid, properly so called, resembles the humic and
ulmic acids very much. It occurs mixed with them in the soil, and
there is no known method by which it can be separated from them.
b. The organic matter extracted from the soil by water alone con-
tains generally both crenie and apocrenic acids. But when a soil is
boiled in a solution of carbonate of soda, and the humic, ulmic,
and geic acids are precipitated by adding muriatic acid, the sour
liquid which rests above still contains crenic and apocrenic acids.
If this sour liquid be fully saturated by carbonate of soda, and then
made slightly acid by vinegar, acetate of copper will throw down
a green precipitate containing the crenic, and, on the addition of
ammonia, a further precipitate containing the apocrenic acid. Or
both of these acids may be thrown down at once, in combination
with alumina, by first adding an excess of ammonia to the solu-
tion, and then dropping in a solution of alum as long as the preci-
pitate exhibits any tinge of colour.
c. The mudesous acid usually exists in the soil in combination
with alumina, and this compound is not unfrequently washed out
from the soil by the waters that trickle through it to the drains
and ditches, or sink down into the subsoil. In the caves on the
coast of Cornwall, the waters that sink down from above deposit on
their sides a crust of this compound of greater or less thickness.
The mudesite of alumina thus deposited is known to mineral col-
lectors by the name of pigotite.
4°. Humin and ulmin.—When a portion of soil, of peat, or
of the black or brown substance produced by the action of sul-
phuric acid upon sugar, is treated with a hot solution of carbonate
of soda, the humic, ulmic, &c. acids are dissolved. But a quantity
of brown or black matter remains behind, which neither potash,
soda, nor ammonia will dissolve. This insoluble part consists of
at least two substances, to which the names of humim and ulmin
have been given respectively. They have the same composition as
the humic and ulmic acids, but they differ from them in being in-
soluble in water or in alkaline solutions. Thus they consist re-
spectively of
Carbon. Water. Hydrogen. C. H. O.
Ulmin, & 40 14 2 or of 40 16 14
Iſumin, 40 15 ... = 40 15 15
. . . . . .sº ; : ..., * . . . . . . . . . . . . . . . . . . . . . .”. . . . . . . . * ~ * * ,- .
jº, > - • • * , --- s • * * .-- ", *
- r g
** . .
t
PROPERTIES OF THE HUMIC, UIMIC, AND GEIC ACIDs. 75
So that, like the humic acids, the humin consists of carbon and wa-
ter only; while the ulmin, like the ulmic acids, contains an excess
of hydrogen. e
These insoluble substances can be of little immediate use in
yielding nourishment to plants. They form what has been called
coaly humus by some agricultural writers. They undergo gradual
changes, however, in the soil—through the action of potash, soda,
lime, and other substances, by which changes they are fendered
solublein water, and capable, therefore, of performingfunctions simi-
lar to those which are assigned to the humic, ulmic, and geic acids.
§ 6. General properties and mutual relations of the humic; ulmic,
and geic acids, and the purposes served by them in the soil.
All the acid substances above described are known to exist in the
organic part of the soil, and probably many more remain to be dis-
covered. They are all produced during the decay of vegetable and
animal matters in the soil in the presence of air and water, and they
perform, as we shall hereafter see, very important purposes in re-
ference to the growth of plants. It will be proper, therefore, to
advert to a few of the properties they are known to possess in com-
mon, and of the relations they bear to each other—more es-
pecially as these general properties and mutual relations are in-
timately connected with the useful functions they are known to
perform in the soil. - - - s
A. General properties of these acids,
1°. The humic and ulmic groups of acids, and the geic acid
properly so called, are all very sparingly soluble in water. They
do not, therefore, appear to enter largely into the roots of plants
in an uncombined state. This is not the case, however, with the
crenic, apocrenic, and mudesous acids, which dissolve readily in
water, and may therefore enter in large quantity along with the
water which the roots drink in from the soil, provided they are
there present in an uncombined state.
2°. But all the acids above named unite readily with potash,
soda, and ammonia, either in the caustic state or in that of carbo-
mates, and form compounds which easily dissolve in water. Such
compounds are produced naturally in the soil and in the ferment.

76 THEIR GENERAL PROPERTIES.
ing manures we add to the soil, are readily taken up by the roots
of plants, and in our climate at least appear to contribute materi-
ally to their growth.
3°. They have all a strong tendency to combine with ammonia.
Hence when extracted from the soil they are almost universally
found to contain a quantity of this important compound. When
prepared in a perfectly pure state, and exposed to the air, they are
soon found to contain traces of ammonia. This ammonia is not
merely extracted from the air; it is actually formed either in
whole or in part, by the mutual action of these acids and of the
constituents of the atmosphere to which they are exposed. Of the
precise way in which this ammonia is formed I shall treat in a sub-
sequent lecture. -
The ammonia they are thus the instruments of producing is one,
of the agents by which the acids themselves are rendered soluble
in water, and thus fitted to become the food of plants.
4°. They all form with lime, magnesia, oxide of iron, and alu-
mina, combinations which are very sparingly soluble in water.
Such compounds exist and are produced in every fertile soil,
and though they may not be largely and immediately useful to the
growing plant, yet they preserve the valuable substances of which
they consist from being readily washed out of the soil, and they
are ready to minister to vegetable growth whenever circumstances
become favourable for their admission into the roots of plants.
5°. The soluble compounds which these acids form with potash,
soda, or ammonia, possess the property of dissolving small quan-
tities of the earthy substances above-mentioned. When the acids
are extracted from the soil, therefore, by boiling solutions of car-
bonate of potash, soda, or ammonia, the dark-brown liquid ob-
tained is always found to contain sensible quantities of lime,
magnesia, oxide of iron or alumina, from which it is scarcely pos-
sible to obtain the acids themselves quite free.
In consequence of this property, these acids almost always carry
łime, magnesia, &c. into the roots of plants, when they are taken
up by them from the soil, and in this way they serve an important
purpose by supplying that mineral or inorganic food which wo
shall by and bye see is essential to the healthy growth of all our
cultivated plants,
MUTUAL RELATIONS OF THESE ACID5. 77
B. Mutual relations of these acids.
These acid substances, as I have already stated, are all formed
from decaying vegetable and animal matters. By what kind of
changes they are produced will readily appear, when in a subse-
quent lecture I shall have shown you what vegetable matter itself
especially consists of. In the meantime it will be easy for you to
understand how closely these acids are related, and how they
change one into the other in the presence of air and moisture.
1°. The ulmic acids, those containing an excess of hydrogen,
are usually the first products of the decomposition of vegetable
matter. These are gradually converted into one or other of the
humic acids, and by a very simple change. Thus suppose
C. H. O.
Užmic acid a — 40 l/k 12 to absorb from the air
2 of oxygen, - 2 and we have
*-*-
Humic acid b = 40 14 14
And by a similar simple change, any of the other ulmic acidsmay
be converted into one or other of the humic acids. **
2°. Again, the humic acids change in a similar way into one or
other of the geic acid group. Thus let the
C. H. O.
Humic acid b = 40 15 15 absorb from the air
2 of oxygen, - 2 and we have
Geic acid – 40 15 17
3°. In like manner the crenic may be formed from the geic, or
the apocrenic from the crenic. Thus, if
e C. H. O.
2 of Crenic acid - 48. 24 32 take up from the air
4 of oxygen - 4 .
we have - 48 24 36
Deduct 12 of water = 12 12 and there remains
1 of Apocrenic acid 48 12 24
so that the crenic acid absorbs oxygen, gives off water, and forms
the apocrenic acid.
78 PROPERTIES OF AMMON [A.
We cannot say that these are the precise changes which take
place in the soil at any one time or on any particular spot, but the
above formulae illustrate the kind of changes which are continually
going on in the soil, and by which the organic matter it contains
is more and more fitted to be useful to living plants. I shall illus-
trate this point to you more fully in a subsequent lecture, when I
come to explain the general law of the decay of animal and ve-
getable matters in the soil.
C. Purposes served by these acids in the soil.
The properties and mutual relations of these acids must already
appear to you to be closely connected with the useful functions
they perform in the soil. These functions are chiefly the follow-
ing: -
1°. They darken the soil, and thus cause it to be more readily
warmed by the sun's rays.
2°. They supply the plant with organic food.
3°. They convey also inorganic food into the roots of plants.
4°. They absorb ammonia from the air where it exists, and from
fermenting manure—they actually produce it from its elements in
favourable circumstances—and they fix and retain it in the soil.
To most of these properties we shall have occasion hereafter to
advert.
§ 7. Ammonia, its properties and relations to vegetable life.
Ammonia is a compound, possessed of many interesting proper-
ties, and is supposed to perform a very important part in the pro-
cess of vegetation. It will be proper, therefore, to study its ma-
ture and properties with considerable attention.
It consists of hydrogen and nitrogen united together in the pro-
portion of three equivalents of hydrogen (3 H or Hs) to one of ni-
trogen N, and is represented by NH3. One hundred parts by
weight contain 82% of nitrogen, and 17% of hydrogen.
Ammonia, like the nitrogen and hydrogen of which it is com-
posed, is a colourless gas, but, unlike these elements, is easily dis-
tinguished from all other gaseous substances by its smell and taste.
It has about ºths of the weight of common air, its specific gra-
vity being 0.59, that of air being 1. Hence when set free upon
AMMONIA IS ABSORBISD IN LARGE QUANTITY BY WATER. 79
the surface of the earth in the gaseous form, it readily ascends and
mingles with the atmosphere.
It possesses a powerful penetrating odour (familiar to you in the
smell of hartshorn and of common smelling salts), has a burning
alcaline” taste, extinguishes a lighted taper as hydrogen and ni-
trogen do, but does not itself take fire like the former. It instantly
suffocates animals, kills living vegetables, and gradually destroys
the texture of their parts.
It is absorbed in large quantities by porous substances, such as
charcoal, which, as already stated, absorbs 95 times its own bulk
of ammoniacal gas. Porous vegetable substances in a decaying
state likewise absorb it. Porous soils also, burned bricks, burned
clay, and even common clay and iron ochre, which are mixed to-
gether on the surface of most of our fertile lands—all these are
capable of absorbing or drinking in, and retaining within their
pores, this gaseous substance, when it happens to be brought into
contact with them.
But the quantity absorbed by water is much greater and more
surprising. If the mouth of a bottle filled with this gas be im-
mersed in water, the latter will rush up and fill the bottle almost
instantaneously; and if a sufficient supply of ammonia be present,
a given quantity of water will take up as much as 670 times its
bulk of the gas. -
This solution of ammonia in water forms the spirit of hartshorn
of the shops. When saturated f it is lighter than pure water,
having a specific gravity of 0.875, that of water being 1. It has
also the pungent penetrating odour of the gas, and its hot, burn-
ing, alcaline taste—is capable of blistering the skin, and of decom-
posing or destroying the texture of animal and Vegetable sub-
stances.
You will remark here the effect which chemical combination has
in investing substances with new characters. The two gases hydro-
gen and nitrogen, themselves without taste or smell and absorbed
by water in minute quantity only, form by their union a compound
body remarkable both for taste and smell, and for the rapidity
with which water absorbs it.
* The term alcºline, as applied to taste, will be best understood by describing it
a state similar to that of the common soda and pearl-ash of the shops.
+ That is when gas is supplied till the water refuses to take up any more.
as
8() EXISTENCE OF AMIMONIA IN NATURE.
Ammonia possesses also alcaline” properties, restores the blue
colour of vegetable substances that have been reddened by an acid,
and combines with acid substances to form salts.
Among gaseous substances, therefore, there are some which,
like carbonic acid, have a sour taste, and redden vegetable blues;
—others, which, like ammonia, have an alcaline taste and restore
the blue colour;-and a third class which, like oxygen, hydrogen,
and nitrogen, are destitute of taste and do not affect vegetable co-
lours. These last are called neutral or indifferent substances.
Ammonia, as above stated, combines with acids and forms salts,
which, at the ordinary temperature of the atmosphere, are all so.
lid substances. Hence if moist carbonic acid gas be mixed with
ammonia in the form of gas, a white cloud is formed consisting of
minute particles of solid carbonate of ammonia—the smelling salts
of the shops. Hence also a feather dipped into acetic acid (vine-
gar), or into dilute muriatic acid (spirit of salt), and then intro-
duced into ammonia, forms a similar white cloud, and becomes
covered with a white down of solid acetate in the one case, or of
muriate of ammonia (sal ammoniac) in the other. The same ap-
pearance is seen on holding the feather to the mouth of a bottle
containing hartshorn (liquid ammonia), from which ammoniacal
gas continually escapes, and by its lightness rises into the air, and
thus comes in contact with the acid upon the feather.
The fact of the production of a solid body by the union of two
gases (ammonia and carbonic or muriatic acid gases) is one of a
very interesting nature to the young chemist, and presents a fur-
ther illustration of the changes resulting from chemical combina-
tion as explained in the previous lecture. -
In nature ammonia exists in considerable quantity. It is widely,
almost universally diffused, but is not known to form large depo-
sits on any part of the earth's surface, or to enter as a constituent
into any of the great mineral masses of which the crust of the globe
is composed. It is produced almost every where on the earth's
* In the previous lecture the term acid was explained as applying to substances
possessed of a sour taste, and capable of reddening vegetable blues or combining with
bases (potash, soda, magnesia, &c.) to form salts; alcalies are such as possess an al-
caline taste (see previous note), restore the blue colour to reddened vegetable sub-
stances, or combine with acids to form Salts. Of Salts, nitrate of soda, nitrate of po-
tash (saltpetre), and sulphate of soda (glauber salts), are examples.
AMMONIA COMBINES WITH ACIDS AND FORMS SALTS. 81
surface during the decomposition of animal and vegetable sub-
stances. It exists most abundantly in a state of combination—in
the forms, for example, of muriate (sal-ammoniac), of nitrate, and
of carbonate of ammonia. It sometimes escapes into the atmo-
sphere in an uncombined state, especially where animal matters
are undergoing rapid decay, but it rarely exists in this free state for
any length of time. It speedily unites with the carbonic acid of
the air—with one or other of the numerous acid vapours which are
continually rising from the earth—or with the nitric acid which is
formed through the agency of natural causes by the union of the
nitrogen and oxygen of which the atmosphere consists.
The influence of ammonia on the growth of plants is of a very
powerful kind. It not only promotes the rapidity and luxuriance of
vegetation, but it exercises also a powerful control over the functions
of vegetable life. In reference to the nature and extent of this ac-
tion, into which we shall hereafter have occasion to enquire, there
are several special properties of ammonia which it will be of im-
portance for us previously to understand.
1°. It has a powerful affinity for acid substances. Hence the
readiness with which it unites with acid vapours when it rises into
the atmosphere. Hence also when formed or liberated in the soil,
in the fold-yard, in the stable, or in compost heaps, it unites with
such acid substances as may be present in its neighbourhood, and
forms saline compounds or salts. All these salts appear to be
more or less influential in the processes of vegetable life.”
2°. Yet this affinity is much less strong than that which is ex-
hibited for the same acids by potash, soda, lime, or magnesia.
Hence if any of these latter substances be mixed or brought into
* To this same property of combining with acid substances is due the highly bene-
ficial action which ammonia occasionally exercises when introduced into the animal
economy. Thus in the swelling of cattle and sheep from the too hasty eating of young
clover, lucerne, &c., two or three table-spoonfuls of ammonia diluted with water are
said to give instant relief. The Swelling is due to fermentation in the stomach and
the consequent evolution of carbonic acid and of some hydro-sulphuric acid gases.
With both of these the ammonia combines and forms solid compounds, while at the
same time it puts an end to the fermentation. The owner of sheep or cattle should never
be without a bottle of liquid ammonia (hartshorn), especially in the spring months.
It is much to be preferred to lime-water or milk of lime, often employed for the same
purpose.
F
82 SPECIAL PROPERTIES OF AMMONIA.
contact with a salt of ammonia, the acid of the salt is taken up by
the potash or lime, while the ammonia is separated in the state of
gas. Thus when sal-ammoniac in powder is mixed with twice its
weight of quicklime, ammonia is given off in large quantity. This
is the method by which pure ammonia is generally prepared; and
one of the many functions performed by lime when employed for
the improvement of land, especially on soils rich in animal and
vegetable matter, is that of decomposing the salts, especially the
organic salts, of ammonia, as will be more fully explained when
we come to treat at length of this important part of agricultural
practice.* . - **
3°. The salts which ammonia forms with the acids are all, like
ammonia itself, very soluble in water. Hence two consequences
follow. First, that the ammonia which rises into the air in the
form of gas, and there combines with the carbonic or other acids,
is readily dissolved, washed out, and brought to the earth again by
the rains and dews;–so that at the same time the air is purified
for the use of animals, and the ammonia is brought down for the
use of plants. And second, that if any salts of ammonia be con-
tained in the soil, they are dissolved by the waters which trickle
through it, and are thus in a condition to be taken up, when
wholesome, by the roots of plants; or to be carried off by the
drains when injurious to vegetation.
4°. I have already alluded to the fact of this gas being absorbed
by porous substances, and to its presence in consequence, in porous
soils, and in burned bricks and clay. With the purer kinds of
unburned clay, however, and with the oxide of iron contained in
red or iron-shot soils, ammonia forms a chemical compound of a
weak nature. In consequence of its affinity or tendency to com-
bine with these substances, they are supposed to attract it from
the air, and from decaying animal or vegetable matters, and to
retain it more strongly than many porous substances can,—yet
with a sufficiently feeble hold to yield it up readily to the roots of
* Owing to this property the admixture of quicklime with compost and manure
heaps is sometimes injurious, by separating and thus causing the escape of the am-
monia which is produced during the decomposition of the animal matters they contain.
This escape of ammonia, even when imperceptible by the sense of smell, is easily de-
tected by holding over the heap a feather dipped in vinegar or in spirit of salt (mu-
rjatic acid), when white fumes are immediately perceived if ammonia he escaping.
*)
e.)
*
AMMONIA DECOMPOSES GYPSUM. 83
plants, when their extremities are pushed forth in search of
food.
5°. In the state of carbonate it decomposes gypsum, forming
carbonate of lime (chalk) and sulphate of ammonia.” The action
of gypsum on grass lands,--so undoubtedly beneficial in many
parts of the world,—has been ascribed to this single property; it
being supposed that the sulphate of ammonia formed at the ex-
pense of the ammonia of the atmosphere is peculiarly favourable
to vegetation. This question will come properly under review
hereafter. I may here, however, remark that if this be the sole
reason for the efficiency of gypsum, its application ought to be
beneficial on all lands, not already abounding either in gypsum or
in sulphate of ammonia. But if the results of experimental farm-
ing in this country are to be trusted, this is by no means the case.
The action neither of this, nor probably of any other inorganic
substance applied to the soil, is to be explained by a reference in
every case to one and the same property only.f
* Gypsum is sulphate of lime—consisting of sulphuric acid (oil of vitriol) and quick-
lime. Carbonate of ammonia consists of carbonic acid and ammonia. When the
two substances act upon each other in a moist state—the two acids which they seve-
rally contain change places—the sulphuric acid as it were preferring the ammonia,
the carbonic acid the lime. *
+ Liebig says—“the striking fertility of a meadow on which gypsum is strewed
depends only on its fixing in the soil the ammonia of the atmosphere, which would
otherwise be volatilized with the water which evaporates.”t—Organic Chemistry ap-
plied to Agriculture, p. 86. -
When we come to consider the subject of mineral manures in general, we shall
study more in detail the specific action of gypsum in promoting vegetation—a very
simple calculation, however, will serve to show that the above theory of Liebig is far
from affording a satisfactory explanation of all the phenomena.
Supposing the gypsum to meet with a sufficient supply of ammonia in the soil, and
that it exercises its full influence—100 lbs. of common unburned gypsum will fix or
form sulphate with nearly 20 lbs. of ammonia containing 16% lbs. of nitrogen. One
hundred weight, therefore, (112 lbs.), of gypsum will form as much sulphate of am-
monia as will contain 224 lbs. of ammonia, and if introduced without loss into the in-
terior of plants this sulphate will furnish them with 184 lbs. of nitrogen.
1°. In the first volume of British Husbandry, pp. 322, 323, the following experi-
ment is recorded. -
f By fizing is meant the forming of sulphate with the ammonia. Rain water is supposed to bring
down with it carbonate of ammomia (common smelling salts), which acts upon the sulphate of lime
(gypsum), in such a way that sulphate of ammonia and carbonate of lime are produced. The carbonate
of ammonia readily volatilizes or rises again into the air, the sulphate does not—hence the use of the
word fia. -
84 ACTION OF GYPSUM IS STILL UNCERTAIN,
6°. The presence or evolution of ammonia in a soil containing
animal and vegetable matter in a decaying state, induces or dis-
Mr Smith of Tunstal, near Sittingbourne, top dressed one portion of a field of red
clover with powdered gypsum, at the rate of five bushels (or four hundred weight-H)
per acre, and compared the produce with another portion of the same field, to which
no manure had been applied. The first crop was cut for hay, and the second ripened
for seed. The following were the comparative results per acre:–
HAY CROP. SEED. STRAW.
CMUt. qrs. lbs. cwt. qrs. lbs.
Gypsumed, * * 60 $ g & 3 21 e s tº 22 3 12
Unmanured, * * * 20 * * 0 20 & sº e 5 0 0
Excess of produce, 40 * * * 3 1 * * g. 17 3 12
The excess of produce in all the three crops upon the gypsumed land is very large.
Let us calculate how much nitrogen this excess would contain. In a previous lecture
(TI. p. 37) it was stated as the result of Boussingault's analysis, that dry clover seed
contains 7 per cent. and the hay of red clover 1% per cent. of nitrogen.:
The seed as it was weighed by Mr Smith would still contain #th of its weight
of water,S and, consequently, only 65d per cent. of nitrogen. Let it be taken at 6
per cent, and let the Straw be supposed to contain only 1 per cent. of nitrogen, the
quantity of this element being found to diminish in the grasses after the seed has
ripened, and to average l per cent. in the straw of wheat, oats, and barley, the weight
of nitrogen reaped in the whole crop will then be as follows:– - º
1°. 40 cwt. of hay (4480 lbs.) at l; per cent. of nitrogen contain 67 lbs.
2°. 85 lbs. of seed at 6 per cent, contain & e . 5 lbs.
3°. 17 cwt. 3 qrs. 12 lbs. or 2000 lbs. of straw at 1 per cent. contain 20 lbs.
Total nitrogen in the excess of crop, * 92 lbs.
But, as above shown, the five bushels or four cwt. of gypsum could fix only 90 lbs.
of ammonia containing 74 lbs. of nitrogen : leaving, therefore, 18 lbs. Or one-fifth of the
whole to be derived from Some other 807tree.
Now this result supposes that none of the gypsum or sulphate of ammonia was car-
ried away by the rains, but that the whole remained in the soil, and produced its
greatest possible effect on the clover—and all in one Season.
But the effect of the gypsum does not disappear with the crop to which it is actu-
ally applied. Its beneficial action is extended to the succeeding crop of wheat, and
on grass lands the amelioration is visible for a succession of years. If, then, the in-
creased produce of a single year may contain more mitrogen than the gypsum can be
supposed to yield, this substance must exercise some other influence over vegetation
than is involved in its supposed action on the indefinite quantity of ammonia in the
atmosphere. -
2°. Again, Mr Barnard of Little Bordean, Hants, applied 2; cwt. per acre on two-
+ A ton of pure gypsum, when crushed, will yield 25 bushels. It should, however, always be ap-
plied by weight.
# Ann. de Chim, et de Phys., lxiii. p. 225.
§ See Lecture II., p. 37.
PROPERTIES OF A.M.MONIA. 85
poses this matter to attract oxygen from the air more rapidly and
abundantly. The result of this is, that organic compounds of an
acid” mature are formed, which combine with the ammonia and
form ammoniacal salts. On the decomposition of these salts by
lime or otherwise, the organic acids which are separated from
them, are always more advanced towards that state in which they
again become fit to act as food for plants.
7°. But the most interesting, and perhaps the most important
property of ammonia, is one which I have already had occasion
to bring under your notice, as possessed by water also, and as pe-
culiarly fitting that fluid for the varied functions it performs in
reference to vegetable life. This property is the ease with which
it undergoes decomposition, either in the air, in the soil, or in the
interior of plants. -
In the air it is diffused through, and intimately mixed with, a
large excess of oxygen gas. In the soil, especially near the sur-
face, it is also continually in contact with oxygen. By the influ-
ence of electricity in the air, and of lime and other bases in the
soil, it undergoes a constant though gradual decomposition (oxi-
dation), its hydrogen being chiefly converted into water, and a
portion of its nitrogen into nitric acid.
year old Sainfoin, on a clayey soil. The increased produce of the first cutting was a
ton per acre, and of the second in October fully a tom, the undressed part yielding
scarcely any hay at all, while the dressed part gave 13 tons. The second year no
gypsum was applied, and the difference is said to have been at least as great.
Supposing the increased produce in all to have been 4 tons of hay, and the nitrogen.
it contained to have been only 1 per cent.—the 4 tons (8960 lbs.) would contain about
90 lbs, of nitrogen. But 2% cwt. would fix only 46 lbs. of nitrogen in the form of
ammonia ; and, therefore, supposing it to have produced its maximum effect, there
remain 44 lbs. or nearly one-half of the whole wrvaccounted for by the theory.
I would not be understood to place absolute reliance on the results of the above
experiments—but the way in which such results may be easily applied for the pur-
pose of testing theoretical views, will, I hope, convince the intelligent practical agri-
culturist how important it is that the results of some of the experiments he is every
year making, should be accurately determined by weight and measure. By this means
data would gradually be accumulated, on which we might hope to found more unex-
ceptionable explanations of the phenomena of vegetation, than the results obtained in
our laboratories have hitherto enabled us to advance.
* Organic acids generally contain more oxygen in proportion to their carbon and
hydrogen, than those organic compounds which are alcaline or neutral.
+ It will be remembered that ammonia is represented by NH3, water by HO, and
86. AMMON IA EASILY DECOMPOSED.
In the interior of plants this and other numerous and varied de-
compositions, in all probability, take place.
The important influence which ammonia appears to exercise
over the growth of plants—the evidence for which I shall present-
ly lay before you—is only to be explained on the supposition that
numerous transformations of organic substances are effected in
the interior of living vegetables—which transformations all imply
the separation from each other, or the re-arrangement of the ele-
ments of which ammonia consists. In the interior of the plant we
have seen that water, ever present in great abundance, is also ever
ready to yield its hydrogen or its oxygen as occasion may require,
while these same elements are never unwilling to unite again for
the formation of water. So it is, to a certain degree, with am-
monia. The hydrogen it contains in so large a quantity is ready
to separate itself from the nitrogen in the interior of the plant,
and in concert with the other organic elements introduced by the
roots or the leaves, to aid in producing the different solid bodies
of which the several parts of plants are made up. The nitrogen
also becomes fixed in certain constituents of the sap, in the colour-
ed petals of the flowers, in the seeds, and in other parts, of which
it appears to constitute a necessary ingredient—passes off in the
form of new compounds, in the insensible perspiration or odorife-
rous exhalations of the plant, or returning with the downward
circulation, is thrown off by the root into the soil from which it
was originally derived. Much obscurity still rests on the actual
transformations which take place in the interior of plants, yet we
shall be able in a future lecture I hope, to arrive at a tolerably
clear understanding of the general nature of many of them.
Such are the more important of those properties of ammonia,
to which we shall hereafter have occasion to advert. The sources,
remote as well as immediate, from which plants derive this, and
the other compounds we have described as contributing to the
mourishment and growth of plants, will be detailed in a subsequent
section.
nitric acid by NO3. It is casy to see, therefore, how, by means of oxygen, anmonia'
should be converted into water and nitric acid. In fact,
l of ammonia + 8 of oxygen = 1 of nitric acid + 3 of water,
N H, 4- 8 o' = N o + 3 H. O.
5
*
PROPERTIES OF NITRIC ACID. 87.
§ 8. Nitric acid, its constitution, properties, and production in
72&ture. .
When the mitre or saltpetre of commerce is introduced into a
retort, covered with strong sulphuric acid (oil of vitriol"), and
heated over a lamp or a charcoal fire, red fumes are given off, and
a transparent, often a brownish or reddish liquid, distils over,
which may be collected in a bottle or other receiver of glass. This
liquid is exceedingly acid and corrosive. In small quantity it
stains the skin and imparts a yellow colour to animal and vege-
table substances. In larger quantity it corrodes the skin, produ-
cing a painful sore, rapidly destroys animal and vegetable life, and
speedily decomposes and oxidizesf all organic substances. Being
obtained from nitre, this liquid is called nitric acid. It consists of
nitrogen combined with oxygen—one equivalent of the former
(N) being united to five of the latter (Os)—and is represented by
NOg. -
This acid contains much oxygen, as the above formula indicates,
and its action on nearly all organic substances depends upon the
ease with which it is decomposed, and may be made to part with a
portion of this oxygen.
In nature, it never occurs in a free state; but it is found in the
surface soil of many inter-tropical (hot) countries in combination
with potash, soda, and lime—in the state of nitrates. It is an im-
portant character of these mitrates that, like the salts of ammonia,
they are all very soluble in water. Those of soda, lime, and mag-
nesia attract moisture from the air, and in a damp atmosphere gra-
dually assume the liquid form. .
Saltpetre is a compound of nitric acid with potash (nitrate of
potash.) It is met with in the surface soil of many districts in
Upper India, and is separated by washing the soil and subsequent-
ly evaporating (or boiling down) the clear liquid thus obtained.
* Sulphuric acid is a compound of oxygen and sulphur, which is prepared by burn-
ing sulphur with certain precautions in large leaden chambers. It is also obtained
directly by distilling greem vitriol (Sulphate of iron) at a high temperature in an iron
still—hence its name oil of vitriol. It is a heavy, oily, acid, and remarkably corro-
sive liquid. In a concentrated state, it is exceedingly destructive both to animal and
to vegetable life. - -
+ When a substance combines with 03:ygen, either in consequence of exposure to
the air or in any other circumstances, it is said to become ovidiscil. -
88 NITRATES OF POTASH AND SODA.
When pure, it does not become moist on exposure to the air. It
is chiefly used in the manufacture of gunpowder, but has also been
recommended and frequently and successfully tried by the prac-
tical husbandman, as an influential agent in promoting vegeta-
tion, sº
In combination with soda, this acid forms nitrate of soda, a com-
pound which is found in deposits of considerable thickness in the
district of Arica in Northern Peru, from whence it is imported in-
to this country, chiefly for the manufacture of nitric and sulphuric
acids. More recently its lower price has caused it to be preferred
to saltpetre, and to be extensively employed in husbandry, espe-
cially as a top-dressing for grass lands. Like the acid itself, these
nitrates of potash and soda, when present in the soil, or when ap-
plied in too large quantities, are injurious to vegetation. This is
probably one cause of the barrenness of the district of Arica in
Peru, and of other countries, where, in consequence of the little
rain that falls, the nitrous incrustations accumulate upon the soil.
In small quantity they appear to exercise an important and salu-
tary influence on the rapidity of growth, and on the amount of
produce of many of the cultivated grasses. This salutary influ-
ence is to be ascribed, either in whole or in part, to the constitu-
tion and nature of the nitric acid, which these salts contain. It is
chiefly with a view to the explanation I shall hereafter attempt to
give you, of the nature of this salutary action, that I have thought
it necessary here to make you acquainted with this acid compound
of nitrogen and oxygen, in connection with the alkaline compound
(ammonia) of the same gas with hydrogen.
Having thus shortly described both the organic elements them-
selves, and such mutual compounds of these elements as appear to
be most concerned in promoting the growth of plants, we are pre-
pared for entering upon the consideration of several very import-
tant questions. These are—
12. From what source do plants derive the organic elements of
which they are composed ?
2°. In what form do plants take them up—or what proof have
we that the compounds above described really enter into plants?
4. e
QUESTIONS TO BE CONSIDERED. 89
3°. By what organs is the food introduced into the circulation
of plants? In consequence of what peculiar structure of these se-
veral parts are plants enabled to take up the compounds by which
they appear to be fed; and what are the functions of these parts,
by the exercise of which the food is appropriated to their own sus-
tenance and further growth 2
4°. By what chemical changes is the food assimilated by plants,
that is—after being introduced into the circulation, through what
series of chemical changes does it pass, before it is converted by the
plant into portions of its own substance 2
5°. By what natural laws or adaptations is the supply of those
compounds, which are the food of plants, kept up 2 Animals are
supported by an unfailing succession of vegetable crops, by the
operation of what invariable laws is food continually provided for
plants? .
. These questions we shall consider in succession.
LECTURE I W.
Source of the organic elements of plants. Source of the carbon. Form in which it
enters into the circulation of plants. Source of the hydrogen. Source of the
oxygen. Source of the nitrogen. Form in which nitrogen enters into the circu-
lation of plants. Absorption of ammonia and nitric acid by plants.
THE first of the series of questions stated at the close of the pre-
ceding lecture, regards the source from which plants derive the
organic elements of which they are composed. They are supported,
it is obvious, at the conjoined expense of the earth and the air—
how much do they owe to each, and for which elements are they
chiefly and immediately indebted to the soil, and for which to the
atmosphere? We must first consider the source of each element
separately.
§ 1. Source of the carbon of plants.
We have already seen reason to believe that carbon is incapable
of entering directly, in its solid state, into the circulation of plants.
It is generally considered, indeed, that solid substances of every
kind are unfit for being taken up by the organs of plants, and that
only such as are in the liquid or gaseous state can be absorbed by
the minute vessels of which the cellular substance of the roots and
leaves of plants are composed. Carbon, therefore, must enter
either in the gaseous or liquid form, but from what source must it
be derived 2 There are but two sources from which it can be ob-
tained, the soil in which the plant grows
its stem and leaves are surrounded. * ,
In the soil much vegetable matter is often present, and the
farmer adds vegetable manure in large quantities with the view of
providing food for his intended crop. Are plants really fed by
the vegetable matter which exists in the soil, or by the vegetable
manure that is added to it?
and the air by which
WHENCE PLANT'S DERIVE THEIR CARBON. 91
This question has an important practical bearing. Let us,
therefore, submit it to a thorough examination.
1°. We know, from sacred history, what reason and science
concur in confirming, that there was a time when no vegetable
matter existed in the soil which then overspread the earth's Sur-
face. The first plants must have grown without the aid of either
animal or vegetable matter—that is, they must have been nourish-
ed from the air.
2°. It is known that certain marly soils, raised from a great
depth beneath the surface, and containing apparently no vegetable
matter, will yet, without manure, yield luxuriant crops. Must
not the carbon in such cases be derived from the air P
3°. Some plants grow and increase in size when suspended in
the atmosphere, and without being in contact with the soil. Others,
again,-bulbous flower roots for example—will grow and flourish
in pure water only, provided they are open to the access of the
atmospheric air. Seeds also will germinate, and, when duly water-
ed, will rise into plants, though sown in substances that contain
no trace of vegetable matter.
Thus De Saussure found that two beans, when caused to vege-
tate in the open air on pounded flints, doubled the weight of the
carbon they originally contained.
Under similar circumstances Boussingault found the seeds of
trefoil increase in weight 2% times, while wheat gave him plants
equal in weight, when dry, to twice that of the original grains.”
The source of the carbon in all these cases cannot be doubted.
4°. When lands are impoverished, you lay them down to grass,
and the longer they lie undisturbed, the richer in vegetable matter
do they in many cases become. When broken up, you find a
black fertile mould where comparatively little organic matter had
previously existed. -
The same observation applies to land long under wood. The
vegetable matter increases, the soil improves, and when cleared
and ploughed it yields, not unfrequently, abundant crops of corn,
Do grasses and trees derive their carbon from the soil? Then
how, by their growth, do they increase the quantity of carbona-
ceous matter which the soil contains? It is obvious that, taken as
* Ann, de Chim, et de Phys. lxvii. p. 1.
92 GROWTH OF PEAT.
a whole, they must draw from the air not only as much as is con-
tained in their own substance, but an excess also, which they im-
part to the soil.
5°. But on this point the rapid growth of peat may be considered
as absolutely conclusive. A tree falls across a little running
stream, dams up the water, and produces a marshy spot. Rushes
and reeds spring up, mosses take root and grow. Year after year
new shoots are sent forth, and the old plants die. Vegetable
matter accumulates, a bog is formed, and finally a thick bed of peat.
Nor does this peat form and accumulate at the expense of one
species or genus of plants only. Latitude and local situation are
the circumstances which chiefly affect this accumulation of vege-
table matter on the soil. In our own country, the lowest layers
of peat are formed of aquatic plants, the next of mosses, and the
highest of heath. In Tierra del Fuego “nearly every patch of
level ground is covered by two species of plants (astelia pumila of
Brown and donatia magellanica), which, by their joint decay, com-
pose a thick bed of elastic peat.” In the Falkland Islands almost
every kind of plant, even the coarse grass which covers the whole
surface of the islands, becomes converted into this substance.*
Whence have all these plants derived their carbon 2 The quan-
tity originally contained in the soil is, after a lapse of years, in-
creased a thousand fold. Has dead matter the power of reprodu-
cing itself? You will answer at once, that all these plants must
have grown at the expense of the air, must have lived on the car-
bon it was capable of affording them, and as they died must have
left this carbon in a state in which it was for the most part unfit
to nourish the succeeding races.
This reasoning appears unobjectionable, and, from the entire
group of facts; we seem to be justified in concluding that plants
every where, and under all circumstances, derive the whole of
their carbon from the atmosphere.
But the justice of this as a general conclusion is only apparent.
In certain extreme cases, as in those of plants growing in the air
and in soils perfectly void of organic matter, it must be absolutely
* Darwin's Researches in Geology and Natural History, pp. 349–50. Dr Greville
informs me that the astelia approaches more nearly to the junceae or rush tribe, and
the donatia to our tufted saxifrages, than to any other British plants.
THE VEGETABLE MATTER OF THE SOIL, 93
true. The phenomena admit of no other interpretation. But is
it as strictly true of the more usual forms of vegetable life, or in
the ordinary circumstances in which plants grow spontaneously or
are cultivated by the art of man P. Has the vegetable matter of
the soil no connection with the growth of trees or herbage?—does
it yield them no regular supplies of nourishment P Does nature
every where form a vegetable mould on which her wild flowers may
blossom and her primeval forests raise their lofty heads 2 Has the
agricultural experience of all ages and of all countries led the prac-
tical farmer to imitate mature in preparing such a soil? Does na-
ture work in vain 2–is all this experience to be at once rejected P
While we draw conclusions legitimate in kind, we must be cau-
tious how, in degree, we extend them beyond our premises.
The consideration of one or two facts will show that our gene-
ral conclusion must be either modified or more cautiously expressed.
1°. It is true that plants will, in certain circumstances, grow in
a soil containing no Sensible quantity of organic matter—but it is
also true, generally, that they do not luxuriate or readily ripen
their seed in such a soil.”
2°. It is consistent with almost universal observation, that the
same soil is more productive when organic matter is present, than .
when it is wholly absent. *
3°. That if the crop be carried off a field of arable land, less or-
ganic matter is left in the soil than it contained when the crop be-
gan to grow, and that by constant cropping the soil is gradually
exhausted of organic matter.
Now it must be granted that tillage alone, without cropping,
would gradually lessen the amount of organic matter in the soil,
by continually exposing it to the air, and thus hastening its de-
cay and consequent change into gaseous substances which escape
into the atmosphere. But two years' open fallow, with constant
stirring of the land, will not rob it of vegetable matter so effectu-
ally as one year of such fallow succeeded by a crop of wheat, with-
out manure. Some of the vegetable matter, therefore, which the
soil contained when the seed was sown, must be carried off the
field in the crop.
**
* Boussingault found peas to ripen their seed fully in pure sand and in the open air,
when watered only with distilled water.—Ann, de Chim, et de Phys. lxix. p. 353.
94 A SOURCE OF FOOD TO PLANTS.
The conclusion, therefore, seems to be reasonable and legiti-
mate, that the crop which we remove from a field has not derived
all its carbon directly from the air—but has extracted a portion of
it immediately from the soil. It is to supply this supposed loss,
that the practical farmer finds it necessary to restore to the land
in the form of manure—among other substances—the carbon also
of which the straw or hay had robbed the soil.
But how is this reconcilable with our previous conclusion, that
the whole of the carbon has originally been derived from the air
The difficulty is of easy solution.
A seed germinates in a soil in which no vegetable matter exists;
it sprouts vigorously, increases then slowly, grows languidly at the
expense of the air, and the plant dies stunted or immature. But,
in dying it imparts a portion of vegetable matter to the soil, on
which the next seed thrives better than the first did—drawing sup-
port not only from the air, but by its roots from the soil also.
The death of this second plant enriches the soil further, and thus,
while each succeeding plant is partly nourished by food from the
earth, yet each, when it ceases to live, imparts to the soil all the
carbon which during its life it had extracted from the air. Let
the quantity which each plant thus returns to the soil exceed what
it has drawn from it by only one ten-thousandth of the whole,
and—unless other causes intervene—the vegetable matter in the
soil must increase.
Thus, whilst it is strictly true that all the carbon contained in
plants has been originally derived from the air—it is not true that
the whole of what is contained in any one crop we raise, is directly
derived from the atmosphere—the proportion it draws from the
soil is dependent upon numerous and varied circumstances.”
The history of vegetable growth, therefore—in so far, at least,
as the increase of the carbon is concerned—may be thus simply
stated:— -
1°. A plant grows partly at the expense of the soil, and partly
at that of the air. After it has reached maturity, or when winter
arrives, it dies. The dead vegetable matter decays. Part of it is
resolved into gaseous matter and escapes into the air, part remains
* For an estimate of the relative quantities of carbon drawn from the soil and from
the air by different crops under different circumstances, see Lecture VIII.
How THE VEGETABLE MATTER INCREASEs. 95
and is incorporated with the soil. If that which remains be greater
in quantity than that which the plant in growing derived from
the soil, the vegetable matter will increase; if less, it will diminish.
2°. In warm climates the decay of dead vegetable matter is more
rapid, and therefore the portion left in the soil will be less than in
more temperate regions—in other words, the vegetable matter in
the soil will increase less rapidly—it may not increase at all.
3°. As we advance into colder countries, the decay and disap-
pearance of dead vegetable matter, in the form of gaseous sub-.
stances which escape into the atmosphere, become more slow—till
at length, between the parallels of 40° and 50°, it begins to accu-
mulate in vast quantities in favourable situations, forming peat bogs
of greater or less extent. While the living plant here, as in warm
climates, derives carbon both from the earth and from the air, the
dead plant, during its slow and partial decay, restores compara-
tively little to the atmosphere, and, therefore, adds more rapidly to
the vegetable matter of the soil.
4°. Again, in one and the same climate, the decay of vegetable
matter, and its conversion into gaseous substances is more rapid,
in proportion to the frequency with which it is disturbed or ex-
posed to the action of the sun and air. Hence this decay may
be comparatively slow in shady woods and in fields covered by a
thick sward of grass, and in such situations organic matter may
accumulate—while, in the same district, it may rapidly diminish
where the soil is uncovered, or where the fields are repeatedly
ploughed and subjected to frequent cropping.” -
Being thus fitted, by nature, to draw their sustenance—now
from the earth, now from the air, and now from both, according
as they can most readily obtain it—plants are capable of living—
though rarely a robust life—at the expense of either. The pro-
portion of their food which they actually derive from each source
will depend upon many circumstances—on the nature of the plant
itself—on the period of its growth—on the soil in which it is plant-
ed—on the abundance of food presented to either extremity—on
the warmth and moisture of the climate—on the duration and in-
* In removing a crop we take away both what the plants have received from the
earth and what they have absorbed from the air—the materials, in short, intended by
nature to restore the loss of vegetable matter arising from the natural decay.
96 PLANTS PARTI.Y SUPPORTED BY THE AIR.
tensity of the sunshine—on the consequent rapidity of growth
and on other circumstances of a similar kind—so that the only
general law seems to be, that, like animals, plants also have
the power of adapting themselves, to a certain extent, to the con-
ditions in which they are placed; and of supporting life for a time
by the aid of such organic sustenance as may be within their reach.
Such a view of the course of mature in the vegetable kingdom,
is consistent, I believe, with all known facts. And that the Deity
has bountifully fitted the various orders of plants—with which the
surface of the earth is beautified and at the same time rendered
capable of supporting animal life—to draw their nourishment, in
some spots more from the air, in others more from the soil, is only
in accordance with the numerous provisions we everywhere per-
ceive, for the preservation and continuance of the present condi-
tion of things. -
By taking a one-sided view of nature, we may arrive at startling
conclusions—correct, if taken as partial truths, yet false, if advan-
ced as general propositions, and fitted to lead into error such as
have not the requisite knowledge to enable them to judge for them-
selves—or such as, doubtful of their own judgment, are willing to |
yield assent to the authority of a name.
Of this kind appears, at first sight, to be the broad statement of
Liebig, that “when a plant is quite matured, and when the organs
by which it obtains food from the atmosphere are formed, the car-
bonic acid of the soil is no further required”—and that, “during
the heat of summer, it derives its carbon exclusively from the at-
mosphere.”
A little consideration will show us that, while the proposition
contained in the former of these two quotations may be entertain-
ed and advanced as a matter of opinion—the latter is obviously in-
correct. In summer, when the sun shines the brightest, and for
the greatest number of hours, the evaporation from the leaves of
all plants (their insensible perspiration) is the greatestſ—the largest
supply of water, therefore, must at this season be absorbed by the
roots, and transmitted upwards to the leaves. But this water, be-
fore it enters the roots, has dissolved carbonic and humic acids and
* Organic Chemistry applied to Agriculture, p. 48.
+ Lindley's Theory of Horticulture, p. 49.
FORM IN WHICH CARBON ENTERS PLANTS. 97
other soluble substances from the air and from the soil, in as large
quantity at this period as at any other during the growth of the
plant; and these substances it will carry with it in its progress
through the roots and the stein.
Are the functions of the root changed at this stage of the plant's
growth? Do they now absorb pure water only, carefully separat-
ing and refusing to admit even such substances as are held in solu-
tion by it 2 Or do the same materials which minister to the growth
of the plant in its earlier stages, now pass upwards to the leaf and re-
turn again in the course of the circulation unchanged and unem-
ployed, to be again rejected at the roots? Does all this take
place in the height of summer, while the plant is still rapidly in-
creasing in size? The opinion is neither supported by facts nor
consistent with analogy.
But such an opinion,-however the hasty words above quoted
may mislead some, is not intended to be advanced even by Lie-
big; for, in the following page he says, that “the power which
roots possess of taking up nourishment does not cease so long as
nutriment is present.” In summer, therefore, as well as in spring
or in autumn, the plant must be ever absorbing nourishment by
these roots, if the soil is capable of affording it—and thus, in the
general vegetation of the globe, the increase of carbon in growing
plants must, at every season of the year, be partly derived from
the vegetable matter of the soil in which they grow.
§ 2. Form in which carbon enters into the circulation of Plants.
If we suppose it to be established that the whole of the carbon
contained in plants has originally been derived from the air—we
have only to inquire in what state this element exists in the atmo-
sphere, in order to satisfy ourselves as to the form of combination
in which it must have been received into the circulation of the ear-
liest living vegetables. In considering the constitution of the at-
mosphere in the preceding lecture, it was stated that carbonic acid,
a compound of carbon and oxygen, is always present in it. Though
diffused through the air in comparatively small quantity only, yet
this gas is every where to be detected, while no other compound
of carbon is to be found in it in any appreciable quantity. It is
probable, therefore, that from this gaseous carbonic acid the whole
G
98 LEAVIES AND ROOTS ABSORB CARBONIC ACID.
of the carbon contained in plants has been primarily derived. This
conclusion is supported by the observation so frequently made, that
the leaves of plants in sunshine absorb carbonic acid, and that
plants die in an atmosphere from which this gas is entirely exclud-
ed. (See Lecture V.) -
But we have seen reason to believe that, under existing circum-
stances, plants also extract a portion of the carbon they contain
from the soil in which they grow. In what state or form of com-
bination do the roots absorb carbon 2
1°. The most abundant among the ultimate products of the de-
cay of vegetable matter in the soil, is the same carbonic acid
which plants inhale so largely from the atmosphere by their leaves.
In a soil replete with vegetable matter, therefore, the roots are
surrounded by an atmosphere more or less charged with carbonic
acid. Hence if they are capable of inhaling gaseous substances,
this gas will enter the roots in the aëriform state—if not, it must en-
ter in solution in the water, which the roots drink in so largely, to
supply the constant waste caused by the insensible perspiration of
the leaves.
Thus from the earth as from the air plants draw a certain por-
tion of their carbon in the form of carbonic acid.
2°. During the early fermentation of artificial manures there is
also developed in the soil a variable proportion of light carbu-
retted hydrogen (p. 66), which is supposed by some to enter occa-
sionally into the roots. That it does enter, however, is doubt-
ful,-and we are safe, I think, in the present state of our know-
ledge, in considering this compound not only as an uncertain
source of the carbon of plants, but as one from which, in the most
favourable circumstances, they can derive only a small supply.
3°. But as water passes through the soil it takes up inorganic
substances — potash, soda, lime, magnesia—and conveys them
through the roots into the circulation of the plants. Can it refuse
to take up and to perform a similar office to the soluble organic
substances—the humic, ulmic, and geic acids—it meets with, as it
sinks through the soil? Or do the spongioles of the roots keep
a perpetual watch over the entering waters, to prevent the intro-
duction of every soluble form of carbon but that of carbonic acidº
Or, supposing such substances introduced into the interior of the
3
ROOTS ABSORB ORGANIC SUBSTANCES ALSO. 99
plant, are none of them digested there and converted to the gene-
ral purposes of food? A statement of two or three facts will af-
ford a satisfactory reply to these several questions.
a. When plants are made to grow in infusions of madder the
radicle fibres are tinged of a red colour.
b. The flower of a white hyacinth becomes red after a few hours,
when the earth in which it is planted is sprinkled with the juice of
the Phytolaca decandra (Biot.)
Therefore organic substances can enter into the roots, and thence
into the circulation of the plant.
c. The colour of the madder does not usually extend upwards to
the leaves and flowers of the living plant.
d. The colour imparted to the flower of the white hyacinth dis-
appears in the sunshine in the course of a few days.
e. Brown solutions of humate of potash are absorbed by the
roots, but the colour is not seen in the sap beyond the spongy ex-
tremities of the roots (Trinchinetti.)
Organic colouring matters, therefore, undergo a chemical change
either in the root, in the stem, in the leaf, or in the flower—some
sooner, some later—and the same is probably the case with most
other organic substances which gain admission into the interior of
plants.
f. Sir Humphry Davy introduced plants of mint into weak solu-
tions of sugar, gum, jelly, the tanning principle, &c., and found
that they grew vigorously in all of them. He then watered
separate spots of grass with the same several solutions, and with
common water, and found all to thrive more than that to which
common water was applied—while those treated with sugar, gum,
and gelatin grew luxuriantly.”
Therefore different organic substances are capable of being in-
troduced into the circulation and there changed, or being changed
at the moment of their introduction, are capable of being converted
by plants into their own substance—in other words, they act as
food, and nourish the plant.
g. The same is proved, less directly, but in an equally satisfac-
tory manner, by the production of mould plants on various animal
and vegetable substances. The mould upon cheese is fed by the
** *
e tº
* Agricultural Chemistry, ſectiº Wi. : •:
:
100 SOURCE OF THE EIY DROGEN OF PLANTS.
organic substances of the cheese itself, without their having been first
converted into carbonic acid or any other gaseous substance. So
mould forms upon syrups, and jellies, and vegetable extracts, the
soluble sugar, and other substancesin which, no doubt directly feed
these growing plants. Even uponsolutions of tartaric acid or vinegar
inclosed in bottles, these vegetable moulds are produced—while the
quantity of acid gradually diminishes. No fermentation or other
evidence of the production of gaseous matter is seen, and yet the
vinegar becomes tasteless, and at the same time thick and ropy
with the minute plants produced in it, (Mulder.) Is it possible
here to resist the conclusion that the vinegar has entered directly
into their circulation, and has been changed into part of their sub-
stance?
h. Further, tuberous roots, like the potato, not unfrequently
throw out shoots under ground or in the potato pits, which never
produce leaves, but at the extremity of which young potatoes are pro-
duced directly from the substance of the parent tuber. Such young
tubers grow even in immediate contact with the old potato with-
out any visible shoot being made; they are not unfrequently found
also in the heart of the old potato itself. Here, them,--as when
a plant grows from a seed, or as when a bud shoots out from a
free in spring, organic matter fully formed proceeds at once to
build up new plants or tubers. It is unreasonable to suppose that
organic matter taken up from the soil cannot be turned by the
growing plant to a similar use.
We may consider it, therefore, to be satisfactorily established
that, while a plant sucks in by its leaves much carbon in the form
of carbonic acid—and perhaps also some of the same gas by its
roots—it derives a variable portion of its immediate sustenance (of
its carbon) from the soluble organic substances that are within
reach of its roots. Of course the quantity thus taken up will vary
with the nature and comparative abundance of the organic matter
contained in the soil.
This fact is never doubted by the practical husbandman. It
forms the basis of many of his daily and most important operations,
while the results of these operations are further proofs of the fact.
::$3...Source of the hydrogen of plants.
The sourcé ºf théºydrºgen of plants is less doubtful, and will
4.
WATER THE PRINCIPAL SOURCE. I01
require less illustration, than the source of their carbon. This ele-
mentary substance is not known to exist in nature in an uncom-
bined state, and, therefore, it must, like carbon, enter into plants
in union with some other element.
1". Water has been already shown to consist of hydrogen in
combination with oxygen. In the form of vapour, this compound
pervades the atmosphere and plays among the leaves of plants,
while in the liquid state it is diffused through the soil, and is un-
ceasingly drunk in by the roots of all living vegetables. In the
interior of plants—at least during their growth—this water is con-
tinually undergoing decomposition, and it is unquestionably the
chief source of the hydrogen which enters into the constitution of
their several parts. In explaining the properties of water I have
already dwelt upon the apparent facility with which its elements
are capable either of separating from, or of re-uniting to each
other, in the vascular system of animals or of plants. The reason
as well as the precise results of these transformations we shall here-
after consider.
2°. In light carburetted hydrogen (CH2) given off as already
stated during the decay of vegetable matter, and said to be always
present in highly manured soils, this element, hydrogen, exists to
the amount of nearly one-fourth of its weight. On the extent,
therefore, to which this gaseous compound gains admission into
the roots of plants, will depend the supply of hydrogen which they
are capable of drawing from this source. Had we satisfactory evi-
dence of the actual absorption of this (marsh) gas by the roots or
leaves of plants, in any quantity, we should have no difficulty in
admitting that plants might, from this source, easily obtain a con-
siderable supply both of carbon and of hydrogen. It would be
also easy to explain how (that is, by what chemical changes), it is
capable of being so appropriated. But the extent to which it
really acts as food to living vegetables is entirely unknown.
3°. Ammonia is another compound, containing much hydrogen,*
which, as I have already stated, exercises a manifest influence on
the growth of plants. If this substance enter into their circula-
tion in any sensible quantity,+if, as some maintain, it be not only
* Its formula being NH, or one equivalent of nitrogen and three of hydrogen, (p.
78.)
102 SOURCE OF THE OXYGEN.
universally diffused throughout nature, but is constantly affecting,
and influencing at all times, the universal functions of vegetation
—there can be no doubt that the hydrogen it contains must, to an
equal extent, be concerned in the production of the various or—
ganic substances, which are formed through the agency of vege-
table life. How far this probable interference of the hydrogen
contained in ammonia with the functions of the vegetable organs,
will tend to explain or illustrate the influence actually exerted by
this compound, we shall, by and bye, more minutely inquire. In
the meantime, the quantity of ammonia, which actually enters into
the circulation of plants in a state of mature, is too little known,
and, making the largest allowance, probably too minute, to permit
us to consider it as an important source of hydrogen to the general
vegetation of the globe.
4°. The soluble organic substances, which enter into the circu-
lation of plants through their roots, the humic, ulmic, and geic
acids, described in the previous lecture, do not all consist of car-
bon and water only. Some of them, the ulmic group for exam-
ple, are combinations of carbon and water, with an excess of hydro-
gen (p. 69). From these compounds, therefore, plants derive an
indefinite supply of hydrogen in a state already half-organized,
and probably, still more easily assimilated or converted into por-
tions of their own substance, than when this element is combined
with oxygen in the form of water. -
We may, therefore, conclude generally in regard to the source
of the hydrogen of plants—that though there are undoubtedly
several other forms of combination in which this element en-
ters into their circulation, and ministers to their growth, yet
that all-pervading water is the main source, from which the
largest proportion of the hydrogen of vegetable substances is
derived.
§ 4. Source of the oxygen of plants.
We can easily and at once perceive the various sources of the
oxygen of plants; though it is difficult in this case also to say how
much they derive from each.
1°. The water which they imbibe so largely consists in great
SOURCE OF THE NITROGEN. • -' I 03
part of oxygen," and is easily decomposed. This alone would
yield an inexhaustible supply. -
2°. The atmosphere contains 21 per cent. of its bulk of oxygen,
and the leaves of plants in certain circumstances—as during the
absence of the sun–are known to absorb this oxygen. The air
in which they live, therefore, is another source of this element.
3°. Carbonic acid contains 72 per cent. by weight of oxygen,
and this gas is also known to be absorbed in large quantity from
the atmosphere by the leaves of plants—while its solution in water
is admitted readily by their roots.
4°. Nearly all the known forms of organic food which plants
take in by their roots, contain in combination a certain proportion
of oxygen, and this oxygen they of course yield to the growing
plant, when they are changed into a part of its substance.
From any one of these, and especially from any of the three
first mentioned sources, an ample supply of oxygen might readily be
obtained by plants, and it may be considered as a proof of the vast
importance of this element to the maintenance of animal and vege-
table life, that it is every where placed so abundantly within the
reach of living beings. It is from the first of these sources, how-
ever, from the water they contain, that plants are believed to
derive their principal supply. The reasons on which this opinion
is founded will appear, when we shall have considered the func-
tions of the several parts of plants, and the chemical changes to
which the food is subjected in the course of the vegetable circula-
tion.
§ 5. Source of the nitrogen of plants.
The quantity of nitrogen present in plants is very small com-
pared with that of any of the other elements which enter into
their composition. Of this you will be reminded, by a reference
to the analyses of hay, oats, potatoes, &c., exhibited in the second
lecture (page 37), which shew that the nitrogen contained in these
several crops, when perfectly dried at 240° F., is respectively 14,
2}, and 13 per cent. In the state in which they are usually given
to cattle they contain a still less per-centage of nitrogen, in conse-
quence of the quantity of water still present in them. Thus raw
* Eight-ninths of the weight of water are oxygen.
104 QUANTITY OF NITROGEN COMPARATIVELY SMALL
potatoes, as they are given to cattle, contain only # of a per cent.
of nitrogen, hay 13 per cent, and oats 11%" per cent, or a hun-
dred pounds of each contain 5 ounces, 1 pound 5 ounces, and
pound 14 ounces respectively.
It would appear at first sight as if this small quantity of nitro-
gen could be of little importance to the plant, especially since, as
we shall hereafter see, it does not enter as a constituent into those
vegetable substances, such as woody fibre, starch, sugar, and gum,
which plants produce in the greatest abundance, and of which their
own stems and branches chiefly consist. The same remark,
however, applies to this, as to many other cases which present them-
selves to the chemist, during his analyses, especially of organized
substances, that those elements which are present only in Small
quantity are as necessary, as essential, to the constitution of the
particular substance in which they occur, as other elements are of
which they contain much ; and that if these small quantities are
removed or absent, not only are the physical and chemical proper.
ties of the substance materially altered, but it is found also to ex-
ercise a very different influence on animal and vegetable life. This
latter observation will present itself to you in a very striking light,
when we come hereafter to study the nutritive properties of the
several kinds of food by which animals are chiefly supported,—and
to see on what elementary bodies their nutritive properties depend,
and by the presence of what substances their relative values are
theoretically indicated.
But a consideration of the absolute quantity of nitrogen con-
tained in an entire crop will satisfy you that, though small in com-
parative amount,” this element cannot be without its due share of
importance in reference to vegetable life. Hay, as above stated,
contains, as it is stacked, 1 }; per cent. of nitrogen, or a ton of
* 0:33, 1:29, and 1.87 per cent.—the potatoes containing also 72 per cent. of water,
the hay 14, and the oats 15 per cent.
+ That is, compared with the carbon and oxygen which plants contain.
: In different crops of hay Boussingault found in three several years the following
proportions of nitrogen –
Hay, as commonly Hay dried at
stacked. 230 F.
In 1836 ............ 1'04 of nitrogen per cent.......... . . . * * * * * * * * } •] 8
1838 ...... ... I'lb ..... . . . . . . . . . . . . . . . . . . . . . • * * * * ~ *- ºr a ſe s s e s & l' 3.
BUT ABSOLUTELY LARGE. J 05
hay contains 30 lbs. of this element. A good crop of hay, on land
which is depastured during the winter, will amount to 2 or 24 tons"
per acre. Taking two tons as an average, the hay from one acre
will contain 60 lbs. of nitrogen, or from 100 acres 6000 lbs., equal
to 23 tons of nitrogen.
Allowing, therefore, nothing for the aftermath, and supposing
the other crops to contain no more nitrogen than the hay does, the
farmer of five hundred acres will annually carry into his stack-yard
at least 13 tons of nitrogen in the form of hay, straw, grain, and
other produce.f
Nature performs all her operations on a large scale, and the
quantity of materials she employs is large in a corresponding de-
gree. Hence, though comparatively small, the nitrogen in vege-
table substances is absolutely large. You cannot suppose, when
viewed in this light, that nitrogen is an element of little consequence
in reference to vegetable life; or that in nature it would be so
constantly and so universally diffused without reference to some
important end. If I may be allowed a familiar illustration of the
mode in which small quantities of matter will affect the sensible
properties of large masses, I would recal to your minds the effects.
of seasoning upon food, in imparting, when added in small quantity
only, an agreeable relish to what would otherwise be insipid. But
I need not dwell on this point, since I shall hereafter have occa-
sion to draw your attention to certain facts in reference to the con-
stitution of the atmosphere, which will satisfy you that by the agency
of comparatively feeble causes, gigantic effects are continually pro-
duced in nature, and that we can scarcely fall into a graver
error in reasoning of natural processes, than by overlooking the
Hay, as commonly Hay dried at
stacked. 230 F.
In 1839 ...... . ... l” … - ..... .................. l'5
... Aftermath...... 2.0 ........................ * * * * * * * * * * * * * * * * * * * * 2-4
* The Rev. Mr Ogle of Kirkley, Northumberland, informs me that some of his
land near the Hall has yielded annually at this rate for 100 years, and without other
manure than the droppings from the cattle which have fed upon it.
+ This average estimate gives but an inaccurate idea of the quantity actually con-
tained in some species of crops. Thus red clover with the aid of gypsum will yield
3 tons of hay per acre. This hay contains one-third more nitrogen than common
hay does, hence an acre of such hay would contain at least 120 lbs, of nitrogen. (See
Electure II., p. 37.)
106 THE ATMOSPHERE THE PRIMARY SOURCE OF NITROGEN.
agency of forms of matter which present themselves to our senses
in minute quantity only. In reference to insect life this truth has
been long established. In the coral reefs you are familiar with
the wonderful results of the persevering labour of minute animals
in one element. When I come to explain the nature and origin
of soils, I shall have occasion to show that even the element on
which you labour—the soil on the cultivation of which your thoughts
and hands are daily employed—is occasionally indebted for some
of its most valuable properties to a similar agency, often unseen
by you, and though working for your good, unheeded and un-
thought of. *:k
Whence, then, is this nitrogen derived by plants? The pri-
mary source it is not difficult to see. We can arrive at it by a
train of reasoning similar to that which led us to the atmosphere
as the original source of the carbon of plants. Nitrogen does not
constitute an ingredient of any of the solid rocks,” nor do we know
any other source than the atmosphere from which it can be ob-
tained in very large quantity. It exists, as we have seen, in many
vegetables, and it is more largely present in animal substances,
but these organized matters must themselves have drawn this ele-
ment from a foreign source, and the atmosphere is the only one
from which we can fairly assume it to have been originally derived.
But though the nitrogen, like the carbon of plants, may thus be
traced to the atmosphere—as its original source—it does not fol-
low that this element is either absorbed directly from the air, or in
an uncombined and gaseous state. Though the leaves of trees
and herbs are continually surrounded by nitrogen, yet the consti-
tution of plants may be unfitted for absorbing it by their leaves.
The nitrogen may not only require to be in a state of combination
before it can enter into the circulation, but it may also be capable
of gaining admission only by the roots. These points are consi-
dered in the following section.
§ 6. Form in which the nitrogen enters into the circulation of plants.
The question as to the form in which nitrogen enters into the
* Except coal, and coal itself is of vegetable origin. Throughout all rocks in which
organic remains are found, more or less animal matter containing nitrogen is to be
met with, but these remains are only accidentally present, and they must have derived
their nitrogen during life, either directly or indirectly, from the atmosphere,
Do THE LEAVES ABSORB NITROGEN ? 107
circulation of plants is one which, to the practical man, is of much
importance. It will be proper, therefore, to discuss it with consi-
derable care. sº
1°. It is considered an essential part of good tillage to break up
and loosen the soil—in order that the air may have access to the
dead vegetable matter, as well as to the living roots which descend
to considerable depths beneath the surface. When thus admitted
to the roots, it is not impossible that some of the nitrogen of the
atmosphere, as well as some of its oxygen, may be directly absorb-
ed and appropriated by the plant. To what extent this absorption
of nitrogen may proceed, however, we have as yet no experimental
results from which we can form any estimate. Whether it takes
place at all or not is wholly a matter of opinion.
2°. The leaves of plants, as will be more fully explained here-
after, absorb certain gaseous substances from the atmosphere, and
we might, therefore, expect that some of the nitrogen of the air
would, by this channel, be admitted into their circulation. This
supposition, however, is not confirmed as a general fact by any of
the experiments hitherto made with the view of investigating the
action and function of the leaves. * We are not at liberty, there-
fore, to assume as certain that any of the nitrogen which our cul-
tivated plants contain has in this way been derived directly from
* See subsequent lecture, $ 5, “On the functions of the leaves.”
The experiments above referred to were made upon plants growing in close ves-
sels, the air contained in which was measured and examined (analysed) both before
the plants were introduced and after they had been some time in the vessel. In these
experiments the bulk of the nitrogen present has sometimes been observed to increase,
but never to diminish in quantity. The conclusion seems satisfactory, that no nitro-
gen is abstracted directly from the atmosphere by the leaves of plants. Yet Bous-
singault very justly remarks, that a diminution in the bulk of the nitrogen too small
to be detected in the ordinary mode of making these experiments, would be sufficient
to account for a considerable portion of that comparatively small quantity of nitrogen
which is present in all living plants. While, therefore, we accord their due weight to
these researches of the vegetable physiologists, we are not to consider them as by any
means decisive of the question. With this rational and cautious conclusion, Liebig
is not satisfied ; he says, “We have not the slightest reason for believing that the ni-
trogen of the atmosphere takes part in the processes of assimilation of plants and ani-
mals; on the contrary, we know that many plants emit the nitrogen which is ab-
sorbed by their roots either in the gaseous form or in solution in water.” But if they
occasionally expire nitrogen by their leaves, why must this nitrogen be exactly that
portion which has previously been absorbed by the roots in the wºmeombined state, and
the quantity of which is so uncertain and so indefinite 2
I08 RAIN WATER DISSOLVES NITROGEN,
the air. It may be, as Boussingault supposes, that leguminous
plants do absorb nitrogen directly ; but it is not yet proved. *
39. There is a little doubt, however, that nitrogen enters the
roots of plants in a state of solution in water. But the quantity
they thus absorb is uncertain—it is supposed to be small, and
must be variable.
When water is exposed to the air in an open vessel, it gradually
absorbs oxygen and nitrogen, though, as has been stated in a pre-
vious lecture, in proportions different from those in which they
exist in the atmosphere. The whole quantity of the mixed gases
thus taken up amounts to about 4 per cent. of the bulk of the
water (Humboldt and Gay Lussac), and in rain water about 3 of
the whole consist of nitrogen. One hundred cubic inches of rain
water, therefore, will carry into the soil about 2% inches of nitro-
gen gas. But in passing through the soil, the water meets with
other soluble substances before it reaches the roots, especially the
deep-seated roots of plants. It takes up carbonic acid, and it
dissolves solid substances, and in doing so it is a property of water
to give off a portion of the other gases which it had previously
absorbed from the air.
But let us suppose that rain water actually takes to the roots,
and carries with it into the circulation of the plant, 2 per cent, of
its bulk of nitrogen, and let us calculate how much of the nitro-
gen it contains, a crop of hay could in this way derive from the
air.
The quantity of rain that falls at York from the first of March
to the middle of June—during which time the grass grows and
generally ripens—is about five inches.f. On a square foot, there-
* Boussingault details a series of experiments in the course of which he made peas,
trefoil, wheat, and oats grow in the same pure siliceous sand containing no organic
matter, and watered them with the same distilled water. The absolute quantity of
nitrogen increased sensibly in the peas and trefoil during their growth ; in the wheat
and oats no change could be detected by analysis. From these results he is inclined
to infer that the green leaves of the former have the power of sensibly absorbing ni-
trogen from the atmosphere, while those of the latter have not this power—at least.
under the circumstances in which the experiments were made. This conclusion, how-
ever, is not certain, as will presently be shown.—See Ann. de Chim, et de Phys. lxvii.
p. 1, and lxix. p. 353.
+ The result of experiments made in 1834 by Prof. Phillips and Mr Edward Gray.
The mean annual fall of rain at York is about 22 inches,—See fifth Report of the
British Association, p. 173.
AND CARRIES IT INTO THE ROOTS. 109
fore, there fall 720 cubic inches of water, containing 2 per cent.
of their bulk, or 14 cubic inches, of nitrogen, weighing 4} grains.
This gives 28 lbs. for the quantity of nitrogen thus brought to
the soil over an entire acre. But if we consider how the rain falls
in our climate, we cannot suppose the grass in a field to absorb
by its roots, and afterwards perspire by its leaves, more than one-
third of the whole. This quantity would carry with it 9 lbs. of
nitrogen into the circulation of the plants, or little more than a
seventh part of the 60 lbs. which, as we have seen, are taken off
the field in a crop of hay.
But then, besides the water which falls in rain, an unknown
quantity descends in the nightly dew. This will be no less
charged with nitrogen than the rain itself; and although we have
no means of estimating either how much dew falls, or how much
of what does fall is absorbed by plants, yet we cannot avoid ac-
knowledging that through its means a further portion of nitrogen
may be directly conveyed into the circulation of plants.
Still, after allowing for this, the present state of our know-
ledge seems to justify us in concluding that our cultivated plants
derive from the air, in an uncombined state, only a small pro-
portion of the nitrogen they are found to contain. -
4". But plants of lower orders appear to be able directly to
appropriate the nitrogen of the atmosphere. According to Mul-
der, the mould which forms on the surface of vinegar contains
nitrogen (a protein compound), and this mould, he says, is formed
on the surface of pure vinegar contained in a closely stoppered
bottle half-filled with the dilute vinegar, and half with pure at-
mospheric air. The nitrogen contained in this minute plant,
therefore, must have been drawn directly from the air.
We cannot, of course, infer from this fact, that higher orders
of plants are capable of taking in this gas from the air, and work-
ing it up into their substance. It may be, however, that the
minute plants of this kind, which everywhere abound upon the soil,
are a means designed in the economy of nature to draw down and
fix the nitrogen of the atmosphere in a state in which it may be
able to minister to the growth of plants more directly useful to
Iſla [].
As far as we yet know, however, the largest supply of the
II () ABSORPTION OF AMMONIA BY PLANTS,
nitrogen they contain is derived from certain of its compounds
with oxygen and hydrogen, which are known to come within the
reach of their roots and leaves.
The most important of these compounds, and those perhaps
the most extensively concerned in influencing vegetation, are am-
monia and nitric acid, the properties of which have been described
in the preceding lecture.
§ 7. Absorption of ammonia by plants.
It will be recollected that ammonia consists of one equivalent
of nitrogen (N), and three of hydrogen (Hg), and is represented
by NH3. One hundred pounds of it contain 824 lbs. of nitro-
gen, and 17% lbs. of hydrogen.
That ammonia enters directly into the circulation of plants, is
rendered probable by a variety of considerations.
1°. Thus it is found to be actually present in the juices of many
plants. In that of the beet-root (Payen), and in those of the
birch and maple trees, it is associated with came sugar (Liebig),
In the leaves of the tobacco plant, and of scurvy grass, in elder
flowers, and in many fungi," it is in combination with acid sub-
stances, and may be detected by mixing their juices with quick-
lime.
2°. Some plants actually perspire ammonia. Among these is
the Chenopodium Olidum (stinking goosefoot), which is described
by Sir William Hooker as “giving out a most detestable odour,
compared to putrid salt fish.” In the odoriferous matter given
off, ammonia is contained, and may be detected by putting a glass
shade over the plant, and after a time introducing a feather moist-
ened with vinegar or dilute muriatic acid. It is also present in
the odoriferous exhalations of many sweet smelling plants and
flowers.i. -
3°. Nearly all vegetable substances, when distilled with water,
yield an appreciable quantity of ammonia. Thus the leaves of
hyssop, and the flowers of the lime tree, yield distilled waters in
which ammonia can be detected (Schübler); the seeds of plants
* Schübler Agricultur Chemie, II. p. 56.
+ Chevalier Jour. de Pharm. X., p. 100.
ſt Schübler, I., p. 152.
AMMONIA. OBTAINED FROM WIEGETABLES. I 11
thus distilled yield it in abundance (Gay Lussac), and traces of
it may be found in most vegetable extracts (Liebig).
4°. Ammonia is also given off, among other products, when
wood is distilled in iron retorts for the manufacture of pyrolig-
neous acid, and by a similar treatment it may be obtained from
many other vegetable substances.
The above facts, however, are not to be considered as proofs
that ammonia enters directly into the circulation of plants either
by their roots or by their leaves. That which is associated with
sugar in the beet, may have been formed by the same converting
power which, in the interior of the plant, is supposed to produce
the sugar from carbonic acid and water. So, that exhaled by the
leaves of the goosefoot, which grows in waste places especially
near the sea, may have been produced during the upward flow of
the sap, or during its passage over the leaf. And we know that
the nitrogen does not exist in the state of ammonia in the seeds of
plants, or in wood, or in coal—though, from all of them it may
be obtained by the processes above described.
The production of ammonia, by the agency of a high tempera-
ture, may be illustrated by a very familiar experiment often per-
formed, though for a very different purpose. The juice and dried
leaf of tobacco contain nitre (nitrate of potash) and a little ammo-
nia. But when tobacco is burned, ammonia in sensible quantity
is given off along with the smoke, chiefly in the state of carbonate
of ammonia. This may be shown by bringing a lighted cigar
near to reddened litmus paper, when the blue colour will be re-
stored; or to a red rose, when the leaves will become green; or
to a rod dipped in vinegar or in dilute muriatic acid, when a white
cloud will appear.”
In this case a portion of the ammonia given off by the tobacco
is formed during the combustion, at the expense of the nitrogen
contained in the nitrate of potash which is present in the leaf.
5°. But there are other circumstances which are strongly in
favour of the opinion, that ammonia not unfrequently does enter,
as such, into the circulation of plants.
a. Thus it is proved, by long experience, that plants grow most
* Runge, Binleitung in die technische Chemie, p. 375.
| 12 AMMONIA MAY BE ABSORBED.
rapidly and most luxuriantly when supplied with manure contain-
ing substances of animal origin. These substances are usually
applied to the roots or leaves in a state of fermentation or decay,
during which they always evolve ammonia. Putrid urine and
night-soil are rich in ammonia, and they are among the most effi-
cacious of manures. This ammonia is supposed to enter into the
circulation of plants along with the water absorbed by their roots,
and sometimes even by the pores of their leaves. We can scarce-
ly be said to have as yet obtained decisive proof that it does so
enter, but probabilities are strongly in favour of this supposition;
and when we come hereafter to consider minutely the mode in
which it is likely to act, when within the plant, we shall find the
probabilities derived from practical experience to be strengthened
by the deductions of theory.
b. Again, the vegetable matter of the soil, to which no manure
has been artificially added, almost invariably contains ammonia.
The humic, ulmic, and geic acids which exist in the soil have a
tendency, as I have already shown, not only to retain but to form
ammonia when undergoing decay in the presence of air and water.
This ammonia they yield to the roots of growing plants, and it ap-
pears to be one of the natural agents by which they themselves are
rendered soluble in water and capable of finding their way into the
interior of plants.
6°. Yet although the above facts so long observed in reference
to the action of animal manures upon vegetation, as well as the
natural production and presence of ammonia in the soil, justify us
in believing that this compound actually enters into the roots, and
perhaps into the leaves, of plants—we ought not hastily to conclude
that all the nitrogen which plants are capable of deriving from
decaying animal and vegetable matter must enter into their circu-
lation in the form of ammonia. Other soluble compounds con-
taining nitrogen are formed during the decay of animal and vege-
table substances—they actually exist largely in the liquid manures
of the stable and fold-yard, and they can scarcely fail, when ap-
plied to the soil, to be to a certain extent absorbed by the roots of
plants. Thus urea is a substance containing much nitrogen, which
exists in the urine or excrements of most animals, and by its de-
composition produces carbonate of ammonia. But being very
ABSORPTION OF NITRIC ACID, l 13
soluble, this substance may enter directly into the roots, and may
be there decomposed and made to give up its nitrogen to the living
plant. To other compound substances of vegetable as well as of
animal origin the same observation may apply;”—so that while the
fact—that animal manure in a state of fermentation is very bene-
ficial to vegetation, may be considered as rendering it highly pro-
bable that the ammonia, which such manure contains, enters di-
rectly and supplies nitrogen to the growing plants—it must not be
entirely left out of view that, in nature, a portion of the nitrogen,
derived from animal substances, may be obtained immediately from
other compounds in which ammonia does not exist.
To what amount ammonia actually enters into the circulation of
plants, or how much of the nitrogen they contain it actually sup-
plies, we have no means of ascertaining. Were it present in great
abundance in the soil, its easy solubility would enable it to enter,
with the water absorbed by the roots, in almost unlimited quantity.
In a subsequent section we shall consider the conditions under
which ammonia is produced in nature, the comparative abundanee
in which it exists on the earth's surface, and the extent of the in-
fluence it may be slipposed to exercise on the general vegetation of
the globe. - *
§ 8. Absorption of Nitric acid by plants.
1°. That ammonia is actually present in the juices of many
living vegetables has been adduced, as a kind of presumptive evi-
dence, that this compound is directly absorbed by plants. A si-
milar presumption is afforded in favour of the direct entrance of
nitric acid, by its invariable presence in combination with potash,
soda, lime, or magnesia, in the juices of certain common and
* Thus it may be applied more strongly to the hippuric acid, which exists in the
urine of the horse, and other herbivorous animals. This acid decomposes naturally
into benzoic acid and ammonia. The sweet-scented vernal-grass (Anthoacanthwm, odo-
ºratwm) by which hay is perfumed, owes its agreeable odour to the presence of this
benzoic acid. It may, therefore, be supposed that, where cattle and horses graze, the
grasses actually absorb the hippwric acid contained in the urine which reaches their
roots, decompose it as it ascends with the sap, appropriate its mitrogen, and exhale the
odoriferous benzoic acid. The very interesting observation has recently been made,
that hippuric acid is often present in human urine, indicating apparently that from
the benzoic acid of the grasscs the hippuric acid is formed during its passage through
the body of the horse. t
H
114 ITS EFFECT ON WEGETATION.
well known plants. Thus it is always contained in the juice of
tobacco leaves of good quality (Payen), in that of the sunflower,
of goosefoot,” and of common borage. f The nettle also con-
tains it, and it has been detected in the grain of barley. It ex-
ists probably in the juices of many other plants in which it has
not hitherto been sought for. Were we, therefore, entitled, from
the mere presence of this acid in plants, to infer that it had really
entered by their roots or leaves, we should have no hesitation in
drawing our conclusion. But, like ammonia, it may have been
formed in the interior of the living vegetable;' and hence the fact
of its presence proves nothing in regard to the state in which the
nitrogen it contains really entered into the circulation of the plant.
2°. But mitric acid, like ammonia, exerts a powerful influence
on the growing crop, whether of corn or of grass. Animal mat-
ters, as we have seen, give off ammonia during their decay, and
manures are rich and efficacious in proportion to the quantity of
animal manure they contain. The crop produced also is valuable,
and is believed to be rich in mitrogen in like proportion. There-
fore, as already stated, it is inferred that ammonia enters directly
into the living plant, and supplies it with nitrogen.
The effect of nitric acid is similar in kind, and perhaps equal in
degree. Applied to young grass or to sprouting shoots of corn,
it hastens and increases their growth, it occasions a larger produce
of grain, and this grain, as when ammonia is employed, has been
found by some experimenters to be richer in gluten, and therefore
more nutritious in its quality. An equal breadth of the same
field yields a heavier produce, and that produce, weight for weight,
according to the only experiments we at present possess—contains
more nitrogen when saltpetre or nitrate of soda have been applied
in certain quantities to the young plants which grow upon it. It
is reasonable to conclude, therefore, that the acid of the nitrates,
in some form or other, is capable of entering into the circulation
* Chenopodium, probably in all the species of this genus.-See Liebig, p. 82.
+ The dried stalks of borage sometimes burn like match paper from the presence
of nitre.—Loudon's Encyclopædia of Gardening. -
: Thomson, Organic Chemistry, p. 882.
Ś When the beet-root arrives at maturity, the sugar begins to diminish, and salt-
petre or other nitrates to be formed, probably at the expense of the ammonia which
the juice previously contained.—Decroizelles, Jour. de Phar. X, p. 42.
IT YIELDS NITROGEN TO PLANTS. II 5
of living plants—and of yielding to them, in whole or in part, the
nitrogen they contain.
But here, again, as in the case of ammonia, we are at fault in
regard to the quantity of their nitrogen which plants in a state of
nature actually derive from nitric acid or from the nitrates. The
compounds of this acid with potash, soda, lime, and magnesia, (the
nitrates of these substances), are all very soluble in water. The
quantity of this fluid, therefore, which enters by the roots of plants
could easily convey into their circulation far more of these mitrates
than would be alone sufficient to supply the whole of the nitrogen
they require—for the formation of all their parts and products.
But so it might of ammonia or its salts, as has already been shown.
I shall hereafter lay before you certain considerations which may
probably lead us to approximate conclusions in regard to the re-
lative influence exercised by these two compounds on the general
vegetation of the globe. -
Conclusions.—Respecting the form in which nitrogen enters in-
to the circulation of plants, we have, therefore, I think fairly ar-
rived at these deductions:—
1°. That the nitrogen of the atmosphere may, to a small extent,
enter directly into the living vegetable either in the form of gas
or in solution in water, but that supposing nitrogen to be in this
way appropriated” by the plant, the quantity so taken up could
form only a small quantity of that which vegetables actually contain.
2°. That ammonia is capable of entering into plants in very
large quantity, and of yielding nitrogen to them—that it is matu-
rally produced in the soil and is thence taken up by the roots of
plants—and that in European agriculture, which employs ferment-
ing animal and vegetable manures as important means of promot-
ing vegetable growth, ammonia does appear to yield to cultivated
plants a considerable proportion of the nitrogen they contain.
3°. That nitric acid, in like manner, is capable of entering into
and giving up its nitrogen to plants; and that where this acid, in
* Liebig and others say that plants are incapable of appropriating or assimilating
the nitrogen which enters into their circulation in the uncombined state, (Liebig,
p. 70.) We shall consider this question hereafter.
I 16 GENERAL CONCLUSIONS.
the form of nitrate of soda, &c., is employed as an instrument of
culture, the crops obtained owe part of their nitrogen to the quan-
tity of this compound which has been applied to the growing plants.
The same inference may fairly be drawn in regard to the effect of
nitric acid—when in the form of nitrates, it exists or is produced
naturally in the soil.
4°. That other compound bodies containing nitrogen—such as
are contained in urine, or are produced during the decay of ani-
mal and vegetable matter—may also enter into the circulation of
plants and yield nitrogen to promote their growth.
On the whole, however, there seem strong reasons for believing
that plants are mainly dependent on ammonia and nitric acid for
the nitrogen they contain; and that they obtain it most readily,
and with least labour, so to speak, from these compounds,--though
nature has kindly fitted them for deriving a supply from other
sources, when these substances are not present in sufficient abun-
dance.
How far each of these compounds is employed by nature, as an
instrument in promoting the general vegetation of the globe, will
be considered in a subsequent lecture.
LECTURE W.
How does the food enter into the circulation of plants P Structure of the several
parts of plants. Functions of the root, its selecting power. Course of the sap.
- Cause of its ascent. Functions of the stem, of the leaves, and of the bark. Cir
cumstances by which the exercise of these functions is modified.
HAviNG now taken a general view of the source from which plants
derive the elementary substances of which their solid parts consist
and of the states of combination in which these elements enter in-
to the vegetable circulation;—the next step in our inquiry is—
how are these substances admitted into the interior of living plants—
and under what conditions or regulations? We are thus led to
study the structure and functions of the several parts of plants, and
the circumstances by which the exercise of these functions is ob-
served to be modified.
§ 1. General structure of plants, and of their several parts,
Plants consist essentially of three parts—the roots, the stem,
and the leaves. The former spread themselves in various direc-
tions through the soil, as the latter do through the air, and the
stem is dependent for its food and increase on the rapidity with
which the roots shoot out and extend, and on the number and
luxuriance of the leaves.
We shall obtain a clearer idea of the relative structure of these
several parts by first directing our attention to that of the stem.
1°. The Stem consists apparently of four parts—the pith, the
wood, the bark, and the medullary rays. The pith and the me-
dullary rays, however, are similarly constituted, and are only con-
tinuations of one and the same substance. The pith forms a solid
cylinder of soft and spongy matter, which ascends through the cen-
tral part of the stem, and varies in thickness with the species and
with the age of the trunk or branch. The wood surrounds the
pith in the form of a hollow cylinder, and is itself covered
by another hollow cylinder of bark. In trees or branches
II 8 STRUCTURE OF THE STEM OF PIANTS.
of considerable age the wood consists of two parts, the oldest or
heart wood, often of a brownish colour, and the newer external
wood or alburnum, which is generally softer and less dense than
the heart wood. The bark also is easily separated into two por-
tions, the inner bark or liber, and the epidermis or outer covering
of the tree. The pith and the outer bark are connected together
by thin vertical columns or partitions, which intersect the wood
and divide it into triangular segments. A cross section of the
trunk or branch of a tree exhibits these thin columns extending in
the form of rays, or like the spokes of a wheel, from the centre to
the circumference. Though they form in reality thin and conti-
nuous vertical plates, yet from the appearance they present in the
cross section of a piece of wood, they are distinguished by the name
of medullary rays.
These several parts of the stem are composed of bundles of small
tubes or hollow cylindrical vessels of various sizes, and of diffe-
rent kinds, the structure of which it is unnecessary for us to study.
They are all intended to contain liquid and gaseous substances,
and to convey them in a vertical, and sometimes in a horizontal di-
rection. The tubes which compose the wood and the immer bark
are arranged vertically, as may readily be seen on examining a
piece of wood even with the naked eye, and are intended to convey
the sap upwards to the leaves and downwards to the roots. Those
of which the pith, the medullary plates, and the outer bark consist
are arranged horizontally, and appear to be intended to maintain
a lateral intercourse between the pith and the bark—perhaps even
to place the heart of the tree within the influence of the external
air.
2°. The root, though prior in its origin to the perfect stem, may
nevertheless for the purpose of illustration be considered as its down-
ward and lateral prolongation into the earth—as the branches are its
upward prolongation into the air.” When they leave the lower part
* The correctness of this comparison is proved by the fact that, in many trees, the
branch if planted will become a root, and the root if exposed to the air will gradually
be transformed into a branch. The banana in the forest, and the currant tree in our
gardens, are familiar instances of trees spontaneously planting their branches, and
causing them to perform the functions of roots. In like manner “if the stem of a
young plumb or cherry-tree, or of a willow, be bent in the autumn so that one-half of
the top can be laid in the earth—and one-half of the root be at the same time taken
STRUCTURE OF THE ROOT AND LEAVES. | 19
of the trunk of the tree, they differ little in their internal structure
from the stem itself. As they taper off, however, first the heart wood,
and then the pith, gradually disappear, till, towards their extremi-
ties, they consist only of a soft central woody part and its covering
of soft bark. These are connected with, or are respectively pro-
longations of the new wood and bark of the trunk and branches.
At the extreme points of the roots the bark and wood terminate
in a white, soft, spongy mass, full of pores and vessels. It is by
these spongy extremities only, or chiefly, that liquid and gaseous
substances are capable either of entering into, or of making their
escape from, the interior of the root.
3°. The branches and twigs are extensions of the trunk;-and
of the former, the leaves may be considered as a still further ex-
tension. The fibres of the leaf are minute ramifications of the
woody matter of the twigs, are connected through them with the
wood of the branches and stems, and from this wood receive the
sap which they contain. The green part of the leaf may be con-
sidered as a special expansion of the bark, by which it is fitted to
act upon the air, in the same way as the spongy mass into which
the bark is changed at the extremity of the root is fitted to act up-
on the water and other substances it meets with in the soil. For
as the fibres of the leaf are connected with the wood of the stem,
so the green part of the leaf is connected with its bark, and from this
green part the sap first begins to descend towards the root.
§ 2. The functions of the root.
The position in which the roots of plants in their natural state
are generally placed, has hitherto prevented their functions from
being so accurately investigated as those of the leaves and of the
stem. While, therefore, the main purposes they are intended to
serve are universally known and understood, the precise way in
which these ends are accomplished by the roots, and the powers
carefully up, sheltered at first and afterwards gradually exposed to the cold—and if in
the following year the remaining part of the top and root be treated in the same way,
the branches of the top will become roots, and the ramifications of the roots will be-
come branches, producing leaves, flowers, and fruit in due season.”—Loudon's En-
cyclopædia of Agriculture. The tree is thus reversed in position, and the roots and
branches being thus mutually convertible cannot be materially unlike in general
Structure,
| 20 ROOTS ABSORB AQUEOUS SOLUTIONS.
with which they are invested, are still, to a considerable degree,
matters of dispute.
1°. It appears certain that they are possessed of the power of
absorbing water in large quantity from the soil, and of transmit-
ting it upwards to the stem. The amount of water thus absorbed
depends greatly upon the nature of the soil and of the climate in
which a plant grows, but much also upon the specific structure of
its leaves, and the extent of its foliage.
2°. The similarity of the roots to the young twigs and leaves
(see note, p. 107,) which absorb gases from the atmosphere, would
lead us to suppose that, when in a proper state of moisture, they
should also be capable of absorbing gaseous substances from the
air which pervades the soil. Experiment, however, has not yet
proved this to be the case.
The property which the roots of most plants have of avoiding
the light, while the leaves eagerly seek it, appears to imply that
the other ordinary functions of the leaves and roots may differ
also. We know, however, that they are capable of absorbing
gases through the medium of water. Thus—
a. If the roots of a plant are placed in water containing carbo-
nic acid in the state of solution, this gas is found gradually to
disappear. It is extracted from the water by the roots.
b. And if the water in which the roots are immersed be con-
tained in a close bottle only partially filled with the liquid, while the
remainder is occupied by atmospheric air, the oxygen in this air
will also slowly diminish. It will be absorbed by the roots
through the medium of the water.”
c. And if, in the place of the atmospheric air in this bottle,
carbonic acid be substituted, the plant will droop, and in a few
days will die. The same will take place, if, instead of common
air or carbonic acid, nitrogen or hydrogen gases be introduced
into the bottle. The plant will not live when its roots are exposed
to the sole action of any of the three.
It is obvious, therefore, First, that the roots of plants absorb
* It will be recollected that water absorbs about 4 per cent. of its bulk of air from
the atmosphere, of which air about one-third is oxygen. If the roots extract this
oxygen from the water, the latter will again drink in a fresh portion from the atmo-
spheric air which floats above it, and will thus lessen the proportion of oxygen it
contains.
4
THE ROOTS ABSORB OXY GEN. 121
gaseous substances from the air which surrounds their roots, at
least indirectly, and through the medium of water, Second, that
from this air they have the power of selecting a certain portion of
oxygen, when this gas is present in it. Third, that though they
can absorb carbonic acid, to a limited extent, without injury to
the plant, yet that a copious supply of this gas, unmixed with
oxygen, is fatal to vegetable life. This deduction is confirmed by
the fact that, in localities where carbonic acid ascends through fis-
sures in the subjacent rocks, and saturates the soil, the growth of
grass is found to be very much retarded. And; lastly, since
nitrogen is believed not to be in itself noxious to vegetable life,
the death of the plant, in water surrounded by this gas, appears to
imply, that the presence of oxygen is necessary about the roots of
a growing and healthy plant, and that one of the special functions
of the roots is constantly to absorb this oxygen.
This supposition is in accordance with the fact, that in the dark
the leaves, and other green parts of plants, absorb oxygen from
the atmosphere; for we have already seen reason to expect that,
from their analogous structure, the roots and leaves, in similar
circumstances, should perform also analogous functions. At the
same time, if the roots do require the access and presence of oxy-
gen in the soil, it would further appear that those of some plants
require it more than those of others;–inasmuch as some genera,
like the grasses and bulbous-rooted plants, love an open and
friable soil, into which the air gains easy admission; while other
genera, like the clovers, prefer a denser, stiffer surface, by which
the air must be more completely excluded.”
3°. We have, in a former Lecture, when treating of the organic
food of plants, shown that solid substances which are soluble in
water, accompany this liquid when it enters into the circulation of
the plant. This appears to be true both of organic and inorganic
substances. Potash, soda, lime, and magnesia, thus find their
way into the interior of plants, as well as those substances of ani-
mal and vegetable origin to which the observations made in the
fourth lecture were intended more especially to apply. Even
silica f enters by the roots, and is found in many cases in consider-
* Sprengel, Chemie II., p. 337. -
f Silica is the name given by chemists to the pure matter of flint or of rock crystal.
*.
I 22 Do sol1D subsTANCES ENTER THE ROOTS?
able quantities in the stem. Some persons have hence been led
to conclude that solid substances, undissolved, if in a minute state
of division, may be drawn into the pores of the root, and may then
be carried by the sap upwards to the stem.
Considered as a mere question of vegetable mechanics, argued
as such among physiologists, it is of little moment whether we
adopt or reject this opinion. One physiologist may state that the
pores by which the food enters into the roots are so minute as to
baffle the powers of the best constructed microscope, and, there-
fore, that no particles of solid matter can possibly gain admission ;
while another may believe solid matter to be capable of a mecha-
mical division so minute as to pass through the pores of the finest
membrane. As to the mere fact itself, it matters not which is
right, or which of the two we follow. The adoption of the latter
opinion implies in itself merely that foreign substances, unneces-
sary, perhaps injurious, to vegetable life, may be carried forward
by the flowing juices until, in some still part of the current, or in
some narrower vessel, they are arrested, and there permanently
lodged in the solid substance of the plant.
By inference, however, the adoption of this opinion implies also,
that the inorganic substances found in plants, those which remain
in the form of ash when the plant is burned,—are, or may be, in
whole or in part, accidental only, not essential to its constitution.
For, since they may have been introduced in a mere state of
minute mechanical division suspended in the sap, they ought
to consist of such substances chiefly as the soil contains in the
greatest abundance, and to vary in kind and relative quantity
with every variation in the soil. In clay land, the ash should
consist chiefly of alumina," in a sandy soil chiefly of silica. But
if, as chemical inquiry appears to indicate, the nature of the
ash is not accidental but essential, and in some degree con-
stant, even in very different soils, this latter inference is inad-
missible: and in reasoning backwards from this fact, we find
Sand and sandstones consist almost entirely of silica. In most of the forms in which
we meet with this substance, it is almost insoluble in water.
* Alumina is the pure earth of clay. It exists in alum, and is hence called alu-
mina. If a little alum be dissolved in water, and hartshorn (liquid ammonia) be then
poured into the solution, a white powder will fall to the bottom. This white powder is
alumina. -
SELECTING POWER OF THE ROOTS. 123
ourselves constrained to reject the opinion that substances are
capable of entering into the roots of plants in a solid state; and
this without reference at all to the mechanical question, as to the
relative size of the pores of the spongy roots, or of the particles
into which solid matter may be divided. -
4°. We are thus brought to the consideration of the alleged
selecting power of the roots, which, if rightly attributed to them,
must be considered as one of the most important functions of
which they are possessed. It is a function, however, the existence
of which is disputed by many eminent physiologists. But as the
adoption or rejection of it will materially influence our reasonings,
as well as our theoretical views, in regard to some of the most
vital processes of vegetation, it will be proper to weigh carefully
the evidence on which this power is assigned to the roots of plants.
a. The leaves, as we shall hereafter see, possess, in a high
degree, the power of selecting from the atmosphere one or more
gaseous substances, leaving the nitrogen, chiefly, unchanged in
bulk. The absorption of carbonic acid, and the diminution of the
oxygen in the experiments above described, appear to be analo-
gous effects, and would seem to imply, in the roots, the existence
of a similar power.
b. Dr Daubeny found that pelargoniums, barley, (hordeum
vulgare), and the winged pea (lotus tetragonolobus), though made
to grow in a soil containing much strontia,” appeared to absorb
none of this earth, for none was found in the ash left by the stem
and roots of the plants when burned. In like manner De Saus-
sure observed that polygonum persicaria refused to absorb acetate
of lime from the soil, though it freely took up common salt.f Too
much reliance, however, is not to be placed in these results, as Mr
Gyde has recently found that beans take up both lime and stron-
tia without injury, if the solutions are sufficiently dilute. -
c. Plants of different species, growing in the same soil, leave
when burned, an ash which in every case contains either different
substances, or the same substances in unlike proportions. Thus
* Watered with a solution of nitrate of strontia. Strontia is an earthy substance
resembling lime, which is found in certain rocks and mineral veins, but which has not
hitherto been observed in the ashes of plants.
+ Lindley's Theory of Horticulture, p. 19.
f Prize Essays of the Highland and Agricultural Society of Scotland for 1845.
124 Is THE NATURE OF THE ASH CONSTANT *
if a bean and a grain of wheat be grown side by side, the stem of
the wheat plant will be found to contain much silica, while the stalk
of the bean contains scarcely amy.*
d. But the same plant grown in soils unlike in character and
composition, contains always, if they are present in the soil at all
—the same kindſ of earthy matters, and with certain variations in
nearly the same proportions. Thus the stalks of corn plants, of
the grasses, of the bamboo, and of many others, always contain
silica, in whatever soil they grow; or at least are capable of grow-
ing with any degree of luxuriance.
With the view of testing this point, Lampadius prepared five
square patches of ground, manured them with equal quantities of
horse and cow dung, sowed them with equal measures of the same
wheat, and on four of these patches strewed respectively five pounds
of finely powdered quartz (siliceous sand), of chalk, of alumina,
and of carbonate of magnesia, and left one undressed. The pro-
duce of seed from each, in the above order, weighed 244, 28%,
26}, 21%, and 20 ounces respectively. The grain, chaff, and straw
from each of the patches left nearly the same quantity of ash—the
weights varying only from 3-7 to 4:08 per cent., and the roots and
chaff being richest in inorganic matter. The relative proportions of
silica, alumina, lime, and magnesia were the same in all.f. Pro-
vided, therefore, the substances which plants prefer be present in
the soil, the kind of inorganic matter they take up, or of ash they
leave, is not, according to these experiments, materially affected by
the presence of other substances, even in somewhat larger quantity.
These facts all point to the same conclusion, that the roots have
the power of selecting from the soil in which they grow, those sub-
stances which are best fitted to promote the growth or to maintain
the healthy condition of the plants they are destined to feed.
e. The existence of such a selecting power in the roots of land
plants is rendered more probable still, by the unquestionable
* It is not strictly correct that the bean will absorb no silica, but the quantity it
will take up will be only ºth of that taken up by the wheat plant—the proportion
of silica in the ash of bean straw being, according to Sprengel, only 7 per cent. while in
wheat straw it is 70 to 80 per cent.
+ For more precise information on this point, see the subsequent lectures “On the
tnorganic constituents of plants.”
+ Meyen Jahresbericht, 1839, p. 1. It is to be doubted if the analyses of Lumpa-
drus which gave him these results are to be entirely depended upon.
PLANTS MAY ABSORB POISONOUS SUBSTANCEs. 125
selecting power of plants which grow in the sea. The water of
the sea contains much soda, and only a minute trace of potash, and
yet some sea seeds, such as the dulse, contain much potash and
little soda. Out of the great abundance of soda with which they
are surrounded, they select the small proportion of potash with
which it is mixed. -
f. It is a matter of frequent observation, however, that the roots
absorb solutions containing substances which speedily cause the
death of the plant. Arsenic, opium, salts of iron, of lead, and of
copper, and many other substances, are capable of being absorbed
in quantities which prove injurious to the living vegetable—and on
this ground chiefly many physiologists refuse toacknowledge that the
roots of plants are by nature endowed with any definite and constant
power of selection at all. But this argument is of equal force
against the possession of such a power by animals or even by man
himself; since with our more perfect discriminating powers, aided
by our reason too, we every day swallow with our food what is
more or less injurious, and occasionally even fatal to human life.”
Mulder denies that the roots have any selecting power. They
admit, by endosmose, everything soluble, and he says, and out of
the common sap, the several parts—the leaves, the seed, &c.—se-
lect what is needful for their own growth. This is merely a shift-
ing of the responsibility, assigning to other parts of the plant a
power which there is no good reason for refusing to the root also.
On the whole, therefore, it appears most reasonable to conclude
that the roots are so constituted as (1*) to be able generally to se–
lect from the soil in preference, those substances which are most suit-
able to the nature of the plant—(2°) where these are not to be met
with to admit certain others in their stead, f-(3°) to refuse admis-
* I may here remark that it is by no means an extraordinary power which these cir-
cumstances seem to shew the roots of plants to possess. In the presence of oxygen, nitro-
gen, and carbonic acid gases in equal quantities, water will prefer and will select the
latter. From a mixture of lime and magnesia, acetic or sulphuric acid will select and
separate the former. Is it unreasonable to suppose the roots of plants—the organs
of a living being—to be endowed with powers of discrimination at least as great as
those possessed by dead matter P
+ This conclusión is not strictly contained in the premises above stated, but the
facts from which it is drawn will be fully explained in treating of the inorganic con-
stituents of plants. It is introduced here for the purpose of giving a complete view
of what appears to be the true powers of discrimination possessed by the root.
126 EXCRETORY POWER OF THE ROOTS.
sion also to certain substances which are likely to injure the plant,
though unable to discriminate and to reject every thing hurtful or
unbeneficial which may be presented to them in a state of solution.
The object of nature, indeed, seems to be to guard the plant
against the more common and usual dangers only—not against
such as rarely present themselves in the situations in which it is
destined to grow, or against substances which are unlikely even
to demand admission into its roots. How useless a waste of skill,
if I may so speak, would it have been to endow the roots of each
plant with the power of distinguishing and rejecting opium and
arsenic and the thousand other poisonous substances which the
physiologist can present to them, but which in a state of nature—
on its natural soil and in its natural climate—the living vegetable
is never destined to encounter
5°. Another function of the roots of plants, in regard to which
physiologists are divided in opinion at the present day, is what is
called their excretory power. -
a. When barley or other grain is caused to germinate in pure
chalk, acetate of lime” is uniformly found to be mixed with the chalk
after the germination is somewhat advanced (Becquerel and Ma-
teucci.)f In this case the acetic acid must have been given off
(excreted) by the young roots during the germination of the seed.
This fact may be considered as the foundation of the excretory
theory as it is called. This theory, supported by the high autho-
rity of Decandolle, and illustrated by the apparently convincing
experiments of Macaire,t has more recently been met by counter
experiments of Braconnot, and is now in a great measure re-
jected by many eminent vegetable physiologists. It may indeed be
considered as quite certain that the application of this theory by
Decandolle and others to the explanation of the benefits arising from
a rotation of crops—is not confirmed, or proved to be correct, by
any experiments on the subject that have hitherto been published.|
* Acetate of lime is a combination of acetic acid or vinegar with lime derived from
the chalk.
+ Ann. de Chim. et de Phys. lv. p. 310.
: Ibid., lii. p. 225. § Ibid., lxxii. p. 27.
| The discordant results of Macaire and Braconnot were as follow :-
19. Macaire observed that when plants of Chondrilla Muralis were grown in rain
EXPERIMENTS OF BRACONNOT. * 127
According to Decandolle, plants, like animals, have the power
of selecting from their food, as it passes through their vascular
water they imparted to it something of the smell and taste of opium. Braconnot
confirmed this, but attributed it to wounds in the roots which allowed the proper
juice of the plant to escape. He says it is almost impossible to free the young roots
from the soil in which they have grown, without injuring them and causing the Sap
to exude, -
29. Euphorbia Peplus (Petty Spurge) imparted to the water in which it grew a
gummi-resinous substance of a very acrid taste. In the hands of Braconnot it yielded
to the water scarcely any organic matter, and that only slightly bitterish.
39. Braconnot washed the soil in which plants of Euphorbia Breoni and Asclepias
Incarnata were growing in pots, and obtained a solution containing earthy and alca-
line salts with only a trace of organic matter.
He also washed the soil in which the Poppy (Papaver Somniferum) had been
grown ten years successively. The solution, besides inorganic earthy and alcaline
salts, gave a considerable quantity of acetic acid (in the form of acetate of lime) and
a trace of brown organic matter. He infers that these several plants do not excrete
any organic matter in sufficient quantity to be injurious to themselves.
49. Macaire observed that when separate portions of the roots of the same plant
of Mercurialis Aºnua were immersed in separate vessels, the one containing pure .
water and the other a solution of acetate of lead, the solution of lead was absorbed
by the plant, was to be traced in every part of it, and afterwards was partially trans-
mitted to the pure water. Braconnot observed the same results, but he found the
entrance of the lead into the second vessel to be owing to the ascent of the fluid up
the outer surface of the one root and down the exterior of the other, and that, by
preventing the possibility of this passage, no lead could be detected among the pure
water.
The conclusions of Macaire, therefore, in favour of the rotation theory of Decan-
dolle must be considered as at present inadmissible, and we shall hereafter see reason
to coincide, at least to a certain extent, in the conclusion of Braconnot, “ that if
these excretions (of organic matter) really take place in the natural state of the
plant, they are as yet so obscure and so little known as to justify the presumption
that some other explanation must be given of the general system of rotation.” Wa-
rious illustrations have been given by different observers of this supposed excreting
power of the roots. Among the most recent are those of Neitner, who ascribes the
luxuriant rye crops obtained without manure after three years of clover, to the ex-
cretions of this plant in the soil, which, like those of the pea and bean to the wheat,
he supposes to be nourishing food to the rye. He also states that the beet or the
turnip after tobacco has an unpleasant taste, and is scarcely eatable, which he attri-
butes to the excretions of the tobacco plant. Meyen ascribes the effect of the clover
to the green manure supplied by its roots and stubble, and that of the tobacco to
the undecomposed organic substances contained in the sap and substance of the
roots and stems of this plant, of which so large a quantity is left behind in the field.”
These objections of Meyen are not without their weight, but we shall hereafter see
that they embody only half the truth.
* Meyen's Jahresbericht, 1839, p. 5.
128 THEORY OF DECAN DOLLE,
system, such portions as are likely to mourish them, and of reject-
ing, by their roots, when the sap descends, such as are unfit to
contribute to their support, or would be hurtful to them if not re-
jected from their system. He further supposes that, after a time,
the soil in which a certain kind of plant grows becomes so loaded
with this rejected matter, that the same plant refuses any longer
to flourish in it. And, thirdly, that though injurious to the plant
from which it has been derived, this rejected matter may be whole-
some food to plants of a different order—and hence the advantage
to be derived from a rotation of crops. -
There seems no good reason to doubt that the roots of plants
do really reject organic substances from their roots. The acetic
acid given off during germination, and the same acid found by
Braconnot in remarkable quantity in the soil in which the poppy
(papaver somniferum) has grown—may be regarded as sufficient
evidence of the fact. Some recent experiments of Mr Gyde, f made
with apparent care, confirm this conclusion,--but the quantity of
such organic matter hitherto detected among what can be safely
viewed as the real excretions of plants, seems by far too small to
account for the remarkable results which attend upon a rotation
of crops.
The consideration of these results, as well as of the general
theory of such a rotation, will form a distinct topic of consideration
in a subsequent part of these lectures. I shall in this place, there-
fore, mention only one or two facts which seem to me capable of
explanation only on the supposition that the roots of plants are
endowed with the power of rejecting—and that they do constantly
reject, when the sap returns to them from the leaf, some of the sub-
stances which they had previously taken up from the soil.
1°. De Saussure made numerous experiments on the quantity
of ash per cent. left by the same plant at different periods of its
growth. Among other results obtained by him, it appeared—
A. That the quantity of incombustible or inorganic matter in
the different parts of the plant was different at different periods of
the year. Thus the dry leaves of the horse chesnut, gathered in
May, left 7.2 per cent, towards the end of July 8.4 per cent, and
in the end of September 8.6 per cent. of ash; the dry leaves of
* Transactions of the Highland and Agricultural Society for 1845, p. 280.
EXPERIMENTS OF DE SAUSSURE. 129
the hazel in June left 6.2, and in September 7 per cent. ; and
those of the poplar (populus nigra) in May, 6.6, and in September
9.3 per cent of ash. These results are easily explaimed on the
supposition that the roots continued to absorb and send up to the
leaves during the whole summer the saline and earthy substances
of which the ash consisted. But
B. He observed also that the quantity of the inorganic sub-
stances in—or the ash left by—the entire plant diminished as it
approached to maturity. Thus the dry plants of the vetch, of the
golden rod (solidago vulgaris), of the turnsol (helianthus annuus),
and of wheat, left respectively of ash, at three different periods of
their growth”—
Before flowering. In flower. Seeds ripe.
per cent. - per cent. per cent.
Vetch ............ | 5 e - e. 12.2 is e - 6.6
Qolden rod...... 9.2 e - © 5.7 e tº e 5,0
Turnsol ..... ... 14.7 e - © 13.7 e Q tº 9.3
Wheat............ 7.9 e tº º 5.4 tº º º 3.3
This diminution in the proportion of ash, might arise either
from an increase in the absolute quantity of vegetable matter in
the plants as they increased in size—or from a portion of the saline
and earthy matters they contained, being again rejected by the roots.
But if the former be the true and sole explanation, the relative pro-
portions of the several substances of which the ash itself consisted,
in the several cases, should have been the same at the several pe-
riods when the experiments were made. But this was by no means
the case. Thus to refer only to the quantity of silica contained in
the ash left by each of the above plants at the several stages of
their growth, the ashes of the t
Before flowering, In flower. Seeds ripe,
per cent. per cent. per cent,
Vetch contained 1.5 e - e. 1.5 e tº tº 1.75
Golden rod...... 1.5 e tº p 1,5 e tº 2 3.5
Turnsol ......... 1.5 & O e 1.5 tº e e 3.75
Wheat......... 12.5 ... 26.0 ... 51.0
If, then, the proportion of silica in the ash increased in some
cases four-fold, while the whole quantity of ash left by the plant
decreased, it appears evident that some part of the saline matter
Davy's Agricultural Chemistry, Lecture III.
I
130 PIROPORTION OF SILICA IN THE ASH OF PLANTS.
which existed in the plant during the earlier periods of its growth
must have been excreted or rejected by the roots, as it advanced
towards maturity.
2°. This conclusion is confirmed and carried farther by another
consideration. The quantity of ash left by the ripe wheat plant,
in the above experiments of De Saussure, amounted to 3.3 per
cent. —of which ash, 51 per cent., or rather more than one-half,
was silica. This silica could only have entered into the circulation
of the plant in a state of solution in water, and must have been
dissolved by the agency of potash or soda. But according to
our most recent analyses, the potash and soda together are to the
silica in the grain and straw of wheat, in the proportions of
Potash and Soda. Silica.
- Grain..... tº º 32.7 tº tº º I •2
Straw ...... 7.2 . . . 77.1
Or, supposing the grain to equal one-half the weight of the
straw—their relative proportions in the whole plant will be nearly
as 47 potash and soda to 155 silica, or the weight of the silica
is upwards of three times the weights of the potash and soda taken
together.
Now silica requires nearly half its weight of potash to render it
soluble in water,” or three-fifths of its weight of a mixture of
nearly equal parts of potash and soda. The quantity of these
alcaline substances found in the plant, therefore, is by no means
sufficient to have dissolved and brought into its circulation at one
time the whole of the silica it contains.
Hence one of two things must have taken place. Either a por-
tion of the potash and soda present in the plant in the earlier
stages of its growth must have escaped from its roots at a later
stage f leaving the silica behind it—or the same quantity of alkali
must have circulated through the plant several times—bringing
* A soluble glass may be made by melting together in a crucible for six hours 10
parts of carbonate of potash, 15 of silica, and 1 of charcoal powder.
+ De Saussure does not state the eacact relative quantities of potash and Soda at
the several periods of the growth of wheat, though they appear to have gradually
diminished. It seems, indeed, to be true of many plants that the potash and soda
they contain diminishes in quantity as their age increases. Thus the weight of
potash in the juice of the ripe or sweet grape, is said to be less than in the unripe or
sour grape—and the leaves of the potato have been found more rich in potash
before than after blossoming (Liebig).
IN WHAT WAY INTRODUCED. 13|
in its burden of silica, depositing it in the vascular system of the
plant, and again returning to the soil for a fresh supply. In
either case the roots must have allowed it egress as well as ingress,
But the fact, that the proportion of silica in the plant goes on in-
creasing as it continues to grow, is in favour of the latter view—
and renders it very probable that the same quantity of alkali
returns again and again into the circulation, bringing with it
supplies of silica and perhaps of other substances also which the
plant requires from the soil. And while this view appears to be
the more probable, it also presents an interesting illustration of
what may probably be one of the many functions discharged by
the potash and other inorganic substances found in the interior of
plants—a question we shall hereafter have occasion to consider at
Some length. - - - -
The above considerations, therefore, to which I might add
others of a similar kind, satisfy me that the roots of plants do pos-
sess the power of excreting some of the substances which are held
in solution by the sap on its return from the stem—and which,
having performed their functions in the interior of the plant, are
no longer fitted, in their existing condition, to minister to its sus-
tenance or growth. This excretory power is not restricted solely
to the emission of inorganic substances. Other soluble matters of
organic origin also are permitted to escape into the soil—though
whether of such a kind as must necessarily be injurious to the
plant from which they have been extruded, or to such a degree as
alone to render a rotation of crops necessary, neither reasoning
nor experiment has hitherto satisfactorily shown.
All we as yet know with certainty upon the subject is in favour
of the opposite view. Mr Gyde watered bean plants till fully
ripe, with water containing the matter excreted from the roots of
beans; and these plants were slightly better in appearance than
others watered during the same time with rain water only. The
excretion of the bean, therefore, does not appear to be injurious to
the bean itself.
6°. The roots have the power of absorbing, and in some measure
of selecting, food from the soil—can they also modify or alter it
as it passes through them P A colourless sap is observed to
* Transactions of Highland and Agricultural Society, 1845, p. 288.
132 CAN THE ROOTS MODIFY THE FOOD 2
ascend through the roots. From the very extremity up to the
foot of the stem, a cross section exhibits little trace of colouring
matter, even when the soil contains animal and vegetable sub-
stances which are soluble, and which give dark coloured solutions.”
Does such matter ever enter the root ? If it does, it must be
speedily changed or transformed into new compounds. *
We have as yet too few experiments upon this subject, to enable
us to speak with certainty in regard to this function of the root.
The observations which have been made, however, render it ex-
tremely probable that a peculiar power of producing chemical
alterations in matters presented to them, resides in the extremities
of the roots. They are thus enabled to change many of the sub-
stances, both organic and inorganic, which they meet with in the
soil, and to extract from them materials by which the plant is to
be fed. -
Can we conceive the existence of any powers in the root, or in
the whole plant, of a still more refined kind? The germinating
seed gives off acetic acid into the soil,-does this acetic acid dis-"
solve lime from the soil and return with it again, as some suppose
(Liebig), into the circulation of the plant?f Is acetic acid pro-
duced and excreted by the seed for this very refined purpose?
We have considered it probable that in the wheat plant potash
and soda may go and come several times during its growth, and
the ripening of its seed. Is this a contrivance of nature to make
up for the scarcity of alcaline substances in the soil—or would the
same mode of operation be employed if potash and soda were pre-
sent in greater abundance P Or where the alcalies are present in
greater abundance, may not more work be done by them in the
same time, may not the plant be built up the faster and the
larger, when there are more hands, so to speak, to do the work 2
Is the action of inorganic substances upon vegetation, to be ex-
plained by the existence of a power resident in the roots or other
* Such as the liquid manure of the fold-yard.
† Braconnot found acetate of lime in very small quantities to be singularly hurtful
to vegetation, and acetate of magnesia a little less so. He only mentions, however,
some experiments upon mercurialis annua," and as De Saussure found that some
plants actually refused to take it up at all, these acetates may not be equally injuri-
pus to all plants.
* Ann. de Chinn, ct de Phys. lxxii. p. 36,
COURSE OF THE SAP. e I 33
parts of plants, by which such operations as this are directed or
superintended? There are many mysteries connected with the
nature and phenomena of vegetable life, which we have been un-
able as yet to induce nature to reveal to us.” But the morning
light is already kindling on the tops of the mountains, and we
may hope that the deepest vallies will not for ever remain obscure.
• $ 3. The course of the sap.
If the trunk of a tree be cut off above the roots, and its lower
extremity be immediately plunged into a solution of madder or
other colouring substance, the coloured liquid will ascend, and
will gradually tinge the wood. This ascent will continue till the
colour can also be observed in the nerves of the leaf. If at this
stage in the experiment the trunk be cut across at various heights,
the wood alone will appear coloured, the bark remaining entirely
untinged. But if the process be allowed to continue after the
colouring matter has reached the leaf, and if, after some further
time, the stem be cut across, the bark also will appear dyed, and
the tinge will be perceptible at a greater distance from the leaf
the longer the experiment is carried on, till at length both bark
and wood will be coloured to the very bottom of the stem.
Or if the root of a living plant, as in the experiment of Macaire
detailed in a preceding note (p. 126), be immersed in a metallic
solution—such as a solution of acetate of lead, which it is capable
of absorbing without immediate injury—and different portions o
the plant be examined after the lapse of different periods of time,
—it will be found that first the stem, afterwards the leaves, then
* The roots of trees will travel to comparatively great distances, and in various
directions, in search of water : the roots of Sainfoin (Esparsette) will penetrate 10 or
12 feet through the calcareous rubbly subsoil, or down the fissures of limestone rocks
on which they delight to grow. Is this the result of some perceptive power in the
plant—or is it merely by accident that the roots display these tendencies 2
Those who are in any degree acquainted with the speculations of the German
physiologists of the greatest name—in regard to the Soul and even the immortality of
plants—will not accuse me of going very far in alluding to the possible existence of
some such perceptive power in plants. Von Martius gets rid of objectors by speak-
ing of them as “scientific men to whom the power of comprehending the transcendental
has been imparted in a lower degree.”—See Meyen's Jahrosbericht, 1839, or Silliman's
A merican Journal for Jamiſtry, 1841, p. 170.
134 .THE SAP ASCENDS THROUGH THE WOOD.
the bark of the upper part of the stem, and lastly that of the lower
part of the stem, will exhibit traces of lead.
These experiments show that the sap which enters by the roots
ascends through the vessels of the wood, diffuses itself over the
surface of the leaves, and then descends by the bark to the extre-
mities of the root.
But what becomes of the sap when it reaches the root ? Is it
delivered into the soil, or does it recommence the same course,
and again, repeatedly perhaps, circulate through the stem, leaves,
and bark? This question has been partly answered by what has
been stated in the preceding section. When the sap reaches the
extremity of the root, it appears to give off to the soil both solid
and fluid substances of a kind and to an amount which probably
differ with every species of plant. The quantity is said to be
greater when the roots have large spongy terminations—and
greater also when the plant is in flower (Gyde). The remainder
of the sap and of the substances it holds in solution, is diffused
through the cellular spongy terminations of the roots, and, with
the new supply of liquid imbibed from the soil, returns again to
the stem in the ascending current.
But what causes the sap thus to ascend and descend? By
what power is it first sucked up through the roots, and afterwards
forced down again from the leaves? Several answers have been
given to this question.
1°. When the end of a wide tube, either of metal or of glass,
is plunged into water, the liquid will rise within the tube sensibly
to the same level as that at which it stands in the vessel. But if
a capillary" tube be employed instead of one with a wide bore,
the liquid will rise, and will permanently remain at a considerably
higher level within than without the tube. The cause of this rise
has been ascribed to an attraction which the sides of the tube
have for the liquid, and which is sufficiently strong to raise it and
to keep it up above the proper level of the water. The force it-
self is generally distinguished by the name of capillary attraction.
Now, the wood of a tree, as we have seen, is composed of a
* Glass tubes perforated by a very fine bore, like a human hair, are called capillary
tubes. Such are those of which thermometers are usually made.
ÖAPILLARY ATTRACTION. 135
mass of fine tubes, and through these the sap has been said to rise
by capillary attraction. But if the top of a vine be cut off when
it is juicy and full of sap, the liquid will exude from the newly
formed surface, and if the air be excluded, will flow for a length
of time, and may be collected in considerable quantity.” Such a
flow of the sap is not to be accounted for by mere capillary attrac-
tion—the sides of tubes cannot draw up a fluid beyond their own
extremities.
2°. To supply the defect of this hypothesis, De Saussure sup-
posed that the fluid at first introduced by capillary attraction into
the extremities of the root, was afterwards propelled upwards by
the alternate contraction and expansion of the tubes of which the
wood of the root and stem is composed. This alternate contrac-
tion and expansion he also supposed to be caused by a peculiar
irritating property of the sap itself, which caused each successive
part of the tube into which it found admission to contract for the
purpose of expelling it. g
Mr Knight also ascribed the ascent of the sap to a similar con-
traction of certain other parts of the stem. And being once
raised, he supposed it to return again or descend by its own
weight. But in drooping branches it is obvious that the sap must
be actually driven or drawn upwards from the leaves on its return
to the root. These explanations, therefore, are still unsatisfactory.
3°. If one end of an open glass tube be covered with a piece of
moistened bladder or other fine animal membrane, tied tightly
over it, and a strong solution of Sugar or salt in water be then
poured into the open end of the tube, so as to cover the membrane
to the depth of several inches—and if the closed end be then intro-
duced to the depth of an inch below the surface of a vessel of pure
water, the water will after a short time pass through the bladder
inwards, and the column of liquid in the tube will increase in
height. This ascent will continue, till in favourable circumstances
the fluid will reach the height of several feet, and will flow out or
run over at the open end of the tube. At the same time the wa-
ter in the vessel will become sweet, or salt, indicating that while so
, much liquid has passed through the membrane inwards, a quantity
has also passed outwards, carrying sugar or salt along with it.f
* Lindley's Theory of Horticulture, p. 47, (note.)
+ Instead of Sugar and common salt, gum or other soluble substances may be dissolved
136 - ENDOSMOSE AND EXOSMOSE.
To these opposite effects Dutrochet, who first drew general attention
to the fact, and applied it to vegetable physiology, gave the names
of Endosmose denoting the inward progress, and Evosmose the out-
ward progress of the fluid. He supposed them to be due to the
action of two opposite currents of electricity, and he likens the
phenomena observed during the circulation of the sap in plants, to
the appearances presented during the above experiment.
Without discussing the degree of probability which exists as to
the influence of electricity in producing the phenomena of endos-
mose and exosmose, it must be admitted that the appearances them-
selves bear a strong resemblance to those presented in the absorp-
tion and excretion of fluids by the roots of plants—and point very
distinctly to at least a kindred cause.
Thus, if the spongy termination of the root represent the thin
porous membrane in the above experiment—the sap with which
the tubes of the wood are filled, the artificial solution introduced
into the experimental tube—and the water in the soil, the water
or aqueous solution into which the closed extremity of the tube is
introduced,—we have a series of conditions precisely similar to
those in the experiment. Fluids ought, consequently, to enter
from the soil into the roots, and thence to ascend into the stem, as
in nature they appear to do.
This ascent, we have said, will continue till the fluid in the tubes
of the wood (the sap) is reduced to a density as low as that of the
liquid entering the roots from the soil. But in a growing tree,
clothed with foliage, this will never happen. The leaves are con-
tinually exhaling aqueous vapour, as one of their constant func-
tions, and sometimes in very large quantity. The sap, therefore,
when it reaches the leaves, is concentrated or thickened, and ren-
dered more dense by the separation of the water, so that when it
in the water introduced at first into the tube, and the denser this solution the larger
the quantity of water which will enter by the membrane, and the greater the height
to which the column will rise. It ceases in all cases to rise only when the portions
of liquid within and without the membrane attain nearly to the same density.” In-
stead of pure water the vessel into which the extremity of the tube is plunged may
also contain a weak solution of Some soluble substance—such as lime or Soda—in
which case, while the sugar, or salt, or gum, will pass outwards, in smaller quantity,
the lime or soda will pass inwards, along with the currents of water in which they are
severally dissolved.
* Contain nearly the same weight of solid matter in solution.
CAUSE OF THE ASCENT OF THE SAP. 137
descends to the root, and again begins its upward course, it will
admit of large dilution before its density can be so far diminished
as to approach that of the comparatively pure water which is ab-
sorbed from the soil. And this illustration of the ascent of the
sap appears the more correct from the obvious purpose it points out
—(in addition to others long recognised)—as served by the evapo-
ration which is constantly taking place from the surface of the leaf.
Still the cause of the ascent of the sap is not the more clear that
we can imitate it in some measure by an artificial experiment.
But it will be conceded by the strictest reasoners on physical phe-
momena, that to have obtained the command, or even a partial con-
trol, over a natural power, is a considerable step towards a clear
conception of the nature of that power itself. If the phenomena
of endosmose can hereafter be clearly and indubitably traced to
the agency of electricity, we shall have advanced still another step,
and shall be enabled to devise other means by which a more per-
fect imitation of nature may be effected, or a more complete con-
trol asserted over the phenomena of vegetable circulation.
§ 4. Functions of the stem.
The functions of the stem are probably as various as those of
the root, though the circumstances under which they are perform-
ed necessarily involve these functions in considerable obscurity.
1°. The pith, which forms the central part of the stem, consists,
as I have already stated, of tubes disposed horizontally. When a
coloured fluid is permitted to enter the lower part of the stem in
the experiments above described, the pith remains colourless in the
centre of the coloured wood. It does not, therefore, serve for the
conveyance of the sap. Nor does it seem to be vitally necessary
to the health and growth of the plant, since Mr Knight has shewn
that, from the interior of many trees, it may be removed without
apparent injury, and in nature, as trees advance in age, it gradu-
ally diminishes in bulk and in some species becomes apparently
obliterated. -.
2°. The vessels of the wood, which surrounds the pith, perform
probably both a mechanical and a chemical function. They serve
to convey upwards to the leaf the various substances which enter
by the roots. This is their mechanical function. But during its
I 38 - FUNCTIONS OF THE STEM.
progress upwards, the sap appears to undergo a series of changes.
When it reaches the leaves it is no longer in the state in which it
ascended from the root into the stem. The difficulty of extracting
the sap from the wood, at different heights, has prevented very nu-
merous experiments from being made on its nature and contents at
the several stages of its ascent. Knight found the sap of the mul-
berry to increase in density and that of the birch in sweetness as
it ascended. The sugar cane, again, is known to sweeten only to
a certain height, so that the changes of the sap must vary with the
species and age of the plant, and with the season of the year at
which the experiment is made. The general result, however, of
all the observations hitherto made is, that those substances which
enter directly from the soil into the root, when mingled with such
as have already passed though the circulation of the plant, undergo,
during their ascent, a gradual preparation for that state in which
they become fit to minister to the growth of the plant. This pre-
paration is completed in a great measure in the leaf, though further
changes still go on as the sap descends through the bark.
This deduction is strengthened by the fact that gaseous sub-
stances of various kinds and in varying quantities exist in the interior
of the wood of the growing plant. These gaseous substances, ac-
cording to Boucherie, are in some cases equal in bulk to one-twen-
tieth part of the entire trunk of the tree in which they exist. They
probably move upwards along with the sap, and are more or less
completely discharged into the atmosphere through the pores of
the leaves. That these gaseous substances not only differ in quan-
tity, but in kind also, with the age and species of the tree, and
with the season of the year, may, I think, be considered as almost
amounting to a proof that they have not been inhaled directly by
the roots, but are the result of chemical decompositions which have
taken place in the stem itself, as the sap mounted upwards towards
the leaves. -
We have seen that the roots exercise a kind of discriminating
power in admitting to the circulation of the plant the various sub-
stances which are present in the soil. The vessels of the stem ex-
hibit an analogous power of admitting or rejecting the solutions of
different substances into which they may be immersed. Thus
Boucherie states that, when the trunks of several trees of the same
DECOMPOSITION TAKES PLACE IN THE STEM. 139
species are cut off above the roots, and the lower extremities are
immediately plunged into solutions of different substances, some
of these solutions will quickly ascend into, and penetrate the en-
tire substance of the tree immersed in them, while others will not
be admitted at all, or with extreme slowness only, by the vessels of
the stems to which they are respectively presented. On the other
hand, that which is rejected by one species of tree will be readily
admitted by another. Whether this partial stoppage of certain
substances, or total refusal to admit them, be a mere contractile
effort on the part of the vessels, or be the result of a chemical
change of the substance itself, or of the fibre or sap with which it
comes into contact, by which change their exclusion is effected or
resisted, does not as yet clearly appear. That it does not depend
upon the lightness and porosity of the wood, as might be supposed,
is shown by the observation that the poplar is less easily penetrat-
ed in this way than the beech, and the willow than the pear tree,
the maple, or the plane.
These various functions of the woody part of the stem are perform-
ed chiefly by the newer wood or alburnum, or, as it is often called,
the sap-wood of the tree. As the heart-wood becomes older, the
tubes of which it consists are either gradually stopped up by the
deposition of solid substances which have entered by the roots, or by
the formation of chemical compounds which, like concretions in
the bodies of animals, slowly increase in size till the vessels become
entirely closed—or they are by degrees compressed laterally by the
growth of wood around them, so as to become incapable of trans-
mitting the ascending fluids. Perhaps the result is in most cases
due in part to each of these causes. This more or less perfect
stoppage of the oldest vessels is one reason why the course of the
sap is chiefly directed through the newer tubes.”
The functions of the bark, which forms the exterior portion of
* As the newest roots are prolongations of the newest wood, it may be supposed
that the fact of these roots being the chief absorbents from the soil, is a sufficient rea-
son why that which is absorbed by them should also pass through the wood with which
they are most closely connected. But that the pores of the heart-wood are really inca-
pable of transmitting fluids, is shown by plunging the newly cut stem of a tree into a
coloured solution,-the newer wood will be dyed, while more or less of the central por-
tion will remain unchanged (Bowcherie.)
s
sº-
140 ESCAPE OF WATERY WAPOUR FROM THE LEAVES.
the stem, will be more advantageously described after we shall have
considered the purposes served by the leaves.
\ § 5. Functions of the leaves. - ". .
The vessels of which the sap-wood is composed extend upwards
into the fibres of the leaf. Through these vessels the sap ascends,
and from their extremities diffuses itself over the surface of the
leaf. Here it undergoes important chemical changes, the extent,
if not the exact nature, of which will appear from a short descrip-
tion of the functions which the leaves are known or are believed to
discharge. * . -
1°. When the roots of a living plant are immersed in water, it
is a matter of familiar observation that the water gradually dimi-
nishes in bulk, and will at length entirely disappear, even when
evaporation from its surface is entirely prevented. The water
which thus disappears is taken up by the roots of the plant, is car-
ried up to the leaves, is there spread out over a large surface ex-
posed to the sun and to the air, and in the form of vapour escapes
in considerable proportion through the pores of the leaf and dif-
fuses itself through the atmosphere. - -
The quantity of water which thus escapes from the surface of the
leaves varies with the moisture of the soil, with the species of plant,
with the temperature and moisture of the air, and with the season
of the year. According to the experiments of Hales, it is also de-
pendent on the presence of the sun, and is scarcely perceptible
during the night. He found that a sun-flower, 3% feet high, lost
from its leaves during 12 hours of one day 30, and of another day
20 ounces of water, while during a warm night, without dew, it
lost only three ounces, and in a dewy night underwent no diminu-
tion in weight.”
* When the escape of vapour from the leaves is more rapid than the supply of wa-
ter from the roots, the leaves droop, dry, and wither. Such is sometimes the case
with growing crops in very hot weather, and it also happens when a twig or flower is
plucked and separated from the stem or root. When thus separated the leaves still
..continue to give off watery vapour into the air, and consequently the sap ascends from
the twig or stalk to supply the place of the water thus exhaled. --
But as the sap ascends it must leave the vessels empty of fluid, and air must rush
in to fill the empty space. This will continue till nearly all the fluid has risen from
the stem into the leaf, and the vessels of the wood have become full of air. But if
the stem of the twig or flower be placed º water, this liquid will rise into it, air will
PURPOSES SERVED BY IT. 141
This loss of watery vapour by the leaf is ascribed to two diffe-
rent kinds of action. First, to a natural perspiration from the
pores of the leaf, similar to the insensible perspiration which is
continually proceeding from the skins of healthy animals; and
second, to a mechanical evaporation like that which gradually
takes place from the surface of moist bodies when exposed to hot
or dry air. The relative amount of loss due to each of these two
modes of action respectively, must differ very much in different
species of plants, being dependent in a great measure on the spe-
cial structure of the leaf. In all cases, however, the natural per-
spiration is believed very greatly to exceed the mere mechanical
evaporation—though the results of Hales, and of other experi-
menters, show that both processes proceed with the greatest rapi-
dity under the influence of a warm dry atmosphere, aided by the
direct rays of the sun. -
Among the several purposes served by this escape of watery
vapour from the surface of the leaf, it is of importance for us to
notice the direct chemical influence it exercises over the growth
of the plant. As the water disappears from the leaf, the roots
must absorb from the soil at least an equal supply. This water
brings with it the soluble substances, organic and inorganic, which
the soil contains, and thus in proportion to the activity with which
be excluded, and the freshness and bloom of the leaves and flowers will be longer
preserved. If the water into which they are introduced contain any substances in
solution, these will rise along with the water, and will gradually make their way
through all the vessels of the wood, till they can be detected in the leaves. By this
means even large trees may in a short time be saturated with saline solutions, capable
of preserving them from decay (Boucherie.) It is only necessary to cut down or saw
through the tree, and insert its lower extremity into the prepared solution, when the
action of the Sun and air upon the leaves, causes it spontaneously to ascend. Thus
corrosive sublimate (the subject of Kyan's Patent,) may be injected with ease, or pyro-
ligmate of iron (iron dissolved in wood vinegar,) which Boucherie recommends as
equally efficient and much more economical,” or chloride of zinc (zinc dissolved in
spirit of salt) which is recommended by others. The process is finished when the li-
quid is found to have risen to the leaf. Coloured solutions may in the same way be
injected, and the wood tinged to any required shade. One of the chief benefits at-
tendant upon the cutting of wood in the winter, appears to be that the absence of
leaves prevents the exhaustion of the sap and the ascent of air into the vessels of the
wood—the oxygen of this air tending to induce decay. But the sap may be retained,
and the air excluded almost as effectually, at any other season of the year, by strip.
ping the tree of its leaves and branches a few days before it is cut down,
* Amºl, de Chim, et de Phys, lxxiv. p. 113.
142 OTHER WOLATII, E SUBSTANCES EXHALED.
the leaves lose their watery vapour, will be the quantity of those
substances which enter from the soil into the general circulation
of the plant. This enables us to understand how substances, very
sparingly soluble in water, should yet be found in the interior of
plants, and in very considerable quantity, at almost every stage of
their growth. -
2°. Besides watery vapour, however, the leaves of nearly all
plants exhale at the same time other volatile compounds in greater
or less abundance. In the petals of flowers we are familiar with
such exhalations—often of an agreeable and odoriferous character.
In the case of plants and trees also which emit a sensible odour,
we readily recognise the fact of volatile substances being given off
by the leaves. But even when the sense of smell gives us no in-
dication of their emission from a single leaf or a single plant—the
introduction of a number of such inodorous plants into the con-
fined atmosphere of a small room after a time satisfies us that even
they part with some volatile matter from their leaves, which makes
itself perceptible to our imperfect organs only when in a concen-
trated state. The probability therefore is, that the leaves of all
plants emit along with the watery vapour which they evolve, cer-
tain other volatile substances also, though often in quantities so
minute as to escape detection by our unaided senses. By the
practical farmer, such exhalations are observed in the smell given
off by rapidly growing barley, and in the disagreeable odour
emitted when turnips are bulbing well. By the emission of these
substances plants probably relieve themselves of what would prove
injurious if retained, though of the chemical nature and composi-
tion of these exhalations little or nothing has as yet been ascer-
tained. -
3°. Along with the watery vapour emitted, many leaves appear,
like the skins of animals, to emit Saline matters of various kinds,
and in variable proportions. These are washed off by the rains, and
are thus returned to the soil. This function of the leaf has not hi-
therto been made the subject of any special chemical investigation.
4°. If the branch of a living plant be so bent that some of its
leaves can be introduced beneath the edge of an inverted tumbler
full of water, and if the leaves be then exposed to the rays of the
sun, bubbles of gas will be seen to form on the leaf, and gradually
4
CHEMICAL FUNCTIONS OF THE LEAF. 143
to rise through the water and collect in the bottom of the tumbler.
If this gas be examinedit will be found to be oxygen gas nearly pure.
If the water contain carbonic acid gas, or if during the experi-
ment a little carbonic acid be introduced, this gas will be found
gradually to disappear, while the oxygen will continue to accu-
mulate.
Or if the experiment be made by introducing a living plant
into a large bell glass full of common atmospheric air, allowing it
to grow there for twelve hours in the Sunshine, and then examining
or analysing the air contained in the glass, the result will be of a
precisely similar kind. The per-centage of oxygen in the air
will have increased.” And if the experiment be varied by the
introduction of a small quantity of carbonic acid gas into the jar,
this gas will be found as before to diminish in quantity, while the
oxygen increases. The conclusion drawn from these experiments,
therefore, is, that the leaves of plants, when earposed to the rays of
the sun, absorb carbonic acid from the air and give off oxygen gas.
It has been already stated that the proportion of carbonic *id
present in the atmosphere is exceedingly small—about gºt of its
bulk; but if for the purpose of experiment we increase this pro-
portion in a gallon of air to five or ten per cent., introduce a liv-
ing plant into it, and expose it to the Sunshine, the Garbonic acid
will gradually disappear as before, while the oxygen will increase.
And if we analyse the air and estimate the exact bulk of each of
these gases present in it at the close of our experiment, we shall
find that the bulk of the oxygen has increased very nearly by as
much as the carbonic acid has diminished. That is to say, if five
cubic inches of the latter have disappeared, nearly five cubic inches
will have been added to the bulk of the oxygen. The above gene-
ral conclusion, therefore, is rendered more precise by this experi-
ment, which appears to shew that under the influence of the sun’s
rays, the leaves of plants absorb carbonic acid from the air, and at
the same time give off NEARLY AN EQUAL BULK of oxygen gas.
And as carbonic acid (CO2) contains its own bulk of oxy-
gen gast combined with a certain known weight of carbon, it is
* It will be remembered that atmospheric air contains about 21 per cent. of oxy-
gen gaS. -
+ This the reader will recollect is proved by burning charcoal in a bottle of oxygen
144 THEY EMIT OXYGEN DURING THE DAY.
further inferred that the oxygen given off by the leaves is the
same which has been previously absorbed in the form of carbonic
acid, and therefore it is usually stated as a function of the leaves—
that in the sunshine they absorb carbonic acid from the air, DECOM--
POSE it in the interior of the leaf, retain its carbon, and again re-
ject or emit the owygen it contained. - -
This conclusion presents a very simple view of the relations of .
oxygen and carbonic acid respectively to the living leaf in the pre-
sence of the sum, and it appears to be fairly deduced from the
facts above stated. It has occasionally been observed, however,
that the bulk of oxygen given off by the leaf has not been pre-
cisely equal to that of the carbonic acid absorbed,” and hence it is
also fairly concluded that a portion of the oxygen of the carbonic
acid which enters the leaf is retained, and made available in the
production of the various substances which are formed in the vas-
cular system of different plants. On the other hand, it is stated
by Sprengel that, if compounds containing much oxygen be pre-
sented to the roots of plants, and thus introduced into the circula-
tion, they are also decomposed, and the oxygen they contain in
part or in whole given off by the leaves, so that, under certain
circumstances, the bulk of the oxygen which escapes is actually
greater than that of the carbonic acid which is absorbed by the
leaves. Such is the case, for example, when the roots are mois-
tened with water containing carbonic, sulphuric, or nitric acids.f
It is of importance to note these deviations from apparent sim-
plicity in the relative bulks of the two gases which are respectively
given off and absorbed by all living vegetables. There are nume-
yous cases of the formation of substances in the interior of plants
which theory would fail to account for with any degree of ease,
were these apparent anomalies to be neglected. This will more
distinctly appear when in a subsequent lecture we shall enquire
how—by what chemical changes—the substances which plants
contain, or of which they consist, are produced from the food
which they draw from the air and from the soil.
gas till combustion ceases, when nearly the whole of the oxygen is converted into
carbonic acid, but without change of bulk.-See Lecture III., p. 59.
* See Persoz Chimie Moleculaire, p. 54.
+ Sprengel Chemie, II, p. 344. -
AND CARBONIC ACID DURING THE NIGHT. I45
The most general and probable expression, therefore, for the
function of the leaf, now under consideration, appears to be that
in the sunshine the leaves absorb from the air carbonic acid, and
at the same time evolve oxygen gas, the bulk of the latter gas
given off being nearly equal to that of the former which is taken.
in—the relative bulks of the two gases varying more or less with
the species of plant, as well as with the circumstances under which
it is caused or is fitted to grow." - -
I have said above, that the gas given off from the leaves in the
presence of the sun, is oxygen gas nearly pure. In a strong Sun-
light it is sometimes given off without any admixture whatever.
In ordinary light, however, it almost always contains a sensible
quantity of carbonic acid, which is greater in the shade than in
the direct sunshine—increasing with the dulness and darkness of
the day—and varies from 1 to 15 per cent of the volume of the
gas collected (Schultz) f a'
5°. Such is the general relation of the leaf to the oxygen and
carbonic acid of the atmosphere in the presence of the sun. Dur-
ing the night their action is reversed, they emit carbonic acid and
absorb oxygen. This is proved by experiments similar to those
above described. For if the plant which has remained under the
bell glass for 12 hours in the sunshine—during which time the
oxygen has sensibly increased, and the carbonic acid diminished in
bulk—be allowed to remain in the same air through the following
night, the oxygen will be found to have decreased, while the car-
bonic acid will be present in larger quantity than on the evening
of the previous day. -
The carbonic acid thus given off during the night is supposed
to be partly derived from the soil through the roots, and partly
from the substance of the plant itself. The oxygen absorbed
either combines with the carbon of the plant to form a portion of
the carbonic acid which is, at the same time, given off, or is em-
ployed in producing some of the other oridized f compounds that
exist in the Sap. -
* As the oxygen given off by the leaves is always the result of a chemical decom-
position, by which carbonic acid or some other compound is deprived of a portion, at
least, of its oxygen or is de-oxidized—this function of the leaves in the presence of
the sun is often spoken of as their de oacidizing power. *
f Die Entdeckung der Wahren Pflanzen nahrung, pp. 28 and 33.
+ Ocidized—containing oxygen in considerable quantity.
IK
i
146 AGENCY OF THE SUN's LIGHT.
As a general rule, the quantity of carbonic acid given off during
the night is far from being equal to that which is absorbed during
the day. Still it is obvious that a plant loses carbon precisely in
proportion to the amount of this gas given off. Hence, when the
days are longest, the plant will lose the least, and where the sun
is brightest it will gain the fastest;-since, other things being
equal, the decomposition of carbonic acid proceeds most rapidly
where the sky is the clearest, and the rays of the sun most power-
ful. It thus appears why in Northern regions, where spring,
summer, and autumn are all comprised in one long day—vegeta-
tion should proceed with such rapidity. The decomposition of
the carbonic acid goes on without intermission, the leaves have no
night of rest, but nature has kindly provided that, where the sea-
Son of warmth is so fleeting, there should be no cessation to the
necessary growth of food for man and beast.*
This comparison of the functions performed by the leaf, during
the day and night respectively, explains the chemical nature of
the blanching of vegetables practised by the gardener, as well as
the cause of the pale colour of plants that grow naturally in the
absence of light.
When exposed to the sun the leaves of these sickly vege-
tables evolve oxygen, and gradually become green and healthy.
Woody matter is formed, and their stems become strong and
fibrous. º -
The light of the sun, in the existing economy of nature, is in-
deed equally necessary to the health of plants and of animals. The
former become pale and sickly, and refuse to perform their most
important chemical functions when excluded from the light. . The
bloom disappears from the human cheek, the body wastes away,
and the spirit sinks, when the unhappy prisoner is debarred from
the sight of the blessed sum. In his system, too, the presence of
* At Berlin and London the longest day has sixteen and a half hours. At Stock-
holm and Upsala, the longest has eighteen and a half hours, and the shortest five and
a half. At Hamburg, Dantzic, and Stettin, the longest day has seventeen hours, and
the shortest seven. At St Petersburg and Tobolsk, the longest has nineteen, and the
shortest five hours. At Torneo in Finland, the longest day has twenty-one hours and
a half, and the shortest two and a half. At Waudorhus, in Norway, the day lasts
from the 21st of May to the 22d of July, without interruption ; and in Spitzbergen
the longest lasts three months and a half.
LEAVES SOMETIMES EMIT A COMBUSTIBLE GAS. 147
light is necessary to the performance of those chemical functions
on which the healthy condition of the vital fluids depends.
The processes by which oxygen and carbonic acid are respectively
evolved in plants have been likened by physiologists to the respira-
tion and digestion of animals. It is supposed that when plants
respire they give off carbonic acid as animals do, and that when
they digest they evolve oxygen. Respiration also, it is said, pro-
ceeds at all times, digestion only in the light of the Sun. Though
these views are confessedly conjectural, they are founded upon
striking analogies, and may reasonably be entertained as matters
of opinion. * -
Still, some facts are known to us which are inconsistent with
this opinion. The fungi and mosses give off carbonic acid at all
times, and most in the sunshine (Hoffman). Do these plants re-
spire only 2 Independent of this opinion, however, the fact itself
is very curious, and shows that these humbler plants must obtain
their organic food in a way very different from that by which it is
conveyed to our trees and shrubs and usually cultivated crops.
6°. According to the experiments of Schultz, the leaves some-
times give off a combustible gas mixed with the oxygen, which
they evolve when exposed to the sun's rays. He found, on one or
two occasions, that a lighted taper, when introduced into the gas
he had collected from the leaves, instead of burning quietly,
caused a violent explosion. It is not unlikely that this explosion
was caused by the presence of light carburetted hydrogen, which,
as in our coal mines, gives rise to a violent explosion when
kindled in the presence of oxygen gas.
7°. Other species of decomposition also, besides that of de-oxida-
tion, go on in the leaf, or are there made manifest. Thus when
plants grow in a soil containing much common salt (chloride of
sodium) or other chlorides, they have been observed to evolve
chlorine” gas from their leaves (Sprengel and Meyen.) This
takes place, however, more during the night than during the day.
Some plants also give off ammonia (see p. 110), while others
* Chlorine is a gas of a greenish yellow colour having an unpleasant taste and a
suffocating odour. When it combines with other substances it forms chlorides. It
exists in, and imparts its smell to, chloride of lime, which is employed for disinfecting
purposes, and it forms three-fifths of the weight of common salt.
I48 CHLORINE GIVEN OFF BY THE LEAF.
(cruciferae) emit from their leaves pure nitrogen gas (Daubeny). *
This emission of nitrogen from the leaves is, according to Schultz,
not an uncommon occurrence, and on a dark day may amount to
nearly two-fifths of the entire bulk of the gas given off.
The evolution of chlorine implies the previous decomposition of
the chlorides, which have been absorbed from the soil; while that
of nitrogen may be due to the decomposition of ammonia, of mi-
tric acid, or of some other compound containing nitrogen, which
has entered into the circulation by the roots. The exact mode
and nature of the decomposition of these latter compounds, and the
purposes served by them in the vegetable economy, will come un-
der our consideration in a subsequent lecture.
The leaf has been described (p. 119) as an expansion of the
bark. It consists internally of two layers of veins or vascular
fibres laid one over the other, the upper connected with the wood
—the lower with the inner bark. It is covered on both sides by
a thin membrane (epidermis) the expansion of the outer bark.
This thin membrane is studded with numerous small pores or
mouths (stomata), which vary in size and in number with the nature
of the plant, and with the circumstances in which it is intended to
grow. It is from the pores in the upper part of the leaf that sub-
stances are supposed to be exhaled, while every thing that is in-
haled enters by those which are observed in the under side of the
leaf. This opinion, however, is not universally received, it being
admitted by some that the power both of absorbing and of emitting
may be possessed by the under surface of the leaf.
8°. We have seen that the chief supply of the fluids which con-
stitute the sap of plants, is derived from the soil. The under
side of the leaves of plants also is supposed to be capable of ab-
sorbing moisture from the air, either in the form of watery va-
pour, or when it falls upon the leaves in the state of dew. Like
the roots also they may absorb with the dew any substances which
the latter happens to hold in solution. And thus plantsmay, in some
degree, be nourished by the volatileorganic substances which ascend
* Three Lectures on Agriculture, p. 59.
+ This is illustrated by the action of a cabbage leaf on a wound. If the upper side
be applied, the sore is protected and quickly heals, while the under side-draws it and
produces a constant discharge. 3
FUNCTIONS OF THE FLOWER-LEAVES. - I 49
from the earth during the heat of the day, and which are again in
a great measure precipitated with the evening dew.
Whether the leaves of all or of any plants absorb nitrogen gas
from the air has not, as I have already stated, (p. 107), been hi-
therto determined with sufficient accuracy. If they do, it must in
general be in very small quantity only. It is doubtful also how far
they regularly absorb any other substances which the air is sup-
posed to contain. Thus it is known that nitric acid exists in the
air in very minute quantity. Some chemists also believe that am-
monia is extensively diffused through the atmosphere in an exceed-
ingly diluted state. Do the leaves of plants absorb these substances?
Is the absorption of them one of the constant and necessary func-
tions of the leaves? The reply to these questions must be very
uncertain, and any principle which professes to be based upon such
a reply must be regarded only as a matter of opinion.
9°. The petals or flower-leaves perform a somewhat different
function from those of the ordinary leaves of a plant. They ab-
sorb oxygen at all times—though more by day than by night—
and they constantly emit carbonic acid. The bulk of the latter
gas which is evolved is less, however, than that of the oxygen taken
in. The absorption of oxygen gas, and the constant production of
carbonic acid is, in some flowers, so great as to cause a perceptible
increase of temperature—and to this slow combustion, so to speak,
the proper heat observed in the flowers of many plants has been
attributed. •
According to some authors, the flower-leaves also emit pure
nitrogen gas.” This fact has not yet been determined by a suffi-
cient number of accurate experiments. It is in accordance, how-
ever, with the results of Boussingault that, when a plant flowers
and approaches to maturity, the nitrogen it contains becomes less,
and with the practical observation that the most nutritive hay is
obtained by cutting grass just as it comes into flower. This evo-
lution of mitrogen, therefore, if satisfactorily established, would
throw an interesting light on the most advantageous employment
of green crops, both for the purposes of manure and for the feed-
ing of cattle.
10°. When the leaves of a plant begin to decay, either natu-
* Sprengel, Chemic, II. p. 347.
150 . FUNCTIONS OF THE BARK,
zº
rally as in the autumn, or from artificial or accidental causes, they
no longer absorb and decompose carbonic acid, even under the in-
fluence of the sun's rays. On the contrary, they absorb oxygen,
like the petals of the flower—new compounds are formed within
their substance—their green colour disappears—they become yel-
low—they wither, die, and drop from the tree—their final function,
as the organs of a living being, is discharged. They then undergo
new changes, are subjected to a new series of influences, and are
made to serve new purposes in the economy of nature. These we
shall hereafter find to be no less interesting and important in re-
ference to a further end, than are the functions of the living leaf
to the growth and nourishment of the plant.” g
That chemical changes of different kinds are continually going
on in the leaves of the flower are shown by many facts. Thus
some, like the cacalia (Recluz), emit an aromatic odour only while
the sun shines upon them, while many others emit a stronger odour
in ordinary daylight than in that of the bright sun. The Cactus
grandiflorus emits its odour at the moment when its flower opens—
that is after sun-set—while the Hesperis tristis, the Pelargonium
triste, the Gladiolus tristis, and the Epidendron noctuum give out
their peculiar Smell only during the evening and night.
Inflammable gases or vapours are also said to be given off by
the leaves of flowers. The Dictumnus Fravinella emits a va-
pour of this kind from its flowers in such abundance on a calm
evening, that it may be set on fire by a candle.f
§ 6. Functions of the bark.
The inner bark being connected with the under layer of vessels
in the leaf, receives from them the Sap after it has been changed
by the action of the air and light, and transmits it downwards to
the root.
The outer bark, especially in young twigs and in the stalks of
the grasses, so closely resembles the leaves in its appearance, that
we can have no difficulty in admitting that it must, not unfre-
quently, perform similar functions. In the Cactus, the Stapelia,
and other plants which produce no true leaves, this outer bark
* See in Lecture, [X. the section “On the law of the decay of vegetable substances.”
+ Dr Black's Chemistry, ii. p. 224, note.
CHEMICAL FUNCTIONS OF THE BARK. 151
seems to perform all the functions which in other vegetable tribes
are specially assigned to the abundant foliage. During its de-
scent through the inner bark, therefore, the sap must in many
cases undergo chemical changes, more or less analogous to those
which usually take place in the leaf.
It is by means of the inner bark that the stems of trees, such as
our forest and fruit trees, are enlarged by the deposition of annual
layers of new wood. The woody matter is formed or prepared in
the leaf, and as the sap descends it is deposited beneath the inner
surface of the inner bark. It thus happens that, as the Sap de-
scends, it is gradually deprived of the substances it held in solu-
tion when it left the leaf, and in consequence it becomes difficult
to say how much of the change, which the sap is found to have un-
dergone when it reaches the root, is due to chemical transforma-
tions produced during its descent, and how much to the deposi-
tion of the woody and other matters it has parted with by the way.
Among other evidences of such changes really taking place dur-
ing the descent of the sap, I may mention an observation of Meyen
(Jahresbericht, 1839, p. 27), made in the course of his experiments
on the re-production of the bark of trees. In these experiments
he inclosed the naked wood in strong glass tubes, and in three ca-
ses out of eight the tubes were burst and shattered in pieces. This
could only have arisen from the disengagement of gaseous sub-
stances, the result of decomposition. While, therefore, such gases
as enter by the roots or are evolved in the vessels of the wood
during the ascent of the sap escape by the leaf along with those
which are disengaged in the leaf itself—it is probable that those
which are produced as the result of changes in the bark, descend
with the downward sap, and are discharged by the root.”
In the bark of the root it is probable that still further changes
take place—and of a kind which can only be effected during
the absence of light. This is rendered probable by the fact
that the bark of the root frequently contains substances which are
not to be met with in any other part of the plant. Thus from the
bark of the fresh root of the apple tree a substance named phlo-
* Sprengel says that the stems, the twigs, and the stalks of the grasses all absorb
oxygen and give off carbonic acid.—Chemie, II., p. 34]. .
152 FUNGTIONS OF THE ROOT MAY BE MODIFIED
ridzine, possessed of considerable medical virtues, may be readily
extracted, though it does not exist in the bark either of the stem
or of the branches. + e
In fine, as the food which is introduced into the stomachs of ani-
mals undergoes continual and successive chemical changes during
its progress through the entire alimentary canal—so, numerous
phenomena indicate that the sap of plants is also subjected to un-
ceasing transformations,—in the root and in the stem as well as in the
leaves, at one time in the dark, at another under the influence of
the sun's rays, exposed when in the leaf to the full action of the
air, and when in the root almost wholly secluded from its pre-
sence ;--the new compounds produced in every instance being
suited either to the nature of the plant or to the wants and func-
tions of that part of it in which each transformation takes place.
To some of these transformations it will be necessary to advert
more particularly, when we come to consider the special changes
—by which those substances of which plants chiefly consist, are
formed out of the compounds on which they chiefly live.
§ 7. Circumstances by which the functions of the various parts
of plants are modified. e
Plants grow more or less luxuriantly, and their several parts are
more or less largely developed, in obedience to numerous and va- -
ried circumstances,
1°. In regard to the special functions of the root, we have already
seen that the access of atmospheric air is in some cases indispensable,
while in others, by shooting vertically downwards, the roots appear
to shun the approach of either air or light. The mechanical con-
dition of the soil, therefore, must modify its fitness for the growth
of this or that kind of plant. It is obvious also that a certain
degree of moisture in the soil, and a certain temperature, are ne-
cessary to the most healthy discharge of the functions of the root.
In hot weather the plant droops, because the roots do not absorb
water from the soil with sufficient rapidity. And though it is
probable that, at every temperature above that of absolute freez-
ing, the food contained in the soil is absorbed and transmitted
more or less slowly to the stem, yet it is well known that a genial
warmth in the soil stimulates the roots to increased activity. The
BY THE NATURE OF THE SOIL. - 153
practice of gardeners in applying bottom heat in the artificial cli-
mate of the green-house and conservatory is founded on this well
known principle,
But the chemical nature of the soil in which plants grow has
also much influence on the way in which the functions of the root
are discharged. As a general fact this also is well known, though
the special qualities of the soil on which the greater or less acti-
vity of vegetation depends, are far from being generally under-
stood. If the soil contain a sensible quantity of any substance
which is noxious to plants, it is plain that their roots will be to a
certain degree enfeebled, and their functions in consequence only
imperfectly discharged. Or if the soil be deficient either in or-.
ganic food, or in one or other of those inorganic substances which
the plants necessarily require for the production of their several
parts—the roots cannot perform their office with any degree of
efficiency. Where the necessary materials are wanting the builder
must cease to work. So in a soil which contains no silica the grain
of wheat may germinate—but the stalk cannot be produced in a
natural or healthy state, since silica is indispensable to its healthy
construction.
2°. The ascent of the sap is modified chiefly by the season of
the year, by the heat of the day, and by the genus and age of the
plant or tree.
a. There seems reason to believe that the plant never sleeps, that
even during the winter the circulation slowly proceeds—though
the first genial Sunshine of the early spring stimulates it to in-
creased activity. The general increased temperature of the air
does not produce this acceleration in so remarkable a manner as
the direct rays of the sun. The sap will flow and circulate on the
side of a tree on which the Sunshine falls, while it remains sensi-
bly stagnant on the other. This is shown by cutting down similar
trees at more and more advanced periods of the spring, and im-
mersing their lower extremities in coloured solutions. The wood
and bark on the Sunny side of the tree will be coloured, while on
the other, both will remain unstained. If a similar difference in the
comparative rapidity of the circulation on opposite sides of a trunk
or branch be supposed to prevail more or less throughout the year,
we can readily account for the annual layers of wood being often
154 WARMTH AFFECTS THE RAPIDITY OF THE CIRCULATION.
*
thicker on the one-half of the circumference of the stem than on
the other. -
The sap is generally supposed to flow most rapidly during the
spring, but if trees be cut down at different seasons, and immersed
as above described, the coloured solution, according to Boucherie,
reaches the leaves most rapidly in the autumn.”
b. The heat of the day, other circumstances being the same, ma-
terially affects, for the time, the rapidity of the circulation. The
more rapidly watery and other vapours are exhaled from the
leaves, the more quickly must the sap flow upwards to supply the
waste. If on two successive days the exhalation from the leaves
of the same plant in the experiments of Hales, above described
(p. 140,) amounted to 20 and 30 ounces respectively, the ascent
of the sap must have been retarded or accelerated on these days
in a similar proportion. Hence, every sensible variation in the
temperature and moisture of the air must also, to a certain extent,
modify the flow of the sap ; must cause a greater or less propor-
tion of that food which the earth supplies to be carried to every
part of the plant, and must thus sensibly affect the luxuriance and
growth of the whole. *
c. But the persistance of the leaves is a generic character, which
has considerable influence upon the circulation in the evergreens,
In the pine and the holly, from which the leaves do not fall in the
autumn, the sap ascends and descends during all the colder
months, at a slower rate, it is true, than in the hot days of sum-
mer—yet much more sensibly than in the oak and the ash, which
spread their naked arms through the wintry air. This is illus-
trated by the experiments of Boucherie, who has observed that in
December and January the entire wood of resinous trees may be
* Boucherie makes a distinction, not hitherto insisted upon by physiologists, be-
tween the circulation on the surface of the tree by which the buds and young twigs
are supported, and the interior circulation which is not perfect until a later period of
the year. Hence in the spring, though the sap is flowing rapidly through the bark
and the newest wood, coloured solutions will not penetrate the interior of the tree
with any degree of rapidity. In autumn, on the other hand—when the fear of ap-
proaching winter has already descended upon the bark—the time of most active cir-
culation has only arrived for the interior layers of the older wood. It is this season
consequently that he finds most favourable for impregnating the trunks of trees with
those solutions which are likely to preserve them from decay.—Ann, de Chim, et de
Phys, lxxiv. p. 135.
ACTION OF THE LEAVES MODIFIED. 155
readily and thoroughly penetrated by the spontaneous ascent of Sa-
line and other solutions, into which their stems may be immersed.
3°. From what has just been stated, it will appear that the
mechanical functions of the stem are subject to precisely the same
influences as the ascent of the sap. As the tree advances in age,
the vessels of the interior will become more or less obliterated,
and the general course of the sap will be gradually transferred to
annual layers, more and more removed from the centre. It is
this transference of the vital circulation to newer and more perfect
vessels that enables the tree to grow and blossom and bear fruit
through so long a life. In animals, on the contrary, the vessels
are gradually worm out by incessant action. None of them,
through old age, are permitted to retire from the service of the
body—and the whole system must stop when one of them is inca-
pacitated for the further performance of its appointed duties. -
In regard to the chemical functions of the stem, it is obvious
that they are not assigned to the mere woody matter of the vessels
and cells. They take place in these vessels, but the nature and
extent of the chemical changes themselves must be dependent
upon the quantity and kinds of matter, which ascend or descend
in the sap. The entire chemical functions of the plant, therefore,
must also be dependent upon, and must be modified by, the nature
of the substances, which the soil and the air respectively present
to the roots and to the leaves.
4°. In describing the functions of the leaf, I have already had
occasion to advert to the greater number of the circumstances by
which the discharge of those functions is most materially affected.
We have seen that the purposes served by the leaf are entirely
different according as the sun is above or below the horizon; that
the temperature and moisture of the air may indeed materially
influence the rapidity with which its functions are discharged—
but that the light of the sun actually determines their nature.
Thus the leaf becomes green and oxygen is given off in the pre-
sence of the sum, while in his absence carbonic acid is disengaged,
and the whole plant is blanched.
How necessary light is to the health of plants may be inferred
from the eagerness with which they appear to long for it. How
intensely does the sun-flower watch the daily course of the sun,
a
156 LIGHT NECESSARY TO THE HEALTH OF PLANTs.
how do the countless blossoms nightly droop when he retires,-
and the blanched plant strive to reach an open chink through which
his light may reach it !”
That the warmth of the sun has comparatively little to do with
this specific action of his rays on the chemical functions of the leaf,
is illustrated by some interesting experiments of Mr Hunt, on the
effect of rays of light of different colours on the growing plant.
He sowed cress seed, and exposed different portions of the soil
in which the seeds were germinating to the action of the red, yel-
low, green, and blue rays, which were transmitted by equal thick-
nesses of solutions of these several colours. “After ten days,
there was under the blue fluid, a crop of cress of as bright a green
as any which grew in full light and far more abundant. The
crop was scanty under the green fluid, and of a pale yellow un-
healthy colour. Under the yellow solution, only two or three
plants appeared, but less pale than those under the green, while
beneath the red, a few more plants came up than under the yel-
low, though they also were of an unhealthy colour. The red and
blue bottles being now mutually transferred, the crop formerly be-
neath the blue in a few days appeared blighted, while on the patch
previously exposed to the red, some additional plants sprung
up.”f -
Besides the rays of heat and of light, the sun-beam contains
what have been called chemical rays, not distinguishable by our
senses, but capable of being recognised by the chemical effects they
produce. These rays appear to differ in kind, as the rays of diffe-
rent coloured light do. It is to the action of these chemical rays
on the leaf, and especially to those which are associated with the
* A potato has been observed to grow up in quest of light from the bottom of a
well twelve feet deep—and in a dark cellar a shoot of 20 feet in length has been met
with, the extremity of which had reached and rested at an open window. In the
leaves of blanched vegetables peculiar chemical compounds are formed. Thus in the
blanched shoot of the potato a poisonous substance called Solamin is produced, which
disappears again when the shoot is exposed to the light and becomes green (Otto.)
In asparagus, in blanched clover, (Piria) and other plants grown in the dark, aspara-
gine is formed, and no doubt other peculiar changes take place, which are not yet un-
derstood.
+ London and Edinburgh Journal of Science, February 1840. Dr Draper of New
York, who has made us acquainted with many new facts in regard to the chemical
action of the rāys of light, has obtained results which differ from those of Mr Hunt.
CHEMICAL RAYS IN THE SUN-BEAM. 157
blue light in the solar beam, that the chemical influence of the
sum on the functions of the leaf is principally to be ascribed.
This decomposing influence of the leaf in the presence of the
sun is often truly extraordinary. The leaves of a vine inclosed
under a receiver have been found to extract the whole of the car-
bonic acid from a current of air passed through the vessel, how-
ever rapid that current might be (Boussingault). How rapidly
must the air that plays among the leaves of a tree yield carbon
for its summer's growth !
It cannot be doubted that the warmth and moisture of a tropi-
cal climate act as powerful stimulants—assistants it may be—to
the leaf, in the absorption of carbonic acid from the air, and in
that rapid appropriation (assimilation) of its carbon, by which the
growth of the plant is hastened and promoted. But the bright
sun, and especially the chemical influence of his beams, may be
regarded as the main agent in the wonderful development of a
tropical vegetation. Under this influence the growth by the leaves
at the expense of the air must be materially increased, and the
plant rendered less dependent upon the root and the soil for the
food on which it lives.”
5°. The rapidity with which a plant grows has an important in-
fluence upon the share which the bark is permitted to take in the
general mourishment of the whole. The green shoot performs in
some degree the functions of the leaf. In vascular plants, there-
fore, which in a congenial climate may almost be seen to grow,
the entire rind of a tall tree may more or less effectually absorb
carbonic acid from the atmosphere, during the presence of the sun.
The broad leaves of the palm tree, when fully developed, render
the plant in a great degree independent of the soil for organic
food—and the large amount of absorbing surface in the long green
tender stalks of the grasses, and of their tropical analogues, must
* The effect of continued sunshine may be often seen in our corn fields in May,
when, under the influence of propitious weather, the young plants are shooting rapidly
up. When such a field is bounded by a lofty hedge running nearly north and south, the
ridges nearest the hedge on either side will be in the shade for nearly one-half of the
day, and will invariably appear of a paler green and less healthy colour. If the hedge
be studded with occasional large trees, the spots on which the shadows of those trees
rest will be indicated by distinct pale green patches stretching further into the field
than the first, and sometimes even than the second ridges,
I58 REMARKABLE EFFECT OF MARL.
materially contribute to the same end. Hence the proportion of
organic matter which has been derived directly from the air, by
any crop we reap, must always be the greater, the more rapid its
general vegetation has been.
It is a fact familiarly known to all of you that, in addition to those
circumstances by which we can perceive the special functions of
any one organ to be modified, there are many by which the entire
economy of the plant is materially and simultaneously affected.
On this fact the practice of agriculture is founded, and the various
processes adopted by the practical farmer are only so many modes
by which he hopes to influence and promote the growth of the
whole plant, and the discharge of the functions of all its parts.
Though manures in the soil act immediately through the roots,
they stimulate the growth of the entire plant; and though the ap-
plication of a top-dressing to a crop of young corn or grass may be
supposed first to affect the leaf, yet the beneficial result of the expe-
riment depends upon the influence which the application may exer-
cise on every part of the vegetable tissue.
In connection with this part of the subject, therefore, I shall
only further advert to a very remarkable fact mentioned by Spren-
gel, which seems, if correct, to be susceptible of important practi-
cal applications. He states that it has very frequently been ob-
served in Holstein that if, on an extent of level ground sown with
corn, some fields be marled, and others left unmarled, the corn on
the latter portions will grow less luxuriantly and will yield a poorer
crop than if the whole had been unmarled. Hence, he adds, if the
occupier of the unmarled field would not have a succession of poor
crops, he must marl his land also.”
Can it really be, that the Deity thus rewards the diligent and
the improver ? Do the plants which grow on a soil in higher con-
* Wenn nämlich auf einer Feldflur Stück um Stück gemergelt worden ist, so wach-
sen die Früchte auf den nicht gemergelten Feldern, auch wenn hier alle früheren ver-
hältnisse ganz die-selben bleiben, nicht mehr so gut, als ehedem ; wodurch die Be-
sitzer jener Felder, wenn sie nicht fortwährend geringe Erndten haben wollen, genö-
thigt sind, gleichfalls zu mergeln. Aus dieser höchst vichtigen Erscheinung, die man
sehr haufig in Holsteinschen bemerkt, &c.—Sprengel Chemie für Landwirthschaft I.
p. 303.
NATURE REWARDS THE IMPROVER • I 59
dition take from the air more than their due share of the carbonic
acid or other vegetable food it may contain, and leave to the te-
nants of the poorer soil a less proportion than they might other-
wise draw from it? How many interesting reflections does such a
fact as this suggest ? What new views does it disclose of the fos-
tering care of the great Contriver—of his kind encouragement of
every species of virtuous labour ! Can it fail to read us a new and
special lesson on the benefits to be derived from the application of
skill and knowledge to the cultivation of the soil?
T, ECTURE WI.
Substances of which plants chiefly consist. Properties and composition of Cellulose,
true wood, woody or incrusting matters. The different varieties of Starch, Inu-
line, Dextrin, Gum, Mucilage, and of Sugar. Mutual relations and transforma-
tions of these substances. Fermentation of Sugar.
WHAT has been stated regarding the structure of plants, has
shown in what way the food is introduced into their circulation.
The next inquiry appears to be how—by what chemical changes
—is the food, when introduced, converted into those substances
of which plants chiefly consist? But in order that we may clearly
understand this point, it is necessary that we know first the mature
and chemical constitution of those substances which are most largely
formed from the food in the interior of the plant. To this point,
therefore, I must previously direct your attention.
If you were to collect all the varieties of plants which are
within your reach—whether such as are cultivated and used for.
food—or such as grow more or less abundantly in a wild state—
and were to extract their several juices and to separate from each
of these juices the chemical compounds it contains—you would
gradually gather together so many different substances, all pos-
sessed of different properties, that you would scarcely be able to
number them.
But if at the same time you compared the weight of each sub-
stance thus collected, with that of the entire plant from which it is
derived, you would find also that the quantity of many of them is
comparatively so minute that only a very small portion of the
vital energies of the plant can be expended in producing them,-
that they may be entirely neglected in a general consideration of
the great products of vegetation. Thus though quinine and mor-
phine, the active ingredients in Peruvian bark and in opium, are
PRINCIPAL CONSTITUENTS OF PLANTS. | 61
most interesting substances—from their effect upon the human con-
stitution, and from their use in medicine—yet they form so small
a fraction of the mass of the entire trees or plants from which they
are extracted, that it would be idle to attempt to convey to you any
motion of the way in which plants grow and are fed, by shewing
you how such substances as these are produced from the food on
which plants live.
While, then, this examination would satisfy you that almost
every species of plant produces in small quantity one or more sub-
stances peculiar to itself, you would observe, at the same time, that
every plant yields a certain quantity of three or four substances com-
mon to and produced by all—and in most cases constituting the
greater portion of their bulk. Thus all trees and herbs produce
wood or woody matter, and of this substance you know that their
chief bulk consists. Again, all the grains and roots you cultivate
contain starch in large quantity, and the growth of this starch is
one of the great objects of the art of culture. The juices of trees,
of grasses, and of cultivated roots, contain sugar and gum, and
sometimes in such quantity as to make their extraction a source
of profit both to the grower and to the manufacturer. The flour
of grain also contains sugar, and along with it certain other sub-
stances, in small quantity, (gluten, albumen, &c.,) which are of
much importance in reference to the nutritive qualities of the dif-
ferent varieties of flour. Sugar is likewise present in the juices
of fruits, but it is there associated with various acid (sour) sub-
stances which disappear to a certain extent or change into sugar as
the fruit ripens.
Of these few substances the great bulk of vegetables of all kinds
consists. They constitute nearly the whole mass of those various
crops which the art of culture studies to raise for the use of man
and beast. To the study of these substances, therefore, I shall at
present confine your attention; and if Ishall afterwards be able to
make you understand how these few compound bodies are produced
in the interior of a plant from the food it takes up, I shall have
conveyed to you as much information in regard to this most inte-
resting branch of our subject as will be necessary to a general ex-
planation of the natural growth and increase of plants, as well as
of the nature and efficacy of those artificial means which the prac-
L
162 CONSTITUTION OF WOOD.
tical farmer employs, in order to hasten their growth or to enlarge
their increase.
§ 1. The matter of wood—cellulose and incrusting substances—:
their composition and properties.
When a portion of the stem of a herbaceous plant, or of the
newly cut wood of the trunk or branch of a tree, is reduced to
small pieces, and boiled in successive portions of water and alco-
hol, as long as anything is taken up, a white fibrous mass remains.
This fibre, from whatever kind of wood or plant it was obtained,
was formerly supposed to consist of one uniform substance only,
to which, when pure, the name of woody fibre or lignin was given,
Later examinations, however, both chemical and microscopical,
have shown that two and sometimes three substances, differing
both in their properties and in their chemical composition, unite
together to form the walls of the cells and the sides of the vessels
of which the fibre of wood is composed.
The fundamental or first formed portion of the walls of the cells
and vessels consist of a substance to which the name of cellulose
has been given. Upon this wall, sometimes within and sometimes
without the cellor vessel, and sometimes on both sides of it, a depo-
sit or incrustation takes place of a different substance; and some-
times on the original wall of cellulose two incrustations of different
kinds are successively deposited. These different modes of build-
ing up the woody matter accompany difference in species, in age,
or are observed in different parts of the plant which is examined.
These newer layers are distinguished by the general names of in-
crusting or woody matters. Sometimes, where two are seen to
overlie one another, they are characterised as the intermediate and
exterior or interior woody matters. We scarcely know as yet the
true composition of any of them, because of the difficulty of sepa-
rating them accurately from one another; but they probably dif-
fer in composition in different plants and in different parts of the
same plant. They are certainly of great importance in vegetable
physiology, as they not unfrequently form a very considerable
proportion of the entire substance of the woody matter of trees
and shrubs, as well as of all our cultivated crops.
l°. Cellulose or cellular fibre.—The pure substance of the cells
CELLULOSE, ITS COMPOSITION. 163
is extracted with difficulty from any of the common kinds of wood.
They must be cut into small pieces, and digested successively in
alcohol, ether, diluted caustic potash, muriatic acid, and Water.
After this treatment different kinds of wood, fruit, and seeds, the
spongy extremities of the roots, the fibre of cotton, and the pith
of the elder tree, give a substance which is white, insoluble in
water, and when dried at 300° to 350° F has the following com-
position—that of pure cotton fibre. -
Pure fibre Equivalents
of cotton. Or at Om S.
Carbon, ............... 44-35 ...... 24
Hydrogen, ............ 6' 14 ...... 2]
Oxygen,................ 49-51 ...... 21
100%
It is, therefore, represented by Cº., H21 O21. The young fibre
of the Phytolacca decandra is represented by C24 H19 O19. It
does not consist of cellulose, therefore, though it possesses some of
its most characteristic properties.
It will be recollected that water consists of oxygen and hydro-
gen, combined in the proportion, by weight, of 8 of the former to
I of the latter (p. 45). Now, if the hydrogen above given be mul-
tiplied by 8, the product will be found to be almost exactly the
weight of the oxygen given—since
- 6'14 × 8 – 49' 12.
In cellular fibre, therefore, the hydrogen and oxygen exist in the
same proportion as in water (1 to 8), and its composition might be
represented by
Carbon ..................... 44'5
Water ..................... 55-5
100
did we not know that, when heated or distilled, this fibre cannot
be resolved into carbon (charcoal) and water alone, and, therefore,
cannot be supposed to consist of these alone.
It is, nevertheless, a remarkable character of this substance,
that these two elements, hydrogen and oxygen, exist in it in the
* Payen, Recherches sur les Developpements des Vegetawa, p. 215.
I64 CELLULOSE, ITS PROPERTIES.
proportions in which they form water, and we shall find the know-
ledge of this fact of great importance to us, when we come to en-
quire how this constituent of vegetables can be produced—from
the food on which they live.
By the action of acids, cellulose is changed into dextrine and
sugar (Payen). This is an important property, inasmuch as what
takes place in our hands may also be performed by nature in the
interior of plants and in the stomachs of animals.
The cellular fibre of plants is distinguished by one property
which is not as yet known to be possessed by any other class
of substances. If a portion of pure fibre be moistened with a
weak solution of iodine, and after it becomes dry is again moist-
ened with a drop of sulphuric acid diluted with one-third of its
weight of water, it will acquire a beautiful violet-blue colour. If
it be now washed with water the iodine will be washed out, and the
blue colour will disappear.
This experiment is easily tried by taking a few threads of cot-
ton and treating them in the above manner—or by moistening
them with the diluted acid for a few minutes till they are convert-
ed into a jelly, and then adding the solution or tincture of iodine.
Pure cellulose, C24 H21 O21, was till very lately supposed to be
the only substance possessed of this property. It has been ob-
served by Mulder, however, that the young fibre of the Phytolacca
decandra (C24 H16 Olo) gives the same blue when treated with
iodine and sulphuric acid. It is probable, therefore, that there
may be a group of fibrous bodies distinguished by this common
character.
When starch is moistened with a solution of iodine, it immedi-
ately acquires a deep violet colour—without the addition of acid.
If the starch be afterwards washed with water, this blue colour
does not disappear. It is supposed that by the action of the acid
the cellular fibre is for the time transformed into starch.
The young parts of plants consist chiefly of cellulose—and it ex-
ists in a tolerably pure state in the pith of the elder tree, in the
fibre of cotton, and generally in light and porous substances.
From such substances, therefore, it is most easily obtained.
Cellulose is the characteristic tissue of the vegetable kingdom.
It forms the fundamental layer of all the cell-walls, and vessels,
+
COMPOSITION OF TRUE WOOD. | 65
and when more or less incrusted, it is converted into wood. No-
thing similar to cellulose has hitherto been met with in vertebrate
animals. It is said, however, to form a considerable proportion
of the hard and solid parts and coverings of certain insects be-
longing to the class called tunicata, the solid substance called
chitine, with which many articulated animals are covered, having
much resemblance to true wood.*
2°. True wood—If a portion of the wood, in its natural state,
be dried and analysed—without being previously digested in alco-
hol, ether, &c., as above described—the proportion of the constitu-
ents is found to vary slightly with the species of tree, but in all
cases the hydrogen is in larger quantity than is necessary to form
water with the oxygen they contain. Thus, according to Payen,
the dry wood of the following trees consists of
Ebony. Walnut. Oak. Beech.
Carbon ...... 52-85 ... 51.92 ... 50:00 . . . 49-25
Hydrogen... 6:00 ... 5-96 ... 620 ... 6-10
Oxygen ...... 41'15 ... 42-12 ... 43.80 ... 44.65
100 100 100 100
The carbon in these several kinds of wood differs as much as
three per cent, but in all of them the product of the hydrogen,
when multiplied by 8, is considerably greater than the per-cent-
age of oxygen. -
Fromberg and Von Baumhauer have also analysed several
kinds of wood with nearly similar results. They deduce for three
different varieties of wood the following formulae:
C. H. O.
The hard wood of stone fruits, § 64 44 39
Softer wood of laburnum and elm, 64 47 45
Wood of Liriodendron tulipifera, . 64 48 47
In all these the hydrogen is in excess, as in those of Payen—
though in the last (the tulip wood,) the excess of hydrogen is very
small—being reduced to one equivalent only. -
3°. Woody matter.—When the solid substance of wood is ex-
amined under the microscope, its cells and vessels are observed to
consist of two or more layers of different kinds of matter—that of
* Schmidt, Loewig, and Koelliker, Chemist, February and April 1846.
T 66 INCRUSTING OR WOODY MATTERS.
which the original sides of the cells and tubes are composed—the
cellular fibre above described—and of one or more solid substances
by which the cells are internally or externally coated and strength-
ened. These later substances are called by Payen incrusting mat-
ters, and by Mulder woody matters—inasmuch as, without their
presence, no true wood can be formed. It is in these latter sub-
stances that the excess of hydrogen, exhibited by the preceding
analyses, is supposed to exist, the true cellular fibre always con-
taining the hydrogen and oxygen in the proportions necessary to
form water, t
It is exceedingly difficult in any case to separate the cellular
from the incrusting matters of wood, so as to obtain the means of
determining by analysis the exact differences in the elementary
composition of the several substances. Payen attempted to ex-
tract the incrusting matters by digesting wood in successive
solutions of caustic potash or soda, which dissolved the woody
matter, and left the cellulose in great measure behind. The addi-
tion of muriatic acid to the alcaline liquid threw down the woody
matters which it held in solution.
In the matter extracted in this way from beech wood and thrown
down by muriatic acid, Payen detected the presence of four dif-
ferent substances. Thus he found,
a. That a part of it was dissolved by alcohol.
b. Of that which was insoluble in alcohol, a part only was dis-
solved by caustic ammonia. The portion insoluble in ammonia
he found to be wanting in the coniferae.
c. Of that which was soluble in alcohol a part was also soluble
in ether.
Thus, beech wood appeared to consist of five substances:
1°. Cellulose, insoluble in water, and in solutions of caustic
alcalies.
2°. Lignose, soluble only in solutions of caustic potash and soda.
3°. Jºignone, soluble in caustic potash, soda, and ammonia.
4°. Lignin, soluble in caustic potash, soda, ammonia, and in
alcohol.
5°. Ligniréose, soluble in the above, and also in ether.
And he found them to be possessed of the following composi-
tions respectively. r
3
COMPOSITION OF WOODY OR, INCRUSTING MATTERS.
167

Cellulose. Lignose. Lignone. - Lignin. Ligniréose.
Carbon,....... 44.35 . 46.10 50.10 62.25 G7.91
Hydrogen, ... 6.14 6.09 5.82 5.93 6.89
Oxygen,...... 49.5l 47.81 44.08 31.82 25.20
|
100 100 100 100 100
In regard to the woody matters in the four latter columns, it
will be observed, from the above table, that they all contain,
a. More carbon than the cellulose, and,
b. More hydrogen than is sufficient to form water with the oxy-
gen they contain.
They cannot, therefore, like cellulose, be considered as com-
pounds of carbon and water only. They all contain an excess of
hydrogen; and this is the reason why solid, or perfect wood, also
contains always an excess of hydrogen. -
These woody matters exist in wood in different proportions.
Payen found, in the beech wood on which his experiments were
made, the following proportions.
Per cent.
Cellulose, 40.0
Lignose, º © e e 25.2
Lignone, o e • 10.8
Lignin, . º © © 21 6
Ligniréose, e g & 2.4
IOO *
These admirable researches of Payen were in part repeated by
Fromberg, and more lately by Mulder, upon vegetable tissues of
Various kinds, and with nearly the same general results. Caustic
potash separates the woody matters, but it also dissolves a portion
of the cellulose. The woody matters themselves, also, are pro-
bably altered by the prolonged digestion in caustic potash; so
that the existence in the wood itself of the several substances,
* Recherches sur les Developpements des Vegetawºc, p. 279 et 280.
168 COMPOSITION OF THE SPIRAL VESSELS.
lignose, lignone, &c. of Payen,-cannot with safety be inferred
from the fact of their being found in the experiments of Payen.
It is shown, indeed, by microscopical examination, that several
—usually two—layers of woody matter, overlie the cellulose in the
woody cells of most kinds of wood—but these layers probably
vary in their nature or composition with the age, with the part of
the plant, with the species, and probably with other circumstances.
Were we sure, therefore, that caustic potash had not actually
produced any of the substances of Payen, we should still be unsafe
in concluding, that any of those woody layers we observe in our
microscopical investigations, had the precise composition assigned
by him to any of the substances he obtained. They all probably
agree with his compounds in containing more carbon than cellu-
lose, and more hydrogen than will form water with their oxygen
—and this is a most valuable deduction, for which vegetable phy-
siology is indebted to Payen.
The spiral threads of the spiral vessels of plants appear, under
the microscope, to consist of two layers only—one (cellulose),
which, after being tinged with a solution of iodine and dried, be-
comes blue when moistened with sulphuric acid, and another,
which retains its yellowish-brown colour. This reaction is dis-
tinctly seen under the microscope. Mulder analysed these spiral
vessels, after purifying them by digestion, in strong acetic acid, in
alcohol, ether, and water, and he obtained the following as their
composition :-
In equivalents
* Or atoms.
Carbon,...... 47.65 & & . * , 64
Hydrogen,... 6.04 ... 49
Oxygen, ......46.31 “... 47
100
Or it may be represented by Cºl Hao Ouz.
But the composition of cellulose is known. If, therefore, we
deduct from the above formula for the spiral threads, that of cel-
lulose—one of its constituents—the remainder ought to represent
the composition of the other constituent. Thus, if from the
COMPOSITION OF WOODY MATTER AND THUE WOOD. | 6.9
* C. H. O.
Spiral threads,......... 64 49 47 we deduct
Cellulose,............... 24, 21 21.
We have 40 28 26
as the formula for the woody matter.”
The walls of the woody cells consist of three layers, which can
be distinguished under the microscope by the effects produced upon
them by the application of various chemical substances. The in-
mermost layer is cellulose, the intermediate layer is identical with
the woody matter of the spiral thread, and the composition of the
exterior layer is unknown.
True wood, therefore, is composed of,
C. H. O.
a. Cellulose,..................... = 24 2] 2I
b. Intermediate woody matter, – 40 28 26
c. Exterior woody matter,...... unknown,
—with a small admixture of other substances, the most important
of which I shall presently describe.
As I have already stated, however, the nature and com-
position of these woody matters may vary with a variety of
circumstances, which future research can alone make known to
TIS. - -
The cellular fibre, and the woody matter, form a large propor-
tion of the vegetable matter produced during the growth of plants.
That such is the case in the more gigantic vegetable productions,
of which the great forests consist, is sufficiently evident, and so far
the above statement is easily seen to be correct. It is also true of
the dried stalks of the grasses and corn-growing plants, of which
they form nearly one-half of the whole weight, but in roots and in
some plants which are raised for food, the quantity of cellular and
woody matter, especially in the earlier stages of their growth, is
comparatively small. Thus, in beet-root it forms only 3 per cent.
of the weight of the root when taken from the ground. If
suffered to remain in the soil till it becomes old, or if the growth
* Mulder's Vegetable and Animal Physiology, p. 426.
170 PROPORTION OF WOODY MATTER IN PLANTS,
be very slow, the beet becomes more woody, as many other roots
do, and the quantity of woody fibre increases.” -
§ 2. Starch—its composition and properties.
Next to woody fibre, starch is probably the most abundant pro-
duct of vegetation. To the agriculturist it is a substance of much
more interest and importance than woody matter or cellular fibre,
from the value it possesses as one of the staple ingredients in
the food of man and animals—and from its forming a large pro-
portion of the weight of the various grains and roots which are the
principal objects of the art of culture.
1°. When the flour of wheat, barley, oats, Indian corn, &c., is
mixed up into a dough with water, and this dough is washed on a
linen cloth with pure water, a milky liquid passes through, from
* The following table shows the per-centage of cellular and woody matter contained
in some common plants—in the green state—when dried in the air—and when dried
at 212° :—
- IN THE GREEN STATE,
Dried in Dried at Woody Water.
the air. 212°. fibre.
per cent, per cent. per cent. per cent.
Barley-straw, ripe............... 50 - * -
Oat-straw, do................ gº 47 * --> tº-º
Maize-straw, do................ 24 * — tºº
Stalks of the field-pea... ....... *- gº 10% 80
Field-bean straw.......... . ... 51 {-} *= &==g
White turnip.................... &= - * =º 3 92
Common beet (beta vulgaris) — gº 3 86
Young twigs of common furze — sº 24 5()
Rape-straw, ripe................. gºe 55 l2% 77
Tare straw, do........ . … 37 tºº ºmº ſº-º:
Vetch plant (v. Saliva)......... 42 tºmº 10% 77%
Do. (v. cracca) in flower...... — *º- 5% 68
Do. (v. narbomensis) do........ - - --- ll k 80
White lupin, in flower......... ** smºs 7 86
Lucerne, in flower.............. tºº * 9 73
Rye grass, do..... .............. *sº gº l] . 68
Red clover, do.......... ... . . ... — º 7 70
White clover, do................. — gºssº 4% 8 1
Trefoil (medium) do............ emsº gºmº 8% 73
Sainfoin (esparselle)............. — gººms 7 76
Trefoil (agrarium) in flower... — gºmº 12 68
f)o, (rubens) do........ — gº 15 00
PREPARATION AND COMPOSITION OF STARCH. 171
which, when set aside, a white powder gradually falls. This white
powder is the starch of wheaten or other flour.
2°. When the pith of the Sago palm is washed, in a similar
manner, with water upon a fine sieve, a white powder is deposited
by the milky liquid which passes through. This powder, when
collected, forced through a metal sieve to granulate (or corn) it,
and dried by agitation over the fire, forms the sago of com-
II] el’C6. - . -
3°. When the raw potato is peeled and grated on a fine grater,
and the pulp thus produced is well washed with water, potato starch
is obtained in the form of a fine white powder, consisting of round-
ed, glossy, and shining particles. -
4°. When the roots of the Maranta Arundinacea of the West
India Islands are grated and washed like the potato, they yield
the arrow root of commerce. From the root of the Manioc, the
cassava is produced by a similar process, and this, when dried by
agitation on a hot plate, forms the tapioca of the shops.
The substances to which these several names are given are, when
pure, similar in their properties, and identical in their chemical com-
position. They are allcolourless, tasteless, and without smell. When
dry and in a dry place, they may be kept for any length of time
without undergoing alteration—they are insoluble in cold wa-
ter or in alcohol, but dissolve readily in boiling water, giving a
solution which gelatinizes (becomes a jelly) on cooling. They are
all distinguished by assuming an instantaneous blue colour when
moistened with a cold solution of iodine—and by being converted
into sugar by the prolonged action of diluted sulphuric acid—and
as it is said also by the tartaric, malic, and oxalic acids (Couver-
chel.)
When dried at 212°, they consist of
Prout. Mulder. - Atoms.
Carbon ...... 44-0 44'47 Ol' 12
Hydrogen ... 6.2 6:28 or 10
Oxygen ...... 49.8 49°25 OT 10
100 | OO
Starch, therefore, may be represented by the formula C1, H16
Oro, or by C2. Hop O30, which differs very little from that of cellu-
172 PER-CENTAGE OF STARCH IN DIFFERENT GRAINS.
lose, C24 H21 O21. In both of these substances hydrogen and
oxygen are united together in the proportions to form water.
That starch constitutes a large proportion of the weight of grains
and roots usually grown for food will appear from the following
table, which exhibits the average quantity present in 100 lbs. of
each substance named :—
Starch per cent.
Wheat flour e tº a a tº g 39 to 77
Rye do. & © to © e G 50 to 61
Barley do. ºr e c e Q sº 67 to 70
Oatmeal e- ºg & e e & 70 to 80
Rice flour e ‘º e tº gº tº 84 to 85
Maize do. e e G © ºr ºf 77 to 80
Buck wheat & © tº tº a tº 52
Pea and bean meal ... 42 to 43
Potatoes, containing 73 to 78 of water, 13 to 15
It thus exists most largely in the seeds of plants, and in some
roots. It is frequently deposited, however, among the woody
fibres of certain trees, as in the willow, and in the inner bark of
others, as in those of the beech and the pine.” Hence probably
one cause of the readiness with which a branch of the willow takes
root and sprouts, and hence also the occasional use of the inner
bark of trees for food, especially in northern countries, and in times
of scarcity. In some roots which abound in sugar, as in those of
the beet, the turnip, and the carrot, only a very small per-centage
of starch can be detected. It is said to be entirely absent from
the extremities of the roots (Payen); and from the young shoots
of plants (Mulder.)
§ 3. Inuline and Lichen Starch—their composition and properties.
1°. Inuline.—In the roots of the dahlia, of helenium, and of ta-
raxacum, there occurs, instead of common starch, a peculiar sub-
stance, to which the name of Inuline has been given. Like com-
mon starch, this substance is insoluble in cold water, but dissolves
in boiling water. It differs from common starch, however,
* Its presence is readily detected in such wood by a drop of the solution of iodine
—which gives a permanent blue to starch, but to the woody fibre only a brownish
atain.
INULINE, ITS COMPOSITION AND PROPERTIES. I 73
a. In not forming a jelly when the solution in boiling water is
allowed to cool. It falls down, as the solution cools, in the form
of a white powder, which dissolves again in boiling water.
b. In giving with a solution of iodine a yellow colour instead of
the blue by which common starch is distinguished.
c. By giving no precipitate with a solution of basic” acetate of
lead as starch does.
After repeated boiling in water, inuline becomes soluble, and
does not fall as the solution cools. It has now undergone a slight
change in composition. Thus the inuline from the three roots
above named consists of
Taraxacum and Helenium. Dahlia.
Insoluble. Soluble. ...º
(Mulder.) (Crookewit.) (Parnell.)
Carbon, 44-75 44-30 43-95
Hydrogen, 6-20 6:23 6-34.
Oxygen, 49-05 49.47 49-71
• 100 100 100
These results are represented respectively by the following for-
mulae:—
Inuline of helenium and } Insoluble, = C24 H20 O20
taraXaCUlm, Soluble = C24 H20, O20
Inuline of the Dahlia, Soluble and
Insoluble, = C24 H21 O21
By prolonged boiling in water, inuline is readily changed into
an un-crystallizable sugar, and the same change is produced, ac-
cording to Payen, by the action of acetic acid. This sugar, as it
is formed, clings to or combines with the inuline, and Mulder sup-
poses the soluble inuline and that from the dahlia to contain a
little sugar, from which it is very difficult to free it, and that to
the presence of this sugar the different formulae above obtained for
these several varieties is to be ascribed.
It appears from these formulae, that, like cellulose and starch,
inuline may be supposed to consist of carbon and water only, and
* Basic acetate of lead is formed by dissolving common acetate or sugar of lead in
water, and boiling the solution upon powdered litharge (oxide of lead.)
174 ICELAND MOSS AND LICHEN STARCH.
that while the insoluble inuline of the helenium has the same com-
position as common starch, that of the dahlia has the composition
and the formula we have previously given for cellulose.
2. Lichen starch.--When Iceland moss is boiled in water, it
gives a solution which, like that of common starch, becomes a jelly
when it cools. This gelatinous substance has the same composi-
tion as common starch, and as a whole, is represented by the same
formula (C12 H10 Co.) Instead of a blue, however, it gives a
green with a solution of iodine. It differs, therefore, from common
starch.
If a weak decoction of Iceland moss be coloured by iodine and the
mixture them allowed to settle, two different layers collect on the
bottom of the vessel—a yellow one below and a blue one above it.
These show that the solution contains both inuline, which gives the
yellow; and common starch, which gives the blue. But the quan-
tity of inuline which can actually be obtained from the decoction,
when the starch is thrown down from it by basic acetate of lead, is so
small that Mulder very fairly concludes, that the jelly of Iceland
moss contains also a third kind of starch, which, like common starch,
is thrown down by basic acetate of lead, while inuline is not, and
which, like inuline, gives a yellow with iodine. It is the mixture of
this yellow with the blue of the common starch which forms the green
by which this moss jelly is characterized. And as the deep blue of
the common starch must be mixed with much yellow to convert in
into a green, he farther infers that this peculiar kind of starch must
form the largest proportion of the jelly-forming matter which is
produced or extracted when Iceland moss is dissolved in water.
It has not as yet, however, been obtained in a separate state.
Other lichens give, when boiled, varieties of starch or mixtures
which differ from that obtained from Iceland moss. The Lichen
fastigiatus gives with boiling water a solution which becomes co-
vered with a skin like that from Iceland moss as it is concentrated,
but does not form a jelly as it cools, and is not acted upon by a so-
lution of nut galls. The dry starch swells into a jelly in cold wa-
ter, but does not dissolve. The Lichen frawineus gives a similar
solution which does not gelatinize on cooling, and gives no preci-
pitate with an infusion of nut galls, or with basic acetate of lead,
PREPARATION OF DEXTRIN. I-75
º.
both of which give precipitates with solutions of common starch
and of that from Iceland moss.
These and many other varieties of starch, which will no doubt
be obtained from other species of lichens, are either mixtures of
different varieties of starch with each other, or with sugar or dex-
trin; or they are peculiar states of transition, which no doubt exist
among the numerous substances we are now considering—all of
which are mutually convertible, and consist of carbon and the
elements of water in nearly the same proportions.
When these lichens are exhausted by water of all their soluble
constituents, what remains behind is principally cellulose. It
would appear, therefore, that in these cellular plants the original
cell-walls are formed of cellulose as in other plants, and that the
substances which yield the lichen starch, when boiled, are deposit-
ed upon it in layers, in the same way as the incrusting or woody
matter is deposited upon the cell-walls of young wood.
§ 4. Deatrin—its composition and properties.
Common starch, which is insoluble in water, is capable of being
converted into a substance which is readily soluble in water, has
little or no taste, and possesses many of the properties of gum.
Thus,
1°. When it is spread upon a tray and gradually heated in an
oven to a temperature not exceeding 300° F., it slowly changes,
acquires a yellow or brownish tint, and becomes entirely soluble
in cold water. It is changed into deatrin. Under the names of
starch gum and British gum this substance is largely manufactur-
ed, and is successfully substituted for gum arabic by the calico
printers in thickening many of their colours.
During the baking of bread, also, a portion of the starch of the
flour is changed into dextrin. Vogel found that flour which con-
tained no dextrin gave, when baked, a bread of which 18 per
cent.—nearly one-fifth of the whole—consisted of soluble dextrin.
2°. If 50 parts of starch, 12 of sulphuric acid, and 140 of wa-
ter be taken, and if, after thoroughly moistening the starch with
one portion, it is poured into the mixture of the remainder of the
water with the acid, and is then heated to 190° F., the starch will
be entirely converted into dextrin. The rapidity of the change
I'76 DEXTRIN A FOOD OF PIANTS.
depends upon the proportion of acid employed, and the tempera-
ture to which the mixture is raised. -
3. If starch be boiled for a length of time in pure water, even
without the presence of an acid, a quantity of dextrin is produced.
It is also formed in the stomachs of animals, the gastric juice hav-
ing the power of changing the starch and even part of the cellu-
lose and of the woody matter of the food into soluble dextrin.
4. If crushed malt be steeped in water for a quarter of an hour,
and the liquid be then poured upon a quantity of starch, and a
gentle heat be applied—the starch will gradually be converted in-
to dextrin and will dissolve in the water.
By any of these methods common starch and even cellulose may
be changed into dextrin. This new substance, though it has diffe-
rent properties, has the same composition as common starch, and
is represented by the same formula C19 Hio Oro.
Dextrin is believed to exist abundantly in the sap of plants,
though it has not hitherto been directly extracted from it. This
arises in part from the ease with which it is changed into sugar,
and from its likeness to gum. In the analysis of plants, therefore,
the dextrin is generally included along with the sugar or gum.
It resembles gum in its want of taste and in its adhesive pro-
perties. It differs from it in being readily converted into grape
sugar by the action of sulphuric acid or of a decoction of malt, which
is not the case with gum.
The solubility of dextrin in water and the close relation of its
composition to that of cellulose, starch, and sugar, render it of
much importance in the growth and nourishment of plants. It
is produced from starch, it ascends in the sap, it is changed here
into sugar, and there into insoluble cellulose, or again into starch,
and thus lends its easy aid to the production of the several sub-
stances which are necessary to the production or completion of the
several parts of which the substance of plants consists. To this
point we shall return in a subsequent lecture.
§ 5. Gum—its composition and properties. -
The variety of gum with which we are most familiar is gum
arabic, or senegal, the produce of various species of acacia, which
grow in the warmer regions of Asia, Africa, and America. It
VARIETIES OF GUM. 177
exudes from the twigs and stems of these trees, and collects in
rounded more or less transparent drops or tears. It is also pro-
duced in smaller quantities in many of our fruit trees, as in the
apple, the plum, and the cherry.
Many varieties of gum occur in nature, but they are all charac-
terised by being insoluble in alcohol, by dissolving and becoming
gelatinous in hot or cold water, and by giving viscid and glutinous
solutions, which may be employed as a paste.
Two distinct species of gum have been recognised by chemists.
1°. Arabin—of which gum arabic and gum Senegal almost en-
tirely consist. It is soluble in cold water, giving a viscid solution,
usually known by the name of the mucilage of gum arabic.
2°. Cerasin—which exists in the gum of the cherry tree. It is
insoluble in cold water, but dissolves readily in boiling water. When
thus dissolved it may be dried without losing its solubility, and is
therefore by boiling supposed to be changed into arabin.
By these characters, the two kinds of gum are not only readily
distinguished, but may be easily separated from each other. Thus
if a native gum or an artificial mixture contain both, simple steep-
ing in and subsequent washing with cold water, will separate the
arabin, after which boiling water will take up the cerasin.
These different kinds of gum possess the same chemical compo-
sition.
According to the analyses of Mulder, they consist of
Atoms.
Carbon, ............ 45°10 ... or 12
Hydrogen, ......... 6'10 ... or 10
Oxygen, ............ 48.80” ... or 10
100
In this analysis, as in those of cellulose, starch, &c., we see
that the per centage of oxygen is equal to that of the hydrogen
multiplied by 8, and consequently that these two elements exist in
gum also in the proportions to form water. We see likewise that
the carbon is in the proportion of 12 atoms or equivalents, to 10
of each of the other constituents, and, therefore, that gum may be
represented by C12 Ho Olo, or C24 H20 O20—a formula which is
identical with those already given for starch and dextrin.
It appears, therefore, that not only may gum, starch, and dewtrim
* Berzelius Arsberättelse, 1839, p. 443.
M
178 COMPOSITION AND PROPERTIES OF MUCILAGE.
be represented by carbon and water, but that they all consist of
carbon and the elements of water, united together in the same pro-
portions. . This is a very remarkable and striking fact, to which we
shall again have occasion to advert (see p. 185)
Gum not only exudes as a natural product from the stems and
twigs of many trees, but is also contained in the juices of many
others, from which it is not known to exude ; while in the sap of
most plants it may be detected in greater or less quantity. It is
not supposed, however, to exist so largely or so universally in the
vegetable kingdom, as dextrin, which is one of those forms of com-
bination through which organic matter passes in the interesting
series of changes it undergoes, during the development and growth
of the plant.
§ 6. Mucilage—its composition and properties.
1°. When gum tragacanth is put into water it swells up, but
does not dissolve. Even boiling water does not dissolve it, but
the whole enlarges greatly in bulk and forms a transparent jelly.
To this species of insoluble gum the name of mucilage is given.
It forms a large proportion of gum Bassora also, and exists abun-
dantly in linseed, rape seed, quince seed, and other oily seeds. It
occurs also mixed with true gum in the exudations of the plum,
cherry, and other trees.
2°. When the roots of salep (orchis), of mallow (althea), or of
symphytum are boiled in water, this mucilage is obtained in the
form of a jelly, and the Silva crispa yields it also when treated in
a similar manner. -
Mucilage extracted from these different plants and matural exu-
dations possesses characters which sometimes slightly differ, but it
has in all cases the same composition. It contains when dried at
301 F., according to Mulder,
From From From
lintseed, quince seed. tragacanth.
Carbon, ......... 45°82 46.20 45-86
Hydrogen, ...... 5-92 6-03 5-84
Oxygen, ......... 48°26 47.77 48°30
100 100 100
and is represented by the formula C24 H19 Olg.
VARIETIES OF SUGAR. J"79
It is, therefore, mearly allied in composition to starch and gum.
Like starch it is converted first into dextrin, and afterwards into
sugar by dilute sulphuric acid (Schmidt). It is, therefore, more
nearly allied to dextrin than to true gum.
§ 7. Of Sugar—its varieties and their chemical composition.
1°. Cane sugar.—Sugar, identical in composition and proper-
ties with that obtained from the sugar-cane, and generally known
by the name of cane-sugar, exists in the juices of many trees,
plants, and roots. In the United States of North America the
juice of the maple tree is extensively collected in spring, and, when
boiled down, yields an abundant supply of sugar. In the Cauca-
sus that of the walnut is extracted for the same purpose. The juice
of the birch also contains sugar, and it may be obtained, in lesser
quantity, from the sap of numerous other trees. The unripe stem
of maize, or Indian corn, contains so much saccharine matter that it
has been proposed to cultivate this plant solely for the manufacture
of Sugar. In the juice of the turnip, carrot, and beet, it is also pre-
sent, and in France and Germany the latter root is extensively em-
ployed for the manufacture of beet sugar. In the unripe grains
of corn, at the base of the flowers of many grasses and clovers when
in blossom, and even in many small roots, as in that of the quicken
or couch-grass (triticum repens), the presence of Sugar may likewise
be readily detected.
Sugar is principally distinguished by its agreeable sweet taste.
When pure, it is colourless and free from smell. It dissolves
readily in alcohol and in large quantity in water. The solution
in water, when much sugar is present, has an oily consistence, and
is known by the name of syrup. From this syrup the sugar gra-
dually deposits itself in the form of crystals of sugar candy. If
the syrup be boiled on too hot a fire, it chars slightly, becomes
discoloured, and a quantity of molasses or uncrystallizable sugar
is formed. Crystallized cane sugar, when heated to 212°F., loses
5.2 per cent, or one equivalent of water, and is then found to con-
sist of
T80 CANE AND GRAPE SUGARS.
Atoms,
Carbon ......... 44'92 ......... OT 12
Hydrogen ...... 6'11 ......... Or 10
Oxygen......... 48-97 ......... Or 10
100 .
If we compare these numbers with those given for starch and
gum in the preceding sections, we see that they are almost identi-
cal—so that cane sugar dried at 212° F also contains oxygen and
hydrogen in the proportions to form water, and may likewise be re-
presented by the formula C12 Ho O10, or C24 H20 O20.
When sugar thus dried, however, is mixed with oxide of lead,
and again heated, it loses more water, and is then represented by
C24 His Ois, a formula which is slightly different from that by
which any of the substances we have yet considered can be repre-
sented.
2°. Grape sugar.—In the juice of the grape a peculiar species
of sugar exists, which, in the dried raisin, presents itself in the
form of little rounded grains. The same kind of sugar gives their
sweetness to the gooseberry, the currant, the apple, pear, plum,
apricot, and most other fruits. It is also the sweet substance of
the chesnut, of the brewers’ wort, and of all fermented liquors,
and it is the solid sugar which floats in rounded grains in liquid
honey, and which increases in apparent quantity as the honey, by
keeping, becomes more and more solid.
Grape sugar has nearly all the sensible characters of cane su-
gar, with the exception of being less soluble in water and also less
sweet,_2 parts of the latter imparting an equal sweetness with 5
of the former.
In chemical composition they differ considerably. Grape sugar
dried at 250°F., loses two equivalents of water, and then consists of
Atoms.
Carbon ......... 40°47 ...... or 12
Hydrogen ...... 6'59 ...... or 12
Oxygen......... 52'94 ...... or 12
I 00
The oxygen here is still eight times greater than the hydrogen,
EUCALYPTUS AND MANNA SUGARS. 18]
and, therefore, in this variety of sugar also, these elements exist in
the proportions to form water. But for every 12 equivalents of car-
bon grape sugar, dried at 250°F., contains 12 of hydrogen and 12 of
oxygen. Itisconsequently represented by C12H12O12, or C24H24O24.
When heated with oxide of lead, the grape, like the came sugar,
loses another equivalent of water, and is then represented by C24
H22O22.
3°. Eucalyptus sugar.—A species of manna exudes and falls from
the branches of certain trees of the genus Eucalyptus, which grow
in New South Wales. This manna contains a peculiar kind of
sugar which crystallizes in minute prisms, which lose much water
by heating to 300°F. The dry sugar then consists, according to
my analysis, of
Atoms
Carbon ......... ... 42°57 ............ 24
Hydrogen......... 6’44 ............ 21
Oxygen............ 5099 ............ 21
100 -
and is represented by C24 H21 O21, which is also the formula for
cellulose.
But like came and grape sugars it loses more water when further
heated with an admixture of oxide of lead. In this perfectly dry
state it is represented by C24 H16 Oto-the formula by which the
fibre of the Phytolacca Decandra is represented.
This kind of sugar is not known to occur extensively in the sap
of plants. We do not know therefore as yet that it performs any
important part in the general vegetable economy.*
4°. Manna sugar.—Besides the cane and grape sugars which
occur in large quantity in the juices of plants, there are other va-
rieties which occur less abundantly, and are therefore of less inte- .
rest in the study of the general vegetation of the globe. Among
* Solutions of cane, grape, and Eucalyptus Sugars are readily distinguished from
each other by the following chemical characters:–1. If the solution be heated and
a few drops of sulphuric acid then added, cane and Eucalyptus sugars will be de-
composed, blackened, and made to fall as a black or brown powder—while a solu-
tion of grape sugar will at the most be only slightly discoloured. 2. If, instead of
sulphuric acid, caustic potash be employed, the came sugar will be unchanged, while
the Eucalyptus and grape sugars will be blackened and thrown down.
182 LIQUORICE AND MILK SUGARS.
these is manna, which partly exudes and is partly obtained by in-
cisions from certain species of the ash tree which grow in the
warmer countries of Southern Europe (Sicily and Italy), and in
Syria and Arabia. It also exists, it is said, in the juices of the
larch tree and of common celery.
Manna contains two varieties of sugar, one which readily cry-
stallizes from its solution in alcohol, and one which retains a sy-
rupy consistence. This crystallizable substance is the peculiar Su-
gar of manna, and the name of mannite is given to it.
This mannite probably exists in plants in much greater abund-
ance than has hitherto been suspected. It has lately been found
by Dr Stenhouse to be the substance which gives their sweet taste
to sea weeds, in some of which it exists in very considerable pro-
portion. Thus he found in dried plants of
Per cent.
Ilaminaria saccharina ... 12:15 Fucus vesiculosus... I to 2
digitata ...... 6.82 Serratus ...... 2
Halydris siliquosa ...... 5 to 6 nodosus ...... trace
Rhodomenia palmata ... 2 Ulva latissima ...... DOT162.
In the fungi it also exists, and may be extracted in quantity
from the expressed juice of the agaricus piperatus and some others.
5°. Liquorice sugar.—Liquorice root contains a species of Su-
gar which becomes dark-coloured or black in the air, and which
is known in this country under the names of Spanish and Ita-
lian juice from the countries in which it is most abundantly ex-
tracted. To the pure sugar chemists give the name of Glycyr-
phizin.
Mannite and the sweet matter of liquorice are not considered as
true sugars—all of which contain carbon in combination with oxy-
gen and hydrogen in proportions to form water—or, in other words,
may be supposed to consist of carbon and water only. This is not
the case with these two sweet bodies which are represented respec-
tively by
Mannite = C5 Hz Og
Glycyrrhizin = C16 H12 Og
They are supposed, therefore, to be products of decomposition
resulting from the changes which naturally take place under cer-
tain circumstances in the grape sugar or other easily altered sub-
PECTIC ACID. I 83
stances which exist in the sap of plants. These changes it would
be out of place here to consider.
6°. Milk sugar.—In milk a sweet substance—a true sugar—
exists, which is of great importance in the animal economy. It is
represented by C24 H19 Olg, the formula by which perfectly dry
Eucalyptus sugar is represented. It differs, however, very much
from this latter sugar in its properties; but as it is not known to
occur in the vegetable kingdom, we shall reserve our consideration
of it till we come to treat of milk, its composition and properties,
These several kinds of sugar differ more or less, not only in
sensible and chemical properties, but also in chemical constitution,
from the more abundant came and grape sugars—but they form
too small a part of the general products of vegetation, ai.d are of
too little consequence in practical agriculture, to render it neces-
sary to do more than thus shortly to notice their existence.*
$ 8. Pectose, pectic acid, and parapectic acid.
Besides the substances already enumerated, there is still another
which occurs in considerable quantity in certain parts of plants,
and which differs from starch, sugar, &c., both in its composition
and in its properties.
1°. Pectic acid.—When the fleshy fruit of the apricot, peach,
or plum—that of the apple or the pear, or the root of the turnip,
the beet, or the carrot—is grated down, washed well with water,
pressed and dried, a comparatively small quantity of fibrous
matter remains behind. If this fibre while still moist be boiled in
a solution of caustic potash, or of carbonate of soda, a variable pro-
portion of it will be dissolved. If to the filtered solution muriatic
acid be added till it is distinctly sour, a white gelatinous substance
will be separated, which falls very slowly, and which, when collect-
ed on the filter, has the appearance of a colourless jelly.
This gelatinous substance is pectic acid. It is without taste, and
is insoluble in water, but dissolves readily in solutions of carbonate
of potash, Soda, or ammonia. According to Mulderſ it consists
when perfectly free from water of
* For a list of plants from which sugar has been extracted, see Thomson's Orga-
nic Chemistry (1838), p. 647.
i Scheikundige Onderzoekingen, iii. p. 213,
184. PARA-PECTIC ACID, PECTOSE, PECTINE.
Atoms.
Carbon............... 44.80 ...... or 14
Hydrogen............ 4.71 ...... Or 9
Oxygen. . . . . . . . . . . . . . . 50.49 ...... or 12
100
and is represented by C14 Ho Oz. As it is obtained in an un-
combined state from the turnip by the process above described, it
contains an atom more water even when dried at 270° F. and is
represented by C14 Ho O12 + HO.
2°. Para-pectic acid—If the washed pulp of the turnip or fruit
be boiled in diluted muriatic acid instead of a solution of potash
or soda, and if to the filtered solution a large quantity of alcohol
be added, a white precipitate falls, which also has a gelatinous ap-
pearance when collected upon the filter. This substance is para-
pectic acid. It differs from the pectic acid in being soluble in
water, but has precisely the same composition, and is represented
by the same formula. In this respect it has the same relation to
pectic acid that dextrin and gum have to starch. Nitric acid
changes the soluble para-pectic into the insoluble pectic acid.
By the action of sulphuric acid both the pectic and para-pectic
are changed into grape sugar (Chodnew.)
3°. Pectose—Though the two substances above described can
be extracted from the plum, the apple, the turnip, &c., they are
not supposed to exist ready formed in the fruits and tubers them-
selves. They are produced during the boiling by the change of
a third substance, not yet known, but which exists in the fruits
and tubers, and to which the name of pectose has been given by
Mulder, who has most thoroughly investigated this subject. He
supposes this pectose to have the same composition as the pec-
tic and para-pectic acids, and to be decomposed in part by boiling in
water, but more completely by boiling in acid or alcaline solutions.
T}uring this decomposition sugar is produced, which Mulder
ascribes to the presence of mucilage or some similar substance in
a state of intimate connection with the pectose.”
4°. Pectin.--When alcohol is added to the expressed juice of
the apple or the turnip, a white jelly falls, to which the name of
pectin was formerly given. The jelly thus obtained, however, is
* Scheikundige Onderzoekingen, iii. p. 249.
MUTUAL RELATIONS OF THESE COMPOUNDs. * 185
only a mixture of para-pectic acid with mucilage, gum, and several
other substances which are present in the expressed juice, and
which fall along with it when the alcohol is added.
§ 9. Mutual relations of cellulose, starch, gum, sugar, and pectic acid.
It may be interesting now to consider for a moment the mutual
relations and differences of the several substances above described—
which occur so largely in the vegetable kingdom, and which are
serviceable to man for so many different purposes. These will be
best seen by comparing the formulae by which they are respective-
ly represented, and the characters by which they are distinguished.
These will be seen at a glance in the following table.
Name. Formula. Characters.
ſInsoluble in water.
1°. Cellulose a com- Become blue when
mon, tº tº C24 H21 O21 moistened with a so-
2°. b from Phytolac- -
| lution of iodine and
ca decandra, . C19 H19 O19 | afterwards with sul-
Uphuric acid.
ſDissolves in boiling
ºr and forms a
- ielly. Becomes blue
3°. Common starch, . C24 H20 O20 | º moistened with
a solution of iodine
U alone.
tº Dissolve in boiling
ſ 4°. Inuline, a common, C24 H29, O21, water andfallon cool-
l b from dahlia, C2, H2. Ogi \ing. Turned yellow
* Uby iodine.
O T : sº ºt Solubleinwater. Gives
5°. Lichen starch, . C24 H20 O20 a yellow with iodine.
Soluble in coldwater.
6°. Dextrin, & C24 H20 O20 Is changed into sugar
by sulphuric acid.
(Swells to a jelly in
"7 O M + , , il. - water. Is changed
7°. Mucilage, e C24 H19 O10 into Sugar by Sulphu-
ric acid.
Soluble in cold or in
hot water, not readily
changed into sugar
by sulphuricacid. By
| nitric acid is changed
Uinto mucic acid.
8°. Gum, º C24 H20 O20
186 MUTUAL RELATIONS OF THESE COMPOUNDS.
Name. Formula. Characters.
ſChanged into grape
sugar by the action
9°. Cane Sugar, . C24 His Ols" { of acids. Blackened
by boiling with dilute
USulphuric acid.
cane Sugar.
Blackened by caustic
potash, but not by
dilute sulphuric acid.
|
- Harder, less soluble
10°. Milk sugar, C24 H19 O10 and less sweet than
11°. Grape sugar, . C24 H22 O22 }
*
Blackened both by
sulphuric acid and by
caustic potash.
| Insoluble in water,
12°. Eucalyptus sugar, C24 H19 O16
soluble in potash and
ammonia.
| Soluble in water,
13°. Pectic acid, . C14H9 O12
14°. Para-pectic acid, C14. He Orº changed into pectic
by mitric acid.
In this table it will be observed,
1°. That in every case, with the exception of the pectic and pa-
ra-pectic acids, the number of equivalents, of oxygen is exactly
equal to that of the hydrogen ; in other words, all these substances
may be supposed to consist of carbon and water only.
2°. The formulae for several different substances are identical,
— thus cellulose, mucilage, milk sugar, and eucalyptus Sugar
are all represented by C24 H19 Olg. Common starch, lichen starch,
dextrin, and gum by C24 H20 O20. Cellulose a, and inuline b, by
C24 H21 O21; in other words, these several groups of substances
consist respectively of the same elements united together in the
same proportions.
This is one of those facts which not only appear very remark-
able to the unlearned, but are scarcely capable of being clearly
comprehended and explained, even by those who have most pro-
foundly studied this branch of natural science. Starch and gum
—how different their properties how unlike their uses | how un-
* Crystallized cane sugar (sugar candy, loaf sugar,) contains four equivalents of
water more, and is represented by C24 Hog Ogg or C24 Hla Ola + 4 H O. In like
manner, crystallized honey or grape Sugar, as it occurs in honey or in the dried grape,
is represented by C24 Hg: Ogg Or C24 H22 O29 + 6 H. O.
MUTUAL TRANSFORMATIONS OF STARCH, GUM, &C. 187
equal their importance to the human race | yet they consist of the
same weights of the same elementary substances, differently con-
joined. The skilful architect can put together the same propor-
tions of the same stone and cement—and the painter can combine
the same colours—so as to produce a thousand varied impressions
on the sense of sight. In the hand of the Deity matter is infinite-
ly more plastic. At His bidding the same particles can unite in
the same quantities so as to produce the most unlike impressions
—and upon all our senses at once.
39. A knowledge of the above close relations in composition,
among a class of substances occurring so abundantly in the vege-
table kingdom—imparts a degree of simplicity to our ideas of this
otherwise complicated subject. It does not appear so mysteri-
ous that we should have cellular fibre, and starch, and gum, and
sugar, occurring together in variable quantities, when we know
that they are all made up of the same materials, in the same or
nearly the same proportions—or that one of these should occasion-
ally disappear from a plant, to be replaced in whole or in part by
another.
A further question, however, arises in our minds. We natu-
rally ask, does nature, in thus removing one of these compounds,
and supplying its place by another, actually form from its elements
the new substance introduced, or does she produce it by a mere
change or transformation of those previously existing? A satis-
factory reply to this question may be derived from the facts de-
tailed in the following section.
§ 10. Mutual transformations of cellular fibre, starch, gum, and
Sugar.
I. —CELLULAIR FIBRE AND WOODY MATTER,
1°. Action of heat.—If wood be reduced to the state of fine saw-
dust, be then boiled in water to separate every thing soluble, af-
terwards dried by a gentle heat, and then heated several times in
a baker's oven, it will become hard and crisp, and may be ground
in the mill into a fine meal. The powder thus obtained is slightly
yellow in colour, but has a taste and smell similar to the flour of
wheat, ferments when made into a paste with yeast or leaven, and
when baked gives a light homogeneous bread, Boiled with water,
I 88 ACTION OF SULPHURIC ACID ON WOODY FIBRE.
it yields a stiff tremulous jelly like that obtained from starch
(Autenrieth).” By the agency of heat, therefore, it appears that
cellular fibre or woody matter or both may be permanently changed
Žnto starch. - -
2°. Action of sulphuric acid—If to three parts of the sulphuric
acid of the shops (oil of vitriol) one part of water be added, and a
portion of cellular fibre be immersed in it for half a minute, and
the whole then rubbed in a mortar with a few drops of a solution
of iodine—the woody fibre will assume a blue colour, showing that
it is for the moment at least changed into starch (Schleidem).
Again, if three parts of fine saw-dust or of fragments of old li–
men be rubbed in a mortar with four of the sulphuric acid of the
shops added by degrees—it will, in a quarter of an hour, be ren-
dered completely soluble in water. If the solution in water be
freed from acid by chalk, and then evaporated, a substance re-
sembling gum arabic is obtained (Braconnot). According to
Schleiden, the fibre may be seen under the microscope gradually
to change from without inwards, first into starch and then into
gum.
Further, if this gum be digested with a second portion of sul-
phuric acid diluted with 8 or 10 times its weight of water, it will
be gradually converted into grape-sugar; or the fibre of wood or
linen may be changed directly into sugar by the prolonged action
of dilute sulphuric acid.
3°. Action of potash.-If saw dust be mixed with from two to
eight times its weight of hydratef of potash and as much water,
and boiled till a crust forms on the surface—and if dilute sulphu-
ric acid be then added till the whole is slightly sour, the unde-
stroyed fibre and woody matter will give an instantaneous deep
blue on the addition of iodine, showing that starch has been formed.
Cellular fibre and woody matter may, therefore, be changed in-
to starch, either by the unaided action of heat, by sulphuric acid,
or by caustic potash,-and the starch thus produced may be fur-
ther transformed, first into gum and then into grape-sugar, by
the prolonged action of dilute sulphuric acid, assisted by a mode-
rate heat.
* Schubler, Agricultur Chemie, i. p. 224.
+ IIydrate of potash is the caustic substance which is obtained by boiling common
pcarl-ash with quick-lime.
ACTION OF HEAT AND SULPHURIC ACID ON STARCH. T 89
II.-STARCH,
1°. Action of heat.—When flour, potato, or arrow-root starch
is spread out upon a tray, then introduced into an oven, and gra-
dually heated to a temperature not exceeding 300°F., it is slowly
changed into dextrin or British gum.
The gum thus prepared not unfrequently possesses a sweet taste,
from the further change of a portion of the gum into sugar.
2°. Action of water.—When starch is dissolved in boiling water,
and is then allowed to stand in the cold, either in a close vessel or
exposed to the air, it gradually changes first into dextrin and
then into sugar. The process, however, is slow, and months must
elapse before the whole of the starch is thus spontaneously trans-
formed in the presence of water (De Saussure). It takes place
more rapidly when starch and water are boiled together for a
length of time.
3°. Action of sulphuric acid. –From what has been already stat-
ed in regard to the action of this acid on cellular fibre, it will rea-
dily be supposed that native starch, of any variety, is likely to un-
dergo transformation when subjected to its influence.
In reality, if 50 parts of starch, 12 of sulphuric acid, and 138 of
water be mixed together, and heated to 190° F., the starch will be
entirely converted into dextrin. By a more prolonged heating
this dextrin is changed into grape sugar. The dextrin or sugar
may be obtained in a separate state by adding to the solution either
chalk or lime, which will combine with and carry down the acid."
One hundred pounds of starch treated in this way will yield from
105 to 122 lbs. of dry grape sugar. -
The rapidity with which this transformation takes place depends
partly upon the temperature and partly upon the proportion of
acid employed. Thus 100 lbs. of starch mixed with 600 of water,
and 10 of sulphuric acid, will be converted into grape sugar after
boiling for seven hours. If by increasing the pressure the tempe-
rature be raised to 250° F., the transformation will be effected in
a few minutes. With only one pound of acid and the same quan-
tity of starch and water, the change will be effected in three hours
* It forms gypsum with it (sulphate of lime), which is a compound of lime and sul-
phuric acid.
190 SULPHURIC ACID WITH GUM AND SUGAR.
by a temperature of 230° F. This mode of converting potato
starch into grape sugar is extensively practised in France, for the
purpose of subsequently fermenting the Sugar and converting it
into brandy.
III. —Gl.J.M.
Action of sulphuric acid.—If powdered gum-arabic be rubbed
in a mortar with the sulphuric acid of the shops, a brownish solu-
tion is obtained, which when diluted with water and treated with
chalk yields a gummy substance similar to the dextrin obtained
in the same way from starch and cellular fibre. Prolonged di-
gestion with diluted acid converts a portion of this gum into su-
gar.”
Mucilage by a prolonged treatment with sulphuric acid is also
converted into sugar (Schmidt).
1". Action of heat.—When crystallized came sugar is heated to
320° F. it melts, and if the temperature be raised to 360° F. it
gives off four atoms of water and is changed into caramel. This
caramel is an uncrystallizable sugar, which is generally present in
artificial syrups, and is often of a brownish colour. It contains
the elementary substances—carbon, hydrogen, and oxygen—in the
same proportions as waterless cane sugar, and is represented by
the same formula C24 His Ols. It is not known to occur in the
natural juices of plants.
2°. Action of sulphuric acid.—When cane sugar is digested
with dilute sulphuric acid aided by a gentle heat, it is rapidly con-
verted into grape sugar. The acid of grapes (tartaric acid) and
many other vegetable acids produce a similar change.
It is obvious that this conversion of cane into grape sugar can
only take place in the presence of water, since grape sugar con-
tains the elements of two atoms of water more than cane sugar,
Dr
Cane Sugar. Water. Dry grape sugar,
C12 Hg Og + 2 H O - C12 H11 O11.
* Berzelius, Traité de Chemie (1831,) v. p. 217.
CHANGE OF CANE INTO GRAPE SUGAR. 19].
3°. When sweet fruits are kept over for a season they frequently
become mealy. This is a change of the sugar into starch or cel-
lulose. Woody winter pears become sweet by keeping—their cel-
lulose is changed into sugar.
We may now revert to the question with which we concluded
the preceding section. Since these different substances are so
closely allied in chemical constitution, and occur so often in con-
nection with each other in the vegetable kingdom—does nature,
when her purposes demand the change, actually transform them,
the one into the other, in the interior of the plant P The answer
may now be safely given, that she certainly does. What we can
so readily perform by our rude art may be still more easily effect-
ed in the living vegetable. Acids and alkalies perform the same
functions within as they do without the plant. That which is dex-
trin or starch in one part of the plant, may become cane or grape
sugar in another, and cellulose or gum in a third. Thus by re-
arranging the same elements—often in the same proportions—
may the various and unlike forms of matter which constitute the
main products of vegetation be readily produced.
Still the facility is only apparent. We can assure ourselves of
the fact of such conversions, because we can at will ourselves in-
duce them. But who operates upon these substances in the inte-
rior of the plant? Whose mind and will directs these changes—
prescribing when, where, and in what order they shall take place 2
How much depends upon the refined and little understood mechan-
ism of the vegetable structure—how much on the nature of the
elements of which it is composed—how much on the living prin-
ciple itself! What is this living principle—how can it direct “
§ 11. Of the fermentation of starch and sugar—and of the relative
circumstances under which cane and grape sugars generally oc-
cur in nature.
It will be of use to us, in connection with the above transforma-
tions, to advert to the property possessed by starch and nearly all
* “Canst thou by searching find out God—canst thou find out the Almighty unto
perfection ?”
192 G RAPE SUGAR ALONE FERMENTS.
the known varieties of sugar of entering into fermentation under
favourable circumstances. When flour is made into a paste with
leaven or yeast it begins to rise and ferment, sooner or later, ac-
cording to the kind of flour and the quantity of ferment added.
When to a decoction of malt or to a solution of starch or of cane
or grape sugar in water a portion of yeast is added, fermentation
is speedily induced; and if not arrested by unfavourable circum-
stances it will continue until the whole of the starch or sugar dis-
appears.
In all these cases it is grape sugar alone that undergoes fermen-
tation." The starch of the moist dough or of the solution of starch,
is partially transformed into grape sugar before fermentation com-
mences. Such is the case also with the decoction of malt and with
cane sugar. The fermentation commences soon after the first por-
tion of grape sugar is formed, and proceeds more or less rapidly
according as this transformation is more or less speedily effected.
Hence, in the art of brewing, the necessity of cautiously regulat-
ing the temperature by which this change of the starch and sugar
is promoted and hastened.
The fermentation itself is the result not of mere transformation
of one form of matter into another having the same elementary
constitution, but of a decomposition of one substance into two others
unlike itself either in properties or in chemical composition. The
grape sugar is resolved into alcohol (spirits of wine), which remains
in the liquid form, and into carbonic acid, which escapes in the
form of gas and causes the fermentation. Thus—alcohol being
represented by C4 H6 O2, and carbonic acid by CO2, if to
2 of alcohol = Cs H19 O. we add
4 of carbonic acid = C, Os we make up
1 of grape sugar = C12 H12 Orº
which grape sugar, as we have said, disappears, while the alcohol
formed from it remains in the Solution, and the carbonic acid
escapes into the air.
It is an interesting fact that the cane and grape sugars occur in
nature in circumstances which are entirely consistent with the
statement in the preceding section, regarding the action of acids
* Rose, Poggen. Annal, lii. p. 297.
SUBSTANCES CONTAINING NITROGEN. 193
on the former variety of this natural product. Fruits contain
grape sugar, which increases in quantity as they ripen or become
less sour. In the sugar cane, in the beet root, and in the maple
and birch trees cane sugar exists, but in their juices no acid is as-
sociated with the sugar. On the contrary, ammonia is known to
be present in most of them along with the came sugar. Hence, it
is inferred that, as in our hands and in our experiments cane su-
gar is changed by the agency of acids into grape sugar, and with
remarkable ease by that acid which exists in the ripe grape, so it
's in the interior of plants. Where sugar occurs in connection
with an acid in the juice of a plant, it is grape sugar in whole or
in great part, because in the presence of an acid body came sugar
cannot permanently exist, but is gradually transformed into the
Sugar of grapes. It thus appears also why fruits so readily enter
into fermentation, and why, evén when preserved with cane sugar,
they will, in consequence of the acid they retain, slowly change
the latter into grape sugar, and thus induce fermentation.”
* Milk also, in favourable circumstances, as when kept at a temperature of 100°F.,
undergoes fermentation, and in some countries of Asia a spirituous liquor is prepared
from mares' and asses’ milk. In this case the milk first becomes sour, a portion of
the milk Sugar being converted into lactic acid, then the acid thus formed converts
the remainder of the milk sugar into grape sugar, and finally this sugar enters into
fermentation. This takes place more readily in consequence of the presence of the
decomposing cheesy matter (casein) of the milk—as is shown by the fact that the in-
troduction of a small quantity of the curd of milk into a solution of grape sugar will
cause it to ferment.
I, ECTURE WII.
Substances of which plants chiefly consist. Fatty substances of plants. Elaine,
margarine, and stearine. Their properties and composition. The fatty acids.
Wax, its composition and relation to the fats. Resins and turpentine. Acid sub-
stances of plants. Acetic, lactic, tartaric, citric, and malic acids,-their composition,
properties, and production in plants or by art. Vegetable substances containing ni-
trogen. Animal and vegetable albumen, gluten, glutin, gladiadin. Animal and
vegetable fibrin. Animal and vegetable casein, emulsin, legumin, avenin. Ca-
sein of the turnip and potato. Protein and its compounds. Their properties, com-
position, and mutual relations, Diastase, its properties and relations to vegetable
life.
OF the substances described in the preceding lecture, by far the
greater part of all vegetable productions consist. But there are
also certain other bodies consisting of carbon, hydrogen, and oxy-
gen only, with which, though they occur in smaller proportion in
plants, it is necessary that you should be made acquainted. These
may all be arranged in two groups, that of vegetable oils or fats,
and that of vegetable acids.
§ 1. Of the fatty substances of plants.
All plants and nearly all parts of plants contain a certain pro-
portion of fat. But in some plants, and in some parts of plants—
as in the oily seeds and nuts—it is much more abundant than in
others.”
The seeds of plants usually contain the largest proportion of fat
or oil, but even the leaves of trees and the straw of our corn plants
are not free from fatty matter. When it is not present in suffi-
cient quantity to be separated by pressure, as it is in the so called
oily seeds, it can be readily extracted from the plant by digesting
* For the proportion of fat in different parts of plants, see Part IV. of these Lec-
tures.
tº 3
FATTY SUBSTANCEs of PLANTs—ELAINE. I95
it in ether. This liquid dissolves the fat, and by distilling the so-
lution so as to separate the ether, the fat or oil remains behind in
a separate state.
The appearance and properties of the fatty substances obtained
from plants differ very much. Whether they be extracted from
seeds, as the lint, rape, poppy, mustard, and madia seed oils are,
—from fruits, like the olive oil,-or from nuts, like the walnut,
almond, cocoa nut, and palm oils, they all differ very much from
each other, and are consequently employed for very different pur-
poses. -
But though they differ so very much in their sensible properties,
they resemble each other very much in their chemical composition,
Thus, *
1°. They all consist, as I have already stated, of carbon, hydro-
gem, and oxygen only.
2°. They all contain too little oxygen to form water with the
whole of their hydrogen, they cannot, therefore, like starch and
sugar, be represented as consisting of carbon and water only.
3°. They all consist of a solid and liquid portion. In some oils,
—olive, linseed, &c., the liquid portion predominates, in others,
like palm oil, cacao butter, &c., the solid portion is in greater
abundance, ---
4°. In nearly all the vegetable fats that have yet been examined,
the solid and liquid portions consist respectively of one or of ad-
mixtures of two different kinds of fat only.
The principal fatty bodies which thus occur mixed together in
the oily substances extracted from plants are the following:
Elaine, .................. which is liquid.
Margarime, ©
e } tº dº e º e º & © e º C & e º 0 e º e both of which are solid.
Stearine,
It will be proper to treat of these three fatty bodies separately,
§ 2. Of elaine, margarine, and stearine,—their properties and
composition.
1°. Elaine.—When almond or olive oils are exposed to a very
low temperature, a portion of them freezes or becomes solid. This
portion may be separated by pressure, and the liquid part which
flows out consists chiefly of élaine.
196 TROPERTIES AND COMPOSITION OF
When linseed or walnut oil is treated in a similar manner a li-
quid portion is obtained, which possesses properties considerably
different from those of the elaine of olive and almond oils.
The elaine of olive oil does not lose its fatty or greasy charac-
ter by exposure to the air, that of linseed or walnut oil, when
spread thinly upon wood or stone, dries up like a varnish, in mak-
ing which, indeed, linseed oil is extensively employed.
It is upon this property of their liquid portions that the distinc-
tion of oils into fatty and drying oils is founded.
All fats, whether of animal or vegetable origin, contain, so far
as is yet known, one or other of these fluid oils.
2°. Margarine.-The solid part of olive, almond, linseed, and
many other vegetable oils—as well as of butter, of the fat of man,
of the goose, and of some other animals, consists of margarine. It
is a white, hard, and brittle fat, which melts at 118° F., and when
pure undergoes no change by exposure to the air. When mixed
with the liquid fat (elaine) it is liable, along with the latter, to un-
dergo a slow alteration through the absorption of oxygen from the
atmosphere. -
3°. Stearine occurs only in small quantity in the solid fat of
plants—the solid part of the oils of almonds, olives, linseed, and
many others consisting almost entirely of margarine. In the fat
of certain animals, however, the horse, the ox, the sheep, the pig,
the goat, &c.—stearine forms nearly the whole of the solid part,
while in the fat of the goose there is much margarine and lit-
tle stearine, and in that of man margarine alone forms the solid
part. -
Stearine is also a hard colourless brittle fat, which melts at 129"
F. and which, when completely freed from elaine by pressure, is em-
ployed, like margarine, in the manufacture of candles.
§ 3. Composition of elaine, margarine, and stearine.
1°. The fats.—These fats, as I have already stated, consist of
carbon and hydrogen, united to a comparatively small quantity of
oxygen. Thus they are represented respectively by
C. H. O.
Elaine from ſat oils and butter, ..... 39 36 5
from linseed oil, ............... 49 40 5 P
fºr "
ELAINE, MARGARINE, AND STEARINE. 197
C. H. O.
Margarine, ............................. 37 37 4
Stearine, ................................ 71 70 6
We see a remarkable difference between these numbers and
those by which cellular fibre, starch, sugar, or the acid substances
found in the soil are respectively represented.
2°. Soaps and fatty acids.--When these fats are boiled with
lime, or with potash, or with soda, they are converted into soaps,
while at the same time a quantity of oil sugar or glycerine is pro-
duced. If the soaps be dissolved in water, and muriatic or sul-
phuric acid is added to the solution, the soap is decomposed, and
the fats are separated in a mew form.
Elaine soap yields a colourless fat oil, to which the name of elaic
acid is given.
Margarine soap yields a colourless, solid, crystallizable fat,
called margaric acid, which melts at 140°F.
Stearine soap gives a solid white crystallizable stearic acid, which
melts at 1889 F.
The composition of these three acids is as follows,
Elaic. Margaric. Stearic.
From fat only.
(Gottlieb.) (Gottlieb.) (Redtenbacher.)
Carbon, ................. 76.51 75-30 76.53
Hydrogen, ............. 12' 12 12:55 12-93
Oxygen, ............... 11:37 12-15 10°54
100 100 I ()0
And they are represented respectively by the following formulae:
C. H. O.
Elaic acid from fat oils," ............ 36 34 4
from drying oils,f ........ 46 38 4 P
Margaric acid, ........................ 34 35 4
Stearic acid, ............................ 68 69 6
The elaic acids absorb oxygen with great rapidity from the air.
It is very difficult, therefore, to obtain them in a pure state, and
hence it is not certain, if the composition of the elaic acids, especi-
ally that from drying oils, be as yet correctly ascertained.
3°. Oil sugar or glycerine.—When the matural fats are convert-
* Gottlieb, Annalen der Chemie und Pharmacie, I,VII. p. 44.
+ Sacc. Chemist, 1845, p. 18.
l98 ELAINE, MARGARINE, AND STEARINE.
ed into soaps, a substance called oxide of lipyle (Cs H2O) is sepa-
rated from them. *
This compound at the moment of liberation unites with water,
and forms the sweet substance to which the name of oil sugar or
glycerine is given. The way in which the sugar is produced is
represented as follows,
C, H. O.
2 oxide of lipyle = 6 4 2
unite with 3 of water (HO) = 3 3
and form one of glycerine 6 7 5
The natural fats, therefore, as they exist in plants and animals,
consist of the fat acids in combination with the oxide of lipyle,_
thus,
Margarine = Csſ H35 O1 + C3 H2O
4°. Other vegetable fats.--Besides the fatty acids above describ-
ed, which by their admixture form the natural fats which occur in
most of our vegetable and animal oils and fats, there are a few
others already known which have been met with in particular plants.
Thus from the oil expressed from the seeds of the Madia sativa,
Luck has obtained a liquid fatty acid represented by Cas Hat Oa.”
This differs considerably from the acid of olive oil, but it may not
have been pure, and the analysis requires repetition.
From cocoa butter Bromeis obtained cocinic acid, represented
by C37 Has OA. In nutmeg butter Playfair found an acid, myri-
stic acid, represented by C2s H29 OA. From palm oil Stenhouse
obtained a solid acid very much resembling the margaric, called
by him palmitic acid, and represented by Cs, Has O, while from
laurel oil Marsson extracted the solid lauro-stearic acid, repre-
sented by C. Has Os, and Sthamer has obtained the same solid fat
acid from the pichurim bean.
It is very likely that other solid and liquid acids may hereafter
be discovered in the numerous vegetable fats and oils which still
remain to be examined, but in the present state of our knowledge
it appears, *
{?
* Annalen der Chemie und Pharmacie, LIV. p. 124.
WAX, DIFFERENT KINDS OF. I99
a. That by far the largest proportion of the known vegetable
fats contain the elaic and margaric acids mixed with a very small
proportion of the stearic, and,
b. That, with the exception of man, the proportion of margaric
acid is much less, and that of stearic acid very much greater in
animal fats than in those which exist in the seeds and other parts
of plants.
§ 4. Of wow, its composition and relation to the fats.
1°. Bees' war.—Wax is a species of fat which is found in the
seed vessels of some fruits, and on the leaves and stems of many
plants. In cases of necessity it can be formed by the bee from
pure sugar when given to it for food.
Common bees-wax, when bleached and otherwise purified, con-
sists of two different substances, one of which is soluble in boiling
alcohol and the other is not. The former is called cerine and the
latter myricine, and they consist respectively of,
C. H. O.
Cerine, .............................. 20 20 2
Myricine, ............................ 20 20 I.
They differ, therefore, only in the proportion of oxygen they
severally contain, which in cerine is double of what is present in
myricine.
2°. Vegetable war.—But wax of other kinds and of a different
composition has been obtained directly from many plants. The
leaves of many trees are covered with wax; the bloom of grapes,
plums, and other fruits is owing to a thin coating of wax. Varie-
ties of it are found on the sugar cane, on the root of the apple tree,
on the berries of the mountain ash, and on the leaves of the palm.
The wax from the leaves of the lilac, the vine, the palm, and
some others is identical with bees-wax (myricine), while that from
the sugar cane, called by Avequin cerosine, is represented by the
formula C1s H30 O2. According to Mulder the wax from the ber-
ries of the mountain ash, and that from the bark of the root of the
apple tree are represented by C20 H16 Og, and that from cork by
C25H10O3.
Five kinds of wax, therefore, are at present known, consisting re.
spectively of
200 COMPOSITION OF WAX.
C. H.
Cerine, .......................... 20 20
Myricine, ....................... 20 20
Cerosime, ........................ 48 50
Wax of mountain ash berries, 20 16
Wax from cork, by ether, ... 25 10 *
It is probable that we shall hereafter become acquainted with
many more. In the meantime there are three facts in regard to
wax which it is interesting to recollect, from their bearing upon a
subject, the feeding of animals, which will hereafter come under
our consideration.
a. Like the fats and oils they all contain very little oxygen com-
pared with the carbon aud hydrogen present in them. Thus,
Margaric acid (free from water) is, Cai Hat Oa, and
Cerine is, .............................. Cao Hao Os
They resemble each other, therefore, not only in containing
little oxygen, but also in containing the same number of equiva-
lents of carbon as they do of hydrogen.
Wax appears, therefore, from its composition to be a kind of
fat, and this view is strengthened by other facts.
b. Avequin states that in the sugar came the quantity of wax is
always largest when the sugar is least abundant, and that when
there is much sugar there is little wax. Thus there appears to be
some relation between sugar and wax.
c. This relation is more strikingly brought out by the experi-
ments upon bees by Gundlach and Milne-Edwards. When shut
up in a hive and supplied with pure sugar only, the bees appear to
get into a diseased state, but at last they are seen to deposit wax
and form combs. This wax must have been produced from the
sugar. It follows, therefore, that the bee has the power in a case
of cmergency of transforming sugar into a kind of fat (wax).
This same power, therefore, may be possessed by other animals,
in other words, sugar eaten as food by man and other animals, or
sugar formed in their stomachs from the starch of their food may,
as in the case of the bee, be transformed into fat and employed in
fattening the animal.
To this point we shall return hereafter.
.
R.ESINS AND TURPENTINE. 201
§ 5. Of resins and turpentine.
l". The resins.—Most trees of the pine tribe when the bark is
injured yield a fluid turpentine, which gradually thickens in the
sun and concretes into a kind of resin. From trees belonging to
other families, especially in warm climates, liquids occasionally
exude, which harden into the various resins known as articles of
commerce. These resins agree with wax and with the fats, in con-
taining for the most part only a small proportion of oxygen. They
are probably formed in the plant, therefore, in a similar manner, and
it is possible that such of them as exist in articles consumed for
food may act in a similar way upon the animal economy. This
latter, however, is a point in regard to which little as yet is known.
The resins like the fats are insoluble in water, but they differ
from many of them in being more readily soluble in both alcohol
and ether.
The resin best known in this country is the common rosin or
colophony of the shops. This is represented by the formula,
C40 Høg O4
It contains less hydrogen in proportion to its carbon than the
fats or wax do, and the same is the case with many of the other
resins.
2°. Turpentine.—When the liquid or natural turpentine that
flows from trees of the pine tribe is distilled in a retort, common
turpentine, oil or spirit of turpentine, or camphene, by all which
names it is known, distills over, and the common rosin remains be-
hind. This turpentine or camphene differs from the fats and re-
sins in consisting of carbon and hydrogen only,–being represent-
ed by C20 H16.
Colophony is formed from it by the simple absorption of oxy-
gen from the air, as may be seen by comparing their respective
formulae. Thus,
2 of turpentine = Cſo Hg2
1 of colophony = Cao Hg2 Ol -
It is a remarkable fact that oil of lemons and oil of turpentine
have precisely the same composition, and are represented by simi-
lar formulae.
I do not dwell upon these compounds, as they possess little prac-
202 AGID subsTANCES OF PLANTs.
tical value either in reference to the culture of the soil or to the
feeding of stock. -
6. Of the acid substances of plants.
Another class of compounds occurring in plants, and consisting,
like those already described, of carbon, hydrogen, and oxygen only,
remains still to be briefly described. These are the vegetable
acids,-so called from their possessing sour or acid properties.
These acids do not as a whole form any large portion of the sub-
stance of our cultivated plants, but the universal existence of some
of this class of bodies in all our fruits, and the very general pro-
duction of others in nature, renders it necessary that their compo-
sition, and the peculiar changes by which they are produced, should
be in some measure explained.
The more important vegetable acids may be divided into three
groups. -
1°. Such as consist of carbon and oxygen only. Of these there
are two, -
Carbonic acid = C Og
Oxalic acid = C, Os
2°. Such as like starch and sugar consist of carbon united to
hydrogen and oxygen in the proportions to form water, which
like starch and sugar may be supposed to consist of carbon and
water only. Of these there are only two with which it is necessary
that you should be made acquainted. These are,
Acetic acid (vinegar) = C, Hà Os
Lactic acid (acid of milk) = C, H, O,
3°. Those which consist of carbon and hydrogen, united to an
excess of oxygen, above what is necessary to form water with the
hydrogen, or which may be represented by carbon, water, and
Oxygen.
The vegetable acids of this kind are very numerous, but I shall
at present draw your attention only to three of them, namely,
Tartaric acid (acid of grapes) = C, H, Og
Citric acid (acid of lemons) = C, H, O,
Malic acid (acid of apples) = C, H, O,
The acids of the first group, the carbonic and oxalic acids—have
already been described in a preceding lecture (pp. 62 to 68).
ACETIC AND LACTIC ACIDS. 203
§ 7. Of the acetic and lactic acids.
I. Acetic acid or vinegar is the most extensively diffused and
perhaps the most largely produced of all the organic acids. It is
formed during the germination of seeds, exists in the juices of many
plants, and is one of the results of the fermentation of Sugar, whe-
ther produced by matural or by artificial means.
Vinegar when pure is a colourless. liquid, having a well known
agreeably acid taste. It may be boiled and distilled over without
being decomposed. The vinegar of the shops is generally very much
diluted, but it can be prepared of such a strength as to freeze and
become solid at 45° F., and to blister the skin and produce a sore
when applied to any part of the body. When mixed with water
it readily dissolves lime, magnesia, alumina, &c., forming salts
called acetates, which are soluble in water, and may, therefore, be
readily washed out of the soil or of compost heaps by heavy falls
of rain. *
When perfectly free from water, acetic acid consists of
Carbon, ............ 47.5 per cent, or 4 atoms.
Hydrogen,......... 5.8 per cent. = 3 atoms.
Oxygen,............ 46.7 per cent. = 3 atoms.
100
It is, therefore, represented by the formula C, Ha Os—in which,
as in the formulae given in the preceding lecture for starch, sugar,
&c., the numbers representing the atoms of hydrogen and oxygen
are equal, and consequently these elements are in the proportion
to form water. Hence, vinegar, like sugar, may be represented by
carbon and water. It may be said to consist of four equivalents
of carbon united to three of water. -
Let us consider for a moment the several processes by which
this acid is usually formed.
1°. By the distillation of wood—This is a method by which
wood vinegar—often called pyroligneous acid—is prepared in large
quantity. Wood which has been dried in the air is put into an
iron retort and distilled. The principal products are vinegar,
water, and tarry matter. The decomposition is of a complicated
description, but, by comparing the constitution of cellular fibre
204 PROPERTIES OF ACETIC ACID,
with that of vinegar, we can readily see the nature of the changes
by which the latter is produced. Thus
C. H. O.
Cellular fibre is g & 24 21 21
6 of vinegar are . o 24, 18 18
& Pifference g 3 3
or cellular fibre may be changed into vinegar by giving off the
elements of three atoms of water (3 HO.)
This change, no doubt, takes place during the distillation of
wood. The encrusting or woody matters undergo similar changes,
and from the excess of hydrogen they contain assist in giving rise
to the tar and other substances which accompany the vinegar and
water during the distillation.
2°. Manufacture of vinegar from cane sugar.—It is a well
known fact in domestic economy, that if cane sugar be dissolved
in water, a little vinegar added to it, and the solution kept for a
length of time at a moderate temperature—the whole will be con-
verted into vinegar without any sensible fermentation. This pro-
cess is frequently followed in the preparation of household vinegar,
and was formerly adopted to some extent in our chemical manu-
factories. It will be recollected that we represented
Dry Cane sugar by C12 Ho Oa, while
3 of Vinegar are also C12 Ho Oo
So that cane sugar may be converted into vinegar simply by a new
arrangement of the particles of matter of which it consists.
Whether this new arrangement takes place directly, or whether
some intermediate change—such as the conversion of the came into
grape sugar—precedes it, has not yet been satisfactorily deter-
mined.
3°. Manufacture of vinegar from alcohol.—In Germany, where
common brandy is cheaper than vinegar, it is found profitable to
manufacture this acid from weak spirit. For this purpose it is
mixed with a little yeast, and then allowed to trickle over wood
shavings moistened with vinegar, and contained in a cask, the
sides of which are perforated with holes for the admission of a cur-
rent of air. By this method oxygen is absorbed from the air, and in
24 hours the alcohol in the spirit is converted into vinegar and water.
LAOTIC ACID, How PRODUCED. 205
The explanation of this process is also simple, alcohol being re-
presented by C. He O2. Thus—
1 of Alcohol = C, He O2 1 of Vinegar = C, H, O,
4 of Oxygen – §= { of Water = H, O,
Sum Ca H6 O6. Sum = C, H, Og
4°. Production of vinegar by fermentation.—When solutions
containing sugar are allowed to ferment, carbonic acid is given off
and vinegar is formed. In such cases the acetic acid is the result,
not of a single transformation but, of a series of changes during
which the vegetable matter has most probably passed through the
several previous stages of grape sugar and alcohol. The carbonic
acid, as has already been explained (p. 192,) is given off during
the fermentation of the grape sugar, and the consequent formation
of alcohol. -
To simple transformations, similar to those above described, we
can trace the origin of the vinegar which is met with in the living
juices of plants, as well as among the products of their decay.
II. Lactic acid, or the acid of milk, is produced in abundance
when milk becomes sour, and hence its mame of acid of milk. It
is not known to existin any quantity in the interior of living plants,
but it is abundantly produced during their decay.
When cabbage is chopped and put into a close vessel, it gradu-
ally becomes sour (Sauer krout), from the production of lactic acid,
When the flour of wheat or of any other kind of grain is mixed
with water and allowed to stand for a few days, it acquires a dis-
agreeable smell and sour taste. The sourness is owing to the pro-
duction of lactic acid.
This acid is also formed during the fermentation of the juices of
the beet, and the turnip, and of the extract of rice, during the
souring of malt, of brewer's grains, of distillery refuse, and of
many other sour vegetable mixtures with which cattle are fed, in
the waste liquor of the tanworks, and under many other circum-
stances. During the digestion of starch and sugar it is largely
produced in the stomachs of animals. -
It may likewise be formed artificially, by dissolving milk Sugar
in water and introducing a piece of the fresh intestinal membrane
206 TARTARIC ACID IN THE GRAPE.
of the sheep or ox (Barreswill), or by mixing a solution of cane
sugar with the fresh curd of milk and allowing the mixture to
stand a few days with occasional stirring (Von Blucher).
When obtained free from water this acid is very sour, but when
diluted with water it has an agreeable acid taste.
It is represented by the formula C6H6 Oc, and may be supposed
to consist of 6 atoms of carbon united to 6 of water.
It is easy, therefore, to understand how it is produced by the
artificial methods above described. Thus,
C. H. O.
1 of milk sugar is ......... 24 24 24
4 of lactic acid is ......... 24 24 24
so that the sugar may be converted into the acid by a simple trans-
position of the elements of which they both alike consist. The ani-
mal membrane and the fresh curd merely promote or assist this
new arrangement of the particles.
In fermenting vegetable substances the action is the same, the
sugar or starch they contain is transformed into lactic acid by the
agency of certain compounds resembling the curd of milk, which
are found to exist in nearly all the parts of plants.
§ 9. Of tartaric, citric, and malic acids.
1°. Tartaric acid—The grape and the tamarind owe their sour-
mess to a peculiar acid to which the mame of tartaric acid has been
given. It is present also, along with other acids, in the mulberry,
in the berries of the Sumach (rhus coriarii), in the needles of the
pine tribes, in the sorrels and some other sour-leaved plants, and
it has been extracted from the roots of the couch-grass and the
dandelion.
When new wine is decanted from the lees, and set aside in vats
or casks, it gradually deposits a hard crust or tartar on the sides
of the vessels. This substance is known in commerce by the name
of argol, and when purified is familiar to you as the cream of tar-
tar of the shops. It is a compound of tartaric acid with potash,
and from it tartaric acid is extracted for use in medicine and in
the arts. The principal employment of the acid is in certain pro-
cesses of the calico printers.
The pure acid is sold either in the form of a white powder or of
COMPOSITION OF TARTARIC ACID. 207
transparent crystals, which are colourless, and have an agreeable
acid taste. It dissolves readily in water, and causes a violent ef-
fervescence when mixed with a solution of carbonate of potash or
of carbonate of soda. Hence it is extensively used in artificial
soda powders and effervescing draughts. When added in sufficient
quantity to a solution containing potash, it causes a white crystal-
line powder to fall, which is cream of tartar (or bitarirate of potash),
and from lime water it throws down a white chalky precipitate of
tartrate of lime. Both of these compounds are present in the
grape.
When perfectly free from water tartaric acid consists of
Carbon,..................... 36-81 or 4 atoms.
Hydrogen, ............... 3:00 or 2 atoms.
Oxygen, .................. 60° 19 or 5 atoms.
100
And is represented by the formula C4H2O3.
If we compare the numbers by which the atoms of hydrogen and
oxygen in this acid are expressed, we see that these elements are
not in the proportions to form water, and that this substance, there-
fore, cannot, like so many of those we have hitherto had occasion
to notice, be represented by carbon and the elements of water alone.
It may be represented by
4 of Carbon ...... = C4
2 of Water ...... = H2 º 4C + 2HO + 3O
and 3 of Oxygen...... - Os
Tartaric acid = C, H, Og -
And, though this mode of representation does not truly exhibit the
constitution of the acid, inasmuch as we have no reason to believe
that it really contains water as a constituent—yet it serves to show
very clearly that in the living plant this acid cannot be formed di-
rectly from carbon and the elements of water, as starch and sugar
may, but that it requires also three atoms of oxygen in eccess to
every four of carbon and two of water. We shall, in the following
lecture, see how micely the functions of the several parts of plants
are adjusted,—at one period to the formation of this acid, and at
another to its conversion into sugar during the ripening of the fruit.
208 COMPOSITION OF CITRIC ACID.
2. Citric acid.—This acid gives their sourmess to the lemon, the
lime, theorange, the cranberry, the red whortleberry, the bird-cherry,
and the fruits of the dog-rose and the woody night-shade. It is also
found in some roots, as in those of the Dahlia pinnata, and of the
Asarum Europaeum (asarrabacca), and mixed with much malic acid,
in the currant, cherry, gooseberry, raspberry, strawberry, common
whortleberry, and in the fruit of the hawthorn.
When extracted from the juice of the lemon or lime, and after-
wards purified, it forms transparent colourless crystals, possessed
of an agreeable acid taste; effervesces like tartaric acid with car-
bonate of soda, and like it, being without injurious action upon
the system, is much employed for effervescing draughts. With
potash it forms a soluble salt, which is a citrate of potash, and from
lime water it throws down a white, nearly insoluble, sediment of
citrate of lime, which re-dissolves when the acid is added in excess.
In combination with lime it exists in the tubers, and with potash in
the roots of the Jerusalem artichoke.
When free from water citric acid consists of
Carbon,............... 41°49 = 4 atoms.
Hydrogen, ......... 3'43 = 2 atoms.
Oxygen,............... 55'08 – 4 atoms.
100
and is therefore represented by C. H. O.
This formula differs from that assigned to the tartaric acid only
in containing one atom of oxygen less—OA instead of Og. In the
citric acid, therefore, there are 2 atoms of oxygen in excess, above
what is necessary to form water with the 2 of hydrogen it contains.
3°. Malic acid——The malic and oxalic acids are more exten-
sively diffused in living plants than any other vegetable acids. If
the lactic and acetic acids be more largely formed in nature, it is
chiefly as products of the decomposition of organic matter, after
it has ceased to exist in, or to form part of, a living plant.
Along with the citric, it has been already stated that the malic
acid occurs in many fruits. It is found more abundantly, how-
ever, and is the chief cause of the sour taste, in the unripe apple,”
the plum, the sloe, the elder-berry, the barberry, the fruit of the
* Hence its name malic acid.
WEGETABLE SUBSTANCES CONTAINING NITROGEN. 209
mountain ash, and many others. It is associated with tartaric acid
in the grape, and in the Agave Americana.
This acid is not used in the arts or in medicine, and therefore is
not usually sold in the shops. It is obtained most readily, in a
pure state from the berries of the mountain ash. It forms colour-
less crystals, which have an agreeable acid taste. It combines with
potash, soda, lime, and magnesia, and forms malates, and it usual-
ly occurs in the fruits and juices of plants in combination with one
or more of these bases. The malate of lime is soluble, while the
citrate, as already stated, is nearly insoluble in water. This malate
of lime exists in large quantity in the juice of the house-leek (sem-
pervivum tectorum), in the Sedum telephium, the Arum macula-
tum, and many other juicy and fleshy-leaved plants.
When perfectly free from water, the malic acid has exactly the
same chemical composition as the citric, and is represented by the
same formula C, H, O, These two acids, therefore, bear the
same relation to each other as starch and gum do. They are
what chemists call isomeric, or are isomeric bodies. We cannot
transform them, however, the one into the other, by any known
means, though there is every reason to believe that they undergo
such transformations in the interior of living plants. Hence one
reason, probably, why the malic and citric acids occur associated
together in so many different fruits.
§ 10. Of vegetable substances containing nitrogen. Animal and
vegetable albumen.
Besides the numerous substances already described as forming
important parts of living plants, there exists in all vegetables a
small proportion of certain compounds into the composition of
which nitrogen enters as an essential constituent. These sub-
stances are so necessary to the existence both of plants and of ami-
mals, and perform functions of so important a kind in reference to
the healthy growth of both, that a knowledge of their nature, com-
position, and mutual relations is almost indispensable to the skilful
practical farmer and breeder of stock.
1°. Animal albumen of the egg.—When a fresh egg is broken
it is seen to consist of two portions,—a central coloured part or
yolk, and a colourless, glairy, semifluid portion—the white of the
O
210 ANIMAL AND WEGETABLE ALBUMEN.
egg. This white part is called the albumen (albus, white) by che-
mists. It may be diffused and apparently dissolved by beating
or by agitation in cold water, but when heated to 165° F. or to
near the boiling point of water, it coagulates or assumes the solid
form. Hence in a boiled egg the glairy colourless fluid of the raw
egg has become opaque, white, and solid.
This solid white matter is called coagulated albumen. When
allowed to dry in the air it becomes brown, hard, brittle, and semi-
transparent like born. It swells and dissolves when put into or
boiled in strong vinegar, (acetic acid.) It dissolves also in hot
solutions of carbonate of soda or potash, and is thrown down again
in a solid form when muriatic or acetic acid is added to the solu-
tion in slight excess.
2°. Animal albumen of the blood.—When the fresh blood of an
animal is allowed to cool, it gradually separates into two portions,
—a red solid part, the clot, and a fluid, nearly colourless part,
the serum. When this serum is heated to 180° F.—nearly to boil-
ing,-a portion of it solidifies or coagulates, and when the liquid is
set aside gradually collects at the bottom of the vessel.
This solid portion is the albumen of the blood. It coagulates
when heated as that of the egg does, and when coagulated dissolves
also in acetic acid and in solutions of carbonated alcalies. It re-
sembles closely in its properties the albumen of the egg, though,
as we shall afterwards see, it differs from it slightly in its compo-
sition.
3°. Vegetable albumen.—If the expressed juice of a plant be
strained through a cloth or filtered through paper and then heated,
it will become turbid and a great quantity of flocks will fall, which
possess all the properties of coagulated albumen. The same is
the case with the juice of the turnip, of the carrot, of mangold
wurtzel, of the potato, the Jerusalem artichoke, the peony root,
and many others. To this substance the name of vegetable albu-
men has been given.
All plants and nearly all their parts yield this substance in
small quantity. When the grain of wheat, oats, barley, or rye,
or of Indian corn, is crushed and rubbed in cold water, the clear
liquor upon being boiled gives a sensible deposit of coagulated al-
bumen. Thus
GLUTEN.—GLUTIN, &C. 211
Wheat yields three-fourths to one and a half per cent.
Oats ...... one-fifth to one-half per cent.
Barley ...... one-tenth to one-half per cent.
Rye ...... two to four per cent.
When the husk of grain or the washed fibre of the grated po-
tato is boiled in acetic acid (vinegar), a portion of a substance is
dissolved out, which possesses the properties of coagulated albumen
when dissolved in the same acid.
It is inferred, therefore, that vegetable albumen exists in plants
in two states, in the soluble form, as it is found in the raw egg
and in the blood, and in the coagulated or solid form of the boiled
white of egg.
The albumen of plants is almost identical in composition with
the albumen of the animal body.
§ 11. Of gluten, glutin, gladiadin, and animal fibrin.
1°. Gluten.—When the flour of wheat is made into a dough,
and this dough is washed with water upon a fine sieve, a milky
liquid passes through, from which starch gradually subsides. This
has been already stated, (p. 170). But on the sieve, when the
water ceases to go through milky, there remains a soft, glutinous,
and elastic substance, which can be drawn out into long strings,
has scarcely any colour, taste, or smell, and is very little dimi-
mished by washing either with hot or with cold water. This sub-
stance is the gluten of wheat. Other kinds of grain also yield the
same substance by a similar treatment, though generally in much
smaller quantity. Thus the grain of
Wheat contains 8 to 24 per cent. of gluten.
Rye ...... 9 to 13 .........
Barley ...... 3 to 6 ..... * * * *
Oats ...... 2 to 5 .........
When the moist gluten is dried in the air at the temperature
of boiling water, it diminishes much in bulk, and hardens into a
brittle semi-transparent yellow substance resembling horn or glue.
In this state it is insoluble in water, but dissolves readily in vine-
gar, in solutions containing caustic potash, or soda, and to a cer-
tain extent in alcohol either cold or hot,
2] 2 GLUTIN, GLADIADIN, AND ANIMAL FIBRIN.
}
2°. Glutin.--When the gluten, freed from water as much as
possible, is boiled in alcohol, a portion of it is dissolved. But if
the alcohol be allowed to cool, a white sediment falls to the bottom
of the vessel, to which the name of glutin is given. It is insoluble
in water but dissolves in alcohol.
But a considerable proportion of the gluten remains behind,
upon which the alcohol has no action. This insoluble part is by
Mulder considered to be identical with coagulated albumen, while
by Liebig it is called vegetable fibrin. It has not yet been obtain-
ed in a pure state from wheaten flour, and therefore its exact com-
position is still unknown. - -
3°. Gladiadin or zein.—When the flour of Indian corn is treated
with ether to dissolve the fat it contains, and is then boiled in al-
cohol, from four to five per cent. of a substance is dissolved out, to
which the name of gladiadin or Zein has been given. It is pro-
bably analogous to glutin, but it has not been analysed, nor have
its properties been as yet rigorously investigated.
4°. Fibrin.—When the muscular or lean part of beef or mutton
is washed long with water to remove the blood, and is then treated
with alcohol to extract the fat, a white fibrous matter remains, to
which chemists give the name of fibrin. It may be obtained also
by whipping fresh drawn blood with a bundle of birch twigs, when
the fibrin of the blood attaches itself to the twigs in long, white
strings. It is insoluble in water, but like coagulated albumen dis-
solves in acetic acid or in alcaline solutions. It differs from al-
bumen in coagulating spontaneously and without heat, as in the
cooling of blood, of which it forms the largest part of the clot, -
but in chemical composition it approaches very near to albumen.
It is supposed to exist in the juices of some plants which like
blood coagulate spontaneously, and as I have already stated, Lie-
big has given the name of vegetable fibrin to that part of the glu-
ten of wheat which refuses to dissolve in boiling alcohol.
§ 12. Of animal and vegetable casein, emulsin, legumin and
avenin.
1°. Animal Casein.--When well skimmed milk is heated and
mixed with a little vinegar or rennet, it coagulates and separates
*g
ANIMAIL AND VEGETABLE CASELN. 213
into two parts, the curd and the whey. When the curd is well
washed with water, and then boiled in ether to extract the butter
which it still contains, it forms the substance to which the name of
casein is given. After being coagulated, casein is insoluble in wa-
ter, but dissolves readily in a weak solution of carbonate of soda.
From this solution it is thrown down again by adding muriatic acid
or vinegar, till it becomes slightly sour.
The casein or curd of milk is separated or coagulated by alco-
hol, or by any weakly acid liquid. Weak vinegar, acid of lemons,
tartaric acid, lactic acid, or diluted muriatic or sulphuric acids, all
precipitate it from its solutions in water. It is readily precipitated
or coagulated by acetic acid, in which respect it differs from albu-
men, which is coagulated by the sulphuric, nitric, and muriatic
acids, but not by the acetic acid. It dissolves readily in solutions
of oxalic or tartaric acid in excess, but very sparingly in vinegar
or in any of the so-called mineral acids. Solutions of casein are
distinguished by forming a pellicle or brat on the surface—such
asis formed on boiled milk—when they are evaporated. This brat
is renewed as often as it is taken off.
2°. Vegetable casein.—If the sap of a plant be boiled, it becomes
troubled, and deposits a portion of albumen. If this albumen be
separated, and a little vinegar or weak muriatic acid be them added
to the clear liquid, it will become opaque, and a white powder will
gradually fall, which has much resemblance to the casein of milk,
and to which the name of vegetable casein has been given by Lie-
big.
3°. Emulsin or Synaptas.—When almonds are steeped in water
and afterwards rubbed to powder, they form a milky liquid, which
may be separated from the undissolved portion of the almond, by
allowing the whole to settle, and then decanting the liquid. If vi-
negar be added to this milky liquid, a white matter falls, which
has much resemblance to pure curd. It differs from it, however,
by being readily soluble in acetic acid in excess, and by containing
a larger per centage of nitrogen. (Dumas.)
4°. Legumin.--When peas or beans are allowed to swell in wa-
ter, and are then rubbed in a mortar with repeated portions of
luke-warm water, to which a few drops of ammonia have been ad-
214 k LEGUMIN AND AVENIN.
ded, a milky liquid is obtained, from which starch subsides, leaving
a slightly opaque solution above. If this solution be evaporated
by a gentle heat, or if vinegar, or diluted muriatic or sulphuric
acids, or a large quantity of alcohol, be added to it, a more or less
grey powder falls, which very much resembles the curd of milk.
Like curd it dissolves readily in caustic ammonia, or in a solution
of carbonate of soda, and is thrown down again or coagulated by
the addition of muriatic, sulphuric, or acetic acid. The name of
legumin was originally given to this substance. Liebig, who con-
siders it to be identical with pure curd, calls it vegetable casein.
Until its true composition, however, has been established by fur-
ther analyses, it is safer to retain the special name of legumin. In
peas, beans, vetches, and clover seeds, it exists to the amount of .
from 15 to 24 per cent.
59. Avenin.—When oatmeal is mixed and shaken for a few mi-
nutes with pure cold water, and then set aside, the starch and husk
fall to the bottom of the vessel, and a slightly milky liquid rests above
them. If this liquid be decanted, and a little vinegar or weak mu-
riatic acid be added, to render it very slightly sour, a white pow-
der falls, which possesses many of the characters of casein or pure
curd of milk. It may be called vegetable casein, but until it has
been rigorously analysed, I have distinguished it by the provisional
name of avenin. (Avena, the oat.)
Avenin exists in the dry oat when freed from the husk to the
extent of about 16 per cent. of its weight.
6". Casein of the turnip and potato.—When the washings of the
grated potato, the turnip, the carrot, the Jerusalem artichoke, the
root of the peony and many other tubers, are boiled to separate
the albumen, and are then rendered slightly acid by vinegar or
muriatic acid, a precipitate—white, grey, and in the case of the po-
tato usually darker coloured, in that of the peony often of a beau-
tiful purple—falls to the bottom. To these substances the gene-
ral name of vegetable casein may be applied.
As above obtained, however, they are in most cases mixtures of
several substances. They are only partly soluble in ammonia, and
the part which does dissolve in ammonia is not wholly soluble in
alcohol, so that there are at least three different substances mixed
3
PROPERTIES AND COMPOSITION OF PROTEIN. 215
together in the precipitates obtained by acids from the expressed
juice and washings of these tuberous roots.
Though, therefore, these precipitates contain nitrogen, and shew
satisfactorily that tubers like other edible parts of plants, contain
compounds which possess some of the characters of the curd of
milk—yet their nature and chemical composition have hitherto been
too little investigated to admit of their being distinguished by the
definite name of casein. Until they are more thoroughly studied,
we can only consider them, as we do the purer legumim and ave-
nin, as casein-like bodies.
§ 13. Of protein, its properties and composition.
When any of the substances above described—animal or vege-
table albumen, casein, fibrin, or gluten—is dissolved in caustic
potash by the aid of heat, and acetic acid is then added to the so-
lution till it is slightly sour, a substance falls in the form of grey-
ish white flocks, to which Mulder has given the name of Protein.
This substance forms the principal part of nearly all the com-
pounds described in the preceding section. They all contain pro-
tein in combination with a small proportion of sulphur or phospho-
rus, or both. Hence protein is -one of the most important sub-
stances which are met with in the animal and vegetable economy.
It exists in the sap of plants and in the fluids of the animal
body. It forms the largest proportion of the muscles of the ani-
mal, and it enters in small quantity into the composition of almost
all the solid parts of the plant.
Protein contains nitrogen, and, according to the analysis of Mul-
der, consists of
By experiment. Equivalents. Calculated.
Carbon, ............... 55:30 40 55-29
Hydrogen, ............ 6-94 31 7:00
Nitrogen, ............ 16-02 5 16:01
Oxygen, ............... 21-74 12 2I-70
100 100
and is represented by the formula C10 Hst Nº Ots.
Protein possesses three characters by which it can readily be re-
cognised.
216 COMPOSITION OF THE SEVERAL
1°. When dissolved by the aid of heat in a solution of caustic
potash, it is partially decomposed, and gives off the odour of am-
Ill OIllèl. .
2°. When dissolved in strong nitric acid, it gives, on the addi-
tion of ammonia, a bright yellow solution or precipitate, of what
Mulder calls the wantho-proteate of ammonia.
3°. When put into concentrated muriatic acid with access of
air, it gradually dissolves and forms a beautiful purple solution.
So far as is known protein always exhibits these properties, and
all its known compounds are distinguished by the same characters.
§ 14. Composition of the several protein compounds found in plants.
The protein compounds as yet known are albumen, casein, and
fibrin obtained from animals; the same or similar substances ex-
tracted from plants; the hair or wool of animals, and the crystal-
line lens of the eye. -
1°. In chemical characters they agree with protein itself in giv-
ing off ammonia when boiled with caustic potash, in giving a yel-
low colour with nitric acid and ammonia, and a purple with strong
muriatic acid.
2°. In chemical composition, so far as is yet known, they differ
from each other only in the proportions of sulphur and phospho-
rus, with which they are respectively combined. This propor-
tion of Sulphur and phosphorus is in all cases very small, as may
be seen from the following analyses made by Mulder:*
Glutin Casein Fibrin Albumen
of wheat. from milk, from blood. from eggs. from blood.
Carbon, ...... 54-75 54-96 54-56 54'48 54-84
Hydrogen, ... 6.99 7-15 6'90 7:01 7.09
Nitrogen, ... 1571 15.80 1572 15-70 15.83
Oxygen, ...... 21.93 21-73 22-13 22:00 21:23
Phosphorus, e e is gº tº & 0.33 O-43 O-33
Sulphur,...... O'62 ()-36 0.36 O-38 0-68
100 100 100 I 00 100
These analyses show,
1°. That the proportion of mitrogen and of all the other ingre-
dients except the sulphur and phosphorus, is very much the same
* See his Chemistry of Vegetable and Animal Physiology, pp. 298 and 302.
PROTEIN COMPOUNDS FOUND IN PLANTS. 217
in all the substances of which the analysis is given in the above
table, and nearly the same also as in protein itself, of which the
composition is given in the preceding page.
2°. That gluten and casein of milk contain no phosphorus while
this substance is present in fibrin and albumen, though in very
Small quantity.
3°. That the quantity of sulphur in glutin and in the albumen
of the blood is sensibly greater than in any of the other substances
analysed. These differences are probably the cause of certain dif-
ferences which have been observed in the chemical properties of
these substances, and they make it necessary to represent them by
different formulae.
If, for the sake of brevity, we represent protein,
e = Cuo Hsi Nº O12 by Pr,
the composition of the several substances above described, in so
far as it is as yet accurately known, is represented by the follow-
ing formulae respectively:-
Casein of milk by . 10 Pr-H S
Glutin of wheat by . 10 Pr -- 2 S
Fibrin of the blood by . 10 Pr -- S + P
Albumen of the egg by 10 Pr-H S + P
Albumen of the blood by 12 Pr-i- 2 S + P
In these formulae S means sulphur, and P phosphorus.
Glutin contains twice as much sulphur as casein, and the albu-
men of the blood twice as much as the albumen of the egg. The
proportions of sulphur and phosphorus in the fibrin of the blood,
and in the albumen of the egg are the same.
The other substances containing nitrogen—protein compounds
—in so far as they have been examined, have a composition ap-
proaching very closely to that of glutin and albumen, but as those
of vegetable origin are very difficult to obtain in a pure state, and
as the true proportions of Sulphur and phosphorus they contain
have not as yet been rigorously determined, we are unable to re-
present them by special formulae.
S 15. General properties and mutual relations of the above protein
compounds. -
For the sake of clearness, and of showing what is really known
218 PROPERTIES AND MUTUAL RELATIONS
of the protein compounds above described—of their composition,
and of their mutual relations and differences—the following brief
outline may be useful :-
So far as they occur in plants they are divisible into four groups.
1°. The albuminous.--These are all coagulated by heat, and by
the stronger or mineral acids, but not by acetic acid.
We are acquainted with three varieties of albumen, all of which
occur in animals and in plants in two states—the soluble and the
coagulated states. In the coagulated state they are insoluble in
water, but readily dissolve in acetic acid, and in solutions of the
carbonates of potash and soda. Representing protein by Pras
before, they consist in each state of
Albumen of the egg, = 10 Pr–H S + P
Albumen of the blood, - 10 Prº-H 2 S + P
Albumen of plants, = Prº-H P
The sulphur and phosphorus in the vegetable albumen have not
been determined. In the soluble state it exists in the juices of
plants, and in all our varieties of corn,-in the coagulated state in
the husk of grain, associated with the fibre of most plants, and pro-
bably with the glutin of wheat.
2°. Fibrinous.-These substances also exist in a soluble and a
coagulated state. Their solutions coagulate spontaneously, as in
the clot of blood, and it is said also in the juice of some plants.
In the coagulated state they melt when heated, dissolve in solu-
tions of acetate of soda or sal-ammoniac, and are thrown down
from these solutions by acetic acid, and by alcohol. It has not
been satisfactorily established, however, that fibrin does exist in
plants. The insoluble part of the glutin of wheat, as I have al-
ready stated, is called by Liebig vegetable fibrin. Its formula is,
Fibrin of the blood, = 10 Pr + S + P
Fibrin of plants, F Pr + 2
3°. Glutinous-These substances are distinguished by being
soluble in alcohol, by which they are extracted from the flour of
different kinds of grain. The formula for glutin is,
Glutin of wheat, = 10 Pr-- 2 S
Gladiadim of maize, = Pr -- ?
4°. Caseous.-Of these the curd of milk is the type, and, like
albumen and fibrin, they are known in a soluble and in an inso-
OF THE PROTEIN COMPOUNDS. 219
luble or coagulated state. Their solutions are not coagulated by
heat, but they are so by weak acids, except the phosphoric, and by
alcohol. In the coagulated state they dissolve in an excess of
oxalic or tartaric acids, in caustic ammonia, and in solutions of the
carbonates of potash and soda. When their solutions are evapo-
rated, a pellicle or brat always forms on the surface, which is
renewed as often as it is removed.
We are acquainted with four varieties of casein, the properties
of which are slightly different, but the chemical composition of only
one of them has as yet been rigorously ascertained.
a. Casein of milk, - 10 Pr–H S
When warm it is curdled or coagulated by alcohol, remmet, or
weak acids. It is soluble in a large excess of alcohol or of acetic
acid.
b. Legumin of the beam, = Pr + P
This substance is not soluble in an excess of alcohol or of acetic
acid.
c. Avenin of oats, = Pr-H S
Of this substance boiling alcohol and hot acetic acid dissolve a
small portion. It is possible, that, as obtained from the oat, it may
be a mixture of two substances of this class.
d. Emulsin of almonds, Pr 2
This substance, according to Dumas, is soluble in excess of ace-
tic acid, and contains 18 per cent. of nitrogen. It is still doubt-
ful whether it is really a compound of protein, or is not rather to
be considered similar to animal cartilage or glue.
§ 16. Of diastase—its properties and relations to vegetable life.
When cold water is poured upon barley newly malted and
crushed, is permitted to remain over it for a quarter of an hour,
is then poured off, filtered, evaporated to a small bulk over boiling
water, again filtered if necessary, and then mixed with much al-
cohol, a white tasteless powder falls—to which the name of diastase
has been given.
1°. If unmalted barley be so treated no diastase is obtained,
This substance, therefore, is formed during the process of malting.
2°. If wheat, or barley, or potatoes, which by steeping in water
yield no diastase, be made to germinate (or sprout), and be after.
220 PRODUCTION OF . DIASTASE,
wards bruised and treated as above, diastase will be obtained. It
is therefore produced during germination.
3°. If the shoot of a potato be cut off within half an inch of its
base, if this lower portion, with the part of the potato to which it is
immediately attached, be separated from therest—and the three parts
(the upper portion of the shoot—the lower portion with its attached
fragment of potato—and the remaining mass of the potato) be then
treated separately with water, only that portion will yield dias-
tase in which the base of the shoot is situated. When a seed
sprouts, therefore, this substance is formed at the base of the germ,
and remains there during its growth.
If the same portion of the potato, or if the grain of barley or
wheat is examined, when the first true leaves of the plant have been ."
fully formed and expanded, the diastase will be found to have in
great part if not entirely disappeared. This substance, therefore,
is first formed when the seed begins to sprout, performs a function
which makes its presence necessary at the base of the germ, and
which function being discharged when the true leaves are formed,
it then disappears. What is the nature of this temporary function,
why the diastase must reside at the base of the sprout in order to
discharge it, and why it should so early cease, will appear from a
detail of the properties of this singular substance.
4°. Properties of diastase.—If the solution obtained from malt
be digested with potato flour, or other starch, at a temperature be-
tween 120° and 140°F., the latter will gradually dissolve and will
form a colourless transparent solution. When this solution is care-
fully evaporated, a yellowish-white powder is obtained, perfectly
soluble in water, to which the name of dectrin" has been given.
This dextrim has the same composition as starch. It is merely
starch changed or transformed in such a way as to become soluble
in cold water, a change analogous to that which it undergoes by
simply boiling in water.
But if the digestion be continued after the starch is dissolved,
the solution will gradually acquire a sweet taste, and if it be now
evaporated it will yield, instead of dextrin, a mixture of gum and
* Because its solution turns to the right a ray of polarized light when passed
through it. l
DIASTASE CHANGES STARCH INTO SUGAR. 221
grape sugar. And if the digestion be still further prolonged, the
whole of the starch will be converted into grape sugar only.
Thus diastase (like sulphuric acid) possesses the property of
transforming starch entirely—first into gum and then into grape
sugar. The intermediate stage of dextrin has not been recog-
mised in the action of sulphuric acid, nor is it easy to arrest the
action of diastase exactly at this point—the most carefully prepared
dextrin always containing a mixture of gum and sugar. One
part of diastase will convert into sugar 2000 parts of starch.
A solution of diastase, when allowed to stand, soon undergoes
decomposition. In this state or after being boiled, it has no fur-
ther effect upon starch. It has not been analysed, because of the
difficulty of obtaining it in a perfectly pure state. It contains mi-
trogen, however, for when moistened and exposed to the air, it de-
composes, and among other products yields ammonia.”
5°. The functions of diastase.—One of the purposes at least for
which it is produced in the living seed, and situated at the base of
the germ—will now be in some measure understood. The starch
in the seed is the food of the future germ, prepared and ready to
minister to its wants whenever heat and moisture concur in awak-
ening it to life. But starch is itself insoluble in water, and could
not, therefore, accompany the fluid sap when it begins to move and
circulate. For this reason diastase is formed at the point where
the germ first issues from the mass of food. There it transforms
the starch, and renders it soluble, so that the young vessels can
take it up and convey it to the point of growth. When the starch
is exhausted its functions cease. It is then itself transformed and
carried into the general circulation. Or when, as in the potato,
much more starch is present than is in many cases requisite, its
function ceases long before the whole of the starch disappears. Its
presence is necessary only until the leaves and roots are fully
formed—when the plant is enabled to provide for itself, and be-
comes independent of the starch of the seed. When this period
arrives, therefore, the production of diastase is no longer perceived.
This I have said is one of the purposes which appears to be
served by diastase in the vegetable economy. That it is the only
* It will be recollected that ammonia contains nitrogen, being represented by
N IIa. —See p. 69.
222 PURPOSES SERVED BY DIASTASE.
one we have no reason to believe. There may be others quite as
interesting which we do not as yet understand. This is rendered
more probable by the fact that the diastase contained in one pound
of malted barley is capable of converting into sugar five pounds”
of starch (Liebig.) And though at the temperature at which the
seed germinates, more of this substance may be necessary to trans-
form the same weight of starch than is required in our hands, when
aided by artificial heat, yet as we never, in the ordinary course
of nature, find any thing superfluous or going to waste, there is
reason to believe that the diastase contributes also directly to the
nourishment and growth of the plant. As it contains nitrogen, it
must be derived from the gluten, the albumen, or the casein con-
tained in the seed. And as a young plant of wheat, when already
many inches above the ground, contains no more nitrogen than was
originally present in the seed itself (Boussingault), this diastase
must be the result of one of those transformations of which glutenf
is susceptible, by which it is rendered soluble, and capable of
aiding in the production of those parts of the substance of the grow-
ing plant into which nitrogen enters as a necessary constituent.
It may not be uninstructive if we pause here for a moment and
consider the beauty of the arrangements we have just been de-
scribing. In passing through a new and interesting country, we
do not hesitate at times, to stop and gaze, and leisurely admire.
We cannot otherwise fully realize and appreciate its beauty. So
* It is the diastase in malt which dissolves the starch of the barley in the process
of brewing, but as the diastase contained in malt is sufficient to dissolve so large a
quantity of starch, it is obviously a waste of labour to malt the whole of the barley
employed. One of malt to three of barley would probably be sufficient in most cases
to obtain a wort containing the whole of the starch in solution. Advantage is taken
of this property in the manufacture of the white beer of Louvain, and of other places
in Flanders, and in Germany, where the light colour is secured by adding a large
quantity of flour to a decoction of a small quantity of barley.
I may here observe that if a solution of diastase be kept for some days in a warm
place, it loses the property of converting starch into sugar, but acquires the power of
gradually changing starch (grape) sugar into lactic acid. If kept still longer the di-
astase acquires the properties of common yeast, and will raise bread, or bring the brew-
er's wort into a regular fermentation. - s
+ That diastase is merely transformed gluten we cannot say, because the exact
chemical constitution of diastase is as yet unknown,
ADAPTATIONS IN THE PRODUCTION OF DIAST ASE. 223
in the domains of science, we cannot be ever hurrying on—we
must linger occasionally, not only that we may more carefully ob-
serve, but that we may meditate and feel.
You see how bountifully mature has provided in the seed for the
mourishment of the young plant, how carefully the food is stored
up for it, and in how imperishable a form—how safely covered also
and protected from causes of decay ! For hundreds of years the
principle of life will lie dormant, and for as many the food will re-
main sound and undiminished till the time of awakening comes.
Though buried deep in the earth, the seed defies the exertions of
cold or rain, for the food it contains is unaffected by cold and ab-
solutely insoluble in water. But no sooner is the sleeping germ
recalled to life, by the access of air and warmth and duly temper-
ed moisture, than a new agent is summoned to its aid, and the
food is so changed as to be rendered capable of ministering to its
early wants. The first movement of the nascent germ—(and how
it moves, by what inherent or imparted force—who shall discover
to us?)—is the signal for the appearance of this agent—diastase
—of which, previous to germination, no trace could be discovered
in the seed. At the root of the germ, where the vessels terminate
in the farinaceous matter, exactly where it is wanted, this sub-
stance is to be found:—there, and there only, resolving and trans-
forming the otherwise unavailable store of food—and preparing it
for being conveyed either to the ascending sprout or to the de-
scending root. And when the necessity for its presence ceases—
when the green leaf becomes developed, and the root has fairly
entered the soil—when the plant is fitted to seek food for itself—
them this diastase disappears—it undergoes itself a new conversion,
and is prepared in another form to contribute to the further in-
crease of the plant.
How beautiful and provident are all these arrangements —how
plastic the various forms of organic matter in the hands of the
All-Intelligent!—how nicely adjusted in time and place its diver-
sified changes What an apparently lavish expenditure of fore-
thought and kind prevision, in behalf even of the meanest plant
that grows'
LECTURE VIII.
Chemical changes by which the substances of which plants chiefly consist are formed
from those on which they live. Changes which take place during germination.
Production of acetic acid, change of the glutin into diastase and of the starch into
sugar. Changes which take place during the growth of the plant. Production of
starch, sugar, cellulose, &c. from the food drawn from the air and from the soil.
Production of oxalic acid in the leaves and stems. Production of the fatty bodies,
of wax and of turpentine. Production of the protein compounds—how and where
they are produced. Changes which take place during the ripening of the seed and
fruit. Gradual increase of the protein compounds in the seed. Production of
the tartaric, citric, and malic acids in the fruit. Changes which take place in au-
tumn after the ripening of the seed or fruit. Changes in annual and in perennial
plants or trees. Rapidity with which these changes take place, and circumstances
by which they are promoted.
|HAVING thus considered the nature and chemical composition of
those substances which constitute the largest part of the Solids and
fluids of living vegetables, we are now prepared for the further
question—by what chemical changes these substances of which plants
consist, are formed out of those on which they live 2
The growth of the plant from the germination of the seed in
spring till the fall of the leaf in autumn, or the return of the suc-
ceeding spring time, may in perennial plants be divided into four
periods—during each of which they either live on different kinds
of food, or expend their main strength in the production of dif-
ferent substances. These periods may be distinguished as fol-
lows:—
19. The period of germination—from the sprouting of the seed
to the formation of the perfect leaf and root.
29. From the expansion of the first true leaves to the period of
flowering.
32. From the opening of the flower to the ripening of the fruit
and seed.
cíRCUMISTANCES FAWOURABLE TO GERMINATION. 225
4°. From the ripening of the seed or fruit till the fall of the
leaf and the subsequent return of spring. On the ripening of the
fruit the functions of annual plants are in general discharged, and
they die; but perennial plants have still important duties to per-
form in order to prepare them for the growth of the following
spring.
The explanation of the chemical changes to which our attention
is to be directed will be more clear, and perhaps more simple, if
we consider them in relation to these several periods of growth.
§ 1. Chemical changes which are observed during germination and
during the development of the first leaves and roots.
The general nature of the chemical changes which take place
during germination is simple and easy to be comprehended,
Let us first consider shortly the phenomena which have been
observed to accompany germination, and the circumstances which
are most favourable to its rapid and healthy progress.
1°. Before a seed will begin to sprout, it must be placed for a
time in a sufficiently moist situation. We have already seen how
numerous and important are the functions which water performs
in reference to vegetable life (p. 51,) in every stage of a plant's
growth. In the seed no circulation can take place—no motion
among the particles of matter—until water has been largely im-
bibed; nor can the food be conveyed through the growing vessels
unless a constant supply of fluid be afforded to the seed and to its
infant roots.
2°. A certain degree of warmth–a slight elevation of tempera-
ture—is also favourable, and in most cases necessary to germina-
tion.
The degree of warmth which is required in order that seeds may
begin to grow, varies with the mature of the seed itself. In North-
ern Siberia and other icy countries, plants are observed to spring
up at a temperature but slightly raised above the freezing point
(32°F.), but it is familiar to every practical agriculturist, that the
seeds he yearly consigns to the soil require to be protected from
the inclemency of the weather, and sprout most quickly when they
are stimulated by the warmth of approaching spring, or by the heat
of a summer's Sun.
The same fact is familiarly shown in the malting of barley,
P
226 EFFECT OF AIR AND LIGHT ON GERMINATION.
where large heaps of grain are moistened in a warm atmosphere.
When germination commences, the grain heats spontaneously, and
the growth increases in rapidity as the heap of corn attains a higher
temperature. It thus appears that some portion of that heat which
the growth of the germ and radicles requires, is provided by na-
tural processes in the grain itself; in some such way as in the bo-
dies of animals, a constant supply of heat is kept up by the vital
processes,—by which supply the cooling effect of the surrounding
air is continually counteracted.
We have seen in a preceding lecture (p. 187), that the transfor-
mations of which starch and gum are susceptible, take place with
greater certainty and rapidity under the influence of an elevated
temperature. It will presently appear that such transformations
are also effected during germination;–there is reason, therefore,
to believe that the external warmth which is required in order that
germination, may begin, as well as the internal heat naturally de-
veloped as germination advances, are both employed in effecting
these transformations. And as the young sprout shoots more ra-
pidly under the influence of a tropical sun, it is probable that those
natural agencies, by which such chemical transformations are most
rapidly promoted, are generally those also by which the progress
of vegetation is in the greatest degree hastened and promoted.
3". It has been observed that seeds refuse to germinate if they
are entirely excluded from the air. Hence seeds which are buried
beneath such a depth of soil that the atmospheric air cannot reach
them will remain long unchanged, evincing no signs of life—and
yet, when turned up or brought near the surface, will speedily
begin to sprout. Thus in trenching the land, or in digging deep
ditches and drains, the farmer is often surprised to find the earth,
thrown up from a depth of many feet, become covered with young
plants, with kinds of weeds long extirpated from, or but rarely
seen in, his cultivated fields. -
4". Yet light is, generally speaking, prejudicial to germination.
The roots of most plants naturally avoid and grow away from the
light (Payen, Durand).
Hence the necessity of covering the seed, when sown in our gar-
dens and corn fields, and yet of not so far burying it that the air
shall be excluded. In the usual method of sowing broad-cast,
much of the grain even after harrowing, remains uncovered; and
SEEDS SPROUT ONLY IN THE PRESENCE OF OXYGEN. 227
the prejudicial influence of light in preventing the healthful ger-
mination of such seeds is probably one reason why, by the method
of dibbling, fewer seeds are observed to fail, and an equal return
of corn is obtained from a much smaller expenditure of seed.
The reason why light is prejudicial to germination, as well as
why the presence of atmospheric air is necessary, will appear from
the following observation:—
5%. When seeds are made to germinate in a limited portion of
atmospheric air, the bulk of the air undergoes no material altera-
tion, but, on examination, its oxygen is found to have diminished,
and carbonic acid to have taken its place. Therefore, during ger-
mination, seeds absorb oxygen gas and give off carbonic acid.
Hence it is easy to understand why the presence of air is neces-
sary to germination, and why seeds refuse to sprout in hydrogen,
nitrogen, or carbonic acid gases. They cannot sprout unless ory-
gen be within their reach. *
We have seen also in a previous lecture that the leaves of plants
in the Sunshine give off oxygen gas and absorb carbonic acid,—
while in the dark the reverse takes place. So it is with seeds
which have begun to germinate. When exposed to light they
give off oxygen instead of carbonic acid, and thus the natural pro-
cess is reversed. But it is necessary to the growth of the young
germ, that oxygen should be absorbed and carbonic acid given off
—and as this can take place to the required extent only in the
dark, the cause of the prejudicial action of light is sufficiently ap-
parent, as well as the propriety of covering the seed with a thin
layer of soil. s
6". During germination, vinegar (acetic acid) and diastase are
produced. That such is the case in regard to the latter substance,
has been explained in a previous lecture (p. 219). That acetic
acid is formed is shown by causing seeds to germinate in powder-
ed chalk or carbonate of lime, when after a time acetate of lime”
may be washed out from the chalk (Braconnot) in which they have
been made to grow. The acid contained in this acetate must have
been formed in the seed, and afterwards excreted or thrown out
into the soil.
7°. When the germ has shot out from the seed and attained to a
* Acetate of lime is a compound of acetic acid (vinegar) and lime, and may be pre-
pared by dissolving chalk in vinegar. It is very soluble in water.
228 CHEMICAL CHANGES DURING GERMINATION.
sensible length, it is found to be possessed of a sweet taste. This
taste is owing to the presence of grape sugar in the sap which has
already begun to circulate through its vessels. -
It has not been clearly ascertained whether the vinegar or the
diastase is first produced when germination commences, but there
seems little doubt that the grape sugar is formed subsequently to
the appearance of both.
8°. The young shoot which rises upwards from the seed consists
of a mass of vessels, which gradually increase in length, and after
a short time expand into the first true leaves. The vessels of this
first shoot—of the young sprout, and of the early radicles also—con-
sist of cellular fibre or cellulose. No true woody matter is formed
—no solid layers of such matter, that is, are deposited upon the
cellular fibre—until the first true leaves are developed.
§ 2. Evplanation of the above chemical changes which take place
during germination.
Having thus glanced at the phenomena which attend upon ger-
mination, let us now consider the chemical changes in consequence
of which these phenomena are produced.
1°. The seed absorbs oxygen and gives off carbonic acid.—We
have already seen that the starch of the seed (C12 H10 Old) may
be represented by carbon and water, by 12 C + 10 HO. Now
it appears that in the presence of the oxygen of the atmosphere, a
portion of the starch is actually decomposed or separated during
germination into carbon and water—the carbon at the moment of
separation uniting with the oxygen, and forming carbonic acid
CO2. This acid is given off into the soil in the form of gas, and
thence partially escapes into the air; but for what immediate pur-
pose it is evolved, or how its formation is connected with the
further development of the germ, has not hitherto been satisfac-
torily explaimed. It is probably one source of the heat which be-
comes manifest during germination, and may possibly be connect-
ed also with the production of diastase. -
2°. Diastase is formed.—When the seed begins to sprout dias-
tase is formed, at the expense or from the elements of the gluten
or albumen of the seed. As the exact composition of diastase is
not known, we cannot explain the precise chemical changes by
which its production is effected. We know only that it contains
H OW AND WHY WINEGAR IS FORMED. 229
nitrogen, that it possesses the property of changing the insoluble
starch of the grain into soluble dextrin and sugar—that it first
performs this function in the seed, and ascends afterwards in the
sap to aid in the production of the gluten and albumen of the
growing plant. ^.
3°. The formation of acetic acid (vinegar) from the starch of the
grain is easy to comprehend. For as we have already seen
1 of starch or of dextrin is ....... ... = C12 H10 O10 and
3 of vinegar are ......... , gº dº º e º º ſº gº tº e º C = C12 Ho Oo
So that the difference is only - Hi O1 or the
elements of an atom of water. Therefore, in this early stage of
the growth of the germ a portion of the starch is deprived of the
elements of an atom of water, and is thus transformed into vinegar.
How it is produced—by what agent this change of starch into
vinegar is effected—is not clear. It may be produced along with
the diastase or by its agency, or it may be formed along with the
cellular fibre of the radicle, as I shall presently explain.
Why is this vinegar formed P. It is almost as difficult to answer
this question satisfactorily as to say with certainty why carbonic
acid is given off by the sprouting seed, though both undoubt-
edly serve wise and useful ends.
a. It has been explained in the preceding lecture how the action
of dilute acids gradually changes starch into dextrin, then into
cane Sugar, and lastly into grape sugar. While it remains in the
sap of the sprouting seed, therefore, the vinegar may aid the dias-
tase in transforming the insoluble starch into soluble food for the
plant, and may be an instrument in securing the subsequent con-
version of cane sugar, which is the first formed, into grape sugar, -
since cane sugar cannot long exist in the presence of an acid (p. 193.)
b. After the acetic acid is rejected by the plant it may serve to
dissolve the lime and other earthy matters contained in the soil.
Liebig supposes the especial function of this acid—the reason why
it is formed in the germ and afterwards given out by the young
roots into the soil—to be, to dissolve the lime, &c., which the soil
contains, and to return again into the pores of the roots, bearing
in solution the earthy substances which the plant requires for its
healthy growth. This is by no means an unlikely function. It is
only conjectural, however, and since the experiments of Braconnot
230 HOW CELLULOSE IS FORMED.
have shewn that acetate of lime, even in small quantity, may be
injurious to vegetation, it becomes more doubtful how far the for-
mation of this compound in the soil and the subsequent conveyance
of it into the circulation of the plant, can be regarded as the spe-
cial purpose for which acetic acid is so generally produced during
germination. .
4°. Cellulose is formed.—The fibre of the rootlet and of the young
sprout consists of cellulose. This is readily formed from the ele-
ments of the starch of the seed, by the mere addition of the ele-
ments of one equivalent of water. Thus
C. H. O.
2 of starch or dextrin ......... = 24 2O 20
and 1 of water.................. - I l
Make 1 of cellulose............... 24 2I 21
The seed therefore first absorbs water, the diastase then changes
the starch into dextrin, and this combining with water forms the
cellulose.
Or in the rootlet the production of cellulose may be connected
with that of acetic acid, without the agency of the elements of
water. Thus
C. H.
1 of cellulose..................... – 24 21 21
and 3 of vinegar ............... = 12 9 9
Make 3 of dextrin ............... 36 30 30
So that the production of cellulose from dextrin only is at one
time associated with that of acetic acid, without the chemical
agency of water, while at another it may be produced alone by a
combination of the dextrin with water or its elements. Circum-
stances,—the presence, perhaps, of different substances in the sap,
—determine which of the two kinds of change shall take place,
5°. Grape sugar appears.-The early sap of the young shoot is
sweet; it contains grape sugar. This sugar is also derived from
the starch of the seed. Being changed into dextrin by the dias-
tase formed at the base of the germ, it is afterwards gradually con-
verted into grape sugar as it ascends. The relation between these
two compounds has been already pointed out. Thus
How THE SUGAR IS FORMED IN THE SPROUT. 231
Starch or dextrin = C12 H10 Olo
Grape sugar ...... = C12 H11 O11
So that the difference is = H, O, ; or the ele-
ments of one atom of water. The water which is imbibed by the
seed from the soil, forms an abundant source from which the whole
of the starch, rendered soluble by the diastase, can be supplied
with the elements of the atom of water which is necessary to its
subsequent conversion into grape sugar.
6°. Woody matter is deposited.—When the true leaf becomes
expanded true woody matter first appears in sensible quantity. The
reason of this we can in some measure explain.
Before the leaves or young shoot become green they give off no
oxygen (Ingenhouss, de Saussure). When they acquire a green
colour through the action of light they begin immediately to perform
this function. At this moment woody matter begins to be formed.
True woody matter always contains an excess of hydrogen.
Starch or dextrin must, therefore, be deprived of a portion of its
oxygen before this woody matter can be formed. Thus the hard
wood of stone fruits may be represented by C64 Had Oso (von
Baumhauer). Suppose 3 of this wood to be formed from the dex-
trim of the sap and we have
te H. O.
3 of hard woody matter = 192 132 117
16 of dextrin 192 160 160
-
Difference - 28 43
Deduct 28 of water - - 28 28
And there remain - 15
Or 15 of oxygen must be given off in order that 3 of woody mat-
ter may be produced—which oxygen is given off through the ac-
tion of light upon the green leaf.
Other kinds of woody matter have a different composition from
that taken above for the sake of illustration—but all contain hy-
drogen in excess, and it is very interesting to connect in this way
the moment of their appearance with the commencement of a new
function in the growing plant.
7°. In the oily seeds and in the turnip and carrot no starch oc-
curs, and, therefore, the explanations above given in reference to
232 - DEXTRIN FORMED FROM MUOILAGE.
the chemical changes produced during germination do not apply
to them. Still in these the changes are equally simple.
a. In the oily seeds, lintseed, quince seed, &c., mucilage takes
the place of starch. This substance swells in water, and finally so
diffuses itself that it can be taken up by the sap of the plant. Now
when ascending with the sap it is readily changed when necessary
into cellulose or dextrin. Thus if to
+ C. H. O.
1 of mucilage, ............... 24 19 19
I of water be added ......... I l
We have 2 of dextrin,
starch, or gum,
The addition of two of water gives C24 Hot O21–the formula for
cellulose. . -
à. The turnip again contains pectic acid C14 H10 O14. Suppose
dextrin to be formed from this, and we may have the following
change :
}=24 20 20.
C. H. O,
From 1 of pectic acid = 14 10 14
Take one of dextrin = 12 10 10
And there remain 2 2
Two of carbon and two of oxygen remain. The oxygen may
be given off by the leaves, and the carbon may combine with water
to form dextrin—or the oxygen may be worked up before the
green leaves appear, in various other ways which we cannot as yet
with any degree of certainty indicate. -
§ 3. Of the chemical changes which take place between the forma-
tion of the green leaf and the eaſpansion of the flower.
When the green leaf is formed the plant or shoot has entered
upon a new stage of its existence. Up to this time it is nourished
almost solely by the food contained in the seed,—it henceforth de-
rives its sustenance from the air and from the soil. The apparent
mode of growth, however, is the same. The stem shoots upwards,
and the roots descend as before, and these parts consist essentially
of the same chemical substances, but they are no longer formed
at the expense of the starch of the seed only, and the chemical
How ARE PLANT's Nourish ED BY CARBONIC ACID 2 233
changes of which they are the result are entirely different. Let
us consider these changes.
A. Changes produced upon the organic food—the carbonic acid—
absorbed from the air or from the soil.
The green leaf absorbs carbonic acid in the sunshine, and gives
off oxygen in nearly equal bulk.” The light of the sun is essential
to the healthy increase of living plants. Their growth, therefore,
is intimately connected with this absorption of carbonic acid.
If carbonic acid be absorbed by the leaf and the whole of its
oxygen given off again,f carbon alone is added to the plant by this
function of the leaf. But it is added in the presence of the water
of the sap, and thus is enabled by uniting with it to form, as it may
be directed, or as may be necessary, any one of those numerous
compounds which may be represented by carbon and water (p. 185),
and of which, as we have seen, the solid parts of plants are in so
large a proportion made up.
There are several ways in which we may suppose the oxygen
given off by the leaf to be set free, and the starch, sugar, and gum,
to be subsequently formed. Thus,
1°. The action of light on the leaf of the plant may directly de-
compose the carbonic acid after it has been absorbed, and cause the
oxygen to separate from the carbon, and escape into the air;--
while at the same instant the carbon thus set free, may unite with
the water of the sap in different proportions, so as to produce either
sugar, gum, or dextrin. Suppose 12 atoms of carbonic acid
(12 CO2) to be thus decomposed, and their carbon to unite with
10 of water (10 HO) we should have
C. H. O.
12 of carbonic acid ............... 12 24
10 of water ............ q e s e º 'º e a s 9 10 10
Sum .............. © e º e º e s e • e e s e e s e e s e 12 10 34
Deduct l of gum or of cane sugar 12 10 10
And there remain & º e s p & G e s is e º e tº tº - - - 24
* Such is sensibly the result of experiment (p. 143). It cannot, however, be con-
sidered as universally true. This point will be examined hereafter (pp. 236 and 240.)
+ It will be recollected that carbonic acid contains its own bulk of oxygen gas: if,
therefore, the leaf give off the same bulk of oxygen as it absorbs of carbonic acid, the
result must be as stated in the text.
234. Is THE CARBONIC ACID DECOMPOSED F
or while 1 of gum would be produced, 24 of oxygen would be
given off by the leaf-the whole of which would have been derived
from the carbonic acid absorbed by the plant.
29. Or the action of the sun's rays may be directed, in the leaf,
to the decomposition, not of carbonic acid alone, but of the water of
the sap also. The oxygen of the water may be separated from the
hydrogen, while at the same instant the latter element (hydrogen)
may unite with the carbonic acid to produce the sugar or starch.
The result here is the same as before, but the mode in which it is
brought about is very differently represented, and appears much
more complicated. Thus, suppose 24 of water to be decomposed,
and to give off their oxygen into the air, 24 of oxygen would be
evolved as in the former case, the whole of which would be derived
from the decomposition of water, and the subsequent changes would
be as follows:
C. H. O.
24 of hydrogen - 24 act On-
12 of carbonic acid = 12 24
Sum, gº tº e 12 24 24 forming
1 of dextrin 12 10 10 and leaving
14 of water 14 14
According to this mode of representing the chemical changes,
water is first decomposed and its oxygen evolved, then its hydro-
gen again combines with the oxygen of the carbonic acid, forming
water. A portion of this water unites at the moment of its forma-
tion with the carbon of the carbonic acid, forming dextrim, &c.,
while the other part of the water remains uncombined in the sap.
This view is not only more complicated, but it supposes the
same action of light to be—continually, at the same time, and in
the same circumstances—both decomposing water and re-forming
it from its elements. While, therefore, there can be no doubt, for
other reasons not necessary to be stated in this place, that the
light of the sun really does decompose water in the leaves of plants,
and more in some than in others—yet it appears probable that the
oxygen evolved by the leaf is derived in a great measure from the
carbonic acid which is absorbed ; and that the principal part of the
solid substances of living vegetables, in so far at least as it is de-
Is CARBONIC OXIDE ASSIMILATED P 235
rived from the air, is produced by the union of the carbon of this
acid with the elements of the water in the sap.
3". Or thirdly, instead of being separated from the whole of its
own oxygen, the carbonic acid may part with half of it only and be
converted into carbonic oxide, (CO) and this carbonic oxide may
combine directly with the hydrogen of decomposed water to form
dextrin, &c. Thus if from
y
C. O.
12 of carbonic acid == 12 24
12 of oxygen are given off - 12
There remain 12 of carbonic oxide – 12 12
If 12 of water are at the same time decomposed, and 12 of oxy-
gen given off, there remain 12 of hydrogen, which at the moment
of liberation unite with this carbonic oxide, and form grape sugar.
Thus
C. H. O.
To the 12 of carbonic oxide ~ 12 12
add 12 of hydrogen from the water = 12
and we have grape sugar F 12 12 J 2
In this way 24 of oxygen are given off as before, and if we sup-
pose 2 of water to be produced also, we shall have dextrin instead
of grape Sugar.
Of the 24 of oxygen thus given off, Persoz, whose view this is,
thinks that only one-half is evolved by the leaf-and the principal
fact on which his opinion rests is one observed by De Saussure,
that plants of Vinca minor gave off by their leaves, in his experi-
ments, only two-thirds of the oxygen contained in the carbonic acid
they absorbed. This result has led Berzelius also to conjecture
that the leaves of plants do not retain merely the carbon of the car-
bonic acid, but some compound of carbon with oxygen, containing
much less of the latter element than the carbonic acid itself does.
(Traité de Chemie, V. p. 69). The principal objection to this
view, however, is the quantity of oxygen it supposes to be rejected
in one form or other by the root. The experiments on which it is
founded, therefore, require confirmation and extension.
2°. We have seen reason to conclude (p. 100) that, while plants
236 Is CARBONIC ACID ABSORBED FROM THE soft,
derive much of their organic sustenance from the air, they are also
fed more or less abundantly by the soil in which they grow. From
this soil they may obtain, besides other substances taken in by their
roots, the carbonic acid which is understood to be continually given
off by the decaying vegetable matter it contains. This carbonic
acid will ascend to the leaf, and there, under the influence of the
sun, will undergo decomposition along with that which is absorbed
by the leaf itself. At least we know of no function of the root or
stem by which the carbonic acid derived from the soil can be de-
composed and deprived of its oxygen before it reaches the leaf.
It is distinctly stated, indeed, by Sprengel,” that when the roots
of a plant are in the presence of carbonic acid, the oxygen given
off by the leaf is greater in bulk than the carbonic acid which it
absorbs. But there is one observation in connection with this
point which it seems to me of importance to make. The leaves
supply carbon to the plant only in the form of carbonic acid, and
they give off a bulk of oxygen gas generally not exceeding that
of the acid taken in. But if the carbon derived from the soil be
also absorbed in the form of carbonic acid, and if the oxygen con-
tained in this portion of acid is also given off by the leaf-either
the quantity drawn from the soil must be small, compared with
that inhaled from the air, or the oxygen given off by the leaf must,
in the ordinary course of vegetation, be sensibly greater than the
bulk of the carbonic acid which it absorbs.
We are too little familiar with the chemical functions of the se-
veral parts of plants to be able to pronounce a decided opinion on
this point; but it appears evident that one or other of the three
following conditions must obtain :- •.
(a.) Either in the general vegetation of the globe the bulk of
the oxygen gas given off by the leaf during the day must always
be considerably greater than that of the carbonic acid absorbed by
it ; or
(b.) The root or stem must have the power of decomposing car.
bonic acid and of separating and setting free its oxygen; or
(c.) The plant can derive no considerable portion of its carbon
from the soil, in the form of carbonic acid.
If the experiments hitherto made by vegetable physiologists be
* See above, p, 144,
pkxTRIN PRODUCED FROM HUMIC ACID. 237
considered of so decisive a character as to warrant us in rejecting
the two former conditions, the third becomes also untenable.
B. Changes produced upon the organic food taken in from the soil.
Without dwelling at present on this point, the above conside-
rations may be regarded as giving additional strength or proba-
bility to the conclusions we formerly arrived at (p. 100) from other
premises—that the roots, besides carbonic acid, absorb certain
other soluble organic compounds, the humic, ulmic, and geic
acids, which are always present in the soil in greater or less quan-
tity, and that the plant appropriates and converts these into its
own substance. These organic compounds may readily, and by
apparently simple changes, be transformed into the starch and cel-
lular fibre of the living vegetable. Thus
1°. Suppose humic acid e (Cao H17 Oz, see p. 59,) to be taken
up by the roots and to combine with water, and we may have
C. H. O.
3 of Humic acid e - 120 5 1 51
With 49 of water - 49 49
Making 10 of dextrin = 120 100 100 ---
Or with 54 of water – 54 54
Making 5 of cellulose = 120 105 || 05
So that the production of the substance of plants from the food
they are capable of deriving from the soil is much simpler in ap-
pearance than from the carbonic acid they derive from the air.
2°. Again, suppose a portion of one of the ulmic acids to be
(p. 69) taken up, then because of the excess of hydrogen contain-
ed in these acids true wood may be formed without the decompo-
sition of water. Thus, if there be taken up
C. H. O.
1 of ulmic acid, b ~ 40 18 16
# of humic acid, c = 24 9 9
And 20 of water ~ 20 20
We have the sum 64 47 45
238 PRODUCTION ON OXALIC ACID IN PLANTS.
which is the composition of the soft wood of the laburnum and the
elm = C64 Haz O3. -
This also is much simpler than the formation of wood appears to
be, if we suppose it to be produced from carbonic acid andwater alone.
3°. In like manner the geic acids will readily serve for the pro-
duction of the same compounds, with a slight alteration in the pro-
cess. Thus, if crenic acid, C24 H12 Olg, be taken up by the roots
we may have cellulose produced while water is also combined and
oxygen given off, as follows—
C. H. O.
To l of crenic acid - 24 12 16
Add 9 of water - 9 9
Sum 24 21 25
And deduct 4 of oxygen = 4
And 1 of cellulose remains = 24 21 21
This is also very simple and intelligible. The water required
is found in the vessels of the plant, while the oxygen, if not em-
ployed for some other purpose, may escape by its leaves.
It is asserted by some that the plant takes up by its roots no ap-
preciable quantity of the acid substances above spoken of, and which
we know occur abundantly in the soil. They are useful, it is said,
only in supplying carbonic acid to be taken up by the roots. I do
not partake in this opinion, for reasons I have elsewhere stated.
It may to some minds appear more likely that they should be so
absorbed by plants—since the chemical changes by which they may
be supposed to be converted into the substances of which plants
chiefly consist are so very simple and easily to be understood.
§ 4. On the production of Oaxalic acid in the leaves, stems, and sap
- of plants. -
In the preceding section we have studied the origin of those
substances only which form the chief bulk of the products of ve-
getation. But during the stage of vegetable growth we are now
considering, other compounds totally different in their nature are
also produced, and in some plants in sufficient quantity to be deserv-
ing of a separate consideration. Such is the case with oxalic acid.
3 o
oxygEN FROM THE LEAVES WARLABLE IN QUANTITY. 239
The circumstances under wheh this acid occurs in nature have
already been detailed. It is found in small quantities in many
plants. The potash in forest trees is supposed to be in combina-
tion with oxalic acid, while in the lichens owalate of lime, as I have
already stated (p. 63), exists often in great abundance, though the
function it performs in these humble plants is not understood.
Oxalate of lime exists also in the form of crystals in the leaves of
the orange tree, of the apple tree, of the cactus, and of a great
many others. In the leaves of the cactus it sometimes forms as
much as 70 per cent. of the whole weight of the dried leaves.*
The production of this acid in the living plantis readily under-
stood when its chemical composition (C, Os) is compared with
that of carbonic acid (CO2). For
2 of carbonic acid = C, Oa, while
1 of oxalic acid = C2 Os
The difference being = Ot
That is to say, 2 of carbonic acid may be transformed into 1 of
oxalic acid by the loss of 1 equivalent of oxygen—or generally car-
bonic acid by the loss of one fourth of its owygen may be converted
2nto oxalic acid.
But the leaf absorbs carbonic acid and gives off oxygen. In
the lichens, therefore, and in those leaves in which the oxalates of
potash or of lime are present, a portion of the carbonic acid ab-
sorbed is, by the action of light, deprived only of one-fourth of its
oxygen, and is thus changed into oxalic acid. This is true not
only of those leaves and stems which, like those of sorrel and of
rhubarb, owe their sourness to the presence of oxalic acid, but also
of the beech and other large trees, in which much potash, and pro-
bably, also, of marine plants in which much soda is found to exist.
It must be owing to the peculiar structure of the leaves of each
genus or natural order of plants that the same action of the same
light decomposes the carbonic acid in different degrees—evolving
in some a less proportion of its oxygen, and causing in such plants
the formation of a larger quantity of oxalic acid.
The fact of the production of this Oxalic acid, to a very consider-
* Payen, Memoires sur le developpements des vegetawa, pp. 303 and 318.
240 oxygłęN FROM THE LEAVES WARIABLE IN QUANTITY,
able amount in many plants, is a further proof of the uncertainty
of those experiments from which physiologists have concluded that
the leaves of plants emit a bulk of oxygen sensibly equal to that
of the carbonic acid absorbed” (p. 143).
I have referred the production of more or less oxalic acid in
different plants to the special structure of each, and this must be
true where, in the same circumstances, different results of this kind
are observed to take place—as where sour sorrels and sweet clovers
grow side by side. Yet the influence of light of different degrees of
intensity on the same plant, may cause the same leaf to produce at
one time sour and at another tasteless substances. This is beauti-
fully shown by the leaves of the Sempervivum arboreum, of the Por-
tulacaria afra, and other plants which are sour in the morning, taste-
less in the middle of the day, and bitter in the evening.f During
the night the oxygen has accumulated in these plants and formed
acids, such as the malic and citric (p, 251), which contain oxy-
gen in excess. As the day advances this oxygen is given off;-
under the influence of light the acids are decomposed, and the
sourness disappears. A difference in the nature of the substances
produced by a leaf, therefore, is not always evidence of a difference
in its structure.
* Were we permitted, in the absence of decisive experiments, to state as true what
theoretical considerations plainly indicate, we should say—
1°. That plants containing much oxalic, tartaric, and other similar acids, and not
deriving much carbonic acid from the soil, must give off from their leaves a bulk of
oxygen less than that of the carbonic acid absorbed.
2°. That plants containing no sensible quantity of such acids, nor fed by carbonic
acid from the soil, may evolve oxygen sensibly equal in bulk to the carbonic acid ab-
sorbed.
3°. That if little of these acids be present, and much carbonic acid or geic acid be
absorbed from the soil, the volume of oxygen given off by the green parts of the plant,
must be sensibly greater than that of the carbonic acid they absorb.
49. That the leaves of plants containing much fat and of the pines and other trees
containing much turpentine,—in which hydrogen is in excess—must at all times give
off oxygen in greater bulk than the carbonic acid they absorb. They must decom-
pose water as well as carbonic acid and evolve the oxygen of both. The same is true,
however, though to a less extent, of all trees; since true woody matter of all kinds
contains always an excess of hydrogen.
The influence of a large supply of ammonia in diminishing the proportion of oxygen
evolved by the leaf is illustrated in a subsequent lecture.
t Sprengel, Chemic, II., p. 321. l
VEGETABLE OILS, FATS, WAX, AND TURPENTINE. 24l
In the juices of plants before the period of flowering, other acids
also are met with besides the oxalic acid, though in much smaller
quantity. As the most important of these, however, occur more
abundantly in fruits, we shall consider the theory of their forma-
tion in a subsequent section.
§ 5. Of the production of vegetable oils, fats, war, and turpentine.
The fatty bodies of all kinds are distinguished by the small
quantity of oxygen they contain in proportion to their hydrogen.
It is impossible therefore to explain their production from the or-
dinary food of plants, without having recourse to the functions
performed by the leaf of throwing off oxygen into the atmosphere.
Thus,
1". To form elaic acid, the fluid acid of fatty oils from grape
sugar, supposed to be present in the sap, we may have
C. H. O.
3 of grape sugar - 36 36 36
1 of elaic acid - 36 34 4
Leaving, tº tº gº tº 2 32
—or 2 of water and 30 of oxygen are separated from grape sugar
during its conversion into the fat. The oxygen must escape by
the leaf.
Or if we suppose the fat to be formed directly from the food
taken in by the leaf-from the carbonic acid—the disengagement
of oxygen must be very much greater. Thus
C. H. O.
36 of carbonic acid - 36 72
and 34 of water - 34 34
Make & 36 34 106
Deduct i of elaic acid = 36 34 4
And there remain, g 102
—or three times as much oxygen as before to be given off by the
leaf.
2°. To form war, precisely a similar evolution of oxygen must
Q
24.2 PRODUCTION OF WAX.
take place. Thus the soluble part of bees' wax cerine, might be
formed from carbonic acid and water as follows:–
C. H. O.
20 of carbonic acid - 2() 40
20 of water - 20 20
20 20 60
Deduct 1 of cerine — 2() 2() 2
And there remain 58
of oxygen to be given of by the leaves.
It is probable that wax is actually produced in this way from
the carbonic acid absorbed from the air, since it is chiefly on the
surface of the leaves and stems of plants, on the petals of flowers,
and on the skins of fruits, that wax is met with in the vegetable
kingdom,--that is to say, it is produced on those parts of the plant
from which oxygen gas is most abundantly given off.
3°. The turpentines and resins are obviously produced in the
same way as wax and the fats. We do not, however, know
whether the abundant turpentine of the pine tribes, which, when
pure, contain no oxygen at all, is produced solely by the action of
the sunshine upon the leaves, or whether some power may not also
be possessed by the interior parts of the tree, by which the disen-
gagement of oxygen from the food may be promoted. It is obvi-
ous that in the cold climates which the pine tribes chiefly frequent,
the effect of the sunshine cannot by any means be so great as in
more southern regions. The peculiar structure, therefore, either
of the leaf or wood of the pine, may have some connection with
the large quantities of resinous matter and of turpentine it is known
to produce.
§ 6. Of the production of protein and its compounds.
In the preceding lecture I have described the several protein
compounds which occur in plants, and have explained their impor-
tance, in reference not merely to the immediate growth of the
plants themselves, but also to the after purposes they are intended
to serve in the feeding of animals,
PRODUCTION OF PROTEIN. 243
There are three questions in reference to these compounds which
it will be interesting to answer, namely,
1°. How are they formed from the food on which the plant
lives P
2". Where—in what part of the plant—are they principally
produced P
3". What is their special function in the plant?
I shall consider these three questions in succession.
1". How are they formed in the plant 2–Protein itself, as we
have seen, contains nitrogen, an element not present in any of the
substances the production of which has just been considered. Its
compounds, such as glutin, albumen, and casein, contain besides
Small proportions of sulphur, or phosphorus, or both.
a. Protein.—I have already stated that there are two main forms
in which, according to our present knowledge, nitrogen enters
into the plant, the forms, namely, of ammonia and of nitric acid.
From either of these, in connection with the other food taken in
by the roots and by the leaves, or with the substances, such as
dextrin, supposed to be already present in the sap, protein may
be produced. Thus if we add
C. H. N. O.
1 of humic acid, d, from the soil = 40 16 16
and 5 of ammonia (NHA) — 15 5
We have g 40 3.1 5 16
Deduct 1 of protein — 40 31 5 12
And there remain only e 4
of oxygen to be given off by the leaves, or to be used up in the in-
terior of the plant for some other purpose.
Or from the ammonia and dextrin already existing in the plant
it may be produced, thus,
C. H. N. O.
3% of dextrin = 40 33 33
5 of ammonia :- 15 5
40 48 5 33
Deduct one of protein 40 3.1 5 12
and we have remaining 17 2I
244 PRODUCTION OF PROTEIN.
which are equal to 17 of water, which will remain in the plant, and
to 4 of oxygen, which, as before, will be given off. -
But if it be formed from nitric acid a much larger proportion of
oxygen will be set free. Thus,
C. H. N. O.
3% of dextrin –– 40 33 33
5 of nitric acid ~ 5 25
40 33 5 58
Deduct 1 of protein – 40 31 5 12
and there remain 2 46
or 2 of water and 44 of oxygen to be liberated.
It is obvious that, if we suppose it to be formed directly from
ammonia, water, and the carbonic acid taken in by the leaves, the
quantity of oxygen given off will be still greater. Thus
C. H. N. O.
40 of carbonic acid = 40 80
31 of water ~ 31 31
5 of ammonia - 15 5
40 46 5 l l 1
Deduct 1 of protein – 40 31 5
and there remain 15 99
or 15 of water and 84 of oxygen require to be separated.
It is by no means unlikely, however, that in the green leaves
protein may occasionally be formed in this way, since from the leaf
oxygen is given off, and in it protein is usually present in very
considerable abundance.
b. The protein compounds.-Protein exists in plants, as I have
stated in the preceding lecture, only in a state of combination. It
is always found combined with sulphur, as in casein or glutin, or
with sulphur and phosphorus, as in albumen and fibrin. These
two elementary bodies are extracted by the roots from the soil.
They exist in the soil only in the state of sulphuric and phospho-
ric acids, which are compounds of Sulphur and phosphorus re-
spectively, with oxygen. This oxygen must of course be given off
or in some way separated from the sulphur and phosphorus, at
the moment of their combination with protein or its elements. Of
WHERE THE PROTEIN AND ITS COMPOUNDS ARE FORMED. 245
the precise way in which this is effected I could only offer you con-
jectures, and, therefore, I do not dwell upon it.
2°. Where—in what part of the plant is protein formed 2—The
experimental researches of Payen appear to throw considerable
light on this subject. It may be formed, as we have seen, from
the food taken in from the soil, from the substances existing in the
sap, or from those it is the special function of the leaves to extract
from the air. But the researches of Payen seem to render it
probable that, at least during certain stages of the plant's growth,
and in certain soils, it is most largely produced from the food
taken in by the roots.
He found, for example, that of all the parts of the plant, before it
began to flower or seed, protein existed in largest quantities in the
extremities of the young roots. Thus, in the dry radicles of sprout-
ed barley he found the protein compounds to form as much as 30
per cent. of their whole weight. Now as the sulphur and phos-
phorus of the protein compounds are wholly derived from the
soil, and as there is reason to believe that the plant takes in all its
nitrogen also by its roots, and that much of it enters in combina-
tion with the humic, ulmic, and geic acids,--it appears probable
that the protein is actually formed,—as we have seen that it may
be, in the extremities of the roots, as soon as the humic acid and
ammonia enter, or as they enter into the plant. That it actually
exists there in large quantities is in favour of this view, though it is
far from being decisive of the question.
The protein compounds exist also in large quantity in the leaves,
and it is not impossible that the nitrogen may in certain cases
ascend to the leaf, and there form protein compounds with the aid
of the carbonic acid absorbed from the air.
Those who think that the air contains ammonia as a necessary
constituent, and that plants take in this ammonia by their leaves,
will of course be inclined to favour the view that the protein com-
pounds are also formed in the leaf.
On the whole I am inclined to think that the protein compounds
are chiefly formed at the extremities of the roots, and that they not
unfrequently undergo decomposition during their ascent in the Sap
and are reformed again in the leaf, seed, or fruit, partly from the
old, and in part perhaps from new materials.
246 FUNCTIONS OF THE PROTEIN COMPOUNDs.
3°. Functions of the protein compounds.—The functions of the pro-
tein compounds in the plant are by no means clearly or fully under-
stood. We have already seen how diastase presides over the changes
which take place in the seed, and by which the food of the young
plant is rendered soluble, and fitted, therefore, to minister to its
growth. This diastase is derived from the protein compounds of
the seed. So whenever important chemical changes are going on
in the interior of the plant, the protein compounds are always pre-
sent. In the cells and vessels of the living vegetable, where the
materials for its enlargement are elaborated—in the leaf, in the pe-
tals of the flower and in the seed vessels, wherever the change of
matter is most active, there protein is always the most abundant.
If not itself the source of activity, it is at least the agent by means
of which the principle of life brings about those numerous chemi-
cal changes by which the several forms of matter are fitted for en-
tering into the composition of the new parts of the growing plant,
as they are successively formed.
Thus protein and its compounds appear to perform two distinct
functions in the plant.
a. They preside over, influence, and modify all the important
chemical changes which take place in the interior of the plant.
b. They also settle down in various parts of the plant, forming
portions of their solid substance—lying dormant probably till new
conditions arise, till a scarcity of the elements of protein becomes
sensible in the soil, or till the demands of the ripening seed or the
filling ear cause a larger demand for the protein compounds than
the sap can readily supply. In such cases the stem and leaves
yield up in a soluble state, to meet the emergency, a portion of the
solid protein which had been deposited in their substance. It is
in this way that during the ripening of their seeds, the straw of
our corn bearing plants loses a portion of its nourishing quality.
§ 7. Of the chemical changes which take place between the opening
of the flower and the ripening of the fruit or seed.
The opening of the flower is the first and most striking step ta-
ken by the plant towards the production of the seed by which its
species is to be perpetuated. That at this period a new series of
4
ACTION OF THE FLOWER LEAVES ON THE AIR. 247
chemical changes commences in the plant is obvious from the fol-
lowing facts :-
1°. That the flower leaves absorb oxygen and emit carbonic acid
both by day” and by night (p. 149).
2°. That they also occasionally emit pure nitrogen gas,
3°. That the juice of the maple ceases to be sweet when the
flowers are matured (Liebig), and that, in the sugar came and beet
root, the sugar becomes less abundant when the plant has begun
to blossom.
These facts sufficiently indicate the commencement of new
changes in the interior of plants at this period of their growth.
That such changes go on until the ripening of the seed is also evi-
dent from these further observations:–
4°. That the husk of the future seed, as in the corn-bearing
grasses (wheat, oats, &c.), is filled at first with a milky liquid which
becomes gradually sweeter and more dense, and finally consoli-
dates into a mixture of starch with gluten and other protein com-
pounds—such as is presented by the flour of different species of
COT’ſ).
5°. That the fruit in which the seeds of many plants is enveloped
is at first tasteless, afterwards more or less sour, and finally sweet.
In a few fruits only, as in the lime, the lemon, and the tama-
rind, does a sufficient quantity of acid remain to be sensible to
the taste, when the seed has become perfectly ripe. The acid and
cellular fibre both diminish while the sugar increases.
69. That fruits, while green, act like the green leaves and twigs
in absorbing carbonic acid from the air—but that, as they approach
maturity, they absorb or retain oxygen and begin to give off car-
bonic acid (De Saussure). The same absorption of oxygen takes
place when unripe fruits are plucked and left to ripen in the air.
After a time the latter also emit carbonic acid (Berard and Fremy.)
This respiration or transpiration of the fruit is essential to its
development. When covered with a coating of varnish its growth
is stopped though it be still left upon the tree (Fremy).
We shall consider separately the formation of the seed and the
ripening of the fruit.
* By day the absorption is the greater, but the bulk of the oxygen taken in is al-
ways greater than that of the carbonic acid given off.
248 FORMATION OF THE SEED,
§ 8. Of the formation of the seed.
In the case of wheat, barley, or other plants, which yield fari-
naceous seeds, we have seen that previous to flowering the chief
energy of the living plant is expended in the production of the
wood of which its stem and growing branches mainly consist; and
we have also been able to understand, in some degree, how this
wood is produced from the ordinary food of the plant. When the
flower expands, however, the plant has in general, and especially
if an annual plant, reached nearly to maturity and woody fibre is
little required. The most important of its remaining functions is
the production of the starch and gluten of the seed, and of the sub-
stances which form the husk by which the seed is enveloped.
In the first stages of the plant's growth the starch of the seed is
transformed into gum and sugar, and subsequently, when the
leaves are expanded, into cellular fibre. In the last stages of its
existence, when it is producing the seed, the sugar of the sweet
and milky sap is gradually transformed into starch—that is to say
a process exactly the converse of the former takes place.
We are able, in some measure, to explain the mode and agency
by which the former transformation is effected—the latter, how-
ever, is still inexplicable. We can ourselves, by the agency of
diastase, transform starch into sugar; and, therefore, can readily
believe such transformations to be effected in the young plant;--
but we as yet know no method of re-converting Sugar into starch;
and, therefore, we can only hazard conjectures as to the way in
which this change is brought about in the interior of the plant dur-
ing the formation of the seed. -
It is said that nitrogen is given off by the flower leaf. We
know that this element is present in the colouring matter of the
petal, as it is in the green of the leaf, and that it is a necessary
constituent of the albumen and gluten, which are always associat-
ed with the starch of the seed. It is plain, then, that the protein
compounds contained in the sap at all periods of the plant's growth
are carried up in great quantity to the flower and seed vessel. In
the leaves of the flower they are partly decomposed, and their ni-
trogen given off—causing a loss of nutritive matter to the plant.
The greater part, however, gradually collects in the ripening seed
RIPENING OF THE FRUIT, 249
to form the future source of nourishment to tribes of new plants
to which the seed is intended to give birth.
The progress of this gathering in, as it were, of the protein com-
pounds from the various parts of the plant into the seed, appears
in the following results of experiments made in my laboratory up-
on the quantity of these compounds contained in the grain of the
oat at various stages of it growth. Gathered at first every fort-
might after the grain was formed, and afterwards every week as it
approached to maturity, it was found after being dried to contain
albumen, casein, &c., in the following proportions:
30th July. 13th Aug, 20th Aug. 27th Aug. 3d Sept.
Protein compounds, 8'50 8-69 8'25 l 1:26 13-84
The apparent diminution on the 20th of August was probably
owing to the plants collected on that day not being so far advanced
as those which had been gathered a week before.
When the seed is thus fully formed and the protein compounds
contained in the sap collected in the grain, the chemical changes
over which they presided gradually cease, circulation languishes
and stops, and the plant becomes dormant for the season or finally
dies,
§ 9. Of the ripening of the fruit.
In those plants again, which invest their seed with a pulpy fruit
—in the grape, the lemon, the apple, the plum, &c.—other changes
take place, at this period, which are more intelligible to us than the
change of the sugar and dextrin of the sap into the starch of the
grain, and other substances are formed, on the production of which
less obscurity rests. At one stage of their growth, these fruits, as
has been already stated, are tasteless—in the next, they are sour—
in the third, they are more or less entirely sweet.
I. In the tasteless state their solid parts consist chiefly of cellular
fibre, tinged externally with the colouring matter of the green parts
of the plant. Their sap contains a solution of dextrin. For a time
this young green fruit appears to perform in reference to the atmo-
sphere the usual functions of the leaf-it absorbs carbonic acid and
gives off oxygen, and thus extracts from the air a portion of the food
by which its growth is promoted, and its size gradually increased.
II. But after a time this fruit becomes sour to the taste, and
250 FORMATION OF TARTARIC ACID IN FRUITS.
its sourness gradually increases—while at the same time it is ob-
served to give off a less comparative bulk of oxygen than before.
Let us consider shortly the theory of the production of the more
abundant vegetable acids contained in fruits. x
1°. The tartaric acid which occurs in the grape is represented
by C. H2 Os (p. 207).
There are two ways in which we may suppose this acid to be
formed in the fruit.
a. Directly from the elements of carbonic acid and water with
evolution of oxygen gas. Thus to
C. H. O.
4 of carbonic acid , = 4 8
add 2 of water - 2 2
and we have 4 2 I ()
Deduct l of tartaric acid 4 2 5
and there remain 5 of oxygen
to be given from the leaf.
In this way tartaric acid could only be formed in the sunshine
when the fruit is green, and when, like the leaves, it is absorbing
carbonic acid, and giving off oxygen into the air.
b. Or it may be formed directly from the dextrin, sugar, or gum
of the sap, aided by the absorption of oxygen from the atmosphere.
Thus if to
C. H. O.
1 of dextrin ................ – 12 10 10
we add 5 of oxygen ...... ~ 5
12 I () 15
and deduct 3 of tartaric acid 12 6 15
we have ........... ......... 4 of
hydrogen in excess, which may either unite with more oxygen to
form water, or be taken up to form the wax with which the sur-
face of the fruit is always covered; and which, as we have seen,
(p. 207), contains a large excess of hydrogen.
In the sorrels and other sour leaved plants, which along with
FORMATION OF MALIC AND CITRIC ACIDs. 251
oxalic contain also tartaric acid in their general sap, the acid may
be formed by either of the processes above explained. In the
sunshine their green parts absorb carbonic acid and evolve oxygen.
If any of these green parts give off only 3 of the oxygen contained
in the carbonic acid they drink in, tartaric acid may be produced
(a). In the dark again they absorb oxygen and give off carbonic
acid. If the bulk of this latter gas which then escapes be less than
that of the oxygen which enters, a portion of the sugar or gum of
the sap may, as above explained (b,) be converted into tartarie
acid. -
We have as yet no experiments which enable us to say by which
of these modes the tartaric acid is really produced in such plants
—or whether it may not occasionally be compounded by both
methods.
In green fruits also, in the sour grape for example, it may, in
like manner, be produced by either method. The only experi-
ments we yet possess, those of De Saussure, though not sufficient
to decide the point, are in favour of the former explanation (a.)
In the estimation of this philosopher, the proportion of the oxygen
of the carbonic acid which is retained by the fruit, is sufficient to
account for the acidity it gradually acquires.
2°. Malic and citric acids.-These acids are represented (p. 208),
by the common formulae C, H, O, They may be produced from
water and carbonic acid, if three-fourths only of the oxygen of the
latter be given off. Thus, if to
4 of carbonic acid = C, Os we add
2 of water ......... = H2 O2
**** Malic Acid.
we have the sum ... C., H2O10 or C, H2O4 + 6 O.
That such retention of one-fourth of the oxygen of the carbonic
acid occasionally takes place in the green fruit is consistent with
the observations of De Saussure. The lime and the lemon are
fruits on which the most satisfactory experiments might be made
with the view of finally determining this point.
III. This formation of acid proceeds for a certain time, the
fruit becoming sourer and sourer;-the sourness then begins to
diminish, sugar is formed, and the fruit ripens. The acid rarely
disappears entirely, even from the sweetest fruits, until they begin
252 CONVERSION OF ACIDS INTO SUGAR.
to decay; a considerable portion of it, however, is in some cases
converted into grape sugar, as the fruit approaches to maturity.
This conversion may take place in either of two ways, t
1°. By the direct evolution of the excess of oxygen. Thus
3 of tartaric acid = C19. He O15
5 of water ......... = H; Og
-*--º Grape Sugar.
Sum ... = C12 H11 O20 = C12 H11 Oil + 8 O.
Or grape sugar may be formed from 3 of tartaric acid and 5 of
the water of the sap, by the evolution, at the same time, of 8 of
oxygen. Three of citric or malic acid would form grape sugar by
the evolution of 6 of oxygen only.
Do fruits, when they have reached their sourest state, begin thus
to give off an excess of oxygen P I know of no experiments which
as yet decide the point.
2°. By the absorption of oxygen and the evolution of carbonic
acid. Thus in the case of tartaric acid,
1 of tartaric acid = C, H2 Os
I of OXygen . . . . . . . . . -: Ol 1-6th of Grape Carbonic
-º-º-º-º-º-º- Sugar. Acid.
Sum • e º e º e º e s - Cl H2 Oc - C2 H2 O2 + 2 C O2
Where 1 of oxygen is absorbed and 2 of carbonic acid given off.
3°. Or in the case of the malic and citric acids,
l of Malic Acid = C, H, O,
2 of Oxygen .... = O2 1-6th of 2 of
– Grape Sugar. Carbonic Acid.
Sum ... = C, H, Og = C, H, O, H- 2 CO,
Where 2 of oxygen are absorbed and 2 of carbonic acid given off.
We know from the experiments of Berard that, when unripe
fruits are plucked, they do not ripen if excluded from the access of
oxygen gas, but that in the air they ripen, absorbing oxygen at
the same time, and giving off carbonic acid. This second method
(2°) therefore, exhibits the more probable theory of the ripening
of fruits after they are plucked;" and if—as they become coloured I.
fruits imitate the petals of the flower in absorbing oxygen from the
air and giving off carbonic acid, it will also represent the changes
which take place when they are permitted to ripen on the tree.
* lºw - - - y - º º
Of the ſreen oranges, for example, which become yellow and in some In CaSull'O'
ripe during their voyage to England.
CHANGES AFTER THE FRUIT HAS RIPENED. 253
That this latter is really the case is rendered probable by the later
experiments of Fremy.*
During the ripening of the fruit, it has been stated that the
woody or cellular fibre it contains gradually diminishes, and is con-
verted into sugar. This is familiarly noticed in some species of
hard or winter pears. In sour fruit, the cellular fibre seldom ex-
ceeds 2% per cent, of their whole weight;-in ripe fruits, however,
it is still less, and as the constitution of this substance is so analo-
gous to that of grape sugar, there is no difficulty in understanding
that it may be readily converted into the latter, through the agency
probably of the protein compounds which are present in the fruits.f
§ 10. of the chemical changes which take place after the ripening
of the fruit and seed.
When the seed is fully ripe, the functions of annual plants are
discharged. They no longer require to absorb and decompose
carbonic acid, for their growth is at an end. Their leaves begin,
therefore, to take in oxygen only, become yellow, and prepare,
along with the entire plant, for being finally resolved again into
those more elementary substances, from which they were originally
compounded.
On trees and perennial plants, however, a further labour is im-
posed. In the ripened seed they have deposited a supply of food
sufficient to sustain the germ that may spring from it until it is
able to seek food for itself; but the young buds already formed—
and which are to shoot out from the stem and branches in the en-
suing spring, are in reality so many young plants for which a
* Chemist, January 1845.
+ The relative proportions of sugar, gum, cellular fibre, acid, &c., in the peach at
three stages of its growth were found to be as follows:—
Unripe. Riper. Fully ripe.
Sugar ............ * * * * * * * * trace ... 6.64 ... 16:48 per cent.
Gum ..................... 4'l Q ... 4'47 ... 5:12
• Cellular fibre ............ 3-61 ... 2:53 ... 1.86
Malic acid ............... 270 ... 2:03 ... 1-80
Vegetable albumen... ... 0-76 ... 0-34 ... 0-17
Water .................. 89'39 ... 84-49 ... 74-87
So that though in this fruit some of the acid and woody fibre had disappeared
during the ripening, yet the greatest portion of the sugar contained in the ripe fruit
had evidently been derived directly from the ordinary food of the plant.
254 RAPID GROWTH OF PIANTS.
store of food has yet to be laid up in the immer bark, and in the
wood of the tree or shrub itself. 4.
In the autumn, the sap of trees and permanent shrubs continues
to flow rapidly till the leaf withers and falls, and the food of the
plant is converted partly into true wood, as was the case during
the earlier period of the year, and partly into starch. The former
is deposited beneath the inner bark to form the new layer of wood
by which the tree is annually enlarged ; the latter—partly in the
same locality, as in the birch and pine—partly throughout the
substance of the wood itself, as in the willow—while in the palm
trees and cycadeae, it is intermingled with the central pith. The
chemical changes by which the food is capable of being converted
into these substances have already been considered (pp. 233 to 238).
They proceed during the entire autumn, do not cease so long as the
sap continues to move, and even in the depth of winter slowly and
silently operate in storing up farinaceous matter—in readiness, like
the starch in the seed, to minister to the nourishment of the young
bud, when the warmth of the coming spring shall awaken it from
its long sleep. .
Along with this starch there is in all cases deposited a sufficient
portion of albumen or some other protein compound to supply the
wants of the young shoot and to preside over the chemical changes
through the agency of which its growth is to be carried on.
§ 11. Of the rapidity with which these changes take place, and the
circumstances by which they are promoted.
But remarkable as those chemical changes are, the rapidity
with which they sometimes take place is no less surprising.
From carbonic acid and water we have seen that the plant, by
very intelligible processes, can extract the elements of which its
most bulky parts consist—and can build them up in many varied
ways, most of which are probably beyond the reach of imitation.
But who can understand or explain the extraordinary activity
which pervades the entire vascular system of the plant, when cir-
cumstances are favourable to its growth?
A stalk of wheat has been observed to shoot up three inches in
as many days, of barley six inches in the same time, and a vine
twig almost two feet, or eight inches a day (Du Hamel). Cu-
THEIR GROWTH AFFECTED BY CIRCUMSTANCES. 255
cumbers have been known to acquire a length of twenty-four inches
in six days, and in the Botanic Garden at Brussels I was shown a
bamboo five inches in diameter, which had increased in height nine
feet in twenty-seven days, sometimes making a progress of six to
eight inches in a day. In our climate we meet with few illustra-
tions of the rapidity with which plants are capable of springing up
in the most favourable circumstances, and the above examples pro-
bably give us only an imperfect idea of the velocity with which the
bamboo, the palm, the tree-fern, and other vascular plants may
grow in their native soil and climate. And with what numerous
and complicated chemical changes is the production of every sen-
sible particle of the substance of these plants attended—how ra-
pidly must the food be selected and absorbed from the air and from
the soil—how quickly transformed and assimilated
The long period of time during which, year after year, these
changes may proceed in the same living vessels, or in the same
tree, is no less wonderful. Oaks have lived to an age of 1500 or
2000 years—Yew trees to 3000 years—and other species are men-
tioned as having flourished from 4500 to 6000 years; while even
a rose tree (rosa canina) now living is quoted by Sprengel as be-
ing already upwards of 1000 years old.”
The rapidity of the growth of a plant, and the length of its life,
are equally affected by circumstances. On a knowledge of these
circumstances, and of the means of controlling or of producing
them, the enlightened practice of agriculture is almost entirely de-
pendent. 4. - - -
Over the natural conditions of climate, &c., on which vegetation
in general depends, we can exercise little immediate control. By
hedge-rows and plantations we can shelter exposed lands, by drain-
ing we can greatly ameliorate cold and wet soils, but, except in
our conservatories and hot-houses, the plants we can expect to cul-
tivate with profit will always be determined by the general climate
in which we live. So the distribution of rain and sunshine are be-
yond our control, and though it is ascertained that a thundery
condition of the atmosphere is remarkably favourable to vegetable
growth, f we cannot hope that such a state of the air will ever be
induced, at the pleasure or by the agency of man. But under the
* Sprengel Lehre vom Dinger, p. 76. + Ibid. p. 73.
256 INFLUENCE OF SALINE SUBSTANCES AND MANURES.
same natural conditions of climate, there are many artificial me-
thods by the use of which it is within our power to accelerate the
growth, and to increase the produce of the most valuable objects
of ordinary culture. --
Thus the germination of seeds in general is hastened by water-
ing with a solution of chlorine (Davy), or of iodine or bromine
(Blengini). Davy found also that radish seed, which germinated
in two days when watered with solutions of chlorine or sulphate
of iron, required three when watered with very dilute nitric acid,
and five when watered with a weak solution of sulphuric acid.
Later experiments have shown that the germination of seeds
may also be hastened by steeping in various saline solutions, as
those of sulphate or muriate of ammonia, nitrate and phosphate of
soda, and various others.
It is familiarly known also in ordinary husbandry, that the ap-
plication of manures hastens in a similar degree the development
of all the parts of plants during every period of their growth—and
largely increases the return of seed obtained from the cultivated
grains. Ammonia and its compounds likewise, and nitric acid and
its compounds, with many other saline substances existing in the
mineral kingdom and occurring in soils, or which are produced
largely in our manufactories, have been found to produce similar
effects.
It would be out of place here to enter upon the important and
interesting field opened up to us by a consideration of the influence
exercised by these and other substances, in modifying, both in kind
and in degree, the chemical changes which take place in living ve-
getables. The true mode of action of such substances—their pre-
cise effects—the circumstances under which these effects are most
certainly produced—and the theoretical views on which they can
be best accounted for—will form a subject of special and detailed
examination in the third part of the present lectures. -
LECTURE IX.
iº
. How the supply of food for plants is kept up in the general vegetation of the globe.
Proportion of their carbon which plants derive from the air. Relation of the quan-
tity annually drawn from the air to the whole quantity in the atmosphere. Sup-
ply of carbonic acid in the atmosphere, how it is kept up and regulated. Produced
by respiration, by combustion, by decay of organic matter. Law of this decay.
Given off from volcanic fissures. Supply of ammonia and nitric acid. Production
of both in mature. Theory of their action on living vegetables. Comparative in-
fluence of nitric acid and ammonia in different climates. Supposed stimulating
influence of these compounds. Concluding observations, &c. +
HAVING shewn in the preceding Lecture in what way and by
what chemical changes, the substances of which plants chiefly con-
sist may be produced from those on which they live, there re-
mains only one further subject of inquiry in connection with the
organic constituents of plants. .
Plants, as we have already seen, derive much of their carbon
from the carbonic acid of the atmosphere; yet of this gas the air
contains only a very small fraction, and so far as experiments have
yet gone, this fractional quantity does not appear to diminish—
how, them, is the supply of carbonic acid kept up 2
Again, plants obtain much of their nitrogen either from ammo-
nia or from nitric acid; and yet, neither in the soil nor in the air
is any large and permanent supply of these compounds known to
exist. How, then, are they continually produced, or from what
source are they constantly brought within the reach of plants?
The importance of these two questions will appear more distinctly
if we endeavour to estimate how much of their carbon plants really
draw from the atmosphere—and how much of the nitrogen they
contain must be derived from sources not hitherto pointed out.
P.
2
58 PROPORTION OF CARBON DIRAWN FROM THE AIR.
§ 1. Of the proportion of their carbon which plants derive from
• the atmosphere.
The general circumstances by which this proportion is affected
have already been briefly stated (p. 95). In regard to the abso-
lute quantity of carbon directly drawn from the air by any crop,
it is perhaps impossible to obtain perfectly accurate results. Se-
veral series of experiments, however, have been published, which
enable us to arrive at useful approximations in regard to the pro-
portion of their carbon which plants, growing in a soil of ordinary
fertility, and in such a climate as that of Great Britain, actually
extract from the air by which they are surrounded.
1°. In an experiment made in 1824, upon common borage
(borago officinalis), Lampadius found that after a growth of five
months (from the 3d of April to the 6th of September) this plant
produced ten times as much vegetable matter as the soil in which
it grew had lost during the same period. In other words, it had
drawn nine-tenths of its carbon from the air.
This result appears at first sight too startling to be received in
evidence of the proportion of their sustenance drawn by plants
from the air in the general vegetation of the globe; and yet De
Saussure estimated the proportion of its weight which a sun-flow-
er had derived from the soil at only one-twentieth of the whole.—
(Recherches Chemiques sur la Vegetation, p. 268.)
2°. The experiments of Boussingault were made, if not with
more care than that of Lampadius, at least upon a greater number
of plants, and were protracted through a much longer period. It
is necessary that we should understand the principle on which they
were conducted, in order that we may be able to judge as to the
degree of confidence we ought to place in the determinations at
which he arrived,
If we were to examine the soil of a field on which we are about
to raise a crop of corn—and should find it to contain on an ave-
rage, say 10 per cent of vegetable matter (or 5 per cent. of car-
bon);-and after the crop is raised and reaped should, on a se-
cond examination, find it to contain exactly the same quantity of
carbon as before, we could not resist the conviction, that, with the
exception of what was originally in the seed, the plant during its
growth had drawn from the air all the carbon it contained.
EXPERIMENTS OF BOUSSINGAULT. 259
The soil having lost none, the air must have yielded the whole
supply.
Or if, after examining the soil of our field, we mix with it a sup-
ply of farm-yard manure, containing a known weight, say one ton
of carbon, and when the crop is reaped find as before that the per-
centage of vegetable matter in the soil has suffered no diminution,”
we are justified in concluding that the crop cannot, at the utmost,
have derived from the soil any greater weight of its carbon than
the ton contained in the manure which had been added to it.
Such was the principle on which Boussingault's experiments
were conducted. He determined the weight of carbon added to
the soil in the form of manure—the quantity contained in the
series of crops raised during an entire rotation or course of crop-
ping, until, in the mode of culture adopted, it was usual to add
manure again—and lastly, that the land was nearly in the same
condition as regarded the presence of vegetable matter at the end
as at the beginning of the rotation. By this method he obtained
the following results in pounds per English acre, in three different
courses of cropping on the same land, and from Jerusalem arti-
chokes, repeated on the same soil year after year, without change
of crop :-f

Carbon Carbon | Difference, or
in the in the Carbon deriv- Course of Cropping,
Manure. Crops. |ed from the air
First Course 3556
8196|| 4640 Five years—potatoes with manure, then wheat,
clover, wheat, oats.
8010; 4.454 Same, only red beet in º: of potatoes.
ºr ral a Six years—potatoes, wheat, clover, wheat
Second Course 4267 10705) 6438 followed by a winter (half) crop of turnips, peas
with manure, rye. ked fall it!
is. º t; 9.15 Three years—naked faſlow with manure,
Third Course 1450 3909| 2459 wheat, wheat. ,-
Jerusalem 3297 | 15631|| 12334 The same crop and manure repeated year after
Artichokes year.
The result of the first and second courses indicates that the
crops which were collected contained nearly 2% times the weight of
carbon present in the manure, and the crops of the third course
nearly three times as much,--while the crop of artichokes (including,
* I need scarcely remark that, in the hands of a good farmer, who keeps his land
in good heart—the quantity of organic matter in the soil at the end of his course of
cropping should be as great, at least, as it was at the beginning of his rotation, before
the addition of the manure.
+ Boussingault, Am. de Chim, et de Phys, 3me Series, I, p. 241.
260 EXPERIMENTS OF BOUSSINGAULT NOT CONCLUSIVE.
of course, the leaves) contained nearly five times as much carbon
as the manure, by the aid of which a yearly crop of equal excel-
lence is regularly raised. In other words, the artichoke extracted
four-fifths of its carbon from the air, the wheat crop AT LEAST two-
thirds.
I shall hereafter have occasion to show you (p. 267), that even
when the soil is lying naked the animal and vegetable matter it
contains is continually undergoing diminution, owing to decom-
position and the escape of volatile substances into the air. It is
fair, therefore, to assume that a considerable portion of the carbon
of the manure and of the soil would naturally disappear during
the several years' cropping above-mentioned, and that therefore
the proportion of carbon derived from the air in Boussingault's
experiments, may have really been considerably greater than is
indicated by the numerical results. -
Such is the conclusion to which Boussingault's experiments seem
logically to lead us. And yet a little consideration will show that
it is by no means securely based. For
It is exceedingly difficult to arrive at any thing like a rigorous
determination of the proportion of vegetable matter contained in
the soil of a whole field. A very small error in this determination
would amount to more than the 10 cwt. we suppose our crops of
corn to carry away from every acre. -
Thus, if a soil 12 inches in depth contain only 5 per cent. of ve-
getable matter, this will give about 60 tons for the quantity con-
tained in a whole acre. Of this 60 tons our 10 cwt. is only the
1% ºth part. Now as 100 lbs. of soil are supposed to contain only
5 lbs. of vegetable matter, an error of 0.05 per cent. in the esti-
mation of it—which should make the per-centage 4.95 instead of
5.00,—would imply that the acre of land contained 10 cwt. of ve-
getable matter less than was actually present.
From my own experience I am free to say that such minute ac-
curacy in the estimation of the amount of carbon contained in a
soil in the form of organic matter, is unattainable with our present
methods, and therefore that the precise results of Boussingault's
agricultural experiments, as above stated, though carefully made,
are not to be confided in.
Though, therefore, the quantity of carbon taken in by plants
N
wBIGHT OF CARBON IN THE ATMOSPHERE, 261
from the air is unquestionably large, we are still as far as ever from
any thing like an accurate estimation of the amount.
But let two-thirds of the entire quantity of carbon contained in
a series of crops, be taken as the average proportion which, on
cultivated land in our climate, must be derived from the air in the
form of carbonic acid—and let the average weight of the dry crop
reaped be estimated at a ton and a half per acre, then, if the crop.
contain half its weight of carbon (p. 35), the plants grown on each
acre must annually extract from the air 10 cwt. or 1120 lbs. of
carbon in the form of carbonic acid.
§ 2. Of the relation which the quantity of carbon eatracted by plants
from the air, bears to the whole quantity contained in the atmo-
sphere. -
But the question will here at once suggest itself to you—does
not the quantity thus extracted from the air—though as yet undeter-
mined in amount—really form a very large proportion of the whole
weight of carbon which is contained in the atmosphere? A simple
calculation will give us clear ideas in regard to this interesting
point. • ‘ - -
We have already seen—by the results of De Saussure and of
Boussingault ( p. 40, note)—that the average quantity of carbonic
acid in the atmosphere of our globe may be estimated at ºn part
of its entire bulk. This is equal very nearly to zoºg of its weight."
Or taking the whole weight of the atmosphere at 15 lbs. on the
square inch—that of the carbonic acid will be 0.009 lbs., or 63
* The mean of 225 experiments made by De Saussure, and of 142 made by Bous-
singault, gave as above stated about ražaw or grºwth part for the mean bulk of the
carbonic acid in the air, which is nearly rºup of its whole weight. Among these
observations the maximum was 5-8 ten thousandths, the minimum 3:15. If we take
the maximum bulk at rºgn of the air—the maximum weight of the carbonic acid
is nearly rººt of that of the atmosphere. In elementary works it is generally stated
in round numbers at , ºrg of the weight of the air, but if the best experimental re-
sults we possess are to be any guide to us, this is at least one-third higher than the
true average. - w
It is also of consequence to remark, that this estimate of the whole weight of the
carbonic acid in the air is founded on the Supposition that, in the highest regions of
the atmosphere, the carbonic acid is present in 'a proportion nearly equal to that in
which it is found immediately above the earth's surface—which is by no means esta-
blished.
262 COMPARED WITH THAT IN AN ENTIRE CROT”.
grs. per square inch. But as carbonic acid contains only 27# per
cent. of its weight of carbon, the weight of this element which
presses on each square inch of the earth's surface is only 173
(17.39) grs. Upon an acre this amounts to 7 tons.”
But if the crop on each acre of cultivated land annually extracts
from the air half a tom of carbon, the whole of the carbonic acid
in the atmosphere would sustain such a vegetation over the entire
globe for 14 years only. And if we even suppose such a vegeta-
tion to extend over no more than one-hundredth part of the earth's
surface, it still appears sufficient to exhaust the carbonic acid of
the air in 1400 years.
A very short period, compared even with the limits of authentic
history, has yet elapsed since experiments began to be made on the
true constitution of the atmosphere; we have no very trustworthy
data, therefore, on which to found a confident opinion in regard
to the permanence of the proportion of carbonic acid which it now
contains. The observations of De Saussure do give a consider-
ably lower estimate of the quantity of this acid in the air than that
which was deduced from the results of earlier experimenters; but
the imperfection of the modes of analysis formerly adopted was too
great, to justify us in reasoning rigorously from the inferences to
which they led. We cannot safely conclude from them that the
proportion of carbon in the atmosphere has really diminished to
any sensible extent during the limited period within which obser-
vations have been made; while the recorded identity of all the
phenomena of vegetation render it probable that the proportion has
not sensibly diminished even within historic times.
From what sources, then, is the supply of carbonic acid in the
atmosphere kept up 2–and if the proportion be permanent, by
what compensating processes is the quantity which is restored to
the atmosphere produced and regulated 2
§ 3. How the supply of carbonic acid in the atmosphere is
renewed and regulated.
On comparing, in a previous lecture, the quantity of rain which
falls with that of the watery vapour actually present in the air, we
saw reason to believe that even in a single year the same portion
* 15,583 lbs.--an acre being 1840 square yards, containing each 1200 square inches.
PRODUCTION OF CARBONIC ACID BY RESPIRATION. 263
of water may fall in rain or dew and ascetid again in watery va-
pour several successive times (p. 58). Is it so also with the car-
bom in the air? Does that which feeds the growing plant to-day,
again mount up in the form of carbonic acid at some future time,
ready to minister to the sustenance of new races, and to run again
the same round of ever-varying change? Such is, indeed, the
general history of the agency of the carbonic acid of the atmo-
sphere;—but when once it has been fixed in the plant it must pass
through many successive changes before it is again set free. The
conditions, also, under which it is restored to the atmosphere are
so diversified—and the agencies by which, in each case, it is libe-
rated are so very distinct—as to require that the several modes
by which the carbon of plants is re-converted into carbonic acid
and returned to the air, should be made topics of separate consi-
deration.
I.—ON THE PRODUCTION OF CARBONIC ACID BY RESPIRATION.
The air we breathe, when it is drawn into the lungs, contains
ºwth of its bulk of carbonic acid; when it returns again from
the lungs, the bulk of this gas amounts, on an average,” to #th
of the whole; or its quantity is increased one hundred times.
The actual bulk of the carbonic acid emitted from the lungs of
a single individual in 24 hours varies exceedingly; it contains,
however, on an average, from 5 to 8 ounces of carbon.f A full
grown man, therefore, gives off from his lungs, in the course of a
year, from 110 to 180 lbs. of carbon in the form of carbonic acid.
If the quantity of carbon thus evolved from the lungs be in pro-
* It varies in different individuals from 2 to 8 per cent. of the expired air. In ani-
mals it varies also with the species. The air from the lungs of a cat contains from
5% to 7 per cent., of a dog from 4% to 6%, of a rabbit from 4 to 6, and of a pigeon from
3 to 4 per cent of the whole bulk-Dulong, Annal. de Chim. et de Phys, third Series,
3. p. 455. -
+ Davy, and Allen, and Pepys, estimated the weight of carbon evolved in a day at
upwards of 11 ounces. Liebig considers that in a state of repose 5 ounces may be
the daily quantity—when moderate exercise is taken, from 7 to 8 ounces;–while ro-
bust persons who undergo violent exertion will sometimes expire as much as 13 ounces
in 24 hours. Dumas, Andral and Gavarret, and Scharling and Hannover, have in
their experiments estimated it in a full grown man at from 7% to 8 ounces in 24 hours.
See Dr Hannover, de quantitate acid; carbonici ah homine erhalafi. Hauniae, 1845.
264 CARBONIC ACID PRODUCED BY RESPIRATION,
portion to the weight of the animal, a cow or a horse ought to
give off six times as much as a man.” From indirect experiments,
however, Boussingaultſ estimated the quantity of carbon actually
lost by a cow through its lungs and its skin at 4 lbs. 14 ounces,
and by a horse at 5 lbs. 7 ounces in 24 hours. Part of this appears,
however, to have passed off in the insensible perspiration from the
skin. *
If we suppose each inhabitant of Great Britain, young and old,
to expire only 80 lbs. of carbon in a year, the twenty millions
would emit seven hundred thousand tons; and allowing the cattle,
sheep, and all other animals to give of twice as much more, the
whole weight of carbon returned to the air by respiration in this
island would he about two millions of tons, equal to the quantity ab-
stracted from the atmosphere by four millions of acres of cultivated
land.
Whence is all this carbon derived? It is a portion of that which
has been conveyed into the stomach in the form of food. Suppose
the carbon contained in the daily food of a full grown man to amount
to one pound—which is a large allowance—then it appears that,
by the ordinary processes of respiration, at least one-third, perhaps
one-half, of the carbon of his food is daily returned into the air.
In other animals the proportion returned may be different from
what it is in man, yet the life of all depends on the emission to a
certain extent of the same gas.; And since all are sustained by
the produce of the soil, it is obvious that the process of animal re-
spiration is one of those methods, by which it has been provided
that a large portion of the vegetable productions of the globe,
should be almost immediately resolved into the simpler forms of
matter from which it was originally compounded, and should be
again sent up into the air to minister to the wants of new races.
* Estimating the ordinary weight of a man at 150, and of a cow at 800 to 900 lbs
–See Sprengel, Lehre vom Dünger, p. 208. e
+ Am... de Chem. et de PhyS., lxxi. pp. 127 and 136.
f That the proportion is as great in the larger animals is probable, since the daily
food of a cow may be stated generally as equivalent to 25 lbs. of hay, containing up-
wards of 10 lbs. of carbon, and if one-third of this only be given off from the lungs,
the quantity of carbon (34 lbs.) evolved will be considerably less than was indicated
by the experiments of Boussingault, though greater than the weight of a COW, cont-
pared with that of a man, requires,
- |
AND BY THE COMBUSTION OF ORGANIC MATTER, 265
II. —ON THE PRODUCTION OF CARBONIC ACID BY COMIB USTION.
Another important source of carbonic acid is familiar to us in
the results of artificial combustion,
In a previous lecture I have shown how, by the action of the
sun's rays upon the leaf, the carbonic acid absorbed from the at-
mosphere is deprived of its oxygen, and its carbon afterwards unit-
ed to the elements of water for the production of wood and of
other substances formed in the sap of plants. During the process
of combustion, this labour of the living leaf is undone—the carbon
is made to combine anew with the oxygen of the atmosphere, and
the vegetable matter is resolved again into the carbonic acid and
water from which it was originally formed.
Thus, when wood is burned in the air, oxygen disappears and
carbonic acid and watery vapour are alone produced. The theory
of this change is simple.
Take as an illustration the soft wood of the Liriodendron tuli-
pifera and let it be burned in the air. We have then
- C. H. O.
I of the wood of liriodendron – 64 48 47
129 of oxygen from the air = 129
Sum 6 48 176
Deduct 64 of carbonic acid 64 128
and there remain 48 48 or
48 of water. -
So that when one of this wood is burned in the air it consumes 129
of oxygen, and forms 64 of carbonic acid, and 48 of water, both of
which escape into the air.
It is the same with all other kinds of vegetable matter—the car-
bon they contain is converted entirely into carbonic acid when they
are fully burned in the presence of oxygen gas.
The same law applies also to all bodies of vegetable origin, among
which nearly all combustible minerals may be reckoned. The peat
and coal we burn in our houses and manufactories, when supplied
with a sufficiency of atmospheric air, are resolved during combus-
tion into carbonic acid and watery vapour.
266 PRODUCES CARBONIC ACID AND WATER.
Some vegetable substances contain a small quantity of nitrogen.
When these are burned, their nitrogen escapes into the atmo-
sphere, generally in an uncombined state, and mingles with the
air. It is the same with animal substances, nearly all of which
contain nitrogen as an essential constituent. During perfect com-
bustion the whole of the carbon is dissipated in the form of car-
bomic acid, while the nitrogen rises along with it for the most
part in an elementary state. .
The result of this uniform subjection of all combustible matter
to the operation of this one law, is the constant production on the
surface of the globe of a vast quantity of carbonic acid;—the re-
conversion of large masses of organic matter into the more ele-
mentary compounds, from which it was originally formed.
How interesting it is to contemplate the relations, at once wise
and beautiful, by which, through the operation of such laws, dead
organic matter, intelligent man, and living plants are all bound
together | The dead tree and the fossil coal lie almost useless
things in reference to animal and vegetable life. Man employs.
them in a thousand ways as ministers to his wants, his comforts, or
his dominion over mature—and in so doing, he himself directly,
though unconsciously, ministers to the wants of those vegetable
races, which seem but to live and grow for his use and sustenance.
It is impossible to say what proportion of the carbon absorbed
during the general vegetation of the globe, is thus annually re-
stored to the atmosphere by the burning of vegetable matter. That
it must be very great, will appear from the single fact, that by far
the greater part of the globe is dependent for its supply of fuel on
the annual produce of its forests;–while even in those more
favoured countries where mineral coal abounds, the quantity of
wood consumed by burning, falls but little short of the entire yearly
growth of the land. º
In connection with this subject, I must draw your attention to
one interesting, as well as important fact. I have spoken of coal
as a substance of vegetable origin, and there is no doubt that all
the carbon it contains once floated in the air in the form of carbo-
nic acid. But the period when it was so mixed with the atmo-
sphere, is remote almost beyond conception. When, therefore,
we raise coal from its ancient bed and burn it on the earth's sur-
COMBIOSTION OF COAL. 267
face, we add to the carbon of the air a portion which has not pre-
viously existed in the atmosphere of our time.
The coal consumed in Great Britain alone is estimated at 20
millions of tons, containing on an average at least 70 per cent., or
14 millions of tons of carbon. But if the annual produce of an
acre of cultivated land contain half a ton of carbon derived from
the air (p. 261), the coal consumed in this country would supply
carbonic acid to the crops grown upon 28 millions of acres. Or,
since in Great Britain about 34 millions of acres are in cultivation
—the coal we annually consume produces a quantity of carbonic
acid which is alone sufficient to supply carbon to the crops that grow
upon SEVEN-EIGHTHs of the arable land of this country.
Add to this the quantity produced by respiration, and the arable
lands of Great Britain may be fed with carbon from these two
sources alone.
III. –PRODUCTION OF CARBONIC ACID BY THE NATURAL DECAY OF
VEGETABLE MATTER, LAW OF THIS DECAY.
Over large tracts of country in every part of the globe, the ve-
getable productions of the soil are never cropped or gathered, but
either accumulate—as occasionally in our peat bogs; or decay and
gradually disappear—as in the jungles of India or in the tropical
forests of Africa and Southern America.
The final results of this decay are the same as those which at-
tend upon ordinary combustion, but the conditions under which it
takes place being different, the immediate results are to a certain
extent different also. *
When a vegetable substance is burned in the air, the oxygen of
the atmosphere is the only material agentin effecting the decompo-
sition. The carbon of the burning body unites directly with this
oxygen and forms carbonic acid.
In the natural process of decay, however, at the ordinary tem-
perature of the atmosphere, vegetable matter is exposed to the ac-
tion of both air and water; these both co-operate in inducing and
carrying on the decomposition, and hence carbonic acid is not, as
in the case of combustion, the chief or immediate result.
A detail of all the steps through which vegetable matter is known
to pass before it is finally resolved into carbonic acid and water,
26S LAW OF THE DECAY QF VEGETABLE MATTER.
would be difficult for you to understand, and is here unnecessary.
A general view of the way in which, by the united agency of air and
water, the decay of organic substances is effected and promoted,
may be made very intelligible, and will sufficiently illustrate the
subject for our present purpose.
1°. In combustion, as we have said, the whole of the vegetable
substance is resolved directly into carbonic acid and water, at the
expense of the oxygen of the atmosphere. In matural decay a
Small and variable proportion only is so changed by the direct ac-
tion of the oxygen of the air, but to the extent to which this change
does take place, carbonic acid is directly formed and sent up into
the air. -
2°. But the elements of the substance itself are often sufficient
to supply the means by which its carbon can be made again to rise
into the atmosphere in the gaseous state. Thus
w C. H. O.
1 of grape-sugar .................. – 12 12 12
and
6 of carbonic acid.................. - 12 with
6 of light carb, hydrogen (CH2) = 6 12
also make................................. 12 12 12
so that when decomposing in the soil, the elements of grape-sugar
may be resolved into carbonic acid and light carburetted hydrogen,
in both of which forms, the carbon will rise into the air prepara-
tory to its becoming again the food of new races of plants.
3°. Or the elements of water may aid in promoting this kind of
conversion. Thus if to
C. H. O.
1 of cellulose ...... - 24, 21 21
we add 3 of water = I
we have ..................... 24, 22 22
which contains the constituents of two of grape sugar. Like this
substance, therefore, cellulose may in the soil be resolved by the
aid of water wholly into carbonic acid and light carburetted hydro-
gen,
}}Y NATURAL DE(AY IT IS FINALLY RIESOLVEl). 269
49. Or the oxygen of the atmosphere may in some cases be alone
sufficient to induce this kind of change. Thus if to
- C. H. O.
1 of tartaric acid ...... = 4 2 5
1 of oxygen be added = 1
*
The sum...........................4 2 6 is equal to
3 of carbonic acid ............... 3 6 and
1 of light carburet. hydrogen 1 2
4 2 6
It is easy to see how any other of the more common vegetable
productions may—either at the expense of its own elements, as in
grape-sugar—or by the aid of those of water, as in cellulose—or
by that of the oxygen of the atmosphere, as in tartaric acid—be
resolved into carbonic acid and light carburetted hydrogen, in cer-
tain proportions,
Now, these different forms of decomposition really do take place
to a variable extent in nature, during the decay of organic sub-
stances in moist situations. Hence the evolution of light carbu-
retted hydrogen from dead vegetable matter in marshy places and
stagnant pools—hence the production of the same gas in compost
heaps, and especially in rich and heated farm-yard manure—and
hence also its occurrence in such vast quantities in many of our
coal mines.
You will now be able to appreciate one of the reasons why this
light carburetted hydrogen has been supposed by some physiolo-
gists (p. 101,) to contribute as food to the ordinary nourishment of
plants. It is produced in nature in many and varied situations,
and it has been found by experiment to exercise a visible influence
on the growth of plants. Being so produced where young plants
grow, is it never imbibed by them?—being possessed of this influ-
ence, is it entrusted with no control over the general vegetation of
the globe? -
However this may be, by far the greatest proportion of both
these gases escapes into the air;-the carbonic acid to fulfil those
purposes which have already been considered,—the light carburet-
270 INTO CARBONIC ACID AND WATER. --
ted hydrogen to undergo a further change, by which it also is re-
solved into carbonic acid and water. Thus, if to
C. H. O.
1 of light carburetted F | 2 we add
hydrogen.........
4 of oxygen............ - 4
— Carbonic Acid. Water.
We have.... 1 2 4 = CO2 + 2 H O
Or 1 of this gas with 4 of oxygen may be changed into 1 of car-
bomic acid and 2 of water.
Now when this gas escapes into the air it becomes diffused
through a large excess of oxygen, and is thus ready, at any in-
stant, to be decomposed. Through the atmosphere, streams of
electricity are continually flowing, and every wandering spark that
passes athwart a portion of this mixture decomposes so much of
the light gas, and produces in its stead the equivalent proportions
of carbonic acid and watery vapour. Thus it happens that, of the
vast quantity of this and other combustible gases which are conti-
nually escaping into the air, so few traces have hitherto been made
discernible even by the aid of the most refined processes of art.
By a wise provision of nature such substances as are void of use
to either animals or plants, if not speedily removed from the air
altogether, are there converted into such new forms of matter as
are fitted to minister to the necessities of living beings.
Though therefore in the matural decay of vegetable matter in
the presence of air and moisture, a portion of its carbon escapes
into the air in the form of light carburretted hydrogen—this com-
pound is but a step towards the final change into carbonic acid and
water. In the soil the vegetable matter is continually undergoing
decay, various substances are produced in greater or less quanti-
ty, some solid, some liquid, and some gaseous, like the light gas
of which we have been speaking, but all of them, like this gas,
are only hastening—some by one road, so to speak, and some by
another—towards that final destination which sooner or later they
are all fated to reach ; when, in the form of carbonic acid and
water, they shall be in a condition to minister again to the nou-
rishment of all plants.
While in the soil, some part of this vegetable matter assumes
SUPPLY OF CARBONIC ACID FROM THIS DECAY. 271
forms in which, without further decomposition, it is capable of en-
tering again into the roots, and of being converted by the living
plant into portions of its own substance. The nature and com-
position of these forms of matter, so far as they are known, have
been considered in a preceding lecture (p. 68 et seq.) In compo-
sition they approach so near to that of the several substances of
which the living plant consists—that it is unnecessary to dwell upon
the mode of their production. The crenic acid, for example, which
is one of those which have undergone the greatest change, may
be produced from cellulose solely by the intervention of the
oxygen of the atmosphere. Thus
C. H. O.
1 of cellulose.................. = 24 21 21
4 of oxygen...... & e e s e e s e s e s e - 4
make ............ 24 21 25
which is equal to 1 of crenic acid, C24 H12 Olg, and 9 of water.
So that this acid may be produced from cellulose by the absorp-
tion of oxygen and the separation of water.
But if not taken up by the roots of plants, this and all similar
compounds undergo further changes, and are ultimately resolved
into carbonic acid and water.
It is upon this final result of the natural decay to which all ve-
getable matter is subject, that the atmosphere depends for its larg—
est supplies of carbonic acid. The rapidity with which organ-
ized bodies perish, and become resolved into gaseous compounds
depends partly upon the climate, and partly on the nature of the
substances themselyes, but all hurry forward to the same end,
and it is with difficulty that we are able for a time to arrest or
even to retard their steps. It is by this perpetual and active obe-
dience of all dead matter to one fixed law that the existing condi-
tion of things is maintained ;--and thus it happens that either by
the respiration of the animals which live upon it, by the process of
combustion, or by that of spontaneous decay, the entire crop of
vegetable produce is apparently, year by year—taking the average
of a series of years—resolved into the forms of matter from which
it was originally built up ;-and the substances on which plants
feed at length restored to the air in the precise proportion in which
they have been taken up from it.
272 EVOLUTION OF THIS ACIL) JN WOLCAN TO COUNTRITS.
IV. ——NATURAL EVOLUTION OF CARBONIC ACID IN WOT,CANIC
COUNTRIES. ..
The above apparent conclusion would be absolutely true, were
there no causes in operation by which the restoration to the air of
a portion of the carbon of animal and vegetable substances is pre-
vented—and were there no other sources, independent of existing
organic matter, from which carbonic acid may be supplied to the
air.
If the whole of the carbon of plants be not returned to the air,
the carbonic acid of the atmosphere may be undergoing dimi-
nution; while—if a large supply be constantly poured into the air
from sources independent of vegetable matter, the proportion of
carbonic acid may be continually on the increase.
We have seen that the combustion of fossil coal adds to the air
a large quantity of carbonic acid which has never before existed in
the atmosphere of our time. In many volcanic districts also, car-
bonic acid is observed to issue in large quantity from cracks and
fissures in the earth;-accompanied sometimes by water, forming
mineral springs, from which the copious emission of gas is readily
perceived;—more frequently, perhaps, rising up alone, and thus
escaping general observation.
It must obviously be exceedingly difficult to estimate the quan-
tity of gas which rises into the air in such circumstances over an
extensive tract of country, fractured and broken up by volcanic
agency—where the outlets are numerous, and the rate at which
the gas escapes very variable. That in many localities it must be
very great, however, there can be no question. In the ancient
volcanic district of the Eifel,-comprising an area of many square
miles around the Laacher See, on the left bank of the Rhine,—the
annual evolution of carbonic acid from springs and fissures has
been estimated by Bischoff at not less than 100,000 tons, contain-
ing 27,000 tons of carbon. In many other districts, especially
where active volcanoes exist, the volume of gas given off may be
quite as great, though no attempts have hitherto been made to es-
timate its real amount.
Yet, though absolutely large, the quantity of carbonic acid dis-
engaged in this way from the earth is really small when compared
either with the entire quantity supposed to be present in the at-
CARBON PERMANENTLY WITH DRAWN FROM THE AIR • 273
mosphere, or with that which is required for the growth of the
yearly vegetation of the globe. Suppose that from a thousand
spots on the earth's surface a quantity of carbonic acid equal to
the above estimate of Bischoff escapes constantly into the air, the
weight of carbon (27 millions of tons) thus diffused through the
atmosphere would be only twice as much as that contained in the
coal which is annually consumed in Great Britain alone. .
Still if the whole of the carbon contained in the produce of the
general vegetation of the globe be ultimately restored to the air—
either by the respiration of animals, by the natural and slow decay
of vegetable matter, or by the more rapid process of combustion,
—the constant addition of carbonic acid derived from volcanoes,
and from the combustion of fossil coal, should gradually, though
slowly, augment the proportion of this gas in the air we breathe;
unless it be perpetually undergoing a permanent diminution, to
at least an equal extent, from the operation of other causes. In
reference to this point there are three circumstances which are pro-
per to be considered:—
1°. It has been observed that, as we recede from the land and
approach the centre of great lakes, or sail into the open sea, the
quantity of carbonic acid in the air gradually diminishes. It is
therefore inferred that the sea is constantly, and to a sensible ex-
tent, absorbing carbonic acid from the atmosphere, without after-
wards restoring it, so far as is yet known, by any compensating
process. - *
2°. The waters which flow into the sea or into great lakes con-
stantly beardown with them portions of animal and vegetable matter.
These fall along with the mud which the waters hold in suspen-
sion, and are permanently imbedded in the deposits of clay, silt,
and sand, which are continually in the course of formation.
3°. In many parts of the world, especially in the latitudes North
and South of 45°, vegetable matter accumulates in the form of
peat, becomes buried beneath clay and sand, and thus is prevented
from undergoing the ordinary process of natural decay. - *
It is impossible to say how much carbon is permanently with-
drawn from the atmosphere by these several agencies. There is
reason to believe that it is quite as great as the quantity added to
the air by the combustion of coal, and by the evolution of carbo-
S
274 CONCLUSIONS AS TO THE SUPPLY OF CARBONIC ACID.
nic acid in volcanic districts. Indeed the supply from these two
sources is only a giving back of a small portion of that carbonic
acid which is abstracted from the air by the agencies just stated,
and which have been in operation during every geological epoch.
Conclusions.—The general conclusions, therefore, which we seem
justified in drawing in regard to the supply of carbonic acid to the
atmosphere—are as follow :—
1°. That a large portion of the carbonic acid absorbed by plants
is immediately and directly restored to the air by the respiration
of the animals which feed upon vegetable productions (p. 264).
2°. That a still larger portion is more slowly returned by the
gradual re-conversion of vegetable substances into carbonic acid
and water, during the process of natural decay (p. 267).
3°. That nearly all the remainder is given back in the results
of ordinary combustion (p. 265).
4°. That a further portion, which has not previously existed in
the atmosphere of our time, is conveyed to it by the burning of
fossil fuel (p. 267), and by the emission of carbonic acid from
cracks and fissures in the surface of the earth (p. 272); yet that
the quantity added from all these sources cannot be supposed to
exceed that which is constantly and permanently separated from
the atmosphere by other causes (p. 273).
The balance of all the evidence we possess is probably in favour
of the opinion that the carbonic acid in the atmosphere is slowly
diminishing; we have, however, no satisfactory evidence either
from theory or experiment that it has undergone any sensible di-
minution in our time.
§ 4. Of the supply of Ammonia to plants.
In a previous lecture it has been shown that in our cultivated
fields plants derive a portion of their nitrogen from the manure
which is added to the soil. But the quantity of this element pre-
sent in the manure, supposing it all taken up and appropriated by
the plant, is seldom equal to that contained in the series of crops
which this manure assists in raising,
Thus in the experiments of Boussingault already described (p.
259), the crops from the first course contained #, from the second
}*r
PROPORTION OF AMMONIA IN THE AIR. 275
3, from the third #, and from the artichokes # more nitrogen than
was present in the manure laid upon the land.
Whence is this excess of nitrogen derived, and in what form does
it enter into the plant? Liebig replies to these questions—that
the whole of the nitrogen absorbed by plants enters into them in the
state of ammonia—that the atmosphere is the great store-house in
which the perpetual supply of ammonia resides—and that the ex-
cess above what is present in the manure is drawn in this form
either from the soil or from the air. This opinion, advanced by
so high an authority, demands our attentive consideration.
I. Ammonia has been detected in many clays and iron-ores, and
traces of it may be discovered in most soils, but it is not known to
be a naturaſ or essential constituent of any of the solid rocks of
which the crust of the globe is composed. These clays and soils,
therefore, may be supposed to have derived their ammonia from
the atmosphere; and Liebig ascribes the fertilizing action of the
air upon stiff clays when fallowed, of burned clay when applied as
a top-dressing, and of gypsum on grass lands (see p. 83, note), to
the larger quantity of ammonia which the surface of the soil is by
these means caused to absorb and retain.
There is no doubt but ammonia is present in the atmosphere in
small and variable quantity. Its presence may be detected in the
rain and snow that falls, and even from the air itself it may be
extracted in appreciable quantity.
The only experiment to determine the absolute quantity of am-
monia in the atmosphere hitherto published was made by Graeger.
He caused a measured quantity of air to pass through dilute mu-
riatic acid, and estimated the amount of ammonia obtained by the
acid. In this way he concluded that five million pounds of air con-
tain three pounds of carbonate of ammonia.” This determination,
however, is open to correction and confirmation.
But whence is this ammonia derived, and is its quantity suffi-
cient to supply the demands of the entire vegetation of the globe 2
When animal substances undergo decay, nearly all the nitrogen
they contain is ultimately separated from their other constituents in
the form of ammonia. During the decay of plants also, a portion
of their nitrogen escapes in the state of ammonia. Of the ammo-
mia thus formed much ascends into the air, chiefly in combination
"Chemical Gazette, Jan, 1846, p. 34,
276 IIOW DECOMPOSED IN THE AIR.
with carbonic acid as carbonate of ammonia (smelling salts), and
much remains in the soil. Were the whole of the nitrogen, con-
tained in plants and animals, to assume the form of ammonia when
they decay, and to remain in the soil or in the air, it would always
be within the reach either of the roots or of the leaves of living
races; and thus the same ammonia" might again and again return
into the circulation of new vegetable tribes, and be always alone
sufficient to supply all the demands of the existing vegetation of
the globe. But, . .
1". Of the ammonia thus formed, a portion is daily washed from
the soil by the rains and carried to the Sea, and much more, pro-
bably, is washed from the air by the waters of the sea itself, or by
the rains which fall directly into the wide oceans; and we know
of no compensating process by which this ammonia can be again
restored to the air, and a second time made useful to vegetation.
2". Besides, of that which still remains in the air much must
undergo decomposition by natural processes. In treating in a pre-
ceding section of the evolution of light carburetted hydrogen dur-
ing the slow decay of vegetable matter (p. 270), I have explained
how, in consequence of its admixture with the oxygen of the at-
mosphere, this gas is finally decomposed with the production of
carbonic acid and water. Ammonia, in like manner, will burn in
oxygen gas, and when mixed with atmospheric air may be decom-
posed by the electric spark—water at the same time being formed
and nitrogen set free. Thus, if with
N. H. O.
1 of ammonia = 1 3 we mix
3 of oxygen – 3 we have
*-ºsmºmºsºmºmºmºs 3 of Water. I of Nitrogen.
the sum 1 3 3 – 3 H O –– N
or, when diffused through the air, 1 of ammonia, with the aid of
3 of oxygen, will yield 3 of watery vapour, while the nitrogen mayf
mingle with the air in an elementary form. *
Can we doubt that ammonia is thus decomposed in the air 2 Not
to speak of other forms assumed by the electricity of the atmo-
* Or ammonia containing the same nitrogen—supposing the hydrogen to have been
changed. -
+ I say may, because it may at the same time combine with oxygen and form nitric
acid.—See the following section, p. 284. -
AMMONIA EVOLVED FROM VOLCANOES. 277
sphere, can the thunder storms of the tropical regions pass unheed-
ed the ammoniacal vapours they may be supposed to meet with in
their course 2
I conclude, them, that of the ammonia which is formed from the
nitrogen actually existing in animal and vegetable substances dur-
ing their decay, only a comparatively small portion ever returns
again to minister to the wants of new races.
Of that which does return also, and is again absorbed, a portion
is subsequently decomposed in the interior of living plants, as is
shown by the evolution of nitrogen from the common leaves of
Some and from the flower leaves of others.
II. But if plants obtain all their nitrogen from ammonia," how is
this waste repaired—whence are new supplies constantly derived 2
We have seen that, in certain volcanic countries, carbonic acid
is evolved in vast quantities from rents and fissures in the earth.
In some of these districts—and this has been observed more espe-
cially in Italy and Sicily, and it is said also to some extent in
China—ammonia is likewise given off, in combination generally
with some acid, and most frequently with the muriatic acid in the
form of sal-ammoniac (muriate of ammonia). “ This ammonia,”
Liebig is correct in saying, “ has not been produced by the animal
organism ;” but he assumes a very doubtful position when he adds:
—“ it easisted before the creation of human beings ; it is a part, a
primary constituent of the globe itself.”f
Where, we might ask, has this ammonia existed during all past
time—from what deep caverns of the earth does it now escape P
This opinion of Liebig, as well as the paramount influence he
ascribes to ammonia over the vegetation of the globe, are based
chiefly on the fact that we know of no means by which ammonia
can be formed by the direct union of the hydrogen and nitrogen of
which it consists.
But the production of ammonia, by the indirect union of these
* “Wild plants obtain more nitrogen from the atmosphere, in the form of ammonia,
than they require for their growth, FOR the water which evaporates through their
leaves and blossoms emits, after a time, a putrid Smell—a peculiarity possessed only
by such bodies as contain nitrogen.”—Liebig, Organic Chemistry applied to Agricul-
ture, p. 85. Does the fact here stated, justify the conclusion which appears to be
drawn from it 2
+ Chºnistry applied to Agriculture, p. 112.
27S PRODUCTION OF AMMONIA DURING THE
elements, is daily going on in nature, and can even be effected by
different processes of art. Thus—
1°. When organic substances, which contain no nitrogen, are
oxidised in the air, ammonia is not unfrequently formed (Berze-
lius). Hence it must be produced in unknown quantity during the
annual decay of all vegetable substances.
There are two ways in which this production of ammonia takes
place in the soil.
a. At the expense of the hydrogen of the organic matter it-
self.
Thus when cellulose, during its decay in the soil, is changed at
the expense of its own elements into ulmic acid—carbonic acid and
water are produced, but at the same time hydrogen is set free.
Thus—
C. H. O.
1 of ulmic acid, a = 40 14 12
8 of carbonic acid = 8 | 6
and 14 of water -- 14 14
Make tº º ſº & º & 48 28 42
Deduct this sum from 2 of 48 42 42
cellulose,.......................
And there remain 14 of hydrogen.
This hydrogen unites in part with the oxygen of the air to
form water, but partly also at the moment of its liberation with
the nitrogen of the air, and produces ammonia, which combines
with the ulmic acid. The exact change above represented may
never take place in nature, but changes of a similar kind do, and
hence the reason why we never find any of the humic or ulmic acids
entirely free from ammonia. *
Again in the further change of the ulmic or humic into the
crenic or apocrenic acids in the soil, an additional separation of
hydrogen takes place, accompanied by the production of ammonia.
Thus if
* See Mulder's Chemistry of Animal and Vegetable Physiology, p. 164.
DEGAY OF ORGANIC MATTER. 279
C. H. O.
1; of humic acid, c = 48 18 18
Take 6 of oxygen from ) - 6
the air
Making 48 18 24
And if from this beformed = 48 12 24
1 of apocrenic acid
There will remain 6 of hydrogen to
be worked up in the production of water, or of ammonia, or of both,
by combination with the oxygen and nitrogen of the atmosphere.
This conversion of humic acidinto apocrenateof ammonia(apocrenic
acid and ammonia), can be performed artificially by treating humic
acid with nitric acid, there is every reason to believe, therefore,
that a similar conversion takes place in the soil by the agency of
the air.
b. Or it may be formed at the expense of the hydrogen of
the water, with which the organic matter is in contact. This
process is very simple and easy to be comprehended. Thus—-let
humic acid decompose water, and take up its oxygen, and we
may have
C. H. O.
# of humic acid c = 8 3 3 decomposing
13 of water = 13 | 3
8 16 16 and giving off
8 of carbonic acid – 8 16
And leaving 16 of hydrogen
to combine with nitrogen to form ammonia.
In one or other of the ways above indicated, the production of
ammonia through the agency of the organic matter in the soil is
continually going on.
2°. When inorganic substances are oxidised in the presence of
air and water—as when moist iron filings are exposed to the air
(Chevallier), and, generally, when iron oxidizes in the open air—
or when certain oxidised substances are decomposed in the air by
means of potassium (Faraday),—or when metals, such as tin fil-
280 INDIRECT PRODUCTION OF AMMONIA.
ings, are rapidly oxidised by means of nitric acid,—in all these
cases, ammonia is produced in variable quantity. Hence the absorp-
tion of oxygen, even by the inorganic substances of the soil, may
give rise to the formation of ammonia. But -
3°. The fact which most clearly illustrates the production of
ammonia in nature, both on the surface of the earth, in the soil,
and far in the interior near the seat of volcanic fires, is this, that
if a current of moist air be made to pass over red hot charcoal,
carbonic acid and ammonia are simultaneously formed.” This is
in reality only a repetition in another form of what takes place, as
above stated, when vegetable matter decays, or iron filings rust in
moist air. The carbon and the iron decompose the watery vapour
in the air, and combine with its oxygen, while, at the instant of its
liberation, the hydrogen of the water combines with the nitrogen
of the air, and forms ammonia.f ..
The source of the ammonia evolved in volcanic districts, there
* This experiment is easily performed by drawing a current of mixed atmospheric
air and steam through a red hot gun-barrel filled with well burned charcoal, and
causing the current, on leaving the barrel, to pass through water acidulated with mu-
riatic acid. After a time, the water, on evaporation, will be found to contain traces
of sal-ammoniac. What thus takes place in a small experiment of this kind must
more readily and more largely take place in the interior of the earth, where combus-
tible substances at a high temperature happen to be exposed to a current of atmo-
spheric air, mixed with watery vapour. -
f Berzelius found ammonia even in the compact iron ore (magnetic oxide) of
Dannemora. It is probable, therefore, that wherever iron exists in the earth in the
state of first oxide, it slowly decomposes water if within its reach, appropriating the
oxygen, and permitting the hydrogen to form ammonia with the nitrogen of the impure
air which surrounds it. w .
A beautiful illustration of the tendency which elementary substances have to unite
with each other at the instant of their liberation, in what chemists call their nascent
state, is mentioned by Runge-Einleitung in die technische Chemie, p. 337.
If 1 part of hydrate of potash and 20 of iron filings be heated together, hydrogen
only is given off. *-
If l of nitrate of potash and 20 of iron filings be heated together, nitrogen only is
given off. - -
But if 40 of iron filings be mixed with l of hydrate and 1 of nitrate of potash, and
then heated, ammonia becomes perceptible. - -
The nitrogen and hydrogen being given off together, and at the same instant, some
portions of each find themselves in a condition to unite, and thus ammonia is produced.
The same result must follow in many natural operations, when hydrogen and nitrogen
are set free from a previous state of combination, at the same time, and in the pre-
sence of one another.
l
SUPPLY OF NITRIC ACID TO PLANTs. 281
fore, is no longer obscure. The existence of combustible matter,
in such districts, and at great depths beneath the surface, can in
few cases be doubted, and the passage of a mixed atmosphere of
common air and steam over such combustible matter, at a high
temperature, appears to be alone necessary to the production of
ammonia. It is unnecessary, then, to have recourse to doubtful.
speculations in order to account for the natural re-production of
ammonia to a certain extent, in the place of that which is con-
stantly undergoing decomposition by the agency of causes such as
those above described. - -
But is the indefinite quantity of ammonia re-produced by these
indirect methods sufficient to replace all that is lost? Can it
be supposed to impart to plants all the nitrogen they require?
These questions will be considered in the following section.
§ 5. Of the supply of nitric acid to plants.
In regard to the action of nitric acid upon vegetation it is
known, .
1°. That when it is spread upon the soil in the form of the
nitrates of soda, or potash, it greatly promotes the growth and
luxuriance of the crop and increases its produce; and
2°. That, when other circumstances are favourable to vegetation
—as in certain provinces of India—the presence of an appreciable
quantity of these nitrates adds largely to the fertility of the soil.”
* For the following, and other interesting notices, regarding Indian agriculture, I
am indebted to Mr Fleming, of Barochan, in Renfrewshire, whose long residence in
the districts to which he alludes, as well as the interest he takes in practical agricul-
ture, renders his testimony very valuable:– - - -
« The districts of Chaprah, Tirhoot, and Shahabad, near Patna, where a large pro-
portion of the saltpetre sent from Bengal is produced, are considered the most fertile
in Bengal, producing 2 and sometimes 3 crops early. The natives of these districts,
particularly a caste called Quirees (hereditary gardeners), who cultivate the best land,
and produce the best crops, are in the habit of irrigating their fields with water from
wells so strongly impregnated with saltpetre and other salts as to be quite brackish,
and they consider onions, turnips, and peas, most benefited by this irrigation. Grain
crops also grow most luxuriantly on lands yielding saltpetre, where there is enough
of rain within a week or two after the seed is sown, but if a drought follows the sow-
ing, and continues for three weeks or a month, the leaf becomes yellow, and the crop
fails. -
“The Hindoos do not generally manure their lands, as the dung of the cattle is
282 IT EXISTS LARGELY IN NATURE.
The same effects are unquestionably produced by the addition
of ammonia or by its natural presence in the soil. The beneficial
influence of both compounds, then, being recognised, the relative
extent to which each operates upon the general vegetation of the
globe will be mainly determined by the circumstances and the
quantity in which they respectively exist or are re-produced.
In regard to the existence of nitric acid, it is not known to form
a necessary constituent of any of the solid rocks of which the crust
of the globe is composed, but it is diffused almost universally
through the soil which overspreads their surface. In the hotter
regions of the earth, in India, in Africa, and in South America
(p. 88), it in some places accumulates in sufficient quantity to form
incrustations of considerable thickness over very large areas, in
many more it can be separated by washing the soil, and over still
larger tracts of country, especially in Central Asia, it renders the
waters of deep wells brackish and often unfit to drink. Even in
the climates of Northern Europe, it is rarely absent from the water
of artificial wells, into which the rains, after filtering through the
surface, are permitted to make their way.”
On the whole, nitric acid and its compounds appear to exist,
ready formed in nature, in larger quantity than either ammonia
or any of its compounds.
Of these nitrates, as they do of ammonia, the rivers must be
continually bearing a portion to the sea, but there are in mature
unceasing processes of re-production, by which not only this waste
of the nitrates is repaired, but that further waste, also, which is
caused by their absorption into the roots and subsequent decom-
position in the interior of plants. Let us shortly consider these
processes of re-production.
1°. When a succession of electric sparks is passed through com-
used for fuel, but the Quirees collect the ashes of cow dung and of burned wood, and
use it as a manure in some cases, chiefly for the poppy plant.
“The Hindoos have for ages been well acquainted with the rotation of crops, and
the advantages of fallowing land,-although a great proportion of the land is almost
constantly in rice, Indian corm, or millet, during the rainy season, and in wheat or
peas during the dry season.”
* It occurs in the wells of the neighbourhood of Berlin (Mitscherlich), in the
form of nitrates of potash, lime, and magnesia in the wells around Stockholm, and
may be expected in all wells that are dug (Berzelius.)—Traité de Chemic, iv. p. 71.
NITRIC ACID FORMED IN THE AIR, 283
mon air, nitric acid (NOs) is slowly but sensibly formed. This
was discovered in the early experiments that were made for the
production of water by the union of dry oxygen and hydrogen
gases, through the means of the electric spark. Monge, in 1783,
found 5 grains of nitric acid in every ounce of water he ob-
tained, while de Genean, in 2 lbs. 3 ounces of water, found 27
grains of nitric acid.” This acid was produced by the union of
oxygen with a quantity of nitrogen which must have been present
in the mixed gases. -
The currents of electricity which in mature traverse the atmo-
sphere must produce the same effect, and the passage of each flash
of lightning through the air must be attended by the formation of
some portion of this acid.
After a thunder storm plants appear wonderfully refreshed.
In thundery weather they grow most luxuriantly, and other things
being equal, those seasons in which there is most thunder are ob-
served to be the most fruitful. Some have ascribed these results
to the immediate agency of electricity on the growth of plants.f
Is it not equally possible that they may be connected with this
necessary production of nitric acid P
In the rain which fell during 17 thunder storms, Liebig found
nitric acid always present, and generally in combination with lime
and ammonia. In the rain which fell on 60 other occasions, he
could detect it only twice. In a storm which visited the town of
Nismes in June 1842, the hail which fell was actually sour with
mitric acid. In minute quantity mitric acid is difficult to detect,
how much, them, must be formed in a single thunder storm, even
in our climate, to make the presence of this acid appreciable in the
rain or hail that falls—how vast a quantity, year by year, in those
warmer climates where such storms are so frequent and so ap-
palling !
In the equinoctial zone, according to Boussingault," a succes-
sion of electric discharges is taking place every day, and perhaps
at every instant, throughout the whole year. Were an observer,
* Black's Lectures, ii. p. 236.
+ Sprengel, Chemie I. p. 99.
† Journal de Pharmacie, April 1845.
§ Am... de Chim, et de Phys, lvii. p. 180.
284 NITRIC ACID FORMED AT THE EXPENSE OF AMMONIA.
possessed of organs sufficiently sensible, to be placed upon the
equator, the noise of thunder would never seem to cease. How 6
large must be the production of nitric acid at this part of the
globel - - *
2°. When a mixture of ammonia and oxygen gas is exploded
by passing an electric spark through it, a quantity of nitric acid
is formed, even when the oxygen is not sufficient to oxidise the
whole of the ammonia" (Bischoff.) Hence, if in the air, as we have
seen reason to believe, the ammonia given off from decaying ani-
mal matters, and from other sources, be decomposed by the at-
mospheric electricity, there will necessarily be formed at the
same instant a portion of nitric acid, at the expense of the nitrogen
of the ammonia itself. This nitric acid will, as necessarily, com-
bine with some of the ammonia which still remains in the air.
Hence the existence and production of nitrate of ammonia in the
atmosphere, and the consequent presence of this acid along with
ammonia in rain water. -
Thus the very cause which in the preceding section was shown
to operate in constantly diminishing the amount of ammonia in the
air, and the operation of which certainly renders improbable the
existence of this compound in the atmosphere in the large quan-
tity supposed by somet—this same cause is at the same moment
constantly re-producing nitric acid. And, though much of what
is thus produced must necessarily, as in the case of ammonia, be
carried down to the sea by the rains, or be directly absorbed by
the waters of the ocean themselves, yet it is obvious that in what-
ever proportion we may suppose the ammonia of the air to reach
the leaves and roots of plants—in no less proportion must the ni-
tric acid, with which it is associated, be enabled to enter into the
circulating system of the various tribes of living vegetables, that
flourish on every quarter of the globe. -
3°. Again we have seen that, during the decay of vegetable
substances in moist air, ammonia is formed at the expense of the
# It was shown above (p. 276), that l of ammonia NH3 requires 3 of oxygen to
decompose it, forming 3 of water, and setting the nitrogen free. But, in reality, as
Bischoff has shown, the nitrogen is not wholly set free, but a portion both of the hy-
drogen and nitrogen of the ammonia combine with oxygen (are oxidised) at the same
instant, forming simultaneously both water (H O) and nitric acid (N Os)
º + See especially Liebig's Organic Chemistry ºpplical to Agriculture, p. 74.
ARTIFICIAL NITRE BEDS. 2S5
hydrogen of the water and of the nitrogen of the air. In conse-
quence of, or in connection with such decay, nitric acid is also
largely produced in mature.
The most familiar, as well as the most instructive example
of this formation of nitric acid is in the artificial nitre-beds of
France and the North of Europe. These are formed by mixing
earth of different kinds with stable manure or other animal and
vegetable matters, and exposing the mixture to the air in long
ridges or conical heaps, which are occasionally watered with liquid
manure, and turned over to expose fresh portions to the air.
After a time, perhaps once a year, the whole is washed, when the
water which comes off is found to contain a variable quantity of
the nitrates of potash, soda, lime, and magnesia, which are em-
ployed for the manufacture of saltpetre. In these nitre-beds it
has been observed that the production of nitric acid either does not
take place at all, or does so with extreme slowness, unless animal
and vegetable matter be present in considerable proportion. And
yet the quantity of nitric acid which is formed is much greater
than could be produced by the oxidation of the whole of the ni-
trogen contained in the organic matters present in the mixture.”
It is also observed that the nitre-beds are more productive when
a portion from one outer face of a heap is lixiviated from time to
time, and the washed earth added to the other side, than when the
whole is lixiviated at once, and again formed into a heap and ex-
posed to the air.
It appears, therefore, that organic matters are in our climate
necessary to cause the formation of nitric acid to commence, but
that after it has begun it will proceed in the same heap for an in-
definite period, and at the expense apparently of the nitrogen of
the air only.
Compost heaps are in many cases only artificial nitre-beds,-
often unskilfully prepared and badly managed,—producing, how-
ever, a certain quantity of nitrates, to the presence of which their
effect on vegetation may not unfrequently be ascribed. To this
fact we shall hereafter recur.
* Dumas Traité de Chemie II., p. 725. He adds, that 100 lbs. of nitre contain
the nitrogen of 75 lbs. of ordinary animal matter, supposed in a dry state, or of 300
or 400 lbs. in its ordinary state of moisture, a much greater relative proportion of
animal matter than is ever added to the heap.
286 NITRE CAVES OF CEYLON AND NORTH AMERICA.
The soils, in the plains of India, and in other similar spots in
the tropical regions, may be regarded as natural nitre-beds, in
which, the decay of organic matter being vastly more rapid than in
our temperate regions, the production of nitric acid is rapid in
proportion.” According to Humboldt the production of mitre is al-
ways the most abundant when the soil is most fertile.
4°. But in many localities in which the presence of organic mat-
ter is not to be recognised in sensible quantity, the production of
this acid is observed to proceed with a constant and steady pace.
Thus, from the walls of certain caves in Ceylon a layer is yearly pared
off, which yields an abundant crop of saltpetre (Dr John Davy).
The celebrated Mammoth cave in Kentucky, situated in a lime-
stone ridge, yields an inexhaustible supply of nitrate of lime. Dur-
ing the war with Great Britain fifty men were constantly employed
in lixiviating the earth of this cave, and in about three years the
washed earth is said to become as strongly impregnated as at first.
Through the cave a strong current of air is continually rush-
ing—inwards in winter and outwards during the summer months.
On the plaster of old walls, especially in damp situations, an ef-
florescence of this and other mitrates is frequently observed
over every part of Europe. In China, according to Davis, the
old plaster of the houses is so much esteemed as a manure, that
parties will often purchase it at the expense of a coating of new
plaster.f Old clay walls, and especially the walls of clay-built
huts, are said to be very fertilizing to the land, when applied as a
top-dressing. The old cottages in the Carse of Gowrie are built
of clay. When these are taken down the clay forms an excellent
top-dressing for oats. Laid on the lea and ploughed in it is said
* We are as yet too little acquainted with the natural history of the district of
Arica in South America, in which, as already stated (p. 88), the nitrate of soda has
been accumulated in such large quantity—to be able to say to what special cause the
accumulation is due. But as, from the description of Mr Darwin, the locality appears
to have been the site of an ancient lake, it is not unlikely that the nitrate may have
been derived from the successive washings of a soil similar to that of India, by rains
or periodical floods which for a long period emptied themselves into or fed the lake.
+ The Ichulin make their own gunpowder. The nitre they obtain from the dust
of the ruined villages in their country, and the sulphur from the shores of the Dead
Sea. Robinson's Palestine, ii. p. 469.
Lumps of nitre were scattered along the base (of the ridge of salt on the S. W. of
the Dead Sea), of which we picked up several, one as large as the fist, p. 492.
6
º
sº
NITRIC ACID FORMED IN THE SOIL. 287
to be equal to dung. In some parts of England, where the land is
poor, the people are said to pile up the soil in the form of walls, in
order to improve its quality. These latter facts seem to indicate
that both in China and in England nitric acid is produced in simi-
lar circumstances, and that to its production the fertilizing action
of the old plaster, of the old clay walls, and of the weathered clay,
is alike to be attributed.
In the cultivated soil also, this acid is formed in ordinary cir-
cumstances. Braconnot found nitrate of potash in the botanic
garden at Nancy, in a portion of soil in which poppies (papaver
somniferum) had grown luxuriantly for ten years in succession—
in larger quantity in the soil surrounding the interlaced roots of
an esclepias incarnata, growing in an ordinary flower-pot, with a
hole in the bottom—as well as in moss earth, in which a plant of
euphorbia breoni had been grown in a pot.” There is little reason
to doubt, indeed, that nitrates are to be found, in greater or less
quantity, in all cultivated soils.
I shall not enter into a detailed inquiry how this nitric acid is
formed. It is probable that as in the atmosphere ammonia may
be decomposed and give rise to the formation of nitric acid, so in
the soil this acid may result from a similar decomposition, proceed-
ing more slowly, but according to the same natural laws. In
warm climates, indeed, it appears certain that the ammonia which
is evolved or formed during the decay of animal and vegetable
substances, does speedily, and to a great extent, undergo oxida-
tion, and thus give rise to the greater abundance of nitric acid
with which the tropical soils abound.
Thus, in the economy of nature, much ammonia is decomposed
in the soil also, and hence another cause,_in addition to those al-
ready detailed in the preceding section,-for the constant diminu-
tion of the quantity of this compound which exists in nature at
any given time. -
But, besides the portion of this nitric acid, which owes its exist-
ence to the decomposition of ammonia, much—by far the greatest
* Am. de Chem. et de Phys., lxxii., p. 33 to 35.
+ For the perfect oxidation of 1 of ammonia, mo less than 8 of oxygen are required.
Thus—
1 of Ammonia 1 of Nitric Acid. 3 of Water
N H a + 8 O = N 0 + 3 H 0.
28S QUANTITY IN WHICH IT IS RE-PRODUCED.
portion, in all probability—derives its origin from the union of the
elements of the atmosphere itself. This direct union is effected in
the air, as has been already shown, by the agency of atmospheric
electricity; but it also takes place in the soil during the oxidation
of the other elements, contained in the organic matters which are
there undergoing decay. The combination of the elements of
ammonia in such circumstances proceeds on the principle—that
bodies, themselves undergoing oxidation, dispose other substances
also which are in contact with them (in this instance the nitrogen of
the air), to unite with oxygen. The presence of lime, potash, soda,
&c. in the soil, further induces to this oxidation,-in consequence of
the tendency of these substances to combine with the mitric acid,
which is formed by the union of the elements of which it consists.
It is impossible, precisely to estimate the quantity of nitric acid
produced in these various ways, through these various agents, and
in these varied circumstances;–or to balance it accurately against
the amount of ammonia continually re-produced, as we have seen,
in mature, wherever the necessary conditions present themselves.
But, as I formerly concluded, that the amount of nitric acid ac-
tually existing in the Superficial deposits of our globe, is greater
than that of ammonia—so I think that, in regard to the re-produc-
tion also of these two compounds, the balance is in favour of the
former.”
* I may introduce in this place another consideration, which is not without its
weight in reference to the supply of nitrogen to plants. It is not impossible that in
ºnoist air nitric acid and ammonia may be simultaneously produced by the same
electric current.
Were the atmosphere perfectly free from watery vapour, nitric acid alone would be
formed by the passage of electricity through it—and ammonia, if already present,
would, as above described, be decomposed by it. But the air is never free from mois.
ture, and the same spark which combines the nitrogen and oxygen to form nitric
acid will or may decompose a portion of the watery vapour into its elements, oxygen
and hydrogen. At the moment of their liberation (in their nascent state, as it is
called,) these elements may simultaneously unite with nitrogen—the one to form ni-
tric acid, and the other to form ammonia, and these two compounds again may com-
bine to form nitrate of ammonia. Thus, 2 equivalents of nitrogen (2 N) with 2 of
oxygen from the atmosphere (2 O) and 3 of water (3 H 0), would give l of nitric acid
and 1 of ammonia.
Nitric Acid. Ammonia.
2 N + 2 O + 3 H O = N Os + N H3
The nitric acid being formed partly at the expense of the oxygen of the air, and partly
of that of the water.
EXTENT OF DOMINION OF THE NITRATES. 289
Since then, nitric acid is fitted, by the solubility of its compounds,
to enter into the circulation of plants in almost any quantity—
since, when applied to them, it does undoubtedly promote, in a re-
markable degree, the growth of plants—and since, in nature, it is
continually reproduced in every country, and under such varied
circumstances—I cannot withhold myself from the conclusion,
that, over the general vegetation of the globe, it holds with ammo-
nia at least an equal sway, and is appointed to exercise at least an
equal influence over the growth of plants, both in their natural and
in their cultivated state.
Still the influence of each is not unvaried by locality or by cli-
mate. The extent of dominion exercised by the nitrates probably
diminishes as we recede from the equator, while that of ammonia
increases, it may be in an equal proportion. The reason of this
probable variation will appear in the following section.
§ 6. Theory of the respective action of nitric acid and of ammonia
wpon vegetation.
These two compounds act so far in a similar manner that they
may both be supposed to yield a direct supply of nitrogen to the
plants into which they enter. They do so, however, under condi-
tions which may be considerably different, and may be attended by
unlike chemical changes,
Is—THEORY OF THE ACTION OF NITRIC ACID.
1°. The mitric acid of the nitrates after it enters into the circu-
Again, with the aid of an atom of water (H O), also derived from the air, this nitric
acid (N 05) and ammonia (N Ha) would readily form nitrate of ammonia (N Ha +
N 05 + H O), and thus not only the presence of this compound in rain water, but
its actual production in the atmosphere would be accounted for,
There remains but one difficulty. In the text I have argued that the ammonia
which ascends from decaying animal substances, in the form of carbonate, would be
in part at least decomposed by the electricity of the atmosphere. Now supposing
this electricity to give rise, as above described, to the production of nitrate of ammo-
nia, what will be the after or secondary action of succeeding electric currents upon
the nitrate so formed : will it decompose it again P If so, to what extent 2 What
proportion of that which is formed will escape this decomposition and be brought to
the earth by the falling rains? We can only form conjectures as to this point. Some
of the nitrate thus formed, however, may reasonably be expected to escape decompo-
sition.
T
290 ACTION OF THE NITRATES IN THE INTERIOR OF PLANTs.
lation of the roots will ascend to the leaf, and will there be decom-
posed in the same way as the carbonic and other similar acids are,
by the action of the Sun's rays. It is only in the light of day that
carbonic acid is decomposed in the green parts of plants—so must
it be, generally, with the nitric acid which ascends to the leaf. Its
oxygen will be given off, while its nitrogen may be retained in the
circulating system of the plant. The extent to which this decom-
position will take place at each passage of the sap through the leaf
will depend, in some degree, on the nature of the base (whether
potash, soda, or lime) with which the acid is in combination, but
much more on the intensity of the light to which the green parts
of the plant are exposed, and on the temperature of the air in
which the plant happens to grow.
2°. It is still uncertain whether this acid is capable of being de-
composed in the roots or stems of plants where it is excluded from
the light, though it is very probable that it may be so—especially
in cases where the juices or solid parts naturally contain substances
in which hydrogen is present in excess (p. 194), or where such
compounds make their way into the circulation of plants, from the
manure that may be applied to their roots.
Thus in the pines, in which turpentine (C40 H52) naturally
abounds, a decomposition of this latter kind may the more readily
occur, inasmuch as it would not necessarily imply the production
and evolution of any gaseous substance. Thus
1 of oil of turpentine ... = Cao H32 with the oxygen of
1 of nitric acid (NO3). = Os give
1 of resin ................... = Cao Hg2 Os
By uniting with the oxygen of the nitric acid, therefore, oil of
turpentine, in such trees, might be changed into resin during its
passage through the stem, while the nitrogen, being set free, might,
at the moment of its liberation, unite with other elements to form
those protein compounds into which this element enters as a ne-
cessary constituent.
The above must be considered merely as an illustration of the
hind of changes which may possibly take place in the interior of
certain plants, and in the absence of light, when the nitrates hap-
pen to be present. Were I to affirm that such changes actually
HOW THE HYDROGEN OF AMMONIA ACTS. 29 |
do occur in the presence of nitric acid, the theoretical chemist
would have a right to expect that several collateral questions should
be discussed, the consideration of which would here be out of
place.”
3°. The nitrates may also act in another way, which does not
involve the necessity of the total decomposition of the acid they
contain. We know that in nature many substances are capable
of inducing chemical changes in other compound bodies, without
themselves undergoing decomposition. Some beautiful illustra-
tions of this have already been given in a previous lecture, when
treating of the action of sulphuric acid upon cellular fibre and
starch (pp. 188, 189). But the fact which most immediately bears
on the influence of the nitric acid in the living plant, is one observed
by Pelouze,_that by solution in this acid in the cold, starch is
converted into a substance (xyloidine) having the composition of
cellular fibre. In the interior of the plant changes of this kind
may be produced by contact only with nitric acid, so that, without
being itself decomposed, this acid may be materially serviceable
in promoting those molecular changes which are necessary to the
healthy and rapid growth of the plant.
II. — TIIISORY OF THE ACTION OF AMMONIA.
1°. Ammonia is capable of contributing to the growth of the
organic part of the plant, by means of the hydrogen, as well as of
the nitrogen it contains. We have seen (pp. 143 and 240) that, ac-
cording to the results of the best experiments, the whole of the oxy-
gen of the carbonic acid which they absorb is not given off by the
leaves of all plants, even in the sunshine,—while in the dark this gas
is largely and directly imbibed from the air. If in the sap of a plant
there be present at the same time a quantity of ammonia, the hy-
drogen of this ammonia may unite directly with the oxygen of the
carbonic acid, forming water and a proportionate quantity of one
or other of the several compounds (p. 185), which may be repre-
sented by carbon and water. Thus
* Nitrate of soda has been recently found to promote the growth of the spruce fir
when making its shoots. It is not difficult to see how nitric acid in resinous trees
may promote the production of cellular fibre or of true wood.
292 HOW THE NITROGEN OF AMMONIA ACTS.
3 of carbonic acid, = Cs Os and the hydrogen of
2 of ammonia, (N Hs) ~ Hg
- *- # of Grape 3 of
& Sugar. Water.
so that where ammonia and carbonic acid are present, and circum-
stances are favourable, sugar or dextrin or starch may be formed
in variable quantity, without the necessary evolution of oxygen
gas. This change will take place in the interior of the leaf. And,
if the direct decomposition of carbonic acid, and the evolution of
its oxygen by the agency of the Sun, take place at the same time
—with a rapidity proportioned to the intensity of the light—this
simultaneous production of sugar, dextrin, &c., from the pre-
sence of ammonia, must aid the increase and growth of the plant;
and may be one main cause of that fertilizing action of this com-
pound, which has been so long and so generally recognised.
When the hydrogen of the ammonia is thus worked up, the
quantity of oxygen which escapes from the leaf must be less in
proportion; and hence another cause for those discrepancies
which have been observed in regard to the bulk of oxygen given
off, compared with that of the carbonic acid taken in, by the leaves
of different plants (p. 292).
2°. But at the same time the nitrogen is set free. This nitro-
gen will either be again combined in the plant with other ele-
ments for the production of the protein and other compounds;
or, if not required for its healthy growth—that is, if more
largely present than is required by the plant—it will be directly
emitted by the leaves, or sent downwards and permitted to escape
by the root. Hence the reason why pure nitrogen is evolved from
the leaves of some plants (p. 149), and why ammonia exercises a
beneficial action upon vegetation, in cases where all the nitrogen
it contains is neither retained nor required by the plant.
Does this decomposition necessarily require the agency of light?
May it not take place in the absence of the Sun ?
I will mention one or two facts which seem to throw light upon
this point.
a. Plants grow in the dark. Though feeble and blanched they
increase largely in bulk: they must, therefore, have the power of
assimilating their food to a certain extent, independent of the sun's
rays.
MODIFYING EFFECTS OF CLIMATE. 293
b. Several species of Poa, Plantago, Trifolium arvense, Chei-
ranthus, &c., become green in the perpetual darkness of mines,
where hydrogen gas is present in the air (Humboldt).
c. When a little hydrogen is mixed with the air, plants become
greenish even in the dark (Sennebier)—and when exposed to the
sun the green becomes unusually intense in such a mixture (Ingen-
houss).
The immediate and visible effect of an application of ammonia,
or of soot, or of any top dressing containing ammonia, is to ren-
der the green colour much more intense—and in the darkest wea-
ther. It is therefore, probable, I think, that the hydrogen of the
ammonia contributes to this immediate effect, and that the ammo-
nia itself may be decomposed and its elements appropriated to the
nourishment of the living vegetable, either by the unaided vital
powers of the plant, or in the presence of a feeble light only.
Hike water, ammonia is peculiarly liable to decomposition, not al-
ways of that perfect kind which, for the sake of simplicity, I have
endeavoured to explain in the present lecture—yet such as to ren-
der the elements of which it consists available to the general nou-
rishment of the plant. -
§ 7. Comparative influence of nitric acid and of ammonia in dif-
ferent climates.
It follows, from what is above stated, that the beneficial influence
of ammonia upon vegetation will be readily perceived in all cli-
mates in which plants are found to flourish. Its effects will be
greater and more rapid where the heat and light are more in-
tense, only because by these agents the functions of all life are
stimulated.
Not so with the mitric acid in the mitrates. In the presence of
organic compounds, that is, in the sap of the plant, it is less easily
decomposed than ammonia. It appears to require the interference
of more powerful agents—of a higher temperature, or of more
brilliant light,-and thus its efficacy upon vegetation will be more
dependent upon season and climate.
Now we have seen that in tropical countries the nitrates are
produced in the greatest abundance, and there the high tempera-
ture and the brilliant sun should render them most useful to vege-
294, SUPPOSED STIMULATING INFLUENCE OF THESE COMPOUNDS.
tation. Such is well known to be the case, and it may be regard-
ed as one of those bountiful adaptations with which all mature is
full—that in these warmer regions, the ammonia produced in the
soil is first converted into nitric acid, that it may remain fived, and
that this acid again is decomposed by the same agents (light and
heat), when it enters the living plant, and is required to minister
to its growth. On the other hand, it may no less be regarded as
a wise provision that, in colder and more uncertain climates—where
warm and brilliant Summers are less to be depended upon—that
compound of nitrogen (ammonia) should more abound, which is
most easily decomposed in the living plant, which is fitted in com-
parative darkness to yield up its nitrogen, and, by the hydrogen
it contains, to compensate in some slight degree for the partial ab-
sence of the Sun's rays.
From these views, therefore, we should draw this further prac-
tical conclusion—that, in our climate, ammonia is sure to promote
vegetation, and in every season—while the mitrates will produce
their maximum effect, other things being equal, in such only as
have abundant warmth and sunshine. Is this conclusion consistent
with observation ?—will it serve to explain any of the apparent
failures which have occasionally been experienced in the employ-
ment of the nitrates ?
§ 8. Supposed stimulating influence of these compounds.
There remains one other point in regard to the effect of these
two compounds upon vegetation, to which I would request your
attention. We have seen that the quantity of nitrogen contained
in a crop raised by the aid of farm-yard manure is very much
greater than that which exists in the manure itself (p. 274), and
the views just exposed serve to indicate the sources from which the
excess is derived. But suppose that upon two patches of ground,
of equal quality, the one of which is manured and the other not,
equal quantities of the same seed be sown, it is at present believ-
ed to be consistent with experience that the crop reaped from the
mamured portion will not only contain more nitrogen than that
reaped from the ummanured portion, but so much more as shall
considerably exceed that contained in the manure also. Thus sup-
pose the crop raised from the unmanured land to contain 100 lbs.
STIMULATING INFLUENCE OF THESE COMPOUNDS. 295
of nitrogen, and that the manure laid on the other portion contain-
ed 100 lbs. also, the quantity of nitrogen contained in the crop
which is reaped from this latter portion, in favourable seasons, will
exceed, and probably very far exceed, 200 lbs. Hence the effect
of the ammonia, &c., in the farm-yard manure, is not merely to
yield its own nitrogen to the plant, but to enable it, in some way
hitherto unexplained, to draw from other sources a larger portion
of the same element than it would otherwise do.
So also with the nitrates. If two equal portions of the same
grass or corn-field, in early spring, be measured off, and one of
them be top-dressed with nitrate of soda or with saltpetre, the
weight of nitrogen contained in the crop of hay or corn reaped
from the latter will generally—so our present experience says—be
found to exceed that contained in the crop from the former, by a
quantity much greater than that which was present in the nitrate
with which the land was dressed.* In addition, therefore, to the
* The following calculation illustrates the statement in the text :—Mr Gray, of
Dilston, applied nitrate of soda to grass land in the proportion of l 12 lbs. to the acre :
The produce without nitrate amounted to 2 tons 81 stones
with 112 lbs. of nitrate to 3 tons 146 stones
Increase § & tº º 1 ton 65 stones
or 3150 lbs.
And a lºg = 284 lbs. the increase of hay from each pound of nitrate of soda." But al-
Iowing this hay to contain only one per cent. of nitrogen, 28 lbs. will contain 4A
ounces of %itrogen, which is nearly double the quantity actually present in the nitrate
employed.
Again in the case of a crop of grain—Mr Alfred Gyde of Painswick applied 1 cwt.
of nitrate of soda per acre to a field of wheat, and compared the produce with that
from an equal portion to which no top-dressing was applied. He obtained from the
CORN. STRAWV.
Bush. Tons. CW t. lbs.
Nitrated o tº * * 36; ] 12 53
Without nitrate © tº 25 19 26
Excess * * ll & 13 27
The nitrated corn weighed, being newly threshed, 66}, the umnitrated 65% lbs. per
bushel. The excess of corn from the nitrated, therefore, amounted to 760 lbs.
The nitrated wheat, according to Mr Gyde, contained 13, the unmanured 11% per
cent of gluten and albumen. The nitrogen in these substances when properly dried
amounts to 16 per cent. If we suppose the gluten in these experiments not to have
* Dry mitrate of soda contains about 16; per cent of nitrogen, being 19 lbs. to the cwt., or two and
three-fifth ounces to the pound, but as it is usually applied it contains from 5 to 10 per cent, of water.
The nitrogen, therefore, may be estimated at 2% ounces in the pound—or 18 lbs, to the cwt.
296 HOW THIS INFLUENCE IS MANIFESTIED,
nitrogen directly conveyed to the plant by these nitrates, they also
exercise some other influence, by which they enable the living ve-
getable to draw from natural sources a much larger supply than
they would otherwise be capable of doing. What is this influence,
and how is it explained P .
This I suppose to be that kind of influence to which writers on
agriculture are in the habit of alluding, when they speak of certain
substances stimulating plants, or acting as stimulants to their
growth—though the term itself conveys to the mind no distinct
idea of the mode of operation intended to be indicated, or of the
way in which the effect is produced.
In the present case, this special action of ammonia and the mi-
trates, and perhaps also of immediate applications of manure in ge-
neral, appears to arise from their affording to the plant, in its early
youth, a copious supply of food containing nitrogen, by whichitis ena-
bled at once to shoot out in a more healthy and vigorous manner.
It thrusts forth roots in greater numbers, and to greater distances,
and can thus extract nourishment from a greater extent and
depth of soil than is ever reached by the sickly plant—it expands
larger and more numerous leaves, and is thus able to draw from
the air more of every thing it contains, which is fitted to supply
the wants of the living vegetable;—as the stout and healthy savage
been perfectly dry, and to have contained only 14 per cent, of nitrogen, and that the
straw—as found by Boussingault—contained only 4 of a per cent. of nitrogen—we
have the quantity of this element contained in the mitrated above what was contained
in the unmitrated crop represented as follows:—
Nitrogen.
In 760 lbs. of wheat at 13% per cent. of gluten . 16 lbs.
In 1656 lbs. containing 2% per cent of gluten in excess. 6
In 1488 lbs. of straw in excess ſº º e e 5
Total nitrogen = 27 lbs.
But the nitrogen contained in 1 cwt. of nitrate of soda amounts only to about 18
lbs, exactly two-thirds of the quantity, which, in consequence of the presence and ac-
tion of the nitrate, the wheat was enabled to obtain and appropriate—above the quan-
tity appropriated by the wheat in the unnitrated part of the field.
It requires no further proof, therefore, if these experiments are to be depended
upon—to shew that the nitrate of soda and the nitrates must act in some other way in
reference to vegetation, than by simply supplying a portion of nitrogen.
I am bound to add, however, that I do not think the above experiments or any
others yet published have been made with sufficient care, and that I consider the
subject as not only perfectly open to, but as deserving of further rigorous examina-
tion.
l
CONCLUDING OBSERVATIONS. 297
can hunt and fish to supportmany lives, while the feeble or sickly can
scarcely secure sustenance for himself alone. Feed a wild animal
well the first few months of its life, and you may set it loose to
prey for itself; starve it in its infancy, and its growth and strength
will be stunted, and it may lead a wretched and hungry life.
Even in soils, then, and situations, which are capable of yield-
ing to the plant every thing it may require for its ordinary growth
—it is an important object of the art of husbandry to discover what
substances are especially necessary or grateful to particular crops,
and to apply these directly, and in abundance, to the new-born
plant, in order that it may acquire sufficient strength, to be able
to avail itself in the greatest degree of the stores of food which lie
within its reach.
Concluding observations regarding the organic constituents of
plants.
We have now considered the most important of those questions
connected with the organic elements of plants, which are directly
interesting to the practical agriculturist. We have seen—
1°. That all vegetable productions consist of two parts—one,
the organic part, which is capable of being burned away in the air,
—the other, the inorganic part, which remains behind in the form
of ash. -
2°. That this organic part consists of carbon, hydrogen, oxygen,
and nitrogen,_associated, when nitrogen is present, with a minute
proportion of sulphur and phosphorus.
3°. That plants derive the greater part of their carbon from the
carbonic acid of the atmosphere, of their hydrogen and oxygen
from water, and of their nitrogen from ammonia and nitric acid.
4°. That a very large proportion of those substances which form
the principal mass of plants, such as starch, cellular fibre, &c.,
consists of carbon united to oxygen and hydrogen in the propor-
tions in which they exist in water,-Or, in other words, may be re-
presented by carbon and water in various proportions.
5°. That the food on which plants live enters by their roots and
leaves, that the leaves, under the influence of the sun, decompose
the carbonic acid, give off its oxygen, and retain its carbon, and
that this carbon, uniting with the elements of water in the sap,
forms those several compounds of which plants so largely consist
298 CONCLUDING OBSERVATIONS.
6°. That the supply of carbonic acid in the atmosphere is kept
up partly by the respiration of animals, partly by the natural de-
cay of dead vegetable matter, and partly by combustion. That
ammonia is produced and supplied to plants chiefly by the natural
decay of animal and vegetable substances, though occasionally it
may be formed in the air (p. 288)—and that nitric acid is produced
partly by the natural oxidation of dead organic matter, and partly
by the direct union of the oxygen and nitrogen of the air, through
the agency of the atmospheric electricity. -
7°. That while both of these compounds yield nitrogen to plants,
they each exhibit a special action on vegetable life, in virtue of the
hydrogen and oxygen they respectively contain—and exercise al-
so a so-called stimulating power, by which plants are induced or
enabled to appropriate to themselves, from other natural sources,
a larger portion of all their constituent elements than they could
otherwise obtain or assimilate.
In illustrating these several points, it has been necessary to en-
ter occasionally into details which, to those who have heard or may
read only the later lectures, may not be altogether intelligible. I
am not aware, however, of having introduced any thing, of which
the full sense will not appear on a reference to the statements by
which it is preceded.
We are now to consider the inorganic constituents of plants,
their nature, the source (the soil) from which they are derived,—
their uses in the vegetable and animal economy, how the supply
of these substances is kept up in mature, and how in practical
husbandry, the want of them may be at once efficaciously and eco-
nomically supplied by art. This division of our subject, though re-
quiring a previous knowledge of the principles discussed in the
foregoing lectures, will be more essentially of a practical nature,
and will lead us to consider and illustrate the great leading prin-
ciple, by which the practical agriculturist ought to be guided in
the cultivation and improvement of his land.
We shall here also find much light thrown upon our path by the
results of Geological enquiry; and it is in the considerations I am
now about to bring before you, that I shall have to direct your at-
tention most especially to the principal applications of Geology to
agriculture. -
P A R T II.
ON THE INORGANIC ELEMENTS OF PLANTs.
LECT URE X.
Inorganic constituents of vegetable substances. Quantity of inorganic matter con-
tained in different plants. Circumstances under which the proportion of inorganic
matter is found to vary. Kind or quality of the inorganic matter found in plants.
Elementary bodies usually found in the ash of plants. Chlorine, muriatic acid, and
iodine. Sulphur, sulphurous and sulphuric acids, and sulphuretted hydrogen.
Phosphorus and phosphoric acid. Potassium, potash,_carbonate, sulphate, oxalate,
tartrate, citrate, and sulphate of potash,_chloride of potassium. Sodium, soda,-
carbonate, sulphate, and phosphate of soda, sulphuret of sodium, and chloride of
sodium.
THE consideration of the inorganic constituents of plants is no
less important to the art of culture than the study of their organic
part, which has engaged our sole attention in the preceding Lec-
tureS.
It has already been shewn, that when vegetable substances are
heated to redness in the air, the whole of the so-called organic
elements—carbon, hydrogen, oxygen, and nitrogen—are burned
away and disappear; while there remains behind a fived portion,
commonly called the ash, which does not burn, and which in most
cases undergoes no diminution when exposed to a dull red heat.
This ash constitutes the inorganic portion of plants.
The organic or combustible part of plants constitutes, in gene-
ral, from 75 to 99 per cent. of their whole weight in the dry state.
Hence the quantity of ash left by vegetable substances in the green
or undried state, is often exceedingly small. It long appeared,
therefore, to many, that the inorganic matter could be of no essen-
tial or vital consequence to the plant—that being, without doubt,
derived from the soil, it was only accidentally present,-and that
it might or might not be contained in the juices and solid parts of
the living vegetable, without materially affecting either its growth
or its luxuriance.
Were this the case, however, the quantity and quality of the
302 QUALITY OF ASH TO A CERTAIN EXTENT CONSTANT.
ash left by the same plant should vary with the soil in which it
grows. If one soil contain much lime, another much magnesia,
and a third much potash, or phosphoric acid, or sulphuric acid,
whatever plant is grown upon these several soils should also con-
tain in greatest abundance the lime, the magnesia, the potash, &c.
which abound in each locality—and the nature, at least, of the ash,
if not its proportion, should be nearly the same in every kind of
plant which is grown upon the same soil.
Careful and repeated experiments, however, have shewn—
1°. That on whatever soil a plant is grown, if it shoots up in a
healthy manner, and fairly ripens its seed, the quantity and quality
of the ash—within certain limits, and having reference to certain
admissible variations,—is nearly the same; and,
2°. That though grown on the same soil, the quantity and qua-
lity of the ash left by no two species of plants is exactly alike—
and that the ash differs the more widely in these respects, the more
remote the natural affinities of the several plants from which it may
have been derived.
Hence there is no longer any doubt that the inorganic consti-
tuents contained in the ash are really essential parts of the sub-
stance of plants, that they cannot live a healthy life or perfect all
their parts without them,--and that it is as much the duty of the
husbandman to supply these inorganic substances when they are
wanting in the soil, as it has always been considered his peculiar
care to place within the reach of the growing plant those decaying
vegetable matters, which are most likely to supply it with organic
food.
For the full establishment of this fact, we are indebted to
Sprengel. Ruckert, in Germany, first announced the principle
that whatever the plant usually contained must be a necessary part
of its substance; Lampadius adopted this principle, and endea-
voured to illustrate it by experiments with inorganic substances as
manures;–De Saussure also made and published many important
and very useful analyses of the inorganic matters left by plants;–
but for the full illustration of the important practical bearing of a
knowledge of the inorganic constituents of plants on the ordinary
processes of agriculture, we are in a great measure indebted to the
writings and numerous analytical researches of Sprengel. More
WEIGHTS OF ASH LEFT BY DIFFERENT PLANTS. 303
lately Liebig has come into this field, and by his talented writings
has attracted a more general and earnest attention to the subject;
while the analyses performed by his pupils have added much to
our previous knowledge of the composition of the ash of plants,
It is difficult to conceive the extent to which the admission of
the essential mature, and, in some respects, constant quality of the
inorganic matter contained in plants, must necessarily modify our
notions and regulate our practice in every branch of agriculture.
It establishes a clear relation between the kind and quality of the
crop, and the nature and chemical composition of the soil in which
it grows—it demonstrates what soils ought to contain, and, there-
fore, how they are to be improved—it explains the effect of some
manures in permanently fertilizing, and of some crops in perma-
mently impoverishing the soil—it illustrates the action of mineral
substances upon the plant, and shows how it may be, and really
is, in a certain measure, fed by the dead earth:-over nearly all
the operations of agriculture, indeed, it throws a new and unex-
pected light. Of this, I am confident, you will be fully satisfied
when I shall have discussed the various topics I am to bring be-
fore you in the present part of my lectures.
§ 1. Of the quantity of inorganic matter contained in different
plants.
The quantity of ash left by the different parts of plants varies
very much. This is seen in the following tables.
1°. Proportion of ash left by 100 lbs, of the seed, husk, and
straw of our usually cultivated grains:
Grain. Husk. Straw.
Wheat, • 1.2 to 2.0 º - - 3.5 to 18.5
Barley, º 2.3 to 3. e --> * 5.2 to 8.5
Oats with husk, 2.6 to 8.9 . 5 to 8 . 4.1 to 9.2
Without do, 1.6 to 2.8 * - - -
Rye, - & 1.0 to 2.4 . 5 to 8 . 2.4 to 5.6
Rice, 4. * O9.7 . 14.25 . -
— dressed, 0.3 to 0.7 e -* e -
Indian corn, . 1.3 e --> e 2.3 to 6.5
Buck wheat, . 2.13 & ** © -
Millet seed, . 3.9 g -*t e *-*
304 WEIGHTS OF ASH LEFT BY DIFFERENT ROOTS AND GRASSES.
Grain.
Field beans, 2.1 to 4.0 °
peas, *, 2.5 to 3.0
Vetches, 2.4
Lentils, 2.06
Lintseed, 3.8 to 4.63
Hemp seed, . 5.6
Mustard seed, 4.2 to 4.3
Coffee, 3.19
-**
Husk. Straw.
*g - 3.1 to 7.0
Pod, 7.1 4.3 to 6.2
*
-*.
Straw. Flaar.
4.5 1.28
Hemp.
1.78
*
2°. Proportion of ash left by 100 lbs. of our different root
crops, and of cabbage, tobacco, and the fungi:
Potato,
Turnip, 0.6 to 0.8 6.0 to 8.0
Beet, ... — 6.3
Jerusalem Artichoke, 6.0
Carrot, 0.7 5.1
Parsnip, 0.8 4.3
Mangold Wurtzel, 1.1 7.0
Cabbage, - *-
Tobacco, 7. sº
Root or tuber.
Undried. JDried.
0.8 to 1.1 3.2 to 4.6
Mushrooms º -*. *-
other fungi,
Ileaves.
Undried. JDried.
1.8 to 2.5 18 to 25
1.5 to 2.9 14 to 20
*s- -
* -**
** 16.42
* 15.76
0.53 7.55
* 18 to 26
* 23
*s-s- 3 to 14
3°. Proportion of ash left by 100 lbs. of the grasses and sea-weeds:
Grasses.
Sea weeds.
Lucerne,
Red clover,
White do.
Rye grass,
Knot grass, .
Holcus lanatus
Poa pratensis,
Scirpus,
Fucus vesiculosus,
Fucus Serratus,
Fucus digitatus,
Fucus nodosus,
Laminaria saccharina
Green.
2.6
1.6
1.7
1.7
-ms
*-*
-º-º:
-mº
Dry.
9.5
7.5
9.1
6.0
2.3
5.6 to 6.8
6.2
2.3
13 to 20
16 to 26
20.40
16.19
9.78
WEIGHTS OF ASH LEFT BY DIFFERENT KINDS OF WOOD. 305
Sea weeds. Dry.
Laminaria latifolia, & * 13.62
Furcellaria fastigiata, e * 18.92
Chondrus crispus, . * & 20.61
Iridaea edulis, . • , , 9.86
Polysiphonia elongata, tº tº 17.10
Delessaria sanguinea, º e 13.17
4°. Proportion of ash left by 100 lbs. of different kinds of trees.
- Wood. Seed. Leaves (dried.)
Larch, . 0.33 & 5.0 * 6.0
Scotch fir, 0.14 to 0.19 § 4.98 º 2.0 to 3.0
Pitch pine, 0.25 . 4.47 . 3.15
Beech, . 0.14 to 0.60 e * * 4.2 to 6.7
Willow, 0.45 * * e 8.2
Birch, . 0.34 e --- † 5.0
Elm, e 1.88 g * g 11.8
Ash, e 0.4 to 0.6 & - º sºme mºs
- Oak, e ().21 º *ºs & 4.5
Poplar, . 1.97 * -- g 9.2
Common furze 0.82 & - tº 3.1
Sugar came, 1.3 to 1.6 & * gº 9.4
Wine, . 2.7 to 2.8 * * * *
- Flower.
Hop, & 5.0 10.90 16.3
Sugar cane, 1.4 to 2 e - © 9.4
In looking at the preceding tables, you cannot fail to be struck
with one or two points, which they place in a very clear light.
a. That the quantity of inorganic matter contained in the same
weight of the different crops we raise, or of the different kinds of
vegetable food we eat, or with which our cattle are fed, is very
unlike. Thus lo) lbs. of barley, or oats, or peas, contain twice
as much inorganic (that is earthy and saline) matter as an equal
weight of wheat or rye—and the same is the case with lucerne and
white clover hays, compared with the hay of rye grass.
b. The quantity contained in different parts of the same plant
is equally unlike. Thus 100 lbs. of the grain of wheat leave only
1 to 2 lbs, of ash, while 100 lbs. of wheat straw leave from 3% to
18% lbs. So the dry bulb of the turnip gives only 7 per cent,
while the dry leaf leaves from 14 to 20 per cent. of ash when it is
burned. The dry leaves of the parsnip also contain nearly 16
D
3()6 IT VARIES WITH THE SPECIES OF PLANT.
per cent., though in its roots, when sliced and dried in the air,
there are only 43 per cent. of inorganic matter.
In trees the same fact is observed. The wood of the elm leaves
less than 2 per cent., while its leaves contain nearly 12 per cent, ;
——the wood of the oak leaves only 4th of a per cent., while from
its leaves 4; per cent., or 22 times as much are obtained. The
leaves of the willow and of the beech also contain about twenty
times as much as the wood of these trees does, when it has been
dried under the same conditions.
These differences cannot be the result of accident. They are
constant on every soil, and in every climate; they must, therefore,
have their origin in some natural law. Plants of different species
must draw from the soil that proportion of inorganic matter which
is adapted to the constitution, and is fitted to supply the wants of
each;--while of that which has been admitted by the roots into
the general circulation of the plant, so much must proceed to, and
be appropriated by, each part, as is suited to the functions it is
destined to discharge. And as from the same soil different plants
select different quantities of saline and earthy matter, so from the
same common sap do the bark, the leaf, the wood, and the seed,
select and retain that proportion which the healthy growth and
development of each requires. It is with the inorganic as with the
organic food of plants. Some draw more from the soil, some less,
and of that which circulates in the sap, only a small portion is ex-
pended in the production of the flower, though much is employed
in forming the stem and the leaves.
On the subject of the present section, I shall add two other
observations.
1°. From the constant presence of this inorganic matter in
plants given under all circumstances—a doubt can hardly remain
that it is an essential part of their substance, and that they cannot
live and thrive without it. But that it really is so, is placed be-
yond a doubt, by the further experimental fact, that if a healthy
young plant be placed in circumstances where it cannot obtain this
inorganic matter, it droops, pines, and dies.
2". But if it be really essential to their growth, this inorganic
matter must be considered as part of the food of plants; and we
may as correctly speak of feeding or supplying food to plants,
AS] I LEFT BY VEGETABLE SUBSTANCES VARIES. 307
when we add earthy and mineral substances to the soil, as when
we mix with it a supply of rich compost, or of well fermented farm-
yard manure.
I introduce this observation for the purpose of correcting an
erroneous impression entertained by many practical men in regard
to the way in which mineral substances act when applied to the
soil. By the term manure they generally designate such substan-
ces as they believe to be capable of feeding the plant, and hence
reject mineral substances, such as gypsum, nitrate of soda, and
generally lime, from the list of manures properly so called. And
as the influence of these substances on vegetation is undisputed,
they are not unfrequently considered as stimulants only.
Yet if, as I believe, the use of a wrong term is often connected
with the prevalence of a wrong opinion, and may lead to grave
errors in practice;—I may be permitted to press upon your consi-
deration, the facts above stated—I may almost say demonstrated—
that plants do feed upon dead um-organized mineral matter, and
that you, therefore, really manure your soil, as well as perma-
mently improve it, when you add to it such substances of this kind
as are found by experience to promote the growth of your crops.
§ 2. Of the circumstances under which the proportion of ash left
by vegetable substances varies.
We have seen above that the proportion of ash left by plants
when burned varies very considerably. I shall here briefly state
to you the circumstances by which this variation is affected. Thus
the proportion is different,
1". In different plants.--The tables above given have already
sufficiently illustrated this fact.
2". In different specimens or varieties of the same plant.—Thus
one sample or variety of wheat will leave 1.7, while another will
leave 2 per cent of ash,-so one sample of wheat straw will give
only 3, while from another I have obtained as much as 18% per
cent of pure white ash. Grown on the same field the upper part
of the straw of two varieties of wheat straw gave me respectively,
Golden Kent, ............ 18:47 per cent. of ash.
Flander's Red ..... ....... 14'86
3". In different parts of the same plant.—This is, illustrated to
308 CIRCUMISTANCES UNDER WHICH THE PROPORTION
a considerable extent in the tables already given. The following
places it in a still clearer light—the several parts of the plants
named leaving of ash per cent. *
Straw Husk
Root. or stem. Leaf. Chaff or pod. Seed.
Oat (Hopeton) — 5-0 8’4 | 6’5 6-8 2-l
(Potato) — 8-6 | 4-6 18-6 7-0 2.2
Pca............ * 52 130 — 6-2 3-0
Turnip......... 8:0 * === 20-0 *==º --- *
Tobacco...... 7:0 10'0 23:0 gººmsº sº 4'0
These numbers shew not only the difference which prevails in
different parts of the same plant—but how very much this diffe-
rence may manifest itself between the several parts of two varieties
of the same plant. Both of the samples of oats which gave the
results above stated were grown in Northumberland, though upon
different properties; and it will be seen that in every part of the
plant the potato oat contained considerably more inorganic matter
than the Hopeton oat. I have not ascertained, as yet, how far
such a difference is constant or universal.
4°. In different portions of the same part of a plant.—This is
especially visible in the different portions of the grain and in dif-
ferent parts of the straw of the corn-plants, or of the tops of young
turnips or potatoes. Thus,
a. Grain of wheat—When the wheat is ground by the miller,
it is sifted into several portions of different degrees of fineness.
These are known by different names in different districts. A
series of these different products, from a home-grown wheat
ground in Durham, gave me the following proportions of ash re-
spectively,
Fine flour. - Boxings. Sharps. Bran.
Per centage of ash, O'93 2.7 5.5 7.6
so that it is in the husk or exterior portion of the grain that the
largest proportion of the ash resides.
b. The straw of wheat and oats.-The upper and under por-
tions of the straw of our corn plants almost invariably contain dif-
ferent proportions of inorganic matter. Thus, when cut into
several portions, wheat, oat, rye, pea, and bean straws have given
me the following per centages of ash.
OF ASH LEFT BY WEGETABLE SUBSTANCES VARIES. 309
Top. Second part. Third part. Bottom.
Wheat straw, . 8-70 7-86 5:36 3.75
Oat straw, tº 9°l 3 * * 7.05
Rye straw, º 2.65 --- * 2.87
Pea straw, & 0 - 09 * *-*. 4 '57
Bean straw, . 3:30 *m. *mº 6'96
Such differences as these I have obtained in a great many ex-
periments, the results of which are not as yet published.
In the examples above given of wheat, oat, and pea straws, the
inorganic matter increases as we ascend the stem. This, however,
is by no means a general law; but, so far as my experience has
yet gone, I am inclined to believe,
First, that when corn grows poor and stunted, or on an unfa-
vourable soil, the quantity of ash left by the under part of the
straw is greatest. Thus in one of many such cases I got in
Top. Bottom.
Oat straw, ............ 6-4 1 8:09
Second, when the straw rushes up very quickly, grows tall and
large, and scarcely ripens, the per-centage of ash also increases
downwards. Thus a single oat straw 53 feet in length gave me
Top. Second part. Third part. Bottom.
Oat straw, 5} feet high, 5:02 7.39 7.14 8°68
Here the two central portions very closely resemble each other.
Third, when the crop is grown upon an average soil, of an
average height, and attains an average degree of ripeness, the ash
increases upwards, being always greatest in the top part of the
straw and at the extremity of the leaves.
c. Turnip tops exhibit similar differences. Thus, from young
turnip tops in the dry state cut at different heights, the following
propositions of ash were obtained.
Top. Middle. Bottom.
Turnip tops, 9th August, 1 6-7 | 6’ 6 21-0
Here the plant was rapidly growing; but it is obvious that a
stem having a bulb attached to it is likely to follow a different law
from one which springs from an ordinary root, and has nothing
below to be particularly mourished. Hence it is, probably, that I
have very rarely found the ash left by the upper part to be greater
than that left by the bottom of the turnip top.
5°. In the same parts at different ages.—In the several parts of
310 CIRCUMSTANCES UNIDER WHICH THE PROPORTION
trees, the quantity of ash is said to increase with the age of the
plant. It is also different—either greater or less—in the several
parts of all our cultivated crops. Thus the leaves and stems of
young potatoes gathered in four successive weeks left respectively,
when dried at 212°, the following per centage of ash:
First Week. Second Week. Third Week. Fourth Week.
Leaves,......... 18°4 19'5 17.2 15.7
(*2.
Stems,......... 24-8 24'9 23°4 26'l
Saline matter exudes from or collects upon the surface of the
leaves of the potato and turnip, part of which at least is washed
off by the rains. The state of the weather, therefore, at the time
of gathering, affects the proportion of ash left by these leaves, and
hence it is difficult to say whether the apparent decrease in the
ash of the leaf, and increase in that of the stem in the above series
of determinations, is to be regarded as anything more than acci-
dental.
Again, the leaf of the oat, on five successive weeks, gave the
following increasing proportions of ash :
18th June. 25th June. 2d July. 9th July. 16th July.
Oat leaves,...... 9-07 10-95 | | 35 12:20 12 6 1
So in the dry chaff of a potato oat grown at Featherhall, near
Corstorphine, the per centage of ash increased as follows:
July. August. Sept.
—º- - –A–
2– ~ /− –S ****
16th. 21st. 30th. 6th. 13th. 20th. 27th. 3d.
6:00 9° 1 1 12:25 13-75 l 8.68 21, 17 22:46 27.47
In both of these cases the increase is constant; and as much of
the ash consists of silica, the access of rainy weather has little in-
fluence in retarding it.
6°. In the same plants grown on different soils.-The soil sup-
plies the inorganic food of the plant. If this food abound in the
soil, the plant will readily obtain it, may grow fast, and may con-
tain much. The contrary will be the case when inorganic food is
scarce. Thus the straw and grain of the same variety of oatgrown
by the Messrs Drummond of Stirling, on seven different experi-
mental soils, gave me respectively the following proportions of
ash;
of ASII LEFT BY VEGETABLE SUBSTANCES VARIES. 3] 1
Straw. Grain.
'On Aberdeen granite (crushed), e g 9:57 per cent. 3:42
On clay slate, do. & 7-85 — 3'54
. On greenstone, do, & •º º 7 '88 — 2.25
On limestone, do. we * tº 1 0°18 — 3-88
£)n chalk, do. p e ve 9°36 — 3- ) 6
On gypsum, do. sº * *g 5'83 — 3-22
{}n siliceous pit sand, º tº • 6'37 — 2-9 |
On blue tile clay, taken 10 feet below the surface, 921 – 3.27
On light loamy soil, * º * 8-79 — 3-96
b. So the top part of wheat straw grown on different soils gave
me very different proportions of ash.
On a light soil resting on chalk, near Newmarket, * * 2.96 per cent.
Grown near North Deighton, Yorkshire, - * wº - 5:55 —
Clay soil of the coal measures, county of Durham, - *- G-70 —
Loamy soil resting on trap, near Edinburgh, * *. * – 7:16 —
Light soil resting on magnesian limestone, near Monkwearmouth, 10:53 —
Clay soil among the mountain limestone rocks, Ravensworth Dale,
Yorkshire, *. -- º l 4'86
3- *
Another variety on the same field, * - **
- 18:47 —
It is impossible to say how much of the above differences is
due to the varieties of wheat grown, to difference of season, &c.;
and therefore, though they are much greater than in the case of
the oat straw—they are not so decisive upon the point we are now
considering as those observed in the different samples of oat straw
in regard to which the soil alone was different.
c. Again, the grain of the same variety of wheat (Hunter's),
grown on different farms near Haddington, gave me the following
proportions of ash:
Deep reddish clay loam, subsoil gravel, l'776 per cent.
Red clay on gravel, º * 1 ‘787 —
Stiff clay on retentive subsoil, - I '903 —
Dight clay on retentive subsoil, * l '917 —
Light turnip land, º tº- l‘820 —
The results with the grain of wheat are not so strikingly diffe-
rent as with the wheat and oat straws, but are sufficiently so to
show that the proportion of ash left by a plant when burned is
connected in a considerable degree with the nature of the soil on
which it grows.
H. O.
7°. With the kind and quantity of manure applied to the crop.
—The kind and quantity of manure applied affects the crop in the
312 OF THE KIND OR QUALITY OF THE
same way as the nature of the soil. In fact, these applications
being made to the soil merely alter its quality, and enable it more
or less rapidly to supply to the plant the several kinds of inorganic
and other food which are necessary to its healthy growth.
The above observations show that the quantity of ash, left by
plants depends upon, or is modified by a great variety of circum-
stances, they indicate also within what limits, or within what ad-
missible variations, the quantity of ash left by a full-grown healthy &
plant can be said to be on all soils nearly the same.
§ 3. Of the kind or quality of the inorganic matter found in
plants.
In regard to the quality or composition of the ash thus left by
plants, several important points have been ascertained.
1°. In nearly all cases the ash contains a sensible proportion of
from eight to eleven different substances. These are chlorine, sul-
phuric acid, phosphoric acid, potash, Soda, lime, magnesia, oxide of
iron, silica. Oxide of manganese, iodine, and alumina, are met with
less universally.
2". These substances occur in different proportions in the ash of
different plants, and of different parts of plants. Thus,
a. In different plants.-A hundred pounds of the ash of the
grain of rye contain, according to our present analyses, 8 pounds
of lime, while in that of wheat or barley there are only 3 or 4
pounds. So the ash of the turnip bulb contains 50 per cent. of
potash and soda, while that of the grain of wheat contains only
about 30 per cent.
b. In different parts of plants.-The ash of wheat straw contains
from 40 to 80 per cent. of silica, while that of the clean grain con-
tains scarcely a trace. On the other hand, the ash of the grain
contains nearly half its weight of phosphoric acid, while that of the
straw contains only 3 or 4 per cent. So in the ash of the turnip
bulb there is less than 12 per cent. of lime, while in that of the
leaf there is upwards of 34 per cent.
3°. The exact differences above mentioned are not always found.
They are in almost every new case represented by new numbers.
But general differences of the above kind are always observed.
Thus, root crops always contain more alkaline matter than grain
3
INORGANIC MATTER FOUND IN PLANTS. 313
crops, and our straw and hay more silica than the stems and leaves
of the bean, pea, or other leguminous crops. So the turnip bulb
and potato tuber in the full-grown plant always contain more
potash and soda, while their leaves and stems contain more lime
and silica. The straw or stems and leaves of our grasses and
corn-bearing plants always contain more silica, and their seeds
more phosphoric acid, though the numbers by which the relative
proportions of these two ingredients are represented may in no two
cases be alike. It is not, therefore, a matter of indifference to the
living vegetable whether it meets with this or with that kind of
inorganic matter in the soil on which it grows—whether its roots
are supplied with potash, with phosphoric acid, or with silica. The
soil must contain all the several substances it requires,-
a. In such quantity as easily to yield to the crop so much of
each as is especially necessary to it.
b. And in such a state of combination or otherwise, that they
can be readily taken up and appropriated by the plant.
4". Several practical observations flow maturally from the above
statements. Thus, -
a. If all the substances I have named are equally necessary,
and are always present in our cultivated crops—the absence or
scarcity of one of them will affect the crop in the same way as if
several of the necessary constituents were so absent or defective.
Thus, though all the other substances be present, yet if lime, or
phosphoric acid, or magnesia be wanting in the soil, the plant will
refuse to grow, because so far as our present knowledge goes, its
several parts cannot be built up without a certain proportion of
every one of these substances.
b. And if one plant requires a given substance in larger quan-
tity than another, the soil in which the former will grow must
contain more of this substance than need be present in a soil in
which the latter will thrive. *
Thus one reason appears why certain plants naturally abound
on certain soils, and why the crops we cultivate grow better upon
one soil than upon another. -
c. If the soil contain a sufficient supply of all the substances we
have named, any crop will grow upon it—in so far as its healthy
growth depends upon an abundant supply of its inorganic constitu-
314 ELEMENTARY SUBSTANCES FOUND IN THE ASII.
ents only. If it is defective in any of them, the practical man un-
derstands that it will be necessary to add them. And if chemical
analyses discover to him, on the one hand, what his soil contains,
and on the other what his crops require—he is prepared to treat
his land upon a clear and economical principle—to give it in the
form of manure that necessary food of the plant of which it con-
tains too little.
Several important points, however, require to be elucidated to
make your way clear to this important practical result. You must
know, for example,
1°. The nature and properties of the several inorganic or mine-
ral substances which are usually present in our cultivated crops,
and those of such of their compounds as are most important, or
most abundant, or which are supposed to minister to the growth
of plants.
2". The proportions in which these several substances usually
occur in the plants, to which your attention is chiefly directed.
3". The proportions in which these substances usually occur, or
ought to be present in a fertile soil.
49. In what form, when absent from the soil, they can be added
most easily, most advantageously, and most economically.
I shall, therefore, draw your attention to these four several
topics in succession,
§ 4. Of the several elementary bodies usually met with in the ash
of plants.
What is understood by the term simple or elementary body
among chemists has already been explained (p. 22), as well as the
number and names of those with which we are at present ac-
quainted.
Of these elementary bodies we have seen that the organic part
of plants consists chiefly of four, namely, carbon, hydrogen, oxy-
gen, and nitrogen, in various proportions. In the inorganic part
there occur mine or ten others, generally in combination, either
with oxygen or with one another.
l
ELEMENTARY SUBSTANCES FOUND IN THE ASPI. 315
The names of these inorganic elements are as follow :
- With Forming
Chlorine, . Metals, Chlorides.
Iodine, & Do. Iodides.
Sulphur, . Do. Sulphurets.
Do. . tº Hydrogen, Sulphuretted hydrogen."
Do. & Oxygen, Sulphuric acid.
Phosphorus, . Do. Phosphoric acid.
Potassium, g Do. Potash.
Do. o Chlorime, Chloride of potassium.
Sodium, tº Oxygen, Soda.
Do. ſº Chlorine, Chloride of sodium or com-
mon salt.
Calcium, © Do. Chloride of calcium.
Do. tº Oxygen, Lime.
Magnesium, O. Magnesia.
Aluminum, . Do. Alumina,
Silicon, . Do, Silica.
Iron and Do. ſ Oxides.
Manganese, } Sulphur, Sulphurets.
Other elementary bodies, chiefly metallic, occur in some plants—
occasionally, and in very small quantity,+but, so far as is yet
known, they do not appear to be either necessary to their growth,
or to exercise any material influence on the general vegetation of
the globe.
Of all the above elementary bodies it may be said, generally,
1°. That with the exception of sulphur, which is given off in va-
pour from active volcanoes, and from rents and fissures in ancient
volcanic countries, they are not known to exist or to be evolved, in
any quantity, anywhere on the surface of the globe in their simple,
elementary, or uncombined state; and that, therefore, in this state
they in no way affect the progress of vegetable growth, or require
to occupy the attention of the practical agriculturist.
2°. They all, however, exist in nature more or less abundantly
in a state of combination (p. 40) with other substances, and chiefly
with oxygen—but in no state of combination are they known to be
generally diffused through the atmosphere of the globe, so as to
be capable of entering plants by their leaves or other superior
parts. They must all, therefore, enter by the roots of plants,
—must consequently exist in the land,-and must all be necessary
* Called also Hydro-sulphuric Acid.
316 PROPERTIES OF CHILORINE.
constituents of that soil in which the plants that contain them are
found to grow.
It will not be necessary, therefore, to consider so much the re-
lative proportions in which these elementary bodies themselves ex-
ist in plants, as that of the several chemical compounds which they
form with oxygen, or with one another—in which states of combi-
mation they exist in the soil, and are found in the circulation and
substance of the plant. As a preliminary to this inquiry, however,
it will be proper to lay before you, a brief outline of the nature and
properties of these compound bodies themselves—and of the direct
influence they have been found to exercise upon vegetable life.
§ 4. Of Chlorine, Muriatic acid, and Iodine.
1°. Chlorine.—If a mixture of common Salt and black oxide of
manganese” be put into a flask or bottle of colourless glass, and
sulphuric acid (oil of vitriol) be then poured upon it, and a gentle
heat applied, a gas of a greenish-yellow colour will be given off,
and will gradually fill the bottle. This gas is known by the name
of chlorine.
It is readily distinguished from all other substances by its green-
ish-yellow colour, and its pungent disagreeable smell. It gradually
extinguishes a lighted taper, but phosphorus, gold leaf, metallic po-
tassium and sodium, and many other metals take fire in it and burn
of their own accord. It is nearly 4% times heavier than common
air, and therefore may be readily poured from one vessel to another.
Water absorbs twice its own bulk of the gas, acquiring its colour,
smell, and disagreeable astringent taste.
Animals cannot breathe it without suffocation—and, when un-
mixed with air, it speedily kills all living vegetables. The solu-
tion of chlorime in water was found by Davy to promote the ger-
mination of seeds.
It does not exist, and is rarely evolved, f in mature in a free or
uncombined state, and therefore is not known to exercise any
direct action upon the general vegetation of the globe. It exists
largely, however, in common salt (chloride of sodium), every 100
lbs. of this substance containing upwards of 60 lbs. of chlorine.
Indirectly, therefore, it may be supposed to influence, in some
* Sold by this name in the shops. 'l See Lecture V., p. 147.
MURIATIC ACID AND IODINE, 317
degree, the growth of plants, where common salt exists naturally
in the soil, or is artificially applied in any form to the land.
In most of our usually cultivated crops it exists in a compara-
tively small proportion only.
2°. Muriatic acid, the spirit of salt of the shops, consists of
chlorine (Cl.) in combination with hydrogen, (H), and is represent-
ed by H Cl.
It is a gas at the ordinary temperature of the atmosphere, but
water absorbs or dissolves between 400 and 500 times its bulk of
it, and the acid of the shops is such a solution of the gas in water,
of greater or less strength. It is prepared by pouring sulphuric
acid, (oil of vitriol,) on common salt, when fumes of the acid are
given off.
Muriatic acid has an exceedingly sour taste, corrodes the skin,
and in its undiluted state is poisonous both to animals and plants.
It dissolves common pearl ash, soda, magnesia, and limestone,
with effervescence; and readily dissolves also, and combines with,
many earthy substances which are present in the soil.
When applied to living vegetables in the state of an exceedingly
dilute solution in water, it has been found upon some soils, and in
some circumstances, to be favourable to vegetation. The steeping
of seeds in very weak solutions of this acid has also been seen in
Germany to promote their growth, and to give an increased crop.
On the banks of the Tyne, and elsewhere, in the neighbourhood
of the so-called alkali” works, long experience, however, has proved
that in the state of vapour its repeated application, even when di-
luted with much air, is in many cases fatal to vegetable life.
Applied in the liquid state upon fallow land, or upon land pre-
paring for a crop, it may assist the growth of the future grain, by
previously forming, with the ingredients of the soil, some of those
compounds which have been occasionally applied as manures, and
which we shall consider hereafter.
3°. Iodine is a solid substance of a lead grey colour, which,
when heated, is converted into a beautiful violet vapour. It exists
* In these works carbonate of soda (the common soda of the shops) and sulphate
of soda (glauber salts) are manufactured from common salt, and in one of the pro-
cesses immense quantities of muriatic acid are given off from the furnace, and used
formerly to escape into the air by the chimney.
3.18 SULPHUROUS AND SULPHURIC ACIDS,
in combination chiefly with sodium, as Iodide of Sodium, in Sea
water and in marine plants; but it has not hitherto been detected
in any of the crops usually raised for food.
Like chlorine, it is poisonous both to animals and plants; and
was found by Davy to assist and hasten germination. It may pos-
sibly exert some hitherto unobserved influence upon vegetation,
when it is applied to the soil in districts where sea-ware is largely
collected and employed as a manure. -
Iodine is slightly soluble in water, and this solution has been
mentioned in a previous lecture (p. 171), as affording a ready
means of detecting starch by the beautiful blue colour it gives with
that substance.
§ 5. Of Sulphur, Sulphurous and Sulphuric acids, and Sulphu-
retted Hydrogen.
1°. Sulphur is a substance too well-known to require any de-
tailed description. In an uncombined state it occurs chiefly in
volcanic countries, but it may sometimes be observed in the form
of a thin pellicle on the surface of stagnant waters—or of mineral
springs, which are maturally charged with sulphurous vapours. In
this uncombined state it is not known materially to influence the
natural vegetation of any part of the globe. It has, however, been
employed with some advantage in Germany as a top-dressing for
clover and other crops to which gypsum in that country is gene-
rally applied. When mixed with the turnip seed, and sown along
with it, the attacks of the fly are said to be prevented.
Sulphur exists largely in many plants—is a constituent as we
have seen (p. 216) of almost all the protein compounds which occur
in plants and animals, and it forms one-twentieth part of the
weight of hair and wool.
2". Sulphurous acid.--When sulphur is burned in the air it
emits a pale blue light, and gives off a gaseous substance in the
form of white fumes of a well known intensely suffocating odour.
These fumes consist of a combination of the sulphur with the
oxygen of the atmosphere, and are known to chemists by the name
of sulphurous acid. This compound is destructive to animal and
vegetable life, but as it is not known to be directly formed to any
extent in nature, except in the neighbourhood of active volcanoes,
EFFECT OF SULPHURIC ACID ON WEGETATION. 319
it probably exercises no extensive influence on the general vegeta-
tion of the globe.
This gas possesses the curious property of bleaching many ani-
mal and vegetable substances. Wool and straw for plaiting are
bleached to an almost perfect whiteness, when they are suspended
in a vessel or room into which a plate of burning sulphur has been
introduced. Gardeners sometimes amuse themselves also in bleach-
ing roses and other red flowers, by holding them over a burning
sulphur match. Some shades of red resist this action more or less
perfectly, and the colour of the bleached flowers may often be re-
stored—by dipping them in a dilute solution of carbonate of soda,
or by holding them over a bottle of hartshorn (liquid ammonia).
3°. Sulphuric acid.—This is the name by which chemists dis-
tinguish the oil of vitriol of the shops. It is also a compound of
sulphur and oxygen only, and is formed by causing the fumes of
sulphur to pass into large leaden chambers along with those of ni-
tric acid, from which they can obtain a further supply of oxygen.
It is met with in the shops in the form of an exceedingly sour
corrosive oily liquid, which deeomposes, chars, and destroys all ani-
mal and vegetable substances, and, except when very diluted, is de-
structive to life in every form. It is rarely met with in nature, in
an uncombined state,_though according to Boussingault, some of
the streams which issue from the volcanic regions of the Andes,
are rendered sour by the presence of a quantity of this acid.
It combines with potash, soda, lime, magnesia, &c., and forms
sulphates, which exist abundantly in nature, and have often been
beneficially and profitably employed as manures.
Where the soil contains lime or magnesia, the acid may often
be applied directly to the land, in a very dilute state, with advan-
tage to clover and other similar crops. It has in France, near
Lyons, been observed to act favourably when used in this way,
while in Germany it has been found better to apply it to the
ploughed land, previous to sowing. A few experiments have also
been made in this country with partial success. Applied alone in
the turnip drills, for example, it has been found to give a fair crop
of turnips without other manure. It is deserving, however, of a
further trial, and in more varied circumstances.
4°. Sulphuretted Hydrogen or Hydro-sulphuric acid.—This gas
320 EFFECT OF SULPHURIC ACID ON WIEGETATION.
is a compound of sulphur with hydrogen, and is almost universally
known by its unpleasant smell. It imparts their peculiar taste and
odour to sulphureous springs, such as that of Harrogate, and gives
their disagreeable smell to rotten eggs. It is often produced in
marshy and stagnant places", and fish ponds, where vegetable mat-
ter is undergoing decay in the presence of water containing gyp-
sum (sulphate of lime) or other sulphates; and it may occasionally
be detected by the sense of smell among the roots of the grass, in
old pasture land, to which a top-dressing is occasionally given.
As in the egg, so also in other decaying animal substances, es-
pecially when the air is in some measure excluded, this gas is
formed. In putrified cow's urine, and in night soil, it is present
in considerable quantity. -
Sulphuretted hydrogen is exceedingly noxious to animal and
vegetable life, when diffused in any considerable quantity through
the air. The luxuriance of vegetation in the neighbourhood of
Sulphureous springs, however, has given reason to believe that
water impregnated with this gas may act in a beneficial manner
when it is placed within reach of the roots of the plants. It seems
also to be ascertained that natural or artificial waters which have a
sulphureous taste give birth to a peculiarly luxuriant vegetation,
when they are employed in the irrigation of meadows.f
The relative composition of these three compounds of sulphur is

thus represented:
One equivalent of Weighing Is º * Or one of sulphur and
Sulphur..... & e º 'º º e ſº tº g º tº e º e 16 S
Sulphurous acid ....... 32 SO2 2 of oxygen.
Sulphuric acid .......... 40 SO3 3 of oxygen.
Sulphuretted hydrogen 17 SH 1 of hydrogen.
* This appears to be especially the case on the coasts of Western Africa, where the
hot sun is continually beating on sea water, often shallow, frequently stagnant, and al-
ways laden with organic matter, either animal or vegetable (Daniel). Near the mouth
of the Tees in this county, where a shallow, dark blue, muddy, samphire-bearing tract
stretches for several miles inland from Seaton Snook, the presence of sulphuretted
hydrogen may be perceived by the smell, when on a hot summer's day, a gentle air
skims along the edge of the Slake. The favourable conditions are, a burning sun, a
very gentle air, and such a condition of the sea—that those parts and pools which are
only reached by the spring tides shall have been several days uncovered.
+ Sprengel, Chemie, I. p. 355.
3
2
|
PEIOSPHORIC ACII).
§ 6. Of phosphorus and phosphoric acid.
1° Phosphorus is a solid substance of a pale yellow colour, and
of a consistence resembling that of wax. When exposed to the
air it slowly combines with the oxygen of the atmosphere, and
burns away with a pale blue flame, visible only in the dark. When
rubbed, however, or exposed to a slight elevation of temperature,
even to the heat of the hand, it readily bursts into a brilliant
flame emitting an intense light accompanied by dense white va-
pours. It does not occur in nature in an uncombined state, and
is not known to be susceptible of any useful application in practiº
cal agriculture.
2°. Phosphoric Acid. –The white fumes given off by phospho-
rus, or rather into which it is changed, when burned in the air or
in oxygen gas, consist of phosphoric acid. The white fumes given
off by a lucifer match when first kindled are also phosphoric acid.
This compound is solid and colourless, attracts moisture from
the air with great rapidity, is exceedingly soluble in water, has an
intensely sour taste, and like sulphuric acid is capable of corroding
and destroying animal and vegetable substances.
It does not exist in mature in a free state, and, therefore, is not
directly influential upon vegetation. It unites, however, with pot-
ash, soda, lime, &c., to form compounds, known by the name of
phosphates. In these states of combination, it is almost universally
diffused throughout nature—and appears to be essentially neces-
sary to the healthy growth and maturity of all living—certainly of
all cultivated vegetables.
In plants and animals it is also found in combination with carbon,
hydrogen, oxygen, nitrogen, and sulphur, forming those important
protein compounds of which I have already spoken (p. 216).
§ 7. Of potassium—potash—carbonate, sulphate, ovalate, tartrate,
citrate, and sulphate of potash—and chloride of potassium.
1°. Carbonate of Potash.-In countries where non-resinous trees
abound, it is usual to burn the wood which cannot otherwise be
employed—as in the clearings in Canada and the United States.
—for the purpose of collecting the ash which remains. This ash
is washed with water and the washings boiled to dryness in iron
pots. In this state it forms the pot-ash of commerce. When this
X
322 WOOD ASH AND CARBONATE OF POTASH.
potash is again dissolved in water, and the clear liquid decanted
and boiled, the pearl-ash of the shops is obtained.
This pearl-ash is an impure form of the carbonate of potash of
chemists. It readily dissolves in water, has a peculiar taste—dis-
tinguished as an alcaline taste—and dissolves in vinegar or in di-
luted sulphuric or muriatic acid, with much effervescence. The gas
given off during this effervescence (or boiling up) is carbonic acid,
the same which, as was shown in a previous lecture, is obtained,
when a diluted acid is poured upon chalk or common limestone.
This carbonate of potash has been long known to exercise a
powerful influence over the growth of plants.
The use of wood-ash as an application both to pasture and to
arable land, goes back to the most remote antiquity; and though
the crude wood-ash contains other substances also, yet much of its
immediate and most apparent effect is due to the carbonate of pot-
ash it contains.
From what has already been stated, at the commencement of
the present lecture, in regard to the presence of potash in the
parts and juices of nearly all plants, you will already in some mea-
sure understand why the carbonate of potash should be useful to
vegetation, and—since this alkali (potash) is present in greater
quantity in some, than in others—why it should appear to be more
especially favourable to the growth of one kind of plant than of
another.
In this way, it is explained why moss and coarse grasses are
extirpated from meadows by a sprinkling of wood ashes—and why
red clover, lucerne, esparsette, beans, peas, flax, potatoes, turnips,
&c., are greatly promoted in their growth by a similar treatment.
This substance, however, has other functions to perform in refe-
rence to vegetation, besides that of simply supplying the crop with
the potash it requires: these functions I shall explain more parti-
cularly hereafter, when I shall have prepared you to understand
the details into which it will be necessary to enter.
29. Potash.-When 12 parts of carbonate of potash are dissolved
in water, and boiled with half their weight of newly-slaked quick-
lime, they are gradually deprived of their carbonic acid, and con-
verted into pure potash,-or as it is often called, from its effect on
animal and vegetable substances, caustic potash.
º)
& J.
POTASSIUM AND CAUSTIC POTASH. 323
The caustic liquid thus obtained decomposes or dissolves most
animal and vegetable substances, whether living or dead. When
applied to the skin, unless it be in a very diluted state, it destroys
it, and produces a painful sore. Potash does not occur in nature
in this caustic or uncombined state, and is not known, therefore,
to exercise any direct influence upon natural vegetation.
When wood-ashes and quick-lime are mixed together in artifi-
cial composts, a portion of the carbonate of potash is likely to be
rendered caustic, and, therefore, more fit to act upon the vegetable
matter in contact with it, by rendering it soluble in water and
thus capable of entering into the roots of plants. To this point I
shall have occasion to return hereafter.
3". Potassium.—When dry caustic potash, obtained by evaporat-
ing the caustic solution above described, is mixed with powdered
charcoal and iron filings, and exposed to an intense heat in an iron
retort, it is decomposed, and metallic potassium distils over, and is
collected in the form of white shining silvery drops. -
It was one of the most remarkable discoveries of Sir H. Davy,
that potash was a compound substance, and consisted of this metal
potassium united to oxygen gas.
Potassium is remarkable for the strong tendency it possesses to
unite again with oxygen and re-form potash. When simply ex-
posed to the air, it gradually absorbs oxygen from the atmosphere;
but if it be heated in the air, it takes fire and burns. When the
combustion has ceased, a quantity of caustic potash remains, the
weight of which is nearly one-fifth greater than that of the potas-
sium employed. It even bursts into a flame when thrown upon
water, depriving that liquid of its oxygen, and liberating its hydro-
gen,*—and it was justly considered as the most astonishing pro-
perty of this metal, when first discovered, that it took fire when
placed upon the coldest ice. When thus burned in contact with
water, potash is formed, as before, and is found dissolved in the
liquid when the experiment is completed.
4". Chloride of potassium.—This is a compound of chlorine with
potassium, which, in taste, properties, and general appearance, has
much resemblance to common salt. It may be formed by adding
pearl-ash to dilute muriatic acid (spirit of salt) as long as any
* For the composition of water, see Lecture II., p. 47.
324 SU LPIIATE AN ID NITRATE OF POTASII.
effervescence appears, and afterwards evaporating to dryness. It
exists in small quantity in sea water, in the ash of most plants, and
frequently in the soil. It is not an article of manufacture, but is
occasionally extracted from kelp, and sold to the alum makers.
Could it be easily and cheaply obtained, there is no doubt that it
might be employed with advantage as a manure, and especially in
those circumstances in which common salt has been found to pro-
mote vegetation. The refuse of the soap-boilers, where soap is
made from kelp, contains a considerable quantity of this compound.
This refuse might be obtained at a cheap rate, and, therefore,
might be usefully collected and applied to the land where such
works are established.
5%. Sulphate of potash.--This compound is formed by adding
pearl-ash to dilute sulphuric acid (oil of vitriol) as long as effer-
vescence appears, and then evaporating the solution. It is a white
saline substance, sparingly soluble in water, and has a disagreeable
bitterish taste. It exists in considerable quantity in wood-ash, and
in the ash of nearly all plants, and is one of the most abundant
impurities in the common potash and pearl-ash of the shops. This
sulphate itself is not an article of extensive manufacture, but it
exists in common alum to the amount of upwards of 18 per cent.
of its weight. -
Dissolved in 100 times its weight of water, the sulphate of
potash has been found to act favourably on red clover, vetches,
beans, peas, &c., and part of the effect of wood ashes on plants of
this kind is to be attributed to the sulphate of potash they contain.
Peat ashes also contain this salt in variable quantity, and to this is
ascribed a portion of their efficacy when applied to the land.
6". Nitrate of potash or salpetre is a well-known saline sub-
stance, of which mention has already been made in the preceding
lectures. It contains potash and nitric acid only, and may be
readily formed by adding pearl-ash to nitric acid as long as any
effervescence appears, and evaporating the solution. It exists, and
is continually reproduced in the soil of most countries, and is well
known to exercise a remarkable influence in accelerating and in-
creasing the growth of plants.
7". Owalates of potash.—These salts are present in the common
and wood sorrels, and in most of the other more perfect plants in
OXALATES AND CITRATES OF POTASH. 325
which oxalic acid is known to exist, (p. 66). The salt of sorrel is
the best known of these oxalates. This salt has an agreeable acid
taste, and is not so poisonous as the uncombined oxalic acid.
When this salt is heated over a lamp, the oxalic acid it contains
is decomposed, and carbonate of potash is obtained. It is sup-
posed that a great part of the potash which is generally extracted
from the ashes of wood and of the stems of plants in the state of
carbonate—existed as an oxalate in the living tree, and was con-
verted into carbonate during the combustion of the wood. This
compound, therefore, in all probability, performs an important
part in the changes which take place in the interior of plants,
though its direct agency in affecting their growth, when applied
externally to their roots, has not hitherto been distinctly recog-
mised. It is probably formed occasionally in farm-yard manure,
and in decaying urine and night-soil, but nothing very precise is
yet known on this subject.
8°. Citrates and tartrates of potash.--These salts exist in many
fruits. The citrates abound in the orange, the lemon, and the
lime—the tartrates in the grape. When heated over a lamp, they
are decomposed, and like the oxalates leave their potash in the state
of carbonate.
In the interior of plants, both potash and soda are most fre-
quently combined with organic acids (Oxalic, citric, tartaric, &c."),
and the compounds thus formed are generally what chemists call
acid salts—that is to say, they generally have a distinctly sour
taste, redden vegetable blues, and contain much more acid than is
found to exist in certain other well known compounds of the same
acids with potash.
The citrates and tartrates are not known to be formed in ma-
ture, except in the living plant, and as they are too expensive to
be ever employed as manures, it is the less to be regretted that few
experiments have yet been tried with the view of ascertaining their
effect upon vegetation.
9°. Phosphates of potash.-If to a known weight of phosphoric
acid pearl-ash (carbonate of potash) be added as long as any effer-
vescence appears, and the Solution be then evaporated, phosphate
of potash is obtained. If to the solution before evaporation a se-
* For an account of the most abundant organic acids, see Lecture VII., p. 202.
326 COMMON SALT.
cond portion of phosphoric acid be added, equal to the first, and
the water be then expelled by heat, BI-phosphate" of potash will
remain.
One or other of these two salts is found in the ash of nearly all
plants. Whether or not the elements of which they consist exist
in this state of combination in the living plant will be considered
hereafter, in the meantime it may be stated as certain that they
are of the most vital importance not only in reference to the
growth of plants themselves, but also to their nutritive qualities
when eaten by animals for food,
These phosphates are occasionally, perhaps very generally, pre-
sent in the soil in minute quantities, and there is every reason to
believe that could they be applied to the land in a sufficiently eco-
nomical form, they would in many cases act in a most favourable
manner upon vegetation. They are contained in the urine of
carnivorous animals and in many other animal manures, and to
their presence a portion of the efficacy of these manures is to be
ascribed.
§ 8. Of sodium, soda, carbonate of soda, sulphate of soda, phos-
phate of soda, sulphuret of sodium, and chloride of sodium.
1°. Chloride of Sodium, common or sea salt, exists abundantly
in sea water, and is found in many parts of the earth in the form
either of incrustations on the surface or of solid beds or masses at
considerable depths. The rock salt of Cheshire, and of many
other districts in which the red sandstone formations prevail, are
well known examples of this latter mode of occurrence.
Common salt may also be detected in nearly all soils; it is
found in the ashes of all plants, but especially and in large quan-
tity in the ashes of marine plants (Kelp), and is sometimes borne
with the spray of the sea to great distances inland, when the winds
blow strong, and the waves are high and broken.
On some rocky shores, as on that between Berwick and Dun-
bar, and along our northern coasts, the spray may be seen occa-
sionally moving up the little coves and inlets in the form of a
distinct mist driving before the wind—and this saline matter has
* So called from bis, twice, because it contains twice as much acid as the former, or
neutral phosphate.
SULPHATE OF SODA. 327
been known to traverse nearly half the breadth of the island be-
fore it was entirely deposited from the air.
It is impossible to calculate how much of the saline matter of
sea water may in this way be spread over the surface of a sea-girt’.
island like ours; but two things are certain—that those places which
are nearer the sea will receive a greater, and those more inland a
lesser, portion ; and that those coasts on which sea winds prevail
will be more largely and more frequently visited than those on
which land winds are more commonly experienced.
It is well known that common salt has been employed in all
ages and in all countries for the purpose of promoting vegetation,
and in no country perhaps in larger quantity or more extensively
than in England. That it has often failed to benefit the land in
particular localities only shows that the soil in those places already
contained a natural supply of this compound large enough to meet
the waists of the crops which grew upon it, or that something else
also was necessary to make or to permit the salt to act beneficially.
The facts above stated, as to the influence of the wind in top-dress-
ing the exposed coast line of a country with a solution of salt, may
serve as an important guide both in reference to the places in
which it may be expected to benefit the land, and to the causes of
its failing to do so in particular districts.
2°. Sulphate of soda, or Glauber's salt, is usually manufactured
from common salt, by pouring upon it diluted sulphuric acid (oil
of vitriol), and applying heat. Muriatic acid (spirit of salt.*) is
given off in the form of vapour, and sulphate of soda remains be-
hind. It may also be prepared, though less economically, by ad-
ding the common soda of the shops to diluted sulphuric acid as
long as any effervescence appears.
This well known salt is met with in variable quantity in the
ashes of nearly all plants, and is diffused in minute proportion
through most soils. Like the sulphate of potash, it has been ob-
served to exercise a beneficial effect on the growth especially of
such plants as are known to contain a considerable proportion of
sulphuric acid. Among these are red clover, vetches, peas, beans,
&c. And as this salt is manufactured largely in this country, and
can be obtained at the low price of eight or ten shillings a cwt. in
* So called by the old chemists, because thus given off by common salt.
328 CARBONATE OF SODA. AS A MANURE.
the dry state,” it is deserving of the attention of the practical far-
mer as likely to be extensively useful as a manure for certain
crops and on certain soils. -
3°. Sulphuret of sodium.—When sulphate of soda is mixed with
saw-dust, and heated in a furnace, the oxygen of the sulphate is
separated, and sulphuret of sodium is produced. By a similar
treatment Sulphate of potash is converted into sulphuret of potas.
sium. These compounds consist of sulphur and metallic sodium
or potassium only. They do not occur extensively in nature, and
are not manufactured for sale; but there is reason to believe that
they would materially promote the vegetation of such plants as
contain much sulphur in combination with potash or soda. The
sulphuret of sodium is present in variable quantity in the refuse
lime of the Soda manufactories, and might be expected to aid the
other substances of which it chiefly consists, if applied in the state
of compost to pulse and clover crops.
4". Carbonate of Soda.-I have described the above compounds
of soda before mentioning this its best known and most common
form, because they are all steps in the process by which the latter
is usually prepared from common salt by the soda manufacturers.
a. When the sulphuret of sodium is mixed with chalk in certain
proportions, and heated in a furnace, it is deprived of its sulphur,
and is converted into carbonate of soda, the common soda of the
shops, - -
This well known salt, now sold in the state of crystals? at from
10s, to 12s, a cwt., has not as yet been extensively tried as a means
of promoting vegetation. The lowness of its price, however, and
the fact that it is an article of extensive home manufacture, con-
joined with the encouragement we derive from theoretical consi-
derations—all unite in suggesting the propriety of a series of ex-
periments with the view of determining its real value to the prac-
tical agriculturists. The mode in which theory indicates that this
compound is likely to act in promoting vegetation—as well as the
crops to which it may be expected to be especially useful, will
come under our consideration hereafter. -
* Not in crystals, the form in which it is commonly sold as a horse medicine.
These crystals contain upwards of half their weight (55 per cent.) of water.
+ Containing 62 per cent. of water. *
l
BI-CARBONATE OF SODA. 329
Applied as a top-dressing to the land for the destruction of the
grub, it has lately been found eminently successful.
b. Besides the common carbonate of soda above described, and
which in the neighbourhood of Newcastle alone is manufactured
from common salt to the amount of 30 or 40 thousand tons every
year, there occur in nature two other compounds of soda with car-
bonic acid, in which the latter substance is present in larger quan-
tity than in the soda of the shops. The sesqui-carbonate, contain-
ing one-half more carbonic acid than the common carbonate, oc-
curs in the soil in many warm climates (Egypt, India, South Ame-
rica, &c.), and at Fezzan, in Africa, is met with as a mineral de-
posit of such thickness as in that dry climate to allow of its being
employed as a building stone.
c. The bi-carbonate, containing still more carbonic acid, is pre-
sent in the waters of many lakes, in Hungary, in Asia, &c., and
in many springs in all parts of the world. There can be no doubt
that the waters of such springs are fitted to promote the fertility,
especially of pasture land, to which they may be applied either by
artificial irrigation, or by spontaneous overflow from natural out-
lets. Some of the Harrowgate waters contain a sensible quantity
of this bi-carbonate, and over a large portion of the Yorkshire coal-
field, a bed of rock is found at various depths, the springs from
which hold in solution a considerable portion of this salt. The
Holbeck water of Leeds, according to Mr West, owes its softness
to the presence of this bi-carbonate, and the water from the coal-
mines in the neighbourhood of Wakefield is occasionally so charged
with it, as to form troublesome Saline incrustations on the bottoms
of the steam-boilers. Where these waters occur in sufficient abun-
dance, they should not be permitted to escape into the rivers, until
they have previously been employed in irrigating the land.
It has occasionally been observed that natural springs in some
localities impart a degree of luxuriance to matural pasture, which
is not to be accounted for, by the mere effect of a constant supply
of water. In such cases, the springs may be expected to contain
some alcaline, or other mineral ingredient, which the soil is unable
to supply to the plants which grow upon it, either in sufficient abun-
dance, or with sufficient rapidity.
4.
330 SODA OR CAUSTIC SODA.
5°. Soda or caustic soda.--When a solution of the common
soda of the shops is boiled with quick-lime, it is deprived of its car-
bonic acid, and like the carbonate of potash (p. 320) is brought into
the caustic state. In this state, it destroys animal and vegetable
substances, and, unless very dilute, is injurious to animal and ve-
getable life.
When common salt (chloride of sodium) is mixed with quick-
lime in compost heaps, it is deprived by the lime of a portion of
its chlorine, and is partially converted into this caustic soda. The
action of the soda in this caustic state is similar to that of caustic
potash. Not only does it readily supply soda to the growing plant,
to which soda is necessary, but it also acts upon certain other sub-
stances which the plants require, so as to render them soluble, and
to facilitate their entrance into the roots of plants. To the pre-
sence of soda in this caustic state, the efficacy of such composts of
common salt and lime in promoting vegetation is in part to be as-
cribed.
6°. Sodium is a soft metal of a silver white colour, and, like
potassium, light enough to float upon water. It is obtained by
heating caustic soda with a mixture of charcoal and iron filings.
It takes fire upon water—though not so readily as potassium—
and combines with its oxygen to form soda. In the metallic state
it is not known to occur in nature, and, therefore, does not directly
act upon vegetation. With oxygen it forms soda,-with chlorine,
chloride of sodium (common salt)—and with sulphur, sulphuret of
sodium,_all of which, as already stated, are more or less benefi-
cial to vegetation.
7°. Nitrate of soda.--When mitric acid is poured upon the com-
mon Soda of the shops, carbonic acid is given off and nitrate of
Soda is produced. It is found however in the native state in
South America, and is imported largely into this country for use
in the arts and in agriculture. It is distinguished from nitrate of
potash (saltpetre) by its property of running to a liquid in a moist
atmosphere.
8”. Phosphates of soda.--When the common soda of the shops
is added to a solution of phosphoric acid in water, till effervescence
ceases, and the solution is evaporated to dryness, phosphate of soda
is formed, and by the subsequent addition of as much more phos-
PHOSPHATES OF SODA. 331
phoric acid—bi-phosphate. These salts occur more or less abun-
dantly in the ash of nearly all plants; they are occasionally also
detected in the soil, and one or other of them is often present in
urine and many other animal manures. As we know from theory,
that these compounds must be grateful to plants, we are justified
in ascribing a portion of the efficacy of such manures, in pro-
moting the growth of vegetables, to the presence of these phos-
phates, as well as to that of the phosphates of potash (p. 323).
They are not known to occur in the mineral kingdom in any large
quantity, neither are they as yet manufactured at a sufficiently
cheap rate; hence their direct action upon vegetation has not
hitherto been made the subject of well conducted separate experi-
ments.
I, ECTURE XI.
Inorganic constituents of plants continued. Calcium, lime, carbonate of lime, sul-
phate of lime, nitrate of lime, phosphate of lime, chloride of calcium, sulphuret of
calcium. Magnesium, magnesia, carbonate, sulphate, nitrate and phosphate of mag-
nesia, chloride of magnesium. Aluminum, alumina, Sulphate and phosphates of alu-
mina. Silicon, silica, silicates of potash, soda, lime, magnesia, and alumina. Iron,
the oxides, sulphurets, sulphates and carbonate of iron. Manganese,_the oxide,
sulphate and carbonate of manganese. Tabular view of the composition per cent.
of the compounds of the inorganic elements above described.
§ 1. Calcium, lime, carbonate of lime, sulphate of lime, nitrate of
lime, phosphates of lime, chloride of calcium, sulphuret of cal-
cium.
1°. Carbonate of Lime.-Chalk, marble, and nearly all the
limestones in common use, are varieties, more or less pure, of
that compound of lime with carbonic acid, which is known to che-
mists under the name of carbonate of lime. It occurs of various
colours and of various degrees of hardness, but in weight the com-
pact varieties are very much alike, being generally a little more
than 2% times (2:7) heavier than water. They all dissolve with
effervescence in dilute muriatic acid (spirit of salt), and by the bub-
bles of gas which are seen to escape when a drop of this acid is ap-
plied to them, limestones may in general be readily distinguished
from other varieties of rock. They dissolve slowly also in rain or
other water which holds carbonic acid in solution; and hence the
springs which issue from the neighbourhood of deposits of lime-
stone are generally charged in a high degree with this mineral
substance.
The value of this carbonate of lime in rendering a soil capable
of producing and sustaining a luxuriant vegetation depends, in
part, on the necessity of a certain proportion of lime to the growth
and full development of the several parts of nearly all plants. But
QUICK-LIME AND CARBONATE OF LIME, 333
it performs also other important offices, which we shall hereafter
have occasion more fully to consider.
2°. Lime or Quick-lime.--When limestone is burned along with
coal or wood in kilns so constructed that a current of air can pass
freely through them, the carbonic acid is driven off, and the lime
alone remains. In this state it is generally known by the name of
burned or quick-lime, from its caustic qualities, and is found to
have lost nearly 44 per cent. of its original weight—20 cwt. of pure
limestone giving 113 cwt. of lime.
The most remarkable property of quick-lime is its strong ten-
dency to combine with water. This is displayed by the eagerness
with which this liquid is drunk in by the lime in the act of slaking,
and by the great heat which is at the same time developed. Slak-
ed lime is a compound of lime with water, and by chemists is call-
ed a hydrate of lime. It contains 24 per cent, of its weight of
water, and one ton of pure quick-lime becomes 263 cwt. of slaked
lime. -
The action of quick-lime upon the land is one of the most im-
portant which presents itself to the observation of the practical ag-
riculturist. Among other effects produced by it is that of hasten-
ing the decomposition of vegetable matter either in the soil or in
compost heaps; but this effect is materially promoted by—if it be
not wholly dependent upon—the presence of air and moisture.
By this decomposition carbonic acid and other compound sub-
stances are produced, which the roots are capable of absorbing and
converting into the food of plants.
In the caustic state lime does not occur in nature, nor when ex-
posed to the air does it long remain in that state. It gradually
absorbs carbonic acid from the atmosphere, and is again converted
into carbonate. This change takes place more or less rapidly in
all cases where quick-lime is applied to the land, but the benefits
arising from burning the lime do not disappear when it is thus re-
converted into carbonate. On the contrary, the state of very fine
powder, into which quick-lime falls on slaking, enables the carbonate
of lime, subsequently formed, to be intermixed with the soil more
thoroughly because it is in a much more minute state of division than
could be obtained by any mechanical means. This we shall hereafter
see to be a most important fact, when we come to study in more de-
334 CHILORIDE OF CALCIUM.
tail the theory of the action of lime in the several states of combi-
nation, and under the varied conditions in which it is employed for
the purpose of improving the land.
3°. Calcium is a silver-white metal, which, by its union with
oxygen, forms lime. It is prepared artificially only with great
difficulty, is not known to exist in nature in an uncombined state,
and therefore exercises no direct action on vegetable growth.
4°. Chloride of calcium.—When chalk or quick-lime is dissolv-
ed in muriatic acid, a solution of chloride of calcium, sometimes
called muriate of lime, is obtained. This solution occurs in sea-
water, in the refuse (mother liquor) of the salt-pans, and is allow-
ed to flow away in large quantities as a waste from certain chemi-
cal works. I have elsewhere” stated the effects it has been ob-
served to produce upon vegetable growth, and have recommended
the propriety of making experiments with a view of rendering use-
ful this and other refuse materials which in our manufactories are
now suffered largely to run to waste.
5°. Sulphuret of calcium is a compound of sulphur and calcium,
which may be formed by heating together chalk and sulphur in a
covered crucible. It is sometimes produced in nature, where
moist decaying vegetable and animal matters are allowed to fer-
ment in the presence of gypsum ; it may sometimes also be detect-
ed in the soil, and in the waters of mineral springs, and is contain-
ed largely in the recent refuse heaps of the soda manufactories.
Like the sulphurets of potassium and sodium, already described,
it is fitted, when judiciously applied, to promote the growth espe-
cially of those plants in which sulphur in considerable proportion
has been recognised as a necessary constituent.
6°. Sulphate of lime, or gypsum, is a well-known white crystal-
line or earthy compound, which occurs as an abundant mineral
deposit in numerous parts of the globe. It is present in many
soils, is contained in the waters which percolate through such soils,
and in those of springs which ascend from rocky beds in which
gypsum exists, and is detected in sensible proportions in the ashes
of many cultivated plants. It is extensively employed in the arts,
and in some countries not less extensively as a means of promot-
ing the fertility of the land.
* See the Author's Suggestions for experiments in practical agriculture.
SULPHATE AND NITRATE OF LIME, 335
The gypsum of commerce contains nearly 21 per cent. of its
weight of water, which it loses entirely on being exposed to a red
heat. In some countries, a variety which is almost entirely free
from water occurs in rocky masses, and is distinguished by the
name of Anhydrite.
Gypsum, when burned, has the property of being reduced with
great ease into the state of an impalable powder. This powder,
however, combines so readily with the water it had lost by burning,
that if it be mixed with water to the consistence of a paste so thin
that it can be poured into a mould, it sets and hardens in a few
minutes into a solid mass. In this way burned gypsum is employ-
ed in making plaster casts and cornices.
Burned gypsum consists of lime and sulphuric acid only—in
the proportions of 41% of the former to 58% of the latter. Its use
as a manure, therefore, will chiefly depend upon its supplying these
two substances to plants by which they are more abundantly re-
quired, and upon soils in which they are already present in compa-
ratively small proportion. - -
7°. Nitrate of lime.—The production of mitrate of lime in arti-
ficial mitre-beds, on old walls, and on the sides of caves and cel-
lars, especially in damp situations, has already been alluded
to in a previous lecture. It may be formed artificially by dis-
solving common limestone in nitric acid, and evaporating the so-
lution. It constitutes a white mass which rapidly attracts water
from moist air, and runs to a liquid. It is produced naturally, and
exists, as I believe, in soils containing lime, more commonly than
has hitherto been suspected. Its extreme solubility in water, how.
ever, renders it liable to be carried downwards into the lower por-
tions of the soil by every shower of rain—or to be actually wash-
ed away, when long continued wet weather prevails.
When heated to dull redness with vegetable matter, the nitrate
of lime is decomposed, and is converted into carbonate, or when
exposed alone to a bright red heat, the nitric acid is expelled, and
quick-lime alone remains. Hence where it really exists in plants,
it cannot be detected in the ash they leave—and when present in
soils it must be separated by washing them in water, before they
are exposed to a heat sufficient to burn away the organic matter
they contain,
336 PII ()SPITATES OF LIME.
The details already entered into in a preceding lecture re-
garding the general action of nitric acid, in promoting the natural
vegetation of the globe, render it unnecessary for me to dwell here
on the special action of its compound with lime—more particular-
ly as the entire subject of the action of lime upon the land will
hereafter demand from us a separate consideration.
The nitrate of lime cannot, as yet, be formed by art at a suffi-
ciently cheap rate to allow of its being manufactured for the use
of the agriculturist.
8°. Phosphates of lime.—Lime combines with phosphoric acid
in several proportions, forming as many different compounds. Of
these by far the most important and abundant in nature—certain-
ly the most useful to the agriculturist, is the earth of bones. It
will be necessary, however, to advert shortly to two others, with
the existence of which it is important for us to be acquainted.
a. Earth of bones is the name given to the white earthy skeleton
that remains, when the bones of animals are burned in an open
fire until every thing combustible has disappeared. This earthy
matter consists chiefly of a peculiar phosphate of lime, composed of
51, per cent. of lime, and 48% of phosphoric acid. This compound
exists ready formed in the bones of all animals, and is the sub-
stance selected in the economy of nature, to impart to them their
strength and solidity. It is found in smaller quantity in those of
young animals, while they are soft and cartilaginous, -and the
softening of the bones, which in after-life sometimes occurs as the
result of disease, is caused by the unnatural abstraction of a greater
portion of this earthy matter than is replaced by the food.
This earthy phosphate constitutes about 57 per cent. of the dried
bones of the ox, is present in lesser quantity in the horns, hoofs,
and mails, and is never absent even from the flesh and blood of
healthy animals. It exists in the seed of many plants, in all the
varieties of grain which are extensively cultivated for food, and in
the ashes of most common plants.
If we consider that, when animals die, their bones are chiefly
buried in the earth; and that, over the entire globe, animal life, in
one or other of its forms, prevails; we shall not be surprised that,
in almost every soil, the earth of bones should be found to exist
in greater or less abundance. Nor can we have any difficulty in
FAIRTH OF BONES. 337
conceiving, if such be the case, whence plants draw their constant
and necessary supplies of this substance.
At the same time, it is true of this compound, as of all the others
we have yet spoken of, as occurring in, and as necessary to, the
growth of vegetables, that some soils contain it in greater abun-
dance than others, and that from some soils, therefore, plants will
not readily obtain as much of this substance as they require. This
is one of the principles on which the use of bone-dust as a manure
depends. -
Eſence of two marls both containing carbonate of lime—that will
be most useful to the land which contains also, as many do, a no-
table proportion of phosphate of lime; and of two limestones that
one will be preferred in an agricultural district, in which animal re-
mains most abound. I shall have occasion to illustrate this point
more fully when, in a subsequent lecture, I come to explain the
natural origin of soils, and to trace their chemical constituents to
the several rocky masses from which they appear to have been derived.
Before dismissing this topic, however, there are one or two pro-
perties of this bone earth which are of practical importance, and to
which, therefore, I must shortly request your attention. It is in-
soluble in water or in solutions of soda or potash, but it dissolves
readily in acids, such as the nitric or muriatic, and also, though
less easily and abundantly, in common vinegar. It exists in milk,
and is supposed to be held in solution by the peculiar acid found
in this liquid, and which I have already described under the name
of lactic acid (acid of milk).
It is slightly soluble also in a solution of carbonic acid, and of
certain other organic acids which exist in the soil, and it is by
means of these acids, that it is supposed to be rendered capable of
entering into the roots of plants. Wherever vegetable matter
exists, and is undergoing decay in the soil, the water makes its way
to the roots more or less laden with carbonic acid, and thus is ena-
bled to bear along with it not only common carbonate of lime as
has been shown in a previous lecture (p. 65), but also such a por-
tion of phosphate as may aid in supplying this necessary food to
the growing plantſ
* If to a solution of bone earth in muriatic acid (spirit of salt), liquid ammonia
- Y
338 BOILED BONES AS A MANUR.E.
In the bones of animals this phosphate of lime is associated with
animal gelatine, which can be partially extracted by boiling bones
in water under a high pressure. It has been observed, however,
that the phosphate, when in a minute state of division, is slightly
soluble in a solution of gelatine, and hence bones, from which the
jelly has been partially extracted by boiling, will be deprived of a
certain proportion of their earthy matter also. They will have lost
their gelatine, however, in a greater proportion, and hence, if again
thoroughly dried, they will contain a larger per-centage of bone-
earth, than when in their natural state. In our large towns, such
as Manchester, bones are frequently boiled for the manufacture of
a jelly or size which is extensively used in the stiffening of calicoes
and other goods, and in France and Germany for the manufacture
of glue. Such boiled bones are said to act more quickly when
applied to the land, but to be less permanent in their effects. This
may be partly owing to their not being so dry as the unboiled
bones, and partly to their being in a more disintegrated state.
Being thus moist they will contain, in the same weight, a compara-
tively smaller quantity both of the animal gelatine, and of the
earthy phosphate, while they will also be more susceptible of speedy
decomposition, when buried in the soil.”
In solutions of common salt and of sal-ammoniac, the earth of
bones is also slightly soluble, and cases may occur where the pre-
(hartshorn) be added, the solution will become milky, and a white powder will fall,
which is the earth of bones in an extremely minute state of division. If this powder
be washed repeatedly with pure water, and be afterwards well shaken with water
which is saturated with carbonic acid, or through which a current of this gas is made
to pass, a sensible portion of the phosphate will be found to be taken up by the water.
This will appear on decanting the clear solution and evaporating it to dryness, when a
quantity of the white powder will remain behind. The mean of 10 experiments made
in this way gave me 30 grains for the quantity of phosphate taken up by an impe-
rial gallon of water. What thus takes place in our hands, happens also in the soil.
Not only does the water which enters the root bear with it a portion of this compound
where it exists in the soil, but the Superabundant water also which runs off the surface
or sinks through to the drains, carries with it to the rivers in its course a still larger
quantity, and thus gradually lessens that supply of phosphates which either exists
naturally in the soil, or has been added as a manure by the practical agriculturist.
* The relative value of crushed bones in these two states is indicated by the price
of the unboiled being about 7 guineas, while that of boiled is only about 4 guineas a
ton. l
AC]]) OR BT-PHOSPIHATE OF LIME. 339
sence of these compounds in the soil may facilitate the conveyance
of the earthy phosphate into the roots of plants.
b. Acid, or Super or Bi-phosphate of Lime.—When burned bones
are reduced to powder, and digested in sulphuric acid (oil of vitriol)
diluted with once or twice its weight of water, the acid combines with
a portion of the lime, and forms sulphate of lime, (gypsum), while
the remainder of the lime and the whole of the phosphoric acid are
dissolved. The solution, therefore, contains an acid phosphate of
lime, or one in which the phosphoric acid exists, in much larger
quantity than in the earth of bones. The true bi-phosphate, when
free from water, consists of 71% of phosphoric acid, and 28% of
lime. It exists in the urine of many animals, and is an important
constituent of the liquid manures of the farm-yard.
If the mixture of gypsum and acid phosphate, above described,
be largely diluted with water, it forms a most valuable liquid ma-
nure, especially for grass land, and for crops of rising corn. In
this liquid state, the phosphoric acid diffuses itself easily and
perfectly throughout the soil, and speedily loses its acid character
by combining with one or other of the basic” substances, almost
always present in every variety of land.
Or if, to the solution before it is applied to the land, a quantity
of pearl ash be added until it begin to turn milky, a mixture of
the phosphates with the sulphates of lime and of potash is obtained,
or—if soda be added instead of potash—of the phosphates with the
sulphates of lime and of soda ; either of which mixtures is still more
efficacious upon most soils than the solution of the acid phosphates
alone.
Or to the solution of bones in the acid, the potash or soda may
be added without further dilution, and the whole then dried up by
the addition of charcoal powder, or even of vegetable mould, till
it is in a sufficiently dry state to be scattered with the hand as a
top-dressing, or buried in the land by means of a drill.
I have above alluded to the employment of bones in France and
Germany for the manufacture of glue. For this purpose, the bro-
* This word has already been used and explained—it is applied to potash, soda,
ammonia, lime, magnesia, and other substances, which have the property of combining
with acids (sulphuric, nitric, &c.) and of thus neutralizing them, or depriving them of
their acid qualities, and effects,
340 NATIVE PHOSPHATE OF LIME OR APATITE 2
ken bones are digested in weak muriatic acid, by which the earthy
matter is dissolved, and the gelatine left behind. The gelatinous ske-
leton is boiled down for glue, and the solution of bone earth was for-
merly thrown away. This solution contains a mixture of the acid
phosphate of lime, with chloride of calcium,_and might be used up
in any of the ways above described, with manifest benefit to the
land. The glue prepared by this method, however, is said to be
frequently inferior in quality, though not necessarily so, I think—
and as the process is not adopted in this country, the opportunity
of making an economical application of this waste material is not
likely to be often presented to the English farmer.
c. Native Phosphate of Lime or Apatite.—In some parts of the
world, a hard mineral substance, commonly known by the name
of Apatite, occurs in considerable quantity. It consists chiefly
of a phosphate of lime, which differs but slightly in composition
from the earth of bones-containing 54% per cent of lime, while
the latter contains only 51% per cent. The composition of this
mineral would lead us to expect it to possess a favourable action
upon vegetation, and this anticipation has been confirmed by some
experiments made with it on a limited scale by Sprengel,” and
more recently by Dr Daubeny.
It occurs occasionally in mineral veins, especially such as are
found in the granite and slate rocks, Masses of it are met with
in Cumberland, in Cornwall, in Finland, in the iron mines of
Arendahl in Norway, and in many other localities. A variety of
it, distinguished by the name of phosphorite, is said to form beds
at Schlachenwalde in Bohemia, and occurs in the form of a large
vein in the province of Estremadura in Spain. From the last of
these localities, though not as yet sufficiently accessible, the time
may come when the high price of bones may induce our enter-
prising merchants to import it—for the purpose of being employed
in a finely powdered or in a dissolved state as a fertilizer of the land.
§ 2. Of magnesium, magnesia, carbonate, sulphate, nitrate, and
phosphate of magnesia, and chloride of magnesium.
1°. Carbonate of Magnesia is a tasteless earthy compound,
which in some parts of the world forms rocky masses and veins of
.* Sprengel, Chemie, i. p. 64.
CAUSTIC OR, CALCINED MAGNESIA. 341
considerable height and thickness. It occurs more largely, how-
ever, in connection with carbonate of lime in the magnesian lime-
stones, so well known in the eastern and northern parts of Eng-
land, and in similar rocks, distinguished by the name of dolo-
mites or of dolomitic limestones, in various countries of Europe.
The pure, exceedingly light, white magnesia of the shops, is partly
extracted from the magnesian limestone, and partly from the resi-
dual or mother liquor of the salt-pans, which generally contains
much magnesia.
When pure and dry, carbonate of magnesia consists of 43% of
magnesia, and 513 of carbonic acid. It dissolves readily in di-
łuted acids (sulphuric, muriatic, or acetic), the carbonic acid at
the same time escaping with effervescence.
Existing as it does in many solid rocks, this carbonate of mag-
nesia may be expected to be present in the soil, and it is found in
the ashes of many plants. Of the ashes of some parts of plants,
as of wheat and some other grains, it forms from one-tenth to one-
eighth of the entire weight.
When exposed to the air in a finely divided state, it gradually
absorbs a quantity of moisture from the atmosphere, equal to two-
thirds of its own weight. In this state, it dissolves in 48 times its
weight of water, though, when dry, it is nearly insoluble. Like
<arbonate of lime it is also soluble in water impregnated with car-
bonic acid, but in a somewhat greater degree. In this state of so-
lution, it may be readily carried into the roots, and be the means
of supplying to the parts of living vegetables, a portion of that
magnesia which is necessary to their perfect growth.
Soils containing much of this carbonate of magnesia are said to
be highly absorbent of moisture, and to this cause is ascribed the
coldness” of such soils. This opinion is, however, open to doubt.
2". Magnesia or Caustic magnesia, the calcined magnesia of the
shops.--When the carbonate of magnesia is heated to redness in
the open air, it parts with its carbonic acid much more readily than
carbonate of lime does, and is brought into the state of pure or caus-
tic magnesia. In this state it does not occur in nature, but it is oc-
casionally met with in certain rocks in combination with about 30
per cent. of water, forming a hydrate of magnesia well known to
* Sprengel, Chemic, i., p. 645.
342 CAUSTIC OR CALCINED MAGNESIA.
mineralogists. When magnesian limestones or dolomites are
burned, the quick-lime obtained often contains caustic magnesia
also in considerable quantity. This mixture is frequently applied
to the land, but with injurious effects, if laid on in too large quan-
tities. The cause of the hot or burning nature, as it is called, of
magnesian lime, is not very satisfactorily ascertained. I shall,
however, state two or three facts, which may assist in conducting
us to the true cause.
a. Quick-lime dissolves in 750 times its weight of water, at the
ordinary temperature of the atmosphere, while pure magnesia re-
quires 5142 times its weight. The magnesia, therefore, is not
likely to injure living plants directly by entering into their roots
in its caustic state, since lime which is seven times more soluble
produces no injurious effect.
b. It seems to be the result of experience, that magnesia in the
state of carbonate is but slightly injurious to the land; some deny
that in this state it has any injurious effect at all. This is doubt-
ful. We may infer, however, with considerable probability, that it is
from some property possessed by magnesia in the caustic state, and
not possessed, or at least not in an equal degree, either by quick-
lime or by carbonate of magnesia, that its evil influence is chiefly to
be ascribed.
e. When exposed to the air, quick-lime speedily absorbs wa-
ter and carbonic acid from the air, forming first a hydrate” in fine
powder, and then a carbonate. Caustic magnesia absorbs both of
these more slowly than lime does, and in the presence of the lat-
ter, or when mixed with it, must absorb them more slowly still,
since the lime will seize on the greater portion of the moisture
and carbonic acid which exists in the air, immediately surrounding
both. When slaked in the air also, the lime may be transformed
in great part into carbonate while the magnesia still remains in
the state of hydrate, and it is a property of this hydrate to attract
carbonic acid more feebly and slowly, even than the newly burned
magnesia as it comes from the kiln. Hence when buried in the
* Compounds of substances with water are called hydrates (from the Greek word
for water). Thus slaked lime, a compound of lime with water, is called hydrate of
line—and the native compound of magnesia with water, alluded to in the text, is
called hydrate of magnesia,
CAUSES OF ITS PECULIAR, ACTION UPON VEGETATION. 343
soil, after the lime has become nearly all transformed into carbo-
nate, the magnesia may still be all either in the dry caustic state,
or in that of a hydrate only.
d. Now there exist in the soil, and probably are exuded from
the living roots, various acid substances, both of organic and of
inorganic origin, which it is one of the functions of lime, when ap-
plied to the land, to combine with and render innoxious. But
these acid compounds unite rather with the caustic magnesia, than
with the lime which is already in combination with carbonic acid
—and form salts" which generally are much more soluble in water
than the compounds of lime, with the same acids. Hence the wa-
ter that goes to the roots, reaches them more or less loaded with
magnesian salts, and carries into the vegetable circulation more
magnesia than is consistent with the healthy growth of the plant.
It is hazardous to reason from the phenomena of animal to those
of vegetable physiology, yet if lime and magnesia have the power
of differently affecting the animal economy, why may they not al-
so very differently affect the vegetable economy 2 And since, in
the same circumstances, and in combination with the substances
they meet with in the same soils, magnesia is capable of entering
more largely into a plant by its roots—may not magnesia be con-
sidered capable of poisoning a plant, when lime in the same condi-
tion would only improve the soil P
e. I have said that it may be doubted whether magnesia in the
state of carbonate is wholly unhurtful to the land. This doubt
rests on the fact that the magnesia retains its carbonic acid more
feebly than lime does—and, therefore, its carbonate is the more
easily decomposed when an acid body comes in contact with both.
Though, therefore, the magnesian carbonate will not lay hold of
all acid matter so readily and surely as caustic magnesia may, still
occasions may occur where, acid matters being abundant in the
soil, so much carbonate of magnesia may be decomposed and dis-
solved as to render the water absorbed by its roots destructive to
the health or life of a plant.
In reference to this point, however, it must be distinctly under-
stood, that magnesia is one of the kinds of organic food most ne-
* Compounds of the bases, potash, soda, lime, magnesia, &c., with acids,
phuric, muriatic, nitric, acetic, (or vinegar), &c., are called salts,
sul-
344 ("I [LORIDE OF MAGNESIUM.
cessary to plants, that a certain quantity of it is absolutely neces-
sary to the growth of nearly all cultivated plants, and that it is
only when it is conveyed to the roots in too large a quantity, that
it proves injurious to vegetable life.
3°. Magnesium is the metallic basis of magnesia. Little is
known of its properties, because of the difficulty of preparing it in
any considerable quantity for the purpose of experiment. It is a
white metal, which, when heated in the air, takes fire and burns,
combining with the oxygen of the atmosphere, and forming mag-
nesia. It is not known to occur in mature in an elementary form,
and therefore is not supposed directly to influence vegetation.
4°. Chloride of Magnesium.—When magnesia is dissolved in
muriatic acid, and the solution evaporated to dryness, a white
mass is obtained which is a chloride of magnesium, consisting of
magnesium and chlorine only. This compound occurs not un-
frequently in the soil, associated with chloride of calcium. It
is met with also in the ash of plants, while in Sea water, and in
that of some salt lakes, it exists in very considerable quantity.
Thus 100 parts of the water of the Atlantic have been found
to contain 34 of chloride of magnesium, while that of the Dead
Sea yields about 24 parts of this compound." Hence it is present
in great abundance in the mother liquor of the salt-pans, and it is
from the refuse chloride contained in this liquor that the magnesia
of the shops is frequently prepared.
The chloride of magnesium has not hitherto been made the sub-
ject of direct experiment as an application to the land. From the
fact, however, that plants require much magnesia and some chlo-
rine, there is reason to believe that, if cautiously applied, it might
prove beneficial in some soils, and especially to grain crops. Its
extreme solubility in water, however, suggests the use of caution
in its application. The safest method is to dissolve it in a large
quantity of water, and to apply it to the young plant by means of
a water-cart. In this way the refuse of the salt-works might, in
some localities, be made available to useful purposes.
The chloride of magnesium is decomposed both by quick-lime
and by carbonate of lime; hence, when applied to a soil contain-
* 100 parts of the water of the Dead Sea contain also about 10% of chloride of cal-
cium, and nearly 6 of common salt.
SULPHIATIC OF MAGNESIA. - 345
ing lime in either of these states, chloride of calcium and caustic
or carbonated magnesia will be produced.
5°. Nitrate of Magnesia is formed by dissolving carbonate of
magnesia in nitric acid, and evaporating the solution. It attracts
moisture from the air with great rapidity, and runs into a liquid.
It is probably formed naturally in soils containing magnesia, in
the same way as mitrate of lime is known to be produced in soils
containing lime. No direct experiments have yet been made as
to its effects upon vegetation; but there can be no doubt that it
would prove highly beneficial, could it be procured at a sufficiently
cheap rate to admit of its economical application to the land.
6°. Sulphate of Magnesia—the common Epsom salts of the
shops—is formed by dissolving carbonate of magnesia in diluted
sulphuric acid. It exists in nearly all soils which are formed from,
or are situated in, the neighbourhood of rocks containing mag-
nesia. In some soils it is so abundant, that in dry weather it forms
a white efflorescence on the surface. This has been observed to
take place in Bohemia, Hungary, and parts of Germany, and it
may be frequently seen in warm summer weather in the neighbour-
hood of Durham.* -
This salt has been found by Sprengel to act upon vegetation
precisely in the same way as gypsum does, and on the same kind
of plants. It must be used, however, in smaller quantity, owing
to its great solubility. Its higher price will prevent its ever being
substituted for gypsum, in top-dressing clovers, &c.—but when
applied to corn plants, to wheat for example, the grain of which con-
tains much magnesia, a small quantity of this sulphate has produced
marked good effects. It will act still more beneficially if used
along with such other substances as are capable of yielding the re-
maining constituents which compose the inorganic matter of the
grain. Its price is not too high to admit of this more restricted
application.f
* It occasionally collects beneath the plaster of old walls in this city. In one of
the lower rooms of the old Exchequer buildings, I found it forming an extensive layer
nearly half an inch thick, beneath the damp plaster. The magnesia is derived from
the magnesian limestone, used both for mortar and for a building stone.
+ Its price in Newcastle, in the state of crystals, is about 10s, a cwt. The impure
salt collected at the alum works on the Yorkshire coast might be obtained for little
346 ALUMINA, A PRINCIPAL CONSTITUENT OF GLAYS.
7°. Phosphate of Magnesia.—Magnesia exists in combination
with phosphoric acid, in the solids and fluids of all animals, though
not so abundantly as the phosphates of lime. In most soils, phos-
phate of magnesia is probably present in minute quantity, since in
the ashes of our different varieties of grain, and in that of the po-
tato, it is found in very considerable proportion.
The action of phosphate of magnesia alone upon vegetation has
seldom been tried. In combination with ammonia, however, in the
form of the ammoniacal phosphate, it has been successfully em-
ployed by Boussingault. As in this state it exists in urine, and
in many animal manures—a portion of their efficacy may be due
to its presence. In peat ashes, which often prove a valuable ma-
nure, it is sometimes met with in appreciable quantity, and their
beneficial operation in such cases has been attributed in part to the
agency of this phosphate. *. .
§ 3. Aluminium, alumina, sulphate and phosphate of alumina—
alum.
1°. Aluminium is another of those rare and little known metals
the existence of which was established by Sir H. Davy. In com-
bination with oxygen it forms alumina, and in this state it exists
in such abundance in nature, as to form a large proportion of the
entire crust of the globe.
2°. Alumina, the earth of Alum.—When common alum is dis-
solved in water, and a solution of carbonate of soda or of ammonia
is added to it, a bulky white powder falls, which, when collected
on a filter, well washed and dried, is nearly pure alumina. This
substance occurs on the surface of the earth in a pure state only
in some rare minerals, such as the corundum, the Sapphire, and
the ruby, but it constitutes a large proportion of all the slaty and
shaley rocks. It is the principal ingredient also of all clays (pipe-
clay for example) and clayey soils, which increase in tenacity in
proportion to the quantity of alumina they contain.
When pure, it is a white tasteless earthy substance, which ad-
heres to the tongue, has a density of 2:00, and is insoluble in wa-
more than half this price. For its effects upon potatoes, when mixed with nitrate of
soda, see the Author's Suggestions for Experiments in Practical Agriculture.
BURNED CLAY AND SULPHATE OF ALUMINA. 34.7
ter, but when newly thrown down from a solution of alum, dis-
solves readily in caustic potash and soda and in most acids. When
heated to redness, however, it becomes hard and dense, as in burned
clay and fire bricks, and can then only be dissolved with extreme
difficulty, even by the strongest acids. Though it exists so largely
in the soil, it contributes but little in a direct manner to the nou-
rishment of plants. The ash they leave contains in general but a
very small per-centage of alumina—in many cases not a trace.
The principal agency of this ingredient of the soil is therefore of
an indirect, perhaps of a mechanical kind.
It has been stated in a preceding Lecture (p. 27,) that charcoal
has the property of absorbing gaseous substances, such as ammonia,
from the atmosphere, and that the action of charcoal powder, in
promoting vegetation, has been in a great measure ascribed to
this property. The same property, we have also seen, is as-
cribed to gypsum, and hence its fertilizing action has been ex-
plained in a similar way. Alumina is said to be equally absorbent
of ammonia; and the use of burned clay as a top-dressing, so
strongly recommended by General Beatson," is ascribed to its
power of abstracting ammonia from the air, and fixing it in the
soil—ready to be conveyed by the rains to the roots of the plants
that grow upon it (Liebig). It has been already shown (p. 83,
note), that this mode of accounting for the action of gypsum
is not satisfactory as a sole cause—in the case of clay, the fact
of its absorbing ammonia is hypothetical,f and therefore the ex-
planation founded upon this fact is not to be implicitly relied upon.
3°. Sulphate of Alumina.—When alumina is digested in dilut-
ed sulphuric acid, it readily dissolves, and forms a solution of sul-
phate of alumina. This solution is characterized by a remarkable
and almost peculiar sweetish astringent taste. When evaporated
* New System of Cultivation. London, 1820.
t Because clays of many varieties—pipe-clay for example—contain traces of am-
monia, which they evolve when moistened with a solution of caustic potash;-it is in-
ferred that they have absorbed this ammonia from the atmosphere. The same infe-
rence is drawn from the fact of its presence in oxide of iron. Liebig's Organic Chemis-
try applied to Agriculture, p. 89.-In neither case does the inference appear to me to
be necessary. Much of the ammonia may have been formed in the soil, during the
oxidation of the iron itself, or during the decay of vegetable and animal substances,
348 PHOSPHATES OF ALUMINA-ALUM.
‘...f
to dryness it yields a white salt, which dissolves in twice its weight
of water only, and when exposed to the air, attracts moisture ra-
pidly, and spontaneously runs to a liquid. This salt exists in some
soils, especially in those of a wet, marshy, and peaty character.
No experiments have yet been made with the view of determin-
ing the direct influence of this compound upon vegetation.
4°. Phosphates of Alumina.-In combination with phosphoric
acid, alumina forms one compound well known to mineralogists,
by the name of wavellite. This mineral, however, occurs in too
small quantity, to be an object of interest to the agriculturist.
Phosphoric acid is disseminated in some form or other through-
out our clayey soils, though in very small and variable quantity.
It is most probable that in these soils a portion of the acid, at least,
is in combination with the alumina in the state of phosphate. One
of the most difficult problems in analytical chemistry is to effect
a perfect separation of a small proportion of phosphoric acid from
alumina, and rigorously to estimate its quantity; hence, in the
greater part of the analyses of soils hitherto published, this most
important ingredient in a fertile soil (the phosphoric acid), when
in combination with, or in presence of alumina, has either been al-
together neglected, or rudely guessed at, or indicated by a rough
approximation only. We have no direct proof, therefore, of the
extent to which the phosphates of alumina exist in different soils.
5°. Alum.—The common alum of the shops owes its well known
sweetish astringent taste to the presence of the above sulphate of
alumina. It consists in 100 parts of about 40 of sulphate of alu-
mina, 14% of sulphate of potash, and 45% of water. Alum is
formed naturally on many parts of the earth's surface, especially
as an efflorescence on certain soils, and on Some rocks when ex-
posed to the air, as on the alum shales of the Yorkshire coast.
It is largely manufactured by calciming and afterwards washing
these alum shales.
Alum has not been extensively tried as a manure. Its compo-
sition, however, would lead us to expect it to exert a beneficial in-
fluence on the growth of many plants—while the price, especially
of the less pure varieties, is such as to admit of its being applied
to the land at a comparatively small cost. From some experi-
SILICA, THE SUBSTANCE OF QUARTZ AND FLIN T. 349
ments made on a small scale, Sprengel considers it highly worthy
the attention of the practical agriculturist.
§ 4. Of silicon, silica, and the silicates of potash, soda, lime,
magnesia, and alumina.
1°. Silica.-The chief ingredient in all sand-stones, and in
nearly all sands and sandy soils, is known to chemists by the name
of silica. Flints are nearly pure silex or silica—common quartz
rock is another form of the same substance—while the colourless
and more or less transparent varieties of rock-crystal and chalce-
domy present it in a state of almost perfect purity. It exists abun-
dantly in almost all soils, constituting what is called their siliceous
portion, and is found in the ashes of all plants without exception, but
in especially large quantity in those of the grasses. Silica is with-
out colour, taste, or smell, and cannot be melted by the strongest
heat. As it occurs in the mineral kingdom—in the state of flint,
of quartz, or of sand—it is perfectly insoluble in pure water, either
cold or hot, does not dissolve in acid and very slowly in alkaline
solutions. When mixed with potash, soda, or lime, and then heated
in a crucible to a high temperature, it melts and forms a glass.
PWindow and plate glass consist chiefly of silica, lime, and soda;
flint glass contains litharge (oxide of lead) in place of the lime.
But though the various forms of more or less pure silica, which are
met with in the mineral kingdom, are absolutely insoluble in wa-
ter, yet it sometimes occurs in mature, and can readily be prepared
in a state in which pure water, and even acid solutions, will take
it up in considerable quantity. In this state it may be obtained
by reducing crown-glass to a fine powder and digesting it in strong
muriatic acid, or by melting quartz sand in a large quantity of pot-
ash or soda, and afterwards treating the glass that is formed with
diluted muriatic acid.
Silica is one of the most abundant substances in mature, and in
combination with potash, soda, lime, magnesia, and alumina it
forms a large portion of all the so-called crystalline (granitic, ba-
saltic, &c.) rocks. The compounds of silica with these bases are
called silicates. By the action of the air, and other causes, these
silicates undergo decomposition, as glass does when digested with
350 SILICA AND SILICON.
muriatic acid, and the silica is separated in the soluble state. Hence
its presence in considerable quantity in the waters of many mineral
and especially hot mineral springs, and in appreciable proportion
in nearly all waters that rise from any considerable depth, or have
made their way through any considerable extent of soil.
In the substance of living vegetables it exists, for the most part,
in a state of combination—as well as in the form of an extremely
delicate tissue, of which the fibres are exceedingly minute, and
therefore expose a large surface to the action of any decomposing
agent, or of any liquid capable of dissolving it. In our compost
heaps containing vegetable matters, these silicates undergo decom-
position,--and the more readily the less they have been previously
dried or the greener they are, and the silica of the plant is libe-
rated in a soluble state. Whether or not, when thus liberated, it
will be carried, uncombined, into the roots of plants by the water
they absorb, will depend upon the quantity of potash or soda in
the compost or in the soil, and upon other circumstances hereafter
to be explained.
2°. Silicon is known only in the state of a dark brown powder,
which has not as yet been met with in nature in an elementary form,
and is prepared by the chemist with considerable difficulty. When
heated in the air, or in oxygen gas, it burns, combines with oxygen,
and is converted into silica. Silica, therefore, in its various forms,
is a compound of silicon with oxygen. It consists of 48 per cent,
of the former, and 52 per cent. of the latter.
3°. Silicates of Potash and Soda.--When finely powdered quartz,
flint, or sand is mixed with from one-half its weight to three times
its weight of dry carbonate of potash or soda, and exposed to a
strong heat in a crucible, it readily unites with the potash or soda,
and forms a glass. This glass is a silicate or a mixture of two or
more silicates of potash or soda. Silica combines with these al-
halies” in various proportions. If it be melted with much potash,
the glass obtained will be readily soluble in water; if with little,
the silicate which is formed will resist the action of water for any
length of time. Window and plate glass contain much silicate of
* Potash, soda, and ammonia are called alkalies ; lime and magnesia are alkalime
earl/s.
SILICATES OF POTASH AND SODA. 351
potash or soda. A large quantity of alkali renders these varieties
of glass more fusible and more easily worked, but at the same time
makes them more susceptible of corrosion or tarnish by the action
of the air. \
The insoluble silicates of potash and soda exist also in many mi-
neral substances. In the felspar and mica, of which granite in a
great measure consists, they are present in considerable quantity.
The former (felspar) contains one-third of its weight of an insolu-
ble silicate of potash, consisting of nearly equal weights of potash
and silica. In the variety called albite or cleavelandite silicate of
soda alone is found, while in some other varieties a mixture of both
silicates is present. In mica from 12 to 20 per cent. of the same
silicate of potash occurs, but soda can rarely be detected in this
mineral. The trap-rocks also (whin, basalt, green-stone), so abun-
dant in many parts of our island, consist almost entirely of sili-
cates. Among these, however, the silicates of potash and soda
rarely exceed 5 or 6 per cent. of the whole weight of the rock, and
are often entirely absent.
These insoluble silicates also exist in the stem and leaves of
nearly all plants. They are abundant in the stems of the grasses,
especially in the straw of the cultivated grains, and form a large
proportion of the ash which is left when these stems are burned.
It is important to the agriculturist to understand the relation
which the carbonic acid of the atmosphere bears to these alkaline
silicates which occur in the mineral and vegetable kingdom. In-
soluble as they are in water, they are slowly decomposed by the
united action of the moisture and carbonic acid of the air, the latter
taking the potash or soda from the silica, and forming carbonates
of these bases. In consequence of this decomposition the rocks in
which they are contained disintegrate and crumble down, while
the soluble carbonate is washed down by the rains or mists, and is
borne to the lower grounds to enrich the alluvial and other soils, or
is carried by the rivers to the sea.
In some cases, as in the softer felspar of some of the Cornish
granites, this decomposition is comparatively rapid; in others, as
in the Dartmoor and many of the Scottish granites, it is exceed-
ingly slow,--but in all cases the rock crumbles to powder long be-
352 SILICATES OF LIME IN THE TRAP-ROCKS,
fore the whole of the silicates are decomposed, so that potash and
soda are always present in greater or less quantity in granitic soils,
and will continue to be separated from the decaying fragments of
rock for an indefinite period of time.
But the silica of the felspar, or mica, or zeolitic” trap, when thus
deprived of the potash with which it was combined, is in that pecu-
liar state, in which, as above described (p. 350), it is capable of
being dissolved to a small extent by pure water, and more largely
by solutions of the carbonates of potash or soda. Hence the same
rains or mists which dissolve the alkaline carbonates so slowly
formed, take up also a portion of the silica, and convey it in a
state of solution to the soils or to the rivers. Thus, with the ex-
ception of the dews and rains which fall directly from the heavens,
few of the supplies of water by which plants are refreshed and
fed, ever reach their roots entirely free from silica, in a form in
which it can readily enter into their roots, and be appropriated to
their nourishment.
In the farm-yard and the compost-heap, where vegetable mat-
ters are undergoing decomposition, the silicates they contain un-
dergo similar decompositions, and, by similar chemical changes
their silica is rendered soluble, and thus fitted, when mixed with
the soil, again to minister to the wants and to aid the growth of
new races of living vegetables.
4°. Silicates of Lime-A mixture of sand or flint with quick-
lime readily melts and forms a glassy silicate or a mixture of two
or more silicates of lime. These silicates are also present in large
quantity in window and plate glass, and in some of the crystallineſ
(granite and trap) rocks. In felspar and mica, which abound, as
we have seen, in the alkaline silicates, it is but rarely that any
lime can be detected. In that variety of granite, however, to which
the name of syenite is given by mineralogists, hornblende takes
the place of mica, and some varieties of this hornblende contain
from 20 to 35 per cent. of silicate of lime. This silicate of lime,
* The trap rocks also more or less abound in zeolitic minerals, of which there is a
great variety, and in which nearly all the alkali present in these (trap) rocks is con-
tained.
+ So called because the minerals of which they consist are generally in a crystal-
lized state.
SILICATES OF LIME IN THE TRAP-ROCKS. 353
(containing 38 per cent of lime), is almost always present in the
basaltic and trap-rocks, and sometimes, as in the augitic" traps, in
a proportion much larger than that in which it exists'in the un-
mixed hornblende. To this fact we shall have occasion to revert
when we come to consider the relative fertility of different soils,
and the causes on which the differences in their several productive
powers most probably depend.
Silicates of lime are also found in the ash, and probablyf exist
in the living stem and leaves of plants.
Like the similar compounds of potash and soda, the silicates of
lime are slowly decomposed by the united agency of the moisture
and the carbonic acid of the atmosphere. Carbonate of lime is
formed, and silica is set at liberty. This carbonate of lime dis.
solves in the rains or dews which descend loaded with carbonic
acid, and the same waters take up also a portion of the soluble
silica, and diffuse both substances uniformly through the soil in
which the decomposition takes place, or bear them from the higher
grounds to the rivers and plains. The sparing but constant and
long-continued supply of lime thus afforded to soils which rest up-
on decayed trap, or which are wholly made up of rotten rock, has
a material influence upon their well-known agricultural capabilities.
5°. Silicates of Magnesia. —In combination with magnesia in
different proportions, silica forms nearly the entire mass of those
common minerals known by the names of Serpentine and talc, In
hornblende also and augite, silicates of magnesia exist in con-
siderable quantity. They must, therefore, be present in soils
which are directly formed from the decomposition of such
rocks. Like the silicates of lime, however — though more
slowly than these—they will undergo gradual decomposition by
the action of the carbonic acid of the atmosphere, and of the acids
produced in the soil by vegetation and by the decay of organic
matter. The magnesia, like the lime, will thus be gradually brought
* Rocks of which the mineral called augite forms a more or less considerable part.
+ I say probably, because if uncombined silica be present in hay or straw along with
carbonate or oxalate of lime, the heat employed in completely burning away the or-
ganic matter may be sufficient to cause the lime and silica to unite and form a silicate
which will afterwards be found in the ash, though none previously existed in the stem,
:: See page 65.
Z,
354 SILICATES OF A LUMINA. --
down, in a state of solution, from the higher grounds, or will be
washed out of the soil, till at length they may wholly disappear
from any given spot.”
6°. Silicates of Alumina.-Silica combines with alumina also in
various proportions, forming silicates, which exist abundantly in
nature in the crystalline rocks, and may also, like the other sili-
cates, be formed by art. Felspar, mica, hornblende, and the au-
gites, which abound in the trap-rocks, all contain much alumina in
combination with silica, and we shall probably not be very far from
the truth in assuming that upwards of one-half by weight of the
trap-rocks in general—as well as of the hornblendes, micas, and
felspars, of which so large a portion of the granitic rocks is com-
posed—consists of silicates of alumina. The alumina itself in
these several minerals varies from 11 to 38 per cent, but generally
averages about 20 per cent. of their entire weight.
These silicates, when they occur alone, unmixed or uncombined
with other silicates, decompose very slowly by the action of the at-
mosphere. They disintegrate, however, and fall to powder, when
the alkaline silicates with which they are associated in felspar, &c.,
are decomposed and removed by atmospheric causes. In this way
the deposits of porcelain clay, so common in Cornwall and in other
countries, have been produced from the disintegration of the fel-
spathic rocks, and the clayey soils which occur in granite dis-
tricts have not unfrequently had a similar origin.
When contained in the soil, the silicates of alumina undergo a
slow decomposition from the action of the various acid substances
to which they are there exposed. A portion of their alumina is
dissolved and separated by these acids, and in this soluble state is
either conveyed to the roots of plants, or if not taken up by the
roots, is washed from the soil by the rains—or by the waters that
arise from beneath.
* I am indebted to Sir Charles Lemon for the analysis of a soil, on part of his own
property, resting on serpentine, and bearing only Erica vagans, which illustrates the
statement in the text. This soil consists of silica 70, alumina with a trace of gypsum
20, oxide of iron 6-2, and vegetable matter 3.8 per cent. If this soil has been form-
ed from the rock on which it rests, the magnesia has been wholly washed out. Its
constitution, however, points rather to a decayed felspar or slate rock, as the source
from which it has been derived,
GENERAL REMARKS ON THESE SILICATES. 355
7". General remarks on these Silicates.—Of all these silicates it
may be remarked in general—
a. That besides existing in the minerals above-mentioned, and
from which they are conveyed into the soil, they are also slowly form-
ed in the soil itself, when the ingredients of which they severally
consist are naturally present in, or are artificially added to, the
soil. Hence, the addition of potash or soda to the land may cause
the production of silicates of these alkalies—probably soluble sili-
cates—which water will be capable of dissolving and bearing to the
extremities of the roots. Hence also, in a sandy soil the addition
of lime may give rise to the production of insoluble silicates of this
earth, and the beneficial effect of the lime upon the land may
thus sooner cease to be strikingly observable than in soils of a dif-
ferent character, where it is not so liable to be locked up in an in-
Soluble state of combination; and,
b. That with the exception of those of potash and soda which
contain much alkali, these silicates are all insoluble in water, and
thus not directly available to the nutrition of plants. Except those of
alumina, however, they are all slowly decomposed by atmospheric
agents, and their constituent elements thus brought, to a certain ex-
tent, within the reach of plants; while, without exception, they are
all capable of decomposition in the soil by the agency of the acid sub-
stances, chiefly organic, which there exist, or which are produced
during the growth and decay of vegetable substances. From this
latter source, the chief supply of the ingredients contained in the
silicates is, in most soils, derived by living plants.
To this cause is attributed the surprising effect often observed
to follow from the addition of vegetable matter to a sandy soil on
which a previous addition of lime had ceased to produce any further
beneficial effect. The organic acids formed by the vegetable mat-
ter during its decay decompose the silicates of lime previously pro-
duced, and thus liberate the lime from its insoluble state of combi-
nation. But when the silicates have been all decomposed by this
agency, the further addition of vegetable matter ceases necessarily
to produce the same remarkable effects.
356 THE OXIIDES OF IRON. -
§ 5. Of Iron—the oxides, sulphurets, sulphates, and carbonate of
sº from.
1°. Owides of Iron.—It is well known that when metallic iron is
exposed to moist air, it gradually rusts and becomes covered with,
or wholly changed into, a crumbling ochrey mass of a reddish
brown colour. This powder is a compound of iron and oxygen
only, containing 69% per cent, of the former, and 303 per cent. of
the latter.
When iron is heated in the smith's forge, and them beat on the
anvil, a scale flies off which is of a black colour, and when crushed
gives a black powder. This also consists of iron and oxygen only,
but the proportion of oxygen is not so great as in the red powder
above described. In both cases the iron has derived its oxygen
from the atmosphere.
To these compounds of iron with oxygen, the name of ovides is
given. There are only two which are of interest to the agricul-
turist, namely,–
Consisting of
Iron. Oxygen. Symbol. Colour.
The first oxide,” 77-23 22.77 Fe Of Black.
The second oxide, 69°34′ 30'66 Fe, Oa Red.
Both of these oxides exist abundantly in mature, and are present
to a greater or less extent in all soils. The second or per-oxide,
however, is by far the most abundant on the earth's surface, and
the reddish colour observable in so many soils is principally due
to the presence of this oxide.
The first ovide often occurs in the soil in a state of combination
with acid substances, but so strong is the tendency of this oxide
to combine with more oxygen, that when exposed to the air, even
in a state of combination, it rapidly absorbs this element from the
atmosphere and changes into per-oxide, or into a mixture of the
two oxides. This change is observable in all chalybeate springs,
in which, as they rise to the surface, the iron is generally held in
solution in the state of the first oxide. After a brief exposure to
the air, more oxygen is absorbed, and a reddish pellicle is formed
* The first is also called the prot-oxide, the Second either the sesqui, or more wsually
the per-oxide of iron.
+ Iron is represented by the symbol Fe, the initial letters of its Latin name (ferrum).
PROPERTIES OF THE FIRST OR PROT-OXIDE. 357
on the surface, which gradually falls and coats the channel along
which the water runs, with a reddish sediment of insoluble per-oxide.
Both oxides are insoluble in pure water, and both dissolve in
water containing acids in solution. The first oxide, however, dis-
solves in much greater quantity in the same weight of acid, and it
is the compounds of this oxide which, especially in boggy soils,
prove so injurious to vegetation.* - -
The second owide possesses two properties which, in connection
with practical agriculture, are not void of some degree of im-
portance. -
a. In a soil which contains much vegetable matter in a state of
decay, the per-oxide is frequently deprived of one-third of its oxy-
gen by the carbonaceous matter, and is thus converted into the
first oxide, which readily dissolves in any of the acid substances
with which it may be in contact. In this state of combination it
is more or less soluble in water, and in some localities may be
brought to the roots of plants in such quantity as to prove injuri-
ous to their growth.
b. The red oxide of iron is said, like alumina (p. 347), to have
the property of absorbing ammonia, and probably other gaseous
substances and vapours, from the atmosphere and from the soil.
In that which occurs in nature, either in the soil or near the Sur-
face of mineral veins, traces of ammonia can generally be detect-
ed. Since then ammonia is so beneficial—according to some in-
dispensably necessary—to vegetation, the property which the per-
oxide of iron possesses of retaining this ammonia when it would
otherwise escape from the soil, or of absorbing it from the atmo-
sphere, and thus bringing it within the reach of plants, must also
* “That layer of the soil (says Sprengel), is always especially rich in iron, over
which the heel of the plough glides in preparing the land. The friction of the soil
continually rubs off particles of iron, which absorb oxygen and change into the first
oxide. Hence this part of the soil is always darker in colour than the rest ; hence
also the reason why the soil, after deep ploughing, remains unproductive sometimes
for several years.”—Chemie, i. p. 428. While we admit that the presence of the first
oxide of iron in the subsoil affects its fertility, when brought to the surface, we may
doubt whether match of that iron can have been derived from the tear and wear of the
plough. It has a tendency to collect in slightly retentive subsoils when washed out
of the upper soil by the rains which sink through it.
+ The carbon of the vegetable matter combines with the oxygen of the oxide to
form carbonic acid.—See p. 98. -
358 PROPERTIES OF THE SECOND OR PER-OXII) E. A
be indirectly favourable to vegetation—where the soil contains it
in any considerable quantity.
An important practical precept is also to be drawn from these
two properties of this oxide. A red irony soil, to which manure
is added, should be frequently turned over, and should be kept
loose and pervious to the air, in order that the formation of prot-
oxide (first-oxide) may be prevented as much as possible; and it
may occasionally be summer-fallowed with advantage, in order
that the per-oxide may absorb from the air those volatile substances
which are likely to prove beneficial to the growth of the future
crops. g
2°. Sulphurets of iron.—Iron occurs in nature combined with
sulphur in two proportions, forming a sulphuret and a bi-sulphuret.
These consist respectively—
Iron. Sulphur. Symbol.
The sulphuret of...... 62-77 37:23 Fe S
The bi-sulphuret of... 45-74 54-26 Fe Se
and are both tasteless and insoluble in water.
The sulphuret (Fe S) occurs occasionally in boggy and marshy
soils, in which salts of iron exist or into which they are carried
by rains or springs. It is not itself directly injurious to vegeta-
tion, but when exposed to the air it absorbs oxygen and forms sul-
phate of iron, which, when present in sufficient quantity, is emi-
mently so.” X-
The bi-sulphuret, or common iron pyrites (Fe S2,) is exceed-
ingly abundant in nature. It occurs in nearly all rocky forma-
tions—and in most soils. It abounds in coal, and is the source of
the sulphureous smell which many varieties emit while burning.
It generally presents itself in masses of a yellow colour and me-
tallic lustre, more or less perfectly crystallised in cubical forms, so
brittle and hard as to strike fire with steel, and of a specific gra-
vity four and a half times greater than that of water. When
heated in close vessels it parts with nearly one-half of its sulphur,
and hence it is often distilled for the sulphur it yields. -
* Yet in small quantity it may be beneficial. Thus Sprengel mentions that the
subsoil of a moor near Hanover, which contains some of this Sulphuret of iron, pro-
duces astonishing effects when laid as a top-dressing on the grass lands. The ex-
planation of this is, that the pyrites absorbs oxygen and is converted into sulphate of
iron, and thus reproduces the remarkable effects observed on the addition of gypsum,
of sulphuric acid, or of sulphate of soda to similar grass lands.
sulPHATE AND CARBONATE OF TRON. 359
In the air it absorbs oxygen—in some cases, as in the waste
coal-heaps, with such rapidity as to heat, take fire, and burn. By
this absorption of oxygen (oxidation), Sulphuric acid and sulphate
of iron are produced. In the alum shales the iron pyrites abounds,
and these are often burned for the purpose of converting the sul-
phur of the pyrites into sulphuric acid for the subsequent manu-
facture of alum.
3°. Sulphates of iron.—Of the sulphates of iron which are
known, there is only one—the common green vitriol of the shops
—that occurs in the soil in any considerable quantity. There are
few soils, perhaps, in which its presence may not be detected,
though it is in bogs and marshy places that it is most generally
and most abundantly met with. It is often exceedingly injurious
to vegetation in such localities, but it is decomposed by quick-
lime, by chalk, and by all varieties of marl, and thus its noxious
effects may in general be entirely prevented. To soils which
abound in lime, it may even be applied with a beneficial effect.
When a solution of this salt is exposed to the air it speedily be-
comes covered with a pellicle of a yellow ochrey colour, which after-
wards falls as a yellow sediment. This sediment consists of per-
oxide of iron, containing a little sulphuric acid; but by the separa-
tion of this oxide the sulphuric acid is left in excess in the solution,
which becomes sour, and still more injurious to vegetation than
before. In boggy places the waters impregnated with iron are
generally more or less in this acid state, and lime, chalk, and marl,
with perfect drainage, are the only available means by which such
lands can be sweetened and rendered fertile.
When iron pyrites is exposed to the air it slowly absorbs oxy-
gen, and is converted into sulphate of iron and sulphuric acid; on
the other hand, the sour solution above mentioned, when placed
in contact with vegetable matter, where the air is excluded, parts
with its oxygen to the decaying carbonaceous matter, and is again
converted into iron pyrites. These two opposite processes are both
continually going on in nature, and often in the same locality,
——the one on the surface, where air is present; the other in the
subsoil, where the air is excluded.
4°. Carbonates of iron.--When a solution of the sulphate of
iron, above described, is mixed with one of carbonate of soda, a
360 OXIDES AND SALTS OF MANGANESE.
yellow powder falls, which is carbonate of iron. This carbonate is
found abundantly in nature. It is the state in which the iron
exists in the ore (clay-iron ore), from which this metal is so large-
ly extracted in our iron furnaces, and in some of the similar ore
found in the subsoil of boggy places, which is distinguished by the
name of bog-iron ore. - *
Like the carbonate of lime, it is insoluble in water, but dissolves
with considerable readiness in water charged with carbonic acid.
In this state of solution it issues from the earth in many of our
chalybeate springs, and it is owing to the escape of the excess of
carbonic acid from the water, when it reaches the open air, that
the yellow deposit of carbonate of iron more or less speedily falls.
The carbonate of iron, being insoluble in water, is not direct-
ly injurious to vegetation. When exposed to the air it gradually
parts with its carbonic acid, and is converted into per-oxide of iron.
The ash of nearly all plants contains a more or less appreciable
quantity of oxide of iron. This may have entered into the roots
either in the state of soluble sulphate or of carbonate dissolved in
carbonic acid, or of some other of those numerous soluble com-
pounds of iron with organic acids, which may be expected to be oc-
casionally present in the soil.
§ 6. Of Manganese—the ovides, chloride, carbonate, and sulphate
of manganese.
1°. Manganese is a metal which, in nature, is very frequently
associated with iron in its various ores. It also resembles this me-
tal in many of its properties. In the metallic state, however, it is
not an object of manufacture, nor is it used for any purpose in the
altS. -
2°. Ovides of Manganese.—Manganese combines with oxygen
in several proportions. The first oxide is of a light green colour,
the second and third are black. The first is not known to occur
in mature in an uncombined state, the two others exist abundantly
in the common ores of manganese, and are extensively diffused,
though in small quantity, through nearly all soils. They are all
insoluble in water, but the two former dissolve in acids and form
salts. Traces of these two oxides are also to be detected in the ash
of nearly all plants.
COMPOSITION OF THE O XII).ES AND CHLORIDES. 361
3°. Chloride, Carbonate, and Sulphate of Manganese.—If any
of these oxides be dissolved in muriatic acid a solution of chloride
of manganese will be obtained.
If this solution of chloride of manganese be mixed with one of
carbonate of soda, a white insoluble powder will fall, which is car-
bonate of manganese.
If this carbonate be dissolved in diluted sulphuric acid, or if any
of the oxides be digested in this acid, a solution of sulphate of man-
ganese will be formed.
The carbonate of manganese, and its oxides, will also dissolve,
though more slowly, in acetic acid (vinegar), and in other organic
acids which may be present in the soil, and will form with them
other soluble salts.
The compounds of manganese exist in plants in much less quan-
tity than those of iron; but as its oxides, like those of iron, are in-
soluble in pure water, this metal most likely finds its way into the
roots of plants in the state of one or other of the soluble compounds
above described.
§ 7. Tabular view of the composition per cent. of the compounds
of the organic elements above described.
Having in the preceding section briefly described the several
compounds of the inorganic elements of plants, which either enter
into the constitution of vegetable substances, or are supposed to
minister to their growth—it may prove useful hereafter, if I exhi-
bit at one view the composition per cent, of the various oxides,
chlorides, sulphurets, and oxygen-acid salts,” to which I have had

occasion to direct your attention.
1°.—Oxygen per cent. in the ovides of the inorganic elements.
Oxygen || Oxygen
per cent per cent
Sulphurous Acid.............. 49.85 || Alumina........................ 46-70
Sulphuric Acid................ 59'86 || Silica ............................ 51.96
Phosphoric Acid.............. 56-04 || Prot-oxide of Iron............ 22.77
Potash .......................... 16:95 || Per-oxide of Iron ............ 30'66
Soda............................. 25'58 || Prot-oxide of Manganese... 22:43
Lime ................ . . . . . . . . . . . . 28-09 || Sesqui-oxide do. 30-25
Magnesia....................... 38-71 || Per-Oxide do. 36' 64
* So called because the acid they contain has or/gen for one of its constituents.
362 COMPOSITION OF THE SALINE COMPOUNDS, 2
2°.—Chlorine or Sulphur per cent. in the chlorides and sulphurets.

Chlorin. |Sulphur
per cent per cent
Chloride of Potassium....... 47-47 || Sulphuret of Potassium ..... 29°11
s—Sodium.......... 60°34 || — Sodium......... 40-88
Calcium......... 63-36 || — Calcium........ 44'00
...— Magnesium..... 73°65 || — Iron............. 37:23
First Chloride of Iron ....... 56-62 || Bi-Sulphuret of ſº 47-08
Second do. do. ......... 66-19 (Iron Pyrites) ſ “ &
3°.—Composition per cent. of the Saline combinations above described.

Acid. Base. Water
Carbonate of Potash...................................... 31.91 | 68-09
Bi-carbonate of do. .................... ... tº 9 e º 'º e º e º 'º e e º e º 'º º tº 48°38 || 51-62
Sulphate of do. ...................................... 45'98 || 54-07
Nitrate of do. ...................................... 53'44 46-56
Binoxalate of do. (Salt of Sorrel) ................... 52-64 || 34:29 || 13-07
Bitartrate of do. (Cream of tartar)................ 70-28 || 24.96 || 4-76 |
Phosphate of do. ...................................... 43°06 || 56.94
Bi-phosphate of do. ...................................... 60°20 || 39-80
Carbonate of Soda (dry)................................. 41:42 58-58
(crystallized)...................... 15:43 21.81 || 62-76
Bi-carbonate of Soda .................................... 58'58 || 41-42 | .
Nitrate of do. ...................................... 63-40 || 36-60 |
Sulphate of do. (dry) .............................. 56-18 || 43-82
*-ºsmºsºmsºmº-º-º-sº do. (Crystallized) .................... 24'85 19:38 55-77
Phosphate of do. ...................................... 53-30 || 46-70
Bi-phosphate of do. ...................................... 69'54 30°46
Carbonate of Lime.......................... ... • * * * * * * * * * * * * 43-71 56.29
Sulphate of do. (Gypsum)............................ 46-31 || 32.90 20.79
— (burned) ............................. 58’47 || 41-53
Nitrate of lime......................................... ... 65-54 || 34°46
Phosphate of Lime (Apatite)........................... 45°52 || 54'48
Bi-phosphate of Lime .................................... 71-48 || 28' 52
Earth of Bones............................................. 48°45 51-55
Carbonate of Magnesia................................... 51-69 48-31
Bi-carbonate of do. .................... Te e s e e o e º e s • e < e < e < 68-15 31-85
Sulphate of do. (Epsom Salts).................. 32°40 | 16.70 || 50-90
Nitrate of do. .................... ................. 72°38 27.62
| Phosphate of do. ..................................... 63-33 36.67
Sulphate of Alumina...................................... 70-07 || 29.93
Phosphate of do. ....................................... 67.57 || 32°43
Silicate of Potash (Soluble).............................. 49-46 50-54
Bi-silicate of do. (do.) .............................. 66-19 33:81
Silicate of Soda. §3 • * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 59-63 | 40°37
Bi-silicate of do. (do.) .............................. 74.71 || 25-29
COMPOSITION OF THE SALINE COMPOUNDS. 363

Acid. I Base. Water.
Silicate of Lime ........................................... 61-85 38-15
Magnesia ...................................... 69-08 || 30-92
Alumina ....................................... 72-95 27.05
Carbonate of Iron ......................................... 38.63 61-37
Sulphate of do. (Crystallized)........................ 31:03 27-19 || 41.78
Carbonate of Manganese ................................ 38-27 | 61-73
Sulphate of do. (crystallized) .............. 33'20 29'54 || 37.26
In our subsequent calculations we shall have frequent occasion
to refer to the numbers in the above tables.
LECTURE XII.
Relative proportions in which the different inorganic or mineral compounds are pre-
sent in the ash of plants. Ash of the grain and straw of wheat. Ash of barley and
barley straw. Ash of the grain, husk, leaf, straw, and chaff of the oat. Relative
proportions of the inorganic constituents in the sevéral parts of the oat plant. Ash
of the grain and straw of rye. Ash of the grain and straw of Indian corn (maize).
Ash of the grain, husk, and straw of rice. Ash of buckwheat and millet. Ash of
the grain and straw of the bean, the pea, the lentil, and the vetch. Ash of hemp,
flax, and camelina, seeds, and of the hemp and flax plants. Flax steep water, and
the fibre and refuse of flax. Ash of the mustard and madia seeds. Ash of the
turnip, beet, Jerusalem artichoke, potato, and cabbage. Ash of the grasses and
clovers. Ash of the tobacco leaf, of the coffee bean, of the sugar cane, of vine
twigs, of the hop plant, of the wood, bark, and fruit of the apple tree, of the wood
and seeds of the oak, the beech, the lime, the elm, and the pine trees, of some com-
mon land weeds, and of the fuci or sea weeds.
HAVING thus made you acquainted with the general properties
of the inorganic elementary bodies which are found in the ash of
plants, and with their most abundant and most important com-
pounds, I now advance to the consideration of the relative pro-
portions in which these substances exist in the ash of the different
kinds of plants which are either cultivated for food, or are raised
for other economical purposes, or which, like our numerous weeds,
interfere with the ordinary proceedings of the practical farmer.
§ 1. Of the ash of the grain and straw of wheat.
The dry grain of wheat leaves, as we have already seen, (p. 303,)
about 2 per cent. of ash when burned, the dry straw from 3 to 18
per cent of ash.
1°. The grain.-It appears from the more recent analyses of the
ash of the grain of wheat grown in different localities, that it va-
ries considerably in composition. The following table exhibits the
results of the greater number of these analyses, the place where
the wheat was grown, and the authority for the analysis, The va-
ASH OF WHEAT AND WHEAT STRAW. 365
riety of wheat is, however, not usually stated. The last column
exhibits the mean of the whole.
Will & Fresenius. Bichon, Thon, Boussingault, Erdmann, Mean of the
Giessen.” Holland.” Kurhesse,” Bechelbrown. Leipsic. Siac analyses.
Red. White.
Potash, ..... 21.87 33.84 6.43 24, 17 30. 12 25.90 23.72
Soda..….. 15.75 ... 27.79 l O-34 * * * 0.44 9.05
Lime,...... .. 1.93 3.09 3.9l 3.01 3 00 1.92 2.81
Magnesia, ... 9.60 1354 12.98 13.57 16 26 6, 27 12.03
Oxide of iron, 1.36 0.31 0 50 () 52 e e is 1.33 0.67
Phos. acid, 49.32 49.21 46. 14 45.53 48.30 60. 39 49.81
Sulph. acid, 0.17 ... 0.27 tº sº as l, 0.1 s & e 0.24
Silica, * gº tº * * * 0.42 1.91 1.31 3.37 1.17
100 99.99 98.44 99.05 | 00 99.62 99.50
a--------, e-m-sº-s-s-s ºn-s-s-s-s-s sº-º-º-º-º ºs-ºs-sº ºn- “m-m-m-sº
Of the differences in this table, part no doubt are due to the va-
riety of wheat examined, part also to soil, climate, season, mode
of culture, degree of ripeness, and other circumstances, the effect
of which we have as yet no means of ascertaining. For all practical
purposes, the mean of the six analyses may at present be regarded
as affording a valuable approximation to the true composition of
the ash of this grain.
2°. The straw-Few analyses of the straw of wheat have yet
been published. The following are the only ones with which I am
as yet acquainted. The third was made in my own laboratory.
- Mean of the
Berthier. Boussingault. Fromberg, two last.
Potash, ) ............... • 10-86 9.56 15.32 12.44
Soda, ) ........... . . . . . . 0.3] tº º & 0.16
Lime, ... . . . . . . . . . . . . . . . . . 5.36 8.83 4.58 6,70
Magnesia, .................. tº º ſº 5. I 9 2.45 3.82
Oxide of iron, ........... . 2,32 1.04 1.56 l. 30
Phosphoric acid, ......... l. 12 3.22 2,92 3.07
Sulphuric acid, ......... ... 0.44 l,04 10.50 5.82
Chlorine, ..... . . . . . . . . . . . 2.82 0.62 1.56 1.09
Silica, ..................... 77.08 70. l 9 60.58 65.38
100 100 99.56 99,78
Per-centage of ash, 4.40 7.00
No analyses of the husk of wheat which surrounds the grain, or
of the bran, in which, as we have already seen, (p. 308), the largest
proportion of the ash of the grain resides, have yet been published.
* Annalen der Chem. und Pharm. l. p. 403.
+ Economie Rurale, ii. p. 347. # Annalen d, Chem, u. Pharm, liv. p. 355.
366 WHAT A CROP OF WHEAT CONTAINS.
If the produce of a field be at the rate of 25 bushels of wheat
per imperial acre, weighing 60 lbs. a bushel, and if the straw ave-
rage twice the weight of the grain,” then the quantity of inorganic
matter carried off the soil by the crop will be per acre,
In 1500 lbs, of grain, at 2 per cent. of ash, 30 pounds.
In 3000 lbs. of straw, at 6 per cent. 180 do.
Total, 220 lbs.
and the composition of the matter thus carried off, according to
the means of the analyses above given, will be,
Grain. Straw. Total.
Potash, .............................. 7.15 lbs. 22.44 lbs. 29.59 lbs.
Soda, ................. ............ 2.73 0.29 3.02
Lime, ..... ... ..................... 0.85 12.09 12.94
Magnesia, ........................... 3.63 6.89 } 0.52
Oxide of iron, ..................... 0.20 2.35 2.55
Phosphoric acid, . ........... .... 15.02 5.54 20.56
Sulphuric acid,............. • - - - - - - - 0.07 } 0.49 10.56
Chlorine, ......... , sº e º e s e º e s e º e º ſº tº & & Aº 1.97 1.97
Silica, ............ ........... ... • * * -e ºs s 0.35 117.94 1 18.29
30 lbs. 180 lbs. 210 lbs. .
When the straw is returned to the land without loss in the form
of manure, then the 30 lbs, contained in the grain are alone car-
ried away permanently from the soil.
§ 2. Composition of the ash of barley and barley straw.
The grain of dry barley leaves about 2% per cent of ash, and
the dry straw from 5 to 8 per cent. (p. 303). The composition of
the ash of the grain from different localities is represented in the
following table:—
* It is often 3 and even 3% times as much.
ASH OF BARLEY AND BARLEY STRAW. 367
Without husk. Mean of
Boussingault.* Bichont Thomson.: Erdmann, S Köchlin.] the four.
Potash, ............ 29'50 3'91 | 6-00 20-91 13-75 3°64
Soda, ............... trace 16-97 8-86 * - e º 6.75 8'14
Lime, ............... 2.90 3'36 3.23 1-67 2-21 2-62
Magnesia, ......... 15.90 10'05 4°30 6'91 8-60 7.46
Oxide of iron, ... ... l'93 O'83 2-10 1.07 l'48
Phosphoric acid, 47:0 40°63 36-80 38°48 39°80 38-93
Sulphuric acid, ... 1-00 0-26 0°l 6 * * * 0-17 0-1 ()
Chlorine,........ ... . trace. * @ & 0° 15 & º & e & º 0-04
Alumina,............ 4e & & e º ºs * * * * 0-83 & © ge 0-21
Silica, ............... 1:30 21.99 29.67 29' 10 27.65 27-10
97.60 99-10 100 | 00 100 99.72
Per-cent. of ash, 240 2.37 3-05 2-70 2-84
The barley as it is carried to market is enveloped by a husk,
which clings close to the grain, and, as we shall afterwards see, is
important to its future growth. In this husk the silica chiefly re-
sides, which in the above table is seen to form so large a propor-
tion of the ash. In the first column the proportion of silica is so
small that I have supposed Boussingault to have detached the
husk from the sample he burned, or he may, though he does not
say so, have analysed a naked barley.
Barley straw consists, according to the only two analyses we
possess, of
Boussingault." Sprengel. Mean.
Potash, ......... .............. *20 3°43 6-31
Soda, ............ - e º e º s e s : * * * : * * * 0-30 0.92 0-61
Lime, ........................... 8'50 10:57 9°53
Magnesia, ..... • . . . . . . . . . . . . . . . 5-00 1°45 3:22
oxide of iron and a little 1:00 0.65 0-83
- oxide of manganese, -
Alumina, ..................... * : * e 2.78 I'39
Phosphoric acid, ............ 3' || 0 3.06 3-08
Sulphuric acid, ............... 1-00 2:25 1.63
Chlorine, ..................... 0-60 1°33 0.97
Silica, .................... ... 67-60 73.56 70°58
96.30 . 100 98 - 15
Per-centage of ash, 7.00 5-24 6. 12
* Economie Rurale, ii. p. 327.
i Annal. d. Chemie u. Pharm. l. p. 418.
f Government Report on the Feeding of Cattle with Malt, p. 86.
§ Annal. d. Chemieu. Pharm. liv. p. 355. | Ibid. p. 347.
| Economie Rurale, ii. p. 327.
368 WPIAT. A. CROP OF BARLEY CONTAINS.
If the produce of an imperial acre of barley amount to 40
bushels, each 53 lbs., and if the straw average one-fourth more
than the weight of the grain,_then the proportion of inorganic
matter carried off from each acre by a crop of barley will be,
In 2120 lbs. of grain at 2% per cent. of ash, 53 lbs.
In 2650 lbs. of straw at 6 per cent. 160
*
- Total, 213 lbs.
and this ash would consist, according to the mean of our present
analyses, of
Grain. Straw. Total.
Potash, ........................ 7-24 10-29 17:53
Soda, ........................ 4.32 0.92 5.24
Lime, ... ......... ... • * * * * * * * * * * | 39 ] 5° 53 ] 6-92
Magnesia, ..................... 3.97 5’25 0.22
oxide of Iron and a little 0.79 1:35 2: 14
oxide of manganese,
Alumina, ..................... 0-12 2.26 2.38
Phosphoric acid, ............ 20-74 5.02 25-76
Sulphuric acid, ............ 0-05 2-66 2.71
Chlorine, ..................... 0.02 1°58 I •60
Silica, ........................ 14-36 115-14 129-50
53 160 213
The total quantity of mineral matter removed from the soil by
a crop of 40 bushels of barley is very nearly the same as by one
of 25 bushels of wheat. But if the straw be in this case, as in that
of wheat, returned in the form of manure, the 40 bushels of the
grain of barley will carry off considerably more valuable matter
than the 25 of the grain of wheat.
By high manuring and other skilful culture we may raise our
wheat crop to 40 bushels, but similar means should increase our
barley crop to 60 bushels—so that in either case it appears likely
that on an average the grain of barley takes a little more from the
land than an equivalent crop of wheat.
§ 3. Composition of the grain, straw, leaf, husk, and chaff
of the oat.
The grain of the oat without its husk leaves about 2 per cent of
ash as wheat does. With the husk it leaves from 2% to 4 per cent.
The husk leaves from 5 to 7 per cent., the straw from 5 to 9, the
leaves from 8 to 15, and the chaff from 16 to 19 per cent.
THE ASH OF THE OAT. 369
The most extensive and patient research into the constituents of
any kind of grain hitherto made, is that which my friend and pupil
Mr Norton performed in my laboratory during the years 1844–45,
and for which a prize of fifty pounds was awarded to him by the
Highland and Agricultural Society of Scotland. I regret that
want of space precludes me from doing more than merely select-
ing a portion of his analytical results. - -
1°. The grain.—The ash of the grain of the oat, with and with-
out the husk, has been found to consist of:—
- Without husk.
With husk. Norton. Mean of
Boussingault.* Potato oat. Hopeton oat. two last.
Alsace. Northumberland.
Potash,..................... 12-90 | 21-22 31°15 26-18
Soda, ...... . ............ tº dº º
Lime, ..................... 3-70 6'69 5°21 5°95
Magnesia, ............... 7-70 11:26 8'64 9°95
Oxide of iron, ............ 1:30 * * * * 0-80 0°40
Phosphoric acid, ......... 14-90 38°48 49' 19 - 43-84
Sulphuric acid,............ 1-00 18°36 2°54 10-45
Chlorine, ... .. - - e s is dº e g º e º s 0°50 0 30 0.22 - 0-26
Carbonic acid,......... ... 1-70 • * * & © -- e & &
Silica, ..................... 53-30 3:60 l-73 2-67
Alumina P ...... .... ... as º º tº e & - 0-13 0-06
97.00 99-91 99.61 99-76
Per-centage of ash, ..... 4°00 2-22 2°14 2-18
The proportion of silica in the analysis of Boussingault is much
too great, while the phosphoric acid is too small. -
My assistant Mr Fromberg made two analyses of oats without
the husk in my laboratory, which are otherwise good, but which
err, I think, in giving too large a per-centage of the oxides of iron
and manganese. They, however, show that the phosphoric acid of
Boussingault is, as I have said, too low. The results were as fol-
lows:—
Grown on Grown on
mossy land. lime sick land. Mean.
Potash, ................. . . . . . . . . 19:12 21:13 20-12
Soda, a tº e s ∈ - e, e º º is e º e s a e º e º e < * * * * * * * * *-* esºs -
Lime,.................... ......... 10°4] 10:28 10-35
Magnesia,...... ........... ...... 9°98 7.82 890
oxide of iron, | tº e & gº tº ge 6-33 4:27 5:30
Oxide of manganese,
* Economie Rurale, ii. p. 327.
370 THE ASH OF OAT HUSK,
Grown on Grown on
mossy land. lime sick land.
Phosphoric acid, ... ............ 46*26 50°44 48-35
Sulphuric acid, .............. ... * @ — sº
Chlorine, .................... ... 3-07 0'54 - 1-81
Silica,...... …................... 3-70 4'41 4'05
98.87 98’89 98-88
Per-centage of ash,..... ......... 2°04 2°02 2:03
2°. The husk.—The husk forms about one-fourth of the weight
of the oat, as it is sold in the market. The proportion, however,
varies considerably—with the variety of the oat—with its plump-
mess—the thinness of the husk, &c. Thus the weight of the husk
per cent, in samples examined in my laboratory was as follows :-
Husk.
Black Tartary oat, ........................ 27'll per cent.
Hopetoun oat, ... ..................... *..... 25°25
Dun oat, ..................... .............. 25°24
- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23-21
Sandy oat, ..................... ........... 23.68
Mean, ....................................... 24°9
The composition of the ash of the oat husk is as follows:
Hopetoun Oat Potato oat
Grown Pon, Grown "Poº ſº. Nijhu. f.o. Noºnum-
lime sick land. mossy land.
berland. berland. Mean.
Fromberg. Fromberg. Norton. Norton. *
º º 999 wº | 7-39 * 12.47 . 8 13
Lime, ............... 4’31 2:05 1°95 4'30 3' 15
Magnesia,............ 1.01 0.64 0.38 2°35 1-09
Oxide of Iron, ...... 1.6] I '80 1°58 0.32 1.33
Oxide of Manganese,0-86 0.72 0.92 - 0-61.
Sulphuric acid,...... 5:01 4.90 11' 61 4:30 6°46
Phosphoric acid, ... 2:65 1 '80 1'04 0.66 1°54
Chlorine, ... ......... 1° 13 0- 19 0-13 1.45 0-73
Silica, ................ 74-73 81,72 73°85 . . 74°28 76. 16
98.30 99°48 98.85 100° 13 99-20
Per-cent. of ash in ; 6°49 7-22 6'46 6°99 6.79
dry husk, ...... - *
The proportion of silica in the ash of the husk, it will be seen,
is very great. -
3°. The Straw.—Oat straw varies considerably in its composi-
tion, for reasons which we shall presently explain. Two of the
more trustworthy of the analyses hitherto published are as follows:
THE LEAF AND CHAFF OF THE OAT. “ 371
Levi:* Boussingault.--
* - Kurhess. Alsace. Mean.
Potash, ... ..... .. . . . . . . . . . . . . . . . . 12:18 26-09 19° 14
Soda,............... . . . . . . . . . . . . 14.69 4.69 9' 69
Lime, ... ........................ 7:29 8.84 8:07
Magnesia, ........................ 4:58 - 2.98 3-78
Oxide of iron, .................. 1-41 2:24 1-83
Phosphoric acid, ............. . . . . 1.94 . 3. 19 2°56
Sulphuric acid,.................. 2° 15 . . 4:37 3° 26
Chlorine, ........... . .......... I '50 5:00 3°25
Silica, ........................... 54°25 42.60 48:42
99.99 100-00 100'00
Per-centage of ash ........................ ſº tº ſº e º sº ſº tº dº 5-10
The proportion of alkaline matter in these straws is much great-
er than in the husk, while the silica is considerably less." -
4°. Leaf and Chaff—The composition of the leaf and chaff,
compared with that of the grain and straw in the same oat, will be
seen in the following analyses by Mr Norton of the ash of the se-
veral parts of a sample of the Hopetoun oat.
. Grain. Husk. Chaff. Leaf. Straw.
Potash and soda,............... 31'56 10-26 7.96 14°89 21.80
Lime, ........................... 5-32 1:95 4°53 6'99 7:23
Magnesia,......... .............. 8-69 0.38 1:84 2-55 2.9}
Oxide of iron, ............... ... 0-88 }*58 0-24 *- 1-40
Oxide of manganese, ......... * (): 92 * — sº-sº
Phosphoric acid, ............... 49 i 9 1'04 gººs *ºn sºms
* – – 5'84 6' 13 3:03
Sulphuric acid, ................. gº 9:61 5-32 14°80 18°45
Chloride of Sodium,..... ...... 0-35 0.24 5' 11 2.29 3:03
Soluble silica, ... ..... ........ 0-89 4°46 1 l'99 5'90 7-34
Insoluble silica, ........ s • * * * * * 0.98 68.39 56.05 45.75 33-14
97.86 98-83 98-88 99'30 98.33
tº-sºmimºs tºm-º: *º- * * º
Per-centage of ash in the g g e § .
dry state, ..... ......... ; 2:14 6-47 16.53 8’44 6' ll
If an imperial acre of land yield 50 bushels of oats, weighing
42 lbs. a bushel, and the straw weigh two-thirds more than the
grain,_the husk being one-fourth of the grain, and the chaff two-
thirds of the husk, the quantity of mineral matter carried off the
soil by a crop of oats will be nearly as follows:—
* Amnal. der Chemie u, Pharm., l, p. 425,
+ Economie Rurale, ii. p. 327.
372 WHAT THE OAT CROP CARRIES OFF.
Grain, 1600 lbs. at 2 per cent. of ash, ............... 32
Husk, 500 lbs. at 6 per cent. do. ............... 30
Chaft, 300 lbs. at 18 per cent. do. ............... 54
Straw, 3500 lbs. at 6 per cent, do. ........... 21()
Total, ..... ........ 326
The whole quantity, therefore, being greater than is carried off
either by a crop of barley or by a crop of wheat.
The proportion of the several inorganic substances carried off
in the ash is as follows:—
Grain. Husk. Chaff. Straw. Total.
Potash,
Soda, “ 8’44 2.44 4.35 60:43 75-66
Lime, .......... ................ ........ 1.95 0.95 2:48 16:95 22:33
Magnesia, .............................. 3-19 0°33 1 * Ol 7'94 12.47
Oxide or iron, ........................... 0-13 0°39 0-13 3-84 4'49
Oxide of manganese, .................. — 0.18 - *s O-18
Phosphoric acid,....................... 14 02 0°46 ** 5°38 19-86
Phosphates of lime, magnesia, & iron, — * 3-19 *-** 3-19
Sulphuric acid, ........................ 3-33 1°95 2.90 7:05 15:23
Chloride of sodium, . “… *-*. tº-º-º-º: 2-79 * 2-79
Chlorine, ................................. 0.08 0-27 * 6'81 7.16
Silica, .................................... 0-86 23:03 37-15 101-60 162-64
* *
32 30 54 210 326
The husk of the oat is never returned to the soil by the farmer
but is sold in the market along with the grain, so that an average
crop of oats carries off a considerably larger proportion of inor-
ganic matter, which is altogether lost to the soil, than an average
crop of either wheat or barley crop does.
§ 4. Of the ash of the grain and straw of rye.
The grain of rye leaves about 2 per cent of ash, the straw
about 4 per cent. te
The composition of the ash of the grain of rye is as follows:"
Will and Fresenius. Bichon. -
Giessen. Cleves. Mean.
Potash, ........ ......... 32.76 1 1-43 w 22-08
Soda, ......…. 4'45 18°89 11-67
Lime, ................... 2-92 7:05 4°93
Magnesia, ............... 10° 13 10.57 10°35
Oxide of iron, ............ 0-82 1.90 1.36
Phosphoric acid,......... 47°29 51-81 4|9'55
* Annalen der Chem. und Pharm. 1. p. 403.
ASH OF Rye. 373
Will and Fresenius. Bichon.
Giessen. Cleves. - Mean.
Sulphuric acid, .......... 1°46 - 0-51 0-98
Silica, ..................... 0.17 0-69 ()*43
l()0 I 02:85 101.35
Per-centage of ash, ............. ................ 2° 425
Like the other husk-less grains it contains much phosphoric acid
and little silica.
The ash of the straw, according to the most trustworthy analy-
sis yet published, consists of . *
Will and Fresenius,
Potash..................................... 17:36
Soda, .................. . . . . . . . . . . . . . . . . . . 0°31
Lime, .................................... 9:06
Magnesia, ..................... ........ 2°41
Oxide of iron, ... ....... ... ........... l'36
Phosphoric acid, ......... ......... 3'82
Sulphuric acid, ..... ...... s & e º sº e 0-83
Chlorine, ................. ..... ......... 0'46
Silica, .................................... 64°50
100-11°
assºsº
Rye is remarkable for the quantity of straw it yields in propor-
tion to the weight of the grain. The straw is often three or four
times as heavy as the grain.
If we take a crop of rye at 26 bushels, each 54 lbs., and the
straw at three times the weight, the quantity of inorganic matter
carried off the land by a crop of rye will be per imperial acre,
Grain, 1400 lbs. at about 2 per cent., .......... . 30 lbs.
Straw 4200 lbs. at 4 per cent, ..................... 170
Total,......... 200 lbs.
—or something less than is carried off by a crop of barley or
wheat.
The proportion of each of the mineral ingredients carried off
by the crop of grain and straw respectively, will be nearly as fol-
lows,
* Annalen der Chemie und Pharm. l. p. 394.
374 ASH OF INDIAN CORN.
Grain, Straw. - Total.
Potash,........... ......... G-54 - 29°48 36°02
Soda, ........ • . . . . . . . . . . . 3:45 0.53 3'98
Lime, ..................... I'46 15-38 . 16'84
Magnesia, ......... . ... 3'06 4-10 7-16
Oxide of iron, ...... ..... 0-40 2:30 2-70
Phosphoric acid, ......... 14'66 - 6°49 21-15
Sulphuric acid, ......... 0-30 l’41 1-71
Chlorine, .................. e tº º 0-78 - 0-78
Silica, ...................... ()-13 109'53 109'66
30 170 200
§ 5. Composition of the ash of the grain and straw of Indian
corn (Zea Mais).
The grain of maize leaves about 1% per cent. of ash—the straw
from 2% to 6% per cent. -
1°. The grain.—Few analyses have hitherto been made of the
ash of the several parts of this plant. The only two analyses we
yet possess of the grain are the following,-
Fromberg. Letellier.”
United States. Dechelbronn. Mean.
gº ºft 30-8 32°48
Lime,........................ 1:59 . }*3. 1'44
Magnesia,.................. 15:44 17.0 16-22
Oxide of iron, ............ 0-60 * 0-30
Phosphoric acid, ......... 39-65 50°]. 44-87
Sulphuric acid,............. 5'54 *e 2-77
Chlorine, .................. 0°36 *- 0- 18
Silica, ..................... 2°09 0-8 l"44
99°44 } 00 99-70
-** *4 *
2". Straw.—Of the straw or stem of the maize, we have two ana-
lyses from plants grown on different soils. The ash of the several
parts of this plant, however, and at different ages, must differ so
much in composition that little can be inferred from the follow -
ing differences as to the effect of diversity of soil.
Composition of the ash of maize straw, grown on two different
soils in the neighbourhood of Grätz. No. 1 on a soil formed from
the debris of primary rocks, No. 2 on a mountain limestone soil.
* Annal. der Chemie und Pharm, l. p. 403.
WHAT INDIAN CORN CARRIES OFF. 375
Hruschauer."
No. 1. No. 2. Mean.
Potash, ..................... 14°46 4°78 9-62
Soda,.................... ... 39-92 12’69 26°30
Lime, ..................... 4°93 11:00 7.97
Magnesia,.................. 1°84 ll"44 6°64
Oxide of iron, ... ......... 0-90 0-73 0-8I
Phosphoric acid, ......... 11-76 22°39 17-08
Sulphate of lime,... ...... 1.01 . 1.37 1' 19
Chloride of sodium, ...... 6.29 - 0°55 3°42
Silica, ... .................. 18-89 - 35°05 26-97
100 100 100
Per-centage of ash, ...... 2:30 6'50 4°40
Between these results we observe great differences both in the
total per-centage of ash left, and in the proportions of every one
of the constituents which the ash contains. This is by no means
unexpected, but it illustrates a fact to which I shall presently draw
your attention more particularly, that our knowledge of the inor-
ganic constituents of plants—of the functions performed by them in
the several parts of plants—and of the proportions required most
perfectly to perform these several functions—is yet in its infancy.
The crop of Indian corn varies, I believe, more than that of any
other grain. Crops of nearly 200 bushels an acre are recorded in
some of the journals of the United States,f but 60 bushels each
60 lbs. is considered a good average return even in favourable dis-
tricts. We have no accurate returns of the proportion which the
weight of the straw and leaves bears to that of the corn of the same
plant. -
Sixty bushels of corn at 1% per cent, of ash would carry off the
land 54 lbs. of inorganic matter, consisting of.-
Potash and soda,.............................. 16.6
Lime, ........ .................................. 0.7
Magnesia, .................................... 9-2
Phosphoric acid, ................. ............ 27-l
Silica, .......................................... 0°4
54 lbs.
According to this analysis of Letellier, the ash of the maize corn
consists almost entirely of the phosphates of potash, soda, and
magnesia.
* Annal. der Chemie und Pharm, liv. pp. 337–339.
+ As in the American Cultivator, (1845) vol. x. p. 123.
376 'ASH OF RICE AND BUCK-WHEAT.
- § 6. Of the ash of rice.
The different varieties of dressed and undressed rice examined
in my laboratory gave the following proportions of water and of
ash per cent.
- Water. Ash in dry state.
Madras rice dressed, .............................. 13°48 0.66
Do. do. undressed, .............. ............ 11.27 0'90
Bengal rice dressed, ... ........................... 13:17 0.50
Do. do. undressed, ........ ... .............. 16:47 0-64
Patna rice dressed, ...................... & ſº e s e e s e s tº a 13°] 0 0°40
Carolina rice dressed,.............................. 13:00 0-36
Rice flour, ................. . ..................... 14°60 0°42
Dressings of rice,.................................... 14°41 I •31
Husk of paddy, ............................. ..... s & e 14:20
Grain of do. .................................... 0.97
The composition of the grain, husk, and top straw of a variety
of paddy analysed in my laboratory was as follows :--
Grain. Husk. Straw.
Potash, ........................... 18°48 1-60 10-27
Soda, .............................. 10.67 1 °58 3.82
Lime,.............................. l 27 l'Ol 0.73
Magnesia, ........................ 11.69 1.96 4°49
Oxide of iron, .................. 0' 45 0.54 0.67
Phosphoric acid, ............... 53°36 1-86 1 -09
Sulphuric acid,.................. * 0.92 3-56
Chlorine, ................... . . . ().27 {}*34 0.33
Silica, ........................... 3-35 89-71 74-09
99.54 99.52 99-05
Per-centage of ash in the dry state, 1:00 14° 18 12-97
§ 7. Of the ash of the grain of buck-wheat and millet.
Buck-wheat leaves nearly the same per-centage of ash (2 per
cent.) as the other husk-less seeds usually consumed for food—the
millet with its husk nearly twice as much or 3.9 per cent. The
composition of the ash of these grains according to the latest ana-
lyses is as follows:
Buckwheat. • Millet,
Bichon." Poleck +
- Cleves.
Potash; ........................... 874 9° 58
Soda, .............................. 20*10 | '3]
Lime, ........................... . 6-66 0.61
Magnesia, ....................... 10-38 7-66
Oxide of iron, .................. 1-05 0.63
* Annal. der Chemie und Pharm. l. p. 410. + Ibid. p. 419.
ASH OF THE FIELD BEAN. 377
Buckwheat. Millet.
Eichon.* Poleck.f
Cleves.
Phosphoric acid, ... ........... 50'07 18° 19
Sulphuric acid, .................. 2°16 tº g tº
Sulphate of lime, ............... * & © 0-60
Chloride of sodium, ............ * * * 1°43
Silica,.............................. 0-69 59-63
99-85 99-64
Per-centage of ash, ............... 2° 125 3-88
Buckwheat contains about the same average proportion of phos-
phoric acid as our other usually cultivated grains. The same is
also the case with the nutritive part of millet. For though in
the above analysis it appears to contain only 18 per cent. of this
ingredient—yet if we throw aside the 60 per cent. of silica pre-
sent in the ash—the proportion of phosphoric acid in what re-
mains amounts to 45% per cent.—so that the pure flour of millet is
probably as rich in phosphoric acid as that of any of our other
kinds of grain. *
§ 8. Of the ash of the grain and straw of the bean, the pea, the
lentil, and the vetch. #
The bean, the pea, the lentil, and the vetch, leave usually from
2 to 3 per cent of ash, and the straw from 4% to 6 per cent.
1°. The bean.-The ash of the field bean (Vicia faba) consists
of,
Bichon.º Buchner.: Boussingault.S
* - (Holland.) (Giessen.) (Alsace.) Mean.
Potash, ..................... 20-82 32-7] 47° 14 33-56
Soda, .... .................. 19-06 12.75 e iº & 10-60
Lime, ..... . . ... ....... ... 7.26 4-72 5-33 5-77
Magnesia, ........... ...... 8.87 6'13 8'98 7.90
Oxide of iron,... ........... 1:03 0.66 tº e & 0°56
Phosphoric acid, ...... 37'94 39°l 1 35'67 37.57
Sulphuric acid, ........ ... 1°34 & 1°66 1-00
Chlorine, .................... 1'48 * * * 0-71 0-73
Silica, .................. . . . . 2°46 O'47 ()'51 I 15
100 °26 96*55 | 00 98.93
Per-centage of ash, ...... 4°00
And that of the Haricot bean (Phaseolus vulgaris) consists of,
* Annal. der Chemie und Pharm. l. n. 410.
... I bid. ).
p. 402.
+ Ibid. p. 419.
§ Economie Rurale, ii. p. 327.
378 ASH OF THE PEA, THE LENTIL, AND THE VETCH.
Thon.* Levi,t Boussingault.:
Kurhesse. Worms. Alsace. Mean.
Potash, ..................... 21-71 38-89 51°36 37.32
Soda, ........................ 21-07 11.78 10°95
Lime, ....................... 5:38 5'90 6-07 5-78
Magnesia, .................. 7-35 9 03 12-03 9:47
Oxide of iron, ............ 0.34 0-11 & ſº de 0-15
Phosphoric acid, ......... 35-33 31-34 28'53 31°73
Sulphuric acid, ........ ... 2:28 2.47 1°36 2°04
Chlorine,..................... sº º ve 0.33 0° 10 © º º
Chloride of Sodium, ...... 3.32 g * - e. 1-40
Silica,........................ 1'48 0'44 1.05 0-99
98.26 100-29 100-50 99.83
Per-centage of ash, .............................. 3.29
2. The pea.—The ash of the field pea, according to the latest
analyses, consists of,
Will and Fresenius's Bichon,S Thon.S Boussingault.]]
Giessen. Holland. Kurhesse. Alsace. Mean.
Potash, ............... 39'51 34°19 35:20 35-30 36-05
Soda, ........ ......... 3'98 12.86 10:32 2°50 7-42
Lime, ............ . 5'91 2.46 2.70 10'10 5°29
Magnesia, . ..... ... 6°43 8°60 6.91 11.90 8°46
Oxide of iron, ...... 1-05 0°96 1°94 traces 0°99
Phosphoric acid, ... 34°50 34°57 34°01 30°10 33°29
Sulphuric acid,...... 4°91 3:56 4°28 470 4°36
Chlorine, ............ tº º a 0-31 & a e l" || 0 *
Chloride of sodium, 3-71 * * * 2°56 * * * * 3:13
Silica, ............... e = } 0-25 0.29 1:50 0°51
100° 97.76 98.2] 97.20 , 99°50
Per-centage of ash, ............ ~ 3:00
3°. The ashes of the lentil" and of the vetch consist, respectively,
according to Levi, of,
Potash, .................. 34-31 30.57
Soda,..................... 13°30 10-91
Lime, .................. 6-24 4-79
Magnesia,............ . . 2°44 8’49
Oxide of iron, ... ..... 1°98 0-75
Phosphoric acid, ...... 35'82 38'05
Sulphuric acid, ... ... e dº sº. 4°10
Chlorine, ............... 4°56 1.21
Silica, . ................ 1-31 2:01
99.96 100-88
Per-centage of ash, ...... 2-06 2:402
* Annal. der Chemie und Pharm. l. p. 402. + Ibid. p. 425.
3: Economie Rurale, ii. p. 327. § Annal. der Chemie und Pharm. l. p. 401.
| Economie Rurale, ii. p. 327. T Annal. der Chemie und Pharm, l. p. 425.
STRAW OF THE BEAN, THE PEA, AND THE WETCH. 379
4". Straw of the bean, the pea, and the vetch.-The only analyses
of the straw of these leguminous plants we yet possess are those of
Sprengel, which assign to that of the bean, the pea, and the vetch
the following composition;
Field bean. Field pea. Common vetch.
Potash, ............... 53° 08 4.73 35' 49
Soda, .................. 1:60 & Cº º 1-02
Lime, ... ..... :......... 1999 54'91 38° 33
Magnesia,............... 6-69 6-88 6:36
Alumina,............... 0.32 1.21 O-29
Oxide of iron, ..... .. 0-22 0°40 (). 17
Oxide of manganese, 0.16 0° 15 0-15
Phosphoric acid, .... . 724 4'83 5*49
Sulphuric acid, ...... 1-09 6-77 2.39
Chlorine, ...... ... ..... 2°56 0-09 . 1'65
Silica, .................. 7.05 20-03 8-66
100.00 100'00 I 00:00
Future analyses will probably introduce considerable corrections
into these results.
The produce of these leguminous crops is very variable. Of
grain,_
The bean gives from 16 to 40 bushels of about 63 pounds.
The pea, e Q e 12 to 84 e tº a 64 ...
The vetch, ... 16 to 40 e - © 66 ...
The mean return from beans is estimated by Schwertz” at 25
bushels, from peas at 15 bushels, and from vetches at 17 bushels
per acre. These can scarcely be considered as fair averages for our
country; but they are the best I can at present obtain.
The straw of all these plants is very bulky but varies also con-
siderably in weight. If we take it on an average for 25 bushels
of beans at 13 tons or 2800 lbs. per acre, and for the other crops
in like proportion—then the loss to the soil by the removal of a
crop of beans, peas, or tares will be nearly as follows:—
Beans 25 bushels: or 1575 lbs. at 2% per cent. of ash 40 lbs.
Straw e - ſº 2800 lbs. at 6 tº gº º = 170
-**
Total, . 210 lbs.
* Leuchtweiss, Annalen der Chemie und Pharm. 1, p. 417
380 WHAT THE BEAN CARIFIES OFF.
Peas.-15 bushels, or 960 lbs., at 2% per cent. = 24 lbs.
Straw, 2000 lbs., at 6 ... = 120
Total, e e 144 lbs.
The smallness of this sum arises from the smallness of the Sup-
posed crop, which in this country, I fear, would not pay the cost of
cultivation.
Vetches.—17 bushels, or 1100 lbs., at 2% per cent. = 28 lbs.
2200 lbs. of straw, at 6 ... ... - 132
160 lbs.
The relative proportions of the several substances carried off by
a crop of 25 bushels of beans would be as follows:—
Beans. Bean straw. , Total.
Potash,.................................... ........ 1360 90-21 103-81
Soda, ..... . . . . . . . . ........................... 4:30 2.72 7.02
Lime, ............. ............................... 2:34 33°99 36-33,
Magnesia,.............. • . . . . . . . . . . . . . . . . . . . . . . . . . . . 3:15 11°38 14°53
Oxide of iron, ................... ............... 0-24 0°55 0-79
Alumina and a little oxide of manganese,. . ... 0°65 0°65
Phosphoric acid, ................................. 15-20 l2:32 27-52
Sulphuric acid,.................................... (): 40 1-85 2.25
Chlorine, .......................................... ()-30 4°35 4-65
Silica, ......................................... ... 0°47 11.98 12°45
40 170 210
The whole quantity of ash carried off by a crop of beans is
therefore nearly the same as by a crop of wheat or barley.
§ 9. Composition of the ash of the seed and straw of the hemp and
Jiaw plants, and of the seed of the gold of pleasure.
As the culture of flax is now spreading very much in this country,
it will be interesting to you to know what the composition of the
ash of its several parts is, and therefore how far and of what sub-
stances it is likely to rob the soil.
The hemp and flax seeds leave from 4% to 54 per cent. of ash
when fully burned, the entire dried plants leave nearly the same
proportion. *
1°. The seed.—The composition of the ash of the seeds of hemp,
flax, and gold of pleasure (Camelina sativa), is exhibited in the fol-
lowing tables. The last two columns are from analyses made in
my laboratory.
ASH OF HEMP AND LINT SEED.
381
Linseed.
Hempseed. 2– —A- -N
* Riga. Dutch.
Potash, ............... 21-67 25'85 17.59 30-01
Soda, .................. 0.66 0-71 6'92 | '88
Lime, .................. 26'63 25-27 8’46 8-12
Magnesia, ............ 1'00 0-22 14'83 14' 52
Oxide of iron,......... 0.77 3:67 1425 0-68
Phosphoric acid, ... 34.96 40° 11 36'42 37:64
Sulphuric acid, ...... *=s * 2.47 2° 16
Sulphate of lime ... 0-18 1.70 *=sº *-mº
Chlorine, ............ * * 0.17 0.29
Chloride of sodium, 0.09 1'55 * *
Silica, .................. 14'04 0.92 10:58 5-60
100 100 98-69 100-90
Per-centage of ash,... 5-60 4'63
The ash of the gold of pleasure seed has not been analysed, but
that of the cakes or expressed seed of this plant, compared with that
of linseed, was found in my laboratory to have the following com-
position. -
English English American
Gold of Pleasure. Linseed cake. Linseed cake.
Alkaline salts, ........................ 34-35 32.72 38'28
Phosphates of lime and magnesia, 45.79 49.44 56°40
Lime, ................................. 3-89 5'06 1-25
Magnesia,.............................. 0 55 1.57 trace
Silica and sand, ..................... 15:42 11:21 4'07
100 100 100
Per-centage of ash, ................. 6-9 7.3 6,4
All these are rich in earthy phosphates. The alcaline phos-
phates are included among the alcaline salts.
2. The straw.—The composition of the ash of the flax and
hemp plants" is as follows:—
The entire plants.
Flax. Hemp.
Potash, ........................... 11.78 10°99
Soda, .............................. 11-82 l”06
Lime, ........................... 14°85 61-75
Magnesia, ........................ 9°38 7-16
Alumina and oxide of iron, ... 7:32 0°54
Phosphoric acid, ............... 13.05 4.73
* Kane's “Industrial Resources of Ireland,” pp. 327 and 341,
382 FLAX STEEP WATER,
The entire plants.
Flax. Hemp.
Sulphuric acid, ............ ... .... 3-19 1°61
Chlorine, ... ... ..... ..... ...... 2.90 2-24
Silica, ........................... 25-71 9-92
100 100
Per-centage of ash (dry), ...... 5°00 4'54
These analyses of Sir Robert Kane's were made, I believe, upon
the ash of the entire plant. Whether it was before or after it was
fully ripe I am not aware.
When the flax plant is steeped in the ordinary way of preparing
it for the flax mill, much of the saline matter it contains is extracted
by the water. A portion of this steep water has been examined
by Sir Robert Kane, and the nature of its saline constituents deter-
mined. He found the dry solid extract obtained from it to leave,
when burned, 42 per cent. of ash, of which the composition was as
follows:
Chloride of potassium, ............... 9:05
Sulphate of potash, .................. 10°48
Carbonate of potash, .................. 9°05
Carbonate of soda, ..................... 31°43
Phosphate of iron and alumina, ... 7.62
Phosphate of lime, ..... ............... 5'00
Carbonate of lime, ..................... 9°52
Carbonate of magnesia, ............... 4'76
Silica, .................................... 13°09
100%
Per-centage of ash in dry extract, 42:01
From this table it appears that the salts of potash and soda, as
we should expect, are principally dissolved out during the process
of steeping. We have as yet no experiments which show how
much of the whole saline matter of the plant, is removed by the
steep water.
It is not by any means all removed. The scutchings or outside
portions taken off at the flax mill contain much mineral matter, and
the flax itself—both the pure fibre and the coarser parts or pob, re-
moved during the dressing—leaves when burned a considerable
proportion of ash. -
The ash of dressed flax, of pob, and of hemp scutchings, analysed
* Kane's Industrial Resources of Ireland, p. 328.
MUSTARD, MADIA, AND RYE GRASS SEED. 383
in my laboratory, gave the following proportions of the several
usual inorganic constituents of plants.
Pob of Scutchings of
Dressed flax, flax. American hemp.
Alkalime salts, chiefly common salt. } 8'93 9°58 3-32
and Sulphate of soda,
Phosphates of lime and magnesia, and | 17.89 14°l2 19.15
a little phosphate of lime,
Sulphate of lime (gypsum), ......... .. * * * & º º 3.26
Carbonate of lime, ........................ 45°56 51'43 26°45
Carbonate of magnesia, .................. 6-38 9°24. 2.80
Insoluble siliceous matter, ............... 21:24 15-63 45°02
100 100 100
Per-centage of ash in the dry fibre,...... 1:29 1.78 14'43 .
Suppose the flax steep water therefore to be returned to the
land, and even the scutchings also, which is rarely the case, the fibre
as it comes from the mill and even as it goes to market, would still
carry off a considerable quantity of valuable matter from the soil.
§ 10. Of the ash of the mustard, madia, and rye grass seeds.
The seeds of the black and white mustard, of the madia sativa,
and of rye grass, (Lolium perenne), leave an ash, which has the
following composition respectively:- -
Chlorine,
Silica, .........................
Per-centage of ash,
* 6 tº * * * * * * * tº º tº 4
Phosphoric acid, ...........
Sulphuric acid, ..............
tº e º & e < * * * * * * * * * * * *
e tº tº ſº $ tº it tº
The mustard seeds, it will be
acid they contain.
Mustard.”
White. Black:
. 10:02 12'66
. 9-61 6' 11
. 21:28 17:34
. 11:25 14:38
. 1'46 ] 12
. 37-41 37-39
. 5'41 7, 17
. 0:20 1.36
... 3'36 2.78
100 100.31
. 4:15 4°3]
9°53
11:24
7-74
15°42
1:08
54'99
100
*sºme
4-97
l'43
19°24
5°5]
2-17
19°59
3:24
trace
43'85
*R* *
100
' 6'85
Madia seed.-- Rye grass seed.j:
Seen, have much resemblance to
the lint and hemp seeds in the proportions of lime and phosphoric
* James, Annalen der Chemie und Pharm., liv. p. 347.
† Souchay, Ibid. p. 349.
# Thomson, Report to Government on Feeding Cattle with Malt, p. 72.
*
The madia seed contains considerably more
phosphoric acid, and the rye grass seed less. The rye grass seed
384 THE TURNIP, THE BEET, AND THE POTATO.
is not an oily seed, as the others are. I have added it to this table
only because no other analysis of grass seed has recently been
published with which I could compare it.
§ 11. Of the ash of the turnip, the beet, the Jerusalem artichoke,
and the potato.
1°. The roots.-The bulbs or tubers of these plants contain
much water,-but in the dry state the turnip leaves from 6 to 8
per cent of ash, the beet and the artichoke about 6, and the potato
about 4 per cent.
The ash of the three former roots consists of,
Jerusalem
Turnips. Beets. Artichokes.
Boussingault." Muspratt Boussingault." Boussingault.”
Potash, .............. ...... 41.96 37:69 48-93 54.67
Soda, ........................ 5'09 16' 62 7:53 traces
Lime, ........................ 13°60 1 1-91 8.78 2.82
Magnesia, .................. 5°34 4'02 5'52 2-21
Oxide of iron, alumina, &c. l'28 0°50 3°14 6-39
Phosphoric acid, ......... 7.58 5°80 7:53 13-27
Sulphuric acid, ............ 13. 60 1270 2:01 2-70
Chlorine,..................... 3:60 3.79 6'52 1.97
Silica, ........................ 7.95 6:15 10'04 15-97
100 99° 18 100 100
Per-centage of ash in the 7-60 5'66 6:30 6:00
dry state, ... ..... • * * * * *
The ash of the potato consists of,
Boussingault.t Fromberg.
From Lanark. From Drummore. Mean.
Potash, ............ 59°95 57-58 49-73 55.75
Soda,............... traces 3'66 1°93 1°86
Lime,............... 2°09 0-81 3°31 2-07
Magnesia, ......... 6°28 4°53 5°03 5°28
Oxide of iron and | 0°59 0°42 0°56 0.52
alumina, ...... R
Phosphoric acid, 1316 9'98 14°58 12.57
Sulphuric acid, 8-27 14°63 18:04 13°65
Chlorine, ......... 3° 14 5° 16 4°51 4:27,
Silica, ........... 6:52 3.68 2:49 423
100 100'45 100° 18 1 00:20
Percentageofash | 4°00 4°01 3.75 3-92
in dry state,
* Economie Rurale, ii. p. 327.
t Ibid. p. 327.
ASH OF TURNIP TOPS. 385
2°. Tops.—The proportion of ash left by the dry tops—stems
and leaves—is much greater than by the dry bulbs or tubers.
The dry tops of the turnip leave from 14 to 20 per cent of ash.
Thºse of the potato leave from 18 to 25 per cent.
a. The Turnip.–The composition of the ash left by the entire
tops—leaves and stems—of the turnip, as determined in my labo-
ratory, is as follows:— .
Potash,.............. ............ 28°65
Soda, ........................... 5'41
Lime, ........................... 23-27
Magnesia, . ..................... 3'09
Oxide of iron, ..... ............ O-86
Phosphoric acid, ............... 9:29
Sulphuric acid, ............... 12°52
Chlorime, ........................ 16-05
Silica, .......................... ... 0-86
100
The proportion of phosphoric acid found in the ash is often very
much greater, as is seen by the following analysis of the ash of
the entire tops made by myself. -
Potash, soda, and carbonic acid, ............ 25.95
Sulphuric acid, ................................. 12.62
Chloride of sodium,.............................. 14°02
Phosphates of lime and magnesia,............ 36-40
Carbonates of lime and magnesia, ............ 10-01
Silica, ....................... ** g e º 'º e º e º gº tº & & s e s ∈ & © e º & 1°00
100
Here more than a third of the whole weight of the ash consisted
of earthy phosphates, and no doubt the proportion varies much
with the period of the plant's growth, and with the part of the tops
which is burned for the collection of ash.
b. The Potato.—The stem of the potato top yields an ash which
differs very considerably in the proportion of phosphoric acid,
lime, and alcaline matter which it contains from that which is left
by the leaf.
Thus the tops of buff potatoes, gathered on the 1st of August,
gave an ash which my assistant, Mr Thomas, found to have the
following composition from the stems and leaves respectively:-
- B b
ASH OF POTATO TOPS,
Stems. Leaves. Mean.
Potash, ........... e e º e < * * * * * 31.58 24.47 28.02
Soda, ........... ......... 24.01 8.50 16.26
Lime, ............... ..... 13.10 20.70 16.90
Magnesia, ................ . 6.56 7.63 7.09
Oxide of iron, ....... ... . . . . 0.74 1.35 1.05
Phosphoric acid, ......... 2.91 12.34 7.62
Sulphuric acid, ......... 6.35 7.40 6.88
Chlorine, .................. l:3.65 11.00 12.33
Silica, ..................... 1.10 6.6}. 3.85
100 | 00 100
Per-centage of ash in the dry state, ... 15.05 14.77 l{.96
From this table it appears that the alcaline matter abounds
more in the stem, and the phosphoric acid, and lime, or the earthy
phosphates, in the leaf. If we suppose the leaves and stem to be
nearly equal in weight, the mean given in the third column will
represent very nearly the composition of the ash of the entire top.
But in the potato top, also, the composition of the inorganic
matter varies with the age of the plant. Thus the ash of the en-
tire tops of the young potato collected on the 3d of May 1846 was
found in my laboratory to consist of -
Potash, ......... • e - - - e º 'º e tº 22, 46
Soda, ........................ 25.22
Lime, ............... ........ 13.11
Magnesia, .................. 5.55
Oxide of iron, ............ 2.49
Phosphoric acid, ........ . 14.96
Sulphuric acid, ............ 1.62
Chlorine, ................. 11.71
Silica, ..................... 2.88
100
Per-centage of ash in the dry tops:
Leaves, ..................... 16.5]
Stems, ..................... 17.65
Thus in the young potato the tops are much richer in alcaline
matter, in phosphoric acid, and in chlorine, than those of the pota-
to when full grown; while the entire per-centage of ash left by the
dried plant is also greater in such as are young. To these facts
I shall again draw your attention in the succeeding lecture.
3°. A good crop of turnips varies from 20 to 40 tons of bulbs
per imperial acre, and of potatoes from 6 to 20 tons, according to
WHAT THE TURNIP CARRIES OFF. 387
the soil, manure, and climate. If we take 20 tons of turnips and 8
tons of potatoes as average crops, and if the tops—which vary very
much in the proportion they bear to the clean bulbs—be taken at
one-third of the weight of the bulbs of the turnip, and at one-half
of that of the tubers of the potato—we shall have the proportion
of inorganic matter carried off by these crops from an imperial acre
as follows:
a. Turnips.--Twenty tons of bulbs contain 2 tons of dry mat-
ter, leaving 7% per cent. of ash, or about 340 lbs. Six and a
third tons of tops contain 1850 lbs. of dry matter, leaving 17 per
cent of ash, or about 310 lbs. Thus the whole crop contains of
mineral matter,
In the bulbs, ...... 340 lbs.
In the tops, ...... 3} 0
*-i-º-º:
Total, 650 lbs.
So that a crop of 20 tons of turnips carries off very much more
inorganic matter from the soil than any of our common corn crops
do.
The composition of this inorganic matter, or the relative pro-
portions of the several substances it consists of, are nearly as fol-
lows:— \
Bulbs. Tops. Total.
Potash, ... ..... 142'66 88-82 231'48
Soda, ........ .... 17-31 16.76 34'07
Lime, ............ 46’24 72°14 ] 18:38
Magnesia, ...... 18° 16 9°58 27.74
Oxide of iron, ... 4:35 2.67 7:02
Phosphoric acid, 2577 28:80 54-57
Sulphuric acid, 46’24 38.8l 85-05
Chlorine, ......... 12:24 49.75 6] '99
Silica, ............ 27.03 2.67 29-70
340 lbs. 310 lbs. 650 lbs.
b. Potatoes.—Eight tons of potatoes contain also 2 tons of dry
matter, which leave when burned from 8 to 10 per cent of ash,
or in all 400 lbs. The tops of the potato weighing 4 or 5 tons
green, contain 1000 lbs. of dry matter, leaving 18 per cent of ash
—or in all 180 lbs. Thus the crop carries off altogether,
In the tubers, ...... .. 400 lbs.
In the tops, ........... 180
Total, 580 lbs.
388 WFIAT THE POTATO CARRIES OFF,
or about 70 lbs. less than is carried off by the turnip crop of 20
tons. But these proportions are, as you know, very variable.
The yield of bulbs and tubers by these two crops is often very
much more than I have taken for the above calculation. In some
districts the crop averages one-half more, and the proportion
of tops in both the turnip and the potato often bears a much
larger proportion to the weights of the roots than I have assumed.
These circumstances must, of course, be taken into consideration
in estimating the effect which any given crop, or any succession of
crops of these roots, is likely to produce upon a given soil.
The relative proportions of the several substances extracted from
the soil by the above crop of potatoes are nearly as follows:—
Tubers. Tops. Total.
Potash, ... ..... 222°56 50 44 273-00
Soda, ............ 7'44 29-27 36-7]
Jime, ............ 8-24 30°42 38.66
Magnesia, ...... 2] '08 1276 33-84
Oxide of iron, ... 2:08 1-89 3.97
Phosphoric acid, 50:20 l3-72 (33-92
Sulphuric acid, 54.48 12:38 66'86
Chlorine, ...... ... 17:04 22-19 39:23
Silica, ............ 16-88 6'93 23-8 l
400 lbs. 180 lbs. 580 lbs.
§ 12. Of the ash of the cabbage.
The fresh leaves of the cabbage, when dried at 212°, lose from
90 to 92 per cent. of water. The dry cabbage leaf, when burn-
ed, leaves from 18 to 26 per cent. of ash. The composition of this
ash, as determined in my laboratory by Mr Fromberg, is as follows:
Potash,........................... 11.70
Soda, ........................... 20-42
Lime, ........................... 20:97
Magnesia,........................ 5'94
Oxide of iron, .................. 0-60
Phosphoric acid,... ........... 12:37
Sulphuric acid, ............... 21'48
Chlorine, ........................ 5-77
Silica, . . . . . .................... 0-75
100
The cabbage when grown in the field yields a heavy though va-
riable crop. The drum-head cabbage sometimes yields 50 tons
WHAT THE CABBAGE CARRIES OFF. 389
an imperial acre, containing 5 tons of dry food, and carrying off
nearly a ton of mineral matter from the soil. Assuming it to
weigh 20 tons, a weight it often greatly exceeds, the crop will
contain,
Water, ............ .. I8 tons.
Dry organic matter, l;
Inorganic,..... ...... 0% or about 900 lbs.
20 tons.
Thus 20 tons of cabbage carry off from the soil one-half more
mineral matter than 20 tons of turnips or 8 tons of potatoes includ-
ing their tops. It ought, therefore, to be an exhausting crop.
These 900 lbs. of mineral matter will consist of
Potash, ........... ............... 105
Soda, ............... .............. 184
Lime, .............. ............... 189
Magnesia, ........................ 54
Oxide of iron, ............... -- e. e. g. 5
Phosphoric acid, ............... 112
Sulphuric acid, .................. 192
Chlorine, ........................ .. 52
Silica, ........... ................. 7
000
If we compare the above numbers, especially those opposite to
the phosphoric and sulphuric acids, with the numbers contained in
any of the other tables, we cannot fail to be struck with the much
larger quantity of these substances required by an average crop of
cabbage than by any other of our usually cultivated crops.
§ 13. Of the ash of the grasses and clovers.
Much still remains to be done in regard to the ashes of our grasses
and clovers. Besides the older analyses of Sprengel, we possess
some which have been more recently made; but our cultivated
grasses are so numerous, and the circumstances which affect the
composition of the ash they yield are so various, that much time
will elapse before we can arrive at any very minutely correct conclu-
sions in regard to their inorganic constituents.
The following tables contain all the more recent analyses, and
a selection of those of Sprengel,
390 ASH OF THE GRASSES AND CLOWERS.
Meadow hay. Rye grass hay. Red White Clover.
Boussingault.* Thom- Spren- Clover. Clover. Boussin-
I. II. son.-- gel. Sprengel. gault:
Potash, ........................... 18'll 29'03 8.03 16.67 26.70 34:00 35'47
Soda,.............................. 1.35 2.44 2.17 7:45 7.07 6-34 0-67
Lime, ........................... 22.95 16:36 6-50 13.89 37.09 25-72 32.80
Magnesia,........................ 6.75 8.82 4:01 l’70 4-45 3'34 8:40
Oxide of iron, alumina, &c. l'69 0.64 0°36 0'59 0.20 2.77 0°40
Phosphoric acid, ............... 5'97 5'63 12-51 0-48 8-80 5'53 8:40
Sulphuric acid,.................. 2.70 3:08 — 6'68 5'98 3-86 3-33
Chlorine, ........................ 2'59 2.97 — 0.11 4-86 2.31 3°47
Silica, ........................... 37.89 31°03 64.57 52-43 4'85 16:13 7-06
100 100 98’ 15 100 100 100 100
Per-cent. of ash in dry state, 6.0 6-2 5'89 5-29 7-48 9-13 7.7
Sprengel’s analysis of rye grass hay looks suspicious in conse-
quence of the small quantity of phosphoric acid it contains. The
meadow hay of Boussingault was made up, no doubt, of a mixture
of grasses of which the species are not mentioned. It will be ob-
served that the meadow and rye grass hays contain a much larger
proportion of silica than the clovers. The two classes, indeed,—
the grasses and the clovers—are related to each other both botani-
cally and chemically, in the same way as the corn plants are related
to the leguminous, such as the pea and the bean. -
Common reed, Lucerne. Esparsette Common
(Arundo Phragmites.) Sprengel. or Sainfoin. asparagus.
Fromberg. Sprengel. Buch.Ş Levi.[
Potash, ..................... 4'80 14 03 29'57 6.75 28-07
Soda, ........................ 6-44 G.28 21'46 3'96
Lime, ........................... 6'06 50-57 31'55 31'01 18'04
Magnesia, ..................... 0-24 3°64 4'14 8'57 4'44
Oxide of iron, alumina, &c. 0.93 0.63 0.95 l'74 5-78
Phosphoric acid, ............ 3. I 9 I 3.68 13° 17 26-64 13-74
Sulphuric acid, ............... 5'49 4'23 4'9() l'68 7.84
Chlorine, ..................... 0.17 3'32 2.26 1' 31 4'40
Silica, .......................... 78-9] 3°46 7.18 1 : 10 13-69
99.79 100 } 00 100-26 99.96
Per-centage of ash, . . . ....... l'62 9° 55 6'96
In this table, again, the sainfoin of Sprengel contains much less
phosphoric acid than that of Buch. This may arise, however, from
other causes than errors of analysis. We do not know as yet
* Economie Rurale, ii. p. 339.
+ Report to Government on feeding cattle with malt.
j: Economie Rurale, ii. p. 327.
§ Annal, und der Chemie Pharm. 1. p. 413. | Ibid. p. 425.
l
ASH OF THE TOBACCO LEAF. 391
what variations naturally exist in the proportions of inorganic mat-
ter in healthy plants of this class. The asparagus has much resem-
blance to lucerne—only it contains more iron and less lime.
The large proportion of silica in the reed shows at once its rela-
tion to the other grasses.
§ 14. Of the ash of the tobacco leaf.
The per-centage of ash left by the dry tobacco leaf varies from
19 to 27 per cent. of its whole weight. This variation is partly
due to the age at which the leaf is gathered, to the warmth of
the climate or season, and to the nature of the soil on which it
is grown. No experiments, however, have hitherto been made to
determine the precise effects of these and other circumstances upon
the leaves of this plant.
Considerable differences have also been found in the quality of
the ash, as will appear in the following analyses of the ash of Sam-
ples of Hungarian tobacco from different localities. The first three
in the following table are from Debreczin, and the fourth from the
Bannat, all of crop 1843.
- I. II. III. IV. Mean.
Potash, ............... .. 29-08 30-67 27-88 18:20 26°46
Soda, ..... ............... 2°26 tº tº º e ‘º e sº e e 0°56
Lime, ..... ............... 27.67 24-79 31' 16 27-86 27-87
Magnesia, ............... 7-22 8'57 7:31 , 15-73 9-72
Chloride of sodium, ... 0-91 5°95 9°34 1 l'4l 6'91
Chloride of potassium, ... s & Gº 4°90 3.92 2-2}
Phosphate of iron, ...... 8.78 6°03 6'39 6-80 7:00
Phosphate of lime, g tº º E. g. * * = © º º * * *
Sulphate of lime, ...... 6'43 5-60 6'43 1 0 1 1 7: 14
Silica, ........... ......... 17.65 18-39 6'59 5-97 12 13
J 00 l ()0 100 100% 100
Per-centage of ash, ... 1890 22:20 24°50 19'80 21:28
The four following are from Funfkirchen, and are of the growth
of four nearly successive years.
1839. 1840. 1841. | 843. Mean.
Potash, .................. |l 2] 8:20 l 9°55 9.68 12°l 4
Soda, ..................... e º 'º tº dº º 0-27 * & © 0-07
Lime, ..................... 47 '03 42-77 44'49 49°28 45°90
Magnesia, ............... 12.77 13.93 11:07 14°58 13:09
* All these analyses are by Will and Fresenius, Annal, der Chemie und Pharm. 1.
p. 39].
392 DIFFERENCES IN THE ASH OF TOBACCO.
1839. 1840. 1841. 1843. Meall.
Chloride of sodium, ... 2:58 3-22 3'54 4'61 3'49
Chloride of potassium, 2.97 8°53 s & & 4'44 3'08
Phosphate of iron, ... 6'30 6-07 4°34 5-19 5°48
Phosphate of lime, ... ... * * * 5°97 e = * l'49
Sulphate of lime, ...... 5' 11 7.96 5:63 6.68 6°35
Silica, ..................... 12-03 9-32 5'14 5'54 8-0 l
100 I 00 | 00 100 100
Per-centage of ash, ... 27°36 23:00 21:08 23-28 23°68
In looking at the above analyses we see,
1". That the proportion of ash varies in the leaf from both loca-
lities, and is therefore independent of the place of growth. The
large per-centage of ash left by the leaf of 1839 may arise from
the powder of the crumbled leaf without the fibres being burned in
this case.
2". The tobacco from Debreczin contained a much larger pro-
portion of potash—that from the Bannat more magnesia, and that
from Funfkirchen much more lime—and this was uniformly the
case in all the samples from these several places. It must have
been caused, therefore, by some constant difference in the soil or
mode of culture in the three districts.
3°. The per-centage both of potash and of lime varied consider-
ably in the leaves from Funfkirchen grown in successive years,
yet they invariably contained a much larger proportion of lime and
less of alcaline matter than the leaves from Debreczin. This again
shows that the effect of seasons is not able to overcome the more
powerful influences of soil and culture.
4°. The proportion of phosphate of iron is large—about 6 per
cent of the whole ash. In only one sample was there any phos-
phate of lime.
5°. The proportion of silica varied considerably. This I am in-
clined to attribute not so much to the soil as to the age and rapi-
dity of growth of the leaf. In the following lecture I shall show
you that in the potato leaf the proportion of silica diminishes as
the plant increases in growth.
§ 15. Of the ash of the coffee bean.
The dry coffee bean leaves about 3 per cent of ash. The only
analysis yet published gives the following as its composition,
THE COFFEE BEAN AND THE SUGAR CANE. 393
Levi.”
Potash, ............... 50°94
Soda, ........ ......... 1476
Lime, .................. 4’33
Magnesia, ............ 10°90
Oxide of iron, ...... 0.66
Phosphoric acid, ... 13.59
Sulphuric acid, ...... trace.
Chlorine, ............ ] .22
Silica, ......... ........ 3°58
99.98
Per-centage of ash, 3:19
This seed, therefore, appears to contain much alcaline matter.
Whether it is so on all occasions we have as yet no means of judg-
in 9-
§ 16. Of the ash of the sugar cane.
The proportion of ash left by the dry stem and leaves of the su-
gar came was found in my laboratory to be as follows:–
Interior of the top part, ... l'54 per cent.
Interior of the bottom part, l'36
The epidermis, ............... l'44
The knots,........ ........... 1°93 . . .
The leaves, .................... 9.38 .
These proportions will no doubt vary in different canes, according
to their age and to many other circumstances.
The ash of the entire came stalk with and without leaves, and from
different localities, has been analysed by Dr Stenhouse with the
following results:—
. Transparent
Stalks from Whole plant Whole plant young canes Mean of
Demerara. from Trinidad, from Berbice. Jamaica. the whole.
Potash,.................. 32-93 16:03 14:20 9°56 18- 18
Chloride of potas.) ... loor 4'91 gººmsmº, 5:63 5' 31
SIllin, . . . . . . . . . . . .
Soda,..................... * 0-35 1-18 0-27 0°45
Chloride of sodium, ... 17:12 3.76 5*04 3°47 7:34
Lime, .... ............ 2:34 l 0° 10 5' 12 12:21 7'44
Magnesia,............... 3.93 6-24 13°51 5'51 7:30
Phosphoric acid, ..... 7-37 6'14 6'53 7-08 7:01
Sulphuric acid, ...... 7.97 8:30 7-22 3°53 6-76
Silica, ...... . ..... ... 17.64 44-17 47:20 51.84 40-21
09:37 ] 00 100 | 00 100
* Annal, der Chemie und Pharm. ), p. 425.
394 ASH OF THE TWIGS OF THE WINE.
It will be seen from the above analyses, that the proportion of
alcaline matter is greater and of silica less in the stalk alone than
in the stalk and leaf together. Hence the silica, as we should ex-
pect, chiefly resides in the leaf as it does in the leaf and chaff of the
Oat.
The chemical history of this valuable plant is highly deserving
of further investigation.
The ash of the came as it is withdrawn from the furnaces in
which the trash is consumed for boiling down the cane juice,
differs much in its composition from that of the ash analysed by
Dr Stenhouse. The nature of this difference and the cause of it
will be explained in the following lecture.
§ 17. Of the ash of the twigs of the vine.
The young branches of the vine when dried leave about 2%
per cent. of ash. The following table represents the composition
of the ash of vine twigs grown in different localities and on different
soils.
Grown on a On a On a soil
soil formed mountain formed
from pri- limestone from 1mica
Lieb- Weim- mary rocks. soil. slate.
frauen. sheimer. Gratz. Gratz. Gratz. Mean.
Potash,................. | 7-32 25°24 34° 13 24- 93 26-4 25-60
Soda, .................. 28'50 2.74 8'03 7-31 8-79 | 1.07
Lime, ... ... ........... 20-75 40°75 32-67 37.59 33°47 34-85
Magnesia, ............ 9-78 7'47 4'66 7-12 9° 16 7-64
Oxide of iron, ......... 4 * 12 1-52 ()' 16 0-24 (). 19 l'25
Phosphoric acid, ...... 5-20 18.87 16:35 I 9°55 I6-87 15-37
Sulphuric acid, ...... l'96 2.88 2-16 2-37 2'44 2.36
Chlorine, ............... I '82 0.53 ()'50 0-35 (): 25 0-68
Silica, ............... .. l'55 gº tº e l'45 0.62 2°48 1-22
| 00+ 100% 100'lli 100.08+ 100:06+ 100'04
Per-centage of ash
& g 2.25 2.325 2.525
in dry twigs, O 525
2.
5
2
5
2.835 2’689
These results do not differ very widely from each other. They
all represent the ash to contain about one-third of its weight of
lime, and this ingredient is very little greater when the plant, as in
the fourth column, was grown upon a limestone soil. -
The greatest difference is in the phosphoric acid of the first
column. The age of the portion burned may have had some in-
* Levi, Annal. der Chemie und Pharm. l. p. 423.
# JIruschauer, Annal. der Chemie und Pharm. liv, pp. 332, 336.
ASH OF THE HOP. 395
fluenceincausing this diversity, as in some other plants with which
we are acquainted, the phosphates diminish with the age of the
part of the stem which is subjected to analysis.
§ 18. Of the ash of the hop.
The flowers of the hop plant leave about 10, the leaves 14 and
the bine or stem 4 per cent. of ash. The ash of these several parts
has been analysed by Mr Nesbit with the following results.
Hop. Leaves. Bine.
Potash, .................. 25°18 14-95 24°35
Soda, ..................... tº º ſº. O'39 e º 'º
Lime, ............... ..... 15'98 49-67 38-73
Magnesia, ............... 5-77 2°39 4°l 0
Phosphate of iron, ...... 7'45 3’51 0°40
Phosphoric acid, ......... 9-80 2-42 6'80
Sulphuric acid, ......... 5*4l 5'04 3'44
Chloride of potassium, 1-67 e º 'º 9°64
Chloride of sodium, ...... 7-24 9°49 6'47
Silica, ..................... 21:50 12°14 6-07
100% 100* 100*
Per-centage of ash in the dry state, 9.87 13°60 3-74
The per-centage of silica in the flower or hop is much greater
in comparison with the other parts of the plant than we should
have anticipated.
Mr Nesbit calculates the produce of an acre at about 500 lbs.
of hops, 150 of leaves, and 300 lbs. of bine.
§ 19. Of the ash of the apple and cherry tree, and of the Chinese
crab.
The wood of the apple and cherry trees leaves only about a
quarter of a per cent, of ash, while the bark leaves 10 per cent.—
or forty times as much as the wood.
The composition of the ash is as follows:
Apple Tree. Cherry Tree.
Wood. Wood. Bark.
Potash, ............ 1924 - 25'90 7'9.4
Soda, ........ . . . . . . 0.69 | 0:47 15-85
Lime, ... ........... 63' 60 35-78 44' 67
Magnesia, ......... 7'46 ] l'47 5*43
Oxide of iron, ...... g is sº 0-07 0-21
* Analysis of the Hop, by J. C. Nesbit, p. 6.
396 THE APPLE AND CHERRY TREE.
Apple tree. Cherry tree.
Wood. Wood. Bark.
Phosphate of iron, 2:41
Phosphoric acid ... 4-15 9:63 3:47
Sulphuric acid, ... 0-93 4'll 0-86
Chlorine, ............ 0-27 e e is 0-40
Silica ............... 1.31 2.57 21-28
100.06% loof 100'll-F
Per-centage of ash, ... 0.28 10:37
2°. Vogel has made a very interesting determination of the re-
lative proportions of the constituents of the ash in the several
parts of the Chinese crab (Pyrus spectabilis). I have embodied
his results in the following table:–
Stem. Leaves. Fruit.
Carbonates of potash and Soda, ... 4'60 6'80 19-00
Phosphates of do. e e º e º e trace. 14° 10
Carbonate of lime, ......... . . . . . . . 82°20 72-90 37-00
Carbonate of magnesia, ............ 4.90 9.80 5'50
Phosphates of lime and magnesia, 8-80 10°50 18-60
Silica, ................................. * * * tº º º 3.70
100'5 100 97.90
It is interesting to remark how the carbonate of lime predomi-
mates in the ash of the stem and leaves, and the phosphates and
alcaline carbonates in the fruit,
§ 20. Ash of the quince, lemon, and thorn-apple seeds.
The ash of these seeds has been analysed by Souchay with the
following results:—
Quince seeds. Lemon seeds. Seeds of Datura
(Pyrus cydonia,) (Citrus medica.) stramonium.
Potash, ............... 27-09 33-89 20-22
Soda, ............ . . . . . . 3.0] 3:56 14:24
Lime, .................. 7.69 12.87 4'll
Magnesia, ............ 13:01 8-67 l 7'56
Oxide of iron, ......... l'l 9 0'24. 3-94
Phosphoric acid, ... 42'02 34-81 34-72
Sulphuric acid, ...... 2-67 3°30
Chloride of sodium, .. 257 2-31
Silica, .................. 0.75 0.35 5' 21
l60: 100: 100+
* Will and Fresenius, Annal, der Chemie und Pharm. I, p. 394.
+ Engelmann, ibid. liv. p. 343.
:: Souchay, Ammal. der Chemie und Pharm. liv. p. 349.
ASH OF THE OAK AND OTHER HARD WOODS, 397
§ 21. Of the ash of the oak, elm, lime, and beech, and of the acorn,
the beech nut, and the chesnut.
1°. The proportion of ash left by the wood of trees differs very
much, not only in different kinds of trees, but in the same kind of
tree grown in different localities, and in different parts of the same
tree. Thus, I caused a short cylinder to be cut off the upper and
lower ends of the trunk of a beech and of an ash respectively. The
wood between the pith and the bark was then cut into three
portions—an outside portion next the bark, a middle and an in-
mer portion—and each was separately burned. The per-centage
of ash was as follows:
Outside. Middle. Centre.
Beech, Top of the trunk, ...... 0.65 0°55 0-61
... Bottom, .................. 0°55 0-37 0.50
Ash, Top, ... .................. 0°50 0.57 0.58
Bottom, .................. 0°49 0°50 0-60
The differences here are small when taken absolutely, but they
are large when compared with the whole proportion of ash obtain-
ed. In the bottom of the beech the centre part contained one-
fourth more, and in the bottom of the ash one-fifth more than the
middle portion. May this not be connected with the fact, that
coloured fluids make their way less easily through the central or
heart wood of our grown trees, than through the newer wood or
alburnum ? Does the inorganic matter gradually fill up the pores
of the older wood P …”
2°. It is not known as yet how far these differences in the quantity
are accompanied by differences in the quality of the ash. Such,
however, are very likely to exist.
The most recent analyses of the ash of these woods are the fol-
lowing.
~ Linden or
Elm.f Lime tree.: Beech wood.S.
Oakwood.” Wood. Bark. Wood. Bark. Neuchatel.
Potash, ......... 8’43 21:92 2'22 35'802 16-144 15'83
Soda, ............ 5-65 13.72 10-09 6.036 5'694 2-88
Lime, ...... ..... 75°45 47-80 72-70 29'030 60-8] ] 63-33
Magnesia, ...... 4°49 7-7] 3-19 4° 147 8'035 11:29
Oxide of iron, O'57 0-88 0.62 7.975 1.237 0.79
* Deninger, Annal. der Chemie und Pharm. liv. p. 343.
t Wrightson, ibid. p. 342. : Hoffman, ibid. lvi. p.
§ Böttinger, ibid. 1. p. 408.
l
2
5
398 BEECH NUT, CHESNUT, AND ACORN.
Linden or
Elm. Lime tree. Beechwood.
Oakwood. Wood. Bark. Wood. Bark, Neuchatel.
Phosphoric acid, 3:46 3.62 l'79 4'849 4-017 3.07
Sulphuric acid, 1° 16 1.28 0-62 5°305 0.748 l'35
Chlorime, ...... 0-01 * * * * * * 0-894 1°334 0° 14
Silica,........ 0.78 3.07 8-77 5'266 2-271 1:32
100 100 100 100°204 100°29] ] 00
Per-centage of ash * g & * & © * * * tº º º 0° 143
in the dry wood,
In all these trees lime is the predominating ingredient, especi-
ally in the bark. The phosphoric acid forms a comparatively small
proportion only.
3°. The ash of the nuts o£ seeds of the beech, the oak, and the
chesnut, have also been analysed with the following results:
Beech Nut. Acorn. Chesnut.
Potash, ... .............. 22.82 64'64 Carbonate of potash, ...... 51*0
Soda, , ............... .. 9°50 tºº Phosphate of potash, ...... 28.0
Lime, .............. ...... 24°50 4'89 Chloride of potassium and
Magnesia, ............... | 1:64 5'57 sulphate of potash, 3.0
Oxide of iron, ............ 2.67 sºmmº - Phosphate of lime ......... 12-0
Phosphate of iron, ...... gºmº. 2’6] Oxide of iron, ............. , 0°25
Oxide of manganese, ... 3'll tºº Silica, ................. ... .. 0.50
Phosphoric acid,......... 20-81 15.62 Loss......................... .. 5’25
Sulphuric acid, ......... 2.20 tºmºmº
Sulphate of lime,......... *º 4-73 100;
Chloride of sodium, ... 0-87 0.98
Silica, ...... . ............ 1-88 0.96
100% 100+
In these seeds, again, the phosphoric acid forms a considerable
proportion of the inorganic matter. In the acorn and chesnut
there is also much potash. •,
§ 22. Ash of the wood of the larch and Scotch fir, and of the
seeds of the Scotch fir and pitch pine.
1°. In the pine trees, also, the proportion of ash varies. Cylin-
ders cut as before from the top and bottom of trunks of the Pinus
abies and Pinus sylvestris, gave at different distances from the bark
the following proportions of ash :—
* Souchay, Annal der Chemie und Pharm. liv. p. 349.
+ Kleinschmidt, ibid, l, p. 418. 3. De Saussure,
ASH OF THE PINE TREE, 399
Outside. Middle, Bottom.
Pinus abies. Top of the stem,... 0-55 0°34 0.27
Bottom, ... ... 0'50 0.36 0-24
Pinus sylvestris. Top, - - - ... 0°50 0°40 0°43
Bottom, ... ... 0°40 0'54 0°46
2°. In these trees the proportion of ash varies as much as in the
beech and oak—but here the proportion of ash increases from the
pith outwards.
The most recent analyses of the wood of the pines we at present
possess are the following:—
- is Common
º LI.” wºul. Pinus larix.” º, 9
Potash,............ ........ 2-79 0.93 15°24
Soda, ..................... ] 5'99 14°59 7.27 9-97
Lime, ... ............... 30°36 33-09 25'85 46'15
Magnesia,................. 1976 20:00 24°50 13°46
Protoxide of manganese, 18°17: 7-61; 13:51: *-
Oxide of iron, ..... . . -- 7-73 t- 3.26
Phosphate of iron, ...... 5' 10 2-28 6- 18 ---
Phosphoric acid, ......... * i-º-º: ºmº 4°49
Sulphuric acid,............ ºmº º - 3:03
Sulphate of lime,......... 3-3] 5*05 2.91 ---
Chlorine, ... ............... -> * tºmº 0-71
Chloride of sodium, ...... 1 48 - 2-52 0.92 *
Silica, ........ e e s a e s - - - - 3'04 5.27 3:60 8-38
100 90-97 99.98 99.95
Per-centage of ash in * I gº. .
the dry woods, 0-143
0' 19 0.322
The most striking difference between the ash of these trees and
that of the hard-woods given in the preceding section, is the large
proportion of magnesia and oxide of manganese which the pine
woods contain. Whether either of these substances is a neces-
sary constituent of these trees, or whether they are present merely
because they happened to be contained in large quantity in the soils
on which the trees grew, can only be satisfactorily determined by
future research.
3°. The ash of the seeds of the pitch pine and the Scotch fir has
been found to have the following composition :-
* Böttinger, Annal. der Chemie et Pharm. 1. pp. 408—412.
i (Tannenholz,) Levi, ibid p. 425.
# These trees grew in the neighbourhood of Giessen,_at no very great distance
from which the well-known dolomite of the mountain limestone, and considerable
manganese mines exist.
400
--
ASH OF TEIE SEED OF THE PINE.
Poleck.”
Pinus picea. Pinus sylvestris.
Potash, ............... .7 22:37
Soda, .... ............. 6-76 1-26
Lime, .................. l'54 1-86
Magnesia, ............ 16.79 15'09
Oxide of iron, ...... l'31 3-0 |
Phosphoric acid, 39.65 45'95
Chloride of sodium,... 0.57 sº e e
Silica, .................. 11-71 10°44
I 00-08 99.98
Per-centage of ash, ... 4'47 4'98
The large proportion of phosphoric acid in these seeds is con-
sistent with the fact that they form an excellent and nourishing
food for many animals, and that those of the larger-comed pines of
the Californian mountains, form almost the entire winter food of
several of the Indian tribes.
§ 23. Ash of some common land weeds.
In connection with the agricultural indications to be drawn from
the matural flora of a soil, it has been thought of consequence to
ascertain the average composition of our more abundant weeds.
It has been supposed that the prevailing weeds, when we know
the inorganic constituents they particularly require, should tell us
pretty nearly the prevailing composition of the soil without the la-
bour of analysing it. Though we ought not, I think, to anticipate
very much precise information of this latter kind from an analysis
of the ashes of these plants—for reasons which I shall afterwards
more fully explaim to you—still out of such analyses, if carefully
conducted, considerable additions to our general knowledge of the
present subject must arise, and the performance of them ought
therefore to be encouraged. -.
The two following tables comprise all the results of this kind
which have hitherto been published.
* Annal. der Chemie und Pharm. l. p. 415.
ASH OF SOME COMMON WEEDS, 401
Common Com. blue Corn- edge.
Chamomile. bottle. cockle. ciº iºni. sº
(Anthemis (Centaurea (Agrostem-
Wild Chamomile.
(Matricaria Chamomilla.)
No. 1. No. 3
& S.
O. l. arvensis.) cyanus.) magithago.) um majus.) calamus.)
Potash, 31.02 38.59 36 61 .85 28.92 S8.72 35.18
Chloride of 9.5 C 15.66
potassium, } 22.50 16.99 8,56 14.24 9.56 3.98
Cº. of } 9 & e * & & tº ge e tº e & © tº tº tº 6 3.03
SOCUlum,
Li." 23.24 19.57 . 19.17 18.57 37.02 27.33 12.27
Magnesia, 6.0] 5.70 4.39 5.47 7.77 5.92 8,24
Protoxide of gº tº e ge tº 4 dº º ſº. s & s tº tº º s & 8 1.51
mangalleSe,
Pºhate of } 2.92 2.85 5.71 2.80 2.27 2.10 2.96
Pºhoric 6.22 9.3ſ) 11.90 7.90 8.41 17.67 13.19
stºric } 6.07 5, 18 5.52 3.22 3.02 2.63 5.40
silica, 2.02 1.82 8. 14 3.95 3.03 1.65 2.56
100.3% 100, # 100. # 100.3% 100.* 100.* 100.3%
Per-centage * * \ ſº
* } as 9.69 9.66 7.32 13.20 6.85 6.90
Hemlock. Foxglove.
(Conium maculatum.) (Digitalis purpurea.)
Potash, .... ......................... 21°69 43’53
Soda, ..... .............. . . ......... 9:64 3-70
Lime, ..... ........................ 14-96 12-67
Magnesia, ........................... 8.39 6'53
Phosphate of iron, ............... 3°49 4'63
Phosphate of lime, ............... 16-77 0'44
Sulphate of lime, .................. 5-88 6'69
Chloride of sodium, ............... 16*6 1 9-03
Silica, .............................. 2.62 12-78
100.05% 100f
Per-centage of ash in dry state, 12.80 10°89
Nothing very striking suggests itself on the inspection of these
results. They may prove useful hereafter, however, when we ob-
tain other analyses of the ash of the same plants by other chemists
and from other localities.
§ 24. Of the ash of some common parasitic plants.
Some plants live or prey parasitically upon other plants. They
draw nourishment from the sap or live on the substance of larger
plants. Is there anything peculiar in the inorganic constituents
of such plants? Do they differ much in regard to these constitu-
ents from plants which seek their food in the soil?
These are interesting physiological questions. They have a
practical importance also in connection with the health of trees in
our artificial plantations and woods—the appearance of parasitic
* Rüling, Annal. de Chemie, und Pharm. lvi. p. 124.
+ Wrightson, ibid, liv. pp. 362–3.
C C
402 ASH OF PARASITIC PLANTS.
mosses and lichens often attending upon disease, being by some con-
sidered as a cause, by others only as a symptom of constitutional
weakness. -
The only parasites yet subjected to this kind of examination are
the misletoe, the ergot of rye, and some parmeliae which grow
upon the apple tree, of which an imperfect analysis has been made
by Will and Fresenius.
The following are the results of this examination:—
Parmelia grown on the
Misletoe. Ergot. bark of the apple tree.
Will and Fresenius.* Engelmann.-- Will and Fresenius.:
Potash, ............... 40.71 45.38 10.07
Soda, .................. 0.63 16.79
Lime,.................. 22,37 1.68 10.33
Magnesia, ............ 1 1,06 5.34 5.33
Oxide of iron, ...... * g is 2.34
Phosphoric acid, ... 19.09 15.44 * g e
Phosphate of iron, 2.1 l * 8 & 14.56
Sulphuric acid, ... 1.62 0.02
Chlorine, ............ 0.70 2,36
Silica, ............... 1.87 15.60
100.16 100.
Per-centage of ash, 0.36 º
There is no remarkable difference to be observed between the
ash of these plants and that of others which grow on the naked soil.
The misletoe differs from the wood of the oak on which it grows,
by containing more potash, magnesia and phosphoric acid and less
lime. The ergot of rye contains much alkaline matter and phos-
phoric acid, with 12 per cent. of silica, which it of course draws
from the sap of the ear as its husk does. The lichen of the apple
tree contains much phosphate of iron, of which the apple tree itself
also contains a sensible quantity.
§ 26. Of the ash of some common sea weeds.
The sea is continually robbing the land. Every stream carries
away saline substances which might have ministered to the growth
of plants.
Along many of our coasts the sea gives back or offers to the
husbandman an abundant marine vegetation in return.
* Annal. der Chemie und Pharm. l. p. 394. y + Ibid, liv, p. 350.
j. Ibid, l, p. 394.
ASII OF SEA-WEEDS, 403
This vegetation in many districts is largely gathered and in
great quantity applied to the soil. What saline substances does
the sea thus return to the land? Are they such as will or can
restore to the soil all that the farmer's crops carry off?
An analysis of the ash of our common sea weeds can alone answer
these questions. These analyses are of interest in connection with
other enquiries also, and therefore a considerable number of them
have been made and published by different analysts.
The following tables comprise nearly all their results.
1°. Composition of the ash of certain fuci of which only one an-
alysis has yet been published.




#
#.
;
|
i
|
:
#
#
|
#
|
|
i
17:50
:
i
16'91 18:00 23.42 3.72
- tº º 19:47| 16.06 5.06| 21:34 I2-70
8'28 - 10:23, 2.92| 2:30 8.7; 7-39
Chloride of 6'80 tº $ tº 20:56; 5'94 7.44 10-93; 11-66. 9-89
Orl (16. Of SO- * "Tº º * I tº • £ſ: - - * {- ... ºff
dium, 33.72 3 26'92] ... • * * 1.66] 13.85 ... 28.39| 20:16, 1876 16'56
Chloride of po- e e
tassium, • tº º ... 10° 10 tº t tº e - © • tº º 0.93
Iodide of sodium, 470 0:27 ... tº a tº © tº e * * * to 4 º' e se 3-62 0'54 l'33. 0-95
*...* *} | 841 495 12.80 3.96 0.76 23:23, 2:09. 3.90. 563 3:34. 9.67 7.24
2
I
j
5
15'8()
2
l
2
3
I
2
§
;
;
l
0
0
7
4
5
l
I
()
i
9
8
l
l
()
9
i
7
}
l
Lime, ............. ... 6.50
Magnesia, ......... 8' 13
!
:
:
l
8
lime,
Phosphate of iron, 0.75 0.64
Oxide of iron, ... • * * • tº º tº e Q e - -
Oxide of man- ). ... . . . ... 0.22. ... . . . ... e e º w a e I e º 'º e e &
gamese,
Sulphuric acid,..., | 10-60) 18:35 12-63. 32.63 42.86. 25.19 28.66 40-42) 13:26, 26-69) 21:06|24-76
Silica, ............... 0°58' 0°40|| 0-69| ... • * * º e e 2.83| 12:38|| 1:56, 1-20 0°43' 1-82
100* |100* |95:21; 100+ 100; 99.79||98-10+100+ 100+ 100+ 100+ 99.98
ÖG2 0.29 634 0.24
ash in weed
dried at 2120
• ?
9-78. 25.83| 13.62| 18.92 20-61 9-86] 17:10) 13:17) 20:40 16:19, 15.63|16:46
Per-centage of }
Among these sea weeds it will be seen that there exists consider-
able difference in regard to the per-centage of ash they leave
when burned. This may depend in part upon the species, but it
must depend also in some measure upon the mode of collecting
and drying the plant, upon its age, and upon the part which was
burned.
In regard to the composition of the ash we see that it contains
all the substances carried off by our usually cultivated crops, but
* Schweitzer. + Forchhammer,
† Gödechens, Annal. der Chemie und Pharm. liv. p. 352.
404 WARIATIONS IN THE ASH OF SEA-WEEDS.
that common salt, as we might expect, and sulphuric acid, are es-
pecially abundant in it.
It cannot fail to strike you as very remarkable that plants which
grow in water containing so little potash and phosphoric acid, as
that of the sea does, should yield an ash in which so large a propor-
tion of potash is occasionally present, and so constant a per-cen-
tage of phosphoric acid.
It is to be remarked that we do not know to what variations the
composition of the ash of any of the above fuci is liable—and there-
fore what dependence can be placed upon the special composition
assigned to each by these single analyses. I have inserted in the
last column a mean of the whole which may be taken as a tolerable
approximation to the proportion and composition of the inorganic
matter contained in such mixed collections of sea weed as are
usually applied to the land or are burned for kelp.
2°. The following table exhibits the results of five analyses of
the Fucus vesiculosus from different localities. These results enable
us to judge of the variations to which the ash of the same species
of sea-weed is liable.
Mouth of Mouth of
the Clyde. the Mersey. North Sea. Denmark. Greenland. Mean.
Potash,......... 15.23 * @ s 17.68 9.03 17.86 11.96
Soda, ......... ll. 16 15.] 0 5.78 7.78 21.43 12.25
Lime, ......... 8.15 16.77 4.71 21.65 3.31 10.92
Magnesia,...... 7. 16 15.19 6.89 l 0.96 7.44 9.53
Chloride of º 25.10 9.89 35.38 3.53 25.93 19.82
dium, ......
Iodide of sodium, 0.37 * c & 0.13 - - - - c. 8 0.25
Phosph. of iron
and phos- | 2.99 5.44 9.67 10.09 5.64
phate of lime,
Oxide of iron, 0.33 4.42 * * * e - ºr a tº a 0.95
Sulphuric acid, 28.16 30.94 23.7l 26.34 | 3.94 24.62
Silica, ............ 1.35 7.69 0.28 | 1.04 - © tº 4.06
100.* 100.-- 100: 100.S 100.S 100.
Per-centage of
ash, (calcu- 16.39 | 3.22 20.56 • - - 16.22 16,60
lated dry,)
* Gödechens, Annal, der Chemie und Pharm. liv. p. 352. + James, Ibid.
+ Schweitzer. S Forchhammer.
4
PROPORTION OF POTASH, &C, IN SEA-WEEDS. 405
In this table we see remarkable differences. Thus of the whole
ash, the
Potash and soda vary from 15 to 40 per cent.
Lime,........................... 3 to 21
Magnesia, ..................... 7 to 15
Common Salt, ............... 3 to 35
Phosphate of lime,............ 3 to 10
Sulphuric acid, ............... 14 to 31
Silica,........................... 1 to ll
How far such differences as these are necessary we cannot tell.
I believe they arise in part from the age of the plant, from the part
selected for burning, and from other circumstances, to which no at-
tention has yet been paid.
When the number of these ruder investigations shall have a little
further increased, the time for more refined enquiries will have
come—when the influence of circumstances in the case of all our
plants will be taken rigorously into account, in the analytical ex-
aminations both of their organic and of their inorganic constituents.
The analyses to which this more careful and scientific method
must lead, will gradually remove from among the data upon which
we shall consider ourselves justified in reasoning, a large propor-
tion of the analytical results, which, as the best we now possess,
I have embodied in the present lecture.
These results, although numerous, form in reality only the be-
ginning of our knowledge of this subject, as will appear more clearly
from the observations which are contained in the succeeding lec-
ture.
LECTURE XIII.
Inorganic constituents of plants continued. To what extent our usually cultivated crops
exhaust the soil of these substances. Effect of a three and afour course rotation. Propor-
tions of saline matter necessary to replace what is carried off by a course of crops. What
inorganic substances are absolutely necessary to the existence of a plant—what to par-
ticular tribes of plants. Can the inorganic constituents take the place of each other
in any, or in all circumstances? Known variations in the quantity and quality of
the ash of plants. Influence of circumstances in modifying these—of soil, of variety,
of the part of the plant examined, and of the period of growth. Is the inorganic
matter found in plants all essential to their growth P Effect of steeping, of germina-
tion, and of mashing on the ash of the grain of barley. Composition of the ash
of barley steep water, of cummins or barley sprouts, of malt, of malt extract and of
brewer's grains or draff. Composition of the ash of the leaves and stems of the oat
at different stages of their growth. Composition of the leaves and stems of the po-
tato at different stages of their growth. Value of our present analyses. Must the
inorganic substances exist in the soil in a peculiar state to suit each plant 3 Power
of the roots to extract food from apparently insoluble combinations. Experiments
of Wiegman and Polstorf.
IN the present lecture, I propose to bring before you a variety
of interesting considerations connected with the ash of plants,
partly of a directly practical, and partly of a more immediately
theoretical character, yet all possessed of important relations to
scientific agriculture.
§ 1. To what eatent do the crops most usually cultivated exhaust
the soil of inorganic food?
The tables I presented to you in the preceding lecture, show
generally what is carried off the land by an average crop of each
of our usually cultivated vegetables. But the actual exhausting
effect of culture depends very much upon the mode in which it is
conducted,—the kind of rotation followed, and the kind of ma-
muring. I shall at present direct your attention to the propor-
tion of the several inorganic substances which are carried off re-
spectively in a three and in a four course system of cropping.
EFFECT OF A THREE COURSE ROTATION. 407
19. The three years' course.—This course of cropping, which is
very common in many countries, assumes various forms. Wheat,
beans, fallow, is a very old course on heavy clay lands,--where the
introduction of the drain must precede other possible improve-
ments. Wheat, oats, fallow is another form of the same, not un-
common in the county of Durham, where beans have been a less
esteemed, chiefly because a more precarious crop. Where this
system is generally adopted, the land is manured on the fallow,
and occasionally a portion of the fallow instead of being naked is
planted with potatoes, or turnips, or clover.
If, as in the preceding lecture, we take the crop of wheat at
25 bushels (p. 366) and that of oats at 50 bushels (p. 371)—the
fallow being wholly naked,—then the crops will, every three years,
carry off the following quantities of the several inorganic sub-
stances from each imperial acre.
Grain and straw. Grain alone.
Potash, | * * * * * * * * * * * & e º 'º & ſº s = * * * * * * * * 108-27 18:32
Soda,...
Lime, ................................. 35-27 2.80
Magnesia, ........................... 22.99 6'82
Oxide of iron, ........................ 7'04 0.33
Oxide of manganese, ........ ...... 0.18 gº
Phosphoric acid,..................... 40°42 29'04
Phosphates of lime and magnesia, 3:19 *-*.
Sulphuric acid, ..................... 25-79 3-40
Chloride of sodium, ............... 2-79 *-m-mº,
Chlorine,.............................. 9. 13 0.08
Silica, ................................. 280-93 1-2}
536 lbs. 62 lbs.
b. Or substituting for the 50 bushels of oats, a crop of 25
bushels of beans, the land would lose every three years per im-
perial acre by the grain alone and by the entire crop respectively,
Grain alone. Grain and straw.
Potash, ................. ............ 20-75 133'40
Soda, ... ........... . . . . . . . . . . . . . . . . . 7:03 10'04
Lime, ................................. 3.19 49.27
Magnesia, ........................... 6-78 25'05
Oxide of iron, ........................ 0°44 3°34
Alumina and oxide of manganese, – 0.65
Phosphoric acid,..................... 30-22 48-08
Sulphuric acid, ..................... 0.47 12.81
Chlorine, .............................. 0-30 6.62
Silica, . . . . . . . . . . . . . . . . . . . . . . . . . '• * * * * * * * ()'82 130-74
7() 420
408 HOW TO REPLACE WILAT IS CARRIED OFF.
If the straw of these crops be returned to the land, then the
grain alone which is taken to market would carry off about 70 lbs.
of saline matter, the half of which consists of phosphoric acid, and
from one-third to one-fifth of potash and soda.
If the straw be not returned, then about 540 lbs. in the one
Case, and 420 lbs. in the other, would be lost by the land, and
must be replaced in some form or other. When the two corn
Crops are taken in succession, more than half of what is drawn
from the soil (265 lbs.) consists of silica. When wheat and beans
are taken one-third only consists of silica, another third of alkaline
matter, and one-eighth of phosphoric acid.
To replace artificially what is carried off in this rotation, a mix-
ture of Saline substances must be added to the soil every three
years in the following proportions:—
Wheat, oats, fallow. Wheat, beans, fallow.
—º-
/- ~\ Z- *
Grain and straw Grain Grain and straw Grain
carried off. only. carried off. only.
Dry pearl-ash, .................. 80 lbs. 14 lbs. 196 lbs. 30 lbs.
Common soda of the shops, 250 — 40 — 50 — 30 —
Ordinary bone dust, ......... 198 — 138 — 228 — 144 —
Epsom salts, .................. 135 — 41 — 105 — 4l —
Common salt, .................. 18 — 1 — 11 — 1 —
681 lbs. 234 lbs. 590 lbs. 246 lbs.
If the grain alone be carried off, we see from the above that the
mixture necessary to replace the saline matter of the two crops of
white corn, has nearly the same weight as that which the wheat and
bean rotation requires. The latter contains 16 lbs. more potash,
and this is the principal difference. If the straw, however, is
carried off, or if any of its saline matter is allowed to be washed
out or otherwise lost before it is returned to the land, it may be me-
cessary, when beans are grown, to restore to the land a much
larger quantity of alkaline matter than in the wheat and oat ro-
tation.
This appears from the third column, in which we see that 196
lbs. of pearl-ash are required to replace the potash removed by the
grain and straw together, a large proportion of which was contain-
ed in the bean straw. This straw, therefore, will require more
careful management than the wheat and oat straw, if we are to re-
turn in the form of manure made from it, all that it has carried
from the land.
-
EFFECT OF A Fouk YEARs' CouTSE. 4.09
2°. The four years' course.-The four course rotation may be
varied very much, according to the nature of the crops it is most
profitable to grow in the particular locality. The principle upon
which it depends, however, is that two corn crops shall not succeed
each other, but that each corn crop shall be succeeded by a green
crop. The defect in practice is that it causes the same crop to re-
turn too frequently—so that the land becomes tired, as it is called,
of some of the crops usually sown, and refuses to grow them. A
very usual four course rotation on light soils is, turnips, barley,
clover and rye grass, wheat.
If the crop of wheat be 25 bushels, of barley 40 bushels, of tur-
mips 20 tons, with 64 tons of tops, of hay 1% tons, being one ton
of rye grass and half a ton of red clover, the quantities of the se-
veral mineral substances carried off in this rotation will be as fol-
lows:—
Grain. Straw, Bulbs. Tops. Hay. Total.
Potash, ....... .................."....... 14’39 32-73 || 42-66 88-82 38°22 316'82
Soda,.… … 7:05 l'21 17-31 || 6-76 12:05 54.38
Lime, ................................. 2.24 27°62 4 6-2.4 72° 14 44'45 192-69
Magnesia,.............................. 7:60 12-14 18:16 9-58 7.09 54.57
Oxide of iron, with a little oxide
l’ll 5°96 4’3 2.67 0°58 14.67
5
of manganese and alumina,
Phosphoric acid,..................... 35'76 10-56 25.77 28-80 || 5' 12 116.0]
Sulphuric acid,........................ 0°12 13:15 46.24 38.8] 9:20 107-52
Chlorine, .............................. 0.02 3:55 12.24 49-75 4-06 69-62
Silica, ................................. l 4'71 233'08 27.03 2.67 78°23 355-72
83 340 340 310 209 1282 lbs.
To replace by art the inorganic ingredients carried off in this
rotation, a mixture of saline substances must be returned to the
soil every four years, in the following proportions:—
Dry pearl-ash, ........................... 465 lbs.
Ordinary bone dust,..................... 552 ..
Spsom salts, .............................. 326 . .
Common salt, ................. ......... l 16 . . .
Quick-lime, ................ ............ 70 ...
1520 lbs.
§ 2. What mineral substances are absolutely necessary to the ewis-
tence of plants of different kinds 2
Such are the substances carried off by our usually cultivated
4] 0 No MINERAL MATTER IN MOULD PLANTS.
crops, and such the proportions in which they must be addded to
the soil, in order to restore what has been carried off. You will
be able, by means of the tables contained in the preceding lecture,
to make similar calculations in regard to any other rotation or to
any other crop or plant you may happen to raise.
In our tables of the ash of plants, we have seen that nine or
ten different substances are always present in greater or less pro-
portion, and I have already stated to you as a fair inference from
this fact, that all these substances are essential to the healthy growth
of an entire plant.
Still there are some very interesting enquiries connected with
this branch of our subject. .
Are there no plants which are capable of growing without the
aid of these mineral substances? Are there none which can grow
well without some of them at least? Are there any of these inor-
ganic substances which always especially abound in, or characte-
rise certain plants or parts of plants, and which may therefore be
considered more necessary than others to these plants? Can any
of the mineral substances take the place of each other in the
growing plant? What functions are the-yeach intended to fulfil
which makes this substitution more or less possible or admissible P
Numerous questions such as these may arise in your minds. I
shall here, therefore, offer you a few observations in reference to
each of the points to which the above questions advert. *
1". Are there no plants which are capable of growing without the
aid of these mineral substances 2—The answer is, that there are.
It has been shown by Mulder that the mould plants which form on
the surface of solutions of pure Sugar, gum, vinegar, and other or-
ganic substances, consist of cellulose and protein compounds, with-
out any mineral matter whatever. They leave no ash when burn-
ed. This very low order of vegetable substances, therefore, can
exist without inorganic matter; but we as yet know no others to
which the same remark applies. None that are cultivated, or that
are employed by man for food or for other useful purposes, are so
constituted. Mineral matter is present in, and is necessary to
them all. But, - -
2°. Are there none of those plants which contain mineral matter
that can grow well without some of the substances which are found
] -
*
'THE ASEI OF YEAST. 4! 1
in the ash of plants 2—This is a very important and interesting
question, and one in regard to which we have already collected
some facts of considerable importance. Some of these facts relate
to our cultivated crops, but I shall first draw your attention to a
plant of a humbler kind.
a. The yeast that forms in our fermenting beer vats consists of
minute globules, which are recognised by the microscope as living -
vegetable productions,—living and multiplying under favourable
conditions, and during their growth and multiplication giving rise
to the change of sugar into alcohol, and the fermentation by which
this change is accompanied.*
The ash of this minute plant—one certainly free from the influ-
ences of the soil, and therefore incapable of being modified by its
nature, as our ordinary land plants may—has been lately analyzed
by Mitscherlicht with the following result.
- Top yeast. Bottom yeast.
Potash, ........... .................... ..... ... ..... ... 39°5 28°3
Phosphate of lime (2 CaO. PO5), ... ......... ..... 2-3 9-7
Phosphate of magnesia (2 MgO, POB)............... I 6-8 23.6
Phosphoric acid combined with the potash, ...... 41°8 39°5
100°4 101*1
Por-centage of ash in the dry yeast, ............... 7-65 7.66
In this plant, therefore, we have potash, lime, magnesia, and
phosphoric acid—four mineral ingredients only—as essential to its
existence. It is possible that there may be other more common
and more abundant plants, in regard to which future analyses may
show that the number of substances essential to their existence are
limited in a similar manner.
* One of the most satisfactory experiments in proof of the organized or vegetable
character of yeast has lately been made by Ludersdorf, (Poggendorff's Annalen, lxvii.
p. 409.) He rubbed yeast carefully in a mortar, till when seen under the microscope
all the globules had disappeared, and then mixed it with a solution of sugar. It
caused no trace of fermentation, while an equal weight of unrubbed yeast in another
similar solution of Sugar occasioned a copious evolution of gas. The fermentation
brought on by yeast is not, therefore, a purely chemical process, it is the result of the
organization of the particles of yeast. A similar experiment had shown De Saussure
that the leaves of plants cease to decompose carbonic acid when their organization is
destroyed ; and Fremy has made the same observation in regard to the skins of fruits.
While the result is purely chemical, therefore, the immediate cause in all these cases
is the surface of an organized body.
+ Journal für Praktische Chemie, xxvi. p. 231.
412 WHAT WHEAT AND WHEAT STRAW REQUIRE.
b. If we now revert to a few of the tables contained in our last
lecture, we see, in regard to
The grain of wheat, That it sometimes contains no soda, no
oxide of iron, oxide of manganese, chlorine, sulphuric acid, or si-
lica. None of these substances, therefore, are indispensable to the
perfection of the grain of wheat when freed from husk. This limits
the substances essential to the grain to potash, lime, magnesia, and
phosphorus—the same exactly as are necessary to the yeast plant.
Here, however, it is only a part of the plant—the seed of the wheat
—we are considering. If we take the whole plant, the result will
be very different. Thus, in the case of the
Straw of wheat, lime, magnesia, and the oxides of iron and
manganese are the only mineral constituents of plants which
have hitherto been found altogether absent from its ash. Thus
potash, soda, phosphorus, sulphur, chlorine, and silica appear alone
to be essential to the formation of the straw of wheat. But for
reasons which I shall presently state to you, I believe that potash
may supply the place of soda in the straw, and that either lime or
magnesia is always necessary—so that in the straw we have seven
substances which appear essential, namely,–potash, lime, magne-
sia, phosphorus, sulphur, chlorine, and silica, and as these include
all that are necessary to the grain, we may infer that the wheat
plant as a whole requires these seven substances for its healthy
growth.
An examination of the ash of the entire plant of barley or of the
oat would lead us to a similar conclusion. The same substances
exactly are essential to them all, only in these the presence of the
oxides of iron and manganese in appreciable quantity is so much
more frequent, that they assume the character of essential consti-
tuents. We know from other circumstances that these substances
must be contained in some of the food we eat, and therefore we
are prepared to concede that they must exist as essential constitu-
ents of some in our cultivated plants.
But the wood, and especially the bark of trees, and the outer
rind of many plants contain much iron, and as these are not in-
tended generally for food, we are entitled to conclude that in many
plants the oxide of iron performs some function as yet unknown
which renders it indispensable to their healthy growth.
SILICA IN THE ASH OF THE STRAW. 413
But though these substances thus appear to be all essential to
the healthy growth of an entire plant, are there not some of them
which are present in larger relative quantities in some plants than
in others, and which may therefore, in respect to quantity, be con-
sidered special or especially necessary to certain plants 2 This
question I shall consider in a separate section.
§ 3. Of the substances which occur in especial abundance in certain
plants or parts of plants.
The tables given in the preceding lecture exhibit some impor-
tant facts in reference to the substances which especially abound
both in different plants and in different parts of the same plant.
Thus,
1°. Silica is not essential to the grain of wheat, but it forms
from 40 to 80 per cent. of the ash of the straw. Though not al-
ways absent from the grain or seeds of our other corn plants or
grasses, it is mever present in large quantity in any of them, while
on the other hand it greatly abounds in their stems. Thus silica
may be said to be the characteristic mineral ingredient of the stems
of our corn plants and grasses.
2". Phosphoric acid in the ripe stems and straw of our corn
plants and grasses, though rarely altogether wanting, is seldom
present in any considerable proportion—while it forms about one-
half the weight of the ash of our different kinds of grain, when
burned without their husk. The same is more or less true of the
seeds of many other plants, as the tables I have so often referred
to abundantly show. Phosphoric acid, therefore, may be consider-
ed as the characteristic mineral ingredient of the seeds of plants.
3°. Similar differences distinguish different plants or orders of
plants. Thus the bean, the pea, the vetch, the clovers, and other
leguminous plants, contain in their stems very little silica. The
grasses, therefore, are distinguished from leguminous plants by the
large proportion of silica they require and contain.
Again the bean-stalk, pea-straw, and clover-hay, generally con-
tain much lime, while that of the grasses contains comparatively
little. They also abound more in alkaline matter than the ash of
the grasses does. Thus lime and alkaline matter may be said to
characterise the stems of the leguminous plants, while silica cha-
racterises that of our corn plants and of the true grasses.
414 RELATIVE PROPORTIONS OF THE MINERAL SUBSTANCES.
4". But our bulbous and tuberous roots have also their charac-
ters. Potash and soda are present to the amount of about 30 per
cent. in the ash of our cultivated corn seeds, and of about 40 per
cent. in the ash of the beam and the pea; but in that of the turnip
and potato they vary from 50 to 60 per cent. Thus a larger pro-
portion of alkali than is present in any of the other crops raised
for human food characterises the turnip bulb, the beet root, and
the potato tuber.
Again the ash of the tops of the potato and turnip contain much
lime—while that of white corn straw and hay contains compara-
tively little. In this respect they agree with the straw of the bean
and the pea;-thus the cultivated roots are characterised by the
large proportion of alkali they contain—while their tops differ
from corn, straw, and hay, but agree with beans, in the large pro-
portion of lime they require.
These differences in the relative proportions of the ingredients
present in their ash, by which our usually cultivated crops are se-
verally characterised and distinguished from each other, are more
fully and clearly represented in the following table:—
... Lime Magnesia. * * silica.
Wheat, ........ 33 3 12 50 0-25 l
Barley, ........ 22 3 7 39 0-10 27
Oats, ........ ... 26 6 10 44 11 3
Rye, ... . . . . . . . . . 34 5 | 0 50 l 0°4
Indian corn, ... 33 l 16 45 3 1
Rice, ............ 30 l 12 53 *== 3
Beans, ........... 44 6 8 38 l I
Peas, ............ 44 5 8 33 4 0°51
Wheat straw, ... 13 7 4 3 6 65
Barley do. ... 7 10 3 3 2 7]
Oat do. ... 29 8 4 3 3 48
Rye do. ... 18 9 2 4 l 65
Maize, do. ... 35 8 7 17 * * * 28
Rice, do. ... 14 & vº 5 l 4 74
Bean do. ... 55 20 7 7 l 7
Pea do. ... 5 55 7 5 7 20
Red clover, ... 36 33 8 8 3 7
Potatoes, ...... 57 2 5 13 14 4
Turnips,......... 47 14 5 8 14 8
Beets,............ 56 .- 9 5 8 2 | ()
Cabbage,......... 32 2] 6 ] 2 22 0-74
Potato tops, ..., 44 17 7 8 7
Turnip do. ... 34 23 3 {) 13 l
CAN POTASH AND SODA REPLACE EACH OTII.E.R. 4, 15
§ 4. Can any of these mineral ingredients take the place of each
other without injury to the growing plant 2
There is reason to believe, from the results of the analyses I
have already presented to you, that some of the inorganic consti-
tuents of plants may take the place of each other without affecting
their healthy growth. Thus,
19. Potash and soda.-The composition of the ash of the seve-
ral varieties of the grain of wheat, as given in p. 365, gives us the
following proportions of potash and soda respectively :—
Potash,............ 21.87 33-84 6:43 24-17 30-12 25'90
Soda, ............ 15.75 * & © 27-79 10°34 * e º 0'44
If these five analyses are all equally to be depended upon, they
show that the grain of wheat may either contain no soda at all, or
that it may contain a large proportion of soda and comparatively
little potash. In other words, the soda may take the place of the
potash, if not altogether, at least to a very large extent. What is
true of the grain, is probably true also of the entire wheat plant.
We do not know all the functions which these alkalies perform
in the living vegetable. It is believed that one of their functions
is to render soluble, and thus to carry into the corn plants and
grasses the silica which exists so largely in their stems. This pur-
pose may be served equally either by potash or soda, and so far,
therefore, it is reasonable to believe, independent of analysis, that
they may take the place of each other in the living plant.
But that this is by no means the only function of these alkalies
is shown by the fact, that the bean, the potato, and the turnip, in
which little silica is present, contain much more alkaline matter
than the corn plants and grasses. In these plants their main func-
tion must be something very different. It is no doubt connected
with the absorption of food from the soil, and with the changes
which the organic substances undergo in the circulation of the
plant. -
Still so far as we yet know, soda is equally fitted to perform
these functions as potash is, and therefore might take its place for
these purposes also. This is so far confirmed by the analyses of the
ash of the bean, which shew that the alkaline matter present in it
may either be all potash, or half potash and half soda.
This is a very important point, and one well worthy of experi-
416 CAN LIME REPLACE POTASH.
mental investigation. For if soda can, in reference to the living
plant, perform all the functions usually discharged by potash with-
out injury to its health or usual mode of growth, the greater abun-
dance and cheapness of this substance will render the manufacture
of artificial saline manures much more easy, and will place them
within the more easy reach of the practical farmer.
2°. Potash or soda and lime.—Can lime take the place of potash
or soda in the living plant? We have no series of analyses of en-
tire plants which are fitted to throw much sure light upon this point.
In regard, indeed, to certain parts of the plant it appears that the
proportion of lime they contain may vary very much, and that as
the lime increases the alkaline matter diminishes. Thus, in—
a. The tobacco leaf-The mean relative proportions of alkaline
matter and of lime found in a series of tobacco leaves grown in two
different localities was as follows:–
I. II.
Potash and soda, ... 27:02...... 12.2]
Lime, .................. 27.87,..... 45'90
Each of these results is the mean of four analyses, and they ap-
pear to show satisfactorily that in the leaf of this plant the lime may
increase while the potash diminishes. In other words the lime may
take the place of a part at least of the potash. So
b. The twigs of the vine, from two localities, gave an ash which
contained of alkaline matter and of lime respectively—
I, II.
Alkalies, 45.82......27-98
Lime, ... 29.75...... 40.75
from which it would appear as if lime in this plant might also take
the place of potash-and soda.
Such facts as these seem to render it probable that lime may
supply the place of alkaline matter to a certain extent—may per-
form some of its functions in some plants. We know too little,
however, of the changes which take place in the relative proportions
of the inorganic substances in the same part of a plant at different
periods of its growth, or of how much of that which is found in the
leaf or twig is really essential to its healthy existence, to be able
to estimate the amount of reliance which ought to be placed upon
the conclusions to which the above facts seem to lead.
LIME AND MAGNESIA REPLACE EACII O'THER. 417
It is not likely that lime should serve the purpose of the alkalies
in rendering silica soluble, and thus making its entrance into the
roots of plants more easy—though even here our knowledge is by
no means certain. As lime is so very abundant it would be both
interesting and important to make out by experiment to what ex-
tent it may perform the functions and supply the place of alkaline
matter in our cultivated crops. -
3°. Lime and magnesia.-Lime and magnesia in combination
with phosphoric acid exist in all plants. They resemble each other
very much, and some facts are known which seem to shew that they
may take the place of each other. In all our published analyses
of wheat, oats and barley, the proportion of magnesia greatly pre-
dominates in the grain, while that of lime is larger in the straw.
This is not in favour of the view that they are capable of taking
the place of each other in the several parts of healthy plants.
On the other hand, in the tobacco leaves from the Bannat, Will
and Fresenius found the potash much less than in other varieties,
while the magnesia was much greater—as if magnesia as well as
lime could take the place of potash. The same was found by
Hruschauer in the stem of Indian corn. Of the inorganic matter
present in the mature leaf and stem, however, we do not really
know how much is accidentally present, and how much is essential
to its healthy existence. We must therefore defer our judgment
in regard to this point.
The most apparently decisive experiments on this relation of
lime and magnesia are those upon the composition of linseed given
in the preceding lecture. German linseed, of which the ash was
analysed by Leuchtweiss, and specimens of Riga and Dutch seed
examined in my laboratory, by my assistant Mr Cameron, con-
tained respectively of lime and magnesia in their ash—
German. Riga. Dutch.
Lime, ......... 25-27 8’46 8-12
Magnesia,...... 0.22 14'83. 14.52
These analyses, if they are to be depended upon, shew that mag-
nesia may either be almost entirely wanting in these seeds, or that
it may be present in large proportion, and that when magnesia is
scarce in them lime is abundant. In other words, that these two
earthy bases may to a certain extent replace each other.
- D d
4.18 INFLUENCE OF CIRCUMSTANCES.
4°. Magnesia and owide of manganese.—The latter of these two
substances is occasionally present and occasionally absent from the
ash of plants. Can they take the place of each other? This is a
point which our present analyses do not decide.
5°. Sulphuric and phosphoric acids.--Some relation seems to ex-
ist between the proportions of the sulphuric and phosphoric acids
present in the Sap of plants at certain stages of their growth. We
do not as yet know what that relation is. The general properties
of these acids render it probable that they may be capable of
inducing similar chemical changes in the sap of the plant, but
it does not appear likely that sulphur can to any large extent take
the place of phosphorus in the several parts of the perfect plant.
We wait, however, for further investigations.
§ 5. Influence of circumstances in modifying the relative propor-
tions of the inorganic constituents of plants.
Whether it be or be not the case that the different substances
to which I have above adverted, may take the place of each other
without affecting the health of the plant, it is certain that so far
as our present analyses go, the relative proportions of the several
inorganic constituents of plants are susceptible of very considerable
variations. Thus,
1°. The soil appears to have much influence in inducing such va-
riations. We have seen that the tobacco leaf and the twigs of the
vine were found to contain more lime when grown upon some soils,
than when grown upon others. Berthier found a similar resultin
the case of pine trees grown upon different soils, while Böttinger
found in the Scotch fir that the proportion of manganese was
greatly increased in a soil in which manganese was supposed to
abound. (See above, p. 399.)
In regard to our usually cultivated crops, we have already seen
that similar differences present themselves, and we are as yet un-
aware of the limits within which these differences are confined.
2°. The manure also affects the composition of the ash. Thus
plants manured with guano have been found to yield an ash differ-
ing much in composition from that of other plants of the same spe-
cies grown on the same soil, and no doubt other manures act in a
similar manner.
3°. The variety in the case of our grain and root crops affects
ASH OF DIFFERENT PARTS OF THE STRAW. All 9
the quality of the ash. On the same soil two varieties of turnips
or oats will be found to contain the several inorganic constituents
in unlike proportions—and the same is probably true to a less ex-
tent of each individual plant. The former fact is seen in the ama-
lyses I have laid before you of the ash of different varieties of wheat
and oats, but it requires many further analyses to enable us to
make out the exact kind and amount of difference to which variety
alone is capable of giving rise.
4°. The part of the plant taken affects much the composition of
the ash obtained. By this I mean not merely that the ash of the
grain differs from that of the straw, or that of both from the ash of
the leaf, but that one part of the leaf or straw will yield a very
different ash from another part of the same leaf or straw.
I have already shown you that the proportion of ash left by the
top of the straw differs—in the wheat plant is often much greater
—than that left by the bottom. So, while the top of a dry oat leaf
gave 16-2, the bottom part gave only 13.7 per cent. of ash.
But the ash left by the several parts in this way is also different
in composition. The following table exhibits this fact in a very
striking light. It shows the composition of the ash of two different
samples of the straw of the Hopeton oat grown on different soils,
and how this ash differs according as it is obtained from the top,
the middle, or the bottom part of the straw.
Straw, No. 1. Straw, No. 2.
Erom sound land. From mossy land.
Top. Middle. Bottom. Top. Middle. Bottom.
Salts soluble in water, chiefly
* * * * *" 41.96 55.92 77.46 71.70 84.03 90.26
sulphates and chlorides, \
Phosphates of lime, magnesia
hosp a es of Ilme, magnesia, 2.94 3:03 0-78 0.77 1°51 2-2}
and iron,
Lime and magnesia, ............ | 1:29 9-70 9° 16 14:34 8-73 2’65
Silica, 43.75 32.05 12.55 13:18 5-72 4'86
.., , ... • s e a s tº * * * * * : * * * * * * * * * * * * * *
gº-º-º-º-º-mºmº
*4
99.94 l 00 99.95 90'99 99'99 99'98
In the first of these straws it will be seen generally that the pro-
portion of alkaline salts was less, and of silica much greater than
in the second. This is to be regarded as the general effect of the
soils on which they grew, and is in conformity with what I had
previously established—that oats grown on mossy land contain less
silica in their straws than such as are grown upon sound land.
But a fact equally striking is that a similar difference prevails
420 1N ORGANIC MATTElt ESSENTIAL TO THE PLANT.
between the top, middle, and bottom of the straw from each loca-
lity. In the top straw the silica and lime are greater, in the bot-
tom straw the alkaline matter predominates. This in fact amounts
almost to a general rule, and when this difference is in excess it is
the cause of that weakness in the bottom part of the straw, which
causes our corn crops to be laid, when the ears are heavy and the
rains or winds beat upon them.
The extreme differences in the above table are very great. The
soluble salts vary from 90 to 42 per cent., and the silica from 5 to
44, and the lime and magnesia from 2% to 14% per cent. How
different the demand we should suppose a crop to make upon the
soil, were we to assume any one of these results as representing
the usual composition of the entire ash of oat straw. And yet how
are we at present to make a proper allowance for such variations
as the above table exhibits?
5°. The period of its growth at which a plant has arrived mate-
rially alters the quality, as well as the quantity, of the inorganic
matter contained in any of its parts. This applies to the seed both
before and after sprouting, and to the young corn or other plant
through all the stages of its growth.
The facts I have to bring before you in reference to this point
are contained in the five following sections.
§ 6. Is the inorganic matter all essential to, or a necessary part
of the substance of the plant 2
There are still further difficulties connected with the quantity
and relative proportions of its several imorganic constituents which
are necessary to a plant. How much of what is actually found in
a plant floats in its liquid sap—how much is attached to its solid
substance as an actual part of its composition In reference to
this point no researches have hitherto been published, and yet it is
one of great practical and theoretical importance. One or two
enquiries on the subject have been made in my laboratory of which
the following are the results. -
a. The potato.—When the tuber of the potato is grated, and
the fibre is well washed on a sieve, the starch and all the substances
soluble in water are more or less completely separated. This fibre
when dried and burned leaves about 14 per cent. of ash, of which
ASH OF THE POTATO FIBR.E. 421
the composition, compared with that of the ash of the entire tuber
(p. 384), was found by my pupil, Mr Filgate, to be as follows:–
Whole tuber. Fibre.
Potash and soda, with a 60-88 3-72
little common salt,
Lime, ................ .......... 2:07 50’ 8.4
Magnesia, .................. .. 5-28 } 0-2 l
Oxide of iron, .............. ... 0.52 3.89
Phosphoric acid,... ........... 12:57 19'66
Sulphuric acid, ..... ... . . 13.65 5-74
Silica, ............ . . . . . . tº y & tº 4-23 5'54
99-20 99-53
Per-centage of ash, ........... 3'92 1° 40
These analyses show,
1". That the fibre leaves only one-third of the quantity of ash
which is left by the whole potato.
2°. That this ash consists chiefly of lime in the state of carbon-
ate and of phosphate.
It appears, therefore, that the alcaline matter of the potato ex-
ists chiefly in the sap, while the phosphate of lime is principally
attached in an insoluble state to the fibre. The lime which is found
in the ash in the state of carbonate probably exists in the potato
in the state of oxalate of lime, crystals of which have been observed
in the potato by the aid of the microscope. Of this crystallised
oxalate it is impossible as yet to say how much is essential to the
healthy composition of the fibre, and therefore how much is really
required to promote the healthy growth of the entire potato.
b. The sugar came again contains much of its saline matter in its
sap. When the whole plant is burned an ash is obtained, of which
the composition has already been given (p. 393). But if, as is
done in the West Indies, the juice of the came is pressed out in a
mill before it is burned, an ash is obtained of which the composi-
tion is very different. Two varieties of this latter ash from Tobago
and Jamaica respectively have been analysed in my laboratory,
and their composition compared with that of the unpressed cane
was found to be as follows:—
Entire cane. Fxpressed cane.
Tobago. Jamaica.
Potash,......... ... ........ 18 l8 l'A9 2.23
Chloride of potassium, .. 5°3] * * * - - -
Soda,........................ 0°45 2:30 2:46
Chloride of sodium,...... 7:34
422 ASH OF THE SUGAR CANE.
Entire came. Expressed cane.
Tobago. Jamaica.
Lime, ........... * * * * * * * * * 7:44 11:19 11.9 |
Magnesia,.......... ....... 7:30 4-76 7-40
Oxide of iron, ......... .. e sº is 5'57 l'55
Phosphoric acid, ......... 7:01 9°40 5-90
Sulphuric acid, ........ • 6-76 2.35 l'56
Chlorine, .................. * = & }*46 * O'08
Silica, .......... .......... 40°2] 61°55 66-22
100 100° 16 99°3]
This table shows how large a proportion of the alcaline matter
exists in a state of solution in the sap, and is therefore not essen-
tial to the composition of the solid part of the plant. This soluble
portion performs important functions in regard to the growth of
the plant, but it must vary in nature and amount with many cir-
cumstances, and the composition of the ash of the entire plant
must vary materially along with it. We do not know as yet how
much, either of the soluble salts of the sap or of the insoluble mat-
ter, attached to the wood is really essential to the growth or to the
luxuriance of the plant,
§ 7. Influence of steeping in water on the quantity and quality of
the inorganic matter in barley. Composition of the ash of bar-
ley steep-water.
The chemical history of our cultivated grains and roots—the
changes which take place in the quality and state of combination
of their inorganic constituents, especially during the several stages
of their growth—these are subjects of inquiry which, in common
with many others of great interest in reference to practical agri-
culture, have as yet never been fairly taken up. We are, indeed,
only at the threshold of that knowledge of the inorganic consti-
tuents of plants, their functions, uses, and possible variations in
quantity and quality without injury to the plant—which will here-
after aid so much in establishing a profitable agriculture on a truly
Scientific basis.
We have already seen that during the germination of seeds—as
in the malting of barley—a very important change takes place in
the organic portion of their substance. The protein compounds
become soluble, are changed in part at least into diastase, and
through the agency of this diastase again the starch is transformed
STEEPING OF BARLEY. 423
into soluble dextrine, by which the young plant is capable of be-
ing fed.
But this change in the organic is accompanied by striking
changes also in the inorganic part of the seed. The state of com-
bination in which the mineral constituents exist, undergoes impor-
tant alterations—what was previously insoluble assumes a soluble
form, and is transferred through the flowing sap to the several
parts of the sprouting germ and roots where its presence is espe-
cially demanded.
It is an interesting question in reference to the inorganic matter
in the seed, whether the known variations in the proportion con-
tained by the seed, involves also a corresponding variation in its
healthy condition or vegetative power. How much of it is essen-
tial to the seed—how much may be taken from it and of what
kind, without impairing its healthy growth? Or how much and
of what kind of matter may be added to it so as to render its
growth more sure, more rapid, or more vigorous? This question
is connected not merely with pure physiology, but with practical
agriculture also-as the propriety and the effect and the mode of
steeping seeds previous to sowing, will all be illustrated by any
clear answer we may hereafter be able to give to it.
A partial light is thrown upon this question by what is observed
during the steeping of barley preparatory to its being converted
into malt. In this process, the barley is put into large tubs and
is covered over with water, in which it is allowed to soak for 24
hours. The water, which by this time has become coloured, some-
times as dark as porter, is drawn off, and fresh water is added.
This is repeated once or twice until the grain is considered to have
sufficiently swollen.
The first steep water varies in colour with the kind of barley,
and with other circumstances. In some cases the barley is dried
previous to steeping, for the purpose of securing a more uniform
sprouting of the grain. This drying may probably render some
of the starch soluble, or give a darker colour to parts of the grain,
and thus affect the colour and modify the proportion of organic
matter taken up by the water in which it is steeped.
This water extracts from the grain a portion of its saline matter.
How much is taken up—what proportion of the whole—I have
424 ASH OF BARLEY STEEP ExTRACT.
hitherto had no means of ascertaining. A sample of the first
steep water, from a maltster in Edinburgh was examined in my
laboratory, and left 414 grains of dry matter from an imperial
gallon—of which 247 grains, or about 60 per cent, consisted of
Saline or inorganic substances.
This saline matter extracted from the seed by steeping in cold
Water consisted of
Fromberg.
Alkalies and alkaline sulphates and chlorides, 80.42
Phosphoric acid in the state of alkaline,
Phosphates,................................. 3:45
Phosphates of lime and magnesia,....... ...... 9°39
Carbonate of lime, ..... ... ..... ............... * * * * 5-82
Poss.............................. .............. ...... 0.92
- 100
Per-centage of ash in the dr
§ * ! .................. 59-76
barley steep extract, .....
The following table shows the composition of the inorganic
matter of another steep water according to an analysis of Dr R.
D. Thomson.
Thomson.
Potash,..................... 38-21
Soda, ..................... 30°34
Lime, ..................... 5:08
Magnesia, ......... ..... 5*46
Oxide of iron, ............ 0°93
Phosphoric acid, ......... 7.99
Sulphuric acid, ...... .. 6°44
Chlorine, .................. 2.57
Silica, ..................... 2.98
100%
The two results differ considerably, as was to be expected in-
deed, from the examination of substances obtained in different
places, and from samples of grain probably very different from
each other.
Both, however, show that a very considerable proportion of al-
kaline matter—potash and soda salts—and of phosphoric acid are
extracted by the water, and not only is the readily soluble phos-
phate of potash extracted, but the sparingly soluble phosphate of
lime and magnesia also, and even a portion of the silica.
* Report to Government on the feeding of Cattle with Malt, p. 87.
GERMINATION OF BARLEYe 425
All these are important substances—supposed to be essential to
the constitution of the grain—and yet it sprouts well in the hands
of the maltster after they have been removed by the process of
steeping. Are they really then essential to the future growth of
the plant 2
What takes place in the steep water, may also take place in a
moist soil, and the rains may wash away what the barley parts
with, from the open soils in which it delights to grow. The ques-
tion thus again recurs—is all the Saline matter which a seed con-
tains really essential to its healthy growth in the soil? Or does
mature cause the seed while growing to take up more than is ne-
cessary, in order that provision may be made for any accidental
loss? Or does what is given to the water that moistens it merely
lodge for a short while in the soil, that the roots may have it to
take up as the young shoots extend ? And would or does the ad-
dition of more of the same kind of matter by the ordinary steeping:
of grain in saline solutions previous to sowing, enable it to deposit
more in the soil for this brief time, that the growing plant may be
better nourished as it advances in size? These are questions not only
interesting in themselves, but intimately connected with all those
useful practical applications of which our knowledge of the ash of
plants is susceptible.
§ 8. Influence of germination on the inorganic matter in barley—
the ash of barley sprouts and of malt.
1°. Barley sprouts.--When barley begins to sprout, it throws its
roots immediately outwards from the one extremity, while the young
germ (acrospire) proceeds beneath the husk towards the upper ex-
tremity of the grain. The maltster arrests the growth before the
young germ escapes from the husk, and when he dries his malt,
the young roots fall off in considerable quantity. They are known
by the name of barley sprouts, malt dust, or cummins, and are
employed both as a manure and in the feeding of cattle.
An examination of the ash of these rootlets throws a very inte-
resting light on the changes which the inorganic matter undergoes,
and the functions it is destined to perform in the sprouting seed.
When dry, they leave on burning 7.25 per cent. of ash, and
this ash consists, according to analyses made in my laboratory, of
426 ASH OF BARLEY SPROUTS.
Lime, ....................... - * g is a sº tº e º s a e # 8 º' s e s is a tº e º a tº 3.09
Magnesia, .......................... ... . . . . . . . . 5'46
Oxide of iron, .................... ... . . . . . . . . . . 1.09
Phosphoric acid, … … … 24'87
Sulphuric acid, .................................... 4'84
Chlorine, .......................................... 7.95
Silica soluble in water, .......................... ] '80
Insoluble silica, ........... ....................... 13.96
99.84
It is, therefore, very rich in alkaline matter, in phosphoric acid,
and in silica. Hence we see that when the young rootis forming,
the sap conveys to it a large proportion of the phosphoric acid of
the grain, and what is more unexpected, a very considerable quan-
tity of silica. Whence is this silica obtained It does not exist
in the grain when freed from husk. It could not be furnished to
the root by the naked grain. It must, therefore, be derived from
the husk, which contains a large proportion of silica.
This supply of silica to the young roots of the barley plant from
the seed appears to be indispensable to its existence, and it is con-
mected with a very beautiful relation between the husk and the
grain in the barley seed, which does not obtain in any other of the
grains usually cultivated in northern Europe.
The husk of the oat can easily be detached from the grain. It
separates naturally, indeed, when the grain softems and swells in
the soil. When so separated before sowing, the naked oat germi-
mates and grows as luxuriantly as when the grain and husk are
sown together. Not so with the grain of barley. The husk of this
grain clings to it, and forms in fact part of its substance. When the
grain swells and softems, the husk opens and separates from the
grain at its upper part, but remains attached at the lower part till
the young plant is far advanced, and the roots it has thrown out
make it independent of the seed,
The silica, as it exists in the husk, is in combination with com-
paratively little potash or soda, and is insoluble in water. The
alkali of the seed, therefore, as one of its functions, makes its way
into the apparently dry and dead husk, and dissolves out its silica
for the nourishment of the young root, and the husk of this pecu-
liar seed retains its attachment to the grain, that this special pur-
- l
ASH OF BARLEY. 427
pose may be effected. This peculiarity in barley is no doubt con-
nected with other interesting properties of this grain, which, when
fully understood, will throw new light upon the most profitable and
most economical cultivation of it.
2°. The Malt.—The steeping and sprouting of the barley hav-
ing removed from it the inorganic matter contained in the steep
water and in the rootlets, the composition of that which remains
in the malted seed ought to differ in some sensible degree from
that of the original barley. We have as yet, however, no compa-
rative analyses sufficiently refined to show how far this is really the
C&SC. -
According to Dr R. D. Thomson, barley loses one-sixth of its
inorganic matter in the process of malting; and when malted, the
ash it leaves has by his analysis the following composition :
Malt. Barley.
Potash, ........................... 14'54 16:00
Soda, .............................. 6-08 8'86
Lime, .............................. 3.89 3:23
Nagnesia, ........................ 9.82 4'30
Oxide of iron,..................... 1°59 0-83
Phosphoric acid,.................. 35' 34 36-80
Sulphuric acid, .................. - 0° 16
Chlorine, ........................... trace. 0° 15
Silica, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28-74 29-67
100% 100%
Per-centage of ash,.. ............ 2-52 3:0.5
I have inserted by way of comparison his analysis of the ash of
barley already given (p. 367).
When we consider that the alkaline matters—the potash and
soda—are the substances extracted in the largest quantity from
the barley during the steeping, as shown by the preceding analysis;
and that the young rootlets also carry off these substances in larger
relative proportion than they exist in the grain, we should expect
to find the proportion of the alkalies in the malt considerably less
than in the raw barley, if it really lose one-sixth of its inorganic
matter during the malting process.
But such is not the case in the analyses of Dr Thomson. The
alkalies appear to have increased while the magnesia is doubled in
quantity, and the silica is increased only by one per cent. These
* Thomson, Report to Government on feeding Cattle with Malt.
4,28 ASH OF A LE EXTRACT.
comparative analyses, therefore, throw no light upon what really
takes place, in reference to the relative proportions of the inorganic
ingredients of barley during the process of malting. The reason
probably is, that the malt of which the ash was analysed may have
been prepared from one sample of barley, while the barley ash
analysed was obtained from another sample.
§ 9. Of the inorganic substances dissolved out of the malt in the
mash tub—the ash of beer extract and of brewers’ draff.
When malt is introduced into the mash tub and there digest-
ed in warm water, the starch of the grain is dissolved out by the
agency of the diastase produced during the germination. But there
is dissolved out at the same time a considerable though as yet unde-
termined proportion of the inorganic matter. The nature and re-
lative proportions of the several substances thus extracted, and of
those which remain attached to the husk, are seen in the following
analyses made in my laboratory, of the ash left by strong ale when
evaporated to dryness and burned, and by the draft or refuse grains
of the brewer.
1°. The ash of ale extract.—A gallon of strong (Edinburgh) ale
gave 7+ ounces of dry extract, which when burned left 5:43 per
cent. of ash—or 170 grains from the imperial gallon. This ash
consisted of— -
Alkaline salts, ........... ........ 50-57
Sulphate of lime,... ... ......... 12-83
Phosphates chiefly of magnesia, 31:32
Silica, ...... ... . . . . . ...... .. 5°28
| 00
We thus see that the potash and soda (alkaline) salts are still
extracted in largest quantity by the water. A considerable pro-
portion of phosphate of magnesia is also dissolved along with com-
paratively little silica. The sulphate of lime found in the ash was
probably derived from the water used in making the ale.
Mitscherlich has published an analysis of the dried extract of a
variety of German beer of which the following is a copy :
Potash, ................................‘.... 40’08
Soda (as common salt,) ............... 0.50
Phosphate of lime (2 CaO. P.O.)...... 2.60
Phosphate of magnesia (2 MgO. P.O.) 20:00
ASH OF MALT DRAFF. 429
Phosphoric acid in combination
with the potash, ............... 20.00
Silica, ......................... . . . . . . . . . . . 16*60
99.78%
*-* *-
Per-centage of ash in the dry extract, 0°307
In this ash also the alkaline salts greatly predominate, though,
as in the Scotch ale, a considerable proportion of phosphate of mag-
nesia was also held in solution.
29. Ash of malt draff—The draft of exhausted brewer's malt,
when dried, left 4.93 per cent. of ash, and this ash consisted of,
Alkaline salts, (chlorides with a small quantity of - 7. 60
sulphates) and alkali,.................................
Phosphoric acid in combination with the alkali, ....... .e. e. e. e. e. . 2' 11
Lime, .................. - ... ..................... ........ 13:00 -
Magnesia, ................................................. 8:21
Oxide of iron, ............................................. 1.13 48°00
Phosphoric acid in combination with the lime, &c. 25-66
Silica, ............ ....................... ... sº - * * * * * * * * * * * * * * g e s e e º e - e. e. e. e. 41'51
99.22
We see, therefore, that the draft has lost nearly all the soluble
alkaline salts, but that it retains a large proportion of the phos-
phates, of the phosphate of lime, and of the silica.
Two interesting conclusions, therefore, present themselves—
1°. That these substances, to the extent in which they are found
in the draft, are situated upon or in the neighbourhood of, or actu-
ally in the substance of the husk.
29. That they are to this extent insoluble, or with difficulty so-
luble in water even when aided by diastase. In the growing plant,
therefore, which they are destined to feed, they must be rendered
soluble by some of those new affinities or agencies which are called
into operation by the principle of life as the young shoot advances
In age.
§ 10. Effect of the growth of a plant towards maturity on the
quantity and quality of its inorganic constituents.
We have seen what mineral matter the young root extracts
from the germinating barley; let us now examine the young shoot
during the several stages of its progress towards maturity.
* Mitscherlich, Journal für Praktische Chemie, xxvi. p. 231.
430 DIFFERENCE BETWEEN YOUNG AND (). LD PLANTS,
In regard to the quantity and quality of the ash left by plants
at different periods of their growth, some experiments of an inte-
resting kind were made by De Saussure. Thus, he observed,
1°. That entire plants of the same wheat, which, a month before
flowering, left 7.9 per cent, of ash, left when in flower 5.4 per
cent, and when fully ripe only 3.3 per cent. The same general
differences he found to prevail in many other plants, so that it
seemed to be warranted as a general conclusion from his experi-
ments that the per-centage of ash left by an entire plant—all its
parts burned together—is less in the ripe, or full grown, or autumn
state, than in the young or spring state of the plant (p. 129).
2°. But in single parts he found the contrary to prevail, so that
generally, the leaves of broad-leaved trees at least, in the autumn
state, give a larger per-centage of ash than in their spring state.
In the wood of trees Grabner found that the proportion of inor-
ganic matter varied with the season of the year.
3°. The quality of the ash De Saussure found also to vary. Thus
in such as contain silica as an essential constituent—in the straws
of our herbs, grasses, and corn plants—the proportion of silica
contained in the ash increased as the plant approached to maturity
(p. 130).
This was a very interesting observation, and several isolated
facts observed by other experimenters had proved that during a
plant's growth some others also of its inorganic constituents vary
in the proportion which they bear to the entire weight of the mi-
neral matter contained in the plant. Thus,
a. Common saltwort (Salsola sali), which grows maturally near
the sea, contains much soda. But Cadet observed that if it be
transplanted inland and its seeds sown there, the young plants
which come up contain much potash and scarcely a trace of soda.
This appeared to show that potash may take the place of soda in
plants to which the latter seems a natural or especial kind of food,
and that plants grown far from the sea may, for that reason, con-
tain less soda than such as are within its reach.
0. Still this was not a perfectly safe conclusion, since young
plants of the Salsola clavifolia in their natural habitat have yielded
much potash and no soda, while the old plants contained much
soda. It may have been so also with the Salsola sali.
EFFECT OF GROWTH ON THE ASH. 431
c. As De Saussure had observed in the wheat plant and in the
leaves of trees, so Mollerat found that in the potato the proportion
of potash decreased as the plant approached to maturity.
These few facts and results comprised nearly all the information
we possessed, until very recently, in regard to the effect of growth
in modifying the quantity or quality of the inorganic substances
present in the different parts of plants. Sprengel, who formerly
devoted so much of his time to the analysis of the ashes of plants,
seems never to have made the variations in the ash which attend
upon the different periods of growth, a matter of distinct consi-
deration; and it has not since been taken up by any other chemist.
This is an inquiry which can only be prosecuted at the season
of the year when the plants are growing. It must be begun when
the plants are gathered young, and must be prosecuted assiduously
as they increase in age. -
During the course of last summer (1845) I caused a series of
such analyses of the young oat and potato to be made in my labo-
ratory; others are now in progress during the present summer, the
results of which I shall be unable to embody in this lecture.
I shall introduce, however, some of those obtained during the past
season, which, though by no means so complete as I hope in after
years to make them, are yet by no means void of interest or prac-
tical importance.
§ 11. Composition of the ash of the leaves and straw of the oat at
successive periods of its growth.
The following table exhibits the quantity and quality of the ash
of the young oat plant gathered in seven successive weeks after it
had attained a sufficient height above the ground to admit of its
being collected for experiment. The straw was by no means ripe
in July, when the last specimen analysed was gathered, but other
occupations prevented the investigation from being carried further
at the time. The analyses were made at my request, chiefly by
my assistant, Mr Fromberg.
432 ASII QF O AT LEAVES OF DIFFERENT AGES.
1°. Composition of the ash of oat leaves at different stages of their
growth.
4th June. 11th June 18th June 25th June, 2d July. 9th July. 16th July.
Potash and A v. &Y tº
| 24.60 23.51 26.21 28.10 18.78 16.09 18.35
Soda, ...
Chloride of
Sodium, | 16.34 13.54 11.30 7.56 7.92 4.09 0.30
Lime, ......... 8.44 7.24 7.33 6.74 6.91 5.93 5.13
Magnesia, ... 5.33 3.11 3.47 3.06 2.39 2.35 1.63
Oxide of iron, 0.6l 0.52 0.72 0.99 0.10 0.34 0.55
Sulphuric acid 11.74 12.85 10.59 7.88 9.50 6.45 13.05
* | 16.16 10.57 10.12 8.76 6.92 6.44 2.91
Silica, so- -
luble in 6.16 18.06 18.90 27.04 34.46 11.25 8.95
Water, ...
Insoluble
Q *7 (\ 0 -
silica, | 1042 10.48 11.4 l 9.46 13 16 4.7.03 49.27
99.80 99.88 100.05 99.59 100.14 99.97 100.14
Per-centage
of ash (in § 10.83 10.79 9.07 10.95 11.35 12.20 12.61
dry state)
The phosphoric acid was combined as follows:—
a. with alkali, 8 03 4.72 5.03 2.92 1.03 0.50
b. lime, mag-
8.13
nesia, and 5.85 5.09 5.84 5.89 5.94 2.91
Ox. of iron
In this table three things are strikingly visible:–
a. The decrease in the alcaline salts;–the proportion of potash
and soda diminishing from 25 to 18 per cent. , and of common
salt from 16 per cent. to almost nothing.
b. The diminution also of the proportion of phosphoric acid as
the leaf advanced in age. The proportion of phosphoric acid in
combination with alcali—the alcaline phosphates—disappearing
entirely, while the earthy phosphates also diminished from 8 to 3
per cent. -
c. The proportion of silica, on the contrary, continued gradu-
ally to increase from 16 to nearly 60 per cent. of the whole ash.
These are very interesting results, and they show very striking-
ly the importance of the alkalies and alkaline phosphates to the
plant in the earlier stages of its growth.
Q
ASH OF OAT STALKS AT DIFFERENT STAGES. 433
2. Composition of the ash of oat stalks at different stages of their
growth.
4th June 11th June. 18th June. 25th June. 2d July. 9th July 16th July.
Potash and
l º 24.94 21.43 26.39 28.86 36.26 30.10 40.66
Soda, ...
*...* 3266 sess 29, 24.5' 11.52 it.82 44
Sodium,
Lime, ...... 2.40 4.22 3.74 2.42 2.64 1.60 4. 12
Magnesia, 0.88 3.20 2.20 2.58 1.17 2.27 1.47
Oxide of iron, 0.39 0.30 0.40 0.38 0.88 0.68 0.62
* 16. 15 13.96 12.55 7.81 2.21 2 5.57 6.31
acid, ..
Sulphuric acid, 6.15 7.82 8.5] 4.87 7.98 9.09 7.84
Silica, ......... 16.29 14.32 20.4] 28.08 36.64 32.39 34.85
99.86 99.90 99.14 99.57 99.40 99.52 100.33
Per-centage
of ash (in 10.49 9.18 9.32 9.17 7,83 7.80 7. 94
dry state)
The phosphoric acid was combined as follows:
a. With alkali, 12. 15 10.41 10.40 5. 39 (). 11 ? 3.29 2,06
b. with lime,
magnesia,
and oxide 2. ll 2.28 3.
2.
4
2
2
5
4.00 3.55 2.15
of iron, ...
In the corn stalk, or growing straw, we observe the same three
changes progressing as in the leaf, though not to the same degree.
The common salt diminishes largely, but the whole per-centage of
alcaline matter does not decrease very much. The phosphoric
acid, however, diminishes rapidly, and as in the leaf it is that por-
tion of the acid which is in combination with the alcaline matter
that chiefly disappears. The silica also increases from 20 to 40
per cent, not forming up to this time so large a proportion of the
whole as in the ash of the leaf. Had the experiments been con-
tinued till the straw was fully ripe, the proportion of silica might
have been found to be considerably greater.
There is, however, one striking difference between the leaf and
the stalk. In the leaf the proportion of ash underwent a gradual
small increase, while in the stalk or straw it regularly diminished
from 10% to less than 8 per cent. This fact shows that in the stem
the organic increases faster than the inorganic portion of its sub-
E €
434 ASH OF POTATO LEAVES.
stance, or that some of the latter is removed from the sap of the
stem, and it is consistent with De Saussure's observation, that the
proportion of ash in the full grown is less than in the young plant.
Still the fact may prove otherwise in oat plants which grow slowly
or in an unfavourable soil.
In the above tables some discrepancies will be seen, which are
to be expected where different plants are collected every week,
differing no doubt both in individual constitution and in the pre-
cise stage of their growth. Yet there is a general agreement
among the whole, with the exception of the phosphoric acid in the
stalk of the 2d of July, which is marked with an interrogation (?)
This is no doubt an error in the analysis, which for want of ma-
terial could not be repeated.
§ 12. Composition of the ash of the leaves and stem of the potato
at successive stages of their growth.
The leaves and stems of young potatoes were collected for five
successive weeks in the early part of 1845, and their examination
continued by my assistant, Mr Thomas, till the pressure of other
business made it necessary to delay the prosecution of the inquiry.
The results obtained were as follows:— -
a. The Leaves.
June 10. June 17. June 24. July 1. July 8.
Soluble salts, chiefly alkaline sulphates 47.08 49.53 48.78 35.43 45.72
and chlorides,...........................
Phosphates of lime and magnesia, . . . . 20.35 24.41 18.65 23.57 24.20
Carbonates of lime and magnesia, ...... 12.35 12.67 19.95 26.21 20.35
Silica, ....................................... 20.22* 13.39 12.62 ± 4.79 9.73
| ()0. } 00. 100. 100. 100.
Per-centage of ash in dry state, ......... 20.38 18.40 19.53 17.24 15.71
Per-centage of water, ..................... 87,41 89.67 88.33 87.59 87.53
b. The Stalks.
June 10, June 17. June 24, July 1. July 8.
Soluble salts, chiefly alkaline sulphates 73.95 63.99 66.00 55.85 59.80
and chlorides,...........................
* Owing to the leaves of the first week being so near the ground, there may have
been some sand mixed with the silica. The weather was dry for several days when
the first leaves were collected, rainy the day before the 2d, rainy the 3d, very rainy
the 4th, and rain the day before the 5th, were gathered.
l
ASH OF POTATO STALKS, * 435
June 10. June 17. June 24. July 1. July 8.
Phosphates of lime and magnesia,...... 10.35 7.17 9.32 7.76 12.48
Carbonates of lime and magnesia, ...... 8.88 22.30 19.90 32.60 23.89
Silica, T 6.82 6.54 4.78 3.79 3.83
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * - e . . . .
~4.
ſº 100. 100. 100. 100. 100.
—4
Per-centage of ash in dry state, ........ 19.02 24.84 24.93 23.42 26.13
. Per-centage of water, ................... ... 92.98 93.68 92.78 92.53 94.26
An inspection of the above table shows,
a. That in the leaves the proportion of ash diminished as the
plant increased in size, while in the stem the contrary was the case.
In the one the quantity of organic matter in the plant ; in the
other the quantity of inorganic matter increased the more rapidly.
b. The proportion of phosphates and of silica in the ash of the
leaf was much greater than in that of the stem, while in the latter
the proportion of alkaline matter or soluble salts was the greater
throughout, (see p. 371).
c. The proportion of alkaline matter in the ash of the leaf re-
mained nearly stationary, while in the stem it diminished as the
plant increased in size.
d. That in both the proportion of silica diminished, while that
of the lime and magnesia increased.
Has the good effect known to be produced by liming the potato
crop after it is above ground and before it is earthed up, any con-
nection with this matural increase in the proportion of lime and
magnesia as the plant advances in age? Does this fact open up a
new field of inquiry leading to a knowledge of the substances which
our cultivated crops require at the several stages of their growth,
and of those, therefore, which we ought to apply to them with the
view of best and most economically promoting their growth at these
successive stages?
If the analysis of plants at the different periods of their growth
is to lead us to results of this kind, we may certainly rejoice to see
the subject further prosecuted.
§ 13. Of the value of our present analyses of the ashes of plants.
If the inorganic matter in our cultivated crops varies so much,
you will naturally ask, what degree of dependence ought to be
436 WALUE OF OUR EXISTING ANALYSES.
placed on those analyses of the ashes of plants which we at present
possess?
To this question it may be answered,
1°. That mone of our analyses of cultivated seeds represents ex-
actly the quality of the ash of any other sample than that of the
one actually analysed. Yet so strong a general likeness prevails
in this respect among the different samples of each of our common-
ly cultivated kinds of grain, that the mean of the whole of the ama-
lyses hitherto made, when, as in the case of wheat, they have been
numerous, may be taken as a tolerable approximation to the true
composition of the inorganic constituents of the several seeds.
2°. Such, however, cannot as yet be considered to be the case
with our analyses of the stems and leaves of any of our cultivated
plants. The composition of the several parts of the stem varies so
much that—as no account has hitherto been taken of the part of the
straw actually analysed, except by my friend and pupil, Mr Nor-
ton—we cannot say that we as yet know what the average compo-
sition of any of them is—what, therefore, they necessarily require
and carry off from the soil.
3°. The same is true of the leaf of the tobacco plant and of the
leaves and tops of the turnip and potato. The period of their
growth at which the parts are collected for analysis must so
much modify the quantity and quality of the ash they yield,
that we have much reason to wish for more extended and more
precise research into the average quality of the inorganic consti-
tuents of these plants also.
The object or main practical purpose for which these analyses
are sought to be attaimed is two-fold:
a. To guide us in our treatment of plants at the various stages
of their growth.
b. To instruct us as to what the ripe plant in its healthy state
finally carries off from the soil.
The latter only of these two applications of such knowledge has
hitherto been kept in view by chemists, and so little has been done
in reference to it that we scarcely know as yet what any one entire
plant, when fully ripe, carries off from the soil.
In reference to the former application, the few imperfect re-
searches detailed in the preceding sections contain all that we yet
STATE OF MINERAL FOOD IN THE SOIL. 437
know. We may well say, therefore, that our knowledge of the
inorganic constituents of plants is yet in its infancy, and that our
present opinions upon the subject ought, therefore, to be permitted
to hang very loosely about us.
§ 13. Must the inorganic food of plants evist in the soil in a peculiar
state of solubility or combination to suit each plant?
Two new and interesting points are raised by the above ques-
tion. *...
1°. Must the inorganic food exist in the soil in a peculiar state
to enable it to feed plants in general P
2°. Must it be in a special state to adapt it best to the mourish-
ment of particular kinds of plants?
In reply to the first question, it appears obvious,
a. That the inorganic compounds must be in a state in which
they will dissolve more or less readily in water, or in water charged
with substances which, like carbonic acid, are abundant in mature.
And yet this is necessary in a less degree—is less essential—than
we should at first suppose. This has been shown by a very inte-
resting experiment made by Wiegman and Polstorf.”
They collected a quantity of pure white quartz sand, digested
it in a mixture of nitric and muriatic acids, and then washed it
well with distilled water. In this sand, which contained 98 per
cent. of silica, they sowed seeds of various kinds—oats, barley, to-
bacco, trefoil, &c.—and as they grew, watered them with distilled
water. The plants when burned gave an ash which invariably
contained more potash, soda, lime, and silica than was present in
the original seeds. The young plants, therefore, by means of
their roots had extracted from the insoluble part of the sand—
which the acid refused to touch—the several substances which were
necessary for their growth. They did not grow luxuriantly, nor
become robust or perfect plants. This was not to be anticipated.
But this extreme experiment shows, that the roots of plants may
gather food where we could hardly expect them to live, and that
the inorganic substances they obtain in the soil, if sufficiently abun-
dant, need not necessarily be in a very soluble state.
b. As to the state of combination in which the mineral food of
* Ueber die Amorganische Bestandtheile der Pflanzen. Braunschweig, 1842.
4.38 MUST IT BE IN A SPECIAL STATE,
plants ought to exist in the soil, experience seems to say that there
are certain states of combination in which substances, otherwise
fitted to be useful to the plant, may in reality exercise an injurious
influence upon it. Thus sulphuric acid in excess in the soil, and
especially in combination with iron, is injurious to vegetation, but
if it be in combination with lime or soda it promotes the growth of
plants. So the humic and ulmic acids, which in sour peaty soils
nourish only a scanty and sour herbage, become propitious to the
growth of valuable crops when combined with lime or with am-
monia. So far, therefore, it does appear that the state of chemi-
cal combination in which a substance exists in the soil may mate-
rially affect its power of influencing or promoting the growth of
plants. But upon this subject we have still very much to learn.
In reply to the second question we have as yet few facts to offer.
We do not know for certain that any class of plants requires its
food to be presented to its roots in any peculiar or special state;
though this is by no means unlikely.
Thus some plants are much longer in growing than others;–
have a greater number of months allowed them to complete their
growth. Such is the case with wheat as compared with barley;
and yet a crop of barley carries off more from the soil than a crop
of wheat. To supply the wants of the barley with sufficient ra-
pidity, therefore, the mineral food ought to exist in a more soluble
state than is necessary for the crop of wheat, unless there be some
special power or superior activity in the roots of the former.
But I do not dwell on this subject, as we as yet know nothing
certain in regard to it. It must be generally true that the inor-
ganic food must exist in the soil in such a state of abundance and
solubility as readily to yield to every plant all it requires for its
healthy and perfect growth, and to yield to each the whole of this
supply, within the time which usually elapses before it arrives at
complete maturity,
LECTURE XIV.
Nature and origin of soils. Organic matter in the soil. General composition of the
earthy part of the soil. Classification of soils from their chemical constituents.
Method of approximate analysis for the purposes of classification. General origin
of soils and subsoils, Structure of the earth's crust. Stratified and unstratified
rocks. Crumbling or degradation of rocks. Diversity of soils produced. Superfi-
cial accumulations. Sketch of the general characters and agricultural capabilities
of the soils of the different parts, of Great Britain.
WHENCE do plants obtain their inorganic constituents? From
the soil only. Let us now, therefore, turn our attention to the
soil.
§ 1. Of the organic matter of the soil.
Soils differ much in respect of their immediate origin, their phy-
sical properties, their chemical composition, and their agricultural
capabilities. Yet all soils which in their existing state are capable
of bearing profitable crops in our climate, possess one common
character—they all contain organic matter in greater or less pro-
portion.
This organic matter consists in part of decayed animal, but
chiefly of decayed vegetable substances, sometimes in brown or
black fibrous portions, exhibiting still, on a careful examination,
something of the original structure of the organized substances
from which they have been derived—sometimes forming only a
fine brown powder intimately intermixed with the mineral matters
of the soil—sometimes scarcely perceptible in either of those forms,
and existing only in the state of organic compounds more or less
void of colour and at times entirely soluble in water. In soils
which appear to consist only of pure sand, or clay, or chalk, or-
440 PROPORTION OF ORGANIC MATTER IN SOILS.
ganic matter in this latter form may often be detected in consider-
able quantity.
The proportion of organic matter in soils which are maturally
productive of any useful crops varies from one-half of a per cent.
to 70 per cent of their whole weight. With less than the former
proportion they will scarcely support a profitable vegetation—with
more than the latter, they require much admixture before they can
be brought into a fertile state of cultivation. It is only in boggy
and peaty soils that the above large proportion is ever found—in
the best soils the organic matter does not average five per cent.,
and rarely exceeds ten or twelve. Oats and rye will grow upon
land containing only one or one and a-half per cent.—barley where
two or three per cent. are present—but good wheat soils contain
in general from 4 to 8 per cent, and if very stiff and clayey, from
10 to 12 per cent. of organic matter.
Though, however, a certain proportion of organic matter is al-
ways found in a soil distinguished for its fertility, yet the presence
of such substances is not alone sufficient to impart fertility to the
land. I do not allude merely to such as like peaty soils contain a
very large excess of vegetable matter, but to such also as contain
only an average proportion. Thus of two soils in the same neigh-
bourhood—the one contained 4-05 per cent. of organic matter,
and was very fruitful, the other 14.9 per cent., and was almost
barren. This fact is consistent with what has been stated in the
preceding lectures, in regard to the influence exercised by the dead
inorganic matter of the soil, on the general health and luxuriance
of vegetation.
§ 2. General composition of the earthy part of the soil.
From what is above stated, it appears that on a general average
the earthy part of the soil in our climate does not constitute less
than 96 per cent. of its whole weight, when free from water. This
earthy part consists principally of three ingredients.
1°. Silica, siliceous sand, or siliceous gravel—of various degrees
of finemess, from that of an impalpable powder, as it occurs in clay
soils, to the large and more or less rounded sandstones of the gra-
vel beds.
2°. Alumina—generally in the form of clay, but occasionally
GENERAL CONSTITUENTS OF THE EARTHY PART OF SOILS. 441
occurring in shaly or slaty masses more or less hard, intermingled
with the soil. .
3°. Lime, or carbonate of lime—in the form of chalk, or of frag-
ments more or less large of the various limestones that are met
with near the surface in different countries. Where cultivation
prevails it often happens that all the lime which the soil contains
has been added to it for agricultural purposes—in the form of
quick-lime, of chalk, of shell sand, or of one or other of the mu-
merous varieties of marl, which different districts are known to pro-
duce.
Soils are rarely found to consist altogether of any one of these
three substances. A soil, however, is called sandy in which the
siliceous sand greatly predominates, and calcareous, where as in our
chalk and limestone districts, carbonate of lime is present in con-
siderable abundance. When alumina forms a large proportion
of the soil, it constitutes a clay of greater or less tenacity.
The term clay, however, or pure clay, is never used by writers
on agriculture to denote a soil consisting of alumina only, for none
such ever occurs in nature. The pure porcelain clays are the
richest in alumina, but even when freed from water by heating to
redness, they contain only from 42 to 48 per cent. of this earth,
with from 52 to 58 of silica. These porcelain clays, besides, occur
only in isolated patches, and never form the soil of any considerable
district. The strongest clay soils which are anywhere in cultiva-
tion rarely contain more than 35 per-cent. of alumina.
Soils in general consist in great part of the three substances
above named, in a state of mechanical mixture. This is always the
case with the siliceous sand and with the carbonate of lime—but
in the clays the silica and the alumina of which they consist are,
for the most part, in a state of chemical combination. Thus, if a
portion of a stiff clay soil be kneaded or boiled with repeated por-
tions of water till its coherence is cntirely destroyed, and if the
water, with the finer parts which float in it, be then poured into a
second vessel, the whole of the soil will be separated into two por-
tions—a fine impalpable powder consisting chiefly of clay, poured
off with the water, and a quantity of siliceous or other sand in par-
ticles of various sizes, which will remain in the first vessel. This
sand was only mechanically mixed with the soil. The fine clay
4.42 COMPOSITION OF PORCELAIN CLAYS.
retains still some mechanical admixtures, but consists chiefly of si-
lica and alumina chemically combined. -
Of the porcelain clays above alluded to, there are several varie-
ties, three of which, containing the largest proportions of alumina,
consist respectively of
I. II. III.
Silica,............ 47-03 46-92 46 - 0
Alumina, ...... 39-23 34°81 40°2
Water, ......... 13-74 18-27 13-8
100-00 100'00 | 00:0°
But, as already stated, these clays rarely form a soil—the stiff-
est clays treated by the agriculturist containing a further portion
of silica, some of which is mechanically mixed, and can be partially
separated by mechanical means.
The strongest agricultural clays (pipe clays), of which trust-
worthy analyses have yet been published, consist, in the dry state,
of 56 to 62 of silica, from 36 to 40 of alumina, 3 or 4 of oxide of
iron, and a trace of lime. Clays of this composition are distin-
guished by the foreign agricultural writers as pure clays. They are
all probably made up of some of the varieties of pure porcelain
clay, more or less intimately mixed with siliceous and ochrey par-
ticles in so minute a state of division that they cannot be separated
by the method of decantation above described.
These clays are adopted by the German and French writers
as a standard with which to compare clay soils in general, and
by a reference to which they are enabled distinctly to classify and
name them. As the use of the term clay in this sense has been
introduced into English agricultural booksi, and as it is really de-
* When heated to redness the whole of the water is driven off from these clays, and
they then consist respectively of—
Silica, ............... 54-5 57-4 53'4
Alumina,............ 45-5 42.6 46'6
100-0 100'0 100'0
which numbers are in accordance with those previously given in the text.
f As in British Husbandry, p. 113, and in Lowdon's Enclycopoedia of Agriculture,
p. 315, where classifications of soils are given chiefly from Von Thaer, though nei-
ther work exhibits with sufficient prominence the meaning to be attached to agri-
cultural clay, as distinguished from alumina, sometimes called pure clay by the che-
mist. -
CLASSIFICATION OF SOILS. 4 #3
sirable to possess a word to which the above meaning can be at-
tached, I shall venture in future to employ it always strictly in this
agricultural sense.
By alumina, then, I shall in all cases express the pure earth of
alum, which exists in clays, and to which they owe their tenacity
—by cI.AY, a finely divided chemical compound, consisting very
nearly of 60 of silica and 40 of alumina, with a little oride of iron,
and from which no siliceous or sandy matter can be separated ºne-
chanically or by decantation.
Of this clay the earthy part of all known soils is made up, by
mere mechanical admixture with the other earthy constituents
(sand and lime), in variable proportions. On a knowledge of these
proportions the following general classification and nomenclature
are founded.
§ 3. Of the classification of soils from their chemical constituents.
Upon the principles above described soils may be classified as
follows:–
1°. Pure clay (pipe-clay) consisting of about 60 of silica and 40
of alumina and oxide of iron, for the most part chemically com-
bined. It allows no siliceous sand to subside when diffused through
water, and rarely forms any extent of soil.
2°. Strongest clay soil (tile-clay, unctuous clay) consists of pure
clay mixed with 5 to 20 per cent. of a siliceous sand, which can be
separated from it by boiling and decantation.
39. Clay loam differs from a clay soil, in allowing from 28 to
40 per cent of fine sand to be separated from it by washing, as
above described. By this admixture of sand, its parts are mecha-
nically separated, and hence its freer and more friable nature.
A loamy soil deposits from 40 to 70 per cent. of sand, by me-
chanical washing.
5°. A sandy loam leaves from 70 to 90 per cent of sand, and
6°. A sandy soil contains no more than 10 per cent. of pure
clay.
The mode of examining with the view of naming soils, as above,
is very simple. It is only necessary to spread a weighed quan-
tity of the soil in a thin layer upon writing paper, and to dry it
for an hour or two in an oven or upon a hot plate, the heat of
444 MARLY AND CALCAREOUS SOILS,
which is not sufficient to discolour the paper—the loss of weight
gives the water it contained. While this is drying, a second
weighed portion may be boiled or otherwise thoroughly incorpo-
rated with water and the whole then poured into a vessel, in which
the heavy sandy parts are allowed to subside until the fine clay is
beginning to settle also. This point must be carefully watched,
the liquid then poured off, the sand collected, dried as before upon
paper, and again weighed. This weight is the quantity of sand in
the known weight of moist soil, which by the previous experiment
has been found to contain a certain quantity of water.
Thus, suppose two portions, each 200 grs, are weighed, and the
one in the oven loses 50 grs. of water, and the other leaves 60
grs, of sand,-then the 200 grs, of moist are equal to 150 grs. of
dry soil, and these 150 grs. of dry soil contain 60 of sand, or 40
in 100 (40 per cent.) It would, therefore, be properly called a
clay loam. -
But the above classification has reference only to the clay and
sand, while we know that lime is an important constituent of soils,
of which they are seldom entirely destitute. We have there.
fore—
7°. Marly soils, in which the proportion of lime is more than 5
but does not exceed 20 per cent. of the whole weight of the dry
soil. The marl is a sandy, loamy, or clay marl, according as the
proportion of clay it contains would place it under the one or other
denomination, supposing it to be entirely free from lime, or not to
contain more than 5 per cent., and, -
8°. Calcareous soils in which the lime exceeding 20 per cent.
becomes the distinguishing constituent. These are also called
calcareous clays, loams, or sands, according to the proportion of
pure clay which is present in them.
The determination of the lime, when it exceeds 5 per cent., is
attended with no difficulty. Thus,
To 100 grs. of the dry soil diffused through half a pint of cold
water, add half a wine glass full of muriatic acid (the spirit of salt
of the shops), stir it occasionally during the day, and let it stand
over might to settle. Pour off the clear liquor in the morning and
fill up the vessel with water, to wash away the excess of acid.
When the water is again clear, pour it off, dry the soil and weigh
SUMMARY OF THE METHOD OF EXAMINATION. 445
it—the loss will amount generally to about one per cent. more than
the quantity of lime present. The result will be sufficiently near,
however, for the purposes of classification. If the loss exceed 5
grs, from 100 of the dry soil, it may be classed among the marls,
if more than 20 grs. among the calcareous soils.
Lastly, vegetable matter is sometimes the characteristic of a soil,
which gives rise to a further division of
9°. Vegetable moulds, which are of various kinds, from the gar-
den mould, which contains from 5 to 10 per cent., to the peaty
soil, in which the organic matter may amount to 60 or 70 per
cent. of its weight when dry. These soils also are clayey, loamy,
or sandy, according to the predominant character of the earthy
admixtures.
The method of determining the amount of vegetable matter, for
the purposes of classification, is to dry the soil well in an oven,
and weigh it; then to heat it to dull redness over a lamp or a
bright fire till the combustible matter is burned away. The loss
on again weighing is the quantity of organic matter.
Summary-The several steps, therefore, which are necessary in
examining a soil with the view of so far determining its composition
as to be able precisely to name and classify it, will be best taken
in the following order:—
1". Weigh 100 grains of the soil, spread them in a thin layer
upon white paper, and place them for some hours in an oven or
other hot place, the heat of which may be raised till it begins
slightly to discolour the paper. The loss is water. -
2". Let it now (after drying and weighing) be burned over the
fire as above described. The second loss is organic, chiefly vege-
table matter, with a little water, which still remained in the soil
after drying.
3". After being thus burned, let it be put into half a pint of
water with half a wine glass-full of spirit of salt and frequently
stirred. When minute bubbles of air cease to rise from the soil
on settling, this process may be considered as at an end. The loss
by this treatment will be a little more than the true per centage
of lime, and it will generally be nearer the truth if that portion of
soil be employed, which has been previously heated to redness.
*
446 EXAMPLE OF SUCH APPROXIMATE ANALYSIS.
4". A fresh portion of the soil, perhaps 200 grains in its moist
state, may now be taken and washed to determine the quantity of
siliceous sand it contains. If the residual sand be supposed to
contain calcareous matter its amount may readily be determined
by treating the dried sand with diluted muriatic acid, in the same
way as when determining the whole amount of lime (3%) contain-
ed in the unwashed soil." Let me illustrate this by an example.
Example.—Along the outcrop of some of the upper beds of the
green sand in Berkshire, Wiltshire, and Hampshire, and probably
also in Buckingham and Bedford, occur patches of a loose friable
grey soil mixed with occasional fragments of flint, which is noted
for producing excellent crops of wheat every other year. It is
known in the valley of Kingscleer, and at Wantage, near New-
bury. I select a portion of this soil from the former locality for
my present illustration. -
1". After being dried in the air and by keeping sometime in
paper, it was dried for some hours at a temperature sufficient to
give the white paper below it a scarcely perceptible tinge: by this
process 104% grs, lost 4 grs.
2". When thus dried it was heated to dull redness. It first
blackened, but gradually assumed a pale brick colour, the change,
of course, beginning at the edges. The loss by this process was
4} grs.
3". After this heating, it was put into half a pint of pure rain
water with half a wine glass of spirit of salt. After some hours,
when the action had ceased, the soil was washed and dried again
at a dull red heat. The loss amounted to 3 grs.
4". Washed with water by decantation 100 grs, of the soil left
70 grs. of very fine sand, or 104 grs, would have left 73 grs.
* The weighings for the purposes here described may be made in a small balance
with grain weights, sold by the druggists for 5s, or 6s., and the vegetable matter
may be burned away on a slip of sheet iron or in an untinned iron table spoon over a
bright cinder or charcoal fire—care being taken that no scale of oxide, which may be
formed on the iron, be allowed to mix with the Soil when cold, and thus increase its
weight. Those who are inclined to perform the latter operation more neatly, may
obtain for about 6s, each—from the dealers in chemical apparatus—thin light platinum
capsules from 1 to 1, inches in diameter, capable of holding 50 or 100 grs. of soil, and
for a few shillings more a spirit lamp, over which the vegetable matter of the soil may
be burned away. With care, one of these little capsules will serve a lifetime.
DIFFERENCE BETWEEN SOIL AND SUBSOIL. 447
The soil, therefore, contained—
Water,........... s - tº e º $ tº º te is e e s tº e s tº a 4 grs. 3.9 per cent.
Organic matter, (less than) ... 4: ... 4'l
Carbonate of lime, (less than)... 3 ... 3-0
Clay................. .. ... sº e º e º 'º e º s sº e 20, ... . . 19:0
Sand, (very fine) ...... ... ... ... 73 ... 70-0
104% 100%
This soil, therefore, containing 70 per cent of sand, separable
by decantation, is properly a sandy loam.
§ 4. Of the distinguishing characters of soils and subsoils.
Beneath the immediate surface soil, through which the plough
makes its way, and to which the seed is entrusted, lies what is com-
monly distinguished by the name of subsoil. This subsoil often
consists of a mixture of the general constituents of soils in propor-
tions originally different from that which forms the surface layer—
as when clay above has a sandy bed below, or a light soil on the
surface rests on a retentive clay beneath.
This, however, is not always the case. The peculiar characters
of the soil and subsoil often result from the slow operation of natu-
ral causes.
In a mass of loose matter of considerable depth, spread over an
extent of country, it is easy to understand how—even though ori-
ginally alike through its whole mass—a few inches at the surface
should gradually acquire different physical and chemical characters
from the rest, and how there should thus be gradually established
important agricultural distinctions between the first 12 or 15 inches
(the soil), the next 15 (the subsoil), and the remaining body of the
mass, which, lying still lower, does not come under the observation
of the practical agriculturist.
* Some of these numbers differ by a minute fraction from those in the previous co-
lumn : this is bocause they are calculated from the more correct decimal fractions con-
tained in my own note book. The organic matter is said to be less than the number
here given, because by simple drying, as here prescribed, the whole of the water can-
not be driven off—a portion being always retained by the clay, which is not entirely
expelled till the soil is raised nearly to a red heat. Hence the loss by this second
heating must always be greater than the actual weight of the organic matter present.
The lime is also less than the number given, because the acid dissolves a little alumina
as well as any carbonate of magnesia which may be present
448 HOW THE SUBSOIL IS PRODUCED.
On the surface plants grow and die. Through the first few in-
ches their roots penetrate, and in the same the dead plants are bu-
ried. This portion, therefore, by degrees, assumes a brown colour,
more or less dark, according to the quantity of vegetable matter
which has been permitted to accumulate in it. Into the subsoil,
however, the roots penetrate less abundantly, and the dead plants
are rarely buried at so great a depth. Still this inferior layer is
not wholly destitute of vegetable or other organic matter. How-
ever comparatively impervious it may be, still water makes its way
through it, more or less, and carries down soluble organic substances,
which are continully in the act of being produced during the de-
cay of the vegetable matter lying above. Thus, though not sensi-
bly discoloured by an admixture of decayed roots and stems, the
subsoil may in reality contain an appreciable quantity of organic
matter which can be distinctly estimated.
Again, the continual descent of the rains upon the surface soil
washes down the salts of potash and Soda, the carbonates of lime,
iron, and magnesia, as well as other soluble substances—it even,
by degrees, carries down the fine clay also, so as gradually to es-
tablish a more or less manifest difference between the upper and
lower layers, in reference even to the earthy ingredients which
they respectively contain.
But, except in the case of very porous rocks or accumulations
of earthy matter, these surface waters rarely descend to any great
depth, and hence after sinking through a variable thickness of sub-
soil, we come, in general, to earthy layers, in which little vegetable
matter can be detected, and to which the lime, iron, and magnesia
of the superficial covering has never been able to descend.
Thus the character of the soil is, that it contains more brown or-
ganic, chiefly vegetable, matter in a state of decay—of the subsoil,
that the organic matter is less in quantity and has entered it chiefly
in a soluble state, and that earthy matters are present in it which
have been washed out of the Superior soil—and of the subjacent
mass that it has remained nearly unaffected by the changes which
vegetation, culture, and atmospheric agents have produced upon
the portions that lie above it.
From what is here stated, the effect of trench and subsoil
ploughing, in altering more or less materially the proportions of
GENERAL ORIGIN OF SOILS. 449
the earthy constituents in the surface soil, will be in some mea-
sure apparent. That which the long action of rains and frosts has
caused to sink beyond the ordinary reach of the plough is, by
such methods, brought again to the surface. When the substances
thus brought up are directly beneficial to vegetation, or are fit-
ted to improve the texture of the soil, its fertility is increased.
Where the contrary is the case, its productive capabilities may for
a longer or shorter period be manifestly diminished.
§ 5. On the general origin of soils.
On many parts of the earth's surface the naked rocks appear
over considerable tracts of country, without any covering of loose
materials from which a soil can be formed. This is especially the
case in mountainous and granitic districts, and in the neighbour-
hood of active or extinct volcanoes, where, as in Sicily, streams of
naked lava stretch in long black lines amid the surrounding ver-
dure.
But over the greater portion of our islands and continents the
rocks are covered by accumulations, more or less deep, of loose
materials—sands, gravels, and clays chiefly—the upper layer of
which is more or less susceptible of cultivation, and is found to re-
ward the exertions of human industry with crops of corn in greater
or less abundance.
This superficial covering of loose materials varies from a few
inches to one or two hundred feet in depth, and is occasionally ob-
served to consist of different layers or beds, placed one over the
other—such as a bed of clay over one of gravel or sand, and a
loamy bed under or over both. In such cases the characters and
capabilities of the soil must depend upon which of these layers
may chance to be uppermost—and its qualities may often be bene-
ficially altered by a judicious admixture with portions of the sub-
jacent layers.
It is often observed, where naked rocks present themselves,
either in cliffs or on more level parts of the earth, that the action
of the rains and frosts causes their surfaces gradually to shiver off,
crumble down, or wear away. Hence at the base of cliffs loose
matter collects—on comparatively level surfaces the crumbling of
the rocks gradually forms a soil—while from those which are suf.
Ff
450 CRUMBLING OR DEGRADATION OF ROCKS,
ficiently inclined the rains wash away the loose materials as soon
as they are separated, and carry them down to form deep deposits in
the valleys.
The superficial accumulations of which we have spoken, as co-
vering the rocks in many places to a depth of one or two hundred
feet, consist of materials thus washed down or otherwise transport-
ed—by water, by winds, or by other geological agents. Much of
these heaps of transported matter is in the state of too fine a pow-
der to permit us to say upon examining it from whence it has been
derived. Fragments of greater or less size, however, are always to be
found, even among the clays and fine sands, which are sufficient to
point out to the skilful geologist the direction from which the
whole has been brought, and often the very rocks from which the
entire accumulations have been derived.
Thus the general conclusion is fairly drawn, that the earthy
matter of all soils has been produced by the gradual decay, degra-
dation, or crumbling down of previously existing rocks. It is evi-
dent therefore—
1°. That whenever a soil rests immediately upon the rock from
which it has been derived, it may be expected to partake more or
less of the composition and characters of that rock.
2°. That where the soil forms only the surface layer of a consi-
derable depth of transported materials, it may have no relation
whatever either in mineralogical characters or in chemical consti-
tution to the immediately subjacent rocks.
The soils of Great Britain are divisible into two such classes.
In some counties an acquaintance with the prevailing rock of the
district enables us to predict the general characters and quality of
the soil; in others—and nearly all our coal fields are in this case
—the general character and capabilities of the soil have no rela-
tion whatever to the rocks on which the loose materials immedi-
ately rest.
§ 6. On the general structure of the earth's crust, and the general
composition of rocks.
1°. Beneath the soil, and the loose or drifted matters on which
it rests, we every where find the solid rock. This rock in most
countries is seen—in mines, quarries, and cliffs—to consist of beds
4)
• X
STRUCTURE OF THE EARTH's CRUST. 451
or layers of varied thickness placed one over the other. To these
layers geologists give the name of strata ; and hence rocks which
are thus made up of many separate layers are called stratified
rocks.
But in some places entire mountain masses are met with, in
which no parting into layers or beds is seen, but which appear to
consist of one unbroken rock of the same material from their up-
per surface downwards, and often as far beneath as we have been
able to penetrate into the earth. Such rocks are said to be un-
stratified. Among these are included the granites, the trap, green-
stone, or basaltic rocks, and the lavas, Geologists have ascertain-
ed that all these unstratified rocks have, like the volcanic lavas,
been in a more or less perfectly melted state—that their present
appearance is owing to the action of fire—and hence they are often
called igneous" rocks. They often also exhibit a more or less cry-
stalline or glassy structure, or contain imbedded in them, nume-
rous regular crystals of mineral substances; hence they are some-
times called also crystalline rocks. The terms igneous, crystal-
line, and unstratified, therefore, apply to the same class of rocks—
the first indicating their origin, the second their structure in the
small, the third their structure in the large, as distinguished from
that of the rocks which occur in beds.
The following diagram exhibits the general appearance of the
stratified rocks as they are found to occur in contact with unstra-
tified masses in various parts of the globe:–
ID
- • - /
2-32=s. C *-º-º-º-º: *—2
*se- *º E\ B
* > *—
A, represents an unstratified mountain mass or other similar
rock rising up through the stratified deposits. The bending up of
the edges of the latter indicates that after the beds were deposited
in a nearly level position, the mass A was intruded or forced up
through them, carrying the broken edges of the beds along with
it.
B, shows the more quiet way in which veins or dikes of unstra-
* Sometimes pyrogenous, produced by fire ; but this is an unnecessarily hard
word.


452 STRATIFIED AND UNSTRATIFIED ROCKS.
tified green-stone, or trap, or lava, cut through the beds without
materially displacing them—as if when in a fluid state it had risen
up and filled a previously existing crack or chasm. In Devonshire,
in the North of Scotland, and in Ireland, the granite rises in many
places exactly as is shown at A, and nearly all our coal fields ex-
hibit in their whin dikes numerous illustrations of what is shown
at B.
C and D exhibit the manner in which the strata overlie one an-
other in nearly a horizontal position—1, 2, 3, indicating different
kinds of rock,--as a lime-stone, a sand-stone, and a clay—which
again are subdivided into beds or thinner layers, by the partings
exhibited in the wood-cut.
The stratified rocks lie sometimes nearly level or horizontal over
large tracts of country—as in the above diagram. Sometimes they
are more or less inclined, or appear to dip in one and to rise in the
opposite direction—as if a surface, formerly level, had been push-
ed down at the one end and raised up at the other, and some-
times they seem to rest entirely upon their edges. Upon the mode
in which they thus lie, the uniformity of the soil, in a district where
it reposes immediately on the rocks from which it is derived, is
materially dependent. In the following diagram the surface from
A.

lin
**
ºxº
lsº *— ”
A to E represents a tract of country in which the rocks have in
different parts these different degrees of inclination—at A verti-
cal, at B more inclined, and from C to E nearly horizontal. Now,
it is obvious that if the outer surface of these several rocks crumble
and form a soil which rests where it is produced—then the quality
of the soil on every spot will be determined by the nature of the
rock beneath. Hence, in proceeding from E over the compara-
tively level strata, we shall find the soil pretty uniform in quality
till we come to the edge of the bed D, thence it will again be uni-
form, though perhaps different from the former, till we reach the
stratum C, when again it will prove uniform over a considerable
space till we begin to climb the hill to B. So the whole hill side
• X
VERTICAL, INCLINED, AND HORIZONTAL STRATA. 453
in ascending to B will be of one and the same kind of soil. But
as we descend on the other side and pass B we get upon the
edges of the beds, and then as we proceed from one bed to another,
the quality of the soil may vary at successive short distances more
or less according as the members of this group of beds are more
or less different from each other. But when we ascend the hill to
A, where the beds, besides being vertical, are also very thin, the
soil may change at almost every step, provided—which is, however,
rarely the case among the rocks (slate rocks) which occur most
frequently in this position—provided the mineralogical characters
of the several vertical layers be sensibly unlike. Such dissimilari-
ties in the angular position of the strata, as are represented in the
above diagram, are of constant occurrence not only in our islands,
but over all parts of the globe; and they illustrate very clearly
one important cause of that want of uniformity in the nature and
capabilities of the soil which is more or less observable in every
undulating and in some comparatively level countries also.
2°. It may be stated, as the general result of an extended exa-
mination of all the stratified rocks yet known, that they consist of
alternations or admixtures of three kinds of rock only—of sand-
stones, of lime-stones, and of clays. The sand-stones are of va-
rious degrees of solidity and hardness, from the loose sand of some
parts of the lower new-red and green-sand formations, to the al-
most perfect quartz rock not unfrequently associated with the
oldest strata. The lime-stones vary in like manner from the soft
chalk to the hard mountain lime-stone and the crystalline statuary
marble; while the clays are found of all degrees of hardness, from
that of the London and Kimmeridge clays which soften in water,
to that of the roofing slates of Cumberland and Wales, and even
to that of the gneiss rocks which rest immediately upon the granite,
and which appear to be only the oldest clays altered by the action
of heat. *
But the stratified rocks, though thus distinguishable into three
main varieties, rarely consist of any one of these substances in an
unmixed state. The sand-stones not unfrequently contain a little
clay or lime—while the lime-stones and clays are often mixed with
sand and with each other.
If the stratified rocks thus consist essentially of these three sub-
454 RELATIVE POSITIONS OF THE STRATA CONSTANT.
stances, the soils formed from them by natural crumbling or de-
cay must have a similar composition. A sandy soil will be formed
from a sand-stone,—a calcareous soil from a lime-stone,—a clay
from a slate or shale, and from a mixed rock, a soil containing
a mixture of two or more of these earthy ingredients in propor-
tions which will depend upon the relative quantities of each which
are contained in the rock from which they have been derived.
§ 7. Relative positions and peculiar characters of the several strata.
1°. The several strata, or series of strata, which present them-
selves in the crust of the globe, always maintain the same relative
positions. Thus the numbers 3, 2, 1, in the annexed diagram, re-
present three series of beds known by the names of the magnesian
lime-stone, the lower new-red sand-stone, and the coal measures,
lying over each other in their natural positions—the lime-stone up-
permost, the sand-stone next, and the coal measures beneath both.
Whenever these three rocks are met with near each other, they
always occupy the same relative position, the coal never appears
above this lime-stone, and the sand-stone, if present, is always be-
tween the two other series of beds. The same is true of every
other group of strata—the order in which they are placed over
each other is universally the same.
2°. These beds are generally continuous also over very large
areas—or are found to stretch, without interruption, over a great
extent of country. Hence when they dip beneath other beds, as
they are seen to do in the above diagrams, we can still, with a high
degree of probability, infer their presence at a greater or less depth,
wherever we observe on the surface those other beds which are
known usually to lie immediately above them. Thus, if in a tract
of country consisting of the magnesian lime-stone (3) above men-
tioned, it is known that deep valleys occur, it becomes probable
that the soil in those valleys will rest upon, and may be formed
from, the underlying red sand-stones or coal-measures; and that

©
THEY ARE OFTEN CONTINUOUS OWIER, LARGE AREAS. 455
it will therefore possess very different agricultural capabilities
from the soil that generally prevails around it. Or in chalk dis-
tricts, beneath which usually lies the green-sand, the presence of
a deep valley cutting through the chalk almost necessarily implies
in the hollow a very different soil from that which is cultivated on
the chalk wolds above. This is the case in the valley of Kingscleer,
where the peculiar wheat soil occurs, of which an approximate ana-
lysis has been given in page 446.
3". It has been already stated that the stratified rocks, though
so very numerous and so varied in appearance, yet consist gene-
rally of repeated alternations of lime-stones, sand-stones, and clays,
or of mixtures of two or more of these earthy substances. But
the several series of strata are nevertheless distinguished from each
other by peculiar and often well-marked characters.
Thus some are soft, crumble readily, and soon form a soil,—
while others, though consisting of the same ingredients, long refuse
to break into minute fragments, and thus condemn the surface of
the country where they occur to more or less partial barrenness.
In others, again, the proportions of sand or lime are so varied,
from bed to bed, that the character of the mixture in each is en-
tirely different—so that while one, on crumbling down, will give a
stiff clay, another will produce a loam, and a third a sandy marl.
Or, in some rocks the remains of vegetables are present in con-
siderable quantity—as in the neighbourhood of our coal beds,-or
the bones or shells of animals occur in greater or less abundance,
by each of which circumstances the agricultural characters and
capabilities of the soils formed from them will be more or less ex-
tensively affected.
Or lastly, an admixture of other earthy substances gives a pe-
culiar character to many rocks. Thus the per-oxide of iron, which
imparts their red colour to many strata—as to the red sandstones
—influences not only the mineralogical character of the rock, but
also the quality of the soil which is formed by its decay. In like
manner the presence of magnesia, sometimes in large quantity, in
many lime-stones, produces an important modification in the che-
mical composition and mineralogical characters of the rock, as well
as in its relations to practical agriculture.
In consequence of these and other similar causes of diversity, if
456 THEIR PECULIAR CHARACTERS ALSO CONTINUOUS.
not every stratum, at least every series of strata, exhibits distin-
guishing and characteristic peculiarities, by means of which it may
be more or less readily recognised. On these peculiarities the spe-
cial agricultural capabilities of those parts of the globe in which
each series of beds occurs are in a great degree dependant.
4°. This peculiar character is also more or less continuous over
very large areas. Thus if a given stratum be found on the sur-
face in any part of England, and again in any part of Russia, the
soil formed from that bed will generally exhibit very nearly the
same qualities in both countries. A knowledge of the geology,
therefore—that is of the kind of rock which appears on the surface
in any part of a country—enables us to predict generally the
kind of soil which ought to rest upon it, if it be not covered by
foreign accumulations, the mineral substances in which it is likely
to be deficient, and where, as when lime is one of them, they may
be obtained at the least cost. And again, a knowledge of the
agricultural capabilities of any one district in which certain rocks
are known to lie immediately beneath the soil, and of the agricul-
tural practice suited to that district, will indicate the probable ca-
pabilities of any other tract in which the same kind of rock is known
to appear on the surface, and of the kind of culture which may be
most successfully applied to it.
It is evident, then, that a familiar acquaintance with the gene-
ral characters and relative positions of all the series of strata that
have hitherto been observed, and of the classification of rocks con-
sidered geologically, to which this knowledge has led, must be fit-
ted to throw much light upon the principles of a general, em-
lightened, and philosophical agriculture.
§ 8. Classification of the stratified rocks, their evtent, and the agri-
- cultural relations of the soils derived from them.
It is a received principle, I may say rather, an obvious fact, that
in the crust of the earth, as in the walls of a building, those layers
which lie lowest or undermost have been first deposited, or are the
oldest. In reference to this their relative age, the stratified rocks
are divided into the primary, or first deposited and most ancient—
the secondary, which are next in order—and the tertiary, which
overlie both.
tº
CLASSIFICATION OF THE STRATIFIED ROCKS. 457
These three series of strata are again sub-divided into systems,
and these into minor groups, called formations,—the several mem-
bers of each system and formation having such a common resem-
blance, either in mineralogical character or in the kind of animal
and vegetable remains found in them, as to show that they were
deposited under very nearly the same general physical conditions
of the globe.
The following table exhibits the names, relative positions, thick-
messes, and mineralogical characters of the stratified rocks, in de-
scending order, as they occur in our islands. The annexed re-
marks indicate also the districts where each of these groups of
rocks forms the surface, and the general agricultural characters of
the soils that rest upon them.
1. THE TERTIARY STRATA—are characterised by containing,
among other fossils, the remains of animals, which are identical
with existing species.
NAME. THICIKNESS, MINERALOGICAL CHARACTERS.
19. Crag. 50 ft. A mass of rolled pebbles mixed
with marine shells—resting on beds
of Sand and Sandy limestone ; the
whole more or less impregnated
with oxide of iron.
ExTENT.-The Crag forms a strip of land a few miles in
width in the eastern part of Norfolk and Suffolk, and in the south-
eastern part of the latter county. It is a flat, and generally, it is
said, a fertile arable district.
2°. Fresh-water Marls and marly lime-stones
Marls. 100 fi. with fresh water shells separated in-
to two series by an estuary deposit
containing marine shells.
ExTENT.—On these beds reposes the soil of the northern half
of the Isle of Wight, the only part of England in which they ap-
pear at the surface.
3°. London Clay. 200 to 500 ft. Stift, almost impervious, brown,
blue, and blackish clay, rich in
marine shells, and containing lay-
ers of limestone nodules.
ExTENT.—The greater part of the county of Middlesex, the
south-eastern half of Essex, and the Southern half of Hampshire,
rest upon the London clay,
458 SOIL OF THE LONDON AND PLASTIC GLAY.
SoLL.—The soil is naturally strong, heavy, wet, and tenacious,
“sticking to the plough like pitch,” and shrinking and cracking in
dry weather. Where it is mixed with sand, it forms a fertile loam;
and hence, where the sand of the subjacent plastic clay is easily
accessible, it may readily be improved by admixture. Repeated
dressings of London manure convert it into rich meadow land, and
even where this cannot be obtained, the difficulty and expense of
arable culture have caused a very large portion of it to be retained
in pasture. That which is under culture is said to be too strong for
turnips and barley, but to grow excellent crops of wheat and beans.
4°. Plastic Clay. 300 to 400 ft. Alternating beds of clay and
sand, of various colours and thick-
nesses. Some of the beds of clay
are pure white, and so fine as to be
used for making pipes.
ExtENT.-This formation surrounds the London clay with an
indented, generally low, and flat belt, of varying breadth, occupy-
ing a large space in Hampshire and Dorset, in Essex, Suffolk, and
Norfolk,-stretching along the northern part of Kent and Surrey,
and throwing out arms into Berks, Buckingham, and Hertford.
Sorl.—The soil is very various, the alternate beds of sand and
clay of different qualities producing soils of the most unlike qua-
lity often within very short distances. The greatest portion of this
tract is in arable culture, but extensive heaths and wastes rest up-
on it in Berks, Hampshire, and Dorset. ſº
In Norfolk and Suffolk, where the lower beds of this sand rest
upon chalk, the soil is readily changed, by an admixture with this
chalk, into a good sandy loam, which will yield large crops of tur-
mips, barley, and wheat, instead of the heath and bent, its sole ori-
ginal produce. This chalking is generally repeated once in eight
years, at an expense of 50s, an acre. In Hampshire and Berk-
shire, the same method is adopted with great success, and the rich
crops now reaped from Hounslow Heath are the result of this me-
thod of improvement.
II. The SECONDARY STRATA—contain no animal remains which
can be identified with existing species. Those which are found in
them are nearly all different from those which occur either in the
tertiary above or the primary strata below.
SOIL OF THE UPPER AND LOWER CHALKS. 459
A.—CRETACEOUS SYSTEM.
5°. Chalk. 600 ft. The upper part softer, and con-
taining layers of flints, with many
marine remains. Below, the chalk
is harder, and towards the bottom
passes into beds of marl—(chalk
marſ).
ExTENT.—The chalk occupies a very large area in the south-
eastern part of the island. It forms a broad band of from 15 to
25 miles in breadth, running north-east and south-west from the
extreme south-western part of Dorset, to the extreme north of
Norfolk, it there turns nearly at a right angle, into the centre
of Lincolnshire, where it is 10 to 15 miles in breadth, and thence
stretches into Yorkshire, in the south-eastern part of which county
it covers a large area, and about Flamborough Head attains a
breadth of 25 miles. In passing through Berkshire and Surrey,
it is partially interrupted by the plastic clay which it embraces on
every side; and hence, in following the outline of this formation
it encircles with a broad fringe the southern edges of Sussex and
Surrey and the northern borders of Kent.
Sorl.-The soils formed from the upper chalk are all more or
less mixed with flints, and they produce naturally a very short but
excellent sheep pasture. A great portion of this chalk-land in
Dorset, Wilts, and Berks has been occupied as a sheep-walk for
ages, though under proper cultivation it is said to be convertible
into good arable land, producing barley, turnips, wheat, and sain-
foin.” The lower chalk soils (chalk marl) consist of a deep, strong,
calcareous grey or white loam, very productive, and when mixed
with the green sand below it, they become still richer, more friable,
* It is an interesting as well as an important fact, that the chalk flints do not con-
sist of pure silica, but contain variable proportions of potash, lime, and alumina.
1. Thus Berzelius analysed two varieties of flint from Limhamn in Scona, (south of
Sweden), and found in 1000 parts of each, the following quantities of these substances:
Oxide of iron
Potash. Lime. and alumina,
Sound flint,.................................... 1 - 17 | 13 p
Do. do. knife, ........................... 1'34 5'74 I'2
Decomposed crumbling white surface of ) 3-2 3.2
the knife, ....... . . . . . . . . . . . . . . . . . . . . . . . . . .
So that the flint is neither incapable of being attacked by the roots of plants, nor
of yielding to them important inorganic food.
460 PRODUCTIVE SOIL OF THE UPPER GREEN-SAND.
and more productive of every kind of crop. They are better suited
for wheat than the soil of the upper chalk, but less adapted for
turnips.
The porous nature of the chalk renders the soil very dry, and
in many localities the only method of obtaining a sufficient supply
of water is by forming ponds to catch and retain the rain-water.
In Norfolk and Suffolk, on the Lincolnshire, and more recently
on the Yorkshire Wolds, great improvement has been effected by
dressing the chalk-soil with fresh chalk brought up from a con-
siderable depth below, and laid on at the rate of 50 to 80 cubic
yards per acre. The explanation of this procedure is to be found
in the fact above stated, that the lower chalk marls, without flints,
produce an excellent soil, fitted therefore, by admixture with the
poorer upper-chalk soils, of materially improving their quality. It is,
, therefore, only in localities where this lower chalk can be obtained,
that the above method of improvement can be with any material ad-
vantage adopted. This is proved by the practice at Sudbury, in
Suffolk, which rests upon the upper beds, where it is found to be
more profitable to import the lower chalk from Kent, to lay upon
these lands, than to dress them with any of the chalks (only up-
per beds) which are immediately within their reach.*
69. Green Sand. 500 ft. The upper beds consist of layers
a Upper, 100. of a greenish sand or sand-stone,
b Gault, 150. often chalky. The gault is a solid
c Lower, 250. compact mass of an impervious blue
clay, sometimes marly. The lower
green sand contains a series of
ochrey resting on a series of green-
ish Sandy strata. The whole of
these beds are in many places full
of fossils. *
ExTENT.—The Green Sand forms a marrow border round the
whole of the northern and western edge of the chalk, except in
Yorkshire, where it has not as yet been discovered at the surface
over any extent of country. It skirts also the southern edge of the
chalk in Surrey and Kent, and its eastern boundary in Iſampshire,
where it attains a breadth of eight or ten miles. It forms likewise
the southern portion of the Isle of Wight.
* A rigorous chemical analysis of characteristic specimens of these two chalks might
lead to intercsting results.
SOIL OF THE PRODUCTIVE UPPER GREEN-SAND. 4.61
Soil.-The upper beds, which are the greenest and most chalky,
form an open friable soil, easily worked, and of the most produc-
tive character. It consists in general of an exceedingly fine sand,
mixed with more or less of clay and calcareous matter (see analy-
sis, p. 446), coloured by greenish grains. It is rich and produc-
tive of every species of crop, and the peculiar richness of this soil
has been remarked not only in England but also in the United
States of North America. In some parts of Bedfordshire the soils
of this formation form the most productive garden lands in the
kingdom. In other localities, again, where the soil is formed from
layers of black or of white silvery sand, it produces naturally no-
thing but heath.
The impervious gault clay forms in Cambridge and Hunting-
dom “a thin, cold clay soil, which, when wet, becomes as sticky as
glue, is most expensive to cultivate as arable land, and maturally
produces a poor, coarse pasture.” Much of this tract, though un-
enclosed, is in arable culture, under two grain crops, (wheat and
beams generally), followed by a naked fallow—the enclosed parts
are chiefly in pasture, and yield a rich herbage.
The strip of gault clay land which skirts the foot of the chalk
hills in Kent, Surrey, and Sussex, is distinguished by the fine oak
trees which grow upon it with great luxuriance.
The lower green-sand presents itself over a comparatively small
surface, is in some localities (Sussex) laden with iron ochre, and is
there naturally unproductive.
B.—OOLITIC SYSTEM.
7°. Wealdem. 950 ft. The upper part consists of a fresh
a Weald Clay, 300. water deposit of brown, blue, or
b Hastings Sand, 400. fawn-coloured clay, often marly and
c Purbeck lime-stone, 250. almost always close and impervious
to water. Beneath this are the iron
or ochrey Hastings sands, which
again rest upon the Purbeck beds
of alternate fresh water lime-stones
and marls.
ExTENT.-The Wealden rocks appear at the surface only in
Sussex and Kent, of which they form the entire central portion,
to an extent of upwards of 100 square miles.
Sorl.-The soil formed from the Weald clay is fine grained
and unctuous—often pale coloured, and containing much fine
462 SOIL OF THE WEALDEN AND UPPER, OOLITE ROCKS.
grained siliceous sand. It forms a paste which dries and hardens
almost like a brick, so that the roots of plants cannot penetrate it.
After lying long in clods in the Sunit even rings like earthen ware
when struck with a hard substance. From the expense of culti-
vating such land, much of it is in wood (Tilgate Forest), and some
in poor wet pasture. On the whole of this tract, therefore, there
is much room for improvement, and especially for a skilful thorough
drainage. When drained it produces a superior sample of wheat,
as well as excellent turnips and mangel wurtzel,-and this pro-
duce has been raised by draining alone from two quarters up to four
and five quarters an acre.
The Hastings sands produce a poor brown Sandy loam, which
naturally yield only heath and brush-wood. Much of this soil is
in pasture, but, under proper cultivation, it yields good crops of
all kinds. Where the ruins of the underlying Purbeck marls are
intermixed with it, the soil is of a superior quality.
89. Upper Oolite, 600 ft. The upper part of this formation
a Portland beds, 100. consists of the oolite” limestones and
b Kimmeridge Clay, 500. calcareous sand-stones long work-
ed at Portland—the lower of the
blue slaty or greyish, often calca-
Teous and bituminous, beds of the
Kimmeridge clay.
ExTENT.—The upper Oolite runs north-east along the northern
edge of the green sand, from the western extremity of Dorset to
the extreme north of Norfolk. It is in general only 2 or 3 miles,
but in a few places expands to 6 or 8 miles in breadth. It ap-
pears again on the western edge of the green sand in Lincolnshire,
and in Yorkshire forms a strip 5 or 6 miles in breadth, which
crosses the country from Helmsley to Filey Bay. In the Isle of
Portland also it is found, and it stretches in a narrow band along
part of the south coast of Dorset.
Soil,—The soil from the Portland rocks, in consequence of the
prevalence of siliceous and the absence of clayey matter, produces
naturally, or when laid down to grass, only a poor and benty her-
bage. Its loose and sandy mature makes it also very cheap to
work, and hence it is chiefly in arable culture. It is easily affect-
ed by drought, but in damp seasons it produces abundant crops—
especially in those parts where the soil is naturally mixed with the
* So named because they consist of Small egg-shaped granules like the roe of a fish.
SOIL OF THE WEALDEN AND UPPER OOLITE ROCKS. 463
detritus of the overlying Hastings sand, and of the calcareous
Purbeck beds.
The Kimmeridge clay forms a tough, greyish, impervious, often,
however, very calcareous soil and subsoil. From the difficulty of
working it, much of the surface over which this formation extends
is laid down to grass, and the old pasture land affords excellent
herbage. The celebrated pasture lands of the vale of North Wilts
rest partly on this clay. The relative thicknesses of the Portland
beds and the Kimmeridge clay will readily account for the fact of
this clay being spread over by far the greatest part of the area oc-
cupied by this formation. In Yorkshire, a clay of a great thickness
is the only member of this series that has hitherto been observed.
On this, as well as on the subjacent Oxford clay, the judicious in-
vestment of capital in skilful drainage would produce a much
greater annual breadth and return of corn.
9°. Middle Oolite. 500 ft. The uppermost bed in this for-
Upper Calcareous Grit, mation is a sand-stone containing
Coral Rag,
Calcareous Grit,
100. a considerable quantity of lime—
next is a coralline lime-stone (coral
Oxford Clay, rag) resting upon other sand-stones
Kelloways Rock, | 400 which contain much lime in their
Blue Clay. upper and little or none in their
lower beds. Below these is an enor-
mous deposit of adhesive tenacious
dark blue clay frequently calcare-
ous and bituminous, and towards
the lower part containing irregular
beds of sand-stones and lime-stones
(Kelloways rock) beneath which the
clay again recurs.
ExTENT.—The middle runs along the edge of the upper oolite
on the north and west—accompanying it from the extremity of
Dorset into Wilts, Oxford, Huntingdom, Lincolnshire, and York-
shire. Until it reaches Huntingdon, it rarely exceeds 6 or 8
miles in width, but in this county and in Lincoln it expands to a
width of nearly 20 miles. In Yorkshire it nearly surrounds the
upper oolite, and on the northern border of the latter formation
attains a width from north to south of 6 or 8 miles.
SoLL.—The higher beds of both the upper and lower calcareous
grits produce good land. They contain lime intermingled with
the other materials of the siliceous sand-stone. The upper calca-
464 IMPERWIOUS SOIL OF THE OXFORD CLAY.
reous grits are no doubt improved by their proximity to the Kim-
meridge clay above them, while the lower calcareous grit is in like
manner benefited by the lime of the super-incumbent coral rag.
The under beds of both groups are the more gritty, and form a
poor, barren, almost worthless soil, much of which in Yorkshire is
still unreclaimed. Upon the hills of the coral rag itself occurs the
best pasture which is met with in that part of the North Riding of
Yorkshire through which this formation extends.
The Oxford clay, which is by far the most important member of
this formation, and forms the surface over by far the largest por-
tion of the area occupied by it—produces a close, heavy, compact
clay soil, difficult to work, and which is one of the most expensive
of all the clays to cultivate. This is especially the case in Bedford,
Huntingdon, Northampton, and Lincoln, in which counties, never-
theless, a considerable extent of it is under plough. In Wilts, Ox-
ford, and Gloucester, it is chiefly in pasture, and as over these dis-
tricts it assumes the character of a clayey loam, the herbage is
thick and luxuriant.
The impervious nature of this clay has caused the stagnation of
water upon its lower-lying portions, the consequent accumulation
of vegetable matter, and the formation of bogs. The extensive
fems of Lincoln, Northampton, Huntingdon, Cambridge, and Nor-
folk, rest upon the Oxford clay. This tract of fenny country is
70 miles in length, and about 10 in average breadth. When
drained and covered with the clay from beneath, it is converted
into a most productive soil. In Lincolnshire, there are about a
million acres of fen, which have their drainage into the Wash,
about 50,000 of which are at present ir-reclaimable, on account of
the state of the outlet.
In the neighbourhood of the sandstones and limestones of the
Kelloways rock, the clay becomes more loamy and less difficult to
work.
Both in Yorkshire and in the southern districts, the Oxford clay
is found to favour the growth of the oak, and hence it is often dis-
tinguished by the name of the oak-tree clay.
10°. #;" | 600 ft. Thin, impure, rubbly beds of
Oolite. shelly limestone form the upper
& Cornbrash, 30. part of this series. These rest up-
b Forest Marble, 50. on alternate beds of oolitic shelly
ARABLE LANDS OF THE OOLITE. 465
c Bradford Clay, 50 lime-stone and sand-stone, more or
d Bath Oolite, 130 less calcareous, having partings of
e Fuller's Earth, 140 clay ; these again upon beds of
f Inferior Oolite, 200 blue marly clay, immediately un-
g Calcareous Sand, der which are the thick beds of the
light-coloured oolite limestone of
Bath. Beneath these follow other
beds of blue clay, with Fuller's
earth, based upon another oolitic
lime-stone, which is followed by
slightly calcareous Sands.
ExTENT.—This formation commences also at the south-western
extremity of Dorset, and runs north-east, swelling out here and
there, and in Gloucester, Oxford, and Northampton attaining a
width of 15 to 20 miles. It occupies nearly the whole of these
three counties, covers almost the entire area of Rutland, a large
portion of the north-east of Leicester, and then, in a narrow strip
stretches north through Lincoln, and disappears at the Humber.
It appears again in the North Riding of Yorkshire, skirting the
outer edge of the middle oolite, on the north of which it attains a
breadth of 15 miles, and stretches across, with little interruption,
from near Thirsk to the north sea. A small patch of it appears
farther north, on the south-eastern coast of Sutherland, on the
east and south of the Isle of Skye, and near the extremity of Can-
tyre in Argyleshire, where it contains some beds of workable coal.
Soil.—It will be understood, from what has been already stated
in reference to other formations, that one which contains so many
different rocks, as this does, must also present many diversities of
soil. Where the upper beds come to the surface, the clay-partings
give the character to the soil—forming a calcareous clay, which,
when dry or drained, is of good quality. In other places they form
a close adhesive clay, which is naturally almost sterile. The Bath
oolite weathers and crumbles readily. The soil upon it is thin,
loose, and dry. The rock is full of vertical fissures, which carry
off the water and drain its surface. When free from fragments of
the rock, the soil is often close and impervious, and, though of a
brown colour, deep, and apparently of good quality, it is really
of little value in its natural state—being what farmers call dead
and sleepy. Most of this land, however, is in arable cultivation.
G O'
5
466 OLID PASTURES OF THE LIAS.
The heavy soils, which rest on the clay containing Fuller's earth,
are chiefly in pasture.
The inferior oolite varies much in its character, containing, in
some places, much lime-stone, while in others, as in Yorkshire, it
forms a thick mass of sand-stones and clays, with occasional thin
beds of coal. In Gloucester, Oxford, Northampton, and Rutland,
these lower beds form a tract of land about 12 miles in width. The
soil is generally soft, Sandy, micaceous, of a brown colour, and of
a good fertile quality. It is deep, contains many fragments of the
subjacent rock, is porous and easily worked. Where the sand-
stones prevail it is of inferior quality. In these counties it is prin-
cipally enclosed, and in arable culture, the sides of the oolite hills
and the clayey portions being in pasture. In Yorkshire, much of
the unproductive moor land of the North Riding rests upon this
formation. A considerable proportion of the arable land in the
county of Sutherland rests on the lower oolite rocks which occur
on its south-east coast. The debris of these rocks has formed a
gravelly and in some places a loamy soil, which, when well limed,
produces heavy crops of turnips.
11°. Lias. 500 to 1000 ft. This great deposit consists chiefly
of an accumulation of beds of blue
clay, more or less indurated—in-
terrupted in various places by beds
of marl, and of blue, more or less
earthy, lime-stones, which especi-
ally abound in the lower part of
the series. The whole is full of
shells, and of the remains of large
extinct animals.
ExTENT.--Wherever the lower oolites are to be traced in Eng-
land, the lias is seen coming up to the surface on its northern or
western edge, pursuing an exceedingly tortuous north-eastern
course, throwing out in its course many arms (outliers), and va-
rying in breadth from 2 to 6 or 10 miles. It may be traced from
the mouth of the Tees, in Yorkshire, to Lyme Regis, in Dorset,
the continuity being broken only by the coal field of Somerset. In
Scotland and Ireland only very small patches of this formation
have yet been detected.
SOIL.-Throughout the whole of this formation the soil consists
of a blue clay, more or less Sándy, calcareous, and tenacious.
UPPER NIEW RED SAND-STON E. 467
Where the lime or sand prevails the soil is more open, and be-
comes a loam ; where these are less abundant, it is often a cold,
blue, unproductive wet clay. This latter, indeed, may be given as
the natural character of the entire formation. Where it rests up-
on a gravelly or open subsoil, or contains a large quantity of ve-
getable matter, it may be cultivated to advantage, and it is found
especially to produce good herbage. In all situations it is an ex-
pensive soil to work, and hence by far the greater portion of itisin old
pasture. The celebrated dairy districts of Somerset, Gloucester,
Warwick, and Leicester rest for the most part on the lias, as does
also much of the best grazing and pasture land in Nottingham and
Yorkshire. Through the long lapse of time an artificial soil has
been produced on the undisturbed surface of these clay districts,
which is peculiarly propitious to the growth of grass. With skil-
ful drainage and judicious culture, it is capable of producing
heavy crops of wheat.
C.—UPPER NEW RED SAND-STONE OR TRIASSIC SYSTEM.
This system consists of an upper sand-stone, an intermediate
limestone, (the muschelkalk,) and a lower sand-stone. The lime-
stone is not found in the British Islands, and it is still doubtful if
either of the sand-stones which lie immediately above it are deve-
loped to any extent in Great Britain.
The distinction between the red sand-stones of this system and
of that which lies immediately below it, is very importantin a geo-
logical point of view. The trias is the lowest system of the se–
condary rocks, and contains the remains of saurian and other
animals, which are entirely distinct from those which are found in
the rock immediately below them. The agricultural characters
of the sandstones of the two systems—the mature of the soils formed
from them are so similar—that they may with propriety be treated
of together. In Great Britain, indeed, we cannot as yet do other-
wise, as the limits of our triassic sandstones have not yet been de-
termined, and they are not, therefore, separately coloured in our
geological maps.
III.--THE PRIMARY STRATA.—In these rocks the remains of
animals which occur, present characters entirely different from those
468 FERTILE MARLS OF THE NEW RED SANDSTONE.
by which the upper rocks are distinguished. These remains all
belong to extinct species, the greater part to extinct genera and
families, and are frequently so unlike to existing races, that it is
often difficult to trace any marked resemblance between the ani-
mals which now live and those which inhabited the waters of the
ancient periods in which these primary strata were deposited.
D.—LOWER NEW RED SANDSTONE OR PERMIAN SystEM.
120. Upper and J.ower The upper and lower new red
sºc & & t &W-
New Red Sand- 500 ft. sandstones consist of alternate lay
ers of sand, sandstones, and marls
St0716s. sometimes colourless, but gene-
rally of a red colour–sprinkled
in the upper series with frequent
green spots. The lower beds are
sometimes full of rolled pebbles
forming a conglomerate. Few of
the sandstones of this formation
are sufficiently hard to form build-
ing stones—many of the layers
consist of loose friable sand, and
the marls universally decay and
crumble to a fine red powder, un-
der the influence of the weather.
ExTENT.—The new red sand-stone extends over a larger por-
tion of the surface of England than any other formation. It
commences at Torbay, in the south of Devon, runs north-east into
Somersetshire; from Bristol ascends both sides of the Severn, ac-
companies it into the vale of Gloucester, stretches along the base
of the Malvern hills, and north of the city of Worcester expands
into a gently undulating plain, nearly 80 miles in width at its
broadest part, comprehending nearly the whole of the counties of
Warwick and Stafford and the greater part of that of Leicester.
From this central plain it parts into two divisions. One of these
runs west over the whole of Cheshire—(in which county it contains
salt springs and mines of rock salt)—the western part of Flint,
and on the south-west surrounds the county of Lancashire. It is
there interrupted by the rising of the older rocks in Westmorland,
but reappears in the eastern corner of this county, runs north-
west through Cumberland, forming the plain of Carlisle—and
thence round and across the Solway Frith till it finally disappears
about 20 miles north of Dumfries. The other arm, proceeding
FERTILE MARLS OF THE NIEW RED SAND-STONE. 469
from the towns of Derby and Nottingham, runs due north through
Nottingham and the centre of Yorkshire, skirting the outer edge
of the lias, and finally disappears in the county of Durham to the
north of the river Tees. The southern portion of this arm has a
width of 20 to 30 miles, until it reaches the neighbourhood of
Knaresborough, where it suddenly contracts to 6 or 8, and does
not again expand to more than 10 or 12 miles.
North of Dumfries-shire these rocks are not known to occur in
our island. In the north-east of Ireland they form a strip of land
a few miles in width, running from Lough Foyle to Lough Neagh,
and thence, with slight interruptions, to the south of Belfast.
SoHL.—These rocks, by their decay, almost always produce a
deep red soil. Where the red clay and marl predominate, this
soil is a red clay or clayey loam of the richest quality, capable of
producing almost every crop, and remarkable therefore for its fer-
tility. It is chiefly in arable culture, because of the comparative
ease with which it is worked ; but the meadows are rich, as in the
Cheshire dairy districts, and produce good herbage. Where the
rocks are more sandy, and contain few marly bands, the soil pro-
duced is poorer, yet generally forms a good sandy loam, suitable
for turnips and barley.
In Devonshire, as in the vale of Taunton and other localities,
where the lias and the red sandstone adjoin each other, or run side
by side, the difference in the fertility and general productiveness
of the two tracts is very striking. On the former, as already ob-
served, good old grass land is seen, but the arable land on the
latter produces the richest and most luxuriant crops to be seen on
any soil in the kingdom. In this county, and in Somerset, the
only manure it seems to require is lime, on every repetition of
which it is said to produce increased crops. The same remarks,
as to its comparative fertility, apply with more or less force to the
whole of the large area occupied by this formation in our island—
wherever the soil has been chiefly formed by the decomposition of
the rock on which it rests. In some localities (Dumfriesshire)
the micaceous marly rock is dug up, and, after being crumbled by
exposure to a winter's frost, is laid on with advantage as a top-
dressing to grass and other lands.
In the South of Lancashire, and along its western coast, and on
470 POOR. THIN SOILS OF THE MAGNESIAN LIMESTONE.
the shores of the Solway, in Dumfries-shire, a great breadth of
this formation is covered with peat.
139. Magnesian - The magnesian limestone is ge-
100 to 500 f#. nerally of a yellow, sometimes of
a gray colour. In the upper part
it occasionally presents itself in
thin beds, which crumble readily
when exposed to the air. In some
Limestone.
places, also, it assumes a marly
character, forming masses which
are soft and friable. In general,
however, it is in thick beds, hard
and compact enough to be used
for a building stone or for mending
the roads. The quantity of car-
bonate of magnesia it contains
varies from 1 to 45 per cent. It
is in the north of England gene-
rally traversed by vertical fissures
which render the surface dry, and
make water in many places difficult
to be obtained.
ExTENT.-The magnesian limestone stretches in an almost un-
broken line nearly due north from the city of Nottingham to the
mouth of the river Tyne. It is in general only a few miles in
width, its principal expansion being in the county of Durham,
where it attains af breadth of 8 or 10 miles.
Soni...—It forms, for the most part, a hilly country, covered by
a reddish brown soil—often thin, light, and poor, where it rests
immediately on the native rock—producing indifferent herbage
when laid down to grass, but under skilful management capable
of yielding average crops of turnips and barley. In the eastern
part of Durham tracts of the poorest land in the county rest upon
this rock, but as this formation is for the most part covered with
deep accumulations of transported materials—the quality of the soil
is in very many places more dependant upon the character of this
superficial covering than upon the nature of the rock beneath.
During the slow degradation of this rock, the rains gradually
wash out great part of the magnesia it contains, so that it seldom
happens that the soil formed from it, though resting on the parent
rock, contains so much magnesia as to be necessarily hurtful to ve-
getation.
SANDY AND COLD CLAY SOILS OF THE COAL MEASURES. 471
E.—CARBONIFEROUS SYSTEM.
14°. Coal Measures. 300 fº. Consisting of alternate beds of
- indurated bluish-black clay (coal
shale or blaes), of siliceous Sand-
stone generally grey in colour and
containing imbedded plants, and of
coal of various qualities and degrees
of thickness. Beds of lime-stone
rarely appear in this formation till
we approach the lowest part of the
series.
ExTENT.—Fortunately for the mineral resources of Great Bri-
tain, the coal measures occupy a large area in our island. Most
of the districts in which they occur are so well known as to require
only to be indicated. The South Welsh coal-field occupies the
south of Pembroke, nearly the whole of Glamorgan, and part of
Monmouthshire. In the north of Somerset are the coal measures
of the Bristol field, which stretch also across the Severn into the
forest of Dean. In the middle of the central plain of the new red
sand-stone lie the coal-fields of Ashby-de-la-Zouch, of Coventry,
and Dudley, and on its western borders are those of Shropshire,
Denbigh, and Flint (North Wales). To the north of this plain
extends on the right the Yorkshire coal-field from Nottingham to
Leeds, while on the left is the sumall coal-field of Newcastle-under-
line, and the broader Lancashire field which crosses the country
from near Liverpool to Manchester. Almost the entire eastern
half of the county of Durham, and of the low country of Northum-
berland, is covered with these measures—but the largest area
covered by these rocks is in that part of the low country of Scot-
land, which extends in a north-easterly direction from the west
coast of Ayrshire to the eastern coast of Fife. They there form a
broad band, having an average breadth of 30 miles, interrupted
often by trap or green-stone rocks, yet lying immediately beneath
the loose superficial matter, over the largest portion of this exten-
sive district. They do not occur further north in our island. In
Ireland they form a tract of limited extent on the northern borders
of the county of Monaghan—cover a much larger area in the south-
east, in Kilkenny and Queen's Counties—and, towards the mouth
of the Shannon, spread on either bank over a large portion of the
counties of Clare, Kerry, and Limerick.
Sorl.-The soil produced by the degradation of the sand-stones
472 MOORLAND'S OF THE MILLSTONE GRIT.
and shales of the coal formation is universally of an inferior quality
when unimproved. The black shales or schists form alone a cold,
stiff, ungrateful clay. The sand-stones alone form thin, unproductive
soils, or barren—almost naked—heaths. Where the clay and sand
are mixed a looser soil is produced, which, by heavy liming, by drain-
ing, and by skilful culture, may be rendered moderately productive.
In the west of the counties of Durham and Northumberland, and
on the higher edges of most of our coal-fields, there are extensive
tracts of this comparatively unproductive sand-stone surface, and
thousands of acres of the improvable cold clays of the shale beds.
These latter soils appear very unpromising, and can only be ren-
dered remuneratively productive in skilful hands. They present
one of those cases on which the active exertions of zealous agricul-
turists, and the efforts of the friends of agriculture, might be ex-
pended with the promise of much benefit to the country.
15°. Millstone Grit. 600 ft. This formation consists in some
localities of an entire mass of coarse
sand-stone, of great thickness—in
others of alternations of sand-stones
and shales, resembling those of the
coal-measures—while in others,
again, lime-stones more or less si-
liceous, are interposed among the
sand-stones and shales.
ExTENT.-A large portion of Devonshire is covered with these
rocks—they form also the high land which skirts to the north and
west the coal-measures of Yorkshire, Lancashire, and Durham,
and over which is the first ascent to the chain of mountains that
runs northward through these three counties. In Scotland, they
have not been observed to lie immediately beneath any part of the
surface. In the north of Ireland they cover a considerable area,
stretching across the county of Leitrim between Sligo and Lough
Erne.
Soil.--The soils resting upon, and formed from, these rocks
are generally of a very inferior description. Where the sand-stones
come to the surface, miles of naked rock appear; other tracts bear
only heath, or, where the rains have only a partial outlet, accumu-
lations of peat. The shale-beds, like those of the coal-measures,
afford a cold, unproductive, yet not unimprovable soil—it is only
where lime-stones occur among them that patches of healthy ver–
l -
SWEET PASTURES OF THE MOUNTAIN LIME-STONE. 473
dure are seen, and fields which are readily susceptible of profitable
arable culture.
It is true, therefore, of this formation in general, that the high
grounds form extensive tracts of moor-land. In the lower districts
of country over which it extends, the soil generally rests not on
the rocks themselves, but on superficial accumulations of transport-
ed materials, which are often of such a kind as to form a soil either
productive in itself or capable of being rendered so by skilful cul-
tivation.
16°. Mountain
Lime-stone.
f In this formation, as its name
} 800 fČ. implies, lime-stone is the predomi-
nating rock. It is generally hard,
blue, and more or less full of orga-
nic remains. In some localities, it
occurs in beds of great thickness—
(Derby and Yorkshire), while in
others—(Northumberland)—it is
divided into numerous layers, with
interposed sand-stones and beds of
shale, and occasional thin seams of
coal.
ExTENT.-The greater portion of the counties of Derby and
Northumberland is covered by this formation, and from the lat-
ter county it stretches along the west of Durham through York-
shire as far as Preston, in Lancashire—forming the mountains of
the well-known Pennine chain, which throw out spurs to the east
and west, and thus present on the map an irregular outline and
varying breadth of country. In Scotland these rocks cover only
a small portion of the county of Berwick, immediately on the Bor-
der; but in Ireland almost the entire central part, forming up-
wards of one-half of the whole island,--is occupied by the moun-
tain lime-stone formation.
Sort.-From the slowness with which this rock decays, many
parts of it are quite naked: in others it is covered with a thin light
porous soil of a brown colour, which maturally produces a short
but thick and sweet herbage. Much of the mountain lime-stone
country, therefore, is in natural pasture.
Where the lime-stones are mixed or interstratified with shale
beds, which decay more easily, a deeper soil is found, especially in
the hollows and towards the bottom of the valleys. These are of.
ten stiff and maturally cold, but when well drained and limed pro-
474 RICH WEIEAT LANDS OF THE OLD RED SAND-STONE,
duce excellent crops of every kind. In Northumberland, much
of the mountain lime-stone country is still in moor-land, but the
excellence of Border farming is gradually rescuing one improv-
able spot after another from the hitherto unproductive waste.” In
Yorkshire and Devonshire also improvements are more or less ex-
tensively in progress, though in all these districts there are large
tracts which it will be almost impossible profitably to reclaim.
F.—OLD RED SAND-STONE OR DEvoNIAN SystEM.
17°. Old Red sand- 500 to The upper part of this formation
- Sü07le. 10,000 ft, consists of red sand-stones and con-
Old Red Conglomerate. glomerates (indurated Sandy gra-
Corn-stone and Marls. vel), the middle of spotted, red,
Tile-stone. and green, clayey marls, with irre-
gular layers of hard, often impure
and siliceous, limestones, (corn-
stones), likewise mottled, and the
lowest of thin hard beds of silice-
ous sandstones, sometimes calca-
reous, mottled, and splitting rea-
dily into thin flags (tile-stones).
ExTENT.-Though occasionally of vast thickness, the old red
Sandstone does not occupy a very extensive area in our island. In
the south of Pembroke it forms a tract of land on either side of
the coal-field—surrounds on the north and east the coal-field of
Glamorgan, and immediately north of this county covers a large
area comprehending the greater portion of Brecknock and Here-
* ſ
ford, and part of Monmouth. A small patch occurs in the Isle of
Anglesey, and in the north-eastern corner of Westmorland—but
it does not again present itself till we reach the western flank of
the Cheviot Hills. It there appears on either side of the Tweed,
and extends over a portion of Berwick and Roxburgh to the base
of the Lammermuirs. On the north of the same hills it again
presents itself, and, stretching to the South-west, forms a conside-
rable tract of country in the counties of Haddington and Lanark.
On the north of the great Scottish coal-field it forms a broadband,
which runs completely across the island in a south-western direc-
tion along the foot of the Grampians, from Stonehaven to the
irth O ide, is to be discovered in the Island of Arran, and a
Firth of Clyde, is to be d d in the Island of Arran, and at
the Mull of Cantire, and—along the prolongation of the same
line——at various places on the northern flank of the great moun-
*
RICH WHEAT LANDS OF THE OLD RED SAND-STONE, 475
tain lime-stone formation of Ireland, and especially in the coun-
ties of Tyrone, Fermanagh, and Monaghan. In the north of
Scotland it lines either shore of the Moray Firth, skirts the coast
towards Caithness, where it covers nearly the whole county, and
still further north forms the entire surface of the Shetland Islands.
Along the north-western coast, it also appears in detached patches
till we reach the southern extremity of the Isle of Skye.
In Ireland, it occurs also on the extreme southern edge of the
mountain lime-stone in Waterford and the neighbouring counties
—and in the middle of this formation on the upper waters of the
Shannon, in the south of Mayo, and round the base of the slate
mountains of Tipperary.
Sorl.—The soil on the old red sand-stone admits of very nearly
the same variations as on the new red sand-stone formation.
Where it is formed, as in parts of Pembroke, from the upper sand-
stones and conglomerates, it is either worthless or it produces a
poor hungry soil, “which eats all the manure, and drinks all the
water.” These upper rocks are sometimes so siliceous as to be al-
most destitute both of lime and clay—in such cases, the soils they
form appear almost valueless, though they are not beyond the
skill of the scientific farmer.
The marly beds and lime-stones of the second division yield
warm and rich soils—such as the mellow lands of Herefordshire,
and the best in Brecknock and Pembrokeshires. The soil in every
district varies according as the partings of marl are more or less
numerous. These easily crumble, and where they abound form a
rich stiff wheat soil—like that of East Lothian and parts of Ber-
wickshire; where they are less frequent the soil is lighter and
produces excellent turnips and barley. Where the subsoil is po-
rous, this land is peculiarly favourable to the growth of fruit trees.”
The apple and the pear are largely grown in Hereford and the
neighbouring counties, long celebrated for the cyder and perry
they produce.
* The most loamy of these red soils of Hereford afford the finest crops of wheat
and hops, and bear the most prolific apple and épar trees, whilst the whole region
(eminently in the heavier clayey tracts) is renowned for the production of the stur-
diest oaks, which so abound as to be styled the “weeds of Herefordshire.” Thus,
though this region contains no mines, the composition of its rocks is directly produc-
tive of its great agricultural wealth.-Murchison, Silurian System, I. p. 108.
/
476 HEATHIS ON THE TILE-STONES OF THE OLD RED SAND-STONE.
The tile-stones reach the surface only on the northern and west-
ern edges of this formation in England. In Ayrshire, in Lanark-
shire, in Ross-shire, and in Caithness, larger tracts of land rest on
these lower beds. In all these districts rich corn lands are pro-
duced from the rocks of the middle series. The fertility of Strath-
more in Perthshire, and of other valleys upon this formation, is
well known—Easter Ross and Moray have been called the gra-
mary of Scotland, and even in Caithness rich corn-bearing (oat)
lands are not unfrequent. Yet in the immediate neighbourhood
of these rich lands, tracts of tile-stone country occur, which are
either covered with useless bog (Ayrshire and Lanarkshire), or
with a thin covering of soil which is usually considered to be al-
most incapable of profitable culture. In this latter condition is
the moor of Beauly on the Cromarty Firth, an area of 50 square
miles, which, till within a few years, lay as an unclaimed common
—and in the county of Caithness still more extensive tracts.
In South Devon and part of Cornwall a very fertile district rests
also on the middle series of these rocks. Instead of red sand-
stones, however, the country there consists of green slates, more
or less siliceous, of sand-stones, and of lime-stones, which by their
decay have formed a very productive soil. These rocks in the
above counties abound in fossil remains, and it is chiefly for this
reason that the term Devonian has been applied to the rocks of the
old red sand-stone formation.
The limestones of this formation vary in composition. Those
of Devonshire, which are of great thickness, are often very pure,
but the thin yellowish beds which occur among the red sands and
clays of this formation in other parts of the country frequently
contain much magnesia.
Thus four samples of limestone collected from as many different
thin beds on the estate of Langton, near Dunse, in Berwickshire,
were found in my laboratory to consist of,
No. 1. No. 2. No. 3. No. 4.
Carbonate of lime, .............................. 43-64 47.00 39-00 43'81
Carbonate of magnesia, ........................ 33° 49 38'04 30.25 30-53
Oxide of iron and alumina, ... ..... ........... ] '06 I '99 1 - 39 3-57
Insoluble siliceous matter,' ...... .............. 21.50 12-07 29-27 13:00
99-60 100'00 90-01 ] 00:00
These limestones are at present seldom burned,—should they
HEATHS ON THE TILE-STONES OF THE OLD RED SAND-STONE. 477
ever be so, they must be applied sparingly to the land, owing to
the large proportion of magnesia they contain.
G.—SILURIAN SYSTEM.
18°. Upper Silurian. 3800 ft. The upper Ludlow rocks con-
l°. LUDLow ForMATION. sist of sand-stones containing more
a Upper Ludlow, or less lime and clay. These rest
b Aymestry limestone, 2000, upon hard, somewhat crystalline,
c Lower Ludlow, earthy lime-stones (Aymestry lime-
2°. WENLOCK FORMATION. stones). The lower Ludlow rocks
a Limestone, | 1800. are masses of shale more free from
b Shale, - lime and sand than the upper beds,
and, from the mode in which they
decay into mud, are locally known
by the name of “ mud-stones.”
The Wenlock or Dudley forma-
tion consists in the upper part of a
great thickness of lime-stone beds
often argillaceous, and abounding
in the remains of marine animals,
and in the lower part of thick beds
of a dull clayey shale—in its want
of cohesion, and in its mode of de-
cay, very much resembling the
mud-stones of Ludlow.
ExTENT.—The principal seat of these rocks in our island is in
the eastern counties of Wales, where they lie immediately beneath
the surface over the eastern half of Radnor, and the north of Mont-
gomery.
SOIL.-The prevailing character of the soils upon these forma-
tions is derived from the shales and mud-stones—and from the
earthy layers of the sandstones and limestones which decay more
readily than the purer masses of these rocks. The traveller is im-
mediately struck in passing from the rich red marls and clays of
the old red sandstone in Hereford, to the dark, almost black,
soils of the upper and lower Ludlow rocks in Radnor, not merely
by the change of colour, but by their obviously diminished value
and productiveness. The upper Ludlow is crossed by many ver-
tical cracks and fissures, and thus, though clayey, the soil which
rests upon it is generally dry, and susceptible of cultivation.
Not so the muddy soils of the lower Ludlow and Wenlock rocks.
They are generally more or less impervious to water, and being
47S MUDIDY SOILS OF THE LOWER LUIDLOW ROCKS.
subject to the drainage of the upper beds, form cold and compa-
ratively unmanageable tracts. It is only where the intermediate
limestones (Aymestry and Wenlock limestones) come to the sur-
face and mingle their debris with those of the upper and lower
rocks, that the stiff clays become capable of bearing excellent crops
of wheat. This fact, however, indicates the method by which the
whole of these cold wet clays might be greatly improved. By per-
fect artificial drainage and copious liming, the unproductive soils
of the lower Ludlow and of the Wenlock shales might be convert-
ed into wheat lands more or less rich and fertile. It unfortunately
happens, however, that in those districts of North and South Wales,
where the dark grey or black “ rotchy” land of the mud-stones pre-
vails, lime is often so scarce, or has to be brought from so great a
distance, as to render this means of improvement at present almost
unattainable.
19°. Lower Siluriam. 3700 ft. The Caradoc beds consist of thick
Caradoc Sandstones, 2500. layers of sand-stone of various co-
Llandeilo Flags, 1200. lours resting upon, and covered by,
and occasionally interstratified with
thin beds of impure lime-stone. The
Llandeilo flags which lie beneath
them consist of thin calcareous
strata, in some localities alternat-
ing with sand-stones and shales.
ExTENT.—These rocks form patches of land in Shropshire and
the north of Montgomery—and skirt the southern and eastern edge
of Caermarthen. None of the Silurian rocks have yet been shown
to extend over any large portion of either Scotland or Ireland.
Sonſ.—The Caradoc sand-stone, when free from lime, produces
only a naked surface or a barren heath. The Llandeilo flags form
a fertile and arable soil, as may be seen in the south of Caermar-
then, where they are best developed, and especially on the banks
of the Towey, which for many miles before it reaches the town of
Caermarthen runs over this formation.
In this formation, as in every other we have yet studied, the soil
changes immediately on the appearance of a new rock at the Sur-
face. The soil of the Wenlock shale is sometimes more sandy as
it approaches the Caradoc beds, and on favourable slopes forms
good arable land and sustains luxuriant woods; but where the Ca-
radoc sand-stones reach the surface, a wild heath or poor wood-land
MOUNTAINOUS COUNTRY OF THE SLATE ROCKS, 479
stretches over the country, until passing Över their edges we reach
the lime-containing soils of the Llandeilo flags, when fertile arable
lands and lofty trees again appear.”
20°. Upper § Lower These rocks, which are many
Cambrian thousand yards in thickness, con-
Rock sist chiefly of thin slates often hard
OC/ES.
and cleaving readily, like roofing
slates, occasionally intermingled
with sandy and thin lime-stone
beds. They contain few organic
I’CIll{llllS.
ExTENT.—These rocks cover the whole of Cornwall, part of
North and South Devon, the Western half of Wales, the entire
centre of the Isle of Man, and a large part of Westmorland and
South Cumberland. In Scotland, they form a band between 30
and 40 miles in width, which crosses the Island from the Mull of
Galloway to St Abb's Head. They form also a narrow strip of
land, which recrosses the Island along the upper edge of the old
red sand-stone from Stonehaven to the Isle of Bute, and, further
north, spreads over a considerable portion of Banffshire. In the
south-west of Ireland they attain a great breadth, are marrower at
Waterford, but form a broad band along the granite mountains
from that city to Dublin. They extend over a large portion of
the counties of Louth, Cavan, Monaghan, Armagh, and Down,
form a narrow band also along the coast of Antrim as far north
as the Giant's Causeway, and, in the interior of Ireland, reappear
in the mountainous district of Tipperary.
SOIL.-The predominance of slaty rocks in this formation im-
parts to the soils of the entire surface over which they extend one
common clayey character. They generally form elevated tracts
of country, as in Wales, Cumberland, Scotland, and Ireland,
where the rigours of the climate combine with the frequent thin-
mess and poverty of the soil to condemn extensive districts to worth-
less heath or to widely extended bogs. Yet the slate rocks them-
Selves, especially when they happen to be calcareous, are capable
of producing fertile soils. Such are found in the valleys, on the
hill sides, and by the margins of the lakes that are often met with
* Such a passage from one formation to another is exhibited in the diagrams in-
serted in pages 451 and 152.
480 HEATH AND BOGS ON THE GNEISS ROCKS,
in the slate districts. More extensive strips or bands of such pro-
ductive land occur also at lower levels, as in the north of Devon,
and in the south of Cornwall. In the latter county, the soils on
the hornblende slate (which lies near the bottom of the slate series)
are extremely fertile, exhibiting a striking contrast with those which
are formed from the neighbouring Serpentime rocks, that extend
over a large area immediately north of the Lizard (see p. 495).
The good effect of this admixture of the hornblende with the
common slate soils is chiefly owing to the large proportion of lime
which the hornblende contains. -
The slate rocks are indeed for the most part very poor in lime.
This is seen by the following table, which exhibits the proportion of
lime found by my friend and pupil Mr Norton in seven varieties
of the slate rocks collected in different parts of the counties of
Wigton and Kirkcudbright.
l. 2. 3. 4. 5. 6. 7.
9 0°26 l'98 0.25 0°22 — 0.19
Lime in state of carbonate per cent. ... 7°l
Lime in state of silicate, .......... ...... 0°24 0°62 0°30 1-09 0°43 0'50 —
Total lime per cent. .................. 7'43 0.88 2.28 1-34 0.65 0-50 0 19
The first and even the third of these rocks would form soils in
which lime would not be absolutely required to make crops grow.
In general, however, after the coldness and stiffness are removed
by thorough draining, a copious addition of lime is the first requi-
site to ensure fertility in the soils of our slate rocks.
The mode in which these rocks lie, or the degree of inclination
which the beds exhibit, exercises an important influence upon the
agricultural character of the soils that rest upon them. In the di-
agram inserted in p. 452, the rocks (A) represent the highly in-
clined, often nearly vertical, position, in which the slate rocks are
most frequently found. The soil formed from them must, there-
fore, rest on the thin edges of the beds. Thus it happens in some
localities that the rains carry down the soluble parts of the soil and
of the manure within the partings of the slates—and hence the
lands are hungry and unprofitable to work.
On the slopes of the clay slate hills of the Cambrian and Silurian
systems—flourish the vineyards of the middle Rhine, the Moselle,
and the Ahr.
IITATHS AND BOGS ON THE GNEISS ROCKS, 481
H.—MICA-SLATE AND GNEISS OR METAMORPHIC SYSTEMS.
21. Mica-Slate. The upper of these formations
Gneiss Rock. consists of thin undulating layers
of rock, composed chiefly of quartz
and mica, alternating occasionally
with green (chlorite) slates, com-
mon clay-slates, quartz rock and
hard crystalline lime-stones. The
gneiss is a hard and solid rock of
a similar nature, consisting of many
thin layers distinctly visible, but
firmly cemented, and as it were
half melted together.
ExTENT.—Two-thirds of Scotland, comprehending nearly the
whole country north and west of the Grampians, consist of these
rocks. In England there is only a small patch of mica slate about
Bolt Head and Start Point in South Devon, and a somewhat
larger in Anglesea; but in Ireland, nearly the whole of the coun-
ties of Donegal and Londonderry on the north, and a large por-
tion of Mayo, Commaught, and Galway, on the west, are covered
by rocks belonging to the mica slate system.
Sorls.-These rocks are, in general, harder still than those of
the Cambrian system, and still more impervious to water, when
not highly inclined. They crumble slowly, therefore, and imper-
fectly, and hence are covered with thin soils, on which, where
good natural drainage exists, a coarse herbage springs, and from
which an occasional crop of corn may be reaped—but on which,
where the water becomes stagnant, extensive heaths and bogs pre-
vail. That they contain, when perfectly decomposed and mellow-
ed, the materials of a fertile soil, is shown by the richness of many
little patches of land, that occur in the sheltered valleys of the High-
lands of Scotland, and by the margins of its many lakes. In gene-
ral, however, the mica-Slate and gneiss country is so elevated that
not only does an ungenial climate assist its natural unproductive-
mess, but the frequent rains and rapid flowing rivers bear down to
the bottoms of the valleys, or forward to the sea, much of the finer
matter produced by the decay of the rocks,—leaving only a poor,
thin, sandy soil behind. -- ^.
On these hard slate and gneiss rocks, extensive pine forests in
Sweden and Norway have long lived and died. In these countries
it is customary in many places to burn down the wood, to strew
II h
4.82 I'ERTILITY DEPEND ANT ON GEOLOGICAL STRUCTURE.
the ashes over the thin soil, to harrow in the seed—to reap thus
one or two barvests of rye, and to abandon it again to nature. A
grove of beech first springs up, which is supplanted by an after-
growth of pine, and finally disappears. -
Such is a general description of the nature and order of succes-
sion of the stratified rocks, as they occur in Great Britain and Ire-
land—of the relative areas over which they severally appear at the
surface—and of the kind of soils which they produce by their na-
tural decay. The consideration of the facts above stated,” shows
how very much the fertility of each district is dependant upon its
geological structure—how much a previous knowledge of that
structure is fitted to enlighten us in regard to the nature of the
soils to be expected in any district—to explain anomalies also in
regard to the unlike agricultural capabilities of soils apparently
similar—to indicate to the purchaser where good lands are to be
expected, and to the improver, whether the means of ameliorating
his soil by liming, by marling, or by other judicious admixture,
are likely to be within his reach, and in what direction they are to
be sought for. There still remain some important branches of
this subject to which I shall briefly draw your attention in the fol-
lowing lecture.
* For much of the practical information contained in this section, I have to ex-
press my obligations to the following works:—For the extreme southern counties, to
De La Beche’s Geological Report on Cornwall and Devon ; and to a paper by Sir
Charles Lemon, Bart., on the Agh'icultural Produce of Cornwall;-for Wales and the
Border counties, to Murchison's Silurian System :-for the Midland counties of Eng-
land, to Morton on Soils –for Yorkshire, to a paper by Sir John Johnston, Bart. in
the Journal of the Royal Agricultural Society ;-and for the Old Red Sand-stone of
the north of Scotland, to the work of Mr Miller on The Old Red Sand-stone. The
reader would read the above section with much greater profit if he were previously
to possess himself of Philips' Outline M.º, of the Geology of the British Islands,
LECTURE XV.
Composition of the granitic rocks and of their constituent minerals. Cause and mode
of their degradation. Qualities of the soils derived from them. Composition of the
trap rocks and the minerals of which they consist. Lime in the trap rocks. Their
extent in the British islands, and nature of the soils formed from them. Superficial
accumulations—their influence upon the character of the soils. Organic constitu-
ents, ultimate chemical constitution, and physical properties of soils.
IT has been stated in the preceding Lecture that the rocks
which present themselves at the surface of the earth are of two
kinds, distinguished by the terms stratified and unstratified. The
former crumble away, in general, more rapidly than the latter,
and form a variety of soils of which the agricultural characters
and capabilities have been shortly explained. The unstratified or
crystalline rocks form soils of so peculiar a character, and possess-
ing agricultural capabilities in general so different from those of
the stratified rocks which occur in the same neighbourhood; and
they, besides, cover so large and hitherto so unfruitful an area in
our island, as to entitle them to a separate and somewhat detailed
consideration.
§ 1. Composition of the Granitic Rocks, and of the minerals of
which they consist.
The name of Granite is given by mineralogists to a rock con-
sisting of a mixture more or less intimate of three simple minerals—
Quartz, Mica, and Felspar. When mica is wanting, and Hornblende
occurs in its stead, the rock is distinguished by the name of Sye-
nite. This mineralogical distinction is often neglected by the geo-
logist, who describes large tracts of country as covered by granitic
rocks, though there may be many hills or mountains of syenite.
In a geological sense, the distinction is often of little consequence;
in relation to agriculture, however, the distinction between a gra-
mite and a syenite is of considerable importance.
The minerals of which these rocks consist are mixed together
484 CON, POSITION OF GRANITE.
in very variable proportions. Sometimes the quartz predominates,
so as to constitute two-thirds or three-fourths of the whole rock,
sometimes both mica and quartz are present in such small quan-
tity as to form what is then called a felspar rock. The mica in
the granites rarely exceeds one-sixth of the whole, while the horn-
blende of the syenites sometimes forms nearly one-half of the entire
rock. These differences also are often overlooked by the geolo-
gist—though they necessarily produce important differences in the
composition and agricultural characters of the soils derived from
the crystalline rocks.
A few other minerals occur occasionally among the granitic
rocks, in sufficient quantity to affect the composition of the soils to
which they give rise. Among these, the different varieties of
tourmaline are in many places abundant. Thus the schoºl rock
of Cornwall consists of quartz and schorl (a variety of tourmaline),
while crystals of schorl are so frequently found in the granites of
Devon, Cornwall, and the Scilly Isles, as to be considered charac-
teristic of a very large portios of them (Dr Boase).
These rocks decay with very different degrees of rapidity, ac-
cording to the proportions in which the several minerals are pre-
sent in them, and to the peculiar state of hardness or aggregation
in which they happen to occur. Both the mode of their decay,
however, and the circumstances under which it takes place, as well.
as the character and composition of the soils formed from them,
are materially dependent upon the composition of the several mi-
nerals of which the rocks consist. This composition, therefore, it
will be necessary to exhibit,
1°. Quartz has already been described (p. 349), as a variety of
silica—the substance of flints, and of siliceous sands and sand-
stones. In granite, it often occurs in the form of rock crystal, but
is more frequently disseminated in small particles throughout the
rocky mass. It is hard enough to scratch glass.
2". Felspar is generally colourless, but is not unfrequently red-
dish or flesh-coloured. On the colour of the felspar they contain,
that of the granites most frequently depends. Several varieties of
this mineral are known to collectors. Besides the common felspar,
however, it is only necessary to specify Albite and Oligoclase, which
in appearance closely resemble felspar, take its place occasionally,
FELSPAR, ALBITE, AND MICA. 485
especially the latter,” in granite rocks, and in chemical composi-
tion differ from it chiefly in containing soda, while the common
felspar contains potash only. These two minerals are readily dis-
tinguished from quartz by their inferior hardness. They do not
scratch glass, and in general may easily be scratched by the point
of a knife.
They consist respectively of
- Felspar. Albite. Oligoclase.
Silica, ............... ..... 65.21 69'00 63-70
Alumina, ...... ........... 18° 13 1922 23.95
Peroxide of iron, ...... tº º & ge s ∈ 0°50
Lime, ..................... e = e g = & 2.05
Magnesia, ...... ........ e is a * * * 0.65
Potash, .................. | 6’ 66 • & e & 1-20
Soda, ..................... tº ſº 1 1.69 8-1 ||
I 00-00 100'00 100° 16
It is to be observed, however, that these minerals do not generally
occur in nature in a perfectly pure state—for though felspar and al-
bite do not essentially contain either lime, magnesia, or oxide of iron,
they are seldom found without a small admixture of one or more of
these substances. It is also found that while pure felspar contains
only potash, and pure albite only soda, abundance of intermediate
minerals occur which, like oligoclase, contain both potash and soda.
Such is the case with the felspars of the Siebengebirge, on the
right bank of the Rhine (Berthier), and with those contained in
the lavas of Vesuvius and the adjacent parts of Italy (Abich).
In these minerals the silica is combined with the potash, soda,
and alumina, forming certain compounds already described under
the name of silicates (p. 350). -
Felspar consists of a silicate of alumina combined with a silicate
of potash—albite of the same silicate of alumina combined with a
silicate of soda, while in oligoclase there is also a little silicate of
lime. -
3°. Mica generally occurs disseminated through the granite in
small shining scales or plates, which, when extracted from the rock,
split readily into numerous inconceivably thin layers. It sometimes
occurs also in large masses, and is of various colours—white, grey,
* Gustav Rose considers that albite never forms any part of granitic masses, but
that oligoclase does so—the albite occurring only in drusy cavities and veins.—Pog-
gendorff's Annalem, lxvi. p. 109.
486 COMPOSITION OF MICA AND HORNBLENDE.
brown, green, and black. It is soft and readily cut with a knife.
The thin shining particles that occur in many sandstones, and es-
pecially between the partings of the beds, and give them what is
called a micaceous character, are only more or less weathered por-
tions of this mineral.
Mica also consists of silicates, though its constitution is not al-
ways so simple as that of felspar. In some varieties magnesia is
present, whilst in others it is almost wholly wanting, as is shewn
by the following composition of two specimens from different loca-
lities:–
Potash Magnesian
Mica. Mica.
Silica, ............... 46'10 ... ... 40’00
Alumina, ............ 31°60 ... ... 12-67
Protoxide of iron, 8-65 ... ... 19:03
Magnesia, ............ - J.'. ... 1570
Potash, ............... 8°39 . . . ... 5-61
* Oxide of manganese, l'40 ... ... 0-63
Fluoric acid, ......... 1-12 . . . ... 2' 10
Water, ............... 1:00 Titanic acid, l'63
98.26 97.37
If we neglect the three last substances which are present only in
small quantities, and recollect that the silica is in combination with
all the other substances which stand beneath it, we see that these
varieties of mica consist of a silicate of alumina, combined in the one
with silicate of iron and silicate of potash, and in the other with
silicate of iron and silicate of magnesia,
4°. Hornblende occurs of various colours, but that which forms a
constituent of the syenites and of the basalts is of a dark green or
brownish black colour, is often in regular crystals, and is readily
distinguished from quartz and felspar by its colour, and from black
mica by not splitting into thin layers, when heated in the flame of
a candle. It consists of silicates of alumina, lime, magnesia, and
oxide of iron, or per cent. of
Basaltic Syenitic
Hornblende. Hornblende.
Silica, ............... 42'24 ... ... 45-69
Alumina, ............ 13'92 ... ... 12' 18
Lime, ............... 12:24 ... ... 13.83
Magnesia, ............ 13-74 ... ... 1879
Protoxide of iron, 14:59 ... ... 7.32
Oxide of manganese, 0.33 ... ... 0-22
Fluoric acid,... ..... - e is tº ... l'50
07:06 00:53
COMPOSITION OF SCHORL. 487
A comparison of these two analyses shows that the proportions
of magnesia and oxide of iron sometimes vary considerably, yet
that the hornblendes still maintain the same general composition.
They are remarkably distinguished from felspar by the total ab-
sence of potash and soda, and by containing a large proportion of
lime and magnesia. From the potash-mica they are distin guished by
the same chemical differences, and from the magnesian mica by con-
taining lime to the amount of ºth part of their whole weight. Such
differences must materially affect the composition and agricultural
capabilities of the soils formed from these several minerals, and they
show the correctness of what I have previously stated to you—that
mineralogical differences in rocks, which may be neglected by the
geologist, may be of great importance in explaining the appear-
ances that present themselves to the philosophical agriculturist.
4. Schorl or Tourmaline usually occurs in the form of long
black needles or prisms, but often in black specks or grains, dis-
seminated through the granitic rock, and usually (in Cornwall) at
the outskirts of the granite, where it comes into contact with the
slate rocks that surround it (De La Beche). It consists of a sili-
cate of alumina in combination with silicates of iron and of soda or
magnesia. Two varieties gave by analysis—
Schorl Tourmaline
from Devonshire. from Sweden.
Silica, ................. ... 35' 20 - - - e - - 37-65
Alumina, .................. 35°50 - - - - - - 33°46
Magnetic oxide of iron, 17.86 - - - * - - 9°38
Magnesia, .................. 0-7() - - - - (- - } 0.98
Boracic acid,........... ... 4:11 "... • * - 3-8:3
Soda, ........................ 2:09 Soda and potash, 2.53
Lime,........................ 0°55 - - * * * 0°25
Oxide of manganese, ... 0.43
96'44 98-08
This mineral, according to these analyses, is characterised by
containing from #th to 1%th of its weight of magnetic oxide of
iron," and sometimes 1%th of magnesia. The presence of Boracic
acidf is also a remarkable character of this mineral, but as neither
* This oxide is composed of the first and second oxides of iron described in p. 356.
f Boracic acid occurs in combination with soda in the common borac of the shops.
It combines with soda, potash, lime, &c., and forms borates. In the schorl it probably
cxists in such a state of combination.
488 DECOMPOSITION OF FELSPAR.
the presence of this substance in any soil nor its effect upon vege-
tation has hitherto been observed, we can form no opinion in re-
gard to its importance in an agricultural point of view.
§ 2. Of the crumbling of the Granitic rocks, and the theoretical
character of the soils formed from them.
The granites, in general, are hard and durable rocks, and but
little affected by the weather. The quartz they contain is scarce-
ly acted upon at all by atmospheric agents, and in very many
cases the felspar, mica, and hornblende yield with extreme slow-
mess to their degrading power. It is chiefly to the chemical decom-
position of the felspar that the wearing away of granite rocks is due,
and the formation of a soil from their crumbling substance.
1°. It has been stated that the felspars consist of a silicate of
alumina in combination with silicates of potash or of soda. Now
these latter silicates are slowly decomposed by the carbonic acid of
the air (see p. 351), which combines with the potash and soda, and
forms carbonates of these alcalies. These carbonates are very
soluble in water, and are, therefore, washed away by the first
shower of rain that falls. The insoluble silica and the silicate of
alumina are either left behind or are more slowly carried away by
the rains in the form of a fine powder (a fine porcelain clay), and
deposited in the valleys or borne into the rivers and lakes, while
the particles of quartz and mica, having lost their cement of fel-
spar, fall asunder, and form a more or less siliceous sand.
Granite soils, therefore, on all hanging grounds,-on the sides
and slopes of hills, that is—are poor and Sandy, rarely containing
a sufficient admixture of clay to enable them to support crops of
corn—while at the bottoms of the hills, whether on flat or hollow
grounds, they are composed, in great measure, of the fine clay
which has resulted from the gradual decomposition of the felspar.
This clay consists chiefly of the silicate of alumina contained
naturally in the felspar—it differs little, in short, from that which
has already been described (p. 442), under the name of pure or
pipe clay, which is too stiff and intractable to be readily converted
into a prolific soil.
It will readily be understood how such soils—decomposed fel-
spar soils—must generally contain a considerable quantity of potash
CLAY FROM THE FELSPAR ROCKS. 489
from the presence of minute particles of silicate of potash still un-
decomposed; and it will be as readily seen that they can contain
little or no lime, since neither in felspar nor in mica has more
than a trace of this earth been hitherto met with.
2°. We have seen, however, that hornblende contains from ºth
to ºth of its weight of lime, and as the same carbonic acid of the
atmosphere which decomposes the felspar decomposes the silicates
of the hornblende also, it is clear that soils which are derived from
the degradation of syenitic rocks, especially if the proportion of
hornblende present in them be large, will contain lime as well as
clay and silica. Thus consisting of a greater number of the ele-
ments of a fertile soil, they will be more easily rendered fruitful
also-must naturally be more fruitful—than those which are
formed from the granites, correctly so called. It is to the presence
of this lime that the superior fertility of the soils derived from the
hornblende slates of Cornwall, already adverted to (p. 480), is
mainly to be ascribed.
3°. Schorl, as above stated, contains much oxide of iron, and
sometimes five or six per cent, of magnesia. It decomposes slowly,
will give the soil a red colour, and though it contains only a trace
of lime, yet the admixture of its constituents with those of the fel-
spar may ameliorate the quality of a soil formed from the decay
of the felspar alone.
It thus appears that a knowledge of the composition of the mi-
merals of which the granites consist, and of the proportions
in which these minerals are mixed together in any locality, indi-
cates what the nature of the soils formed from them must be —an
indication which perfectly accords with observation. The same
knowledge, also, showing that such soils never have contained, and
never can, maturally, include more than a trace of lime, will satisfy
the improver, who believes the presence of lime to be almost me-
cessary in a fertile soil, as to the first step to be taken in endea-
vouring to rescue a granitic soil from a state of nature—will ex-
plaim to him the reason why the use of lime and of shell sand on
such soils should so long have been practised with the best effects,
—and will encourage him to persevere in a course of treatment
which, while suggested by theory, is confirmed also by practice.
49 () GRANITE ROCKS OF GREAT BRITAIN .
§ 3. Evtent of the granitic rocks in Great Britain and Ireland,
and observed qualities of their soils.
19. Evtent of granitic rocks.-In England, the only extensive
tracts of granite occur in Cornwall and Devon, presenting them-
selves here and there in isolated patches from the Scilly Isles and
the Land's End to Dartmoor in South Devon. In the latter loca-
lity, the granite rocks cover an area of about 400 square miles.
Proceeding northwards, various small out-bursts" of granite ap-
pear in the Isle of Anglesey, in Westmorland, and in Cumber-
land, and north of the Solway, in Kirkcudbright, it extends over
150 or 200 square miles;–but it is at the Grampian Hills that
these rocks begin to be most extensively developed. With the ex-
ception, indeed, of the patches of old red sand-stone already no-
ticed, nearly the whole of Scotland, north of the Grampians—and
of the western islands, excluding Skye and Mull, consists of gra-
mitic rocks.
In Ireland, a range of granite (the Wicklow) mountains runs
south by west from Dublin to mear New Ross—the same rock forms
a considerable portion of the mountainous districts in the north-
west of Donegal, and in the south of Galway, covers a less exten-
sive area in Armagh, and presents itself in the form of an isolated
patch in the county of Cavan.
2°. Observed qualities of the granitic soils.—From what has been
already stated in regard to the composition of granite, it is clear
from theory that no generally uniform quality of soil can be ex-
pected to result from its decomposition, and this deduction is con-
firmed by practical observation. Where quartz is more abundant,
or where the clay is washed out, the soil is poor, hungry, and un-
fruitful—such, generally, is its character on the more exposed
slopes of the hills in the Western Isles,f and in the north of Scot-
land. In the hollows and levels, where matural drainage exists,
stiff clay soils prevail, which are often cold and unfruitful, but are
capable of amelioration—where the depth of earth is sufficient–by
* This expression is in some measure theoretical, and implies—what is the gene-
rally received opinion—that the granite rocks were forced up from beneath in a fluid
state, like the lavas of existing volcanoes—that they, as well as the trap rocks, are,
in short, only lavas of a more ancient date.
t Macdonald's Agricultural Survey of the IIebrides, p. 26.
GRANITE SOILS OF ENGLAND AND SCOTLAN D. 49 |
draining and abundant liming or marling. Where there is no
natural drainage, vegetable matter accumulates, as we have seen
to be the case on the surface of all impervious rocks—and bogs
are formed. In the north of Scotland, and in Ireland, and in
the high lands in Dartmoor (Devon), these are every where seen
in such localities, and it is said that two-thirds of the Hebrides are
covered with peat bogs more or less reclaimable.
In Cornwall and Devon, the granitic soils (growan soils as they
are there called) are observed to be more productive, as the hills di-
minish in height. Thus Dartmooris covered only with heath, coarse
grass, and peat; while in the Scilly Isles the growan land pro-
duces good crops of wheat, potatoes, barley, and grass; and the
same is observed at Moreton Hampstead, in Devon, where tole-
rable crops of barley are grown, and potatoes, which are highly
esteemed in the Exeter and London markets (De La Beche). No
doubt the climate has something to do with these differences; but
the less the elevation, and the consequent washing of the rains, the
more the clay will remain mixed with the siliceous sand, and the
less completely will the potash be separated from the felspar; while
in aid of these causes, a small difference in the composition of its
constituent minerals, often not to be detected by the eye, may ma-
terially affect the character of the granitic soils of different localities.
According to Dr Paris, the presence of much mica deteriorates
these soils; while that which is formed at the edges of the granite,
where it comes in contact with the slate rocks, is of a more fertile
quality. The latter remark, however, does not universally apply,–
especially where the granite, as at the edges of Dartmoor, contains
much schorl, (De La Beche)—and the presence of mica, in the
richest soils of the red marl, would seem to imply that this mineral
is fitted materially to promote the fertility of a soil in which the
other earthy ingredients are properly adjusted.
The more elevated and thin granitic soils are said to be fitted
for the growth of larch; the lower and deeper soils, which admit
of the use of the plough, have been found to yield a three-fold re-
turn of corn by the addition of lime alone.
These observed characters completely accord with the theoreti-
cal qualities of the granitic soils, as explained in the preceding sec-
tion.
&
492 THE TRAP ROCKS--GREEN-STONE AND BASALT.
§ 4. Of the Trap rocks, and the minerals of which they consist.
Of the trap rocks there are several varieties, of which the most
important are distinguished by the names of Green-stone, Basalt,
and Serpentine.
1°. The Green-stones consist of a mixture more or less intimate
and in variable proportions of felspar and hornblende, or of felspar
and augite. They are distinguished from the granites by the ab-
sence of mica and quartz, and by the presence of the hornblende
or augite, often in equal, and not unfrequently in greater, quan-
tity than the felspar. In the granites, the felspar and quartz to-
gether generally form upwards of £g of the whole mass.
Augite is a mineral having much resemblance to hornblende,
and like it occurring of various colours. In the trap rocks it is
usually of a dark green approaching to black. It generally contains
much lime and oxide of iron in the state of silicates. The compo-
sition of two varieties compared with that of basaltic hornblende is
as follows:–
Black Augite Augite from the Basaltic
- from Sweden. lava of Vesuvius. IIornblende.
Silica, ... .................... 53°36 50-90 42'24
Lime, ........................ 22:19 22'06 12.24
Magnesia, .................. 4'99 14.43 13-74
Protoxide of iron, ........ 17:38 6°25 14°59
Protoxide of manganese, 0.09 e º ºs 0°33
Alumina, ........ ............ is ſº tº 5-37 13.92
98.01 99-91 97.06
The predominance of this mineral (augite) or of hornblende in
the green-stone rocks must necessarily cause a very material dif-
ference in the nature of the soils produced from their decay, com-
pared with those which are formed from the granitic rocks in which
the felspars are the predominating mineral ingredient.
2°. Basalt consists of a mixture, in variable proportions, of au-
gite, magnetic oxide of iron, and zeolite, with or without felspar.”
It differs in appearance from green-stone, chiefly by the darkness
of its colour, and by the minuteness of the particles of which it is
composed, which in general cannot be distinguished by the naked
eye.
* In addition to augite, magnetic iron, and zeolite, many basalts contain also a con-
siderable proportion of certain varietics of felspar, especially of one to which the name
of nephelimc has been given.
4
- LIME IN THE TRAP ROCKS. 493
Zeolite is a generic term applied to a great number of mineral
species which occur in the basalts, and often intermixed with the
green-stone rocks. They differ from felspar by their greater solu-
bility in acids, and by generally containing lime, where the latter con-
tains potash or soda. - -
It may be stated, indeed, as the most important agricultural dis-
tinction between the granitic and the true” trap rocks, that the
latter abound in lime, while, in the former, it is often entirely ab-
sent. If in a green-stone only one-fourth of its weight consist of
augite, every 20 tons of the rock may contain one ton of lime. If
in a basalt the augite and zeolite amount to only two-thirds of its
weight, every mine tons may contain one ton of lime. The prac-
tical farmer cannot fail to conclude that a soil formed from such
rocks must possess very different agricultural capabilities from the
soils we have already described as being formed from the decom-
position of the granites.
The lime contained in the trap rocks is partly in the state of car-
bonate, partly in that of a silicate soluble in acids (zeolite?) and
partly in that of an insoluble silicate (augite, &c.)
With the view of determining the absolute proportion of lime
contained in different rocks of this kind, the state in which it ex-
ists, and the relative agricultural values of the soils formed from
them, in so far as it depends upon the presence of this ingredient,
I have caused numerous specimens of trap to be examined in my
laboratory. The results are exhibited by the following table:–
Lime in state of silicate.
* Lime in state Total. Equal of
Locality. of carbonate. soluble. monº Lime. dº.
Balcarras hill, Fife (recent) 0.8 4-26 5-75 10-81 19-21
Pentland hills, (decaying) 8-2 0-12 2.78 11’ 10 1975
Salisbury crags, (recent) ... 3.02 2:18 2-48 7-68 13:64
Do. do. (decomposed) 0.72 0.71 0.91 2:34 4°16
Rothsay, (recent)...... , - - - - - - 0.79 0°41 G'66 7-86 13-97
Do. (decayed) ......... 0.68 0.51 G'85 8'04 14-29
Do. (more decayed)... 0-60 ()'68 6-88 8’ 16 14' 50
Langton, Berwickshire, ... 4-26 0.08 & gº 2°48 4'40
Colquhalzie, Perthshire, ... 5:49 s sº e 1-05 6'54 1 l'6]
* Serpentine is not generally included among the true trap rocks: it is placed
among them here as it often is by geologists, because in many places, as at the Lizard,
it occurs along with true green-stone.
+ This was the solid part of a grey porous amygdaloidal trap, the lime being pro-
bably most largely contained in the amygdaloidal (zeolitic) nodules.
... This was a reddish micaceous trap.
494. EXTENT OF THE TRAP ROCKS.
This table shows—
a. That the absolute quantity of lime in the rock, and the rela-
tive proportions of it which exist in the states of carbonate and si-
licate vary very much.
b. That when it decays, as in the case of the Salisbury crag
trap, the proportion of lime diminishes—the rains wash it out.
c. That the lime, estimated in the state of carbonate, as is done
in the last column, is often equal to about 20 per cent. of the weight
of the rock—or 5 tons of trap contain as much lime as one ton of
pure lime-stone.
This cannot fail to affect the agricultural value of the soils
formed from them. -
3°. Serpentine is a greenish yellow mineral, consisting of silica
in combination with magnesia and a little iron, and occasionally a
few pounds in the hundred of lime or alumina. The distinguish-
ing ingredient is the magnesia, which generally approaches to 40
per cent. of the whole weight of the mineral. Rocks of serpentine
are generally mixed with magnetic iron ore, and with portions of
other minerals in greater or less abundance.
§ 5. Evtent of the trap rocks in the British Isles, and nature of
the soils formed from them.
1°. Eatent of the trap rocks.-The serpentine rock occurs to any
extent only in Cornwall, about the Lizard Point, where it covers
an area of 50 square miles. The greenstones and basalts are only
met with here and there in small patches, until we go north to the
Cheviot Hills, which consist of these and other varieties of trap.
It is in the low country of Scotland, however, intermixed with and
surrounding the great coal district of that part of the island, that
the greatest breadth of trap is seen. It there stretches across the
island in a south-west direction, and in detached masses, from the
Friths of Tay and Forth to the island of Arran, covering an area
of 800 or 1000 square miles. In the prolongation of the same
line it re-appears in the north-east of Ireland, and extends over
the whole of the county of Antrim and a small part of London-
derry and Armagh. In the most northerly portion of this tract
the well known columnar basalt of the Giants' Causeway occurs.
On the west coast of Scotland the trap rocks cover nearly the
SoTLS OF THE TRAP ROCKs. 495
whole of the islands of Mull and of Skye–to the west of the for-
mer of which islands lies Staffa with its celebrated basaltic caves.
2°. Soils of the trap rocks.—The soil of the serpentine rocks at
the Lizard is far from fertile. They form a flat table land, which
retains the water and thus forms swamps and marshes. Even
where a natural drainage exists it rarely produces good grass, or
average crops of corn. It is remarkable for growing a peculiar,
very beautiful heath—erica vagans—which so strictly limits itself
to the serpentine soil as distinctly to mark the boundary by which
the serpentine is separated from other rocks (De La Beche.) From
the composition of serpentine we might be led to suppose that the
comparative barrenness of the soils formed from it is due to the
large quantity of magnesia which this mineral contains. It would
appear, however, that these soils often contain very little magnesia,
the long action of the rains and of other agents having almost en-
tirely removed it (see p. 354), and yet they still retain their bar-
renness. But they contain no lime, and, therefore, after draining,
the first great step to take in order to improve such soils, is to give
them a good dose of lime. How this step is to be followed up
will depend upon the effect which this treatment is found to pro-
duce.
The soil of the green-stones is generally fertile, and it is more
so in proportion as the hornblende or augite predominates—that
is, generally, in proportion to the darkness of its colour.
In Cornwall and South Devon, where scattered masses of trap
occur, consisting chiefly of hornblende and felspar, they “afford
the most fertile soils of any in the district when their decomposi-
tion has taken place to a sufficient depth” (De La Beche). Where-
ever the trap rocks (locally dunstones) are observed at the surface,
“it is deemed a fortunate circumstance, being a certain indication
of the fertility of the incumbent soils.” The superior fertility of
the neighbourhood of Penzance is owing to the presence of these
rocks (Dr Paris), and where their detritus has been mixed with
that of other rocks—as with the worthless granite soils—it ameli-
orates and improves their quality.
The same general character is exhibited by the trap soils
of other districts of the island. The height of the Cheviot Hills
* Worgan's View of the Agriculture of Cornwall, p. 10.
496 FERTILITY OF THE GREEN-STONE SOILS
renders the climate in many places unfavourable to arable culture,
yet they produce the sweetest pasture,” while the low country
around them has been largely benefited by admixture with their
crumbling fragments. The whole of the lowland tract of Scot-
land, over which these rocks extend—comprehending the counties
of Ayr, Renfrew, Lamark, Linlithgow, Fife, and portions of Perth,
Stirling, Edinburgh, and Haddington—exhibit the fertile or fer-
tilizing character of the decomposing greenstone. In Cornwall it
is dug up as a marl and applied to the land, and in the neighbour-
hood of Haddington I have seen a farming tenant (a leaseholder)
removing twelve inches of trap soil from the entire surface of a
field, for the purpose of spreading a layer of an inch in depth over
twelve times the area in another part of his farm. There can be
no doubt that this mode of improvement is within the reach of
many proprietors and farmers—especially along the southern bor-
ders of Perthshire, and near the more elevated parts of Ayr and
Lanark.
To the north of Ireland, and to the Western Islands, the above
remarks, with slight modifications, arising from local causes, will
also apply. For example, where the surface is flat, and the rock
impervious, water will collect, and heaths and bogs will be pro-
duced, which only draining can remove. They apply also to other
countries where trap rocks abound—the only fertile tracts in Abys-
sinia, for instance, being found in valleys and on mountain slopes,
where the soil is composed of the detritus of trappeam rocks (Dr
Rüppell).
Yet there are exceptions to this general rule.
Where the felspar largely predominates in the rock, thesoil formed
from it will partake more or less of the cold and naturally barren
character of the stiffer granitic soils. Such appears to be the case
* It is a singular fact observed here and there among the Cheviot Hills on the
border, that where sheep are folded or pastured on hills of trap which are covered
with delicate herbage, they are attacked by what is locally called the piniºg ill,—
they pine away, become indolent, and are unwilling to move. The cure is to drive
them to a neighbouring sand-stone pasture, where they become again active, and begin
to thrive. The pining hills on each farm are well known, and the tenant has no he-
sitation in pointing to this and to that hill as those on which the sheep are sure to
pine, if kept upon them only.
IN SCOTLAND, ENGLAND, AND IRELAND, 497
with some of the traps which occur in the border counties of Eng-
land and Wales (Murchison).
In the Isle of Skye, again, a local peculiarity of a different kind
obtains, the effect of which upon the soil is also to render it poor
and unproductive. In that island the singularly beautiful ridge
of the Cuchullen Hills consists of a variety of trap in which the
augite so far predominates as to form nearly the whole of the
mountain masses. But the augite in this case is a variety to which
the name of hypersthene has been given, and which contains much
magnesia and oxide of iron, but scarcely a trace of either lime or
alumina. The rock is very hard, and decays with extreme slow-
mess; yet however rapid its decay might be, it could never pro-
duce a fertile soil. We have seen that the serpentine and granite
soils are essentially deficient in lime, but a hypersthene soil is in
want both of lime and of clay. It would be still more difficult,
therefore, to render the latter productive—even Supposing the
magnesia of the hyperstheme,” as in the case of the Serpentine soils,
to be mostly washed away by the rains.
Thus we perceive how exactly the study of the composition of
the different varieties of the trap rocks explains the observed diffe-
rences in the quality of the soils derived from them. When the
minerals they contain abound in lime, the soils they yield are fer-
tile—when those minerals predominate in which lime is wanting,
the soils are inferior, sometimes scarcely capable of cultivation,
Again, the granites abound in potash; but except in the syenites
they rarely contain lime, and their soils are generally poor. Let
them be mixed with the trap soils, and they are enriched. This
would seem fairly and clearly to imply that the fertility of the one
is mainly due to the presence of lime, and the barrenness of the
other to the absence of this earth. -
On this subject I will only further add, that the more modern
volcanic lavas which overspread Italy, Sicily, parts of France,
* The hypersthene of Skye has been found to consist of
Silica, ......................... . 51°35 | Protoxide of iron, ......... 33.92
Lime, ........................... 1-84 || Water, ................. ...... 0-50
Magnesia, ..................... 11:09
98-70
The composition probably varies in different parts of the rock, some containing more
magnesia and less iron than is here represented.
I i
498 THE IIY PERSTHENE SOILS OF SIK.Y.E.
Spain, and Germany, are closely related to the trap rocks in their
general composition—and the fertility which overspreads thousands
of square miles of decomposed lava streams and ejections of volanic
ashes, in Italy and Sicily, is too well known to require any detailed
description.
§ 6. Of superficial accumulations of foreign materials, and of the
means by which they have been transported.
Abundant proof, I think, has now been advanced to satisfy you
that a close general relation exists between the soil and the rocks
on which it rests, and that the geological structure of a country,
as well as the chemical composition of the minerals of which its se-
veral rocky masses consist, has a primary and fundamental influ-
ence upon the agricultural capabilities of its surface.
And yet I should be leading you into a serious error, were I to
permit you to suppose that this intimate and direct relation is al-
ways to be observed—that in whatever district you may happen to
be, you will find the soil taking its general character from the sub-
jacent rocks—and that where the same rocks occur, similar soils
are always to be expected. On the contrary, in very many loca-
lities the soil is totally different from that which would be produced
by the degradation or decomposition of the rocks on which it rests.
To infer, therefore, or to predict, that on a given spot, where, ac-
cording to the geological map, red sand-stone for example pre-
vails, a marly or other red sand-stone soil would necessarily be
found—or that where the coal-measures are observed, poor, un-
grateful land must exist—would be to form or to state opinions
which a visit to the several localities would in many instances show
to be completely erroneous—and which would bring undeserved
discredit upon geological science.
In such cases as these geology is not at fault. New conditions
only have supervened, which render the matural relations between
soils and rocks in those places less simple, and consequently more
obscure. Yet a further study of geological phenomena removes
the obscurity—shows to what cause it is owing that in many dis-
tricts the soil is such as could never have been formed from the
Subjacent rocks—again places the enlightened agriculturist in a
condition to pronounce generally from what rocks his soils have
TRANSPORTED MATERIALS OFTEN MASK THE ROCKS. 499
been derived—generally also what their agricultural capabilities
are likely to be, and by what mode of treatment those capabilities
may be most fully developed. -
Of the surface of Great Britain and Ireland it may indeed be
truly said, that it exhibits extensive tracts in which the character
of the soil is directly influenced by, and may be inferred from, the
character and composition of the subjacent rock. To these dis-
tricts the rules and observations contained in the preceding sec-
tions directly and clearly apply. But other extensive tracts also
occur in which the character of the soil is independent of that of
the rocks on which it immediately rests—the cause of this appa-
rent difficulty we are now to consider.
1°. I have already had occasion to explain to you in what way
all rocks crumble more or less rapidly, and give origin to soils of
various kinds. Were the surfaces of rocks uniformly level, and
that of every country flat, the crumbled materials would generally
remain on the spots where they were formed. But as already
shown in the diagrams, inserted in pages 451 and 452, the rocks
rarely lie in a horizontal position, but rest almost always more or
less on their edges, and the surface in such a country as ours is
often mountainous or hilly, and everywhere undulating. Hence
the rains are continually washing off the finer particles from the
higher, and bearing them to the lower grounds—and on occasions
of great floods, vast quantities even of heavy materials are borne
to great distances, and spread sometimes to a great depth and over
a great extent of country.” Thus the spoils of one rocky forma-
tion are borne from their native seat and are strewed over the sur-
face of other kinds of rock of a totally different character. The
fragments of the granite, gneiss, and slate rocks of the high lands
are scattered over the old red sand-stones which lie at a lower le-
vel—and those of the blue-limestone mountains over the millstone
grits, the coal measures, and the new red sand-stones, which stretch
away from their feet.
2°. But the effects produced by this matural cause, though they
may be judged of in kind, can never be estimated in degree by
what we perceive in our own temperate climates—in our country of
small rivers and gentle rains. How must such effects exceed in
* Witness the still recent floods in Morayshire.
500 HOW THE MATERIALS HAVE BEEN TRANSPORTED.
magnitude, in districts where, as in the Ghauts, that separate the
level land of the Malabar coast (the Concan) from the high table-
land of the Deccan,—120 inches of rain occasionally fall in a sin-
gle month, and 240 inches or 20 feet, on an average, every year
from June to September And to what vast distances must ma-
terials be transported by great rivers such as the Mississippi, the
River of the Amazons, the Ganges, and the Indus, which main-
tain a course of thousands of miles, before they empty themselves
into the sea What necessary connection can the deposits of mud
and sand, which yearly collect at the mouths and in the places
overflowed by the waters of these great rivers, have with the na-
ture of the rocks on which these transported materials may happen
to rest ? .
3". But the constant motion of the waters of the sea washes
down the cliffs on one coast, and carries away their ruins to be de-
posited, either in its own depths, or along other more sheltered
shores. Hence sand-banks accumulate—as in the centre of our
own North Sea ; or the land gains upon the water in one spot
what it loses in another—as may be seen both on the shores of
our own island, and on the opposite coasts of Germany and France.
What necessary relation can the soils thus gained from the sea
have to the rocks on which they rest? Suppose the bottom of the
North Sea to become dry land, what necessary mineral relation
would then exist between the soils which would gradually be formed
on its hundreds of square miles of sand-banks, and the rocks on
which those sand-banks immediately repose 2
4°. Again, the sea, in general, carries with it and deposits in
its own bosom the finest particles of clay, lime, and other earthy
matters, and leaves along its shores accumulations of fine siliceous
sand. This sand, when dry, the sea winds bear before them and
strew over the land, forming sand hills and downs, sometimes of
considerable height and of great extent. Such are to be seen here
and there in our own islands, but on the Eastern shores of the Bay
of Biscay, and on the coasts of Jutland—both exposed to violent
sea winds—they occur over much larger areas. Before these winds
the light sands are continually drifting, and, year by year, advance
further and further into the country, gradually driving lakes before
them, swallowing up forests and cultivated fields, with the houses
4
EFFECT OF WINDS. 501
of the cultivators,” and burying alike the fertile soils and the rocks
from which they were originally derived. -
You have all read of the fearful sands of the African deserts
and of their destructive march when the burning winds awaken.
History tells of populous cities and fertile plains, where nothing
but blown Sands are now to be seen, and geology easily leads us
back to still more remote periods, when the broad zones of sandy
desert were but narrow stripes of blown sand along the shores of
the sea, or beds of comparatively loose sandstone, which here and
there came to the surface, and which the winds have gradually re-
moved from their original site, and waſted widely over the land.
Wherever these sand-drifts spread, it will also be clear to you,
that there may be no necessary similarity between the loose mate-
rials on the surface, and the kind of rock over which these mate-
rials are strewed.
5". Along with these I shall mention only one other agent by
which loose materials are gradually transported to considerable
distances. - -
It is observed in elevated countries, where the snow never en-
tirely melts, and where glaciers or sheets of ice hang on the moun-
tain sides——descending towards the plains as the winter's cold comes
on, and again retreating towards the mountain tops at the approach
of the summer's heat—that the edges of the glaciers bear before
them into the valleys, and deposit along their edges, banks, or co-
nical ridges of sand and gravel (Moraines.) These consist of the
fragments of the rocky heights, worn and rounded by the friction
of the sheets of ice, beneath which they have descended from above,
and from the edges of which they finally escape into the plain.
These ridges of sand and gravel accumulate till some more sud-
den thaw than usual, or greater summer's heat, arrives, when they
are more or less completely broken up by the rush of water that
ensues, and are dispersed over the subjacent tracts of level land.
When the rocks are of a kind to rub down so fine as to form
much mud as well as sand or gravel, the ridges are of a more
clayey character. And where the edges of the glaciers descend
to the borders of lakes or seas—as in the Tierra del Fuego—this
mud is washed away and widely spread by the waters, while the
* In the Landes, the advance of the downs is estimated at 60 to 70 feet every year.
502 EFFECT OF GLACIERS,
gravel and sand remain nearer their original site; or, finally, when
the ice actually overhangs the water, huge fragments break off
now and them,-loaded with masses of gravel and sand, or even
with rocks of large size,_which fragments float away often to great
distances and drop their stony burdens here and there, as they
gradually melt and disappear.
To these facts, let it be added, that recent geological researches
of a very interesting kind, seem to show that nearly all the elevat-
ed tracts of country in the temperate regions of Europe and Ame-
rica—in our own island, among other localities—have been co-
vered with such glaciers at a comparatively recent period, (geolo-
gically speaking), and that these glaciers have gradually retreated,
step by step, to their present altitudes, halting here for a time, and
lingering there;—and we shall find reason to believe that traces
of transported materials, moved from their original sité by this
agent also, are to be looked for on almost every geological for-
mation.
And such the geological observer finds to be in reality the case.
§ 7. Of the occurrence of such accumulations in Great Britain,
and of their influence in modifying the character of the soil.
Such accumulations, for example, present themselves over a
large portion of our own island. Thus, in Devonshire, the chalk
and green sand are so completely covered by gravels, consisting of
the fragments of older rocks from the higher grounds, mixed with
chalk-flints and chert, that nearly the whole of this tract possesses
one common unproductive character, and is widely covered with
downs of furze and heath (De La Beche). In like manner the
chalk, green sand, and plastic clay of a large portion of Norfolk
and Suffolk, and of parts of the counties of Essex, Cambridge,
Huntingdom, Bedford, Hertford, and Middlesex, are covered with
till (stiff unstratified clay), containing large stones (boulders), or
with gravels, in which are mixed fragments of rocks of various
ages, which must have been brought sometimes from great dis-
tances, and perhaps from different directions (Lyell). So over the
great plain of the new red sand-stone, in the centre and west of
England—in Lancashire, Cheshire, Shropshire, Staffordshire, and
Worcestershire–drifted gravels of various kinds are widely spread,
l
|DRIFT IN GREAT BRITAIN. 503
It may indeed be generally remarked, that over the bottoms of all
our great valleys, such drifted fragments are commonly diffused—
that upon our wider plains, they are here and there collected in
great heaps—and that on the lower lands that border either shore
of our island, extensive deposits of clay, sand, or gravel, not un-
frequently cover to a great depth the subjacent rocks.
The practical agriculturist will be able to confirm this remark,
in whatever district almost he may live, by facts which have come
within his own knowledge and observation. I shall briefly explain,
by way of illustration, the mode in which such accumulations of
drifted matter overlie the eastern or lower half of the county of
Durham. . -
The eastern half of the county of Durham reposes, to the north
of the city of Durham, chiefly upon the coal measures, (sand-stones
and shales); to the south, chiefly on the magnesian lime-stone and
the new red sand-stone. These coal measures rise, here and there,
into considerable elevations, as at Gateshead Fell, near Newcastle,
and Brandon Hill, near Durham, where the rocks lie immediately
beneath the surface, and are covered by comparatively little trans-
ported matter. The magnesian lime-stone, also, in many locali-
ties, starts up in the form of round hills or ridges, on which re-
poses only a poor thin soil, formed in great measure by the crumb-
ling of the rock itself. Yet, generally speaking, this entire district
is overspread with a thick sheet of drifted matter, consisting of
clays, sands, and gravels.
This drift is made up of three separate layers, to be observed
more or less distinctly in taking a general survey of the county,
though there are few spots where they can all be seen reposing
immediately one over the other.
1°. The upper layer consists of clay–on the higher grounds,
poor, stiff, yellow—on the hill sides and slopes of the valleys, often
darker in colour—but almost everywhere full of rounded trap
boulders from a few pounds to many tons in weight. These are
generally dug up when they obstruct the plough, and are sold for
mending the roads.” The clay varies in depth, from one or two,
to fifty or sixty feet.
* In some parts of Northumberland these trap boulders are still more numerous.
In the country which stretches between the north and south Tyne, the old grass fields
are full of them. A friend of mine informs me that in ploughing out a nine acre field
504 - DRIFT IN THE COUNTY OF DURHAM.
2°. Beneath the clay occurs an accumulation of fine, generally
yellow, more rarely red, sand, intermixed with occasional layers
and round hills of gravel—with frequent black streaks of rounded
coal dust, and here and there with nests of rounded lumps of coal
from half an inch to five or six inches in diameter. This coal is
sometimes so abundant as to be collected and sold for burning.
The gravels, where they overlie the coal measures, consist chiefly
of rounded, and on the upper part occasionally of large, angular
masses of coal sand-stones—with here and there a fragment of trap,
of mountain lime-stone, or of some of the older rocks to be met
with in the mountainous district towards the west. Over the magne-
sian lime-stone, however, in the south-eastern division of the county,
towards the foot of the south-eastern slope of the magnesian lime-
stone hills, the gravels, which exhibit in some places (Wynyard)
an irregular stratification, contain many rounded masses of magne-
sian lime-stone, and even of new-red sand-stone—the evident de-
bris of adjacent rocks long ago broken up.
3°. The undermost layer which rests immediately upon the sub-
jacent rocks consist of a stiff unstratified blue clay, often full of
trap boulders, but containing also occasional large rounded masses
of blue lime-stone—and smaller pebbles of quartz, of granite, and
of the older slate rocks. In many localities this clay is wanting,
and the sands or gravels rest immediately upon the carboniferous
or magnesian lime-stone rocks—while in some tracts, both this and
the upper clay appear to degenerate into a stony most unmanage-
able clayey gravel. I am not aware that the large whin (trap)
boulders are ever met with in the beds of sand.
The following diagram exhibits the mode in which these drifted
materials present themselves in the neighbourhood of the city of
Durham. The cross (f) indicates very nearly the site of Durham
on the banks of the river Wear.
on his estate in that district there were dug out and carried off no less than 900 tons
of such rolled stones, great and small !

DRIFT NEAR THE CITY OF DUIRFIAM. 505
No. 1 represents the coal measures.
2. The lower new-red sand-stone, here soft and pale yellow.
3. The magnesian lime-stone rising into a high escarpment from
3 to 6 miles south of the city.
4. Yellow loose sand—with rolled sand-stones and coal-drift—
occasionally stratified. It forms the numerous picturesque round
hills in the neighbourhood of the city, and varies from a few feet
to not less than 120 feet in thickness. -
5. Is the upper clay, with boulders. N indicates Framwellgate
Moor to the north of the city, where it is only a few feet thick.
At S, on the southern slope of the escarpment, it sometimes rests
immediately on the rock as here represented—in which case it is
difficult to decide whether it should be considered as the under or
the upper clay—though in other spots both sand and clay, or gra-
vel and clay, present themselves.
It will at once occur to you, from the inspection of this diagram,
that the general character of the soil in the county of Durham,
wherever such accumulations of drifted matter occur, is not to be
judged of from the mature of the rocks on which they are known
to rest.
Another fact, not unworthy of your attention, is the rapid alter-
nations of light and heavy soil, of sands or gravels and clays, which
present themselves in the same district, I may say in the same
farm, and often in the same field. This arises from the irregular
thickness of the deposit of sand or gravel over which the upper
clay rests. The surface of this sand is undulating, as if it had
formed a country of round hills before the clay was deposited upon
it. This appears in the following diagram, which represents the
way in which the several layers are seen to occur in the Crimdon
cut on the Hartlepool railway :—
§§§s
§§§
# N
W § Nº W § \\ N. '." § &
*Yvº §§ § § A. - * Wºº
N § §§ XN
§
Here 1 is the magnesian lime-stone, not visible; 2, the under
avr wri * * e & 2 & &
clay, with boulders; 3, the sand rising in round hills, and here
and there piercing to the surface; and 4, the upper boulder clay.












506 THE SOILS OFTEN CHANGE FROM S.AND TO CLAY,
In the county of Durham it is a very usual expression that the
tops of the hills are light turnip soil—but that they fall off to clay.
Both the meaning and the cause of this are explained by the above
diagram. -
Nor is this mode of occurrence rare among the alternate sands
and clays of which the Superficial accumulations in various parts
of the country consist. Nearly the same circumstances give rise
to the rapid changes so frequently observed in the character of the
soil, as we pass from field to field, not in this county only, but in
various other parts of our island.
§ 8. How far these accumulations of drift interfere with the general
deductions of Agricultural Geology.
Thus it appears that, over the eastern half of the county of Dur-
ham, and over large portions of other counties, the soils are found
to rest upon and to derive their character from accumulations of
drifted materials more or less different in their nature from the
rocks that lie beneath.
But in the preceding lecture I have endeavoured to show you
that soils are derived from the rocks on which they rest, and to
impress upon you the close general relation which exists between
the kind of rocks of which a country is composed, and the kind of
soils by which its surface is overspread.
How are these apparent contradictions to be reconciled ? How
is any degree of order to be evolved out of this apparent confu-
sion ? Are the general indications of agricultural geology (Lec-
ture xiv. § 8,) still, in any degree, to be relied upon P
They are, and for the following, among other reasons:
1°. It is still generally true that, where a considerable extent of
country rests upon any known rock, the soil in that district derives
its usual character from the nature of that rock. Thus, though
large portions of Cheshire and Lancashire are covered with drift,
yet the soil of these counties, taken as a whole, has the general
character of the soils of the new-red sand-stone, which in that part
of England is so largely developed.
2°. Where the drift overspreads any large area, it is found to
become gradually mixed up with the fragments, large and small,
of the rocks upon which it reposes. Thus in the neighbourhood
DRIFT USUALLY BROUGHT FROM SHORT DISTANCES. 507
of Durham, the round hills of sand and gravel with intermingled
coal consist in great part of the ruins of the sand-stones of the
country itself—while the clays, also, are partly derived from the
shale beds which occur intermingled with the sand-stones of the
same coal measures. Hence the soils of the northern half of this
county, in general, still partake of the usual qualities of those of
the coal measures and mill-stone grit (pp. 471 and 472). In the
western and higher part of the district they lie more immediately
on the rocks from which they have been derived, while on the east-
ern half they rest on a mixture of the accumulated ruins of the
same rocks, which have been transported by natural agents to a
greater or less distance from their natural site.
It is true that there are mixed up with these many portions of
other rocks brought from a still greater distance, but these bear
but a small proportion to the entire mass, and hence have, gene-
rally speaking, but little influence in altering the mineral charac-
ter of the whole. -
3°. It may indeed be stated as generally true, that the greater
proportion of the transported materials which lie upon any spot
has been brought only a comparatively small distance. Thus the
sands and gravels in the county of Durham—to the west of the
magnesian lime-stone—consist chiefly of the fragments of the coal
measures. East and south of the magnesian lime-stone escarp-
ment (diagram, p. 504), they become mixed with rounded masses
of this lime-stone. On the new-red sand-stone of the south-east
of the county, they consist chiefly of magnesian lime-stone, mixed
with fragments of the red sand-stone—and on crossing the Tees,
the debris of the lias hills begins to appear among them.
In countries, therefore, where drifted sands and gravels prevail
on the surface, they generally consist of the fragments of rocks
which lie at no great distance—generally towards the higher
ground—the matural tendency being for the debris of one kind of
rock, or of one formation, to overlap to a greater or less extent the
surface of the adjoining rock or formation. By this overlapping,
the geographical position of a given soil is removed to a greater or
less distance beyond the line indicated by the geological position of
the rocks from which it is derived. Thus, a coal measure soil
may overspread part of the magnesian lime-stone—a red sand-
508 GENERAL DEDUCTIONS OF GEOLOGY STILL TRUE.
stone soil may partially cover the lias, and so on—the general
characters and distinctions of the soil peculiar to each rock being
still preserved beyond the spaces upon which they have been acci-
dentally intermingled. - - . . . . . .
4°. To this, and to each of the other statements above made,
there are many local exceptions. For instance, what is true of
sands and gravels, will not so well apply to the fine mud of which
many clays are formed. Once commit these to the water, and if
it has any motion, they may be transported to very great distances
from their original site. Rivers, lakes, and seas, are the agents
by which these extensive diffusions are effected. The former pro-
duce what are called alluvial formations or deposits; which are
generally rich in all the inorganic substances that plants require,
and hence yield rich returns to the agricultural labourer. They
are usually, however, distinguished, and their boundaries marked,
by the geologist—so that the soils which repose upon them do not
contradict any of the general deductions he is prepared to draw,
in regard to the general agricultural capabilities of a country, from
the kind of rocks of which it consists. - - g
Thus, though the occurrence of extensive fields of drift over
various parts of almost every country does throw some further dif-
ficulty over the researches of the agricultural geologist, and re-
quires from him the application of greater skill and caution before
he pronounce with certainty in regard to the agricultural capabi-
lities of any spot before he visit it—yet it neither contradicts the
general deductions of the geologist nor the special conclusions he
would be entitled to draw in regard to the ability of any country,
when rightly cultivated, to maintain in comfort a more or less
numerous population. The political economist may still, by a sur-
vey of the geological map of a country, pronounce with some con-
fidence to what degree the agricultural riches of that country
might by industry and skill be augmented—and which districts
of an entire continent are fitted by nature to maintain the most
abundant population. The intending emigrant may still, by the
same means, say in what new land he is most likely to find a pro-
pitious soil on which to expend his labour, or such mineral re-
sources as will best aid his agricultural pursuits;–while a careful.
AGRICULTURAL MAPS. 509
study of the geological map of his own country, will still enable
the skilful and adventurous farmer to determine in what counties
he will meet with soils that are suited to that kind of practice with
which he is most familiar—or which are likely best to reward him
for the application of the newest and most approved methods of
culture.
Still some aids to this kind of knowledge are yet wanting.
We have geological maps of all our counties, in which the boun-
daries of the several rocky formations are more or less accurately
pointed out, and from these maps, as we have seen, much valuable
agricultural information may be fairly deduced. We have also
agricultural maps of many counties,” compiled with less care, and
often with the aid of little geological knowledge. But agriculture
now requires geological maps of her own—which shall exhibit not
only the limits of the rocky formations, but also the nature and
relative extent of the superficial deposits (drifts), on which the soils
so often rest, and from which they are not unfrequently formed.
These would afford a sure basis on which to rest our opinions in
regard to the agricultural capabilities of the several parts of a
county in which, though the rocks are the same, the soils may be
very different. To the study of these drifted materials, the attem-
tion of geologists has lately been much directed, and from their
labours agriculture will not fail to reap her share of practical bene-
fit. The geological survey, also, so ably superintended by Mr De
La Beche, is collecting and recording much valuable information
in regard to the agricultural geology of the southern counties. It
is not unworthy the consideration of our leading agricultural socie-
ties, however, whether some portion of their encouragement might
not be beneficially directed to the preparation of agricultural maps,
which should represent, by different colours, the agricultural capa-
bilities, according to our present knowledge, of the several parts of
each county, based upon a knowledge of the soils and subsoils of
each parish or township, and of the rocks, whether near or re-
mote, from which they have been severally derived.
Before leaving this subject, I will call your attention to one
practical application of this knowledge of the extensive prevalence
* As those contained in the County Reports published by the Board of Agriculture.
5 || 0 ACCUMULATIONS OF PEAT.
of drifts, which is not without its value. Being acquainted with
the nature of the rocks in a country, and with its physical geogra-
phy—that is, which of these rocks form the hills, and which the
valleys or plaims—we can predict, in general, that the materials of
the hills will be strewed to a greater or less distance over the
lower grounds, and that these lower soils will thus be more or less
altered in their mineral character. And when the debris of the
hills is of a more fertile character than that of the rocks which
form the plains, that the soils will be materially improved by this
covering;-the soil of the mill-stone grit, for example, by the de-
bris of the mountain lime-stone, or of a decayed green-stone or a
basalt. On the other hand, where the higher rocks are more un-
fruitful, and the low lands are covered with sterile drifted sands,
brought down from the more elevated grounds—a knowledge of
the nature of the subjacent rock may at once suggest the means of
ameliorating and improving the unpromising surface-drift. Thus,
the loose sand of Norfolk is fertilized by the subjacent chalk marl :
and even sterile heaths, (Hounslow), on which nothing grew be-
fore, have, by this means, been made to produce luxuriant crops
of every kind of grain.
§ 9. Of superficial accumulations of Peat.
Of Superficial accumulations, that of peat is one which, in the
United Kingdom, covers a very large area, In Ireland alone,
the extent of bog is estimated at 2,800,000 acres. None of the
drifted materials we have considered, therefore, would appear so
likely to falsify the predictions of the geologist, who should judge
of the soils of such a country from information in regard to the
rocks alone on which they rest—from a geological map, for exam-
ple—as the occurrence of these peat bogs. Yet there are certain
facts connected with the formation of peat which place him, in
Some measure, on his guard, in reference even to accumulations of
vegetable matter such as these.
1°. There is a certain range of temperature within which alone
peat seems capable of being produced. Thus, at the level of the
sea, it is never found nearer the equator than between the 40° and
45° of latitude; while its limit towards the poles appearsº be
WHERE PEAT IS TO BE EXPECTED. - §II
within the 60th degree. It is a product, therefore, chiefly of the
temperate regions.
Still on the equator itself, at a sufficient altitude above the sea,
the temperature may be cool enough to permit the growth of peat.
Hence, though on the plains of Italy no peat is formed, yet on
the higher Apennines, it may here and there be met with, among
the marshy basins, and on the undrained mountain sides.
2°. The occurrence of stagnant water is necessary for the pro-
duction of peat. Hence on impervious beds of clay, through which
the rains and springs can find no outlet, the formation of peat
may be expected. Thus on the Oxford clay repose the fens of
Lincoln, Cambridge, and Huntingdom (p. 464.) On impervious
rocks, also, peat bogs form for a similar reason. The new red
sand-stone is occasionally thus impervious, and on it, among other
examples, repose the Chat moss, the tract of peat, mostly in cul-
tivation, which lies west of a line drawn between Liverpool and
Preston, and the large extent of boggy country which stretches
round the head of the Solway Firth. On the mountain lime-
stone, the old red sand-stone, the slate, and the granite rocks,
much peat occurs, and it is on these latter formations that the ex-
tensive bogs of Scotland and Ireland chiefly rest.
But though these two facts are of some value to the politician
and to the geologist, in indicating in what countries and on what
formations peat may be expected to occur, yet they are of com-
paratively little importance to the practical agriculturist. It is of
far more consequence to him that the moment he casts his eye
upon the face of a country he can detect the presence or absence
of peat—that none of the perplexities which beset the nature and
origin of other superficial accumulations attach to this—that he can,
at once, judge both of its source and of its agricultural capabili-
ties. Though produced on a given spot, because rocks of a cer-
tain character exist there, yet its origin is always the same, its
qualities more or less uniform, the improvement of which it is
susceptible in some measure alike, and the steps by which that
improvement is to be effected liable to variation, chiefly according
as this or that ameliorating substance can be most readily obtained.
LECTURE XVI.
Exact chemical composition of soils. Their organic constituents. Mode of separat-
ing them. Analysis of soils. Inorganic constituents of soils. Composition of cer-
tain characteristic soils. Fertile soils, barren soils, soils capable of improvement.
Indications of analysis. Physical properties and mechanical relations of soils.
Their relations to water and to heat. Natural functions of or purposes served by
the soil.
IN the two preceding lectures we have considered the general
composition and origin of soils, and their relation to the geological
structure of the country in which they are found, and to the che-
mical composition of the rocks on which they rest. We have also
discussed some of the causes of those remarkable differences which
soils are known to present in their relations to practical agricul-
ture. But a more intimate and precise acquaintance with the che-
mical constitution of soils is necessary to a complete understand-
ing of the causes of these differences—of the exact effect which
its chemical composition has upon the fertility of a soil—and of
the remedy which in any given circumstances ought to be applied.
Some persons have been led to expect too much from the che-
mical analysis of a soil, as if this alone were necessary at once to
explain all its qualities and to indicate a ready method of impart-
ing to it every desirable quality, while others have as far depre-
ciated their worth, and have pronounced them in all cases to be
more curious than useful.” The truth here, as on most other sub-
jects, lies in the middle between these extreme opinions.
If you have followed me in the views I have endeavoured to
press upon you in regard to the necessity of inorganic food to
plants—which food can only be derived from the soil, and which
must vary in kind and quantity with the species of crop to be raised,
—you will at once perceive that the rigorous analysis of a soil may
* Boussingault, Annal. de Chim, et de Phys., lxvii. p. 9.
NATURE OF THE ORGANIC CONSTITUENTS OF SOILs. 513
impart most useful knowledge to the practical man in the form
of suggestions for its improvement. It may indeed show that to
apply the only available substances to the soil which are capable
of remedying its defects, would involve an expense for which, in
existing circumstances, the land would not yield an equivalent re-
turn. Yet even in this latter case the results of analysis will not
be without their value to the prudent man, since they will prevent
him from adding to his soil what he knows it already to contain,
and will set him upon the search after some more economical
source of those ingredients which are likely to benefit it the most.
It will be proper, therefore, to turn our attention briefly to the
consideration of the exact chemical composition of soils. .
§ 1. Of the evact nature of the organic constituents of soils.
We have already seen in a preceding lecture (p. 71) that all
soils contain a greater or less admixture of organic—chiefly vege-
table—matter, the total amount of which may be very nearly de-
termined by burning the dried soil at a red heat till all blackness
disappears. This vegetable matter we have also shown to consist of
several different chemical compounds, to which we shall here only
briefly allude. *
1°. Humus.-The general name of humus is given to the fine,
brown, light powder which imparts their richness to vegetable
moulds and garden soils. It is formed from the gradual decom-
position of vegetable matter, exists in all soils, forms the substance
of peat, and consists of a mixture of several different compounds
which are naturally produced during the decay of the different
parts of plants. It is distinguished into mild, sour, and coaly
humus.
The mild gives a brown colour to water but does not render it
sour, gives a dark brown solution when boiled with carbonate of
soda, evolves ammonia when heated with caustic potash or soda or
with slaked lime, and when burned leaves an ash which contains
lime and magnesia. The sour gives, with water, a brown solution
more or less acid. This variety is less favourable to vegetation than
the former, and generally indicates a want of lime in the soil. The
coaly humus gives little colour to water or to a hot solution of car-
bonate of soda, leaves an ash which contains little lime, occurs gene-
K k
b14. - IIUMIC, ULMIC, AND GEIC ACIDs.
rally on the surface of very sandy soils, and is very unfruitful. It
is greatly ameliorated by the addition of lime or wood ashes.
2°. Humic, ulmic, and geic acids.--When a fertile soil or a piece
of dry peat is boiled with a solution of the common carbonate of
soda of the shops, a brown solution, more or less dark, is obtained,
from which, when diluted muriatic acid (spirit of salts,) is added till
the liquid has a distinctly sour taste, brown flocks begin to fall.
This brown flocky matter consists of humic, or ulmic, or geic acid,
or a mixture of all the three. The composition, properties, and
mutual relations of these acids have already been described (pp. 71
to 78). -
They combine with lime, magnesia, alumina, and oxide of iron,
forming compounds (salts) which are respectively distinguished by
the names of humates, ulmates, and geates. They probably all ex-
ist in our soils ready formed, in variable proportions, and in com-
bination with one or more of the earthy substances above mention-
ed—lime, alumina, &c. They are produced by the decay of ve-
getable matter in the soil, which decay is materially facilitated by
the presence of one or other of these earthy substances, and by
lime especially,–om the principle that the formation of acid com-
pounds is in all such cases much promoted by the presence of a
substance with which that acid may combine. They predispose
organic substances to the formation of such acids, and consequently
to the decomposition by which they are to be produced.
We have already seen that plants derive a variable proportion
of their carbon from the soil, and chiefly through the medium of
these or similar acids. They dissolve readily in ammonia, and
animal manures which give off this compound in the soil facilitate
their entrance into the roots of those plants, which are cultivated
by the aid of such manures. They are also soluble in carbonate
of potash and carbonate of soda, which are contained in wood ashes
and in the ashes of weeds and of soils which are pared and burned.
When these substances, therefore, are applied to the land, they may
combine with, and, among their other beneficial modes of action, may
serve to introduce, these acids in larger quantity into the plant.
When exposed to the air these acids undergo decomposition in
the soil. They absorb oxygen from the air, and are changed into
crenic and apocrenic acids, and finally into carbonic acid and water,
CRENIC AND APOCRENIC ACIDS. 515
3°. Crenic and apocrenic acids. When soils are digested or
washed with hot water, a quantity of organic matter is not unfre-
guently dissolved, which imparts to the water a brownish yellow
colour. When the solution is evaporated to dryness, there re-
mains, besides the soluble saline substances of the soil, a variable
proportion of brown extractive looking matter, which is a mixture
of the acids here named with the ulmic, humic, and geic acids—all
in combination with potash, soda, lime, alumima, and other bases.
They are present also in the solution from which the humic acid
is thrown down by muriatic acid, as above described (see p. 74.)
These acids, as I have said, are formed in the soil during the
decay of vegetable matter, and are distinguished by a chemical
composition, and by properties which have already been explained.
Owing to their easy solubility these acids are more readily
washed out of the soil by the rains, and hence are rarely present
in any considerable quantity in specimens of soil which are sub-
mitted to analysis. They are frequently, however, met with in
springs and in the drainings of the land. They have even been
found in minute quantity in rain water, and as they have also been
detected in distilled water,” it is probable that they ascend into the
air in very small proportion with the watery vapour that rises during
the ordinary evaporation of water from the surface of the earth.
Both acids form insoluble compounds with the peroxide of iron
—and hence are found in combination with many of the ochrey
deposits from ferruginous springs, and with the oxide of iron by
which so many soils are coloured. The apocrenic acid has also a
peculiar tendency to combine with alumina, with which it forms a
compound insoluble in water, and in this state of combination it
probably exists not unfrequently, especially in clayey soils.
When heated with newly slaked quick-lime these acids give off
ammonia and carbonic acid. By the action of the air, and of lime
in the soil, they are probably decomposed in a similar mammer,
though with much less rapidity.
4°. Mudesous acid is another dark brown acid substance, which
is also produced naturally in the soil. It resembles the apocrenic,
in having a strong tendency to combine with alumina. In union
with this acid it is slowly washed out of the soil by the rains, or
* Firsten zu Salm-Horstmar. Poggend, Annal, liv, p. 254.
5] 6 oTHER ORGANIC COMPOUNDS IN THE SOIL.
filters through it when the water can find an outlet beneath.
This is seen to be the case in some of the caves on the Cornish
coast, where the waters that trickle through from above have gra-
dually deposited on their roof and sides a thick incrustation of
mudusite of alumina, known to mineralogists under the name of
Pigotite, (see p. 73.) -
Besides these acids, it is known that the formic, malic, and ace-
tic (vinegar) acids are produced in the soil during the slow decay
of vegetable matter of different kinds (Mulder). It is probable
that many other analogous compounds are likewise formed—which
are more or less soluble in water, and more or less fitted to aid in
the nourishment of plants. Indeed, organic substances in the soil
pass through many successive stages of decomposition, at each of
which they assume new properties, and become more or less capable
of aiding in the support of living races. The mature of the changes
undergone by vegetable matter at these successive stages is difficult
to investigate, because of the obstacles which lie in the way of ex-
actly separating from each other thesmall quantities of the different
organic compounds that occur mixed up together in the soil.
5°. Ulmin and humin are the names given to the black insoluble
organic substances in the soil. They have the same composition
as the ulmic and humic acids respectively (p. 74).
§ 2. Of the mode of separating the organic constituents of the soil.
The Several organic constituents of the soil may be separated in
the following manner:— -
1°. When a soil on being washed with hot water imparts a colour
to the solution, the liquid must be filtered and evaporated to perfect
dryness. On treating with water what remains after the evaporation,
the humic and ulmic acids, and most of their compounds remain in-
soluble, while the crenic and apocrenic acids are taken up by the
water along with the soluble saline matter which the soil may have
contained. By evaporating this second solution to perfect dryness,
weighing the residue, and then heating it to dull redness in the
air, the loss by burning will indicate something more than the
quantity of these acids present in the soil. By burning the dried
insoluble matter, also, the quantity of humic and ulmic acids pre-
sent in it may in like manner be determined.
ºx
eX
PREPARATION OF THESE ORGANIC SUBSTANCES. 517
2°. After being washed with pure water, the soil is to be boiled
with a solution of carbonate of soda, repeated once or twice as long
as a brown solution, more or less dark, is obtained. Being filter-
ed, and then rendered sour by muriatic acid, brown flocks fall,
which being collected on the filter, perfectly dried and weighed
give the quantity of humic, and of ulmic, and geic acids if any be
mixed with it in the soil. As this dry humic acid generally contains
Some earthy matter, it is more correct to burn it, and to deduct
the weight of the ash which may be left. We are at present ac-
quainted with no means by which the humic, ulmic, and geic acids
can be separated from each other. -
3°. The insoluble (coaly) humus still remains in the soil. On
boiling it now in a solution of caustic potash for a length of time,
and till a fresh solution ceases to become brown, the coaly humus
is entirely dissolved—being converted according to Sprengel into
humic acid. The addition of muriatic acid to this solution, till
it has a Sour taste, throws down the humic acid in the form of
brown flocks, which may be collected, dried, and weighed as be-
fore. -
4". If there be any cremate, apocrenate, or mudesite of alumina
in the Soil it is also dissolved by the potash, but is not thrown
down when the solution is rendered distinctly sour by muriatic
acid. But if the solution be filtered to separate the brown flocks,
and a solution of common soda be then added to it, the cremate
and mudesite of alumina fall in the form of a yellowish powder.
If this powder be well dried at 300 F., and be then burned, the
loss will indicate the proportion of organic acid matter in combi-
mation with the alumina. -
5". There may still remain in the soil a quantity of half decay-
ed roots which the potash has not dissolved. If the whole per
centage of the organic matter in the dry soil be determined by
burning a weighed portion, and if from this the sum of the other
substances determined as above be deducted, the remainder will
be proportion of undecayed roots. These of course consist chiefly
of cellulose and woody matter.
In general it is considered sufficient to ascertain only the whole
loss by burning, and the quantity taken up by carbonate of soda,
the proportion of the other substances, with the exception of the
518 IMPORTANT PRINCIPLES PREVIOUSLY ESTABLISHED.
wº.
roots, being in most cases so small as to be capable of being pre-
cisely estimated by great precautions only.
§ 3. On the exact chemical constitution of the earthy part of the soil.
In reference to the general origin of soils—to their geological
relations—and to the simplest mode of classifying them,--I have
shown you that the earthy part of nearly all soils consists essen-
tially of sand, clay, and lime. But in reference to their che-
mical relations to the plants which grow, or may be made to
grow upon them, it is necessary, as you are now aware, to take a
more refined and exact view of their composition. This will ap-
pear by referring to three important principles established in the
preceding lectures.
1°. That the ash of plantsgenerally contains a certain sensible pro-
portion of mine or ten differentinorganic substances (p. 312 and 410).
2°. That they can, in general, only derive these substances from
the soil, which must, therefore, contain them (p. 439). And—
3°. That the fertility of a soil depends, among other circum-
stances, upon its ability to supply readily and in sufficient abun-
dance all the inorganic substances which a given crop requires,
Now the quantity of some of these substances which is necessary
to plants is so very small, that nothing but a refined analysis of a
soil is capable, in many cases, of determining whether they are pre-
sent in it or mot—much less of explaining to what its peculiar de-
fects or excellencies may be owing—what ought to be added to it
in order to render it more productive—or why certain remarkable
effects are produced upon it by the addition of mineral or animal
l]] all Ull'C.S. -
Thus, for example, half a grain of gypsum in a pound of soil
indicates the presence of nearly two cwt. in an acre, where the soil
is a foot deep, +a quantity great enough, when applied as a top-
dressing to the land, to produce in many cases a remarkable luxu-
riance in the red clover crop. In 100 grains of the soil, this
quantity of gypsum amounts only to 1%gth of a grain,-a propor-
tion which only a very carefully conducted analysis would be able
to detect, and yet the detecting of which may be requisite to ex-
plain the unlike effects which are seen to follow the application of
gypsum or other top-dressings to different soils.
l
WHY REFINED ANALYSES ARE NECESSARY. 519
Again, the phosphoric acid is a no less necessary constituent of
the soil, than the sulphuric acid contained in gypsum. This acid
is generally in combination either with lime, with oxide of iron, or
with alumina—and, as it is much more difficult to detect and esti-
mate than the sulphuric acid, more care and skill are required to
determine its amount with any degree of accuracy. And as it is
generally present even in fertile soils in a very small proportion, it
is obvious that safe and useful conclusions in regard to this sub-
stance can be drawn only from such analyses as have been made
rigorously, according to the best methods, and with the greatest
attention to accuracy.
There are cases, no doubt, where a rough analysis may be of use,
where the cause of peculiarity is at once so obvious from the result
that further research is unnecessary—as where mere washing with
water dissolves out such a noxious substance as sulphate of iron
(green vitriol). But such cases are comparatively rare, and it more
frequently happens, that the cause of the special qualities of a soil
only begins to manifest itself when a carefully conducted analysis
approaches to its close. I shall, therefore, briefly describe to you
the methods to be adopted, in order to arrive at these more accu-
rate experimental results.” -
§ 4. Of the evact chemical composition of certain natural soils, and
of the results to be deduced from it.
But the importance of this attention to rigorous analysis will
more clearly appear, if I exhibit to you the composition of a few
of the numerous soils analysed by Sprengel and others in connec-
tion with the agricultural qualities and capabilities by which they
are severally distinguished. +
Is–FERTILE SOILS.
Soils are fertile which, besides being in a proper mechanical or
physical condition, contain the necessary organic substances, and
also a sufficient supply of all the mineral constituents which the
plants to be grown upon them are likely to require.
* As these methods of analysis involve considerable detail, I have transferred them
to the Appendix,
† The analyses of Sprengel are taken from his work on soils, Die Bodenkwndc.
520 THE SOIL OF RICH ARABLE LANDS.
10. Pasture—The following numbers exhibit the co mposition
of the surface soil in three fertile alluvial districts of Hanover,
where the land had been long in pasture.
Soil near From the banks of the Weser,
Osterbruch. near Hoya. near Weserbe.
Silica, quartz-sand, and silicates, ... 84.510 71°849 83°318
Alumina,............................... . 6'435 9:350 3.085
Oxides of iron, ........................ 2°395 - 5'410 5'840
Oxide of manganese, .................. 0°450 0.925 0-620
Lime, ................................. - 0-740 0'987 0.720
Magnesia, .............................. 0.525 0°245 0-120
Potash and soda extracted by water, 0.009 ... 0-007 0-005
Phosphoric acid,......... . . . . . ..... 0-120 0° 131 0.065
Sulphuric acid, .................. ... 0-046 0° 174 0.025
Chlorine in common salt, ............ 0-006 0-002 0:006
Humic acid, ....... .......... • * * * * * ... 0-780 l'270 - 0-800
Insoluble humus, ............... --... 2°095 7.550 4' 126
Organic matters containing nitrogen 0960 2°000 1-220
Water... ................................. ()-()29 0 1 00 • 0.050
l()0 100 100
These soils had all been long in pasture; the second is especially
celebrated for fattening cattle when under grass. It will be ob-
served that in none of them is any of the mineral ingredients
wholly wanting, though in all the quantity of potash and soda ca-
pable of being extracted by water is very small. This is ascribed
to the fact of their having been long in pasture, the supply of these
substances being gradually withdrawn by the roots of the grasses.
It is well known how, in our ordinary soils, grass is often reno-
wated—how the mosses, especially, are destroyed—by a dressing
of wood ashes, which owe their effect to the alkali they contain.
In the above soils the gradual decomposition of the silicates and
of the roots of the grasses themselves would continue to supply a
certain portion of alkaline matter for an indefinite period of time.
You will perceive that the soil which is the most celebrated for
its fattening power is also the richest in alumina, lime, phosphoric
acid, sulphuric acid, and vegetable matter. Whether these mine-
ral substances are really of consequence in laying on the fat of
animals, we shall consider in a subsequent lecture
2". Arable.—The following table exhibits the composition of
three soils, celebrated for yielding successive crops of corn for a
long period without manure.
SOILs POSSESSING A NATURAL SOURCE OF FERTILITY. 521
l. * 3.
From Nebtsein, From the banks of the From the polder
near Olmutz, Ohio, North America. of Alt-Arenberg,
- in Moravia. Soil. Subsoil. in Belgium.
Silica and fine sand, . ... ... 77-209 87-143 94.261 64'517
Alumina, ..................... 8'514 5-666 1.376 4'810
Oxides of iron, ............... 6'592 2:220 2-336 8°3] 6
Oxide of manganese,......... 1-520- 0°360 | 200 O'800
Lime,............. … ... . 0.927 0°564 0.243 *...* 9:403
Magnesia, ..... ............... 1:160 0-312 0.310 º 10.361
Potash chiefly combined with ! 0° 140 0 12ſ) • * - | 0-100
Silica, ........ ............ 0-240
Soda, ditto, ............... ... 0.640 0.025 l 0.013
Phosphoſie acid, º 0-651 0'060 trace 1-221
with lime & oxide of iron,
Sulphuric acid in gypsum, 0-011 0.027 0-034 0-000
Chlorine in common Salt, 0-0 || 0 0.036 trace () •003
Carb. acid united to the lime, – 0-080 *sºm-º.
Humic acid, .................. 0.978 1°304 -º-º-º-mºm 0.447
Insoluble humus, ........... 0°540 1.072 +-º-º-º: *mºse
organic substances contain- 1.108 roll -* -s
ing nitrogen, ...............
100 100 100 100
Of these soils, the first had been cropped for 160 years succes-
sively, without either manure or naked fallow. The second was a
virgin soil, celebrated for its fertility. The third had been un-
manured for 12 years, during the last mine of which it had been
cropped with beans—barley—potatoes—winter barley and red
clover—clover—winter barley—wheat—oats—maked fallow.
Though the above soils differ considerably, as you see, in the
proportions of some of their constituents, yet they all agree in this
—that they are not destitute of any one of the mineral compounds
which plants necessarily require in sensible quantity. You will
also observe how comparatively small a proportion of vegetable
matter, less than half a per cent, is contained in the fertile Belgian
soil—a fact to which I shall by and bye recall your attention. The
large proportions of lime and magnesia in this soil are also impor-
tant characters. -
3°. Soils which have a natural source of fertility.—Some soils,
which by their composition are not fitted to exhibit any great de-
gree of fertility, or for a very long period, are yet, by springs or
otherwise, so constantly supplied with soluble saline, and other
substances, as to enable them to yield a succession of crops, without
522 SOILS POSSESSING A NATURAL SOURCE OF FERTILITY.
manure, and without apparent deterioration. Such is the case
with the following soil from near Rothenfelde, in Osnabruck, which
gives excellent crops, though manured only once in 10 or 12
years:–
Silica and coarse quartz sand, e e 86-200
Alumina, © te - 2°000
Oxides of iron and a little phosphoric acid, e 2.900
Oxide of manganese, e 0-100
Carbonate and a little phosphate of lime, wº 4°160
Carbonate of magnesia, . & - 0°520
Potash and soda, * - e ‘ 0.035
Phosphoric acid, te * 0-020
Sulphuric acid, . • tº 0-021
Chlorine, . e 0-0 || 0
Humic acid, te ſe t 0°544
Insoluble humus, * e tº 3:370
Organic matter containing nitrogen, . .” 0° 120
100
You will see that, although in this soil all the inorganic sub-
stances are really present, yet the potash and soda, the phosphoric
and sulphuric acids, and the chlorine, are not in such abundance
as to justify us in expecting it to grow any long succession of
crops, without exhibiting the usual evidences of exhaustion. But
it lies on the side of a hill which contains layers of lime-stone and
marl, through which the surface waters find their way. These
waters afterwards rise into the soil of the field, impregnated with
those various substances of which the soil is in want, and thus, by
a natural mamuring, keep up a constant supply for each succeed-
ing crop.
This example is deserving of your particular attention, inasmuch
as there are many soils, in climates such as ours, which are yearly
refreshed from a similar source. Few spring waters rise to the
surface which are not fitted to impart to the soil some valuable in-
gredient, and which, if employed for the purposes of irrigation,
would not materially benefit those lands especially, on which our
pasture grasses grow. The same may also be said of the waters
which are carried off in some places so copiously by drains.
Whether these waters rise from beneath in springs, or, falling in
rain, afterwards sink through the soil, they in either case carry
into the brooks and rivers much soluble matter, which the plants
SPRINGS OFTEN ENRICII THE SOIL. 523
would gladly extract from them. On sloping grounds it would
prove a profitable economy to arrest these waters, and, before they
escape, to employ them in irrigation. -
The fact that nature thus on many spots brings up from beneath,
or down from the higher grounds, continual accessions of new
soluble matter to the soil, will serve to explain many apparent ano-
malies, and to account for the continued presence of certain sub-
stances in small quantity, although year by year portions of them
are carried off the land in the crops that are reaped, while no re-
turn is made in the shape of artificial manure. It will also in some
instances account for the fact that, after a hard cropping, prolong-
ed until the soil has become exhausted, a few years' rest will com-
pletely re-invigorate some soils, and render them fit to yield new re-
turns of abundant corn. Other causes, as we shall hereafter see,
generally operate in bringing about this kind of natural recovery,
but there can be no question that in circumstances such as I have
now adverted to, this recovery may be effected in a much shorter
period of time.
4°. Importance of depth and uniformity of soil.—If the surface
soil be of a fertile quality, and other circumstances be favourable,
ample returns will be sure from any cultivated crops. But where
the subsoil is similar in composition to that of the surface—not only
may the fertility of the land be considered as almost inexhaustible,
but those crops also which send their roots far down will be able
permanently to flourish in it. This factisillustrated by the composi-
tion of the following soils from the neighbourhood of Brunswick:—
1. 2.
/--——º- ——s
Soil. Subsoil. Subsoil.
Silica and fine quartz sand, ... ... 94'724 97'340 90'035
Alumina, ........ , a # 8 º' & & e º s & tº s & s º a l'638 0-806 1976
Oxides of iron, .................. | 1:9 l'I26 5'815
tº 60 šºv
Oxide of manganese, ......... | 0.075 0-240
Lime, ................................. l:028 0.296 0-022
Magnesia, .......................... trace 0.095 (). 115
Potash and soda, .................. 0.077 ()' ſ l 2 0-300
Phosphoric acid, .................. 0°024 0.015 O'008
Sulphuric acid, ..................... 0-0 l () trace l' 399
Chlorine, ........................... 0.027 trace trace
Humic acid, ........................ 0°302 (). 135
Tnsoluble humus, . . . ......... 0-2 l ()
] ()() l 00 I () ()
**
524. ExACT CONSTITUENT OF SOME UNFRUITFUL SOILs.
The first of these soils produced excellent crops of all deep-root-
ed plants—lucerne, sainfoin (esparcette), hemp, carrots, poppies,
&c.—and with the aid of gypsum, red clover and leguminous
plants (vetches, peas, and beans), in great luxuriance. The for-
mer of these facts is explained by the great similarity in composi-
tion which exists between the surface and the under soils. To
deep-rooted plants also the magnesia, in which the surface is defi-
cient, is capable of being supplied by the under soil. The effect
of the gypsum is accounted for by the almost total absence of sul-
phuric acid in the subsoil, but which the application of gypsum
has introduced into the upper soil.
The second soil was taken from a field in which sainfoin died re-
gularly in the second or third year after it was planted. This was
naturally attributed to something in the subsoil. And by the
analysis above given, it was found to contain much sulphuric acid
in combination with oxide of iron, forming sulphate of iron (green
vitriol). This salt being noxious to plants, began to act upon the
crop of Sainfoin as soon as the roots had gone so deep as to draw
sufficient supplies from the subsoil, and it thus gradually poisoned
them, so that they died out in two or three years.
FI. —BARREN OR UNFRUITFUL SOILS.
Soils are unfruitful or altogether barren, either when they con-
tain too little of one or more of the inorganic constituents of
plants, or when some substance is present in them in such quan-
tity as to become hurtful or poisonous to vegetation. The pre-
sence of sulphate of iron in the subsoil just described is an illus-
tration of the latter fact ;-in what way the deficiency of certain
substances really does affect the agricultural capabilities of the soil
will appear from the following analyses:—
º 2. 3. 4.
Moor-land soil, Another Sandy Soil on the
near Aurich, soil, from soil, near Muschel-
East Friesland. the same Wettingen, kalk,
neighbour- in Lüne- near Mühl-
Soil. Subsoil. hood. burg. hausen.
Slica and quartz sand, 70°576 95-190 61-576 96 : 000 77-780
Alumina, ...... ........ 1.050 2.520 0°450 0°500 9-490
Oxides of iron, ......... 0.252 1'460 0.52.4 ° 2'000 5'800
Oxide of manganese, ... trace 0.048 trace . trace ()' ] 05
Lime, ............... ..... do. (): 33 (): 320 ()' ()0] ()'866
Magnesia, ...…. 0.012 (). I 25 (): 130 trace ().723
1.
Moor-land soil,
near Aurich,
East Friesland. ,
2. 3. 4.
Another Sandy Soil on the
soil, from soil, near Muschel-
the same Wettingen, kalk,
CAUSES OF THEIR. UNFRUITFULNESS. 525
neighbour- in Lüne- near Mühl-
Soil. Subsoil. hood. burg. hausen.
Potash, .................. ti-ace 0.072 trace trace trace
Soda, ..................... do. 0-180 do. do. do.
Phosphoric acid, ......... do. 0-034 do. do. 0.003
Sulphuric acid, ....... ... do. 0.020 do. do. trace
Carbonic acid, ... ......... & 4 - e & g tº gº tº O'200
Chlorine, .................. trace 0-0 15 trace trace trace
Humic acid, ............ l 1910 ll 470 0-200 0.732
Insoluble humus, ... ... 16:200 25'530 1.299 0-200
Water,..................... 4-096
100 1:00 100 100 100
Each of these analyses is deserving of attention.
1°. That the barrenness of the moor land soils (1 and 2) is to
be attributed to their deficiency in the numerous substances of
which they contain only traces, may almost be said to be proved by
the fact—one long recognised and acknowledged on many of our
moor-land and peaty soils—that when dressed with a covering of
the subsoil they become capable of successful cultivation. The
analysis of the subsoil in the second column shows that it contains a
notable proportion of all those mineral constituents in which the
soil itself is defective—and to the effect of these, therefore, the im-
provement produced upon the soil, by bringing it to the surface, is
in a great measure to be attributed. -
2°. The Sandy soil, No. 3, is evidently barren for the same reason
as the moor-land soils, 1 and 2. The soil, No. 4, rests on lime-
stone, and was mixed with 7 per cent. of lime-stone gravel, and
contains a great number of the substances which plants require—
but its unfruitfulness was ascribed to the want of potash and soda,
of sulphuric acid, and of chlorine. Wood ashes and a mixture of
common salt with gypsum or sulphate of soda would probably have
remedied these defects.
3°. Among the fertile arable soils to which I have directed your
attention (p. 521 and 523), was one from Belgium, and another from
Brunswick, in which the proportion of organic matter was less than
half a per cent of their whole weight. In the above table, on the
other hand, we have two nearly barren soils, containing each 11 per
cent, of humic acid, besides a much larger proportion of insoluble
526 WHAT RENDERS A SOIL FERTILE.
organic matter. It is obvious, therefore, that the fertility of a soil
is not dependant upon its containing this or that proportion of ve-
getable matter, either in a soluble or an insoluble form. It is cer-
tainly true that many very fertile soils do contain a considerable
quantity of organic matter, in a form in which it may readily
yield nourishment to the roots of plants. Yet such soils are not
fertile merely in consequence of the presence of this organic
matter, as a source of organic food to the plant. It may be pre-
sent, and yet the soils, like those above-mentioned, may remain
barren. Where soils become fertile apparently by the long ac-
cumulation of such vegetable matter in the soil, it is not merely
because of the increase of purely organic substances such as the
humic and ulmic acids, but, because the decaying vegetable matter
which produces them contains also, and yields to the soil, a con-
siderable abundance of some of those inorganic substances which
plants necessarily require. The organic matter is an indication of
their presence in such soils. But they may be present without the
organic matter. They may either be duly proportioned in the soil
by nature—or they may be artificially mixed with it, and then this
use of the organic matter may be dispensed with. It is of more
importance to bear this in mind, because not only vegetable physi-
ologists, but some zealous chemists also, have laid too great a stress
upon the quantity of soluble and insoluble organic matter contained
in a soil, and have been led to consider it as a safe index of the
relative fertility of different soils.
The history of Science shows, by many examples, that those men
who adopt extreme views, who attempt to explain all phenomena
of a given kind, by reference to a single specific cause—though
wrong in their own opinions, have yet been of great use in the ād-
vancement of certain knowledge. Their arguments, whether well
or ill founded, lead to discussion, to further investigation, to the
discovery of exceptional cases, and, finally, to the general adoption
of modified views which recognise the action of each special cause
in certain special cases, but all in subordination to some more ge-
neral principle.
Thus, if some ascribe the fertility of the soil to the presence of the
alkalies in great abundance, others to that of the phosphates, others
to that of lime, others to that of alumina, and others, finally, to that
COMPOSITION OF READILY IMPROVABLE SOILs. 527
of vegetable or animal matter in a soluble state—all these extreme
opinions are reconciled, and their partial truths recognised, in one
general principle, that a soil to be fertile must contain all the sub-
stances which the plant we desire to grow can only obtain from the
soil, and in such abundance as readily to supply all its wants; while
at the same time it must contain nothing hurtful to vegetable life.
III.-SOILS CAPAIBLE OF IMPROVEMENT BY THE ADDITION OF
MINERAL MATTER.
On the principle above stated depends in very many cases the
mode of improving soils by the addition of mineral substances, as
well as the method of explaining the remarkable effects occasionally
produced by their admixture with the land. The following ana-
lyses will place this matter in a clearer light:—
& l Q 3 4
Soil near Pa- Near Draken- Near Gan- Near
dingbiittel, on burg, on the dersheim, in Bruns- .
the Weser. Weser. Brunswick. wick.
Silica and quartz Sand,...... 93.720 92°014 90°22'l 95.698
Alumina, ..................... 1740 2’652 2' 106 0.504
Oxide of iron, ........ ...... 2°060 3.192 3°951 2-496
Oxide of manganese, ...... 0.320 0.480 0.960 trace
Lime, ........................ 0°] 21 0'24.3 0°539 0.038
Magnesia, ..................... O-700 0-700 0-730 0.147
Potash (chiefly in º 0.062 0-125 0.066 \
nation with silica,)...... **, O'000
Soda, ...... (do.) ............ 0-109 0.026 0.010
Phosphoric acid, ............ 0 1 03 ().078 0.367 0°l 64
Sulphuric acid,............... 0.005 trace trace 0.007
Chlorine in common salt,... 0-050 trace 0.010 ():010
Humic acid, ............ ..... O'890 0-340 0-900 0-626
Other organic matter, ...... 0°] 20 0 - 150 0-140 0-220
100 100 . 100 100
The first of these soils produces naturally beautiful red clover—
the second produces very bad red clover. On comparing the con-
stitution of the two soils we see the second to be deficient in sulphuric
acid and chlorime. A dressing of gypsum and common salt would
supply these deficiencies, and might be expected to render it capa-
ble of producing this kind of clover. The third soil is remarkable
for growing luxuriant crops of pulse, when manured with gypsum.
The almost total absence of sulphuric acid explains this effect. The
fourth soil was greatly improved by soap-boiler's ash, which sup-
plied it with lime, magnesia, manganese, and other substances.
528 CAPABILITIES OF SOIL ASCERTAINED BY ANALYSIS.
Iv.—SOILS OF WHICH THE CAPABILITIES ARE TO BE ASCERTAINED
BY ANALYSIS.
Mulder has published the following analyses made in his labo-
, ratory by von Baumhauer of the soil of a tract of land in North
Holland, gained by embankment from the sea.
The three samples of soil were taken from the surface, from a
depth of 15 inches, and from one of 30 inches respectively; and the
question asked was—is this soil likely to become fertile after the salt
water shall have been washed out of it? The answer was—it issure
to become fertile after the rains have sweetened it; because it con-
tains in abundance all the organic and inorganic substances which
are essential to the growth of plants. The correctness of this opi-
mion appears from the following results of the analyses:–
Fifteen Thirty
Surface. inches deep. inches deep.
Organic matter and combined water, .. 8.324 7,700 9.348
Humic acid, .... ..... '............... . . . . . 2.798 3.911 3.428
Crenic acid, ................... : . . . . . . . . . . . . . 0.77] 0.731 0.037
Apocrenic acid, ........................... 0.107 0.160 0.152
Potash, .............…......... ‘.... ... l.026 l.430 1.52]
Soda, ... ......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.972 2.069 1.937
Ammonia,.................................... 0.060 0.078 0.075
Lime. ...................... e is a e s tº is a 2 s • * * * * * 4,092 5.096 2,480
Magnesia, .......... ..... .................. 0.130 0.140 0.128
Peroxide of iron, ........................... 9,039 10.305 11.864
Protoxide of iron, ....................... ... 0.350 0.563 , 0.200
Protoxide of manganese, .................. 0.288 0.354 0.284
Alumina, ........ ..................... ...... 1.364 2,576 2.410.
Phosphoric acid, .................. ........ 0.466 0.324 0.478
Sulphuric acid, .............................. 0.896 1. 104 0.576
Carbonic acid, ... ........... ............... 6,085 6.940 4.775
Chlorine, ...... ... • * * * * * * * * * * * * * * * * * * * * * * * * * * * 1.240 1.382 1.4.18
Soluble silica, ....................... . . . . . . . 2.340 2.496 2.286
Insoluble silicates, ........................ 57.646 5.1.706 55:372
LOSS, ............. * * * * * * * * , - - - - - - - - - - - - - - - - - - ... 1.006 ().935 1.231
100.* 100.* 100.*
I need not further multiply examples to show you how much
real knowledge is to be derived from a rigidly accurate analysis,
* Von Baumhauer, Mulder's Scheckundige Owderzoekºngen, Deel, 2, Stuck, 6, p. 513.
PHYSICAL PROPERTIES OF SOILS. 529
not only in regard to the agricultural capabilities of a soil, but
also in regard to the matural and necessary food of plants, and to
the manner in which mineral manures act in promoting and in-
creasing their growth. The illustrations I have already present-
ed will satisfy you—
1". That a fertile soil must contain all the inorganic constituents
which the plant requires, and mone that are likely to injure it.
2° That if the addition of a given manure to the soil render it
more fertile—it is because the soil is defective in one or more of
those substances which the manure contains, or that the manure, as
is often the case with lime, renders more available to the plant
what is already present in the soil.
3°. That if a given application to the land fail to improve it—
of gypsum, of bone-dust, of common salt, of sulphate of potash for
example—it is because enough of the substance applied is already
present, or because something else is still wanting to render the
previous additions available.
4°. That the result of extended experience in our country—that
the clay soils are best for wheat, and sandy soils, such as that of
Norfolk, for barley—is not to be considered as anything like a
law of nature, setting aside the clay land for the special growth of
wheat, and denying to the Sandy soils the power of yielding abun-
dant crops of this kind of grain. Almost every district can pre-
sent examples of well cultivated fields, where the contrary is proved
—and the wheat crops which are yearly reaped from the sandy
plains of Belgium demonstrate it on a more extended scale.
Chemically speaking, a soil will produce any crop abundantly,
provided it contain an ample supply of all that the crop we wish
to raise requires from the soil. But in practice soils which do
contain all these substances plentifully, are yet found to differ in
their power of yielding plentiful returns to the husbandman. Such
differences arise from the climate, the exposure, the colour, the fine-
ness of the particles, the lightness or porosity of the soil—from the
quantity of moisture it is capable of retaining, or from some other
of its numerous physical properties. These physical properties,
therefore, it is necessary shortly to consider.
§ 4. Of the physical properties of soils.
To the physical properties of soils was formerly ascribed a much
L l
530 THE ABSOLUTE WEIGHT OF SOILS.
more fundamental importance than we can now attach to them.
Crome and Schübler regarded the fertility of a soil as entirely de-
pendant upon its physical properties. Influenced by this opinion,
the former published the results of an examination of numerous
soils in the Prussian provinces, which are now possessed of no
scientific interest; because they merely indicate the amount of clay,
sand, and vegetable matter which these soils severally contained.”
The latter completed a very elaborate examination of the physical
properties of soils, which is highly useful and instructive;f but the
defective mature of which, in accounting for their agricultural capa-
bilities, became evident to the author himself, when the more cor-
rect and scientific views of Sprengel afterwards became known to
him. In giving, therefore, their due weight to the physical pro-
perties, we must not forget that in nature they are subordinate
to the chemical composition of soils. Plants may grow upon a soil,
whatever its physical condition—if all the food they require be
within their reach—while, however favourable the physical con-
dition may be, nothing can vegetate in a healthy manner, if the
soil be deficient in some necessary kind of food, or contain what is
destructive to vegetable life. - -
Of the physical properties of soils the most important are their
density, their power of absorbing and retaining water and air, their
capillary action, their colour, and their consistence or adhesive
power. There are one or two others, however, to which it will be
necessary shortly to advert.
I. —MECHANICAL RELATIONS OF SOILS.
1°. The density and absolute weight of a soil.--Some soils are
much heavier than others, not merely in the ordinary sense of
heavy and light, as denoting clayey and sandy soils, but in refe-
rence to the absolute weight of equal bulks. Thus a cubic foot of
dr y Siliceous or calcareous sand—weighs about ...... 1 10 lbs.
Half sand and half clay, .............................. 95
Of common arable land, from..... ............ 80 to 90
Of pure agricultural clay, (p. 442) ......... . . ..... 75
Of garden mould, richer in vegetable matter,...... 7
Of a peaty soil, from ........................... 30 to 5
# Recorded in his Grundsätze der Agricultu, Chemie.
+ Der Boden und sein werhilltniss zu den Gewächsen.
FINENESS OF THE PARTICLES OF SOILs. 531
Sandy soils, therefore, are the heaviest. The weight diminishes
with the increase of clay, and lessens still further as the quantity
of vegetable matter augments.
In practice the denser a soil is, the less injury will be done to
the land by the passage of carts and the treading of cattle in the
ordinary operations of husbandry. In a theoretical point of view
it is of consequence to vegetation, first, in so far as, according to
the experiments of Schübler, the denser soils retain their warmth
for a longer period when the sun goes down, or a cold wind comes
on ; thus a peaty soil will cool as much in an hour and a half
as a pure clay in two or a sand in three hours: and second, in so
far as the air gains slow and imperfect admission into soils which
are very close or compact in their character.
2°. Of the state of division of the constituent parts of the soil.-
With the relative weight of different soils, their state of division is
in some degree connected. Some soils consist of an admixture of
exceedingly fine particles both of sand and clay, while in others,
coarse sand, stones, and gravels, largely predominate. The state
of a soil in this respect has a material influence upon its productive
character, and consequently upon its money value, since the la-
bours of the husbandman, in lands of a stiffer and more coherent
nature, are chiefly expended in bringing them into this more fa-
vourable powdery condition. In the description and examination
of a soil, therefore, this property ought by no means to be passed
lightly over, since it is one in regard to which a mere chemical
analysis gives us little or no information. -
In some parts of the country the farmer diligently gathers the
stones off his land, while in others the practice is condemned as
hurtful to the arable crops. The latter fact is explained by sup-
posing that these stones in winter afford shelter to the winter-corn,
and in warmer seasons protect the ground in some degree from
the drying winds, and retain beneath them a supply of moisture of
which the neighbouring roots can readily avail themselves. Some-
thing probably depends, however, upon the nature or composition
of the stones themselves, and upon what, by their decomposition,
they are capable of yielding to the soil.
39. Firmness and adhesive power of soils.--When soils dry in
the air they cohere and become hard and stiff in a greater or less
degree. Pure siliceous sands, alone, do not at all cohere when
532 ADHESION OF SOILS TO THE PLOUGH.
dry—while pure clays become hard and very difficult to pulverize.
In proportion to the quantity of sand with which the latter are
mixed, do their tenacity and hardness diminish. The difficulty of
reducing clays to a fine powder in unfavourable seasons, or of
bringing them into a good tilth, may be overcome, therefore, by
an admixture of sand or gravel, but there are few localities where
the expense of such mixing does not present an obstacle to its adop-
tion on any large scale. Thorough draining, however, subsoil
ploughing, and careful tillage, will gradually bring the most re-
fractory soils of this character into a condition in which they can
be more perfectly and more economically worked.
Soils also adhere to the plough in different degrees, and, there-
fore, present a more or less powerful obstruction to its passage.
All soils present a greater resistance when wet than when dry, and
all considerably more to a wooden than to an iron plough. A
sandy soil, when wet, offers a resistance to the passage of agricul-
tural implements, equal to about 4 lbs. to the square foot of the
surface which passes through it—a fertile vegetable soil or rich
garden mould a resistance of about 6 lbs., and a clay from 8 to
25 lbs. to the square foot. Such differences will naturally form
no inconsiderable item in the calculations of the intelligent farmer
when he estimates the cost of working, and the consequent rent he
can afford to pay for soils, otherwise equal in value.
II.-RELATIONS OF SOILS TO WATER.
1°. Power of imbibing moisture from the air.—When a portion
of soil is dried carefully over boiling water, or in an oven, and is
then spread out upon a sheet of paper in the open air, it will gra-
dually drink in watery vapour from the atmosphere, and will thus
increase in weight. In hot climates and in dry seasons this pro-
perty is of great importance, restoring as it does to the thirsty soil,
and bringing within the reach of plants, a portion of the moisture
which during the day they had so copiously exhaled.
Different soils possess this property in unequal degrees. During
a night of 12 hours, and when the air is moist, according to Schüb-
ler, 1000 lbs. of a perfectly dry
Quartz sand will gain o 0 lbs. Clay loam & sº 25 lbs.
Calcareous sand . º 2 Pure agricultural clay . 37
Loamy soil te . 21
RELATIONS OF SOILS TO WATER. 533
and peaty soils, or such as are rich in vegetable matter, a still
larger quantity. - -
Sir Humphry Davy found this property to be possessed in the
highest degree by the most fertile soils. Thus, when made per-
fectly dry, 1000 lbs. of a
Very fertile soil from East Lothian gained in an hour 18 lbs.
Very fertile soil from Somersetshire ę . 16
Soil worth 45s. per acre from Mersea, in Essex . 13
Sandy soil worth 28s., from Essex º . 11
Coarse sand worth only 15s. * * ... 8
Soil of Bagshot Heath & ë 3%
Fertile soils, therefore, possess this property in a very conside-
rable degree, and, though we cannot, by determining this property
alone, infer with safety what the fertility of a soil is likely to prove
—since peaty soils and very strong clays are still more absorbent
of moisture, and since this property is only remotely connected
with the special chemical composition of a soil—yet among arable,
Sandy, and loamy lands it certainly does, as Sir Humphry Davy
states, afford one means of judging of their relative agricultural
capabilities. -
2°. Power of containing or holding water.—If water be poured
drop by drop upon a piece of chalk or of pipe-clay, it will sink in
and disappear, but if the dropping be continued, the pores of the
earth will by degrees become filled with water, and it will at length
begin to drop out from the under part as it is added above. This
property is exhibited in a certain degree by all soils. The rain
falls and is drunk in, the dew also descends, and is thus taken pos-
session of by the soil. But after much rain has fallen the earth
becomes saturated, and the rest either runs off from the surface or
sinks through to the drains. This happens more speedily in some
soils than in others. Thus from 100 lbs, of dry soil, water will
begin to drop—if it be a
Quartz sand, when it has absorbed 25 lbs.
Calcareous sand, e 29
Loamy soil, tº e 40
English chalk, g º 45—J.
Clay loam, º * 50
Pure clay & * 70
but a dry peaty soil will absorb a very much larger proportion
* Sir H. Davy's works, vol, vii. p. 326.
534 THEIR POWER OF RETAINING WATER.
(Schübler), before it suffers any to escape. Useful arable soils
are found to be capable of thus containing from 40 to 70 per cent.
of their weight of water. In Germany it is supposed that, if the
quantity be less than this, the soils are best adapted for pine planta-
tions, if greater, for laying down to grass.
In dry climates this power of holding water must render a soil
more valuable, whereas in climates such as ours, where rains ra-
ther over-abound, a simple determination of this property will
serve to indicate to the practical farmer on which of his fields it is
most important to him, in reference to surface water, that the ope-
ration of draining should be first and most effectually performed.
The more water the soil contains within its pores, the more it has
to part with by subsequent evaporation; and, therefore, the colder
it is likely to be. The presence of this water also excludes the
air in a great degree, so that for these, as well as for other reasons,
it is desirable to afford every facility for the speedy removal of
the excess of water from such soils as absorb it, and are capable of
containing it in a very large proportion.
3°. Power of retaining water when exposed to the air.—Unless
when rain or dew are falling, or when the air is perfectly saturat-
ed with moisture, watery vapour is constantly rising from the sur-
face of the earth. The fields, after the heaviest rains and floods,
gradually become dry, though this, as every farmer has observed,
takes place in some fields with much greater rapidity than in others.
Generally speaking, those soils which are capable of arresting and
containing the largest portion of the rain that falls, retain it also
with the greatest obstimacy, and take the longest time to dry.
Thus a sand will become as dry in one hour as a pure clay in three,
or a piece of peat in four hours. This, therefore, not only ex-
plains, and shows the correctness of, the well-known distinctions of
warm and cold soils, but exhibits another strong argument in fa-
vour of a perfect drainage of stiff soils, and of such as contain a
large proportion of decaying vegetable matter.
4°. Capillary power of the soil.-When water is poured into
the sole of a flower-pot, the soil gradually sucks it in and becomes
moist even to the surface. The same takes place in the soil of the
open fields. The water from beneath—that contained in the sub-
soil—is gradually sucked up to the surface. Where water is pre-
CAPILLARY POWER OF THE SOIL. 535
sent in excess, this capillary action, as it is called, keeps the soil
always moist and cold.
The tendency of the water to ascend, however, is not the same
in all soils. In those which, like sandy soils and such as contain
much vegetable matter, are open and porous, it probably ascends
most freely, while stiff clays will transmit it with less rapidity.
No precise experiments, however, have yet been made upon this
subject, chiefly, I believe, because this property of the soil has not
hitherto been considered of the importance it really possesses, in
reference to the general vegetation of the globe. Let us attend
a little to this point.
I have already drawn your attention to the fact, that the speci-
mens of soil which are submitted to analysis generally contain a
very small proportion of Saline matter, and yet that in a crop
reaped from the same soil a very considerable proportion exists.
This I have attributed to the action of the rains which dissolve out
the soluble saline matter from the surface soil, and, as they sink,
carry it with them into the subsoil; or from sloping grounds, and
during very heavy rains, partly wash it into the brooks. Hence
from the proportion of soluble matter present at any one time in
the surface soil, we cannot safely pronounce as to the quantity which
the whole soil is capable of yielding to the crop that may be grown
upon it. For when warm weather comes and the surface soil
dries rapidly, then by capillary action the water rises from beneath,
bringing with it the soluble substances that exist in the subsoil
through which it ascends. Successive portions of this water eva-
porate from the surface, leaving their saline matter behind them.
And as this ascent and evaporation go on as long as the dry
weather continues, the saline matter accumulates about the roots
of plants, so as to put within their reach an ample supply of every
soluble substance which is not really defective in the soil. I be-
lieve that in Sandy soils, and generally in all light soils, of which
the particles are very fine, this capillary action is of great impor-
tance, and is intimately connected with their power of producing
remunerating crops. They absorb the falling rains with great ra-
pidity, and these carry down the soluble matters as they descend
—so that when the soil becomes soaked, and the water begins to
flow over its surface, the saline matter being already buried deep,
536 ITS IMPORTANCE TO WIFGETATION.
is in little danger of being washed away. On the return of dry
weather, the water re-ascends from beneath and again diffuses the
soluble ingredients through the upper soil.
In climates, such as ours, where rains and heavy dews frequently
fall, and where the soil is seldom exposed for any long period to
hot summer weather unaccompanied by rain, we rarely see the full
effect of this capillary action of the soil. But in warm climates,
where rain seldom or never falls, the ascent of water from beneath,
where springs happen to exist in the subsoil, goes on without inter-
mission. And as each new particle of water that ascends brings
with it a particle, however small, of saline matter (for such waters
are never pure), which it leaves behind when it rises into the air
in the form of vapour, a crust, at first thin, but thickening as time
goes on, is gradually formed on the surface of the soil. Such crusts
are seen in the dry season—in Greece, in India, in Egypt, and in
many parts of Africa and America. In hot, protracted summers they
may be seen on the .surface of our own fields, but they disappear
again with the first rains that fall. Not so where rains are un-
known. And thus on the arid plains of Peru, and on extensive
tracts in Africa, a deposit of saline matter, sometimes many feet
in thickness, is met with on the surface of wide plains, in the hol-
lows of deep valleys, and on the bottoms of ancient lakes. Such
an incrustation, probably so formed, is the bed of nitrate of soda
in Peru, from which all our supplies of that salt are drawn; such
are the deposits of carbonate of soda (troma) which form a consider-
able article of commerce in some parts of Africa; and such the
mineral soda (urao) extracted from the soil in the American State
of Columbia.
5°. Contraction of the soil on drying.—- Some soils in dry weather
diminish very much in bulk, shrink in, and crack. Thus, after
being soaked by rain, pure clay and peaty soils diminish in bulk
about one-fifth when they are again made perfectly dry—while
sand has the same bulk in either state. The more clay or vegetable
matter, therefore, a soil contains, the more it swells and contracts
in alternate wet and dry weather. This contraction in stiff clays
can scarcely fail to be occasionally injurious to young roots from
the pressure upon the tender fibres to which it must give rise,
y
while in light Sandy soils the compression of the roots is nearly .
4
RELATIONS OF THE SOIL TO THE ATMOSPHERE. 537
uniform in all weathers, and they are undisturbed in their natural
tendency to throw out off-shoots in every direction. Hence another
good quality of light soils, and a less obvious benefit which must
necessarily result from rendering soils less tenacious by admixture
or otherwise.
III. — RELATIONS OF THE SOIL TO THE ATMOSPHERE.
Power of absorbing oxygen and other gaseous substances from the
air.—1°. The importance of the oxygen of the atmosphere, first
to the germination of the seed, and afterwards to the growth of
the plant, I have already sufficiently insisted upon. It is of con-
sequence, therefore, that this oxygen should gain access to every
part of the soil, and thus to all the roots of the plant. This ac-
cess can be facilitated by artificially working the land, and thus
rendering it more porous. But some soils, in whatever state they
may be in this respect, have been found to absorb oxygen with
more rapidity, and in larger quantity, than others. Thus clays
absorb more oxygen than sandy soils, and vegetable moulds or
peats more than clays. This difference depends in part upon the
natural porosity of these different soils, and in part also upon the
chemical constitution of each. If the clay contain iron or manga-
mese in the state of first or prot-oxides, these will naturally absorb
oxygen for the purpose of combining with it, while the decaying
vegetable matter will, in like manner, in such as contain it largely,
drink in much oxygen to aid their natural decomposition.
2°. Besides the gases, oxygen and nitrogen, of which the air
principally consists, the soil absorbs also carbonic acid from the
atmosphere, and portions of those various vapours, whether of
ammonia and other effluvia which rise from the earth, or of nitric
acid formed in the air, and these, in the opinion of some chemists,
contribute very materially to its natural fertility. This, however,
is very much a matter of conjecture, and no experiments have
been made as to the relative capabilities of different soils thus to
extract vegetable food from the surrounding air. One fact, how-
ever, seems to be clearly ascertained, that all soils, namely, absorb
gaseous substances of every kind most easily and in the greatest
abundance when they are in a moist state. A fall of rain or a
descent of dew, therefore, will favour this absorption in dry sea-
538 RELATIONS OF THE SOIL TO HEAT.
sons, and it will also be greatest in those soils which have the
power of most readily extracting watery vapour from the air during
the absence of the sum. Hence the influence of the dews and of
gentle showers on the progress of vegetation is not limited to the
mere suſpply of water to the thirsty ground, and of those vapours
which they bring with them as they descend to the earth, but is
partly due also to the power which they impart to the moistened
soil, of extracting for itself new supplies of gaseous matter from
the surrounding atmosphere.
IV.-RELATIONS OF THE SOIL TO HEAT.
There are some of the relations of soils to heat, which have con-
siderable influence upon their power of promoting vegetation.
These are the rapidity with which they absorb heat from the air,
the temperature they are capable of attaining under the direct ac-
tion of the sum's rays, and the length of time during which they
are able to retain this heat.
1°. Power of absorbing heat.—It is an important fact, in refe-
rence to the growth of plants, that during sun-shine, when the
Sun's rays beat upon it, the earth acquires a much higher tempe-
rature than the surrounding air. This temperature, even in our
British summers, very often ascends to 110°, and sometimes to
nearly 150', while the air in the shade is between 70° and 80° only.
Thus the roots of plants are supplied with that amount of warmth
which is most favourable to their rapid growth.
Dark-coloured—such as black and brownish red—soils absorb
the heat of the sun most rapidly, and therefore become warm the
soonest. They also attain a higher temperature—by a few de-
grees only, however, (3" to 8%), than soils of other colours, and
thus, under the action of the same sun, will more rapidly promote
vegetation. In climates, such as ours, where the presence of the
sun is often wished for in vain in time of harvest, this property of
the soil possesses a considerable economical value. In other parts
of the world, where sun-shine abounds, it becomes of less impor-
tance.
Every one will understand that the above differences are ob-
served among such soils only as are exposed to the same sun un-
der the same circumstances. Where the exposure or aspect of the
POWER OF SOILS TO RETAIN HEAT. 539
soil is such as to give it the prolonged benefit of the sun's rays, or
to shelter it from cold winds, it will prove more propitious to ve-
getation than many others less favourably situated, though darker
in colour and more free from superfluous moisture.
2°. Power of retaining heat.—But soils differ more in their power
of retaining the heat they have thus absorbed. You know that
all hot bodies, when exposed to the air, gradually become cool.
So do all soils; but a sandy soil will cool more slowly than a clay,
and the latter than a soil which is rich in vegetable matter. The
difference, according to Schübler, is so great, that a peaty soil
cools as much in one hour as the same bulk of clay in two, or of
sand in three hours. This may, no doubt, have considerable in-
fluence upon growing crops, inasmuch as, after the sun goes down,
the sandy soil will be three hours in cooling, while the clays will
cool to the same temperature in two, and rich vegetable mould in
one hour. But on those soils which cool the soonest, dew will
first begin to be deposited,—and it is doubtful, where the soils are
equally drained, whether, in summer weather, the greater proportion
of dew deposited on the clays and vegetable moulds may not more
than compensate to the parched soil, for the less prolonged dura-
tion of the elevated temperature derived from the action of the
sun's rays. It is also to be remembered, that vegetable soils ab-
sorb the sun's heat more rapidly than the lighter coloured sandy
soils, and thus the plants which grow in the former, which is sooner
heated, may in reality be exposed to the highest influence of the
sun's warmth, for at least as long a period as those which are
planted in the latter.
The only power we possess over these relations of soils to heat
appears to be that, by top-dressing with charcoal, with soot, with
peat, or with dark-coloured composts, we may render it more ca-
pable of rapidly absorbing the Sun's heat, and by admixture with
sand, more capable of retaining the heat which it has thus obtained.
| Such are the most important of the physical properties of soils.
Over some of them, the skilful farmer possesses a ready control.
He can drain his land, and thus render it cheaper to work and
more easy to reduce to a fine powder. He can plough, subsoil,
540 POWER OF MODIFYING THE PHYSICAL CHARACTERS.
and otherwise work it well, and thus can make it more open and
porous, more accessible both to air and water. When it is light
and peaty, he can press it with rollers, or he can lay heavy mat-
ter over it—clay, and sand, and lime-stone rubble—and can thus
increase its density. He can darken its colour in some localities
with peat composts, and can thus make it more absorbent of heat
and moisture, as well as more retentive of the rain that falls. But
here his power ends, and how far any of the changes within his
power can be prudently attempted will depend upon the expense
which, in any given locality, the operation would involve. And
even after he has dome all which mere mechanical skill can suggest,
the soil may still disappoint his hopes, and refuse to yield him re-
munerating crops of corn.
“A soil,” says Sprengel, “is often neither too heavy nor too
light, neither too wet nor too dry, neither too cold nor too warm,
neither too fine nor too coarse;—lies neither too high nor too low,
is situated in a propitious climate, is found to consist of a well-
proportioned mixture of clayey and Sandy particles, contains an
average quantity of vegetable matter, and has the benefit of a warm
aspect and favouring slope.” It has all the advantages, in short,
which physical condition and climate can give it, and yet it is un-
productive. And why? Because, answers chemical analysis, it
is destitute of certain mineral constituents which plants require for
their daily food. The physical properties, therefore, are only ac-
cessory to the chemical constitution. They bring into favourable
circumstances, and thus give free scope to the operation, upon the
seeds and roots of plants, of those chemical substances which ma-
ture has kindly placed in most of our soils, or by the lessons of
daily experience is teaching the skilful labourer in her fields to
supply by art.
And yet the study of the physical properties of soils is not with-
out its use, even in a theoretical point of view. It shows both the
use of the fundamental admixture of sand, clay, and vegetable
matter, of which our soils consist, and for what special end all the
mechanical labours of the husbandman are undertaken, and why
they are so necessary. Plants must be firmly fixed—therefore the
soil must have a certain consistency, their roots must find a ready
* Bodenkumde, p. 203,
GENERAL FUNCTIONS OF THE SOIL. • 541
passage in every direction—therefore the soils must be somewhat
loose and open. Except for these purposes, we see little immediate
use for the sand and alumina which form so much of the substance
of soils—till we come to study their physical properties. The si-
liceous sand is in a great degree insoluble, and the alumina exists
in plants in very minute quantity only, while, during the progress
of matural vegetation, the proportion of vegetable matter in the soil
actually increases. The immediate agency, therefore, of these sub-
stances is more physical than chemical. -
The alumina of the clays is of immediate use in combining
with acid substances formed in the soil, and in absorbing and
retaining both water and air for the use of the roots—while the
vegetable matter is advantageous in reference to the same ends,
as well as to the power of absorbing quickly and largely the warmth
of the sun's rays. The soil, in short, in reference to vegetation,
performs the four following distinct and separate, but each of them
important and necessary functions;–
1". It upholds and sustains the plant, affording it a sure and
safe anchorage.
2". It absorbs water, air, and heat, to promote its growth.
These are its mechanical and physical functions.
3". It contains and supplies to the plant both organic and inor-
ganic food as its wants require; and
4". It is a work-shop in which, by the aid of air and moisture,
chemical changes are continually going on, by which changes these
several kinds of food are prepared for admission into the living
roots.
These are its chemical functions.
All the operations of the husbandman are intended to aid the
soil in the performance of one or other of these functions. To the
greater number of these operations—the methods adopted by the
practical farmer for improving the soil—it is my intention, in the
following division of these lectures, briefly to direct your attention.
&
PART III.
ON THE IMPROVEMENT OF THE SOIL BY
MECHANICAL AND CHEMICAL MEANS.
LECTURE XVII.
The physical qualities and chemical constitution of a soil may be changed by art.
Nature of the plants dependent upon that of the soil on which they grow. Me-
chanical methods of improving the soil. Effects produced by draining. Theory
of springs. Effect of ploughing, subsoiling, deep ploughing and trenching. Artifi-
cial improvement by mixing with clay, sand, or marl.
THE facts detailed in the preceding lecture may be considered
as affording sufficient proof that the ability of the farmer to grow
this or that crop upon his land, is very much restrained by its na-
tural character and composition. Each soil establishes upon it-
self, so to speak, a vegetation suited to its own nature, one that
requires most abundantly those substances which actually abound
in the soil, and which is best adapted to its existing physical cha-
racter—and the art of man cannot long change this natural con-
nection between the living plant and the kind of land in which it
delights to grow. -
But he can change the character of the land itself. He can
alter both its physical qualities and its chemical composition, and
thus can fit it for growing other races of plants than those which
it naturally bears—or, if he choose, the same races in greater abun-
dance and with increased luxuriance. It is, in fact, in the pro-
duction of such changes, that nearly all the labour and practical
skill of the husbandman—apart from local peculiarities of climate,
&c.—is constantly expended. For the attainment of this end he
drains, ploughs, subsoil-ploughs, harrows, crushes, and otherwise
works his land. For this end he clays, sands, marls, and manures
it. By these and similar operations the land is so changed as to
become both able and willing to mourish and ripen those peculiar
plants which the agriculturist wishes to raise. On this practical
department of the art of culture, the principles explaimed and illus-
trated in the preceding parts of these lectures throw much light.
M II).
546 THE CHARACTER OF THE LAND MAY BE CHANGED.
They not only show the reason why certain practices always suc-
ceed in the hands of the intelligent farmer, but why others also
occasionally and inevitably fail. They tell him which practices of
his neighbours he ought to adopt, and which of them he had
better modify or wholly reject, and they direct him to such new
modes of improving his land as are likely to add the most to its
permanent productive value.
The operations of the husbandman in producing changes upon
the land, are either mechanical or chemical. When he drains,
ploughs, and subsoils, he alters chiefly the physical characters of
his soil—when he limes and mamures it, he alters its chemical com-
position. These two classes of operations, therefore, are perfectly
distinct. Where a soil contains naturally all that the crops we
desire to grow are likely to require, mere mechanical operations
may suffice to render it fertile—but where one or more of the in-
organic constituents of plants are wanting, draining may prepare
the land to benefit by further operations, but will not be alone
sufficient to remove its comparative sterility. I shall, therefore,
consider in succession these two classes of practical operations:—
I". Mechanical methods of improving the soil, including drain-
ing, ploughing, mixing with clay, Sand, &c.
2°. Chemical methods, including liming, marling, and the ap-
plication of vegetable, animal, and mineral manures. -
To satisfy you fully, however, in regard to the absolute neces-
sity for such changes, if we would render the land fit to produce
amy given crop, let me illustrate, by a few brief examples, the in-
timate relation observed in nature between the kind of soil and
the kind of plants that grow upon it,
§ 1. On the connection between the kind of soil and the kind of plants
* that grow upon it.
That a general connection exists between the kind of soil and
the kind of plants that grow upon it, is familiar to all practical
mem. Thus clay soils are generally acknowledged to be best
adapted for wheat—loamy soils for barley—sandy loams for oats
or barley—such as are more Sandy still for oats or rye-and those
which are almost pure sand for rye alone of all the corn-bearing
crops.
PLANTS PECULIAR TO CERTAIN SOILS. 547
But in a state of nature, we find special differences among the
spontaneous productions of the soil, which are more or less readily
traceable to its chemical composition in the spots where the plants
are seen to grow. Thus—
1°. On the sandy soils of the sea shores, and on the salt steppes
of Hungary and Russia, the sand-worts, salt-worts, glass-worts,
and other salt-loving plants abound. When these lands are in-
closed and drained, the excess of the salt is gradually washed out
by the rains, or in some countries is removed by reaping the Saline
plants annually, and burning them for soda (barilla), when whole-
some and nutritive grasses take their place; but the white clover
and the daisy, and the dandelion must first appear, before, as a
general rule, it can be profitably ploughed up and sown with corn.
2°. The dry drifted sands, more or less remote from the sea,
produce no such plants. They are distinguished by their own
coarse grasses, among which the Elymus arenarius (upright sea
lyme-grass) often, in our latitudes, occupies a conspicuous place.
On the downs of North Jutland, it was formerly almost the only
plant which the traveller could meet with over an area of many
miles.
3°. On ordinary sandy soils leguminous plants are rare, and
the herbage often scanty and void of nourishment. With the pre-
sence of marl in such soils, the natural growth of leguminous
plants increases. The colt's-foot also, and the butter-bur, not
only grow naturally where the subsoil is marly, but infest it some-
times to such a degree as to be with great difficulty extirpated.
So true is this indication of the nature of the soil, that in the
lower valleys of Switzerland these plants are said to indicate to
the natives where they may successfully dig for marl.” On calca-
reous soils, again, or such as abound in lime, the quicken or couch-
grass is seldom seen as a weed,f while the poppy, the vetch, and
the darnel abound.
4°. So peaty soils, when laid down to grass, slowly select for
themselves a peculiar tribe of grasses, especially suited to their own
mature, among which the Holcus lanatus (meadow soft-grass) is re-
markably abundant. Alter their constitution by a heavy liming,
* Prize Essays of the Highland Society, I. p. 134,
+ Sprengel, Bodenkwnde, p. 201.
548 SOILS AND THEIR VEGETATION NATURALLY CHANGE.
º
and they produce luxuriant green crops and a great bulk of straw,
but give a coarse thick-skinned grain, more or less imperfectly filled.
Alter them further by a dressing of clay, or keep them in arable
culture, stiffen them with composts, and enrich them with bones,
and they will be converted into rich and sound corn-bearing lands.
5°. In the waters that gush from the sides of lime-stone-hills—
on the bottoms of ditches that are formed of lime-stones or marls
—and in the springs that have their rise in many trap rocks, the
water-cress appears and accompanies the running waters, some-
times for miles on their course. The mare's-tail (equisetum), on
the other hand, attains its largest size by the marshy banks of
rivulets in which not lime but silica is more abundantly present.
So the Cornish heath (Erica vagans) is found only over the serpen-
time soils of Cornwall, and the red broom rape (Orobanche rubra)*
only on decayed traps in Scotland and Ireland.
These facts all point to the same natural law, that where other
circumstances of climate, moisture, &c., are equal, the natural ve-
getation—that which grows best on a given spot—is intimately con-
nected with the chemical composition of the soil.
But both the soil, and the vegetation it willingly mourishes, are
seen to undergo slow but natural changes. Lay down a piece of
land to grass, and, after a lapse of years, the surface soil—originally,
perhaps, of the stiffest clay—is found to have become a rich, light,
vegetable mould, bearing a thick Sward of nourishing grasses, al-
most totally different from those which maturally grew upon it
when first converted into pasture. So in a wider field, and on a
larger scale, the same slow changes are exhibited in the vast natu-
ral forests that are known to have long covered extensive tracts
in various countries of Europe. ... •x
Thus it is a matter of history that Charlemagne hunted in the
forest of Gerardmer, then consisting of oak and beech—though
now the same forest contains only pines of various species. On
the Rhine, between Landau and Kaiserlautern, oak forests, of se-
veral centuries old, are seen to be gradually giving way to the
beech, while others of oak and beech are yielding to the encroach-
ments of the pine. In the Palatinate, the Scotch fir (Pinus sylves-
tris) is also succeeding to the oak. In the Jura, and in Tyrol,
the beech and the pine are seen mutually to replace each other—
* Hooker's Flora Scotica.
NATURAL ROTATION AMONG FOREST TREES. 549
and the same is seen in many other districts. When the time for
a change of crop arrives, the existing trees begin to languish one
after another, their branches die, and finally their dry and naked
tops are seen surrounded by the luxuriant foliage of other races.”
In Georgia (United States) the Castamea pumila is rapidly dis-
appearing, the Laurus geniculata, which, until lately, formed large
clumps in the pine barrens, is now rarely to be seen amid the forests
of Pinus palustris, whole forests of the Gordonialiseanthus are
seen to die out in two or three years, and the Quercus rubra and
Laurus sasafras are showing similar symptoms of decay.f
These facts not only show how much the vegetable tribes are
dependent upon the nature of the soil—they appear to indicate, also,
the existence of slow natural changes in the chemical composition
of the soil itself, which lead necessarily to changes in the vegeta-
tion also.
We can ourselves, in the case of ancient forests, effect such
changes. When in the United States of America aforest of oak or
maple is cut down, one of pine springs up in its place; while on
the site of a pine forest, oaks and other broad leaved trees speedily
appear. - --
But if the full natural time for such changes has not yet come, the
new vegetation may be overtaken, and smothered by the original
tribes. Thus, when the pine forests of Sweden are burned down, a
young growth of birch succeeds, but after a time the pines again ap-
pear and usurp their former dominion. The soil still remains more
propitious to the growth of the latter than of the former kind of tree.
We may, therefore, take a practical lesson from the book of na-
ture. If we wish to have a luxuriant vegetation upon a given
spot, we must either select such kinds of seeds to sow upon it as
are fitted to the kind of soil, or we must change the nature of the
land so as to adapt it to our crop. And, even when we have once
prepared it to yield abundant returns of a particular kind, the
changes we have produced can only be more or less of a tempo-
rary mature. Our care and attention must still be bestowed upon
it, that it may be enabled to resist the slow matural causes of alte-
ration, by which it is gradually unfitted to mourish those vegetable
tribes which it appears now to delight in maintaining.
* Le Baron de Mortemart de Boisse, Voyage dams les Landes, p. 189,
# Mr Jones, Silliman's Journal, May 1846, p. 450.
550 OF DIRAINING AND ITS EFFECTS.
Let us now turn our attention, therefore, to the methods by
which these beneficial changes are to be effected and maintained.
§ 2. Of draining, its mode of action and its effects.
Among the merely mechanical methods by which those changes
are to be produced upon the soil, that are to fit it for the better
growth of valuable crops, draining is now allowed to hold the first
place. That it is an important step in heavy clay lands, and that
it must be the first step in all cases where water abounds in the
surface soil, will be readily conceded; but that it can be beneficial
also in situations where the soils are of a sandy nature, where the
subsoil is light and porous, or where the inclination of the field
appears sufficient to allow a ready escape to the water, does not
appear so evident and is not unfrequently, therefore, a matter of
considerable doubt and difficulty. It may be useful, then, briefly
to state the several effects which in different localities are likely to
follow an efficient drainage of the land:—
1°. It carries off all stagnant water, and gives a ready escape
to the excess of what falls in rain.
2°. It arrests the ascent of water from beneath, whether by ca-
pillary action or by the force of springs—and thus not only pre-
serves the surface soil from undue moisture, but also frees the sub-
soil from the lingering presence of those noxious substances, which
in undrained land so frequently lodge in it and impair the growth
of deep-rooted plants,
3°. It allows the water of the rains, instead of merely running
over and often injuriously washing the surface, to make its way
easily through the soil. And while thus filtering through, not
only does the rain-water impart to the soil those substances useful
to vegetation, which, as we have seen,* it always contains in greater
or less abundance; but it washes out of the upper soil, and when the
drains are deep enough, out of the subsoil also, such noxious sub-
stances as maturally collect and may have been long accumulating
there—rendering it unsound and hurtful to the roots. The latter is
one of those benefits which gradually follow the draining of land.
When once thoroughly effected, it constitutes a most important
permanent improvement, and one which can be fully produced by
no other available means. It will be permanent, however, only so
* See pages 19, 53, 108, and 283.
IT WASHES AND AERATES THE SOIL. 551
long as the drains are kept in good condition. The same openness
of the soil which enables the rains to wash out those soluble noxious
substances, which have been long collecting, permits them to carry
off also such as are gradually formed, and thus to keep it in a
sound and healthy state; but let this openness be more or less
impaired by a neglect of the drainage, and the original state of
the land will again gradually return.
4°. This constant descent of water through the soil causes a
similar constant descent of fresh air through its pores, from the
surface to the depth of the drains. When the rain falls, it enters
the soil and more or less completely displaces the air which is con-
tained within its pores. This air either descends to the drains or
rises into the atmosphere. When the rain ceases, the water, as it
sinks, again leaves the pores of the upper soil open, and fresh air
consequently follows it. The air is in fact sucked in after the water,
as the latter gradually passes down to the drains. Thus, where a
good drainage exists, not only is the land refreshed by every
shower that falls—not only does it derive from the rains those im-
portant substances which occasionally, at least, are brought down by
them from the atmosphere, and which are in a great measure lost
where the waters must flow over the surface—but it is supplied also
with renewed accessions of fresh air, which experience has shown
to be so valuable in promoting the healthy growth of all our cul-
tivated crops.
5°. But other consequences of great practical importance fol-
low from these immediate effects. When thus readily freed from
the constant presence of water, the soil gradually becomes drier,
sweeter, looser, and more friable. The hard lumps of the stiff
clay lands more or less disappear. They crumble more freely,
offer less resistance to the plough, and are in consequence more
easily and more economically worked. These are practical benefits,
equivalent to a change of soil, which only the farmer of stubborn
clays can adequately appreciate.
6°. The soil is also warmed. When full of water the large
evaporation from the surface keeps it constantly cool, and retards
the growth of the crops. Remove the water and the evaporation
in a great measure ceases. Thus plants grow quicker and more
luxuriantly. The air which descends, and the rain carry this
milder temperature into the under soil. When it reaches the
552 SECURES A DRY SEED-TIME AND AN EARLY HARVEST,
surface of the earth, the rain water is usually of the same tempera-
ture as the air through which “it has fallen—and as it sinks it
gradually warms the soil through which it passes. In summer
also when the hot sum has warmed the surface, the rain itself when
it reaches the earth becomes sensibly warmed by the hotter soil, and
descends to the subsoil with this greater warmth. It thus conveys
downwards and distributes more generally and to a greater depth
the effect of the sun's rays, and gives the roots of plants the bene-
fit of what the gardeners call bottom heat.
7°. Hence with the permanent state of moisture, the permanent
coldness, as it is correctly called, of many soils also rapidly disap-
pears. The backwardness of the crops in spring, and the lateness
of the harvests in autumn, are less frequently complained of—for
the drainage in many localities produces effects which are equivalent
to a change of climate. “In consequence of the drainage which
has taken place in the parish of Peterhead, in Aberdeenshire, dur-
ing the last 20 years, the crops arrive at maturity ten to fourteen
days sooner than they formerly did ;” and the same is true to a
still greater extent in many other localities.
8°. On stiff clay lands, well adapted for wheat, wet weather in
the autumn not unfrequently retards the sowing of winter corn—
in such as are undrained often completely prevents it—compelling
the farmer to change his system of cropping, and to sow some other
grain, if the weather permit him, when the spring comes round.
An efficient drainage carries off the water so rapidly as to bring
the land into a workable state soon after the rain has ceased, and
thus, to a certain extent, it rescues the farmer from the fickle do-
minion of the uncertain seasons.f To the skilful and intelligent
farmer, who applies every available means to the successful pro-
secution of his art, the promise even in our age and country is
sure—“that seed-time and harvest shall never fail.”
* Mr Gray, in the Prize Essays of the Highland and Agricultural Society, II. p.
171. This opinion was given in 1830, since which time many other extensive im-
provements have been made in that part of the island.
+ “Formerly,” says Mr Wilson, of Cumledge, in his account of the draining of a
farm in Berwickshire, “this part of the farm was so wet, that—though better adapted
for wheat than any other crop—the season for sowing was frequently lost, and after an
expensive fallowing and liming, it was sown with oats in spring, of which it always
produced very poor crops. It is now so dry as to grow very good crops of turnip or
rape, and, except in two instances, I have always sown my wheat in capital order.”—
Ibid. I. p. 243.
AND IS EQUIVALENT TO A DEEPENING OF THE SOIL. 553
9°. But on land of every kind this removal of the Superfluous
water is productive of another practical benefit. In its conse-
quences it is equivalent to an actual deepening of the soil.
When land, on which the surface water is in the habit of resting,
becomes dry enough to admit the labours of the husbandman, it is still
found to be wet beneath, and the water, even in dry seasons, not
unfrequently remains where the roots of the crops would otherwise
be inclined to come. Or, if the surface soil permit a ready pass-
age to the rains, and the waters linger only in the moist subsoil,
still—though the farmer may not be delayed in his labours—the
subsoil repels the approach of the roots of his grain, and compels
them to seek their nourishment from the surface soil only. But
remove the water, and the soil becomes dry to a greater depth.
The air penetrates and diffuses itself wherever the water has
been. The roots now freely and safely descend into the almost
virgin soil beneath. And not only have they a larger space
through which to send out their fibres in search of food, but in
this hitherto ungenial soil they find a store of substances—but
sparingly present, it may be, in the soil above—which the long-
continued washing of the rains, or the demands of frequent crops,
may have removed, but which may have been all the while accu-
mulating in the subsoil, into which the roots of cultivated plants
could rarely with safety descend. It is not wonderful, then, that
the economical effects of draining should be found by practical
men to be not only a diminution in the cost of cultivation, but a
considerably augmented produce also both in corn and grass; or
that this increased produce should alone be found sufficient to re-
pay the entire cost of thorough-draining in two or three years.
An obvious practical suggestion arises out of the knowledge of
this fact. The deeper the drains, provided the water have still a
ready escape, the greater the depth of soil which is rendered avail-
able for the purposes of vegetable nutrition. Deep rooted plants,
such as lucerne, often fail, even in moderately deep soils, because
an excess of water or the presence of some noxious ingredient
which deep drains would remove, prevents their natural descent
in search of food. Even plants, which, like wheat or clover, do
not usually send down their roots so far, will yet, where the sub-
soil is sound and dry, extend their fibres for three or more feet in
depth, in quest of more abundant nourishment.
554 EFFECT OF A GENERAL DRAINAGE OF THE SOIL,
Not only, then, do deep drains permit the use of the subsoil
plough without the chance of injury, not only are they less liable
to be choked up by the accumulated roots of plants which matu-
rally make their way into them in search of water, but they also
increase the value and permanent fertility of the land, by increas-
ing its available depth. In other words, that kind of drainage
which is most efficiently performed, with a regard to the greatest
number of contingencies, will not only be the most permanent,
but will also be followed by the greatest number of economical ad-
vantages.
10°. Nor do the immediate and practical benefits of draining
end with the attainment of these beneficial results. It is not till
the land is rendered dry that the skilful and enterprising farmer
has a fair field on which to expend his exertions. In wet soils,
bones, wood-ashes, rape-dust, nitrate of soda, and other artificial
manures are almost thrown away. Even lime exhibits but one-
half of its fertilizing virtue, where water is allowed to stagnate
in the soil. Give him dry fields to work upon, and the well-in-
structed agriculturist can bring all the resources, as well of modern
science as of old experience, to bear upon them, with a fair chance
of success. The disappointments which the holder of undrained
lands so often meets with, he will less frequently experience. An
adequate return will generally be obtained for his expenditure in
mamuring and otherwise improving the soil, and he will thus be
encouraged to proceed in devoting his capital to the permanent
amelioration of his farm—not less for his own than for his land-
lord’s benefit.
Viewed in this light, draining is only the first of a long series
of improvements, or rather it is a necessary preparative to the
numerous improvements of which the soil of our islands is Suscep-
tible—which improvements it would be a waste of money to at-
tempt, until an efficient system of drainage is established. And
when we consider how great a national benefit this mere prepara-
tory measure alone is fitted directly to confer upon the country,
you will agree with me in thinking that every good citizen ought
to exercise his influence in endeavouring, in his own district, more
or less rapidly to promote it. It has been calculated that the
drainage of those lands only, which are at present in arable cul-
UPON THE AW ERAGE PRODUCTION OF FOOD. 555
ture (10 millions of acres), would at once increase their produce
by 10 millions of quarters of the various kinds of grain now grown
upon them ;–and that a similar drainage of the uncultivated lands
(15 millions of acres) would yield a further increased produce of
twice as much more. This increase of 30 millions of quarters is
equal to nearly one-half of our present consumption” of all kinds
of grain—so that were it possible to effect at once this general
drainage, a large superfluity of corn would, by this improvement
alone, be raised from the British soil. -
This general drainage, however, cannot possibly be effected in
any given time. The individual resources of the land-owners are
in many cases insufficient to meet the expense, and such calcula-
tions as the above are useful, mainly, in stimulating the exertions
of those who have capital to spare, or such an excess of income as
can permit them to invest an annual portion permanently f in the
soil.
11°. He who drains and thus improves his own land, confers a
benefit upon his neighbours also. In the vicinity of wet and boggy
lands the hopes of the industrious farmer are often disappointed.
Mists are frequent and rains more abundant on the edges of the
moor, and mildews retard the maturity, and often seriously in-
jure the crops. Of undrained land, in general, the same is true
to a less extent, and the presence of one unimproved property in
the centre of an enterprising district, may long withhold from the
* 65 millions of quarters. See an excellent paper on this subject in the Quarterly
Agricultural Journal, xii. p. 505, by Mr Dudgeon of Spyelaw, in Roxburghshire, a
county in which the practical benefits of draining have been extensively experienced,
and are therefore well understood.
+ To drain 25 millions of acres, at L.6 an acre, would cost 150 millions sterling, a
sum equal, probably, to the whole capital at present invested in farming the land. If,
as is now said, the land can be efficiently drained with pipe tiles at a cost of L.3 an
acre, this mode of improvement may be expected to progress much more rapidly, as
it is brought within the means of a greater number, and will give a larger return upon
the capital expended.
† By an efficient drainage the soil is permanently benefited, but it is not so clear
that the money it costs is permanently invested or buried in the soil. If the cost be
re-paid by the increase of produce, in three years, the money is not invested, it is only
lent for this period to the soil. “I drain so many acres every year,” said the holder
of a large Berwickshire farm to me, “ and I find myself always repaid by the end of
the third season. If I have spare capital enough, therefore to go on for three years,
I can gradually drain any extent of land, by the repeated use of the same sum of
money.”
556 HOW POROUS SOILS ARE BENEFITED BY DRAINING.
adjoining farms that full measure of benefit which the money and
skill expended upon them would in other circumstances have im-
mediately secured.
So true is it in regard to every new exercise of human skill and
in every walk of life, that we are all mutually dependent, every
one upon every other; and that the kindly co-operation of all can
alone secure that ample return of good, which the culture either
of the dead earth or of the living intellect appears willing, and we
may hope is ultimately destined, to confer upon our entire race.
12°. You will now be able to perceive in what way even light
and sandy soils, or such as lie on a sloping surface, may be greatly
benefited by draining. Where no open outlet exists under a
loamy or sandy surface soil, any noxious matters that either sink
from above, or ooze up from beneath, will long remain in the sub-
soil, and render it more or less unwholesome to valuable cultivated
plants. But let such an outlet be made by the establishment of
drains, and that which rises from beneath will be arrested, while
that which descends from above will escape. The rain-waters
passing through will wash the whole soil also as deep as the bottom
of the drains, and the atmospheric air will accompany or follow them.
The same remarks apply to lands which possess so great a natu-
ral inclination as to allow the surface water readily to flow away.
Such a sloping surface does not necessarily dry the subsoil, free it
from noxious substances, or permit the constant access of the air.
Small feeders of water occasionally make their way near to the
surface, and linger long in the subsoil before they make their
escape. This is in itself an evil; but when such springs are im-
pregnated with iron the evil is greatly augmented, and from such
a cause alone a more or less perfect barrenness not unfrequently
ensues. To bring such lands by degrees to a sound and healthy
state, a system of drains or outlets beneath is often sufficient.
It is to this lingering of unwholesome waters beneath, that the
origin of many of our moor-lands, especially on higher grounds,
is in a great measure to be attributed. A calcareous or a ferru-
ginous spring sends up its waters into the subsoil. The slow ac-
cess of air from above, or it may be the escape of air from the wa-
ter itself, causes a more or less ochrey deposit,” which adheres to
* If the water contain sulphate of iron, the air from above will impart to its iron an
additional quantity of oxygen, and cause a portion of it to fall in a state of peroxide,
ORIGIN OF MOOR-LANDS AND OF THE MOOR-BAND PAN. 557
and gradually cements the stones or earthy particles, among which
the water is lodged. Thus a layer of solid stone is gradually
formed—the moor-band pan of many districts—which neither
allows the roots of plants to descend nor the surface water to es-
cape. Hopeless barrenness, therefore, slowly ensues. Coarse
grasses, mosses, and heath, grow and accumulate upon soils not
originally inclined to nourish them, and by which a better herbage
had previously been long sustained. Of such lands many tracts
have been reclaimed by breaking up this moor-band pavement,
but such an improvement, unless preceded by a skilful drainage,
can only be temporary. The same natural process will again be-
gin, and the same result will follow, unless an outlet be provided
for the waters from which the petrifying deposit proceeds.
It ought to be mentioned, however, that where a ready passage
and escape for the water is provided by an efficient drainage, and
especially in light and porous soils, the saline and other soluble
substances they contain will be liable, in periods of heavy rain, to
be more or less completely washed out and carried off by the wa-
ter that trickles through them. While, therefore, the establish-
ment of drains on all soils may adapt and prepare them for fur-
ther improvements, and may make them more grateful for every
labour or attention that may be bestowed upon them—yet after
drainage they must be more liberally dealt with than before, if the
increased fertility they at first exhibit is to be permanently main-
tained or increased.
13°. I would not here willingly neglect to call your attention
to a higher benefit still, which the skilful drainage of an extensive
district is fitted to confer upon its whole population. Not only is
this drainage equivalent, as above stated, to a change of climate in
reference to the growth and ripening of plants, but it is so also in
reference to the general health of the people and to the number
and kind of the diseases to which they are observed to be exposed.
If the iron or lime be present in the state of bicarbonate, the escape of carbonic acid
from the water will cause a deposit of carbonate of iron or of lime. Any of these de-
posits will cement the earthy or stony particles together. Iron, however, is often held
in solution by an organic acid (the crenic acid, p. 73), which becomes insoluble, and
falls along with the iron when the latter has absorbed more oxygen from the atmo-
sphere. Hence the large quantity of organic matter which bog iron ores, moor-band
pans, and deposits from Springs and drains so often contain.
558 RENDERS A COUNTRY MORE SALUBRIOUS.
I may quote in illustration of this fact the interesting observa-
tions of Dr Wilson on the comparative state of health of the la-
bouring population in the district of Kelso during the last two pe-
riods of ten years. In his excellent paper on this subject, in the
Quarterly Journal of Agriculture,” he has shown that fever and
ague, which formed nearly one-half of all the diseases of the popu-
lation during the former ten years, have almost wholly disappeared
during the latter ten, in consequence of the general extension of
an efficient drainage throughout the country; while, at the same
time, the fatality of disease, or the comparative number of deaths
from every hundred cases of serious ailment, has diminished in the
proportion of 4-6 to 2'59. Such beneficial results, though not im-
mediately sought for by the practical farmer, yet are the inevitable
consequence of his successful exertions. Apart, therefore, from
mere considerations of pecuniary profit, a desire to promote the
general comfort and happiness of the entire inhabitants of a district
may fairly influence the possessors of land to promote this method
of ameliorating the soil; while the whole people, on the other hand,
of whatever class, ought “gratefully to acknowledge the value of
those improvements which at once render our homes more salu-
brious and our fields more fruitful.” -
§ 3. Of the theory of Springs.
In the general drainage of the land a double object is sought
to be attained. In very rainy districts, the first wish of the farmer
is to carry off the surface water from his fields—but where less
rain falls, that which ascends from beneath in springs, attracts at
least an equal share of the husbandman's regard. In draining,
with a view to the removal of this latter source of superfluous mois-
ture, a knowledge of the true theory of springs, as indicated by an
examination of certain geological phenomena, is of the greatest
possible service to the practical man, in pointing out the sources
from which the water that injures his land proceeds, as well as the
lines along which it may be most efficiently and most economically
carried off.
1°. The rain which falls on the surface of an extensive tract of
country partly escapes into the rivers, and partly sinks into the
* Volume xii. p. 317.
•)
e.)
WATER IS ARRESTED BY IMPERWIOUS BEDS. 5.99
earth. This latter portion descends through the covering of soil
and other loose materials till it reaches the rocks on which they
rest. If these rocks are porous, like many sand-stones, or are
traversed by cracks and vertical fissures, as many sand-stones and
lime-stones are, it descends through them also till it reaches a
bed, such as one of indurated clay, so close and compact as to re-
sist its further passage. By this impervious bed the water is ar-
rested, and is, therefore, compelled to spread itself laterally, and
gradually to accumulate in the beds that lie above it. Thus, if
the outline from A to C in the annexed diagram represent the Sur-
B

–5
El-H –
I)
}=====Fº
i
_{ I
- Y
ſ
T
*
#E
face of an undulating country, in which the subjacent rocks (1, 2,
3, 4,) are covered by a considerable thickness of loose materials,
the rain which falls on the surface between A and B will sink
more or less rapidly to the bed (1), and, if this be impermeable to
water, will rest there, or will slowly drain off in the direction of B
and C along the inclined surface of the rock. But if (1) be porous,
it will sink through it to the surface of the bed (2), and through
this also, if permeable, to (3) or (4), until it reach a stratum through
which it cannot pass. On the surface of this latter bed, or among
the rocks above it, the water will accumulate until, flowing down-
wards towards C, it is enabled either to sink into the deeper rocks,
or to make its escape again to the surface at a lower level.
But if the rocks beneath, as is shown in the same diagram from
E to F, be traversed by vertical fissures passing through two or
more beds, or, like B, E, through a great number of beds, the wa-
ter that falls on the surface will readily find a passage downwards
to a considerable depth, and to the same cracks the water that
lodges among the unfissured rocks from D to E will also gradu-
ally make its way.
The practical effects of these several conditions on the drainage
of a country are very obvious. If the stratum (1) be impervious
to water, the surface from A to B may be full of water, and may
urgently demand the introduction of drains, whereas if (1) and (2)
560 MAY ALSO COLLECT BENEATH THEM.
be porous, the surface water will gradually sink, and the apparent
necessity for artificial drainage will become much less striking.
On the other hand, where the rocks are filled with frequent cracks,
as from B to C, the surface water may descend and disappear so
rapidly, as to render useless even the sinking of wells—and, in
dry summers, greatly to retard the progress of the crops, or even
seriously to injure the produce of the harvest. In such a fissured
state are the magnesian lime-stone rocks in some parts of the
county of Durham—and such is the consequent scarcity of water
on some farms, that when, in long droughts, the supply preserved
in artificial tanks begins to fail, the cattle must be driven to water,
sometimes for miles, to the nearest living brook.
2°. But water often finds its way to great depths without pass-
ing through the superior strata, and even where they are abso-
lutely impervious to the rains that fall upon them. Thus along
A.
the country from A to B, and especially towards A, the surface
soil rests upon the upper edges of the strata. Suppose now the
beds 1, 2, 3, to be impervious to water, the rain that falls wher-
ever these rocks lie immediately beneath the surface will either re-
main stagnant, or will flow off by some natural drainage. Thus
from the highest point C in the above diagram, the water will de-
scend on either hand towards a and b. At Ö it may remain stag-
nant and form a bog, for it cannot descend through the bed (2),
which forms the bottom of the valley, and the same is true of the
hollow c, in which other portions of the water may rest. All this
tract of country, therefore, will be more or less cold, wet, and con-
sequently unproductive. But let the bed (4), the edge (or outcrop)
of which forms the surface at a, be porous or permeable, then the
water which falls upon that spot, or which descends from the higher
grounds about C and A, will readily sink and drain off, descend-
ing from a towards d along the inclined bed till it finds an out-
let in the latter direction.
Thus it may readily happen that a naturally dry and fertile val-

SPRINGS PRODUCED BY WALLEYS AND SLIPS. 56]
ley, as at a, may exist at no great distance from others, b and e,
which are marshy and insalubrious, and in which artificial drainage
alone can develope the agricultural capabilities of the soil. It ap-
pears also that, though in any district the rocks which lie immedi-
ately beneath the surface may contain no water, and may allow
none to pass through them, yet that other beds, perhaps at a great
depth beneath, may contain much. It is, in fact, this accumula-
tion of water below impervious beds that gives rise to many natu-
ral springs, and enables us by artificial wells to bring water to the
surface—often where the land would otherwise be wholly uninha-
bitable.
3°. Thus in undulating countries, where hill-sides frequently
present themselves, or valleys are scooped out among the rocks, as
in the following wood-cut, the water that has fallen over the high
grounds towards A, and has entered as above described, or has
sunk down to the several strata 1, 2, 3, &c., will find a ready out-
let along the slope of the valley, and will give rise to springs at a,
b, c, or d, according as the water has lodged in the one or the
other of these beds. These springs will fill the surface soil with
water, which will also descend into the bottom of the valley, and,
if no sufficient outlet be provided for it, will, according to its quan-
tity, give rise to a lake, a bog, or a morass. On the slope towards
B the same springs are not to be expected, since the rains which
sink through the surface on this side of the valley, and lodge in the
porous rocks beneath, will, by the inclination of the beds, be drawn
off in the opposite direction, till a second valley or some other
available outlet present itself for their escape. This explains why
the land on one side of a valley or of a hill is often much drier
than on the other, and why, even in the absence of the improver's
skill, a soil apparently more fertile may exist, and better crops be
reaped.
4°. Again, such an outlet for the waters that rest among inclin-
ed strata is not unfrequently afforded, without the intervention of
N n

562 SLIPS ARREST AND THROW UP THE WATER.
valleys, and even in level or hilly countries, by the existence of
slips or faults in the rocks beneath. Such a slip or shifting of the
beds is represented in the following diagram, in which B D is a
crack, along which the strata from B to C appear to have slipped
downwards, so that the thin bed (2), for example, which terminates
at b on the one side of the crack, begins again at a lower level c
on the other side, and so with the other beds that lie above and
below it. None of them is exactly continuous on the opposite sides
of the slip. From such cracks or faults in the beds, springs of
water often rise to the surface, even on hill tops, as at B, and they
may be thus thrown or forced out from either of two causes—
a. These slips are often of considerable width, and are usually
found to be filled with impervious clay. This is the case at least
among the coal-measures, which have been the most extensively
explored. The effect of this wall of clay is to dam back at B D
the water which descends along the inclined beds towards C from
the country beyond A, and thus to arrest its further progress.
But the pressure of the water behind forces that which has reached
the fault B D to seek a way upwards, and, as spaces not unfrequent-
ly exist between the wall of clay and the rocks between which it
stands, the water finds a more or less ready outlet at the surface
B, and either gushes forth as a living and welcome spring, or oozes
out unseen among the soil, rendering it cold, wet, and unproduc-
tive. Thus from b the water accumulated in the bed (2) may rise
to the surface, or from f that which exists in (4) or from any other
bed in which water exists, and from almost any depth.
b. But even where no such wall of clay exists, the waters may
still find their way to the surface along lines of fault, and from
great depths. Thus suppose the thin bed (2) to be full of water,
and that it is covered by an impervious bed (1), then the water
which tends downwards from a to b will be arrested at the fault,
and dammed back by the impervious extremity of (1) against
which it now rests. If an outlet can be found, it will therefore

WELLS IN THE BASIN OF LONDON. 563
rise towards the surface. And as the rocks incline upwards in the
direction of A, the pressure from behind may easily cause the wa-
ter to ascend to the summit of the hill at B, and to gush out in a
more or less copious spring.
5°. Where no natural outlets of the kind above described exist
in a district, there may be a great scarcity of water on the sur-
face, while abundance, as we have already seem (2°), may exist in
the rocks beneath, ready and willing to rise if a passage be opened
for it. Such is the case with the site of the City of London, re-
presented below:—
Lon- River
St Alban's. Hampstead. don. Thames. Sydenham. Knockholt.
: : : f E
SECTION ACROSS THE LONDON BASIN FROM ST ALBAN's To KNOCKHOLT.
(Buckland's Bridgewater Treatise, plate 69.)
3. Plastic Clay and Sand.
4. Chalk, both full of water.
The rain-water which falls between a and A on the one hand,
and upon the plastic clay and chalk between d and B on the other,
sinks into these two beds and rests in them till it finds an escape.
It cannot rise through the great thickness of impervious clay on
which London and its neighbourhood stands, unless where wells
are sunk, as above represented at a, b, c, d, either into the plastic
clay (3), or into the chalk (4), when the water ascends copiously
till it reaches the general level of the country about St Alban's,
the lowest part of the basin where the permeable beds form the
surface. Hence in the vale of the Thames at b, it rises above the
surface, and forms a living spring, while at other places, as at
a, c, d, it has still to be pumped up from a greater or less depth.*
It is the existence of water beneath the surface where the soils rest
on impermeable beds, and the known tendency of these waters to
rise when a boring is sunk to them, that have given rise to the
1. Marine Sand.
2. London Clay (almost impermeable).
* In January 1840, there were stated to be in the London clay upwards of 200 such
wells, of which 174 were in London, and of which latter 30 taken together were known
to yield 30 millions of gallons weekly. This number of wells has since been increas-
ed, and is still increasing. The borings are generally carried down into the chalk, be-
cause the water which ascends from the plastic clay has been found to bring with it
much sand, which both obstructs the pipes and is injurious to the pumps.


564 ARTESIAN WIELLS.
establishment of Artesian” wells, so frequently executed, and with
so much success, in recent times. •
There is probably no geological fact that promises hereafter.
to be of more practical value to mankind than this, when good
government and the arts of peace shall obtain a permanent rest-
ing-place in those countries where, without irrigation, the soil
remains hopelessly barren. Wherever a living spring bursts
out in the sands of Arabia, in the African deserts, or in the
parched plaims of South America, an island of perennial verdure
delights the eye of the weary traveller, and wherever in such coun-
tries the labour of man has been expended in digging wells, and in
raising water from them for artificial irrigation, the same beauty
and fertility always appear. It has recently been found that the
Oases of Thebes and Garba, in Upper Egypt, where the blown
sands now hold a scarcely disputed dominion, are almost riddled
with wells sunk by the ancient Egyptians, but for the greater part
long since filled up. The re-opening of such wells might restore
to these regions their long lost fertility, as the sinking of new ones
by our easier and more economical methods might reclaim many
other wide tracts, and convert them to the use of man. In con-
templating what man may do, when his angry passions and his pre-
judices do not interfere with the exercise of his matural dominion
over dead matter, it is not unreasonable to hope that, guided by
such indications of natural Science, human industry may hereafter,
by slow degrees, re-establish its power in long deserted regions of
country, spreading abundance over the broad wilderness, staying
the Arab's wandering foot, and fixing his household in a permanent
and plenteous home. .
6°. It not unfrequently happens that alternate layers of sand
S. - Šs 3ºxº
§§§ gºš
Š =é–4. Šºsº **ºx:
Ø %22 - >; ×55:33 ź .*.*.*.*.
% % wº 2.2%%
I. –{p
and clay overspread the rocks of a country, and act in arresting
or in throwing out the surface water in the same manner as the
C clay. S sand.
* So called from the district of Artois, in France, in which it was formerly supposed
that such borings had been longest or most extensively practised.








EFFECT OF ALTERNATE LAYERS OF SAND AND CLAY. 565
solid strata beneath. Thus under the surface A B here represent-
ed, alternate layers of sand and clay overspread the inclined beds
of rock, and alone affect not only the quality but the state of dry-
ness also of the soil.
The rain which falls on the upper bed of sand will sink no fur-
ther than the first bed of clay, and will appear as a spring, or will
form a wet band along the side of the hill, at a. That which falls
or exists in the second bed of sand will in like manner come to day
at b c, and d e, filling the two valleys more or less with water,
and forming wet tracts of country resting upon a lower bed of
impervious clay.
In endeavouring to form a satisfactory opinion as to the best
mode of draining a piece of land, it is of great importance to be
able to determine not only the immediate natural source of the
water we are desirous to remove, but also the probable quantity it
may be necessary to carry off, and the permanence of the supply.
It is well known, for example, that in many spots, when the long
accumulating waters are once carried off, there remains only a small,
and probably intermitting supply, for which an outlet is afterwards
to be left and kept open ; while in other localities a constant
stream of water is seen to pass along the drains. In connection
with this point it is of consequence to make out whether the water
is thrown out by surface clays, as in this latter diagram, or flows
from among the solid rocks at a greater or less depth—as shown
in the preceding wood-cuts. That which is thrown out by beds of
clay is in most cases derived only from the rains that fall, and is,
therefore, liable to intermit, to cease altogether, or to become more
copious, according as the season is dry or otherwise ; while that
which escapes from a bed of rock, being more or less independent
of the seasons, will less frequently vary in quantity. Thus it hap-
pens that where only surface water stagnates in the soil of a dis-
trict, a warm, dry, and long continued summer may cause it to
yield a crop of unusual excellence, while other soils fed by springs
from beneath may, even in such seasons, still retain moisture enough
to render them unfit to rear and ripen a profitable crop of corn.
7°. There remains one other interesting principle commected with
this subject, which I must briefly explaim to you. Let C and D
in the accompanying wood-cut be two impervious beds through
566 AIBSORBENT BEDS.
which the water finds no escape, and from which the rains pass off
A.
*.
NNNNN
only by the matural inclination of the ground, and let E be a porous
bed from which the water finds a ready escape somewhere towards
the right. Then if a boring be sunk through C and D in any
part of this tract of country, the water will descend, and will be
absorbed by the bed E. Such dry, porous, or absorbent beds
exist in many localities, and the skilful drainer may occasionally
avail himself of their aid in easily and effectually freeing land from
water, which could not without great cost be permanently drained
by any other method. Where water collects on a surface resting
upon chalk, or upon the loose sands beneath it, this method of
boring is frequently had recourse to in some of our southern
counties. One danger, however, is to be guarded against in try-
ing this method, that the bore-rod, namely, may enter a bed which
is full of water, and from which, as in Artesian wells, it may rea-
dily, and in considerable quantity, ascend. Such a boring, it is ob-
vious, would only add to the evil, and might render necessary a
larger outlay in establishing an efficient system of drainage by the
ordinary method, than would otherwise have been required.”
* It sometimes happens that in sinking an old well deeper for the purpose of ob-
taining a better supply of water, the original springs disappear altogether. This is
owing to the occurrence at this greater depth, of an absorbent bed, in which the Wa-
º ter disappears. By descending still further, a second Sup-
ply of water may often be found, but which will naturally
ascend no further than the absorbent bed, by which the
whole supply will be drunk up, if not prevented by the
insertion of a metal pipe. Advantage is sometimes taken
of the known existence of such absorbent strata, not only
for the purposes of draining, but also for removing waste
water of various kinds. An interesting example of such
application is to be seen at St Denis, in the Place aux
Gueldres, where the water from the bed f at the depth of
200 feet ascends through the inner tube a-from another
bed e, at 160 feet, through the tube b, while between it and
the outermost tube, through the space c, it is sent down
again after it has been employed in washing the square,
and disappears in the absorbent stratum d.




4
ORDINARY PLOUGHING. 567
I do not enter into any further details in regard to the applica-
tion of these principles to the practice of draining, being satisfied
that when you have once mastered the principles themselves, the
applications will readily suggest themselves to your own minds
when circumstances require it.
- § 4. Of ordinary ploughing.
Ploughing.—Apart from the obvious effect of ploughing the
land, in destroying weeds and insects, the immediate advantage
sought for by the farmer is the reduction of his soil to a state of
minute division. In this state it is not only more pervious to the
roots of his corn, but it also gives a more ready admission to the
air and to water. -
Of the good effects produced by the easy descent and escape of
water from the surface, I have already spoken (p. 550), but the
permeability of the soil to air is no less useful in developing its
natural powers of production. How important the presence of the
air is both to the maintenance of animal and to the support of ve-
getable life, we have had frequent occasion to observe. By its
oxygen the breathing of animals is sustained, and by its carbonic
acid the living plant is fed. On the earthy particles also which
the soil contains, the influence of these gaseous substances, though
not so visible and striking, is of almost equal consequence in the
economy of nature. Among other immediate benefits derived from
the free access of air into the soil, we may enumerate the following:
1°. The presence of oxygen in the soil is necessary to the heal-
thy germination of all seeds (p. 227), and it is chiefly because they
are placed beyond its reach, that those of many plants remain
buried for years without signs of life, though they freely sprout
when again brought to the surface and exposed to the air. We
have also seen reason to believe (p. 121), that the roots of living
plants require a supply of oxygen in order that they may be main-
tained in a healthy condition. Such a supply can only be ob-
tained where the soil is sufficiently open to permit the free circula-
tion of the air among its pores.
2°. In the presence of air the decomposition of the vegetable mat-
ter of the soil proceeds more rapidly. It is more speedily resolved
into the humic, ulmic, and geic acids, into water, carbonic acid, and
568 DECOMPOSITION OF ROCKY FRAGMENTS.
ammonia, those forms of matter which are fitted to minister to the
growth of new vegetable races. In the absence of the air also, not
only does this decomposition proceed more slowly, but the substances
immediately produced by it are frequently unwholesome to the plant,
and therefore fitted to injure, or materially to retard, its growth.
3°. When the oxygen of the air is more or less excluded, the
vegetable matter of the soil takes this element from such of the
earthy substances as it is capable of decomposing, and reduces them
to a lower state of oxidation. Thus it converts the red or per-oxide
of iron into the prot-oxide (p. 356), and it acts in a similar man-
ner upon the oxides of manganese (p. 360). It also takes their
oxygen from the sulphates (as from gypsum), and converts them
into sulphurets. These lower oxides of iron and manganese are
often injurious to vegetation, and it is one of the beneficial pur-
poses served by turning up the soil in ploughing, or by otherwise
loosening it so as to allow the free admission of atmospheric air,
that the natural production of these oxides is either in a great mea-
sure prevented, or that when produced they speedily become harm-
less again by the absorption of an additional dose of oxygen.
4°. Further, there are few soils which do not contain, in some
quantity, fragments of one or other of those compound mineral
substances of which, in a previous lecture, we have seen the crys-
talline rocks to consist—of hornblende, of mica, of felspar, &c., in
a decomposing state. From these minerals, as they decompose,
the soil, and therefore the plants that grow in it, derive new sup-
plies of several of those inorganic substances which are necessary
to the healthy mourishment of cultivated crops. The continued
decomposition of these mineral fragments is aided by the access of
air, and, in an especial manner, by the carbonic acid which the air
contains. A state of porosity, therefore, or a frequent exposure
to the air, is favourable to the growth of the plant, by presenting
to its roots a larger abundance not only of organic but also of in-
organic food.
5°. Again, that production of ammonia and of nitric acid in the
soil, to which I drew your especial attention on a former occasion
(pp. 278 and 285), as apparently of so much consequence to ve-
getable life, takes place more rapidly, and in larger quantity, the
more frequently the land is turned by the plough, broken by the
OF SUBSOILING AND FORKING. 569
clod-crusher, or stirred up by the harrow. Whatever amount of
either of these compounds, also, the surface soil is capable of ex-
tracting from the atmosphere, the entire quantity thus absorbed
will evidently be greater, and its distribution more uniform, the
more completely the whole soil has been exposed to its influence.
It is for this, among other reasons, that, as every farmer knows,
the better he can plough and pulverise his stiffer land, the more
abundant in general are the crops he is likely to reap.
6°. Nor lastly, though in great part a mechanical benefit, is it
one of little moment that when thus every where pervious to the
air, the roots also can penetrate the soil in every direction. None
of the food around them is shut up from the approach of their mu-
merous fibres, nor are they prevented, by the presence of noxious
substances, from throwing out branches in every direction. A
deep soil is not absolutely necessary for the production of valuable
crops. A well-pulverised and mellow soil, to which the air and
the roots have every where ready access, will, though shallow, less
frequently disappoint the hopes of the husbandman,—than where
a greater depth prevails, less permeable to the air, and therefore
less wholesome to the growing roots.
§ 5. Of subsoil ploughing and forking.
And yet as a general rule, it cannot be denied that a deep soil
is greatly superior in value to a shallow soil of the same mature.
It is so both to the owner and to the occupier, though in too many
cases the available qualities of deep soils have hitherto been more
or less overlooked and neglected.
The general theoretical principle on this subject—that the deeper
the soil the longer it may be cropped without the risk of exhaus-
tion ; and the greater the variety of crops, deep as well as shallow-
rooted, which may be grown upon it—is so reasonable in itself, as
to command a ready acquiescence. But a soil is virtually shallow
where a few inches of porous earth, often turned by the plough,
rest upon a subsoil, hard, stiff, and almost impervious, and the
practical farmer will rarely be willing to allow the depth of the
latter to influence his opinion in regard to the general value of the
land. And in this he is so far correct, that a subsoil must be dried,
opened up, mellowed by the air, and rendered at once pervious
570 IT IS AN AUXIIIARY TO THE DRAIN.
and wholesome to the roots of plants, before it can be made avail-
able for the growth of corn. This may be effected, after draining,
by the use of the subsoil plough, an instrument at present equalled
only by the fork, for giving a real, practical, and money-value to
stiff and hitherto almost worthless clayey subsoils. It is an auxi-
liary both to the surface plough and to the drain, and the source
of its efficacy will appear from the following considerations:—
1°. The surface plough turns over and loosens the soil to the
depth of 6 to 10 inches—the subsoil plough tears open and loosens
it to a further depth of 8 or 10 inches. Thus the water obtains a
more easy descent, and the air penetrates, and the roots more
readily make their way among the particles of the under-soil. So
far it is an auxiliary to the common plough, and assists it in aerat-
ing and mellowing the soil.
2°. But though it opens up the soil for a time to a greater
depth, the subsoil plough will in most cases afford no permanent
cure for the deficiencies of the subsoil, if unaided by the drain. If
the soil rest upon an indurated substratum—upon a calcareous or
ochrey pan—this plough may tear it up, may thus allow the Sur-
face water to sink, and may greatly benefit the land; but the
same petrifying action will again recur, and the benefit of the sub-
soiling will slowly disappear. Or, if the subsoil contain some nox-
ious ingredients, such as salts of iron, which the admission of air
is fitted to render harmless, then the use of this plough may afford
a partial amelioration. But in this case, also, the effect will be
only temporary. Since the source of the evil has not been removed,
the same noxious compounds will again be naturally produced, or
will again, in fresh supplies, be conveyed into the soil by springs.
Or, if the subsoil be a stiff clay, containing no noxious ingredient,
it may be cut, or for the time torn asunder, but scarcely will the
plough have passed over it till the particles will be again cemented
together, and probably, by the end of a single season at the fur-
thest, the under-soil may be as solid and impermeable as ever.
It is as the follower of the drain, therefore, in the course of im-
provement, that the subsoil plough finds its most beneficial and
most economical use. After land has been drained, the water may
still too slowly pass away, or the air may have too imperfect an en-
trance into the subsoil from which the drains have removed the
PREVIOUS DRYNESS OF THE SUBSOIL NECESSA.R.Y. 57.1
water. In the former case, the subsoil plough must be employed,
in order that the drain may become fully efficient; in the lat-
ter, that the under-layers may be opened up to all the beneficial
influences which the atmosphere is fitted to exert upon them. In
this respect it is an auxiliary to the drain. But as the full effect
which the subsoil plough is capable of producing upon stiff and
clayey subsoils can only be obtained after they have been brought
to such a state of dryness that the sides of the cut or tear, which
the plough has made, will not again readily cohere, it is of impor-
tance that the drains should be allowed a considerable time to ope-
rate before the use of this plough is attempted. The expense of
the process is comparatively great, and this expense will be in a
great measure thrown away upon clay lands, which are undrained,
or from which the water, either through defective draining, or from
the want of sufficient time, has not been able fully to flow away.
There are few kinds of clay land on which the judicious use of
this valuable instrument will not prove both actually and economi-
cally useful, though from the neglect of the above necessary pre-
caution, it has been found to fail in the hands of some. Such fail-
ures, however, do not justify us in ascribing to defects in the in-
strument, or in the theory upon which its use is recommended,
what necessarily arose, and could have been predicted, from our
own neglect of an indispensable preliminary observation of the
state of the soil upon which it was to be used. *
The same end which is gained by the use of the subsoil plough
may also be attained by employing the fork. With this simple
three-pronged implement the subsoil is loosened or turned over to a
depth of ten or twelve inches after the top soil has been taken off
and thrown forward by the common spade. It does its work very
beautifully, and loosens the subsoil even more completely than the
subsoil plough. It has the advantage of cheapness, of being easily
used, of requiring no horse power, and therefore of being within
the reach of the humblest farmer, of performing its work at least as
well, and it is said upon the whole at as cheap a rate as the subsoil
plough.
§ 6. Of deep-ploughing and trenching.
Deep-ploughing and trenching differ from ordinary and subsoil
572 OBJECT AND EFFECT OF DEEP PLOUGHING.
ploughing in this, that their special object is to bring to the sur-
face and to mix with the upper-soil a portion of that which has
lain long at a considerable depth, and has been more or less un-
disturbed.
The benefit of such an admixture of fresh soil is in many loca-
lities undoubted, while in others the practical farmer is decidedly
opposed to it. On what principle does its beneficial action depend,
and in which circumstance is it likely to be attended with disad-
vantage 2
1°. It is known that when a heavy shower of rain falls it sinks
into the soil, and carries down with it such readily soluble sub-
stances as it meets with on the surface. But other substances also,
which are more sparingly soluble, slowly and gradually find their
way into the subsoil, and there more or less permanently remain.
Among these may be reckoned gypsum, and especially those sili-
cates of potash and soda already spoken of (p. 351), as apparently
so useful to corn-growing plants. Such substances as these natu-
rally accumulate beyond the reach of the ordinary plough. In-
soluble substances likewise slowly sink. This is well known to be
the case with lime, when laid upon or ploughed into the land. So
it is with clay, when mixed with a surface soil of sand or peat.
They all descend till they get beyond the reach of the common
plough—and more rapidly it is said (in Lincolnshire) when the
land is laid down to grass than when they are constantly brought
to the surface again in arable culture. Thus it happens that after
the surface soil becomes exhausted of one or other of those inor-
ganic compounds which the crops require, an ample supply of it
may be still present in the subsoil, though, until turned up, un-
available for the promotion of vegetable growth. .
There can be little question, I think, that the greater success
which attends the introduction of new implements in the hands of
better instructed men, upon farms long held in arable culture, is
to be ascribed in part to this cause. One tenant, during a long
lease, has been in the habit of ploughing to a depth of three, or at
most, perhaps, of four inches—and from this surface the crops he
has planted have derived their chief supplies of inorganic food.
He has limed his land in the customary manner, and has laid up-
on it all the manure he could raise, but his crops have been usually
PRACTICAL OBSERVATIONS. 573
indifferent, and he considers the land of comparatively little value.
But another tenant comes, and with better implements turns up
the land to a depth of 7 or 8 inches. He thus brings to the sur-
face the lime and the accumulated manures which have naturally
sunk, and which his predecessor had permitted year after year to
bury themselves in his subsoil. He thus has a new, often a rich,
and almost always a virgin soil to work upon—one which from be-
ing long buried, may require a winter's exposure and mellowing
in the air, but which in most cases is sure to repay him for any
extra cost. The deep ploughing which descends to 14 inches, or
the trenching which brings up a new soil from the depth of 20 or
30 inches, is only an extension of the same practice. It is justi-
fied and recommended upon precisely the same principle. It not
only brings a new soil, containing ample nourishment, to the im-
mediate roots of plants, but it affords them also a deeper and more
open subsoil through which their fibres may proceed in every di-
rection in search of food. The full benefits of this deepening of
the soil, however, can only be expected where the subsoil has pre-
viously been laid dry by drains; for it matters not how deep the
loosened and permeable soils may be, if the accumulation of water
prevent the roots from descending.
2°. Two practical observations, however, may here be added,
which the intelligent farmer will always weigh well before he
hastily applies this theoretical principle—sound though it undoubt-
edly be—in a district with which he has no previous acquaintance.
It is possible that the deeper soil may contain some substance de-
cidedly noxious to vegetation. In such a case it would be impro-
per at once to mix it with the upper soil. Good drains must be
established, they must be allowed some time to act, and the sub-
soil plough will be used with advantage, before any portion of such
an under soil can be safely brought to the surface. The subsoil
plough and the drain, indeed, are the most certain available re-
medies for such a state of the subsoil. In many localities, how-
ever, the exposure of such an under-soil to a winter's frost, or to
a summer fallow, will so far improve and mellow it, as to render
it capable of being safely mixed with the surface soil. Unless,
however, this mellowing be effected at once, and before admixture,
574 - EFFECT OF INSECTS.
a long time may elapse ere the entire soil attain to its most per-
fect condition.*
Again, it is known that some districts, for reasons perhaps not
well understood, are more infested than others with insects that
attack the corn or other crops. These insects, their eggs, or their
larvae, generally bury themselves in the undisturbed soil, immedi-
ately beyond the ordinary reach of the plough. If they remain
wholly undisturbed during the preparation of the soil, some spe-
cies remain in a dormant state, and the subsequent crop may in a
great measure escape. Plough the land deeper than usual, and
you bring them all to the surface. Do this in the autumn, and leave
your land unsown, and the frost of a severe winter may kill the
greater part, so that your crops may thereafter grow in safety.
But cover them up again along with your winter corn, or let this
deep ploughing be done in the spring, and you bring all these in-
sects within reach of the early sun, and thus call them to life in
such numbers as almost to ensure the destruction of your coming
crop. It is to something of this kind that I am inclined to attri-
bute the immediate failures which have attended the trial of deep
ploughing in certain parts of England. Thus, in Berkshire, cer-
tain soils which are usually ploughed to a depth of only two inches,
yielded almost nothing when deeper ploughing was more lately
tried upon them—the crop was almost entirely destroyed by insects.
So also in the north of Yorkshire, where deep ploughing has re-
cently been attempted, the wheat crop on land so treated was ob-
served to suffer more from the worm than on any other spot.
Such facts as these, therefore, show the necessity of caution on the
* The Marquis of Tweeddale, in his home-farm at Yester, has raised his land in
value eight times (from 5s. to 40s. per acre), by draining and deep ploughing. After
draining, the fields of stiff clay, with streaks of sand in the subsoil, are turned over to
a depth of 12 or 14 inches, by two ploughs (two horses each) following one another,
the under 6 inches being thrown on the top. In this state it is left to the winter's
frost, when it falls to a yellow marly looking soil. It is now ploughed again to a
depth of 9 or 10 inches, by which half the original soil is brought again to the surface.
By a cross ploughing this is mixed with the new soil, after which the field is prepared
in the usual way for turnips. But it is observed that if the ploughing has been so
late that the subsoil has not had a proper exposure to the winter's cold, the land on
such spots does not for many years equal that which was earlier ploughed. The rea-
son is, that when once mixed up with the other soil the air has no longer the same easy
access to the several parts of the subsoil. -
IMPROVEMENT OF THE SOIL BY MIXING. 575
part of the practical man, and especially of the land agent or
steward, however correct may be the principles on which his gene-
ral practice is founded. Failures such as the above do not show
the principle on which deep ploughing is recommended to be false,
or the practice to be in any case reprehensible; but it does show
that a knowledge of natural local peculiarities, and some study of
ancient local practice, may, in an important degree, influence our
mode of procedure in introducing more improved methods of hus-
bandry into any old agricultural district.
§ 7. Improvement of the soil by mixing.
There are some soils so obviously defective in composition, that
the most common observer can at once pronounce them likely to
be improved by mechanical admixtures of various kinds. Thus
peaty soils abound too much in vegetable matter; a mixture of
earthy substances, therefore, of almost any common kind is readily
indicated as a means of improvement. In like manner we natu-
rally impart consistence to a sandy soil by an admixture of clay,
and openness and porosity to stiff clays by the addition of sand.
The first and obvious effect of such additions is to alter the phy-
sical qualities of the soil—to consolidate the peats and sands, and
to loosen the clays. But we have already seen that the fertility
of a soil, or its power of producing a profitable return of this or
that crop, depends mainly on its chemical composition. It must
contain in sufficient abundance all the inorganic substances which
that crop requires for its daily food. Where this is already
the case, as in a rich stiff clay, a decided improvement may be
produced by an admixture of siliceous sand, which merely Sepa-
rates the particles mechanically, and renders the whole more po-
rous. But let the clay be deficient in some necessary constituent
of a fertile soil, and such an addition of siliceous sand would not
produce by any means an equal benefit. It may be proper to add
this sand with the view of producing the mere physical alteration,
but we must add some other substance also for the purpose of pro-
ducing the necessary chemical change.
The good effects which almost invariably follow from the addi-
tion of clay to peaty or sandy soils are due to the production at
one and the same time of a physical and of a chemical change.
They are not only rendered firmer or more solid by the admixture
576 EFFECTS OF CIAY AND MARL.
of clay, but they derive from this clay at the same time some of
those mineral substances which they previously contained in less
abundance.
The addition of marl to the land acts often in a similar two-fold
capacity. It renders clay lands more open and friable, and to all
soils brings an addition of carbonate, and generally of phosphate
of lime, both of which are proved by experience to be not only
very influential but to be absolutely necessary to healthy vegetation.
That much benefit to the land would in many instances accrue
from such simple admixtures as those above adverted to, where
the means are available, will be readily granted. The only ques-
tion on the subject that ought to arise in the mind of a prudent
man, is that which is connected with the economy of the case. Is
this the most profitable way in which I can spend my money P Can
I employ the spare labour of my men and horses in any other way
which will yield me a larger return ? It is obvious that the an-
swer to these questions will be modified by the circumstances of
the districtin which he lives. It may be more profitable to drain,_
or labour may be in great request and at a high premium,-or a
larger return may be obtained by the investment of money in pur-
chasing new than in improving old lands. It is quite true that
the country at large is no gainer by the mere transfer of land from
the hands of A to those of B, and that he is undoubtedly the most
meritorious citizen who, by expending his money in improving the
soil, virtually adds to the breadth of the land, in causing it to yield
a larger produce. Yet it is no less true that the employment of in-
dividual capital in such improvement is not to be expected gene-
rally to take place unless it be made to appear that such an in-
vestment is likely to be as profitable as any other within the reach
of its possessor. It seems to be established beyond a doubt that
in very many districts no money is more profitably invested, or
yields a quicker return, than that which is expended in draining
and subsoiling—and yet in reality one main obstacle to a more
rapid increase in the general produce of the British soil is the
practical difficulty which exists in convincing the owners and oc-
cupiers of the soil that such is the case, or would be the case, in
regard to their own holdings. The more widely a knowledge of
the entire subject, in all its bearings, becomes diffused, the less
3
bºr
CLAY AND SAND OF THE EAST OF DURHAM. 577
it is to be hoped will this difficulty become—for the economist,
who regards the question of improvement as a mere matter of pro-
fit and loss, cannot strike a fair balance unless he knows the seve-
ral items he may prudently introduce into each side of his account.
Thus in reference to the special point now before us, it seems
reasonable to believe that, in a country such as that here repre-
sented, where alternate hills of sand (3), and hollows, and flats of
N N § #s § 3$=
NS W & Wºº & Wº §
§§
§ *
"Nº," Wº * : * &W
§ ",". Nº §
\
clay (4) occur, there may be many spots where both kinds of soil—
being near each other—might be improved by mutual admixture,
at a cost of labour which the alteration in the quality of the land
might be well expected to repay. In this condition is a consider-
able portion of the eastern half of the county of Durham, and,
especially, I may mention the neighbourhood of Castle Eden, where
a cold, stiff, at present often poorly productive clay rests upon
red, rich-looking, loamy sand, in many places easily accessible,
and by admixture with which its agricultural capabilities may be
expected to improve. In this, as in many other localities, those
having a pecuniary interest in the land often rest satisfied that
their fields are incapable of such improvement, or would give no
adequate return for the outlay required, without carefully collect-
ing and comparing all the facts from which a true solution of the
question can alone be drawn.
Besides such general admixtures for the improvement of land,
the geological formation of certain districts places within the reach
of its intelligent farmers means of improvement of a special kind,
of which they may often profitably avail themselves. Thus both
in Europe and America the green-sand soils (p. 460) are found to
be very fertile, and the sandy portions of this formation are often
within easy distance of the stiff clays of the gault, and of the poor
soils of the chalk, with either of which they might be mixed with
most beneficial effects. The soils that rest on the new, and even
on some parts of the old red sand-stone, are in like manner often
O O
































578 SPECIAL MANURES.
within an available distance of beds of red marl of a very fertiliz-
ing character (p. 468 and 474), while in the granitic and trap dis-
tricts the materials of which these rocks consist may, by a judicious
admixture, be made materially to benefit some of the neighbour-
ing soils. To this point, however, I shall draw your attention again
in the succeeding lecture when treating of mineral manures.
LECTURE XVIII.
Improvement of the soil by chemical means. Principles on which all manuring de-
pends. Mineral, vegetable, and animal manures. Saline manures. Carbonate of
potash (Pearl-ash) and carbonate of soda. Theory of the action of potash and
soda. Sulphates of potash, soda, lime, and magnesia. Theory of the action of these
sulphates. Common salt. Nitrates of potash and soda. Their action on different
crops, and theory of their action. Phosphate of lime. Super-phosphate of lime.
Ammoniacal phosphate of magnesia. Phosphate of potash. Theory of the action
of the phosphates. Silicates of potash and soda. Silicate of lime. Are silicates
necessary to the land or to the crops ?
THE mechanical methods of improving the soil, described in the
preceding section, are few in number and simple in theory. They
are so important, however, to the general fertility of the land, that
were they judiciously employed over the entire surface of our
islands, they would alone greatly increase the average produce of ,
the British and Irish soils. I may, indeed, repeat what was stated in
reference to draining, (p. 554), that the full effect of every other
means of improving the soil will be obtained in those districts only
where these mechanical methods have already been had recourse
to.
The chemical methods of improving the soil are founded upon
the following principles, already discussed and established:—
1°. That plants obtain from a fertile soil a variable proportion
of their organic food;—of their nitrogen probably the greatest part.
2°. That they require inorganic food also of various kinds, and
that this they procure solely from the soil.
3°. That different species of plants require a special supply of
different kinds of inorganic food, or of the same kinds, in different
proportions.
4°. That of these inorganic substances one soil may abound or
be deficient in one, and another soil in another; and that, there-
580 ACTION OF CHEMICAL SUBSTANCES IN THE SOILe
fore, this or that plant will prefer to grow on the one or the other
accordingly.
On these few principles the whole art of improving the soil by
chemical means—in other words of beneficially manuring the soil
—is founded.
It must at the same time be borne in mind, that there are
three distinct methods of operation by which a soil may be im-
|proved :— -
1". By removing from it some noxious ingredient. The only
method by which this can be effected is by draining, providing
an outlet by which it may escape, or by which the rains of heaven,
or water applied in artificial irrigation, may wash it away.
2". By changing the nature or state of combination of some
noxious ingredient, which we cannot soon remove in this way; or
of some inert ingredient which, in its existing condition, is unfit to
become food for plants. These are purely chemical processes,
and we put them respectively in practice when we add lime to
peaty soils, or to such as abound in the sulphate or other hurtful
salts of iron (p. 359), when by admitting the air into the subsoil
we change the prot-oxide into the per-oxide of iron (p. 356), or
when by adding certain known chemical compounds we produce
similar beneficial chemical alterations upon other compounds al-
ready existing in the soil.
3". By adding to the soil those substances which are fitted to
become the food of plants. This is what we do in strictly manur-
ing the soil—though we are as yet unable in many cases to say
whether that which we add promotes vegetation by actually feed-
ing the plant and entering into its substance—or only by prepar-
ing food for it. There is reason to believe, however, that many
substances, such as potash, soda, &c., act in several capacities,
now preparing food for the plant in the soil, now bearing it into
the living circulation, and now actually entering into the perfect
substance of the growing vegetable.
In order to steer clear of the difficulty which this circumstance
throws in the way of an exact classification of the chemical sub-
stances applied to the soil, I shall consider generally under the
name of manures, all those substances which are usually applied to
the land for the purpose of promoting vegetable growth–whether
CARIBONATES OF POTASH AND SODA. 58]
those substances be supposed to do so directly by feeding the
plants, or only indirectly, by preparing their food, or by convey-
ing it into their circulation.
Manures, them, in this sense are either simple, like common salt
and nitrate of soda, or they are mixed, like farm-yard manure
and the numerous artificial manures now on sale. Or, again, they
consist of substances of mineral, of vegetable, or of animal origin.
We shall, as the most convenient, consider the various substances
employed in improving the soil—or what is in substance the same
thing, in promoting vegetation, in the following order:-
1". Saline and mineral manures—including those substances,
whether simple or mixed, natural or artificial, which are of a sa-
line mature or of mineral origin. The greater number of these
consist entirely of inorganic or mineral matter. -
2". Vegetable manures.—These are all of natural origin, and
are all mixtures of organic and inorganic matter.
3". Animal manures, which are also mixtures, but owing to their
immediate origin, differ remarkably in composition from vegetable
substances.
In the present and the succeeding lecture we shall treat of the
saline and mineral manures only.
§ 1. Of the carbonates of potash and soda, and the theory of their
action upon living plants.
1". Carbonate of potash.--This substance, in the form either of
crude potash or of the pearl-ash of the shops, has hitherto been
little employed as an application in the culture of the land. As an
ingredient in the artificial mixtures of which we shall hereafter
treat, it is fitted to be of much use in practical farming.
2". The carbonate of soda is sufficiently low in price (L.8 a ton)
to allow of its being applied with advantage under many circum-
stances. In the case of grass lands, which are overrun with moss,
or of such as abound largely in vegetable matter or in noxious
sulphate of iron, a weak solution applied with a water cart might
be expected to produce good results. It might be applied in the
same way to fields of sprouting corn, or in fine powder as a top-
dressing in moist weather—and generally wherever wood ashes are
found useful to vegetation.
582 QUANTITY WHICH MAY BE APPLIED TO THE SOIL.
Many experiments have shown that either of these substances may
be employed in the field with advantage to the growing crop, both
in directly promoting its growth and in destroying insects, such as
the grub and the wire-worm, which are injurious to vegetable life.
In gardening they greatly hasten the growth and increase the pro-
duce of the strawberry,” and in garden culture, generally, where
the cost of the manure employed is of less consequence, more ex-
tended trials would, no doubt, lead to useful results.
The quantity of these substances which ought to be applied,
will depend much upon the nature of the soil in each locality, and
on the kind of manuring to which it has previously been subjected.
By referring to our previous calculations (p. 409), it will be seen
that nearly 500 lbs. of these carbonates would be necessary to re-
place all that is extracted from the soil by the entire crops during
a four years' rotation. But in good husbandry every thing is re-
turned to the soil in the form of manure which is not actually sent
to market and sold for money. That is—the grain only of the
corn crops, the dairy produce, and the live stock are carried off
the land.j Less than 40 lbs. per acre of the mixed carbonates
would replace all that is contained in the grain, and if we suppose
as much more to be present in the other produce sold, we have 80
lbs. for the quantity necessary to be restored to the land by the
good husbandman every four years, in order to keep his farm per-
manently in the same condition in respect to the presence of these
substances. There are, however, in most soils certain natural
sources of supply (p. 352), from which new portions of these
alcalies are continually conveyed to them. Hence it is seldom ne-
cessary to add to the land as much of these substances as we carry
off; and therefore from 40 to 60 lbs. per acre, of either of them
in the state of dry carbonates, may be considered as about the
largest quantity which, in a well-managed farm, need be added in
order to give a fair trial to their agricultural value. Half a cwt.
of the dry potash will cost less than 15s., and of the soda about 5s,
* Mr Fleming, of Barochan, has informed me that he found this to be the case
with the common potash ; and Mr Campbell, of Islay, with the common soda of the
shops. They should be applied early in the spring, and in the state of a very weak
solution. Wood-ashes would probably produce a similar effect.
i In bad husbandry much more is carried off the land by the waste of liquid and
other manure.—See the succeeding chapter “On animal manures.”
ACTION OF POTASH AND SODA UPON WEGETATION, 583
or one cwt. of a mixture of the two in equal quantities will cost
about 20s. at their present prices.
3". Theory of the action of potash and soda.-But upon what
theoretical grounds is the beneficial action of potash and soda upon
vegetation explained 2 This question, to which I have already
more than once adverted (pp. 130 and 415), it will be proper here
briefly to consider.
a. The first and most obvious purpose, served by the presence
of these alcalies in the soil, is that of yielding readily to the grow-
ing plant such a full supply of each as may be essential to its
healthy growth. If the roots can collect them from the soil slow-
ly only, and with difficulty, the growth of the plant will necessarily
be retarded; while in situations in which they naturally abound,
or are artificially supplied, its growth will as certainly prove both
more early and more abundant—provided no other essential food
be deficient in the soil. -
In reference to this mode of action it may occur to you that
potash is the more likely of the two to be beneficial to our culti-
vated crops, inasmuch as the ash of those plants which are raised
for food is generally much more rich in potash than in soda.
But this may possibly arise from the more abundant presence of
potash in the soil generally, since it is not unlikely, as we have al-
ready seen (p. 415), that soda may take the place of potash in the
interior of plants without materially affecting their growth.* This
opinion will prove useful to practical agriculture if it lead to ex-
periments from which the relative action of each of these carbo-
mates, in the same circumstances, may be deduced,—and the specific
influence of each, in promoting the growth of particular plants, in
some degree determined. Potash (or wood ashes) aids the growth
of corn after turnips or potatoes (Lampadius)—would soda do the
same 2 Carbonate of Soda assists in a remarkable manner the
growth of buck-wheat (Sprengel)—would the same good effects
follow from the use of potash 2 In our artificial or manufactured
manures does soda produce the same beneficial effects as an ad-
mixture of potash P
b. Another purpose which these carbonates are supposed to
serve, is that of combining with, and rendering soluble, the vege-
* Berzelius, Chimie, WI. p. 733, (Edit. 1832.)
584 THEY PREPARE THE FOOD OF PLANTS,
table matter of the soil, so as to bring it into a state in which it
may be readily conveyed into the roots of plants. They may in
this case be said to prepare the food of plants. That they are
really capable of forming readily soluble compounds with the hu-
mic, ulmic, and other organic acids which exist in the soil, is cer-
tain. Those, however, who maintain with Liebig that plants im-
bibe all their carbon in the form of carbonic acid, will not be will-
ing to admit that this property of the above carbonates can either
render them useful to vegetation, or account for the beneficial ac-
tion they have so often been observed to exercise. In this opinion
I do not concur. I am prepared, therefore, to concede that pot-
ash and soda, in the form of carbonates, may act beneficially upon
vegetation—by preparing the organic matter of the soil for entering
into the roots of plants, and thus ministering to their growth.
This preparation also may be effected either by their directly com-
bining with the organic matter, as they are known to do with the
humic and other acids which exist in the soil; or by their dispos-
ing this organic matter, at the expense of the air and of moisture,
to form new chemical compounds which shall be capable of enter-
ing into the vegetable circulation. This disposing influence of the
alcalies, and even of lime, is familiar to chemists under many other
circumstances.
This mode of action of the carbonates of potash and soda can be
exercised in its fullest extent only where vegetable matter abounds
in the soil. It is stated by Sprengel" accordingly, as the result of
experiment, that they are most useful where vegetable matter is
plentiful, and that they ought to be employed more sparingly, and
with some degree of hesitation, where such organic matter is defi-
cient.
c. We have already seen, during our study of the composition
of the ash of plants, how very important a substance silica is, es-
pecially to the grasses and to the stems of our various corn-bear-
ing plants. This silica exists very frequently in the soil in a state
in which it is insoluble in pure water, and yet is more or less read-
ily taken up by water containing carbonate of potash or carbonate
of soda. And as there is every reason to believe that nearly all
the silica they contain is actually conveyed into the circulation of
* Lehre vom Dingcº, p. 402.
THEY INDUCE CHANGES IN THE SAP. 585
plants by the agency of potash and soda, it is not unlikely that a
portion of the beneficial action of these substances, especially upon
the grass and corn crops, may be due to the quantity of silica they
are the means of conveying into the interior of the growing plants.
d. Another mode in which these substances act, more obscure-
ly, perhaps, though not less certainly, is by disposing the organic
matters contained in the sap of the plant to form such new combi-
nations as may be required for the production of the several parts
of the living vegetable. I have on a former occasion illustrated
(p. 188) the very remarkable changes which starch may be made
to undergo, without any essential alteration in its chemical com-
position—how gum and sugar may be successively produced from
it, without either loss or gain in respect of its original elementary
constitution. We have seen also how the presence of a compara-
tively minute quantity of diastase or of sulphuric acid is capable of
inducing such changes, first rendering the starch soluble, and then
converting it into gum and into sugar. Analogous, though some-
what different, changes are induced by the presence in certain so-
lutions of small quantities of potash or soda, as, for example, in
milk——the addition of carbonate of soda to which gradually causes
(persuades?) the whole of the sugar it contains to be converted into
the acid of milk. Such changes are induced or facilitated by the
presence of acid and of alcaline substances in the sap of plants;
and though we can as yet only guess at the precise nature of these
changes, yet there seems good ground for believing that to facili-
tate their production is one of the many purposes served by the
constant presence of inorganic substances in the sap of plants. In-
deed so important is this function considered by some writers upon
the mourishment of plants,” that they are inclined to ascribe, erro-
neously however, as I believe, to this mode of action the main in-
fluence upon vegetation, of nearly all the inorganic substances
which are found in the ash of plants, and therefore are known to
enter into their circulation.
e. I only allude to one other way in which these substances may
be supposed to have an influence upon vegetation. We have al-
ready seen how important a part the mitric acid produced in the
atmosphere or in the soil may be supposed to perform in the ge-
* See especially Hlubeck's Ermährung der Pflanzen und Statik des Londbaues.
586 SULPHATES OF POTASH AND SODA.
neral vegetation of the globe. This acid is observed to be more
abundantly—either fixed or actually produced in the soils or com-
posts which contain much potash or soda. It may be, therefore,
that in adding either of these to our fields we give to the soil the
means of bringing within the reach of the roots of our crops a more
ready supply of nitric acid, and hence of nitrogen, so necessary a
part of their daily food,
§ 2. Of the sulphates of potash, soda, magnesia, and lime, and the
theory of their action.
1°. Sulphates of potash and soda.--It is nearly 100 years since
Dr Home, of Edinburgh, observed that these salts produced a be-
meficial effect upon vegetation. Applied to growing corn he found
them to increase the produce by one-fourth. Other experiments
made in Germany, and more recently in this country, have shown
that they may be applied with manifest advantage both to field
crops and to fruit and forest trees.
Sulphate of soda when applied to hay and rye, at the rate of 84
lbs. of the dry salt, and to potatoes at the rate of 100 lbs., gave
per imperial acre, with
Dressed with
Undressed. Sulphate. Increase.
Hay,... ............... ... 4480 lbs. 5288 lbs. 808 lbs
Winter rye, | grain,..... 640 lbs. 896 lbs. 256 lbs.
! straw,...... 4096 lbs. 4608 lbs. 512 lbs.
Potatoes, ... ............... 16% tons. 18} tons. l; tons.
The grain of the dressed rye was much heavier than that of the
undressed, and, though nitrate of soda and sal-ammoniac applied
to other parts of the same field caused a larger increase in the crop
of rye, yet the increase obtained by the use of the sulphate was
cheaper per bushel than that obtained by the use of either of the
other substances.
On beans and peas also the effect produced by this salt was very
striking—its action being exerted in some cases not upon the
straw but upon the pods, increasing their number and enlarg—
ing their size. In other cases it has increased both the straw
and the pods, and applied in the drills at the rate of 13 cwt. per
Scotch acre, it has alone added 16 bushels an acre to the produce
of beans (Girdwood).
SULPHATES OF MAGNESIA AND LIME. 587
Unlike the nitrate of soda, the sulphate renders the crop paler
in colour, even when the produce is increased.”
The results of these experiments, therefore, are such as to en-
courage further trials. The quantity applied should not be less
than one cwt. of the dry salt per acre, and it may be drilled in
with the grain, may be sown broad-cast on the surface, and har-
rowed in ; or it may be applied in the state of a very weak solu-
tion with a water-cart, or sprinkled on the young crop when the
ground is moist or when rain is soon expected. -
2°. Sulphate of Magnesia (Epsom salts) was found by Dr Home
to promote vegetation almost in an equal degree with the Sulphates
of potash and soda, but the high price of this compound, among
other causes, has hitherto prevented it from being tried upon an ex-
tensive scale. The manufacture has of late years, however, been so
much extended and simplified, that the refined salts for medicinal
purposes may be purchased as low as 8s, a cwt., and the impure salts
of the Yorkshire and other alum works at a much lower rate.
I have elsewhere recommended the application of sulphate of soda
at the rate of 1 cwt. of the dry salt or of 2 cwt. of crystals per acre.
The Epsom salts are only sold in crystals, and 13 cwt. (cost 12s.)in
this form should be nearly equal in efficacy upon the land to 2 cwt. of
crystallized sulphate of soda. In this proportion, therefore, it would
be proper to apply it as a top-dressing to young wheat, barley, clover,
peas, beans, or other leguminous plants, and to the potato either in
the drill with the manure, or to the young crops after the plants have
come up.
3°. Sulphate of Lime (Gypsum) has been long and extensively
applied to the land in various countries and to various crops. In
Germany its influence has been most generally beneficial upon
grass and red clover, while in many parts of the United States it is
applied with advantage to almost every crop. In the former country
and in England, it is usually dusted over the young plants in early
spring; in America it is frequently sown with the seed, or, in the case
of Indian corn and potatoes, put into the drills or holes along with the
manure. The propriety of adopting the one rather than the other of
these methods will depend upon the nature of the soil and upon the
climate. Gypsum requires much water to dissolve it, and in dry
* See the Author’s “Suggestions for Beperiments in Practical Agriculture.”
588 TEIEORY OF THE ACTION OF THESE SULPHATES.
soils, climates, or seasons, it might readily fail to influence the crop
at all, if applied in the form of a top-dressing only.
It would appear that the time and mode of its application has
more influence upon its activity than we might suppose—since, ac-
cording to Professor Körte, when applied to clover at different pe-
riods in the spring, the produce of different parts of the same field
was in the following proportions:— -
Undressed,........... ......A • * * * * * • * * * * * * * *, , , s , a 100 lbs.
Top-dressed on the 30th of March,......... 132 lbs.
e & e º 'º e º e º e s e º 'º $ tº º e º e º e º & löth of April, ...... ... 140 lbs.
• * * * * * * * * * * * * * * * * * * * * * * * 27th of April, ..... ... 156 lbs.”
The effect of a top-dressing of gypsum seems therefore, accord-
ing to this experiment, to be greatest when it is applied after the
leaves have been pretty well developed.j -
4°. Theory of the action of these sulphates.—It does not seem
difficult now to account for the general action of these several sul-
phates of potash, soda, magnesia, and lime. The explanation may
be deduced partly from the recent chemical analyses of the ashes
of plants, and partly from agricultural experiments more lately
made by practical men.
a. It has been found, for example, that sulphur is a constant and
apparently necessary constituent of the gluten, albumen, and other
protein compounds always present in the several varieties of corn
and pulse. Every hundred pounds of these substances contain from
one half to two pounds of sulphur. This sulphur they must obtain
from the soil, and one cause of the efficacy of the above sulphates is
unquestionably that they are fitted easily to yield to the growing plant
the supply of sulphur they necessarily require—while, if they are
more efficacious upon the leguminous than upon other kinds of plants,
it is because the latter produce or contain a larger proportion of that
kind of organic matter in which sulphur is constantly present.
That such is really the true explanation of their general action is
proved by the observation—that sulphuric acid applied to the land in
a very diluted state exerts an influence upon the crops precisely si-
milar to that observed when gypsum or sulphate of sodaí is used.
* Möglinsche Jahrbucher, I. p. 85, quoted in Hlubeck’s Pflanzenmährung.
+ Can the result here mentioned have any connection with the fact observed by
Peschier, that gypsum laid upon the leaves of plants is gradually converted into car-
bonate, its sulphuric acid being absorbed P -
† See “Suggestions for Baperiments in Practical Agriculture.”
RELATIVE EFFICIENCY OF THESE SULPHATES. 589
In reference to this mode of action it is of consequence to know
the relative efficiency of equal weights of the several salts. This
will obviously depend upon the relative proportions of sulphur or
sulphuric acid they contain—supposing the circumstances in which
they are applied to be equally favourable to the introduction of
each into the circulation of the plant. Their relative value upon
this view is as follows:—
100 lbs. of burned gypsum are equal to, or contain as much sul-
phuric acid as,
126 lbs. of common or unburned gypsum :
128 lbs. of sulphate of potash;
104 lbs. of sulphate of soda——dry;
235 lbs. of sulphate of soda—crystallized;
180 lbs. of sulphate of magnesia—crystallized;
and as of all these the gypsum is by far the cheapest, it should
form, in reference to this general action of the above sulphates, in
all cases the most economical application to the land.
b. But they have each also their special action dependant partly
upon their physical properties, and partly on their chemical compo-
sition. .
Thus the facility with which they can respectively enter into the
roots of plants depends upon their relative solubility in water, which
is very unlike. An imperial gallon of pure water at the ordinary
temperature will dissolve of
Gypsum (burned,) ... .... ... & a tº 8 º' tº $ tº º e s tº 4 º' s about # lb.
Gypsum (unburned,) ........ -e e º 'º & e º e º 'º e g º e º gº # lb.
Sulphate of potash, ......................... e º 'º e a l; lbs.
Sulphate of soda, dry, ........................... 14 lbs.
Sulphate of Soda, crystallized,.................. 3% lbs.
Sulphate of magnesia, ............ . . ........... 4 lbs.
In rainy weather, therefore, and in moist climates, it would still
be most economical to apply the gypsum, since, though very spar-
ingly soluble, water would be sufficiently abundant to dissolve as
much as the plant might require. But in times of only moderate
rain, and especially in dry seasons, the use of the sulphates of soda
and magnesia, which are also low in price, is recommended by the
comparative ease with which they may be taken up by water and
conveyed to the roots.
c. Again, the chemical composition of these sulphates—the na-
B90 THE SPECIAL ACTION OF THESE SULPHATES.
ture of the substance with which the sulphuric acid is combined in
them respectively—determines in a still greater degree the na-
ture and extent of their special action.
If the soil already abound in potash, in soda, in lime, or in mag-
nesia, the good effects produced by these compounds may depend
entirely upon the sulphuric acid they contain. But suppose the
land to be deficient in lime, then the gypsum we add will act not
only in virtue of the sulphuric acid, but of the lime also which it
contains, and thus its apparent effect will be much more striking
than when the land is naturally calcareous, or has been previously
dressed with lime.” So if it be deficient in potash, the sulphate of
potash will be more efficient than it could be expected to prove
upon a soil in which sulphuric acid alone is wanting. And so also,
if lime and potash abound, and soda or magnesia be deficient,
the sulphates of these latter bases will exercise a special action up-
on the soil, by supplying it at the same time with sulphuric acid
and with soda or magnesia also. Thus on land to which lime has
been abundantly added, according to the ordinary practice of hus-
bandry, the sulphate of soda has a better chance of proving useful
to vegetation than the sulphate of lime, not only because it is more
soluble, and is, therefore, more independent of the seasons, but be-
cause it is capable, along with the sulphuric acid, of supplying soda
also, of which the soil may be deficient though it abound in lime.
But the demands or composition of the different crops to which
they are applied, though grown upon the same soil, will often cause
one of these sulphates to produce a more decided and useful effect
than another. We have already seen (see table, p. 414,) that to
some plants potash and soda are necessary in larger quantity than
lime and magnesia,—upon these plants the sulphates of potash and
soda will be more likely to produce beneficial effects than those of
lime and magnesia. Again, some appear constantly to demand
more lime, and others more magnesia, and hence the sulphate of
lime may upon some crops produce a greater, upon other crops a
less effect than the sulphate of magnesia.
The special effects of these several sulphates are thus to be ex-
* “I applied gypsum and sulphate of soda to my turnip crop last year, (1841); the
former nearly doubled my crop—but the latter was scarcely perceptible.”—Mr Bur-
met, of Gadgirth, Ayr.
TJSE OF THE NITRATES OF POTASH ANI) SODA. 59T
plained by a reference conjointly to the composition of the soils
and of the plants to which they are at the same time applied.
§ 3. Of the nitrates of potash and soda, their observed effects upon
different crops, and the theory of their action.
10. Nitrates of Potash and Soda.-The efficacy of these two
substances as manures in certain circumstances is now generally
acknowledged. Both of them, and especially the nitrate of soda,
are comparatively abundant in nature; and as they are not only
beneficial in many cases, but can be employed with a profit, and
as many experiments have in consequence been made with them
upon various crops, I shall briefly state the most important facts
which have hitherto been established in regard to their action upon
the growing plant.
2°. Apparent effects of the Nitrates.—The first visible effect of
the nitrates upon every crop is to impart a dark green colour to
the leaves and stems. 2°. They then hastem, increase, and not
unfrequently prolong the growth of the plant. 3°. They generally
cause an increase both in the weight of hay or straw, and of corn
—though the colour and growth are occasionally affected without
any sensible increase in the weight of the crop. 4°. The hay or
grass is always more greedily eaten by the cattle than that which
has not been dressed, even when the quantity is not affected;—but
the grain is usually of inferior quality, bringing a somewhat less
price in the market, and yielding a smaller produce of flour.
Its principal action seems to be expended in promoting the
growth—that is, in increasing the production of woody matter,
either in the stem or the ear, without so much affecting, except
indirectly, the quantity of seed.
Illustrations.—a. Mr Pusey observed that the increase of his
wheat crop, on the Oxford clay, where nitrate of soda was applied,
arose from there being no underling straws with short ears as in
the undressed. All were of equal length and consequent full-
mess and ripeness." The nitrate had merely promoted and equa-
lized the growth of the whole.
b. “It affected the tops of the potatoes, but the produce of bulbs
W8S less both by weight and measure,” (Mr Grey, of Dilston).
* Royal Agricultural Journal, II, p. 120. -
592 THEY AFFECT THE GROWTH OF THE STEM.
“On peas, in a thin sandy soil, subsoil gravel, it had much effect
on the colour and strength of the stems, and on the state of for-
wardness, but when ripe, though the straw was stronger, there was
no difference in the crop of peas” (Captain Hamilton, of Rozelle).
“On land in high condition it did harm by forcing the straw at
the expense of the ear” (Mr Barclay). “It appeared to act strongly,
and there was a greater bulk of straw, but the increase of grain
was only 50 lbs. per acre” (Sir Robert Throckmorton). In another
experiment of Mr Barclay's the straw was very strong, and much
of the wheat laid, but the undressed sold for 6d. a bushel more,
and there was no profit.
In all these cases the nitrate promoted chiefly the growth of
the stem, or the production of woody matter. The inferior qua-
lity of the grain and smaller yield of flour was owing to this action.
The grain was enveloped in a thicker covering of the woody husk
which forms the skin or bran.
c. “The turnips after the nitrated wheat are decidedly better,
the tops are still growing and luxuriant, while on the other part
they are beginning to fall” (Hon. H. Wilson.) In some cases,
therefore, they prolong the growth even of a second crop.
From the above statements we seem to derive an explanation
why the effects of the nitrate should have been so universally ob-
served upon the grasses and clovers—while in regard to its ap-
plication to corn crops they indicate this important—
PRACTICAL RULE.—Not to apply the nitrates upon land or
under circumstances where there is already a sufficient tendency
to produce straw.
3°. Effects of the nitrates upon the QUANTITY of the crop.–
Cases have occurred where the nitrates have failed to produce any
apparent effect at all—others where the colour was affected and
the growth promoted without any ultimate increase of crop—and
others again where the application of these salts was decidedly in-
jurious. These failures are deserving of a close consideration ;
but let us first attend to the amount of benefit derived from their
use where it has been attended with success.
EFFECT OF THE NITRATES ON HAY AND STRAW.
593.
I.—EFFECT on CoMMON AND CLOVER HAY.

Locality.
PRODUCE PER, ACR.E.
Quantity of nitrate of soda
applied per acre, and nature
of soil.
Aske Hall,
At Erskine,
Mr Muskett.
Mr Bishop.
Earl of Zetland.
Farnham, Suffolk,
Methven Castle,
2
Lord Blantyre. <>
Barochan,
Mr Fleming.
Dilston, 2
Mr Grey.
2
Undressed. | Dressed.
Tons. cwt. Tons. cwt.
12 3 4
0% 3 0%
1 2 10
6 2 4%
11 2 19,
10 3 18
4}. 3 l;
1% 2 3
1 cwt., on a thin light soil,
subsoil clay upon lime-
Stone.
120 lbs., good light soil, Sub-
soil gravel.
Ditto, clay soil on clay sub-
soil. -
160 lbs., stiff clay, after wheat.
Ditto, light clay loam, drain-
ed, after barley.
1 cwt., meadow hay, soil not
mentioned.
150 lbs., clover hay, soil not
mentioned.
cwt., mitrate of potash and
1% of nitrate of soda, had
each the same effect on a
heavy damp loam, parti-
ally drained.
l
On the other hand, Mr Barclay says that, on his heavy clay
lands (plastic clay), in Surrey, near the edge of the chalk, it is al-
most always a failure; and the Messrs Drewitt of Guildford, that
on their chalk soils, the additional produce of hay, whether on up-
land or meadow, does not repay the expense.
II.—ON BARLEy.

Hoºv. H. Wilson.
PRODUCE.
Locality. Undressed. | Dressed. | Quantity per acre, and kind of soil.
grain. Straw.igrain. Straw.
Bush. cwt. Bush. cwt. -
Surrey, 44} 16} | 553, 20% |1 cwt. on light soil wi - ~~~l-- ~ :
Mr Barclay. } q 73 4. cwt. On light soil with chalk subsoil.
Newton Hall,
Northumberland. 47 26 59 36 |l cwt. on strong turnip land.
Mr Jobling.
Suffolk 1 cwt. on a poor sandy soil, where the
3 18 32 turnips on the preceding year were
nearly destroyed by the land blowing.
In Berkshire, on the other hand, it failed (1839), for barley on
the light lands, causing them in some cases to be burned up (Mr
Pusey), but the season was droughty.
P p
594 EFFECT UPON RYE AND OATs.
III.-ON WINTER RyF.
Mr Fleming, of Barochan, applied 160 lbs. per acre to rye,
upon a strong clay, after potatoes, and obtained—
Undressed. Dressed.
Grain, ............ 14 bushels. .................. 26 bushels.
Straw, ............ l ton 7 cwt................ 2 tons 19 cwt.
being a very large increase both in grain and straw.
IV.-UPON OATs.
PRODUCE,
Locality Undressed. Dressed. Quantity per acre, and
allly. kind of soil.
Grain. Straw. Grain. Straw.
Bush. - Cwt. Bush. Cwt.
Bakewell,
Derbyshire, | 48% 25; 64 38; 1 cwt. ; heavy soil, clay
Mr Greaves. subsoil.
Court Farm,
Hayes, 46 31 60; 46; 1 cwt. ; land saturated
Mr Newman. with water, and out of
Leatherhead, condition. -
Surrey, 40 6 l 60 90 |l cwt. ; a loam contain-
Mr Barclay. ) ing flints, on a subsoil
of chalk.
}. º 54 26 4.1% 20 Sharp loam ; subsoil clay
or sandstone (1842),
great drought, second
Erskine, | crop after old lea.
2
5
#
5
O
3
2
Lord Blantyre, 49 Good loam ; subsoil gra-
1842. vel and sand after, old
pasture.
Mr Everett, in Norfolk, obtained an increase of 15 bushels per
acre, by the use of ; cwt. per acre; and Mr Calvert, of Ockley
Court, of 20 bushels of grain, and 9% cwt. of straw, by applying
13 cwt. of nitrate of soda. At Kirkleathem (North Yorkshire),
it had an excellent effect upon oats, on strong land,-and on the
strong clays of the Weald of Surrey and Sussex it is said by Mr
Dewdney, of Dorking, to be universally beneficial, particularly
when sown on ley ground—paying the grower 27s. to 30s. per
acre. “When it has failed the mitrate has been sown early, and
when the land was in a dry state. In these instances the crop was
more or less blighted.” On the other hand, Mr Barclay states
that, on his strong heavy land (plastic clay), near the edge of the
chalk, in Surrey, it gave no profit, though, as shewn in the pre-
ceding table, it was profitably applied to barley.
In most cases, therefore, the mitrate of soda seems capable of
producing a large increase in the oat crop—the few failures which
are noted must be due either to the state of the weather or to Some
EFFECT UPON WIHEAT. 595
peculiarities in the physical condition or chemical composition of
the soils on which they were observed. - -
V.—ON W HEAT.

gravelly soil ; an equal
weight of wit’ate of potash
Mr Dugdale. | produced only $ bushel of
PRODUCE.
Locality. Undressed. Dressed. Quantity P. º and kind
Grain. Straw. Grain. Straw. tº
- Bush. Cwt. ' | Bush. Cwt.
Farnham, Suffolk -
Mºjº." | 18% 27 l; º ; a poor Spongy Sandy
Painswick, Glouces- SOll.
ter, 33% 43% 1 cwt. ; a stone-brash, soil
Mr Hyett. abounding in carbonate of
Fairford Park, Glou- lime.
cester, 26 15 33} | 21; 1 cwt. ; on a light stone-brash
Mr Raymond Barker poor thin soil. -
ſ|| 42 34 54 38% |l cwt. nitraße of soda, on a
increase (?) .
cwt. nitrate of soda on a
strong clay. Both portions
were previously limed.
| 14} 18, 20 1 cwt. ; on a very thin crop,
. injured by an unfavourable
autumn.—Soil not stated.
3
2
3
6
#
l
Court Farm, Hayes,
Mo' Newman.
2
5
#
Brandon Suffolk, 27; 32 1 cwt. ; on a fair light soil.
Hon. Mr Wilson. || 30, 36 Do., loamy, better land.
Surrey, 33} | 20 39% 23 |1 cwt. ; soil loamy, resting
Mr Barclay. 3] 24% 33% 27# on chalk, straw strong, and
7 much wheat laid.” -
Fai'i • I wº 2 24% 39% 34; Do. on heavy soil, resting on
fºſal º } 2lå 20+ 26 25% the Oxford clay. B. all
tº 20% 20% 24; 24, these very different results
were obtained in the same
Ockley Court, - }=y field. g &
M, Calvert. 33 25; 45; 37; Pº.º laid, Soil
Newton Hall & • .
. * }}. 30 29} 36 35% |l cwt. Soil not mentioned.
Cirencester, 273 16 31} | 20% |1 cwt. nitrate of potash.
I), Dawbery. 27# 15% Do. nitrate of soda, soil and
subsoil clay, resting on the
corn-brash.
|180 lbs. nitrate of soda.
Do. mitrate of potash.-Soil
not mentioned.--
5
2
Rozelle, near Ayr, { 35 3] : 47
Captain Hamilton, * 42
7
6
On the Norfolk soils, a few miles from Holkham, I was informed
* The dressed grain sold at 4s. less than the undressed, and there was no profit ;
the nitrate failed on heavy land, and on land in high condition.
+ The produce of straw, especially from the Saltpetre, is very surprising. It is
stated at 518 and 764 stones for the two lots respectively. I suppose the acres to be
Scotch, and the stones 14 lbs.
596 FFFECT UPON TURNIPS.
in 1845 by Mr Blyth, that he used much nitrate of soda
for his
Wheat and oats, and found it always to pay—his wheat returning
from 4 to 7 bushels increase for every cwt. of nitrate applied.
VI.-ON TURNIPs.
At Rozelle the Swedes were improved several tons an
acre by
the use of mitrate of soda (Mr Hamilton). At Dorking it was
very beneficial as a top-dressing to the Swedes and white turnips,
when sown broad-cast at the rate of 1 cwt, per acre (Mr Dewdney).
In neither of these cases is the soil described. On thin stomy land
upon chalk at Elmshurst, Bucks, turnips manured with
nitrate
*r,
alone, were very superior to those to which 10 loads an acre of
farm-yard manure had been applied (Mr Burgess). The only
numerical results with which I am acquainted are those
Barclay on a loamy soil resting on chalk. His crop of
WaS -
30% cwt. when dressed with bones and wood ashes,
each 15 bushels.
31 cwt. when dressed with 1 cwt. of mitrate of soda,
drilled in. &
35 cwt. when seed and nitrate were both broad-
Cast.
38 cwt. when the seed was drilled and the nitrate
applied broad-cast. -
On the other hand, Lord Zetland thought it did no
of Mr
turnips
good to
turnips; Mr Vansittart that on strong land well dunged it did
harm; and the Messrs Drewitt that on their dry rubbly chalk it
had no effect on this crop, though it improved in a remarkable
degree the succeeding crop of barley.
We are still in want of more numerous and better observations,
especially in regard to turnips. The above discordances will
either vanish when we obtain a larger collection of results, or they
will find an explanation in the more accurate observations we may
expect to obtain in regard to the climate, soil, and geological po-
sition of the locality in which each experiment is made.
49. Effect of the nitrates on the QUALITY of the crop.–This I
have already in some measure alluded to. It so affects the grass
and clover as to make it more relished by the cattle.
This is
THEY AFFECT THE QUALITY OF THE CROP. 597
usually expressed by saying that the crop is sweeter, but since
cattle are known to be fond of saline substances, it may be that the
grasses are, by these salts, only rendered more savoury. It ge-
merally also gives a grain (of wheat) of an inferior quality—which
has a thicker skin, and yields more bran. This may possibly
arise from its having been generally allowed to ripen too long.
A question still undetermined is, whether the flour of nitrated corn
is more nutritive than that obtained from corn which has been un-.
dressed ?
It is generally supposed that those samples of flour which con-
tain the most gluten are also the most nutritive. But hitherto the
only experiments which have been made with the view of deter-
mining the relative quantities of gluten in samples of grain from the
same field, one portion of which had been nitrated, and the other
not, are, one made by Dr Daubeny, and one reported by Mr Hyett.
In these experiments the flour of the several wheats gave—
In Dr. Daubeny's In Mr Hyett’s
Experiment. Experiment.
Nitrated, .... ........................... 15 per cent, of gluten ... 234 per cent.
Unnitrated, .................. ........... 13 per cent. of gluten ..., 19 per cent.
Excess of gluten in the nitrated, ... 2 per cent. ... 43 per cent.
both of which results, if correct, favour the supposition that one effect
of the nitrates upon the quality of the grain is to increase the pro-
portion of gluten, and thus to render them, as is generally believed,
more nutritive. This is a result which theoretically we might be led
to anticipate were there no large increase in the quantity of the pro-
duce—for then we might naturally expect the nitrogen of the ni-
tric acid to be expended solely in enriching the grain with gluten.
But the additional weight of crop contains in many cases more ni-
trogen than we add to the soil when we dress it with one cwt. of ni-
trate of soda per acre; there is, therefore, no excess of nitrogen which
we can suppose to go to such an enriching of the more abundant
crop of grain. For this reason, among others, I am inclined to
doubt whether further careful examination will confirm the above
results that the flour from nitrated grain is richer in gluten, and,
therefore, more nutritious. At all events increased experiments
are to be wished for.
5°. Effect of nitrate of soda compared with that of other manures.
598 AFTER-EFFECTS OF THE NITRATES.
—Mr J. Waite of Doncaster has published the results of two ex-
periments upon the effects of nitrate of soda upon grass, compared
with that of bone dust, rape dust, and farm-yard manure. The
soil was a thin gravel not more than three inches thick, resting
upon a hungry red subsoil. His results and observations are as
follows:—
Per acre. Produce per acre.
l°. Nitrate of soda, ..... 2 cwt. 30 cwt. 1 qr.
Bone dust, ............... 5 cwt. 20 cwt. 1839
Rape dust, ............... 5 cwt. 15 cwt.
2°. Nitrate of soda, ...... 2 cwt. 59 l l 9
Fold yard
old yard, ) . 20 yds. 44 2 7
Rotten manure,
Excess of produce, ... . ... 14 3 12
Mr Waite adds the following observations:—
a. The grass from the nitrate was not more succulent, both
kinds of grass losing nearly three-fourths by drying into hay.
b. The nitrated grass was eaten, by sheep and horses, to the
roots before that from either of the other manures was touched,
though in the same field. It had, therefore, a more agreeable taste.
c. The eddish or after-grass was equally luxuriant and equally
relished by the cattle, and gave a second crop by the middle of
September.
d. In the year following the crop of hay without further ma-
muring was equally great, from the manured and from the nitrat-
ed land, though the latter had been mowed twice the previous
year, and the former only once.
6". After-effects of these nitrates.—It is not always that good
effects, such as those mentioned by Mr Waite, are observed upon
the crop which succeeds that to which the nitrate of soda has been
applied. It is most frequently noticed in cases where, from
drought or dryness of soil, the salt has been prevented from exert-
ing its full and legitimate action upon its first application. Thus
a. Failing to improve turnips on a rubbly chalk soil, it greatly
benefited the succeeding crop of barley (Mr Drewitt, Guildford,
Surrey).
Producing little effect on tares (upon a clay soil 7) it improved
very much the turnip crop which followed (Mr Barclay, Leather-
head, Surrey).
4
THEIR, ACTION AIFFECTIED BY CIRCUIMSTANCES. 599
b. In the following instances the benefit was seen on two suc-
cessive crops:–
After producing an increase of one-sixth in the wheat crop both.
grain and straw, on a light sandy soil (subsoil?) the turnips of the
following year were decidedly better where the nitrate had been
sown (Hon. H. Wilson, Brandon, Suffolk).
After improving the crop of wheat, the after-crop of hay was
also better (Mr Grey of Dilston). w
At Upleathem, the second cut of clover was nearly as much
improved as the first (Mr Vamsittart), and at Dilston the aftermath
hay was greater in quantity, and better relished by the cattle (Mr
Grey). -
c. Mr Rodwell of Alderton, Woodbridge, remarked that the
white clover failed after barley on which nitrate had been used.
Might not this be owing to an excess of luxuriance in the barley
choking and killing the tender shoots of clover?
The solubility of these nitrates is so great that in our climate,
in seasons of ordinary rain, and on lands which are well drained
and have a moderate degree of inclination, we should expect that
they would be in a great measure washed out of the land in a sin-
gle year. Hence one reason—even supposing little of the salt to
have entered into the roots of the crop to which they are ap-
plied—why we are not entitled generally to expect any marked
effect from it upon a second crop. But let the season be so dry,
or the soil so retentive, and the land so level, as to prevent its be-
ing all taken up by the roots, or washed away by the rains during
one year, and we may then look for beneficial after-effects, such as
those above described.
7°. Circumstances necessary to ensure the success of these saline
manures.—This explanation will appear more satisfactory if we
glance for a moment at the general conditions which are necessary
to ensure the success of these or any other saline manures. Thus,
a. They must contain one or more substances which are meces-
sary to the growth of the plant.
b. The soil must be more or less deficient in these substances.
c. The weather must prove so moist or the soil contain so much
water maturally as to admit of their being dissolved, and conveyed
to the roots.
600 CASES IN WEIGH THE NITRATES HAVE FAILED. .
d. They must not be applied in too large a quantity, or allowed
to come in contact with the young shoots in too concentrated a
form. The water that reaches the roots or young leaves must
never be too strongly impregnated with the salt, or if the weather
be dry, the plant will be blighted or burned up. - -
e. The soil must be sufficiently light to permit the salt easily to
penetrate to the roots, and yet not so open as to allow it to be rea-
dily washed away by the rains. In reference to this point the na-
ture of the subsoil is of much importance. A retentive subsoil
will prevent the total escape of that which readily passes through
a sandy or gravelly soil, while an open subsoil again will retain
nothing that has once made its way through the surface.
8°. Cases in which the nitrates have failed.—A knowledge of the
above conditions will enable us in many cases to explain why the
nitrates, and other generally useful substances, fail in certain cir-
cumstances to exhibit any beneficial effect. -
a. Thus on the light soils of Berkshire the nitrate of soda failed
for barley, causing it often to be blighted or burned up. This, no
doubt, arose from the drought which may act in one or other of
several ways. Either it may prevent the salt from being dissolved
at all, and thus hinder its action altogether for the time, or it
may retard the solution till the plant has attained such a state of
maturity, that it is no longer capable of being equally benefited
by the introduction of the salt into its roots—or after being dis-
solved, and having partially descended into the soil, the drought
may cause it to ascend again with the water which rises to the sur-
face in consequence of the evaporation, and may thus present it to
the plant in so concentrated a form as to injure the young shoots—
or, finally, the action of the Sun upon the green leaf, into which a por-
tion of the salt has already been conveyed by the roots, may be so
powerful as to concentrate the saline solution, or to increase its de-
composition to such an extent as to cause injury, and consequent
blight to the leaf itself. -
b. Again, at Cheadale, in Cheshire (Mr Austin), the nitrate of
Soda is said to have had a good effect on wheat and grass where
the subsoil was clay, but none where the subsoil was gravel, or
the soil light and sandy. Here the supply of water in the soil
may have been such as to fit it for entering readily into the roots
3
*ś
when THEIR USE IS BENEFICIAL. . . 601
in a proper state of dilution, when the retentive subsoil kept it
within reach of the roots, and yet sufficient, at the same time, to
wash it away altogether where the soil and subsoil were too open
to be able to retard its passage. - -
. c. But the occasional occurrence of droughts or the mere physi-
cal distinctions of lands as light or heavy, are not sufficient to ac-
count for all the recorded differences in the effect of the nitrates.
Thus on the clays of the Weald in Sussex (Mr Dewdney), and on
the Oxford clay in Berkshire (Mr Pusey), the use of the nitrate
has been attended with general benefit upon oats and wheat, while
on the plastic clay in Surrey, Mr Barclay states it to have been uni-
formly unsuccessful or unprofitable. The cause of these differences
is to be sought for either in the state of drainage, or in the previous
Cropping and manuring, or in the mode of preparing, or in the
chemical composition or physical properties, of the several clays,
which are known to be very unlike. But further observation is
wanting before we can speak with any degree of confidence upon
the subject. - -
To some an explanation may appear to be most easily given by
supposing the one soil to have been rich in soda, while the other
was defective in this substance. I shall advert to this point in ex-
plaining the theory of the action of the nitrates of potash and soda.
9°. Circumstances in which the employment of the nitrates is
most beneficial—a. It appears to succeed most invariably in lands
which are poor—or out of condition—or on which the corn is thin.
Every farmer knows that the most critical time with his crop, as
with his cattle, is during the earliest stage of its growth. If it
come away quickly and strong during the first few weeks, his hopes
are justly high, but if it droop and linger after it is above the
ground, his fears are as justly excited. It is in this latter condition
of things that an addition of nitrate comes to the aid of the feeble
plant, re-animating the pining shoots, and making the thin corn
tiller. On rich lands and thickly growing crops it only causes an
over-growth of already abundant straw. According to the expe-
riments of Mr Barclay, it is most advantageous when sown broad-
Cast. - .
b. Whatever may be the chemical nature of the surface soil,
the success of the nitrate seems to be most sure where the land is
not wholly destitute of water, where the soil is open enough to
602 THEORY OF THE ACTION OF THE NITRATES.
allow it readily to descend, and yet the subsoil sufficiently reten-
tive to prevent it from being readily washed away.
c. I throw it out as a suggestion, which has occurred to me from
a comparison of the results contained in the above tables, with the
kind of soils on which the experiments were made—that probably
the presence of lime in the soil may tend to insure the success of
the nitrate. In many of the instances of large crops obtained by
its aid the land was either maturally rich in lime, or it had, in the
ordinary course of husbandry, been previously marled or limed.
10°. Theory of the action of the nitrates.—The nitric acid of
these salts contains 26 per cent. of its weight of nitrogen—or one
cwt. of pure dry nitrate of soda contains about 19 lbs. of nitrogen.
This nitrogen we know to be a necessary constituent of plants—
one which they obtain almost wholly from the soil—but which
nevertheless is generally present in the soil in an available state in
comparatively small quantity only.” We have already seen rea-
son (p. 285) to believe that mitric acid exists naturally in the soil,
and is the form in which a large portion of their nitrogen is con-
veyed into the roots of plants. When we add it to our fields, there-
fore, we only aid mature in supplying a compound by which vege-
tables are usually sustained. And as the young plant will neces-
sarily languish in the absence of one essential kind of food, al-
though every other kind it may require be present in abundance,
it is easy to see how the growth of a crop—languidly proceeding
upon a soil deficient in nitrogen—may be suddenly re-animated
by an application of nitrate of soda to its roots. That this is the
true way in which the nitrates generally act is supported by the
observation that it is in the poorest soils that they are most useful
to the husbandman.
We have seen also, that one function of the leaf in the presence
of the sum is to decompose carbonic acid, and give off its oxygen
(p. 143). It exerts a similar action upon the mitric acid of the
mitrates, and upon the sulphuric acid of the sulphates, discharging
their oxygen into the air, and thus leaving the nitrogen and sul-
phur at liberty to unite with the other elementary substances con-
tained in the sap—for the production of the several compounds of
which the parts of the growing plant consist.
* The nitrogen contained in the organic matter of the soil is equal to from to l;
Ibs. of ammonia in 1000 lbs. of dry soil. (Krocker.)
THIEY HELP THE PLANT TO OTHER FOOD, 603
Nor, as we have also seen in a previous lecture (p. 295), is the
good effect of these nitrates upon the crop limited to the supply of
that quantity of nitrogen only which they themselves contain. The
excess of crop raised by their aid often contains very much more
nitrogen than they have been the means of conveying to the roots—
even supposing it all to have been absorbed and appropriated by
the plant. This arises from the circumstance that the more the
plant is made to thrive above ground, the more numerous and ex-
tended become its roots also, and these roots are thus enabled to
gather from the deeper and more distant soil those supplies of ni-
trogenous and other necessary food, which would have remained
beyond their reach had the plant been allowed to continue in its pre-
viously feeble or more languid condition. This has been called
the stimulating effect of manures, and some substances have been
said to act only in this way upon vegetation. This, however, ap-
pears to me to be a mistake. The supposed stimulating is always
a secondary effect, and necessarily follows from the use of every
kind of manure, which by feeding the plant gives it greater strength,
and thus enables it to appropriate other supplies of food which
were previously beyond its reach, or which, from the absence of
one or more necessary constituents, it could not render available
to its natural growth.
In this way the mitrates act as such—in contra-distinction to the
sulphates and the compounds of potash and soda with other acids.
But there is every reason to believe that the potash and soda them-
selves often aid the effect of the nitric acid with which they are as-
sociated. In soils deficient in these alcalies the nitrates would act
beneficially, even though nitric acid were already present in abun-
dance,—while, on the other hand, a field that is defective in both
constituents of the Salt (mitric acid and potash or soda), will be more
grateful for the same addition of it than ome in which either of
them already abounds. In this way, it is not unlikely that the
discordant results of experiments, even on the same farm, and es-
pecially when the soils are different, may occasionally be explained.
ll. SPECIAL effects of the nitrates of potash and soda.-On this
alcaline constituent of the two nitrates will depend the special ac-
tion of each when applied to the same soil under the same circum-
stances. It has not yet been clearly made out that any definite
special action can be ascribed to them, yet some experiments bear-
604. COMPARATIVE EFFECTS OF THESE TWO NITRATES,
ing upon this point have already been published, to which it will
be proper to advert. From the study of the special action of given
manures upon given crops, practical agriculture has much good to
expect. -
a. At Rozelle; near Ayr (1840), nitrate of potash caused oats
to come away darker and stronger, and to give a heavy crop, while
in the same field nitrate of soda produced no benefit. The soil was
inferior, light, and sandy, with a red irony subsoil (Captain Hamil-
ton). It is added that the crop was injured by the early drought,
from which it never recovered. This fact renders the special ef-
fect of the mitrate of potash in this case doubtful.
b. In the experiments upon wheat, made by the same gentleman
on the same farm—it is to be presumed upon a similar soil,
Grain. Straw.
Nitrate of Soda gave ....... 46 bush., and 52 cwt. ;
Nitrate of potash gave ..... 42 bush., and 76 cwt. ;
the produce of straw being here also greatly in favour of the pot-
ash Salt.
c. Dr Daubeny also, in the experiment upon wheat above detail-
ed, found the mitrate of potash to increase the produce considerably,
while the nitrate of soda caused no increase whatever. The soil
was stiff clay upon the corn-brash, (p. 464.) -
These superior effects of the potash salt may be ascribed
to the greater deficiency of the several soils in potash than in
soda, a supposition which in the case of the Rozelle experiment is
consistent with the fact, that common salt, when tried upon the
same land, produced no good effect. If, however, as we have seen
to be not at all unlikely (p. 415), potash and Soda are capable of
replacing each other in the living vegetable without materially af-
fecting its growth, this explanation cannot be the true one. Fur-
ther experiments, however, if carefully conducted, will not fail to
clear up this question.
d. On a gravelly soil Mr Dugdale obtained an increase of 12
bushels of wheat by the use of mitrate of soda, while nitrate of pot-
ash increased the crop by only half a bushel.
This result may be explained after the same manner as the pre-
ceding—the soil may have already abounded in potash.
e. In Perthshire, upon a moist loam, Mr Bishop obtained an
USE OF COMMON SALT As A MANURE. 605
equal increase of hay from the use of both nitrates; each having
caused the production of a double crop.
The equality in this case may have arisen either from the effects
being wholly due to the nitric acid, both potash and soda being
already abundant in the soil, or from the potash and soda perform-
ing the same functions in the plant as they ought to do if they are
capable of replacing each other, (p. 415.) The former supposition
is consistent with the situation of the locality in a granite country,
and is further supported by the fact, that on the same soil and field
ammoniacal liquor, which contains no alcali, produced a still larger
increase of produce.
All these attempted explanations, however, proceed upon the
supposition that the experiments have been both carefully made
and faithfully recorded, which may possibly not have been the
CàSC.
§ 4. Use of the chlorides of sodium (common salt), calcium, and
- magnesium. -
1°. Chloride of sodium or common salt.—The use of common
salt as a manure has been long recommended. In some districts
it has been highly esteemed, and is still extensively and profitably
applied to the land. It has, like many other substances, however,
suffered in general estimation from the unqualified terms in which
its merits have been occasionally extolled. About a century ago
(1748), Brownrigg" maintained that the whole kingdom might be
enriched by the application of common salt to the soil, and since
his time its use has been at intervals recommended in terms of al-
most equal praise. But these warm recommendations have led
sanguine men to make large trials which have occasionally ended
in disappointment, and hence the use of salt has repeatedly fallen
into undeserved neglect.
It is certain that common Salt has in very many cases been ad-
vantageous to the growing crop. It often benefits our green crops,
and it appears specially to increase the weight of corn per bushel.
Some of the more carefully observed results which have hitherto
been published are contained in the following table.
* On the art of making common salt, p. 158. (London, 1748).
606
RESULTS FROM THE USE OF COMMON SALT.
Locality Produce per Acre. Quantity applied per acre, and
Ocallty. Unsalted. | Salted. kind of soil.
UPON W HEAT. Bushels. Bushels.
16# 22} ll bushels, after barley.
ll. 2] 6% do., after beans.
16 17; Do. Sown with the seed, after
M. G. Sinclair. *- 23# Do. dug in with the seed. peas.
| 2 28; 5% bushels, applied be- after
fore sowing, turnips
-- 28; ll bushels, do. do. pS.
Great Totham,
Essex, 13} 26% 5 bushels, light gravelly soil.
M? Cwth. Johnsom.
Barochan, Paisley, <) ; <) in ºn Yr-ty tº *** f \ ºr º
Mr Fleming. 2, O 32 160 lbs., heavy loam, after potatoes.
ON BARLEY.
Suffolk, * -
Mr Ramsom. 30 5] 16 bushels.
ON HAY. Tons. Cwt.|Tons. Cwt. .
At Aske Hall, near o 6 bushels, thin light soil, clay Sub-
e 2 10 || 3 12 & -
Richmond. - * soil.
At Erskine, near 2 () 2 12|| 5 bushels, light soil on gravel.
Renfrew. 2 1 2 8 Do., clay soil on clay.

But it is as certain that in many cases when applied to the land,
common salt has failed to produce any sensible improvement of
the growing crop. And as failures are longer remembered, and
more generally made known than successful experiments, the fact
of their frequent occurrence has prevented the use of salt in many
cases where it might have been the means of much good.
2°. Cause of the failure of common salt.—It is not, indeed, to
be wondered at, that amid conflicting statements as to its value,
the practical farmer should have hesitated to incur the trouble and
expense of applying it—So long as no principle was made known
to him by which its application to this soil rather than to that, and
in this rather than the other locality, was to be regulated.
a. We know that plants require for their sustenance and growth
a certain supply of each of the constituents of common salt, which
supply they must generally obtain from the soil. If the soil in any
field contain maturally a sufficient quantity of common salt—or of
chlorine and soda, in any other state of combination—it will be
unnecessary to add this substance, or if added, it will produce no
beneficial effect. If, on the other hand, the soil contain little, and
has no natural source of supply, the addition of Salt may cause a
considerable increase in the crop.
CAUSES OF THE FAILURE OF COMMON SALT. 607
Now there are certain localities in which we can say before hand
that common salt is likely to be abundant in the soil. Such are
the lands that lie along the sea coast, or which are exposed to the
action of prevailing sea winds. Over such districts the spray of
the sea is constantly borne by the winds and strewed upon the
land, or is lifted high into the air, from which it descends after-
wards in the rains.” This consideration, therefore, affords us the
important practical rule in regard to the application of common
salt—that it is most likely to be beneficial in spots which are remote
from the sea, or are sheltered from the prevailing sea winds.
It is an interesting confirmation of this practical rule that nearly
all the successful experiments above detailed, were made in loca-
lities more or less remote from the sea, while most of the failures
on record were experienced near the coast. This consideration, it
may be hoped, will induce many practical men to proceed with
more confidence in making trial of its effects on inland situations.
It is very desirable that the value of this practical rule, suggested
in a former lecture (p. 326), should be put to a rigorous test.f
b. But some plants are more likely to be benefited by the ap-
plication of common salt than others. This may be inferred from
the fact that certain species are known to flourish by the sea-shore,
and where they grow inland to select such soils only as are matu-
rally impregnated with much saline matter. Observations are
still wanting to show which of our cultivated crops is most favour-
ed by common salt. It is known, however, that the grass of salt
marshes is peculiarly nourishing, and is much relished by cattle,
and that the grass lands along various parts of our coast produce
a herbage which possesses similar properties. It is said also that
the long tussack grass which covers the Falkland Islands luxuri-
* Dr Madden has calculated that the quantity of rain which falls at Penicuick in a
year, brings down upon each acre of land in that neighbourhood, more than 600 lbs.
weight of common salt. This would be an enormous dressing were it all to remain
upon the land. Heavy rains, however, probably carry off more from the soil than
they impart to it. It is the gentle showers that most enrich the fields with the saline
and other matters they contain.
+ A number of failures have been described in the sixth volume of the “Transactions
of the Highland and Agricultural Society,” to nearly all of which Dr Madden has shown
that the above principle applies—the farms on which the experiments were made being
more or less freely exposed to the winds from the east or west sea.—Quarterly Jour-
mal of Agriculture, Sept. 1842 (p. 574.)
608 YWHEN APPLIED AS A MANU R.E.
ates most when it is within the immediate reach of the driving spray
of the southern ocean. Among our cultivated crops, therefore,
one may delight more in common salt than another, and if we
consider how much alcaline matter is contained in the tops and
bulbs of the turnip and the potato, we are almost justified in con-
cluding generally that common salt will benefit green crops more
than crops of corn, and that it will promote more the development
of the leaf and stem than the filling of the ear,
If this be so, we can readily understand how a soil may already
contain abundance of salt to supply with ease the wants of one
crop, and yet too little to meet readily the demands of another
crop. The application of salt to such a soil will prove a failure
or otherwise, according to the kind of crop we wish to raise.
c. Failures have sometimes been experienced also on repeating
the application of salt to fields on which its first effects were very
favourable. In such cases it may be presumed that the land has
been already supplied with salt, sufficient, perhaps, for several
years' consumption—and that it now requires more the applica-
tion of some other substance.
If it be desired, experimentally, to ascertain whether the land
already contains any sensible supply of common salt, the readiest
method is to collect a pound of the soil in dry weather, to wash it
well with a pint or two of cold distilled water, and then to filter
through paper, or carefully to pour off the clear liquid after the
whole of the soil has been allowed to subside. A solution of ni-
trate of silver in water (common lunar caustic of the shops) will
throw down from the clear liquid a white precipitate, becoming
purple in the sun, which will be more or less copious according to
the quantity of salt in the soil. If this precipitate be collected,
dried in an oven, and weighed, every 10 grains will indicate very
nearly the presence of 4 grains of common salt. The quantity of
this precipitate to be expected, even from a soil rich in common
salt, is, however, very small. If a pound of the dry soil yield a
single grain of salt, an acre should contain about 500 lbs., where
the soil is 12 inches deep—where it has a depth of only 6 inches
it will contain nearly 250 lbs. of salt in every acre.
3°. Chlorides of calcium and magnesium.—These compounds
are rejected in large quantities as a refuse in some of our chemi-
TIHEORY OF THE ACTION OF THESE CHLORIDES. 609
cal manufactories—and they are contained, especially the latter,
in considerable abundance in the refuse liquor of our salt pans.
They have both been found useful to vegetation, and where they
are easily to be obtained, they are deserving of further trials.
Like common salt, it is in inland situations that they are fitted to
be most generally useful. Where salt springs are found in the in-
terior of Germany, the refuse obtained by boiling down the mother
liquors after the separation of the salt has been often applied with
advantage to the land.
4°. Theory of the action of these chlorides.—Common salt and
the chlorides of calcium and magnesium are not unfrequently
found in the sap of plants—they may be supposed, therefore, to
enter into the roots without necessarily undergoing any previous
decomposition. But we have already seen (p. 147) that the green
leaves under the influence of the sun, have the power of decom-
posing common Salt—and no doubt the other chlorides also—and
of giving off their chlorine into the surrounding air. When they
have been introduced into the sap therefore, by the roots, the
plant appropriates so much of the chlorine they contain, as is ne-
cessary for the supply of its natural wants and evolves the rest.
When common salt is thus decomposed, soda remains behind in
the sap, and this is either worked up into the substance of the plant
or performs one or other of those indirect functions I have already
explained to you (p. 583), when illustrating the probable action of
potash and soda upon the vegetable economy. When the other
chlorides (of calcium or magnesium) are decomposed, lime or
magnesia remains in the sap, and is in like manner either used up
directly in the formation of the young stem and seed, or is em-
ployed indirectly in promoting the chemical changes that are con-
tinually going on in the sap. The living plant, when in a healthy
state, is probably endowed with the power of admitting into its
circulation, and of then decomposing and retaining so much only
of these several chlorides, or of their constituents, as is fitted to
enable its several organs to perform their functions in the most
perfect manner.
In the soil itself, in which organic matter of animal and vege-
table origin is present, common salt is fitted to promote certain
chemical changes, such as the production of alcaline mitrates—and
Q Q
610 PHOSPHATES OF LIME,
probably silicates—by which the growth of various kinds of plants
is in a greater or less degree invigorated. In the soil, also, from
their tendency to deliquesce, or run into a liquid, all these chlorides
attract water from the air, and thus help to keep the soil in a
moister state. When applied in sufficient quantity they destroy
both animal and vegetable life, and have, in consequence, been
often used with advantage for the extirpation of weeds, and for
the destruction of grubs and other vermin that infest the land.
§ 5. Use of the phosphates of lime, magnesia, potash, and soda,
and the theory of their action.
1°. Native phosphate of lime, already described (p. 340), when
reduced to fine powder, or better when dissolved in sulphuric acid,
has been found in a considerable degree to promote the growth
of plants. Should it ever become an abundant article of commerce
it will merit the attention of the practical agriculturist.
2°. Bone earth or burned bones, have also been frequently ap-
plied to various crops with a profitable return. In some experi-
ments recently published by Mr John Hannam" and others, the ef-
fect of burned bones was greater even than that of common bone
dust. To the cause of this greater effect of burned bones in some
cases, I shall draw your attention when I come to treat of the use
of bones as a manure.
In our sugar refineries charred bones are used to discolour the
syrup. After two or three successive charrings they become unfit
for this use, and are sold as a manure. Mr Fleming of Barochan
has published numerous experiments, in which the good effects of
this refuse bone ash were proved upon almost every crop.
3°. Bi-phosphate of lime.—When burned bones are treated
with three-fifths of their weight of sulphuric acid, diluted with its
own bulk of water, the bone earth is gradually decomposed and a
mixture of bi-phosphate of lime with gypsum is produced. If
the mixture, after occasional stirring for some days be boiled down
to dryness, it will consist of nearly equal weights of gypsum and bi-
phosphate, and may be employed as a manure with much advan-
tage and usually with very considerable profit. .
Or if the liquid be allowed to settle, the greater part of the gyp-
* In the Quarterly Journal of Agriculture and in the Journal of the Royal Agricul-
tural Society.
|USE OF BI-PHOSPHATE OF LIME. 611
sum will fall to the bottom, and the liquid may be poured off and
evaporated to dryness by itself. In this case the bi-phosphate of
lime is obtained nearly free from gypsum, and in a state in which
it can readily be applied to the land.
Under the name of bi-phosphate of lime a substance is now sold
in the manure market, but whether it consists of the latter purer
bi-phosphate, or of the former mixture of bi-phosphate with gypsum,
I have had no opportunity of determining.
Numerous experiments have also been published, exhibiting the
results of its action in comparison with that of other manures, but
whether the substance employed was pure bi-phosphate or the above
mixture with gypsum the experimenters have not stated. I insert,
however, a few of these series of comparative results as they have
been published by the experimenters themselves.
a. Upon turnips.-Sir J. M. Tylden applied 4 cwt. of bi or su-
per-phosphate alone, and obtained a better crop than with 4 cwt. of
guano. Mr Pusey tried it against bone dust and bones dissolved
in sulphuric acid, with the following results per imperial acre:
w Manure. Cost. Produce.
Ö bushels of bones, ............... ....... 55s 11% tons.
OS,
4% do. with 100 lbs. of sulphuric acid,... 22s. 12; ...
2 cwt. Superphosphate, ............ ........ 17s. 13+ ...
These crops are all small, but they show that 2 cwt. of this su-
per-phosphate was superior in its effects to 20 bushels of bone dust
in its ordinary state.
b. Upon wheat.—Mr Strouts of Kingsdown in Kent tried its
effect as a top dressing in spring against other top dressings, and
against farm-yard manure ploughed in before the wheat was sown
in autumn. The following were his results per imperial acre :
Manure. Cost. Produce in bushels. Increase in bushels.
Nothing, ........................... 29}
30 carts farm-yard dung, ..... e 40% 11%
3} cwt. Peruvian guano, ... ... .. 42s. 40% 11%
5 cwt. rape dust, .................. 32s. 6d. 38; 9%
6% cwt. urate, ........ ............ 32s. 6d. 38; 9;
63 cwt. Super-phosphate,......... 44s. 53; 24;
The result is here very much in favour of the super-phosphate.
Mr Lawes has also published numerous experiments upon the
use of the super-phosphate, which are highly in favour of its em-
ployment. They seem, however, to bring out the interesting fact,
that the super or bi-phosphate does not produce so marked an ef-
612 AMIM ONIACAL PHOSPFIATE OF MAGNESIA.
fect when applied a second or third time to the same land as it did
at first.
4°. Phosphate of magnesia and ammonia.-If to the purer bi-
phosphate prepared as above and dissolved in water, a solution of
sulphate of magnesia (Epsom salts,) be added, and if after being
well stirred together, the mixture be allowed to settle, a further
quantity of gypsum will gradually fall to the bottom. If the clear
liquid be poured off, and ammoniacal liquor—into which a little
quicklime has been previously stirred and the whole allowed to
settle—be added to it till the mixture on being well stirred still
smells of ammonia, a fine powder will fall, which is the phosphate
of magnesia and ammonia, or ammoniacal phosphate of magnesia.
This compound has been tried by Boussingault as a mamure with a
profitable effect.* Mixed with half its weight of bi-phosphate of
lime, this would prove one of the most useful forms in which phos-
phoric acid can be applied to the land. I strongly recommend ex-
periments to be made with it.
5°. Phosphates of potash and soda.—These salts are at present
sold at too high a price to admit of their being used largely as ma-
mures. If the bi-phosphate of lime be dissolved in water, and a
solution of pearl ash be added as long as a white powder falls, and
if the clear liquid be then poured off and boiled to dryness, an im-
pure phosphate of potash will be obtained. If instead of pearl ash
the common soda of the shops be employed, phosphate of soda
will be formed. With either or both of these it is desirable that
experiments should be made.
6°. Theory of the action of these phosphates.—The theory of the
action of these phosphates is very simple. We have seen in our
previous lectures how necessary phosphoric acid is to the growing
plant. We have seen also that soils vary in their composition,
some containing more of this and other ingredients and others less.
Upon a soil that does not contain a sufficient supply of phosphoric
acid in some available form of combination, none of our usually
cultivated crops can flourish—the addition of these phosphates to
the soil, therefore, is beneficial, generally, because they supply this
necessary ingredient to plants.
But some plants require potash and soda in larger quantity than
* Chemical Gazette, November 1, 1845, p. 457.
SILICATES OF POTASH AND SODA. 613
lime. Upon these an alcaline phosphate may produce a greater
effect than one of lime or magnesia. When, on the other hand,
lime and magnesia are largely required, the phosphates of these
earths may prove more strikingly useful.
The ammoniacal phosphate of magnesia has a third means of be-
neficial action in the ammonia it contains.
The composition of the soil also—its abundance in lime, magne-
sia, soda, or potash —will modify the special influence which the Se-
veral phosphates above described are fitted respectively to exercise.
§ 6. Use of the silicates of potash, soda, and lime. Are they
necessary to the crop or to the land 2
1°. Silicates of potash and soda.-These compounds, which have
been already described (p. 350), are supposed to act an important
part in the growth of the grasses, and of the corn-bearing plants,
by supplying, in a soluble state to the roots, the silica which is so
necessary to the strength of their stems. This opinion is supported
by the results of some experiments made by Lampadius, who found
a solution of silicate of potash to produce remarkable effects upon
Indian corn and upon rye.*
We know, however, that potash and soda applied alone more or
less remarkably invigorate our growing crops. It is difficult there-
fore to say, in regard to experiments like those of Lampadius, whe-
ther it was the potash alone, or whether the silica also had something
to do with the more luxuriant growth of the rye crop which follow-
ed the application of the silicate of potash.
It is believed that the laying of heavy crops of corn is often due
to an unnatural weakness of the stem, caused by a deficiency in the
proportion of silica which it ought in a healthy state to contain—
and the application of silicate of potash has been recommended as
likely to supply this deficiency, and to remove the evil supposed to
attend it. It is certainly desirable both to investigate by analysis
the proportion of silica which a healthy straw ought to contain,-
and to try by experiment how far the application of a soluble sili-
cate to the growing plant will make its stem stronger. But these
experiments must be made in comparison with an equal amount of
potash or soda, uncombined with silica, and the straw must be
* Lehre von dent mineralischen Dunſmittelm, p. 25, (1833.)
614 ARE SILICATES NECESSARY AS MANURES
afterwards analysed, for the purpose of ascertaining how far its
composition has been affected by the application.
2°. Silicate of lime.—The first, or grey slag of our iron furnaces,
contains much lime in combination with silica. When crushed or
broken, or when scraped off the roads which are repaired with this
slag, it would form an excellent application to peaty or stiff clay
soils, and would by its lime prepare the land for green crops, and
by its silica perhaps still further for the growth of corn.
3°. Is the application of silicates necessary to the land or to the
crops?—If corn crops be taken off the land and sold in the mar-
ket, we know that they will carry off phosphoric acid among other
substances from the soil, and that if this soil is to be kept in a pro-
ductive state, the phosphoric acid must be returned toit again in some
form or other. But it is doubtful how far the same thing is true
of silica. This substance exists in nearly all our soils in so large
a quantity—so much of it also is in a state in which the roots of
plants can take it up—so much silica is likewise held in solution by
nearly all our spring waters which rise into the soil—that it isdoubt-
ful, as I have elsewhere” more fully explained, whether, as a general
rule, the application of a silicate to any crop, is likely to benefit it
much by the mere silica it is capable of supplying. There seems
in most cases to be a sufficient supply of available silica within the
reach of our crops on all our soils. Still this opinion is not as yet
fortified by actual experiments. Until such are carefully made,
therefore, and the resulting crops analysed, any opinions we may
entertain on the subject must be considered as provisional only,
and open to correction.
* Proceedings of the Agricultural Chemistry Association, p. 53.
I, ECTURE XIX.
Saline manures continued. Salts of ammonia, sulphate, muriate, carbonate, and ni-
trate of ammonia. Special action of the salts of ammonia. Natural mixtures of
saline substances—wood, sea-weed (kelp), straw, sugar cane, peat, and coal, ashes.
Crushed granite, trap, and lava. Artificial saline mixtures. Manufactured ma-
nures. Principles on which they are to be compounded. Manures for wheat, barley,
oats, rye, maize, turnips, potatoes, and cabbages.
§ 1. Of the salts of ammonia and their special action on vegetation.
THERE is reason to believe that ammonia in nearly every form
of combination is fitted, in a greater or less degree, to promote the
growth of cultivated plants. None of its compounds, however,
are known to occur any where in nature in such quantity as to be
directly available in practical agriculture, and only a very few can
be produced by art at so low a price as to admit of their being
used with profit.
1". Sulphate of ammonia.--An impure sulphate of ammonia is
manufactured by adding sulphuric acid to fermented urine, or to
the ammoniacal liquor of the gas works, and evaporating to dryness.
When prepared from urine, it contains a mixture of those phos-
phates which exist in urine, and which ought to render it more
valuable as a manure. The gas liquor yields a sulphate which is
blackened by coal tar—a substance which, while not injurious
to vegetation, is said to be noxious to the insects that infest our
corn fields. In any of the above forms this salt has been found
to promote vegetation, chiefly by increasing and hastening the
growth of the green parts of the plant. Accurate experiments
are yet wanting, however, to show to what kind of crops it may be
applied with the greatest advantage—and what amount of increase
may be expected from the application of a given weight of the
Salt.
Pure crystallized sulphate of ammonia is soluble in its own
616 SAL-AMIMONIAC AND CARBONATE OF AMMONIA.
weight of water. 100 lbs. contain about 35 lbs. of ammonia, 53
lbs. of acid, and 12 lbs. of water.
Applied at the rate of 13 cwt. per Scotch acre, in addition to
the farm-yard manure, it gave Mr Fleming of Barochan, in two
separate experiments, an increase of l; tons of potatoes, when ap-
plied as a top dressing to the young potatoes, and of 4% tons when
mixed with the manure at the time of planting. As a top dress-
ing to young corn it has also been profitably employed, both upon
wheat and upon oats. Mr Fleming found 1 cwt. per Scotch acre
to add 9 bushels to his crop of oats grown upon moss, and to give
nearly one-half more straw. Mixed with wood ashes, Mr Burmet
found it to add 8 bushels an acre to his wheat crop.
This salt sells at present at about 16s, a hundred weight.
2". Sal-ammoniac or muriate of ammonia.-This salt, in the
pure state in which it is sold in the shops, is too high in price to
be economically employed by the practical farmer. An impure
salt, however, is prepared from gas liquor, which may be sold at
a sufficiently cheap rate to admit of an extensive application to the
land. Among other numerical results from the use of this salt
with which I am acquainted, are those given by Mr Fleming, who
applied it at the rate of 20 lbs. per acre to wheat on a heavy loam,
and to winter rye, on a tilly clay, both after potatoes, and obtain-
ed the following increase of produce per acre:–
Grain. Straw.
Rye, undressed, ......... 14 bushels. 36% cwt.
dressed, ... ........ 19 ...... 43% ,
Tricrease, ......... 5 bushels. 7 cwt.
Wheat, undressed, ... 25 bushels, each 61 lbs.
dressed,... ... ... 26; bushels, each 62 lbs.
Increase, ......... l; bushels.
The increase in these experiments was not large, but the quaſi-
tity of sal-ammoniac employed was too small to produce a decided
effect.
3°. Carbonate of ammonia—the smelling salts of the shops—
is obtained in an impure form by the distillation of horns, hoofs,
and even bones. It is also found in the state of impure crystals,
in considerable quantity, in some of the varieties of guano (Pa-
tagonian) now imported into this country. In this impure form
it may possibly be obtained at so low a price as to place it with-
USE OF AMMONIACAL LIQUOR. 617
in the reach of the practical farmer. It is supposed by some that
this carbonate is too volatile—or rises too readily in the form of
vapour—to be economically applied to the land. In the form
of a weak solution, however, put on by a water cart—or in moist
showery weather simply as a top-dressing, especially to grass lands
and on light soils—or in a state of mixture with other manures—it
may be safely recommended where it can be cheaply procured.
4°. Ammoniacal liquor.—This is proved by the success which
has in many localities been found to attend the application of the
ammoniacal liquor of the gas works. This liquid holds in solu-
tion a variable quantity of sulphate of ammonia and of sal-ammo-
niac,” but in general it is richest in the carbonate of ammonia.
The strength of the liquor varies in different gas works; chiefly
with the kind of coal employed for the manufacture of the gas.
One hundred gallons may contain from 20 lbs. to 40 lbs. of am-
monia, in one or more of the above states of combination. No
precise rule, therefore, can be given for the quantity which ought
to be applied to the acre of land, but as the application of a larger
quantity can do no harm, provided it be sufficiently diluted with
water, one hundred gallons may be safely put on at first, and more
if experience should afterwards prove it to be useful.
On grass and clover, upon a heavy moist loam, Mr Bishop ap-
plied 105 gallons an acre, diluted with 500 gallons of water, and
obtained, of hay, from the
Undressed,............ # lb. per square yard, or 20% cwt. per acre.
Dressed,............... l, lb. ... & e e or 613 cwt.
Increase, ......... 1 lb. . . . * * * or 41 cwt.f
The increase here is so great, that the general use of this liquor
—hitherto, in most country towns at least, allowed to run to waste
—cannot be too strongly recommended. On the dressed part, ac-
cording to Mr Bishop, the Timothy grass was particularly luxu-
riant. -
These experiments with the gas liquor show, as I have said, that
impure carbonate of ammonia may be safely applied to the land
without any previous preparation. If it is wished, however, to fix
* Each gallon of the ammoniacal liquor of the Manchester gas works is said to
contain 2 ounces of Sal-Ammoniac. In these works the Cannel coal of Wigan is
employed. p
+ Prize Essays of the Highland Society, xiv. p. 350,
618 SPECIAL ACTION OF THE SULPHATE AND NITRATE,
or render it less volatile—which in warm and dry seasons may
sometimes be desirable—this may be effected by adding powdered
gypsum, in the proportion of 1 lb. to each gallon of the ammonia-
cal liquor, and frequently stirring; or more effectually, by adding
either sulphuric acid, or the waste muriatic acid of the alcali
works. *
5°. Nitrate of ammonia.-If it be correct that those substances
act most powerfully as manures which are capable of yielding the
largest quantity of nitrogen to plants, the nitrate of ammonia ought
to promote vegetation in a greater degree than almost any other
Salime substance we could employ. According to the experiments
of Sir H. Davy, f however, this does not appear to be the case,
though Sprengel has found it more efficacious than the mitrates
either of potash or of soda. This question as to the relative action
of the nitrate of ammonia is very interesting theoretically, but it
directly concerns practical agriculture very little, since the high
price of this salt is likely to prevent its being ever employed in the
ordinary operations of husbandry.
6°. Special action of the different salts of ammonia. — The
theory of the action of ammonia itself upon vegetation I have in a
former lecture (p. 291) endeavoured to explain to you. But the
special action of the several saline compounds of ammonia above
described will depend upon the nature of the acid with which it
may be in combination.
The sulphate will partake of the action of the sulphates of pot-
ash, soda, or lime (gypsum), in so far as it may be expected to
exhibit a more marked effect upon the leguminous than upon the
corn crops, and upon the produce of grain than on the growth of
the leaves and the stem. This special action may be anticipated
from the sulphuric acid it contains. And if this reasoning from
analogy be correct, we should expect the Sulphate of ammonia to
rank among the most useful of manures—since the One constitu-
ent (ammonia) will promote the general growth of the plant, while
both will afterwards lend their influence to the filling of the ear.
The nitrate again has been found to act more upon the corn
* 100 gallons thus saturated with acid will convey to the soil about 100 lbs, of
sulphate of ammonia or of Sal-ammoniac.
+ Davy's Agricultural Chemistry, Lecture VII.
3
MIXED SALINE MANURES OF NATURAL ORIGIN. 619
crops than upon the leguminous plants and clovers (Sprengel)—a
result which is to be explained by the absence of sulphuric acid,
which appears to aid especially in the development of the latter
class of plants.
On this subject, however, experiments are too limited in num-
ber, in general too inaccurately made, and our information in con-
sequence too scanty to enable us as yet to arrive at Satisfactory
conclusions.
§ 2. Of mixed saline manures of vegetable origin—the ashes of
wood, sea-weeds, sugar cane, peat, and coal.
The principle already so frequently illustrated, that plants re-
quire for their rapid and perfect development a sufficient supply of
a considerable number of different inorganic substances, will na-
turally suggest to you that in our endeavours to render a soil pro-
ductive, or to increase its fertility, we are more likely to succeed
if we add to it a mixture of several of those substances, than if we
dress it or mix it up with one of them only. This theoretical con-
clusion is confirmed by universal experience.
Nearly all the matural manures, whether animal or vegetable,
which are applied to the land, contain a mixture of Saline substan-
ces, each of which exercises its special effect upon the after-crop
—so that the final increase of produce obtained by the aid of these
manures, must be ascribed not to the single action of one of their
constituents, but to the joint action of all. In the ashes of plants
these saline substances are unmixed with organic matter, and there-
fore any action such ashes are found to exercise must be wholly due
to the saline substances they contain.
1°. Wood ashes.—From what has already been said in regard
to the composition of the ashes of plants, we should naturally ex-
pect them to be peculiarly efficacious in promoting the growth of
living plants. This expectation has been confirmed by the effects
which have almost universally been found to follow the use of
wood ashes and of the ash of other vegetables in the cultivation of
the land.
The quality of the ash left by plants when burned, as we have
already had occasion to remark (pp. 312 and 418), varies with a
great number of circumstances. It always consists, however, of a
620 COMPOSITION OF WOOD ASHES.
mixture in variable proportions of carbonates, silicates, sulphates
and phosphates of potash, soda, lime, and magnesia, with certain
other substances present in smaller quantity, yet more or less ne-
cessary, to vegetable growth. Thus, as we have already seen, (pp.
397 to 400), the ashes of the wood of the oak, the beech, the Scotch
fir, and the larch, consist respectively of

Oak. Beech. sº Larch.
Potash, ............ . ............... 8’43 15°83 2-79 15°24
Soda, ... ........................... 5'64 2-79 15'99 7.27
Chloride of Sodium, ............... ():02 0-23 1'48 ()'92
Lime, ...... • * tº s ∈ & & & & © tº tº e º e s s & sº e º a tº * * * * 74°63 62-37 30°36 25'85
Sulphate of lime, .................. 1.98 2.3] 3.31 2.91
Magnesia, ........................... 4.49 | 1:29 1976 24°50
Oxide of iron, ..................... 0.57 0.79 * & e & ©
Phosphate of iron,.................. & * * 5' 10 6- 18
Protoxide of manganese, ......... & & e is º 18:17 13°5]
Phosphoric acid, .................. 3:46 3.07 º & is e º
Silica, ................................. 0.78 1.32 3'04 3:60
100' 100 I ()(). 99.98
The composition of these several ashes is very different, and
their effect, when applied to the land, will therefore be different
also. The alcaline matter, the lime, and the phosphoric acid they
all contain, cannot fail to prove beneficial to almost every crop.
In this country wood ashes, mixed with bone dust, are employ-
ed in many districts as a manure for turnips, and often with great
success. As much as 15 bushels (7; cwt.) of ashes are drilled
in per acre with 15 bushels (6 cwt.) of bones. The large
quantity of alcaline matter present in the turnip crop (p. 384) may
be supposed to explain the good effects which wood ashes have up-
on it. They have been found in a similar degree to increase the
produce of the potato.
The immediate benefit of wood ash is said to be most perceptible
upon leguminous plants (Sprengel) such as lucerne, clover, peas,
beams, and vetches. Applied as a top dressing to grass lands it
roots out the moss and promotes the growth of white clover. Up-
on red clover its effects will be more certain if previously mixed
with one-fourth of its weight of gypsum. In small doses of two
or three hundred weight (4 to 6 bushels) it may be safely applied
even to poor and thin soils, but if used alone, in large and re-
peated doses, its effects will be too exhausting unless the soil be
|USE OF WOOD ASHES AS A MANUR.E. 621
either naturally rich in vegetable matter, or be mixed from year
to year with a sufficient quantity of animal or vegetable manure.
In so far as the immediate effect of wood ashes is dependent up-
on the soluble saline matter they contain, their effect may be imi-
tated by a mixture of crude potash with carbonate and sulphate of
soda, and a little common salt. If the wood ash of this country
contain usually one-fifteenth only of its weight of soluble matter,
as was the case with a variety examined by Bishop Watson, the
following quantity of such a mixture would be nearly equal in effi-
cacy to the saline matter of one ton of wood ash,
Crude potash * * & © tº 60 lbs. at a cost of 15s.
Crystallized carbonate of soda 60 ... e & e 7s.
Sulphate of soda ... * * * 20 9
Common salt & s & & ſº e 22 ZS.
160 lbs. 24s.
Where the wood ash costs only a shilling a bushel (or L.2 a
ton), it would obviously be more economical to employ this mix-
ture, were the efficacy of wood ashes dependent solely upon the
soluble saline matter they are capable of yielding on the first wash-
ing with water. But they contain also a greater or less quantity
of imperfectly burned carbonaceous matter, the effect of which up-
on vegetation cannot be precisely estimated, and a large propor-
tion—nine-tenths, perhaps, of their whole weight—of insoluble
carbonates, silicates, and phosphates of potash, lime, and magne-
sia, which are known more permanently to influence the fertility of
the land to which they are applied.
2°. Washed or liviviated wood ashes.—In countries where wood
ashes are washed for the manufacture of the pot and pearl ash of
commerce (p. 321), this insoluble portion collects in large quan-
tities. It is also present in the refuse of the soap makers, where
wood ash is employed for the manufacture of soft soap. The com-
position of this insoluble matter varies very much, not only with
the kind of wood from which the ash is made, but also with the
temperature it is allowed to attain in burning. The former fact is
illustrated by the following analyses made by Berthier, of the in-
soluble matter left by the ash of five different species of wood care-
fully burned by himself:-
622
yº. inn r, l Ri Pitch [Scotch
Oak. Lime. Birch. Pine. | Fir. Beech.
Silica, 3-8 2-0 5°5 || || 3-0 4°6 5-8
Lime, & 54.8 || 51.8 52.2 27.2 42-3 || 42.6
Magnesia, 0.6 2.2 3-0 8-7 || 10-5 7:0
Oxide of iron, - º e & 0-l O'5 22:3 0: 1 l'5
Oxide of manganese, * * e 0.6 3’5 5' 5 0°4 4'5
Phosphoric acid, 0-8 2.8 4’3 1-8 1-0 5.7
Carbonic acid, 39.6 39-8 31-0 || 21.5 36-0 || 32.9
Carbon, * * * * G - * * * e tº e 4'8 g
99.6 |100 || 00 100 90.7 || 00

The numbers in these several columns differ much from each
other. The composition of the insoluble part he obtained was diffe-
rent in every case, no doubt, from that which would have been left
by the ash of the same wood burned on the large scale, and in the
open air. This is to be inferred from the total absence of potash
and soda in his lixiviated ash—while it is well known that common
lixiviated wood ash contains a notable quantity of both. This
arises from the high temperature at which wood is commonly burn-
ed, causing a greater or less portion of the potash and soda to
combine with the silica, and to form insoluble silicates which re-
main behind along with the lime and other earthy matter, when
the ash is washed with water. It is to these silicates as well as to
the large quantity of lime, magnesia, and phosphoric acid it con-
tains, that common wood-ash owes the more permanent effects upon
the land, which it is known to have produced. When the rains
have washed out or the crops carried off the more soluble part from
the soil, these insoluble compounds still remain to exercise a more
slow and lasting influence upon the after-produce.
Still from the absence of this soluble portion, the action of lixi-
viated wood ash is not so apparent and energetic, and it may there-
fore be safely added to the land in much larger quantity. Applied
at the rate of two tons an acre, its effects have been observed to
continue for fifteen or twenty years. It is most beneficial upon
clay soils, and is said especially to promote the growth of oats.
I am not aware that in any part of the British Islands this re-
fuse ash is to be obtained in large quantity. In Bohemia it is
used in the manufacture of glass, but in North America much of
it is thrown away as waste, which might be advantageously restor-
ed to the land.
COMPOSITION AND USE OF KELP. ($2.3
3°. Ash of sea weeds.-Kelp is the name given in this country"
to the ash left by marine plants when burned. It used to be exten-
sively prepared in the Western Islands, but the low price at which
carbonate of soda can now be manufactured has so reduced the
price and the demand for kelp as almost to drive it from the mar-
ket. As a natural mixture, however, which can now be obtained
at a cheap rate (about L.3 a ton), and which has been proved to
be useful to vegetation in a high degree, f it is very desirable that
more extended experiments should be instituted with the view of
determining the crops and soils to which it can be most advanta-
geously and most economically applied.
Like wood ashes, kelp varies in composition with the species
and age of the marine plants (sea weeds), from which it is pre-
pared, and like them also it consists of a soluble and insoluble
portion. Two samples from different localities in the Isle of
Skye, analyzed by Dr Ure,S consisted of—
SOLUBLE PORTION, Heisker. Rona.
Carbonate of soda with sulphuret of sodium, 8-5 5°5
Sulphate of soda, ................................. 8:0 19-0
Common salt, .................................... *
Chloride of potassium,...... ... ..... ........... 36'5 37-5
53-0 62-0
INSOLUBLE PORTION.
Carbonate of lime, ... .......................... 24.0 10-0
Silica,.......... . & ſº ſº e s e s tº e º e º e & & e s 6 tº e º g º ſº e º 'º e º ſº e º e 8:0 & © e
Alumina and oxide of iron, ..................... 9:0 10-0
Gypsum, .............. ........................... tº $ tº 9°5
Sulphur and loss, .............................. * & © G-0 8-5
100 100
Besides these constituents, however, the soluble portion con-
tained iodide of potassium or sodium in variable quantity, and the
insoluble part more or less potash and Soda in the state of silicates,
and of potash in the state of sulphate.
* In Brittany and Normandy it is called varec, the same word as our wrack or wreck
(wrec.) That of Spain is known by the name of barilla.
+ Prize Essays of the Highland Society, vols. i. and iv.
: The kelp used at Tennant's work in Glasgow is said to leave 60 per cent of
insoluble matter.
§ Dictionary of Arts &nd Manufactures, p. 726.
& Y
£24. ÜOMPOSITION AND USE OF KIELP.
The general efficacy of kelp as a manure may be inferred from
the composition of the ashes of the various sea weeds presented to
you in a previous lecture (p. 403), though from the way in which
kelp is prepared, and the variable mixture of plants usually burned
to produce it, its special composition cannot be inferred even from
an average of the several analyses of the ashes of sea-weeds hi-
therto published. This is seen in the following table, in the two
columns of which I have contrasted the mean of twelve analyses
of sea-weeds (p. 403) with that of an Irish kelp lately examined
by Dr Hodges.
Ash of sea
weeds, (mean.) Irish kelp.
Potash, ............... . . . 17.50 8.22
Soday........................ 12.70 15°48
Chloride of sodium, ..... l 6'56 19:39
Chloride of potassium,... O'93
Iodide of sodium,......... 0.95 • * *
Lime, ... ........ ........ 7.30 5' 17
Phosphate of lime, ...... 7-24 10'04
Phosphate of magnesia, 4- 0-90
Magnesia, .................. 9'89 8-13
Oxide of iron, ...... . . . . 0-24 º “º
Sulphuric acid, ........... 24-76 20:17
Silica, ..................... l'84 2-7]
Carbonic acid, &c. ...... & & © 14°96
100 100
These two columns exhibit a general similarity between the
commercial kelp and the ash of mixed sea weeds. The first co-
lumn contains more potash, showing that kelp may often be richer
in this ingredient than that which was examined by Dr Hodges.
The second contains more phosphate of lime, an ingredient very
valuable in reference to the growth of plants.
Kelp may be applied to the land in nearly the same circum-
stances as wood-ash—but for this purpose it would be better to
burn the sea weed at a lower temperature than is usually employ-
ed. By this means, being prevented from melting, it would be
obtained in the state of a fine powder, and would be richer in
potash and Soda.
It might lead to important results of a practical nature, were a
series of precise experiments made wth such finely divided kelp as
4
USE OF THE ASHES OF STRAW. 625
a manure"—especially in inland situations—for though the vari-
able proportion of its constituents will always cause a degree of
uncertainty in regard to the action of the ash of marine plants—
yet if the quantity of potash it contains be on an average nearly
as great as is stated in the mean of the published analyses above
given—kelp will really be one of the cheapest forms in which we
can at present apply potash to the land.
4°. Straw ashes.—The ashes obtained by burning the straw of
wheat, barley, oats, rye, rice, and Indian corn contain a natural
mixture of saline substances, which is exceedingly valuable as a
manure to almost every crop. The proportion of the several con-
stituents of this mixture, however, is different, as we have already
seen, according as the one or the other kind of straw is burned.
Thus, 100 parts of these several varieties of ash consist respective-
ly of about


Wheat. Barley. Oats. | Rye. Rice * Rape.
Potash, e tº 12:44 6-31 || 19. 14 || 17-36 || 10-27 | 9-62 21:17
Soda, . e 0-16 || 0.6l 9-69 || 0-31 || 3-82 27-66 | 12.62
Lime, tº 6-70 9:53 8-07 || 0-06 || 0-73 8°46 19:03
Magnesia, ge 3-82 || 3:22 || 3-78 || 2:41 4°49 || 6’ 64 3°49
Alumina, e gº º º * * * * * * & |
Oxide of iron, * 1:30 | }. 2'22 | 1.83 | 1.36 0.67 0-81 | \, 2.48
Oxide of manganese, • * * * tº * * * & © tº & & Cº
Phosphoric acid, . 3-07 || 3:08 2.56 || 3-82 l'09 || 17-08 || 1 1-15
Sulphuric acid, & 5'82 | 1.63 || 3:26 0.83 || 3:56 || 0.70 || 14-85
Chlorine, & 1-09 || 0'97 || 3-25 || 0:46 0-33 || 2:06 || 12-84
Silica, e & 65°38 70°58 || 48-42 64.50 || 74-09 || 26.97 || 2:37
99-78 98°15 100' |100'll 99-05 || 00' | 100.
That such ashes should prove useful to vegetation might be in-
ferred not only from their containing many mineral substances
which are known to act beneficially when applied to the land, but
from the fact that they have actually been obtained from the parts
of plants. If inorganic matter be necessary to the growth of
wheat, then Surely the peculiar mixture contained in the ash of
wheat straw is as likely as any other to promote the growth of the
young wheat plant. The question may even be raised whether or
not in some soils, rich in vegetable matter, the ash alone would not
produce as visible an effect upon the coming crop, as the direct
* For some other suggestions on this subject, I beg to refer the reader to the Prize
Essays and Thansactions of the Highland and Agricultural Society, xiv. p. 508.
R. r -
626 SOILS ON WIHICH STRAW ASII MAY BE USED,
application of the entire straw, whether in the dry state, or in the
form of rotted farm-yard manure. And this question would seem to
be answered in the affirmative, by the result of many trials of straw
ashes, which have been made in Lincolnshire. In this county the
ash of five tons of straw has been found superior in efficacy to ten
tons of farm-yard manure.” This is perfectly consistent with
theory, yet as vegetable matter appears really essential to a fertile
soil, and as the quantity of this vegetable matter in the soil is
lessened by every corn crop we raise, it cannot be good hus-
bandry to burn the straw and to manure for a succession of rota-
tions with its ashes only. The richest soil by this procedure must
ultimately be exhausted. On the other hand, where much vege-
table matter exists, and especially what is usually called inert ve-
getable matter, it may be an evidence of great skill in the practi-
cal farmer to apply for a time to his land the ashes only of his
straw—or some other similar saline mixture in its stead.
The practice of burning the stubble on a windy day has been
found in the East Riding of Yorkshire, to produce better clover,
and to cause a larger return of wheatf—for this purpose, however,
the stubble must be left of considerable length. In Germany,
rape-straw—which the above table shows to be rich in saline and
earthy matter, and, therefore, exhausting to the land—is spread
over the field and burned in a similar manner. The destruction
of weeds and insects which attends this practice, is mentioned as
one of its collateral advantages.f
In the United States, where, according to Captain Barclay, the
straw is burned merely in order that it may be got rid of, it
would cost little labour to apply the ash to the soil from which the
straw was reaped, while it would certainly enlarge the future pro-
duce—and in Little Russia, where, from the absence of wood, the
straw is universally burned for fuel, and the ashes afterwards con-
signed to the nearest river, the same practice might be beneficially
adopted. However fertile, and apparently inexhaustible, the soils
in these countries may appear, the time must come when the pre-
* Survey of Lincolnshire, p. 304, quoted in British Husbandry, ii. p. 334.
+ British Husbandry, ii. p. 333.
# Sprengel, Lehre vom Dünger, p. 355.
§ Agricultural Town in the United States, pp. 42 and 54.
COMPARATIVE EFFECTS OF STRAW AND STRAW ASEI. 627
sent mode of treatment will have more or less exhausted their pro-
ductive powers.
It is not advisable, as I have already said, wholly to substitute
the ash for the straw in ordinary soils, or in any soils for a length
of time, yet that it may be partially so substituted with good effect
—or that straw ashes will alone give a large increase of the corn
crop, and therefore should never be wasted—is shewn by the fol-
lowing comparative experiments, conducted, as such experiments
should be, during an entire rotation of four years. The quantity
of manure applied, and the produce per imperial acre were as fol-
low:—
15 cwt. barley straw || 3 tons stable dung in 2 tons of rotten
No Manure. burned on the the dung, eight months
ground. Straw state. §
1°. Turnips 22 lbs. 8% cwt. 183 cwt. 16# cwt.
2°. Barley | 1.4% bush. 30% bush. 30% bush. 36% bush.
3°. Clover | 8 cwt. 18 cwt. . . 20 cwt. 21 cwt.
4°. Oats 32 bush. 18 bush. 38 bush. 40 bush.
The kind of soil on which this experiment was made is not stat-
ed,” but it appears to show, as we should expect, that the effects
of straw ash are particularly exerted in promoting the growth of
the corn plants and grasses which contain much siliceous matter
in their stems—in short, of plants similar to those from which the
ash has been derived. -
Theory of the action of straw ash.--That it should especially
promote the growth of such plants appears most natural if we con-
sider only the source from which it has been obtained, but it is
fully explained by a further chemical examination of the ash itself.
The soluble matter of wood ash in general contains only a small
quantity of silica—while that part of the straw ash which is taken
up by water contains very much.
Thus a wheat ash analyzed by Berthier contained of
Per Cent.
Soluble salts,................. ...... º 19
Insoluble matter,... ........... tº e e s e º s 81
100
and that which was dissolved by water consisted of
* British Husbandry, ii. p. 248.
628 THEORY OF TRIE ACTION OF SUGAR, CANE ASFI.
Per Cent.
Potash and Soda, ..... ........... ...... 50
Chlorine, ... .... ............. . . . . . . . . . . . 13
Sulphuric acid, .................... ...... 2
Silica, ........... ........................ 35
100
so that it was a mixture of soluble silicates and chlorides with a little
sulphate of potash and soda. Mr Norton also found in my labo-
ratory, that 14 cwt. of the ash of oat straw contain one cwt. of
silica readily soluble in water. These soluble silicates will find
an easy admission into the roots of plants, and will supply to the
young stems of the corn plants and grasses the silica which is in-
dispensable to their healthy growth.
5°. Ash of the sugar cane. — In tropical countries where the
sugar cane is cultivated, it is usual to employ the canes after they
have gone through the mill, as fuel for boiling down the syrup.
Thus much cane ash is produced, which is often more or less
melted by the fire, and has hitherto in most places been thrown
away. This, however, ought not to be done. Like the ash of all
other plants it may be usefully applied to the land. -
The composition of this came ash should, it might be supposed,
approach very near to the mean of those of the several varieties of
cane ash, of which the analysis has been given in a previous
lecture. (P. 393.) But such is by no means the case. A large
proportion of the alcaline matter of the came is contained in its
sap. When put through the crushing mill this sap or juice is
squeezed out, and the exhausted cane when burned will therefore
leave an ash much poorer in alcaline matter than the uncrushed
cane would have done. This is shown by the results of two ana-
lyses made in my laboratory of varieties of came ash from the fur-
nace, which were sent to me from Jamaica and Tobago respec-
tively. The following table exhibits their composition contrasted
with the mean composition of the ash of four varieties of entire
cane. (P. 393).
Entire ash. Furnace ash.
Jamaica. Tobago.
Potash, ........... , & & e º e s is ſº tº e º e s s e º & 8 18:18 2-23 l'49
Soda, .............. .................. 0°45 2°40 1 : 10
Chloride of potassium, ............ 5' 31
Chloride of sodium, , ..... ..... 7:34 0-13 2-42
COMPOSITION AND USE OF DUTCH ASHES. 629
Entire ash. Furnace ash.
Jamaica. Tobago.
Lime, ........ .............. ... ...... 7'44 1 l'91 ll 19
Magnesia, ........................... 7.30 7-40 4-76
Oxide of iron, .................. .. * * 1°55 5'57
Phosphoric acid, .................. 7:01 5°90 9°40
Sulphuric acid, .......... .......... 6-76 l'56 2.35 *.
Silica,...... ...... ............. ...... 40°21 66-22 6] '55
100 99-30 99.83
Notwithstanding the smaller proportion of alcaline matter it con-
tains, however, this ash properly applied ought to be of great use
both to the sugar cane and to the coffee tree. It may be advantage-
ously mixed with one-fourth to one-half its weight of wood ashes,
with one-sixth of its weight of common salt, or with its own weight
of guano. Wood ash, came ash, and Peruvian guano, with a little
common salt, would probably make a still better mixture.
6°. Turf or peat ashes are also applied with advantage to the land
in many districts. They consist of a mixture in which gypsum is
usually the predominating useful ingredient—the alcaline salts being
usually present in small proportion only. Of ashes of this kind those
imported from Holland, and generally distinguished by the name
of Dutch ashes, are best known, and have been most frequently
analysed. The following table exhibits the composition of some
varieties of ashes from the peat of Holland and from the heath of
Iuneburg, examined by Sprengel:—

Dutch ashes (grey.) Luneburg Ashes (reddish.)
Best || Inferior Worst Good Producing
quality. quality. quality. quality. little effect.
Silica,.................. 47°l 55'9 70-4 31.7 43°3
Alumina, ............ 4'5 3'5 4°l 5-1 9.7
Oxide of iron, ...... 6'6 5'4 4°1 17.7 ] 9.3
Do. of manganese, 1-0 4’3 0-2 0.5 3.5
Lime, ............ . . . . 13°6 8-6 6-1 31.9 7.]
Magnesia, ............ 4°9 1.6 3-9 1-0 4°6
Potash, ............... 0.2 0-2 0.1 0°l * *
Soda, .................. l:0 3-9 0°4 O'] e & ©
- Gypsum.
Sulphuric acid, ...... 7.2 G-4 3°4 6-2 *2
Phosph. of Lime.
Phosphoric acid, .... 2-0 0-8 1-3 1.2 O-2
- Common Salt.
Chlorine, ....... . ... 1-2 3-0 0°5 0.1 0°]
Carbonic acid, ...... 4°1 6'4 5'5 4'4 12.0
Charred turf. ... ... 6'6 * * * ſe
1000 | 1000 | 1000 | 1000 100 * 0%
* Sprengel Lehre vom Dunger, p. 363 et seq.
630 ljSE OF DUTCH PEAT ASHES,
In the most useful varieties of these ashes it appears, from the
above analyses, that lime is present in large proportion—partly
in combination with sulphuric and phosphoric acids, forming gyp-
sum and phosphate of lime—and partly with carbonic acid, form-
ing carbonate. These compounds of lime, therefore, may be re-
garded as the active ingredients of the above peat ashes.
Yet the small quantity of saline matter they contain is not to be
considered as wholly without effect. For the Dutch ashes are often
applied to the land to the extent of two tons an acre”—a quantity
which even when the proportion of alkali does not exceed one per
cent., will contain 45 lbs. of potash or soda, equal to twice that
weight of sulphates or of common salt. To the minute quantity
of saline matters present in them, therefore, the above peat ashes
may owe a portion of their beneficial influence, and from the almost
total absence of such compounds in the less valuable sorts, their in-
ferior estimation may have in part arisen.
In Holland, when applied to the corn crops, they are either plough-
ed in, drilled in with the seed, or applied as a top dressing to the
young plants in autumn or spring. Lucerne, clover, and meadow
grass are dressed with the ashes in spring at the rate of 15 to 18
cwt. per acre, and the latter a second time with an equal quantity
after the first cutting. In Belgium the Dutch ashes are applied to
clover, rape, potatoes, flax, and peas—but never to barley. In
Luneburg the turf ash which abounds in oxide of iron is applied
at the rate of 3 or 4 tons per acre, and by this means the physical
character of the clay soils, as well as their chemical composition, is
altered and improved.
In England, peat is in many places burned for the sake of the
ashes it yields. Among the most celebrated for their fertilizing
qualities, are the reddish turf ashes of Newbury, in Berkshire.
The soil from beneath which the turf is taken abounds in lime,
and the ashes are said to contain from one-fourth to one-third of
their weight of gypsum.f They are used largely both in Berk-
shire and Hampshire, and are chiefly applied to green crops, and
especially to clover. In the proportion of 50 bushels an acre—
costing 12s. 6d., they increase the clover crop fully one-fifth. (Mor-
ton.)
* A bushel of Dutch ashes is said to weigh about 4 lbs.
i British Husbandry, ii. p. 334.
4.
COMPOSITION AND USE OF SCOTCH PEAT ASHES. 631
In Scotland peat is often burned as a step in the process of re-
claiming mossland. The ashes are usually spread where they are
made, and are rarely sold as a manure. The value and composition
of the ash varies with the kind of peat and the mode of burning.
The ash of the white or upper peat is generally richer in alcaline
and other salts soluble in water, as well as in gypsum. It is there-
fore greatly to be preferred as an application to the land.
The following table represents the composition of the ash of an
upper and under peat from the Paisley moss, prepared by Mr
Fleming of Barochan, compared with that of a sample of Dutch
ashes imported into Leith. The analyses were made in my labo-
ratory:—
Upper or Lower or
white black Dutch
- peat. peat. ashes.
Organic matter, (charred peat),...... .......................... 54:12 3.02 25-77
Sulphates and carbonates of potash, soda, and magnesia so-
luble in Water, ................................................... 6'57 5' 1 2.78
Alumina, soluble in acids, .......................................... 2.99 2'48
Oxide of iron, ................................... ..................... 4'61 18.66 11 : 19
Sulphate of lime, (gypsum), ........................................ 10°49 21-23 16.35
Phosphate of lime, ... ............................................ ... 0-90 0-40 | 24
Carbonate of lime, .................. ......... ....................... 8'54 3°50 1.21
Carbonate of magnesia, ............................................. - - - © º e 3°39
Insoluble siliceous matter, .......................................... 10-88 43.91 37-24
99-10 98.36 99.17
The ash of the white peat contained more than half its weight of
charcoal. A hundred pounds of the ash free from charcoal would
therefore contain twice as much of all the other ingredients as is
represented in the table—thirteen of soluble salts, twenty-one of
gypsum, seventeen of carbonate of lime, and so on. It is there-
fore much richer than the black peat, while both are more valuable
than the Dutch ashes.
The charcoal, however, is not without its use, so that in Lincoln-
shire peat only half burned is said to be worth double the quantity
burned to a clean ash as in the common way.” In the preparation
of such ashes, therefore, two practical rules ought to be attended to.
a. Not to burn the peat too far or to a clean ash, if it be in a
sufficiently fine powder, an entire half of the charcoal may be ad-
vantageously left.
* Journal of the Roy, Agr.Soc., v. p. 507.
632 COMPOSITION AND USE OF COAL ASHES,
b. When burned remove it under cover, or protect it from the
action of the rains as quickly as possible, that the soluble salts upon
which so much of its virtue depends may not be washed out of it.
How often are wood and other ashes left in heaps upon a field
until the rains have exhausted them of nearly all their most valua-
ble ingredients' -
6°. Coal ashes are a mixture of which the composition is very
variable. They consist in general, of lime, often in the state of
gypsum, with magnesia, silica, alumina, and oxide of iron, mixed
with a variable quantity of bulky and porous cinders or half-burn-
ed coal. The ash of a coal from St Etienne, in France, and of an
Oolite coal from Cantyre, in Argyleshire, were found to consist of
St Etienne. Cantyre.
(Berthier.) (Thomas.)
45°5 .
Silica, ......................... '• * * * * * * * * * * * * * * * * * * *
Alumina, insoluble in acids, ............... 62 43'9
Alumina, soluble in acids, .................. 5
Lime, ....................... ...... ........... 6 3-2
Magnesia, .................................... 8 3.3
Oxide of manganese, ....................... 3 & sº
Oxide and sulphuret of iron, ... . . . ...... 16 l'4
Sulphuric acid, ............................. tº a l'7
Chlorine, ...................... * * * * * * * * * * * * * * * * * * * 0°l
Potash and soda, ........... ... ............. • * * * * 0°3.
100 99°4
Such a mixture as this would no doubt benefit many soils by the
alumina as well as by the lime and magnesia it contains; but in the
English and Scotch coal ashes a small quantity of alkaline matter,
chiefly soda,” is generally present. The constitution of the ash of
our best coals, therefore, may be considered as very nearly resem-
bling that of peat ash, and as susceptible of similar applications.
When well burned, it can in many cases be applied with good ef-
fects as a top-dressing to grass lands which are overgrown with
moss; while the admixture of cinders in the ash of the less perfect-
ly burned coal produces a favourable physical change upon strong
clay soils.
§ 3. Mixed saline manures of mineral origin. Crushed granite,
trap, and lava.
1°. Crushed granite.—We have already seen that the felspar
* From the common salt with which our coal is so often impregnated,
CRUSHED GRANITE, DECAYED TRAPS, AND LAWAS. 633
existing in granite contains much silicate of potash and silicate of
alumina. It is in fact a matural mixture, which in many instances
may be beneficially applied, especially to soils which abound in
lime. It is many years since Fuchs proposed to manufacture pot-
ash from felspar and mica by mixing them with quicklime, calcin-
ing in a furnace, and then washing with water. By this means
he said felspar might be made to yield one-fifth of its weight of
potash.” Mr Prideaux has lately proposed to mix up crushed
granite and quicklime, to slake them together, and to allow the
mixture to stand in covered heaps for some months, when it may
be applied as a top-dressing, and will readily give out potash to the
soil. Fragments of granite are easily crushed when they have
been previously meated to redness, and there can be little doubt,
I think, that such a mixture as that recommended by Mr Pri-
deaux, would unite many of the good effects of wood ashes and of
lime. .*
k. Decayed trap.–I need not again remind you of the natural
fertility of decayed trap soils (p. 496), and of the improvement
which in many districts may be effected by applying them to the
land. When granite decays, the potash of the felspar is washed
out by the rains, and a comparatively unproductive soil often re-
mains—when trap decays, on the other hand, the lime by which it
is characterised is not soon dissolyed out, so that the soil which is
produced is not only fertile in itself, but is capable of being
employed as a fertilizing mixture for other soils. Thus when it is
much decayed it is dug out from pits both in Cornwall and in Scot-
land, and is applied like marl to the land.
l. Crushed lavas.-Of the fertile and fertilizing nature of the
crushed or decayed lavas I have also already spoken to you (p.
497). In St Michael's, one of the Azores, the natives pound the
volcanic matter, and spread it on the ground, where it speedily be-
comes a rich mould capable of bearing ºxuriant crops. At the
foot of Mount Etna, whenever a crevice appears in the old lavas, a
branch or joint of an Opuntia (Cactus Opuntia—European Indian-
Fig) is stuck in, when the roots insinuate themselves into every
fissure, expand, and finally break up the lava into fragments.
These plants are thus not only the means of producing a soil, but
* Journal of the Royal Institution, i. p. 184.
634 ARTIFICIAL MIXTURES OF SALINE MANURES.
they yield also much fruit, which is sold as a refreshing food
throughout all the towns of Sicily."
These are all so many natural mineral mixtures of which we
may either directly avail ourselves, or which we may imitate by
art.
§ 4. Of artificial mixtures of saline manures, and their effects.
We have seen that many saline substances applied singly to our
crops very much promote their growth.
. But we have also seen that all our cultivated crops require the
ingredients of several Saline compounds to form a healthy plant.
Hence we naturally draw the inference, that artificial mixtures of
two or more saline substances, are likely to be still more useful
and more generally so, than any one substance applied alone.
This has been confirmed by numerous experiments. Thus,
1°. Sulphate with nitrate of soda-If instead of dressing pota-
toes with dry sulphate of soda alone, (p. 586), a mixture of this
salt with an equal proportion of the nitrate of soda be applied at
the rate of 2 cwt. per imperial acre, the produce is in the same
circumstances much greater. Thus Mr Fleming, in 1841, ob-
tained in the same potato field, all equally manured with farm-
yard dung, the following different results,
Produce per Imp. Acre.
With dung alone ........................ 16% tons
Dressed with nitrate of soda .......... 20 tons
With sulphate and nitrate mixed, .. 26% tons.
Again, in 1842, he obtained on another field of potatoes top-
dressed on the 1st of June,
Produce per Imp. Acre.
1. Dung alone gave... ................... ..... ........................... 12% tons
2. Dressed with 2 cwt. Sulphate ................................. .... ... 123 tons
3. Dressed with 1 & cwt. nitrate .......................................... 16 tons
4. Dressed with 3 cwt. nitrate and 13 cwt. of dry sulphate of soda 18 tons.
i Still such results are not constant. It is only where the soil is
deficient in the constituents of both salts, that the application of
the mixture of the two is likely to be more useful than either of
them put in alone. It may even happen, as in the case of the sul-
phate in this experiment, that one substance when applied alone
* Decandolle, quoted in the Quart. Jowrm, of Agr., iv. p. 737.
EFFECTS OF MIXTURES OF SALINE MANURES. 635
may produce no increase of crop, and yet may increase the good
effect of another which is applied along with it.
2°. Sulphate of soda with sulphate of ammonia.-The same
mutually increasing effect of two substances was seen by other
experiments in the same field. Thus, -
Per Imp. Acre.
Dung alone gave .................................... 12# tons
2 cwt. Sulphate of soda in addition... ....... ... 12# tons
1 cwt. Sulphate of ammonia................ ..... 12% tons.
The produce being sensibly equal in the three cases, and the top-
dressings apparently thrown away. But a mixture of
13 cwt. Sulphate of soda, with
e | gave 18% tons.
# cwt. Sulphate of ammonia
3". Sulphate of magnesia, with nitrate of soda.-In the same
field also,
1% cwt. of nitrate of soda gave ............ 16 tons
13 cwt. of Sulphate of magnesia ......... 13} tons.
While a mixture of +
1 cwt. of each of the two gave.................... 22% tons.
4°. Sulphate of lime (gypsum) with common salt.—Gypsum and
common Salt are known to have been often used with advantage
alone. Mixed and applied at the rate of 2 cwt. of gypsum to 1
cwt. of common salt, Mr Alexander of Ballochmyle found it to
invigorate an apparently-worthless bean crop to such degree that
it became the admiration of the district.
5°. Sulphate of ammonia with wood ashes.—Mr Burnet in 1842
applied to his wheat crop a mixture of sulphated urine, (called sul-
phate of ammonia), with wood ashes, with the following result:
Per Imp. Acre.
No dressing .......................... ... 31} bushels
Sulphated urine, 2 cwt.
40 bushels.
Wood ashes, 4 cwt.
I have inserted this experiment for the purpose of illustrating
the beneficial result which may follow from the introduction of a
third substance into the mixture, as seen in the following example.
6°. Sulphate of ammonia, wood-ashes, and sulphate or nitrate of
soda.--To other portions of the same field, Mr Burmet applied a
mixture consisting of the sulphated urine and the wood ashes with
2 cwt. of Sulphate of soda in one case, 2 cwt. of common salt in
the second, and 1 cwt. of nitrate of Soda in the third. The result
636 MR FLEMING's MIXTURES OF SALINE MANURES.
was 49 bushels an acre, or an increase of 10 bushels from the ad-
dition of the soda salt. - -
This is probably to be explained by the circumstance, that while
the Sulphated urine supplied ammonia and some of the phosphates
of the urine, and the wood ashes the potash, the soda salts yielded
the soda which the growing crop required, and hence the increased
produce of the part of the field on which this more compound
mixture was applied. That an equal effect was produced by
the sulphate of soda and the common salt when mixed with the
wood ashes and sulphated urine, appears to show that it was the
soda they each contained which was the useful ingredient.
7%. Mr Fleming's mixtures.—Other mixtures of a more compli-
cated kind have been lately tried by numerous practical men, and
especially by Mr Fleming of Barochan, and by his intelligent over-
seer, Mr Gardner. - •
Among other mixtures which he has applied with good effect,
especially to his turnip and potato crops, I may mention the fol-
lowing. They are mixed together in the proportions and quanti-
ties in which he applied them to the imperial acre. They are used
instead of, and in the same way as so much guano, always with
one-half or two-thirds the usual dose of farm-yard manure.
First mixture.—1 cwt. animal charcoal, (burned bones),
56 lbs. sulphuric acid,
28 lbs. carbonate or sulphate of magnesia,
28 lbs. nitrate of soda,
28 lbs. muriate of ammonia.
Second mixture.—1 cwt. animal charcoal, (burned bones),
56 lbs. Sulphuric acid,
14 lbs. carbonate of magnesia,
1 cwt. common salt,
1 cwt, gypsum,
28 lbs. nitrate of soda,
28 lbs. Sulphate of magnesia.
8". Mr Huatable's mixture for turnips.-An interesting experi-
ment upon the effect of mixed manures in raising turnips, was
made in 1845 by the Rev. Mr Huxtable.* Upon a field of five
acres of barren chalk on which scarcely any thing grew, he sowed
* Journal of the Royal Agricultural Society, vi. p. 355.
3
MANUFACTURE OF MIXED SALINE MANURES, 637
Swede turnips in two feet drills, and manured them with the fol-
lowing mixture per imperial acre.
2 cwt. of Ichaboe guano,
30 bushels wood ashes, watered with 10 lbs. of sulphuric acid,
50 lbs. of burned bones, dissolved in 22 lbs. of sulphuric acid.
The whole mixed up with 30 bushels of saw dust.
The mixture was dibbled in at distances of 12 inches in the
drills, and the seed deposited upon the manure with the hand.
The turnips came away well, and to the surprise of the practical
men in the neighbourhood, yielded 20 tons an acre. The cost
of the mixture was two pounds an acre. Such an experiment
as this goes a great way to shew that the barrenness of unpro-
ductive land, so far from being a necessary is in many cases only
an accidental circumstance. Greater skill and enterprise on the
part of practical men will by and bye cover with remunerating
crops many tracts of country which have hitherto been regarded as
of comparatively little value.
§ 5. Of the manufacture of mixed saline manures for different crops.
The manufacture of artificial manures is now arresting so much
attention, and is likely to become of so much importance in the
future progress of agriculture, that it will be proper briefly to
state the principles by which it ought to be regulated.
These principles are three in number:
1°. The manure must contain all those inorganic or mineral
substances which the crop we wish to grow carries off the soil, and
in the relative proportions in which they are respectively found in
the ash of the plant. -
The only exception to this rule is—that if one or more of these
substances abound in the soil, they may be omitted from the ma-
nure prepared for that soil; if any of them abound in all soils,
they may be uniformly omitted.
2°. The organic part of a plant always contains a certain pro-
portion of gluten or of some similar compound of which nitrogen
is a constituent. The nitrogen which is necessary to the produc-
tion of this gluten is derived from the soil. A manure, therefore,
which shall restore to the soil all that any crop has carried off or
will require to make it grow in a healthy manner, must contain
638 EIOW TO BE REGULATED.
Some compound of nitrogen which the roots of plants can take up.
Ammonia, the nitrates of potash and soda, the cartilage of bones,
which contains much nitrogen, skin, hair, flesh, blood, rape dust,
bran, and other similar substances, are all fitted more or less per-
fectly to perform this part in the nourishment of plants.
3°. We have seen in a previous lecture that one of the most
important functions performed by the organic matter in the soil is
to produce ammonia and nitric acid at the expense of the nitro-
gen of the atmosphere. This function is of great consequence to
the growth of plants. It supplies that loss of nitrogen which the
soil is continually undergoing by the agency of vegetation and
other natural causes.
But by continued arable culture, the proportion of organic mat-
ter in the soil gradually diminishes. Hence the necessity of add-
ing animal but especially vegetable matter in considerable quan-
tity to arable land, if it is to be kept in good condition. When
laid down to grass the vegetable matter naturally increases.
When the soil is already rich in vegetable matter, or when the
straw is returned to the soil in the form of farm-yard manure, the
addition of this vegetable matter becomes unnecessary. On the
other hand, it is the necessity for this addition of vegetable matter
which renders it better husbandry to employ half dung along with
guano, or with any artificial saline manure.
Thus a well prepared artificial or manufactured manure ought
to contain, º
a. The saline substances found in the ash of the plant we wish
to grow.
b. A proportion of some saline or other substance capable of
yielding nitrogen to the crop. -
c. A constant or occasional admixture of vegetable matter to
make up the natural waste of this kind of matter which the soil
undergoes during constant cropping.
The supply of nitrogen must bear some relation to the known
wants and period of growth of the crop to which it is to be applied
—while the mixture of inorganic substances must be specially pre-
pared for each crop, in conformity with the composition of the ash
it has been found to leave when burned. In the following section
I shall lay before you special recipes for the manufacture of arti-
SPECIAL MANURE FOR, WEHEAT. 639
ficial manures adapted to the growth of each of our commonly cul-
tivated crops.
§ 6. Composition of special manures for wheat, barley, oats, rye, In-
dian corn, rice, potatoes, turnips, cabbage, tobacco, the sugar cane,
coffee, and flaw. -
The principal substances required to form inorganic mixtures
such as are obtained in the ash of plants, are potash, soda,
lime, magnesia, phosphoric acid, and sometimes sulphuric acid and
chlorine. The oxides of iron and manganese and the silica abound
sufficiently in most soils in a state in which they can readily be
taken up by plants. It is unnecessary, therefore, in most cases, to
introduce them into our artificial manures, and I have in conse-
quence omitted them in the whole of the following recipes.
In putting these substances together in the requisite proportions,
it is of the first consequence that economy should be consulted—-
that each ingredient should be employed or introduced into the
mixture in that form in which it can be procured most abundant-
ly, and at the cheapest rate—provided that in such a state it is
likely to be equally efficient as a manure.
The importance of this remark will immediately appear.
1°. Special manure for wheat.—The average composition of the
ash of wheat given in a previous lecture (p. 365,) omitting the si-
lica, the oxide of iron, and the small quantity of sulphuric acid, is
represented very nearly by the following mixture:
Carbonate of potash (dry)............... 5 lbs.
Phosphate of potash (crystallized)...... 37 —
Phosphate of soda (crystallized) ...... 32 —
Phosphate of magnesia.................. 32 —
Phosphate of lime ........................ 6 —
112 lbs.
Of this mixture 112 lbs. are equivalent to 100 lbs. of the ash.
These phosphates of potash, soda, and magnesia, however, al’e
at present either not to be had in the manure market, or they are
too high in price to allow of their being used with economy. I
recommend therefore the following mixture as more easily pre-
640 MOST ECONOMICAL MIXTURE.
pared. It contains all the ingredients of the above recipe, with
50 lbs. of cartilage and 170 lbs. of gypsum besides.
Bone dust........................... 180 lbs, dissolved in
Sulphuric acid (of the shops)...... 90 —
Pearl-ash (dry)..................... 30 –
Carbonate of soda (dry) ......... 20 —
Carbonate of magnesia............ 70 —
390 lbs.
These 390 lbs. are equal to 100 lbs. of wheat ash, but as they
contain 50 lbs. of cartilage, in which much nitrogen is present, it is
unnecessary to add any mitrate or salt of ammonia for the pur-
pose of supplying the nitrogen which a plant ought to obtain from
a perfect manure.
In preparing such manures, the acid is diluted with twice its
bulk of water; the bones are then completely dissolved in it, and
with the still wet bones the other ingredients are intimately mixed.*
Five bushels of wheat carry off about 6 lbs. of inorganic matter
from the soil. For every bushel of wheat, therefore, which we have
carried off, or hope to grow, we must add about 5 lbs. of the above
mixture to the land—that is, about 2 cwt. for a crop of 40 bushels
of wheat. The mixture may be made for less than 10s, a cwt,
* In these recipes,
a. For every 100 lbs. of dry carbonate of potash (pearl ash), may be substituted,
126 lbs. of sulphate of potash, or
108 lbs. of chloride of potassium.
b. For every 100 lbs. of dry carbonate of soda, may be substituted
209 lbs. of dry sulphate of soda, or 110 lbs. of common salt.
c. For every 100 lbs. of carbonate of magnesia, may be substituted
265 lbs. of crystallized sulphate of magnesia, or
300 lbs. of a mild lime rich in magnesia.
d. For every 100 lbs. of carbonate of lime (chalk), may be substituted
170 lbs. of sulphate of lime, (gypsum), or
137 lbs. of burned gypsum.
e. For every 100 lbs. of bone dust, may be substituted
60 lbs. of burned bones.
But in this case, 30 lbs. of horn shavings or of some other animal substance, must be
added to supply the place of the cartilage of the bone. Or instead of this, 12 lbs. of
an ammoniacal salt, or 20 lbs. of a nitrate, must be added to the quantity of the
mixture contained in the recipes given in the text.
SPECIAL MANURES FOR BARLEY, OATS, AND RYE. 64l
2°. Special manure for barley.—The following mixture, pre-
pared in the same way as that for wheat, is adapted to the average
composition of barley.
Bone dust, ........................ 150 bº) ºf
Sulphuric acid, .................. 75 225 lbs
Carbonate of potash (dry), ............... 20 ..
Carbonate of soda (dry), .................. 14 ...
Carbonate of magnesia, .................. 16 ...
275 lbs.
This weight represents 100 lbs. of the ash of the grain of bar-
ley, and so much must be added to the soil for every 100 lbs.
of inorganic matter, or ash carried off by the crop. A bushel of
barley contains about 14 lbs. of inorganic matter, so that for a
crop of 50 bushels, 200 lbs. of the above mixture must be added
to the land.
3°. Special manure for oats.--To replace 100 lbs. of the inor-
ganic matter of the oat according to the mean composition of its
ash, the following mixture is adapted:
Bone dust, ........................
Sulphuric acid, … 44 } 132 lbs.
Carbonate of potash (pearl ash), ......... 18 ...
Carbonate of soda, ........................ 10 ...
Carbonate of magnesia, .................. 14 ...
174 lbs.
Five bushels of oats contain 6 lbs. of inorganic matter. A
crop of 50 bushels, therefore, will carry off 60 lbs, and will require
105 lbs. of the above mixture to replace it.
4°. Special manure for rye.—The following mixture is adapted
to the composition of the ash of the grain of rye:
Bone dust,........................ *} 285 lb
Sulphuric acid,......... ....... 95 */ S.
Carbonate of potash (dry), ............... 32 ...
Carbonate of soda (dry), .................. 20 ...
Carbonate of magnesia, .................. 22 ...
359 lbs.
S S
642 SPECIAL MANURES FOR RICE, MAIZE, AND THE POTATO.
*-
5°. Special manure for rice.—To supply what is carried off by
100 lbs. of the ash of the grain of rice, including the husk, the
following mixture may be applied:
Bone dust,........................... 26
Sulphuric acid, ..................... 13 } 39 lbs
Carbonate of potash (dry), ...... 5 ..
Carbonate of Soda (dry), ......... 3 ...
Carbonate of magnesia, ......... 4 ...
51 lbs.
Rice, when covered with its husk, leaves 3% per cent. of ash, so
that for every 350 lbs. of paddy carried from the field, 50 lbs. of
the above mixture must be added. This quantity is much smaller
than is required to be added for any of the other grains. The
reason is—that the husk of the paddy forms one-fifth of its whole
weight, and leaves 1:14 per cent of ash, nine-tenths of which con-
sist of silica (p. 376)—while the clean grain leaves only 1 per cent.
Of the whole ash left by the paddy, therefore, about five-sevenths
consist of silica, which I think it unnecessary to return to the soil;
so that there remain only two-fifths to be added in the form of ma-
nure, and that is done by the above mixture.
6°. Special manure for Indian corn (maize.)—A hundred
pounds of the ash of maize will be replaced by the following mix-
ture:
Bone dust, ............... 152
Sulphuric acid, ......... 76 228 lbs
Carbonate of potash (dry),......... 40 .
Carbonate of Soda (dry), ......... 13 ...
Carbonate of magnesia, ........... . 35 ..
316 lbs.
Every bushel of maize leaves about a pound of ash. About
3 lbs. of the above mixture, therefore, will require to be added for
every bushel of corn that is reaped.
7°. Special manure for the potato.—The average composition of
the potato tuber suggests the following mixture: --
SPECIAL MANURE FOR THE TURNIP. 643
Bone dust, ........................ 50 U. .
Sulphuric acid, .................. 25 j 76 lbs.
Carbonate of potash (dry),...... 80 ...
Carbonate of soda (dry), ...... 5 ...
Carbonate of magnesia, ...... 12 ...
172 lbs.
A larger portion of soda might probably be used with equal
advantage and a smaller proportion of potash. This would make
the mixture cheaper.
8°. Special manure for the turnip.–To the average composition
of the turnip bulb, the following mixture is adapted:
Bone dust, … *} 45 lbs.
Sulphuric acid, .................. 15.
Carbonate of potash (dry), ... 62 ...
Carbonate of soda (dry), ...... 9 . .
Carbonate of magnesia,......... 12
128 lbs.
A ton of bulbs contains eighteen pounds of inorganic matter;
for every ton of turnips, therefore, which is carried off or exported
from the land twenty-four pounds of the above mixture must be
added.
But if both bulbs and tops are carried off, then the mixture
must have the following composition:
Bone dust, ............. & O e s e º e º e º e
Sulphuric acid, .................. 16 } 48 lbs.
Carbonate of potash (dry),...... 52 ...
Carbonate of soda (dry), ...... 9 ...
Carbonate of magnesia, ......... 19 ...
128 lbs.
This mixture is calculated upon the supposition that the green
tops are upon an average one-third of the weight of the bulbs,
and that, on the other hand, the tops contain, weight for weight,
three times as much inorganic matter as the bulbs. Thus the tops
carry off from the land upon the whole about as much as the bulbs
do.
644 SPECIAL MANURES FOR, CABBAGE AND TOBACCO.
Hence a ton of bulbs with their tops carry off about 36 lbs, of
inorganic matter, so that for every ton of bulbs with their tops
carted off the field, and not returned again in the form of animal
manure, 48 lbs. of the second mixture must be added.
9°. Special manure for the cabbage.—The cabbage containsmuch
alcaline matter. The following mixture will replace what is con-
tained in 100 lbs. of its ash.
Bone dust, .................. 48
is tº ...7.2 lbs.
Sulphuric acid, ............... 24
Carbonate of potash (dry), ......... 17 ...
Carbonate of soda (dry), ............ 35 ...
Carbonate of magnesia, ............ 13 ...
Carbonate of lime (chalk), ..........27 ...
The fresh cabbage plant contains 92 per cent. of water, and the
dry leaf when burned yields from 10 to 25 per cent of ash. A
ton of cabbage, therefore, carries off as a mean 30 lbs. of inor-
ganic matter from the soil, to replace which 50 lbs. of the above
mixture must be added to the land.
10°. Special manure for tobacco.—Tobacco leaves, as we have seen
(p. 391), contain a large per-centage of inorganic matter. All the
ingredients which are necessary to replace 100 lbs. of the ash of
tobacco leaves are present in the following mixture:—
Bone dust,............... 15 }~ 23 lbs.
Sulphuric acid, ......... 8
Carbonate of potash (dry), ... 31 ...
Carbonate of soda (dry), ...... 5 ...
Carbonate of magnesia, ...... 25
Carbonate of lime (chalk), ... 60 ...
144 lbs.
11°. Special manure for the sugar cane.—From the sugar caneitself,
as we have seen (p. 393), much less ash is obtained than from its
leaves. The following mixture contains what is necessary to re-
place 100 lbs. of the ash of the whole cane, according to the ave-
rage composition given in a preceding lecture (p. 393).
SPECIAL MANURE FOR COFFEE AND THE SUGAR CANE. 645
Bone dust, tº º ſº e g g g tº e tº e º ſº tº º 26 }. 39 lbs.
Sulphuric acid,......... 13
Carbonate of potash (dry), ... 33 ...
Carbonate of soda (dry), ...... 8 ...
Carbonate of magnesia, ...... 17 ...
97 lbs.
I do not know how much ash is left by the green came when
burned, and therefore I cannot say how much of the above mixture
should be added for every ton of canes gathered from the field.
Instead of applying the entire mixture as above given, the came
ash from the boiling furnaces (p. 629), may be mixed or ground
up with potash and soda in the following proportions:
Cane ash, ........................ 67 lbs.
Carbonate of potash (dry), ... 29 ...
Carbonate of soda (dry), ...... 4 ...
100 lbs.
Instead of the carbonate of potash, two or three times as much
Wood ashes may be employed with economy and advantage.
As there is little bone dust in this mixture, and therefore little
nitrogen, an addition of Peruvian guano or of 10 per cent of an
ammoniacal salt would improve it for use on poorer soils.
12°. Special manure for the coffee tree.—The coffee bean leaves
about 3 per cent. of ash (p. 393)—or a ton and a half of coffee car-
ries off 100 lbs. of inorganic matter from the soil. The following
mixture will replace what is thus lost by the land. It ought to be
dug in about the roots of the coffee tree early in spring, in quan-
tity proportional to the annual yield of the tree in coffee.
Bone dust, ............ 52 ... 78 lbs,
Sulphuric acid,......... 26 J
Carbonate of potash (dry), ... 75 ...
Carbonate of soda (dry), ...... 25 ...
Carbonate of magnesia, ...... 24 ...
202 lbs.
13°. Special manure for the flaw crop.–Public attention is at
present so much drawn to the cultivation of flax, that the follow-
646 SPECIAL MANURE FOR THE FLAX PLANT.
ing recipe for supplying what is carried off by the seed and stem of
this plant respectively cannot fail to be interesting.
a. The substances contained in 100 lbs. of the ash of the seed are
supplied by the following mixture:
Bone dust, .................. 144 } 216 lbs.
Sulphuric acid, ............
Carbonate of potash (dry), ......... 36 ...
Carbonate of soda (dry), ............ 6 ...
Carbonate of magnesia, ............ 22 ...
280 lbs.
Linseed leaves 6% per cent. of ash, so that for every 100 lbs. of
linseed reaped, 13 lbs. of the above mixture require to be added
to the land.
b. The following mixture will supply what is contained in 100
lbs. of the ash of the stem of the flax.
Bone dust, .................. 50
Sulphuric acid, ............... 25 75 lbs.
Carbonate of potash (dry), ......... 17 ...
Carbonate of Soda (dry), ............ 20 ...
Carbonate of magnesia, ............ 21 ...
133 lbs.
The dry stem of the flax plant leaves 5 per cent. of ash; every
ton therefore carries off the land 112 lbs. of inorganic matter, to
replace which 150 lbs. of the above mixture must be added. If
this be carefully done, and if that which the seed carries off be
also replaced, and if the fermented scutchings be returned to the
land, the culture of flax will cease to be exhausting.
In regard to the above special manures, I would observe fur-
ther,
a. That I have omitted all mention of vegetable matter in the
recipes I have given. If the soil be rich in vegetable matter—if
straw or green herbage or farm-yard manure be ploughed in—or
if vegetable composts be added to the land every two or three years,
the consideration of this vegetable matter may be left entirely out
IREFUSE OF MANUFACTORIES MAY BE USED. 647
of view. Where such is not the case, saw-dust may be mixed
with the saline substances, or dried peat or any other convenient
vegetable substance.
b. The silica of the plant and the oxide of iron are omitted from
the above prescriptions, because, as I believe, they are usually pre-
sent in sufficient quantity in the soil, and in a form in which the
roots of plants can readily take them up. If the soil to which the
mixture is to be applied is known to contain any of the ingredients
of the above special manures in sufficiently large quantity, then
these may be omitted altogether in preparing the mixtures. Mag-
nesia, for example, is present in many soils in such abundance as
to make the addition of it in a manure by no means necessary.
This is one of those beneficial results which flow from a knowledge
of the composition of the soil.
c. Instead of the pure ingredients or salts mentioned in the pre-
scriptions, the refuse of manufactories, or other mixtures, natural
or artificial, may be employed, provided their composition is accu-
rately known. By the use of such substances the manufacture of
these manures may be considerably cheapened,—a circumstance
which illustrates the importance of having the refuse materials of
all our manufactories carefully analysed.
d. In all the crops above-mentioned, with the exception of flyx
and the turnip, I have supposed the straw or tops to be returned
to the land in some form or other. Where this is not done, as in
the case of Indian corn and rice, an additional manuring must be
given, with a mixture made up as the above are in conformity with
the average composition of the ash of the stem or straw of these
plants. (See p. 374 and 376.) -
*/
LECTURE XX.
Use of lime as a manure. Value of lime in improving the soil. Of the composition
of common and magnesian lime-stones. Burning and slaking of lime. Changes
which slaked lime undergoes by exposure to the air. Various natural states in
which carbonate of lime is applied to the land. Marl-shell and coral sand,-
lime-stone sand and gravel-crushed lime-stone. Chemical composition of various
marls, corals, and shell and lime-stone sands. Their effects on the soil. Use of
chalk as a manure. Is lime indispensable to the fertility of the soil P States of
combination in which lime exists in the soil. Quantity of lime to be applied.
Ought it to be applied in large or small doses P Form in which it may be most
prudently used. Use and advantage of the compost form. When it ought
to be applied in reference to the season—to the rotation—and to the appli-
cation of manure. Its general and special effects on different soils and crops,
Circumstances by which its action is modified. Effects of an overdose—over-
liming. Length of time during which its effects are perceptible. Theory of the
action of lime. Sinking of lime into the soil. Why the application of lime must
be repeated. Of lime as the food of plants. Chemical action of lime—exerted
chiefly on the organic matter of the soil. I'orms in which organic matter exists in
the soil, and circumstances under which it may be decomposed. General action of
alcaline substances upon organic matter. Special effects of caustic lime upon the
organic matter in the soil. Action of carbonate of lime upon this organic matter.
Comparative utility of burned and unburned lime. Action of lime upon organic
substances which contain nitrogen. How these chemical changes benefit vegetation.
Why lime must be kept near the surface. Action of lime upon the inorganic or
mineral matter of the soil. How lime exhausts the land. Is this exhaustion ne-
cessary 2 Action of lime on living animals and vegetables. Suggestions of theory.
Use of silicate of lime.
HAVING explained the action of the most important saline and
mixed mineral substances which are or may be beneficially applied
to the soil, I have now to draw your attention to the use of lime
—the most valuable and the most extensively used of all the mi-
neral substances that have ever been made available in practical
agriculture. It has with much reason been called “the basis of
all good husbandry.” It deserves, therefore, your most serious
attention as practical men, and the application on my part of every
chemical light by which its usefulness may be explained and your
practice guided. This consideration will justify me in dwelling
upon it with some detail, and in illustrating the various points,
4
COMPOSITION OF COMMON LIME-STONES. 649
both theoretical and practical, which present themselves to us, when
we study the history of its almost universal application to the soil.
§ 1. Of the composition of common and magnesian lime-stones.
1°. Common lime-stones.—Lime is never met with in nature ex-
cept in a state of chemical combination (p. 42) with some other
substance. That which is usually employed in agriculture is met
with in the state of carbonate.
Carbonate of lime, or common lime-stone, consists of lime in
combination with carbonic acid. When perfectly pure and dry,
these substances are contained in it in the following proportions:
g g Per cent.
Carbonic acid, 43.7
Lime, ......... 56-3 or one ton of pure dry carbonate of lime
tºmºsºmºmºsºs contains 11} cwts, of lime.
100
Lime-stones, however, are seldom pure. They always contain a
sensible quantity of other earthy matter, chiefly silica, alumina,
and oxide of iron, with a trace of phosphate of lime, sometimes of
potash and Soda, and often of animal or other organic matter.
In lime-stones of the best quality the foreign earthy matter or im-
purity does not exceed 5 per cent. of the whole—while it is often
much less. The chalks and mountain lime-stones are generally
of this kind. In those of inferior quality the impurity may amount
to 12 or 20 per cent., while many calcareous beds are met with in
which the proportion of lime is so small that they will not burn
into agricultural or ordinary building lime—refusing to slake or
to fall to powder when moistened with water. Of this kind is the
Irish calp, the lime-stone modules which are burned for the manu-
facture of hydraulic limes or cements, and many beds of lime-
stone in various parts of the country, to which little attention has
hitherto been paid." .*
Two such lime-stones, which occur in beds on the small coal-
field of Broxburn, a few miles west of Edinburgh, were found in
my laboratory to consist of
* Thus that of Aberthaw contains about 86 per cent. of carbonate of lime and 11
of clay, &c.; that of Yorkshire 62 of carbonate of lime and 34 of clay; and that of
Sheppy 66 of carbonate of lime and 32 of clay. These lime-stones are burned, and
then crushed to an impalpable powder, which sets almost immediately when mixed up.
with water.
650 COMPOSITION OF HYDRAULIC LIME-STONES.
No. 1. †No. 2, below No. 1.
Carbonate of lime, ........... ............ 56-32 62-72
Carbonate of magnesia, .................. 2-14 7-89
Oxide of iron, ........................... .. 3'36 3'95
Soluble alumina (soluble in acids),...... 0-22 O' [8
Alumina in state of silicate,............... 15°()2 2.11
Lime in state of silicate, ....... • * * * * * * * * * * 0.18 0-83
Silica, ... .................................... 21:08 20. 13
Water, ....................................... 1.90 0-98
100-22 98.79
These lime-stones when burned do not slake, but if ground to
powder they set immediately when mixed with water, and form an
excellent cement. It is easy to ascertain the quantity of earthy
matter in a lime-stone, by simply introducing a known weight of
it into cold diluted muriatic acid, and observing or weighing the
part which, after 12 hours, refuses to dissolve or to exhibit any ef-
fervescence. It is to the presence of these insoluble impurities
that lime-stones in general owe their colour, pure carbonate of
lime being perfectly white.
2. Magnesian lime-stone.—Though often nearly white, the mag-
nesian lime-stones of our island are generally of a yellow colour.
They cannot by the eye be distinguished from common lime-stones
of a similar colour, but they are characterised by containing a car-
bonate of magnesia, sometimes in large proportion. Pure carbo-
nate of magnesia consists of
Per cent.
Carbonic acid, 51.7
Magnesia,......48-3 l or one ton of pure dry carbonate of magne-
sia contains 95 cwts, of magnesia.
100
It contains, therefore, a considerably larger proportion of car-
bonic acid than is present in carbonate of lime,
Magnesian lime-stone is very abundant, is indeed the prevailing
rock in many parts of England (p. 470), but the proportion of car-
bonate of magnesia it contains varies very much not only in diffe-
rent localities, but often in different beds in the same quarry.
Thus several varieties of this lime-stone, examined by myself, from
different parts of the county of Durham, contained the two car-
bonates in the following proportions. The letters A and B in the
following table indicate different beds or layers of stone in the
same quarry.
COMPOSITION OF MAGNESIAN LIME-STONES.
*
651

Alumina,
Carbonate | Carbonate | Oxide of Insoluble
of of Iron, and matter
Lime. Magnesia. | Phospho- e
ric acid.
Garmondsway ...... 97.5 2.5 trace trace |Hard compact grey.
Stony-gate ............ 98.0 1°6] 0.27 | 012 ||º:
Fulwell ............... 95-0 2. l 0°3 26 (Hºlºrys.
talline yellow.
Seaham (A) ......... 96'5 2-3 0-2 1-0 H. flºaned
... (B) ......... 95-0 1-3 . O-2 3.5 Hard porous brown.
Hartlepool ..... ...... 54°5 44'93. 0.33 0.24 |Oolitic yellow.
Humbledon Hill (A)| 57.9 41°8 P 028 (Pººnerinal co-
(B) 60°41 38.78 p 0-81 { Consisting in part of
g encrinal columns.
Ferryhill............... 54°l 4472 l'58 4'6 Yellowish compact.
Some of these varieties contain very little carbonate of magnesia,
and, therefore, are found to produce excellent lime for agricultural
purposes—while in others this substance forms nearly one-half of the
whole weight of the rock. Similar differences prevailin almost every
district where the magnesian lime-stone is found. Thus in York-
shire, the upper or Knottingley lime-stone usually contains scarcely
any—while the under or Weldom lime contains from 30 to 40 per
cent. of carbonate of magnesia.
This admixture of magnesia in greater or less quantity is not
confined to the lime-stones of the magnesian lime-stone formation
properly so called. It is found in sensible quantity in the lime-
stones of nearly every geological formation, and there are few ma-
tural lime-stones of any kind in which traces of it may not be dis-
covered by a carefully conducted chemical examination.
This fact appears from the following table, showing the compo-
sition of limestones from various geological formations, as deter-
mined in my laboratory:—

Organic matter, ... ..
Carbonate of lime, ...
Carbonate of magnesia
Oxide of iron and
alumina,
Insoluble siliceous
matter,
Coal Mountain Qld red Slate rocks.
}]]68 Sll]'éS. lime-stone. sandstone.
Burdie- * *
house Stanhope, Nº. Langton, Ardgour, i.
near Ed- Durham. |a. Berwickshire. Argyle. In Wel
e derland Il CSS.
inburgh.
p p ()'50 p p g p
80°52 95-06 || 94'32 47°00' 39-05 || 89°99 || 93-82
0.91 2°46 2:00 38.04 30-25 5' 20 1:64
5'87 1:00 l 1:99) 1:39 O'96 0.09
2.93
11:56 || 1:32) 12.97. 29-27 || 3:72 || 3:55
98’86 99.84 . 90°75 100. 90-06 || 99.87 || 00:
652 OF THE BURNING AND SIA|KING OF LIME.
The impure lime-stone from the thin beds which occur in the old
red sandstone of the upper part of Berwickshire are very rich in
magnesia, Experience shows that all such lime-stones must be add-
ed sparingly to the land.
The simplest method of detecting magnesia in a lime-stone is to
dissolve it in diluted muriatic acid, and then to pour clear lime
water into the filtered solution. If a light white powder fall, it is
magnesia. The relative proportions of magnesia in two lime-stones
may be estimated pretty nearly by dissolving an equal weight of
each, pouring the filtered solutions into bottles which can be cork-
ed, and then filling up both with lime water. On subsiding, the
relative bulks of the precipitates will indicate the respective rich-
mess of the two varieties in magnesia. -
§ 2. Of the burning and slaking of lime—composition of the hydrates
of lime and magnesia.
1°. Burning.—When carbonate of lime or carbonate of mag-
nesia is heated to a high temperature in the open air the carbonic
acid they severally contain is driven off, and the lime or magnesia
remains in the caustic state. When thus heated the carbonate of
magnesia parts with its carbonic acid more speedily and at a lower
temperature than carbonate of lime.
On the large scale this burning is conducted in lime-kilns, one
ton of good lime-stone yielding about 11 cwts, of burned, shell,
quick or caustic lime, (p. 649).
2°. Slaking.—When this shell or quick-lime, as it is taken from
the kiln, is plunged into water for a short time and then withdrawn,
or when a quantity of water is poured upon it, heat is developed,
the lime swells, cracks, gives off much watery vapour, and finally
falls to a fine, bulky, white, grey, or reddish powder. These ap-
pearances are more or less rapid and striking according to the
quality of the lime, and the time that has been allowed to elapse
after the burning, before the water is applied. All lime becomes
difficult to slake when it has been for some time exposed to the
air. When the slaking is rapid, as in the rich limes, the heat pro-
duced is sufficient to kindle gunpowder strewed upon it, and the
increase of bulk is from 2 to 3} times that of the original lime
shells. If the water be thrown on so rapidly or in such quantity
as to chill the lime or any part of it, the powder will be gritty, will
HYDRATES OF LIME AND MAGNESIA. 653
contain many little lumps which refuse to slake, will also be less
bulky and less minutely divided, and therefore will be less fitted
either for agricultural or for building purposes. -
When quick-lime is left exposed to the open air, or is covered
over with sods in a shallow pit, it gradually absorbs water from the
air and from the soil, and falls, though much more slowly, and with
little sensible development of heat, into a similar fine powder. In
rich limes the increased bulk may be 3 or 3} times; in the poorer
or such as contain much earthy matter, it may be less than twice
that of the newly burned shells.
3°. Composition of hydrate of lime.--When quick-lime is thus
slaked it combines with the water which is added to it, and becomes
converted into a compound which among chemists is known by
the name of hydrate of lime. This hydrate consists of
Per cent.
Lime,...... 76 or one ton of pure burned lime becomes
Water, ... 24 J about 26% cwt. by perfect slaking.
100
It is rare, however, that lime is so pure, or so skilfully and per-
fectly slaked, as to take up the whole of this proportion of water,
or to increase quite so much as one-third part in weight. -
4°. Composition of hydrate of magnesia.--When calcined or
caustic magnesia is slaked, it also combines with water, but with-
out becoming so sensibly hot as quick-lime does and forms a hy-
drate, which consists of
Per cent.
Magnesia, 69-7 or one ton of pure burned magnesia be-
85 5 d
Water, ... 30.3 ſ comes 283 cwts, of hydrate.
*-
100
When magnesian lime is slaked, the fine powder which is ob-
tained consists of a mixture of the two hydrates of lime and mag-
nesia, in proportions which depend of course upon the composition
of the original lime-stone.
An important difference between these two hydrates is this, that
the hydrate of magnesia will harden under water or in a wet soil
in about 8 days, forming a hydraulic cement. Hydrate of lime
will not so harden, but a mixture of the two in the proportions in
654 FURTHER CHANGES UNDERGONE BY SLAKED LIME.
which they exist in the Hartlepool, Humbledon, and Ferry-hill
lime-stones (above, p. 651), and in the Weldon lime-stone of
Yorkshire, will harden under water, and form a solid mass.
In the minute state of division in which lime is applied to the
Soil, the particles, if it be a magnesian lime, will, in wet soils,
or in the event of rainy weather setting in immediately after
its application, become granular and gritty, and cohere occa-
sionally into lumps, on which the air will have little effect. This
property is of considerable importance in connection with the fur-
ther chemical changes which slaked limes undergo when exposed
to the air or buried in the soil. -
§ 3. Changes which the hydrates of lime and magnesia undergo by
prolonged exposure to the air.
When the hydrates of lime or magnesia obtained by slaking are
exposed to the open air, they gradually absorb carbonic acid from
the atmosphere, and tend to return to that state of carbonate in
which they existed previous to burning. They sometimes require
a very long time, however, before they are completely brought into
this state. In some walls 600 years old, the lime used for mortar
has been found to have absorbed only one-fourth of the carbonic
acid mecessary to convert the whole into carbonate; in others,
built by the Romans 1800 years ago, the proportion absorbed has
not exceeded three-fourths of the quantity contained in natural
lime-stones. In damp situations the absorption of carbonic acid
proceeds most slowly. -
1°. Change undergone by pure lime during spontaneous slaking.—
In consequence, however, of the strong tendency of caustic lime
to absorb carbonic acid, a considerable quantity of the hydrate of
lime first formed, when lime is allowed to fall spontaneously in
the air, becomes changed into carbonate during the slaking of the
rest. But, when it has all completely fallen, the rapidity of the
absorption ceases, and the fine slaked lime consists of
Carbonate of lime, ..................... 57-4
e e 2.
Hydrate of lime, lime,... 32.4 } 42-6
water, 10-2
*=yes-s
100
or, a ton of lime, left in the open air till it has completely fallen to
CHANGES AFTER SLAKING IN THE ORDINARY WAY. 655
powder, contains about 8% cwt. in the state of hydrate. If left to
slake in large heaps, the lime in the interior of those heaps will
not absorb so much carbonic acid till after the lapse of a very con-
siderable time. More caustic lime (hydrate) also will be present
if it be left to slake, as is often done for agricultural purposes, in
shallow pits covered with sods, to defend it from the air and the
rains.
After the lime has attained the state above described,—which is
a chemical compound * of carbonate with hydrate of lime, the
further absorption of carbonic acid from the air proceeds very
slowly, and is only completely effected after a comparatively long
period.
2°. When slaked in the ordinary way lime falls to powder,
without having absorbed any notable quantity of carbonic acid.
Numerous small lumps also remain, which, though covered with
a coating of hydrate, have not themselves absorbed any water.
The aborption of carbonic acid by this slaked lime is at first very
rapid, so that where the full effect of caustic lime upon the soil
is required, it ought to be ploughed in as early as possible. But
the absorption gradually becomes more slow, a variable propor-
tion of the compound of carbonate and hydrate above described is
formed, and even when thinly scattered over a grass field, an en-
tire year may pass over without effecting the complete conversion
of the whole into carbonate.
The following table shows the changes in composition and
weight which a ton of pure lime-stone undergoes during the pro-
cesses of burning, slaking, and subsequent exposure to the air.



& After exposure
Composition. Native After After | Spontaneously to the air or
lime-stone. burning. slaking. slaked. in the soil.
Cwts. Cwts. Cwts. Cwts. Cwts.
Lime, ............ 1} 11} 1.1% 11} 11}
Carbonic acid, ... 8; *- *m-. 2; 8;
Water, ... ........ sº-sº-º: * 3% l; -
Total weight, 20 l l; 14; 15; 20
3°. Calcined or burned magnesia, either in the pure state, or
when mixed with quick-lime, as it is in the magnesian limes—ab-
* This compound consists of one atom of carbonate of lime (CaO + CO2) com-
bined with one of hydrate (CaO + HO), and is represented shortly by Ca Č4. Öa H
—in which Ca denotes calcium (p. 334), Ca O or Ča oxide of calcium or lime,
CO2 or Č carbonic acid, (p. 64), and HO or H water (p. 47.)
656 OF CALCINED AND SLAKED MAGNESIA.
sorbs carbonic acid more slowly, and by mere exposure to the
air will probably never return to its original condition of carbonate.
When allowed to slake spontaneously, three-fourths of it be-
come ultimately changed into carbonate, and form a compound of
hydrate and carbonate similar to the common uncalcined magne-
sia of the shops. This compound usually consists of
Carbonate of magnesia, ............ 69°37
Hydrate of magnesia,............... 16:03
Water, .............................. 14:60
100%
and it undergoes no further change by continued exposure to the
air.
But if slaked by the direct application of water, magnesia, like
lime, forms a hydrate only, without absorbing any sensible quan-
tity of carbonic acid. The hydrate thus produced is met with in
the form of mineral deposits (magnesite) on various parts of the
earth's surface, and in this mineral form is not known to undergo
any change or to absorb carbonic acid though exposed for a great
length of time to the air. When magnesian limes are slaked by
water, therefore, the magnesia they contain may remain in whole
or in part in the caustic state (of hydrate), and may change with
extreme slowness even when exposed to the air. When left to spon-
taneous slaking, one-fourth of it at least will always remain in the
caustic state, however long it may be exposed to the air.
Should a lime be maturally of such a kind, or be so mixed with
the ingredients of the soil as to form a hydraulic cement or an or-
dinary mortar, which will solidify when rains come upon it, or
when the natural moisture of the soil reaches it—the absorption of
carbonic acid will in a great measure cease as it becomes solid,
and a large proportion of the lime will remain caustic for an in-
definite period.
§ 4. States of chemical combination in which lime may be applied
to the land.
There are, therefore, four distinct states of chemical combina-
tion, in which pure lime may be artificially applied to the land.
* It is represented by the formula 3 (Mg Č + H) + M. H. The common mag-
nesia of the shops contains sometimes more and sometimes less water than is here
given.
STATES IN WHICH LIME IS APPLIED. 657
10. Quick-lime or lime shells, in which the lime as it comes from
the kiln is uncombined either with water or with carbonic acid.
29. Slaſhed lime or hydrate of lime, in which by the direct appli-
cation of water it has been made to combine with about one-fourth
of its weight of water.
In both these states the lime is caustic, and may be properly
spoken of as caustic lime. -
39. Spontaneously slaked lime, in which one-half of the lime i
combined with water and the other half with carbonic acid. In
this state it is only half caustic.
49. Carbonate of lime—the state in which it occurs in mature,
and to which burned lime, after long exposure to the air, more
or less perfectly arrives. In this state lime possesses no caustic
or alcaline (p. 79, note) properties, but is properly called mild
lime. -
5%. Bi-carbonate of lime may be adverted to as a fifth state of
combination, in which, as I have previously explained to you (p.
65), nature often applies lime to the land. In this state it is com-
bined with a double proportion of carbonic acid, and is to a
certain extent soluble in water. Hence, springs are often im-
pregnated with it, and the waters that gush from fissures in lime-
stone rocks spread it through the soil in their neighbourhood, and
sweeten the land.
I shall hereafter speak of these several states under the names
of quick-lime, hydrate of lime, spontaneously slaked lime, carbo-
mate of lime, and bi-carbonate of lime. By adhering to these
strictly correct names, we shall avoid some of that confusion into
which those who have hitherto treated of the use of lime as a ma-
nure have unavoidably fallen. The term mild, you will under-
stand, applies only to that which is entirely in the state of carbo-
720te. -
Magnesia, in the magnesian limes, may in like manner be either
in the state of calcined magnesia, of hydrate of magnesia, of spon-
taneously slaked—meaning by this the compound of hydrate with
carbonate—of carbonate of magnesia, or of bi-carbonate of magne-
sia. The last of these is soluble in 48 times its weight of water.
Hence a gallon of water will dissolve 5 ounces of the bi-carbonate
containing 13 ounces of magnesia.
T t
658 NATURAL FORMS OF CARBONATE OF LIME.
§ 5. Of the various natural forms in which carbonate of lime is
applied to the land.
In the umburned or natural state, lime is met with on the earth's
surface in numerous forms—in many of which it can be applied
largely, easily, and with economy to the land.
l°. Marl-Of these forms, that of marl occurs most abundant-
ly, and is most extensively used. By the term marl is understood
(p. 444) an earthy mixture, which contains carbonate of lime, and
effervesces more or less sensibly when an acid (vinegar or diluted
muriatic acid—spirit of salt) is poured upon it. Generally, also,
the tenacious marls, when introduced into water, lose their cohe-
rence, and gradually fall to powder. This latter test is often em-
ployed to distinguish between marly and other clays, yet the fall-
ing asunder, though it afford a presumption, is not a sure proof
that the substance tried is really a marl.
Marls are of various colours, white, grey, yellow, and blue.
They possess also various degrees of coherence—some occurring
in the form of a more or less fine, loose, sandy powder; others be-
ing tenacious and clayey ; and others, again, hard and stony.
These differences arise in part from the kind and proportion of the
earthy matters they contain, and in part, also, from the nature of
the locality, moist or dry, in which they are found. The hard and
stony varieties are usually laid upon the surface of the field, and
exposed to the pulverising influence of a winter's frost before they
are either spread over the pasture or ploughed into the arable
land. Some rich marls consist in part or in whole of broken and
comminuted shells, which clearly indicate the source of the calca-
reous matter they contain.
The characteristic property of true marls of every variety is, I
have said, the presence of a considerable per-centage of carbonate
of lime in the state of a fine powder, and, in general, diffused uni-
formly through their entire mass. To this calcareous matter the
chief efficacy of these marls is owing. They often contain, how-
ever, other chemical compounds to which the special efficacy of
certain varieties has sometimes been ascribed. It may not be im-
proper therefore to direct your attention to the following table, in
which the composition of several foreign marls is represented, after
the analyses of Sprengel,
COMPOSITION OF DIFFERENT MARLS. 659
COMPOSITION OF MARLS FROM
Luneburg Osna- Magde- || Bruns- | Weser-
***ē. bruck. burg. wick. marsh.
Powdery. Stony. Clayey. | Loamy. | Powdery.
Quartz-sand and silica, ...... 5-6 23:0 58°4 73°4 78-9
Alumina, (soluble), ......... ()'4 10-0 8’4 1. 3.1
Oxides of iron, ............... 4'2 1-9 6-7 3.2 3-8
Oxide of manganese, ...... trace trace 0.3 0.3 0.3
Carbonate of lime, ..... ... 85-5 35'0 18-2 18' l 8-2
Carbonate of magnesia,...... 1:25 0.9 3.8 l'5 3.0
Sulphuret of iron, ........... tº gº tº 7.3 tº e sº tº e
Potash and soda, ............ 0-05 trace 1.6 0-8 0-9
Common salt, ............... O'03 trace trace trace 0.1
Gypsum, ......... . . . . . . . . . . . . . 0.06 ()'9 2-l 0.1 0.5
Phosphate of lime, (bone 2-3 0.5 O'5 0-7 1.2
earth), ..................
Nitrate of lime,............... 0.01 g & &
Organic matter, ............... 0.6 20:5
| 00 } 00 100 } 00 | 00

Several reflections will occur to you on looking at these tables
—such as
First—that marls differ very much in composition, and there-
fore must differ very much also in the effects which they are capa-
ble of producing when applied in the same quantity to the same
kinds of land. .
Second—that, among other differences, the proportion of car-
bonate of lime is very unlike—in some varieties amounting to 85
lbs. out of every hundred, while in others as little as 8 lbs. are
present in the same weight. Very different quantities of these se-
veral marls must therefore be applied to the land if they are to
produce an equal liming or to add equal quantities of lime to
the soil. Each of three persons may be adopting the best prac-
tice with his own marl—though the one add only 12 to 20 tons
per acre, while the second adds 50 to 60, and the third 100 to 120
tons.
Third—that the proportion of phosphate of lime (bone-earth)
is in some marls considerably greater than in others. Thus every
ton of the first of the above marls would convey to the soil 52 lbs.
of bone-earth—about as much as is contained in a cwt. of bone-
dust—while the second would add only 11 lbs. In so far as their
effects upon the land depend, or are influenced by the presence of
this substance, therefore, their agricultural value must also be very
different. And
06() UNIIRE EFFECTS OF DIFFERENT MARLS.
Fourth—that the mechanical effects of these marls upon the soil
to which they are added must be very unlike, since some contain
70 or 80 lbs. of sand in every hundred—while others contain a
considerable quantity of clay. The opening effects of the one marl,
and the stiffening effects of the other, when they are laid on in
large quantities, cannot fail to produce very different alterations in
the physical characters of the soil.
In Scotland beds of marl occur in many places at the bottom of
existing lakes and below deposits of peat which occupy the place of
more ancient lakes. These marls are generally pure white, and
are made up for the most part of the shells and other remains of
animals more or less minute which have lived in the waters of
the lake. They contain not unfrequently a considerable propor-
tion of animal matter, which adds much to their agricultural
value, Such is the case with two marls from the north of Scot-
land, analysed in my laboratory, and of which the following is the
composition :
Near Tain, Near Wick,
Ross-shire. Caithness.
Organic (animal) matter, ...... . ...... 14.13 0.36
Carbonate of lime, ............... º º a º e º e 81.4l 86.68
Carbonate of magnesia, ........... ...... 0.60 2.02
Phosphate of lime,.................. * * * * p 0.03
Alumina and oxide of iron, ............ 0.76 0.95
Silica, ...... … 2.62 3.96
99.52 100.
The silica in these marls is chiefly derived from the remains of
very minute infusorial animals, which are often still alive in the
marl when recently dug up. It is not unlikely that some of it
may be in a condition in which the roots of plants may be able to
take it up.
2°. Shell sand.—The sands that skirt the shores of the sea are
found in many localities to be composed, in large proportion, of
the fragments of broken and comminuted shells. These form a
calcareous sand, mixed occasionally with portions of animal matter,
and with saline substances derived from the sea.
On the coast of Cornwall this is the case in numerous places.
From these spots the sand is transported to a distance of many
miles into the interior for the purpose of being laid upon the land.
4
SHELL SANDS OF OUR SEA COASTS. 661
It has been estimated” that seven millions of cubic feet are at pre-
sent employed every year in that county for this purpose.
On the western coast of Scotland, also, and on the shores of the
island of Arran and of the Western Isles, this shell sand abounds,
and is applied extensively, and with remarkably beneficial effects,
both to pasture lands and to the peaty soils that cover so large an
area in this remote part of Scotland. It is chiefly along the coasts
that it has hitherto been extensively employed, and it is transported
by sea to a distance of 80 or 100 miles. “In the island of Barray
alone, there are four square miles of shells and shell sand of the
finest quality and of an indefinite depth.”f When covered with a
dressing of this shell sand the peaty surface becomes covered with
a sward of delicate grass—and the border of green herbage that
skirts the shores of these islands, in so many places, is to be as-
cribed either to the artificial application of such a dressing or to
the natural action of the sea winds in strewing the fine sand over
them, when seasons of storm occur.
The coast of Ireland is no less rich in shell sand in many parts
both of its northern and southern coasts. A century and a half
ago, it is known to have been used in the north of Ireland—and
nearly as long ago to have been brought over to Galloway on the
opposite coast of Scotland for agricultural purposes (Macdonald).
On the coasts of France, and especially in Brittany, it is obtained
in large quantity, and is in great demand. It is applied to the
clay soils and to marshy grass lands with much advantage, and is
carried far inland for this purpose. It is there called trez, and is
laid on the land at the rate of 10 to 15 tons per acre. On the
southern coasts of France, where shell sand is met with, it is known
by the name of tanque or tangue.
The shell sand of Cornwall contains from 40 to 70 per cent. of
carbonate of lime, with an equally variable small admixture of
animal matter and of sea salt. The rest is chiefly siliceous sand.
Other varieties have a similar composition. Two specimens of
tangue from the south of France, analysed by Vitalis, and one of
* De la Beche's Geological Report on Cornwall, &c. p. 480.
+ Macdonald's Agricultural Survey of the Hebrides, p. 401.
:: Payen and Boussingault, Annales de Chim, et de Phys., third series, iii. p. 92.
662 COMPOSITION OF SHELL SANDS.
shell sand from the island of Isla, partially examined by myself,
consisted of
Tangue, from the Shell Sand,
South of France. from Isla.
Sand, chiefly siliceous, ......... 20.3 40 }* 65-7
Alumina and oxide of iron, ... 4-6 4-6 71-7 to 65-7
Carbonate of lime,......... ..... 66-0 47-5 28 to 34
Phosphate of lime, ... ... ..... ? 2 0.3
Water, and loss, ....... .... .. 9° 1 7.9
100 100 100
On the coast of Normandy an interesting variety of what may
be called infusorial sand occurs along and mixed with the shell
sand. It is in the state of a fine meal, and is greatly preferred by
the local farmers to the usual shell sand which abounds along the
shore.
This fine sand was amalysed in my laboratory and found to con-
sist of
Organic matter, ............ 5-06
Carbonate of lime, ....... ... 43.50
Sulphate of lime, (gypsum) 0:32
Magnesia, ......... e s e s e e e º e trace
Common salt, ............... 101
Chloride of calcium, ...... O'73
Alumina, ................ ..... 0-17
Oxide of iron, ............... 1-20
Siliceous matter, ..... © e º a tº a º 47.69
99.68
From the above analysis it appears that the value of this mealy
sand does not depend solely upon the lime it contains. It is de-
rived in some measure also from the 5 per cent. of organic matter,
and the 2 per cent. of soluble salts which are present in it. The
minute state of division in which the lime exists is also in its favour.
When examined under the microscope, this sand is seen to con-
sist of minute crystals of carbonate of lime, of broken limbs and
claws of very small crustaceous animals, and of the shells or sheaths
of numberless infusoria. These shells or sheaths belong in large
proportion to species, which, instead of lime, absorb silica from the
- 3
USE OF CORAL SAND. 663
water in which they live, and form flinty instead of calcareous shells
or sheaths. - -
The siliceous matter in the marl exists in the state of an exceed-
ingly fine powder, and it is from these infusorial animals that it
appears chiefly to be derived.
39. Coral sand is similar in its nature to the shell sand with
which it is often intermixed on the sea shore. It is collected in
considerable quantities, however, by the aid of the drag—being
torn up by the fishermen in a living state—on the coasts of Ire-
land (Bantry Bay and elsewhere), and on the shores of Brittany,
especially near the mouths of the rivers. The coral sand raised
on Bantry Bay alone produces L.4000 or L.5000 a-year to the
boatmen who collect it, and to the peasants who convey it up the
country. In this fresh state it is preferred by the farmer, pro-
bably because it contains both more saline and more animal
matter. This animal matter enables it to unite in some measure
the beneficial effects which follow from the application of marl and
of a small dressing of farm-yard or other valuable mixed manure.
Payen and Boussingault ascribe the principal efficacy of the shell
and coral sands to the small quantity of animal matter which is
present in them. These chemists estimate the relative manuring
powers of different substances applied to the land by the quantities
of nitrogen which they severally contain, and thus, compared with
farm-yard manure, attribute to the shell and coral sands the fol-
lowing relative values:—
Contain of Relative
Nitrogen. Values.
100 lbs. of farm-yard manure, ............ 0°40 Jbs. 100
of coral sand (Merl), ...... . . . . O'512 lbs. 128
of shell sand (Trez), ..... ......... 0°l 3 lbs. 32y”
That is to say, that, in so far as the action of these substances
is dependent upon the nitrogen they contain, fresh coral sand is
nearly one-third more valuable than farm-yard manure, while fresh
shell sand is only equal in virtue to one-third of its weight of the
same substance.
Though much importance is not to be attached to such methods
of estimating the relative values of manuring substances by the
proportions of any one of the ingredients they happen to contain—
* Annales de Chim. et de Phys., third Series, iii. p. l ()3.
664 COMPOSITION OF CORALS.
yet the fact, that so much animal matter is occasionally present in
living corals, accounts in a satisfactory manner for their immediate
effects upon the land. The animal matter acts directly and dur-
ing the first year; the carbonate of lime often shows its beneficial
influence most distinctly when two or three years have passed.
But the phosphoric acid in the recent corals is not without its
value as an application to the land. They all contain a small pro-
portion of phosphate of lime, which the roots of plants will no
doubt succeed in extracting. An elaborate examination of about
forty species of recent corals has lately been published by Mr
Silliman of Yale College, showing especially the proportion of
phosphates and of organic matter they respectively contain, From
the results of his inquiry I extract the following:

Porites. Madrepora. Pocillipora. Astraea.
No. 2.
No. 3.
No. 1.
No. 2.
No. 1.
No. 2.
No. 1.
No. 2.
Carbonate of lime, ...
Phosphates, flº)
rides, and silica, ſ”
Organic (animal) }
matter, a € $
93.875
1 '501
4'564
89°864
0.705
9° 431
92°815
0-600
(3°585
93.297
2°450
4'253
93'60
1 ‘90
4°50
93-848
0 °550
5' 602
96.551
0-262
3.187
91.782
2-100
6' 118
100°
100'
100°
100°
100-
100'
100'
100°
The proportion of animal matter in some of these corals is
large, as was the case with the coral sand examined by Boussin-
gault and Payen. The percentage of phosphates is small; but if we
consider that many tons of coral sand are laid upon a single acre,
we shall see that the application even of the phosphates may on the
whole be very considerable. If we take the proportion of phos-
phate of lime at only a quarter of a per cent, ten tons of the coral
will contain 55 lbs., or as much as is present in a hundred weight
of common bone dust.
49. Limestone sand and gravel.-In countries which aboundin lime-
stone, there are found scattered here and there, in the hollows and on
the hill sides, banks and heaps of sand and gravel, in which round-
ed particles of lime-stone abound. These are distinguished by the
names of lime-stone sand and gravel, and are derived from the de-
cay or wearing down of the lime-stone and other rocks by the ac-
tion of water. Such accumulations are frequent in Ireland. They
are indeed extensively diffused over the surface of that island, as
we might expect in a country abounding so much in rocks of
LIME-STONES MAY SOMETIMES BE CRUSHED. 665
mountain lime-stone. In the neighbourhood of peat bogs these
sands and gravels are a real blessing. They are a ready, most
useful, and largely employed means of improvement, producing,
upon arable land, the ordinary effects of liming, and, when spread
upon boggy soils, alone enabling it to grow sweet herbage and to
afford a nourishing pasture. The proportion of carbonate of lime
which these sands and gravels contain is very variable. I have ex-
amined two varieties from Kilfinane, in the county of Cork (?). The
one, a yellow sand, contained 29 per cent. of carbonate of lime—
the residue, being a fine red sand, chiefly siliceous; the other, a
fine gravel of a grey colour, contained 40 per cent of carbonate of
lime in the form chiefly of rounded fragments of blue lime-stone,
the residue consisting of fragments of sand-stone, of quartz, and of
granite.
The application of such mixtures must not only improve the
physical characters of the soil, but the presence of the fragments
of granite, containing undecomposed felspar and mica (p. 486),
must aid the fertilizing action of the lime-stone with which they
are mixed. -
5°. Crushed lime-stone.—The good effects of calcareous marls
and of lime-stone gravels naturally suggest the crushing of lime-
stone as a means of obtaining carbonate of lime in so minute a
state of division that it may be usefully applied to the soil. Lord
Kames was, I believe, the first who in this country endeavoured
to bring this suggestion into practical operation. He caused ma-
chinery to be erected for the purpose in one of the remotest dis-
tricts of Scotland, but the plan seems never to have obtained a
proper trial. -
One of the results which, as we have already seen, follows from
the burning of rich lime is this, that it naturally falls to a very
fine powder as it slakes. Where coal or other combustible is cheap,
therefore, it may be reduced to a fine powder by burning, at a less
cost than it could be crushed.
Yet there are two cases or conditions in which crushing might
be resorted to with equal advantage and economy.
First, where coal is dear or remote, while lime-stone and water
power are abundant. There are many inland districts in each of
the three kingdoms where these conditions exist, and in which,
666 PIHYSICAL AND CHEMICAL EFFECTS OF MARLS.
therefore, the erection of cheap machinery might afford the means
of greatly fertilizing the land; and
Second, there are in many localities rocks rich in calcareous
matter, which are nevertheless so impure, or contain so much other
earthy matter, that they cannot be burned into lime. Yet, if crush-
ed, these same masses of rock would form a valuable dressing for
the land. Many lime-stones of this impure character, which are
really useless for building purposes—which do not fall to powder
when burned, and which have, therefore, been hitherto neglected
as useless—might, by crushing, be made extensively available for
agricultural purposes. The siliceous lime-stones (corn-stones) of
the old red sand-stone, the earthy beds of the mountain lime-stone,
and many of the calcareous strata of the silurian system, might
thus be made to improve more extensively the localities in which
they are severally met with. The richer limes now brought from
a great distance, and at much expense—as on the Scottish borders
—might be in a great measure superseded by the native produce
of the district.
§ 6. Effects of marl and of the coral, shell, and lime-stone sands
wpon the soil.
The effects which result from the application of the above natu-
ral forms of carbonate of lime are of two kinds.
1°. Their physical effect in altering the natural texture of the
soils to which they are added. This effect will necessarily vary
with the nature of the earthy matter associated with the lime. Thus
the clay marls will improve, by stiffening, such soils as are light
and sandy—the shell sands and lime-stone gravels, by opening and
rendering more free and easier worked such soils as are stiff, in-
tractable, and more or less impervious—while either variety will
impart solidity and substance to such as are of a peaty nature or
over-abound with other forms of vegetable matter.
2°. Their chemical effect in actually rendering the soil produc-
tive of larger crops. This effect is altogether independent of any
alteration in the physical properties of the soil, and is nearly the
same in kind, whatever be the variety of marl, &c., we apply. It
differs in degree, chiefly according to the proportion of calcareous
matter which each variety contains. This action of the pure car-
OBSERVED EFFECTS OF MARLS, ETC. 667
bonate of lime they contain is modified in some cases by the pro-
portion of phosphate or sulphate of lime with which it may be mix-
ed, and by the animal and saline matters which are present in the
recent corals and shell sands.
The several effects of marls and calcareous sands being depen-
dent upon circumstances so different, it is not surprising that the
opinions of practical men should, in former times, have been di-
vided in regard to the action of this or that marl upon their re-
spective soils. In no two localities was the substance applied to
the land exactly alike, and hence unlike results must necessarily
have followed, and disappointment been occasionally experienced
from their use. And yet the importance of rightly understanding
the kind and degree of effect which these manuring substances
ought to produce may be estimated from the fact, that a larger
surface of the cropped land in Europe is improved by the assistance
of calcareous marls and sands—than by the aid of burned lime and
of farm-yard mamure both taken together.
It is not easy in any case to estimate with precision what por-
tion of the effect caused by a given marl is due to its chemical and
what to its physical action. Even the pure limes, when applied in
large doses, produce a change in the texture of the soil, which on
stiff lands is beneficial, and on light or sandy fields often injurious.
In all cases, therefore, the action of lime applied in any form may
be considered as partly physical and partly chemical—the extent
of the chemical action in general increasing with the proportion of
lime which the kind of calcareous matter employed is known to
contain.
3°. The observed effects of marls and shell sands, in so far as
they are chemical, are very analogous to those produced by lime
as it is generally applied in the quick or slaked state in so many
parts of our islands.
They alter the nature and quality of the grasses, and banish in-
jurious weeds when applied to pasture—they cover even the un-
drained bog with a short rich grass—they extirpate heath, and
bent and useless moss, and bring up white clover where it was
never seen before—they exterminate the weeds which infest the
unlimed corn fields—they increase the quantity and enable the land
to grow better samples, as well as more valuable kinds of grain–
668 OF THE USE OF CHALR AS A MANUR.E.
they manifest a continued action for many years after they have been
applied—like the purer limes they act more emergetically if aided
by the occasional addition of other manure—and like them they
finally exhaust” a soil from which successive crops are reaped, with-
out the requisite return of decaying animal or vegetable matter.
But to these and other effects I shall have occasion to draw your
attention more particularly in a subsequent part of the present
lecture.
§ 7. Of the use of chalk as a manure.
Chalk is another form of carbonate of lime which occurs very
abundantly in mature, and which, from its softness, has in many
parts of England been extensively applied to the land in an un-
burned state.
The practice of chalking prevails more or less in all that part
of England (p. 459) over which the chalk formation extends. It
is usually dug up from pits towards the close of the autumn or
the beginning of winter, when full of water, and is laid upon the
land in heaps. During the winter's frost the lumps of chalk fall
to pieces, and are thus easily spread over the fields in spring.
The quantity laid on varies with the quality of the soil and of
the chalk itself, with the more or less perfect crumbling it un-
dergoes during the winter, and with the purpose it is intended to
serve. It gives tenacity and closeness to gravelly soils,f opens
and imparts freeness to stiff clays, and adds firmness to such as are
of a sandy nature,
If a physical improvement of this kind be required, it is laid on
at the rate of from 400 to 1000 bushels an acre. But some chalks
contain much more clay than others, and are employed, therefore,
in smaller proportions.
For the improvement of coarse, sour, marshy pasture, it is ap-
plied at the rate of 150 to 250 bushels an acre, and speedily
brings up a sweet and delicate herbage. It is also said to root out
sorrel from lands that are infested with this plant.
* Of shell marl the same quantity exhausts sooner than clay marl (Kames). This
is owing chiefly to the larger proportion of lime contained in the former. •
+ Mr Gawler, North Hampshire, states that a gravel thus stiffened, instead of
12 to 16 bushels of wheat, yielded afterwards 24 to 30 bushels, British Husbandry,
i. p. 280.
DIFFERENCE BETWEEN THE UPPER AND LOWER CHALK. 669
These effects are precisely such as usually follow from the ap-
plication of marl, and, like marl, the repetition of chalk exhausts
the land, if manure be not afterwards added to it in sufficient
quantity.
But the chalking of the Southern Downs and of the Wolds of
Lincolnshire and Yorkshire would appear to differ in some respects
from ordinary marling. On the thin soils immediately resting
upon the chalk, experience has shown that repeated dressings of
chalk, recently dug up, may be applied with much benefit. To
a stranger, also, it appears singular that an admixture of that chalk
which lies immediately beneath the soil is not productive of the
same advantage. Even the chalk of an entire district is, in some
cases, rejected by the local farmer, who will rather bring another
variety from a considerable distance, than incur the less expense
of laying on his land that which is met with on his own or on his
neighbour's farms. Thus the Suffolk farmers prefer the chalk of
Kent to lay on their lands, and are at the cost of bringing it across
the estuary of the Thames, though chalk rocks lie almost every
where around and beneath them. -
The cause of the diversities which thus present themselves in the
practice of experienced agriculturists is, partly at least, to be
sought for in the qualities of the different varieties of chalk em-
ployed. Careful analyses have not yet shown in what respects
these chalks differ in chemical composition, and until this is as-
certained we must remain in some measure in the dark, both as
to the way in which a dressing of chalk acts in improving a soil
already rich in chalk, and why chalk from one locality acts more
beneficially than from another.
With one thing, however, we are familiar, that the upper beds
of chalk abound in flint, and where they form the surface support
a thin and scanty herbage—while the under chalks are more tena-
cious and apparently more rich in clay, and support generally a
soil which yields valuable crops of corn. An admixture of the
lower, therefore, ought to improve the soils of the upper; and as
the chalks of Kent consist of these lower beds, we can understand
why the practical farmer in Suffolk should prefer them to the
upper chalks of his own neighbourhood. Still we cannot, as yet,
give the scientific reason why the one chalk should be better than
670 EFFECTS OF CHALK ON THE WOLT)S.
the other. A rigorous chemical analysis can alone determine
with certainty why the one should produce a different effect from
the other.
Chalks may differ in the proportion of clay or of organic matter
with which they are associated—in the quantity of silica (the sub-
stance of flints) or of silicates they contain, in the amount of
magnesia or of phosphate of lime which can be detected in them
—or of Saline matter which a careful examination will discover,
and they may even differ physically in the fineness of the ultimate
particles of which the substance of the chalk is composed.* All
such differences may modify the action of the several varieties in
such a way as, when accurately investigated, to enable us to ac-
count for the remarkable preference manifested by practical men
for the one over the other. Until such an investigation has been
carefully made, it is unfair hastily to class among local prejudices
what may prove to be the results of careful as well as long prac-
tical experience. - x
On the chalk Wolds of Lincolnshire and Yorkshire the practice
of chalking even the thin soils is now comparatively old in date.
The lowest chalks are there also much preferred,—they are laid
on at the rate of 60 to 80 cubic yards per acre, and they cause a
great improvement, especially upon the deep lands, as they are
called, where the soil is deepest. Corn does not yield so well,
nor ripen so early, on these deep soils as where a thinner covering
rests upon the chalk. It is naturally also unfit for barley or tur-
nips, the latter plant being especially infested with the disease
called fingers and toes f (Strickland). But a heavy chalking re-
moves all the above defects of these deep soils, and for a long
period of time. The corn ripens sooner, is larger in quantity, and
better in quality, and the turnips grow perfectly free from disease.
These, however, are to be regarded as only the usual effects of
a large addition of lime to a soil in which previously little existed.
It is a fact which will naturally strike you as remarkable, that soils
which rest upon chalk, as well as upon other lime-stone rocks,
even at the depth of a few inches only, are often, and especially
* Ehrenberg has discovered that chalk is in a great measure composed of the ske-
letons, shells, or other exuviae (spoils) of marine microscopic animals,
+ British Husbandry, iii. p. 124,
Is LIME INDISPENSABLE TO A FERTILE SOIL? 671
when in a state of nature, so poor in lime that scarcely a particle
can be detected in them. That lime in any form should benefit
such soils is consistent with uniform experience. I shall presently
have an opportunity of directing your attention to the two concur-
ring causes by the joint operation of which lime is sooner or later
wholly removed from the soil, even where, as in the Wolds, it rests
immediately upon the chalk.
§ 8. Is lime indispensable to the fertility of the soil 2
It is the result of universal experience wherever agriculture has
been advanced to the state of an art, that the presence of lime is
useful to the soil.
Not only is this fact deduced from the results of innumerable
applications of this substance to land of every quality, but it is
established also by a consideration of the known chemical compo-
sition of soils which are maturally possessed of unlike degrees of
fertility. *y
Thus sandy or siliceous soils are more or less barren if lime be
absent—while the addition of this substance, in the form of marl or
otherwise, renders them susceptible of cultivation. So clay soils, in
which no lime can be detected, are often at once changed in their
agricultural character by a sufficient liming. Felspar soils contain
no lime, and they are very unproductive—and the same is true of
such as are derived immediately from the degradation of the ser-
pentine rocks.
Trap soils, on the other hand—such as are derived from de-
cayed basalts or green-stones—are poor in proportion as felspar
abounds in them. Where augites and zoolites are present in large
proportion in the trap from which they are formed, the soils are
rich, and may even be used as a marl. The only remarkable che-
mical difference in this latter case is, that lime is not deficient (p.
492), and to this difference their greater fertility may fairly be
ascribed.
But let it be granted that lime is useful to or benefits the soil in
which it exists, you may still ask—is lime indispensable to the soil?
—is it impossible for even an average fertility to be manifested
where lime is entirely absent 2
672 LIME ALWAYS PRESENT IN FERTILE SOILS.
There are two different considerations, from each of which we
may deduce a more or less satisfactory answer to this question.
1°. The results of all the analyses hitherto made of soils natu-
rally fertile show that lime is universally present. The per-centage
of lime in a soil may be small, yet it can always be detected when
valuable and healthy crops will grow upon it.
2°. The results of our analyses of the ash of plants are of a simi-
lar kind. Lime is uniformly found in the sap and substance of all
the plants we grow. This shows, if not the absolute necessity
of lime to the growth of plants, at least that they absorb it by
their roots from the soil, and make use of it in some way in aid of
their growth. In so far as our practice is concerned, this is very
much the same as if we could prove lime to be absolutely indis-
pensable.
The ash of the leaf and bulb of the turnip or potato, of the
grain and straw of our corn-bearing plants, and of the stems and
seeds of our grasses, all contain lime whenever and wherever they
are grown. And most of them attain high health and luxuriance
only where lime is easily procured by their roots.
But though lime thus appears to be a necessary food of plants
—without which their matural health cannot be maintained, nor
the functions of their several parts discharged,—still the quantity
which must be present in the soil to supply this food is not neces-
sarily large. Even in favourable circumstances we have seen (p.
409) that the average crops during an entire rotation of four years
may not carry off more than 200 lbs. of lime from an imperial acre
of land, a quantity which even one-fifth of a per cent. of lime in
the soil would be able to supply for half a century, could the roots
readily make their way everywhere to take it up.
Still we may safely hold, I think, that this quantity of lime at
least is indispensable—if cultivated plants are to flourish and ripen.
So much, at least, must in practice be every year added to culti-
wated land in one form or another, where the crops are in whole
or in part carried off the land. Where it is not added either ar-
tificially or by some matural process, infertility must gradually
ensue. We shall presently see that lime has other functions to
perform in the soil, and that there are natural causes in constant
STATE IN WHICH LIME EXISTS IN THE SOIL. 673
operation in our climate which render a larger addition than this
indispensable to continued fertility.
§ 9. State of combination in which lime exists in the soil.
This lime, which we have concluded to be an indispensable con-
stituent of fertile soils, may be present in several distinct states of
combination. -
1°. In that of chloride of calcium.—This compound, as We have
already seen (p. 334), is very soluble in water, and is not unfre-
quently to be detected in the sap, especially of the roots of plants.
Its solubility, however, exposes it to be readily washed out of the
soil by the rains, and perhaps for this reason it is not one of those
forms of combination in which lime is recognised as a uniform or
necessary constituent of the soil. Its presence may be detected
by boiling half a pound of the soil in distilled water, filtering and
evaporating the solution to dryness. If the dry mass become moist
on exposure to the air, and if, after being dissolved in water, it
give a white precipitate with oxalate of ammonia, and after being
rendered sour by a few drops of nitric acid, a white precipitate
again with nitrate of silver, it may be inferred to contain chloride
of calcium.
2°. In that of sulphate of lime or gypsum.—In this state also it
is not a constant, and in a few cases only an abundant, constituent
of the soil. Its presence may be detected by the deposition of mi-
mute crystals on the sides of the vessel during the evaporation of
the solution obtained by boiling the soil in distilled water. Or,
its presence may be inferred if, after observing that oxalate of am-
monia causes a precipitate in one small portion of the solution, it
be found that mitrate of baryta also throws down a white precipi-
tate from another small portion, to which a few drops of acid have
been previously added. -
3°. In the state of phosphate.—This compound is probably pre-
sent, though always in small proportion, in every soil which is ca-
pable of raising a nutritious vegetation. It may be readily de-
tected by treating 500 grains of the dry soil for 12 hours with
dilute muriatic acid, and occasionally stirring. If to the filtered
solution caustic ammonia be added, a brownish precipitate will
U Ul
674 SILICATE OF LIME IN THE soil.
usually fall. If this precipitate be separated, and treated with
acetic acid (vinegar), it will all dissolve if no phosphoric acid be
present. If this experiment be carefully performed, and a residue
remain undissolved, the presence of phosphoric acid in the solution,
and of phosphate of lime in the soil, may be safely inferred.
4°. In the state of silicate, lime rarely exists in the soil in any
considerable quantity. It is chiefly in such as are derived from
the decay of the trap rocks or of some varieties of granite (sienite),
that silicate of lime is to be expected to occur.
If, after being treated with diluted muriatic acid, as above de-
scribed, the soil be digested for some hours at a gentle heat with
concentrated muriatic acid—a solution will be obtained from which
ammonia will again throw down a brown precipitate. If oxalate
of ammonia now cause a white precipitate of oxalate of lime, and
if, on evaporating to dryness, the solution leave a portion of silica
insoluble in acids, we may infer that the soil most probably con-
tains some lime in the state of silicate.
A virgin soil, taken from a depth of three feet on a part of the
old Caledonian Forest, at Gadgirth, near Ayr, was found in my
laboratory to consist of
Organic matter,..................... 5.29
Salts of potash and soda, ......... 0.43
Gypsum (sulphate of lime), ...... trace
Carbonate of lime, .................. trace
Lime in the state of silicate, ...... 4.15
Carbonate of magnesia,............ 0.51
Oxide of iron, ..................... 5.81
Alumina soluble in acids,......... 2.05
Alumina in the state of silicate, 11.12
Phosphoric acid, .................. 0.02
Silica, ..... ........................ 69. 16
98.54
The large proportion of lime in the state of silicate (4 per cent.)
contained in this soil, shows how much of the original rock from
which it was derived remains undecomposed. When exposed
by trenching to the action of the air, this silicate would gra-
dually undergo decomposition, and other compounds of lime be
CARBONATE AND HUMATE OF LIME IN THE SOIL. 675
formed, by which the growth of plants would be more readily pro-
moted.
5°. In the state of carbonate, lime is generally supposed most
usually to exist, and most abundantly in all soils. If on pouring
diluted muriatic acid upon a soil, a visible effervescence or escape
of minute bubbles of gas manifest itself, or if, when the experiment
is made in a tube closed at one end, and inverted over water or
mercury, bubbles of gas collect in the upper end of the tube—the
soil contains a carbonate of some kind. If after ammonia has been
added to the solution, oxalate of ammonia throws down a white
precipitate of oxalate of lime—the soil contains carbonate of lime.
6°. In the state of humate.—In combination with humic acid
(p. 72) lime exists most frequently in soils which abound in vege-
table matter—in peaty soils, for example, to which quick-lime or
marl of any kind has been added for the purpose of agricultural
improvement. The presence of lime in the state of humate is only
to be detected by carefully determining the relative weights of the
carbonic acid given off during the action of dilute muriatic acid
upon the soil, and of the lime contained in the solution thus ob-
tained. If for every 100 grains of carbonic acid there be more
than 77.24 grains of lime, the remainder or excess has existed in
the soil in combination with humic or some analogous organic acid
(p. 71.) -
Few investigations have as yet been made in regard to the pro
portion of lime which exists in the soil in the state of humate. It
has generally been taken for granted—either that a soil was desti-
tute of lime if it exhibited no sensible effervescence with dilute
muriatic acid, or when further research was made, and the quan-
tity of lime taken up by this acid rigorously determined, that the
whole of this lime must have existed in the soil in the state of car-
bonate. That this is not necessarily the case, however, appears to
be proved by the examination of certain soils in Normandy, which
contain as much as 14 or 15 per cent of lime, and yet exhibit no
effervescence, and contain no carbonate. The whole of the lime
in these soils is said to be in the state of humate.
M. Dubuc, who has published the analyses of these soils, attri-
butes much of their fertility—perhaps hastily—to the presence of
the humate of lime. Thus he says that the soils of
676 QUANTITY OF LIME TO BE APPLIED TO THE SOIL.
Containing per cent.
Of carbonate. Of humate. Yield of wheat.
º Neubourg, and o 18 to 20 l 2 to 15 fold.
istot, .................. ſ T*~.
Pavilli, .................. - O 5 8 to 10
Bieville, .................. 24 O 8 to 10
Clay of Ouche, ......... O I 4 to 5
the first two yielding a wheat crop every second year, the third
only at longer intervals.
Whatever degree of influence on the fertility of the soil it may
appear proper to attribute to the existence of lime in the soil in the
state of humate, it is manifestly of some importance that its pre-
sence in this state of combination should be more frequently and
more carefully sought after.
The only one of the above compounds which is usually added in
large doses to the land, for the purpose of producing the ordinary
effects of lime, is the carbonate. Gypsum is applied only in com-
paratively small doses for certain special purposes, and does not
always produce a sensible effect. It is incapable, therefore, of per-
forming all those purposes in the soil which are served either by
quick-lime or by the carbonate. Humate of lime is probably formed
in our lime composts, especially when much vegetable matter is
contained in them, and may thus be not unfrequently applied di-
rectly to the land.
, § 10. Of the quantity of lime which ought to be added to the soil.
The quantity of lime which ought to be added to the soil is de-
pendant upon so many circumstances, that it is impossible to give
any general rule by which, in all cases, the practical man can safely
regulate his procedure.
1°. To soils which contain no lime, or to which it is added for
the first time, a larger dose must be given. -
We have seen that a certain minimum portion of lime is indis-
pensable to a productive soil, that, namely, which will readily yield
to our growing crops the lime they require for the formation of
their own substance.
But there is reason to believe that the proportion of lime which
the soil ought to contain, if it is to be successfully subjected to
MORE OUGHT TO BE LAID UPON CLAY LANDS. 677
arable culture, ought to be much larger than we should suppose
to be necessary to the fulfilment of this one condition. All I have
been able to collect from the numerous analyses of soils made of
late years in my laboratory, inclines me to think that in land to-
lerably rich in vegetable matter, 5 or 6 per cent. of carbonate of
lime are necessary to bring it into the most fertile condition. It
may contain much more without being lessened in value, but to
the extent of 5 or 6 per cent, the carbonate of lime in rich soils
may with advantage be increased.
But if a soil be naturally very poor in lime, exceedingly large
doses of lime must be given to it, before 5 or 6 per cent. of car-
bonate shall have been added to it. Thus to add 1 per cent. of
lime—nearly two of carbonate—eight tons of lime shells, or 300
bushels of slaked lime, must be mixed with a soil six inches in
depth, or half the quantity if it be kept within three inches of
the surface. Even what is usually considered as a very large dose
of lime, therefore, does not, if it be well mixed, materially alter
the constitution of the soil.
2°. But experience has proved that the quantity of lime which
a skilful farmer will add to his land will vary with many other cir-
cumstances besides the depth of his soil, and the proportion of lime
it already contains. Thus— -
a. On clay lands more lime is necessary than on light and sandy
soils. This may be partly ascribed to the physical effect of the
lime in opening and loosening the stiff clay—but independent of
this action the particles of lime are liable to be coated over and
enveloped by the fine clay, and thus shut out from the access of
the air. These particles, therefore, must be more numerous in
such a soil, if as many of them are to be exposed to the air as in
lighter land, through which the atmospheric air continually per-
meates.
b. On wet and marshy soils, a larger application still may be
made with safety, and partly for the same reason.
The moisture surrounding the lime shuts out the air, without
the ready access of which lime cannot perform its important func-
tions. The same moisture tends to carry down the lime and lodge
it more speedily in the subsoil. The continued evaporation also
keeps such soils too cold (p. 59), to allow the chemical changes,
678 MORE ON WET AND MARSHY SOILS,
which lime in favourable circumstances produces, to proceed with
the requisite degree of rapidity. The soluble compounds which
are formed as the consequence of these changes are, in wet and
marshy soils, dissolved by the moisture and so diluted as to en-
ter in smaller quantity into the roots of plants. And lastly, in
certain cases, new compounds of the lime with the earthy and stony
matters of the soil are formed, which may either harden into vi-
sible lumps of mortar and cement, or into smaller particles of in-
durated matter, in which the lime is no longer in a state to be
readily taken up by the roots of plants, or to act with an equal de-
gree of efficacy as an improver of the soil. º
In cold and wet clays, in which all these evil conditions occa-
sionally meet, it is not surprising, therefore, that large doses of
lime should sometimes have been added without producing any
sensible benefit whatever.” Af
c. Again, when the soil is also rich in vegetable matter, lime
may be still more abundantly applied. Thus, when a field is at
once wet or marshy, and full of vegetable matter, lime may be laid
on more unsparingly than under any other circumstances. For
in this case, besides the action of the excess of water, as above ex-
plained, the vegetable matter combines with and masks the ordi-
mary action of a considerable quantity of the lime. By this com-
bination, no part of the ultimate influence of the whole lime upon
the soil is necessarily lost. In most cases it only diminishes the
immediate effect, which the same quantity applied to other soils
would have been seen to produce. In favourable circumstances
its action is retarded and prolonged, the compounds it forms with
the vegetable matter decomposing slowly, and, therefore, remain-
ing long in the soil.
To the exact chemical nature of the compounds thus formed, as
soon as lime is mixed up with a soil rich in vegetable matter, and
to the chemical changes which these compounds gradually under-
go, it will be necessary to direct our attention when we come to
study the theory of the action of lime, as an improver of the soil.
d. Not only the natural depth of the soil, as already stated, but
* “An instance is mentioned, in the Nottingham Report, of 720 bushels having
been laid on an acre of cold clay land without any benefit whatever.”—British Iſus-
#(ºndry, i. p. 296.
AND SUCH AS ARE RICH IN VEGETABLE MATTER. 679
also the depth to which it is usually ploughed, and to which it is
customary to bury the lime, will materially affect the quantity
which can be safely applied. A dose of lime which would mate-
rially injure a soil into which the plough rarely descends beyond
two or three inches, might be too small an application where six
or eight inches are usually turned over. When new soil, also,
is to be brought up, which may be supposed to contain no lime,
or in which moxious substances are present, a heavier dose of lime
must necessarily be laid upon the land. -
3°. Such are the circumstances in which large applications of
lime may be usefully applied to the land. In soils of an opposite
character not only will smaller quantities of lime produce an
equally beneficial effect, but serious injury would often be inflicted
by spreading it too lavishly upon our fields.
The more dry and shallow the soil, the more light and sandy, the
less abundant in vegetable matter, the more naturally mild its lo-
cality, and the drier and warmer the climate in which it is situat-
ed—the less the quantity of lime which the prudent farmer will
venture to mix with it. To the neglect of these natural indica-
tions the exhaustion and barrenness that have occasionally follow.
ed the application of lime are in part to be ascribed. It is only in
rare cases, such as the presence of much noxious mineral matter
in the soil, that these indications can be safely neglected.
§ 11. Ought lime to be applied in large doses at distant intervals,
or in smaller quantities more frequently repeated 2
The quantity of lime which ought to be applied must, as we have
seen, vary with the quality of the land, and with the conditions
in which it is placed. Hence the practice in this respect neces.
sarily varies in every country and in almost every district.
But a difference of opinion also prevails amongst practical men,
as to whether that quantity of lime which land of a given kind may
require ought to be applied in large doses at long intervals, or in
small quantities frequently repeated. The indications of theory
in reference to this point are clear and simple.
a. A certain proportion of lime is indispensable in our climate
to the production of the greatest possible fertility. Let us suppose
a soil to be wholly destitute of lime—the first step of the improver
680 OUGHT LIME TO BE APPLIED
would be to add to it this indispensable proportion. This would
necessarily be a large quantity, and, therefore, to land limed for
the first time theory indicates the propriety of adding a large dose.
b. Every year, however, a certain variable proportion of the
lime is removed from the soil by natural causes. The effect of this
removal in a few years becomes sensibly apparent in the diminish-
ed productiveness of the land. After the lapse of five or six years,
during which it has been gradually mixing with the soil, the bene-
ficial effects of a large dose of lime are generally the most strik-
ing—after this they gradually lessen, till at the end of a longer or
shorter period, the land reverts to its original condition. To keep
land in its best possible state, therefore, the natural waste ought from
time to time to be supplied by the addition of smaller doses of lime
at shorter intervals. -
Such is obviously the most natural course of procedure, and he
who farms his own estate, and has therefore no strong inducement
to do otherwise, will, on the first breaking up of new land, give it
a heavy liming, and whether he afterwards retain it in arable cul-
ture or lay it down to grass, will at intervals of 4, 6, or 8 years
give it a new dose of one-fourth to one-eighth of the original
quantity. But local circumstances and customs interfere in many
well farmed districts with this most natural treatment of the soil.
In the county of Roxburgh, for example, on entering upon his
farm, which he holds on a lease of 19 or 21 years, the tenant be-
gins by liming that portion of his land which is in fallow, or in
preparation for turnips, at the rate of 240 to 300 bushels of quick-
lime per acre. A similar liming is given to the other portions as
they come into fallow, so that at the end of his first rotation (4 or
5 years) the whole of his land has been limed at the same rate.
He now continues cropping for three or four rotations (14 to 16
years), when, if he is sure of remaining on his farm, he begins to
lime again with the same quantity as before. If he is to quit, how-
ever, he takes the best crops he can get, but incurs no further out-
lay in the addition of lime. His successor follows the same course
—begins by expending perhaps L. 1000 in lime, and before he
leaves at the end of his lease, has, by continued cropping, brought
back his land nearly to the same state in which he found it,
In the district of Kyle and other parts of Ayrshire, again, lime
3 :
IN LARGE OR SMALL DOSEs 681
is laid on—often when preparing for the wheat crop, either by
ploughing in the seed furrow, or by harrowing in with the seed—
at the rate of 40 bushels of shells an acre, and this dose is of course
repeated every 4 or 6 years, according to the length of the rota-
tion. If we consider the probable difference in the soil and cli-
mate, the proportion of lime added in the two districts does not
materially differ. In Ayrshire from 8 to 10 bushels, and in Rox-
burgh from 10 to 12 bushels are added for each year." In both
counties, however, many farms may be met with in which the treat-
ment of the land in this respect differs from that which is gene-
rally followed. -
In Flanders a similar difference in the practice prevails in dif-
ferent districts. In some the land is limed only once in 12 years,
in others every third, fourth, or sixth year, according to the length
of the rotation. In the former case from 40 to 50 bushels are ap-
plied per acre, in the latter from 10 to 12 bushels every third
year. In both modes of procedure the quantity of lime applied by
the year is nearly the same—between 3} and 4 bushels per acre.
These quantities are very much less than those employed in our
island, but the soils are also greatly lighter, and the climate, as
well as the general treatment of the land, very different.
We may consider it, therefore, as a principle recognised or in-
volved in the agricultural practice both of our own and of foreign
countries, that nearly the same annual addition of lime—8 to 10
bushels per acre—ought to be made to the land, whether it be
applied at long intervals or at the recurrence of each rotation.
There is, therefore, on the whole, no saving in the cost of lime,
whichever method you adopt. A slight consideration of the sub-
ject, however, may satisfy us that there is a real difference in the
comparative economy or profit of the two methods.
Let us suppose two acres of the same clay land to be limed at
the rate of 200 bushels each acre, and that the one is cropped for
20 years afterwards without further liming, while the other at the
* According to General Beatson (New System of Cultivation, 1820), upwards of 100
bushels an acre, at a cost of L.7, 16s, used to be applied to the clay lands of Sussex
—on the fallow, before wheat—every four years. This was 25 bushels per acre for
each year. In such lands as these the saving in the article of lime alone, which
would follow a judicious drainage, would be very great.
682 COMPARATIVE ECONOMY OF THE TWO METHODS.
end of every 5 years is dressed with an additional dose of 40 to
50 bushels. In both cases the land would have attained its most
productive condition in five or six years. Let us suppose that in
this condition it produces annually a crop of (or equivalent in nu-
tritive value to) 30 bushels of wheat, and that no sensible diminu-
tion appears on either acre before the end of the first ten years.
Then during the second ten years the crops would gradually les-
sen upon the one acre, while, in consequence of the repeated ad-
ditions of lime, the amount of produce would remain sensibly
the same upon the other acre. Suppose the produce of the former
gradually to diminish from 30 to 20 bushels during these ten
years, or that while the one has continued to yield 30 bushels
during the whole period, the other has, on an average, yielded
only 25 bushels during the latter ten years—and we have the fol-
lowing difference in the crops yielded by the two acres during the
second ten years.
10 crops, of 30 bushels each, amount to 300 bushels.
10 crops, of 25 bushels each, amount to 250 bushels.
Difference in favour of *}
liming, .....................
50 bushels per acre,
or nearly two whole crops every lease of twenty years.
Thus it appears,
1°. That, according to the practice of different countries, the
quantity of lime which ought to be added, and consequently the
cost of adding it, is very nearly the same, whether it be applied in
larger doses at longer intervals, or in smaller doses more frequent-
ly repeated.
2°. That, after the first heavy liming, the frequent application
of small doses is the more natural method—and -
3°. That it is also the most economical or profitable method.
It is possible that other considerations, such as the tenure by
which your land is held, may appear sufficient to induce you to
depart from this method; but there seems every reason to believe
that it will best reward those who feel themselves at liberty to fol-
low the indications at once of sound theory and of enlightened
practice.
One thing, however, must be borne in mind by those who, in
adopting the best system of liming, do not wish both to injure their
FORM IN WEIICH LIME SHOULD BE, APPLIED. 683
land and to meet with ultimate disappointment. Organic matter
—in the form of farm-yard manure, of bone or rape dust, of green
crops ploughed in, or of peat, and other composts—must be abun-
dantly and systematically added, if at the end of 20 or 40 years
the land in which the full supply of lime is kept up is to retain its
original fertility. High farming is the most profitable—for the
soil is ever grateful for skilful treatment—but he who farms high
in the sense of keeping up the supply of lime, must also farm high
in the sense of keeping up the supply of organic and other ma-
mures in the soil—otherwise present fertility and gain will be fol-
lowed by future barrenness and loss. If this is not to be done, it
were better to add lime at long intervals, since, as the quantity of
lime diminishes, the land begins to enjoy a little respite, and has
had time in some measure to recover itself—the cropping in both
instances being the same—before the new dose is laid upon its
surface.*
§ 12. Form and state of combination in which lime ought to be
applied to the land,
The form and state of combination in which lime ought to be
applied to the land depend upon the nature of the soil, on the kind
of cropping to which it is subjected, and on the special purpose
which the lime is intended to effect. The soil may be heavy or
light, may be in arable culture or laid down to grass, may be
scourged with frequent corn crops, or may be prudently farmed
with alternate grain and green crops, and each of these conditions
indicates a different mode of procedure in the application of lime.
So the lime itself may be intended either to act more immediately
or to be more permanent in its action. Or it may be applied for
the purpose of destroying unwholesome herbage, of quickening
inert vegetable matter, of generally sweetening the soil, or simply
* “In the neighbourhood of Taunton, in Somersetshire, and over all the soil of the
new red sand-stone, the farmers lime their land every time it comes in course of fal-
low for turnips, and this produces excellent crops, even without dung.”—Morton on
Soils, third edition, p. 181. The practical reader must not consider this custom of
the Somersetshire farmers as at all at variance with what is stated in the text ; he
must conclude, rather,-if the sentence here quoted is meant to imply that they lime
their arable land so repeatedly, and add no other manure—that they will, sooner or
later, cease to boast of its fertility.
684 SIIOULD BE IN A MINUTE STATE OF DIVISION.
of adding to the land a substance which is indispensable to its fer-
tility. The skilful agriculturist will modify the form and mode of
application according as it is intended to serve one or other of these
purposes. -
From the considerations already presented to you (§ 3) in re-
gard to the changes which quick-lime undergoes in the air, it ap-
pears to be expedient,
1°. To slake lime quickly and to apply it as soon as possible af-
terwards upon stiff clays, and upon boggy, marshy, or peaty soils
—upon such also as contain much inert or abound in other forms
of vegetable matter. -
2°. To bents and heaths which it is desirable to extirpate, it
should be applied in the same caustic state, and to unwholesome
subsoils which contain much iron (sulphate of iron) as soon as they
are turned up by the plough. In both these cases the unslaked
lime-dust from the kilns might be laid on with advantage.
3°. Where it is to be spread over grass lands without destroy-
ing the herbage, it is in most cases safer to allow the lime to slake
spontaneously, and in the open air rather than in a covered pit.
It is thus obtained in an exceedingly fine powder, which can be
easily spread, and, while it is sufficiently mild to leave the tender
grasses unharmed, it contains a sufficient quantity of caustic lime
(p. 654) to produce those chemical changes in the soil on which
the efficacy of quick-lime depends.
4°. Where lime is applied to the fallow, is ploughed in, and is
then well harrowed or otherwise mixed with the soil, it is general-
ly of little consequence in which of the above states it is laid on.
The chief condition is, that it be in the state of a fine powder, and
that it be well spread and intimately mixed with the soil. Before
these operations are concluded the lime will be very nearly in the
state of combination in which it exists in spontaneously slaked lime
—whatever may have been the state of causticity in which it has
been applied.
5°. To light and thin soils, to sands and gravels which are poor
in vegetable matter, to drained peats or to heathy moorlands, caus-
tic lime, if applied at all, ought to be laid on sparingly, and with
caution. To heaths and mosses when first reclaimed, it may be
proper to add the first moderate dressing of lime in a caustic
COMPARATIVE ECONOMY OF LIME AND MARL. 685
state; but after they have been some time in arable culture, long
slaked mild lime, or lime composts, are safer forms of application.
Where the land is in permanent pasture not intended to be broken
up, it is of comparatively less consequence in what form the lime
is laid upon the land.
The above remarks apply only to localities where burned lime
is usually or alone used for agricultural purposes. There may be
localities where marl also exists, or shell or lime-stone sand, in
greater or less abundance, and in such places it may be a question
of some importance to determine which it would be better or more
economical to apply. In such a case you may safely proceed upon
the principle, that the lime in the marls, or shell sand, will ulti-
mately produce precisely the same effects upon your land as the
lime from the kiln, provided you lay on an equal quantity, and in
an equally minute state of division. The effect will only be a little
more slow, and the full fertility of the land a year or two longer
in being brought out. You would therefore consider
1°. How much of the marl or sand must I add to be equal to a
ton of lime-shells? This will depend on the per-centage of lime
which the marl contains. Suppose it to contain 20 per cent., or
one-fifth of its weight of lime,” then five tons of the marl will be
equal to one ton of lime shells. But as the lime in the marls and
sands is never in so minute a state of division as in slaked lime, the
same quantity of lime in the former cannot be so equally diffused
through the soil as in the latter state. An allowance must there-
fore be made on this account, and an additional quantity laid on
equal to one-fourth or one-fifth of the whole, for the purpose of
equalizing the effect. e
2°. Which of the two—the quick-lime or its equivalent of marl
—can I obtain and apply at the less cost 2 This will not be diffi-
cult to calculate, the proportion of lime contained in the marl be-
ing once ascertained.
3°. This question of economy being decided, it is necessary to
consider the kind and quantity of the earthy matter with which
the lime in the marl is mixed. If it be a lime-sand or sandy marl,
* Not carbonate of lime, but of lime in the state in which it comes from the kiln.
100 lbs. of carbonate contain 56 lbs. of quick-lime, p. 649.
686 ADVANTAGE OF THE COMPOST FORM.
it may be unfit to apply to light and sandy soils; if it be a stiff
unctuous clay marl, it may only render stiffer and more difficult to
work the clay lands on which you may propose to spread it. In
such cases as these, however economical the use of marls or lime-
stone sands may be, the intelligent farmer will prefer the addition
of quick-lime wherever it is readily accessible.
Sussex is one of those districts in which the ancient use of marl
has given place to the employment of burned lime (Beatson), chiefly,
I believe, from the nature of the local marl being less adapted to
the stiff clay lands of that county.
§ 13. Of the use and advantage of the compost form.
As there are many cases in which lime ought to be applied un-
mixed and in the caustic state, so there are others in which it is
best and most beneficially laid upon the land in a mild state, and
in the form of compost. -
1°. When lime is required only in small quantities, it can be
more evenly spread when previously well mixed with from 3 to 8
times its bulk of soil. sº
2°. On light, sandy, and gravelly soils, when of a dry character,
unmixed lime will bring up much cow-wheat (melampyrum) and
red poppy. If they are moist soils, or if rainy weather ensue, the
lime is apt to run into mortar, and thus to form either an imper-
vious subsoil, or lumps of a hard conglomerate, which are brought
up by the plough, but do not readily yield their lime to the soil.
These bad consequences are all avoided by adding the lime in the
form of compost. - -
3°. Applied to grass lands—unless the soil be stiff clay, or wet
and undrained, or where coarse grass and weeds or moss are to be
extirpated,—it is better and safer, and has generally been found
more beneficial, to apply it in the compost form.
4°. In the compost form the same quantity of lime acts more
immediately. While lying in a state of admixture with soil and
vegetable matter, those chemical changes which lime either induces
or promotes have already to a certain extent taken place, and thus
the sensible effect of the lime becomes apparent in a shorter time
after it has been laid upon the land. The experience of every
practical man has long proved how very much more enriching
WHEN OUGHT LIME TO BE APPLIED F 687
composts of earth, decayed vegetable substances, ditch scourings,
and other refuse are, and how much more obvious in their effects
upon the soil, than the simple application of lime alone.
5°. It is stated as the result of extended trial in Flanders and
in parts of France, that a much smaller quantity of lime laid on
in this form will produce an equal effect. -
6°. The older the compost the more fertilizing is its action.
This fact is of the same kind with that generally admitted in re-
spect to the action of marls and unmixed lime—that it is more
sensible in the second year, or in the second rotation, than in the
first.
In conclusion, it may be stated that this form of application is :
especially adapted to the lightest and driest soils, to such as are
poorest in vegetable matter, and to such as consist of dry and
powdery peat. In this form, lime has imparted an unexpected
fertility even to the white and barren sands of the Landes (Puvis),
while upon the dry hills of Derbyshire it has produced an almost
equal benefit.
§ 14. When ought lime to be applied ?
This question may refer either to the period in the lease, in the
rotation, or of the year in which lime may most beneficially be
laid upon the land. We have already considered this point in so
far as it refers to the lease, while discussing the propriety of ap-
plying lime in large or in small doses.
In regard to the period of the year and of the rotation, there
are three principles by which the procedure of the practical man
ought chiefly to be directed.
1°. That lime takes some time to produce its known effects upon
the soil.—It ought, therefore, as a general rule, to be applied as
long as possible before the crop is sown—that is, in the early
autumn, where either winter or spring corn is about to be sown,
on the maked fallow, where the land is allowed to be at rest for a
year, on the grass fields before breaking up, where the pasture
is to be immediately succeeded by corn—or early in the winter or
spring months, where turnips or other root crops are to be grown.
2°. That quick-lime expels ammonia from decomposed and Jer-
menting manure.—When such manure, therefore, is applied to the
688 LIME HASTENS ORGANIC DECOMPOSITION.
land, as it is in all our well-farmed districts, quick-lime should not
be so laid upon the land as to come into immediate contact with it.
If both must be applied in the same year, they should be laid on
at periods as distant from each other as may be convenient, or if
this necessity does not exist, the lime should be spread either the
year before or a year after the period in the rotation at which the
fermented manure is usually applied.
It is for this reason, as well as for the other already stated (1°),
that lime is applied to the naked and winter fallows, to the grass
before breaking up, or along with the winter wheat after a green
crop which has been aided by fermented manure. When plough-
ed into the fallows, or spread upon the grass, it has had time to
be almost completely converted into the mild state (that of carbo-
mate), before the manure is laid on. In this mild state it has no
sensible effect in expelling the ammonia of decomposing manure.
Again, when it is applied in autumn along with, or immediately
before the seed, the volatile or ammoniacal part of the manure has
already been expended in mourishing the green crop, so that loss
can rarely accrue from the admixture of the two at this period of
the rotation.
The excellent elementary work of Professor Lowe" contains the
following remark:—“It is not opposed to theory that lime should
be applied to the soil at the same time with dung and other animal
and vegetable substances, as is frequent in the practice of farmers.”
This is strictly correct only in regard to marls, shell, coral, and
lime sand, &c., or to perfectly mild lime, which may all be mixed
with manure in any state without causing loss. Of quick or caus-
tic lime it is correct only when the animal or vegetable matter has
not yet begun to ferment. With recent animal or vegetable mat-
ter quick-lime may be mixed up along with earth into a compost,
not only without the risk of much loss, but with the prospect of
manifest advantage.
3°. That quick-lime hastens or revives the decomposition of inert
organic matter.—This fact also indicates the propriety of allowing
the lime as much time as possible to operate before a crop is taken
from land in which organic matter already abounds. Or where fer-
* Elements of Practical Agriculture, third edition, p. 63.
GENERAL EFFECTS OF LIME. 689
menting manure is added, it advises the farmer to wait till spon-
taneous decomposition becomes languid, when the addition of lime
will bring it again into action and thus maintain a more equable
fertility.
In a work upon soils, which I have frequently commended to
your notice,” you will find the following observations:—“Writers
on agriculture have stated that lime hastens the decay of vegetable
matter, whereas the fact is, that it retards the process of the de-
composition of vegetable matter. If straw of long dung be mixed
with slaked lime, it will be preserved; while if mixed with an equal
portion of earth, the earth will hasten its decay.” The two facts
stated in this last sentence are, I believe, correct, yet it is neverthe-
less consistent both with theory and with universal observation,
that lime in the soil promotes the decomposition of organic mat-
ters, both animal and vegetable. This will appear more clearly
when we come to study the precise nature of the action of lime
upon organic substances in general.
The above remarks, in regard to the best time for applying
lime, refer chiefly to quick-lime, the state in which, in this country,
it is so extensively used. Marls and shell-sands can cause no loss
when mixed with the manure, and therefore may with safety be
laid on at any period of the rotation. The same remark applies
with greater force to lime composts. These may be used precisely
in the same way as, and even instead of, the richer manures—may
be laid, without risk, upon grass lands of any quality, and at any
period—or as a top-dressing on the young corn in spring, when
the grass and clover seeds are sown by which the corn crop is to
be succeeded. And as the compost acts more speedily than lime
in any other form, it is especially adapted for immediate applica-
tion to the crop it is intended to benefit. To wet lands also it is
well suited, and to such as are subject to much rain, by which,
while the surface is naked, the soluble matters produced in the
soil are liable to be much washed away. -
§ 15. Of the effects produced by lime.
The effects of pure lime upon the land, and upon vegetation,
* Morton “On Soils,” third edition, p. 181.
*S.
X X
690 EFFECTS OF LIME UPON THE LAND.
are ultimately the same, whether it be laid on in the state of hy-
drate or of carbonate. If different varieties produce unlike effects—
the quantity of lime applied being the same—it is because in mature
lime is always more or less mixed with other substances which are
capable of modifying the effects that pure lime would alone pro-
duce. The special effects of marls, &c., when they differ from
those of burned lime, are to be ascribed to the presence of such
admixtures. In general, however, the chemical action of the marls
and calcareous sands is precisely the same in kind as that of lime
in the burned and slaked state, and so far the effects which we
have already seen to be produced by marls (p. 666), represent also
the general effects of lime in any form.
These general effects may be considered in reference to the land
on which it is laid, and to the crops which are, or may be, made
to grow upon it.
I.— EFFECTS OF LIME UPON THE LAND.
Pure lime, like the marls and shell sands, produces both a
mechanical and a chemical effect upon the soil. The former is
constant with all varieties of tolerably pure lime, and is easily
understood. It opens and renders freer such soils as are stiff and
clayey, while it actually consolidates such as are light and Sandy.
In some districts it is said to stiffen one-half as much as clay. In
large doses it causes moorish and peaty soils in arable culture
to heave, loosen, and become hollow under the foot, but it is
upon such soils alone that its mechanical effects are usually un-
favourable.
From its chemical action the benefits which follow the use of
lime are chiefly derived. These benefits are principally the fol-
lowing:
1°. It increases the fertility of all soils in which lime does not
already abound, and especially adds to the productiveness of such
as are moist or contain much inert vegetable matter.
2°. It enables the same soils to produce crops of a superior
quality also. Land which, unlimed, will produce only a scanty
crop (3 or 4 fold) of rye or oats, by the addition of lime alone,
will yield a 6 or 7 fold return of wheat. From some clays, also,
apparently unfit to grow corn, it brings up luxuriant crops.
EFFECTS OF LIME UPON THE CROPS. 691
3°. It increases the effect of a given application of manure;
calls into action that which, having been previously added, appears
to lie dormant; and, though manure must be plentifully laid upon
the land, after it has been well limed, yet the same degree of pro-
ductiveness can still be maintained at a less cost of manure than
where no lime has been applied.
4°. As a necessary result of these important changes, the money
value and annual return of the land is increased, so that tracts of
country which had let with difficulty for 5s, an acre, have in many
localities been rendered worth 30s, or 40s, by the application of
lime alone. (Sir J. Sinclair.)
II. —EFFECTS OF LIME ON TEIE PRODUCTIONS OF TELE SOIL.
1°. It alters the natural produce of the land, by killing some
kinds of plants and favouring the growth of others, the seeds of
which had before lain dormant. Thus it destroys the plants which
are natural to siliceous soils and to moist and marshy places.
From the corn-field it extirpates the corm marigold (Chrysan-
themum segetum),” while, if added in excess, it encourages the
red poppy, the yellow cow-wheat (Melampyrum pratense), and
the yellow rattle (Rhinanthus crista galli), and when it has
sunk, favours the growth of the troublesome and deep-rooted colts-
foot.
Similar effects are produced upon the natural grasses. It kills
heath, moss, and sour and bentyf (agrostis) grasses, and brings up
a sweet and tender herbage, mixed with white and red clovers,
more greedily eaten and more nourishing to the cattle. Indeed
all fodder, whether matural or artificial, is said to be sounder and
more mourishing when grown upon land to which lime has been
abundantly applied. On benty grass the richest animal manure
often produces little imprºvement until a dressing of lime has been
laid on.
It is partly in consequence of the change which it thus produces
* Bönninghausen.
+ In Liddesúale, on the Scottish border, is a large tract of land in what is there
called flying bent, not worth more than 3s, an acre. If surface-drained and limed at
a cost of L.2 to L.3 an acre, this becomes worth 12s, an acre for sheep pasture. An
intelligent and experienced border farmer assures me that such land would never for-
get 40 to 60 bushels of lime per acre. This, of course, must not be taken literally,
692 IT IMPROVES THEIR QUALITY.
in the nature of the herbage, that the application of quick-lime to
old grass lands, some time before breaking up, is found to be so
useful a practice. ‘ile coarse grasses being destroyed, tough grass
land is opened and softened, so as to be afterwards more easily
worked, while, when turned over by the plough, the sod sooner
decays and enriches the soil. It is another advantage of this prac-
tice, however, that the lime has time * to diffuse itself through the
soil, and to induce some of those chemical changes by which the
succeeding crops of corn are so greatly benefited.
2°. It improves the quality of almost every cultivated crop.–Thus,
upon limed land,
a. The grain of the corn crops has a thinner skin, is heavier per
bushel, is generally a finer sample and yields more flour, while this
flour is said also to be richer (?) in gluten. On the other hand,
these crops, after lime, run less to straw, and are more seldom laid.
Even where there is no diminution of straw it is stronger, harder,
and holds up the ear better. In wet seasons (in Ayrshire) wheat
preserves its healthy appearance where lime has been applied, while
on unlimed land, of equal quality, it is yellow and sickly. A more
marked improvement is said also to be produced both in the quan-
tity and in the quality of the spring-sown than of the winter-sown
crops. (Puvis).
b. Potatoes from all soils are more agreeable to the taste and
more mealy after lime has been applied, and this is especially the
case on heavy and wet lands, which lie still undrained.
c. Turnips are improved both in quantity and in quality when
lime is laid on in preparing the ground for the seed. It is most effi-
cient, and causes the greatest saving of farm-yard manure where it
is applied in the compost form, and where the land is already rich
in organic matter of various kinds.
d. Peas are grown more pleasant to the taste, and are said to
be more easily boiled soft. Both beans and peas also yield more
grain. -
e. Rape, after a half-liming and manuring, gives extraordinary
* A comparatively long period is sometimes permitted to elapse before grass land
is broken up after liming. Thus at Netherby, “lime or compost is always applied to
the third year's pasture, which is renovated by it, and in two or three years breaks up
admirably for oats.”
LIME SHOULD BE KEPT NEAR THE SURFACE. 693
crops; and the same is the case with the colsa, the seed of which is
largely raised in France for the oil which it yields.
f. On flaw alone it is said to be injurious, diminishing the strength
of the fibre of the stem. Hence, in Belgium, flax is not grown on
limed land till seven years after the lime has been applied. This
point deserves further investigation,
3°. It hastens the maturity of the crop.–It is true of nearly all
our cultivated crops, but especially of those of corn, that their full
growth is attained more speedily when the land is limed, and that
they are ready for the harvest from 10 to 14 days earlier. This
is the case even with buck-wheat, which becomes sooner ripe, even
when it yields no larger a return, when lime is applied to the land
on which it is grown. -
4°. The liming of the land is the harbinger of health as well as
of abundance. It salubrifies no less than it enriches the well cul-
tivated district. I have already drawn your attention (p. 558) to
this as one of the incidental results which follow the skilful intro-
duction of the drain over large tracts of country. Where the use
of lime and of the drain go together it is difficult to say how much
of the increased healthiness of the district is due to the one im-
provement, and how much to the other. The lime arrests the
noxious effluvia which tend to rise more or less from every soil at
certain seasons of the year, and decomposes them, or causes their
elements to assume new forms of chemical combination, in which
they no longer exert the same injurious influence upon animal life.
How beautiful a consequence of skilful agriculture, that the health
of the community should be promoted by the same methods which
most largely increase the produce of the land l Can you doubt
that the All-benevolent places this consequence so plainly before
you, as a stimulus to further and more general improvement—to
the application of other knowledge still to the amelioration of the
soil P
§ 16. Circumstances by which the effects of lime are modified.
These effects of lime are modified by various circumstances. We
have already seen that the quantity which must be applied to pro-
duce a given effect, and the form in which it will prove most ad-
Vantageous, are, in a great measure, dependant upon the dryness
694, LIME IMPROVES POOR SOILS THE MOST.
of the soil, upon the quantity of vegetable matter it contains, and
on its stiff or open texture. There are several other circumstances,
however, to which it is proper still to advert. Thus,
1°. Its effects are greatest when well mixed with the soil, and
hept near the surface within easy reach of the atmosphere. The
reason of this will hereafter appear. .
2°. Among arable soils of the same kind and quality, the effects
are usually greatest upon such as are newly ploughed out, or upon
subsoils just brought to day. In the case of subsoils, this is owing
partly to their containing in many cases very little lime, and partly
to the presence of noxious ingredients, which lime has the power
of altering. In the case of surface soils newly ploughed out, the
greater effect, in addition to these two causes, is due also to the
large amount of vegetable and other organic matter which has
gradually accumulated within them. It is the presence of this or—
ganic matter which has led to the establishment of the excellent
practical rule—“ that lime ought always to precede putrescent ma-
nures when old leys are broken up for cultivation.”
3°. Its effects are greater on certain geological formations than
on others. Thus it produces much effect on drifted (diluvial) sands
and clays—on the soils of the plastic and Wealden clays (pp. 458
and 461)—on those of the new and old red sand-stones, of the gra-
mites, and of the slate rocks usually poor in lime (p. 480)—and,
generally, on the soils formed from all rocks which contain little
lime, or from which the lime may have been washed out during
their gradual degradation. -
On the other hand, it is sometimes applied in vain to the soils
of the oolites (p. 465), and other calcareous formations, because
of the abundance of lime already present in them. The advantage
derived from chalking thin clay soils resting immediately upon
the chalk rock (p. 459), is explained by the almost entire ab-
sence of lime from these soils. The clay covering of the chalk
wolds has probably been formed, not from the ruins of the chalk
rock itself, but from the deposit of muddy waters, which rested up-
on it for some time before those localities became dry land.
4°. Lime produces a greater proportional improvement upon poor
soils than on such as are richer, (Dr Anderson). This also is
easily understood. It is of poor soils in their natural or unim-
TEIE LAND MAY BE SATURATED WITH LIME. 695
proved state of which Dr. Anderson speaks." In this state they
contain a greater or less quantity of organic matter, but are nearly
destitute of lime, and hence are in the most favourable condition
for being benefited by a copious liming. Experience has proved
that by this one operation such land may be raised in money value
eight times, or from 5s, to 40s. per acre; but no practical man
would expect that arable land already worth L.2 per acre could,
by liming or any other single operation, become worth L.16 per
acre of annual rent. The greater proportional improvement pro-
duced upon poor lands by lime is only an illustration, therefore,
of the general truth—that on poor soils the efforts of the skilful
improver are always crowned with the earliest and most apparent
Sll CC0SS, -
5°. In certain cases, the addition of lime, even to land in good
cultivation, and according to the ordinary and approved practice
of the district, produces no effect whatever. This is sometimes ob-
served where the custom prevails, as in some parts of Ayrshire and
elsewhere, to apply lime along with every wheat crop, and on such
farms especially where the land is of a lighter quality. Where
from 40 to 60 bushels of lime are added at the end of each rotation
of 4 or 5 years, the land may soon become so saturated with lime
that a fresh addition will produce no sensible effect. Thus Mr
Campbell of Craigie informs me of a trial made by an intelligent.
farmer in his neighbourhood, where alternate ridges only were limed
without any sensible difference being observed. No result could
show more clearly than this—that for one rotation at least the expense
of lime might be saved, while at the same time the land would run
the less risk of exhaustion. I suppose, of course, that, besides being
limed, the land had been liberally manured also. Another fact
mentioned by Mr Campbell, however, throws some doubt upon this
supposition. The lime never fails to produce obvious benefit where
the land is allowed to be 4 or 5 years in grass—where it is applied,
that is, only once in 8 or 9 years, and only where the land is rich
* “I never met,” he says, “with a poor soil in its natural state, which was not be-
nefited in a very great degree by calcareous matter when administered in proper quan-
tities. But I have met with several rich soils, which were fully impregnated with
dung, on which lime applied in any quantity produced not the smallest sensible ef.
fect,”
(396 LIME DOES NOT BENEFIT EXHAUSTED SOILS.
in vegetable matter. The fair inference is, therefore, that in this
district as well as in others where similar effects are observed—too
much lime with perhaps too little farm-yard manure is habitually
added to the land, whereby not only is a needless expense incur-
red, but a speedier exhaustion of the soil is insured. Good hus-
bandry, therefore, indicates either the application of a smaller dose
at the recurrence of the wheat crop–the occasional omission of
lime altogether for an entire rotation, or a more liberal habit of
mamuring.
6°. On poor arable lands, which are not naturally unproduc-
tive, but which are worn out or exhausted by repeated liming and
cropping, lime produces no good whatever.” (Anderson, Brown,
Morton). Such soils, if they do not already abound in lime, are,
at least, equally destitute of numerous other kinds of food, orga-
nic and inorganic, by which healthy plants are nourished,—and
they are only to be restored to a fertile condition by a judicious
admixture of all. This truth is confirmed by the practical obser-
vation, that on soils so exhausted farm-yard manure along with the
lime does not produce the same good results as in other cases. All
that the soil requires is not supplied in sufficient abundance by
these two substances laid on alone.
7°. On lands of this kind, and on all in which vegetable matter
is wanting, lime may even do harm to the immediate crop. It is
apt to singe or burn the corn sown upon them (Brown)—an effect
which is probably chemical, but which may in part be owing to its
rendering more open and friable soils which through long arable
culture are too open already (Morton).
8°. A consideration of the circumstances above adverted to ex-
plains why, in some districts, and even in some whole provinces,
the use of lime in any form should be condemned and even en-
tirely given up. The soil has been impoverished through its un-
skilful application—or, by large admixtures of lime or marl for a
series of years, the soil has been so changed as to yield no adequate
return for new additions. Thus for a generation or two the prac-
* “It is scarcely practicable to restore fertility to land, even of the best natural
quality, which has been thus abused ; and thin moorish soils, after being exhausted
by lime, are not to be restored.” (Brown). This opinion of Mr Brown's means only
that, with the knowledge of his time, this difficulty could not be economically over-
C OTIl Q.
EFFECTS OF AN OVER-DOSE OF LIME. 697
tices of liming and marling are abandoned, to be slowly and re-
luctantly resumed again when more knowledge becomes diffused
among practical men, or when natural causes have removed the
lime from the soil, and produced an accumulation of those other
substances which, when associated with it, contribute to the pro-
ductiveness of the land.
§ 17. Effects of an overdose of lime—overliming.
There are several effects which are familiar to the practical man
as more or less observable when lime in any form is laid too lavish-
ly upon the land. Thus,
1°. By an overdose of quick-lime some soils are hardened to
such a degree as to become impervious to water or to the roots of
plants. Several parts of the Carse of Gowrie were formerly ren-
dered so hard by the addition of lime as to be unfit for vegetation
(Kames).” This effect I have never seen; it will be observed, I
should think, only in soils which are maturally wet and undrain-
ed, or where much rain has fallen and lingered on the land after
the lime has been applied.
2°. Some soils are rendered so loose by lime as to be capable
of holding no water (Kames). Upon stiff clays a very large ap-
plication, indeed, will be required to produce this effect. It hap-
pens chiefly upon moorish or peaty soils under arable culture.
In many parts of Scotland the supposed effects of overliming,
on thin moorish soils or on reclaimed peat, are frequently seen.
The land is hollow under the tread—the foot sometimes sinks into
it—it is open, light, and porous. Turnips and barley grow well
on it; but oats and clover refuse to give profitable crops. It, in
fact, is too light and open for these crops, which require a certain
degree of tenacity in the soil in which their roots are to fix them-
selves.
This condition of the soil is usually ascribed to too large addi-
tions of lime being made, and the expression overlimed applied to
land in this state seems to imply that too large a proportion of lime
is actually contained in it.
With the view of ascertaining how far this is really the case, I
procured from Ballindalloch, in Inverness-shire, several specimens
of soil in this overlimed, light, porous, condition—incapable of
* Lord Kames's Gentlemaº Farmer, edit. 1802.
69S TREATMENT OF OVERLIMED TAND.
growing oats and clover, and subjected them to analysis. The
following was the result of the examination of three of the speci-
Ille]].S :
Bow Moon Bow Moori Mistly Park
Park soil. Park subsoil. soil and Subsoil.
Organic matter, , ......... .. 10.29 9.54 5.65
Salts soluble in water,......... 0.45 0.15 0.50
Oxide of iron, .............. ... 2.49 3.68 0.50
Alumina, ........................ 1.71 2.54 1.1 !
Carbonate of lime, ............ 1.40 0.69 l.l. ()
Oxide of manganese, ......... trace 0.72 trace
Carbonate of magnesia, ... .. do. trace do.
Insoluble matter, chiefly sand, 81.77 82.79 91.20
98.]] 100.11 100.06
In these soils, therefore, lime was by no means in excess; on
the contrary, they might contain a larger quantity with obvious ad-
vantage. -
The evil, therefore, is not a chemical but a mechanical one, and
the cure, therefore, ought to be a mechanical one also. Means
must be taken to bring such soils and to preserve them in a more
solid condition. For this purpose several methods are to be re-
commended, such as,
a. Eating off the turnips and clover with sheep. This method
is, in fact, found to solidify it at Ballindalloch, so as to make it
capable of bearing oats.
b. Rolling the young corn with Croskill's clod crusher or some
similar implement, by which the surface may be pressed together
and the plants properly rooted.
c. Ploughing shallow, and as seldom as possible. The evil has
arisen from the long and frequent ploughing, which such land has
been unable to bear. The use of the cultivator may be in many
cases substituted for that of the plough, and thus the loosening of
the land in a great degree prevented.
d. Paring the land with the breast plough, as is practised bene-
ficially in Berkshire, Gloucester, and other districts, and either
burning or rotting the surface, may be tried also with the prospect
of advantage. No deep ploughing being thus indulged in, a firm
seed bed is left for the grain, and, if well manured, any crop may
be grown.
LENGTH OF TIME DUIRING WIFIICH LIME ACTS. 699
3°. But the most injurious effect of an overliming, especially
when laid on in repeated doses for a succession of years, is the ex-
haustion by which it is succeeded. To the nature and cause of
this exhaustion, I shall draw your attention in a subsequent part
of the present lecture. (See § 33.)
§ 18. Length of time during which lime acts.
It is the fate of nearly all the superficial improvements of the
soil, that they are only temporary in their duration. The action
of lime ceases after a time, and the land returns to its original
condition. The length of time which must elapse before this takes
place will depend, among other circumstances, upon the quantity
of lime added to, or originally contained in, the soil—upon the
kind of cropping to which it is subjected—on the nature of the
soil itself—on the slope and exposure and natural moisture of the
land,-and not a little on the climate in which it is situated, and
on the quantity of rain that falls.
We have seen that on the arable lands of the south of Scotland
20 years is the longest period during which the doses there ap-
plied act profitably upon the crops—while in other parts of the
country renewed applications are considered necessary at much
shorter intervals. Mr Dawson, of Frogden, who introduced the
practice of liming into the Border counties of Scotland, observed
that, when harrowed in with the grass seeds, its effect in improving
the subsequent pasture was sensible for 30 years after. In the
Southern and Midland counties of England also a heavy marling
or chalking is said to last for 30 years,” and the same period
is assigned to the sensible effect of the ordinary doses of lime-
sand in Ireland, and of shell-sands and marls in several parts of
|France. - *
The effect of the lime lessens gradually, and though at the end
of an assignable number of years it becomes almost insensible, yet
it does not altogether cease till a much later period. This period
is in some cases so protracted that intelligent practical men are in
many districts to be met with who believe—that certain grasslands
would never forget a good dose of lime (p. 691, note).
* Applied at a cost of 30s. to 50s. per acre, according to the locality.—Mr Pusey,
Royal Agricultural Journal, iii. p. 185.
3
700 LIME NATURALLY SINKS INTO THE SOIL.
§ 19. Of the sinking of lime into the soil.
One of the causes of this gradual diminution of the action of
lime is to be found in the singular property it possesses of slowly
sinking into the land, until it almost entirely disappears from the
surface soil. It has been long familiar to practical men, that when
grass lands, which have been limed on the sward, are after a time
broken up, a white layer or band of lime is seen beneath the sur-
face, at a greater or less depth in proportion to the time which has
elapsed since the lime was applied. Upon arable land the action
of the plough counteracts this tendency in some measure, bring-
ing up the lime again from beneath, and keeping it mixed with
the surface mould. Yet, through ploughed land it sinks at length,
especially where the ploughing is shallow, and even the industry
of the gardener can scarcely prevent it from descending beyond
the reach of his spade.
The chief cause of this sinking is to be found in the extreme
minuteness of the particles into which slaked lime naturally falls.
If a portion of slaked lime be mixed with water a little of the lime
is dissolved, but much more is held in suspension in an extremely
divided state, forming a milky liquid. When this milk of lime is
allowed to stand undisturbed, the fine particles subside very slowly,
and are easily again disturbed, but if thrown upon a filter they are
arrested immediately, and the lime-water passes through clear. Sup-
pose these fine particles to be mixed with the soil, and the rain to
fall upon them, it will carry them downwards through the pores of
the soil till the close subsoil acts the part of a filter, and arrests
them. This tendency to be washed down is common not only to
lime, but to all minutely divided earthy matter of a sufficiently in-
coherent nature. Hence the formation of that more or less imper-
vious layer of finely divided matter which so often forms the sub-
soil beneath free and open surface soils. And that lime should
appear alone or chiefly to sink on any cultivated field, may arise
from this circumstance—that the continued action of the rains had
long before carried downwards the finer incoherent particles of
other kinds which existed naturally in the soil, and therefore could
find little else but the lime on which this action could be exer-
cised.
This explanation is satisfactory enough in the case of light and
PRACTICAL REMEDIES FOR THIS SINKING.. 701
open soils, which are full of pores, but it appears less so in regard
to stiff clays and to loamy soils which are not only close and ap-
parently void of pores, but seem themselves to consist of particles
in a sufficiently minute state of division to admit of their being car-
ried down by the rains in an equal degree with lime itself. This
difficulty induced Lord Dundonald to suspect the agency of some
chemical principle in producing the above effect.” As the lime,
however, is unchanged after it has descended, is still in a powdery
state, and exhibits no appearance of having been dissolved, it is
difficult to imagine any chemical action by which such a sinking
could have been brought about.
It is possible that in grass lands the earth-worms, which con-
tribute so much to the gradual production of a fine mould, may,
by bringing up the other earthy matters only, contribute to the
apparent sinking of the lime, as well as of certain other top-dress-
ings.f
Of course the above explanations are not intended to apply to
the sinking of lime-gravel and shell-sand, which, like sand and
clay laid upon peat, probably sink by their own weight.
The effects of this sinking are to remove the lime from the sur-
face soil, and to form a layer of calcareous matter which in wet or
impervious bottoms hardens and forms a more or less solid bed or
pan, through which the rains and roots refuse to penetrate, and
which the subsoil plough in some districts can tear up with diffi-
culty. On our stiffer soils it encourages the growth of the trou-
blesome coltsfoot, and in the open ditches that of the wholesome
water-Cress,
The practical remedies for this sinking, when it has taken place,
are of two kinds.
1°. The ploughing of a deeper furrow, by which the lime is again
brought to the surface. This indeed is one of the direct benefits
which in many localities attend the use of the trench plough (p.
572).
2°. The sowing of deep-rooted and lime-loving crops, such as
* “In clayey and loamy soils, which are (?) equally diffusible with lime, and near-
ly of the same specific gravity, the tendency which lime has to sink cannot be account-
ed for simply on mechanical principles.”—Lord Dundonald's Agricultural Chemistry,
p. 45.
+ See in a subsequent lecture the remarks on laying down to grass.
702 ... WHY LIMING MUST BE REPEATED.
lucerne and Sainfoin, which in such soils not only thrive, but bring
up in their stems, and restore to the surface a portion of the lime
which had previously descended, and thus make it available to the
after-crops.
§ 20. Why liming must be repeated.
Lime which sinks, as above described, does not wholly escape
from the soil, but may by judicious management be again brought
to the surface. Such a sinking, therefore, does not necessarily call
for the addition of a fresh dose of lime, nor does it explain the
reason why in practice the application of lime to the land must at
certain intervals be every where repeated.
We have already seen that the influence of the lime we have laid
upon our fields after a time gradually diminishes—the grass be-
comes sensibly less rich and fuller of weeds year by year, the crops
of corn less abundant, the sample of grain inferior, and the kind of
grain it will ripen less valuable. Does the lime, you might ask,
actually disappear from the soil, or does it merely cease to act?
This question has been most distinctly answered by an experiment
of Lampadius. He mingled lime with the soil of a piece of ground
till it was in the proportion of 1:19 per cent. of the whole, and he
determined subsequently, by analysis, the quantity of lime it con-
tained in each of the three succeeding years.
Carbonate of lime.
The first year it contained ......... 1.19 per cent.
The second year ..................... 0.89
The third year ....................... O-52 ...
The fourth year ................... ... 0-24 ...”
There can be no question, therefore, that the lime gradually dis-
appears or is removed from the soil.
The agencies by which this removal is effected are of several
kinds.
1°. In some cases it sinks, as we have already seen, and escapes
into the subsoil beyond the reach of the plough or of the roots of
our cultivated crops.
2°. A considerable quantity of lime is annually removed from
the soil by the crops which are reaped from it. We have already
* Schübler, Agricultun Chemie, ii. p. 141.
THE RAINS WASH IT FROM THE SOIL. 703
seen (p. 409), that in a four years' rotation of alternate green and
corn crops the quantity of lime contained in the average produce
of good land amounts to about 200 lbs. This is equal to 50 lbs.
of quick-lime or 90 lbs. of carbonate of lime every year. The
whole of this, however, is not usually lost to the land. Part at
least is restored to it in the manure into which a large proportion
of the produce is usually converted. Yet a considerable quantity
is always lost—escaping chiefly in the liquid manure and in the
drainings of the dung-heaps—and this loss must be repaired by the
renewed addition of lime to the land. \
3°. But the rains and natural springs of water percolating
through the soil, remove, in general, a still greater proportion.
While in the quick or caustic state, lime is soluble in pure water.
Seven hundred and fifty pounds of water will dissolve about one
pound of lime. The rains that fall, therefore, as they sink through
the soil, dissolve and carry away a portion of the lime so long as
it remains in the caustic state.
Again, quick-lime, when mixed with the soil, speedily attracts
carbonic acid, and becomes, after a time, converted into carbonate,
which is nearly insoluble in pure water. But this carbonate, as
we have already seen (p. 65), is soluble in water impregnated with
carbonic acid—and as the drops of rain in falling absorb this acid
from the air, they become capable of dissolving an appreciable
quantity of the finely divided carbonate which they meet with in
the soil. Hence the water that flows from the drains in our cul-
tivated fields is always impregnated with lime, and sometimes to so
great a degree as to form calcareous deposits in the interior of the
drains themselves, when the fall is so gentle or the length of the
drain so great as to allow the water to linger for a sufficient time
before it escapes into the air.
It is impossible to estimate the quantity of lime which this dis-
solving action of the rains must gradually remove. It will vary
with the amount of rain which falls in each locality, and with the
slope or inclination of the land; but the cause is at once univer-
Sal and constantly operating, and would alone, therefore, render
necessary, after the lapse of years, the application of new doses of
lime both to our pastures and to our arable fields.
4°. During the decay of vegetable matter, and the decomposi-
704 THEORY OF THE ACTION OF LIME.
tion of mineral compounds, which take place in the soil where lime
is present, new combinations are formed in variable quantities
which are more soluble than the carbonate, and which therefore
hasten and facilitate this washing out of the lime by the action of
the rains. Thus chloride of calcium, nitrate of lime, and gypsum
are all produced—of which the two former are eminently soluble
in water—while organic acids also result from the decay of the
organic matter, with some of which the lime forms readily soluble
compounds (salts) easily removed by water.
The ultimate resolution of all vegetable matter in the soil into
carbonic acid and water (p. 227), likewise aids the removal of the
lime. For if the soil be every where impregnated with carbonic
acid, the rain and spring waters that flow through it will also be-
come charged with this gas, and thus be enabled to dissolve a
larger portion of the carbonate of lime than they could otherwise
do. Thus theory indicates, what experience, I believe, confirms,
that a given quantity of lime will disappear sooner from a field,
the more abundant the animal and vegetable matter it may contain.
§ 21. Theory of the action of lime.
Lime acts in two ways upon the soil. It produces a mechanical
alteration, which is simple and easily understood, and is the cause
of a series of chemical changes, which are really obscure, and are
as yet susceptible of only partial explanation. •.
In the finely divided state of quick-lime, of slaked lime, or of
soft and crumbling chalk, it stiffens very loose soils, and opens the
stiffer clays, while in the form of lime-stone gravel or of shell
sand, it may be employed either for opening a clay soil or for giv-
ing body and firmness to boggy land. These effects, and their
explanation, are so obvious, that it is unnecessary to dwell upon
them.
The purposes served by lime as a chemical constituent of the
soil are at least of four distinct kinds. -
1°. It directly supplies a kind of inorganic food which appears
to be necessary to the healthy growth of all our cultivated plants.
2°. It neutralises acid substances which are maturally formed in
the soil, and decomposes other noxious compounds which are not
unfrequently within reach of the roots of plants, producing in
OF LIME AS A DIRECT FOOD OF PLANTS, 705
their stead others which are not only harmless, but often directly
useful to vegetation.
3°. It changes the inert vegetable matter in the soil, liberates
the inorganic substances it contains, and thus gradually renders it
useful to vegetation.
4°. It aids and promotes the decomposition of the mineral or
rocky fragments of which so much of all our soils consists, and
thus enables the inorganic substances they contain to become use-
ful to the growth of plants,
These several modes of action it will be mecessary to illustrate
in succession.
§ 22. Of lime as a direct food of plants.
In considering the chemical nature of the ash of plants (pp. 364
to 409), we have seen that lime in all cases forms a sensible pro-
portion of that of an entire plant. Hence the reason why lime
is regarded as a necessary food of plants, and hence also one cause
of its beneficial influence in general agricultural practice.
The quantity of pure lime contained in the crops produced upon
one acre during a four years' rotation, amounts to about 200 lbs.
—equal to 360 lbs. (3; cwt.) of carbonate of lime, in the state
of marl, shell sand, or pure lime-stone gravel. It is obvious,
therefore, that one of the most intelligible purposes served by lime,
as a chemical constituent of the soil, is to supply this lime, which
in some form or other must enter into the roots of plants.
But the different crops which we grow contain lime in unlike
proportions. Thus the average produce of an acre of land under
the following crops contains of lime—
Grain or roots. Straw or tops. Total.
Wheat,......... (25 bush.)... . ... 1 12 13 lbs.
Barley,........ (40 bush.) ........ lº, 15% 17 ...
Oats,............ (50 bush.)........ 3 19 22 ...
Rye,............ (26 bush.)......... 1% 15% 17 ...
Beans, ......... (25 bush.)......., 2% 34 36% ...
Turnips, ......(20 tons)......... 46 72 ll 8 ...
Potatoes, ...... (8 tons) ......... 8 31 39 ...
Red clover, ... (2 tons) ......... -- 77 77 . . .
Rye grass,...... (2 tons) ......... - 30 30 ...
These quantities are not constant, and generally all our crops
contain more lime when grown upon land to which lime has been
Y y
706 LIME TAKEN UP BY PLANTS AS FOOD.
2’
copiously applied. But the very different quantities contained in
the several crops as above exhibited, shew that one reason why lime
favours the growth of some crops more than others is, that some ac-
tually take up a larger quantity of lime as food. These crops,
therefore, require the presence of lime in greater proportion in the
soil, in order that they may be able to obtain it so readily that no
delay may occur in the performance of those functions or in the
growth of those parts to which lime is indispensable.
Another circumstance also must be taken into account in con-
nection with the above-quantities of lime found in our different
crops. Whatever kind or amount of food obtained from the soil a
plant may require to bring it to maturity, it must collect the whole
during the time usually allotted to its growth. Thus the longer a
crop is in the ground, the slower it grows, and the longer it usually
takes to arrive at maturity, the more time it has to collect its food
by means of its roots. Barley germinates and ripens its seed with-
in three months—in Sicily sometimes within six weeks; while
wheat is from six to ten months in the ground. The roots of
barley, therefore, must do much more work in the same time than
those of wheat. They must among other things take up 17 lbs.
of lime in three months, while wheat takes up on an average
only 13 lbs, in six months. Now to effect this in the same soil, it
must send out more roots in quest of food than the wheat plant
will require to do, and thus it must waste more of its vegetative
strength underground. But if we make the supply of food in
the soil more abundant, we diminish the labour of the barley plant
and greatly facilitate its growth.
Thus we are enabled to conclude that the proportion of lime in
the soil ought to be adapted not only to the proportion which the
perfect plant is found to contain and require, but to the period
also which is allotted to its natural growth. For crops which run
their course quickly, a larger proportion of lime as well as of all
other kinds of food will be required than is necessary for crops
that are longer in coming to perfection. Has this fact anything
to do with the earlier harvests upon well-limed land, and with its
peculiar fitness for the growth of barley?
3
ACTS CHIEFLY UPON THE ORGANIC MATTER OF THE SOIL. 707
§ 23. The chemical action of lime is everted chiefly upon the
organic matter of the soil.
There are four circumstances of great practical importance in
regard to the action of lime, which cannot be too carefully consi-
dered in reference also to the theory of its operation. These are—
1°. That lime, unless in the form of compost, has comparatively
little effect upon soils in which organic matter is deficient.
2°. That its apparent effect, at least upon the corn crops, is in-
considerable during the first year after its application, compared
with that which it produces in the second and third years, A
3°. That its effect is most sensible when it is kept near the sur-
face of the soil, and gradually becomes less as it sinks towards the
Subsoil. And
4°. That under the influence of lime the organic matter of the
soil disappears more rapidly than it otherwise would do, and that
after it has thus disappeared fresh additions of lime are much less
beneficial than before. ar
It is obvious from these facts, that in general the main beneficial
purpose served by lime is to be sought for in the nature of its che-
mical action upon the organic matter of the soil—an action which
takes place slowly, which is hastened by the access of air, and
which causes the organic matter itself ultimately to disappear.
§ 24. Of the forms in which organic matter usually exists in the
soil, and the circumstances under which its decomposition may
take place. -
I.—The organic matter which lime thus causes to disappear is
presented to it in one or other of five different forms:
1°. In that of recent, often green, moist, and undecomposed
roots, leaves, and stems of plants.
2°. In that of dry, and still undecomposed, vegetable matter,
such as straw.
3°. In a more or less decayed or decaying state, generally black
or brown in colour—and often in Some degree soluble in water.
4°. In what is called the inert state, when spontaneous decay
ceases to be sensibly observed. And * -
5°. In the state of chemical combination with the earthy sub-
708 INFLUENCE OF CIRCUMSTANCES
stances—forming humates, ulmates, &c. with the alumina, and
with the lime or magnesia which exist in the soil.
Upon these several varieties of organic matter lime acts with
different degrees of rapidity. -
II.-The final result of the decomposition of these several forms
of organic matter, when they contain no nitrogen, is their conver-
sion into carbonic acid and water only (p. 270). They pass, how-
ever, through several intermediate stages before they reach this
point—the number and rapidity of which, and the kind of changes
they undergo at each stage, depend upon the circumstances under
which the decomposition is effected. Thus the substance may de-
compose— -
1°. Alone, in which case the changes that occur proceed slowly,
and arise solely from a new arrangement of its own particles.
This kind of decomposition rarely occurs to any extent in the soil;
and then only in such as are very compact and impervious to air
and water. - -
2°. In the presence of water only.—This also seldom takes place
in the soil. Trees long buried in moist clays impervious to air,
exhibit the kind of slow alteration which results from the presence
of water alone. In the bottoms of lakes, ditches, and boggy places
also, from which inflammable gases arise, water is the principal
cause of the more rapid decomposition.
3°. In the presence of air only.—In mature organic matter is
never placed in this condition, the air of our atmosphere being al-
ways largely mixed with moisture. In dry air decomposition is
exceedingly slow, and the changes which dry organic substances
undergo in it are often scarcely perceptible.
4°. In the presence of both water and air.—This is the almost
universal condition of the organic matter in our fields and farm-
yards. The joint action of air and water, and the tendency of the
elements of the organic matter to enter into new combinations,
cause new chemical changes to succeed each other with much ra-
pidity. It will of course be understood that moderate warmth is
necessary to the production of these effects.”
* A familiar illustration of the conjoined efficacy of air and water in producing a
chemical change, is exhibited in their action upon iron. If a piece of polished iron
be kept in perfectly dry air it will not rust. Or if it be completely covered over with
|UPON THE DECAY OF ORGANIC MATTER. 709
. 5°. In the presence of lime or of some other alcaline substance
(potash, soda, or magnesia).--Organic matter is often found in the
soil in such a state that the conjoined action of both air and water
are unable to hasten its decomposition. A new chemical agency
must then be introduced, by which the elements of the organic
matter may again be set in motion. Wood ashes, kelp, carbonate
of soda, &c. act in this way more or less powerfully, but lime is
the agent which for this purpose is most largely employed in prac-
tical agriculture.
\
§ 25. General action of alcaline substances upon organic matter.
It is this action of alcaline matter upon the organic substances
of the soil in the presence of air and water that we are principally
to investigate.
When organic matter undergoes decay in the presence of air
and water only, it first rots, as it is called, and blackens, giving
off water or its elements chiefly, and forming humus—a mixture
of humic, ulmic, and some other organic acids (p. 70), with decay-
ing vegetable fibre. It then commences, at the expense of the
oxygen of the air and of water, to form other more soluble acids
(malic, acetic, lactic, crenic, mudesic, &c.), among which is a por-
tion of carbonic acid—and, by the aid of the hydrogen of the wa-
ter which it decomposes, one or more of the many compounds of
carbon and hydrogen, which often rise up, as marsh-gas does, and
escape into the air (p. 268.)
Thus there is a tendency towards the accumulation of acid sub-
stances of vegetable origin in the soil, and this is more especially
the case when the soil is moist, and where much vegetable matter
abounds. The effect of this super-abundance of acid matter is, on
the one hand, to arrest the further matural decay of the organic
matter, and, on the other, to render the soil unfavourable to the
healthy growth of young or tender plants.
pure water in a well-stoppered bottle, from which air is excluded, it will remain bright
and untarnished. But if a polished rod of iron be put into an open vessel half full of
water, so that one part of its length only is under the water—then the rod will begin
very soon to rust at the surface of the water, and a brown ochrey ring of oxide of iron
will form around it, exactly where the air and water meet. From this point the rust
will gradually spread upwards and downwards. So it is with the organic matter of
the soil. Wherever the air and water meet, their chemical action upon it, at ordi-
mary temperatures, soon becomes perceptible.
710 INFLUENCE OF ALCALINE SUBSTANCES.
The general effect of the presence of alcaline substances in the
soil is to counteract these two evils. They combine with and thus
remove the sourmess of the acid bodies as they are formed. In
consequence of this the soil becomes sweeter or more propitious to
vegetation, while the matural tendency of the vegetable matter to
decay is no longer arrested.
It is thus clear that an immediate good effect upon the land
must follow either from the artificial application or from the na-
tural presence of alcaline matter in the soil—while at the same
time it will cause the vegetable matter to disappear more rapidly
than would otherwise be the case. But the effect of such sub-
stances does not end here. They actually dispose or provoke—
pre-dispose chemists call it—the vegetable matter to produce acid
substances, in order that they may combine with them, and
thus cause the organic matters to disappear more rapidly than
they otherwise would do—in other words, they hasten forward the
exhaustion of the vegetable matter of the soil. -
Such is the general action of all alcaline substances. This ac-
tion they exhibit even in close vessels. Thus a solution of grape
sugar, mixed with potash, and left in a warm place, slowly forms
melassic acid—while in cold lime-water the same sugar is gradu-
ally converted into another acid called the glucic. But in the
open air other acids are formed in the same mixtures, and the
changes proceed more rapidly. Such is the case also in the soil,
where the elements of the air and of water are generally at hand
to favour the decomposition.
But the nature of the alcaline matter which is present has much
influence upon the rapidity also with which such changes are pro-
duced. The most powerful alcaline substances—potash and soda
—produce all the above effects most quickly; lime and magnesia
are next in order, and the alumina of the clay soils, though much
inferior to all these, is far from being without an important influ-
€11C0. -
|Hence one of the benefits which result from the use of wood-
ashes containing carbonate of potash, when employed in small
quantities, and along with vegetable and animal manures, as they
are in this country; but hence also the evil effects which are found
to follow from the application of them in too large doses, or too
LIME ALONE DOES NOT HASTEN DECAY. 711
frequently repeated. Thus in countries where wood abounds,
and where it is usual, as in Sweden and Northern Russia, to burn
the forests and to lay on their ashes as manure, the tillage can be
continued for a few years only. After one or two crops the land
is exhausted, and must again be left to its natural produce.
§ 26. Special effects of caustic lime upon the several varieties of
organic matter in the soil.
The effects of lime upon organic matter are precisely the same
in kind as those above described, as being produced by alcaline
matter in general. They are only less in degree, or take place
more slowly, than when soda or potash is employed. Hence, the
greater adaptation of lime to the purposes of practical agricul-
ture.
1°. Action of caustic lime alone upon vegetable matter.—If the
fresh leaves and twigs of plants, or blades and roots of grass, be
introduced into a bottle, surrounded with slaked lime, and corked
—they will slowly undergo a certain change of colour, but they
may be preserved for years, without exhibiting any striking change
of texture (Mr Garden). If dry straw be so mixed with slaked
lime, it will exhibit still less alteration. In either case also the
changes will be even less perceptible if, instead of hydrate of lime,
the carbonate (or mild lime), in any of its forms, be mixed with
these varieties of vegetable matter. On some other varieties of
vegetable matter, such, for example, as are undergoing rapid
decay, or have already reached an advanced stage of decomposi-
tion,-an admixture of slaked lime produces certain perceptible
changes immediately, and mild lime more slowly, but these changes
being completed, the tendency of lime alone is to arrest rather than
to promote further rapid alterations. Hence, the following opi-
nions of experienced practical observers must be admitted to be
theoretically correct—in so far as they refer to the action of lime
alone.
“If straw of long dung be mixed with slaked lime it will be
preserved” (Morton.”)
“Lime mixed in a mass of earth containing the live roots and
seeds of plants will not destroy them” (Morton).f
* On Soils, 3d edition, p. 181. † Ibid.
712 ACTION OF CAUSTIC LIME UPON ORGANIC MATTER.
“Sir H. Davy's theory, that lime dissolves vegetable matter, is
given up; in fact, it hardens vegetable matter.” (Mr Pusey)."
These opinions, I have said, are probably correct in so far as
regards the unaided action of lime. They even express, with an
approach to accuracy, what will take place in the interior of com-
post heaps of a certain kind, or in some very dry soils. That
they cannot, however, apply to the ordinary action of lime upon
the soil is proved by the other result of universal observation—
that lime, so far from preserving the organic matter of the land to
which it is applied, in reality wastes it—causes, that is, or disposes
it to disappear.
2°. Action of caustic lime on organic matter in the presence of air
and water.—In the presence of air and water, when assisted by a
favouring temperature, vegetable matter, as we have already seen,
undergoes spontaneous decomposition. In the same circumstances
lime promotes and sensibly hastens this decomposition,-altering
the forms or stages through which the organic matter must pass——
but bringing about more speedily the final conversion into car-
bonic acid and water. During its natural decay in a moist and
open soil, organic matter gives off a portion of carbonic acid gas,
which escapes into the air, and forms certain other acids which
remain in the dark mould of the soil itself. When quick or
slaked lime is added to the land, its first effect is to combine with
these acids—to form carbonate, humate, &c., of lime—till the
whole of the acid matter existing at the time is taken up. That
portion of the lime which remains uncombined, either slowly ab-
sorbs carbonic acid from the air or unites with the carbonate al-
ready formed, to produce the known compound of hydrate with
carbonate of limef—waiting in this state in the soil till some fresh
portions of acid matter are formed with which it may combine.
But it does not inactively wait; it persuades and influences the
organic matter to combine with the oxygen of the air and water
with which it is surrounded, for the production of such acid sub-
stances—till finally the whole of the lime becomes combined either
with carbonic or with some other acid of organic origin.
* Royal Agricultural Journal, iii. p. 212.
+ That compound, namely, which is produced when quick-lime slakes sponta-
neously in the air.—See page 654,
IN THE PRESENCE OF AIR AND WATER. 713
Nor at this stage are the action and influence of lime observed
to cease. On the contrary, this result will, in most soils, be ar-
rived at in the course of one or two years, while the beneficial
action of the lime itself may be perceptible for 20 or 30 years.
Hence there is much apparent ground for the opinion of Lord
Kames, “ that lime is as efficacious in its (so called) effete as in its
caustic state.” Even the more strongly expressed opinion of the
same acute observer, “ that lime produces little effect upon vege-
tables till it becomes effete,”—derives much support from expe-
rience—since lime is known to have comparatively little effect
upon the productiveness of the land till one or two years after its
application, and this period, as I have said, is in most soils suffi-
cient to deprive even slaked lime of all its caustic properties.
Of the saline compounds” which caustic lime thus forms, either
immediately or ultimately, some, like the carbonate and humate,
being very sparingly soluble in water, remain more or less per-
manently in the soil; others, like the acetate of lime, being readily
soluble, are either washed out by the rains or are sucked up by
the roots of the growing plants. In the former case they cause
the removal of both organic matter and of lime from the land; in
the latter they supply the plant with a portion of organic food,
and at the same time with lime—without which, as we have fre-
quently before remarked, plants cannot be maintained in their
most healthy condition.
§ 27. Action of mild or carbonate of lime upon the vegetable matter
* of the soil.
The main utility of lime, therefore, depends upon its prolonged
after action upon the vegetable matter of the soil. What is this
action, and in what consist the benefits to which it gives rise?
In answering this question, it is of importance to observe that
all the effects produced by alcaline matter in general—whether by
lime or by potash, in the caustic state, are produced in kind also
by the same substances in the state of carbonate. The carbonic
acid with which they are united is retained by a comparatively
feeble affinity, and is displaced with greater or less ease by almost
* Saline compounds or salts are always formed when lime, magnesia, potash, Soda,
&c. combine with acids.
71.4 ACTION OF CARBONATE OF LIME.
every other acid compound which is produced in the soil. With
this displacement is connected an interesting series of beautiful
changes, which it is of consequence to understand.
You will recollect that the great end which mature, so to speak,
has in view, in all the changes to which she subjects organic matter
in the soil, is to convert it—with the exception of its nitrogen—
into carbonic acid and water. For this purpose it combines, at
one time, directly with the oxygen of the air, and at another
decomposes water and unites with the oxygen or the hydrogen
which are liberated, or with both to form new chemical combina-
tions. Each of these new combinations is either immediately pre-
liminary to or is attended by the conversion of a portion of the
elements of the organic matter into one or other of those sub-
stances on which plants live. Now during these preliminary or
preparatory steps, acid compounds are among others constantly
produced. With these acids, the earbonate of lime, when present
in the soil, is ever ready to combine. But in so combining, it gives
off the carbonic acid with which it is already united, and thus a
continual, slow, evolution of carbonic acid is kept up as long as
any undecomposed carbonate remains in the soil.
I do not attempt to specify by name the various acid substances
which are thus formed during the oxidation of the organic matter,
and which successively unite with the lime—because the entire
series of interesting and highly important changes, which organic
substances undergo in the soil, has as yet been too little investi-
gated, to permit us to do more than speak in general terms of the
mature of the chemical compounds which are most abundantly
produced. Of two facts, however, in regard to them we are certain—
that they are simpler in their constitution than the original organic
matter itself from which they are derived—and that they have a
tendency to assume still simpler forms, if they continue to be ex-
posed to the same united action of air, water, and alcaline substances.
Hence the compounds which lime has formed with the acid sub-
stances of the soil, themselves hasten forward to new decomposi-
tions,—unite with more oxygen, liberate slowly portion after por-
tion of their carbon in the form of carbonic acid, and of their hy-
drogen in the form of water—till at length the lime itself is left
again in the state of carbonate, or in union with carbonate acid
IT PROMOTES THE FORMATION OF ACID SUBSTANCES. 715
only. This residual carbonate begins again the same round of
changes through which it had previously passed. It gives up its
carbonic acid at the bidding of some more powerful organic acid
produced in its neighbourhood, while this acid, by exposure to the
due influences, undergoes new alterations till it also is finally re-
Solved into carbonic acid and water.
Two circumstances are deserving to be borne in mind in refe-
rence to these successive decompositions—first, that in the course
of them more soluble compounds of lime are now and then form-
ed, some of which are washed out by, the rains, and escape from
the soil, while others minister to the growth of plants;–and se-
cond, that very much carbonic acid is produced as their final re-
sult—of which also part is taken up by the roots of plants, and
part escapes into the air. Thus at every successive stage a portion
of organic matter is lost to the soil. If this quantity be greater than
that which is yearly gained in the form of roots or decayed leaves
and stems of plants, or of manure artificially added, the soil will be
gradually exhausted—if less, it will every year become more rich
in vegetable matter.
It is also to be borne in mind that although, for the purpose of
illustration, I have supposed the carbonate of lime first formed in
the soil to be subsequently combined with other acids, which gra-
dually decompose and leave it again in the state of carbonate,_
yet it will rarely happen that the whole of the carbonate of lime
in the soil will be in any of these new states of combination. In
general a part of it only is thus at any time employed in working
up the acid substances produced. But it is necessary that it should
be universally diffused through the soil in order that it may be
every where at hand to perform the important part of its functions
above explained. It is only where little lime is present, or where
decaying vegetable matter is in exceeding abundance, that the
whole of the carbonate can at one and the same time disappear
(p. 675).
The changes, therefore, which lime and organic matter, suppos-
ed to be free from nitrogen, respectively undergo, and their mutual
action in the soil, may be summed up as follows:—
1°. The organic matter, under the influence of air and moisture,
716 SUMMARY OF THE CHANGES PRODUCED BY LIME.
spontaneously decomposes, and besides carbonic acid which escapes,
forms also other acid substances which linger in the soil.
2°. With these acids the quick-lime combines, and either by its
union with them or with carbonic acid absorbed from the air, gra-
dually loses its caustic state. * &
3°. The production of acid substances by the oxidation of the
organic matter—goes on more rapidly under the disposing influ-
ence of the lime, whether caustic or carbonated. These acids com-
bine with the lime, liberating from it, when in the state of carbo-
mate, a slow but constant current of carbonic acid, upon which
plants at least partly live.
4°. The organic acid matter which thus unites with the lime con-
tinues itself to be acted upon by the air and water, aided by heat
and light—itself passes through a succession of stages of decompo-
sition, at each of which it gives off water or carbonic acid, retain-
ing still its hold of the lime, till at last being wholly decomposed
it leaves the lime again in the state of carbonate ready to begin
anew the same round of change.
5°. During this series of progressive decompositions, certain
more soluble compounds of lime are formed, by which plants are
in part at least supplied with this earth, and which with the aid of
the rains carry off both lime and organic matter from the soil.
And, again, the more rapid the production of the acid sub-
stances which result from the union of the organic matter with
oxygen, the more abundant in general also is the production of
those gaseous and volatile compounds which they form by uniting
with hydrogen—so that, in promoting the formation of the one
class of bodies lime also favours the evolution of the other in
greater abundance, and thus in a double measure contributes to
the exhaustion of the soil.
The disposing action of lime to this twin form of decomposition,
few varieties of organic matter can resist,-and hence arises the
well-known efficacy of lime in resolving and rendering useful the
apparently inert vegetable substances that not unfrequently exist
in the soil. .
§ 28. Of the comparative utility of burned and unburned lime."
Is there no advantage, then, you may ask, in using caustic or
4
COMPARATIVE UTILITY OF BURNED AND UN BURNED LIME. 717
burned rather than carbonated or unburned lime 2 If the ulti-
mate effects of both upon the land be the same, why be at the ex-
pense of burning Among other benefits may be enumerated the
following:— * x
1°. By burning and slaking, the lime is reduced to the state of
an impalpable powder, finer than could be obtained by any avail-
able method of crushing. It can in consequence be diffused more
uniformly through the soil, and hence a smaller quantity will pro-
duce an equal effect. This minute state of division also promotes
in a wonderful degree the chemical action of the lime. In all
cases chemical action takes place between exceedingly minute par-
ticles of matter, and among solid substances the more rapidly, the
finer the powder to which they can be reduced. Thus a mass of
iron or lead slowly rusts or tarnishes in the air, but if the mass of
either metal be reduced to the state of an impalpable powder—
which can be done by certain chemical means—it will take fire
when simply exposed to the air at the ordinary temperature, and
will burn till it is entirely converted into oxide. By mere mecha-
mical division the apparent action of the oxygen of the air upon
metals is augmented and hastened in this extraordinary degree—
and a similar result follows when lime in an impalpable state is
brought into contact with the vegetable matter upon which it is in-
tended to act.
2°. The effect of burned lime is more powerful and more imme-
diate than that of unburned lime in the form of chalk, marl, or
shell sand. Hence it sooner neutralizes the acids which exist in the
soil, and sooner causes that decomposition of vegetable matter of
every kind to commence, upon which its efficacy, in a great degree
depends. Hence, when it can easily be procured, it is better fitted
for sour grass or arable lands, for such as contain an excess of ve-
getable matter, and especially for such as abound in that dead or
inert form of organic matter which requires a stronger stimulus—
the presence of more powerful chemical affinities, that is—to bring
it into active decomposition. In such cases the lime has already
done much good before it has been brought into the mild state—
and remaining afterwards in this state in the soil, it still serves, in
a great measure, the same slower after-purposes, as the original
addition of carbonate would have done. -
718 ITS ACTION ON ORGANIC MATTER CONTAINING NITROGEN.
3°. Besides, if any portion of it, after the lapse of two or three
years, still linger in the caustic state (p. 655), it will continue to
provoke more rapid changes among the organic substances in the
soil, than mild lime alone could have done.
4°. Further quick-lime is soluble in water, and hence every
shower that falls and sinks into the soil carries with it a portion of
lime, so long as any of it remains in the caustic state. It thus
reaches acid matters that lie beneath the surface, and alters and
ameliorates even the subsoil itself.
5°. It is not a small additional recommendation of quick-lime,
that by burning it loses about 44 per cent. of its weight, thus en-
abling nearly twice the quantity to be conveyed from place to place
at the same cost of transport. This not only causes a direct sav-
ing of money, as when the burned chalk of Antrim is carried by
sea to the Ayrshire coasts;–but an additional saving of labour also
upon the farm, where the number of hands and horses is often
barely sufficient for the necessary work, -
§ 29. Action of lime on organic substances which contain nitrogen.
I have hitherto, for the sake of simplicity, directed your attem-
tion solely to the action, whether immediate or remote, which is
exercised by lime upon organic matter supposed to contain no ni-
trogen. Its action upon compounds in which nitrogen exists is no
less beautiful and simple, perhaps even more intelligible and more
obviously useful to vegetation.
There are several well-known facts which it is here of importance
for us to consider— -
1°. That the black vegetable matter of the soil always contains
nitrogen. Even that which is most inert retains a sensible pro-
portion of it. It exists in dry black peat to the amount of about
2 per cent, or more of its weight, and still clings to the other ele-
ments of the organic matter, even after it has undergone those pro-
longed changes by which it is finally converted into coal. Since
nitrogen, therefore, is so important an element in all vegetable
food, and so necessary in some form or other to the healthy growth
and maturity of plants, it must be of consequence to awaken this
element of decaying vegetable matter, when it is lying dormant,
ANALOGOUS DEGAY OF ALL ORGANIC SUBSTANCEs. 719
and to cause it to assume a form in which it can enter into and be-
come useful to our cultivated plants.
2°. That if vegetable matter of any kind be heated with slaked
lime, the whole of the nitrogen it contains, in whatever state of
combination it may previously exist, will be given off in the form
of ammonia. The same takes place still more easily if a quantity
of hydrate of potash or of hydrate of soda be mixed with the hy-
drate of lime. Though it has not as yet been proved by direct
experiment—yet I consider it to be exceedingly probable that what
takes place quickly in our laboratories, at a comparatively high
temperature, may take place more slowly also in the soil, and at
the ordinary temperature of the atmosphere.
3°. That when animal and vegetable substances are mixed with
earth, lime, and other alcaline matters, in the so-called nitre beds
(p. 285), ammonia and mitric acid are both produced, the quantity
of nitrogen contained in the weight of these compounds extracted
being much greater than was originally present in the animal and
vegetable matter employed (Dumas). Under the influence of al-
caline substances, therefore, even when not in a caustic state, the
decay of animal and vegetable matter in the presence of air and
moisture causes some of the nitrogen of the atmosphere to become
fixed in the soil in the form of ammonia or of nitric acid. What
takes place on the confined area of a nitre bed, may take place also
in the wider area of a well limed and well manured field.
In the action of alcalies in the nitre bed, disposing to the pro-
duction of nitric acid, we observe the same kind of agency, which
we have already attributed to lime, in regard to the more abundant
elements which exist in the vegetable matter of the soil. It gently
persuades all the elements—nitrogen and carbon alike—to unite
with the oxygen of the air and of water, and thus ultimately to form
acid compounds with which it may itself combine.
The action of lime upon such organic matters containing nitro-
gen as usually exist in the soil, may, therefore, be briefly stated
as follows:— -
1°. These substances, like all other organic matter, undergo in
moist air—and, therefore, in the soil—a spontaneous decomposi-
tion, the general result of which is the production of ammonia, and
of an acid substance with which the ammonia may combine. This
720 LIME AIDS IN THE EVOLUTION OF NITRGGEN.
change is precisely analogous to that which takes place in such sub-
stances as starch and woody fibre, which contain no nitrogen. In
each case, one portion of the elements unites with oxygen to pro-
duce an acid, the other with hydrogen to form a compound pos-
sessed of alcaline or indifferent properties. Thus,
With oxygen. With hydrogen.
Carbonic, ulmic, Marsh gas or
Vegetable produces and other other carburet-
matter acids. ted hydrogens.
Amimal Carbonic, nitric,
matter produces ulmic, and Ammonia.
other acids.
If the ammonia happen to be produced in larger relative quan-
tity than the acids with which it is to combine, or if the carbonic
be the only acid with which it unites, a portion of it may escape
into the air. This rarely happens, however, in the soil, the ab-
sorbent properties of the earthy matters of which it consists being
in most cases sufficient to retain the ammonia, till it can be made
available to the purposes of vegetable life.
When caustic (hydrate of) lime is added to a soil in which am-
monia exists in this state of combination with acid matter, it seizes
upon the acid and sets the ammonia free. This it does with com-
parative slowness, however—for it does not at once come in con-
tact with it all—and by degrees, so as to store it up in the pores
of the soil till the roots of plants can reach it, or till it can under-
go a further change by which its nitrogen may be rendered more
fixed (p. 721).
Carbonate of lime, on the other hand, still more slowly per-
suades the ammonia to leave the acid substances (ulmic, nitric P
&c.), with which it is combined, and yielding to it in return its
own carbonic acid, enables it in the state of soluble carbonate of
ammonia to become more immediately useful to vegetation.
2°. But in undergoing this spontaneous decay even substances
containing nitrogen reach at length a point at which decomposi-
tion appears to stop—an inert condition in which, though nitrogen
be present as in peat, they cease sensibly to give it off in such a
form or quantity as to be capable of ministering to vegetable
growth. Here caustic lime steps in more quickly, and mild lime
AMIMONIA AND NITRIC ACID FORMED. 721
by slower degrees, to promote the further decay. It induces the
carbonaceous matter to take oxygen from the air and from water
and to form acids, and the nitrogen to unite with the hydrogen of
the water for the production of ammonia—thus helping forward
the organic matter in its natural course of decay, and enabling it
to fulfil its destined purposes in reference to vegetable life.
3°. But the ammonia which is thus disengaged in the soil by
decaying organic matter, though not immediately worked up, so
to speak, by living plants, is not permitted to escape in any large
quantity into the air. The soil, as I have already stated, is usually
absorbent enough to retain it in its pores for an indefinite period
of time. And as in mature and upon the earth's surface the ele-
ments of matter are rarely permitted to remain in a state of repose,
the ammonia, though retained apparently inactive in the soil, is
yet slowly uniting with a portion of the surrounding oxygen and
forming mitric acid (p. 287, note). When no other alcaline mat-
ter is present, this mitric acid, as it is produced, unites with
some of the ammonia itself which still remains, forming nitrate
of ammonia—but if potash or lime be within its reach, it unites
with them in preference, and forms the nitrate of potash or of
lime. .
But lime, if present, is not an inactive spectator, so to speak, of
this slow ovidation of ammonia. On the contrary, it promotes this
final change, and by being ready to unite with the nitric acid as
it forms, increases and accelerates its production, at the expense
of the ammonia which it had previously been instrumental in
evolving.
4°. One other important action of lime, by which the same com-
pounds of nitrogen are produced in the soil, may in this place be
most properly noticed. It is a chemical law of apparently exten-
sive application, that when one elementary substance is undergoing
a direct chemical union with a second and in contact with a third,
a tendency is imparted to the third to unite also with one or with
both of the other two, although in the same circumstances it would
not unite with either, if present alone. Thus, when the carbona-
ceous matter of the soil is undergoing oxidation in the air—that
is, combining with its oxygen—it imparts a tendency to the nitro-
gen of the atmosphere when it is in contact with it also to unite
Z Z,
722 How THESE CHANGES BENEFIT VEGETATION.
with oxygen, which when mixed with that gas alomé" it has no
known disposition to do. The result of this is the production of a
small, and always a variable, proportion of mitric acid during the
decomposition in the soil, of organic matter which itself contains
mo mitrogen.
Again, it is an equally remarkable chemical law, that elemen-
tary bodies which refuse to combine, however long we may keep
them together in a state of mixture, will yet unite readily when
presented to each other in what is called by chemists the nascent
state—that is, at the moment when one or other of them is pro-
duced, or is separated from a previous state of combination.
Thus when the organic matter of the soil decomposes water in
the presence of atmospheric air, its carbon unites with the greater
part of the oxygen and hydrogen which are set at liberty, and at
the same time with more or less of the oxygen of the atmosphere
—but at the same instant the mitrogen of the atmosphere, which
is everywhere present, seizes a portion of the hydrogen and forms
ammonia. Thus a variable—in any one limited spot, a minute, but
over the entire surface of the globe, a large—quantity of ammo-
mia is produced during the oxidation even of the purely carbona-
ceous portion of the organic matter of the soil.
Now in proportion as the presence of lime promotes this decay
of vegetable and other organic matter in the soil—in the same pro-
portion does it promote the production of ammonia and mitric acid,
at the expense of the free nitrogen of the atmosphere, and this may
be regarded as one of the valuable and constant purposes served
by the presence of calcareous matter in the soil.
§ 30. How these chemical changes directly benefit vegetation.
You will scarcely, I think, inquire how all these interesting che-
mical changes which attend upon the presence of lime in the soil
are directly useful to vegetation, and yet it may be useful shortly
to answer the question.
1°. Lime combines with the acid substances already existing in
the soil, and thus promotes that decomposition of vegetable matter
which the presence of those acid substances retards. The further
* The atmosphere consisting, as you will recollect, of nitrogen and oxygen (p. 40.)
& Y
e)
WHY LIME MUST BE KEPT NEAR THE SURFACE. 723
decompositions which ensue are attended at every step by the pro-
duction either of gaseous compounds—such as carbonic acid and
light carburetted hydrogen, which are more or less abundantly ab-
sorbed by the roots and leaves of plants, and thus help to feed them
—or of acid and other compounds, soluble in water, which, enter-
ing by the roots, bear into the circulation of the plant not only or—
ganic food but that supply of lime also which healthy plants require.
2°. The changes it induces upon substances in which nitrogen is
present are still more obviously useful to vegetation. It eliminates
ammonia from the compounds in which it exists already formed,
and promotes its slow conversion into nitric acid, by which the ni-
trogen is rendered more fixed in the soil. It disposes the nitrogen
of more or less inert organic matter to assume the forms of ammo-
nia and nitric acid, in which states experience has long shown that
this element is directly favourable to the growth of plants. And
3°. It influences, in an unknown degree, the nitrogen of the at-
mosphere to become fixed in larger proportion in the soil, in the
form of nitric acid and ammonia, than would otherwise be the case
—and this it does both by the greater amount of decay or oxida-
tion which it brings about in a given time, and by the kind of com-
pounds which, under its influence, the organic matter is persuaded
to form. The amount of nitrogenous food placed within reach of
plants by this agency of lime will vary with the climate, with the
nature of the soil, with its condition as to drainage, and with the
more or less liberal and skilful manner in which it is farmed.
§ 31. Why lime must be kept near the surface.
Nor will you fail to see the important reasons why lime ought
to be kept near the surface of the soil—since
1°. The action of lime upon organic matter is almost nothing in
the absence of air and moisture. If the lime sink, therefore, be-
yond the constant reach of fresh air, its efficacy is in a great de-
gree lost. .
2°. But the agency of the light and heat of the sun, though I
have not hitherto specially insisted upon their action—are scarcely
less necessary to the full experience of the benefits which lime is
capable of conferring. The light of the sun accelerates nearly all
the chemical decompositions that take place in the soil—while some
724 . ACTION OF LIME UPON SALINE SUBSTANCES.
it appears especially to promote. The warmth of the sun's rays.
may penetrate to some depth, but their light can only act upon
the immediate surface of the soil. Hence the skilful agriculturist
will endeavour, if possible, to keep some of his lime at least upon
the very surface of his arable land. Perhaps this influence of light
might even be adduced as an argument in favour of the frequent
application of lime in small doses, as a means of keeping a portion
of it always within reach of the sun's rays; and this more especially
on grass lands, to which no mechanical means can be applied for
the purpose of bringing again to the surface the lime that has sunk.
There are, at the same time, as you will recollect, good reasons
also why a portion of the lime should be diffused through the body
of the soil, both for the purpose of combining with organic acids
already existing there, and with the view of acting upon certain
inorganic or mineral substances, which are either decidedly inju-
rious, or by the action of lime may be rendered more wholesome to
vegetation. . . . *. a &
In order that this diffusion may be effected, and especially that
lime may not be unnecessarily wasted where pains are taken by
mechanical means to keep it near the surface, an efficient system
of under drainage should be carefully kept up. Where the rains
that fall are allowed to flow off the surface of the land, they wash
more lime away the more carefully it is kept among the upper soil
—but where a free outlet is afforded to the waters beneath, they
carry the lime with them as they sink towards the subsoil, and
have been robbed again of the greater part of it before they escape
into the drains. Thus on drained land the rains that fall aid lime
in producing its beneficial effects, while in undrained land they in
a greater or less degree counteract it.
&
§ 32. Action of lime upon the inorganic or mineral matter of the soil.
I have hitherto spoken only of the action of lime upon the
purely organic part of the soil—that which contains only carbon,
hydrogen, oxygen, and nitrogen. But its operation in regard to
the inorganic substances contained in the soil are no less important.
1°. The decaying vegetable matter in the stems, roots, and
leaves of plants, which form the so-called humus of the soil, con-
tains a large proportion of the inorganic matter which was neces-
ACTION OF LIME UPON MINERAL MATTER. 725
sary to their existence in the living state. As they decompose
this inorganic matter is liberated. By promoting and hastening
this decomposition, therefore, lime sets free this mineral matter,
and provides at once abundant organic and inorganic food to the
growing plant. This result of the action of lime is no less impor-
tant in reference to its fertilizing quality, than that by which it
causes the production of those numerous changes in the purely
organic matter of the soil to which I have already adverted.
If the vegetable matter decay rapidly, it will supply in abun-
dance all the materials, both organic and inorganic, which new
races of plants require to form their entire substance. If it be
in an inert state or decompose slowly, the food it contains remains
locked up and comparatively useless to vegetation. In quicken-
ing the decay of this inert or slowly decomposing matter, it is easy
to see, therefore, how lime should render the land more fertile, and
should do so more sensibly where vegetable matter is abundant.
2°. The mineral and rocky fragments in the soil are acted upon
in a similar manner.
Among the earthy constituents of the soil we have already seen
that there often exist fragments of felspar and other minerals de-
rived from the granitic and trap rocks, as well as portions of the
slaty and other beds from which the soils are formed, and which,
as they crumble down, yield more and more of those inorganic
substances on which plants live.
The decomposition of these minerals and rocks proceeds more or
less slowly under the conjoined action of the oxygen, the carbonic
acid, and the moisture of the atmosphere. But the presence of lime
promotes this decomposition, (p. 633), and the consequent libera-
tion of the inorganic substances they contain.
The silicates of potash and soda are among the most important
compounds which these minerals and rocky fragments contain.
These silicates, after being heated to redness with quick-lime,
readily yield a portion of their potash or soda to water poured
upon the mixture. The same result follows, but more slowly,
when, without being heated, they are mixed together into a paste
with water, and left for a length of time at the ordinary tempera-
ture of the atmosphere. It is reasonable, therefore, to suppose,
that in the soil of our fields a similar decomposition will slowly
726 ACTION OF LIME UPON MINERAL MATTER.
take place when quicklime is intimately mixed with it. It will take
place also, though still more slowly, when lime is added in the
form of carbonate. -
By some the liberation of potash and soda in this way is sup-
posed to be the most important action exercised by lime in render-
ing the land more productive. With this extreme opinion I do
not agree, though it must be conceded, I think, that in numerous
instances a certain amount of benefit must follow from the chemical
action it is thus fitted to exercise.
I have spoken of lime as liberating the inorganic constituents
of the decaying vegetable matter of the soil. The stalks of the
grasses and the straw of our corn-bearing plants contain also sili-
cates of potash and soda, which lime sets free in hastening the de-
composition of the vegetable matter of which they form a part.
Besides liberating, it further decomposes these silicates, as it does
those of the minerals in the soil, and sets their potash and soda
free to perform those important functions, they are known to ex-
ercise in reference to the growth of plants (p. 583). I am inclined
to consider this part of the action of lime as of nearly equal im-
portance to vegetation with that which it exercises upon the mineral
silicates.
While the alkali is set free in a soluble state, the lime unites
with a portion of silica forming a silicate of lime, of which traces
are to be met with in nearly all soils. This silicate is again slowly
decomposed by the agency of the carbonic acid of the atmosphere,
as I have already explained when speaking of this compound as
one of the causes of the known fertility of soils, formed from
the decay of trap rocks, (p. 495.)
3°. Potash and soda exist sometimes in considerable quantity
in our stiff clay soils, in combination with the silica and alumina,
of which they chiefly consist. From their extreme tenacity the air
is in a great measure excluded from these soils, and hence chemi-
cal decomposition proceeds in them very slowly. The addition of
lime alters their physical character, and by making them more
open admits the air, and thus promotes its decomposing action
upon them. But it also acts chemically, in the same way as upon
the silicates already spoken of, and thus compels them to give up
ACTION OF LIME UPON MINERAL MATTER, 727
more freely to the roots of plants those mineral substances by
which their growth is to be made more luxuriant.
4°. Upon many saline substances also which are contained in the
Soil, lime produces a beneficial effect. Thus,
a. Salts of iron.—Either in the caustic or mild state, lime pos-
sesses the property of decomposing the sulphate of iron, which
especially abounds in moorish and peaty soils, and in some loca-
lities So Saturates the under soil as to make it destructive to the
roots of plants. Sprengel mentions a case in which the first year's
clover always grew well, while in the second year it always died
away. This upon examination was found to be owing to the salts
of iron contained in the subsoil, which caused the death of the
plants as soon as their roots began to penetrate to it.
When land is rendered unproductive by the presence of salts of
iron, lime will bring it into a wholesome state, without other aid
than those of the drain and the subsoil plough. If sulphate of
iron be the cause of the evil, the lime will combine with the acid
and form gypsum, while the first oxide of iron which is set free
will, by exposure to the air, be converted into the second or red
oxide, in which state iron in favourable circumstances is beneficial
to vegetation.
The drain and the subsoil plough are useful auxiliaries to the
lime in neutralizing the effects of iron, because they allow the
rains to descend and gradually to wash away the noxious matter
which has accumulated in the under soil,--because they allow the
descending water to carry with it portions of the lime in a state
of solution, and thus to spread its good effects over the whole soil,
—and because they admit successive supplies of air as deep as the
bottom of the drains, by which, while the action of the lime is
promoted, those other good effects also are produced which the
oxygen of the atmosphere can alone accomplish.
b. Salts of magnesia and alumina. –Lime decomposes also the
sulphates of magnesia and alumina, both of which, but especially
the former, are occasionally found in the soil in too large propor-
tion, and being very soluble in water, may be taken up by the
roots in such quantity as to prove hurtful to growing plants.
With the sulphuric acid of these salts, the lime forms gypsum as
it does when sulphate of iron is present in a soil to which it is
728 ACTION OF LIME UPON MINERAL MATTER.
added, besides removing the evil effects of these very soluble sul-
phates, therefore, it exercises the beneficial action which gypsum is
known to produce upon many of our cultivated crops.
Alumina has the property of combining readily with the humic,
crenic, mudesous, and other organic acids. Hence clay soils al-
most always contain a portion of alumina in combination with or-
ganic matter. These organic compounds are decomposed by lime
and by the more energetic action of this substance, their consti-
tuents are sooner made available to the wants of new races of plants.
c. Common salt and sulphate of soda.-I shall mention only one
other, but a highly important, decomposing action, which lime ex-
ercises in soils that abound in vegetable matter. In the presence
of decaying organic substances the carbonate of lime is capable of
slowly decomposing common salt, producing carbonate of soda and
chloride of calcium. It exercises also a similar decomposing ef-
fect, even upon the sulphate of soda, and, according to Berthollet,”
incrustations of carbonate of sodaf are observed on the surface of
the soil, wherever carbonate of lime and common salt are in contact
with each other. If we consider that along all our coasts common
salt may be said to abound in the soil, being yearly sprinkled over
it by the salt sea winds——we may safely conclude, I think, that the
decomposition now explained must take place extensively in all
those parts of our island which are so situated, if lime in any of
its forms either exists naturally or has been artificially added to the
land. The same must be the case also in those districts where
salt springs occur, and generally over the new red sand-stone for-
mation, in which mineral salt more especially abounds.
And if we further consider the important purposes which the
carbonate of soda thus produced may serve in reference to vege-
tation—that it may dissolve vegetable matter and carry it into the
roots—that it may form soluble silicates, and thus supply the ne-
cessary siliceous matter to the stems of the grasses and other plants
—and that rising, as it naturally does, to the surface of the soil,
it there, in the presence of vegetable matter, provokes to the for-
mation of nitrates, so wholesome to vegetable life—we may regard
the decomposing action of lime by which this carbonate is pro-
* Dumas, Traité de Chemic, ii. p. 334.
+ Of Troma or Natron, which is a sesſfut-carbonate of soda.
4
EXHAUSTING EFFECTS OF LIME. 729
duced from common salt, as in many localities fully equal in im-
portance to that by which it liberates alcaline matter from the mi-
neral silicates, or from those which exist in the parts of plants.
§ 33. Of the exhausting effect of lime.—Is eahaustion a necessary
consequence of the use of lime?
The exhausting effect of lime, either in the mild or caustic state,
has long been known and generally recognised. “An over-dose
of shell marl,” says Lord Kames, “laid perhaps an inch thick,
produces for a time large crops, but at last renders the soil capa-
ble of bearing neither corn nor grass, of which there are many
examples.”
An interesting illustration at once of the beneficial operation
and of the exhausting power of mild lime is afforded by the
observed effects of long continued marling upon certain poor
soils in the province of Isere in France. The marl there em-
ployed is sandy, and contains from 30 to 60 per cent. of carbo-
mate of lime. It is very like the lime-stone gravel of Ireland
or the shell sand of the Western Islands. A layer of this mark
one-third of an inch thick, applied at intervals to a soil capable of
producing in its natural state no other grain but rye every other
year, and of giving only three returns for the seed, causes it to grow
wheat and to yield for the first 10 or 12 years an eightfold return
for the seed. But after 40 years' marling, the farmers now com-
plain that the land will yield only a fourfold return of wheat. It
still grows the more valuable corn, but produces only half the for-
mer crops. -
Similar results have followed from the excessive application or
long-continued use of lime in any of the forms in which it is
usually applied. From this exhausting tendency has arisen the
proverb, almost universally diffused,—that lime enriches the fa-
thers but impoverishes the sons. It is of great practical conse-
quence, therefore, to inquire,
1°. How does lime cause the soil to become poorer?
2°. Is this a necessary consequence of the use of lime, or may it
be prevented P
1°. How does evhaustion follow from the use of lime 2–Lime acts
in several ways so as ultimately to lead to this result. Thus,
730 EXHAUSTING EFFECTS OF LIME,
a. It produces, as we have seen, a more rapid decomposition of
the purely organic substances of the soil. It causes this organic
matter, therefore, to disappear more quickly from the soil, and con-
sequently lessens sooner than would otherwise be the case the good
effects in reference to the growth of plants which this organic matter
is intended to exercise.
b. As the organic matter decays, the mineral substances which
exist in it are also liberated in larger proportion than if the land
had not been limed, and are thus brought into a condition in which
they can be more abundantly removed from the soil by the agency
of natural causes.
c. The same is true of the soluble substances contained in the
mineral and rocky fragments which are mixed with the soil.
Whatever amount of action lime may exercise in liberating potash,
soda, magnesia, silica, or phosphoric acid from these fragments, it
will to that extent make these substances more easily and quickly
removable from the soil.
But as the absolute quantity of potash and soda in all our soils
is really enormous, though the proportion compared with their
other constituents is small, it does not at first appear how the mere
removal of a certain small part of these substances, should have a
very serious effect upon the general fertility of any piece of land.
Still it is not difficult to comprehend one way, in which, by the
action of lime, the liberation of alcaline and other valuable matter
from this source may by the action of lime be for a time rendered
large, and may afterwards, for another period, be very greatly di-
minished.
All the mineral fragments are of an appreciable size. The lime
acts upon the exterior of these fragments, and liberates, we shall
suppose, the alcaline matter. But the surface of the fragment
does not on that account necessarily crumble down and expose a
fresh face to the action of the lime. On the contrary the old sur-
face may adhere, surrounding the fragment with a coating through
which the lime cannot act, and may thus prevent the further libera-
tion of alcaline or other soluble substances, though these may still
be abundant in the interior of the mineral mass. In this way the
surface of all stones—except lime-stones—which lie immediately be-
neath a layer of peat, come to have the same uniform grey siliceous
EXEIAUSTING EFFECTS OF LIME, - 731
covering, so that the nature of the stones can only be discovered by
breaking them. The acid matter of the peat dissolves the iron from
red sand-stones—the alumina from clay —the lime, magnesia, and
alcaline matter from fragments of whin-stone—and even upon flint
acts in a similar manmer, leaving the same insoluble siliceous coat-
ing upon all. It is so with the fragments of rock upon which lime
acts in the soil—and it is easy, therefore, to understand how any li-
beration of alcaline matter from such fragments may at one time be
large, and yet may afterwards diminish in a very sensible degree.
d. Now these various substances, organic and inorganic, being
decomposed, and their constituents set free more abundantly and
more rapidly, the roots of plants obtain them more readily and in
greater abundance, and thus the plants grow more rapidly and to .
a larger size, and perfect all their parts more completely. In
other words larger crops are grown, and by these larger crops
much more matter of every kind is carried off the soil.
But we have seen that besides the nitrogen and other purely or-
ganic elements which the plant draws from the soil, it takes up
also at least nine mineral substances in greater or less proportion.
The larger the crops the greater the quantity of these which is
carried off—and therefore, in so far as lime is the means of causing
larger crops to grow, in like proportion must it be the means of
causing the land to be more rapidly exhausted. The more rapid
exhaustion of limed land is caused mainly by the production and
removal of a larger amount of produce in a given time.
e. One other consideration appears to have a direct bearing
upon this subject. In our climate the rains which fall upon the
soil cannot fail to wash soluble matters out of it. When the land
is thoroughly drained and subsoiled so that the rain sinks where it
falls, and makes its way through nearly three feet of soil before it
escapes, it is a question whether, in ordinary circumstances, it will
carry away much more than it brings with it from the air. The
vegetable matter of the soil, as we have already seen, tends to re-
tain the soluble saline matter and to keep it from being washed
away, and this is another of the useful purposes on account of
which its presence in considerable proportion becomes desirable in
such soils as we wish to maintain in fertility.
But the lime, as we have seen, diminishes the proportion of ve-
*.
732 EXIHAUSTING EFFECTS OF LIME.
getable matter in the soil, and at the same time increases the amount
of soluble matter set free. That is to say, it brings more valuable
matter into a soluble condition, while it renders the soil less capable
of retaining it. The rains therefore ought to have more power
over highly and frequently limed land in washing out the valuable
kinds of food for plants which it contains. They may in fact be
one of the natural instruments by which the exhausting of limed
land is directly and immediately produced.
2°. But is this exhaustion a necessary consequence of the use of
lime?—To this question the considerations above presented enableus
to answer in the negative. We have already laid down as a princi-
ple in practical agriculture, that in our climate the addition of suc-
cessive doses of lime at certain intervals is necessary to the highest
fertility of the land. It is the part of enlightened practice so to
treat the land besides, that this addition of lime shall not prove an
instrument of final exhaustion. The exhaustion produced by the use
of lime has always been observed in places where either successive
doses of lime had been laid on as the sole application to the land,
or where too scanty supplies of other manure had been yearly given
to the fields.
Now where lime only is laid upon the land it is most unreason-
able to expect its fertility to be maintained, Besides the purely or-
gamic matter carried off—nine mineral substances are yearly remov-
ed from the soil by the crops, and only one of these, the lime, is re-
turned in the form of an artificial application. Cam anything else
but exhaustion follow from such practice? .
Again, the crops are greatly larger than before, and therefore the
quantity of all these substances carried off must be much greater
than usual. Can any thing but a more speedy exhaustion, therefore,
be expected, than if only the ordinary poor crops had been reaped?
Nor do small manurings of other kinds suffice to prevent
this exhaustion. If an ordinary manuring be applied and an ex-
traordinary crop or series of extraordinary crops be carried off
the land, exhaustion must follow as certainly, though more slowly,
than if nothing but lime had been laid on.
To keep land in good condition, we must, as a general rule, add
as much of every thing as we carry off. Let this be done upon
limed land and no exhaustion need be feared. If the land yield us
ACTION OF LIME ON ANIMAL AND WEGETABLE LIFE. 733
large crops, we ought as liberally to manure it. We cannot take
out of the land constantly and add nothing without impoverishing
it ; but we can add enough to supply all we carry off, and yet farm
our land profitably.
This is now understood by our best practical men, and in Ger-
many is expressed by the rhyme—
The use of marl without manure
Will only make the farmer poor?
§ 34. Action of lime on animal and vegetable life.
It is only necessary to allude, in conclusion, to one or two
other useful purposes which lime is said to serve, in reference to
animal and vegetable life. Thus,
1°. It is said to prove fatal, especially in the caustic state, to
worms, to slugs, to the wire worm, and to many other insects in-
jurious to the farmer, and to destroy their eggs and larvae. In
Scotland it has been found in some instances to check the ravages
of the fly when spread over the young turnip leaves as soon as they
appear above ground.
On newly ploughed up lea, either lime or salt will equally kill
the insects which so frequently attack the corn, and for the de-
struction of which the system of paring and burning has so fre-
quently been adopted. Mr Briggs of Overton divided a field
ploughed up from clover, and which was intended for wheat, into
three parts. To the first he applied lime at the rate of a ton an
acre, to the second, common salt at the rate of five cwt., and to the
third, mothing but the seed. The wheat was equally good on the
two former portions, but on the third it failed so completely that
it had to be sown over again.
On the other hand, lime is propitious to the growth of the land
snail and similar creatures which bear shells. In highly limed
land the former may be seen crowded at the roots of the hedges,
from which they make frequent incursions upon the young crops,
and are, I believe, especially hurtful to the turnips.
* Ohne mist
Ist das Geld für mergelen verquist.
+ When the wheat crop is attacked by slugs above ground, nothing will do so much
good as slaked lime sown over the crop before sunrise.--Hillyard, Royal Agricultural
Journal, iii. p. 302. - *
734 LIME KILLS INSECTS AND SEEDS.
2°. It is found to prevent smut in wheat. For this purpose the
seed is steeped in lime water and afterwards dried with slaked lime,
or lime water is poured upon the heap of corn, which is turned
over, and left for 24 hours (Hillyard).
3°. It is also said to prevent the rot and foot-rot in sheep fed
upon pastures on which, before liming, the stock was liable to be
affected by these diseases (Prideaux).
4°. In regard to its action upon living plants, it is certain that
it extirpates the coarser grasses from sour pastures and brings up
a more tender herbage; but practical men appear to differ in regard
to its effect upon the roots and seeds of the more troublesome weeds.
According to some, the addition of lime to a compost, or to the
soil, will kill the roots of weeds and render unproductive such
noxious seeds as may happen to be present. According to others
this is a mistake. I believe the truth to be, that lime will lead to
their destruction and decay, if the circumstances are favour-
able or if proper pains be taken to effect it. But air and mois-
ture are necessary to insure this, as they are to effect the rapid de-
cay of dead organic matter. If the ingredients of the compost be
duly proportioned, or if the dose of lime added directly to the land
be sufficiently large, and if in each case the mixture be occasionally
turned, the final destruction of roots and seeds may in general be
safely calculated upon.
5°. I have already mentioned that lime is regarded in many dis-
tricts as a remedy for the disease in turnips called fingers and toes.
It is not yet established whether this disease proceeds originally
from some weakness in the plant, from a defect in the soil, or from
the attacks of an insect. Circumstances are mentioned which fa-
vour each opinion, and it is very difficult to decide among them.
The cure, however, is of more consequence than the cause, and it
is satisfactory to know, that lime, when properly applied, is seldom
known to fail.
Something, however, depends upon the season of the year, upon
the mode of applying it, and upon the quantity laid on. Mr Wil-
son of Cumledge, in Berwickshire, limed a field known to be sub-
ject to finger and toe, preparatory to growing turnips on it
again. One part of the field was limed in the autumn, to the other
part, which could not be overtaken, the lime was applied in the fol-
USE OF SILICATE OF LIME. 735
lowing spring. The turnips on the first part were sound and healthy,
those on the second part as badly affected by the disease as ever.
Without drawing any conclusions from this experiment as to the
cause of the disease, it shows clearly that the time and manner of
applying the remedy has much to do with its failure or success.
§ 35. Use of silicate of lime.
There is one compound of lime which, though occurring occa-
sionally in all soils, has not hitherto been applied to the improve-
ment of the land even in localities where it most abounds. This
compound is the silicate of lime. I have already directed your at-
tention to the presence of this compound in the trap rocks, and to
the fertile character which it imparts to the soils which are formed
by the natural degradation of these rocks.
In those districts where the smelting of iron is carried on, the
first slag that is obtained consists in great part of silicate of lime.
This slag accumulates in large quantities, and is frequently em-
ployed in mending the roads. It is not unworthy the attention of
the practical farmer—as an improver of his fields—especially where
caustic lime is distant and expensive, or where boggy and peaty soils
are met with in which vegetable matter abounds. On such land
it may be laid in large quantity. It will decompose slowly, and
while it imparts to the soil solidity and firmness, will supply both
lime and silica to the growing crops, for a long period of time.
-*.
I have thus drawn your attention to the most important topics
connected with the use of lime, so efficacious an instrument in the
hands of the skilful and improving farmer for ameliorating the con-
dition and increasing the productiveness of his land. If I have ap-
peared to dwell long upon this subject, it is because of the value
which I know to be attached by practical men to a correct exposi-
tion of the virtues of lime and of the theory by which its effects are
to be explained. I believe that in the theoretical part I have been
able to point out to you the leading chemical principles upon which
its influence depends—if any thing is still dark, it is because our
knowledge is not yet complete. A few years more, and we may
hope to have the mists which still linger over this and many other
branches of agricultural chemistry in a great measure cleared away.
LECTURE XXI.
Of organic manures. Vegetable manures. Green manuring—ploughing in of spurry,
the white lupin, the vetch, buck-wheat, rape, rye, white mustard, turnips, borage,
red clover, madia sativa, old grass, vine twigs, hop bine. Will green manuring
alone prevent lands from becoming exhausted P Practice of green manuring. Na-
tural green manuring. Improvement of the soil by laying down to grass, by eating
off with sheep, and by planting. Use of sea-weed. Dry vegetable manures—dry
straw, chaff, rape-dust, malt-dust, bran, oat husk, Saw-dust, cotton seeds, dry leaves.
Decayed vegetable matter—use of peat, tanners’ bark, and composts of vegetable
matter. Charcoal powder, soot, coal dust, coal tar. Relative value, theoretical and
practical, of different vegetable manures.
By organic manures are understood all those substances either
of vegetable or of animal origin, which are applied to the land for
the purpose of increasing its fertility. It will be convenient to
consider these two classes of organic substances separately.
The parts of vegetables may be applied to the soil in three dif-
ferent forms—in the green, in the dry, and in the more or less na-
turally decayed, fermented, or artificially decomposed state.
§ 1. Of green manuring, or the application of vegetable matter in
the green state.
By green manuring is meant the ploughing in of green crops in
their living state—or of green vegetables left or spread upon the
land for the purpose.
J*. We have seen in the preceding lecture how important air
and water are to the decomposition of organic matter. Now green
vegetable substances contain within themselves much water, un-
dergo decomposition more readily, therefore, than such as have
been dried, and are more immediately serviceable when mixed
with the soil.
2°. In the sap of plants also there generally exist certain com-
pounds containing nitrogen (protein compounds, p. 216), which
not only decompose very readily themselves, but have the property
GREEN VEGETABLES READILY DECAY, 737
of persuading or inducing the elements of the other organic matters
with which they are in contact, to assume new forms or to enter
into new chemical combinations. Hence, in green plants which
have ceased to grow, the sap almost invariably decomposes even
when preserved from the contact of both air and water. When this
decomposition has once commenced in the sap it is gradually com-
municated to the woody fibre and to the other substances of which
the mass of the stems and roots of plants is composed. Hence,
recent vegetable matter will undergo a comparatively rapid de-
composition, even when buried to some depth beneath the soil—
and the elements of which it consists will form new compounds
more or less useful to living plants, in circumstances where dry
and many forms even of partially decomposed vegetable matter
would undergo no change whatever.
3°. Further—when green vegetable matter is allowed to decay
in the open air, the carbon it contains is gradually resolved more
or less completely into carbonic acid, which escapes into the air
and is so far lost. But when buried beneath the surface, this for-
mation of carbonic acid proceeds less rapidly, and other interme-
diate compounds—preparatory to the final resolution of the whole
into carbonic acid and water—are produced in greater quantity
and linger in the soil. Thus by burying vegetable substances in
his land in their green state, the practical man actually saves a
portion of the organic food of plants, which would otherwise so
far run to waste.
4°. Finally. Green vegetable substances, by exposure to the
air, gradually give up a portion of the saline matter they contain
to the showers of rain that fall. This more or less escapes and is
lost. But if buried beneath the soil this Saline matter is restored
to the land, and where the green matter thus buried is in the state
of a growing crop, both the organic and inorganic substances it
contains are more equally diffused through the soil than they could
be by any other known process.
On one or other of these principles depend nearly all the special
advantages which are known to follow from green manuring and
from the employment of green vegetable matter in the preparation
of composts.
3 A
*
738 AND GREATLY ENRICII THE SOIL.
§ 2. Important practical results obtained by green manuring.
But this explanation of the principles on which the efficacy of
green manuring depends, does not fully illustrate the important
practical results by which, in many localities, it is uniformly fol-
lowed.
Let us glance at these results.
1°. The ploughing in of green vegetables on the spot where
they have grown may be followed as a method of manuring and
enriching all land—where other manures are less abundant. Grow-
ing plants bring up from beneath, as far as their roots extend,
those inorganic substances which are useful to vegetation—and re-
tain them in their leaves and stems. By afterwards ploughing in
the whole plant we restore to the surface what had previously sunk
to a greater or less depth, and thus make it more fertile than be-
fore the green crop was sown.
2°. This manuring is performed with the least loss by the use
of vegetables in the green state. By allowing them to decay in
the open air, there is, as above stated, a loss both of organic and of
inorganic matter—if they be converted into fermented (farm-yard)
manure, there is also a large loss, as we shall hereafter see, and
the same is the case, if they are employed in feeding stock, with a
view to their conversion into manure. In no other form can the
same crop convey to the soil an equal amount of enriching matter
as in that of green leaves and stems. Where the first object, there-
fore, in the farmer's practice is, so to use his crops as to enrich his
land—he will soonest effect it by ploughing them in in the green
state.
3°. Another important result is, that the beneficial action is al-
most immediate. Green vegetables decompose rapidly, and thus
the first crop which follows a green manuring is benefited and in-
creased by it. But partly for this reason also the green manur-
ing—of corn cropped land—if aided by no other manure, must
generally be repeated every second year.
4°. It is said that grain crops which succeed a green manuring
are never laid—and that the produce in grain is greater in pro-
portion to the straw, than when manured with fermented dung.
5°. But it is deserving of separate consideration, that green ma-
muring is especially adapted for improving and enriching soils which
MOST USEFUL TO POOR AND SANDY SOILS. 739
are poor in vegetable matter. The principles on which living plants
draw a part—sometimes a large part—of their sustenance from
the air have already been discussed, and I may presume that you
sufficiently understand these principles and admit the fact. Living
plants, then, contain in their substance not only all they have drawn
up from the soil, but also a great part of what they have drawn
down from the air. Plough in these living plants, and you neces-
sarily add to the soil more than was taken from it—in other words,
you make it richer in organic matter. Repeat the process with a
second crop and it becomes richer still—and it would be difficult
to define the limit beyond which the process could no further be
carried. .
Is there any soil then, in the ordinary climates of Europe, which
is beyond the reach of this improving process? Those only are
so on which plants refuse to grow at all, or on which they grow so
languidly as to extract from the air no more than is restored to it
again by the natural decay of the organic matter which the soils
already contain.
But for those plants which grow maturally upon the soil, agri-
cultural skill may substitute others, which will increase more ra-
pidly, and produce a larger quantity of green leaves and stems for
the purpose of being buried in the soil. Hence, the selection of
particular crops for the purpose of green manuring—those being
obviously the fittest which in the given soil and climate grow most
rapidly, or which produce the largest quantity of vegetable matter
Čn the shortest time and at the smallest cost.
§ 3. Of the plants which in different soils and climates are em-
ployed for green manuring.
On this principle is founded the selection of different plants in
different soils and climates for the purpose of green manuring.
That which in Italy will yield the largest produce of leaves and
stems, at the least cost, and in the shortest time, may not do so in
the north of England or of Germany—and that which will enrich
a poor clay or an exhausted loam may refuse even to grow, in a
healthy manner, upon a drifting sand. -
1". Spurry (Spergula Arvensis.)—It is to poor dry Sandy soils
that green mamuring has been found most signally beneficial, and
740 MANURING WITH GREEN SPURRY AND WHITE LUPINS.
for such soils no plant has been more lauded than spurry. It
may either be sown in autumn on the corn stubble or after early
potatoes, to be ploughed in in spring preparatory to the annual crop,
or it may be used to replace the naked fallow, which is often hurt-
ful to lands of so light a character. In the latter case, the first
sowing may take place in March, the second in May, and the third
in July—each crop being ploughed into the depth of three or four
inches, and the new seed then sown and harrowed. When the
third crop is ploughed in, the land is ready for a crop of winter
COI’ll.
Von Voght” states that by such treatment the worst shifting
Sands may be made to yield remunerative crops of rye-that the
most worthless sands are more improved by it than those of a better
natural quality—that the green manuring every other year not
only nourishes sufficiently the alternate crops of rye, but gradually
enriches the soil—and that it increases the effect of any other
manure that may subsequently be put on. He adds, also, that
spurry produces often as much improvement if eaten off by cattle
as if ploughed in, and that when fed upon this plant, either green
or in the state of hay, cows not only give more milk, but of a richer
quality.
2°. White lupins.—In Italy, and in the south of France, the
white lupin is extensively cultivated as a green manure. In Ger-
many, also, it has been found to be one of those plants by which
unfruitful sandy soils may be most speedily brought into a pro-
ductive state. The superiority of this plant in enriching the soil
depends upon its deep roots, which descend more than two feet
beneath the surface—upon its being little injured by drought, and
little liable to be attacked by insects—on its rapid growth–and
upon its large produce in leaves and stems. Even in the north of
Germany it is said to yield, in three and a half to four months, 10
to 12 tons of green herbage. It grows in all soils except such as
are marly and calcareous, is especially partial to such as have a
ferruginous subsoil, and besides enriching, also opens stiff clays
by its strong stems and roots. - -
3°. The vetch is inferior in many of its qualities to the white
lupin—yet in Southern Germany it is often sown on the stubble,
* Wortheile der grimen Bedingwng,
4
USE OF THE VETCH, BUCK-WHEAT, &C. 74.1
and ploughed in after it has been touched with the frost, and has
begun to decay. In England also the winter tare ploughed in
early in spring has been found highly advantageous." It is a more
precarious, however, and a more expensive crop than either of the
former, and requires a better soil for its successful growth.
4°. Buck-wheat is also too uncertain a crop in this country, and
the high price of its seed renders it inferior in value to spurry on
sandy soils. It is superior to this latter plant, however, on poor
heaths. In Southern Germany it is sown on the stubble and
ploughed in when it is 18 or 20 inches high.
5°. Rape can only be sown upon a soil which is already in some
measure rich, but it has the advantage of continuing to grow very
late in the autumn, and of beginning again very early in spring.
It sends down deep roots also, and loosens clayey soils by its thick
stems. In the light soils of Alsace it is sown after early peas and
potatoes, and manures the land for the succeeding crop of wheat or
rye.
6°. Rye is pronounced by Von Voght to be the best of all green
manures for sandy soils, but it is also the most expensive. It is a
very sure crop and begins to grow very early in the spring, but it
is not deep rooted. It has been used with advantage in Northern
Italy and in Germany.
7°. White mustard is often sown in Norfolk with or without a
light manuring, and ploughed in as a preparation for wheat. It
is also sown on the stubble and ploughed in as a manure for the
turnip crop, and is said to destroy the wire-worm.
8°. Turnips have been sown in Sussex with good effect as a stub-
ble crop for ploughing in in spring, and in Norfolk and elsewhere
the portions of the turnip bulbs which are left when they are eaten
off by sheep contribute, when ploughed in, to enrich the land for the
barley that is to follow. Turnip tops are in many places ploughed
in with much benefit to the land. In the Lothians the turnip tops
are considered to be worth two pounds an acre to the succeeding
barley crop. Potato tops also cut or pulled green are ploughed
in with equal advantage.
* British IIusbandry, i. p. 407.
+ “I find no better way of mamuring for wheat after turnips, than ploughing in the
tops while still green, as soon as the turnips are taken off the land.”—Mr Campbell of
Craigie.
742 BORAGE AND REL) CLOWER. .
9°. Borage has been strongly recommended in Germany, and
especially by Lampadius. It is stated by this experimenter that
borage draws from the air ten times as much of the elements of its
organic matter as it does from the soil, and that therefore it is ad-
mirably fitted for enriching the land on which it grows. The Ma-
dia sativa is also recommended in Silesia as a green manure.
10°. Red clover is often ploughed in as a manure. On the
Rhine it is sown for this purpose, being ploughed in before it be-
gins to flower. In French Flanders two crops of clover are cut,
and the third ploughed in, and in some parts of the United States
of North America the clover which alternates with the wheat crop
is ploughed in as the only manure.” White clover is not so valu-
able for this purpose, for neither is it so deep rooted nor does it
yield so large a crop of stems and leaves.
11°. Old grass.-Perhaps the most common form of green ma-
muring practised in this country is that of ploughing up grasslands
of various ages. The green matter of the sods serves to manure
the after-crop, and renders the soil capable of yielding a richer
return at a smaller expense of manure artificially added. The
vegetable matter of ditch scourings and hedge cleanings, when
made into composts, acts in a similar manner.
In regard to all these forms of green manuring it is to be ob-
served that they enrich the soil generally, and are therefore well
fitted to prepare it for after-crops of corn.
12°. Vine twigs have long been found of much value when bu-
ried at the roots of the vines. In the weald of Kent also it has
been found that if the hop bines are chopped and dug in, or better,
if they are made into a compost with earth and laid on in spring,
a larger produce of hops is obtained with half the usual manuring
than where the bones are burned and the land treated in the usual
way.
In these cases the green manure not only restores to the land
those substances which plants in general require, but in the special
proportions also in which they are necessary to the vine and to the
hop.
* Barclay's Agricultural Tour in the United States.
3
&O
GREEN MANURING WILL NOT PRESERVE 743
§ 4. Will green manuring alone prevent land from becoming
eachausted 2
If by green manuring is meant the growing of vegetable matter
upon one field, and ploughing it in green into another, as is some-
times done, it may be safely said that, when judiciously practised,
land may by this single process be secured for an indefinite period
against exhaustion. But if we plough in only what the land itself
produces, and carry off occasional crops of corn, the time will ul-
timately come when any soil thus treated will cease to yield remu-
merating crops. A brief consideration of the subject will explain
this.
Suppose a loose sand to be improved by repeatedly sowing and
ploughing in crops of spurry or white lupins, the green leaves and
stems fix the floating elements of the atmosphere, and enrich the
soil with organic matter, while the roots, more or less deep, bring
up saline substances to the surface, and thus supply to the plant
what is no less necessary to its healthy growth. But the rains
yearly wash away from the surface, and the corn crops remove a
portion of this saline matter. This portion the crops grown for
the purpose of green manuring yearly renew by fresh supplies
from beneath. But no subsoil contains an inexhaustible store of
those saline substances which plants require. Hence, though by
skilful green manuring waste land may be brought to a remunera-
tive state of fertility, it will finally relapse again into a state of na-
ture, if no other methods are subsequently adopted for maintaining
its productiveness. The process may be a slow one, and practical
men may be unwilling to believe in the possibility of a result which
does not exhibit itself within the currency of a single lease, or dur-
ing a single life-time—yet few things are more certain than, that
in general the soil must sooner or later receives supplies of saline
manure in one form or another, or else must ultimately become
unproductive. It may be considered as a proof of this fact that,
in all densely peopled countries in which agriculture has been
skilfully prosecuted, the manufacturing of such manures is becom-
ing an important branch of business, giving employment to many
hands, and affording an investment to much capital.
The following table, in addition to other particulars, exhibits the
relative proportions of dry organic and saline matter, capable of
744
THE LAND FROM FINAL EXHAUSTION.
being added to the surface soil by a few of those plants which are
employed for the purposes of green manuring :-

1000. lbs contain
Average|.
Kind of plant produce in the green state, Depth of Crops in Soil for which they
per imp.Organic | Saline Roots. a year. are fitted.
acre. matter. matter.
lbs. lbs. lbs. inches.
Spurry,......... 6,500 199 21 |12 to 15 2 or 3 |Dry, loose, sandy.
*** * • . Any except marly
• I J. -
White lupin,... 25,000 188 12 24 to 26|| 1 or 1% or calcareous.
Vetch, ......... 11,000 || 233 17 |15 to 20 2 Strong soil.
Buck-wheat, ..., 8,000 170 10 |12 to 15| 2 Dry, Sandy, or moorish.
Rape, .......... 16,000 2] 4 I6 2 1 or 13, IRich soil.
§ 5. Of the practice of green manuring.
In the practical adoption of green manuring it is of importance
to bear in mind—
1". That a sufficient quantity of seed must be sown to keep the
ground well covered, one of the attendant advantages of stubble
crops being that they keep the land clean and prevent it from be-
coming a prey to weeds. -
2". That the plants ought to be mown, harrowed, or rolled, and
at once ploughed in before they come into full flower. The flower-
leaves give off nitrogen into the air, and as this element is suppos-
ed especially to promote the growth of plants, it is desirable to re-
tain as much of it in the plant and soil as possible. Another rea-
son is that, if allowed to ripen, some of the seed may be shed and
afterwards infest the land with weeds.
3". That they should be ploughed in to the depth of 3 or 4
inches only, that they may be covered sufficiently to prevent waste,
and yet be within reach of the air, and of the early roots of the
succeeding crop.
§ 6. Of natural manuring with recent vegetable matter.
Besides the method of ploughing in, which may be distinguish-
ed as artificial green manuring, there is another mode in which
recent vegetable matter is employed in nature for the purpose of
enriching the soil. The natural grasses grow and die upon a
meadow or pasture field, and though that which is above the sur-
face may be mowed for hay, or cropped by cattle, yet the roots
remain and gradually add to the quantity of vegetable matter be-
neath, The same is the case to a greater or less extent with all
OF NATURAL GREEN MANURING. 745
the artificial corn, grass, and leguminous crops we grow. They
all leave their roots in the soil, and if the quantity of organic
matter which these roots contain be greater than that which the
crop we carry off has derived from the soil, then instead of ex-
hausting, the growth of this crop will actually enrich the soil in
so far as the presence of organic matter is concerned. No crops,
perhaps, the whole produce of which is carried off the field, leave a
sufficient mass of roots behind them to effect this end, but many
plants when in whole or in part eaten upon the field, leave enough
in the soil materially to improve the condition of the land—while
in all cases those are considered as the least exhausting, to which
are naturally attached the largest weight of roots. Hence, the main
reason why poor lands are so much benefited by being laid down
to grass, and why an intermediate crop of clover is often as bene-
ficial to the after crop of corn as if the land had lain in naked
fallow.”
An interesting series of experiments on the relative weights of
the roots and of the green leaves and stems of various grasses,
made by Hlubek, throws considerable light upon their relative effi-
cacy in enriching the soil by the vegetable matter they diffuse
through it in the form of roots. The grasses were grown in beds
of equal size (180 square feet), in the agricultural garden at Lay-
bach, and were mown in the fourth year after sowing, just as they
were coming into flower. The roots were then carefully taken up,
washed, and dried. The results were as follow :-


produce in Prºdu% in y º: º
Kind of Grass. Roots. .." 0 ..
Grass. [Hay. Fresh. Dry, of Hay.
lbs. 15s. lbs. lbs. lbs.
1. Festuca Elatior—Tall Fescue-grass, 124 36 56 22 61
2. Festuca Ovina–Sheep’s Fescue-grass, 9() 30 | . . . 80 266
3. Phleum Pratense—Timothy-grass, 90 25 56 17 60
4. Dactylis Glomerata—Rough Cock's-foot, 202 || 67 * * * 22% 33
5. Lolium Perenne–Perennial Rye-grass, 50 | 17 | ... 50 300
6. Alopecurus Pratensis—Meadow Foac-tail, 106 || 35 sº º 24 70
7. Triticum Repens—Creeping Couch or 120 | 60 ... 70 1 16
Qwicken-grass, - *
8. Poa Annua—Annual Meadow-grass, & a ge g: g & g tº º * & tº 1 11
9. Bromus Mollis and Racemosus—Soft 105
a o
&md Smooth Brome-grass, -
10. Anthoxanthum Odoratum—Sweet scent- { 93
ed Vernal-grass, sº -
* If the third crop be ploughed in, the land is actually enriched.—Schwertz.
# Ernährung der Pflanzen, p. 466.
746 WEIGHT OF ROOTS LEFT IN THE SOIL.
A mixture of white clover, ribwort, hoary plantain, and
couch grass, in an old pasture field, gave 400 lbs. of dry roots to
100 lbs. of hay. In a clover field, at the end of the second year,
the fresh roots were equal to one-third of the whole weight of
green clover obtained at three cuttings—one in the first, and two
in the second year—while in the dry state there were 56 lbs. of
dry roots to every 100 lbs. of clover hay which had been carried
off.
The fourth column of the above table shows how large a quan-
tity of vegetable matter some of the grasses impart to the soil, and
yet how unlike the different grasses are in this respect. The
sheep's-fescue and the perennial rye-grass—besides the dead roots,
which detach themselves from time to time—leave, at the end of
the fourth year, a weight of living roots in the soil which is equal
to three times the produce of that year in hay. If we take the
mean of all the above grasses as an average of what we may fairly
expect in a grass field—then the amount of living roots left in the
soil when a four-year-old grass field is ploughed up, will contain one-
fifth more dry matter than that year's crop of hay.
In an old pasture or meadow field, again, when ploughed up,
the dry matter left in the form of living roots is equal to four times
the weight of that year's hay crop. If a ton and a half of hay have
been reaped—then about six tons of dry vegetable matter remain
in the soil in the form of living roots.
In the case of clover, at the end of the second year the quantity
of dry vegetable matter left in the form of roots is equal to up-
wards of one-half the weight of the whole hay which the clover has
yielded. Suppose there be three cuttings yielding 4 tons of hay,
them 2 tons of dry vegetable matter are added to the soil in the form
of roots, when the clover stubble is ploughed up.
But the quantity of roots, like that of green produce, is depen-
dant upon a variety of circumstances. It will sometimes, there-
fore, be greater, and sometimes less than is above stated. It may
be received as a rule—not without exception perhaps, yet still as
a general rule—that whatever causes an increased produce above
ground, will cause a corresponding increase in the growth of roots.
Thus nitrate of soda, which gives us a larger yield of hay, makes
the roots also stronger and deeper, and the sward tougher and
IMPROVEMENT BY LAYING DOWN TO GRASS. 747
more difficult to plough. Hence it is that the farmer is anxious
that his clover crop should succeed, not merely for the increased
amount of green food or of hay it will give him, but because it will
secure him also a better after-crop of corn.
This burying of recent vegetable matter in the soil, in the form
of living and dead roots of plants, is one of those important ameli-
orating operations of mature, which is always to some extent going
on, wherever vegetation proceeds. It is one by which the practi-
cal man is frequently benefited unawares, and of which—often
without understanding the source from whence the advantage
comes—he systematically avails himself in some of the most skilful
steps he takes with a view to the improvement of his land.
§ 7. Improvement of the soil by laying down to grass.
One of the most common of these methods of improvement is
that of laying down to grass. This may be done for two, three, or
four years only, or for an indefinite period of time. In the latter
case, the land is said to be laid down permanently, or to perma-
ment pasture.
1°. Temporary pasture or meadow.—If the land be sown with
grass and clover-seeds, only as an alternate crop between two sow-
ings of corn, the effect is fully explained by what has been already
stated (§ 6). The roots which are left in the soil enrich the sur-
face with both organic and inorganic matter, and thus fit it for
bearing a better after-crop of corn.
If, again, it be left to grass for three or five years, the same
effect is produced more fully, and therefore this longer rest from
corn is better fitted for soils which are poor in vegetable matter.
The quantity of organic matter which has accumulated becomes
greater every year, in consequence of the annual death of stems
and roots, and of the soil being more closely covered, but this in-
crease is probably never in any one after-year equal to that which
takes place during the first. The quantity of roots which is pro-
duced during the first year of the young plants’ growth on soils to
which the grass takes well, must, we may reasonably suppose, be
greater than can ever afterwards be necessary in an equal space
of time. Hence, one good year of grass or clover will enrich the
748 PERMANIENT PASTURE OR MEADOW.
soil more in proportion to the time expended, than a rest of two or
three years in grass, if annually mowed, -
Or if, instead of being mown, the produce in each case be eaten
off by stock, the result will be the same. That which lies longest
will be the richest when broken up, but not in an equal proportion
to the time it has lain. The produce of green parts, as well as of
roots, in the artificial grasses, is generally greatest during the first
year after they are sown, and therefore the manuring derived from
the droppings of the stock, as well as from the roots, will be great-
est in proportion during the first year. That farming, therefore,
is most economical—where the land will admit of it—which per-
mits the clover or grass seeds to occupy the soil for one year only.
Still, one year of clover hay, and a second of pasture, ought with
good management to leave the land in still better condition than
after the clover hay alone. On many soils, under ordinary ma-
nagement, it is the only practice of the two which can safely be
recommended. -
And if, after the first year's hay is removed, the land be pas-
tured for two or three successive years, it is possible that each suc-
ceeding year may enrich the surface soil as much as the roots and
stubble of the first year's hay had done; so that if it lay three
years it might obtain three times the amount of improvement.
This is owing to the circumstance that the whole produce of the
field remains upon it, except what is carried off by the stock—but
very much, it is obvious, will depend upon the nature of the soil,
and upon the selection of the seeds being such, as to secure a to-
lerable produce of green food during the second and third years.
2°. Permanent pasture or meadow.—But when land is laid down
to permanent grass, it undergoes a series of further changes, which
have frequently arrested attention, and which, though not difficult
to be understood, have often appeared mysterious and perplexing
to practical men. Let us consider these changes.
a. When grass seeds are sown for the purpose of forming a
permanent sward, a rich crop of grass is obtained during the first,
and perhaps also the second year, but the produce after three or
four years lessens, and the value of the pasture diminishes. The
plants gradually die and leave blank spaces, and these again are
slowly filled up by the sprouting of seeds of other species, which
THE SOIL AND GRASSES GRADUALLY CHANGE. 749
have either lain long buried in the soil, or have been brought thi-
ther by the winds. •.
This first change, which is almost universally observed in fields
of artificial grass, arises in part from the change which the soil it-
self has undergone during the few years that have elapsed since
the grass seeds were sown, and in part from the species of grass
selected not being such as the soil, at any time, could permanently
sustain.
b. When this deterioration, arising from the dying out of the
sown grasses, has reached its utmost point, the sward begins gra-
dually to improve, natural grasses suited to the soil spring up in
the blank places, and from year to year the produce becomes
greater and greater, and the land yields a more valuable pasture.
Practical men often say that to this improvement there are no
bounds, and that the older the pasture, the more valuable it be-
COmeS.
But this is true only within certain limits. It may prove true
for the entire currency of a lease, or even for the life-time of a
single observer, but it is not generally true. Even if pastured by
stock only and never mown, the improvement will at length reach
its limit or highest point, and from this time the value of the sward
will begin to diminish.
c. This, again, is owing to a new change which has come over
the soil. It has become, in some degree, exhausted of those sub-
stances which are necessary to the growth of the more valuable
grasses—less nutritive species, therefore, and such as are less will-
ingly eaten by cattle, take their place.
Such is the almost universal process of change which old grass
fields undergo, whether they be regularly mown or constantly pas-
tured only—provided they are left entirely to themselves. If mown
they begin to fail the sooner, but even when pastured they can be
kept in a state of full productiveness only by repeated top-dress-
ings, especially of Saline manures—that is, by adding to the soil
those substances which are necessary to the growth of the valuable
grasses, and of which it suffers a yearly and unavoidable loss.
Hence, the rich grass lands of our fathers are found now in too
many cases to yield a herbage of little value. Hence, also, in
nearly all countries, one of the first steps of an improving agricul-
750 IIOW THE CHANGE IS EIFFECTED.
ture is to plough out the old and failing pastures, and either to
convert them permanently into arable fields, or, after a few years'
cropping and manuring, again to lay them down to grass.
But when thus ploughed out, the surface soil upon old grass
land is found to have undergone a remarkable alteration. When
sown with grass seeds, it may have been a stiff, more or less grey,
blue, or yellow clay—when ploughed out it consists to a certain
depth of a rich brown, generally light and friable vegetable mould.
Or when laid down it may have been a pale-coloured, red, or yel-
low sand or loam. In this case the surface soil is still, when turn-
ed up, of a rich brown colour—it is lighter only and more sandy
than in the former case, and rests upon a subsoil of sand or loam
instead of one of clay. It is from the production of this change
that the improvement caused by laying land down to grass prin-
cipally results. In what does this change consist? and how is it
effected P -
If the surface soil upon stiff clay lands, which have lain long in
grass, be chemically examined, it will be found to be not only much
richer in organic matter, but often also poorer in clay than the
soil which formed the surface when the grass seeds were first sown
upon it. The brown mould which forms on lighter lands will
exhibit similar differences when compared with the soil on which it
rests; but the proportion of clay in the latter being originally
small, the difference in respect to this constituent will not be so
perceptible.
The effect of this change on the surface soil is in all cases to
make it more rich in those substances which cultivated plants re-
quire, and therefore more fertile in corn. But strong clay lands
derive the further important benefit of being rendered more loose
and friable, and thus more easily and more economically culti-
vated.
The mode in which this change is brought about is as follows:–
1°. The roots, in penetrating, open and loosen the subjacent
stiff clay. Diffusing themselves every where, they gradually raise
the surface soil by increasing its bulk. The latter is thus con-
verted into a mixture of clay and decayed roots, which is of a dark
colour, and is necessarily more loose and friable than the original
or subjacent unmixed clay.
AGENCY OF THE RAINS AND WINDS. 751
2P. But this admixture of roots affects the chemical composition
as well as the state of aggregation of the soil. The roots and stems
of the grasses contain much inorganic—earthy and saline—matter,
which is gathered from beneath, wherever the roots penetrate, and
is by them sent upwards to the surface. A ton of hay contains
about 200 lbs. of this inorganic matter. Suppose the roots to con-
tain as much, and that the total annual produce of grass and roots
together amounts to four tons, then about 800 lbs. of saline and
earthy matters are every year worked up by the living plants, and
in a great measure permanently mixed with the surface soil. Some
of this, no doubt, is carried off by the cattle that feed, and by the
rains that fall, upon the land—some remains in the deeper roots,
and some is again, year after year, employed in feeding the new
growth of grass—still a sufficient quantity is every season brought
up from beneath, gradually to enrich the surface with valuable in-
organic matter at the expense of the soil below.
3°. Nor are mechanical agencies wanting to increase this matu-
ral difference between the surface and the under soils. The loosen-
ing and opening of the clay lands by the roots of the grasses allow
the rains more easy access. These rains gradually wash out the
fine particles of clay that are mixed with the roots, and carry them
downwards, as they sink towards the subsoil. Hence the surface
soil, as the brown mould forms, is slowly rendered more open,
while the under soil becomes even stiffer than before, This sink-
ing of the clay is in a great measure arrested when the soil be-
comes covered with so thick a sward of grass as to break the force
of the rain-drops or of the streams of water by which the land is
periodically visited. Hence the soil of some rich pastures contains
as much as 10 or 12, of others as little as 2 or 3 per cent. of alu-
mina.
4°. The winds also here lend their aid. From the naked arable
lands, when the weather is dry, every blast of wind carries off a
portion of the dust. This it suffers to fall again as it sweeps along
the surface of the grass fields—the thick sward arresting the par-
ticles and sifting the air as it passes through them. Every where,
even to remote districts, and to great elevations, the winds bear a
constant small burden of earthy matter;" but there are few practical
* It has been observed that on spots purposely sheltered from the wind and rain
752 WHY RICHEST PASTURES ON CLAY LANDS.
agriculturists who, during our high winds, have not occasionally
seen the soil carried off in large quantities from their naked fields.
Upon the neighbouring grass lands this soil falls as a natural top-
dressing, by which the texture of the surface is gradually changed
and its chemical composition altered.
5°. Another important agency also must not be overlooked.
In grass lands insects, especially earth-worms, abound. These
almost nightly ascend to the surface, and throw out portions of
finely-divided earthy matter. On a close shaven lawn the quan-
tity thus spread over the surface in a single night often appears
surprising. In the lapse of years the accumulation of the soil
from this cause must, on old pasture fields, be very great. It has
often attracted the attention of practical men,” and so striking has
it appeared to some, that they have been inclined to attribute to
the slow but constant labour of these insects, the entire formation
of the fertile surface soils over large tracts of country (Darwin).f
I have directed your attention to these causes chiefly in explana-
tion of the changes which by long lying in grass the surface of our
stiff clay lands is found to undergo. But they apply equally to
other soils also—the only difference being that, in the case of such
as are already light and open, the change of texture is not so great,
and therefore does not so generally arrest the attention.
Upon this subject I may trouble you further with two practical
remarks— º
1°. That the richest old grass lands—those which have remained
longest in a fertile condition—are generally upon our strongest
clay soils (the Oxford and Lias clays, pp. 464 and 466). This is
owing to the fact that such soils maturally contain, and by their
comparative impermeability re-tain, a larger store of those inor-
ganic substances on which the valuable grasses live. When the
surface soil becomes deficient in any of these, the roots descend
on every side, the quantity of dust that is collected, when pressed down, is in 3 years
equal to one line, or in 36 years to one inch in thickness.--Sprengel, Lehre vom Diim-
ger, p. 443.
* The permanence of a fine carpeting of rich and sweet grass upon a portion of his
farm is ascribed (by Mr Purdie) to “the spewings of the worms, apparently immense-
ly numerous, which incessantly act as a rich top-dressing.”—Prize Essays of the High-
land Society, i. p. 191.
+ Geological Transactions.
WHY ARTIFICIAL PASTURES DETERIORATE • 753
further into the subsoil and bring up a fresh supply. But these
grass lands are not on this account exempt from the law above ex-
plained, in obedience to which all pastured lands, when left to ma-
ture, must through lapse of time become exhausted. They must
eventually become poorer; but in their case the deterioration will
be slower and more distant, and by judicious top-dressings may be
still longer protracted.
2°. The natural changes which the surface soil undergoes, and
especially upon clay lands when laid down to grass, explain why
it is so difficult to procure, by means of artificial grasses, a sward
equal to that which grows naturally upon old pasture land. As
the soil changes upon our artificial pastures, it becomes better fit-
ted to mourish other species of grass than those which we have
sown. These naturally spring up, therefore, and cover the soil.
But these intruders are themselves not destined to be permanent
possessors of the land. The soil undergoes a further change, and
new species again appear upon it. We cannot tell how often dif-
ferent kinds of grass thus succeed each other upon the soil, but we
know that the final rich sward which covers a grass field when it
has reached its most valuable condition, is the result of a long Se-
ries of natural changes which time only can bring about.
The surface soil of an old pasture field, which has been ploughed
up, is made to undergo an important change both in texture and
in chemical composition, before it is again laid down to grass.
The same grasses, therefore, which previously covered it will no
longer flourish, even when they are sown. Hence the unwilling-
mess felt by practical men to plough up their old pastures—but
hence, also, the benefit which results from the breaking up of such
as are old, worn out, or covered with unwholesome grasses. When
again converted into pasture land, new races appear, and a more
mourishing sward is produced.”
§ 8. Improvement of the soil by eating off with sheep.
I have said above that the greatest enriching of the soil takes
place when the vegetable matter is ploughed in in the green state.
* For an excellent article on the superior feeding qualities of recent artificial grasses
over many old pasture lands by Mr Boswell, of Kingcausie, see the Quarterly Jowr-
mal of Agriculture, Vol. iv. p. 783.
3 B
754. IMPROVEMENT BY EATING OFF WITH SHEEP.
This statement appears to be contradicted by the result of experi-
ence in regard to the eating off with sheep. In regard to this
practice, two facts are, I believe, generally recognised.
1°. That it is most beneficial, generally speaking, where the
soil is richest in vegetable matter. (Sprengel.)
This is consistent with all that has already been said. The sheep
eat off the crop, dissipate a portion of its carbon by their lungs,
and return to the soil the nitrogen and saline matter in a more
concentrated state. It is in this way that on soils which can bear
this loss of carbonaceous matter, eating off does more good than
ploughing in green. It was also observed by Von Voght,
2°. That land is sometimes more improved by eating off a crop
of clover or spurry with sheep, than by ploughing it in green.
There are two cases in which it is easy to understand how this
should be the case. Thus,
a. When the land is already rich, especially in vegetable matter,
the loss, as above explained, is of less consequence and is not sen-
sibly felt. The eating off changes the green produce more rapidly.
The saline matter of the plants is separated from them, and ap-
pears in the urine of the sheep. A more rapid production of am-
monia also is caused in the soil, than when the green crop is directly
ploughed in. The effect, therefore, upon the after corn may be
more immediate and striking. Still, even here, after the lapse of
time, the eating off with growing sheep will not be found the most
beneficial to the land, unless some other manure—such as bones—be
added to it. The sheep always carry off something from the fields,
if they thrive upon them, and this must ultimately tell upon its fer-
tility. But,
b. It is on light soils of all kinds that the eating off is confess-
edly better than the ploughing in. Such soils require to be con-
solidated by the tread of the sheep. Ploughing in green manure
would tend only to render them lighter, so that, in these cases, a
consideration of the mechanical condition of the soil must be al-
lowed to outweigh all our purely chemical reasoning. In the case
of the so-called overlimed land (p. 698), to plough in green crops
would be entirely inadmissible; whereas, to eat them off with sheep
is the very best and simplest means of rendering them productive.
IMPROVEMENT OF THE SOIL BY PLANTING. 755
§ 9. Improvement of the soil by the planting of trees.
It has long been observed by practical men, that when poor, thin,
unproductive soils have been for some time covered with wood,
their quality materially improves. In the intervals of the open fo-
rest, they will produce a valuable herbage—or when cleared of
trees they may for some time be made to yield profitable crops of
COI’ll, -
This fact has been observed in almost every country of Europe,
but the most precise observations upon the subject with which I
am acquainted are those which have been made in the extensive
plantations of the late Duke of Athol. These plantations consist
chiefly of white larch, (Laria Europaea,) and usually grow upon a
hilly soil, naturally poor, and resting on gneiss, mica-Slate, and
clay-slate (pp. 479 to 481). In six or seven years the lower branch-
es spread out, become interlaced, and completely overshadow the
ground. Nothing, therefore, grows upon it till the trees are 24
years old, when the spines of the lower branches, beginning to fall,
the first considerable thinning takes place. Air and light being thus
re-admitted, grasses (chiefly holcus mollis and lanatus) spring up,
and a fine sward is gradually produced. The ground, which pre-
viously was worth only 90, or 1s, per acre as a sheep pasture, at
the end of 30 years becomes worth from 7s, to 10s, an acre.
The soil on this part of the Duke's estate is especially propitious
to the larch—and, therefore, this tree both thrives best and in the
greatest degree improves the soil. Thus in oak copses, cut every
24 years, the soil becomes worth only 5s, or 6s. per acre, and this
during the last six years only, . Under an ash plantation, the im-
provement amounts to 2s. or 3s. per acre; under Scotch fir, it
does not exceed 6d. an acre—while under spruce and beech the
land is worth less than before.*
The main cause of this improvement, as of that which is pro-
duced by laying down to grass, is to be found in the natural ma-
muring with recent vegetable matter, to which the soil year by year
is so long subjected. Trees differ from grasses only in this, that
while the latter enrich the soil both by their roots and by their
* Mr Stephens in the Thansactions of the Highland Society, xi. p. 189; also Lou-
don's Encyclopædia of Agriculture, p. 1346.
756 PRODUCED BY THE SHEDDING OF THE LEAVES.
leaves, the former manure its surface only by the leaves which they
shed.
The leaves of trees, like those of the grasses, contain much in-
organic matter, and this when annually spread upon the ground
slowly adds to the depth as well as to the richness of the soil.
Thus the leaves of the following trees, when dried in the air, con-
tain respectively of inorganic matter: *—
April. August. November.
per cent. per cent. per cent.
Oak,........................ Tº e s a , , , 5 ... ... 4%
Ash, ...... ....... ......... - . . . . . 6} ...... *
Beech, ..................... - . . . . . 7 ...... 6%
Birch, ......... ........ .. -- . . . . . . 5 ..... <-º:
Elm,....... ......... ..... Tº . . . . . . 11; ...... --
Willow, ... .............. – . . . . . . 8} ...... s-ºs-
White larch, ............ 6 J. ...... T - - - - - - *mºmº,
Scotch fir, ............... - . . . . . li ...... -sº
In looking at the differences among these numbers—especially
in the case of the elm and of the Scotch fir—one would naturally
suppose that the diversity of their effects in improving the land is
in some measure to be ascribed to the quantity and kind of the
inorganic matter which the leaves of these several trees contain.
And to this cause, no doubt, some effect is to be ascribed in locali-
ties where all the trees thrive equally. -
But upon the quantity of leaves produced, as much in general
will depend, as upon the relative proportions of organic and inor-
gamic matter which these leaves may respectively contain. And
as the quantity of leaves is always greatest where the tree flourishes
best or finds a most propitious soil—the improvement of the soil
itself, by any particular tree, will be always in a great measure
determined by its fitness to promote the growth of that kind of
tree, ->
On the soil planted by the Duke of Athol, the larch shot up
luxuriantly, while the Scotch fir lingered and languished in its
growth. Thus the quantity of leaves produced and annually shed
by the former was vastly greater than by the latter tree. Had the
Scotch fir thriven better than the larch, the reverse might have
been the case, and the value of the soil might have been increased
in a greater proportion by plantations of the former tree.
* Sprengel, Chemie für Landwirthe, ii. passim. See also Lecture ix. p. 262.
RELATIVE EFFECTS OF DIFFERENT KINDS OF TREES. 757
Other special circumstances also will account for the relative
degrees of improvement produced by the larch and by some of the
other trees—for example the oak. In the oak copse the soil in 16
years became worth 6s, or 8s. an acre. If, therefore, instead of
being cut down for their bark at the end of 24 years, the trees had
been allowed to grow up into an oak forest, the permanent improve-
ment of the pasture, even on this soil, would probably have been
at least as great as under the larch. The above experiments,
therefore, are in reality not so decisive in regard to the relative
improving power of the several species of trees as they at first sight
appear. The most rational natural rule by which our practice
should be guided seems to be contained in these three propositions—
1°. That the soil will be most improved by those trees which
thrive best upon it.
2°. Among those which thrive equally, by such as yield the
largest produce of leaves; and—
3°. Among such as yield an equal weight of leaves, by those
whose leaves contain the largest proportion of inorganic matter—
which bring up from beneath, that is, and spread over the surface
in largest quantity, the materials of a fertile soil.
4°. It may be added, that deep-rooted trees will improve the
surface more than such as, like the ash, spread themselves along
at the depth sometimes of a few inches only, and thus draw their
sustenance from the surface soil itself.
The mode in which the lower branches of the larch spread out
and overshadow the land is not without its influence upon the ulti-
mate improvement which the soil exhibits. All vegetation being
prevented, the land, besides receiving a yearly manuring of vege-
table mould, is made to lie for upwards of 20 years in uninterrupt-
ed naked fallow. It is sheltered also from the beating of the rain
drops, which descend slowly and gently upon it, bearing principles
of fertility instead of Washing out the valuable saline substances it
may contain.
Beneath the overshadowing branches of a forest, the soil is also
protected from the wind, and to this protection Sprengel attributes
much of that rapid improvement so generally experienced where
land is covered with wood. The winds bear along particles of
earthy matter” which they deposit again in the still forests; and
* See note, p. 751.
7.58 MANURING WITH SEA-WEED.
thus gradually form a soil even on the most naked places. This
slow general cause of accumulation may not be without its effect,
and should not be forgotten, but it does not explain why, in the
same range of country, the soil which is covered by forests of one
kind should improve more rapidly, than those which are shelter-
ed by trees of another species.
§ 10. Of the use of sea-weed as a manure.
Among green manures of great value and extensive application
must be included the sea-weed or sea-ware of our coasts. The ma-
rine plants of which it consists differ from the green vegetables
grown upon land,-
1°. By the greater rapidity with which they undergo decay.
When laid as top-dressings upon the land they melt down, as it
were, and in a short time almost entirely disappear. Mixed with
soil into a compost or with quick-lime, they speedily crumble down
into a black earth, in which little or no trace of the plant can be
perceived. This rapid decay is owing very much to the peculiar
nature of the organic matter they contain.
This organic matter consists chiefly of a peculiar mucilaginous
substance, which quickly falls away, but it is also rich in compounds
of nitrogen, by which the decay of the whole plant is very rapidly
promoted. Some varieties, such as the dulse, abound in the peculiar
Sugar of mamma.
Thus the dry fucus saccharinus or dulse has been found to con-
tain about
Compounds of nitrogen, (protein compounds,”) 13:74
Mannite, (manna sugar, f)........................... 12:15
Mucilage and cellular fibre, ......... ............... 45.95
Inorganic matter, (ash,)...... e e º 'º e º e º e s a e º 'º a ......... 28°16
100
The dry plant is thus much richer in nitrogen than any of our
green crops grown upon the land, and therefore not only decays
more rapidly, but is fitted to supply nitrogen to the plant more
abundantly, and therefore more rapidly to promote its growth.
2°. By the greater proportion of Saline or other inorganic matter
* Payen. + Stenhouse,
IT ADDS SALINE MATTER, TO THE LAND. 759
which these plants, in their dry state, contain. It is these substances
which are obtained in the form of kelp when dry sea-weeds are
burned in the air.
The quantity of ash left by our usually cultivated grasses varies
from 5 to nearly 10 per cent. of their weight in the dry state, but the
fucus vesiculosus, which is reckoned the most valuable for the manu-
facture of kelp, leaves from 15 to 20 per cent. The dry fucus saccha-
rinus, of which the composition is given above, left upwards of 28 per
cent. Green sea-ware, therefore, imparts to the soil upwards of
twice as much inorganic matter as an equal weight of almost any
other green manure. *
In regard to this inorganic matter it is of importance to bear
in mind, -
a. That it consists for the most part of those substances which
all our cultivated crops require. The addition of these to the land,
therefore, cannot fail, if other things are favourable, to promote its
fertility. (P. 403.)
b. That the Saline and other inorganic matters which are con-
tained in the sea-weed laid upon our fields, form a positive addition
to the land. If we plough in a green crop where it grew, we re-
store to the soil the same saline matter only which the plants have
already taken from it during their growth, while the addition of
sea-weed imparts to it an entirely new supply. It brings back from
the sea a portion of that which the rivers are constantly carrying
into it, and is thus valuable in restoring, in some measure, what
rains and crops are constantly removing from the land.
Sea-weed is collected along most of our rocky coasts—and is
seldom neglected by the farmers on the borders of the sea. In
the Isle of Thanet, it is sometimes cast ashore by one tide and
carried off by the next;-so that after a storm the teams of the
farmers may be seen at work even during the night in collecting
the weed, and carrying it beyond the reach of the sea.” In that
locality, it is said to have doubled or tripled the produce of the
land. On the Lothian coasts, a right of way to the sea for the
collection of sea-ware increases the rental of the land 25s. to 30s.
an acre. In the Western Isles it is extensively collected and em-
* British /Iusbandry, ii. p. 418.
+ Kerr's Berwickshire, p. 377.
760 MODE IN WEHICH IT IS APPLIED.
ployed as a manure"—and on the north-east coast of Ireland, the
farming fishermen go out in their boats and hook it up from con-
siderable depths in the seaf-while on the west coast it is half
dried and carted many miles inland as a dressing for the fields.
It is applied either immediately as a top-dressing, especially upon
grass land—or it is previously made into a compost with earth,
with lime, or with shell-sand. Mixed with lime in this way, it is
used with advantage as a top-dressing for the young wheat crop, Í
and mixed with shell-sand, it is the general manure for the potato
among the Western islanders. § It gives large crops of this root,
but they are said to be generally inferior in quality (waxy) when
raised with sea-ware alone. \
It may also be mixed with farm-yard manure or even with peat
moss, both of which it brings into a more rapid fermentation. In
some of the Western Isles, and in Jersey, it is burned to a light,
more or less coaly powder, and in this form is applied successfully
as a top-dressing to various crops. The most economical method
is to make it into a compost with absorbent earth and lime, or to
plough it in at once in the fresh state.
In the Western Islands one cart load of farm-yard manure is
considered equal in immediate effect—upon the first crop, that is—
to 2% of fresh sea-weed or to 1; after the weed has stood two
months in a heap. The sea-weed, however, rarely exhibits any
considerable action upon the second crop.
Sea-weed is said to be less suited to clay soils, while barren
sand has been brought into the state of a fine loam by the constant
application of sea-weed alone, for a long series of years. ||
When laid upon newly ploughed up heath or benty land it
hastens the decay of the plants and roots, reduces the sod, and fa-
cilitates the levelling and improvement of the land.
Conflicting opinions are given by different practical men, in re-
gard to the crops to which it is best suited. But the explanation
of most of these and similar discordances is to be found in the an-
* “Sea-weeds constitute one-half of the Hebridean manures, and nine-tenths of those
of the remoter islands.”—Macdonald's Agriculture of the JHebrides, p 40l.
+ Mrs Hall's Ireland. -
j: British Husbandry, ii. p. 419.
§ Transactions of the Highland Society, 1842–43, p. 766.
| Macdonald's Hebrides, p. 407.
TJSE OF STRAW AS A MANURE. 761
swers to the three following questions—what substances does the
crop require in largest quantity ?—how many of these abound in
the soil –can the manure we are about to use supply all or any
of the remainder ? If it can, it may generally be expected to do
good. Thus simply and closely are the kind of crop, the kind of
soil, and the kind of manure, in most cases, connected together.
§ 11. Of manuring with dry vegetable substances.
The main general difference between vegetable matter of the
same kind, and cut at the same age, when applied as a manure in
the green and in the dry state, consists in this—that in the former
it decomposes more rapidly, and, therefore, acts more speedily.
The total or final effect upon vegetation will probably in either
case be very nearly the same. . -
But if the dry vegetable matter have been cut at a more ad
vanced age of the plant, or have been exposed to the vicissitudes of
the weather while drying, it will no longer exhibit an equal efficacy.
A ton of dry straw, when unripe, will manure more richly than a
ton of the same straw in its ripe state—not only because the sap of
the green plant contains the materials from which the substance of
the grain is afterwards formed—but because, as the plant ripens,
the stem appears to restore to the soil a portion of the saline, es-
pecially of the alcaline, matter it previously contained. After it
is cut, also, every shower of rain that falls upon the sheaves of
corn or upon the new hay, washes out some of the saline substances
which are lodged in its pores, and thus diminishes its value as a
fertilizer of the land. These facts place in a still stronger light
the advantages which necessarily follow from the use of vegetable
matter in the recent state, for manuring the soil.
1°. Dry straw.—It is in the form of straw that dry vegetable
matter is most abundantly employed as a manure. It is only,
however, when already in the ground in the state of stubble, that
it is usually ploughed in without some previous preparation. When
buried in the soil in the dry state, it decomposes slowly, and pro-
duces a less sensible effect upon the succeeding crop. It is usually
fermented, therefore, more or less completely, by an admixture of
animal manure in the farm-yard before it is laid upon the land.
During this fermentation a certain unavoidable loss of organic,
762 USE OF CHAPE AND BRAN.
and generally a large loss of saline matter also takes place.” It
is, therefore, theoretically true of dry, as it is of green, vegetable
matter, that it will add most to the soil, if it be ploughed in with-
out any previous preparation,
Yet this is not the only consideration by which the practical
man must be guided. Instead of a slow and prolonged action
upon his crops, he may require an immediate and more powerful
action for a shorter time, and to obtain this he may be justified in
fermenting his straw with the certainty even of an unavoidable
loss. Thus the disputed use of short and long dung becomes alto-
gether a question of expediency or of practical economy. But to
this point I shall again recur when treating of farm-yard manure
in the succeeding lecture.
2°. Chaff partakes of the mature of straw, but it decomposes
more slowly when buried in the soil in the dry state. It is also
difficult to bring into a state of fermentation, even when mixed
with the liquid manure of the farm-yard. Still it ought never to
be wasted, but in some form or other always returned to the land.
3°. Bran.-The bran and pollard of wheat are highly recom-
mended as manures. Drilled in with the turnip seed, at the rate
of 5 or 6 cwt. an acre, at a cost of 22s. 6d. per acre, it has been
found to bring forward the crops more rapidly than when farm-
yard dung alone was used, and to increase the crop by one-half.
If moistened with urine, and slightly fermented, the action of bran
would be hastened and rendered more powerful.
The composition of bran explains the cause of its value as a ma-
mure. It consists of -
Water,........................ 13:1
Gluten,.................. . . . . . . 19:3
Oil, ............. .............. 4-7
Husk and a little starch, ... 55-6
Saline matter (ash), ......... 7.3
100
It thus appears to contain a large per-centage both of gluten,
from which the plant can obtain nitrogen, and of saline matter
* See in the succeeding lecture the Section upon miced animal and vegetable ma-
20,2{}^CS.
USE OF OAT-HUSK AND RAPE-DUST. 763
also, from which its inorganic constituents may readily be sup-
plied. -
4°. Oat husk.—The husk of the oat, which is very generally
thrown away in many parts of Scotland, might be beneficially fer-
mented and employed as a manure. It is less rich in nitrogen
than the bran of wheat, but contains a larger per-centage of mine-
ral matter. (P. 370.)
5°. Rape-dust.—When rape-seed is exhausted of its oil, it comes
from the press in the form of hard (rape) cakes, which, when crush-
ed to powder, form the rape-dust of late years so extensively em-
ployed as a manure. It is occasionally mixed with farm-yard dung,
and applied to the turnip crop—in some districts the turnip crop is
raised by means of rape-dust alone—but it is most frequently used,
I believe, as a top-dressing for the wheat crop, either harrowed in
with the seed in October, or applied to the young corn in spring.
Rape-dust requires moisture to bring out its full fertilizing vir-
tues; hence it is unfitted for very dry soils, and is best adapted to
clay soils or to such as rest upon a stiff subsoil. It is seldom ap-
plied, therefore, to the barley crop, and upon wheat it fails to pro-
duce any decidedly good effect in very dry seasons. Several inte-
resting circumstances have been experimentally ascertained in re-
gard to the action of rape-dust, to which it is proper to advert:—
a. That in very dry seasons it may produce little benefit upon
turnips, potatoes, and other crops, while in the same circumstances
the effect of guano may be strikingly beneficial. Thus in one expe-
riment, made in 1842, upon unmanured land sown with turnips—
16 cwt. of rape-dust gave 3; tons of bulbs per acre.
2 cwt. of guano gave 5 do.
Unmanured gave - 3% do.
And in another, in the same season, upon unmanured land—
l ton of rape-dust gave 14} tons of bulbs per acre.
3 cwt. of guano gave 23% do.
Unmanured gave - 12} do.
Again, Upon potatoes, planted without other manure, in 3 expe-
riments, the produce per acre, in tons, was as follows—
l ton 3 cwt. 4 cwt.
Unmamured. rape-dust. guano. guano.
White Don potatoes, – & tº - 12} * * * * 18% *º
Red Don potatoes,... 6; * g e 10 * 6 & * * e g 14}
Connaught cups, ... 5; & 9 º' ! 3 * * * -* * * 13}
764. ACTION OF RAPE-DUST ON OATs, WHEAT, AND BEANs.
In none of the above experiments did the action of the large
quantity of rape-dust equal that of the comparatively small quan-
tity of guano—though, from being buried in the soil, the difference
was less striking in the case of the potato crops.
b. Rape-dust may actually cause the crop to be less than the
land alone would naturally produce—if in a dry season it be laid
on in any considerable quantity.
Thus in 1842, in an experiment upon Oats, made at Lennox
Ilove, in East Lothian—
16 cwt. of rape-dust gave 45 bushels.
2 cwt. of guano gave 68 do.
Unmanured soil gave 49 do.
f In this property of injuring the crop, when rain does not hap-
pen to fall, rape-dust resembles very much those saline substances
which, as we have seen, may often be applied with much advan-
tage to the land.
c. Yet it would appear to exercise less of this evil influence upon
wheat and beams, even in similar circumstances. Thus in the same
season, 1842, and in the same locality, Lennox Love, a crop of
wheat, with—
16 cwt. of rape-dust gave 51 bushels per acre.
2 cwt. of guano gave 48 do.
Unmanured gave - 47% do.
And a crop of beans, with—
16 cwt. of rape-dust gave 38 bushels.
2 cwt. of guano gave 35; d.o.
Unmanured gave - 30 do.
In both of these cases, notwithstanding the drought, the rape-
dust improved the crop, and though not sufficiently so to pay the
cost of the application, yet to a greater extent than the same quan-
tity of guano. It is deserving of investigation, therefore, whether
rape-dust be more especially adapted to wheat and beans. Even
in favourable seasons it may possibly prove more economical than
guano as a manure for these two crops,
d. But even in favourable seasons, and to the wheat crop, there
is reason to believe that rape-dust cannot be economically applied
in more than a certain, perhaps variable, quantity per acre. Thus
four equal plots of ground (nearly half an acre each,) sown with
COTTON SEED AND COCOA-NUT’ CARES. 765
wheat, were top-dressed with rape-dust in different proportions
with the following results:— -
With 7 cwt. the produce was 26 bushels of market corn.
With 10 cwt, the produce was 28 do.
With 15 cwt. the produce was 29% do.
With 26 cwt. the produce was 27# do.
Unmanured the produce was 22}* do.
In this experiment not only was the crop diminished when more
than 15 cwt. was added, but the increased produce was not sufficient
to defray the additional cost of the application, when more than 7
cwt. of rape-dust was put on. .
e. It may be noticed as another curious fact, that the natural
action of rape-dust is modified by the presence or absence of certain
other substances in the soil. Common salt and sulphate of soda,
when mixed with it under certain circumstances, were found at
Lennox Love to produce less effect upon wheat than when the
same quantity of rape dust was applied alone. The same may pro-
bably happen when it is applied without admixture, to soils in which
these saline compounds happen to be already present in conside-
rable quantity. This subject deserves further investigation.
6°. Lintseed, poppy-seed, cotton seed, and cocoa-nut cakes.—The
cake which is left when other oils are extracted from the seeds or
fruits in which they exist is also, in almost every case, useful as a
manure. Thus the seeds of the cotton plant yield an oil and leave
a cake which is now used as a manure in the United States,
though little known as yet, I believe, in this country. The cocoa-
nut-cake is employed in Southern India partly in feeding cattle
and partly as a manure for the cocoa-nut tree itself. Some trials
have recently been made with it among ourselves, but I am igno-
rant of the precise results. In this country lintseed cake is made
in large quantity, but as it is relished by cattle, is fattening, and
enriches the droppings of the stock fed upon it, it is seldom applied
directly to the land. In France and some parts of Belgium,
where the poppy is largely cultivated for the oil yielded by its
seeds, the cake which these seeds leave is highly esteemed as a
manure. It is now imported into this country, and is used both
as a manure, and as a food for sheep and cattle.
7°. Malt-dust.—When barley is made to sprout by the maltster
<g * British Husbandry, i. p. 412.
766 USE OF MALT-DTUST AND SAW-DTUST.
and is afterwards dried, the small shoots and rootlets drop off, and
form the substance known by the name of malt-dust. One hun-
dred bushels of barley yield 4 or 5 bushels of this dust. It is sold
at the rate of from 5s, to 8s, a-quarter, and has been applied with
success as a top-dressing to the barley and wheat crops. It may
also be drilled in with turnips, dusted over the young grass in
spring, or sown with the hand in the potato drills. It is better to
moisten it with liquid manure, and thus to ferment it slightly before
it is used. -
The value of malf-dust depends in part upon the large per-
centage (29 per cent.) of protein compounds, gluten, albumen,
&c., which it contains, and in part upon its organic constituents,
of which, as we have already seen, (p. 426), the phosphates of po-
tash and Soda form a large proportion.
8°. Saw-dust is usually rejected by the agriculturist, in conse-
quence of the difficulty which is generally experienced in bringing
it into a state of fermentation. It decomposes slowly when plough-
ed into the soil in its dry state, but it nevertheless gradually bene-
fits the land, and should not, therefore, be permitted in any case
to run to waste. It forms an excellent absorbent also for liquid
manures of any kind, which it preserves from sinking too rapidly
when they are to be applied to porous, -sandy, or chalky soils,
while these liquids again hasten the decomposition of the saw-dust
and augment its immediate effect upon the land. In localities
favourable for the collection of sea-weed, it may also be more ra-
pidly fermented by an admixture with this substance. It forms
a useful ingredient in some of the mixed manures which have
recently come into use.
9°. Dry leaves may either be dug into the land at once, or may
be laid up in heaps, when they will gradually decay, and form, in
most cases, an enriching manure. They gradually improve the
soil on which they annually fall, but the same quantity of leaves
will do more good if collected and immediately dug in, or if made
into a compost heap, than if left to undergo a slow natural decay
on the surface of the land. -
§ 12. Of the use of decayed vegetable matter as a manure.
The most abundant forms of partially decayed vegetable matter
USE OF PEAT AS A MANUR.E. - 767
which come within the reach of the practical farmer, are peat and
tanner's bark.
1°. Peat.—To soils which are deficient in vegetable matter, a
judicious admixture of peat must prove advantageous, because it
will supply some at least of those substances which are necessary
to the production of a higher degree of fertility. But peat decays
very slowly in the air, and hence its apparent effect when mixed
with the soil is very small. It may gradually ameliorate its qua-
lity, especially if the soil be calcareous, but it will not immediately
prepare the land for the growth of any particular crop. But if
the obstacles to its further decomposition be removed—that is, if
by artificial means its decay be promoted—then its immediate and
apparent effect upon the soil is increased, and it becomes an ac-
knowledged fertilizing manure. Different methods have been suc-
cessfully practised for bringing it into this more rapid state of de-
cay or fermentation.
a. The half-dried peat may be mixed with from one-fourth to
one-half its weight of fermenting farm-yard manure—the whole
heap being carefully covered over with a layer of peat to prevent
the escape of fertilizing vapours. By this method—first introdu-
ced to public notice by the late Lord Meadowbank—the entire mix-
ture is gradually brought into an equable state of heat and fer-
mentation, and as a manure for the turnip crop, is said to be as
efficacious as an equal weight of unmixed farm-yard manure.
b. Or the liquid manure of the farm-yard may be employed for
the same purpose, either in whole or in part. If the heap of mixed
peat and dung be watered occasionally with the liquid manure,
the fermentation will be more speedily effected, and at a less ex-
pense of common farm-yard dung. Or the half-dried peat may
be used unmixed, as an absorbent for the liquid of the farm-yard,
by which, without other aid, it will be brought into a state of fer-
mentation with comparative rapidity. In this latter way it is very
extensively used in Ireland and in the Highlands of Scotland. It
forms the bulk of the manure usually applied in raising potatoes
upon the con-acre land of Ireland, and upon the small holdings of
the crofters in the Western Isles, and on the west coast of Scotland.
c. Or instead of the liquid manure, the ammoniacal liquor of
768 FERMENTATION OF PEAT AND TANNER's BARK.
the gas-works may be employed, with less permanent benefit cer-
tainly, but still with great advantage.
d. Or the peat may be mixed with from one-sixth to one-fourth
of its bulk of fresh sea-weed, the rapid decay of which will gra-
dually reduce the entire heap into a fertilizing mass. With sea-
weed and shell-sand indeed it forms an excellent manure.
e. Or rape-dust in the proportion of 1 ton to 30 cubic yards
may be mixed with the half-dried peat from two to six weeks be-
fore the time of sowing the turnip crop. The fermentation of the
rape-dust takes place so quickly, that this short time is usually
sufficient to convert the whole into a uniform and rapidly decaying
compost.
In short it is only necessary to mix half-dried peat with any
substance which undergoes rapid spontaneous decomposition—
when it will more or less speedily become infected with the same
tendency to decay, and will thus be rendered capable of minister-
ing to the growth of cultivated plants.
2°. Tanner's bark is more difficult to reduce or to bring into a
rapid state of decomposition. Any of the methods above recom-
mended for peat, however, will to a certain extent succeed also
with the spent bark of the tan pits. But in the case of substances
so solid and refractory as the lumps of bark are, the admixture of
a quantity of lime and earth, so as to form a compost heap, is per-
haps the most advisable mode of procedure. The way in which
lime promotes the decay of woody fibre in such heaps has already
been explained.
§ 13. Use of charred vegetable matters as a manure.
Soot and charcoal are the principal substances of this class which
have been more or less extensively employed for the purpose of
increasing the productiveness of the land.
1°. Soot is a complicated and variable mixture of substances
produced during the combustion of coal. Its composition, and
consequently its effects as a manure, vary with the quality of the
coal, with the way in which the coal is burned, and with the height
of the chimney in which it is collected.
Soot has not been analysed since the year 1826, when a variety
COMPOSITION OF SOOT. - 769
examined by Braconnot was found by him to consist in a thousand
parts of
Ulmic acid P (a substance resembling that portion of the vegetable matter 302.0
of the soil which is soluble in caustic potash or Soda—p. 514), ... ... ... ! e
A reddish brown soluble substance, containing nitrogen, and yielding am- -
monia when heated,... ........................................................... : 200.0
Asboline, ............................................................................ * * * * * 5.0
Carbonate of lime, with a trace of magnesia (probably derived in part from 146.6
the sides of the chimney), .................. ....... ... .. * * * * * * * * * * * * * * * * * * * * * e
Acetate of lime, .................................... .............. . . s e e º e s e s is a e e s & e & © e 56.5
Sulphate of lime (gypsum),........................................................ ... 50.0
Acetate of magnesia, ..................................................... .......... . 5.3
Phosphate of lime, with a trace of iron,...................... * * * * * * * * * * * * * * * * * * * * * * * 15.0
Chloride of potassium,................................... . . . . ........................ 3.6
Acetate of potash, ........................... .......................... ............... 4.1.0
Acetate of ammonia, ... .......................... ................. .................. 2.0
Silica (sand),........................... ... • e s a e s e º e º e º s = • * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 9.5
Charcoal powder, ..................................................................... 38.5
Water, ....................... ........................................................ ... 125.0
1000*
The earthy substances which the soot contains are chiefly derived
from the walls of the chimney, and from the ash of the coal, part
of which is carried up the chimney by the draught. These, there-
fore, must be variable, being largest in quantity where the draught
is strongest, and where the earthy matter or ash in the coal is the
greatest. The quantity of gypsum present depends upon the sul-
phur contained in the coal,—that which is freest from sulphur will
give a soot containing the least gypsum. The ammonia and the
brown soluble substance containing nitrogen will vary with the quan-
tity of nitrogen contained in the coal and with certain other causes
—so that the composition of different samples of soot may be very
unlike, and their influence upon vegetation therefore very unequal.
The consequence of this must be, that the results obtained in one
spot, or upon one crop, do not indicate the precise effect which
another specimen of soot will produce in another locality, and upon
another crop even of the same kind. And thus it happens that
the use of soot prevails more, and is attended with more beneficial
effects, in some districts than in others.
a. In general it may be assumed that where ammonia or its
salts will benefit the crop, soot also will be of use, and hence its
* Annales de Chemic et de Physique, xxxi. p. 37.
3 C
770, SOOT LIAS A SPECIAL EFFECT UPON RYT-GRASS,
successful application to grass lands. From its containing gypsum
it should also especially benefit the clover crops. Yet Dr Ander-
son says, “I have used soot as a top-dressing for clover and rye-
grass in all proportions, from one hundred bushels per acre to six
hundred, and I cannot say that ever I could perceive the clover in
the least degree more luxuriant than in the places where no soot had
been applied. But upon rye-grass its effects are amazing, and in-
crease in proportion to the quantity applied so far as my trials have
gone.” And his general conclusion is, that soot does not affect
the growth of clover in any way, while it wonderfully promotes that
of rye-grass. This experiment certainly deserves repetition. It
may be true of one locality and not of another where the soil or
mode of manuring is different.
b. The presence of ammonia in soot causes it, when laid in heaps,
to destroy all the plants upon the spot; and Dr Anderson adds
the interesting observation, “that the first plant which appears
afterwardsisconstantly the common couch-grass(Triticum repens).”f
c. This ammonia also causes soot to injure and diminish the
crop in very dry seasons. Thus the produce of a crop of beans,
after oats, in 1842, upon an
Unmanured part of the field was ...... 29; bushels.
Dressed with 4 bushels of soot,......... 28 bushels.
It also diminished, in a small degree, the potato crop in the
same year in the experiments of Lord Blantyre, at Erskine.
With manure alone, the produce was ............... 11 tons 17 cwt.
With 30 bushels of soot sprinkled over the dung, 11 tons 4 cwt.
Like rape-dust and Saline substances, therefore, soot seems to
require moist weather, or a naturally moist soil to bring out all
its virtues.
d. Yet even in the dry season of 1842, its effect upon wheat
and oats in the same locality (Erskine) was very beneficial. Thus
the comparative produce of these crops, when undressed and when
top-dressed with 10 bushels of soot per acre was as follows:—
Unmanured,...............Wheat 44 ...... Oats 49.
Top-dressed with soot, ...Wheat 54 ...... Oats 55.
But the dressed wheat was inferior in quality to the undressed
* Dr Agderson's Essays (edit, 1800), ii, p. 304, + Ibid. p. 305.
ACTION OF SOOT UPON WHEAT, OATS, AND GRASS. 771
—the former weighing only 58, the latter 62 lbs. a bushel. In
the oats there was no difference. Are we to infer from these re-
sults that, even in dry seasons, soot may be safely applied to crops
of corn, while to pulse and roots it is sure to do no good? Fur-
ther precise observations, no doubt, are still necessary—and the
more especially as experiments upon oats and wheat in the same
year, made in the still drier locality of Lennox Love, gave a de-
crease in the produce of grain—while in some experiments upon
turnips, made by Mr Fleming, 50 bushels of soot, applied alone,
gave an increase of 4 tons in the crop. .
e. An experiment of Lord Blantyre's enables us to judge of the
efficacy of soot in a dry season, compared with that of nitrate of
soda and of guano upon the produce of hay. Thus the crop of
hay, per imperial acre, from the
Cost.
Tons. Cwt. £ S. d.
Undressed portion, weighed ...... . . . . ... l 8 ......
Dressed with 40 bushels of soot, ............ 1 15 ...... 0 1 1 8
160 lbs. nitrate of soda, ...... l 19 ...... 1 15 9
—— 160 lbs. of guano, ............ 2 2 ...... 1 15 9
In this experiment the soot proved a more profitable application
than either of the other manures.
f. In regard to this substance, I shall only advert to one other
observation—but it is an important one—made by Mr Morton,
when describing the management of a well-conducted farm in
Gloucestershire.” “The quantity of soot used upon this farm
amounts to 3000 bushels a-year, one-half of which is applied to
the potato, the other half to the wheat crop.” All the straw grown
upon this farm is sold for thatch, and for the last 30 years the only
manure that has been purchased to replace this straw is the soot,
which is brought from Gloucester, Bristol,f and Cheltenham.
Soot no doubt contains many things useful to vegetation, yet where
all the produce is carried off, and soot only added in its stead—
even the rich soils of the vale of Gloucester cannot be expected to
* That of Mr Dimmery, described in the Journal of the Royal Agricultural Society,
i. p. 400.
f At Bristol the price of soot is 9d. a bushel, at Gloucester only 6d., yet the for-
mer is preferred, even at the higher price. It is of better quality, owing, it is said, to
the greater length of the chimneys—it may be also owing to the quality of the coal
and to the way it is burned.
772 USE OF CHARCOAL DUST AND COAL TAR.
retain a perpetual fertility. The slow changes which theory indi-
cates may altogether escape the observation of the practical man,
who makes no record of the history of his land, and yet may be ever
gradually proceeding so as ultimately to produce a sensible effect.
2°. Charcoal-Wood-charcoal, from its porous nature, and its
tendency to absorb animal odours and other unpleasant effluvia,
has been found, when reduced to fine powder, to be an excellent
admixture for night soil, for liquid manure, and for other sub-
stances which undergo putrescent decay. It is therefore employed
to a considerable extent by the manufacturers of artificial manures.
lt is also applied with advantage as a top-dressing to various
crops. In an experiment by Mr Fleming upon Swedish turnips,
50 bushels of charcoal powder increased the crop by 3 tons an
acre. Its efficacy is due in part to its power of absorbing from the
air, or of retaining in the soil, those gaseous substances which
plants require, and in part to the slow decay which it is itself ca-
pable of undergoing. In moist charcoal powder seeds are said to
germinate with great ease and certainty.
3°. Coal-tar.—Another product of coal, the tar of the gas-
works, has recently been recommended as an admixture for peat
and similar composts. Applied to the wheat stubble with a water
cart at the rate of 180 gallons per acre, and allowed to remain for
several months before it was ploughed in, it has been found large-
ly to benefit the after-crop of roots.
§ 14. Of the theoretical value of different vegetable substances as
772(17??&?’65.
Vegetable manures are known to differ in fertilizing virtue.
Thus, 1 ton of rape-dust is said to be equal to 16 of sea-weed or
to 20 of farm-yard manure. On what principles do these unlike
fertilizing virtues depend?
1°. According to Boussingault and other French authorities,
the relative efficacy of all manures depends upon the proportions of
nitrogen they severally contain.” And taking farm-yard manure—
consisting of the mixed droppings and litter of cattle—as a stan-
dard, they arrange vegetable substances as manures in the follow-
ing order of value:–
* Annales de Chemie et de Phys, 3d Series, iii. p. 76.
THEORETICAL VALUE OF VEGETABLE MANURES. 773
Equal effects are produced...by
Farm-yard manure, ................ ..... ... 1000 lbs.
Potato and turnip (?) tops, ................ 750
Carrot tops, ......... . . . ..................... 470
Natural grass, ......... . . . . . . . . . . . . . . . . . . . . . . . 760
Clover roots,................. . . . . . . . . . . . • * * * * * * 250
Fresh sea-weed,........................ 450 to 750
Sea-weed dried in the air, ... ............. 300
Pea Straw,............................. * - - - - - - - - 220
Wheat straw, ............... . ...... 750 to 1700
Oat Straw, .................................... 1 400
Barley straW, ................................. 1750
Rye straw,................. ......... 1000 to 2400
Buck-wheat straw, ......... ................. 850
Wheat chaff. .......... ....... .............. 470
Bran, ......................... . . . . . . . . . . . . . . . 200
Fir Saw-dust,........................ 1700 to 2500
Qak do. .................. • . . . . . . . . . . . . . . . . . 750
Oak leaves,.............. - - - - - - - - - - - - - - - - - - - - - 340
Soot, from coal, ....................... ..... 300
Lint and rape-dust, .................... ... 8ſ)
The numbers in this table agree with the results of experiment
in so far as they indicate that green substances generally, when
ploughed in as manures, should enrich the soil more than an equal
weight of farm-yard manure—that the roots of clover should be
more enriching still—and that sea-weed is likewise a very valuable
manure. They agree also with practical observation in placing
pca, and probably beam straw, far above the straws of wheat, oats,
&c. in fertilizing power, and in representing pea straw, bran, and
rape-dust as more powerful than any of the other substances in the
table. So far, therefore, a certain general reliance may be placed
upon the fertilizing value of a substance as represented by the pro-
portion of nitrogen it contains.
But if we bear in mind that plants, as we have frequently had
occasion to mention, require inorganic as well as organic food, we
shall be satisfied that the mere presence of nitrogen in a substance
is not sufficient to render it highly nutritive to growing plants.
Were this so the salts of ammonia would be the richest manures
of all, and would best mourish and bring to perfection every crop
and in all circumstances—which experience has proved them by
no means the case. Hence *
774 INORGANIC MATTER IN VEGETABLE MANUIRES.
2°. The value of vegetable substances as manures must depend
in some degree upon the quantity and kind of inorganic matter they
contain. In reference to the quantity of inorganic matter which
they respectively impart to the soil, their relative values are repre-
sented by the following numbers:–
One ton contains of inorganic
matter about
Potato tops, green, ...... .... ..... ...... 45 lbs.
Turnip tops, do. ................. ... ..... 48
Carrot tops, do. ................. ........ 45
Rye-grass, do. ........................... 38
Vetch, do. ........................... 38
Green sea-weed, do. ...... ............ ...... 33
Hay, ............... .... ................ 90 to 180
Pea Straw, ...................................... l 12
Bean straw, ............................. 70 to 150
Wheat straw, ............. ............ 70 to 360
Oat straw, ......... . .................. 100 to 180
Barley straw, . . . . ........ ..... 100 to 120
Rye straw, ........................... 60 to 130
Bran, ................ ......................... 150
Fir saw-dust, ......... ....................... 6
Oak Saw-dust, ............ .................... 5
Soot, ............ .. ... • e e s e º s e s is e s - e s º e º s = e s is e s s e º e 500 . . .
Rape-dust, ... .............. .................. 120 .
This table places the several vegetable substances in an order
of efficacy considerably different from the former, in which they
are arranged according to the quantity of nitrogen they respec-
tively contain. We know that wood-ashes, kelp, and the ashes of
straw do promote the fertility of the land, and therefore the abso-
lute as well as the relative efficacy of the above vegetable substan-
ces must depend in some degree upon the quantity of inorganic
matter they contain. But we should be wrong were we to ascribe
the total effect of any of them to the inorganic matter alone.
3°. Even the carbonaceous matter of plants contributes its aid
in increasing the produce of the soil by supplying, either directly
or indirectly, a portion of the necessary food of plants. This has
already been shewn in various parts of the preceding lectures.
It is the property of substances which contain a larger propor-
tion of nitrogen to undergo rapid decay in the presence of air and
moisture, and thus to produce a more immediate and sensible ac-
tion upon growing plants. But the carbon changes more slowly,
INFLUENCE OF THE CARBON ACEOUS MATTER, 775
and the inorganic matter also separates slowly from decaying ve-
getables in the soil—and hence the apparent effects of these con-
stituents are less direct and striking. Thus the immediate and vi-
sible effect of different vegetable substances applied in the same state,
may be measured by the relative quantities of nitrogen they contain—
their permanent effects by the relative quantities of inorganic and of
carbonaceous matters. In the case of rape-dust, for example, the
immediate effect is determined chiefly by its nitrogen—the perma-
ment effects, by the ash it leaves when burned, or when caused to
undergo complete decay in the air.
LECTURE XXII.
Animal manures. Flesh, blood, and skin. Wool, woollen rags, hair, horn, and bones.
On what does the fertilizing action of bones depend ? Application of bone dust to
pasture land. Forms in which bones are applied to the land—fermenied and dis-
solved bones. Animal charcoal, the refuse of the sugar refineries, and animalized
carbon. Fish, fish-refuse, shell fish, sea blubber, whale blubber, and oil. Relative
fertilizing values of the animal manures previously described. Droppings of fowls,
pigeon's dung, goose dung, &c. Dung of sea-fowl—guano. Average composition
of different varieties. Effects of upon different crops. Liquid manures. The urine
of various animals—Of man, the cow, horse, sheep, and pig. Their general relations
and composition. Composition of the drainings of dung heaps. Waste and value of
Waste of human urine. Use of sewer water. Action of lime and gypsum upon
urine—urate—sulphated urine. Waste of cow's urine—mixing with water, gypsum,
and sulphate of iron. Mixed animal and vegetable manures. Night soil. Poudrette,
modes of preparing it. Taffo. The droppings of the horse, the cow, the sheep, and
the pig. Quantity of manure produced from given weights of vegetable food. Re-
lative fertilizing values of different animal excretions. Influence of circumstances on
the quality of the manure. Effects of digestion upon vegetable food. Why equal
weights of vegetable matter and of the droppings of animals fed upon it possess dif-
ferent fertilizing powers. Farm-yard dung. Loss undergone by farm-yard manure
during fementation. State in which it ought to be applied to the land. Top-dress-
ing with fermenting manures. Improvement of the soil by irrigation.
ANIMAL substances have always been considered as more ferti-
lizing to the land than such as are of vegetable origin. Their ac-
tion is in general more immediate and apparent, and it takes place
within such a limited period of time that the farmer can calculate
upon its being exercised in benefiting the crop to which it is applied.
The reason of this more immediate action will presently appear,
§ 1. Offlesh, blood, and skin.
1°. Flesh.--The flesh of animals is not only a rich manure in it-
self, but the rapidity with which it undergoes decay in our climate
enables it speedily to bring other organic substances with which it
may be mixed into a state of active fermentation. It is only the
flesh of such dead animals, however, as are unfit for food that can
be economically applied to the land as a manure.
The flesh of animals consists of a lean part—called the muscular
fibre, or by chemists fibrin—and a fatty part, intermixed with the
COMPOSITION OF BIOGID. 777
lean in greater or less proportion, according to the condition of
the animal. Of these two it is the lean part which acts most imme-
diately and most energetically in promoting vegetation. Lean beef, in
the recent state, contains 77 per cent. of its weight of water, so that
100 lbs. consist of 77 lbs. of water and 23 lbs. of dry animal matter.
2°. Blood.—The blood of animals is more extensively employed
as a manure. It is carried off in large quantities from the slaugh-
ter-houses of the butchers, and makes rich and fertilizing com-
posts. In some parts of Europe it is dried, and in the state of a dry
powder is applied with much effect as a top-dressing to many
crops. In Paris it is sold in this state at about 8s, a cwt.
Liquid blood consists of fibrin—the substance of lean meat—of
albumen—the same substance as the white of eggs—of a red colour-
ing matter, and of certain saline substances dissolved in a considera-
ble quantity of water. When blood cools it gradually congeals, and
separates into two parts, a gelatinous red portion, called the clot, and
a liquid, nearly colourless, part, called the serum. The clot con-
tains most of the fibrin and colouring matter, and a portion of the
albumen; the serum, the greater part of the albumen and of the
soluble saline substances which are present in the blood.
The relative composition of fresh muscular fibre and of liquid
blood is thus represented in 100 parts:—
Water. Dry animal matter.
Muscular fibre, ............ 77 -
Blood.................. ...... 79 to 82.5 tº º º 17.5 to 21%
It appears singular that the solid muscle of animals should con-
tain so nearly the same quantity of water as their liquid blood does.
But it is no less striking that the dry animal matter which re-
mains, when lean muscular fibre and when blood are fully dried,
has nearly the same apparent composition. Thus, according to the
analyses of Playfair and Boeckman, dry flesh and dry blood con-
sist respectively of
Dry beef. Dry ox blood.
Carbon, ........... . . . . . . . . . 51-83 51°96
Hydrogen, ............... 7.57 7-25
Nitrogen, .................. 15:01 15-07
Oxygen, ... ............ . . 21:37 21:30
Ashes, ........... ......... 4-22 4'42
100 100+
* Thomson's Animal Chemistry, pp. 285 and 367.
+ Liebig's Organic Chemistry applied to Physiology, p. 314.
778 COMPOSITION OF SIKIN.
The organic part, therefore, of blood and of flesh is nearly iden-
tical in ultimate composition, and the final result of equal weights
of each, when applied as manures to the land, should be nearly the
same. Both contain much nitrogen in a form in which, when com-
mitted to the soil, they can readily supply this important element to
the growing plant.
Both flesh and blood when burned leave a portion of ash behind,
which from dry flesh is about 4:23, and from dry blood 4.43 per
cent. This ash contains nearly all the inorganic substances which
plants require, and is especially rich in soda and phosphoric acid.
The following table represents the composition of the ash of the
blood of several animals, according to the analyses of Enderlin:*
- Ox. Calf. Sheep. Hare.
Phosphate of soda (tribasic), ...... 16-77 30° 18 13° 30 28°45
Chloride of sodium (common salt), 59:34
2. • K ‘52
Chloride of potassium,............... 6-12 | 52'65 G6'57 50'5
Sulphate of Soda, ..................... 3'85 2.94 5:38 3.72
Phosphates of lime and magnesia, 4:19 3'49
* - . | 13.02 16'51
Oxide and phosphate of iron, ...... 8'28 9.28
Gypsum and loss, .................... 1'45 l'46 O'83. 0-80
100 100 100 100
3°. Skin.-The skins of nearly all animals find their way ulti-
mately into the soil as manure, in a more or less changed state.
Therefuseparings from the tan-yards, and from the curriers'shops,
though usually employed for the manufacture of glue, are sometimes
used as a manure, and with great advantage. They may either be
ploughed in sufficiently deep to prevent the escape of volatile mat-
ter when they begin to decay, or they may be made into a compost
by which their entire virtues will be more effectually retained.
Skin differs considerably in composition from flesh and blood.
It contains, in the recent state, about 58 per cent. of water, and
leaves, when burned, only 1 per cent of ash. The combustible or
organic part consists of
Carbon, ......... .............. 50-99
Hydrogen, ..................... 7:07
Nitrogen, ................. .... 18-72
Oxygen,........... & a tº s e º e e º º e º e 23-22
100
* Annalen der Chemie, l. p. 62, (1844).
l
USE OF WOOL, HAIR, AND HORN. 779
It contains, therefore, 3% per cent, more nitrogen than flesh or
blood. So far as the fertilizing action of these substances depends
upon the proportion of this constituent—glue, the parings of skins,
and all gelatinous substances will consequently exhibit a greater
efficacy than flesh or blood.
§ 2. Wool, woollen-rags, hair, and horn.
1°. Wool, in the form of the waste of the spinning-mills, and
especially in that of woollen-rags, acts very efficaciously as a ma-
mure. The rags are used with good effect upon light chalks and
gravels. They are sometimes ploughed in for wheat along with
the clover stubble, or in the winter with the corn stubble, when
the land is intended for turnips, and are somtiémes, especially in
the compost form, applied as a top-dressing to clover and grass
lands.” They are used most extensively, however, in the hop-
grounds, being dug in round the roots of the hop plant, to which
they continue for a long time to supply much nourishment. The
estimation in which they are held may be judged of by the price
they bring, which is from L. 5 to L. 10 a ton.
2°, Hair also is fitted to produce effects similar to those which
follow the use of wool. It can seldom, however, be obtained by
the farmer at so economical a rate as to enable him to trust to it
as an available resource when other manures become scarce.
3°. Cony dust.—In the workshops where the wool or fur is
taken off rabbit skins, much dust collects on the floors, which, with
the parings and worthless fragments of the skins, are sold together
under the name of comy dust. For this the North Lincoln far-
mers pay 7s, a quarter of 28 lbs., or 3d. a pound, and apply it up-
on their light soils, without other admixture, to raise their turnip
crops. They lay on from 16 to 20 bushels per acre, and find it to
give better crops than 16 bushels of bones. On heavier soils they
prefer the bones.
This is an interesting fact, as it shows that the large proportion
of earthy matter in bones is not, as some allege, the only constitu-
ent to which their efficacy is to be referred. Skins, as well as
hair, wool, and cony dust, are used with success as manures, and
yet they contain comparatively little inorganic matter.
* British Husbandry, i. p. 425.
780 COMPOSITION OF WOOL, HAIR, AND HORN.
4°. Horn, in the form of horn shavings, parings, and turnings,
is justly considered a very powerful manure. Even in the state of
shavings, however, it undergoes decay almost as slowly as wool-
len rags; and therefore, like them, will be most safely and econo-
mically employed when previously rotted, by being made into a
compost. Horn dust has, however, been used with advantage in
the turnip drills, and even as a top-dressing for grass.
Wool, hair, and horn differ from flesh, blood, and skin, by con-
taining very much less water in their natural state, and by under-
going, in consequence, a much slower decay, and exhibiting a
much less immediate action upon any crop to which they may be
applied. The intelligent farmer will bear this important distinc-
tion in mind, in any opinion he may form as to the relative effi-
cacy of these several substances as general fertilizers of the land.
In chemical composition, these three substances are nearly iden-
tical, and they do not differ widely from the lean of beef or from
dried blood. When burned they leave only a small quantity of
ash:—
Of ash.
Wool leaves, ............ 2.0 per cent.
Hair (human), ......... 0-3 to l'8 ...
Horn, .................... 0.7
The ash of a hundred pounds of human hair was found by Van
Laer” to consist of
Soluble chlorides and Sulphates,... ........... .. 0:51 lbs.
Oxide of iron, .......... ... . . . .................... 0'39 ...
Insoluble sulphates, and phosphates and silica, 0.20 ...
l’l
The organic part, when perfectly dry, contains of
Human hair. Wool. Horn.
Carbon,............... 50'65 50°65 51'99
Hydrogen, ...... . . 6:36 7:03 6-72
Nitrogen, ............ 17'14 17-71 17:28
y: ©ſ) • Q 5
Oxygen, ......... º | | 24'6] 24.0]
Sulphur, ......... 5:00
100 100 100
The organic part of these three substances, therefore, is nearly
identical in composition, and hence, when equally decomposed, they
ought to produce nearly the same effects upon the young crops. They
* Van Laer, An, der Pharm. xlv. p. 178.
6 &"
FAT AND WATER IN BONES. - 781
contain a little more nitrogen than dried flesh and blood, and a
little less than dried skin, and therefore in so far as their fertilizing
action depends upon this element, they occupy an intermediate
place between these several substances.
They are remarkable for containing a large proportion of sul-
phur, 5 lbs. in 100, with about half-a-pound of phosphorus:
These substances cannot fail to affect their fertilizing value.
§ 3. Of the composition of bones.
Few substances have of late years done so much to increase the
agricultural produce of various parts of England as the use of
crushed bones for manuring the land.
1°. Recent bones contain a variable quantity of water and fat.
The proportion of fat depends upon the position of the bone in the
body, and upon the condition of the animal. The proportion of
water depends partly upon the solidity of the bone and partly up-
on its age. According to Denis, the radius of a female,
Water with a little fat;
Aged 3 years, contained ............... 33.3 per cent.
Aged 20 years, do. ............... 13-0 do.
Aged 78 years, do. ............... 15'4 do.
The proportions of water and fat are greater in the spongy than
in the solid bones. In the bones of different animals Dr Stark
found them to vary as follows:–
Water per cent. Fat per cent.
Human bones, ............ 7 to 20 13 to 29
Ox bones, .................. do. 15 to 19
Sheep bones, ............ do. 14 to 25
Birds, ..................... 12 to 25 3 to 15
Fishes, ..................... 50 to 80 P
The quantity of water thus present in bones performs an im-
portant part in determining the action which bone-dust is known
to exercise upon the land. The oil is sometimes extracted by
boiling the bones. During this boiling they absorb more water,
and thus, when laid upon the land, undergo a more rapid decom-
position, and exercise, in consequence, a more immediate and ap-
parent, and therefore, as some may think, a more powerful ferti-
lizing action.
2°. But bones differ from the other animal substances already
7
82 TILE INORGANIC MATTER CONTAINED IN BONES.
described chiefly by containing a much larger proportion of inor-
ganic matter, leaving, when burned, a greater per-centage of ash.
The quantity of inorganic matter contained in bones is not exactly
constant. It is greater in the bones of some parts of the body
than in those of others. In human bones, when perfectly dry and
free from fat, it varies from 65 to 71% per cent. -
Dr Stark of Edinburgh has lately published" an elaborate se-
ries of results obtained by burning bones of various kinds, from
which I extract the following general results.
When perfectly dry and free from fat, the bones of the following
animals contain of earthy matter and of cartilage respectively, as
the mean of many trials.
Earthy matter. Cartilage.
Bones of man, ............... 66.6 33.4
Do. the Ox, ............ 64.5 35.5
Do. the horse, ......... 66.7 33.3
Do, the pig, ... .... ... 64.7 35.3
Do. the dog, ............ 65.7 34.3
Do, birds, ............... 66.2 33.8
Do. fishes, ............... 67.1 32.9
The difference in the average proportion of the earthy matter
in the bones of different animals is not great therefore, and their
efficiency as manures, in so far as it depends upon this proportion,
will be very much the same. -
3°. This inorganic or earthy part consists in great part of phos-
phate of lime (earth of bones, p. 336), but it contains also a con-
siderable though variable proportion of carbonate of lime, with
smaller quantities of several other ingredients. The proportion
of carbonate of lime appears to be smallest in the bones of carmi-
vorous animals. -
Thus, for every 100 parts of phosphate of lime there exists in—
Carbonate of lime.
Human bones about ............... ................. 20.7
Bones of the sheep, ................................. 24.1
Do. OX, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5
Do. fowl, , ................. … I 1.7
Do. haddock, .......... . . . . . . ......... 6.2
Do. frog, ... ... ....... . . . . . . . . . . . . . . . . . . . . . . 5.8
Do. lion, ....... . . . . . ............ ........ 2.6
These proportions are not to be considered as constant—because
* Edinburgh Medical and Surgical Journal, No. 163.
&
GENERAL COMPOSITION OF BONES. 783
they vary not only in the different bones of the same animal, but
also in bones from the same part of the body of different animals
of the same species.* But the existence of such differences must
render unlike the fertilizing action of the bones of different animals,
in so far as this action depends—and it does so to a great degree—
upon the quantity of phosphate of lime which they respectively
contain.
4°. Besides the phosphate and carbonate of lime, bones contain
certain other inorganic substances, which are found in small quan-
tity in the ash. What these substances are will appear in the fol-
lowing table, which represents the composition of the bones of some
animals, as analysed by Dr Thomson—
Ileum Ileum Vertebras
of a sheep. of an ox. of a haddock.
Organic or combustible matter,..... ... 43.3 48.5 39.5
Phosphate of lime,...... . ...... . ...... 50.6 45.2 56.1
Carbonate of lime, ... .... ............... 4.5 6.1 3.6
Magnesia, … 0.9 0.2 0.8
Soda, ....................... . . ..... • * c & © e & 0.3 ().2 0.8
Potash, ........ ............ .............. 0.2 0.1 *
99.8 100.3 100.8
The soda exists in bones probably in the state of common salt,
and the magnesia in that of phosphate. An appreciable quantity
of fluoride of calcium, with traces of iron and magnesia, are also
generally found in bones, in addition to the substances indicated
by the preceding analyses.
5°. When bones are heated to redness in the open air the or-
ganic part burns away, and leaves the white earthy matter in the
form, and nearly of the bulk, of the original bone. But if a dry
bone be covered with diluted muriatic acid, the earthy or inorganic
part is slowly dissolved out, and the organic part—the cartilage
or gelatine—will alone remain, retaining also the form and size
of the original bone. In this state it is flexible and somewhat soft,
and by prolonged boiling may be dissolved in water, and manu-
factured into glue.
This organic or combustible part of bones is identical in che-
mical domposition with skin and glue, and is nearly the same as
wool, hair, and horn, of which the analyses have already been given.
* Thomson's Animal Chemistry, p. 242.
º
784 CAUSE OF THE FERTILIZING ACTION OF BONES.
In so far, therefore, as their efficacy depends upon this organic
constituent, dry bones must be greatly inferior to an equal weight
of any of the other animal substances above described in their dry
state, because of the much greater proportion of earthy matter
which bones contain.
§ 4. On what does the fertilizing action of bones depend ?
Bones contain, as we have seen, a large proportion both of or-
ganic and of inorganic matter;-on which of these two constituents
does their fertilizing action most depend ? Some regard the phos-
phate of lime or bone earth, as the only source of the benefits so
extensively derived from them—and it is by supposing the soil to
be already sufficiently impregnated with this phosphate that Spren-
gel accounts for the little success which has attended the use of
bones in Mecklenburg and North Germany. Others, again, at-
tribute the whole of their influence to the organic part—the gela-
time—which bones contain. Neither of these views is correct as a
general rule. Plants, as we have seen, require a certain supply
of phosphoric acid, lime, and magnesia, which are all present in the
in organic part of bones. So far, therefore, they are capable of de-
riving valuable inorganic food from bone-dust. But the organic
part of bones will decompose, and therefore will act nearly in the
same way as skin, wool, hair, and horn do—which substances it
resembles in ultimate composition. It cannot be doubted, there-
fore, that a considerable part of the effect of bones upon our crops,
in most soils, must be due to the gelatine which they contain.
The principal facts, now known in regard to the action of bones,
may be thus stated:—
1°. The organic matter of bones acts like that of skin, woollen
rags, cony dust, horn-shavings, &c., but as bone dust contains only
about one-third of the organic matter which is present in an equal
weight of any of the above substances, its total effect, in so far as it
depends upon this organic matter, will be less in an equal proportion.
2°. But as the organic matter of bones contains more water than
horn or wool, it will decay more rapidly than these substances
when the bones are ground and mixed with the soil, and will there-
fore be more immediate in its action. Hence, the reason why wool-
len rags and horn-shavings must be ploughed in in the preced-
EFFECT OF BOILING AND BURYING UPON BONES. 785
ing winter, if they are to benefit the subsequent wheat or turnip
crops, while bone-dust can be beneficially applied at the sowing of
the seed.
3°. When bones are boiled the oil is separated, and a portion
of the gelatine is at the same time dissolved out.” The bones
are, therefore, rendered less rich as a manure. But as they at the
same time take up a considerable quantity of water, boiled bones
will decompose more rapidly when afterwards mixed with the soil,
and may thus appear to act as beneficially as unboiled bones.
Hence the reason why in Cheshire, where boiled bones are used
to a considerable extent, many practical men are of opinion that
their action upon the crops is not inferior to that of bones from
which the oil has not been extracted by boiling. The immediate
effect may indeed be equal, or even greater, than that of unboiled
bones, but the total effect must be less in proportion to the quantity
of organic matter which has been removed by boiling. Cases, how-
ever, may occur in which the skilful man will prefer to use boiled
bones because they are fitted to produce a more immediate effect
where—as in the pushing forward of the young turnip plant—such
an effect is particularly required.
4°. When bones are buried in a more or less entire state, as they
occasionally are about the roots of vines and fruit trees, they gra-
dually decay, and sensibly promote the growth of the trees to
which they are applied. Yet after the lapse of years these same
bones may be dug up nearly unaltered either in form or in size.
The bones of a bear and of a stag, after being long buried were
found by Marchand to consist of
Bones of the bear buried Femur of a
deep. shallow. Stag.
Animal matter, ..................... I 6-2 4-2 7-3
Phosphate of lime, ................. 56-0 62. 1 54° 1
Carbonate of lime, .................. | 3 | 13°3 19°3
Sulphate of lime,..................... 7.1 12-3 12.2
Phosphate bf magnesia, ............ 0°3 0°5 2. I
Fluoride of calcium, ..... ......... 2:0 2-l 2-l
Oxides of iron and manganese, ... 2:0 2-l 2.9
Soda, ................................. | 1 l'3 &º-º-º:
Silica, ..... ..................... . . . . 2-2 2. l *
T ()0 100 | 00
* The prolonged boiling of bones, for the purpose of dissolving a portion of the gela-
3 D
786 THE ANIMAI, MATTER OF BONES HAS AN EFFECT.
The most striking change undergone by these bones was the
lative proportions of the phosphate and carbonate of lime had been
comparatively little altered. The main effect, therefore, produced
by bones when buried at the roots of trees, and their first effect in
nearly all cases, most be owing to the animal matter they contain
—the elements of this animal matter, as it decomposes, being ab-
Sorbed by the roots with which the bones are in contact.
Such facts as this prove, I think, the incorrectness of the one-
sided opinion too hastily taken up by many—that the principal or
sole efficacy of bones is, in all cases, to be ascribed to their earthy
ingredients, and especially to the phosphate of lime they contain.
This opinion of Sprengel and Liebig rests mainly on two facts
put forward by the former.” Bones, he says, have failed to pro-
duce in North Western Germany the good effects for which they
are so noted in England, yet in the same districts, farm-yard and
other animal manures exhibit their usual fertilizing action. It
cannot, therefore, he concludes, be the animal matter of bones to
which their beneficial influence is to be ascribed. But to this
conclusion we may fairly demur, when we know how often on
heavy and undrained lands bone-dust fails even among ourselves.
Let bones be tried for the turnip crop—a crop still almost un-
known in Northern Germany—and upon well-drained soils simi-
lar to those of our best turnip lands, and I venture to predict, in
opposition to Sprengel's experience, that bones will no longer fail
even in Mecklenburg. -
Again, having drawn this conclusion in regard to the inutility
of the animal matter, Sprengel states that the marl which is ap-
plied to the land in Holstein and the neighbouring province, con-
tine, is practised to a considerable extent as a mode of manufacturing size or glue. In
the large dying establishments in Manchester, the bones are boiled in open pans for 24
hours, the fat skimed off and sold to the candle-makers, and the sizé afterwards boiled
down in another vessel till it is of sufficient strength for stiffening the thick goods for
which it is intended, or till it forms a jelly when allowed to cool. The size liquor, when
exhausted by the manufactured,or no longer of sufficient strength for stiffening, is ap-
plied with much benefit as a manure to pasture and artificial grass lands, and the bones
are readily bfought up by the Lancashire and Cheshire farmers. The boiled bones
must evidently lose all the fertilizing virtue which the size liquor acquires.
* Lehre vom Dünger, p. 153. -
7/
THE EARTHY MATTER OF BONES HAS AN EFFECT. 787
tains phosphate of lime, and hence the reason why the earthy mat-
ter of the bones applied does not improve the land. In so far as the
efficacy of bones depends upon their earthy constituents, the use of
a marl containing phosphate of lime” will, no doubt, greatly super-
sede them ;-but in so far as it depends upon the ānimal matter
they contain, bones will exhibit their natural fertilizing action,
however rich the soil may already be in those compounds of which
their earthy or incombustible part consists. -
5°. Yet it may be assumed as certain that the phosphate and
carbonate of lime which bones contain so largely, are of much ef-
fect in promoting vegetation. All our cultivated plants require
and contain both phosphoric acid and lime, and from the vege-
tables on which they feed, all animals derive the entire substance
of their bones. Phosphoric acid and lime, therefore, must exist in
the soil on which plants grow, or they will neither thrive them-
selves nor be able properly to nourish the animals they are destin-
ed to feed. If a soil, then, be deficient in phosphate of lime or its
constituents, it is clear that the addition of bones will improve its
fertility, not only by the animal but by the earthy matter also
which they are capable of supplying.
Thus bones perform a double function in the soil, and it is scarcely
possible in any case to say how much of their good effect is due
to the organic, and how much to the inorganic substances they con-
tain. *
From the calculations previously made (p. 409), it appears, that
in a four course shift of turnips, barley, clover, and wheat, the
crops carry off about 116 lbs. of phosphoric acid, or 240 of phos-
phate of lime, a quantity which is contained in about 480 lbs., or
ten bushels of common bone-dust. Were the only use of bones
to supply this phosphate, it would be unnecessary to add more
than ten bushels during a four course rotation, or 23, bushels a
year—and it would make no difference whether the bones were
burned, to destroy the animal matter before they were applied, or
whether they were laid on in the form of common bone dust.
* Most lime-stones and shell-sands contain an appreciable quantity of this phos-
phate, and may, therefore, to some extent, supersede the use of the earthy matter of
bones. Much of the marl of Holstein consists of the detritus of chalk rocks, anciently
broken up and carried off—by the waters of the sea with which that part of Europe
was covered at a geological epoch not very remote.
788 CAUSE OF THE PROLONGED EFFECT OF BONES.
In fact, those who entertain this extreme opinion, in regard to
the earthy matter of bones, not only say that they may be burned,
but that they ought to be burned before they are applied; and they
quote one or two experiments to show that, when applied in this
form, they sometimes give a larger crop than when employed in
the usual way.
But little weight is to be attached to one or two experiments of
this kind, when opposed to others, in which opposite results have
been obtained. Both classes of results are easily understood and
explained. Thus,
a. If a soil is rich in phosphates, and yet poor in organic mat-
ter, then bones may benefit the crops chiefly or solely by the ani-
mal matter they bring within reach of the roots. In such a case
as this, the use of burned bones might be followed with little or
no good effect at all. Again,
b. If the soil be rich in organic matter, and contain little phos-
phoric acid, then the bones may fertilize it by its phosphates alone.
In this case the bones might be used with advantage in a burned
State.
As a general rule, however, to burn bones is to destroy a large
quantity of what may be valuable matter, of what is really valu-
able to most soils. The only advantage that burned bones possess
is, that they are easily ground to fine powder, and may then be
spread over a larger surface, and, therefore, more intimately mixed
with the soil than even bone dust can be. Being separated from
the animal matter, the root can more directly avail itself of their
phosphates, if these should happen to be deficient in the land.
6°. It is remarkable for how long a period the good effects of
bones, in some cases, eontinue to be observed.
Some lands remember a single dressing of bones for 16 or 20
years; and some after the application of 2 or 2% tons of bones have
yielded 10 to 15 successive crops of oats, and have been sensibly
benefited for as many as sixty years after the bones were applied."
This prolonged effect is due in part to both constituents of
bones. The organic matter of bones is always slow in disappear-
ing. It is slower the deeper they are buried, and in some soils
the process is more slow than in others. The long-buried bones
* British Husbandry, i. p. 398.
FERTILITY OF ANCIENT BATTLE FIELDS. 789
of the bear and of the stag, of which the analysis is given above
(p. 785), had lain in the soil for an unknown period, and yet they
still contained a sensible proportion of animal matter. So it is
with the bones used for manure, when they are not crushed too
fine. They long retain a portion of their organic matter, which
they give out more slowly, and in smaller quantity, every year that
passes, yet still in such abundance as to contribute sensibly to the
nourishment, and in some degree to promote the growth, of the
crops which the land is made to bear.” So it would be with the
horns and hoofs of cattle, if laid on in equal quantity, for they also
decay with exceeding slowness. .
The inorganic matter—the phosphates—are also taken up slowly.
Year by year the roots of the growing crops take up what the
plants require, and the duration of the good effects of the bones is
in proportion to the quantity originally applied.
We have seen that a rotation of four crops, turnips, barley,
clover, and wheat—carry away from the soil the phosphoric acid
of about 480 lbs. of bone dust. They exhaust it to this extent,
however, only when all the crops are taken off the land—nothing
eaten on the field by stock, and nothing returned in the form of
farm-yard manure. This, however, is rarely if ever the case.
The land, therefore, is never exhausted to the full extent above
stated. But even if it were, an application of two tons of bones
would supply the phosphoric acid required for ten rotations or for
forty years of cropping. It is not surprising, therefore, that the
good effects of bones should be observed for so very long a time,
Of this permanent or lasting effect a very large share is to be as-
cribed to the inorganic constituents of the bones.
He who candidly weighs the considerations above presented will,
I think, conclude that the whole effect of bones can scarcely in any
* This opinion derives a singularly interesting confirmation from the fact, that a
portion of the soil of an arable district in Sweden, “ which from time immemorial had
grown excellent wheat without manure,” was found by Berzelius to contain minute
fragments of bone capable upon boiling with water of yielding a weak solution of gela-
tine. It was concluded, therefore, that the spot had been an ancient battle field, and
that its prolonged fertility was due to the bones of old time buried in it, and still
to some extent undecomposed (Marchand).
790 APPLICATION OF BONE-DUST TO PASTURE LANDS.
case be ascribed exclusively either to the one or to the other of their
principal constituents. He will believe that in the turnip hus-
bandry the organic part performs a prominent and immediately
useful office, and that the earthy part affords a ready supply of
certain kinds of inorganic food, which in many soils plants cannot
easily obtain. He will assign to each constituent its separate and
important function, being constrained, at the same time, to con-
fess—that while in many cases the earthy part of bones, applied
alone, might fail to benefit the land, there are few cultivated fields
in which the organic part applied alone would not in some de-
gree promote the growth of our cultivated crops.
§ 5. Of the application of bone-dust to pasture lands.
If the soil be deficient in phosphate of lime, bone-earth alone, as
we have said, (p. 340), or the mineral phosphate, may be advan-
tageously applied to increase its fertility. In a four-years' rota-
tion of turnips, barley, clover, and wheat, if bones be used for the
turnip crop in larger quantity than ten bushels an acre, the land
is likely every rotation to become richer in bone-earth, and, there-
fore, if laid down to grass after a few rotations—the application of
earthy phosphates cannot be expected materially to affect its pro-
ductiveness. But pasture lands are treated differently, and the
earth of bones, even if applied alone, may often upon them be
productive of very considerable benefit.
The application of bone-dust to permanent pasture has of late
years been practised with great success in Cheshire. Laid on at
the rate of 30 to 35 cwt., or at a cost of L. 10 per acre, it has in-
creased the value of old pastures from 10s, or 15s, to one of 30s.
or 40s. per acre. After a lapse of 20 years the same land, though
becoming sensibly less valuable, has remained still worth two or
three times the rent it paid before the bones were laid on.
This lengthened good effect, the earthy phosphates have the
largest share in producing. I have already shown that the orga-
mic matter lingers long, even in buried bones—but a consideration
of the necessary effect of long-continued pasturage upon soils to
which nothing is artificially added, lends a singular support to the
view that bone-earth alone may nºt an important and beneficial part
PEIOSPHATE OF LIME YEARLY CARRIED OFF. 791
upon old meadow and other grass lands. Take the instance of a
dairy farm in the neighbourhood of a large town.
1°. The milk is all carried off the farm either directly or in the
shape of butter, cheese, veal, pork, &c. Every 30 gallons of milk
contain 1 lb. of the phosphates of lime and magnesia—as much as
is contained in 13 lbs. of dry bone, or in 24 lbs. of common bone-
dust. If the average yield of a good cow be taken at 3000 quarts
or 750 gallons a-year, its milk will contain 25 lbs. of phosphates—
as much as is present in 62 lbs. of bone-dust.
2°. But for every cow an annual calf is reared and sold off. Let
this calf contain but 20 lbs. of bone—then for every cow it main-
tains, a dairy farm will lose of earthy phosphates upon the whole as
much as is contained in 82 lbs. of bone-dust. A ton of bones every
twenty-seven years would be required to supply these.
Suppose a farm to be pastured for centuries, as those of Che-
shire have been, and the produce to be carried off in the form of
milk, butter, veal, and pork—we may reasonably suppose that it
will at length begin to feel the want of those phosphates which
year by year have been drawn from its surface. It is reasonable
also to suppose that the addition of these deficient phosphates would
impart new vigour to the soil, would cause new grasses to sprout,
and a more milk-yielding herbage to spring up.
Such is the reasoning upon which I some years ago attempted
to found an explanation of the singularly striking effects produced
by bone-dust on the grass lands of Cheshire. It is not, however,
to be supposed that either in Cheshire or elsewhere the beneficial
action of bone-dust is to be ascribed solely to its earthy constitu-
ents. The value of its animal matter is not to be forgotten.
§ 6. Forms in which bones are applied to the land—dissolved bones.
1°. Bone-dust-When bones first began to be applied to the land
as a manure, they were laid on in fragments of a considerable size.
Broken to the size of what were called two inch bones, was not an
uncommon mode of application. Inch bones, and then half inch
bones, and bone-dust followed—each successive reduction in size,
demanding the use of machinery of a more perfect and expensive
kind.
When applied of a larger size, the dose was necessarily larger
79.2 FERMENTING AND DISSOLVING.
also. Reduced to powder, the same weight of bones could be
spread over a greater surface, and thus be made to go further—
while they also decomposed more readily in the soil, and became
sooner converted into the food of plants. Eighty bushels of bones
were at one time not unusual, forty bushels are still applied in
some of our less improved districts, as in parts of Ayrshire and
Lanarkshire; but from twenty to thirteen bushels an imperial acre
is the quantity of bone-dust now very generally applied to the tur-
mip crop in our best favoured districts.
2°. Fermented bones.—When bone dust is buryied in the soil, it
speedily heats, ferments, and decomposes. The rapidity with which
this takes place, however, depends upon the nature and natural
moisture of the soil, on the fall of rain, and on the quantity of
bone dust put into the drills. But as this decomposition hastens
on the growth of the young plant, and carries it more rapidly into
the rough leaf, it is desirable to promote it. Some intelligent far-
mers, therefore, are in the habit of laying in a heap the bone dust
about to be used, and covering it over with earth for a week or
ten days before the turnips are sown. It is thus made to heat and
soften, and when put into the drills is at once ready to minister to
the growth of the sprouting germ.
Some prefer to ferment the bones still farther by mixing them
with farm-yard dung; and in the Doncaster report on this subject
it is given as the result of trials made by 13 different persons, that
the same weight of bones invariably produced a better effect when
applied in this way than when used in the form of dry bone dust.
3°. Dissolving the bones.—Another method of more thoroughly
reducing the bones than is effected either by grinding or ferment-
ing them, has lately been tried with much success. This is by dis-
solving them in muriatic acid, (spirit of salt), or what is better and
is more generally adopted, in sulphuric acid. The bones are mix-
ed with from one-fourth to one-half their weight of the sulphu-
ric acid (oil of vitriol) of the shops, previously diluted with twice its
bulk of water, in any convenient vessel. Or the bone dust may
be laid in a heap upon an earthen or stone floor, and watered with
the diluted acid in successive portions, and turned over at each ad-
dition. The bones are soon attacked by the acid. They boil
up at first, owing to the escape of carbonic acid from the carbonate
AIDWANTAGE OF DISSOLVING BONES. 793
of lime they contain, and are afterwards gradually dissolved or
melted down, so that the lumps of bone at last entirely crumble
down and disappear. In this state the prepared bones may be
dried up by saw dust, by peat dried and powdered, or by dry ashes
or vegetable mould, and then applied in the usual manner with the
hand or with the drill. Or it may be mixed with one or two hun-
dred times its bulk of water, and spread upon the land with a water
cart.
Or the bones may be put in the centre of a hole made in a large
heap of ashes, the acid poured on, and the whole covered up and
allowed to stand for a week or ten days. The bones are then
found to be in a great measure reduced, and may at once be ob-
tained in a dry state fit for the drill, by mixing them thoroughly
with the heap of ashes. This latter method is the least trouble-
some, but it is not so efficient, and a portion of the sulphuric acid
is drunk up by the ashes, and is prevented from acting upon the
bones. -
By this method of preparing them, the particles of bone are
more completely separated from each other than by any other
means, and can thus be spread more thinly over the soil and be
made to go farther. The phosphoric acid or phosphate of lime is
brought into a state in which it is soluble in water, and can thus
readily be taken up by the roots of plants, while the sulphuric
acid is also a new manuring substance which the farmer in this
way is enabled to apply to his soil.
The practical or money benefit derived from this mode of pre-
paring them is, that a much smaller application of bones is neces-
sary to produce an equal effect upon the land or to raise an equal
crop. This has been proved by numerous experiments, of which
the following are the general results.
1°. That eight, four, and in some cases two bushels of dissolved
bones have produced as good a crop of turnips as sixteen or twenty
bushels applied in the usual way. The crops also start more
quickly and grow more rapidly.
2°. That the effect is greater the more complete the solution and
subdivision of the bones. Hence they are more beneficial,—give
larger crops, that is, when applied in a liquid state and in a state
of great dilution.
794 REFUSE CHARCOAL OF THE SUGAR REFINERs.
This method of using bones may therefore be considered as an
important improvement in the economy of manures. It is espe-
cially adapted to dry, poor, and sandy soils, such as the reclaimed
warrens of North Lincoln, in which bones are said to lie for years
undecayed.*
§ 7. Of animal charcoal, the refuse of the sugar refineries, and
animalised carbon.
1°. Animal charcoal (bone black).--When bones are charred or
distilled at a red heat in close vessels, they leave behind a coaly
residuum, to which the name of animal charcoal is usually given.
By this calcination the animal matter is almost entirely decompos-
ed. The charcoal still retains, however, a little nitrogen, and
though it is seldom employed as a manure, yet it is not wholly
without effect in promoting the growth of our cultivated crops.
Thus in 1842, when applied to Swedish turnips, Mr Fleming ob-
tained from the unmanured soil 12 ton 5 cwts, per acre; with 20
tons of farm-yard manure, 18% tons; but when manured with 10
cwts, of animal charcoal, 21 tons 2 cwts, of clean bulbs.
Another form of animal charcoal is the black refuse of the
prussiate of potash manufactures—obtained by melting pearl ash
with horns, hoofs, and woollen rags. This variety contains very
little bone earth, and derives a part of its value from the potash
which is left in it. It forms an excellent admixture with the better
kinds of guano. s § . l
2°. Refuse charcoal of the sugar refiners.--The animal charcoal
above described is chiefly employed for the purpose of removing
the colour from solutions of raw sugar., Blood is also used for
clarifying the same solutions, and quick-lime for neutralizing the
acid matter they contain—thus rendering the syrups more capable
of easy crystallization. Hence the animal charcoal, the blood,
the lime, and the colouring and other matters separated from the
sugar, become mixed together, and form the refuse of the sugar
refiners. This refuse often contains from one-fifth to one-fourth
of its weight of blood, and hence—in France especially, where it
is extensively employed as a manure—it is considered from four to
* For further particulars in regard to the use of dissolved bones, see Proceedings of
the Agricultural Chemistry Association, p. 33.
ANIMALIZED CARBON.—USE OF FISH. 795
six times more powerful than the pure animal charcoal alone. In
the western parts of France this mixture has for some years
been in great repute among agriculturists, and, in addition to that
which is produced at home, has been largely imported from other
countries. Into the ports upon the river Loire alone there were
entered, in 1839, upwards of ten thousand tons.” . It sells at about
L.5 a ton. - - -
The value of this substance as a manure varies with the propor-
tion of blood which it contains. In this country blood is used
much more sparingly in the refining of sugar than it used to be,
and hence the refuse of our refineries is probably less valuable as a
manure now than it was in former years.f
Another refuse, sometimes sold at the sugar works, consists of
the bone charcoal burned over and over again after being used,
till the animal matter is nearly all burned away, and it is no longer
of any use in clarifying syrup. In this state it forms, when dry,
a gray powder, and consists of bone earth mixed with a variable
proportion of lime, alumina, and gypsum. It is an excellent ma-
mure, inferior in a small degree to the bone or animal charcoal,
and is sold for about L.4 a ton.
3°. Animalized carbon.—The estimation in which the refuse
charcoal of the sugar works was held, has led to the manufacture
of very useful imitations of it under the name of animalized car-
bon. A calcareous soil, rich in vegetable matter, f is charred in
close vessels, and is then mixed at intervals with repeated portions
of night soil as long as it disinfects it or removes its smell—and
to this mixture is added 4 or 5 per cent. of clotted and partially
dried blood. This animalized carbon is said to be of much value
as a manure. The main objections to it are its liability to adulte-
* Boussingault, An. de Chim, et de Phys., 3d, series, iii. p. 96.
+ The refining “consists in putting the sugar into a large square copper cistern along
with some lime water, a little bullock's blood, and from 5 to 20 per cent of bone black,
and injecting steam through the mixture. Instead of the blood many refiners employ
a mixture of gelatinous alumina and gypsum, called finings, prepared by adding lime
water to a solution of alum, and collecting the precipitate.” (Ure). Hence the reason
why, in England at least the refuse charcoal of the sugar works is not always rich in
blood.
# An intimate mixture of peat and marl or shell-sand would answer well.
796 |USE OF SHELL FISH AND FISH REFUSE,
ration, and the uncertainty to which, even when skilfully and con-
scientiously prepared, its composition must be liable.
§ 8. Offish, fish refuse, shell-fish, sea blubber, whale blubber,
and oil.
1°. Fish.—In some parts of the world, and occasionally on the
shores of our own island, fish are met with in such abundance, that
they can be economically employed as a manure for the land.
They are either spread over it in a recent state, or—which is more
economical—are made into a compost with earth, or with earth
and marl, which proves rich and fertilizing.
That the bones of fish have the same composition as those of
land animals, has already been shown (p. 782). Their muscular
parts or flesh have also very nearly the same composition as the
flesh of the sheep and the ox. In regard to the proportions of ni-
trogen they respectively contain in the dry state, the following re-
sults have been obtained by Schlossberger and Kemp. All the
substances were analysed in the raw state after being separated as
completely as possible from adhering fat.
Nitrogen per cent. Nitrogen per cent.
Mutton, ............ l2:30 Herring, ......... 14°48
Beef, ........ * * * * * * * 14:0 Haddock,......... l 4'64
Eel, ............... . 6.9 | Flounder, ...... 14:28
Salmon, ............ 12:35 Skate,............ 15' 39
It was the large quantity of fat in the eel that caused the pro-
portion of nitrogen in the muscle of this fish to be so small.
Since then the bones of fish have the same composition as those
of land animals, and since the proportion of nitrogen, so impor-
tant to the value of a manure, is so nearly the same in both, the
bodies of fish must possess the same fertilizing value as those of
other animals. This we have already seen to be very great.
2°. Fish refuse.—The pilchards of Cornwall and the herrings,
cod, and ling of our northern coasts, when cleaned for salting,
yield a large quantity of refuse,” which is peculiarly valuable to
the farmers in the neighbourhood of the principal fishing stations.
In the north of Scotland, a compost prepared from this fish re-
fuse is generally esteemed as a manure for barley and green crops,
* Fourteen barrels of herrings yield one of refuse.
|USE OF WHALE BLUBBER AND OIL. 797
but when extensively used, “renders the soil unfit for the produc-
tion of oats.” Such soil is said to be poisoned.*
Nothing so soon rots a tough sward when turned over by the
plough as a top-dressing of fish refuse.
This refuse consists chiefly of oily matter and of the entrails of
the fish. In these latter much nitrogen is present. The dried
milt of the herring contains 14.69 per cent., and therefore, in so
far as its organic part is concerned, is as valuable a manure as the
muscle or body of the herring would be.
3°. Shell Fish.-On some parts of our coasts, shell fish of vari-
ous kinds abound so much, that they are collected by the adjoining
farmers in a living state in large quantities, and are applied to the
land, either directly or in the form of a compost. In the upper
part of the Solway Frith, cockles, muscles, and periwinkles are col-
lected for this purpose, and give excellent crops of turnips. Of
course the shells convey a large quantity of carbonate of lime to the
soil, but it is the animal matter of the decomposing fish which di-
rectly promotes the growth of the crop to which they are applied.
The animal matter of these fish has not been analysed, but that
of the oyster in the dry state contains 5% per cent. of nitrogen.f
It is probable, therefore, that the animal matter of these shell-
fish is not, weight for weight, so fertilizing as that of either the
vertebrated fishes or of land animals. Analysis, however, may
still show this to be otherwise.
4°. Sea blubber or jelly fish, (medusae). My attention has re-
cently been drawn by Lord Murray to the great abundance in
which jelly fish are often left by the sea, especially upon our
western Coasts.
These fish speedily decay and diminish to a very small bulk.
In doing so they become rich in ammonia, and give off a very dis-
agreeable odour caused by the production of hydrosulphuret of
al]] [I] OIllà.
I have not yet had an opportunity of determining how much
water the recent jelly fish contain. Should this not prove too
great, they might be both usefully and economically collected and
* Sinclair's Statistical Account of Scotland, vii., p. 20), quoted in British Husban-
dry, i. p. 421.
+ Schlossberger and Kemp.
798 RELATIVE VALUES OF ANIMAL MANURES.
applied as a manure. Mixed with earth into a compost they would
make an excellent top-dressing for grass land.
5°. Whale blubber.—When the oil is expressed from whale
blubber, a skinny or membranous refuse remains, which has hitherto
been employed only as a manure. It is made into a compost with
earth, which is several times turned, and the mixture is most use-
fully employed after it has lain not less than 9 or 12 months. It
may be applied either to grass or to arable land.
6°. Whale oil, and that of other fish, when made into a compost
with earth and a little lime or wood ashes, yields a manure which
was much recommended by the late Dr Hunter of York.” Merely
mixed with absorbent earth, and applied at the end of one month,
impure whale oil, at the rate of 40 gallons per acre, gave the late
Mr Mason of Chilton, near Durham, a crop of 20% tons of tur-
mips, while 40 bushels of bones gave him only 22 tons. More
lately, also, it has been found that the mixture of a few gallons of
oil with the usual quantity of bone-dustincreased to a considerable
degree the turnip crop to which it was applied.
During a recent visit to North Lincoln, I found pure whale oil,
costing 3s, 3d, a-gallon applied with advantage to light Sandy soils,
at the rate of 5 gallons an acre instead of half dung. The oil is
intimately mixed with ashes, and is laid up in a heap to heat, which
it soon does. Mixed with 16 bushels of bones and 12 bushels of
pigeon's dung, it produced a better crop of turnips than 10 tons of
dung mixed with the above quantities of bones and pigeon's dung.
This practice is theoretically interesting, and is deserving of fur-
ther investigation.
§ 9. Relative fertilizing values of the animal manures already
described.
No sufficiently decisive experiments are yet upon record, from
which the relative values of the several animal manures above de-
scribed can be satisfactorily deduced. That they differ in fertiliz-
ing power every farmer is aware, but it is not yet decided by
actual trial, in what proportion one of them exceeds the other.
I have already stated the theoretical opinion entertained by
some, that the efficacy of all manures is in proportion to the quan-
* See his Georgical Essays, vol. i. ii. and v.
NOT WHOLLY DEPENDANT UPON THEIR NITROGEN. 799
tity of nitrogen they contain. Adopting this principle as true, it is
easy to assign to each substance its proper place in an artificial
table. The last column in the following table shows the quantity
of each substance in its ordinary state of dryness, which will be me-
cessary to produce the same effect as 100 lbs. of common farm-
yard manure, supposing this effect to be determined by the nitrogen
alone.

Water Ash Nitrogen Equal effects
per cent. per cent. per cent. produced by
Farm-yard manure ......... 80 P % 100 lbs.
Flesh ..... ................ ... 77 l 3} l6 ...
Fish . ........... ............. 80 2 24%; 17%...
Blood........................... 79 to 83 l 3 16 ...
Blood dried” .................. 12 to 20 3% 12 to 13 8 . .
Skin ............ . . ........... 58 & 8 12 ...
Wool, hair, and horn 9 to 1 | l to 2 | 6 6 ...
Bones...... .................... 14 40 to 60 5 to 9 ll to 20
Refuse charcoal of the 48 70 to 90 l 50 .
Sugar works
Animalized carbon . ....... 45 9 l 50 .
I have already had occasion to remark, however, that this mode
of classifying manures is not altogether to be depended upon.
Since—
1°. It does not take into account the quantity of inorganic mat-
ter they severally contain, which, as shown in the third column, is
particularly large in bones, and is by some considered as the
(most?) important and influential constituent of this manure. It
is probably owing to the inorganic matter they contain that the
effect of the animal charcoal of the sugar-refiners and of the ani-
malized carbon is, by eagerience, five times greater than the pro-
portion of nitrogen found in them would indicate.f Nor is any
effect ascribed to such substances as the sulphur, -in hair and wool
forming nearly 5 per cent of their whole weight, which cannot
be wholly without influence upon the plants, by which, as they de-
cay, the constituents of these several manures may happen to be
absorbed. -
2°. It passes by the practical influence of the quantity of water
which the several substances contain. Flesh, fish, blood, and skin,
* As it is sold for manure at Paris and elsewhere, p. 795.
+ Boussingault and Payen, Ammal. de Chim. et de Phys., 3d Series, iii. p. 94.
800 OF THE DROPPINGS OF BIRDS.
in their recent state, contain so much water that they begin al-
most immediately to decompose, and thus expend most of their fer-
tilizing virtue upon the first crop to which they are applied. Hair
and wool, horn and bone, on the other hand, retain so little water
that they decay with much greater slowness. And hence, the re-
action continues for more than a single year, from this cause alone.
3°. If pure oil, which contains no nitrogen at all, will yet pro-
duce an enriching manure by mere mixture with the soil (p. 797),
or will increase greatly the effect of bones—we must obviously
seek for some other principle upon which to account for the effect
of manures, besides or in addition to the proportion of nitrogen
they contain. It is true that impure or refuse whale oil, when
used for composts, may contain some nitrogen, but when pure oil
is used, such can scarcely be the case to any great extent.
While, them, we put so much faith in theory as to believe that
substances which contain much nitrogen are very likely to prove
valuable manures,--we must not allow ourselves to be so carried
away by the simplicity of the principle as to believe either that the
relative effects of manures upon our crops may be always estimat-
ed by the proportion of nitrogen they contain, or that a substance
may not largely increase the produce of our fields in which no ni-
trogen is present at all. Indeed the effects of saline substances
alone are sufficient to satisfy us how untrue to mature this latter
opinion would be.
§ 10. Of the droppings of fowls—pigeons' dung, and guano.
The droppings of birds form some of the most powerful of known
manures. This arises in part from the circumstance that in the
economy of birds there is no final separation between the liquid
and solid excretions. Both escape mixed together from the same
aperture.
1°. P.geons' duºg is much prized as a manure wherever it can
be obtained in any considerable quantity. In Belgium it is es-
teemed as a top-dressing for the young flax, and the yearly pro-
duce of 100 pigeons is sold for about 20s. Its immediate effect
depends upon the quantity of soluble matter it contains, and this
varies much according to its age and to the circumstances under
4
oF THE DROPPINGS OF BIRDs. 80?
which it has been preserved. Thus Davy” and Sprengel obtained
respectively of
Recent. Six months old After fermen-
• - a * . . . (Davy.) (Sprengel.) tation (Davy).
Soluble matter in 23 per cent. — 16 per cent. – 8 per cent.
pigeons' dung
The soluble matter consists of uric acid, urate, sulphate, and
carbonate of ammonia, common salt, and sulphate of potass;–the
insoluble part of phosphate of lime, with a little phosphate of
magnesia, and a variable admixture of sand and other earthy
matters.f When exposed to moisture, pigeons' dung, especially
if recent, undergoes fermentation, loses a portion of its ammonia-
cal salts, and thus becomes less valuable. When it is intended to
be kept, it should be mixed with a dry vegetable soil, or made in-
to a compost with earth and saw-dust, with a portion of pulverized
or charred peat, or with such a disinfecting charcoal as that which
is employed in the manufacture of the animalized carbon above
described.
In warm climates, pigeons' dung dries rapidly, and may be kept
for a considerable time without losing its fertilizing virtue. A
specimen of pigeons' dung from Egypt, lately imported into this
country for sale as a manure, when analysed in my laboratory,
was found to consist of
Soluble matter, ............ 23.9
Jnsoluble do. ............ 76.1
100 z
And the whole taken together was composed of
Water, ............................. ........... ........ “s s e a s >e ‘e e º . * * * * * * * * * * * * * * * * * g s e º a e º e º e º º 0.65
Organic matter, containing 3.27 per cent. of nitrogen, equal to 3.96 of ammonia, 59.68
Ammonia, ..... •e s - ~ * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * 1.50
Alkaline salts, . ............................. ........................... ................. 0.42
Phosphates of lime and magnesia, ...................................................... 7.96
Carbonate of lime,.......... ................................. .............................. 2.37
Siliceous matter (chiefly sand), ..................... . . . .............. ............... 21.42
| 00.
* Davy's Agricultural Chemistry, Lecture VI.
+ Sprengel's Lehre vom Diinger, p. 140.
3 E
S()2 IEEN's, GOOSE, AND Rook's DUNG.
The pigeon's dung of Bechelbronn was found by Boussingault”
to contain 84 per cent. of nitrogen, and therefore to be much
richer than that of Egypt above analysed,
2. Hens' dung often accumulates, decomposes, and runs to waste
in poultry yards. With a little care, it might be collected in con-
siderable quantities, and would be about equal in value to that of
the pigeon.
3° Goose dung is probably less rich than that of hens or pigeons,
because this bird feeds less upon grain, and derives a considerable
portion of its mourishment from the grass which it crops, when al-
lowed to go at liberty over the fields. Its known injurious effects
upon the grass on which it falls arise from its being in too concem-
trated a state. In moist weather, or where rain soon succeeds, it
does no immediate injury, and even though in dry weather it may
kill the blades on which it drops, it brings up the succeeding shoots
with increased luxuriance.
4°. Rooft's dung unites with the leaves of the trees among which
the birds live, in enriching the pasture beneath them. In old rookeries
the soil is observed also to be slowly elevated above the surround-
ing land. This surface soil I have found upon analysis to be es-
pecially rich in phosphate of lime, which has gradually accumulat-
ed and remained in it, while the volatile and soluble parts of the
droppings of the birds have slowly disappeared.
5°. Guano is the name given to the accumulated dung chiefly
of sea birds, which is found upon the rocky promontories, and on
the islands that skirt the coast of South America and South Africa.
In America it abounds chiefly from the 13th to the 21st degree of
south latitude; but it has also been met with in considerable quan-
tity on the coast of Patagonia. In these parts of the world, the
climate being generally very dry, the droppings of the birds have
decomposed with exceeding slowness, and upon some spots have
continued to accumulate for many centuries, forming layers, more
or less extensive, of 10, 20, and at certain places, it is said, even 60
(?) feet in thickness. The more ancient of these deposits are occa-
sionally covered by layers of drift Sand, which tend further to pre-
serve them from decay. In our moist climate the dung of the sea
fowl is readily washed away by the rains, so that even where sea
* Economie Rurale, ii. p. 128,
º
COMPOSITION OF DIROPPINGS OF SEA FOWI. S()3
birds most abound, no considerable quantity of guano can ever be
expected to collect. -
The solid part of the droppings of birds, when recent, consists
chiefly of uric acid, with a little urate of ammonia, and a variable
per-centage of the phosphates of lime and magnesia, and some
other saline compounds. The liquid part, like the urine of other
animals, contains much urea, with some phosphates (?), Sulphates,
and chlorides,
The following table represents the composition of the solid part
of the droppings of three different varieties of eagle, as determined
by Coindet.*
American American
Senegal hunting fishing
eagle. eagle. eagle.
Uric acid, ........................ 89.79 90°37 84'65
Ammonia,........... ... ... . . . . 7'85 8-87 9-20
Phosphate of lime,........... . . . 2°36 0.76 6-15
1()0 J 00 100
The uric acid and urea, however, gradually undergo decompo-
sition, and are changed into carbonate and other salts of ammonia.
If applied to the land when this stage of decomposition is attained,
they form an active, powerful, and immediately operating manure;
but if allowed to remain exposed to the air for a lengthened period
of time, the salts of ammonia, and especially the carbonate, gradu-
ally volatilize, and the efficacy of what remains becomes greatly
diminished. Hence, the guano which is imported into this country
is very variable in quality, some samples yielding only 1 or 2 per
cent. of ammonia, while others are said to give as much as 25 per
cent.
The following table represents the general composition and ap-
pearance of the different kinds of guano imported into this country
so largely during the last three years. It contains an abstract of
the results of the analyses of several hundred varieties made in my
laboratory.
* Gmelin. Handbuch der Chemie, ii. p. 1456.
804. COMPOSITION OF DIFFERENT WARIETIES OF GUANO,
- Organic matter
Water
and ammoniacal
Variety. per cent. salts. Phophates.
From From From
Bolivian,........................ ... e s is e & 5 to 7 56 to 64 25 to 29
Peruvian, ........................... 7 to 10 56 to 66 16 to 23
Chilian or Valparaíso, .......... | 0 to 13 50 to 56 22 to 30
Ichaboe, .............................. 18 to 26 36 to 44 21 to 29
Saldanha Bay, ......... ........... 17 to 34 14 to 22 45 to 56
Algoa Bay, .......... ... … 2 to 24 23 43 to 70
Patagonian, ........................ 14 to 40 16 to 38 17 to 40
Possession Island, ................. 18 to 25 22 to 24 42 to 47
Paternoster Island,.................. 24 to 29 20 to 22 32 to 40
South African or Bird's Island,... 14 to 25 19 5 to 22
Halifax Island, ..................... 25 21 23
Australian,........................... 18 20 30
Holmes’ Bird Island,............... 24 39 25
Angra Pequena,... ... ............... 23 53 12
The above table shows that there are great differences among
the several varieties of the African guanos, and consequently great
differences also in their agricultural and commercial values.
They all contain a variable proportion of sand and small stones,
and that from Algoa Bay sometimes as much as 40 or 50 per cent.
of gypsum. -
The Peruvian guano being richest in nitrogen” is the most
valuable, but nearly all the samples of genuine guano hitherto
brought into the English market may be advantageously applied
as a manure to most of our crops.
From a very remote period guano has been the chief manure
applied to the land on the parched shores of Peru—and at the pre-
sent day it is not only employed for the same purpose in the pro-
vinces which lie along the coast, but it is also carried across the
desert of Atacama many leagues inland, “on the backs of mules
over rough mountain paths, and at a great expense, for the use of
the agricultural districts of Peru and Bolivia.” It has been es-
timated that a hundred thousand quintals; are, at the present day,
annually sold in Peru. There also the quantity and the price
* The presence of ammonia in guano is readily ascertained by mixing it with a
little slaked lime—when the odour of ammonia will be immediately perceived, and
will be strong in proportion to the quantity contained in the guano.
+ Silliman's Journal, xliv., p. 10.
† The quintal is equal to 101 lbs. avoirdupois.
ITS ACTION UPON TURNIPS, POTATOES, AND WHEAT.
805
vary—the recent white guano selling usually at 3s. 6d., the more
recent red and grey varieties at 2s. 8d. per cwt. (Winterfeldt)."
In this country, the latter—the only variety imported—sells at pre-
sent (1846), at about 10s. a cwt.
In regard to the effects of guano upon various crops in this
country numerous experiments have been made and published, and
the agricultural community is now satisfied of its great value as a
manure when obtained of good quality. I insert, therefore, only a
very few of the results which have been obtained.
Top-dressed with
1°. Farm-yard dung,
Guano,
2°. Farm-yard dung,
Guano, i.
Bones,
Guano, t
Rape-dust,
Bone-dust, .
1°. Guano,
Rape-dust, .
2°. Guano,
Rape-dust, .
Bone-dust, .
Swedish Turnips.
20 tons.
3 cwt.
20 tons.
2} cwt.
32 bush.
Produce per acre.
tonS.
18
23
16
17
15
Yellow Turnips.
5 cwt.
15 cwt.
30 bush.
Potatoes.
3 cwt.
1 ton.
4 cwt.
1 ton.
45 bush.
4 cwt.
1 ton.
45 bush.
Wheat.
1 cwt.
16 cwt.
3 cwt.
2 cwt.
32
24
17
Locality.
CWt.
11 Barochan, near
8 | Paisley.
l Parish of Wraxall,
17 Somerset.
2 Barochan, near
ll -
Paisley.
cases the manures were
put in alone with the
15 ſ potato cuttings, no
9 - -
Y
6 Barochan. In all these
6
0
3°. Guano, sº
Rape-dust, .
Bone-dust, .
1°. Guano, e
Rape-dust, .
Undressed
2°. Guano,
Undressed,
3°. Guano,
Undressed, i.
14 other manure being
0 afterwards added.
14
bush. lbs.
48 0 | Lennox Love, near
51, 0}. Haddington—drought
47%. 0 ) very great.
; : | Barochan.
32 20 Gadgirth, near
31 31 Ayr.
* For further particulars regarding guano the reader is referred to a paper in the
Journal of the Royal Agricultural Society, ii. p. 30l.
f Mixed with 1 cwt. of charcoal powder.
†: Mixed with 20 bushels of wood-ashes.
§ The undressed grain was of superior quality, yielding 76% per cent. of fine flour,
while that dressed with guano gave only 68% per cent.
806 ITS ACTION UPON BARLEY, OATS, BEANS, AND HAY.
Produce per acre
Top dressed with bush. Ibs. Locality.
4°. Guano, ſº l cwt. . 46 lb
Nitrate of soda, l cwt. . 54 18 ). Erskine, Renfrewshire,”
|Undressed, . º 44 4
5°. Guano, e 13 cwt. . 45 0 o #vy fºllºw •
Nitrate of soda, • 13 cwt. . 41 0 l sºyººster
Undressed, . . . 39 0 Snlre...}.
Barley.
Guano, & 3 e (34 () *
Undressed, . * º 47 15 | Barochan.
Oats.
1 *. Guano, e 2 cwt. . 70 0 Ilennox Love, near
Undressed, . e - 52 0 Haddington.
2°. Guano, & 1 cwt. . 48 16 | -
Nitrate of soda, 1 cwt. . 50 0 }. Erskine, Renfrewshire.
Undressed, . e - 49 ()
JBeans.
Guano, e 2 cwt. . 33%
Rape-dust, . l 6 cwt. 35 Lennox Love, near
Nitrate of soda, 1 cwt. . 33 Haddington,
|Undressed, º 29;
Hay.
tons. CWt.
1°. Guano, e I} cwt. 1 18
Nitrate of soda, l; cwt. 2 10 % Barochan, near Paisley.
Undressed, o l 8
2°. Guano, 13 cwt. 2 2
Nitrate of soda, 13 cwt. l 17 § Erskine, Renfrewshire.
Undressed, * } ] 0
An inspection of the above results appears to indicate that guano
is more uniformly successful with root crops, than when applied as
a top-dressing to corn and grass. The unusual drought which pre-
vailed in 1842, when these experiments were made, no doubt mate-
rially diminished its action, when used as a top-dressing—and the
results upon the corn crops in moister seasons since, have shown that
it may be generally employed with economy upon all our crops.
The favourable influence of guano does not cease with the first
season. As the phosphate of lime operates in prolonging the fer-
tilizing operation of bones, so the large, though variable, quantity
* The grain dressed with guano weighed half a pound per bushel less than the
others.
+ See also Mr Grey of Dilston's experiments and remarks, Royal Agricultural Jour-
mal, iv. p. 212 to 214.
: The guano gave 4 cwt. more straw than the mitrate, and 11 cwt. more than the
undressed. The undressed grain also weighed half a pound less per bushel than either
of the other two, -
SOLII) MATTER IN THE URINE OF DIFFERENT ANIMALS. 807
of this phosphate which it contains renders guano capable of per-
manently improving the soil.
By exposure to the air, guano gradually gives off a portion of
its volatile constituents; it ought, therefore, to be kept in covered
vessels or casks. In our climate also, the drier varieties of Peru-
vian absorb moisture from the air, and should therefore be pur-
chased as soon as possible after importation. When applied as a
top-dressing it may be conveniently mixed with an equal weight of
gypsum or wood-ashes—with charcoal powder, or with fine dry soil.
As a matter of good husbandry it is better to use guano with
half dung than to apply it alone. By this means the supply of
vegetable matter in the soil is kept up, and other valuable substan-
ces added to it which the guano does not contain. Or if guano
be used alone in one rotation, farm-yard manure should be em-
ployed in the next.
§ 11. Of liquid animal manures—general relations of the urine of
man, of the cow, the horse, the sheep, and the pig.
Of natural liquid manures, the most important and valuable,
though the most neglected and the most wasted also, consist of
the urine of man and of the animals he has domesticated.
The efficacy of urine as a manure depends upon the quantity of
solid matter which it holds in solution, upon the nature of this so-
lid matter, and especially upon the rapid changes which the orga-
nic part of it is known to undergo. The following table exhibits
the average proportions of water, and of solid organic and inorga-
nic matters contained in the urine of man and of our most useful
domestic animals in their healthy state—and the average quantity
voided by each in a day:—

Water Solid matter in 1000 parts. Aver. quan-
Urine of in tity voided
1000 parts. Organic. Inorganic. Total. in 24 hours.
Man," ........... ... 930 to 970 22 to 52 8 to l8 || 30 to 70 3 lbs.
Horse, ............... 886 to 940 27 to 79 || 33 to 45 60 to 124 3 9
Cow. .................. 880 to 930 50 to 70 20 to 47 || 70 to 120 | 40+
Sheep, ............... 930 to 960 28 to 50 | 12 to 20 | 40 to 70 p
Pig, ........ ..... ... 926 to 983 9 to 56 9 to 18 18 to 74 p
* Alfred Becquerel. See Thomson's Animal Chemistry, p. 477. It is to be ob-
served that the proportions of water and of solid matter in urine vary with the food,
and with a great variety of circumstances,
t A milk cow voids less than this in a proportion which varies with the quantity of
808 - COMPOSITION OF HUMAN URINE.
From the above table it appears that the proportion of solid mat-
ter, both organic and inorganic, is very much the same on an ave-
rage in the urine of the horse and the cow. The larger quantity
voided by the cow, however, makes the urine it produces in a given
time much more valuable than that of any other of our domestic
animals. -
It might be supposed at first that in all animals the quantity of
urine voided would have a close connection with the quantity of
water which each was in the habit of drinking. But this is by no
means the case. Thus it is the result of experiment that in man
the drink exceeds the urine voided by about one-tenth part only—
while
Of water in 24 hours. Of urine in 24 hours.
A horse, which drank 35 lbs., gave only 3 lbs.
A cow, which drank 132 lbs., gave 18 lbs., and
19 lbs. of milk (Boussingault).
How very large a quantity of the liquid they drink must escape
from the horse and the cow in the form of insensible perspiration I
That this should be very much greater, indeed, than in man, we are
prepared to expect from the greater extent of surface which the
bodies of these animals present.
Let us now examine more closely the composition of urine, the
changes which by decomposition it readily undergoes, and the ef-
fect of these changes upon its value as a manure.
§ 12. Composition of human urine. Of urea and the changes it
wndergoes.
1°. Human urine.—The exact composition of the urine of a
healthy individual in its usual state was found by Berzelius to be
as follows:—
Water... ............ . . . . . . . . . . . . . . . . . . . . 933.0 Phosphate of Soda .................... . 2.9
Urea ........ sº e º is a s = e º e º e º e º ºs º ºs ... . . 30°l Phosphate of ammonia ......... . ... 1.6
Uric acid ............ ... < * < e < * * * * * * * * * * * * 1-0 | Common Salt . . . . . . .................. 4°5
Free lactic acid, lactate of ammonia, Sal-ammoniac.......................... 1.5.
and animal matter not sepa- Phosphates of lime and magnesia,
rable ........................... . . . . l 7-l with a trace of silica and fluo-
Mucus of the bladder ............... 0°3 ride of calcium ..................... l' :
Sulphate of potash.............. ...... .7 *-*m-.
Sulphate of soda............ ........... 3.2 | 000
milk she gives. Boussiugault found a milk cow to yield daily 18 lbs. of urine and 19.
$bs, of milk.--Ann. de Chim, et de Phys., lxxi. pp. 123, 124.
TJREA CHANGES INTO CARBONATE OF AMMONIA. 809
From what I have already had occasion to state in regard to the
action upon living plants, of the several sulphates, phosphates, and
other saline compounds, mentioned in the above analysis, you will
see that the fertilizing action of urine would be considerable, did
it contain no other solid constituents. But it is to the urea which
exists in it in very much larger quantity than any other substance,
that its immediate and most marked action in promoting vegetation
is chiefly to be ascribed. --
2°. Urea is a white salt-like substance very soluble in water, and
consisting of-
Per cent.
Carbon, ......................... ....... 20-0
Hydrogen, ... ................. ... ..... 6'6
Nitrogen, .................. . . ....... 46-7
Oxygen, ................................. 26-7
100
It is, therefore, far richer in nitrogen than flesh, blood, or any
of those other richly fertilizing substances, of which the main effi-
cacy is supposed to depend upon the large proportion of nitrogen
they contain. -
But urea possesses this further important property, that when
urine begins to ferment—as it is known to do in a few days after
it is voided—it changes entirely into carbonate of ammonia.” Of
the ammonia thus formed a portion soon begins to escape into the
air, and hence the strong ammoniacal odour of fermenting urine.
This escape of ammonia continues for a long period, the liquid be-
coming weaker and weaker, and consequently less valuable as a
manure the longer it is exposed to the open air. Experience has
shown that recent urine is liable at first, and especially in dry
weather, to exercise an unfavourable action upon growing plants,
and that it acts most beneficially after fermentation has freely be-
gun, but the longer time we suffer to elapse after it has reached
* This takes place by the decomposition at the same time of two atoms of the
water in which it is dissolved. Thus urea is represented by C, H, N, O, ; two of
water by 2 H O ; and carbonate of ammonia by N. He + CO2 ; and the change is thus
shown—
2 of 2 of
Urea. Water. Carbonate of ammonia.
C, H, Na O2 + 2 H O = 2 (NH 2 + C 0,...)
8.10 COMPOSITION OF THE URINE OF THE COW,
the ripe state, the greater the quantity of valuable manure we per-
mit to go to waste.
§ 13. Composition of the urine of the cow, the horse, the sheep, the
pig, the goat, and the hare.
The urine of these animals, as I have already stated, varies much
in composition with the food, the age, the condition, and the con-
stitution of the animal, and with the circumstances in which it is
placed. *
The analysis of one sample of sheep’s urine, made in my labora-
tory by my assistant Mr Fromberg,” and of two samples of those
of the horse, the ox, the pig, the goat, and the hare, by Von Bibra, f
gave the following results.

Horse, Ox. Sheep. Goat. Pig. Hare.
Extract, matter * * * * tº º e .ao' e & • *. • A s • I <) || “...??) , ſº ſ
(sol. in º) 21:32 19°25 22:48 16 º * 3'40 1-00 0°56 1 °42 1 - 12 32°68
Do. do. * a * ‘Y e g e • * , • tº - - • * {
(sol. in alcohol) 25 50 18:26, 14.2] 10:20, 33-30 4'54 4'66 3.87 3.09 9°58
Salts, sol. in water] 23:40 40’00 24'42 25.77| 19.57 8:50 8-70 9'09 8 48; 23.70
Salts, insol. in do. 18.80 1.55] 2.22 0-52) ()-80 0.40} 0-88 0-80) 12:64
Urea, ... ............ 12'44 8:36, 1976 IO-21 12-62 3-78 0.76 2.73 2.97 8'54
Hippuric acid,... 12-60 1 °23 5°50 13|| 2 1.25 0-88) ... $ 9 º'
Mucus, ............ 0-05 0.06 0-07 0.06 0.25 0-06 0-05 0-05 0.07] ...
Water, ............ 885-89 912-84 912-01 923-11 928-97 980-07 983-99 981.96 982°57) 912.86
1000 1000 |00 1000 | 998.63|1000 1000 1000 1000 1000
This table illustrates the fact that the composition of the urine,
not only of different animals, but of the same animal at different
times, varies very much. This is seen very strikingly in the first
table in the numbers opposite to urea, a substance upon which, as
I have already explained, the value of urine as an application to
the soil in a large degree depends. It is in this substance, and in
the hippuric acid, that nearly all the nitrogen exists, which dur-
ing the fermentation appears in the form of ammonia—and the
above table shows that in these two constituents the urine of the
ox is on an average fully as rich as that of the horse.
In the milk cow the contrary is probably the case, as Boussin-
gault found the urine and the dry extract of the urine of the horse
and of the milk cow to contain respectively of nitrogen and saline
matter per cent, as follows:—
Solid matter Natural urine. Dry extract.
in the urine. Nitrogen. Saline matter. Nitrogen. Saline matter
Cow......... ...... Il-7 0°44 4°68 3-8 40’0
Horse, ............ 12' 4 1 : 55 4'5] 12:5 36'4
* Proceedings of the Agricultural Chemistry Association of Scotland, p. 88.
i Annalem der Chemie wild Pharmacie, liii. p. 101.
HORSE, SHEEP, PIG, GOAT, AND HARE. SI I
These results make the urine of the cow, though equally rich in
saline matter, very much poorer in nitrogen than that of the horse,
and therefore much less fertilizing. In a dairy of milk cows this
is probably the case, as much of the nitrogen of their food is by
these animals returned in the curd of the milk they yield.
In the fold yard, however, when cattle are put up to fatten, this
is not the case. Their urine, therefore, will be richer and warmer,
as farmers call it. It will ferment more readily, will reduce the
straw with which it is mixed more easily and more completely, and
will make it into more valuable manure.
The saline matter or ash left by the dry extract of the several
kinds of urine above analysed was found to consist of,


Hare.
Horse. Ox. Sheep. Goat. Pig. L-L-
Winter. Summ
Carbonate of lime, ... 12:50, 31°00' 1-07 || 0-82 little
magnesia, 9:46, 1307| 6.93|| 0:46 || 7-3 - - -
•- potash,. . 46-09 ) 40'33 77-28 ... little | 12:1 - - - * * *
soda, ... 10.33| * * . . . . 42'25 | 53° 0 - © tº 9-84| 8-73
Chloride of sodium, ...| 6'94 5'60|| 0-30 || 32.0] | 14-7 || 53- 1 7-12 22:49
— potassium, ... e - - ... | 12:00 ... little little little
Sulphate of soda, 13° 04: 9:02 ... 7.72 25.0 7:0 16-82. 29.97
potash, ... ... ... 13:30 2.98 | . . . - 4 - - - - • * >
Phosphate of soda, ... - - - - - - 19-0 53-05 4:39
lime, ... ... e - - - - .*7 e = ... - 12:00
magnes. ... e e e - - - { 0.70 g s s 8-8 13° 17 22:42
Silica, .................. ()'55 } ()-98 | 0-35 | ] '06 | . . .
Oxide of iron and loss, l'09 0.77 - - - -
100 100 || 00 | 00 100 100 100 100
The most important results exhibited in the above table are,
1°. That the urine of the horse, the cow, the sheep, and the
goat contains either no phosphoric acid at all, or only a mere trace.
In that of the pig, again, as in human urine, a considerable pro-
portion is present in combination with soda, while in that of the
hare a very large quantity exists. -
2°. That the saline matter of the urine consists chiefly of com-
mon salt, and of the carbonates and sulphates of potash and soda.
Upon their potash, Soda, sulphuric acid, and ammonia, there-
fore, the value of the fermenting urine of our domestic animals
depends. They cannot yield phosphoric acid to the plant. This
is conveyed to the soil by their solid excretions.
§ 14. Composition of the drainings of dung heaps.
The drainings of dung heaps—the usual liquid manure of our
812 COMPOSITION OF THE DRAININGS of D'UNG HEAPS.
farm yards—differs in composition according to circumstances.
When the urine of cattle is mixed with it in considerable quantity,
it is found to contain a portion of the constituents not only of the
solid and liquid excretions of the stock, but also of the straw and
other vegetable matter which has fermented along with it. It
varies in strength, however, very much with the quantity of rain
or other water with which it is mixed, or which falls upon the dung
heaps from which it flows.
The following table exhibits the composition of two specimens of
such liquid manure, sent to me from Coltness, near Hamilton, and
analysed in my laboratory.
Drainings of
Cow dung washed Farm-yard dung
by rain. watered with cow's urine.
1°. An Imperial gallon contained,
Ammonia,................................. 9.60 grains. 21.30 grains.
Solid organic matter, .................. 200.80 77.60
Solid inorganic matter or ash, ...... 268.80 518.40
479.20 grains. 617.30 grains.
2°. The inorganic matter in a gallon con-
sists of:—
Alcaline salts, ........................... 207.80 420.40
Phosphates of lime and magnesia, co-
loured with a little phosphate of 25.10 44.50
iron, ....................... ...... ... …
Carbonate of lime, ... ................. 18.20 31.10
Carbonate of magnesia and loss, .. 4.30 3.40
Silica and a little alumina, ..... ... l 3.40 | 9.00
268.80 518.40.
The liquids were both neutral; but ammonia was given off when
they were boiled, or when caustic lime was added. This was espe-
cially the case with the second liquor.
In this table we see,
1". That the liquid which flows from a dung heap watered with
urine is greatly richer in ammonia and in Saline matter than that
which flows from the solid excretions newly washed by the rain.
2". The liquid in both cases contains a considerable proportion
of phosphate of lime. This we have seen does not exist in cow's
urine alone. In both cases it has been washed out of the solid
dung.
WASTE OF HUMAN URINE. 813
3". Both contain also an appreciable quantity of silica not ex-
isting in urine. This is derived from the straw of the fermenting
farm-yard dung, or from the grass which has passed through the
digestive organs of the cow.
We see, therefore,
a. That fermenting manure can yield in a soluble state every
mineral ingredient which a plant requires.
b. That liquid manure from a farm-yard may therefore often be
more valuable to vegetation than urine alone, because of its con-
taining those constituents of plants which are not present in urine,
—and, t
c. That, therefore, the liquid which runs from the farm-yard
ought to be no less carefully preserved than the pure urine of our
cattle.
Yet how much of both are allowed to run to waste How
little is their true value in general understood | -
§ 15. Of the waste of human urine. Use of sewer water as a ma-
nure. Action of lime and gypsum upon urine—urate, sulphated
write.
How much of human urine, as well as of the liquid of our farm-
yards, is annually allowed to run to wastel
1°. Waste of human urine.—The quantity of solid matter con-
tained in the recent urine voided in a year by a man, a horse, and
a cow, and the weight of ammonia they are respectively capable of
yielding, may be represented as follows:—
Quantity of urine. Solid matter. Yielding of ammonia.
Man,....... ... e º is tº e º º 1000 lbs. 67 lbs. 12 to 17 lbs.
Horse, ............ 1 000 60 to 120 - 20 P
CoW, ............... 7000 to 13,000 700 to 1500 36 to 70°
How much of this enriching matter, as I have said, is permitted
to run to waste P If we estimate the urine of each individual on
an average at only 600 lbs., then there are carried into the com-
mon sewers of a city of 15,000 inhabitants, a yearly weight of
600 thousand pounds, or 270 tons of manure, which, estimating
it at L.8 a ton, is worth L.2160.
The saving of all this manure would be a great national benefit,
* The numbers given above are only to be considered as approximations, as much
depends upon food and many other circumstances.
814. USE OF SEWER WATER AS A MANUR.E.
though it is not easy to see by what means it could be effectually
accomplished. What is thus carried off by the sewers and con-
veyed ultimately to the sea, is drawn from and lost by the land,
which must, therefore, to a certain extent, be impoverished. Can
we believe that in the form of fish, of sea tangle, or of spray, the
sea ever delivers back a tithe of the enriching matter it daily re-
ceives from the land P
2°. Use of sewer water as a manure.—It is very difficult to col-
lect and use up the waste water of towns. The great bulk and weight
of the liquid are objections to its being carried to great distances
on account of the heavy cost of transport. In the neighbourhood
of some large towns, as that of Edinburgh, the water from the
sewers has been employed with great ease and success for the pur-
poses of irrigation. Circumstances, however, do not admit of this
method being generally adopted. A company, however, has re-
cently been formed in London, “the London Sewerage Company,”
which proposes to pump it out of the sewers and to convey it in
pipes many miles into the country. It is there to be employed in
watering the corn and green crops, and in irrigating the grass
fields, and great local benefits are anticipated from its use in this
way. Should this first attempt prove successful, we may hope to
See a similar plan adopted in our other large towns.
3°. Action of lime-water upon urine,—Human urine contains
urea in large quantity, which, as the urine ferments, is changed in-
to carbonate of ammonia. It contains also soluble salts of various
kinds, which are all useful to the land. But phosphoric acid, as
we have seen, is also present in human urine in appreciable quan-
tity, and it has been thought, that though we may not be able to
use up the whole urine, this phosphoric acid might be separated
from it without great difficulty in the solid state and in a portable
form, so as readily and economically to be employed as a manure.
When lime-water is poured into human urine it causes a cloudi-
mess to appear, and a sediment to collect. In this sediment is
contained all the phosphoric acid of the urine in combination with
lime, and mixed with a variable proportion of organic matter which
the fine sediment has carried down along with it.
The precipitate thus obtained from urine by lime-water was found
by Dr Stenhouse to consist of
ACTION OF LIME WATER AND GYPSUM UPON U1R1NI. S] 5
Dried at 212. Dried in the air,
Water and organic matter, ... 12'66 56-90
Nitrogen, & e s e s is e s e º e s e º e º e s e º e ... 0-88 l'91
Lime, . . . . . . . . . . . . . . . . . . . . . . . . . . 44°96 |
Magnesia, ......... . ............... 1.32 Al 19
Phosphoric acid, .................. 40° 18 ſ
** 100 100
A mixture of this kind would certainly be of considerable value
as an application to the land. It has been proposed, therefore, to
collect the urine in large tanks, to treat it with lime water in this
way, and to separate and dry the sediment. It is no serious ob-
jection to the method, that all the other valuable ingredients in the
urine are allowed to run to water. When an economical method
of collecting these also in the solid form is discovered, it ought
of course to be adopted. The point of most importance at pre-
sent is the cost at which the above solid sediment can be prepared.
I need not observe that this method is not available in the case
of horse or cow's urine, which contains no phosphates, (p. 810).
4°. Action of gypsum on human urine.—Instead of lime water
gypsum has been recommended and used for mixing with urine,
and this with two objects.
a. Urate.—When gypsum is added to human urine, and fre-
quently stirred, so that a portion of it is dissolved, the lime it con-
tains combines with the phosphoric acid, and, as in the case of lime
water, causes it to fall in the form of insoluble phosphate. This
phosphate falls mixed with gypsum and a portion of the organic
matter of the urine.
In some of the large cities of France, Germany, and England,
the urine has been collected in tanks mixed with a seventh part of
its weight of powdered gypsum, allowed to stand for a few days,
and then drawn from the sediment. Under the name of urate this
sediment has been extensively prepared and much lauded as a ma-
nure. It is doubtful, however, if it possesses in any case the money
value which the manufacturers have naturally enough attached
to it.
b. When the gypsum (sulphate of lime) is introduced into fer-
mented urine containing carbonate of ammonia, the two acids, the
carbonic and the sulphuric, change places—forming carbonate of
lime which falls with the other sediment, and Sulphate of ammo-
816 LOSS OF LIQUID MANURE IN THE FARM-YARD.
nia, which remains in solution. This sulphate of ammonia does
not volatilize, or escape into the air as the carbonate does, and
thus the addition of gypsum to fermented urine is frequently adopt-
ed for the purpose of fixing the ammonia. This is only of use,
however, when the urine is to be applied in a liquid state; but it
is applicable to urine of all kinds.
The only effect of this second action of the gypsum upon the
composition of the urate is to mix with the sediment which falls
from fermented urine a portion of carbonate of lime.
Urate, therefore, is a mixture of phosphate, sulphate, and car-
bonate of lime, with a little organic matter, but it preserves and
retains in the solid form very little of the other saline matter of
the urine. - -
5. Sulphated urine.—A method of effecting this latter object has
been adopted by Messrs Turnbull of Glasgow. They add diluted
suphuric acid to the urine, as the ammonia is formed in it, and
subsequently evaporate the whole to dryness. From the use of
this substance, when prepared from human urine, very favourable
results may be expected.
§ 16. Waste of cow's urine—dilution with water—use of gypsum,
and of sulphate of iron.
19. Loss of cow's urine.—When left to ferment for five or six
weeks without any addition of water, the urine of the cow loses a
considerable proportion of volatile matter chiefly in the form of
ammonia. To preserve this volatile matter several methods have
been recommended.
a. An admixture of gypsum for the purpose of fixing the am-
monia on the principle explained above when treating of the ma-
nufacture of urate.
b. Or the addition of green vitriol (sulphate of iron), by which
carbonate of iron is thrown down and sulphate of ammonia formed.
This salt has the advantage of gypsum, in being more soluble in
water, and is employed to some extent in Switzerland.
3°. The sulphuric acid of the shops is also recommended. As
the urine begins to smell of ammonia small portions of the acid are
added from time to time. From 150 to 200 lbs. of acid would be
required to fix the whole of the ammonia formed in the urine of a
LOSS OF LIQUID MANURE IN THE FARM-YARD. 817
single cow in the course of a year—but the addition of 100 lbs.
for each cow will be enough to prevent any very sensible loss.
Mr Kinninmonth states that 3000 gallons of cow's urine mixed
with acid are equal in fertilizing value to 6 cwt. of Peruvian guano,
and superior to 20 cwts, of farm-yard dung. He adds 3 lbs. of
acid diluted with water to a cask of urine containing 160 gallons.
As he estimates the urine of a milk cow at only 2000 gallons a-
year, this amounts to about 40 lbs. of acid for each cow.
4". Simple dilution with twice its bulk of water is said by Spren-
gel to be perfectly efficient. The principal inconvenience attend-
ing this method is the large addition it makes to the cost of trans-
port, when the liquid has to be carted to the land. Where it is
employed for irrigation, however, the increased bulk is no objec-
tion.
5°. An admixture of rich vegetable soil, and especially of half
dried peat, is nearly as efficient as any of the above substances,
while it is, at the same time, in most localities more easily-obtained
and less costly.
But these remarks apply only to the liquid manure when col-
lected. How much larger a waste is incurred by those who make
no effort to collect the urine of their cow-houses or stables! The
recent urine of one cow is valued in Flanders—where liquid ma-
nures are highly esteemed—at 40s. a-year. Multiply this by eight
millions, the number of cattle said to exist in the United Kingdom,
and we have sixteen millions of pounds sterling, as the value of
this cow's urine. It is impossible to say how much of it runs to
waste, but we are safe in estimating its value at several millions a-
year. The practical farmer who uses every effort to collect and
preserve the manure which nature puts within his reach, is deserv-
ing of praise when he expends his money in the purchase of ma-
mures brought from a distance, of whatever kind they may be;—
but he, on the other hand, is only open to censure who puts for-
ward the purchase of foreign manures as an excuse for the neglect
of those which are running to waste around him. Let every stock
farmer, with the help of the facts above stated, make a fair calcu-
lation of what is lost to himself and to the country by the hitherto
unheeded waste of the urine of his cattle, and he will be able clearly
3 IP
81.8 SOLID ANIMAL MANURES.
to appreciate the importance of taking some steps for preserving it
in future.
§ 12. Of solid animal manures—night soil, poudrette, taffo, the
dung of the cow, the horse, the sheep, and the pig.
1°. Night soil is in general an exceedingly rich and valuable
manure, but its disagreeable odour has in most countries rendered
its use unpopular among practical men. This unpleasant smell
may be in a great measure removed by mixing it with powdered
charcoal or with half-charred earthy peat, or with a charred mix-
ture of clay and vegetable matter. Quick-lime is in some places
employed for the same purpose; but though the smell is thus got
rid of, a large portion of the volatile ammonia produced during
the decomposition of the manure is at the same time driven off by
the lime.
In general, night soil contains about three-fourths of its weight
of water, and when exposed to the air undergoes a very rapid de-
composition, gives off much volatile matter—consisting of am-
monia and carbonic acid, with sulphuretted and phosphuretted
hydrogen gases—and finally loses its smell.
The composition ef might soil, and consequently its value as a
manure, varies with the food, the age, the health, and with many
other circumstances. The excrements of a healthy man were found
by Berzelius to consist of
Water, ..... ............................... • - - - - - - 733
Albumen, .................................. ... ... 9
Bile, ............ ... ....................... ..... 9
Mucilage, fat, and other animal matters, ...... 167
Saline matter,........................ .......... ... 12
Undecomposed food, .............................. 70
1000
Of the excrement when freed from water 1000 parts left 132 of
ash, consisting of-
Carbonate of soda, .......................................... ....................... 8
Sulphate of soda, with a little sulphate of potash, and phosphate of soda, 8
Phosphate of lime and magnesia, and a trace of gypsum, .................. 100
Silica, ................................................ ........................... .. 16
132
There are various ways of using night soil. The most common
4
POUDRETTE–PREPARATION OF. 819
in this country is to mix it with coal ashes and other manures, and
in this form to apply it to the land. A less frequent but very
profitable method is to pour water upon it and then to use it in the
liquid form. In Flanders this method is much adopted in ordi-
nary field husbandry, and the nurserymen and market gardeners
around London employ it with remarkable success.
Poudrette.—In the neighbourhood of large towns, however, it
is dried and manufactured in various ways into a portable manure,
which is sold under the various names of humus, dried night soil,
and poudrette. There are various modes of preparing this arti-
ficial manure.
a. In the suburbs of Paris the night soil is placed in a large
shallow receiver, capable of holding a six months’ supply. It is
then allowed to ferment, and the liquid part is drawn off from time
to time into other receivers at lower levels. The sediments are
finally collected and dried, and the liquid parts are discharged into
the nearest stream.
In this state the fermented might soil has lost by far the largest
proportion of its ammonia, and is capable of yielding only 1% to
2% per cent. of nitrogen. *
b. Another method by which the disagreeable odour is more
speedily destroyed, is to mix the night soil with quick-lime and
then dry it. This method, however, drives off the ammonia per-
haps still more effectually, and thus renders the manure less valu-
able. -> -
c. To hasten the drying, some mix the solid part of the might
soil with burned gypsum, or with chalk, or with Dutch ashes,
pounded charcoal, and saw dust. In this way more of the nitro-
gen may be preserved, but the bulk and weight of the manure are
also increased, and often in a greater proportion. -
d. Night soil is most speedily and completely disinfected by
mixing it with animal charcoal, either from bones or from the prus-
siate of potash manufactories. It is also completely effected by
mixing it with animalized carbon, (p. 795) prepared by calcining
in a close retort a porous clay intimately mixed or impregnated
with vegetable or animal matter.
One of the best ways of quickly preparing a dry might soil, is
to mix it with one or other of these varieties of animal charcoal.
820 TAFFO.—COW DUNG.
The composition of any poudrette offered for sale, however, is not
to be depended upon, since there are so many different modes of
preparing it. The agricultural value of any sample can only be
determined by analysis.
The following table represents the composition of four different
varieties of dried night soil, offered for sale in Scotland, as deter-
mined in my laboratory.
1. 2. 3. 4.
Water, ....................... ........................ 20.04 15.12 13.97 27.46
Organic matter, (containing a little nitrogen)... 9.39 21.52 49.53 9.14
Ammonia,............................................. 0.53 2.25 p ?
Phosphates of lime, magnesia, and iron,......... 5.04 7.53 13.12 4.37
Carbonate of lime, ..... ............. ............ 22.62 19.80 2.56 6.89
Carbonate of magnesia, .......................... 0.90 * * gºmºmº
Gypsum, (sulphate of lime)... .................... 2.32 * *-*. *
Alkaline salts, ........................................ 1.33 9.27 12.35 7.10
Insoluble siliceous matter, ........................ 37.42 24.46 8.44 45.04
99.59 99.95 99.97 100.00
Taffo.—In China fresh night soil is mixed with clay and formed
into cakes, which when dried are sold under the name of taffo, and
form an extensive article of commerce in the neighbourhood of the
larger cities.
2°. Cow dung forms by far the largest proportion of the animal
manure which in modern agriculture is at the disposal of the prac-
tical farmer. It ferments more slowly than night-soil, or than the
dung of the horse and the sheep. In fermenting it does not heat
much, and it gives off little of an unpleasant or ammoniacal odour.
Hence it acts more slowly, though for a longer period, when ap-
plied to the soil.
The slowness of the fermentation of cow dung is ascribed, first,
to the large proportion of water, about 90 per cent, which it usually
contains; second, to the less perfect mastication which the food of
the cow undergoes; and lastly, to the smaller proportion of nitro-
gen present in it compared with horse dung.
The last of these reasons, to which we should be inclined to
ascribe the most importance, is not consistent with the analysis of
Boussingault, who found in the recent and dry dung of a milk
cow and of a horse respectively, the following proportions of water,
nitrogen, and Saline matter per cent.
COW DUNG—HORSE DUNG, 82I
Fresh dung. Dry dung.
Cow. Horse. Cow. Horse.
Water, ............... 90-60 75.31 tºº ſº
Nitrogen, ............ 0-22 0°54 2-3 2.2
Saline matter, ...... 1° 13 4°02 12-0 16-3
From this analysis it appears, that though the recent cow dung
contains more water than horse dung, yet that the dry matter of
the former is richer in nitrogen than that of the latter. Were
this generally the case, it ought, one would suppose, after becom-
ing a little drier, to ferment or be as warm as horse dung.
However this may be, the two circumstances—that the nitrogen
of the food is discharged chiefly in the urine—and that the cow
voids a much larger quantity of urine than the horse—incline me
to believe that cow dung must generally contain less nitrogen than
that of the horse, and that this is really one cause of its greater
coldness. The correctness of this opinion can only be tested by a
series of careful analyses, which I invite agricultural chemists to
undertake. At the same time it is proper to add, that the pecu-
liar state of combination in which the nitrogen exists in two bo-
dies, supposing the proportion in both to be the same, may modify
very much the rapidity of the decomposition they respectively un-
dergo in the same circumstances. -
Though fermenting with such apparent slowness, fresh cow dung
undergoes in forty days a loss of one-fifth of its solid matter (Gaz-
zeri). Though this result was observed in Italy, yet there is suf-
ficient loss in our climate also to make it worth the while of an
economical farmer to get his cow dung early into heaps, and to
shelter it as much as possible from the sun and air.
3°. Horse-dung is of a warmer nature than that of the cow. It
heats sooner, for reasons above stated, and evolves much ammonia.
Even when fed upon the same food the dung of the horse should
be richer than that of the cow, because of the large quantity of
urine the latter animal is in the habit of voiding.
In the short period of twenty-four hours, horse-dung heats and
begins to suffer loss by fermentation. If left in a heap for two or
three weeks scarcely seven-tenths of its original weight will remain.
Hence the propriety of early removing it from the stable, and of
mixing it as soon as possible with. Some other material by which
the volatile substances given off may be absorbed and arrested.
822 PIG's DUNG—SHEEP's DUNG.
The colder and wetter cow or pig's dung will answer well for this
purpose, or soil rich in vegetable matter, or peat, or Saw-dust, or
powdered charcoal, or any other absorbent substance which can
readily be obtained. If a chemical agent be preferred, moisten-
ed gypsum may be sprinkled among it, or diluted sulphuric acid.
There is undoubtedly great loss experienced from the general me-
glect of night-soil; but in most cases the dung of the horse might
also be rendered a source of much greater profit than it has hi-
therto been. -
4°. Pig's dung is still colder and less fermentable than that of
the cow. It is characterized by an exceedingly unpleasant odour,
which it imparts to the crops, and especially to the root crops
which are manured with it, Even tobacco, when manured with
pig’s dung, is said to be so much tainted that the leaves subse-
quently collected are unfit for smoking.” It is a good manure for
hemp and other crops not intended for food, but is best employed
in a state of mixture with the other mamures of the farm-yard.
The dung of pigs put up to fatten like that of the fatting ox is often
rich in nitrogen. A specimen examined by Boussingault was found
to contain per cent.
Recent. Dry.
Water,..................... 81 *-*
Nitrogen,... ............... 0-63 3.37
being richer in nitrogen even than horse-dung.
5°. Sheep's dung is a rich dry manure, which ferments more
readily than that of the cow, but less so than that of the horse. A
specimen examined by Zierl consisted of—
Water, ............................. ...... 68.0 per cent.
Animal and vegetable matter, ...... 19°3
Saline matter, or ash, .................. 12.7
100
Boussingault found in another specimen per cent.
Recent, Dry.
Water,....... ............. 63.0 º-
Nitrogen,......... & e º e º 'º e º & I'll 2.99
The food of the sheep is more finely masticated than that of the
cow, and its dung contains a little less water, and is richer in ni-
trogen; hence probably its more rapid fermentation. When crops
* Sprengel, Lehre vom Dünger, p. 38.
MANURE PRODUCED BY DIFFERENT ANIMALS. 823
are eaten off by sheep, their manure is more evenly spread over
the field, and is, at the same time, trodden in. When thus spread
it decomposes more slowly than when it is collected into heaps,
and the ammonia and other useful products of the decomposition
are absorbed in great part by the soil as they are produced. Those
soils, in which a considerable quantity of vegetable matter is al-
ready present, are said to be most benefited by sheep's dung, be-
cause of the greater readiness with which the volatile matters it so
soon begins to give off are absorbed by such a soil.
Sheep's dung, according to Sprengel, lengthens the straw of the
corn crops, and produces a grain rich in gluten—and unfit there-
fore for seed, for the manufacture of starch, or for the purposes of
the brewer and the distiller. It may be doubted, however, whe-
ther these can as yet be safely considered as the universal effects
of sheep's dung upon every soil, and when the animals are fed
upon every kind of food. It is by eating off with sheep that the
light soils of Norfolk are made to produce the fine sample of bar-
ley so highly prized by our brewers and distillers.
§ 13. Of the quantity of manure produced from the same kinds of
jood by the horse, the cow, and the sheep.
The carefully conducted experiments of Block give the follow-
ing as the total quantities of manure, solid and liquid, produced
from 100 lbs. of the different kinds of food by the cow, the horse,
and the sheep :-

Quantity of manure in lbs. produced by
f Water in
4 hº l & C e
From 100 lbs. O the Cow. the Horse. the Sheep. º
fresh. dried.] fresh. dried, fresh. dried.
Rye, ............... ... • * * * * * * * * * * * & e ... 212 53 | ... tº gº º 75
Oats, ...... .................... . . . . . . . 204 || 5l ... 49 75
*...* *}. 268 |18 |168|| 3 || 17 | 0 || 36 to a
chopped -
Hay. ................'.... 275 44 || 172 43 | 123 || 42 | do. do.
Potatoes, (containing 72 l
per cent. of wate). 87% | 1.4 & © e ... 38 || 13 | do. do.
Turnips, (containing 75 7 l. g
per cent of water), 37% | 6 84
Carrots, (87 per cent. of l.
water), 37} | 6 | ... * * * * * * * * * * * 84
Green clover, (79 per ct. 3. 1. l
of water), 65} | 9% 8% 86
after 8 days. after 3 weeks.
R; º (used for * 228 96 || 269 97
after 8 weeks.
206 95 54 to 64
824 FERTILIZING VALUES OF ANIMAL EXCRETIONS.
One important theoretical result is presented by this table—
that the manure voided by an animal contains very much less solid
matter than the food it has consumed. We shall presently see how
this fact is to be explained (p. 829), and, at the same time, what
light it throws upon the quality of the manure produced.
The most valuable practical results from the above experiments
al’e—
19. That for 100 lbs. of dry fodder the horse or the cow will
give on an average 216 lbs. of fresh, or 46 lbs. of dry manure—
the sheep 128 lbs. moist or 43 lbs, dry.
2°. That root crops, on an average give about half their weight
of fresh, or one-twelfth their weight of dry manure—the potato
giving more, and the turnip less.
3°. That green crops give about half their weight of fresh, or
one-eighth of dry manure.
It is to be observed, however, that the results in the above table
and the results we have drawn from it will be modified by the
kind of cattle kept and the mode of feeding adopted upon every
farm.
§ 14. Of the relative fertilizing values of different animal excretions.
1°. The theoretical value of different animal excretions calculat-
ed solely from the quantity of nitrogen which the specimens exa-
mined were found respectively to contain, is thus given by Payen
and Boussingault. The numbers opposite to each substance indi-
cate the weights of that substance which ought to produce an equal
effect with 100 lbs. of farm-yard manure in the recent and in the
dry states:—
Equal effects ought to be produced by
in the undried state, artificially dried,
Farm-yard dung,... ..... 100 lbs. 100 lbs.
Cow * tº º f tº e º e º g º & 125 ... 84 ...
Do. urine,.................. 9] ... 51 ...
Horse, ..................... 73 ... 88 ...
Mixed excrements of the
Pig, ........................ Ö3 ..., 58 ...
Horse, ..................... 54 ... 64 ...
Sheep, ........ ............ 36 ... 65 ...
Pigeon,..................... 5 ... 22 , , ,
Poudrette, ............ ... 10%... 44 .
Another variety, ......... 2(; , , 73 ...,
THEIR VALUE AFFECTIED BY MANY CIRCUMSTANCES. 825
Too much reliance is not in any case to be placed upon the
principle of classifying manures solely by the proportion of nitro-
gen they contain—much less can we depend upon the order of
value it assigns to substances, the composition of which is liable to
constant change from the escape of those volatile compounds in
which the nitrogen principally exists.
2°. A series of experiments made by Hermbstädt upon the
quantity of grain of different kinds, raised in the same circum-
stances by equal weights of different manures, gave the following
results:— -
Number of seeds reaped from
Manure applied. Wheat. Barley. Oats. Rye.
Ox blood, ... ............ 14 16 12% 14
Night soil,............... - 13 14% 13%
Sheep's dung, ......... 12 16 14 13
Human urine, ......... - 13% 13 13
Horse dung, ............ 10 13 14 ll
Pigeon dung,......... . . . - I 0 12 9
Cow dung,............... 7 11 16 9
Vegetable matter,...... 3 7 13 • 6
Unmamured, ............ tº- 4 5 4
If the results contained in this table were to be depended upon,
it would appear that, in so far as the quantity of the produce is
concerned, these manures severally exercise a special action upon
certain crops—that night-soil, for example, is most propitious to
rye, cow dung to oats, and sheep's dung to barley and wheat.
And the latter fact would seem at once to justify and to recom-
mend the eating off with sheep preparatory to either of the lat-
ter crops.
None of these kinds of manure, however, is constant in compo-
sition, and the following observations will satisfy you that implicit
reliance ought not to be placed either upon the relative practical
values of the different animal manures as they appear in the latter
table, nor on their theoretical values as exhibited in the former.
§ 15. Influence of circumstances on the quality of animal manures.
The quality of the droppings of animals considered as manures
is affected by a great variety of circumstances—such as
1°. By the kind of food upon which the animal is fed.—Thus
might Soil is more valuable in those countries and districts in which
much flesh meat is consumed, than where vegetable food forms
826 INFLUENCE OF EXERCISE, OF THE STATE OF GROWTH,
the principal diet of the people. Sprengel states, that in the neigh-
bourhood of Hildesheim the farmers give a higher price for the
house manure of the Lutheran than for that of the Roman Catholic
families, because of the numerous fasts which the latter are requir–
ed to observe.” That which is collected in the closets of the fa-
shionable restorateurs is more valuable than that of the barracks
around Paris.f
Every keeper of stock also knows that the manure in his farm-
yard is richer when he is feeding his cattle upon oil-cake, than
when he gives them only the ordinary produce of his farm; 12
loads of the dung of animals fed (while fattening) chiefly upon oil-
cake was found to give a greater produce than 24 loads from store
stock fed in the straw-yard. (Complete Grazier, sixth edition,
p. 103.)
“I proved by experiment many years ago that one ton of ma-
mure taken from a yard in which cattle were fed upon full turnips
with a portion of oil-cake and beam meal was worth three tons of
that (though apparently in equally good state) which was made in
a yard where young cattle were kept on straw during the might,
with a run out in the fields, getting a few turnip tops in the day.”
(Mr Grey of Dilston, Royal Agricultural Journal, iv. p. 212.)
2°. By the quantity of urine voided by the animal.-Upon the
unlike quantities of urine they produce appears to depend very
much the unlike richness of the dung of the horse and of the cow.
The latter animal, when full grown and not in milk, voids from 6
to 13 times as much urine as the former (p. 813); and though an
equal bulk of this urine is often poorer in solid matter, yet the en-
tire quantity contains much more than is present in that of the
horse. But if the cow discharges more in its urine it must void
less in its solid excretions. Hence, supposing the food of a full
grown horse and of a cow to be very nearly the same, the dung of
the former—the less urine-giving animal—must be the richer,
the warmer, and the more valuable—as it is really known to be.
3°. By the amount of evercise or labour to which the animal is
subjected.—The greater the fatigue to which an animal is subject-
ed the richer the urine is found to be in those compounds (urea
* Lehre vom Diinger, p. 142.
+ Boussingault, Economie Rurale, ii. p. 132.
AND OF THE OBJECT FOR WHICH THE ANIMAL Is FED. 827
chiefly) which yield ammonia by their decomposition (Prout). The
food of two animals, therefore, being the same, and other things
also being equal—the solid excretions will be richer and more fer-
tilizing in that which is kept in the stall or fold-yard, the urine in
that which is worked in the open air or pastured in the field. To
this cause also is to be attributed the fact, stated in Marshall’s Sur-
vey of Norfolk, “that the droppings of cattle after being driven are
less valuable as manure.”
4°. By the state of growth to which the animal has arrived.—
A full grown animal has only to keep up its weight and condition
by the food it eats. Every thing which is not necessary for this
purpose, therefore, it rejects either in its solid or in its liquid excre-
tions. A young animal, on the other hand, adds to and increases
its bone and muscle at the expense of its food. It rejects, there-
fore, a smaller proportion of what it eats. Hence the manure in
fold-yards, where young cattle are kept, is always less richer than
where full grown animals are fed.
5°. By the purpose for which the animal is fed.—Is it to be im-
proved in condition ? Then the food must supply it with the ma-
terials for increasing the size and strength of its muscles—with al-
bumen, or fibrin, or other substances containing nitrogen. In such
substances, therefore, or in nitrogen derived from them, the drop-
pings must be poorer, and as a manure less valuable.
Is the animal to be fattened 2 Then its food must supply fatty
matters, or their elements, of which nitrogen forms no part. Most
of the nitrogen of the food, therefore, may pass off in the excre-
tions, and hence the richest manure yielded at any time by the
same species of animal is that which is obtained when it is full
grown, and, being largely fed, is rapidly fattening.
Is the cow kept for its milk? Then the milk it yields is a daily
drain upon the food it eats. Whatever passes into the udder is
lost to the dung, and hence, other things being equal, the dung of
a milk cow will be less valuable to the farmer than that of a full
grown animal from which no milk is expected, or than that of the
same animal when it is only laying on fat.
6°. By the length of time during which the manure has been
kept.—In 24 hours, as we have seen, the dung of the horse begins
to ferment and to lessen in weight. All rich manures in like man-
828 CHANGES PRODUCED UPON THE FOOD
mer—the dung of all animals especially—decompose more or less
rapidly and part with their volatile constituents. The value we
assign to them to-day, therefore, will not apply to them to-morrow,
and hence the droppings of the same animal at the same age, and
fed in the same way will be more or less valuable to the farmer
according to the length of time during which they have been per-
mitted to ferment.
7°. Lastly. By the way in which the manure has been pre-
served.—The mixed dung of the farm-yard must necessarily be
less valuable where the liquid manure is allowed to run off—where
it is permitted to stand in pools and ferment—or where it has been
exposed to the washings of the rain. Twenty cart loads of such
dung may hasten the growth of the turnip crop in a less degree
than half the weight will do, where the manure has been sheltered,
or where the liquid has been carefully collected and returned upon
the heaps—-to hastem and complete their fermentation, and to sa-
turate them with enriching matter.
Since, then, the quality or richness of the dung of the same ani-
mal is liable to be affected by so many circumstances—it is obvi-
ous that no accurate general conclusions can be drawn in regard
to its precise fertilizing virtue when applied to this or to that crop
—or its relative fertilizing value when compared with equal weights
of the dung of other animals. The results obtained in one set of
analyses, as in that of Boussingault, or in one series of practical
experiments, as in that of Hermbstädt (p. 825), will not agree with
those obtained in any other—because the substances themselves
with which our different experiments are made, though called by
the same name, are yet very unlike in their chemical properties
and composition. *
§ 16. Of the changes which the food undergoes in passing through
the bodies of animals.
It is the result of long experience that vegetable matter is more
sensibly active as a manure, after it has passed through the body
of an animal, than if applied to the land in its unmasticated and
undigested state. In becoming animalized, therefore—as it has
BY PASSING THROUGH THE BODIES OF ANIMALS. 829
been called—vegetable substances have been supposed to undergo
some mysterious, because not very obvious or intelligible, internal
change, by which this new virtue is imparted to them. Yet the
change is very simple, and when explained is not more satisfactory
than it is beautiful.
You will recollect, as I have already stated to you (p. 824), that
the weight of dry manure voided by an animal is always considera-
bly less than that of the dry food eaten by it. Upon the nature
and amount of this loss which the food undergoes, depends the qua-
lity of the manure obtained.
This you will readily comprehend from the following statement:
1°. Every thing which enters into the body in the form of food
must escape from the body in one or other of three different forms.
It must be breathed out from the lungs, perspired by the skin, or
rejected in the solid or liquid excretions. We have already seen
(p. 263), that the function of the lungs is to give off carbon in the
form of carbonic acid, while they drink in oxygen from the air—
and that the quantity of carbon thus given off by a healthy man
varies from 5 to 13 or more ounces in the 24 hours. From the
skin also, carbon escapes along with a small and variable propor-
tion of saline matter. The weight of carbon given off by the skin
has not been accurately ascertained. Let us leave it out of view
for a moment, and consider solely the effect of respiration upon
the nature of the solid and liquid excretions.
Suppose a healthy man, taking a moderate degree of exercise,
to give off from his lungs 6 ounces of carbon in 24 hours, and to
eat during the same time 2 lbs. of potatoes, half a pound of beef,
and half a pound of bread. Then he has
Taken in his food Carbon. Nitrogen. Saline matter.
In the potatoes............ 1716 grs. 47 grs. 196 grs.
In the bread............ .. 1004 ... 34 ... 22 ...
In the beef ............... 790 ... 120 ... 35
3510 grs. 201 grs. 253 grs.
And he has given Off | 2625 grs.
in respiration
Leaving to be rejected
sooner or later in | 885 grs. 201 grs. 253 grs.
the excretions
In this supposed case, therefore, the carbon, nitrogen, and sa-
line matter were to each other nearly as the numbers
830 THE FOOD AND DUING OF THE HORSE COMPARED.
Carbon. Nitrogen. Saline matter,
35 - 2 * 2% in the food,
and as 9 - 2 * 2% in the excretions ;
or, in other words, the carbon being in great part sifted out of the
food by the lungs, the excretions are necessarily much richer in
nitrogen and in saline matter, weight for weight, than the mixed
vegetable and animal matters on which the man has lived.
But the immediate and most sensible action of animal and ve-
getable substances, as manures, depends upon the proportion of
nitrogen and saline matters they contain. This proportion, them,
being greater in the excretions than in the crude vegetables, the
cause of the higher estimation in which the former are held by the
practical farmer is sufficiently clear.
2°. In the above case I have supposed the allowance of food to
be such only as a person of sedentary habits would consume, and
the quantity of carbon given off from the lungs to be such as his
habits would occasion. But if the weight of carbon given off from
the lungs and skin together amount, as it often does, to 15 ounces,”
the quantity of food must be greatly increased beyond the quantity
I have stated, if the health and strength are to be sustained. By
such an increase of food—the carbon being removed by respira-
tion—the proportion of nitrogen and of saline matters in the ex-
cretions may be still further increased, or as manures they may
become still richer and more immediately fertilizing.
3°. In an experiment made by Boussingault upon a horse fed
with hay and oats—and of which both the food and the excretions
were carefully analysed, the following results were obtained:—
In 24 hours the horse consumed—
- Carbon. Nitrogen. Saline matter.
Hay, 16% lbs., containing ............ 45,500 grs. 1,500 grs. 8,960 grs.
Oats, 5 lbs.................. ..... ......... 15,000 650 1,180
Total in the food ... ..................... 60,500 2,150 10,140
And gave off from the lungs and skin 37,960
Leaving to be rejected in the excre- | 22,540 2,150 10,140
tions ................................ ...
while there was actually found in the | 22,540 1,770 10, 540
mixed dung.......... e e º e s - e s - e = e s e º
* Liebig estimates the quantity of carbon which escapes from the lungs and skin of a
healthy man, taking moderate exercise, at 1393 ounces (Hessian), or 15% ounces avoir-
dupois, in 24 hours.
Each containing about 14 per cent. of water-Annales de Chim, et de Phys., lxxi.
p. 136.
THE FOOD AND DUNG OF THE HORSE COMPARED. 831
In this case, then, the carbon, nitrogen, and Saline matter were
contained in the proportions of
Carbon. Nitrogen. Saline matter. -
28 - l - 5 in the food,
and of 10% tºº l º 5 in the dung;
the analysis of the dung itself proving that in passing through the
body of an animal, the food—
a diminishes very considerably in weight;
b loses a large but variable proportion of its carbon;
e but parts with scarcely any of its nitrogen and saline mat-
ter—and therefore -
d that the fertilizing virtues of the dung above that of the food
of animals—weight for weight—depends mainly upon the larger
proportion of these two constituents (the nitrogen and, the saline
matter) which the dung contains.
I have only further to remind you upon this subject, that the
state of combination also in which the nitrogen exists in the excre-
tions has a material influence in rendering their action more im-
mediate and sensible than that of unchanged vegetable matter. It
passes off for the most part in the form of urea and hippuric acid,
which are resolved into ammonia and its compounds more rapidly
than the albumen of the dried or even of the recent plant, and is
thus enabled sooner to exert an appreciable influence upon the
growing crop.
§ 17. Of farm-yard manure. Loss it undergoes by fermentation.
State in which it ought to be applied to the land.
The manure of the farm-yard consists, for the most part, of
cow’s-dung, pig's-dung, and straw, mixed and trodden together, in
order that the latter may be brought into a state of decomposition.
Where green crops are extensively grown and many cattle are
kept, horse-dung forms only a small proportion of the whole ma-
nure of the farm-yard.
On an average, the quantity of recent manure obtained in the
farm-yard amounts to a little more than twice the weight of the
dry food of the cattle and of the straw spread in the farm-yard or
in the stables (p. 824). That is to say, for every 10 cwt. of dry
fodder and bedding taken together, 20 to 23 cwt. of fresh dung
$32 STATE IN WEITCH FARM-YARD MANURE CAN BE
may be calculated upon. But if green clover or turnips (every
100 lbs. of which contain from 70 to 90 lbs. of water) be given to
the cattle, an allowance must be made for the water they contain
—the quantity of mixed manure to be expected being only 2 or
2} times the weight of the dry food and fodder.
But recent manure loses weight by lying in the farm-yard, The
moisture evaporates, and volatile matters escape by fermentation.
By the time that the straw is half-rotten this loss amounts to one-
fourth of the whole weight, while the bulk is diminished one-half.
If allowed to lie still longer the loss increases, till at length it may
approach to one-half of the whole, leaving a weight of dung little
greater than that of the food and straw which have been consumed.
The weight of common mixed farm-yard dung, therefore, obtained
from 10 cwt. of dry food and straw, at different periods, may be
thus stated approacimately—
10 cwt. of dry food and straw yield of recent dung 23 to 25 cwt.
At the end of six weeks,.......................... • * * e º e ge 21 ...
After eight weeks, . ..................................... 20 ...
When half-rotten, ......... e e º 'º & e = e º 'º $ 3 s e a s e º ºs e s e s e º e g s 15 to 17 ...
When fully rotten, ........................... ........... 10 to 13 ...*
These quantities are supposed to be obtained in the common
open farm-yards, with the ordinary slow process of fermentation.
An improved, quicker, or more economical mode of fermenting the
mixed dung and straw may be attended with less loss, and may
give a larger return of rich and fully rotten dung.
A knowledge of these facts shows clearly what is the most eco-
nomical form in which farm-yard manure can be applied to the
land. *
1°. The sooner the manure produced from a given quantity of
food and straw is ploughed in, the greater the quantity of organic
matter we add to the land. When the only object to be regarded,
therefore, is the general enriching of the soil, this is the most eco-
nomical and the most expedient form of employing farm-yard ma-
Illll’62.
2°. But where the soil is already very light and open, the plough-
* The most complete work now in existence upon the general subject of agricultu-
ral statics, is that of Hlubek, Die Ermährung der Pflanzen wºnd die Statik des Land-
battes. 6
MOST ECONOMICALLY APPLIED TO THE LAND. 833
ing in of recent manure containing much straw may make it still
more so, and may thus materially injure its mechanical condition.
In such a case the least of two evils must be chosen. It may be bet-
ter husbandry—that is, more profitable to the farmer—to allow
the manure to ferment and consolidate in the farm-yard, with the
certainty of a considerable loss, than to diminish the solidity of
the land by ploughing it in in a recent state.
3°. Again—in the soil, a fermentation and decay similar to that
which takes place in the farm-yard, will slowly ensue. The bene-
fit which generally follows from causing this fermentation to take
place in the field rather than in the open yard is, that the products
of the decomposition are taken up by the soil, and thus waste is in
a great measure prevented. But in very light and open soils, this
absorption of the products of decay does not take place so com-
pletely. The rains wash out some portions, while others escape
into the air, and thus by burying the recent manure in such soils,
less of that waste is prevented which if left in the open air it is
sure to undergo. It may even happen, in some cases, that the
waste in such a soil will not be greatly inferior to that which me-
cessarily takes place in the farm-yard. The practical man, there-
fore, may question whether, as a general rule, it would not be safer
in farming very light arable lands, to keep his manure in heaps
till it is well fermented, and to adopt those means for preventing
waste in the heaps themselves which science and practical skill
point out to him.
It may be regarded indeed as a prudent general maxim—
one, however, which must not be maintained in regard to any
particular tract of land in opposition to the results of enlightened
experience—that recent farm-yard manure (long dung) is not suit-
ed to very light soils, because it will render them still lighter, and
because in them the manure may suffer almost as much waste as
in the farm-yard;—and, therefore, that into such soils it should
be ploughed in the compact state (short dung), and as short a
time as possible before the sowing of the crop which it is intended
to benefit.
4°. But upon loamy and clay soils the contrary practice is re-
commended. Such soils will not be injured, they may even be
benefited by the opening tendency of the unfermented straw, while
3 G -
834 AFFECTED BY THE PUIRPOSE IT IS TO SERVE.
at the same time the products of its decomposition will be more
completely retained—the land consequently more enriched, and
the future crops more improved by it. On such soils, the recent
dung ploughed in, in the autumn, has been found more influential
upon the crops of corn which followed it, either in winter or in
spring, than a proportional quantity of well-fermented manure.
By such treatment, indeed, the whole surface-soil is converted into
a layer of compost, in which a slow fermentation proceeds, and
which reaches its most fertilizing condition when the early spring
causes the young corn to seek for larger supplies of food.
5°. But the nature of the crop he is about to raise will also in-
fluence the skilful farmer in his application of long or short dung
to his land. If the crop is one which quickly springs up, runs
through a short life, and attains an early maturity—he will apply
his manure in such an advanced state of fermentation as may en-
able it immediately to benefit the rapidly growing plant. In this
case also, it may be better to lose a portion by fermenting his ma-
nure in the farm-yard, than by applying it fresh, to allow his crop
to approach towards maturity before any striking benefit begins to
be derived from it.
6". So also the purpose for which he applies his manure will re-
gulate his procedure. In manuring his turnips the farmer has two
distinct objects in view. He wishes, first, to force the young plants
forward so rapidly that they may get into the second leaf soon
enough to preserve them from the ravages of the fly—and after-
wards to furnish them with such supplies of food as shall keep them
growing till they have attained the most profitable size. For the
former purpose fermented manure appears to be almost indispen-
sable—if that of the farm-yard is employed at all—for the latter,
manure in the act of slow and prolonged decomposition, is the
most suitable and expedient.
It is because bone-dust, especially when fermented or dissolved in
sulphuric acid, is admirably adapted for both purposes, that it has
become so favourite a manure in many districts for the turnip crop.
The gelatine of the outer portions of the fragments of bone soon
heats, ferments, and gives off substances by which the young plant
is benefited—while the gelatine of the interior of the bone decays,
little by little, so that during the entire season this manure con-
4
TOP-DRESSING WITH FERMENTING MANURES. 835
tinues to feed the maturing bulb with the constituents both of the
organic and of the inorganic portions of the bone. Rape-dust,
when drilled in, acts in a similar manner, if the soil be sufficiently
moist. Its effects, however, chiefly from its containing less earthy
matter, are not so permanent as those of bones.
The considerations I have now presented will satisfy you that
the disputes which have prevailed in regard to the use of long and
short dung have arisen from not keeping sufficiently distinct the
two questions—what is theoretically the best form in which farm-
yard dung can be applied in general?—and what is theoretically
and practically the best form in which it can be applied upon this
or that soil, to this or to that crop, or for this or that special object 2
§ 18. Of top-dressing with fermenting manures.
If so large a waste occur in the farm-yard where the mamure is
left long to ferment—can it be good husbandry to spread ferment-
ing manure as a permanent top-dressing over the surface of the
fields 2 This, also, is a question in regard to which different
opinions are entertained by practical men.
That a considerable waste must attend this mode of application
there can be no doubt. Volatile matters will escape into the air
and saline substances may be washed away by the rains, and yet
there are many good practical farmers who consider this mode of
applying such manure to be in certain cases as profitable as any
that can be adopted. Thus—
1". It is common in spring to apply such a top-dressing to old
pasture or meadow lands, and the increased produce of food in the
form of grass or hay is believed, in many places, to be at least
equal to what would have been obtained from the same quantity
of manure employed in the raising of turnips. Where such is
really the case experience decides the question, and pronounces
that, notwithstanding the loss which must occur, this mode of ap-
plying the manure is consistent with good husbandry. But if the
quantity or market value of the food raised by a tom of manure ap-
plied in this way is not equal to what it would have raised in the
form of turnips and corn, then it may as safely be said that the
most economical method of employing it has not been adopted.
But theory also throws some interesting light upon this question.
836 BONES OR RAPE-DUST ALONE NOT SUFFICIENT
Old grass lands can only be manured by top-dressings. And
if they cannot continue, and especially such as are meadowed, to
yield an average produce unless there be now and then added to
the soil some of those same substances which are carried off in the
crop, it appears to be almost necessary that farm-yard dung should
now and then be applied in some form or other. It is true that
hay or straw or long dung contains all the elements which the grow-
ing grass requires, but if spread on the surface of the field and
there allowed to ferment and decay, the loss would probably be
still greater than when, for this purpose, it is collected into heaps
or strewed in the farm-yard. Thus the usual practice of laying
on the manure in a highly fermented state may be the most eco-
nomical.
2°. Again, where the turnip crop is raised in whole or in part
by means of bones only, of rape-dust, or of other artificial manures,
as they are called, it is usual to expend a large proportion of the
farm-yard dung in top-dressing the succeeding crop of clover.
Thus the land obtains two manurings in the course of the four
years' rotation—bones or rape-dust with the turnips—and ferment-
ed dung with the clover. This second application increases the
clover crop in some districts one-fourth, and the after-crop of wheat
or barley very considerably also:
Here, also, it is clear, that if manure be necessary to the clover,
it can only be applied in the form of a top-dressing. But why is
it necessary—as experience says it is—and why should farm-yard
manure, which is known to suffer waste, be applied as a top-dress-
ing rather than rape-dust, which in ordinary seasons is not so
likely to suffer loss? I offer you the following explanation:—
If you raise your turnip crop by the aid of bones or rape-dust
alone, you add to the soil what, in most cases, may be sufficient to
supply nearly all the wants of that crop, but you do not add all
which the succeeding crops of corn and clover require. Hence if
these crops are to be grown continuously, and for a length of time,
some other kind of manure must be added—in which those neces-
sary substances or kinds of food are present which the bones and
rape-dust cannot supply. Farm-yard manure contains them all.
* Such is the case upon some of the farms in the Vale of the Tame (Staffordshire),
where the turnips are raised With rape-dust only, and wheat follows the clover.
TO SUPPLY ALL THE WANTS OF A ROTATION. 837
This is within the reach of every farmer. It is, in fact, his natu-
ral resource in every such difficulty. He has tried it upon his
clover crop in the circumstances we are considering, and has neces-
sarily found it to answer. Instead of laying it upon his clover he
might, indeed, have manured the corn crops which succeeded his
turnips, but then, in a four course rotation, his manure would have
been less equally divided among his crops than when applied upon
the clover, which is his third crop since the manure was put in for
his turnips. - -
Thus to explain the results at which he has arrived in this spe-
cial case, chemical theory only refers the practical man to the ge-
neral principle upon which all scientific manuring depends—that
he must add to the soil sufficient supplies of everything he carries
off in his crops—and, therefore, that without some such dressing
as he actually applies to his clover crop, he could not long con-
tinue to grow good crops of any kind upon his land, if he raise his
turnips with bones or rape-dust only.
It might, I think, be worthy of trial, whether the use of the fer-
mented dung for the turnips, and of the rape-dust for top-dressing
the after-crops, would not, in the entire rotation, yield a larger
and more remunerating return.
3. But experience has shown that top-dressing with fermented
manure is more advantageous than ploughing it in, in cases to
which reasoning like the above does not apply. Thus in growing
peas upon the sandy loams of Prussia, Von Thaer states that “re-
peated comparative experiments made during several seasons have
satisfied him that dung, whether rotten or fresh and long, when
spread upon the land after the sowing of peas, is not only more
advantageous to the crop then in the ground, but is also more
favourable to the growth of the succeeding corn than if it had been
buried by the plough.” And further, that “experience had de-
monstrated the correctness of this opinion in a manner so striking
as to destroy all those theoretical principles by which it might seem
to be contradicted.”
In this case of Von Thaer's I am inclined to ascribe the superi-
ority of top-dressing to the mechanical condition of the soil.
* Von Thaer, Principes Raisonnés d'Agriculture, second edition, ii. p. 386, quoted
in British IIusbandry, ii. p. 218,
838 IMPROVEMENT OF THE SOIL BY IRRIGATION.
It was naturally light enough for peas and corn. To plough in
the manure would make it still lighter. In spite of the loss by
exposure to the air, therefore, it was not only more profitable, but
was in reality better husbandry, under the circumstances, to spread
it over the surface of the land.
§ 17. Of the improvement of the soil by irrigation.
Irrigation, as it is usually practised in our climate, is only a more
refined method of manuring the soil. In warm climates and in
very dry seasons, in which the parched plant would wither and die
unless a constant supply of water were artificially afforded to it,
irrigation may act beneficially by merely yielding this supply to
the growing crops; but in our latitudes only a small part of its
beneficial effects can be ascribed to this cause. It is to pasture
and meadow lands almost alone that irrigation is applied by British
farmers, and the good effect it produces is to be explained by a re-
ference to various natural causes.
1°. If the water be more or less muddy, bearing with it solid
matter which deposits itself in still places, the good effects which
follow its diffusion over the soil may be ascribed to the layer of
visible manure which it leaves everywhere behind it. Thus the Nile
and the Ganges fertilize the lands over which their annual floods
extend, and in this way some of our smaller streams improve the
fields over which they either naturally flow or are artificially led.
2°. Or if the water hold in solution, as the liquid manures of
the farm-yard do, animal or vegetable substances on which plants
are known to feed, then to diffuse them over the surface is a simple
act of liquid manuring, from which the usual benefits follow. Such
is the irrigation practised in the neighbourhood of our large towns,
where the contents of the common sewers are discharged into the
waters which subsequently spread themselves over the fields.” In
so far also as any streams can be supposed to hold in solution the
washings of towns or of higher lands—and there are few which
are not more or less impregnated in this manner—so far may their
beneficial action, when employed for purposes of irrigation, be as-
cribed to the same cause. -
* For an interesting account of the effects of such irrigation in the neighbourhood
of Edinburgh, see Stephens, on Irrigation and Draining, p. 75.
IMPROVEMENT OF THE SOIL BY IRRIGATION. 839
3°. But spring waters which have run only a short way from
their source are occasionally found to be valuable irrigators. In
such cases also, the good effect may be due in whole or in part to
substances held in solution by the water (p. 53.) Thus, in lime-
stone districts, and especially those of the mountain lime-stone for-
mation (p. 473)—in which copious springs are not unfrequently
met with—the water is generally impregnated with much carbon-
ate of lime, which it slowly deposits as it flows away from its source.
To irrigate with such water—which in some parts of England is
extensively done—is, in a refined sense, to lime the land, and at
the same time to place within the reach of the growing plants an
abundant supply of this substance, in a form in which it can readily
enter into their roots.”
4°. In other districts, again, the springs and mountain streams
contain gypsum and common Salt, and sulphate of soda and sulphate
of magnesia, and soluble silicates, and thus are capable of impart-
ing to plants many of those inorganic forms of matter, without
which, as we have seen, they cannot exhibit a healthy growth.
The composition of our rivers and hill streams differs very
much. Some contain more and some less of this mineral matter.
Some are richer in lime, some in alcaline matter, and some in
soluble silica. There is scarcely a stream which traverses our
country that would not improve the grass lands upon its borders if
made to flow regularly and skilfully over it, but the kind and
amount of benefit to be derived from it would be modified by the
kind and proportion of the mineral substances contained in it.
The following table shows the composition of the waters of four
streams taken in comparatively dry weather. The three former
are on the eastern side of Berwickshire—the last in the county
of Durham. They contained respectively in an imperial gallon,
as determined in my laboratory,
From the From the From Biglaw. From the
River Ale. River Eye. Burn. River Wear.
Organic matter,............ 1.75 l'64 2.58 0-92 alkaline
Potash, ..................... l'68 0.80 0.72 | l'50 sulphates
Soda, ........................ tº- 0°44 l'94 &chlorides.
Gypsum,......... . ......... 0-6.[ ] '46 2.94 ()'88
Carbonate of lime,......... 5'28 3'48 7.32 7-92
magnesia, ... l'00 l'?4 3°64 2.04
* Some of the water used in the well-known scientific irrigations at Closeburn Hall,
in Dumfriesshire, appears to have been impregnated with lime, See Stephens, p. 43.
840 THE WATER SHOULD NOT BE STAGNANT.
« . From the From the From Biglaw From the
River Ale River Eye. Burn. River Wear,
Chloride of magnesium, 1-82 0-80 1:25 -
Oxide of iron, ............ 0.56 0°48 0-60 - 0°56
Sulphuric acid, . .......... l'44 0'98 1-80 0-06
Chlorine, .................... (): 36 0-70 1.65 1 - 10
Silica,........................ 0-24 O'08 0.32 1.20
14-77 12-10 24-76 17:08
This table illustrates the three propositions I have above stated—
a. That the waters of some streams are much richer in mineral
matter than those of others. ".
b. That all contain traces of nearly every substance which plants
require. Phosphoric acid is the only mineral food of plants which
was not sought for in these waters. According to Sprengel it
occurs in minute quantity in many of our little streams, and ac-
cording to Graham it can be detected in the water of the London
wells, which are sunk to the London clay.
c. That some are richer than others in lime, magnesia, or pot-
ash, and consequently that the effects of these waters must be dif-
ferent, when made to flow over the land.
4°. Again, it is observed that the good effects of irrigation are
produced only by running water—coarse grasses and marsh plants
springing up when the water is allowed to stagnate.” This is
explained in part by the fact that a given quantity of water will
soon be deprived of that portion of matter held in solution, of
which the plants can readily avail themselves, and that when this
is the case it can no longer contribute to their growth in an equal
degree. -
But there is another virtue in running watter, which makes it
more wholesome to the living plant. It comes upon the field
charged with gaseous matter, with oxygen and nitrogen and car-
bonic acid in proportions very different from those in which these
gases are mixed together in the air (p. 52). To the root, and to
the leaf also it carries these gaseous substances. The oxygen is
worked up in aiding the decomposition of decaying vegetable mat-
ter. The carbonic acid may be absorbed by and may feed the
plant. Let the same water remain on the same spot, and its Sup-
ply of these gaseous substances is not only soon exhausted, but it
* Low’s Elements of Agriculture, 3d edition, p. 472.
RUNNING WATER, CONVEYS GASEOUS FOOD. 841
becomes charged with soluble organic substances, which are not
grateful to the growing plant. But let it flow over the field, ex-
posing every moment a new surface to the moving air, and it sucks
in oxygen again from the atmosphere, it gives off any noxious
gases it may have taken up from the soil, and at the same time the
organic substances it holds in solution are changed and deprived
of their unwholesome properties. Such are some of the reasons
why it is of so much consequence to keep water in motion when
it is conveyed upon the land. Allow it to stagnate over the finer
grasses, and they soon find themselves in circumstances in which
it is not consistent with their nature to exhibit a healthy growth.
They droop, therefore, and die, and are succeeded by new races,
to which the wet land is more congenial.
5°. It is known also, that even running water, if kept flowing
without intermission for too long a period, will injure the pasture.
This is because a long immersion in water induces a decay of ve-
getable matter in the soil which is unfavourable to the growth of
the grasses—producing chemical compounds which are not natu-
rally formed in those situations in which the more valuable grasses
delight to grow, and which are unwholesome to them. Although,
therefore, the water continues to supply those various kinds of food
by which the grasses are benefited, yet it becomes necessary to with-
draw it for a time, that air may be admitted, and injurious after-
consequences avoided,
6°. Lastly.—Irrigation is most beneficial where the land is well
drained beneath—where the water, after the irrigation is stopped,
can sink and find a ready outlet. The same benefits indeed flow
from the draining of irrigated as from that of arable land. The
soil and subsoil are at once washed free of any noxious substances
they may naturally contain, or may have derived from the crops
they have grown, and are manured and opened up by the water
which passes through them. As the water descends also, the air
follows it, to change and mellow the under-soil itself.
Such are the main principles upon which the beneficial action
of irrigation depends, and they appear to me satisfactorily to ac-
count for all the facts upon the subject with which I am acquainted,
I pass over the alleged beneficial action of water in keeping the
temperature of irrigated, or rather of flooded fields, from sinking
842 A GOOD DRAINAGE NECESSARY,
too low. As irrigation is practised in our islands, little of the good
done to watered meadows can be properly attributed to this cause.
I have now drawn your attention to the most important and
readily available means, mechanical and chemical, by which the
soil is to be improved. Let us next study the products of the
soil—their composition, their differences—the purposes they are
intended to serve in the feeding and nourishment of animals—and
how these purposes may be most completely and most economically
fulfilled.
P A RT IV.
ON THE PRODUCTS OF THE SOIL, AND THEIR
|USE IN THE FEEDING OF ANIMALS.
LECTURE XXII.
Of the produce of the soil. Average produce of England and Scotland. Circum-
stances by which the produce of the land is affected. Influence of climate, of sea-
son, of soil, of the kind and variety of crop, of the method of culture, of the kind
and quantity of manure, and of the course of cropping. Theory of the rotation of
crops. Why lands become tired of clover (clover-sick) and other special crops.
Theory of fallows. Composition of wheat—proportion of bran and fine flour.
Composition of the bran and of the flour. Influence of soil, climate, variety, mode
of culture, and kind of manure on this composition. Of barley—its composition,
effects of germination upon. Composition of oats, rye, rice, maize (Indian corn),
and buckwheat. Alleged influence of manure on the proportion of gluten contained
in wheat and other species of corn. .
HAVING now considered the most important of those means by
which the soil may be improved, it will be proper to direct our at-
tention to the produce of the land—to the chemical nature of the
crops you raise, to the differences which exist among them, and to
the purposes they are fitted to serve in the feeding of man and
other animals. -
Agricultural products are of three distinct kinds.
1°. Such as are directly reaped from the soil in the form of
corn, potatoes, hay, &c.
2°. Such as are the result of a kind of natural process of manu-
facture, by which the direct produce of the soil is more or less eco-
nomically converted into the beef and mutton of the feeder of stock.
3°. Such as are the results of a further conversion at the hands
of the dairy farmer, and are sent to market in the form of butter
and cheese.
Thus three distinct topics of consideration present themselves in
connection with the produce of the soil, the nature of the imme-
diate products themselves—the economy of the feeding of stock—
and the preparation of butter and cheese. We shall study these
several topics in their natural order. -
§ 1. Of the maximum or greatest possible, and the average or
actual, produce of the land.
There is a wide difference in most countries between the actual
846 MAXIMUM AND AVERAGE PRODUCE
amount of food produced by the land, and that which, in the most
favourable circumstances, it would delight to yield.
An imperial acre of land in our island has been known to yield of
Wheat, ........................ 80 bushels.”
Barley, ................... .... 80 ...
Oats, ... ....................... 100 ...f
Indian corn, .................. 170
Beans, ........................ 70 ...
Potatoes, ................... ... 30 tons.
Turnips,........................ 60 ...i.
The average produce of the land, however, is far below these
quantities. It is not easy to arrive at a tolerable approximation
even to the true average produce of the island. Mr Macculloch
estimates that of
Wheat at 26 bushels an acre.
Barley at 32
Oats at 36
Sir Charles Lemon gives for the average produce of all Eng-
* “ Brigg, Lincolnshire.—I sowed Fullard's celebrated white spring wheat on the
8th of March. The crop averaged at the rate of 10 quarters per acre—four roods to
the acre. “T. SPRING...”
See also Note, p. 851.
In the county of Middlesex the produce of wheat varies from 12 to 68 bushels—
of barley from 15 to 75—and of oats from 32 to 96 bushels.-Middleton’s View of
the Agriculture of Middlesex, 1798, pp. 176, 183, and 188.
The large money returns obtained from an acre of land by the market gardeners near
London afford no fair criterion either of what the land of an entire farm may be made
to produce in money, or of the actual amount of human food which it may be possible
to grow upon it. Mr Colman states that the returns from an acre in one case, as
given to him on the spot, were
Radishes,............. . . . . . . . . . . . . . . L. 10
Cauliflowers, ...... .............. 60
Cabbages, ........................ 30
Celery, 1st crop, .................. 50
2d crop, ................. 40
Endive, ............ .............. 30
E.220
This is a large money return ; but the price of such articles is very variable, and the
Sum throws no light on the possible maximum produce of a richly cultivated soil.
ºf American Cultivator, 1843, p. 123. Though these large crops are occasionally
obtained in the United States, yet the average yield, I believe, does not exceed 25 or
30 bushels,
i: Perhaps this is not the maicinum.—In the Second Report of the Royal Agricul-
tural Improvement Society of Ireland, p. 57, a crop of turnips is mentioned, which
weighed 56 tons—tops and bulbs amounting together to 76 tons,
OF THE LAND IN GREAT BRIT AIN. 847
land, and for the highest and lowest county averages, the following
numbers:–
Average for Highest cº Lowest
all England county average county average
in bushels. in bushels. in bushels.
Wheat............ 21 26 Nottinghamshire. 16 Dorset.
Barley. ....,...... 32} 40 Huntingdon. 24 Devon.
Oats, ............ 35% 48 Lincolnshire. 20 Gloucester.
Potatoes,......... 241 360 Cheshire. 100 Durham.
While in Scotland, according to Mr Dudgeon, the average pro-
duce of corn is—
Good land. Lighter land.
Wheat..... ...... 30 to 32 bushels. 22 to 26 bushels.
Barley,............ 40 to A4 ... 34 to 38
Oats,............... 46 to 50 ... 36 to 43
If these numbers of Sir Charles Lemon and of Mr Dudgeon
are to be depended upon, the averages for the whole island can-
not be far from
Wheat, ..................... 24 bushels.
Barley, .............. ...... 34
Oats, ... . ...... 37
Rye, ... . . . . . . . . . . . . . 25 . . .
Potatoes, . ......... ...... 6 tons.
Turnips, .................... 10 ...
Though even these, especially in regard to the root crops, must
be considered as in a considerable degree hypothetical.”
In other countries similar differences prevail between the maxi-
mum and average crops. In the United States of America, for ex-
ample, a single acre has been known to yield nearly 200 bushels
of Indian corn, though the average produce does not exceed 25
bushels per imperial acre. *
What is the cause of these striking differences between the maxi-
mum produce of certain parts of a country, and the average pro-
duce of the whole? Are such differences necessary and unavoid-
able 2 Can the less productive lands not be made to yield a larger
return ? Can the naturally poor be made by art to yield crops
equal to those of the naturally rich P Can the large crops of the
richer districts not be further increased, and their amount kept up
for an indefinite succession of seasons?
* In 1821, Mr Wakefield estimated the average produce of wheat in all England
at 17 bushels only–Devonshire producing an average of 20, and the lands near the
coast of Kent, Norfolk, Suffolk, and Essex, 40 bushels per acre. At present the ave-
rage of the rich state of Ohio in the United States does not exceed 15 bushels of wheat.
848 INFLUENCE OF CLIMATE, SEASON, AND SOIL.
These interesting questions direct us to the true foundation of
all agricultural improvement. The answer of skill and science is,
that, though all circumstances cannot as yet be controlled, and
differences to a certain amount are therefore unavoidable, yet that
means are already known by which the fertility of the richer lands
may be maintained or increased and the crops of the less productive
indefinitely enlarged.
§ 2. Of the circumstances—climate, season, soil, &c.—by which
the produce of food is affected.
The quantity of food produced by a given extent of land is af-
fected by the climate, by the season, by the soil, by the nature of
the crop, by the variety sown or planted, by the general method
of culture, by the kind and quantity of manure employed, and by
the rotation or course of cropping that is adopted.
1°. Climate.—That the warmth of the climate, the length of the
summer, and the quantity of rain that falls, influence in a remark-
able degree the amount of food which a district of country is fitted
to raise, is familiar to every one. The warmth of the equatorial
regions maintains a perpetual verdure, while the short northern
summers afford only a few months of pasture to the stunted cattle.
The difference of latitude between the extreme ends of our island
produces a similar difference, though in a less degree. The almost
perennial verdure of the southern counties cannot be hoped for in
the north of Scotland, and yet the corn and turnip crops of the
eastern parts of Ross-shire are equal to those of the most favour-
ed districts of Britain. Is this to be regarded solely as the triumph
of skill and industry over the difficulties presented by nature?
2°. Season.--The influence of the seasons, wet or dry, warm or
cold, has been observed by the farmer in all ages, and it cannot be
entirely overcome. The heavy crop of this year may not be reap-
ed again on the next, because an unusual cold may arrest its
growth. And yet intelligence, skill, and good husbandry will do
much even here. The moreskilful the farming, the fewer the number
of failures which the intelligent man will have occasion to lament,
and the greater the attention which is paid to the mechanical and
physical condition of the soil, the less will be the influence of a
change of season on the average produce of the land.
3°. Soil-Diversity of soil is held to be a sufficient reason for
3
OF THE KIND OF CROP AND THE WARIETY OF SEED. 849
large differences both in the kind and in the weight of the crop.
A poor sand is not expected to give the same return as a rich clay.
Yet in regard to the capabilities of soils under skilful management,
practical agriculture has yet much to learn.
Are there any methods hitherto little tried by which soils of known
poverty may be compendiously and cheaply treated, so as to produce
a greatly larger return ? Science says that there are, and she points
to a wide field of experimental research, by the diligent culture of
which this great result will hereafter be generally attained. Into
a poor or exhausted soil introduce those substances which a given
crop requires, and if the soil be otherwise properly treated and the
climate favourable, the crop may be expected to grow. Such is
the simple principle, under the guidance of which agricultural
practice may hope to overcome the influence of diversity of soil.
4°. Kind of crop—The amount of food, either for man or beast,
which a given field will produce, depends considerably upon the
kind of crop which is grown upon it. Thus a crop of 30 bushels
of wheat will yield only about 1400 lbs. of fine flour, while a crop
of 6 tons of potatoes will give about 3500 lbs. of an agreeable,
dry, and mealy food. Thus the gross weight of food for man is
in the one case 2% times what it is in the other. In like manner,
it is said, in the publications of the Board of Agriculture, that
a crop of clover, of tares, of rape, of potatoes, turnips, or cabbages,
will furnish at least thrice as much food for cattle as one of pas-
ture grass of medium quality.”
5°. Variety of seed sown.—The variety of seed sown has also
an important influence on the amount of produce which is reaped.
I do not refer to the well known necessity of changing the seed if
the same land is to continue to yield good crops—but to the ge-
neral fact that two varieties of the same species will often yield
very unlike weights of corn, of turnips, or of potatoes. I may
quote as an illustration the experiments of Colonel Le Couteur
upon wheat. He found, on the same soil and under the same
treatment, that the varieties known by the name of the White
downy and the Jersey Dantzic yielded respectively:
Grain. Weight ºff bush. Straw. Fine flour. Fine do. 35 cent.
White downy 48 bush. - 62 lbs. - 4557 lbs. - 2402 lbs. - 803 lbs.
Jersey Dantzic 43% bush. - 63 lbs. - 4681 lbs. - 2161 lbs. - 79.3 lbs.
* Loudon's Encyclopædia of Agriculture, p. 910.
3 H
S50 INFLUENCE OF THE METHOD OF CULTURE.
while on a different soil and treated differently from the above, two
other varieties yielded—
Grain. Weight iſ bush. Straw. Fine flour. Fine do. 5 cent.
Whittington 33 bush. .. 61 lbs. - 7786 lbs. - 1454 lbs. - 725 lbs.
IBelle-W
*Y". 52 bush. - 61 lbs. - 5480 lbs. - 2485 lbs.” - 78, Ibs.
Talavera
In each of these cases, therefore, and especially in the last, a
striking difference presented itself both in the absolute and in the
relative weights of grain and of straw reaped under precisely simi-
lar circumstances, by the use of different varieties of the same spe-
cies of seed. Nor are the above by any means extreme cases. In
the same field I have known the Golden Kent and the Flanders
Red varieties, sown in the same spring, to thrive so differently,
that, while the former was an excellent crop, the latter was almost
a total failure. It will require a very refined chemistry to explain
the cause of such diversities as these.
§ 3. Influence of the method of general culture, of the kind of ma-
nuring, and of the rotation followed, upon the produce of food.
In addition to the circumstances above alluded to, the quantity
of food that is raised depends very much upon the method of cul-
ture which is adopted. Thus, in land of medium quality, our
opinion in regard to the quantity of food it is likely to yield would
be greatly affected by the answers we should obtain to the follow-
ing questions:—
1°. Is the land in permanent pasture, or is it under the plough 2–
With the exception of rich pastures, it is said that land, under clo-
ver or turnips, will produce three times as much food for cattle as
when under grass. If such a green crop then be made to alternate
with one of corm, the same land would every two years produce as
much food for stock as it would during three years if lying in grass
—besides the crop of corn as food for man, and of straw for the
production of manure.
This statement may possibly be a little exaggerated, or may re-
present truly the comparative produce of food in special cases only
—yet there seems sufficient reason for believing, as a general rule,
that a very much larger amount of food may be reaped from land
under arable culture, than when laid away to permanent pasture.
* Journal of the Royal Agricultural Society of England, I., p. 123.
( INFLUENCE OF THE METHOD OF OULTURE. ' 85I.
2°. What kind and quantity of manure are applied ?–The influ-
ence of manure is so generally recognised as well as that of some
kinds of manure above others, that I need not here dwell upon it.
I insert, however, the following extract from a letter by Mr Blon-
del of Frie Baton, in Guernsey, regarding a large crop of wheat,
as a very pertiment illustration. -
“The field on which the wheat was grown was let by me, in
1839, for five years, having been fifteen years in lucerne. My
tenant ploughed it up; but he neglected it so much during the
whole term of the lease that he barely obtained from it sufficient
to pay the rent; and many persons who were not aware of the na-
ture of the soil, seeing the badness of the crops, declared the land
worthless. When, however, on the expiration of the lease, in 1844,
I obtained possession of the field, I was determined to show that
it was owing to the want of manure and proper management, and
not to the quality of the soil, that it was unproductive. A part of
the field being wet, I drained it; and then, manuring it well with
sea-weed ashes, and stable-dung, I sowed it with parsnips and po-
tatoes, of both of which I had a good crop. In the autumn of the
same year I again manured a VERGEE, or Guernsey acre, of this
field, partly with sea-weed ashes and partly with guano, and sowed
it with 70 lbs. Guernsey weight, or 77 lbs. English, of red wheat;
and the crop yielded as follows: 535 sheaves, which gave 2675
lbs, of straw, and 1626 lbs. of grain, equal to 9 quarters and 23
bushels. The land is a stiff heavy loam.” -
3°. In what way is the manure applied ?–But much depends also
upon the manner in which the manure is expended, or the kind of
crop to which it is applied.
I have already (p. 837) directed your attention to the loss which
must necessarily be sustained by top-dressing with farm-yard ma-
nure, and yet how, in certain modes of cropping and manuring the
land, it may be not only advisable but necessary to do so. Yet the
comparative return of food obtained from the use of such manure
* “102 lbs. Guernsey are equal to 112 lbs. English ; and the Guernsey quarter bears
the same proportion to the imperial as the Guernsey acre does to the English ; con-
sequently the above produce of 9%. Guernsey quarters to the VERGEE or acre, is equi-
valent to 9% imperial quarters to the English acre.” See, note p. 846.
852 AND OF THE MODE OF APPLYING THE MANURE,
when applied as a top-dressing to grass land for instance, and
when buried with the turnip crop in the usual manner, is very un-
like.
Thus, suppose an acre of grass land, of such a quality as to pro-
duce annually without manure 13 tons of hay, to be top-dressed
every spring or autumn with 5 tons of farm-yard manure per acre
—and suppose another acre of the same land in arable culture to
be manured for turnips with 20 tons of farm-yard manure at once.
Then the grass land, by the aid of the manure, would not produce
more than double its matural crop, or 2% tons an acre, that is, 10
tons of hay in the four years. This, I believe, is making a large
allowance for the effect of the manure.
But the arable land, in the four years, if of the same quality,
may be expected to produce— g -
Turnips,...... . . . ..................... 20 tons.
Barley, ..... ........................... 36 bushels.
Clover, .... ........................... 24 tons.
Wheat, ..... ........................... 28 bushels.
Besides upwards of 4 tons of straw.
In all these taken together there must be much more food than
in the ten tons of hay.
If we consider the money profit, however, to the farmer, the re-
sult may be different. The cost of raising the ten tons of hay, ex-
clusive of rent, may be reckoned at one-half the produce, and of
the several crops in the four years' rotation at three-fourths of the
produce. We thus have for the clear return or profit to the far-
mer—exclusive of the interest of his capital, which forms part of the
expense of raising the crops—
In the one case, In the other case,
half the produce. a fourth of the produce.
5 tons of hay. 5 tons of turnips.
9 bushels of barley.
# ton of clover.
7 bushels of wheat.
l ton of straw.
Let the clover and the straw together equal in value only one
ton of the hay, and the money value in the two cases will stand as
follows:—
YAND IN GRASS MAY BE THE MORE PROFITABLE. 853
- L. S. d
Hay, 4 tons, at L. 5, := 20 0 0
Turnips, 5 tons, at 10s. = L.2 10 0
Barley, 9 bush., at 4S. = H 16 0
Wheat, 7 bush., at 7s. = 2 9 ()
6 15 0
Leaving a gain upon the grass land of L. 13 5 0
Or L.3, 6s. an acre every year.
Thus, though more food is raised by converting the land to ara-
ble purposes—though more capital may be profitably employed up-
on the same extent of surface, and more people may be sustained
by it, yet more profit may be made by the farmer whose means are
small by keeping the land in meadow. But this result can be ob-
tained only where a ready market exists for the hay, where it is al-
lowed to be sold off the farm, and where abundance of manure can be
obtained for the purpose of top-dressing the grass every year. It is
only in the neighbourhood of large towns that all these circum-
stances usually co-exist, and hence one cause of the value of grass
land in such localities.”
The farmer, however, is never prohibited from selling his corn
off the farm, or his fat stock, or his dairy produce, and thus at a
distance from large towns he must turn his attention to the raising
of one or other of these kinds of produce. -
Of the two ways of employing his grass or green crops—in rear-
ing and fattening cattle, namely, and in the production of butter
and cheese—we shall hereafter see reason to believe that theoreti-
cally the latter ought both to be the most profitable in money to
the farmer, and to produce at the same time the greatest amount
of food for man.
3°. What rotation or course of cropping is adopted 2–If the land
be cropped with corn, year after year, the produce of food, even on
the richest soils, will sooner or later diminish, till at length the crop
will not be sufficient to defray the expense of cultivation. The
tillage of such lands must then be abandoned, and it must be left
to a slow process of natural restoration. No arable land will con-
tinue to produce so much food if year by year it be made to raise
the same crop, as if the crop be varied—and especially as if corn,
* For a very instructive article on the breaking up of grass land by Mr John Bra-
vender, see Journal of the Royal Agricultural Society, vii. p. 161.
854 THEORY OF THE ROTATION OF CROPS.
root, and leguminous crops be made to succeed each other in a
skilful alternation. Such at least is the result of practical experi-
ence up to the present time.
Upon the introduction of the alternate husbandry, it was found
that upon lands formerly in pasture, not only could one-third
more stock be kept than before, but that in addition a crop of
corn could be reaped every second year. On the other hand,
those which had been cropped with corn alone, or which after
two white crops had usually been left to maked fallow, yielded
more corn in a given number of years than before, while a green
crop every second year was raised on them besides. It cannot be
doubted, therefore, that a change of cropping influences, in a great
degree, the amount of food which the same piece of land is fitted
to produce, with a profit to the farmer.
It remains to be seen how far the application of scientific prim-
ciples to the culture of the soil can modify this result of experi-
€11C0.
§ 4. Of the theory of the rotation of crops.
Upon what principles do the beneficial effects of this change of
cropping depend ? What is the true theory of a rotation of crops?
It was supposed by Decandolle—
1°. That the roots of all plants give out or excrete certain sub-
stances peculiar to themselves—and
2°. That these substances are unfavourable to the growth of
those plants from the roots of which they come, but are capable of
promoting the growth of plants of other species—that the excre-
tions of one species are poisonous to itself, but nutritive to other
species.
Upon these suppositions he explained in a beautiful and appa-
rently simple and convincing manner the beneficial effects of a ro-
tation or alternation of different crops. If wheat refused to grow
after wheat, it was because the first crop had poisoned the land to
plants of its own kind. If after an intervening naked fallow a se-
cond wheat crop could be profitably grown, it was because during
the year of rest the poisomous matter had time to decompose and
become again fitted to feed the new crop. And if, after beans or
turnips, wheat grew well, it was because the excretions of these
3
THE SOIL BECOMES DEFICIENT 85.5
plants were agreeable to the young wheat, and fitted to promote
its growth.
Thus easily explained were the benefits both of a rotation of
crops and of naked and other fallows—and supported at once by
its own beauty and by the great name of Decandolle, this explana-
tion obtained for many years an almost universal reception.
But though there seems reason to believe (p. 128) that the
roots of plants really do give out certain substances into the soil
—there is no evidence that these excretions take place to the ex-
tent which the theory of Decandolle would imply—none of a satis-
factory kind that they are noxious to the plants from which they
are excreted (p. 127, note)—and nome that they are especially
nutritive to plants of other species. Being unsupported by de-
cisive facts and observations, therefore, the hypothesis of Decan-
dolle must, for the present, be in a great measure laid aside, and
we must look to some other quarter for a more satisfactory theory
of rotation.
In so far as chemical principles are concerned, the true general
reason why a second or third crop of the same kind will not grow
well, is—not that the soil contains too much of any, but that it con-
tains too little of one or more kinds of matter. If after a skilful
manuring turnips grow luxuriantly, it is because the soil has been
enriched with all that the crop requires. If a healthy barley crop
follow the turnips, it is because the soil still contains all the food
of this new plant. If clover thrive after this, it is because it ma-
turally requires certain kinds of mourishment which neither of the
former crops has exhausted. If, again, luxuriant wheat succeeds,
it is because the soil abounds still in all that the wheat crop needs
—the failing vegetable and other matters of the surface being in-
creased and renewed by the decaying roots of the preceding crop
of clover. And if now turnips refuse again to give a fair return,
it is because you have not added to the soil a fresh supply of that
manure without which they cannot thrive. Add the manure, and
the same rotation of crops may again ensue.
We have already had frequent occasion, in studying the inor-
gamic constituents of plants, to observe that different species re-
quire very unlike proportions of the several kinds of inorganic
food which they derive from the soil. Some require a large pro-
856 IN CERTAIN KINDS OF WEGETABLE FOOD.
portion of one kind, some of another kind. If a soil, therefore,
abound especially in one of these varieties of inorganic food, one
kind of plant will especially flourish upon it—while, if it be great-
ly deficient in another substance, a second plant will remarkably
languish upon it. If it abound in both substances, then either
crop will grow well, or they may be alternately cultivated with a
fair return from each.
Upon this principle, the mechanical and physical conditions of
the soil and the mode of treatment being the same—the true gene-
ral explanation of the benefit of a rotation of crops appears to de-
pend. There may be special cases in which peculiar qualities of
soil or climate may intervene and give rise to appearances, or cause
results to which this principle does not apply, but for the general
practice it seems to afford a satisfactory explanation.
It may be said that this explanation seems to imply that the same
kind of crop may be reaped from the same soil for an indefinite
number of years, by simply adding to it what the crop carries off.
This is certainly implied in the principle—the mechanical and phy-
sical conditions of the soil being favourable. And if we knew ex-
actly what substances to add for each crop, in what proportions, and
at what times, we might possibly attain this result, except in cases
where the soil undergoes some gradual chemical alteration within
itself, which it may require a change of treatment to counteract.
At all events it does not seem impossible, chemically speaking, to
obtain crop after crop of the same kind—and we may hope hereafter
not only to be able to effect this, but to do it in a sufficiently eco-
nomical manner.
Two practical rules are suggested by the fact that different plants
require different substances to abound in a soil in which they shall
be capable of flourishing.
1°. To grow alternately as many different classes or families of
plants as possible—repeating each class at the longest possible in-
tervals of time.
In this country we grow chiefly root crops—corn plants ripened
for seed—leguminous plants sometimes for seed (peas and beans),
and sometimes for hay or fodder (clover and tares),-and grasses;
and these different crops in alternate years. Every four, five, or
six years therefore, the culture of the same class of plants comes
PRACTICAL RULES SUGGESTED BY THEORY. 857
round again, and a demand is made upon the soil for the same
kinds of food in the same proportion.
In other countries—tobacco—flax—rape, poppy, or madia, cul-
tivated for their oily seeds—or beet for its sugar, can be cultivated
with profit, and being interposed among the other crops, they
make the return of each class of plants more distant. A perfect
rotation would include all those classes of plants which the soil,
climate, and other circumstances allow to be cultivated with a
profit.
2°. A second rule is to repeat the same species of plant at the
greatest convenient distance of time. In corn crops there is not
much choice, since in a four years' course two corn crops, out of
the three (barley, wheat, oats), usually grown in our islands, must
be raised. But of the leguminous crops we have the choice of
beans, peas, vetches, and clovers—of root crops, turnips, carrots,
parsnips, beets, mangold wurtzel, and potatoes—while of grasses,
there is a great variety. Instead, therefore, of a constant repeti-
tion of the turnip every four years, theory says—make the carrot
or the potato take its place now and then, and instead of perpetual
clover, let tares, or beans, or peas occasionally succeed to your
crops of corn. The land loves a change of crop, because it is
better prepared with that food which the new crop will relish,
than with such as the plant it has long fed before continues to re-
quire.
This is one reason why new species of crop, or new varieties,
when first introduced, succeed remarkably for a time, and give
great and encouraging returns. But if they are continued too
long—till the soil has been exhausted in some degree of those
substances in which the new crops delighted—they cease to yield
as before, and fall into undeserved disrepute. Give them a proper
place in a long rotation, and they will not disappoint you.
It is constant variety of crops, which, with rich manuring, makes
our market gardens so productive—and it is the possibility of grow-
ing in the fields many different crops in succession, that gives the
fertility of a garden to parts of Italy, Flanders, and China.”
* A method of superseding in some measure the necessity of a rotation of crops is
described by Mr James Wilson as long practised in Shetland, in the neighbour-
hood of Lerwick. “It is known that bear has been grown in the same patch for
858 WWIIY LAND BECOMES CLOVER, SICK.
§ 5. Why land becomes tired of clover (clover sick.)
It is known that upon many well cultivated farms, I may say
over whole districts, and upon the continent as well as among our-
selves, the land becomes now and then tired or sick of clover,
and this crop failing, the wheat which succeeds it in a great mea-
sure fails also. The land is skilfully managed and has been well
manured, and the failure of the clover crop is, therefore, a matter
of surprise as well as of disappointment.
The explanation of this result involves considerations of a me-
chanical as well as of a chemical kind.
1°. Let us first consider the chemical view of the question, and
let the rotation in a supposed case of failure be turnips, barley,
clover, and wheat.
If farm-yard manure in sufficient abundance and of good qua-
lity be applied along with the root crop, the land obtains a certain
more or less abundant return of all those substances which the last
rotation of crops had carried off from it, and which the new ro-
tation will require for food. When the clover comes round, there-
fore, a supply of proper food is ready for it, as well as for the
wheat which is to follow.
But if the turnip crop be raised by means of bones only, the lime
and phosphoric acid which the earth of bones contains are almost
the only kinds of inorganic food which are conveyed to the plants
by the manure. By the aid of the animal matter and the small
supply of other substances in the bones, (p. 783), good crops—and
especially of the turnips and corn which immediately follows them
—may be raised for a few rotations, but at every return the clover
and wheat will become more unhealthy, till they at length appear
to sicken upon the land. Neither bones nor rape-dust nor any
such single animal or vegetable substance can replace farm-yard
manure for an indefinite period, because it does not contain all the
substances which the entire rotation of crops requires.
perhaps 100 years successively, and this they managed by scarifying other parts of the
ground (the out-field portion), and renovating the arable patch by spreading it over
the surface.” This was varying the soil instead of the crop. A five years’ rotation,
however, is now getting into favour ; and the average produce, after liming, is found
to be increased by it four-fold. In this district much herring refuse is employed as a
manure, and the improved land lets at 20s, an acre.-Wilson's Voyage round the
Coast of Scotland, ii. p. 268.
WHY LAND BECOMES CLOWER SICK. 859
If wood-ashes be used along with the bones the bad effects I
have described will be much longer delayed—they may even upon
some soils be delayed indefinitely, since wood-ashes favour the
growth of clover and other leguminous plants, because they con-
tain many of those substances which the clovers require (p. 620).
Or if the bones or rape-dust be mixed with wood-ashes, with gyp-
sum, or with artificial manures (p. 639), in which the necessary
food of the crops is present, a similar good result may be expected.
In short, it is not generous manuring alone, but manuring of the
right kind which is to cause any given crop to grow on the same
spot at frequently recurring intervals. -
2°. But physiological and mechanical are often of no less value
than chemical considerations in connection with the cause of such
failures. Thus,
a. Clover is a deep-rooted plant, and is found to grow best in a
stiff soil. This is an ultimate fact—a habit of the plant—for which
science can as yet give no reason, and which, so far as we know,
no chemical constitution of the soil can alter.
b. By long protracted arable culture soils originally stiff become
gradually lighter, and from this cause less adapted to the clover
plant which used to flourish upon it. It is a familiar expression
among practical men in many parts of the country, that their soil
has become too light for wheat; and the use of the roller to con-
solidate the land after the grain has been sown is found to improve
the crops of this grain, when from long culture they had begun to
diminish in quantity. In like manner, when chemistry would fail
to renew the clover crop, the adoption of mechanical means to stiffen
the soil, or a change of husbandry, such as eating off with sheep,
or laying down to grass, by which the effects of frequent plough-
ing are more or less counteracted—may be successful in causing
the land again to yield a profitable return of this valuable crop.
c. Again, the shelter of the corn among which the clover is
sown and springs up, makes the young plant tender—so that if
the soil be such as to prevent it from taking a deep hold before the
cold of winter comes, it may be cut down by the effects of climate
alone, even when the chemical constituents of the soil are fully
adapted to its growth.
While, therefore, we avail ourselves of every resource which
860 TIHE THEORY OF FAILLOWS.
chemistry can present, either in explanation of the cause or as a
preventive of the recurrence of such failures, we shall only show our
ignorance of other considerations which ought not to be forgotten,
if we expect to cure every ailment in our crops by the aid of che-
mical Science—assign, as some are ready to do, a chemical reason
for every unfortunate occurrence in the growth of our crops—or
demand or lead others to hope for a kind of benefit from chemistry
which it can never afford to practical agriculture.
§ 6. Of the theory of fallows.
By fallowing, or leaving the land uncropped for a time, it has
been known in all ages that the produce of the land was in many
cases capable of being largely increased. How is this increase to
be accounted for? We speak of leaving the land to rest, but it
can never really become wearied of bearing crops. It cannot,
through fatigue, stand in need of repose. In what, then, does the
efficacy of naked fallowing consist?
1°. In strong clay lands one great benefit derived from a naked
fallow is the opportunity it affords for keeping the land clean. In
such soils it is believed by many that weeds cannot possibly be
extirpated without an occasional fallow. It is certain that naked
fallows are had recourse to in many places for the purpose of
cleaning the land, where if it could easily be kept free from weeds
by other means they would not be adopted. Is it not the case on
some farms that a neglect of other available methods of extirpating
weeds has rendered necessary the assistance of a naked fallow,
while on similar farms in the same neighbourhood they can easily
be dispensed with ?
2°. In a naked fallow, where the seeds are allowed to sprout,
and young plants to shoot up, which are afterwards ploughed in,
the land is enriched by a green manuring of greater or less extent.
If weeds abound, the enriching is the greater—-if they are more
scanty, it is less—but in almost every instance where land lies
without an artificial crop during the whole summer, a crop of ma-
tural herbage springs up, the burying of which in the soil must be
productive of considerable good.
3°. When land is assiduously cropped, the surface in which the
roots chiefly extend themselves becomes especially exhausted. In
FALLOWS MAY REPLACE DEEP PLOUGHING AND DRAINING, 86]
indifferently worked land some parts of this surface may be more
exhausted than others. By leaving such soils to themselves, the
rains that fall and more or less circulate through them equalize
the condition of the whole surface soil—in so far as the soluble
substances it contains are concerned. The water especially, which
in dry weather ascends from beneath by capillary action, brings
with it saline and other soluble compounds, and imparts them to
the upper layers of the soil. Thus, by lying fallow, the land be-
comes equably furnished over its whole surface, and to a greater
or less depth, with all those substances required by plants which
are anywhere to be found in it. The roots of the crop, therefore,
can more readily procure them, and thus the plants more readily
and more quickly grow. In some cases, this beneficial action of
the naked fallow will, to a certain eatent, make up for shallow plough-
ing, and for insufficient working of the land.
4°. It is known that the subsoil in many places is of such a na-
ture that it must be turned up to the surface, and exposed for a
considerable period to the action of the air before it can be safely
mixed with the upper soil. Stiff clay lands acquire this noxious
quality to a greater or less degree during the ordinary course of
cropping. Air and water do not find their way through them in
sufficient quantity to retain them in a healthy condition, and thus
they require an occasional fallow with repeated ploughings, that
the air and the rains may have access to their innermost parts.
The chemical changes which are induced by this exposure to the
air and rain are of a kind to render the Soil more propitious to the
growth of crops, and thus, upon very stiff lands, one of the bene-
fits of fallowing is to be accounted for. -
We have seen that one of the important benefits of draining is
the permeability it imparts to the soil. The surface water is per-
mitted to escape downwards, and as it sinks to the drain the air
follows it, so that the very deepest part of the soil from which the
water runs off, is rendered wholesome by the frequent admission
of new supplies of atmospheric air.
It thus appears that in a certain sense draining and fallowing
may take the place of each other—that where there is no sufficient
drainage, fallowing is more necessary and will partially supply its
S62 WEGETABLES AND MINERALS DECOMPOSE.
place, and that where a good drainage exists, the use of naked
fallows even upon stiff clay lands becomes less necessary.
5°. I have already had occasion to speak of the existence of or-
ganic (animal and vegetable) matter in the soil, in a so-called inert
state—a state in which it undergoes decay very slowly, and there-
fore only in a small degree discharges those functions for which
vegetable matter in the soil is specially destined. In stiff clays
also, the roots of plants, without actually attaining this inert state,
yet decay with extreme slowness in consequence of their being al-
most sealed up from the access of the air. In both cases the fre-
quent and prolonged exposure which a naked fallow occasions, in-
duces a more rapid decay of this vegetable matter, or brings it into
a state in which its elements more readily assume those new forms
of combination, which are capable of ministering to the sustenance
and growth of plants.
Among the other compounds which are produced during this
prolonged exposure and more rapid decay of the organic matter of
the soil, ammonia and nitric acid are two which appear to exercise
a considerable influence upon the future fertility of the land. The
favourable action of the mitrates in promoting vegetable growth is
now well known, and the more rapid formation of these compounds,
when the land lies naked to the action of the Sun and air, must
not be neglected among the fertilizing influences of the summer
fallow.
6°. The soil, besides the clay, siliceous sand, and lime of which
it chiefly consists, contains also fragments of mineral substances of
a compound nature—offelspar, mica, hornblende, &c.—which con-
stitute or which occur in the granitic and trap rocks. These slowly
decompose in the soil—more rapidly also the more freely they are
exposed to the air—and the potash, soda, lime, magnesia, silica,
&c. which they contain, are by this decomposition rendered more
soluble, diffused more equably, and brought within the more easy
reach of the roots of plants. When such minerals, therefore, exist
in the soil, the effect of a naked fallow is to produce an accumula-
tion of their constituent substances in the soil, and when these con-
stituents are of a kind to favour the growth of any given plant, the
fallow must be so far favourable in preparing the land for an after-
crop of that particular species of plant. You are not to be misled,
THE SOIL IS MANURED BY THE SEA AND THE AIR. 863
however, by any broad and unguarded statements of scientific men,
so as to imagine that the beneficial effects of fallowing are in any
case to be ascribed solely to the operation of this one cause.”
7°. The rains bring down upon every soil small but periodical
supplies of all those saline substances—common salt, gypsum, salts
of lime, of magnesia, and of potash—which exist in the sea, and of
nitrate of ammonia, produced or present in the air. If any soil be
deficient in these, then a year's rest from cropping, by allowing them
to accumulate, may cause the succeeding herbage to exhibit a more
luxuriant growth. -
8°. The same remark applies to soils into which springs from
beneath bring up variable quantities of lime and other substances
which the waters hold in solution. Such springs are, no doubt, of
much benefit in some districts, and when the supply they convey is
scanty, a year's accumulation may impart additional fertility to the
fallowed land. *
9°. Besides that beneficial action of the air to which I have al-
ready adverted (4° and 5°), and which is to be ascribed mainly to
the influence of the oxygen it contains—the exposure of the naked
soil to the atmosphere for a length of time is said by some to be
productive of another good effect. The atmosphere contains a
small and variable proportion of ammonia. Of this ammonia, a
portion is brought down by the rains, and a portion is probably
absorbed by the leaves of plants as they spread themselves through
the air. But the clay, the oxide of iron, and the organic matter
of the soil are supposed also to have the power of extracting this
ammonia from the atmosphere and retaining it in their pores. If
so, the more and the longer the soil is exposed to the air, the
more of this substance will it extract and absorb. If turned over
by frequent ploughing, it will be able to drink it in more abun-
dantly, from the greater surface it can present to the passing
winds; and if, besides, it be kept naked for an entire year a still
larger accumulation must take place.
As this ammonia is known in many cases to be favourable in a
high degree to the growth of plants, it is not unreasonable to be-
lieve that if thus absorbed in quantity from the air, which is still a
* Fallow is the term applied to land left at rest for further disintegration.—Lie-
big's Organic Chemistry applied to Agriculture, p. 149.
S64 OF GREEN OR FALLOW CROPS.
matter of much doubt, it should be one source at least of the aug-
mented fertility of fallowed land. r
To one or other—or to all of these causes combined—the ac-
knowledged benefit of maked fallows is in a great degree to be
ascribed.
Of green or fallow crops little need be said in addition to what
I have already laid before you in reference to the rotation of crops.
The green crop extracts from the soil a large supply of that alca-
line matter, of which the corn crops require less, (p. 409,) and per-
haps in this way they prepare it for the growth of corn. It is more
probable, however, that the additional vegetable matter and ma-
mure which the green crops either directly or indirectly introduce
into the soil, and the large supplies of inorganic matter which such
of them as are deep-rooted bring up from beneath, are the chief
chemical sources of the benefits usually derived from them.
§ 7. Of the grain of wheat—relative proportions of bran and flour.
The grain of wheat in the hands of the miller is readily sepa-
rated into two portions—the husk, which forms the bran, and the
greater portion of the pollard—and the kernel, which, when
ground, forms the wheaten flour. The relative weights of these
two parts vary very much. Some varieties of grain are much
smoother, more transparent, and thinner skinned than others, and
yield in consequence a larger return of the finest flour. In good
wheat the husk amounts to 14 or 16 per cent. of the whole weight"
—though the quantity separated by the miller is sometimes not
more than ºth (or 11 per cent.) of the weight of the wheat. In
making the fine white flour of the metropolis and other large towns,
about ºth of the whole is separated in the form of pollard and bran.
The proportion of the husk that can be separated at the mill de-
* Boussingault found as much as 38% per cent. of husk on a winter wheat grown
in the botanic garden of Paris. Three lots of good English wheat, ground at Mr Rob-
son's mill, in Durham, gave per cent. respectively—
Fine flour, ............ 74°2 75'ſ 77-9
Boxings, ............... 9:0 8'3 6. I
Sharps, .................. 5'8 6-6 5-6
Bran, .................. 7.8 7:0 6. ()
Waste, .................. 3.2 3-0 3.5
100 ] 00 100
RELATIVE WEIGHTS OF ELOUR AND BRAN. 865
pends considerably upon the hardness of the grain. From such as
is soft it peels off in flakes under the stones, whereas, when the
grain and husk are flinty, much of the latter is crushed and ground
—adding to the weight of the flour, but giving it a darker colour,
and lowering its quality.
The country millers generally separate their wheaten flour, by
sifting, into four parts only—fine flour, boxings, sharps or pollard,
and bran. In London and Paris no less than six or seven quali-
ties are manufactured and sold by the millers.” The value of the
wheat to the miller depends very much upon the quantity of fine
flour it will yield, though he cannot always judge accurately of
this point by simple inspection.
Five experimental wheats raised by Mr Burmet of Gadgirth,
from the same seed differently manured, gave respectively 54%,
633, 653, 66%, 68%, and 76% lbs. of fine flour from 100 of wheat,
so that the kind of manure applied to the land appears materially
to affect the relative proportions of flour and bran.
Again, Colonel le Couteur's samples of wheat (p. 849) of diffe-
rent varieties, grown under the same circumstances, gave from one
field 803 and 79% lbs., and from another 724 and 784 lbs. from
100 of wheat—So that upon the variety of seed sown also, though
in a less degree, the quantity of fine flour is dependent.
It is to be remarked, however, that the age and dryness of the
wheathas much influence on the grinding quality, and consequently
on the proportion of fine flour yielded, not merely by the same va-
riety, but even by different portions of the same crop or sample.
§ 8. Of the composition of bran.
The composition of the husk or bran of wheat varies very much.
This will be evident from what has already been said in regard to
the different degrees of ease with which it is detached from the
* These are called respectively in London and Paris—
London. Paris, Called.
Fine flour. White flours, 1st quality, de blé.
Seconds. ...... 2d ... de le gruau.
Fine middlings. ...... 3d ... de 2e gruau.
Coarse middlings. Brown meals, 4th ... de 3e gruau.
Pollard. ..... 5th ... de 4e gruau.
Twentypenny. Bran, fine and coarse.
Bran. Waste, &c., Remoulage and Recoupe.
3 I
866 COMPOSITION OF BRAN.
grain, and the different proportions of the substance of the grain
which remain attached to it. -
a. When heated to 212° F., bran gives off a considerable pro-
portion of water, in this country usually about 12 per cent. of its
weight. -
b. When boiled in ether, a portion of a fatty oil is extracted
from it, which usually amounts to 5 or 6 per cent.
c. If it be boiled in vinegar, a quantity of coagulated albumen
is dissolved, which is separated again from the solution by the ad-
dition of carbonate of ammonia. The albumen in bran sometimes
amounts to as much as 16 per cent.—some of it, however, is in a
state in which it is not dissolved by acetic acid, though it may be
taken up by a solution of caustic potash. -
d. Lastly, when burned, the bran leaves a quantity of ash, which
amounts to 6 or 7 per cent. of its weight.
The proportions of water, oil, and fat do not vary very much
in pure bran, in so far as my experience goes. The following ta-
ble exhibits the proportions of these three ingredients, contained
in six samples of clean bran, from as many samples of wheat
grown on as many different farms in the neighbourhood of Dur-
ham,--as determined in my laboratory.
1. 2. 3. 4. 5. 6.
Oil, ............ 5:26 6-17 6°l 6 6'53 6-49 0.10
Water, ...... 12.92 11-82 lº-02 12-06 12.91 13-2 3
Ash, ............ 6'90 6'09 6'09 7-08 6-07 6-37
The albumen varies in a greater degree, but the average com-
position of bran is represented very nearly as follows.
Water, ................. . . . . . . . . . . . | 3-1
Albumen, (coagulated)............ 19°3
Oil, .......................... ......... 4-7
Husk and a little starch, ......... 55°6
Salime matter, (ash) ............... 7.3
l 00
This composition fully explains the value of the dry and appa-
rently un-nutritious bran in the feeding of pigs and other stock.
§ 9. Of the composition of wheaten flour.
1°. Proportion of water.—When wheat is kept for a year it loses
a little water, becoming one or two pounds a bushel heavier than
GLUTEN, ALBUMEN, AND CASEIN IN WHEAT. 867
before. When put into the mill and ground it becomes very hot,
and is said to give off so much watery vapour, that the flour and bran,
though together about twice as bulky, are nearly 3 per cent, lighter
than the grain before it was ground. A further loss of weight
is said to take place when the flour is kept long in the sack. If
fine flour be slowly heated to a temperature not higher than 220
for several hours, it loses a quantity of water, which, in upwards
of 20 samples of English flour which I have examined, has varied
from 15 to 17 per cent. of the whole weight.* It may, therefore,
be assumed that English flour contains nearly a sixth part of its
weight of water—or every six pounds of fine flour contain nearly
one pound of water. -
2°. Albumen, casein, starch, gum, and sugar.—When the flour
of wheat is made into a dough, and is then washed carefully with
successive portions of water upon a fine gauze or hair sieve, as
long as the liquid passes through milky, the flour is separated in-
to two portions—the starch, which subsides from the water, and
the gluten, which remains on the sieve. If the clear water be
poured off, after the starch has subsided, and be heated nearly to
boiling, it becomes troubled, and flakes of vegetable albumen are
seen to float in it. On setting aside to cool, the flaky powder falls
to the bottom, and may be collected, dried, and weighed. If to the
water, after filtration, acetic acid be added, a small quantity of a
white substance falls, which has much resemblance to the curd of
milk, and to which, therefore, the provisional name of casein is
given, (p. 213), or if it be evaporated to dryness on the water bath,
a residue will be obtained, which consists chiefly of soluble sugar,
gum, and saline matter, with a little fatty matter, and sparingly
soluble casein. Í - -
* Four Samples of wheat dried in my laboratory, lost respectively, of water per cent.
Water per cent.
English, Lammas red, ......... l 5' 1
Seminoff wheat,.................. 13-2
St Petersburg, .................. 16-)
Burletta wheat, ................. ... 13-1
If, then, as is usually stated, the grain actually loses water in the grinding, it must af.
terwards absorb it again,_Since the flour contains still more than the grain,_and the
alleged loss of weight must be due to some other cause.
t This substance begins to form a pellicle on the surface, when the liquid is concen-
trated by evaporation, and though it is generally present only in small proportion
868 STARCH, SUGAR, GUM, AND OIL IN WHEAT.
3°. Glutin and oil.—If, further, the crude gluten be boiled in
alcohol, a solution is obtained, which, on cooling, deposits a white
flocky substance having much resemblance to casein. When the
clear solution is concentrated by evaporation, water separates from
it an adhesive mass, which consists of a little oil mixed with a
substance to which the name of glutin is given. By digesting the
mixed mass in ether the oil is dissolved out from the glutin, and
may be obtained in a pure state by evaporating the ethereal solu-
tion. This oil possesses the general properties of the fatty oils, or
of butter. As it is partly washed out, however, along with the
starch, the whole of the fatty matter of the flour is best obtained
by boiling a portion of it at once in a considerable quantity of
ether. It varies from 1% to 3 per cent. of the weight of the flour,
and it seems to vary with the kind of treatment or culture to which
the grain has been subjected. Thus seven samples of wheat grown
by Mr Burnet of Gadgirth, with the aid of different manures, gave
samples of fine flour, which upon examination yielded respectively
the following proportions of fatty oil:—
Per cent.
1°. From the undressed soil,........................... ... tº tº e º & sº e is 1°4
2°. Dressed with guano and Wood-ash,...................... . . | 9
3°. With artificial guano and wood-ash, ..................... 2.2
4°. With sulphated urine and wood-ash,... . . . … ... s. s is e º e 2.2
5°. Do. do. and Sulphate of Soda, ......... 2-0
6°. Do. do. and common salt, ............... 2.7
7°. DO. do. and nitrate of Soda,............... 2-3
But the proportion of oil, &c. in the outer part of the grain of
wheat is greater than in the inner part. This appears from the
proportion of fat yielded by the several parts of a sample of grain
grown in the neighbourhood of Durham. Thus,
The fine flour gave of oil, ........................... 1°5 per cent.
The boxings, s s e s s # 8 º' & © s a # * * * * * * * * * * * g e º e º & 2-36
The pollard or sharps, ..................... • * * * * * 3-56
The bran, * * * * * * * * * * * * * * * * * * * * * * * s tº a ... 3" 25
The less husk in it, therefore, the less oil a flour is likely to
contain. -
4°. Gluten.—The crude gluten, after boiling in alcohol, has
much resemblance to the fibre of lean beef. It has, therefore,
(3 to 1 per cent.) yet the comparative quantities present in two samples of flour may
be judged of by the abundance in which the pellicle is formed.
3
COMPOSITION OF WHEATEN FLOUR, 869
been called by Liebig vegetable fibrin. Mulder supposes it to be
coagulated albumen. I think it likely to have a composition dif-
ferent from both, and therefore prefer at present to call it by its
old name of gluten, &
5°. When burned, the grain of wheat leaves an ash, containing,
among other substances, the phosphates of lime and magnesia,
which are to be considered also as among the usual constituents of
wheaten flour.
The Saline and other inorganic matter of grain resides chiefly
in the husk, as may be seen by the relative quantities of ash left
by the flour, bran, &c. of several samples of English and foreign
wheat, as determined in my laboratory— -
ASH LEFT PER CENT. BY DRY

WHERE GROWN.
Fine Flour. Boxings. Sharps. Bran.
1° Sunderland Bridge, near • * } . * & &
Durham, 5 | 24 4 - 0 5-8 6'9
2° Kimblesworth, do. ............ 1° 15 3.8 4°9 6-7
3° Houghall, do. ..... ... ......... 0.96 3.0 5-6 7.]
4° Plawsworth, do. ... ........... 0.93 2.7 5'5 7:6
5° Stettin,.................... ...... I 1 4-5 6'2 6'9
6° Odessa, ...... ............ .... 1. I 4-9 6-6 8:0
Thus, fine wheaten flour, in addition to the water it contains,
and to the small quantity of bran which is ground up along with
it, consists of
Gluten, Starch,
Albumen, Sugar,
Casein, - Gum,
Glutin, Oil or fat,
besides the Saline substances, chiefly phosphates, which remain in
the form of ash, when the flour is burned. All these substances
vary in quantity in different samples of flour, their relative pro-
portions appearing to depend upon a variety of circumstances as
yet little understood. In the various analyses of flour that have
hitherto been published, little attention has been paid to the per-
centage of oil, of glutin, or of casein, which the specimens exa-
mined have severally contained. In general, the weight of the
crude gluten only has been estimated, without extracting from it
either the oil or the glutin.
870 COMPOSITION OF WHEATEN FLOUR.
The following table exhibits the approximate composition of
some varieties of French and Odessa flour as determined many
years ago by Vauquelin.” The gluten includes the glutin and
much of the fat. • .

*-
COMPOSITION OF THE FLOUR OF
French Wheat. Odessa. Wheat.
Paris' • ,
1st quality. 2d quality. Bakers’ W. Soft Wheat,
Flour. heat. 1st quality. 2d quality.
Water, ...... 10-0 12-0 10-0 12-0 10-0 8:0
Gluten, ... 11:0 7.3 10-2 l 4'6 12-0 l2:0
Starch, ..... 7 1-5 72:0 72-8 56'5 62-0 70-8
Sugar, ... . 4*7 5'4 4-2 8'5 7-4 4'9
Gum,........ 3-3 3-3 2-8 4'9 5-8 4°6
Bran,......... gº & º * & 4 * g e 2-3 1.2 * * *
| 00:5 100 100 98.8 98’4 100-3
§ 10. Of the influence of soil and climate on the composition of
wheaten flour.
1°. Influence of the soil.—The nature of the soil has a sensible
influence upon the composition of the grain that is reaped from it.
The proportion of gluten, for example, is said to be generally
greater in grain which is reaped from calcareous soils, or from
such as abound in organic matter. In the north of Ireland, this
fact is stated in regard to the wheat grown in the limestone dis-
tricts; and the millers of the midland counties of England (on
the new red sandstone) are accustomed to mix, with their native
corn, that of the chalk districts to the east and south, for the pur-
pose of giving additional strength to their flour. It is not yet de-
cided, however, on what chemical constituent, or on what other
circumstance the strength of wheaten flour depends.
2°. Influence of the climate.—The wheat of warm climates also
is supposed usually to contain more gluten. Thus flour, prepared
from some eastern wheats, compared with that from others of
French growth, was found to contain water and dry gluten in the
following proportions:—
* Dumas' Traité de Chimie, vi. p. 388.
4
INFLUENCE OF CLIMATE, AND OF WARIETY 871
- Water Gluten
per cent. per cent.
French, Saissette,..................... 15:1 12.7
•e e º Rochelle, .................. 129 -* 11.2
tº º º Briè, ........................ 13.5 10-7
e ſº º Tuzelle, ..................... 13-0 8-3
Odessa, ................................. 13-0 15-0
Taganrog,” ............. .................12.6 22.7
It is by no means an ascertained fact, however, that climate
alone will cause the growth of a wheat richer in gluten,
The quantity of gluten contained in English flour has general-
ly been stated much too high. Thus, Sir Humphry Davyf says
that he obtained from the flour of g
Gluten Gluten
ſe g per cent. per cent.
English winter wheat,...... 19 Barbary wheat,...... 23
spring wheat,......24 Sicilian wheat, ...... 21
—and others have given numbers nearly as high. But the gluten
is very difficult to dry, and I believe that the large per-centage of
this substance assigned by previous experimenters has arisen from
the water not being sufficiently expelled from it by prolonged heat-
ing to 220° F. I select the following from a greater number of
determinations, carefully made in my laboratory:—

Weight ||Water Gluten
KIND OF WHEAT. per in in fine | WHERE GROWN. .
bushel. | Flour. | Flour.
lbs. per ct, per ct.
Red English,... 62% 17.5 8°l At Sunderland Bridge, near Durham.
Gé & 6 as º gº 62% 16°4 9°5 At Kimblesworth, near Durham.
46 {& & © e 63 15-0 8°5 At Houghall, near Durham.
66. “ . . . 62; | 6-8 99 || Near North Deighton, Yorkshire.
White “ tº e & 63 15°5 7°5 At Plawsworth, near Durham.
“ Scotch,... 61% l6°3 9°4 At Gadgirth, near Ayr.
Red Stettin, ... 63 14°6 8-6 -
“ Odessa, ... 61 15-9 11:5
In all these cases the quantity of gluten falls far short of that
assigned to English flour by Davy; yet we may safely, I think,
conclude from them that English flour seldom contains more than
10 per cent. of dry gluten. The flour from North Deighton which
* Taganrog, at the head of the Sea of Asof, exports the produce of the banks of
the Don.
f Agricultural Chemistry, Lecture III.
872 OF SEED, ON THE COMPOSITION OF WHEAT.
gave 99 per cent. was grown upon a thin limestone soil, and may,
perhaps, owe its larger per-centage to this circumstance.
But these numbers do not indicate the total quantity of nitrogen-
holding food which these flours contained. For though the crude
gluten always contains a variable quantity of fatty matter, which,
if extracted, would considerably lessen its weight, yet, on the
other hand, the water employed in washing out the starch holds in
solution some albumen and casein, which, having the same compo-
sition, might be added to the gluten, and would sensibly increase
its weight. Thus in a sample of flour grown in Ayrshire I found—
Gluten,............... 9.3 per cent.
Albumen,............ 0.45 per cent.
Casein, .......... .... 0.40 per cent.
Making in all, ... 10:15 of substances which con-
tain nitrogen in nearly equal proportions.
But further still in the mode of washing by which the gluten is
obtained, a variable proportion of the gluten passes through the sieve
with the starch and subsides along with it. This variable proportion
we have no means of directly estimating, and thus the method of
washing, even when the albumen and so-called casein are collected
and weighed, may be expected to give results in regard to the pro-
portion of these nitrogenous substances which is below the truth.
The only certain method is to determine the proportion of nitrogen
in the whole flour or grain by a direct analysis, and from this to
calculate that of the gluten and other protein compounds (p. 216).
By this method Horsford found the proportion of these com-
pounds in six different samples of wheat and wheaten flour to be
as in the second column of the following table. The first column
represents the proportion of water; and the third the proportion
of the protein compounds when this water is deducted.


Per-centage of substances
containing nitrogen.
Per-centage
of water.
In ordinary Dried at
State. 212°.
Wheat flour from Vienna, No. 1, ............... 13.85 | 6’51 19°l 6
Do. Do. No. 2, . . . . ........ 13-65 11' 96 13°54
Do. Do. No. 3, ............... 12.73 19.17 21.97
Talavera wheat from Hohenheim, ............... 15'43 13-98 16'54
Whittington wheat from do. .............. | 3’93 14:72 17.1 l
Sandoming wheat from do. ............... | 5' 48 14:51 || 17-18
INFLUENCE OF THE TIME OF CUTTING. 873
§ 10. Influence of variety of seed, of mode of culture, of time of
cutting, and of special manures on the composition of wheat.
1°. Variety of seed and mode of culture.—The influence of these
two circumstances upon the relative proportions of bran and gluten
are shown by the following results of the examination by Boussin-
gault” of several varieties of wheat grown in the Botanic Garden
at Paris—


Husk or Bran Flour in the Water in the Gluten, &c. in
in the grain. grain. flour. the flour.
per cent. per cent. per cent. per cent.
Cape wheat,...... ........ | 9 81 7. 20:6
Russian wheat,..... ...... | 8 82 6'4 24'8
Dantzic wheat,............ 24 76 7.3 25'8
Red Foix wheat, ......... 18°5 8 || “5 0.3 26°l
Barrel wheat, ...... ...... 22 78 8.8 27.7
Winter wheat, ............ 38 ($2 14-1 33
In all the samples the bran and gluten are both very high, but
they vary much in the several varieties.
The gluten includes the albumen, casein, and other substances
containing nitrogen, but though grown in the rich soil of a botanic
garden, I fear the sum of these has, in several of the above sam-
ples, been estimated too high. The same variety of wheat grown
in the open fields in Alsace, and in the Botanic Garden of Paris,
gave, -
Per cent.
Grown in the Botanic Garden, .............. 26-7 of gluten.
Grown in the open fields, .................. 17.3 of gluten.
2°. The time of cutting affects the weight of produce, as well as
the relative proportions of flour, bran, and gluten. Thus from 3
equal patches of the same field of wheat upon thin limestone soil
at North Deighton in Yorkshire, cut respectively 20 days before
the crop was fully ripe, 10 days before ripeness, and when fully
ripe—the produce was in grain—
20 days before. 10 days before. - fully ripe.
J 66 lbs. 220 Ibs. 209 lbs.
and the per-centage of flour, sharps, and bran, yielded by each,
and of water and gluten in the flour, as found in my laboratory,
was as follows:—
* Annales de Chim, et de Phys. lxv. p. 311.
874 INFLUENCE OF SPECIAL MANURES.

IN THE GRAIN PER CENT. IN THE FLO UR PER CENT.
WHEN CUT.
Flour. Sharps. Bram. || Water. Gluten.
20 days before it was ripe, .... .. 74-7 7.2 17.5 15.7 9°3
10 days before, ..................... 79-l 5'5 13-2 15°5 9.9
Fully ripe, .................... ...... 72°2 || 1 1-0 | 16.0 15°9 9:6
In so far as these experiments go, therefore, it appears that
when cut a fortnight before it is ripe, the entire produce of grain
is greater, the yield of flour is larger, and of bran considerably
less, while the proportion of gluten contained in the flour appears
also to be in favour of that which was reaped before the corn was
fully ripe.*
3°. Special manures.—It is said that the employment of manures
which are rich in nitrogen not only causes a larger crop, but also
produces a grain which is much richer in gluten. The experi-
ments which have hitherto been chiefly relied upon in proof of this
result are those of Hermbstädt. On ten patches, each 100 square
feet, of the same soil (a sandy loam) manured with equal weights
of different manures in the dry state, he sowed equal quantities
(; lb.) of the same wheat—collected, weighed, and analysed the
produce. His results are represented in the following table:–

Ox Night| Sheep's Goat's Human | Horse Pigeon | Cow Vº Unma-
blood. soil. dung. dung. | urine. dung. dung. dung. IIlanllyſe. nured.
14 || 14 I 2 12 12 1() 7 3
Return ...... fold. | fold. | fold. fold. | fold. | fold. | fold. | fold. fold. | fold.
Water, ...... 4-3 || 4-2 4'2 4’3 4-2 4 °3 4’3 4'2 4-2 4-2
Gluten, ...... 34-2 || 33-9 32-9 32-0 35°l 13.7 12.2 12-0 9.6 0-2
Albumen, ... 1-0 | 1.3 1 °3 1 °3 1-4 I - I ().9 l.0 ()'8 0.7
Starch, ...... 4] '3| 4l '4 42.8 42°4 39-9 GI '6 63-2 62-3 65-9 66-6
Sugar, ...... 1-9 | 1.6 1 5 ] '5 l'4 1-6 1 9 I •0 I •9 1.9
Gum, ......... 1-8; 1.6 ] '5 1 * 5 1-6 | 6 1.9 1 ‘9 I '9 1-8
Fatty Oil,... ().9 || 1:1 1-0 0.9 1-0 1-0 0-9 1 - 0 I ‘0 1-0
Soluble
Phos- 0. 5| 0-6 0.7 0.7 0.9 0.7 ()'5 ()' 5 0.5 0.3
H. &c.|
UlSK Olſ º &
bran, ...... }139 14-0 || 13.8 || 14-2 || 14-2 || 14-0 || 14-0 || 14-9 || 14-0 || 14-0
99.8 || 09:7 | 99.7 90.7 | 99.7 || 99.6 99.8 99.7 99.8 99.7
The large per-centage of gluten obtained by the use of the first
five manures is very striking, if the determinations are really to be
depended upon, which I doubt very much. They are certainly in-
teresting in a theoretical point of view, and are deserving of careful
repetition. In reference to their bearing upon practical farming,
however, it must not be forgotten—that the results of small ex-
* See a paper by Mr John Hannam, Quarterly Journal of Agriculture, lviii. p. 173.
MR BURNET's EXPERIMENTs. 875
periments are never fully borne out when they are repeated on the
large scale—that the relative value of different animal manures is
materially affected by the kind of food on which the animal has
lived—that independent of manures, there are circumstances not
yet made out which materially affect the produce of single patches
—and that it will rarely be in the power of the practical farmer
to apply at pleasure to his fields the several manures in the rela-
tive proportions used by Hermbstädt. Thus, if instead of 20 tons
of farm-yard manure he wished to try blood or urine alone, he
must apply 24 tons of the former, and 70 tons of the latter in their
natural state—quantities which it might be both difficult to pro-
cure and inconvenient to apply.
The most practically useful results yet published in regard to
the action of different manures upon the weight of the crop, the
proportion of flour yielded by it, and of gluten in the flour, are
those obtained by Mr Burnet of Gadgirth. These results were as
follow :-



Produce Fine Flour Gluten
Kind of manure. per acre per cent. from per cent.
in bushels. the grain. in the flour,
Nothing, .......................................... 31% 763 9°4
Sulphated urine and wood-ashes, .......... - 40 66% 10-5
Do. do. and Sulphate of soda, ...... 49 63% 9-7
Do. do. and common Salt,............ 49 653 9:6
Do. do. and nitrate of Soda, ......... 48% 543 l 0:0
We perceive here a slight increase in the per-centage of gluten
when the manures were applied, but nothing which at all resembles
the great differences given by Hermbstädt, or which renders it
probable that by skilful management, as some have supposed, we
may hereafter be able to raise in our fields whole crops of corn
which shall yield a flour containing 20 or 30 per cent. of gluten.
§ 11. Of the effects of germination, and of baking, upon the flour
of wheat. -
The effects of germination and of baking upon the flour of wheat
are very analogous to each other. In both cases, a portion of the
starch is changed into gum and sugar.
1°. Germination.—I have already described to you (p. 219) the
very beautiful change which takes place during the sprouting of
876 ISFFECTS OF GERMINATION AND BAKING.
the seeds of plants—how a portion of their gluten is changed into
diastase, and how, by the agency of this diastase, the starch of the
seed is changed into gum and sugar, (p. 221.) In an experiment
made by De Saussure, 100 parts of the farina of wheat had by
germination lost 6 parts of starch, and in their stead had acquired
3% of gum and 2% of sugar. The effect of this change—which
proceeds as the plant continues to grow—is to make the starch
soluble, and thus capable of entering into the circulation of the
young plant.
2°. Baking.—It is the larger proportion of gluten usually con-
tained in the flour of wheat that renders it so much better fitted for
the baking of bread than the flour of most other kinds of grain.
If the gluten be washed out of the flour, and put alone into the
oven, it will swell up, become full of pores, and assume a large
size. The comparative baking qualities of different samples of
flour may be judged of by the height to which, in similar vessels,
and in conditions otherwise similar, the gluten of equal weights of
flour is thus observed to rise.
We have already seen that by heating in an oven, dry starch is
gradually changed into gum (British gum, p. 189), and into a spe-
cies of sugar—becoming completely soluble in water. Such a
change is produced upon a portion of the starch of wheaten flour
when it is baked in the oven. Thus in 100 parts of the flour, and
of the bread of the same wheat, Vogel found respectively—
Starch. Sugar. Gum.
In the flour, ............ 68 5 * * *
In the bread, ......... 53}, 3% 18
So that in the bread a very considerable proportion of gum had
been produced at the expense of the starch of the flour.
The yeast which is added to the dough in baking, acts in the
same way as when it is added to the sweet wort of the brewer. It
induces a fermentation by which the sugar of the flour is changed
into carbonic acid and alcohol. The carbonic acid is liberated in
the form of minute bubbles of gas throughout the whole substance
of the dough and causes it to rise. The alcohol is distilled off in
the oven. If too much water have been added to the dough—or
if it have not been sufficiently kneaded—or if the flour be too finely
ground—or if the paste be not sufficiently tenacious in its nature,
these minute bubbles will run into each other, will form large air
WHEATEN FLOUR IN BAKING . 877
holes in the heart of the bread, and will give it that open irregu-
larly porous appearance so much disliked by the skilful baker.
Good bread should be full of smallpores and uniformly light. Such
bread is produced by a strong flour, one which will bear the largest
quantity of water, will rise well, and will retain its bulk.
The quantity of water which wheaten flour retains when baked
into bread depends in some degree upon the quality of the flour.
In the Acts of Parliament relating to the assize of bread, it is as-
sumed that a sack of flour (280 lbs.) will produce 80 quartern
loaves, or 320 lbs. of bread. According to this calculation the
flour should take up and retain when baked one-seventh of its weight
of water. But the quantity of water retained by the flour now in
use is very much greater, and the profit to the baker, therefore,
very much more than this calculation supposes.
This is shown by the quantity of water which is lost by wheaten
bread, whether of first or second quality, when it is dried by pro-
longed heating, at a temperature not exceeding 220° F. The
home-made bread (white and brown) baked in my own house, and
in two other private houses in Durham, lost of water by drying in
this way—
After being baked. Water per cent.
1°. White, ..................... 24 hours. 43°3
Brown,” ........ ......... .. 24 do. 44' 0
2°. Brown, ......... .......... 42 do. 44'l
White, ... .................. 36 do. 42.9
3°. White, ..................... 9 do. 44'l
So that wheaten bread one day old contains about 44, and two
days' old, about 43 per cent. of water. Something, however, will
depend upon the size of the loaves and the dryness and tempera-
ture of the atmosphere in which they are kept.
This proportion is almost exactly the same as that contained in
the white bread of Paris. According to Dumas, the water in the
common white bread of Paris amounts to—
Hours baked. Water per cent.
2 45-7
4% 45°3
10 43'0
24 43’5
* The brown bread is made from the whole grain of the wheat as it comes from the
millstones—nothing being separated by sifting.
878 TAKES UP HALF ITS WEIGHT OF WATER.
We may assume, therefore, 44 per cent, as very nearly the ave-
rage quantity of water contained in good white bread both in Eng-
land and in France. Bread baked for public establishments con-
tains more water, not being generally so well fired, or being baked
in the form of many loaves stuck together, instead of in separate
tins as is done with home-made bread. Such is the case with the
soldier's bread of our own country, and the barrack bread of Paris
(pain de munition), which contains about 51 per cent of water.
English wheaten flour contains, on an average, about 16 per
cent. of water. If, therefore, the bread baked from it as it comes
from the mill, contain 44 per cent., every hundred pounds consist
of—
Dry flour, ......... ............. * @ is e = e º a s & 56 | 66!
Water in the flour (naturally), ...... 10% &J
Water added by the baker, .................. 33%
100
Or, the flour in baking takes up half its weight of water. A hun-
dred pounds of flour, therefore, as it comes from the mill, will give
very nearly 150 pounds of bread. Thus, the flour and the bread
contain respectively,–
Flour contains Bread contains
Dry flour, ............ 84
Natural water, ...... 16 16
* Water added, 50
100 *=m-sº
Weight of bread, 150
A sack of flour, therefore, or 280 lbs. ought to give about 420
lbs. of well baked bread. Something must be deducted from this
for the loss by fermentation, and for the dryness of the crusts.
Allowing 5 per cent, for these, a sack of flour should give 400 lbs.
of bread of the best quality,” or 100 quartern loaves. The cost of
fine white bread, therefore, compared with that of corn and flour,
ought to be very nearly as follows:–
* Unmixed with potatoes, which are employed by many bakers in considerable
quantity. Mixed with the yeast, they are said to make the bread lighter.
RELATIVE COST OF CORN, FLOUR, AND BREAD. 879
Cost of Flour, Cost of Bread, Market price of
per sack. per stone. per quartern loaf. Grain per qr.”
35s. ls. 9d. - 4%d. 47s.
40s. 2s. 0d. 4#d. 52s.
45s. 2s, 3d. 5%d. 60s.
50s. 2s. 6d. 6d. 67s.
55s. 2s. 9d. 6#d. 728.
60s. 3s. 0d. 7#d. 80s.
The economy of baking at home, therefore, at the usual prices
of bread, seems to be very considerable.
§ 12. Of the supposed relation between the per-centage of gluten
in flour, and the weight of bread obtained from it.
It has been assumed by recent chemical writers that the quantity
of water absorbed by flour, and consequently the weight of bread
obtained from it, depends, in whole or in great part, upon the
proportion of gluten which the flour contains. The following facts,
however, do not accord with this supposition.
1". Household bread, made respectively from the flour of a
French wheat and of a wheat from Taganrog, retained nearly the
same per-centage of water, though the one sample contained up-
wards of twice as much gluten as the other. Thus—
Gluten per cent. Water per cent.
in the flour. in the bread.
Flour of Briè, ........... ......... 10-7 47-4
Flour of Taganrog,............... 22.7 47-0
This one fact might be supposed to settle the question, but I
shall mention others. -
29. The flour from Odessa wheat contains about one-fourth
more gluten than French flour in general, and yet it absorbs very
little more water (Dumas). This Dumas accounts for by the fact
that the starch of the Odessa wheat forms hard transparent horny
particles, which take less water to moisten them than the impalpable
powder yielded by the softer French wheats—so that the gluten
does not appear to produce its full effect. I do not know how far
this explanation is consistent with the fact that the hard flinty
* This column has been calculated for me, from the price of the flour, by Mr
John Robson, miller, in Durham. The practical rule is, that 6 bushels of corn should
give one sack of flour, and that the miller should have the offal for his trouble.
S80 EFFECT OF ALUM, ETC. UPON BREAD.
wheats give the best biscuit flour—what the baker calls the strong-
est, which rises best and absorbs the most water.”
3°. Rice contains very little gluten—not more than from 6 to 8
per cent.—and yet it is stated as the result of numerous trials that
an admixture of a seventh part of rice flour causes wheaten flour
to absorb more water.f
4°. If the hard wheats be ground too fine they lose a part of
their apparent strength, the flour becomes dead, as it is sometimes
called, and refuses to rise as it would do if sent to the baker in a
more gritty and less impalpable state.
5°. Lastly, the admixture of very minute quantities of foreign
matter, by way of adulteration, is said to have a remarkable influ-
ence upon the quantity of water which the flour will absorb. In
some parts of Belgium it appears to have been the practice to adul-
terate the bread with a small quantity of sulphate of copper.f
This salt is dissolved in water, and the solution added to the water
with which the dough is to be made, in the proportion of about one
grain to two pounds of flour. It gives the bread a fairer co-
lour, and thus permits the use of inferior flour, and it causes the
bread to retain about 6 per cent, more water without appearing
moister. Even in the small proportion of one grain of the sul-
phate to 6 or 7 lbs. of flour it produces a very sensible effect.
(Kuhlman).
Other adulterations also exercise a similar influence. Alum
improves the colour of the bread, raises it well, and causes it to keep
water, but it requires to be added in larger quantity than the more
poisonous sulphate of copper. Common salt likewise makes the
paste stronger, and causes it to retain more water, so that the ad-
dition of salt is a real gain to the baker.
From all these facts, therefore, we may infer that, besides the
relative proportions of gluten, other circumstances not yet investi-
gated or appreciated, materially affect the relative weights of bread
obtained by the baker from different samples of wheaten flour.f
* That such is the case also in foreign countries, see a letter from the British con-
sul at Lisbon, in Davy's Agricultural Chemistry, Lecture III.
f Dumas' Traité de Chimie, vi., p. 396.
† Blue vitriol—a violent poison.
+ Besides these admixtures which are employed by the bakers, others are used by
COMPOSITION OF BARLEY. 88.1
§ 14. Of the composition of barley, and the influence of different
manures upon the relative proportions of its several constituents.
The grain of barley consists of nearly the same substances as
that of wheat, but its composition has not been so frequently in-
vestigated, The husk or bran of barley forms from 10 to 18 per
cent. of its weight, varying as in wheat and oats with the variety,
Soil, mode of culture, &c.
The average composition of fine barley meal is nearly as fol-
lows:– -
Water, .... ...................... 14
Gluten, albumen, &c. ......... l4
Starch, .......................... 68
Fatty matter, .................. 2
Saline matter or ash, ... ..... 2
100
The whole grain of two varieties of barley grown at Hohen-
heim, were found by Mr Horsford to contain the following per
centage of water and protein compounds (gluten, &c.) respectively.
the millers for the purpose of whitening their grain or flour, especially, it is said, in
the south of Ireland. A recipe for this bleaching or sprinkling mixture, sent me by
an Irish correspondent, is as follows.—
Sulphuric acid, ......... ... 2 ounces,
Common alum, ............ .. 8 ounces,
Boiling water, .... .......... 6 pints.
When the alum is dissolved, the solution is sprinkled on 20 stones of dried wheat,
which is allowed to absorb the liquid for about five hours before being ground.
Another mixture, said to be used extensively in the counties of Cork and Limerick,
consists of—
2 stone-weight of alum,
2 pounds of pearl ash,
8 pounds of rock salt,
These are each dissolved separately, the first in hot water, and them mixed together
along with
2 lbs. spirit of salts (muriatic acid)
1 lb. of magnesia,
1 quart oil of vitriol,
20 gallons of lime water.
This is sprinkled over the wheat with a watering-pan, in the proportion of one pint to
every five stones of the grain, and when the whole is absorbed, the wheat is ground with-
out any delay. Flour made by the above treatment is said to sell for 5s, a sack more
than when prepared from the best quality of wheat without any previous preparation.
In this last statement there may perhaps be a little exaggeration. Other recipes are
in use, which are said to render the bran yielded by the grain unwholesome to cattle.
3 K
882 COMPOSITION OF BARLEY.
Gluten, &c., in
Water. Ordinary state. Dry state.
Jerusalem barley, ... .................. 16.79 12:26 14-74
Common winter barley,. ............ 13.80 15°35 17.81
Barley differs from wheat in containing very little gluten. If
barley meal be made into a dough and washed with water upon a
sieve, nearly the whole passes through—the husk almost alone re-
maining behind. If the watery solution when it becomes clear be
boiled, a very little albumen coagulates and falls. On adding acetic
acid a very little casein is also precipitated. But if the starch which
had subsided from the meal be digested in the cold with water con-
taining ammonia, a solution is obtained, from which acetic acid
throws down a voluminous precipitate. Whether this substance,
which is a protein compound, be a variety of casein or of albumen
naturally insoluble in cold water, but rendered soluble by the pre-
sence of ammonia, has not yet been determined. -
Three qualities of barley are recognized in the market, and are
sold at different prices. First, the hard and flinty, fit for being
manufactured into pot barley. This brings the highest price.
Second, malting barley, which is next in value; and third, feeding
barley, which is fit for neither of the above purposes.
The mature of the soil and manure employed appears to have
much influence in producing these differences. Indeed, the effect
of soil upon the barley crop is known to all practical farmers—so
that the terms barley-land and wheat-land are the usual desigma-
tions for light and heavy soils adapted especially to the growth of
these several crops. On clay lands the produce of barley is great-
er, but it is of a coarser quality, and does not malt so well—on
loams it is plump and full of meal—and on light chalk soils the
crop is light, but the grain is thin in the skin, of a rich colour, and
well-adapted for malting.” The barley of the light lands in Nor-
folk is celebrated in the north of England for its malting proper-
ties—and the brewers refuse the barley of the county of Durham,
even at a lower price, when Norfolk barley is in the market.
When unfit for malting, barley affords a fattening food for pigs
and for some other kinds of stock.
* “The barley on the compact clays (in Hants) is of a coarser quality, but produce
greater—on the light chalk soils it is well calculated for malting—the skin is thin
and colour rich but light—in fulness of meal and plumpness of appearance it never
equals the barleys grown in Staffordshire, and upon loamy lands.”—Mr Gawler in
British Husbandry, iii. p. 12.
4
EFFECT OF MALTING UPON BARLEY. * S83
The different qualities of the same variety of barley, grown un-
der different circumstances, have been supposed by some to be
connected with differences in the proportions of gluten they seve-
rally contain. With the view of testing this opinion in reference
to the pot and malting barleys, I caused a sample of each quality
of a variety of barley (common English) grown at Bathgate, in
different fields, to be analysed by my assistant, Mr Fromberg.
He found them to contain respectively the following proportions
of water and nitrogen in their ordinary state of dryness:
Nitrogen, equal
Water. to gluten, &c.
Soft or malting barley,... . .... . . . . . . . . . . . 13°55 10°93
Flinty or pot barley,................. ...... 13° 8-03
The proportion of gluten, &c. in both is comparatively small,
but, according to this result, the hard barley contains the least
gluten and albumen.
§ 15. Effect of malting upon barley.
During germination good barley increases in bulk one-half. In
order that it may do so, it must be uniformly ripe—a quality of
great value to the maltster. This maximum bulk is generally ac-
quired in 24 hours after it has been moistened and laid in heaps.
In drying, however, the barley again diminishes in bulk, so that
the dried malt rarely exceeds by more than ºrth or ºth the bulk
of the grain as it came from the market. The well dried malt,
however, is lighter by 4th than the barley from which it is made
—100 lbs. of barley yielding about 80 lbs. of malt. This is not
all loss of substance, since by a similar drying the barley itself be-
fore malting would lose about 12 per cent. of water. The loss of
substance, therefore, is only about 8 per cent. This diminution
of solid matter arises in part from the loss of the little roots which
form the malt dust, or cummins, and of which 4 or 5 bushels are
obtained from 100 bushels of barley.
The colour of the malt varies with the temperature at which it
is dried. If the heat does not exceed 100°F. a very pale malt is
obtained, which gives a very white beer. A heat not rising above
180° gives an amber coloured malt—while for brown malt the tem-
perature may rise as high as 260° F. By mixing these varieties,
beer of any colour may be made. But in the porter breweries it
is usual to prepare a quantity of malt of a brownish-black colour,
884. COMPOSITION OF OATS.
(burned malt,) by adding a portion of which, any required shade of
colour is imparted to the liquor.
During germination a variable quantity of the gluten is convert-
ed into diastase, (p. 220), and about two-fifths (40 per cent.) of its
starch into sugar or gum (dextrin). The quantity of diastase
produced, depends upon the extent to which the germination has
proceeded. It is greatest at the moment when the gemmule is
about to burst from the seed and to form the young shoot.
I have already explained the beautiful purpose served by this
diastase in converting the insoluble starch of the grain into soluble
sugar and gum. When the beer is to be made wholly from malt,
it is unnecessary to continue the germination till the largest quan-
tity of diastase is produced. It is sufficient if the gemmule, on
holding up a grain of the barley, be seen within the skin to have
attained one-half or two-thirds of the length of the seed, The di-
astase then produced is more than enough to convert the whole of
the starch of the grain into sugar (p. 222). But if raw grain, as
in some of our distilleries, is to be added to the malt, then the
malting should be prolonged till the bud is about to burst through
the husk, so that the largest possible supply of diastase may be
contained in it. In this way also malt is prepared when it is to
be employed in the manufacture of syrup (glucose) from potato
flour—a branch of industry which has now become of importance
in France and other countries.
§ 16. Of the composition of the oat, and the effect of manures in
* modifying that composition.
1°. Relative proportions of straw, chaff, and grain.-The mean of
ten experiments made upon oats grown in the neighbourhood of
Glasgow, gave, as the relative proportions of the straw, chaff, and
grain of the oat,
Straw. Chaff. Grain. Total.
4527 529 2998 8054
Ol' 45 5 30 80
O).” 9 l 6 16
So that on an average a good crop of oats should give from 16 of
gross produce, 6 of grain, 1 of chaff, and 9 of straw.
2°. Proportions of husk and meal.—The proportion of husk in the
several varieties of the oat differs in a greater degree, probably,
COMPOSITION OF THE HUSK AND OAT, 885
than in any other grain.
Thus, the potato-oat is known to be
richer in meal, the Tartary-oat in husk. The round grain of the
former is chiefly grown in Scotland for grinding into meal, the
latter in England for feeding horses.
But even the round potato-oat varies much in the produce of
meal which it gives. Many samples yield only half their weight
of oatmeal, others 9 parts out of 16, while some give as much as
three-fourths of their weight. In one variety of oat Vogel found
66 per cent. of meal and 34 of husk, which is equal to 10% of meal
from 16 of grain. The mean of 8 samples of Scotch oats gave
Mr Norton,
Grain,...76-28 ſ The maximum of husk being 282, and the
Husk, ...23.68 minimum 22-0.
Soil, season, climate, variety of seed sown, and the kind and
quantity of manure applied—all affect not only the amount of pro-
duce yielded by the oat, but the proportion of husk and the che-
mical composition of the grain itself.
O O
3°. Composition of the husk.-The husk consists chiefly of cellu-
lar fibre, with a little oil, sugar, coagulated albumen, and 6 to 8
per cent. of inorganic matter, which is chiefly silica (p. 370.) The
husk of the oat, therefore, though not without value, either for
food or as a manure, is far inferior in these respects to the bran of
wheat.
The composition of the husk of two varieties of oats, as deter-
mined in my laboratory by Professor Norton, was as follows. (The
gluten, &c. were determined only in one of the samples, though in-
serted in both.)
Hopeton oat. Potato oat.
Oil, ................. ....... . . . . . . . . . . . . . . . . . . . . . l'50 (): 92
Sugar and gum, ............ . . . . . . . . . . . . . . . . . . . ()-47 0-75
Gluten and coagulated albumen, ............ | ‘88 1-88
Cellulose,.......................................... 89'68 89°46
Saline matter, (ash), ........... ............... . 6-47 (5'99
100 100
4°. Composition of the oat.—The composition of a French oat,
including the husk, as given by Boussingault, (Economie Rurale,
ii. p. 468) is as follows.
By drying at 250°F, it lost 20:8 per
cent of water, and then contained of
886 COMPOSITION OF OATS,
Starch, .......................... ............ ... 46°l
Gluten, Avenin, Albumen, &c. ............ 13.7
Oil, ............................ * - - - - - - - - - - - - - - - - 6-7
Sugar, .............. ... • - - - - - - re is e º 'º e º is tº e & e º e º º & © 6-0
Gum, .................. ....................... 3-8
Husk, ash, and loss, ...... . . . * * * * * * * * * * * * * 23-7
100-0
Four varieties of Scotch oats examined in my laboratory by
Professor Norton and Mr.Fromberg, gave them, exclusive of husk–
Hopeton oats, - Potato oats,
Northum- Hopeton oats, Hopeton oats, Northumber-
berland. Ayrshire. Ayrshire. land.
Starch, ........................... 65°24 (34°80 64-79 65'60
Sugar, ................... ... ... 4-51 2°58 2°09 0-80
Gum, . ........................... 2-10 2°41 212 . 2-28
Oil, ......... ................... 5'44 6-97 6’41 7-38
Avenin, ... * ... 1576 16-26 17.72 16'29
Protein jºy
Albumen, mpounds | ... 0°46 } .29 l'76 2.17
Giulin, ...) compounds. 2.47 1°46 l:33 l'45
Epidermis,........................ 1 - 18 2-39 2-84 2-28
Alkaline salts and loss,......... 2.84 1-84 0.94 | 75
100.00 N. 100-00 F. 100-00 F. 100'00 N.
Two observations are suggested by the above numbers.
' a. That the oat is very rich in oil or fatty matter. In this re-
spect, indeed among our cultivated grains, it is inferior only to
maize or Indian corn.
b. That the proportion of protein compounds in the oat is also
very large. In different samples the proportion differs as was to be
expected; but fine Scotch oatmeal, freed from husk and from the
epidermis or seeds, usually contains a larger per-centage of these
important compounds than the finest English wheaten flour. In
so far as nutritive value depends upon this ingredient, therefore, it
ought to be a more mourishing food,
The proportions of nitrogen and of protein compounds in 9
samples of dry oats, as determined in my laboratory by Professor
Norton, were as follows:—

Imperial
Oats from Barnbar- oats, New
Hopeton oats, Potato oats. roch, Wigtonshire. York, United
States.
Nitrogen ..... 2:19, 2.35| 2:28, 2.76] 2.82 || 2.89| 5:51 2:49 3:00
Protein com-
pounds, ... 14:00 | 14-78. 14.04] 17:36|| 17-77 | 18-24) 22:01 15-66 | 8-86
COMPOSITION OF OATS. 887
The differences here are very great, the proportion varying from
14 to 22 per cent.
The proportions of water and protein compounds in three varie-
ties of oat grown in Germany, as determined by Mr Horsford, were
as follows. The protein compounds, as in Mr Norton's experiments,
are calculated from those of the nitrogen.
Per-centage of substances con-
Per-centage taining nitrogen.
of water.
In thesubstancel In the substance
in ordinary state dried at 212°.
|Kamschatka oats from Hohenheim, ... 12-7] 13° 32 15-26
Early white oat from do. e & © 12'94 15.67 18:00
Do. |Do. freed from husk, ... ... | 2.94 18.78 21:57

Here, in the dry state, the oat still appears, when freed from
husk, to contain 21; per cent. of protein compounds.
We see that the proportion is greater in the grain when freed
from husk. This arises from the circumstance, that the latter, as
we have already seen, contains a smaller quantity of these com-
pounds than the former. This appears in the following determi-
nation made by Mr Norton of the proportions of nitrogen and pro-
tein compounds in the husk, grain, and whole oat of the same sam-
ple.
Husk. Grain. Whole oat.
Nitrogen,........... ...... 0.30 2.82 2: 18
Protein compounds, ... l'88 17.77 13.72
5°. Avenin.--When oatmeal is mixed with water it does not form
a dough as wheaten flour does, and if the mixture be washed upon a
sieve with water, nearly the whole of the meal will be washed through.
In fact, only the coarse parts of the meal will remain behind.
If the milky liquid be left till the starch is all deposited, and it
has become nearly clear, and be then heated to 2009 F., a small
portion of albumen will coagulate and fall in flocks, as is the case
with water used in washing the dough of wheat. If, after the li-
quid has cooled, acetic acid be added to it, a white powder will
fall, which has much resemblance to the casein or curd of milk,
but to which, until its composition is determined, it is safer to ap-
ply the provisional name of avenine (avena, the oat). It is a pro-
tein compound as the gluten of wheat is, and abounds in the oat as
888 QUALITY OF THE OAT—SOIL.
the latter does in the grain of wheat. It is a substance, indeed,
upon which much of the nutritive value of the oat depends.
6°. Quality of the oat.—The quality of the oat, or of the meal
prepared from it, varies with many circumstances. One important
quality found to vary in the ordinary use of the oat in Scotland
is its thriftiness in making oatmeal porridge, gruel, or hasty pud-
ding.
a. Effect of Soil.-The meal made from oats grown upon clay
land is the best in quality, the thriftiest, keeps the longest, and gene-
rally brings the highest price in the market.
I sometime ago visited a farm in Forfarshire, part of which con-
sisted of a sharp gravelly soil on a slope, and part of flat boggy
land resting on marl. Oats were usually grown on both soils; and
I asked what difference the tenant observed in the quality of the
grain obtained from each? “In appearance,” he answered, “there
is no difference; I could take the samples to market and get the
same price for each. If I wanted them for seed I would buy either of
them indifferently at the same price; but for meal for my own eating
I would give two shillings a boll more for the oats of the sharp land.
The sharp land meal,” he added, “gives a dry knotty brose and a
short oat cake; that from the bog land may do for porridge, but
it makes bad soft brose and a tough cake.”
b. Variety.—The variety of oat from which the meal is made has
an influence upon this thriftiness. Mr Watson of Keillor informs
me that in his neighbourhood the difference is such that a plough-
man, who can consume his weekly allowance of two pecks of meal
if made of the potato oat or of the early Angus, is often unable to
do so if the meal is made from the common Angus oat.
c. Manure.—The manure and general treatment of the soil has
no doubt much influence in giving rise to differences, such as those
above adverted to ; but no practical experiments in the field, fol-
lowed by accurate analyses in the laboratory, have yet been made
to determine the precise extent and nature of this influence,
Such conjoined experiments would be of the greatest possible
benefit to scientific agriculture. Many years ago Hermbstädt
published a series of such experiments and analyses, the results of
which I published in the former edition of these lectures; they ap-
pear now, however, from defects in the mode of analysis, adopted,
COMPOSITION OF R.Y.E. 889
to be so unworthy of confidence, that I have now thought it right
to omit them.
§ 17. Composition of Rye.
Rye has more resemblance to wheat than either barley or oats,
especially in the fitness of its flour for baking into bread. It con-
tains, however, more sugar—recent rye-bread having almost inva-
riably a sweet taste.
The most recent analysis of rye is that of Boussingault of a sam-
ple grown at Bechelbron. He found,
a. That the grain of rye yielded 24 per cent. of bran and 76 of
flour.
b. That the flour by drying at 25° F. loses 17 per cent. of
water. In my laboratory a sample of rye meal dried at 212° F. lost
only 14% per cent.
c. That the dry flour had the following composition—
Gluten, albumen, &c.,.................. 10°5
Starch, ... .............. ............. .... 64'0
Fatty matter, ................... ...... 3°5
Sugar, ........... .... ................... 3-0
Gum, ................................... 1 1-0
Epidermis and salts, ........... ...... 6-0
Loss,.......................... ... ........ 2-0
100
In two samples of rye flour from Vienna, and two of rye from
Hohenheim, Horsford found the following proportions of water and
protein compounds (gluten, &c.)
Protein compounds.
Water. In natural state. In dry state.
Rye flour, No. 1, ...... 13-78 10:34 11-74
No. 2, ... . . 14°68 15'96 1871
Grain of rye, No. 1. ... 13-94 15-27 17.75
No. 2, ... ly-82 13°59 15-77
The difference between the two samples of flour is very great,
and suggests the propriety of further examination.
It was found by Dombasle that 100 of rye flour gave, when
baked, 145 of bread—nearly the same as is given by wheaten
flour. I found rye bread when leavened to lose 44, and when yeast-
ed 46 per cent. of water. One hundred pounds of flour in these
cases, supposing it to contain naturally 16 per cent. of water, must
have yielded from 150 to 160 lbs. of bread.
3
890 COMPOSITION OF RICE.
The nature of the soil, the climate, the manure, and the variety
materially affect the quality of the grain of rye, though no ac-
curate chemical investigations have as yet been made upon the
subject. Those of Hermbstädt do not show any striking difference
to have been produced upon the composition of the grain by the
application of different manures. I insert them here, though, in
the present state of our knowledge, they are in reality of very little
value.



Soluble Return
* * Water. Husk. Gluten, Albu- Starch. Su- Gum Oil. Phos- for 1 of
MANUR.E. SC DOlćIl. gar. phates, “. l
CNCC, &c. ( Seed.
Ox-blood ...... 10°] | 10-4 12-0 || 3-6 52.2 || 3:6 || 6’2|1-0|| 0:8 || 14
Night-soil...... 10-0 || 10-7 || 11.9 || 3:2 52°4 || 3’5 || 6’ 3 || 0°9' 0-9 13%
Sheep's dung 10-0 || 10-8 l l 9 || 3-4 52'3 || 3:6 || 6-1 || 1 || 0:6 13
Goat's dung ... 10-0 || 10:8 11.9 || 3-4 52.2 || 3:5 || 6-0 | 1-0|| 0-9 12%
Human urine | 10°l | 10:8 || 12-0 || 3:5 50-2 || 3-3 || 4-6 || 1 , || 4-2 13
Horse dung ... 10-0 || 10-7 ll:9 || 2:8 51*2 || 4-0 || 4-6 1-0|| 3-6 11
Pigeon’s dung | 10:1 | 10-5 | 11-6 || 3:7 52.2 || 3-7 || 4-7 || 0-0|| 2-3 9
Cow dung...... 10-0 || 10-4 10-8 || 2:0 54".3 3’9 || 5-7 || 0-9| 1.8 9
Veget. manure 10-0 || 10-7 8.8 2.6 55°l 4-8 || 5-2 || 0-9 l'7 6
Unmanured...! 10-0 | 10°l 8-6 || 2:6 56-3 || 4-7 || 5'4 || 0-9| 1.3 4
Rye delights in a sandy soil, and is usually cultivated in such as
are poor in vegetable matter, and upon which other varieties of
grain refuse to thrive.
The substance extracted from rye, and called gluten by Hermb-
städt, is different from the gluten of wheat, and is more like the
glutin extracted from the latter grain. When dough made of rye
flour is washed with water, it nearly all diffuses itself through the
liquid, leaving little more than the husk or bran behind. The
starch deposits itself from the milky liquid, or may be separated
by the filter. When the liquid is evaporated to dryness, and the
dry mass boiled in alcohol, the so-called gluten is dissolved out,
and may be separated from the alcohol by distillation. It must
then be washed with water to free it from sugar, and with ether to
separate the oil. Like the glutin of wheat, it is now insoluble in
water, and is less cohesive than gluten.
§ 18. Composition of rice, maize or Indian corn, and buck-wheat.
1". Rice.—Many varieties of rice are grown, the composition of
which no doubt differs considerably. No chemical investigations,
however, have as yet been made to elucidate this subject.
COMPOSITION OF RICE. 89.1
Rice is surrounded with a husk or epidermis which, as in the
case of barley, clings to it very closely. A specimen of paddy or
unhusked rice examined in my laboratory was found to consist of
Husk..................................... 20*91
Grains. . ................................ 79°09
100
Five varieties of rice freed from the husk examined in my labo-
ratory gave respectively of water and ash the following proportions,
Water. Ash.
Madras rice, ...... ........ 13°5 0°58
Bengal rice, ............... 13°l 0°45
Patna rice, ............... 13-1 (): 36
Carolina rice, ............ 13-0 0.33
Carolina rice flour. ...... 14.6 0-35
By exposure to the air the dried rice in a few days reabsorbed
nearly all it had lost by drying.
The grain of rice had previously been analysed by Braconnot,
but his results have been superseded by the later one of Payen.
The latter chemist found dry rice to consist of
Starch, ........ ............ 86-9
Gluten, &c. ............... 7:5
Fatty matter, ............ 0-8
Sugar and gum,........... 0.5
Epidermis, ............... ... 3-4
Saline matter, (ash) ...... 0.9
100
The quantity of protein compounds, 7.5 per cent, found by Payen
is much greater than had been previously detected by Braconnot, ow-
ing entirely, however, to the state of analytical knowledge at the
time when the experiments of Braconnot were made. Boussingault
has since found 7.5 per cent, as Payen did, and Horsford that com-
mon rice contained 15.14 per cent of water and 6.27 per cent of
protein compounds in its ordinary or 7.4 per cent. in its dry state.
The proportion of fatty matter in rice is smaller than in any of
the other cultivated grains, in so far at least as our present expe-
riments go. In this as in most other kinds of grain, the largest
proportion of fat is situated in the exterior part of the seed. In
cleaning rice for our market, the exterior of the rice-grains is taken
off, and in the dust or refuse thus obtained a considerable per cent-
age of fatty matter exists. Thus the siftings separated from rice
892 COMPOSITION OF MAIZE AND BUCK-WHEAT.
before it is put into the mill, and the dust or meal separated by
the cleaning process, were found in my laboratory to contain re-
spectively 5% and 5 per cent. of fatty matter. Hence one reason
why this refuse has been found valuable in the feeding of stock.
The large quantities of rice consumed by the native inhabitants
of India, and of other warm countries, has often appeared surpriz-
ing to foreigners. Chemists formerly explained this alleged fact
by supposing that the small per-centage of gluten then believed to
be contained in it, was insufficient to sustain the body—when no
other food is used—unless this grain be eaten in exceedingly large
quantities. Another explanation, I believe, must now be sought
for to explain the matter satisfactorily.
2° Maize or Indian corn is celebrated for the large return of
food which it yields from a given extent of land, and for its re-
markably fattening qualities when given to poultry, pigs, and cattle.
In the ordinary state it contains about 14 per cent. of water, and
when artificially dried consists, according to Payen,” of
Husk, .................. 5.9
Gluten, &c. ............ 12-3
Starch, .............. 71.2
Sugar and gum, ...... 0.4
Fatty matter, ...,...... 9.0
Saline matter or ash, 1.2
*-*-
100
Boussingault found in maize 12% per cent. of protein compounds,
and in three varieties grown in Germany, and examined by Hors-
ford, the proportions of water and of protein compounds were as
follow :-

Per-centage of substances con-
taining nitrogen.
Water per cent.
In the substance. In the substance
in ordinary state. dried at 212°.
Maize flour from Vienna,...... 13'36 11-53 l 3'66
Do. from Hohenheim, 14-96 12°48 14°68
3°. Buck-wheat is said to be a very mourishing grain, but we
know little as yet of its chemical history. It was analysed by
Zenneck, who found it in the dry state to consist of
* Amnal de Chemic et de Phys, 3me serie, viii. p. 79.
COMPOSITION OF MAIZE AND BUCK-WHEAT. 893
Husk, .............................. 26.9
Gluten, &c.,........................ l 0-7
Starch, ............................. 52°3
Sugar and gum, ..... * e º ºs tº e º e º º & © tº 8-3
Fatty matter, ... ................. 0°4
98.6
This analysis, however, is evidently imperfect.
Horsford found the grain of buck-wheat and buck-wheat flour
made from another sample to contain respectively of water and
protein compounds,
Protein Compounds
Water. in natural state. in dry state.
Buck-wheat grain, ......... 14° 19 7.94 9-96
Buck-wheat flour, ... . . . . . 15:12 5'84 6-89
There are considerable differences, it thus appears, between the
flour and the husk, but the flour of buck-wheat seems to come very
near to rice flour in nutritive quality.
LECTURE XXIII.
Composition of peas, beans, and vetches. Effect of soils and manures upon the boil-
ing and other qualities of peas and beams. Composition of potatoes, proportion
of water, starch, protein compounds, &c. Influence of soil, manures, and other cir-
cumstances in modifying their composition. Composition of the yam and the sweet
potato. Composition of the turnip, mangold wurtzel, the carrot, the parsnip, the
beet, and the cabbage. Relative nutritive values of the potato, turnip, mangold
wurtzel, and other similar roots. Of the green stems of the pea, vetch, clover,
spurry, and buck-wheat. Of the grasses when made into hay. Of hemp, line,
rape, camelina, and other oil-bearing seeds and oil-cakes. Composition of mush-
rooms and other fungi. General differences in composition among different vege-
tables, and their relative values as food. Average composition and produce of
nutritive matter per acre of each of our usually cultivated crops.
§ 1. Composition of beans, peas, and vetches.
THE seeds of leguminous plants contain a large proportion of
a substance analogous to the gluten of wheat, like it containing
about 16 per cent. of nitrogen, and to which the name of legumin
has been given. The properties and composition of this substance
I have already described, (pp. 214 and 216). But, like the flour
of wheat, barley, and oats, they contain smaller proportions of
other protein compounds also. Thus—
a. If fine bean or pease meal be digested for some hours in pure
water, heated to about 100°F. with occasional stirring, be then
strained through linen and afterwards filtered through paper, a
clear solution is obtained, from which, on the addition of acetic
acid, a white flocky precipitate falls. This is legumin.
b. If the clear liquid, after the separation of this legumin upon
the filter, be boiled, it becomes again troubled, and deposits white
or greyish flocks. These consist of albumen, which was in a so-
luble state in the meal, but has been coagulated by the boiling.
c. If, when these flocks are separated by filtration, carbonate of
COMPOSITION OF PEAS, BEANS, AND LENTILS. 895
ammonia be added to the sour solution, a farther white precipitate
falls. This also consists of albumen, which has not been precipi-
tated by the boiling, being held in solution by the excess of acetic
acid in which coagulated albumen is soluble.
d. When the starch or refuse of meal, which was collected on
the linen cloth and first filter, is again digested in warm water,
containing a little ammonia, a solution is obtained, from which, on
the addition of acetic acid, a fourth precipitate is obtained. This
is most probably albumen also, existing in the meal in the coagu-
lated state—insoluble in water, but soluble in dilute ammonia.
Thus the pea and beam contain at least two protein compounds,
legumin and albumen. It is not unlikely that future investigations
may show that one or more of the three latter substances obtained
by the above process may be different from albumen.
The entire composition of the bean and pea have not been sub-
mitted as yet to a careful investigation. Their approximate com-
position is thus stated by Einhof.”

Composition of the grain. Composition of the meal.
Water. Husk. Meal. Starch. Legumin. Gum, &c.
Peas,..................... 14:0 10:5 75-5 6-5 23 12
Field Beans,............ ] 5'5 16.2 | 68.3 G9-0 19 | 12
According to Braconnot and Einhof, certain species examined by
them consisted of
& & Lentils
Kidney |Field beans e
Peas. T; ’ dried,
beans. (Einhof.) (Einho ;
Water, ... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12'5 23:0 15-6 & J &
Husk, .................................... 8:3 7:0 10-0 18.7
Legumin, albumen, &c., . ............ 26-4 23.6 Il-7 38°5
Starch, ......................... ...... 43°6 43°0 50' I 32.8
Sugar, ......... . ........................ 2-0 0.2 ) 8.2 3.1
Gum, &c.,................................. 4-0 1.5 6:0
Oil and fat, ... ........................ . . . 1-2 0-7 P p
Salts and loss, ................ ......... 2.0 1-0 4'4 0-9
I 00-0 100'0 I 00-0 100.0t
* Zierl Encyclopaedie, II. p. 52.
+ By drying, the lentils lost 14 per cent of water.
it Dumas Traité de Chemie, vi. p. 397, compared with Thomson's Vegetable Chemºs-
try, p. 884, Schubler's Agricultur Chemie, ii. p. 194, and Sprengel's Chemie fur Land
wirthe, ii. p. 358.
896 EFFECT OF SOILS AND MANURES UPON PEAS.
Boussingault gives the following results, which he says are also
imperfect. (Economie Rurale, ii. 492.)

- lº Feverolles. | Peas. Lentils.
€a IlS.
Water, .............................. ........... 17.5 12.5 9:6 12.5
Husk... ............ ................ .......... 8:0 10°0 1 1-0 12-0
Legumin, albumen, &c. ..................... 22-0 27.5 20-4 22-0
Starch, ........................ ... * * * * * ſº e º & g º 41*0 38°5 47.0 40’0
Sugar, .............. ........................... 0-3 2-0 2-0 1-5
Gum, &c. ............. ....... • * * * * & © tº e º & © & & g º & 4-0 4°5 5-0 7.0
Oil and fat, ........ • * * * * * * * * * * * * * * * * * * * * * * is e º e 3-0 2-0 2-0 2.5
Salts and loss, ....................... ......... 3-2 3.0 3.0 2.5
99-0 100'0 100.0 I 00-0
These analyses all agree in showing that the seeds of legumi-
mous plants are richer in substances containing nitrogen (legumin
and albumen) than any other of our usually cultivated grains.
The same result was obtained by Mr Horsford, who found the re-
lative proportions of water and of protein compounds in two va-
rieties each of beans and peas grown in Germany to be as follows:
Per centage of substances
Per centage containing nitrogen.
of water.
In the bean or pea |In beam or pea
in ordinary state. dried at 212°.
Table peas from Vienna, .................. 13° 43 24°41 28.02
Field peas from Giessen, ... ............... 19° 50 23°49 20:18
Table beams from Vienna, ............... 13°41 24-7 1 28'54
Large white beams from Giessen,......... 15'80 24'67 29-31

It is very desirable that a more full analytical examination
should be made of these very valuable grains.
§ 2. Effect of soils and manures upon the quality of peas and
beans.
The quality of the seeds of leguminous plants also is affected by
the mode of culture to which they are subjected, and by the kind
of soil in which they are raised.
1°. Effect of animal manures.—The dung “ of sheep or horses
has been found to impart a better flavour to the pea, and to render
EFFECT OF SOILS AND MANURES UPON PEAS. 897
the husk thinner than when that of hogs or oxen has been
used.” -
2°. Effect of saline manures.—The useful effect of gypsum and
of other sulphates upon leguminous plants has been already spoken
of (pp. 586, 587.) The beneficial influence also of a mixture of gyp-
sum and common salt upon sickly crops of beans and peas was very
strikingly displayed in some interesting experiments made by Mr
Alexander of Ballochmyle, (p. 635.)
3°. Effect of lime.—Dr Anderson says, “that the pea cannot
be reared to perfection in any field which has not been either na-
turally or artificially impregnated with some calcareous matter,”
but that “a soil which could hardly have brought a single pea to
perfection, although richly manured with dung, if once limed will
be capable of producing abundant crops of peas ever (?) afterwards,
if duly prepared in other respects.”f
4°. Boiling or melting quality of peas.-But the most singular
circumstance in connection with this class of seeds, to which the
attention of the agricultural chemist has hitherto been directed, is
the property possessed by peas and beans of boiling soft or moulder-
ing into a pulp more or less easily, according to the kind of land
in which they are raised, or to the species of manure with which
they are dressed. The observations, however, which I have found
upon record in reference to this point are of a contradictory cha-
racter. Thus— .
a. Sprengel says, “that peas which are raised after liming or
marling boil soft more easily, and are more agreeable to the taste
than when raised after manure.”f
b. A French authority, on the other hand, quoted by Loudon,'
says, that “stiff land or Sandy land that has been limed or marled,
or to which gypsum has been applied, produces peas that will not
melt in boiling, no matter what the variety may be. The same ef-
fect is produced on the seeds and pods of beans and of all legumi-
mous plants. To counteract this fault in the boiling, it is only ne-
cessary to throw into the water a small quantity of the common
soda of the shops.”
* British Husbandry, ii., p. 217. i Essays, ii., p. 302.
# Die Lehre vom Diinger, p. 297. § Encyclopaedia of Agriculture, p. 837,
3 I,
898 SOME PEAS REFUSE TO BOIL SOFT,
e. The author of the British Husbandry, (ii. p. 217,) states,
“ that shell marl or lime is found to forward this crop more than
any other mineral manure, though it is said to communicate a de-
gree of hardness to the grain which renders it unfit for boiling.”
Independently of all applications to the soil, I believe it is ge-
merally observed that good boilers are produced upon light, Sandy,
and gravelly soils; while heavy, wet, undrained (and newly broken
up F) land usually produces bad boiling peas and beans. Thus
melting peas (sidder peas as they are locally called) for the Bir-
mingham market, are grown on the slopes of the gravelly hill of
Hopwas, two miles from Tamworth, on the Lichfield road—the
red clay lands of the vale of the Tame producing in general pig"
peas or beans only. It is on similar soils that melting barley and
mealy potatoes are produced, and the effect upon the three crops
may probably be due to a common cause.
At all events it is probable
, a. That the boiling quality of the pea crop is not owing to the
quality of the seed—since peas of both varieties have been raised
from the same seed.* -
b. That it is not generally owing to the seasons, since some land
produces hard peas every year. If the wetness of the soil, indeed,
have any influence, a rainy season may cause the production of bad
boilers upon land from which soft peas are usually reaped.
5°. Chemical difference between these two varieties of pea.—Why
does one of these varieties of pea or beam melt more readily than
the other? Does this mechanical difference indicate or depend
upon any chemical difference P This point has not yet been in-
vestigated. One potato, we know, boils mealy, and another waxy,
and one sample of barley melts better in the mash-tub than another.
Do melting peas and barley, and mealy potatoes contain a larger
proportion of starch or of some other constituent, than samples which
are possessed of an opposite quality? Or does the difference de-
pend upon the relative proportions of the legumin and albumen—
the absolute quantity of protein compounds being nearly the same 2
It would be very interesting to clear up these points.
* Much used for the feeding of pigs.
+ Some, however, suppose it to depend upon the age of the seed, or the time of
sowing.—British Husbandry, ii., p. 217,
COMPOSITION OF POTATOES. 899
It is only when peas and beans are raised for the food of man
that the possession of the melting property becomes a matter of
importance. It is rather because they are more agreeable to the
palate, than because they are ascertained to be more nutritive that
they are preferred in this state.
If it be doubtful how far it is a difference in the chemical com-
position of the seeds of leguminous plants which makes them melt
more or less easily, it is no less so by what quality in the soil or
manure this difference in quality is produced 2 In regard to lime
the evidence is contradictory. A portion of the effect of gypsum
upon leguminous crops is supposed to arise from its yielding sul-
phur to the growing plants, and thus promoting the production
of legumin and albumen, which contain sulphur. Wet and clay
lands may also favour the production of legumin more than that
of starch—or of albumen in greater or less proportion compared
with the legumin, but in what way any of these results, suppos-
ing them to take place, can give the bean a hard or a soft quality,
we have as yet no data for determining.
§ 3. Of the composition of potatoes, and the effect of circumstances
in modifying their quality and composition. -
The composition of the potato is very different from that of any
of the other agricultural products we have yet considered. Like
all the other root and green crops we cultivate, it is distingushed
from grain and pulse by the large per-centage of water it contains.
In other respects it agrees with them. It contains the same kind
of nutritive matter which are found in the grains. It differs only in
the relative proportions in which these substances are found in it.
1°. Per-centage of water.—The mean proportion of water con-
tained in the potato is about 75 per cent., or three-fourths of its
whole weight. But this proportion varies with the age or state of
ripeness of the potato, with the part of the potato examined, with
the variety, with the rapidity of growth, with the length of time
they have been kept out of the ground, the place in which they are,
and possibly also with the soil, manure, and climate.
a. Influence of the state of ripeness, &c.—The quantity of dry solid
matter contained in the potato depends very much upon the state
of ripeness to which it has attained. The ripest leave 30 to 32
900 PER-CENTAGE OF WATER.
per cent of dry matter, the least ripe only 24 per cent. The
mean result of Körte's examination of 55 varieties of potato, gave
him for the solid matter 24.9, and for the starch 11.85 per cent.*
The result of 27 analyses made in my laboratory gave for the
maximum proportion of water in young potatoes 82, and the
maximum in full grown potatoes 68.6 per cent. The mean
of 51 determinations made upon potatoes of all ages was 76 per
Cent.
b. Water in different parts of the potato.—As a general rule,
not without exceptions, however, the proportion of water is greater
in the rose or upper end of the potato from which the young shoots
spring, than in the heel end by which it is attached to the rootlet.
The proportion in the middle of the potato is sometimes interme-
diate and sometimes greater than either. This appears in the fol:
lowing, selected from among many similar results obtained in my
laboratory.
1. 2. 3. 4. 5. 6. 7. 8.
Rose end, ...... 82.88 79-60 64.41 88-89 80-07 76'56 71.97 82-60
Middle,......... & © e e & * * * & ſº e 73-77 75°30 79.91 85-13
Heel end, ...... 80-15 77-83 63-08 88 07 65.33 71-78 74.64 74.80
c. The influence of variety upon the quantity of water in pota-
toes of the same year, grown in the same field and under the same
circumstances, has also appeared from many experiments I have
caused to be made. Thus while the cup potato gave 74, the variety
called buffs gave 77 per cent. But it is impossible always to de-
termine how much is really due to variety, and how much to the
period of growth or other causes.
2°. Proportion of starch.-A large proportion of the solid matter
of the potato consists of starch. When the potato is grated upon
a fine grater under a stream of water, the starch passes through in
the form of a fine white powder, and the fibre or cellular matter
remains behind. -
The average proportion of starch in the potatoes of this country,
according to numerous experiments made in my laboratory during
the year 1846, is,
In the natural state, * * * * * * * * * * * * * * * * * * 1572 per cent.
In the dry state, free from water,..... ... 64'20 per cent.
* Schübler, Agricultur Chemie, ii., p. 213.
THE PROPORTION OF STAROH WARIES. 901
But this proportion varies with many circumstances. Thus,
a. The heel end usually contains most starch, and the centre
least. In three varieties we obtained of starch per cent.
Belfast rounds. Red potato. Kidneys.
Rose end, ............... 19:15 16:42 14'84
Centre, .................. 14'40 13-73 13.87
Heel end, ........ ...... 1870 20.93 17:48
b. The variety also affects the proportion of starch. Thus I
obtained the following among many other results from potatoes
grown in Scotland in 1846:
4. Per cent.
Red potato, (Lanarkshire,) ...... ..... 14'08 of starch.
Small Americans, ........................ 17-80 ......
Orkney potatoes,........................... 17:42 ... ...
Buffs, (Forfarshire) .................... 20-71 ......
Kidneys, .................................... 14:03 ... ..
Cups, (Argyleshire,) ....... ............ 15° 14 ... ...
Different varieties grown on the same soil also differ in their
yield of starch.
Thus the following varieties of potato grown by Mr Fleming
at Barrochan, in Renfrewshire, in 1842, yielded respectively of
starch—
Per cent.
Connaught cups, ...........'• • - - - - - - - - - - - 21
Irish blacks, ... ...................... .... 16%
White doms, .............................. 13
Red dons, .... ................. … 10;
—while, according to a starch manufacturer in that neighbourhood,
11% per cent. had been the average quantity obtained from the
common rough red of good quality during the previous four years.
The difference in the quantity of starch yielded by the above-
named varieties is the more striking when taken in connection with
the weight of each per acre, raised from the same land treated in
the same way. These weights were as follows:–
Containing of
Manure. Produce per acre. starch.
Chºps, with 4 cwt. of guano 13% tons 2‘9 tons.
Red doms, with 4 cwt. of guano 144 tons l"5 tons.
White doms, with 3 cwt. of guano 183 tons 2-4 tons.
So that of these three crops, that of cups, which weighed the
least, gave the largest produce of starch. They yielded nearly twice
as much as the red dons, which were half a ton heavier, and one-
902 THE PROPORTION OF FIBRE WARIES.
fifth more than the white dons, the crop of which was greater
by five tons an acre. Such differences as these, in the relative
quantities of starch, which may be obtained from an acre of the
same land by the growth of different varieties of potato, are deserv-
ing of the attentive consideration of the practical man.
c. The soil, locality, or mode of treatment also affect the pro-
portion of starch in the potato. Thus the same variety of potato
grown in different localities gave me.
Mid-Lothian. Forfarshire.
Buffs, ......... 14.89 20-7 l
Argyleshire. Mid-Lothiam.
1. 2.
Cups, ......... 15:14 23.82 18'94
d. The effect of keeping upon potatoes is to diminish the pro-
portion of starch. Their weight diminishes from 4 to 7 per cent,
and the proportion of starch lessens at the same time. Thus Payen
found the same variety of potato to yield in
Per cent. Per cent.
October, ........ 17.2 February,...... 15°2
November, ... ... 16'8 March, ......... 15-0
December, ...... 15-6 April, ......... 14-5
January, ... ..... 15-5
This diminution is probably owing to the conversion of a por-
tion of the starch into sugar and gum. When potatoes are render-
ed unfit for food by being frozen and suddenly thawed, the quan-
tity of starch which they are capable of yielding when immediately
grated has undergone no diminution.
3°. The proportion offibre is very variable, but in the ordinary
state of the potato it averages about 3, and in the dry state about
13 per cent of the whole weight. It varies, however, very much—in
some being as small as 1%, in others as much as 10 per cent, even
in their natural state of dryness. I give the following as some of
the extreme determinations of the fibre in the natural and in the
dried state, obtained from Scotch potatoes grown in 1846. I have
included also the proportion of starch:—
Fibre. Starch.
In natural In dry In natural. In dry
State. State. state. State.
Cups, Mid-Lothian, ...... I-75 I 0.91 18.94 75'14
|Buffs, do. ...... 4'45 | 7-70 14.89 59° 16
Whites, do. ...... 5'69 19:51 16.73 57-31
Orkney potatoes,............ 8:41 24-10 17:42 49'91
White, Argyle, ... ... . ... l O'60 32' 12 18:07 60-82

PROPORTIONS OF OIL, GUM, AND SUGAR. 903
From these results it appears that the proportion of fibre varies
very much, though in most cases a portion of starch, and always a
small quantity of coagulated albumen, adheres to the fibre and adds
to its apparent weight. It is to the presence of this starch and al-
bumen that the nutritive properties of the potato fibre—the pulp
of the potato mills—is partly owing, though the tender fibre (cel-
lulose) is capable of being partially dissolved or digested in the
stomachs of the animals that are fed upon it.
4°. Proportion offat.—When the potato is sliced, dried, and di-
gested in ether, a portion of fat is extracted from it, which is usu-
ally smaller, however, than from any of our grain crops. It wa-
ries from 0-15 to 0:52 per cent. in the potato in its ordinary state,
but it averages about 0:24 in the one, and 1.0 per cent. in the
other.
5°. Proportions of gum and sugar—In the watery solution which
floats above the starch when a potato has been grated in a stream of
water, and the water allowed to settle, there is always contained a
small quantity of sugar, and of that species of gum which is form-
ed by the action of sulphuric and other acids (p. 175) upon starch,
and to which the name of dextrin is given. The maximum, mini-
mum, and average of these substances in the healthy potato is
nearly as follows, as deduced from numerous analyses made in my
laboratory—
Maximum. Minimum. Mean.
Sugar. Gum. Sugar. Gum. Sugar. Gum.
In natural state,... 5°l 0°94 l. 1 0-07 3.3 0-55
In dry state, ... 232 3-0 5'5 0°35 13:47 2.25
In diseased potatoes the sugar is sometimes upwards of 7, and
the gum of 2 per cent. in the natural state of the potato. This, how-
ever, is the result of a natural change of the starch into these sub-
stances as a result of the progress of disease. In all cases when
these two substances are unusually large, the starch is small in
like proportion. -
6°. Proportion of protein compounds.--When the water with
which the grated potato has been washed is filtered and then boil-
ed, a small quantity of albumen coagulates and falls in flocks. If
after this is separated, and the liquid allowed to cool a little, acetic
acid (vinegar) is added to it, a white powder falls, which, like that
obtained in the same way from Oatmeal, peas-meal, or from wheat
9()4 GLUTEN, &C. IN THE POTATO.
or barley flour, has much resemblance to the curd of milk, and
therefore for the present, and till it has been carefully analysed,
is called casein. Further, if the dry potato in powder be boiled in
alcohol, the solution evaporated, and water added to it, a white glu-
tinous substance is separated, resembling the gluten of wheat.
Lastly, if the dry fibre or pulp be boiled in acetic acid, and carbo-
nate of ammonia afterwards added to the clear solution, a portion
of white matter falls, which is believed to be albumen existing in
or attached to the fibre in a coagulated state. *
Thus the potato contains all the different protein compounds
usually found in the cultivated grains, though in its natural watery
state they are present in it in small and variable proportions only.
Thus in the natural state of the potato
Per cent.
The gluten varies from .................. 0-11 to 0-56
The albumen .............................. 0.03 to 0-75
The casein ................. , a e e s tº e º & sº e º e º 'º e 0'02 to 2°44
But the average sum of these three constituents extracted in the
way I have described, is about 1:4 per cent. of the weight of it in
its natural state, or 5.8 per cent. when freed from water.
But by the method of extraction above described, the whole of
the protein compounds is not obtained, and therefore their actual
proportion in the potato is incorrectly estimated. By determining
the nitrogen, and from its amount calculating the protein com-
pounds, a higher number is obtained for their proportion in the dry
potato. Thus Horsford obtained for the per-centage of these com-
pounds in the dry matter of potatoes grown at Giessen,
In white potatoes,............... 9.96 per cent.
In blue, ....................... ... 7-66
And my assistant, Mr Fromberg, obtained from 7:3 to 14 per cent.
in different portions, samples, and varieties of potatoes. He found
also that not only is the proportion different in different varieties,
but that it is greater also in young potatoes than in old, and in
the one end or in the centre of the potato than in the other end.
According to Boussingault, the proportion of these protein com-
pounds diminishes the longer the potato is kept. Thus in newly
dug potatoes he found them to amount to 24, but in long kept pota-
toes to only 1% per cent of their weight. These are equivalent to 9
3
AVERAGE COMPOSITION 905
per cent, and 6 per cent, respectively in the dry potatoes at the
two periods. s -
In potatoes attacked with the prevailing disease, the proportion
of protein compounds diminishes. They are partially decomposed,
producing ammonia and other compounds. -
The proportion of protein compounds, chiefly coagulated albu-
men, in the potato fibre is also greater than we should suppose—
being found by Fromberg to vary from 32 to 6.3 per cent. of
the weight of the fibre in the dry state, the mean being between 3%
and 4 per cent. This must contribute, as I have already said, to
the nourishing properties of the refuse of our potato-mills.
7°. Proportion of saline matter.—The potato when dried and
burned leaves a quantity of ash, which varies from 0-76 to 1:58
of the weight of the potato in its natural state, or from 2:3 to 4-7
per cent. of the weight of the potato in its dry state. This ash, as
we have already seen, (p. 384,) consists in large proportion of pot-
ash and soda salts.
It is a curious circumstance in reference to the inorganic matter
of the potato, that a considerable proportion of the lime it contains
exists in the state of crystallized oxalate of lime. These crystals are
in many cases readily seen by the microscope, but what functions
they perform—whether they are a natural and necessary or a dis-
eased product—it is impossible as yet, with any degree of confi-
dence, to pronounce. When the potato is burned this oxalate is
decomposed, and the lime is found in the ash in the state of car-
bonate—unless it combine during the heating with some of the
phosphoric or other fixed acids contained in the potato.
8°. Average composition of the potato.—The several ingredients
of the potato vary, as I have stated above. Its average composi-
tion is nearly as follows:—
a. Taking the mean of the results of Einhoff, Lampadius, and
Henry.
In natural state. In dry state.
Water, .................... ............ 75°28 ſº tº gº -
Starch, ................................. 14:25 58-12
Dextrin, (gum,) and sugar, ......... 2.08 8'24
Protein compounds,................. I'l () 4'50
Fibre, ............................... 7-12 29-14
90.7 | 00
906 OF THE POTATO.
b. Taking the mean of the numerous analyses of healthy pota-
toes made in my laboratory in 1846.
Natural. Dry.
Water, ... .............. ........... . . . 75'52 gº & e
Starch, ... ... . ... ..................... 1572 64:20
Dextrins. ...... .................... ..... 0°55 2.25
Sugar........ ........................... ... 3:30, 13:47
Albumen, casein, gluten, ...... ....... l'41 5-77
Fat, ... ................................... 0-24 1:00
Fibre.................................. . . . . . 3.26 13°3]
10 | 00
When the above substances are separated from each other in the
way I have described, a portion of the albumen and glutin still
adheres to the fibre, and of both with some of the so-called casein,
to the starch, so that the true per-centage of protein compounds is
something higher than in the above table.
In round numbers, indeed, the average composition of the dry
potato may be represented pretty nearly as follows:—
Starch,.... ........................... 64
Sugar and gum, ..................... 15
Protein compounds, ........ ...... 9
Fat,.................................... l
Fibre, ...... .......................... 11
100
The dry potato, therefore, in nutritive value is not far behind
the average of our finer varieties of wheaten flour, and is about
equal to that of rice (p. 891).
§ 4. Influence of soils and manures upon the quantity and quality
of the potato crop.
The potato thrives best on a light loamy soil—neither too dry,
nor too moist. The most agreeably flavoured table potatoes are
almost always produced from newly broken up pasture ground,
not manured, or from any new soil.” When the soil is suitable,
they delight in much rain, and hence the large crops of potatoes
obtained in Ireland, in Lancashire, and in the west of Scotland.
No skill will enable the farmer to produce crops of equal weight
on the east coast, where rains are less abundant. It has not been
shown, however, that the weight of starch produced in the less rainy
* Loudon's Encyclopædia of Agriculture, p. 847.
EFFECTS OF SALINE MANURES. 907
districts is defective in an equal degree. Warm climates and dry
seasons, as well as dry soils, appear to increase the per-centage of
starch.
Potatoes are considered by the farmer to be an exhausting crop,
and they require a plentiful supply of manure. By abundantly
manuring, however, the land in the neighbourhood of some of our
large towns, where this crop is valuable, has been made to pro-
duce potatoes and corn every other year, for a very long period.
19. Saline manures exercise a remarkable influence in promoting
the growth and increasing the quantity of the potato crop in some
localities. The most striking effects of this kind hitherto observed
in our island have been produced by mixtures of the nitrate of
soda, with the sulphate of soda, or with the sulphate of magnesia.”
The effect of such mixtures affords a beautiful illustration of the
principle I have frequently before had occasion to press upon your
attention—that plants require for their healthy growth a constant
supply of a considerable number of different organic and inorganic
substances. Thus upon a field of potatoes, the whole of which was
manured alike with 40 cart loads of dung, the addition of
a. Nitrate of soda alone gave an increase above dung alone
of .......................................... 3} tons.
Sulphate of soda alone gave no increase.
While one-half of each gave ............... 5}
b. Sulphate of ammonia alone gave ......... l; tons.
Sulphate of soda, no increase.
But one-half of each gave .................. 6;
c. Nitrate of soda alone gave an increase of 34 tons.
Sulphate of magnesia alone gave ......... #
And one-half of each gave.................. 9;
Such results are very interesting, and if followed up by an
examination of the quality and composition of the several samples
of potatoes produced—cannot fail to lead to very important practi.
cal and theoretical conclusions.
2°. Failure of seed potatoes.—The seeds of all cultivated plants
* See the Author's Suggestions for Experiments in Practical Agriculture,
908 EEFECT OF SALINE SUBSTANCES UPON DISEASED POTATOES.
are known at times to fail, and the necessity of an occasional change
of seed is recognised in almost every district. In the Lowlands of
Scotland potatoes brought from the Highlands are generally pre-
ferred for seed, and on the banks of the Tyne, Scottish potatoes
bring a higher price for seed than those of native growth. This
Superior quality is supposed by some to arise from the less perfect
ripening of the up-land potatoes, and by others to some peculiar
effect or quality of new land, on which skilful farmers, who do not
import or buy, raise the potatoes they intend for the next year's
seed.
These may in part be true explanations of the fact. The better
quality of unripe seed may arise from its containing a larger per-
centage of nitrogenous (protein) compounds, if, as many believe,
whatever increases the per-centage of starch, increases also the risk
of failure in potatoes that are to be used for seed. The subject is
deserving of further investigation.
It may be doubted, however, whether the relative proportions of
starch are to be considered as the cause of the relative values of
different samples of seed potatoes. This proportion may prove a
valuable test of the probable success of two samples when planted,
without being itself the reason of the greater or less amount of
failure. With the increase of the starch it is probable that both
the albumen and the saline matter of the potato will in some de-
gree diminish, and both of these are necessary to its fruitfulness
when used for seed.
The value of the saline matter is beautifully illustrated by the
observation of Mr Fleming, that the potatoes top-dressed with sul-
phate and nitrate of soda in 1841, and used for seed in 1842,
“presented a remarkable contrast to the same variety of pota-
to, planted alongside of them, but which had not been so top-dres-
sed in the previous season. These last came away weak, and of a
yellowish colour, and under the same treatment in every respect
did not produce so good a crop by fifteen bolls (3; toms) an acre.”
This observation, made in 1842, was confirmed by the appearance
of the crops of 1843, upon Mr Fleming's experimental fields. In
later years, however, even his doctored seed has not escaped the
destructive ravages of the disease of 1845 and 1846.
COMPOSITION OF THE YAM AND THE SWEET POTATO. 909
§ 5. Composition of the yam and the sweet potato.
The destruction of the potato crop in Europe having turned
public attention very much to the nature and value of the produc-
tions of other countries, it has been thought by some that the yam
and sweet potato may possibly form useful articles for importation.
Of both roots or tubers, I believe there are several cultivated
varieties. Two varieties of the former, the water and the Guinea
yam,_and one of the latter, were imported from Barbadoes dur-
ing the last summer, (1846,) and put into my hands for examina-
tion by my friend Mr Milne. They were analysed in my labora-
tory, and were found to consist respectively of

Water yam. Guinea, yam. ||Sweet potato.
Water, ................................ , º ſº tº 64'80 75'53 59-31
Starch, .................................... 24" | 0 17:45 | 6’ 62
Dextrin, ........... ..................... 0.36 0-21 0-55
Impure Sugar, ........................... 3-92 3:47 7.99
Albumen, ..... ........................... 0-25 0-70 trace.
Casein, (so called, impure),...... . ... 2’69 1-74 2'66
Fibre, and a little oil and coagu- .** & * , 8
lated albumen, b | e is e 3.76 I 61 12.88
99-88 100-71 99°41
In these analyses we see,
a. That the Guinea yam has much resemblance in composition to
the potato, -the proportion of water being the same, and that of
starch being only a little more than in the potato.
b. That the water yam contains 11 per cent. less water than the
potato according to this analysis, and 8 or 9 per cent. more starch.
c. That the Sweet potato contains less water and about the same
proportion of starch as the potato, with 5 per cent. more sugar, to
which its sweetness is owing, and nearly 10 per cent. more fibre.
d. That of protein compounds, (albumen, &c.) capable of being
separated and collected, these three samples all yielded a larger
per-centage than the potato.
When burned, however, for the determination of the nitrogen
and the protein compounds calculated from the latter, they do not
appear to exist in either the yams or the sweet potato in so large
a proportion as in the average of our cultivated potatoes. At
least my assistant Mr Fromberg found by this method the propor-
tion of protein compounds to be—
910 IARGE CROPS OF TURN IPS,
- Natural state. Dried at 212°.
Water yam, ...... . ...... 2-08 5°92
Guinea. yam,... ...... ... ... l'49 6-16
Sweet potato, ........ , , , 2.27 5'50
These numbers are less than those which represent the weight
of albumen and of so-called casein actually extracted; and though
these latter substances were necessarily impure, yet the subject is
obviously open to further investigation.
§ 6. Composition of the turnip.
The potato, among cultivated roots, is characterised by the large
proportion of starch it contains. The turnip, carrot, beet, mangel
wurztel, and parsnip, differ from it in containing much more su-
gar, with little or no starch, but in its stead a large proportion of
a substance to which the names of pectose and pectic acid are
given. The nature and properties of these substances, and the
mode of extracting the latter from the above roots has already
been described (p. 183). - e
The turnip is a root which to the skilful cultivator yields a very
large return of nutritive matter. Crops of thirty tons of bulbs
per imperial acre are not unfrequently grown, but very much
greater returns are occasionally published. -
Thus in 1814, the Duke of Portland's farm, in the parish of
Dundonald, yielded, of a variety not mentioned,—
Scotch acre. Imperial acre.
Without leaves, ........................ 76 tons. 61 tons.
With leaves, ........................... 90 ... 72 ...
And in the parish of Irvine, in the same county, Mr Taylor of
Stonearth grew, of white turnips, 68% tons per Scotch, or 55 tons
per imperial acre. *
The first of these crops is equal to 6 tons, the latter to 5% tons
of dry nutritive matter per imperial acre.
These roots contain a very large per-centage of water, a cir-
cumstance which renders them less fit for human food, and because
of the cost of transport, makes it necessary in most cases to con-
sume them near the spot where they are grown.
Many varieties of turnip are cultivated, but they have not been
subjected to a rigorous chemical analysis, -an object of much im-
portance to practical husbandry. The following table represents
I &
COMPOSITION OF THE TURNIP, 9|| |
the composition of certain varieties of Scotch turnips which have
been examined in my laboratory. -

Grown on different On same soil. On same soil.
soils. - -
* Purple.|Yellow|Purple.|Yellow
No. 1 |No. 2. No. 3. N. N. N. N.
Water, ..................... .... 89-30 | 89°42 89-00 || 88°46 88-60 87°45 || 88.31
Sugar, ........................... 5'61 | 6’21 6'54 || 6-90 || 6-92 8:39 || 7-67
Gum, ........................ ...! 0-11 || 0 1 1 || 0 || 6 || 0-09 || 0-09 /
Albumen,...... ............... 0-72 0.47 || 0:36 || 0-19 || 0-22 || 0-32 || 0:21
Pectic and meta-pectic acids, 1-76 || 1:33| l'51 - - -º - - -
Oil, .......... ................... 0-19 || 0°22 || 0-18 || 0:26 || 0-30 || $ 3.84 || 3.81
Cellular fibre, .................. 1.63 l’75 || 1:59 || 3:39 || 3:00 -
Saline matter, .................. 0°54 || 0:49 || 0'59 || 0-68 0.62
99.86 || 00 99.93 99.97 99.75 || 00 || 00

The first three of these analyses represent the composition of
the same variety of turnip grown on different soils by Mr Mylne,
farmer, near Trament, the next two were grown on the same soil
by the late Mr Aitchison of Dromore, near Musselburgh, and the
two last were grown on the same spil, near Haddington, by Mr
Roughead. Most of the analyses were made for practical purposes,
and therefore all the ingredients were notin every case determined
separately, as the table shews.
The proportion of sugar contained in these roots is greatest when
they are young and diminishes as they ripen. In the beet it has
been observed that the nitrates of potash and ammonia are present
in considerable quantity, and that in the old beet these nitrates be-
come more abundant as the sugar diminishes. In the beet also,
when raised by the aid of rich manure, the production of nitrates
is increased more than that of Sugar. According to Payen, the
beet, when raised with street manure, contains 20 times as much
saltpetre as when raised in the ordinary manner. The same may
possibly be the case with the common cultivated turnips.
The proportion of albumen and other protein compounds is not
truly represented in the analyses above given. When the potato
is grated in water, and the clear liquid boiled as in the case of the
potato, a portion of albumen coagulates and falls, and on Separat-
ing this and adding a little acetic acid, a small proportion of a sub-
stance resembling casein is thrown down. Alcohol extracts from
the fibre a portion of glutin, (?) so that the turnip contains all the
912 COMPOSITION OF MANGóLD wuPTZEL.
same principal varieties of the protein compounds which are pre-
sent in our other cultivated crops. By this method of separating
them, however, it is impossible to obtain exact results, and the
quantity obtained is generally less than the truth. By the method
of combustion, however, which gives the proportion of nitrogen,
and of thence calculating the protein compounds, a more accurate
determination is in general obtained. Thus, three varieties of
turnips grown in Germany gave Mr Horsford by this method the
following proportions of protein compounds, in their natural and
in their dried state respectively. .
In natural state. Dried at 212°.
Yellow turnip, ..................... 1°54 # 9:25
Red turnip, ........................ 2-83 15°50
Kohl Rabi, ........................ l'54 12°64.
According to these results, the dry matter of the yellow turnip
contains a little more of the protein compounds than the average
of our cultivated potatoes, while that of the red turnip and the Kohl
Rabi are as rich in these ingredients as the average of our barley,
wheat, or oat crops. It would be interesting to test these results
by a greater number of such analyses.
§ 7. Composition of mangold wurtzel, and of the beet, carrot,
parsnip, and cabbage.
1°. Mangold wurtzel-Very large crops of this very valuable
root are obtained from some soils. The crop from which the spe-
cimens were taken for the subjoined analyses, was grown by Col. Kin-
loch of Logie, in Forfarshire, upon land forked 24 feet deep, and
was “considered to be fully 40 tons an acre,” (Scotch.) This root
is a very valuable food for cattle, is much relished by them, fat-
tens well, and gives a rich milk. The orange-globe is preferred
to the other varieties usually cultivated. Three of these examined
in my laboratory by my assistant Mr Cameron, yielded per cent:
Long red. Short red. Orange globe.
Water, ..... ............ 85-18 84°68 - 86°52
Gum, ..................... 0.67 0.50 0°] 3
Sugar, ... ............... 9.79 ] ] '96 10'24
Casein, (so called), ... 0-39 0-26 0.33
Albumen, ............... ()'09 0-18 0.03 .
Fibre and pectic acid, 3:08 3.31 2°45
99-20 } 00-80 99-7ſ)
COMPOSITION OF THE CARROT, BEET, AND PARSNIP. 913
It appears from the above results that all the varieties contain a
little less water, and, therefore, more solid nutritive matter than the
turnip.
When burned, they left of ash respectively per cent.,
Long red. Short red. Orange globe.
In the natural state, ............... 1:14 0.75 0.84
When dried at 212°,... ........... 7.96 4'90 6:23
Few accurate determinations have yet been made of the per-cent-
age of protein compounds in this root. The sum of the albumen
and casein above given represents them as forming only 0-5 or ;
per cent. of their weight when fresh. This is no doubt too little
—an error which, as in the case of the turnip, necessarily attends
the method of analyses adopted. My assistant Mr Fromberg found
by the method of combustion, in the above three varieties of man-
gold wurtzel the three following proportions of protein compounds
respectively,– #
Long red. Short red. Orange globe.
Protein in the wet state, ......... 1:60 2-12 I '94
Protein in the dry state, ......... 10'79 I 3-88 14'40
It is probable also that the so-called red turnip examined by
Horsford, and said by him to contain only 81.6 of water and 2-83
of protein compounds, or 15:50 per cent. when dried at 212°, was
in reality a variety of mangold wurtzel. This root may therefore
be considered rich in these compounds.
It is a practical objection to this crop, which does not apply to
the Swede turnip, that it is unable to stand the frost, and must
therefore be taken up and stored when severe weather is expected.
It is said also by some, that this root induces paralysis in cattle that
are fed upon it. I should not think this a very likely or frequent
consequence of its use. -
2°. The carrot, the beet, and the parsnip.–These roots have been
examined respectively by Hermbstädt, Payen, and Crome, with
the following results:—
Common carrot, Sugar beet, Parsnip,
(Hermbstädt.) (Payen.) (Crome.)
Water,'..................... .. 80.0 85.0 79.4
Starch and fibre, ............ 9.0 3.0 6.9
Gum, ... . . . . . . . . . . ............ 1.75 2.0 6.1
Sugar, ........................ 7.8 l 0.0 5.5
Oil,......... . . . . . . . . . . . . . . . . . . . 0.35 *-m-º: &=º-e
Albumen, ..................... l. 1 p 2.l
100. 100. 100.
- 3 M
914, NUTRITIVE PROPERTIES OF THE POTATO,
The above analyses are very imperfect and require to be repeated.
Horsford determined the proportions of water and protein com-
pounds in a carrot and a red beet grown at Giessen. The follow-
ing were his results per cent, :
Protein compounds
Water. in natural state. dried at 212°.
Carrot, ..... ..... 86.10 1.48 10.66.
Red beet,......... 82.25 2.04 11.56
The dry matter of these roots is by the above experiments richer
than that of the potato in compounds containing nitrogen.
3° The cabbage.—I regret to say that our present knowledge of
this valuable esculent is almost nothing. In my laboratory the
proportion of water in the leaves of several varieties of cabbage
has been found to average 92 per cent., and in the stalk 84 per
cent. The dry solid matter of the leaf contains from 7 to 20 per
cent. of inorganic or mineral matter, in which there is much sul-
phuric and phosphoric acids.
The dry matter of the cabbage is unquestionably very nutritive,
though the proportion of protein or supposed muscle forming con-
stituents, has not as yet been determined. .
The flower of the cabbage, however, (cauliflower) in the dry state,
has been found to contain as much as 64 percent. of those compounds,
gluten, albumen, &c.—or more than any other cultivated vegetable.
The common mushroom in the dry state is the only vegetable, as
yet known, which approaches to this proportion (p. 925.)
Were it possible to dry cabbage, therefore, it would form a very
concentrated food.
§ 7. Relative nutritive properties of the potato, turnip, carrot,
mangold wartzel, and cabbage.
The large proportion of water in the turnip, carrot, and man-
gold wurtzel is a point of much importance in reference to their
nutritive and economic value. This proportion varies in different
samples and varieties, though the extent of this variation has not
yet been ascertained by a sufficiently numerous set of experiments.
The following table exhibits the different results hitherto pub-
lished. Those marked J. were obtained in my laboratory.
x
3
TURNIP, CARROT, AND MANGOLD WURTZEL,

Einhof. Playfair. Hermbstädt. Horsford. J. |
White turnip, ... 92 87 79 & º & s & ©
Yellow (Swedish) 87% 85 80 83 88, 88%
Purple top do.... & e & $ 8 º' $ gº & 874, 88%
Kohl Rabi, ...... 86 78 88 & © e
Red turnip, ...... * 81% & & e
Mangold wurtzel, e is a 84%, 85, 86%
Cabbage, ......... * * * 92
Payen. *
Sugar beet, ...... 85 tº e e
Red beet,......... tº º ſº 82
Hermbstädt. -
Red carrot, ...... 86 * * 80 86 87, 80
White do, ..... 87 80
The differences among these results, or their important relation to
the economic value of the several roots, will become more striking
if we deduct the water and represent the proportions of dry solid
matter which they severally contain according to the different ex-
This appears in the following table, which exhibits
the per centage of dry matter in the different roots named.
perimenters.

Varieties of turnip. Mangold wurtzel. Beet. Carrot. d5
Öſ)
cº
visit, Yel-|Purple Rohlſpan |Long | Short |Orange Sug- white #
White, low. top. rabi. Red red. red. globe. Red. all. Red.|White. &
Einhof,...... 8 12, 14 14 ſº.
Playfair, | 3 || 15 - - * * * 13
Hermbstädt, 21 20 22 | ... e -e & © & 20
Horsford, ... 17 | ... 12 18; ... * * * & © & 18 14
11|| 1 || || oung. 13
Johnston, .. 12"| 12, 15, 15 14% | young 20 | 20 | 8
Payen, ...... 15
In reference to the nutritive value of these roots, the above table
presents to us three considerations.
1°. That in the same kind of root and even in the same variety
the proportion of solid nutritive matter varies very much. Thus
the white turnip, according to three authorities, contains 8, 13,
and 21 per cent of nutritive matter—while in the yellow turnip the
solid matter varies from 11% to 30, in the kohl-rabi from 12 to 22,
and in the red carrot from 14 to 20.
My own experience, however, and it is supported by all the
other results, inclines me to reject the numbers of Hermbstädt as
too high. They would, I fear, form a very unsafe basis for any
reasoning as to the economic value of most of the root crops of the
above kinds which are raised in this country.
Rejecting these, therefore, we have the solid matter in the yel-
low turnip varying from 11% to 17 per cent., or from 2 to 3—some
916 COMPOSITION OF THE GREEN STEMS OF THE PEA, &c.
crops containing one-half more nutritive matter, that is, in the same
weight than other crops. In other words, 20 tons of one crop may
be as feeding as 30 tons of another. This is a very important fact
in reference to the actual value in feeding cattle of any given crop
of yellow turnips, and has probably much to do with the very dis-
cordant results, obtained by different farmers from the use of this
kind of food in feeding or fattening their stock.
2°. Taking the mean of the other proportions of water in the
white and yellow turnips, the mangold wurtzel and the carrot, we
have for the relative amount of solid food in these four roots the
following numbers:–
Turnips.
White, Yellow. Mangold Wurtzel. Carrot.
10}, 13% 15 14
so that the yellow turnip and the carrot, in so far as these numbers
are to be depended upon, are worth one-third more than the white
turnip,-while the mangold wurtzel is nearly one-half more mu-
tritive than the white turnip, and about a ninth part more so than
the yellow turnip.
3°. But if we compare these numbers with the average propor-
tion of solid matter contained in the potato—25 per cent., we see
that even the mangold wurtzel contains only #ths of the solid nou-
rishment which the potato does, while it of course conveys into the
stomach a proportionably large quantity of water. Another point,
however, is to be borne in mind in comparing these two roots,
—that the protein compounds exist in the solid matter of the
mangold as well as in that of the yellow turnip in larger average
proportion than in that of the potato. Thus they contain re-
spectively, when dried at 212° F.—
Protein compounds. Other nutritive matter.
The dried potato, ... .............. 8 per cent.
yellow turnip, ........ 9} ... 80
mangold wurtzel, ... 15} 75
or the proportion of protein compounds in the mangold wurtzel is
nearly twice as great as in the potato. This is a very important fact,
and is deserving of further investigation. If, as at present sup-
posed, the protein compounds serve the purpose when eaten, of Sup-
plying to animals the materials of their muscle, the mangold wurt-
zel ought to be considerably superior in this respect to the potato.
Even in their natural state this should be the case, since 100 pounds
4
COMPOSITION OF THE GRASSES WHEN MADE INTO HAY. 917
of the mangold wurtzel contain of these protein compounds, accord-
ing to the above determination, 2}, while the potato contains on
an average only 2 pounds. -
It is to be desired, therefore, that the mangold wurtzel should
be more generally cultivated wherever circumstances are favour-
able to its growth.
$ 8. Composition of the green stems of peas, vetches, clover, spurry,
and buck-wheat. -
The stems and leaves of plants which are given as green food to
animals, differ much in composition, according to the age they
have attained, to the rapidity of their growth, to the nature of the
soil and season, and to the mode of culture. They are generally
supposed to be richest in nutritive matter when the plant has just
come into flower. -
The following table exhibits the approximate composition of the
green stems of some clovers and vetches, as they have been given
by Einhof and Crome:—

•r—
Cº 2-S l;
~4 2– q2 |3 -- *—
Tº 2-N £- S) g da º $3 Tö º:
# = | $ 2:\ | < 2\| 9 º' | 9 |< 3 ºs $ 2\ | 3 -ºs F.2S
& S | 3 2 + 9 || F 2 || 5 || 3: E 2 9 || > 9 | ET 32
§ F | * * | * = | 5 G | St |# = F | 2: E | T = | + =
: £ 3 #| #3 | ". . . ; ; # 3 || 33 || 3 &
c -- * - CTS - rº * | * $2 *4 -: *- c -T s: r-
㺠3 e =e. He = |##e #e £e £e
|- *-* 2.4 || -- ſº- P-
Ü 37. Sº O
Water, ............... 80-0 || 76-0 |30-0 || 75.0 77.0 82°5 77.5 79.5 86-0
Starch, ............... 3-40 | 1.4 || 1:0 2-2 || 2:3 4*7 2 6 3.8 I 3
Woody fibre, ...... I 0-3 || | | 3-9 || || 5 || || 4:3 || 2:0 | 10-0 || 10.4 || 1 || '5 7:0
Sugar, ............... 4'55 || 2 | | | ‘5 0-3 | .. a •
Albumen, ......... ()-90 2-0 || 1:5 1-0 || 2:3 0-2 } 9 0.7 1 8
Extractive mat 0.65 3.5 || 3:4 || 4.4 5.2 2-6 7-6 || 36|| 2.9
ter and gum,
Fatty matter, . - - - (). 1 || 0:2 0.6 9 p } 1.0
Phosphate of lime, 0:19 1-0 || 0:8 0.8 || 0:8 ?
| 00 100 99.9 100 99.6 | } 00 100 | 10() | 100 -
In regard to these and other similar green crops, our informa-
tion is still very deficient. The above analyses are all imperfect,
and it is much to be desired that a complete chemical investiga-
tion of these useful plants should be made. l
§ 9. Composition of the grasses when made into hay.
1°. An elaborate examination of the grasses of this country, in
918 CELLULAR FIBRE AND GLUTEN IN THE GRASSES.
the dry state, with the view of determining their relative nutritive
properties, was made by the late Mr Sinclair, gardener to the
Duke of Bedford. His method was to boil in water equal weights
of each species of hay till every thing soluble was taken up, and
to evaporate the solution to dryness. The weights of the dry mat-
ter thus obtained he considered to represent the nutritive values of
the grasses from which the several samples of hay were made.
The results of Mr Sinclair, however, have lost much of their
value since it has been satisfactorily ascertained—
a. That the proportion of soluble matter yielded by any species
of grass when made into hay, varies not only with the age of the
grass when cut—but with the soil, the climate, the season, the ra-
pidity of growth, the variety of seed sown, and with many other cir-
cumstances which are susceptible of constant variation.
b. That animals have the power of digesting a greater or less
proportion of that part of their food which is insoluble in water.
Even the cellular fibre of the hay is not entirely useless as an ar-
ticle of nourishment—experiment having shown that the manure
often contains less of this insoluble matter than was present in the
food consumed” (Sprengel).
c. That some of the substances which are of the greatest import-
ance in the nutrition of animals—such as gluten, albumen, casein,
and legumin—are either maturally insoluble in water or are more
or less perfectly coagulated and rendered insoluble by boiling with
water. Mr Sinclair, therefore, must have left behind, among the
insoluble parts of his hay, the greater proportion of these import-
ant substances. Hence the nature and weight of the dry extracts
he obtained could not fairly represent either the kind or quantity
of the nutritive matters which the hay was likely to yield when in-
troduced into the stomach of an animal.
For these reasons I do not think it necessary to dwell upon the
results of his experiments.f
* This will not appear surprising when it is recollected that, by prolonged digestion
in diluted Sulphuric acid, insoluble Woody fibre or cellulose may be slowly changed into
soluble gum or sugar (see p. 188). The proportion of the woody fibre which will be thus
worked up in the stomach of an animal, will depend, among other circumstances, up-
on the constitution of the animal itself, upon the abundance of food supplied to it, and
upon the more or less perfect mastication to which the food is subjected.
t They will be found at length in the Appendix to Davy's Agricultural Chemistry,
or in a tabulated form in Schubler's Agricultur Chemie, ii. p. 208.
I’ATTY AND INORGANIC MATTER IN THE GRASSES. 919
2°. Cellular or woody-fibre in the grasses.—In the stems of the
grasses (in hay and straw), cellular fibre is a predominating ingre-
dient. They are by no means destitute of starch, gum, sugar, and
fatty matter, but they are distinguished from all the other usual
usual forms of animal food, by the large quantity of insoluble cel-
lular fibre, and of saline or earthy matter which they contain. The
proportion of cellular fibre in the more common grasses in their
usual state of dryness when made into hay and straw, is thus given
by Sprengel:— *
Per cent. Per cent.
Wheat straw ripe, ...... .......... , 52 Pea straw, ripe, ..................... 30
Barley straw, do. ............ . . . 50 Bean straw, do. * . e º & E & © e º is tº & e º 'º 51
Oat straw, do. ......... . ...... 40 Vetch hay, do. ........... . ... 42
Rye straw, do. ......... - * : * * * * * * 48 Red clover, do. .................. 28
Indian corn, do. .............. .... 24 Rye grass, do. ................. 35
The above numbers, however, can be considered only as approxi-
mations. The riper the straw or grass, the less soluble matter
does it contain, and every farmer knows how much soil, season,
and manure affect the quality of his artificial grasses. One field
will grow a hard wiry rye-grass, while another will produce a soft
and flexible plant, yielding a highly nutritious hay. -

3°. Gluten, albumen, &c. in the grasses.—Boussingault has de-
termined, by combustion, the proportion of nitrogen in our most
common varieties of hay and straw, and thence calculated that of the
protein compounds (gluten, &c.) which they contain. His results
are as follow :
Wifrnor Or gluten, | Equal nutritive
sº &c. effects should be
e per cent. produced by
Hay from mixed grasses, ...... - łł § 100 lbs.
Do, aftermath, ... . . . . . . ......... 1'54 9°3 75* ...
Do. from clover in flower, ......... 1'5 9-3 75 ..
Pea straw, .............................. 1-95 12:3 64t ...
Lentil straw, ... ...................... ] '01 6-4 114 ...
Indian corn straw,................. ... 0-54 3°4 240 ...
Wheat straw,. ........................ * º º * * * 520 ...
Barley straw, ..................... . . . . . * & tº gº & 520 ...
Oat straw, ............ . . . . . . . . . . . . . . . . . & º e ſº 550 ...
* It is usually supposed that the aftermath is not so valuable as the first produce
Schwertz, however, considers it more nourishing by one-tenth part. There can evi-
dently be no general rule on the subject.
+ “The value of all straw for fodder must depend on the mode in which it is har-
vested. In Scotland, the order in which the farmer places his straw for fodder is—
920 COMPOSITION OF HEMP AND LINT SEEDs.
The third column represents the relative feeding properties of
the dry grasses named, in so far as it depends on the proportion of
gluten and albumen they contain. g -
4°. Fatty matter in the grasses.—Besides woody fibre, starch,
gum and gluten, dry hay and straw also contain a variable pro-
‘portion of fatty matter. According to Liebig, it does not exceed
1:56 per cent, in hay, while, according to Dumas and Boussingault,
as much as 3, 4, or even 5 per cent of fat can be extracted from
it. Numerous experiments made in my own laboratory confirm
these latter results. - *
5°. Inorganic matter in the grasses—The proportion of saline
and earthy matter contained in the grasses is an important feature
in their composition. This, as we have already seen, is much
larger than in any of the other kinds of food usually given to ani-
mals, being seldom less than 5, and occasionally, as in the clovers,
(p. 390,) amounting to as much as 10 per cent, of their weight
when in the state of hay or straw. A large proportion of the ash
left by the stems of the corn plants, and by many grasses, consists
of silica. The straw of the bean, pea, and vetch, and the different
kinds of clover hay contain very little silica, its place in these plants
being chiefly supplied by a large proportion of phosphoric acid in
combination with potash and soda.
§ 10. Composition of hemp, line, rape, and other oil-bearing seeds.
The oily seeds are important to the agriculturist from their long
acknowledged value in the feeding and fattening of cattle. Lint-
seed is extensively used for the latter purpose, both in its entire
state, and in the form of the cake which is left after the greater
part of the oil has been expressed from it. All these seeds, how-
ever, are not equally palatable to cattle. Some varieties they even
refuse to eat. Among the latter is the rape-seed, from which so
much oil is expressed, and the cake left by which is now so exten-
sively employed as a manure. - - -
These seeds are distinguished from those of the corn plants, by
containing, instead of starch or sugar, a predominating proportion
of mucilage (p. 178) and of oil. They resemble the oat in con-
1st, pea ; 2d, bean ; 3d, oat; 4th, wheat; 5th, barley. While in England, where the
bean is quite withered before it is cut, it stands last in the scale.”—Mr Hyett, Royal
Agricultural Journal, iv. p. 148.
*
PROPORTION OF OIL IN DIFFERENT SEEDS. 921
taining, instead of gluten, a substance soluble in water, which pos-
sesses many of the properties of the casein or curd of milk.
We are in possession of a somewhat imperfect analysis of hemp
seed, and of the seed of the common lint, according to which the
varieties examined consisted in 100 parts of
Hemp seed Line seed
x * * (Bucholz). (Leo Meier).
Oil, .................... .......... . . . . . . . . . . . 19:1 1] 3
Husk, &c., . . ........................... • * * 38°3 44'4
Woody fibre and starch, ............... 5-0 1°5
Sugar, &c., ........................ . ...... l'6 10-8
Mucilage... .............................. .. 9:0 7-l
Soluble albumen, (casein 7) ... .... ..... 24-7 15° l P
Insoluble, do. .............................. g is e 3-7
Fatty matter, ... .......... ... ............ 1:6 3. I
Loss,.............. .......... ... a s & e º ºs e º & © e º 'º e º 'º º 0.7 3-0
100 100
The above analyses show that, besides the oil, these seeds con-
tain considerable proportions of gum and sugar, and a large quan-,
tity of a substance here called soluble albumen, which, as I have
said, has much resemblance to the curd of milk. Besides their fatten-
ing properties, therefore—which these seeds probably owe in a great
measure to the oil they contain—this peculiar albuminous matter
ought to render them very nourishing also;-capable of promoting
the growth of the growing, and of sustaining the strength of the
matured animal. - -
The proportion of oil contained in different seeds of this 'class,
and even in the same species of seed when raised in different cir-
cumstances, is very variable. These facts will appear from the
following table, which represents the proportions of oil that have
been found in 100 lbs. of some of the more common seeds:–
- Oil per cent. -- Oil per cent.
Line seed, .... ... ........... . . 11 to 22 Sum-flower,........ ..... ...... -
Hemp seed, ............... ..... 14 to 25 Walnut kernels, ............ 40 to 70
Rape seed,........... . . ......... 40 to 70 Hazelnut, ..................... 60 -
Poppy seed, .... ................ 36 to 53 Beech-nut kernel, ............ 15 to 17
White mustard,.................. 36 to 38 Plum stone do. ............ 33
Black do., ............ . ...... 15 Sweet almond, ........... ... 40 to 54.
Swedish turnip, .................. 34 Bitter do...................... 28 to 46
It seems to be a provision of nature, that the seeds of nearly all
plants should contain a greater or less proportion of oil, lodged
for the most part in, or immediately beneath, the husk. Among
other purposes this oil is intended to aid in preserving the seed. We
922 COMPOSITION OF OIL-CAKES.
shall hereafter see that it is of much importance also to the practical
agriculturist in reference to the feeding of his stock.
§ 11. Composition of linseed and gold of pleasure cakes.
Of the expressed seed or cake sold as lintseed cake of the
best quality, two samples, said to be of English and American
growth, respectively, have been analysed in my laboratory. By
way of comparison the cake of the seed of the Camelina sativa, or
gold of pleasure, was examined at the same time. The following
were the results:—

English English American
Gold of Pleas. Linseed Cake. Linseed Cake.
Water,................ . . . . . . . . . . . . . . . . . . . . . 9.95 10' 05 10-07
Mucilage, ......... .... ................ 35.08 39' 10 36'25
Albumen and gluten, ..................... 25'50 22° 14 22:26
Oil, ......................................... | 2:42 1 l’93 12:38
Husk, ..... ................. . . . . . . . . . . . 10° 16 9-53 12-69
Saline matter (ash) and Sand, ... ..... 6-89 7:25 6 35
100 100 100
These analyses are interesting in several respects. They shew—
a. That the per-centage of the protein compounds, here called
gluten and albumen, is in these cakes nearly equal to that contain-
ed in peas and beams. For the production of milk in cheese coun-
tries, therefore, and for laying on muscle, oil-cakes are as valu-
ble as beans, peas, or clovers. -
b. The proportion of oil remaining in these cakes is greater than
is naturally present in any species of grain or pulse usually culti-
wated for food. Oats contain as a maximum about 7, and Indian
corn about 9 per cent. of oil, but these cakes contain 12 per cent.,
and are, therefore, in their ability to supply fat to an animal, su-
perior to any of our cultivated grains.
c. All the three cakes resemble each other in their general
composition, and, no doubt, differences exist between different
samples of the same cake equal to those which the above table ex-
hibits, in the several samples of different kinds of cake. This is
especially interesting in reference to the gold of pleasure cake re-
cently introduced into the English market, which has a peculiar
flavour, but is said to be relished by cattle, and which, according
to the analysis, possesses feeding properties equal to those of the
best English and American linseed cakes,
SPECIAL DIFFERENCES AMONG SEEDS AND ROOTs. 923
It is difficult to say, as yet, in what form the protein compounds
exist in these oil-cakes. That a portion of them is in the state of
soluble albumen is shewn by rubbing the powdered cake in a mor-
tar with successive portions of cold water, filtering, and then heat-
ing the dilute solution nearly to boiling, when a portion of albumen
coagulates, falls to the bottom, and may be collected. By boiling
the insoluble residue in acetic acid, a portion of coagulated albu-
men is dissolved, and may also be collected by neutralizing the
acid solution. My assistant Mr Thomas obtained in this way,
from the three cakes in one trial, the following quantities of albu-
II] ell—
Soluble. Coagulated. Total.
English linseed cake, ........... ... 3'69 3.08 6-77
American, ... ........................ 3 30 2.88 6.18
Gold of pleasure,............ ........ 3-75 2.92 6-67
The whole albumen thus obtained, however, did not amount to
more than about one-fourth of the weight of the protein compounds
actually contained in the cake, as determined by combustion and
given in the preceding table. The remainder must be in the state
of casein, gluten, &c., or, perhaps, in that of a compound peculiar
to these oily seeds. These compounds, however, are probably all
modified in the cake by the heat which is applied to the seed during
the process of extracting the oil.
The composition of the Saline matter or ash of these cakes has
been already given, (p. 381).
§ 12. General differences in composition among the different kinds
of vegetable food.
It may be useful shortly to recapitulate the leading differences
in chemical composition which exist among the different kinds of
vegetable food to which I have directed your attention in the pre-
sent lecture.
We have seen that each of the varieties of food contains a greater
or less proportion of three different classes of chemical substances—
an organic substance containing nitrogen, an organic substance
containing no nitrogen, and an inorganic substance. But it is in-
teresting to mark how in each class of those vegetable products
which we gather from the earth for our sustenance, the organic
substances vary either in composition or in chemical characters,
while the inorganic matter alters also at least in quantity. Thus—
924 COMPOSITION OF THE MUSHROOM AND OF THE FUNGI.
19. In the seeds of the corn plants—wheat, oats, &c., the predo-
minating ingredient is starch, in connection with a considerable
proportion of gluten, albumen, &c. and a small quantity of saline
matter consisting chiefly of the phosphates of potash and of mag-
nesia, (p. 365.)
2°. In the seeds of leguminous plants—the pea, the bean, the vetch,
&c., starch is still the predominating ingredient, but it is connect-
ed with a large quantity of legumin, and with a greater proportion
of inorganic matter in which phosphate of magnesia is less gene-
rally abundant, (p. 377.) -
3°. In the oil-bearing seeds—those of hemp, lint, &c., a new sub-
stance, mucilage, appears, while oil becomes a predominating ingre-
dient. These are connected with a large proportion of a nitroge-
nous substance, resembling the curd of milk, and with a quantity
of Saline matter a little greater than is found in the pea, and in
which phosphate of potash abounds. {e
4°. In the potato—starch is the greatly predominating ingredient
united with albumen, &c. nearly in the same proportion as in the
grain of rice. The proportion of inorganic matter in the dry potato
is about the same as in the pea and the bean. It is richer in potash,
but much poorer in phosphoric acid than the ash of any of our
- cultivated grains, (p. 384.)
5°. In the turnip—sugar and pectic acid another new substance,
take the place of the starch. These are associated with albumen and
other protein compounds, and with a proportion of inorganic mat-
ter considerably greater than is found in the potato. The ash
abounds in potash, but is comparatively poor in phosphoric acid.
6°. In the stems of the grasses and clovers—woody:fibre or cellulose
becomes the predominating ingredient, associated apparently with
albumen, and with a larger proportion of inorganic matter than is
found in any of the other crops. In the straws and in the grasses
which are cut for hay, silica forms a large proportion of this inor-
ganic matter. In the clovers, lime and magnesia partly take its place.
The natural differences above described not only exercise an
important influence upon the mode of culture by which the diffe-
rent crops may be most successfully and most abundantly raised,
but also upon the way in which they can be most skilfully and eco-
nomically employed in the feeding of animals. To this latter point
we shall return hereafter.
AWERAGE COMPOSITION OF THE DIFFERENT CROPS. 9.25
§ 13. Composition of the mushroom and other fungi.
The mushroom, the truffle, the morel, and other similar fungi
have long been known and eaten as a luxury in various countries.
When the flesh of the mushroom is exhausted by water, alcohol,
and ether, a white fleshy substance remains, which has much re-
semblance to the fibrin obtained by the same method from the lean
part of beef or mutton. To this substance the name of fungin has
been given. It contains much nitrogen, and is no doubt very nu-
tritive,
The fungi in general contain more water even than turnips.
The proportion of mineral matter or of ash they leave is variable,
but in the common mushroom, it forms about one-eighth of the dry
solid matter. In this ash there is present a large proportion of
phosphates and invariably a little manganese. The following
table exhibits the results of the only precise chemical investigations
of the fungi that have hitherto been made.

Nitrogen. Ash.
Water.|Dry matter.
In the dry matter. In the dry matter.
Common mushroom,” 05:00 5:00 8'089 14:00
Agaricus campestris, *-
arvensis, ...... 90°6] 9:30 7-260 10.82
Stalk of ditto,... ..... * † & * * * 8:300 1 l'60
Agaricus deliciosus, ..... 86-90 13- 10 4'680 6'90
—glutinosus, ... 93-71 6:20 4°6 || 0 4'80
russula,......... 0 1 20 8.80 4:250 9-50
* cantharellus, 90-60 9°40 3:220 ] ] .20
- muscarius, ...| 90°56 9°44 6'340 . 9:00
Boletus aureus, ..... ..] 94' 35 9'65 4:700 6-80
Lycoperdon echinatum, ... e sº º 6' 160 5' 20
Polyporus fonmentarius, gº º ºs g 4'460 3:00
Daedalea quercina. ...... * * * e e ºs 3- 100 3" | 0
The proportion of nitrogen in the dry matter of these fungi, as
above shown, is very great. If we suppose that this nitrogen exists
in the fungi in the form of a protein compound resembling gluten
or albumen, which is very likely, the proportion of this protein
compound in the dry matter of some of the above species is greater
than is found in any of our cultivated crops. Thus in the six spe-
cies at the head of the above list there would be of protein com-
pounds in their ordinary and in their dry states, respectively, the
following per-centages of the albuminous substance:–
* Payen, Mémoires sur les développements des vegetaux, p. 44. All the other
analyses are made by Schlossberger and Doepping, Annalen der Chemie, vol. x. Nov.
30, 1844.
926 AVERA GE COMPOSITION OF DIFFERENT CROPS.
Protein compounds.
In natural state. Dried at 212°:
Common mushroom, ...... ........ 2.9 56-6
Agaricus arvensis, ...... . ... ...... 4°6 45-7
Stalk of do. ...... ........... 5.2 52°3
Agaricus deliciosus, ........ . . . . 3'8 29'5
—glutinosus, ......... , e s . * * 1.7 29:0
- russula, .............. ... • * * 2'4 26-8
In so far as these protein compounds are concerned, the dried
mushroom is more nutritive than any vegetable we grow, with the
exception of the bean and the pea, and the flowers (cauliflower) and
perhaps the young leaves (p. 914) of cabbage. Even the last of
the six specimens above-named contains in the dried state as much
of these compounds as the bean or the pea.
§ 14. Average composition and produce of nutritive matter per
acre, by each of the usually cultivated crops.

1°. Average composition.—The relative proportions of the seve-
ral most important constituents contained in our cultivated crops,
varies, as we have seen, with a great number of circumstances.
The following table exhibits the average composition of 100 parts
of the more common grains, roots, and grasses, as nearly as the
present state of our knowledge upon the subject enables us to re-
present it:—
* Husk | Starch, Gluten, 4’ ºn r + \} * i º
Water. |or woodygum, and albumen, . .
fibre. sugar. legumin,&c. * Iſla,Lt.Cºl.
Wheat, ............ 15 15 55 10 to 19 2 to 4 2
Barley, ............ 15 15 60 12 to 15 2 to 3 3
Oats, ............... 16 20 ($0 14 to 19 5 to 7 4
Rye, ............... 12 10 to 20 60 10 to 15 3 to 4 2
Indian corn, ...... 14 6 70 12 5 to 9 l;
Buck-wheat, ...... 15 25 50 8 0.4 P 4
Rice, ............... 13 3 75 7 0-7 0%
Beans, ............ 14 8 to ll 40 24 to 28 2 to 3 3
Peas, ............... 14 9. 50 24 2. l 3
Potatoes, ......... 75 4 | 8 2.0 0.3 # to 1%
Turnips, ........... 88 2 9* 1°5 0.3 } to #
Carrots, ............ 85 3 10 1.5 0°4 1 to 2
Mangold wurtzel, 85 2 11 2-0 2 # to 1%
Meadow hay,...... 14 30 40 7.1 2 to 5 || 5 to 10
Clover hay, ...... 14 25 40 9-3 3 to 5 9
Pea straw. ......... 10 to 15 25 45 12:3 l'5 4 to 6
Oat do. ............ 12 45 35 1-3 0.8 9 ($
Wheat do.......... 12 to 15 50 30 1-3 2 to 3% 5
Barley do.......... do. 50 30 ] '3 9 5
Rye do. ............ do. 45 38 1.3 P 4
Indian corm, do.... I 2 25 52 3.0 I-7 3 to 7
* In the turnip, carrot, and mangold wurtzel it will be remembered that pectic
acid takes the place of starch.
GROSS PRODUCE PER ACRE. 927
Some of the above numbers are approximations only. The pro-
portions of fatty matter especially are in many instances very un-
certain.
2°. Gross produce per acre.—The gross produce, per acre, of
the different crops varies in different districts of the country. The
weight of each crop in pounds, however, will, in general, approach
to one or other of the quantities represented by the numbers in
the following table :-
Produce Weight Total weight.
per acre. per bushel. in pounds.
Wheat,............... 25 bush. 60 lbs. 1500
- 30 ... 1800
Barley, ............... 35 ... 53 lbs. 1850
* 40 ... 2120
Oats, .................. 40 ... 42 lbs. 1680
*m-. 50 ... 2100
Rye, .................. 25 ... 54 lbs. 1350
• * * 30 ... 1620
Indian corn, ......... 30 ... 60 lbs. 1800
Buck-wheat, ...... 30 ... 46 lbs. 1380
Beans, ............... 25 ... 64 lbs. 1600
assº 30 ... . 1920
Peas, ........... . ... 25 ... 66 lbs. 1650
Weight of produce. Weight of produce.
Potatoes,....... ....... 6 tons, Carrots, ..... ......... 25 tons.
sº 12 tons, Meadow hay, ........ l; tons.
Turnips, ............... 20 tons. Clover hay,............ 2 tons.
gº 30 tons.
Wheat straw, ...... 3000 lbs. Rye straw, ......... 4000 lbs.
3600 . . . 4800 ...
Barley straw,.. ...... 2100 ... Bean straw, ......... 2700 ... ?
2500 . . . 3200 . . .
Oat Straw,..... ...... 2700 . . . Pea straw, ... ......... 2700 ... ?
3500 ...
3°. Average produce of nutritive matter per acre.—In the gross
produce above given, there are contained, according to the first
table, the following average proportions of nutritive matter of va-
rious kinds:—
928
AWERAGE PRODUCE PER, ACRE.
Average Produce of Nutritive Matter of different kinds from an
acre of the usually cultivated crops.
*

Gross Husk or Starch, Saline
produce. Woody fibre, sugar, Gluten, &c. Oil or fat. matter.
&c.
bush | libs. lbs. lbs. lbs. lbs. lbs.
Wheat, ...... ..... 25 1,500 225 825 | 150 to 280 || 30 to 60 | 30
• * * * * * * * * * * * 30 | 1,800 270 900 180 to 340 36 to 72 36
Barley, ..........., 35 | 1,800 270 1080 || 2 || 0 to 260 || 36 to 54 50
- * * * * * * * * * * 40 2.100 315 1260 || 250 to 3 l () || 42 to 63 60
Oats, .... .......... 40 | 1,700 340 1000 || 2:30 to 320 80 to 120 70
• * * * * * * * * * * * * * 50 2,100 420 1050 | 290 to 400 || 75 to 150 80 |
Rye, ... ........... 25 | 1,300 | 130 to 260 || 780 || 130 to 200 40 to 50 26
* * * * * * s is e s - a s e a 30 | 1,600 | 160 to 320 960 230 to 350 || 48 to 64 32
Indian corn, ...... 30 1,800 100 1260 216 90 to 170 27
Buck-wheat, ...... 30 | 1,300 320 650 100 9 5 P 2]
Beans, ............ 25 | 1,000 160 640 || 380 to 450 | 32 to 48 48
- * * * * * - - - - - e. 30 1,900 190 760 || 450 to 530 38 to 57 57
Peas, ............... 25 | 1,600 130 800 380 34 48
tons.
Potatoes, ....... . 6 || 3,500 540 2400 270 45 120
* - & & © tº º 'º - e. e. e. 12 27,000 1080 4800 540 90 240
Turnips,........... 20 |45,000 900 4000 670 I 30 300
- - - ºr ºf sº e - - - - - 30 |67,000 1340 6000 l 000 200 450
Carrots. ............ 25 56,000 1680 5600 840 200 800
Mangold wurtzel, | 20 |45,000 900 495.0 900 P 450
Meadow hay,...... 14| 3,400 1020 1360 240 70 to 170 220
Clover hay, ... ... 2 4,500 ] 120 1800 420 135 to 225 400
Pea Straw, ........ . 2,700 675 1200 330 40 135
Wheat straw, 3,000 I 500 900 40 60 to 100 l 50
- - - e º - - - - - e. 3,600 1800 1080 48 70 to 120 180
Oat straw, ......... 2,700 1210 950 36 p 135
• * * * * * * * * * * * 3,500 1570 1200 48 9 175
Barley straw, ...... 2,100 1050 630 28 2 105
• * * * * * * * * * * * 2,500 1250 7:50 33 ? 125
Rye straw, ......... 4,000 1800 1500 53 2 16()
- * * g = < * - - - e. e. 4,800 2200 1800 64 P 200
The most uncertain column in this table is that which represents
the quantity of oil or fat contained in the several kinds of produce,
The importance of the whole table to the practical man will ap-
pear more clearly when we come to treat of the feeding of stock.
LECTURE XXIV.
‘Of milk and its products. Properties and composition of the milk of different ani-
mals. Circumstances which affect the quality and quantity of milk—species, size,
variety, age, health, and constitution of the animal, time of milking, kind of food,
&c. Mode of separating and estimating the several constituents of milk. Sugar
of milk, and acid of milk (Lactic acid), their composition and properties. Souring
of milk—cause of Cream—composition and variable proportions of mode of es-
timating its quantity—the galactometer. Churning of milk and cream. Composi-
tion of butter. Butter-milk. The solid and liquid fats contained in butter—mar-
garin and claim—their separation and properties. Rancidity and preservation of
butter.
OF the indirect products of agriculture, milk and the butter and
cheese manufactured from it, are among the most important. In
our large towns these substances may almost be considered as ne-
cessaries of life, and many extensive agricultural districts are en-
tirely devoted to the production of them. The branch of dairy
husbandry also presents many curious and interesting questions to
the scientific inquirer, and upon these questions modern chemistry
has thrown much light. To the consideration of this subject, there-
fore, it is my intention to devote the present lecture.
1. Of the properties and composition of milk.
1°. Properties of milk.-The milk of most animals is a white
opaque liquid, of an agreeable sweetish taste, and a slight but pecu-
liar odour—which becomes more distinct when the milk is warmed.
It is heavier than water—usually in the proportion of about 103 to
100. Or its specific gravity varies from 1020 in woman’s milk,
to 1041 in sheep's milk, that of water being 1000.
When newly drawn from the animal, cow's milk is almost always
slightly alcaline. It very soon loses this character, however, when
exposed to the air, and hence even new milk often exhibits a slight
degree of acidity. It is said that if the animal remain long un-
milked, the milk will begin to sour in the udder, and that hence it
is sometimes slightly acid when fresh drawn from the cow.
3 N
930 PROl’ERTIES OF MILK.
When left at rest for a number of hours, it separates into two
portions, throwing up the lighter part to the surface in the form of
cream. If the whole milk, or the cream alone, be agitated in a
proper vessel (a churn), the temperature of the liquid undergoes a
slight increase, it becomes distinctly sour, and the fatty matter
separates in the form of butter. If a little acid, such as vinegar
or diluted muriatic acid, be added to milk warmed to about 100°
F., it immediately coagulates and separates into a solid and a li-
quid part—the curd and the whey. The same effect is produced
by the addition of rennet or of sour milk, and it takes place natu-
rally when milk is left to itself until it becomes sour. At a very
low temperature, or when kept in a cool place, milk remains sweet
for a considerable time. At the temperature of 60°F. it soon
turns or acquires a sour taste, and at 70° or 80° it sours with still
greater rapidity. If sour milk be kept in a warm place it under-
goes fermentation, and may be made to yield an intoxicating liquor.
By longer exposure to the air it gradually begins to putrefy, be-
comes disagreeable to the taste, emits an unpleasant odour, and
ceases to be a wholesome article of food.
The milk of each species of animal is distinguished by some cha-
racters peculiar to itself.
Ewe's milk does not differ in appearance from that of the cow,
but it is generally more dense and thicker, and gives a pale yellow
butter, which is soft, and soon becomes rancid. The curd is sepa-
rated from this milk with greater difficulty than from that of the
COW.
Goat's milk generally possesses a characteristic unpleasant colour
and taste, which is said to be less marked in animals of a white
colour or that are destitute of horns. The butter is always white
and hard, and keeps long fresh. This milk is considered to be very
wholesome, and is often recommended to invalids. .
Ass’s milk has much resemblance to that of the woman. It
yields little cream, and the butter is white and light, and soon be-
comes rancid. It contains much sugar, and hence soon passes to
the state of fermentation.
2°. Composition of milk.-Milk, like the numerous vegetable
products we have had occasion to consider, consists, besides water,
of organic substances destitute of nitrogen—sugar and butter; of
4.
COMPOSITION OF MILK, 931
an organic substance containing nitrogen in considerable quantity
—the curd or casein ; and of inorganic or saline matter, partly
soluble and partly insoluble in pure water.
The proportions of these several constituents vary in different
animals. This appears in the following table, which exhibits the
composition of the milk of several animals in its ordinary state, as
found by Henry and Chevallier:-
Woman. Cow. Ass. Goat. Ewe.
Casein, (pure curd,) ... 1-52 4'48 1.82 4:08 4'50
Butter, ...... ........... 3°55 3.13 0.11 3-32 4:20
Milk Sugar, ............ 6'50 4.77 6'08 5'28 5:00
Saline matter, ......... 0°45 0-60 0°34 0°58 0-68
Water, .................. 87-98 87-02 9] '65 86'80 85.62
100 100 100 100 100
From the numbers in the above table, it appears that the milk
of the cow, the goat, and the ewe, contains much more cheesy mat-
ter than that of the woman or the ass. This similarity of asses'
milk to that of the human species, together with its deficiency in
butter, are probably the cause why, from the most remote times,
it has been recommended to invalids, as a light and easily digested
drink.
§ 2. Of the circumstances by which the composition or quality of
milk is modified.
But the composition or quality of milk varies with a great variety
of circumstances. Let me direct your attention to a few of these.
1°. Distance from the time of calving.—The most remarkable
departure from the ordinary composition of milk is observed in the
beistings, colostrum, or first milk, yielded by the animal after the
birth of its young. This milk is thicker and yellower than ordi-
nary milk, coagulates by heating, and contains an unusually large
quantity of casein or curdy matter. Thus the first milk of the cow,
the ass, and the goat consisted, in some specimens examined by
Henry and Chevallier, of
Cow. Ass. Goat.
Casein....... . . . . 15: 1 1 1-6 24°5
Butter,............ 2.6 0.6 5-2
Milk sugar,...... *- 4’3 3-2
Mucus, ......... 2-0 0-7 3-0
Water,............ 80' 3 82.8 64 - 1
- asºmº- -
| 00 | 00 | 00
932 CIRCUMSTANCES AFFECT ITS QUALITY.
The increase in the proportion of curd is peculiarly great in the
first milk of the ass and the goat.
This state of the milk, however, does not long continue. It gra-
dually assumes its ordinary qualities. After ten or twelve days
from the time of calving, its peculiarities disappear, though in the
celebrated dairy districts of Italy it is considered that the milk does
not reach perfection until about eight months after calving.”
2°. Age of the animal.-It is observed that milk of the best
quality is given only by cows which have been already three or
four times in calf. Such animals continue to give excellent milk
till they are 10 or 12 years of age, and have had seven or eight
calves, when they are generally fattened for the butcher.
3°. Climate and season of the year.—Moist and temperate cli-
mates are favourable to the production of milk in large quantity.
In hot countries, and in dry seasons, the quantity is less, but the
average quality is richer. Cool weather favours the production
of cheese and sugar in the milk, while hot weather increases the
yield of butter (Sprengel).f
In spring the milk is more abundant and of finer flavour. In
autumn and winter, other things being equal, it yields less cheese,
but a larger return of butter. Where cattle are fed upon pas-
ture grass only, this observed difference may be derived from a
matural difference in the quality of the herbage upon which the
cow is fed.
4°. Health and general state of the animal.-It is obvious that
the quality of the milk must be affected by almost every change
in the health of the animal. It is also sensibly less rich in cream,
as soon as the cow becomes pregnant, and the same is observed to
be the case when it shows a tendency to fatten. The poorer the
apparent condition of the cow, good food being given, the richer in
general is the milk.
5°. Time and frequency of milking.—If the cow be milked only
* Cataneo, Il latte e i Suoi prodotti, p. 27.
+ Chemie für Landwirthe, ii. p. 620.
† British Husbandry, ii. p. 804. This opinion seems to contradict that of Spren-
gel in the preceding paragraph. Does this difference arise from the locality and other
unlike circumstances in which the observations of the two writers were severally made
—or are there no accurate experiments upon the subject from which a correct result
can be drawn
* }
* x
INFLUENCE OF THE HEALTH OF THE ANIMAL. 933
once a day, the milk will yield a seventh part more butter than an
equal quantity of that which is obtained by two milkings in the
day. When the milk is drawn three times a day, it is more abun-
dant but still less rich. It is also universally remarked, that the
morning's milk is of better quality than that obtained in the even-
ing.
6°. Period at which it is taken, during the milking.—The milk in
the udder of the cow is not uniform in quality. That which is first
drawn off is thin and poor, and gives little cream. That which is
last drawn—the stroakings, strippings, or afterings—is rich in qua-
lity, and yields much cream. Compared with the first milk, the
same measure of the last will give at least eight and often sixteen
times as much cream (Anderson). The quality of the cream also,
and of the milk when skimmed, is much better in the later than in
the earlier drawn portions of the milk.
7°. Treatment and moral state of the animal.—A state of com-
parative repose is favourable to the performance of all the impor-
tant functions in a healthy animal. Amy thing which frets, dis-
turbs, torments, or renders it uneasy, affects these functions, and,
among other results, lessens the quantity or changes the quality of
the milk. Such is observed to be the case when the cow has been
newly deprived of her calf—when she is taken from her companions in
the pasture field—when her usual place in the cow-house is changed
—when she is kept long in the house after the spring has arrived—
when she is hunted in the field or tormented by insects—or when
any other circumstance occurs by which irritation or restlessness is
caused, either of a temporary or of a permanent kind. I do not
enquire at present into the physiological nature of the changes
which ensue—to the dairy farmer it is of importance chiefly to be
familiar with the facts.
8°. The race or breed and size of the animal.-The quality of
the milk depends much upon the race and size of the cow. As a
general rule, small races, or small individuals of the larger races,
give the richest milk from the same kind of food. Thus the small
Highland cow gives a richer milk than the Ayrshire. The small
Alderneys gives a richer cream than any other breed in common
use in this country.
A very striking illustration of the difference in the quality of
934 INFLUENCE OF THE BREED ON THE QUALITY OF MILK.
the milk of the Alderney and Suffolk breeds, in the same circum-
stances, is given by Mr Malcolm, in his Compendium of Modern
Husbandry. He kept an Alderney and a Suffolk cow, the latter
the best he ever saw. During seven years, the milk and butter being
kept separate, it was found, year after year, that the value of the
Alderney exceeded that of the Suffolk, though the latter gave more
than double the quantity of milk at a meal.-British Husbandry,
ii. p. 397.
The small Kerry cow is said to equal the Alderney in the rich
quality of its milk, while the small Shetlander has been found in
the north of Scotland to give from the same food a more profita-
ble return of rich milk than any of the larger races. All these
breeds are hardy, and will pick up a subsistence from pastures on
which other breeds would starve.
The old Yorkshire stock, a cross between the short-horn and the
Holderness, is preferred by the London cow-keepers as giving the
largest quantity of milk, though poor in quality.
The long-horns are preferred in Cheshire and Lancashire be-
cause of their producing a greater quantity of cheese. The Ayr-
shire kyloe, on ordinary pasture, is said to be unrivalled for abun-
dant produce (Ayton)—though the milk is not so rich as that of
the smaller breeds. Various crosses have been tried in different
parts of the island—and in almost every district it has been found
that the produce of some particular stock is best adapted to the
climate, the soil, the matural grasses, the prevailing husbandry, or
to the kind of dairy produce which it is the interest of the farmer
to raise in his own peculiar neighbourhood.
In the south of Europe, the Swiss breeds are considered the best
for dairy purposes, and of these that of the Canton of Schweitz,
which, in size, is intermediate between the large cattle of Fribourg
and Berne, and the small breed of Hasti. They have enormous
udders, and give much milk, but like that of the Suffolk cows it is
less rich in butter and cheese.
The influence of breed alone upon the quality of the milk is well
illustrated by the result of a series of trials made at Bradley Hall
in Derbyshire. During the height of the season, and when fed
upon the same pasture, cows of four different breeds gave per
day—
VALUE OF THE HOLDERNESS AMD AYRSHIRE BREEDS. 935
Or 1 lb. of butter was
Breed. Milk. Butter. yielded by
Holderness, ............ 29 quarts and 38% oz. 12 quarts of milk.
Alderney, ............... 19 ............ 25 oz. 12 ... . . . . . . . .
Devon, .................. 17 ............ 28 oz. 9: ............
Ayrshire, ... .......... 20 ............ 34 oz. 9% ... .........
The Ayrshire cows gave the richest milk, and a larger quantity
of both milk and butter than the Alderneys or Devons, but the
Holderness breed surpassed them all. It gave 3 lb. more butter
than the Ayrshire, and nearly one-half more milk. It would ap-
pear, therefore, to be admirably adapted to the purposes of the
town dairyman, whose profit arises from milk and cream only. It
does not appear what is the relative value of this breed in the pro-
duction of cheese.
9°. The kind of food.—But the kind of food has probably more
influence upon the quality of the milk than any other circumstance.
It is familiar to every dairy farmer that the taste and colour of his
milk and cream are affected by the plants on which his cows feed,
and by the food he gives them in the stall. The taste of the wild
onion and of the turnip, when eaten by the cow, are often percep-
tible both in the milk and in the butter. If madder be given to
cows the milk is red; if they eat saffron it becomes yellow. It has
also been observed from the most remote times, that when fed up-
on one pasture a cow will yield more cheese, upon another more
butter. From this has arisen the practice more or less observed
in all dairy districts of varying the food of the cattle—of giving
some artificial food in addition to that obtained in the natural pas-
tures—of leaving the animal at liberty to roam over wide pastures,
and thus to seek out for itself, as the sheep does on extensive sheep
walks, those different kinds of herbage which are necessary to the
production of a rich and valuable milk—or in more inclosed dis-
tricts, and where different soils exist on the same farm, of turning
them during the former part of the day into one field, and during
the latter part into another. *
Various sets of experiments have been made with the view of
determining the relative quantities of butter and cheese produced
by the same animals, when fed upon different kinds of food. Ac-
cording to theory, the leguminous plants—clover, tares, &c., and
the cultivated seeds of such plants—such as peas and beams—ought
936 EXPERIMENTS WITH DIFFERENT KINDS OF FOOD.
to promote the production of cheese ; while oil-cake, oats, and other
kinds of food which contain much oily matter, ought to favour the
yield of butter also. The most recent experiments we possess, how-
ever, do not lend any decided confirmation to these theoretical
views. The results published by Boussingault," Playfair, f and
Thomson, are all more or less unsatisfactory; and it is much to be
desired that conjoined practical and analytical researches should be
carefully made upon this subject.
10°. State of pregnancy.—I have already stated that the rich-
mess in cream diminishes as soon as the cow becomes pregnant.
The same is no doubt true also of the amount of cheese which the
same volume of milk will be capable of yielding. It must either
become poorer in every respect, or considerably less in quantity
as soon as the cow is with calf, since a portion of the food which
might otherwise have been employed in the production of milk,
must now be directed to the nourishment of the young animal in
the womb of the mother.
11°. Individual form and constitution of the animal.—But it is
well known that animals of the same breed, fed on the same food,
will yield milk not only in different quantities, but also of very
different quality. In regard to the form, Mr Youatt states, that
the “Milch cow should have a long thin head, with a brisk but
placid eye, should be thin and hollow in the neck, narrow in the
breast and point of the shoulder, and altogether light in the fore-
quarter, but wide in the loins, with a little dewlap, and neither
too full fleshed along the chine, nor showing in any part an incli-
nation to put on much fat. The udder should especially be large, .
round, and full, with the milk veins protruding, yet thin skinned,
but not hanging loose or tending far behind. The teats should
also stand square, all pointing out at equal distances and of the
same size, and although neither very large nor thick towards the
udder, yet long and tapering towards a point. A cow with a
large head, a high backbone, a small udder and teats, and drawn
up in the belly, will, beyond all doubt, be a bad milker.”f Thus
* Anmales de Chim. et de Phys. lxxi. p. 79.
+ Memoir of the Chemical Society, i. p. 174.
: Youatt's Cattle, p. 244, quoted in Brit. Husbandry, ii. p. 397.
EFFECT OF INDIVIDUAL FORM AND CONSTITUTION. 937
while much depends upon the breed, the form of the individual
also has much influence upon its value as a milker.
12°. But independent of form, the quality of the milk is greatly
affected by the individual constitution of every cow we feed. Thus
in a report upon the produce of butter yielded by each cow of a
drove of 22, chiefly of the Ayrshire breed—all of which we may
presume to have been selected for dairy purposes with equal re-
gard to their forms—and which were all fed upon the same pas-
tures in Lanarkshire, the yield of milk and butter by four of the
cows in the same week is given as follows:—
Milk. - Butter.
A yielded 84 quarts, which gave e 34 lbs.
F and R. each 86 5% lbs.
G yielded 88 — 7 lbs.”
Shewing that, though the breed, the food, and the yield of milk
was nearly the same, the cow G produced twice as much butter as
the cow A–or its milk was nearly twice as rich. This result
would have been still more interesting had we known the relative
quantities of grass consumed by these two cows respectively.
I will not insist upon other causes by which the quality of the
milk is more or less materially affected. It is said that when stall
fed the same cow will yield more butter, and when pastured in the
field more cheese—that the age of the pasture also influences the
yield of butter—and that salt mingled with the food improves both
the quantity and the quality of the milk. There are, probably,
few circumstances capable in any way of affecting the comfort of
the animal, which will not also modify the quality of the milk it
yields.
§ 3. Of the circumstances which affect the quantity of the milk.
The epithet good-milker applied to a cow has very different sig-
nifications in different districts and countries. In England and
Holland the cows give the largest quantity of milk—after these
are the Swiss, then the Saxon, next the German in general, and
lowest of all the French. -
There are three circumstances which principally affect the quan-
tity of milk—the breed namely, the kind of food or pasture, and
the distance from the time of calving.
* Prize Essays of the Highland Society, new series, ii. p. 258.
9.38 CIRCUMSTANCES AFFECT THE QUANTITY OF MILK.
1°. The breed.—The smaller breeds of cattle yield, as is to be
expected, a smaller daily produce of milk—though from the same
weight of food they occasionally give even a greater volume of
milk than the larger breeds. *
Good ordinary cows in this country yield, on an average, from
8 to 12 quarts a-day. The county surveys state the average daily
produce of dairy cows to be, in
- Quarts. Quarts.
Devonshire, ......... 12 Lancashire,......... 8 to 9
Cheshire, ............ 8 Ayrshire, ......... 8
But the best Ayrshire kyloes will yield an average of 12# quarts
daily, during 10 months of the year (Ayton).
Quarts.
The yearly produce of the best Ayrshire kyloes is stated by
Mr Ayton at ..... ........... ................................... 4000
Of average Ayrshire stock at................................ ...... 2400
Good short-horns, grazed in summer, and fed on hay and
turnips in winter, yield (Dickson) ..... ............... . . . . . 4000
Mixed breeds in Lancashire (Dickson) ........................ 3500
Large dairy of mixed long and short horns, at Workington
Hall, taking an average of 4 years, (Mr Curwen) ........ 3700
Crossed breeds in many localities are found more productive in
milk than pure stock of any of the native races of cattle.
2°. Food and pasture.—In the same animal the quantity of milk
is known to be greatly influenced by the kind of food. This is
best understood in the neighbourhood of large towns, where the
profit of the dairyman is dependent upon the quantity” rather
than upon the quality of his milk. Hence the value of highly
succulent foods—of the grass of irrigated meadows—of mashed
and steamed food—of brewers' grains—of turnips, potatoes, and
beets—and of other similar vegetable productions which contain
much water intimately mixed with their nutritive matter, and thus
tend both to aid in the production of milk and to increase its
quantity.
3°. Distance from the time of calving.—It is a well-known fact
that cows in general after the first two months from the time of
* It is quoted, even by foreign writers, as a fair joke against the dairy establish-
ments of our large towns, that among the advantages possessed by one which was ad-
vertised for sale, much stress was laid upon a never-failing pump. —See Il latte e i Suoi
prodotti, p. 67.
MODE OF SEPARATING THE CONSTITUENTS OF MILK. 939
calving, though fed upon the same food in equal quantity, begin
gradually to give less milk, till at the end of about 10 months
they become altogether, or nearly, dry. In the best Ayrshire
kyloes, the rate of this decrease is thus represented by Mr Ay-
ton :-
Quarts per day. Quarts.
First fifty days, ........... 24, or in all ...... 1200
Second do. ... ........ 20, .................. 1000
Third do. ............ 14, .................. 700
Fourth do. ............ 8, .................. 400
Fifth do. ............ 8, .............. . . . 400
Sixth do. ............ 6, .................. 300
Some cows indeed do not run dry during any period of the year,
but these may be considered as exceptions to the general rule.
By feeding them upon brewers' grains, mashes, and succulent
grass, the milk-sellers near our large towns occasionally keep the
same cow in profitable milking condition for three years and up-
wards.” Such cows are generally fattened after they have be-
come dry—indeed as they cease to give milk, they generally lay
on fat in its stead—and, as soon as they are considered ripe, are
sold off to the butcher.
§ 4. Of the mode of separating and estimating the several constitu-
ents of milk.
1°. If a weighed quantity of milk be allowed to stand for a suf-
ficient length of time, the cream will rise to the top, and may be
easily skimmed off. If this cream be gently heated, the butter in
an oily form will gradually collect upon the surface, and after be-
ing allowed to cool, may be separated from the water beneath, and
its weight determined.
2°. If the skimmed milk be gently warmed, and a little vinegar
or rennet then added to it, the curd will separate, and may be col-
lected in a cloth, pressed, dried, and weighed.
3°. If a second equal portion of the milk be weighed and then
evaporated to dryness by the heat of boiling water, and again
* Even on shipboard I have heard of a cow being kept in milk during the whole of
a three years’ cruise—the food being principally pease soup. After the first year,
however, the milk is said to become thinner and more watery.
940 HOW TO ESTIMATE THE BUTTER, SUGAR, AND CASEIN.
weighed, the loss will be the quantity of water which the milk con-
tained.
4°. If now the dried milk be burned in the air till all the com-
bustible matter disappears, and the residue be weighed, the quan-
tity of inorganic saline matter will be determined.
5°. Supposing those processes to be performed with tolerable
accuracy, the difference between the sum of the weights of the wa-
ter, butter, curd, and ash, and the whole weight of the milk em-
ployed, will nearly represent that of the sugar contained in the
given quantity of milk.
For many purposes a rude examination of milk after this man-
ner may be sufficient, but where anything like an accurate analy-
sis is required, more refined methods must be adopted. In such
cases the following appears to be the best which has hitherto been
recommended.*
a. The butter.—The weighed quantity of milk is mixed with
one-sixth of its weight of common unburnt gypsum previously re-
duced to a very fine powder. The whole is then evaporated to
dryness, with frequent stirring at the heat of boiling water (212°
F.) A brittle mass is obtained, which is reduced to fine powder.
By digesting this powder in ether, the whole of the butter is dis-
solved out, and by evaporating the ether, may be obtained in a
pure state and weighed. Or the powder itself, after being treated
with ether, may be dried and weighed. The butter is then esti-
mated by the loss.
b. The sugar.—After the removal of the butter, alcohol is
poured upon the powder and digested with it. This takes up the
sugar with a little saline matter soluble in alcohol. By evaporat-
ing this solution and weighing the dry residue, the quantity of su-
gar is determined. Or, as before, the powder itself may be dried
and weighed, and the sugar estimated by the loss. If we wish to
estimate the small quantity of inorganic Saline matter which has
been taken up along with the sugar, it may be done by burning
the latter in the air, and weighing the residue.
c. The saline matter.—A second weighed portion of milk is now
evaporated carefully to dryness and again weighed. The loss is
the water. The dried milk is then burned in the air. The weight
* Haidlen, Amnal. der Chem. & Phan'. xlv. p. 263. -
ExTRACTION AND PROPERTIES OF THE SUGAR OF MILK. 941
of the incombustible ash indicates the proportion of inorganic Sa-
line matter contained in the whole milk.
d. The casein or curd.—The weight of the butter, sugar, saline
matter and water being thus known and added together, the defi-
ciency is the weight of the casein.
§ 5. Of the sugar of milk, and of the acid of milk or lactic acid.
Before I can hope to make you understand the mature of the
changes which take place during the souring, the churning, and
the curdling of milk, it will be necessary to make you acquainted
with the sugar of milk, and with lactic acid or the acid of milk.
1°. Sugar of milk.--When the curd is separated from milk, the
raw whey afterwards boiled—and the floating curd skimmed off or
separated by straining through a cloth, the whey is obtained nearly
free from butter and cheese. By mixing it while hot with well
beat white of egg, the remainder of the curd is coagulated, and
may be removed by again straining through cloth. If the clear
whey, thus obtained, be boiled down in a pan to about one-fourth
of its bulk, then poured into an earthen dish, and set aside for a
few days in a cool place, minute hard white crystals gradually de-
posit themselves upon the sides and bottom of the vessel. These
crystals are sugar of milk. A second portion may be obtained by
evaporating the remaining whey still further, and again setting
aside. If the whey be at once evaporated to dryness, a white mass
of impure sugar is prepared, which in many places is used as an
article of food. Of the purer variety large quantities are extract-
ed from milk by the Swiss shepherds, and in their country it forms
an important article of commerce.
The sugar of milk is less sweet than that of the grape or of the
sugar cane. It is harder also, and much less soluble in water, and
is gritty between the teeth. This sugar undergoes no change
when exposed to the air, either in the dry state or when dissolved
in water. But if a little of the curd of milk (casein) be introduced
into the solution it gradually becomes sour, lactic acid is formed,
and the liquid begins to ferment. Carbonic acid is given off, as
is the case during the fermentation of other liquids, and alcohol is
produced. In milk the sugar and curd are naturally intermixed,
and it is the presence of the cheesy matter, as we shall hereafter
942 THIE ACID OF MILK OR LACTIC ACID.
see, which at favourable temperatures always causes milk of every
kind first to become sour and then to ferment.
The gluten of wheat, diastase, and animal membranes of various
kinds produce a similar effect upon solutions of sugar of milk. A
piece of bladder, or of the gut or stomach of an animal, immersed
into a solution of the sugar, changes it by degrees into lactic acid,
and upon this influence depends the effect of the calf's stomach,
in the form of rennet, in the curdling of milk. The effect of
such membranes is most speedy after they have been some time
taken from the body of the animal, a fact which also accords with
the long experience of the dairy districts in the preparation of ren-
net. -
When a little sulphuric or muriatic acid is added to a solution of
milk sugar, it is slowly converted into grape sugar. This change
is hastened very much by boiling it with the acid. It is supposed
that previous to the fermentation of milk the sugar it contains is
changed in a similar way into the sugar of grapes.
Milk sugar has not hitherto been formed by art. It exists in the
milk of all mammiferous animals, and from this source alone have
we hitherto been able to obtain it.
2°. The acid of milk—lactic acid.—When milk is exposed to
the air for a length of time it acquires a sour taste, which gradually
increases in intensity till at length the whole begins to ferment.
This sour taste is owing to the production of a peculiar acid, to
which the name of acid of milk or lactic acid has been given. The
same acid is formed during the fermentation of the juices of the
beet, and of the turnip, in sour cabbage (sauer kraut), and sour
malt, in brewers' grains which have become sour, in the sour ve-
- getable mixtures with which cattle are often fed, in the waste li-
quor of the tanners, in the fermented extract of rice—and in large
quantity during the fermentation of the gluten in the manufacture
of starch from wheaten flour, or of a mixture of oat-meal or bean-
meal with water, which is allowed to stand and sour.
The acid, therefore, differs from the sugar of milk in this re-
spect that it can readily be formed, and in any quantity, by arti-
ficial means. As it is not employed for any economical purposes,
I shall not trouble you with the methods by which this acid is ob-
tained in a state of purity,
MUTUAL RELATIONS OF SUGAR AND LACTIC ACID. 943
It is rarely found in milk when first drawn from the cow, but
it very soon begins to be formed in it. It is produced from the
sugar, through the influence of the cheesy matter of the milk.
The pure acid may be mixed with cold milk without causing it to
curdle, but if the mixture be heated, the curd forms and speedily
separates. It is for the same reason that milk may be distinctly
sour to the taste, and yet may not coagulate. But if such milk be
heated it will curdle immediately. So cream when sour may not
appear so, till it is poured into hot tea, when it will break and leave
its cheesy matter floating on the surface. &
§ 6. Of the mutual relations which exist between lactic acid and
the cane, grape, and milk sugars. -
It is important, and I think it will prove interesting to you, to
understand the beautifully simple relation which exists between the
sugar of milk and this lactic acid, which plays so important a part
in nearly all your dairy operations. f
Cane sugar, grape sugar, milk sugar, and lactic acid, as they
exist in solution in water or in milk, may all, like starch, sugar,
and gum (p. 185), be represented as compounds of carbon with
water—or of carbon with hydrogen and oxygen in the proportions
in which they exist in water. Thus they consist respectively of—
. 12 Carbon + l2 Water
Cane sugar...... Cl2 + H12 + O.12 or 12C + 12HO*
* 12 Carbon + 14 Water
Grape sugar ... 12C + 14H + 14O or 12C + 14HO
24 Carbon + 24 Water
Mill sugar...... 240 + 24H + 240 or 24c - 24Ho
- 6 Carbon + 6 Water
Lactic acid...... 6C + 6H + 6O or 60 + 6HO
4 Carbon + 3 Water
Acetic acid 4C + 3 H + 3O or 4C + 3FIO
(vinegar) ſ ‘’’
I have added acetic acid to this list, to show you that the lactic
acid bears a similar relation to the sugars as this acid does. You
will recollect that starch, gum, and woody fibre, have also a simi-
* C, H, and O, as in our former lectures, representing respectively carbon, hydro-
gen, and oxygen, and HO water—a compound of hydrogen with oxygen.
944 CHANGE OF MILK SUGAR INTO LACTIC ACID.
lar relation to the sugars—and that by certain apparently simple
transformations these several substances are capable of being con-
verted into grape sugar. In like manner all these sugars by a
similar simple transformation are readily converted into one or
other of the two acids above named. Starch, gum, and cellulose
in favourable circumstances are transformed into sugar (p. 187
and 188), and the sugars again in favourable circumstances are fur-
ther transformed into the lactic or the acetic acids. -
We have seen that animal membranes or the curd of milk have
the property of changing these sugars into lactic acid. This they
do, though excluded from the action of the air, and without the
escape of any gas. The above formulae show with what apparent
simplicity this may be accomplished. -
In fact cane sugar, milk sugar, and lactic acid, as above repre-
sented, consist of the same elements united together in the same pro-
portions. It is easy to conceive therefore in what way the one may
be transformed into the other. Thus
C. H. O.
1°. Two of lactic acid are represented by...... 12 12 12
And one of came sugar ..................... 12 12 12
The transforming action of the animal membrane, or of the casein
in its state of incipient decay, is therefore simply to cause the ele-
ments of the sugar to assume a new arrangement—in which, instead
of came sugar, they form a substance having the very different pro-
perties of lactic acid. Again,
C. H. O.
2°. One of milk-sugar is represented by ...... 24 24 24
And 4 of lactic acid also equal ............ 24 24 24
The change which takes place when milk becomes sour, therefore,
is easily understood. Under the influence of the casein the ele-
ments of a portion of the milk sugar are made to assume a new
arrangement, and the sour lactic acid is the result. There is no
loss of matter, no new elements are called into play, nothing is ab-
sorbed from the air or given offinto it—but a simple transposition
of the elements of the sugar takes place, and the new acid com-
pound is produced.
These changes appear very simple, and yet how difficult it is to
APPARENT SIMPLICITY OF THESE CHANGES. 945
conceive by what mysterious influence the mere contact of a decay-
ing membrane or of the casein of milk, can cause the elements of
the Sugar to break up their old connexion, and to arrange them-
selves anew in another prescribed order, so as to form a compound
endowed with properties so very different as those possessed by
lactic acid. It is beautiful to see the simple means by which in
nature so many important ends are accomplished—to observe how
they are all veiled to the uninstructed—and how every slight
accession to our knowledge opens up new wonders to us even in those
ordinary operations with which during our whole lives we have been
most familiar.
From these intellectual, in addition to other rewards, which con-
stantly follow the study of mature, you will with me draw the con-
clusion—which is ever pressing itself upon our attention—that it
is the will and intention of the Leity, that all his works should be
thoroughly studied and investigated. But you will, I think, agree
with me in drawing this conclusion, because of the further and
higher moral effect also which such investigations tend to pro-
duce upon the mind. Every fresh discovery, as it opens up new
fields of knowledge, forces upon us more distinctly the sense of our
own ignorance. In the case before us we are delighted by the
apparent simplicity with which the several transformations of starch
into sugar, and of the latter into lactic acid, may be brought about
and seem almost to understand how it is dome, since it can be ef-
fected by a simple transposition of their elements. But the after-
thought occurs—by what kind of power is this change effected 2
The materials are certainly present, but how are they made to
shift their relative positions, and move into their new places? We
have conquered one intellectual difficulty only to encounter another
apparently still harder to overcome.
It was said first, I believe by Priestley,” “that the greater the
circle of light, the greater is the boundary of darkness by which it
is confined.” Thus they who know the most are the most strongly
impressed with the sense of their own want of knowledge. What
a fine result this is of large acquirements' And how touchingly
was it expressed by Sir Isaac Newton, when he likened his great
discoveries to the gathering of a few pebbles along the sea-shore
* Experiments and Observations, ii. p. ix. (edition 1781).
3 O
946 sourTNG AND PRESERVING OF MILK.
—the vast ocean of natural knowledge lying still unexplored before
him
.*
§ 7. Of the souring and preserving of milk.
The natural souring of milk requires now little explanation. It
arises from the gradual conversion of the sugar into the acid of
milk by the action of the casein. There are, however, one or two
circumstances connected with it to which it may be proper to ad-
Vert. -
1°. If milk be kept at a low temperature, it may be preserved
for several days without becoming sensibly sour. This is effected
in Switzerland by immersing the milk vessels in a shallow trough
of cool water, which, by means of a running stream, can at any
time be renewed. In such circumstances the action of the cheesy
matter in converting the sugar into lactic acid is very slow.
2°. But if the milk be kept at the temperature of 65° or 70° F.
it becomes sour with great rapidity, and if afterwards raised to the
boiling point curdles immediately. An easy way of preserving
milk or cream sweet for a longer time, or of removing the sour-
mess when it has already come on, is to add to it a small quantity
of the common soda, pearl ash, or magnesia of the shops. Enough
is added, when a little of the milk poured into boiling water no
longer throws up any curd. As the small quantity of soda or
magnesia thus added is not unwholesome, cream may in this way
be kept sweet for a considerable time, or may have its sweetness
restored when it has already become sour.
3". I have already observed to you that animal membranes, the
curd of milk, or any of those substances which possess the power
of changing sugar into lactic acid, lose that power if the solution
in which they are present be raised to the boiling temperature.
Hence if milk be introduced into bottles, be then well corked, put
into a pan with cold water, and gradually raised to the boiling
point, and after being allowed to cool be taken out and set away
in a cool place, the milk may be preserved perfectly sweet for up-
wards of half a-year.
If the solution containing the sugar and cheesy matter be again
exposed to the air after boiling, it will gradually resume the pro-
perty of transforming the sugar into lactic acid. Hence, if milk
- 3
SEPARATION OF CREAM FROM THE MILK. 947
be boiled, it is preserved sweet for a longer period of time, but the
casein gradually resumes its transforming property, and at the end
of a few days turns it sour. If, however, the milk be boiled every
morning or every second morning, the souring property of the
casein is at every boiling destroyed again, and the milk may thus
be kept fresh for two months or more.
4°. Another mode of preserving milk is to evaporate it to dry-
ness by a gentle heat, and under constant stirring. By this means
a dry mass is obtained which may be preserved for a length of
time, and which when dissolved in water is said to possess all the
properties of the most excellent milk. It is known in Italy by the
name of latteina. *
§ 8. Of the separation and measurement of cream, the galactometer,
the composition of cream, and the preparation of cream-cheese.
1°. Separation of cream.—The fatty part of the milk which ex-
ists in the cream, and which forms the butter, is merely mixed with
and held in suspension by the water of which the milk chiefly con-
sists. In the udder of the cow it is in some measure separated
from, and floats on, the surface of the milk, the later drawn por-
tions being always the richest in cream. During the milking, the
rich and poor portions are usually mixed intimately together again,
and thus the after-separation is rendered slower, more difficult, and
less complete. That this is really so, is proved by two facts—first
that if milk be well shaken or stirred, so as to mix its parts inti-
mately together before it is set aside, the cream will be consider-
ably longer in rising to the surface—and second, that more cream
is obtained by keeping the milk in separate portions as it is drawn,
and setting these aside to throw up their cream in separate vessels,
than when the whole milking is mixed together. When the col-
lection of cream, therefore, is the principal object, economy sug-
gests that the first, second, third, and last drawn portions of the
milk should be kept apart from each other. Even in large dairies
this could easily be effected by having three or four pails, in one of
which the first, in another the second milk, and so on might be col-
lected. -
Cream does not readily rise through any considerable depth of
* Il laſte e i swoi prodotti, p. 19.
() #8 . TISES MORE QUICKLY IN WARM WEATHER,
milk; it is usual, therefore, to set it aside in broad shallow ves-
sels in which the milk stands at a depth of not more than two or
three inches. By this means the cream can be more effectually
separated within a given time.
But the temperature of the surrounding air materially affects
the quantity of cream which milk will yield, or the rapidity with
which it rises to the surface and can be separated. Thus it is said
that from the same milk an equal quantity of cream may be ex-
tracted in a much shorter time during warm than during cold wea-
ther—that, for example, milk may be perfectly creamed in
J lours.
36 when the temperature of the air is 50° F.
24 ... ....................................... 55° F.
18 to 20....................... ............ 68° F
10 to J2 .................................... 77° F
—while, at a temperature of 34° to 37° F., milk may be kept for
three weeks, without throwing up any notable quantity of cream
(Sprengel).
The reason of this is that the fatty matter of the milk becomes
partially solidified in cold weather, and is thus unable to rise to
the surface so readily as it does when in a warm and perfectly fluid
state. -
The above remarks apply to milk of ordinary quality and con-
sistency. In very thin or poor milk, in which little cheesy matter
is contained, the cream will rise more quickly.
2°. Measurement of cream—the galactometer.—The richness of
milk is very generally estimated by the bulk of cream which rises
to its surface in a given time. For the purpose of testing this rich-
mess, a simple instrument, dignified by the learned name of a ga-
lactometer (milk-gauge), has been recommended and may often be
useful. It consists of a narrow cylindrical vessel or long tube of
glass, divided or graduated into 100 equal parts. This vessel is
filled up to 100 with the milk to be tested, and at the end of 24 or
36 hours, the quantity of cream which has risen is estimated by
the number of degrees of space which it occupies at the top of the
milk. If it cover 3 degrees the milk yields 3 per cent., if 7 de-
grees 7 per cent. of cream. This instrument, however, will give
a result which will be generally less than the truth, because the
cream will always rise slowly through 5 or 6 inches of milk—the
UOMPOSITION OF CREAMI. . 949
smallest length which the instrument can conveniently be—and
most slowly in the richest and thickest milk. Unless considerable
care be taken, therefore, this mik-gauge may easily lead to erro-
neous conclusions in regard to the relative degrees of richness of
different samples of milk.
3°. Composition of cream.—Cream does not consist wholly of
fatty matter (butter), but the globules of fat as they rise bring up
with them a variable proportion of the casein or curd of the milk,
and also some of the milk sugar. It is owing to the presence of
sugar that cream is capable of becoming sour, while the casein gives
it the property of curdling when mixed with acid liquids or with
acid fruits. -
The proportion of cheesy matter present in cream depends up-
on the richness of the milk and upon the temperature at which the
milk is kept during the rising of the cream. In cool weather the
fatty matter will bring up with it a larger quantity of the curd
and form a thicker cream, containing a greater proportion of cheesy
matter. The composition of cream, therefore, is very variable—
much more so than that of milk—and depends very much upon
the mode in which it is collected.
A specimen of cream, examined by Berzelius, which had a spe-
cific gravity of 1:0244, consisted of
Per cent.
A-
Butter, separated by agitation, .............................. 4-5
Cheesy matter, separated by coagulating the butter-milk,... 3-5
*/º/, ............................................................ 92.0
| 00
Some of the butter remained, as is usually the case, in the
5 y
butter-milk, and added a little to the weight of the curd which
5 to “"
was afterwards separated, but the result of this analysis is sufficient
to show that cream in general contains a very considerable pro-
portion of cheesy matter—sometimes almost as much cheese as
butter.”
t
* The clouted cream of Devonshire and other western counties, as well as the butter
prepared from it, probably contains an unusually large quantity of curd. It is pre-
pared by straining the Warm milk into large shallow pans into which a little water has
previously been put, allowing these to stand from 6 to 12 hours, and then carefully heat-
*
950 CREAM-CHEESE AND MASCARPONE. -
I would remark, however, that this cream examined by Berze-
lius must have been of an exceedingly poor quality—little richer,
indeed, than common milk, since 100 lbs. of it would only have
yielded 4 lbs. of butter. A hundred pounds of cream of good
quality, when skilfully churned, will yield in this country 24 lbs.
or about one-fourth of their weight of butter, or one wine gallon
of cream, weighing 84 lbs., will give nearly 2 lbs. of butter.”
4. Cream-cheese.—You will now readily understand the nature
of what is called cream-cheese
how it differs from ordinary cheese
and from butter, and why it so soon becomes first sour, and then
rancid. g
In preparing this cheese the cream is generally, I believe,
either tied up in a cloth or put into a shallow cheese vat, and al-
lowed to curdle and drain without any addition. The cheesy
matter and butter remain thus intimately intermixed, and it is more
or less rich, according as the proportion of butter to the cheesy
matter in the cream is greater or less. This cheese becomes soon
rancid and unpleasant to the taste, because the moist curd, after a
certain length of exposure to the air, not only decomposes and be-
comes unpleasant of itself, but disposes the butter to change also,
and thus imparts to it a disagreeable taste and smell.
In Italy cream cheeses, called mascarponi, are made by heating
the cream nearly to boiling, and adding a little sour whey as the
oily matter begins to separate. The whole then coagulates, and
the curd is taken out and set to drain in shapes. As the sour whey
is apt to give this cheese an unpleasant flavour or a yellow colour,
it is said to be better to take 20 grains of tartaric acid for each
quart of cream, to dissolve it in a little water, and to add this, in-
ing them over a slow fire, or on a hot plate, till the milk approaches the boiling point.
The milk, however, must not actually boil, nor must the skin of the cream be broken.
The dishes are now removed into the dairy, and allowed to cool. In summer the cream
should be churned on the following day—in winter it may stand over two days. The
quantity of cream obtained is said to be one-fourth greater by this method, and the milk
which is left is proportionably poor. When milk on which no cream floats is heated
nearly to boiling in the air, a pellicle of cheesy matter forms on its surface. Such a pel-
licle may form in a less degree in the scalding process of Devonshire, and may thus in-
crease the bulk of the cream. The Corstorphine cream of Mid Lothian resembles the
clouted cream very much, and is made in a very similar way.
* A series of analyses of cream, collected under different circumstances, might
throw some useful light upon the manufacture and preservation of butter,
SEPARATION OF BUTTER BY HEATING THE CREAM. 951
stead of the sour whey, to the hot cream. The acid runs offin the
whey of the cream, and the cheese is colourless and free from fo-
reign flavour. The mascarponi, like the English cream-cheeses,
are covered with leaves or straw, are little pressed or handled, and
must be eaten fresh.
§ 9. Of the separation of butter by churning or otherwise.
Milk is a kind of natural emulsion in which the fatty matter ex-
ists in the state of very minute globules, enclosed in very thin films
Ol' envelopes, and suspended in a solution of casein and sugar.
Cream is a similar emulsion, differing from milk chiefly in contain-
ing a greater number of oily globules and a much smaller propor-
tion of curd and water. In milk and cream these globules appear
to be surrounded with a thin white shell or covering, probably of
casein, by which they are prevented from running into one another,
and collecting into larger oily drops.
But when cream is heated for a length of time these globules,
by their lightness, rise to the surface, press nearer to each other,
break through their coverings, and unite into a layer of melted
fat. In like manner, when milk and cream are strongly agitated
by any mechanical means, the temperature is found to rise, the
coverings of the globules are broken or separated, and the fatty
matter unites into small grains, and finally into lumps, which form
our ordinary butter. This union of the globules appears to be
greatly promoted by the presence of a small quantity of acid—since
in the practice of churning it never takes place until the milk or
cream has become somewhat sour. -
These two facts afford an explanation of the various methods
which are in different places adopted for the preparation of butter.
1°. By heating the cream.—When rich cream is heated nearly
to boiling, and is kept for some time at that temperature, the but-
ter gradually rises and collects on the surface in the form of a fluid
oil. On cooling, this oil becomes solid, and may be readily re-
moved from the water and curd beneath. The fatty matter of the
milk is thus obtained in a purer form than when butter is prepar-
ed in the usual way. It may, therefore, be kept for a longer pe-
riod without salt and without becoming rancid, but it has neither
952 CIIURNING SOUR AND CLOUTED CREAM.
the agreeable flavour nor the consistence of churned butter, and is
therefore scarcely known in our climate as an article of food.*
The same oily kind of butter may also be obtained by melting
the churned butter and pouring off the transparent liquid part
which floats upon the top. This is the only form in which sweet
butter is known in many parts of Russia. In warm weather it has
the consistence of a thick oil, is used instead of oil for many culi-
nary purposes, and is denoted, indeed, by the same Russian word.
It may be kept for a considerable time without salt,
2°. By churning the cream—a. Sour cream.–Cream for the
purpose of churning is usually allowed to become sour. It ought
to be at least one day old, but may with advantage be kept seve-
ral days in cool weather—if it be previously well freed from milk
and be frequently stirred to keep it from curdling.
This sour cream is put into the churn and worked in the usual
way till the butter separates. This is collected into lumps, well
beat and squeezed free from the milk, and in some dairies is wash-
ed with pure cold water as long as the water is rendered milky.
In other localities the butter is not washed, but, after being well
beat, is carefully freed from the remaining milk by repeated Squeez-
ings and dryings with a clean cloth. Both methods, no doubt,
have their advantages. In the same circumstances the washed
butter may be more easily preserved in the fresh state, while the
unwashed butter will probably possess a higher flavour.
b. Sweet cream.—If sweet cream be put into the churn the but-
ter may be obtained, but in most cases it requires more labour
and longer time, without, in the opinion of good judges, affording
in general a finer quality of butter. In all cases the cream be-
comes sour during the agitation and before the butter begins dis-
tinctly to form.
c. Clouted cream.—The churning of the clouted cream of this
and other countries forms an exception to the general rule just
stated, that more time is required in the churning of sweet creams.
Clouted cream may be churned the morning after it is made,-that
is, within 24 hours of the time when the milk was taken from the
cow—and from such cream it is well known that the butter sepa-
* It is said, that when melted butter is poured into very cold water, it acquires the
consistency and appearance of common butter.
CHURNING THE WHOLE MILK. 953
rates with very great ease. But in this case the heating of the
cream has already disposed the oily matter to cohere, an incipient
running together of the globules has probably taken place before
the cream is removed from the milk, and hence the comparative
ease with which the churning is effected. I suppose there is some-
thing peculiar in butter prepared in this way, as it is known in
other countries by the name of Bohemian butter. It is said to be
very agreeeble in flavour, but it probably contains more cheesy
matter than the butter from ordinary cream.
3°. Churning the whole milk.-Butter in many districts is pre-
pared from the whole milk. This is a much more laborious me-
thod—from the difficulty of keeping in motion such large quanti-
ties of fluid. It has the advantage, however, it is said, of giving
a larger quantity of butter; and in the neighbourhood of large
towns in Scotland and Ireland the ready sale obtained for the
butter-milk is another inducement for the continuance of the prac-
tice.
At Rennes, in Brittany, the milk of the previous evening is
poured into the churn along with the warm morning's milk, and
the mixture is allowed to stand for some hours, when the whole is
churned. In this way it is said that a larger quantity of butter is
obtained, and of a more delicate flavour. * -
In the neighbourhood of Glasgow, according to Mr Ayton, the
milk is allowed to stand 6, 12 or 24 hours in the dairy till the
whole has cooled, and the cream has risen to the surface. Two
or three milkings, still sweet, are then poured together with their
cream, into a large vessel, and are left undisturbed till the whole
has become distinctly sour, and is completely coagulated. The
proper sourness is indicated by the formation of a stiff brat
upon the surface which has become uneven (Ballantyne). Great
care must be taken, however, to keep the brat and curd umbroken
until the milk is about to be churned, for if any of the whey be se-
parated the air gains admission to it and to the curd, and fermen-
tation is induced. By this fermentation the quality of the butter
may or may not be affected, but that of the butter-milk is almost
sure to be injured.
In Holland the practice is a little different. The cream is not
* Il latte e i Suoi prodotti, p. 112.
954 COMPOSITION OF BUTTER,
allowed to rise to the surface at all, but the milk is stirred two or
three times a day, till it gets sour, and so thick that the wooden
spoon will stand in it. It is then put into the churn, and the
working or the separation of the butter is assisted by the addition
of a quantity of cold water.
By churning the sour milk in one or other of these ways, the
butter is said to be “rich, sound, and well-flavoured.” If it be
greater in quantity—which appears to be the opinion of those who
follow the method in this country, in Germany, and in Holland—
it is, according to Sprengel, because the fatty matter carries with
it from the milk a larger quantity of casein than it does in most
cases from the cream alone (?) \,
§ 10. Of the composition of butter.
Butter prepared by any of the usual methods contains more or
less of all the ingredients which exist in milk. It consists, how-
ever, essentially of the fat of milk intimately mixed with a more or
less considerable proportion of casein and water, and with a small
quantity of sugar of milk. Fresh butter is said by Chevreul to
contain about one-sixth of its weight (16 per cent.) of these latter
substances, and five-sixths of pure fat. The proportion of cheesy
matter in good English butter is usually very small. Two samples
of fresh butter from cream, examined in my laboratory, yielded
only 0.5 and 0.7 per cent, respectively of cheesy matter.
It is probable, however, that the proportion of cheesy matter
contained in butter varies very much. The thickness and richness
of the milk—the mode of preparing the butter, whether from the
whole milk or from the cream—the way in which the cream is se-
parated from the milk, whether by clouting or otherwise—and the
mature of the food and pasture, must all affect in a very conside-
rable degree the relative proportions of the fatty and cheesy mat-
ters of which our domestic butter consists.
Besides the casein and sugar, butter also usually contains some
colouring substance derived from the plants on which the cow has
fed, and some aromatic or other similar ingredients to which its
peculiar flavour is owing, and which are also derived from the food
on which the animal lives. {
The fat of butter may be readily separated from all these sub-
BUTTER CONSISTS OF FAT, CASEIN, AND SUGAR. 955
stances, and obtained in mearly a pure state. Fresh newly churn-
ed butter is melted in a cylindrical jar at a temperature of 140°
to 180° F., the fluid oil poured off into water heated to the same
temperature, and repeatedly shaken with fresh portions as long as
any thing soluble is taken up. When left at rest in a warm place,
the melted fat rises to the surface in the form of a nearly colour-
less transparent oil, which, on cooling, hardens into a colourless
IIl{\SS.
This pure fat may be preserved foramuch longer time than common
butter without becoming rancid (Thenard). It is the various sub-
stances with which its fatty matter is mixed that give to the latter
its tendency to become so speedily rancid and to acquire an un-
pleasant taste. To the numerous precautions which have been
adopted with the view of counteracting this tendency, and of pre-
serving the sweet taste of butter, I shall presently direct your at-
tention.
§ 11. Of the average quantity of butter yielded by milk and cream,
and of the yearly produce of a cow.
I have already made you acquainted with some of those nume-
rous circumstances by which the quality of milk is affected. These
same circumstances will necessarily more or less affect the quan-
tity of butter also, which a given weight or measure of milk can
be made to yield.
Thus in the King-William's-town dairy (County Kerry), the
average quantity of milk and butter yielded by the Kerry and
Ayrshire breeds respectively was, in a whole year—
Ayrshire cow, 1328 quarts, of which 9% to 9% quarts gave 1
lb. of butter.
Rerry cow, 1264 quarts, of which from 8 quarts to 83 gave 1 lb.
of butter. -
Showing, as I have before stated (p. 934), that the small Kerry
cow, upon the same pasture, will give a richer milk even than the
Ayrshire.
In Holstein and Lunenburg again, it is considered, on an ave-
rage, that 15 quarts of milk will yield 1 lb. of butter. The milk
in that country, therefore, must be very much poorer in butter.”
* Journal of the Royal Agricultural Society, i. p. 386.
956 QUANTITY OF BUTTER YIELDED BY MILK.
The result of numerous trials, however, made upon the milk and
cream of cows considered as good butter-givers, in this country,
has established the following average relation between milk,
Cream, and butter:-
Milk. Cream. Butter.
18 to 21 lbs. ! * | 4 lbs.
yield
or 9 to 11 qts. or 2 qts." or 1 lb.
The cow, therefore, that yields 3000 quarts of milk should pro-
duce, where butter is the principal object of the farmer, about
300 lbs. of butter, or 1 lb. a day for 300 days in the year.
This is not a large daily produce, since some cows have been known
to give for a limited time as much as two or even three pounds
of butter in a single day. It is a large quantity, however, taken as
the average of a lengthened period of time, and hence such cases
as that of Mr Cramp's cow, which for four years continuously
yielded nearly a pound and a half of butterf every day, are natu-
rally quoted as extraordinary.
In most districts the average of the whole year is much less
than a pound a day even for ten months only. In Devon, for the
first twenty weeks after calving, a good cow will yield 12 quarts of
milk a day, from which, by the method of scalding, a pound and a
quarter of butter can be extracted.
In South Hollandſ a good cow will produce during the sum-
mer months about 76 lbs. of butter. In the high pastures of
Scaria in Switzerland, a cow will yield during the ninety days of
summer about 40 lbs. of butter, or less than half a pound a day.
In Holstein and Lunenburg it is considered a fair return if a cow
yields 100 lbs. of butter, and even in EnglandS 160 to 180 lbs. are
reckoned a fair annual produce for a cow, or from 8 to 9 ounces
a day for ten months in the year.
Quantity of milk and butter yielded by Ayrshire cows.-Mr
* The quarts spoken of in this lecture are old wine quarts, of which 5 make an im-
perial gallon. A wine gallon of milk or cream weighs about 8 lbs. 4 oz., an imperial
gallon about 10 lbs. 5 oz. About two imperial gallons, therefore, should yield a pound
of butter.
+ It gave in four years 2132 lbs. of butter from 23,559 quarts of milk, or 16 quarts
a day, of which 11 quarts gave a pound of butter.
† Lowdon's Encyclopaedia.
§ British Husbandry, ii. p. 404.
PRODUCE OF AYRSHIRE COWS. 95.7
Alexander of Ballochmyle has furnished me with the following
proportions of cream and butter yielded by his dairy of 38 cows,
at Wellwood, in the higher part of Ayrshire, near Muirkirk, dur-
ing six several days in November and December 1843:-
Cream Butter
Date. in imp. galls. in pounds.
November 1 l6 ſº $ 43;
• * * * * * 7 {} 19} e 47;
* c & e s e 14 . tº 18; e * 43
21 e 21} & 47
sº e º 'º e > 29 . 18 e & 39
T)ecember 7 e ] 9 ſº 43}
In all 112} gallons gave 263% lbs.
or, seven quarts of cream in November gave four pounds of butter.
The cream appears from the table to have become gradually less
rich, though the whole quantity did not diminish. This is consis-
tent with the observation, that milk usually becomes less rich in
cream as the autumn advances—especially when the cows are pas-
tured.
Mr Alexander remarks, that “the proportion of cream varies
in his dairy from one-fifth to one-tenth of the bulk of the milk, and
that Guernsey or Highland, or any black or black-marked cow, gives
more cream from the same quantity of milk.” That is, they give
a richer milk. -
This is a curious physiological fact, and is probably related to
an observation made in the fattening of these races, that the same
quantity of food goes further in fattening a black or black-marked
than a dun or white beast. I do not suppose that any thing of this
kind has been observed in the Durham breed—as white animals, of
pure blood, are often great favourites with the breeders of Tees-
water stock.
§ 12. Of the circumstances which affect the quality of butter.
It is known that the butter produced in one district of the coun-
try, differs often in quality from that produced in another, even
though the same method of manufacture be adopted. In different
seasons also the same farms will produce different qualities of but-
ter. Thus it is said that cows which are pastured yield the most
pleasant butter in May, when the first green fodder comes in—
that the finest flavoured is given by cows fed upon spurry (Spren-
958 FIRST AND SEGOND MILK AND CREAM.
'gel)—that it is generally hardest when the animal lives upon dry
food—and that autumn butter is best for long keeping. These
differences may all be ascribed to varieties or natural differences
in the pasture or fodder upon which the cow is fed.* The con-
stitution of the animal also is known to affect the quality of the
butter—since there are some animals which with the best food will
never give first-rate butter. - -
In all such cases as these, however, the quality of the butter is
almost entirely dependent upon that of the milk from which it is
made, so that whatever affects the quality of the milk must influ-
ence also that of the butter prepared from it. But as I have al-
ready considered the circumstances by which the quality of the
milk is principally modified (p. 931), I shall not further advert to
this subject at present, -
But from the same milk, and even from the same cream, by dif-
ferent modes of procedure, very different qualities of butter may
be obtained. The mode of making or extracting butter, there-
fore, is highly worthy of your attention. Let us consider a few
of the more important circumstances under which different quali-
ties of butter may be extracted from the same quality of milk or
cream. -
1°. First and second drawn milk.—If the milk be collected in
two or three successive portions, as it comes from the cow, the last
drawn portion will be much richer than that which has been taken
first. The cream yielded by it will also be richer, and of a finer
and higher flavour. Whether, therefore, the butter be extracted
directly from the whole milk, or from the cream, that which is ob-
tained from the three successive portions, will differ in quality al-
most as much as the several portions of milk themselves.
A practical application of this fact is made in some of the High-
land counties of Scotland, and in other districts, where the calves
are allowed to suck, or are fed with, the first half of the milk as it
comes from the cow—the latter and richest half only being reserv-
* The influence of the food given in the stall, and of the plants eaten in the pasture,
upon the colour and flavour of the butter, is familiar to all practical men. The tur-
mipy taste of the butter in winter—the garlic taste in summer, where the wild onion
grows in the pastures—and the alleged effect of raw potatoes in winter, in giving a rich
colour to the butter, are common examples of this kind.
TOO RAPID CHURNING OR OVER-CHURNING. 959
ed for dairy purposes. This second milk is found to afford an ex-
quisite butter. - -
2°. First and second cream.—In like mammer the first cream
that rises upon any milk is always the richest, and gives the finest
flavoured butter. The after-creamings are not only poorer in but-
ter, but yield it of a whiter colour and of inferior quality.
This fact again is well understood, and has been long practically
applied in the neighbourhood of Epping, which is celebrated for the
excellence of its butter. The cream of the first 24 hours is set
aside and churned by itself. The second and third creams pro-
duce a pale, less pleasant butter, which always sells for an inferior
price. Any admixture of the after-creamings causes a correspond-
ing diminution in the value of the butter produced. To produce
the most exquisite butter the cream of the first eight hours only
ought to be taken.
3°. Mode of creaming.—The rapidity with which cream rises to
the surface, either maturally or when influenced by art, affects the
quality of the cream, and consequently that of the butter made
from it. In warm weather it rises more quickly than in cold, and
more quickly still when the milk is heated, as in the preparation
of clouted cream. The butter (Bohemian butter) obtained from
such cream —from cream thus rapidly brought to the surface—
may be expected to differ both in flavour, in consistency, and in
composition, from that yielded by the cream of the same milk when
allowed to rise in the usual manner.
4". Sourness of the cream.—For the production of the best but-
ter it is necessary that the cream should be sufficiently sour before
it is put into the churn. Butter made from sweet cream (not
clouted), is neither good in quality nor large in quantity, and
longer time is required in churning. It is an unprofitable method
(Ballantyne).
5°. Quickness in churning.—The more quickly milk or cream is
churned, the paler, the softer, and the less rich the butter. Cream,
according to Mr Ayton, may be safely churned in an hour and a
half, while milk ought to obtain from two, to three hours. The
churning ought also to be regular, slower in warm weather that
the butter may not be soft and white, and quicker in winter that
the proper temperature may be kept up. -
960 TEMPERATURE OF THE MILK AND CREAM,
A barrel-churn has been invented by a Mr Walcourt, which,
being placed in a trough of water of the proper temperature,
readily imparts the degree of heat required by the milk or cream
without the necessity of adding warm water to the milk, and churns
the whole in ten or twelve minutes. It is said also to give a larger
weight of butter from the same quantity of milk, and my friend Mr
Burnett of Gadgirth, who has tried the churn, says it is also of
superior quality. If the quality be really as good by this quick
churning, the alleged inferiority in the quality of butter churned
quickly in the common churn cannot be due to the mere rapidity
of churning alone.
6°. Over-churning.—When the process of churning is continu-
ed after the full separation of the butter, it loses its fine yellowish-
waxy appearance, and becomes soft and light coloured. The
weight of the butter, however, is said by Dr Traill to be considerably
increased, and that, for this reason, the practice of over-churning
is frequently followed in Lancashire in the manufacture of fresh
butter for immediate sale.
7°. Temperature of the milk or cream.—Much also depends up-
on the temperature of the milk or cream when the churning is
commenced. Cream when put into the churn should never be
warmer than 53° to 55° F. It rises during the churning from 4°
to 10° F, above its original temperature. When the whole milk
is churned, the temperature should be raised to 65° F., which is
best done by pouring in hot water into the churn while the milk is
kept in motion.*
The importance of attending to the temperature and to the quick-
ness of churning, when the best quality of butter is required, is
shown by the two following series of results obtained in the churn-
ing of cream at different temperatures and with different degrees
of rapidity.
The first series was obtained in August and September of 1823,
by Dr Barclay and Mr Allan. The quantity of cream churned in
* Ballantyne, Transactions of the Highlamd Society, New Series, I., p, 24. Some
object to this method of adding hot water, saying that it renders the butter pale and
less valuable in the market. This is by no means universally the case, and the keep-
ing the milk in motion, while the water is added, may possibly, in some cases, make
the difference. In other cases it may be owing to natural differences in the quality
of the milk operated upon,
MR BALLANTYNE's EXPERIMENTs. 9öi
each experiment was 15 wine gallons, weighing from 8lbs. to 84
lbs. per gallon.

Temperature. «» º
temperature. é.i. Qºf Quality of the Butter.
No. Beginning End. * per gallon. -
Hours. lbs. oz.
1 50° 60° 4 l 15, Very best, rich, firm, well tasted.
2 55° 65° 3# 1 15} |Not sensibly superior to the former.
3 58° 679 3 1 14 Good, but softer.
4 60° . 68° 3 1 123 Soft and spongy.
5 66° 75° 2% 1 104 |Inferior in every respect.
The results of these experiments prescribe the temperature
of 50° to 55° F. for the cream when put into the churn, and from
3% to 4 hours as the most eligible for producing butter, both in
the largest quantity and of the finest quality. Something, how-
ever, appears to depend upon the quality of the cream ; since the
indications of the next series of experiments differ considerably
from the above, in so far at least, as regards the length of time ex-
pended in churning. - -
The following experiments were made in Edinburgh, by Mr
Ballantyne, between June and August 1825. The quantity of
cream he used at each churning was 8 wine gallons—weighing 8
lbs. to the gallon, except that of the fourth experiment, which
weighed 4 ounces less.

Temperature. - t
- Time in Quantity of
No. Of the When but-|churming. º Quality of the butter.
cream.] ter came. per gallon.
Hours. lbs. oz.
I 56° F 60° F 14, 2 1 Inferior ; white and softer than
o tº 92 No. 2
2 52° 56° 2 2 0 ! The flavour and quality of these two
3 52° 56° 2 2 0 butters could not be surpassed.
4 65° 679 # 1 15 Soft, white, and milky.
5 50° 53\" 3 1 15% } Good—evidently injured by long
churning.
Most excellent. High in flavour
lo J.o O
6 53% - 57% 1} 2 03 } and colour, and solid as wax.
|
To obtain butter from cream, therefore, both finest in quality
and largest in quantity, these two series of experiments prescribe
the following temperatures of the cream, and times in the churn-
ing:—
3 P
962 ADVANTAGES OF CHURNING THE WHOLE. MILK.
- Temperature. . Time.
First, ......... 50° to 55° 3} to 4 hours.
Second, ...... 53].” 14 to 1;
In the temperature both agree. It is probable that the nature
of the cream obtained at different seasons or in different localities
may render a longer time necessary in the churning on some occa-
sions or in some places than in others. It is certain that the sourer
the cream, the sooner generally will the butter come.*
8°. Churning the entire milk.-It is in connection with the tem-
perature at which milk and cream may respectively be best and
most economically churned, that the chances of obtaining a butter
of good quality at every season of the year appear to be greater
when the whole milk is used, than when the cream only is put in-
to the churn. .
Cream, when the churning commences, should not be warmer
than 55° F.—milk ought to be raised to 65° F. In winter, either
of these temperatures may be easily attained. In cold weather it
is often necessary to add hot water to the cream to raise it even
to 55°. But in summer, and especially in hot weather, it is diffi-
cult, even in cool and well-ordered dairies, to keep the cream down
to this comparatively low temperature. Hence if the cream be
churned in hot weather a second rate butter, at best, is all that
can be obtained.
Milk, on the other hand, requires a temperature of 65°–ten de-
grees higher than cream—and therefore neither summer nor win-
ter weather materially affects the ease of churning it. In winter,
its temperature is raised by hot water, as that of cream is, and
even in summer there can be few days in our climate—where the
milk is kept in a well-contrived dairy—in which it will not be me-
cessary to add more or less hot water in order to raise the milk to
65° F. Thus, where the entire milk is churned, the same regu-
lar method or system of churning can be carried on throughout
the whole year. No difficulty is to be apprehended from the state
of the weather, mor, so long as the quality of the milk remains the
same, is there reason to apprehend any change in the quality of
the butter. The winter butter and the summer butter may be alike
firm, finely flavoured, and rich in colour.
* In Sweet cream when the butter is long in coming, the addition of a little vinegar,
brandy, or whisky, will hasten the churning.
TEIE FATTY SUBSTANCES IN BUTTER. - 963
The alleged advantages of churning the entire milk rather than
the cream may be thus stated:—
a. The proper temperature can be readily obtained both in win-
ter and in summer. w
b. A hundred gallons of entire milk will give in summer 5 per
cent, more butter than the cream from the same quantity of milk
will give (Ballantyne).
c. Butter of the best quality can be obtained without difficulty
both in winter and in summer. -
d. No special attention to circumstances or change of method
is at any time required. The churning both in winter and summer
is equally simple and easy. -
e. The butter is not only of the best quality while fresh, but is
also best for long keeping, when properly cured or salted (Ballan-
tyne). -
Against these advantages it is stated, that except in the neigh-
bourhood of large towns, the butter-milk is of little value—while
from the skimmed-milk, a marketable cheese can always be manu-
factured. But this ought to be no objection, where churning the
whole milk would otherwise be preferred, since it is little more
difficult to make cheese from the sour butter-milk than from the
sweet skimmed-milk. To this point I shall direct your attention
hereafter.
9°. Cleanliness.--It seems almost unnecessary for me to allude
to cleanliness as peculiarly necessary to the manufacture of good
butter. But I do so to bring under your notice the fact, that cream
is remarkable for the rapidity with which it absorbs and becomes
tainted by any unpleasant odours. It is very necessary that the
air of the dairy should be sweet, that it should be often renewed,
and that it should be open in no direction from which bad odours
Cà,1] COIllC. -
§ 13. Of the fatty substances of which butter consists, and of the
acid of butter (butyric acid.) and the capric and caproic acids.
1°. Butter-fat.—I have already mentioned to you that if the
butter as it is taken from the churn be melted in water of a tem-
perature not exceeding 180° F., and be then washed with repeat-
ed portions of warm water, a nearly colourless fluid oil is obtained,
964 THE FATTY SUBSTANCES IN BUTTEß.
which, if not transparent, becomes so when filtered through paper,
and when cool congeals into a more or less pure white solid fat.
If this fat be put into a linen cloth and submitted to strong pres-
sure in a hydraulic or other press at the temperature of 60° F., a
slightly yellow, transparent oil will flow out and a solid white fat
will remain behind in the linen cloth. The solid ſat is known to
chemists by the name of margarine. The liquid oil is the same
which occurs in olive and other fatty oils, and is distinguished by
the name of elaine.
The pure fat of butter consists almost entirely of these two sub-
stances, there being generally present in it only a small quantity
of certain fatty acids, which I shall presently introduce to your
notice. Thus a specimen of butter made in the month of May
gave a fat, which was found by Bromeis to consist of about—
Per cent.
Margarine, ..... ........................... ... 68
Elaine, ........................ : . . . . . . . . . . . . . . . . . 30
Butyric, caproic, and capric acids, .... .... 2
100%
But the proportion of the solid and fluid fatsin butter varies very
much. It is familiar in every dairy that the butter is harder and
firmer at one time or with one mode of churning than with another,
—and this greater firmness depends mainly upon the presence of
the solid fat (margarine) in larger proportion. According to Bra-
connot, summer butter contains much more of the oily fat than
winter butter does: and he states their relative proportions in these
two seasons, in the butter of the Vosges, which he examined, to be
as follows:—
Summer. Winter.
Margarine, ............ 40 65
Elaine, .................. 60 35
100 100
Of course these proportions are not to be considered as constant.
Indeed, the proportion of oil here given for summer butter is much
greater than in the butter examined by Bromeis. It is probable,
therefore, that the relative proportions of the two fats are affected
by climate, by season, by the race, the food, and the constitution
of the animal, by the way in which the butter is made, by the
* Annal. der Chem, whd Phar., xlii. p. 70.
MARGARINE, MARGARIC ACID, AND BUTTER-OIL. 965
manner in which it is kept, and by other circumstances not hither-
to investigated.
2°. Margarine.—This solid fat, which exists so largely in butter,
is also the solid ingredient in olive oil, and in goose and human fat.
Butter, therefore, appears to be a most natural food for the human
race, since it contains so large a proportion of one of those sub-
stances which enter directly into the constitution of the human
frame.
Margarine is white, hard, and brittle, and melts at 118° F.
In the pure state it may be kept for a length of time without un-
dergoing any sensible change, but in the state of mixture in which
it exists in milk and butter it is apt to absorb oxygen from the at-
mosphere, and to be partially changed into elaine and into one or
other of those fatty acids which are present in butter in smaller
quantity. - -
3°. Margaric acid—When the solid fat (margarine) is introduc-
ed into a hot solution of caustic potash, it readily dissolves and
forms a soap. If the solution of this soap in water be decomposed
by the addition of diluted sulphuric acid a white fatty substance
separates, which, after being collected, dried, and dissolved in hot
alcohol, crystallizes as the solution cools, in the form of pearly
scales. This substance is known by the name of the margaric (or
pearly) acid. Margarine consists of this acid in combination with
a sweet substance known by the name of glycerine, or oil-sugar.
Margaric acid is represented by the formula 34C + 34 H +
4 O, or Caº Had Of: To this formula it will be necessary in a
few minutes to revert. -
4°. Elaine.—The liquid fat expressed from butter has the ap-
pearance of an oil, sometimes colourless, but often tinged of a yel-
low colour. It has the taste and smell of butter—mixes readily
with alcohol, and becomes solid when cooled down to 32°F.—the
freezing point of water. It dissolves without difficulty in a solu-
tion of caustic potash, and forms a soap.
Elaic acid of butter.—When the solution of the oil in caustic
potash is diluted with much water, and decomposed by the addi-
tion of diluted sulphuric acid, an oily substance is separated, which
is different from the original elaine, possesses acid properties, and
is known by the name of elaic acid. Elaine consists of this
*
966 CONSTITUTION OF NATURAL FATS AND OILs.
acid in combination with oil-sugar. Margarine, as I have already
mentioned, consists of margaric acid in combination with the same
sugar.”
* Such is the apparent composition of the two fatty substances, margarine and elaine,
inasmuch as when they are dissolved in a solution of caustic potash, and their solutions
afterwards decomposed by an acid, they are resolved respectively— -
Margarine—into mangaric acid and oil-sugar.
Elaime—into claic acid and oil-sugar. -
But, for the benefit of my chemical readers, (my other readers will please to pass
over this note), it is necessary to state -
1°. That a compound is supposed to exist consisting of 3 atoms of carbon united to 2
of hydrogen—Ca Ha, to which the name of lipyle is given.
2°. That this radical Ca Ha unites with an atom of oxygen forming Ca H2 O, or
0&ide of lipyle.
3°. That in neutralfatty bodies, such as margarine, this oxide exists in combination
with a fatty acid. Thus, for example, that
Maguine come of} . . . . . .
Forming, together, l of margarine, .... ... ... e. e. g.: = & a g º º = Cs, Has Oa
And - -
**}:... tº #: ;
Forming, together, l of elaine,........................ = Cso Has Oa
4°. And that when this oxide of lipyle is separated from its combination with the
fatty acids it unites with a quantity of water, and forms glycerine or oil-sugar. Thus
2 of oxide of lipyle........................... = Ce Ha O2 united to
3 of water .................................... 2- HaO a give
1 of glycerine (oil-sugar), .................. = Cs H, Og
5°. The above is the view of Berzelius, but Redtenbacher suggests+ that a known
substance called acrolein may exist in the fats in combination with the fatty acid.
This acrolein is represented by Ce H, Og, which is exactly the constitution of 2 of
lipyle. So that according to this view the solid fat of butter would consist of
2 of margaric acid ................. ...... = Css He s Os
l of acrolein .................. ........... = Cs H4 Og
2 Of margarine, a * * * * * * * * * * * * * * * * * * * * * * * * s is e e = C, 4 Hz, Olo
and, by a like substitution of acrolein for oxide of lipyle, may the constitution of elaine
be represented. 2
The principal known fact in favour of this view of Redtenbacher is, that when gly-
ceriné is distilled with anhydrous phosphoric acid, acrolein is produced. He supposes
that the acid takes the elements of 3 atoms of water from glycerine, forming acrolein ;
since if from
# Ammal. der Chem, whd Phar.., xlvii. p. 141.
&
RELATION OF THE MARGARIC AND ELAIC ACIDS. 96.7
When pure, this oily acid is colourless and transparent, and is
remarkable for the rapidity with which it absorbs oxygen from the
atmosphere, and becomes converted into new chemical compounds.
It is represented by the formula 36 C + 33 H + 3 O, or Cas
Has Os, being also combined with an atom of water, (HO), when
obtained in a separate state. It is then represented by Cas H4
O4.
Let us compare this formula with that of the margaric acid.
1 of margaric acid ...... = Csa Hsi O1
and one of elaic acid ...... = Css Has Os
The difference is ......... — C2 + Hi + O1
or if two of carbon be taken from the elaic acid, and one of water
(HO) added to it, it will become converted into margaric acid.
Thus
C. H. O.
From I of elaic acid, ......... 36 33 3
Take 2 of carbon, ............... 2
34 33 3
And add 1 of water, (HO),...... 1 1
And we have margaric acid, = 34 34 4
Now this change is one which may be very simply effected by
the ordinary processes of life. By the absorption of four equiva-
lents of oxygen from the air directly—from the air which reaches
the blood through the medium of the lungs—or from other sub-
stances it meets with after it has been introduced into the stomach
—the two of carbon may be removed in the form of carbonic acid,
and if one of water, which is everywhere present, be taken up at
the same time, the margaric acid will be produced. Thus
1 of glycerine ........................ ...... Ce H, O, we take
3 of Water ... ....... ........ ... ............ == Hà Oa
Acrolein remains, ...... .................... = Cs H4 Og
The conversion of acrolein into glycerime, when it is separated from the fatty acids,
is supposed to proceed, as in the case of lipyle, from its combination with the water
at the moment of extrication. Further researches are yet required to clear up this
subject.
968 BUTYRIC, CAPRIC, AND CAPROIC ACIDS.
C. H. O
To one of elaic acid, ............... 36 33 3
Add 4 of oxygen, .................. 4
And one of water, ................. º 1 1
And we have ......... a • , a e s e s = e a v e s a 36 34 8.
From this take two of carbonic acid, 2 4.
And margaric acid remains, ...... 34 34 4
Now such a change as this may take place in the lungs, so as
out of the elaic acid of the food to produce the margaric acid of
the human fat—or in the milk of an animal while in its udder, so
as to cause it to yield a harder butter when churned. Or when it
is exposed to the air after being drawn from the cow, or even in the
churn itself, it may happen that a portion of the elaic acid of the
milk may absorb oxygen and become changed into the margaric
acid. It may also be that this change, this absorption of oxygen,
is promoted by warm and retarded by cold weather, and that thus
the butter is rendered softer or harder according to the season.
It is likely, however, that the relative proportions of the soft and
hard fat in butter at different times of the year may depend also
upon natural differences in the herbage at the several seasons, or
upon other causes which have not as yet been investigated,
5°. Butyric, capric, and caproic acids.-These substances, as I
have already stated to you, exist in butter only in small quantity
—to the amount of 2 or 3 per cent. To these acids, and especially
to the capric and caproic, butter owes its disagreeable smell when
it becomes rancid. They do not exist naturally, to any unpleasant
extent, in perfectly fresh butter—they are gradually formed in it,
however, when fresh butter is exposed to the air. I do not enter
into any detail of their properties, or of the mode of extracting
them from butter, because these points are of less interest or im–
portance to you. It is necessary only, to a clear understanding of
the kind of changes which take place when butter becomes rancid,
that I should exhibit to you the formulae by which these acid bo.
dies are severally represented. These are the following—
Butyric acid ...... = Cs Hs O,
Caproic acid ...... = C12 Ho Og
Capric acid ......... = Cls Hiſ Os
PROPERTIES OF THE CURD OF MILK. 969
Of the way in which these substances are produced from the solid
and fluid parts of butter we shall treat in a succeeding section.
§ 14. Of casein or the curd of milk and its properties.
The casein or cheesy matter of milk may be obtained nearly
pure by the following process:–Heat a quantity of milk which has
stood for 5 or 6 hours, as if you intended to prepare clouted cream,
(p. 952), let it cool, and separate the cream completely. Add now
to the milk a little vinegar and heat it gently. The whole will
coagulate, and the curd will separate. Pour off the whey, and
wash the curd well by kneading it with repeated portions of water.
When pressed and dried, this will be casein sufficiently pure for
ordinary purposes. It may be made still more pure by dissolving
it in a weak solution of carbonate of soda, allowing the solution to
stand for twelve hours in a shallow vessel, separating any cream
that may rise to the surface, again throwing down the curd by vine-
gar, washing it frequently, and occasionally boiling it with pure wa-
ter. By repeating this process two or three times, it may be obtained
almost entirely free from the fatty and saline matters of the milk.
Casein thus prepared reddens vegetable blues, and is therefore
a slightly acid substance. It is very sparingly soluble in water—
400 lbs. of cold water dissolving only 1 lb. of pure casein (Roch-
leder). It dissolves readily, however, and in large quantity, in a
weak solution of the carbonate of potash or of soda, and to some
extent even in lime-water. These solutions are coagulated by the
addition of an acid—of sulphuric acid, of vinegar, or of lactic acid
—and the curd readily separates on the application of a gentle heat.
If a large quantity of acid be added, a portion of the casein is re-
dissolved. This property of dissolving in weak alcaline (potash or
soda) solutions, satisfactorily explains what takes place during the
curdling of milk, as we shall hereafter see.*
* The casein prepared by the process given in the text is a mixed substance, and
the properties above described are not therefore those of a pure chemical compound.
This appears from the following statement of Mulder.
Casein A. When milk is allowed to stand till the cream can be well separat-
ed—is then coagulated by muriatic acid, the curd collected on a linen cloth, wash-
ed with dilute muriatic acid, and then with cold water, and is afterwards digested in
water for several days at a slight elevation of temperature, the curd dissolves entirely
by the aid of the acid which adheres to it. Some fat floats on the top. If this be
taken off and the liquid thrown upon a proper filter, it passes through very slowly,
but quite clear.
As - ^ -
970 ACTION OF CASEIN UPON SUGAR,.
The casein of milk is similar in chemical composition (p. 216)
to the fibrim of wheat, the legumin of the pea and bean, and the
albumen of the egg or of vegetable substances. Hence the opi-
nion first suggested by Mulder has been pretty generally received,
that the cheesy matter contained in an animal's milk is derived di-
rectly, and without any remarkable change, from the food on which
it lives. The probability of this opinion will come naturally under
our consideration in the following lecture.
Casein possesses still one property more remarkable than any of
its others, and exceedingly interesting to the practical agriculturist.
I shall explain this property a little more in detail.
§ 15. Of the relations of casein to the sugars and the fats.
1°. Relation to the sugars.-a. Production of lactic acid—I have
already adverted (p. 941) to the remarkable property which casein
possesses of gradually converting milk or other sugars into lactic
acid. If a small quantity of this substance, either in the state of
fresh curd or in the purer form above described, be introduced
into a solution of cane-sugar, or of sugar of milk, lactic acid be-
From this solution carbonate of ammonia in small quantity precipitates a pure white
casein A, which falls slowly, and the liquor passes slowly through the filter. The pre-
cipitate redissolves in excess of carbonate of ammonia, and is re-precipitated by acetic
acid. After being boiled with alcohol and ether, and them dried at 270° F., this casein
forms a pure white semi-transparent hard substance which contains sulphur, and is
casein properly so called—exhibiting all the reactions of a protein compound.
Casein B. When the clear filtered liquid from A, containing carbonate of ammo-
nia, is treated with diſute muriatic acid in excess, a new precipitate falls, which read-
ily subsides, and from which the liquid flows readily through the filter. Washed,
treated with alcohol and ether, (the former of which dissolved a small portion of mat-
ter which is precipitated by mixture with ether in minute flocks), and dried at 270°
F., it is yellow, semi-transparent, horny, exhibits the reactions of protein with nitric and
muriatic acids, but gives no black stain when treated with caustic potash on polished sil-
ver. It contains no sulphur, therefore, but chlorine is present in it to the amount of 2%
per cent. It appears to contain protein, but the proportion of nitrogen was less by
the only trial made than protein contains. This casein B is present in the curd in .
much smaller quantity than casein A. Schlossberger” considers it to form probably
the membrane of the milk globules—the casein A being the so-called globulim.
Schlossberger is understood to be occupied with the study of these different portions
or ingredients of the curd of milk. Such a research must lead to results not only the
oretically interesting, but practically useful also, especially in reference to the manu-
facture of cheese and the better preservation of butter.
* Schlossberger, An, der Chem, und Phar., lviii. p. 92.
4.
*y
PRODUCTION OF BUTYRIC ACID. 971
gins very soon to be formed. Thus the casein it contains is the
cause of the souring of milk. In like manner it is the legumin,
called by some vegetable casein, contained in bean or pease-meal,
which makes it so soon become sour when mixed with water.
b. Production of butyric acid.—But the transforming action of ca-
sein does not end when this change is produced. After a longer
time a further alteration is effected by its means. A fermentation
commences during which carbonic acid and pure hydrogen gases
are given off, and butyric acid is produced (Pelouze and Gelis).
Let us consider the nature of this new change.
Butyric acid is represented by Cs Hs O, and lactic acid, as we
have seen, by C. He Os; therefore, if from -
C. H. O.
4 of lactic acid ............ = 24 24 24 we take
3 of butyric acid ......... = 24, 24 12
There remain ...... 12
That is to say, 4 of lactic acid, in order to be converted into
3 of butyric acid, must give off 12 of oxygen. But during the
fermentation which accompanies this change no oxygen is given
off. The gases which escape are carbonic acid and hydrogen.
The oxygen given off by one portion of the lactic acid, there-
fore, must combine with the elements of another portion, and
convert it into these gases. This may happen in the following
Iſlal Ill] Cl’.
To lj, of lactic acid...... = Co Ho Oo
Add 12 of oxygen ...... - 12
And we have ... Co Hg O21
This is equal to
C. H. O
9 of carbonic acid......... – 9 18
3 of water ................. - 3 3
6 of hydrogen ............ F. 6
9 9 2 I
or, while 4 atoms of lactic acid are converted into 3 of butyric acid,
1% of lactic acid are at the same time converted into 9 of carbonic
3
972 ACTION OF CASEIN UPON SUGAR AND FAT MIXED.
acid gas, 6 of hydrogen gas, and 3 of water. The gases escape
and cause the fermentation, while the water remains in the solution.*
The butyric acid thus produced is a colourless, transparent, vo-
latile liquid which emits a mingled odour of vinegar and of rancid
butter. To the production and presence of this acid, therefore, in
the milk or cream, or in the manufactured butter, the rancidity of
this important dairy product is partly to be ascribed.
2°. Relation to the fatty bodies.—It is probable that in certain
circumstances the casein of milk is capable of inducing chemical
changes in the fatty bodies as well as in the sugars, but this con-
jecture has not, as yet, been verified by rigorous experimenal in-
vestigation. ... •
3°. Relation to fats and sugars mixed.—It is known, however,
to act upon fatty bodies when mixed with sugar. Thus, if a small
quantity of casein be added to a solution of sugar, lactic acid is
produced for a certain length of time, but it ceases to be sensibly
formed before the whole of the sugar is transformed into this acid,
If now a quantity of oily matter be added to the mixture, the pro-
duction of lactic acid will recommence, and may continue till all
the sugar is changed. If more sugar be added by degrees, the
formation of acid will go on again, and, after a while, will cease.
The introduction of a little more oil will again give rise to the pro-
* I have taken in the text the smallest numbers by which the general change could
be represented in the simplest way. According to Pelouze and Gelis, however, the
hydrogen given off is sensibly one-third of the bulk of the carbonic acid when the bu-
tyric fermentation is in its vigour. To satisfy this condition, therefore, much higher
numbers must be taken ; such as the following:—
20 of lactic acid...... = C, 2 o H 2 o On 2 o are converted into
15 of butyric acid ... = C, 2 o H1 20 Oso
Giving off ... = Oso
And these 60 of oxygen decompose 6 of lactic acid, as above described. Thus, to
6 of lactic......... = Cas Has Oa e
Add 60 of oxygen = Oso
36 of carbonic acid + 12 hydrogen + 24 water.
And we have... Cas Has Oos = 36CO2 + 12H + 24HO,
where the carbonic acid gas is exactly three times the bulk of the hydrogen gas pro-
duced.
Every chemist is aware, however, that in decompositions of this kind, it is seldom
that one single product is obtained alone. Though the above formula, therefore, re-
presents truly how butyric acid may be produced from lactic acid under the circum-
stances, yet other substances are not unfrequently formed during the actual experi-
ment, by which the result is more or less complicated.
y
CHANGES WHICH RENDER BUTTER. RANCID. 973
duction of acid, and, at length, the acid will cease to be formed,
while both sugar and oil are present. The casein originally add-
ed has now produced its full effect, (Lehmann).
It appears, therefore, that in the presence of sugar, casein is ca-
pable of changing or decomposing the fatty bodies also, and of
giving birth to oily acids of various kinds. Now, in milk, in cream,
and in butter, the casein is mixed with the sugar of the milk and
the fats of the butter, and thus is in a condition for changing at
one and the same time both the sugar into lactic or butyric acid,
and the butter into other acids of a fatty kind. Among those
acids into which the butter-oil is convertible are the capric and ca-
proic acids, which are still more unpleasant to the smell and taste
than the butyric acid, and which are known to be present in rancid
butter. -
Š.16. Of the rancidity and preservation of butter.
We are now prepared, in some measure, to understand the
changes that take place when butter becomes rancid—and the way
in which those substances act which are usually employed for pre-
Serving it in a sweet and natural state.
19. When butter becomes rancid, there are two substances which
change—the fatty matters and the milk sugar with which they are
mixed. There are also two agencies by which these changes are
induced—the casein present in butter, and the oxygen of the at-
mosphere. The quantity of casein or cheesy matter which butter
usually contains is very small, but, as we have seen, it is the sin-
gular property of this substance to induce chemical changes of a
very remarkable kind, upon other compound bodies, even when
mixed with them in very minute quantity.
2°. In the state in which it comes from the cow, this substance, ca-
sein, produces no change on the sugar or on the fatty matters of
the milk. But after a short exposure to the air it alters in some
degree, and acquires the power of transforming milk sugar into
lactic acid. Hence, as we have seen, the milk begins speedily to
sour. Further changes follow, and, among other substances, buty-
ric acid is formed. -
In butter the same changes take place. The casein alters the
sugar and the fatty matters, producing the butyric and other acids,
to which its rancid taste and smell are to be ascribed.
974 INFLUENCE OF THE CHEESY MATTER.
In the manufacture of butter, therefore, it is of consequence to
free it as completely as possible from the curd and sugar of milk.
This is done in some dairies by kneading and pressing only; in
others, by washing with cold water as long as the latter comes off
milky. The washing must be the most effective method, and is
very generally recommended for butter that is to be eaten fresh.
In some dairies, however, washing is carefully avoided when the
butter is to be salted for long keeping.
There are two circumstances which, in the case of butter that is
to be kept for a length of time, may render it inexpedient to adopt
the method of washing. The water may not be of the purest kind,
and thus may be fitted to promote the future decomposition of the
butter. Sprengel says that the water ought to contain as little
lime as possible, because the butter retains the lime and acquires
a bad taste from it.
But the water may also contain organic substances in solution
—vegetable or animal matters, not visible perhaps, yet usually
present even in spring water. These the butter is sure to extract,
and they may materially contribute to its after decay, and to the
difficulty of preserving it from rancidity. -
Again, the washing with water exposes the particles of the but-
ter to the action of the oxygen of the atmosphere much more than
when the butter is merely well squeezed. The effect of this oxy-
gen, in altering either the fatty matters themselves, or the small
quantity of casein which remains mixed with them, may contribute
to render some butters more susceptible of decay.
3°. But the casein, after it has been a still longer time or more
fully exposed to the air, undergoes a second alteration, by which
its tendency to transform the substances with which it may be in
contact, is considerably increased. It acquires the property also
of inducing chemical changes of another kind, and it is not im-
probable that the more unpleasant smelling capric and caproic
acids may be produced during this period of its action.
In the preservation of butter, therefore, for a length of time, it
is of indispensable necessity that the air should be excluded from
it as completely as possible. In butter that is to be salted also, it
is obvious that the sooner the salt is applied and the whole packed
close, the better and sweeter the butter is likely to remain.
HOW TO PURIFY SALT FOR BUTTER. 975
4°. The action of this cheesy matter and its tendency to decay,
are arrested or greatly retarded by the presence of saturated solu-
tions of certain saline and other substances. Of this kind is com-
mon salt, which is most usually employed for the purpose of pre-
serving butter. Saltpetre also possesses this property in a less
degree, and is said to impart to the butter an agreeable flavour.
A syrup or strong solution of sugar will likewise prevent both meat
and butter from becoming rancid. Like saltpetre, however, it is
seldom used alone, but it is not uncommon to employ a mixture
of common salt, saltpetre, and sugar, for the preservation of but-
ter. Where the butter has been washed, this admixture of cane-
sugar may supply the place of the milk-sugar which the butter
originally contained, and may impart to it a sweeter faste.
The salt should be as pure as possible, as free, at least, from
lime and magnesia as it can be obtained, since these substances are
apt to give it a bitter or other disagreeable taste. It is easy,
however, to purify the common salt of the shops from these impu-
rities by pouring a couple of quarts of boiling water upon a stone
or two of salt, stirring the whole well about, now and then, for a
couple of hours, and afterwards straining it through a clean cloth.
The water which runs through is a saturated solution of salt, and
contains all the impurities, but may be used for common culinary
purposes or may be mixed with the food of the cattle. The salt
which remains on the cloth is free from the soluble salts of lime
and magnesia, and may be hung up in the cloth till it is dry
enough to be used for mixing with the butter or with cheese.
The quantity of salt usually employed is from ºrth to gath part
of the weight of the butter—with which it ought to be well and
thoroughly incorporated. The first sensible effect of the salt is to
make the butter shrink and diminish in bulk. It becomes more
solid and squeezes out a portion of the water—with which part of
the salt also flows away. It is not known that the casein actually
combines with the salt, mor, if it did, considering the very small
quantity of this substance which is present in butter, could much
salt be required for this purpose. But the points to attend to in
the salting of butter are to take care that all the water which re-
mains in the butter shall be fully saturated with salt—that is to
say, shall have dissolved as much as it can possibly take up—and
976 : EVIL EFFECT OF THE AIR UPON BUTTER.
that in no part of the butter shall there be a particle of cheesy
matter which is not also in contact with salt. If you exclude the
air, the presence of a saturated solution of salt will not only pre-
serve this cheesy matter from itself undergoing decay, but will
render it unable also to induce decay in the sugar and fat which
are in contact with it.”
It is really extraordinary that such rigid precautions should be
necessary to prevent the evil influence of half a pound of cheesy
matter, or less, in a hundred pounds of butter.
5°. Though the curd or casein appears to be the enemy against
whose secret machinations the dairy farmer has chiefly to guard,
yet the oxygen of the atmosphere is a second agent by which the
fatty matters of butter are liable to be brought into a state of de-
composition, and the presence of which, therefore, should be ex-
cluded as carefully as possible.
We have seen (p. 968) that by the action of oxygen the liquid
elaic acid may be changed into the solid margaric acid of butter.
This is the first stage in the decomposition, which, when once begun,
generally spreads or extends with increasing rapidity.f
Again, this fluid acid of butter absorbs oxygen with great ra-
pidity from the air, and during its rapid change does not always
cease to absorb oxygen when the solid acid has been formed. On
the contrary, other compounds are produced, such as the butyric
* Mr Ballantyne thus describes the method of salting butter practised at his dairy
farm of 30 cows, near Edinburgh :—“The butter is drawn warm from the churn, and
it is an invariable rule never to wash it or dip it into water, when intended to be salted.
The dairymaid puts it into a clean tub, which is previously well rinsed with cold water,
and then works it with cool hands till all the milk is thoroughly squeezed out. Half
the allowed quantity of salt is then added, and well mixed up with the butter and in
this state it is allowed to stand till next morning, when it is again wrought up, any
brine squeezed out, and the remainder of the salt added. It is then packed into kits,
which, when full, should be well covered up, and placed in a cool dry store—a small
quantity of salt is usually sprinkled on the surface. The proportion of salt used at
this dairy is half a pound to fourteen pounds of butter.”—Journal of Agriculture,
New Series, vol. i. p. 26.
+ Tallow, as is well known to candlemakers, and especially to the manufacturers
of stearin candles, becomes harder by keeping, indeed sometimes is unfit for use un-
til it is a year old—candles in a damp place become harder by keeping—and in tal
low that has lain long in a wet mine, the oily part has been found entirely changed
into the solid fat of tallow (Beetz). A similar change, therefore, is not unlikely in
butter also—and the changed butter ought to be more solid and dense than before.
l
PRODUCTION OF THE RANCID FATS. 977
capric and caproic acids, in which more oxygen is contained.
Thus if to
- C. II. ()
1 of Margaric acid, ........... .e. e. e. e. e s e º e s e º e º e º e º e > * * 34 34 4
we add 18 of oxygen, .............................. 18
- 34 34 22
and deduct 2 of carbonic acid and 2 of water, ... 2 2 6
we have 4 of butyric acid, ........................ 32 32 16
The change of the margaric into the butyric acid, therefore, is
of a similar mature to the change of the elaic into the margaric.
Again, if to
C. H. (3
2 of Margaric acid, ................................. 68 68 8
we add 46 of OXygen, . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
68 68 54
and deduct 8 of carbonic acid and 23 of water, 8 23 39
we have 5 of caproic acid, ........................ 60 45 15
So that water and carbonic acid are here also given off, and oxy-
gen absorbed as before—only in larger quantity.
In like manner the capric acid is produced either before or along
with the other acids by the absorption of oxygen from the air.
It is to the production of these acids, as I have already stated, that
the disagreeable smell and taste of rancid butter is owing. The
changes take place in succession as I have described them, or simul-
taneously, and quickly or slowly, according to circumstances, and
hence the different degrees of perfection in which preserved butter
is met with at different times, in different localities and in diffe-
rent SeaSOns.
To the action of the oxygen of the air, as above described,
is partly to be attributed that peculiar kind of rancidity, which,
without penetrating into the interior of well packed butter, is yet
perceptible on its external surface, wherever the air has come in
contact with it. A knowledge of this action of the atmosphere,
therefore, urges strongly the necessity of closely incorporating and
kneading together the butter in the cask or firkin—of leaving no
air holes or openings for air—of making the cask itself not only
water tight but air tight—and of never finally closing it till the
butter has shrunk in as far as it is likely to do, and until the va-
cancies, which may have arisen between the butter and the cask,
have been carefully filled up again. .
- 3 Q
LECTURE XXV.
Manufacture of cheese. Natural and artificial curdling of milk. Preparation of ren-
net. Theory of the action of rennet. Circumstances by which the quality of
cheese is affected. Circumstances under which cheese of different qualities may be
obtained from the same milk. Average quantity of cheese yielded by different va-
rieties of milk. Produce in cheese of a single cow. General composition of &heese
—proportions of water, curd, and fat. Preparation of fermented liquor from milk.
Milk vinegar. Saline constituents of milk and cheese—their nature and relative
proportions. Purposes served by milk in the animal economy.
§ 1. Of the natural and artificial curdling of milk.
When milk is left to itself for a certain length of time, it be-
comes sour and curdles. The curd and whey, however, do not
readily separate unless a gentle heat be applied, when the curd
contracts in bulk, and either squeezes out the whey and floats upon
it, or, when cut into pieces or placed in a perforated cheese vat, al-
lows the whey freely to flow from it. If the mixed curd and whey
from the entire milk, be allowed to simmer for a length of time
over a slow fire, the buttery part will separate from the cheese,
and will float on the top in the form of a fluid oil.
1°. Natural curdling.—The natural curdling of milk is pro-
duced by the lactic acid, which, as we have seen (p. 942), is always
formed from the milk-sugar when milk is allowed to stand for any
length of time in the air. It does not curdle immediately upon
becoming sour, for a reason which I shall presently explain.
2°. Artificial curdling.—But it is not usual in the manufacture
of cheese to allow the milk to sour and curdle of its own accord.
The process is generally hastened by the artificial addition of an
acid, or of some substance, such as rennet, by which the natural
production of lactic acid is accelerated. Almost any acid substance
will have the effect of curdling milk. Muriatic acid (spirit of
salt), diluted with water, is said to be extensively, though not uni-
3
HOW ACIDS ACT IN CURDLING MILK. - 979
versally employed in Holland for this purpose. In other countries
vinegar,” tartaric acid, lemon juice, cream of tartar, and salt of
sorrel have been occasionally used, and in Switzerland—especially
in the manufacture of the Schabzieger cheese—it is customary to
add merely a little sour milk, for the purpose of producing the
curd. -
3°. Chemical action of the acid.—But how does the acid act in
causing the milk to curdle, and why is it necessary to allow a little
time to elapse and to apply also a gentle heat before the curd will
completely separate 2 -
In regard to casein or the cheesy matter of milk, we have seen
a. That though nearly insoluble in pure water, it dissolves
readily in water containing in solution a small quantity of potash
or soda, either in the caustic or carbonated state. In other words,
the casein, which is an acid substance, unites chemically with the
potash or the soda, and forms a compound which is soluble in water.
b. That when an acid is added to this solution, it takes the pot-
ash or soda from the casein and combines with it, leaving the curd
again in its original nearly insoluble state, and causing it, there-
fore, to separate from the water. º
Now in milk, as it comes from the cow, the casein is in chemi-
cal combination with a small quantity of soda, by which it is ren-
dered soluble in the water of which the milk chiefly consists.
When the milk stands for a time in the air, the sugar of milk, as
we have seen, is transformed into lactic acid—this acid takes the
soda from the casein, and forms lactate of soda, and the cheesy
matter, in consequence, being itself insoluble in water, separates
in the form of curd. The application of a gentle heat acts in two
ways. It aids the acid in more completely taking the soda from
the casein, and causes the latter at the same time to shrink in, to
become less bulky, and thus to separate readily from the whey,
If we add an acid artificially to milk, the effect is exactly the
* “To coagulate a cotyla of milk we add a cyathus of Sweet vinegar” (Dioscorides).
Milk is also curdled by ardent spirits, by the juice of the fig, and by a decoction of
the flowers of the artichoke, of the white and yellow bed-straw (galium), and of the
crow-foot (ramunculus flammula and lingula). The Tuscan ewe-cheese is curdled with
the juice of the fresh, or with a decoction of the dried flowers of the wild thistle, or
with the flowers of the artichoke, which give a cheese of finer colour and less pungent
taste.
980 PREPARING AND SALTING THE GALF's STOMACH.
same. Either muriatic acid, or tartaric acid, or vinegar, or sour
milk will, in the same way, take the soda from the casein, and ren-
der it insoluble. And that this is the true action of the acid is
readily proved by adding a little soda to curdled milk, when the
curd will be re-dissolved, and the milk will become sweet. Add
acid to it now, or let it sour naturally a second time, and the curd
will again be separated.
The action of rennet is in some degree different, though no less
simple and beautiful. Let us first, however, consider what relinet
is, and how it is prepared.
§ 2. Of the preparation of rennet.
Rennet is prepared from the salted stomach or intestines of the
suckling calf, the unweaned lamb, the young kid, or the young
pig.” In general, however, the stomach of the calf is preferred,
and there are various ways of curing and preserving it.
1°. Preparing the stomach.-The stomach of the newly killed
animal contains a quantity of curd derived from the milk on which
it has been fed. In most districts (Switzerland, Gloucester, Che-
shire) it is usual to remove by a gentle washing the curd and slimy
matters which are present in the stomach, as they are supposed to
impart a strong taste to the cheese. In Cheshire the curd is fre-
quently salted separately for immediate use. In Ayrshire and
Limburg, on the other hand, the curd is always left in the stomach
and salted along with it. Some even give the calf a copious draught
of milk shortly before it is killed, in order that the stomach may
contain a larger quantity of the valuable curd. From what we
have seen of the action of curd alone in souring milk the latter
method is likely to produce the largest quantity of active rennet.
2°. Salting the stomach.-In the mode of salting the stomach
similar differences prevail. Some merely put a few handfuls of
salt into and around it, then roll it together, and hang it near the
chimney to dry. Others saltit in a pickle for a few days, and then
hang it up to dry (Gloucester), while others again (Cheshire) pack
several of them in layers with much salt both within and without,
and preserve them in a cool place till the cheese-making season of
* Dried pig's bladder is often employed instead of the dried kid's stomach for
curdling goat’s milk on Mont D’or,
METHODS OF MAKING THE RENNET. 98]
the following year. They are then taken out, drained from the
brine, spread upon a table, sprinkled with salt, which is rolled in
with a wooden roller, and then hung up to dry. In some foreign
countries, again, the recent stomach is minced very fine, mixed
with some spoonfuls of salt and bread-crumb into a paste, put into
a bladder, and then dried. In Lombardy the stomach, after being
Salted and dried, is minced and mixed up with salt, pepper, and a
little whey or water into a paste, which is preserved for use.”
In whatever way the stomach or intestine of the calf is prepared
and preserved, the almost universal opinion seems to be, that it
should be kept for 10 or 12 months before it is capable of yielding
the best and strongest rennet. If newer than 12 months, the ren-
net is thought in Gloucestershire “to make the cheeses heave or
swell, and become full of eyes or holes.”f
3°. Making the rennet.-In making the rennet different customs
also prevail. In some districts, as in Cheshire, a bit of the dried
stomach is put into half a pint of lukewarm water with as much
salt as will lie upon a shilling, is allowed to stand over might, and
in the morning the infusion is poured into the milk. For a cheese
of 60 lbs. weight, a piece of the size of half-a-crown will often be
sufficient, though of some skins as much as 10 square inches are
required to produce the same effect (Dr Holland).
It is perhaps more common, however, to take the entire stomachs
(dried maws, vells, reeds, or yirningſ they are often called), and to
pour upon them from one to three quarts of water for each stomach,
and to allow them to infuse for several days. If only one has been in-
fused, and the rennet is intended for immediate use, the infusion
requires only to be skimmed and strained. But if several maw-
skins be infused—or, as is the custom in Cheshire, as many as have
been provided for the whole season—about two quarts of water are
taken for each, and, after standing not more than two days, the in-
fusion is poured off, and then completely saturated with salt. Du-
ring the summer it is constantly skimmed and fresh salt added
* Cattaneo, Il latte e i swot prodotti, p. 204.
+ British Husbandry, ii. p. 420.
# In Northumberland the dried stomach is sometimes called the keslap, which is
evidently the German käse-lab, cheese-rennet. Loppert and lappert, applied in Nor-
thumberland and the West of Scotland respectively to sour, curdled milk, is derived
from the same German lab, rennet, or laber, to coagulate.
982 SALTING THE STOMACH A SECOND TIME.
from time to time. Or a strong brine may at once be poured upon
the skins, and the infusion, when the skins are taken out, may be
kept for a length of time. Some even recommend that the liquid
remnet should not be used until it is at least two months old.
When thus kept, however, it is indispensable that the water should
be fully saturated with salt.
In Ayrshire, and in some other counties, it is customary to cut
the dried stomach into small pieces, and to put it, with a handful
or two of salt and one or two quarts of water, into a jar, to allow
it to stand for two or three days, afterwards to pour upon it another
pint for a couple of days, to mix the two decoctions, and, when
strained, to bottle the whole for future use. In this state it may
be kept for many months.”
In all the methods above described, the exhausted skins are
thrown away. Where they are cut into pieces, as in Cheshire and
Ayrshire, they cannot of course be put to any second use, but
where they are steeped whole, there is reason to believe that they
might be used with almost equal advantage a second or even a
third time. Accordingly, it has long been the custom in the
north of England to re-salt the stomach after it has been once
steeped, and when long dried, as before, to use it a second and
even a third time for the preparation of rennet. When we ex-
plain the mode in which remnet acts, you will see why the same
skin may be expected to yield a good rennet, after being salted
again and again for an indefinite number of times.
In making remnet, some use pure water only, others prefer clear
whey, others a decoction of leaves—such as those of the sweetbriar,
the dog-rose, and the bramble—or of aromatic herbs and flowers,
while others, again, put in lemons, cloves, mace, or brandy. These
various practices are adopted for the purpose of making the ren-
net keep better, of lessening its unpleasant smell, of preventing
any unpleasant taste it might give to the curd, or finally of directly
improving the flavour of the cheese. The acidity of the lemon
* A table-spoonful of this rennet, according to Mr Aiton, will coagulate 30 gallons
of milk, and will curdle it in five or ten minutes, whereas the English rennet requires
from one to three hours. This superiority he ascribes to the custom of leaving the
curdled milk in the stomach. He denies also that this milk gives any harsh taste to
the cheese,
THEORY OF THE ACTION OF RENNET. - 983
will, no doubt, increase also the coagulating power of any rennet
to which it may be added.
4°. How the rennet is used.—The rennet thus prepared is pour-
ed into the milk previously raised to the temperature of 90° or 95°
F., and is intimately mixed with it. The quantity which it is ne-
cessary to add varies with the quality of the rennet—from a table-
spoonful to half a pint for 30 or 40 gallons of milk. The time ne-
cessary for the complete fixing of the curd varies also from 15 mi-
nutes to an hour or even an hour and a half. The chief causes of
this variation are the temperature of the milk, and the quality and
quantity of the rennet employed.
But how does the rennet act in causing this coagulation ? Be-
fore we can answer this question it is necessary to enquire what
rennet really is. -
§ 3. Theory of the action of rennet.
It has been stated, and hitherto almost generally received, that
the only effective substance contained in rennet is the gastric juice
derived from the stomach of the calf. To this persuasion is, no
doubt, to be ascribed the custom both of preserving the natural
contents of the stomach—and of generally throwing away the bag
after being once salted, dried, and extracted. The gastric juice'
which exudes from the interior surface of the stomachs of all ani-
mals is known to curdle milk readily, and, therefore, it was matu-
ral to ascribe the action of rennet to the presence of this substance,
and to infer that, being once extracted, it was in vain to expect
much advantage from salting and infusing the membrane a second
time. But the three facts—
a. That in most places it is customary to wash the interior of
the stomach before salting it, and thus to remove the greater part
of the gastric juice it may contain ; -
b. That besides, in many places, the bags are laid up in brine
for weeks and months, and are then drained out of this brine be-
fore they are dried—by which any gastric juice remaining must
be almost entirely removed,—and -
c. That after being dried and steeped once for the preparation
of rennet, experience has proved that they may again be salted
and used over again ; --
—these three facts, I think, show that the efficacy of rennet does
984 THE SUBSTANCE OF THE STOMACH CHANGES
not depend upon any thing originally contained in the stomach, but
wpon something derived from the substance of the stomach itself.
Now when considering the properties of milk-sugar and of lac-
tic acid, I have stated that if a piece of the fresh membrane of the
stomach or intestine, or even of the bladder of an animal, be ex-
posed to the air for a few days, and be then immersed in a solu-
tion of milk-sugar, it will gradually transform the sugar into lae-
tic acid. In milk this membrane would produce a similar effect,
aiding and hastening the natural souring and curdling effect
of the casein. By exposure to the air, the surface of the mem-
brane has undergone such a degree of change or decomposition,
as enables it to induce the elements of the sugar to alter their mu-
tual arrangement, and to unite together in such a way as to form
lactic acid. - -
If the moist membrane be exposed for a longer time to the air
this change of its surface will penetrate deeper, and it will become
more effective in inducing the transformation of the sugar into
Ractic acid. But, at the same time, a portion of its surface may
run into a state of putrefaction, and besides acquiring a disagree-
able odour may become capable also of bringing on fermentation
and putrefactive decay in the solutions upon which it may be made
to act. It is not expedient, therefore, to attempt to heighten the
transforming effect of animal membranes by exposing them for a
greater length of time to the air in a moist and fresh state.
But if the membrane be salted, and thus preserved from the
rapid action of the air, it will be protected from putrefaction in a
great degree, while, at the same time, it will undergo that gradual
change upon its surface to which its power of transforming solutions
of sugar is ascribed. And this change will be materially hastened
and increased and made to penetrate deeper, if the salted mem-
brane be subsequently dried slowly in the air by a gentle heat, and
be afterwards kept for a length of time where the air has more or
less ready access to it. Such is the mode of treatment to which
the calf's stomach is subjected for the preparation of remmet, and
it is an important practical observation that the membrane should
be kept at least 12 months, if it is to acquire very powerful coa-
gulating properties. -
It is necessary further to remind you that when malt is steeped
in water for a few minutes a substance, named diastase, is extract-
WHEN EXPOSED A SHORT TIME TO THE AIR. 985
ed from it, which possesses the remarkable property of changing
starch into sugar in a very short time, and in large quantity
(p. 221). Now, if this diastase be exposed to the air for a length of
time, it undergoes a change similar to that experienced by the Sur-
face of animal membranes, and acquires the property of transform-
ing sugar into lactic acid. After undergoing this change it still
dissolves readily in water, and if a solution of it be poured into one
of sugar, the transformation of the latter into lactic acid gradually
proceeds. There exist, therefore, substances soluble in water, which
possess the same power as slightly decayed but insoluble animal
membrane, of converting sugar into lactic acid.
During the protracted drying and decay of the salted stomach,
the change undergone by the surface of the membrane is such as
to produce a quantity of matter capable of dissolving in water, and
which also possesses the property of quickly converting the sugar
into the acid of milk. This matter, water extracts from the dried
skin, and it forms the active ingredient in rennet.
I need not further explain to you upon what this activity de-
pends—since as you already know any thing which will rapidly
change sugar into lactic acid will also, if gently warmed, rapidly
curdle milk.
Thus the action of rennet resolves itself simply into a curdling
of milk by the action of its own acid. It is the same thing as when
sour milk in Switzerland is at once mixed with that from which the
cheese is to be made ; or it is only a more speedy way of bringing
about the curdling that takes place when milk sours naturally and
is then gently warmed till the curd separates.
But how, it may be asked, is the coagulation effected so much
more rapidly by the action of rennet than when the milk is left to
sour of its own accord It is because the whole of the animal mat-
ter in the rennet is already in the state in which it easily transforms
the sugar into acid, and being intimately mixed with the whole milk
in a warm state it produces acid mear every particle of the cheesy
matter. From this cheesy matter the acid formed takes away the
soda that holds it in Solution, and thus renders it insoluble or cur-
dles the milk. In milk, on the other hand, which is left to sour
and curdle of itself, the casein must first be changed by the action
of the air before it can transform the sugar and produce acid. Thi
986 RENNET CHANGES THE SUGAR INTO THE ACID OF MILK.
†
change takes place more or less slowly, and chiefly at the surface of
the milk where it is in contact with the air. The souring, therefore,
must also proceed slowly, as well as the curdling of which it is the
CallSC, º
It is no objection to this explanation of the action of rennet, that
neither the milk nor the whey become sensibly sour during the Se-
paration of the curd. The acid, as it is produced, combines direct-
ly with the soda previously united to the curd, and renders the lat-
ter insoluble—while, if any excess of acid do happen to be formed,
it is in great part taken up and retained mechanically by the curd,
and thus is not afterwards sensibly perceived in the whey.
Using the same skin a second time.--If this then be a true ex-
planation of the action of rennet—if the coagulating ingredient in
it be merely a portion of the changed membrane of the stomach
itself—it is obvious that the bag, after being once used, may be
again salted and dried with advantage. The slow decay may, after
a second salting, become still slower, and thus it may require to be
longer kept after the second than after the first salting, before it
will give a rennet as powerful as that which was first extracted from
it. But unless it be only the immer membrane of the stomach
and intestines which is capable of undergoing that kind of change
upon which the coagulating power depends, there is no apparent
reason, as I have already stated to you, why the same maw-skin
may not be salted, dried, and steeped many times over.
Use of whey.—Again, in the making of rennet there seems some
propriety in the use of whey rather than of water. The whey may
contain a portion of the rennet which had been added to the milk
from which it was extracted, and may thus be able of itself to cur-
dle milk. It is sure also to contain some milk-sugar, which, being
changed into acid when the whey is poured upon the dried stomach,
will add to the coagulating power of the remnet obtained.
Use of the curdled milk contained in the stomach.-Does the view
we have taken of the action of rennet throw any light upon the use
of the curdled milk found in the stomach 2 Is it of any service, or
ought it to be rejected P
We are certain that it must be of service in coagulating milk,
since in Cheshire, according to Dr Holland, it is frequently taken
out and salted by itself for immediate use. But a slight conside-
ration of the properties of casein, as I have already stated them to
CHEESE OF DIFFERENT QUALITIES-HOW OBTAINED. 987
you, will explain why this curdy matter should be serviceable for
such a purpose.
You will recollect that casein, after being exposed to the air for
a short time, acquires, like animal membranes, the property of con-
verting sugar into lactic acid, and of curdling milk. Now the
curdy matter taken from the stomach of the calf, after being ex-
posed to the air, acquires this property as completely as a more
pure curd will do. If salted and kept, it will be changed still fur-
ther, and will acquire this property in a greater degree. In short,
keeping will affect the curd precisely in the same way as it does
the membrane of the stomach itself, and will render it alike fit to
be employed in the preparation of rennet. Nor is it unlikely that
fresh well-squeezed curd, if mixed with much salt and kept in
slightly covered jars for 10 or 12 months, might yield a rennet
possessed of good coagulating properties. -
It thus appears that, so far as economy is concerned, the curdy
matter contained in the calf's stomach ought to be preserved and
salted for use. If in any district this curd be suspected to impart
an unpleasant flavour to the cheese, this bad effect may probably
be remedied by taking it out of the stomach, washing it well with
water—as is dome in some dairy districts—mixing it with salt, and
then returning it into the stomach again.
Another practical conclusion may also be drawn from this ex-
planation of the action of the stomach. Since it is the membrane
alone that acts, there can no loss accrue by carefully washing the
stomach as well as the curd it contains. On the contrary, by so
doing, we may remove from its inner surface some substances
which, if allowed to remain, might afterwards act injuriously upon
the flavour or upon the other qualities of the cheese.
§ 4. Of the circumstances by which the quality of cheese is
affected.
All cheese consists essentially of the curd mixed with a cer-
tain proportion of the fatty matter and of the sugar of milk. But
differences in the quality of the milk, in the proportions in which
the several constituents of milk are mixed together, or in the
general mode of dairy management, give rise to varieties of cheese
almost without number. Nearly every dairy district produces
w
988 LSE OF CREAMED OR. UNCREAMED MILR.
one or more qualities of cheese peculiar to itself. It will not be
without interest to attend briefly to some of these causes of diver-
sity. -
1°. Natural differences in the milk.-It is obvious that whatever
gives rise to natural differences in the quality of the milk must af-
fect also that of the cheese prepared from it. If the milk be poor
in butter, so must the cheese be. If the pasture be such as to give
a milk rich in cream, the cheese will partake of the same quality.
If the herbage or other food affect the taste of the milk or cream,
it will also modify the flavour of the cheese.
2°. Milk of different animals.--So the milk of different animals
will give cheese of unlike qualities. The ewe-milk cheeses of
Tuscany, Naples, and Languedoc, and those of goat's milk made
on Mont D'or and elsewhere, are celebrated for qualities which are
not possessed by cheeses prepared from cow's milk in a similar way.
Buffalo milk also gives a cheese of peculiar qualities, which is ma-
nufactured in some parts of the Neapolitan territory.
Other kinds of cheese again are made from mixtures of the milk
of different animals. Thus the strong tasted cheese of Lecca and
the celebrated Roquefort cheese are prepared from mixtures of
goat with ewe-milk, and the cheese of Mont Cenis" from both of
these mixed with the milk of the cow.f
3°. Creamed or uncreamed milk.-Still further differences are
produced according to the proportion of cream which is left in or
is added to the milk. Thus if cream only be employed, we have
the rich cream-cheese, which must be eaten in a comparatively re-
cent state. Or, if the cream of the previous might's milking be
added to the new milk of the morning, we may have such cheese as
the Stilton of England, or the small, soft, and rich Brie cheeses,
so much esteemed in France. If the entire milk only be used, we
have such cheeses as the Cheshire, the Double Gloucester, the Ched-
dar, the Wiltshire, and the Dunlop cheeses of Britain, the Kinne-
gad cheese, I believe, of Ireland, and the Gouda and Edam cheeses
* Lecca is a province in the Eastern part of the Neapolitan territory; Roquefort,
a town in the pastoral department of Aveiron, in the South of France, famed for its
sheep ; and Mont Cenis, a mountain in Savoy. •
+ The milk of 2 goats is mixed with that of 20 sheep and 5 cows.
4
BUTTER-MILK CHEESE. 989
of Holland. Even here, however, it makes a difference whether
the warm milk from the cow is curdled alone, as at Gouda and
Edam, or whether it is mixed with the milk of the evening before,
as is generally done in Cheshire and Ayrshire. Many persons are
of opinion that cream, which has once been separated, can never
be so well mixed again with the milk, that a portion of the fatty
matter shall not flow out with the whey and render the cheese less
rich.
If, again, the cream of the evening's milk be removed, and the
skimmed milk added to the new milk of the next morning, such
cheeses as the Single Gloucester are obtained. If the cream be
taken once from all the milk, the better kinds of skimmed-milk
cheese, such as the Dutch cheese of Leyden, are prepared—while
if the milk be twice skimmed, we have the poorer cheeses of Fries-
land and Groningen. If skimmed for three or four days in suc-
cession, we get the hard and horny cheeses of Essex and Sussex,
which often require the axe to break them up.
4°. Butter-milk cheese.—But poor or butterless cheese will also
differ in quality according to the state of the milk from which it is
extracted. If the new milk be allowed to stand to throw up its
cream, and this be then removed in the usual way, the ordinary
skimmed-milk cheese will be obtained by adding rennet to the
milk. But if, instead of skimming, we allow the milk to stand till
it begins to sour, and then remove the butter by churning the
whole, we obtain the milk in a sour state (butter-milk). From this
milk the curd separates naturally by gentle heating. But being
thus prepared from sour milk and without the use of rennet, but-
ter-milk cheese differs more or less in quality from that which is
made from sweet skimmed-milk.
The acid in the butter-milk, especially after it has stood a day
or two, is capable of coagulating new milk also, and thus, by mix-
ing more or less sweet milk with the butter-milk before it is warmed,
several other qualities of mixed butter and sweet milk cheese may
readily be manufactured.
If, as is stated by Mr Ballantyne, the churning of the whole
milk gives butter in larger quantity, of better quality, and more
uniformly throughout the whole year, the manufacture of these
butter-milk cheeses is deserving of the attention of dairy farmers,
990 ~ WHEY, VEGETABLE, AND POTATO CHEESES.
especially in those districts where butter is considered as the most
important produce.
5°. Whey-cheese.—The whey which separates from the curd,
and especially the white whey, which is pressed out towards the
last, contains a portion of curd, and not unfrequently a consider-
able quantity of butter also. When the whey is heated, the curd
and butter rise to the surface, and are readily skimmed off. This
curd alone will often yield a cheese of excellent quality, and so
rich in butter, that a very good imitation of Stilton cheese may
sometimes be made with alternate layers of new milk-curd and this
curd of whey. - - r
6°. Mixtures of vegetable substances with the milk.-Other va-
rieties of cheese are formed by mixing vegetable substances with
the curd. A green decoction of two parts of sage-leaves, one of
marigold, and a little parsley gives its colour to the green cheese of
Wiltshire; some even mix up the entire leaves with the curd.
The celebrated Schabzieger cheese of Switzerland is made by
crushing the skim-milk cheese after it is several months old to fine
powder in a mill, mixing it then with one-tenth of its weight of fine
salt and one-twentieth of the powdered leaves of the mellilot tre-
foil (trifolium melilotus cerulea), and afterwards with oil or butter
—working the whole into a paste which is pressed and carefully
dried.
Potato cheeses, as they are called, are made in various ways.
One pound of sour milk is mixed with five pounds of boiled pota-
toes and a little salt, and the whole is beat into a pulp, which, after
standing five or six days, is worked up again, and then dried in the
usual way. Others mix three parts of dry boiled potatoes with two
of fresh curd, or equal weights, or more curd than potato is em-
ployed, according to the quality required. Such cheeses are made
in Thuringia, in Saxony, and in other parts of Germany. In Sa-
voy, an excellent cheese is made by mixing one of the pulp of pota-
toes with three of ewe milk curd, and in Westphalia a potato cheese
is made with skimmed milk. This Westphalian cheese, while in the
pasty state, is allowed to undergo a certain extent of fermentation
before it is finally worked up with butter and salt, made into shapes
and dried. The extent to which this fermentation is permitted to:
go determines the flavour of the cheese.
TEMPERATURE AND HEATING OF THE MILK. 99.1
§ 5. Circumstances under which cheese of different qualities may
be obtained from the same milk.
But from the same milk, in the same state, different kinds or
qualities of cheese may be prepared according to the way in which
the milk or the curd is treated. Let us consider also a few of the
circumstances by which this result may be brought about.
1°. Temperature to which the milk is heated.—The temperature
of new or entire milk, when the remnet is added, should be raised
to about 95° F.—that of skimmed-milk need not be quite so high.
If the milk be warmer the curd is hard and tough, if colder it is
soft and difficult to obtain free from the whey. When the former
happens to be the case, a portion of the first whey that separates
may be taken out into another vessel, allowed to cool, and then
poured in again. If it prove to have been too cold, hot milk or
water may be added to it—or a vessel containing hot water may
be put into it before the curdling commences—or the first portion
of whey that separates may be heated and poured again upon the
curd. The quality of the cheese, however, will always be more or
less affected when it happens to be necessary to adopt any of these
remedies. To make the best cheese, the true temperature should
always be attained, as nearly as possible, before the remnet is added.
29. Mode in which the milk is warmed.—If, as is the case in some
dairies, the milk be warmed in an iron pot upon the naked fire,
great care must be taken that it is not singed or fire-fanged. A
very slight imattention may cause this to be the case, and the taste
of the cheese is sure to be more or less affected by it. In Cheshire
the milk is put into a large tin pail, which is plunged into a boiler
of hot water, and frequently stirred till it is raised to the proper
temperature. In large dairy establishments, however, the safest
method is to have a pot with a double bottom, consisting of one
pot within another—after the manner of a glue-pot—the space be-
tween the two being filled with water. The fire applied beneath,
thus acts only upon the water, and can never, by any ordinary
neglect, do injury to the milk. It is desirable in this heating not
to raise the temperature higher than is necessary, as a great heat
is apt to give an oiliness to the fatty matter of the milk.
3°. The time during which the curd stands is also of importance.
It should be broken up as soon as the milk is fully coagulated.
992 QUALITY AND QUANTITY OF THE RENNET.
The longer it stands after this the harder and tougher it will be-
COID.C.
4°. The quality of the rennet is of much importance not only
in regard to the certainty of the coagulation, but also to the flavour
of the cheese. In some parts of Cheshire, as we have seen, it is
usual to take a piece of the dried membrane and steep it over-night
with a little salt for the ensuing morning's milk. It is thus sure
to be fresh and sweet if the dried maw be in good preservation.
But where it is customary to steep several skins at a time, and to
bottle the rennet for after-use, it is very necessary to saturate the
solution completely with salt and to season it with spices, in order
that it may be preserved in a sweet and wholesome state. In some
parts of Scotland the remnet is said to be frequently kept in bottles
till it is almost putrid, and in this state is still put into the milk.
Such remnet may not only impart a bad taste to the cheese, but is
likely also to render it more difficult to cure, and to bring on pu-
trefaction afterwards and a premature decay. -
5°. The quantity of rennet added ought to be regulated as care-
fully as the temperature of the milk. Too much renders the curd
tough ; too little causes the loss of much time, and may permit a
larger portion of the butter to separate itself from the curd. It is
to be expected also that when rennet is used in great excess, a
portion of it will remain in the curd, and will naturally affect the
kind and rapidity of the changes it afterwards undergoes. Thus
it is said to cause the cheese to heave or swell, out from fermenta-
tion. It is probable also that it will affect the flavour which the
cheese acquires by keeping. Thus it may be that the agreeable
or unpleasant tastes of the cheeses of certain districts or dairies
may be less due to the quality of the pastures or of the milk itself,
than to the quantity of rennet with which it has there been custom-
ary to coagulate the milk. -
6°. The way in which the rennet is made, no less than its state
of preservation and the quantity employed, may also influence the
flavour or other qualities of the cheese. For instance, in the ma-
nufacture of a celebrated French cheese—that of Epoisse—the
rennet is prepared as follows:–Four fresh calf-skins, with the
curd they contain, are well washed in water, chopped into small
pieces, and digested in a mixture of 5 quarts of brandy with 15
WAY IN WHICH THE CURD IS TREATED. §93
of water, adding at the same time 24 lbs. of salt, half an ounce of
black pepper, and a quarter of an ounce each of cloves and fennel
seeds. At the end of six weeks the liquor is filtered and preserv-
ed in well corked bottles, while the membrane is put into salt-
water to form a new portion of rennet. For making rich cheeses,
the rennet should always be filtered clear.”
Again, on Mount D'or, the rennet is made with white wine and
vinegar. An ounce of common Salt is dissolved in a mixture of
half a pint of vinegar with 2; pints of white wine, and in this solu-
tion a prepared goat's stomach or a piece of dried pig's bladder is
steeped for a length of time. A single spoonful of this rennet is
said to be sufficient for 45 or 50 quarts of milk. No doubt the
acid of the vinegar and of the wine aid the coagulating power de-
rived from the membrane.
Rennets prepared in the above ways must affect the flavour of
the cheese differently from such as are obtained by the several
more or less careful methods usually adopted in this country.
7°. When acids are used alone—as vinegar, tartaric acid, and
muriatic acid sometimes are—for coagulating the milk, the flavour
of the cheese can scarcely fail to be in some measure different from
that which is prepared with ordinary rennet.
8°. The way in which the curd is treated.—It is usual in our
best cheese districts carefully and slowly to separate the curd from
the whey—not to hasten the separation, lest a larger portion of
the fatty matter should be squeezéd out of the curd and the cheese
should thus be rendered poorer than usual. But in some places
the practice prevails of washing the curd with hot water after the
whey has been partially separated from it.
Thus at Gouda in Holland, after the greater part of the whey
has been gradually removed, a quantity of hot water is added, and
allowed to remain upon it for at least a quarter of an hour. The
heat makes the cheese more solid and causes it to keep better.
In Italy, again, the so-called pear-shaped caccio-cavallo cheeses
and the round palloni cheeses of Gravina, in the Neapolitan terri-
tory, are made from curd, which, after being scalded with boiling
whey, is cut into slices, kneaded in boiling water, worked with the
hand till it is perfectly tenacious and elastic, and then made into
* Il latte e i swoi prodotti, p. 274.
3 R
994 HOW THE WHEY IS SEPARATED.
shapes, The water in which the curd is washed, after standing
24 hours, throws up much oily matter, which is skimmed off and
made into butter. -
The varieties of cheese prepared by these methods no doubt de-
rive the peculiar characters upon which their reputation depends
from the treatment to which the curd is subjected—but it is ob-
vious that none of them can be so rich as a cheese from the same
milk would be, if manufactured in a Cheshire, a Wiltshire, or an
Ayrshire dairy. -
9°. The separation of the whey is a part of the process upon
which the quality of the cheese in a considerable degree depends.
In Cheshire more time and attention is devoted to the perfect ex-
traction of the whey than in almost any other district. Indeed,
when it is considered that the whey contains sugar and lactic acid,
which may undergo decomposition, and a quantity of rennet, which
may bring on fermentation—by both of which processes the fla-
vour of the cheeses must be considerably affected—it will appear
of great importance that the whey should be as completely removed
from the curd as it can possibly be. To aid in effecting this, a
curd-mill for chopping it fine after the whey is strained off is in
use in many of our larger dairies, and a very ingenious pneumatic
cheese press for sucking out the whey was invented by the late Sir
John Robison, of Edinburgh.*
But the way in which the whey is separated is not a matter of
indifference, and has much influence upon the quality of the cheese,
Thus in Norfolk, according to Marshall, when the curd is fairly
set, the dairy-maid bares her arm, plunges it into the curd, and
with the help of her wooden ladle breaks up minutely and inti-
mately mixes the curd with the whey. This she does for 10 or 15
minutes, after which the curd is allowed to subside, and the whey
is drawn off. By this agitation the whey must carry off more of
the butter and the cheese must be poorer. -
In Cheshire and Ayrshire, again, the curd is cut with a knife,
but is gently used and slowly pressed till it is dry enough to be
chopped fine, and thus more of the oily matter is retained. On
the same principle, in making the Stilton cheese, the curd is not
cut or broken at all, but is pressed gently and with care till the
* Transactions and Prize Essays of the Highland Society, vol. x., p. 204,
KIND OF SALT, AND HOW IT IS APPLIED. 995
whey gradually drains out. Thus the butter and the curd remain
intermixed, and the rich cheese of Stilton is the result.
Thus you will see that while it is of importance that all the whey
should be extracted from the curd, yet that the quickest way may
not be the best. More time and care must be bestowed in order
to effect this object, the richer the cheese we wish to obtain. You
will see, also, how the quality of the milk or of the pastures may
often be blamed for deficiencies in the richness or other qualities of
a cheese, which are in reality due to slight but material diffe-
rences in the mode of manufacturing it. -
10°. The kind of salt used is considered by many to have some
effect upon the taste of the cheese. Thus the cheese of Geromé,
in the Vosges, is supposed to derive a peculiar taste from the Lo-
rena salt with which it is cured. In Holland, also, the efficacy of
one kind of salt over another for the curing of cheese is generally
acknowledged.* It is indeed not unlikely that the more or less
impure salts of different localities may affect the flavour of the
cheese, but wherever the salt may be manufactured, it is easy to
obtain it in a uniform and tolerably pure state, by the simple pro-
cess of purification, which I have already described (p. 975).
11°. The mode in which the salt is applied—In making the large
Cheshire cheeses, the dried curd, for a single cheese of 60 lbs., is
broken down fine and divided into three equal portions. One of
these is mingled with double the quantity of salt added to the
others, and this is so put into the cheese-vat as to form the
central part of the cheese. By this precaution the after-salting on
the surface is sure to penetrate deep enough to cure effectually the
less salted parts. In the counties of Gloucester and Somerset the
curd is pressed without salt, and the cheese, when formed, is made
to absorb the whole of the salt afterwards through its surface.
This is found to answer well with the small and thin cheeses made
in these counties, but were it adopted for the large cheeses of
Cheshire and Dunlop, or even for the pine-apple cheeses of Wilt-
shire, there can be no doubt that their quality would frequently
be injured. It may not be impossible to cause the salt to pene-
trate into the very heart of a large cheese, but it cannot be easy
* British Husbandry, ii., p. 424.
996 ADDING CREAM OR BUTTER TO THE CURD.
in this way to salt the whole cheese equally, while the care and at-
tention required must be greatly increased. -
12°. Addition of cream or butter to the curd.—Another mode of
improving the quality of cheese is by the addition of cream or but-
ter to the dried and crumbled curd. Much diligence, however, is
required fully to incorporate these, so that the cheese may be uni-
form throughout. Still this practice gives a peculiar character to
the cheeses of certain districts. In Italy they make a cheese after the
manner of the English,” into which a considerable quantity of but-
ter is worked; and the Reckem cheese of Belgium is made by add-
ing half an ounce of butter and the yolk of an egg to every pound
of pressed curd. * -
13°. The colouring matter added to the cheese is thought by many
to affect its quality. In foreign countries saffron is very generally
used to give a colour to the milk before it is coagulated. In Hol-
land and in Cheshire annatto is most commonly employed, while in
other districts the marigold or the carrot, boiled in milk, are the
usual colouring matters.
The quantity of annatto employed is comparatively small—less,
than half an ounce to a cheese of 60 lbs.-but even this quantity
is considered by many to be an injurious admixture. Hence a na-
tive of Cheshire prefers the un-coloured cheese, the annatto being
added to such only as are intended for the London or other distant
markets. -
14°. Size of the cheese.—From the same milk it is obvious that
cheeses of different sizes, if treated in the same way, will at the end
of a given number of months possess qualities in a considerable de-
gree different. Hence, without supposing any inferiority, either in
the milk or in the general mode of treatment, the size usually
adopted for the cheeses of a particular district or dairy, may be the
cause of a recognized inferiority in some quality which it is desira-
ble that they should possess in a high degree.
15°. The method of curing has very much influence upon the
after-qualities of the cheese. The care with which they are salted
—the warmth of the place in which they are kept during the first
two or three weeks—the temperature and closeness of the cheese-
* Il latte e i swoi prodotti, p. 277.
MODE OF CURING THE CHEESE. 997
room in which they are afterwards preserved—the frequency of
turning, of cleaning from mould, and of rubbing with butter—all
these circumstances exercise a remarkable influence upon the after-
qualities of the cheese. Indeed in very many instances the high
reputation of a particular dairy district or dairy farm is derived from
some special attention to one or either or to all of the apparently
minor points to which I have just adverted.
In Tuscany the cheeses, after being hung up for some time at a
proper distance from the fire, are put to ripen in an underground
cool and damp cellar; and the celebrated French cheeses of Ro-
quefort are supposed to owe much of the peculiar estimation in
which they are held, to the cool and uniform temperature of the
subterranean caverns in which the inhabitants of the village have
long been accustomed to preserve them.
In Ross-shire it is said to be the custom with some proprietors to
bury their cheeses under the sea sand at low water, and that the
action of the sea-water in this situation renders them more juicy
and of an exquisite flavour.
16°. Ammoniacal cheese.—The influence of the mode of curing
upon the quality is shown very strikingly in the small ammonia-
cal cheeses of Brie, which are very much esteemed in Paris. They
are soft un-pressed cheeses, which are allowed to ripen in a room
the temperature of which is kept between 60° and 70°F. till they
begin to undergo the putrefactive fermentation and emit an ammo-
niacal colour. They are generally unctuous, and sometimes so
small as not to weigh more than an ounce.
A little consideration, indeed, will satisfy you, that by varying
the mode of curing, and especially the temperature at which they
are kept, you may produce an almost endless diversity in the quality
of the cheeses you bring into the market.
17°. Inoculating cheese.—It is said that a cheese possessed of no
very striking taste of its own, may be inoculated with any flavour
we approve of by putting into it with a scoop a small portion of the
cheese which we are desirous that it should be made to resemble.
Of course this can apply only to cheeses otherwise of equal rich-
ness, for we could scarcely expect to give to a single Gloucester the
flavour of a Stilton, by merely putting into it a small portion of a
rich and esteemed Stilton cheese.
998 AVERAGE PRODUCE OF CHIEESE IN AYRSHIRE,
§ 6. Of the average quantity of cheese yielded by different varieties
of milk, and of the produce of a single cow.
There appear to be very great differences in the proportions of
cheese yielded by milk at different seasons and in different locali-
ties.
In milk, of an average quality, there are contained from 4 to 5
per cent. of casein or dry cheesy matter (p. 921), which, if all ex-
tracted, would give
6 lbs. to 7 lbs. of skimmed-milk cheese, or
9 lbs. to 10 lbs. of entire milk cheese,
This is very nearly the proportion actually obtained in some of
the best dairy districts in the summer season. Thus
In Ayrshire—10 lbs. of milk, or n gave 1 lb. of whole milk
& 1 imperial gallon, ſ cheese;
or 136 wine quarts gave 1274 lbs. of cheese three months old.*
In Gloucester—7 lbs. of milk, or }gave 1 lb of double Gloucester.
3% wine quarts,
this is a much larger proportion, and is probably much above the
average of the county.
In Holstein, it is said that 100 lbs. of milk will give about
}rom 100 lbs. of milk.
New skimmed-milk cheese, .... ..... * * * * * * * * * * 6 lbs.
Butter, ........... .................. ................. 3}
Butter-milk, ... ........ ...... . . . ..... ............ 14
Whey, ...................... .......................... 76#
100 lbs.
But this statement is so far indefinite that it affords us no means
of judging how much curd is left in the butter-milk, nor how much
water was present in the new cheese. Indeed all the statements
hitherto recorded are deficient in this respect, that the dryness of the
cheese is not accurately expressed. (See next section).
In Cheshire, the average produce of a cow is reckoned at 360
lbs. of whole milk cheese, or about 1 lb. per day for the whole year.
* Mr Alexander of Ballochmyle informs me that the result of his experience with a
dairy of 40 cows in the higher part of Ayrshire, near Muirkirk, is, that
90 imperial quarts of sweet milk give an Ayrshire stone of 24 lbs. offull milk cheese
while the same quantity of skim milk gives only 16 lbs. of skimmed-milk cheese. That
is very nearly
9 lbs. of new milk gave 1 lb. of full milk cheese.
14 lbs, of skim milk gave 1 lb. of skim milk cheese,
PRODUCE OF CHEESE IN CHESHIRE, HOLSTEIN, ETC. 999
Taking 8 wine quarts of milk as the average daily yield of a cow in
that county, we have as the average produce of the milk the whole
year through— - -
1 lb. of cheese from 8 wine quarts, or 16 lbs. of milk.
It is indeed undoubted, that the proportion of cheese varies very
much with the season of the year and with the dryness of the weather.
Though, therefore, in summer 7 or 8 lbs. of milk may sometimes
yield a pound of cheese, it is possible that as much as 20 lbs. of
milk may at other seasons be required to give the same quantity.
Thus in - - -
South Holland, the summer produce of a cow is reckoned at
about 200 lbs. of skimmed-milk cheese, and 80 lbs. of butter; or
in a week 10 lbs. of skimmed-milk cheese, and 4 to 7 lbs. of but-
ter. Of whole milk cheese some eaſpect as much as 3 or 4 lbs. a
day. - *.
In Switzerland, generally, a cow giving 12 quarts of milk a day
will, during the summer, yield a daily produce of 1% lbs. of whole
or full milk cheese—or 10% quarts of milk, about 21 lbs. will give
a pound of cheese. - g
In the high pastures of Scaria, again, in the same country, one
cow will give for the 90 days of summer about 60 lbs. of skimmed-
milk cheese and 40 lbs. of butter—or 11 ounces of cheese per day.
It appears, therefore, as we should otherwise expect, that the
average produce of cheese is affected by many circumstances—but
that in this country 8 to 10 lbs. of good milk in the summer season,
will yield one pound of whole milk cheese.
§ 7. Of the average composition of cheese.
The different varieties of cheese prepared according to the mu-
merous methods above described, differ much, not only in quality
but in chemical composition. They all contain more or less of
the several constituents of milk, but the proportions in which its
curd and fat are found in them undergo great variations. The
curd of the milk is alone essential to the production of cheese,
but the proportion which this curd often bears to the other consti-
tuents of cheese I have found to be unexpectedly small.
My friend and pupil Mr Jones has for some time been engaged
in my laboratory in the chemical examination of different varieties
1000 AWERAGE COMPOSITION OF CHEESE.
of cheese—the only one hitherto made—and has obtained very in-
teresting results, of which I shall here present an abstract.
The method he has adopted in analysing cheese is as follows:—
a. A weighed portion of the cheese in a powdery state is digest-
ed in repeated portions of ether, aided by a very gentle heat. By
evaporating the ethereal solution, the butter is obtained, which is
heated to 212°F. as long as it loses weight, and its proportion
thus determined.
b. That which the ether leaves behind is dried and weighed in
like manner. This gives the proportion of casein and saline mat-
ter. -
c. This curd is then burned, and the weight of ash determined,
from which the proportion of saline matter is calculated.
d. The difference between the sum of the three weights thus ob-
tained and that of the cheese employed is the water contained in the
cheese. This last determination may be checked by drying a
weighed portion of the cheese at 212° as long as it loses weight.
In the case of fat or rich cheeses, however, this is a very tedious
process. *- -
The composition of different cheeses determined in this way was
found by Mr Jones to be as follows:—
1°. Skimmed milk cheese, made-in the parish of Carnwath, La-
markshire, on a poor, cold, wet, upland moor farm, on which a
dairy of 28 cows is kept:—
Per cent.
Water, ........................... .. 43°82
Casein, ............................. 45'04
Butter, .............................. 5°98
Ash, .................... ............ 5' 18
100-02
The striking thing in this result is, that an apparently very dry,
crumbly, skim-milk cheese of 12 months old, as this was, should
still retain nearly half its weight of water.
2°. Double Gloucester, made in June 1845, and analysed in
June 1846:—
Per cent,
Water, ... ........................... 35'81
Casein, ..... ..... .................. 37.96
Butter, ... ........ * e º º is tº ſº º e º e º s e s is 21.97
Saline matter, ..................... 4°25
* NORTH WILTS AND LANARKSHIRE BRICK CHEESES. 100l.
This, as we should expect, is much richer in butter than the
former. Every five pounds of it contain one of butter.
3°. North Wilts.-Mr Jones has analysed four varieties of North
Wilts cheese from different dairies. The first was made in June
1845, and examined in June 1846; the second made in Sep-
tember 1845 and examined in September 1846; the third made
in July 1846, and examined in September 1846; and the fourth
made in May 1846, and examined in September 1846. They
were found to consist respectively of—
1. 2. 3. 4.
Water, ............... 38°58 36-34 40°58 44°80
Casein, ............... 25'00 31° 12 28° 25 28° 16
Butter, ............... 30° 11 28-09 27:44 23-04
Saline matter, ...... 6.29 4'41 3-73 3'99
99.98 99.96 I 00-00 99-99
The last two, the four and six months old samples, contain most
water. The oldest (No. 2) contains the least, and yet in every 3 lbs.
of this there are more than 1 lb. of water. The June cheese is the
richest, though in all of them every 7 lbs, contain nearly 2 lbs. of
butter. The difference in the proportion of Saline matter is also
remarkable. This arises either from the quantity of salt added to
one cheese being greater than was added to the others—or to the
proportion of salt in one part of the same cheese being greater than
in another part. This may very well be, where the practice pre-
vails of rubbing in salt into the outside of the cheese (p. 995.)
4°. A Lanarkshire brick, made on the 20th of June 1845 and
analysed on the 6th of July of the same year, contained
Water,....... .................. 41'55
Casein, ........................... 25-84
Butter, ........................... 29-60
Saline matter, .................. 2.78
99.77
This new cheese approached in composition very nearly to
that of the North Wilts. Probably its form and size may account
for its containing only 1 per cent. more water than the six months
old Wiltshire.
5°. Dunlop or Ayrshire cheese.—A cheese twelve months old,
from the Wellwood dairy of Mr William M. Alexander of Bal-
I 002 DUNLOP, CHEDDAR, AND EWE MILK CHEESES.
lochmyle, proved to be the richest of any hitherto examined in my
laboratory. It contained w
Per cent.
Water, ................ .......... 38°46
Casein, .......................... 25'87
Butter, ..... ..... p = • * * * * * * * * * * * * * 31-86
Saline matter, .................. 3.81
100'00
This cheese was prepared from the milk alone, without any ad-
dition of cream, and yet, as We See, it contained nearly one-third
of its weight of butter. This accounts for the observation made in
regard to it, that, when roasted, it appears to run all away to oil.
In eating such cheese few people would at first believe that the
quantity of butter they swallow is nearly one-fourth greater than
that of curd.
6°. Cheddar cheese. — A Sample of cheese about a year old,
made upon a rich deep soil in the marsh near Cheddar, Somerset-
shire, gave Mr Jones ---
Water, ........................... 36'04
Casein, ...... .................... 28'98
Butter, .................... ...... 30-40
Saline matter, .................. 4°58
100
This cheese, as its reputation would lead us to expect, is also
very rich. -
7°. Ewe milk cheese.—A sample of what is commonly called
ewe milk cheese, from the Cheviot Hills, but which is in reality
made from a mixture of cow's and ewe's milk, was found to con-
sist of
Water, ........... ............... 40° 13
Casein, ........................... 33°40
Butter, ... ....................... 19-88
Saline matter, .................. 6'59
100
The following table exhibits a comparative view of the compo-
sition of all the varieties of cheese above mentioned:—
l
º)
1.
0
0
t)
PROFIT OF MAKING BUTTER, AND CIIFESE.

,"v d) --> Q) * ,--> I ; C >, * ~ P-, cº- t
- CC Aſ) " . ;4 - *-* KO . Cº. cº
a 5 || 3 || || 5 j; S, 3 : 3 TE st St. #: H
º CO HS CO :- ... CN HS CO > Co cº
F & 3 - «S r— . <! : «S º: - . 7. Ars TN
HS ~ P-, Cl) • QºS :- <!" | Q) Cºo GD
<H. --> --> e Q *H ºc
; : ##| | #: #: ; ;3|#é 5: # £º
rö - § - : - * T | < q2 - | E rº -: ă ă r-
cd q) E rºd R op # = ||.2">,73 || 3: * , QD go Nº.
8 : | Tö # ~ 2: § 3 ''d 3° 3, 2. č 35 | is “º rè st
: ga 32 c Oſ) 3 3 = %, 3.3% 92 – || 3 º' & Co
* Hy :- Pº, # --> 2 3 3 + 7.5 "º Tº Tº = - 3,3 r–4
Q1) 35 Tº GD § 3 & |.S. § cº; § 00 F.
3 Tº to C * S-2 3 $3 tº C 2-, 3 5 §3 |>. Tº § –
§ 3 § 3 ; "S 3 3, T.F. & |-o 2. TG 3 § 3
* {3, 3 . à || 3 º' | g : « * • Go (a 3 :
5 * | 3 as P 5 of 3 ſº º $2 scº 2-s] gº of 2 Pº Q -
3 || 3 tº £ 3 | # 3 T ≤ |.5 ± 3.3 sº * cº c -->
22 F | FF cº, F. : | H rº ||}} < ce || 3 c5 §2, F 7: F : TS Taj
* T ~ P … ºf £, (, ; , ;"|iº as gº * 3, P : 3
ă 6 | p 2 Atº * | c. 3 ºf 3 g : rº- CC ce rº
T -R r–3 p. , ºf St. º 'º -| Cº. 3 || P: B. Sº ºf tº .5 st: ~| IS 3
à & | 3 E +2 co *: ; TE = ? | 3 P 2.2 | # = |* cº ºr T. 3,
ÜD ſº Z. Z. C S: Z. Z. O
Water, ..... 43'82 | 35.81 || 35'58 36-34 38-46 || 41'55 | 40-58 44-80 || 36'04
Casein,...... 45-04 || 37.96 || 25'00 || 31-12 25.87 28:84 28-25 || 28-16 || 28.98
Fat, ......... 5'98 || 2] '97 || 30-11 || 28-09 || 31.86 29-60 | 27.44 23-04 || 30-40
Ash, ......... 5'18 || 4-25 | 6’29 || 4:41 8.8l 278 373 || 3:99 || 4:58
I00:02 || 99.99 || 99.98 || 99.96 ||100-00 || 99.77 |100'00 | 99.99 |100
(1.) Made in the parish of Carnwath, Lanarkshire, on a poor,
cold, wet, upland moor farm. Dairy 28 cows. (2.) From a rich
loam with gravel subsoil. (3.) This is a small cheese, little big-
ger than a brick. Generally eaten when a fortnight old. (4.)
From a loam with running Sandy-clay subsoil. (5.) From strong
clay soil, inclined to be very grassy. (6.) From a rich deep soil
in the marsh near Cheddar, Somersetshire.
The above cheese, if free from water, would contain respectively,
according to the results of Mr Jones, the following per-centages
of casein:— : 3
Skimmed-milk,............ tº a º e s s 80'17 per cent.
Double Glo'ster, ... ...... .... 59 - 13
North Wilts, (No. 1,) ......... 40-73
Dunlop (Wellwood) cheese, 42-03
Lanarkshire brick, ............ 44'20
Cheddar cheese, ...... • - - - - - - - 45'3]
The differences among the above numbers are sufficiently strik-
ing—especially the greatly larger proportion of the nutritive casein
contained in the skimmed-milk cheese in the dried state.
The proportions of casein in the four latter varieties agree very
well, however, with some results obtained by Schlossberger and
Kemp, who determined the proportion of nitrogen in several va-
rieties of cheese. The second column in the following table exhi-
bits the proportions of nitrogen found by them in the dry cheeses
—the third, the proportions of casein calculated from that of the
nitrogen. -
1004 COMPARATIVE PROFIT OF BUTTER AND CHEESE.
Nitrogen. Casein.
per cent, per cent.
Dunlop cheese, ..................... 6°03 37'99
Gouda Cheese,... ... ............... 7.11 44'79
Cheshire, ...... ......... . . . . . . . . . . . . . 6-75 42-53
Double Glo'ster,...... w8 e º e e º ºs e e º º ſº e º is 6'98 43.97
Very old mouldy do.,............... 5-27 33°10
The differences between the proportions of casein in this table
and those found by Mr Jones are only such as may exist among
cheeses of different ages and from different dairies.
§ 8. Profit of making butter and cheese compared with that of selling
the milk. *
For the following particulars in reference to this point I am in- x
debted to Mr Alexander of Ballochmyle. The produce of cheese
and butter is the average of his experience at his farm of Well-
wood, in Ayrshire.
There are three ways in which the milk is usually disposed of.
It is sold in the state of new milk, or it is made into full milk cheese,
and the whey given to pigs—or it is made into butter, and the
skimmed or butter-milk sold, or made into cheese, or given to pigs.
The profit of each of these three methods, at the Ayrshire prices, is
as follows approximately:- -
8. d.
a.—90 quarts of new milk, at 2d. a quart, are sold for 15 0
b.—90 quarts of new milk give 24 lbs. of full milk cheese, 9 ()
which, at 4d. per lb., are sold for ............... .. |
The whey is worth, at least ... .... ..... ... s. s e < * * * * * * * * > → 0 6
9 6
- S. d.
c.—90 quarts of milk, churned altogether, give 9 lbs. of | 6 9
butter, at 9d. ........ ................. • * * * * * s e i s & © º g º ºs *
90 quarts of butter-milk, at #d. per quart ... ......... 3 9
10 6
In the country, where the butter-milk cannot be sold, it is given
to the pigs, and does not yield so large a return.
8. d.
d.—90 quarts of new milk give 14 to 18 quarts of cream, 6 9
yielding 9 lbs. of butter at 9d., as before ...... e º e .
18 quarts of butter-milk, at #d. ... .................... 0 9.
70 quarts of skim-milk, at #d... ..... e s tº e º g g g º & * * * e - e & e- 2 11
10 5
When the skim-milk cannot be sold, it may be given to the pigs,
MILK SPIRIT AND MILK WINEGAR, 1005
or it may be made into skim-milk cheese. In the latter case the
profit is as follows:— -
s. d.
e.—Butter and butter-milk, as before ..................... 7 6
70 quarts of skim-milk give 16 lbs. of cheese, which, 4 0
at 3d per lb. ..........................................
I 1 6
Thus we have 90 quarts of milk—
8, d.
a—sold as new milk, worth ...... * . . . . . . . . . . 15 0
b—made into full-milk cheese............... 9 6
c—made into butter and butter-milk, where
the latter can be sold ............... 10 6
d—made into butter and skim-milk, where
the latter can be sold ............... 10 5
e—made into butter and skim-milk cheese l l 6
It is to be remarked, however, that when the new or skim-milk
is sold there is no expense of labour in churning or making cheese,
which adds greatly to the profit of dairy establishments near large
toWinS.
In the country, therefore, according to these calculations, the
most profitable way is to make butter and skim-milk cheese. The
farmer is thus in a great measure independent of an adjoining po-
pulation. The small quantity of butter-milk he thus obtains he
will easily be able to dispose of or otherwise employ to advantage.
According to Mr Ayton, it is still more profitable to feed calves
with the milk, but I find many people differ from him on this point.
At all events, a good and ready market is required for the veal.
§ 9. Of the fermented liquor from milk, and of milk vinegar.
Milk is capable of undergoing what is called the vinous fermen-
tation, and of yielding an intoxicating liquor. The Tartars pre-
pare from mare's milk a liquor of this kind, to which the name of
houmiss is given. When made from cow's milk it is called airen,
and is less esteemed because generally of a weaker quality. The
Arabians and Turks prepare a similar liquor, which the former
call leban, and the latter yaourt. In the Orkney Islands, and in
some parts of the north of Scotland and of Ireland, butter-milk
is sometimes kept till it undergoes the vinous fermentation, and
acquires intoxicating qualities.
It is the sugar contained in milk which, by the fermentation, is
I 006 SALINE CONSTITUENTS OF MILK.
changed into alcohol. As mare's milk, like that of the ass, con-
tains more sugar than that of the cow, it gives a stronger liquor,
and is therefore naturally preferred by the Tartars. By distilla-
tion ardent spirits are obtained from koumiss, and when carefully
made in close vessels, a pint of the liquor will yield half an ounce
of spirit. The koumiss is prepared in the following manner:—
To the new milk, diluted with a sixth of its bulk of water, a
quantity of rennet, or what is better, of sour koumiss, is added,
and the whole is covered up in a warm place for 24 hours It is
then stirred or churned together till the curd and whey are inti-
mately mixed, and is again left at rest for 24 hours. At the end
of this time it is put into a tall vessel, and agitated till it becomes
perfectly homogeneous. It has now an agreeable sourish taste,
and in a cool place may be preserved for several months in close
vessels. It is always shaken up before it is drunk. This liquor,
from the cheese and butter it contains, is a nourishing as well as
an exhilarating drink, and is not followed by the usual bad effects
of intoxicating liquors. It is even recommended as a wholesome
article of diet in cases of dyspepsia or of general debility.
Milk vinegar—If the koumiss be kept in a warm place the
spirit disappears and vinegar is formed. In some parts of Italy a
milk vinegar of pleasant quality is prepared by adding homey, Sugar,
spirit, and a little yeast to the boiled whey, and setting the mix-
ture aside to ferment in a warm place.*
§ 10. Of the composition of the saline constituents of milk and
cheese.
19. Ash of milk.--When milk is boiled down to dryness, and
the dry residue burned, a small quantity of ash remains behind.
The proportion which the weight of this ash bears to that of the
whole milk is variable—as the qualities of the milk itself are—so
that 1000 lbs. will leave sometimes only 2 lbs., at others as much
as 7 lbs. of ash. This ash consists of a mixture of common salt
and chloride of potassium (p. 323), with the phosphates of lime,
magnesia, and iron. The relative proportions of these several
substances yielded by 1000 lbs. of the milk of two different cows,
were as follows (Haidlenf):—
* Il latte e i swoč prodotti, pp. 415 and 450.
+ Ammal. der Chem, whd Phan., xlv., p. 273,
ASH OF CHEESE. º I 0.07
I. II.
Phosphate of lime, . ............ 2°31 lbs. 3:44 lbs.
Phosphate of magnesia, ......... 0.42 ... 0°64 ...
Phosphate of peroxide of iron, 0.07 ... 0.07 . .
Chloride of potassium, ...... ... 1'44 ... l'83 ...
Chloride of sodium,......... ..... 0-24 ... 0°34 ...
Free Soda, ......... . • * * * * * * * * * * * ()'42 ... 0°45 ...
4'90 6-77
It is probable that the phosphates and chlorides existed as such
in the milk as it came from the cow. The free soda is believed to
have been in combination with the casein, and to have kept it dis-
solved in the milk. You will recollect that the explanation I have
given of the curdling of milk is, that the acid produced in, or add-
ed to, the milk takes this soda from the casein, and renders it in-
soluble in water, and that in consequence it separates in the form
of curd (see p. 979). ... •
2° Ash of cheese.—The saline matter of cheese is only derived
in part from the milk. The phosphates of lime and magnesia at-
tach themselves to the curd in the making of cheese, while the
soluble salts remain for the most part in the whey. But the cheese
is cured with salt, and the quantity added varies with many cir-
cumstances. Hence the ash of cheese consists chiefly of the earthy
phosphates, mixed with common salt, and with a very small propor-
tion of chloride of potassium. In the following table furnished to
me by my pupil Mr Jones, the chloride of potassium is included with
the common salt. It represents the proportions of earthy phos-
phates and of common salt in six of the varieties of cheese of which
the analysis is given in a previous section (p. 1003).


Skim- |Double Dun- ||North | North || ewe-
milk. Glo's- lop. Wilts. | Wilts. milk.
(I.) ter. (2.) (3.) | (4.) (5.) (6.)
Earthy phosphates in a 100 of ash,... 54-06 || 53:64 53.38 || 6461 56'42 31:12
Earthy phosphates in a 100 of the Q. * e & g .”
cheese, ....... ....... • * * * * is e s tº is º. s e 2-80 || 2:28 || 2:03 2 41 || 2:25 | 1.74
Common salt in a 100 of the ash, ... ... 28.70 || 32°37 | 16.86 26-28 || 45-64
Common salt in a 100 of the cheese, * @ tº 1:23 l:33 || 0-63 1-05 || 3:0]
(1.) Made June 1845, analysed June 1846. (2.) Made June
1845, analysed July 1846. (3.) Made by Mr Alexander of Bal-
lochmyle, at Wellwood 1845, analysed 1846. (4.) Made July
1008 USE OF MILK IN THE ANIMAL ECONOMY.
1846, analysed September 1846. (5.) Made May 1846, analys-
ed September 1846. (6.) Made 1846, analysed February
1847.
The following table represents the per centage of water, ash,
phosphates, and common salt, found in four other varieties of
cheese. -
º

Skim- | Double North
milk. Glo'ster. Dunlop. Wilts.
Water, ............................ ... º s tº e º e e º ºs e º tº 55'81 42-37 41'55 36-59
Ash, ... . ........................ .............. 4'90 5'll 3:38 7-61
Earthy phosphates in 100 parts of the ash, 52-64 48°60 59°35 tº gº º
Earthy phosphates in 100 parts of º 2.58 || 2:48 2.01
cheese ....................................
Common salt in 100 parts of the ash,...... 42° 13 27.53
Common salt in 100 parts of the cheese,... 2:06 l'4l
These cheeses were all made in 1845, and examined in 1846.
The most practically useful result exhibited in the above tables
is, that every 100 lbs. of cheese contain, and therefore carry away
from the land about 24 lbs. of earthy phosphates. A ton of cheese,
therefore, takes away about 60 lbs.
§ 11. Purposes served by milk in the animal economy.
Milk is the food provided for the young animal, at a period
when it is unable to seek food for itself. It consists, as we have
seen, of
1°. The casein or curd.—This being almost identical in compo-
sition with the lean part or fibrin of the muscles serves to promote
the growth of the flesh of the animal.
2°. The fat or butter, which is mainly expended in supplying
fat to those parts of the body in which fat is usually deposited.
3°. The sugar, which is probably consumed in the lungs du-
ring respiration. -
4°. The saline matter, from which come the salts contained in
the blood, and the earthy part of the bones of young and growing
animals fed upon milk.
These several purposes served by milk will come under our con-
sideration in the following lecture.
4
LECTURE XXVI.
Of the feeding of animals, and the purposes served by their food. Substances of
which the parts of animal bodies consist. Whence do animals derive these sub-
stances—are they all present in the food? Use of the starch, gum, and sugar con-
tained in vegetable food. Living functions of a full-grown animal. Of the respiration
of animals. General origin and purposes served by the fat in carnivorous and
herbivorous animals. Of the digestive process in animals. Purposes served by
food and digestion. The food sustains the full-grown animal. Necessity of a mixed
food. It sustains and increases the fattening animal. Relative fattening powers of
different kinds of food. How circumstances affect this fattening property. Pur-
poses served by food in the pregnant—in the young and growing animals, such as
the calf—and in the milk cow. Effect of different kinds of food on the quality
of milk. Fattening of the cow as the milk lessens in quantity. Experimental,
economical, and theoretical value of different kinds of food for these several purposes.
Circumstances which affect these values. Effect of soil and manure. Effect of the
form in which the food is given. Use of sour, steamed, baked, ground, mixed, and
prepared food. Effect of the constitution of the animal, ventilation, light, warmth,
exercise, activity. Use of malt as food for cattle. Use of salt in feeding, Can a
substitute be suggested for oil cake 2 Comparative value of green food in the recent
and in the dried state. Effect of different modes of feeding on the manure and the
soil. Recapitulation.
HAVING in the preceding lectures considered the composition
of the direct products of the soil–grains, roots, and grasses—and
of the most important indirect products—milk, butter, and cheese
—the only part of our subject which now remains to be discussed
is the relative values of these several products in the feeding of
animals. -
Under this head it will be necessary to enquire how far these
values are affected by the age, the growth, the constitution and
race of the animal—by the purposes for which it is fed—and by
the circumstances under which it is placed while the food is admi-
nistered to it.
§ 1. Of the substances of which the parts of animals consist.
The bodies of animals consist of solid and fluid parts.
1°. The solid parts are chiefly made up of the muscles, the fat,
and the bones.
3 S
I ()10 COMPOSITION OF RECENT MUSCLE.
a. The muscles, in their natural state, as I have already had oc-
casion to mention (p. 777), consist in 100 parts of about
Dry matter, . . ............... ...... 23
Water, ......... . .................. 77
100
So that, to add 100 lbs. to the weight of an animal in the form of
muscle, only 23 lbs. of solid matter require to be incorporated
with its system.
When the muscular or lean part of beef, mutton, &c. is washed
in a current of water for a length of time—the blood, to which the
red colour is owing, and all the soluble substances gradually dis-
appear, and the muscle becomes perfectly white. In this state,
with the exception of some fatty and other matters which still re-
main intermixed with it—the white mass forms what is known to
chemists by the name offibrin. This name is given to it because it
forms the fibres which run along the muscles and constitute the
greater portion of their substance.
The following table exhibits the relative proportions of muscu-
lar fibre and other substances contained in the flesh of several dif-
ferent animals in its natural state”:— -

Ox. Calf. Pig. Roe, Pigeon. Chicken. Carp. Trout.
lo 29
Muscular fibre,
.*.*.*.*}| 17.5 150-162 |168 180 17-0 | 16.5 | 120 111
stance,
Soluble albumen
and colouring
matter of blood
(hematosłm,)
Alcoholic extract,
containing Sa-
line matter,
Watery extract,
containing Sa-
line matter. ſ
Phosphate of lime,
with a little al-
bumen,f
Water and loss, 77°5 || 79-7-78-2 || 78.3 || 76.9 || 76-0 || 77-3 || 80'l 80.5
2-2 || 3-2- 26 || 2-4 2-3 4°5 3.0 5-2 || 4-4
1-5 || 1:1- 14 | 1.7 1 * 0 || 1:4 1-0 || 1:6
2-4
1-3 || 1 °0- 1.6 || 0 8 1.5 || || 2 1-7 || 0:2
trace | 0' l-trace | trace 0°4 | ... 0' 6 & gº º 2-2
100 100 100 ||100 || 00 100 || 00 100 || 00
* Schlossberger, Annalen der Pharmacie, December 1842, p. 344.
f This phosphate of lime is over and above that which exists naturally in, and is
inseparable from, the muscular fibre itself and from the albumen.
COMPOSITION OF THE FAT. 10] I
The proportions in the above table are not to be regarded as
constant; they seem, however, to shew that the muscular part of
fishes contains a less proportion of insoluble fibrin than that of
land animals generally does. The purified muscle of both fishes
and land animals consists, for the most part, of this fibrin, the com-
position of which was explained in a previous lecture (p. 216).”
When dried beef is burned it leaves about 44 per cent of in-
combustible ash—or 100 lbs. of the muscle of a living animal in
its natural state contain about one pound of saline or inorganic
matter. --
Of this inorganic matter, it is of importance to know that about
two-thirds consist of phosphate of lime. Thus to add 100 lbs. to
the muscular part of a full grown animal, there must be incorpo-
rated with its substance about—
Water, ................ ............. 77 lbs.
Fibrin, with a little fat,............ 22 —
Phosphate of lime, .......... .... #—
Other Saline matters,............... $—
100
b. The fat of animals consists, like the fat of butter, of a solid
and fluid portion. The fluid fat is in great part Squeezed out
when the whole is submitted to powerful pressure.
The fluid portion of the fat, called by chemists elaine, so far as
it has yet been examined, appears to be identical in all animals. It
is also the same thing exactly as the fluid part of olive oil, of the
oil of almonds, and many other fruits, and as the fluid part of
butter. It exists in larger quantity in the fat of the pig than in
that of the sheep, and hence pork fat is softer than beef or mutton
suet. From lard it is now expressed on a great scale in the Unit-
* Since the composition of fibrin, given in p. 216, was printed, Mulder has publish-
ed some corrected analyses, which give to fibrin the following composition :-
Carbon, ..................... . . 52-66
Hydrogen, ..................... 6'93
Nitrogen,... .................... 15:51
Oxygen, ............. • * * * * * * * * * * 23°53
Sulphur, ........................ 1*04
Phosphorus, ... ...... ..... ... ... 0°33
100
—See Liebig's Question to Mulder, &c. p. 104.
| 0 || 2 OF WHAT BONES CONSIST.
ed States of America, for burning in lamps and for other uses.
The manufacturers of stearine candles express it from beef and
mutton fat, but chiefly for the purpose of obtaining the solid part
in a harder state, that it may make a more beautiful and less fu-
sible candle. The fluid oil of animal fats, however, is known to
differ from the liquid part of linseed and other similar oils which
dry and form a kind of varnish when exposed to the air, and are
thence called drying oils.
The solid part of the fat of animals is known to vary to a cer-
tain extent among different races. Thus the solid fat of man is
the same as that of the goose, and as that which exists in olive
oil and in butter. To this the name of margarine is given. But
the solid fat of the cow, the sheep, the horse, and the pig differs
from that of man, and is known by the name of stearine.
The solid and fluid parts are mixed together in different propor-
tions in the fat, not only of different animals, but of the same ani-
mals at different periods, and in different parts of its body. Hence
the greater hardness observed in the suet than in other portions of
the fat of beef and mutton, and hence also the different quality and
appearance of the fat of an ox, according to the kind of food up-
on which it has been fed or fattened.
c. The bones, like the muscles, consist of a combustible and an
incombustible portion, but in the bones the inorganic or incom-
bustible part is by much the greater. To the organic matter of
bones the name of gelatine or glue is given, and it can be partly
extracted from them by boiling. The proportion of gelatine which
exists in bones varies with the kind of animal—with the part of the
body from which the bone is taken—and very often with the age
and state of health of the animal, and with the way in which it has
been accustomed to be fed. It is greater in spongy bones, in the
bones of young animals, and probably also in the bones of such as
are in high condition. In perfectly dry bone it rarely exceeds
from 35 to 40 per cent. of the whole weight.
The incombustible portion consists for the most part of phos-
phate and carbonate of lime. The relative proportions of these
two earthy compounds also vary with the kind of animal, with its
age, its condition, its food, and its state of health. To form 100
lbs. of bone, the animal will usually require to incorporate with its
own substance about
THE INORGANIC PART OF HAIR, HORN, AND WOOL. 1013
35 pounds of gelatine,
55 pounds of phosphate of lime,
4 pounds of carbonate of lime,
3 pounds of phosphate of magnesia,
3 pounds of soda, potash, and common Salt,
100 --
d. Hair, horn, and wool are distinguished from the muscular
parts of the animal body by the large proportion—about five per
cent.—of sulphur which they contain. They consist of a substance
which in other respects closely resembles gluten and gelatine in
its chemical composition (page 780). When burned, they leave
from one to two per cent, of ash, which in the case of a variety of
human hair, which left 1.1 per cent. of ash, was found by Van
Laer to consist of
Per cent.
Soluble chlorides and Sulphates, ............................................... 0°51
Oxide of iron, ............................ ..... ............ ... • e e s a s a e º e s - e º e º e º e s (). 39
Phosphate and Sulphate of lime, phosphate of magnesia and silica,...... 0-20
I 1
The inorganic matter contained in hair is therefore, generally
speaking, the same in kind as that which exists in the muscular fi-
bre and in the bone. It contains the same phosphates of lime and
magnesia—the same sulphates and the same chlorides, among
which latter common salt is the most abundant. The absolute
quantity of ash or inorganic matter varies, as well as the relative
proportions in which the several substances are mixed together in
the different solid parts of the body, but the substances themselves
of which the inorganic matter is composed are nearly the same,
whether they be obtained from the bones, from the muscle, or from
the hair. - -
2°. Of the fluid parts of the body, the blood is the most import-
ant, and by far the most abundant. The body of a full grown man,
of moderate dimensions, contains about 12lbs. of blood,” that of a
full grown ox, six times as heavy, cannot contain less than 70 or
80 lbs. Blood consists of about
Per cent.
Water, ............ ... . . ... ...80
Organic matter, ............... 19
Saline matter, .................. l
100
* Lehmann, Physiologische Chemic, I., pp. 113 and 338.
1014 EARTHY AND SALINE MATTER IN BLOOD.
The organic matter consists chiefly of fibrin, which, when the
blood coagulates, forms the greater part of the clot—and of albu-
men, which remains dissolved in the serum or fluid part of clotted
blood, but which, like the white of egg, runs together into insolu-
ble clots when the serum is heated. -
The saline matter remains dissolved in the serum after the al-
bumen has been separated by heating, and consists chiefly of phos-
phates, sulphates, and chlorides—nearly the same compounds as
exist in the soluble part of the ash left by the solid parts of the
body.
Besides this soluble saline matter which remains in the serum,
a portion of phosphate of lime and a small quantity of phosphate of
magnesia exist also in the fibrin and in the albumen of the blood.
Thus in the dry state these substances contain respectively of the
mixed phosphates -
Albumen of ox blood,...18 per cent. Berzeli
Fibrin of human blood, 0.7 per ...} (Berzelius.)
Thus the same saline and earthy compounds, which form so large
a portion of the bones, are distributed every where in sensible propor-
tions throughout all the more important solids and fluids of the body.
§ 2. Whence does the body obtain these substances 2 Are they con-
tained in the food 3
Whence does the body derive all the substances of which its se-
veral parts consist?
The answer to this question appears at first sight to be easy. They
must be obtained from the food. But when the enquiry is further
considered, a reply to it is not so readily given.
It is true, indeed, that the organic part of the food contains car-
bon, hydrogen, oxygen, and nitrogen—the elements of which the
organic parts of the body are composed. The in-organic matter
also which exists in the food contains the lime, the magnesia, the
potash, the soda, the sulphur, the phosphorus, and the iron, which
exist in the inorganic parts of the animal body—so that the
question seems already resolved. The body obtains from the food
all the elements of which it consists, and if these be not present
in the food, the body of the animal cannot be properly built up and
Supported.
4.
Is THE FIBRIN FORMED IN THE BODY P | 015
but to the chemist and physiologist the more important part of
the question still remains. In what state do these elements enter
into the body ? Are the substances of which the food consists de-
composed after they are taken into the stomachº Are their parts
first torn asunder, and then reunited in a different way, so as to form
the chemical compounds of which the muscles, bones, and blood con-
sist? Are the vital powers bound to labour, as it were, for the existence
and support of the body ? Do they compound or build up out of their
ultimate elements the various substances of which the body is compo-
sed—or do they obtain these substances ready prepared from the vege-
table food on which animals in general are fed 2 The answer which
recent chemical researches give to this second question forms one of
the most beautiful contributions which have been made to animal
physiology in our time.
1°. We have seen that the flour of wheat and of our other cul-
tivated grains consists in part of gluten, of albumen, or of casein.
These substances all contain nitrogen, and are nearly identical in
composition with each other, and with the fibrin of which the muscles
of animals chiefly consist.” The substance of the muscles exists
ready formed, therefore, in the food which the animal eats. The
labour of the stomach is in consequence restricted to that of selecting
these substances from the food, of slightly altering and of subsequent-
ly dispatching them to the several parts of the body, where they are
required. The plant compounds and prepares the materials of the
muscles—the stomach only picks out the bricks, as it were, from
the other building materials, and sends them forward to be placed
where they happen to be wanted.
2°. Again, we have seen that in all our crops, so far as they
have been examined, there exists a sensible proportion of fatty or
oily matter more or less analogous to the several kinds of fat which
exist in the bodies of animals. In regard to this portion, there-
fore, of the body, the vegetable performs also the larger part of
* The chemical reader, who is aware of the exact state of our knowledge upon this
subject, will perceive that I speak here of the identity of these substances only in so
far as the proportions of carbon, hydrogen, oxygen, and nitrogen are concerned. It is
unnecessary to allude in this place to the different proportions of sulphur and phos-
phorus they are known to contain—as the more popular mature of this work will not
permit me to discuss the refined, though singularly beautiful, physiological questions
with which these differences are connected.
TOI 6 WHENCE THE FAT AND BONES OF ANIMALS.
the labour. It builds up fatty substances out of their elements—
carbon, hydrogen, and oxygen. These substances the stomach ex-
tracts from the food, and the body appropriates them—after they
have been more or less slightly changed, in order to adapt them
to their several purposes. There may possibly be other sources
of fat, as we shall hereafter see, but the simplest, the most natu-
ral—and probably, where a sufficient supply exists, the only one
had recourse to by the healthy animal—is the fat which is found,
ready formed, in the vegetable food it eats.
3°. Further, the bones, the muscles, and the blood, contain phos-
phate of lime, phosphate of magnesia, common salt, and other
saline compounds. These same compounds exist, ready formed,
in the vegetable food, associated generally with the gluten, the
albumen, or the casein, it contains. The materials of the harder
parts of the body, therefore—(the phosphates) as well as the in-
organic saline substances which are found in the blood, and in the
other fluids of the body—are all formed in or by the plant, or are
by it extracted from the soil and incorporated with the food on
which the animal is to live.
Not only, therefore, do the mere elements of which the parts of
the bodies of animals are formed, exist in the vegetable food—but
they occur in it, put together and combined, nearly in the state in
which they are wanted in order to form the several solids and fluids
of the body. The plant, in short, is the compounder of the raw
materials of living bodies, The animal uses up these raw mate-
rials—cutting them into shape when necessary, and fitting them
to the several places into which they are intended to be built.
This is a very simple, and yet a very beautiful view of one of
the many forms of chemical connection which exist between the
processes and purposes of animal and vegetable life.—Nature
seems to divide the burden of building up living bodies between
the vegetable and the animal kingdoms—the lower appearing to
exist and to labour, only for the good of the higher race of beings.
§ 3. Of the respiration of animals, and of the purposes served by
the starch, gum, and sugar, contained in vegetable food.
But, besides the gluten of plants and seeds, which supplies the
materials from which the muscular parts of animals are formed,
3
THE FUNCTION OF RESPIRATION. 101.7
the oil which is converted into the fat of animals, and the saline
and earthy matters of plants which supply the salts of the blood
and the earth of the bones—vegetable food in general contains a
large proportion of starch, sugar, gum, and other substances which
consist of carbon and the elements of water only (p. 185). What
purpose is served by this part of the food 2 Is it merely taken in-
to the stomach and again rejected, or is it decomposed and made
to serve some vital purpose in the economy of the living animal?
From the fact that so large a part of all vegetable food consists of
these substances, we might infer that they were destined to serve
some important purpose in the animal economy. To the herbivo-
rous animal they are, in fact, almost necessary for the support of
a healthy life.
In order to understand this fact it will be necessary briefly to
advert to the respiration of animals—the chemical changes pro-
duced by it, and the purposes it is supposed to serve in the animal
economy.
1°. Of the function of respiration.—All animals possessed of
lungs alternately inhale and exhale the atmospheric air. They
breathe, that is, or respire. The air they draw into their lungs,
supposing it to be dry, consists by volume very nearly of
Nitrogen, ........ ..................... 79°16
Oxygen, .............................. 20.80
Carbonic acid, ........................ 0'04
100
—the proportion of carbonic acid being very small. But as it is
breathed out again it consists of about
Nitrogen, ......... . .............. ... 79°16
Oxygen, ... ......... . ............... 16'84 to 12
Carbonic acid, ........................ 4'00 to 8
| 00
—the proportion of oxygen being considerably less, that of car-
bonic acid very much greater, than before. On an average the
matural proportion of carbonic acid in the air is found to be in-
creased 100 times after it is expelled by breathing from the lungs.
Now carbonic acid consists, as we have previously seen, of car-
bon and oxygen. In breathing, therefore, the animal throws off
10 18 HOW THE RESPIRATION IS FED.
into the air a quantity of carbon—in the form of carbonic acid—
which varies at different times, in different species of animals, and
in different individuals of the same species. By a healthy man the
quantity of carbon thus thrown off varies from 5 to 13 ounces, and
by a cow or a horse from 3 to 5 pounds, in 24 hours. All this
carbon must be derived from the food. The animal eats, there-
fore, not merely to support or to add weight to its body, but also
to supply the carbon which is wasted by respiration.
2°. How the respiration is fed—What part of the food supplies
the waste caused by respiration ? How is the respiration fed P
In animals which live upon flesh—carnivorous animals—it is
the fat of their food from which the carbon given off by their lungs
is derived. When the fat fails in quantity the lean or muscular
part of the flesh they eat is decomposed for the purpose of supply-
ing carbon to their lungs.
In an animal to which no food is given for a time—the lungs
are fed, so to speak, from fat also. But in this case it is the living
fat of the animal's own body. When digestion is fully performed
and hunger is keenly experienced—the body begins to feed upon
itself—the lungs still play, respiration continues for many days
after food has ceased to be administered, but the carbon given off
is derived from the substance of the body itself. The fat first dis-
appears—escapes with the breath—and afterwards the muscular
part is attacked. Hence the emaciation which follows a prolong-
ed abstinence from food.
In animals which live upon vegetable food again—herbivorous
animals—it is the starch, gum, and Sugar, of the food which sup-
ply the carbon for respiration. It is only when the food does not
contain a sufficient supply of these compounds that the oil first,
and then the gluten, are decomposed, and made to yield their car-
bon to the lungs. -
In man, who lives on both kinds of food, and in the domestic
dog, and the pig, which also eat indifferently both animal and ve-
getable food, the carbon of respiration may be derived in part from
the fat, and in part from the starch and sugar which they eat—ac-
cording as they are chiefly supported by the one or by the other
kind of food. . -
It may be asked how we know that such are the parts of the
FAT SUPPORTS RESPIRATION IN SOME, 1019
food, to which the duty of supplying the demands of the lungs is
especially committed. There are several considerations which lend
force to this opinion. Of these I will draw your attention to one
Or two. & - &
a. Why is the fat rather than the lean part of the food of car-
nivorous animals devoted to the service of the lungs, and why do
starving animals lose their fat first? Because the chemical decom-
position by which carbon can be derived from the fatis simpler and
more easily effected than that by which it can be obtained from
muscular fibre. By combination with oxygen, fat can be convert-
ed into carbonic acid and water only, of which the former will pass
off by the lungs and the latter in the urine. The muscular fibre,
on the other hand, contains much nitrogen (p. 862, note), and, if
deprived of its carbon for the uses of respiration, must undergo
very complicated decompositions, and form a series of compounds,
the use of which, in the animal economy, it is not easy to perceive.
Besides, in producing the carbonic acid of the lungs from the
fat of the animal food or of the living body—there is less waste of
material. Fat consists wholly of the three elements, carbon, hy-
drogen, and oxygen. These all disappear entirely in the form of
carbonic acid and water—both of which are used up. Muscle, on
the other hand, besides nitrogen, contains a constant proportion of
sulphur and phosphorus. If the muscle, then, be decomposed for
the purpose of Supplying carbon to the lungs, not only the large
quantity of nitrogen, but the sulphur and phosphorus also, would
go to waste, and would pass off in the urine. In nature, however,
such waste is rarely seen to take place; and, therefore, as a gene-
ral rule, the respiration will be supported by the muscular fibre—
only when other kinds of food are deficient.
b. But in the stomachs of herbivorous animals, why are the starch
and sugar especially appropriated to the use of the lungs? The
food of animals which live upon vegetable substances contains fat
as well as starch—why then is the starch in this case dissipated by
the process of respiration, while the fat is applied as it is supposed
to another use P The answer to this question is both beautiful and
satisfactory.
Starch, gum, and sugar, consist of carbon and water only, and
we can conceive them in their passage through the body to be ac-
1020 STARCH AND SUGAR IN OTHER RACES.
tually separated into these two substances—in which case the car-
bon has only to combine with oxygen and form carbonic acid, to
be ready to pass off by the lungs. Here, therefore, only one che-
mical combination is required—the union of carbon with oxygen.
It is the simplest way in which we can conceive carbon to be sup-
plied for the use, or for the purposes of the lungs.”
But it is otherwise with fat. Though nearly all kinds of fat
consist entirely of carbon, hydrogen, and oxygen—yet they cannot
be supposed to consist only of carbon and water. They contain
much more hydrogen than is necessary to form water with the oxy-
gen which is present in them. If, then, the carbon of these fats
be separated, this excess of hydrogen will also be set free, and if
the former be made to combine with oxygen to form carbonic acid,
the latter must also combine with oxygen to form water. Thus
two chemical changes must go on simultaneously, for which more
oxygen will be required, and which involve more labour in the sys-
tem than when the carbon alone is to be combined with oxygen. It is
natural, therefore, that where bothstarch and oilarepresent together,
the former should be first converted to the uses of the lungs, the
latter only when the supply of starch or sugar has been exhausted.
There appears, therefore, to be a beautiful adaptation to the
wants and convenience of animals in the large proportion of starch,
gum, and sugar, which the more abundant varieties of vegetable
food contain. In obtaining carbon from these, the least possible
labour, so to speak, is imposed upon the digestive organs of the
herbivorous races. The starch and sugar abound because much
carbon is required, while fatty matter or oil is present in smaller
quantity, because comparatively little of this is necessary to the per-
formance of the usual healthy functions of the animal body. And
it is another adaptation of the living body to the circumstances in
which it may be placed, that when starch or sugar cannot be ob-
tained, the oil of the food is consumed for the supply of carbon to
the lungs—and failing this, the gluten and albumen also of the ve-
getable food or the muscular fibre of the animal food or even of
the living animal itself.
* The chemical reader will understand that I am here only giving a popular view
of the final result of the several changes through which the carbon no doubt passes
before it escapes in the form of carbonic acid,
PURPOSES SERVED BY RESPIRATION. 1021
3°. Purposes served by respiration.—But for what purpose es-
sential to life do animals respire? If the starch and sugar be so
necessary to feed the respiration—the breathing itself must be of
vital importance to the living animal.
Some doubts still exist upon this point. It is generally believed,
however, that carbon is consumed or given off from the lungs for
the purpose of sustaining the heat of the living body. When starch,
or sugar, or gum are burned in the open air, they are changed
into carbonic acid and water, and at the same time produce much
heat. It is supposed that in the body the same change—the con-
version of starch and Sugar into carbonic acid and water—taking
place, heat must in like manner be produced. A slow combus-
tion, in short, is supposed to be going on in the interior of the ani-
mal—the heat of the body being greater, in proportion to the
quantity of carbonic acid given off from the lungs. In favour of
this view many strong reasons have been advanced, but there are
also objections against it of considerable weight, which cannot as
yet be satisfactorily removed.
Were we to adopt this opinion in regard to the main purpose
served by respiration as the true one, it would afford a very dis-
tinct reason for the large amount of starch existing in all our cul-
tivated crops. Respiration, according to this view, is necessary to
supply heat to the animal, and this respiration is most simply and
easily fed by the starch contained in the vegetable food. Here the
life and labours of the plant again minister to the life and labours of
the animal.
§ 4. Of the origin and the purposes served by the fat of animals.
1°. The immediate origin or source of the fat of animals de-
pends upon the kind of food with which the animal is fed. Car-
mivorous animals obtain or extract it ready formed from the flesh
they eat—herbivorous animals from the vegetable food on which
they live.
It has only been lately shown that the corn, hay, roots, and her-
bage, on which cattle are fed, contain a sufficient quantity of oily
matter ready formed to supply all the fat which accumulates in
their bodies—or which, by the milk cow, is yielded in the form
of butter. Before the different kinds of food had been analysed,
I ()22 ORIGIN OF THE FAT OF ANIMALS.
with the view of determining the quantity of oil and fat they seve-
rally contain, it was supposed that the fat of animals was derived
almost solely from the starch and sugar or gum, of which so large
a proportion of vegetable food consists. This opinion, how-
ever, has given way before the advance of analytical research. Ani-
mals fatten quickest upon Indian corn, or oats, or oil cake, or oil
mixed with chopped straw, or upon oily seeds and nuts—or, as in
the case of poultry, on a mixture of meal and suet—because these
kinds of food contain a large proportion of fatty matter ready form-
ed which the animal can easily extract, and after a slight chemical
change can convert into a portion of its own substance.
The conversion of starch or sugar into fat in the animal body
implies a chemical change of a less simple nature—one which seems
to impose upon the vital principle a greater amount of labour than is
implied in the simple appropriation of the fat which exists ready
formed in the food. If, then, there be in the food as much fat as is
necessary to supply all that the animal appropriates to itself, and
if it is observed to lay on or appropriate more when the food is
richer in fatty oils, we are led to believe that the natural purpose
served by the oil in the vegetable food is to supply the fat of the
animal body. In other words, the vegetable ministers to the ani-
mal, and lessens its labour by preparing beforehand the mate-
rials out of which the animal is to build up the fatty parts of its
body. -
But though this is the general source of the fat of animals, circum-
stances may occur in which the only vegetable food which the ani-
mal can procure, does not contain a sufficient proportion of fat to
supply all the wants of its body—or to enable it to perform the se-
veral natural functions it is destined to fulfil. Thus wax is a kind
of fat, and it has been shown (Milne-Edwards) that, when fed up-
on pure sugar, the bee is capable of forming wax from its food.
When fed upon such sugar it not only lays up a store of honey,
but after a time it continues to build its cells of wax. Now the
starch of the food is readily changed into Sugar. It may be so
changed in the stomach of man and of other animals. That power
which the bee possesses they also may in cases of emergency be able
to exercise. Where a sufficient supply of oil for the necessary
uses of the animal is not contained in the food it eats, it may form
FORMATION OF FAT FROM STARCH. 1023
an additional portion from the starch or sugar in which its food
abounds.
According to the present state of our knowledge, therefore, the
most probable opinion in regard to the origin of the fat of animals
seems to be expressed in these two propositions—
a. That the fat of animals is contained ready formed, and is
usually derived from the vegetable or other food on which they
live—and that when the food abounds largely in fat, the animal
lays it more quickly and abundantly upon its own body.
b. That when the food does not contain a sufficient proportion of
fat to enable the animal comfortably to perform the various func-
tions of its body, it has the power to form an additional quantity
from the starch or sugar it eats—but that it will not so readily
fatten or lay on large additions of fat upon its body when fed
upon farinaceous, saccharine, or other food in which oil is not na-
turally contained.”
* For the sake of the chemical reader I may be permitted here to show by what
kind of chemical changes—1°, the fat of animals in general may be derived from the
starch or sugar of their food ; and 2°, how the peculiar kinds of fat contained in the
body of any given animal may be formed from the peculiar kinds of fat contained in
its food.
1°. How fat may be formed from Starch or sugar.—These two substances, as we
have already seen, may be represented by carbon and water only—
Carbon. Water.
Starch, ......... consisting of 12 + 10, represented by C, a Hio Oro
Cane Sugar, consisting of 12 + 11, represented by C1, H, O, ,
Fat, again, margarine for example, the solid fat of the human body, is represented
by Can H3 g Og. Compare this with 4 of starch, and we have
*
4 of starch,............... = Cas Hao Oao
1 of margarine, ......... = Caº Hà e Os
Difference, ... ..... = C, 1 H4 Oa a
This difference is equal to, or may be represented by,
11 of carbonic acid + 4 of water + 9 of oxygen
ll CO2 + 4 HO + 9 O
So that by the separation of carbonic acid, which may be given off from the lungs
—of water which may or may not remain in the system—and of a portion of oxygen
which may be used up in various ways in the blood—the starch or sugar of the food
may be converted into fat.
That in some such way these substances may be changed into the fat of animals
was first insisted upon and explained by Liebig ; and it is probable, as I have said in
the text, that in cases of emergency fat is really formed in the animal body from such
kinds of food. But when Liebig put forth his views on this subject, it was not known
that vegetable substances naturally contained so large a proportion of fat as has since
been found in them. The necessity for the constant production or formation of fat
in the body itself, therefore, is not now so apparent, and the soundest opinion, accord-
1024 CHANGES OF OX FAT INTO HUMAN FAT.
2°. The purposes served by the fat.—In all healthy animals
which take a sufficient quantity of exercise to maintain them in a
ing to our present knowledge, seems to be that, while the vegetable food usually sup-
plies all the fat ready formed which the animal requires, yet that a conversion of a
certain part of the starch, gum, Sugar, and even of the cellular fibre of the food into
fat, may take place, when all the wants of the body are not supplied by the fat which
the food naturally contains. Of course this opinion applies only to animals in perfect
health. In certain diseased states of the body a larger and more constant production
of fat from the food may take place, as appears to be the case in animals which no
diminution of food seems to prevent from laying on fat.
2°. How the peculiar kinds offat in the body may be derived from the peculian kinds
of fat in the food.
a. We have already seen that the solid fat of butter, of olive oil, and of the goose,
is identical with the solid fat of the human body. When eaten by man, therefore,
these several kinds of fat may be at once conveyed, without change, from the stomach
to the several parts of the body where they are required. From this circumstance
these kinds of fat seem remarkably fitted for the food of man.
b. The solid fat of the ox and the sheep is called stearine. Upon this man lives
much and converts it into the solid fat (margarine) of his own body. This may take
place after the following manner:—
2 of margarine ............... = C, 4 Hz 2 Oro
1 of stearine .................. = C, He o O.
Difference,............ = Cs Ha Os
If we double this difference, we have Ce He Os which is the formula for lactic acid.
Recent researches, however, have failed in detecting this acid in the blood. If it be
formed at all, therefore, it must exist only in a transition state, and must be speedily
converted into other compounds. The final result may possibly be the evolution of
the 3 of carbon (Ca) by the lungs in the form of carbonic acid.
c. That the body or its parts possess the power of easily transforming these different
kinds of fat one into the other, we know, also, from other facts. Thus the calf lives
upon milk, and from the two kinds of fat contained in the cream of the milk, it forms
the solid and liquid fats of its own body. The stearine of the animal in this case
may be formed from the margarine of the butter, being exactly the converse of the
previous case, while the butter oil or elaine is already the same as the liquid fat of the
tallow.
d. The cow and the calf together, however, illustrate very clearly the existence of
this transforming power of the animal body. We are unacquainted, as yet, with the
composition of the several kinds of fat which occur in our ordinary vegetable food—
but we know that out of these the cow can form the two kinds of fat—the stearine
and elaine—which exist in its own tallow, and at the same time the two kinds of fat
—margarine and butter-oil—which are found in its milk. The calf, again, can change
these two latter fats into those which its own body, as well as that of its mother, re-
quires. And, lastly, man by eating the fat of the calf can re-convert it into marga-
rine and those other fatty substances which are found in the various parts of his body.
Substances which can thus so frequently and so readily be changed, the one into the
other, must be very closely connected, and the mode in which their mutual transfor-
mations are effected will, no doubt, prove to be simple when these transformations are
rightly understood.
THE BODY NATURALLY WASTES. 1025
healthy condition, the principal purposes served by the fat are
simple and the same. It lubricates the joints—covers and protects
the internal viscera—keeps the muscles separate, and enables them
to play freely among each other—makes the hair and skin soft and
flexible, and, by filling up hollows, contributes to the roundness
and plumpness of the parts, and defends the extremities of the
bones from external injury. When exercise is taken, a portion of
the fat of the body appears to be more or less changed and re-
moved, and is afterwards found in the perspiration, or in the dung.
It is to make up for this natural waste that all animals, even when
the fat of their body undergoes no increase, require a certain sup-
ply to be daily given to them in their food. -
The accumulation of fat in animals seems to be an effort of na-
ture to lay in a store of food in time of plenty, which may be made
available in the performance of the usual functions of the animal
when a time of scarcity comes. If the food contain too little oil
to lubricate the joints and to supply the natural waste of this kind
of matter, then the store of fat which has been accumulated in time
of plenty is drawn upon, a portion of it is worked up, so to speak, and
the fat of the body diminishes in quantity. We have seen also that
the respiration of carnivorous animals is supported at the expense
of the fat which they eat—and that the leanness which attends upon
starvation is owing to the fat of the living body being consumed in
supplying the carbon given off from the lungs. Another purpose,
therefore, for which animals seem to be invested with the power of
laying on fat, is, that a store of food for the purposes of respiration
may be carried about in the body itself, to meet any unusual de-
mand which the food may not be able wholly to supply.
§ 5. Of the natural waste of the parts of the body in a full-
grown animal.
We have seen that, if the food of the animal be unable to supply
The chemical reader will understand that it is for the sake of simplicity only that
I have in this note compared together the entire fats stearine, margarine, &c., instead
of the fatty acids only which they are known to contain. -
The reader will consult with much advantage and satisfaction upon this subject a
work by Professor Mulder of Utrecht, (The Chemistry of Animal and Vegetable Phy-
siology,) of which a translation from the Dutch, by my assistant Mr Fromberg, is now
in progress of publication by the Messrs Blackwood.
3 T.
I 0.26 FOOD NECESSARY TO MAKE UP FOR THIS WASTE.
the carbon given off from the lungs, and the fat which the move-
ments of the limbs require, the parts of the body themselves are
laid under contribution in order to supply these substances. Thus
when the food is stinted, the body necessarily undergoes a waste
from this cause.
But this is not a constant waste. It is prevented by the use of
a larger quantity of food. The parts of the body, however, do un-
dergo a constant and natural waste, to make up for which is one
of the main purposes served by the food.
It has been ascertained by physiologists, that all the parts of the
body undergo a slow and insensible process of renewal. The hair
and the nails we can see to be constantly renewed. They grow,
or are thrust outwards. But the muscles and even the bones are
by little and little removed inwardly and rejected in the excretions
—the place of that which is removed being supplied by new por-
tions of matter derived from the food.
This removal, though unfelt by us, goes on so rapidly, that in
a space of time, which varies from one to five years, the whole body
of the animal is renewed. There does not remain, it is said, in any
of our bodies, a single particle of the same matter which formed
their substance three or five years ago. It is just as if we were
to take a single old brick every day out of the corner of a house,
and put in a new one—the form and dimensions of the house
would remain unaltered, and yet in the course of a few years its
walls would be entirely renewed.
In full-grown animals, some parts of the body are renewed more
rapidly than others—the muscles, for example, more frequently
and rapidly than the bones and the brain. In young animals,
again, the whole body is oftener renewed than in such as are ad-
vanced in years, but all the parts of all animals are believed to be
more or less quickly removed and replaced.
The new materials which are conveyed to the different parts of
the body are derived directly from the food. The fibrin of the
muscles is replaced from the gluten, albumen, &c. which the food
contains—the fat from its oil—and the earthy matter of the bones
and the salts of the blood, from the phosphates and saline sub-
stances which are naturally present in it. On the other hand,
those parts which are extracted from the muscles and bones, and
- 4
ALBUMEN WIHIOH THE DAILY FOOD MUST CONTAIN, 1027
carried off in the excretions, are decomposed during their removal.
New chemical compounds are produced from them which are found
in the urine and dung of the animal, and which give to these ex-
cretions their richness and value in the manuring of the soil.
§ 6. Of the kind and quantity of food necessary to make up for
the natural waste in the body of a full-grown animal.
The substances which constantly disappear from the body in
consequence of the natural waste above described, are of three
kinds—the fibrin and other analogous organic compounds, which
form the muscles and the cartilage of the bones—the earthy phos-
phates (of lime and magnesia) which form so large a proportion of
the bones, and exist in small quantity in the muscles also—and the
soluble saline substances which abound in the blood and in the other
fluids of the living animal. In the solid and liquid excretions, a
large quantity of each of these three classes of compounds is car-
ried out of the body. How much of each must be contained in
the daily food of a full-grown animal in order that it may be kept
in its actual condition"?
1°. Quantity of fibrin or other analogous compounds (albumen or
casein) which the daily food must contain.-The most accurate ex-
periments that have yet been made upon this subject (Lecanu)
appear to show that a full-grown man rejects in his urine alone
about half an ounce of nitrogen (230 grs.) every 24 hours. This
quantity of nitrogen is contained in about three ounces of dry mus-
cular fibre, which must, therefore, every day be decomposed or
removed in order to yield it. -
But if the body is to be kept in condition, this quantity of fibrin
must be daily restored again by the food. Now, to supply three
ounces of dry fibrin, there must be eaten about—
30 ounces of wheaten flour; or
45 ... of wheaten bread; or
14 ... of fresh beef or mutton; or
12 ... of pease or bean meal; or
7 ... of cheese;*
Or, if we live wholly upon potatoes or milk, we must eat no less
* Supposing the wheaten flour to contain 10 per cent. of gluten, and the cheese
42 per cent. of its weight of dry curd. -
| 028 THE MUSCULAR, FIBRE MUST BE REPLACED.
than seven or eight pounds of the former daily, or drink three or
four imperial pints of the latter—if we would restore to the body
as much of the substance of its muscles and cartilage as is daily
removed from it by the urine.
But the urine is not the only channel through which nitrogen
is given off from the animal body. A variable proportion is found
in the solid excretions or dung, which has been derived from the
substance of the body itself. A small quantity of nitrogen is also
believed to be given off from the lungs in breathing, and from the
skin in the perspiration, which nitrogen must have been either di-
rectly or indirectly derived from the food. And, lastly, of the
fibrin or other food containing nitrogen which may be introduced
into the stomach, a portion must pass the mouths of the absorbent
vessels as it descends through the intestines, and thus escape with
the dung, without having performed its part in the ordinary nou-
rishment of the body.
It is impossible to make any correct estimate of the amount of
nitrogen which escapes from the animal in the several ways just
noticed—in the solid excretions, from the lungs, and from the skin
—or of the quantity of food which is necessary to supply its place.
If we suppose the loss through all these sources taken together to
be equal to one half or two-thirds of that which is found in the
urine, then the whole quantity of dry fibrin which the food ought
to contain would amount to four and a-half or five ounces in the
day. To supply this, we must eat of bread, beef, cheese, potatoes,
or milk, one-half more than the quantities already specified.
No experiments have hitherto been published from which we
can determine the average quantity of nitrogen rejected in the ex-
cretions of the horse, the cow, or the sheep, and, consequently, the
amount of Waste which takes place in ordinary circumstances in
the muscles and cartilage of these animals. If we suppose that in
the horse or cow it is in direct proportion to their weights, com-
pared with that of a full grown man—or five times greater than in
a man—then the loss of dry fibrin would amount to 20 or 25
ounces in the 24 hours. To supply this, the animal must eat the
following quantities of one or other of the kinds of food here men-
tioned :-- -
THE SALINE MATTER, MUST BE REPLACED. I ()29
120 lbs. of turnips. 17 lbs. of clover hay.
l 15 ... of wheat straw. 12 ... of pea straw.
75 ... of carrots. l2 ... of barley.
64 ... of potatoes. 9 ... of oats.
20 ... of meadow hay. 5 ... of beans.”
Or instead of the whole quantity of any one of these, a half or
quarter or any other proportion of each may be taken, and a mix-
ture in this way made up on which the animal will probably be
found to thrive better than if fed upon any one of these kinds of
food alone. . .
2°. Quantity of fived saline matter and of earthy phosphates
which the food ought to contain.—A full grown animal rejects in
its dung, its urine, and its perspiration, as much saline and earthy
matter as its food contains. If its body is merely maintained in
its existing condition, only that which is removed from it by the
daily waste is restored to it by the daily food, Thus whatever
quantity of saline and earthy matter is present in the food, an equal
quantity is found in the excretions of the living animal.
But how much of that which is found in the excretions has ac-
tually formed part of the living body, and been removed from it in
consequence of the natural waste? This we have no means as yet
of determining. It must be considerable, but it varies with many
circumstances, and the experiments which have hitherto been made
and published, do not enable us to say how much the average waste
really is, and how much of the several more common kinds of food
ought to be consumed by a full grown animal, in order to supply
it with the necessary daily proportion of saline and earthy sub-
Stances.
The benefits said to be derived from the use of salt in the feed-
ing of stock show how a judicious admixture of saline matter with
the food may render its other constituents more available than they
would otherwise be, to the support and increase of the animal
body.
§ 7. The health of the animal can be sustained only by a mixed
food.
From what I have already stated you see that the vegetable
* These numbers are calculated from the table given in p. 926.
1030 A MIXED FOOD NECESSARY TO ANIMALs.
food eaten by a full grown animal for the purpose of keeping up
its condition should contain—
1°. Starch or sugar to supply the carbon given off in respi-
ration. -
2°. Fat or fatty oil to supply the fatty matter which exists more
or less abundantly in the bodies of all animals, and is wasted in the
perspiration and otherwise. .
3°. Gluten or albumen to make up for the natural waste of the
muscles and cartilage.
4°. Earthy phosphates to supply what is removed from the bones
of the full grown animal by the daily waste, and
5°. Saline substances—sulphates and chlorides—to replace what
is daily rejected in the excretion, and in the perspiration.
Hence the food upon which any animal can be fed with the hope
of maintaining it in a healthy state must be a mixed food. Starch,
or Sugar alone, or pure albumen or gelatine alone, will not sus-
tain the animal body, because these substances do not contain what
is necessary to build up all its parts, or to supply what is daily
given off during respiration and in the excretions. The skilful
feeder, therefore, will not attempt to maintain his stock on any
kind of food which does not contain a sufficient supply of every
one of the kinds of matter which the body requires.
Two other points he will also attend to. First, he will occasion-
ally change the kind of food, or will vary the proportions in which
he gives the different kinds of fodder to his feeding stock. This
practice is founded on the fact that, although every crop he raises
contains a certain proportion of all the substances which the ani-
mal requires, yet some contain one of these in larger quantity than
others do, and by an occasional change or variation he may hope
more fully to supply to the animal the necessary quantity of each.
Second, he will adapt the kind and quantity of food to the age
of the animal, and to the other purposes for which it is fed. This
rule depends partly upon the same fact, that different vegetables
contain the several kinds of necessary food in different proportions,
but in a great degree also upon the further fact, that the animal
requires these substances in different proportions, according to its
age and to the special purpose for which it is fed. Let me direct
your attention to this latter fact a little more at length. -
ADDITIONAL FOOD REQUIRED FOR FATTENING. 1031
§ 8. Of the kind and quantity of additional food required by the
fattening animal.
In the animal which is increasing in size or in weight, the food
has a double function to perform. It must sustain and it must in-
crease the body. To increase the body an additional quantity of
food must be consumed, but the kind or nature of this additional
food will depend upon the kind of increase which the animal is
making or is intended to make.
One of the important objects of the stock farmer is to make his
full grown animals lay on fat, so that they may as quickly as pos-
sible, and at the least cost, be made ready for the butcher. To
effect this object, he adjusts the kind and quantity of the food he
gives, to the practical object he wishes to attain.
We have already seen reason to believe, that the natural and
immediate source of the fat of animals is in the oily matter which
the food contains. If we wish only, or chiefly, to lay on fat, there-
fore, we ought to give some kind of food which contains a larger
proportion of fatty matter than that upon which the animal has
been accustomed to live. This is what the practical man has ac-
tually learned to do. To his sheep and oxen he gives oil-cake” or
, linseed oil mixed with chopped straw, to his dogs cracklings,f to
his geese and turkeys Indian corn, which contains much oil, and
to his poultry beef or mutton Suet. *-
Experiments are yet wanting to determine with accuracy the
proportion of fat contained in all the different kinds of food usually
consumed by animals. Nearly all we yet know upon this subject
is exhibited in the tabular view of their composition to which I have
already directed your attention (p. 926). -
One thing, however, of considerable practical value has been re-
cently ascertained—that the oily matter of seeds exists chiefly near
their outer surface,—in or immediately under the skin or husk.
This fact is shown in the case of wheat, by the following results of
* A writer in the Albany Cultivator (IX. p. 120) states, that beech nuts, the cake
left when they are pressed for the oil, and the oil itself, though they fatten pigs and
wood-pigeons, are poison to horses.
+. Cracklings are the skinny parts of the suet from which the tallow has been for
the most part Squeezed out by the tallow chandlers. Might cattle not be fattened
upon cracklings crushed and mixed with their other food 2
1032 FATTY MATTER IN THE HUSKS OF SEEDS.
the examination of two varieties of this grain, one grown near Dur-
ham, the other in France. The result as to the French grain is
given by Dumas:–
PER-CENTAGE OF FATTY OIL.
* English. French.
Fine flour,...... ......... 1 5 . . . . . l'4
Pollard,....... ...... ‘.... .. 2°4 ..... 4-8
Boxings, ................. 3-6 ...... -
Bran,........................ 33 ...... 5' 2
This fact of the existence of more fat in the husk than in the in-
ner part of the grain, explaims what often seems inexplicable to
the practical man—why bran, namely, which appears to contain
little or no nourishing substance should yet fatten pigs and other
full grown animals, when given to them in sufficient quantity along
with their other food. It also explains why rice dust should be
found to fatten stock," though the cleaned and prepared rice con-
tains but little oil, and is believed, therefore, to be unfitted for
laying on fat upon animals with any degree of rapidity. No doubt
the dust from pearl-barley and from oats, as well as the husk of
these grains, might be economically employed by the stock feeder
where they can readily be obtained.
§ 9. Kind and quantity of additional food required by a growing
animal. *
The young and growing animal requires also that its food should
be adjusted to its peculiar wants. In infancy the muscles and
bones increase rapidly in size when the food is of a proper kind.
This food, therefore, should contain a large supply of the phos-
phates, from which bone is formed, and of gluten or fibrin, by
which the muscles are enlarged. Some kinds of fodder contain a
larger proportion of these phosphates. Such are corn seeds in ge-
meral, and the red clover among grasses. Some again contain
more of the materials of muscles. Such are beans and peas
among our usually cultivated seeds, and tares and other legumi-
mous plants among our green crops. º
Hence the skilful feeder or rearer of stock can often select with
judgment that kind of food which will specially supply that which
the animal, on account of its age or rapid growth, specially re-
* Rice dust is very good food for fattening pigs, makes excellent pork, and is very
profitable when given along with whey.
3
ADDITIONAL FOOD REQUIRED FOR GROWTH. 1033
quires—or which, with a view to some special object, he wishes his
animal specially to lay on. Does he admire the fine bone of the
Ayrshire breed 2–he will try to stint it while young of that kind of
food in which the phosphates abound. Does he wish to strengthen
his stock, and to enlarge their bones?—he will supply phosphates
liberally while the animal is rapidly growing.
An interesting application of these principles is seen in the mode
of feeding calves adopted in different districts. Where they are
to be reared for fattening stock, to be sold to the butcher at two
or three years old, they are well fed with good and abundant food
from the first, that they may grow rapidly, attain a great size, and
carry much flesh. If starved and stunted while young, they often
fatten rapidly when put at last upon a generous diet, but they
never attain to their full natural size and weight. .
When they are reared for breeding stock or for milkers, similar
care is taken of them in the best dairy countries from the first,
though in some the allowance of milk is stinted, and substitutes
for milk are early given to the young animals.
But it is in rearing calves for the butcher that the greatest skill
in feeding is displayed, where long practice has made the farmers
expert in this branch of husbandry. To the man who has a calf
and a milk cow, the principal question is, how can I, in the locality
in which I am placed, make the most money of my calf and my
milk? Had I better give my calf a little of the milk, and sell the
remainder in the form of new milk—or had I better make butter
and give the skimmed milk to my calves—or will the veal, if I give
my calf all the milk, pay me a better price in the end? The re-
sult of many trials has shown, that in some districts the high price
obtained for well fed veal gives a greater profit than can be deriv-
ed from the milk in any other way.
While the calf is very young—during the first two or three weeks
—its bones and muscles chiefly grow. It requires the materials of
these, therefore, more than fat, and hence half the milk it gets, at
first, may be skimmed, and a little bean meal may be mixed with
it to add more of the casein or curd, out of which the muscles are
to be formed. The costive effect of the bean meal must be guarded
against by occasional medicine, if required.
In the next stage, more fat is necessary, and in the third week
1034 USE OF BONE-MEAL RECOMMENDED.
at latest, full milk, with all its cream, should be given, and more
milk than the mother supplies if the calf requires it. Or, instead
of the cream, a less costly kind of fat may be used. Oil-cake,
finely crushed, or linseed meal, or even linseed oil, may supply at
a cheap rate the fat which, in the form of cream, sells for much
money. And, instead of the additional milk, bean meal in larger
quantity may be tried, and if cautiously and skilfully used, the best
effects on the size of the calf and the firmness of the veal may be
anticipated.
In the third or fattening stage, the custom is, with the same
quantity of milk, to give double its natural quantity of cream—
that is, to supply in this way the fat which the animal is wished
chiefly to lay on. This cream may either be mixed directly with
the mother's milk, or what is better, the afterings of several cows
may be given to the calf along with its food. For the expensive
cream there might no doubt be substituted many cheaper kinds of
fat which the young animal might be expected to appropriate as
readily as it does the fat of the milk. Linseed meal is given with
economy. Might not vegetable oils and even animal fats be made
up into emulsions which the calf would readily swallow, and which
would increase his weight at an equally low cost P A fat pease-
soup has been found to keep a cow long in milk; might it not be
made profitable also to a fattening calf.
The selection of articles of food which will specially increase the
size of the bones in the growing animal, by supplying a large quan-
tity of the phosphates, is at present limited in a considerable degree.
The grain of wheat, barley, and oats is the source from which these
phosphates are most certainly and most abundantly supplied to the
animals that feed upon them. But in many cases corn is too ex-
pensive a food, and those kinds of corn which contain the largest
proportion of the phosphates supply only a comparatively small
quantity in a given time to the growing animal. Why should not
bone-dust or bone-meal be introduced as an article of general food
for growing animals 2 There is no reason to believe that animals
would dislike it—none that they would be unable to digest it.
With this kind of food at our command, we might hope to mini-
ster directly to the weak limbs of our growing stock, and at plea-
FOOD REQUIRED DURING PREGNANCY. T 035
sure to provide the spare-boned animal with the materials out of
which a limb of great strength might be built up.
Chemical analysis comes further to our aid in pointing out the
kind of food, we ought to give for the purpose of increasing this or
that part of the animal body. Thus in regard to the same growth
of bone, it appears that, while linseed and other oil cakes are main-
ly used with the view of adding to the fat, some varieties are more
fitted at the same time to minister to the growth of bone than others
are. Thus, four varieties of oil-cake examined in my laboratory,
contained respectively of earthy phosphates and of other inorganic
matter in 100 lbs. the following quantities:–
PER-CENTAGE OF
Earthy Phosphates. Other inorganic matter.
British linseed cake,............ 2.86 2.86
Dutch, do. ............ 2.7 0 2'54
Poppy cake,................. . • * * 5-22 1 *24
Doddar cake, ........ ......... 6-67 3.37
The numbers in the first column, opposite to poppy and dodder
cake, show that these varieties of oil-cake contained a much larger
proportion of the phosphates than the others did, and consequently
that an equal weight of them would yield to growing stock more of
those substances which are specially required to build up their in-
creasing bones.
§ 10. Kind and quantity of additional food required by a pregnant
animal.
The food of the pregnant animal must sustain the full-grown
mother, and must add at the same time to the substance of her un-
born young. The quantity of food which is necessary to sustain
the mother—if herself full-grown, which is often far from being the
case—varies with many circumstances. -
It is said that in the stall an ox or a cow will eat from one-fourth
to one-fifth of its weight of turnips in a day, or one-fiftieth of dry
food, such as hay and straw. With this allowance of food the ani-
mal would probably increase in weight in some degree,_but ac-
cording to Riedesel one-sixtieth of its weight of dry hay is neces-
sary merely to sustain it. From what we have already seen of the
composition of the different grasses, it is obvious that the quantity
1036 FOOD REQUIRED BY A COW IN MILK.
required will be much affected by the kind of hay with which the
animal is fed.
To nourish the young calf in the womb of its mother, an addi-
tional quantity of food must be given, and this quantity must be
increased as the state of pregnancy advances. And though the
kind of additional food which is given must readily supply the ma-
terials of the growing bones and muscles of the foetus, yet it must
contain also a larger quantity of starch or sugar also than the mo-
ther in her ordinary state would require. This is owing to the cir-
cumstance that the mother must now breath for two animals, for
herself and her young. The quantity of blood is increased, more
oxygen is taken in by the lungs, and more carbon is given off in
the form of carbonic acid. To supply this carbon more farina-
ceous or saccharine food must be eaten from the time when preg-
nancy takes place, and it must increase as the young animal en-
larges in size. -
Except in the way of feeding the mother, in all respects well, I
am not aware that any experiments have been made with the view
of specially influencing the condition of the future calf by the kind
of food given to the mother. A certain proportion of bone and
muscle no doubt must be supplied to the young animal by the food
given to the mother, or the bones and muscles of the mother her-
self will be laid under contribution to supply it—but it does not
appear impossible to influence the size of the bone by the quantity
of phosphates which are given in the food, or the growth and de-
velopment of the muscles by that of the gluten, albumen, or casein
with which the mother is fed. Might not an addition of bone-meal
to the food of the pregnant cow give a calf of larger bone?
Would not bean-meal or skim-milk add to the size of its muscles?
§ 11. Kind and quantity of additional food required by a milking
animal. .
After the young animal is born, the mother has still to feed it
with her milk. And as the calf grows rapidly, the food it requires
increases daily with its bulk, and the demands upon the mother,
therefore, every day become greater. At this period, therefore, the
cow must obtain larger supplies of food, to sustain herself and to pro-
duce a sufficient quantity of milk for her calf, than at any other period.
USE OF THE ADDITIONAL STARCH TO THE MILK COW. 1037
If these adequate supplies are not given, a portion is daily taken
from her own substance—her body becomes leaner, and her limbs
more feeble, while her young also is stinted and puny in its growth.
By and bye, however, the calf begins to pick up food for itself.
It begins to live partly upon vegetables. The mother is in con-
sequence relieved of a part of her burden—her udders are less
drawn upon—the quantity of milk secreted becomes less—she be-
gins again to lay muscle and fat upon herself—her udders at
length become dry, and she slowly recovers her original plump
condition. She has, indeed, at this period a tendency to fatten if
the same supply of food is continued to her, and in many districts
it is customary to feed her off at this time for the butcher.
What I have already said of the artifices by which the food
given to the cow may possibly be made to influence the bodily cha-
racter of the future calf, applies equally to the means of more or
less effectually promoting the growth of the young animal while it
is fed solely upon milk. The kind of food given to the mother
may make the milk richer in curd, which will promote the growth
of muscle—or richer in phosphates, by which the enlargement of the
bones of the calf will be assisted. Scarcely any two samples of milk,
indeed, are found, upon analysis, to contain the same proportion
of phosphates and other Saline substances, and there is little reason
to doubt that if an unusual quantity of these be given in the food
of the mother, an unusual quantity will be found also in the milk
she produces. . -
For the production of milk the mother requires an adequate ad-
ditional supply of all the substances which we have seen to be ne-
cessary to the support of the unborn foetus—of the starch as well
as of the gluten and saline substances of the food. But it is inte-
resting to mark the very different purposes to which the additional
supply of starch in her food is now applied.
The pregnant mother requires this starch to supply the carbon
given off more abundantly during her increased respiration. She
breathes, as I have already said, for her young and for herself,
and therefore gives off more carbon from her lungs.
But when the young animal is born it breathes for itself. It
must, therefore, be supplied with that kind of food which seems
specially intended to meet the wants of respiration.
I ()38 IT IS CHANGED INTo MILK SUGAR.
The additional starch eaten by the mother, therefore, instead of
being breathed away in her own lungs, is conveyed in the form of
Sugar into the food of the young animal. It is changed into the
Sugar of the milk, and the natural function of this sugar is to Sup-
ply the carbon which the young animal gives off when it begins
to breathe for itself.
It is not difficult to understand the kind of process by which
the starch of the mother's food is converted into the sugar of her
milk. For if to - º
2 of starch = 24 C -- 20 H + 20 O,
we add 4 of water = 4 H + 4 O,
we have 24 C + 24 H + 24 O, which is the for-
mula for milk sugar. In passing through the digestive organs of
the cow, therefore, the elements of the 2 of starch require only to
be combined with those of 4 of water to be converted into the
Sugar of milk. -
But though it is not difficult to understand in what way this
change may be effected, yet it is exceedingly interesting to find
that such a chemical change as this should be made to commence at
a certain special epoch with a view to a certain special end.
Milk is a perfect food for a growing animal, containing the curd
which is to form the muscles, the butter which is to supply the fat,
the phosphates which are to build up the bones, and the sugar which
is to feed the respiration. Nothing is wanting in it. The mother
selects all the ingredients of this perfect food from among the other
useless substances which are mingled in her own stomach with the
food she eats—she changes these ingredients chemically in such a
way as to present them to the young animal in a state in which it
can most easily and with least labour employ them for sustaining
its body—and all this she begins to do at a given and appointed
moment of time. How beautiful, how wonderful, how kindly pro-
vident is all this
§ 12. Feeding a cow for dairy purposes.
But apart from its natural use in the economy of nature, milk
may be regarded as a material for manufacture—an important
article of agricultural husbandry. As a mere producer of milk
TO PRODUCE MILK FOR CHEESE OR BUTTER. I 039
for other purposes than the feeding of calves, the cow will be diffe-
rently fed, according to the purpose for which her milk is intended
to be employed, or the form in which it is to be carried to market.
a. The town dairyman, who sells his new milk to daily custom-
ers, requires quantity rather than quality. He gives his cattle,
therefore, succulent food in which water abounds—green grass—
forced rapidly forward by irrigation or otherwise—green clover,
young rye, brewers' grains, or hay tea.” In this way, without the
actual addition of water, and, therefore, with a clear conscience, he
can make his milk thin, and increase its bulk.
b. Those, again, who desire much rich cream, or who grow milk
for the manufacture of butter, pay less attention to the bulk of the
milk itself than to that of the cream they can collect from its sur-
face. The proportion of butter is increased by the use of food
which contains much fatty matter—of any of those kinds of food,
indeed, by which an ox can be made rapidly to lay on fat. Oil-
cake has by some been objected to as likely to give a taste to the
milk, but it may be safely used at the rate of two or three pounds
a-day; and gives an abundant and well flavoured cream.
c. In cheese countries, again, it is the curd that is chiefly in re-
quest. No doubt the value of a cheese depends much upon the
proportion of butter it contains diffused throughout its substance,
but the weight of cheese produced upon a farm depends also very
much upon the quantity of curd which the milk of the dairy yields.
Where skim-milk cheese is made, the weight of produce obtained
depends almost solely upon the richness of the milk in curdy
matter. Clovers, vetches, and pea straw abound in legumin, from
which curd may be formed, and thus give a rich and productive
milk to the cheese maker, while bean-meal and pease-meal, in so
far as they can be given to the cow with safety, may with advan-
tage be employed to produce the same effect. As every thing
which tends to lay on fat on the animal is likely to increase the
proportion of butter in its milk, so also every thing which promotes
the growth of muscle will add to the richness of the milk in curd
or cheese.f *
* A mixed hay tea and pease soup, which is excellent for making cows give milk,
is prepared by putting hay into a pot in alternate layers, sprinkling between each a
handful of pease-meal, adding water and bringing to a boil. -
+ In butter districts, which are remote from large towns, the butter-milk is usually
I040 SMALL ANIMALS LESS PROFITABLE TO FEED.
§ 12. Influence of size, condition, warmth, evercise, and light on
the quantity of food necessary to make up for the natural waste.
But the quantity of food of any kind which an animal will re-
quire is affected by many circumstances. Thus—
1°. The size and condition of the animal will regulate very much
the quantity of food which is necessary to sustain it. The larger
the muscles and bones the greater will be the daily waste, and the
greater the quantity, therefore, of the food necessary to replace it.
If an animal require a 50th or a 60th of its weight of dry food
daily, of course its size and weight will regulate almost entirely
the quantity of food it ought to eat.
A knowledge of this circumstance is occasionally of economical
value to the stock feeder or dairy farmer, and will modify very
much the line of conduct he may be inclined to adopt as the most
profitable.
A large animal requires more food to keep it in its actual con-
dition—to make up, that is, for the natural waste. If you wish to
convert much produce into much rich dung, therefore, keep large
animals. They will convert a large quantity of vegetable matter
into manure without adding any thing to their own substance.
If one-fiftieth of its weight of dry food be necessary to sustain it,
then an animal of 100 stones weight will convert two stones of hay
daily into dung. Whatever it eats beyond the two stones, will go
to the increase of its weight.
But a small animal, of 50 stones, requires only one stone a day
to sustain its body, or converts one stone wholly into dung. What-
ever it eats beyond this quantity, therefore, will or may go to the
production of increased beef and bone. Hence, if I have a given
quantity of vegetable produce, I ought to be able to manufacture
more beef from it by the use of small cattle than of large, provid-
ed my large and small stock are equally pure in breed, are equally
quiet, and are as kindly feeders.
The same reasoning applies to dairy cows of different breeds.
given to the pigs. In the United States of America it is sometimes given as winter
food to the cow herself. A peck and a-half of potatoes boiled, and the sour milk
mixed with it, are said to keep her in full milk from September till May. This really
seems an excellent as well as a natural method of supplying the casein and other con-
stituents of the milk.
INFLUENCE OF EXERCISE AND WARMTH. I ()4].
If I give two stones of hay to a small Shetland cow, she may not
convert more than one of them into dung, the other she may con-
sume for the production of milk. But if I give the same quantity
to a cow of double the size, nearly the whole two stones may be
converted into dung—may be employed in sustaining the animal—
and if she yield any milk at all, it will be poor and thin.
This reasoning accounts for the fact which has been long ob-
served, that small breeds of cattle give the richest milk, and that
such as the small Orkney breed yield the largest produce of but-
ter and cheese from the same quantity of food. They waste less
of their food in sustaining their own bodies. Lean, spare cows
also require less to sustain them ; and hence the skin-and-bone
appearance of the best milkers among the Ayrshire and Alderney
breeds. {
2. The quantity of exercise which an animal takes, or of fatigue
it is made to undergo, requires a proportionate adjustment in the
quantity of food. The more it is exercised the more frequently
it breathes, the more carbon it throws off from its lungs, the more
starch or sugar, consequently, its food must contain. If more is
not given to it, the fat or other parts of the body will be drawn
upon, and the animal will become leaner.
Again, the natural waste of the muscles and bones is said to be
caused by, or at least to be in proportion to, the degree of motion
to which the several parts of the body are subjected. Take more
exercise, therefore, move one or more limbs oftener than usual,
and a larger part of the substance of these limbs will be decom-
posed, removed, and rejected in the excretions. Hence the reason
why hard work requires good food, and why the strength of all
animals is diminished, if they be subjected to great fatigue and are
not in an equal degree supplied with nourishing food, by which
the wasting parts of the body may be again built up.
3°. The degree of warmth in which the animal is kept, or the
temperature of the atmosphere in which it lives, affects also the
quantity of food which the animal requires to eat. The heat of
the animal is inseparably connected with its respiration. The more
frequently it breathes, the warmer it becomes, and the more car-
bon it throws off from its lungs. It is believed, indeed, by many
that the main purpose of respiration is to keep up the heat of the
3 U
I 042 EXPERIMENT OF ME CHILDERS.
body, and that this heat is produced very much in the same way
as in a common fire, by a slow combustion of that carbon which
escapes in the form of carbonic acid from the lungs. Place a man
in a cold situation, and he will either starve or he will adopt some
means of warming himself. He will probably take exercise, and
by this means cause himself to breathe quicker. But to do this
for a length of time, he must be supplied with more food. For
not only does he give off more carbon from his lungs, but the ex-
ercise he takes causes a greater natural waste also of the substance
of his body.
So it is with other animals. The greater the difference between
the temperature of the body and that of the atmosphere in which
they live, the more food they require to “feed the lamp of life”—
to keep them warm, that is, and to supply the natural waste.
Hence the importance of plantations as a shelter from cold winds
to grazing stock—of open sheds to protect fattening stock from the
nightly dews and colds—and even of closer covering to quiet,
gentle, and delicate breeds of cattle or sheep, which feed without
restlessness and quickly fatten. -
A proper attention to the warmth of his cattle or sheep, there-
fore, is of great practical consequence to the feeder of stock. By
keeping them warm he diminishes the quantity of food which is
necessary to sustain them, and leaves a larger proportion for the
production of beef or mutton. -
Various experiments have been lately published by Mr Childers,
Mr Morton, and Mr Huxt{ble, which confirm the opinions above
deduced from theoretical considerations. In that of Mr Childers,
20 sheep were folded in the open field, and 20 of nearly equal
weight were placed under a shed in a yard. Both lots were fed
for three months—January, February, and March—upon turnips,
as many as they chose to eat, half a pound of linseed cake, and
half a pint of barley each sheep per day, with a little hay and salt.
The sheep in the field consumed the same quantity of food, all the
barley and oil-cake, and about 19 lbs. of turnips per day, from first
to last, and increased on the whole 36 stones 8 lbs. Those under
the shed consumed at first as much food as the others, but after
the third week they eat 2 lbs. of turnip each less in the day, and
in the ninth week, again, 2 lbs. less, or only 15 lbs. a-day. Of
EFFECT OF THE ABSENCE OF LIGHT. I ()43
the linseed-cake they also eat about one-third less than the other
lot, and yet they increased in weight 56 stones 6 lbs., or 20 stones
more than the others. -
Thus the cold and exercise in the field caused the one lot to
convert more of their food into dung, the other more of it into
mutton.
But why did the sheltered sheep also consume less food? Why
did they not eat the rest of the food offered them, and convert it
also into mutton P Because the stomach of an animal will not do
more than a certain limited amount of work in the way of digest-
ing, after the wants of the body are fully supplied. When cir-
cumstances cause the sustaining quantity of food to increase, the
digestive powers are stimulated into unusual activity, and though
plenty of food be placed before the animal it may be unable to
consume and digest more than is barely sufficient to keep it in con-
dition. If the sustaining portion be lessened, by placing the ani-
mal in new circumstances, more food may be digested than is ab-
solutely necessary to supply the daily waste—that is to say, the
animal may increase in weight. But the unusual stimulus being
removed, it may not now be inclined, perhaps not be able, to digest
so large a quantity as it did before when that large quantity was
necessary to sustain its body—that is to say, that while it increases
in weight it will also consume less food.
4°. The absence of light has also a material influence upon the
effect of food in increasing the size of animals. Whatever excites
attention in an animal, awakens, disturbs, or makes it restless, ap-
pears to increase the natural waste, and to diminish the effect of
food in rapidly enlarging the body. The rapidity with which
fowls are fattened in the dark is well known to rearers of poultry.*
In India, the habit prevails of sewing up the eyelids of the wild
hog-deer, the spotted deer, and other wild animals when netted in
the jungles, with the view of taming and speedily fattening them.
The absence of light, indeed, however produced, seems to soothe
* It is astonishing with what rapidity fowls (dorkings) increase when well fed, kept
in confined cribs, and in a darkened room. Fed on a mixture of 4 lbs. of oatmeal,
1 lb. of suet, and 3 lb. of Sugar, with milk for drink five or six times a-day in summer,
a dorking will add to its weight 2 lbs. in a week, sometimes 1% lbs. in four days. A
young turkey will lay on 3 lbs. a-week under the same treatment.
1044 MR MORTON's EXPERIMENT IN FEEDING.
and quiet all animals, to dispose them to rest, to make less food
mecessary, and to induce them to store up more of what they eat in
the form of fat and muscle.
The experiment made by Mr Morton, on the feeding of sheep,
shows the effect at once of shelter, of quiet, and of the absence of
light upon the quantity of food eaten and of mutton produced from
it.
Five sheep, of nearly equal weights, were fed each with a pound
of Öats a-day and as many turnips as they chose to eat. One was
fed in the open air, two in an open shed—one of them being con-
fined in a crib—two more were fed in a close shed in the dark—
and one of these also was confined in a crib, so as to lessen as
much as possible the quantity of exercise it should take. The in-
crease of live weight in each of the five, and the quantity of turnips
they respectively consumed, appear in the following table:–

LIVE WEIGHT. Increase
Turnips for each
- Increase. eaten. 100lbs. of
Nov. 18. | March 9. turnips.
lbs. lbs. lbs. lbs. lbs.
Unsheltered, ..................... .. 108 131.7 23.7 1912 1-2
In open sheds, ................. ....] 102 129.8 27-8 1394 2. ()
Do., but confined in cribs, ...... 108 130-2 22.2 1238 1-8
In a close shed in the dark, ...... 104 132-4 28°4. 886 3. I
Do., but confined in cribs, ...... 11 I 131°3 20.3 886 2-4
From this table it appears, as we should have expected—
a. That one-third less turnips was eaten by the animal which
was sheltered by the open shed, than by that which was without
shelter, while in live weight it gained four pounds more.
b. That in the dark the quantity of turnips eaten was one-half
less, and the increase of weight a little greater still.
c. But that when confined in cribs—though the food eaten might
be a little less—the increase in weight was not so great. The ami-
mal, in fact, was fretful and restless in confinement, and whatever
produces this effect upon an animal prevents or retards its fat-
tening.
d. That the most profitable return of mutton from the food con-
sumed, is when the animal is kept under shelter and in the dark.
Such a mode of keeping animals, however, must not be entered
EFFECT OF THE SOURING OF FOOD." - } 045
upon hastily or without due consideration. The habits of the breed
must be taken into account, the effect of confinement upon their
health must be frequently attended to, and above all the ready ad-
mission of fresh air and a good ventilation must not be forgotten.
By a neglect of the proper precautions, unfortunate results have
frequently been obtained and a sound practice brought into dis-
repute.
5°. Ventilation and cleanliness indeed are important helps to
economy in the feeding of all animals. Shelter and warmth will
do harm, if free and pure air is not admitted to the fattening stock.
The same is true of cleanliness, so favourable to the health of all
animals. The cleaner their houses and skins are kept, the more
they thrive under any given form of treatment in other respects."
This is especially true of pigs. An experiment is related in
which six pigs were for seven weeks fed alike. Three were curry-
combed and well looked after, while the other three were left to
themselves. After the expiration of the seven weeks, the former
had consumed five bushels of pease less than the latter, and yet
weighed two stones four pounds more.
6°. Individual constitution, in animals as in man, has much in-
fluence upon the effect produced by a given weight of food. Ani-
mals, like men, often put their food “into an ill skin.” This is
well known to every stock-feeder; and in selecting such as are
likely to thrive when well treated, his superior skill is often seen
in the cattle fair or public market.
§ 13. Influence of the form or state in which the food is given, on
the quantity required by an animal.
The state in which the food is given to his stock, has often an
important influence upon the profits of the feeder. Thus—
1°. The souring of the food, in some cases, makes its use more
economical. Arthur Young details several series of experiments
on the fattening of pigs, in which bean meal was given mixed with
water in the sweet state, and after it had been allowed to stand
several days to Sour. In every case in which it was given sour the
pork obtained gave a profit upon the price of the meal, while in every
case in which the same meal was given sweet and in equal quan-
* “A master's eye makes a fat horse.”
1046 THE BOILING OR STEAMING | OF FOOD,
tity, the price obtained for the pork was less than that which was
paid for the meal.
Upon sour food, indeed, pigs are universally observed to fatten
best. In Holstein, it is customary to collect waste green herbage
of every kind, and to let it sour in water. It then fattens pigs
which would scarcely thrive on it before. During this souring of
vegetable matter in water, it is lactic acid—the acid of milk—which
is chiefly produced. This acid, therefore, would appear to favour
the increase of size in the pig, and to this cause may be owing the
profitable use of sour whey in feeding this kind of stock in cheese-
making districts.
. I have been told by some cowfeeders who use brewers' grains,
that the dry cows, when fattening off, relish the grains most when
slightly sour, and fatten most quickly upon them. From others,
however, I have obtained a contrary opinion, and have been assured
that fattening stock of all kinds like the grains best, and thrive
best upon them, when perfectly sweet and fresh. It is a matter of
doubt, therefore, whether or not the souring of food generally of
all kinds and for all kinds of stock, can be safely tried or recom-
mended. *
2°. The boiling or steaming of hay, chopped straw, and other
dry food, and even of potatoes and turnips, is recommended by
many as an economical practice. I believe that the general result
of the numerous experiments which have been made upon this sub-
ject in various parts of the country is in favour of this opinion in so
far as regards fattening and growing stock. It seems a more
doubtful practice in the case of horses which are intended for heavy
and especially for fast work—though even for these animals the
use of steamed food is beginning to be adopted by some of the most
extensive coach contractors.” Pigs and sheep are said to fatten
well on boiled peas and beans. *
3°. Baking of food.—Baked potatoes are said to form the most
fattening of all food for pigs, (American Cultivator, x. p. 196.)
4°. Crushing the food.—It is also of much importance that
the food should be so crushed that it may not pass through the sto-
mach undigested. In regard to Indian corn, for example, it is said
* Stephens' Book of the Farm.
USE OF MALTED OR SPROUTED GRAIN. 104.7
to go 3 to # further in fattening pigs when crushed than when
given whole.
5°. Age of the food.—It is a curious fact not less worthy of the
attention of the chemist than it is of the practical man, that the age
of the food singularly affects its value in the mourishment of ani-
mals. Thus new oats are not considered fit for hunters before the
months of February or March. They affect the heels and limbs
with something like grease, and make the horse unfit for fast work.
Nor is it merely water which the grain loses by the five or six
months' keeping—for if it be dried in the kiln it is still unfit for
use from its stimulating in an extraordinary degree the action of
the kidneys. Some chemical change takes place in the interior of
the oat which has not yet been investigated.
The potato, on the other hand, by keeping loses much of its
nutritive value, even before it has begun to sprout—and every
feeder knows that turnips which have shot into flower, add much
less than before to the weight of his fattening stock.
§ 14. Use of malted or sprouted grain.
Malted barley is by many persons recommended as superior in
feeding or fattening quality to barley in its ordinary condition or
in the state of meal. There are several considerations involved
in this question which at present is exciting considerable attention
in this country.
a. We have seen that during the sprouting of grain a portion
of a substance called diastase is produced, which has the property
of converting the starch first into dextrine (starch gum) and then
into sugar. The main purpose of this conversion is that the sub-
stance of the grain may be rendered soluble and thus capable of
feeding the young plant.
b. During this germination and change of the starch, however,
a portion of carbonic acid is given off, so that the grain undergoes
a diminution or loss of its substance. It is found to contain less
nutritive matter when malted by about six or seven per cent.
c. The grain at the same time throws out rootlets, which, when
it is dried in the malt kilns, fall off and form the malt dust, or
cummins of the maltster. Thus the barley suffers a further loss—
these cummins containing a considerable portion of the Saline mat-
| ()48 TJSE OF MALTED OR SPROUTED GRAIN.
ter and gluten of the grain, and hence their value as a manure
and as an admixture with the more watery food of cattle.
From these facts it is clear that though malt may contain as
much nutritive matter as barley, weight for weight, it must con-
tain less than the barley from which it was produced. In other
words, a quarter of barley must be more nutritious in itself than
the malt produced from it.
This conclusion, however, does not affect the results of obser-
vation as to the superior value of malt over barley as an admixture
or partial food for cattle. : -
I believe no cattle feeder or fattener of sheep would recommend
the use of malt as the sole nourishment of any of his stock. It is
said to be too laxative to be given alone; but independent of that,
it wants bulk, and, even were there no duty on malt, would pro-
bably be too expensive. He would give it as he does barley-meal,
or bean-meal, or oil cake, as an addition to the other more bulky
food on which his beasts chiefly live. Used in this way, the evidence
appears satisfactory that it produces a more marked and profitable
effect than the proportion of barley from which the malt might
have been produced. -
It is impossible to arrive at any precise conclusions as to the
actual superiority in value of the malted grain. But Mr Hudson
of Castle Acre, a well known practical agriculturist, states it as the
result of his experience, that—
a. Five quarters of malt are equal to one ton of oil cake, when
given with the same quantities of chopped straw and a few
Swedes. - -
b. That 14 lbs. of oil cake, or 1% pecks of barley meal, or I
peck of malt per day, would produce equal effects in fattening a
beast of 60 stone given with the same quantity of hay and Swedes.
He even says that the malt would lay on more flesh than either of
the others.
In regard to sheep Mr Bloomfield states that he gave a pint of
malt per day for six weeks to a large lot of Southdown and Lei-
cester shearlings, and he had never seen anything to equal its fat-
tening properties.
It is added as a further recommendation, that sheep and cattle
prefer the malt very much to barley —a circumstance of very con-
USE OF MALTED OR SPROUTED GRAIN. I049
siderable importance, where, for quick fattening, the consumption
of food is to be increased. -
I conclude, therefore, that as a partial food—as a substitute for
oil cake in whole or in part—the malted is superior to the unmalt-
ed barley. But on what principle is this superior efficacy to be
explained? It appears to me to be very simple and satisfactory.
Some have said that it merely acts as a condiment. But how a
condiment, in the ordinary sense of the term, can act as malt is
said to act, I do not understand. Or that it is because the malt
contains sugar ready formed, and that a little molasses given with
the food would do as well. Experience does not confirm this opi-
mion, and the true explanation contradicts it.
When ground malt is put into warm water and digested for some
time at a moderate temperature, the starch of the malt is gradu-
ally dissolved and converted into sugar by the agency of the di-
astase which the malt contains. The Sweet worts of the brewer
are thus obtained.
If with the decoction of malt a quantity of wheaten flour, or
ground oats, or potato starch be mixed, they are also gradually
changed, and the starch they respectively contain is converted
into sugar. The malt, in fact, as I have formerly had occasion to
state, has the power of dissolving and changing a larger quantity
of starch and gluten than itself contains, and brewers and distil-
lers take advantage of this power, by using, where they are per-
mitted, a mixture of malted and raw grain for the preparation of
their worts.
What takes place in the vat of the manufacturer takes place
also in the stomach of the animal. The food it eats must be dis-
solved in the stomach before it can be useful as food. What is
not dissolved passes through the intestinal canal and is rejected.
The malt aids and hastens the solution of the food. It attacks
that which the ordinary or unaided digestive powers of the stomach
could not overtake. It thus supplies more liquid food to the ab-
sorbent vessels in the same period of time, and more thoroughly ex-
hausts of nutritive matter the whole food which the animal eats.
This true and simple explanation shows,
a. That it is not because it contains sugar that it is more nutri-
tive than barley, and that molasses would not supply its place.
1050 USE OF A MIXTURE OF MALT AND BOILED POTATOES.
-- &
b. That it does not act as a condiment or seasoning, but as a
chemical agent. -
c. Why a small proportion of malt may produce a very strik-
ing effect. While it at the same time suggests to the practical
man,— . -
d. That above a certain proportion of malt may not be so pro-
fitable as a mixture of malt and barley-meal, or simply a mixture
of a small proportion with the usual more or less soluble food by N
which the stock is principally sustained.
I think it very probable that the general use of it in this way
as a dissolving and converting agent in the stomach would be at-
tended with very profitable results. -
§ 15. Use of a mixture of malt and boiled potatoes.
This last conjecture is very much sustained by the result of
the experiments made by Mr Böggild in Denmark, and after him
by many practical men in Norway, upon the increased feeding qua-
lity of boiled or steamed potatoes when mixed with a small pro-
portion of powdered malt. The memoir of Mr Böggild on the
subject has been published in a separate form and extensively cir-
culated among the native peasantry by the Agricultural Society of
Norway; and in a communication I have lately received from Den-
mark the method is said to have met with very general adoption.
Mr Böggild boils his potatoes, and them, by a peculiar machine,
cuts or mashes them very fine. He then adds a very little water if
necessary, along with a tenth or twelfth of crushed malt, and digests
for some time at a gentle heat. By this means a large portion of
the starch of the potato is converted into starch, gum, and sugar,
and experience has shown that in this state it is far more nutritive
than when eaten in the usual way.
The same weight of potatoes given in this form to milk cows is
said to cause them to yield two or three times as much milk. Their
value in stall-feeding cattle is said to be doubled,—so that from
25 lbs. of potatoes 1% lbs. increase of weight is obtained—and
horses thrive and are profitably fed upon this mixed mash.
In this case, the advantage derived, above what the boiled po-
tatoes with a tenth or twelfth of their weight of barley would give,
4
EUONOMICAL USE OF MIXED AND PREPARED FOOD. 1051
must be owing to that solvent and converting agency of malt
which I have explained in the preceding section.
§ 16. Economical use of mixed and prepared food in feeding cattle.
The opinion is now beginning to be very generally entertained
among practical men, that a mixed food is more economical,—
causes equal weights of the same kinds that is to go farther,-than
the use of any one kind of food alone;—and that a previous pre-
paration or cooking of a part at least of this mixed food is more
profitable than the use of the whole of it in a raw state.
The use of hay alone to keep stock over winter is therefore
abandoned where circumstances admit of it—while on the other the
use of turnips alone, either for cattle or for sheep, is given up by
skilful feeders who have other food at command. -
It is unnecessary for me to enter into any details upon this sub-
ject, as the results of experience in this matter only coincide with
the indications of theory. We know that the composition of dif-
ferent kinds of food is unlike, and, therefore, that a judicious mix-
ture of several kinds is more likely to supply all that the animal
wants, at less cost and with less waste than when any of them is
given alone.
The two following are among the most striking illustrations of
the value of mixed and prepared food which have lately been pub-
1ished by practical men.
1°. Mia!ed food.—Turnips when employed alone are by practical
men in the southern part of the island seldom valued at more than
5s, to 8s, a ton for feeding sheep or cattle. But by feeding his
sheep in sheds and pulling the turnips for them, Mr Huxtſble
finds that a week's food, consisting of
119 lbs. of Swedes, tº
} give 2 lbs. 4 oz.
7 pints of oats, §
of mutton (dead weight),
7 lbs. of oat straw,
from which he calculates at the average price of mutton that his
turnips used in this way pay him 17s. 6d. a ton, exclusive of the
value of the dung. He states also that similar results by his me-
thods may be always obtained.”
The admixture of corn, therefore, and feeding under cover,
* Royal Agric. Journal, February 1846.
1052 ECONOMICAL USE OF MIXED AND PREPARED FOOD.
seem in his hands to have largely added to the value possessed by
the turnip when used alone and eaten off in the field.
2°. Mixed and prepared food.-The use of linseed in feeding
cattle has lately been much recommended, especially by Mr Warnes,
who makes a valuable compound by boiling the seed in water, and
thickening the gruel by an admixtyire of tail corn, ground barley,
or chopped straw. This compound is said to be nutritiveXand
profitable, to be relished by the cattle, and to produce a very en-
riching manure.
I lately visited the farm of my friend Mr Hutton of Sowber
Hill, near Northallerton, for the purpose of witnessing the mode
of manufacturing and administering a prepared linseed mixture
he has for some time been in the habit of employing, and by which
he is enabled to keep and fatten off more than twice the number
of stock he could do before upon the same quantity of turnips—
thus greatly increasing at once his own profits, and the store of
rich manure, by which the general produce of his land in corn is
to be augmented.
His method, suggested, I believe, by Mr Marshall of Beadale,
is to crush the linseed, to boil it by a steam heat for three hours,
with two gallons of water to each pound of the seed, and then to
mix the hot liquid with chopped straw and tail corn in the follow-
ing proportions:—
Linseed.......................................................... ...... 2 lbs
Cut straw........ ... .................................................. l 0 lbs
Ground corn.......................................................... 5 lbs
This quantity is given to each full-grown beast per day, in two
messes. The liquid is poured upon the mixed corn and straw on
the floor of the boiling house, is turned over three times at inter-
vals, and at the end of two hours is given to the cattle. They
have two hot messes a-day, and are fed punctually at the same
hour.
The times of feeding are, turnips at 6 in the morning, prepared
food at 10, turnips at 1, and prepared food again at 4 in the after-
noon. The allowance of turnips is 60 lbs. of Swedes per day, or
75 of hybrids, or 112 lbs. of globes.
Under this system the cattle thrive remarkably, are still and
quiet, lie down during the greater part of the day, and though they
BEANS AND OIL INSTEAD OF OIL-CAKE, 1053
cause a large outlay at first in the purchase of linseed, they amply
repay it in the value of the dung, and in the higher price they
return for the turnips, and for the tail corn, than could be obtained
in any other manner.
§ 17. Can a substitute be recommended for oil-cake in the
feeding of cattle 2
This is a question which is interesting in many points of view.
It implies two things—first, can a compound of other kinds of food
be made up which shall be as good for feeding cattle, and form as
rich a manure, as oil-cake P and, second, can this mixture be sold
at a cheaper rate than oil-cake? We may be able to fulfil the first
condition—but, unless the mixture is cheaper than oil-cake, we can
scarcely hope to supply its place to the farmer—we can never ex-
pect to supersede it.
1. Oil-cake contains from 22 to 25 per cent. of protein com-
pounds, (albumen, gluten, &c.) In this respect the pea and the
bean are the only seeds that approach to it—the pea containing
about 24, and the bean sometimes as much as 28 per cent. of such
protein compounds. The bean, therefore, is the only other vege-
table food we possess which can be made the basis of an artificial
imitation of the cake from oily seeds.
2°. The next peculiarity in oil-cakes is the large proportion of
fatty matter they still contain. In the best English and foreign
cakes, the unextracted oil appears to amount to nearly 12 per
cent. This also is greater than any other food usually given to
our cattle contains. Oil or fat, in some cheap form or other, must,
therefore, be added to any mixture which is to rival oil-cake. If,
with 90 lbs. of beans, we could mix, grind up, or otherwise incor-
porate 10 lbs. of oil or fat, we should have a compound nearly
equal, in all but one respect, to an equal weight of the cake from
the natural seed. Thus 100 lbs. of English oil-cake and 100 lbs.
of beans, so prepared, would consist respectively of
Linseed Cake. Prepared Beans.
40
Starch, Sugar, and gum or mucilage, ... 39
Gluten, albumen, &c., ......... ........... 22 25
Fat, ........ ............................ ... T2 12
Saline matter, .............................. 7 3
Water" and husk,........................... 20 20
100 100
* The proportion of this water would vary in different samples of beams,
1054 SUBSTITUTE FOR OIL-CARE.
On comparing these two columns, we see that the mixed beans
have the advantage in regard to starch and gluten, and are defec-
tive only as regards the inorganic or saline matter. Of this last
the beans contain only one-half as much as oil-cake, and conse-
quently, as compared with them, will be deficient in alkaline matter
and in phosphates. -
The difference in composition between the saline matter of the
beam and that of the oily seeds, so far as they have hitherto been
analysed, does not appear to be very great, the main difference
being that the beans contain more alkaline matter and the oily seeds
more lime. An addition of 6 lbs. of ordinary bone-meal, recently
ground, and in a fresh and sweet state, would supply the deficiency
of lime and phosphates, and would make a mixture equivalent in
chemical composition, and, therefore, I should hope, equal in fat-
tening and other virtues, to an equal weight of oil-cake.
First Prescription.—Thus the proposed mixture would consist
of- -
Bean meal, ..... .................. 90 lbs.
Oil or fat, ..... .............. ...... 10 ...
Bone meal,................ . . . . . . . . . . . . 6 -,
106 lbs.
These would require to be mixed, ground, or boiled up together,
and might be given as food either in a dry or in a wet state. Or
they may be made into a cake—which would keep for any length
of time, by drenching the mixed powder with a weak solution of
glue, (made by boiling bones in water,) and then compressing the
whole into a mould.
The principle of this mixture being known, other modifications
of it may be devised, but if formed of vegetable food, the bean or
some other kind of pulse must be the basis of them all. The
proper proportioning of the fat to the protein compounds is a mat-
ter of vital moment. The relative proportions in which these two
classes of substances exist in them, form the main distinction be-
tween the beam and the oily seeds. The small quantity of oil con-
tained by the bean is one of the chief reasons why it cannot be
given with safety in very large proportion to the greater number
of our domestic animals. ſº
Second Prescription.—The principal difficulty attending the
ARTIFICIAL OIL-CAKE. . 105.5
above prescription will be in procuring and mixing the fat with
the beam-meal. But the same end may be attained in a different
way. Fresh linseed, of good quality, contains upwards of 20 per
cent. of oil. A mixture, therefore, of
Bruised Jinseed,..................... 40 lbs.
Bean meal, .......................... 60 ...
Bone meal,......... ...... • * * * e º e s e e 4
would contain of the several constituents which are essential to the
value of the mixture about
Starch, .............................. 40 lbs.
Protein compounds, ............... 27
Fat,.................................... 11
Saline matter, .................... 7 ...
Water and husk, .................. 15 ..
100
This mixture approaches very closely to the composition of oil-
cake. There seems, therefore, to be a very good theoretical reason for
the practice recommended by Mr Warnes, and adopted as above
described by Mr Hutton and others, of using a mixture of bruised
linseed, or of linseed jelly, along with the other food given in the
ordinary feeding of stock. The oil and saline matter of the lin-
seed actually make the starch and protein compounds of the rest
of the food go farther.
It would be a simple process, by the aid of a gentle heat, to com-
press into hard, durable, and tenacious cakes, the above mixture
of linseed, crushed beams, and bone-meal.
Third Prescription.—But there is a third method of making a
mixture of this kind. I do not, however, offer you the following
prescription with the same degree of confidence, chiefly because
our knowledge is still defective upon some points involved in it,
but I present it for your consideration, with the hope that some of
you will submit it to the test of experiment.
It is the protein compounds—those yielding nitrogen to the ani-
mal—which are especially abundant in the oil-cakes, and, there-
fore, difficult to supply in equal proportion, except by the use of
a very limited number of vegetable substances. But an animal
substance might be obtained in comparatively large quantity, from
which a compound capable of supplying nitrogen to the animal
might be artificially made up with comparative ease. This sub-
1056 Al{TIFICIAL OIL-CAKE-G ELATINE MIXTURE.
stance is gelatine or glue. By boiling bones in water the gelatine
is readily extracted, and by concentrating the solution and mixing
with it the other ingredients of oil-cake, in a dry state, a compound
or cake might be formed, which would probably feed well, and
might be preserved for any length of time. With this gelatine we
could mix the meal of any grain, or starch of any kind, selecting
that which was cheapest and most easily obtained. The glue of
commerce contains a variable quantity of water—sometimes not
less than a third of its whole weight—were we to employ such glue,
we might take in round numbers—
30 lbs. Glue equal to ............ dry Gelatine, 20 lbs.
Gluten, &c. 6 ...
72 ... Barley-meal equal to Starch, 40 .
Fat, 3 ..
10 ... of Oil or Fat, ... .......................... 10 ...
112 lbs.
so that 1 cwt. of this mixture would, with the addition of 6 lbs. of
bone-meal, be equivalent to 100 lbs. of oil-cake.
But the manufacturers of such an article as this would not use
the glue of commerce; they would prepare their own jelly by
boiling bones, and would save labour and fuel by adding the starch
and fat during the concentration of their glue. The bones would
also yield a certain quantity of oil, and would thus render it un-
necessary to add so large a proportion of this necessary ingredient.
I have said that our knowledge is at present deficient upon some
of the points which are involved in the supposed efficacy of the
above admixture, and that I am not so confident in recommending
the manufacture and use of this as of the other two mixtures. The
point of uncertainty is this. The gelatine contains a larger pro-
portion of nitrogen even than albumen or the other compounds of
protein, and, therefore, may possibly be capable of nourishing the
animal even more than these substances. But its true effect, when
introduced into the stomach of animals, has not yet been fully es-
tablished. It is not certainly known, for example, that the gela-
time will readily form the substance of muscle, because, before do-
ing so, it must undergo a certain chemical change, which the di-
gestive apparatus of the healthy animal may not be able, comfort-
ably and with ease to itself, to effect. This, however, is only a
SUPPOSED FATTENING PROPERTIES OF COMMON SALT. 1057
supposition, supported by certain experiments made in unnatural
conditions, and, therefore, by no means conclusive. From nume-
rous considerations, I think it likely that such a mixture as the
above will resemble oil-cake in its feeding and other properties,
and therefore I recommend it as worthy of a trial.
The mechanical question—how such mixtures could be most
perfectly and cheaply made ; and the economical question—as to
the relative cost of these several mixtures, and of the oil-cakes they
are intended to supersede, I do not enter upon, Every practical
man can easily inquire into and answer these questions for himself.
When beans are low in price, the mixture, if proved on trial to
be equally efficacious, would keep down the price of oil-cake. In-
deed the price of cake would be regulated at all times, more or less,
by that of any substance or mixture which could be efficaciously
used as a substitute for it. x *
§ 18. Of the supposed fattening property of common salt.
It is known that wild animals are fond of salt, and in some
countries eagerly frequent salt-licks for the purpose of obtaining it.
Our domestic animals also are known to relish it, and as the consti-
tuents of common salt are always present in the fluids of the animal
body, it is believed by many to be absolutely necessary, and by
more to be useful, in promoting the health of the stock to which it
is given.
It is the opinion of some also that it has an actual feeding or
fattening tendency, —making the same amount of food go far-
ther in sustaining the life of an animal, or in adding to its weight.
That it has any such direct tendency, however, is rendered very
doubtful by the result of some recent experiments by Boussingault.
He selected a number of heifers, divided them into two lots, and fed
them respectively for forty-four days on the same quantity of food,
giving to the one lot a daily allowance of salt, and to the other
none. At the end of the time, both lots had increased equally in
live weight, and were apparently in equal health.
It does not appear, therefore, that in all circumstances common
Salt is likely to add to the nutritive value of the food with which it
is mixed. There may be circumstances, however, in which the use
of salt may cause animals to increase more rapidly in weight; and
3 x
1058 SUPPOSED FATTENING PROPERTIES OF COMMON SALT.
in reference to this point there are several circumstances which de-
serve the consideration of the practical man.
1°. When animals are fattening, it is often of great consequence
to induce them to consume a large quantity of food in a limited pe-
riod of time. The addition of salt has the effect of giving a relish
to the food, so as to awaken an appetite in an otherwise apparently
satiated beast. It is thus induced to eat, and to perform upon it-
self, though in a less degree, the operation of cramming, by which
poultry are so quickly fattened.
2°. When hay or other similar food becomes musty and offen-
sive to cattle, a sprinkling of salt often removes their dislike, and
induces them to eat what they would otherwise reject. The same
food may in this way also be made to go further.
3°. When salt is given to cattle they are more inclined to
drink; in reality they drink much more water than when no salt
is given. In some cases this may be an advantage, especially when
the water contains any ingredients by which the health of the stock
is likely to be promoted. But the thirst produced by the salt is
often made to act in another way. To cattle tied up to fatten
a lump of Salt is presented, of which, by constant licking, they
consume a large quantity. . But no water is given them, and they
are, therefore, driven, by way of slaking their thirst, to consume a
greater weight of the watery turnip. In this way again the pro-
cess of cramming is promoted, and a speedier fattening ensues.
4°. Lastly.—Though, in the experiment of Boussingault, the use
of salt added nothing to the comparative weight, it may be different
with other kinds of food, and with crops raised in other localities.
Thus it may be assumed that a certain quantity of salt is neces-
sary to the healthy condition of an animal. This salt it obtains
from its food or from its drink. But the quantity of salt in the
food varies with the kind of food, with the soil on which it is grown,
with the manner by which its growth is promoted, and probably with
the proximity or exposure to the sea of the locality in which the
crop is raised. If the soil or manure is rich in common salt, or
if the sea spray freely reach it, the crop may abound in it to such
a degree as readily to supply all that the animal to which it is given
may require. If the contrary is the case, the addition of salt may
be necessary to the perfect health of the animal, and therefore
to its profitable nourishment and growth.
UNLIKE FEEDING QUALITIES OF GREEN GRASS, &C, 1059
The water again of our springs and rivers which always contains
Salt is more or less rich in this substance according as the soil or
rock through which it comes is so, or according as it is near or re-
mote from the sea. Thus in some districts what the food does not
supply the drink may make up, while in others both food and drink
together may leave a deficiency which the practical farmer may
find it advantageous and profitable to supply. Though not directly
fattening, salt may in such cases, by promoting or maintaining the
health of an animal, actually tend to a more rapid increase of its
weight.
§ 19. Of the alleged unlike feeding qualities of green grass and
dried hay.
It is very generally believed that the grass of a field when cut
and given to stall-fed cattle, will go farther than when the cattle
are turned out to crop it for themselves. It is even said that the
produce “of one acre of grass when soiled will go as far as four acres
when pastured, and that one acre of clover cut and used in this way
is equal to six of meadow pasture.” These proportions may not
in all cases be the true ones, but the facts that cattle tread down
the grass in the field, eat more when in the open air, do not crop
the grass uniformly, &c. sufficiently explain why the produce of a
field should go further when soiled than when eaten in the field.
But it is also believed by many that a ton of grass or clover in
the green state will go further—will yield more nutriment, that is
—if eaten green, than if made into hay before it is given to the cattle.
Some say that one ton in the green state will go as far as two tons
when made into hay; a statement which can Scarcely be founded al-
together upon a misconception. It must, one would suppose, have
some true foundation in actual experience.
And this is the more likely, from the circumstance that this
opinion is almost universally entertained among practical men in
foreign countries as well as at home. It is also consistent with
what we know of the chemical nature of the several nutritive sub-
stances which exist in the grasses. As a plant ripens, the starch,
gum, and sugar existing in its sap gradually change into cellular
and woody fibre, which are more insoluble in the stomach than
the starch, and are thus less nutritious. The protein compounds,
* British Husbandry, i. p. 180.
1060 UNLIKE FEEDING QUALITIES GF GREEN GRASS, &c.
also, the albumen, &c., likewise become less soluble, and from these
two classes of changes it arises that fully ripe grass or straw is in
practice found less nutritious as a whole, weight for weight, than
when cut at an earlier period. - .
A similar change is undergone, though perhaps to a less and
more variable extent, during the drying of green herbage after it
is cut. The nutritive matters it contains become less solitble, less
easily digested, and, therefore, in ordinary circumstances, less feed-
ing than in the undried plant. In passing through the digestive
apparatus of an animal, more of it escapes solution, and therefore
the same amount of real food in this dry form is found to produce
less effect, - -
Experience and theory, therefore, are both in favour of the opi-
nion that a given weight of grass or clover should go farther when
eaten green than when previously dried and made into hay.
It is the general persuasion of the correctness of this opinion,
that caused practical men to adopt so many precautions of properly
winning their hay, and to give the preference to the speedily
made green hay of England above the sun baked and bleached hay
of so many parts of Scotland.
It was the same persuasion, also, which suggested the method
now adopted in some parts of Germany, of putting the green grass
in tight pits with alternate layers of salt and straw, and thus pre-
serve it in the green state all the year round.” In this state it is
said to be much more nutritive than when made into hay.
Some experiments, however, have lately been published by Bous-
singault, the result of which is, that the green grass or clover is
not more nutritious than the same weight dried into hay.
He selected a heifer of ten months old as the subject of his ex-
periments, each of which was of ten days duration. Every morn-
ing two equal weights of green clover or grass were cut, of which
the one was given to the animal green, and the other made into
hay, and preserved in a bag by itself till the end of the ten days,
when the experiment with the green food was concluded. The
animal was weighed on the 11th morning fasting, and then the se-
veral portions of dry hay given to it day by day in the order in
* I have described this method in the Quarterly Journal of Agriculture for Octo-
ber 1843. -
+ Annales de Chemie et de Physique, 3d Series, XVII. p. 296.
UNLIKE FEEDING QUALITIES OF GREEN GRAss, &c. 1061
which they had been cut and dried, and the animal weighed again
on the 21st morning fasting. This experiment was repeated twice
with red clover, green and dried, and once with meadow grass and
hay, and the results were as follows. The weight of the animal
before the experiments began was 270 kilogrammes. -
Weight on the Loss or gain
1st. ll the 21st. by green food. Gain by dry food.
1°. Red Clover,................ 270 267 272 — 3 5
2°. Red Clover, ............... 306 301 308 — 5 * 7
3°. Meadow Grass and Hay, 329 333 34.3% + 4 10%
These experiments, showing a constant increase in weight by
the use of dry food, seem to decide that the dry clover and mea-
dow grasses are more mourishing than when green. It was found,
however, by repeated weighings, when upon the same food, that the
weight of the animal sometimes varied as much as 6 kilogrammes.
Upon 5 of the differences in the above table, therefore, no reliance
can be placed, as they may have been derived from circumstances
independent of the food. Hence there remains only the one dif-
ference of 10% in favour of the dry food. - -
I do not think any great reliance is to be placed upon this ap-
parent result in favour of dry food. The experiment was made
only upon one animal, of which the constitution might be peculiar,
and ten days was too short a time to accustom an animal to the al-
ternate extremes of green and dry food. Besides, the hay was
only ten days old, and therefore, supposing it to have been dried in
the same way as an entire crop would have been, it must have been
in a much less hardened condition than if it had been six or twelve
months in stack. And lastly, the laxative effect which green food
given alone often produces upon animals, especially when first fed
upon it, may have been the cause of the less favourable result
from the use of the green grass and clover. -
The question, therefore, remains very much as it was, and, till
more trustworthy experiments show the contrary, it is safer, I think,
to believe that the green crop is really more nutritive in its recent
than in its dried state.
§ 20. Can we correctly estimate the relative feeding properties of
different kinds of produce under all circumstances 2
Since the several nutritive effects of different kinds of food are
dependent upon so many circumstances—upon the state of the ani-
mal itself—the purpose for which it is fed—the mode in which it
1062 EXPERIMENTAL NUTRITIVE WALUES.
is housed and protected—the form and period at which the food is
given—the state of dryness in which it is consumed—can it be pos-
sible to classify them in an order which will indicate their relative
feeding values in all cases and for all purposes.” This is obviously
impossible. We may perhaps arrange them in the order of their
relative values in reference to some one of the several purposes for
which food is given. We may show in as many differentiables
the order of their relative values in laying on fat—in increasing
the muscles—or in promoting the growth of bone; but we cannot
arrange theoretically, nor can experiment ever practically classify,
all our common vegetable productions in one invariable order,
which shall truly represent their relative values in reference to
each of these three different points.
1°. Experimental values.—This, however, practical writers have
often attempted to do. Making their experiments in different cir-
cumstances, with different varieties of the same produce, upon dif-
ferent kinds of stock, or upon animals fed for different purposes,
they have obtained results of the most diversified kind, and have
classified the several kinds of fodder in the most unlike order. I
select a few of the results given by practical men for the sake of
illustration. Taking 10 lbs. of meadow hay as a standard, then,
to produce an equal nutritive effect, the different quantities of each
of the other kinds of fodder represented by the numbers in the
following table ought to be used
whose names are given.
according to the several authors
Experimental quantities of fodder which must be used to produce
an equal nutritive effect, according to—

Schwertz. Block. Petri.
5%aer. Pabst. |Meyer. Middleton.
Meadow hay, ... ......... l () 10 1() 1() l () 10 10
Aftermath hay, ........ | ] gº 8 sº 10 tº º gº º º e e
Clover hay, ............... 10 10 9 9 10
Green clover in flower ) e 43 e sº º 45 42
and lucerne,.........
Lucerne hay, ........... 9 * * * 9 9 10 is a 4.
Wheat straw, ... ... ..... - & & e 20 36 45 30 15
Barley straw, ..... ... ... 40 | 9 18 40 20 15
Oat Straw, ........ ... ... 40 20 20 40 20 15
Pea Straw, ........... ... # s • 16 20 13 15 ] 5
Potatocs, .................. 20 22 20 20 20 | 5
Old potatoes, ............ & º º 40 & sº tº & © & g sº * * e tº $ gº
Carrots, ........... ...... 27 37 25 30 25 23 34
Turnips, ..... * * * * * * * * * * 45 53 60 52 45 20 80
Wheat, .................. 4 3 5 6 tº tº tº e e
Barley,................... 3 6 ge s & 5 5
Oats, ..................... 4 7 e tº º 6
--
THEORIETICAL NUTRITIVE VALUES. I ()63
From an inspection of this table, we should naturally conclude
either that the different kinds of fodder vary very much in quality,
or that those who determined their relative values by experiment
must have tried their effects upon very different kinds of stock, fed
probably also for different purposes. Both of these conclusions
are no doubt true. We know that the same kind of produce does
vary very much in chemical constitution, but it is not likely that
different samples df the same kind of turnip are so unlike each
other that 29 lbs. of one will go as far in feeding the same ani-
mal as 80 lbs. of another. These great differences in the table,
therefore, seem to show that different kinds or varieties of fodder
have been used, or under different circumstances, or results so dis-
cordant could scarcely have been obtained.
A certain value, it is true, attaches to the numbers in the table
when those given by the different authors nearly agree. Thus, about
20 lbs. of potatoes and 30 of carrots appear to be equal in nutritive
value to 10 lbs. of hay. It must be confessed, however, that this
subject of the eagerimental value of different kinds of farm produce
in feeding stock of the same kind for the same purposes is still almost
wholly uninvestigated. Will none of the skilful stock feeders, of
whom so many are now springing up, turn their attention to this
interesting field of experimental enquiry P
2°. Theoretical values.—But the theoretical values of different
kinds of food in reference to a particular object, can be determined
by analytical investigations made in the laboratory. This has been
done in a very able manner by Boussingault, in reference to the
value of different kinds of fodder in the production of muscle. These
values, according to his analyses, are as follow, 10 of hay being
again taken as a standard :—
Theoretical quantities of different kinds of vegetable produce which
will produce equal effects in the growth of muscle (Boussin-
gault):—
Hay,..... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Oat straw, ........................... 55
Clover hay, cut in flower, ......... 8 | Pea straw, ... ................. ... ... 6
Lucerne, do. . . . . . . . . . . . . . . . . . . . . . . 8 || Vetch straw, ........................ 7
Aftermath, do......................... 8 | Potato leaves, ......... .............. 36
Green clover, in flower, ............ 34 || Carrot leaves, ..... • * * * * * * * * * * * * * * | 3
Green lucerne,........................ 35 | Oak leaves, ................. . ...... 13
Wheat straw, .............. ......... 52 | Potatoes, ......... ................ ... 28
Rye straw, ........................... 61 | Old Potatoes, ..... ............ . ... 41
Barley Straw, ........................ 52 | Carrots, ..... ........ ... ..... ...... 35
1064 EFFECT OF MODES OF FEEDING ON THE MANUR.E.
Turnips, .............................. 6] | Rye, ... ................................ 5
White cabbage, ............ ........ 37 | Barley, ... ... ... ....... ........ ...... 6
Vetches, .......... ... e. e. e. e. e º º is a s s tº dº º is e º & 8 2 Oats, ........... ..................... 5
Peas,........ .............. ......... .. 3 | Bran, ................................. 9
Indian corn, .... ................. ... 6 Oil-cake, .............................. 2
Wheat,.................. ........ ... 5
This table possesses much value. It cannot, however, be relied
upon as a safe guide in all cases by the feeder, because of the dif-
ferences in the composition of our crops, which arise from the
mode of culture and the kind of manure employed. But it pos-
sesses a high value from this circumstance—that as muscle in
most animals forms the larger portion of their bulk, the order in
which different kinds of vegetable food promote the growth of this
part of the body, may in most cases be adopted as the order also
of their relative values in sustaining animals and keeping them in
ordinary condition. The same remark, however, will not apply
to all animal food, since we may have a variety of this kind of food,
such as gelatine, which would greatly promote the growth of
muscle, but which, from being unmixed with other substances ne-
cessary to the animal, is capable of ministering so little to the wants
of the other parts of the body that it will not even support life for
any length of time.
§ 21. Effect of different modes of feeding on the manure and on
- the soil. *
There remains still one practical point in connection with the
feeding of stock, to which I think you will feel some interest in
attending.
The production of manure is an object with the European
farmer of almost equal importance with the production of milk or
the fattening of stock. What influence has the mode of feeding
or the purpose for which the animal is fed, upon the quantity and
quality of the manure obtained P
1°. The quantity of the manure depends upon the quantity of
food which is necessary to sustain the animal. With the exception
of the carbon, which escapes from the lungs in the form of car-
bonic acid, and a comparatively small quantity of matter which
forms the perspiration, the whole of the food which sustains the
body is rejected again in the form of dung.
Now the sustaining food increases with the size of the animal,
- 4
IN THE FULL-GROWN AND FATTENING ANIMAL. 1065
with the coldnéss of the temperature in which it is kept, and with
the quantity of exercise it is compelled to take. Large, hardly
worked, much driven, and coldly housed animals, therefore, if ample
food is given them, will produce the largest quantity of manure.
It might be possible, indeed, to keep large animals for no other
purpose but to manufacture manure—by giving them an unlimited
supply of food, using means to persuade them to eat it, and caus-
ing them at the same time to take so much exercise as to prevent
them from ever increasing in weight.
2°. Quality of the manure.—The quality of the manure depends
almost entirely upon the kind of food given to an animal, and upon
the purpose for which it is fed. -
a. The full-grown animal, which does not increase in weight,
returns in its excretions all that it eats. The manure that it forms
is richer in Saline matter and in nitrogen than the food, because,
as I have already explained to you in detail (p. 827), a portion of
the carbon of the latter is sifted out as it were by the lungs, and
diffused through the air during respiration. In other respects,
whatever be the nature of the food—the quantity of saline matter
or of gluten it contains—the dung will contain nearly the same
quantities of both or of their elements.
b. The case of the fattening animal again is different. Besides
the sustaining food, there is given to the animal some other fodder
which will supply an additional quantity of fat. If this additional
food be only oil, then the dung will be little affected by it. It will
be little richer than the dung of the full-grown animal to which
the same sustaining food is given. -
But if the additional food contain other substances besides fat
—saline substances, namely, and gluten—then these will all pass
into the dung and make it richer in precise proportion to the quan-
tity of this additional food which is given. Thus if oil-cake be
given for the purpose of laying on fat—the usual sustaining food
at the same time being supplied—the dung will be enriched by all
those other fertilising constituents present in the oil-cake which
are not required or worked up by the fattening animal.
Hence it is that the dung of fattening stock is usually richer
than that of stock of other kinds. Oil-cake would be a rich ma-
nure were it put into the soil at once; it is not surprising, there-
1066 WHY OLD PASTURES CONTINUE RICH.
fore, that after it has parted with a portion of its oil it should still
add much to the richness of common dung. -
A knowledge of the kind of material, so to speak, which the
animal requires to fatten it, explains in a considerable degree an-
other practical fact of some consequence through which it is not easy
at first sight to see one's way. There are in various parts of the
island certain old pastures which, from time immemorial, have been
celebrated for their fattening qualities. Full-grown stock are
turned upon them year after year in the lean state, and after a few
months are driven off again fat and plump and fit for the butcher.
This, I have been told when on the spot, has gone on time out of
mind, and yet the land, though no manure is artificially added,
never becomes less valuable or the pasture less rich. Hence the
practical man concludes that the addition of manure to the soil is
unnecessary, if the produce be eaten off by stock—that the drop-
pings of the animals which are fed upon the land are alone suffi-
cient to maintain its fertility.
But the reason of this continued richness of such old pastures is
chiefly this—that the cattle, when put upon them, are usually full
grown—they have already obtained their full supply of bone and
nearly as much muscle as they require. While on the fields they
chiefly select fat from the grasses they eat, returning to the soil
the phosphates, Saline substances, and most of the nitrogen which
the grasses contain. Their bodies are no doubt constantly fed or
renewed by new portions of these substances extracted from the
food they eat, but they return to the soil an equal quantity from
the daily waste of their own bodies—and thus they gain from, and
carry off the land, little more than the fat in which they are ob-
served daily to increase. !
But as the materials of the fat may be, and no doubt originally
are, derived wholly—perhaps indirectly, yet wholly—from the at-
mosphere, the land is robbed of nothing in order to supply it, and
thus may continue for many generations to exhibit an equal de-
gree of fertility.
I give this only as a general explanation, by which the difficulty
may be solved, where no other more likely explanation can be
found in the local circumstances of the spot, or of the district in
which such rich old pastures exist.
3
CASE OF THE GROWING ANIMAL AND THE MILK Cow. 1067
c. The growing animal, again, does not return to the soil all it
receives. It not only discharges carbon from its lungs, but it also
extracts phosphates from its food to increase the size of its bones,
gluten to swell out its muscles, and Saline substances to mingle
with the growing bulk of its blood. The dung of the growing
animal, therefore, will not be so rich as that of the full-grown ami-
mal fed upon the same kind and quantity of food. Hence from
the fold-yard, where young stock are reared, the manure will not
be so fertilizing, weight for weight, as from a yard in which full-
grown or fattening animals only are fed.
d. The milk cow exhausts still farther the food it eats. In the
lean milk cow, which has little muscle or fat to waste away, and
therefore little to repair, the sustaining food is reduced to the
smallest possible quantity. This small portion of food is all that
is returned to the husbandman in her dung. The phosphates,
salts, and gluten, and even the starch of the remainder of the food
she eats, are transformed in her system, and appear again in the
form of milk. The dung of the milk cow must be very much
poorer, and less valuable, compared with the food she eats, than
that of any other kind of stock.
It is true that the bulk of her dung may not be very much less
than that of a full-grown animal which is yielding no milk, but
this bulk is made up chiefly of the indigestible woody fibre and
other comparatively useless substances which her bulky food con-
tains. The ingredients of the milk have been separated from these
other substances as the food passed through her body, and hence,
though bulky, the dung of the milk cow is colder and less to be
esteemed than that of the dry cow or of the full-grown ox.
Nothing can more strikingly illustrate the difference between
the effect of the digestive organs of the fattening ox and those of
the milk cow upon the food they consume, than the well-known
and remarkable difference in quality which exists between distillery
dung, obtained from fattening cattle fed upon the refuse of the dis-
tilleries, and coufeeders' dung, voided by milk cows fed upon near-
ly the same kind of food—namely, the refuse of the breweries.
§ 22. Summary of the views illustrated in the present lecture.
The topics discussed in this lecture are of So interesting al kind,
I068 SUMMARY OF THE VIEWS ILLUSTRATED.
and so beautifully connected together, that you will permit me, I
am sure, briefly to draw your attention again to the most import-
ant and leading points.
1°. It appears that all vegetables contain ready formed—that is,
formed during their growth from the food on which they live—those
substances of which the parts of animals are composed.
2°. That from the vegetable food it eats, the animal draws di-
rectly and ready formed the materials of its own body—phosphates
to form the bones—gluten, &c., to build up its muscles—and oil
to lay on in the form of fat.
3°. That during the process of respiration a full grown man
throws off from his lungs about 8 ounces of carbon every 24 hours,
a cow or horse five times as much ; and that the main office of the
starch, gum, and sugar of vegetable food is to supply this carbon.
In carnivorous animals it is supplied by the fat of their food—in
starving animals by the fat of their own bodies—and in young ani-
mals, which live upon milk, by the milk sugar it contains.
4°. That muscles, bones, skin, and hair undergo a certain ne-
cessary daily waste of substance—a portion of each being removed
every day and carried out of the body in the excretions. The
main function of the gluten, the phosphates, and the saline sub-
stances in the food of the full grown animal is to replace the por-
tions of the body which are thus removed, and to sustain its ori-
ginal condition. Exercise increases this natural waste, and accele-
rates the breathing also, so as to render necessary a larger sustain-
ing supply of food—a larger daily quantity to keep the animal in
condition.
5°. That the fat of the body is generally derived from the fat
of the vegetable food—which fat undergoes during digestion a
change or transformation by which it is converted into the peculiar
kinds of fat which are specially fitted to the body of the animal
that eats it. In carnivorous animals, the fat is also derived directly
from the fat of their food—which is, in like manner, changed in
order to adapt it to the constitution of their own bodies. In cases
of emergency, it is probable that fat may be formed in the animal
from the starch or sugar of the food.
6°. In the growing animal, the food has a double function to
perform, it must sustain and it must increase the body. Hence,
DOUBLE FUNCTION OF THE FOOD. I ()69
if the animal be merely increasing in fat, the food, besides what is
necessary to make up for the daily waste of various kinds, must
also supply an additional proportion of oil or fat. To the grow-
ing animal, on the other hand, it must supply also an additional
Quantity of gluten for the muscles, and of phosphates for the bones.
If to each of a number of animals, equal quantities of the same
kind of food be given, then those which require the smallest quantity
of food to sustain them will have the largest proportion to convert
into parts of their own substance. Hence, whatever tends to in-
crease the Sustaining quantity—and cold, exercise, and uneasiness do
so—will tend, in an equal degree, to lessen the value of a given
weight of food, in adding to the weight of the animal’s body.” To
the pregnant and to the milk cow the same remarks apply. The
food is partly expended in the production of milk, and the smaller
and leaner the cow is, less food being required to sustain the body,
the more will remain for the production of milk.
7°. Lastly, that the quantity and quality of the dung—while they
depend in part upon the kind of food with which the animal is fed
—yet even when the same kind of food is given, are materially af-
fected by the purpose for which the animal is fed. If it be full-
grown and merely kept in condition, the dung contains all that was
present in the food, except the carbon that has escaped from the
lungs. If it be a growing animal, then a portion of the phosphates
and gluten of the food are retained to add to its bones and muscles,
and hence the dung is something less in quantity and considerably
inferior in quality to that of the full-grown animal.
So it is in the case of the milk cow, which consumes compara-
tively little in sustaining her own body, but exhausts all the food
that passes through her digestive organs, for the production of the
milk which is to feed her young.
The reverse takes place with the fatening ox. He takes little
else from the rich additional food he eats, but the oil with which
it is intended that he should invest his own body. Its other con-
* It is an important practical fact, however, that the larger the animal becomes
the greater also the necessary quantity of the sustaining food becomes—other circum-
stances of exercise, temperature, &c. being the same. Hence it cannot be so profit-
able to feed animals to a very large as to a moderate size, unless the increased size be
attended also with greater drowsiness or inclimation and opportunity for repose.
I 070 'CONCLUDING SECTION.
stituents are for the most part rejected in his excretions, and hence
the richness and high price of his dung.
Such are the main points I have endeavoured to illustrate to you
in this Lecture—they involve so many interesting considerations,
both of a theoretical and of a practical kind, that had my limits
permitted I could have wished to dwell upon them at still greater
length.
§ 23. Concluding Section.
I have now brought the subject of these Lectures to a close. I
have gone over the whole ground which in the outset I proposed to
tread. It is the first time, I believe, that much of it has been trod-
den by scientific men, and I have endeavoured in every part of our
journey to lay before you, as clearly as I could, everything we knew
of the country we passed over, in so far as it had a practical bear-
ing or was likely to be susceptible hereafter of a practical applica-
tion.
In the first part, I directed your attention to the organic portion
of plants—showed you of what substances it consisted—on what
kind of organic food plants live—and by what chemical changes
the peculiar organic compounds of which they consist are formed
out of the organic food on which they live.
In the second part, I explained in a similar way the nature, com-
position, and origin of the inorganic portion of plants. I dwelt,
also, upon the mature, origin, and natural differences which exist
among the soils on which our crops are grown, and from which the
inorganic constituents of plants are altogether derived. This led
me to explain the connection which exists between Agriculture and
Geology, and the kind of light which this interesting science is fit-
ted to throw upon the means of practically improving the soil.
In the third part, I dwelt upon the various means which may
be adopted for increasing the general productiveness of the land—
whether these means be of a mechanical or chemical nature. The
whole doctrine of manures was here discussed, and many sugges-
tions offered to your notice, which have already led to interesting
practical results.
TOPICS DISCUSSED IN THE SEVERAL PARTS. 107.1
In the fourth part, I explained the chemical composition of the
several kinds of vegetable produce which are usually raised for
food—showed upon what constituents their nutritive values depend
—and how soil, climate, and manure affect their composition and
their value as food. The nature and composition of milk and of
its products—butter and cheese—the theory of their manufacture,
and the circumstances upon which their respective quantities and
qualities depend—and, lastly, the way in which food acts upon and
supports the animal body, and how the value of the manures they
make is dependant upon the purpose for which the animal is fed—
these subjects have also been considered and discussed in this fourth
part. .
In discussing new topics I have had occasion to bring before
you many new views. This, however, I have not done lightly or
without consideration. And as I felt it to be one of the greatest
advantages which attended the periodical form in which the first
edition of these Lectures was brought before the public, that it al-
lowed me leisure to think, to inquire, and to make experiments in
regard to points upon which it was difficult at first to throw any
satisfactory light, so in preparing this new edition I have found
much benefit from the period of reflection and enquiry which the
interval, between the publication of the two editions has allowed
me. It is gratifying to me to know that the general diffusion which
these Lectures, as well as my other works on the subject, have ob-
tained, has already done some service to the agriculture of the
country.
APPENDIX TO PAGE 519.
OF THE EXAMINATION AND ANALYSIS OF SOILS.
Selection of specimens of soils.-In the same field different varieties
of soil often occur, and some recommend that in collecting a specimen
for analysis, portions should be taken from different parts of the field
and mixed together, by which an average quality of soil would be ob-
tained. But this is bad advice, when the soils in different parts of the
field are really unlike. Suppose one part of a field to be clay, and an-
other sandy, as is often the case in this country, and that an average
mixture of them is submitted to analysis, the result you get will apply
neither to the one part of the field nor to the other—that is, it will be
of little or no value. In selecting a specimen of soil, therefore, one or
two pounds should be taken from each of four or five parts of the field
where the soil appears nearly alike ; these should be well-mixed together
and dried in the open air or before the fire. Two separate pounds
should then be taken from the whole for the purpose of analysis, or, if it
is to be sent to a distance, should be tied up in clean strong paper, or,
what is much better, should be enclosed in clean well-corked bottles.
§ I.—OF THE PHYSICAL PROPERTIES OF THE SOIL.
1°. Determination of the density of the soil–In order to determine
the density of the soil, a portion of it must be dried at the temperature
of boiling water (212°), till it ceases to lose weight, or upon a piece of
white paper in an oven at a heat not great enough to render the paper
brown. A common phial or other small bottle perfectly clean and dry
may then be taken, and filled up to a mark made with a file on the neck,
with distilled or pure rain water, and then carefully weighed. Part of
the water may then be poured out of the bottle, and 1000 grains of the
dry soil introduced in its stead ; the bottle must then be well shaken to
allow the air to escape from the pores of the soil, filled up again with
water to the mark on the neck, and again weighed. The weight of the
soil divided by the difference between the weight of the bottle with soil
and water, and the sum of the weights of the soil and the bottle of water
together, gives the specific gravity.
3 Y
1074
Thus, let the bottle with water weigh 2000 grains, and with water
and soil 2600 grains, then—
- - Grains.
The weight of the bottle with water alone = ................................. 2000
The weight of the dry soil ........... ............................. ............... 1000
Sum, being the weight which the bottle with the soil and water would have
had could the soil have been introduced without displacing any, of the | 3000
water
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * e s s is e = e s e s e s e e s e e s e º e = e º e s a e s is e s e s ∈ s e
Difference, being the weight of water taken out to admit 1000 grains of dry
soil .
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * is & tº a tº & º & © º & e º & g º 'º e º s s e º ºs e º g tº s tº £ tº s & s º e | 400
Therefore, 1000 grains of soil have the same bulk as 400 grains of
water, or the soil is 24 times heavier than water, since #9 == 2.5 its
specific gravity.
2°. Determination of the absolute weight.—The absolute weight of
a cubic foot of solid rock is obtained in pounds by multiplying its specific
gravity by 68%–the weight in pounds of a cubic foot of water. But
soils are porous, and contain more or less air in their interstices accord-
ing as their particles are more or less fine, or as they contain more or
less sand or vegetable matter. Fine sands are heaviest, clays next in
order, and peaty soils the lightest. The simplest mode of determining
their absolute weight, therefore, is to weigh an exact imperial half pint
of the soil in any state of dryness, when this weight, multiplied by 150,
will give very nearly the weight of a cubic foot of the soil in that state.
3°. Determination of the relative proportions of gravel, sand, and
clay.—Five hundred grains of the dry soil may be boiled in a flask half
full of water till the particles are thoroughly separated from each other.
Being allowed to stand for a couple of minutes, the water with the fine
matter floating in it may be poured off into another vessel. This may
be repeated several times till it appears that nothing but sand or gravel
remains. This sand and gravel is them to be washed completely out of
the flask, dried, and weighed. Suppose the weight to be 300 grains,
then 60 per cent.* of the soil is sand and gravel. The sand and gravel
are now to be sifted through a gauze sieve more or less fine, when the
gravel and coarse sand are separated, and may be weighed and their
proportions estimated.
These separate portions of gravel and sand should now be moistened
with water and examined carefully with the aid of a microscope, with
* As 500 : 300 : : 100 to 60 per cent.
1075
the view of ascertaining if they are wholly silicious, or if they contain
also fragments of different kinds of rock—sand-stones, slates, granites,
traps, lime-stones, or iron-stones. A few drops of strong muriatic acid
(spirit of salt) should also be added—when the presence of lime-stone
is shown more distinctly by an effervescence, which can be readily per-
ceived by the aid of the glass,—of per-oxide of iron by the brown colour
which the acid speedily assumes,—and of black oxide of manganese by
a distinct smell of chlorine which is easily recognised. In the subequent
description of the soil, these points should be carefully noted.
Suppose the sand and gravel to contain half its weight of fine sand,
then our soil would consist of coarse sand and small stones 30 per cent.,
fine sand 30 per cent, clay and other lighter matters 40 per cent.
4°. Absorbing power of the soil.-A thousand grains of the perfectly
dry soil, crushed to powder, should be spread over a sheet of paper and
exposed to the air for twelve or twenty-four hours, and then weighed.
The increase of weight shows its power of absorbing moisture from the
air. If it amount to 15 or 20 grains, it is so far an indication of great
agricultural capabilities. -
5°. Its power of holding water.—This same portion of soil may now
be put into a funnel upon a double" filter and cold water poured upon
it, drop by drop, till the whole is wet and the water begins to trickle
down the neck of the filter. It may now be covered with a piece of
- glass and allowed to stand for a few hours, occasionally adding a few
drops of water, until there remains no doubt of the whole soil being
perfectly soaked. The two filters and the soil are them to be removed
from the funnel, the filters opened and spread for a few minutes upon
a linen cloth to remove the drops of water which adhere to the paper.
The wet soil and inner filter being now put into one scale, and the outer
filter in the other, and the whole carefully balanced, the true weight of
the wet soil is obtained. Suppose the original thousand grains now to
weigh 1400, then the soil is capable of holding 40 per cent of water.{
69. Rapidity with which the soil dries.—The wet soil with its filter
may now be spread out upon a plate and exposed to the air, in what
may be considered ordinary circumstances of temperature and moisture,
for 4, 12, or 24 hours, and the loss of weight then ascertained. This
will indicate the comparative rapidity with which such a soil would dry,
and the consequent urgent demand for draining, or the contrary. As
great a proportion of the water is said to evaporate from a given weight
* That is, one filter within another.
+ 1000 : 400, the increase of weight as 100 : 40.
1076
of sand saturated with water, in 4 hours, as from an equal weight of
pure clay in 11, and of peat in 17 hours—when placed in the same cir-
cumstances.
7°. Power of absorbing heat from the sun.-In the preceding ex-
periment, a portion of pure quartz sand or of pipe clay may be employed
for the purpose of obtaining a comparative result as to the rapidity of
drying. The same method may be adopted in regard to the power of
the soil to become warm under the influence of the sun's rays. Two
small wooden boxes, containing each a layer of one of the kinds of soil,
two inches in depth, may be exposed to the same sunshine for the same
length of time, and the heat they severally acquire determined by a
thermometer, buried about a quarter of an inch beneath the surface.
Soils are not found to differ so much in the actual temperature they are
capable of attaining under such circumstances—most soils becoming 20°
or 30° warmer than the surrounding air in the time of summer—as in
the relative degree of rapidity with which they acquire this maximum
temperature—and this, as stated in the text, appears to depend chiefly
upon the darkness of their colour. The determination of this quality,
therefore, except as a matter of curiosity, may, at the option of the ex-
perimenter, be dispensed with.
§ II.-OF THE ORGANIC MATTER PRESENT IN THE soil.
19. Determination of the per-centage of organic matter.—The soil
must be thoroughly dried in an oven or otherwise, at a temperature not
higher than between 250° to 3009 F. Humic and ulmic acids will
bear this latter temperature without change. An accurately weighed
portion (100 to 200 grains) must then be burned in the open air, till all
the blackness disappears. This is best done in a small platinum capsule
over an argand spirit or gas lamp. The loss indicates the total weight
of organic matter present. It is scarcely ever possible, however, to ren-
der soils absolutely dry without raising them to a temperature so high
as to char the organic matter present, and hence its weight, as above
determined, will always somewhat exceed the truth, the remaining water
being driven off along with the organic matter when the soil is heated
to redness. This excess, also, will in general be greater in proportion
to the quantity of clay in the soil, since this is the ingredient of most
soils from which the water is expelled with the greatest difficulty.
29. Determination of the humic acid—This acid, whether merely
mixed with the soil, or combined with some of the lime and alumina it
contains, is extracted by boiling with a solution of the common soda of
3
1077
the shops. Into about two ounces by measure of a saturated solution of
this salt, contained in a flask, 300 or 400 grains of soil, previously re-
duced to coarse powder, are introduced, an equal bulk of water added,
and the whole boiled or digested on the sand bath with occasional shak-
ing for an hour. The flask is then removed from the fire, filled up with
water, well shaken, and the particles of soil afterwards allowed to sub-
side. The clear liquid is then poured off. If it has a brown colour it
has taken up some humic acid. In this case the process must be re-
peated once or twice with fresh portions of the soda solution, till the
whole of the soluble organic matter appears by the pale colour of the
solution to be taken up. These coloured solutions are then to be mixed
and filtered. This filtering generally occupies considerable time, the
humic and ulmic acids clogging up the pores of the filter in a remark-
able manner, and permitting the liquid to pass through sometimes with
extreme slowness.
When filtered, muriatic acid is to be slowly added to the coloured li-
quid—which should be kept in motion by a glass rod—till effervescence
ceases, and the whole has become distinctly sour. On being set aside
the humic acid falls in brown flocks. A filter is now to be dried and
carefully weighed,” the liquid filtered through it, and the humic acid
thus collected. It must be washed in the filter with pure water—ren-
dered slightly sour by muriatic acidt—till all the soda is separated from
it, when it is to be dried in the filter at 250° F., till it ceases to lose
weight. The final weight, minus that of the filter, gives the quantity
of humic acid contained in the portion of soil submitted to examination.
As it is rarely possible to wash the humic acid perfectly upon the filter,
rigorous accuracy requires that the filter and acid should be burned after
being weighed, and the weight of ash left, minus the known weight of
ash left by the filter,S deducted from that of the acid as previously de-
* This is best effected by putting the filter into a covered porcelain crucible of
known weight, and heating it for ten minutes over a lamp or otherwise, at a tempera-
ture which just does not discolour the paſper, allowing then the crucible to cool under
cover, and when cold weighing it. The increase above the known weight of the cru-
cible is that of the filter, which, besides being recorded in the experiment book,
should also be marked in several places on the edge of the filter with a black lead
pencil.
f This is to prevent in some measure the humic acid from passing through the fil-
ter, which it is very apt to do, when the saline matter is nearly washed out of it.
† This is ascertained by collecting a few drops of what is passing through upon a
piece of clean glass or platinum, and drying them over the lamp, when, if a perceptible
stain or spot is left, the substance is not sufficiently washed. -
§ The ash left by the paper employed for filters should always be known. This is
ascertained, once for all, by drying a quantity of it in the way described in the pre-
1078
termined. It is to be observed here that by this, which is really the
only available method we possess of estimating the humic acid, a cer-
tain amount of loss arises from its not being wholly insoluble, the acid
liquid which passes through the filter being always more or less of a
brown colour.* -
8". Determination of the insoluble humus-Many soils after this
treatment with carbonate of soda are still more or less of a brown colour,
evidently due to the presence of other organic matter. To separate this,
Sprengel recommends to boil the soil, which has been treated with car-
bonate of soda, and which we suppose still to remain in the flask, with a
solution of caustic potash, repeated, if necessary, as in the case of the
soda solution. By this boiling, he states that the vegetable matter,
which was insoluble in the carbonate of soda, is changed in constitution
and dissolves in the caustic potash, giving a brown solution, from which
it may be separated in brown flocks by the addition of muriatic acid, and
then collected and weighed as above described. I doubt, however, if
all the insoluble humus, as it is called, is rendered soluble by this action
of caustic potash. .
Fn some soils, also, distinct portions of vegetable fibre, such as por-
tions of roots, &c., are present, and may be separated mechanically, dried,
and weighed. -
4". Of other organic substances present in the soil.-The sum of the
weights of the above substances deducted from the whole weight of or-
ganic matter, as determined by burning, gives that of other organic sub-
stances present in the soil. The quantity of these, though in general
comparatively small, is yet sometimes very large, especially when the
soil contains much per-oxide of iron, and, unless they are soluble in wa-
ter, there is no easy method of separating them, and determining their
weight. The following two methods, however, may be resorted to :—
a. Half a pound or more of the moist soil may be boiled with two
separate pints of distilled water, the liquid filtered and evaporated to a
small bulk. From clay soils, when thus boiled with water, the fine par-
ticles do not readily subside. Sometimes, after standing for several days,
the water is still muddy, and passes muddy through the filter, but, after
vious note, weighing it in this dry state, burning it, and again weighing the ash that is
left. In good filtering paper, the ash ought not to exceed one per cent.
* The portion which thus remains in solution may be precipitated by adding a small
quantity of a solution of alum, and afterwards pouring in ammonia in excess. The
alumina falls coloured by the organic matter, and after being collected on a filter,
washed, and dried, the weight of organic matter in the precipitate may be determined
approximately as deseribed under 12° (2*). -
I 0.79
being evaporated, as above recommended, to a small bulk, most of the
fine clayey matter remains on the paper when it is again filtered. As
soon as it has thus passed through clear, the liquid may be evaporated
to perfect dryness at 250° F., and weighed. Being now treated with
water—a portion will be dissolved—this must be poured off, and the in-
soluble remainder again perfectly dried and weighed. If this remainder
be now heated to redness in the air, any organic matter it contains will
be burned off, and its weight ascertained by the loss on again weighing.
This loss may be considered as humic acid rendered insoluble by dry-
ing.” It does not require to be added to the weight of humic acid al-
ready determined (10%), because in that experiment a portion of soil was
employed which had not been boiled in water, and from which therefore
the carbonate of soda would at once extract all the humic acid. The
present experiment need only be made when it is desirable to ascertain
how much humic acid a soil contains in a state in which it is soluble in
water. Where ammonia, potash, or soda is present in the soil, some che-
mists consider this quantity to be very considerable, and to exercise an
important influence upon vegetation.
That which was taken up by water from the dried residuum is again
to be evaporated to dryness, dried at 150°, weighed, and burned at a
łow red heat. The loss is organic matter, and may have been crenic
or apocrenic, or some other of the organic acids formed in soils, the
compounds of which, with lime, alumina, and prot-oxide of iron, are
soluble in water. If any little sparkling or burning like match-paper be
observed during this heating to redness, it may be considered as an in-
dication of the presence of nitric acid—in the form of nitrate of potash,
soda, or lime. In this case the loss by burning will slightly exceed
the true amount of organic matter present, owing to the decomposition
"and escape of the nitric acid also. The mode of estimating the quan-
tity of this acid, when it is present in any sensible proportion, will be
hereafter described.
b. The caustic potash employed to dissolve the insoluble humus (119)
takes up also any alumina which may have been in combination with the
humic acid or may still remain united to the apocrenic, the mudesous,t
or other organic acids. When the solution is filtered and the humic
acid separated by the addition of muriatic acid till the liquid has a dis-
* It may also partly be apocrenic acid, especially if there be any iron in the ash
which remains.
f Except where gypsum is present in the insoluble portion, which is not unfre-
quently the case, when the loss will be partly water—since gypsum, after being dried
at 250°, loses still about 20.8 per cent. of water when heated to redness.
T 080
tinctly sour taste, this alumina, and the acids with which it is in com-
bination, still remain in solution. After the brown flocks of humic acid,
however, are collected on the filter, the alumina may be thrown down
from the filtered solution by adding caustic ammonia to the sour liquid,
until it has a distinctly ammoniacal smell. The light precipitate which
falls must be collected on a filter and washed with hot water till the
potash is as completely separated as possible. It is then to be dried at
300° F. and weighed—heated for some time in a close crucible over the
lamp, at a temperature which begins to discolour it, and again weighed.
Being now burned in the air till it is quite white, and weighed, the last
loss may be considered as mudesous or some similar acid. *
The reason why this second method of drying over the lamp is here
recommended, is, that alumina and nearly all its compounds part with
their water with great difficulty, and even with the precautions above
indicated, it is not unlikely that a larger per-centage of organic mat-
ter may thus be indicated than in reality exists in the soil. The check
which the accurate experimenter has upon all these determinations is
this, that the sum of the several weights of the humic acid, the insoluble
humus, the vegetable fibre, and of the crenic, apocrenic, and mudesous
acids, if present, should be somewhat less than that of the whole com-
bustible organic matter, as determined by burning the dry soil in the
open air (9%). This quantity we have seen to be in most cases greater
than the truth, because any remaining water or any mitric acid the soil
may contain are at the same time driven off. -
I may further remark upon this subject that the quantity of alumina
thus dissolved by the caustic potash is in most soils very small, and
the quantity of organic matter by which it is accompanied in many cases
so minute, that the determination of it may be considered as a matter of
curiosity, rather than one of practical importance.
§ III.-QUALITATIVE DETERMINATION OF THE SOLUBLE SALINE
MATTER IN THE SOIL.
With a view to determine the nature of the soluble saline matter in
the soil, a preliminary experiment must be made. An unweighed por-
tion must be introduced into five or six ounces of boiling distilled water
in a flask, and kept at a boiling temperature, with occasional shaking,
for a quarter of an hour. It may then be allowed to subside, after
which the liquid is to be filtered till it passes through clear. It is then
to be tested in the following manner. Small separate portions are to be
put into so many clean wine glasses, and the effect produced upon these
by different chemical substances carefully noted. If with a few drops of
1081
1. Nitrate of Baryta, it gives a white powdery precipitate, which
does not disappear on the addition of nitric or muriatic acid, the
solution contains sulphuric acid. If the precipitate does disap-
pear, it contains carbonic acid. In this latter case, the liquid will
also effervesce on the addition of either of the acids above men-
tioned.
2. If with ovalate of ammonia it gives either immediately, or after a
time, a white cloud, it contains lime,” and the greater the milkiness,
the larger the quantity of lime may be presumed to be.
3. If with nitrate of silver it gives a white curdy precipitate, insolu-
ble in pure nitric acid, and speedily becoming purple in the sum, it
may be presumed to contain chlorime.
5. If with caustic ammonia it gives a pure white gelatinous precipi-
tate, it contains either alumina or magnesia, or both. In this
case, muriatic acid must be added till the precipitate disappears,
and the solution is distinctly acid. If on the addition of ammonia
in excess, the precipitate re-appears undiminished in quantity, it
contains alumina only. If it is distinctly less in quantity, we
may infer the presence of both magnesia and alumina ; and if no
precipitate now appears, that it contains magnesia only. If a large
quantity of magnesia is present, it may be necessary to re-dissolve
and acidify the solution a second time. On the re-addition of am-
monia the precipitate would entirely disappear.
If the precipitate, by ammonia, has more or less of a brown
colour, the presence of iron, and perhaps manganese, may be in-
ferred. If, on the second addition of ammonia, the colour of the
precipitate has disappeared, it has been due to manganese only—
if it still continues brown, it is owing chiefly or altogether to the
presence of oxide of iron. If the colour of the precipitate produ-
ced by ammonia is very dark, it consists almost entirely of oxide
of iron, and may contain little or no alumina, when it is only more
or less brown, the presence of both alumina and oxide of iron may
with certainty be inferred.
5. If, after the first addition of ammonia, the solution be filtered to
separate the alumina, the oxides of iron and manganese, and the
magnesia that may be thrown down—if oxalate of ammonia be
then added till all the lime falls, and the liquid be again filtered,
* The learned reader will understand why, for the sake of simplicity, I take no no-
tice of substances not likely to be present in the soil—as, for example, baryta, which
would here be thrown down along with the lime, or of oxalic acid, which, equally with
the sulphuric or carbonic (a), would give a white precipitate with nitrate of baryta.
- 1082
evaporated to dryness, and then heated to incipient redness in the
air, till the excess of oxalate of ammonia is destroyed and driven off
—and if a soluble residue then remains,” it is probable that potash
or soda, or both, are present. If, on dissolving this residue in a
very little water, the addition of a few drops of a solution of tartaric
acid to it produces a deposit of small colourless crystals (of cream
of tartar), or if a drop of a solution of bi-chloride of platinum pro-
duces in a short time a yellow powdery precipitate, it contains pot-
ash. If no precipitate is produced by either of these—re-agents
as they are called—the presence of soda may be inferred. If the
yellow precipitate, containing potash and platinum, be separated by
a filter, and the solution, after being treated with sulphuretted hy-
drogen, and filtered to separate the excess of bi-chloride of plati-
num, be evaporated to dryness—if, then, a soluble saline residue
still remains, the solution contains soda as well as potash.
It is to be observed, that some magnesia, if present, may accom-
pany the potash and soda through these several processes. After
the separation of the potash, a little caustic ammonia will detect
the presence of magnesia, but it will rarely be found so far to in-
terfere with this preliminary examination as to prevent the experi-
menter from arriving at correct results (see p. 12, f)
6. If the addition of bi-chloride of platinum to the solution directly
filtered from the soil gives a yellow precipitate, it contains either
potash or ammonia. If, when collected on the filter, dried, and
heated to bright redness in the air, white fumes are given off by .
this yellow precipitate, and only a spongy mass of metallic platinum
remains behind, the solution contains ammonia only. If, with the
platimum, is mixed a portion of a soluble substance having a taste
like that of common salt, and giving again a yellow precipitate with
bi-chloride of platinum, it contains potash—and if the spongy pla-
timum contained in the burned mass, after prolonged heating,
amounts to more than 57 per cent. of its weight, or if it is to the
soluble matter in a higher proportion than that of 4 to 3, the solu-
tion contains both potash and ammonia.
The presence of ammonia in the saline substance, or in the con-
centrated solution, is more readily detected by adding a few drops
of a solution of caustic potash, when the smell of ammonia be-
comes perceptible, or if in too small quantity to be detected by the
* Not precipitated from its solution by ammonia, for if precipitated it is partly at
least chloride of magnesium.
1083
smell, it will, if present, restore the blue colour to reddened litmus
paper. This experiment is best made in a small tube.
. If, when the solution, obtained directly from the soil, is evapo-
rated to dryness, and the residue heated to redness in the air, a
deflagration or burning like match-paper is observed, nitric acid
is present. Or if the dry mass, when put into a test tube with a
little muriatic acid, evolves distinct red fumes on being heated, or
enables the muriatic acid to dissolve gold-dust, and form a yellow
solution; or, if to a colourless solution of green vitriol (sulphate
of iron), introduced into the tube along with the muriatic acid, it
imparts more or less of a brown colour—in any of these cases the
presence of nitric acid may with certainty be inferred. It will be
only on rare occasions, however, that salts, so soluble as the ni-
trates, will be found in sensible quantity in the small portion of a
soil likely to be employed in these preliminary experiments.
. If ammonia throws down mothing (see under 4) from the solution,
and if no precipitate appears when chloride of calcium or magnesium
is afterwards added, the solution contains no phosphoric acid. But
if ammonia causes a precipitate, and after this is separated by the
filter, if nothing further falls on adding either of the above chlo-
rides, the phosphoric acid, if any is present, will be contained in the
precipitate which is upon the filter. Let this, after being well
washed with distilled water, be dissolved off with a little pure mi-
tric acid diluted with water, and then neutralised as exactly as
possible with ammonia. If a solution of acetate (sugar) of lead
now throws down a white precipitate, phosphoric acid is present.
The phosphate of lead—the white precipitate which falls—melts
readily before the blowpipe, and, on cooling, crystallises into a bead
with beautiful crystalline facets. -
Or—if the precipitate thrown down by ammonia is wholly or
in part insoluble in pure acetic acid (vinegar,) that which is undis-
solved contains phosphoric acid in combination with iron. If ace-
tic acid dissolves the whole, it may be inferred that no phosphoric
acid is present in the soil.
But if no precipitate is thrown down by ammonia, instead of the
chloride of calcium above recommended a few drops of a dilute
solution of sulphate of peroxide of iron may be mixed with the
solution, after adding the ammonia, and the whole well shaken. If
the precipitate which now falls dissolves wholly in acetic acid, no
phosphoric acid is present, and vice versa.
1084
These preliminary trials being made, notes should be kept of all the
appearances presented, as the method to be adopted for separating and
determining the weight of each substance will depend upon the number
and nature of those which are actually found to be present.
§ IV. DETERMINATION OF THE QUAN TITIES OF THE SEVERAL
CONSTITUENTS OF THE SOL UB L E SA LIN E MATTER.
The quantity of soluble saline matter extracted from a moderate quan-
tity of any of our soils is rarely so great as to admit of a rigorous ama-
lysis, and the preceding determination of the kind of substances it con-
tains will be in most cases sufficient. Cases may occur, however, as in
some soils from warm climates, in which much saline matter may be
obtained ; it will be proper, therefore, briefly to state the methods by
which the respective quantities of each constituent may be accurately
determined.
1°. Estimation of the Sulphuric Acid.—The solution being gently
warmed, a few drops of nitric acid are to be added until the solution
is slightly acid, and any carbonic acid that may be present is ex-
pelled, after which mitrate of baryta is to be added to the solution
as long as any thing falls. The white precipitate (sulphate of ba-
ryta) is them to be collected on a weighed filter, well washed with
distilled water, dried over boiling water as long as it loses weight,
and them weighed. The weight of the filter being deducted,”
every 100 grains of the dry powder are equal to 34:37 grains of
sulphuric acid.
2. Estimation of the Chlorine,—The solution of mitrate of silver
must be added as long as any precipitate falls, the precipitate then
washed, dried at 212° F., and weighed as before. Every 100 grs.
of chloride of silver indicate 24.67 grs. of chlorime, or 40.88 grs.
of common salt.
3. Estimation of the Lime.—A little diluted muriatic acid being
added to throw down the excess of silver, and a little sulphuric
acid to separate the excess of baryta, added in the former opera-
tions, and the precipitates separated by filtration—caustic ammonia
is to be poured in till the solution is distinctly alkaline. If no pre-
cipitate falls, oxalate of ammonia is to be added as long as any white
powder appears to be produced. The solution must then be left
* Or the whole may be heated to redness in the air, and the filter burned away. In
this case the weight of ash left by the paper must be ascertained by previous trials, and
the due proportion deducted from the weight of the sulphate.
1085
to stand over might—that the whole of the lime may separate,_
the white powder afterwards collected on a filter, washed, dried,
and burned with the filter at a low red heat. The grey powder .
obtained is carbonate of lime, every 100 grains of which contain
43.71 grains of lime.
4. Estimation of the Owide of Iron and of the Alumina-But if a
precipitate falls on the addition of ammonia, as above prescribed—
the solution may contain magnesia, alumina, and the oxides of iron
and manganese. In this case the precipitate is to be re-dissolved
by the addition of muriatic acid till it is distinctly acid, a little ni-
tric acid added, and the liquid heated to peroxidize the iron, and
then ammonia added in slight excess. If any precipitate now falls,
it will consist only of alumina and peroxide of iron, unless magne-
sia and oxide of manganese be present in large proportion, when a
variable quantity of each may fall at the same time.
The precipitate is to be collected on the filter as quickly as possible,
—the funnel being at the same time covered with a plate of glass
to prevent as much as possible the access of the air, washed with
distilled water, and then re-dissolved in muriatic acid. This is best
effected by spreading out the filter in a small porcelain dish, adding
dilute acid till all is dissolved, and then washing the paper well
with distilled water. A solution of caustic potash added in earcess
will at first throw down both the oxide of iron and alumina, but
will afterwards, on being gently heated for some time, re-dissolve
the alumina, and leave only the oxide of iron. This is to be col-
lected on a filter, re-dissolved in muriatic acid, precipitated by am-
monia, collected on a filter, washed, dried, heated to redness, and
weighed. Every 100 grains of this peroxide of iron are equal to
89.78 grains of protoxide, in which state it has most probably ex-
isted in the original solution.
To the potash solution muriatic acid is added till the alkali is sa-
turated, or till the solution reddens litmus paper,” when the addi-
tion of ammonia precipitates the alumina. As it is difficult to wash
this precipitate perfectly free from potash, it is better to dissolve it
again in muriatic acid, as was done with the peroxide of iron, and
to re-precipitate it by caustic ammonia. When well washed, dried,
and weighed, this precipitate gives the true quantity of alumina
present in the portion of Salt submitted to analysis.
* Litmus paper is paper stained by dipping it into a solution of litmus, a vegetable
blue colour, prepared and sold for the purpose of detecting the presence of free acids,
by which it is reddened.
1086
5. Separation of the two ovides of iron.—Both oxides of iron exist
together in nearly all soils, mixed together in various proportions.
The simplest method of separating them, though it requires to be
done with considerable care, is as follows:—
A piece of chalk or lime-stone is introduced into a flask with a
long neck, into which a cork can readily be fitted, and diluted mu-
riatic acid poured upon it. The chalk is dissolved, and carbonic acid
is given of in sufficient quantity to expel the common air, and to fill
the flask with carbonic acid. A cork is then put lightly into the neck
of the flask, or it is closed with the finger inverted, and the solution
allowed to flow out, so as to leave the flask filled with carbonic acid,
mixed with as little common air as possible. It will do no harm
that a little of the lime solution moisten the interior of the flask.
A weighed portion of the soil is now to be introduced into the
flask, muriatic acid poured upon it, and the whole digested in the
usual way till the oxides of iron are all dissolved. Bits of chalk
are now to be introduced in excess, and the whole boiled. By this
means any per-oxide which the solution contains will be precipitated
by the lime of the chalk, while the whole of the prot-oxide will re-
main in solution. The flask is now to be filled with boiling dis-
tilled water, corked carefully, and the whole allowed to settle and
become clear. The solution is them decanted or filtered rapidly if
necessary, and the insoluble matter washed with distilled water.
The solution contains all the iron which the weighed portion of soil
contained in the state of prot-oxide. It is boiled with a little nitric
acid to convert the iron into per-oxide, which is then thrown down
by ammonia, collected, washed, dried, and weighed. The weight
of this portion deducted from that of the whole iron estimated by
the previous process in the state of per-oxide, gives the proportion
which exists in the soil in the state of prot-oxide. A hundred parts
of prot-oxide of iron are equal to 111:39 of per-oxide.
6. Estimation of the Manganese.—To the ammoniacal solutions from
which the oxalate of lime has been precipitated (3°) a solution of
hydro-sulphuret of ammonia is to be added. The manganese will
fall in the form of a flesh-red sulphuret. When this precipitate has
fully subsided, it must be collected on the filter and washed with
water containing a very little hydro-sulphuret of ammonia. The
filter is then put into a glass or porcelain basin, the precipitate dis-
solved off by dilute muriatic acid, and the solution filtered if neces-
sary. A solution of carbonate of potash then throws down carbo-
4
1087
mate of manganese, which is collected on the filter, washed, dried,
and heated to redness in the air. Of the brown powder obtained
100 grains indicate the presence of 93-84 grains of protoxide of
manganese in the salt or solution under examination.
. Estimation of the Magnesia-—If no potash or soda be present in
the residual solution, the determination of the magnesia is easy. A
few drops of muriatic acid are added, and the whole gently heated,
and afterwards filtered, to separate the sulphur of the excess of hy-
dro-sulphuret of ammonia previously added. The solution is then
evaporated to dryness, and the dry mass heated to redness to drive
off all the ammoniacal salts previously added. A few drops of di-
luted sulphuric acid are added to what remains, to change the whole
of the magnesia into sulphate, the mass again heated to redness and
weighed. One hundred grains of this sulphate indicate the presence
of 34-01 grains of pure magnesia. -
But if potash or soda be present—the weight of which it is de-
sirable to determine—the simplest method is to take a fresh portion,
15 to 20 grains, of the saline matter under examination. If any sul-
phuric acid is present in it, add nitrate of baryta drop by drop to the
solution till the whole of the acid is exactly thrown down—avoiding,
if possible, any excess of baryta being left in the solution—then preci-
pitate the alumina, and oxides of iron, and manganese, and the lime,
if any of these be present, and, finally evaporate to dryness and heat
to redness as before. The dry mass is now to be dissolved in water,
adding, if necessary to complete the solution, a few drops of muriatic
acid. A quantity of red oxide of mercury is then to be added to the
concentrated solution, the whole boiled down to dryness, and the
dry mass gradually heated to dull redness. The mercury is vola-
tilized in the state of corrosive sublimate, carrying with it the chlo-
rine which had been combined with the magnesia. Water now dis-
solves out the potash and soda only, and leaves the magnesia in the
caustic state. This is to be collected on a filter, washed—not with
too much water—heated to redness, and weighed.
. Estimation of the Potash and Soda.-The solution containing the
potash and soda is to be evaporated to dryness, and heated to red-
ness to drive off any mercury it may contain. The weight of the
mass, which consists of a mixture of chloride of potassium with chlo-
ride of sodium (common salt), is accurately determined ; it is then
dissolved in a small quantity of water, and a solution of bi-chloride
of platinum added to it in sufficient quantity. Being evaporated
1088
by a very gentle heat nearly to dryness, weak alcohol is added,
which dissolves the chloride of sodium and any excess of salt of
platinum which may be present. The yellow powder is collected
on a weighed filter, washed well with alcohol, dried by the heat
of boiling water, and weighed on the filter. Every 100 grains indi-
cate the presence of 19-33 grains of potash, or 30.56 grains of chlo-
ride of potassium. g
The quantity of chloride of sodium is estimated from the loss.
The weight of the chloride of potassium above found is deducted
from that of the mixed chlorides previously ascertained; the re-
mainder is the weight of the chloride of sodium. Every 100 grains
of chloride of sodium (common salt) are equivalent to 53-29 of
soda. . - tº;
9. Estimation of the Ammonia.—If ammonia is present in the solu-
tion along with potash and other substances, the method by
which it can be most easily estimated is to introduce the solu-
tion as it is obtained by the action of the acid upon the soil, into
a large tubulated retort, to add water until the solution amounts to
nearly an English pint—then to introduce a quantity of caustic pot-
ash or caustic baryta, till the solution is distinctly alkaline, and to ,
distilby a gentle heat into a close receiver, containing a little dilute
muriatic acid, until fully one-half has passed over. Bi-chloride of
platinum is then to be added to the solution which has come over,
previously rendered slightly acid by muriatic acid, and the whole
evaporated nearly to dryness by a very gentle heat. Dilute alco-
hol is then added to wash out the excess of the salt of platinum,
and the yellow powder is collected on a filter, washed with alcohol,
dried by a very gentle heat, and weighed. One hundred grains in-
dicate the presence of 7-69 grains of ammonia. -
Or the yellow powder, without being so carefully dried, may be
heated to redness, when only metallic platinum will remain. One
hundred grains of this metallic platinum indicate the presence of
17.39 grains-of ammonia.
10. Estimation of the Phosphoric Acid.-If phosphoric acid is pre-
sent in the solution, it will be contained in the precipitate thrown
down by ammonia (4). As it will never be found but in very small
quantity, the rigorous determination of its amount is a matter of con-
siderable difficulty. The following method in addition to or in place
of those already described (§ III. 8) may be adopted. The preci-
pitated alumina, oxide of iron, &c., thrown down by ammonia, after
1089
being dried, may be mixed with three times their weight of pure
dry carbonate of soda, and fused together in a platinum crucible,
and the fused mass then treated with cold distilled water till every
thing soluble is taken up. The filtered solution is next to be gently
heated and exactly neutralised with nitric acid, when a solution of ni-
trate of silver will throw down a white precipitate of phosphate of
silver, which is to be collected, dried, and weighed. Every hundred
grains of it are equal to 23:51 of phosphoric acid, or 48-50 of bone
earth.
Or the filtered solution may be treated with muriatic acid, am-
monia added in excess, and then a solution of chloride of calcium.
Bone earth will fall, which is to be collected, washed, heated to red-
ness, and weighed. One hundred grains of it contain 48.45 of phos-
phoric acid. The former method is probably the better, but neither
of them will give more than an approximation to the truth.
That portion of the fused mass which cold water has refused to
take up is to be dissolved in muriatic acid, and again precipitated by
ammonia. The clear solution which passes through is to be added
to the first ammoniacal solution (3), from which the lime is not yet
thrown down, as, when little alumina and oxide of iron are present,
a small portion of lime and magnesia, if contained in the salt under
examination, may have fallen along with them in combination with
phosphoric acid. . - -
The alumina and oxide of iron which rest on the filter are to be
separated and estimated as already described (4.)
11. Estimation of the Carbonic Acid.—The lime and magnesia dis-
solved by cold diluted muriatic acid are partly in combination with
carbonic acid and partly with the humic, ulmic, and other vegetable
acids. To determine the carbonic acid, 100 grains of the soil, dried
at 212°, are to be introduced into a small weighed flask, and then
just covered by a weighed quantity of cold diluted muriatic acid.
After 12 hours, when the action has ceased, a small tube is to be
introduced into the flask and air sucked through it till the whole
of the carbonic acid is drawn out of the flask. The loss of weight
will indicate the amount of carbonic acid very nearly. It will give
the amount of carbonic acid rather above the truth. It would
be more rigorously ascertained by fitting into the mouth of the flask
a tube containing chloride of calcium, and then heating the solution
to expel the carbonic acid. - -
Every hundred grains of carbonic acid indicate the presence of
3 Z
1090
77-24 grains of lime in the state of carbonate. The weight of lime
in this state, deducted from the whole weight obtained as above
(3), gives the quantity which is in combination with other organic
acids.
§ IV.--OF THE IN SOL UB LE EARTHY MATTER OF THE SOIL.
1°. When the soil has been washed with distilled water as above di-
rected, it is to be treated in the cold with diluted muriatic acid, and
allowed to stand with occasional stirring for 12 hours. By this means
the carbonates of lime, magnesia, and iron, and the phosphates of lime
and alumina are dissolved—with any lime, magnesia, oxide of iron, or
alumina, which may have been in combination with organic acids. The
iron, alumina, and phosphoric acid are to be precipitated by ammonia,
the lime by oxalate of ammonia, and such other steps taken as may be
necessary, according to the methods already described. .
2°. The undissolved portion may now be treated with hot concentrat-
ed muriatic acid, kept warm and occasionally stirred for two or three
hours, and the solution afterwards evaporated to dryness. The dry
matter is then to be moistened with a few drops of muriatic acid, and
subsequently treated with water. What remains undissolved is silica,
which must be collected on a filter, dried, heated to redness, and weighed.
The solution may contain oxide of iron, alumina, lime, magnesia, pot-
ash, and soda. Any of the four last substances, which may be detected
in it, have most probably existed in the soil, in combination with silica
—in the state of silicates.
3°. But the soil may still contain alumina, not soluble in hot muriatic
acid. To ascertain if this be the case, and, to separate and determine
this portion of the alumina, if present, either of two methods may be
adopted. -
a. The residual soil may be drenched with concentrated sulphuric
acid and heated for a considerable time in a loosely covered plati-
num crucible, till the sulphuric acid is nearly all driven off. On
treating with water, and adding ammonia to the filtered solution,
alumina, and oxide of iron, if any have been present, will be thrown
down. If any alumina be thus separated, the treatment with sul-
phuric acid must be repeated, till, on treating with water and am-
monia, as before, no more alumina appears.
b. Or that portion of the soil on which hot muriatic acid refuses to
act may be mixed with twice its weight of carbonate of soda, and
heated in a platinum crucible till the whole is completely fused
3
1091.
The mass is then to be treated with diluted muriatic acid till every
thing soluble is taken up ;-the imsoluble matter is silica. The fil-
tered solution is to be evaporated to dryness, the dry mass moisten-
ed with muriatic acid, and again treated with water. If anything
is left undissolved it will be silica, which must be added to that
previously obtained, and if any alumina be contained in the solu-
tion, it will be precipitated by ammonia, and may be collected, wash-
ed, dried, and weighed, as already described. The solution may
also be tested for magnesia, and if any be present it may be sepa-
rated by the process already described. -
The former of these two methods is to be preferred as the simpler,
though it also will require considerable care and attention. That which
the sulphuric acid leaves behind must be washed, dried, heated to red-
mess, and weighed. It will be found to consist chiefly of quartz sand,
and finely divided silicious matter.
The accuracy and care with which the whole of these processes have
been conducted, is tested by adding together the weights of the several
substances that have been separately obtained. If this sum does not
differ more than one per cent, from the weight of the soil employed, the
results may be considered as deserving of confidence. One of the points
in which a beginner is most liable to err is in the washing of the several
precipitates he collects upon his filters. As this is a tedious operation,
he is very likely to wash them, at first, only imperfectly, and thus to
have an excess of weight when his quantities are added together—
whereas a small loss is almost unavoidable. The precipitates should al-
ways be washed with distilled water, and the washing continued till a
drop of what passes through leaves no stain when dried upon a bit of
glass or on a bright platinum spatula.
The following scheme exhibits the successive steps which are to be taken in order to separate the several inorganic substances or bases from the so-
• - lution in muriatic acid by the methods above described. -
Digest the soil in distilled water, dry at 250°, weigh, digest with dilute muriatic acid for 12 hours, and filter the solution. This solution should be
decidedly sour, and may contain lime, magnesia, alumina, oxide of iron, oxide of manganese, potash, soda, and phosphoric acid.
A.
9 To the clear solution add oxalate of ammonia, and cover it from the air.
-A-
1 Add caustic ammonia in excess.
N.
2 Oxide of iron, alumina, and phosphoric acid are precipi-
tated. Digest in acetic acid.
will fall, p. 47.
ll Add hydrosulphuret of ammonia.
13 Render sour by muriatic
acid, boil, filter, evapo-
rate to dryness, and heat
to incipient redness to
drive off all the ammo-
niacal salts. Redissolve
in a little water, mix
with a little pure red
oxide of mercury, eva-
porate again to dryness,
heattoredness,and treat
with water.
2– *—
15 The solution contains the chlo.
rides of potassium and sodi-
um, if present. Evaporate to
dryness, weigh, re-dissolve in
Water, and add bi-chloride of
platinum to separate the pot-
ash, p. 46.
−N
12.If manganeseis pre-
sent it falls as sul-
phuret; dissolve in
muriatic acid, pre-
cipitate by carbon-
ate of soda, wash, .
heat to redness in
the air, and weigh.
~
14 Caustic magne-
sia remains ;
wash, heat to
redness, and
weigh.
,-
mains in Solution, and its
weight is found by deduct-
ing from the weight of the
mixed chlorides (15) that
of the chloride of potas-
sium (16).
17 The chloride of sodium re. 16 wash the preci.
pitate with weak
alcohol, dry by
a gentle heat,
and weigh. "
10 Oxalate of lime falls,
wash, heat to red-
ness to convert it
into carbonate, and
weigh.
ºr-
6 Solution contains alumina
and oxide of iron ; add
ammonia,and digest the
precipitatein a solution
of caustic potash.
2-
8 Add muriatic
acid till the
solution is
sour ; then
ammonia in
excess. Alu-
mina falls ;
wash . and
Weigh,
— — ——
—y
7 Oxide of
iron re-
mains ;
wash &
weigh.
3 Phosphates of alumina and
iron remain undissolved.
Fuse with carbonate of
soda, and wash with dis-
tilled water.
—‘-
is dissolved.
Neutralise by
nitric acid, &
add nitrate of
silver, when
phosphate of
silverwill fall ;
or by muriatic
acid, and add
chloride of
calcium and
caustic am-
monia, when
bone - earth,
5 Phosphoric acid 4 Alumi-
na and
oxide of
iron re-
main ;
dissolve
in muri-
aticacid
and add
&l, Iſld 10-
nia to
the so-
1ution.
(6).
ă
GENERAL INDEX.
- PAGE
Absorbing power of the soil, determi-
nation of 1075
Absorbent beds * o 566
Absorption of heat by the soil, its
determination & 1076
Accumulations of drift in Great Bri- .
tain e * * * 502
Acetic acid, how produced from
wood, cane sugar, and alcohol 204
its properties and com-
position e e 203
why given off during
germination & & 132
Acid, acetic, its properties and com-
position & * 203
apocrenic & o 73
carbonic, its properties, and
relation to vegetable life 62
crenic wº 73
geic 73
humic & 72
— hydrosulphuric 320
lactic 94.2
— mudesous 74
— muriatic e e 317
nitric, its influence upon vege-
tation tº . 114
its properties 87
— of milk . e . 942
oxalic, its properties, and rela-
tion to vegetable life 66
pectic, its properties and com-
position . g e 183
— phosphate of lime 339
— phosphoric gº 32 l
— its gomposition 361
— Sulphuric 319, 320
its composition 36]
sulphurous 3.18
--- its composition 361
: ulmic e e * 73
Acids, their action in curdling milk 979
Acorn, ash of º © 398
Acre of land, nutritive matter pro-
duced by . 928
Apocrenic acid 73
Acrolein, its composition 966
Affinity of water for lime 54
for clay 54
104.7
Age of food, its influence
PAGE
Agricultural Chemistry Association ,
of Scotland & 16
or pipe-clays, composí.
tion of * & . 442
products, kinds of 845
Agriculture, branches of Science con-
nected with e 14
- British, prospects of 8
importance of 3
in Caithness 7
China. wº 6
Ross-shire . ... 7
-- Sutherland. 7
scientific, not taught 9
- not taught in
our colleges e wº 11
Air contained in Snow, composition
of º & 49
water, composition
of & e e 52
descends towards the drains 550
partly supports plants 96
Albite and felspar, composition of 485
Albumen, animal and vegetable 209
of the blood 210.
*mem==ºs of the egg 209
in flour . . & 867
* proportion of, in potatoes 904
turnips 911
quantity necessary to sup-
ply the daily waste in the animal
body . . 1027
vegetable, preparation of 210
Alburnum, or new wood of plants 118, 139
Alcohol, its conversion into acetic
acid o & & 204
Ale extract, composition of its ash 428
Alison, Mr, his opinion of the pro-
spects of British agriculture . 8
Alkaline substances, action of upon
organic matter 709
Alum ſº & 348
earth of • g 346
Alumina. & Q 346
in the soil, how detected 1081
how determined 1085
—— soluble, determination of 1079
its composition g 361
phosphate of 348
its composition 362.
1094.
PAGE
Alumina, silicate of, its composition 363
silicates of 354
*=e sulphate of 347
its composition 362
Aluminium * 346
Alum, its effects upon bread 880
Ammonia absorbed by burnt clay 83
by charcoal 26
by porous sub-
Stances * e 79
- red oxide of iron 357
the soil 863
tºº - a source of hydrogen to
plants * l()]
—— carbonate of g 80
its influence on
vegetation e * 616
combines with acids and
forms salts & e 81
contained in snow 49
decomposed in the air 276
—— easily decomposed by plants 86
formed by the decay of ani-
mal substances 275
in the soil l 12, 863
found in the juices of plants 110
—— how supplied to plants 274
in the soil, how detected 1081
determined 1088
its properties and relations to
vegetable life e 78
muriate of, its influence on
vegetation e •
nitrate of, its influence on
vegetation . e
obtained from vegetable sub-
stances by distillation 110, 111
616
6 || 8
GENERAL INDEX,
oxidized in the soil e 85
perspired by plants | 10
produced in the soil 278
proportion of, in the atmo-
sphere º a 275
salts of, decomposed by lime 82
special action of its salts 618
—— supposed to be absorbed
from the air by gypsum . 83
supposed to enter into the
roots alid leaves of plants
- theory of its action upon
plants . * 29]
Ammoniacal cheese 997
liquor, its influence on
vegetation 5 e 617
Analysis of milk, how conducted 939
—— of soils, comprehensive table
of tº © * | 092
of soils, use of 528
value of e § 435
Animal body, natural waste of 1025
— charcoal as a manure 794
112 |
TAGE
Animal charcoal, properties of . 27
economy, purposes served
by milk in the e
— and vegetable life, water ne-
cessary to . e * 5].
excretions, relative value of,
as manures e ſº 824
growing, additional food re-
quired by 1032
action of lime upon 733
—— supported by oxygen 28
manures, relative values of 799
their effects in in-
creasing the produce 825
* their qualities af.
fected by circumstances 825
milking, additional food re-
quired by 1033, 1036
—— pregnant, additional food
required by I ()35
substances produce ammo-
nia during their decay 275
Animalized carbon 795
its relative value
&S 9. Yı) ºnll]"G e & 799
Animals, breathing of purposes serv-
ed by 1021
****
in different circumstances,
what to be considered for their
condition
respiration of
——— the materials of its body
derived from plants
substance of their bodies
derived from their food . 1014
Anthoxanthum odoratum, benzoic
acid in & e l 13
Apatite 340
1069
1017
(phosphate of lime) its com-
position º e 362
Apple tree wood, ash of 395
Apocrenic acid in the soil 515
Arabine e o 177
Area of Great Britain e 4
Art of culture, a chemical art . | 9
Artesian wells in Egypt 564
at St Denis 566
Artichoke, inorganic matter in 304
Artificial oil cake © 1055
Ascent of the sap, its causenot made
Out tº & º
Ash left by plants at different periods
of their growth * 128
Ash of acorn g 398
apple tree wood 395
asparagus 390
barley 367
bean 377
beech § e 397
——— beech nut & 398
GENERAL INDEX.
PAGE
Ash of beet 384
blue bottle 40l
bones 783
buck-wheat 376
— cabbage 388
— chamomile 401
cherry tree 395
— chesnut e 398
— Chinese crab • 396
— clover 390
—— coffee º • 393
— common parasitic plants 401
— corn-cockle 401
— elm 397
— ergot 402
flax 38]
flax seed, 381
foxglove e • 401
fungus of the apple tree 402
hay . o 390
hemlock 401
hemp 38 l
hempseed 381
hop 395
Indian corn e 374
Jerusalem artichoke 384
larch e 399
lemon seeds 396
lentil 379
— lime tree 397
linseed e * 38]
linseed cake (American) 381
(English) 381
lucerne ge • 390
Madia sativa 383
millet 376
misletoe 402
tº- mustard 383
oak wood 397
Oats e 369
peas 378
pitch pine seeds 400
—— poppy 40]
—— potato 384
—— potato tops 385
—— quince seeds 396
reed, common 390
rice * 376
—— rye . ſº 372
rye grass seed 383
Sainfoin - º 300
same sea-weeds vary with
the locality º 404
sea-weed 623
Scotch fir 399
—— — seeds 400
Straw - 625
*-- its effects on vegetation 626
º Sugar-cane º 393
- its value as a manure 629
tºss- sweet sedge 401
PAGE
Ash of turnip bulb 384
turnip tops 885
— twigs of vine 394
vetch 377
— wheat 365
-— coal 632
Sea weeds 402
common weeds 401
Ash, or inorganic matter 305
proportion varies on different
soils • º 3] ]
— — quality of, in plants 302
Asparagus, ash of 390
Ass’ milk 930
Atmosphore, a source of oxygen to
plants © 03
composition of, before
and after breathing 0.17
- – its composition and re-
lation to vegetable life 40
constitution of, adapta-
tions in . º 41
diffuses itself everywhere 41
moisture in 40
proportion of carbonic
*-*-
º 64
proportion of oxygen in 28
Atomic weights, or equivalent numbers 44
acid in
Augite, its composition 492
Avenine º 887
Avenin, its preparation 214
Ayrshire cheese, its composition 1001
Baking, its effects upon flour 876
of food 1046
Bark, functions of . - 150
its functions modified by cir-
cumstances º © 157
of the root, changes produced in 151
Barley, ash of º 367
composition of 88.1
effects of the nitrates upon 593
inorganic matter in 303
nutritive matter produced by
an acre of 928
— special manure for 641
Sprouts, the composition of
their ash º 426
steeping, the influence on the
inorganic matter in 422
steep water, Saline matter in 424
straw, ash of - 367
its theoretical value as
a l]].8.Ill]]'6 º 773
nutritive matter pro-
duced by an acre of 9.28
Barrel churn, use of 960
Barren soils, composition of . 524
Basalt, its composition º 492
Bean, ash of . . 377
mixture, as a substitute for oil-
cake 1054
- PAGE
Boucherie, his mode of preserving
wood º g
Boussingault, his experiments on the
absorption of carbon by plants 259
his experiments on the
fattening properties of common
salt
-
his experiments on the
feeding qualities of green and
dried clover º e”
his table on the theo-
retical nutritive qualities of food 1064
Braconnot, his experiments on the
excretory power of the roots 126
Bran, composition of 762, 865
its theoretical value as a ma-
Inll I’6” º e . 773
Branches and twigs of plants, their
structure e º 119
Bread, effects of alum upon . 880
-- Sulphate of copper
upon & &
water contained in
Breathing or respiration, quantity of
carbon given offin Great Britain
in a year d -
Buck-wheat, ash of - " .
composition of its green
-
877
264
376
stems 917
employed as green ma-
In ll]"G
303
892
pro-
928
inorganic matter in
—— its composition
nutritive matter
duced by an acre of .
straw, its theoretical va-
lue as a manure ë
Burnet, Mr, his experiments upon
wheat o e
Burned bones, their action upon
plants º ->
Burnt clay absorbs ammonia
Burning of lime - e
Butter and cheese, comparative profit
of making e o
annual produce of a single
COW
F096
PAGE
Beans, boiling and pig, chemical dif-
ference between º 898.
inorganic matter in 304
– nutritive matter produced by
an acre of º 928
peas and Vetches, their compo-
sition - 895
Bean straw, ash of 379
Beech, ash of * * 397
inorganic matter in 305
nut, ash of . - 398
kernel, proportion of oil
in º º 92]
Bees-wax, its composition 199
Beet, ash of - 384
inorganic matter in 304
its composition 913
its comparative nutritive quality 915
Beistings, or first milk, its composi-
tion 932
Beneficial influence of snow 48
Benzoic acid contained in grasses 113
Bi-carbonate of soda º 329
Bi-phosphate of lime - 339
its effects upon
turnips and wheat 611
Birch, inorganic matter in 305
Birds’ bones, composition of 78.1
Bitter almonds, proportion of oil in 921
Black mustard, proportion of oil in 921
Blood, albumen of, its composition 217
ash of 777
composition of 777, 1013
its relative value as a ma-
Illll'C - 799
dried, its relative value as a
TO 8.Illll'C 799
Blue bottle, ash of 401
Bodies, simple and compound, what 23
Boiled bones contain less gelatine 785
Boiling and pig beans, chemical dif-
ference between º 898
of food . & , 1046
peas e g- 807
Bone dust, its application to grass
land º e © 790
earth, dissolved by carbonic acid 338
its composition © 362
its action upon plants 610
Bones, burned, their action upon
plants. e • 6] 0
cause of their fertilizing action 784
composition of 78]
— earth of e . 336
forms in which they are applied
to the land º º 79]
how dissolved in sulphuric acid 793
long buried, composition of 785
their relative value as manure 799
Borage, as a green manure e 742
Border counties, changed condition of 7
Botany, its connection with agriculture 14
GENERAL INDEX.
773
635
6|| 0
652
º 956
composition of 954, 964
fatty matters existing in 964
its quality affected by cir-
cumstances 957
obtained by churning 952
by heating the cream.951
quantity of, yielded by milk
and cream º 955
— rancidity of e '973
Butter milk cheese º 989
Butyric acid, its composition 968
Cabbage, ash of º 388
— inorganic matter in 304
—— its comparative nutritive
quality 91.5
GENERAL INDEX,
PAGE
Cabbage, sour, lactic acid in 942
— special manure for . 644
Cabbages, their composition 9 l 4
Caithness, agriculture in & 7
Calcareous soils, their composition 444
Calcium & * o 334
chloride of 334, 608
chloride of, its composition 362
Sulphuret of
sulphuret of, its composition 362
Calf, food required by 1033
Calf's blood, ash of ſº . 778
muscular fibre, composition of 1010
Cambrian rocks, their extent and na-
ture of their soils o 479
Cane sugar, its conversion into acetic
acid º - 204
its properties and compo-
sition g e 179
Capillary attraction 134
Capric acid 968
Caproic acid • . 968
Caradoc sandstone, the nature of its
soil e & o 478
Carbon absorbs gases 26
animalized e 795
form in which it enters into
the roots of plants º 97
given off by respiration in
Great Britain in a year 264
in the food, its service ] 068
of plants, proportion of de-
rived from the atmosphere 258
whence derived . 9]
properties of, and relations
fo vegetable life º 25
quantity extracted from the
air in a year
Carbonate of ammonia & 80
decomposes
gypsum - º 83
its influence
on vegetation 616
Carbonates of iron © 359
Carbonate of lime e o 3.32
how detected in
the soil e e 675
its composition ($49
- its special action
on organic matter in the soil 713
of magnesia 340
its composition 651
of manganese
of potash 321
theory of its ac-
tion upon plants 581
*- of soda. e º 328
theory of its action
upon plants º 581
Carbonic acid absorbed by leaves
and roots
334.
1097
. . PAGE
Carbonic acid absorbed by the
leaves of plants 64, 143
water 65
a source of oxygen to
plants e -> 103
-*-*. contained in lime-
Stone e C © 64
estimation of 1089
given off by ripening
fruits º - 252
— given off from the
lungs tº e e 66
given off in volcanic
countries º - 272
how it is changed in
the interior of the plant 233
its power to dissolve
bone earth e 338
-*- — its properties and re-
lations to vegetable life 62
proportions of in the
atmosphere & e 64
— produced by combus-
tion e e 267
produced by decay of
vegetable matter 267
produced by respira-
tion º 263, 1027
oxide, its composition and
properties 68
Carboniferous system 47 l.
Carburetted hydrogen, a source of
hydrogen to plants e 101
Carp's muscular fibre, composition
of º e º 1010.
Carrot, inorganic matter in 304
its comparative nutritive
quality 9 J 5
its composition 913
+-º-º: mangold-wurtzel, beet, and
cabbage º - 915
-º- nutritive matter produced
by an acre of e 928
* tops, their theoretical value
&lS &l, Illa, lllll'G 773
Casein, how it produces butyric acid 971
its properties 212, 969
— relation to the fats 972
— relation to the sugars 970
— produces lactic acid 970
proportion of, in potatoes 904
vegetable 213, 969
Caustic lime, its special action upon
organic matter in the soil 711
magnesia e - 34l
*- less soluble than
lime 342
potash e © 322
Soda º 330
Cellular fibre and woody matter,
mutual transformations of 187
1098
- PAGE .
Cellular fibre in the grasses, pro-
portion of e 919
Cellulose - e 167
how it is formed during ger-
mination º & 230
its properties - 164
its relation to starch, gum,
sugar, and pectic acid º 185
- or cellular fibre, its compo-
sition º e | 63
Cerasine 177
Cerine 200
Cerosine 200.
Chaff, as a manure 7.62
Chalk, extent and soil of 459
its uses as a manure 668
Chamomile, ash of o . 401
Characteristic properties of organic -
Substances º 23, 34
Charcoal absorbs disagreeable odours 27
-- mºs saline substances 27
animal, as a manure 794
refuse of the sugar refiners 794
removes colouring sub-
stances and purifies water 26
Cheddar cheese, its composition 1002
Cheese and butter, comparative
profit of making 1004
— ash of º 1007
average composition of 999
quantity of, yielded by milk 998
— Ayrshire e 1001
— Cheddar º 1002
Dunlop 1001
ewe milk | 002
— from butter milk 989
— how analyzed e 1000
how different qualities may be:
obtained from the same milk
how made in Ayrshire and
Cheshire - w
its quality affected by circum-
stances º ©
produce of, by a single cow
skim milk and double Glo'ster,
composition of
Cheeses, vegetable and potato
Chemical combination, nature, and
laws of e º 42
methods of improving the
soil, principles of tº 579
Chenopodium Olidum perspires am-
monia e º 1] 0
Cherry tree, ash of . 395
Cheshire, cheese yielded by a cow in 998
991
994
998
990
Chesnut, ash of o - 398
Chicken's muscular fibre, composi-
tion of & º 10] 0
China, agriculture in º 6
Chinese crab, ash of 396
Chloride of calcium 334, 608
Chlorides of calcium and magnesium,
theory of their action e
GENERAL INDEX.
PAGE
Chloride of magnesium 344, 608
— of manganese g 361
of potassium 323
of sodium 326
of sodium, its use in vege-
tation g e {305
Chlorine given off by the leaves of
plants - 148
in the soil, how detected 108;
in the soil, how determined 1084
its properties 316
Churning of cream 952
temperature at which it
should be carrried on 961
the whole milk 952
Cirencester Agricultural College . 10
Citrate of lime 208
– of potash 208, 325
Citric acid, its properties and com-
position e -- 208
Clay absorbs water e o 54
effects of 576
Clays, porcelain, composition of 442
Cleanliness saves food 1045
Climate improved by drainage 585
influence of, on produce of
food º tº 848
its influence on the proper-
ties of milk º w
Clouted cream e 952
Clover, a deep rooted plant 859
ash of . Sº . 390
composition of its green stems 917
hay, nutritive matter pro-
duced by an acre of e 928
—— introduced into Germany 6
—— roots, their theoretical value
&S al. Iſla Dllll'é e ſº 773
—— Why land becomes tired of 858
—— sick, why land becomes 858
Coal ashes, their composition 632
measures, their extent and na-
ture of their soils 471
Coal mines, gas of º * 69
Coffee bean, ash of º 393
inorganic matter in 304
tree, special manure for 645
Cold produced by evaporation 59
College, Agricultural, at Cirencester 10
Colophony, its composition 201
Colostrum, or first milk, its compo-
sition 931
Colouring matters changed by the roots 99
Combustible gas given off by plants 147
part of plants, propor- -
tion of t º 30|
Combustion of wood and coal, carbo-
nic acid produced by 267
Common furze, inorganic matter in 305
— salt e e 326
—— Salt, cause of its failure 606
—— salt, how detected in the soil 608
GENERAL INDEX.
PAGE
Common salt, how purified 975
- salt, its use in vegetation 605
—— salt, on its supposed fattening
properties -> s 1057
—— salt, proportion of in 100 of
cheese - e 1007
—— salt, with gypsum, their ef-
fects upon beans t ($35
—— weeds, ashes of 40]
Composition, average, of different
crops º & g
— and properties of car-
bonic oxide º - 68
— of air contained in Snow 49
— of air contained in water 52
—— of wheaten flour 87 ()
Compounds of the inorganic elements,
their composition p 36]
Conclusive view of the work 1070
Connection between the Soil and the
926
—y-
1().99
plant - e 546
Constitution of the atmosphere, adap-
tation in º & . 41
Cony dust, as a manure 779
Coral sand, composition of 663
Corals, composition of 664
Corn-cockle, ash of 401
Corrosive sublimate, its use in pre-
serving wood . e 141
Cow dung, its composition and value
as a manure e 821
Cows, small breeds of, give rich
milk g - e 934
urine, its practical value as a
IY) all Ull'C . - 817
urine, its composition 807
Crag, the, of Norfolk 457
Cream cheese 950
clouted 952
composition of 949
measurement of 948
separation of - & 947
of tartar (bitartrate of potash) 362
Crenic acid º * º 73
how changed in the inte-
rior of plants * 238
- in the soil e 515
Crop, kinds of, influence of on pro-
duce of food 849
Cropping, exhaustion by e | 9
Crops, effects of lime upon 691
rotation of, theory of 854
Crushed granite as a manure 633
— lava as a manure G33
—— limestone 665
Crushing of food s 1046
Crust of the earth, its general struc-
ture o - 450
Crystalline rocks, what 451
Culture, influence of, on produce of
food - e 850
PAGE
Culture lightens the soil 859
Curd of milk, its properties 212,-969
Curdled milk, use of, in making
rennet . º 986
Curdling of milk . . º 97.8
Dairy purposes, feeding a cow for 1038
Daubeny, Dr, his experiments on
the selecting powers of the
rootS º o 123
Davy, Sir H., his work on Agricul-
tural Chemistry - 13
Day, length of, in different latitudes 146
Decandolle, his excretory theory 127
opinion of, on rotation
of crops e 855
Decayed trap as a manure 633
Deep ploughing, why beneficial 571
Definite proportions in which bodies
combine º - 43
Density of the soil, determination
Of º 1073
De Saussure, his experiments on the
Selecting powers of the roots 123
*-ºs- his theory on the ascent
of the sap - 135
Dew, cause of e - 56
Dextrin, how formed from carbonic
acid in the plant 234
its composition and pro-
perties © 175
Diamond, form of carbon 26
Diastase, beauty of its action 223
functions of, in the plant 221
— its formation and proper-
ties g e º 219
Dissolved bones 792
Draft, composition of its ash 429
Drainage removes moor band pan 557
- influence upon health 558
Draining improves the climate 555
its mode of action and
effects e º 550
- loosens and opens the soil 551
- of dung heaps, their com-
position & - 8] 1
*-*- prepares for further im-
provement 554
— warms the soil 55}
Drift, difficulties arising from the
presence of º - 506
in Durham, soils produced by 503
- Sands and clays, how transported 500
Sands and clays often conceal
the rocks e 499
Sand, plants growing on 546
Dry leaves, as a manure 766
Dung, its quality affected by the
purpose for which the animal
is fed tº - 1069
heaps, drainings of, its compo-
sition e - 811
1 100
PAGE
Dung stones of Devonshire 495
Dunlop or Ayrshire cheese, its com-
position -> 100 l
Dutch ashes, their composition 629
Dutrochet's theory of endosmose -
and exoSmose | 36
Earth of alum 346
bones ſº e 336
bones, its composition 362
Earthy matter of bones, its value as
&l 1]]{llllll'C 787
the soil, insoluble,
its determination and analy-
sis º 1090, 1001
Egypt, Artesian wells in 564
Elaic acid e º 197, 968
how changed into marga-
ric acid º e 967
how formed in plants 24 l
Elaine º º 196, 965
Elementary bodies contained in the
ash of plants . - 315
ººm- schools, teaching of
agriculture in - | 1
** substances contained
in organic matter - 35
Elm, ash of e 397
inorganic matter in 305
Elymus arenarius growing on drift
sands e & 547
Emulsin or synaptas, its preparation
and properties - 2] 3
Endosmose, what . . | 36
Epidermis or outer bark of plants 118
Epsom salts, (sulphate of magnesia)
their composition º 362
Equivalent numbers or atomic
weights e º 44
Ergot, ash of º 402
Eucalyptus sugar, its properties and
composition - | 8 |
Eureca, district of, nitrate of soda
in e º 88, 286
Evaporation, cold produced by 59
of snow - 55
of water, its influence
on vegetation - 59
Ewe’s milk e e 030
milk cheese, its composition 1002
Excretions of one plant not inju-
rious to another º l 31
plants e 85.5
Excretory power of the roots | 26
theory of Decandolle 127
Exercise, influence of, on the quantity
of food required | ()4]
Exhausting effect of lime 729
Exhaustion by cropping e 19
136
Exosmose, what º -
Experimental agriculture neglected 9
GENERAL INDEX.
PAGE
Experimental results of the nutritive
effects of food, table of
Fallowing may replace ploughing
and draining - º 861
Fallows, theory of © . 860
Farm-yard manure, its loss by fer-
mentation
1062
g 832
theoretical
value . - e 773
state in which
it ought to be applied to the
land o º s'
Fat, accumulation of, in animals
may be formed by starch or
Sugar . º
of animals, its composition
its relation to re-
spiration e º
its source
of the animal body, whence de-
833
1025
1033
1011
1 019
] 021
rived & - 1068
of the body, how formed from
the fat of the food e 1024
proportion of, in potatoes 903
purposes served by 1024
Fattening animal, additional food re-
quired by - e 1031
——— animal, quality of its ma-
]]'ll]"G . - º 1065
- properties supposed of
common salt . } 057
Fatty matter in grasses 920
substances of plants 195, 198
Feeding, mode of, how it affects the
manure and the soil
qualities of grass and hay,
comparison of - &
Felspar decomposed by the carbonic
acid in the air e te 488
and albite, composition of 485
1064
1059
Fermentation of starch and sugar 192
Fermented bones & 792
liquor of milk | 005
Fermenting manures, top dressing
with & tº 835
Fertile soils, composition of 520, 521
Fibre, muscular, of animals, compo-
sition of º º 10 |
potato, the composition of its
ash e - 42]
proportion of, in potatoes 902
Fibrim, daily waste of 1027
of animals produced from
their food º
vegetable and animal, its
properties and composition 212, 101 l
Filgate, Mr, his analysis of the ash of
potato fibre º 421
Fir saw dust, its theoretical value as
&l, Ill:llllll’e 773
GENERAL INDEX.
PAGE
Fish bones, composition of 781
their relative value as a manure 799
refuse as a manure 796
their use as a manure 796
Flax, ash of g e 38]
dressed, ash of 383
— pob of, ash 383
— seed, ash of 381
special manure for 646
Fleming, Mr, his mixed manures ($36
Flesh, its relative value as a manure 799
of animals, its composition 777
Flour, ash in different parts of 869
effects of baking on 876
wheaten, composition of 866
— wheaten, influence of Soil and
climate on composition of 890
Flower leaves of plants, their func-
tions sº gº & 149
of plants, changes that take
place in 247
Food, additional, required by fatten-
ing animals g
additional required by growing
animals G º . 1032
additional required by a milk-
ing animal 1033, 1036
additional required by a preg-
mant animal
age of, its influence * 104.7
boiling or steaming and baking
of
— grown in Great Britain, its re-
lation to the number of the peo-
ple * g tº 4
how it is changed in the body
of the animal e - º 828
influence of the form in which
it is given & e 1045
kinds of, affects the quality of
the milk . ſº 935
mixed, necessary to health
economical use of in
1029
feeding g 1051
produce of varied by circum-
stances 848
quantity required, influenced
by exercise and warmth
restores the daily waste of the
1041
animal body e ... 1058
saved by shelter and want of
light * 1042
saved by ventilation and clean-
liness . 1045
souring of 104.5
Forests in Germany, natural changes
in e e º 548
in Sweden, natural changes
in g & & 549
in United States, natural
changes in .
549
1101
- PAGE
Forking the land, why beneficial 569
Four years' course, of effect in ex-
hausting the soil 409
Fox-glove, ash of º e 401
Fresh sea weed, its theoretical value .
tlS &l, Inhalllll'C & 773
Fromberg, Dr, his analysis of oats 886
— analysis of pota-
toes - 904
Fruit, ripening of . 249
Fuller's earth, soil of . 466
Full grown animal, quality of its ma-
Illul’C e tº e 1065
Fungi absorb nitrogen directly from
the air & g 109
give off carbonic acid 147
their composition. 925
Fungus of the apple tree, ash of 402
Galactometer tº 948
Gas, combustible, given off by plants 147
of the coal mines 69
Gaseous substances absorbed by car-
bon 26
taken in by the
roots of plants, 12]
Gases dissolved by water g 51
Gault, soil of,
46 I
Geic acid 73
in the soil 5] 4
Gelatine extracted from bones by
boiling . 785
mixture as a substitute for
oil cake g 1056
General properties of humic and ul-
mic acids {º 75
Geology, its connection with agricul-
ture, gº º I5
Germany, introduction of clover into 6
Germination, acetic acid given off
during g 128
carbonic and acetic acid
given off during tº 227
: chemical changes ac-
companying it g 225
- effects of upon wheat 875.
— explanation of the
changes which accompany 228
oxygen necessary for 227
why acetic acid is given
off during & º I 32
Gladiadin or zein, its preparation
212
Glo'ster cheese, its composition l 000
Gluten and albumen, proportion of,
in grasses sº sº 919
in flour 868
- its effects on the
Weight of bread obtained, 879
its preparation and properties 211
proportion of in potatoes 904
Glutin, its preparation and proper-
ties e * 212
II ()2
PAGE
Glycerine or oil sugar 198
Gneiss and mica slate systems . 4.18
Goat's milk, 930
urine, composition of its ash 810, 81 l
Golden rod, ash left by, at different
periods of its growth 129
Gold of pleasure cake, ash of 38]
composition of 922
Goose dung, its use as a manure 802
Goosefoot, stinking, perspires ammo-
nia e e ll ()
Gouda cheese, preparation of 993
Graeger, his determination of the pro-
portion of ammonia in the atmo-
sphere g e
Granite, crushed, as a manure
soils, their observed qualities
Granitic rocks, their composition
their extent in Great
Britain and Ireland
Grape sugar alone ferments
— how formed from carbonic
acid in the plant
— how it is formed
germination e
its properties and compo-
275
633
490
483
490
192
during
sition e *
Grass land, application of bone dust
to 790
lands increase in vegetable mat-
ter 9]
laying down to, how it improves
the soil & & 747
Grasses, fatty matter in 020
inorganic matter in 304, 920
proportion of albumen and
gluten in * 919
cellular or
919
woody fibre in
Gravel, sand, and clay in the soil,
GENERAL INDEX.
determination of their propor-
tions g
Great Britain, area of e 4
population of . 4
*-* successive agricultural
improvements in &
Green manure, will it prevent the
land from being exhausted . 7.43
: manuring 736
results obtained
from tº 736
— natural 744
Greensand, extent and soil of 460
soil, composition of 447
Greenstones, their composition . 492
Green vitriol, its use in fixing the
ammonia of urine
Grits, calcareous, soil of & 463
Growan soils of Cornwall e 491
Growing animal, quality of its ma-
nure w 1067
PAGE
Guano & 804
result of experiments on dif-
ferent crops - 805
Guinea, yam, e 909
Gum, action of sulphuric acid upon 190
its composition and properties 176
—— its relation to cellulose, starch,
Sugar, and pectic acid 185
— proportion of, in potatoes 90.3
Gyde, Mr, his experiments on the
excretions of plants 128
Gypsum te 334
decomposed by carbonate of
ammonia {} g 83
instances of its effects 84
— in the soil 673
— its action on urine 815
— (Sulphate of lime) 362
(sulphate of lime) burned 362
Supposed to absorb ammonia
from the air tº 83
theory of its action upon
plants - e 587
— with common salt, their ef- ... *
fects upon beans ` 635
Hair as a manure 779
composition of 1013
Hard wood of plants g 128
Hare’s blood, composition of its ash 778
urine, its composition 810
— composition of its ash 811
Hartshorn, spirit of & 79
Hastings sand, soil of 462
Hay, ash of e * 39()
composition of grasses when
made into º e 91R
Hazel nut, proportion of oil in 921
Heat, action of upon cellular fibre
and woody matter 187
carried off by evaporation 60
radiation of sº * 57
Health, influence of drainage upon 558
Hemlock, ash of Ҽ 401
Hemp, ash of . 38]
seed, ash of * 381
*-ºs-ºs-ºs-s-s composition of 0.21
*º inorganic matter in 304
* proportion of oil in 921
scutchings of, ash 383
Hen’s dung, its use as a manure 802
Hodges, Dr, his analysis of kelp 624
Holcus lanatus growing on peaty soils 547
Holland, cheese yielded by a cow in 999
Hop, ash of & 395
inorganic matter in ... 305
Horn, composition of 780, 1013
its use as a manure 780
Hornblende, composition of 486
*=sº-mes soils, why generally fer-
tile * 489
Horse dung, its value as a manure 821
*...
GENERAL INDEX.
PAGE
Horse urine, its composition 807, 810
ash of º 81 l
Horsford, Mr, his analysis of oats 887
Human bones, composition of 781
urine, composition of . 808
Humate of lime in the soil 676
Humic acid tº •. 72
in the soil o 514
soluble, deter-
mination of & 1079
—— in the soil, determination of 1076
and ulmic acids, general pro-
perties of © o 75
how changed
in the interior of plants 237
ulmic, and crenic acids, their
mutual relations * 77
Humin . e * > . 74
in the soil 516
Humus -- 71
in soils e g 513
insoluble, determina-
tion of gº * 1078
Huxtable, Rev. Mr, his mixture for
turnips ge 636
Hydrate of lime, its composition 653
——- of magnesia, its composition 653
Hydraulic limestone, its composition 650
Hydrogen, its properties and relation
to vegetable life tº tº 29 |
sºmº-º-º-º: Jight, carburetted . 69
*º-sº of plants, whence derived 101
sulphuretted 320
Hydro-sulphuric acid 320
Hypersthene, of Skye, its composition,
and nature of its soils 497
Igneous rocks, what 45l
Improvement of the soil by mixing 575
slowly introduced . 8
Impervious rocks 539
Indian corn, ash of 374
inorganic matter in 303
its composition 892
nutritive matter produ-
ced by an acre of e 928
or maize, special mia-
nure for g 642
— straw, ash of 375
Inoculating cheese 997
Inorganic constituents of plants 30]
of plants, their
proportion modified by circum-
Stances * * 4.18
matter, a food of plants 306
essential to plants 306
in beans, peas,
vetches, lentils, lintseed, hemp
seed, mustard seed, coffee, po-
tato, turnip, beet, artichoke,
carrot, parsnip, mangold-wurt-
zel, cabbage, tobacco, mush-
rooms, grasses, sea-weeds
*º-º
304
| 103
PAGF.
Inorganic matter in different parts of
the same plant tº
in larch, Scotch
fir, pitch - pine, beech, willow,
birch, elm, ash, oak, poplar,
common furze, sugar cane, vine,
hop
306
in wheat, barley,
oats, rye, rice, Indian corn,
buck-wheat, millet-seed *
proportion of, in
the grasses * gº
quality of in dif.
ferent plants tº
in dif-
ferent parts of plants
quantity of, con-
tained in different plants
quantity of diffe-
rent in different parts of plants
quantity of diffe-
rent in different plants
quantity of in dif.
305
ferent plants º 303
substances, can they re-
place each other in plants
Insoluble matter in hay, can animals
digest ? & g
Instruction, agricultural, introduced
into elementary schools e 11
Inuline, composition of 173
Iodine, properties of & 317
Iron, bi-sulphuret of, (iron pyrites),
its composition e . 362
carbonate of its composition 363
carbonates of ſº . 359
first chloride of, its composi-
tion g g *
its oxides e
per-oxide, its composition
prot-oxide, composition of
pyrites, (bi-sulphuret of iron),
its composition g
pyrolignite of its use in pre-
Serving wood e *
red oxide of, absorbs ammonia
second chloride of its compo-
sition e &
sulphates of e &
sulphate of (crystallized), its
composition * e
sulphuret of its composition 362
sulphurets of . & 358
Irrigation, how it improves the soil 838
where most beneficial 841
Isomeric bodies * * 45
-4 15
362
356
361
36 |
362
141
358
362
359
363
Jelly fish as a manure 787
Jerusalem artichoke, ash of 384
Jones, Mr, his analysis of cheese 1000
Juices of plants, ammonia in 110
Kelp, its efficacy as a manure 624
Kimmeridge clay, soil of 463
1 104 GENERAL
PAGE
Kingscleer soil, composition of 447
Knight, Mr, his theory of the ascent
of the sap & tº 135
Knowledge, incitements to the pur-
suits of º º 35
limited nature of our 94
Koumows, how prepared from mare's
milk • 1006
Kyan, his mode of preserving wood 141
Lactic acid * º 206, 942
—#— its relation to cane, milk,
and grape Sugars 943
Lanarkshire cheese, its composition 1001
Land, arable and in pasture, compa-
rative profit of º 852
average produce of in Great
Britain º e 847
effects of lime upon 690
maximum produce of 846
Larch, ash of its composition 399
inorganic matter in 305
Latitudes in which peat is formed 95
length of day in different 146
Lava, crushed, as a manure 633
Law of multiple proportions 46
Laying down to grass, how it im-
proves the soil . e 747
Leaf, its functions modified by cir-
cumstances 155
Leaves and roots absorb carbonic acid 97
give off volatile substances 142
of plants absorb carbonic acid 64
absorb watery vapour 141
give off chlorine 148
give off nitrogen 148
structure of 148
their functions 140
Lectures, outline of . . . 22
Legumin, its preparation and pro-
perties © e 214
Lemon seeds, ash of 396
Lentil, ash of 377
Lentils, inorganic matter in 304
their composition 895
Lias, extent and soil of 466
Liber, or inner bark of plants 1 J 8
Lichen starch, composition of 174
Lichens, oxalate of lime in 67
Light, absence of, saves food 1043
avoided by the roots of plants 120
carburreted hydrogen 69
Soils, improved by drainage 556
Lignin e º 167
Lignireose 167
Lignone 167
Lignose © 167
Lime, a food of plants 705
acid, phosphate of 339
biphosphate of -> 339
its action upon
turnips and wheat 611
its composition 362
INDEX.
PAGE
Lime, burned and unburned, their
comparative utility 716
burning of - 652
can it take the place of mag-
nesia in plants 2 417
can it take the place of potash
and Soda in plants 2 4 16
carbonate of 332
- how detected in
the soil 675
its composition 649, 362
its special action
upon organic matter in the soil 713
caustic, its special action upon
organic matter in the soil 711
change of, by exposure to the
air e e 655
decomposes salts of ammonia 82
effects of an overdose of 697
form in which it ought to be
applied to the land 683
hastens the ripening 693
humate of, in the soil 676
hydrate of, its composition 653
improves the quality of the crop 692
in the compost form, its advan-
tage - e 686
in the soil, how detected 1081
- how determined 1084
is it necessarily exhausting 732
its action on animal and vege-
table life e & 733
on common salt and
Sulphate of soda e
on mineral matter of
the soil & , e 724
- on the salts of iron 727
on the salts of mag-
nesia and alumina 727
on substances con-
taining nitrogen º 718
upon the organic
matter of the soil º 707
its composition . 361
--- its effects modified by circum-
stances & 693
upon the crops ($9 l
upon the land 690
its exhausting effect 729
length of time during which it
acts e 699
necessary to the fertility of the
soil - e 671
nitrate of 335
— its composition 362
— phosphates of 336
in the soil 673
(apatite) its com-
position e e 362
phosphate of, native 340
profit from frequent applica-
tions of * , * 682
GENERAL INDEX.
PAGE
Lime promotes the formation of ni-
tric acid e tº 721
proportion of, contained in dif.
ferent crops G e 706
in a soil, how de-
termined e & 444
in trap rocks 493
quantity to be added to the soil 676
quick . . - o 333
relative proportion of in diffe-
rent crops . e 414
should it be added in small or
large doses P 679
— silicate of e 614
in the soil 674
- its composition 363
its use as an applica-
tion to the land º . 735
sº-
silicates of 352
slaking of º . 652.
state in which it exists in the
soil º tº * 673
states in which it may be ap-
plied to the land 657
sulphate of • e 334
*- - (gypsum) burned,
its composition º . 362
gypsum), its com-
position * - . 362
theory of its action
upon plants 587
super-phosphate of 339
theory of its action 704
water, its action on urine 814
— when ought it to be applied 687
— why must it be kept near the
surface º • 723
Limestone, hydraulic, its composition 650
— its composition 649
magnesian, its composition 651
sand e - 664
of the old red sandstone,
their composition e 476
plants growing upon 548
tree, ash of, its composition 397
Liming, why it must be repeated 702
Linseed, ash of - e 381
composition of 92.1
inorganic matter in 304
proportion of oil in 92]
use of, in feeding cattle 1052
cake (American), ash of 38]
*s- (English), ash of 38]
composition of 922
Lint and rape dust, their theoretical
values as manures e 773
Lipyle, its composition 966
Liquid animal manures, their com-
position e * 807
Liquor fermented, from milk 1005
Liquorice sugar, its properties and
composition º 182
1] 05
PAGE
Liriodendrom tulipifera, composition
of its wood tº - 165
Lixiviated wood ashes, their compo-
sition º e 622
Llandeilo flags, their soils 478
Loams, clay and sandy, composition
Of º e - 443
London clay, extent and soil of 457
wells in 563
Long dung 833
Lucerne, ash of 390
Ludlow formation, its extent and the
477
nature of its soils g
Luneburg ashes, their composition 629
Lupins employed as green manure 740
Macaire, his experiments on the ecº-
cretory power of the roots | 26
Madia sativa, ash of º 383
Magnesia, bi-carbonate of its compo-
sition 362
calcined, changes of, by
exposure to the air
-> 656
can it take the place of
lime in plants? 4.17
Of
oxide of manganese in plants 418
carbonate of 340
its composi-
tion 362, 650
- *-*. caustic 341
less soluble than
lime e º - 342
—— hydrate of, its composition 653
in the soil, how detected 1081
how determined 1087
its composition . 361
its influence on vegetation 343
—— nitrate of - 345
its composition 362
phosphate of 346
* its composi-
tion - 362
relative proportions of in
different crops e
silicate of 353
its composition 363
-*. states in which it may be
applied to the land e 657
-assºs sulphate of 345
(Epsom salts).
its composition º
theory of its
action upon plants . 587
Magnesian limestone, its composition 651
its extent, and
nature of its soils 470
Magnesite g 656
Magnesium º & * . 344
- chloride of 344, 608
its composition 362
Maize, its composition 892
— special manure for 642
4 A
| 106
PAGE
Malic and citric acids, how produced
in the fruit e º 251
Malic acid, its properties and com-
position e e 208
Malt compared with other kinds of
food * º 1048
ash of e o 427
how it acts on the stomach 1049
use of as food 104.7
with boiled potatoes 1050
— dust as a manure & 766
draft, composition of, its ash 429
Malting barley º 883
its effects on barley 883
Mammoth cave in Kentucky 286
Man, Wrine of its composition 807, 808
Mangånese º e 360
carbonate of . 361
- its composi-
tion . * º 363
chloride of 361
*-- oxides of 360
oxide of, can it take the
place of magnesia in plants 4.18
peroxide,its composition 361
|protoxide of its com-
position 361
- Sesqui-oxide, its compo-
sition º g 361
Sulphate of º 361
º (crystallized)
its composition o 363
Mangold-wurzel, inorganic matter in 304
its composition 912
- nutritive matter pro.
duced by an acre of 928
Manna contained in sea weeds 182
Sugar, its properties and com-
position º e 18]
Manufacture of mixed saline manures 637
Manure and soil, how affected by the
mode of feeding . º
farm yard, state in which it
ought to be applied to the land 833
influence of, on the proportion
of ash in plants e
farm yard, its loss by fer-
mentation e
its effects upon rye
its quality depends on the
kind of food and the purpose
for which the animal is fed
its quantity depends on the
quantity of food taken by the
animal g | 064
kind, and quantity, influence
of, on the produce of food 85.1
of the fattening animal, qua-
lity of
1064
3.11
832
890
1065
te 1065
full grown animal,
quality of 1065
GENERAL INDEX.
PAGE
Manure of the growing animal, qua-
lity of 1067
B-ma-e- milking animal, qua-
lity of e ©
quantity of, produced by dif-
ferent animals . & 823
Manures, Saline, their influence on
] 067
the composition of the potato 907
supposed influence of, on
composition of wheat 874
Margaric acid 197, 965
Margarine . 196, 965
Margarine, its true composition 966
Marl and shell sands, their effects
upon the soil 667
effects of 576
German, composition of 659
Scotch, composition of 660
Marly soils, their composition 444
Marsh gas . e º 69
Marshal, Mr, his prepared food for
cattle e 1052
Matter, different kinds and states of 22
Maximum produce of the land 846
Meadow hay, nutritive matter pro-
duced by an acre of 928
Melting peas º 897
Mica, its influence on the soil 491
slate and gneiss systems and
soils o e 48]
— varieties and composition of 486
Milk, acid of . 206, 942
ash of, its composition 1007
composition of -- 931
cow, form or points of a good
O)16} & e 936
—— how the starch of her
food is changed into the sugar
of her milk 103
--— composition of, varied by cir-
cumstances o . 93]
— curdling of . 978
curd of its properties 212, 969
its properties 929
— mode of analyzing 939
— purposes served by, in the ani-
mal economy 2 tº
quantity of, affected by cir-
Cumstances 937
— spirit e º 1005
— souring and preserving of 946
— Sugar a 183, 94l
vinegar º e 1005
Milking animal, additional food
1033, 1036
quality of its ma-
required by
Illll: C - 1067
Millet, ash of e 376
seed, inorganic matter in 303
Millstone grit, extent and nature of
its soils t e 472
GENERAL INDEX. j
PAGE
Mineral matter, difference of, in dif-
ferent parts of plants
essential to plants
substances, can they replace
each other in plants - 415
decompose in the
soil e º * 862
in yeast 4ll
necessary to plants 409
relative proportion
of, in different crops
419
420
Misletoe, ash of, its composition 402
Mixed food, its economical use in
feeding - 1051
-* necessary to health 1029
manures of Mr Fleming 636
saline manures, manufacture of 637
Mixing of the soil, improvement by 575
Moor band pan, removed by drain-
age e º 557
Morton, Mr, his experiment on the
effects of shelter | 044
Mosses give off carbonic acid 147
Mountain lime-stone, its extent and
the mature of its soils - 473
Mucilage, its composition and pro-
perties º 178
Mudesous acid 74
in the soil 515
Multiple proportions, law of 46
Muriate of ammonia, its influence
on vegetation 616
Muriatic acid, properties of 317
Mustard, ash of © 383
— seed, inorganic matter in 304
Muscular fibre of animals, composi-
tion of - 1010
Mushroom, composition of 925
inorganic matter in 304
Myricine . 200
Native phosphate of lime . 340
Natural grass, its theoretical value
3S a, Illa, IlllFC e - 773
waste of the animal body 1025
circumstances modi-
fying the quantity of food ne-
cessary to make up for l 040
Nature and laws of chemical com-
bination • . © 42
Night soil, its composition 820
its value as a manure 818
smell of, removed by
charcoal © º 27
Nitrate of ammonia, its influence
on vegetation 618
lime 335
magnesia 345
potash º 323
potash, effects of, upon
vegetation tº 591
Nitrate of potash produced in India
87
107
PAGE
Nitrate of soda dº 330
its effects upon tur-
nips e º 596
produced in Peru 88
with sulphate of -
magnesia, their effects upon
potatoes e e 635
with sulphate of soda, its
effects upon vegetation 634
Nitrates, cases in which they have
failed e - 600
circumstances in which
they are most beneficial 60}
- of potash and soda, their
special action - • G03
their effects as compared
with other manures - 597
their effects upon barley 593
on the quality
of the crop - 596
on the grasses 593
on rye and
Oats & • 594
on wheat 595
their presence in plants 114
theory of their action up-
on vegetation 602
Nitre beds, how formed 285
Nitric acid and ammonia, compara-
tive influence upon vegetation 293
may be
produced together in the air 288
formed in the air 282
formed by the decay of
Organic matter in the soil 289
formed in caves e 286
how supplied to plants 281
its formation promoted
by lime * . 72]
in the soil, how detected 1081
its influence upon vege-
tation . . l 14
its properties 87
theory of its action upon
plants . e º 289
Nitrogen directly absorbed by the
roots e e l()7
form in which it enters
into plants * e 107
— given off by the leaves of
plants . e - 148
in plants comparatively
Small but absolutely large 105
of plants, its source l O4, 115
per-centage of, in different
fishes º - 796
– proportion of, in cheese 1004
preparation of, properties
and relation to vegetable life 31
proportion of, in potatoes 904
Norton, Professor, his analysis of oats 886 °
INDEX.
PAGE
Organic elements, form in which they
enter into plants . " .
– elements, relative proportions
of, in plants g &
matter, action of alkaline
substances upon ge e
forms in which it ex-
ists in the soil ©
elementary substan-
ces contained in g
in the soil, action of
39
709
707
35
707
1076
lime upon
of the soil, determi-
nation of § gº
Substances cannot be formed
by art
35
characteristic
23, 34
in the soil, a
source of hydrogen to plants
in the soil, a
Source of oxygen to plants
of the soil, how
Separated &
Over-churning, effects of .
properties of
102
103
1 108 GENERAL
PAGE
Nutritive effects of food, table of
experimental results of 1062
theo-
retical estimation of | 063
Nutritive matter produced by an
acre of land 928
properties of food, by what
circumstances they are affected 1061
Oak, inorganic matter in g 305
leaves, their theoretical value
aS a liman lll'62 e & 773
saw-dust, its theoretical value
aS Iſlanlll'6 e { } 773
wood, ash of its composition 397
ash of e & 369
— chaft, ash of 371
composition of 885
— husk as a manure 763
ash of & . 370
——— composition of its ash 885
leaf, ash of e . 371
proportion of ash in, at
different ages sº º 10
leaves, composition of, their ash
varies at different stages of their
growth . tº 4.32
stalks, composition of their ash
at different stages of their growth 433
37]
straw, ash of . g
* its theoretical value as a
Thanull'e * e 773
*ms- nutritive matter produ-
ced by an acre of . . 928
Oats, different varieties of, their com-
position . wº & 886
effects of nitrate of soda upon 594
soil and manure upon 888
inorganic matter in 303
nutritive matter produced by
an acre of g º 928
special manure for . 04]
Oil as a manure 800
— in flour ge • . 868
— proportion of, in the oily seeds 92.1
— cake, artificial 105.5
substitute for, in feeding
cattle g * . 1053
— cakes, their composition 922
— sugar, or glycerine, its composi-
tion e tº . 198
Oily seeds, proportion of oil in 92]
Old grass, as a manure 742
Oligoclase, composition of . 485
Oolite, inferior, extent and soil of 465
middle, extent and soil of 463
Oolitic system sº e 461
Oolite, upper, extent and soil of 462
Organic acids soluble in the soil, de-
termination of 1079
and inorganic matter 22
516
969
limed soils, proportion of lime in 698
liming, effects of 697
Ox blood, composition of its ash 778
— bones, composition of 78l
— muscular fibre, composition of 1010
— urine, composition of its ash . 811
Oxalate of lime in lichens and other
plants 67
potash . 324
Oxalic acid, how produced in the in-
terior of plants . 239
its properties and rela-
tions to vegetable life ($6
Oxalate of potash exists in sorrel 67
Oxford clay, soil of 464
Oxide of iron in the soil, how detect-
ed º 1081
how deter-
mined & e 1085
of manganese in the soil, how
detected e 1081
how
determined 1086
Oxides of iron . o 356
manganese 360
Oxygen absorbed by ripening fruits 252
given off by plants, its re-
lation to the carbonic acid ab-
sorbed * * & . . 240
given off by the leaves of
plants 28, 143
of plants, source of 102
—— properties of, and relations
to vegetable life 8
supports animal life 28
GENERAL INDEX.
PAGE
Para-pectic acid . & . 184
Parasitic plants, ashes of, their com-
position e e . 401
Parsnip, inorganic matter in . 304
—— its composition . . 913
Pastures, old, why they remain rich 1066
Payen, his analysis of woody fibre 167
Pea, ash of . e e 378
— straw, its theoretical value as a
Ina, Illll’e tº e . 773
— straw, ash of g e 379
nutritive matter produced
by an acre of . * 928
Peas, boiling and pig, chemical dif-
ferences between e 898
composition of their green
stems º 917
effect of manure upon 897
inorganic matter in 304
nutritive matter produced by
an acre of e g 928
their composition 895
Peat and vegetable soil, their use in
fixing the ammonia of the urine 817
ashes, their composition 629
— &S & IIla, Illil'é 630
— growth of e : • 92
extent of, in Great Britain and
Ireland . º e 510
* in Tierra del Fuego tº 92
its use as a manure 767
latitudes in which it is found 95
Peaty soils, plants growing on 546
Pectic acid, its properties-and com-
position © º l 83
* *m's its relation to cellulose,
starch, gum, and Sugar 185
Pectin g l 84
Pectose gº 184
Pervious or porous rocks 559
Petals, or flower leaves, their functions 149
Phloridzine in the root of the apple
tree * 151.
Phosphate of alumina 348
— of lime in the soil 673
of magnesia 346
of magnesia and ammonia 612
— of soda 330
Phosphates of lime 336
of potash 325, 612
of soda & e 612
proportion of, in 100 of
cheese . e & 1007
proportion which ought
to be contained in the food 1029
*
theory of their action
upon plants º e 612
Phosphoric acid, can it take the place
of Sulphuric acid in the plant # 418
in the soil, how de-
108 ||
tected
1109
- - PAGE
Phosphoric acid in the soil, how de-
termined ſº I 088
gººm-tº-º-º: — its composition 361
———— properties of 32]
— relative proportion
of, in different crops 414
Phosphorus, properties of 321
Physiology, its connection with agri-
culture . sº 14
Phytolacca decandra, fibre of, its
composition 3. º 163
Pigeon’s dung, its composition and
llS62 &S 8, Illalllll'é e 800
muscular fibre, composition
of . & o 10 || 0
Pigotite, what * 73, 516
Pigs, feeding of, upon sour food 1046
-— dung, its value as a manure 822
muscular fibre, composition of 1010
urine, composition of its ash 8 ll
urine, its composition 807, 810
Pine forests in Scotland 18
Pipe, or agricultural clays, composi-
tion of * e & 442
Pitch-pine, inorganic matter in 305
seeds, ash of, its com-
position & * 400
Pith of plants, the structure and
functions of wº * 137
Plant, chemical changes in after the
ripening of the seed 253
rapidity with which chemical
changes are produced in 254
relation of, to the soil 548
Planting, improvement of the soil by 755
Plants, ash left by, at different pe-
riods of their growth tº 128
decompose water 55
— excretions of * 855
— formation of their seeds 248
-— give off combustible gas 147
— inorganic constituents of 301
——— mineral substances necessary
to tº e tº 409
number of simple substances
in inorganic part or ash of 25
gº partly supported by the air 96
perspire ammonia * | 10
proportion of their carbon
derived from the atmosphere 258
relative proportion of organic
elements in & * 37
substances of which they
consist & & 160
their functions modified by
circumstances te 152
their general structure 117
——— whence they derive their
carbon e © 9 |
whence they derive their
hydrogen 10l., 102
PAGE
Potassium sulphuret of, its composi-
tion * º e
Potato and turnips, so-called casein
in * o ſº 215.
tops, their theo-
retical value as manures 773, 799
ash of 384
—— average composition of 906
— cheeses & 990
— composition of 899
fibre, the composition of its
& 42}
304
sm-mº-
ash o
inorganic matter in -
its comparative nutritive qua-
lity e * &
leaves and stem, composition
of their ash at different stages of
91.5
their growth 434
sweet, its composition 909
tops, ash of . * 385
boiled, used with malt 1050
influence of soils and manures
On * 634, 906
nutritive matter produced by
an acre of & . . 928
-- special manure for 643
Poudrette, its preparation and value
81S al, Illa, Illll'C & * 819
Prepared food, economical use of in
feeding - 105]
Preservation of butter 973
Preserving of milk 946
Primary strata e e 467
Products, agricultural, kinds of 845
Proportion of water in plants 37
Proportions, definite, in which bodies
combine & g 43
Protein compounds found in plants,
their composition
ºsmºsºmas *s in the fungi 926
proportion of in
potatoes * g 904
their functions
in the plant 246
their general pro-
perties and mutual relations
their gradual in-
crease in the seed as it ripens 249
how produced in plants 243
its properties and composition 215
in what part of the plant it
is formed g e 245
Protoxide of iron in the soil, how de-
termined tº &
Purposes served by the ulmic, humic,
218
1110
PAGE
Plants, whence they derive their
oxygen :- & 102, 103
Plastic clay, extent and soil of 458
Ploughing deep, why beneficial 57.1
effect of, explained by
science & w 20
ordinary, why beneficial 567
Subsoil, why beneficial 569
Plum stone kernel, proportion of oil in 921
Poplar, inorganic matter in 305
Poppy, ash of its composition 401
Seed, proportion of oil in 924 |
Porcelain clays, composition of 442
Porous substances absorb ammonia 79 |
Portland beds, soil of 462 |
Pot barley gº * 883
Potash, action of, upon cellular fibre
and woody matter e 188
and soda, can they take the
place of each other in plants P 415
and soda, relative proportion
of, in different crops 414
bi-carbonate of, its composi-
tion & •. º 362
binoxakate of (salt of Sorrel),
its composition * 362
bi-phosphate of, its composi-
tion e ge e 362
— bi-silicate of, (soluble,) its
composition º 362
bi-tartrate of, (cream of tar-
tar), its composition 362
carbonate of 321
its composition 362
— caustic, properties of 322
— citrate of 325
— contained in sea-weeds 125
in the soil, how detected 1081
how determined 1087
its composition 361
nitrate of 323
its composition 362
— its effects upon ve-
getation tº 591
oxalate of 324
325, 612
its composition 362
phosphate of
silicate of 350
silicates of e. . 613
silicate of (soluble) its com-
position & * 362
sulphate of 323
its composition 362
theory of its ac-
*==== ** **-*-
tion upon plants 586
tartrate of 325
theory of its action upon
plants 583
Potassium, chloride of 323
its composition 362
—— properties of 323
GENERAL INDEX.
and crenic acids in the soil 78
Pyroligneous acid 204
Pyrolignite of iron, its use in preserv-
ing wood & 14 1
Quality of ash constant 3()2
Quartz and rock crystal 484
GENERAL INDEX.
PAGE
Quick lime o 334
Quince seeds, ash of tº , 396
Radiation, degree of different by dif-
ferent bodies º & 57
Rain, cause of . e & 56
water carries nitrogen into the
roots of plants 108
— removed by drains 550
Rancidity of butter 973
Rape as green manure 74.1
dust as a manure . 763
its action on different crops 764
its theoretical value as a
Ina (lūl'C º * 773
seed, proportion of oil in 92]
Red clover as a green manure 742
oxide of iron absorbs ammonia 357
Sandstone, new, its extent and
nature of its soils g
old, its extent and
nature of its soils *
limestones from,
468
474
476
390
composition of
Reed, ash of . e tº
Refuse charcoal of the sugar works,
relative value as a manure
Rennet, how it is used g
its influence on the quality
of cheese . 992
799
983
preparation of 980
theory of its action 983
Resins, their composition 20]
Respiration, how kept up 10 18
— of animals 1017
or breathing, quantity
of carbon given off in Great
Britain in a year 264
— purposes served by 1021
Rice, ash of ſº 376
inorganic matter in 303
its composition 89.1
Special manure for 642
straw, ash of e 376
River waters, their composition 839
their use in irrigating 839
Rock crystal and quartz 484
Roe, its muscularfibre,composition of 1010
Rook's dung, its use as a manure 802
Root of plants, its structure 118
Roots absorb nitrogen 107, 108
colouring matters changed by 99
of plants avoid the light 120
functions of 120
Roots absorb water ... e. 120
of plants, soluble substances
absorbed by e & 122
their functions mo-
dified by circumstances . 152
*-* extract insol.ble
437
matter from the ground
111 ||
PAGE
Roots, selecting power of 123
their excretory power 126
Ross-shire, agriculture in wº 7
Rotation of crops gº e ‘ 18
influence of, on
the profit * tº 852
. practical rules
concerning * & 856
*—- theory of 854
theory of Decan-
dolle ſº 855
Royal Agricultural Society of Eng-
land . e e 14
Ruckert, principle announced by 203
Rye grass, ash of 390
seed, ash of 383
ash of 372
as green manure * 74l
effects of manure upon . - 890
of nitrate of soda upon 594
inorganic matter in 303
its composition g 889
nutritive matter produced by
an acre of & 928
special manure for 641
straw, ash of . & 373
its theoretical value as
al, Illa,I\ll TC º * 773
nutritive matter pro-
duced by an acre of 928
Sainfoin, ash of * * 390 2
Sal-ammoniac, its influence on ve-
getation sº * 6 16
Saline manures, circumstances ne-
cessary to ensure their success 599
mixture of, their
effects e * 634
g-º their influence on
the potatoes * 634, 907
— matter in the sap of plants 421
in the soil, qualitative
determination of * 1080
Rººm ºt of plants varies at dif.
ferent periods of their growth 430
— Substances absorbed by char-
coal e & e 27
—- brought down by
the rain o * * 863
Salt, how applied to cheese in
Cheshire * & 995
of Sorrel (binoxalate of pot-
ash) its composition 362
Salts of ammonia decomposed by
lime o e 82
Saltpetre caves in Ceylon 286
Sandy Soils, plants growing on 546
Sap of plants, its ascent modified
by circumstances 153, 154
its course 133
*-**m; — Saline matter in 421
1112
PAGE
Saw dust as a manure 766
De Saussure's experiments upon the
ash left by plants at different
periods of their growth 129
School, Yeoman, at York g I ()
Schorl or tourmaline, composition .
of & gº * 487
Scotch fir, ash of t e 399
inorganic matter in 305
* seeds, ash of 400
peat ashes, their composi-
tion w & & 631
Scotland, agriculture taught in the
schools of ſº e 11
Season, influence of, on produce of
food e ſº 848
Seasons, their influence on the pro-
perties of milk e 932
Sea blubber as a manure 797
— weed, ash of e 623
composition of its orga-
nic part & e 7.58
* dry, its theoretical value
àS 8, 1] \{l Illil'C. - tº 773
— its use, as a manure 7.59
Sea weeds, ashes of e 402
ash of, varies with the
locality 404
contain manna | 82
tº-mº contain much potash 125
inorganic matter in 304
, Seed, gradual increase of protein
compounds in & 249
of plants, formation of 248
variety of, its influence on the
composition of wheat 873
Selecting power of the roots 123
Serpentine, its composition 494
Sewer water, its use as a manure 814
Sheep, Mr Huxtable's food for 105]
bones, composition of . 781
eating off with, improvement
of the soil by e & 753
importance of shelter to 1044
Sheep's blood, composition of its ash 778
dung, its value as a manure 822
urine, composition of its ash 81 l
— its composition 807, 810
Shell fish, as a manure * 797
— Sand, composition of (362
in Scotland . ë . 661
its effects on the soil . 667
Shelter, Mr Childer's experiments on
the saving of food by 1042
Short dung º 833
Silica tº * 349
general remarks upon 355
—- its composition . e 361
relative proportion of, in different
crops e & e 414
GlºW ERAT, INDEX.
PAGE
Silica, relative proportions of, in grain
and straw º 13
Silicate of lime . e 614
in the soil 674
-- its use as an applica-
tion to the land º . 735
— magnesia 353
- potash 350
Soda, 350
Silicates of alumina 354
lime tº 352
*- potash and soda 6.13
are they necessary to the
crop 2 614
Silicon ſe º . 350
Silliman, Professor, his analyses of
corals g e g 664
Silurian system, lower 478
— upper 477
Simple substances, number of . 24
Skim milk cheese, its composition 1000
Skin, its relative value as a manure 799
of animals, its composition 778
Slaking of lime - tº ($52
Slate rocks, properties of lime in 480
Slips in the strata, springs produced
by § • , º
throw up water 562
Smith, Mr, of Deanston, his opinion
of the prospects of agriculture
in Britain gº e e 8
Snow, beneficial influence of e 48
contains ammonia g 49
evaporation of tº e 55
Soaps, their composition 197
Soda, bi-carbonate of 329
- its composition 362
bi-phosphate, its composition 362
bi-silicate of, (soluble) its com-
position 362
carbonate of e 328
(dry) its composi-
tion º * g 362
* (crystallized) its
composition e 362
caustic te 330
in the soil, how detected 1081
how determined 1088
its composition * . 361
nitrate of § 330
--- its composition 362
with sulphate of, its
effects upon vegetation 634
— phosphate of te 330
— phosphates of * & 612
— phosphate of, its compositio 362
— silicate of tº * 350
silicates of § * 6 13
silicate of, (soluble) its compo-
sition - e sº 362
GENERAL INDEX.
PAGE
Soda, sulphate of t 326
*mºm-m-m-mºsºmsºmº- (crystallized), its
composition * e 362
(dry), its composi-
tion {º * * 362
theory of its action
upon plants 583, 586
Sodium . ſº te 33()
chloride of 326
tºm-mºº-º- its composition 362
sulphuret of e . 328
its composition 362
Soil, absolute weight of, determina-
tion of & •
and manure, their influence on
the proportion of mineral matter
in plants ºf te
1074
4.18
and plant, connection between 546
— contracting of, on drying 536
— deepened by draining 553
— density and weight of 530
density of, determination of 1073
— effects of, on the quality of oats 888
— firmness and adhesive power of 531
improvement by laying down to
grass . º fe 747
must contain all the plant re- -
quires º 3] 3
organic matter in . . 439
general composition of its earthy
part e * 440
— importance of depth of . 523
improvement of, by eating off
with sheep e * 753
of, by irrigation 838
of, by mixing 575
of, by planting 755
— influence of, on produce of
food * 849
of, on the composition
of wheaten flour e 870
insoluble earthy matter of, its
determination and analysis
its power of holding water, de-
I 090
termination of * 1075
ºs--a smº- ºr--º-º-º-º-º-º absorbing heat 538
Oxygen, &c.
from the air tº 537
capillary power of 534
power of retaining heat 539
rapidity with which it dries, de-
termination of &
— rendered more friable by drain-
ling & e º
rendered warmer by draining 55l
separation of the organic con-
1075
stituents of te 516
Vegetable matter of, its con-
nection with the growth of
plants & . 93
Virgin, from Gadgirth, compo-
sition of ſº 674
III.3
PAGE
Soil, what a fertile, must contain 529
Soils, analysis of, comprehensive ta-
ble of G & ... 1092
and manures, their influence
on the potato 906
barren, composition of 524
capable of improvement, com-
position of g { } 527
analysis of, its use: 528
chemicalmethods of improving 546
classification of . . 443
fertile, composition of 520, 521
=
general origin of 449
influence of, on the proportion
of ash in plants tº . 311
— mechanical methods of im-
proving & 646
properties of 530
organic substances in .*. 513
specimens of, selection for an-
alysis . fº 1073
— their power of containing water 533
— of imbibing mois-
ture from the air 532
— of retaining water 534
— their relation to water 532
unfruitful, composition of . 524
Solid substances dissolved by water 51
Soluble matter in hay & 918
substances absorbed by the
roots of plants 122
Soot as a manure 768
its composition and use as a
1]] all lll’e tº , º 768
from coal, its theoretical value
alS &l IY):UD lll'O' g . 773
Sorrel, oxalate of potash in. . 67
salt of (binoxalate of potash)
its composition º
Souring of milk . § 946
Sowing of corn earlier on drained
land & 552
Special manure for barley 64 1
—— for cabbage . ... 644
— for coffee tree 645
for flax 646
for Indian corn or
maize te e 042
for maize , , . 642
—— for oats 641
—— for potatoes 643
—— for rice ($42
—— for rye 64 1
for sugar cane . . § 645
—— for tobacco 644
—— for turnips 643
——- for wheat 639
Spiral threads, their composition | 69
Springs produced by slips in thestrata 561
theory of . º 558
Spring water never pure, and why 53
—-— removed by draining 550
INDEX.
IPAGE
Sugar of liquorice, its properties and
composition tº e 182
– of manna, its properties and
composition 18]
—— of milk 183, 941
proportion of in potatoes 903
in turnips 9 II
Sugars, cane, grape, and milk, their
relations to lactic acid
Sulphate of alumina
ammonia and wood ashes,
their effects upon wheat
its action upon
943
347
635
ſºme
vegetation º g 0 15
with sulphate
of soda, their effects upon pota-
toes
te g g 635
of copper, its effects upon
tº e 880
334
673
bread
– of lime
in the soil
theory of its action
upon plants 587
with common salt,
their effects upon beans
of magnesia
G35
g 345
- theory of its
action upon plants &
with nitrate of
soda, their effects upon potatoes
=– of manganese ſº
of potash
587
635
361
* 323
theory of its ac-
tion upon plants
soda g
theory of its action
586
326
upon plants sº e 586
* with sulphate of
ammonia, their effects upon po-
tatoes & *
with nitrate of soda, its ef.
fects upon vegetation
Sulphated urine &
Sulphates of iron . *
theory of their action upon
plants te
Sulphur, properties of
Sulphuret of calcium
Sulphurets of iron
Sulphuret of sodium
Sulphuretted hydrogen, properties
of 320
635
III.4. GENERAL
PAGE
Spontaneous slaking of lime 654
Spurry, composition of its green
StemS e & . 917
employed for green manuring 739.
Stagnant water removed by draining 550
Starch, action of sulphuric acid upon 189
of water upon . 189
and cellular fibre, mutual
transformation of , , . 187
and sugar may produce fat 1023
their use in respi-
101.9
171
ration
its composition
its relation to cellulose, gum,
sugar, and pectic acid
per centage of, in different
varieties of flour 172
proportion of, in potatoes 901
Steaming of food - © 1046
Stearic acid, its composition l 97
Stearine, its properties and composi-
tion g tº . 196
Steeping, influence of, upon the inor-
ganic matter of barley . 422
Stem, its functions modified by cir-
cumstances * , 155
of plants, its structure . 117
Stimulating influence of ammonia
and the nitrates . tº 294
Strata always maintain the same re-
lative position g . 454
continuous over large areas 454
tertiary . d . 457
Stratified rocks, classification of 456
what 451
Straw, as a manure 76 |
ash, theory of its action upon
vegetation ſº *- 627
varies in different parts of 309
ashes, their composition 625
Structure of the leaves of plants 148
Study, rewards of g e 33
Subsoil ploughing, why beneficial 569
Substances containing oxygen decom-
posed by plants . e 144
Sugar and starch may produce fat 1023
— their use in respi-
10] 9
190
ration &
- cane, action of heat upon
action of sulphuric acid
upon & º 190
Asºº ash of 393, 628
*s-s-s inorganic matter in 305
its properties | 79
sm-m-m- special manure for 645
its relation to cellulose,
starch, gum, and pectic acid l 85.
Sugar of eucalyptus, its properties
and composition * . 181
of grapes, its properties and
composition J 80
634
816
359
588
3.18
334
358
328
Sulphuric acid, action of upon cane
Sugar . . 190
cellu-
lar fibre and woody matter ] 88
gum 190
starch 189
effects on vegetation 320
can it take the place
of phosphoric acid in the plant 418
GENERAL INDEX.
- PAGE
Sulphuric acid in the soil, how de-
tected tº ſº 108.1
how de- -
termined & e 1084
— its composition 361
- — its use in fixing am-
monia o & 816
properties of 3.19
——— relative proportions of
in different crops º
Sulphurous acid, its composition 361
— properties of 3.18
Sun-flower seed, proportion of oil in 921
Super-phosphate of lime - 339
Sutherland, agriculture in e 7
Swedish turnip seed, proportion of
oil in º º 921
Sweet almonds, proportion of oil in 921
potato, its composition 909
Sedge, ash of 401
Sweet-scented vernal grass, benzoic
acid in & - 113
Switzerland, cheese yielded by a cow in 999
Synaptas or emulsin . e 213
Table, comprehensive, for the analy-
ses of soils e e 1092
Taffo, prepared in China 820
Tanner's bark, as a manure 768
Tartaric acid, how produced in the
grape © & 250
its properties and
composition º 206
Tartrate of lime 207
of potash e tº 325
Temperature at which milk should
be churned © 961
Tierra del Fuego, peat in 92
Tertiary strata e 457
Theory of fallows e 860
the action of lime . 704
rotation of crops 854
springs 558
Thorn apple, ash of . 396
Three years' course, effects of, in
exhausting the soil 407
Time of cutting, influence of, on the
composition of wheat 873
Tobacco, inorganic matter in 314
special manure for 644
—— leaf, ash of . . 391
leaf, proportion of lime and
alkalies in 4 l 6
Top-dressing with fermenting ma-
Illll'êS e e 835
Tourmaline or schorl, composition of 487
Tournesol, ash left by, at different
periods of its growth 129
Trap, decayed, as a manure 633
rocks, general fertility of their
soils e te 495
------- proportion of lime in 493
1115
PAGE
Trap rocks, their extent in Great
Britain 494
what 492
Trees manure the soil by their leaves 756
Trenching, why beneficial 57.1
Triassic system o . 467
Trouts, their muscular fibre, compo-
sition of © 1 010
True wood, its composition 165
Turf ashes, their composition 629
Turnip and potato, so-called casein in 215
bulb, ash of - 384
its comparative nutritive qua-
lity º - gº 91.5
its composition 911
large crops of 910
Turnips, action of bi-phosphate of
lime upon ($1.1
as a green manure 74.1
effects of nitrate of soda upon 596
Mr Huxtable’s mixture for (336
nutritive matter produced by
an acre of 928
Special manure for 643
— inorganic matter in 304
— tops, ash of - . 385
their theoretical value
a.S & Iſla lllll"G 773, 799
Turpentine, its composition 201
Twigs of plants, their structure 119
Ulmic acid 73
in the soil 514
Ulmin 74
in the soil - e 516
Ulster Chemico-Agricultural Society 16
Unfruitful soils, composition of . 524
United States, teaching of agricul-
ture in schools of & ll
Unstratified rocks, what . 451
Urate, its preparation and use as a
Iſlalllll'e e . 815
Urea, a source of nitrogen to plants 112
its composition 809
Urine of man, horse, cow, sheep, and
pig, their composition 807
brecipitate from, by lime water 815
Saline matter of, its composition 810
waste of 813, 816
Valleys and slips give rise to springs 561
Springs produced by 561
Variety of seed, influence of, on pro-
duce of food e 849
Vegetable cheeses º 99()
food general differences
among e e . 924
life, action of lime upon 733
properties and rela-
tion of carbonic acid to - 62
properties and rela-
tion of oxalic acid to 66
relations of ammonia to 78
1 || || 6
PAGE
Vegetable life, relation of the atmo-
sphere to tº e 40
relation of carbon to 25
hydrogen
to & e
nitrogen
to 31
oxygen to 28
water to 47
- IT]{LIllll'CS & 761
* matter, carbonic acid pro-
duced by its decay e 267
law of its decay 267
of the soil, ammo-
nia in - 112
in the soil, its con-
nection with the growth of plants 93
moulds, composition of 445
substances 285
decomposed in
the soil e tº 862
their theoreti-
cal value as manures •
Vegetables contain all that the ani-
mal requires . &
Vegetation, effects of Sulphuric acid
Oll
769
1015
g gº & 320
influence of ammoniacal
liquor upon 617,
magnesia on 343
— natural changes in 548
Ventilation saves food 1045
Vetch, ash left by, at different periods
of its growth º 129
ash of
straw, ash of te *
Vetches, composition of their green
378
379
Stems * { } º 917
employed as green manure 740
imorganic matter in 304
their composition 895
Vine, ash of twigs 394
—— inorganic matter in 305
twigs, as a green manure 742
proportion of lime and al-
kalies in e e
Volatile substances given off by the
leaves of plants . 142
Volcanos, carbonic acid given off by 272
Walnut kernels, proportion of oil in 921
Warmth, its influence on the quantity
of food required . 104 l
Waste, natural, of the animal body,
1025, 1040
Water, a source of hydrogen to
plants e tº * . 101
a source of oxygen to plants 103
absorbed by the roots | 20
absorbs ammonia 79
affinity by which its elements
are held together g
416
51
GENERAL INT) EX,
PAGE
Water, affinity of, for lime & 54
composition of the air con-
tained in & g . 52
decomposed in the interior of
plants . . o gº 55
freezing of, in the soil 47
in flour º & 866
its composition and relation
to vegetable life * > tº 47
its relation to soils 532
necessary to animal and ye-
getable life . o º 51
never pure in nature 52
proportion of in bread 877
plants 37
potatoes 900
-- purified by charcoal 26
*— thrown up by slips in the
strata © © . 562
use of, in diluting urine
—— yam, its composition
Watery vapour absorbed by the leaves
l
of plants fº &
Watson, Bishop, his analysis of wood
ashes 621
Wax from cork 200
how formed in plants 242
of bees, its composition 199
of mountain ash berries . 200
Weald clay, soil of 462
Wealden, extent and soil of 461
Wells in the city of London 563
Wenlock formation, the nature of its
soils tº { } . 478
Wheat, action of bi-phosphate of
lime upon e º
ash left by, at different pe-
riods of its growth | 29
ash of & º 365
chaff, its theoretical value as
al, Iſlanll]'é 773
effects of germination upon 875
saline manures upon 635
the nitrates upon 595
grain of, proportions of bran
and flour in e tº
influence of seed, soil, and
climate, on composition of . 873
inorganic matter in 303
Mr Burmet's experiments on 635
—— mineral substances in grain
and straw of tº g
nutritive matter produced by
864
412
an acre of 928
-— special manure for 639
straw, ash of 365
its theoretical value as
&l 1118LU, Ull'C. ge 773
tº . § tº
straw, nutritive matter pro-
duced by an acre of 928
Wheaten flour, composition of 866
GENERAL INDEX.
PAGE
Whale blubber as a manure 797
oil as a manure e 797
Whey cheese * tº 990
White mustard as green manure 74]
— proportion of oil in 92]
Wiegman and Polstorf, their experi-
ments e 437
Willow, inorganic matter in 305
Wiltshire cheese, its composition 1001
Winds, their effect in transporting
sands • e
Wood ashes, lixiviated, their compo-
sition & * 622
their action on vegeta-
tion 619
composition 620
composition of different kinds
of . dº e 38
its conversion into acetic acid 204
— modes of preserving 14]
Il 17
PAGE
Wood, preservation of 140
the vessels of, their functions 138
true, its composition & 165
Woody fibré in the grasses, propor-
tion of e
matter and cellular fibre,
mutual transformations of 187
composition of 166, 169
properties of, in dif-
ferent plants 170
Wool and woollen rags as manures 779
composition of 10.13
hair, and horn, their relative
values as manures † ... 799
its composition 780
Yam, composition of . 909
Yeast, Saline substances in the ash of 411
Zein, or gladiadin 202
Zeolite, what 493
EDINBURGH : PRINTED BY STARK AND COMPANY.,
OLD ASSEM B I. Y. CLOSE.
W I L L I A M B L A C K W 00 D & S 0 N S
IIAVE LATELY PUBLISHED
I
ELEMENTS OF AGRICULTURAL CHEMISTRY AND
GEOLOGY.
By JAMES F. W. JOHNSTON, M.A., F. R. SS. L. & E., F. G. S.
Honorary Member of the Royal Agricultural Society, Chemist to the Agricultural
Chemistry Association of Scotland, and Reader on Chemistry and Mineralogy in the
University of Durham. *
A New Edition, greatly enlarged, price 5s.
This little Work is intended to give a familiar and condensed outline of the
subjects treated of more fully in the Lectures.
“This is a little book which we heartily desire to see brought into general circula-
tion in agricultural districts. Practically useful while explaining first principles, and
scientific without pretence, it is just the work to catch and rivet the attention of the
more shrewd and intelligent portion of our agricultural population. The style is de-
lightfully clear, the facts important, brought to bear on the daily business of the far-
mer's life with startling effect ; and the subjects broached so interesting and exten-
sive, that the attention can scarcely fail to be sufficiently awakened to pursue the
study of scientific agriculture a little further.”—Britannia.
“Of all the different works which have lately been published on the Chemistry of
Agriculture, that now before us appears to be most likely to be of real service to the
practical man.”—Loudon's Gardeners’ Magazine.
II.
BY THE SAME AUTHOR,
A CATECHISM OF AGRICULTURAL CHEMISTRY
AND GEOLOGY. :
Sixteenth Edition, price 10d.
The Publishers make a deduction when a quantity is taken for Schools,
or for Distribution. - -
“We would recommend every farmer in Britain, let his knowledge of agriculture
be extended or limited, to procure a copy of the Catechism for himself; and this re-
commendation we would support by the facts, that the memories of the initiated are
apt to get rusty ; so much so that a little rubbing-up may be "necessary ; while the
uninitiated, unaware of the science of agricultural chemistry, by a simple perusal will
be able to discover it clearly, and mould its principles to obtain the highest advantage
to themselves.”—Scientific Agriculturist.
III.
BY THE SAME AUTHOR,
W H A T C A N B E D O N E F O R. E N G L IS H
A. G. R. I C U L T U R E P
A LETTER TO THE MARQUIS OF NORTHAMPTON,
President of the Royal Society.
Price ls.
2
IV
THE CHEMISTRY OF
VEGETABLE AND ANIMAL PHYSIOLOGY.
By Dr G. J. MULDER,
Professor of Chemistry in the University of Utrecht.
TRANSLATED FROM THE DUTCH
- By Dr P. F. H. FROMBERG,
First Assistant in the Laboratory of the Agricultural Chemistry Association of
- Scotland.
WITH AN INTRODUCTION AND NOTEs,
By JAMES F. W. JOHNSTON, F. R. SS. L. & E.
Parts I, and II. are published, price 4s. each.
“In introducing the following work to the British public, I believe I am rendering
a service to the science of the country. The patient research by which it is charac-
terised, and the sober sagacity of the views it contains, cannot fail to recommend it to
that large portion of the community who are now interested in the application of ve-
getable and animal physiology to agriculture and to medicine. With every opinion
expressed by the author I do not concur, and I have here and there ventured to add
brief notes, where the difference of opinion appeared to be of sufficient moment ; but
in the general views which the book contains, so far as it has yet appeared, I antici-
pate that the soundest of our scientific men will agree with me in concurring.”—Ad-
vertisement by Professor Johnston.
V.
A MANUAL OF PRACTICAL DRAINING,
By HENRY STEPHENS, Esq., F. R. S.E.,
Author of the “Book of the Farm.”
Second Edition.
8vo, Illustrated with Sixty-three Engravings on Wood.
Price 3s. 6d.
“A complete manual of draining in all its branches, clearly and concisely written ;
the various systems and practices in use are fairly discussed and commented upon,
their peculiar advantages pointed out, and their applicability to the various descrip-
tions of soil shown. The method of construction of the different drains is described,
their relative cost summed carefully up, with plain and simple directions to the farmer
to guide him in the choice of the particular system of draining he should adopt, as
well as the mode in which it should be done. The merest tyro in agriculture will be
able, after making himself master of the principles laid down in this work, and the
manner in which they are to be brought to bear in increasing the fertility of the soil,
to put into practice that system of thorough draining most applicable to the nature
and character of the soil upon which he wishes to operate.”—Bolton Free Press.
“Thanks to Henry Stephens, Esq., author of “The Book of the Farm,” who has
brought out a cheap work on draining that will do more to set men really right on the
subject than all who have gone before him—a work such as only could be expected
from a man of great genius, sound and philosophic judgment, founded on scientific
research and great practical experience.—Farmers' Gazette, Dublin.
VI.
THE BOOK OF THE FARM,
A SYSTEMATIC WORK ON PRACTICAL AGRICULTURE,
- DETAILING THE LABOURS OF -
THE FARMER, FARM-STEWARD, PLOUGHMAN, SHEPHERD, HEDGER,
CATTLE-MAN, FIELD-WORKER, AND DAIRY-MAID.
By HENRY STEPHENS, F.R.S. E.
In Three large Volumes, royal octavo, Price L.4, 10s.

º
#:
º
wº
Kººr
rºº rº º - º
tº S.S.Sºººººººººººº.
: * ~ * ~ * ºr erº-ºes erºsiº
w
ſ. »
}}
">
Lº
º
●
ºſ;#####
º:
ºs-
Bºº.…Sººº.
ºº:
º
ºs-ºs-ºs- & Rºº ºr * * *
º * ---
º
** **
ſ)
ºſ ſºſiºſ
ſ.ſ. "ĶÅLºſ:{}}）;
§§:ſſſſſſſſſſ
ģ###
}
$（'#ffff;
ķ#3;|-
№ 2)
St.
º
‘;
ºſſºſ
sººſ 'rſſ';
§§
-§§
§§
ķ}}
ģğ];&#8|×###
§.
######
§§
§§
¿
}
#ff88;;:
#########
#########
ķŘſ
ſ.ſ.:№
}}
§§
§$%
* ''
####
ſae
ſ.}
3, ſº
ſº: ：
* … wº
ſae
wſ
ſae
?
};
};
ķğji
#####
ķ
ſºſ，}
8
ſi
§
§§
ķ
ſºļºjºšºſ
ſae e' ， .
9
∞
ț¢ſ
ſ)-
};
șº
ſºſ
. $ſ:
+ ' ' + ::
!,####+j\
•
###########
-rę
:Rºſſſſſſſs!！！!}{（ſ）}{ſ}{ſ}\}\,¿ ºſº，
}}}}}}}}}}}}}###########
¿#####}}}}}}}}%}}"
º №. ！! ;ºſ， sº ſ rºyºſ， ș， ț¢ © ®]（?!}|
ſºſtaeº ^ ： f■■■ ■ ■ ■ ■ ■
§§§Jae, §.º.v.
d.§§）.
į.
įº.
º.s. № jº..."
* （º.ſ.
* * * *gs we w a
º
º
* * *.*.*
** **
ºr º
k
§.
};
H
· ·
º.ſ.
ſ.
Sº
å{}{}， {{:::::::·. （， ， ，5
ķ
}
“E”
rº,
* -
í
iſi
!r:
{}·
łºſł
U|}}};
sº are
º *...***
#########
{{#:;}}}{!！}
a wºº e º ºs e º ºr es
** * * * * * *
ſº
ºf
}}·* {
}}####ſae- -- ··-ſº ſº， º 5 ***·|-·*:'，
ķ:��- -~：·-- · --ſſ: „...vſ.· aerº，+*}: rºſ:
jºſ• ·-·· ----| 2- ---* „ºg“ „“%{
------º-
º
sº
ºr- vº º sºrºrºº:
Kºś.
Sºº-ººººº &
sº
§§
º -
§ §º:
evº º ºs' " º
*...* *
ºr * * * * * * * * * *
-º-º-º-º-º:
• *, * * *-
º, º ºr ==e-
º- - - - - -
ſ
» n * f|-
& : &∞
*№ſºſ;
！
º gº
*-º-º-º-º-
º
. ſae aelº ，
ſ （ ）ſae
º.ſ.§-ſ,ºſſi
, ， , ， ， ，© :
ķº
$º
º º
wº-ºº- i.
%#ffff;##
§§
º:
º º ºr ſº
º
º
§:
* s , º, we ºw
H
ß
~
º
º
Rº:
#
º
sº
ºr sº
º
º
§
§
§
•º º wºre * * * -e- -
sº
Fº:
sº
sº
gº
sº
ºw
º
Fº
RC&S.
º
º
ºfrº.
sº
º
Sºº
Kº:
º wſº（ſ.
ſ šº t ≠º.~·， ， ， ， ！
[3]ķiſ，-·ſ, ºli
،··
* ºr ºº
º
wº
ſº
ºr sº
- Fº
* * * * *
Sºº
º
0
* *
* E.;
R -
Cº.
Sº
º
* *** **
º-º-
º:
&
* *
sº sº
ºr.
º
*
º
ºº:: * , º, .
º
a" sºvº
sºlºiz.:-
~
ºr ~ *, * * * ~ *
*
º sº º a
º
º
º
·-, ! ' ^ſºººººººº!!）:
- ····'#■ ■ Tr. º.\，}{ſF（ſ）\，·
·º.º.， º wł-------. ， . . … º·· ··ſ.º.º ： （ ）{·#*（?：\ſ*）?（?：（?:\ſ*）^#*（?:#（ſ.i º º º
º'：#:####··ſ',··， ， ， -ſ',''，'','';$2&#3* - ,-ºſººf,º）;¿?#:-·（ſr:））;
··， ！·-· ·· ●* … ：-） :-º w| * * · · · -•·∞，r-，
%ĢģĶķ·：Ķķ，ļ，· ·| 1-··-- ·· ··º , ، ، ،）;?,!,:, ..., （* *,: ， ; ::::::№ º--' ， ， ， .#{ſ}}}}}}§§
?!！?!!?!！?！！?！!！， ，·. ， , ，·， ， ， ，·
：
}º ： ? ' • <fºr||№
ºčis',%ſ', ſ.º.º.* ſ- ， :， :，:"*.*）
$ſ;„“ ; ſae·- ·' * * * .·ſaerae”,º,
º :， , . '3'.“§§§§）;
·· ſººſ·|}'，''，'º','!'），';};}"· ·ffff;&######¿ģ
|- ---- -->-•| * |ķaer:。ſºſ，ºſſºſ
2.·~~ .….…-------- ·· ·" .…'.ſ'
#. · ſae.· · · · * ·-------· |--5{，,，-º ： * ºº º-ſ'）;ſº
#
№ſ ſae
ķAbº „ſ，
∞ √° ſ√≠√∞
-§§
* * *-ºs.º.º.º.
w
º
aeſº
ſaeº.º.¿??¿?，
ſº:#;&#%ſ,%ſ,%ſ，%ſ',
3țiffſ,’
rº - tº ºs
ſ ： »
， ·*} ， , rºjſ###!
ººººº…º.º.）aeſº， ºſ·ſiº·:·º·:
Ķ：#-|-- *ſoºſ#ffffff;
X
G.
ºſ ſºſº •
º ，►
ſſſſºſ，ſaeſae ſa
#3;
º
º:
º
sº º –
º
ģ·
¿ſº}，-
ģ;·#ffff;;;;;;;ſ.
, ，'%ſ%ſ',’,
ſº ：
º "E.E.
a.º.
--|-， ，， ， ， ）.#######
..'， #ffffffff;ſaeºſſaepſiſ， lºſ#ffffff;}， #ffffffffffffff;############
ſº ººkrºjºſſae-------ſae' º ~º· - |-$:$ſ';';';
· ·####1;ſººſ ‘ſºſ！·-$ſ;· ·--*：'，
- ·| №’ſ;→ķ|- -};&#;- -
·}，· ·--…* …，∞.'，··}
######################（ſºłº:8.ſ - ： * · * （º.|-§ ¶ （×）ae * ， ， ， ，··***-- （…-..-..-…-------¿ģ
ſaeſł·|--··aeſºſſſſ！!!№ſił， ！- - - - - -; ： :w ：Pºſº, ſ'i
¿-• … »|- -···sºſ, ºſſº- !################·#####
ſſſſſſſſ-- -&#3°·----ſae , , , ，aeº，ae| 1:::::ſiſſiſſiſſae
#####??!！！!！！!！…· ; ºr,- ſ'，'º'，'! *'， ： ，· · · · ·'ſi'','','',';';$':::::：############· ----·
¿?¿--··-|-; : ！! |##########};
----ſae ni ····…''， ſºprºſºs ºſ ae^ ae·º ，
¿?··};Jº};---------ſººſ
§:... Sºº