<y 
 
 LECTURES 
 
 ON THK 
 
 APPLICATIONS OF CHEMISTRY AND GEOLOGY 
 
 AGRIC 
 
 "The profit of Uie e&nb is forU^thekiag.himself is »eiHdbvai^&eld."—£cclt». t. 9. 
 
 BY J^ 
 
 ^•M.LOW OF THE GEOLOGICAL AND CHEMICAL SOCIETIBS, 
 
 H(ji |rary Merrier of the Royal Agricultural Society, Foreign Member of the Koyal 
 fedish Acaflemy of Agriculture, &c. <kc. ; Chemist to the Agricultural 
 I Chemislry Association of Scotland, and Reader in Chemistry 
 and Mineralogy in the University of Durham. 
 
 WITH AN APPENDIX, 
 
 CONTAININO 6DOOE9TIONS FOB SZPERIMENTS IN PBACTICAL AORICCLIUnA 
 
 NEW YORK: 
 PUBLISHED BY WILEY & PUTNAM, 
 
 161 BROADWAY. 
 
 1847. 
 
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VENERABLE CHARLES THORP, D.D., F.R.S., &c., &c., 
 
 ARCHDEACON OP DURHAM, AND WARDEM OP THE UNIVERSITY OP DURHAM. 
 
 My dear Sir, — 
 I cannot more appropriately dedicate tlie following Lectures than to the head 
 of t!ie 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 enlight- 
 ened intentions of yourself and the other Founders of the University of Dur- 
 ham, who have contributed so largely of their fortune and their influence for 
 the promotion and diffusion of sound and us-ful leiirn'ing. That you have so 
 long and so successfully laboured to carry these intentions into effect, is ano- 
 ther reason why I desire to dedicate my work especially to you. 
 
 I need scarcely add how much pleasure it aifords me to embrace this public 
 opportunity of testifying my own personal regard and esteem. 
 Believe me, my dear Sir, 
 
 With much respect, 
 
 Your obedient humble servant, 
 
 JAMES F. W. JOHNSTON. 
 
 Durham, Ut June, 184 1. 
 
PREFACE. 
 
 The First Part of the following Lectures was addressed 
 to a Society* of |)ractical agriculturists, most of whom pos- 
 sessed no knowledge whatever of scientific Chemistry or Ge- 
 ology. They coinnience, therefore, with llie discussion of 
 those elementary principles which are necessary to a proper 
 understanding of each branch of the subject. Every thing 
 in such liCctures, which is not — or may not be — easily un- 
 derstood by those to whom they are addressed, is worse than 
 useless. It has been my wish, therefore, to employ no scien- 
 tific terms, and to refer to no philosophical principles, 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 un- 
 derstood ; such persons will, I hope, do me the justice to be- 
 gin 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 understanding 
 of those which follow. Thus, Part L is devoted to the or- 
 ganic ele?ne/its 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 substance of plants; — Part 
 II., to the itiorganic elements of plants, comprehending the 
 study of the soils from which these elements are derived, and 
 
 * The Durham County Agricultural Society, and the Members of the Dur- 
 ham Farmers' Club. 
 
VI j-nrFAC?:. 
 
 the general relations of geology to agriculture ; — Part III., to 
 the various methods, mechanical and chetnical, by which 
 the soil may be improved, and especially to tJte nature of 
 manures, by which soils are made more productive, and the 
 amount of vegetable produce increased; — and Part IV., 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 
 quality of dairy produce. 
 
 By this method I have endeavoured to ascend from the 
 easy to the apparently difficult ; and I trust that the willing 
 and attentive reader will find no difficulty in keeping bv my 
 side during the entire ascent. 
 
 The Author has much pleasure in tiow presenting these 
 Lectures to the public in a complete form. He has only to 
 express a hope that the delay which has occurred in the pub- 
 lication of the latter part of the work has enabled him to ren- 
 der it more useful, and therefore more worthy of the public 
 approbation. 
 
 Durham, June, 1844, 
 
 Note. — The rapid sale of a large impression having rendered a second 
 edition of the first and second Parts necessary before the entire comple- 
 tion of the work, such alterations, corrections, and additions only have 
 been made as could be introduced without altering the original paging of 
 the work. Several oversights, however, have been corrected, and some 
 omissions supplied, which presented themselves in the earlier edition. 
 
CONTENTS. 
 
 PART Z. 
 
 ON THE ORGANIC CONSTITUENTS OF PLANT& 
 
 LECTURE I. 
 
 IMPORTANCE OF AGRICULTURE. 
 
 Introduction..... p. II 
 
 Diflerent kinds and states ofmatter 21 
 
 Carbon, its properties and relations to ve- 
 getable life 23 
 
 Oxygen, its properties and relations to ve- 
 life. 
 
 getable 
 
 .24 
 
 Hydrogen, its properties and relations to 
 vegetable life p. 25 
 
 Nitrogen, its properties and relations to 
 vegetable life 26 
 
 Rewards of study 27 
 
 LECTURE II. 
 
 CHARACTERISTIC PROPERTIES OF ORGANIC SUBSTANCES. 
 
 Characteristic properties of organic sub- 
 stances 28 
 
 Relative proportions of organic elements.. 29 
 Of the form or state of combination in 
 which the organic elements enter into 
 and minister to the growth of plants 31 
 
 On the constitution of the atmosphere 31 
 
 I The nature and laws of chemical combi- 
 nation 32 
 
 Of water, and its relations to vegetable life.. 36 
 [ Of the cold produced by the evaporation 
 I of water, and its influence on vegetation.. 43 
 
 LECTURE III. 
 
 CARBONIC AND OXALIC ACIDS, THEIR PROPERTIES AND RELATIONS. 
 Carbonic acid, its properties and relations I Light carburetted hydrogen, the gas of 
 
 to vegetable life 45 
 
 Oxalic acid, its properties and relations to 
 
 vegetable life 47 
 
 CartK>nic oxide, its constitution and pro- 
 perties 48 
 
 marshes and of coal mines 49 
 
 Ammonia, its properties and relations to 
 
 vegetable life 50 
 
 Nitric acid, its constitution and properties ..56 
 Questions to be considered 57 
 
 LECTURE IV. 
 
 SOURCE OF THE ORGANIC ELEMENTS OF PLANTS 
 58 
 
 Source of the carbon of plants. 
 
 Form in which carbon enters into the cir- 
 culation of plants 63 
 
 Source of the hydrogen of plants 54 
 
 8oiu°ce of the oxygen of plants 66 
 
 Source of the nitrogen of plants ib. 
 
 Form in which the nitrogen enters into 
 
 the circulation of plants 88 
 
 Absorption of ammonia by plants 70 
 
 Absorption of nitric acid by plants 72 
 
 Conclusions 74 
 
 LECTURE V. 
 
 HOW DOES THE FOOD ENTER INTO THE CIRCULATION OF PLANTS 1 
 
 General structure of plants, and of their 
 
 several parts 75 
 
 The functions of the root 76 
 
 The course of the sap 86 
 
 Functions of the stem 88 
 
 Functions of the leaves 89 
 
 Functions of the bark 96 
 
 Circumstances by which the functions of 
 
 thevariouspartsofplantsaremodified.. 97 
 Effecta of marling lOl 
 
CONTENTS or PART I. 
 
 LECTURE VI. 
 
 SUBSTANCES OF WHICH PLANTS CHIEFLY CONSIST. 
 
 Woody fibre or Usnin — its constitution 
 
 and properties p. 103 
 
 Starch — its constitution and properties. . . .106 
 
 Gum — its constitution and properties 108 
 
 Of Sugar — its varieties and chemical con- 
 stitution 109 
 
 Mutual relations of woody fibre, starch, 
 
 gum, and sugar Ill 
 
 Mutual transformations of woody fibre, 
 starch, gum, and sugar U3 
 
 Of the fermentation of starch and sugar, 
 and of the relative circumstances under 
 whicli cane and grape sugars generally 
 occur in nature p. 116 
 
 Of substances which contain nitrogen. — 
 Gluten, vegetable albumen, and diastase. 116 
 
 Vegetable Acids.— Acetic acid, oxalic acid, 
 tartaric acid, citric acid, malic acid 121 
 
 General obsei-vations on the substances 
 of which plants chiefly consist 126 
 
 LECTURE VII. 
 
 CHEMICAL CHANGES BY WHICH THE SUBSTANCES OF WHICH PLANTS CHIEFLY 
 CONSIST ARE FORMED FROM THOSJi -ON WHICH THEY I,IVE. 
 
 Of the chemical changes between the 
 
 Chemical changes which take place du- I 
 ring germination, and during the devel- { 
 opement of the first leaves and roots.... 130 
 
 Of the chemical changes from the for- 
 mation of the true leaf to the expansion | 
 of the flower 134 
 
 On the production of oxalic acid in the 
 leaves and stems of plants 137 
 
 openinj: of the flower and the ripening 
 
 of the fruit or seed 130 
 
 Of the chemical changes which take place 
 after tlie ripening of the fruit and seed.. 143 
 
 Of the rapidity with which these changes 
 take place, and the circumstances by 
 which they are promoted i). 
 
 LECTURE VIII. 
 
 HOW THE SUPPLY OF FOOD FOR PLANTS IS KEPT UP IN THE GENERAL 
 VEGETATION OF THE GLOBE. 
 
 Of the supply of ammonia to plants 156 
 
 Of the supply of nitric acid to plants 159 
 
 Theory of the action of nitric acid and 
 
 ammonia 163 
 
 Comparative influence of nitric acid and 
 
 of ammonia in different climates 166 
 
 Stimulating influence of these compounria. ib. 
 Concluding observations regarding the 
 
 organic constituents of plants 168 
 
 Of the proportion oY their carbon which 
 plants derive from the atmosphere.. 145 
 
 Of the relation which the quantity of car- 
 bon extracted by plants from the air, 
 bears to the whole quantity contained 
 in the atmosphere 147 
 
 How the supply of carbonic acid in the 
 atmosphere is renewed and regulated.. 14S 
 
 Oeneral conclusions in relation thereto... 155 
 
CONTENTS OF PART II. 
 
 LECTURE IX. 
 
 INORGANIC CONSTITUENTS OP VEGETABLE SUBSTANCES, 
 
 Of the relative proportions of inorganic I 
 
 matter in vegetable substances p. 178 | 
 
 Kind of inorganic matter found in plants. .180 
 Of the several elementary bodies usually 
 imet with in the ash of plants 182 | 
 
 Of those compounds of the inorganic ele- 
 ments whicli enter directly into the 
 circulation, or exist in tlie substance 
 and ash of plants 133 
 
 LECTURE X. 
 
 INORGANIC CONSTITUENTS OP PLANTS CONTINUED. 
 
 Inorganic constituentsof plants continued. 200 I To what extent do the crops most usual- 
 Tabular view of the constitution of the | ly cultivated exhaust the soil of inor- 
 
 compounds of the inorganic elbments I ganic vegetable foodi 220 
 
 above described 214 | Of the alleged constancy of the inorganic 
 
 On the relative proportions of tlie differ- I constituents of plants, in kind and 
 
 ent inorganic compounds present in quantity i^ 
 
 (he ash of plants. 216 j 
 
 LECTURE XI. 
 
 NATURE AND ORIGIN OP SOILS, 
 
 or the organic matter hi the soil 229 I On the general structure of the earth's 
 
 General constitution of the earthy part of | crust 237 
 
 the soil 230 I Relative positions and peculiar charac- 
 
 Of the classification of soils from their ) ters of the several strata .239 
 
 chemical constituents 232 I Classification of the stratified rocks, their 
 
 Of the distinguishing characters of soils j extent, and the agricultural relations of 
 
 and subsoils. 235 the soils derived from them 241 
 
 Of the general origin of soils 236 | 
 
 LECTURE XII, 
 
 COMPOSITION OP THE GRANITIC ROCKS, 
 
 Composition of the granitic rocks.... ...257 
 
 Of ihe degradation of the granitic rocks, 
 
 and of the soils formed from them . . .260 
 Of the trap rocks, and the soils formed 
 
 from them 263 
 
 Of superficial accumulations of foreign 
 
 materials, and of the means by which 
 
 they have been transported 266 
 
 AND OP THEIR CONSTITUENT MINERALS. 
 
 Of the occurrence of such accumulations 
 in Great liritain, and of their influence 
 in modifying the character of the soil.. 270 
 
 IIow far these accumulations of drift in- 
 terfere will) the general deductions of 
 Agricultural Geology 272 
 
 Of superficial accumulations of peat. .... .275 
 
 LECTURE XIII. 
 
 EXACT CHEMICAL CONSTITUTION OP SOILS. 
 
 Of the exact nature of the organic con- I Of the exact chemical constitution of 
 ttituents of soils, and of the mode of | certain soils, and of the results to be 
 separating them 277 I deduced from them 282 
 
 Of the exact chemical constitution of Of the physical properties of soils 290 
 
 tbecaitby part of the soil 281 ] Conclusion .., S97 
 
CONTENTS. 
 
 F.A.RT ZII. 
 
 ON THE IMPROVEMENT OF THE SOIL BY MECHANICAL AND 
 CHEMICAL MEANS. 
 
 LECTURE XIV. 
 
 THE QUALITIES OF THE SOIL MAY BE CHANGED BY ART. 
 
 Connection between the kind of soil and i Of the theory of springs p. 312 
 
 the liind of plants that grow upon it. p. 304 Of ploughina and subsoiling 318 
 
 Of drainin<r, and its eflTects 306 Of deep-ploughing and trenching 321 
 
 Practical effects of draining 311 ' Improvement of the soil by mixing 323 
 
 LECTURE XV. 
 
 IMPROVEMENT OF THE SOIL BY CHEMICAL MEANS. 
 
 Of saline manures 327 
 
 Theory of the action of potash and soda. 328 
 Sulphaces of potash, soda, magnesia, and 
 
 lime (gypsum) 331 
 
 Theory of the action of these sulphates. 332 
 
 Nitrates of potash and soda 335 
 
 Effect of these nitrates on the quantity 
 
 of various crops 336 
 
 Effect of the nitrates on the quality of 
 
 the crop 339 
 
 Cases in which they have failed 341 
 
 Theory of the action of these nitraies. . .343 
 Special effects of the nitrates of potash 
 
 and soda ,344 
 
 Use of common salt 345 
 
 Chlorides of calcium and magnesium. ..317 
 Phosphate of lime and earth of bones. . ..348 
 
 Silicates of potash and soda 349 
 
 Sails of ammonia ib. 
 
 Of mixed saline manures 352 
 
 Wood ashes ib. 
 
 Use of kelp 355 
 
 Straw ashes 356 
 
 Turf peat or Dutch-ashes 359 
 
 Crushed granites and lavas 361 
 
 Results of experiments with mixed ma- 
 nures 362 
 
 LECTURE XVL 
 
 OF THE USE OF LIME AS A MANURE. 
 
 Of the composition of common and 
 magnesian lime-stones 364 
 
 Of the burning and slaking of lime 366 
 
 Changes which the hydrates of lime 
 and magnesia undergo by prolonged 
 exposure to the air 367 
 
 Slates of chemical combination in which 
 lime may be applied to the land 369 
 
 Of the various natural forms in which 
 corftona^e of lime is applied to the land. 370 
 
 Effects of marl, and of ihe coral, shell, 
 and lime-slone sands upon the soil. . . .374 
 
 Of the use of chalks, as a manure 375 
 
 Is lime indispensable to the fertility of 
 the soil 1 377 
 
 States of combination in which lime ex- 
 ists in the soil 373 
 
 Of the quantity of lime which ought to 
 be added to the soil 381 
 
 Ought lime to be applied in large doses 
 at distant intervals, or in smaller quan. 
 
 titles more frequently repeated 1 383 
 
 Form and state of combination in which 
 
 lime ought to be applied to the land. . .386 
 Use and advantase of the compost form. 388 
 
 When ought lime to be applied 1 389 
 
 Of the effects produced by lime upon 
 
 the land and upon the crops 390 
 
 Circumstances by which the effects of 
 
 lime are modified 393 
 
 Effects of an overdose of lime 395 
 
 Length of time during which Hme acts.. 396 
 
 I Of the sinking of lime into the soil 397 
 
 I Why liming must be repeated 393 
 
 j Theory of the action of lime 400 
 
 ; oriime as the food of plants ib. 
 
 I The chemical action of lime is exerted 
 I chiefly ou the organic matter of the soil.401 
 
 ^ 
 
C0ICTBNT8 or PART HI. 
 
 Of the forms In which organic matter 
 usually exists in the soil, and the cir 
 cumstances under which its decom- 
 position may take place p. 401 
 
 General action of aJkaline substances 
 upon oreanic matier 403 
 
 Special effects of caustic lime upon the 
 several varieties of organic matter in 
 the soil 404 
 
 Action of mild (or carbonate of) lime 
 upon the vegetable matter of the 
 soil 406 
 
 Of the comparative utility of burned and 
 
 unbumed lime p. 409 
 
 Action of lime on organic substances 
 
 which contain nitrogen 409 
 
 How these chemical changes directly 
 
 benefit vegetation 412 
 
 Why lime must be kept near the surface.ib. 
 Action of lime upon the inorganic or 
 
 mineral matter of the soil 413 
 
 Action of lime on animal and vegetable 
 
 hfe 415 
 
 Use of silicate of lime 416 
 
 LECTURE XVII. 
 
 OF ORGANIC MANURES. 
 
 Of green manuring or the application of 
 vegetable matter in a green state 417 
 
 Important practical results obtained by 
 greon manuring 418 
 
 Of the plants which in different soils 
 and climates are employed for green 
 manuring ....419 
 
 Will green manuring alone prevent land 
 from becoming exhausted 1 421 
 
 Of the practice of green manuring 422 
 
 Of natural manuring with recent vegeta- 
 ble matter. ib. 
 
 Weisrht of roots left in the soil by the 
 different grasses and clovers 423 
 
 Improvement of the soil by laying down 
 to grass 424 
 
 Improvement of the soil by the planting 
 of trees 429 
 
 Of the use of sea- weed as a manure 431 
 
 Of manuring with dry vegetable sub- 
 stances 433 
 
 Use of rape-dust 434 
 
 Use of decayed vegetable matter as a 
 manure 435 
 
 Use of charred vegetable matters — soot, 
 (fee, as manures 437 
 
 Of the theoretical value of different 
 vegetable substances as manures 440 
 
 LECTURE XVIII. 
 
 ANIMAL MANURES. 
 
 Of flesh, blood, and skin 443 
 
 Of wool, woollen rags, hair, and horn. . .445 
 
 Of the composition of bones 446 
 
 On what does the fertilizing action of 
 
 bones depend ? 447 
 
 Of the application of bone-dust to pas- 
 ture lands 451 
 
 or animal charcoal, the refuse of the su 
 
 gar refineries, and animalized carbon. .452 
 or fish, fish refuse, whale blubber, and 
 
 oil , 453 
 
 nelative fertilizing value of the animal 
 
 manures alreaily described 454 
 
 Of the droppings of fowls — pigeons' 
 
 dung and guano 456 
 
 Results of experiments with guano 459 
 
 Of liquid animal manures— the urine of 
 man, of the cow, the horse, the 
 
 sheep, and the pig .400 
 
 Of the waste of liquid manure — of urate 
 and of sulphated urine 463 
 
 Of solid animal manures— night soil, 
 the dung of the cow, the horse, the 
 sheep, and the pig 465 
 
 Of the quantity of manure produced 
 from the same kind of food by the 
 horse, the cow, and the sheep.. .. .. 468 
 
 Of the relative ferlilizina values of dif. 
 ferent animal excretions 469 
 
 Influence of circumstances on the quali- 
 ty of animal manures 470 
 
 Of the chan-xes which the food under- 
 goes in passing through the bodies of 
 animals .... 472 
 
 Of farm-yard manure, and the loss it un- 
 dergoes by ferinentine 474 
 
 Of top-dressing with fermenting ma- 
 nures 477 
 
 Of eating off with sheeii , 478 
 
 Of the improvement of the soil by irri- 
 gation 479 
 
CONTENTS. 
 
 PART ZV. 
 
 ON THE PRODUCTS OF THE SOIL, AND THEIR USE IN THE FEEDING 
 OF ANIMALS. 
 
 LECTURE XIX. 
 
 OF THE PRODUCE OF THE SOIL. 
 
 Of the maximum or greatest possible an J 
 Ihe average or actual produce of the 
 
 land P-487 
 
 Of the circumstances by which ilie pro- 
 duce of food is affected — climate, sea- 
 son, soil, &c 488 
 
 Influence on the mode of culture on the 
 
 produce of food 490 
 
 Of the theory of the rotation of crops. . .. 492 
 
 Why land becomes tired of clover 494 
 
 Of the theory of fallows 495 
 
 Of viheat and wheaten flour. . .'. 498 
 
 Of the composition of wheaten flour.... 499 
 
 Of the influence of soil and climate on 
 the composition of wlieaten flour. ..... 501 
 
 Inflaence of variety of seed, of mode of 
 culture, of time of cutting, and of special 
 manures on the composition of wheat. 502 
 Of the effects of germination and of bak- 
 ing upon the flour of wheat 501 
 
 Of the supposed relation between Llie per- 
 centage of gluten in flour, and the 
 
 weight of bread obtained from it 507 
 
 Of the composition of barley, and the in- 
 fluence of different manures upon the 
 relative proportions of its several con- 
 stituents 508 
 
 Effect of malting upon barley 509 
 
 Of the composition of oats, and effect of 
 manures in modifying that composition. 510 
 
 510 
 51i 
 
 Of the composition of rye, and the effect 
 of different manures upon its composi- 
 tion p. 
 
 Composilion of rice, Indian corn, and 
 buck- wheat 
 
 On the alleged general tlfeci of different 
 manures in modifying the amount of 
 gluten and albumen in wlieat, barley, 
 oats, and rye, 513 
 
 Composition of peas, beans, and vetches. 515 
 
 Etfjct ol soils and manures on the quahty 
 of peas and beans 513 
 
 Of Che Composition of potatoes, am! the 
 effWcl of circumstances in modifying 
 their composition 680 
 
 Of [he composition of the turnip, tlie car- 
 rot, tlie beet, anil'Jie parsnip 523 
 
 Of the composition of the green stems of 
 peas, vetclies, clover, spurry, and 
 buck wlieal 525 
 
 Of the composilion of (he grasses when 
 made into hay 526 
 
 Of hemp, line, rape, and other oil bearing 
 seeds 528 
 
 General differences in composition amoiif 
 the different kinds of vegetable food. .. 529 
 
 Average composition and produce of nu- 
 tritive matter per acre, by each of the 
 usually cultivated crops 530 
 
 LECTURE XX. 
 
 OF MILK AND ITS PRODUCTS. 
 
 Of the properties and composition of 
 milk 533 
 
 Of the circumstances by which the com- 
 position or quality of milk is modified. 534 
 
 Of the circumstances which affect the 
 quantity of the milk 540 
 
 Of the mode of separating and estimating 
 the several constituents of milk 542 
 
 Of the sugar of milk, and of the acid of 
 milk or lactic acid 543 
 
 Of the mutual relations which exist be- 
 tween lactic acid and the cane, grape, 
 and milk sugars 544 
 
 Of the souring and preserving of milk. . . 546 
 
 Of the separation and measurement of 
 cream — the g;ilactometer — the compo- 
 silion of cream, and the preparation of 
 cream cheese 647 
 
 Of the separation of butter by churning 
 or otherwise 549 
 
 Of the composition of butler 651 
 
 Of the average quantity of butler yielded 
 by milk and cre,im, and of the yearly 
 produce of a cow 552 
 
 Of the circumstances which affect the 
 quality of butler 653 
 
 Of the fatty substances of which butter 
 consists, and of the acid of butter (but/* 
 
CO>'TE>T3 or PART IV. 
 
 ric acid), and the capric and caproic 
 acids P' 5S7 
 
 Of casein or Ihe curd of milk and its pro- 
 perties 561 
 
 Onhe relations of casein to the sugars 
 
 and fats 562 
 
 Of the rancidity and preservation of butter 563 
 Of the natural and artificial curdling of 
 
 milk 566 
 
 Of the preparation of rennet 567 
 
 Theory of the action of rennet 569 
 
 Of Ihe circumstances by which the quali- 
 ty of cheese isafTected 573 
 
 Circumstances under which cheese of 
 different qualities may be obtained from 
 Ihe same milk 575 
 
 Of the average quantity of cheese yielded 
 by different varieties of milk, and of 
 the produce of a single cow p. 590 
 
 Of the fermented liquor from milk, and of 
 milk vinegar 581 
 
 Of the composition of the saline constitu- 
 ents of milk ib. 
 
 Purposes served by milk in the animal 
 economy ^ 582 
 
 On the churning of milk in the French 
 churn ib. 
 
 Quantity of milk a"nd batter yielded by 
 Ayrshire cows 583 
 
 Profit of making butter and cheese com- 
 pared with thalof selling the milk 584 
 
 LECTURE XXI. 
 
 OF THE FEEDtNG OF ANIMALS, AND THE PURPOSES SERVED BY THE FOOD. 
 
 Of the substances of which the parts of 
 animals consist 586 
 
 Whence does the body obtain these sub- 
 stances 1 are they contained in the 
 food? 589 
 
 Of the respinition of animals, and of the 
 purposes sci-\'ed by the starch, gum, 
 and sunar contained in vegetable food.. 591 
 
 Of the origin and purposes served by the 
 fat of animals . 59-1 
 
 Of the natural waste of the parts of the 
 body in a full grown animal 597 
 
 Of the kind and quantity of food necessa- 
 ry to make up for ihe natural waste in 
 the body of a full grown animal 598 
 
 The hcaliii of an animal can be sustained 
 only by a miiced food 600 
 
 Of the kind and quantity of additional 
 food required by the fattenins animal.. 601 
 
 Kind and quantity of additional food re- 
 quired by a growing animal 602 
 
 Kind and quantity of additional food re- 
 quired by a prejtnant animal 604 
 
 Kind and quantity of additional food re- 
 quired by a milking animal 605 
 
 Induence of size, condition, warmth, ex- 
 ercise, and light on the quantity of food 
 necessary to make up lor the natural 
 waste 607 
 
 Influence of the form or state in which 
 the food is given on the quantity re- 
 quired by an animal 611 
 
 Influence of soil and culture on the nutri- 
 tive value of agricultural produce 612 
 
 Can we correctly estimate the feeding 
 properties of ditTerent kinds of produce 
 under all circumstances? 613 
 
 ElTect of different modes of feeding on 
 the manure and on the soil 615 
 
 Summary of the views illustrated in this 
 lecture 617 
 
 Concluding section C19 
 
 > 
 
CONTENTS 
 
 ^PSESTDXX. 
 
 1. Suzsestions for experiments in 
 
 practical a;!;riculture p. 1 
 
 II. EITei't of sudden aliernatioiis of 
 
 temperature 11 
 
 III. Results of experiments in practical 
 agriculture m ule ilnrinj; the spring 
 and Slimmer of 1841 — 
 
 At A^lte Hall 13 
 
 At Erskine 16 
 
 At Barnclian— 
 
 1. On liay 17 
 
 2. On winter rye 18 
 
 3. On wheal 19 
 
 4. On potatoes 20 
 
 5. On miss oats 21 
 
 6. On oafs, with sulphate and ni- 
 
 trate of soda, as a topdressini. .22 
 
 7. On peas and beans, with sulphate 
 
 of soda 23 
 
 8. On nifraienf soda as a lop-dress- \ 
 
 ing for goo.-;eherry and currant 
 
 bushes 23 I 
 
 IV. Snyseslions fi>r comfiarative ex- i 
 
 periments with {jiuano ami other i 
 
 manures 24 
 
 V. Of the examination and analysis of 
 
 soils 27 I 
 
 Determination oftlie i)hysical pro- 1 
 
 perlies of tlie soil ih. 
 
 Of the organic matter present in 
 
 tliesoil 29 
 
 Of the soluble saline matter in the 
 
 soil 31 
 
 Determination of the quantity of 
 
 the several coiistiuients of the 
 
 soluble saline matter .... ....33 
 
 Of the insoluble earthy matter of 
 
 the soil 37 
 
 VI. Different tlieories of the action of 
 
 yypsum 39 
 
 VII. Suggestions for experiments with 
 
 the silicates of potash and soda. . .40 
 VIII. Results of experiments in practical 
 agriculture made in 1342 — 
 A. Experiments on turnips — 
 
 1. Made at Lennox Love 42 
 
 2. Made at Barochan 43 to 45 
 
 3. Made at Sonlhbar 46 
 
 4. Made at Muirkirlt ib. 
 
 6. Effect of gypsu-m on the tur- 
 nip crop 47 
 
 Vni. Results of experiments in practi- 
 cal .iKricnlture made in 1842 — 
 
 B. Experiments on potatoes — 
 
 1. Those of Mr. Campbell, of 
 
 Craiijie p. 47 
 
 2. Those of Mr. Fleming, of 
 
 Btro-han 47 to 51 
 
 C. Experiments upon barley 51 
 
 I>. Experiments iip.in oats — 
 
 1. Tho<eof Lord Blantyre 52 
 
 2. Those of Mr. Fleming 53 
 
 E. Experiments upon wheat — 
 
 1. Those of Lord Blanlvre 5-1 
 
 2. Those of Mr. Flenii.'i 54 
 
 3. Those of Mr. Burnet, of Gad- 
 
 girtli ib. 
 
 F. Experiments upon pasture and 
 
 other grasses — 
 
 1. Those of Mr. Alexander 65 
 
 2. Those of Mr. Fleming ."16 
 
 3. Tlioso of Mr.Oampbelsoflsla.ib. 
 
 G. Experiments upon mixed crops 
 
 hy Mr. Alexander 57 
 
 H. Exp-^rimeuls ii|)on beans — 
 
 1. Those of Mr. Alexander ib. 
 
 2. Those of Lord Blantyre ib. 
 
 I. ElTecl of the top dressings ap- 
 
 plied in 1S41 upon the crop 
 of 1S12 53 
 
 II. Remarks upoiilhe experiments 
 
 of 1842 ib. 
 
 A. The experimf^nts ou turnips.. .59 
 
 B. The experimenis on potatoes. 04 
 C The experimenis on barley... 67 
 
 D. The experiments on oats ib. 
 
 E. The ex)ierinients on wheat 68 
 
 F. The experiments on grass 71 
 
 G. The experiments on mixed 
 
 crops 73 
 
 11. The experimenis on beans ib. 
 
 IX. Results of additional experiments 
 
 made in 1842. 75 
 
 Remarks on these experiments. ..7S 
 X. Experiments in practical agricul- 
 lure made in 1843 by Mr. 
 Fleming, of Barochan — 
 
 1. With guano upon polatoes. ..8.T 
 
 2. Oil hay 85 
 
 3. Ou oats fci6 
 
 4. On turnips 87 
 
 Remarks on tbe.-te experiments... 89 
 
LECTURES 
 
 APPLICATIONS OF CHEMISTRY AND GEOLOGY 
 
 AGRICULTURE. 
 
 ^art K. 
 
 ON THE ORGANIC ELEMENTS OF PLANTS. 
 
LECTURE I. 
 
 Importance of Agriculture— Relation of the growth of food to the population of Great Britain- 
 Recent proiiress ami prospects of English Agriculture— Application of Chemical and Geo- 
 logical Science to the art of culture — to the improvementof soils— the rotation of crops — 
 the application of manures, <tc.— Outline of the Course of Lectures— Number and nature 
 of the elementary bodies — The organic elements Carbon, Ijydrogen, Oxygen, and Nitro 
 gen, their properties and their relations to vegetable life. 
 
 Were I about to address you iu a single or detached Lecture only, I 
 should think it my duty to select some one branch of the art of culture 
 for sjiecial illustration, and withotil much introductory matter to pro- 
 ceed at once to the exposition of the principle or principles on which it 
 depended. As the present, however, is only the first of a Series of Lec- 
 tures I hope to have the honor of delivering to you, I tnay be permitted 
 to introduce my subject with a few prefatory remarks, which will here 
 find iheir ap[)ropriaie place. 
 
 In regard lo the importance of Agriculture it may appear superfluous 
 in tne to address you. That art on which a thousand millions of men 
 are dependent for their very sustenance — in the prosecution f)f which 
 nine-tenths of the fixed capital of all civilized nations is embarked — and 
 probably two hundred millions of men ex[)end their daily toil — that art 
 tnusf cojifessedly be the most important of all ; the parent and precursor 
 of all other arts. In every country then, and at every period, the in- 
 vestigation of the principles on which the rational practice of this art is 
 foi.nded, ought to have commanded the principal attention of the great- 
 est mintls. To what other object could they have been more benefi- 
 cially directed ? 
 
 But tliere are periods in the history of every country when the study 
 of Agriculture becomes more urgent, and in that coutitry acquires a 
 vastly superior itnportance. When a tract of land is tliinly peopled, 
 like the newly settled districts of North Ainerica, 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 |)ariial sup- 
 ply of other countries also. But when the population becomes more 
 dense, the same imperfect or sluggish system will no longer sufifice. 
 The land must be better tilled, its special (qualities and defects must be 
 studied, and tneans must gradually' be adopteil for extracting the maxi- 
 mutn produce from every portion susceptible of cultivation. 
 
 The British islands are in this latter condition. Agriculture now is 
 of vastly more 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 aijout 9 millions of inhabitants ; it now contains nearly 20. 
 The land has not increased in tpianiity, but the consumption of food has 
 probably more than doubled. The importation from abroad lias not in- 
 crease'! to any important extent; by improved management, therefore, 
 the satne area of land has b;'en caused to yield a double produce. 
 
 But the population will continue to increase; can we expect that the 
 food raised froin the land will continue to increase in the satne ratio? 
 
4^2 OK IMPROVEMENTS IN AGRICULTURE. 
 
 This is an important question, to which we can give only an inaperfect 
 and somewhat unsatisfactory answer. 
 
 The superficial area of Great Britain comjirises about 57 millions of 
 acres, of which 34 millions are in cultivation, about 13 millions are in- 
 capable of culture, antl tlie remaining 10 millions are waste lands susceji- 
 tible of improvement. The present [)opu!aiion, therefore, is supported 
 by the [)ro{luce of 34 millions of acres, or every 34 acres raises food for 
 about 20 people. Suppose the 10 millions of acres which are suscepti- 
 ble of improvement to be broujjht into sucli a stale of culture as to 
 maintain an equal proportion — the most favourable supposition — 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 20 
 years,* so that by 1860, unless some general improvement take jilace 
 in the agriculture of the country, the demands of the population will 
 have completely overtaken the productive powers of the land. 
 
 But though we caiuiot say how far the fertility of tiie soil mav be in- 
 creased, or how long it may be able to keep a-head of the growing 
 numbers of the people, we have our own past experience, tlie example 
 of other countries, and the indications of theory, all concurring to per- 
 suade us that the limit of its productive j)owers 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 
 iusbandry 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 general drainage of the soil, the in- 
 vention of improved ploughs and other agricultural implements, as well 
 as the introduction of belter and more economical modes of usina; them, 
 the application of bone manure, and more recently of thorough draining 
 and subsoil ploughing, 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 tor the growth of corn. 
 
 The result of each new improvement, I have said, has seemed more 
 astonishing than the f )rmer. For after a waste [)iece of land has been 
 brought into an average state of productiveness, we are not prepared foi 
 any great improvement upon it by new labours; nor could we readily 
 believe that, half a century after such laud had been in culture, its pro- 
 duce or its value should at once be doubled, by a better draining, a 
 deeper ploughing, or by sprinkling on its surface a small quantity of a 
 saline substance imported from a foreign country. 
 
 Yet the example of tlie Chinese shows us tliat 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 oliers surer rewards to patient industry, or 
 to renewed attempts at imjjrovement. 
 
 In China we see a peo[)le whom we call semi-barbarians, multiply- 
 ing within their own liiDits till their numbers are almost incredible* 
 
 ' For more precise data and calculations see Porter's Progress qf the Nation. 
 
PROSPECTS OF SCIENTIFIC AGRICCLTURE. 13 
 
 practising froin the most remote ages, and in the most skilful manner, 
 various arts which the progress of modern science has but recently in- 
 troduced into civilized Europe; cultivating their soil with the most assid- 
 uous labour, am] stimulating its fertility by means which we have hith- 
 erto neglected, despised, or been wholly ignorant of — but which the dis- 
 coveries of the present time are poinliiig out as best fitted to secure the 
 amplest harvests — and have thus been enabled to compel their limited 
 soil to yield a sufficient sustenance to its almost unlimited po])ulation.* 
 
 Experience and example, therefore, encourage us to look forward to 
 still further improvements in the art of culture, and, independent of such 
 as may be derived from purely mechanical principles, iheoreiical 
 cnemistry seems to point out tiie direction in which important advances 
 of another kind may reasonably be anticijialed. The Chinese are said 
 lo be not only familiar with the relative value and efficiency of the va- 
 rious manures, but also to understand how to prepare and apply without 
 loss tljat which is best fitted to stimulate and supjiort each kind of j)lant. 
 How far this statement is exaggerated we are unable at present to de- 
 termine, but it is in this direction that chemistry appears likely to pro- 
 mote the advance of European agriculture. The practical farmer al- 
 ready rejoices in liaving in one ton of bone dust the equivalent of 14 
 tons of farm-yard manure; some of the most skilful li\ing chemists 
 predict that methods will hereafter be discovered for comjuessing into a 
 siill less bulky form the substances required by plants, and that we 
 shall live to see extensive manufactories established for the preparation 
 of these condensed manures. f 
 
 * An intelligent correspondent reminds nie that the aericulfiiral skill of the Cliinese is 
 questioned by recent writers on the customs of that couniry. This doubt is fimnded chiefly 
 on the rudeness of iheir asricultural implements and the srarcily of caille, whelher horses 
 or cows, among them. But in this densely peopled country the hoe they en'ploy serves 
 the purpose of every other implement (/?ai;s's China, ii. 282). and where the place of cat- 
 tle is supphed 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 
 provinces as it has liitlierlo been supposed. Many writers have eslimaled !he entire 
 population at 300 millions, while recent statists reduce it to 175 millions. Taking even the 
 higher estimate, the population is not more dense than in England and Holland^ — the area 
 of China proper being 1,'iOO.OOO square miles, or eiuht limes that of France. It is considera- 
 bly less dense, indeed, if we lat^e into account the number of horses and caille which in 
 Europe are reared and fed on the proiluce of the land. We may hereafter e.xppct more ac- 
 curale information, however, especially regarding the interior of this interesting country. — 
 See Appendix A. 
 
 1 Should the o|)inions above expressed appeartoo sanguine to some, or be treated by any 
 of niy readers as OTere/y thR()retical.\vion\(\ refer them to the words of Mr. Smith ofDean- 
 ston, Ihe inventor of the subsoil plough, and the introducer of the greatest practical im- 
 }irovement in modern agricullure. Alter staiini; that a< ^eos^ liircefourlhx of the irhnle ara- 
 ble land in Ihe country is under very indifferent culture, chieHy from the want of complete 
 draining and deep working, and, adverting to die increased produce it may be made lo 
 yield, he says, •' it is not at all improbable thai Brilain may become an e.xportinj; country in 
 grain in the course of the next (wenly years." — Keviarks on ITirirou^k Draining nrtd JJeep 
 Ploughing, by James Smith, Esq., of Deaiisinn Works, p. d'i. Were the population lo 
 remain stationary, Mr. Smilh niay be right; at all events, this opinion shows Uiat even 
 practical men do not despair of altaining to a pitch of improvement in agriculture whicli 
 theoretical writers dare not venture to predict. 
 
 But among all per.sons of enlarged information a sindlar opinion prevails. Thus the 
 eloquent author of a recent work on the principles of popuialiou says, '• the single alteration 
 of substituting the kitchen-garden husbandry of Flanders in our plains, and the terraced 
 culture of Tuscany in our hills, for the present system of agricultural management, would 
 at once double the produce of the British islands, and procure ample subsistence for twice 
 the number of its present inhabitants." — Alison's Principles of Population, I. p. 216. These 
 hopes are not lo be rejected or suppressed ; for, though they may never be fully realized, 
 vet they are, as It were, the seeds of exertion, from which ample harvests of good may 
 norcafter be reaped. 
 
 3 
 
14 NEGLECT or SClENTJnC AGRICULTURE IN SCHOOLS. 
 
 Thus mucli may be said in regard to the future hopes and prospects 
 of scientific agriculture.* But how few practical men are acquainted 
 with what is already known of the principles of the important art by 
 which ihey live! Trained u]> in ancient methods — attached generally 
 to conservaiive princijjles in every shape — ihe practical agriculturists, 
 as a body, have always been more opposed to change than any oilier 
 la.'-ge class of the community. They liave been slow to believe in the 
 su|)eriorily of any methods of culture which differetl from their own, 
 from those of their fathers, or of the district in which they live — and, 
 even when the superiority could no longer be denied, ihey have been 
 almost as slow to adopt them. 
 
 But the awakening spirit of the time is making itself felt in the re- 
 motest agricultural districts; old prejudices are dying out, and the cul- 
 tivators of this most ancient, most important, and noblest of all the arts, 
 are becoming generally anxious for information, and eager for improve- 
 ment. f 
 
 Two circumstances have contributed to retard the approach of this 
 better slate of things. 
 
 In the first place, the agricultural interest in England has hiiherlo 
 expended its /nain strength in attempting to secure or maintain impor- 
 tant political advantages in the state. The encouragement of experi- 
 mental agriculture has been in general neglected, while the difllision 
 of |)raclical knowledge has been either wholly overlooked or considered 
 subordinate to other objects. No national eifurts have been made for 
 the general imfirovement of the methods of culture. While for the 
 other important classes of the community special schools have been es- 
 tablished, in which the elements of all the branches of knowledge most 
 necessary for each class have been more or less completely laugiit, and 
 a more enlightened, because better instructed, race of men gradually 
 trained up, no such schools have been instituted for the ber.efit of ilie 
 agriculturist. In our Universities, in which the holders of 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. J With the practice of the art, the theory has also been 
 
 Those who liave access to the Journal of the Royal EngliBh Agricullural Society will 
 find in the first number a pa|ier by Mr. Pusey, " On the present stale of llje si ience of Agri- 
 cnlmre in England," in which much valuable information is contained, and of a more prac- 
 tical Itind than I have been able to introduce. Tliis paper ought to be printed in a separate 
 form, and circulated widely among those who are not members of the Royal English Agri- 
 cultural Society. 
 
 t This opinion has been confirmed by the numerous communications I have received 
 from all parts of the country since the publication of these Lectures was announced, and in 
 wliicli I am assured that tlie want of knowledge is generally felt, and a supply in a sufficient- 
 ly elementary form desired, by all classes of agriculturists. I conclude, therefore, that Lie- 
 big means the following sentence to apply to his German countrymen : " What can be ex 
 pected from Ihe present (aeneration of) farmers, which recoils wirli seeming distrust and 
 aversion from all the measis of assistance ofTered it by chemistry, and which does not un- 
 derstand the art of making a rational application of chemical discoveries." I do not think 
 chemists ought in fairness to blame the practical agriculturists for not under.slandinii the 
 art of applying chemical discoveries to the improvement of the culture of the land. They 
 must Srst know what the discoveries are ; and the error has hitherto been, that no steps 
 have been taken to ditfuse this preliminary knowledge. 
 
 X However satisfied young men may be to avoid ihe labor of additional study while at 
 College, how miny in after life regret that their early attention had not been directed to 
 some o! I hose branches of knowledge which are applicable to common life. Thus the late 
 Lord Dudley, in hia letters to the Bishop of Llanduff, invariably laments, " as mistak^:* in 
 
 r 
 
EJTCOCRAGEMENT OF AGRICULTURAL LITERATURE. 15 
 
 neglected. Scientific men have had no inducement to devote their 
 time and talents to a subject which held out no promise of reward, 
 either in the shape of actual emolument or of honorary distinction. 
 And thus has arisen the second of those circumstances, by which I con- 
 sider the approach of a better state of things to have been retarded- 
 name!}', the want of an Agricultural Literature. 
 
 With the exception of a small number of periodical publications, 
 none of these even too well sujiported, 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 belialf of agricultural knowledge in general — while the 
 single work of Sir Humphry Davy is nearly all that cheiriical science 
 has, in this country, been induced to contribute to the advancement of 
 agricultural theory during the last li)rty years.* 
 
 Many of you have probably read this work of Sir Humphry Davy, 
 and are prepared to acknowledge its value. Yet how many things 
 does lie pass over entirely, how many things leave unexj)lained ! Since 
 his time, not only have numerous practical observations and discoveries 
 been made, but the entire science of animal and vegetable chemistry 
 has been regenerated. We are not, therefore, to expect in his work a 
 view of the present state, either of our theoretical 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 agricultural chemistry of Davy are not to be tried by its 
 accordance with actual knowledge, but with what was known in l'812, 
 when its distinguished author read his course of lectures for the last 
 time before the Board of Agriculture. 
 
 We may with certainty predict, hov/ever, that neither the practice 
 nor the theory of agriculture will be permitted to experience in future 
 that want of general encouragement under which during the last half 
 
 his early life, his unacquaintance with the rudiments of agriculture— his ignorance of bota- 
 ny and geology." — (See also a note to the Review of these Letters in the Quarterly Review 
 for December, 1S40. ) 
 
 For this state of things we shall soon have at least a partial remedy. It is a remarkable 
 fact tliat nearly all the new educational institutions of the higher class, on the Oontinent of 
 Europe, of which so many have been founded within the present century, and all those 
 which have been established in Ameri-.a, I believe, without exception, have incorporated 
 into their course of general study one or more of the newer sciences. Can we have a more 
 consentaneous and universal testimony to their value and importance than this? The Uni- 
 versity of London has been induced, by the same public demand for this species of instruc- 
 tion, to include Chemistry and Botany in its course of arts; and circumstances only have 
 caused Geology to be omitted for a time. Its numerous alBliated institutions have followed 
 its steps; and hence the Catholic College of St. Culhbert, at Ushaw, has in this respect an- 
 ticipated its Protestant neighbor at Durham. 
 
 But should the agricultural interest rest satisfied with this introduction of one or two 
 branches, suppose it generally done, into the University course of stufly? Many are of 
 opinioti that it ought not, and that the general interests of practical agriculture would be 
 manifestly promotpd, among other means, by the establishment of agricultural colleges, in 
 which all the branches necessary to be known by enlightened agriculturists of every class 
 should be specially and distinctly taught. Whether such Colleges might be beneficially 
 annexed to the existing Universities, is a question deserving of serious consideration. 
 
 ' The latest edition of Lord Dundonald's "Treatise on the intimate connection between 
 Chemistry and Agriculture," which I have seen, is dated London, 1S03. 
 
 I should be doing injustice to a good chemist and a zealous agriculturist, were I not to 
 direct the attention of my readers to a series of excellent articles on chemical agriculture 
 by Dr. Madden, inserted in the numbers of the Quarterly Journal of Agriculture for the last 
 two years. 
 
 Since the above went to press, Three Lectures on Agriculture have appeared from the 
 pen of Dr. Daubeny, of Oxford, whose name will secure them an extended circulation. 
 
16 GKMKRAL SCIKACK AM) AGRICULTUKK. 
 
 ?entury they have in England been permitted to languish. The public 
 mind has been awakened, and the establishment of Agricultural Associ- 
 ations, provincial and l(jcal, are manifestations of the interest now fell 
 upon the subject in all parts of the country. It requires only the general 
 exhibition of such an interest, and the adoption of some general means of 
 encouragement, to stimulate botii practical ingenuity and scientific zeal 
 to expend themselves on this most valuable branch of national industry. 
 
 Science is never unwilling to lend her hand to the practical arts ; on 
 the contrary, she is ever forward to profler her assistance, and it is not 
 till her advances have been rejected or frecjuently repulsed, that she re- 
 frains from aiding in their advancement. 
 
 Need I advert, in proof of this, to the unwearied labours of the vege- 
 table [iliysiologists — or to the many valuable observations and experi- 
 ments recorded in the memoirs of scientific chemists. In these memoirs, 
 or in professedly scientific works, such observations have not untre- 
 qiientiy been jienniltcd to rest; — tlie public mind being unprepared 
 either to appreciate their value or to encourage the exertions of those wir.o 
 were willing to give them a practical and popular form. 
 
 And how numerous are the branches of science connected with this 
 art ? Need I speak of botany, which is, as it were, the foundation on 
 which the first elements of agriculture rest ; or of vegetable physiology, 
 to the indications of wliich it has liitherto almost exclusively looked for 
 improvement and increased success; or of zoology, which alone can 
 throw light on the nature of the numerous insects that prey upon your 
 crops, and so often ruin your hopes, — and which can alone be reason- 
 ably expected to arm you against their ravages, and instruct you to ex- 
 tirpate them ? Meteorology among her oilier 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 tl)e year. Do you 
 doubt the importance of such knowledge to the proper cuUivation of tlie 
 land ? Consider the destructive efTects of a late frost in spring, or of a 
 continued heat in summer, and your doubts will be shaken. A wet sea- 
 son in our climate brings with it many evils to the practical agriculturist ; 
 but what efiiict must the rain have on the soil, in countries where nearly 
 as much falls in a month, as in England dming the course of a whole 
 year ;* — wliere every thing soluble is sjieedily washed from the land, and 
 nothing seems to be left but a mixture of sand and gravel ? It may 
 iiideed be said with truth, that no department of natural science is inca- 
 ])able of yielding instruction — that scarcely any knowledge is superflu- 
 ous — to the tiller of the soil. 
 
 It is thus that all branches of human knowledge are bound together, 
 and all the arts of life, and all the cultivators of them, mutually de- 
 pendent. And it is by lending each a helping hand to the others, thai 
 the success of all is to be secured and accelerated ; while with the gene- 
 ral progress of the whole the advance of each individual is made sure. 
 
 The recent contributions and suggestions of geology are the best 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 several soils, the cause of the 
 
 * ^t Canton, m the month of May. the &U of rain is often as much as 20 inches. 
 
 y 
 
GF.OLOGT CO^^■LCT£D V.'ITH AG RICUI.TURK. 17 
 
 diversities which even in the same farm, ii may be in th.e same fielrl, 
 they not unfrequently exhibit;* the nature and diirerences among your 
 subsoils, and the advantages you may expect from breaking them up or 
 brinoing them to the surface. 
 
 Geology is essentially a popular science, and the talents of its emi- 
 nent English cultivators are admirably fitted to make it still more so. 
 Hence, a certain amount of knowledge of this science has been of late 
 years very generally diffused, and its relations to agriculture are be- 
 coming every day belter understood. The Highland Society of Scot- 
 land, among its many other usefid exertions, has done very much to 
 connect agriculture and geology with the sphere of its own labours, 
 while the Journal of the Royal Agricultural Society of England mani- 
 fests 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. That Dr. Buckland, Mr. Murchi- 
 son, and Mr. De la Beche have each engaged to make a gratuitous sur- 
 vey of the subsoils in several extensive agricultural districts, at the re- 
 quest of the Council of this Society, f shows lliat, where their services are 
 estimated, our most eminent scientific men will not hesitate to devote them 
 to the development of the most important branches of national industry. 
 
 The time, therefore, is peculiarly favourable for the increase and diffu- 
 sion of agricultural knowledge. The growth of our population re- 
 quires 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 justified, 
 therefore, in anticipating hereafter a constant and general difiusion of 
 light, a steady progress of agricultural improvement ? 
 
 Having thus glanced at the stale and prospects of scientific agricul- 
 ture in general, and especially of the art of culture in England, permit 
 me to advert to a few of those questions of daiU' occurrence atiiong you, 
 to which chemistry alone can give a satisfactory answer. I shall not in 
 this place allude to the subject of manures — which form alone an entire 
 cliapter of most recondite chemistry, and which I shall take up in its 
 proper place, but I shall select a few isolated topics, the bearing of 
 chemical knowledge upon which is sufficiently striking. 
 
 Some soils are naturally barren, but how few of our agriculturists are 
 able, in regard to such soils generally, to say why ; how few who pos- 
 sess the knowledge requisite for discovering the cause I Of these bar- 
 ren lands some may be improved so as amply to repay the outlay : some, 
 from their locality or from other causes, are in the present state of our 
 knowledge irreclaimable. How important to be able to distinguish be- 
 tween these two cases ! 
 
 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 Jolinstone, Bart., inserted in the Jour- 
 nal of the Enalish Agricultural Society, I. p. 271, entitled "On the Application of Geology to 
 Agriculture." See also an able paper by the Rev. Mr. Thorpe, of which a vahmble report is 
 contained in the Doncaster Chronicle of December 5th, and which will be published in the 
 proceedings of the Geolosical and Polytechnic Society of the West Riding of Vorkshire. 
 
 t Journal of the Royai Agricultural Society, Report of their Council, I. p. 183. 
 
 To form a just idea of the value and importance of such surveys, it is only necessary to 
 read chap, xv., pp. 463 to 480, of Mr. De la Beche's "Geological Report on Cornwall and De- 
 von," or Professor Hitchcock's "Report on a re-examination of the Economic Geology of 
 Massachusetts." 
 
16 CHEMISTKY AJJD AGRICULTURE. 
 
 Some apparently good soils are yet barren in a high degree. In en- 
 deavouring to improve snch 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 bhmders and much expense, he discovers some fact, to hiin- 
 selfnew, but to others long known, and forming only one of many ana- 
 logous facts, flowing from a common, and probably well understood, 
 principle. 
 
 " The application of chemical tests to such a soil," says Sir Humphry 
 Davy, " is obvious. It must contain some noxious principle, [or be de- 
 ficient in some necessary element. — J.] which may be easily discovered 
 and probably easily destroyed. Are any of the salts of iron present, 
 they may be decomj)osed by lime. Is there an excess of siliceous sand, 
 the system of improvement must dejjcnd on the application of clay and 
 calcareous matters. Is there a defect of calcareous matter, the remedy 
 is obvious. Is an excess of vegetable nmtter indicated, it may be re- 
 moved by liming, paring, and burning. Is there a deficiency of vege- 
 table 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 chemistry 
 of our time. Not only is the nature of soils better understood, but we 
 know in many cases what a soil must contain before 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? 
 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 
 districts — whence the gigantic wheat stalk of a virgin soil ? Why do 
 the same forest trees propagate themselves for ages on the same sp<ns 
 without iiiipo\erishing the soil — vvhy do the natural grasses, ihe longer 
 they are iindislurbed, render the land only the more fertile ? 
 
 These, one would think, are scarcely chemical tjuestions, and ytX. to 
 all of them, and to a tliousand such, chemistry alone can and will give 
 a satisfactory answer. 
 
 The rotation of crops is a practical rule, the benefit of which has 
 been proved by experience ; it becomes a true |)hilosophical principle 
 of action, when we discover the causes from which this benefit springs. 
 Botany lias thrown considerable light, and of an interesiing and impor- 
 tant kind, upon this practice, but chemistry has fully cleared it up and 
 establisiied liie principle. 
 
 Sir Huni|)hry Davy s|)eaks of ilie use of lime. Can you explain the 
 mysterious, and apparently fickle and diversified, agency of this sub- 
 stance in reference to vegetation? Are the advantages so fre(|uently 
 attendant upon its use to be ascribed to the chemical character of ilie 
 soil to which it is applied, to the kind and quantity of the vegetable 
 matter it contains, or to the geological nature of the rocks on which it 
 rests? Are they dependent upon the drainage and exposure of the 
 
THEORETICAL KNOWLEDGE iSTILL VERY DEFECTIVE. 19 
 
 land — on the kind of crop to be raised — on the general climate of the 
 district — on tlie maxima and minima of temperature — or on the quanti- 
 ty of rain which falls? 
 
 So wiih gypsum. W!iy are its elfects lauded in one district, doubted 
 in another, and decried in a iliird! Are no rules or principles to he, 
 discovered, by which these diversified effects are to be explained, and 
 the true purpose and fit use of these and other mineral substances clear- 
 ly pointed out? Such principles are yet to be sought for; but if 
 sought by the way of well devised and accurately conducted experi- 
 ment, they are sure to be discovered. 
 
 The land is exhausted by frequent cropping. What language more 
 familiar, what statement more true than this? Yet how few under- 
 stand what exhaustion implies; how few can explain either how it 
 takes place, by what means it can be remedied, or how, if left to her- 
 self, nature at length does apj)ly a remedy ! 
 
 Have you any doubt in regard to the prevailing ignorance on this 
 subject ? To be satisfied, you have only to look with an ex])erienced 
 eye on the agricultural practice of tiie county of Durham. Are there 
 not thousands of acres in the centre of this county which exhibit a de- 
 gree of unproductiveness not natural to the soil ; — wliich have been 
 overcroj)ped, and worn out, and impoverished? A soil comparative- 
 ly fertile by nature has been rendered unfertile by art. That which 
 was naturally good has been rendered as unproductive and unprofitable 
 as that which was naturally bad. Has this state of things arisen from 
 ignorance, from design, or from necessity ? 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 have retarded if 
 not wholly yjre vented it. 
 
 The same knowledge will enable them to reclaim these lands again, 
 and gradually restore them to a more fertile condition ; for the changes 
 which the soil undergoes in such circumstances are all chemical 
 changes, — either in the relative quantities of the substances it contains, 
 or in the state of combination in which they exist. 
 
 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 introduce 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 manure powerful in its action, is (he effect of some 
 permanent, while that of others is speedily exhausted ? — does a mixture 
 of animal and vegelalijc manure prepare the land best for certain kinds 
 of grain'' — do you employ common salt, or gypsum, or saltpetre, or ni- 
 trate of soda, wiih advantage ? — in all these cases you observe chemical 
 results which you would be able to control and modify did you possess 
 the requisite cliemical knowledge. 
 
 It is not wonderful that even theoretical agriculturists should be far 
 behind in the knowledge of those principles on which their most impor- 
 tant operaiions depend. The greatest light has been thrown upon the 
 art of culture by the researches of organic chemistry, a branch which 
 may be said to have started, if not ijiio existence, at least into a new 
 life, within the last ten years. Every day too is addinir to the number 
 
 2 ' ■' 
 
20 OUTLINE OF THE COURSE OF LECTURES. 
 
 and value of its discoveries, and the agriculturist may well be pardoned 
 for not keeping jiace with the advances of a department cf science, 
 which even the |)rofessed and devoled chemist can scarcely overtake. 
 
 I might advert also to the mechanical operations of ploughing, wheth- 
 er common or subsoil, of fallowing, draining, weeding, and many 
 others, as being only so many methods by which chemical action is in- 
 duced or facilitated ; — to the growth of plants, and even to such ob- 
 served diHerences as that of the relative (juantity of leaves and tubers in 
 the potatoe, and of grain and straw in our corn-fields, as interesting 
 cases on which scientific chemistry throws a flood of light. I might 
 shew how the feeding 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 husbandry, is derived from the resuhs of chemical research. 
 
 But I do not dwell on any of these points: they will all hereafter 
 come under our review in their appropriate order, and will afford me an 
 opportunity of laying before you many important facts, as well as, I 
 hope, valuable practical deductions and observations. 
 
 While, however, I feel justified in saying thus much of the light 
 which existing cliemical knowledge throws on the natural processes of 
 vegetation, and on the artificial methods of practical agriculture, I 
 would not lead you to supjjose that our knowledge is by any means 
 complete, that there are not many points over which much darkness 
 still rests — tliat 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 ob- 
 servation without diminishing their imjiorlance or detracting from the 
 value of the facts they embody. Human science is progressive in all 
 its branches, and to refuse to follow the indications of existing know- 
 ledge because it is to some extent uncertain, would be as foolish as to 
 refuse to avail ourselves of the morning's light, because it is not equal 
 to that of the midday sun. 
 
 1 advance, therefore, to the special object of these lectures, and I shall 
 first present you with a rapid outfine 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 
 throw light upon, what is to follow, that we may be able to advance 
 front, the first rudiments to the most difficult and abstruse parts of our 
 subject, without any chance of the illustrations being even difficult to 
 comprehend. This end I do not hope perfectly to attain, but it will be 
 my constant aim, and, with due attention 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 enter into the substances 
 of plants or contribute to their growth and nourishment. 
 
 II. The general structure and functions of the several parts of plflota 
 
ORGANIC AND I.-SORGAMC MATTER. 2i 
 
 — their mode of growth — and llie manner in which their fooa is nli- 
 sorl)ed, changed, and converted into parts of"i1ieir substance. 
 
 III. Tlie origin, nature, and principal differences of soils — with the 
 circumstances on which their relative fertility depends, or under which 
 it is modified. 
 
 IV. The nature and differences of manures, and their mode of action, 
 whether directly in supplying food to the plant, or indirectly in hasten- 
 ing and increasing their growth. 
 
 V. The nature and diversities of the food raised as the result of cul- 
 ture — espscially in reference to their several equivalents or powers of 
 supporting animal life. 
 
 Under this head the feeding of cattle and the variations in the quan- 
 tity and quality of dairy produce, will form subjects of consideration. 
 
 These different branches, I believe, comprehend the whole subject 
 of chemical agriculture ; in regard to all of them we shall derive either 
 from chemistry or geology much important information. 
 
 § 1. Different kinds and stales of 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 atmosphere by which we are surrounded, or in the bo- 
 dies of animals and plants — all are capable of being divided into the two 
 great groups of organic and inorganic mailer. The solid rocks and soils, 
 the atmosphere, the waters of the seas and oceans, every thing 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 organized matter. 
 These generally exhibit a kind of structure readily visible by the eye, 
 as in the pores of wood, and in the fibres of hemj), or of the lean of 
 beef,* and are tlius readily distinguished from inorganic matter, in 
 which no such structure is observable. 
 
 But in many substances of organic origin also, no structure is obser- 
 vable. 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 general name of organic matter. 
 So wlien animals and plants die, their bodies undergo decay, but the 
 mailer of which they are composed is 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 
 lias been derived, have been long ago obliterated. 
 
 .\gain, lieat chars and destroys wood, starcl), 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 fron: 
 vegetable or animal products by these and similar processes are included 
 under the general designation of organic bodies. 
 
 * Ttie pores of wood and fibres and minute vessels in animals being the organs or instru- 
 ments of life, the substances themselves are called organized or organic. 
 
22 NUMBER OF ELEMENTARY BODIES. 
 
 Now if we take a portion of almost any of those numerous forms 
 of matter whicli we meet with either in the inorganic or in the organic 
 kingdoms, we fint], that on subjecting it to certain chemical processes, it 
 is capable of being resolved or separated into more than one substance. 
 Thus coal wlien put into a gas retort is resolved into tar, coal gas, and 
 certain oilier substances. Wood, when treated in the same way, yields 
 pyroiigneous acid, tar, and water, and leaves behind a residue of char- 
 coal. ]f again we subject charcoal to the action of heat (not in the 
 open air), or to any oiVier process we can devise, we can never separate 
 any thing further from it. After all our operations we obtain only 
 charcoal. 
 
 So a piece of common lead ore, when healed in a similar manner, 
 will, if pure, give oHfsulpiiuronly, and leave the lead behind, from which 
 nothing but lead can afterwards be extracted. 
 
 Thus it is evident tiiat wood and the ore of lead differ from charcoal 
 and metallic lead in this respect, that the former consist of more than one 
 kind of matter, the latter of one kind of matter only. Hence charcoal 
 and lead are called simple or elementary bodies, while wood and all oth- 
 er substances which are ca])able of being resolved into two or more 
 different kinds of matter are called compound bodies. 
 
 The diversified forms of matter which present themselves to our no- 
 tice in the mineral 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 re- 
 sults of modern chemistry which to the mind not yet familiarized 
 with chemical discoveries appears most wonderful, — tnat these num- 
 berless fijrms of matter are capable of being resolved into, and there- 
 fore are composed or made up of, only 55* of those simple or ele- 
 mentary substances, the nature of which has been above explained. 
 Occasionally these elementary substances occur in a separate state, as 
 in native [so called when found in the malleable state,] gold and silver, 
 but they are generally found associated together, forming substances 
 from which several of the 55 simple bodies niay be extracted. 
 
 All the material substances in nature consist of one or more of these 
 55 elementary bodies. This is sufficiently surprising, yet it is, if pos- 
 sible, still more remarkable that nearly the entire mass of every vege- 
 table substance may be resolved into one or more oi four only of these 
 simple substances. 
 
 AVhen a portion of animal or vegetable matter is burned it cither en- 
 tirely disappears or leaves beiiind it only a small quantity of ash. Ani- 
 mal and vegetable oils and fats, gum,- sugar, and starcl), when burned, 
 disappear entirely ; a piece of wood or of lean meat leaves a small 
 quantity of earthy (inorganic) matter behind. 
 
 Now all that disappears wlien any portion of vegetable matter, of any 
 kind, is burned, consists generally of three, and only in some rare cases 
 
 ■ The names of these elementary bodies are as follows :— Oxygen, hydrogen, nitrogen, 
 sulphur, selenium, phosphorus, chlorine, bromine, iodine, fluorine, carbon, boron, silicon, 
 potassium, sodium, lithium, barium, strontium, calcium, maiinesium, aluminium, glucinium, 
 ytti'ium, zirconium, thorium, cerium, lauthanium. manganese, iron, cobalt, nickel, zinc, 
 cadmium, lead, lin, bismuth, copper, uranium, mercury (quicksilver), silver, palladium, 
 iridium, platinum, gold, osmium, titanium, tantalum (columbium), tungsten, molybdenum, 
 vanadium, chromium, antimony, tellurium, arsenie. 
 
PROPERTIES OF CARBON. 23 
 
 of more rtian four, of the elementary bodies. These four are carbon, 
 oxygen, hydrogen, and nitrogen. With the exception of the matter ii" 
 destructible by fire (the ash), chemical analysis* has hitherto failed to detect 
 the presence, in aiiy notable quantity, of more than these four substances. 
 The same remarks apply with almost equal truth to animal substances. 
 The destructible part of these also consists of the same four elements. 
 
 To the agriculturist, therefore, an acquaintance with these four con- 
 stituent parts of all that lives and grows on the face of the globe is 
 indispensable. It is impossible for him to coniprehend the laws by 
 which the operations of nature in the vegetable kingdom 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 
 oro-flwiic constituents of plants, in order that we may be prepared for the 
 further inquiries — by what means or in what form they enter into the cir- 
 culation of plants — and how, when they have so entered, they are con- 
 verted into those substances of which the skeleton of the plant consists 
 or which are proiiuced in its several organs. 
 
 ^ 2. Carbon — its properties and relations to vegetable life. 
 
 Carbon is the name given by chemists to the substance of wood char- 
 coal in its purest form. When wood is distilled in close vessels, or 
 burned in heaps covered over, so as to j^revent the free access of air, 
 wood charcoal is left behind. When this process is well performed, the 
 charcoal consists of carbon with a slight admixture only of earthy and 
 saline matters, which remain behind on burning the charcoal in the air. 
 
 Heated in the air, charcoal burns with little flame, and, with the ex- 
 ception of the ash which is left, entirely disappears. It is converted into 
 a kind of air known among chemists by the uaine of carbonic acid, which 
 ascends as it is formed and mingles with the atmosphere. 
 
 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. Tiie diamond is the purest form of carbon, and at a high 
 temperature it burns in the air or in oxygen gas, and, like charcoal, dis- 
 appears in the state of carbonic acid gas. 
 
 Orthis carbon all vegetable substances contain a very large portion. 
 It forms from 40 to 50 per cent., by weight, of all the parts of plants 
 which are culiivatcd for the food of animals or of man, [that is, of these 
 plants in their dried state.] In the economy of nature, therefore, it per- 
 forms a most important part. 
 
 The light porous charcoals obtained from wood [especially from the 
 willow, the pine, and the box], and from animal substances, possess 
 several interesting properties, which are of practical application in the 
 art of culture. 1°. They have the power of absorbing in large quanti- 
 ty into their pores, the gaseous substances and vapours which exist in 
 
 Under the general name of chemical analysis are comprehended the various processes 
 by which, as above explained, natural forms of matter may be resolved or separated into 
 the several elements or simple substances of which they consist. 
 
24 PROPERXrES OF OXYGEN. 
 
 the atmosphere ;* and on this property, as I shall explain hereafter, the 
 use of charcoal powder as a manure probably in some measure depends. 
 2°. They also separate from water any decayed animal matters or col- 
 ouring substances which it may hold in solution ; hence its use in filters 
 for purifying and sweetening impure river or spring waters, or for clari- 
 fying syrups and oils. This action is so powerful that port wine is 
 rendered perfectly colourless by filtering through a well prepared char 
 coal. 
 
 In or upon the soil charcoal for a time will act in the same manner, 
 ■will absorb from the air moisture and gaseous substances, and from the 
 rain and trom fl(jvving waters organized matters of various kinds, any 
 of which it will be in a condition to yield to the plants which grow 
 around it, when they are such as are likely to contribute to their 
 growth. 
 
 3°. 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 aiil of aquanlity of ciiarcoal — and hence the refuse charcoal of the 
 sugar refiners is found to deprive night-soil of its disagreeable odour, and 
 to convert it into a dry and ])orlable manure. 4°. They exhibit also 
 the still more singular property of extracting from water a portion of the 
 saline substances they may happen to hoki in solution, and thus allow- 
 ing it to escape in a less impure form. The decayed (half carbonized) 
 roots of grass, which have been long subjected to irrigation, may act in 
 one or all of these ways on the more or less impure water by which 
 they are irrigated — and thus gradually arrest and collect the materials 
 which are fitted to promote the growth of the coming crop. 
 
 § 3. Oxygen — its projjcrties and relations lo vegetable life. 
 
 Oxygen is a substance with which we are acquainted only in the gas- 
 eous or aeriform state. f By the unaided senses it cannot be distin- 
 guished from common 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 stimu- 
 lated and excited, a state of fever comes on, and after a time the ani- 
 mal dies. 
 
 By these two characters, oxygen is distinguished from every other ele- 
 mentary body. It exists in the atmosphere lo the amount of 21 percent, 
 of its bulk, and in this state of air is necessary to the existence of ani- 
 mals and of plants, and to the su|)portof combustion on the face of the 
 globe. It exists also largely in water, every nine pounds of this liquid 
 containing eight pounds of oxygen. 
 
 ' Thus of ammonia thfiy absorb 95 limes their own bulk, of sulphuretted hydrogen 55 times, 
 of oxygen 9 limes, of liyilioKJ'n Dearly twice Uieir bulk, andof aqueous vapour so much as to 
 increase their weight from 10 to 20 per cent. 
 
 t In this state it is readily obtained by heating in a glass retort the red oxide of mercury 
 of the shops, or a white salt known by the name of chlorate of potash 
 
PROPERTIKS OF HYDROGEN. 25 
 
 But the quantity of this subsiance which is stored up in the solid 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, and of the stones on 
 which we tread — of the soils wliich you daily cultivate, and much more 
 than one-half by weight of the bodies of all living animals and plants, 
 consist 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 substance should have been formed by the Creator in 
 such abundance as to constitute nearly one-half by weight of the entire 
 crust of our globe, but it must strike you as remarkable, lliat 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 wonderful mechanism, be 
 bound up and imprisoned in such vast stores in the solid mountains of 
 the globe, be destined to pervade and refresh all nature in the form of 
 water, and to beautify and adorn the earth in the solid parts of animals 
 and plants. But all nature is full of similar wonders, and every step 
 you advance in the study of the principles of the an by which you live, 
 you will not fail to mark the united skill and bounty of the same great 
 Contriver. 
 
 Oxygen gas is heavier than common air in the proportion of about 11 
 to 10 [its specific gravity by experiment is 1'10"26, air being 1] ; it is 
 also capable of being absorbed by water to a certain extent. One hun- 
 dred measures of water dissolve 6J of this gas. [De Saussure. Ac- 
 cording to Dr. Henry, 100 volumes of water absorb only 3J of oxygen.] 
 Rain, spring, and river waters, ahvaj's contain a portion 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. 
 
 In an atmosphere of pure oxygen gas, plants refuse to vegetate, and 
 speedily perish. 
 
 § 4. Hydrogen — its jifoperties and relations to vegetable life. 
 
 Hydrogen is also known to us only in the state of gas, and when per 
 fectly pure agrees with oxygon 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 abundantly as either carbon or oxygen. It 
 forms a small per centage of the weight of all animal and vegetable 
 substances, and constitutes one-ninth of the weight of 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 ex- 
 tinguished, 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 combus- 
 tion water is formed. [See the Second Lecture.] 
 
 It does not support life, animals cease to breathe when introduced into 
 it, and plants gradually wither and die. It is the lightest of all known 
 substances, being about 14i times lighter than common air, so that if the 
 stopper be removed from a bottle in which it is contained it almost imme- 
 
26 PROPERTIKS OF NITROGE.N. 
 
 diately escapes, [its specific gravity, by experiment, is 0-0687, air be- 
 ing 1.] It is the element whicli is employed to give buoyancy to 
 balloons ; and by this great levity and its relations to flame if is readily 
 distinguislied from all other known substances. 
 
 Water absorbs it only in very small quantities, 100 gallons taking up 
 no more than about lA gallons of liydrogen gas. But, as already ob- 
 served, 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 Irealth and growth of the highest orders 
 of living beings. 
 
 Hydrogen gas is readily obtained from water by putting into it a few 
 pieces of metallic iron or zinc, and adding a little sulphuric acid (oil of 
 vitriol). Bubbles of the gas are liberated from tlie surface of the meti.1, 
 ascend through the water, and may be collected on the surface. 
 
 § 5. Nitrogen — its properties and relations to vegetable life. 
 
 Nitrogen is also known to us only in the form of gas. It exists in the 
 atmosphere to the amount of 79 ))er cent, of its bulk. It is without 
 colour, taste, or smell. Animals and plants die in this gas, and a taper 
 is instantly extinguished when introduced into it ; the gas itself under- 
 going no change. It is lighter than atmospheric air, in the proportion 
 of 97i to 100, [its density is 0-976, air being 1.] It is an essential 
 constituent of the air we breathe, serving to temper the ard'n-r with 
 which combustion would proceed and animals live in uuJuuted oxygen 
 gas. It forms a part of very many animal and of some vegetable sub- 
 stances, but it is not known to enter into the composition of any of the 
 great mineral masses of which the earth's crust is made up. In coal 
 alone, which is of vegetable origin, it has been delected 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 tiiem ; 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 dissolve about li volumes of this 
 gas.* Spring and rain waters absorb it as they do oxygen, from the at- 
 mospheric air, and bear it in solution to the roots, by which it is not un- 
 likely that it may be conveyed directly into the circulation of plants. 
 
 Such are the several elementary bodies of which the organic or de- 
 siructible part of vegetable substances is formed. With one exception 
 they are known to us only in the form of gases ; and yet out of these 
 gases much of the solid parts of animals and of ])lanis are 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 certainty, and in abundance. How difficult 
 to understand the intricate processes by which nature works up these 
 
 * Henry De Saussure says, that pure water absorbs 4 per cent, of its bulk of thi» gas. 
 
REWARDS OF STUDY. 27 
 
 raw materials into her many beautiful productions — ^yet how interest- 
 ing 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 can- 
 not 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 in- 
 stead of a new sense, and makes us acquainted with properties the ex- 
 istence of which, without such aid, we should not even have suspected. 
 Has the Deiiy 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 understanding wliich when cultivated is better than twenty new 
 senses. The cliemist in his laboratory is better armed for the investi- 
 gation of nature, than if his organs of sense had been many times mul- 
 tiplied. 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 researches 
 are carried, the more willing does nature seem to reveal her secrets to 
 him, and the more ra[)idly do his chemical senses increase. Do you 
 think that the rewards of study and patient experimental 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 commonest oper- 
 ations, and over the results you have comparatively little control — but 
 the light is ready to spring up, the means are withio your reach — you 
 have only to employ your minds as diligently as you labour with your 
 hands, and ultimate success is sure. 
 
 ;^6L0Gic^ 
 , 1890 
 
LECTURE 11. 
 
 Characteristic properties of organic substances— Relative proportions of organic eJements— 
 Variabie proportions of inorganic elements in planls^Forni in wiiich tlie organic elo 
 ments are tatien up by plants — Tlie atmosphere, its constitution and relations to vegetabla 
 life — Nature and laws of chemical combination — Water and its relations to vegetable life 
 
 § 1. Characferislic properties of organic substances. 
 
 Of the flnir elementary substances described in ilie former lecture, the 
 organic part of all animal and vegetable substances consists. What is 
 understood by the term organic has also been explained. 
 
 But ors;anic substances pi)s«ess 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 
 cultttre, entirely depends. These characteristic properties are chiefly 
 the following : 
 
 1°. They are all easily decomposed or destroyed by a moderately 
 high temperature. Tf wood or straw be heated in the air, as over the 
 flame of a candle, it becomes charred, burns, and is in a great measure 
 dissipated. So sugar and starch darken in colour when heated, black- 
 en, and take fire. Tlie same is true of all vegetable substances. But 
 limestone, clay, and other earihy or stony matters, undergo no appar- 
 ent change in such circumstances — they are not decomposed. 
 
 2°. When exposed to the air, especially if it be warm and moist, 
 vegetable and aniinal subsiances pulrify and decay.* They decom- 
 pose of their own accord, and after a time almost entirely disappear. 
 Such is not the case with inorganic matters. If the rocks and stones 
 crumble, their particles may be washed away by the rains to a lower 
 level, but they never putrify or wholly disappear. 
 
 3°. Tliey consist almost entirely of two or more of the four organic 
 elements only. The mineral substances we meet with on the earth's 
 ■surface, and collect for our cabinets, often contain portions of many ele- 
 TTientary bodies; but, Vv'ith fev>' exceptions, the organic part of all plants, 
 that which lives and grows, contains only the four siinpie substances 
 described in my former lecture. 
 
 4°. They are disiinguished also by this important character, that 
 ihey cannot be formed by human art. Many of the inorganic com- 
 pounds which occur in th.e mineral crust of the globe can be produced by 
 the chemist in his laboratory, and were any corresponding benefit likely 
 to be derived from the expenditure of time and labour, ihere is reason to 
 believe that, with a few exceptions, nature Tiiight be imitated in the for- 
 mation of any of her mineral productions. But in regard to organic sub- 
 stances, whether animal or vegetable, the chemist is perfectly at fault. 
 He can form neither woody fibre, nor sugar, nor starch, nor muscular 
 fibre, nor any of those substances which constitute the chief bulk of ani- 
 mals and plants, and which serve for the food of animated beings. 
 
 * For an explanation of the exact nature and end of this putrefaction, see the subsequen' 
 Lecture, '■'On the decay of animal and vegetable substance*." 
 
TROSPECTS OF SCIENCE. 29 
 
 This is an important and striking, and is, I believe, li5\ely to remain a 
 ])ernianent distinction, between most substances of organic and of inor- 
 ganic origin. 
 
 Looking back at tlie vast strides which organic chemistry has made 
 within the last twenty years, and is still continuing to make, and trust- 
 ing to the continued progress of human discovery, some sanguine chem- 
 ists venture to anticipate the time when the art of man shall not only 
 ac(|uire a dominion over that principle of life, by the agency of which 
 plants now grow and alone produce food for tnan and beast, but shall be 
 al)le also, in many cases, to imitate or dispense with the operations of that 
 principle: and to predict that the time will come when man shall man- 
 ufacture by art those necessaries and luxuries for which he is now wholly 
 dependent on the vegetable kingdom. 
 
 And, having conquered the winds and the waves by the agency 
 of steam, is man really destined to gain a victory over the uncertain sea- 
 sons 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 influ- 
 ence 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 fiusband- 
 man — to pity the useless toil and the sleepless anxieties of the ancient 
 tillers of the soil ? Is the order of nature, through all past time, to be re- 
 versed — are the entire constitution of socielj', and tlie habits and pur- 
 suits of the whole human race, to be completely altered by the pro- 
 gress of scientific knowledge? 
 
 By placing before man so many incitements to the pursuit of know- 
 ledge, 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 tran- 
 quil pleasures of a country life — the innocent enjoyments of the return- 
 ing seasons — the cheerful health and happiness that wait upon labour 
 inthe free air and beneath the bright sun of heaven. And for what? — 
 only to imprison him in manufactories, to condemn liim 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 de- 
 rive from organic chemistry such power over dead matter as to be able 
 to fashion it into food for living animals. With such consequences be- 
 fore us it seems almost sinful to wish for it. 
 
 Yet, that this branch of science will lead to great ameliorations in the 
 art of culture, there is every reason to believe. It will explain old meth- 
 ods — it will clear up anomalies, reconcile contradictory results by ex- 
 plaining the principles from which they flow — and will suggest new meth- 
 ods by which better, speedier, or more certain harvests may be reaped. 
 
 § 2. Relative proportions of organic elements. 
 Though the substance of plants consists chiefly 'of the four organic ele- 
 ments, yet these bodies enter into the constitution of vegetables in very 
 ditferent proportions. This fact has already been adverted to in a gen- 
 eral manner: it will appear more distinctly by the following statement 
 of (he exact quantities of each element contained in 1000 parts by 
 
30 RELATIVE PROPERTIES OF ORGAMC ELEMENTS. 
 
 weight of some of the more imjjortant kinds of vegetable substance you 
 are in the habit of cuhivatinc; : — 
 
 
 Hay from 
 
 
 
 
 
 
 
 
 
 young Clover 
 
 
 Clover- . 
 
 ALf:er-math 
 
 
 
 
 
 
 3 iiios. oKI. 
 
 Oats. 
 
 Seed. 
 
 Hay. 
 
 Pea.?. 
 
 Wheat. 
 
 Hay. 
 
 Potatoes. 
 
 Carbon . 
 
 507 
 
 507 
 
 491 
 
 471 
 
 465 
 
 455 
 
 458 
 
 441 
 
 Hydrogen 
 
 66 
 
 64 
 
 58 
 
 56 
 
 61 
 
 57 
 
 50 
 
 58 
 
 Oxygen 
 
 389 
 
 367 
 
 350 
 
 349 
 
 401 
 
 431 
 
 387 
 
 439 
 
 Nitrogen 
 
 38 
 
 22 
 
 70 
 
 24 
 
 42 
 
 34 
 
 15 
 
 12 
 
 Ash . . 
 
 . not stated 
 
 40 
 
 28 
 
 100 
 
 31 
 
 23 
 
 90 
 
 50 
 
 1000* 1000; 1000* lOOOf lOOOf. lOOU* lOOOf lOOOf 
 
 The numbers in the above table represent the constitution of the 
 
 plants and seeds, taken in the state in which they are given to cattle or 
 
 are laid up for preservation, and then dried at 230° Fahrenheit. By 
 
 this drying they lost severally as follows : 
 
 1000 parts of Potatoes . . lost . . . 722 parts of water 
 ditto of Wheat . . — ... 166 ditto 
 ditto of Hay ... — ... 158 ditto 
 ditto of Aftermath Hay — . 136 to 140 ditto 
 ditto of Oats ... — ... 151 ditto 
 
 ditto of Clover Seed . — ... 112 ditto 
 ditto of Peas ... — ... 86 ditto 
 In crops as they are reaped, therefore, and even as iliey are given for 
 food, much water is present. When artificially dried, the carbon ap- 
 proaches to one-lialf of (heir weight — the oxygen to more than one- 
 lhird§ — the hydrogen to little more than 5 per cent. — and the nitrogen 
 rarely to more than 2i per cent. These proportions are variable, but 
 they represent very nearly the relative weights in which these elements 
 enter into the constitution of those foriiis of vegetable matter which are 
 raised in the greatest quantity for the support of animal life. 
 
 But, besides the organic part, vegetable stibstances contain an inor- 
 ganic portion, wliich remains behind in the form of ash when the plant is 
 consumed by fire, or of dust when it decomposes and disappears in 
 consetjuence of" natural decay. 
 
 In the dried hay, oats, &c., of which the cotnposition is represented 
 in the above table, we see that the quantity of ash is veiy variable, in 
 oals being as small as 4 per cent., while of hay every hundrerl j)ounds 
 left 10 of ash. A similar difference is observed generally to ])revail 
 throughout the vegetable kingdom. Each variety of j)lant, when 
 burned, leaves a weight of ash, more or less peculiar to itself. Herba- 
 ceous plants generally leave more than the wood of trees — and difTer- 
 ent parts of the same plant yield unlike quantities of inorganic matter.|| 
 
 * Boussingault Annates de Chim. et de Phys. (1838) lxvii. p. 20 to 38. 
 
 t Ditto ditto (lS39)Lxxt. p. 113 to 136. 
 
 i Ditto ditto (1838) lxix. p. 3:J6. 
 
 § This will appear no way inconsistent with the statement in the former Lecture, that 
 oxygen constitutes one-half by weiglil of all //r?7i^ plants, when it ia recollected that of the 
 water driven olT in drying these plants eight-ninths by weight consist of oxygen, and that 
 600 lbs. of grass, for example, yield only from 80 to 100 lbs. of hay. 
 
 n Thus of the oak, the dried bark left (iO of ash— the dried leaves 53 — the dried alburnuir 
 4— and the dried wood only 2 parts in a thousand of ash. — De Saussure. 
 
ON THE CONSTITCTION OF THE ATMOSPHERE. 31 
 
 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 sliall be prepared to consider the chemi- 
 cal nature, the source, and the functions, of the inorganic compounds 
 which exist in living animal and vegetable substances. 
 
 § 3. Of the form or state of combination in which the organic elements 
 enter into and ndnister to the growth of plants. 
 
 From the details already presented in the preceding Lecture, in re- 
 gard to the properties of carbon and nitrogen, and the circumstances 
 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 insoluble in water, cannot obtain admission into 
 the pores of the roots, the only parts of the plants with which, in nature, 
 it can come in contact. The latter (hydrogen) does not occur either in 
 the atmosphere or in the soil in any appreciable quantity, and hence, in 
 its simple state, forms no part of tlie food of plants. Oxygen and nitro- 
 gen, again, both exist in the atmosphere in the gaseous state, and the 
 former is known to be iniialed, under certain conditions, by the leaves 
 of plants. Nitrogen may also in like manner be absorbed by the leaves 
 of living plants, but, if so, it is in a quantity so small as to have hitherto 
 escaped detection. The two latter substances (oxygen and nitrogen) 
 are also slightly soluble in water, and, besides being inhaled by the 
 leaves, may occasionally be absorbed in minute (juantity along with the 
 water taken in by the roots. But by far the largest proportion of these 
 two elementary bodies, and the whole of the carbon and hydrogen 
 which find their way into the interior of plants, have jireviously entered 
 into a state of mutual combination — forming what are called distinct 
 chemical compounds. Before describing the nature and constitution of 
 these compounds, it will be proper to explain, 1°. the constitution of the 
 atmosphere in which plants live, and, 2°. the nature of chemical com- 
 bination and the laws by which it is regulated. 
 
 § 4. On the constitution of the atmosphere. 
 
 The air we breathe, and in which plants live, is composed principal- 
 ly of a Tnixture of oxygen and nitrogen gases, in the proportion very 
 nearly of x'l of the former to 79 of the latter. It contains, however, as 
 a constituent necessary to the very existence of vegetable life, a small 
 per centage of carbonic acid. On an average this carbonic acid 
 amounts to about 775^*0 o^h part* 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 l^nd. Tt 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 is also imbued with moisture. Watery vapour is every 
 where diffused through it, but the quantity varies with the season of 
 the 3'ear, with the climate, with the nature of the locality, with its alti- 
 
 • 0-04 per cent. The mean of 104 experiments made by Saussure at Geneva at all times 
 of the year and of the day gave 415 volumes in 10000. The maximum waa 5-74, smd tha 
 minimum 315. 
 
32 NATURE or CHEMICAL COMBINATIOPf . 
 
 tilde, and wiih its distance from the equator. In temperate climates, 
 it oscillates on the same spot between JJ and 1^ 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 wliich are capable of rising from the surface 
 of the earth in the form of vapour; such, for example, as are given off 
 by decaying animal or vegetable matter — which are the produce of 
 disease in either class of bodies — or which are evolved during the oper- 
 ations of nature in the inorganic kingdom, or by the artificial processes 
 of man. Among these accidental vapours are to be included those 
 miasmata, which, in certain parts of the world, render whole dLstricts 
 unhealthy, — as well as certain compounds of ammonia, which are infer- 
 red to exist in the atmosphere, because they can be delected in rain 
 water, or in snow which has newly fallen. 
 
 In this constitution of the atmosphere we can discover many beauti- 
 ful adaptations to the wants and structure of aniinals and ])lants. The 
 exciting effect of pure oxygen on the animal economy is diluted by the 
 large atlmixture with nitrogen ; — the quantity of carbonic acid present 
 is sufficient to supply food to the plant, while it is not so great as to 
 prove injurious to the animal ; — and the watery vapour suffices to 
 maintain the requisite moisture and flexibility of the parts of both or- 
 ders of beings, without in general being in such a proportion as to prove 
 hurtful to either. 
 
 The air also, by its subtlety, diffuses itself everywhere. 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 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 be- 
 fore, replaced by other air when the rays of the sun are withdrawn. 
 
 By tiie action of these and other causes a constant circulation is, to 
 a certain extent, kept up, — between the atmosphere on the surface, 
 which plays among the leaves and stems of plants, and the air which 
 mingles with the soil and ministers to the roots. The jirecise effect and 
 the importance of this provision will demand our consideration in a fu- 
 ture lecture. 
 
 § 5. The nature and laws of chemical comhination. 
 
 The terms combine and combination in chemical language have a 
 strict and precise application. If sand and saw-dust be rubbed togeth- 
 er in a mortar they may be intimately intermingled, but by pouring wa- 
 ter on the mass we can separate the particles of wood and leave the 
 sand unchanged behind. So if we stir oatmeal and water together, we 
 may cause them perfectly to mix together, but by the aid of a gentle 
 heat we can expel the water and obtain dry oatmeal in its original 
 condition. Or, by putting salt into water, it will dissolve and disappear, 
 and form what is called a solution, but by boiling it down, as is done 
 in our salt-pans, the wafer may be entirely removed and the salt 
 procured of the weight originally employeJ and possessed of its original 
 properties. 
 
 In none of these cases has any chemical action taken place, or any 
 
CBKMICaL DECDMPOSITIO:*. 33 
 
 permanent change been produced, upon any oftlie substances. The two 
 former were merely mixtures. 
 
 In alt cases of chemical action a permanent chavge taJces place in some 
 of Oie substances employed ; and tliis change is the resulteither of a chem- 
 ical combination, or of a chemical dr- om position. 
 
 Thus when sulphur is burned in tlie air, it is converted into white va- 
 pours possessed of a powerful and very un[)]easanl odour, and which 
 continue to be given olF until the whole oftlie sulphur is dissipated. 
 
 Here a solid substance is permanently changed into noxious vapours 
 which disappear in the air, and this change is caused by ihe combination 
 of the sulphur with the oxygen of the atmosphere. 
 
 In like manner when limestone is put into a kiln and strongly heated 
 or burned, it is changed or converted into ciuicklime — a substance very 
 iliflerent in its properties from the natural limestone employed. But 
 -''lis 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. 
 
 Again, 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 bedewed with moisture, and drops of wa- 
 ter collect upon it. How remarkable the change which hydrogen un- 
 dergoes during this combustion! It 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 
 formed! The former a liquid, the latter gases; the former an enemy 
 to all combustion, while of the latter, the one (hydrogen) burns readily, 
 the other (oxygen) is the very life and support of combustion in all oth- 
 er bodies. 
 
 1°. It appears, therefore, that chemical combination or decomposition 
 is always attended by a permanent change. 
 
 2^. That when combination takes place, a new substance is formed 
 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 co/njwuvd. 
 Thus water is a compound (not a mixture) of the two elementary bodies 
 oxygen and hydrogen. 
 
 Now when such combination takes place, it is found to do so always 
 in accordance with certain fixed laws. Thus : 
 
 I. Bodies unite together only in constant and definite proportions. We 
 can 7nix together oxygen and hydrogen gases, for example, in any pro- 
 portion, 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 oxy- 
 gen, the rest of this gas remaining unchanged. A quantity of water will 
 be formed by this union, in which the whole of the hydrogen will be 
 contained, combined with all the oxygen that has disappeared. Under 
 no circumstances 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. And as oxygen is nearly sixteen times 
 heavier than nitrogen, it is obvious that one gallon of the former is about 
 
34 EQUIVALENT NUMBERS — ISOMERIC BODIES 
 
 eight times heavier than two gallons of the latter, so that by weight these 
 two gases, when thus burned, unite togetlier nearly in the proportion 
 ofl to 8, — 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 re- 
 gard to all bodies, and in all cases of chemical combination. Thus we 
 have seen that — 
 By weight. By weight. 
 
 1 of hydrogen combines with 8 of oxygen to form water. 
 
 So 6 of carbon combine . . . 8 carbonic oxide, 
 
 and 14 of nitrogen 8 nitrous oxide. 
 
 Hence 1 of hydrogen, G of carbon, and 14 of nitrogen unite respec- 
 tively with the weight (8) of oxygen. These several numbers, there- 
 fore, are said to be equivalent to each other (they are equivalent numbers). 
 Or they represent the fixed and definite proportions in which these seve- 
 ral substances combine together (they are definite jnoportioyials). Soine 
 chemists consider these numbers to represent the relative weights of the 
 atoms or stnal lest particles of wlilch the several substance.s are made up, 
 and hence not (infrequently 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 shortly by the initial letter of their names. Thus 
 hydrogen is represented by H, carbon by C, and nitrogen by N, and 
 these letters are used to denote not only the substances themselves, but 
 that quantity which is recogni.sed as its equivalent, proportional, or 
 atomic weight. Thus : 
 
 Equivalent 
 Symbol. or aroniic Name, 
 
 weights. 
 
 H denotes 1 by weight, of hydrogen. 
 
 C . . . 6 carbon. 
 
 O . . . 8 oxygen. 
 
 N . . . 14* nitrogen. 
 
 Chemical comhination is expressed shortly by placing these letters in 
 juxta-position, 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 nitrogen. 
 
 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 2 H O, 3 H O, or 3 (H + O), mean two 
 or three equivalents of water, 3 H, or H3 three equivalents of hydrogen, 
 and 4 C or C4, 2 N or Ng, four of carbon and two of nitrogen respec- 
 tively. 
 
 n. Not only are the quantities of the substances which unite together 
 definite and constant, but the properties or qualities of the substances 
 formed are in general equally so. The properties of pure water or o*" 
 
 • More correctly 1, 613, 8013, and 1419. 
 
tAW OF MULTIPLE PROPORTIONS. 35 
 
 carbonic acid are constant and invariable under whatever circumstances 
 they may be formed, and the elements of which they 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 known which contain the same elemeiits united together 
 in tlie same proportions, and wliich, nevertheless, possess very diti'erent 
 ])roperties. Oil of turpentine and oil of lemons are in this condition. 
 They both consist of the same elements, carbon and hydrogen, united 
 together in the same pro[iortions, and yet their sensible properties as well 
 as their chemical relation.-^* are very dissimilar. 
 
 Cane sugar, starch, and gum, all of them abundant products of the 
 vegetable kingdom, consist also of the same elements, carbon, hydro- 
 gen, and OKygen, united together in the same proportions, and may even 
 be represented by the same formula (C,2 Hjo t),o),t ^"^1 yet these 
 substances are as unlike to each other in their properties, as many 
 bodies are of which the chemical composition is very dillerent. To 
 compounds thus differing 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 hereafter. 
 
 3^. Another important law by which chemical combinations are 
 regulated, is known by the name of the law of multijile proportions. 
 Some substances are observed to be capable of uniting together in more 
 than one proportion. Thus carbon unites with oxygen in several pro- 
 portions, forming carbonic oxide, carbonic acid, oxalic acid, &c. Now 
 when such is the case, it is found that the quantity (the weight) of each 
 substance which enters into the several compounds, if not actually re- 
 presented by the ecjiiivalent number or atomic weight, is represented by 
 some simple multiple ol that number. Thus two equivalents of carbon 
 unite with 2, 3, or 4 equivalents of oxygen, to form carbonic oxide, 
 oxalic acid, and carbonic acid respectively, — while one of nitrogen unites 
 with 1, 2, 3, 4, or 5 of oxygen to form a series of compounds, of which 
 the last (N O5), nitric acid, is the only one I shall have frequent occa- 
 sion to speak of in the jiresent lectures. 
 
 This law of multiple proportions, though of great importance in 
 chetnical 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 chemical com- 
 bination, I proceed to make you ac(|uainted with those chemical com- 
 pounds of the organic elements which are known or are supposed to 
 minister to the growth of plants. 
 
 The number of compounds which the four organic elements form 
 with each other is almost endless ; but of this number a very few only 
 
 By the chemical relations of a substance are meant the effects which are prodiice-i 
 upon It t)y contact with other chemical substances. 
 
 t TW\s formula means that starch, gum, and sugar, consist of 12 equivalents of carbon 
 united to 10 of hydrogen and 10 of oxygen. 
 
36 RELATIONS OF WATER TO VEGETABLE LIFE. 
 
 are known to minister directly to the growth or nourishment of plants. 
 Of these, water, carbonic acid, ammonia, and nitric acid, are the most 
 important ; but it will be necessary shortly to advert to a few others, of 
 the occurrence or production or action of which we may hereafter have 
 occasion to speak. 
 
 § 6. Of water and its relations to vegetable life. 
 
 Water ia 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 
 volume of oxygen to 2 of hydrogen. 
 
 It is more universally diffused throughout nature than any other 
 chemical compound with which we are acquainted, performs most im- 
 portant functions in reference to animal and vegetable life, and is en- 
 dowed with properties by which it is wonderfully adapted to the exist- 
 ing condition of things. 
 
 We arc familiar with this substance in three several states of cohe- 
 sion, — in the solid form as ice, in the fluid as water, and in the gaseous 
 as steam. At 32" F. and at lower temperatures, it continues solid, at 
 higher temperatures it melts and forins a liquid (water), which a 
 212° F. begins to boil and is converted into steam. By this change its 
 bulk is increased 1700 times, and it becomes nearly two-fifths lighter 
 than common air, [common air being 1, steam is 0-62.] It therefore 
 readily rises into and diffuses itself tlirough the atmosphere. 
 
 I. There are only one or two circumstances in which water in tne solid 
 form materially atlects 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 separate the particles of the 
 soil from each other. This expansion of the water in dry soils may not 
 be equal to the natural contraction of the soil itself, yet still it is sutH- 
 cient to cause a considerable separation of the earthy particles through- 
 out 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 being previously 
 separated by the crystals of ice, and now loosened by the thaw, fall off 
 or crumble down, and thus the soil becomes exposed to the mellowing 
 action of the atmosphere, which is enabled everywhere to pervade it. 
 On heavy clay land this effect of the winter's frost not unfrequently 
 proves very beneficial.* 
 
 2°. In the form of snow it has been often supposed to be beneficial to 
 winter wheat and other crops. That a heavy fall of snow will shelter 
 and protect the soil and crop from the destructive effects of any severe 
 cold which ma}'^ follow, there can be no doubt. It forms a light porous 
 covering, by which the escape of heat from the soil is almost entirely 
 prevented. It defends the young shoois also from those alternations of 
 temperature to which the periodical return of the sun's rays continually 
 
 ' Tliis alternate contraction and expansion is often injurious to the practical farmer in 
 thrmcing out his winter wheat. Some varieties are said to be more thrown out than others, 
 and tills peculiarity is sometimes ascribed to the longer ami stronger roots which shool from 
 one variety tlian from another; it may, however, be occasionally owing to the ditfereni na- 
 ture of the soils in which the trials have been made, or when, in the same soil, to the diffei'- 
 ent states of dryness at different times. 
 
ACTION A>D PROPERTIES OF SNOW. 37 
 
 exposes ihem ;* and when a thaw arrives, by slowly melting, it allows 
 the lender herbage gradually to accustom itself to the milder atmosphere. 
 
 Ill this manner there is no doubt that a fall of snow may often be of 
 great service to the practical farmer. But some believe that winter 
 wheat actually thrives under snow. On this point I cannot speak from 
 personal knowledge, but I will here mention two facts concerning snow, 
 whicli may possibly be connected with its supposed nourishing quahty. 
 
 [n tlie tirst place, snow generally contains a certain rjunntity of ammo- 
 nia, oi of animal matter which gives oH' ammonia during its decay. 
 This quantity is variable, and is occasionally so small as to be very dif- 
 ficult of detection. Liebig found it in the snow of the neighbourhood of 
 Gicssen, and I have this winter detected traces of it in the snow which 
 fell in Durhainf during two separate storms. This ammonia is present 
 in greater (juantily 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 
 may there be imbibed. Rain water also contains ammonia, but when 
 rain falls in large quantity it runsoff the land, and may do less good than 
 the snow, whicli lies and melts gradually. [For the j)roperties of am- 
 monia, see Lecture III.] 
 
 Another singular property of snow is the power it possesses of ab- 
 sorbing oxygen and nitrogen from the atmosphere, in proportions very 
 different from those in which they exist in the air. The atmosphere, as 
 already stated, contains 21 percent, of oxygen by volume (or bulk), but 
 the air which is present in the pores of snow has been found by various 
 observers to contain a much smaller quantity. Boussingault [Annalen 
 der Physick (Poggendorf), xxxiv., p. 211,] obtained from air disengaged 
 by melting snow 17 per cent, of oxygen only, and De Saussure found 
 still less. The difficulty of respiration experienced on very high moun- 
 tains has been attributed to the nature of the air liberated from snow 
 when melted by the sun's rays. Whether the air retained among the 
 pores of the snow,' which in severe winters covers our corn-fields, be 
 equally deficient in oxygen with that examined by Boussingault, and 
 whether, if it be, the abundance of nitrogen can at all affect vegetation, 
 are matters that still remain undetermined. 
 
 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 dbcernible. 
 
 Pure water is a colourless transparent fluid, destitute of either taste or 
 
 * The effects of such alternations are seen on the occurrence of a night's frost in spring. 
 If the sun's rays fall in ihe early morning, on a frozen shoot, it droops, withers, and tjlack- 
 ens— 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. This efff ct of sudden allcrnations of temperature on or- 
 gainic matter explains many phenomena, to which it would here be out of place to advert. 
 
 A thick light covering of porous earth not beaten down presen-es the polatoe pit fiom the 
 effects of the frost better than a solid compact coaling of clay, in the same way as snow 
 protects the herbage belter than a sheet ol^ ice; and it is because of the porosity of the 
 covering, that ice mav b'e pre.served more effectually, and for a longer period, in a similar 
 pit, than in many well-constructed icehouses. 
 
 t By adding two drops of sulphuric acid to four pints of snow water, evaporating to dry- 
 ness, and mixing the dry mass with quicklime or caustic potash. The residual mass con> 
 tained a brown organic matter, mixed with the sulphate of ammonia. 
 
38 WATER NECESSARY TO LIFE ITS SOLVENT POWER. 
 
 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 col- 
 lecting for the use of man. [See page 30.] 
 
 Not only does it enter thus largely into the constitution of all ani- 
 mals and plants, but in the existing economy of nature it« presence in 
 large quantities is absolutely necessary to the persistence of animal and 
 v<?getable life. In the midst of abundant springs and showers, plants 
 shoot forth with an amazing rapidity, while they wither, droop, and die, 
 when water is withheld. How much the manifestation of life is de- 
 pendent upon its presence, is beautifully illustrated by some of the hum- 
 bler 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 
 foliage when placed in water [the Spaniards call it Triste de Corazon, 
 Sorrow of the Heart. — BurneVs \'Vanderings,\y. 12.1 Tiius life lingers 
 as it were, unwilling to depart and rejoicing to display itself again, when 
 the moisture returns.* 
 
 There are, however, three sjiccial properties of water, which are in 
 a high degree interesting and important to the practical agriculturist, 
 and to which I beg to direct your particular attention. These are: 
 
 1°. Its solvent ])ower; 
 
 2^. lis affinity for certain solid substances ; and, 
 
 3°. The degree of affinity by which its own elements are held to- 
 gether. 
 
 1°. When pure boiled water is exposed to the air, it gradually ab- 
 sorbs a quantity of the several gases of which the atmosphere is com- 
 posed, and acquires more or less of a sparkling appearance and an agree- 
 able taste. The air which it thus absorbs amounts to about J^th of its 
 own bulk, and is entirely expelled by boiling. When thus expelled, 
 this air, like that obtained from snow, is found on examination to contain 
 the oxygen, nitrogen, and carbonic acid in proportions very different from 
 those in which they exist in the atmosphere. In the latter, oxygen is 
 present to the amount of only 21 per cent, by volume, wliile the air ab- 
 sorbed by water contains 30 to 32 per cent, of the same gas. In like 
 manner, the mean quantity of carbonic acid in the air does not exceed 
 Y rtno fr^h parts (0-05 per cent.) of its bulk, while that expelled from water, 
 wnich has been long exposed to the air, varies from 11 to 60 ten thou- 
 sand parts (0-11 to0'6t per cent.) 
 
 ' 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 preserved for a long 
 time in a state of torpor, and afterwards revived by immersion in water. The Veiithium 
 Arrnatum has been brought from the Mauritius in a dry state, wliile snails are said to have 
 been revived after bein;; dried for 15 years. The vibrio tritici (a species of worm), was re- 
 stored by Mr. Bauer, after an apparent death of nearly six years, by merely soaking it in 
 water. The PurcidtiTia Anastobea,a. small microscopic animal, may be made to undergo 
 apparent death and resuscitation many times, by alternate drying and moistening. Accord- 
 ing 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. 
 
 t Of these gases when unmixed, water absorbs very different quantities. Thus 100 vo- 
 lumes of water at 60° F., absorb3-55 of oxygen, t-53 of hydrogen, 1-47 of nitrogen, (Senrt/,) 
 106 of carbonic acid, or 7800 of ammoni^. 
 
ITS AFFINITY FOR SOtID SUBSTANCES. 39 
 
 Thus when water falls in rain or trickles along the surface of the 
 land, it absorbs these gaseous substances, 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 vegetables. 
 
 Again, w'ater possesses the power of dissolving many solid substances. 
 If sugar or salt be mixed with water in certain quantities, they 
 speedily disappear. In like manner, many other bodies, both simple 
 and compound, are taken up by this liquid in greater or less quan- 
 tity, and can only be recovered by driving off the water, through the aid 
 of heat. 
 
 Thus it happens that the water of our springs and rivers is never 
 pure, but holds in solution more or less of certain solid substances. 
 Even rain water, washing and purifying the atmospliere as it descends, 
 brings down portions of solid matter which had previously risen into the 
 air in the form of vapour, and as it afterwards flows along or sinks into 
 the surface of the soil, it meets with and dissolves other solid substances, 
 the greater portion of which it carries with it wherever it enters. In 
 this way solid substances are conveyed to the roots of plants in a fluid 
 form, which enables them to ascend with the sap ; and the supply of 
 these naturally solid substances is constantly renewed, by the succes- 
 sive passage of new portions of flowing water. We shall hereafter be 
 able to see more clearly and to appreciat-e more justly this beautiful ar- 
 rangement of nature, as well as to understand how indispensable it is to 
 the continued fertility of the soil. 
 
 Nor is it merely earthy and saline substances which the water dis- 
 solves, as it thus percolates through the soil. It takes up also sub- 
 stances of organic origin, especially portions of decayed animal and ve- 
 getable matter, — such as are supposed to be capable of ministering to 
 the growth of plants, — and brings them within reach of the roots. 
 
 This solvent i)ower of water over solid substances is 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 absorb, is ascribed, among other causes, the peculiar 
 character of the vegetable productions, as well as their extraordinary 
 luxuriance, in many tropical countries. 
 
 2°. But the affinity which water exhibits for many solid substances is 
 little less important and remarkable. 
 
 When newly burned lime is thrown into a limited quantity of water 
 the latter is absorbed, while the lime heats, cracks, swells, and finally 
 falls 10 a white powder. When thus perfectly slaked, it is found to be 
 one-third heavier than before — every three tons having 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 cannot 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 wo shall return when we hereafter consider the various ways 
 
40 USKS OF WATERY VAPOUR IN VEGETATION. 
 
 in which lime acts, when it is employed by the farmer for the purpose 
 of improving his land. [See the subse([uent lecture, " On the action of 
 lime ivhcn employed as a manure.'"] 
 
 For clay also, water has a considerable affinity, though by no means 
 etjual to that which it displays tor quicklime. Hence, even 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 is drooj)ing or burned up. 
 
 A similar affinity for water is one source of the advantages which are 
 known to follow from the admixture of a certain amount of vegetable 
 matter with the soil ; though, as in the case of charcoal, its porosity* 
 is probably more inlluential in retaining moisture near the roots of 
 the plants.f 
 
 3°. The degree of affinity by which the elements 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 free, while the 
 metal combines with the oxygen. 
 
 So in the interior of plants and animals, water undergoes continual 
 (decomposition and recomposiiion. In its fluid slate, 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 substan- 
 ces, that they are ready to separate from each other at every impulse — 
 yielding now oxygen to one, and now hydrogen to another, as the pre- 
 duction of the several com[)Ounds which each organ is destined to elab- 
 orate respectively demands. Yet witli the same readiness do they 
 again re-aiiach themselves and cling together, when new metainorphoses 
 recjuire it. It is in the form of water, indeed, that nature introduces 
 the greater portion of the oxygen and hydrogen which perform so im- 
 portant a part in the numerous and diversified changes which take place 
 in the iiiterior of plants and animals. Few things are really more won- 
 derful in chemical physiology, than the vast variety of transmutations 
 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° Fahr. 
 when it begins to boil, but it disappears or evaporates from open vessels 
 at almost every temperature, with a rapidity pro|>oriioned to the previ- 
 ous dryness of the air, and to the velocity and temperature of the at- 
 mospheric currents which pass over it. Even ice and snow are grad- 
 
 * Affinity for water causes vegetable matter to combine chemically witti it, porosilt/ causes 
 it merely to ilrink ia the water meclianically, and to retain it, ujichanged, in its pores. 
 
 t For an exposition of the intimate relation of water to the chemical constitution of the 
 solid pans of living vegetables, see a subsequent Lecture, " On the nature and production 
 of the substances oj which plants chiefly consist." 
 
FORMATION OF CLOUDS AND RAIN. 41 
 
 ually dissipated in the coldest weather, and sometimes with a degree 
 af velocity which at first sight seems truly surprising.* 
 
 It thus happens that the atmosphere is constantly impregnated with 
 watery vapour, which in this gaseous state accompanies the air where- 
 ever 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 appreciate the influence which, in this highly 
 comminuted form, water exercises over the general economy of organic 
 nature. 
 
 Bui 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 suspension is depend- 
 ent upon its temperature. At high temperatures, in warm climates, or 
 in warm weather, it can sustain more — at low temperatures less. 
 Hence when a current 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 sus- 
 pension, and therefore leaves behind in the form of a mist or cloud, a 
 portion of its watery burden. In rills subsequently, or sjjrings, the 
 aqueous particles which float in the midst, re-appear on the plains be- 
 neath, bringing nourishment! at once, and agrealeful relief to the thirsty 
 soil. 
 
 So when two currents of air charged with moisture, but of unequal 
 temperature, meet in tlie atmosphere, they mix, and the mixture has 
 the mean temperature of the two currents. But air of this mean tem- 
 perature is incapable of holding in suspension the mean quantity of wa- 
 tery vapour ; 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 those accidental 
 vapours which, though unwholesome to man, are yet fitted to minister 
 to the growth of plants. 
 
 The dew, celebrated through all times and in every tongue for its sweet 
 influence, presents the most beautiful and striking illustration of the agen- 
 cy of water in the economy of nature, and exhibits 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 tiie 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 equilibrium of heat), while 
 
 * 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 56 grains more before the 
 close of the day, when exposed to a smart breeze on a housetop. From an acre of snow 
 this would be equal to lOUO cations of water during the night only. — ProuV s Bridgewater 
 Treatise, p. 302; Eiicyclupcbd. 3Ietropol., art. Meteorology. 
 
 In Von Wrangell's account of his visit to Siberia and the Polar sea, translated by Majoi 
 Sabine (p. 390), it is slated that, in the intense cold, not only living bodies— but the very 
 S7WW — smokes and fills the air with vapour. 
 
 t For the nature of this nourishment see the subsequent Lectures, " On the inorganic con 
 $tUuents of plants." 
 
42 DESCENT OF DEW. UNIVERSAL BOUNTY OF NATURE. 
 
 tlie surface as a whole tends gradually towards a cooler state. But 
 while the sun shines this cooling will not take i)lace, for tlie earth then 
 receives in general more heat than it gives oili and if tlie clear sky be 
 shut out by a canopy of clouds, these will arrest and again throw back 
 a portion of the heat, and prevent it from being so speedily dissipated. 
 At night, then, when the sun is absent, the earth will cool the most ; 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 to- 
 wards 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 forsake a portion 
 • of the watery vapour ii has hitheito retained. This water, like the float- 
 ing mist on the hills, descends in particles almost infinitely minute. 
 These particles collect on every leaflet, and suspend themselves from 
 every blade of grass, in drops of" pearly dew." 
 
 And mark liere a beautiful adaptation. Different substances are en- 
 dowed with the property of radiating their heat, and of thus becoming 
 cool with different degrees of rapidity, and those substances which in 
 »he air become cool first, also attract first and most abundantly the par- 
 ticles of falling dew. Thus in the cool of a summer's evening the grass 
 plot is wet, while the gravel walk is dry; and the thirsty pasture and ev- 
 ery green leaf are drinking in the descending moisture, while the naked 
 land and the barren highway are still unconscious of its fall. 
 
 How beautiful is the contrivance by which water is thus evaporated or 
 distilled as it were into the atmosphere — largely perhaps from some par- 
 ticular spots, — then difllised equably through the wide and restless air, — 
 and afterwards jirecipitated again in refreshing showers or in long-mys- 
 'erious dews!* But how much more beautiful the contrivance, 1 might 
 almost say the instinctive tendency, by which the dew selects the objects 
 on which it delights to fall ; descending first on every living ]}lant, copi- 
 ously ministering to the wants of each, and expending its superfluity 
 oidy on the unproductive waste. 
 
 And equally kind and bountiful, yet provident, is nature in all her 
 operations, and through all her works. Neither skill nor materials are 
 ever wasted ; and yet she ungrudgingly dispenses her favours, apparent- 
 ly 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 un- 
 bounded goodness, but of tmiversal charity — above all other men — on 
 the attention of the tiller of tlie soil. Does the corn spring more 
 freshly when scattered by a Protestant hand — are the harvests more 
 abundant on a Catholic soil. — and does not the sun shine alike, and the 
 dew descend, on the domains of each political parly ? 
 
 ' The lieaiily oTthig arrangement appears more striking when we consider tliat Ihe wliole 
 olthe watery vapour in Ihe air, if it lell at once in Ihe lorm of rain, would not amount to 
 more tlian 5 inclies in deplh on the whole surface ofllie globe. In England ilie 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 lo as much as ISO inches. The mean fall of rain 
 over Ihe whole earth i.? est i ma led at 32 or 33 indies ; but if we suppose il lo beoidy 10 or 15 
 inches. Ihe water wliich thus frills will require to be two or three times re-distilled in the courso 
 of every year. This is exclusive of dew, which in many countries amounts lo a very 
 larce quantil/.— See Prout's Bridgeicater Treatise, p. 309. 
 
COLD PRODUCED BY EVAPORATION, AND ITS INFLUENCE. 43 
 
 So science, from her daily converse with nature, fails r^ot sooner or 
 later lo take her hue and colour from the perception of this universal 
 love and bounty. Party and sectarian differences dwindle away and 
 disappear from the eyes of him who is daily occupied in the coniempla- 
 lion of the boundless munificence of the great Impartial; he sees him- 
 self standing in one comnion relation to all his 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 contribute to the general welfare 
 of all. 
 
 It is in this sense too that science, humbly tracing the footsteps of the 
 Deity ii; all his works, and from tliem deducing his intelligence and his 
 universal goodness — it is in this sense, iJiat science is of no sect, and of 
 no party, but is equally the province, and tlie projjerty, and the friend of all. 
 
 § 7. Of the cold pwd need by the evaporation ofu-alcr, and its 
 injiuence on vegetation. 
 
 Beautiful, however, and beneficem as are the jtrovisions by which, in 
 nature, v.'atery vapour is mad'j to serve so many useful purposes, there 
 are circumstances in which, and olien through the neglect of man, the 
 |)resence of water becomes injurious to vegetation. 
 
 The ascent of water, in the form of vapour, peimits the soil to dry, 
 and fits it for the labours oi' the husbandman; while its descent in dew 
 refreshes the plant, exhausted by the heat and excitement of a long 
 summc's day. But the same tendency (o ascend in va|X)ur, 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 coW, applied to such soils, though derived probably from 
 no theoretical views, yet expresses very truly their actual condition. 
 The surface of ilie fields in localities 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 immediately beneath the soil in two 
 such fields, when in the hottest day a marked difference of temperature 
 will, in general, be i>ercef)tible. The 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 tem|)eralure 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. Bui since, as already stated, it becomes no hot- 
 ter, the heat received from the fire must be carried off by the steam. 
 
 Now this is universally true. IVhenever icater is converted into 
 steam, the ascendivg vapour carries off nmch heat along icithit. 
 
 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 — and tJie surface of the stone, the leaf, or the field, must become 
 colder. That stone or leaf also must become coldest from which the 
 largest qtnmtity of vapour rises. 
 
 3 
 
44 WET AND COLD SOILS IMPROVED BY DRAINmO. 
 
 Now, let two adjoining fields be wet or moist in differeni degrees, that 
 which is wettest will ahnosl at all times give otFthe 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 healing rays, and cause them 
 te re-ascend in the watery vapour. Let summer come, and while the 
 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 hereafter 
 more particularly advert to the important influence which a high tempe- 
 rature 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 fit it for deriving the greatest possible benefit from the 
 presence of the sun's rays. In the mean time you are willing to con- 
 cede that warmth in the soil is favourable to the success of your agricul- 
 tural pursuits. What, then, is the cause of the coldness and poverty, 
 the fickleness and uncertainty of produce, in land of the kind now al- 
 luded to ? It is the presence of too much water. What is the remedy ? 
 A removal of the excess of water. And how ? By effectual drainage. 
 
 There are other benefits to the land, which follow from this removal 
 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 shows you that 
 the first effect upon the soil is the same as if you were to place it in a 
 warmer chmate, and under a milder sky — where it could bring to ma- 
 turity other fruits, and yield more certain crops. 
 
 The application of this merely rudimentary knowledge will enable 
 you to remove from many improvable spots the stigma of being poor and 
 cold; an appellation hitherto a])plied to them, — not because they are by 
 nature unproductive, but because ignorance, or indolence, or indifference, 
 has hitherto prevented their natural capabilities from being either ap- 
 preciated or made available. 
 
 Note. — In reference to tlie supposed fertilizing effect of snow, adverted to in the above 
 lecture, I may mention a fact observed by Heyer, and quoted by Liebig, (p. 125), that willow 
 branches immersed in snow water put forlh roots three or four times longer than when put 
 into pure distilled water, an<l that the latter remained clear while the snow water became 
 coloured. This shows that snow contains somethins; not present in distilled water, which 
 is capable of accelerating the jjrowth of plants. The experiment would have been more 
 instructive in regard to natural operations, had the effect of the snow water been coin> 
 pared with that of an equal bulk of rain water, collected under similar circumstances. 
 
LECTURE III. 
 
 Carbonic and oxalic acids, their properties and relations to vegetable life— Carbonic oxide 
 and liglit carburelted hydrogen, tlieir properties and production in nature — Ammonia, its 
 properties and relations to vegetable life. 
 
 § 1. Carbonic acid, its properties and relations to vegetable life. 
 
 When charcoal is burned in the air it combines slowly with oxygeu, 
 and is transformed into carbonic acid gas. In oxygen gas it burns more 
 rapidly and vividly, producing ibe same compotiud. 
 
 This gas is colourless, like oxygen, hydrogen, and nitrogen, but is 
 readily distinguished irom all these, by its acid taste and smell, by its solu- 
 bilit}' ill water, by its great density, and by its reddening vegetable blues. 
 Water at 60 F. and under the ordinary pressure of the atmosphere, dis- 
 solves rather more than lis own bulk of iliis gas (100 dissolve 106), and, 
 however the pressure may be increased, it still dissolves the same bulk. 
 
 All gases diminish in bulk uniformly as the pressure to which they 
 are subjected is increased. Thus under a pressure of two atmospheres 
 they are reduced to one-half their bulk, of three atmosjjheres to one- 
 third, and so on. When water, therefore, is saturated with carbonic 
 acid under great pressure, as in the manufacture of soda water, though 
 it still dissolves only its own bulk, yet it retains a weight of the gas 
 which is proportioned to the pressure applied. For the same reason 
 also, when the pressure is removed, as in drawing the cork from a bot- 
 tle of water so impregnated, the gas expands and escapes, causing a 
 lively eftervescence, and the water retains only its own bulk at the ex- 
 isting pressure. This solution in water has a slightly sour taste, and 
 reddens vegetable blues. These jjroperties it owes to the presence of 
 the gas, which is therefore what chemists call an acid body, and hence its 
 name of carbonic acid. [Acids have generally a sour taste, redden 
 vegetable blues, or combine with bases, such as lime, soda, potash, &c., 
 to form salts."] 
 
 Tiiis gas is one-half heavier than atmospheric air, its density being 
 l'5"i4, and hence it may be poured through the air from one vessel to 
 another. Hence also, when it is evolved from crevices in the earth, in 
 caves, in wells, or in the soil, this gas diffuses itself through the atmos- 
 phere and ascends into the air, much more slowly than the elementary 
 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 
 roaches to a considerable distance from its source, before it is lost among 
 the still air. 
 
 Burning bodies are extinguished in carbonic acid, and living beings, 
 plunged into it, instantly cease to breathe. Mixed with one-ninth of its 
 bulk of this gas the atmospheric air is rendered unfit for respiration. It 
 is, however, the principal food of plants, being absorbed by their leaves 
 and roots in large quantity. Hence the presence of carbonic acid in the 
 atmosphere is necessary to the growth of plants, and they have beenob- 
 
46 CARBONIC ACID. — EVIDKNCE OF UNITY OF DJ^SISN. 
 
 served to thrive better when the quantity of this gas in the air is con- 
 siderably augmented. Common air, as has been already stated, does 
 not contain more on an average thaUgT^^oth of its bulk of carbonic acid, 
 but De Saussure found that jilants in the sunshine grew better when it 
 was increased to y'^th of the bulk of the air, but beyond this quantity 
 they were injured by its presence, even when exposed to the sun. 
 When the carbonic acid amounted to one-half, the plants died in seven 
 days ; when it reached two-thirds of the bulk of the air, they ceased to 
 grow altogether. In the shade any increase of carbonic acid beyond 
 that which naturally exists in the atmosphere of our globe, was found 
 10 be injurious. 
 
 Tbese circumstances it is of importance to remember. Did the sun 
 always shine on every part of the earth's surface, the quantity of carbo- 
 nic acid in the atmosphere might probably have been increased with ad- 
 vantage to vegetation. But every such increase would have rendered 
 the air less fit for the respiration of existing races of animals. Thus 
 we see that not only the nature of living beings, both plants and ani- 
 mals, but also the periodical absence of the sun's rays, have been taken 
 into account in the present arrangement of things. 
 
 In perpetual sunshine plants would flourish more luxuriantly in air 
 containing more carbonic acid, but they would droo]) and die in the 
 shade. This is one of those \Hook oi unity of design which occasion- 
 ally force themselves upon our attention in every department of nature, 
 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 time of his periodical presence, as well as to the nature of 
 animal and vegetable life. 
 
 Carbonic acid consists of one equivalent of carbon and two of oxygen, 
 and is represented by COo. It unites with bases (potash, soda, lime, 
 &c.), and forms compounds known by the name of carbonate. Thus 
 pearlash is an impure carbonates of j^otash, — the common soda of the 
 shops, carbonate of soda, — and limestone or chalk, carbonates of lime. 
 From these compounds it may be readily disengaged by pouring upon 
 them diluted muriatic or sulphuric acids. From limestone it is also 
 readily expelled by heat, as in 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 ofcarbonic acid dri- 
 ven off. [Hence by burning limestone on the spot where it is quarried, 
 nearly one-half of the cost of traus])ort is saved,] 
 
 Common carbonate of lime, in its various forms of chalk, hard lime 
 stone, or marble, is nearly insoluble in water, but it dissolves readily in 
 water containing carbonic acid. Thus, if a current of this gas be pass- 
 ed through lime-water, tiie liquid speedily becomes milky from the 
 formation and precipitation of carbonate of lime, but after a short time 
 the cloudiness disappears, and the whole of the lime is re-dissolved. 
 The ap])lication of heat to this clear solution exjiels the excess of car- 
 - bonic acid, and causes the carbonate of lime again to fall. 
 
 By exposure to the air, we have already seen that water always ab- 
 sorbs a quantity of carbonic acid from the atmosphere. As it after- 
 wards trickles through the rocks or through soil containing lime, it grad- 
 
CARBONIC ACID RENDERS LIME SOLUBLE. 47 
 
 ually dissolves a portion of this earth, equivalent to the quantity of gas 
 it holds in solution, and thus reaches the surface impregnated with cal- 
 careous matter. Or it carries it in its progress below the surface to the 
 roots of plants, where its earthy contents are made available, either di- 
 rectly or indirectly, to the promotion of vegetable growth. To the hme 
 thus held in solution, spring and other waters generally owe their hard- 
 ness, SLnA il is the expulsion of the carbonic acid, by heat, that causes 
 the deposition of the sediment so often observed when such waters are 
 boiled. 
 
 I propose hereafter to devote an entire lecture to the consideration of 
 the action of lime upon land, as it is employed for agricultural pur- 
 poses, but I may here remark, that this solvent action of the carbonic 
 acid in rain water is one of the principal agents in removing the lime 
 from your soils, and in rendering a fresli application necessary after a 
 certain lapse of time. It is the cause also of that deposit of calcareous 
 matter at the raoutlis of drains which you not unfrequenlly see in lo- 
 calities where Ume is laid abundantly upon the land. The greater the 
 quantit3'- of rain, therefore, which falls in a district, the less permanent 
 will be the elTects of liming liie land — the sooner will it be robbed of 
 this important element of a fertile soil. Still carbonic acid is only one 
 of several agents which act almost unceasingly in thus removing the 
 lime from the land, a fact I shall hereafter have occasion more fully to 
 explain. 
 
 In nature, carbonic acid is produced under a great variety of circum- 
 stances. It is given otf from the lungs of all animals during respira- 
 tion. It is formed during the progress of fermentation. Fermented li- 
 quors owe their sparkling iiualities to the presence of this gas. Dur- 
 ing the decay of animal and vegetable substances in the air, in com- 
 post heaps, or in the soil, it is evolved in great abundance. In certain 
 volcanic countries it issues in large quantity from springs and from 
 cracks and fissures in the surface of the earth; while the vast amount 
 of carbon contained 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 
 several 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. Oxalic acid, its properties and relations to vegetable life. 
 
 Oxalic acid is a notlier compound of carbon and oxygen, which, though 
 not known to minister either to their growth or nourishment, 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 oi'rumex, — in which it is the cause of the acidity of 
 the leaves and stems, — in the roots of these plants also, in the leaves and 
 roots of rhubarb, and in the roots of tormentilla, bistort, gentian, saponaria, 
 and many others. It is this combination with potash, formerly extracted 
 from wood sorrel, which is known in commerce by the name of salt of 
 sorrel. In combinaiion with lime it forms the principal solid parts of 
 
48 PROPKHTIES OF OXALIC ACID. 
 
 many lichens, especially of the partJieli^e and variolarice,* some of which 
 contain as much oxalate of lime as is equivalent to 15 or 20 parts of pure 
 acid in 100 of the dried plant. 
 
 The crystallized oxalic acid of the shops forms transparent colourless 
 crystals, of an intensely sour taste. These crystals dissolve readily in 
 twice their weight of cold water, and the solution, when sufficiently di- 
 lute, is agreeably acid to the taste. This acid is exceedingly 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 con- 
 sists 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 oxalates, 
 and it is characterised by the readiness with which it combines with lime 
 to form oxalate of lime. If a solution of the acid be poured into lime wa- 
 ter, the mixture immediately becomes milky from the formation of this 
 compound, which is insoluble in water. f It is this oxalate of lime which 
 exists in the lichens, while oxalate of potash exists in the sorrels. 
 
 Oxalic acid is one of those comr)ound8 of organic origin which we can- 
 not form, as we can form carbonic acid by the direct union ofits elements. 
 In all our processes for preparing it artificially, we are obliged to have re- 
 course to a substance jireviously organized in the livin-g plant. It may 
 be prepared from sugar, starch, or even from wood, by various chemical 
 processes. The usual method is to digest potato starch with five times its 
 weight of strong nitric acid (aquafortis), diluted with ten of water, till red 
 fumes cease to be given oHJ aiid then to evaporate the solution. The ox- 
 alic acid separates in crystals, or, as it is usually expressed, crystallizes in 
 the solution thus concentrated by eva])oration. 
 
 It 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 formed or elaborated 
 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 subse- 
 quent lecture. 
 
 § 3. Carho7uc oxide, its constitution and properties. 
 
 When carbonic acid (CO2) is made to pass through a tube containing 
 
 red-hot charcoal, it undergoes a remarkable change. Its gaseous form 
 
 remains unaltered, but it combines with a second equivalent of carbon 
 
 (becoming CgOj), which it carries ofiTin the aeriform state. The new 
 
 ' Thfiparmelia crudata?Lni\variolaria communis are mentioneii as peculiarly rich in this 
 acid, which useil to be extractpil from them for sale. A S|)ecle3 of parmelia, 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 gelatinous substance similar to that obtained from Iceland moss. 
 This lichen is used for food by the Kirghuis. A similar lichen is collected about Bagdad for 
 a similar purpose. 
 
 t Subslances that are insoluble are generally without action on the animal economy, and 
 may be introduced into the stomach without producini; any injurious effect. Hence tliis ox- 
 alate of lime, though it contains o.ialic 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 quantity. The acid combines with the lime, as in 
 the experiment described in the text, and forms'insoliible oxalate of lime. The common 
 maanesia of the shops will serve the same purpose, forming an insoluble oralateofmngnr.sia. 
 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 phe- 
 nomena are not visible, and to act with as much eonfideace as if we could really see them. 
 
LIGHT CARBURKTTED UYDROGKN. 49 
 
 gas thus produceo is known b}' the name of carbonic oxide. It consists 
 of one equivalent of carbon united to one of oxygen, and is represented 
 by Co O21 or simply CO. 
 
 This gas is colourless, without taste or smell, lighter than common 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 is converted into carbonic acid. It is j)roduced along with 
 carbonic acid during the imperfect combustion of coals in our fires and 
 furnaces, but is not known to occur in nature, or to minister directly to 
 the growth of j)lants. 
 
 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 re- 
 presented by their chemical (brmulce : — 
 
 Carbonic acid consists of one of carbon and two of oxygen, or COg ; 
 
 Carbonic oxide, of one of carbon and one of oxygen, or CO ; 
 
 So that if carbonic acid be present in a plant, and be there deprived 
 of one equivalent of its oxygen, by any vital action, it will be converted 
 into carbonic oxide. 
 
 Oxalic acid consists of two of carbon and three of oxygen, or C2O3. 
 
 If we add together the formula; for 
 
 Carbonic acid = CO2 and 
 Carbonic oxide = CO, we have 
 
 Oxalic acid = C2O3. 
 
 Hence this acid may be formed in the interior of plants, either by the 
 direct union of carbonic oxide and carbonic acid, or by depriving two of 
 carbonic acid (2CO2 or C2O4) of one equivalent of oxygen. 
 
 When in a subsequent lecture we have studied the structure and func- 
 tions of the leaves of plants, we shall see how very easy it is to under- 
 stand the process by which oxalic acid is formed and deposited in the in- 
 terior of plants, and by which carbonic oxide also may be, and probably 
 is, produced. 
 
 § 4. Light carhuretted hydrogen — ihc 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 oH", 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 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, by experiment, is 
 0-5576.] A lighted taper, plunged into it, is immediately extinguished, 
 while the gas takes fire and burns with a [)ale yellow flame, yielding 
 more liglit, however, than pure hydrogen gas, which it otherwise re- 
 sembles. Animals introduced into it, instantlj' cease to breathe. 
 
 It consists of one eipiivalent of carbon (C) united to two of hydrogen 
 (2H or Ho), and is represented by CH,. When burned in the air or 
 
So PnOPKRTIES OF AMMONIA. 
 
 in oxygen gas, the carbon it contains is converted into carbonic acid 
 (COo), and the hydrogen into water (HO). 
 
 Like oxalic acid this gas cannot, by any known process, be produced 
 from the direct union of the carbon and hydrogen of which it consists. 
 It is readily obtained, however, by healing acetate of potash in a retort, 
 with an equivalent proportion of caustic baryta. [Acelate of potash is 
 prepared by pouring vinegar (acetic acid) on common pearlash and 
 evaporating the solution.] 
 
 In nature it is largely evolved in coal mines, and is the principal com- 
 bustible ingredient in those explosive atmospheres which so frequently 
 cause disastrous accidents in mining districts. 
 
 This gas is also given off along with carbonic acid during the fermen- 
 tation of compost heaps, or of other large collections of vegetable mat- 
 ter. It is said also to be generally ];)resent in well manured soils, 
 [Pkrsoz, Chi'/iie Molcculairc, p. 547,] and is supposed by many to con- 
 tribute in such cases to the nourishment of plants. It is, however, very 
 sparingly solui)le in water, so that in a stale of solution, it cannot enter 
 largely into the pores of the roots, even tbo»gh it be aburxlanlly present 
 in the soil. How far it can with ))raj)riety be regarded as a general 
 source of food to plants, will be considered in the following lecture. 
 
 § 5. Ammonia, its properties and relations to vegetable life. 
 
 Ammonia is a compound of hydrogen and nitrogen. It is possessed 
 of many interesting properties, and is supposed to perform a very im- 
 portant part in the process of vegetation. It will be proper, therefore, 
 to illustrate its natt?re and properties with considerable attention. 
 
 Ammonia, like the nitrogen and hydrogen of which it is coiriposed, is 
 a colourless gas, but. unlike its elements, is ensil}' distinguished from 
 all other gaseous subslnnres by its smell and taste. 
 
 It possesses a powerful j)enetrating odour (familiar to you in the smell 
 of hartshorn and of common smelling sails), has a burning acrid alka- 
 line* taste, extinguishes a lighleil taper as hydrogen and nitrogen 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 char- 
 coal — which, as already staled, absorbs 95 times its own bulk of ani- 
 inoniacal gas. Porous vegetable substances in a decaying state likewise 
 absorb it. Porous soils also, burned bricks, burned clay, and even com- 
 mon clay and iron ochre, which are mixed together on the surface of 
 most of our fertile lands — all these are capable of absorbing or drinking 
 m, and retaining within their pores, this gaseous substance, when it hap- 
 pens to be brought into contact with them. 
 
 But the quantify absorbed by water is much greater and more sur- 
 prising. If the mouth of a bottle filled with this gas be inmiersed 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 nnich as G70 times its bulk of the gas. 
 
 This solution of ammonia in water is the spirit of hartshorn of the 
 shops. When saturated [that is. when gas is supplied till the water re- 
 
 • The term alkaline, as applied to taste, will be best understood by describing it as a taste 
 imilar to that of the common soda and pearlaslj of the sliops. 
 
ITS combj.natiox with acids. 51 
 
 fuses to take up any more,] it is lighter than pure water, [its specific 
 gravity is 0-875, water being 1,] has the pungent penetrating odour of the 
 gas, and its hot, burning, alkaline tasie — is capable of blistering the 
 skin, and decomposing or destroying liie texture of animal and vegeta- 
 ble substances. 
 
 You will remark here the effect which combination has in investing 
 substances with new characters. The two gases hydrogen 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. 
 
 Ammonia possesses also alkaline properties,* it restores the blue 
 colour of vegetable substances that have been reddened by an acid, and 
 it combines with acid substances to form salts. 
 
 Amona; gaseous substances, therefore, there are sotne which, like car- 
 bonic acid, have a sour taste and redden vegetable blues ; others which, 
 like atnmonia, have an alkaline ta«te and restore the blue colour; and 
 a third class which, like oxygen, hydrogen, and nitrogen, are destitute of 
 taste and do not afreet vegetable colours. These last are called neu- 
 tuil or inditTerent substances. 
 
 .\nunonia, as above stated, combines with acids and forms salts, 
 which at the ordinarv temperature of the atmosphere are all solid sub- 
 stances. Hence if carbonic acid gas be mixed with ammoniacal 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 vinegar or dilute muriatic acid (spirit of salt), and then in- 
 troduced into ammoniacal gas, forms a similar white cloud, and be- 
 comes covered with a white down of solid acetate orofrnuriate of ammonia 
 (sal ammoniac). Tlie same appearance is readily seen by holding the 
 feather to the moutti of a bottle containing hartsliorn (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 feathers. 
 
 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 inter- 
 esting nature to the young chemist, and presents a further illustration 
 of the changes resulting from chemical combination as explained in 
 the previous lecture. 
 
 Ammonia is little more than half the weight of common air, [more 
 nearly three-fifths, its specific gravity being 0-59, that of air being 1,] 
 hence when liberated on the earth's surface it readily rises into and 
 mingles with the atmosphere. It consists of h\'drogen and nitrogen 
 united together in the proportion of three equivalents of hydrogen (3H 
 or Hi) and one of nitrogen (N), [see Lecture H.] and hei\ce. it is re- 
 presented by the symbol (N -f 3H), or more shortly by NHg. 100 
 parts by weight contain 82i of nitrogen and 174 of hydrogen, [correct- 
 ly 82'o45 and 17-455 respectively.] 
 
 In nature, ammonia exists in considerable quantity It is widely, 
 
 • In the previous lecture, tlie term acid was explained as applying to substances possess- 
 ed of a sour taste, and capable of reddenins; vegetable blues or combining witti basts (pot- 
 ash, soda, masnrsia, &c.) to form salts ; alkaJies are such as possess an alkaline taste (see 
 previous Note), restore llie blue colour to reddened vegetable substances, or combine witti 
 nddg to form salts. Of salts, nitrate of soda, saltpetre (nitrate of potash), and glauber salta 
 Csulphate of soda), are examples. 
 
 3* 
 
62 ITS EXISTENCE IK NATURE, AND SPECIAL PROPERTIES. 
 
 almost universally, ditfused, but is not known to form large deposits 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 com- 
 posed. It exists most abundantly in a stale of comhination — in the 
 forms, for example, of muriate (sal ammoniac), of nitrate, and of carbon- 
 ate of ammonia. It frequently escapes into the atmosphere in an un- 
 combined state, especially where animal matters are undergoing decay, 
 but it rarely exists in tliis free state for any length of time. It speedily 
 unites with the carbonic acid of the air, with one or other of the numer- 
 ous acid vapours which are continually rising from the earth, or with 
 the nitric acid which Is formed at the expense of the nitrogen and oxy- 
 gen of which the atmosphere coi:tsists. 
 
 The influence of ammonia orv vegetation appears to be of a very 
 powerful kind. It seems not only to promote the rapidity and luxu- 
 riance of vegetation, but to exercise a powerful control over the func- 
 tions of vegetable life. In reference to the nature and extent of this 
 action, intj which we shall hereafter have occasion to inquire, there 
 are several special properties of ammonia which it will be of impor- 
 tance for us previously to understand. 
 
 1°. It has a powerful atlinity* i(>r acid substances. Hence the 
 readiness wiih which it unites with acid vapours when it rises into the 
 atmosphere. Hence also when formed or lilierated in the soil, in the 
 fold-yard, in llie stable, or in compost heaps, it. unites with such acid 
 substances as may be jiresejit in the soil, &c. and form;? saline com- 
 pounds or salts. All these salts appear to be inore or less influential in 
 the processes of vegetable life. 
 
 2°. Yet this affinity is much less strong than that whicli is exhibited 
 for the same acids by potash, soda, lime, or magnesia. Hence if any 
 of these substances be mixed or brought into contact with a salt of am- 
 monia, the acid of the latter is taken U|) by tiie potash or lline, while 
 the aminonia is sepanited in a gaseous slate. Thus when sal ammo- 
 niac in powder is mixed with twice its weight of f|uick-lime, ammoni- 
 acal gas is liberated in large quantify. This is the method bv which 
 ])ure ammonia is generally prepared; and one of the many functions 
 performed by lime when em|)!oyed for the improvement of land, espe- 
 cially on soils rich in animal and vegetable matter, is that of decompo- 
 sing the salts, especially the organic salts, of annnonia, — as will be 
 more fully explained when we come to treat at length of this important 
 part of agricultural practice. f 
 
 3°. The salts which amnionia forms with the acids are ;\11, like am- 
 monia itself, very soluble in water. Hetice two consecpiences follow. 
 First, that which rises into the air in rlie form of gas, and there com- 
 bines with the carbonic or other acids, is readily dissolved, washed out 
 
 ' By affinity is infant the tendency which bodies have to unite antl to remain united or 
 combined. Thus ammonia foi'ms a solid substance with tlie vapour of vinesar rhe moment 
 the two substances come into coniacl; they have, therefore, a strong tendency to unite, or 
 an affinity for each otiier. 
 
 t Sec Lecture XVI. "Ow the ti-se of lime." Owing to llii,3 properly tlie action of lime iipor; 
 compost heaps is often injiirions, by causing the evolution of the ammonia produced during 
 the decomposition of the animal matters they contain. This escape of ammonia, even 
 when iniperceptible by the sense of smell, is easily delected by holding over the heap a fea- 
 ther dipped in vinegar or in spirit of salt (muriatic acid), when white fumes are immediate- 
 ly perceived if ammonia be present. 
 
DECOMPOSKS GYPSUM. §3 
 
 and brought to the earlli again by the rains and dews; so that at the 
 same time the air is purified for the use of animals, and the ammo- 
 nia brought down for the use of plants. And second, whatever salts of 
 anmionia are contained in the soil, being dissolved by the rain, are in 
 a coniliti(»n to be taken up, when wholesome, by the roots of plants; or 
 to be carried off by the drains when injurious to vegetation. 
 
 4°. 1 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 ferrugi- 
 nous)* soils, ammonia is supposed to form a chemical compound of a 
 weak nature. In consequence of its afKnity or feeble tendency to com- 
 bine with these substances, they attract it from the air, and from decay- 
 ing animal or vegetable matters, and retain it more strongly than many 
 porous substances can, — yet with a sufficiently feeble hold to yield it 
 up, readily as is supposed, to the roots of plants, when their extremities 
 are pushed forth in search of food. In this case the carbonic, acetic, 
 and other acids given off, or supposed to be given off by the roots, exer- 
 cise an influence to which more particular allusion will be made here- 
 after. 
 
 6°. In the state of carbonate it decomposes gypsum, forming carbon- 
 ate of lime (chalk) and sulphate of amraonia.f The action of gypsum 
 on grass lands, so undoubtedly ijcneficial in many parts of the world, 
 has been ascribed to this single property; it being supposed that the 
 sulphate of ammonia formed, is peculiarly favourable to vegetation. 
 This f|uestion will come properly under review hereafter. I may here, 
 however, remark that if this be the sole reason for the efiSciency of gyp- 
 sum, its application ought to be beneficial on all lands not already 
 abounding either in gypsum or in 8ulj)hate of ammonia. J But if the 
 
 ' Soils reddened by the presence of oxide of iron. 
 
 t Gypsum is sulphate of lime— consistina; of sulphuric acid (oil of vitriol) and quicklime. 
 Carbonate of ammonia consists of carbonic acid and ammonia. When the two substances 
 act upon each other in a moist state— tlie iwo acids chini;e places — the sulphuric acid, as it 
 were., pieferriv^ the ammonia, the carbonic acid tlie lime. 
 
 t I.iehig says— "the striking fertility of a moailow on which gypsum is strewed depends 
 onli/ on its fixing in the soil the ammonia of the atmosphere, which would otherwise be vola- 
 Jilized with the water which evaporatf s." — Organic Chemistri/ applied to Agriculture, p. 86. 
 ^}Ay fixing is meant, the forming of sulphate with the ammonia. Rain water is supposed to 
 bring down with it carbonate of ammunia (common smelling salts), which acts upon the SMi- 
 phate (if Ii7ne dypsum) in such a way that sulphate of ammonia -.ind carbonate of litne axe 
 produced. The carbonate of ammonia roadily volatilizes or rises again into the air, the sul- 
 phate does not— hence the use of the v;ot6 fix] 
 
 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 calcula- 
 tion, however, will serve to shew that the above theory of Liebig is far from affording a satis- 
 factory 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 7/7i6»rHed gypsum will fix or form sulphate 
 with iiparly 20 lbs. of ammonia containing IGJlbs. of nitrogen. One hundred weight, there- 
 fore, (ll'iilbs.) will form a.s much sulphate as will contain 22i lbs. of ammonia, and if intro- 
 duced without loss into the interior of plants will furnish therri with ISJ lbs. of nitrogen. 
 
 1°. In the first volume of British Husbandry, pp. 322, 323, the following experiment is 
 recort|.>cl : 
 
 Mr. Smith, of Tunsial, near Sitlinghnuriie. top-dressed one portion of a field of red clover 
 with powdered gypsum at the rate of five bushels (or lour hundred weiglil") per acre, and 
 compare.l the produce with another portion of the same fielil, to which no manure had- been 
 
 (■ A ton of pure gypsum, when crushed, will yield 25 bushels. It should, however, al- 
 wavs be applied by weight.] 
 
54 MODE IN WHICH GVPSUM ACTS. 
 
 resulls of experimental farming in this country are to be trusted, this is 
 by no means the case. The action neither of this, nor probably of any 
 oiher inorganic substance applied to the soil, is to be explained by a 
 reference in every case to one and the same projierty only. 
 
 7°. The presence or evolution of ammonia in a soil containing animal 
 and vegetable matter in a decaying state, induces or disposes this mat- 
 ter to attract oxygen from the air more rapidly and abundantly. The 
 result of this is, that organic acid compounds are formed, which combine 
 
 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. 
 
 cirl. grs. Ihs. ctot. qrs. iba. 
 
 Gypsumed SO 3 21 22 3 12 
 
 Unmanured 20 20 5 
 
 Excess of produce . . 40 3 1 17 3 12 
 
 The excess of produce in all the three crops upon the gypsumed land is very large : let ua 
 calculate how much nitrogen this e.j!cess would contain. Iti a proviou.s lecture (II. p. 30) it 
 was staled as the result of Boussinj^ault's anulyse-s, that dry clover seetl contained 7 per 
 rent. o(^ nitrogen, and the same experimenter found in the hay of red clover IJ per cent, (or 
 70 and 15 lbs. respectively in 1000.) 
 
 The seed as it was weighed by Mr. Smith would still contain one-ninth of its weight of 
 water, and, conserpiently, only G.!3rd per cent, of niirosen, [.see Lecture II. p. 30.] Let it 
 betaken at 6 per cent, and let lUa straw be supposed to contain only 1 percent, of nitro- 
 gen, the quantity of this element beiiia found to diminish in tiie grasses aftf-r the seed has 
 ripened, and averaging 1 per cent, in ihe straw of vvheat, oats, and barley, the weight of ni- 
 trogen reaped in the whole crop will then be as follows : 
 
 1. 40 cwt. of hay (4i?0 lbs.) at 1§ per cent, of nitrogen, contain 67 lbs. 
 
 2. 85 lbs. of seed at 6 per cent, contain ft 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 shewn, the five bushels cir tour cwt. of gypsum could fix only 90 lbs. of am- 
 monia containing 74 lbs. of nitrogen, leaving, therefore, 18 lbs. or onefijlh uj the whole, to be 
 derived from snme other source. 
 
 Now this result su)iposes that none of the gypsum or sulphate of ammonia was carried 
 away by Ihe rains, but that the whole remained in the soil, and produced its greatest possible 
 effect on the clover — and all in erne season. 
 
 But the etfecl of llie gypsum does not disappear with llie crop to which it is actually ap- 
 plied. Its beneficial action is extended to the succeedins crop of wheat, ami on grass lands 
 the amelioration is visible for a succession of ye.irs. If, then, the increased produce of a 
 single year may conlain more nitrogen than the gypsum can be supposed to yield, this sub- 
 etance must e.vercise some other influence over vegetation than is involved in its supposed 
 action on the indefinite (juantily of ammonia in the atmo.=phere. 
 
 2°. Again, Mr. Barnard, of Little Bordean, Hants, applied 2| cwt. per acre on two-year 
 old sain foin, on a clayey soil. The inrreaseii produce of the first cutting was a ton per 
 acre, and in October luily a Ion, the undressed part yieliiing scarcely any liay at all, while 
 the dressed part gave l^ tons. The second year no gypsum was applied, and the diflcrence 
 is said to have been at least as great. 
 
 Supposing the increased produce in all to have been 4 Ions of hay, and the nitrogen it con- 
 tained to have been only one per cent. — Ihc 4 tons (8960 lbs ) would contHJu about 90 Ihs. of 
 nitrogen. But 2J cwt. would fix only 46 lbs. of nitrogen in Ihe form of ammonia ; and there- 
 fore, supposing it to have produced its maximum elTect, there remain 44 lbs. or nearly one 
 half of the ichole, mtaccoiinted fur by the theoiij . 
 
 1 would not be under.'^tood to place absolute reliance on the results of the above experi- 
 ments ; but the way in which such results may he easily applied for the |)urpose of testing 
 theoretical viev^'s, will, 1 hope, convince tlie intelligent pr.ic.tical agriculturist how important 
 it is, that the results of some of the experiments he is every year makinjr should be accu- 
 rately determined hy weight andmeaswe. By this means data would gradually be accu- 
 mulated, on which we might hope to found mure unexcepijonahle explanations lUIhe phe- 
 nomena of vegetation, than the results obtained in oiu- laboratories have hitherto etiabled 
 us to advance. 
 
 In a subsequent note it will bo shewn that the mode in which Ihe nitrates of soda and 
 potash act — in other words, the theory of llieir action upon vegetation — may be tested by a 
 similar simple calculation, and the importatice of precise experiments maile on Ihe farm 
 will then still further appear. It is in Ihe hope of inducing some of my readers to make 
 comparative trials and publish nccnrate results, that I have introduced into the Appendix 
 (No. 1.) an outline of the mode in which such experiments may most usefully be performed. 
 
I.N'5-'LU1':>CK OF AMMONIA OVER PLANTS. 65 
 
 with the ammonia, and form ammoniacal salts.* On the decomposi- 
 tion of these salts by lime or otherwise — the organic acids Avhich are se- 
 parated from them, are always more advanced towards that state in 
 which they again become fit to act as food for plants. 
 
 6°. But the most interesting, and perhaps tlie most important proper- 
 ty of aminonia, is one which I have already had occasion to bring under 
 your notice, as possessed by water also, and as peculiarly fitting iliat 
 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 surface, it is also 
 continually in contact with oxygen. By the influence of electricity in 
 the air, and of lime and other bases in the soil, it undergoes a constant 
 though gradual decom])()sition (oxidation), its hydrogen heing chiefly 
 converted into water, and a portion of its nitrogen into nitric acid.f 
 
 In the interior of plants this and other numerous and varied decom- 
 positions in all probability take place. 
 
 The important influence which ammonia appears to exercise over the 
 growth of plants — the evidence for which I shall presently lay before 
 you — is only to be explained on the supposition that numerous transfor- 
 mations of organic substances are effected in the interior of living vege- 
 tables — which transformations all imply the separation from each other, 
 or the re-arrangement of the elements 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 oc- 
 casion may require, while tliese same elements are never unwilling to 
 unite again for the formation of water. So it is, to a certain degree, 
 with aminonia. 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 con- 
 cert with the other organic elements introduced by the roots or »he 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 the coloured 
 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 com- 
 pounds, in the insensible perspiration or odoriferous 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. iVIuch 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 importnnt of those properties of ammonia, to which 
 we shall hereafter have occasion to advert. The sources, remote as 
 well as imineiliate, from which plants derive this, and other compounds 
 we have described as contributing to the nourishment and growth of 
 plants, will be detailed in a subsequent section. 
 
 ■ Organic ac!(& generally contain more oxygon in proportion to their carbon anO hydro, 
 gen, than those whicti are alkaline or neutral. 
 
 t It will be remembereil that ammonia is represented by NH3, water by HO, and nitric 
 acid by NO5. It is easy to see, therefore, how, by means of oxygen, ammonia should be 
 converted into water and nitric acid. 
 
56 PROPERTIES OF NITRIC ACID. 
 
 § 6. Nitric acid, its constitution and properties. 
 
 When ilie nitre 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 olF, and a transparent, often 
 brownish or reddish lic^uid, distils over, which may be collected in a bot- 
 tle or other receiver of glass. This liquid is exceedingly acid and cor- 
 rosive. In small quantity it stains the skin and imparts a yellow colour 
 to animal and vegetable substances. In larger quantity it corrodes the 
 skin, producing 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 5 of the latter (O^), and is represented by NO5. 
 
 This acid contains much oxygen, as its formula indicates, and its ac- 
 tion on nearly all organic substances depends upon the ease with which 
 it is decomposed, and may be made to jiart with a portion of this oxygen. 
 
 In nature, it never occurs in a free state ; but it is found in many iti- 
 terlropical (hot) countries in combination with potash, soda, and lime — in 
 the state of nitrates. It is an important character of these nitrates that, like 
 the salts of ammonia, they are all very soluble in water. Those of so- 
 da, lime, and magnesia attract moisture from the air, and in a damp at- 
 mosphere gradually 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 subsequently evaf)orating (or boil- 
 ing down) the clear li(]uid thus obtained. When pure, it does not be- 
 come moist on exposure to the air. It is cliiefly used in the manufac- 
 ture of gunpowder, but has also been recommended and frequently and 
 successfully tried by the practical Imsbandman, as an influential agent 
 in promoting vegetation. 
 
 In combination with soda, it is found in deposits of considerable thick- 
 ness in the district of Arica in Northern Peru, from whence it is im- 
 ported into this country, chiefly for the manufacture of nitric and sulphu- 
 ric acids. More recently its lower price has caused it to be extensively 
 employed in husbandry, especially as a top-dressing for grass lands. 
 Like the acid itself, these nitrates of potash and soda, when present in 
 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 conseiiuence of I lie little rain that falls, the nitrous incrusta- 
 tions are accumulated upon the soil. In small quanlitj' they appear to 
 exercise an important and salutary influence on the rapidity of growth, 
 and on the amount of produce of many of the cultivated grasses. This 
 salutary influence is to be ascribed, cither in whole or in part, to the 
 constitution and nature of the nitric acid which these salts contain. It 
 
 ' Sulphuric acid is a compound of oxygen and sulphur, which is prepared by burning sul- 
 phur with certain precautions in lar<;e leaden chambers. It is also obtained directly by dis- 
 tilling; ^reen vitriol (sulphate of iron) at a high temperature in an iron st.iU — hence its name oil 
 ofvitnnl. It is a heavy, oily, acid, and remarkably corrosive liquid. In a concentrated state 
 it is exceedingly destructive both to animal and to vegetable life. 
 
 t When a substance combines with oxygen, cither in consequence of exposure to the air 
 or in any other circumstances, it is said to become oxidized. 
 
QUESTIONS TO BE CONSJDEREI). 67 
 
 is chiefly with a view to the explanation I shall hereafter attempt to 
 give of the nature of this salutary action, that I have thou2;ht it neces- 
 sary here to make you acquainted wiih tliis ucid Cv)in pound of nitrogen 
 and oxijgcn, in connection witlithe alkaline compound (ammonia) of the 
 same gas with liydrogen. 
 
 Having thus shortly described both the organic elements themselves, 
 and such chemical compounds of these elements as appear to be most 
 concerned in promoting the growth of plants, we are prepared for enter- 
 ing upon the consideration of several very important questions. These 
 questions are — 
 
 1°. 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 com pounds above described really enter iuio plants? 
 
 3°. By what organs is the food introduced into the circulation of 
 plants? In consequence of what peculiar structure of these several 
 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 converted and appropriated to their own sustenance 
 and further growth ? 
 
 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 ? 
 
 b°. By what natural laws or adaptations is the supply of those com- 
 pounds, which are the food of plants, kept up ? Animals are supported 
 by an unfailing succession of vegetable crops, — by the operation of what 
 invariable lasvs is food continually provided for plants ? 
 
 These questions we shall consider in succession 
 
LECTURE IV. 
 
 Source of the organic elements of plants— Source of the carbon— Form in which it enters 
 into I he circulation of plants — Source of the hydrogen— Source of the oxygen— Source of 
 the nitrogen — Form in which nitrogen enters into the circulation of plants — Absorption of 
 ammonia and nitric acid by plants. 
 
 The first af the series of questions stated at tlie close of the preceding 
 lecture, regards tlie source from which plants derive the organic ele- 
 ments 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 elemmt separately. 
 
 § 1. Source of tlie carbon of plants. 
 
 We have already seen reason to believe that carbon is incapable of 
 entering direr!!y, in its solid slate, into the circulation of ])lynts. It is 
 generally consiilered, indeed, that solid subsiancesof every kind are un- 
 fit for being taken up by the organs of plants, and that only snch as are 
 in the liquid or gaseous stale, can be absorbed by the minute vessels of 
 which the cellular substances of the roots and leaves of plants are com- 
 posed. Carbon, therefore, must enter either in the gaseous or liquid 
 form, but from what source must it be derived 1 Theie are but two 
 sources from which it can be obtained, — the soil in which the plant 
 grows — and the air by which its stems 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 mat- 
 ter which exists in the soil, or by the vegetable manure that is added to 
 it? 
 
 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 n time when no vegetable matter existed 
 in the soil which overspread tlie earth's surface. The first plants must 
 have grown without the aid of either animal or vegetable matter — that 
 is, they must have been nourished from the air. 
 
 2°. It is known that certain marly soils, raised from a great depth 
 beneath the surface, and containing ajjparently no vegetable matter, 
 will yet, without manure, yield luxuriant crops. The carbon in such 
 cases must also have been derived from the air. 
 
 3°. You know that some plants grow and increase in size when sus- 
 pended in the air, and without being in contact with the soil. 
 
 Yon know, also that many plants — 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 watered, will rise into plants, though sown in substances 
 that contain no trace of vegetable matter. 
 
AVHENCK PLANTS DERIVE THEIR CARBON. 59 
 
 Thus De Saussure found that two beans, when caused to vegetate 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 
 increased in weight 2i times, and wheat gave plants equal in weight, 
 when dry, to twicethat of the original grains, [Ann. deChim.etde Phys. 
 Ixvii., p. 1.] 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 thev lie undisturbed the richer in vegetable matter does the 
 soil become. When broken up, you find a black fertile mould where 
 little trace of organic matter had previously existed. 
 
 The same observation applies to lands long under wood. The vege- 
 table matter increases, the soil improves, and when cleared and plough- 
 ed it yields abundant cro|)S of corn. 
 
 Do grasses and trees derive tlieir carbon from the soil ? Then, how, 
 by their growth, do they increase the quantity of carbonaceous matter 
 which the soil contains ? It is obvious that, taken as a whole, they 
 must draw from the air not only as much as is contained in tlieir own 
 substance, but an excess also, which they impart 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, 
 and finally a thick bed of peat is formed. 
 
 Nor does this peat form and accumulate at the expense of one spe- 
 cies or genus of plants only. Latitude and local situation are the cir- 
 cumstances wliich chiefly efTpct this accumulation of vegetable 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 
 Terra del Fuego, " nearly every patch of level ground is covered by 
 two species of plants (as^eh'a pumila oP Brown, and donatia magellan- 
 ica), which, by their joint decay, compose a thick bed of elastic jieat.'* 
 "In the Falkland Islands, almost every kind of plant, even the coarse 
 grass whicli covers ihc whole surface of the island, becomes converted 
 into this substance."* 
 
 Whence have all these plants derived their carbon? The quantity 
 originally contained in the soil is, after a lapse of years, increased ten 
 thousand fold. Has dead matter the power of reproducing itself? 
 You will answer at once, that all these plants must Jiave grown at the 
 f,xpense of the air, must have lived on the carbon it was capable of af- 
 fording them, and as they died must have left this carbon in a state un 
 fit to nourish the succeeding races. 
 
 This reasoning appears unobjectionable, and, from the entire group of 
 •ficts, we seem justified in concluding lliat plants every where, and 
 under all circumstances, derive the whole of their carbon from the at- 
 mosphere. 
 
 ' Dartrin's Researches in Gentogy and Natural Iliatury^ pp. 31950. Dr. Gerville informs 
 iTie that llie astelia approaches more nearly to the jnnceteor ttasA <n'6e,and i\\e donatia \.oo\xt 
 fufteil saxifroijes, than to any othi;r Bi'ilish plants. 
 
60 THE VEGETABLE MATTER OF THE SOIL. 
 
 In certain extreme cases, as in those of plants growing in the air and 
 in soils perfectly void of organic matter, this conclusion must be abso 
 lufcly 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 or- 
 dinary circumstances in which plants grow spontaneously or are culti- 
 vated by the art of man ? Has the vegetable matter of the soil no 
 connection willi the growth of the trees or herbage ? — does it yield them 
 no regular supplies of nourishment ? Does naiure every where form a 
 vegetable mould on which her wild flowers may blossom and her pri- 
 meval forests raise their lofty heads ? Has the agricultural experience 
 of all ages and of all countries led die practical farmer to imitate nature 
 in preparing such a soil ? Does nature work in vain ? — is all this ex- 
 perience to be at once rejected ? 
 
 Wliile we draw conclusions, legitimate in kind, we must be cautious 
 how, in degree, we exlend them beyond our premises. 
 
 The consideration of one or two facts will shew that our general con- 
 clusion must eitlier be modified or more cautiously expressed. 
 
 1°. It is true that |)Iants 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 wiili almost universal observation, that the same 
 soil is more iirodnctive when organic matter is present, than when it is 
 ■wholly absent. 
 
 3°. That if the crop be carried ofl" a field, less organic matter is left 
 in the soil tlian it contained when the cro]) began to grow, and that by 
 constant cropping the soil is gradually exhausted of organic matter. 
 
 Now it must be granted tliat tillage alone, without cropping, would 
 gradually lessen the amount of organic matter in the soil, by continually 
 exposing it to the air and hastening its decay and resolution 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 eflectually as a year of fallow succeeded by a crop of wheat. 
 Some of the vegetable matter, therefore, which the soil contained when 
 the seed was sown, must be carried off tlie field in the crop. 
 
 The conclusion therefore seems to l)e reasonable and legitimate, that 
 the crop which we remove from a field lias not derived all its carbon di- 
 rectly 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 fiirm of manuje — among 
 other substances — the carbon also of whicli the straw or hay had robbed 
 the soil. 
 
 But how is this reconcileable with our previous conclusion, that the 
 whole of the carbon is derived from the air ? The dilliculty is of easy 
 solution. 
 
 A seed germinates in a soil in which no vegetable matter exists ; it 
 sprouts vigorousl}', increases then slowly, grows languidly at the expense 
 of the air, and the plant dies stunted or immature. But in dying it im- 
 parts vegetable matter to the soil, on which the next seed thrives better 
 ■^drawing support 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, 
 
HOW THK VKGKTABLh; MATTKH INCREASKS. 61 
 
 while each succeeding plant is partly nourij^hed by food from the earth, 
 yet each, when it ceases to live, imparts to the soil all the carbon which 
 during its life it has 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 inter- 
 vene — the vegetable matter in the soil must increase. 
 
 Thus while it is strictly true that the carbon contained in all plants 
 }ias been oris:inaUy 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 nu- 
 merous 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 thfit 
 of the air. When it reaches maturity, or when winter arrives, it dies. 
 The dead vegetable matter decays, a part of it is resolved into gaseous 
 matter and escapes into the air, a part remains and is incorporated sviih 
 the soil. If that which remains be greater in quantify than that which 
 the plant in growing derived from the soil, the vegetable matter will in- 
 crease; 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 raj)idly — it may not increase at all. 
 
 3°. As we advance into colder countries, the decay and disappearance 
 of dead vegetable matter, in the form of gaseous substances which escape 
 into the atmospliere, become more slow — till at length, between the par- 
 allels of 40° and 45°, it begins to accumulate in vast quantities in favour- 
 able 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 little to the atmosphere, and therefore adds rapidly to the vege- 
 table matter of the soil. 
 
 4°. Again, in one and the same climate, the decay of vegetable mat- 
 ter, and its conversion into gaseous substances, is more rapid in propor- 
 tion to the frequency with which it is disturbed or exposed 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 it rapidly diminishes 
 in an uncovered soil, or in fields repeatedly ploughed and subjected to 
 frequent cropping.* 
 
 Being thus fitted, bv 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, — tliough rarely a robust 
 life, — at the expense of either. The proportion of their food which they 
 actually derive from each source, will depend upon many circumstan- 
 ces — on the nature of the jilant itself — on the period of its growth — on 
 the soil in which it is planted — on the abundance of food presented to 
 
 • In removinj; a crop we take away both what the plants have received from the earth and 
 what they liave absorbed from the air — the materials, in short, intended by nature to restore 
 the loss of vegetable matter arising from the natural decay. 
 
62 PLANTS PARTLY SUPPORTKD BY THE AIR AND BY THE SOIL. 
 
 cither extremity — on the warmth and moisture of the climate — on the du- 
 ration and intensity of the sunshine, and other circumstances of a similar 
 kind — so that the only general law seems to be, that, like animals, plants 
 have also the power of adapting themselves, to a certain extent, to the 
 conditions in which they are placed ; and of supporting life by the aid of 
 6uch sustenance as may be within their reach. 
 
 Such a view of the course of nature in the vegetable kingdom, is con- 
 sistent, I believe, with all known facts. And that (he Deity has bounti- 
 fully fitted the various orders of plants — with which the surface of the 
 earth is at once beautified and rendered capable of supporting animal 
 life — to draw tlieir nourisliment, in some spots more from the air, in oth- 
 ers more from the soil, is only in accordance with the numerous provisions 
 we everywhere perceive, for the preservation and continuance of the 
 present condition 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 advanced as 
 general propositions — and fitted to lead into error, such as have not tlie 
 requisite knowledge to enable them to judge ti)r themselves — or such as, 
 doubtful of their own judgment, are willing toyield assent lo the author- 
 ity of a name. 
 
 Of this kind appears, at first sight, to be the statement of Liebig, that 
 " wlfen a plant is quite matured, and when the organs by which it ob- 
 tains food from the atmosphere are formed, the carbonic acid of the soil 
 is no further required" — and that, "during the heat of sumnier it derives 
 its carbon exclusively from tlie atmosphere." — [Organic Chemistry ap- 
 plied to Agriculture, p. 48.] 
 
 A little consideration will shew us that, while the proposition contained 
 in the former (piotation may be entertained and advanced as a matter of 
 opinion — the latter is obviously incorrect. In summer, when the sun 
 shines the brightest, and for the greatest number of hours, the evapora- 
 tion from the leaves of all plants (their insensible perspiration) is the 
 greatest — the largest supply of water, tlierefore, must at this season be 
 absorbed by the roots, and transmitted upwards to the leaves. — [Lindley's 
 Theory of Horticulture, p. 46.] — But this water, before it enters the roots, 
 has derived carbonic acid and 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 stem. 
 
 Are the functions of the root changed at this stage of the plants' 
 growth ? Do they now absorb pure water only, carefully separating and 
 refusing to admit even such substances as are held m solution? Or 
 do the same materials which minister to the growth of the plant in its 
 earlier stages, now pass upwards to the leaf and return again in tlie 
 course of the circulation unchanged and unemployed, to be again re- 
 jected at the roots ? Does all this take place in the height of summer, 
 while the plant is still rapidly increasing in size ? The opinion is nei- 
 ther supported by facts nor consistent with analogy. 
 
 But such an opinion,— however the words above quoted may mislead 
 some, — is not intended to be advanced by Liebig; for, in the following 
 page he says, that " the power which roots possess of taking up nourish- 
 ment does not cease so long as nutriment is present." In summer, 
 
LEAVKS AfJD ROOTS ABSORB CAUBO.MC ACID. 63 
 
 therefore, as well as in spring or in autumn, the plant must be ever ab- 
 sorbing nourisliment by these roots, if llie soil is capable of aflbrding it — 
 and thus, in the general vegetation of tlie 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. 
 
 Supposing it to be established that the whole of the carbon contained 
 in plants has originally been derived from the air — we have only to in- 
 ([uire in what state this element exists in I he atmosphere, in order to 
 satisfy ourselves as to the form of combination in which it is and has 
 been received into the circulation of plants. In considering the consti- 
 tution of tlie atmosphere in the preceding lecture, it was stated that car- 
 bonic acid, a compound of carbon and oxygen, is always present in it — 
 and tliai, though this gas is difi'uscd through the air in comparatively 
 small quantity only, yet it is everywhere to be detected, — while no 
 other compound of carbon is to be found in it in any appreciable (juanti- 
 ty. We must conclude, therefore, that from this gaseous carbonic acid 
 the whole of the carbon contained in jilants has been priniarity derived. 
 This conclusion is confirmed by the observation so frequently made, 
 that the leaves of plants in sunshine absorb carbonic acid, and that 
 plants die in an atmosiihere from which this gas is entirely excluded. 
 
 But wc have seen reason to believe that, under existing circumstan- 
 ces, plants also extract a portion of the carbon ihcy contain from the 
 soil in which they grow. In what state or form of combination do the 
 700^5 absorb carbon ? 
 
 The most abundant product of the decay of vegetable matter in the 
 soil, is the same carbonic acid whicii 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 aeriform state — if 
 not, it must enter in solution in the water, which the roots drink in so 
 largely, to supply the constant waste caused by the insensible perspira- 
 tion of the leaves. 
 
 During the early fermentation of artificial manures there is also de- 
 velofied in the soil a variable proportion of light carburetted hydrogen 
 (Lecture III., p. 49), which is supposed by some to enter occasionally 
 into the roots. That it does enter, however, is doubtful, — and we are 
 safe, I think, in considering this compound not only as an uncertain 
 source of the carbon of plants, but as one from which, in the most fa- 
 vourable circumstances, ihey can derive only a small supply. 
 
 Thus, from the earth as from the air, the most unfailing supply of food 
 is tlie gaseous carbonic acid. 
 
 But as the water passes through the soil it takes up inorganic substan- 
 ces — potash, soda, lime, magnesia — and conveys them through the roots 
 into tlie circulation of the plants. Can it refuse to take up and to perform 
 a similar office to the soluble organic substances it meets with, as itsinks 
 through the soil ? Or do the spongioles of tiie roots keep a perpetual 
 v/atch over the entering waters, to prevent the introduction of every so- 
 luble form of carbon but that of carbonic acid ? Or, supposing such 
 
64 ROOTS ABSORB ORGANIC SUBSTANCES ALSO 
 
 substances intro(Juced into the interior of the plant, are none of them 
 digested tliere and converted to the general purposes of food ? A state- 
 ment, of nvo or three facts will atlibnl a saiisfactoi-y reply to these several 
 questions. 
 
 1'^. When plants are made to grow in infusions of madder the radicle 
 fibres are tinned of a red colour. 
 
 2^. The flower of a white hyacinili becomes red after a few hours, 
 when the earth in which it is planted is sprinkled with the juice of the 
 pJiytulaca decandra (BLoi). 
 
 Therefore orgmiic subsfavces can enter into the roots, and thence into 
 the circulation, of the plant. 
 
 3°. The colour of the madder does not usually extend upwards to 
 the leaves and flowers of the plant. 
 
 4°. The colour imparted to the flower of the white hyacinth disap- 
 pears in the sunshine in the course of a few days. 
 
 Organic colouring wallers, therefore, undergo a chemical change eitJier 
 in the stem, in the leaf, or in the flotver — some sooner, some later — and 
 the same is probably the case with most other organic substances which 
 gain admission into the interior of plants. 
 
 5°. Sir Humphry Davy introduced ])lants of mint into weak solutions 
 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 tlirive more than that to which connrion wafer was ap[)licd — vvhile 
 those treated with sugar, gum, and gelatiije grew luxuriantly. — [Davy's 
 Agricultural Chen^istry, Lecture VI.] 
 
 IMierefore difTerent (frgaiiie substances — being introduced into the cir- 
 culation and there changed — are converted by plants into their own sub- 
 stance, or act as food, and nourish the ]>lant. 
 
 We may consider it, therefore, to be satisfactoril}' established that, 
 while a plajit sucks in by its leaves aud roots much carbon in the form of 
 carbonic acid, it derives a variable portion of its immediate sustenance 
 (of its carbon) from the soluble organic substances tliat are within reach 
 of its roots. 
 
 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 tlie fact. 
 
 The nature of the soluble substances which are formed during the de- 
 cay of animal and vegetable substances — and Avhich the roots of plants 
 are supposed to take up — will be considered in a subsequent lecture.* 
 
 § 3. Source of the hydrogen of plants. 
 
 The source of the hydrogen of plants is less doubtful, and will re- 
 quire less illustration, than the source of the carbon. This elementary 
 substance is not known to exist in nature in an uncombined state, and, 
 therefore, it nmst, like carbon, enter into plants in union with some other 
 element. 
 
 1 °. Water has been already sliewn to consist of hydrogen in combina- 
 
 • This part of the sutijert might have been discussed here without appearing out of place 
 —but it will come in more approi)riaIely, I think, when treating of the nature and mode of 
 action of vegetable manwca. 
 
SOCRCE OF THK HYDROGEN OF PLANTS. 65 
 
 tion with oxygen. In tlie form of vapour, this compound pervades the 
 atmosphere, and plays among the leaves of plants, while in the liquid 
 state it is diffused through llie soil, and is unceasingly drunk in by the 
 roots of all living vegetables. In the interior of plants — at least during 
 their growth — this water is continually 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 and 
 precise results of these transformations we shall hereafter consider. 
 
 2°. In light carburetted hydrogen (CH2), given off'as already staled 
 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 i)f its weight. On the extent, therefore, to which this 
 gaseous comjiound gains admission into the roots of plants, will de- 
 pend the supply of hydrogen which they are capable of drawing from 
 this source. Had we satisfiictory evidence of the actual absorption of 
 this (marsh) gas by the roots or leaves of plants, in any {|uantity, we 
 should have no difficulty in admitting that plants might, from this source, 
 easily obtain a considerable supply both of carbrin and of hydrogen. It 
 would be also easy to explain how (ihat is, by wliat chemical changes,) 
 it is capable of being so appropriated. But the extent to whicli it really 
 acts as food to living vegetables is entirely unknown. 
 
 3°. Ammonia is another compound, containing much hydrogen, [its 
 formula being NHj, or one equivalent of nitrogen and three of hydro- 
 gen.] whicli, as I have already stated, exercises a manifest influence on 
 the growth of plants. If this substance enter into their circulation in 
 any sensible (luantity, — ii", as some maintain, it be not only universally 
 diffused throughout na!i<re, 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 organic substances which are formed or 
 elaborated by the agency of vegetable life. How far this probable in- 
 terference of the hydrogen of ammonia with the functions of the vegeta- 
 ble organs, will tend to explain or illustrate the influence actually exert- 
 ed by this compound, we shall, by and by, more accurately inquire. In 
 the mean time, the quantity of atnmonia, which actually enters into the 
 circulation of plants in a state of nature, is too little known, and making 
 the largest allowance, probably too minute, to permit us to consider it as 
 an imj)i)rtant source of hydrogen to the general vegetation of the globe. 
 
 4°- The soluble organic substances, which enter into the circulation 
 of plants through the roots, as shewn in the jireceding section, do not 
 consist of carbon and water only, but of combinations of carbon with 
 hydrogen and oxygen in various proportions. From these substances, 
 therefore, plants derive an uncertain and indefinite supply of hydrogen 
 in a state already half-organized, and probably still more easily assimi- 
 lated or converleil into portions 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 
 
66 SOURCE OF THE OXYGEN AND NITROGEN. 
 
 forms of combination in which this element mny enter into tlieir circula- 
 tion, in uncertain quantity — yet that all-pervading^ water is the main 
 and constant source from wliich tlie hydrogen of vegetable substances is 
 derived. 
 
 § 4. Source of the oxygen of plants. 
 
 We can at once jjerceive, and without difficulty, the various sources 
 of the oxygen of plants : though it is difficult in this case also to say 
 how much tliey derive from each. 
 
 1°. The water whicli they imbibe so largely consists in great part of 
 oxygen, and is easily decomposed, [eight-ninths of the weight of water 
 are oxygen.] 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 are known to absorb this 
 oxygen. The air in which they live, therefore, might be another 
 source. 
 
 3°. Carbonic acid contains 72 per cent, by weight of oxygen, and 
 this gas is also known to be absorbed in large (juantity from the aimos- 
 phere by the leaves of plants — while its solution in water is admitted 
 readily by the roots. 
 
 From an}' one of these sources an ample supply of oxygen might 
 readily be obtained, and it may be considered as a proof of the vast im- 
 portance of this element to the maintenance of animal and vegetable 
 life, that it is everywhere placed so abundantly within the reach of 
 living beings. It is from the first of these sources, however, from the 
 water they contain, that plants are believed to derive iheir principal 
 supply. The reasons on which this opinion is founded will appear 
 when we shall have considered the functions of the several parts of 
 plants, and the chemical changes to which the food is subjected in the 
 course of the vegetable circulation. 
 
 § 5. Source of the nitrogen of plants. 
 
 The quantity of nitrogen present in plants is very small, compared 
 with that of any of the other elements which enter into their constitu- 
 tion. Of this you will be reminded, by a reference to the analyses of 
 hay, oats, and potatoes, exhibited in the second lecture (page 30), whicli 
 shew that the nitrogen contained in these several crojis. when perfectly 
 dried at 240° F., is respectively 1^, 2t, and 11 percent. In the state 
 in which they are usually given to cattle they contain a still less per 
 centage of nitrogen, in consecjuence of the (]uanlity of water still present 
 in them. Thus raw potatoes as they are given to cattle contain only \ 
 of a per cent, of nitrogen, hay 1^^ percent., and oats ly^* per cent., or a 
 luindred pounds of each contain 5 ounces, 1 pound 5 ounces, and 1 j)ound 
 14 ounces respectively. 
 
 It would appear at first sight as if tliis small quantity of nitrogen 
 coulil be of little importance to the plant, especially since, as we shall 
 hereafter see, it does not enter as a constituent into those vegetable sub- 
 stances, such as woody fibre, starch, sugar, and gum, which plants pro- 
 duce in the greatest abundance, and of which their own stems and 
 
 • 33, 1-29, and 1-87 per cent. —the potatoes conlaining alsio 72 percent, of water, the hay 
 14, and the oats 15 per cent. 
 
QUANTITY OF NITROGEN IN PLANTS. 67 
 
 branches chiefly consist. The same remark, however, applies to this, 
 as to many other cases which present themselves to the chemist, during 
 his analyses, especiallv of organized substances, — thai those elements 
 whicli 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 arc the physical and chemi- 
 cal properties of the substance materially altered, but it is found also to 
 exercise 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 shall see on what 
 elementary body their relative nutritive properties depend, or by the 
 amount of which their relative value appears at least to be indicated. 
 
 But a consideration of the absolute (piantity of nitrogen contained in 
 an entire crop will satisfy you that though small in comjiarative amount, 
 [that is, compared with the carbon ami oxygen whicli plants contain,] 
 this element cannot be without its due share of importance in reference 
 to vegetable life. Hay, as above stated, contains, as it is stacked, li* 
 per cent, of nitrogen, or a ton of 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 2h tonsf per acre. Taking 2 tons as an average, the hay 
 from one acre will contain 60 lbs. of nitrogen, or from 100 acres 6000 lbs., 
 equal to 2| 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. t 
 
 Nature performs all her operations on a large scale, and the quantity 
 of materials she employs are large in a corresponding degree. Hence, 
 though comparatively small, the nitrogen in vegetable substances is ab- 
 solutely 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 should he so constantly and universally dif- 
 fused 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 recall to your 
 minds the efl'ects of seasoning upon food, in imparting, when added in 
 small quantity only, an agreeable relish to what would otherwise be 
 
 ■ In different crops of hay Boxiggingaidt found io three several years the following pro- 
 (tortious of niu-ogen : 
 
 
 Hay, 
 
 as commonly 
 
 Hay dri<d at 
 
 
 
 stacked. 
 
 
 200° F. 
 
 In 1836 
 
 
 118 
 
 
 IKM of nitrogen per cent. 
 
 " 1838 
 
 
 1.3 
 
 
 115 " " 
 
 " 1839 
 
 
 15 
 
 
 1-3 " " 
 
 Aftermath 
 
 
 21 
 
 
 2 •' " 
 
 t The Rev. Mr. Ogle, of Kirkley, Northumberland, informs me that some of his land 
 near the Hall has yielded annually at tliis rate for 100 years, and without other manure than 
 «he droppings from the cattle which have fed uixin it. 
 
 t This avera^ estimate pives but an inaccurate idea of the quantity actually contahied 
 in some species nf crops. Thus red clover with tlie aid of gypsum will yield 3 tons of hay 
 per acre. Tliis hay contains more than twrice the quantity oi" nitrogen (Boussingault) tliat 
 common hay does, hence an a«re of such hay would contain at least 180 lbs. of nitrogen, 
 f See Lecture H, p. 30 ) 
 
 4 
 
68 THE ATMOSPHERE THE PRIMARV SOURCE OF MTROGEPf. 
 
 insipid. But I need not dwell on this point, since I shall hereafter have 
 occasion to draw your attention to certain I'acts in reference to the con- 
 stitution of the atmosphere, which will satisfy you that, i)y the agency 
 of comparativelj/ feeble causes, gigantic etrects are continually produced 
 in nature, — and that we can scarcely fall into a graver error in reason- 
 ing of natural processes, than by overlooking the agency of forms of mat- 
 ter 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 la- 
 bour 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 wliich you labour — the earth, 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 un- 
 seen by you, and though working for your good, unheeded and un- 
 thought of. 
 
 Whence, then, is this nitrogen derived by plants? The ]mmary 
 source it is not difficult to see. We can arrive at it by a train of reason- 
 ing similar to that whicli 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 obtained 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 element from a foreign source, and the atmosphere is the only one 
 from whicli 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 orginal source — it does not follow 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, the constitution 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 considered in the foHowing 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 circula- 
 tion of plants is one which at the present moment engages much attention. 
 It will be proper, therefore, to discuss it with considerable care. 
 
 1°. It is considered an essential ])art of good tillage to break up and 
 loosen the soil, in order that the air may have access to the dead vege- 
 table matter, as well as to the living roots which descend to considerable 
 depths beneath tlie surface. When ihus admitted to the roots, it is im- 
 possible that some of the nitronen of the atmosi)here, as well as some of 
 its oxygen, may be directly absorbed and appropriated by the plant. 
 To what extent this absorption of nitrogen may proceed, however, we 
 
 * Excppt coal, and coal itself is of vegetable origin. Throughout all rocks in which or- 
 ganic 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 
 daring life, either directly or indirectly, from the atmosphere. 
 
RAIN WATKS, DISSOLVES IT. gg 
 
 have as yet no experimental results from which we can form any esti- 
 mate. Whether it takes place at ail or not, is wholly a matter of opinion. 
 
 2°. Tholeavesofplants, as will be more fully explained hereafier, 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 view, however, is not confirmed 
 by any of the ex])eriments hitherto made with the view of investigating 
 the action and functions of the leaves.* We are not at liberty, there- 
 fore, to assume that any of the nitrogen which plants contain has in this 
 way been derived directly from the air. It may be the case ; but it is 
 not yet proved. 
 
 3*^. There is little doubt, however, that nitrogen enters the roots of 
 plants in a state of solution. But the quantity they thus absorb is un- 
 certain — it is su|»posed to be small, and must be variable. 
 
 When water is exposed to the air in an open vessel it gradually ab- 
 soibs oxygen and nitrogen, though, as has been stated in a previous lec- 
 ture, in proportions dilierent from those in which they exist in the atmos- 
 phere. The wliole quantity of the mixed gases thus taken up amounts 
 to about 4 j)er cent, of the bi:lk of the water (Humboldt and Gay-Lus- 
 sac), and in rain water about | of the whole consist of nitrogen. One 
 hundred cubic inches of rain water, therefore, will carry into the soil 
 about 2| inches of nitrogen 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 car- 
 ries with it into the circulation of the plant, 2 per cent, of its bulk of 
 nitrogen, and let us calculate how much of the nitrogen it contains a 
 crop of hay could in this way derive from the air. 
 
 * See subsequent lecture " On the structure arid functions of lite several parts of plants." 
 Tlie experiments above referred to were made upon plants growing In close vessels, the 
 air contained in which was measured and examinea (analysed) both before the plants were 
 introduced and after Ihey had been some time in the vessel. In these experiments tlie 
 bulk of the nitrogen present has sometimes been observed to increase, but never to dimin- 
 ish, in fjuantity. The conclusion seems satisfactory, that no nitrogen is abstracted directly 
 from the atmosphere by the leaves of plants. Yet BouseingauU' very justly remarks, that 
 a diminution in the bulk of the nitrogen loo small to be detected in t,he 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, there- 
 fore, we accord their due weight to tj>ese researches of the vegetable physiologists, we are 
 not to consider ihem a.s by any means decisive of the queslion. With this rational and cau- 
 tious conrlusion, Liebig is not salisfied ; ho says, " We have not the slightest reason for be- 
 lieving that the nitrogen of the atmosphere takes part in the processes of assimilation of plants 
 and animals; 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." (p. 70.) But if 
 they occasionally expire nitrogen by their leaves Why must this nitrogen he exactly that 
 portion which has previously been absorbed by (he roots in U^ie uacomtiined state, and th« 
 quantity of which is so uncertain and so indefinite 1 
 
 [1 Boussingault details a series of experiments in the coarse of which he made pea.^, tre- 
 foil, wheat, and oats, grow in tlie 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 delected by analysis. From these results he is inclined lo infer that tiie green leaves of 
 the former liave the power of sensibly absorbing nitrogen from the atmosphere, while those 
 of the latter have not tliis power — at least under the circumstances in which the experi- 
 ments were made. This conclusion, however, is not certain, as will presently be shewn. — 
 See Arm. de Chim. et de Phys. Uvii. p. 1, and Ixix. p. 353] 
 
70 ABSOKPTION OF AMMONIA BT PLANTS. 
 
 The quantity of rain that falls at York from the first of March to tte 
 middle of June — during which time the grass grows and generally ri- 
 pens — is about, five inches.* On a square foot, therefore, there fall 720 
 cubic incites of water, containing 2 per cent, of their bulk, or 14 cubic 
 inches of nitrogen, weigliing 4i grains. Tliis gives 23 lbs. for the quan- 
 tity 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. 
 
 Such a calculation as this affords at the best but a very rude approxi- 
 mation to the truth — it seems, however, to justify us in concluding that 
 plants can derive froin the air, and in an uncombined state, only a small 
 portion of the nitrogen they are found to contain — and that they proba- 
 bly draw a larger supply from certain coinpounds of this elementary sub- 
 stance with hydrogen and oxygen — 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 ammonia and nitric 
 acid, the properties of which have been described in the preceding 
 lecture.f 
 
 § 7. Absorption of ammonia hy plants. 
 
 That ammonia enters directly into the circulation of plants is ren- 
 dered 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, and in those of the birch and maple 
 trees, it is associated with cane 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 substances, and may be detected by 
 mixing their juices with quick-liine. — [Schiibler Agricultur Chemie, 
 II., Y>^56.] 
 
 2°. Some plants actually perspire ammonia. Among these Ls 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 con- 
 tained, and may be detected by putting a glass shade over the plant, 
 and after a time introducing a feather moistener! witli vinegar or dilute 
 muriatic acid. — [Chevalier Jour, de Pharm. X., p. 100.] It is also pre- 
 sent in the odoriferous exhalations of many sweet-smelling plants and 
 flowers. — [Schiibler, I., p. 152.] 
 
 3°. Nearly all vegetable substances, when distilled with water, yield 
 an appreciable quantity of ammonia. Thus the leaves of hyssop, and 
 
 * Tlie rnsuUofexpeTiments made in 1834 by Prof. Phillips and Mr. Eilward Gray. The 
 mean annual fall of rain at York is about 22 inches.— (See fifih Report of the British Associa- 
 tion, p. 173.) 
 
 t It will he recollected that ammonia consisl.s of one equivalent of nitrogen (N) united to 
 three of hydrogen (Ha), being represented by NHs; and that nitric acid consists of" one of ni- 
 trogen (N) and five of oxygen (.05), its formula being NOs.— See Lecture III., p 34. 
 
AMMONIA OBTAINED FROM VEGETABLES. 71 
 
 the flowers of the lirae tree, yield distilled waters in which ammonia 
 can be detected (Schiibler), the seeds of plants thus distilled yield it in 
 abundance (Gay-Lussac), and traces of it may be found in most vege- 
 table extracts (Liebig). 
 
 4°. Ammonia is also given off, among other products, when wood is 
 distilled in iron retorts for the manufacture of pyroligneous acid, and by 
 a similar treatment it may be obtained from many other vegetable sub- 
 stances. 
 
 Tlie above facts, however, are not to be considered as proofs that am- 
 monia enters direcdy 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, has produced 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, ma}' 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 temperature, 
 may be illustrated by a very familiar experiment often performed, 
 though for a very different purpose. The juice and dried leaf of tobac- 
 co contain nitre (nitrate of potash) and a little ammonia. But when 
 tobacco is burned, ammonia in sensible quanlity 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 restored; 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. — [Runge, Einlcilung in die tec/mische 
 Chemie, p. 375.] 
 
 Tn this case a portion of the ammonia given off by the tobacco has 
 most probably been 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. 
 
 Thus it is proved, by long experience, that plants grow most rapidly 
 and most luxuriantly when supplied with manure containing 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 efficacious of manures. This ammonia 
 is supposed to enter into the circulation of plants along whh the water 
 absorbed by their roots, and sometimes even by the pores of their leaves. 
 We can scarcely 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. 
 
 But though the facts so long observed in reference to the action u an- 
 
72 OTHER IMMEDIATE SOURCES OF NITROGEN. 
 
 imal manures upon vegetation, justify us in believing that ammonia 
 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 ca- 
 pable of deriving from decaying animal matter must enter into their cir- 
 culation in the form of ammonia. Other soluble compounds containing 
 nitrogen are formed during the decay of animal substances — they ac- 
 tually exist largely in the liquid manures of the stable and fold-yard, 
 and they can scarcely fail, when applied to the soil, to be to a certain 
 extent absorbed by the roots of plants. This urea is a substance con- 
 taining much nitrogen, which exists in the urine or excrements of most 
 animals, and by its decomposition produces carbonate of ammonia. 
 But being very soluble, this substance may enter directly Into the roots, 
 and may be there decomposed, and made to give up its nitrogen to the 
 livmg plant. To other compound substances of animal origin the same 
 observation may apply,* — so that while the fact, that animal manure in 
 a state of fermentation is very beneficial to vegetation, may be consi.l- 
 ered as rendering it higlily probable that the ammonia which such 
 manure contains, enters directly and supplies mucli nitrogen to thj 
 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 ob- 
 tained immediately from other compounds in which ammonia does not 
 exist. 
 
 To what amount, ammonia actually enters into ilie circulation of 
 plants, or how much of the nitrogen they contain it actually sujjjilies, 
 we have no means of ascertaining. Were it abundantly present in the 
 soil, its great 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 abundance in which it exists on the earth's surface, 
 and the extent of the influence it may be supposed to exercise on the 
 general vegetation of the globe. 
 
 § 8. Ahsoiylion of nitric acid hy ^''lants. 
 1°. That ammonia is actually present in the juices of many living 
 vegetables has been adduced, as a kind of presumptive evidence, that 
 this compound is directly absorbed by plants. A similar presumption 
 is offered in favour of the direct entrance of nitric acid, by its invariable 
 presence in cotnbinatlon with potash, soda, lime, or magnesia, in the 
 juices of certain common and well known plants. Thus it is said to be 
 always contained in the juices of the tobacco plant, of the sunflower, of 
 the goosefoot,7 and of common borage. The nettle is also said to con- 
 lain it, and it has been detected in the grain of barley. J ft exists pro- 
 bably in the juices of many other plants in which it has not hitherto 
 
 ' Thus it may be applied more strongly to tlie kippuric acid, whicli exists in tlie urine of 
 tile horse, and other herbivorous animals. This acid decomposes naturally into benzoic 
 acid and ammonia. Ttie sweet-scented veruat-grass (Anihoxanthntii Ock/ratiim) by wliich 
 hay is perlumed, 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 ab.'orb Ihe 
 hippuric acid contained in the urine, wliich reaches their roots, decompose it as it ascends 
 with the sap. appropriate its nitrogen, and exhale the odoriferous benzoic acid. 
 
 t Chenopodium, probably in all the species of this genus. — See Liebig, p. 82. 
 
 J Grisenthwaite (iV««7 Theory of Agriculture, p. 105) says, ii; is always present in barley in 
 the form of nitrate of soda. — <S'fe Api>ettdi3S. 
 
ABSOKPTION OF NITRIC ACID ITS EFFECT ON VEGETATION. 73 
 
 been sought for. Were we, therefore, entitled, from the mere presence 
 of this ncid 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 ve- 
 getable ;* and hence the fact of its presence proves nothing in regard to 
 the state in which the nitrogen it contains entered into the circulation of 
 the plant. 
 
 2°. But nitric acid, like ammonia, exerts a powerful influence on the 
 growing crop, whether of corn or of grass. Animal matters, as we have 
 seen, give off ammonia during iheir decay, and manures are rich and 
 efficacious in proportion to the quantity of animal manure they contain. 
 The crop produced also is valuable and rich in nitrogen in like propor- 
 tion. Therefore, 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 de- 
 gree. Applied to the young grass or sprouting shoots of grain, it has- 
 tens and increases their growth, it occasions a larger produce of grain, 
 and this grain, as when ammonia is employed, is richer in gluten, and 
 more nutritious in its quality. f An equal breadth of the same field 
 yields a heavier produce, and that produce, weight for weight, contains 
 more 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, 
 
 • When tlie beet-root arrives at maturity, tlie st«g-nr Ijegins to diminish, and saltpetre or 
 other nitrates to be formed, probably at the expense of the ammonia which the juice pre- 
 viously contained.— Decroizelles, Jour, de Phar., X., p. 42. 
 
 t The analogous efTecIs of ammoniacal manures and of the nilrates on the relative quan- 
 tities of gluten and starch in grain, are shown by the following experiments : 
 
 Hermbstaedt sowed equal quantities of the same wheat, on equal plots of the same ground, 
 and manured them with equal weights of different manures. Then from 100 parts of each 
 sample of grain produced, he obtained starch and gluten in the following proportions : 
 
 Gluten. Starch. Produce. 
 
 Without manure 9-2 66-7 3 fold. 
 
 With vegetable manure (rotted 
 
 polatoe liaulm) 9-6 e.'i-Ot 5 " 
 
 With cow dung 120 6-2 3 7 " 
 
 With pigeons' dung )2-2 632 9 « 
 
 Witli horse dung 137 61 04 10 " 
 
 With goats' dun? 32 9 42 4 12 « 
 
 With sheep dims 32-9 42 S 12 " 
 
 With dried night-soil 33 14 4144 14 « 
 
 With dried oxblond 34 24 413 14 " 
 
 With dried liunian urine - - - 3-') 1 39 3 12 "* 
 
 The manures employed by Hermbstaedt are supposed, during termcntation, to evolve 
 more ammonia in the order in which they are here placed, beginning at the top of the list ; 
 while the amount and Ititidoflhe produce obtained by the use of each, afford the chief evi- 
 dence in favour of the opinion Uiat this ammonia actually enters into and yields nitrogen to 
 the plant. 
 
 Mr. Hyett found in flour raised on two patches of the same land in Gloucestershire, the 
 one dressed with nitrate of soda, the other undressed, the following proportions: 
 
 Gluten. Starch. 
 
 In the nitrated - - - 23-25 49-5 
 
 In the unnitrnted - - 19- 55-5 
 
 And Mr. Daubeny, [Three Lectures on Agriculture, p. 76,] in flour from wheat top-dressed 
 with saltpetre, found — 
 
 In the nitrated 1.5 per cent, of gluten. 
 
 In the unnitrated - - • - 13 " " 
 
 These d'fTerence.s are not so striking aa in the case of ammonia, but they are precisely 
 the same in kind, anrl lead to the same general conclusion in regard to the nature of the in- 
 fluence of the nitrates on vegetation. Accurate and repeated experiments on the precise 
 effects of the nitrates are still muchio be desirerl. 
 
 [^ Schubler. Grumlsiltze der AgricuUur Chemie, II. p. 170.] 
 
/4 GENERAL CONCLUSIONS. 
 
 is capable of entering into the circulation of living plants — and of yield- 
 ing to them, in whole or in part, the nitrogen they contain. 
 
 But here, again, as in the ca.se of ammonia, we are at fault in regara 
 to the quantity of nitrogen which plants in a state of nature actually 
 derive from nitric acid or 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, whicli 
 enters by the roots of plants, could easily convey into their circulation 
 far more of these nitrates than would be alone sufficient to supply tlie 
 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 lias already 
 been shown. I shall hereafter lay before j'ou certain considerations 
 which may probably lead us to approximate conclusions in regard to 
 the relative influence exercised by tliese two compounds on the general 
 vegetation of the clobe. 
 
 Conclusions. — Respecting the form in which nitrogen enters into the 
 circulation of plants, we have therefore, 1 think, fairly arrived at these 
 deductions: 
 
 1°. Tliat 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 su[)posing nitrogen to be in this way appropriated* by 
 the plant, the (juantity 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, and that in European agri- 
 culture, which employs fermenting animal manure as an important 
 means of i)romoiing vegetable growth, it does ajjpear to yield to cultiva- 
 ted plants a considernhle i>orlion of the nitrogen tliey 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 is emploj'^ed as 
 an instrument of culture, the crops obtained owe part of their nitrogen 
 to the ciuantity of this compound which has been apf)lied to the grow- 
 ing 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 j)ro- 
 duced naturally in the soil. 
 
 4°. That other compound bodies, such as are contained in urine, or are 
 produced during the decay of animal 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 nitro- 
 gen they contain ; and that tliey obtain it most readily, and witli least 
 labour, so to speak, from these compounds, — though nature has kindly 
 fitted them for deriving a stinted sujiply from other sources, w^hen these 
 substances are not present in sutficient abundance. 
 
 How far each of these compounds is em[)loyed by nature, as an in- 
 strument in promoting the general vegetation of the globe, will be con- 
 sidered in a subsefjuent lecture. 
 
 * Liebig and others say that plants are incapable of appropriating or assimilating the nitro 
 gen wliich enters into their circulation in the simple state. We shall consider this ques- 
 tion hereafter. 
 
LECTURE V. 
 
 How does the food enter into the circulation of plants — Structure of the several parts of 
 plants — Functions of the root — Course of the sap — Cause of its ascent — Functions of 
 tlje stem— of the leaves— and of the bark — Circumstances 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 into the vegeta- 
 ble circulation, — the next step in our inquiry Ts — hoiv are these substan- 
 ces admitted into the interior of living plants — and under what condi- 
 tions or regulations? We are thus led to study the structure and func- 
 tions of the several parts of plants, and the circumstances by which the 
 exercise of these functions is observed to be modified. 
 
 § 1. General structure of plants, and of their several parts. 
 
 Plants consist essentinlly of three parts — the roots, the stem, and the 
 leaves. The former spread themselves in various directions through 
 tlie 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 ex- 
 tend, 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. 
 
 The stem consists apparently of four parts — the pith, the wood, the 
 bark, and the medullary rays. The pith and the medullary rays, how- 
 ever, are similarly constituted, and are only firolungatious of one and 
 the same substance. The ))ith forms a solid cylinder of soft and spongy 
 matter, which ascends through the central 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 of 
 considerable age the wood consists of two parts, the oldest or lieart 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 portions, the inner bark or liber, and 
 the epidermis or outer covering of the tree. The pith and the bark are 
 connected together by thin vertical columns or partitions, which inter- 
 sect 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 continuous 
 vertical plates, yet from the appearance they present in the cross sec- 
 tion of a piece of wood, they are distinguished by the name of medulla- 
 ry rays. 
 
 These several parts of the stem are composed of bundles of small 
 tubes or hollow cylindrical vessels of various sizes, and of different 
 kinds, the structure of which it is unnecessary for us to study. They 
 
 4* 
 
76 STRUCTURE OF THE STEMS, ROOTS, AND LEAVES OF PLANTS. 
 
 are all intended to contain liquid and gaseous substances, and to convey 
 them in a vertical, and sometimes in a horizontal, direction. The 
 tnbes which compose tlie wood and bark are arranged vertically, as may 
 readily be seen on examining a piece of wood even witli the naked eye, 
 and are intended to convey the sap upwards lo the leaves and down- 
 wards to the roofs. Those of which tlie pith and medullary jilates con- 
 sist are arranged liorizontally, and appear to be intended'to maintain a 
 lateral intercourse between the pith arrd the bark — perhaps even to place 
 the heart of the tree within the influence of the external air. 
 
 The root, though prior in its origin to the stem, may nevertheless for 
 the purpose of illustration be considered as its downward and lateral 
 prolongation into ihe earth — as tlic branches are its upward jirolonga- 
 tion into the air.* When they leave the lower i)art 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, then the \n\h, gradual- 
 ly disappear, till, towards their extremities, they consist only of a soft 
 central woody part and its covering of soft bark. These are connected 
 •with, or are respectively prolongations of, the new wood and bark of the 
 trunk and branches. At the extreme points of the roots the bark be- 
 comes white, soft, spongy, and fnll of pores and vessels. It is by these 
 spongy extremities only, or chiefly, that li(]uid and gaseous substances 
 are capable either of entering into, or of making their escape from, the 
 interior of the root. 
 
 The branches and twigs are extensions of the trunk ; and of the 
 former, the leaves nray be considereil as a still further extension. The 
 fibres of the leaf are Kiinule ramifications of iJie woody matter of the 
 twigs, are connected through ihem wiih the wood of the brandies and 
 stems, and from this wood receive the sap which ihey contain. The 
 green part of the leaf may be considered 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 tl)e extremiiy of the root, 
 is fitted to act upon llie water and other substances it meets with in the 
 soil. For as the fibres of ihe 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 functiovs of tlt,e root. 
 The position in which the roots of plants in their natural slate are ge- 
 nerally placed, has hitherto ))revented their functions from being so ac- 
 curately investigated as those of tlie leaves and f>f the stem. While, 
 therefore, the main ])ur|ioses they are intended to serve are universally 
 
 • The correctness orttiis comparison is proveii by the fact tliat, in many trees, llic t>ranch 
 if planted wiU become a roof, anrl ihe root, if exposeci In the air, will (iradiially be Irans- 
 formed into a branch. The banana in the forest, and Ihe currant tree in onr paniens, are 
 familiar instances of trees spontaneously planting tl>eir brunches, ami csusinj; lh"ni lo per- 
 form the functions of roots. In like manner, " if the slern of a ynuna plum or cherry-tree, 
 or of a willow, be bent in llie autumn so that one-half of the fop can be laid in lite earUi and 
 one-halfof llie root be at the same time taljen carefully u])— slieherej at llisl and after- 
 wards gradually exposed lo the cold— an(i if in the followini; year Ihe remaining: (lart of the 
 top and root he treated in the same way. tlie branches of Ihe top will become roots, and the 
 ramifications of Ihe roots will become branches, producing leaves, flowers, and fruit in due 
 season. — ['i.owirin's E7i.ci/c!opadiaof A^icidtare.] The tree is thus reversed in position, 
 and the roots and branches being thus mutually convertible cannot be materially unlike in 
 general structure. 
 
ROOTS ABSORB AQUEOUS SOLUTIONS, AND OXVGEN. 77 
 
 Known and understood, the precise way in which these ends are accom- 
 l)lished by the roots, and ilie powers with which they are invested, are 
 still to a considerable degree matters of dispute. 
 
 I. It appears certain that they are pcjssessed of the power of absorb- 
 ing water in large quantity from the soil, and of transmitting it upwards 
 to the slcni. 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. 
 
 II. The analogy of the leaves and young twigs would lead us to 
 suppose that, when in a proper stale of moisture, the roots should 
 also be capable of absorbing gaseous substances from the air which 
 pervades the soil. Experiment, however, has not yet shown this to be 
 the case. 
 
 We know, however, that they are capable of absorbing gases through 
 the medium of water. For if the roots of a plant are placed in water 
 containing carbonic acid in tlie state of solution, this gas is found gradu- 
 ally to disappear. It is extracted from the water by the roots. And if 
 the water in whicii the roots are immersed be contained in a bottle only 
 partially filled with the liquid, wliile the remainder is occupied by at- 
 mosplieric air, tiie oxygen in this air will also slowly diminish. It will 
 be absorbed by tiie roots through the medium of the water.* 
 
 Again, 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, nitro- 
 gen 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, that the roots of plants absorb gaseous sub- 
 stances from the air which surrounds their roots, at least indirectly and 
 through the medium of water. It appears also that from this air they 
 have the power of selecting a certain portion of oxygen when this gas is 
 present in it. Thirdly, that though they can absorb carbonic acid to a 
 limited amount 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 fissures 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, is supjjosed to imply that the pre- 
 sence 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. 
 
 Tills supjiosition is in accordance with the fact that, in the dark, the 
 leaves of plants absorb oxygen from the atmosphere; for we have al- 
 ready seen reason to expect that, from their analogous structure, the roots 
 and leaves in similar circumstances should ])erform also analogous func- 
 tions. At the same lime, if the roots do require the access and presence 
 
 * It will be rucoUecteil that wafer absorbs about 4 per cent, of its bull? of air from the at- 
 mosphere, of which about one-tliird is oxyiien. If the roots e.xtract this oxy^ren from the 
 water, the latter will again drink in a fresh portion from the atmosiiheric air which floats 
 above it. 
 
178 DO SOLID SUBSTANCKS ENTER THE ROOTS? 
 
 of oxygen in the soil, it would further appear that those of some plants 
 require it more tlian those of others ; inasmuch as some genera, like the 
 grasses, love an open and fiiuble soil, into which the air is more com- 
 pletely excluded. — [Sprengel, Cliemie, II., p. .3.'37.] 
 
 III. We have in a former lecture (IV. j). G4) concluded from facta 
 there stated, that solid substances, which are soluble in water, accom- 
 pany 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 animal and vegetable origin to v/hich the 
 observations made in the fourth lecture were intended more especially to 
 apply. Even silica,* considered to be almost insoluble in water, enters 
 by the roots, and is found in some cases in considerable quantities in the 
 stem. Some persons have hence been led to conclude that solid sub- 
 stances, 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 
 ste m . 
 
 Considered as a mere (juestion of vegetable mechanics, argued as such 
 among physiologists, it is of little moment whether we adopt or reject 
 this opiuion. One [jhysiologist may state that tiie pores by which the 
 food enters into the roots are so minute as to batBe the powers of the best 
 constructed mici'oscope, and, therefore, that to no particles of solid mat- 
 ter can they by possibility give admission — while another may believe 
 solid matter to be capable of a mechanical division so minute as to jiass 
 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, 
 unnecessary, perhajxs injurious to vegetable life, may be carried tcjrward 
 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, ihe adoption of this opinion implies also, that 
 the inorganic substances found in plants, — those which remain in the 
 form of asii when the plant is burned, — are acci(lc7ital on\y, 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 they ought to vary in kind and relative (piantity with 
 every variation in the soil. In a clay land the ash should consist chiefly 
 of alumina, f in a sandy soil chiefly of silica. But if, as chemical in- 
 quiry ap[)ears to indicate, the nature of the ash is not accidental, but es- 
 sential, and in some degree constan;., even in very different soils, this 
 latter inference is inadmissible; — and in reasoning backwards from this 
 fact, we find ourselves constrained to reject ilie o[)inion that substances 
 are capable of entering into Ihe roots of plants in a solid slate — 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 ))articles into which solid mat- 
 ter may be divided. 
 
 * Silica is the name given by chemists to tlie pure matter of flint or of rock ci7stal. Sand 
 and sandstones consist almost entirely of ti lica. 
 t Alumina is the pure earth of clay. 
 
SELECTING POWER OF THE ROOTS. 79 
 
 IV. We are thus brought to the consideration of the alleged selecting 
 power of the roots, which, if rightly attributed to them, must be con- 
 sidered as one of the most important functions of which they are pos- 
 sessed. It is a function, however, the existence of which is disputed by 
 many eminent jjhysiologists. But as the adoption or rejection of it will 
 materially influence our reasonings, as well as our theoretical views, it? 
 regard to some of the iriost vital processes of vegetation, — it will be pro- 
 per to weigh carefully the evidence on which this power is assigned to 
 the roots of plants. 
 
 1°. The leaves, as we shall hereafter see, possess in a high degref 
 the power of selecting from the atmosphere one or more gaseous sub- 
 stances, leaving the nitrogen, chiefly, unchanged in bulk. The absorp 
 tion of carbonic acid and the diminution of the oxygen in the experi 
 ments above described, appear to be analogous effects, and would seem 
 to imply in the roots the existence of a similar power. 
 
 2°. Dr. Daubeny found that pelargoniuins, barley {hordeum vulgare), 
 and the winged pea {lolus tetragonolohus), though made to grow in a 
 soil containing 'much strontia,* appeared to absorb none of this earth, foi 
 none was found in the ash left by the stem and roots of the plant whec 
 burned. In like manner De Saussure observed that polygonum persi- 
 caria refused to absorb acetate of lime from the soil, though it freely took 
 up common salt. — [Lindley's Theory of Horticulture, p. 19.] 
 
 3°. Plants of different species, growing in the same soil, leave, when 
 burned, an ash which in every case contains either different substances, 
 or the saine substances in unlike proportions. Thus if a bean and a 
 grain of wheat be grown side by side, the stem of the plant from the lat- 
 ter seed will be found to contain silica, from the former none.f 
 
 4°. But the same plant grown in soils unlike in character and com- 
 position, contains always — if they are present in the soil at all — very 
 nearly the same kindj of earthy matters in nearly the same proportion. 
 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 growing 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 a mixture 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 produce of seed 
 from each, in the above order, weighed 24i, 28|, 26i, 2li, and 20 ounces 
 respectively. The grain, chalF, and straw, from each of the patches 
 left nearly the same cpiantity of ash — the weights varying onlj"^ from 3-7 
 to 4-03 per cent., and the roots and chaff^being rirhest in inorganic mat- 
 ter. The relative proportions of silica, alumina, lime, and magnesia, 
 
 * Watered with a solution of nitrate of strontia. Strontia is an earthy substance resem 
 bling lime, wliich is found In certain rocks and mineral veins, but which has not hitherto been 
 observed in the ashes of plants. 
 
 t It is not strictly correct that the bean will absorb no silica, but the quantity it will lake up 
 will be only one-thirteenth of that taken up by the wheat plant — the per centage of silica in 
 the ash of bean straw beins, according to Spvengei, only 0-22, while in wheat straw it is 2-87 
 per cent. Pea straw contains four times as much as that of the bean, or 996 per cent. 
 
 i For more precise information on this point, see the subsequent lectures, " Onihe inor- 
 ganic constituents of plants," (Part 11.) 
 
80 PLANTS MAY ABSORB POISONOUS SUBSTANCES. 
 
 were the same in all. — [Meyen Jahresberichf, 1839, p. 1.] Provided, 
 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 mate- 
 rially affected by the presence of other substances, even in somewhat 
 larger quantity. 
 
 These facts all point to the same conclusion, that the roofs have the 
 power of selecting froni tlie soil in which they grow, those substances 
 which are best fitted to promote tlie growth or to maintain the healthy 
 condition of the plants they are destined to feed. 
 
 5°. It lias been stated above that the roots of certain plants refuse to 
 absorb nitrate of strontia and acetate of lime, though presented to them 
 in a state of solution — the same is true of certain coloured solutions which 
 have been found incapable of finding their way into the circulation of 
 plants whose roots have been immersed in them. On the other hand, 
 it is a matter of frequent observation that tlie roots absorb solutions con- 
 taining substances which speedily cause the death of the ])lant. 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 ihe 
 living vegetable — and on this ground chiefly many physiologists refuse to 
 acknowledge that the roots of plants are by nature endowed with anv 
 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.* 
 
 On the whole, therefore, it appears most reasonable to conclude that 
 the roots are so constituted as (1°) to be able generally to select from the 
 soil, in j)referc7ice, those substances which are most suitable lo the nature 
 of the plant — (2°) where these are not to be met with, to admit certain 
 others in their steadf — (3°) to refuse admission also to certain substan- 
 ces likely to injure the plant, though unable to discriminate and 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 agaiast such as rarely 
 present themselves in the situations in which it is destined to grow, or 
 against substances which are unlikely even to demand admissi.on into its 
 roots. How useless a waste of skill, if I may so speak, would it have 
 been lo endow the roots of each plant with the jiower of distinguishing 
 and rejecting opium and arsenic and the thousand other poisonous sub- 
 stances which the pliysiologist can present to them, but which in a state 
 of nature — on its natural soil and in its natural climate — the living vege- 
 table is never destined to encounter I 
 
 ' I may here remark that it is by no means an extraordinary power which these circum- 
 stances seem to show the roots of plants to possess. In tlie presence of oxygen, nitro>jen, 
 and carbonic add, 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 Ihe former. 
 Is it unreasonable to suppose the roo'.sof plants— the organs of a living being — to be endovvcd 
 with powers of discrimina'.ion at least as great as those possessed by dead matter? 
 
 t This conehisinn is not strictly contained in the premises above stated, but the facts from 
 which it is drawn will be fully explained in treatini; of the inore.anic constituents of plants. 
 It is introduced here for Ihe purpose of giving a complete view of what appears to be the 
 true powers of discrimination possessed by the root. 
 
EXCRETORY POWER OF THE ROOTS. 81 
 
 V. Anotliej function of tJie roots of plants, in regard to which physiol- 
 ogists are divided in opinion at the present day, is what is called their 
 excretory power. 
 
 1°. When barley or other grain is caused to geriniiiale in pure chalk, 
 acetate of lime* is uniformly found to be mixed with it after the germi- 
 nation is somewhat advanced (Becquerel and Mateucci, A?in. de Chan, 
 ct de Phys., 1 v., p. 310.) 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 authority of Decan- 
 dolle, and illustrated by tiie apparently cojivincing experiments of Ma- 
 caire, {Ann. de Chim. el de Phys., lii., p. 2"25,) has more recently been met 
 by counter-experiments of Braconnot, (Ixxii. p. 27,) and is now in a great 
 measure rejected by many eminent vegetable physiologists. It may in- 
 deed be considered as quite certain tha.t the a|)plication of this theory by 
 Decandolle and others to the explanation of the benefits arising from a 
 rotation of crops, is not conHrmed, or ]) roved to be correct, by any exper- 
 iments on tlie subject that have hitherto been puljlished.f 
 
 According to Decandolle, |)lants, like animals, have tlie power of se- 
 lecting from tlieir food, as it passes through their vascular system, such 
 portions as are likely to nourish them, and of rejecting, by their roots, 
 
 ' Acetate of lime is a combination ofapetic acid or vinegar with lime derived from the chalk. 
 
 t The discordant results of Macaire and Braconnot were as follow : 
 
 1^ Macdire observed that when pla.tits o( Chondi iUa Muralis were grown in rain water 
 they imparted lo 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 im|)ossible to free the young roots from the soil in which they have grown, 
 without injuring them and causing the sa|i to exude. 
 
 2°. Bu/j/wrO/a Peptus (Petty Spurge) imparted to tlie water in which it ffrew a gummi- 
 rcsinous sub.slance of a very acrid taste. In the hajids of Braconnot it yielded to Ute water 
 scarcely any or;ianic matter, and that only siiiiluly bitterish. 
 
 3^. Bracoruiot washed llie soil in which p\naisot JDuphoi'Ma Breuni a.ii<] Asdepias Incur- 
 nata were growing in pots, and obtained a solution containing earthy and alkaline salts with 
 only a trace of organic matter. 
 
 lie also washed the soil in which the P>>ppy (Papaver Sommferum) had been grown ten 
 years successively. The solution, besides inorganic earthy and alkaUne salts, gave a consid- 
 erable quantity of acetic acid (in the form of acetate of lime) and a trace of brown organic 
 matter. lie iiifrs that these several plants do not excrete any organic matter in sufficient 
 quantity to be injurious lo themselves. 
 
 4°. Macaire observed that when separate portions of the roots of the same plant of Mercu- 
 Tialis Annua were immersed in separate vessels, tlie 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 transmitted to the pure water. Bra- 
 connot observed Oie same results, but he found the entrance of the lead into the second vessel 
 to be owing to the ascent of the fluid up Uie outer surface of the one root and down the exterior 
 of the other, and that, by preventing the possibihty of this passage, no lead could be detected 
 among the pure water. 
 
 ITie' conclusion,^ of Macaiie, therefore, in favour of the rotation theory of Decandolle 
 miLSt be considered as at present inadmUsible, and we shall hereafter see reason to coin- 
 cide, at least to a cert/iin e.\tent, in the conclusion of Braconnot. "that if these excretions 
 (of oritamc matter) really Lake place in the natural state of the plant, they are as yet so ob- 
 scure and so little known as to justify the presumption that some other explanation nmst 
 be given of thegeneral system of rotation." Various illustrations have been given by ditTer- 
 ent ob:=orvers of this supposed excreting power of the mots. Among the most recent are 
 those n{ Nietner, Who ascribe* the luxiuiaiit rye crops obtained without manure after three 
 vcars of clover, to the excretions of this plant in the soil, whicli, like lliose of the pea and 
 l)ean to Uie wheat, he supposes 'o 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 lie 
 attributes to the excretions of the tobacco plant. Meyen ascribes the effect of the clover to 
 the srecn manure su|'plied by its roots and stubble and Uiat of the tobacco to the undecom- 
 posf'd organic substances contained in the sap and substance of the roots and stems of this 
 plant, of which so large a iiuantity is left behind in the field.— [Meyen's To/jresfierjcW, 1839, 
 p. 5.]— These objections of Meyen are not without their weight, but we shall hereafter see 
 that they embody only half the truth. 
 
83 EXPERIMENTS OP DE SAUSSUHE. 
 
 when the sap descends, such as are unfit to contribute to their support, 
 or would be hurtful to them if not rejected from their system. He further 
 supposes that, after a time, the soil in which a certain kind of plant 
 orows becomes so loaded with this rejected matter, that the same plant 
 refuses any longer to flourish in it. A.nd, thirdly, that though injurious 
 to the plant from which it has been derived, this rejected matter may be 
 wholesome food to plants of a difierent 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 at 
 times — it may be constantly — reject organic substances from their roots. 
 The acetic acid given otf during germination, and the same acid found 
 by Braconnot in remarkable quantity in the soil in which the poppy 
 {papaver somnifenim) has grown — may be regarded as sufficient evi- 
 dence of the fact — but the quantity of such organic matter hitherto de- 
 tected among what may be safely viewed as the real excretions of plants, 
 seems by far too small to account for the remarkable natural results at- 
 tendant upon a rotation of crops. 
 
 The consideration of these results, as well as of the genernl theory of 
 such a rotation, will form a distinct topic of consideration in a subsequent 
 part of these IccMires. I shallj therefore, only mention 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 tlie sap returns from the leaf, some of 
 the substances which they had previously taken up from the soil. 
 
 1°. De Saussure made numerous experiments on the (juantity of ash 
 pe cent, left by the same plant at ditferent periods of its growth. Ainong 
 other results obtained by him, it appeared — 
 
 A. That the quantity of incombustible or inorganic matter in the dif- 
 ferent parts of the plant was different at different periods of the year. 
 Thus the dry leaves of the horse chestnut, gathered in May, left 7-2 per 
 cent., towards the end of July 8-4 per cent., and in the end of Septem- 
 ber 8'6 per cent, of ash ; the dry leaves of the hazel in June left 6-2, 
 and in September 7 per cent.; and those of the poplar (jjopulus nigra) 
 in May 6-6, and in September 9-.3 per cent, of ash. These results are 
 easily explained 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 substances in 
 — or the ash left by — tiie entire plant, diminished as it approached to 
 maturity. Thus ihe dry plants of the vetch, of the golden rod {solida- 
 go vulgaris), of the turnsol (lielianthus amiuus), and of wheat, left res- 
 pectively of ash, at three different periods of their growth, [Davy's 
 Agricultural Chemistry, Lecture HI,] — 
 
 Before flowering. In flower Seeds ripe. 
 
 per cent. per cent. per cent. 
 
 Vetch 15 12'-2 6-6 
 
 Golden rod ... 9-2 6-7 5-0 
 
 Turnsol .... 14-7 13-7 9-3 
 
 Wheat .... 7-9 5-4 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 ac- 
 
PROPORTION OF SILICA IN THE ASH OF PLANTS. 83 
 
 companying their increase 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 explanation, the relative proportions of the 
 several substances of which the ash itself consisted, in the several cases, 
 should have been the same at the several periods 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 
 
 Before flowering. In flower. Seeds ripe. 
 
 per cent. per cent. per cent. 
 
 Vetch contained ... 1'6 1-5 1-75 
 
 Golden rod 1-5 1-5 3-5 
 
 Ttirnsol 1-5 1-5 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 
 ajipears evident that some part of that which existed in the ])iant during 
 tlie earlier ])eriods 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 con- 
 sideration. 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 percent., or rather more than one-half, was silica. This 
 silica, it is believed, could only have entered into the circulation of the 
 plant in a state of solution in water, and could only be dissolved by the 
 agency of potash or soda. But, according to Sprengel, the potash, soda, 
 and silica, are to each other in the grciin and straw of wheat, in the pro- 
 portions of — 
 
 Potash. SoLla. Silica. 
 
 Grain .... 0-225 0-24 0-4 
 
 Straw .... 0-20 0-29 2-87 
 
 Or, supposing the grain to equal one-half the weight of the straw — 
 their relative proportions in the whole plant will be nearly as 21 potash, 
 27 soda, 205 silica, or the weight of the silica is upwards of four times 
 the weights of ihe potash and soda taken together. 
 
 Now silica requires nearly lialf its weight of potash to render it solu- 
 ble in water,* or three-fifths of its weight of a mixture of nearly equal 
 parts of potash and .soda. The quantity of these alkaline substances 
 found \n the plant, therefore, is by no means sufficient to have dissolved 
 and brought into its circulation the whole of the silica it contains. One 
 of two things, therefore, must have taken place. Either a portion of 
 the potash and soda |)resent in the plant in the eai'lier 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 in its burden of silica, deposit- 
 
 ■ A soluble glass may be made by melting togellier in a crucible for si.v hours 10 parts of 
 carbonate of potash, 15 of silica, and 1 of charcoal powder. 
 
 t De Saussure does not state the exact relative quantities of potash and soda at the several 
 periods of tlie growth of wheat, though ihoy appear to have firadi ally diminished. It 
 seems, indeed, to be true of many platils, that the potash and soda they contain diminishes 
 .n quantity as tlieir age increases. Thus Ihe weight of potash in Ihe juice of the ripe or 
 jweet grajie, is snid to be less than in Ihe unripe or sour grape — and the leaves of the potato 
 have been found mure rich in polasli before than after blossoming (Liebig). 
 
84 CAN THE ROOTS MODIFY THE FjOU OF F.'.ANTS ? 
 
 ing it in the vascular system of the plant, and again returning to the 
 soil for a fresh supply. In either case the roois must have allowed it 
 egress as well as ingress. But the fact, that the proportion of silica in 
 the plant goes on increasing as it continues to grow, is in favour of the 
 latter view — and renders it very probable that the same quantity of al- 
 kali returns again and again into the circulation, bringing with it sup- 
 plies of silica and probably of other substances wliich the plant requires 
 from the soil. And while this view appears to be the more probable, it 
 also presents an interesting illustration of vvhat may probably be the 
 kind of function discharged by the potash and otlier inorganic substances 
 found in the substance of plants — a question we shall hereafter have oc- 
 casion to consider at some length. 
 
 The above considerations, therefore, to which I might add others of a 
 similar kind, satisfy ine that the roots of plants do possess the power of 
 excreting various 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 sustenance or growth. Nor is it likely that this excre- 
 tory power is restricted solely to the emission of inorganic substances. 
 Otiier soluble matters of organic origin are, no doubt, permitted to es- 
 cape into the soil — though whether of such a kind as must necessarily 
 be injurious to llie plant from which they have been extruded, or to such 
 a degree as alone to render a rotation of crops necessary, neither reason- 
 ing nor experiment has hitherto satisfactorily shown. 
 
 VI. 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? A colourless sap is observed to ascend through the 
 roots. From tlie very extremity up to the fool of the stem a cross sec- 
 tion exhibits little trace of colouring matter, even when tlie soil contains 
 animal and vegetable substances wliich are soluble, and which give dark 
 coloured solutions, [such as the liquid manure of the fold-yard.] Does 
 such matter never 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 
 decide with any degree of certainty in regard to this function of the root. 
 
 It is probable, however, that as the sap passes through the plant, it is 
 constantiy, though gradually, undergoing a series of changes, from tiie 
 time when it first enters the root till it again reaches it on its return from 
 the leaf. 
 
 Can we conceive the existence of any powers in tlie 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 dissolve lime from the 
 soil and return with it again, as some suppose (Liebig). into the circula- 
 tion of ibe i^lant?* Is acetic acid firnduced and excreted by the seed 
 for this very refined purpose? We have concluded that in the wheat 
 ])lant the potash and soda probably go and come several times during its 
 growth, and the ripening of its seed. Is this a contrivance of nature to 
 
 ' Braconnot fouml acetate of lime in very small quantities to be sinjnlarly Imrtful to ve^e- 
 tafion, and acetate of majinesia a little If ss so. He only mentions, however, some experi- 
 ments upon merciirialis annua, [Ann. de Cliim. et de P/ii/s. Ixxii. p. 36,] and as Saussure 
 found that some plants actually refused to taliu it up at all. hiose acetates may not be equally 
 injurious to all plants. 
 
THE SAP ASCENDS THKOUGH THE WOOD. 85 
 
 make up for the scarcity of alkaline substances in the soil — or would tlie 
 same mode of operation be employed if potash and soda were present 
 in greater abundance? Or where the alkalies are present in greater 
 abundance, might not more work be done by them in the same 
 time, — might not the plant be built uj) the faster and the larger, when 
 there were more lianils, so to speak, to do the work? Is tlie action of 
 inorganic substances upon vegetation to be explained by the existence 
 of a |)ovver resident in the roots or other 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 unable as yet to induce nature to reveal to us.* 
 But the morning light is already kindling on the tops of tlie mountains, 
 and we may hojie that the deepest vallies will not forever remain obscure. 
 
 § 3. The course of the sap. 
 
 If the trunk of a tree be cut offabove the roots, and the lower extrem- 
 ity be immediately plunged into a solution of madder or otlier colotiring 
 substances, the coloured li(iuid 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 ;ipj)car coloured, 
 the bark remaining entirely untinged. But if the process be allowed 
 still to continue when the coloured matter has reached the leaf, and after 
 some further lime the stem be cut across, the baik also will apj)ear dyed, 
 and the tinge will be perceptible further and further from the leaf the 
 longer the experiment is carried on, til! 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 f)f Macaire de- 
 tailed in a i)receding note, be immersed in a metallic solution — such 
 as a solution of acetate of lead, — which it is capable of absorbing with- 
 out immediate injury, and diflTerent portions of the plant be examined 
 after the lapse of dilliirent periods of time, — first the stem, afterwards 
 the leaves, then the bark of the upper part of the stem, and lastly that 
 of the lower ])art of the stem, will exhibit traces of lead. 
 
 These experiments show that the sap vvhich enters by the roots as- 
 cends through the vessels of the wood, difluses itself over the surface 
 of leaves, and then descends by the bark to the extremities of the root. 
 
 But what becomes of the sap when it reaches the root? Is it deliver- 
 ed into the soil, or does it recommence the same course, nnd again, re- 
 peatedly perhaps, circulate through the stem, leaves, and bark ? This 
 question has been partly answered by what has been stated in the pre- 
 ceding section. When the sap reaches the extremity of the root, it ap- 
 pears to give off to the soil both solid and fluid substances of a kind and 
 
 ■ Th<? roots of trees will travel to comparatively great disfances, and in various directions, 
 in searcli of water : the roots of sainfoin (.Esparsetie) will penetrate 10 or 12 feet through the 
 calcareous rubbly suhsoil, or down the fissures of limestone rocks on which they deli^'ht to 
 grow. l3 this the result of some perceptive power in tlie plant — or is it merely by accident 
 that the roots display those tendencies 1 
 
 Those who are in any degree acquainted with the speculations of the German physiolo- 
 gists of the greatest name — in regard to the soul and even \he immortality of plants — will not 
 accuse me of goina very far in alluding lo the possible existence of some such perceptive 
 power in plants. Von Marlins goLs riit'of objectors by speaking of them as "scientific men 
 lo whom the power of comprehending tlie transcerulenlal k/is been iTitpur ted in a lower ile<^rte." 
 See Mey eii' 3 Jahresbe.richt, 1*39, or iHtlirtian's Jcurnal for January, 1841, p. 170. " 
 
86 CAPILLARV ATTRACTIO.V. 
 
 to an amount which probably diflfer with every species of plant. The 
 remainder ol'tlie sap and of llie substances it holds in solution must be 
 diffused through the cellular spongy terminations of tbe roots, and, with 
 the new supply of liquid imbibed from the soil, returned again to the 
 stem with the ascending current. 
 
 But what causes the sap thus to ascend and descend ? By what 
 power is it Hrst sucked up through the roots, and afterwards forced down 
 again from the leaves? Several answers have been given to this ques- 
 tion. 
 
 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 
 witiiout the lube. The cause of this rise has been ascribed to an attrac- 
 tion which the sides of the tube have for the liquid, and which is suffi- 
 ciently strong to raise it and lo keep it up above the proper level of tlie 
 water. The force itself is generally distinguished by the name oi capil- 
 lary attraction. 
 
 Now, the wood of a tree, as we have seen, is composed of a mass of 
 fine tubes, and through these the sap has been said to rise by cajnllary 
 attraction. But if the top of a vine be cut otF when it is juicy and full 
 of sap, the lifjuid will exude from tlie newly formed surface, and if the 
 air be excluded, will flow for a lerigih of time, and may be collected in 
 a considerable quantity [Lindley's Theory of Horticulture, p. 47, note]. 
 Such a flow of the sap is not to be accounted for by mere capillary at- 
 traction — the sides of tubes cannot draw up a fluid beyond their own 
 extremities. 
 
 2°. To supply the defect of this hypothesis, De Saussure supposed 
 that the fluid at first introduced by capillary attraction into the extremi- 
 ties of the root, was afterwards propelled upwards by the alternate con- 
 traction and expansion of the tubes of which the wood of the root and 
 stem is composed. This alternate contraction 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 ad- 
 mission to contract for the purpose of expelling it. Mr. Knight also as- 
 cribed the ascent of the sap to a similar contraction of certaiti other parts 
 of the stem. Being once raised, he supposed it to return again or de- 
 scend 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 re- 
 turn to the root. These explanations, therefore, are still unsatisfactory. 
 
 3^. If one end of an open glass lube be covered with a piece of mois- 
 tened bladder or other fine animal membrane, tied tightly over it, and a 
 strong solution of sugar 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 introduced to the depth of an inch below the sur- 
 face of a vessel of pure water, the water will after a short time pass 
 through the bladder inwards, and the column of li(|uid in the tube will 
 increase in height. This ascent will continue, till in favourable circum- 
 
 * Glass tubes perforated by a very fine bore, like a human hair, are called capillari/ tabes. 
 Such are those of which thermometers are usually made. 
 
CAUSK Of THE ASCENT OF THE SAP. 87 
 
 Stances the fluid will reach the height of several feel, and will flow out 
 or run over at the open end of the lube. At the same time the water in 
 the vessel will become sweet, indicating that while ho much licjiiid has 
 passed through the membrane inwards, a quantity has also passed out- 
 wards, carrying sugar along with it.* To these opjiosite effects Dulro- 
 chel, who first drew attention to the fact, gave the names of Endosmose, 
 denoting the Inward progress, and Exosmose, the outward progress of the 
 fluid. He supposed them to be due to the action of two oi)posiie cur- 
 rents 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 in- 
 fluence of electricity in producing the phenomena of endosmose and ex- 
 osmose, it must be admitted that the appearances themselves bear a 
 strong resemblance to tiiose ))resented in the absorption 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 experimen- 
 tal 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 vvith 
 foliagp, this will never happen. The leaves are contiinially exhaling 
 aqueous vapour, as one of their constant functions, and sometimes in 
 very large quantify. The sap, therefore, when it reaches the leaves, is 
 concentrated or thickened, and rendered iriore dense by the separation 
 of the water, so that when it descends to the root, and again begins its 
 upward course, it will admit of large dilution before its density can be 
 so far diminislied as to approach that of the comparalively ])ure water 
 which is absorbed 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 evaporation 
 which is constantly taking f)lace from the surface of the leaf. 
 
 Still the cause of (he 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 phenomena, that to 
 have obtained the command, or even a partial control, over a natural 
 
 * Instead of sugar, common salt, gum, or other soluble substances may be dissolved in 
 the water iniroiluced at first into the lube, ami ihe denser this solution tlie larger the quantity 
 of water wliieh 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 llie portions of liquid williin and without 
 the membrane attain nearly lo the same density [i. e. contain nearly the same weight of solid 
 matter in solution.) Instead of pure water the vessel into which the extremity of Ihe tube 
 is plunged may also contain a weak solution of some soluble substance — such as lime or soda 
 — in which case while the sugar, orsalt, 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. 
 
OO DFXOMPOSITION TAKES PLACK IN THK STr.M. 
 
 power, is a consideralile step towards a clear conception of tlie nature of 
 that power itself. ]f the phenomena of endosmose can liereafier he 
 clearly and indubiiably traced to the agency of eiectriciiy we shall have 
 advanced still another step, and shall be enabled to devise other means 
 by wliich a more jierfect imitation of nature may be ertected, or a more 
 complete control asserted over the phenomena of vegetable circniaiion. 
 
 §4. Functions of the stem. 
 
 The functions of the stem are probably as various as those of the 
 root, though the circumsiatices under which lliey are performed neces- 
 sarily involve these functions in considerable obscurity. 
 
 The pith which tbrnis the central part of tlie stem consists, as 1 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 untinclured in the centre of the col- 
 oured wood. It docs not, tiierefore, 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. Kniglit has shown that, from the interior of many trees, 
 it may be removed without apparent injury, and in nature, as trees ad- 
 vance in age, it gradually diminishes in bulk, and in some species be- 
 comes apparently obliterated. 
 
 The vessels of the wood, which surrounds the pith, perform proba- 
 bly boili a itiechnnical and a chemical I'unction. They serve to convey 
 upwards to the leaf the various substances which enter by the ro(jis. 
 This is their mechanical function. Bui during its progress upwards, 
 the sap appears to undergo a series of changes. When it reaches the 
 leaves it is no longer in the stale in which it ascended from the root iuio 
 the stem. Tlie ditliculty of extracting the sap from the wood, at dif- 
 ferent heights, has prevented very rigorous experiments from being 
 made on ils nature and contents at the several stages of its ascent. 
 These it is obvious must vary with the species and age of the plant, and 
 with the season of the year at which tlie experiment is made. But the 
 general result lo be drawn from such observations as have hitherto been 
 made, is, that those substances which enter directly into the root, when 
 iningled wiih such as have already jiassed through the circulation of the 
 Iilaul, undergo, during their ascent, a gradual prejiaralion for that stale 
 in wliich ihey become tit to minister to the growth of the plant. This 
 preparation is coni])leted in a great measure in the leaf, though further 
 changes still go on as the sa|) descends through the bark. This deduc- 
 tion is strengthened by the fact that gaseous substances of various kinds 
 and in varying quantities exist in the interior of the wood of the grow- 
 ing plant. These gaseous subtances, according to Boucherie, are in 
 some cases ecpial in bulk lo one-twentieth part of ihe entire trunk of the 
 tree in which they exist. They jirobably move upwards along wiih 
 the saj), and are more or less completely' discharged into the atmospiiere 
 through the pores of the leaves. That these gaseous substances not 
 onl}' differ in quantity, 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 direct- 
 ly by the roots, but are the result of chemical decompositions which 
 
FDNCTIONS OF THK STF.M A.ND LF.AVKS. 89 
 
 have taken place on the stem itself, as the sap monnted u])wards to- 
 wards I he leaves. 
 
 We have seen that the roots exercise a kind of discriminating power 
 in admitting to the circulation of the plant the various Kubslances which 
 are present in the soil. The vessels of the stem exhibit an analogous 
 jiower 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 species are cut oli' above the roots, 
 and the lower extremities immediately plunged into solutions of differ- 
 ent substances, some of these solutions will quickly ascend into and pen- 
 etrate the entire substance of the tree immersed in them, while others 
 will not be admitted at all, or with extreme slowness only, by the ves- 
 sels of the stems to which they are respectively presented. On the 
 other hand, that which is rejected by one sjiecies will be readily admit- 
 ted by another. Whether this partial stoppage of, or total refusal lo ad- 
 mit, certain substances, be a mere contractile effi)rt on the ()art of the 
 vessels, or be the result of a chemical change by which their exclusion 
 is effected or resisted, does not as yet clearly a])]iear. That it does not 
 depemi upon the lightness and porosity of the wood, as might be sup- 
 posed, is shown by the observation that the poplar is less easily pene- 
 trated in this way than tlie bL'ecli, and tlie willow than the pear tree, 
 the maple, or the |)lane. 
 
 These various functions of the W(jody part of the stem are j)erformed 
 chiefly by the newer wood or alhurnmti, 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, whicii, like concretions in the bodies of ai:;imals, 
 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 transmitting the ascending fluids. Per- 
 haps the result is in most cases due in part to both these causes. This 
 more or less perfect stoppage of the oldest vessels is one reason why the 
 course of the sap is clilefly directed through the newer tubes.* 
 
 The functions of the bark, which forms the exterior portion of the 
 stem, will be more advantageously described, after we shall have con- 
 sidered 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 extrcnulies diflbses itself over the surface of the leaf. Here it un- 
 dergoes important chemical changes, the extent, if not the exact nature, 
 of which v/ill appear from a short description of the functions which the 
 leaves are known or are believed lo discliarge. 
 
 1°. When the roots of a living plant are imiTiersed in water, it is a 
 
 * AslVie newest sools are proloiigaiions of the newest wood, it ma^ be supposeti (hat the 
 factof llieso roots being the chief absorbents from the soil, is a suliicient reason why that 
 wliicli is absorbed by them should also pass up tlirough the wood witli which they are most 
 closely connected. But that the pores of the heart wood are really incapable o'f transmit- 
 ting 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 portion will remain unchanged. 
 
90 ESCAPK OF WATERY VAPOUK KKOM THK LEAVES. 
 
 matter of familiar observation that llie water gradually diminishes in 
 hulk, and will at length entirely disapjiear, even when eva|)oration into 
 the air is entirely prevented. The water which ihns disappears is taken 
 up by the roots of tlie plant, is carried up to the leaves, is there spread 
 out over a large surface exposed to ihe sun and to l!ie air, and in the 
 form of vapour esca|)es in considerable proportion through the pores of 
 the leaves and ditluses itself through ilie atmosphere. 
 
 The quantity of water which thus escapes from llie 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 dependent on 
 tiie presence of the sun, and is scarcely perceptible during lire night. 
 He found that a snn-flower, 3i 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 diminution in weight.* 
 
 This loss of waiery vapour by the leaf is ascribed to two ditH.-rent 
 kinds of action. First, to a natural perspiration from the pores of the 
 leaf, similar to the insensible perspiration which is continually proceed- 
 ing from the skins of liealihy animals; and second, to a mechanical 
 eva[)oration 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 special structure of the leaf. In all cases, however, the 
 natural perspiration is believed very greatly to exceed the mere mechan- 
 ical evaporation — though the results of Hales, and of other experimen- 
 ters, show that both processes proceed with the greatest rapidity under the 
 influence of a warm <lry atmosphere, aided by the direct rays of the sun. 
 
 Among the several jjurposes served by this escape of watery vapour 
 from the surface of the leaf, it is of importance for us to notice the direct 
 
 ' When the escape of vapour from the leaves is more rapid than the supply of water from 
 the roots, the leaves droop, dry, and wither. Such is sometimes the case with growing 
 crops in very hot weather, and it always happens when a twig or flower is plucked and sep- 
 arated from the stem or root. When thus separated the leaves slill continue to give off wa- 
 tery vapour into the air, and consequently the sap ascends from the twig or stalk to supply 
 the place of the water tlius 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 tlie fluid has risen from the stem into 
 the leaf, and the vessels of the wood are full of air. But if the stem of the twis or flower be 
 placed in water this liquid will rise into it, air will be excluded, and Ihe freshness and bloom 
 of Ihe leaves and flowers will be longer preserved. If the water into wliich they are intro- 
 duced contain any substances in solution, these will ri.se along with the water, and will grad- 
 ually 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 solu- 
 tions, capable of presert'ing them from decay. It is only necessary to cut down or .saw 
 through Ihe tree and insert its lower extremity into the prepared solution, when the aclloii 
 of the sun and air upon the leaves will cause it spontaneously to ascend. Thus corrosive 
 sublimate (the subject of Kyan's Patent) may be injected with ease, or pyrulig7iife if iron, 
 (iron dissolved in wood vinegar,) which Boucherie recommends as e(|ually eflicif-nt and 
 much more economical, \A71n. de Chim. et de Phys. Ixxiv. p. 113.] The process is finished 
 when the liquid is found to have risen to the leaf. Coloured soknions may in the same way 
 be injected and the wood tinged to any required shade. One of the chief benefits attendant 
 upon the cutting of wood in the winter, appears to be ihat 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 stripping the tree of its leaves and branches a 
 few days before it is cut down. 
 
OTHER VOLATILE SUBSTANCES EXHALED. 91 
 
 chemical influence it exercisesover ilie 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, organ- 
 ic and iiioriranic, which the soil contains, and thus in proportion to the 
 activity with which the leaves lose their watery vapour, will be the 
 quantity of (hose 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 iu 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 wiih such exha- 
 lations — often of an agreeable and odoriferous cliaracler. In the case of 
 plants anil trees also which emit n sensible odour, we readily recognise 
 jjje fact of volatile substances being given ofl' by ihe leaves. But even 
 when liie sense of smell gives us no indication of their emission from a 
 single leaf or a single ])lant, the introduction of a number of such in- 
 odorous plants into the confined atmosphere of a small room after a time 
 satisfies us that even ihey part vviih some volatile matter from their 
 leaves, which makes itself perceptible to our imperfect organs only when 
 in a concentrated stale. 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 emission of these 
 substances the plant probably relieves itself of what would prove inju- 
 rious if retained, though of the chemical nature and composition of these 
 exiialations little or nothing has yet been ascertained. 
 
 3°. 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 die leaf, and gradually to rise through the water 
 and collect in the bottom of the tumbler. If this gas be examined it 
 will be found to be pure oxygen. 
 
 If the water contain carbonic acid gas, or if during the experiment a 
 little carbonic acid be introduced, this gas will be found gradually to dis- 
 appear, while the oxygen will continue to accumulate. 
 
 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 
 12 liours in the sunshine, and then examining or aiialysing the air con- 
 tained in the glass, the result will be of a preci^iely similar kind. The 
 per centage of oxygen in liie air will have increased.* And if the ex- 
 periment be varied by the introduction of a small quantity of carbonic 
 acid gas into the jar, this gas will be foimd as before to diminish in quan- 
 tity, while the oxygen increases. The conclusion drawn from these 
 experiments, therefore, is, that the leaves of plants, when exjioied to the 
 rays of the sun, absorb carbonic acid from the air and give offinire oxy- 
 gen gas. 
 
 It has been already stated that the proportion of carbonic acid present 
 
 • It will be remembered Uiai aimospheric air contains aboul 21 per ceut. of oxygen gs» 
 
 5 
 
93 OXV(iEN 13 EMlTTfcU DURING THE DAV, 
 
 in the atmosphere is exceedingly small, [about l-2500th of this bulk- 
 see Lecture II., p. 30 ;] but ifllbr tlie purpose of experiment we increase 
 this proportion in a gallon of air to five or ten per cent., introduce a liv- 
 ing plant into it, and expose it to the sunsliine, the carbonic 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 oxygen 
 has increased generally by as much as the carbonic acid has diminished. 
 That is to say, if five cubic inches of the latter have disappeared, five 
 cubic inches will have been added to the bulk of tlie oxygen. The 
 above general conclusion, therefore, is rendered more precise by this ex- 
 perime'nl, which appears to show 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 a:s kqual bulk, of oxygen gas. 
 
 And as carbonic acid (COs) contains its own bulk of oxygen gas* 
 combined Avith a certain known weight of carbon, it is further inferred 
 that the oxygen given oHT by the leaves is the same which has been pre- 
 viously 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 car- 
 bonic acid from the air, dkcompose it in the interior of the leaf, retainits 
 carbon, and again reject or emit the oxygen it contained. 
 
 This conclusion presents a very simple view of the relations of oxygen 
 and carbonic acid respectively to the living leaf in the presence of the 
 sun, 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 precisely equal to that of the carbonic 
 acid absorbed, [see Persoz, Chimie Moleculaire, p. 54,] 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 vascular system of 
 different plants. On the other hand it is stated by Sprengel, that if com- 
 pounds containing much oxygen be presented to the roots of plants, and 
 thus introduced into the circulation, 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 moistened 
 with water containing carbonic, sulphuric, or nitric acids. — [Sprengel 
 Chemie, II., p. 344.] 
 
 It is of importance to note these deviations from apparent simplicity 
 in the relative bulks of the two gases which are respectively given off 
 and absorbed by all living vegetables. There are numerous 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 pubsetiuent 
 lecture we shall inquire hoiv or by what chemical changes the substan- 
 ces which plants contain, or of which they consist, are produced from 
 the food which they draw from the air and from the soil. 
 
 * This the reader will recollect Is proved by burning charcoal in a bottle of oxygen 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. 4& 
 
AND CARBONIC ACID DURING THE NIGEIT. 93 
 
 Tlie most general and probable expression, therefore, for the fund ion 
 of the leaf, now untler consideration, appears lo be tliat in the sunsljine 
 the leaves absorb from the air carbonic acid, and at the san:e time 
 evolve oxygen gas, the bulk of the latter gas given olF 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.* 
 
 4°. Such is the relation of the leaf to the oxygen and carbonic acid 
 of the atmosphere in the presence of the sun. During 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 sun- 
 shine — during which time the oxygen has sensibly increased, and the 
 carbonic acid diminished in bulk — be allowed lo remain in the same air 
 ihrough the following night, the oxygen will be found \o have decreased, 
 •\\hile the carbonic acid will be present in luiger (juantity than in the 
 evening of tiic previous day. 
 
 The carbonic acid ilius given off during the night is supposed to be 
 partly derived from the soil through the roots, and pfirlly from the sub- 
 stance 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 employed in producing some of the 
 oilier oxidixed [containing oxygen in considerable ([uantity] compounds 
 that exist in the sap. 
 
 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 v;ill 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 powerful. Hence we see why in Northern regions, 
 where spring, summer, and autumn are all comprised in one long day 
 — vegetation 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 ])rovided that, where the season 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 respecti\ely, 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 vegetables evolve 
 oxygen, and gradually become green ;ind healihy. Woody matter is 
 formed, and the stems become strong and fibrous. 
 
 The light of the sun, in the existing ecouoni}' of nature, is indeed 
 equally necessary lo the health of plants and of animals. The former 
 
 by ..... 
 
 gen or de-oxidized, this function of the leaves in the presence of the sun is often spoker 
 
 as their de-oxidizing power. 
 
94 LEAVES SOMETIMES EMIT CHLOKIIVE. 
 
 become pale and sickly, and refuse to perforin their most important 
 chemical functions when excluded from the light. The bloom disap- 
 pears from the human cheek, the body wastes awa3^ and the spirit 
 sinks, when the unhappy prisoner is debarred from the sight of the blessed 
 sun. In /(is system, too, the presence of light is necessary to tlie jierfor- 
 mance of those chemical functions on which the healthy condition of the 
 vital fluids depends. 
 
 The processes by which oxygen and carbonic acid are resj)ectively 
 evolved in plants have been likened by physiologists to the respiration 
 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, proceeds at all times, diges- 
 tion only in the light of the sun. Though these views are confessedly 
 conjectural, they are founded upon striking analogies, and may reason- 
 ably be entertained as matters of opinion. 
 
 6°. Other species of decomposition also, besides that of de-oxidization, 
 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 by Sprengel and Meyen to evolve 
 chloride* gas from their leaves. This takes place, however, more dur- 
 ing the night than during the day. Some plants also give off ammonia, 
 (Lecture IV., p. 70,) while others (crucifene), according to Dr. Daube- 
 ny, [in his Three Lectures on Agriculture, p. 59,] emit from their leaves 
 pure nitrogen gas. 
 
 The evolution of chlorine imi)lies the previous decomposition of the 
 chlorides, which have been absorbed from the soil; while that of nitro- 
 gen may be due to the decomposition of ammonia, of nitric acid, or 
 of some other compound containing nitrogen, which has entered into the 
 circulation by the roots. The exact mode and nature of the decompo- 
 sition of these substances, and the purjioses served by them in the vegeta- 
 ble economy, will come under our consideration in a subsetpicnt lecture. 
 
 The leaf has been described (p. 76) 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 mend)rane (epider- 
 mis), the expansion of the outer bark. This thin menibane is studded 
 with numerous small pores or mouths (stomata), which vary in size and 
 in number with the nature of the plant, and with \he circumstances in 
 which it is intended to grow. It is from the pores in the upper part of 
 the leaf that substances are supposed to be exhaled, while every thing 
 that is inhaled enters by those which are observed in the under side of 
 tlie leaf.f Tliis opinion, however, is not universally received, it being 
 admitted by some that the power both of absorbing and of emitting 
 may be possessed l)y tlie under surface of the leaf. 
 
 7°. We have seen that the chief su])i)ly of the fluids which constitute 
 
 * Chlorine is a gas ofagreenish yell. i\v colour, having an unpleasant taste and a suffocating 
 odour. Wlien it combines wilh otlicr substances it forms chlorides. It exists in, and im- 
 parts its smell to, chloride of lime, wliicli is pmployed for disinlecling purposes, and it 
 forms upwards of half the weight of common salt. 
 
 t This is illustrated by the action of a cabbage leaf on a wound. If the upper side be ap- 
 plied, the sore is protected and (juickly heals, while the under side dratcs it and produces a 
 coostatit discharge. 
 
rUNCTIONS OF THK FLOWER-LEAVES. 95 
 
 the sap of plants, is derived from the soil. The under side of the 
 leaves of plants is also su})posed by some to be capable of absorbing 
 moisture from the air, either in the form of watery vapour, or when it 
 falls upon the leaves in the state of dew. Like the roots also they may 
 absorb with the dew any substances the latter happens to hold in solu- 
 tion. And thus plants may, in some degree, be nourished by the vola- 
 tile organic substances which ascend from the earth during the heat of 
 the day, and which are again in a great measure precipitated with tiie 
 evening dew. 
 
 Whether the leaves ever absorb nitrogen gas from the air has not as 
 yet been determined with sufficient accuracy. If they do, it must in gene- 
 ral be in very small quantity only, since it has hitherto escaped detec- 
 tion. In like manner it is doubtful how far they regularly absorb any 
 other substances which the air is supposed to contain. Thus it is known 
 that nitric acid exists in the air in very minute (juantity. Some chem- 
 ists also believe that ammonia is extensively diffused through the atmos- 
 phere in an exceedingly diluted state. Do the leaves of plants absorb 
 these substances ? Is the absorption of them one of the constant and ne- 
 cessary functions of the leaves ? The reply to these (]uestions must be 
 very uncertain, and any principle which professes to be based upon such 
 a reply must be reganied only as a matter of opinion. 
 
 8^. The petals of flower-leaves perform a somewhat different function 
 from those of the ordinary leaves of a plant. They absorb oxygen at 
 all times — though more by day than by night — and they constantly emit 
 carbonic acid. The bulk of the latter gas evolved, however, is lessthan 
 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 combus- 
 tion, so to speak, the proper heat observed in the flowers of many plants 
 has been attributetl. 
 
 According to some authors, the flower-leaves also emit pure nitrogen 
 gas. — [Sprengel, Chemie, II., p. .347.] This fact has not yet been deter- 
 mined by a sufficient number of accurate ex])eriments; it is in accord- 
 ance, however, with the results of Boussingault, that, when a plant 
 flowers and approaches to maturity, the nitrogen it contains becomes 
 less. If confirmed, this evolution of nitrogen would throw an interest- 
 ing light on the most advantageous employment of green crops, both for 
 the purposes of manure and for the feeding of cattle. 
 
 9°. When the leaves of a plant begin to decay, either naturally as in 
 autumn, or from artificial or accidental causes, they no longer absorb 
 and decompose carbonic acid, even under the influence of the sun's rays. 
 On the contrary, they absorb oxygen, like the |)etals of the flower, new 
 compounds are formed within iheir substance — their green colour disap- 
 jjcars — they become yellow — 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 refer- 
 ence to a further end, than are the (unctions of the living leaf to the 
 growth and nourishment of the plant. — [See subsequent lecture, " 0?i the 
 law of the decay of organic substances."} 
 
96 cnr.jiicAL rr.NCTioNS of the bark. 
 
 § G. Functions of the hark. 
 
 Tlie inner bark being connected with the under layer of vessels in the 
 leaf, receives from tliem 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 unfrequenlly, perform 
 similar functions. In the Cactus, the Siapelia, and other plants whicli 
 produce no true leaves, this outer bark seems to perform all the functions 
 which in other vegetable tribes are specially assigned to the abundant 
 foliage. During its descent through the inner bark, therefore, the sap 
 must in very man}' cases undergo chemical changes, more or less analo- 
 gous to those which usually take place in the leaf. 
 
 It is by means of ihe 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 fibre is formed or prepared in 
 the leaf, and as the sap descends it is dejiosited beneath the inner sur- 
 face of the inner bark. It thus hapj)ens that, as the sap descends, it is 
 gradually deprived of the substances it held in solution when it left the 
 leaf, and in consequence it becomes difficult to say liow much of the 
 change, which the sap is found to have undergone when it reaches tlie 
 root, is due to chemical transformations produced during its descent, and 
 how much to the dejKJsition of the woody fibre and other matters it has 
 parted with by the way. 
 
 Among other evidences of such changes really taking place during 
 the descent of the sap, I may mention an observation of Meyen [Jahres- 
 bericJU, 1839, p. 27], made in the course of his experiments on the re- 
 production of the bark of trees. In these experiments he enclosed the 
 naked wood in strong glass tubes, and in three cases out of eight the 
 tubes were burst and shattered in pieces. This could only have arisen 
 from the disengagement of gaseous substances, the result of decomposi- 
 tion. 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 proba- 
 ble that those which are produced as the residt 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 ellected 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 ap- 
 ple tree a snbstanc^e named phloridzinc, possessed of considerable medi- 
 cal virtues, may be readily extracted, though it does not exist in the 
 bark either of the stem or of the branches. 
 
 In fine, as the food which is introduced into the stomachs of animals, 
 undergoes continual and successive cheiriical changes during its pro- 
 gress through the entire alimentary canal — so, numerous phenomena 
 indicate that the sap of plants is also subjected to unceasing transforma- 
 
 * Sprengel says that the stems arul twigs, and the stalks of the grasses, all absorb oxygen 
 and give off carbonic acid. — Cheinie. II., p. 341. 
 
FUNCTIO>S OF TIIK nOOl" MODIFIKD BY THE SOIL. 97 
 
 tion?, — in ihe root and in llie stem as well as in the leaves, — at one time 
 in the dark, at another under tlie influence of the sun's rays, — exposed 
 when in the leaf to the full action of the air, — and when in the root al- 
 most wholly secluded from its presence; — the new compounds pro- 
 duced in every instance heing suited either to the nature of the plant or 
 the wants and functions of that part of it in which each transformation 
 takes place. 
 
 To some of these transformations it will he 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 these 
 compounds on which they chiefly live. 
 
 § 7. Circumstances by which the functions of the various parts of plants 
 are modifed. 
 Plants grow more or less luxuriantly, and their several parts are 
 more or less largely developed, in obedience to numerous and varied 
 circumstances. 
 
 I. 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. It is obvious also that a certain de- 
 gree of moisture in the soil, and a certain temperature, are necessary 
 to the most healthy discharge of the functions of the root. In hot wea- 
 ther the plant droops, because the roots do not absorb water from the 
 soil with sufficient rapiditj^ And though it is probable that, at every 
 temperature above that of absolute freezing, 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 in- 
 creased activitjf. The practice of gardeners in applying bottom heat in 
 the artificial climate of the green-house and conservatory is founded on 
 this well-known principle. 
 
 But the nature of the soil in which plants grow has also much influ- 
 ence 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 ilie greater or less activity of vegetation depends, are far 
 from being generally understood. 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 iinperfectly discharged. Or if the soil be deficient either in organic 
 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 
 he stalk cannot be produced in a natural or healthy state, since silica is 
 indispensable to its healthy construction. 
 
 II. 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. 
 
 There seems reason to believe that the plant never sleeps, that even 
 during the winter the circulation slowly proceeds, though the first 
 
98 ALSO THE RAPIOrTY OF THE CI!lClTI,ATIO?f . 
 
 genial sunshine of the early spring stimulates it to increased activity. 
 The general increased temperature of tlie air does not produce this ac- 
 celeration in so remarkable a manner as tlie direct rays of the sun. The 
 sap will flow and circulate on tlie side of a tree on whicli the sunshine 
 falls, while it remains sensibly stagnant on the other. This is shown by 
 the cutting down similar trees at more and more advanced peri(xls of 
 the spring, and immersing their lower extremities in coloured solutions. 
 The wood and bark on one 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 ofien thicker on 
 the one half of the circumference of the stem than on the other. 
 
 The sap is generally supposed to fiow most rapidly during the spring, 
 but if trees be cut down at ditferent seasons, and immersed as above 
 described, the coloured solution, according to Boucherie, reaches the 
 leaves most rapidly in the autumn.* 
 
 The heal of t!ie day, other circumstances being the same, materially 
 affects, for the time, the rapidity of the circulation. The more rapidly 
 watery and other vapours are exhaled from the leaves, the more quick- 
 ly must the sap flow upwards to sup|)ly the waste. If on two succes- 
 sive days the loss by the leaves be, as in the experiment of Hales, above 
 described, (p. 90,) as 2 to 3, the ascent of the sap must be accelerated 
 or retarded 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 transport of that 
 food which the earth supplies, to be carried to every part of the plant, 
 and must thus sensibly atlect the luxuriance and growth of the whole. 
 
 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 tlie autumn, the 
 sap ascends and descends during all the C(jlder months, — at a sknver 
 rate, it is true, tlian in the hot days of summer, yet much more sensibly 
 than in the oak and ash, which spread their naked arms through the 
 wintery air. This is illustrated by the experiments of Boucherie, who 
 has observed that in December and January the entire wooil of resinous 
 trees may be readily and thoroughly penetrated by the spontaneous as- 
 cent of saline and other solutions, into which their stems may be im- 
 mersed. 
 
 III. From what has just been stated, it will appear that the mechani- 
 cal functions of the stem are subject to precisely tiie 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 
 
 * Boucherie makes a distinction, not hillierto insisted upon by physiologists, between the 
 circulation on the surface of the tree by which the buds and youm; twigs are supported, and 
 the interior circulation, which is not perfect until a latter period of tlie year. Hence in tlie 
 spring, though the sap is liowing rapidly through tlie baric ind the newest wood, coloured 
 solutions will not penetrate the interior of the tree with any degree of rapidity. In autumn, 
 on tliC other hand — when the fear of approaching winter has already descended upon the 
 bark — the lime of most active circulation has only arrived for the interior layers of the older 
 wood. It is ihis 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. e: iU Phys , Ixxiv. , p 135. 
 
CHEMICAI. RAYS IN THE SUN-BKAM. 99 
 
 removed from the centre. It is tliis transference of the vital circula- 
 tion to newer and more perfect vessels that enables the tree to grow and 
 blossom and bear fruit through so long a life. In animals the vessels 
 are gradually worn 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 incapacitated for the 
 further [lerformance 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 chemi- 
 cal changes themselves must be dependent upon the quantity and kinds 
 of matter which ai^cend or descend in the sap. The entire chemical 
 functions of the ])lant, therefore, must be deiiendeni upon and must be 
 modified by the nature of the substances which the soil and the air re- 
 spectively present to the roots and to the leaves. 
 
 IV. In describing the functions of the leaf, I have already had occa- 
 sion to advert to the greater number of the circumstances by which the 
 discharge of those functions is most materially nRected. We have seen 
 that the purjioses served by the leaf are entirely different according as 
 the sun is nbove or bt-lnw the liorizon ; that the temperature and mois- 
 ture of the air may indeed materially influence the rapidity with which 
 its functions are discharged — but that the liglitof the sun actually deter- 
 mines their nature. Thus t!ie leaf becomes green and oxygen is given 
 off" in the presence of ihe sun, while in his absence carbonic acid is dis- 
 engaged, and the whole plant is blanched. 
 
 How necessary light is to the iiealth of plants may be inferred from 
 the eagerness with which tliey appear to long for it. How intensely 
 does the sun-flower watch the daily course of the sun, — 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 witli this 
 specific action of his rays on the chemical functions of the leaf, is illus- 
 trated 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 wliich the seeds were 
 germinating, to the action of the red, yellow, green, and blue rays, 
 which were transmitted by equal thicknesses of solutions of these seve- 
 ral 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, unhealthy colour. Under the yellow solution, only two or three 
 plants appeared, but less pale than those under the green, — while be- 
 neath the red, a few more plants came up than under the yellow, though 
 they also were of an unhealthy cokiur. The red and blue bottles being 
 now mutualK' transferred, the crop formerly beneath the blue in a few 
 
 * A potato has been observed to grow up in quest of liglit from the bottom of a well 
 twelve feet deep — and in a dark cellar a shoot of 20 feet hi length has tjeen 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. Tlius in the stalk of the potato a 
 poisonous substance called aolanin is produced, which disappears agm when the stalji is ex- 
 posed to the light and becomes green. 
 
 L.ciC. 5* 
 
100 FUNCTIONS OF THE GREEN TWIGS. 
 
 d.iys appeared blighted, while on the patch previously exposed to the 
 rcil, some additional plants s{>rung up."* 
 
 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 recognized by the chemical effects they produce. 
 These rays appear to differ in kind, as the rays of different coloured 
 light do. It is to the action of these chemical rays on the leaf, and 
 especially to those which are associated with the blue light in the solar 
 beam, that the chemical influence of the sun on the functions of the leaf 
 is principally to be ascribed. 
 
 It cannot be doubled that the warmth and moisture of a tropical cli- 
 mate act as powerful stimulants — assistants it may be — to the leaf, in 
 the absorption of carbonic acid from the air, and in tliat rapid ap])ropria- 
 tion (assimilation) of its carbon by which the growth of the plant is has- 
 tened and promoleil. But the bright sun, and especially the chemical in- 
 fluence of [lis beams, must be regarded as the main agent in the wonderful 
 development of a tropical vegetation. Under this influence the growth 
 by the leaves at tlie expense of the air must be materially increased, 
 and the plant be rendered less dejiendent upon the root and ihe soil for 
 thfe food on wliich it lives. f 
 
 V. The rayiidity with which a plant grows has an important influence 
 upon the share v/hich the bark is permitted to take in the general 
 nourishment of the whole. The green shoot ])erforms in some degree 
 the functions of the leaf. In vascular plants, therefore, whicli in a con- 
 genial 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 tlie presence of the sun. The broad lea^'es of llie jialm tree, 
 when iully developed, render tlie ])lant in a great degree independent of 
 the soil for organic food — and tlie large amount of absorbing surface in 
 the long green tender stalks of the grasses, and of their tropical ana- 
 logues, must materially contribute to the same end. Hence the pro- 
 portion of organic matter derived from the air, in 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, besides those circum- 
 stances by which we can ])ercei\e the sjiecial functions of any one or- 
 gan to be modified, there are many by which the entire economy of the 
 plant is materially and simulianeousK' affected. On this fact the prac- 
 tice of agriculture is founded, and the various |)rocesses adojited by the 
 practical farmer are only so many modes by which he hopes to influ- 
 
 ' London and Edinburgh Journal of Scinnw, February, IS4Q. 
 
 Might not our clieap blue glass be useJ with ailvaniage in glazing hot-houses, conserva- 
 tories, ifcc. 1 
 
 t Tlie effect of continued sunshine may be often seen in our corn fields In May, when, 
 under the influence of piojiifinus wealVier, the youiij; plants are sliooilng rapidly up. When 
 Buch a field is bounded by a lolty hedge running nearly north and south, the ridges nearest 
 the hedge on citlier side will be in Ihe shttde for nearly one-half of the day, and will invaria- 
 bly appear of a paler green and less healthy colour, ff the hedge be studded wiih occasional 
 large trees, the spots on which the shadows of those trees rest will be indicated by distinct 
 pale green patches stretching fwther into the field than the first, and Bometiines even than 
 the second ridges. 
 
EFFECT OF MARLING. REWARDS OF NATURE. 101 
 
 eiice and proinoie 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 tliough the application of 
 a top-dressing may he supposed first to affect the leaf, yet the beneficial 
 result of the experiment depends upon the influence which the dressing 
 may exercise on every part of the vegetable tissue. 
 
 In connection with this part of the subject, therefore, T shall only 
 further advert to a very remarkable fact mentioned by Sprengel, which 
 seems, if correct, to be susceptible of important practical applications. 
 He states that it has very frequently been observed in Holstein, that if, 
 on an extent of level ground sown with corn, some fields be marled, and 
 others left unmarled, thecorn on the latter portions will grow less luxuri- 
 antly and will yield a poorer crop than if the tvhole 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 he that nature thus rewards the diligent and the impro- 
 ver? Do the [)lants which grow on a soil in higher condition take from 
 the air more than their due share of the carbonic acid or other vegetable 
 food it may contain, and leave to the tenants of the poorer soil a less pro- 
 portion than they might otherwise draw from it ? How many interest- 
 ing reflections does such a fact as this suggest ! What new views does 
 it disclose of the fostering care of the great Contriver — of his kind encour- 
 agement of every species of virtuous labour ! Can it fail to read to 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 ? 
 
 ' Wenn namlich auf einer Feldllur Sliick um Stiick gemorgelt worden ist, so wachsen 
 die Friichte auf den nicht gemergelten Feldern, audi wenn hier alle friilieiea verhaltnisse 
 ganz dicselben bleibeii,niclit melirsogut, als eliedein; wodurcti die Besitzer jener Felder, 
 wenn sie nicht fortwahrend geringe Erndlen haben wollen, genbthigt sind, gleichfalls zu 
 mergeln. Aus dieser hiichst vichtigen Ersclieinung, die man se)tr hdufig in Holsteinschen 
 bemerkt, &c. — Sprenge\,Chemie/ur Landicirtltschaft, I., p. 303. 
 
LECTURE VI. 
 
 Substances of whicli plants cliiefly consist— Woody fibre, Slarch, Gum, Sugars— Their mu- 
 tual relations and Iransrormatioris— Gluten,Vegetable Albumen, Diastase — Acetic, Tartaric, 
 Malic, Citric, and Oxalic Acids — General observations. 
 
 From what has been stated regarding the structure of plants, it will be 
 understood 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 tliose substances of which plants chiefly 
 consist. But in order that we may clearly understand this point, it is 
 necessary that we know Hrst the naiure and clietnical coiis;tiiution of ihe 
 substances which are most larsely 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 tlie 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 theii 
 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 ])ossessed of different properties, that you would 
 scarcely be able to number tliein. 
 
 Bui if at the same time you compared the iveight of eacli substance 
 thus collected wiih tliat of tlie 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 jjortion of the vital energies of the plant 
 zan be expended in producing them, — that they may be entirely neglect- 
 ed in a general consiilcraiion of the great y)r(xliirts of vegetation. Thus 
 though quinine and morphine, the active ingredients in Peruvian bark 
 and in opium", are most interesting substances, from their effect upon the 
 human constitution, and their use in medicine, yet they form so small a 
 fraction of the mass of the entire trees or plants from which they are ex- 
 tracted, that it would be idle to attempt to convey to you any notion of 
 the way in whicli plants grow and are fed, by showing you how such 
 substances as these are produced from the food on wliich plants live. 
 
 While, however, the examination would salisfy you that alinost 
 every species of plant produced in small tjuantiiy one or more sub- 
 stances peculiar to itself, you would observe, at the same lime, that 
 every plant yielded a certain quantity of two or three substances com- 
 mon to and prodt'ced by all, and in most cases constituting the greater 
 portion of their bulk. Thus all trees and herbs produce wood or woody 
 fibre, 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 production of this starch is otie of the great objects of 
 the art of culture. The juices of trees, and of grasses, and of cultivated 
 roots, contain sugar and gum, and sometimes in such quantity as to 
 make their extraction a source of prqfit both to the grower and to the 
 
CONSTITUTION OF WOODY FIBRE. 103 
 
 manufacturer. The flour of grain contains sugar also, and along with it 
 Iwo other substances, in small quantity, gluten and vegetable albumen, 
 which are of much importance in reference to the nutritive qualities of 
 the ditTerent varieties of flour. Sugar is also present in the juices of 
 fruits, but it is there associated with various acid (sour) substatices 
 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 con- 
 sists. 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 I shall afterwards be able to make you under- 
 stand how these few compound bodies are produced in the interior of a 
 plant from the food it takes up, I shall succeed in conveying to you as 
 mucli information in regard to this most interesting branch of our subject 
 as will be necessary to a general explanation not only of the natural 
 growth and increase of plants, but of the nature and efficacy of those 
 artificial means which the practical farmer employs, in order to hasten 
 their growth or enlarge their increase. 
 
 § 1. Woody fibre or lignin — its constitution and properties. 
 1°. When a portion of the stem of a herbaceous plant, or of the new- 
 ly cut wood of the trunk or branch of a tree, is reduced to small pieces, 
 and boiled in successive portions of water and alcohol, as long as any 
 thing is taken up, a white fibrous mass remains, to which the name of 
 woody fibre or lignin has been given. This substance has no taste or 
 smell, and is perfectly insoluble in water. It is nearly identical in its 
 chemical constitution and properties, whether it be obtained from the 
 porous willow, or from the solid box tree, and the fibres of linen and of 
 cotton consist essentially of the same substances. 
 
 According to the analysis of Dr. Prout, this woody fibre when dried 
 at 350° F., consists of 
 
 From Box Wood. From the Willow. 
 
 Carbon 50-0 49-8 
 
 Hydrogen .... 5*55 5'58 
 
 Oxygen .... 44-45 44-62 
 
 100 100 
 
 It will be recollected that water consists of oxygen and hydrogen, 
 combined in the proportion, by weight, of 8 of the former to 1 of the lat- 
 ter. (See Lecture II., p. 36.) Now if the hydrogen above given be 
 multiplied by 8, the product will be found to be almost exactly the 
 weight of the oxygen given — since 
 
 5-55 X 8 = 44-40, and 
 5-58 X 8 = 44-64. 
 In woody fibre, therefore, the hydrogen and oxygen exist in the same 
 proportion as in water, and its composition, therefore, might be repre- 
 sented by 
 
 Carbon 50-0 
 
 Water . 50-0 
 
 100 
 
104 COMPOSITION OF WOOD. 
 
 did we not know that woody fibre, when heated or distilled, cannot be 
 resolved into carbon (charcoal) and water alone, and, therefore, cannot 
 be supposed to consist of these alone. 
 
 It is a remarkable cliaracter of this substance, liowever, that these two 
 elements, hydrogen and oxygen, exist in it in the proportions to form 
 water, and we shall find the knowledge of this fact of great importance 
 to us, when we come to inquire how this constituent of vegetables is 
 formed — from the food on which they live. 
 
 2°. If a portion of the wood of a tree be dried and analyzed icithout 
 
 being previously digested in water, alcohol, and ether, as long as any 
 
 thing is taken up, the proportion of the constituents 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 . . . 52-65 51-92 50-00 49-25 
 
 Hydrogen . . 6-00 5 96 6-20 6-10 
 
 Oxygen . . . 41-15 42-12 43-60 44-65 
 
 100 100 100 100 
 
 The carbon in these several kinds of wood difTers as much as three 
 per cent., but in each of them the product of the hydrogen, when multi 
 plied by 8, is con.siderably greater than the per centage of oxygen. 
 
 3°. When the solid substance of wood is examined under the micro- 
 scope it is observed to consist of two portions or kinds of matter, that of 
 which the original sides of the cells and tubes is composed, called the 
 cellular matter — the true woody fibre — and of a solid substance by whicli 
 the cells are internally coated and strengthened, called the incrusling 
 matter. It is in this latter substance that the excess of hydrogen, exhi- 
 bited by the preceding analysis, is supposed to exist, the true woody 
 fibre containing always the hydrogen and oxygen in the proportions ne- 
 cessary to form water.* 
 
 * Payen at first considered this incrusling matter as a peculiar substance, for which he 
 proposed the name of sderogene. His first mode of separating it from the cellular matter 
 was by trealinj the finely rasped wood (of the oak and beech) with nitric acid, which dis- 
 solved out the incrusting matter and left the cellular matter behind. His second mode was 
 to digest the wood with dilute sulphuric acid, by which the cellular matter was dissolved 
 out, and the incrusting matter left. It is obvious, however, that no reliance whatever can be 
 placed on tlie analyses of substances so treated, since they cannot fail to have undergone a 
 chemical change by being exposed to the action of these strong acids. Further examination 
 has satisfied Payen that the incsrusting matter consists of at least three substances, of which 
 one is soluble in water, alcohol, and ether, another in alcohol only, while the third is insolu- 
 ble in any of these liquids. Tiiey are composed, according to his analyses, of 
 
 Soluble in Soluble in 
 
 Insoluble. alcohol only. water and alcohol. 
 
 Carbon ... 48 628 68-53 
 
 Hydrogen ... 6 59 704 
 
 Oxygen ... 46 31-3 24-43»' 
 
 100 100 100 
 
 It is impossible to say how far the substances analysed by Payen are to be considered as 
 pure, or as actually existing in the pores, or in the incrusting matter of the woody fibre, but 
 it is obvious that the presence of a variable quantity of such substances will necessarily 
 cause that excess of hydrogen, in the entire wood, which appears in the analysis of the ebo- 
 ny, walnut, oak, and beech woods, given in the text. That such an excess of hydrogen 
 above what is necessary to form water with the oxygen, does exist in the wood of most trees 
 
 (^ Ueyen's Jahreabericht, 1839, p. 10.] 
 
COMPOSITION OF CELLULAR MATTER. 105 
 
 It 1$ exceedingly difficult in any case to separate the cellular from the 
 incrusting matter of wood, so as to obtain the means of determining by 
 analysis the exact difference in their elementary constitution. Under 
 the impression that in very light and ])orous substances he should ob- 
 tain the cellular matter in a purer form, Payen analysed the fibre of 
 cotton — the pith of the elder, the cellular substance of the cucumber, of 
 the mushroom, and of other fungi, the spongy matter which forms the 
 extremities of the roots of plants, and various other similar substances, 
 and in all these varieties he found the hydrogen and oxygen to exist in 
 the proportions to form water. The mean of his analyses was very 
 nearly as follows — which for the purpose of comparison I shall contrast 
 with that of Dr. Prout : 
 
 Woofiy fibre of box and Cellular matter of vascu- 
 
 willow — Dr. Prout. lar plants — Payen. 
 
 Carbon . . . 50-()0 44-80 
 
 Hydrogen . . 5-55 6-20 
 
 Oxygen . . . 44-45 49-0 
 
 100 100* 
 
 In both these analyses the hydrogen is very nearly 8 times that of 
 the oxygen. All these substances, therefore, may be represented by 
 carbon and water, though the woody fibre of Dr. Prout contains 5 per 
 cent, more carbon tlian the cellular iriatter of Payen. 
 
 If we calculate the number of equivalents of each element contained 
 in these two varietiesf of vegetable fibre composed as above exhibited, 
 we find in the one 12 of carbon, 8 of hydrogen, and 8 of oxygen; in 
 the other, 12 of carbon, 10 of hydrogen, and 10 of oxygen. They may. 
 therefore, be conveniently represented by the following formulae : 
 
 Woody Fibre by C,2 Hg Cg 
 
 Cellular Fibre. ... by C,, H n, C,o 
 It is not unlikely that both of these forms of matter may exist, as 
 well in the perfect wood of trees as in the less consolidated pith of the 
 elder, or in the fibres of cotton — and that they may occur intermingled 
 also in varying proportions with other substances, containing hydrogen 
 in excess.^ 
 
 in its natural state, is a fact to which it will be important to advert when we consider here- 
 after the chemical changes which the food undergoes in the interior of the plant. 
 * Meyen's Jahresbericht, 1839, p. 10. 
 
 t This is done very simply by dividing the carbon by 6, and the oxygen by 8(see page 
 36), thus— 
 
 Carbon ... 50 -;- 6 = R-33 C which numbers ) 12 
 Hydrogen • - 5 55 = 5-55 < are to each / 8 
 Oxygen ■ - • 44-45 -4- S =: 55-5 ( otiier as ) 8 
 t The existence of q variety of cellular fibre identical in constitution with common starch, 
 as this of Payen is, (see subsequent section, p. 106,) was previously rendered probable by 
 the observations of Dr. Schleiden, that tlie embryo of the Scholia latiJoHa. consisting of 
 pores and vessels, the sides of wliich exliibit distinct concentric layers, is entirely soluble 
 in water, witli the exception of the outer rind ; and that its solution becomes blue on the 
 addition of iodine. It would appear as if the cellular substance were in this case wholly 
 composed of Starch. CPoggendorf's Annalen. xlili., p. 393.) It may, however, be in such a 
 slate of tenuity in the embryo of lliis plant, as to be easily changed'into starch by the action 
 of hot water; and it is still by no means certain that the cellular fibre analyzed by Payen 
 may not also have undergone a change by the treatment to which it was previously subject- 
 ed. I am unable, however, to speak decidedly on this subject, as I have not seen the de- 
 tails of M. Payen's several papers. (See subsequent section, on the mutual transformation 
 of woody flfrre, starch, gum, and sugar, p. 112.) 
 
J06 PER CENTAGF, OT V/OODY FIBRE IN PLANTS. 
 
 I have spoken of these varieties of woody fibre as constituting a largo 
 portion of the entire mass of 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 general statement is easily seen to be correct. It is also 
 true of the dried stalks of the grasses and the corn-growing plants, of 
 which it forms nearly one-half the weight, — but in roots and some 
 plants which are raised for food, the quantity of woody fibre, especially 
 in the earlier stages of their growth, is comparatively small.* Thus in 
 the beet root it forms only 3 per cent, of the whole weight when taken 
 from the ground. If suffered to remain in the soil till it becomes old, 
 or if the growth be very slow, the beet becomes more woody, as many 
 other roots do, and the quantity of ligneous fibre increases. 
 
 § 2. Starch — its constitutimi and properties. 
 
 Next to woody fibre, starch is probably the most abundant product of 
 vegetation. To the agriculturist it is a substance of much more interest 
 and importance than the woody or cellular fibre, from ilje value it pos- 
 sesses as one of the staple ingredients in the food of man mid animals-— 
 and from its fiirming a large portion of the weight of tlie various grains 
 and roots which are the principal objects of tlie art of culture. 
 
 1°. When ihe flour of wheat, barley, oats, Indian corn, &c., is mixed 
 up into a dough with water, and this dough washed oti a linen cloth 
 with pure water, a milky liquid passes through, from which, when set 
 aside, a white ])owder gradually falls. This white powder is \he 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, when collected, forced through a 
 metal sieve to granulate (or corn) it, and dried by agitation over the 
 fire, is the sago of commerce. 
 
 * The following table shows the per centage of woody fibre contained in some commop 
 plants in the green state, and when dried in the air, and at 212° : 
 
 IN THE GREEN STATE. 
 
 Dried in the air. Dried at 212°. Woody fibre. Water, 
 
 percent. percent. percent. percent. 
 
 Barley straw, ripe 50 — — — 
 
 Oat straw, do. — 47 — — 
 
 Maize straw, do. 24 — — — 
 
 Stalks of Uie field pea - ... — _ lo^ SO 
 
 Eield bean straw 51 — — — 
 
 White turnip — — 3 92 
 
 Common beet (beta vulgaris) - — — 3 86 
 
 Young twigs of common furze- — — 24 50 
 
 Rape straw, ripe — 55 123^ 77 
 
 Tare straw, do. 37 — — — 
 
 Vetch plant (v. saliva) ■ - - 42 — 10>i 77 J^ 
 
 Do. (V. cracca) in flower — — 5)^ 68 
 
 Do. (V. narbonensis) do. — — ll>^ 80 
 
 White lupin, in flower, - - . — — 7 gg 
 
 Lucerne, in flower, .... — — 9 73 
 
 Rye grass, do. — — 11 68 
 
 Red clover, do. — — 7 79 
 
 White clover, do. — — 4>^ 81 
 
 Trefoil (medium) do. • - - ~ — 8H 73 
 
 Sainfoin (esparsette) .... — — 7 75 
 
 Trefoil (agrarium) in flower - — — 12 68 
 
 Do. (rubens) do. • - — — 15 60 
 
PREPARATION AND DECOMPOSITION OF STARCH. lO''' 
 
 3°. When the raw potato is peeled and grated on a fine grater, and 
 the pulp thus produced well washed with water, potato starch is ob- 
 tained in the form of a fine white powder, consisting of rounded, glossy 
 and shining particles. 
 
 4°. When the roots of the Maranta Arundinacea ofthe West India 
 Islands are grated and washed like the potatoe, they yield ihe arrow 
 root of commerce. From the root of the Manioc, the cassava is pro- 
 cured by a similar process, and this, when dried by agitation on a hot 
 plate, is the tapioca of the shops. By this method of drying, both sago 
 and tapioca undergo a partial change, wliich will be explained in a sub- 
 sequent section (see p. 113.) 
 
 The substances to which these several names are given are, when 
 pure, similar in their properties, and identical in their chemical consti- 
 tution. They are all colourless, tasteless, without smell, when dry 
 and in a dry place may be kept for any length of time without under- 
 going alteration, are insoluble in cold water or alcohol, dissolve readily 
 in boiling water, giving a solution which gelatinizes (becomes a jelly) 
 on cooling — and in a cold solution of iodine* they all become blue. 
 
 When dried at 212°, they consist, according to Dr. Prout, with whose 
 analysis those of other chemists agree, of 
 
 Carbon 44-0 per cent., or 12 atoms. 
 
 Hydrogen .... 6-2 per cent., or 10 atoms. 
 Oxygen 49-8 per cent., or 10 atoms. 
 
 100 
 Starch, therefore, may be represented by the formula C,2 H,o 0,(,, 
 which is identical with that deduced in the preceding section for the 
 cellular fibre of Payen. Both substances, therefore, contain the same 
 elements (carbon, hydrogen and oxygen), united in the same propor- 
 tions, and in both, as well as in the common fibre of wood, the hydrogen 
 and oxygen exists in the jjroportion to form water. 
 
 That starch constitutes a large portion ofthe weight of grains and roots, 
 usually grown for food, will appear from the following table, which ex- 
 hibits the ijuantity present in 100 lbs. of each substance named : 
 
 Starch per cent. 
 
 Wheat flour 39 to 77 
 
 Rye " 50 to 61 
 
 Barley " 67 to 70 
 
 Oatmeal 70 to 80 
 
 Rice flour 84 to 85 
 
 Maize " 77 to 80 
 
 Buckwheat 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 fibre of certain 
 trees, as in that of the willow, and in the inner bark of others, as in 
 
 ' Iodine is a solid siitistance, of a lead-grey colour, possessed of a peculiar powerful 
 odour, and forming when heated a beautiful violet vapour. It exists in small quantity in sea 
 water, and in some marine plants. Its solution in water readily shows the presence of 
 starch, by the blue colour it imparts to it. 
 
108 VARIETIES OF GUM. 
 
 those of the beech and the pine.* Hence the readiness with which a 
 branch of the willow takes root and sprouts, and hence also the occa- 
 sional use of the inner bark of trees for food, especially in northern coun- 
 tries, and in times of scarcity. In some roots which abound in sugar, 
 as in those of ihe beet, the turnip, and the carrot, only 2 or 3 per cent, 
 of starch can be detected. 
 
 § 3. Gum — Us constitution and proiur ties. 
 
 The variety of gum wiih 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 exudes from the 
 twigs and stems of these trees, and collects in rounded more or less 
 transparent drops or tears. It is also produced in smaller quantities in 
 many of our fruit trees, as the apple, the plum, and the cherry ; it is 
 present in some herbaceous plants, as in the althaea and malva officinalis 
 (common and marsh mallow) ; and it exists in lint, rape, and many 
 other seeds. When treated with boiling water these plants and seeds 
 give mucilaginous solutions. 
 
 Many varieties of gum occur in nature, but they are all characterised 
 by being insoluble in alcohol, by dissolving or becoming gelatinous in 
 hot or cold water, and by giving mucilaginous — viscid and glutinous — 
 solutions, which may be employed as a paste. 
 
 Three distinct species of gum have been recognised by chemists: 
 
 1°. Arahin — of which gum arabic and gum Senegal almost entirely 
 coasist. It is readily soluble in cold 7oater, giving a viscid solution, usu- 
 ally known by the name of the mucilage of gum arabic. 
 
 2°. Cerasin — which exists in the gum of the cherry-tree. It is inso- 
 luble 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. 
 
 3°. Bassorin — existing in what is called bassora gum — and forming 
 a large portion of gum tragacanth.f It swells and becomes gelatinous in 
 cold water, but does not dissolve in water eitlier cold or hot. 
 
 By these characters, the three kinds of gum are not only readily dis- 
 tinguished, but may be easily separated from each other. Thus if a 
 native gum or an artificial mixture contain all the three, simple steeping 
 in and subsequent washing with cold water, will separate the arabin — 
 boiling water will then take up the cerasin, and the bassoriti will remain 
 behind. 
 
 These different kinds of gum all possess the same chemical constitu- 
 tion. According to the analyses of Mulder, they consist of 
 Carbon . . . 45-10 per cent., or 12 atoms. 
 Hydrosen . . 610 " or 10 " 
 
 Oxygen . . . 48-80J " or 10 «' 
 
 100 
 
 * Its presence is readily detected in such wood by a drop of the solution of iodine — which 
 ^ives a permanent blue to starch, but to the woody fibre only a brownish stain. 
 
 t This gum exists along with starch in tlie roots of the various species of orchis, especially 
 of those which are used for making sa/ep(Meyen). 
 Berzelius Arsberdttelse, 183^, p. 443. 
 
VARIETIES AND CONSTITUTION OF SUGAR. 109 
 
 In these analyses, as in those of starch and woody fibre, we see tliat 
 the per centage of oxygen is equal to thatof tlie hydrogen multi])licd by 
 8, anil consequently that these two elements are, as already stated, in 
 the proportion to form water. But we see also that the carbon is in the 
 proportion of 12 atoms or equivalents to 10 of each of the oihe.r con- 
 stituents, and therefore gum may be represented by Cjj H, ^ O, ^ — a 
 forumla which is identical with that already given for starch and cellu- 
 lar fibre. 
 
 It appears, liierefore, that not only may gii7n,starcli,and cellular fibre be 
 represented by carbon and water, but that they all consist of carhon and 
 the elements of water, united together in the same jno])ortions. 
 
 Gum not only exists in many seeds, and exudes as a natural product 
 from the stems and twigs of many trees, but is also contained in the 
 juices of many other trees, from which it is not known to exude ; and in 
 the sap of most plants it may be detected in greater or less quantity. It 
 may be considered, indeed, as one of those substances which are [tro- 
 duced most largely and most abundantly in the vegetable kingdom, 
 since, as will hereafter appear, it is one of those forms of conibinalion 
 through which organic matter passes in the interesting series of changes 
 it undergoes during the development and growth of the plant. 
 
 § 4. Of Sugar — its varieties and chemical constitution. 
 
 1°. Cane Sugar. — Sugar, identical in constitution and properties 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 extensive- 
 ly collected in spring, and when boiled down yields an abundant supply 
 of sugar. In the Caucasus that of the walnut is extxacted for the same 
 purjjose. The juice of the birch also, contains sugar, and it may be ob- 
 tained, in lesser quantity, from the sap of many other trees. In the 
 juice of the turnip, carrot, and beet, it is also present, and in France and 
 Germany the latter root is extensively cultivated 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 pre- 
 sence of sugar may likewise be readily detected. 
 
 Sugar is principally distinguished by its agreeable sweet taste. 
 When jiure, 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 gradually deposits itself in the 
 Cortn of sugar candy. If the syrup be boiled on too hot a fire, it chars 
 slightly, becomes discoloured, and a quantity of molasses is formed. 
 Pure cane-sugar, free from water, consists of 
 
 Carbon . . . 44-92 per cent., or 12 atoms. 
 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 identical — so that 
 
110 CANE, GRAPE, MANNA, AND LiqUORICK SUGARS. 
 
 cane-sugar also crxitains oxygen and hydrogen in the proportions to form 
 water, and may likewise be represented by the formula C,, H,o O,o. 
 
 2°. Grape sugar. — In the juice of the grape a peculiar species of su- 
 gar exists, which, in tlie dried raisin, presents itself in the form of little 
 rounded grains. The same kind of sugar gives their sweetness to the 
 gooseberry, ilie currant, the a|)[ile, pear, plum, apricot, and most other 
 fruits. It is also the sweet substance of the chesnut, of the brewers' 
 wort, and of al] 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 sugar, 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 constitution they differ considerably. Thns grape sugjn 
 dried at 250^^ F., consists of 
 
 Carbon . . . 40-47 per cent., or 12 atoms. 
 Hydrogen . . G-59 " or 12 " 
 
 Oxygen . . . 52-94 " or 12 " 
 
 100 
 
 Tlie oxygen here is still eight times greater than the hydrogen, ana, 
 therefore, in this variety of sugar also, these elements exist in the pro- 
 portions to form water. But for every 12 equivalents of carbon, dry 
 grape sugar contains 12 of hydrogen and 12 of oxygen. It is conse- 
 quently represented by Ci^ Hjo 0,2, and contains the elements of two 
 atoms of water (H2 O2) more than cane sugar.* 
 
 3°. Manna sugar, sugar of liquorice, Sfc. — Besides the cane and grape 
 sugars which occur in large quantity in the juices of plants, there are 
 other varieties whicli occur less abundantly, and are therefore of less in- 
 terest in the study of tlie general vegetation of the globe. Among these 
 is manna, which partly exudes and is partly obtained by incisions 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 tlie juice of the larch tree, of common celery, and of 
 certain trees which are met with in New South Wales. Liquo»ice root 
 also contains a species of black sugar, which is known in this country 
 under the names of Spanish and Italian juice, from the countries where 
 it is grown. In the musliroom and other fungi a colourless variety, ap- 
 parently jif'ciilirir, has also been met wiih, — and milk owes its sweet- 
 ness to a s|)ecies (jf sugar formed in the interior of the animal along with 
 the other substances which the milk contains. 
 
 These several kinds of sugar difler more or less, not onlj' in sensible 
 and chemical proj)erties, but also in chemical constitution, from the more 
 abundant cane and grape sugars — but they form too smalJ a part of the 
 general products of vegetation, and are of too little consequence in pracii- 
 
 ' Solutions of cane and grape sugar are readily distinguished from each other by the fol- 
 lowing clieuiical characters: — 1. If the solution be heated and a few drops of sulphuric acid 
 then added, cane sugar will be decomposed, blackened, and made to fall as a black or brown 
 powder — while a solution of grape sugar will at tlie most be only slightly discoloured. 2. If, 
 instead of sulphuric acid, caustic potash be employed, the cane sugar will be unchanged, 
 while the grape sugar will be blackened and thrown down. 
 
C,3 
 
 Hs Oa 
 
 Ci2 
 
 Hi 0, 
 
 C,2 
 
 H] Oi 
 
 Ci2 
 
 Hi Oi 
 
 Cl 2 
 
 Hio 0,0* 
 
 Clo 
 
 H 1 2 Ol 2 f 
 
 MUTUAb Ri;LAT10iNb Of VVOOUV >: nR:0, STARCH, (iUM, KTC. Ill 
 
 cal agriculture lo render it necessary to do more than thus shortly ad- 
 vert to their exisience.* 
 
 § 5. Mutual relations of woody Jibic, starch, gum, and sugar. 
 It may be interesting now lo consider tor a moment the mutual rela- 
 tions of the several substances, woody fibre, starch, gum, and sugar — 
 above described — which occur so largely in the vegetable kingdom, and 
 are serviceable to man for so many ditierent purposes. These relations 
 will be best seen on comparing the formulaj by which they are respec- 
 tively ;-epresented. TIjus — 
 
 Woody Fibre (lignin) is represented by 
 
 Cellular Fibre (according to Payen) by 
 
 Starch (dried at 212° F.) "by 
 
 Gum (any of llie 3 varieties) by 
 
 Cank Sugar (free from water) by 
 
 Grape Sugar (dried at 130° F.) by 
 
 In these formuhe we observe — 
 
 1°. That tlie eijivalents of tlie oxygen are ecjual to those of the hydro- 
 gen in all the formulae, and, therefore, that all these substances may be 
 supposed in consist of carbon and water. 
 
 2°. The n)rmui<E for cellular fibre, starch, gum, and ctme sugar, are 
 identical. They consist of the same elements united together in the same 
 proportions. 
 
 This is one of those facts which not only appear very remarkable to 
 the unlearned, but are scarcely capable of being clearly comprehended 
 and explained, even by those who jjave most profoundly studied this 
 branch of naturnl science. Starch and sugar — how difierent their 
 properties I how unlike their uses ! how iinetjual their ini])ortance to the 
 hmiian race I yet they consist of the same weights of the same substances, 
 difl'erently conjoined. The skillul architect can put logelher the same 
 l)roportions 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 iiand of Deity matter is infinitely more jilastic. 
 At His bidding the same j)arlicles can unite in ihe same (|uantity so as 
 to produce the most unlike impressions — and on all our senses at once. 
 
 3°. A knowledge of the abo\'e close relations in composition, among 
 a class of substances occurring so abundantly in the vegetable kingdom, 
 imparts a degree of simplicity to our ideas of this otherwise complicated 
 subject. It does not ajipear so mysterious that we should have woody 
 fibre, and starch, and gum, anc) sugar, occurring together in variable 
 quantities, wiien we know that tliey are all made up of the same ma- 
 terials, in the same or nearly llie same proi)oriioiis — or that one of these 
 should occasionally disappear from a plant, to be replaced in whole or 
 in i)art by another. 
 
 * Fnra list iif plajils from which sugar lias been cxtraolcd, see Thomson'^ Organic Chemis. 
 /ry (1338), p. 647. 
 
 t Crystallized cane sugar (sugar candy) loses 5 3 percent, of water in favourable circum- 
 stances. Tills is equal lomie equivalent (IIO), so rliai if dry sugar be Cr.!HioOo. crystallized 
 sujar is C S Hii On — or Cvi H.uOio+HO, since I here i.s tio iloiibtthat Ihi.i one equivalent of 
 tlie hydro^irn and oxygen exists in ciysiallized siiaar in Ihe srale of vvatrr. 'n like manner, 
 crysliillized honey or grape suaar — as it occurs in honey or in the dried urapc — loses 9 per 
 cent, of water when heated lo 250° F. This is equal lo two equivalents (2HO), so that crys- 
 UUizeii grapo s\xffix id repretieuled by Ci2 liA On or Cl2 IIlJ Oiv+-2HO. 
 
112 MUTUAL TRANSFORMATIONS OF STARCH, GUM, ETC. 
 
 A furlher question, however, arises in our minds. We naturally ask, 
 — does nature, in thus removing one of these compounds, and supplying 
 its place by anotiier, actually form from its elements the new substance 
 introduced, or docs she produce it by a mere change or transformation 
 of those previously existing. A satisfactory reply to this question may 
 be derived i'rom the facts detailed in the following section. 
 
 § 6. Mutual transformations of icoody fibre, sfarcJi, gum, and sugar. 
 
 I. WOODY FIBRE. 
 
 1°. Action of heat. — Tf wood be reduced to the slate of fine saw-dust, be 
 then boiled in water to separate everything soluble, afterwards dried by 
 a gentle heat, and then heated several times in a baker's oven, it will be- 
 come 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 Hour of wheat; it ferments when made into a paste 
 with yeast or leaven, and when baked gives a light homogeneous bread. 
 Boiled with water, it yields a slifl" tremulous jelly, like that from 
 starch (Aulenrieth. — Scliiibler, Agricultur Chemie, i., p. 224.) By the 
 agency of heat, therefore, it appears that the ivoody fibre may he changed 
 into starch. 
 
 2°. Action of sulphuric acid. — If to three parts of the sulphuric acid 
 of the sho[)S (oil of vitriol) one part of water be added, and a portion of 
 delicate woody 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 in part at least 
 changed into starch* (Schleiden). 
 
 Again, if three parts of fine saw-dust or of fragments of old linen he 
 rubbed in a mortar with four of the sulphuric acid of the shops added 
 by degrees — it will, in a (juarler of an hour, be rendered completely so- 
 luble in water. If the solution in water be freed from acid by chalk, and 
 then evaporated, a substance resembling gum arable is obtained (Br;i- 
 connot). According to Scldeiden, the fibre may be seen uiider the mi- 
 croscope gradually to change froii] without inwards, first into starch and 
 (hen into gum. 
 
 Further, if this gum be digested with a second portion of sulphuric 
 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 iTiay be changed 
 directly into sugar by the prolonged action of dilute sulphuric acid. 
 
 3^. Auction of pxjtask. — If saw-dust be mixed with frcjin two to eiclit 
 limes its weight of hydratef of potash and as much water, and boiled 
 till a crust formson the surface, and if dilulesul|)liuric acid Ije tliei: added 
 till the v/hole is slightly sour, the undestioyed woudy fibre will give an 
 
 * It will be rpcnllected that starch is characterized by giving a blue colour with a solution of 
 iodine (see p. 107). 
 
 The simplest way of trying this experiment is, to take a quantity of clean cotton— to wet 
 it with water, squeezing out again as much as possible — then to spread it out upon a flat dish 
 and moisten it quickly and tliorougtily with |]ic acid diluted as above After half a minute, 
 add the solution of iodine, stir quickly with a glass rod, and immediately add water, when 
 the blue compound of iodine and starch will speedily deposit itself.— (Schleiden, Po^. Annal., 
 xliii., p. 396.) 
 
 ) Hydi'ate of potash is the caualic substance which is obtained by boiliiu; common pearl- 
 •£h wii;^ quick lime. 
 
ACTION OF HEAT OJf STARCH. 113 
 
 instantaneous deep blue on the addition of iodine, showing that starch 
 has been formed. 
 
 Woody fibre, therefore, may be changed into starch, either by the un- 
 aided action of heat, by that of sulphuric acid, or by boiling with caustic 
 potash, — and the starch thus produced may be further transformed, first 
 into gum and then into grape sugar, by the prolonged action of dilute 
 sulphuric acid, assisted by a moderate heat. 
 
 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 gradually 
 heated to a temperature not exceeding 300° F., it slowly changes, ac- 
 quires a yellow or brownish tint according to the temperature employed, 
 and becomes entirely soluble in cold water. It is changed into gun. 
 Under the names of starch-gum, or British-guni, this substance is large- 
 ly manufactured in this country, and is successfully substituted for gum 
 arabic by the calico-printers in thickening many of ilieir colours.* 
 
 The gum thus prepared not unfre(juently also possesses a sweet taste, 
 from the fnrtlier change of a portiun of the gum into sugar. 
 
 2°. Action of water. — When siarch 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 into gum or sug;ir. The |)rocess, however, 
 is slow, and months must elapse before the whole of the starch is thus 
 spontaneously transformed in the presence of water (De Saussiire). It 
 takes place more rapidly when starch and water are boiled together for 
 a lengtli of lime. 
 
 3°. Action of sulphuric acid. — From what has been already stated in 
 regard to the action of this acid on woody fibre it will readily be supposed 
 that native starch, of any variety, is likely to undergo transformation 
 when subjected to its influence. 
 
 In reality, if 50 parts of starch, 12 of sulphuric acid, and 139 of water 
 be taken, and if the starch be thoroughly moistened with a portion of the 
 water, and then poured into the mixture of the acid with the remainder 
 of the water, and heated to 190^ F., the starch will be entirely convert- 
 ed into gum. By further and more prolonged heating this gum is 
 changed into grape sugar. The gum 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.f Onehundred pounds of starch 
 treatixl in this way will yield from 105 to 122 lbs. of dry grape sugar. 
 
 The rapidity with which this transformation takes place depends 
 partly u|)on the temperature and partly upon the jjroportion of acid em- 
 ployed. Thus 100 lbs. of starch mixed with 600 of water and 10 of 
 sulphuric acid, will be converted into grape sugar by boiling for seven 
 hours. If by increasing the pressure the tem[)erature be raised to 250° 
 F., the transformation will be ellected in a. few minutes. With only one 
 
 * During the baltins of breail ttiis corversion ofsfargli into gum takes place to a consider- 
 able extent. Thus Vogel fouml thai Hour which contained no jjuni gave, when baked, a 
 bread of which 18 per cent., or nearly one fii'lh of the whole weight, consisted of gum. 
 Thus one cf the effects of baking is to render the flour-starch more soluble, and therefore (7) 
 more easily digestible. 
 
 t It forms s'jpauin with it (sulphate of lime) which is a compound of lime and sulphuric 
 acid 
 
114 CHANGE OF CANE INTO GRAPE SUGAR 
 
 pound of acid and the same quantity of starch and water, the change 
 will be efTecled in iJirec hours by a temperature of 230° F. This mode 
 of converting potato starch into grape sugar is said to be extensivety 
 practised in France, for the purpose of subsequently fermenting the 
 sugar and convening it into brandy. 
 
 HI. CUM. 
 
 Action of sulphuric acid. — If powdered gum arabic be rubbed in a 
 mortar with the sulphuric acid of the shops, a brownish solution is ob- 
 tained, which, when diluted with water and treated with chalk, yields a 
 gummy substance similar to that obtained in the same way from starch 
 and woody fibre. Prolonged digestion with diluted acid converts a por- 
 tion of this gum into sugar. — [Berzelius, Traite de Chemie, (1831), v., 
 p. 217.] 
 
 IV. — CANE SUGAR. 
 
 1°. Action of heat. — When crystallized cane sugar is heated to 320° 
 F. it melts, and if the temperature be raised to 360° F. it gives off two 
 atoms of water and is changed into caramel. This caramel is an un- 
 crysfallizable sugar, which is generally present in artificial syrups, and 
 is often of a brownish colour. It contains the elements of an atom of 
 water less than cane sugar, and is represented by C,2 Hg Og. It is 
 not known to occur in the natural juices of plants. 
 
 2°. Action of sulphuric acid. — When cane sugar is digested with di- 
 lute sulphuric acid, aided by a gentle heat, it is rapidly converted into 
 grape sugar. The acid of grapes (tartaric acid) and many other vege- 
 table acids produce a similar cliange. 
 
 It is obvious that this conversion of cane into grape sugar can only 
 take place in the presence of water, inasmuch, as has already been 
 shown (p. 110), grape sugar contains the elements of two atoms of water 
 more than cane sugar, or 
 
 Cane sugar. Water. Dry grape sugar. 
 
 We may revert now 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 connection 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 inte- 
 rior of the plant? The answer may now be safely given, that she cer- 
 tainly does. What we can so readily perform by our rude art may be 
 still more easil}^ effected in the living vegetable. That which is starch 
 or gum in one part of the plant, may become cane or grape sugar in 
 another, and woody fibre in a third. Thus by re-arranging the same 
 kind and quantity of the several elements, ma}' the various and unlike 
 forms of matter which constitute the main products of vegetation be 
 readily jiroduced. 
 
 Still the facility is only apparent. We can assure ourselves of the 
 fact of such conversions, because we can at will induce them- But who 
 operates upon these substances in the interior of the plant ? Whose 
 mind and will directs these changes — prescribing when, where, and in. 
 
GRAPE SUGAR ALONK FKRME^tTS. 115 
 
 what order they shall lake place ? How much depends upon the re- 
 fined and little understood mechanism of the vegetable structure — liow 
 much on the living principle itself! What is this living principle — 
 liovv can it direct !* 
 
 § 7. Of the fermentation of starch and sugar — and of the relative circum- 
 stances under tvhich cane and grape sugars generally occur in nature. 
 It will be of use to us, in connection with the above transformations, 
 to advert to the property possessed by starch and nearly all the known 
 varieties of sugar of entering into fermentation under favourable cir- 
 cumstances. When flour is made into a paste with leaven or yeast it 
 begins to rise and ferment, — sooner or later, according 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 
 "infavournhle circumstances it will continue until the whole of the 
 starch or sugar disappears. 
 
 In. all these cases it is grajje sugar alone that undergoes fermentation. 
 [Rose, Poggen. AnnaL, lii., p. 297.] The starch of the moist dough or 
 of the solution is partially transformed into gra[)e sugar before fermenta- 
 tion commences. 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 accord- 
 ing as this transformation is more or less speedily effected. Hence, in 
 the art of brewing, the necessity of cautiously regulating the tempera- 
 ture by which this change of the starch and sugar is promoted and hast- 
 ened. 
 
 The fermentation itself is tlie result not of a mere transformation of 
 one form of matter into another having the same elementary constitu- 
 tion, but of a decomposition of one substance into two others unlike itself 
 either in properties or in chemical composition. The grape sugar is re- 
 solved into alcohol (spirits of wine), which remains in the liquid, and into 
 carbonic acid, which escapes in the form of gas and causes the fermen- 
 tation. Thus alcohol being represented by C4 Hg Oj, and carbonic acid 
 by CO,, 
 
 2 of alcohol r= Cg H,, O4 and 
 
 4 of carbonic acid = C4 O^ make up 
 
 I of grape sugar ^^\i^\2^\2' 
 
 It is an interesting fact that the cane and grape sugars occur in na- 
 ture in circumstances which are entirely consistent with the statement 
 in tlie preceding section, regarding the action of acids on the former 
 variety of this natural product. Fruits contain grape sugar, which in- 
 creases in quantity as they ripen or become less sour. In the sugar 
 cane, the beet root, and the maple and birch trees, cane sugar exists, 
 but in their juices no acid is associated wiih the sugar. On the contra- 
 ry, ammonia is known to be present in most of them along with the 
 cane sutjar. Hence it is inferred, that as in our hands and in our exper- 
 iments cane sugar is changed by the agency of acids into grape sugar, and 
 
 • " Oanst thou by searching (ind out God— Canst tho'i firul out the Almighty unto perfection V 
 
 
 
116 SUBSTANCES CONTAINIING NITROSEIV. 
 
 with remarkable ease by that acid which exists in the ripe grape, so it is 
 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, be- 
 cause in the presence of an acid body cane sugar cannot permanently ex- 
 ist, but is gradually transformed into the sugar of grapes. It thus ap- 
 pears also why fruits so readily enter into fermentation, and why, even 
 when preserved with cane sugar, they will, in consetjuence of the acid 
 they retain, slowly change the latter into grape sugar, and thus induce 
 fermentation.* 
 
 § 8. O/" substances ivliich contain Nitrogen. — Gluten., Vegetable 
 Albumen, and Diastase. 
 
 The substances described in the preceding sections consist of carbon, 
 hydrogen, and oxygen only, and of them the great bulk of the vegeta- 
 ble productions of the globe consists. But there are certain other sub- 
 stances occurring along with starch and sugar, into which nitrogen enters 
 as a constituent, and which, though not formed in the vegetable king- 
 dom in very large quantity, are yet of such interest and importance in 
 other respects, as to make it necessary shortly to advert to them. 
 
 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. Tliis lias been already 
 stated. But on the sieve, when the water ceases to go through milky, 
 there remains a soft adherent, tenacious, and elastic substance, which 
 can be drawn out into long strings, has scarcely any colour, taste, or 
 smell, and is scarcely diminished by washing either with hot or with 
 cold water. This substance is the gluten oi wheat. The flour of other 
 kinds of grain also yield it by a similar treatment, though generally in 
 much smaller quantity. This appears from the following table : — 
 
 The grain of 
 
 Wheat contains 8 to 35 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 or 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 vinegar, in alcohol either 
 cold or hot, and in solutions containing caustic potash, or soda, [the 
 common joearZ-as/i or soda of the shops boiled with quick-lime.] 
 
 2°. Vegetable Albumen. — To the white of egg the name of albumen 
 (albus, white) has been given by chemists. It possesses the well known 
 property of coagulating or of forming a white sohd insoluble substance, 
 when it is heated either alone or after being mixed whh water. 
 
 When the starch has subsided from the milky liquid which passes 
 
 • Milb also, in favourable circumstances, as when kept at a temperature of 100° F., uYi- 
 dergoes fermentation, and in some countries of Asia a spirituous liquor is prepared from 
 mares' and asses' milk. In this case the milli: first becomes sour, then the acid thus form- 
 ed converts the milk sugar into crape suijar, atid finally this sugar enters into fermenta- 
 tion. This takes place more readily in consequence of the presence of the decomposing 
 cheesy matter (casein) of the milk— as is sliown by the fact that the introduction of a small 
 quantity of the curd of milk into a solution of grape sugar will cause it to ferment. 
 
GLUTEN, VEGETABLE ALBUMEN, A>D DIASTASE. 117 
 
 through the sieve in preparing the gluten of wheat, the water rests trans- 
 parent and colourless above the white sediment. If this water be heated, 
 it will become Tiiore or less troubled, and white films or particles will 
 separate, which may be easily collected, and which possess all the pro- 
 perties of coagulated albumen, or boiled white of egg. To this sub- 
 stance the name oC vegetable albumen lias been given. When the fresh 
 prepared gluten of wheat is boiled in alcohol a portion of albumen gene- 
 rally remains undissolved, showing that water does not completely wash 
 it out from the gluten. 
 
 Vegetable albumen, when fresh and moist, has neither colour, taste, 
 nor smell, is insoluble in water or alcohol, but dissolves in vinegar and 
 in caustic potash or soda. When dry it is biiiile, more or less coloured, 
 and opaipie. In the seeds of plants, it exists only in small quantity^ 
 tlius the grain of 
 
 Wheat contains | to li per cent. 
 Rye ... -2 to 3| 
 Barley . . . ,-V l'> i 
 Oats ... 4 to i 
 It occurs more largely however in the fresh juices of plants, in those 
 of cabbage leaves, turnip roots, and many others. When these juices 
 are heated the albumen coagulates and is readily separated. 
 
 Gluten and vegetable albumen appear to be as closely related as sugar 
 and starch are to each other. Like these two substaiices, they consist 
 of the same elements, united together in the same proportions, and are 
 capable of similar mutual transformations. According to the most re- 
 cent analyses, those of Dr. Scheerer, they consist of 
 Carbon = 54-76 
 Hydrogen = 7*06 
 Oxygen = 20-06 
 Nitrogen = 18-12 
 
 100 
 
 When exposed to the air in a moist state these substances undergo de- 
 composition. They ferment, emit a most disagreeable odour, and pro- 
 duce, among other compounds, vinegar and ammonia. 
 
 The important influence which gluten and vegetable albumen are 
 supposed to exercise over the nourishing properties of the different kinds 
 of food in which they occur, will be considered in a subsequent part of 
 these lectures.* 
 
 3°. Diastase. — When cold wateris 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 alcohol, a white 
 tasteless powder falls — to which the name oC diastase has been given. 
 
 • There occur in the animal kingdom— in Ihe bodies of animals— three other forms of the 
 substance above described under the names of gluten and vegetable albumen. These are 
 albumen or white of egg, already mentioned, — cajtein, the curd of cheese, — and fibrin, the 
 Bubslance of the muscular fibre of animals. 
 
 P. Casein. — When the curd of cheese is well washed with water, and then boiled in 
 alcohol to free it from oily matter, it forms the casein of chemists. While moist it is soft 
 and colourless, but as it dries it hardens, assumes a yellow colour, and becomes semilrans- 
 parent. Even when moist it is perfectly insoluble either in cold or in hot water. It is solu- 
 
118 ^ PRODUCT13N OF DIASTASE. 
 
 If unmalted barley be so treated no diastase is obtained. This sub- 
 stance, therefore, is formed during the jJTOcess of malting. 
 
 If wheat, or barley, or potatoes, which by sleeping in water yield no di- 
 astase, be made to germinate (or sprout), and be afterwards bruised and 
 treated as above, diastase will be obtained. It is therefore produced 
 during gerynination. 
 
 If the shoot of a potato be cut off within half an inch of its base, this 
 lower portion, with the part of the potato to which it is immediately at- 
 tached, separated from the rest — and llie three parts (the upper portion 
 of the shoot — the lower portion with its attached fragment of potato — 
 and the remaining mass of the potato) treated with water, — only that 
 portion will yield diastase in which the base of the shoot is situated. 
 When a seed sprouts, therefore, this substance is foniied at the base of 
 the germ, and there remains during its growth. 
 
 If the same portion of the potato, or if the grain of barley or wheat is 
 
 ble, however, in water containing vinegar, or to which a little carbonate of potasli or soda 
 has been added. It may be kept for any length of lime in a dry place, without undergoing 
 decay. The changes undergone by old cheese are ciiiefly due to the oily and other sub- 
 stances with which the curd is mixed. It h.is been remarked, that when the gluten of wheat 
 is left for a length of time in a moist state it undergoes a kind of fermentation and gradually 
 acquires the smell and taste of cheese (Rouelle.) 
 
 2°. Fibrin. — When lean beef or mutton is long washed in water till it becomes colourless, 
 and is then boiled in alcohol to separate tlie fat, a colourless, elastic, fibrous mass is obtained, 
 which is the fibrin of chemists. In recently drawn blood it exists in the liquid state, but coa- 
 gulates spontaneously when exposed to tlie air, and forms the greater part of the dol of 
 blood. It dissolves in a solution of caustic potash or of nitre, and in vinegar. 
 
 3°. Albumen. — This substance in the liquid state exists in the while of egg, and in the 
 serum of the blood. It coagulates by heating to 160° F , or if previously mixed with water 
 by raising to 212° F. 
 
 These three substances, in addition to their well Known sensible properties, are distin- 
 guished as follows : 
 
 1°. Liquid casein in milk, is not coagulated by heating alo7ie — the addition of rennet orof 
 a little acid (vinegar or spirit of salt) is necessary, when it curdles readily. 
 
 2°. Liquid albumen in white of egg, coagulates by heat alone, as when an egg is put into 
 hot water. 
 
 3°. Liquid fibrin in the blood coagulates by mere exposure to the air, or more rapidly by 
 agitation in contact with the air. 
 
 Like starch and sugar these three substances are mutually convertible by known means. 
 Thus fibrin, if unboiled, dissolves by digestion at 80° F. in a saturated solution of nitre, and 
 acquires the properties of liquid albumen; and if to liquid albumen a little caustic potash be 
 added, and afterwards much alcohol, it will be thrown down in the form and with the pro- 
 perties of casein. 
 
 All these substances appear to contain the same organic constituents in the same propor- 
 tions. 
 
 Boussingault first showed the identity in chemical constitution of gluten and vegetable al- 
 bumen. — [Pog. All., xl., p. 2.53.] Mul<ler afterwards proved a similar identity between vege- 
 table albumen and the white of egg, fibrin, and casein — [Ann. de Chim. et. de Phys., Ix-v., p. 
 301.] Mulder supposes them to ilitTer from each other by the presence in unlike quantities 
 of a small admixture of sulphur, phosphorus or phosphate of lime. 
 
 Those who are not familiar with the history and with the nature of cliemical research, can 
 form no idea of the time and labour which li.isby different chemists been expended on this 
 one branch. The persevering industry of Dr. Mulder, of Rotterdam, appeared to have 
 cleared up the entire subject by a long series of investigations and analyses, — [for an out- 
 line of his results, see Berzelius Arsheriitilese, 1839, p. 61 1,]— when first Vogel, then Prosper 
 Denis, and latest Liebig and Dr. Si-hcerer. have arrived at different results. Our ideas are 
 thus again unfixed, and our partial generalizations set aside for future emendation. 
 
 The analysis inserted in the text, as representing the composition of i»luten and vegetable 
 albumen, is that given by Dr. Scheerer for the purest form o( fib/in. I have selected it in 
 preference to the results cither of Rousslngault orof Mulder, because it is the most recent, 
 and has been obtained with a knowledjie of all the previous researches,— and assuming the 
 chemical identity of this entire iiroup of substances, is the most likely to represent their 
 conslilution with accuracy. It differs from the analysis of Mulder miJi/ in stating the nitro- 
 gen at 2 per cent, higher than was done by that chemist. The recent iinprovements in the 
 mode of determining the true quantity of nitrogen in organic substances, appear to justify 
 U6 in expecting the result of Scheerer to be in this respect the more con-ecW 
 
DIASTASE CHANGES STARCH INTO SUGAR. 119 
 
 examined, when the first true leaves of the plant have been fully 
 formed and expanded, the diasiasi 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 sub- 
 stance. 
 
 Properties of diastase. — If the solution obtained from mall be digested 
 with potato, flour, or other starch, at a temperature between 120° and 
 140° F., the latter will gradually dissolve and will form a colourless 
 transparent solution. When this solution is carefully evaporated a yel- 
 lowish white powder is obtained, j^erfectly soluble in water, to which 
 the name of dextrine has been given, [because its solution turns to the 
 n'g'Ai a ray of polarized light when passed through it.] This dextrine 
 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 so- 
 lution will gradually acquire a sweet taste, and if it be now evaporated 
 it will yield, instead of dextrine, a mixture of gum and grape sugar. 
 And if the digestion be still further prolonged, the whole of the starch 
 will be converted into grape sugar only. — [See above, § 6, p. 113.] 
 
 Thus diastase {like sulphuric acid) possesses the property of trans- 
 forming starch entirely — first into gum, and then into grape sugar. The 
 intermediate stage of dextrine has not been recognized in the action of 
 sulphuric acid, nor is it easy to arrest the action of diastase exactly at 
 this point — the most carefully prepared dextrine 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 decom 
 position, and after being boiled, it has no further etfect u])on starch. It 
 has not been analysed, because it is difficult to obtain it in a pure stale. 
 It contains nitrogen, however, for, when moistened and exposed to the 
 air, it decomposes, and, among otiier products, yields ammonia.* 
 
 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. TJie starch in the seed is the food 
 of the future germ, prepared and ready to minister to its wants when- 
 ever heat and moisture concur in awakening it to life. But starch is it- 
 self 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 
 
 ■ It will be recollected that ammonia contains nitrogen, being represented by NH3.— See 
 |,eiiure III., p. ."ij. 
 
100 ADAPTATIONS IN THE PRODUCTIONS OF DIASTASE. 
 
 carried inio tlie general circulation. Or when, as in ihe potato, much 
 more starch is present tlianis in many cases requisite, its function ceases 
 long before the whole of the starch disappears. Its presence is necessa- 
 ry only until tlie leaves and roots are fully formed — when the plant is 
 enabled to provide for itself, and becomes independent of the starch of 
 the seed. When this period arrives, therefore, the production of dias- 
 tase 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 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 transform the same weight of starch than is re- 
 quired in our hands, when aided by artificial heat, — yet as we never in 
 the ordinary course of nature find any tiling superfluous or going to 
 waste, there is reason to believe that the diastase may be intended also 
 to contribute directly to the nourishment and growth of the plant. As 
 it contains nitrogen, it must be derived from the gluten or vegetable al- 
 bumen of the seed ; and as a young plant of wlieat, when already many 
 inches from the ground, contains no more nitrogen than was originally 
 present in the seed itself (Boussingault), this diastase may only be the 
 result of one of those transformations of which glutenf is susceptible, 
 and by whicli it is rendered soluble, and capable of aiding in the pro- 
 duction of those parts of the substance of the growing plant into wiiich 
 nitrogen enters as a necessary constituent. 
 
 It may not be uninstructive if we pause here for a moment and con- 
 sider the beauty of the arrangements we have just been describing. 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 apjireciate its beauty. So in the domains of science, 
 we cannot be ever hurrying on — we must linger occasionally, not only 
 that we may more carefully observe, but that we may meditate and 
 feel. 
 
 You see how bountifull}'' nature has provided in the seed for the nour- 
 ishment of the young plant, how carefully the food is stored up for i,', 
 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 remain sound and undimin- 
 ished 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 absolutely insoluble in water. But no sooner 
 
 • It is the diastase in malt which dissolves the starch of the barley in the process of brew- 
 ing', but as the didslase contained in malt is sufficient to dissolve so large a quantity of starch, 
 it is obviously a waste of labour to malt Ihe 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 propejiy in the manufacture of 
 Ihe while 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. 
 
 t That diastase is merely transjormed gluten we cannot say, because the exact chemical 
 constitution of diastase is as yet unl<nown. 
 
VEGETABLK ACIDS. 121 
 
 is tlie sleeping germ recalled to life, by the access of air and warmth 
 and duly tempered 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 impartial force, who shall discover to us ?) 
 — is the signal for the api:)earance of this agent — diastase — of which, 
 jirevious to germination, no trace could be discovered in the seed. At 
 the root of ihe germ, where the vessels terminate in the farinaceous 
 matter, exactly where it is wanted, this substance is to be found; — there, 
 and there only, resolving and transforming the otherwise unavailable 
 store of food, and preparing it for being conveyed either to the ascending 
 sprout or to the descending root. And when the necessity for its pre- 
 sence 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 — 
 then this diaslase disappears, it undergoes itself a new conversion, and is 
 prepared in another form to contribute to the further increase of the plant. 
 How beautiful and provident are all these arrangements! — how plas- 
 tic the various forms of organic matter in the hands of the All-Intelli- 
 gent! — how nicely adjusted in time and place its diversified changes ! 
 What an apparently lavish expendiline of forethought and kind previ- 
 sion, in behalf even of the meanest plant that grows ! 
 
 § 9. Vegetable Acids. — Acetic acid, Oxalic acid, Tartaric acid. 
 Citric acid. Malic acid. 
 Another class of compound substances remains to be shortly consid- 
 ered, — those, namely, which possess sour or acid properties, and which 
 are known to be present in large quantity in many plants, and more 
 especially in the greater number of unripe fruits. They do not, taken 
 as a whole, form any large portion of the entire produce, either of the 
 general vegetation of the globe or of those plants which are cultivated 
 for food ; yet the growth of fruit — as in the grape, orange, and apple 
 countries — is sutficienily extensive, and the general interest in the cul- 
 tivation of fruit trees sufficiently great, to require that the nature of the 
 substances contained in fruits, and the peculiar changes by which they 
 are formed, should be in some measure considered and exjjlained. 
 
 I. ACETIC ACID. 
 
 Acetic arid or vinegnr is the most extensively diffused, and the most 
 largely produced, of all the organic acids. It is formed during the ger- 
 mination of seeds, and u exists in the juices of many ]>lants, but it is 
 most abundantly evolved during the fermentation, whether natural or 
 artificial, ofnenrly all vegetable substances. When pure it is a colour- 
 less liquid, haviiig 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 dihitcd, but it can be prepared of such a 
 strength as to freeze a"nd 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 all soluble in water, and may, 
 therefore, be readily washed out of the soil or of compost heaps by 
 heavy falls of rain. 
 
122 PREPARATION OF ACETIC ACID. 
 
 When perfectly free from water, acetic acid consists of— 
 Carbon . . . 47'5 per cent., or 4 atoms 
 Hydrogen . . 5-B " or 3 " 
 
 Oxygen . . . 46-7 " or 3 " 
 
 100 
 
 It is therefore represented by the formula C4 II3 O3 — in which, as in 
 those given in the preceding sections for starch, sugar, &c., the numbers 
 representing tlie atoms of hydrogen and oxygen are e(|ual, and conse- 
 quently these elements are in the proportion to furm water. Hence, 
 vinegar, like sugar, may be represented by carbon and water. 
 
 Let us consider for a moment tlie several processes by wliich this acid 
 IS usually foriued. 
 
 1°. By the distillation of icood. — This a inethorl by whicl) wood 
 vinegar — often called pyroiigneotis acid — is |)repared in large fpiantity. 
 Wood which has been dried in the air is put into an iron retort and distil- 
 led. The principal products are vinegar, water, and tarry matter. 
 The decomposition is of a complicated description, but by comparing 
 the constitution of woody fibre with tiijtt of vinegar, we can readily see 
 the nature of the changes by which the latter is produced. 
 Woody Fibre is = Ci, Hg O, 
 3 of Vinegar are = C,2 Hg O9 
 
 Difference = H, O, ; or the elements 
 
 of one atom of water. One portion of the woody hbre, therefore, com- 
 bines with the elements of an atom of water, obtained by the decomjMV 
 sition of another portion, and thus vinegar is produced. 
 
 2°. Maniifaclure 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 tlie solution kept for a length of time at a 
 moderate temperature, the whole will be converted into vinegar without 
 any sensible fermentation. This i)rocess is frequently fallowed in tlie 
 preparation of household vinegar, and was fi)rnierly ad(>]>ted to some ex- 
 tent in our clieniical manufactories. It will be recollected that we re- 
 presented Cane Sugar by C,, H,o 0,q, while 
 3 of Vinegar — C,o Hg O9 
 
 Difference Hj O, ; or the elements 
 
 of an atom of water, which cane sugar must lose in order to be convert- 
 ed into vinegar. Whether the change in this instance takes place by 
 the direct conversion of cane sugar into vinegar, or whether the former 
 is previously transformed into grape sugar, has not been satisfactorily de- 
 termined. 
 
 3°. Manufacture of Vinegar from Alcohol. — In Geruiany, where 
 common brandy is chea|)er than vinegar, it is found profitable to manu- 
 facture this acid from weak spirit. For this purpose it is mixed with a 
 little yeast, and then allowed to trickle over wo(xl shavings moistened 
 with vinegar, and contained in a cask, the sides of which are perforated 
 with holes for the admission of a current of air. By this method oxy- 
 gen is absorbed from the air, and in 24 hours the alcohol in the spirit is 
 converted into vinegar and water. 
 
TARTARIC ACID IN THE GRAPE. 123 
 
 The explanation of this process is also simple, alcohol being repre- 
 sented by C4 H^ O2. Tiius — 
 
 Alcohol ^ C4 Hg O., ] f Vinegar =; C4 H3 O3 
 
 4ofOxY6E.N= O4 'I 3 of Water = H3 O3 
 
 Slim C4 Hrg Og j I Sum = C4 Hg 0^ 
 
 4°. Production of Vinegar by fermentation. — When vegetable mat- 
 ters are allowed to ferment, carbonic acid is given off and vinegar is 
 formed. In such cases this acid is the result of a series of changes, du- 
 ring which that |)ortion of the vegetable matter which has at length 
 reached the state of vinegar has most probably passed through the seve- 
 ral previous stages of grape, sugar, and alcohol. The carbonic acid, as 
 has already been explained (p. 115), is given offduring 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, and among the products of their decay. 
 
 II. TARTARIC ACID. 
 
 The graj)e and the tamarind owe their sourness to a peculiar acid to 
 u'hich the name ui tartaric acid has been given. It is also present, along 
 with other acids, in the mulberry, in the berries of the sumach {rhus co- 
 riarii), and in the sorrels, and has been extracted from the roots of the 
 C(juch-grass and the dandelion. 
 
 Wlien 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 ves- 
 sels. This substance is known in commerce by the name of argol, and 
 when purified is familiar to you as the cream of tartar of the sliops. 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 use of the 
 acid is in certain processes of the calico printers. 
 
 The pure acid is sold either in the form of a v/hite powder or of trans- 
 parent crystals, which are colourless, and have an agreeable acid taste. 
 It dissolves readily in water, and causes a violent elTervescence when 
 mixed with a solution of the carbonate of potash or of soda. As it has 
 no injurious action upon the system, it is extensively used in artificial 
 soda powders and elTervescing draughts. When added in sufficient 
 c[uaniity to a solution containing potash, it causes a white crystalline 
 powder to fall, which is cream of tartar (or bitarlrate of potash), and from 
 lime water it throws down a white chalky precipitate oitartrate of lime. 
 Both of these compounds are present in the grape. 
 
 When perfectly free from water this acid consists of — 
 Carbon , . . = 36-81 or 4 atoms. 
 H^'drogen . . = 3-00 or 2 atoms. 
 Oxygen . . . = GO-19 or 5 atoms. 
 
 100 
 It is therefore represented by the formula C4 Ho O5, 
 
 If we compare the numbers by which the atoms of hydrogen and ox- 
 ygen in this acid are expressed, we see that these elements are not in the 
 proportion to form water, and that this substance, therefore, cannot, like 
 
 6» 
 
124 CONSTfTUTION OF TARTARIC AND CITRIC ACIDS. 
 
 f) many of those we liave hitherto liad occasion to notice, be represented 
 by carbon and tlie elements of water alone. 
 It may be represented by 
 
 4 of Carbois . . = C4 ) 
 
 2 of Water . . = Ho O^ V or, 4C+2H+30 
 and 3 of Oxygen . . = O^ > 
 
 Tartaric Acid =: C4 H, O5 
 And, though this mode of representation does not truly exhibit the con- 
 stitution of the acid, inasmuch as we have no reason to believe that it 
 really contains water as such — yet it serves to show very clearly that in 
 the living plant this acid cannot be formed directly from carbon and the 
 elements of water, as starch and sugar may, but that it requires also 
 three atoms of oxygen in excess 10 every five of carbon and two of water. 
 We shall, in the following lecture, see how nicely the functions of the 
 several parts of the plant are adjusted, — at one |)eriod to the formation of 
 this acid, and at another to its conversion into sugar during the ripening 
 of the fruit. 
 
 III. CITRIC ACID, OR ACID OF LEMONS. 
 
 This acid gives their sourness to the lemon, the lime, the orange, 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 soine roots, as 
 in those of the dahlia pinnata, and the asarum europaeum {asarrabacca), 
 and mixed with much malic acid, in the currant, cherr}', gooseberry, 
 raspberry, strawberry, common whortleberry, and the fruit of the haw- 
 thorn. 
 
 When extracted from the juice of the lemon or lime, and afterwards 
 purified, it forms transparent colourless crystals, possessed of an agreea- 
 ble acid taste ; effervesces like tartaric acid with carbonate of soda, and 
 like it, therefore, is much employed for effervescing draughts. With 
 potash it firms a soluble salt, which is a citrate of potash, ami from lime 
 water it throws down a white, nearly insoluble, seiYiiaei-A of citrate of 
 lime, which re-dissolves when the acid is added in excess. In combi- 
 nation 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 C4 Ho O^. 
 
 This formula ditlers from that assigned to the tartaric acid only in 
 containing one atom of oxygen less, O4 instead of O5. In the citric 
 acid, therefore, there are 2 atoms of oxvgen in excess, above what is 
 necessary to form water with the 2 of hydrogen it contains. 
 
 IV. MAI.IC ACID. 
 
 The malic and oxalic acids are more extensively diffused in living 
 plants than any other vegetable acids. If acetic acid be more largely 
 
CONSTITUTION OF MALIC AND OXALIC ACIDS. 125 
 
 formed in nature, ii is cliiefly as a product of the decomposition of or- 
 ganic matier, when it has already ceased to exist in, or to form part of, 
 a living plant. 
 
 Along with the citric acid, it has been already stated that the malic 
 occurs in many fruits. It is found more abundanliy, however, and is the 
 chief cause of the sour taste, in the unripe apple, [hence its name malic 
 acid,] tlie i)lum, the sloe, the elderberry, the barberry, the fruit of the 
 mountain ash, and many others. It is associated with the tartaric acid 
 in the grape and in the Agave americaua. 
 
 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 colourless crystals, 
 which have an agreeable acid taste. It combines with potash, soda, 
 lime, and magnesia, and forms malates, and, in combination with one or 
 more of these bases, it usually occurs in the fruits and juices of plants. 
 The malaU of lime is soluble, while the citrate, as already stated, is 
 nearly insoluble, in water. This malate exists in large cpiantily in the 
 Juice of the house-leek {sempervlvum lector um), in the Sedum telephium, 
 the Arum maculatum, and many other juicy and fleshy-leaved plants. 
 
 When perfectly free from water, the malic acid has exactly the same 
 chemical constitution as the citric, and is represented by the same for- 
 mula C4 H2 O4. These two acids, therefore, bear the same relation^ 
 fo each other as we have seen that starch, gum, and sugar do. They 
 are what chemists call isomeric, or are isomeric bodies. We cannot 
 transform then), however, the one into the other, by any known means, 
 though there is every reason to believe that they may undergo such 
 transformations in the interior of living plants. Hence probably one 
 reason also why the malic and citric acids occur associated together in 
 so many different fruits. 
 
 V. OXALIC ACID. 
 
 Tliis acid has already been treated of, and its properties and composi- 
 tion detailed, in a preceding lecture (Lecture lit., p. 47). It forms co- 
 lourless transparent crystals, having an agreeably acid taste, and it 
 effervesces with the carbonates of potash and soda, but on account of its 
 poisonous qualities, it is unsafe to administer it as a medicine. It oc- 
 curs in combination with potash in the sorrels, in rhubarb, and in the 
 juices of many lichens. Those Uchens which incrust the sides of rocks 
 and trees, not unfrequently contain half their weight of this acid in com- 
 bination with lime. It can be formed artificially by the action of nitric 
 acid on starch, sugar, gum, and many other organic substances. 
 
 When perfectly free from water, oxalic acid contains no hydrogen ; 
 but consists of — 
 
 Carbon . . . 33-75 = 2 atoms 
 
 Oxygen . . . 66-25 = 3 " 
 
 100 
 and it is re,presented by C, O^. When heated with strong sulphuric 
 acid, it is decomposed and resolved into gaseous carbonic acid (CO3) and 
 carbonic oxide (CO) in equal volumes. This change is easily under- 
 stood since CO^ -f CO = C„ O3. 
 
12j5 STARCH CONVERTED I.NTO WOODY FIBRE. 
 
 § 10. General observations on the substances ofivhich plants chiefly consist. 
 
 It may be useful here shortly to review the most important facts and 
 conclusions which have been adverted to in the present lecture. 
 
 1°. The great bulk of plants consists of a series of substances capable 
 of being represented by, and consequently of being formed in nature 
 from., carbon and the elements of water only. Such are woody fibre, 
 starch, gum, and the several varieties of sugar (p. 111). 
 
 2°. Yet the crude mass of wood, as it exists in a full-grown 
 tree, containing various substances in its pores, cannot be represented 
 by carbon and the elements of water alone. It apj)ears always to 
 contain a small excess of hydrogen, which is greater in some trees than 
 in others. Thus in the chesnut and the lime, this excess is greater than 
 in the pines, while in the latter it is greater than in the oak and the ash. 
 [For a series of analyses of diiTerent kinds of wood by Peterson and 
 Schodler, see Thomson's Organic Chemistry, p. 849.] 
 
 3°. These substances are, in many cases, mutually convertible even 
 in our hands. They are probably, therefore, still more so in nature. 
 
 It is to be observed, however, that ail the transformations we can as 
 yet effect are in one direction only. We can produce the above com- 
 pounds from each other in tlie order of ligniu or starch, gum, cane sugar, 
 grape sugar — that is, we can convert starch into gam, and gum into 
 sugar, but we cannot reverse the process, so as to form cane from grape 
 sugar, or starch from gum. 
 
 The only apparent exception to this statement vviih which we are at 
 present acquainted, occurs in the case of starch. Wlien this substance 
 is dissolved in cold concentrated nitric acid, and then mixed largely with 
 water, a substance [the Xyloidin of Braconnot] falls to the bottom, 
 which is a compound of the nitric acid with woody fibre (C,2 Hj O3.) 
 [Pelouze, see Berzelius Arsberdttelse, 1839, p. 416.] In this instance, 
 if the above observation is correct, there appears to be an actual con- 
 version of starch into woody fibre. 
 
 But what 2ve are as yet unable to perform may, nevertlieless, beeasily 
 and constantly effected in the living plant. Not only may what is starch 
 in one part of the tree be transformed and conveyed to another part in 
 the form of sugar, — but that which, in the form of sugar or gum, ]>asses 
 upwards or downwards with the circulating sap, may, b}' the instrumen- 
 tality of the vital processes, be deposited in tjie stem in ilie form of 
 wood, or in tiie ear in that of starch. Indeed we know that such actu- 
 ally does take place, and that we are still, therefore, very far from being 
 able to imitate nature in her ]jower of transforming even this one group 
 of substances only. 
 
 4°. Among, or in connection with, the great masses of vegetable mat- 
 ter which consist mainly of the above substances, we have had occasion 
 to notice a few v\ hich contain nitrogen as one of their constituents — and 
 which, though forming only a small fraction of the products of vegetable 
 growth, yet appear to exercise a most important influence in the general 
 economy of animal as well as vegetable life. The functions performed 
 by diastase in reference to vegetable growth, and to the transformations 
 of organized vegetable substances, have already been in some measure 
 illustrated, — we shall hereafter have an opportunity of considering more 
 
IMPORTANCK OF THK VEGETABLli ACIO« 127 
 
 fully t.:e influeDce whicli gluten and vegetable albumen exercise ovei 
 the general elliciency of tlie products of vegetation in the support of ani- 
 mal life, and over the changes which these products must undergo, be- 
 fore they can be converted into the substance of animal bodies. In a 
 former lecture (Lecture IV., p. 66), I have had occasion to draw your 
 attention to the comparatively small proportion in which nitrogen exists 
 in the vegetable kingdom, and to show that it must nevertheless be con- 
 sidered as much a necessary and constituent element in their composi- 
 tion as the carbon itself; the very remarkable properties we have al- 
 ready discovered in the compounds above mentioned strongly confirm 
 this fact, and iUustrate in a striking manner the influence of apparently 
 feeble and inadequate causes in producing important natural results, 
 
 5°. With the exception of acetic acid, which in constitution is closely 
 related to sugar* and gum, all the acid substances to which it has been 
 necessary to advert, contain an excess of oxygen above what is neces- 
 sary to form water with the hydrogen tliey contain. Thus 
 
 Vinegar = C^ H3 O3 contains no excess of oxygen. 
 
 Taktakic Acid = C4 H^ Oj . . 3 of oxygen in excess. 
 
 Malic Acid ? nun o 
 
 iTRic Acid ^ 4 _ 4 
 
 Oxalic Acid = Co O3 . . 3 
 It requires alittle consideration to enable us to appreciate the true im- 
 portance of these and other organic acids, in the vegetable economy. At 
 first sight they appear to form a much smaller part of the general pro- 
 ducts of vegetation than is really the case. We must endeavour to 
 conceive the quantity actually produced by a single tree loaded with 
 thousands oflemons, oranges, or apples, — or again, how much is formed 
 during the growth of a single comparatively small plant of garden rhu- 
 barb in spring, if we would obtain an adequate idea of the extent to 
 which lliese acids are constantly formed in nature. On the other hand, 
 we must recollect also that tlie greater portion of the acid of fruits disap- 
 pears as they ripen, if we would understand the true nature of the in- 
 terest which really attaches to the study of these substances, of the 
 changes to which they are liable, and of the circumstances under which 
 in nature these changes take place. 
 
 6°. I will venture here to draw your attention for a moment to the na- 
 ture and exiCMt of that remarkable power over matter, which the chem- 
 ist, as above explained, appears to possess. Such a consideration will 
 be of value not only in illustrating how far we really can now, or may 
 hereafter, expect to be able to influence or control natural operations, 
 [see Lecture II., p. 32,] but what is probably of more value siill, exhibit- 
 ing the true relation which man bears to the other parts of creation; and, 
 in some measure, the true position he is intended to occupy among them. 
 1°. We have seen that the chemist can transform certain substances 
 one into the other, in a known order ; but that as yet he cannot reverse 
 that order. Thus far his power over matter is at present limited; but 
 this limit he may at some future period be able to overpass, and we 
 
 ' It is identical in constitution witli caramel (p. 114)— the uncrystallizable sugar of syrups. 
 For 
 
 Vinegar. Caramel. 
 
 (C* H3 O3 X 3) = Ci2 H9 09. 
 
128 POWER OF THE CUKMIST OVER MATTER. 
 
 know not how far. The discovery of a new aj^ent, or of a new mode 
 of treatment, may enable liim to accomplish what he has not as yet the 
 means or the slvill to perform. 
 
 2°. He has it in his power to form, actually to produce, some of the 
 organic or organized substances which occur in living plants. He can 
 form gum, and grape sugar, in any quantity. Thus far he can imitate 
 and take the place of the living 'principle itself. 
 
 Numerous other cases are known, in which he dis|)lays a similar 
 power. By the action of nitric acid upon starch or sugar, [see Lecture 
 IH., p. 47,] he can form oxalic acid, which, as has already been shown, 
 occurs very largely in the vegetable kingdom. By the action of heat 
 upon citric acid, he can decompose it and produce an acid which is 
 met with in the Wolfsbane (Aconitum napellus), and hence is called 
 aconitic acid.* Also by the action of sulphuric acid he can change 
 salicine nnd phlorizinc — substances extracted respectively from the bark 
 of the willow and from that of the root of the apple tree — into a resinous 
 matter and grape sugar. So, of the compounds which are found in the 
 solids and fluids of animal bodies, there are some which he has also 
 succeeded in forming by the aid of his chemical art. 
 
 Elated by such achievements, some chemists appear willing to hope 
 that all nature is to bd subjected to their dominion, and that they may 
 hereafter be able to rival the living principle in all its operations. It is 
 true that what we now know, and can accomplish, are but the begin- 
 nings of what we may fairly expect hereafter to effect. But it is of con- 
 sequence to bear in mind the true position in which we now stand, and 
 the true direction in which all we at present know seems to indicate that 
 our future advances in knowledge, and in control over nature, are likely 
 to proceed. And this leads me to observe — 
 
 3°. That our dominion is at present limited solely to transforming 
 and decomposing. We can transform woody fibre into gum or sugar — 
 we cannot form either gum or sugar by the direct union of their elements. 
 We can resolve salicine by the acid of sulphuric acid into resin and 
 grape sugar; but we cannot cause the elements of wliich they consist to 
 unite together in our hands, so as to form any one of the three. We 
 cannot even cause the resin and the sugar to re-unite and rebuild the sali- 
 cine from which they were derived. 
 
 So we can by heat drive off the elements of water from the citric and 
 cause the aconitic acid to appear; but we cannot persuade the unwilling 
 compounds, when thus separated, to return to their former condition of 
 citric acid ; and, if we could, we should still be as far removed from the 
 power of commanding or compelling the direct union of carbon, hydro- 
 gen, and oxygen, in such proportions, and in such a way, as to build up 
 either of the two acids in question. 
 
 Again, we can actually form oxalic acid by the action of nitric acid 
 
 'These two acids ditrerfrom eacl) other only uy the elements of an atom of water. Thus 
 Citric A.cid . . = C4 " 4 
 Aconitic Acid . := C.i Hj O3 
 
 Difference . . = HiO or HO, one of water. 
 It is easy to see, therefore, how, by the evolution of the elements of an atom of water, the 
 one acid may be changed into the other. The scientific reader will e.xcuse me (if on the 
 grounds of simplicity alone) for representing, both here and in the text, the citric acid by 
 C Ha Oj, instead of by C12 Hs On + 3HO, which Liebig and his pupils prefer. 
 
TEUE PROSPECTS OF CHEMICAL SCIENCE. 129 
 
 upon Starch, or wood, or sugar, or any other of a great variety of vegeta- 
 hle substances — but- we cannot prepare it by 'be direct union of its ele- 
 ments. We can only as yet procure it troin substances which have 
 already been organized — which have been themselves produced by the 
 agency of the living principle. 
 
 The same remarks apply with slight alteration to those substances of 
 animal origin to which I have above alluded as being within the power 
 of the chemist to produce at will. There is hardly an exception to the 
 rule, that in producing organic substances, as they are called, the chem- 
 ist must employ other organic substances which are as yet beyond his 
 art — which, so far as we know, can only be formed under the direction 
 of the living principle. Thus the sum of the chemist's power in imita- 
 ting organic nature consists, at present, in his ability — 
 
 1°. To transform one substance found only in the organic kingdom 
 into some other substances, produced more or less abundantly in the 
 same kingdom of nature. This power he exercises when he converts 
 starch into sugar, or fil)rin into albumen or caseiti. 
 
 2°. To resolve a more complex or compound substance into two or 
 more which are less so, and of which less complex substances some may 
 be known to occur in vegetable or animal bodies. 
 
 3^. To decompose organic compounds by means of his chemical agents, 
 and as tlie result of such decompositions to arrive at one or more com- 
 pounds, such as are formed under the direction of the living principle. 
 
 In no one case can he form the substances of ivliich animals and plants 
 chiefly consist, out of those on which animals and plants chiefly live. 
 
 But this is the common and every-day result of the agency of the liv- 
 ing principle. Is there as yet, then, any hope that the chemical labo- 
 ratory shall suj^ersede the vascular systein of animals and j)lants ; or 
 that the skill of the chemist who guides the operations within it, shall 
 ever rival that of the principle of life which presides over the chemical 
 changes that take place in animal and vegetable bodies ? 
 
 The true place, therefore, of human skill — the true prospects of chem- 
 ical science — are jiointed out bv these considerations. No science has 
 accumulated so many ami such various treasures as chemistry has done 
 during the last 20 years — none is at present so widely extending the 
 bounds of our knowledge at this moment as the branch of organic chem- 
 istry — men may therefore be excused for enlerlaining more sanguine 
 expectations from the progress of a favourite science than sober reason- 
 ing would warrant. Yet it is of importance, 1 think, and especially in 
 a moral point of view, that amid all our ardour, we should entertain 
 clear and just notions of the kind and extent of knowledge to which we 
 are likely to attain, and — as knowledge in chemistry is really power 
 over matter — to what extent this power is likely ever to be carried. 
 
 At present, if we judge from our actual knowledge, and not from our 
 hopes — there is no prospect of our ever being able to imitate or rival 
 living nature in actually compounding from their elements her nume- 
 rous and varied productions. That we may clearly understand, and be 
 able to explain many of her operations, and even to aid her in effecting 
 them, is no way inconsistent with an inability to imitate her by the re- 
 sources of art. This will, I trust, appear more distinctly in the subse- 
 quent lecture. 
 
VII. 
 
 Chemical changes by which the substances of which plants chiefly consist are formed from 
 those on which they live. — Changes during germination — during the growth of the plant — 
 during the ripening of fruit. — Autumnal changes. 
 
 Having lliiis considered the nature and chemical constitution of those 
 substances which constitute by far tlie largest part of the solids and 
 fluids of living vegetables, we are now prepared for the further question 
 — hy what chemical changes these substances of lohich plants consist, are 
 formed out of those on which they live? 
 
 The growth of a plant from the germination of the seed in spring till 
 the fall of the leaf in autumn, or the return of the succeeding spring- 
 time, may in perennial plants be divided into four periods — during which 
 they either live on different fooil, or expend their main strength in the 
 production of different substances. These periods may be distinguished 
 as follows : — 
 
 1°. The fteriod of germination — from the sprouting of i!ie seed to the 
 formation of ilie perfect leaf and root. 
 
 2°. From ihe expansion of the first true leaves to tlie ]ieriod of flow- 
 ering. 
 
 3°. From the opening of the flower to the ripening of tlie fruit and 
 seed. 
 
 4^^. From ihe 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 func- 
 tions of annual plants are in general discharged, and they die; but per- 
 ennial plants have still important duties to perform 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 
 ihem in relation to these several periods of growth. 
 
 § 1. Chemical changes tcMch take place during germination and during 
 the develojunent 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 fa- 
 vourable to its rapid and healihy progress. 
 
 1°. Before a seed will begin to sprout, it must be placed for a time in 
 a sufficiently moist sii nation. We have already seen how nimierous 
 and important are the functions which water performs in reference lo 
 vegetable life (Lecture II., p. 36,) in every stage of a plant's growth. 
 In the seed no circulation can take place — no motion among the pani- 
 cles of matter — until water has beer largely imbibed ; nor can the food 
 be conveyed through the growing vessels, unless a constant supply of 
 fluid be afforded to the seed and its infant roots. 
 
 2°. A certain degree of "^varmth — a slight elevation of temperature- 
 is also favourable, and in most cases necessary, to germination. 
 
ErFECT OF AIR AND LIGUT ON GERMINATION. 131 
 
 The degree of warmih wliich is recjuired in order that seeds may be- 
 gin to grow, varies with the nature of the seed itself. In Northern Si- 
 beria and other icy countries, plants are observed to spring up at a tem- 
 perature but slightly raised above the freezing point (32° F.,) but it is 
 familiar to every practical agriculturist, that the seeds he yearly con- 
 signs 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 a[)proaching spring, or by the lieat of a summer's sun. 
 
 The same fact is familiarly shown in the malting of barley, vt'here 
 large heaps of grain are moistened in a warm atmosphere. When ger- 
 mination ct)mmences, 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 natural processes in the grain 
 itself; in some such way as, in the bodies of animals, a constant supply 
 of heat is kept up by tlie vital processes — by which supply the cooling 
 elTect of the surrounding air is continually counteracted. 
 
 We have seen in ihe preceding lecture, that the transformations 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 atiected during ger- 
 mination; there is reason, therefore, to believe that the external warmth 
 which is required in order that germmation luay begin, as well as the 
 internal heat naturally developed as germination advances, are both 
 employed in effecting these transformations. And, as the young sprout 
 shoots more rapidly under the influence of a tropical sun, it is probable 
 that those natural agencies in general, by which such chemical transfor- 
 naations are most rapidly promoted, are also those by which the pro- 
 gress of vegetation is in the greatest degree hastened and promoted. 
 
 3"^. It has been observed that seeds refuse to germinate if they are en- 
 tirely 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 sjjeedily begin to sprout. Thus in 
 trenching the land, or in digging deep ditches and drains, the farmer is 
 often surprised to fliid the earth, thrown up from a depth of many feet, 
 become covered with young plants, of species long extirpated from or 
 but rarely seen in his cultivated iields. 
 
 4°. Yet light is, generally speaking, prejudicial to germination. 
 Hence the necessity of covering the seed, when sown in our gardens 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, nmch of the grain, even after 
 iiarrowing, remains uncovered ; and the prejudicial influence of light in 
 preventing the healthful germination of sucli seeds is no doubt one rea- 
 son why, by the method of dibbling, fewer seeds are observed to fail, and 
 an equal return of curn 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 fol- 
 lowing observation : — 
 
 5°. When seeds are made to germinate in a limited portion of atmos- 
 
132 SEEDS SPROUT ONLY IN THE PRESENCE OF OXYGEN. 
 
 pheric air, the bulk of the air undergoes no material alteration, but on 
 examination its oxygen is Ibund to have diminished, and carbonic acid 
 to iiave taken its place. Therefore, during germination, seeds absorb 
 oxygen gas and give off carbonic acid. 
 
 Hence it is easy to understand why the ))resence of air is necessary 
 to germination, and why seeds refuse to sprout in hydrogen, nitrogen, 
 or carbonic acid gases. They camiot sprout unless oxygen be ivithin 
 ilieir reach. 
 
 We have seen also in a previous lecture that the leaves of plants in 
 the sunshine give oft' oxygen gas and absorb carbonic acid, — while in 
 the dark the reverse takes place. So it is with seeds which have begun 
 to germinate. Wlien exposed to the light they give oil' oxygen instead 
 of carbonic acid, and thus the natural process is reversed. But it is ne- 
 cessary to the grov.'th of the young germ, that oxygen should be absorb- 
 ed, and carbonic acid given ot^ — and as this can take place to the requir- 
 ed extent only in the dark, the cause of the prejudicial action of iiglit is 
 sufficiently apparent as well as the propriety of covering the seed with a 
 thin layer of soil. 
 
 6^. During germination, vinegar (acetic acid) and diastase are pro- 
 duced. That such is the case in regard to the latter substance, has been 
 proved in the previous lecture, (j). 118.) That acetic acid is formed is 
 shown by causing seeds to germinate in powdered 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 aceiate must have been formed in the seed, and after- 
 wards excreted or thrown out into the soil. 
 
 7°. When the germ has shot out from the seed aijd attained to a sen- 
 sible length, it is found to be possessed of a sweet taste. This taste is 
 owing to the presence oi grape sugar in the sap which has already be- 
 gun to circulate through Us vessels. 
 
 It has not been clearly ascertained whether the vinegar or the dias- 
 tase is first produced when germination commences, but there seems 
 little doubt that the grape sugar is formed subsequently to the appear- 
 ance 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 
 lime expand into the first true leaves. The vessels of this first shoot do 
 not consist of unmixed woody fibre. It is even said that no true wood 
 is formed till the first true leaves are developed. — [Lindley's Theory of 
 Horticulture.] 'i'he vessels of the young sprout, iherelure, and of the 
 early radicles, probably consist of the cellular fibre of Payen. They 
 are unipieslionably li)rmed of a substance which is in a state of transition 
 between starch or sugar and woody fibre, and which has a constitution 
 analogous! lo that of boih. 
 
 Having thus glanced at liie phenomena which attend ujion germina- 
 tion, let us now consider the chemical changes by which these phenom- 
 ena are accompanied. 
 
 1°. The seed absorbs oxygen and gives oft" carbonic acid. We have 
 
 Acetate of lime is a compound ofaceticacid (vinegar) and lime, and may be prepared by 
 dissolvmg chalk in vinegar. It is very soluble in water. 
 
 t By analogous I mean winch may be represented by carbon and water. 
 
HOW AND WHY VINEGAR IS FORMED. 133 
 
 already' seen ihal the starc-li of ilie seed (C,o H,c On,) may be repre- 
 senied by carbon and vvaier, — by 12C -j- lOHO. Now it appears ibat 
 in conlacl with the oxygen of the atmospiiere, a portion of the starch is 
 actually separated into carbon antl water, the carbon at ihe niotnent of sepa- 
 ration uniting with the oxygen, and forming carbonic acid (CO^). Tliis 
 acid is given ofl' into the soil in the form of gas, and thence |)artially es- 
 capes into the air; but tor wluii immediate purpose it is evolved, or how 
 its formation is connected with tlie further development of the germ, has 
 not hitherto been explained. 
 
 2\ The formation of acetic acid (vinegar) from the siarcli of the 
 grain is also easy to comprehend. For, as we iiave already seen, 
 Starch . . . =:C,o H o Oio 
 3 of Vinegar . . =C,2 Hg Og 
 
 Difference ^ H, O, ; or the elements of 
 
 an atom of water. Therefore, in this early stage of tiie growth of the 
 germ a portion of the starch is de|>rived of the elements of an atom of 
 water, and at the same time transformed into vinegar. 
 
 Why is this vinegar formed? It is almost as difficult to answer this 
 question as to say why carbonic acid is evolved from the seed, though 
 both undoubtedly serve wise and useful ends. 
 
 It has been explained in the preceding lecture how the action of dilute 
 acids gradually changes starch into cane sugar, and the latter into grajje 
 sugar. While it remains in the sap of the sprouting seed, the vinegar 
 may aid the diastase in transforming the insoluble starch into soluble 
 food for the plant, and may bean instrument in securing the conversion 
 of the cane sugar, which is the first formed, into grape sugar, — since 
 cane sugar cannot long exist in the presence of an acid. 
 
 After the acetic acid is rejected by the ])lant, it may act as a solvent 
 on the lime and other earthy matters contained in the soil. Liebig sup- 
 poses the especial function of this acid — the reason why it is formed in 
 the germ and excreted into the soil — to be, to dissolve the lime, &c., which 
 the soil contains, and to return into the pores of the roots, bearing in so- 
 lution the earthy substances which the plant requires for iis healihy 
 growth. This is by no means an unlikely function. It is only conjec- 
 tural, however, and since the experiments of Braconnot have shown that 
 acelalc of Lime, even in small quantity, may be injurious to vegetation, 
 it becomes more doubtful liow far the formation of this compound in the 
 soil, and liie subsecjuent conveyance of it into the circulation of the plant, 
 can be regarded as the special purpose for which acetic acid is so gene- 
 rally produced during germination. 
 
 3°. The early saj) of the young shoot is sweet ; it contains grape su- 
 gar. This sugar is also derived from the starch of the seed. Being 
 rendered soluble''by the diastase formed at the base of the germ, the 
 starch is gradually converted into grape sugar as it ascends. The rela- 
 tion between these two compounds has been already pointed out. 
 
 Starch =C,2H,oO,(, 
 
 Grape Sugar . . . =Ci2H,2 0,2 
 
 Difference . . . . = H^ O^, ; or the ele- 
 
 ments of two atoms of water. The water which is imbibed by the seed 
 12 
 
134 now THE SUGAR IS FORMKD IN THE SPROUT. 
 
 from the soil, fiji-ms an abumlaiit source from wliich the whole of the 
 starch, rendered soluble by ihe diastase, can be sup])lied with the ele- 
 ments of the two atoms of water wliich are necessary to its subsequent 
 conversion into grape sugar 
 
 4°. The diastase is formed when the seed begins to sprout, at the ex- 
 pense of the ijluien or vegetable albumen of the seed, but as its true 
 constitution is not yet known, we cannot explain the exact chemical 
 changes by which its production is eliected. 
 
 5°. When the true leaf becomes exj)anded, true wood first appears 
 in sensible tpi amity. By what action of the sun's rays upon the leaf 
 the sugar already in solution in the sap is converted into woody fibre, 
 we cannot explain. The conversion itself is in appearance simple 
 enough, since 
 
 Grape Sugar . . . := 0,^ H12 0121 and 
 Woody Fibre . . . =Ci2 Hg O^ 
 
 Difference . . . . = H4 O4 ; or the former 
 
 must part with the elements of lour atoms of water only, to be prepared 
 for its change into the latter, lint the true nature of the molecular* 
 change by which this transformation is brought about, as well as the 
 causes which lead to it and the immediate instruments by which it is 
 effected, are all still mysterious. 
 
 §2. Of the chemical chans;es which take flace from the formation of the 
 true leaf to the expansion ofthefloiver. 
 
 When tlie true leaf is formed the plant 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 derives its sustenance from the 
 air and from the soil. The apparent mode of growth is the same, the 
 stem shoots ui)wards, the roots descend, and they consist essentially of 
 the same chemical substances, but they are no longer formed at the ex- 
 pense of the 'Jtarch of the seed, and the chemical changes of which they 
 are the result are entirely different. 
 
 1°. The leaf absorbs carbonic acid in the sunshine, and gives off ox- 
 ygen in e(jinl biilk.f It is in the light of the sun that plants increase in 
 size — their growth, therefore, Is intimately connected with this absorp- 
 tion of carbonic acid. 
 
 If carbonic acid be absorbed by the leaf ami the whole of its oxygen 
 given off again, t 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 he directed, or as 
 may be necessary, any one of those numerous compounds which may 
 
 * All bodies are stipposerl lii consist of particles or j«o?«fM/es of exceeding minuteness, 
 and all chemiciil chanj:es which lake place in the same mass of matter are supposed to be 
 owing to the different ways in which these particles arrange themselves. We may form a 
 remote idea of the way in which ditfercnt positions of the same particles may produce dif- 
 ferent substances, by considering Imw different (irrures in Mosaic may be produced by dif- 
 ferent arrangements of the same number of equal and similar fragments of various colours. 
 
 t Such lasensihly the result of experiment. How far this result can be considered as uni- 
 versally true, will be examined hereafter 
 
 } It will be recollected that carbonic acid contains its own bulk of oxygen gas : if, therefore, 
 the leafgiveotf the same bulk of oxygen as it absorbs of Ci^rbonic acid, Ihe result must be aa 
 stated in the text. 
 
HOW PLANTS ARE NOURISHED BT CARBONIC ACID ? 135 
 
 be represenip'l by carbon and water, (p. Ill,) and of wliicli, as we have 
 seen, the solid parts of plants are chiefly made up. 
 
 There are two ways in which we may suppose the oxygen given off 
 by the leaf to be set free, and the starLli, sugar, and gum, to be subse- 
 quently formed. 
 
 A. The action of liglit on ilie leafof the plant may directly decompose 
 tlie carbonic, acid after it has been absorbed, and cause the oxyen to sep- 
 arate from the carbon, and escape into the air ; — while at the same in- 
 stant the carbon thus set free, may unite with the water of the sap in 
 dlHIerent proi)ortions, so as to produce either sugar, gum, or starch. 
 Suppose 12 atoms of carbonic acid (12 COo) lo be thus decomposed, and 
 their carbon to unite with 10 of vvaier (10 H.O), we should have 
 from 12 of Carbonic Acid . = C12 
 
 which united to 10 of Water . . . r= H,o 0,o 
 
 would give 1 of Gum or of Cane Sugar = C,^ H,o Om 
 while 24 of o\\'gen would be given off; the whole of which would have 
 been dericcd from the carbonic acid absorbed by the plant. 
 
 B. Or the action of the sun's rays may be directed, in the leaf, to the 
 decomposition, not of carbonic acid, but of the icaterot'ihc sap. The oxy- 
 gen of the water may be separated from ihe hydrogen, while at the same 
 instant the latter element (hydrogen) may unite with t!ie carbonic acid 
 to produce the sugar or starch. The result here is the same as before, 
 hut the mode in which it is brought about is verj' differently represented, 
 and appears i^iuch more complicated. Thus, suppose 24 of water 
 (24 HO) to be decomposed, and to give oil' their oxj'gen into the air, 24 of 
 oxvgen would be evolved as in the former case, the whole of which would 
 be derived from the decomposition of water, while there would remain 
 24 of Hydrogen . . =r H , 
 
 Let this act on 12 of Carbonic Acjd = C,o O,. 
 
 and we have as the result C,2 Ho^ O24 ; 
 
 Sraroh, &t. Watpr. 
 
 or Ci2 H,„ Oio + 14HO. 
 
 According to this mode of representing the chemical changes, water is 
 first decomposed and its oxygen evolved, then its hydrogen again com- 
 bines wiih the carbon and oxygen of the carbonic acid, and forming two 
 ])roducts — water and sugar or starch. This view is not only more com- 
 plicated, but it supposes ihe same action of light to be — continually, at 
 liie same time, anrl in the same circumsiances — both decomposing wa- 
 ter and re-forming it from ils elements. While, tlierefore, there can be 
 no doubt, for oiher reasons not necessary to be stated in this place, that 
 ilic light of ihe sun really does decompose water in the leaves of plants, 
 niul tnorein some than in others — yet it appears probable that the oxygen 
 evolved by the leaf is derived in a^reat measure from the carbonic acid 
 which is absorbed; and that the principal part of the solid substance of 
 living vegf'tables, in so far at least as it is derived lYom the air, is pro- 
 duced by the union of the carbon of this acid with the elements of the 
 water in the sap.* 
 
 ■ I miglit not to pass uniioticerl the opinion of Peisoz (Chemie Mnteculaire), tiiat tlie 
 iilarch, gum, &c., of plants arc formed by llic union of carbonic oxide (CO) wilii the neces- 
 
136 IS CARBONIC ACID ABSORBED FROM THE SOIL ? 
 
 We have seen reason to conclude (p. 63) iliai, while ])lants derive 
 much of their siistennnce frotn tjie air, they are also led more or less 
 abundantly by the soil in which they grow. From this soil they ob- 
 tain through their ronis the carbonic acid which is continually given off 
 by tlie decaying vegetable matter it contains. This carbonic acid will 
 ascend to the leaf, and will there 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 tlie soil can 
 be decomposed and deprived of its oxygen before it reaches the leaf. 
 
 It is distinctly stated, indeed, by Sprengel, [see above, p. 92,] that 
 when the roots of a plant are in tlie presence of carbonic acid, the oxy- 
 gen given off by the leaf is greater in bulk than liie carbonic acid ab- 
 sorbed. But there is one observation in connection with this point which 
 it seems to me of iiriportance to make. The leaves supply carbon to 
 the plant only in the form of carbonic acid, and they give otia bulk of 
 oxygen gas not exceeding that of the acid taken in, [see note, below.] 
 But if the carbon derived from the soil be also absorbed in the form of 
 carbonic acid, and if the oxygen contained in this portion of acid is also 
 given oirby tlie leaf — either the (juantity 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 great- 
 er than the bulk of the carbonic acid which it al)sorbs. 
 
 We are too little familiar with the chemical functions of the several 
 parts of plants to be able to pronounce a decided oj)inion 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 oxy- 
 gen gas given off bj' the leaf during the day nmst always be considera- 
 bly greater than that of the carbonic acid absorbed by it; or 
 
 (h). The root or stem must have the [)o\ver of decomposing carbonic 
 acid and of separating and setting free its oxyijen ; or 
 
 (c). Tlie plant can derive no considerable portion of its carbon from 
 the soil, in the form of carbonic acid. 
 
 If the ex])eriments hitherto made by the vegetable physiologists be 
 considered of so decisive a character as to warrant us in rejecting the 
 two former conditions, the third becomes also untenable. 
 
 sary proportions of oxygen and hyclrnijipn derived from tlie water of the sap. Tliis opinion 
 implies that, in the leaf, carbonic acid (C'Oa ) is decomposed into carbonic oxide and oxy- 
 gen (CO -f O), and that water likewise, is decomposed, — the oxyaen prodnced by both de- 
 compositions bein? given off either into the air by the leaves, or into the soil by the roots. 
 The production ofgrai)e sugar, therefore, accordina to this hypothesis, would be thus repre- 
 sented:— There are retained, and given off. 
 From 12 of Cakbonic Acid = l'2CO-2 • • - Ci2 O12 Oia 
 From 12 of Water- - - = I2HO - - • His On 
 
 C|-^Hl2 0ii O;.^ 
 
 grape sn^ar 
 
 Of tlie 24 of oxygen thus ffiven otf, the opinion of Persox is, that only one-half is evolved 
 by the leaf, — and the principal fact on which his opinion rests is that observed by De Saus- 
 sure, that plants of Vinca minor gave ofTby their leaves, in his experiments, only two-thirds 
 of the oxygen contained in the carbonic acid they absorbed. This result has led Herzclius 
 also to conjecture that the leaves of plants ilo not retain merely the carbon of the carbonic 
 acid, but ?nme compound ofcarbon with oxygen, contauiing much less of this element than 
 the carbonic acid does (7';u)7e rfc CVicmie, V , p. fi9). The principal ohjcclion to this view, 
 however, is the quantity of oxygen it supposes to be rejected by the root. The experiments 
 on which it is founded require confirmation and extension. 
 
HOW SUGAR 19 TRANSFORMED INTO STARCH. 137 
 
 3". Without dwelling at present on this point, tiie above considera- 
 tions may be regarded as giving additional strength or probability to the 
 conclusions we formerly arrived at (p. 63) from other premises — that 
 'Jie roots, besides carbonic acid, absorb certain other soluble organic 
 compounds, which are always present in tlie soil in greater or less 
 quantity, and that the plant appropriates and converts these into its own 
 substance. Some of these organic compounds may readily, and by ap- 
 parently simple changes, be transformed into the starch and woody fibre 
 of the living vegetable. The illustration of this fact will be reserved 
 until, in the second part of these lectures, I come to treat of the vegeta- 
 ble portion of soils, and of the chemical nature and constitution of the 
 organic compounds of which it consists, or to which it is capable of giv- 
 ing rise. 
 
 4°. The chemical changes above explained (a), show how, from 
 carbonic acid and the elemenis of water, substances possessed of the 
 elementary constitution of sugar and gum may, by the natural processes 
 of vegetable life, obtain the elemenis of which tliey consist, and in the 
 requisite proportions. They tlirow no light, however, upon the me- 
 chanism by whicii these elements are constrained, as it were, to assume 
 Jirsl the form of gum or sugar, or soluble starch, and afterwards, in 
 another part of the plant, of insoluble starch and woody fibre. 
 
 It is known that the sap deposits starch andAvoody fibre in ihe stem, 
 only in its descent from the leaf, — and it is, therefore, inferred that llie 
 action of light upon the sap, as it passes ihroilgh the green parts, is ne- 
 cessary to dispose the elements to arrange themselves in the form of 
 vascular fibre or lignin. And as, by the agency of nitric acid, starch 
 appears to be convertible into woody fibre (p. 126), it is not unlikely 
 that the soluble substances, containing nitrogen, which are present in 
 the sap may — as diastase does upon starch — exercise an agenc}' in trans- 
 forming the soluble sugar, gum, &c., of the sap into the insoluble starch 
 and woody fibre of the seed and the stem. We are here, however, upon 
 uncertain ground, and I refrain from advancing any further conjectures. 
 
 Two great steps we have now made. We have seen how the germ 
 lives and grows at the expense of the food stored u]i in the seed — and 
 how, when it has obtained roots and leaves, the plant is enabled to ex- 
 tract from the air and from the soil such materials as, in kind and quan- 
 tity, are fitted to build up its several parts during its future growth. 
 That considerable obscurity still rests on the details of what takes place 
 in the interior of ihe plant, does not detract from the value of what we 
 have already been able to ascertain. 
 
 § 3. On the production of oxalic acid in the leaves and stems of plants. 
 
 In the preceding section we liave studied the origin of those sub- 
 stances only which form the chief bulk of the j)roducts of vegetation, 
 and which are characterized by a chemical roiisiiiuiion of such a kind 
 as enables them to be represenied by carbon aixl water. 15ut during 
 the stage of vegetable growth we are now considering, other compounds 
 totally different in their nature are also prodiici^d, and in some plants in 
 sufficient quantity to be deserving of a separate consideration. Such is 
 the case with oxalic acid. 
 
 The circumstances under which this acid occurs in nature have al- 
 
138 PRODUCTION OF OXALIC ACID IN TLANTS. 
 
 ready been detailed. It is fouml in small quantifies in ninny plants. 
 The potash in forest trees is su[)posed to be in combination with oxalic 
 acid, while in the lichens oxalate of lime serves a purpose simiinr to that 
 performed by the woody fibre of the more perfect plant; it forms the 
 skeleton by which the vegetable structure is supported, and through 
 which its vascular system is didused. 
 
 The production of this acid in the living plant is readily understood 
 when its chemical constitution (Co O3) is compared with that of car- 
 bonic acid (CO2). For 
 
 2 of Carbonic Acid = C2 O4 
 1 of Oxalic Acid = Co O3 
 
 Difference . . . O, 
 
 That is to say, 2 of carbonic acid are transformed into 1 of oxalic acid 
 by the loss of 1 equivalent of oxj'gen — or generally, carbonic acid by the 
 loss of one-fourth of its oxyoen may beconverted into oxalic acid. 
 
 But the leaf absorbs carbonic acid and gives off' oxygen. In the lichens, 
 therefore, which contain so much oxalic acid, a large portion of the car- 
 bonic acid absorbed is, by the action of light, deprived of only one-fourth 
 of its oxygen, and is thus changed into oxalic acid. The same is true to 
 a smaller extent of the sorrel leaves and stems, which owe their sour- 
 ness to the presence of oxalic acid — of the leaves and stems of rhubarb 
 also — in a still smaller degree of the beech and other large trees, in 
 which much |)otash, and probably also of marine plants, in which 
 much soda is found to exist. It must be owing to the peculiar strscture 
 of the leaves of each genus or natural order of plants, that the same ac- 
 tion 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 considerable 
 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.* 
 
 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 ])lace — as where sorrels and sweet clovers grow side by side. Yet 
 the influence of light of different degrees of intensity on the same plant, 
 is beautifully shown by the leaves of the Sempcrvivum arboreum, of the 
 Portulacaria afra, and other plants which are sour in the inorning, tasteless 
 
 Were we permiUeii, in Die absence of decisive experiments, to state as true what llieo- 
 retical consiileratlons plainly indicate, we should say — 
 
 1°. That plants containing niucli oxalic or other similar acids, and not deriving much car- 
 bonic acid from the soil, must give olT 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 arid absorbed. 
 
 3°. That if little of these acids be present, and much carbonic acid be ab.-^orbed from the 
 soil, the volume of oxygen given off by the green parts of the plant must be sensibly greater 
 than lliat of the carbonic acid they ab.sorb. 
 
 4°. That the leaves of the pines ami other trees containing much turpentine — in which 
 hydrogen is in excess— must at all times give otToxyupn in greater bulk tlian tlie-carbonic 
 acid they absorb. They must decompose water as well as carbonic acid, and evolve the 
 oxygen of both. 
 
ACTIOrf OF THE FLOWER LEAVES ON THE AIR. 139 
 
 in the middle of the day, and hitler in tJie evening. — [Sprenge , Chemie, 
 II., p. 321.] During the night the oxygen has accumulated in these plants 
 and formed acids containing oxygen in excess (p. 127.) As the day ad- 
 vances this oxygen is given off"; under the influence of light the acids are 
 decomposed, and the sourness disappears. 
 
 In the juices of plants before tiie period of flowering, other acids are 
 met with besides tlie 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 formation in the following section. 
 
 § 4. 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 taken by 
 the plant towards the production of the seed by which its species is to be 
 perpetuated. That al this period a new seriesof chemical changes com- 
 tiiences in the plant is obvious from the f)llowiiig tacts : — 
 
 1^. That the flower leaves absorb oxygen and emit carbonic acid both 
 by day* and by night (p. 95.) 
 
 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 cane and beetroot, 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 [)lantsat this period of their growth. That such changes 
 go on until the ripening of the seed is also evident from these further ob- 
 servations : — 
 
 1°. 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 consohdates into a mix- 
 ture of starch and gluten, such as is presented by the flour of different 
 species of corn. 
 
 2°. 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 oidy, as in tlie lime, the lemon, and the tamarind, does a suf- 
 ficient quantity of acid remain to be sensible to the taste, when the seed 
 has become perfectly ri|ie. The acid and cellular fibre both diminish 
 while the sugar increases. ' 
 
 3°. That fruits, while green, act upon the air like the green leaves and 
 twigs — but that, as they approach maturity, they also absorb or retain 
 oxygen gas (De Saussure.) The same absorption of oxygen takes place 
 when unripe fruits are i)lucked and left to ripen in the air (Berard.) 
 After a time the latter also emh carbonic acid. 
 
 I. FORMATION OF THE SEED. 
 
 In the case of wheat, barley, or other plants, which yield farinaceous 
 seeds, we have seen that ]irevious to flowering the chief energy of the 
 living plant is expended in the production of the woody fibre of which 
 its stem and growing branches mainly consist; and we have also been 
 able to understand, in some degree, how this woody fibre is produced 
 froin the ordinary food of the plant. When the flower expands, how- 
 
 • By day the absorpiion is ihe greater, but the bulk of the oxygen taken in is alwajra 
 greater than that of the cart>oiiic acid siven off. 
 
140 FORMATION OF THE SEED, AND RIPENING OF THE FRUIT. 
 
 ever, the plant has in general, and especially if an annual plant, reached 
 nearly to maturity, and woody fibre is little required. The most im- 
 portant of its remaining functions is tlie production of the starch and glu- 
 ten of the seed, and of the substances which Ibrm 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 woody 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, however, is still 
 inexplicable. We can ourselves, by the agency of diastase, transform 
 starch into sugar ; and, ilierefore, can readily believe such transforma- 
 tions 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 during 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, and that it is a 
 necessary constituent of the albumen and gluten, which are always as- 
 sociated with the starch of the seed. It is plain, then, that the nitrogene- 
 ous substances [substances containing nitrogen,] contained in the sap at 
 all periods of the plant's growth, are carried up in great quantity to the 
 flower and seed vessel. These substances are supposed to be concerned as 
 immediate agents in effecting the transformations which there take place. 
 More than this, however, we cannot as yet venture even to conjecture. 
 
 II. RIPENING OF THE FRUIT. 
 
 In these 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, of a more intelligible kind, 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 they consist of little more than the substance 
 of the leaf — of vascular, or woody fibre, filled with a tasteless sap, and 
 tinged with the colouring matter of the green parts of the plant. For a 
 time, this young fruit appears to perform in reference to the atmosphere 
 the usual functions of the leaf — it absorbs carbonic acid and gives oflfoxy- 
 gen, and thus extracts from the air a portion of the food by which its growth 
 is promoted, and its size gradually increased. 
 
 [I. But after a time this fruit becomes sour to the taste, and its 
 acidity gradually increases — while at the same time it is observed to 
 give off" a less comparative bulk of oxygen than before. Let us consi- 
 der shortly the theory of the production of the more abundant vegetable 
 acids contained in fruits. 
 
 1°. The tartaric acid which occurs in the grape is represented by 
 C4 H2 O, (p. 124). 
 
 There are two ways in which we may suppose this acid to be formed 
 
FORMATION OF TARTARIC, MALIC, AND CITRIC ACIDS. 141 
 
 in ilie fruit — either direoilj' from tlie elements of carbonic acid and \vn- 
 ter with the evolution of oxygen gas — or from the gum and sugar al- 
 ready present in the sap aided by the ahsorption of oxygen from the at- 
 mosphere. Thus 
 
 A. 4 of Carbonic Acid == C., 0> 
 2ofWATKR . . = H, Ol 
 
 Tartaric Acid. 
 
 Sum . . = C^ Ho Oio or C4 H. O5 -f 50. 
 That is, one equivalent of tartaric acid may be formed from 4 of carbon- 
 ic acid absorbed by the leaf or fruit, and 2 of the water of the sap, while 
 5 of oxygen are at the same time given oH by the leaf. Or, 
 
 B. W Grape Sugar be C,o H,o Ojo 
 
 i of Grape Sugar = C^ H3 O3 
 
 3ofOxTGKN . . = O3 
 
 Tartaric Acid. Water. 
 
 Sum . . = C, H3 Og or C^ H,, O5 -f HO. 
 Tlic't is, by the absorption from the air of a quantity of oxygen equal to 
 that which it already contains, grape sugar may be converted into tar- 
 taric acid and water. 
 
 In the sorrels and otiier sour-leaved plants, which contain 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 | of 
 the oxygen contained in the carbonic acid they drink in, tartaric acid 
 may be produced (A.) In the dark they absorb oxygen and give off 
 carbonic acid. If the bulk of this latter gas which 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 tartaric acid. 
 
 We have as yet no experiments which enable us to say by which of 
 these modes the tartaric acid is really jiroduced 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 experiments 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. 127) by 
 the common formula- C4 Hg O4. They may be produced from water 
 and carbonic acid, if three-fourths only of the oxygen of the latter be 
 given off. Thus 
 
 4 of Carbonic Acid = C4 Og 
 2 of Water . . = H3 O2 
 
 Malic Acid. 
 
 Sum . . = C4 H2 0,0 = C4 H2 O4 + 60. 
 
 That such a retention of one-fourth of the oxygen of the carbonic acid 
 occasionally takes place in the green fruit, is consistent with the obser- 
 vations of De Saussure. The lime and the lemon are fruits on which 
 the most satisfactory experiments might be made with the view of fi- 
 nally determining this point. 
 
142 CONVERSION OF ACIDS INTO SUGAR. 
 
 III. This formation of acid proceeds for a certain time, the fruit be- 
 coming sourer and sourer; tiie acidity tben begins to diminish, sugar is 
 formed, and the fruit rii>ens. The acid rarely disappears entirely, even 
 from the sweetest fruits, until tliey begin to decay ; a considerable por- 
 tion of it, however, must be converted into grape sugar, as the fruit ap- 
 proaches to maturity. This conversion may take place in either of two 
 ways. 
 
 1°. By the direct evolution of the excess of oxygen. Thus 
 
 3 of Tartaric Acid = C,o H^ O,^ 
 
 6 of Water . . . = " Hg Og 
 
 Grape Sugar. 
 
 Sum . . . =r C,2 Hi3 O,, = Ci2 Hi2 O.^ + 90. 
 
 Or grape sugar njay be formed from 3 of tartaric acid and 6 of the water 
 of the sap, by the evolution, at the same time, of 9 of oxygen. Citric 
 and malic acids, in the same proportion, 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 ojT an excess of oxygen? 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 Actiy = C4 H2 Og 
 1 of Oxygen . . . = O, 
 
 ■ ^o't^ of Grape Carbonic 
 
 Sugar. Acid. 
 
 Sum . . . = C4 H3 Oe = Ca Ho O., + 2 CO^ 
 Where one of o.Kygen is absorbed and two of carbonic acid given offj 
 Or in the case of the malic and citric acids, 
 
 1 of Malic Acid' = C4 H^ O4 
 
 2 of Oxygen . . = Oo 
 
 • Xth of Grape Carbonic 
 
 Sugar. Acid. 
 
 Sum . . = C, H., O, = C, H2 O. +.2 CO, 
 
 Where 2 of oxygen are absorbed and 2 of carbonic acid given off. 
 
 We know fro^i the experiments of Berard that, when unripe fraits 
 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 ex- 
 hibits the iTiore probable theory of the ripening of fruits after they are 
 plucked; and if — as they become coloured — 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 per- 
 mitted to ripen on the tree. 
 
 During the ri|>en'ing of the fruit, it has been stated that the woody or 
 cellular fibre it contains gradually diminishes, and is converted into su- 
 gar. This is familiarly noticed in some species of hard or winter pears, 
 in sour fruit, the cellular fibre seldom exceeds 2^ per cent, of their 
 whole weight ; — in ripe fruits, however, it is still le.ss, and as the con- 
 stitution of this substance is so analogous to that of grape sugar, there is 
 no ditficulty in understanding that it may be readily converted into the 
 latter, though the iinmediate agency by which the transformation is 
 effected is as yet unknown to us. 
 
CHANGES AFTER THE FRUIT HAS RIPKNED. 143 
 
 § 5. Of the chemical changes rvhich lake place after the ripening of 
 the fruit and seed. 
 
 When the seed is fully ripe, the functions of annual plants are dis- 
 charged. 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 
 plan(, for being finally resolved again into those more elementary sub- 
 stances from which they were originally compounded. 
 
 On trees and perennial plants, however, a further labour is imposed. 
 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 ensuing spring, — are in reality so 
 many young plants for which a store of food has yet to be laid up in the 
 inner bark, and in the wood of the tree or shrub itself. 
 
 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 woody fibre, as was the case during the earlier 
 period of the year, and partly into starch. The former is deposited be- 
 neath 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 ca- 
 pable of being converted into these substances have already been con- 
 sidered. They proceed during the entire autumn, do not cease so lona; 
 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. 
 
 § 6. Of the rapidity with ichich 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 whicli 
 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 circumstances 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). Cucumbers 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 illustrations of the rapidity with which plants 
 are capable of springing up in the most favourable circunistances, and 
 the above examples probably give us only an iinperfect idea of the ve- 
 
144 INFLUENCE OF SALINE SUBSTANCES AND MAKUHES. 
 
 locity with which the bamboo, the paJm, the tree fern, and other vascu- 
 lar plants, may grow in liieir native soil and climate. And with what 
 numerous and complicated chemical changes is the production of every 
 grain of the substance of these plants attended — how rapidly 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 ])roceed 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 mentioned as having flour- 
 ished from 4500 to 6000 years ; while even a living rose tree {rosa 
 canina) is quoted by Sprengel as being already upwards of 1000 years 
 old. — [Sprengel, Lehre vom Dilnger, p. 76.] 
 
 The rapidity of the growth of a ])lanl, and the length of its life, are 
 equally affected by cucumslances. On a knowledge of these circum- 
 stances, and of the means of controlling or of producing thein, the en- 
 lightened practice of agriculture is almost entirely dependent. 
 
 Over the natural conditions on which vegetation in general depends, 
 we can exercise little control. By hedge-rows and planlations we can 
 shelter exposed lands, but, except in our conservatories and hot-Jiouses, 
 the plants we can expect to cultivate wilii profit will always be deter- 
 mined by the general climate in which we live. So the distribution of 
 rain and sunshine are beyond our control, and though it is ascertained 
 that a thundery contliiion of the atmosphere is remarkably favourable to 
 vegetable growth, [Sprengel, Lehre vom Dilnger, p. 73], 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 same natural conditions of cli- 
 mate, there are many ariificial methods 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 watering with 
 a solution of chlorine (Davy), or of iodine or bromine (Blengini), and 
 Davy found that radish seed which germinated in two days when wa- 
 ered with solutions of chlorine or sul|)hate of iron, re([uired three when 
 watered with very dilute nitric acid, and five with a weak solution of 
 sulphuric acid. 
 
 It is familiarly known also in ordinary ]iusbandry» that the applica- 
 tion of manures hastens in a similar degree the development of all the 
 parts of plants during every period of their growth — and largely increases 
 >he 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 occurringin 
 soils, or which are produced largely in our manufactories, have been 
 Toiind to produce similar effects. 
 
 h would be out of place here to enter upon the important and interest- 
 ing 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 vegetables. The true mode 
 of action of such substances — their precise effects — the circumstances 
 under which these effects are most certainly i)r(;duced — and the theoreti- 
 cal 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 VIII. 
 
 How the supply of food for plants is kept up in the general vegetation of the globe. — Propor- 
 tion of their food drawn by plants from the air.-Supply of carbonic acid. —Supply of ammo- 
 nia and nitric acid.— Production of both in nature.— Theory of their action on living vege- 
 tables. — Concluding observations. 
 
 Having shown in the preceding Lecture in what way, and by what 
 chemical changes, the substances of which plants chiefly consist may 
 be produced from those on which they live, — there remains only one 
 further subject of inquiry in connection with the organic constituents of 
 plants. 
 
 Plants, as we have already seen, derive much of their sustenance from 
 the carbonic acid of the atmosphere ; yet of this gas the air contains only 
 a very small fraction, and in so far as experiments have yet gone, this 
 fractional quantity does not appear to diminish — how, then, is the sup- 
 ply of carbonic acid kept up ? 
 
 Again, plants most probably obtain much of their nitrogen either from 
 ammonia or from nitric acid ; and yet, neither in the soil nor in the air 
 do these compounds permanently exist in any notable quantity, — whence 
 then is the supply of these substances brought within the reach of plants? 
 
 The importance of these two questions will appear more distinctly, if 
 we endeavour to estimate how much of iheir carbon plants really draw 
 from the atmosi)here — and how much of the nitrogen they contain must 
 be derived from sources not hitherto jiointed out. 
 
 § I. Of the proportion of their carhcm which plants derive from the 
 atmosphere. 
 
 On this subject it is perhaps impossible to obtain perfectly accurate 
 results. Several series of experiments, however, have been published, 
 whicli enable us to arrive at very useful approximations in regard to the 
 proportion 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 wliieh ihey 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 3rd of April lo 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 draion nine-tenths of its car- 
 bon from the air. 
 
 2°. The experiments of Boussingaujt were made, if not with more 
 care, at least upon a greater number of jjlants, and were protracted 
 through a much longer period. It is necessary that we should under- 
 stand the principle on which they were conducted, in order that we 
 may be prepared to place confidence in the determinations at which he 
 arrived. 
 
 * The above experiment may have been correctly made, but the result appears at first 
 sight too startlin? lo he readily rpceived a.s indicative of the proportion of their sustenance 
 ilrawn by plants from the air in the genera! vegetation of the globe. 
 
146 
 
 PROPORTION Of CARKO.N DRAWN !■ ROM THK AIR. 
 
 If we were to examine the soil of a Held on which we are about to 
 raise a crop of corn — and should find it to coniain a certain per-centage, 
 say 10 per cent, of vegetable matter (or 5 per cent, of carbon) ; — and 
 after the crop is raised and reaped should, on a second examination, 
 find it to contain exactly the same quantity of carbon qs 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. The soil having lost none, the air must 
 have yielded the whole supply. 
 
 Or if after examining the soil of our field we mux with it a supply 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 vege- 
 table 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 it.s carbon than the ton contained in the ma- 
 nure which had been added to it. 
 
 Such was the principle on which Boussingaull's experiments were 
 conducted. He determined the per-centage of carbon in the soil before 
 the experiment was begun — the weight added in the form of manure — 
 the quantity contained in the series of crops raised during an entire rota- 
 tion or course of cropping, until in the mode of culture adopted it was 
 usual to add manure again — and lastly, the proportion of carbon re- 
 maining in the soil. By this method he obtained the following results 
 in pounds per English acre, in tliree different courses of cropping, and 
 on the same land : — 
 
 Difference, or 
 
 Carbon derived Remarks. 
 
 from the air. 
 
 ( The first was a 5 years' 
 course — of potatoes or 
 red beet wiiji manure, 
 wheat, clover, wheat.» 
 oats; the second and 
 iT)ost productive rota- 
 lion was abandoned on 
 account of the climate ; 
 the third was a 3 years* 
 course. 
 
 The result of the first course indicates that — the land remaining, in 
 equal condition at the end of the four years as it was at the beginning — 
 the crops collected during these years contained three times the (]uanfity 
 of carbon present in the manure, and therefore the jAmits, during their 
 grotvth, must on the whole have derived two-thirds of their carbon from 
 the air. 
 
 It will be shown in a subsequent section that even when the soil is 
 lying naked the animal and vegetable matter it contains is continually 
 undergoing diminution, owing to decomposition and the escape of vola- 
 tile substances into the air. It is fair, therefore, to assume that a con- 
 
 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. 
 
 
 Carbon 
 
 in the 
 
 manure. 
 
 Carbon 
 
 in 
 
 the crops. 
 
 First Course 
 
 2513 
 
 7544 
 
 Second do. 
 
 _ 
 
 ,^^ 
 
 Third do. — 
 
 6031 
 
 6839 <! 
 
 3921 
 
WEIGHT UF CARBON IN THE ATMOSPHERE. 147 
 
 siilcrnble ponion of the carbon of the manure and of the soil would 
 naturally disappear during the four years' cropping above-mentioned, 
 and tliat, therefore, the proportion of carbon derived from the air in 
 Boussingaull's experiments, must have been really considerably greater 
 tlmn is indicated by tlie numerical results. 
 
 Let two-thirds of the entire quantity of carbon contained in a series of 
 crops be taken as the average proportion, [Lecture IL, p. 31,] 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,* the plants grown on each acre must annually ex- 
 tract from the air 10 cwt. or 1 120 lbs. of carbon in the form of carbonic acid. 
 
 § 2. Of the relation rohich the quantity of carbon extracted hy plants from 
 the air, bears to the whole quantity contained in the atmosphere. 
 
 But the (juesiion will here at once suggest itself to you — does not the 
 quantity thus extracted from the air really form a very large proportion 
 of the whole weiglu 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 iliat, by tlie results of De Saussure, the aver- 
 age quantity of carbonic acid in the atmosphere of our globe may be 
 estimated at o^^Tf part of its entire bulk. This is ecpial very nearly 
 to jj^yTf of its weight. f Or taking the whole weight of the atmosphere 
 at 15 lbs. on the scjuare incii — liiat of the carbonic acid will be 0*009 lbs. 
 or 63 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 stjuare inch of the earth's surface isonly 17| (17"39) grs. Upon 
 an acre this amounts to 7 tons. J 
 
 But if the crojj on each acre of cultivated land annually extracts from 
 the air half a ton of carbon, the whf)!e of the carbonic acid in the atmos- 
 phere would sustain such a vegetation over the entire globe for 14 years 
 only. And if we even suppose such a vegetation to extend over one 
 hundredth part of the earth's surface only, it still appears sufficient to 
 exhaust the carbonic acid of the air in 1400 years. 
 
 ' Boussingault states, that of all the plants usually cultivated for foofi— so far as his expert- 
 merits have gone— the Jerusalem arlictioke draws the largest portion of its sustenance from 
 the air — or yields the greatest ireight of food from Die smaHrst ir eight of man-ure. It is true 
 generally indeed that all those plants, vvliich,"like tlie Jenisaleni artichoke and the white 
 carrot, fsrnw freely on sandy soils containing little vegetable matter and with the addition 
 of little manure, extract the greatest proportion of their sustenance from the air. Such 
 plants, llierelore, are likely to prove the most profitable articles of culture where such soils 
 and a scarcity of manure simultaneously prevail. 
 
 t The mean of 22.') experiments made by Ue Saussure between 1827 and 1829 gave as 
 above staled about 4-10000 or l-2.500lh part for the mea"n bulk of the carbonic acid in the air, 
 which is nearly lj-l(500lhs of its whole weiglit. Among these observations the maximum 
 was 5-8 ten thousandths, the minimum 3-15. If vre lake the maximum biil/c at 6-lOOOOtha 
 of the air — the maximum iceigM of the carbonic acid is nearly 9-lOOOOllis of that of the at- 
 mosphere. In elementary works it is generally stated in round numbers at l-lOOOth of the 
 weight of the air, but if the best e.vperimental results we possess are to be any guide to us, 
 this is at least one-third too high. 
 
 It is al.-so of consequence to remark, that this estimate of the whole weight of the carbonic 
 acid in the air is founded on the supposition ihat, in the highest regions of the atmosphere 
 the carbonic acid is present in a proportion nearly equal to lhat in which it is found imme 
 diately above the earth's surface — which is by no means established. 
 
 X 15533 lbs. — an acre being 4S40 square yards, containing each 1296 square inchesi 
 
 •7* 
 
146 HOW TUK SUPPLY OF CARBONIC ACID IS RENEWED. 
 
 A very short period, compared even with the limits of authentic his- 
 tory, has yet elapsed since experiments began to be made on the true 
 constitution of the atmosphere ; we have no very trustwortliy data, 
 therefore, on which to found a confident ojiinion in regard to llie ]>ernia- 
 nence of the proportion of carbonic acid which it now contains. The 
 later observations of De Saussnrc do give a considerably lower estimate 
 of the quantity of this acid in tlie air than tliat which was deduced from 
 the result.s of the earlier experimenters; but the imperfection of the 
 modes of analysis formerly adopted was t(x> great, to justify us in rea- 
 soning rigorously from the inferences to which they led. We cannot 
 safely conclude from them that the proportion of carbon in the atmos- 
 phere has really diminished to any sensible extent during this limited 
 period; while the recorded identity of all the phenomena of vegetation 
 renders it probable that the proportion has not sensibly ditninished even 
 witliiu historic times. 
 
 From what sources, then, is the supply of carbonic acid in the atmos- 
 phere kept up? — and if the ])roportion be permanent, by what compen- 
 sating processes is the quantity which is restored to the atmosphere 
 produced and regulated ? 
 
 § 3. I-Iow the supph I of carbonic acid in tJie atmosphere is renewed 
 
 and regulated. 
 On comparing, in a previous lecture, the riuaniity of rain which falls 
 with that of the watery vapour actually jiresent in the air, we saw rea- 
 son to believe that even in a single year the same portion of water may 
 fall in rain or dew and ascend again in watery vapour several succes- 
 sive times. Is it so also with the carbon in the air? Does that which 
 feeds the growing jilanl to-day, again mount up in 'he form of carbonic 
 acid at some future time, ready to minister to the sustenance of new 
 races, and to run again ihe same round of ever- varying change ? Such 
 is, indeed, the general history of the agency of the carbonic acid of the 
 atmosphere ; but when once it has been fixed in the plant it must pass 
 through many successive changes before it is again set free. The con- 
 ditions, alsf), under which it is restored to the atmosphere are so diver- 
 sified, and the agencies by which, in each case, it is liberated, are so 
 very distinct, as to require tliat the several modes by which the carbon 
 of plants is reconverted inti> carbonic acid and returned to the air, siiould 
 be made topics of separate consideration. 
 
 I. ox THE PRODUCTION OF CARBONIC ACID BY RESPIRATION. 
 
 The air we breathe when it is drawn into the lungs, contains ^^^^th 
 of its bulU of carbonic acid ; when it returns again from the lungs, the 
 bulk of this gas amounts, on an average,* to ^^ih of the whole; or its 
 quant.iti/ is increased one hundred times. 
 
 The actual bulk of the carbonic acid emitted from the lungs of a sin- 
 gle individual in 24 hours varies exceedingly ; it has been estimated 
 however, on an average, to contain upwards of five ounces of carbon. f 
 
 * It varies in different indiviiliials from 2 to 8 per cent, of Itie expired air. In animals it 
 varies also with the speries. Ttie air from Ihe lungs of a cat contains from W to 7 per cent., 
 of a doa from A\ to (ij, of a rabbit from 4 to 6. and of a pi^i'on from 3 to 4 per cent, of the 
 whole bulk. — Dulong, Anna!., de fhhn. et de P/njs., third faeries, I , p. 465. 
 
 t Davy, and Allen, and Pepys, estimated the weight of carbon evolved in a day at upwards 
 of 11 ounces, a quantity which all writers have concurred in receiving with suspicion. 
 
TUK COMBUSTION OF ORGANIC MATTER. 149 
 
 A full grown man, therefore, gives off from his lungs, in the course of a 
 year, upwards of 100 lbs. of carbon in tlie form of carbonic acid. 
 
 If the t|uanuiy of carbon thus evolved from the lungs be in proportion 
 to the weight of the animal, a cow or a horse ought to give off six limes 
 as much as a man.* From indirect experiments, however, Boussin- 
 gault estimated the quaniity of carbon actually lost in this way by a cow 
 at 2200 grammes in 24 hours, and by a horse at 2400 grammes. — [Ann. 
 cle Chim. eldc Pliys., Ixxi., pp. 127 and 13G.] These quantities are equal 
 to 6 or 7 times the amount of carbon given off from the lungs of a man. 
 
 If we suppose each inhabitant of Great Britain, young and old, to ex- 
 j)ire only 80 lbs. of carbon in a year, ihc twenty millions would emit 
 seven hundred thousand tons ; and, allowing the cattle, sheep, and all 
 other animals, to give oB' twice as much more, the whole weight of 
 carbon returned to the air by respiration in this island would be about 
 two millions of tons, or the ipianiity abstracted 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 iuto the stomach in the form of food. Suppose the car- 
 bon 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 ordi- 
 nary processes of respiration, at least one-third of tlie 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 ex- 
 lent of the same gas.f And since all are sustained by the produce of 
 the soil, it is obvious that the process of animal respiration is one of 
 those methods by which it has been provided that a large portion of the 
 vegetable productions of ilie globe should be almost immediately re- 
 solved into the simpler forms of matter from which it was originally 
 compounded, and again sent up into the air to minister to the wants of 
 new races. 
 
 II. — ON THE PRODUCTION OF CARBONIC ACID BY COMBUSTION. 
 
 Another imporlant source of carbonic acid is familiar to us in the re- 
 sults of artificial combustion. 
 
 In the jjrevious lecture 1 have shown how, by the action of the sun's 
 rays upon the leaf, the carbonic acid absorbed from the atmosphere is 
 deprived of its oxygen, and its carbon afierwards united to the elements 
 of water for the i)roduction of woody fibre. During the process of com- 
 bustion, 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 carbonic acid and water. 
 
 Thus, when wood (wo(xly fibre) is burned in the air, oxygen disap- 
 j)ears, and carbonic acid and watery vapour are alone produced. The 
 theory of this change is simple. 
 
 • Eslimating the ordinary weight of a man at 150, and of a cow at 800 to 900 lbs. — See 
 Sprongel, Lchre vcm Lhinger, p. 208. 
 
 ' That the proportion must ha less in the larger aiiimals is certain, since the daily food of 
 a cow may bo stated fient-rally as equivalent to 25 lbs. of hay, containing npwards of 10 lbs. of 
 carbon. If one third of this were given ofTfrorn the lungs, the quantity of carbon (3J lbs.) 
 evolved would be ten times greater than was indicated by the experiments of Boussinsault, 
 ajid nearly double of what the weight of a cow, compared wUh inat of a man, requires. 
 
150 PRODUCES CARBO.MC ACIU AND VVATKR. 
 
 It wi)l be recoUeclrd (p. 135) thai, in forjning an equivalent of woody 
 fibre or of sugar, 24 of oxygen were given off", chiefly by the leaf — so in 
 again resolving these substances into carbonic acid and water, 24 of oxy, 
 gen are absorbed. Thus — 
 
 1 of Woody Fibrk = C,2 Hg O3 
 24 of Oxygen . =; 0.,i 
 
 12 of 8 of 
 
 Carbonic Acid. Water. 
 
 Sum. . . =Ci2H3 0.32 = 12CO2 + 8HO. 
 
 Or, 1 of Cane Sugar =Ci2HjoO,(, 
 24 of Oxygen . . = Oo^ 
 
 12 of 10 of 
 
 Carbonic Acid. Water. 
 
 Sum . . . =C,2 H,o O34 =12C02+ lOHO. 
 
 The same law holds in regard to all other vegetable substances. They 
 are resolved into carbonic acid and water, in proportions which neces- 
 sarily vary with the chemical constiturion of each; 
 
 It applies also to all bodies of vegetable oric^in, among whicli nearly 
 all combustible minerals may be reckoned. The peat and coal we burn 
 in our houses and manufactories, when supplied with a sufficiency of 
 atmo.spheric air, are resolved during combustion into carbonic acid and 
 watery vapour. 
 
 Some vegetable substances contain a small quantity of nitrogen. 
 When these are burned, this nitrogen escapes into the atmosphere, — 
 generally in an uncombined state, — and mingles with the air. So in 
 aniinal substances, nearly all of which contain nitrogen as an essential 
 constituent. During perfect cot^bostion the wliole of the carbon is dis- 
 sipated in the form of carbonic acid, while the nitrogen rises along with 
 it in an elementary state 
 
 The result of tliis unifjrm subjection of a.ll combustible matter to the 
 operation of this one law, is the constant production on the surface of 
 the globe of a vast (juantity of carbonic acid ; — tl7e re-conversion of large 
 masses of organic maUer into the more elementary compoiuids 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 fossile coal lie almost useless things in reference to 
 animal and vegetable life, — man employs ihem in a thousand ways as 
 ministers to his wants, his comforts, or his dominion over nature— and 
 in so doing, himself directly iliough unconscioiisly 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 durinnr 
 the general vegetation of the globe, is thus annually restored to the at- 
 mosphere by the burning of vegetable matter. That it must be very 
 great, will appear from the single fact, tiial by far the greater part of tlie 
 globe is dependent for its supply of fuel on the annual produce of its 
 forests; — while even in those ruore 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. 
 
LAW OP TrtE DKCAY OP VEfiETABLE MATTER. 151 
 
 lu connection with this subject, I must draw your attention to one in- 
 teresting, as well as imiiortant, fact. I have spoken of coal as a sub- 
 stance of vegetable origin, and there is no doubt that all the carbon it 
 contains once floated in the air in the form of carbonic acid. But the 
 period when it was so mixed with the atmosphere is remote almost be- 
 yond conception. When, therefore, we raise coal from its ancient bed 
 and burn it on the earth's surface, we add to the carbon of the air a por- 
 tion which has not previously existed in the attiiosphere of our time. 
 
 The coal consumed in Great Britain alone is estimated at 20 millions 
 of Ions, containing on an average al 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 (p. 147) of carbon derived from the air, the coal con- 
 sumed 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 (p. 12), the coal we annually consume produces 
 a quantity of carbonic acid tohich is alone sufficient to supply food to the 
 crops that grow upon seven-eighths of the arable land of this country. 
 
 IH. PRODUCTION OF CARBONIC ACID BY THE NATURAL DECAY OF VEGE- 
 
 . TABLE MATTER. LAW OF THIS DECAY. 
 
 Over large tracts of country in every part of the globe, the vegetable 
 productions of the soil are never cropped or gathered, but either accumu- 
 late—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 South- 
 ern America. 
 
 The fined results of this decay are the same as those which attend 
 upon ordinary combustion, but the conditions under which it takes place 
 being ditlerent, the immediate results are to a certain extent different 
 also. 
 
 When a vegetable substance is burned in the air, the oxygen of the at- 
 mosphere is the only material agent in effecting the decomposition. 
 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 temperature 
 of the atmosphere, vegetable matter is exposed to the action of both air 
 and waier ; these both co-operate in inducing and carrying on the decom- 
 position, 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 Hnally resolved into carbonic acid and water, 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 pre- 
 sent purpose. 
 
 In combustion, as we have seen, the whole of the vegetable substance 
 is resolved directly into carbonic acid and water, at the expense of the 
 oxygen of the atmosphere. In natural decay a small and variable por- 
 tion only is so changed, but to the extent to which this change does take 
 place carbonic acid is directly formed and sent up into the air. Suppose 
 such a change — a slow combustion in reality — to take place to a certain 
 
152 BY NATURAL DECAY IT IS FINALLY RESOLVED 
 
 extent, and let us consider what becomes of the remainder of the vegeta 
 ble matter. 
 1°. If we add 
 
 e of Carbonic Acid . . = Cg Ojg 
 
 to 6 of Light Carburetted ? p tt 
 
 Hydrogen (CHa) ^ — ^e "12 
 
 we have the sum . . = C,2 H13 0,2 ; or, one of 
 grape sugar; — that is, one of grape sugar may be formed out of the ele- 
 ments of 6 of carbonic acid, and 6 of Hght carburetted hydrogen. Or, 
 conversely, grape sugar being already produced, it may he resolved or 
 decomposed into these two compounds in the same proportions, without 
 the aid of tlie oxygen of the atmosphere. 
 2°. So if to 
 
 1 of Woody Fibre = C,2 H3 O3 
 we add 4 of Water . . = H4 O4 
 
 Carbonic Light Carbu- 
 
 Acid. retled Hydrogen, 
 we have, as before, C,o 11,2 Oi3 = 6COo + 6 CHg; 
 Or by the aid of ihe elements of 4 atoms of water, woody fibre may be 
 resolved into 6 of carbonic acid and as many of light carburetted 
 hydrogen. 
 
 3°. Again, in the case of a vegetable acid, if to 
 
 1 of Tartaric Acid = C, Hg O5 
 we add 1 of Oxygen . . = O, 
 
 Carbonic Light Oarbu- 
 
 Acid. retled Hydrogen. 
 
 we have C, Hg 0« = 3 CO2 + CH, ; 
 That is, by the aid of one of oxygen from the air, one of tartaric acid 
 may be resolved into 3 of carbonic acid, and 1 of liglit carburetted 
 liydrogen. It is easy to see how any other of the more common vegeta- 
 ble productions may — either at the expense of its own elements, as in 
 grape sugar — or by the aid of those of water, as in woody fibre — or of 
 the oxygen of the atmosphere, as in tartaric acid — be resolved into car- 
 bonic acid and light carburetted hydrogen, in certain proportions. 
 
 Now, such a resolution does really take place to a considerable extent 
 in nature, during the decay of organic substances in moist situations. 
 Hence the evolution of light carburetted 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 physiologists (p. 50) 
 to contribute as food to the ordinary nourishment of plants. It is pro- 
 duced in nature in many and varied situations, and it has been found 
 by experiment to exercise a visible influence upon the growth of plants; 
 — being so produced where young plants grow, is it nevef imbibed by 
 them ? — being possessed of tliis influence, is it entrusted witli no control 
 over the general vegetation of the globe ? 
 
 However this may be, by far the greatest portion of both these gases 
 escapes into the air ; — tlie carbonic acid to fulfil those purposes which 
 
INTO CARBOMC ACID ANU WATKR. 153 
 
 have already been considereil, — t!ie light carburetted hydrogen to under- 
 go a further change, by wliich it also is resolved into carbonic acid and 
 water. Thus, if to 
 
 1 of Light Carburetted Hydrogen = CHo we add 
 4 of Oxygen = O4 
 
 Carbonic Acid. Water. 
 
 We have CH, O, or CO2 + 2 HO 
 
 Or one of this gas with 4 of oxygen may be changed into 1 of carbonic 
 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 instant, to be decom- 
 posed. 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 ha|)pens that of the vast (juaiiiiiy of this and other combustible 
 gases which are continuaily esca|)ing into the air, so few traces are dis- 
 cernible even by the aid of the most refined processes of art. By a wise 
 provision of natuYe such substances as are void of use to either animals 
 or plants, if not speedily removed from the air altogether, are there con- 
 verted into such new forms of matter as are fitted to minister to the ne- 
 cessities of living beings. 
 
 Though therefore in the natural decay of vegetable matter in tlie pre^ 
 sence of air and moisture, a certain portion of its carbon escapes into the 
 air in the form of light carburetted hydrogen, this compound is but a 
 step towards the final change into carbonic acid and water. In the soil 
 the vegetable matter is continually undergoing decay^ various sub- 
 stances are produced in greater or less (pianlity, 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 nour- 
 ishment of all plants. 
 
 While in the soil some part of this vegetable matter assumes forms 
 which are capable of entering again into the roots of li\^ng ])lants, and, 
 without further resolution in llie air, of being converted by the living 
 plant into portions of its own sub.stance. The nature and composition 
 of these forms of matter, so far as they are known, will be considered in 
 a subsequent lecture. — [See Part H., Lectures XL-XHL, " On the 
 constilution of soils."] 
 
 It is upon the final result of this natural decay to which all vegetable 
 matter is subject, that the carbonic acid of the atmosphere depends for 
 its largest supplies. The rapidity with which organized bodies perish, 
 and become resolved into gaseous compounds, depends J)artly upon the 
 climate and partly on the nature of the substances themselves, — but all 
 liurry 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 obedience of all dead matter to one fixed law that ihe exist- 
 ing condition of things is maintained ; — and thus it happens that either 
 by the rcsjuration of the animals wliich live upon it, by the process of 
 
154 EVOLUTION OP CARBONIC ACID IN VOLCANIC COUNTRIES. 
 
 combustion, or by thai of spontaneous decay, the entire crop of vegeta- 
 ble 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 (o 
 the air in the precise proportion in which they have been taken from it. 
 
 VI. NATURAL EVOLUTION OF CARBONIC ACID IN VOLCANIC 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 prevented — and no 
 other sources, independent of existing organic matter, from which car- 
 bonic acid may be supplied to the air. 
 
 If the whole of the carbon be not returned to the air, the carbonic acid 
 of the atmosphere may be undergoing diminution ; 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 (o the air a 
 large quantity of carbonic acid which has never before existed in the at- 
 mosphere of our lime. In many volcanic districts also, carbonic acid is 
 observed to issue in large (juantiiy from cracks and fissures in the earth ; 
 — accompanied sometimes by water, forming mineral springs, from 
 which the copious emisson 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 quantity 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 Bischof at not less than 
 100,000 tons, containing 27,000 tons of carbon. In many other districts, 
 especially where active volcanoes exist, the volume of gas given oflT 
 may be quite as great, though no attempts have hitherto been made to 
 estimate its real amount. 
 
 Yet though absolutely large, the quantity of carbonic acid disengaged 
 in this way from the earth, is really small when compared either with 
 the entire quantity supposed to be present in the atmosphere, or with 
 that which is retjuired for the growth of the yearly vegetation of the 
 globe. Suppose that from a thousand spots on the earili's surface a 
 quantity of carbonic acid equal to the above estimate of Bischof escapes 
 constantly into tlie air, the weight of carbon (27 millions of tons) thus 
 diffused through the atmosphere would be only ecjual to that which is 
 yearly drawn from the air by 54 millions of acres of land under cultiva- 
 tion (p. 147), and 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 mat- 
 
155 CARBUN PERMANENTLY WITHDRAWN I'UOM THE Alfl. 
 
 ter, or ny the more rapid process of combustion, — the constant addition 
 of carbonic acid derived from volcanoes, and from the combustion of fos- 
 sil coal, should gradually, though slowly, augment the proportion of this 
 gas in the air we breathe ; — unless it be perpetually undergoing a per- 
 manent diminution, to at least an equal extent, from the operation of 
 otiier causes. In reference to this point there are three circumstances 
 which are proper to be considered : — 
 
 1°. It has been observed that, as we recede from the land and ap- 
 proach the cenire 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 extent, absorbing carbonic 
 acid from the atmos|)bere, without afterwards restorii]g it, so far as is 
 yet known, by any compensating process. 
 
 2°. The waters which flow info the sea or great lakes constantly 
 bear down with them jxirtions of animal and vegetable matter. These 
 fall along with the mud whicli the waters hold in suspension, 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 inatter 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 withdrawn 
 from the atmosphere by these several agencies. There is reason to be- 
 lieve that it is quite as great as the quantity added to the air by the 
 combustion of coal, and by the evolution of carbonic acid in volcanic 
 districts. Indeed, the supply from these two sources appears to return 
 only a small portion of that carbonic acid which is abstracted from the 
 air by the ageucies just siaicd, and which have been in operation during 
 every geological epoch. 
 
 Conclusions. — The general conclusions, therefore, which we seem jus- 
 tified in drawing in regard to the supply of carbonic acid to the atnios- 
 ])here 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. 
 
 2°. That a still larger portion is more slowly returned by the gradual 
 re-conversion of vegetable substances into carbonic acid and water dur- 
 ing the process of natural decay. 
 
 3°. That nearly all the remainder is given back in the results of or- 
 dinary combustion. 
 
 4°. That a further portion, wliich has not previously existed in the 
 atmosphere of our time, is conveyed to ii by the burning of fossil fuel, 
 and by the emission of carbonic acid from cracks and fissures in the 
 surface of the earth ; yet that the quantity thus added cannot be sup- 
 posed to exceed that which is constantly and permanently separated 
 from the at mosfihere by otljer causes. 
 
 The balance of all the evidence we possess is probably in favour of 
 'he opinion that the carbonic acid in the atmosphere is slowly diminish- 
 
156 AMMONIA IN THK AIR — HOW DECOMPOSID. 
 
 ing; we have, however, no satisfactory evidence either from theory or 
 experiment that it has undergone any sensible diminution 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 present in the manure, 
 supposing it all taken up and appropriated by the plant, is seldom equal 
 to that contained in tJie series of crops which this manure assists in raising. 
 
 Thus, in the experiments of Boussingault already described (p. 144), 
 the manure added previous to the first, or four years' course, contained 
 
 157 parts of nitrogen, while the crops contained 251 parts, — or nearly 
 two-thirds more than could be derived from the artificial manure. 
 
 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 tlie nitrogen absorbed by plants enters in the state of ammonia, and 
 that the excess above what is present in the manure is drawn either 
 from the soil or from tlie air. This opinion, advanced by so high an 
 authority, demands our attentive consideration. 
 
 Ammonia has been detected in many clays, and traces of it may be 
 discovered in most soils, but it is not known to be a natural 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 stiflTclays when fallowed, of burned clay 
 when applied as a top-dressing, and of gypsum on grass lands [see note 
 to page 53], to the larger quantity of ammonia which the surface of the 
 soil is by these means caused to absorb and retain. 
 
 There is no question that ammonia is present in the atmosphere in 
 small and variable quantity (p. 37). Whence is this amtnonia derived, 
 and is its quantity sufficient to supply the demands of the entire vegeta- 
 tion of the globe ? 
 
 When animal substances undergo decays nearly all the nitrogen they 
 contain is ultimately separated from the 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 ammonia thus formed, much 
 ascends into the air, chiefly in combination with carbonic acid as carbonate 
 of ammonia (smelling salts), and much remains in the soil. Were the 
 whole of the nitro^n contained 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 leaves of 
 the living races; and thus the same ammonia, [or ammonia containing 
 the same nitrogen — supposing the hydrogen to have been changed] 
 might again and again return into the circulation of new vegetable tribes, 
 and be always alone sufficient to supply all the demands of the exist- 
 ing vegetation of the globe. 
 
 But of ttie ammonia thus formed, a portion is daily washed from the 
 soil by the rains and carried to the sea, and much more probably is 
 
 In another work (CAemico/ Geology) now prpparing for publication, I have discussed 
 this question in conneclion with purely Geological considerations and without reference to 
 our time : but it would be out of place lo introduce liere any train of reasoning whicli is not 
 calculated to throw light on the phenomena of the existing vegetation ol the globe. 
 
AMMONIA KVOLVilD FHUM VOLCA^uKS. 167 
 
 waslicd tVom tne air by the waters of tliesea itself, or by the rains wiiich 
 fall directly into the wide oceans ; and we know of no compensating 
 process by wliich this ammonia can be restored to the air, and again 
 made useful to vegetation. 
 
 Besides, of that which still remains in the air much must undergo 
 decomposition by natural processes. In treating in a preceding section 
 of the evolution of light carburetted hydrogen during the slow decay of 
 vegetable matter (p. 153), I have shown how, in conse(|uence of its ad- 
 mixture with the oxygen of ilie atmosphere, this gas is finely decom- 
 posed, while carbonic acid and water are produced. Ammonia in like 
 manner will burn in oxygen gas, and when mixed with atmospheric air 
 may be decomposed by the electric spark — water at the same time being 
 formed and nitrogen set free. Thus, 
 
 if with 1 of Ammonia = NH3 
 we mix 3 of Oxygen = O3 
 
 3 of water. 1 of nitrogen. 
 
 we have the sum Nlij O3 = 3 HO + N 
 
 or, when diffused throtigh the air, 1 of ammonia, with the aid of 3 of 
 oxygen, will yield 3 of watery vapour, while the nitrogen may* mingle 
 with the air in an elementary form. Can we doubt that ammonia 
 is thus decomposed in ilie air'.' Not to speak of other forms assumed 
 by the electricity of the atmosphere, can the thunder-storms of the tropi- 
 cal regions pass unheeded the ammoniacal vapours tliey must meet 
 with in their course ? 
 
 I conclude, then, that of the ammonia which is Ibrmetl from tiie nitro- 
 gen actually existing in animal and vegetable substances daring their 
 decay, only a comparaii.vebj small portion ever returns again to minister 
 to the wants of new races. f 
 
 But if plajils obtain all their nitrogen from ammonia, f how is this 
 waste re])aired — whence are new supplies constantly derived ? 
 
 We have seen that, \n certain volcanic countries, carbonic acid is 
 evolved in vast ([uantities from rents and fissures in the earth. In some 
 of these districts — and this has been observed more esiiecially in Italy 
 and Sicily, and it i.s said also to sonje extent in China — ammonia is 
 likewise given of}", in combination generally with some acid, and most 
 frcipiently with the muriatic acid in the f)rm of sal-anmaoniac (muriate 
 of ammonia). •' This ammonia,'''' Liebig is correct in saying, "/ias not 
 been produced hij the animal organism ;" but he assumes a very doubt- 
 ful position when he adds, "if existed before the creation of human be- 
 ings ; it is apart, a primary constituent of the globe itself.^'' — [Organic 
 Chemistry applied to Agriculture, p. 112.] 
 
 Where, we might ask, has this ammonia existed during all past time 
 — from what deep caverns of the earth does it now escape ? 
 
 ' I say may, because it may at the same time combine with oxygen anJ form nitric acid. 
 — See the following section, p. 239. 
 
 1 1 might ailU, that of tlie ammonia whicti does return, and is again absorbed, a portion is 
 subsequently decompused in the interior of living plants, as is shown by tlie evolution of 
 nitrogen from the common leaves of some and the flower leaves of others. 
 
 X " Wild plant.s obtain mor': nitrogen fiotn the atmosphere, in the/orm of ammonia, than they 
 require for Iheir growth, fok the w.iler whicli evajiorates through their leaves and blossoms 
 emits, alter a lime, a pulrid smell — a peruliarity possessed only by such bodies as contain 
 nitrii<:en."— =[Liebig, Organic Ckemialry appliad tu AgricuJture, p. 85.] Does the fact here 
 stated, justify the conclusion which appears to be drawn from it 1 
 
158 INDIRECT PRODUCTION OF AMMOiMA. 
 
 This opinion of Liebig, as well as the paramount influence he as- 
 cribes to ammonia over the vegetation of the globe, are based chiefly on 
 the fact tliat 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 tlie production of ammonia, by the indirect union of tliese ele- 
 ments, is daily going on in nature, and can even be effected by differ- 
 ent processes of art. Thus — 
 
 1°. When organic substances, which contain no nitrogen, are oxidized 
 in the air, ammonia is not unfre(]tientiy f(jrmed (Berzelius). Hence 
 it must be produced in unknown (juantity during the annual decay of 
 all vegetable substances. 
 
 2°. When organic substances are oxidized in the presence of air and 
 water — as when moist iron fihngs are exposed to the air (Chevallier), 
 or when certain oxidized substances are decomposed in the air by 
 means of potassium (Faraday), or when metals, such as tin filings, are 
 rapidly oxidized by means of niiric acid, ammonia is also produced in 
 variable quantity, tlence the absorption of oxygen, even by the inor- 
 ganic substances of ihe soil, may izive rise to the formation of ammonia. 
 But, 
 
 .3^. The fact which most clenrly illustrates the production of am- 
 monia 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 currant of 
 moist air be made to pass over red-hot charcoal, carbonic acid and am- 
 monia are simultaneously formed.* This is in reality only a re])(!tilion 
 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 instanlf of its liberation, the hydrogen of the water com- 
 bines with the nitrogen of the air, and forms a.mmonia. 
 
 The source of the ammonia evolved in volcanic districts, therefore, is 
 no longer obscure. The existence of combustible matter in such dis- 
 tricts, 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 
 he alone necessary to the production of ammonia. It is unnecessary, 
 then, to have recourse to doubtful speculations in order to account ibr 
 the natural reproduction of aii^moi^ia, to a certain extent, in the place 
 
 ' Tliis experiment is easily performed by drawing a. current of mixed atmospheric air 
 and steam tliroiij;h a led-hot gun-barrel filled with well-burned charcoal, and causing the 
 current, on leaving the barrel, to pass through water acidulated with niurialic 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 moi-c readily and more largely 
 lake place in tlie interior of the earih, where combustible substances at a high temperature 
 happen to be exposed to a current of atmospheric air, mixed with watery vapour. 
 
 t A beautiful ilhisrration of the tendency wliicli elemenlai"y substances have to unite with 
 each other at the inufnnt of their liberation in what chemists call their nascent state, is men- 
 tioned by Range. — Einleitung in die teclinisrhe Chemie, p. 37.3. 
 
 If 1 part of hydrate of polasih and 20 of iron filings be heated together, hydrogen only is 
 giren off. 
 
 If I of nitrate of potash and iMof iron filing.s be heated together, nitrogen only is givfnoff. 
 
 But if 40 of iron filings be mixed with 1 of hydrate and I of nitrate of potash, and then 
 heated, ammonia becomes perceptible. 
 
 The nitrogen and hydrogen being given off together, at the same instant, some portions 
 of each find Uieniselves 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 lime, and in the presence of one another. 
 
KITRIC ACID KXISTS LARGKLY IN >:ATURK. 150 
 
 ot that wliicli is constantl}' undergoing decomposiiion by the agency ol 
 Ciiuses such as iliose above described. 
 
 But is the iudeRnile quantity of ammonia reproduced by these indi- 
 rect methods sufficient to rei)lace all ihat is lost? Can it be supposed 
 to inij)art to plants all the nitrogen ihey 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, in the form of nitrates of soda, potash, &c., it is 
 spread uj)on the soil, it greatly promotes the growth and luxuriance of 
 the crop and increases its produce ; and 
 
 2°. That, when other circumstancs are favourable to vegetation — as 
 in certain districts in India — the presence of an appreciable quantity of 
 these nitrates adds largely to the fertility of the soil.* 
 
 Tiie same efiects are un(iue?.tioiiably produced by the addition of am- 
 monia or by its natural presence in the soil. The beneficial influence 
 of both compounds, then, being recognized, the relative extent to which 
 each operates upon the general vegetation of the globe will be main- 
 ly determined b}' ihe circumstances and the quantity in which they res- 
 pectively exist or are reproduced. 
 
 In regard to the existence of nitric acid, it is not known to form a 
 necessary constiiiienl of any of the solid rocks of which the crust of the 
 globe is composed, but is difl'used almost universally through the soil 
 which overspreads the surface. In the hotter regions of the earth, in 
 India, in Africa, and in South America (p. 56), it in many places accu- 
 mulates in sufficient (luanlity to form incrustations of considerable thick- 
 ness over very large areas, and in many more it can be separated by 
 washing the soil. Even in the climates of Northern Europe, it is rare- 
 ly absent from the water of artificial wells, into which the rains, aftei 
 filtering through the surface, are permitted to make their way.f 
 
 On the whole, nitric acid and its compounds. ap])ear to exist, ready 
 formed in nature, in larger quantity than either ammonia or any of its 
 compounds. 
 
 ' For the following, and other interesting notices, regarding Indian agricultare, I am in- 
 debted to Mr Fleming, ol'Barochan, in Renfrewshire, whose long residence in the districts 
 to wiiicli he alludes, as well as the interest he lakes in practical agriculture, renders his tes- 
 limony very valuable : 
 
 "The districts of Chaprah, Tirhoot, and Shahabad, near I'atna, where a large proportion 
 of the saltpetre sent from Uengal is produced, are considered the most fertile in Bengal, 
 producing 2 and sometimes 3 crops yearly. The natives of these districts, particularly a 
 caste caJIed Quirees (lieretlitary gardener.'*), who cultivate the best land, and produce the 
 best crops, are in the habit of irrigating their fields with water from wells so strongly im- 
 pregnated with saltpetre and other salts as to be quite brackish, and they consider onions, 
 turnips, and peas, most benefitted by this irrigation. Grain crops also grow most luxuriant- 
 ly oti lands yielding saltpetre, wtiere there is enough of rain within a week or two after the 
 seed is sown, but if a drought follows the sowing, and continues for 3 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 used for 
 fuel, but the Quirees collect the ashes of cow dung and of burned wood, and use it as a ma- 
 nure in some cases, chiefly for Ihe poppy plant. 
 
 "The Hindoos have forages been well acquainted with Ihe rotation of crops, and the ad- 
 vantages of fallowing land, allhoui;h a great proportion of the land is almost constantly in 
 rice, Indian corn, or millet, during the rainy season, and in wheat or peas during the dry 
 season." 
 
 t It occurs in the wells of the neighbourhood of Berlin (Mitscherlich), in the form of ni- 
 trates of potash, lime, and magnesia, in the wells around Stockholm, and may be expected 
 in all wells that are dug (Berzelius). — Traite de Chemie, iv., p. 71. 
 
160 FORMATION OF NITRIC ACID. 
 
 Of these nitrates, ns the}' do of nmmonia, the rivers must be continu- 
 ally bearing a portion lo the sea, but there are in nature unceasing pro- 
 cesses of rej)ro(Uiction, by wliicli not only this waste of the nitrates is 
 repaired, but that further waste, also, which i'^ caused by their absorp- 
 tion into tlie roots and subsequent decomposition in the interior of phints. 
 Let us shortly consider these processes of reproduction. 
 
 1°. Wiien a succession of electric sj)arks is passed through common 
 air, nitric acid (NO5) is slowly but sensibly formed. The currents of 
 electricity which in nature traverse the atmospliere must produce the 
 same effect, and the passage of each flash of liglitning through the air 
 must be attended by the formation of some portion of this acid. 
 
 After a thunder-storm jilants appear wonderfully refreshed; in thun- 
 dery weather they grow most luxuriantly, and other things being e(]ual, 
 those seasons in which there is much thunder are observed to be the 
 most fruitful. Some have ascribed these results to the immediate agency 
 of electricity on the growth of plants. — [Sprengel, Ckeniie, I., p. 99.] 
 It is not equally possible that tiiey may be connected with this necessary 
 production of nitric acid .' 
 
 In the rain which fell during 17 thunder-storms, Liebig found nitric 
 acid always present and generally in combination with lime and am- 
 monia. In the rain which fell on GO other occasions, he could detect it 
 only twice. In minute quantity nitric acid is difficiilt to detect. How 
 inuch then must be formed in a thunder-storm, even in our climate, to 
 make the presence of this acid always appreciable in the rain that falls 
 — how vast a quantity in those warmer climates where such storms are 
 so frequent and so a[)palling! 
 
 2°. When a mixture of ammonia with 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 oxidize the whole of the am- 
 monia* (Bischof). Hence, if in the air, as we have seen reason to be- 
 lieve, the ammonia given off from decaying animal matters, and from 
 other sources, he decomposed by the atmospheric 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, combine with some of the ammonia which still remains in. 
 the air. Hence the existence and production o^ nitrale of ammonia in 
 the atmosphere, and the consequent presence of tliis acid along with am- 
 monia 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 whieli certainly renders improbalile the existence 
 of this com[)ound in the atmosphere in the large (]uaniity supposed by 
 some [see especially Liebig's Organic Chemistrji applied to Agriculture, 
 p. 74], this same cause is at the same moment constantly rejiroducing 
 nitric acid. And, though much of what is thus produced must neces- 
 sarily, as in the case of ammonia, be carried down to the sea by the 
 rains, or be directly absorbed by the waters of llie ocean themselves, yet 
 
 * It was shown above (p. 157), that 1 of ammonia ( NH3 ) requh'es 3 of oxyjjen to decom- 
 pose it, forming 3 of water, ami setting the nitrojjen free. But, in reality, as Biscliof has 
 shown, tlie nitrogen is not wholly set free, but a portiou both of its hydrogen and nitrogen 
 combine with oxygen (are oxidized) at the same instant, forming simultaneously both water 
 (HO), and nitric acid ( NO5 ). 
 
ARTIFICIAL NITRE BEDS. 161 
 
 it is obvious that in whatever proportion we may suppose the ammonia 
 of the air to reach the leaves and roots of plants, in no less proportion 
 must the nitric 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 substan- 
 ces in moist air, ammonia is formed at the expense of the hydrogen of 
 the water and of the nitrogen of the air. In consequence of, f)r in con- 
 nection with, such decay, nitric acid is also largely produced in nature. 
 
 The most familiar, as well as the most instructive examples 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 occa- 
 sionally watered with liquid manure, and turned over, to expose fresh 
 portions to the air. After a time, perhaps once a year, tiie whole is 
 washe<i, wlien the water wjiich comes off is found to contain a variable 
 (]uantity of the nitrates of [)Otash, soda, lime, and magnesia, which are 
 emploved for the manufacture of saltpetre. In tliese nitre beds it has 
 been observed that the production of nitric acid either does not take plaec 
 at all, or onlv with extreme slowness, unless animal and vegetable mat- 
 ter be present in considerable proportion. And yet the (piantity of nitric 
 acid which is formed is much greater than could be produced by the 
 oxidation of the whole of the nitrogen 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 the 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 
 exposed to the air. 
 
 If ap])earp, therefore, that organic matters are in our climate necessa- 
 ry to cause the formation of nitric acid to commence, but that after it has 
 begun it will proceed in the same heap for an indefinite ])eriod, and at 
 the expense apparently oflhe nitrooen nf the air only. 
 
 Compost heaps are in general only artificial nitre beds, often unskil- 
 fully prepared and badly managed, [iroducing, however, a certain quan- 
 tity of nitrates, to the presence of which their effect on vegetation may 
 not unfrequently be ascribed. To tfiis fact we shall hereafter recur. 
 
 The soils in the plains of India, and in other similar spots in the trop- 
 ical regions, may be regarded as nalurnl nitre beds, in which, the decay 
 of organic matter being vastly more rapid than in our temperate regions, 
 tiie production of nitric acid is rapid in proportion.! 
 
 4^. But in many localities in which tlic presence of organic matter is 
 
 * Dumas, Traite. de Chemie, II., p. 725. He aiiiis, that 100 lbs. of nitre contain the nitrogen 
 of 75 lbs. of nnllnnry animal inaiter, supposed in a dry slate, or of 3i30 or 400 lbs. in its ordi- 
 nary slate of moisture. — a much greater relative proportion of animal matter than is ever 
 added to the <icap. 
 
 t We are as yet too little acquainted with the natural history of tlie district of Arica in 
 Soulli America, in which, as already slated (p. 5()), the nitrate of soda has been accumulateu 
 in sucli 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 an- 
 cient 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 pe- 
 riod emptied themselves into or fed the lake. 
 
1( 2 NITRE CAVES. — NITRIC ACID FORMED IN THE SOIL. 
 
 not to be recognized in sensible quantity, the production of lliis 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 limestone ridge, yields an 
 inexhaustible supply of nitrate of lime. During 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 rushing — inwards in winter, and outwards during 
 the summer months. On the plaster of old walls, especially in damp 
 situations, an eflfloresccnce of tliis and other nitrates is frecpiently ob- 
 served over every part of Europe. In China, accdiding to Davis, the 
 old plaster of the houses is so much esteemed as a manure, that parlies 
 will often ])urcliase it at the expense of a coating of new j)lasler. Old 
 clay walls, and especially the walls of clay-built huts, are said to be 
 ver_y fertilizing to the land, when applied as a top-dressing, and in some 
 parts of England, where the land is poor, the peo|)le are said to ])ile up 
 the soil in the form of walls, in order to improve its (|uality. These lat- 
 ter facts seem to indicate that both_in China and England nitric acid is 
 produced in similar circiimstances, and that to its production the ferti- 
 lizing action of tlie old j)laster, and of the ucaihered clay, is alike to be 
 attributed. 
 
 In ihe cultivated soil also, this acid is formed in ordinary circum- 
 stances. Braconnot found nitrate of potash in the botanic garden at 
 Nancy, in a portion of soil in which poppies {papaver sommferitm) 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 hreoni had been grown in a pot. — 
 [A7in. de Chim. et de Phys., Ixxii., p. 33 to 35.] 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, proceeding more slowly, but accord- 
 ing 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 oxidation,* 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 for the constant diminution of the 
 quantity of this compound in addition to those already detailed in the 
 preceding section. • 
 
 But, besides the portion of this nitric acid, which owes its existence to 
 
 • For the perfect oxidation of 1 of ammonia, no less than 8 of oxygen are required. Thus 
 1 of 1 of 3 of 
 
 Ammonia. Nitric Arid. Waier. 
 
 Nils + SO = N05 -I- 3 HO. 
 
QUANTITY IN WHICH IT IS REPRODUCED. 163 
 
 the decomposition of ammonia, much, by far the greatest proportion 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 beea 
 already shown, by the agency of atmospheric electricity; but it also 
 takes place in the soil during the oxidation of the other elements con- 
 tained in the organic maiters which are there undergoing decay. The 
 combination of the elements of ammonia in such circumstances proceeds 
 on the princijile that bodies, themselves undergoing oxidation, dispose 
 other substances in contact with theni (in this instance the nitrogen of 
 the air) to unite with oxygen also. The presence of lime, potash, &c. 
 in the soil, further induces to this oxidation by the tendency of these sub- 
 stances to combine with the acid which is formed by this union of the 
 elemenis of which nitric acid consists. — It is impossible precisely to es- 
 timate the fjuaniiiy of nitric acid produced in these various vi^ays, through 
 these various agents, an 1 in these varied circuin.stances, or to balance it 
 accurately against the amount of ammonia continually reproduced, as 
 we have seen, in nature, wherever the necessary conditions present 
 themselves. But, as I formerly concluded, that the amount of nitric 
 acid actually existing in the superficial deposits of our globe is greater 
 than that of ammonia, so I think that, in regard to the reproduction also 
 of these two compounds, the balance is in favour of the former. 
 
 Since, then, nitric acid is fitted, by the solubility of its compounds, to 
 enter into the circulation of plants in any quantity — since, when applied 
 to them, it does undoubtedly promote, in a remarkable degree, the growth 
 of plants — and since, in nature, it is continually reproduced in every 
 country, and under such varied circumstances — I cannot withhold my- 
 self from the conclusion, that, over the general vegetation of the globe, 
 it holds with ammonia at least an equal sway, and is appointed to exer- 
 cise 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 climate. 
 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 (he action of nitric acid and ammonia. 
 These two compounds act so far in common as to yield a supply of 
 nitrogen to the plants into »vhich they enter. They do so, however, un- 
 der conditions which way be considerably different, and may be attend- 
 ed by unlike chemical changes. 
 
 I. THEORY OF THE ACTION OF NITRIC ACID. 
 
 1°. The nitric acid of the nitrates entering into the circulation of the 
 roots will ascend to the leaf, and will there be decomposed in the same 
 wav as the carbonic and other similar acids are, by the action of the 
 suii's rays. It is only in the light of day that carbonic acid is decom- 
 ])osed 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 decomposition will take place at each passage 
 
 8 
 
164 THEORY OF THE ACTION OF NITRIC ACID AND OF AMMONIA. 
 
 of the sap through the leaf will depend, in some degree, on the nature 
 of the base (whether potasli, 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 decom- 
 posed in the roots or stems of plants where it is excUided from the light, 
 though it is very probable that it may be so, especially in cases where 
 the juices naturally contain substances in which hydrogen is present in 
 excess, 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 wiiicli turpentine (C40 H3,) naturally abounds, 
 such a decomposition may the more readily occur, inasmuch as it would 
 not necessarily imply the production and evolution of any gaseous sub- 
 stance. Thus 
 
 1 of Oil of Turpentine, = C40 H32 with the oxygen of 
 
 1 of Nitric Acid (NO5) = O5 gives 
 
 1 of Resin, = C40 H32 O5 
 
 By uniting with the oxygen of the nitric acid, therefore, oil of turpen- 
 tine, in such trees, might be changed into resin during its passage 
 through the stem, while the nitrogen, being set free, might, at the mo- 
 ment of its liberation, unite with other elements to form those parts or 
 productions of the tree into which this element enters as a necessary 
 constituent. 
 
 The above must be considered merely as an illustration of the kind of 
 changes which may possibly take place in the interior of certain plants, 
 and in the absence of light, when the nitrates happen to be present. 
 Were I to affirm that such changes actually 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 de- 
 composition. Some beautiful illustrations of this have already been 
 given in a previous lecture, when treating of the action of sulphuric acid 
 upon starch and woody fibre, [Lecture VI.. pp. 113, 114.] But the fact 
 which most immediately bears on the influence of the nitric acid in the 
 living plant, is that mentioned in p. 126, — that by solution in this acid 
 in the cold, starch is converted into a substance having the composition 
 of woody fibre. In the interior of the plant changes of this kind may 
 be produced by simple contact only, with the nitric acid, so that, with- 
 out being decomposed, it may be materially serviceable in promoting 
 those molecular changes which are necessary to the healthy and rapid 
 growth of the plant. 
 
 II. THEORY OF THE ACTION OF AMMONIA. 
 
 1°. Ammonia is capable of contributing to the growth of the plant, 
 by means of the hydrogen, as well as of the nitrogen it contains. We 
 
«S AMMONIA DECOMPOSED IN THE DARK? 165 
 
 have seen [notes to pages 136 am] 138,] that, according to the resnlr? 
 of the best experiments, the whole of the oxygen of the carbonic acid 
 absorbed, is not given off by the leaves of all plants even in the sun- 
 shine, — while in the dark this gas is largely' and directly imbibed from 
 llie air. If in the sap of a ])lant there be present at the same time a 
 quantity of ammonia, the hydrogen of ihis ammonia may unite directly 
 with the oxygen of the carbonic acid, forming water and a proportionate 
 quantity of one or other of tbe several compounds (p. 112), which may 
 be represented by carbon and water. Thus 
 
 3 of Carbonic Acid, = C3 Og and the hydrogen of 
 
 2 of Ammonia (NH3) = Hg 
 
 if of Grape 3 of 
 
 Sugar. Water. 
 
 give . . . . C3 He 0« = C3 H3 O3 + 3HO 
 so that wlien^ ammonia is present, and circumstances are favourable, 
 sugar or starch inay be formed in varialile quanjity, without the neces- 
 sary evolution of oxygen gas. This cliange will take jjlace in the inte- 
 rior 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, &c., from the presence of ammo- 
 nia, must aid the increase and growth of the plant ; and may be one 
 main cause of the fertilizing action of this compound, which has been so 
 long and so generally recognized. 
 
 When the hydrogen of the ammonia is thus worked up, the quantity 
 ofoxj'gen which escapes from the leaf must be less in proportion; and 
 hence another cause (p. 138) for those discrepancies which have been 
 observed in regard to the bulk of oxygen given off", compared whh that 
 of the carbonic acid taken in, by the leaves of different plants. 
 
 But at the same time the nitrogen is set free. This nitrogen will 
 either be again compounded in the plant with other elements, 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. 95), 
 and why awimonia 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. 
 
 1°. Plants grow in the dark. Though feebfe and blanched, they in- 
 crease largely in bulk; they must, therefore, have ilie power of assimi- 
 lating their food to a certain extent, independent of the sun's rays. 
 
 2°. Several species of Poa, Plantago, Trifolium arvense, Cheiran- 
 thus, &c., become green in the perpetual darkness of mines (Hum- 
 boldt). 
 
 3°. When a little hydrogen is mixed with the air, plants become 
 greenish, even in the dark (Sennebier) ; and when expcsed to the sun, 
 the green becomes unusually intense in such a mixture (Ingenhouss). 
 
166 MODIFTIifG EFFECT OF CLIMATE. 
 
 The immediale and visible effect of an application of ammonia, or of 
 soot, or of any lop-dressing containing ammoTjia, is to render the green 
 colour much more intense, and in the darkest weather. It is therefore 
 ])robable, I think, that the hydrogen of the ammonia contributes to this 
 immediate effect, and tliat the ammonia itself may be decomjiosed 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. Like waler, ammonia \s jieculiarly liable to decom- 
 position, not always 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 nourish- 
 ment of the plant. 
 
 § 7. Comparative influence of nitric acid and of ammonia in different 
 climates. 
 
 It follows, from what is above stated, that the beneficial influence of 
 ammonia upon vegetation will be readily perceived in all climates in 
 which plants are found to flourish. Its effects will be greater and more 
 rapid where the heat and light are more intense, — only because by these 
 agents the functions of all life are stimulated. 
 
 Not so with the nitric acid in the nitrates. In the presence of organic 
 compounds, that is, in the sap of the plant, it is less easily decomposed 
 than ammonia. It requires the interference of more powerful agents— 
 of a liigher 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 temperature and the bril- 
 liant sun should render them most useful to vegetation. Sucli is well 
 known to be the case, and it may be regarded as one of those bountiful 
 ada|)tations with which all nature is full — that in these warmer regions, 
 the ammonia produced in the soil is first converted into nitric acid, that 
 it may remain fixed, 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 band, it may no less be regardeff 
 as a wise provision, that in colder and more uncertain climates, where 
 warm and brilliant summers are less to be depended upon, that com- 
 pound of nitrogen (ammonia) should more abound, which is most easily 
 decomposed in the living plant, which is fitted in comparative darkness 
 to yield up its nitrogen, and by the hydrogen it contains, to compensate 
 in some slight degree for the partial absence of the sun's rays. 
 
 From these views, therefore, we sliotrld draw this further practical 
 conclusion — that in our climate, ammonia is sure to promote vegetation, 
 and in every season, while the nitrates will produce their maximum effect, 
 othei 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 employment of the nitrates ? 
 
 § 8. 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. 
 
STIMULATING INFLUENCE OF NITRIC ACID AND OF AMMONIA. 167 
 
 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, and the views just exposed serve to indicate 
 the sources from which the excess is derived. But suppose that upon 
 two patches o( ground, of equal (|ualily, the one of which is manured 
 and the other not, equal quantities of the same seed be sown, it is 
 consistent with experience — that the crop reaped from the manured 
 portion will not only contain more nitrogen than that reaped from the 
 unmanured portion, but so much more as shall considerably exceed that 
 contained in the manure itself. Thus suppose the crop raised from the 
 unmanured land to contain 100 lbs. of nitrogen, and that the manure laid 
 on the oiher portion contained 100 lbs. also, 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 tlie 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 con- 
 tained in the crop of hay or corn reaped from the latter, will generally 
 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 nitrogen di- 
 
 ' The foUowins calculations illustrate the statement in the text :— Mr. Gray, of Dilston, 
 {see Journal of Royal English Agricultural Society,] applied nitrate of soda to grass land in 
 the proportion of 1 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, 1 ton G5 stones, or 3150 lbs. 
 And 3150-;- I12 = 2S,V lbs. the increase of hay from each pound of nitrate of soda.' But al- 
 lowing this hay to contain only one per cent, of nitrogen, 28 lbs. will contain 4}^ ounces of ni- 
 trogen, which is nearly double the quantity actually present in the nitrate employed. 
 
 Again, in the case of a crop of grain — Mr. Hyett a|iplied nitrate of soilato a field of wheat, 
 and compared the produce willi that from an efjual portion to which no top-dressing was 
 applied. 
 
 CORN. STRAW. 
 
 Bush. pks. pts. Cwt. qrs. lbs. 
 
 Nitrated 43 2 11 31 2 3 
 
 Without nitrate . . 33 2 6 23 1 21 
 
 Excess, 10 5 8 10 
 
 Calculating the bu.shol of corn at 60 lbs., the excess of corn amounted to 6(X) lbs., containing 
 24/i per cent, or 147 lbs. of gluten and albumen. The nitrogen in these substances, when 
 properly dried, is from 15 to 17 per cent. If we suppose the gluten not to have been quite 
 dry, and allow only 14 per cent, of nitrogen, 147 lbs. would contain 20,'-^ lbs. of this element. 
 Bm the nitrated corn contained 5 per cent, more gluten and albumen than the unnitrated, 
 which in 33 bushels (20(X) lbs.) gives 100 lbs. of gluten in excess, containing 14 lbs. of nitrogen. 
 And 8 cwt. of straw (900 lbs.) contained one-third of a per cent, of nitrogen, [Boussingault,] 
 or in all 3 lbs. 
 
 Therefore the quantity of nitrogen present in the nitrated crop above that in the unnitrated 
 was as follows : 
 
 1°. In GOO lbs of wheat at 2434 percent, of gluten 20>^ lbs. Nitrogen. 
 
 2°. In 2000 lbs. of wheat at 5 percent, of gluten contained in excess, 14 lbs. do. 
 3°. In 900 lbs. of straw at one third per cent 3 lbs. do. 
 
 Total nitrogen =.3734 lbs. 
 
 But the nitrogen in 1 cwt. of dry nitrate of soda, as already stated, is only 19 lbs. or little 
 
 [' Dry nitrate of soda contains about 16)^ percent, of nitrogen, being 19 lbs. to the cwl., 
 
 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 2X ounces in the pound.] 
 
168 HOW THIS INFLUENCE IS MANIFESTED. 
 
 rectly conveyed to the plant by these nitrates, they also exercise some 
 other influence, by which they enable the living vegetable 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 ? 
 
 This I suppose to be that kind of influence to which writers on agri- 
 culture are in the habit of alluding, when they speak of certain substan- 
 ces stimulating plants, or acting as Mirmdants to their growth, though the 
 term itself conveys to the mind no distinct idea of the mode of operation 
 intended to be indicated — of the way in which the effect is produced. 
 
 In the present case, this special action of ammonia and the nitrates, 
 and perhaps also of immediate applications of manure in general, ap- 
 pears to arise from their affording to the plant, in its early youth, a copi- 
 ous supply of nitrogenous food, by which it is enabled at once to shoot 
 out in a more healthy and vigorous manner. It thrusts forth roots in 
 greater numbers, and to greater distances, and is thus enabled to extract 
 nourishment froui a greaier extent and depth of soil than is ever reached 
 by the sickly plant- — it es}>aH-ds larger and more niimero)us leaves, and 
 thus can extract from the air iraore of every thing it contains which is 
 fitted to supply the wants of ilie living vegetable; as tlie stout and 
 healthy savage can hunt and tish to support many 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 leatll a wretched and hungry life. 
 
 Even in soils, then, and situations, wiiich are capable of yielding to 
 the plant every thing it may re<]uire for its ordinary growth, it is an im- 
 portant object of the art of husbandry to discover what substances are 
 especially necessary or grateful to particular crops, and to apply these 
 directly, and iyi abundance, to the new-born plant, — in order that it may 
 acquire sufficient strength to be able to avail itselfin the greatest degree 
 of the stores of food wbieh lie wiihi-n its reach. 
 
 Concluding observations regarding the organic constitwents of plants. 
 
 "VVe have now considered I be most important of those questions con- 
 nected with the organic elements of pFants, whicli are directly interesting 
 to the practical agriculturist. We have seen — 
 
 1°. That all vegetable productions consist of two parts — one the or- 
 ganic part, whicb is capable of being burned away in the air — the other, 
 the inorganic part, which remains behind in xha form of ash. 
 
 2°. That this organic part consists of carbon, hydrogen, oxygen, and 
 nitrogen only. 
 
 3°. That plants derive the greater part of their carbon from carbonic 
 acid, of their hydrogen and oxygen from water, and of their nitrogen 
 from ammonia and nitric acid. 
 
 4"^. Tliat by far the largest portion of those substances which form 
 the principal mass of plants, such as starch and woody fibre, consists of 
 carbon united to oxygen and hydrogen in the prop0.rtions in which they 
 
 more llian half Ihe quantity, which irk conseqiience orthe presence and action of the nitrate 
 the wheat was enabled to obtain and appropriate above the quantity appropriated by the 
 wheat in the unnilrated part of tlie field. 
 
 It requires no further proof, therefore, to show that the nitrate of soda and the nitrates must 
 act in some other way in refere7tce to vegetation, than by simply supplying a portion oj nitrogen. 
 
CONCLUDING OBSERVATIONS. 169 
 
 exist in water, — or, in other words, may be represented by carbon and 
 w'Bter in various proportioas. 
 
 5°. That the food on which they live enters by the roots and leaves 
 of plants, — 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 chiefly consist. 
 
 6°. That the supply of carbonic acid in the atmosphere is kept up 
 partly by the respiration of animals, partly by the natural decay of dead 
 vegetable matter, and partly by combustion. That ammonia is sup- 
 plied to plants chiefly by the natural decay of animal and vegetable 
 substances — and nitric acid partly by the natural oxidation of dead or- 
 ganic matter, and partly by the direct union of oxygen and nitrogen, 
 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 also a so-called 
 stimulating power, by which plants are induced or enabled to appro- 
 priate 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 enter oc- 
 casionally 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 thfe full sense will 
 not appear on a reference to the statement by which it is preceded. 
 
 We are now to consider the inorganic constituents of plants, — their na- 
 ture, — the source (the soil) from which they are derived, — their uses in 
 the vegetable and animal economy, — how the supply of these substan- 
 ces is kept up in nature, — and how, in practical husbandry, the want of 
 them may be at once efficaciously and economically supplied by art. 
 This division of our subject, though requiring 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 principle 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 inquiry ; and it is in the considerations I am now 
 about to bring before you, that I shall have to direct your attention most 
 especially to the principal applications of Geology to Agriculture. 
 
LECTURES 
 
 ON THE 
 
 APPLICATIONS OF CHEMISTRY AND GEOLOGY 
 
 TO 
 
 AGRICULTURE. 
 
 mvt m, 
 
 ON THE INORGANIC ELEMENTS OF PLANTS. 
 
LECTURE IX. 
 
 Inorganic constituents of vegetable substances. — Relative proportions of organic and inor- 
 ganic matter in plants. — Unlike proportions in unlike species. — Kind of inorganic matCei 
 which exists in different species. — Nature and properties of the several inorganic elemen 
 tary bodies found in plants. 
 
 The consideration of the inorganic constituents of plants is no less 
 important to tlie art of culture than the study of their organic elements, 
 which has engaged our sole attention in the preceding part of these lec- 
 tures. 
 
 It has already been shown that when vegetable substances are heated 
 to redness in the air, the whole of the so-called organic elements — car 
 bon, hydrogen, oxygen, and nitrogen — are burned away and disappear ; 
 while there remains behind a fixed portion, commonly called the ash, 
 which does not burn, and which in most cases undergoes no diminution 
 when exposed to a red heat. This ash constitutes the inorganic portion 
 of plants. 
 
 The organic or combustible part of plants constitutes, in general, 
 from 88 to 99 per cent, of their whole weight, even after they are dried. 
 Hence the quantity of ash left by vegetable substances in the green 
 slate is often exceedingly small. It therefore long appeared to many, 
 that the inorganic matter could be of no essential 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 
 aflfeciing either its growth or its luxuriance. 
 
 Were this the case, however, the quantity and quality of the ash left by 
 the same plant should vary vvitli the soil in which it grew. If one soil 
 contained much lime, another much magnesia, and a third much potash, 
 whatever plant was grown upon these several soils should also contain 
 in greatest abundance the litne, the magnesia, or the potash, which 
 abounded 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 shown— 
 
 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 is nearly the same ; and 
 
 2^. That though grown on the same soil, the quantity and quality of 
 the ash left by no two species of plants is the same — 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 constituents 
 contained in the ash are really essential parts of the substance 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 
 
178 
 
 WEIGHTS OF ASH LEFT BY DIFFERENT SPECIES. 
 
 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. 
 Others, as De Saussure, have published many important and very use- 
 ful analyses of the inorganic matters left by plants, but for the illustra- 
 tion of the important practical bearing of this knowledge of their inor- 
 ganic constituents on the ordinary processes of agriculture, we are, I 
 believe, in a great measure indebted to the writings and numerous ana- 
 lytical researches of Sprengel. 
 
 It is difficult to conceive the extent to which the admission of the es- 
 sential nature and 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 con- 
 tain, and, therefore, how they are to be improved — it explains the effect 
 of some manures in permanently fertilizing, and of some crops in per- 
 manently 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 unexpected light. Of this, I 
 am confident, you will be fully satisfied when I shall have discussed the 
 various topics I am to bring before you in the present part of my lectures. 
 
 § 1. Of the relative proportions of inorganic matter in different 
 vegetable substances. 
 As above stated, the inorganic matter contained in different vegetable 
 productions varies from 1 to 12 per cent, of their whole weight. The 
 following table exhibits the weight of ash left by 100 lbs. of the more 
 commonly cultivated plants — according to the analyses of Sprengel 
 [Ckemie, vol. ii., passim] : — 
 
 Grain of Perct. 
 Wheat . . 1-18 lbs. 
 Rye . . . 1-04 
 Barley . . 2-35 
 Do. dried at 212, 2-52 J 
 Oats . . . 2-58 
 Field Beans . 2-14 
 Peas . 2-46 
 
 Dry straw of Perct. 
 
 Wheat 
 
 . 3-51 lbs. 
 
 Oats . 
 
 . 5-74 
 
 Barley . 
 
 . 5-24 
 
 Rye . 
 
 . 2-79 
 
 Beans . 
 
 . 3-12 
 
 Peas . 
 
 . 4-97 
 
 Potato . . . 
 Turnip . . . 
 Do. while . 
 Carrot . 
 Parsnip . 
 Leaf of Potato 
 
 Turnip . 
 
 do. white 
 
 Carrot 
 
 Parsnip . 
 
 Cabbage 
 
 Undried. 
 0-83 lbs. 
 0-63 
 0-8 J. 
 0-66 
 0-82 
 
 1-8 
 
 2-18 J. 
 1-98 
 3-00 
 0-53 
 
 Dried in air. ' 
 2-65 lbs. 
 7-05 
 
 5-09 
 4-34 
 4-79 
 2-91 
 
 10-42 
 
 15-76 
 
 7-55 
 
 Lucerne 
 Red Clover 
 White Clover 
 Rye Grass . 
 
 Green. 
 
 2-58 lbs. 
 1-67 
 1-74 
 1-69 
 
 In tiav. 
 9-55 ibs 
 7-48 
 9-13 
 5-3 
 
 .V* .®'^*^6 substances in this r.olumn the potato lost by drying in the air 69 per ct. of water, 
 the turnip 91, the carrot 87, the turnip leaf 86, the carrot leaf, the parenip, and the parsnip 
 leaf, each 81, and the cabbage leaf 93 per cent. > j- n if 
 
IT VARIES WITH THE SPECIES OF PLANTS. 179 
 
 In the parts of trees dried in the air there are found of inorganic 
 matter — 
 
 
 Wood. 
 
 Leaves. 
 
 Wood. 
 
 LeaveB. 
 
 In the Elm 
 
 . 1-88 
 
 11-8 
 
 In the Oak . . 0-21 
 
 4-5 
 
 Willow 
 
 . 0-45 
 
 8-23 
 
 Birch . . 0-34 
 
 6-0 
 
 Poplar . 
 
 . 1-97 
 
 9-22 
 
 Pitch pine 0-25 
 
 3-1.5 
 
 Beech . 
 
 . 0-36 
 
 6-69 
 
 Comm. furze 0*82 
 
 3-1 J. 
 
 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. 
 
 1°. That the quantity of inorganic matter contained in the same 
 weight of the different crops we raise, or of the different kinds of vegeta- 
 ble food we eat, or with which our cattle are fed, is very unlike. Thus 
 100 lbs. of barley, or oats, or peas, contain twice as much inorganic 
 (earthy and saline matter, that is,) 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. 
 
 2°. The (juantity contained in different parts of the same plant is 
 equally unlike. Thus 100 lbs. of the grain of wheat leave only ];^lbs. 
 of ash, while 100 lbs. of wheat straw leave 3| lbs. So the dry bulb of 
 the turnip gives only 7 per cent., while the dry leaf leaves 13 per cent, 
 of ash when it is burned. The dry leaves of the parsnip also contain 
 nearly 16 per cent., though in its root, when sliced and dried in the air, 
 there are only 4i per cent, of inorganic matter. 
 
 In trees the same fact is observed. The wood of the elm contains 
 less than 2 per cent., while its leaves contain nearly 12 per cent. ; — the 
 wood of the oak leaves only ^ih 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 con- 
 stant 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 developemeut 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 tlie 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, and 
 from its being always found in nearly the same proportion in the same 
 species of plants, — 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 beyond a doubt, by the further experimen 
 
180 QUALITY OF THE ASH FROM DIFFERENT PLANTS. 
 
 tal fact, that if a healthy young plant be placed in circumstances where 
 it cannot obtain this inorganic matter, it droops, ])ines, 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 cor- 
 rectly speak of feeding or supplying food to plants, 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 substances as they believe to be 
 capable oi 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 vegeta- 
 tion 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 consideration 
 the fact above stated — I may almost say demonstrated — that plants 
 do feed upon dead unorganized mineral matter, and that you are, there- 
 fore, really manuring your soil, and permanently improving it, when 
 you add to it such substances of a proper kind. 
 
 § 2. Of the kind of inorganic matter found in plants. 
 
 I have said above, of a proper kind — for it is not a matter of indiffer- 
 ence to a plant, what kind of earthy or saline matter it takes in by its 
 roots. Each species of plant, we have seen, withdraws from the soil a 
 quantity of inorganic matter, which is peculiar to itself, and which, as a 
 whole, is nearly constant. 
 
 So also each species, in selecting for itself a nearly constant weight 
 of inorganic matter, while it chooses generally the same kind of saline 
 and earthy ingredients as other plants do, to make up this weight, yet 
 picks them out in proportions peculiar to itself Thus for example, lime 
 is present in the ash of nearly all plants, but while 100 lbs. of the ash 
 of wheat contain 8 pounds of lime, the same weight of the ash of barley 
 contains only 4i lbs. So also potash is contained in the ash of most 
 plants grown for food, but in the ash of the turnip, there are 37| per 
 cent, of potash, while in that of wheat there are only 19 per cent. Again, 
 in different parts of the same plant, a like difference prevails. The ash 
 of the turnip bulb contains 16i percent, of soda, — that of the leaf, little 
 more than 12 per cent. On the other hand, the lime in that from the 
 bulb constitutes less than 12 per cent, of its weight, wliile in that of the 
 leaf it amounts to upwards of 34 per cent. 
 
 These relative proportions among the different kinds of inorganic mat- 
 ter contained in the ash of plants — like the whole weight itself of the 
 ash — is nearly constant in the same species, and in the same part of a 
 plant, when it is grown in a propitious soil. It is not, therefore, as I have 
 already said, a matter of indifference to the living vegetable, whether 
 it meets with this or with that kind of inorganic matter in the land on 
 which it grows — whether its roots are supplied with lime, or with potash, 
 or with soda. The soil must contain all these substances, and in such 
 
THE SOIL MUST CONTAIN WHAT THE PLANT REqUIRKS. 181 
 
 quantity as easily to yield to the crop so much of each as the kind of plant 
 specially requires. And if one of these necessary inorganic forms of 
 matter be rare or wholly absent, the crop will as certainly prove sickly 
 or entirely fail, as if the organic food supplied by the vegetable matter 
 of the soil were wholly withdrawn. It is, therefore, as much the end of 
 an enlightened agricultural practice to provide for the various require- 
 ments of each crop in regard to inorganic food, as it is to endeavour to 
 enricli the land with purely vegetable substances. 
 
 Since, also, as above shown, not only the relative quantity of inor- 
 ganic matter, but its kind or quality, likewise, is different in different 
 plants, — it may be, that a soil on which one crop cannot attain to ma- 
 turity may yet surely and completely ripen another — a fact which is 
 proved by every-day experience. The soil, which is unable to supply 
 with sufficient speed all the lime or the potash required for one crop, 
 may yet easily meet the demands of another, and afford an ample re- 
 turn to the husbandman when the time of harvest comes.* 
 
 On the other hand, this consoling, at once, and stimulating reflection 
 must arise in the mind of the practical agriculturist from the considera- 
 tion of the above facts — that if the soil contain all the inorganic substan- 
 ces required by plants, and in sufficient quantity, it will grow, if rightly 
 tilled, any crop which is suited to the climate, — or conversely to make 
 it capable of growing any crop, he has only — along with his usual sup- 
 plies of animal or vegetable rnatter — to add in proper quantity these in- 
 organic substances also. 
 
 Here a crowd of questions cannot fail to start up in your minds. You 
 will ask, for example, 
 
 1°. What are the several inorganic substances usually present in 
 cultivated plants, and what their respective proportions ? 
 
 2°. Which of them are most generally present in the soil? 
 "3°. In what form can those which are less abundant be added most 
 easily, most advantageously, and most economically ? 
 
 We shall consider in succession these, and along with them other 
 
 * On the same principle, also, some of the interesting facts connected with the grafting of 
 trees are susceptible of a satisfactory explanation. 
 
 The root of a tree selects from the soil llie kind and guu/iYi/ of inorganic matter which 
 are required for the healthy maturity of its own parts. Any other tree may be grafted on it, 
 which in its natural state requires the same kind of inorganic matters in nearly the same 
 proportion. This is the case generally with varieties of the same species — more rarely 
 with trees or plants of different species — and least frequently with such as belong to differ- 
 ent genera. The lemon may be grafted on the orange, because the sap of the latter con- 
 tains all the earthy and saline substances which the former requires, and can supply them 
 in sufficient quantity to the engrafted twig. But the fig or the grape would not flourish or 
 ripen fruit on the same stock — because these fruits require other substances than the root of 
 the orange cares to extract from the soil, or in greater quantity than the sap of the orange 
 can supply them. 
 
 It is not for want of organic food, for of this the sap of nearly all plants is full — and we 
 have seen in our previous lectures, how the sugar of the fig, the tartaric acid of the grape, 
 and the citric acid of the lemon, may all be produced by natural processes from the same 
 common organic food. When we plant a tree or sow a crop on a soil which does not con- 
 lain ail that the tree or crop requires, the tree must slowly perish, — the crop cannot yield a 
 profitable return. So it is in grafting. TTie sap of the stock must contain all that the erigrafted 
 bud or shoot requires in every stage of its growth. Or to recur to our former illustration — 
 if the potash or lime required by the grape be not taken up and in sulBcient quantity by 
 the root of the orange, it will be in vain to graft the former upon the latter with the hope of 
 its coming to maturity or yielding perfect fruit. 
 
 This principle may also serve to explain many other curious and hitherto obscure cir» 
 cumslances connected with the practice of the gardener. 
 
182 
 
 KLEMEISTART SUBSTANCES FORMED IN THE ASH. 
 
 subsidiary questions, which will hereafter present themselves to our 
 notice. 
 
 § 3. OJilie several elementary bodies usually met with in the ash of plants 
 What is understood by the term element or elementary body among 
 chemists has already been explained (Lect. I., p. 22), as well as the 
 number and names of those elements with which we are at present ac- 
 quainted. 
 
 Of these elementary bodies we have seen that the organic part of plants 
 contains rarely more than four, namely, carbon, hydrogen, oxygen, and 
 nitrogen, in various proportions. In the inorganic part there occur nine 
 or ten others, generally in combination, either with oxygen or with one 
 another. 
 
 The names of these inorganic elements are as follow : 
 
 Name. In 
 
 combination with 
 
 Forming 
 
 Chlorine . 
 
 Metals 
 
 Chlorides. 
 
 Iodine . . 
 
 do. 
 
 Iodides. 
 
 Sulphur . 
 
 do. 
 
 Sulphurets. 
 
 
 Hydrogen 
 
 Sulphuretted Hydrogen.* 
 
 
 Oxygen 
 
 Sulphuric Acid. 
 
 Phosphorus 
 
 do. 
 
 Phosphoric Acid. 
 
 Potassium . 
 
 do. 
 
 Potash. 
 
 
 Chlorine 
 
 Chloride of Potassium. 
 
 Sodium . . 
 
 Oxygen 
 
 Soda. 
 
 
 Chlorine 
 
 Chloride of Sodium or } 
 Common Salt. ^ 
 
 Calcium . 
 
 do. 
 
 Chloride of Calcium. 
 
 
 Oxygen 
 
 Lime. 
 
 Magnesium 
 
 do. 
 
 Magnesia. 
 
 Aluminium 
 
 do. 
 
 Alumina. 
 
 Silicon 
 
 do. 
 
 Silica. 
 
 Iron and ? 
 
 do. 
 
 ^ Oxides. 
 
 Manganese ^ 
 
 Sulphur 
 
 ( Sulphurets. 
 
 Other elementary bwlies, chiefly metallic, occur in some plants — occa- 
 sionally, 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 ma- 
 terial influence on the general vegetation of the globe. 
 
 Of all the above elementary bodies it may be said, generally, 
 
 1°. That wiih the exception of sulphur,f 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 stale; and that, therefore, 
 in this state ihey in no way alFecf 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 with other substances, and chiefly with oxygen, [for 
 an explanation of the meaning and of the laws of chemical combination, 
 see Lecture II., p. 32] — but in no state of combination are they known 
 to be generally diffused through the atmosphere of the globe, so as to be 
 
 * Called also Hydro-sulphuric Acid. 
 
 t Given off in vapour from active volcanoes, and from rents and fissures 'n ancient volcanic 
 countries. 
 
CHLORIISE AND MURIATIC ACID. 183 
 
 capable of entering plants by their leaves or other superior parts. They 
 must all, therefore, enter by the rools of plants, — must consequently ex- 
 ist in the land, — and must all be necessary constituents of that soil in 
 which the plants that contain them grow. 
 
 It will not be necessary, therefore, to consider so much the relative 
 proportions in which these elementary bodies themselves exist in plants, 
 as that of the several chemical compounds which they form with oxy- 
 gen, or with one another — in which states of combination they exist in 
 the soil, and are found in the circulation and substance of the plant. As 
 a preliminary to this incjuiry, 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 those compounds of the inor ganic elements which enter directly into 
 the circulation, or exist in the substance and ash of plants. 
 
 I. CHLORINE AND MURIATIC ACID. 
 
 Chlorine. — If a mixture of common salt and black oxide of manga- 
 nese [sold by this name in the shops] be put into a flask or bottle of 
 colourless glass, and sulphuric acid (oil of vitriol) be poured upon it, a 
 gas of a greenish-yellow colour will be given off, and will gradually fill 
 the bottle. This gas is distinguished by the name o^ chlorine. 
 
 It is readily distinguished from all other substances by its greenish- 
 yellow colour, and its pungent disagreeable smell. It extinguishes a 
 lighted taper, but phosphorus, gold leaf, metallic potassium and sodium, 
 and many other metals, take fire in it and burn of their own accord. It 
 is nearly 4i 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 astrin- 
 gent taste. 
 
 Animals cannot breathe it without suffocation — and, when unmixed 
 with air, it speedily kills all living vegetables. The solution of chlorine 
 in water was found by Davy to promote the germination of seeds. 
 
 It does not exist, and is rarely evolved, [see Lecture V., p. 94,] in 
 nature in a free or uncombined state, and therefore is not known to ex- 
 ercise 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. Indi- 
 rectly, therefore, it may be supposed to influence, in some degree, the 
 growth of ])lants, where common salt exists naturally in the soil, or is 
 artificially applied in any form to the land. 
 
 Muriatic acid, the spirit of salt of the shops, consists of chlorine in 
 combination with hydrogen. It is a gas at the ordinary temperature of 
 the atmosphere, but water absorbs between 400 and 500 times its bulk 
 of it, and the acid of the shops is such a solution in water, of greater or 
 less strength. 
 
 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 contained in the soil. 
 
181 lODIME, SULPHUR, A^D SULPHUROUS ACID. 
 
 Wlien applietl to living vegetables in ihe state of an exceedingly di- 
 lute soiiiiion in water, it has been supposed upon some soils, and in 
 some circumstances, to be favourable to vegetation. Long experience, 
 however, on the banks of the Tyne, and elsewhere, in the neighbour- 
 hood of the so-called alkali* works, has proved that in the state of va- 
 pour its repealed application, even when diluted with much air, is in 
 many cases fatal to vegetable life. 
 
 Poured in a liquid state upon falloro land, or land preparing 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. 
 
 Chlorine is represented by CI, and muriatic acid by HCl. 
 
 II. IODINE. 
 
 Iodine is a solid substance of a lead grey colour, which, when heated, 
 is converted into a beautiful violet vapour. It exists in combination 
 chiefly wiih sodium, as Iodide of Sodium, in sea water and in marine 
 plants ; Inn it lias not liiiherto been delected 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 possibly 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 men- 
 tioned in a previous lecture (VL, p. 107), as affording a ready means 
 of detecting starch by the beautiful blue colour it gives with this sub- 
 stance. 
 
 III. SULPHUR, SULPHUROUS AND SULPHURIC ACIDS, AND SUL- 
 PHURETTED HYDROGEN. 
 
 1°. Sulphur is a substance too well known to require any detailed 
 description. In an uncombined state it occurs chiefly in volcanic coun- 
 tries, 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 natu- 
 rally charged with sulphurous vapours. In this state it is not known 
 niaterialiy to influence the natural vegetation in an}' part of the globe. 
 It has, however, been employed with some advantage in Germany as a 
 top-dressing for clover and other crojis to which gypsum in that country 
 is generally applied. The mode in which it may be supposed to act 
 will be considered hereafter.* 
 
 2°. Sulphurous acid. — When sulphur is burned in the air it gives off" 
 a gaseous substance in the formof white fumes of a well known intensely 
 suffocating odour. These fumes consist of a combination of the sulphur 
 
 ' In these works carbonate of soda (the common soda of the shops) anit sulphate of soda 
 (glauber salt) are manufactured from common salt, and in one of the processes immense 
 quantities of muriatic acid are given off from the furnace, and used to escape into the air by 
 the chimney. 
 
 t The refuse heaps of the alkali works on Ihe Tyne contain much sulphur and more gyp- 
 sum—but the farmers, perhaps, naturally enough, consider that if the works themselves do 
 harm to their crops, the refuse of the works cannot do them much good. There are thou- 
 sands of tons of this mixture which may be had for the leading away. 
 
SULPHURIC ACID, AND SULPH URKTTKU HVDROtifN. 185 
 
 wliich disaf)f)ears wiih the oxygen of the atmospliere, and are known 
 to chennisls by the name of sulpliurous acid. This coinpound is des- 
 trnclive to animal and veget il)lc life, but as it is not linown to be directly 
 formed to any extent in nature, except in the neighbourhood of acti\e 
 volcanoes, it probably exercises no extensive influence on the general 
 vegetation of the globe. 
 
 This gas possesses the curious property of bleaching many animal and 
 vegetable substances. Wool and siraw for plaiting are bleached to an 
 almost perfect vvhileness — when they are susj)ended in a vessel or room 
 inio which a plate of burning sulphur has been introduced. Gardeners 
 sometimes amuse themselves also in bleaching roses and other red 
 flowers, by holding ihcmover a burning sulphur malch. Some shades of 
 red resist this action more or less ])erfeeily, and the colour of the bleached 
 flowers may often be restored — 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 distinguish 
 the oil of vitriol of the sho[)s. It is also a com[)ound of sulphur and oxy- 
 gen only, anil is formed by causing the fumes of sulphur to pass into 
 large leaden chambers along with certain other substances, from which 
 they can obtain a further supply of oxygen. 
 
 It is tnet with in the shops in the form of an exceedingly sour corrosive 
 licpiid, which decomposes, chars, anrl destroys all animal and vegetable 
 substances, and, except when very diluted, is destructive to life in every 
 form. It is rarely met with in nature, in an uncomlnned state, — though 
 according to Boussingault, some of the streanis which issue from the 
 volcanic regions of the Andes are rendered sour by the presence of a 
 quantity of this acid. 
 
 It condiines with (xitash, soda, lime, magnesia, &c., and forms sul- 
 2)ha(es which exist abundantly in nature, and have often been benefi- 
 cially and profitably employed as manures. 
 
 Where the soil contains lime or magnesia, the acid may often be ap- 
 plied directly to the land, in a very dilute slate, with advantage 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, jirevious to sowing. A few 
 experiments have also been made in this country with partial success. 
 It is deserving, however, of a further trial, and in more varied circum- 
 stances. 
 
 4°. Sulphuretted Hydrogen. — This gaseous compound of sulphur 
 with hydrogen, is almost universally known by its unpleasant smell. 
 It imparts their peculiar taste and odour to sulphurous sjirings, 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 
 
 * This appears to be especially ttie case on the coasts of Weslern Africa, wliere the 
 hot sun is continually beating on sea water^ often shallow, frrquenlly stagnant, and always 
 iaflen with organic niatler, either animal or vefietable (I)aniell). Near the moulh of tlie 
 Tees in this county, where a shallow, dark bVue, muddy, samphire-bearing tract stretches 
 for several miles inland from Sealon Snnok, the presence of sulphuretted hydrogen may be 
 perceived tiy 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 con- 
 dition of the sea— that those parts and pools which are only reached by the j i)ring tides 
 shall have been several days uncovered. 
 
186 PHOSPHORUS AND PHOSPHORIC ACID. 
 
 vegetable matter is iinciera^oing decay in tlie presence of water contain- 
 ing gypsum, or other sulphates ; and it may occasionally be detected by 
 the sense of" smell among the roots of the sod, in old pasture land, to 
 which a fo|)-dressing is occasionally given. 
 
 As in the egg, so also in other decaying animal substances, especially 
 when the air is in some measure excluded, this gas is formed. In pu- 
 trified cow's urine, and in night soil, it is present in considerable quan- 
 tity. 
 
 Sulphuretted hydrogen is exceedingly noxious to animal and vegeta- 
 ble life, when diffused in any considerable quantity through the air by 
 Avhich they are surrounded. The luxuriance of the vegetation in the 
 neighbourhood of sulphurous springs, however, has given reason to be- 
 lieve that water impregnated with this gas, may act in a beneficial 
 manner when it is placed within reach of the roots of plants. It seems 
 also to be ascertained that natural or artificial waters which have a sul- 
 phurous taste, give birth to a peculiarly luxuriant vegetation, when they 
 are einployed in the irrigation of meadows. — [Sprengel, Chemie, I., 
 p. 355.] 
 
 The relative constitution of these three cotnpounds of sulphur is thus 
 represented ; — 
 
 Is repre- Or 1 of Sulphur 
 
 Dne equivalent of Weighing sented by and 
 
 Sulphur 16 S 
 
 Sulphurous Acid . . 32 SO2 2 of Oxygen 
 
 Sulphuric Acid . ... 40 SO3 3 of Oxygen 
 
 Sulphuretted Hydrogen 17 SH 1 of Hydrogen.* 
 
 IV. 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 
 coinbines 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 vapours. It does not occur in nature in 
 an uncombined state, and is not known to be susceptible of any useful 
 application in practical ggriculture. 
 
 2°. Phosphoric Acid. — The white fumes given off by phosphorus, or 
 rather into which it is changed, when burned in the air or in oxygen 
 gas, consist of 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 nature in a free state, and, therefore, is not directly 
 influential upon vegetation. It unites, however, with potash, soda, lime, 
 &;c., to form compounds, known by the name o( phosphates. In these 
 states of combination, it is almost universally diffused throughout nature 
 — and appears to be essentially necessary to the healthy growth and 
 maturity of all living — certainly of all cultivated vegetables. 
 
 For the properties of oxygen and hydrogen see above, pages 24 and 25, and for their 
 equivalent or atomic weights see page 34, 
 
WOOn-ASH AND CARBONATE OF POTASH. 187 
 
 V. POTASSIUiU, POTASH, CARBONATE, SULPHATE, OXALATE, TARTRATE, 
 
 CITRATE, AND SULPHATE OF POTASH, AND CHLORIDE OF POTASSIUM. 
 
 1°. Carbonate of Potash. — In countries where rioii-resinous trees 
 abound, it is usual to burn the wood whicli cannot otherwise he employ- 
 ed — as in the clearings in Canada and the United States — for the pur- 
 pose of collecting the ash whicli remains. This ash is washed with 
 water and the washings boiled to dryness in iron pots. In this state it 
 forms the pol-nsh of comnnerce. Wlien tliis 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 chem- 
 ists. It readily dissolves in water, has a peculiar taste — distinguished 
 as an alkaline taste — and dissolves in vinegar or in diluted 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 limesfane- 
 
 This carbonate of potash has been long known to exercise a powerful 
 influence over the growth of plants. 
 
 The use of wood-ash as a fertilizer both of pasture and of 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 ap- 
 parent effect is due to the carbonate of jjotash it coi^tains. 
 
 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 measure under- 
 stand 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 extirpa- 
 ted from meadows by a sprinkling of wood ashes— and why red clover, 
 lucerne, esparsette, beans, peas, flax, and potatoes, &c., are greatly 
 promoted in their growth by a similar treatment. This substance, how- 
 ever, has other functions to perlijrm in reference to vegetation, besides 
 that of simply supplying the crop with the potash it requires ; these func- 
 tions I shall explain more particularly hereafter, when you will perhaps 
 be better prepared for understanding the details into which it will be ne- 
 cessary to enter. 
 
 2°. 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 converted into 
 pure potash, — or as it is often called, from its effect on animal and ve- 
 getable substances, caustic potash. 
 
 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 un- 
 combined state, and is not known, therefore, to exercise any direct in- 
 fluence upon natural vegetation. 
 
 When wood-ashes and quick-lime are mixed together in artificial 
 
188 POTASSIUM, CAUSTIC POTASH, AND CHLORIDK OF POTASSIUM. 
 
 composts, il is not unlikely tlint a portion of the carbonate of potash may 
 be rendered caustic, and, therefore, be more fit to act upon the vegetable 
 matter in coniact \\ iih it — by rpniieriny; it soluiile in water and tluis ca- 
 pal)le of enterinn; inio ilie roots of plants. "^I'o this pnint I shall have 
 occasion to return hereafier. In the mean time, it is ]>roper to remark, 
 that if pearl-ash be mixed, as above [jrescribed, with half its weight of 
 quick-lime, and ihen boiled with less than ten or tu-elve times its iceight 
 of water, a part of the potash, only is rendered caustic — the lime being 
 unable to deprive the pearl-ash (carbonate of potash) of its carbonic 
 acid, unless it be largely diluted. Hence, in dry composts, or mixlures 
 of this sid)stance with quick-lime, it is unlikely that any large portion of 
 the |)otash can be at once brought to the caustic stale. This fact is 
 really of importance in reference to the theory of the conjoined action of 
 quick-lime and wood or pearl-ash, when mixed together in artificial ma- 
 nures, and applied to the land. 
 
 3°. Potassium. — When dry caustic potash, obtained by evaporating 
 tlie caustic solution above described, is mixed with powdered charcoal 
 and iron filings, and exposed to an intense heat in an iron retort, it is de- 
 composed, and metallic potassium distils over, and is collected in the 
 form of white shining silvery tlrops. 
 
 It was one of the most retnarkable discoveries of Sir H. Davy, that 
 ])otasli was a compound substance, and consistedof 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 exposed to the 
 air, it gradually absorbs oxygen from the atmosphere ; but if it be heat- 
 ed 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 potassium employed. It even bursts into a 
 flame when thrown upon water, depriving that liquid of its oxygen, and 
 liberating its hydrogen, — and it was justly considered as the most aston- 
 ishing properly of this metal, when first discovered, that it took fire 
 when placed upon the coldest ice. [For tlie composition of water, see 
 Lecture II., p. 36.] When thus burned in coniact with water, potash 
 is formed, as beli)re, and is found dissolved in the liquid when the ex- 
 periment is compleicd. 
 
 4°. Chloride of Potassium. — This is a compound of chlorine with po- 
 tassium, which, in taste, properties, and general appearance, has much 
 resemblance to common salt. It may be formed by dissolving pearl- 
 ash in dilute muriatic acid (spirit of salt) as long as any efit;rvescence 
 appears, ami 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 cheap- 
 ly obtained, there is no doubt that il might be employed wiih advantage 
 as a manure, and especially in those circumstances in which common 
 salt has been found to proinote vegetation. The refuse of the soap-boil- 
 ers, 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. 
 
SULPHATE, NITRATE, OXALATES, AND CITRATES OF POTASH. 180 
 
 5°- Sulphate of Potash. — This compound is formed by adding pearl- 
 ash to dilute sulphuric acid (oil of vitriol) as long as effervescence ap- 
 I)ears, ami then evaporating the solution. It is a white saline sub- 
 stance, sparingly soluble in water, and has a disagreeable bitterish tasle. 
 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 sho|)s. 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, vetciies, beans, peas, &c., 
 and part of the effect of wood ashes on plants of this kind is to be attri- 
 buted to the sulphate of potash they contain. Turf ashes are also said 
 to contain this salt in variable (]uanli^, and to this is ascribed a portion 
 of their efficacy also when applied to the land. 
 
 6°. Nitrate of Potash, or saltpetre, is a well known saline substance, 
 of whicli mention has already been made in the |)receding lectures. [See 
 ji. 56, and pp. 159 to 1G3.] It contains potash and nitric acid only, and 
 may be readily formed by dissolving pearl-ash in nitric acid, and eva- 
 porating the solution. It exists, and is continually reproduced in the 
 soil of inost countries, and is well known to exercise a remarkable influ- 
 ence in ac-celeraiing and increasing the growth of plants. 
 
 7°. Oxalates of Potash. — These salts exist in the common and wood 
 sorrels, and in most of the other more perfect plants in which oxalic 
 acid is known to exist. [See pj). 47 and 1.37.] The salt of sorrel is the 
 best known of these oxalates. This sail has an agreeable acid taste, 
 and is not so |)oisonous as the uncombined oxalic acid. 
 
 When this salt is heated over a lamp, the oxalic acid it contains is de- 
 composed, and carbonate of potash is obtained. It is supposed that a 
 great jiart of the potash extracted from the ashes of wood and of the 
 stems of plants in general, in the state of carbonate, existed as an oxa- 
 late in the living tree, and was converted into carbonate during the com- 
 bustion of the woody fibre and other organic matter. This compound, 
 therefore, in all probability, performs an important jiart in the changes 
 which take place in the interior of plants, though its direct agency in 
 aff'ecting their growth when applied externally to their roots has not 
 hitherto been distinctly recognized. 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 decom- 
 l)osed, and like the oxalates leave the potash in the state of carbonate. 
 
 In the interior of plants, both potash and soda are most frequently 
 combined with organic acids (oxalic, citric, tartaric, &c., for an ac- 
 count of the most abundant of which see Lecture VI., p. 121,) and the 
 compounds thus formed are generally what chemists call acid salts^ 
 that is to say, they generally have a distinctly sour taste, redden vege- 
 table blues, and contain much more acid than is found to exist in cer- 
 tain other well known compounds of the same acids with potash. 
 
 The citrates and tartrates are not known to be formed in nature, ex- 
 
190 PHOSPHATES OF POTASH, AND CHLORIDE OF SODIUM. 
 
 cept in the living plant, and as they are too expensive to be ever em- 
 ployed as manures, it is the less to be regretted that few experiments 
 have yet been tried with the view of ascertaining their effect upon vege- 
 tation. 
 
 9°. Phosphates of Potash. — If to a known weight of ])hosi)lioric acid 
 (p. 186) 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 second por- 
 tion of phosphoric acid be added, equal to the first, and the water be 
 then expelled by heat, Bi-phosphate of potash will remain, [so called 
 from bis, twice, because it contains twice as much acid as the former, or 
 neutral phosphate.] 
 
 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 tliis state of 
 combination in the living plant will be considered hereafter, in the mean 
 time it may be stated as certain that they are of the most vital impor- 
 tance not only in reference to the growth of plants themselves, but also 
 to their nutritive ([ualities when eaien by animals for food. 
 
 These [)hosphates are occasionally, perhaps very generally, present 
 in the soil in minute quantities, and there is every reason to believe 
 that could they be applied to the land in a sufficiently economical form, 
 they would in many cases act in a most favourable manner upon vege- 
 tation. They are contained in urine and other animal manures, and to 
 their presence a portion of the efficacy of these manures is to be ascribed. 
 
 VI. SODIUM, SODA, CARBONATE OF SODA, SULPHATE OF SODA, SULPHU- 
 
 RET OF SODIUM, CHLORIDE OF SODIUM. 
 
 1°. Chloride of Sodium, comnton or sea salt, exists abundantly in sea 
 water, and is found in many parts of the earth in the form either of in- 
 crustations on the surface or of solid beds or masses at considerable depths. 
 The rock salt of Cheshire is a well known example 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 quantity 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 Dunbar, the 
 spray may be seen occasionally moving up the little coves and inlets in 
 the form of a distinct mist driving before the wind, and the saline matter 
 has been known to traverse nearly half the breadth of the island before 
 it was entirely deposited from the air. 
 
 It is impossible to calculate how much of the salinematterof sea water 
 may in this way be spread over the surface of a sea-girt land 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 coun- 
 
SULPHATE OF SODA, SULPHUUET OF SODIUM, CARBONATE OF SODA. 191 
 
 try perhaps in larger (]uantity or more extensively than in England. 
 Thai it has often failed to benefit the land in particular localities, only 
 shows that the soil in those places already contained anatural supply of 
 this compound large enough to meet the wants of the crops which grew 
 upon it. The facts above stated as to the influence of the wind in top- 
 dressing the exposed coast-line of a country with a solution of salt, inay 
 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 sul])huric acid (oil of vitriol), 
 and applying heat. Muriatic acid (spirit of salt, so called by the old 
 cheriiists, because thus given off' by common salt,) is given otT in the 
 form of vapour, and sulphate of soda remains behind. It may also be 
 prepared, tliough less economicall}', by adding ihe conmion soda of the 
 sho|)3 lo diluted sulphuric aciii as long as any eilervescence appears. 
 
 This well known salt is met with in variable quantity in the ashes of 
 nearly all plaiits, and is diffused in minute proportion through most 
 soils. I have elsewhere [see Appendix,] directed your attention to the 
 beneficial effect wliicli it has been observed to exercise on the growth 
 especially of such ])lants as are known lo contain a considerable propor- 
 tion of sulphuric acid. Among these are red clover, vetches, peas, &c. 
 And as tiiis salt is manufactured largely in this country, and can be ob- 
 tained at the low price of ten shillings a cwt. in the dry state,* I have 
 recommended it lo the practical farmer as likely to be extensively useful 
 as a manure for certain crops and on certain soils. The kind of crops 
 and soils have as yet in great measure to be determined by practical 
 trials. — [See the results of Mr. Fleming's Experiments, given in ihe 
 Appendix.] 
 
 3°. Sulphurct of Sodium. — When sulphate of soda is mixed with 
 saw-dust, and heated in a furnace, the oxygen of the salt is separated, 
 and sulphuret of sodium is produced. By a similar treatment sulphate 
 of potash is converted into sulphuret of potassium. These compounds 
 consist of sulphur and metallic sodium or potassium only. They do 
 nol occur extensively in nature, and are not manufactured for sale; but 
 there is reason to believe that they would materially promote the vege- 
 tation of such plants as contain much sulphur in combination with pot- 
 ash or soda. The sulphuret of sodium is present in variable quantity in 
 the refuse lime of the alkali works, already spoken of, and might be ex- 
 pected to aid the other substances of which it chiefly consists, in contri- 
 buting to the more rapid growth of 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, be- 
 cause they are all steps in the process by which the latter is usually pre- 
 pared from common salt, by the soda manufacturers. 
 
 "When the sulphuret of sodium is mixed with chalk in certain propor- 
 tions, and heated in a furnace, it is deprived of its suljjhur, and is con- 
 verted into carbonate of soda, the common soda of the shops. 
 
 This well known salt, now sold in the state of crystals, [containing 62 
 
 * Not in crystals, the form in which it is commonly sold as a horse medicine. These 
 crystals contain upwards of half Iheir weight (55 per cent.) of watep. 
 
 9 
 
192 SODA OR CAUSTIC SODA. 
 
 per cent, of waler,] at from 10s. to 12s. a cwt., has not as yet been ex- 
 tensively tried as a means of promoting vegetation. The lowness of its 
 price, liowever, and the fact that it is an article of extensive home man- 
 ufacture, conjoined with the encouragement we derive from theoretical 
 considerations — all unite in suggesting the i)ropriety of a series of ex- 
 periments with the view of determining its real value to the practical 
 agriculturist. 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 considera- 
 tion hereafter. 
 
 Besides the common carbonate of soda above described, and which in 
 the neighbourhood of Newcastle 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 carbonic acid, in which the latter 
 substance is present in larger quantity than in the soda of the shops. 
 The sesgui-carhonaie, containing one half more carbonic acid, occurs in 
 the soil in many warm climates (Egypt, India, South America, &c.), 
 and at Fezzan, in Africa, is met with as a mineral deposit of such 
 thickness as in that dry climate to allow of its being employed as a 
 building stone. 
 
 The 6i-carbonate is contained in the waters of many lakes, in Hunga- 
 ry, 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 outlets. 
 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, ac- 
 cording to Mr. West, owes its softness to the presence of this carbonate, 
 and the water from the coal-mines in the neighbourhood of Wakefield 
 is occasionally so charged with it, as to form troublesome saline incrus- 
 tations on the bottoms of the steam boilers. Where these waters occur 
 in sufficient abundance, 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 locali- 
 ties impart a degree of luxuriance to natural 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 alkaline, or 
 other mineral ingredient, which the soil is unable to supply to the plants 
 which grow upon it, either in sufficient abundance, or with sufficient 
 rapidity. 
 
 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 carbonic acid, 
 and like the carbonate of potash (p. 187) is brought into the caustic state. 
 In this state it destroys animal and vegetable substances, and, unless 
 very dilute, is injurious to animal and vegetable 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, 
 aud is partially converted into this caustic soda. The action of the soda 
 in this state is similar to that of caustic potash. Not only does it readi- 
 
SODIUM, PHOSPHATES OF SODA, AND CARBONATE OF LIME. 193 
 
 ly supply soda to the growing ]>lant, to which soda is necessary, but it 
 also acts upon certain other substances wiiich the plants require, so as 
 to render them soluble, and lo faciliiaie their entrance into the roots of 
 plants. To the presence of soda in this caustic state, the efficacy of 
 such composts of common salt and lime in promoting vegetation, is in 
 part to be ascribed. 
 
 6°. Sodium is a soft metal of a silver white colour, and, like potassi- 
 um, 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 oxy- 
 gen to form soda. In the metallic state it is not known to occur in na- 
 ture, and, therefore, does not directly act upon vegetation. With oxy- 
 gen 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 beneficial to vegetation. 
 
 7°. Phosphates of Soda. — When the common soda of the shops is added 
 to a solution of phosphoric acid in water, till efiervescence ceases, and 
 ihe solution is evaporated to dryness, phosphate of soda is formed, and 
 by the subse(|uenl addition of as much more phosphoric acid — Z)j-phos- 
 phate. These salts occur more or less abundantly in the ash of nearly 
 all plants ; they are occasionally also detected in the soil, and one or 
 other of them is ahiiost always present in urine and other animal ma- 
 nures. As we know from theory that these compounds must be grate- 
 ful to plants, we are justified in ascribing a portion of the efficacy of animal 
 manures, in promoting the growth of vegetables, to the presence of these 
 phosphates, as well as to that of the phosphates of potash (p. 190). 
 They are not known to occur in the mineral kingdom in any large quan- 
 tity, neither are they articles of manufacture, hence their direct action 
 upon vegetation has not hitherto been made the subject of separate ex- 
 periment. 
 
 VII. CALCIOM, LIME, CARBONATE OF LIME, SULPHATE OF LIME, NI- 
 TRATE OF LIME, PHOSPHATES OF LIME, CHLORIDE OF CALCIUM, SUL- 
 PHURET OF CALCIUM. 
 
 1°. Carbonate of Lime. — Chalk, marble, and nearly all the lime- 
 stones in common use, are varieties, more or less pure, of that com- 
 pound of lime with carbonic acid which is known to chemists as car- 
 bonate of lime. It occurs of various colours and of various degrees of 
 hardness, but in weight the compact varieties are very much alike, be- 
 ing generally a little more than 2^ times {2*7) heavier than water. 
 They all dissolve with efiervescence in dilute muriatic acid (spirit of 
 salt), and by the bubbles of gas which are seen to escape when a drop 
 of this acid is applied to them, limestones may in general be readily dis- 
 tinguished from other varieties of rock. They dissolve slowly also ia 
 water which liolds carbonic acid in solution ; and hence the springs 
 which issue from the neighbourhood of deposits of limestone are gene- 
 rally charged in a high degree with this mineral substance. 
 
 The value of this carbonate of lime in rendering a soil capable of pro- 
 ducing and sustaining a luxuriant vegetation depends, in part, it is true, 
 on the necessity of a certain proportion of lime to the growth and full 
 developementof the several partsof nearly all plants, but it performs also 
 
194 QUICK-LIME, CALCIUM, AND CHLORIDE OF CALCIUM. 
 
 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 guick-lime, 
 from its caustic qualities, and is found to have lost nearly 44 per cent, of 
 its original weight. 
 
 The most remarkable property of quick-lime is its strong tendency to 
 coinbine 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. Slaked lime is a compound of 
 lime with water, and by chemists is called a hydrate of lime. It con- 
 tains 24 percent, of its weight of water. 
 
 The action of quick-lime upon the land is one of the most important 
 which presents itself to the observation of the jjractical agriculturist. 
 Among other effects produced by it is that of hastening the decomposi- 
 tion 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 substances are produced, which the roots are 
 capable of absorbing and converting into the food of plants. 
 
 In this caustic state lime does not occur in nature, nor when exposed 
 to the air does it long remain in this 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 reconverted into carbonate. On the contrary, 
 the state of very fine powder, into which (]uick-lime falls on slaking, 
 enables the carbonate of lime, subsequently formed, to be intermixed 
 with the soil in a much more minute state of division than could be ob- 
 tained by any mechanical means. This we shall hereafter see to be a 
 most important fact, when we come to study in more detail the theory 
 of the action of lime in the several states of combination, 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 not known to exist in nature in an uncombined state, 
 is prepared artificially only with great difficulty, and therefore exercises 
 no direct action on vegetable growth. 
 
 4°. Chloride of Calcium. — When chalk or quick-lime is dissolved in 
 muriatic add, a solution of chloride of calcium is obtained. This solu- 
 tion occurs in sea-water, in the refuse (mother-liquor) of the salt-pans, 
 and is allowed to flow away in large quantities as a waste from certain 
 chemical works. I have elsewhere stated the effects it has been ob- 
 served to produce upon vegetable growth, [see Appendix,] and have re- 
 commended the propriety of making experinients with the view of ren- 
 dering useful soine of those materials which in our manufactories are 
 now suffered largely to ruu to waste. 
 
 6°. Sulphuret of Calcium is a compound of sulphur and calcium, 
 which maybe formed by heating together chalk and sulphur in a covered 
 
SULPHATE AND NITRATE OF LIME. 195 
 
 cruciDie. It is sometimes produced in nature, where moist decaying 
 vegetable and animal matters are allowed to ferment in the presence of 
 gypsum ; it may sometimes also be delected in the soil, and in the waters 
 of mineral springs, and is contained largely in the recent refuse heaps 
 of the alkali works. Like the sulphurefs of potassium and sodium, al- 
 ready described, it is fitted, when judiciously applied, to jsromote the 
 growth especially of those plants in which sulphur has been recognized 
 as a necessary constituent. 
 
 6°. Sulphate of Lime, or gypsum, is a well known white crystalline 
 or earthy compound, which occurs as an abundant mineral deposit in 
 numerous ]iarts 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 detect- 
 ed in sensible proportions in the ashes of many cultivated plants. It 
 is extensively emploj^ed in the arts, and in some countries not less ex- 
 tensively as a means of promoting the fertility of the land. — [See Appen- 
 dix, p. 1.] 
 
 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 oc- 
 curs in rocky masses, and is distinguished by the name of Anhydrite. 
 
 Gypsum, when burned, has ths property of being reduced with great 
 ease into the state of an impalpable powder. This powder, however, 
 combines so readily with the 21 per cent, of water it had previously lost, 
 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 employed in making plaster casts 
 and cornices. 
 
 Burned gypsum consists of lime and sulphuric acid only — in the pror 
 portions of 41^ of the former, to 58^ of the latter. Its use as a manure, 
 therefore, will be specially to promote the growth of those plants by 
 which these two substances are more abundantly required, and upon 
 soils in which they are already present in comparatively small propor- 
 tion. 
 
 7°. Nitrate of Lime. — The production of nitrate of lime in artificial 
 nitre-beds, on old walls, and on the sides of caves and cellars, especially 
 in damp situations, has already been alluded to in Lecture VIII., [p. 
 161.] It may be formed artificially by dissolving common limestone in 
 nitric acid, and evaporating the solution. It constitutes a \ihite mass, 
 which rapidly attracts water from the 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 solubili- 
 ty in water, however, renders it liable to be carried downwards into the 
 lower portions of the soil by every shower of rain — or to be actually 
 washed 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 de- 
 tected in the ash, — and when present in soils, it must be separated by 
 
196 PHOSPHATE Of LI WE. 
 
 ■washing them in water, before they are exposed to a heat sufficient to 
 burn away the organic matter they contain. 
 
 The details already entered into in the preceding lecture (pp. 159 to 
 163) regarding 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 particularly 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 sufficiently 
 cheap rate to allow of its being manufactured for the use of the agricul- 
 turist. 
 
 Phosphates of Lime. — Lime combines with phosphoric acid in sev-> 
 eral proportions, forming as many different compounds. Of these by 
 far the most important and abundant in nature, certainly the most use- 
 ful to the agriculturist, is the earth of hones. It will be necessary, how 
 ever, to advert shortly to two others, with the existence of whicli 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 disappearfd. This earthy matter consists 
 chiefly of a peculiar phosphate of lime, composed of 51i per cent, of 
 lime, and 48i of phosphoric acid. This compound exists ready formed 
 in the bones of all animals, and is the substance selected in the economy 
 of nature to im})art 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 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 jiresent in lesser quantity in the horns, hoofs and nails, 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 tor focxl, and in the ashes of most common plants. 
 The ashes of leguminous, cruciferous, and composite plants, are es- 
 pecially rich in this compound. 
 
 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 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 c^^, as occurring in, and as necessary to the growth of, 
 vegetables, — that some soils contain it in greater abundance than others, 
 and that from some soils, therefore, certain plants will not readily obtain 
 as much of this substance as they require. This is the natural principle 
 on which the use of bone-dust as a niEinure chiefly depends. 
 
 Hence of two marls both containing carbonate of lime, that will be 
 HiDst useful to the land which contains also, as many do, a notable por- 
 tion of phosohate of lime; and of two limestones, that will be preferred 
 
BOILED BONES AS A MANURE. 197 
 
 in an agricultural district in which animal remains most abound. I 
 shall have occasion to illustrate this point more fully, when in a subse- 
 quent 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 proper- 
 ties of this bone earth which are of practical importance, and to which, 
 therefore, I must shortly request your attention. It is insoluble 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 solu- 
 tion by a peculiar acid found in this liquid, and which is distinguished by 
 the name o( 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 enabled to bear along with it not only common 
 carbonate of lime, as has been shown in a previous lecture (p. 47), but 
 also such a portion of phosphate as may aid in supplying this necessary 
 food to the growing plant.* 
 
 In the bones of animals the phosphate is associated with animal gela- 
 tine, 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 ex- 
 tracted 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 
 this country, bones are seldom boiled, I believe, either for the jelly they 
 give, or as in France and Germany for the manufacture of glue, though 
 in certain localities they are so treated in open vessels for the sake of the 
 oil they are capable of yielding. Such boiled bones are said to act more 
 quickly when applied to the land, but to be less permanent in their ef- 
 fects. This may be chiefly owing to their not being so perfectly dry as 
 the unboiled bones. Being thus moist, ihey will contain, in tifc same 
 w-eight, a comparatively smaller quantity boih of the animal gelatine 
 
 * If to a solution of bone earth in muriatic acid (spirit of salt), liquid ammonia (hartshorn) 
 be added, the solution will become milky, ami a white powder will fall, which is the earth 
 of bones in an extremely minute slate of division. If this powder be washed by repeated affu- 
 sions of pure water, and be aftervvards well sliaken with water which is saturated with car- 
 bonic 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 
 solution and cvaporatins; it to dryness, when a quaniity of the white powder will remain be- 
 hind. The mean of 10 experimenis made In this way save me 30 grains for the quaniity of 
 phosphate taken up by an impei ial gallon of water. What takes place in this way in our 
 hands, happens also in the soil. Not only does that which enters the root bear with it a por- 
 tion of this compound where it exists in the soil, but the superabundant water also which 
 nms off the surface or sinks through to Llie drains, carries with it to the rivers in its cours^ 
 a still larjjcr quantity of this soluble compound, and thus gradually lessens that supply of 
 phosphate which eitlier exists naturally in the soil, or has been added as a manure by the 
 practical agriculturist. 
 
198 ACID OR BI-FHOSPHATE OF LIME. 
 
 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 presence of 
 these compounds in the soil may facilitate the conveyance of the earthy 
 phosphate into the roots of plants. 
 
 B. Acid or Wi-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 phos- 
 phoric acid exists, in much larger quantity than in the earth of bones. 
 The true bi-phosphale, when free from water, consists of 71i of phos- 
 phoric acid, and 28i of lime. It exists in the urine of most animals, and 
 is therefore an important constituent of liquid manures of animal origin. 
 
 If the mixture of gypsum and acid phosphate, above described, be 
 largely diluted with water, it will form a most valuable liquid manure, 
 especially for grass land, and for crops of rising corn. In this liquid 
 state, the phosphoric acid will diffuse itself easily and perfectly through- 
 out the soil, and there will speedily lose its acid character by combining 
 with one or other of the basicf 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 will be obtained, or — if soda be 
 added instead of potash — of the phosphates with the sulphates of lime 
 and of soda; either of which mixtures will be still more efficacious 
 upon the land, ihanihe soluU!.)n 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 band as a top-dressing, or buried m 
 the land by means of a drill. 
 
 I have above alluded to the employment of bones in France and Ger- 
 many, for the manufacture of glue. For this purpose the broken bones 
 are digested in weak muriatic acid, by which the earthy matter is dis- 
 solved, and the gelatine left behind. The gelatinous skeleton is boiled 
 down fcff glue, and the solution of the bone earth is 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 inferior in quality, and as the process is not adopt- 
 ed 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. 
 
 ' 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 Ion. 
 
 t 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 (sul- 
 phuric, nitric, &c.) and of thus neutralizing them, or depriving them of their acid qualities 
 and effects. 
 
NATIVE PHOSPHATE OF LIME. 199 
 
 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 its constitution from the earth of bones, 
 — containing 54^ per cent, of lime, while the latter contains only 51^ per 
 cent. The comixisition 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. — [Ckemie, I., p. 64.] 
 
 It occurs occasionally in mineral veins, especially such as are found 
 in the granitic and slate rocks. Masses of it are met with in Cumber- 
 land, in Cornwall, in Finland, in the iron mines of Arendahl in Nor- 
 way, and in many other localities. A variety of it distinguishetl by the 
 name of phosphorite is said to form beds at Schlachenwalde in Bohemia, 
 and in the province of Estremadura in Spain. From the last of these 
 localities being the most accessible, the time may come when the high 
 price of bones may induce our enterprising merchants to import it, for 
 the purpose of being employed in a finely powdered state as a fertilizer 
 of the land. 9* 
 
LECTURE X, 
 
 Inorgftntc constituents of plants continued. — Magnesia, Alumina, Silica, and the Oxides of 
 Iron and Manganese. — Tabular view of the constitution of the inorganic substances de- 
 scribed.— Proportions in which these several substances are found in the plants culiivatcd 
 for food. —Extent to whicli these plants exhaust the soit of inorganic vegetable food.— State 
 in which the inorganic elements exist in plants. 
 
 § 1. Inorganic constituenla ofijlants conLinued. 
 
 Vni. MAGNF.SIDM, MAGNK9IA, CARBONATE, SULPHATE, NITRATE, AND 
 
 PHOSPHATE OF- MAGNESIA, CHLORIDE OF MAGNESIUM. 
 
 1°. Carbonate of Magnesia is a tasfeless earthy compound, which in 
 some parts of the world forms rocky masses and veins of considerable 
 height and thickness. It occurs more largely, however, in connection 
 with carbonate of lime in the magnesian limestones, so well known in 
 the eastern and northern parts of England, — and in similar rocks, dis- 
 tinguished by the name of dolomites or of dolomitic limestones, in va- 
 rious countries of Europe. The pure, exceedingly light, white magne- 
 sia of the shops, is partly extracted from the magnesian limestone, and 
 partly froiri the mother liquor of the salt pan», which generally contains 
 much magnesia. 
 
 When pure and dry, carbonate of magnesia consists of 43^ ofinagne- 
 sia, and 51§ of carbonic acid. It dissolves readily in diluted acids (sul- 
 phuric, muriatic, and acetic,) the carbonic acid at the same lime esca- 
 ping with effervescence. 
 
 Existing as it does in many solid rocks, this carbonate of magnesia 
 may be expected to be present in the soil, and it is found in the ashes of 
 many plants. Of the ashes of sotne parts of plants it consiitutes one- 
 sixth of the entire weight. 
 
 When exposed to the air in a finely divided state, it gradually absorbs 
 a quantity of moisture from the almosphere, etjual to two-thirds of its 
 own weight. In this state, it dissolves in 48 limes its weight of water, 
 though, when dry, it is nearly insoluble. Like carbonate of lime it is 
 also soluble in water impregnated with carbonic acid, but in a some- 
 what greater degree. In this slate of solution it may be readily carried 
 into the roots, and be the means of supplying to the pans of living ve- 
 getables a portion of that magnesia which is necessary to their perfect 
 growth. 
 
 Soils containing much of tliis carbonate of magnesia are said to be 
 highly absorbent of moisture, and to ihis cause is ascribed tlie coldness of 
 such soils. — [Sprengel, Chemic, I., p. 645.] 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 lime 
 does, and is brought into the state of pure or caustic magnesia. In this 
 elate it does not occur in nature, but it is occasionally met with in com- 
 
CAUSTIC OR CALCINED MAGNESIA. 201 
 
 bination with about 30 per cent, of water. When raagnesian lime- 
 stones or dolomites are burned, the quick-lime obtained often contains 
 caustic magnesia also in considerable quantity. This mixture is fre- 
 quently applied to the land, and, as is well known in many parts of 
 England, with injurious etfects, if laid on in too large quantities. The 
 cause of this hot or burning nature, as it is called, of magnesian lime, is 
 not very satisfactorily ascertained. I shall, however, state two or three 
 facts, whicli may assist in conducting us to liie true cause. 
 
 1°. Quick-lime dissolves in 750 times its weight of water, at the or- 
 dinary temperature of the atmosphere, while pure magnesia requires 
 5142 times its weight. The magnesia, therefore, is not likely to injure 
 living plants direclly by entering into their roots in its caustic state, since 
 lime which is seven times more soluble produces no injurious eff&ct. 
 
 2''. It seems lo be the result of experience, that magnesia in the state 
 of carbonate is but slightly injurious to the land ; some deny that in this 
 stale it has any injurious effect at all. Tliis I fear is doubtful ; we may 
 infer, however, witli some degree of probability, that it is from some 
 pro|)erty possessed by magnesia in the caustic state, and not possessed, 
 or at least in an equal degree, either by quick-lime or by carbonate of 
 magnesia, that its evil influence is chiefly to be ascribed. 
 
 3°. When exposed to the air, quick-lime speedily absorbs water 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 latter, 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 tiie state of hydrate, and it is a property of this hydrate 
 to attract carbonic acid more feebly and slowly, even tlian the newly 
 burned magnesia as it comes from the kiln. Hence when buried in the 
 soil, after the lime has become nearly all transformed into carbonate, the 
 magnesia may still be all either in the dry caustic state, or in that of a 
 hydrate only. 
 
 4°. 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 applied 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 I'orm salts, j which generally are 
 7nuc}i more soluble in water than the compounds of lime with the same 
 acids. Hence the water that goes to the roots reaches them more or 
 less loaded with magnesian salts, and carries into the vegetable circula- 
 tion more magnesia than is consistent with the healthy growth of the 
 plant. 
 
 It is hazardous to reason from the phenomena of aniinal to those of 
 
 • Compounds of substances with water are caUed hydrates (from the Greek word for wa- 
 ter.) Thus slaked lime, a compound of lime with water, is called hydrate of lime — and the 
 native compound of magnesia with water, alluded to in the text, is called hydrate of mag- 
 nesia. 
 
 t Compounds of the fcases, — potash, soda, lime, magnesia, &c., — with acids, — sulphuric, 
 muriatic, nitric, acelic (or vinegar), &c., — are called salts. 
 
202 MAGNKSIUM, AND CHLORIDE OF MAGNESIUM. 
 
 vegetable physiology, yel if lime and magnesia have ihe power of dif- 
 ferently affecting the animal economy, why may they not also very 
 differently affect tlie vegetable economy ? And since in the same cir- 
 cumstances, 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 considered capable of poi- 
 soning a plant, when lime in the same condition would only improve 
 the soil ? 
 
 I have said that it may be doubted whether magnesia in the state of 
 carbonate is wholly unhurtfiil 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 mag- 
 nesian 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 de- 
 composed and dissolved as to render the water absorbed by its roots 
 destructive to the health or life of a plant. 
 
 In reference to lliis point, however, it must be distinctly understood, 
 that magnesia is one of the kinds of inorganic food most necessary to 
 plants, that a certain (|uantity of it in the soil is absolutely necessary to 
 the growth of nearly all cultivated plants, and that it is only when it is 
 conveyed to the roots in loo large a (juantity, that it proves injurious to 
 vegetable life. 
 
 6°. Magnesium is the metallic basis of magnesia. Little is known 
 of its properties, owing to the difHculty of preparing it in any consider- 
 able quantity for the purpose of experiment. It is a while meial, which, 
 when heated in the air, takes fire and burns, combining with the oxygen 
 of the atmosphere, and forming magnesia. It is not known to occur in 
 nature in an eleinentary form, and therefore is not supi)osed directly Kj 
 influence vegetation. 
 
 6°. Chloride of Magnesium. — When calcined or carbonated magne- 
 sia is dissolved in muriatic acid, and the solution evaporated to dryness, 
 a white mass is obtained which is a chloride of ma gnesitun, consisting of 
 magnesium and chlorine only. This compound occurs notunfrequently 
 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 (juantity. Thus 100 parts of the water of 
 the Atlantic have been found to contain .3i of cldoride of magnesium, 
 while that of the Dead Sea yields about 24 j)arts of ihis compound.* 
 Hence it is present in great abundance in the inother rupior of the salt 
 pans, and it is from the refuse chlori<le in this liquor tliat the magnesia 
 of the shops, as above staled, is frequently prepared. 
 
 The chloride of magnesium has not hitherto been made the subject of 
 direct experiment as a fertilizer of the land. From ilie fact, however, 
 that plants require much magnt^sia and some chlorine, 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. Tlie safest method is to 
 
 * 100 parts of the water of the Dead Sea contain also about lOJ of ohlorido of calcium, 
 and nearly 8 of common salt. 
 
MTRATK, SL'LPHATK, AND PHOSPHATK OF MACNKSIA. G03 
 
 dissolve it in a large quantity of water, and to api)ly it to the young 
 plant by means of a water-cart. In this way the refuse of the salt 
 works iniglit, in some localities, be made available to useful purposes. 
 
 Tlie chloride of magnesium is decomposed both by rjuick-lime and by 
 carbonate of lime ; hence when applied to a soil containing lime ir 
 either of these states, cliloride of calcium and caustic or carbonated mag 
 nesia will be produced. 
 
 7°. Nitrate of Magnesia is formed by dissolving carbonate of magne 
 sia 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 nitrate of 
 lime is known to be produced in soils containing lime. [See Lecture 
 VIII., p. 169.] No direct experiments have yet been made as to its 
 efiects upon vegetation ; but there can be no doubt that it would prove 
 highly beneficial, could it be procured at a sufficiently cheap rate to ad- 
 mit of its economical application to the land. 
 
 8°. 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 magnesia. In some soils it is so 
 abundant that in dry weather it forms a while efflorescence on the sur- 
 face. This has been observed to take place in Bohemia, Hungary, and 
 j)arts of Germany, and it may be frequently seen in warm summer 
 weather in the neighbourhood 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 ([uantity, owing to its great solubili- 
 ty. Its higher price will prevent its ever being substiluled for gypsum, 
 as a top-dressing for clover, &c., but It is worth the trial, whether corn 
 plants, the grain of which contains much magnesia, might not be bene- 
 fitted by the application of a small quantity of this sulphate — along with 
 such other substances as are capable of yielding the remaining constit- 
 uents which compose the inorganic matter of the grain. Its price is not 
 too high to admit of this more restricted application. f 
 
 9°. Phosphate of Magnesia. — Magnesia exists in combination with 
 phosphoric acid, in the solids and fluids of all animals, though not so 
 abundantly as the phos])hates of lime. In most soils phosphate of mag- 
 nesia is probable present in minute quantity, since in the ashes of some 
 varieties of grain it is found in very considerable proportion. 
 
 Its action upon vegetation has never been tried directly, but as it 
 exists in urine, and in most animal manures, a portion of their efficacy' 
 may be due to its presence. In turf ashes, which often prove a valua- 
 ble manure, it is sometimes met with in appreciable quantity, and their 
 beneficial operation in such cases has been attributed in part to the agen- 
 cy of this phosphate. 
 
 ■ It occasionally collects beneath the plaster of old walls in Durham. 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 metgnesia is derived from the magnesian lime- 
 stone, used both for mortar and for building stone. 
 
 t It.s price in Newcastle in the state of crystals, is about 10s. a cwt. The impure salt col- 
 lected at llie alum worlts on the Yorkshire coist, might be obtained, I should suppose, for 
 little more than half this price. 
 
204 ALCMliNA THE I'RI.NCIPAL, CONSTITUKNT OF CLAYS. 
 
 IX. 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 combination 
 with oxygen it forms alumina, and in this state it exists in such abun- 
 dance in nature, as to form a large portion of the entire crust of the 
 globe. 
 
 2°. Alumina, the earth of Alum. — When common alum is dissolved 
 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 ingre- 
 dient 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 adheres to 
 the tongue, has a density of 2*00, and is insoluble in water, but dissolves 
 readily in caustic potash and soda and in most acids, at least when new- 
 ly thrown down from a solution of alum. 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 nourishment of plants. The ash they 
 leave contains in general but a very small per-centage of alumina, as 
 will more clearly appear hereafter, — the principal agency, therefore, of 
 this ingredient of the soil is most probably of an indirect, perhaps of a 
 mechanical kind. 
 
 It has been stated in a preceding Lecture (p. 23), that charcoal has 
 the property of absorbing gaseous substances, such as amtnonia, 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 (p. 136), is ascribed to gypsum, and 
 hence its fertilizing action has been explained in a similar way. Alum- 
 ina is said to be equally absorbent of ammonia ; and the use of burned 
 clay as a top-dressing, so strongly recommended by General Beatson, 
 [New Syste7n of Cultivation, London, 1820,] is ascribed to its power 
 of abstracting ammonia from the air, and fixing it in the soil ready to be 
 conveyed by the rains totlie roots of the plants that grow upon it [Liebig, 
 p. 90.] It has been already shown (p. 136,) that this mode of ac- 
 counting for tbe action of gyjjsum is not satisfactory as a sole cause — in 
 the case of alumina, the fact of its absorbing ammonia is hypothetical,* 
 and therefore the explanation founded upon this fact is not to be impli- 
 citly relied upon. 
 
 3°. Sulphate of Alumina. — When alumina is digested in diluted sul- 
 
 Because clays of many varieties — pipeclay for example — contain traces of ammonia, 
 which they evolve wlien moistened with a solution of caustic potash,— it is inferred that 
 they have absorbed this ammonia from the atmosphere. The same inference is drawn 
 from the fact of its presence in oxide of iron. — [Liebig's Organic Chemistry applied to Agri- 
 culture, 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.— See above, Lecture VIII., p. 15S. 
 
SOLPHATE AND PHOSPHATKS OF ALUMINA, ALUM. 205 
 
 phuric acid, it readily dissolves, and forms a solulion of sulphate of 
 alumina. This solulion is characteri/.e'd by a remarkable and almost 
 peculiar sweetish astringent taste. When evaporated to dryness it yields 
 a wliite sail, which dissolves in twice its weight of water only, and when 
 exposed to the air, attracts moisture rapidly, and spontaneously runs to 
 a liquid. This salt exists in some soils, especially in those of wet, 
 marshy, and peaty lands. 
 
 No experiments have yet been made with the view of determining its 
 direct influence upon vegetation. 
 
 4°. Phosphates of Alumina. — In combination with phosphoric acid, 
 alumina forms one coiTipound well known to mineralogists, by the name 
 o{ 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 throughout 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 combina- 
 tion with the alumina in the state of {)hosphaie. One of the most ditfi- 
 cult problems in analytical chemistry is to effect a perfect separation of a 
 small proportion of phosphoric acid from alumina, and rigorously to esti- 
 mate 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 altogether 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 alumi- 
 na. It consists in 100 parts of about 40 of sulphate of alumina, 14i of 
 potash, [described p. 189,] 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 exposed to the air, — as on the 
 alum shales of the Yorkshire coast. It is largely manufactured by cal- 
 cining, and afterwards washing these alum shales. 
 
 Alum has not been extensively tried as a manure. Its composition, 
 however, would lead us to expect it to exert a beneficial influence on the 
 growth of many plants — while the price, especially of the less pure va- 
 rieties, is such as to admit of its being ap[;lied to the land at a compara- 
 tively small cost. From some experiments made on a small scale, 
 Sprengel considers it highly worthy the attention of the practical agri 
 culturist. 
 
 X. — SILICA, SILICO>', SILICATES OF POTASH, OF SODA, OF LIME, OF 
 MAGNESIA, AND OF 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 chalcedony present it in a state of almost 
 perfect purity- It exists abundantly in almost all soils, constituting 
 what is called their siliceous portion, and is found in the ashes of all 
 plants without exception, but especially in those of the grasses. Silica 
 
206 SILICA, SILICON, SILICATES OF POTASH AND SODA. 
 
 is without 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 heated in a crucible to a 
 high temperature, it melts and forms a glass. Window and plate glass 
 consists 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 water, yet it sometimes occurs in nature, 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 
 potash or soda, and afterwards treating the glass that is formed with di- 
 luted muriatic acid. 
 
 Silica is one of the most abundant substances ia nature, and in com- 
 bination with potash, soda, lime, magnesia, and alumina, it forms a 
 large portion of all the so-called crystalline (granitic, basaltic, &c.) 
 rocks. The compounds of silica, with these bases, are called silicates. 
 By the action of the air, and otber causes, these silicates undergo decom- 
 position, as glass does when digesied with 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 beneath the surface, or have made their way 
 through any considerable extent of soil. 
 
 In the substance of living vegetables it exists, for the most part, in 
 this state of combination — as well as in the form of an extremely deli- 
 cate 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 the compost heaps these silicates 
 undergo decomposition, — and the more readily the less they have been 
 previously dried, or the greener they are, — and the silica of the plant is 
 liberated in a soluble state. Whether or not, when thus liberated, it 
 will be carried, uncornbined, into ihe roots of the plants by the water 
 tliey 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 ditficulty. When heated in 
 the air, or in oxygen gas, it bums, combines with oxygen, and is con- 
 verted 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 to three times its weight of 
 dry carbonate of potash or soda, and exposed to a strong heat in a cruci- 
 ble, 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 iiotash or soda- 
 
DECOMPOSED BY THE CARBONIC ACID OF THE AIR. 207 
 
 Silica combines wilh these alkalies* in various proporlions. If it be 
 naelted 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 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 mineral 
 substances. In the felspar and mica, of which granite in a great mea- 
 sure consists, they are present in considerable quantity. The former 
 (felspar) contains one-third of its weight of an insoluble 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 abundant in many parts of our island, consist almost 
 entirely n( silicates. 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 stems 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 [p. 178.] 
 
 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. Insoluble as they are in 
 water, they arc slowly densmposed 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 rock disintegrates and crumbles down, while the so- 
 luble 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 exceedingly slow, — but in all 
 cases the rock crumbles to powder long before the whole of the silicates 
 are decomposed, so that porash 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 zeoliticf trap, when thus de- 
 prived of the potash with which it was combined, is in that peculiar state, 
 in which, as above described [p. 206], it is capable of being dissolved 
 in small quantity by pure water, and more largely by a solution of 
 carbonate of potash or soda. Hence the same rains or mists which dis- 
 
 * Potash, soda, and ammonia are called alhalics ; lime and magnesia are alkaline earths. 
 See Lecture III , p. 51, note. 
 
 t The trap-rocks always 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 contained. 
 
208 SILICATKS OF LIME IN THE TRAP-ROCKS. 
 
 solve 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 exception of the dews and rains which fall directly frqm 
 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 theii 
 nourishment. 
 
 In the farm-yard and the compost-heap, where vegetable matters are 
 undergoing decomposition, the silicates they contain undergo similar de- 
 compositions, 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 jilate-glass, and in some of the crystalline* (granite and 
 trap) rocks. In felspar and mica, which abound, as we have seen, in 
 the alkaline silicates, it is rare that any lime can be detected. In that 
 variety of granite, however, to which the name of syenite is given by 
 mineralogists, hornblende lakes the place ol' mica, and some varieties of 
 this hornblende contain from 20 to 35 jjer cent, of silicate of lime. This 
 silicate (containing 38 per cent, of lime) is almost always present in the 
 basaltic and trap-rocks, and sometimes, as in the augiticf traps, in a 
 proportion much larger than that in which it exists in the unmixed horn- 
 blende. To this fact we shall have occasion to revert when we come 
 to consider the relative fertility of diHerenl soils and the causes on which 
 the difference of their several productive powers most probably depends. 
 
 Silicates of lime are also found in the ash, and probably^ 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 dissolves in the rains or 
 dews which descend loaded with carbonic acid, [see page 46,] 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 af- 
 forded to soils W'hich rest upon decayed traj), or which are wholly made 
 up of rotten rock, has a material influence upon their well-known agri- 
 cultural capabilities. 
 
 5°. Silicates of Magnesia- — In combination with magnesia in differ- 
 ent proportions, silica Ibrms 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 considerable quantity. 
 
 ' So called because the minerals of which they consist are generally in aayslailized state. 
 
 t Rocks of which the mineral called augite forms a more or less considerable part. 
 
 t I say probaMy, because if uncombined silica be preseni in hay or straw along with car- 
 bonate or oxalate of lime, the lieat employed in completely burning away the organic matter 
 may be sufficient to cause the lime and silica to unite and form a silicate which will after- 
 wards be found in the ash, though none previously existed in the stem. 
 
SILICATES OF ALUMINA. 209 
 
 They must, therefore, be present in greater or less qunntity in soils 
 \vhich are directly formed from the decomposition of such rocks. Like 
 tiie 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 down, in a state of solution (p. 200), from the 
 higher grounds, or washed out of the soil, till at lengih it may wholly 
 disappear from any given s|rot.* 
 
 6°. Silicales of Alumina. — Silica combines with alumina also in vari- 
 ous pro])ortions, forming silicates, which exist abundantly in nature in 
 the crystalline rocks, and may also, like the other silicates, be formed 
 by art. Felspar, mica, hornblende, and the augiies, 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 up- 
 wards of one-half by weight of the trap-rocks in general — as well ns of 
 the hornblendes, micas, and felspars, of which so large a part of the 
 granitic rocks is composed-.^consists of silicales of alumina. The alu- 
 mina 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 ihe atmosphere. 
 They disintegrate, however, and fall to powder, wlien the alkaline sili- 
 cates 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 pro- 
 duced from the disintegration of the felspathic rocks, and the clayey soils 
 ■which occur in granite districts have not unfrequenily had a similar origin- 
 
 "When contained in the soil, the silicates of alumina undergo a slow 
 decomposiuon from the action of the various acid substances to which they 
 are 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 is washed from the soil by the rains — or by the waters that 
 arise from beneath. 
 
 The ash of plants contains only a very small proportion of alumina, 
 yel even this small riuanliiy they cannot derive from the silicates of this 
 substance, since these are all insoluble in water — as alumina itself is. 
 They obtain it, therefore, from some of those soluble compounds of alu- 
 mina of which I have spoken as being either occasionally present (pp. 
 204-5), or as being naturally formed in the soil. 
 
 General remarks on these Silicates. — Of all these silicates it may be 
 remarked in general — 
 
 1°. That besides existing in the minerals above-mentioned, and from 
 which they are conveyed into the soil, they are also slowly formed in the 
 
 ' I am indebted to Sir Charles Lemon for the analysis of a.soil, on part of his own proper- 
 ty, resting on serpentine, and bearing only Erica vagaris, which illustrates the statement in 
 the text. Tills soil consists of silica 70, alumina with a trace of gypsum 20, oxide of iron 6 2, 
 and vegetable mailer 38 percent. If this soil has been formed 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 llie source from which it has been derived. 
 
210 GENERAL REMARKS ON THESK SILICATES. 
 
 soil itself, when the ingredients of which they severally consist are na- 
 turally present in, or are artificially added to, the soil. Hence, the ad- 
 dition of potash or soda to the land may cause the production of sili- 
 cates of these alkalies — probably soluble silicates — which \yater will 
 be capable of dissolvins; 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 ilie lime upon the land may thus sooner cease to be observable than 
 in soils of a different character, where it is not so liable to be locked up 
 in an insoluble state of combination ; and 
 
 2°. That with the exception of those of potash and soda, which con- 
 tain 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 extent, within the 
 reach of plants; while, without exception, they are all capable of de- 
 composition in the soil by the agency of the acid substances, chiefly or- 
 ganic, which there exisr, 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 fol- 
 low 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 matter during its de- 
 cay decompose the silicates of lime previously produced, and thus liber- 
 ate the lime from its insoluble state of combination. But when the sili- 
 cates have been all decomposed by this agency, the further addition of ve- 
 getable matter ceases necessarily to produce the same remarkable effects. 
 
 XI. THE OXIDES, SULPHURETS, SULPHATES, AND CARBONATES OF IRON. 
 
 1°. Oxides of Iron. — It is well known that when metallic iron is ex- 
 posed to moist air, it gradually rusts and becomes covered with, or whol- 
 ly changed into, a crumbling ochrey mass of a reddish brown colour. 
 This powder is a compound of iron and oxygen only, containing 69j per 
 cent, of the former, and 30 j per cent, of the latter. 
 
 When iron is heated in the smith's forge, and then 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 n( oxides is given. 
 There are only two which are of interest to the agriculturist, namely, 
 
 CONSISTING OP 
 
 Iron. 
 
 Oxygen. 
 
 Symbol. 
 
 Colour. 
 
 77-23 
 
 22-77 
 
 Fe Of 
 
 Black 
 
 69-34 
 
 30-66 
 
 Fe,03 
 
 Red, 
 
 The first oxide* . 
 The second oxide 
 
 ■ Theirs* is also called the ^roj-oxide, the second either the sesqui, or more usually the 
 per oxide of iron, 
 t Iron is represented by the symbol Fe, the initial letters of its Latin name (ferrum). 
 
THE OXIDES or IROIT. 211 
 
 Both of (liese ex st abundantly in nature, 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 obser- 
 vable in so many soils is principally due to the presence of this oxide. 
 
 The first o.ride rarely occurs in the soil except in a state of combina- 
 tion with some acid substance, — and so strong is its tendency to combine 
 with more oxygen, that when exposed to the air, even in a state of com- 
 bination, it raiiidly absorbs this element from the atmosphere and 
 changes into per-oxide. 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 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, dissolves in 
 much greater quantit}' in the same weight of acid, and it is the com- 
 pounds of this oxide which are usually present in the soil, and which, in 
 bogffv lands, prove so injurious to vegetation.* 
 
 The second oxide possesses two properties which, in connection with 
 practical figriculrure, are not voiilofsome degree of importance. 
 
 1°. In a soil which contains much vegetable matter in a state of de- 
 cay, the per-oxide is frequently deprived of one-third of its oxygen by 
 the carbonaceous matter,f 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 i.< more or less soluble in 
 water, and in some localities may be brought to the roots of plants in 
 such quantity as to prove injurious to their growth. 
 
 2°. The red oxide of iron is said, like alumina (p. 197), to have the 
 properly 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 surface of mineral veins, 
 traces of ammonia can generally be delected. Since then ammonia is 
 so beneficial — according to some So indispensably necessary — to vegeta- 
 tion, the proper!}' which ilie per-oxide of iron possesses of retaining this 
 ammonia when it would otherwise escape from the soil, or of absorbing 
 it from the atmosphere, and thus bringing it within the reach of plants, 
 must also 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 pro- 
 perties of this oxide. A red irony soil, to which manure is added, 
 shniild be frequently turned over, and should be kept loose and pervious 
 lo tiie air, in order that the formation of prot-oxide (first oxide) may be 
 
 '•Tli»l layer of soil (says Sprengel), is always especially ricli in iron, over which the heel 
 )f the plough alifies in preparing the land. The friction of tlie soil continually rubs off par- 
 ides of iron, which absorb oxygen and cliange into [he first oxide. Hence this part of the 
 oil i.s always darl^erin colour than llie rest ; hence also the reason why ti]e soil after deep 
 iloughina, remains unproductive sometimes for several years." — Chemie, I., p. 428. While 
 ve ailmit that tiie presence of the first oxide of iron in the subsoil affects its fertility, vphen 
 jrought to the surface, we may doubt wljether much of that iron can have been derived 
 rem the tear and wear of the plough. 
 
 t The carbon of the vegetable matter combines with the oxygen of the oxide to form car- 
 xmiv acid. — See p. 63. 
 
212 SULPHORETS, A^D SULPHATES OF IRON. 
 
 prevented as much as possible ; and it may occasionally be summer- 
 fallowed with advaniage, in order also that the per-oxide inay absorb 
 from the air those volatile substances which are likely lo prove benefi- 
 cial to the growth of the future crops. 
 
 2°. Sulphurets of Iron. — Iron occurs in nature combined with sulphur 
 in two proportions, forming a sulphurel and a 6i-sulphuret. These 
 consist respectively — 
 
 Iron. Sulphur. Symbol. 
 
 The sulphuret . . . 6-->-77 37-23 Fe S 
 The bi-sulphuret of . 45-74 54-26 Fe S, 
 and are both tasteless and insoluble in water. 
 
 1°. The first of these, the sulphuret (Fe S), occurs occa.sionally in 
 boggy and marsliy soils, in which salts of iron exist, or into which they 
 are carried by rains or springs. It is nolitself directly injurious to vege- 
 tation, but when exposed to the air it absorbs oxygen and forms sulphate 
 of iron, which, wlien present in sufficient tjuaniity, is eminently so.* 
 
 2°. The hi-sulphuret, or common iron pyrites (Fe S^,), is exceedingly 
 abundant in nature. It occurs in nearly all rocky furmations — and in 
 most soils. It abounds in coal, and is the source of the sulphurous smell 
 which many varieties emit while burning. It generally presents itself 
 in masses of a yellow colour and metallic lustre, more or less perfectly 
 crystallized in cubical forms, so brittle and hard as to strike fire with 
 steel, and of a specific gravity four and a half times greater than tljat of 
 water (Sp. gr. 4, 5). When heated in close vessels it parts with nearly 
 one-half of its sulpliur, and hence is often distilled for the sulphur it 
 yields. 
 
 In the air it absorbs oxygen, in some cases — as in the waste coal 
 heaps — with sucli rapidiiy as to heat, take hre, and burn. By this ab- 
 sorption of oxygen (oxidation), sulphuric acid and sulphate of iron are 
 ]>roduced. In the alum shales the iron [)yriies abounds, and these are 
 often burned for the purpose of convening the 9ul{)hur and sulphuric 
 acid for the subsequent manufacture of alum. 
 
 3°. Sulpliates of Iron. — Of the sulphates of iron which are known, 
 there is oidy one — ihe common green vitriol oi \\\e sho])s — that occurs in 
 the soil in any considerable ([uantiij'. There are few soils, perhaps, in 
 which its presence may not be detecled, 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 de- 
 composed by quick-lime, by chalk, and by all varieties of marl, and 
 thus its noxious etlects may in general be entirely ])revented. To soils 
 which abound in lime, it may even be apiilied with a beneficial effect. 
 
 When a solution of this salt is exposed to the air it speedily becomes 
 covered with a pellicle of a yellow ochrey colour, which afterwards falls 
 as a yellow sediment. This sediment consists of ^)er-oxide of iron, con- 
 taining a little sulphuric acid; but by the se[)aration of this oxide the 
 sulphuric acid is left in excess in the solution, ^\■hich becomes sour, and 
 
 ' Yet in small quantity it may be beneficial. Thus Sprengel mentions that the sub.soil of 
 a moor near Hanover, which contains some of this fulphnret of iron, produces astonishing 
 effects when laid as a top-dressing on the grass lands. Tlie e.\planaliun of this is, that ihe 
 pyrites absorb oxygen and is converted into sulphate, and thus re-produces the remarkable 
 efTecIs observed on the additionof gypsum, of sulphuric acid, or of sulphate of .soda, to simi- 
 lar grass lands. 
 
CARBONATES OF IRON, OXIDES AND SALTS OF MANGANESE. 213 
 
 Still more injurious to vegetation than before. In boggy places the 
 waters impregnated with iron are generally more or less in this acid 
 slate, 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 lo the air it slowly absorbs oxygen, 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 in progress 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 yellow powder 
 falls, which is carbonate of iron. This carbonate is found abundantly in 
 nature. It is the state in wliich the iron exists in tlie ore (clay-iron ore,) 
 from which this metal is so largely extracted in our iron furnaces, and 
 in the similar ore often found in the subsoil of boggy places, which is 
 (lislinguished by the name of bog-iron ore. 
 
 Like the carbonate of lime, it is insoluble in water, but dissnives with 
 considerable readiness in water charged with carbonic acid. In tliis 
 slate of solution it issues from ihe earth in most 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, cannot be directly in- 
 jurious to vegetation. When exposed to the air it gradually parts with 
 its carbonic acid, and is convened into per-oxide of iron. 
 
 The ash of nearly all plants contains a more or less appreciable quan- 
 tity 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 compounds of iron with organic 
 acids, which may be expected lo be occasionally present in the soil. 
 
 xii. — maxgankse: oxides, chlorides, carbonates, and sulphates 
 OF manganese. 
 
 1°. Manganese is a metal which, in nature, is very frequently asso- 
 ciated with iron in its various ores. It also resembles this metal in 
 many of its |)roperties. In the metallic state, however, it is not an ob- 
 ject of manufacture, nor is it used for any purpose in the arts. 
 
 2°. Oxides of Manoanese. — Manganese combines with oxygen in 
 several proportions. The first oxide is of a light green colour, the se- 
 cond and third are black. The first is not known lo occur in nature in 
 an uncombined state, the two others exist abundantly in the common 
 ores of manganese, and are extensively dilTused, though in small quan- 
 tity, 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 delected in the ash of nearly all plants. 
 
 3°. Chloride, Carbonate, and Sulphate of Manganese. — If any of 
 
>14 
 
 COMPOSITION OF THE OXIRES AND CHLORIDES. 
 
 these oxides be dissolved in muriatic acid a solution of chloride of man- 
 ganese will be obtained. 
 
 If liiis solution of chloride of manganese be mixed with one of car- 
 bonate of soda, a while insoluble powder will fall, which is carbonate of 
 maganese. 
 
 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 manganese 
 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 comi)ounds of manganese exist in ])lants in much less quantity 
 than those of iron; but as its oxides, like those of iron, are insoluble in 
 pure water, this metal most likely finds its way into the state of one 
 or other of the soluble compounds above described. 
 
 §2. 
 
 Tabular view of the constitution of the compounds of the inorganic 
 elements above described. 
 
 Having in the preceding section briefly described the several compounds 
 of the inorganic elements of plants, wliicli either enter into the constitution 
 of vegetable substances, or are supposed to minister to their growth — it 
 may prove useful hereafter, if I exhibit 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. 
 
 We shall have occasion to refer to the numbers in the following tables 
 in our subsequent calculations. 
 
 Oxygen per cent, in Hie oxides of the inorganic elements. 
 
 Oxygen 
 
 per cent, 
 . 49-85 
 . 59-86 
 . 56-04 
 
 Sulphurous Acid . 
 Sulphuric Acid 
 Phosphoric Acid . 
 
 Potash 16-95 
 
 Soda 25-58 
 
 Lime 28-09 
 
 Magnesia 38-71 
 
 Alumina . . . 
 
 Silica .... 
 
 Prot-oxide of Iron 
 
 Per-oxide of Iron . 
 
 Prot-oxide of Manganese 22-43 
 
 Sesqui-oxide do. . . 30'25 
 
 Per-oxide do. . . 36-64 
 
 Oxygen 
 per cent. 
 46-70 
 51-96 
 22-77 
 30-66 
 
 2°. — Chlorine or Sulphur per cent, in the chlorides and sulphurets. 
 
 Chloride of Potassium 
 
 Sodium 
 
 Calcium 
 
 Magnesium 
 
 First Chloride of Iron 
 Second do. do. 
 
 Chlorine 
 per cent. 
 47-47 
 60-34 
 63-38 
 73-66 
 56-62 
 66-19 
 
 Sulphurel of Potassium 
 
 Sodium 
 
 Calcium . 
 
 Iron 
 
 Bi-Sutphuret of Iron, 
 (Iron Pyrites) . 
 
 Sulphur 
 per cent, 
 29-11 
 40-88 
 44-00 
 37-23 
 
 47-08 
 
 * So called because the acid they contain lias oxygen for one of its constituentSi 
 
COMPOSITION OF THE SALINE COMPOUNDS. 
 
 215 
 
 3°. — Co -n position percent, of the Saline comhinalions above described. 
 
 1 
 
 Acid. 
 
 Base. 
 68-09 
 
 Water. 
 
 Carbonaie of Potash 
 
 31-91 
 
 \ 
 
 Bi-carbonate of do. ... 
 
 48-38 
 
 51-62 
 
 
 Sulphate of do. 
 
 45-93 
 
 54-07 
 
 
 Nitrate of do. 
 
 53-44 
 
 46-56 
 
 
 Binoxalate of do. (Salt of sorrel) . 
 
 5-2-64 
 
 34-29 
 
 13-07 
 
 Bitarirate 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 
 
 
 Niirate of do. 
 
 63-40 
 
 36 60 
 
 
 Sulphate of do. (dry) 
 
 56-18 
 
 43-82 
 
 
 do. (crystallized) 
 
 24-85 
 
 19-38 
 
 55-77 
 
 Phosphate of do. 
 
 53-30 
 
 46-70 
 
 
 Bi-phosphate of do. 
 
 1 
 
 69-54 
 
 30-46 
 
 
 Carbonate of Lime .... 
 
 43-71 
 
 56-29 
 
 
 I Sulphate of do. (Gypsum) . 
 
 'Ki-3l 
 
 32-90 
 
 20-79 
 
 (burned) 
 
 58-47 
 
 41-53 
 
 
 Nitrate of Lime .... 
 
 65-54 
 
 34-46 
 
 
 Phos})haie of Lime (Aj)atiie) 
 
 45-52 
 
 54-48 
 
 
 j Bi-pliusphate of Lime 
 
 71-48 
 
 28-52 
 
 
 Eartli of Bones .... 
 
 48-45 
 
 51-55 
 
 
 Carbonate of Magnesia 
 
 51-69 
 
 48-31 
 
 
 Bi-carbonate of do. ... 
 
 68-15 
 
 31-85 
 
 
 Sulpliate 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 A.lumina 
 
 70-07 
 
 29-93 
 
 
 Phosphate of do. ... 
 
 67-57 
 
 32-43 
 
 
 j ^ — 
 Silicate of Potash (soluble) 
 
 49-46 
 
 50-54 
 
 
 Bi-silicate of do. (do.) 
 
 66-19 
 
 38-81 
 
 
 Silicate of Soda (do.) 
 
 59-63 
 
 40-37 
 
 
 Bi-silicaieofdo. (do.) 
 
 74-71 
 
 25-29 
 
 
 Silicate of Lime .... 
 
 61-85 
 
 38-15 
 
 
 Magnesia .... 
 
 69-08 
 
 30-92 
 
 
 Alumina .... 
 
 72-95 
 
 27-05 
 
 i 
 
 Carbonate of Iron .... 
 
 38-63 
 
 61-37 
 
 1 
 
 Sulphate of do. (crystallized) 
 
 31-03 
 
 27-19 
 
 41-78 
 
 1 
 
 Carbonate of Manganese . 
 
 38-27 
 
 61-73 
 
 1 
 37-26 
 
 Sulphate oi do. (crystallized) 
 
 33-20 
 
 ■29-54 
 
 10 
 
216 COMPOSITION OF THE ASH OF WHEAT AND OF BAKLF.T. 
 
 § 3. On the relative proportions of (he different inorganic compounds 
 present in the ash of plants. 
 
 Having thus made you acquainted with the general properties and 
 composition of the several compound substances of which the ash of 
 plants consists, we now advance to the consideration of the relative pro- 
 portions in which these substances exist in the ash of the different kinds 
 of plants usually cultivated for food. 
 
 We have seen (p. 178) that different species of plants leave very dif- 
 ferent quantities of ash when burned ; — the ash left by different species 
 contains also the above earthy and saline substances in very unlike pro- 
 portions. This fact has already been stated generally (p. 180) ; we are 
 now to illustrate it more fully, and to show the important practical de- 
 ductions to which it leads. 
 
 I. OF THE ASH OF WHEAT. 
 
 According to the analysis of Sprengel, 1000 lbs. of wheat leave 11*77 
 
 lbs., and of wheat straw 35-18 lbs. of ash, consisting of — 
 
 Grain of Straw of 
 
 Wheat. Wheat. 
 
 Potash 2-25 lbs. 0-20 lbs. 
 
 Soda 2-40 0-29 
 
 Lime 0-96 2-40 
 
 Magnesia 0-90 0-32 
 
 Alumina, with a trace of Iron 0-26 090 
 
 Silica 4-00 28-70 
 
 Sulphuric Acid .... 0-50 0-37 
 
 Phosphoric Acid .... 0-40 1-70 
 
 Chlorine 0-10 0-30 
 
 11-77 lbs. 35-18 lbs. 
 If the produce of a field be at the rate per acre of 25 bushels of 
 wheat, each 60 lbs., and if the straw* be equal to twice the weight of 
 the grain, the quantity of each reaped per acre will be 
 
 Grain . . . 1500 lbs. ) r- j mc u u i 
 
 Straw . . . 3000 lbs. I ^'"""^ ^ P™'^"^^ "^^^ ^"'^^^^' 
 so that the quantity of the different inorganic compounds carried off from 
 the soil of each acre will be, in the grain i more than is represented in 
 the second column, and in the straw 3 times as much as is represented 
 in the third column. 
 
 II. — OF THE ASH OF BARLEY. 
 
 A thousand pounds of the grain of barley (two-rowed, hordeum disti- 
 chon,) leave 23i lbs., and of the ripe dry straw 52-42 lbs. of ash. This ash 
 consists of — 
 
 The proportion of the straw to the seed in grain of all kinds is very variable. In wheat 
 It is said to average twice the weight of the grain, but it is very often, even in heavy crops. 
 3 to 9}i times that weight. 
 
OF THK ASH OF OATS. 217 
 
 Grain. Straw. 
 
 Potash 2-78 lbs. 1-80 lbs. 
 
 Soda 2-90 0-48 
 
 Lime 1-06 5-54 
 
 Magnesia 1-80 0-76 
 
 Alumina 0-25 1-46 
 
 Oxide of Iron. . . . a trace. 0*14 
 
 O.vide of Manganese . — 0'20 
 
 Silica 11-82 38-56 
 
 Sulphuric Acid . . . 0-59 1-18 
 
 Phosphoric Acid . . 2-10 1-60 
 
 Chlorine 0-19 0-70 
 
 23-49 lbs. 52-42 lbs. 
 If the produce of a crop of l)arley amount to 38 bushels of 63 lbs. each 
 per acre, and the straw exceed the grain in weight one-sixth, the weight 
 of each reaped per acre will be about 
 
 2000 lbs. of grain, ? ,, , r oo u i_ i 
 
 2300 lbs. of straw, \ ^'"""^ ^ P™*^"^*^ °^28 bushels ; 
 and the inorganic matters carried off from the soil by each will be ob- 
 tained by muUiplying those contained in the second column (above) by 
 2, and in the third by 21. 
 
 III. OF THE ASH OF OATS. 
 
 In 1000 lbs. of the grain of the oat are contained about 26 lbs., and of 
 the dry straw about 57^ lbs. of inorganic matter, consisting of — 
 
 Grain. Straw. 
 
 Potash 1-50 lbs. 8-70 lbs. 
 
 Soda 1-32 0-02 
 
 Lime 0-86 i-52 
 
 Magnesia 0-67 0-22 
 
 Alumina 0-14 0-06 
 
 Oxide of Iron. . . . 0-40 0-02 
 
 Oxide of Manganese . 0-00 0-02 
 
 Silica 19-76 45-88 
 
 Sulphuric Acid ... 35 0-79 
 
 Phosphoric Acid . . . 0-70 0-12 
 
 Chlorine 0-10 0-05 
 
 25-80 lbs. 57-40 lbs. 
 
 If an acre of land yield 50 bushels, each 54 lbs., of oats, and two-thirds* 
 
 more in weight of straw, there will be reaped per acre, 
 
 Of grain 2250 lbs., > ^ , rcnu ui 
 
 r\(- , , nrf^r, n } I'^oiTi a produco of 50 bushels; 
 Ui straw 37o0 lbs., ^ ' 
 
 and the weight of the inorganic matters carried off will be equal to 2i 
 
 times the quantities contained in the second column, and 3| times those 
 
 contained in the third column. 
 
 * Of all kinds of grain, the oat gives the most variable proportion of straw, that which is 
 obtained at one time, and in one locality, being two or three times greater than that reaped 
 in another. 
 
218 ASH OF RTK, BEANS, PEAS, AND VETCHES. 
 IV. OF THE ASH OF RYE. 
 
 The weight of ash contained in 1000 lbs. of the grain of rye is lOi lbs., 
 and of the straw 28 lbs. This ash consists of 
 
 Grain. Straw. 
 
 Potash I ..30 lbs 3 0-32 lbs. 
 
 Soda i 5^~lbs. ^(j.jj 
 
 Lime 1-22 1-78 
 
 Magnesia 1-78 0-12 
 
 Alumina 0-24 ) 
 
 Oxide of Iron. . . . 0-42^ 
 
 Oxide of Manganese . 0*34 — 
 
 Silica 1-64 22-97 
 
 Sulphuric Acid . . . 0-23 1-70 
 
 Phosphoric Acid . . 0-46 0-51 
 
 Chlorine 0-09 0-17 
 
 0-25 
 
 10-40 lbs. 27-93 lbs. 
 Rye is remarkable for the quantity of straw it yields, which is often 
 from 3 to 4 times the weight of the grain. The return in grain reaches 
 about the same average as that of wheat. From an acre of land yield- 
 ing a crop of 25 bushels, each 54 lbs., there would be reaped 
 
 Of grain 1350 lbs.; of straw 4000 lbs. ; 
 the whole weight of inorganic matters contained in which is equal to ^ 
 more than is represented in the second column, added to 4 times the weights 
 contained in the third coluirin. 
 
 V. OF THE ASH OF BEANS, PEAS, AND VETCHES. 
 
 The ash of the seed and straw of the field bean, the field pea, and the 
 common vetch (vicia sativa,) dried in the air, contains in 1000 lbs. the 
 several inorganic compounds in the following proportions: 
 
 
 
 PI ELL 
 
 1 BEAN. 
 
 FIELI 
 
 ) PEA. 
 
 COMMON 
 
 VETCH. 
 
 
 Seed. 
 
 Straw. 
 
 Seed. 
 
 Straw. 
 
 Seed. 
 
 Straw. 
 
 Potash . 
 
 ... 
 
 4-15 
 
 16-56 
 
 8-10 
 
 2-35 
 
 8-97 
 
 18-10 
 
 Soda . . 
 
 • • . 
 
 8-16 
 
 0-50 
 
 7-39 
 
 .^- 
 
 6-22 
 
 0-52 
 
 Lime 
 
 . 
 
 1-65 
 
 6-24 
 
 0-58 
 
 27-30 
 
 1-60 
 
 19-55 
 
 Magnesia 
 
 . 
 
 1-58 
 
 2-09 
 
 1-36 
 
 3-42 
 
 1-42 
 
 3-24 
 
 Alumina 
 
 
 0-34 
 
 0-10 
 
 0-20 
 
 0-60 
 
 0-22 
 
 0-15 
 
 Oxide of Iron . . 
 
 — 
 
 0-07 
 
 0-10 
 
 0-20 
 
 0-09 
 
 0-09 
 
 Oxide of M 
 
 anganese 
 
 : 
 
 0-05 
 
 — 
 
 0-07 
 
 0-05 
 
 0-08 
 
 Silica . 
 
 . 
 
 1-26 
 
 2-20 
 
 4-10 
 
 9-96 
 
 2-00 
 
 4-42 
 
 Sulphuric Acid 
 
 0-89 
 
 0-34 
 
 0-53 
 
 3-37 
 
 0-50 
 
 1-22 
 
 Phosphoric 
 
 Acid . 
 
 2-92 
 
 2-26 
 
 ]-90 
 
 2-40 
 
 1-40 
 
 2-80 
 
 Chlorine 
 
 
 0-41 
 
 0-80 
 
 0-38 
 
 0-04 
 
 0-43 
 
 0-84 
 
 21-36 31-21 24-64 49-71 22-90 61-01 
 On comparing the numbers in these columns, we cannot fail to remark,— 
 
 . 1°. How much potash there is in the straw of the bean and the vetch. 
 2°. That while there is only a trace of soda in any of the three straws, 
 
 there is a considerable quantity in all the seeds. 
 
ASH OF THE TURNIP, CARROT, PARSNIP, AND POTATO. 219 
 
 3°. How !arge a proportion of lime exists in tlie straw of the pea and 
 of the vetch — compared with that of the bean — and how much larger the 
 proportion is in all the straws than in any of the grains — and 
 
 4°. That the quantity of silica in pea straw is double of what is con- 
 tained in the straw of the vetch, and 4 times that of the bean straw. 
 
 The ])roduce of straw from these three varieties of pulse is very bulky, 
 but varies in weight from 1 to Ij tons — or is on an average about 2300 
 lbs. per acre. The produce of grain is still more variable. 
 
 The bean gives from 16 to 40 bushels, of about 63 lbs. 
 The pea . . 12 to 84 " " 64 lbs. 
 
 The vetch . . 16 to 40 " " 66 lbs. 
 
 The mean return from beans is estimated by Schwertz [Anleitung 
 Zum Praktischen Ackerbau, II., p. 346,] at 25 bushels (1600 lbs.), from 
 peas at 15 bushels (1000 lbs.), and from vetches at 17 bushels (1100 
 lbs.) per acre. 
 
 Tlie (juantity of the several inorganic matters, therefore, carried off 
 from an acre in the straw of these crops, will be about 2i times the 
 weights given in the table — and in the grains, where the crop is near 
 the above average, 1| times the weights in the tables for beans and for 
 peas, and for vetches very nearly the actual weights above given. 
 
 VI. OF THE ASH OF THE TURNIP, CARROT, PARSNIP, AND POTATO. 
 
 These four roots, as they are carried from the field, contain respective 
 ly in ten thousand pounds — 
 
 
 TURNIP. 
 
 CARROT. 
 
 PAR.SNIP. 
 
 POT 
 
 UTO. 
 
 
 
 
 
 
 A 
 
 
 Roots. 
 
 Leaves. 
 
 
 
 Roots. 
 
 Tops. 
 
 Potash . . . 
 
 23-86 
 
 32-3 
 
 35-33 
 
 20-79 
 
 40-28 
 
 81-9 
 
 Soda .... 
 
 10-48 
 
 22-2 
 
 9-22 
 
 7-02 
 
 23-34 
 
 0-9 
 
 Lime .... 
 
 7-52 
 
 62-0 
 
 6-57 
 
 4-68 
 
 3-31 
 
 129-7 
 
 Magnesia . . . 
 
 2-54 
 
 5-9 
 
 3-84 
 
 2-70 
 
 3-24 
 
 17-0 
 
 Alumina . . . 
 
 0-36 
 
 0-3 
 
 0-39 
 
 0-24 
 
 0-50 
 
 0-4 
 
 Oxide of Iron . . 
 
 0-32 
 
 1-7 
 
 0-33 
 
 0-05 
 
 0-32 
 
 0-2 
 
 Oxide of Manganese 
 
 — 
 
 — 
 
 0-60 
 
 — 
 
 — 
 
 — 
 
 Silica .... 
 
 3-88 
 
 12-8 
 
 1-37 
 
 1-62 
 
 0-84 
 
 49-4 
 
 Sulphuric Acid . 
 
 8-01 
 
 25-2 
 
 2-70 
 
 1-92 
 
 5-40 
 
 4-2 
 
 Phosphoric Acid . 
 
 3-67 
 
 9-8 
 
 5-14 
 
 1-00 
 
 4-01 
 
 19-7 
 
 Chlorine . • • 
 
 2-39 
 
 8-7 
 
 0-70 
 
 1-78 
 
 1-60 
 
 5-0 
 
 63-03 180-9 66-19 41-80 82-83 308-4 
 
 These roots, as already stated (note, p. 178), contain very much water, 
 so that, in a dry state, ihe projwrtion of inorganic matter present in them 
 is very much greater than is represented by the above numbers. I 
 have, however, given the quantities contained in the crop as it is carried 
 from the field, as alone likely to be of practical utility. 
 
 The crops of these several roots vary very much in different localities, 
 being in some places twice and even thrice as much as in others — every 
 nine tons, however, which are carried off the ground, contain about 
 twice the weight of saline and earthy matters indicated by the numbers 
 in the table. 
 
220 ASH OF THE GRASSES AND CLOVERS. 
 
 VII. OF THE ASH OF THE GRASSES AND CLOVERS. 
 
 The following table might have been much enlarged. I have 
 thought it necessary, however, to introduce in this place only those 
 species of grass and clover which are in most extensive use. I have 
 also calculated the weights given below, for these plants in the state of 
 hay 07ily, as the succulency of the grasses, — that is, the quantity of wa- 
 ter contained in the green crop, — varies so much that no correct esti- 
 mate could be made of the quantity of inorganic matter present in hay 
 or grass, from a knowledge of its weight in the green state only : 
 
 
 Hye Grass 
 
 Red 
 
 White 
 
 
 
 
 Hay. 
 
 Clover. 
 
 Clover. 
 
 Luceine. 
 
 Sainfoin. 
 
 Potash . . . 
 
 8-81 
 
 19-95 
 
 31-05 
 
 13-40 
 
 20-57 
 
 Soda .... 
 
 3-94 
 
 6-29 
 
 5-79 
 
 6-15 
 
 4-37 
 
 Lime 
 
 7-34 
 
 27-80 
 
 23-48 
 
 48-31 
 
 21-95 
 
 Magnesia . . 
 
 0-90 
 
 3-33 
 
 3-05 
 
 3-48 
 
 2-88 
 
 Alumina . . 
 
 0-31 
 
 0-14 
 
 1-90 
 
 0-30 
 
 0-66 
 
 Oxide of Iron . 
 
 — 
 
 — 
 
 0-63 
 
 0-30 
 
 — 
 
 Oxide of Mangane 
 
 se — 
 
 — 
 
 — 
 
 — 
 
 — 
 
 Silica 
 
 27-72 
 
 3-61 
 
 14-73 
 
 3-30 
 
 5-00 
 
 Sulphuric acid . 
 
 3-53 
 
 4-47 
 
 3-53 
 
 4-04 
 
 3-41 
 
 Phosphoric acid 
 
 0-25 
 
 6-57 
 
 5-05 
 
 13-07 
 
 9-16 
 
 Chlorine . . . 
 
 0-06 
 
 3-62 
 
 2-11 
 
 3-18 
 
 1-57? 
 
 52-86 74-78 91-32 95-53 69-57 
 
 The above quantities are contained in a thousand pounds of the dry 
 hay of each plant. 
 
 On comparing the numbers opposite to potash, lime, magnesia, alu- 
 mina, silica, and phosphoric acid, we see very striking ditferences in 
 the quantities of these substances contained in equal weights of the 
 above different kinds of hay. These differences lead to very important 
 practical inferences in reference, — 
 
 1°. To the kind of soil in which each will grow most luxuriantly. 
 
 2°. To the artificial means bj'^ which the growth of each may be pro- 
 moted — in so far as this growth depends upon (he supply of inorganic 
 food to the growing plant. 
 
 3°. To the feeding properties of each, and to the kind of stock they 
 are severally most fitted to nourish. 
 
 To these and other important practical deductions suggested by the 
 above tabulated analyses — as well as by those previously given — of the 
 inorganic matters contained in the several varieties of vegetable produc- 
 tions usually raised for food, we shall hereafter have frequent occasion 
 to revert. In the mean time, a preliminary inquiry demands our at- 
 tention, which we shall proceed to consider in the following section. 
 
 § 4. To what extent do the crops most usually cultivated, exhaust the soil 
 of inorganic vegetable food? 
 
 A bare inspection of the tabular results exhibited in the preceding 
 section gives but a faint idea of the extent to which the inorganic ele- 
 mentary bodies are necessarily withdrawn from the soil in the ordinary 
 course of cropping. 
 
EFFECT OF A THREE YEARs' COURhE OF CROPPING. 221 
 
 L Lei us consider the effect upon the soil of a still too common three 
 years' course of croppiug—falloiv, wheal, oats.* If the produce of such 
 a course be 25 bushels of wheat and 50 bushels of oats, there would be 
 carried from the soil every three years in pounds — 
 
 WHEAT. OATS. 
 
 Grain. Straw. Gi-ain. Straw. 
 
 Potash .... 3-3 0-6 3-75 32-7 40-35 
 
 Soda 3-5 0-9 3-3 — 7-7 
 
 Lime 1-6 7-2 2-5 57 16-9 
 
 Magnesia. ... 1-5 1-0 1-7 0-8 5-0 
 
 Oxide of Iron . . — — 1-0 — 1-0 
 
 Silica 6-0 66-0 50-0 172-0 314-0 
 
 Sulphuric Acid . . 0-75 1-0 0-9 3-0 5-65 
 
 Phosphoric Acid . 0-6 5-0 1-43 0-5 7-53 
 
 398-13 
 The gross weiglit carried off in these crops is large — amounting to 
 about 400 lbs. It will vary, however, with the kind of wheat and oats 
 which are grown, and may often be greater than this. — [See the follow- 
 ing section (§ 5) of the present Lecture.] The greatest portion of the 
 matter carried off, however — upwards of three-fourths of the whole — 
 consists of silica; the rest of the materials are equal to 
 60 lbs. of dry pearl-ash, 
 36 lbs. of the common soda of tlie shops, 
 28 lbs. of bone-dust, 
 12 lbs. of gypsum, 
 5 lbs. of tjuick-lime, 
 
 5 lbs. of magnesia, — or for the last three may be substi- 
 tuted 33 lbs. of common Epsom salts and 17 lbs. of quick-lime. 
 
 The form in which the silica may be restored to the soil in a state in 
 which the plant can absorb it, will be considered hereafter. 
 
 Though large as a whole, the weight of eacli of the ingredients, taken 
 singly, is not great; and yet it is not difficult to understand that if a 
 constant drain be kept up on the soil year after year, and the practical 
 farming ado|)ted is of such a kind as not to restore to the soil a due pro- 
 portion oC each of the substances carried off — the time must come when, 
 under ordinary circumstances, the soil will no longer be able to supply 
 the demands of a healthy and luxuriant vegetation. 
 
 II. Let us next consider the effect of a four-years' course system in 
 withdrawing these inorganic substances from the soil. And for this 
 purpose let us adopt one suited to the lighter soils — as to that of Norfolk — 
 turnips, barley, clover and rye grass, wheat. 
 
 Let the crop of turnips amount to -25 tons of roots per acre, of barley to 
 38 bushels, of clover and rye grass each to one ton of hay, and of wheat 
 as before to 26 bushels. Then we have from the entire rotation in 
 pound.s — 
 
 • Common, among other counties, in that of Durham. There are cases, however, in 
 which this three year.s' course may not be indefensible, and it never could be compared with 
 some of the so-called improved rotations in East Lothian in the time of Lord Karnes ; as for 
 in8tance,/(i//oif, barley, clover, manure on the clover stubble, then wheat, barley, oats. — See 
 Tlie Gentleman Farmer (ia»2), p. 147. 
 
3F A FOUR-YKARS 
 
 COURSE. 
 
 
 
 BAI 
 
 ILEV. 
 
 Straw. 
 
 Red 
 Clover. 
 
 Rye 
 
 Grass. 
 
 WHEAT. 
 
 Total 
 
 Grain. 
 
 Grain. 
 
 Straw. 
 
 
 6-6 
 
 4-5 
 
 45-0 
 
 28-5 
 
 3-3 
 
 0-6 
 
 233-0 
 
 5-8 
 
 11 
 
 12-0 
 
 9-0 
 
 3-5 
 
 0-9 
 
 96-6 
 
 2-1 
 
 12-9 
 
 63-0 
 
 16-5 
 
 1-5 
 
 7-2 
 
 1490 
 
 3-6 
 
 1-8 
 
 7-5 
 
 2-0 
 
 1-5 
 
 1-0 
 
 32-9 
 
 0-5 
 
 3-4 
 
 0-3 
 
 0-8 
 
 0-4 
 
 2-7 
 
 10-3 
 
 23-6 
 
 90-0 
 
 S-0 
 
 62-0 
 
 6-0 
 
 86-0 
 
 299-2 
 
 1-2 
 
 2-8 
 
 10-0 
 
 8-0 
 
 0-8 
 
 1-0 
 
 72-8 
 
 4-2 
 
 3-7 
 
 15-0 
 
 0-6 
 
 0-6 
 
 5-0 
 
 51-5 
 
 0-4 
 
 1-5 
 
 8-0 
 
 0-1 
 
 0-2 
 
 0-9 
 
 256 
 
 222 
 
 Turnip 
 
 Roots. 
 
 Potash 145-5 
 
 Soda 64-3 
 
 Lime 45-8 
 
 Magnesia .... 15-5 
 
 Alumina .... 2-2 
 
 Silica 23-6 
 
 Sulphuric Acid . 49-0 
 
 Phosphoric do. . 22-4 
 
 Chlorine .... 14-5 
 
 970-9* 
 On comparing the numbers in the last column — containing the total 
 quantity of matter abstracted — with those contained in the three years' 
 rotation (p. 221), we see how very much larger an addition must be 
 made to the land every fourth year, if we are to restore to it any thing 
 like an equivalent for the inorganic matter carried otT. 
 
 It will be especially observed tliat the quantity of potash, and of soda, 
 and indeed of nearly every ingredient except the silica, carried ofi" in 
 this course of cropping, is much greater, even in proportion to the time 
 it occupies, than in the three-year shift — and that nine-tenths of the j^ot- 
 ash and soda withdraicn from the soil are contained in the green crops. 
 
 To place the relative etlect of the green and corn crops upon the soil 
 in a clearer light, I shall exhibit the several quantities of common antl 
 artificial salts and manures which it would be necessary to add to each 
 acre at the beginning of this rotation, in order to supply the various inor- 
 ganic substances about 10 be taken from the land in the next four years' 
 cropping. These quantities are as follow, in pounds : — 
 
 For the For the 
 
 Total. Green Crops. Corn Crops. 
 
 Dry Pearl-ash 325 316 9 
 
 Crystallized Carbonate of Sodaf 333 290 43 
 
 Common Salt 43 38 5 
 
 Gypsum — 30 — 
 
 Quick-lime 150 100 7 
 
 Epsom Salts 200 150 50 
 
 Alum 83 27 56 
 
 Bone-dust 210 150 60 
 
 With the exception of the silica, the substances above-named, in the 
 quanthies given, will replace all the inorganic matters contained in \he 
 whole crop reared, the turnip tops alone not included. A single glance 
 at the second and third columns shows how much greater a proportion 
 of all these substances is necessary to return what the green crops have 
 taken from the land. 
 
 That the fertility of the soil depends in some considerable degree on 
 
 ' This is exclusive of the turnip tops, which I have omitted, from not knowing what pro- 
 portion their weight in the green state generally bears to that of the roots. 
 
 t Or for every 100 lbs. of the common carbonate of soda may be substituted 40 lbs. of 
 common salt or 60 lbs. of dry nitrate of soda. 
 
WHY WHEAT PHEPERS A HKAVY SOIL. 223 
 
 the quantity of the alkaline and other compounds present in it, there can 
 be no question. — since not only do we find extraordinary natural luxuri- 
 ance of vegetation where some of these happen to be present in the soil, 
 but we can often greatly increase the apparent productiveness of our 
 fields by spreading such substances over tbem in sufficient quantity. 
 
 How comes it, then, that the green crops which carry off all these 
 substances in the greatest quantity by very much, should yet least injure 
 the land, — nay, should ratlier renew and prepare it again for the growth 
 of crops of corn ? 
 
 This is one of the most interesting practical questions which can y:)re- 
 senl itself to us in the existing state of theoretical agriculture; — but it 
 would carry us away from our more immediate object, were we prema- 
 turely to enter upon the discussion of it in this place. It will hereafter i 
 demand our especial attention, when we shall have become familiar! 
 with the nature and origin of soils. ) 
 
 I may be permitted, however, to draw your attention here for a mo-' 
 ment— as neither out of place, nor uninteresting, for many reasons, — lol 
 an opinion expressed by Liebig on the question why icheat prefers stiff 
 and clayey soils. " Again," he says, "how does it happen that wheat! 
 does not flourisli in a sandy soil, and that a calcareous soil is also un-l 
 suitable for its growth, unless it be mixed with a considerable quaniliy 
 of clay? It is because these soils do not contain alkalies in sufficient 
 (piantity, the growth of wheat being arrested by this circumstance, even' 
 should all other substances be presented in abundance." — [Organic 
 Chemistry applied to Agriculture, p. 151,] 
 
 Without dwelling on the fact that excellent crops of wheat are reaped 
 in some parts of our island from sandy and calcareous* soils — what kind 
 of crops, we may ask, can be reared with success on the lighter soils to 
 which wheat seems least adapted ? The turnip rejoices in light land, 
 and the potato not unfrequently attains the greatest perfection on a sandy 
 soil. Yet ten tons of potato roots, or twenty of turnip bulbs, — exclu- 
 sive of the tops — contain nearly ten times as much of the two alkalies, 
 potash and soda, as fifty bushels of wheat with its straw included. f 
 What ground is there, then, for the explanation given by Liebig — of the 
 peculiar cpialities of the so-called wheat lands? We might witli far 
 greater show of reason assume the converse of his proposition, and infer 
 that wheat does not prefer sandy soils, because they are too rich in alkali! 
 It is singular, and would almost seem to strengthen this converse propo- 
 sition, that beans, peas, and vetches, which are so often resorted to as a 
 good preparative for wheat, contain also a much larger quantity of alkali 
 than the latter grain. Thus the grain and straw together of twenty-six 
 bushels of beans contain 71 lbs., of twenty bushels of peas 26 lbs., and 
 of twenty bushels of vetches 74 lbs. of potash and soda taken together. 
 
 As I have already stated, however, we are not yet prepared for dis- 
 cussing this very curious and interesting question. 
 
 " On the thin ch.Ttk soils of the Yorlcshlre Wolrls a crop of wheat is taken every four or 
 five years, yielding an average of 34 or 25 bushels. The rotation is turnips, barley, clover or 
 beans, wheat. 
 
 t According to the analyses of Sprengel given in the previous pages, ten tons of potatoes 
 contain 143 lbs. of alkalies, twenty tons of turnips 154 lbs., and fifty bushels of wheat with 
 its straw only 16 lbs. 
 
 10* 
 
224 ARE THE INORGANIC CONSTITUENTS REAttY CONSTANT 
 
 § 5. Of the alleged constancy of the inorganic constituents of plants, in 
 Jdnd and quantity. 
 
 In the preceding lecture (ix., p. 177), it was stated that the ash of the 
 same plant, if ripe and healthy, is nearly the same in kind and quality 
 in whatever circumstances (if favourable) of soil and climate it may 
 grow. This general observation, however, is consistent with certain 
 differences in the above respect, which are not without interest in their 
 bearing upon agriculture both in theory and practice. Thus, 
 
 1°. The different parts of the same plant contain quantities of inor- 
 2;anic matter, not only different in liieir gross weights, but unlike also in 
 he relative proportions of the several substances of wliich the entire ash 
 ijonsisis. Both of these points have been previously illustrated (pp. 179, 
 180), and they are placed in the clearest light by the tabulated analyses 
 introduced into the preceding section. 
 
 2°. The (juantlty and relative proportions of the (hfferent inorganic 
 substances also vary with the season of the year at which the examina- 
 tion is made. Thus, according to De Saussure, plants of the same wheat 
 ■^'hich a month before flowering left 7c> per cent, of ash, left when in 
 flower only 5*4, and when ripe 3-3 per cent. The quantity of potash 
 in the potato leaf diminishes very much as the plant approaches to ma- 
 turity (Molierat) — and the same lias been observed in many saltworts 
 and other sea-side plants. In the young plant of the salsola clavifolia 
 there is much potash and nosoda, butas its age increases tiie latter alkali 
 appears, and gradually takes the place of the former.* 
 
 It is probably true, therefore, of all plants — that the ash botli in kind 
 and quantity is affected by the age at which the plant has arrived. It 
 would appear that the unlike chemical changes which take place in the 
 interior of the plant, at the successive periods of its growtli, require the 
 presence of different chemical agents — or that the production of new 
 parts demands the co-operation of new substances. 
 
 3°. Similar differences are sometimes observed also when the same 
 plant is grown in different soils. Thus it is known that the straw of the 
 oat grown upon boggy land is very different in colour and lustre, from 
 that yielded by the same variety of seed, when grown upon sound and 
 solid soil. I lately examined two such portions of straw from the same 
 seed — grown on the same farm on the estate of Dunglass, the one on 
 boggy, the other on sound stiff land, when the straw from the 
 Sound land left 6-64 per cent, of ash, and from the 
 Boggy larid " 6*2 per cent, of ash ; 
 while the silica contained in the ash from tlie 
 
 Sound land amounted to 3-42 per cent., and from the 
 
 Boggy land " to 1-90 per cent, of the weight of the straw. 
 
 A remarkable difference, therefore, existed in the relative proportions, 
 
 ■ Meyen, Jhhresbericht, 1839, p. 120. In regard to tliese salt-loving plants, which generally 
 abound in soda, a curious observation was long ago made by Cadet. He states that if a plant 
 of common salt- wort (salsola salt) be transplanted into an inland district— and seed from Ihia 
 plant be afterwards sown, the second race of plants will contain much potash, but scarcely a 
 trace of soda.— Gnielin's Handbuch der Chemie, II. p. 1492. Polash may thus take the 
 place of soda for a time, but removed from its native habitat, the plant would in a few gene- 
 rations die out and disappear. 
 
THE ASH FROM WHEAT STRAW IS VARIABLE. 225 
 
 at least of the silica, in these two varieties of straw, and this difference 
 can be attributed only to the unlike nature of the soils in which the two 
 samples were grown. But on boggy soils ihe oat plant is unhealthy, 
 and in general neither fills its ear, nor ripens a perfect seed ; — the dif- 
 ference in the ash in tiiiscase, therefore, cannot be considered as entirely 
 opposed to the general proposition, that in a healthy state, plants at 
 the same period of their growth always yield nearly the same weight 
 of ash. 
 
 But that different experimenters have obtained very unlike quantities 
 of ash, from the most common cultivated plants, apparently in a state 
 of health, when grown under different circumstances of soil and climate, 
 — does appear to contradict this general proposition. Thus 100 lbs. of 
 ripe wheat straw leave of ash 
 
 4-3 lbs. De Saussure ; 
 4-4 lbs. Berthier; 
 3-5 lbs. Sprengel ; 
 15-5 lbs. Sir H. Davy; 
 while the straw of one variety of red wheat grown on a clay-loam, at 
 Aykley Heads, near Durham, gave me 6-6 per cent., and that of two 
 other varieties of red wheat, grown near Dalton, in Ravensworth Dale, 
 Yorkshire, a country abounding in limestone — and on the same field — 
 left respectively 12-15 and 16'5 per cent, of ash. The difl^erence of 4 
 per cent, between these last two results, shows that the quantity of ash 
 depends much upon the variety of grain examined — though to what ex- 
 tent all the great differences obtained, as above shown, are to be ascribed 
 to this cause alone, it is impossible to say, until numerous other experi- 
 menrs shall have been instituted. 
 
 One thing, however, is manifest, that the quantities of inorganic mat- 
 ter necessarily contained in a crop of wheat, given in a previous page 
 (p. 216) on the authority of Sprengel, must be considered as probably 
 far below the mean proportion, since some varieties yield, in the form 
 of ash, about six times as much as is there stated. 
 
 Every one knows how uncertain general conclusions are, — or expla- 
 nations of natural phenomena, — when deduced from single observations 
 only, and of this truth the above results present us with a useful illus- 
 tration. Thus Liebig, in his Organic Chemistry applied to Agriculture 
 p. 152, to which we have had frequent occasion to refer — explains 
 why land will refuse to grow wheat, and may yet produce good crops 
 of oats or barley in the following manner : — "One hundred parts of the 
 stalks of wheat yield 15-5 parts of ashes (H. Davy) : the same quantity 
 of the dry stalks of barley 8-54 (Schrader), and one hundred parts of the 
 stalks of oats only 4-42. The ashes of all are of the same composition. 
 We have in these facts a clear proof of what plants require for their 
 growth. Upon the same field which will yield only one harvest of 
 wheat, two crops of barley and three of oats may be raised." 
 
 In this passage it has been assumed that the ash of wheat and other 
 straws is constant in quantity, that wheat straw always contains much 
 more than that of oats or barley, and that the ash is in each case of the 
 same composition (see above, pp. 216 to 217), — all of which premises 
 being incorrect, the conclusion must of course be rejected. 
 
 But the straw of barley and oats also, according to different authorities, 
 
226 ASH FROM OAT AND B.MihiA is t RAW ALSO VARIABLE. 
 
 leaves very unlike f]uaniitie8 of asli. Thus, according to Sprcngel and 
 
 Schrader, 100 lbs. of 
 
 Sprengel. achradsr. 
 
 Oat 3traw leave . 5-74 lbs. 4-4Q lbs. 6-6 J. 
 
 Barley straw . . 5-24 lbs. 8-54 lbs. 
 We cannot help conceding, therefore, generally, in regard lo the cereal 
 grasses, that different variktiks, at least, of the same plant, inay contain 
 inorganic matter in different proportions. 
 
 But certain analyses which have been made seem to demand a still 
 further concession. Thus De Saussure found that the ash left by the 
 same tree or shrub — by the fir or thejuniper for example — differed both 
 in kind and in quantity, according as it grew upon a granitic or calca- 
 reous soil. Berlhier also found the ash of a piece of Norway pine {pi- 
 nus abies) to differ very much from that of the wood of the same pine 
 grown in France. From these and a few other observations, the con- 
 clusion has been very generally drawn by vegetable physiologists, that 
 the ash of plants in general is determined both in kind and quantity by 
 the soil in which they grow. 
 
 This is very likely to be true to n certain extent, as we have seen in 
 the straw of the bog oat above adverted to, but a sufficienl number of 
 accurate comparative analyses of the ash of cultivated plants* has not 
 yet been published, to enable us to determine the precise influence of the 
 soil in all cases. It is impossible, however, that the prevailing charac- 
 ter of the soil can have more than a general influence on the character of 
 the ash of any living vegetable — so long as the plant retains a healthy 
 state. The experiments of De Saussure do not appear to have been 
 made with sufficient care,f while the only comparative experiment of 
 Berthier is open to objections (jf another kind. 
 
 I have said that the quantity and kind of the ash is likely to be affected 
 by the character of tlie soil to acertain extent. The following considera- 
 tions seem to embody nearly all the sources of such variation, of which 
 we can at present speak with any degree of certainty :— 
 
 1°. Plants at different periods of their growth require for the jiroduc- 
 tion of their several pans, and therefore appropriate from the soil, differ- 
 ent inorganic substances ;t hence the ash will vary with the age of the 
 plant. 
 
 * Five samples of (he same variety of wheat (Hunter's wheat) grown on different soils in 
 the neighbourhood of Haddington, gave me very nearly the same proportions of ash. Thus 
 the sample grown on a 
 
 Per CPnl. 
 1°. Deep reddish clay loam, sji6so(7 gravel, left 1776 
 
 2°. Red clay on gravel 1787 
 
 3°. Stiff clay on retentive subsoil 1903 
 
 4°. Light clay on rather retentive subsoil . . 1-917 
 
 5°. Light turnip laml 18'^ 
 
 These results approach very near each otlier. The differences are perliaps too slight to 
 justify us in concluding that the aah is greatest in quantity when the subsoil is most reten- 
 tive. 
 
 t The accuracy of De Saussure's analyses is rendered very doubtful by the fact that, in 
 the ashof all the different trees and shrubs he examined, he found a large quantity, in that 
 of the juniper as much as 43 per cent, of alumina, and in that of the pine from 12 to 16 per 
 cent., wiiile Berthier, whose skill is undisputed, found no alumina in the ash of any of the 
 numerous trees on vyhichhis experiments were made. 
 
 t This fact indicates an exceedingly interesting field of chemical research in connection 
 with practical EigricuUure. What substance will bring this or tliat seed into early leaft — 
 what will hasten its growth in middle life 7 — what will bring it to early maturity 1 The wheat 
 
SOME SUBSTANCKS ACT A3 MKDIA OR AUKNTS O.NLY. 227 
 
 2*^. If the substances necessary for the perfection of one or more parts 
 of a plant abound in the soil, its chief developennent will take the direc- 
 tion of those parts. Thus one plant will run to leaf or straw, another to 
 flov/er and seed. Thus also in the grain of one crop of wheat more glu- 
 ten is produced than in that of another, and as this gluten appears to 
 contain the phosphates of lime and magnesia, as essential constituents, 
 the ash will necessarily vary with the gluten of the seed. 
 
 3^. Some substances ajjpear to enter into the circulation of plants not 
 so much as actual and necessary constituents of the parts of the vegetable, 
 as to serve as media or agents by which other compounds, both organic 
 and inorganic, may be conveyed to the plant. Thus common salt ap- 
 pears to enter many plants for the purpose of supplying soda, its chlo- 
 rine being discharged by the leaf. Silica enters the plant chiefly in the 
 form of silicate of potash or soda. When it reaches its proper destina- 
 tion — the stalks of the grasses for instance — this silicate is decomposed 
 chiefly by the carbonic acid, which is always present in the pores of the 
 green stem, the silica is dejiosited and the alkali proceeds downwards 
 with the sap as a soluble carbonate, or in combination with some other 
 organic acid. Thus the same portion of alkali may return many times 
 into the circulation with this or with other materials which the parts of 
 the plant require, and every new burden it deposits will necessarily 
 cause a new variation in the relative proportions of the several inorganic 
 constituents which are afterwards detected in the ash. 
 
 4°. As the water which enters by the roots always brings with it some 
 soluble substances, the quantity of these conveyed into the plant will be 
 materially affected by the amount of evaporation from the leaves; and 
 hence, after a long drought, the leaves of the turnip, the ])otato, and 
 other plants, will yield a larger proportion of ash than will be obtained 
 frotn them in moist and rainy weather. 
 
 5°. In the mineral kingdom it is found that one substance may not 
 unfreiiuently take the place, and perform the functions, of another. Thus 
 potash and soda replace each other in certain ininerals, as do also lime 
 and magnesia and the phosphoric and arsenic acids. It has been sup- 
 posed that a similar interchange may take place in the vegetable king- 
 dom — that when the plant cannot get potash it will take soda — that 
 when it can get neither, it will appropriate lime, — and so on. Such a 
 conjectural interchange may possibly take place in a small degree, for a 
 limited time, and in certain ])lants, without materially affecting their ap- 
 parent health — but it is not by trusting to such resources of nature that 
 a luxuriant vegetation or plentiful crops will ever be reared by the prac- 
 tical agriculturist. 
 
 Admitting, however, all these sources of variation in the kind and 
 (|uantity of the ash obtained from different plants, the sound practical 
 conclusions from all we know on the subject at present seem to be — 
 
 1°. That certain inorganic substances, in certain proportions, are ne- 
 cessary to all plants usually cultivated for food — if they are to be reared 
 or maintained in a healthy stale. 
 
 stalk and the potato require more potash while in rapid growth. This growth may be con- 
 tinued and prolonsed by the presence of ammonia ; while lime is said to bring it sooner to 
 a close, and to give an earlier harvest. How valuable would be the multiplication of such 
 facts ! 
 
228 BASIS OK EA'LIGUTENED PRACTICAL AGIUCULTURi;. 
 
 2°. That we must seek for these necessary substances in the inorganic 
 constituents which are present in the richest crops of every kind — in the 
 produce of the most fertile soils.* 
 
 3°. That where these necessary substances are not jiresent in ax\y 
 soil, we may infer that it will prove unfit to yield a luxuriant crop of a 
 given kind ; or, on the other hand, where these substances are not to be 
 detected in the ash of the plant, that the fault of the crop, if any, may be 
 ascribed to their partial or total absence from the soil on which it grew. 
 
 These conclusions form the basis of an enlightened and scientific prac- 
 tical agriculture. This basis, however, requires to be strengthened and 
 enlarged by further experimental investigations. 
 
 ' " I have examined," says Sprengel, " the finest seed-corns from many localities, and t 
 have invariably found the quantities not only of the organic substances — starch, sugar, &c. — 
 but also of the inorganic compounds in all the celebrated seed-corns, so perfectly alike, that 
 one would have thought they had all grown on one and the same soil." — Lehre vom Dunger, 
 p. 43. 
 
LECTURE XI. 
 
 Nature and origin of soils. — Organic matter in the soil. — General constitution of the earthy 
 part of the soil. — Classification of soils froni their chemical constituents. — Method of ap- 
 proximate analysis for the purposes of classification. — General origin of soils and subsoils. 
 — Structure of the earth's crust. — Siratitied and iinstralitied rocks. — Crumbling or degra- 
 dation of rocks. — Diversity of soils produced. — Superfjcial accumulations.— 'fabular view 
 of the character and agricultural capabilities of the soils of the different parts of Great 
 Britain. 
 
 Such are the inorganic compountls .which minister to the growth of 
 plants, and such the proportions in which they severally occur in the 
 living vegetable. Whence are these inorganic constituents all derived? 
 
 We have seen that the atmosphere, when pure, contains no inorganic 
 matter, anc? that if dust, spray, or vapours occasionally float in the air, 
 and are carried by the winds to great distances — yet that they are 
 only accidentally present, and cannot be regarded as a source from 
 which the general vegetation of the globe derives a con.stant supply of 
 those mineral substtmces which are necessary to its healthy existence. 
 
 The soil on which they grow is the only natural source from which 
 their inorganic food can be derived. We are led, therefore, as the next 
 subject of our study, to inquire into the nature and origin of soils.* 
 
 § 1. Of the organic matter in the soil. 
 
 Soils ditTer much as regards their immediate origin, their physical 
 properties, their chemical constitution, and their agricultural capabili- 
 ties; yet all soils which iu their existing state are capable of bearing a 
 ])rofitable crop, jjossess one common character — they all contain organic 
 matter in a greater or a less proportion. 
 
 This organic matter consists in part of decayed animal, but chiefly of 
 decayed vegetable substances, sometimes in brown or black fibrous por- 
 tions, exhibiting still, on a careful examination, something of the origi- 
 nal structure of the organized substances from which they have been de- 
 rived — sometimes forming only a fine brown powder intimately inter- 
 mixed with the mineral matters of the soil — sometimes scarcely percep- 
 tible 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, organic matter in this latter form may often be detected in con- 
 siderable quantity. 
 
 The proportion of organic matter in soils which are naturally produc- 
 tive of any useful crops, varies from one-half to 70 per cent, of their 
 whole weight. With less than the former proportion they will scarcely 
 support vegetation — with more than the latter, they require much ad- 
 mixture before they can be brought into profitable cultivation. It is 
 
 ■ On the subject of this and the following lecture, the reader will consult with advantage 
 an excellent little work, " On the nature andproperty of soils" by Mr. John Morton. 
 
230 PROPORTION OF ORGANIC MATTER IN SOILS. 
 
 only in boge;y and peaty soils that the latter large proportion is ever 
 found — in tffe best soils iheorganic matterdoes not average five percent., 
 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, 
 may occasionally be detected. 
 
 Though, however, a certain proportion of organic matter is always 
 found in a soil distinguished for its fertility, yet the presence of such sub- 
 stances 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 neighbourhood — the one contained 4*05 
 per cent, of organic matter, and was very fruitful — the other 4*19 per 
 cent., and was almost barren. This fact is consistent with what has been 
 stated in the two preceding lectures, in regard to the influence exercised 
 by the dead inorganic matter of the soil, on the general health and luxu- 
 riance of vegetation. 
 
 § 2. General constitution 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 cliiiiMte does not constitute less than 96 per 
 cent, of its whole weight, when free from waier. This earthy part con- 
 sists principally of three ingredients: — 
 
 1°. 0( Silica, siliceous sand, or siliceous gravel — of various degrees 
 of fineness, from that of an impalpable powder as it occurs in clay soils, 
 to the large and more or less rounded sandstones of the gravel beds. 
 
 2°. Alumitia — generally in the form of clay, but occasionally occur- 
 ring in shaly or slaty masses more or less hard, intermingled wiih the 
 soil. 
 
 3°. Lime, or carbonate of lime — in the form of chalk, or of fragments 
 more or less large of the various limestones that are met with near the 
 surface in different countries. Where cultivation prevails it often hap- 
 pens 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 numerous varieties of marl which different dis- 
 tricts are known to produce. 
 
 It is rare that a sui)erficial covering is anywhere met with on the 
 surface of the earth, which consists solely of any one of these three sub- 
 stances — a soil, however, is called sandy in which the siliceous sand 
 greatly predominates, and calcareous, where, as in some of our chalk 
 and limestone districts, carbonate of lime is present in considerable abun- 
 dance. When alumina forms a large proportion of the soil, it constitutes 
 a clay of greater or less tenacity. 
 
 The term clay, however, or jjure 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 free from water they contain only from 42 to 48 per cent, 
 of this earth, with from 52 to 58 of silica. These occur, however, only 
 in isolated patches, and never alone form the soil of any considerable 
 
COMPOSiTJON OF I'ORCELAIN AND AG RI t IL^ LT. AL CLAYS. 'J31 
 
 rlistrict. The strongest clay soils which are anywhere in cultivation 
 raely c^nitain more than 35 per cent, oi'ahmiina.* 
 
 Soils in general consist in great part of the three substances above 
 named in a state o{ 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 are, for the most part, in a state of cheinical com- 
 bination. Thus, if a portion of a stiff clay soil be kneaded or boiled 
 ■with re])eated portions of water till its coherence is entirely 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 sejiarated into two por- 
 tions — a fine impalpable powder consisting chiefly of clay, poured ofl' 
 with the water, and a quantity of siliceous or other sand in particles of 
 various sizes, which will remain in the first vessel. This sand was 
 only mechanically mixed with the soil. The fine clay retains still some 
 mechanical admixtures, but consists chiefly of silica and alumina c'uem- 
 ically combined. 
 
 Of the porcelain clays above alluded to, there are several varieties, 
 three of which, containing the largest proportion of alumina, c(k>^ist res- 
 pectively of — 
 
 
 I. 
 
 11. 
 
 III. 
 
 Silica . 
 
 . 47-03 
 
 46-92 
 
 46-0 
 
 Alumina 
 
 . 39-23 
 
 34.81 
 
 40-2 
 
 "Water . 
 
 . 13-74 
 
 18-27 
 
 13-8 
 
 100-00 100-00 100-Of 
 But, as already stated, these clftys rarely form a soil — the stiffest 
 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 trustworthy 
 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 distinguished by the foreign agri- 
 cultural writers as pure clays. They are all probably made up of some 
 of the varieties of porcelain clay, more or less intimately mixed with 
 siliceous and ochrey i)artieles — in so minute a stale 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 to which they can liken clay soils in general, and by compari- 
 son with which they are enabled distinctly to classify and name them. 
 As the use of the term clay in this sense has been introduced into Eng- 
 
 • In an interesting paper on subsoil plouehing by Mr. H. S. Thompson, in the report of 
 the Yorkshire Agricultural Society fnr 1837, p. 47, it is stated that the iias clays, which form 
 the subsoil in certain parts of Yorkshire, contain sometimes, in the dry slate, as muck as St 
 per cent of alumina (?) 
 
 t When heated to redness the whole of the water is driven off from these clays, and they 
 then consist respectively of— 
 
 Silica 545 57-4 534 
 
 Alumina 45-5 42 6 466 
 
 1000 1000 1000 
 
 which numbers are in accordance with those given at the foot of the preceding page. 
 
232 CLASSIFICATION OF SOILS. 
 
 lish agricultural books,* and as il is really desirable to possess a word to 
 which the above meaning can be attached, 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 clay, a 
 finely divided chemical compound, consisting very nearly of 60 of silica 
 and 40 of alumina, tvith a little oxide of iron, and from which no siliceous 
 or sandy matter can be separated mechanically 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 frorn their chemical constituents. 
 
 Upon the principles above described soils may be classified as fol- 
 lows : — 
 
 1°. Pure clay (pipe-clay) consisting of about 60 of silica and 40 of 
 alumina and oxide of iron, lor the most part chemically combined. It 
 allows no siliceous sand to subside wlien ditlused 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 15 per cent, of a siliceous sand, which can be separated 
 from it by boiling and decantation. 
 
 3°. Clay loam differs from a clay soil, in allowing from 15 to 30 per 
 cent, of fine sand to be separated from it by washing, as above described. 
 By this admixture of sand, its pjiVts are mechanically separated, and 
 hence its freer and more friable nature. 
 
 4°. A loamy soil deposits from 30 to 60 per cent, of sand by mechani- 
 cal washing. 
 
 5°. A sand,y loam leaves from 60 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 quantity 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 which is not sufficient to dis- 
 colour 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 incorporated 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 ])oint 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. oi^ moist arc equal to 150 ol^ dry, and this 150 of dry 
 
 ■ As in Brilish Husbandry, p. 113, and in London's Encydopcbdia of Agriculture, p. 315, 
 wl^ere classifications of soils are given chiefly from Von Thaer, though neither work ex- 
 hibits with sufficient prominence the meaning to be attached to agrivuUurcl clay, as distin- 
 guished from alumina, sometimes ccdled pure clay by the chemist. 
 
MAKLY AND CALCAREOUS SOILS, AND VEGETABLK MOULDS. 233 
 
 soil contain 60 of sand, or 40 in 100 (40 per cent.) It woultl, therefore, 
 be properly called a loam, or loamy soil. 
 
 But ihe above classitication has reference only to the clay and sand, 
 while we know that lime is an iiiiporiant constituent of soils, of which 
 they are seldoin entirely destitute. We have, therefore, 
 
 7°. Marhj soils, in which the proportion of lime is more than 5 but 
 does not exceed 20 per cent, of the whole weii^ht of the dry soil. The 
 marl is a sandy, loamy, or clay marl, according as the pro|X)rlion of 
 clay it contains would place it under the one or other denomination, sup- 
 posing it to be entirely free Crom 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 calcareous clays, calca- 
 reous loams, or calcareous sands, according to the j)roportion of clay and 
 sand which are present in them. 
 
 The determination of the lime also, wl.ien it exceeds 5 per cent., is 
 attended with no dit^culty. 
 
 To 100 grs. of the dry soil diffused through half a pint of cold water, 
 and half a wine-glass full of muriatic acid (the spirit of salt of the shops), 
 stir it occasionally duiing the day, and let it stand over-night to settle. 
 Pour off the clear li(|uor 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 offj dry the soil and weigh it — tlie loss will amount generally to about 
 one per cent, more than the quantity of lime |)resent. 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 garden 
 mould, which contains from 5 to 10 percent., to the ])eaty soil, in which 
 the organic matter may amount to 60 or 70. These soils also are clayey, 
 loamy, or sandy, according to the jiredominant 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, to be taken in examining a 
 soil with the view of so far determining its constitution as to be able pre- 
 cisely 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 inay be raised till it only does not 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 vegetable 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 
 
234 SUMMARY OF THE METHOD OF KXAMI.NATION. 
 
 with lialf 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 gen- 
 erally be nearer ihe truth if that portion of soil be employed which has 
 been previously heated lo redness. 
 
 4°. A fresh portion of the soil, perhaps 200 grs. in its moist state, may 
 now be talien and washed to determine the ([uantity of siliceous sand it 
 contains. If the resiilual sand be supposed lo contain calcareous matter 
 its amount may readily be determined by treating the dried sand with 
 diluted muriaiic acid, in the same way as wiien determining the whole 
 amount of lime (3°.) contained in the unwashed soil.f 
 
 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 
 inixed with occasional fragments of flint, which is noted for producing 
 excellent crops of wheat every otiier year. It is known in the valley of 
 Kingsclere, at Wantage, and Newbury. I select a portion of this soil 
 from the latter locality for my jjresent illustration. 
 
 1°. After being dried in the air, and by keeping some lime in paper, it 
 was exposed for some hours to a temperature sufficient to give the white 
 paper below it a scarcely perceptible tinge : by this process 104i grs. 
 lost 4 grs. 
 
 2°. When thus dried, it was heated to dull redness. It first black- 
 ened, and then 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 full 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. 
 
 The soil, therefore, contained 
 
 Water 4 grs. 
 
 Organic matter (less than) . . 4i 
 Carbonate of lime (less than) . 3 
 Clay and sand 93^ 
 
 104| 
 4°. By boiling and washing with water, 291 grs. of the undried soil 
 left 202i grs. of very fine sand chiefly siliceous, — 104i, therefore, would 
 have left 73 grs., or the soil contained per cent. — 
 
 * A more rigorous method of determining Uie lime when less than 5 per cent, will be 
 given in the following lecture. 
 
 t The weighings for the purposes here described may be made in a small balance with 
 grain weights, sold by the druggists for 53. or 6s., and the vegetable matter may be burned 
 away on a slip of sheet iron or in an untinned iron tablespoon over a bright cinder or char- 
 coal tire — care being taken that no scale of oxide, which may be formed on the iron, be al- 
 lowed to mix with the soil when cold, and thus to increase its weight. Those who are in- 
 clined 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>2 inches in diame- 
 ter, capable of holding )(X) 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 life- time. 
 
DIFFERKNCE BETWEKN SOIL AMD SUBSOIL. 235 
 
 Water 3-9 per cent. 
 
 Organic matter (less than) . • 4'1 
 
 Carbonate of lime (less than) . 3"0 
 
 Clay 19-0 
 
 Sand (very fine) 70.0 
 
 100-0* 
 This soil, therefore, containing 70 per cent, of sand, separable by 
 decanfation, 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 commonly dis- 
 tinguished by the name of subsoil. This subsoil occasionally consists 
 of a mixture of the general constituents of soils naturally different from 
 that whicii 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 natural causes. 
 
 In a mass of loose matter of considerable dejith, spread over an extent 
 of country, it is easy to understand how — even thougli originally alike 
 through its whole mass — a few inches at the surface should gradually 
 ac(|uire different physical and chemical characters from the rest, and 
 how there should ihus be gradually established important agricultural 
 distinctions between the first 12 or 1.5 inches (the soil), the next 15 (the 
 subsoil), and the "-emaining body of the mass, which, lying still lower, 
 does not come under the observation of the practical agriculturist. 
 
 On the surface, plants grow and die. Through the first few inches 
 their roots penetrate, and in the same the dead plants are buried. This 
 portion, therefore, by degrees, assumes a brown colour, more or lessdark, 
 according to the quantity of vegetable matter which has been i)ermitted 
 to accumulate in it. Into the subsoil, however, the roots rarely |iene- 
 trafe, and the dead plants are still more rarely buried at so great a depth. 
 Still this inferior layer is not wholly destitute of vegetable or other or- 
 ganic matter. I lovvever comparatively impervious it may be, still water 
 makes its way through it, more or less, and carries down soluble organic 
 substances, which are continually in the act of being produced during the 
 decay of the vegetable matter lying above. Thus, though not sensibly 
 discoloured by an admixture of decayed roots and stems, the subsoil in 
 reality contains an appreciable quantity of organic matter which may 
 be distinctly estimated. 
 
 Again, the continual descent of the rains upon the surface soil washes 
 down the carbonates of lime, iron, and magnesia, as well as other soluble 
 earthy substances — it even, by degrees, carries down the fine clay also, 
 
 ' Some of these numbers fiiffer by a minute fraction from those in tlie precefling page : 
 this is because they are calculated from the more correct decimal fractions contained in my 
 own note-book. The organic matter is said to be less than the number here aiven, because 
 by simple drying, as here prescribed, the whole of the water cannot be driven otF— a portion 
 b>»inii always retained by the clay, which is not entin-ly expelled, till the soil is raised nearly 
 to a red heat. Ilencc the loss by this second heating must always be greater than the actual 
 weight of organic matter present. The lime is also less than the number given, because, aa 
 already stated, the acid dissolves a little alumina as well as any carbonate of magnesia which 
 may be present. 
 
236 HOW THK SUBSOIL IS PRODUCED. 
 
 SO as gradually to establish a more or less manifest difference between 
 the upper and lower layers, in reference even to the earthy ingredients 
 which tliey rcs[icctively contain. 
 
 But, excei)lin the case of very porous rocks or accumulations of earthy 
 matter, these surface waters rarely <lescend to any great depth, and hence 
 after sinlcing through a variable thickness of subs(jil, we come, in gene- 
 ral, to earthv 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 organic, 
 chiefly vegetable, matter, in a state of decay — of the sm/;.5i9?7, that the or- 
 ganic matter is less in quaniity and has entered it cliiefly in a soluble 
 state, and that earthy matters are present in it which have been washed 
 out of the su|)crior soil — and of the suhjacent mass, that it has remained 
 nearly unaftecied by the changes which vegetation, culture, and atmos- 
 pheric agents have produced upon the portions that lie above it. 
 
 From what is here staled, the effect of trench and subsoil ploughing, 
 in altering more or less materially the proi)ortions of the earthy constitu- 
 ents in tfiesurt ace soil, will he in some measure apparent. That which 
 the long action of rains and frosts has caused to sink beyond the ordinary 
 reach of the plough is, by such meihods, brought again to the surface. 
 When the substances tlius brought up are directly beneficial to vegeta- 
 tion or are fitted 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 a 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 mate- 
 rials from which a soil can be formed. This is especially the case in 
 mountainous and granitic districts, and in the neighbourhood of active 
 or extinct volcanoes, where, as in .Sicily, streams of naked lava stretch 
 in long black lines amid tlie surrounding verdure. 
 
 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 reward 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 observed 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 char- 
 acter may often he beneficially altered by a judicious admixture with 
 portions of the subjacent 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 com- 
 paratively level surfaces the crumbling of the rock gradually forms a soil— 
 
CRUMBLING OR DKGRADATION OF ROCKS. 237 
 
 while from those which are sufficiently inclined the rains wash away 
 the loose materials as soon as they are separated, and carry them down 
 to the vallies. 
 
 The superficial accumulations of which we have spoken, as covering 
 the rocks in many places to a depth of one or two hundred feet, consist 
 of materials thus washed down or otherwise transported — by water, by 
 winds, or by other geological agents. Mucli of these heaps of transported 
 matter is in the state of too fine a powder to permit us to say from whence 
 it has been derived — but fragments of greater or less size are always lo 
 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 accumula- 
 tions have been derived. 
 
 Thus the general conclusion is fairly drawn, that the earthy matter of 
 all soils has been ])ro(kiced by the gradual decay, degradation, or crumb- 
 ling dnwn qJ previously existing rocks. It is evident therefore — 
 
 1°. That whenever a soil rests immediately upon therockfrom which 
 it has been derived, it may be expected to partake more or less of the 
 composition and cbaraclers of that rock. 
 
 2°. That where the soil forms only the surface layer of a considerable 
 depth of transported materials, it may have no relation whatever eilher 
 in ii.ineralogical characters or in chemical constitution to the immedi- 
 ately subjacent rocks. 
 
 The soils of Great Britain are divisible into two such classes. In 
 some counlies an acquaintance with the prevailing rock of the district 
 enables us to predict ilie 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 relation whatever to the 
 rocks on which the loose materials rest. 
 
 § 6. On (he general structure of the earth'' s crust. 
 
 Beneath the soil, and the loose or drifted matters on which it rests, we 
 everywhere find the solid rock. Tliis rock in most countries is seen— 
 in mines, quarries, and cliffs — to consist of beds or layers of varied thick- 
 ness placed one over the other. To these layers geologists give the 
 name of strata; and hence rocks which are thus made up of many se- 
 parate layers are called stratijied 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 upper surface down- 
 wards, and often as far beneath as we have been able to penetrate into 
 the earth. Such rocks are said to be unstratified. Among these are 
 included the granites, the trap, green-stone, or basaltic rocks, and the 
 lavas. Geologists have ascertained that all these unstratified rocks have, 
 like the volcanic lavas, been in a more or less perfectly melted state — 
 thai their ])resent appearance is owing to the action of fire — and hence 
 they are often called igneous* rocks. They often also exhibit a more or 
 less crystalline or glassy structure, or contain, imbedded in them, nu- 
 merous regular crystals of mineral substances ; hence they are some- 
 times called also crystalline rocks. The terms igneous, crystalline, and 
 
 * Sometimes p^o^enoM, produced by fire ; but this is an unnecessarily hard word. 
 
238 
 
 STRATIFIED AND UNSTRATIFIKD ROCKS. 
 
 iinstratifiecl, therefore, apply to the same class of rocks — ihe first iiullca- 
 ting their ori.oi7i, 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 strati- 
 fied rocks as they are found to occur in contact with unstratified masses 
 in various parts of the globe : — 
 
 A represents an unstratified mountain mass or other similar ro?k rising 
 up through the stratified deposits. T!ie lieiiding up of the edges of the 
 latter indicates that after the beds were deposited in n nearK' level posi- 
 tion, the mass A was intruded or forced up tlirough ihem, carrying the 
 broken edges of the beds along with it. 
 
 B shows the more (juiet way in which veins or dykes of unstratified 
 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 ciiasm. 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 exhibit in their whin dykes 
 numerous illustrations of what is shown at B. 
 
 C and D exhibit the manner in which the strata overlie one another 
 in nearly a horizontal position — 1, 2, 3, indicating difTerent 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 direc- 
 tion — as if a surface, formerly level, had been pushed down at the one 
 end and raised up at the other, — and sometimes they seem to rest entire- 
 ly upon their edges. Upon the mode in which they thus lie, the unifor- 
 mity of the soil, in a district where it reposes immediately on the rocks 
 from which it is derived, is materially dependent. In the following dia- 
 gram the surface from A to E represents a tract of country in which the 
 
 rocks have in different parts these different degrees of inclination, at A 
 vertical, 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 comparatively level strata, we 
 shall find the soil pretty uniform in rjuality till we ccJme to the edge of 
 
VERTICAL, INCLINED, AND HOKIZONTAL STRATA. 239 
 
 (he bed D, thence it will again be unilijrin, though perhaps dillerent from 
 the former, till we reach the stratum C, when again it will prove uni- 
 form over a considerable spare till we begin lo climb the hill to B. So 
 the whole hill-side 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 lo another, 
 the quality of the soil may vary every few yards, more or less, ac- 
 cording as the members of this group of beds are more or less differ- 
 ent 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 — pro- 
 vided the mineralogical characters of the several vertical layers be sen- 
 sibly unlike. Such dissimilarities in the angular position of the strata, 
 as are rejiresented in the above diagram, are of constant occurrence, not 
 only in our islands, but in all parts of the globe ; and they illustrate very 
 clearlv one important natural cause of that want of uniformity in the na- 
 ture and capabilities of the soil which is more or less observable in every 
 undulating and in some comparatively level countries also. 
 
 It may be stated, as the general result of an extended examination 
 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 various degrees of solidity and 
 hardness, from the loose sand of some parts of the lower new-red and 
 green-sand formations, to the almost perfect quartz rock not unfrecjuently 
 associated with the oldest strata. The lime-stones vary in like manner 
 frotn 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 
 slate. 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 substances, 
 the soils formed from them by natural crumbling or decay 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 
 earth}' ingredients — in proportions which will depend upon the relative 
 f)uantities 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 themselves 
 in the crust of the globe, always maintain the same relative positions. 
 Thus the numbers 3, 2, 1, in the annexed diagram, represent three series 
 of beds known by the names of the magnesian lime-stone, the lower new- 
 
 11 
 
240 THKSE STRATA ARE OFTEN CO.NTl.NUOUS OVKU LARGK AUKAS. 
 
 -xx'VW^VX \V 
 
 red sand-stone, and ilie coal-measures, lying over each other in their 
 natural positions — the lime-stone uppermost, the sand-stone next, and 
 the coal beneath both. VV^henever 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 between 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 coun- 
 try. Hence when they dip beneath other beds, as they are seen to do 
 in the above diagrams, we can still, wiili 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 immediate- 
 ly above them. Tims, if in a tract of country consisting of the magne- 
 sian lime-stone (3) above-mentioned, it is known that deep vallies occur, 
 it becomes probable that the soil in those vallies will rest upon, and may 
 be formed from, the underlying red sand-stones or coal-measures; and 
 that it will therefore possess very different agricultural capabilities from 
 the soil that generally prevails around if. Or in chalk dis'ricts, 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 differ- 
 ent soil from that which is cultivated in the chalk wolds above. This is 
 the case in the valley of Kingsclere, where the peculiar wheat soil oc- 
 curs, of which an approximate analysis has been given in page 234. 
 
 3°. It has been already slated that the stratified rocks, though so very 
 numerous and so varied in appearance, yet consist generally 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 readil3^ 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 entirely 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 considera- 
 ble quantity, — as in the neighbourhood of our coal-beds — or the bones or 
 shells of animals in greater or less abundance, by each of which the 
 agricultural characters and capabilities of the soils formed from them, 
 will be more or less extensively affected. 
 
 Or lastly, the mixture of other earthy substances gives a peculiar 
 
THEIR PECULIAR CHARACTERS ALSO COr^TINUOUS. 241 
 
 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 
 inai^nesia, sometimes in large quantity, in man}' lime-stones, produces 
 ari important modification in the chemical constitution 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 not 
 every stratum, at least every series of strata, exhibits distinguishing and 
 characteristic peculiarities, by m.eans of which it may be more or less 
 readily recognized. On liiese peculiarities the special agricultural ca- 
 pabilities of those parts of the globe in which each series of beds occurs 
 are in a great degree dependent. 
 
 4^. This peculiar character is also more or less continuous over very 
 large areas. Thus if a given stratum be founrl on the surface 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 iu both 
 countries. A knowledge of the geology, therefore, — that is, of the kind 
 of roi'k which appears on the surface in every part of a country — ena- 
 bles us to predict generally the kind of soil which ought to rest upon it, 
 if it be not covered by foreign accumulalions ; wliile, on the other hand, 
 a knowledge of the agricultural cajiabiliiies of any one district in which 
 certain rocks are known to lie iiiimeiliately beneath the soil, and of the 
 agricultural practice suited to that district, will Indicate the probable ca- 
 pabilities of any other tract in which the same kiud of rock is known to 
 appear on the surface, and of the kind of culture which may be most 
 successfully applied to if. 
 
 It is evident, then, that a familiar acquaintance with the general 
 characters and relative positions of all the series of strata that have hith- 
 erto been observed, and of the classification of rocks considered geologi- 
 cally, to which tiiis knowledge has led, must be fitted to throw much 
 light upon the principles of a general, enlightened, and philosophical 
 agriculture. 
 
 § 8. Classification of the stratified rocks, their extent, and the agricultu- 
 ral 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 re- 
 ference to this their relative age, the stratified rocks are divided into the 
 primary, the first deposited and most ancient — the secondary, which are 
 next in order — and the tertiary, which overlie both. 
 
 These three series of strata are again subdivided into systems, and 
 these into minor groups, called formalions, — the several members of 
 each system and formation having such a common resemblance, either 
 in mineralogical character or in the kind of animal and vegetable re 
 mains 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, thicknesses 
 and mineralogical characters of the stratified rocks, in descending order 
 as they occur in our islands. The annexed remarks indicate also the 
 
242 CLASSIFICATION OF TIIK STRATIFIED ROCKS, 
 
 dislricts where each of these groups of rocks forms the surface, and the 
 general agricultural character of the soils that rest upon ihem. 
 
 I. Tertiary Strata — characterized by containing, among other fos- 
 sils, the remains of animals, which are identical with existing species 
 
 NAME AND THICKNESS. MINERALOGICAL CHARACTERS. 
 
 1°. Craa;. 50/1, -A- mass of rolled pebbles mixed with 
 
 mai-ine shells — resting on beds of sand 
 and sandy lime-stone ; the whole more 
 or less impregnated with oxide of iron. 
 Extent. — The Crag forms a stripe of land a few miles in width ui the east- 
 em part of Norfolk and SuflfoOc, and in the south-eastern part of the latter coun- 
 ty. It is a flat, and generally, it is said, a fertile arable district. 
 
 2°. Fresh-water Marls. 100 ft. Marls and marly lime-stones, with 
 
 fi'esh-water shells divided into two se- 
 ries by an estuary deposit, containing 
 marine shells. 
 Extent. — On these beds reposes the sod of the northern half of the Isle of 
 
 Wight, the only part of England in which they appear at the surface. 
 
 3°. London Clay. 200 to 500 fl. Ftiff, almost impervious, brown, blue, 
 
 and blackish clay, rich in marine shells, 
 and containing layers of lime-stone no- 
 duliis. 
 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. 
 Soil. — 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 mi.xed with sand, it fomis a fertile loam ; and hence where the sand of the 
 subjacent plastic clay is easily accessible, it may readily be improved by ad- 
 mixture. Repeated dressings of London manure convert it into ricli meadow 
 land, and even where diis cannot be obtained, the dithculty and expense of cul- 
 ture 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/^ Alternating beds of clay and sand, of 
 
 various colours and thicknesses. Some 
 of the be<is 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, gen- 
 erally low, and flat belt, of varying breadth, occupying a large space in FI amp- 
 shire" and Dorset, in Essex, Suffolk, and Norfolk, — strttching along the north- 
 ern part of Kent and Surrey, and throwing out arms into Berks, Buckingham, 
 and Hertford. 
 
 Soil. — The soil is very various, die alternate beds of sand and clay of differ- 
 ent qualities producing soils of the most imlike quality often within very short 
 distances. The greatest portion of diis tract is in arable culture, but there are 
 extensive heaths and wastes in Berks, Hampsliirc, and Dorset. 
 
 In Norfolk and Suffolk, where the lower be^s 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 turnips, barley, and wheat, instead of the 
 heath and bent, its sole original produce. This chalking is generally repeated 
 once in 8 years, at an expense of 50s. an acre. In Hampshire and Berkshire, 
 the same method is adopted with great success, and the ricli crops now reaped 
 from Hounslow Heath are the resiilt of this method of improvement. 
 
SOIL OF THE UPPER AND LOWER (JHALKS. 243 
 
 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 tlie tertiary 
 above or the primary strata below. 
 
 A. — Cretaceous System. 
 
 5°. Chalk. 600 ft. The upper part softer, and contain- 
 
 ing layers of flints, witli many marine 
 remains. Below, the chalk is harder, 
 and towards tlic bottom passes into 
 beds of marl — (chalk marl). 
 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 breadtli, running 
 north-east and south-west from tlie 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 1 5 miles in breadth, and thence stretches 
 into Yorkshire, in the south-eastern part of which comity it covers a large area, 
 and about F'lamborough 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 tliis for- 
 mation it encircles with a Ijroad fringe the soutlieni edges of Sussex and Surrey 
 and the northern borders of Kent. 
 
 Soil. — The soils formed from the upper chalk are all more or less mixed 
 witl> 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 occu- 
 pied as a sheep-walk for ages, though under proper cultivation it is said to be 
 convertible into good arable land, producing barley, turnips, wheat, EUid sain- 
 foin. The lower chalk soils (chalk marl) consist of a deep, strong, calcareous 
 grey or white loam, vcryproductivr., and when mixed with the green sand be- 
 low it, becoming still richer, more friable, and more productive of every kind of 
 crop. It is better suited for wheat than the upper chalk, but is less adapted for 
 turnips. 
 
 The porous natm-e of the chalk i-enders the soil very dry, and in many locali- 
 ties the only method of obtaining a sufficient supply of water is by forming 
 ponds to catch and retain the rain-water. 
 
 In Norfolk and Suff'olk, on the Lincolnshire, and more recently on tlie York- 
 shire Wolds, great improvement has been eff'ected by dressing Uie chalk-soil 
 with fresh chalk brought up from a considerable depth below, and laid on at the 
 rate of 50 to SO cubic yai-ds per acre. The explanation of this procedure is to 
 be found in the fact above stated, that the lower chalk marls, without flints, pro- 
 duce an excellent soil, fitted therefore, by admixtiu'e with the poorer upper-chalk 
 soils, for materially improving theu' quality. It is, therefore, only in localities 
 where this lower chalk can be obtained, that the above method of improve- 
 ment can be with any material advantage adopted. This is proved by the 
 practice at Sudbury, in Suff'olk, 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 upper beds) wliich 
 are immediately within their reach.* 
 
 The upper beds consist of layers of 
 a greenish sand or sand-stone, often 
 chalky. The gault is a solid compact 
 mass of an impervious blue clay, some- 
 times marly. The lower green sand 
 contains a series of ochrey resting on a 
 
 • A rigorous chemical analysis of characteristic specimens of these two chalks might lead 
 to interesting results. 
 
 Green Sand. 
 
 500 ft. 
 
 a Upper, 
 
 100. 
 
 b Gault, 
 
 150. 
 
 c Lower, 
 
 250. 
 
244 UPPER GREEN SAND, WEALDEN, AND UPPKR OOLITK ROCKS. 
 
 series of greenish sandy strata. The 
 whole of these beds are m many places 
 full of fossils. 
 
 Extent. — The Green San.l forms a narrow border round the whole of the 
 northern and western edge of tlie chalk, except in Yorksliire, where it has not 
 as yet been anywhere discovered at the suriace. It skirts also the southern 
 edge of the chalk in Surrey and Kent, and its ea.stern boundaiy in Hampshire, 
 where it attains a breadth of eight or ten miles. It forms likewise the southern 
 portion of the Isle of Wight. 
 
 Soil. — The upper beds, which are the greenest and most chalky, form an 
 open fi-iable soil, easily worked, and of the most productive character. It con- 
 sists in general of an exceedingly fine sand, mixed v/ith more or less of clay 
 and calcareous matter (see analysis, p. 234), coloured by greenish grains. It is 
 rich and productive 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 fonii 
 the most productive garden lands in the kingdom. In other localities, again, 
 where tire soil is formed from layers of black or of white silvery sand, it produ- 
 ces naturally nothing but heath. 
 
 The impervious gault clay forms in Cambridge and Huntingdon " a thin, 
 cold clay soil, which, when wet, becomes as sticky as glvie, is most expensive 
 to cultivate as arable land, and naturally produces a poor, coarse pasture." 
 Much of tliis tract, though unenclosed, is yet generally in arable culture, under 
 two crops and a naked fallow — the enclosed parts are chiefly in pasture,, £ind 
 yield a rich herbage. 
 
 The lower green-sand presents itself over a comparatively small surface, 
 is in some localities (Sussex) laden with iron ochre, and is there naturally un- 
 productive. 
 
 B. — Oolitic System. 
 
 7°. Wealden, 950 ft. The upper part consists of a fresh- 
 
 a Weald Clay, .300. water deposit of brown, blue, or fawn- 
 
 b Hastings Sand, 400. coloured clay, often marly and almost 
 
 rf- c Purbeck lime-Stone, 250. always close and impervious to water. 
 
 Beneath this are the iron or ochrey 
 Hastings sands, which again rest upon 
 the Purl>eck beds of alternate fresh-wa- 
 ter lime-stones and marls. 
 Extent. — The Wealden rocks appear at the suiface only in Sussex and 
 Kent, of which they form the entire central portion. 
 
 Soil. — The soil formed fixim the Weald tJlay is fine grained and unctuous — 
 often pale coloured, and containing much fine grained siliceous sand. It forms a 
 paste which dries and hardens almost like a brick, so that the roots of plants 
 cannot penetrate it. From tlia expense of cultivating such land, much of it 
 is in wood (Tilgate Foi-est). and some is in poor wet pasture. On the whole 
 of this tract, therefore, there is much room fir imjirovement. The Hastings 
 sands produce a poor brown sandy loam which naturally yields only heath and 
 brush-wood. Much of this soil is in pastwe, but, under proper cultivation, it 
 yielas good crops of all kinds. Where the ruins of tlie Purbeck marls are in- 
 termixed with it, the soil is of a superior quality. 
 
 8°. U])per Oolite. 600 ft. Theupper part of this formation con- 
 
 a Portland Beds, 100. sists of the oolite* limestones and cal- 
 
 b Kimmerido-e Clay, 500. careous sand-stones long worked at 
 
 Portland — the lower of the blue slaty 
 
 ' So named because they consist of small «^^-shaped granules, like the roe of a fish. 
 
IMPERVIOUS SOIL OF THE OXFORD CLAV. 245 
 
 or grejdsh, often calcareous and bitu- 
 minous beds of the Kimmeridge clay. 
 
 Extent. — The Upper Oolite runs north-east along the noithern 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 appears again on the western edge of the green 
 sand in Lincolnshire, and in Yorkshire forms a stripe 5 or 6 miles in breadth, 
 which crosses the country from Helmsley to Filey Bay. In the Isle of Port- 
 land also it is found, and it stretches in a narrow stripe along part of the south 
 coast of Dorset. 
 
 Soil. — The soil from tlie 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 herbage. Its loose and sandy nature 
 makes it also veiy cheap to work, and hence it is chiefly in arable culture. It 
 is easily affected by drought, but in damp seasons it produces abundant crops 
 — especially in tliose pwts where the soil is naturally mixed with the detritus 
 of the over-lying Hastings sand, and of the calcareous Purbeck beds. 
 
 The Kimmeridge clay forms a tough, greyish, unpervious, 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 rests partly on this clay. The relative thicknesses of the Portland 
 beds and the Kimmeridge clay will readily account for the fact of this clay be- 
 ing spread over by far the greatest part of the area occupied by this formation. 
 In Yorkshire, clay of a great thickness is the only member of this series that 
 has hitherto been obsei-ved. On this, as well as on the subjacent Oxford clay, 
 the judicious investinent of capital might produce a much greater annucd breadth 
 of corn. 
 
 ^°. Middle Oolite. 500 Jl. The uppermost bed in tliis foi-mation 
 
 Upper Calcareous Grit, 1 is a sand-stone containing a consider- 
 
 Coral Rag, > 100. able quantity of lime — next is a coral- 
 
 Calcareous Grit, S 1'"^ ILme-stone (coral rag) resting upon 
 
 Oxford Clay, } other sand-stones, which contain much 
 
 Kelloways Rock, > 400. lime in dieir upper and Utile or none in 
 
 Blue Clay, ) their lower beds. Below tliese is an 
 
 enoiTnous deposit of adhesive tenacious 
 dark Vjlue clay, frequently calcareous 
 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 adjoins the upper oolite on the north and west — ac- 
 companying it from the extremity of Dorset, into Wilts, Oxford, Huntingdon, 
 Lincolnshire, and Yorkshire. 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 neaily 20 miles. In Yorkshire it nearly surrounds the upper oolite, and 
 on the noi'them border of the latter formation attains a width from north to 
 south of 6 or 8 miles. 
 
 Son.. — The higher beds of botli the upper and lower calcareous grits produce 
 good land. They cimtain lime intermmgled witli the other materials of the 
 siliceous sand-stone. The upper calcareous grits are no doubt improved by 
 their proximity to the Kimmeride-e clay above them, wliile the lower calcareous 
 
 ¥it is in like manner benefitted by the lime of the super-incumbent coral rag. 
 he under beds of both groups are the more gritty, and fonn a poor, barren, 
 almost wortUess soil, much of which in Yorksliire is still unreclaimed. 
 Upon the hills of the coral rag itself occurs the best pasture which is met with 
 
246 ARABLE LANDS OF THE OOLITE. 
 
 in that pai-t ofthe Nordi Riding of Yorksliire tlirough wluch this formation 
 extends. 
 
 The Oxford clay, which is by far the most unportant member of this forma- 
 tion, and forms the surface over by far tlie largest portion 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, iS'ortliampton, and Lincoln, in which coun- 
 ties, neveriheless, a considerable extent of it is under the plough. In Wilts, 
 Oxford, and Gloucester, it is chiefly in pasuure, and as over these districts it as- 
 sumes the character rather 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 fens of Lincoln, INorthampton, Hunt- 
 ingdon. Cambridge, and TS'oifolk, 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 capable of being converted 
 into a most productive soil. Li Lincolnshire, there are about a million acres 
 of fen, which have their drainage into the Wash, about ."iOjOOO of which are at 
 present UTCclaimable, on account of the state ofthe outlet. 
 
 In the neighbourhood ofthe Kelloways rock the clay becomes more loamy 
 and less difficult to work. 
 
 Botli in Yorkshire and in the southern districts, the Oxford clay is found to 
 favour the growth of the oak, and hence it is often distinguished by the name 
 ofthe oak tree clay. 
 
 10°. Inferior Oolite. 600/1. Thin, impure, rubbly beds of shelly 
 
 a Cornbrasli, SO. lime-stone form the upper part of this 
 
 b Forest Marble, 50. series. These rest upon alternate beds 
 
 c Bradford Clay, 50. of oolitic shelly lime-stone and Band- 
 
 it Bath Oolite, 130. stone, more or less calcareous, having 
 
 e Fuller's Earth, 140. partings of clay ; these again upon beds 
 
 / Inferior Oolite, ^ onn of blue marly clay, immediately under 
 
 g Calcareous Sand, \ which are the thick beds ofthe light-co- 
 
 loured oolite lime-stone of Bath. Be- 
 neath these follow other beds of blue 
 clay, with Fuller's earth, based upon 
 another oolitic lime-stone, which is fol- 
 lowed by slightly calcareous sands. 
 Extent. — This formation commences also at the soutii-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 Jut- 
 land, a large portion of the north-east of Leicester, and then, in a narrow stripe, 
 stretches north through Lincoln, and disappears at the Humber. It appears 
 again in the North Riding of Yorkshu-e, 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, and 
 on the east and south of the Isle of Sky. 
 
 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 — fonning a calca- 
 reous clay, which, when dry or drained, is of good quality. In other places it 
 forms a close adhesive clay, which is naturally almost sterile. The Bath oolite 
 weathers and crumbles readily. The soil upon it is thin, loose, and diy. The 
 rock is full of vertical fissures, which cany off the water and drain its surface. 
 
OLD PASTURES OF THE LIAS. 247 
 
 When free from fi-agments 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 
 worthless, or, as the farmers call it, dead and slecpij. Most of this land, how- 
 ever, is in arable cultivation. The heavy soils, which rest on the clay contain- 
 ing 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 in- 
 ferior quality. In these counties it is principally enclosed, and in arable culture, 
 the sides of the oolitic hills and the clayey portions being in pasture. In York- 
 shire, much of the unproductive moor land of the North Ridmg rests upon this 
 formation. Nearly all the arable land in the county of Sutherland rests on the 
 nan-ow stripe of the lower oolite rocks which occurs on its south-east coast. 
 The debris of these rocks has formed a loamy soil, which, when well limed, 
 produces heavy crops of turnips. 
 
 11°. Lias. 500 (o 1000 ft. This great deposit consists chiefly of 
 
 an accumulation of beds of blue clay, 
 more or less indurated — interrupted in 
 various places by beds of marl, and of 
 blue, more or less earthy, lime-stones, 
 which especially abound in the lowef 
 part of the series. The whole is full of 
 shells, and of the remains of large ex- 
 tinct animals. 
 ExTEKT. — Wherever the lower oolites are to be traced in England, 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 varying 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 no traces of this formation have yet been detected. 
 
 Soil. — Throughout the whole of this formation the soil is a blue clay, more 
 or less sandy, calcareous, and tenacious. Where the lime or sand prevails the 
 soil is more open, and becomes a loam ; where they are less abundant, it is of- 
 ten a cold, blue, unproductive, wet clay. This latter, indeed, may be given as 
 the natural character of the entire formation. Where it rests upon a gravelly 
 or open subsoil, or contains a large quantity of vegetable matter, it may be 
 cultivated to advantage, and it is found especially to produce good herbage. In 
 all situations, it is an expensive soil to work, and hence by far the greater por- 
 tion of it is in old pasture. The celebrateil dairy districts of Somerset, Glou- 
 cester, Warwick, and Leicester, rest for the most part on the lias, as does .-^Iso 
 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 un- 
 disturbed surface of these clay districts, which is peculiarly propitious to the 
 gi-owth of srrass. With skilful drainage and judicious culture, it is capable of 
 producing heavy crops of wheat. 
 
 C. — New Red Sand-stone System. 
 12°. Upper and Lower ) (.„„ - The ujiper and lower red sand-stones 
 
 RedSand-slones. l^^^ J consist of alternate layers of sand, sand- 
 
 stones, and marls sometimes colourless, 
 but generally of a red colour — sprinkled 
 in the upper series with frequent green 
 
 11* 
 
240 FERTILE MARLS OF THE NEW RED SAND-STOHE. 
 
 spots. The lower beds are sometimes 
 full of rolled pebbles. Few of the sand- 
 stones of this formation are sufficiently 
 hard toform building stones — many of 
 the layers consist of loose friable sand, 
 and the marls universally decay and 
 crumble to a fine red powder under the 
 influence of the weather. 
 Extent. — The new red gand-stone extends over a larger portion of the surface 
 of England than euiy other fonnation. It commences at I'orbay, in the south 
 of Devon, runs north-east into Somersetshire ; from Bristol ascends both sides 
 of the Severn, accompanies it into the vale of Gloucester, stretches along tlie 
 base of the Malvern hills, and north of the city of Worcester expands into a 
 
 fently undulating plain, nearly 80 miles m width at its broadest part, compre- 
 ending 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 di- 
 visions. 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 Westmoreland, but re-appears in 
 the eastern corner of this county, runs north-west through Cumberland, form- 
 ing 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, jiroceed- 
 ing from the towns of Derby and Nottingham, runs due north through Notting- 
 ham and the centre of Yorkshire, skirting the outer edge of the lias, and finally 
 disappears in the county of Durham to the nortli of the river Tees. The south- 
 ern portion of this arm has a width of 20 to 30 miles, until it reaches the neigh- 
 bourhood 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 stripe of land a few miles in width, run- 
 ning from Lough Foyle to Lough Neagh, and thence, with slight interruptions, 
 to the south of Belfast. 
 
 Sou.. — These rocks, by their decay, almost always produce a deep red 
 soil. Where the red clay and marl predominate, this soil is a red claj' or 
 clayey loam of the richest quality, capable of producing almost eveiy crop, and 
 remarkable therefore for its fertility. It is chiefly in arable culture, because of 
 the comparative ease with which it is worked, but the meadows are rich, and 
 produce good herbage. Where the rocks are more sandy, and contain few 
 marly bands, the soil produced 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 sand-stone 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 observed, 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 mcreased 
 crops. The same remarks as to its comparative fertility, apply with more or 
 less force to the whole of the large area occupied by tliis formation in our island 
 — wherever the soil has been chiefly formed by tlie decomposition of the rock 
 on which it rests. In some localities (Dumfries-shire) tlie micaccmis, marly 
 rock is dug up, and, after being cnnnbled 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 the shores of 
 the Solway, in Dumfries-shire, a great breadth of this formation is covered with 
 peat. 
 
SOILS OF THE MAGNESIAN LIMESTONE AND COAL MEASURES. 249 
 
 bne-stone. The magnesian lime-stone is gene- 
 
 rally of a yellow, sometimes of a grey, 
 ■ colour. In the upper part it occasion- 
 ally presents itself in thin beds, which 
 cnimble more readily when exposed to 
 the air. Jn some 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 build- 
 ing stone or for mending tlie roads. The 
 quantity of carbonate of magnesia it 
 contains varies from 1 to 45 per cent. 
 It is in the north of England generally 
 traversed by vertical fissiu-es, which ren- 
 der the surface diy, and make water in 
 many places difficult to be attained. 
 Extent. — The magticsmn lime-stoTie stretches in an almost unbroken 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 tlie 
 county of Durham, where it attains a breadth of 8 or 10 miles. 
 
 Soil. — 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 the county of Durham tracts of the poorest land 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 
 dependent 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 vegetation. 
 
 D. — Carboniferous System. 
 
 14°. Coal Measures. 300/(!. Consisting of alternate beds of indu- 
 
 rated bluish-black clay (coal shale), of 
 siliceous sand-stone generally grey in 
 colour and containing imbedded plants, 
 and of coal of various qualities and de- 
 grees 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 Britain, 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 Glamor- 
 gan, and part of Monmouth-shire. In the north of Somerset are the coal mea- 
 sures 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 Notting- 
 ham to Leeds, while on the left is the small 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 
 
250 MOOR-LANDS OF THK MILLSTONE GRIT. 
 
 of the low country of Northumljerland, is covered with these measures — but 
 the largest area covered by these rocks is in that part of the low countiy of 
 fc:cotland 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 gi-cen-stone rocks, 
 yet lying immediately beneath tlie loose superficial matter, over the largest por- 
 tion of this extensive district. They do not occur further north in our island. In 
 Ireland they form a tract of limited extent on the northern borders of tlic county 
 ofMonaghan — cover a much larger area in the south-east in Kilkenny and 
 dueen's countie.s — and towards the mouth of the Shannon, spread on either 
 bank over a large portion of the counties of Clare, Kerry, and Limerick. 
 
 Soil. — The soil produced by the deoradation of the sand-stones and shales 
 of the coal formation is universally of inferior quality. 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. When the clay 
 and sand are mixed a looser soil is produced, wliich, 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 wordiless sand-stone 
 surface, and thousands of acres of the improveable cold clays of the shale beds. 
 These latter soils appear very unpromising, and can only be rendered remune- 
 ratively productive in skilful hands. They present one of those cases in which 
 the active exertions of zealous agriculturists, and the efforts of the friends of 
 agriculture, might be expended with the promise of much benefit to the country. 
 
 15°. Millstone Grit. GOO ft. Tliis formation consists in some lo-' 
 
 calities 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 siliceous, 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 run northward through these three counties. In Scot- 
 land, they have not been observed to lie immediately beneath any part of the sur- 
 face. In the north of Ireland they cover a considerable area, stretching across 
 the county of Leitrim between Sligo and Lough Erne. 
 
 Son,. — 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, accumulations of peat. The shale-beds, like those of the 
 coal-measures, afford a cold, unproductive, yet not unimproveable soil — it is 
 only where lime-stones occur among them that patches of healthy verdure are 
 seen, and fields which are readily susceptible of profitable arable cultur ;. 
 
 It is trae, therefore, of this formation in general, that the high grounds form 
 extensive tracts of moor-land. In the lower districts of countiy over which it 
 extends, the soil generally rests not on the rocks themselves, but on superficial 
 accumulations of transported 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 
 cultivation. 
 
 16°. Mountain ) q„^ ^, In this formation, as its name implies, 
 
 Limestone. \ •' lime-stone is the predominating rock. 
 
 It is genertdly hard, blue, and more or 
 
SWEET PASTURES OF THE MOUNTAIN LIME-STONE. 251 
 
 less full of organic remains. In some 
 localities, it occurs in beds of vast thick- 
 ness — (Derby and Yorkshire) — while 
 in others — (Northumberland) — it is di- 
 vided into numerous layers, with inter- 
 posed sand-stones and beds of shale, and 
 occasional thin seams of coal. 
 Extent. — The greater portion of the counties of Derby and Northumberland 
 are covered by this formation, and from the latter county it stretches along the 
 west of Durham through Yorkshire as far as Preston, in Lancashire — forming 
 the mountains of the well known Pennine chain, wliich tlirow out spurs to the 
 east and west, and thus present on the map an irregular outline and varying 
 breadth of country. In iScoilaiid these rocks cover only a small portion of the 
 county of Berwick, immediately on the Border; but in Ireland, almost the en- 
 tire central part, forming upwards of one-half of the whole island, is occuj^ied 
 by the mountain lime-stone formation. 
 
 Son,. — From the slowness with which this rock decays, many parts of it are 
 quite naked; in others, it is covered with u thin light porous soil of a brown 
 colour, which naturally 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 siiale beds, whicli de- 
 cay more easily, a deeper soil is found, especially in the hollows and towards 
 the bottom of the valleys. I'hese are often stiff and naturally cold, but when 
 well drained and limed )iroducc excellent crops of every kind. In Northumber- 
 land, much of the mountain lime-stone country is still in moor-land, but the ex- 
 cellence of border firming is gradually rescuing one improveable spot after ano- 
 ther from the hitherto unproductive waste. In Y'orkshire and Devonshire also 
 improvements are more or less extensively in progress, though, in all these dis^ 
 tricts, there are large tracts Vvhich can never be re-claimed. 
 
 E. — Oi,D Rkd Sand-stone or Devonian System. 
 
 17°. Old Red Sand- } 500 /o The upper part of this formation con- 
 
 stone. \ 10,000 ft. ^'sts of red sand-stones and conglomer- 
 
 Old Red Conglomerate. a'es (indurated sandy gravel), the mid- 
 
 Com-stone and Marls. die of spotted, red and green, clayey 
 
 ^ Tile-stone. marls, with irregular layers of hard, of- 
 
 ten impure and siliceous lime-stones 
 (cornstones) likewise mottled, and the 
 lowest of thin hard beds of siliceous 
 sand-stones, sometimes calcareous, mot- 
 tled, and splitting readily into thin flags 
 (tile-stones). 
 Extent. — Though occasionally of vast thickness, the old red sand-stons does 
 not occupy a re?-i/ 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 lliis county covers a 
 large area comprehending the greater portion of Brecknock and Heretbrd, and 
 part of Monmouth. A small patch occurs in the Isle of Anglesey, and in the 
 north-eastern corner of Westmoreland — but it docs not a:rain 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 it- 
 self, and stretching to the south-west, forms a considerable tract of country in 
 the counties of Haddington and Lanark. On the north of the great Scottish 
 coal-field it forms a broad band, which runs completely across the island in a 
 south-westeni directioti along the foot of the Grampians, from Stonehaven to 
 
252 RICH WHEAT LANDS OF THE OLD RED SAND-STONE. 
 
 the Firth of Clyde, is to be discovered 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 mountain lime-stone formation of Ireland, and 
 especially in the counties of Tyrone, Fermanagh, and Monaghan. In the 
 north of Scotland, it lines either shore of the Moray Firth, skirts the coast to- 
 wards Caithness, where it covers nearly the whole county, and still further 
 north, forms the entire surface of the Shetland Islands. Along the north-west- 
 ern coast, it also appears in detached patches till we reach the southern ex- 
 tremity of the Isle of Sky. 
 
 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 soutli of Mayo, and 
 round the base of the slate mountains of Tipperary. 
 
 Soil. — The soil on the old red sand-stone admits of very nearly the same 
 variations as on the new red sand-stone fonnation. 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 hungiy soil, " which eats all the manure, and 
 drinks all the water." These upper rocks are sometimes so siliceous as to be 
 almost destitute both of lime and clay — in such cases, tlie soils they form are 
 almost valueless. 
 
 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 Pembroke shires. The soil in every district varies according as the partings 
 of marl are moi'e 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 porous, this land is peculiarly fa- 
 vourable to the growth of fruit trees.* The apple and tlie pear are largely grown 
 in Hereford and the neighbouring counties, long celebrated for the cider and 
 perry they produce. 
 
 The tile-stones reach the surface only on the northern and western edges of 
 this formation in England. In Ayrshire, in Lanarkshire, in Ross-shire, and in 
 Caithness, larger tracts of land rest on these lower beds. In all these districts 
 rich corn lands are produced from the rocks of the middle series. The fertility 
 of Strathmore in Perthshire, and of other vallies upon this formation, is well 
 known — Easter Ross and MuiTay have been called the granary 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 almost incapable of profitable culture. 
 In this latter condition is the moor of Beauly on the Cromarthy 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 veiy fertile district rests also on tlis 
 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 most loamy of these red soils of Hereford afford the finest crops of wheat and hops, 
 and bear the most prolific apple and pear trees, whilst the whole region (cminenlly in the 
 heavier clayey tracts) is renowned for the production of the sturdiest oaks, which so abound 
 as to be styled the " weeds of Herefordshire." Thus, though this recion contains no mines, 
 the composition of its rocks is directly productive of its great agricultural wealth. — Murchu 
 son, Silurian System, I., p. 193. 
 
HUDDT S OILS OF THE LOWER LUDLOW ROCKS. 253 
 
 III. Primary Strata. — In these rocks slates abound, and lime- 
 stones are more rare. Organic remains are also less frequently met 
 with than in the superior rocks. These remains belong all to extinct 
 species, the greater part to extinct genera and families, and are frequent- 
 ly so wholly unlike to existing races that it is often difficult to trace any 
 resemblance between the animals which now live and those whichappear 
 to have inhabited tlie waters of those ancient periods. 
 
 F. — Silurian System. 
 
 18°. Upper Silurian. 3800_/2. The upper Ludlow rocks consist of 
 
 1°. Lui.LOW FORMATION. sand-stones more or less calcareous and 
 
 a Upper Ludlow > argillaceous. These rest upon hard, 
 
 b Aymestry Lime-stone \ 2000 somewhat crystalhne, earthy lime-stones 
 
 c Lower Ludlow S (Aymestry lime-stones.) 1 he lower 
 
 ■' Ludlow rocks are masses of shale more 
 
 2=. Wenlock formation. free from hme and sand than the upper 
 
 I ou^^'^^°"^ \ 1800 beds, and from the mode in which they 
 
 Shale J decay into luud are locally known by 
 
 the name of " mud-stones." 
 
 The Wenlock or Dudley formation 
 consists in the upper part of a great 
 thickness of lime-stone beds often argil- 
 laceous, 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 decay, very much resembling 
 the mud'Stoncs of Ludlow. 
 Extent. — The principal seat of these rocks in our island is in the eastern 
 counties of Wales, where they lie immediately beneath tlie surface over the 
 eastern half of Radnor, and the north of Montgomery. 
 
 Son,. — The prevailing character of the soils upon these formations is derived 
 from the shales and mud-stones — and from the earthy layers of the sand-stones 
 and lime-stones which decay more readily than the purer masses of these rocks. 
 The traveller is immediately struck in passino" from the rich red marls and 
 clays of the old red sand-stone in Hereford, on 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 up- 
 per Ludlow is crossed by many vertical cracks and fissures, and thus, though 
 clayey, the soil which rests upon it is generally dry, and susceptible of cultiva- 
 tion. 
 
 Not so the miiddy soils of the lower Ludlow and Wenlock rocks. They are 
 generally more or less impervious to water, and being sul^ject to the drainage 
 of the upper beds, form cold and comparatively unmanageable tracts. Itisonly 
 where the intermediate lime-stones (/\ymestry and Wenlock lime-stones) come 
 to the surface 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. Ey perfect artificial drainage and copious limeing, 
 the unproductive soils of the lower Ludlow and of the Wenlock shales might be 
 converted into wheat lands more or less rich and fertile. It unfortunately hap- 
 pens, however, that in those districts of North and South Wales, where the 
 dark grey or black "rotc/nj" land of the mud-stones prevails, lime is often so 
 scarce, or has to be brought from so great a distance, as to render this means of 
 improvement almost unattainable. 
 
254 MOUNTAINOUS COUNTRY OF THK SLATE ROCKS. 
 
 19°. Loiver Silurian. 3700 ft. The Caradoc beds consist of thicK 
 
 Caradoc Sand-stones 2500 '^y^''^ ""^ sand-stone of various colours, 
 Llandeilo Flags 1200 '"es'.'nS "pon, and covered by and oc- 
 
 ° casionally interstratined with, thin beds 
 
 of impure lime-stone. The Llandeilo 
 flags which lie beneath them consist of 
 thin calcareous strata, in some locali- 
 ties alternating with sand-stones and 
 shales. 
 Extent. — These rocks fonn patches of land in Shropshire and the north of 
 Montgomeiy — and skirt the southern and eastern edge of Caemiarthen. None 
 of the Sihn-ian rocks have yet been found to extend over any large portion of 
 either Scotland or Ireland. 
 
 Soil. — The Caradoc sand-stone, when free from lime, produces only a 
 naked surface or a barren heath. The Llandeilo flags fonn a fertile and arable 
 soil, as may be seen in the south of Caermarthen, where they are best devel- 
 oped, 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 im- 
 mediately on the appearance of a new rock at the smface. 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 Caradoc sand-stones reach the surface, a wild heath or poor 
 wood-land stretches over the country, until passing over their edges we reach 
 the lime-containing soils of the Llandeilo flags, when fertile arable lands and 
 lofty trees again appear.* 
 
 G. — Cambr;an System. 
 
 20°. Upper S^- Lower Cam- ? These rocks, which are many thou- 
 
 hrian RocliS. S sand yards in thickness, consist chiefly 
 
 of thin slates, often hard and cleaving 
 readily, like roofing slates, occasionally 
 intermingled with sandy and thin lime- 
 stone beds. They contain few organic 
 remains. 
 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 Westmoreland 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. Abbs Head. They form also a narrow stripe 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, s])iead over a consider- 
 able portion of Banflshire. In the south-west of Ireland they attain a great 
 breadth, are narrower 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, Monaglian, Armagh, and Down, — fonn a nanow 
 stripe also along the coast of Antrim as far north as the Giant's Causeway, — 
 and, in the interior of Ireland, re-appear in the mountainous district of Tip- 
 perary. 
 
 Son,. — The predominance of slaty rocks in this formation imparts 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 chmate combine with the fre- 
 quent thinness and poverty of the soil to condemn extensive districts to worth- 
 
 * Sucli a passage from one formation to another is exhibited in tlie diagrams inserted in 
 page 238. 
 
HEATHS AND BOGS ON THE GNEISS ROCKS. 255 
 
 less heath or to widely extended bogs. Yet the slate rocks themselves, especi- 
 ally 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 in the slate districts. More extensive stripes or bands 
 of such productive land occvu- 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 seriesjare extremely fertile, exhibiting a 
 striking contrast with those which are formed from theneiglibouring Serpentine 
 rocks, that extend over a large area immediately north of tlie Lizard (see p. 2(35.) 
 
 Where the clay-slate soils occur, therefore, however cold and stiff' they may 
 be, a favourable climate, drainage, if upcessaiy, and lime, either naturally pre- 
 sent, or artificially adde.l, appear to be the first requisites to insure fertility. 
 
 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 diagram inserted in page 238, the 
 rocks (A) represent the highly inclined, often nearly vertical position, in which 
 the slate rocks are most frequently found. The soil formed from them must, 
 therefore, rest on the thin edges of the beds. Thus it happens in many lo- 
 calities that the rains carry down the soluble parts of the soil and of the manure 
 within the partings of the slates — and hence tlie lands are hungry and unprofit- 
 able to work. 
 
 On the slopes of the clay slate hills of the Cambrian and Silurian systems, 
 flourish the vmeyards of the middle Rhine, the Moselle, and the Ahr. 
 
 H. — Mica-Slate and Gnetss Systems. 
 
 21°. Mica-Slate, Gneiss Rock. The upperof these formations con- 
 
 sists of thin undulating layers of rock, 
 consisting chiefly of quartz and mica, 
 alternating occasionally with green 
 (chlorite) slates, common clay-slates, 
 quartz rock and hard crystalline lime- 
 stones. The gneiss is a hard and 
 solid rock of a similar nature, consist- 
 ing of many thin layers distinctly vi- 
 sible, 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 somevvhat larger in Anglesey ; but in Ireland, nearly the wliole 
 of the counties of Donegal and Londonderry on the north, and a lai-ge portion 
 of Mayo, Connaught, and Galvvay, on the west, are covered by.rocks belonging 
 to the mica slate system. 
 
 Soils. — 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 imperfectly, 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 prevail. That they 
 contain, when perfectly decomposed and mellowed, the materials of a fertile soil, 
 is shown by the richness of many little patches of land, that occur in the shel- 
 tered valleys of the Highlands of Scotland, and by the margins of its many 
 lakes. In general, however, the mica-slatf^ and gneiss country is so elevated 
 that not only does an ungenial climate assist its natural unproductiveness, but 
 the frequent rains and rapid flowing rivers bear down to the bottoms of the val- 
 lies 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. 
 
256 FERTILITY DEPENDENT ON GEOLOGICAL STRUCTURE, 
 
 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 bum down the wood, to strew the ashes over the thin soil, to harrow 
 in the seed — to reap thus one or two harvests 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 succesi^ion of 
 the stratified rocks, as they occur in Great Britain and Ireland — of tlie 
 relative areas over which they severally a[ipear at the surface — and of 
 the kind of soils which they produce by their natural decay. The con- 
 sideration of the facts above stated,* shows how very much the fertility 
 of each district is dependent upon its geological structure — how mucli a 
 previous knowledge of that structure is fitted to enlighten us in regard lo 
 the nature of the soils lo be expected in any district — lo explain anoma- 
 lies also in regard to the unlike agricultural capabiUties of soils appar- 
 ently similar — to indicate to the purchaser where good or better lands 
 are lo be expected, and to the improver, whether the means of amelio- 
 rating his soil by liineing, by marling, or by other judicious admixture, 
 are likely to he within his reach, and in what direction they are lo be 
 sought lor. There still remain some important branches of this subject 
 to which, at the risk of fatiguing you, it will be my duty briefly lo draw 
 your attention in the following lecture. 
 
 * For much of the practical information contained in this section, I have to express my 
 obligations to the following works: — For the extreme southern counties, to De La Bechc'.s 
 Geological Report on Cornwall and Devon ; anJ to a paper by Sir Charles Lemon, Bart., on 
 the Agricutlurai Produce of Cornwall ; — for Wales and the Border counties, to Murchison's 
 Silurian System ; — for ihe Midland counties of England, to Morton on Soils, a work I have 
 in a previous note recommended to the attention of the reader; for Yorkshire, to a paper by 
 Sir J.ihn Johnston, Bart., in Ihe Journal of the Rox/iii Agricultural Socie/y ; — and for Ihe OM 
 Red Sanil stone of the north of Scotland, to the very interesting little work of Mr. Miller on 
 7'h.e Old Red Sandstone. The reader would read the above section with much greater 
 profit if he were previously to possess himself of Phillip's Outline Map of the Geology of the 
 British Islands. 
 
LECTURE XII. 
 
 romposilion of the granitic rocks and of their constituent minerals— Cause and made of 
 itieir degradation— Soils derived from them— Superficial accumulations — Their influence 
 upon the character of the soils — Organic constituents, ultimate chemical constitution, and 
 pliysical properties of soils. 
 
 It has been stated in the preceding Lecture, (§ 6, p. 237), that the rocka 
 which present themselves at the surface of the earth are of two kinds, 
 clistinn;uished by the terras stratified and unstratified. The former 
 crumble away, in general, more rapidly than the latter, and form a va- 
 riety of soils of which tlie agricultural characters and capabilities have 
 been shortly explained. The unstratified or crystalline rocks form soils 
 of so peculiar a character and possessing 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 hitherio so 
 unfruitful an area in our island, as to entitle them to a separate and 
 somewhat detailed consideration. 
 
 § 1. Composition of the Granitic Rocks. 
 
 The name of Granite is given by mineralogists to a rock consisting of 
 a mixture more or less intiinate 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 Syenite. This mineral- 
 ogical distinction is often neglected by the geologist, 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 distinc- 
 tion is often of little consetjuence; in relation to agriculture, however, 
 ihe distinction between a granite and a syenite is of considerable im- 
 poriaiice. 
 
 'J'lie minerals of which tiiese rocks consist are mixed together in very 
 variable proportions. Sometimes the <]uartz predominates, so as to con- 
 stitute two-thirds or three-fourths of the whole rock, sometimes both 
 mica and quartz are present in such sinall qtiantity as to form what is 
 tiien called a felspar rock. The mica rarely exceeds one-sixth of the 
 whole, while the hornblende of the syenites sometimes forms nearly 
 one half of the entire rock. These differences also are often overlooked 
 by tiie geologist — 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 
 suflScient quantity to affect the composhion of the soils to which they 
 give rise. Ainong these, the different varieties of tourmaline are in 
 many places abundant. Thus the schorl 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 
 
25J COMPOSITION OF GRANITK, FELSPAR, AND ALBITE. 
 
 Scilly Isles, as to be considered characteristic of a very large portion of 
 them (Dr. Boase). 
 
 These rocks decay with very different degrees of rapidity — accord- 
 ing to the proportions in which the several minerals are present in 
 them, and to ihe peculiar state of hardness or aggregation in which they 
 happen to occur. Both the mode of their decay, however, and the cir- 
 cumstances 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 minerals of which the rocks consist. 
 This composition, therefore, it will be necessary to exhibit. 
 
 1°. Quartz has already been described (p. 206), 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 it is more frequent- 
 ly disseminated in small particles throughout the rocky mass. It is 
 hard enough to scratch glass. 
 
 2°. Felspar is generally colourless, but is not unfrequently reddish 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, which, in appearance, closely resembles fel- 
 spar, often takes its place in granite rocks, and in chemical constitution 
 differs from it only in containing soda, while the common felspar con- 
 tains potash. These two minerals are readily distinguished 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 concist respectively of — 
 
 
 Felspar. 
 
 Albite. 
 
 Silica . . 
 
 . . 65-21 
 
 69-09 
 
 Alumina . 
 
 . . 18-13 
 
 19-22 
 
 Potash . . , 
 
 . . 16-66 
 
 — 
 
 Soda . . . 
 
 . . — 
 
 11-69 
 
 100-00 100-00 
 
 It is to be observed, however, tliat these minerals do not generally oc- 
 cur in nature in a perfectly pure state — for though they do not essential- 
 ly 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 a kind of intermediate mineral occurs which contains 
 both potash and soda. Such is the case with the felspar of the Siebeni;e- 
 birge, on the right bank of the Rhine (Berthier), and with those con- 
 tained in the lavas of Vesuvius and the adjacent parts of Italy (Abicli). 
 
 in these two minerals the silica is combined with the potasli, soda, 
 and alumina, forming certain compounds already described under the 
 name o[ silicates (p. 207). 
 
 Felspar consists of a silicate of alumina combined with a silicate of 
 jMash. Albite of the same silicate of alumina combined witli a silicate 
 of soda. 
 
 '3'^. Mica generally occurs disseminated through the granite in small 
 shining scales or plates, which, when extracted from the rocki split readi- 
 ly into numerous inconceivably thin layers. It sometimes occurs al^o 
 
COMPOSITION OF SlICA AND HORNBLENDE. 259 
 
 in large masseSj aud is of various colours — white* grey, brown, green^ 
 and black. It is soft and readily cut with a knife. The thin shining 
 particles that occur in many sandstones, and especially between the 
 partings of the beds, and give them what is called a micaceous charac- 
 ter, are only more or less weathered portions of this mineral. 
 
 Mica also consists of silicates, though its constitution is not always 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 com- 
 position of two specimens from different localities. 
 
 Potasti. Magnesian. 
 
 Mica. Mica. 
 
 Silica 46-10 40-00 
 
 Alumina .... 31-60 1-2-67 
 
 Prot-Oxide of Iron . 8-65 19.03 
 
 Magnesia .... — 15-70 
 
 Potash 8-39 5-61 
 
 Oxide of Magnesia . l-40" 0-63 
 
 Fluoric Acid" . . . 1-12 2-10 
 
 Water 1-00 Titanic Acid 1-63 
 
 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 
 iiiifa 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 con- 
 stituent 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 aud f,'lspar by its colour, and from black mica by not split- 
 ting into thin layers, when heated in the flame of a candle. It consists 
 of silicates of alimiiua, lime, maguesia, and oxide of iron, or per cent, 
 of— 
 
 Basalllc 
 Hornblende. 
 
 Silica 42-24 
 
 Alumina .... 13-92 
 
 Lime 12-24 
 
 Magnesia .... 13-74 
 Prot-Oxide of Iron . 14-59 
 Oxide of Manganese 0-33 
 Fluoric Acid ... — 
 
 97-06 99-53 
 
 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 re- 
 markably distinguished from felspar by the total absence of jwtash and 
 soda, and by containing a large proportion of lime and magnesia. From 
 the potash-mica they are distinguished by the same chemical differen- 
 ces, and from the magnesian mica by containing lime to the amount of 
 
260 COMPOSITION OF SCHORL. 
 
 .-jth part of their whole weight. Such differences must materially af- 
 fect the constitution 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 ex- 
 plaining the appearances that present themselves to the philosophical 
 agriculturist. 
 
 4°. Schorl usually occurs in the form of long black needles or prisms 
 disseminated through the granitic rock, and generally (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 silicate of alumi- 
 na in combination with silicates of iron and of soda or magnesia. Two 
 varieties gave by analysis^ 
 
 Schorl Tnurmaline 
 
 from Devonshire. from Sweden. 
 
 Silica, . . . . •. 35-20 37-63 
 
 Alumina, .... 35-50 33-46 
 
 Magnetic Oxide of Iron, 17-86 9-38 
 
 Magnesia, .... 0-70 10-98 
 
 Boracic Acid, . . . 4-11 3-83 
 
 Soda 2-09 Soda & potash, 2-53 
 
 Lime, 0-55 0-25 
 
 Oxide of Manganese, 0-43 — 
 
 96-44 9808 
 
 This mineral, according to these analyses, is characterised by con- 
 taining from ^ to y'n^ of its weight of magnetic oxide of iron,* and some- 
 times Y^ of magnesia. The presence of Boracic acidf is also a remark- 
 able character of this mineral, but as neither the presence of this sub- 
 stance in any soil, nor its effect upon vegetation, have hitherto been ob- 
 served, we can form no opinion in regard to its importance in an agri- 
 cultural point of view. 
 
 § 2. Of the degradation of the Granitic rocks, and of the soils formed 
 from them. 
 
 The granites, in general, are hard and durable rocks, and but Utile af- 
 fected by the weather. The quartz they contain is scarcely acted upon at 
 all by atmospheric agents, and in very many cases the felspar, mica, 
 and hornblende yield with extreme slowness to their degrading power. It 
 is chiefly to the cheynical deco7npositio7i of the felspar that the wearing 
 away of granite rocks is due, and the formation of a soil from their crum- 
 bling substance. 
 
 It has been stated that the felspars consist of a silicate of alumina in 
 combination with silicates of potash or of soda. New these latter sili- 
 cates are slowly decoinposed by the carbonic acid of the air (see p. 207), 
 which combines with the potash and soda, and forms carbonates of these 
 alkalies. These carbonates are very soluble in water, and are, there- 
 
 • This oxide is composed o( the first and second oxides of iron described in p. 210. 
 
 t Boracic acid occurs in combination with soda in the common borax of the shops. It 
 combines with soda, potash, lime, &c., and forms borates. In the schorl it probably exists 
 in such a state of combination. 
 
CLAY FROM THR FELSPAR ROCKS. 261 
 
 fore, 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 slow- 
 ly carried away by the rains in the form of a fine powder (a fine porce- 
 lain 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 com- 
 posed, in great measure, of the fine clay which has resulted from the 
 gradual decomposition of the felspar. 
 
 Tliis clay consists chiefly of the silicate of alumina contained natural- 
 ly in the felspar — it differs little, in short from that which has already 
 been described (p. 161), under the name of pure or pipe clay, which is 
 t(X) stiff and intractable to be readily converted into a prolific soil. 
 
 It will readily be understood how such soils — decomposed felspar soils 
 — must generally contain a considerable quantity of potash from the 
 presence of minute particles of silicate of potash still undecomposed ; 
 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 
 l)een hitherto met with. 
 
 We have seen, however, that hornblende contains from i^th to |thof 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 syeniiic 
 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 great- 
 er number of the elements 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 pre- 
 sence of this lime that the superior fertility of the soils derived from the 
 iiornblende slates of Cornwall, already adverted to (p. 255), is mainly 
 to be ascribed. 
 
 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 contain only a trace of lime, yet the ad- 
 mixture of its constituents with those of the felspar may possibly amelio- 
 rate the quality of a soil formed from the decay of the felspar alone. 
 
 It thus appears that a knowledge of the constitution of the minerals of 
 which the granites are composed, and of the proportions in which these 
 minerals are mixed together in any locality, clearly indicates what the 
 nature of the soils formed from them must be — an indication which per- 
 fectly accords with observation. The same knowledge, also, showing 
 that such soils never have contained, and never can, naturally, include 
 more than a trace of lime, will satisfy the improver, who believes the 
 presence of lime to be almost necessary in a fertile soil, as to the first 
 step to be taken in endeavouring to rescue a granitic soil from a state of 
 nature — will explain 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 ef- 
 
262 GRANITE ROCKS OF GRKAT BRITAIN AND IRELAND. 
 
 fects, — and will encourage Iiini to persevere in a course of treatment 
 which, while sngi^ested by theory, is confirmed also by practice. 
 
 Extent of granitic rocks in Great Britain and Ireland. — In England, 
 the only extensive tracts of granite occur in Cornwall and Devon, pre- 
 senting themselves here and there in isolated patches from the Scilly 
 Isles and the Land's End to Dartmoor in South Devon. In the latter 
 locality, the granite rocks cover an area of about 400 square miles. Pro- 
 reeding northward, various small out-hursts* of granite appear in the 
 Isle of Anglesey, in Westmoreland, and in Cumberland, 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 ex- 
 tensively developed. With the exception, indeed, of the patches of old 
 red sandstone already noticed, nearly the whole of Scotland, north of the 
 (irainpians — and of the western islands, excludingSkye and Mull, con- 
 sists of granitic rocks. 
 
 In Ireland, a range of granite (the Wicklow) mountains runs south by 
 west from Dublin lo near New Ross — the same rock forms a consider- 
 able portion of the mountainous districts in the north-west of Donegal, and 
 in the south of Gahvay — covers a less extensive area in Armagh, and pre- 
 sents itself in the form of an isolated patch in the county of Cavan. 
 
 Soils of the granitic rocks. — From what has been already stated in re- 
 gard to the composition of granite, it is clear from theory that no geiic- 
 rally uniform quality of soil can be expected lo result from its decompo- 
 sition, and this deduction is confirmed by practical observation. Where 
 r]uartz is more abundant, or where the clay is washed out, the soil is 
 poor, hungry, and unfruitful — such, generally, is its character on the 
 more exposed slopes of the hills in the Western Isles, and in the north 
 of Scotland. — [Macdonald's Agricultural Survey of the Hebrides, p. 26.] 
 In the hollows and levels, where natural drainage exists, stiff clay s<nls 
 prevail, which are often cold and unfruitful, but are capable of amelio- 
 ration where the depth of earth is sufficient, by draining and abundant 
 liming or marling. Where there is no natural drainage, vegetable mat- 
 ter accumulates, as we have seen to be the case on the surface of all im- 
 pervious rocks — and bogs are formed. In the north of Scotland, and in 
 Ireland, and in the high lands of Dartmoor (Devon), these are every- 
 where seen in such localities, and it is said that two-thirds of the He- 
 brides 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 diminish 
 in height. Thus Dartmoor is covered only with heath, coarse grass, 
 and peat ; while in the Scilly Isles the growan land produces good crops 
 of wheat, potatoes, barley, and grass ; and the same is observed at 
 Moreton Hampstead, in Devon, where tolerable crops of barley are grown, 
 and potatoes, which are highly esteemed in the Exeter market (De La 
 Beche). No doubt the climate has something to do with these differ- 
 ences ; but the less the elevation, and the consequent washing of the 
 rains, the more of the clay will remain mixed with the siliceous sand ; 
 
 * This expression is in some measure theoretical, and implies — what is the generally re- 
 ceived opinion — fhat Ihe granite rocks were forcerl up from beneatli in a fluid state, like the 
 lavas of existing volcanoes — that tliey, as well as the trap rocks, are, in short, only lavas of 
 a more ancient date (see p. 237). 
 
THE TRAr-UUCKS iiRKKN STOA K. 263 
 
 while in aid of both these ciiuses, a small diileieiu'e in the composition 
 of its constituent minerals, olien not to be dit-iected by the eye, may ma- 
 terially aftect the character of the granitic soils. 
 
 According to Dr. Paris, the presence of much mica deteriorates these 
 soils; while that which is formed at (he edges of the granite, when it 
 comes in contact with the slate rocks, is of a more fertile quality. The 
 latter remark, however, does not universally apply, — es[)ecially where 
 the granite, as at the edges of Dartmoor, contains much schorl, (De La 
 Beciie) — and the presence of mica, in the richest soils of the red marl, 
 would seem to imply that this mineral is lilted materially to promote 
 the fertility of a soil in which the other earthy ingredients are properly 
 adjusted. 
 
 Tlie more elevated and thin granitic soils are said to be fitted for tlie 
 gfowtli of larch ; the lower and deeper soils, which admit of tlie use of 
 ti;e plougii, have been found to yield a three-fold return of corn by the 
 use of lime alone. 
 
 § 4. Of the trap rocks, and tlie soils formed from lliem. 
 
 Of the trap rocks there are several varieties, of which the most impor- 
 tant are distinguished by the names of Greenstone, Basalt, and Ser- 
 pentine. 
 
 The Green-stones consist of a mixture more or less intimate of felspar 
 and hornblende, or of felspar and avgite. They are distinguished from 
 (he granites by the absence of mica and quartz, and by tlie presence of 
 the hornblende or augile, often in equal, and not unfrequently in greater 
 (]«antlty than the felspar. In the granites, the felspar and quartz to- 
 gether generally form upwards of y^ of the whole mass. 
 
 Ausite is a mineral having much resemblance to hornblende, and, 
 like it, occurring of various colours. In the trap rocks it is usually of a 
 <lark green approaching to black. It generally contains much lime and 
 oKide of iron in the state of silicates. The composition of two varieties 
 cx)mpared with that oi basaltic hornblende is as follows : — 
 
 Black Augite AiifiUe from the Basaltic 
 
 frum Swetkn. lava of Vesuvius. HornblPiide. 
 
 Silica 53-36 ,50-90 4-2-24 
 
 Lime 22-19 22-96 12-24 
 
 Magnesia 4-99 14-43 13-74 
 
 Prot-Oxide of Iron . . . 17-38 6-25 14-.59 
 
 Prot-Oxide of Manganese . 0-09 — 033 
 
 Alumina — 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 difference in 
 the nature of the soils produced from their decay, compared 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 augite, 
 magnetic oxide of iron, and zeolite.* It differs in appearance from green- 
 
 • " Wj7/j or without felspar." In addition to aticite, maenelic iron, and zeolite, many ba- 
 salts contain also a considerable portion of certain varieties of felspar, especially of one to 
 which the name oinefthehmha^ been given. 
 
 12 
 
264 EXTENT AND SOIL OF THK TRAP- ROCKS. 
 
 Stone, chiefly by the darkness of its colour, anJ by the minuteness of the 
 particles of which it is composed, which, in general, cannot be distin- 
 guished by the naked eye. 
 
 Zeolite is a generic term applied to a great number of mineral speciea 
 which occur in the basalts, and often intermixed with the green-stone 
 rocks. Tkeij differ from felspar in their greater solubility in acids, atid 
 by generally containing lime, where the latter contains potash or soda. 
 
 it may be stated, indeed, as the most important agricultural distinc- 
 tion, between the granitic and the true* trap-rocks, that the latter abound 
 in lime, while in the former, it is often entirely absent. 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 nine tons may contain a 
 ton of lime. The practical farmer cannot fail to conclude that a soil 
 formed from such rooks must possess very different agricultural capabil- 
 ities from the soils we have already described as being formed from the 
 decomposition of the granites. 
 
 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 distinguishing ingredi- 
 '^nt 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. 
 
 Extent of the trap rocks in the British Isles. — The serpentine rock oc- 
 curs to any extent only in Cornwall, about the Lizard Point, where it 
 covers an area of 50 square miles. The green-stones and basalts are 
 only met with here and there in small patches, until we get so far nortli 
 as the Cheviot Hills, which consist of these and other varieties of trap. 
 It is in the low country of Scotland, however, intermixed with and sur- 
 rounding 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 souili- 
 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 anc! 
 a small part of Londonderry and Armagh. In the most northerly [)ortion 
 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 
 whole of the islands of Mull and of Skye — to the west of the former of 
 which islands lies StafTa with its celebrated basaltic caves. 
 
 Soil of the trap rocks. — The soil of the serpentine rocks at the Lizard 
 is far from fertile, retaining the water and thus forming 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 pecu- 
 liar, 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 
 
 * iSferpen^ine is not generally included among the true trap rocks: it is included amons 
 them here as it often is by geologists, because in many places, as at the Lizard, it occurs 
 along with true green-stone. 
 
FERTILITY OF THE OnHK.N-STO.NK SOILS. 265 
 
 composition of serpentine we might be led to suppose that tlie coinpara- 
 live barrenness of the soils formed from it is due lo the large quaniiiy 
 of magnesia which this mineral coniauis ; and this may, in some cases, 
 be partly the cause. Jt would appear, however, that these soils often 
 coniain very little magnesia, the long action of the rains and of other 
 agents having almost entirely removed it (see p. 209), and yet they still 
 retain their barrenness. 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 
 dejiend upon the effect which this treatment is found to produce. 
 
 Tlie 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 lo the darkness of its colour. 
 
 Ill Cornwall and South Devon, where scattered masses of trap occur, 
 consisting chicily of hornblende and felspar, they "aflbrd the most fertile 
 s<iilsof any in the district when their decomposition has taken place to 
 a sufKcient depth" (De La Beche). Wherever the trap rocks (locally 
 diin-sLo)ics) are observed at the surface, "it is deemed a fortunate cir- 
 cumstance, being a certain indication of the fertility of the incunjbent 
 soils." — [Worgan's View of the Agriculture of Cornwall, p. 10.] The 
 superior fertility of the neighbourhood of Penzance is owing to the pre- 
 sence of these rocks (Dr. Paris), and wiiere their detritus has been mix- 
 ed with that of other rocks — as with the worthless granite soils — it ame- 
 liorates and improves their qualit3^ 
 
 The same general character is exhibited by the trappean soils of other 
 districts of the island. The height of the Cheviot Hills renders the cli- 
 mate in many places unfavourable to arable culture, yet ihey produce 
 the sweetest pasture,* while the low country around them has been 
 largely benefitted by admixture with their crumbling fragments. The 
 whole of that lowland tract of Scotland, over which these rocks extend — 
 comprehending the counties of Ayr, Kenfrew, Lanark, Linlithgow, 
 Fife, and portions of Perth, Sterling, Edinburgh, and Haddington, — ex- 
 hibit the fertile or fertilizing character of the decomposing green-stone. 
 In Cornwall it is dug up as a marl and applied lo the land, and in the 
 neighbourhood of Haddington I have seen a farming tenant {(i leasehold- 
 er) removing twelve inches of traj? 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 borders of Perthshire, and near 
 the more elevated of Ayr and Lanark. 
 
 To the north of Ireland, and to the Western Islands, the above re- 
 marks, with slight modifications, arising from local causes, will also ap- 
 ply. For example, where the surface is flat, and the rock impervious, 
 water will collect and heaths and bogs will be produced, which only 
 
 ' It is a singular fact observed here aniJ 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 pining ill, — Ihey pine away, become indolent, 
 and are unwilling to move. The cure is to drive Ihtni lo a iidirnbounng so !id stone posture, 
 where Ihey bcconie again active, and begin lo thrive. The pining hills on each farm are 
 Weil known, and the tenant has no hesitation in pointing to tlii» and lo that hill as those oa 
 whicti ihe sheep are sure to pine, if kept upon them oniy. 
 
266 THE HTPKRTHENK SOILS OF SKYE. 
 
 draining can remove. They apply also to other countries where trap 
 rocks abouiul — the only fertile traci.s of Abyssinia, for insance, being 
 found in vallies and on mountain slopes, where the soil is composed of 
 the detritus of trappean rocks (Dr. Riippell , 
 
 Yet there are exceptions to this general rule. 
 
 Where the felspar is largely predominant, the soil formed from the 
 rock will partake more or less of the cold and barren character of the 
 stiflTer granitic soils. Such appears to be the case with some of the traps 
 which occur in the border counties of England and Wales (Murchison). 
 
 In the Isle of Skyc, again, a local peculiarity of a different kind ob- 
 tains, the effect of which upon the soil is also to render it poor and un- 
 productive. In that island the singularly beautiful ridge of the Cuchul- 
 len Hills consists of a variety of trap in which the augite so far predomi- 
 nates as to form nearly ti^e whole of the mountain masses, But the 
 augite in this case is a variety to which the name of hyperslhene has 
 been given, and which contains much magnesia and oxide of iron, but 
 scarcely a trace of either lime or alumina. The rock is \erv hard, and 
 decays with extreine slowness; yet however rapid its decay might be, 
 it could never produce a fertile soil. We have seen that the serpentine 
 and granite soils are esseniially deficient in lime, but a liypersihene soil 
 is in want both of lime and of clay. It would be still more difficult, 
 therefore, to render the latter productive — even supposing, as in the case 
 of the serpentine soils, that the magnesia of ihe hvpersihene* were most- 
 ly washed away by the rains. 
 
 Thus we perceive how eacily the study of the composition of tlie dif- 
 ferent varieties of the traf) rocks explains the observed differences in the 
 quality of the soils derived from them. When the irjinerals ihey contain 
 abound in lime, the soils they yield are feriil-e — when those minerals 
 predominate in which lime is wanting, the soils are inferior, sometimes 
 scarcely capable of cidiivation. Again, the granites abound in potash; 
 but except in the syenites they rarely contain lime, and their soils are 
 generally poor. Let tliem be mixed with the ira[) soils, and ihcy are 
 enriched. This would seem fairly and clearly to imply that the fertility 
 of the one is mainly due to the presence of litne, and the barrenness of 
 the other to the absence of this earth. 
 
 On this subject I will only further add, thnt the more modern volcanic 
 lavas which overspread Italy, Sicily, pans of France, Spain, and Ger- 
 inany, are closely related to the trap rocks in their general romi)osition 
 — and the fertility wdiich overspreads thousands of square miles of de- 
 composed lava streams and ejections of volcanic ashes in Italy and Si- 
 cily, is too well known to require any detailed descrij^iion. 
 
 § 5. Of superficial accumulations of foreign materials, and of the means 
 hy which tliey have been transported. 
 Abundant proof, I think, has now been advanced that a close relation 
 
 * The hypersthene of Skye has bpen found to consist of— 
 
 Silica 5135 1 Protoxide of iron 3302 
 
 Lime I 84 | Water 0-50 
 
 Magnesia 11 09 I 
 
 I 9S70 
 The composilion probably varies in different parts of ihe rock, some containing more mag- 
 nesia and less iron than is here represented. 
 
TRANSPORTED MATKRIALS Ot TEN MASK TUE ROCKS. 267 
 
 fyenerally exists between the soil and the rocks on which it rests, and 
 that tlie geological structure of a country, as well as the chemical consti- 
 luiioii of the minerals of which its several rocky masses consist, have a 
 primary and fundamental influence 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 always to be ob- 
 seived — that in whatever district you may liappen to be, you will find 
 the soil taking its general character from the subjacent rocks — and that 
 where the same rocks occur, similar soils are always to be expected. 
 On the contrary, in very many localities the soil is totally different from 
 that which would be produce(l by the degradation or decomposition of 
 the rocks on which it rests. To infer, therefore, or to predict, that on a 
 given spot, where, according to the geological map, red sand-stone for 
 example prevails, a marly or other red sand-stone soil will necessarily 
 be found — or that where the coal measures are observed, poor, ungrate- 
 ful 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 geologi- 
 cal science. 
 
 In such cases as these geology is not at fault. New conditions only 
 have supervened which render the natural relation 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 districts the soil is such as could 
 never have been formed from the subjacent rocks — again places the en- 
 lightened agriculturist in a condition to pronounce generally from what 
 rocks his soils have been derived — generally also what their agricultural 
 capabilities are likely to be, and by what mode of treatment those capa- 
 bilities 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 
 com|)05ition of the subjacent rock. To these districts the rules and ob- 
 servations contained in the preceding sections 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 ftf this apparent difficulty we are now to consider. 
 
 1^. I iiave 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 genefelly remain on the spots 
 where they were formed. But as already shown in the diagrams, in- 
 serted in page 238, 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 ave continually vvashing off the finer par- 
 ticles 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 — [witness the still recent floods in Morayshire.] 
 
2(36 EFFECT OF RAINS, RIVERS, AND TIDF.P. 
 
 Thus tlie spoils of one rocky foiiiuiiio;! tire borne from their r)a!i\e soil, 
 and are strewed over the surface of oiher Kinds of rock of a totally dil- 
 ferent character. The fra^Mieuts of the izraniie, gneiss, and slate rocks 
 of ihe high lands are scattered over the old red sand-stones which lie at 
 a lower level — and those of the blue lime-stone mountains over the mill- 
 stone grits, the coal measures, and the new red sand-stones, which stretch 
 away from their feet. 
 
 2°. But the eU'ecis produced by this natural cause, though they may 
 be judged of in kind, can never be estimated in degree by what we per- 
 ceive in our own temperate climates — in our country of small rivers and 
 gentle rains. How must such ellects exceed in magnitude, in districts 
 ■where, — as in the (xhauts, that separate the level land of the Malabar 
 coast (the Concan) from tlie high table-land of the Deccan, — 120 inches 
 of rain occasionally fall in a single month, and 240 inches or 20 feet, on 
 an average, every year from June to September! And to what vast 
 distances must materials be transported by great rivers, such as the Mis- 
 sissippi, the River of 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 nature 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 cliHson one coast, and carries away their ruins to be deposited, 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? Supjiose 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? 
 
 4°. Again, the sea, in general, carries with it and deposits in its own 
 bosom the finest particles ol 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 strewover the land, form- 
 ing 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 tife Bay of Biscay, and on the coasts of Jiuland, — 
 both exposed to violent sea winds, — ihey occur over much larger area*. 
 Before these winds the light sanils 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 of the cultivators, and burying alike the fertile soils and tlie rocks 
 from which they were originally derived. [In the Landes, the ad- 
 vance of the downs is estimated at 66 to 70 feet every year.] 
 
 You have all read of the fearful sands of the African deserts, and of 
 
KFKtCTS OF VVi;<r>S, AND OF GLACiERS. 260 
 
 iheir destructive march when the burning winJs 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 mure 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 
 sand-stone, which liere and there came to the surface, and which the 
 winds have gradually removed from their original site, and wafted widely 
 over the land. 
 
 Wherever these sand-drifts spread, it will also be clear to you, that 
 tliere may be no necessarj' similarity between the loose materials on 
 the surface and tlie kind of rock over which these materials are strewed. 
 
 b'^. Along with these I shall mention only one other great agent by 
 which loose materials are gradually transported to considerable dis- 
 tances. 
 
 It is observed in elevated countries, where the snow never entirely 
 melts, and where glaciers or sheets of ice hang on the mountain sides, — 
 descending towards the plains as the winter's cold comes on, and agaia 
 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 of conical ridges of sand and gravel 
 (Moraines). These consist of the fragments of the rocky heights, worn 
 and rounded by the friction of the slieets of ice beneath which they 
 have descended from above, and from the edges of which they finally 
 escape into the j)lain. 
 
 These ridges of sand and gravel accumulate till some more sudden 
 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 charac- 
 ter. And where the edges of the glaciers descend to the borders of lakes 
 or seas — as in the Tierra del Fuega — this mud is washed away and 
 widely spread by ihe waters, while the gravel and sand remain nearer 
 their original site ; or, finally, when the ice actually overhangs the wa- 
 ter, huge fragments break oH'now and then — loaded with masses of gra- 
 vel and sand, or even with rocks of large size, — which fragments float 
 away often to great distances and droj) 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, tend to show that nearly all the elevated tracts of 
 country in the temperate regions of Europe and America — in our own 
 island among other localities — have been covered with glaciers at a 
 comparatively recent period, (geologically speaking,) and that these gla- 
 ciers 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 origi- 
 nal site by this agent also — are to be looked for on almost every geolo- 
 gical formation. 
 
 And such the geological observer finds to be in reality the case. 
 
270 DRIFTS IN GREAT BRITAIN. 
 
 § 6. Of the occurrence of sue! i accumulations in, Great Britain, andoj 
 their influejice in moclifying the character of the soil. 
 
 Such accuniulalions, fjr 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 charac- 
 ter of infertility, 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 Norlolk and Sufiolk, and of jiarts of the counties of 
 Essex, Cambridge, Huntingdon, Bedford, Hertford, and Middlesex, are 
 covered with till, (stiff" unstratiRed clay,) containing large stones, (boul- 
 ders,) or with gravels, in which are mixed fragments of rocks of various 
 ages, which must have been brought from great distances, and perhaps 
 from dilTerent directions (Lyell.) So over the great plain of the new 
 red sand-stone, in the centre and west of England — in Lancashire, 
 Cheshire, Shropsliire, Staffordshire, and Worcestershire — drifted gra- 
 vels of various kinds are widely spread. It may indeed be generally 
 remarked, that over the bottoms of all our great vallies, such drifted 
 fragments are commonly diffijsed — 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 de[)Osits of clay, sand, or gra- 
 vel, not unfrequently 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, i>y facts which have come within 
 his own knowledge and observation. 1 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 eleva- 
 tions, as at Gateshead Fell near Newcastle, and Brandon Hill near Dur- 
 ham, where the rocks lie immediately beneath the surface, and are cov- 
 ered by comparatively little transported matter. The magnesian lime- 
 stone, also, in many localities, starts up in the form of round bills or ridges, 
 on which reposes only <a poor thin soil, formed in great measure by the 
 crumbling of the rock itself. Yet, generally speaking, this entire dis- 
 trict 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 clays — on the higher grounds, poor, 
 stifT, 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 
 
 * III some parts of Nortliumberland these n-ap tioulders are still more numerous. In the 
 country which stretches between the north and soutli Tyne, the olJ grass fields are full ol 
 them. A friend of mine informs me that in jilou^hini! outa nhieacre fiel<l on his estate in 
 that district, there were dug out and carried olT no less than 900 toi.s of such rolled stones 
 great and small ! 
 
DUIFT NEAR THE CUT OF DURHAM. 
 
 271 
 
 pounds to many tons in weight. These are generally dug up when they 
 obstruct the plougli, and are sold for mending the roads at about 5s. a 
 ton. 'J'hisclay varies iti depth, from one or two, to fifty or sixty feet. 
 
 "2-. Beneath the clay occurs an accumulation of fine, generally yel- 
 low, 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 abun- 
 dant 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 districts towards the west. Over the magnesian 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 gra- 
 vels which exhibit in some places (Wynyard) an irregular stratification, 
 contain many rounded masses of magnesian lime-stone, and even of 
 new-red sand-stone — ilie evident debris of adjacent rocks long ago bro- 
 ken UJ). 
 
 3°. The undermost layer which rests immediately upon the subjacer 
 rocks consists of a siilF 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 localitier, this clay is wanting, and the sands or gravels rest im- 
 mediately 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 unmanageable 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 mate- 
 rials present themselves in the neighbourhood of the city of Durham. 
 The cross (t) indicates very nearly the site of Durham on the banks of 
 the river Wear. 
 
 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— occa- 
 sionally stratified. It forms the numerous piciuresiiue 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, where it is only a few feet thick. At S, on the southern slope of 
 the escarpment, it some'imes rests immediately on the rock as here re- 
 
 12* 
 
273 
 
 THE SOILS OFTEN CHANGE FROM SAND TO CLAT. 
 
 presented — in which case it is difficult to decide whether it should be con- 
 sidered as the under or the upper clay — though in other spots both sand 
 and clay, or gravel 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 from the 
 nature of the rocks on which they are known to rest. 
 
 Another fact, not unworthy of your attention, is the rapid alternations 
 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 de- 
 posit 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 Crindon cut on the Hartlepool railway: — 
 
 Here 1 is the magnesian lime-stone, not visible ; 2, the under clay, 
 with boulders ; 3, the sand rising in round hills, and here and there 
 piercing to the surface ; and 4, the upper boulder 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 exjilained 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 ilie 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. 
 
 § 7. Hoiv 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 
 
DRIFT MIXKD UP WITH THE DETRITUS OK THE SPOT. 273 
 
 degree of order to be evolved out of this apparent confusion? Are the 
 general indications of agricultural geology (Lecture xi., §8, ) still, in any 
 degree, to be relied upon ? 
 
 They are, and for tlie following, among oilier reasons : 
 
 1°. It is still generally true that where a considerable extent of coun- 
 try rests upon any known rock, the soil in that district derives its usual 
 character from the nature of thai rock. Tlius though large portions of 
 Cheshire ami Lancashire are covered with drift, yet the soil of these 
 counties, taken as a whole, has the general characters of the soils of 
 ihe new-red sand-stone, which in that part of England is so largely de- 
 veloped. 
 
 2°. Wliere the drift overspreads any large area, it is found to become 
 gradually mixed up with the fragments, large and small, of the rocks 
 upon whicli it reposes. Thus in the neighbourhood of Durham, the 
 round hills of sand and gravel with intermingled coal consist in great 
 ])art of the ruins of the sand-stones of tlie country itself — while the 
 claj's, no doubt, are p'lrtly derived from the siiale beds which occur ia- 
 lermingled with the sand-stones of the same coal measures. Hence the 
 soils of tlie northern hall' of this county, in general, 8till partake of the 
 usual qualities of those of the coal measures and mill-stone grit (pp. 
 249 and 250). In the western and higher part of the district they lie 
 juore immediately on the rocks from which they have been derived, 
 while on the eastern half they rest on a mixture of the accumulated 
 ruins of the same rocks, wliich have lx=en transported by natural agents 
 to a greater or less distance from tl'<?ir natural site. 
 
 It is true that there are mix^'< "P with these many portions of other 
 rocks brought from a still ^' eater distance, but these bear but a small 
 proportion'to tlie entire mass, and hence have, generally speaking, but 
 little influence in a'''^""g '^^'^ mineral character of the whole. 
 
 3°. Jl may i'--teed be stated as generally true, that the greater propor- 
 tion of the transported materials which lie upon any spot has been 
 brought ^-'''y 3- comparatively small distance. Tluis the sands and gra- 
 vels "1 i^'e county of Durham — to the west of the magnesian lime- 
 si^ne — consist chiefly of the fragments of the coal measures. East and 
 south of the magnesian lime-stone escarpment (diagram, p. 271), they 
 become mixed with rounded masses of this lime-stone. On the new- 
 red sand-stone of the south-east of tlie 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 legins to appear 
 among them. 
 
 In countries, therefore, where drifted sands and gravels prevail on the 
 surface, lliey generally consist of the fragm.ents of rocks which lie at no 
 great distance — generally towards the higiier ground — the natural ten- 
 dency 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 liiagnesian lime-stone — 
 a red sand-stone soil may partially cover the lias, and so on — the general 
 
274 GKNERAL DKDUCTIO>S OK GEOLOGY STILL TRUE. 
 
 characters and dislinctions of tlie soil peculiar to each rock being still 
 preserved beyond the spaces upon which tliey have been accidentally 
 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 t!ie fine mud of whicb 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 produce what are called alluvial formations or de- 
 posits ; which are generally rich in all the inorganic substances that 
 ])lants require, and hence yield rich returns to ihe agricultural labourer. 
 They are usually, however, distinguished, and their boundaries marked, 
 by the geologist — so that the soils which repose upon them do not con- 
 tradict any of the general deductions he is prepared to draw, in regard to 
 the general agricultural capahilities of a country, from the kind of rocka 
 of which it consists. 
 
 Thus though the occurrence of extensive fields of drift over various 
 parts of almost every country, does throw some further ditBcuity over 
 the researches of the agricultural geologist, and requires from him the 
 appUcation of greater skill and caution before he pronounce whli cer- 
 tainty in regard to the agricultural capabilties of any spot before he visjt 
 it— yet it neither contradicts lUe general deductions of the geologist nor 
 the special conclusions he would be entitled to draw in regard to the 
 ability of any country, when riglitly cultivated, to maintain in comfort 
 a more or less numerous population. Tu-^ political economist may still, 
 by a survey of the geological map of a com^ry, pronounce wiih some 
 confidence to what degree the agricultural richt^ of that country might 
 by industry and skill be brought — and which distnc'ss of an entire conti- 
 nent are fitted by nature to maintain the most abun.\-xnt po|)ulation. 
 The intending emigrant mny still, by the. same means, say "-.ri what new 
 land he is most likely to find a propitious soil on which to e.-.nend his 
 labour — or such mineral resources as will best aid his agricultural puj-. 
 suits; — while a careful study of the geological map of his own country 
 will still enable the skilful and adventurous /anner 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 ajiproved methods of 
 culture. 
 
 Still there are some aids to this kind of knowledge yet wanting. We 
 have geological maps of all our counties, in whicli the boundaries of the 
 several rocky formations are more or less accurately pointed out, and 
 from these maps, as we have seen, much valuable agricultural informa- 
 tion may be fairly deduced. We have also agricultural maps of many 
 counties, compiled with less care, and often with the aid of little geolo- 
 gical knowledge, as that of Durham in Bailey's ' View of the Agricul- 
 ture of the County of Durham,' published in 1810. But agricidture 
 now requires geological maps of her own — which shall exhibit not only 
 the limits of 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 
 
Agricultural maps — accumulatio.ns of pkat. 275 
 
 sure basis on which to rest our opinions in regard to the agricultural ca- 
 pabilities of the several pans of a county in which, though the rocks are 
 the same, the soils may be very different. To the study of these drifted 
 materials, in connection with the action of ancient glaciers (p. 269), the 
 atteniion of geologists is at present much directed, and from their labours 
 agriculture will not fail to reap her share of practical benefit — the geolo- 
 gical survey, also, so ably sui)erintended by Mr. De La Beche, is col- 
 lecting and recording much valuable information in regard to the agri- 
 cultural geology of the southern counties — but it is not unworthy the con- 
 sideration of our leading agricultural societies — whether some portion of 
 their encouragement might not be beneficially directed to the preparation 
 of agricultural maps, which should represent, by different colours, the agri- 
 cultural capabilities of the several parts of each county, based upon a 
 knowledge of the soils and sub-soils of each parish or township, and of 
 the rocks, whether near or remote, from which they have been severally 
 derived. 
 
 Before leaving this subject, T will call your attention to one practi- 
 cal application of this knowledge of the extensive jirevalence of drifts, 
 ^^■hicll is not without its value. Being ac(|uainted with the nature of the 
 rocks in a country, and with its ])hysical geography — that is, which of 
 these rocks form the hills, and which the valleys or plains — we can pre- 
 dict, in general, that t!i» materials of the hills will be strewed to a greater 
 or le.«s distance over the lower grounds, and that these lower soils will 
 thus be inore or less altered in their mineral character. And when the 
 debris of the hills is of a more fertile character than that of tlie 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 debris of 
 the mountain lime-stone, or of a decaj'ed green-stone or a basalt. On 
 the other hand, where the higher rocks are more unfruitful, 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 unpromis- 
 ing surface -drift. Thus the loose sand of Norfolk is fertilized by the 
 subjacent chalk marl; and even sterile heaths (Hon nslow), on which 
 nothing grew before, have, by this means, been made to produce luxu- 
 riant crops of every kind of grain. 
 
 § 8. Of sujKrJicial accumulallons of Peat. 
 
 Of superficial accumulations, that of peat is one which, in tlie Unitei^ 
 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 con- 
 sidered, therefore, would appear so likely to falsify the predictions of the 
 geologist, who should judge of the soils of such a country from informa- 
 tion in regard to the rocks alone on which they rest — from a geological 
 map for example — as the occurrence of these peat bogs. Yet there are 
 certain facts connected witli the formation of peat, which place him in 
 some measure on his guard in reference even to accutnulations of vege- 
 table matter such as these. 
 
 1°. There is a certain ranae of temperature within which alone peat 
 seems cai>able 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; 
 
278 WHERE PEAT IS TO BE EXPECTED. 
 
 while its limit towards the poles appears to be within the 60tli 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 pennit the growth of peat. Hence, 
 though on the plains of Italy no peat is formed, yet, on the higher Ap- 
 penines, it may be here and there met with, among the marshy basins, 
 and on the undrained mountain sides. 
 
 2°. The occurrence of stagnant water is necessary for the production 
 of peat. Hence, on impervious beds of clay, through which the rains 
 and springs can find no outlet, the formation of peat inay be expected. 
 Thus on the Oxford clay repose the fens of Lincoln, Cambridge and 
 Huntingdon (p. 245). On impervious rocks also, peat bogs form for a 
 similar reason. The new-red sand-stone is occasionally thus impervi- 
 ous, and on it, among other examples, repose the Chat moss, the tract of 
 peat, mostly in cultivation, 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 old red sand- 
 stone, the mountain lime-stone, the slate, and the granite rocks, much 
 peat occurs, and it is on these latter formations that the extensive 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 comparatively little impor- 
 tance 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 at- 
 tach to this — that he can, at once, judge both of its source and of its agri- 
 cultural capabilities. Though produced on a given spot, because rocks 
 of a certain character exist there, yet its origin is always the same — its 
 qualities more or less uniform, — the improvement of which 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 amelio- 
 rating substance can be most readily obtained. _ 
 
LECTURE XIII. 
 
 E'.aci chemical constitution of soils— Iheir organic constituents— Analysis of soils — Compo* 
 eition of certain characteristic soils — Physical characters of soils. 
 
 1.x the two preceding lectures we have considered the general constl- 
 tulio;-; and origin of soils, and their relation to the geological structure of 
 the country in which they are found, and to the chemical composition of 
 the roi-ks'on which they rest. We have also discussed some of the 
 causes of those remarkable ditJerences v/hich soils are known to present 
 in their relations to practical agriculture. But a more intimate and pre- 
 cise ac(]uaintance with the chemical constitution of soils is not unfre- 
 quently necessary to a complete understanding of the causes of these dif- 
 ferences — olthe exact effect which its chemical constitution 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 ton much from the chemical 
 analysis of a soil, as if tl\is alone were necessary at once to explain all its 
 qualities, and to indicate a ready method of imparling to it every desir- 
 able ([uality, — while others have as far depreciated their worth, and have 
 pronounced them in all cases to be more curious than usefid. — [Boussin- 
 gault, ' Annal. de Chim. et de Phj's.' Ixvii., p. 9.] The truth here, as 
 on most other subjects, liesinthe middle between these extreme opinions. 
 
 If you have followed me in the views I have endeavoured to press upon 
 3'ou in regard to the necessity of inorganic food to plants — which food 
 can only be derived froin 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 impart most valuable knowledge 
 to the practical man in the form of useful 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 could never give an equiva- 
 lent return. Yet even in this latter case tlie results of analysis will not be 
 without their value to the prudent man, since they will deter him from 
 adding to his soil what he knows it already to contain, and vv'ill set him 
 upon the searclj after some more economical source of those ingredients 
 which are likely to benefit it most. 
 
 It will be proper, therefore, to tumour attention briefly to the conside- 
 ration of the exact chemical constitution of soils. 
 
 § 1. Of the exact nature of the organic constituents of soils, and of the 
 mode of separating them. 
 We have already seen in Lecture XI., p. 229, that all soils contain a 
 greater or less admixture of organic — chiefly vegetable — matter, the 
 total amount of which may be very nearly determined by burning the 
 dried soil at a red heal till all blackness disappears {p. 233). But this 
 vegetable matter consists of several different chemical compounds, the 
 nature and relative weights of which it is occasionally of consequence to 
 be able to determine. 
 
2/8 NATURE OF THK ORGAMC CONSTITUENTS OF SOILS. 
 
 1°. Humus. — The general name of humus is given to llie fine, brown 
 light powder which imparls their richness to vegetable moulds and gar- 
 den soils. It is formed from the gradual decomposition of vegetable 
 matter, exists in all soils, forins 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 leaves an ash when burned which contains lime and magnesia. 
 The sour gives, with water, a brown solution of a more or less sour 
 taste, [or reddens vegetable blues — see page 45.] This variety is 
 less favourable to vegetation than the former, and indicates a want of 
 lime in the soil. The coaly humus gives little colour to water or to a 
 hot solution of carbonate of soda, leaves an asli which contains little 
 lime, occurs generally on the surfiice of very sand\' soils, and is very un- 
 fruitful. It is greatly ameliorated by the addition of lime or wood 
 ashes. 
 
 2°. Hmnic acid. — 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 muri- 
 atic acid (spirits of salt) is added till the liquid has a distinctly sour 
 taste, brown flocks begin to fall. This brown flocky matter is hianic acid. 
 
 3°. Ulmic acid. — If, instead of a solution of carbonate of soda, one 
 of caustic ammonia, (the harlshorn of the shops,) be digested upon the soil 
 or peat by a gentle heat, a more or less dark brown solution is obtained, 
 which, on the addition of muriatic acid, gives brown flocks as before, 
 but which now consists of ulmic acid. 
 
 These two acids combine with lime, magnesia, alumina, and oxide of 
 iron, forming compounds (salts) which are respectively distinguished by 
 the names of humates and ulmaics. They probably both exist, ready 
 formed, in the soil in variable proportions, and in combination with one 
 or more of the earthy substances above mentioned — lime, alumina, &c. 
 They are ])roduced by the decay of vegetable matter in the soil, which 
 decay is materially facilitated by the presence of one or other of these 
 substances, and by lime especially — on the principle that the formation 
 of acid compounds is in all such cases iriuch promoted by the jiresence 
 of a substance wiih which that acid may combine. They jncd impose 
 organic substances to the formation of such acids, and consecjuently to 
 the decomposition by which they are to be produced. These two acids 
 consist respectively of 
 
 Hiimic acid. Ulmic acid. 
 
 Carbon 63 57 
 
 Hydrogen 6 4J 
 
 Oxygen 31 38| 
 
 100 100 
 
 Some writers upon agriculture have supposed that these acids con- 
 tribute very materially to the support of growing ])lants. But Liebig 
 
CRENIC AND AFOCnENIC ACIDS. 279 
 
 has veryproperly olijected to this opinion,* that they are so very sparingly 
 soluble in water that we cannot suppose them to enter directly into the 
 roots — even were all the water they absorb to be saturated with them — 
 in such quantity as to contribute in a great degree to the organic matter 
 contained in almost any crop.f 
 
 We have indeed seen reason to conclude on other grounds, that only a 
 small, ihougli a variable, proportion of the carbon of plants is derived 
 from the soil, yet of this proportion a certain (juantity may enter by the 
 roots in the form of one or other of these acids, or of their earthy com- 
 pounds. They are readily soluble in ammonia; and animal manures 
 which give off this compound in the soil may therefore facilitate their 
 entrance into the roits of those plants wiiich are cultivated by the aid of 
 such manures. They are also soluble in carbonate of potash and car- 
 bonate of soda, which arc contained in wood ashes and in the ash of 
 weeds and of soils which are pared and burned. When these substan- 
 ces, therefore, are applied to tlie land, they may combine with, and, 
 among their other beneficial modes of action, may serve to introduce, 
 these acids in larger rpiantiiy into the plant. 
 
 When exposed to the air, the humates and ulmates contained in the 
 soil unilergo decomposition, give oS" carbonic acid, and are changed into 
 carbonates. The admission of air into the soil facilitates this decompo- 
 sition, which is suii])osed to be continually going forward — and it is in the 
 form of this gas that plants are considered by some to imbibe the largest 
 portion of that carbon for which they are indebted to the soil. 
 
 4°. Crenic and Aprorrenic acids. — When soils are digested or washed 
 with hot water, a quantity of organic matter is not unfrequently dissolved, 
 whicii imparts to the water a brownish yellow colour. When the solu- 
 tion is evaporated to drjmess, there remains l)esides the soluble saline 
 substances of the soil, a variable portion of brown extractive looking 
 matter also, which is a mixture of the two acids here named, with the 
 ulmicand huniic — all in combination with lime, alumina, and other bases. 
 When this residue is dried at 230° F., the two latter acids, and their 
 compounds, become insoluble, while the crenales antl apocrenates, more 
 especially the fl)rmer, remain soluble in water, and may be separated 
 by wasliing with tliis liquid. 
 
 These acids also are formed in the soil during the decay of vegetable 
 inatter. They are distinguished from the two previously described by 
 containing nitrogen asan essential constituent, and by forming compounds 
 with lime, &c., which are, for the inost part, readily soluble in water. 
 Hence they will both prove more nourishing to plants — in virtue of the 
 nitrogen they contain — and in consequence of their solubility, will be able, 
 where they exist, to enter more readily, and in greater abundance, into 
 the roots than either the ulmic or the humic acid. 
 
 Owing to this solubility, also, they are more readily washed out of the 
 soil by the rains, and hence are rarely present in any considerable quan- 
 
 ' Organic Chemistry applied lo Agriculhtre, first edition, pp. 11 and 12. 
 
 t TT!mic acid requires 2500 times its weigtit of water to dissolve it— ulmate of lime 2000 
 times, and ulinate of ahiniind 4200 limes — but all are still le?s soluble after Ihey have been 
 perfectly dried, or exposed to the action of a hard winter's frost. The ulmates of potash, 
 soda, and alumina, are all dissolved in water with considerable ease. 
 
280 OTHKR ORGANIC COMPOUNDS IN THE SOIL. 
 
 tity in specimens of soil which are subn:iittecl to analysis. They are fre- 
 quently, however, met wit!i in springs and in the drainings of the land. 
 Tiiey have even been found in minute quantity in rain-water,* it is pro- 
 bable that tliey ascend into the air in very small proportion with the 
 watery vapour that rises. This exhibits another form, therefore, in 
 which the rains may minister to the growth of plants (see page 36). 
 
 Both acids form insoluble compounds with the [)en)xide of iron — and 
 hence are found in coml)ination with many of tlie ochrey deposits from 
 ferruginous springs, and with the oxide of iron by which so many soils 
 are coloured. The apocreiiic acid has also a pec-uiiar tendency to com- 
 bine with alumina, with which it forms a compound insoluble in water, 
 and in this stale of combination it probably exists not unfrequently, espe- 
 cially in clayey soils. 
 
 When heated with newly slaked quick-lime these acids give off am- 
 monia and carbonic acid. By tbe action of the air, and of lime in the 
 soil, they are probably decoinposed in a similar manner, though with 
 mucli less rapidity. 
 
 5°. 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 fillers 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 gradually deposited on their roof and sides a thick in- 
 crustation of mudesiie of alum'ma.\ 
 
 Besides these acids, it is known that the malic and the acetic (vine- 
 garj are occasionally produced in the soil during the slow decay of vege- 
 table matter of different kinds. It is probable that many other analo- 
 gous compounds are likewise formed — which are more or less soluble in 
 water, and more or less fitted to aid in the nourishment of plants. There 
 is every reason to believe, indeed, that 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 subject is difficult to investigate, be- 
 cause of the obstacles which lie in the way of exactly separating from 
 each other the small quantities of tlie different organic compounds that 
 occur mixed up together in the soil. But it seems quite clear, that while 
 some agricultural chemists have erred in describing the ulmic and hu- 
 mic acids as the immediate source of a large portion of the carbon of 
 plants, others have no less misstated — as I apprehend — the true course 
 of nature, who deny any direct influence to these and other substances 
 of vegetable origin, and limit their use in the soil to the supply of car- 
 bonic acid only, which, on their ultimate decomposition, they arc capa- 
 ble of yielding to the roots. The resources of vegetable life are not so 
 limited; but as the human stomach can, and does, on occasion, convert 
 into nourishment many different compounds of the same elements, — so, 
 no doubt, many of those organic compounds which are produced in the 
 soil, or in fermenting manure during the decay of animal and vegetable 
 
 * Fiirsten zu Salm-Horstmar. Poggend. Annal. liv., p. 254. 
 t Known to mineralogi.sts under the name oi Pigotite. 
 
SEPARATION OF THKSK ORGANIC SUBSTA^CES. 281 
 
 bodies, — when once admitted, in consequence of tbeh solnbility, into tJie 
 circulatino; sj'stein of j)lants, — are converted into portions of their sub- 
 stance, and really do minister to their natural growth. 
 
 Separation of these Organic Conslitucnis. — 1°. When on washing 
 with hot water a soil 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 acid and liumates remain 
 insoluble, while the crenic and ajiocrenic acids are taken uj) by the wa- 
 ter along with the soluble saline matter which the soil may have con- 
 tained. By evaporating this second solution to perfect dryness, weigli- 
 ing the residue, and then heating it to dull redness in the air, tlie loss 
 will indicate something more than the quantity of these acids present in 
 the soil. By burning the dried insoluble matter, also, the quantity of 
 huinic acid present in it may in like manner be determined. 
 
 2°. After being washed with |iure 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 filtered, and then ren- 
 dered sour by muriatic acid, brown flocks fall, which being collected on 
 the filter, perfectly dried and weighed, give the quantity of humic acid 
 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. 
 
 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 hnmus 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 before. 
 
 4°. If there be any mudesite of alumina in the soil, it is also dis- 
 solved by the potasii, but is not thrown down when the solution is ren- 
 dered sour by muriatic acid. The entire weight of organic matter in the 
 soil being therefore determined by burning it in the air, after being 
 perfectly dried, the difference between this weight and the sum of those 
 of the humic acid and insoluble hnmus will be the proportion of the 
 other acids present. Thus, if, by burning in the air, the soil lose 6 per 
 cent., and give 2 per cent, of humic acid, and 2 of insoluble humus, there 
 remain 2 per cent, for other organic substances in the soil. 
 
 In general, it is considered sufficient to ascertain only the wdiole loss 
 by burning, and the quantity taken up by carbonate of soda, the propor- 
 tion of the other substances present being in most cases so small as to be 
 capable of being precisely estimated by great precautions only. 
 
 § 2. On the exact chemical constitution of the earthy part of the soil. 
 
 In reference to the general origin of soils — to their geological rela- 
 tions — and to the simplest mode of classifying them, — I have shown you 
 that the earthy part of nearly all soils consists essentially of sand, clay, 
 and lime (p. 230). But in reference to their chemical 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 
 
282 WHY REFINED ANALYSES ARE iVECESSARY. 
 
 constitution. This will appear by referring to three important princi- 
 ples established in the preceding lectures. 
 
 1°. That the ash of |)lants generally contains a certain sensible pro- 
 portion of ten or twelve different inorganic substances (pp. 216 to 221). 
 
 2°. That ihny can, in general, only derive these substances from ilie 
 soil, which must, therefore, contain them (p. 181). And — 
 
 3°. That the fertility of a soil depends, among other circumstances, 
 upon its ability to supply readily and in sufficient abundance all the in- 
 organic substances which a given crop requires (p. 228.) 
 
 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 present in it or 
 not — much less of explaining to what its peculiar aefects 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 aniinal manures. 
 
 Tlius, 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 much greater than need be added to a soil in which gypsum 
 is almost entirely wanting, in order to produce a remarkable luxuriance 
 in the red clover crop. In 100 grains of the soil, this quantity of gyp- 
 sum amounts only to seven-thousandths of a grain — {y^no^ °^ 0-007 
 grs.) — a proportion which only a very carefully conducted analysis 
 would be able to detect, and yet the delecting of which may alone be able 
 to explain the unlike etfects which are seen to follow the application of 
 gypsum to different soils. 
 
 Again, the phosphoric acid is a no less necessary constituent of the 
 soil than the sulphuric acid contained in gypsum. This acid is gener- 
 ally in combination either with lime, with oxide of iron, or with alu- 
 mina — and, as it is much more difficult even to delect than the sulphuric 
 acid, requires m.ore care and skill to determine its quantity with any 
 degree of accuracy, — and is generally present even in fertile soils in a 
 still smaller proportion — it is obvious that safe and useful conclusions can 
 be drawn only from such analyses as have been made rigorously, accord- 
 ing 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 that further research 
 is unnecessary — as where mere washing with water dissolves out a 
 noxious substance, such as sulphate of iron (green vitriol). Bui 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 accurate experimental results. [As these methods of analysis 
 involve considerable detail, 1 have transferred thenj to the Appendix.— >- 
 See Ajypendix, p. 25.] 
 
EXACT CONSTITUTION OF SOME FERTILE SOILS. 283 
 
 §3. Of the exact chemical constitution of certain soils, and of the results 
 to he deduced from them. 
 
 But the importance of this attention to rigorous analysis will more 
 clearly appear, if I exhibit to you the constitution of a few of the nume- 
 rous soils analyzed by Sprengel, in connection with the agricultural (}uali- 
 ties and capabilities by which they are severally distinguished. 
 
 The following analyses are selected from a much greater number made 
 b}- Sprengel, and embodied in his work on soils, "Die Bodenkunde." 
 
 I. FERTILE SOILS. 
 
 Soils are fertile which contain a sufficient supply of all the mineral 
 constituents which the plants to be grown upon thein are likely to re- 
 quire. 
 
 1°. Pasture. — The following numbers exhibit the constitution of the 
 surface soil in three fertile alluvial districts of Hanover, where the land 
 has 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 0-6-20 
 
 Lime 0-740 0-987 0-720 
 
 Magnesia 0-5-25 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 1-270 0-800 
 
 Insoluble Humus .... 2-995 7-550 4-126 
 
 Organic matters containing Nitrogen 960 2-000 1-220 
 
 Water T 0-0-29 0-100 0-050 
 
 100 100 100 
 
 These soils had all been long in pasture, the second is especially cele- 
 brated for fattening cattle when imder grass. It will be oi)served that in 
 none of them is any of the mineral ingredients wlioUy wanting, though 
 in all the quantity of potash and soda capable of being extracted by 
 water is very small. This is ascribed to the fact of their having been 
 long in pasture, during which the supply of these substances is gradually 
 withdrawn by the roots of the grasses. It is well known how, in our or- 
 dinary soils, grass is often renovated — how the mosses, especially, are de- 
 stroyed — by a dressing of wood ashes, which owe their e(!ect to the alkali 
 llicy contain. In the above soils the gradual decomposition of the sili- 
 cates would continue to supply a certain portion of alkaline matter for aa 
 indefinite period of time. 
 
 You will perceive that the soil which is the most celebrated for \is fat- 
 tening power, is also the richest in alumina, lime, phosphoric acid, sul- 
 phuric acid, and vegetable matter. 
 
284 
 
 THE SOIL OF RICH ARABLE LANDS. 
 
 2°. Arable. — The following table exhibits the constitution of three 
 soils, celebrated for yielding successive crops of corn for a long period 
 without manure. 
 
 1. 
 
 
 2. 
 
 3. 
 
 From Nebtsein, 
 
 From the 
 
 banks of the 
 
 From the polde, 
 
 near Olmutz, 
 
 Ohio, Nortli America. 
 
 of Alt-Arentiergr 
 
 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 
 
 2-2-.^0 
 
 2-336 
 
 8-316 
 
 Oxide of Magnesia . . 1-520 
 
 0-360 
 
 1-200 
 
 0-800 
 
 Lime 0927 
 
 0-564 
 
 0-243 
 
 Garb of 
 Lime 9-403 
 
 Magnesia 1-160 
 
 0-312 
 
 0-310 
 
 Carb.of _ 
 Mag. 10-361 
 
 Potash chiefly combined 
 
 
 
 
 vv'ith Silica .... 0-140 
 
 0-120 I 
 
 • 240 
 
 \ 
 
 5 0-100 
 
 Soda, ditto .... 0-640 
 
 0-025 \ 
 
 } 0-013 
 
 Phosphoric Acid combined 
 
 
 
 
 with Lime and Oxide of 
 
 
 
 
 Iron 0-651 
 
 0-060 
 
 trace 
 
 1-221 
 
 Sulphuric Acid in gypsum 0-011 
 
 0-027 
 
 0-034 
 
 0-009 
 
 Chlorme in common salt. 0-010 
 
 0-036 
 
 trace 
 
 0-003 
 
 Carbonic Acid united to the 
 
 
 
 
 Lime — 
 
 0.080 
 
 — 
 
 — 
 
 Humic Acid .... 0-978 
 
 1.304 
 
 
 
 0-447 
 
 Insoluble Humus . . . 0-540 
 
 1.072 
 
 — 
 
 _ 
 
 Organic substances con- 
 
 
 
 
 taining Nhrogen . 1-108 
 
 1011 
 
 — 
 
 — 
 
 100 
 
 100 
 
 100 
 
 100 
 
 Of these soils, the first had been cropped for 160 years successive!}', 
 without either manure or naked fallow. The second was a ^'irgin soil, 
 celebrated for its fertility. The third had been unmanured for twelve 
 years, during the last nine of which it had been cropped with beans 
 — barley — potatoes — winter barley and red clover — clover — winter bar- 
 ley — wheat — oats — naked flillow. 
 
 Though the above soils dirter con.siderably, as you see, in the propor- 
 tions of some of the constituents, yet they all agree in this — that they are 
 not destitute of any one of the inineralcompounds,wliich plants necessa- 
 rily require in sensible (piantiiy. You will also observe how compara- 
 tively 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- 
 by recall your attention. 
 
 3°. Soils tvhich have a natural source of fertility. — Some soils, which 
 by their constitution are not fitted to exhibit any great degree of fertility, 
 or for a very long period, arc 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 manure, and without apparent dete- 
 rioration. Such is the case with the following soil from near Roihen- 
 
SPRINGS OFTEN ENUICH THE SOIL3. 285 
 
 felde, in Osnabruck, which gives excellent crops, though manured only 
 once in 10 or 12 years. 
 
 Silica and coarse Quartz Sand .... 86*200 
 
 Alumina 2-000 
 
 Oxides of Iron and a little Phosphoric Acid . 2-900 
 
 Oxide of Manganese 0-100 
 
 Carbonate and a little Phosphate of Lime . 4-160 
 
 Carbonate of Magnesia 0-520 
 
 Potash and Soda 0-035 
 
 Phosphoric. Acid 0-020 
 
 Sulphuric Acid 0-021 
 
 Chlorine 0-010 
 
 Humic Acid 0-544 
 
 Insoluble Humus 3-370 
 
 Organic matter containing Nitrogen . . . 0-120 
 
 100 
 
 You will see that, although in this soil all the inorganic substances 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 ex- 
 pecting 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 con- 
 tiins 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 manuring, keep up a constant supply for each suc- 
 ceeding crop. 
 
 This example is deserving of your particular attention, inasmuch as 
 tliere are many soils, in climates such as ours, which are yearly refresh- 
 ed from a siinil.ar source. Few spring waters rise to the surface which 
 are not fitted to impart to the soil some valuable ingredient, and which, if 
 employed for the purposes of irrigation, would not materially benefit 
 these lands especially on which our pasture grasses grow. The same 
 may also be said of the waters which are carried oflf in some places so 
 co])i()uslv by drains. Whether these waters rise from beneath in springs, 
 or, falling in rain, afterwards sink through the soil, they in either case 
 cairy into the brooks and rivers much soluble matter, which the plants 
 would gladly extract from them. On sloping grounds it would be a 
 praiseworthy economy to arrest these waters, and, before they escape, 
 to fMiiploy them in irrigation. 
 
 The fact that nature thus on many spots brings up from beneath, or 
 down t'roni the higher grounds, continual accessions of new soluble mat- 
 ter to the soil, will serve to explain many apparent anomalies, and to ac- 
 count for the continued presence of certain substances in small quantity, 
 although year by year portions of them are carried ofT the land in the 
 crops that are reaped, while no return is made in the shape of artificial 
 manure. It will also in some instances account for the fact that, after a 
 hard cropping, prolonged until the soil has become exhausted, a few 
 years' rest will completely re-invigorate it, and render it fit to yield 
 
286 
 
 I.Ml'ORTANCE OF DKPTH OF SOIL. 
 
 new returns of abtiudaiii 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 circmnstances such as I have now 
 adverted to, this recovery may be effected in a much shorter period 
 of time. 
 
 4°. Importance of depth and unifortnity of soil. — If the surface soil be 
 of a fertile quality, ample returns will be sure from many 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 whicii send their roots far down will 
 be able permanently to flourish in it. This fact is illustrated by the 
 composition of the following soils from the neighbourhood of Bruns- 
 wick : — 
 
 1. 
 
 2. 
 
 Soil. 
 
 Silica and fine Quartz Sand . 94-724 
 
 Ahimina 1"638 
 
 Oxides of Iron . . . . } i-gso 
 Oxides of Manganese . . ^ 
 
 Lime . . ': 1-028 
 
 Magnesia trace 
 
 Potash and Soda 0-077 
 
 Phosphoric Acid 0-024 
 
 Sulphuric Acid 0-010 
 
 Chlorine 0-027 
 
 Humic Acid 0-302 
 
 Insoluble Humus .... 0-210 
 
 Subsoil. 
 
 Subsoil. 
 
 97-340 
 
 90-035 
 
 0-806 
 
 1-976 
 
 5 1-126 
 
 5-815 
 
 I 0075 
 
 0-240 
 
 0-296 
 
 0-022 
 
 0-095 
 
 0-115 
 
 0-112 
 
 0300 
 
 0-015 
 
 0-098 
 
 trace 
 
 1-399 
 
 trace 
 
 trace 
 
 0-135 
 
 — 
 
 — 
 
 — 
 
 100 
 
 100 
 
 100 
 
 The first of these soils produced excellent crops of all deep-rooled 
 plants — lucerne, sainfoin (esparsette), hemp, carrots, poppies, &c. — and 
 with the aid of eypsum, red clover, and leguminous plants (vetches, 
 pea.s, and beans), in great luxuriance. The former of tliese facts is ex- 
 plained by the great .similarity in constitution which exists between tlie 
 surface and the under soils. To deep-rooted plants al.so the magnesia, 
 in which the surface is deficient, is capable of being supplied by the under 
 soil. The effect of the gypsum is accounted for by the almost total ab- 
 sence of sulphuric acid in the 8ub.soiI, but which the application of gyp- 
 sum has introduced into tlie upper soil. 
 
 The second soil was taken from a field in which sainfoin died regu- 
 larly in the second or third year after it was planted. This was naturally 
 attributed to something in the subsoil. And by the analyses 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 supjilies from the subsoil, 
 and it thus gradually poisoned them, so that they died out in two or three 
 years. 
 
EXACT CONSTITUENTS OF SOME UNFRUITFUL SSIIS. 
 
 287 
 
 n. — BARREN OR UNFRUITFUL SOILS. 
 
 Soils are unfruiifiil or aliogeiher barren, either wlien they contain too 
 liltle of one or more of (lie inorganic constituents of plants, or when some 
 subsiiince is preseni in them in such quantity as to become hurtful or 
 poisonous to vegetation. The presence of sulphate of iron in the subsoil 
 just described is an illustration of the latter fact. In what way the defi- 
 ciency of certain substances really docs ailed the agricultural capabilities 
 of the soil will appear from the following analyses: — 
 
 1. 2. 3. 4. 
 
 Moor land soil, Another Sandy Soil on the 
 
 near Aiiiich, soil from soil from Muschel- 
 
 East FriesUnil. the same Wetliiigen kalk, 
 
 neii^fibour- iii Liine- near Miihl- 
 Soil. Subsoil. Iiood. burg- liausen. 
 
 Silica and auartz Sand . . 70-57f)— 05 100 61570 90 000 77 780 
 
 Alumina 1050— 2 5-20 0450 0500 9 490 
 
 Oxides of Iron 0-25-2— 1 -400 0524 2 000 5 800 
 
 Oxide of JVlanganese . . . trace — 0048 ' trace trace 01 05 
 
 Lime do.— 0-33fi 320 001 OStiC 
 
 Magnesia 0012— 125 0-130 trace 0-7-28 
 
 Potash trace — 072 trace do. trace 
 
 Soda do. — 0-1 SO do. do. do. 
 
 Phosphoric Acid .... do. 0034 do. do. 0-003 
 
 Sulphuric Acid do. 0020 do. do. trace 
 
 Carbonic Acid — — — — 0-200 
 
 Chlorine trace — 015 trace trace trace 
 
 HumicAcid 11-910- — 11-470 0200 0732 
 
 Insoluble Bumus .... 16-200— — 2iJ 530 1-299 0-200 
 
 Water — — — — 4096 
 
 100 100 100 100 100 
 
 Eacli of these analyses is deserving of attention. 
 
 1^. That the barrenness of the moor-land soils (1 and 2) is to be at- 
 tributed to their deficiency in tiie numerous substances of which they 
 contain only traces, may almost be said to be ]iroved by the fact — one- 
 long recognised and acknowledged on many of our own moor-lands and 
 peaty soils — that when dressed with a coveting of the subsoil they be- 
 come capable of successful cultivation. The analysis of tiie sub.soil ia 
 the second column shows that it contains rt/Z those mineral constituents in 
 U'hick the soil itself is deficient — and to the eftect of these, therefore, the 
 improvement produced ujKtn the soil by bringing it to the surface is alto- 
 gether to be attributed. 
 
 2°. The sandy soil, No. 3, is evidently barren for the same reason as 
 the moorland soils, 1 and 2. The soil No. 4 rests on lime-stone, and 
 was mixed with 7 percent, of lime-stotie gravel, and contains a great 
 number of the substances which plants retpiire — but its unfruiifulness is 
 to be ascribed to the want of ])otash 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 soils to which 1 recently directed your attention 
 (p. 284) was one from Belgium, in which the pro])ortion of organic 
 matter was less than half a per cent, of its whole weight. In the above 
 table, on tlje other hand, we have two nearly barren soils, containing 
 
 IS 
 
288 WHAT RENDERS A SOIL FERTILE. 
 
 each 11 per cent, of humic acid, besides a much larger proportion of in- 
 soliil)!e organic matter. It is obvious, therefore, that the fertility of a 
 soil is not dependent upon its containing this or that proportion of vege- 
 table matter, either in a soluble or an insoluble form. It is certainly 
 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 present, and yet the soils, like those above-mentioned, 
 may remain barren. Where soils become fertile apparently by the 
 long accumulation of such vegetable matter in the soil, it is not vierely 
 because of the increase of purely organic substances, such as the humic 
 and ulmic acids, but, because, as I have already had occasion to mention 
 to you, the decaying vegetable matter which produces them contains 
 also, and yields to the soil, a considerable 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 pro- 
 portioned in the soil by nature— -or ihey may be artificially mixed with 
 it, and then liiis use of the organic matter may be dispensed with. It is 
 of more importance to bear this in mind, because not only vegetable 
 physiologists, but some zealous chemists also, have laid great stress upon 
 the quantity of soluble and insoluble organic mailer contained in a soil, 
 and have been led to consider it as a safe index of the relative fertility 
 of difftjrent 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 — have ever been of 
 very great use in the advancement of certain knowledge. Their argu- 
 ments, whether well or ill founded, lead to discussion, to further investi- 
 gation, 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 of ve- 
 getable matter in a soluble state — all these extreme opinions are recon- 
 ciled, and their partial truths recognised, in one general principle, that 
 a soil to be fertile must contain all the substances which the plant we de- 
 sire 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 CAl'ABLE OF IMPROVEMENT BT 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 effbcts occasionally pcoduced by 
 their mixture with the land. The following analyses will place this 
 matter in a clearer light : — 
 
COMPOSITION OF UEAniLy n'mOVEABLK SOILS. 
 
 289 
 
 
 1. 
 
 2. 
 
 3. 
 
 4. 
 
 
 Soil near Pa- 
 
 Near Uraken- 
 
 Near Ganders- 
 
 Near 
 
 
 dingbiittel, on 
 
 burjr, on the 
 
 heim, in 
 
 Bruns- 
 
 
 the Weser. 
 
 Weser. 
 
 Brunswick. 
 
 wick. 
 
 Silica and Quarlz Sand 
 
 . 93-720 
 
 92014 
 
 90-221 
 
 95-698 
 
 Alumina . 
 
 . 1-740 
 
 2-652 
 
 2-106 
 
 0-504 
 
 Oxide of Iron . 
 
 . 2-060 
 
 3-192 
 
 3-951 
 
 2-496 
 
 Oxide of Manganese . 
 
 . 0-3-30 
 
 0-480 
 
 0-960 
 
 trace 
 
 Lime 
 
 . 0-1-21 
 
 0-243 
 
 0-539 
 
 0-038 
 
 Magnesia . 
 
 . 0-700 
 
 0-700 
 
 0-730 
 
 0-147 
 
 Potash (chiefly in combina- 
 
 
 
 
 tion with Silica) 
 
 . 062 
 
 0-125 
 
 0-066 I 
 
 0090 
 
 Soda (do.) 
 
 . 0-109 
 
 0026 
 
 0-010 s 
 
 Phosphoric Acid 
 
 . 0-103 
 
 078 
 
 0-367 
 
 0-164 
 
 Sulphuric Acid 
 
 . 0-005 
 
 trace 
 
 trace 
 
 0-007 
 
 Chlorine in common Salt 
 
 . 0-050 
 
 trace 
 
 0-010 
 
 0010 
 
 Humic Acid 
 
 . 0-890 
 
 0-340 
 
 0-900 
 
 0-6-26 
 
 Other Organic matter 
 
 . 0-120 
 
 0-150 
 
 0-140 
 
 0-220 
 
 100 
 
 100 
 
 100 
 
 100 
 
 The first of these soils produces naturally heauliful red clover — the 
 second produces very had red clover. On comparing the constitution of 
 the two soils, we see the second to be deficient in sulphuric acid and 
 chlorine. A dressing of gypsum and common salt would supply these 
 deficiencies, and render it ca|)able of producing this kind of clover. The 
 third soil is remarkable for growing luxuriant crops of pulse, when ma- 
 nured with gypsum. The almost total absence of sulphuric acid ex- 
 plains this effect. The fourth soil was greatly improved by soap-boiler's 
 ash, which supplied it with lime, magnesia, manganese, and other sub- 
 stances. 
 
 I need not further multiply examples to show you how much real 
 knowledge is to be derived from a rigidly accurate analysis, not only in 
 regard to the agricultural capabilities of a soil, but also it) regard to the 
 natural and necessary food of plants, and to the manner in which 
 mineral manures act in jiromoling and increasing their growth. The 
 illustrations I have already presented will satisfy you — 
 
 1°. That a fertile soil must contain all the inorganic constituents which 
 the plant requires, and none that are likely to do it an injury. 
 
 2°. That if the addition of a given manure to the soil render it more 
 fertile — it is because the soil was defective in one or more of those sub- 
 stances which the manure contained. 
 
 3°. That if a given a])plication to the land fail to iinprove it — of gyp- 
 sum, of bone-dust, of common salt, 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 
 
 clav soils are best for wheat, and sandy soils, such as that of Nor- 
 
 ' folk, for barley, is not to be considered as anything like a law of nature, 
 
 selling aside the clay land for the special growth of wheat, and denying 
 
290 FHYSICAL PROPtliTIES OF S01i,9. 
 
 to the sanrlj' soils the power of yielding abundant crops ofihis itind of 
 grain. Almost every district can presenl cxamjilcs 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 ahundanily, pro- 
 vided it contain an ample supply of all that the crop we wish to raise 
 may happen to require. But, in practice, soils which do not contain all 
 liiese substances plentifully, arc yet found to difler in their jjower of 
 yielding plentiful returns to the husbandman. Such diH'erences arise 
 from the climate, the exposure, the colour, the fineness of the particles, 
 the lightness or porosity of the soil — from the quantity of moisture it 13 
 capable of retaining, or from some other of its numerous physical pro- 
 perties. 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 
 more fundamental importance than we can now attach to them. Crome 
 and Schiibler regarded the fertility of a soil as entirely dependent upon 
 its physical properties. Influenced by this opinion, the former published 
 the results of an examination of numerous soils in the Prussian provin- 
 ces, which are now jiossessed of no scientific interest; because they 
 merely indicate the amount of clay, sand, and vegetable matter whicli 
 these soils severally contained.* The latter completed a very elaborate 
 examination of the physical properties of soils, which is very useful and 
 instructive ;f but the defective nature of which, in accounting for their 
 agricultural capabilities, became evident to the author himself, when the 
 more correct and scientific views of Sprengel, illustrated in the preced- 
 ing section, afterwards became known to him. In giving, therefore, 
 their due weight to the jihysical properties, we must not forget that in 
 nature they are subordinate to the chemical constitution of soils. Plants 
 may gvovf upon a soil, whatever its physical condition — if all the food 
 they require be within their reach — while, however favourable the phy- 
 sical condition may be, nothing can vegetate in a healthy manner, if the 
 soil be deficient in some necessary kind of food, or contain what is de- 
 structive to vegetable life. 
 
 Of the physical properties of soils the most important are their den- 
 sity, 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. MF.CHAMCAL RELATIONS OK SOILS. 
 
 1°. The density and absolute tceight 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 reference to the absolute weight 
 of equal bulks. 
 
 ' Recorded in his Grundsdtze der Agricutlur Chemie. 
 t I^T Boden und aein verhaltmss zu den Gewachsen. 
 
ABSOLUTE WEIGHT AND FJRM^ESS OF SOIM. 291 
 
 Thus a cubic foot of dry 
 
 Siliceous or Calcareous Sand — weighs about . 110 lbs. 
 
 Half Sand and half Clay 95 
 
 Of common arable Land, from . . . . 80 to 90 
 Of pure agricultural Clay (page 231) ... 75 
 Of garden Mould, richer in vegetable matter . 70 
 Of a peaty Soil, from 30 to 50 
 
 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 thporetical point of view it is of conse- 
 quence to vegetation, chiefly in so far as, according to the experiments 
 of Schiibler, 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. 
 
 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 exceed- 
 ingly fine particles both of sand and clay — while in others, coarse sand, 
 stones and gravels, largely predominate. There can be no doubt that the 
 state of the soil in this respect has a material influence upon its produc- 
 tive character, and consequently upon its money value, since the labours 
 of the husbandman in lands of a stiffer and more coherent nature are 
 chiefly expended in bringing them into this more favourable powdery con- 
 dition. In the description and examinatioa of a soil, therefore, this pro- 
 perty 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 informa- 
 tion. 
 
 In some parts of the country, the farmer diligently gathers th^j 
 stones off" his land, while in others the practice is condemned as hurtful 
 to the arable crops. The latter fact is explained by supposing that 
 these stones in winter aflTord 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. 
 
 3°. 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 dry — while pure 
 clays be-corae hard and very difficult to pulverize. In proportion to the 
 quantity of sand witli which tlie latter are mixed, do their tenacity and 
 hardness diminish. The ditficulty of reducing clays to a fine jiowder in 
 the open field, or of bringing them into a good tilth, may be overcome, 
 therefore, by an admixture of sand or gravel, but there are few localities 
 wliere the expense of such an operation does not present an insur- 
 mountable obstacle. Thorough draining, however, subsoil ploughing, 
 and careful tillage, will gradually bring the most refractory soils of this 
 character into a condition in which they can be more perfectly and more 
 economically worked. 
 
m^ 
 
 ADIIKSION OF SOILS TO THE PLOUGH. 
 
 Soils also adhere to the plough in clitTerent degrees, and, therefore, pre- 
 sent a more or less powerful obstruction to ils passage. All soils ])resenl 
 a greater resistance when icpJ. than when dry, and all considerably more 
 to a wooden than to an iron ploush. A sandy soil when wet offers a re- 
 sistance to the passage of agricultural implements, equal to about 4 lbs. 
 to the square foot of the surface which passes through it — a fertile vege- 
 table soil or rich garden mould about 6 lbs., and a clay from 8 to 25 lbs. 
 to the square foot. These differences will naturally form no inconsider- 
 able items in the calculations of the intelligent farmer when he estimates 
 the cost of working, and the consequent rent he can afford to pay for this 
 or that soil, 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 gradually drink in watery 
 vapour from the atmosphere, and will thus increase in weight. In hot 
 climates and in dry seasons this property 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 ex- 
 haled. » 
 
 Different soils possess this property in unequal degrees. During a 
 night of 12 hours, and when the air is moist, according to Schiibler, 1000 
 lbs. of a perfectly dry 
 
 Clay Loam ... 25 lbs. 
 Pure Agricultural Clay 27 
 
 Quartz Sand will gain lbs. 
 Calcareous Sand. . 2 
 Loamy Soil . . 21 
 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 perfectly dry, 1000 
 lbs. of a 
 
 Very fertile Soil from East Lothian gained in an hour 18 lbs. 
 
 Very fertile Soil from Somersetshire 16 
 
 Soil worth 45s. per acre from Mersea, in Essex . . 13 
 
 Sandy Soil worth 28s., from Essex 11 
 
 Coarse Sand worth only 15s 8 
 
 Soil of Bagshot Heath 3* 
 
 Fertile soils, therefore, possess this property in a very considerable de- 
 gree, and, though we cannot, by deterujining 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 
 constitution of a soil — yet among arable, sandy, and loamy lands, it cer- 
 tainly 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 disap- 
 pear, but if the dropping be continued, the pores of the earth will by de- 
 
 • Sir H. Davy's Works, vol. vii., p. 326. 
 
RELATIONS OF SOILS TO WATKB. 293 
 
 grees 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 possession 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 106 lbs. of dry soil, 
 water will begin to drop — if it be a 
 
 Quartz Sand, when it has absorbed 25 lbs. 
 
 Calcareous Sand 29 
 
 Loamy Soil 40 
 
 English Chalk 45— J. 
 
 Clay Loam 50 
 
 Pure Clay 70 
 
 but a dry peaty soil will absorb a very much larger proportion (Schii- 
 bler), before it suffers any to escape. Useful arable soils are found to be 
 capable of thus containing from 40 to 70percent. of their weight of water. 
 If the quantity be less than this, the soils are said to be best adapted for 
 pine plantations, — 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 rather over- 
 abound, asim[)le 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 operation 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 con- 
 taining 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 saturated with mois- 
 ture, watery vapour is constantly rising from the surface 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 of his 
 fields with much greater rapidity than in others. Generally speaking, 
 those soils which are capable of arresting and containing the largest por- 
 tion of the rain that falls, retain it also with the greatest obstinacy, 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 explains, and sliows the correctness of, the well-known distinctions 
 of warm and cold soils, but exhibits another strong argument in favour 
 of a perfect drainage of stiff soils and of such as contain a large proportion 
 of decaj'ing 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 subsoil — is gradually sucked 
 up to the surface. Where water is present in excess, this capillary action, 
 as it is called, keeps the soil -always inoist and cold. 
 
294 CAPILLARY POWER OF THE SOIL. 
 
 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 vege- 
 tahle matter, are open and porous, it probably ascends most freely, while 
 stiff clays will transmit it wiih less rapidity. No precise experiments, 
 however, have yet been made upon this subject, chiefly, I believe, be- 
 cause this property of the soil has not hitherto been considered of such 
 importance as it really is, 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 specimens of 
 soil which are submitted to analysis generally contain very little saline 
 matter, and yet ihat in a crop reaped from the same soil a very consider- 
 able proportion exists. This I liave attributed to the action of the 
 rains which dissolve out tlie 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 
 lime 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 evaporate from the surface, 
 leaving their saline matter behind them. And as this ascent and eva- 
 poration go on as long as the dry weather continues, the saline matter 
 accumulates about the roots of the plants so as to put within their reach 
 an ample supply of every soluble substance which is not really defective 
 in the soil. I believe that in sandy soils, and generally in all light soils, 
 of which the particles are very fine, this capillary action is of great im- 
 portance, and is intimately connected witli their power of producing 
 remunerating crops. They absorb the falling rains with great rapidity, 
 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, 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 ca- 
 pillary 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 intermission. 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), whicii 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 India, in Egypt, and in many 
 parts of Africa and America. In hot, protracted summers tliey 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 unknown. 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 
 
ITS IMPORTANCE TO VEGETATION. 295 
 
 wide plains, in the hollows 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 (urao) extracted from the soil in the 
 South American State of Colombia. 
 
 5°. Contraction of the soil on drying. — Some soils in dry weather di- 
 minish 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 vvhen 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 occa- 
 sionally injurious to young roots from the pressure upon the tender fibres 
 to which it must give rise, while in light and sandy soils the compres- 
 sion of the routs is nearly uniform in all weathers, and they are undis- 
 turbed in their natural tendency to throw out off-shoots in every direction. 
 Hence another good quality of liglil soils, and a less obvious benefit 
 which must necessarily result from rendering soils less tenacious by ad- 
 mixture or otherwise. 
 
 III. RELATIONS OF THE SOIL TO THE ATMOSPHERE. 
 
 Pcnver 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 llie growth of the plant, I have 
 already sufficiently insisted upon. It is of conseciuence, therefore, that 
 this oxygen should gain access to every part of the soil, and tiujs to all 
 the toots of the plant. This access can be facilitated by artificially 
 working the land, and thus rendering it more porous. But some soils, 
 in whatever state they may be m this res])ect, 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 con- 
 stitution of each. If the clay contain iron or manganese in the state of 
 first or prot-fi\\des, 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 princi- 
 pally 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 foriued 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 conjec- 
 ture, 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, however, 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. The fall of rains, or the de- 
 scent of dew, therefore, will favour this absorption in dry seasons, and ii 
 will also be greatest in those soils which have the power of most readily 
 
 13* 
 
^^ POWER OF SOILS TO RETAIN HEAT. 
 
 extracting watery vapour from the air during the absence of the sun. 
 Hence the influence of the dews and of gentle showers on the progress 
 of vegetation, is not limited to the mere su[)ply 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 considera- 
 ble 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 action of the sun's rays, and the 
 length of time during which they are able lo retain this heat. 
 
 1°. Power of absorbing heat. — It is an important fact, in reference to 
 the growth of plants, that during sunshine, when the sun's rays beat upon 
 it, the earth acquires a much higher temperature than the surrounding 
 air- This temperature very often amounts 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 degrees only, how- 
 ever (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 lime of harvest, this property of the soil possesses a considerable eco- 
 nomical value. In other parts of the world, where sunshine abounds, 
 it becomes of less importance. 
 
 Ever}' one will understand that the above differences are obser\'ed 
 among such soils only as are exposed to the same sun under the same 
 circumstances. Where the exposure or aspect of the 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 vegetation than many others less 
 favourably situated, though darker in colour and more free from super- 
 fluous inoisture. 
 
 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 Schiib- 
 ler, 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 influence upon growing crops, inasmuch as, after the sun 
 goes down, the sandy soil will be three hours in cooling, while the clava 
 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, (he greater proportion of dew deposited on 
 the clays and vegetable moulds m*v not more tbail compensate to iht.' 
 
POWER OF MODIFYING THE PHYSICAL CHARACTERS. 297 
 
 parched soil — for the less prolonged duration of the elevated tempera- 
 ture derived from the action of the sun's rays. It is also to be remem- 
 bered, that vegetable soils at least absorb the sun's heat more rapidly 
 than the lighter coloured saudy soils, and thus the plants which grow in 
 the former, which is sooner heated, may in reality be exposed to tho 
 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, ap- 
 pears to be, that by top-dressing with charcoal, with soot, or with dark- 
 coloured composts, we may render it more capable of rapidly absorbing 
 the sun's heat, and by admixture with sand, more capable of retaining 
 the heat which it has thus obtained. 
 
 Sucn 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 re- 
 duce to aj^fine powder. He can plough, subsoil, 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 lay heavy matter 
 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 com- 
 posts, 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 done all which mere mechanical 
 skill can suggest, the soil may still disappoint his hopes, and refuse to 
 yield him remunerating 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." — 
 [Bodenkunde, p. 203.] It has all the advantages, in short, which 
 physical condition and climate can give it, and yet it is unproductive. 
 And why ? Because, answers chemical analysis, it is destitute of cer- 
 tain mineral consti'uenls which plants require for their daily food. The 
 physical properties, therefore, are only accessory to the chemical consti- 
 tution. They bring into favourable circumstances, and thus give free 
 scope to the operation, upon the seeds and roots of plants, of those che- 
 mical substances which Nature 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 without its 
 use, even in a theoretical point of view. It shows both llie 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 oi 
 the husbandman are undertaken, and why they are so necessary. Plants 
 
29S GENERAL FUNCTIONS OF THE SOIL. 
 
 must be firmly fixed, tnerefore tlie soil must have a certain consistency, 
 — their roots must find a ready jiassage in every direction ; therefore the 
 soils must be somewliat loose and open. Except for lliese purposes, we 
 see I'Kle immediate use for the sand and alumina whicli form so much 
 ai .i\e substance of soils — till we come to study their physical properties. 
 The siliceous sand is insoluble, and tiie alumina exists in plants in very 
 minute quantity only, while during the progress of natural vegetation, 
 llie proportion of vegetable matter in the soil actually increases. Tiie 
 immediate agency, therefore, of these substances is not chemical but 
 physical. 
 
 The alumina of the clays is of immediate use in absorbing and retain- 
 ing both water and air for the use of tlie roots — while tiie vegetable mat- 
 ter is advantageous in reference to the same ends, as well as to the power 
 of absorbing cjuickly and largely the warmth of the sun's rays. The 
 sol!, in short, in reference to vegetation, jierforms the four following dis- 
 tinct and separate, but eacli of them important and necessary, func- 
 tions : — 
 
 1°. It upholds and sustains tiie plant, affording it a sure and safe an- 
 chorage. 
 
 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 plaul both organic and inorgairc 
 food as its wants require ; and 
 
 4°. It is a workshop in wiiich, by the aid of air and moisture, cliemi 
 cal changes are continually going on ; by which changes these several 
 kinds of food are ])repared for admission into tlie 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 oilier of these functions. To the most important 
 of these operations — the methods adopted by the practical farmer for 
 improving the soil — it is my intention, in tlie following division of these 
 Lectures, briefly to direct your attention. 
 
LECTURES 
 
 ox THE 
 
 APPLICATIONS OF CHEMISTRY AND GEOLOGY 
 
 TO 
 
 AGRICULTURE. 
 
 ON THE IMPROVEMENT OF THE SOIL BY ME- 
 CHANICAL AND CHEMICAL MEANS. 
 
LECTURE XIV. 
 
 The physical qualities and chemical constitution of a soil may be changed by art. — Nature 
 of the plants dependent apon ihal of the soil on which they grow. — Mechanical methods 
 of improving the soil. — Effects produced by draining. — Theory of springs. — Effect of 
 ploiigliing, subsoiling, deep ploughing atid trenching. — Artificial improvement by mixing 
 with clay, sand, or marl. 
 
 The fact.s detailed in the preceding lecture may be considered as af- 
 fording sufficient proof that the ability of the farmer to grow this or that 
 crop upon his land, is very much restrained by its natural character and 
 constituiion. Each soil establislies upon itself — so to speak — a vegeta- 
 tion suited to its own nature, one that requires most abundantly those 
 substances which actually abound in the soil — and the art of man can- 
 not long change this natural connection 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 ]3hysical qualities and its chemical constitution, and thi'S can fit 
 it f()r growing other races of plants than those it naturally bears — or, if he 
 choose, the saiiie races in greater abundance, and with increased luxuri- 
 ance. It is, in fact, in the production of such changes, that nearly all the 
 labour and practical skill of the husbandman — apart from local peculiari- 
 ties of climate, &c. — is constantly expended. For the attainment of 
 this end he drains, ploughs, subsoil- ploughs, and otherwise works his 
 land. For this end he clan's, samls, marls, and manures it. By these 
 and similar operations the land is so changed as to become both able and 
 willing to nourish and ripen those pecuhar plants which the agriculturist 
 wishes to riiise. On this practical department of the art of culture, 
 t.he principles explained and illustrated in the preceding parts of these 
 li'Ctures, throw much light. They not only explain the reason why cer- 
 tain practices always succeed in the hands of the intelligent farmer, but 
 why others also occasionally and inevitably fail — they tell hiin which 
 practices of his neighbours he ouglit 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 
 lie liines and tnanures it, he alters its chemical constitution. These two 
 classes of operations, therefore, are perfectly distinct. Where a soil con- 
 tains all that the crops we desire to grow are likely to require, mere me- 
 chanical operations may suffice to render it fertile — but where one or 
 more of the inorganic constituents of plants are wanting, draining may 
 prepare the land to benefit by further operations, but it will not be alone 
 sufficient to remove its comparative sterility. I shall, therefore, con- 
 sider in succession these two classes of practical operations : — 
 
 1°. Mechanical inethods of improving the soil, including draining, 
 ploughing, mixing -with clay, sand, &c. 
 
304 PLANTS PECULIAR TO CKRTAKN SOILS. 
 
 2°. Chemical methods, including liineing, marling, and the application 
 of vegetable, animal, and mineral manures. 
 
 To satisfy you fully, however, in regard to the absolute necessity 
 for such changes, if we would render the land fit to produce any given 
 crop, let me illustrate, by a tew brief examples, the intimate 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 ujyon 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 men. 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. 
 
 But in a state of nature, we find special differences among the spon- 
 taneous produce of the soil, which are more or less readily traceable to 
 its chemical constitution 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 sands are inclosed 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 bnrning 
 them for soda (barilla), when wholesome 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 arcnarius (upright sealyme-grass) often, in our 
 latitudes, occupies a conspicuous place. On the downs of North Jut- 
 land, 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 herb- 
 age often scanty and void of nourishment. With the presence of marl 
 in such soils, tlie natural growth of leguminous plants increases. The 
 colt's-foot also, and ihe butter-bur, not only grow naturally where the 
 subsoil is marly, but infest it sometimes 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 vallies of Switzerland these plants are said to 
 indicate to the natives where they may successfully dig for marl, (Prize 
 Essays of the Highland Society, I., p. 134). On calcareous soils, again, 
 or such as abound in lime, the quicken or couch-grass is seldom seen as 
 a weed, {Sprengel, Bodenkunde, p. 201), while the poppy, the vetch, and 
 the darnel abound. 
 
 4°. So peaty soils, when laid down to grass, slowly select for them- 
 selves a peculiar tribe of grasses, especially suited to their own nature, 
 among which the holcus lanatus (meadow soft-grass) is remarkably 
 abundant. Alter their constitution by heavy limeing, and they produce 
 
NATUnAL ROTATION AMONG FOREST TREES. 305 
 
 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, and stiffen them with 
 composts, and they will be couverted 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 I hat have their rise in many trap rocks, the water-cress appears 
 and accompanies the running waters, sometimes 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 serpentine soils of Cornwall, and the red broom rape 
 {orobanche rubra, Hooker's Flora Scotica), only on decayed traps in 
 Scotland and Ireland. 
 
 These facts all point to the same natural law, that where other circum- 
 stances of climate, moisture, &c., are equal, the natural vegetation — that 
 which grows best on a given spot — is entirely dependent upon the chemical 
 constitution of the soil. 
 
 But both the soil and the vegetation it willingly nourishes, 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 lich, light, vegetable mould, 
 bearing a thick sward of nourishing grasses, almost totally different from 
 those which naturally 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 natural forests that are known to have long covered 
 extensive tracts in various countries of Europe. 
 
 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 several centuries old, are seen 
 to be gradually giving way to the beech, while otliers of oak and beech 
 are yielding to the encroacliments of the pine. In the Palatinate, the 
 Scotch fir (pinus sylvestris) is also succeeding to the oak. In the Jura, 
 and in the Tyrol, the beech and the pine are seen mutually to replace 
 each other — 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 arc seen surrounded by the luxuriant foliage of other races [Le Ba- 
 ron de Mortemart de Boisse, Voyage dans les Landes, p. 189.] These 
 facts not only show how much the vegetable tribes are dependent upon 
 the chemical nature of tlie soil — they indicate, likewise, the existence 
 of slow natural changes in the constitution of the soil, which lead neces- 
 sarily to a change of vegetation also. 
 
 We can ourselves, in the case of ancient forests, effect such changes. 
 When in the United States a forest of oak or maple is cut down, one of 
 pine springs up in its place ; while on the site of a pine forest, oak and 
 other broad-leaved trees speedily appear. 
 
 But if the full time for such changes has not come, the new vegeta- 
 tion may be overtaken, and smothered by the original tribes. Thus, 
 
306 OF DRAINING, AND ITS EFFKCTS. 
 
 when the pine forests of Sweden are biirnetl down, a young growth of 
 birch succeeds, but after a time the pines again appear and usurp their 
 former dominion. The soil remains, still, 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 nature. 
 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 adapt it to our 
 crop. And, even when we have once prepared it to yield abundant re- 
 turns of a particular kind, the changes we have produced can only be 
 more or less of a temporary nature. Our care and attention must still 
 be bestowed upon it, that it may be enabled to resist the slow natural 
 causes of alteration, by which it is gradually unfitted to nourish those 
 vegetable tribes which it appears now to delight in maintaining 
 
 Let us now turn our attention, therefore, to the methods by which 
 these beneficial changes are to be effected and maintained. 
 
 § 2. Of draining, 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 con- 
 ceded ; 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 capillary 
 action or by the force of springs — and thus not only preserves the sur- 
 face soil from undue moisture, but also frees the subsoil from the linger- 
 ing presence of those noxious substances, whicli in undrained land so fre- 
 quently lodge in it and impair the growth of deep-roofed 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 thus, while filtering through, not only does the 
 rain-wafer impart to the soil those substances useful to vegetaiion, which, 
 as we liave seen, [see Lecture II., p. 37, Lecture I V^., p. G9, and Lecture 
 VIII., p. 159,] 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 substances as naturally 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. Wlien once thoroughly effected, it consfi- 
 tutes a most important permanent improvement, and one which can be 
 fully produced by no other available means. It will be permanent, 
 however, only so long as the drains are kept in good condition. The 
 
SECURES A DRY SEED-TIME AND A.\ EARLY HARVEST. 307 
 
 same openness of the soil which enables the rains to wash out those so- 
 luble noxious substances, which have been long collecting, permits them 
 to carry oflf 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°. Tliis constant descent of water through the soil causes a similar 
 constant descent of fresh air through its pores, I'rom 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 contained 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 is in fact 
 sucked in after the water, as tlie latter gradually passes down to the 
 drains. Thus, where a good drainage exists, not only is the land re- 
 freshed by every shower that falls — not only does it derive from the 
 rains those important 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 cultivated crops. 
 
 5°. But other consequences of great practical importance follow 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 dis- 
 appear. They crumble more freely, offer less resistance to the plough, 
 and are in consequence more easily and economically worked. These 
 are practical benefits, equivalent to a change of soil, which only the 
 farmer of stubborn clays can adequately appreciate. 
 
 6°. With the permanent state of moisture, the coldness of many soils 
 also rapidly disappears. The backwardness of the crops in spring, and 
 the lateness of the harvests in autumn, are less fre(juently complained 
 of — for the drainage in many localities produces effects which are equi- 
 valent to a change of climate, " In consequence of the drainage which 
 has taken place in the parish of Peterhead, in Aberdeenshire, during the 
 last 20 years, the crops arrive at maturity ten or fourteen days sooner 
 than they formerly did ;"* and the same is true to a still greater extent 
 in many other localities. 
 
 7°. On stiff clay lands, well adapted for wheat, wet weather in au- 
 tumn not unfrequenlly retards the sowing of winter corn — in undrained 
 lands, 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 dominion of the uncertain seasons.f To the skilful and iu- 
 
 * Mr. Gray, in the Prizp. Essays of the Highland and Agricultural Soriett/,ll, p. 171. 
 This opinion was given in 1830, since which time many other extensive improvements have 
 been made in tliat part oTihe island. 
 
 1 " Formerly," says Mr. Wilson, of Cumledge, in his account of the drainage of a farm 
 in Berwickshire, " this part of the farm was so wet, that — though better adapted for wheat 
 than any other crop — the seaaon for sowing was frequently lost, and after an expensive fak 
 
308 IS EQUIVALENT TO A DEEFEMNG OF THE SOIL. 
 
 telligent farmer, who applies every available means to the successful 
 prosecution of his art, the promise even in our age and country is sure 
 — "that seed-time and harvest shall never fail." 
 
 6°. But on lauds of every kind tliis removal of the superfluous water 
 is productive of anotiier practical benefit. In its consequences it is equi- 
 valent to an actual deepening of the soil. 
 
 When land on which the surface water is in the habit of resting, be- 
 comes dry enough to admit (he labours of the husbandman, it is still 
 found to be wet beneath, and the waters, even in drj' seasons, not unfre- 
 quently remain where the roots of the crops would otherwise be inclined 
 to come. Or, if the surface soil permit a ready passage to the rains, and 
 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 tlie 
 surface soil only. But remove the waters, and the soil becomes dry to 
 a greater depth. The air penetrates and dilTuses itself wherever the 
 waters have been. Tiie roots now freely and safely descend into the 
 almost virgin soil beneath. And not only have they a larger space 
 through which to send 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 tlie time accumulating in the subsoil, into which the 
 roots of cultivated plants could rarely with safety descend. It is not 
 wonderful then that the economical eftecis of draining should be Ibund 
 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 repa}' the 
 entire cost of thorough-draining in two or three j'cars. 
 
 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 available 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 that of wheat or clover, do not usually send down their roots so far, 
 will yet, where tlie subsoil is sound and dry, extend their fibres for three 
 or more feet in depth, in quest of more abundant nourishment. 
 
 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 naturally make their way 
 into them in search of water, — but ihey also increase the value and per- 
 manent fertility of the land, by increasing 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, hut will also be followed by the greatest number of eccnotni- 
 cal advantages. 
 
 lowing and liDieins, it was sown wiih oats in spring, of which il 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." — Priae Essays of the Highland 
 and Agricultural Society, I., p. 243. 
 
Ei'FECT OF A GENERAL DRAINAGE OF THE SOIL. SOD 
 
 9°. Nor (lo the immediate and practical benefits of draining end with 
 the atfaimnent of ihese beneficial results. It is not till the land is ren- 
 dered dry thiit tbe skilful and enterprising farmer has a fair field on 
 which to expend his exertions. In wet soils, boiies, wood-aslies, 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-instructed agriculturist can bring all the resources, 
 as well (jf modern science as of old experience, to bear upon them, with 
 a fair chance of success. The disappointments which the holder of un- 
 drained lands so often meets with, he will less frequently experience. 
 An adequate return will generally be obtained for his expenditure in 
 manuring and otherwise improving his soil, and he will thus be encour- 
 aged to proceed in devoting his capital to the permanent amelioration of 
 his farm — not less for his own than for his landlord's benefit. 
 
 V^iowed in this light, draining is only the first of a long series of im- 
 provements, or rather it is a necessary preparative to the numerous im- 
 provements of which the soil of islands is susceptible — which improve- 
 ments it would be a waste of money to attempt, until an efficient system 
 of drainage is established. And when we consider how great a national 
 benefit tliis mere preparatory 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 pnmioi.e it. It has been calculated that the drain- 
 age of those lands only, which are at present in ai'able culture (10 mil- 
 lions 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 pre- 
 sent consumption* oi all kinds of grain — so that were ii possible to effect 
 at once this general drainage, a large superfluity of corn would 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 not suffi- 
 cient to meet the expense, f- and such calculations as the above are use- 
 ful, inairdy, in stimulating the exertions of those who have capital to 
 spare, or such an excess of income as can permit them to invest an an- 
 nual portion perraanentlyf in the soil. 
 
 10"^. He who drains and thus improves his own land, confers a 
 benefit upon his neighbours also. In the vicinity of wet and boggy 
 
 * 65 millions ofqnartfrs. See an excellent paper on this subject in the Quarterly AgrU 
 eulturiO Journal, xii , p. 505, by Mr. Dmlgeon, of Spyelaw, in Roxburghshire, a county in 
 which thi; practical benefits of draining have been extensively experienced, and are therefore 
 well tinrterslood. 
 
 t To drain 25 millions of acres, at JEG an acre, would cost 150 millions sterling, a sum equal, 
 probal;ly, lo the wliole capital at present invested m farming the land. 
 
 J Uy an efliiMent drain.ige the soil is permanently benefiltrd, hut it is not so clear that the 
 niiiney it co-its is pe)?«anfn//i/ !?/ rested or buried in the "soil. If the cost be repaid by the 
 incr^-ase of proiiuce, in three years, the money is not invested, it is only lent for this period 
 to ihe soil. •■ I drain so many acres every year," said the holder of a large Berwickshire 
 farm lo me, "and I find myself always repaid by the end of the third season. If I have 
 spare capital enough, therefore, lo go on for three years, I can gradually drain any extent of 
 land, by the repeated use of the same sum of money." 
 
310 RKNDERS A COUNTRY MORE SALUBRIOUS. 
 
 lands ihe hopes of tlie industrious farmer are often disappointed. Mists 
 are frequent and rains more abundant on the edges of the moor, and 
 mill-dews retard the maturity, and often seriously injure the crops. Of 
 undrained land, in general, the same is true to a less extent, and tlie 
 presence of one unimproved property in the centre of an enterprising 
 district, may long withhold from the adjoining farms that full measure 
 of benefit which the money and skill expended upon them would in 
 other circumstances have immediately 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. 
 
 11°. 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 gene- 
 ral health of the people, and to the number and kind of the diseases to 
 which they are observed to be exposed. 
 
 I may quote in illustration of this fact the interesting observations of 
 Dr. Wilson on the comparative state of health of the labouring popula- 
 tion in the district of Kelso during the last two periods often years. In 
 his excellent paper on this subject, in the Quarterly Journal of Agricul- 
 ture, (volume xii., p. 317), he has shown that fever and ague, which 
 formed nearly one-half of all the diseases of the population during the 
 former ten years, have almost wholly disappeared during the latter ten, 
 in consequence of the general extension of an efficient drainage through- 
 out the country ; while, at the same time, the fatality of disease, or the 
 comparative number of deatlis from every hundred cases of serious ail- 
 ment, has diminished in proportion of 4*6 to 2'59. Such beneficial re- 
 sults, though not immediately sought for by the practical farmer, yet 
 are the inevitable consecjuence of his successful exertions. Apart, there- 
 fore, 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 im- 
 provements which at once render our homes more salubrious and our 
 fields more fruitful." - 
 
 The practical benefits of draining, therefore, may be stated generally 
 as follows : — 
 
 A. It is equivalent not only to a change of soil, but also to a change 
 of climate, both in reference to the growth of plants and to the health 
 of the population. 
 
 B. It is equivalent also to a deepening of the soil, both by removing 
 the water and by allowing those noxious ingredients to be washed out 
 
BENEFITS POROUS SOILS. — ORIGIN OF MOOR-LAND. 311 
 
 of the subsoil which had previously prevented the roots from descend- 
 inp. 
 
 C It is a necessary preparation to the many other means of improve- 
 ment which may be applied to the land. 
 
 You will now be able to perceive in what way it is possible that 
 even light and sandy soils, or such as lie on a sloping surface, may be 
 greatly benefitted by draining. AVbere 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 subsoil, 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 tlie bottom of the drains, and the atmos- 
 pheric air will accompany or follow them. 
 
 Tlie same remarks apply to lands which possess so great a natural 
 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 impregnated with iron the evil is greatly 
 augmented, and from such a cause alone a more or less perfect barren- 
 ness not unfrequently ensues. To bring such lands by degrees to a 
 sound and healthy state, a mere outlet beneath is often alone sufficient. 
 
 It is to this lingering of unwholesome waters beneath, that the origin 
 of many of our moor-lands, es]:)ecially on liigher grounds, is in a great 
 measure to be attributed. A calcareous or a ferruginous spring sends up 
 its waters into the subsoil. Tiie slow access of air from above, or it 
 may be the escape of air from water itself, causes a more or less ochrey 
 deposit,* which adheres to 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-land 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 in- 
 clined 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-land pavement, hut such an improvement, 
 unless preceded by a skilful drainage, can only be temporary. The 
 same natural process will again begin, and the same raeult 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 
 
 ' If (he water contain s«/pAa/e of iron, tlie air from above will impart to its iron an ad- 
 ditional quantity of oxygen, and cause a portion of it to fall in the state of peroxide. If the 
 iron or lime be present in the state of fcicarbonate, the escape of carbonic acid from the 
 water will cause a deposit of carbonate of iron or of lime. Any of these deposits will 
 cement the earthy or stony particles together. Iron, however, is sometimes held in solu- 
 tion by an organic acid (crent'c), which becomes insoluble, and falls along with the iron 
 when the latter has absorbed more oxygen from the atmosphere. 
 
312 THEORY OF SPRINGS. 
 
 contain will be liable, in periods of heavy rain, lo be more or less com- 
 pletely washed out and carried olf by the water that trickles through 
 them. While, therefore, the establishment of drains on all soils may 
 adapt and ])repare them for further improvements, and may make them 
 more grateful for every labour or attention (hat may be bestowed upon 
 ihem — yet after drainTiire they must be more liberally dealt with than 
 before, if the increased fertility they at first exhibit is (o be permanently 
 maintained or increased. 
 
 § 3. Of the theory of Springs. 
 
 In the <Teneral drainage of the land a double object is sought fo be at- 
 tained. In very rainy districts, tlie first wish of the farmer is to carry 
 off the surface water from his fields — but where less rain falls, that 
 whicli ascends from beneath in springs, attracts at least an equal share 
 of ihe husbandman's regard. In draining, with a view to the removal 
 of this latter source of superfluous moisture, a knowledge of the true 
 tlieory of springs, as indicated by an examination of certain geological 
 phenomena, is of the greatest jiossible service lo the practical man, in 
 pointing out the sources from which the water that injures his land pro- 
 ceeds, as well as the lines along which it may be most efficiently and 
 most economically carried ofT. 
 
 1°. The rain which fails on the surface of an extensive tract of country 
 partly escapes into the rivers, and partly sinks into the earth. This 
 latter portion descends through the covering of soil and other loose ma- 
 terials till it reaches the rocks on which they rest. U these rocks are 
 jiorous, like many sand-stones, or are traversed by cracks and vertical 
 fissures, as many sand-stones and lime-stones are, it descends through 
 tliem also till it reaches a bed, such as one of indurated clay, so close and 
 compact as to resist its further passage. J3y this impervious bed the wa- 
 ter is arrested, 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 surface of an 
 unilulating country, in which the subjacent rocks (1, 2, 3, 4) are covered 
 by a considerable thickness of loose materials, the rain which falls from 
 A to B will sink more or less rapidly to the bed (1), and, if this be im- 
 permeable to water, will rest there, or will slowly drain otf in the di- 
 rection of B and C along the inclined surface of the rock. But if (!) 
 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 readies the 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 
 downwards towards C, it is enabled either to sink among the deeper 
 rocks or to make its escape again to the surface. 
 
 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, or, like 
 the one represented from B to E, through a great number of beds, the 
 
WATER IS ARRKSTED BY IMPKRVIOUS BEDS. 
 
 313 
 
 water that falls on ihe surface will readily find a passage downwards to 
 a considerable depifi, and to the same cracks the water that lodges 
 among the unfissured rocks from D to E will also gradually make its way. 
 
 The practical effects of these several conditions on the drainage of a 
 country are very obviou-i. If the stratum (1) be impervious to water, 
 the surface from A to B may be full of water, and may urgently de- 
 mand the introiiuclion of drains, wliereas if (1) and (2) be porous, the 
 surface water will gradually sink, and the ap[)arent necessity for artifi- 
 cial drainage will become iriuch 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 the sinking of wells — and, as 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 niagnesian lime-stone rocks in 
 some i)arts of the county of Durham — and such is the consequent scar- 
 city 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". T)Ut water often finds its way to greater depths without passing 
 through the siiperior strata, and even where they are absolutely iinpervi- 
 «us to the rains that fall upon them. Thus along the country from A to 
 B, and especially towards A, the surface soil rests upon the upi)er edges 
 
 of the strata. Suppose now the beds I, 2, 3, to be impervious to water, 
 the rain that falls wherever these rocks lie imuiediately beneath the sur- 
 face will either remain stagnant, or v/ill How ortby some natural drain- 
 age. Thus from the highest point C in the above diagram, the water 
 will descend on either hand towards a and b. At h it may remain stag- 
 nant, Ibr it cannot descend through the bed (2), whicli forms the bottom 
 of the valley, and the same is true of the hollow <■, in which other por- 
 tions of the water will rest. All this tract of country, therefore, will be 
 more or less cold, wet, and consequently unproductive. But let the bed 
 (4), the edge (or outcrop) of which forms the surface at a, be porous or 
 |jermeable, tlien the water which falls upon that spot or wliich descends 
 from the higher grounds about C and A, will readily sink and drain oflf", 
 descending from a towards d along the inclined bed till it finds an outlet 
 in the latter direction. 
 
 Thus it may readily happen that a naturally dry and fertile valley, as 
 at a, may exist at no great distance from others, b and c, which are 
 marshy and insalubrious, and in which artificial drainage alone can de- 
 velope the agricullural capabilities of the soil. It appears also that, 
 though in any district the rocks which lie immediaiely beneath the sur- 
 face may contain no water, and may allow none to pass through them, 
 yet that other beds, perhajis at a great depth beneath, may contain much.. 
 It is, in fact, this accumulation of water beneath impervious beds that 
 14 
 
314 
 
 SPRINGS PRODUCKD BY VALLET9 AND StlPS. 
 
 gives rise to so many natural springs, and enables us by artificial wells 
 to bring water to the surface — often where ihe land would otherwise be 
 wholly uninhabitable. 
 
 3°. T1h}s in undulating countries, wliere Inll-sides frequently pre- 
 sent themselves, or valleys are scooped out among the rocks, as in the 
 following wood-cur, the water that has fallen over the high grounds to- 
 
 wards A, and has entered as above described, or has sunk down to tlie 
 several strata 1, 2, 3, 6cc., will find a ready outlet along the elope of the 
 valley, and will give rise to springs at a, b, c, or d, according as the wa- 
 ter has lodged in the one or the other of these beds. These springs will 
 fill the surface soil witli water, which will also descend into the bottom (?f 
 the valley, and, if no sufficient outlet be provided for it, will, according 
 to its (juantity, give rise to a lake, a bog, or a morass. On tiie slope to- 
 wards 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 po- 
 rous rocks beneath, will, by the inclination of the beds, be drawn oR" 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 Ihe other, and ^^"hy, 
 even in the absence of the improver's skill, an appaiently more fertile 
 soil may exist, and better crops be reaped. 
 
 4°. Again, such an outlet lor tlie waters that rest among inclined strata 
 is not unfre(piently afiorded, without the intervention of 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 
 
 annexed 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 h on the one side of the crack, begins again 
 at a lower level c on tlie other side, and so with the other beds that lie 
 above and belosv it. None of ihem is exactly continuous on the oppo- 
 site 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 — 
 
 1. These slips are often of considerable width, and are usually found 
 to be lilled with impervious clay. This is the case at least among the 
 coal measures, which have been the most extensively explored. The 
 eflre<rt of thii? wall of clay is to dam back at B D tJie water which de- 
 
SLIPS ARREST AXD THROW OP THE WATER. 
 
 315 
 
 scen'ls alona; the incline<l beds towards C frotn the country beyond A, 
 an I thus to arrest its further progress. But the pressure of the water 
 behinl forces that which has rea-.-hed the fauU B D to seek a way up- 
 wards, and, as spaces not unfrequently exist between the wall of clay 
 and the rocks between which it stands, the water finds a more or less 
 realy outlet at the surface B, and either gushes forth as a living and 
 welcome spring, or oozes out uussen among the soil, rendering it cold, 
 wet, and unprol active. Tiius from h the water accumulated in the bed 
 (0) may rise to the surface, or from/ that which exists in (4), or from 
 any other bed in which water exists, and from almost any depth. 
 
 •2. But eveu where no such wall of clay exists, the waters may still 
 fin 1 th^ir way to the surface along lines of tault, and from great depths. 
 Thu^ suppise the thin bed (-2) to be full of water, and that it is covered 
 by aa impjrviou-5 bed (1), theu the water whicl\ tends downwards from 
 a t ) b will be arrested at the fault, and dammed back by the impervious 
 extreuiity of (1) against which it no\V rests. If an outlet can be found, 
 it will therefore rise towards the surface. And as the rocks incline up- 
 wards in the direction of A, the pressure from beliind may easily cause 
 tiie water to ascend to the summit of the iiill 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 surface, while 
 abuiilance, as we iiave already seen (2^), may exist in the rocks be- 
 neath, ready anl willing to rise if a passai^e be opened for it. Such is 
 the case with the site of the city of London, represented below : — 
 
 Ilimpstead. 
 
 London. Thames. Sydenham. 
 
 SECfiON ACROSS THE LONDOM BASIN FROM ST. ALBAN'S TO KVOCKHOLT. 
 
 (^Dncklmid's BridsKicciter Treat lie, plate 69.) 
 1. Mirine Sirid. 2. London Clay (almost impcrmeabli'). 3. Plastic Clay and Sdnd. 
 4. Ctialk, bo'.h lull of wiuer. 
 
 The rain-water which fails between a and A on the one hand, and 
 upon the plastic clay and chalk between d and B on the otlier, sinks into 
 these two beds and rests in them till it finds an escape. It cannot rise 
 through the great thickness of imjiervious clay on whicli London and its 
 n:-ighborhiol 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, wliile at other places, as at a, c, d, 
 it has still to be pumped up from a greater or less depth.* It is the ex- 
 
 ' In Jannary ISIO, there were stated to be in the London clay upwards of 200. such vvells, 
 of which 171 were jn London, and of which latjer 30 ukAn tosetlior wera knowa to yield 30 
 
315 ARTESIAN WELLS.— SPllJ?fG3 IN DESKRTS AMD PAaCli£D PLAIPIS. 
 
 istence of water beneath the surface Aviiere the soils rest on impermea- 
 ble beJs, and the known tenrlency ofthe.se waters to rise when a boring 
 is sunk to them, that have given rise to the estaljUshment of ylrteszaa* 
 wells, so fretjuently executed, ami witli so n^uch success, in recent times. 
 There is probably no geological fact that promises hereafter to be of more 
 practical value to mankin<l, when good government and the arts of peace 
 shall obtain a permanent resting-place in those countries where, without 
 irrigation, the soil remians hopelessly barren. Wherever a living spring 
 bursts out in the sands of Arabia, in tiie African deserts, or in the parched 
 jtlains of South America, an island of perennial verdure delights the eye 
 of the weary traveller, and wherever in such countries the labour of man 
 has been expended in digging wells, and in raising water from them for 
 artificial irrigation, ilie same beauty and fertility always appear. It 
 has recently been fi)und 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 tlie ancient Egyptians, but for the 
 greater part long since filled up. Tlie 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 contem plating 
 what man may do, when his angry passions and his prejudices do not 
 interfere with the exercise of his natural 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 vmfrequently happens that alternate layers of sand and clay 
 overspread the rocks of a couirtry, and act in arresting or in Ihrowhiff out 
 the surface water in the same manner as the solid strata beneath. Thus 
 
 under the surface A B here represented, alternate layers of sand and clay 
 overspread the inclined beds of rock, and alone affect not only the qual- 
 ity but the state of dryness also of the soil. 
 
 The rain which falls on the upper bed of sand will sink no further 
 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, 
 
 millions of gallons weetsly. This number of wells has since been increaaeit, ami ia stiH 
 iiicreasinii. The birini's are aentrally carried down into the chalk, because the water which 
 ascenils from the plastic clay has been found to bring with it much sand, which botli ob- 
 structs the pipes anil is injurious to tlie pumps. 
 
 ■ So called from the district o( Artois, in France, in which it was formerly supposed that 
 such borings had been longest or most e.vtensively practised. 
 
EFKKCT OF ALTERNATE LAYERS OF SAND A>D CLAT. 317 
 
 filling the two vallies more or less with water, and forming wet tracts of 
 country resiina; 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 onl}' the immediate natural source of the water we are desirous tore- 
 move, but also the probable quantihj it may be necessary to carry ofT, 
 and the permanence of the supply. Jt is well known, for example, that 
 in many spots, when the accumulated waters are once carried off", there 
 remains only a small and probably intermitting supply, for which an 
 outlet is afterwards to he 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 
 tiirown 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 prece- 
 ding 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 in- 
 termit, to cease altogeifier, or to become more copious, according as the 
 season is dry or otherwise ; while that which escapes from a bed of rock, 
 being independent of the seasons, will seldom vary in quantity. Thus 
 it happens that where surface water only stagnates in the soil of a district, 
 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 ma5% 
 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 connected with this 
 subject, which I must briefly explain to you. Let C and D in the ac- 
 
 companying wood-cut be two impervious beds through which the water 
 finds no escape, and from which the rains pass off" only by the natural in- 
 clination 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 wa- 
 ter will descend, and will be absorbed by the bed E. Such dry, porous 
 or absorbent beds exist in many localities, and the skilful tlrainer 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 rest- 
 ing upon chalk, or u()on the loose sands beneath it, this method of boring 
 is frequently had recourse to in some of our southern counties. One dan- 
 ger, however, is to be guarded against in trying 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 readily, and in considerable (juantity, 
 ascend. Such a boring it is obvious would only add to the evil, and 
 might render necessary a larger outlay in establishing an efficient sys- 
 
318 
 
 PLOru.'II.NG AND SUBSOILl.NU. 
 
 tern of drainage by the ordinary niciiiod, than would oUierwJse have been 
 required.* 
 
 I do nol enter into any t'nrther details in re.G;ard to the ap])lication of 
 these principles to the jiract.ice ofdraininE;, being satisfied that when you 
 have once mastered the principles themselves, the applications will 
 readily suggest themselves to your own minds vvlien circumstances re- 
 (juire it. 
 
 § 4. Of j^l-ov siting and suhsoiling. 
 
 I. Ploughing. — Apart from the obvious elTt?ct of ploughing the land, 
 in destroying weeds and insects, the immediaie advantage sought for 
 by the farmer is tlie reduction of his soil to a state of minule division. 
 In this state it i^ not only more pervious to the roofs of his corn, but it 
 also gives a more ready admission to the air and to water. 
 
 Of the good eirects |)rodiiopd by the easy descent and escape of water 
 from the surface, I have already spoken (p. 306), but the permoability 
 of the soil to air is no less useful in developing its natural powers of pro- 
 duction. How important the presence of the air is both to the mainten- 
 ance of animal and to the suj'port of vegetable liie, we have had fre- 
 quent occasion to observe, liy its oxygen the breathing of animals is 
 sustained, and by its carbonic acid the living plant is fed. On tlie earthy 
 particles, of which the soil consists also, the influence of these gaseous 
 substances, though not so visible and striking, is of almost ctjual conse- 
 quence in the economy of nature. Among other immediaie 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 healthy 
 germination of all seeds (page 132), and it is chiefly because they are 
 placed beyond its reach, that those of many plants remain buried for 
 years without signs of life, tliough they freely sprout when again brought 
 to the surface and exposed to the air. We have also seen reason to be- 
 lieve (page 77), tiiat tlie roots of living plants require a supply of 
 oxygen in order that they may be maintained in a Ijealfhy condition. 
 Such a supply can only be obtained where the soil is sufficiently open 
 to permit the free circulation of the air among its pores. 
 
 ' It somelimes happens that in sinking an old well deeper 
 for the purpose of obtairiinj; a b'^lter supply of water, the 
 original sprinss disappear altoael her. This ia owing lo llie 
 occurrence at this gr-ater depth, of an abso'bnnt bed, in 
 whicii tlie water disappears. Hy liescendiiig still t'nrther, a 
 secnnil supply of water mny often be foutnl, b'lt which will 
 nattirallv ascend no further than the absorbent bed, by which 
 the whole supply will be drunk up, if nut prevented by the 
 insertion of a netal pijie. Advantage is sometimes taken of 
 the known existence of such absorbent strata, not only for the 
 jiurposes of draiiiinn, but also for removing w.isti; water of 
 variou.s kinds. An interestitii: example ofsuch application is 
 to be seen at t>t. Denis, in the Place anx (Jueldres, where the 
 water from the beil/at ttie depth of '200 feet a'^cends thronah 
 the inner tube a — from anoiherbed e, at 100 feet, Ihro'.iiih the 
 tube ')— while between it arid the outermost tube, through the 
 spac!^ c, it is sent djjwn again after it has been employed in 
 washing the square, and disappears in the absorbent stra- 
 tutnci. 
 
DKCOMPOSrno.N OV llOCKV MOUNTAINS. 31!) 
 
 2°. In tlm prescdco of air ilio derom position of tlic vrgftuble matter 
 of the soil [)iocepil.-! more r;i|ji(ily — it is more speedily resolved into those 
 simpler Ibrms of matter, carbonic acid and water chielly (page 152), 
 which are fitted to minister to the growth of new vegetable races. In 
 the absence of the air also, not only does this decomjiosition proceed 
 more slowly, but the substances immediately produced by it are fre- 
 rpieittly unwholesome to the plant, and therefore fitted to injure, or ma- 
 terially to retard, its growth. 
 
 3^. When the oxygen of the air is more or less excluded, the vege- 
 table matter of lix; soil takes this element from such of the earthy sub- 
 stances as it is capable of decomposing, and reduces iliem to a lower 
 stale of oxidation. Thus it converts llic red or prr-o\'\de of iron into 
 tli(^ ^7ro<-oxide (p. 211), and it acts in a similar manner ujion the oxides 
 ot' manganese (p. 21,'{). It also lakes their oxygen fnjni the sul]ihaies (as 
 from gypsum), an 1 converts them into sulphurets. These lower oxides 
 n!" iron and manganese ar(^ injuricjus to vegetation, and it is one of the 
 beneH(rial purposes served by turning u|) 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 prevente<l, or that when produced th;^y speedily become harmless 
 again by the absorption of an additional dose of oxj'gen. 
 
 4"^. Further, there are few soils which do not contain, in some quan- 
 tity, fragments of one or other of those com])Ound mineral substances of 
 •vvhicii, iu a previous lecture, (xii., p. 257,) wc have seen the crystalline 
 rocks to consist — of hornblende, of mica, of felspar, &c., in a decom- 
 posing state. From these minerals, as they decoiu pose, the soil, and 
 therefore the plants that grow in it, derive new supplies of several of 
 those inorganic substances whicli are necessary to the healthy nourish- 
 ment of cultivated cro{)s. ^I'he continued decom])osiiion of these mine- 
 ral fragments is aided by the access of air, and near its surface, in an es- 
 pecial 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 present ing to it5 roots a larger abiuidance not only 
 of organic but also ol' inorganic food. 
 
 5^. Again, that production of ammonia and of nitric acid in the soil, 
 to wliicli 1 drew your especial attention on a former occasion (pages 157 
 ami inO), as ajiparently of so much consequence to vegetable life, takes 
 place more ra])idlv, and in larger (|uantity, the more frequently the land 
 is turned bv the plough, broken by the clod-crusher, or stirred up by the 
 harrow. Whatever amount of either of these compounds, also, the sur- 
 face soil is capable of extracting fiom the atmosphere, the entire (]uan- 
 tity thus absorbed will evidently be greater, and its distribution more 
 uniform, the mote completely the uliole soil has been exposed to its in- 
 fluence. It is for this, among other reasons, that, as every fartiier knows, 
 the better he can plough and pulverise his laud, the icore 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 numerous fibres, nor are they 
 prevented, by the presence of noxious substances, from throwing out 
 
320 EFFECT OF THE SUBSOIL-PLOUGH- 
 
 branches in every direction. A deep soil is not absolutely necessary fo 
 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 disap])oint the hopes of the husbandman, 
 — than where a greater depth prevails, less permeable to the air, and 
 therefore less wholesome to the growing roots. 
 
 II. Subsoil Ploughing. — And yet, as a general rule, it cannot be de- 
 nied that a deep soil is greatly superior in value to a shallow soil of the 
 same nature. It is so both to the owner and to the occu])ier, though in 
 too many cases the available qualities of deep soils have hitherto been 
 more or less overlooked and neglected. 
 
 The general theoretical princijjle on this subject — that the deeper the 
 soil the longer it may be cropped without the risk of exhaustion, 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 ac- 
 quiescence. But a soil is virtually shallow where a few incl)cs of jiorous 
 earth, often turned by the plough, rest upon a subsoil, h.ard, stifi^ and al- 
 most impervious, — and the practical farmer will rarely be willing to 
 allow the depth of the latter to influence his opinion in regard to the gene- 
 ral 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 and wholesome to the roots of plants, before it can be made 
 available for tlie growth of corn. This may be effected, after (/raining, 
 by the use of the stibsoil jdough, an instrument at jiresent, I believe, 
 unequalled for giving a real, practical, and money-value to stifl' and 
 hitherto almost worthless clayey subsoils. It is an auxiliary both to the 
 surface jdnugh 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 roots more readily make their way among 
 the particles of the under-soil. So far it is an auxiliary to the common 
 plougli, and assists it in aerating 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 perinanent cure for the defi- 
 ciencies of the subsoil, if unaided by the drain. If the soil rest upon 
 an indurated substratum — upon a calcareous or ochrey ^aw — this plough 
 may tear it up, may thus allow the surface water to sink, and may great- 
 ly benefit the land ; but tlie same petrifying action will again recur, and 
 the benefit of the subsoiling will slowly disappear. Or, if the subsoil 
 contain some noxious ingredients, such as salts of iron, which the ad- 
 mission of air is fitted to render harmless, then the use of this plough 
 may afliird 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 maybe cut, or 
 for the time torn asunder, but scarcely will the plough have passed over 
 it till the panicles will be again cemented together, and probably, by the 
 
PKEVIOUS DRYNESS OK THE SUBSOII. NECESSART. 321 
 
 end of a single soafoii at the furthest, the unc^er-soil may be as solid and 
 impermeable as ever. 
 
 It is as the Ibllower of the drain, therefore, in the course of improve- 
 ment, that the subsoil plough finds its most beneficial and most economi- 
 cal use. After land has been drained, the water may still too slowly 
 pass away, or the air may have too imperfect an entrance into the sub- 
 soil from which the drains have removed the water. In the former case, 
 the subsoil plough must be employed, in order that the drains may be- 
 come fully efficient; in the latter, that the under-layers may be opened 
 up to all ihe 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 eflcct 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 i:ot again readily cohere, it is of importance that the 
 drains should be allowed a consitlerable lime to operate 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 
 detective draining, or from the want of sufficient time, has not been able 
 fully to flow away. There are few kinds of claj'land on which llie ju- 
 dicious use of this valuable instrument will not j)rove both actually and 
 econnmically useful, (hough from the neglect of the above necessary pre- 
 caution, it has been found to fail in the hands of some. Such failures, 
 however, do not justify us in ascribing to some fancied defect in the in- 
 strument, or in the theory upon which its use is recommended, what ne- 
 cessarily arose, and could have been predicted, from our own neglect of 
 an indispensable preliininarv observation. The sanguine anticij^ations 
 of its inventor, INJr. yiiiith, of Deanston, may not be fully realized, yet 
 the value of tiie subsoil ])lough itself, and the benefits it is fitted to confer, 
 when rightly used, appear to me to be both theoretically and practically 
 established. 
 
 § 5. Of dcej)-j)Ioughing and Ircvching. 
 
 Deep-ploughing and trenching differ from ordinary and subsoil plough- 
 ing in this, — that their special object is to bring to the surface and to mix 
 with the upper-soil a portion of that which has lain long at a consider- 
 able depth, and has been more or less undisturb.ed. 
 
 The benefit of such an admixture of fresh soil is in many localities un- 
 doubted, wliile in others the practical farmer is decidedly ojiposed to it. 
 On what j)rinciple does its beneficial action depend, and in what circum- 
 stances is it likely to be attended with disadvantage ? 
 
 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 substances 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 silicates of pola.-h and soda al- 
 ready spoken of (page 206), as apparently so useful to corn-growing 
 plants. Such substances as these naturally accumulate beyond the 
 reach of the ordinary plough. Insoluble substances likewise slowly 
 14* 
 
322 OBJKCT AND KFFKCT Or nEKP-PLOUGUl.NG. 
 
 sink. This is well known to be tlie case with lime, when laid upon or 
 ploughed into the land. So it is with clayi when mixed with a burface 
 soil of sand or peat. They all descend till ihey get beyond the reach of 
 the common j)lough — and more rapidly it is said (in Lincolnshire) 
 when laid down to grass, than when they arc constantly brought to 
 the surface again in arable culture. Thus it happens that after the sur- 
 face soil becomes exhausted of one or other of those morgan ic compounds 
 vv'hich the crops retjnire, an ample supply of it may be still present in 
 the subsoil, though, until turned up, unavailable for the promotion of ve- 
 getable growth. 
 
 There can be little question, I think, that the greater success vvl)ich 
 attends the introduction of new implements in the hands of better in- 
 structed men, upon farms long held in arable culture, is to be ascribed in 
 part '0 this cause. One tenant, during a long lease, has been in the 
 habit of ploughing to a depth of three, or at most, ])erhaps, of four 
 indies — and from this surface the crops he has planted have derived their 
 chief supplies of inorganic food. He has hmcd liisland in the customary 
 manner, and has laidupon it all the manure he could raise, but his crops 
 have been usually inditferent, and he considers the land of comparative- 
 ly little value. i3ut 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 whicii his predecessor had permitted year after year to bury ihtin- 
 selvesin his subsoil. He thus has a new, often a rich, ami almost always 
 a virgin soil to work upon — one whicii, from being long buried, may re- 
 quire a winter's exposure and mellowing in the air, but which in most 
 rases 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 justified and reconmiended upon ])recisely the same 
 principle. It not only brings a new soil, containing ample nourishment, 
 to the inmiediate roots of plants, but it alTbrds them also a deeper and 
 more open subsoil, tlnough which their hbrcs may proceed in every di- 
 rection in search of food. The full benefits of this deepei;ing of the soil, 
 however, can only be expected where the subsoil has pre\ iousiy been 
 laid dry by drains ; for it matters not how deep the loosened and perme- 
 able soils rnay 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 apjilies 
 this theoretical principle — sound thougii it undoubtedly be — in a district 
 with which he has no previous acquaintance. It is possible that the 
 deeper soil may contain some substance decidedly noxious to vegetation. 
 In such a case it would be improper at once to mix it with the uj)per 
 soil. Good drains must be established, they must he allowed some time 
 to act, and the ^ibsoil plough will be used with advantage, before any 
 portion of such an under-soii can be safely brought to the surface. The 
 subsoil jjlough and the drain, indeed, as I have already mentioned, are 
 the most certain available remedies for such a state of the subsoil. In 
 many localities, however, 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 ren- 
 
EFKECT OF INSF.CTS. IMPROVKMKNT OK THF, SOiL. 323 
 
 der it capable of lieing safely mixed with the surface soil. Unless, how- 
 ever, this mellowing be etiected at once, and before admixture, a long 
 time may elapse ere the entire soil attain to its most perfect condition.* 
 
 Ai^ain, it is known that some districts, for reasons perhaps not well un- 
 derstood, are more infested than others with insects that attack the corn 
 or other crop?. These insects, their ccgs, or their larvai, generally bury 
 themselves in the undisturbed soil, immediately beyond the ordinary 
 reach of the plough. If ihey remain wholly undisturbed during the 
 prep'iration of the soil, some species remain in a dormant state, and the 
 subsecpient crop may in a great measure escajie. Plough the land deep- 
 er than usual, and you bring them all to the surface. Do this in the 
 autunm, and leave your land unsown, and the frost of a severe winter 
 may kill the greater part, so that your croj)s 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 insects 
 witliin reach of the early sun, arid tlius call them to lite in such num- 
 bers as almost to ensure the destruction of your coining crop. It is to 
 something of this kind that I am inclined to auribute the irnmediaie fail- 
 ures whicii have attended tlie trial of deep ploughing in certain parts of 
 England. Thus in Berkshire, certain soils which are usually ploughed 
 to a depth of only tivo inches, yielded almost nothing when deeper plough- 
 ing was iriore lately tried upon them — the crop was almost entirely de- 
 stroyed by insects. So also in the north of Yorkshire, where deep 
 ploughing has recently been attempted, the wheat crop on land so treated 
 was observed to suller mdre from the worm than on any other spot. 
 Such iacis as these, therefore, show the necessity of caution on the part 
 of the practical man, and especially of the land agent or steward, how- 
 ever coirect may be the principles on which his general practice is 
 founded. Failures such as the above do not show the [)rinciple on whicli 
 deep ploughing is recommended to be false, or the practice to be in any 
 case reprehen<lcd : but it docs show that a knowledge of natural local 
 peculiarities, and some study of ancient local practice, may, in an im- 
 j)ortant degree, influence our mode of procedure in introducing more 
 im[)roved metiiods of husbandry into any old agricultural district. 
 
 § G. Improvement of the soil by mixing. 
 There are some soils so obviously defective in constitution, that the 
 itiost 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, there- 
 fore, of almost any common kind, is readily indicated as a means of im- 
 provement. In like manner we naturally impart consistence to a sandy 
 
 * The Marquis of Tweodale, in liis honiefarm at Yoslers, lias raised tiis land in value 
 eisrhl tinios ((rom us. !•> 4ns. per acre), by draiiiin!? and deep plongliing. After draining, the 
 fields of slili'clay, wiiji s^lreaiis of sand in the swb.soil, are tunied over to a depih of I2or 14 
 inches, hy two ploughs (two horses eacii) foUowin^j one another, tlje under 6 inches being 
 tlirown on the top. In Uiis slaie it is left tollie winter's frost, when it falls to a yellow marly 
 looking soil li is now ploughed again to a depth of 9 or 10 inches, by which half the origi- 
 nal soil is brought a;;ain to llic surface. Byacross plougliing tljisis mixed with the new 
 soil, after which the field is prepared in the usual way for turnips. But it is observed that if 
 ttie ploughing has been so late ttiat tlie 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 reason is, that when once mixed up with the other soil, the air has no longer the same 
 easy access into its pores. 
 
324 EFFECTS OF CLAY AND MARL. 
 
 soil by an aJmixture of clay, and openness and porosity to stiff'clays by 
 the addition of sand. 
 
 Tiie first and obvious eflect of such additions is to alter the physical 
 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 in 
 the first place on its chemical constitution. It must contain in sutlicient 
 abundance all tlie inorganic substances which that crop retiuires for 
 its daily food. Where this is already the case, as in a rich stitrday, a 
 decided improvement may be produced by an admixture with siliceous 
 sand, which merely separates tlie particles meciianically, and renders 
 the whole more porous. But let the clay be deticient in some necessary 
 constituent of a fertile soil, and such an addition of siliceous sand would 
 not produce by any means an etmal benefit. It may be prop(.>r 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 producing (he 
 necessary chemical change. 
 
 The good effects which almost invariably (^>llow from the addition of 
 clay to peaty or sandy soils are due to the production at one and the same 
 time of a pliysical and of a chemical change. They are not only ren- 
 dered firmer or more solid by the admixture of clay, but they derive 
 from this clay at the same time soine of those mineral substances which 
 they previously contained in less aliundance. 
 
 The addition of marl to the land acts often in a similar two-fold capa- 
 city. 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 
 whicli 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 tliose above adverted to, where the means 
 are available, will be readily granted. The only question on the sub- 
 ject 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? 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 answer to these questions will be modi- 
 fied by the circumstances of the district in 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 purchasing 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, 
 virlually adds to the bretidth of the land, in causing it to yield a larger 
 produce. Yet it is no less true that the employment of individual capi- 
 tal in such improvement is not to be ex])ected ^eneralhj to take place, 
 unless it be made to appear that such an investment 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 ex- 
 pended in draining and snbsoiling — and yet in reality one main obstacle 
 
CLAV AND SAND. — SPECIAL MIXTURES. 325 
 
 to a more rapid increase in the general produce of the British soil is the 
 practical difficulty whicli exists in convincing the owners and occupiers 
 of the soil that sucli 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 it is to be hoped will tliis diffi- 
 culty become — for the economist, who regards the question of improve- 
 ment as a mere matter of profit and loss, cannot strike a fair balance 
 unless he knows the several items he may prudently introduce into each 
 side of his account. 
 
 Thus in reference to the special point now before us, it seems reason- 
 able to believe that, in a country such as that here represented, where 
 alternate hills of sand (3), and hollows, and flats of clay (4) occur, there 
 
 vss^^^^^M 
 
 ^^^ 
 
 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 quaiit}'- of the land might be well expected to repay. 
 In this condition is a considerable jOTrtion of the eastern half of the 
 county of Durham, and, especially, I may mention the neighbourhood 
 of Castle Eden, whore a cold, stitf, at present often poor 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 
 im])rove. In this locality, and in many others besides, those having a 
 pecuniary interest in the land rest satisfied that their fields are incapable 
 of such improvement, or would give no adequate return for the outlay 
 rcqiiired, without troubling themselves to collect and compare all the 
 facts from which a true solution of the question can alone be drawn. 
 
 IJesidcs such general admixtures for the impnwement of land, the 
 geological formation of certain districts places within the reach of its in- 
 telligent Hirmers means of improvement of a special kind, of which they 
 may often profitably avail themselves. Thus both in Europe and Ame- 
 rica, the green-sand soils (p. 243) are found to be very fertrle, and 
 the sandy ]iortions 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 tliey might be mixed with most beneficial effects. The soils that 
 rest on the neio, and even on some pnns of yhe old red sand-slone, are 
 in like tnanner often within an available distance of beds of red marl of 
 a very fertilizing character (p. 248), while in the granitic and trap 
 districts the materials of which these rocks consist, if mixed w'lth judg- 
 m(;nt, maybe made materially to benefii soine of the neighbouring soils. 
 To this point, however, I shall draw your attention again in my next lec- 
 ture, when treating of mineral manures. 
 
LECTURE XV. 
 
 Improvement of the soil by chemical means. — Principles on which all manurins 'lependg. 
 — Mineral, vegetable, and animal manures. — Saline manures. ^Carbonates.— Pearl-ash. 
 —Sulphates. — Glauber sails. — Chlorides. — Common Salt. — Nitrates. — Nitrate of soda. — 
 
 PhospliHtes. — Phosphate of lime. — Silicates. Silicate of potash. — Saline mixtures 
 
 Vegetable ashes. — Prepared granite. — Use of lime. 
 
 Thk mechanical methods of improving the .soil, describerl in the pre- 
 ceding section, are few in number and simple in theory. They are so 
 iin[iortant, however, to the general fertility of ilie land, that were they 
 judiciously employed over the entire surface of our islands, tliey 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. 308), 
 that the full effect of every other means of improving the soil will he 
 ohiained in those districts only where these mechanical inethods have 
 alre.ody been had recourse to. 
 
 The chemical methods of improving the soil are founded upon the 
 following principles, alreatly discussed and established : — 
 
 1^. Tliat 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 dif- 
 ferent kinds of inorganic food, or of the same kinds, in different pro- 
 portions. 
 
 4°. That of these inorganic substances one soil may abound or be 
 deficient in one, and another soil in another ; and that, therefore, this or 
 tiiat plant will prefer lo grow on the one or the other accordingly. 
 
 On these few principles the whole art of iinproving the soil by che- 
 mical 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 dis- 
 tinct methods of operation by which a soil may be improved : — 
 
 1"^. By removing from it some noxious ingredient. The only metliod 
 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 ap])lit'd 
 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 re- 
 spectively in practice when we add lime to peaty soils, or to such as 
 abound in sulphate of iron (p. 212), when by admitting the air 
 into the subsoil we change the prot-oxide into the per-oxide of iron, 
 (p. 210,) or when by adding certain known chemical compounds we 
 produce similar beneficial chemical alterations upon other compounds 
 already existing in the soil. 
 
ACTIONT OF CHEMICAL SUBSTANCES l.V THE SOIL. 327 
 
 3°. By adding to the soil those substances whicli are fitted to become 
 the food of plants. Tliis is what we do in strictly 7nanuriiig ihe soil — 
 thoiigl) we are as yet unable in many cases to say whether that which 
 we add promotes vegetauon by actually feeding the plant and entering 
 into its substance — or only by preparing food lor it. There is reason to 
 believe, liowever, 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 
 j)erfect substance of the growing vegetable. In order to steer clear of 
 the dithculty which this circumstance throws in the way of an exact 
 classification of the chemical substances applied to the soil, 1 shall con- 
 sider generally under the name oi' manures, ull those substances which are 
 usually applied to the land for the purpose of promoting vegetable growth ; 
 whether those substances be supposed to do so directly by feeding the 
 plants, or only indirectlj% by pre[)aring their food, or by conveying it into 
 their circulation. 
 
 Manures, then, in this sense, are either simjdp, like common salt and 
 nitrate of soda, or they arc mixed, like farm-yard manure and the nu- 
 merous artificial manures now on sale. Or, again, they consist of sub- 
 stances of mineral, of vegetable, or of animal origin. Tiie latter is the 
 more natural, and is by I'ar the most useful, classification. We shall, 
 therefore, consider the various substances employed in improving the 
 soil — or what is in substance the same thing, in promoting vegetation, — 
 in the H)!lowing order : — 
 
 ]^. Mineral manures — including those substances, whether simple or 
 mixed, which are of mineral origin, or which consist eniirely of inor- 
 ganic or mineral matter. Under this head the use of lime and of the 
 ashes of plants will fall to he considered. 
 
 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 im- 
 mediate origin, ditier remarkably in coa.stituiion from Aegetable sub- 
 stances. 
 
 §1. Of mineral manures. 
 
 Mineral manures may be conveniently considered under the two heads 
 of saline and earthy manures. 
 
 A. SALINE MANURES. 
 
 1^. Carbonate of potash. — This substance, in the form either of crude 
 potash or of the jicarl-ash of the shops, has hitherto been considered too 
 hiiih in price to admit of its extensive application in the culture of the 
 land. 
 
 •^°. Carbonate of soda. — This remark, however, does not apply to 
 the carbonate of soda (common soda of the shops), which is sutticiently 
 low in price (d£ll a ton) to allow of its being applied with advantage 
 under many circumstances. In the case of grass-lands, which are over- 
 run with moss — of such as abound largely in vegetable niatier 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 
 
328 QUANTITY OF SALINE ^MANURES USEFUL TO THE SOIL. 
 
 in moist weatlier — and generally wherever wood ashes are found useful 
 to vegetation. 
 
 Many experiments have shown that both of these substances may be 
 employed in the field with advantage to the growing crop — but further 
 trials are necessary to show how far the practical farmer may safely use 
 them with the hope of profit. In gardening, they greatly hasten the 
 growth and increase the produce of the strawberry,* and in garden cul- 
 ture, generally, where the cost of the manure employed is of less con- 
 sequence, more extended trials would, no doubt, lead to useful results. 
 
 The quantity of these substances which ought to be applied to our 
 fields, in order to produce the beneficial eHect which theory and practice 
 both lead us to expect, will depend much upon the natureof the soil in 
 each locality and on the kind of manuring to which it has previ(jusly 
 been subjected. By referring to our previous calculations (page 222,) 
 it will be seen that upwards of 800 lbs. of these carbonaiesf would 
 be necessary to replace all that is extracted from the soil by the entire 
 crops during a four years' rotation. Bin in good husbandry every thing 
 is returned to the soil in tlie form of manure which is not actually 
 sent to market aud sold for money. That is — the grain only of the corn 
 crops, the dairy produce, and the live stock, are carried ofi' the land.| 
 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 to be present in the 
 other produce sold, we have 80 lbs. for the quantity necessary to be re- 
 stored to the land by the good husbandman every linir years, in order to 
 keep his farm permanently in the same condition. There are, however, 
 in most soils, certain natural sources of supply (pp. 207, 208) by wdiich 
 new portions of these alkalies are continually conveyed to them. Hence 
 it is seldom necessarj^ to atld 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, 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 agri- 
 cultmal value. Half a cwt. of the potash will cost less than 15s., and 
 of the soda less than 6s., or of a mixture, in equal quantities, less than 
 2Is. at their present prices. 
 
 Theory of the action of potash and soda. 
 
 But upon what theoretical grounds is the beneficial action of potasli 
 and soda upon vegetation ex |)lained ? This question, to which I have 
 already more than once drawn your attention (pp. 83 and 187), it will 
 be proper here briefly to consider. 
 
 a. The first and most obvious purpose, served by the presence of lliese 
 alkalies in tlie soil, is that of yielding readily to the growing plant sucii 
 a full supply of each as may be essential to its healthy growth. If llie 
 roots can collect them from the soil slowly only, and with difiiculty, the 
 growth of tlic plant will necessarily be retarde<l ; while in situations 
 
 ' Mr Fleming, of narnclian, has informed me that he found this to be the case with the 
 cnmtiion potasti ; and Mr. Campbell, of Itsiay, with the common soda of the shops, Tlicy 
 should be applinl early in the sprinff, atMi in the slate of a very weal; soliUiou. Wut d- 
 ashes would probably produce a similar eirect, 
 
 t 390 lbs. of dry pearl ash and 440 lbs. of crystallized caibonate of soda. 
 
 } In bnd husbandry much more is carried off the land by the waste of liquid and other 
 manure.— See the succeeding chapter, " On animal manures '' 
 
POTASH A>"D SODA PREPARE THE FOOD OF PLANTS. 329 
 
 where tliey naturally abound, or are ardficially suppUeil, the crops 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 i.. will occur to you that potash i.g 
 the more likely of the two to be beneficial to our cultivated crops, inas- 
 much as the ash of those |)lants which are raised tor food is generally 
 much more rich in potash than in soda. [See the tabular details given ui 
 Lecture X., § 3., p. 216 el seq.^ But this may possibly arise from the 
 more abundant presence of potash in the soil generally, since some 
 chemists are of opinion that soda may take the place of potash in the in- 
 terior of plants, without materialhj affecting their groivth, [Berzelius 
 C.ti/nic, VJ., p. 733, edit. 1832.] This hyp.oihesis, whatever may be 
 its theoretical value, will prove useful fo praciical agriculture ifitlcadto 
 experiments from whicii the relative action of each of these carbonates, 
 in the same circumstances, may be deduced, — and the specific influ- 
 ence of each, in promoting the growth of particular plants, in some de- 
 gree determined. Potasli (or wood-ashes) aids the growth of corn after 
 turnips or potatoes (Lampadius) — would soda do the same ? Carbon- 
 ate of soda assists in a remarkable manner the growth of buck-wheat 
 (Sprengel) — would the same good efTects follow from the use of potash ? 
 
 b. Another purpose which these carbonates are supposed to serve, is 
 that of combining with, and rendering soluble, the vegetable matter of 
 the soil, so as to bring it into a state in which it may be readily con- 
 veyed into the roots of plants. They may in this case be said to pre- 
 pare the food of plants. That they are really capable of forming 
 readily soluble compounds with the huinic acid, and widi certain other 
 organic substances which exist in the soil, is certain. Those, however, 
 who maintain with Liebig that plants imbibe all their carbon in the 
 form of carbonic acid, will not be willing to adn)it that this property of 
 the above carbonates can either render them useful to vegetation, or ac- 
 count for the beneficial action they have so often been observed to exer- 
 cise. From this opinion we have already seen reason (pp. 63 and 64,) 
 to dissent, and we are jircpared, therefore, to concede that potash 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 
 l)lants, and thus administering to their growth. 
 
 This prey)aration 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 disposing this or- 
 ganic matter, at the expense of the air and of moisture, to form new 
 chemical compounds which shall be capable of entering into the vege- 
 table circulation. This disposing influence of the alkalies, and even ol 
 lime, is familiar to chemists under many other circumstances. 
 
 This mode of action of the carbonates of potash and soda can be ex 
 ercised in its fullest extent only where vegetaiile matter abounds in the 
 soil. It is stated by Sprengel [LeJire vom Diinger, p. 402.] according- 
 ly, as the result of experiment, that they are most useful where vegeta- 
 ble matter is plentiful, and that they ought to be employed more spar- 
 ingly, and with some degree of hesitation, where such organic matter is 
 deficient. 
 
 c. We have already seen, during our study of the composition of the 
 
330 POTASH AND SODA RK.N DKR. SILICA SOLURLK, V.TC. 
 
 ash of plants (page 216 et seq.) how very important a substance silica i^, 
 especially to ihe grasses and llic stcin.s of our various corn-bearing plants. 
 This silica exists very frequently in the soil in a state in which it is insol- 
 uble in pure water, and yet is more or less readily taken up by water 
 containing carbonate of potash or carbonate of soda; and as there is eve- 
 ry reason to believe tiiat nearly all the silica they contain is actually con- 
 veyed into the circulation of plants by the agenc}' of potash and soda, (in 
 the state of silicates — see pp. 83 and 207,) it is not unlikely that a portion 
 of the Ijsneticial action of these substances, especially uptjn the grass and 
 corn crops, may be due to the quantity of silica they are the means cf 
 conveying iiUo the interior of the growing plants. 
 
 d. Another mode in whicii (best; substances act, more obscurely, per- 
 haps, though not less certainly, is by disposing the organic matters con- 
 taine I in the sap of the plant to form such new combinations as may be 
 rejuiretl for the production of the several parts of the living vegetable. I 
 have on a former occasion illustrated ( |)p. 112-114.) to you the very re- 
 markable changes which starch may be made to undergo, without any 
 essential' alteration in its chemical composition — how gum and sugar 
 may b3 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 comparatively minute quantity of diastase (p. 118) or of 
 sulphuric acid (p. 11.3) is ca[)able of inducing such clianges, first rendering 
 the starch soluble, and then converting it into gum and into sugar. Ana- 
 logous, though soinewhat dilferent changes, are induced by liie presence 
 in certain solutions of small (jnantities of potash* or sotla, as, fijr example, 
 in milk — the addition ofcarbonatc of soda to which gradually causes (per- 
 suades ?) the whole of tlie sugar it contains to be converted into the aciil of 
 milk. Such changes also must be produced or facilitated by the presence 
 of acid and of alkaline 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 facilitate their production is one of 
 the many purposes served by the constant presence of inorganic substances 
 in the sap of plants; indeed so important is this function considered by 
 some writers upon the nourishment of plants, (see especially Hlubeck's 
 Erndkrung dcrPJlanzen und SLalik desLand baues,) that they are inclined 
 to ascribe to it, erroneously however, as I believe, the riuiin intluence 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 otie other way in which these substances may be sup- 
 posed to have an intiuence upon vegetation. We have already seen (Lee. 
 Vfn, § .5, (3, 7, pp.l-5D to 1(37,) how important a part the nitric acid produ- 
 ced in the atmosphere or in the soil may be sup|)Osed to perform in ihe gen- 
 eral vegetation of the globe. This acid is observed to be more abundantly 
 — either fiKed or actually produced in the soils or cotii posts wliich contain 
 much potash or soda. It maybe, therefore, that in adding either of these 
 to our tields, 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. 
 
 3°. Sulphates of Potash and Soda. — It is nearly 100 years since Dr. 
 
 * It is also shown (p. Ui2,) that, by means of potash, wood/ fibre may be converted 
 into starcti. 
 
EKFKCTS PP.OUUCKD BV SULPHAl'K OK SODA. 331 
 
 Home, of F^dinbnrgh, observed that these salts produced a beneficial 
 elVect upon vegetation. Applied to growing corn, they increased the 
 produce by one-fourth. Other experiments, since made in Germany, 
 have shown that they may be applied witfi manifest advantage both to 
 field crops and to fruit trees (Sprengel), but liie price lias hitherto been 
 considered too high to admit of their being economically used in ordinary 
 husbandry. 
 
 The manufacture of sulphate of soda in England, however, has of 
 late years become so much extendetl, and the price in consetpience so 
 much reduced, that I was induced in the spring of the year 1841, (when 
 the publication of these lectures was commenced.) again to recommend 
 it to the attention of the practical agriculturists of the country — as likely, 
 either alone or mixed with other substances, to increase in manv locali- 
 ties uot only the produce but the profit also to be derived fioni the land. 
 (See Appendix, also published at the end of this volume, — " Sugirestions 
 for Experiments in Practical Agriculture," No. I.) IVlany ex])eriments 
 were in con<equence made in \ari(n!s parts of the country, the details of 
 some of which are given in the Appendix. When applied at the rate of 
 half a cwt. of tlie dry salt (or one cwt. of crystals) per acre, it produced 
 liule etVect upon the liay crop, tlie cpiantity being probably too small. 
 Applied to hay and rye, at the rate of 84 lbs. of the dry salt, and to pota- 
 toes at the rate of 100 lbs., it gave per imperial acre, with 
 
 Unilrpssed. Dressed wilh Sulnliate. Increase. 
 
 Hay 4480 lbs. 5288 lbs. 808 lbs. 
 
 ( grain, G40 lbs. 896 lbs. 25(5 lbs. 
 
 Winter Kye y^^^^^^.^,^ 4095 ^^g^ 4(^08 lbs. 512 lbs. 
 
 Potatoes .... 16] tons. 1 85^ tons. 1| tons. 
 
 The grain of the dressed rye was much heavier than that of the other, 
 and, though nitrate of soda and sal-ammoniac applied to other parts of 
 the same fiehl caused a larger increase in the crop of rye, yet the increase 
 obtained by the use of the sulphate was cheajJcr per bushel than that ob- 
 tained by the use of either of the other substances. 
 
 On beans and peas also the efieci produced by it (Appendix, page 23,) 
 was very striking — its action Ireing exerted not upon the straw but u[)on 
 the pods, increasing their nimiber and enlarging their size. 
 
 The results of these experiments, therefore, are such as to encourage 
 further trials. The quantity applied should jiot be less than one cwt. 
 of the dry salt per acre, and it should be put on either in the state of a 
 very weak solution wilh a water-cart, or sjirinkled on the young crop 
 when the ground is moist or when rain is sotjn expected. 
 
 4°. Sidphalc of Alagnesia (Epsom Salts) was found by Dr. Home to 
 promote vegetation almost in an eqnaldegree with the sulphates of f)Otash 
 nnd soda, but the usually high price of this compound, among other 
 causes, has hitherto prevented it from being tried upon an extensive 
 scale. The manufaciurc of this article also has of late years, however, 
 been so much extended and simplified, that the refined salts for medi- 
 cinal pur|)Oses may be |)urchased as low as 8s. a cwt. (at Messis Cook- 
 son's, Jarrow Alkali Works, near Newcastle,) and the impnre salts of the 
 Yorkshire and other alum works at a much lower rate. So much capi- 
 tal indeed has now been embarked in the manufacture of the sulphates 
 and carbonates of soda and magnesia (p. 192), and it is so desirable 
 
532 USE OF SULPHATK OF L!ME OR GYPSUM. 
 
 on mnny accounts to (Jiscover new outlets for the products of these impor- 
 tant manufactories, tliat were there only theoretical reasons for believing 
 them likely to benefit practical agriculture, it would be desirable to make 
 trial of their effects upon the land. But their favorable influence has 
 already been shown, and it remains, therefore, only to work out the de- 
 tails by wln'ch their application to this or that soil or crop shall be so 
 regulated as to yield a fair and constant profit to the farmer who em- 
 ploys them. 
 
 1 have elsewhere (Appendix, p. 4,) recommended the application of 
 sulphate of soda at the rate of 1 cwt. of the dry salt, or of 2 cwt. of crys- 
 tals (cost 10s. or lis.) per acre. The Epsom salts are only sold in crys- 
 tals, and 1|- cwt. (cost 12s.) in this form should be nearly equal in effi- 
 cacy upon the land to 2 cwt. of crystallized sulphate of soda. In this 
 proportion, therefore, it would be proper to apply it to the young crops, 
 es])ecially of wheat, clover, peas, beans, and other leguminous plants. 
 
 .5°. Sulphate of Lime yGypsutn) has been long and extensively applied 
 to the land in various countries and to various crops. In Germany itsinflu- 
 cnce has been most generally beneficial upon grass and red clover, while 
 in many parts of the United States it is applied wiih 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 potatoes, put info 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 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 ap5)ear that the time and mode of its application has more 
 influence upon its activity than we might suppose — siuce, according to 
 Professor Korle, when applied to clover at different periods in the spring, 
 the produce of different parts of the same field was in the following 
 proportions : — 
 
 Undressed, ] 00 lbs. 
 
 Top-dressed on the 30th of March, 132 lbs. 
 
 13lh of April 140 lbs. 
 
 " " 27th of April 156 lbs.* 
 
 The effect of a top dressing of gypsum seems therefore to be greatest 
 when it is applied after the leaves have been pretty well developed. f 
 
 Theory of the action of these sulphates. 
 
 a. It does not seem difficult nowr to account for the ceneral action of 
 these several sulphates of potash, soda, magnesia, and lime. The ex- 
 planation may be deduced partly from recent chemical analyses, and 
 partly from agricultural experiments more lately made by practical men. 
 
 It has been found, for example, that sulphur is a constant and appa- 
 rently necessary constituent of the gluten and albumen of the several 
 varieties of grain, and of the legumin, which forms the largest part 
 
 t MligUnsche Jahr bucher, I, p. 85, quoted in Hlubck's PJlanzcnniihriing, 
 
 \ Cau ilie result tiere mentioned have any connection wiih the fact observed by Peschler, 
 
 that gypsum laid npou the leaves of plants is gradually, converted into carbonate, its Eulphuric 
 
 acid being absorbed 7 
 
TflEORY OF THE ACTION Of THESE SULPHATES. 333 
 
 of the substance of tJie pea, the bean, the vetch, and of the seeds of 
 other leguminous plants. This sulphur they must obtain from ihe soil, 
 and one cause of the efficacy of the above sulphates is unquestionably 
 that tliey are fitted easily to yield to the growing plant the supply 
 of sulphur they necessarily require — while, if they are iriore efjicacious 
 upon the leguminous than upon other kinds of plants, it is because 
 the latter produce a larger proportion of that kind of organic matter in 
 which sulj)hur is constantly present. 
 
 That such is really the true explanation of their ^f«era^ action is 
 proved by ihe observation — that sulphuric acid applied to the land in a 
 very diluted state exerts an influence upon the crops precisely similar to 
 that observed when gvpsum or sulphate of soda is used. (See Appendix, 
 Nos. Land II.) 
 
 In reference to this mode of action it is of conse([uence to know the 
 relative efficiency of the several salts. This will obviously depend upon 
 the relative proportions of sulpliur or sidphuric acid they contain — sup- 
 posing ti)e circumstances in which they are applied to be equally favour- 
 af)le to the introduction of each into the circulation of tije jilant. Their 
 relative value upon this view is as follows .•' — 
 
 100 lbs. of burned gypsum are equal to, or contain as much sulphuric 
 acid, as 
 
 12(3 lbs. of common or unburncd gyj)sum. 
 
 128 lbs. of sulphate of potash. 
 
 10-1 lbs. of sulphate of soda — dry. 
 
 235 lbs. of sulphate of soda — crystallized. 
 
 180 lbs. of suli)hate 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 sulj)haics, in all cases, the 
 most economical application to the land. 
 
 b. But thev have each also their s/;raa? action dependent partly upon 
 their phvsical properties, and partly on their chemical constitution. 
 
 Thus it will be of little use mixing any of tliem with the soil, unless 
 they become capable of entering into ilie roots of the plants which are 
 growing upon it. The facility with which this can be ctlccted depends 
 upon tlieir solubility in water, whi.di is very unlike. Thus an imperial 
 gallon of ))ure water at the ordinary temperature will dissolve of 
 
 Gy|)sum (burned,) about ^- lb. 
 
 Cxypsum (nnburned,) {lb. 
 
 Sulphate of Potash, 1^ lbs. 
 
 Sidphate of Soda, i//-?/, l| lbs. 
 
 Sul|)hate of Soda, crystallized, 3^ lbs. 
 
 Sulphate of Magnesia, 4 lbs. 
 
 In rainy weather, therefore, and in moist climates, it would still be 
 nio-l econouncal to apply the gyj)sum, since, though very sparingly 
 solidjle, water would be sufficiently abundant to dissolve as mucli as the 
 plant might recpiire. But in timeso("only nxjdcrate rain, and especially 
 in drv' 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 constitution of these sulphates — tlie nature of 
 the substance with which the sulphuric acid is combined — determines in 
 
334 SPECIAL ACTION UPON GRASSES AND CtOVERS. 
 
 a still greater degree tlie nature and extent of their special action. If* 
 the soil already abound in potash, in soda, in lime, or m magnesia, then 
 the iufluenee of tiiese compounds may depend entirely uj)on tlie sul- 
 phuric acid they contain. But suppose tlie land to be deficient in liine, 
 •then the ijypsura we add will act not only in virtue of the sulphuric acid, 
 but of the lime also which it contains, and thus its apparent etlect will 
 be much more striking thau 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 winch sulpliuric acid alone is wanting. And so 
 also, if liuie and potash abound, and soda or magnesia be deficient, the 
 sulphates of these latter bases will exercise a special action upon the 
 soil, by supplying it at the same time with sulphuric acid and with soda 
 or magnesia also. Thus on land to wliich lime has been abundanilv 
 added,^ according to the ordinary practice of husbandry, the sulphate of 
 soda has the best chance of proving useful to vegetation, not only because 
 it is more soluble, and is, therefore, more indej)eudent of the seasons, 
 but because it is capable of supplying two difitirent substances — sulphuric 
 acid and soda — neither of which are directly added in the ordinary 
 manuring of the land, but both of which the plants may find difliculty 
 in obtaining. 
 
 d. Another consideration will indicate further sjyecial applications of 
 these several sulphates, independent of the sulphuric acid which they 
 in common contain. If we refer to the table (p. 220, ) in which is exhibit- 
 ed the constitution of the ash of the several clovers and grasses, we find 
 the constituents of our sulphates to be present in ]U0 parts of the ash in 
 tlie tbllowing proportions : — 
 
 Kye Grass . ^^^ Clover. ^'^^ Lucenie. Sainfoin. 
 
 Potash 8-81 19-95 31-05 13-40 20-57 
 
 Soda 3-94 5-29 5-79 G-15 4-37 
 
 Lime 7-34 27-80 23-48 48-31 21-95 
 
 Magnesia .... 0-90 3-33 3-05 3-48 2-88 
 
 Sulphuric Acid . . 3-53 4-47 3-53 4-04 3-41 
 
 Of the two clovers the red contains more lime and Tnuch less potash, 
 therefore the sulj)hate of lime is more likely to benefit the red clover, 
 and the sulphate of potash the white, which is consistent with the results 
 of experiment. A similar diirerence exists between lucerne and sainfoin, 
 to the former of which lime and soda are more necessary than the latter. 
 The first column under rye grass shows, on the other hand, how very 
 much smaller a proportion of all the four — potash, soda, lime, and mag- 
 nesia — is required by this green crop than by the others; and therefore 
 that the same weight of any one of these sulphates, which, when applied 
 as a top dressing to one crop (rye grass), would cause it to thrive luxuri- 
 antly, may be insufficient to su[)ply the most necessary wants of another 
 crop (clover or sainlljin.) Not only the kind of mineral manure, there- 
 fore, which we mix with the soil, but the c/uinlity also, must be deter- 
 mined by the kind of crop we intend to raise. (For the theoretical opinions 
 of other authors in regard to the action of gypsum, see Appetidix, No. VI.) 
 
 6°. ]\ Urates of Potash and Soda. — The efficacy of these two substan- 
 ces as manures in certain circumstances is now generally acknowledged, 
 
t'HET af'Pect thk growth or* the stem. 335 
 
 though the disappoiniaients whicli have ocasionally aitendeJ their use 
 uaturally cause the practical farmer to hesitate still, before lie applies 
 them ill any ijuantity to his laud. As these salts, especially the nitrate 
 of soda, are comparatively abundant in nature, — as they are really be- 
 neficial in many cases, and can be employed with a profit, — as their use 
 in practical agriculture has recently excited considerable interest — and 
 as many experiments have in consequence been made with them upon 
 various crops, — -I shall briefly direct your attention to the most impor- 
 tant facts which have yet been established in regard to their action upon 
 the growing i)laiit. 
 
 a. Apparent effects of the Nitrates. — The first visible effect of tlie ni- 
 trates upon every crop is to impart a dark green colour to the leaves and 
 stems. S"^. They then hasten, increase, and not unfrequently prolong 
 the growtli 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 of the crop. 4°. 
 The hay or grass produced is always more greedily eaten by the cattle 
 than that which has njt been dressed, even when the (juantiiy is not 
 affected ; — but the grain is usually of inferior quality, bringing a some- 
 what less |)rice in the in;irket, and yielding a smaller produce of flour. 
 
 Its principal action seems to be expended in promoting tlie growth^ 
 that is, increasing the production of woody fibre, either in the stem or the 
 car, without so much affecting, except indirectly, the quantity of seed. 
 
 Illustrations. — 1^. Mr. Pusey observed that the increase of his wheat 
 crop, on the Oxford clay, where nitrate of soda was applied, arose from 
 tliere being no underling straws with short ears as in the undressed, but 
 all were of equal length and consequent fullness and ripeness. The 
 nitrate had merely promoted the growth. (See Roval Agricultural Jour- 
 nal, II., p. 1-20.) 
 
 2°. "It affected the tops of the potatoes, but the produce of bulbs was 
 less both by weight and measure" (Mr. Grey, of Dilston). "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 forwardness, but when ripe, 
 though the straw was stronger, there was no difference in the croji of 
 peas" (Colonel Campbell, 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 Throckmor- 
 ton). In another experiment of Mr. Barclay's the straw was very strong, 
 and much of the wheat laid, but the undressed sold for 4s. 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 fibre. The inferior quality of the grain and 
 yield of flour was owing to this action. The grain was enveloped in a 
 thicker covering of the woody matter which forms the skin or bran. 
 
 3^. "The turnips afttir thf nitrated wheat are decidedly better, the tops 
 are still growing and luxuriant, while on the other part tliey are begin- 
 ing to fall" (Hon. H. Wilson). They seem, therefore, in some cases, at 
 least, to ))rolong the growth. 
 
 From the above statements we seem to derive an explanation why the 
 effects of the nitrate should have been so universally observed upon the 
 
336 
 
 EFFECT UPON THE aUANTITY OF THE CROl'. 
 
 grasses and clovers — while iti regard to its application to corn crops, 
 they indicate this important — 
 
 Practical Rule. — Not to apply the nitrates upon land or under cir- 
 cumstances where there is already a sufficient tendency to produce 
 straw. 
 
 6. Effects of the nitrates upon the auANTiTY of the crop. — Cases have 
 occurred where the nitrates liave tailed to produce any apparent effect 
 at all — others where the color was affected and the growth promoted 
 without any ultimate increase ofcrop — and others again, where the ap- 
 plication of these salts was decidedly injurious. These failures are de- 
 serving 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. 
 
 I. — Effect on Common and Clover Hay. 
 
 Locality. 
 
 Prorluce per acre. 
 
 Undreise.i. 
 
 Aske Hall, Earl of 
 Zetland 
 
 2 i; 
 
 At Erskine, Lord ( 2 Oj 
 Blantyre { 2 1 
 
 Barochan, Mr. ^ ^ ^ 
 Fleming 
 
 Dilston, Mr. Grey 
 
 Farnham, Suffolk 
 Mr. Muskett 
 
 Methven Castle, 
 Mr. Bishop 
 
 Quantity of Nitrate of Suda applie.I pfracre, 
 aiiJ nature of soil. 
 
 3 4 j 
 
 2 10 
 2 4i 
 
 2 19i \ 
 
 3 18 
 3 1^ 
 
 2 2 
 
 1 cwt., on a thin light soil, subsoil 
 clay upon limestone. 
 
 1 20 lbs., good light soil, subsoil gravel. 
 Do. clay soil on clay subsoil. 
 
 ifiOlbs., stiff clay, after wheat. 
 Do. light clay loam, drained, after 
 barlej'. 
 
 1 cwt., meadow hay, soil not stated. 
 
 150 lbs , clover hay, soil not stated. 
 
 1 cwt. nitrate of potash and H of ni- 
 trate of soda, had each the same ef- 
 fect on a heavy damp loam, partially 
 drained. 
 
 On the other liand, Mr. Barclay says that, on his heavy clay lands 
 (plastic clay), in Surrey, near the edge of the chalk, it is almost al- 
 ways a failure; and the Messrs. Drewitt, of Guildford, that on their 
 chalk soils, the additional produce of hay, whether on upland or mea- 
 dow, does not repay the expense. 
 
 
 
 II.— 
 
 On Barley. 
 
 Loca'i'y. 
 
 Produce. 
 
 Quantity per acre, and kind of soil. 
 
 Uiidres^wU 
 
 Dlcssed. 
 
 
 bsliU. 
 
 Sli,\w 
 cwt. 
 
 Grain. 
 
 Sti aw 
 
 
 
 cwl. 
 
 
 Surry, Mr.Barclay 
 
 44 J 
 
 i<H 
 
 55i 
 
 201 
 
 1 cwt., on light soil, with chalk subsoil. 
 
 Newton Hall, Nor- 
 
 i 
 
 
 
 
 
 thumberland, Mr. 
 
 [47 
 
 26 
 
 59 
 
 30 
 
 1 cwt., on strong turnip land. 
 
 Jobling 
 
 s 
 
 
 
 
 
 Suffolk, Hon. H. 
 Wilson 
 
 i- 
 
 - 
 
 32 
 
 -1 
 
 1 cwt., on a poor sandy soil, where 
 the turnips the preceding year were 
 nearly destroyed by the land blowing. 
 
 
EFFECT ON WINTER RYE AND OATS. 
 
 337 
 
 In Berkshire, on the other hand, it failed (1839), for barley on the 
 li^ht lands, causing thein in some cases to be burned up (Mr. Pusey), 
 but the season was droughty. 
 
 III. — On Winter Rye. 
 
 Mr. Fleminor, 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 . , 1 ton 7^ cwt. . . 2 tons, 19^ cwt. 
 
 IV. — Upon Oats. 
 
 Locality. 
 
 PRODUCE. 
 
 Gluantity per acre 
 
 Undressed. 
 
 Dressed. 
 
 
 
 
 
 
 and kind of soil. 
 
 
 grain. 
 
 straw. 
 
 grain. 
 
 straw. 
 
 
 bush. 
 
 cwt. 
 
 bush. 
 
 bush. 
 
 
 Bakewell Derbyshire, 
 
 
 
 
 
 
 Mr. Greaves . . . 
 
 48 i 
 
 25 f 
 
 6i 
 
 38f 
 
 1 cwt. ; heavy soil, 
 clay subsoil. 
 
 Court Farms, Hayes, 
 
 
 
 
 
 1 cwt. ; land satu- 
 
 Mr. Nncman . . . . 
 
 46 
 
 31 
 
 Wi 
 
 46i 
 
 rated with water, 
 and out of condi- 
 
 Leatherhead, Surrey, 
 
 
 
 
 
 tion. 
 
 Mr. Barclay .... 
 
 40 
 
 61 
 
 60 
 
 90 
 
 1 cwt.; a loam con- 
 taining flints, on a 
 subsoil of chalk. 
 
 Mr. Everett, in Norfolk, obtained an increase of 15 bushels per acre, 
 by the use off cwt. per acre ; and Mr. Calvert, of Ockley Court, of 20 
 bushels of grain, and 9i cwt. of straw, by applying IJ cwt. of nitrate 
 of soda. At Kirkleatham (Nortli Yorkshire), it had an excellent effect 
 upon oats, on strong land — and on the strong clays of the Weald of Sur- 
 rey 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 303. per acre. "When it has failed, the nurate 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. 
 
 In most cases, therefore, the nitrate of soda seems capable of pro- 
 ducing 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 peculiarities in 
 the physical condition or chemical constitution of the soils on which they 
 were observed. 
 
 15 
 
 i 
 
338 
 
 EFFECT OF THE NITRATES ON WHEAT. 
 
 V. — On Wheat. 
 
 Locality. 
 
 Undressed. Dressed. 
 
 Farnliam, Suffolk, I 
 Mr. Muskett, . \ 
 
 Painswick, Glou- \ 
 cesler, Mr. Ht/cU, ji 
 
 Fairford Park, do. ) 
 Mr. Raym. Darker \ 
 Mr.Dufrdale, . , 
 
 Do. 
 
 CourtFarm, Hayes ) 
 
 Mr. Newman, . \ 
 Brandon, Suffolk, i 
 
 Ho7i. Mr. Wilson, \ 
 Surrey, Mr. Bar- \ 
 
 day, ( 
 
 Faringdon, 3Ir. I 
 
 Pusey, . . , . < 
 
 Ockley Court, Mr. ( 
 Calvert, . . .\ 
 
 Newton Hall, Mr. \ 
 Jobling, . . .\ 
 
 Cirencester, Dr. 
 Daribeny, . . . 
 
 Rozelle, near Ayr, 
 Col. Cavipbell, . 
 
 18J 
 33i 
 
 26 I 
 
 42 1 
 
 32 
 
 14? 
 
 27* 
 
 30 i 
 
 33 f 
 
 31 
 
 27 
 
 2l| 
 
 20i 
 
 33 
 
 35 
 
 .wt 
 
 baahlF 
 
 — 
 
 27 
 43 J 
 
 15 
 
 33i 
 
 34 
 
 54 
 
 
 36i 
 
 18i 
 
 20 
 
 32 
 
 — 3G 
 
 20 
 241 
 
 24 i 
 2()i 
 20 i- 
 
 25| 
 
 39Aj 
 
 39*1 
 2o 
 
 24. 
 
 452 1 
 
 29i 36 
 16 3U 
 
 3u' 47 
 i 42 
 
 21 
 
 38i 
 
 25i 
 
 23 
 
 271 
 34* 
 
 25* 
 24'- 
 
 37i 
 
 Quantity per acre, and kind of goil. 
 
 U cwt. ; a poor spongy sandy soii. 
 
 I cwt. ; a stone-brash soil abounding 
 in carbonate of lime. 
 
 1 cwt. ; on a light stone-brash poor 
 thin soil. 
 
 1 cwt. nitr. of soda, on a. gravelly soil ; 
 an equal weight nilratf. of potash pi-o- 
 duced only \ bushel of increase (1). 
 
 I cwt. nit. of soda on a strong clay. 
 Both portions previously limed. 
 
 1 cwt.; on a very thin crop, inj'd by an 
 unfavorable autumn. Soil not stated, 
 
 I cwt. ; on a fair light soil. 
 
 Do., loamy, better land. 
 
 I cwt. ; soil loamy, resting on chalk, 
 straw strong,and much wheat laid.* 
 
 Do. on heavy soil, resting on the Ox- 
 ford clay. J3iitall these very different 
 rcsul/s were oblaincd in the same field. 
 
 Do.; corn generally laid; soil not 
 mentioned. 
 
 35*|l cwt.; soil not mentioned. 
 20*4 cwt. nitrate of potash. 
 15* Do. nitrate of soda, soil and subsoil 
 clay, resting on the corn-brash. 
 180 lbs. nitrate of soda. 
 76 Do. nit, of potash. Soil not stated.t 
 
 VI. — On Turnips. 
 
 At Rozelle the Swedes were improved several tons an acre by the 
 use of the nitrate of soda (Mr. Campbell). At Dorking it was very be- 
 neficial as a top-dressing lo the Swedes and white turnips, when so\vn 
 hroad-cast at the rate of IJ cwt. per acre (Mr. Dewdney). In neither 
 of these cases is the soil described. On thin stony land upon chalk at 
 F-lrashurst, Bucks, turnips manured with nitrate alone, were very su- 
 perior to those to which 10 loads an acre of farm-yard manure had been 
 applied (Mr. Burgess). The only numerical results with which 1 am 
 acquainted are those of Mr. Barclay on a loamy soil resting on chalk. 
 His crop of turnips was 
 
 ' Ttie 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. 
 
 t The produce of straw, especially from saltpetre, is very surprising. It is stated at 519 
 and 764 stones for the two lots respectively. 1 suppose the acres to be Scotch, and the 
 etones 11 lbs. 
 
EFFKCT UPON TURNIPS, AND THK QUALITY OF THE CROP. 339 
 
 30i cwt. when dressed with bones and wood ashes, each 15 bushels. 
 31 cwt. wFien dressed with 1 cwt. of nitrate of soda, drilled in. 
 35 cwt. when seed and nitrate were both broad-cast. 
 38 cwi. when the seed was drilled and the nitrate broad-cast. 
 
 On the other hand, Lord Zetland thought it did no good to turnips ; 
 Mr. Vansittart, that on strong laud well dunged it did harm ; and the 
 Messrs. Drevvitt, tliat on their dry rubbl^' chalk it had no effect on this 
 crop, though it improved in a remarkable degree the succeeding crop 
 of barley. 
 
 We are obviously in want of more numerous and better observations, 
 especially in regard to turnips. The above discordancies will either 
 vanish when we obtain a 2 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 position of the locality in 
 which each experiment is made. Those practical men who are really 
 desirous of aiding the ])rogress of scientific agriculture, — by which pro- 
 gress not only the national welfare, but their own individual interests 
 also are likely to be promoted, — will do more towards this end by one 
 single experiment in whii'h weights and measures are carefully deter- 
 mined, and the soil, the climate, the geological position and the lie of 
 the land, accurately described, tlian by any number of mere general 
 sfatcnients, such as those I have here laid before you in regard to the 
 effect of ifie nitrates u])on the turnip cro]>. 
 
 c. Effect, of (he nitrates on the quality of the crop. — This I have 
 already in some measure alluded to. Jt so affects the grass and clover 
 as to make it more relished by the cattle. Tliis is 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 generally also gives a grain (of wheat) 
 of an inferior quality — which has a thicker skin, and yields more bran. 
 This may ]>os-;iljlv arise from its having been generally allowed to ripen 
 too long. [See Mr. John Hannam's valuable experiments on the 
 orcr-ripening of corn in the Quarterly Journal of Agricultnre.] A 
 ijuestion still undetermined is, whether the flour of nitrated corn is more 
 nutritive than that obtained from corn which has been undressed. 
 
 It is generally sujiposed that those samples of flour which contain the 
 most gluten are also the most nutritive. But hitherto the only experi- 
 ments which liave been made with the view of determining the relative 
 (juantities of gluten in samples of grain from the same field, one ]ior- 
 lion of which had been nitrated, and the other not, are, one made by 
 Mr. Daubeny, and one reported by Mr. Hyett, to the latter of which 1 
 liave already had occasion, for another purpose, to direct your attention. 
 [8ce note, p. 1G7.] 
 
 In these experiments the flour of the several wheats gave — 
 
 In Dr. Daiitieiiy's In Mr. Ilyett's 
 
 Experiment. Experiment. 
 
 Nitrated 15 per cent, of gliuen 23| per cent. 
 
 Unnitrated 13 per cent, of gluten 19 per cent. 
 
 Excess of gluten in the nitrated, 2 per cent. 4j per cent. 
 
340 AFTEK-EFl'ECTS OF THE NITRATES. 
 
 both of which results favour the supposition that one etTect of the ni- 
 trates upon the quality of the grain is to increase the proportion of gluten, 
 and thus to render them, as is generally believed, more nutritive. This 
 is a result which theoretically we might be led to anticii)ate, were there 
 no large increase in the cpiantity of tiie produce — for then we might 
 naturally expect the nitrogen of the nitric acid to be expended solely in 
 enriching the grain with gluten. But the increase of crop contains in 
 many cases more nitrogen than we add to the soil when we dress it with 
 one cwt. of nitrate of soda per acre; there is, therefore, no excess of ni- 
 trogen 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 prove the flour from 
 nitrated grain to be always richer in gluten, and, therefore, more nutri- 
 tious. At all events increased experiments are to be wislied for. 
 
 d. After-effects of these nitrates. — It is comparatively seldom that 
 any good effects have been observed upon the crop which succeeds that 
 to which tlie nitrate of soda has been applied. Where ihey have been 
 noticed it has been cliiefly in cases where from some cause (drought or 
 dryness of soil ctiielly) the salt has been prevented from exerting its full 
 and legitimate action upon its first application. Thus, 
 
 1°. Failing to improve turnips on a rubbly chalk soil, it greatly be- 
 nefitted tlie succeeding crop of barley (Mr. Drewitf, Guildford, Surrey). 
 
 Producing little effect on tares (upon a clay soil ?) it improved very 
 much theturnipcrop which followed (Mr. Barclay, Leatherhead. Surrey.) 
 
 2°. In the following instances the benefit was seen on successive 
 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 fol- 
 lowing 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.) 
 
 At Upleathain, the second cut of clover was nearly as much im- 
 proved as the first (Mr. Vansittart), and at Dilston the aftermath li-jy 
 was greater in quantity, and better relished by the cattle (Mr. Grey). 
 
 3°. A curious effect is noted by Mr. Rodwell, of Alderton, Wood- 
 bridge — the white clover failed after barley on lohich nitrate had been 
 used ! \ 
 
 The solubility of these nitrates is so great, that in our climate, in sea- 
 sons of ordinary rain, and on lands having a moderate degree of incli- 
 nation, we should expect that they would be in a great measure wa'^hed 
 out of the lantl in a single year. Hence one reason — even supposing 
 little of the salt to have entered into the roots of the growing crop — 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 being all taken up by the roots, 
 or washed away by the rains during one year, and we may then look 
 for after-effects, such as those above described. 
 
 e. Circumstances necessary to ensure the success of these saline ma- 
 nures. — This explanation will appear more satisfactory if we glance for 
 
THKIR ACTION AFFECTED BY CIRCUMSTANCES. 341 
 
 a moment at the general conditions which are necessary to ensure the 
 success of these or any other saline manures. 
 
 1°. They must contain one or more substances which are necessary 
 to the growth of the plant. 
 
 2°. The soil must be more or less deficient in these substances. 
 
 3^. The weather must prove so moist or the soil be so springy as to 
 admit of their being dissolved, and conveyed to the roots. 
 
 4°. 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. 
 
 5°. The soil must be sufficiently light to permit the salt easily to 
 ])enetrate to the roots, and yet not so open as to allow it to be readily 
 washed away by the rains. In reference to this point the nature of the 
 subsoil is of uiuch importance. A retentive subsoil will prevent the 
 total escape of that wluch 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. 
 
 f. Cases in which the nitrates have failed. — A knowledge of the 
 above conditions will enable us in many cases to explain why the ni- 
 trates, and other generally useful substances, have failed to exhibit any 
 beneficial e.Ttct. 
 
 1'^. 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 hin- 
 der its action altogether Jbr the time, — or it may retard the solution till 
 tlie plant has attained such a state of maturity, that it is no longer ca- 
 pable of being equally benefitted by the introduction of the salt into its 
 roots — or after being dissolved, and having partially descended into the 
 soil, the drought may cause it to ascend again with the water which 
 rises to the surface 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 portion of the salt has already been conveyed by the roots, may be so 
 powerful as to concentrate the saline solution, or to increase its decom- 
 position to such an extent as to cause injury, and consequent blight to 
 the leaf itself. 
 
 2^. Again, a*. Cheadale, in Cheshire, (Mr. Austin), the nitrate of soda 
 is said to have had a good effect on wheat and gras.s where the subsoil 
 was clay, but none where the subsoil was gravel, or the soil light and 
 sandy. Here the supplv of water in the soil may have been such as to 
 fit it for entering readily into the roots in a ])roper state of dilution, when 
 the retentive subsoil kept it within reach of the roc^ts, — and yet sufficient, 
 at the same time, to wash it away altogether where the soil and sub- 
 soil were too open to be able to retard its passage. 
 
 3^. But the occasional occurrence of droughts or the mere physical 
 distinctions of lands as light or heavy, are not sufficient to account for all 
 the recorded differences in the effect of the nitrates. Thus on the clava 
 
342 WIIKX TIIK U3K OF NITRATES IS liKNEFICIAt. 
 
 of the Weald in Sussex (Mr. Dewdney), and on the Oxford clay in 
 Berkshire (Mi. Pnsey), the use of the nitrate has heen attended with 
 general benelit upon oats and wheat, while on the plastic clay in Sur- 
 rey (Rlr. Barclay), it has been unilbrmly unsuccessful. The cause of 
 these ditTerences is to be sought for, most probably, in the chemical con- 
 siitution of the several clays, which are knowu to be very unlike. Tiie 
 Weald clay is a fresh-water formation, contains much fine grained 
 siliceous matter (page 244), and is, therefore, comparatively per- 
 vious to water. The Oxford clay soils in Berkshire abound in lime, 
 and must, therefore, be in some degree pervious, while the ])lastic clay 
 of Surrey, where they are stirtest, contain little lime and partake moie 
 of the impervious character of pipe clays. It may possibly be in such 
 differences as these that we are to find an explanation of the discordant 
 results of different experimenters, but mucli further observation is still 
 wanting before we can sjjcak with any degree of confidence upon the 
 subject. 
 
 To some an explanation may appear to be most easily given by sup- 
 ])0sing the one soil to have been rich in soda, while the other was de- 
 fective in this substance. I shall advert to this point iu explaining the 
 theory of the action of the nitrates of jiotash and soda. 
 
 ,"•. Circumstances in which the employment of the nitrates is most bene- 
 ficial. — 1°. It a[)pears 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 liis cattle, is 
 during the earliest stage of its growfli. If it coine 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 ex- 
 cited. 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 lo 
 the experiments of Mr. Barclay, it is most advantageous when sown 
 Droad-cast.* 
 
 2°. Whatever may he 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 enougli to allow it readily to 
 descend, and yet the subsoil sufficiently retentive to prevent it from 
 being readily washed away. 
 
 3°. I throw it out as a suggestion which lias 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 pre- 
 sence of lime in the soil may tend to insure the success of the nitrate. 
 In many of the instances of large crops uhtained by its aid the land was 
 either i.aturally rich in lime, or it had, in the ordinary course of hus- 
 bandry, been previously marled or limed. 
 
 h. Theory of the action of the nitrates. — The nitric acid of these salts 
 
 ' A valiiaMe prorppt also b. tn prorecd cautiously in Uie use of these expensive Bub- 
 Stanros — making small tiiajs at ti^Bt, and ijic reasint; llie qiiantilios employect as success 
 may warrant. Ry thia mode of procedure, large loases, of v.'hicli I have heani, would 
 have been avoided. 
 
THKORY Of THK ACTION OK THE MTRATKS. ,143 
 
 contains 26 per cent, of its weiglil of nitrogen — or one cwt. of pure dry 
 nitrate of soda contains about 19 lbs. of nitrogen. Tliis nitrogen we 
 know to be a necessary constiiuont of plants — one which they obtain 
 almost wliolly from the soil — but which nevertheless is generally pre- 
 sent in the soil in small quantity only. We have already seen reason 
 (Lee. VIII., p. 159,) to believe that nitric 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, therefore, 
 we only aid nature in su})plyiiig a compound bv which vegetables are 
 usually sustained. And as the young plant will necessarily languish 
 in the absence of one essential kind of food, although every other kind 
 it may require be present in abundance, it is easy to see how the 
 growtli of a crop — languidly proceeding upon a soil deficient in niti^ogen 
 — 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 obseivation that it is in the poorest soils that they 
 are most useful to the husbandman. 
 
 We have already seen, also, that one function of the leaf in the pre- 
 sence of the sun is to decompose carbonic acid, and give off its oxygen 
 (Lee. v., sec. 5.) It exerts a sitiiilar action upon the nitric acid of the 
 nitrates, and upon the sulphuric acid of the sulphates, discharging iheir 
 oxygen into the air, and thus leaving the nitrogen and sulphur at liberty 
 to unite with tiie other elementary substances contained in the sap — for 
 the ))roduction of the several compounds of which the parts of the 
 growing plant consist. 
 
 Nor, as shown in a previous lecture, (Vllt., sec. 8,) 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, the more 
 numerous and extended become its roots also, and these roots are thus 
 enabled to gather from the deeper and more distant soil those supplies 
 of nitrogenous and other necessary food, which would have remained 
 beyond their reach had the plant been allowed to remain in its pre- 
 viously feeble or more languid condition. This has been called the 
 stimulating etFect of manures, and some substances have been said to 
 act only'iu this way upon vegetation. This, however, appears to me to 
 be a mistake. The supposed stimulating is always a secondary effijct, 
 and necessarily follows from the use o^ every kind of manure, which by 
 feeding the plant gives it greater strength, and thus enables it to appro- 
 priate other supplies of food which were previously beyond its reach, or 
 which from the absence of one necessary constituent it could not render 
 available to its natural growth. 
 
 In this way the nitrates act as such — in contra-distinclion to the sul- 
 phates and ofher salts of |)otash and soda. But there is every reason to 
 believe that the potash and soda themselves often aid the effect of the 
 nitric acid with which they are associated. In soils deficient in these 
 alkalies the nitrates would act beneficially, even though nitric acid 
 
344 COMPARATIVE EFFECTS OF THKSE TWO NITRATES. 
 
 were already present in abundance, — while, on the other hand, a field 
 that is defective in both consfituenis of the salt (nitric acid and potash 
 or soda), will be more grateful for the same addition of it than one 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 
 especially when the soils are different, may occasionally be explained. 
 
 i. Special effects of the nitrates of potash and soda. — On this alka- 
 line constituent of the two nitraies will depend the special action of each 
 when applied to the same soil under the same circumstances. It has 
 not yet been clearly mride out that any definite special action can be 
 ascribed to thetn, yet some exjieriments bearing 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. 
 
 1°. At Rozelle, near Ayr (1840), nitrate of potash caused oats to 
 come away darker and stronger, and give a heavy crop, Avhile in the 
 same field nitrate of soda produced no benefit. The soil was inferior, 
 liglit, and sandy, with a red irony subsoil (Capt. Hamilton). It is add- 
 ed that the crop was injured by the early drought, from which it never 
 recovered. This fact renders the special efTect of the nitrate of potash 
 in tliis case doubtful. 
 
 2°. In the experiments upon wheat, made by the same gentleman 
 on the same farm, — it is to be presumed \i\mn a similar soil, — 
 
 Nitrate of soda gave . . 46 bush, grain, and 52 cwt. straw ; 
 
 Nitrate of potash gave . . 42 bush, grain, and 76 cwt. straw ; 
 
 the produce of straw being here also greatly in favour of the potash salf. 
 
 3^. Dr. Daubeny also, in the experiment upon wheat above detailed, 
 found the nitrate of potash to increase the produce considerably, while 
 the nitrate of soda caused no increase whatever. The soil was stilFclay 
 upon the corn-brash. 
 
 These superior effects of the potash salt may certainly be ascribed to 
 the greater deficiency of the several soils in potash than in soda, a sup- 
 position which in the case of the Rozelle experiment is consistent with 
 the fact, that common salt, when tried upon the same land, produced 
 nogood effecl. If however, as some suppose, (p. 328), potash and soda 
 are capable of re-placing each other in the living vegetable without ma- 
 terially affecting its growth, this explanation cannot be the true one. 
 Further experiments, however, if carefully conducted, will not fail to 
 clear up this question. 
 
 4°. On a gravelly soil Mr. Dugdale obtained an increase of 12 bush- 
 els of wheat by the use of nitrate of soda, while nitrate of potash in- 
 creased the crop by only half a bushel. 
 
 This result maij be explained after the same manner as the preceding 
 — the soil may have already abounded in potash. 
 
 6°. In Perthshire, upon a moist loam, Mr. Bishop obtained an equal 
 increase of hay from the use of both nitrates; each having caused the 
 production of a double crop. 
 
 The equality iu this case may have risen from the efl^ects being 
 wholly due to the nitric acid, both potash and soda being already abun- 
 dant in the soil. This is consistent with the situation of the locality in 
 
OSE OF COMMON SALT AS A MANURE. 
 
 345 
 
 a graniie countrj', and is further supj>orted by the fact, that on the same 
 S(iil and field, aminoniacal liquor, which contains no alliali, produced a 
 still lar;jer increase of produce. 
 
 You will understand, however, that all these attempted explanations 
 proceed upon the supposition that the experiments have been both 
 carefully made and faithfull}' recorded. 
 
 7°. 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 gene- 
 ral estimation from the unqualified terms in which its merits have been 
 occasionall}^ extolled. About a century ago (1748J, Brownrigg* main- 
 tained 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 
 renoininended in terms of almost equal praise. But these warm re- 
 commendations have led sanguine men to make large trials, which 
 have occasionally ended in disappointment, and hence the use of salt 
 hn^ repeatedly fallen into undeserved neglect. 
 
 It is certain that common salt has in very many cases been advanta- 
 geous to the growing crop. Some of the more carefull}' observed re- 
 sults which have hitherto been published, are contained in the follow- 
 iti: table : 
 
 Locality. 
 
 UPON WHEAT. 
 
 Mr. G. Sinclair ' 
 
 Produce per acre. 
 Unsalted.i Salted. 
 
 Great Totham, Essex, 
 Mr. Culh. Johnson 
 
 Barochan, Paisley, 
 Mr. Flcniins 
 
 
 ON BARLEY. 
 
 Suffolk, Mr. Ransom. 
 
 ON HAY. 
 
 At Aske Hall, near 
 Richmond 
 
 At Erskine, near Ren- 
 frew 
 
 Quantity applied per acre, and kind of soil. 
 
 buslieis. 
 Kii 
 lis 
 16 
 
 12 
 
 13i 
 25 
 
 30 
 
 2 10 
 
 busliels. 
 
 22i 
 21 
 I7f 
 23i 
 
 28i 
 28i 
 
 261 
 32 
 
 11 bushels, after barley. 
 
 6i do., af.er beans. 
 
 Do. sown with the seed, ) after 
 Do. dug in with the seed, \ peas. 
 
 bh do. > appied before sowing, after 
 
 11 do. ) turnips. 
 
 5 bushels, light gravelly soil. 
 
 160 lbs., heavy loam, after potatoes. 
 
 51 
 
 16 bushels. 
 
 6 bushels, thin light soil, clay subsoil. 
 
 5 bushels, light soil on gravel. 
 iDo., clay soil on clay. 
 
 But it is as certain that in many cases, when applied to the land, 
 coinmon salt has failed to produce any sensible improvement of the 
 growing crop. And as failures are long remembered, and more gene- 
 rally made known than successful experiments, the fact of their fre- 
 quent occurrence has prevented the use of salt in many cases where it 
 might have been the means of much good. 
 
 " On the art of maktrig common sail, p. 158 (I,ondon, 1748). 
 15* 
 
346 CAUSES OF THK FAILURE OF COMMON SALT. 
 
 Cause of these failures. — 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. 
 
 1°. We know that plants require for their sustenance and growth a 
 certain supply of eacii of the constituents of common salt, which supply, 
 in general, they must obtain from the soil. If the soil in any field 
 contain naturally a sufficient quantity of common salt — or of chlorins 
 and soda, in any other state of combination — it will be unnecessary to 
 add this substance, or, if added, it v.'ill 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. 
 
 Now there are certain localities in which we can say beforehand 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 pre- 
 vailing 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 in the 
 air, from which it descends afterwards in the rains.* This considera- 
 tion, therefore, affords us the important practical rule in regard to the 
 application of common salt — lliat it is most likebj 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 localities 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 moreconfiilence in making 
 trial of its effects on inland situations. It is very desirable that the 
 value of this practical rule, which I suggested to you in a former lec- 
 ture (see p. 190), should be put to a rigorous tesl.f 
 
 2°. But some plants are more likely to be benefitted by the applica- 
 tion of common salt tlian 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 naturally impregnated 
 with much saline matter. Observations are still wanting to show which 
 of our cultivated crops is most favoured by common salt. It is known, 
 however, that the gas 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 
 also said that the long tussack grass which covers the Falkland Islands, 
 
 ' Dr. Madden has calculaterl that the quantity of rain whii-h falls at I'eniciiick in a ynr, 
 brings down npon each acre of land in lliat neighborhood more than OUO lbs. weijiht of com- 
 mon salt. This would be an enormoii.q dressina; were it all lo remain upon the hnd. 
 Heavy rains, however, probably carry otf more from the soil than they imparl lo it. It is 
 the gentle showers that most enrich the fields with the saline and other matters tliey con- 
 tain. 
 
 t A number of failures are described in the sixth volume of Ihe "■ TransactioJis nf t/ie 
 Highland and As^ricullural Society." Dr. Mailden has recently shown tliat to nearly all 
 these cases the above principle applies — Uie farms on which they were tried heinj more or 
 less freely e.xposed to the winds from the east or west sea. — Quarterly Journal of Agri- 
 culture, Sept. 1842, p. 574. 
 
.? 
 
 WHEN APPLIED AS A MANURE. 347 
 
 luxuriates most when it is within the immediate reach of the driving 
 spray of the southern sea. It may well be, therefore, that among our 
 cultivated crops one may delight more in common salt than another, — 
 and if we consider how much alkaline matter is contained in the tops 
 and bulbs of the turnip and the potatoe, we are almost justified in con- 
 cluding that generally common salt will benefit green crops more than 
 crops of corn, and that it will promote more the developement of the ; 
 leaf and stem than the filling of the ear. j 
 
 If this be so, we can readily understand how a soil may already con- 
 tain abundance of salt to supply with ease the wants of one crop, and 
 yet too Utile to meet readily the demands of another crop. The appli- 
 cation of salt to such a soil will prove a failure or otherwise, according 
 to the kind of crop we wish to raise. 
 
 3^. Failures have sometimes been experienced also on repeating the 
 application of salt to fields on which its first eflt^cts were very favour- 
 able. In such cases it may be presumed that the land has been already 
 supplied will) salt, sufficient ])erhaps for many years' consumption,— 
 and that it now re(iuircs the application of some other substance. 
 
 If it be desired, experimentally, to ascertain whether the land already 
 contains a sufficient supi>ly of common salt, the readiest method is to 
 collect half a pound of the soil in dry weather, to wash it well with a 
 j)int or two of cold distilled water, and then lo 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 nitrate of silver (common lunar-caus- 
 tic of the shops) will throw down a white precipitate, becoming purple 
 in the sun, which will he more or less copious according to the quantity 
 of salt in the soil. If this precipitate be collected, dried in an oven, 
 and weislied, every 10 grains will indicate very nearly the presence of 
 4 grains of common salt. The (piantity of this precipitate to be expect- 
 ed, even from a soil rich in common salt, is, however, very small. If 
 half a pound of the dry soil yield a single grain of salt, an acre should 
 contain about 1000 lbs. of salt where the soil is 12 inches deep — where 
 it has depth of only 6 inches, it will contain nearly 500 lbs. in every 
 acre. 
 
 8°. Chlorides of Calcium and Mas,nesium. — These compounds are 
 rejected in large quantities as a refuse in some of our chemical manu- 
 factories — and they are contained, especiall}' the latter, in considerable 
 abundance in the refuse liquor of our salt pans. They have both been 
 shown to be useful to vegetation (see Appendix), and where they are 
 easily to be obtained, they are deserving of further trials. Like com- 
 mon salt, it is generally in inland situations that they are fitte^d to be 
 the most useful. Where salt springs are found in the interior of Ger- 
 many, the refuse obtained by boiling down the mother liquors after the 
 separation of the salt has been often ap[)lied with advantage to the land. 
 
 Theory of the action of these chlorides. — Common salt and the chlo- 
 rides of calcium 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 
 (Leo. v., § 5)," that the green leaves under the influence of the sun, 
 have, the power of decomposing common salt — and no doubt the other 
 
348 PHOspHATi: or LiaiE and earth of sokes. 
 
 chlorides also — and of giving ofl' their chlorine into the surrounding air. 
 When they have been introduced into the sap therefore, by the roots, the 
 plant first appropriates so much of the ciilorine they contain as is neces- 
 sary for the supply of its natural wants, and evolves tlie 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 1 have already explained to you 
 (p. 328) when illustrating the probable action of potash and soda upon 
 the vegetable economy. When the other chlorides (of calcium or mag- 
 nesium) 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 employed indirecll}' in promoting the chemical 
 changes that are continually going on in the sap. The living plant, 
 Avhen in a healthy state, is probably endowed with the power of admit- 
 ting into its circulation, and of then decomposing and retaining, so much 
 only of these several clilorides, 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 the presence of organic matter of animal and 
 vegetable origin, comnjon salt is fitted to promote certain chemical 
 changes, such as the production of alkaline nitrates — and probably sili- 
 cates — by which the growth of various kinds of plants is in a greater 
 or less degree increased. In the soil, also, from thek tendency to deli- 
 quesce, or run into a liciuid, all these chlorides attract water frc;m 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 extirpa- 
 tion of weeds, and for the destruction of grubs and other vermin that 
 infest the land. 
 
 9°. Phosphate of Lime and Earth of Boves. — The cattle that graze 
 in our fields derive, as you know, all the earthy materials of which cer- 
 tain parts of their bodies consist from the vegetables on whicli they feed. 
 These vegetahles again must derive them from the soil. Thus the 
 earth of bones, or the ])hosphoric acid and lime of which it consists 
 (p. 196), must exist in the soil on wliich nutritive plants grov/, and it 
 must occasionally occur that a soil will be deficient in these substances, 
 and will, therefore, supply them with difficulty to the crops it rears. 
 The benefit which in this country is so often experienced from the use 
 of bones as a manure, has been ascribed, iv part, to the supjily of bone- 
 earth, with which it enriclies the land. (See Apjicndix, No. I.) It 
 is not, however, to be inferred from this, that wherever bcnes are use- 
 ful, the application of bone-earth alone — in the form of burned bones, 
 or of the native phosphate of lime, (p. 199,) will necessarily prove 
 advantageous also. Burned bones were formerly employed in Eng- 
 land, but the practice has gradually fallen into Misuse, and the same is, 
 I believe, the case in Germany. This is no proof, however, that the 
 native phosphate of Estremadura — already, it is said, imported in'o 
 Ireland for agricultural purposes, — would not benefit many soils if ap- 
 plied in the state of a sufficiently fine powder. Until carefully con- 
 ducted experiments, however, shall have been made, and the numerical 
 
USK OF SULPHATE OF AMMONIA. 349 
 
 results precisely ascertained, it would be improper to incur mucli risk 
 either in bringing this substance to our shores or in applying it to our 
 fields. 
 
 10°. Silicates of Potash and Soda. — These compounds, which have 
 been already described (p. 206), are supposed lo act an important 
 I)art in tlie growtli oC the grasses, and of the corn-bearing plants, by 
 supplying, in a soluble state to the roots, the silica whicli is so necessary 
 to the strength of their stems. This supposition has been strengthened 
 by the results of some experiments made by Lampadins, wlio found a 
 solution of siUcate of potash to produce remarkable etlects upon Indian 
 corn and upon rye. {Lclire von den mineralischen Diing7nitteln, p. 25, 
 1833.) It is possible to manufacture then:i at a cheap rate, and it would 
 be desirable to ascertain by further trials how far the employment of 
 these compounds, as artificial manures, can be safely recommended or 
 adopted with the hope of remimeratiou.* 
 
 11°. Sails of Amnionia. — Tliere is reason tobelieve that ammonia in 
 every state of combination is fitted, in a greater or less degree, to pro- 
 mote the growtii of cultivated plants. None of its compounds, how- 
 ever, are known to occur anywhere in nature in such quantity as to l)e 
 directly available in f)ractical 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. 
 
 a. Sulphate of Ammonia. — An impure sulphate is manufactured by 
 adding sidphuric acid to fermented urine, or to the amraoniacal liquor 
 of the gas works, and evaporating to dryness. When prepared from 
 urine, it cf)ntains a mixture of those phosphates 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 these economical forms tliis 
 salt has been found to promote vegetation ; but accurate experiments 
 are yet wanting to show in what way it acts — whether in promoting tlie 
 growth of the green parts or in filling the ear, or in both — to what kind 
 of crops it may be applied witli the greatest advantage — and what 
 amount of increase may be expected from the application of a given 
 weight of the salt. It is from the rigorous determination of such points 
 that the practical farmer will be able to deduce the soundest practical 
 precepts, and at the same time to assist most in the advancement of 
 theoretical asiricnllure. 
 
 The crystallized sulphate of ammonia is soluble in its own weight of 
 water. 100 lbs. contain about 35 lbs. of ammonia, 53 lbs. of acid, and 
 12 lbs. of water. It may be applied at the rate cf froin 30 lbs. to 60 lbs. 
 per acre. 
 
 b. Sal-Ammortiac or Muriate of Ammonia. — This salt, in the pure 
 state in wliich it is sold in the shops, is too high in price to be economi- 
 cally employed by the practical farmer. An imyjure salt might, how- 
 ever, be prepared from the gas liquor, which could be sold at a sufficiently 
 
 ' I have bfen informed by Dr. riayfair that a number of experiments with a soluble 
 silicate of soitu, manufactured at Manchester, have this summer (18-12) been made at bis 
 eusgestion, tlie results of wtilch will, no doubt, prove very interesting. 
 
350 SAL-AMMONIAC AND CARBONATE OF AMMONIA. 
 
 cheap rate to admit of an extensive application to the land.* The only 
 numerical results from the use of this salt with which I am acquainted, 
 are those given by Mr. Fleming, who applied it at (he rate of 20 lbs. 
 per acre to wheat on a heavy loam, and to winter rye, on a tilly clay, 
 both after potatoes, and obtained the following increase of produce per 
 
 acre : — 
 
 Grain. Straw. 
 
 E-TE, vmdres.sed . 14 bushels 36^ cwt. 
 
 Do. dressed . . 19 do. 43l do. 
 
 Increase ... 5 bushels. 7 cwt. 
 
 Wheat, undressed 25 bushels, each 61 lbs. 
 Do. dressed . 264 bushels, each 62 lbs. 
 
 Increase , . . 1| bu.shels. 
 
 The increase of these experiments was not very large, but the quan- 
 tity of sal-ammoniac employed was probably not great enough to pro- 
 duce a decided etfect. It is a valuable fact forthe farmer, however, and 
 not uninteresting in a theoretical point of view, that a part of the same 
 wheat field, dressed with Ij cwt. of common salt per acre, gave a pro- 
 duce of 40 bushels of grain (see Appendix, p. 19.) 
 
 c. Carbonate of Ammonia — is obtained in an impure form by the dis- 
 tillation of horns, hoofs, an i even bones. In this impure form it is not 
 generally l)rought into the market, but in this state it might possibly be 
 atibrded at so low a price as to place it within the reacli of the practical 
 farmer. It is supposed by some that this carbonate is too volatile — or 
 rises too readily in the forin of vapour — to be economically a|)plied 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, it may be safely recommended where 
 it can be cheaply procured. 
 
 d. Ammoniacal Liquor. — This is proved by the success which has in 
 many localities been foimd to attend the application of tlie ammoniacal 
 liquor of the gas works. This liquid holds in solution a variable quan- 
 tity of sulphate of ammonia and sal-ammoniac,f but in general it is 
 richest in the carbonate of ammonia. 
 
 The strength of the liquor varies in dilTerent gas works; chiefly ac- 
 cording to the kind of coal employed for the manufacture of the gas. 
 One hundred gallons may contain from 20 lbs. to 40 lbs. of ammonia, 
 in one or other of the above states of combination. No precise rule, 
 therefore, can he 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 applied 
 
 ' ny mixins, for example, the waste muriatic acid, or the waste cliloricle of calcium, 
 with gas liquor, ami evaporating the mixture to dryness. 
 
 t 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 VVigan is employed. 
 
SPECIAL ACTION OF THE SULPHATE AND NITRATE. 351 
 
 105 galloT^s an acre, diluted with 500 gallons of water, and obtained, of 
 hay, from the 
 
 Undressed ... j^ lb. per square yard, or 20^ cwt. per acre. 
 
 Dressed .... Ij lb. do. or 61i cwt. do. 
 
 Increase ... 1 lb. do. or 41 cwt.* do. 
 
 The increase lierh is so very great that further trials with this liquor- 
 hitherto, in most country towns at least, allowed to run to waste — can- 
 not be too strongly recommended. On the dressed part, according to 
 Mr. Bishop, the Timothj' grass was particularly luxuriant. 
 
 These experiments with the gas liquor show, as I have said, that im- 
 pure carbonate of anmionia may be safely applied to the land without 
 any previous jjreparation. If it is wished, however, to fix it or to ren- 
 der it less volatile — which in warm and dry seasons may sometimes be 
 desirable — this may be effected by mixing it with powdered gypsum, in 
 the proportion of 1 lb. to each gallon of the ammoniacal liquor, or by 
 adding directly sulphuric acid, or tlie waste of muriatic acid of the al- 
 hali works. + 
 
 e. 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 olher saline substance we 
 could employ. According to the experiments of Sir H. Davy, (Davy's 
 Agricultural Chemistry, Lecture Vll.) however, this does not appear 
 to be the case, though Sprengel has found it more efficacious than the 
 nitrates 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 likelv to prevent its being ever employed in the ordinary 
 ojierations of husbandrv. 
 
 /. 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. 1G4) endeavoured to explain to you. But the special action of the 
 several saline compounds of ammonia above described will depend upon 
 the qualities of the acid with which it may be in combination. 
 
 The sulphate will partake of the action of the sulphates of potash, 
 soda, or lime (gv))sum), — 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 ma- 
 nures — since the one constituent (ammonia) will promote the general 
 growth of the plant, while the other will expend its influence more in 
 the filline; of the ear. 
 
 The nitrate again has been found to act more upon the crops of corn 
 than upon the leguminous plants and clovers (Sprengel) — a result which 
 
 ' Prize Essays of the Highlartd Society, xiv., p. 339. 
 
 t too gallona itiiis saturated with acid will convey to the soil about 100 lbs. of sulphate of 
 ammonia or of sal-ammoniac. 
 
352 MIXTURE OF NITRATE WITH SULPHATE OF SODA. 
 
 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 number, in 
 general too inaccurately made, and our informalion in consequence too 
 scanty, to enable us as yet to arrive at satisfactory conclusions. 
 
 12°. Mixed Saline Manures. — The principle already so frequently 
 illustrated, that plants require for their rapid and perfect development 
 a sufficient supply of a considerable number of different inorganic sub- 
 stances, will naturally suggest to yon tliat in our endeavours to render 
 a soil productive, or to increase its fertility, we are more likely to suc- 
 ceed 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 conclu- 
 sion is confirmed b}' universal experience. 
 
 Nearly all the natural manures, whether animal or vegetable, whicli 
 are applied to the land, contain a mixture of saline substances, 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 as- 
 cribed not to the single action of one of their constituents, but to the 
 joint action of all. An important practical prnljlem, therefore, pro- 
 pounded by scientific agriculture in its present state, is — what mixtures 
 of saline substances are most likely to be generally useful, what others 
 specially useful, to this or to that crop? The complete solution of this 
 problem will require the joint aid of chemical theory and of agricultu- 
 ral experiment, — of experiments often varied and probably long con- 
 tinued. But that we may finally expect to solve it, will appear from 
 what has already been accurately observed in regard to the effect of 
 certain artificial mixtures upon some of our cultlvnied crops. Thus — 
 
 a. Mixture of Nitrate u-ith Sulphate of Soda. — If, instead of dressinjj 
 young potatoes with nitrate or with sulpliate of soda alone (page 331), 
 we employ a mixture of the two, the growth of the plant is much more 
 promoted and tlie crop of potatoes much more largely increased. Thus 
 Mr- Fleming (in 164]) applied to his potatoe crop a mixture of e(|ual 
 weights of nitrate and of drj' sulphate of soda, in the proportion of 200 
 lbs. of the mixture to the imperial acre, with the following remarkable 
 result : — 
 
 Undressed, ... 66 bolls, each 5 cwt., per acre. 
 
 Dressed, .... 107 bolls. 
 
 Increase, . . . 41 bolls,* or 10 tons per acre ! 
 
 The stems also were six and seven feet high. Tlie addition of nitrate 
 of soda to a portion of the same field gave a produce of onlv 80 bolls. 
 Similar effects, of which, however, I have not yet obtained the numeri- 
 cal results, have been observed on the same crop in various localities 
 during the present season (1842). 
 
 The effect of this one artificial mixture holds out the promise of 
 much good hereafter to be obtained by the judicious trial of other mix- 
 tures — probably of a greater number of substances — upon all the c;rops 
 we are in the habit of raising for food. 
 
 b. Wood ashes. — This opinion is strengthened by the effects which 
 
 ■ See Appendix, p. 20. »^ 
 
COMPOSITION OF AVOOD ASHES, AND USK AS A MANURE. 353 
 
 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 varies, as we have 
 already had occasion to remark (p. 216), with a variety of circum- 
 stances. It always consists, however, of a mixture in variable propor- 
 tions of carbonates, silicates, sulphates, and phosphates of potash, soda, 
 lime, and magnesia, with certain other substances present in smaller 
 quantity, yet more or less necessary, it may be presumed, to vegetable 
 growth. Thus, according to Sprengel, the ash of the red beech, the oak 
 and the Scotch fir ( pinus sylves(ris), consists of 
 
 ■n^A ij„„„K o^i, Scnich Pilcli Pine. 
 
 Ued Beech. Oak. j,,._. (Berthier.) 
 
 Silica 5 52 2G 95 6 59 7 50 
 
 Alumina 2-33 
 
 Oxideoflron. . . . 3-77 8l4 1703 11-10 
 
 Oxide of Manganese . 3.85 — — 2 75 
 
 Lime 25 00 1738 2318 13(i0 
 
 Magnesia 500 144 502 4.35 
 
 Potash 2211 16 20 2-20 14-10 
 
 Soda 3-32 673 2 22 20-75 
 
 Sulplun-ic Acid . . . 7-64 336 223 345 
 
 Phosphoric Acid. . . 562 1-92 2-75 090 
 
 Chlorine 184 2 41 230 
 
 Carbonic Acid . . . 1400 1547 3648 1750 
 
 100 100 100 960 
 
 The composition of these different kinds of ash is very unlike — that 
 of the pitch pine, for example, being greatly richer in potash and soda, 
 and poorer in lime and phosphoric acid, than that of the Scotch fir — 
 while the beech is richer than any of the others in potash and lime and 
 in the sulphuric and phosphoric acids. The several effects of different 
 kinds of wood ashes when applied to the land will therefore be different 
 also. 
 
 In England, wood ashes are largely employed in many districts, 
 mixed with bone dust, as a manure for turnips, and often with great 
 success. As much as 15 bushels (7^ cwt.) of a.shes are drilled in per 
 acre with 15 bushels (6 cwt.) of bones. The large quantity of alkali 
 present in the turnip crop (p. 219) may be supposed to explain the 
 good effects which wood ashes have upon it, and may lead us to expect 
 that they would in a similar degree increase the produce of the carrot 
 and of the potatoe.* 
 
 The immediate benefit of wood ash is said to be most perceptible upon 
 leguminous plants (Si)rengel), such as lucerne, clover, peas, beans, and 
 vetches. As a top-dressing to grass lands it roots out the moss and pro- 
 motes the growth of white clover. Upon red clover its effects -will be 
 more certain if previously mixed with one fourth of its weight of gyp- 
 sum. 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 in large and 
 repeated doses its effects will be too exhausting, unless the soil be either 
 
 ' This inferenre has been verified by Mr. Wharton, of Dryburn, who has obtained an 
 excellent crop of potaloea from newly ploughed-out land by manuring with wood ashes 
 only. 
 
354 SPONTANEOUS COMBUSTION OF WOOD ASHKS. 
 
 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 upon the 
 soluble saline matter they contain, their eff^ect may be imitated by q 
 mixture of crude potash with carbonate and sulphate of soda, and a lit- 
 tle common salt. The wood ash of this country contains only about 
 one-fifteenth of its weight of soluble matter (Bishop Watson), so that 
 the following quantity of such a mixture wonld be nearly equal in effi- 
 cacy to the saline matter of one ton of wood ash. 
 
 Crude of Potash GO lbs. at a cost of 15s. 
 
 Crsytallized Carbonate of Soda . . 60 " " " 7s. 
 
 Sulphate of Soda 20 " > „ „ „ 
 
 Common Salt 20 " ^ 
 
 160 24s. 
 
 Where the wood ash costs only a shilling a bushel (or c€2 a ton), it 
 would obviousl}' be more economical to employ this mixture, were the 
 efficacy of wood ashes dependent solely upon the soluble saline matter 
 they are capable of yielding on the first washing with water. But they 
 contain also a greater or less quantify of imperfectly burned carbonace- 
 ous matter, the effect of which upon vegetation cannot be precisely 
 estimated, and a large proportion — nine-tenths, perhaps, of their whole 
 weight — of insoluble carbonates, silicates, and phosphates of potash, 
 lime, and magnesia, which are known more, permanently to influence 
 the fertility of the land to which they are applied.* 
 
 c. Washed or liximated. icood-ashcs. — In countries where wood ashes 
 are washed for the manufacture of the pot and pearl ash of commerce 
 
 * Some discussion has lately arisen in America (Sil/iman's Journal, xlii. p. 165, and 
 xliii. p. 80), in regard to the fact, in itself sufficipnily interesting, that wood ashes, when 
 thrown tocether in heaps, not unfrequenlly take fire, becoming red hot throughout their 
 whole mass, and sometimes occasioning serious accidents. Such ashes always contain a 
 quantity of minutely divided carbonaceous matter, which, like the impalpable charcoal 
 powder of the gunpowder manuficlories, may have the property of absorbing much air 
 into its pores, and of thus undergoing a spontaneous elevation of temperature. I throw it 
 out, however, as a more probable conjecture, thai during the combustion of tbe wood a 
 portion of the potash has been decomposed by the charcoal, and converted into potassium 
 (potash consisting of potassium and oxygen, p. 187. When exposeii to the nir and to 
 moisture this potassium gradually absorbs oxygen and spontaneously burns, again form- 
 ing potash. That such a decomposition may take place where wood or other vegetable 
 matter is burned with little access of air will, readily be granted, but it is not so obvious 
 that it can take place in an open fire. But even in an open fire, or in an open capsule, par- 
 ticles of potassium may remain in tlie pores of the unhui-neri charcoal, or more frequently 
 may be covered over with a glaze of melted potash, by which further combustion will be 
 prevented. That this really does happen, any one must have satisfied himself who has 
 been in the habit of burning vegetable substances for the purpose of determining the pro- 
 portion of ash they leave. The glaze of melted alkaline master often renders the com- 
 plete combustion a very difficult and tedious ma"er. That potassium is formed durinir Ihia 
 process is rendered further probable by the observation that the quanlity of potash ob- 
 tained from wood or other vegetable ash is less when the wood has been burned at a high 
 than a low temperature. The potassium, which is volatile, may have been dissipated in 
 vapour. 
 
 It is probable that a spontaneous combusi inn similar to that observed in America may 
 occasionally take place in tbe heaps of ashes left to staml upon our fields after paring and 
 burning— and hence probably has arisen the practical rule, to spread the ashes as soon as 
 possible after the burning is finished. If allowed to remain, they are said '• ^o ta/ce hnhl of 
 the land," and when it is of clay, to burn it into brick. An instance of such combustion is 
 mentioned as having occurred at Chatteris, in the Isle of Ely. whpre an entire common 
 was burned 16 or 18 inches deep, down to the very gravel.— .See Bn'lish Ilusbandnj, IJ , 
 p. 350. 
 
COMPOSITION OF LIXIVIATKD WOOD ASUKS. 355 
 
 (p. 187), this insoluble portion collects in large quantities. It is also 
 present in the refuse of the soap rnaliers, where wood ash is em- 
 ployed for the manufacture of soft soap. The composnion of this inso- 
 luble matter varies very much, not only with tlie 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 illuslrated by the following analy- 
 sis made* by Berthier, of tiie insoluble matter left by the ash of five dif- 
 ferent species of wood carefully burned by himself: — 
 
 Oak. Lime. Birch. Pitch Pine. Scotcli Fir. Beech. 
 
 Silica 3-8 
 
 Lime 54 8 
 
 Magnesia .... 06 
 Oxide of Iron . . — 
 Oxide of Manganese — 
 Phosphoric Acid . 8 
 Carbonic Acid . . 39 6 
 Carbon .... — 
 
 20 
 
 55 
 
 130 
 
 40 
 
 5-8 
 
 518 
 
 52-2 
 
 27-2 
 
 42 3 
 
 42 
 
 2-3 
 
 30 
 
 87 
 
 10-5 
 
 70 
 
 1 
 
 05 
 
 223 
 
 01 
 
 1-5 
 
 OG 
 
 35 
 
 5-5 
 
 04 
 
 4-5 
 
 2-8 
 
 4-3 
 
 18 
 
 10 
 
 57 
 
 39 8 
 
 310 
 
 21-5 
 
 3G-0 
 
 32-9 
 
 — 
 
 — 
 
 — 
 
 4-8 
 
 — 
 
 !>9-6 100 100 100 99 7 100 
 
 The numbers in these several columns differ very much from each 
 other, but the constitution of the insoluble part of the ash he obtained 
 probably differed in every case from that which would have been left 
 by the use 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 
 the lixiviated ash — while it is well known tliat common lixiviated wood 
 ash contains a notable quantity of both. Tiiis arises from tlie high tem- 
 perature at which wood is commonly burned, causing a greater or less 
 portion of the potash and soda to combine with the silica, and to fi>rm 
 insoluble silicates, which remain behind along with the lime and other 
 earthy matter, when the ash is washed with water. It is to these sili- 
 cates, as well as to the large quantity of lime, magnesia, and phosphoric 
 acid it contains, 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 
 emluring influence upon the after-produce. \ 
 
 Still i'roin the absence of this soluble portion, the action of lixiviated 
 wood ash is not so apparent and energetic, and it may therefore be safely 
 added to the land in much larger quantify. Applied at the rate of two 
 tons an acre, its effects have been observed to continue for 15 or 20 
 years. It is most beneficial upon clay soils, and it is said especially to 
 promote the growth of oats. 
 
 I am not aware that in any part of the British Islands this refuse ash 
 is to be obtained in large quantity, but in North America much of it is 
 thrown away in waste, which might be advantageously res:ored to the 
 land on which the wood had grown. 
 
 d. Kelp is the name given in this country* to the ash left by marine 
 plants when bumed. It used to be extensively prepared in the Western 
 
 ■ In Brittany and Normandy it is called xarec, while that of Spain is known by the name 
 of barilla. 
 
356 COMPOSITION AND USE OF KELP. 
 
 Islands, but the low price at which carbonate of soda can now be man- 
 ufactured has so reduced the price and the demand for kelp as almost 
 to drive it from the market. As a natural mixture, however, which 
 can now be obtained at a cheap rate (about <£3 a ton), and which has 
 been proved to be useful to vegetation in a high degree, (Prize Essays 
 of the Highland Society, vols. 1 and 4,) it is very desirable that accu- 
 rate experiments should be instituted with the view of determining the 
 precise extent of its action, as well as the crops and soils to which it can 
 be most advantageously 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 prepared, 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, (Dic- 
 tionary of Arts and Manu-factures, p. 726), consisted ot^ — 
 
 Normandy, 
 Soluble Portion. Heisker. Rona. Gay-Lussac. 
 
 Carbonate of Soda with Sulphuret of Sodium . 8-5 5-5 — 
 
 Sulphate of Soda 80 190 — 
 
 Common Salt . . . . . . • ^ -jp & q-r p, i ^^'^ 
 
 Chloride of Potassium S (250 
 
 530 620 
 
 Insoluble Portion. 
 
 Carbonate of Lime 240 100 — 
 
 Silica 80 — — 
 
 Alumina and Oxide of Iron . . . . 9 100 — 
 
 Gypsum — 95 — 
 
 Sulphur and loss 60 85 — 
 
 100 100 
 
 Besides these constituents, however, the soluble portion contains 
 iodide of polasium or sodium in variable quantity, and the insoluble 
 more or less of potash and soda in the state ot silicates. 
 
 Kelp may be apphed to the land in nearly the same circumstances as 
 wood-ash — but for this purpose it would probably be better to burn the 
 sea weed at a lower temperature than is usually employed. By this 
 means, being prevented from melting, it would be obtained at once 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 witli this finely divided kelp as a manure* 
 — especially in inland situations — for though the variable 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 chloride 
 of potassium it contains to be on an average nearly as great as is stated 
 above in the analysis of Gay-Lussac — kelp will really be the cheapest 
 form in which we can at present apply potash to the land. 
 
 e. Straw ashes. — The ashes obtained by burning the straw of oats, 
 barley, wheat, and rye, contain a natural mixture of saline substances, 
 which is exceedingly valuable as a manure to almost every crop. The 
 
 ' For somp o[lier suggestions on liiis subject, I heg to refer the reader to the Prize Ea- 
 say3 and Transactions of the Highlwid and Agricultural Society, xiv., p. 503. 
 
SOILS ON WHICH STRAW ASH MAt BE USED. 357 
 
 proportion of the several constituents of this mixture, however, is differ- 
 ent, according as the one or the other kind of straw is burned. Thus, 
 100 parts of each variety of ash — in the samples analyzed by Sprengel 
 (C/iemie, II.) — consisted of — 
 
 
 Oats. 
 
 Barley. 
 
 Wheat. 
 
 Rye. 
 
 Rape. 
 
 Potash . 
 
 . 15 2 
 
 34 
 
 06 
 
 12 
 
 18 8 
 
 Soda 
 
 . trace. 
 
 09 
 
 08 
 
 04 
 
 11-2 
 
 Lime 
 
 . 26 
 
 10-5 
 
 6-8 
 
 6-4 
 
 169 
 
 Magnesia 
 
 . 04 
 
 1-4 
 
 09 
 
 0-4 
 
 31 
 
 Silica 
 
 . 800 
 
 735 
 
 81-6 
 
 82-2 
 
 21 
 
 Alumina 
 
 01 
 
 2-8 > 
 
 
 
 
 Oxide of Iron . 
 
 . trace. 
 
 02 V 
 
 26 
 
 0.9 
 
 2-3 
 
 Oxide of Manganese 
 
 . trace. 
 
 03) 
 
 
 
 
 Phosphoric Acid 
 
 . 02 
 
 .3 5 
 
 4-8 
 
 1-8 
 
 99 
 
 Sulphuric Acid 
 
 14 
 
 22 
 
 10 
 
 61 
 
 133 
 
 Chlcirine . 
 
 01 
 
 1-3 
 
 09 
 
 0-6 
 
 11-4 
 
 Carbonic Acid 
 
 — 
 
 — 
 
 — 
 
 — 
 
 110 
 
 100 100 100 100 100 
 
 The most striking differences in the above table are the comparatively 
 large quantity of potash in the oat straw — of lime in that of barley — 
 of |ihosphoric acid in that of wheat — of sulphuric acid in that of rye — 
 and of all the saline substances in rape straw. These differences are 
 not lo be considered as constant, nor will the numbers in any of the 
 al)ove columns represent correctly the composition of the ash of any 
 variety of straw we may happen to burn (see p. 183), but they may 
 he safely depended upon as showing the general composition of such 
 ashes, as well as the general differences which may be expected to pre- 
 vail aipong them. 
 
 That such ashes should prove useful to vegetation might be inferred 
 not only from their containing many saline substances which are known 
 to act beneficially when applied to the land, but from the fact that they 
 have actually been obtained from vegetable substances. H inorganic 
 matter be necessary to the growth of wheat, then surely the mixture of 
 such matters contained in the ash of wheat straw is more likely than 
 any other we can apply to promote the growth of the young wheat 
 plant. A question might even be raised, whether or not in some soils, 
 rich in vegetable matter, the ash alone would not produce as Aisible an 
 ffll'ct upon the coming crop, as the direct application of the straw, either 
 in the dry slate or in the ibrm of rotted farm-yard manure. And this 
 question would seem to be answered in the affirmative, by the result 
 of maiiY trials of straw ashes which have been made in Lincolnshire. 
 In this county the ash of five tons of straw has been found sujierior in 
 erti'-acy to ten ions farm-yard manure, (Survey of Lincolnshire, p. 
 304, (|uoted in British Husbandry, IL, p. 334.) This is perfectly con- 
 slr^tent witli theory, yet asveceiable matter appears really essential to a 
 feiiile soil, and as the quantity of this \egetable matter is lessened in 
 some degree by every corn crop we raise, it cannot be good husbandry 
 to manure for a succession of rotations with saline substances only. 
 The richest .soil by this procedure must ultimately be exhausted. On 
 the other hand, where much vegetable matter exists, and especially 
 what is usually called I'wcrf vegetable matter, it may be an evidence of 
 
358 COMPARATIVE EFFECTS OF STRAW AND STRAW ASH. 
 
 great skill in the practical farmer to apply for a time the ashes only of 
 his straw — or some other saHne mixture to his land. 
 
 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 wheat, (British Husbandry, ii., p. 333) — 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 tiiis practice, is mentioned as one of its 
 collateral advantages, (S|)rengel, Lehre vom Diinger, p. 355.) 
 
 in the Uniied States, where, according to Captain Barclay, the straw 
 is burned merely in order that it may be got rid of (Agricultural Tour 
 in the United States, pp. 42 and 54,) it would cost little labour to apply 
 the ash to the soil fro[n which the straw was reaped, while it would 
 certainly enlarge the future produce — and in Liille Russia, where fron* 
 ibe absence of wood the straw is universally burned for fuel, and the 
 ashes afterwards consigned to the nearest river, the same practice 
 migiit be beneficially adopted. However fertile, and a|)parenlly inex- 
 haustible, the soils in this country may appear, the time must come 
 when the present mode of treatment will have more or less exliausted 
 their productive 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 shown by the following comparative experi- 
 ments, conducted as such experiments should be, during an entire rota- 
 tion of four years. The (pianiity of manure applied, and the produce 
 per imperial acre, were as follows : 
 
 15 cwl. barley 3 tons stable dung 2 tons of rotten 
 No manure. straw burned in the straw dung eight 
 
 on [he ground. stale. months old. 
 
 1°. Turnips, 22 lbs. 8* cwt. 18| cwt. 16M cwt. 
 
 2°. Barley, 14| bush. 30} bush. 30i bush. 30^ bush. 
 
 3°. Clover, 8 cwt. IS cwt. 20 cwt. 21 cwt. 
 
 A°. Oats, 32 bush. 18 bush. 38 bush. 40 bush. 
 
 The kind of soil on which this experiment was made is not stated, 
 (British Husbandry, ii., p. 248,) but it appears to show, as we should 
 expetrt, that the etlects of straw ash are particularly exerted in promot- 
 ing the growth of the corn plants and grasses which contain much sili- 
 ceous 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 especiallj' pro- 
 mote the growth of such plants appears most natural, if we consider 
 only the source from which it has been obtained, but it is fully ex- 
 ])lained by a further chemical examination of the ash itself. The so- 
 luble matter of wood ash in general contains but 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— 
 
COMPOSITION AND USIC OF DUTCH ASHES. 
 
 359 
 
 Soluble sails 
 Insoluble matter 
 
 19 per cent. 
 81 
 
 100 
 and that which was dissolved by water consisted of 
 
 Silica 
 
 Chlorine . 
 Potash and soda 
 Sulpiiuric acid . 
 
 35 per cent. 
 13 " 
 50 " 
 2 " 
 
 100 
 
 so that it was a mixture of soluble silicates and chlorides with a little 
 sulphate of potash and soda. These soluble silicates will find an easy 
 admission into the roots of plants, and will readily supply to the young 
 stems of the corn plants and grasses the silica which is indispensable to 
 tlieir liealthy growth. 
 
 f. Turf or j)cat ashes, obtained by the burning of peat of various 
 qualities, are also applied with advantage lo the land in many districts. 
 Tlipy consist oi'a mixture in which gypsum is usually the predominat- 
 ing useful ingredient — the alkaline salts being present in very small 
 proj)ortion. Of ashes of this kind those made in Holland, and 
 generally distinguished by the name of Dutch ashes, are best known, 
 and have been most frequently analyzed. The fijllowing table exhi- 
 bits the composition of some varieties of ashes from the peat of Hol- 
 land and froin the lieath of Luneburg, examined by Sprengel : — 
 Dutch Ashes (grey) 
 
 Best 
 quality. 
 
 Silica- 471 
 
 Alumma 45 
 
 Oxide of Iron 66 
 
 Do. of Matiganese . ... 1-0 
 
 Lime 13G 
 
 Magnesia 49 
 
 Potash 2 
 
 Soda 10 
 
 Sulphuric Acid 7'2 
 
 Phosphoric Acid .... 20 
 
 Chlorine 1-2 
 
 Carbonic Acid 41 
 
 Charred Turf 66 
 
 Inferior 
 qiulity. 
 55-9 
 35 
 5-4 
 43 
 8-6 
 16 
 0-2 
 39 
 
 6-4 
 
 0-8 
 
 30 
 6.4 
 
 grey) 
 
 Luneburg Ashes (reddish). 
 
 — \ 
 Worst 
 quality. 
 704 
 
 Good 
 quality. 
 31-7 
 
 Producing 
 little elfect. 
 433 
 
 4 1 
 
 5 1 
 
 9-7 
 
 41 
 
 17-7 
 
 19-3 
 
 02 
 
 0-5 
 
 35 
 
 6.1 
 
 319 
 
 71 
 
 3-9 
 
 10 
 
 4-6 
 
 01 
 
 01 
 
 — 
 
 04 
 
 01 
 
 — 
 
 34 
 
 62 
 
 Gypsum 
 02 
 
 
 PI 
 
 osph. of Lime 
 
 1-3 
 
 1-2 
 
 0-2 
 Common Salt 
 
 0-5 
 
 01 
 
 1 
 
 5-5 
 
 44 
 
 120 
 
 1000 
 
 1000 
 
 1000* 
 
 1000 1000 
 
 In llie most useful varieties of these ashes it appears, from the above 
 analyses, that lime abounds — partly in combination with sulphuric and 
 jihosphoric acids, fortning gypsum and phosphate of lime — and partly 
 with carbonic acid, forming carbonate. These compounds of lime, 
 therefore, may be regarded as the active ingredients of peal ashes. 
 
 * Sprengel Lelire vom Danger, p. 363 et Kj. 
 
360 COMPOSITION AND USK OF COAL ASHES. 
 
 Yet the small quantity of saline matter they contain is not to be con- 
 sidered as wholly without elT'ect. For the Dutch ashes are often ap- 
 plied to tlie land lo the extent of two tons an acre — a quantify which, 
 even when the proportion of alkali does not exceed one per cent., will 
 contain 45 lbs. of potash or soda, equal to twice lliat weight of sulphates 
 or of common sak. To the minute quantity of saline matters present in 
 them, therefore, peat ashes may owe a portion of their beneficial in- 
 fluence, and to the almost total absence of such compounds from the 
 less valuable sorts, their inferior estimation may have in part arisen. 
 
 In Holland, when applied to the corn crops, they are either ploughed 
 in, drilled in with the seed, or applied as a top dressing to the young 
 shoots in autumn or spring. Lucerne, clover, and meadow grass are 
 dressed with it in spring at the rate of 15 to 18 cwt. per acre, and the 
 latter a second time with an e(iual quantity after the first cutting. In 
 Belgium the Dutch ashes are ap])lied to clover, rape, potatoes, flax, 
 and peas — but never to barley. In Luneburg tlie turf ash which 
 abounds in oxide of iron is applied at the rate of 3 or 1 tons per acre, 
 and by this means the i)hysical character of the clay soils, as well as 
 their chemical constitution, 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 (|ualities are 
 the reddish turf ashes of Newbury, in Berkshire. The soil from be- 
 neath which the turf is taken abounds in lime, and the ashes are said to 
 contain from one-f(jurih to one-third of their weight of gypsum, [Bri- 
 tish Husbandry, ii., }). 334.] They are used largely both in Berkshire 
 and Hampshire, and are chiefly applied to green crops, and especially 
 to clover.* 
 
 g. Coal ashes are a mixture of which the composition is very varia- 
 ble. They consist, however, in general, of lime often in the state of 
 gypsum, of silica, and of alumina mixed with a (piantity of bulky and 
 porous cinders or half burnt coal. The ash of a coal from St. Etienne, 
 in France, after all the carbonaceous mailer had been burned away, 
 was found by Berthier to consist of 
 
 Alumina, insoluble in acids .... 62 per cent. 
 
 Alumina, soluble ...... 5 " 
 
 Liine ........ 6 " 
 
 Magnesia 8 " 
 
 Oxide of Manganese ..... 3 " 
 
 Oxide and Sulpburet of Iron .... 16 " 
 
 100 
 
 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 Scoich coal ashes a small quantity of alkaline matter, 
 chiefly soda,f is generally present. The constitution of the ash of our 
 best coals, tlierefore, may be considered as very nearly resembling that 
 of peat ash, and as susceptible of similar applications. When well 
 
 ' 50 bushels per acre (at 3(1. a busliel, or 12s. 6d. an acre) increase the clover crop fully 
 one fifili.— Morion " On Soils," p. 170. 
 
 t From the common salt with which our coal is so often impregnated. 
 
CAME ASHES. CRUSHKD AND DECAYED TRAPS AND LAVAS. 361 
 
 burned, it can in many cases be applied with good eflecfs as a top-dress- 
 iog to grass lands which are overgrown with moss ; while the admix- 
 ture of cinders in the ash of the less perfectly burned coal produces a 
 favourable physical change upon strong clay soils. 
 
 h. Cane Ashes. — I may allude here to the advantage which in sugar- 
 growing countries may be obtained from the restoration of the cane ash 
 to the fields in which the canes have grown. After the canes have been 
 crushed in the mill they are usually employed as fuel in boiling down 
 tlie syrup; and the ash, which is not unfrequemly more or less melted, 
 is, I believe, almost uniformly neglected — at all events, is seldom ap- 
 plied again to the land. According to the principles I have so often 
 illustrated in the present Lectures, such procedure must sooner or later 
 exhaust the soil of those saline substances which are most essential to 
 the growth of the cane plant. If the ash were applied as a top-dressing 
 to the young canes, or put into the cane holes near the roots — having 
 been previously mixed with a quantity of wood-ash, and crushed if it 
 hapi^en to have been melted — this exhaustion would necessarily take 
 place much more slowly. 
 
 i. Crushed Granite. — We have already seen that the felspar existing 
 in granite contains much silicate of potash and alumina. It is, in fact, 
 a natural 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 potash from felspar and mica by mixing them 
 with quicklime, calcining 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. (Journal of the Royal Institution, I., p. 184.) 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 easi- 
 ly crushed when they have been previously heated to redness, and there 
 can be little doubt, I think, that such a mixture as that recommended 
 by Mr. Prideaux would unite many of the good effects of wood ashes 
 and of lime. 
 
 k. Cruslied Trap. — I need not again remind you of the natural fer- 
 tility of decayed trap soils (Lee. XII., §4,) 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 
 an unproductive soil remains — when trap decays, on the other hand, the 
 lime by which it is characterised is not soon dissolved 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 Scotland, and 
 is applied like marl to the land. 
 
 I. Crushed Lavas. — Of the fertile and fertilizing nature of the crushed 
 or decayed lavas I have also already spoken to you (Lee. XII., § 4). 
 In St. Michael's, one of the Azores, the natives pound the volcanic mat- 
 ter and spread it on the ground, where it speedily becomes a rich mould 
 capable of bearing luxuriant crops. At the foot of Mount Etna, when- 
 ever a crevice appears in the old lavas, a branch or joint of an Opuntia 
 16 
 
362 EXPEIllMKNTS WITH MIXED MANURES. 
 
 {Cactus Opuntia, — European Indian-Fig) is stuck in, when the roots in- 
 sinuate themselves into every fissure, expand, and finally break up the 
 lava into fragments. These plants are thus not only tlie means of pro- 
 ducing a soil, but they yield also much fruit, which is sold as a refresh- 
 ing food throughout all the towns of Sicily. (Decandolle, quoted in the 
 Quart. Journ. of Agr., IV. p. 737.) 
 
 These are all so many natural mineral mixtures of which we may 
 either directly avail ourselves, or which we may imitate by art. 
 
 Experiments with mixed manures. 
 
 Note. — As a valuable appendix to the preceding observations on 
 mixed manures, I am permitted to insert the following very interesting 
 results obtained during the present season, 1842, from experiments made 
 on the estate of Mr. Burnet, of Gadgirth, near Ayr. The crop to which 
 the several manures were applied was wheatof the ecZfpsc variety, sown 
 on the 29th of October, 1841, and reaped on the 15th of August last. 
 The soil is a loam with subsoil of clay, tile drained and trenched plough- 
 ed. It had been in beans the previous year, and gave six quarters per 
 acre, which were sold at 46s. a quarter. No manure had been applied 
 with the bean crop, and except a good dose of lime before sowing the 
 wheat, nothing but the saline mixtures niemioned below was applied 
 with this latter crop. 
 
 PRODUCE. 100 lbs. grain 
 
 Application per imperial acre. , • ^ Weight per produced of 
 
 Straw. Grain. bushel. fine flour. 
 
 ctct. bush. lbs. lbs. lbs. 
 
 Sulphate of Ammonia, 2 cwt.»» 35 39 ^^ gQ ^ 
 
 Wood-ashes, 4 cwt j 
 
 Sulphate of Ammonia, 2 cwt. i 
 
 Sulphate of Soda, 2 cwt. . . > 44f 49 6 60 63i 
 
 Wood-ashes, 4 cwt ) 
 
 Sulphate of Ammonia, 2 cwt. 1 
 
 Common Salt, 2 cwt. . . . > 45 49 60 65§ 
 
 Wood-ashes, 4 cwt. . . . ) 
 
 Sulphate of Ammonia, 2 cwt. ) 
 
 Nitrate of Soda. 1 cwt. • ■ [ 44^ 4S 20 59 54| 
 
 Wood-ashes, 4 cwt. . . . ) 
 
 No Application 29' 31 38 61i 76| 
 
 The reader will observe here that though the first mixture produced 
 a large increase hoth of straw and grain, a still larger additional increase 
 was caused by mixing with the substances of which it consisted either com- 
 mon salt or sulphate of soda or nitrate of soda. Each of these three sub- 
 stances produced nearly the same effect. The soda, therefore, more 
 than the acid with which it was combined, must in these cases have act- 
 ed beneficially. The comparatively small proportion of fine flour yield- 
 ed by the nitrated wheat, and the comparatively large proportion ob- 
 
 'Tiie sulphate of ammonia was prepared from urine, and, therefore, contained other ad- 
 mixtures (page 349). The straw was strongest, coarsest, and longest in ripening, where 
 this sulphate was applied. The two guanos produced little luxuriance, but the lots to which 
 Ihey were applied were soonest ripe. 
 
IMPORTANCE OF SCCII EXPERIMENTS. 363 
 
 tained from that to which no application was made, are also highly de- 
 serving of notice. 
 
 Mr. Burnet has transmitted to me samples of the flour from these 
 several gro\rths of wheat, with the view of determining the relative 
 proportions of gluten they contain. The result of this examination, 
 which cannot fail to be interesting, will be given in a succeeding Lec- 
 ture — before which, however, I hope the whole of Mr. Burnet's experi- 
 ments will be laid before the public. 
 
 It will be observed that Mr. Burnet has exercised a sound discretion 
 in making and trying mixtures not hitherto specitically recommended. 
 It is by the result of such varied experimental trials, made by intelli- 
 gent practical men, on dilFerent soils and crops, and with mixtures of 
 which the constitution is exaclly known, that \\'e shall be able hereafter to 
 correct our theoretical principles — as well as to simplify and render 
 more sure our general practice. 
 
 [Since writing the above, lam informed that the silicate of potash, re- 
 ferred to at p. 349, is manufactured by Messrs. Dymond, of London, and 
 may be obtained from the London dealers at 56s. a cwt. I expect aUo, 
 that a silicate ofsoda will soon be brouglit into the market by the Messrs. 
 Cooksons, of the Jarrow Alkali Works, at a much lower price. The 
 probable efficacy of these substances, as manures, has, no doubt, been 
 extolled too highly by some — their real efficacy, however, is well de- 
 serving of investigation. I insert in the Appendix No. VII, therefore, 
 some suggestions for experiments with these substances, in the hope that 
 during the spring of 1843, some experiments on the subject may be 
 made. 
 
LECTURE XVII. 
 
 tJse of lime as a manure. — Value of lime in improving the soil — Of the composition of 
 common and maanesian lime-stones. — Burnine and slal^ing of lime. — Changes wlii«h 
 slaked lime undergoes by exposure lo the air. — Various natural slates in which carbonate 
 of lime is applied to the land. — Marl — shell and coral sand, — lime stcne sand and gravel, 
 —crushed limestone.- -Chemical composition of variou.s marls, and shell and lime-sione 
 sands. — Their efTect.s on the soil. — Use of chalij. — Is lime necessary to the soil"! — Ex- 
 hausting effect of lime. — Analogy between this action of lime and that of wood-ashes. 
 Quantity of lime to be applied. — Etfocts of an overdose. — Form in which it may be n>ost 
 prudently used — When it ought to be applied in reference to the season — lo the rotation 
 — and to the application of manure.— Its general and special etTf cts on different si'ils and 
 crops. — Circumstances which influence its action. — Length of lime during whicli its ef- 
 fects are perceptible. — Theory of the action of lime. — Necessity and nature ol' liie ex- 
 hau.^tion which it sometimes produces. — Sinking of lime into the soil. — Why tlie appli- 
 cation of lime must be repeate<l. — Action of lime on living animals and vegetatiles. 
 Suggestions of theory. — Use of silicate of lime. 
 
 Having explained to you the action of the most important sahne 
 and mixed mineral substances which are or may be beneficially ap- 
 plied to the soil, I have now to draw your attention to the use of lime 
 ^-the most valuable and the most extensively used oi^all the mineral 
 substances that have ever been made available in practical agricul- 
 ture. It has, and with much reason, been called " the basis of all 
 good husbandry" — it well deserves, therefore, your most serious atten- 
 tion as practical men, and on my part the application of every chem- 
 ical light by which its usefulness maybe explained and your practice 
 guided. This consideration also will justify me in dwelling upon it 
 with some detail, and in illustrating separately the various points, 
 both of theory and practice, 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 except 
 in a state of chemical combination (Lee. L, § 5,) with some other 
 substance. That whicli is usually employed in agriculture is met 
 with in the state of carbonate. 
 
 Carbonate of lime, or common lime-stone, consists of lime and car- 
 bonic acid, and when perfectly pure and dry, in the following propor- 
 tions : — 
 
 per cent. 
 
 Carbonic acid 43-7 "j 
 
 Lime 56-3 I or one ton of pure dry carbonate of 
 
 I lime contains \\\ cwts. of lime. 
 
 100 J 
 
 Limestones, however, are seldom pure. They always contain a sen- 
 sible 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 and other organic matter. In liiue-stones of the 
 best quality the foreign earthy matter or impurity does not exceed 5 per 
 cent, of the whole — while it is often verv much less. The chalks and 
 
COMMON AND MAGNESIAN LIME-STONES. 365 
 
 mountain lime-stones are generally of this kind. In those of inferior 
 quality it 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 caip and the lime-stone nodules which are burned for the man- 
 ufacture of hydraulic limes or cements.* It is easy to ascertain the 
 quantity of earthy matter contained in lime-stone, by simply intro- 
 ducing a known weight of it into cold diluted muriatic acid, and ob- 
 serving or weighing the part which, after 12 hours, refuses to dis- 
 solve or to exhibit any effervescence. It is to the presence of these 
 insoluble impurities that lime-stones in general owe their color, pure 
 carbonate ol" lime being perfectly white. 
 
 2^. Magnesian limestone. — Though often nearly white, the mag- 
 nesian lime-stones of our island are generally of a yellow color. They 
 cannot by the eye be distinguished from common lime-stones of a simi- 
 lar color, but they are characterised by containing a greater or less 
 proportion of carbonate of magnesia, which is more or less easily de- 
 tected by analysis. Pure carbonate of magnesia consists of 
 
 per cent. 
 
 Carbonic acid. .51-7 ~] 
 
 Magnesia 48-3 ! or one ion of pure dry carbonate of magnesia 
 
 [ contains 9g cwts. of magnesia. 
 
 100 J 
 
 It contains, therefore, a considerably larger proportion of carbonic 
 acid than is present in carbonate of lime. 
 
 Magnesian lime-stone is very abundant, is indeed the prevailing 
 rock in many parts of England (Lee. XL, sec. 4,) but the proportion 
 of carbonate of magnesia it contains is very various in different lo- 
 calities. Even in the same quarry different beds contain very unlike 
 proportions of magnesia, and are therefore more or less fitted for 
 agricultural purposes. Thus several varieties of this lime-stone, ex- 
 amined by myself, from different parts of the county of Durham, 
 contained the two carbonates in the following proportions : 
 
 « « rt c c'-'= ° — l; 
 
 Gaimondsway 975 2 5 trace trace Hard compact gjey. 
 
 Stony-gate 980 161 027 0-12 Ciystallinefine grained yellow 
 
 _ , „ nr. f\ n t n'> o c i Honcy-combed crystalline 
 
 Fulwell 950 2i 3 2-6 j ^J,^^ ^ 
 
 Sealiam (A) 90-5 23 0-2 10 Hard fine-grained compact. 
 
 " (B) 950 1-3 0-2 3 5 Hard porous brown. 
 
 Hartlepool 54,5 4493 0-33 024 Oolitic yellow. 
 
 HumbledonHill(A)57-9 41-8 1 028 Perfect encrinal columns. 
 
 " (B) fiO-41 38-78 1 0-81 Consistingin part encrinal col. 
 
 Ferry Hill 541 44-72 1-58 4-6 Yellowish compact. 
 
 Some of these varieties, as Ave see, contain very little carbonate of 
 
 ' Thus that or Aherthaw contains about 8fi of carbonate of lime and 11 of clay, &c.\ 
 that of Yorksliire 62 of carbmiate of lime and 34 of clay ; of Sheppy 66 of carbonate of 
 lime and 32 of clay. These lime-slones are burned, and then cruslied to an impalpable 
 powder, which sets almost immediateiy when mized up with water. 
 
366 OF THE BURNING AND SLAKING UF XIJME. 
 
 magnesia, and therefore, are found to produce excellent lime for agri- 
 cultual purposes — while in others this substance forms nearly one- 
 half of the whole weight of the rock. Similar differences are found 
 to prevail in almost every locality. 
 
 This admixture of magnesia in greater or less quantity is not con- 
 fined to the lime-stones of the magnesian lime-stone formation pro- 
 perly so called. It is found in sensible quantity in certain beds of 
 lime-stone in nearly every geological formation, and there are few 
 natural lime-stones of any kind in which traces of it may not be dis- 
 covered by a carefully conducted chemical examination. 
 
 The simplest method of detecting magnesia in a hme-stone is to dis- 
 solve it in diluted muriatic acid, and then to pour clear lime water inta 
 the filtered solution. If a light wliite powder fall, it is magnesia. The 
 relative proportions in two lime-stones maybe estimated pretty nearly 
 by dissolving an equal weight of each, pouring the filtered solutions 
 into bottles which can be corked, and ihen filling up both with lime 
 water. On subsiding, the relative bulks of the precipitates will Lndi^ 
 cate the respective richness of the two varieties in magnesia^ 
 
 § 2. Of the burning and slaking of lime. 
 
 Burning. — When carbonate of lime or carbonate of magnesia 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 
 good lime-stone yielding about 11 cwts. of hurried, shell, quick, or 
 caustic lime. 
 
 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 vapor, and finally falls to a fine, bulky, 
 more or less wliite powder. Th«se appearances are more or less rapid 
 and striking according to the quality of tlie hme, and tlie time that has 
 been allowed to elapse after the hurning, before the water was applied. 
 All lime becomes difficult to slake when it has been for some time ex- 
 posed to the air. When the slacking is rapid as in the rich limes, the 
 heat produced 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 po\vder will be gritty, will con- 
 lain 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-time is left in 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 tails, though niucli more slowly, and with little sensible deve- 
 lopment of heat, into a similar fine powder. In the rich limes the in- 
 crease of bulk may be 3 or 2\ times; in the poorer, or such as contain 
 much earthy matter, it may be less than twice. 
 
FURTHER CHANGES UNDERGONE BT SLAKED LIME. 367 
 
 Hydrate of lime. — Wlien qiiick-lime is thus slaked it combines with 
 the water which is added to it, and becomes converted into a milder or 
 less caustic compound, which among chemists is known by the name of 
 hydrate of lime. This hydrate consists of 
 
 Lime . . 76 percent. ) or one ton of pure burned lime becomes 
 Water . . 24 " \ nearly 25 cwt. of slaked lime. 
 
 100 
 
 It is rare, liowever, that lime is so pure or so skilfully and perfectly 
 slaked as to take up the whole of this proportion of water, or to increase 
 quite so much as one-fourth part in weight. 
 
 Hi/drale of Magnesia. — When calcined or caustic magnesia is 
 slaked, it also combines with water, but without becoming so sensibly 
 hot as quick-lime does, and forms a hydrate, which consists of 
 
 Magnesia . 69-7 per cent. ) or one ton of pure burned magnesia be- 
 
 Water . . 30-0 " ^ comes 281 cwt. of hydrate. 
 
 100 
 
 When magnesian lime is slaked, the fine powder which is obtained 
 consists of a mixture of these two hydrates, in proportions which depend 
 of course upon the composition of the original lime-stone. 
 
 An important difference between these two hydrates is, that the hy- 
 drate 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 iriixture of the two in the proportions in which they exist 
 in the Hartlepool, Humblcdon, and Ferryhill lime-stones (page 365), 
 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 
 ensuing immediately after its application, become granular and gritty, 
 and cohere occasionally into lumps, on which the air will have little 
 affect. This properly is of considerable importance in connection with 
 the further cheniicai 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 ex- 
 posed to the open air, they gradually absorb carbonic acid from the at- 
 mosphere, and tend to return to the state of carbonate in which they ex- 
 isted previous to burning. By mere exposure to tlie air, however, they 
 do not attain to this state within any assignable time. In some walls 
 600 years old, the lime has been found to have absorbed only one-fourth 
 of the carbonic acid necessary 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 ab- 
 sorb carbonic acid, a considerable quantity of the hydrate of lime first 
 
368 OF CALCINED AND SLAKED MAGNESIA. 
 
 formed, during spontaneous slaking, becomes changed info carbonate 
 
 during the slaking of the rest. But, when it has all completely fallen, 
 
 the rapidity of the absorption ceases, and the Hne slaked lime consists of 
 
 Carbonate of lime 57'4 
 
 Tj 1 . c \- S lime . . . 32*4 7 .^ „ 
 Hydrate of lime < ^ inn} 42-6 
 
 •^ I water. . . 10'2 ^ 
 
 100 
 or, a ton of lime, left in the open air till it has completely fallen to 
 powder, contains about 8i 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 considerable 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, and which is a 
 chemical compound* of carbonate with hydrate of lime, the further ab- 
 sorption of carbonate acid from the air proceeds very slowly, and is only 
 completely effected after a very long period. 
 
 2°. When slaked in the ordinary way lime falls to powder, without 
 liaving absorbed any notable quantity of carbonic acid. Numerous 
 small lumps also remain, which, though covered with a coating of hy- 
 drate, have not themselves absorbed any water. The absorption 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 it gradually becomes more slow, 
 a variable proportion of the compound of carbonate and hydrate above 
 described is formed, and even when thinly scattered over a grass-field, 
 an entire year may pass over without effecting the complete conversion 
 of the wliole into carbonate. 
 
 3°. Calcined or burned magnesia, whether in the pure state or mixed 
 with quick-lime, as in the magnesian limes, absorbs 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 become 
 ultimately changed into carbonate, and form a compound of hydrate 
 and carbonate which is identified with the common uncalcined magne- 
 sia of the shops. This compoundf 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, 
 
 ' This compound consistsofone atom of carbonate of lime(Ca O -|- CO2) combined with 
 one of hydrate (Ca O -J- HO,) and is represented shortly by Ca C -f- C'a H — in which Ca 
 denotes calcium (Lee. JX., § 4,) Ca O or Ca oxide of calcium or lime, CO2 or C carbonic 
 acid (Lee. III., § 1,) and 11 O or H water (Lee. IL § 6.) 
 
 t It is represented by the formula 3 (Mg C H- il) -J- Mg If. 
 
STATES IN WHICH LIME IS APPLIED. 369 
 
 forms a hydrate only, without absorbing any sensible quantity of car- 
 bonic acid. The hydrate thus produced is met with in the form of 
 mineral deposits on various parts of the earth's surface, and this mineral 
 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), which will change 
 but slowly even when exposed to the air. When it is left to sponta- 
 neous slaking, one-fourth of it at least will always remain in the caustic 
 state, houever long it may be exposed to the air. 
 
 Sliould a lime be naturally of such a kind, or be so mixed with the 
 ingredients of the soil as to form a hydraulic cement or an ordinary 
 mortar, which will solidify when rains come upon it, or when the natu- 
 ral 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 
 tlie lime will remain caustic for an indefinite period. 
 
 § 4. Stales of chemical combination in which lime may he applied to 
 the land. 
 
 There are, therefore, four distinct states of chemical combination, in 
 which pure lime may be artificially applied to the land. 
 
 I''. Quick-lime or lime-shells, in which the lime as it comes from the 
 kiln is uncombined eithei" with water or with carbonic acid. 
 
 2°. Slaked lime or hydrate of lime, in which by the direct application 
 of water it has been made to combine with about one-fourth of its 
 weight of water. 
 
 In both these slates the lime is caustic, and may be properly spoken 
 of as caustic lime. 
 
 3°. Spontaneottsly slaked li?ne,m which one-half of the lime is com- 
 bined with v%-ater and the other half with carbonic acid. In this state 
 it is only half caustic. 
 
 4°. Carbonate of lime — the state in which it occurs in nature, and to 
 which burned lime, after long exposure to the air, more or less perfectly 
 arrives. In this state lime possesses no caustic or alkaline (p. 48, § 5, 
 note) properties, but is properly called mild lime. 
 
 5°. Bi-carbonate of lime may be adverted to as a fifth state of com- 
 bination, in which, as I have previously explained to you (pp. 45-6, 
 § 1), nature usually apphes lime to the land. In this state it is combined 
 with a double proportion of carbonic acid, and is to a certain extent 
 readily soluble in water. Hence, springs are often impregnated with 
 it, and the waters that gush from fissures in the lime-stone rocks spread 
 it through the soil in their neighbourhood, and sweeten the land. 
 
 1 shall hereafter speak of these several stales under the names of 
 quick-Ume, hydrate of lime, spontaneously slaked lime, carbonate 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 manure have unavoidably 
 fallen. The term mild, you will understand, applies only to that which 
 is entirely in the state of carbonate. 
 
 Magnesia, in the magnesian limes, may in like manner be either in 
 the state of calcined magnesia, of hydrate of magnesia^ oi spontaneously 
 16* 
 
370 VARIOUS NATURAL FORMS OT CARBONATE OF LhME. 
 
 slaked — meaning by this the compound of hydrate with carbonate — of 
 carbonate^ or of Bi-carbonate of magnesia, the latter of which is so- 
 luble in water to a very considerable extent. (It dissolves in 48 times 
 its weight of water — or a gallon of water will dissolve 5 ounces of 
 the Bi-carbonate containing 1| ounces of magnesia.) 
 
 § 5. Of the varirms natural forms in which carbonate of lime is 
 applied to the land. 
 
 In the unburned 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 abundantly, 
 and is most extensively used in almost every country of Europe. By 
 the term marl, is understood, as I explained to you, when treating of 
 soils (Lee. XL, § 3,) 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 co- 
 herence, and gradually fall to powder. This test is often employed 
 to distinguish between marly and other clays, yet the falling asunder, 
 though it afford a presumption, is not an infallible proof that the sub- 
 stance tried is really a marl. 
 
 Marls areof various colors, white, grey, yellow, blue, and of various 
 degrees of coherence, some occurring in tlie form of a more or less fine, 
 loose, sandy powder, others being tenacious and clayey, and others, 
 again, hard and stony. Tliese 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 vipon the land, 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. Same rich marls 
 consist in part or in whole of broken and comminuted shells, which 
 clearly indicate the source of the calcareous matter they contain. 
 
 COMPOSITION OP MARLS PPJIM 
 
 I.unebuig. Osiiabruck Mas'lebufg. lininswick. We=ennRrfh. Bruji?wi.lt. 
 
 powdery. stumj. clayey. Loamy. powdery. stony. 
 
 auartz-Sandfc Silica.. 5-6 2,]-0 5S-1 734 789 71-1 
 
 Alumina 04 100 8-4 1-9 3 1 40 
 
 Oxides of Iron 4 2 19 0-7 3 2 38 65 
 
 Do. of Magnesia trace trace 03 03 0-3 Tl 
 
 Carbonateof Lime.... 85-5 350 18-2 18 1 8-2 133 
 
 Do. of Magnesia 1-25 0-9 38 15 30 2-6 
 
 Sulphuret of Iron — 73 — — — — 
 
 Potash & Soda com- ) q.q, ^^.^^^ ^.g ^g Q.y q .^ 
 bmed with bihca. . J 
 
 Common Salt 0-03 trace trace trace 1 trace 
 
 Gypsum 0-OG 0-9 2-1 1 5 trace 
 
 Pfiosphate of Lime ) g.^ ^.^ ^,^ q^ j.o ^.g 
 
 (bone earth) ^ 
 
 Nitrate of Lime 001 _ _ _ _ — 
 
 carbon 
 
 Organic Matter 06 205 _ _ — _ 
 
 100 100 100 100 100 100 
 
UNLIKE EFFECTS OF DIFFERENT MARLS. 371 
 
 The characteristic property of true marls of every variety is, I have 
 Baid, the presence of a considerable per centage of carbonate of lime in 
 the state of a fine powder, and, in general, ditlused uniformly through 
 the entire mass. To this calcareous matter the chief efficacy of these 
 marls is no doubt to be ascribed, yet as they always contain other chem- 
 ical compounds to which the special efficacy of certain varieties has 
 sometimes been ascribed, it may not be improper to direct your attention 
 to the preceding table, in which the constitution of several marls, from 
 different localities, is represented, after the analyses ot Sprengel. 
 
 Several reflections will occur to you on looking at these tables — such 
 as, 
 
 First— that marls differ very much in composition, and therefore 
 must differ very much also in the effects which they are capable of pro- 
 ducing when applied in the same quantity to the same kinds of land. 
 
 Second — that, among other differences, the proportion of carbonate 
 of lime is very unlike — in some varieties amounting to 85 lbs. out of 
 every hundred, while in otJiers as little as 5 lbs. are present in the same 
 weight. You will understand, therefore, how very different the quan- 
 tity applied to the land must be, if these several varieties are to produce 
 an equal hming or to add equal quantities of lime to the soil. You 
 will see that each of three persons may be adopting the best practice 
 with his own marl — though the one add only 12 to 20 tons per acre, 
 while the second adds 50 to PiO, 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 with every ton 
 of the first of the above marls you would lay on the soil 52 lbs. of bone 
 earth — about as much as is contained in a cwt. of bone dust — while 
 with the second you would only add 11 lbs. In so far as iheir effects 
 upon the land depend, or are influenced by the presence of this sub- 
 stance, therefore, they must also be very different. And, 
 
 Fourth — that the mechanical effects of these marls upon the soil to 
 whicii they are added must be very unlike, since some contain 70 or 
 SO lb.'', of sand in every hundred — while others contain a considerable 
 quantity of clay. The opening effects of the one marl, and the stiflT- 
 ening effects of the other, when they are laid on in large quantities, 
 cannot fail to produce very different alierations in the physical cha- 
 racters of the soil. 
 
 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 calcare- 
 ous sand, mixed occasionally with portions of animal matter, and, 
 when taken fresh from the sea-shore, with some saline matter derived 
 from the sea. 
 
 Such is the case in many places on the coast of Cornwall. 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. It has been 
 estimated (De la Beche's Geological Report on Cornwall^ ^c, p. 480) 
 that seven millions of cubic feet are at present 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 
 
372 coMPoatTiON of shell and coral lands. 
 
 applied extensively, and with remarkably beneficial effects, both to the 
 pasture lands and to the peaty soils that cover so large an area in thia 
 remote part of Scotland. It is chiefly along the coasts that it has hith • 
 erto been extensively employed, and it is transported by sea to a dis- 
 tance of SO 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" (Macdonald's Agricultural Surveij of the Hebrides, 
 p. 401.) 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 ascribed either to the artificial applications of 
 .such 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 such sand in many parts both 
 of its northern and southern coasts. A century and a half ago, it is 
 known to have been used for agricultural pvirposes in the north of Ire- 
 land — and nearly as long ago to have been brought over to the oppo- 
 site (Galloway) coast of Scotland with a view of being applied to the 
 land (Macdonald.) In the south, according to Mrs. Hall, (Mrs. Hall's 
 Ireland,') the coral sand raised in Bantry Bay alone produces X4000 
 or £5000 a-year to the boatmen who procure it and to the peasants 
 who convey it up the country. 
 
 On the coast of France, and especially in Brittany, opposite to Corn- 
 wall, on the other side of the English channel, it is obtained in large 
 quantity, and is in great demand (Payen and Boussingault, Annales de 
 Chim. et de Phys., third series, iii., p. 92. ) 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 
 ta7ig-ue. 
 
 The shell sand of Cornwall contains from 40 to 70 per cent, of car- 
 bonate of hme, with an equally variable small admixture of animal 
 matter and of sea salt. The rest is chiefly siliceous sand. Other va- 
 rieties have a similar composition. Two specimens o^tangiie from the 
 south of France, analysed by Vitalis, and one of shell sand from the 
 island of Isla, partially examined by myself, consisted of 
 
 Tangiie from the Shell Sand 
 
 ;. South of France. from Isla. 
 
 Sand, chiefly siliceous 20-3 40 } ^. „ ^- - 
 
 Alumina and Oxide of Iron 4-6 4-6 \'^'' ^° ^^'' 
 
 Carbonate of Lime 66-0 47.5 28 to 34 
 
 Phosphate of Lime ? ? 0-3 
 
 Water, and loss 9-1 7-9 — 
 
 100 100 100 
 
 3°. 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 fish- 
 ermen in a living state — on the coasts of Ireland (Bantry Bay and 
 elsewhere,) and on the shores of Brittany, especially near the mouths of 
 the rivers. In this fresh state it is preferred by the farmer, probably be- 
 
USE or LIMK-STONE SAND AND GRAVEL. 373 
 
 cause it contains both more saline and more animal matter. This ani- 
 mal 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 following relative 
 values: — 
 
 Contain of Relative 
 
 Nitrogen. value. 
 
 100 lbs. of Farm-yard Manure . . . 0-40 lbs. 100 
 
 do. of Coral Sand {Med) . . . 0-512 lbs. 128 
 
 do, of Shell Sand (Trez) . . . 0-13 lbs. 32^* 
 
 That is to say, that, in so far as the action of these substances is de- 
 pendent upon tlie 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, as I have already had frequent occasion to observe to you, 
 much weight is not to be attached to such methods of estimating the re- 
 lative values of manuring substances by the proportions of any one of 
 the ingredients they happen to contain — yet the fact, tliat so much ani- 
 mal matter is occasionally present in the living corals, accounts in a 
 satisfactory manner for the immediate effects of this form of calcareous 
 application. This animal matter acts directly and during the first year; 
 the carbonate of lime begins to show its beneficial influence most dis- 
 tinctly when two or three years have passed, 
 
 4°. Lime-stone Sand and Gravel. — In coimtries which abound in 
 lime-stones, there are found scattered here and there, in the hollows and 
 on the hill-sides, banks and heaps of sand and gravel, in which rounded 
 particles of lime-stone abound. These are distinguished by the names 
 of lime-stone sand and gravel, and are derived from the decay or wear- 
 ing down of the lime-sione and other rocks by the action of water. 
 Such accumulations are frequent in Ireland. They are indeed exten- 
 sively diff'used over the surface of that island, as we might expect in a 
 country abounding so much in rocks of 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 im- 
 provement, 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 carbon- 
 ate of lime these sands and gravels contain is very variable. I have 
 examined two varieties from Kilfinane, in the county of Cork (?). The 
 one, a yellow sand, contained 26 per cent, of carbonate of lime — the re- 
 sidue, 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 con- 
 sisting of fragments of sand-stone, of quartz, and of granite. 
 
 • Annates de Chim. et de Phys.., third series, lii., p. 103. 
 
374 CRUSHED LIME-STONES. — EFFECTS OF MARLS. 
 
 The application of such mixtures must not only improve the physi- 
 cal characters of the soil, but the presence of the fragments of granite, 
 containing undecomposed felspar and mica (Lee. XII., § 1), must con- 
 tribute materially to 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-stones 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 be- 
 lieve, the first who in this country endeavoured to bring this suggestion 
 into practical operation. He is said to have caused machinery to 
 be erected for the purpose in one of the remotest districts of Scotland, 
 but from some cause 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 possibly 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 re- 
 sorted to with equal advantage and economy : 
 
 First, where coal is dear or remote, while lime-stones and water 
 power are abundant. Tliere are many inland districts in each of the 
 three kingdoms where these conditions exist, and in which, therefore, 
 the erection of cheap machinery might afford the means of greatly fer- 
 tilizing the land ; and. 
 
 Second, there are in many localities rocks rich in calcareous mat- 
 ter, which are nevertheless so impure, or contain so much other earthy 
 matter, that they cannot be burned into lime. Yet, if crushed, 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 fiom 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, 
 upon the soil. 
 
 The effects which result from the application of the above natural 
 forms of carbonate of lime are of two kinds. 
 
 1°. 'Yhe'ir physical effect in altering the natural texture of the soils to 
 which I hey are added. This eflTect will necessarily vary with the na- 
 ture 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 litne-stone gravels, by opening and rendering more 
 
OBSERVED EFFECTS OF MARLS. 375 
 
 free and easier worked such s(jils as are stiflT, intractable, and more or 
 less impervious — while either will impart solidity and substance to 
 such as are of a peaty nature or over-bound with other forms of vege- 
 table matter. 
 
 2°. Their chemical efTect in actually rendering the soil productive of 
 larger cro]is. Tills eflect is altogether independent of any alteration in 
 the physical properties of the soil, and is nearly tlie same in kind, what- 
 ever 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 carbonate of lime they contain is 
 supposed to be modified in some cases by the proportion of phosphate of 
 lime, &c. (p. 370.) with which it may be n>ixed — it is certainly modified 
 by the animal and saline matters which are present in the recent cor- 
 als and shell sands. 
 
 The several effects of marls and calcareous sands being dependent 
 upon circuinstnnces so diflerent, it is not svirprising that the opinions of 
 practical men should, in former times, have been divided in regjird to 
 the nction of this or that marl upon their respective soils. In no two 
 localities was the substance applied to the land exactly alike, and 
 hence unlike results must necessarily have followed, and disappoint- 
 ment been occasionally experienced from their use. And yet the im- 
 portance 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 farm-yard manure put together. 
 
 It is not easy in any case to estimate with precision what portion 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 ben- 
 eficial, and on light or sandy fields often injurious. In all cases, there- 
 fore, the action of lime applied in any form may be considered as part- 
 ly physical and partly chemical — the extent of the chemical action in 
 general increasing with the proportion of lime which the kind of cal- 
 careous matter employed is known to contain. 
 
 The observed etlects of marls and shell sands, in so far as they are 
 chemical, are very analogous to those produced by lime as it is gener- 
 ally applied in the (juick or slaked state in so many parts of our islands. 
 
 They alter the nature and quality of the grasses when applied to 
 pasture — they cover even the und rained bog with a short rich grass — 
 they extirpate heath, and bent, and useless moss — they exterminate 
 the weeds which infest the unlimed corn fields — they increase the 
 quantity and enable the land to grow a belter quality of corn — they ma- 
 nifest a continued action for manyj^ears after they have been applied — 
 like the jmrer limes they act more energetically if aided by the occa- 
 sional acldition of other manure — and like them they finally exhaust* 
 a soil from which 'the successive crops are reaped, without the requisite 
 return of decaying animal or vegetable matter. 
 
 * or shell marl the same quantity exhausts sooner than clay mirl (Karnes"). This is 
 owing cliiefly to the larger proportion of lime contained in the former. 
 
376 OF THE USE OF CHALK AS A MANURE. 
 
 But to these and other effects I shall have occasion to draw your at- 
 tention more particularly in a subsequent part of the present lecture. 
 
 § 7. O/" the use of chalk as a manure. 
 
 Chalk is another form of carbonate of lime which occurs very abun- 
 dantly in nature, and which, from its softness, has in many parts of 
 England been extensively applied to the land in an unburned state. 
 
 The practice of chalking prevails more or less extensively in all 
 that part of England (Leo. XI., § 8,) over which the chalk formation 
 extends. It is usually dug up from pits towards the close of the au- 
 tumn or beginning of winter, when full of water, and laid ujron the 
 land in heaps. During the winter's frost the lumps of chalk fall to 
 pieces, and are readily spread over the fields in spring. The quantity 
 laid on varies with the (juality of the soil and of the chalk itself, and 
 with the more or less perfect crumbling it undergoes during the season 
 of winter, and with the purpose it is intended to serve. It gives tena- 
 city and closeness to gravelly soils,* opens and imparls freeness to stitf 
 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 ciialks con- 
 tain much more clay than others, and are employed, therefore, in small- 
 er proportions. 
 
 For the improvement of coarse, sour, marshy pasture, it isap])lied at 
 (he 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 tiiat 
 are infested with this plant. 
 
 These effects are precisely such as usually follow from the applica- 
 tion 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 T^in- 
 colnsliire and Yorkshire would appear to diffi^r 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 ap- 
 pears 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 farmer, 
 and he 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 neighbors' 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 al- 
 most everywhere around and beneath them. 
 
 The cause of the diversities which thus present themselves in the 
 practice of experienced agriculturists, partly at least, is to be sought for 
 in the qualities of the different varieties of chalk employed. Careful 
 analyses have not yet shown in what respects these chalks differ in che- 
 mical constitution, and until this is ascertained we must remain in 
 
 * Mr. Gawler, North Hampshire, stales that a gravel thus stiffened, instead of 12 to 16 
 bushels of wheat, yielded afterwards 24 to 30 bushels.— British Husbandry, I, p. 2S0. 
 
EFFECTS OF CHALK ON THE WOLDS. 377 
 
 some measure in die 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 should act so much more beneficially than 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 tenacious 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 
 ihese lower beds, we can understand why the practical farmer in Suf- 
 folk should prefer ihem to the upper chalks of his own neighbourhood. 
 Still we cannot, as yet, give the scientific reasons why the one chalk 
 should be better than the other. A rigorous chemical analysis can 
 alone determine with certainty why the one should produce a differ- 
 ent effect from the other. 
 
 Chalks may diHer in the proportion of clay or of organic matter with 
 which they are associated — in the quantity of silica (the substance 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 sub- 
 stance 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 account 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 long j)rac- 
 tical experience. 
 
 On the chalk Wolds of Lincolnshire and Yorkshire the practice of 
 chalking even the thin soils is now comparatively old in date. The 
 lowe.'it 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 improve- 
 ment, 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 turnips, the latter plant being espe- 
 cially infested with the disease called fingers and toes {British Hus- 
 bandry, iii., p. 124 ] (Strickland). But a heavy chalking removes 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 yon 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 when in a state of nature, 
 so desiilute of lime that not a particle can be detected in them. That 
 lime in any form should benefit such soils is consistent with uniforna 
 
 ' Elirenberg has discovered tliat chalk is in a great measore composed of the skeleton8| 
 shells, or other exuviat (spoils) of marine microscopic animals. 
 
378 LIMK ALWAYS PRESENT IN FERTILE SOILS. 
 
 experience. I shall presently have an opportunity of directing your 
 attention to the two concurring causes by the joint operation of which 
 lime is sooner or later wholly removed trom the soil, even where, as in 
 the Wolds, it rests immediately upon the chalii. 
 
 § 8. 7s lime indispensable to the fertility of the soil 1 
 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 result of innumerable applica- 
 tions of this substance to lands of every quality, but it is established 
 also by a consideration of the known chemical conslilutiou of soils 
 which are naturally possessed of unlike degrees of fertility. 
 
 Thus sandy or siliceous soils are more or less barren if lime be ab- 
 sent — while the addition of this substance in the form of marl or other- 
 wise renders them susceptible of cultivation. So clay soils, in which 
 no lime can be detected, are often at once changed in character by a 
 sufficient liming. Felspar soils contain no lime, and they are barren — 
 and the same is true of such as are derived immediately from the de- 
 gradation of the serpentine rocks. 
 
 Trap soils, on the other hand — such as are derived from decayed 
 basalts or green-stones — are poor in proportion as felspar abounds in 
 them. Where augites and zeolites are present in large proportion in 
 the trap from which they are formed, tlie soils are rich, and may even 
 be used as marl. The only difference in this latter case is, that lime is 
 not deficient (Lee. XII., § 4), — and to this ditlerence the greater fertility 
 may fairly be ascribed. 
 
 But let it be conceded 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 lor even an average fertility to be manifested where 
 lime is entirely absent ? 
 
 There are two different considerations, from each of which we may 
 deduce a more or less satisfactory answer to this question. 
 
 1°. The result of all the analyses hitherto made of soils naturally 
 fertile show that lime is universally present. The per-ceatage oflime 
 in a soil may be very small, yet it can always be detected when valua- 
 ble and healthy crops will grow upon it. Thus the fertile soil of the 
 
 Marsh lands in Holstein contains 0-2 per cent, of carbonate of lime. 
 
 Salt marsh in East Friesland 0'6 " " 
 
 Rich pasture near Durham . 1*31 " " 
 
 But though the per ceutage oflime in these cases appears small, the 
 absolute quantity of lime present in the land is still large. Thus sup- 
 pose the first of these soils, which contains the least, to be only six 
 inches in depth, and each cubic foot to weigh only 80 lbs. — it would 
 contain about 3500 lbs. of carbonate of lime, upwards of a ton and a 
 half, in every acre. Arid this lime would be intimately mixed with the 
 whole soil, in which state it is always most effective in itsoperation. It 
 may also be inferred with safety, that if the upper six inches contained 
 this proportion of lime, the under soil would probably be richer still, 
 since lime tends not so much to diffuse itself through, as to sink down- 
 wards into the soil. 
 
STATE IN WHICH LIME EXISTS IN THE SOIL. 379 
 
 2°. The results of all the chemical examiuations hitherto made in 
 regard lo the nature of the inorganic matter contained in the sap and 
 substance of plants indicate, — if not the absolute necessity of lime to the 
 growth of plants, — at least tliat in nature all cultivated plants do ab- 
 sorb it by tlieir 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 indispensable. 
 
 The ash of the leaf and bull) of the turnip or potatoe, 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 attained. 
 
 Grant, then, that lime appears to be, perhaps virtually is, a necessary 
 food of plants, willioiit which their natural health cannot be maintained, 
 nor functions discharged, — still the quantity which must be present in 
 the soil to supply this food is not necessarily large. Even in favor- 
 able circumstances we have seen (Lee. X., § 3,) that the average crops 
 during an entire rotation of four years may not carry otFmore than 250 
 lbs. of lime from the acre of laud, a quantity which even the marsh 
 sr)ils of Holstein would be able to supply for half a century, could the 
 roots readily make their way into every part of the soil. 
 
 Siill we may safely hold, I think, that this quantity of lime at least 
 is indispensable — if cultivated plants are to flourish and ripen. So 
 nuici), al least, must in practice be every year added to cultivated 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 artificially or by some natu- 
 ral 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 operation in our climate which render a 
 larger addition than this desirable at least, if not indispensable to con- 
 tinued fertility. 
 
 § 9. Stale of comhinatlon in ivhich lime exists in the soil. 
 
 This lime, which we have concluded to be an indispensable constitu- 
 ent of fertile soils, may be present in several distinct states of combi- 
 nation. 
 
 1°. In that of chloride of calcium. — This compound, as we have al- 
 ready seen (Lee. IX., § 4,) is very soluble in water, and is not unfre- 
 quenilv 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 com- 
 l)inatif)n in which lime is recognised as a uniform or necessary consti- 
 tuent 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, an<l 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. 
 
380 HUMATK OF LIMK IN TIIK ROIL. 
 
 Its presence may be detected bj' the deposition of minute 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 ammonia causes a precipitate in one 
 small portion of the solution, it be found that nitrate of baryta also 
 throws down a white precipitate from another small portion. 
 
 3°. In the state of phosphate. — This compound is probably present, 
 though always in small j^roportion, in every soil which is capable of 
 raising a nutritious vegetation. It may be readily detected by treating 
 600 grains of the dry soil for 12 hours with dilute muriatic acid, and oc- 
 casionally stirring. If to the filtered solution caustic ammonia be add- 
 ed, a brownish precipitate will usually fall. If this precipitate be se- 
 parated, 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 Jime in the soil, may be safely inferred. 
 
 4°. In the state of silicate, lime rarely exists in the soil in any con- 
 siderable 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 dilute sulphuric acid, as above described, 
 the soil be digested for some hours at a gentle heat with concentrated 
 muriaiic 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 contains some lime in the state of sili- 
 cate. 
 
 . 5°. In the state of carbonate, lime is generally supposed most usually 
 to exist, and most abundantly in all soils. If on pouring dilute muri- 
 atic 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 some carbonate. 
 If after ammonia has been added to the solution, oxalate of ammonia 
 throws down a white precij)itate of oxalate of lime — the soil contains 
 carbonate of li?tie. 
 
 6°. In the state of humate.— in combination with humic acid (Lee. 
 XIII., I 1,) 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 improve- 
 ment. The presence of lime in the state of humate is only to be detect- 
 ed by carefully determining the relative weiglits 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 obtained, (see Appendix.) If for 
 every 100 grains of carbonic acid there be more than 77*24 grains of 
 lime, tlie remainder or excess has existed in the soil in combination with 
 humic or some analogous organic acid.* 
 
 ' To such analogous acids belonff the crenic and aponrenic acids (Lee. XllI , § 1.) The 
 existence of these acids in the soil is by no means problematical. Accordine to Professor 
 Hermann, of Moscow, they exist in the rich black soil (Tchornoi Zem.) of Little Russia, 
 to the amount of 4 per cent. 
 
QUANTITY OF LIME TO BE APPLIED TO THE SOIL. 381 
 
 Few investigations liave as yet been made in regard to the proportion 
 of lime which exists in the soil in the state of humate. It has gene- 
 rally been taken for granted — either that a soil was destitute of lime if 
 it exhibited no sensible efiervescence with dilute muriatic acid, — or 
 when further research was made, and the quantity of hme taken up by 
 this acid rigorously determined, that the whole of this lime must have 
 existed in the soil in the state of carbonate. That this is not necessarily 
 the case, however, appears to be proved by some recent ejiaminations 
 of certain soils in Normandy, which contain as much as 14 to 15 per 
 cent, of lime, and yet exhibit no etTervescence, and contain no carbo- 
 nate. The whole of the lime is said to be in the state of humate. 
 
 M. Dubuc, who has published the analyses of these soils, attributes 
 much of their fertility to the .presence of the humate of lime. Thus he 
 says that the soils of 
 
 Containing per cent. 
 Of Carbonate. Of Humate. Yields of Wheat. 
 
 Lieuvin, Neubourg, and Sistot, 18 to 20 12 to 15 fold. 
 
 Pavilli 5 8 to 10 " 
 
 Bieville 24 8 to 10 " 
 
 ClayofOuche - 1 4 to 5 " 
 
 Tlie first two j^ielding a wheat crop ever}' second year, the third only at 
 longer intervals. 
 
 Whatever degree of influence on the fertility of the soil it may ap- 
 pear 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 
 soiigln after. 
 
 The only one of the above compounds which is usually added to the 
 land, for the purpose of producing the ordinary effects of lime, is the 
 carbonate. Gypsum is applied only in small quantity for certain spe- 
 cial purposes, and does not always produce a sensible effect. It is in- 
 capable, therefore, of performing those purposes in the soil which are 
 served either by quick-lime or by the carbonate. The humate of lime 
 is probably formed in our lime composts, especially when much vege- 
 table matter is contained in them, and may thus be not imfrequently 
 applied directly to the land. 
 
 § 10. Of the quantity of lime which ought to be added to the soil. 
 
 The quantity of lime wliich ought to be added to the soil is dependent 
 upon so many circumstances, that it is impossible to state 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. 
 
 W(! have seen that a certain minim.um portion of lime is indispensa- 
 ble to a productive soil. If we suppose this smallest quantity to be no 
 greater than in the surface of the marsh lands of Holstein (p. 378) — 
 then with a soil six inches in depth, which contains no lime, we ought 
 to mix a ton and a half, say 40 bushels of slaked lime, and by succes- 
 sive yearly additions to supply the annual waste. 
 
 But to mix this feeble dose of lime intimately with the soil to a depth 
 of six inches would obviously require an expenditure of labor which 
 
382 MORE OUGHT TO BE LAID ON CLAY, WET, AND MARSHY SOILS, 
 
 the practical farmer could rarely afford. It would be greater economy, 
 therefore, in most cases to add a dose several times larger, and this not 
 only because the same amount of labor would diffuse it more general- 
 ly through the wliole soil, but because tbis larger liming would render 
 less necessary the immediat^ddilion of new supplies to repair the un- 
 avoidable waste. 
 
 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 arable cul- 
 ture, ought to be much larger than is above assumed as the smallest 
 or minimum quantity. If we suppose one per cent, to be necessary, 
 then eight tons of lime-shells, or upwards of 300 bushels of slaked lime, 
 must be mixed with a soil six inches in depth, to impart to it this pro- 
 portion — or half the quantity, if it bekept-within tliree inches of the sur- 
 face. Even 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 circum- 
 stances besides the depth of his soil, and the proportion of lime it al- 
 ready contains. Thus — 
 
 a. On clay lands more lime is necessary than on light and sandy 
 soils. This may ba partly ascribed to the jihysical 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 llius shut out I'rom the access of the air. These parti- 
 cles, therefore, must be more numerous in sucli a soil, if as many of 
 them are to be exposed lo the air as in lighter land, through which the 
 atmospheric air continually jiermeates. 
 
 h. On wet and marshy soils, a larger application still may be made 
 whh safety, and partly for the same reason. 
 
 Tiie moisture surrounding the lime shuts out the air, without the 
 ready access of which lime cannot perform its importantfunctions. 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 (Lee. II., § 7), to allow the chemical changes, which lime in fa- 
 vorable circumstances produces, to proceed with the requisite degree 
 of rapidit3^ Tlie soluble compounds which are formed as the conse- 
 quence of these changes are, in wet and marshy soils, dissolved by the 
 moisture, and so diluted as to enter 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 visible lumjis of mortar and cement, or into smaller parti- 
 cles of indurated matter, in which the lime is no longer in such a stale 
 as to be able lo act in an equal degree as an improver of the soil. 
 
 In cold and wet clays, in which all these evil conditions occasionally 
 meet, it is not surprising, therefore, that large doses of lime should 
 sometimes have been added without producing any sensible benefit 
 whatever. (" An instance is mentioned in the Nottingham Report of 
 720 bushels having been laid on an acre of clod clay land without any 
 benefit whatever." — British Husbandry, i., p. 296.) 
 
 c. Again, when the soil is also rich in vegetable matter, lime may 
 be still friore abundantly applied. Thus, when a field is at once wet 
 
AND SUCH AS ARE RICH IN VEGETABLE MATTER. 333 
 
 or marshy, and full of vegetable matter, as our peat bogs are, lime may 
 be laid on more unsparingly than under any other circumstances. 
 For in this case, besides the action of the access of water, as above ex- 
 plained, the vegetable matter combines with and masks the ordinary 
 action of a considerable quantity of the lime. By this combination, no 
 pan of the ultimate influence of the whole lime upon the soil is neces- 
 sarily lost ; in most cases the immediate effect only is lessened, which 
 the same quantity applied to other soils would have been seen to pro- 
 duce. In favorable circumstances its action is retarded and prolonged, 
 the compounds it forms with vegetable matter decomposing slowly, and, 
 therefore, remaining long in the soil. 
 
 To the exact chemical constitution 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 undergo, it will 
 be necessary to direct our attention when we come to study the theory 
 of the action of lime, as an improverof the soil. 
 
 d. Not only the natural depth of the soil, as already stated, but 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 materally injure a soil into 
 which the plougii rarely descends beyond two or three inches, might be 
 loo small an application where six or eight inches are usually turned 
 over by the plough. When new soil, also, is to be brought up, which 
 may be supposed to contain no lime, orin which noxious 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 lav- 
 ishly upon your fields. 
 
 The more dry and shallow the soil, the more light and sandy, the 
 less abundant in vegetable matter, the more naturally mild its locality, 
 and the drier and warmer the climate in which it is situated — the less 
 the quantity of lime which the prudent farmer will venture to mix with 
 it. It is to the neglect of these natural indications that the exhaustion 
 and barrenness that have occasionally followed the application of lime 
 are 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 ? 
 
 The quantity of lime which ought to be applied to the land must, as 
 we have seen, vary with its quality, and with the conditions in which it 
 is placed. Hence ihe practice in tliiarespect necessarily varies in every 
 county and in almost every district. 
 
 But a difference of opinion also prevails among 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, orin small quantities 
 frequently repeated. The indications of theory in reference to this point 
 are clear and simple. 
 
384 OUGHT LIME TO BE APPLIED IN LARGE OR SMALL DOSES. 
 
 A certain projiortion of lime is indispensable in our climate to the 
 production of the greatest possible fertility. Let us suppose a soil to be 
 wliolly destitute of lime — the first step of the improver would be to add 
 to 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. 
 
 Every year, however, a certain variable proportion of the lime is re- 
 moved from the soil by natural causes. The effect of this removal in a 
 few years becomes sensibly apparent in the diminished productiveness 
 of the hind. After the lapse of five or six years, during which it has 
 been gradually mixing with the soil, the beneficial effects of the lime is 
 generally the most striking — 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 sui^plied 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 oth- 
 erwise, will, on the first breaking up of new land, give it a heavy 
 liming, and whether he afterwards retain it in arable culture or lay it 
 down to grass, will at intervals of 4 to 6 years give it a new doseof one- 
 fourth to one-eighth of the original quantify. But local circumstances 
 and customs interfere in many well-farmed districts with this most na- 
 tural treatment of the soil. In the county of Roxburgh, for example, 
 on entering upon his farm, which holds on a lease of 19 or 21 years, the 
 tenant begins 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 crop- 
 ping for three or four rotations (14 to 16 years), when if he is sure of re- 
 maining on his farm he begins to lime again with the same quantity as 
 before. If he is to ([uit, however, he takes the best crops he can get, 
 but incurs no further outlay in the addition of lime. His successor fol- 
 lows tlie same course — begins by expending ])erhaps c£lOOO in lime, 
 and betiire he leaves at the end of his lease, lias, by continued cropping, 
 brouglit 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 is laid 
 on — often when preparing for the wheat crop, either by ploughing in the 
 second furrow, or by harrowing in with the seed — at the rate of 40 bush- 
 els of shells an acre, and this dose is of course repealed every 4 or6 years, 
 according to the length of the rotation. If we consider the probable dif- 
 ference in the soil and climate, the proportion of lime added in the two 
 dis!i!cls does not materiallyditler. In Ayrshire from 8 to 10 bushels, and 
 in Roxburgh from 10 to 12 busliels, are added for each year.* In both 
 counties, however, many farms may be met within which the treatment 
 of the land in this respect differs from that which is generally followed. 
 
 * According to GeiiPral Beatson (.New System of Cultivation, 1820), upwards l(X)bustieIs 
 an acre, ;U a cost of jG?. IGs., used to be applied to the clay laiida uf Sussex— on the fallow, 
 befiire wheat — every foui years. This was 25 bushels per acre lor each year. In such 
 lands as these the saving in the article of lime alone, which would follow a judicious drain- 
 age, would be very great. 
 
COMPARATIVE ECO.NOMY OF THK TWO METHODS. 385 
 
 In Flan.Jera a similar difference in ihe practice prevails in different 
 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 applied per acre, in the lat- 
 ter from 10 to 12 bushels every third year. In both niodesof procedure 
 the quantity of lime applied by the year is nearly the same — between 
 3i 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 recognized or involved 
 in the agricultural practice both of our own and of foreign countries, 
 that nearly the same annual addition of lime 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, ijo saving in the cost of lime, 
 whichever method you adopt. A slight consideration of the subject, 
 however, may satisfy us that there is a real difference in the compara- 
 tive economy or profit of the two methods. 
 
 Let us suppose two acres of the same clay land to be limed respec- 
 tively with 200 bushels each, and that the one is cropped for twenty 
 years afterwards without further liming, while the other at the end of 
 every five years is dressed with an additional dose of 40 to 50 bushels, 
 fn both ca*es the land would have attained the most productive con- 
 dition in five or sis years. Let us suppose that in this condition it jtro- 
 duced animally a crop of (or equivalent in nutritive value to) 30 bushels 
 of wheat, and that on neither acre did a sensible diminution appear be- 
 fore the end often years. Then during the second ten the crops would 
 grailually lessen in the one acre, wliile, in consequence of the re- 
 addition of the lime as it disappears, the amount of produce w'ould re- 
 main sensibly the same in the other acre. Suppose the produce of 
 the former gradually to dimmish 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. If now tlie second large dose of 200 bushels 
 be added to this latter acre, the cost of liming both will have become 
 sensibly the same, but the amount of produce or of profit from the two 
 acres during the second ten years will stand thus — 
 
 10 crops, of 30 bushels each, amount to 300 bushels. 
 10 crops, of 25 bushels each, amount to 250 bushels. 
 
 Difference in favour of frequent liming, 50 bushels per acre, 
 or nearly two icliole 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 fre(|uently 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 
 17 
 
386 MANUUK MUST EK ADDKD WHKRE LIME ABOUNDS. 
 
 this method ; but there seems every reason to believe that it will best 
 reward those who feel themselves at liberty to follow the indications at 
 once of sound theory and of enlightened practice. 
 
 One thing, however, must be borne in mind by those who, in adopt- 
 ing the best system of liming, do not wish both to injure their land and 
 to meet wiih 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 abundantly 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 manures in the soil — otherwise present fertility and gain will be 
 followed 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 slate of combination in ivhich lime ought to he 
 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, in arable culture, 
 or laid down to grass, 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 unwhole- 
 some herbage, of quickening inert vegetable matter, of generally sweet- 
 ening the soil, or simply of adding to the land a substance which is in- 
 dispensable to its fertility. 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 regard to 
 the changes which quick-lime undergoes in the air, it appears to be ex- 
 j)edient, 
 
 1°. To slake lime quickly, and to apply it immediately upon clay, 
 boggy, marshy, or peaty lands — upon such also as contain much inert 
 or generally which 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, or to unwholesome subsoils which 
 contain much iron (sulphate of iron), as soon as they are turned up by 
 the plough. In both liiese cases the unslaked lime-dust from the kilns 
 might be laid on with advantage. 
 
 ♦ " 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 fallow for tur- 
 nips, and this produces excellent crops, even without dung." — Morton on Soils, thirti edition, 
 p. 181. The practical reader must not consider this custom of ttie Somersetshire farmers 
 as at all at variance with what is stated in the text : he must conclude, rather,— if the sen- 
 tence tiere quoted is meant to apply that they lime their arable land so repeatedly, and ycj 
 »dd no organic manure— that they will, sooner or later, cease to boast of its fertility. 
 
COMPARATIVE KCONOMY OF LIME ANB MARL. 387 
 
 3°. Where it is to be spread over grass lands without destroying the 
 lierbage, it is in most cases safer to allow the lime to slake spontaneous- 
 ly, and ill 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 sutticiently mild to leave the tender grasses unharmed, it contains 
 a sufficient quanthy of caustic lime (p. 368) to produce those chemical 
 changes in the soil on which the efficacy of quick-lime depends. 
 
 4°. Where lime is ap])lied to the fallow, is |)loughed in, well har- 
 rowed or otherwise mixed with the soil, it is generally of little conse- 
 (]uence in which of the above states it is laid on. The chief condition 
 is, that it be in the slate of a fine jKJwder, and that it be well spread 
 and iniiinately mixed with the soil. Before these operations are con- 
 cluded 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. 
 
 You will understand that 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 ques- 
 tion 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. &c., will ultimately produce 
 precisely the same etl'ects 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 efTect 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°. H(nv much of the marl or sand must I add to be equal to a Ion 
 of lime-shells ? This will depend on the per-cenlage of lime which 
 the marl contains. Suppose it to contain 20 per cent., or one-fifth of its 
 weight of lime, (not carbonale of lime, but of lime in the state in which 
 it comes fro'n the kiln, 100 lbs. of carbonate containing 56 lbs. quick 
 li)ne, p. 364,) 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 the slaked lime, ilie same quantity of lime in 
 the former cannot be so eijually diffused through the soil as in the lat- 
 ter stale. An allowance must therefore be made on this account, and 
 an additional quantity equal to one-lburth or one-fifth of the whole add- 
 ed, for tiie purpose of equalizing the efTect. 
 
 2°. Which of the two, the quick-lime or its cfjuivalent of marl, can 
 I obtain and apply at the less cost ? This will not be dlflicult to calcu- 
 late, the proportion of lime contained inihe marl being once ascertained. 
 
 3°. Tliis (]uestion of economy being decided, it is necessary to con- 
 sider the kind and quantity of the earthy matter with which the lime 
 in ihe marl is mixed. If it be a lime-sand or sandy marl, it may be un- 
 fit to ajiply to light and sandy soils ; if it be a stiH' unctuous clay marl, it 
 may only render stiller 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 ac- 
 cessible. 
 
388 USE APTD ADVANTAGE OP TflE COMPOST FORM. 
 
 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 ana advantage of the compost form. 
 
 As there are many cases in wliich lime ought to be applied unmixed 
 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 tiie 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. 
 
 2°. On lighr, sandy, and gravelly soils, when of a dry character, un- 
 mixed lime will bring up much cow-wheat {melam'pyrum) 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 impervious subsoil, 
 or lumps of a iiard conglonteraie, 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 lauds — 'unless the soil be stiff clay — or much 
 coarse grass is to be extirpated, — >it is generally better and safer to apply 
 it in the compost form. Tho action of the lime on the tender herbage 
 is by this means moderated, and its exhausting ellect lessened upon 
 soils which contain little vegetable matter. 
 
 4°. In the compost form the same quantity of lime acts more imme- 
 diatel3^ While lying in a state of mixture, those chemical changes 
 which lime either induces or promotes have already to a certain extent 
 taken place, and thus the sensible eHTect of the lime becomes apparent 
 in a shorter time after it has been laid upon the land. 
 
 5°. This is still more distinctly the case when, besides earthy mat- 
 ter, decayed vegetable substances, ditch scourings, and other refuse, are 
 mixed with the lime. The experience of every practical man has long 
 proved how very mucli more enriching such composts are, and more 
 obvious in their effects upon the soil, than the simple application of 
 lime alone. 
 
 6°. 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 fi)rm 
 will produce an equal effect. For this, one cause may be, tliat the rains 
 are prevented from acting upon the mass of compost as they would do 
 upon the open soil — in washinn; out either the lime itself or the saline 
 substances which are produced during its contact with the earlhv and 
 vegetable matter with which it is mixed. 
 
 1°. The older the compost the more fertilizing is its action. This 
 fact is of the same kind with that generally admitted in respect to the 
 action of marls and unmixed lime — that it is more sensible in the se- 
 cond year, or in the second rotation, than in the first. 
 
 In conclusion, it may be stated that this form of application is especi- 
 ally adapted to the lightest and driest soils, and to snch as are poorest in 
 vegetable matter. In this (ijrm, lime hasimparterl an unexpected feriilify 
 even to the white and barren sands of the Landes (Puvis,) and upon 
 the dry hills of Derbyshire it has produced an almost etjual benefit. 
 
PERIOD FOR THE APPLICATION OF LIME. 339 
 
 § 14. When ought lime to be apjilied ? 
 
 This question may refer either to the period in the lease, in the rela- 
 tion, 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 propjiefy of applying lime in large or 
 small doses. 
 
 In regard to the period of the year and of the rotation, there are three 
 princijiles by which the procedure of the practical man ought chiefly to 
 be directed. 
 
 1°. That lime takes some lime to 2^roduce its known effects upon the 
 soil. — It ought, therefore, to be ap|)lied 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 naked fallow where the land 
 is allowed to be at rest for a year, — or on the grass fields before break- 
 ing up, where the pasture is to be immediately succeeded by corn. 
 
 2°. That quick-lime expels ammoniafrom decomposed and fermenting 
 manure. 
 
 When sucli manure, therefore, is applied to the land, as it is in all 
 our well-farmed districts, qiuck-lime should not be so laid upon the 
 land as to come into immediate contact with it. If both must be ap- 
 plied 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 a year before or a year after the period in 
 the rotation at which the 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 fallow, to the grass before breaking up, or 
 along with the winter wheat after a green crop which has been aided 
 by fermented manure. When ploughed into the fallow, or spread upon 
 the grass, it has had time to be almost completely converted into the 
 mild state (that of carbonate,) before the manure is laid on. In this 
 mild state it has no sensible efTect in expelling the ammonia of decom- 
 posing 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 nourishing 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. (Elements of 
 Practical Agriculture, third edition, p. 63,) contains the following re- 
 mark : — " 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 sub- 
 stances, as is frequent in the practice of farmers." This is strictly cor- 
 rect only in regard to marls, lime-sand, &c., or to perfectly mild lime, 
 any of which may be mixed, without loss, with manure in any state. 
 Of quick or caustic lime it is correct only when the animal or vegetable 
 matter has not yet begun to ferment. With recent animal or vegetable 
 matter, quick-lime may be mixed uj) along with earth into a compost, 
 not only without the risk of much loss, but with the prospect of mani- 
 fest advantage. 
 
 3°. That quick-lime hastens or revives the decomposition of inert or- 
 ganic matter. — This fagt also indicates the propriety of allowing the 
 
390 LIME HASTE^S ORGA^MC DKCOMFOSITION. 
 
 lime as much time as possible to operate before a crop is taken from 
 land in which organic matter already abounds. Or where fermenting 
 manure is added, it advises the farmer to wait till sponianenus decom- 
 position 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, (Morton "■On Soils," third edition, p. 181,) 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 decomposition of vegetable matter. If straw or long 
 dung be mixed with slaked lime, it will be preserved ; wliilc 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 
 nevertheless consistent both witli theory and universal observation, that 
 lime i?i the soil promotes the decom|JOsition of organic matters, both 
 animal and vegetable. This will appear more clearly when we come 
 to study the precise nature of the action of lime u[)on organic substan- 
 ces in general. 
 
 The above remarks, in regard to llie best time for applying lime, re- 
 fer chiefly to quick-lime, the state in which, in England, it is so exten- 
 sively used. Marls and shell-sands can cause no loss when mixed 
 with the manure, and therefore may with safety be laid on at any pe- 
 riod of the rotation. The same remark applies with greater force to the 
 lime composts. These may be used i)reciscly 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 com in spring, when the grass and clover seeds are sown by 
 which the corn crop is to be succeeded. And as lite compost acts 
 more sj)eedily than lime in any other form, it is especially adapted for 
 immediate application 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, bj' 
 which, while the surface is naked, the soluble matters produced in the 
 soil are likely to be very much washed away. 
 
 § 15. Of the effects jnoduced by lime. 
 
 The effects of pure lime upon the land, and upon vegetation, are ul- 
 timalely the same, whether it be laid on in a state of hydrate or of car- 
 bonate. If different varieties produce unlike efTects, the quantity of 
 lime applied being the same, it is because in nature lime is always 
 more or less mixed with other substances which are capable of modi- 
 fying the effects which pure lime would alone produce. The special 
 effects of marls, &c., when they differ from those of burned lime, are 
 to be ascri!)ed to the jiresence of such adtnixtures. In general, how- 
 ever, 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 
 fur the effects which we have already seen to be produced by marls, 
 (p. 374,) represent also the general effects of lime in any form. 
 
 These general elTects may be considered in reference to the land on 
 which it is laid, and to the crops which are, or 7nny be, made to grow 
 upon it. 
 
KFIECTS OK LIME UPO.N T.iF. LA.ND AND CROPS. 391 
 
 I. EFFECTS OF LIME UPON THE LAND. 
 
 Pure lime, like the marls, produces both a mechanical and a chemi- 
 cal eflect upon (he 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 stiti'and clayey, while it increases the porosity of such 
 as are already' light and sandy. To the former its meclianical action is 
 almost always favourable, to the latter not unfrequently the reverse. 
 
 From its chemical action the benelits which follow the use of lime 
 are cJiiefly derived. These benelits are principally the following: — 
 
 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 
 H)ld.) of rye, by the addition of liiue alone, will yield a 6 or 7 fold re 
 turn of wheal. From some clays, also, apparently unfit to grow corn 
 it brings up luxuriant crops. 
 
 3°. It increases the eticct of a given application of manure; calls 
 into action that which, having been previously added, appears to lie 
 dormant ; and though, as we have already seen, (p. 386,) manure must 
 be plentifully laid upon the land, after it has been well- limed, yet the 
 same degree of productiveness can still be maintained at a less cost of 
 manure than where no lime has been applied. 
 
 4°. As a necessary result of these imjiortant changes, the money 
 value and annual return of the land is increased, so that tracts of coun- 
 try which had let with diHiculty for 5s. an acre, have in many locali- 
 ties been rendered worth 30s. or 40s. by the application of lime alone, 
 (Sir J. Sinclair.) 
 
 II. EFFECTS OF LIME 0^' THE PRODUCTIONS OF THE SOIL. 
 
 1°. It. alters the natural produce of the land, by killing some kinds 
 of plants and favouring the growth of cithers, the seeds of which had 
 before laiti 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 corn-marigold, (chrysanthemum segetum, [Bonninghau- 
 sen,]) while, if added in excess, it encourages the red poppy, the yel- 
 low covv-wheal, {melam-py rum j^r alev.se,) and the yellow rattle, {rhinan- 
 ihus crista galli,) and when it has sunk, favours the growtii of the trou- 
 blesome and deep-rooted coltsfoot. 
 
 Similar effects are produced upon llie natural grasses. It kills heath, 
 inoss, and sour and benty* (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 
 natural or artificial, is said to be sounder and more nourishing when 
 grown upon land to which lime has been abundantly applied. On 
 benty grass the richest animal manure often produces little improvemeiil 
 until a dressing of lime has been laid on. 
 
 * In Liddisdale, on the Scottish border, is' a large tract of land in what is there called 
 Jluing biinl, not worth more than 3s. an acre. If surface-drained and limed at a cost of 
 £i to £'i an acre, this becomes worili 12s. an acre for sheep pasture. An intelligent and 
 experienced border farmer assures me that such land would never forget 40 to 60 bushels 
 of lime per acre. 
 
392 LIME IMPROVES THE qUAlITY OF THE CROP. 
 
 It is partly in consequence of the change which it thus produces in 
 the nature of the herbage, that the application of (lulck-linic to old grass- 
 lands, some time before breaking up, is found to be so useful a ]5ractice. 
 The coarse grasses being destroyed, tough grass land is opened and 
 softened, and is afterwards more easily worked, while, when turned 
 over by the plough, the sod sooner decays and enriches the soil. It is 
 another advantage of ibis practice, however, that the Ume 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 benefitted. 
 
 2°. It improves the quality oj almost every cultivated crop. 'J^hus, 
 upon limed land, 
 
 a. The grain of the corn crops has a thinner skin, is heavier, and 
 yields more flour, while tbis flour is said also to be richer in gluten. 
 On the other hand, these croj^s, after lime, run less to straw, and aie 
 more seldom laid. In wet seasons, (in Ayrshire,) wheat preserves its 
 healthy appearance, while on unllmed land, of equal quality, it is yel- 
 low and sickly. A more marked in^provement is said also to be pro- 
 duced both in the quantity and in the quality of the spring-sown than of 
 the winter-sown crops, (Puvis.) 
 
 h. Potatoes grown upon 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 imdrained. 
 
 c. Turni2^s are often improved both in quantity and in quality when 
 it is laid on in preparing the ground for the seed. It is rnost etficient, 
 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 mat- 
 ter of various kinds. 
 
 cl. Peas are grown more jdeasant to the taste, and are said to be 
 more easily boiled soft. Both beans and peas also yield more grain. 
 
 c. Rape, after a half-Wnnns, and manuring, gives extraordinary crctps, 
 and the same is the case with tlie colsa, the seed of which is largely 
 raised in France for the oil which it yields. 
 
 /'. On flax 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. 
 
 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, though 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 cultivated 
 
 district. I have already drawn your attention (p. 310) to this as one 
 
 of the incidental results which follow the skilful introduction 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 improvement, and how much 
 
 * A comparatively long period is sometimes permitted to elapse before the 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 admi- 
 rably foroala." 
 
LIMK SHOULD BE KEPT NEAR THE SURFACE. 393 
 
 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 decom- 
 jwses them or causes their elements to assume new forms of chemical 
 combination, in vvliich they no longer exert the same injurious influ- 
 ence upon animal life. How beautiful a consequence of skilful agri- 
 culture, that the health of the community should be promoted by the 
 same methods which most largely increase the produce of the land ! 
 Can you doubt that the All-benevolent places this consequence so 
 plainly before you, as a stimulus to further and more general improve- 
 ment — to the application of other knowledge still to the amelioration of 
 the soil ? 
 
 § 16. Circumstances by ichich 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 produce 
 a given effect, and the form in which it will prove most advantageous, 
 are, in a great measure, dependent upon the dryness of the soil, upon 
 the quantity of vegetable matter it contains, and on its stiff" or open tex- 
 ture. There are several other circumstances, however, to which it is 
 projier still to advert. Thus, 
 
 1°. Its effects are greatest when well mixed with the soil, and hept 
 near the surface uilhin easy reach of the atmosphere. The reason of 
 this will hereafter a[)pear. 
 
 2°. On arable soils of the same kind and quality, the effects are 
 greatest upon such as are newly ploughed out, or upon subsoils just 
 brought to da}'. In the case of subsoils, tliis is owing partly lo their 
 containing naturally very little lime, and partly to the presence of nox- 
 ious ingredients, which lime has the power of neutralizing. In the case 
 of surface soils newly ploughed out, tlie greater effect, in addition to these 
 two causes, is due also to the large amount of vegetable and other or- 
 ganic matter which has gradually accumulated within them. It is the 
 presence of this organic matter which has led to the establishment of 
 (he excellent practical rule — " that lime oufi-ht always to precede putres- 
 cent manures ivhcn old leys are broken up for cultivation." 
 
 3^. Its etfecls 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 (Lee. XL, § 8) — 
 on those of the new and old red sand-stones, of the granites, and of 
 many slate-rocks — and, generally, on the soils formed from all rocks 
 which contain little lime, or from which the lime may have been washed 
 out dm-ing their graiiual degradation. 
 
 On iheother hand, it is often applied in vain to the soils of the oolites 
 (Lee. XL, § 8), and other calcareous formations, because of the abund- 
 ance of lime already present in them. The advantage derived from 
 chalking thin clay soils resting immediately upon the chalk rock (Lee. 
 XL, § 8, and i)age 376), is explained by the almost entire absence ot 
 lime from these soils. The clay covering of the chalk wolds has pro- 
 bably been formed, not from the ruins of the chalk rock itself, but 
 from the deposit of muddy waters, which rested upon it for some time 
 before those locahties became dry land. 
 
 4°. Lime produces a greater inoportional improvement upon poor soils 
 17» 
 
394 LAND MAY BE SATURATED WITH LIMK. 
 
 than on sucli as are riclier (Dr. Anderson.) This is also easily under- 
 stood, It is of poor soils in iheir natural stale of which Dr. Anderson 
 speaks.* In this state they contain a greater or less quantity of organic 
 matter, hut are nearly destitute of lime, and hence are in tlie most favour- 
 able condition for heing benefitted 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 tliat arable land already worth £2 per acre, could, by 
 liming or any other single operation, become worth ^£16 per acre of an- 
 nual rent. The greater proportional improvement produced upon poor 
 lands Ijy lime is only an illustration, therefore, of the general truth — 
 that on j)Oor soils the efibrts of the skilful improver are always crowned 
 with the earliest and most apparent success. 
 
 5°. In certain cases, the addition of lime, even to land in good culti- 
 vation, and according to the ordinary and approved practice of the district, 
 produces no elTect whatever. This is sometimes observed where the 
 custom prevails, as in some parts of Ayrsliire and elsewhere, to apply 
 lime along with every wheat crop (p. 384,) 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 rotatioti of 4 or 5 years, the land 
 may soon become so saturated with lime that a fresh addition will j)ro- 
 duce no sensible etlect. Tlius Mr. Campbell, of Craigie, informs me 
 of a trial made by an intelligent firmer in his neighbourhood, v.'l)ere al- 
 ternate ridges only were limed without any sensible dilFerence being ob- 
 served. No result could show more clearly tlian this — that for one ro- 
 tation at least the expense of lime might be saved, while at the same time 
 the land would run the less risk of exhaustion. Another fact mentioned 
 by Mr. Campbell proves the soundness of this conclusion. 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. The fair inference is, therefore, that in this district as well as 
 in others where similar effects are observed, too mucli lime is habitually 
 added to the land, whereby not only is a needless expense incurred, but 
 a si)eedier exhaustion of the soil is insured. Good husbandry, therefore, 
 indicates either the application of a smaller dose at the recurrence of the 
 wheat crop — or the occasional omission of lime altogether for an entire 
 rotation. The practical farmer cannot have a better mode of ascer- 
 taining when his land is tluis fully supplied witli lime — than by mak- 
 ing the trial ujion alternate ridges, and marking the elFect. 
 
 6°. On poor arable lands, which are not naturally so, but which are 
 worn out or exhausted by repeated liming and ciojiping, lime produces 
 no good whatever! (Anderson, Brown, Morton.) Such soils, if thc}'^ do 
 not already abound in lime, are, at least, equally destitute of numerous 
 other kinds of foo<l, organic and inorganic, by which healthy ])lau(s are 
 nourished, — and they are only to be restored to a fertile condition by a 
 
 ' " I nevpr met," he says, "with a poor soil in its natural state., wliich was not benefifed 
 in a very great degree by calcari'oiis matter when administprert in proper ruiaiilitips. But 
 I have met with several rich soils, which are fully impregnated with dang, on which lime 
 applied in any quantity produced not the smallest sensible elTeci." 
 
 t " 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.) 
 
LIME DOES KOT BENKFIT EXHAUSTED LANDS. 395 
 
 judicious admixture of all. This truth is confirmed by the practical 
 observation, that on soils so exhausied farm-yard manure along with 
 the lime does not produce the same good results as in other cases. All 
 tliat the soil requires is not supplied in sufficient abundance by these 
 two substances laid on alone. 
 
 7°. On lands of this kind, aud 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 already, by long arable culture, too open. 
 (Morton.) 
 
 8°. A consideration of the circumstances above adverted to explains 
 why, in some districts, and even in some whole provinces, the use of 
 lime in any, form should be condemned and even entirely given up. 
 The soil has been impoverished through its unskilful application — or, 
 by large a(hnixtures of lime or marl lor a series of years, the soil has 
 been so changed as to yield no aderiuate return for new additions. Thus 
 for a generation ortwo the practices of liming and marling are abandoned, 
 to be slowly and reluctantly resumed again, when natural causes have 
 reinoved the lime from the soil, and produced an accumulation of those 
 other substances wiiicli, when associated with it, coniribute to the pro- 
 ductiveness of the land. 
 
 § 17. Effects of an overdose of lime. 
 
 There are several effects which are familiar to the practical man as 
 more or less observable when lime in any form is laid too lavishly upon 
 the land. Tims 
 
 1°. It is rendered so loose by an overdose as to be capable of hold- 
 ing no water (Kames). Upon stiff clays a very large quantity indeed 
 will be required to produce this effect. 
 
 2°. Bv an overdose of quick-lime the land is hardened to such a degree 
 as to be impervious to water or to tlie roots of plants. Several parts of 
 the Carse of Gowrie are tinis rendered so hard as to be unfit for vegeta- 
 tion — (Lord Kames' Gentleman Farmer, edit. 1802). This effect will 
 be observed only in soils which are naturally wet and undrained, or 
 where mucli rain has fallen and lingered on the land after the lime 
 has been applied (p. 388). 
 
 3°. But the most injurious effect of an over-liming, whetlier it be 
 laid on at one or at successive periods, is the exhaustion by which it is 
 succeeded. *' An overdose of shell-marl," saj'sLord Kames, "laid per- 
 haps an inch thick, produces for a time large crops, but at last renders 
 the soil capable of bearing neither corn nor grass, of which there are 
 many examples in Scotland." The same is true of hme in any form. 
 The increased fertility continues as long as there remains an adequate 
 supply of organic (animal and vegetable) matter in the soil, but as that 
 disappears the crops every year diminish both in quantity and in quality. 
 
 An interesting illustration of this exhausting power of 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 employed is a 
 sandy marl, containing from 30 to 60 per cent, of carbonate of lime— 
 
396 LENGTH OF TIME DURING WHICH LIME ACTS. 
 
 very much like the lime-sand of Ireland or tlie shell-sand of the West- 
 ern Islands already described (p. 371). A layer of this marl one-third 
 of an inch thick, applied at intervals to a soil producing in its natural 
 state only a three-fold return of rye every other year, causes it to yield 
 for the first 10 or 12 years an eight fold return of wheat. But after 40 
 years' marling, the farmers now complain that the land will give only a 
 four-fold return of wheat. But the cause of this reduction is to be 
 found in the constant cropping with corn, in the growing of no green 
 crops, and in the addition of no manure. Yet even with this treat- 
 ment the land is still more productive than before the marling was com- 
 menced. It produces four returns instead of three, and it grows wheat 
 where before only rye would thrive and ripen. 
 
 From the possession of this exhausting property has arisen the al- 
 most universally diffused proverb, that lime enriches the fathers hut 
 impoverishes the sons. The fault, however, is not in the lime, but in 
 the improvident fothers, who in this case, as in so many others, exhaust 
 and inconsiderately squander the inheritance of their sons. If care 
 be taken to keep up the supply of organic matter in the soil — by copi- 
 ous additions of manure or otherwise (p. 380) — lime may be added 
 freely and a system of high farming kept up, by which both the pres- 
 ent holder of the land and his successors will be cqiially benefitted. 
 
 The opinion expressed by some of the highest authorities among 
 practical men, that too much lime cannot be added, provided the soil 
 abound sufficiently in vegetable matter, may perhaps be rather over- 
 stated ; but it undoubtedly embodies the result of long-continued gen- 
 eral observation — that the exhausting effectof lime may be postponed 
 indefinitely by a liberal management of the land.* 
 
 § 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 ori- 
 ginally 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 on the climate in which it is 
 situated. 
 
 We have seen that on the arable lands of the south of Scotland 20 
 years is the longest period during which the doses there applied act 
 beneficially upon the crops — while in other parts of the country re- 
 newed applications are considered necessary at much shorter intervals. 
 Mr. Dawson, of Frogden, who introduced the practice oi'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. A heavy marling or chalking* in the southern and 
 
 ' In Germany the necessary union of manure and marl is in the nioulli of every peasant 
 
 Ohiie mist 
 
 1st das Geld fiir mergeln verquist. 
 
 t Applied at a cost of 30b. lo 50s. per acre, according to the locality.— Mr. Pusey, Royal 
 Agricultural Journal, iii., p. 185. 
 
LIME NATPRALLY SINKS INTO THE SOIL. 397 
 
 Midland counties of England is said also 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 grass lands would never forget a 
 good dose of lime (p. 391, note). 
 
 § 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 at a greater or less depth beneath the surface, but 
 lodging, generally, where it has attained its greatest depth between the 
 upper, loose ajid fertile, and the lower, more or less impervious and un- 
 productive soil. In arable lands the action of the plough counteracts 
 tliis tendency in some measure, bringing up the lime again from be- 
 neath, 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 minute- 
 ness of the particles into which slaked lime naturally falls. If a por- 
 tion of slaked lime be mixed with water it forms a milky mixture, in 
 which some lime is dissolved, but much more is held in sxispension in 
 an extremely divided state. When this millc is allowed to stand undis- 
 t'.irbed, the fine particles subside very slowly, and are easily again dis- 
 turbed, but if thrown upon a filter they are arrested immediately, and 
 the lime-water passes through clear. Suppose 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 i.^ common not only to lime, but to all minutely divided earthy 
 matter of a S7f^cie7itly incoherent nature. Hence the formation of that 
 more or less impervious layer of finely divided matter which so often 
 forms the subsoil beneath free and open surfiice soils. And that lime 
 should appear alone or chiefly to sink on any cvdtivated field, may arise 
 from this circumstance — that the continued action of the rains had long 
 betbre 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 exercised. 
 
 This explanation is satisfactory enough in the case of light and open 
 soils. Avhich are full of pores, but it appears less so in regard to stiff" 
 clays and to loamy soils, which are not only close and apparently void 
 of pores, but seem themselves to consist of particles in a sufficiently 
 minute slate of division to admit of their being carried down bv the 
 
398 EFFECTS OF SINKING, AND REMEDIES FOR IT. 
 
 rains in an equal degree with lime itself. This difficulty induced Lord 
 Dundonald to suspect the agency of some chemical principle in produ- 
 cing the above effect.* As the lime, however, is unchanged after it has 
 descended, is still in a poAvdery 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 contribute so 
 much to the grackial 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-dressings.f 
 
 Tlie effects of this sinking are to remove the lime from the surface 
 soil, and to form a layer of calcareous matter which in wet or imper- 
 vious bottoms will harden and form a more or less solid bed or pan, 
 through which tiie rains and roots refuse to penetrate, and v^hich the 
 subsoil plough in some districts can tear up with difficulty. On our 
 stiller soils it encourages the growth of the troublesome coltsfoot, and in 
 the. open ditches of the wholesome water-cress. 
 
 The practical remedies for this sinking are of two kinds : 
 
 1^. Tlie ploughing of a deeper furrow, and hence one of the benefits 
 which in many localities follow the use of tiie trench plough (p. 322). 
 
 2°. The sowing of deep-rooted and lime-loving crops, such as lucerne 
 and saintbin, 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 pre- 
 viously descended, and thus make it available to the after-crops. 
 
 § 20. Why liming must he 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 Jid- 
 dition ofa fresh dose of lime, nor does it explain the reason Avhy in prac- 
 tice 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 becomes 
 sensibly less rich year by year, the crops of corn less abundant, the kind 
 of grain it will ripen less valuable. Does the lime, you might ask, ac- 
 tually disappear Irom the soil, or does it merely cease to act? This 
 question has been most distinctly answered by an experiment of Lam- 
 padius. 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 sub- 
 sequently, by analysis, the quantity of lime it contained in each of the 
 three succeeding j'ears. 
 
 The first year it contained . 1-19 per cent, carbonate of lime. 
 The second year .... 0-89 " " 
 
 The third year 0-52 " " 
 
 The fourth year 0-24 " « % 
 
 ' " In clay(\y and loamy soil.?, which are (?> equally ditTusible with lime, and nearly of the 
 sinie specific sravily, the tendency which lime has lo sink cannot be accounted for simply 
 on mechaiUL-al principles " — Lord Uimdonald's AgricuUural Chemistry, p. 45. 
 
 f See in a snbseqnent lecture the remarks on laying donrn to grass; also tlie Author's 
 Elements of Agricultural Cliemistry, p. !il2. 
 
 } Schiibler, Agricv'tnra! Chemie, ii , p. 141. 
 
WHY LIMING MUST BE REPEATKD. 399 
 
 There can be no question, therefore, that the Hrae gradually disappears 
 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 culti- 
 vated crops. 
 
 2°. A considerable quantity of lime is annually removed from the 
 soil by the crops which are reaped from it. We have already seen 
 (Lee. X., § 4.) 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 248 lbs. This is equal to 60 lbs. of quick-hrae or 
 107 lbs. of carbonate of lime ei'enj year. The whole of this, however, 
 is not usually lost to the land. Part at least is restored to it in the ma- 
 nure into which a large proportion of the produce is usually converted. 
 Yet a considerable qitantity is always lost — escaping chiefly in the 
 liquid manure and m the drainings of the dung-heaps — and this loss 
 nnist 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 hme. The 
 rains tliat fall, therefore, cannot fail, as they sink through the soil, to 
 dis.-jolve and carr}- away a portion of the lime so long as it remains m 
 liie caustic state. 
 
 Again, quick-lime, when mixed with the soil, sjieedily attracts car- 
 bonic acid, and becomes, after a time, converted into carbonate, which 
 is nearly insoluble in pure water. But this carbonate, as we have , 
 already seen (Lee. III.. § 1), is soluble in water impregnated with car- 
 bonic acid — and as the drops of rain in falling absorb this acid from the 
 air, they become capable, v.'hen they reach the soil, of dissolving an 
 appreciable quantity of the finely divided carbonate which they meet 
 wiih upon our cultivated lands. Hence the water that flows from 
 tiie drains upon such lands is always impregnated with lime, and 
 sometimes to so great a degree as to form calcareous deposits in the in- 
 terior of the drains themselves, where the fall is so gentle as to alloAV the 
 water to linger a sufficient length of time in tlie soil. 
 
 It is impossible to estimate tlie quantity of lime which this dissolving 
 action of the rains must gradually remove. It will vary with the 
 amount of rain which fills in each locality, and v.^ith the slope or inclina- 
 tion of the land ; but the cause is at once universal and constantly oper- 
 ating, 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 ihe decay of vegetable matter, and the decomposition of 
 mineral compounds, which take place in the soil where lime is present, 
 new combinations are Ibrmed in variable quantities which are more so- 
 luble than the carbonate, and which thereibre hasten and facilitate this 
 washing out of tlie lime by the action of the rains. Thus chloride of 
 calcium, nitrate of lime, and gypsum, are al! produced — of which the 
 two former are eminently soluble in water — while organic acids also re- 
 sult from the decay of the organic matter, with some of Vv'hicli the lime 
 forms readily soluble compounds (salts) easily removed by wnter. 
 
400 ACTION OP LIME DPON THE SOIL, AND A3 THE FOOD OF PLANTS. 
 
 The ultimate resolution of all vegetable matter in the soil into carbo- 
 nic acid and water (Lee. VIII., § 3,) hicewise aids the removal of the 
 lime. For if the soil be everywhere impregnated with carbonic acid, 
 tlie rain and spring waters that flow through it will also become charg- 
 ed with this gas, and thus be enabled to dissolve a larger portion of the 
 carbonate of lime than they could otherwise do. Thus theory indi- 
 cates, what I believe experience confirms, that a given quantity of lime 
 will disappear the sooner from a field, the more abundant the animal 
 and vegetable matter it contains. 
 
 § 21. Theory of llie action of lime. 
 
 Lime acts in two ways upon the soil. It produces a mechanical al- 
 teration which is simple and easily understood, and is the cause of a 
 series o^ 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 stiller 
 clays, — while in the form of limestone gravel or of shell-sand, it may 
 be employed either for opening a clay soil or for giving body and firm- 
 ness to boggy land. These effects, and their explanation, are so obvi- 
 ous to you, iliat it is unnecessary to dwell upon them. 
 
 The purposes served by lime a.s a chemical constituent of the soil are 
 at least of four distinct kinds. 
 
 1°. It supplies a kind of inorganic food which appears to be necessa- 
 ry to the healthy growth of all our cultivated plants. 
 
 2=. It neutralizes acid substances which are naturally formed in the 
 soil, and decomposes or renders harmless other noxious compounds 
 which are not unfrequently within reach of the roots of plants. 
 
 3°. It clianges the inert vegetable matter in the soil, so as gradual- 
 ly to render it useful to vegetation. 
 
 4°. It causes, focilitates, or enables other useful compounds, both 
 organic and inorganic, to be produced in the soil, — or so promotes 
 the decomposition of existing compounds as to prepare them more 
 speedily for entering into the circulation of plants. 
 
 These several modes of action it will be necessary to illustrate in 
 some detail. 
 
 § 22. Of lime as the food of plants. 
 
 In considering the chemical nature of the ash of plants (Lee. X., 
 § 3 and 4), we have seen that lime in all cases forms a considerable 
 proportion of its whole weight. Hence the reason Avhy lime is re- 
 garded as a necessary food of plants, and hence also one cause of its 
 benefi -ial influence in general agricultural practice. 
 
 The quantity of pure lime contained in the crops produced upon one 
 acre during a fom* years' rotation amounts, on an average, to 242 lbs. 
 which are equal to about 430 lbs. (say 4 cwt. ) of carbonate of lime, in 
 the state of marl, shell-sand, or lime-stone gravel. (See Lee. X., § 3.) 
 It is obvious, therefore, that one of the most intelligible purposes served 
 by lime, as a cliemical constituent of the soil, is to supply this compara- 
 tively large quantity of lime, which in some form or other must enter 
 into the roots of plants. 
 
Straw or fops. 
 
 Tolal. 
 
 7-2 
 
 8-7 lbs. 
 
 12-9 
 
 15-0 lbs. 
 
 5-7 
 
 8-2 lbs. 
 
 93-0 
 
 138-8 lbs. 
 
 259-4 
 
 266-0 lbs. 
 
 126-0 
 
 126-0 lbs. 
 
 33-0 
 
 33-0 lbs. 
 
 ACTS CHIEFLY UPON THE ORGANIC MATTER OF THE SOIL. 401 
 
 But the different crops which we grow contain lime in unlike propor- 
 tions. Thus the average produce of an acre of land under flie follow- 
 ing crops contains of lime — 
 
 Grain or roots. 
 
 Wheat, 25 bushels, ... 1-5 
 
 Barley, 38 bushels, . . . 2-1 
 
 Oats, 50 bushels, .... 2-5 
 
 Turnips, 25 tons, .... 45-8 
 
 Potatoes, 9 tons, .... 6-6 
 
 Red clover, 2 tons, ... — 
 
 Rye gra.'^s, 2 tons, ... — 
 These quantities are not constant, and wheat especially contains 
 much more lime than is above stated, Vv'hen it is grown upon land to 
 which lime has been copiously applied. But the very ditferent quanti- 
 ties contained in the sev^eral crops, as above exhibited, shew that one 
 reason ichy lime favours the groivth of some crops more than others i.s, 
 that some actually 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 tliat no delay 
 may occur in the performance of those functions or in the growth of those 
 parts to which lime is indispensable. 
 
 § 23. The chemical action of lime is exerted 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 considered in refe- 
 rence also to the tlieory of its operation. These are — 
 
 P. That lime has little or no effect upon soils in which organic mat- 
 ter is deficient. 
 
 2^. That its apparent effect is inconsiderable during the first year 
 after its application, compared with that which it produces in the second 
 and third years. 
 
 3°. That its effect is most sensible when it is kept near the surface 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 produce no further good 
 effect. 
 
 It is obvious from these facts, that in general the main beneficial pur- 
 pose served by lime is to be sought for in the nature of itg chemical ac- 
 tion upon the organic matter of the soil — an action which takes place 
 .slowly, which is hastened by the access of air, and Avhich causes the 
 organic matter itself ultimately to disappear. 
 
 § 24. Of the forms in which organic matter usually exists in the soil, 
 and circumstances under which its decomposition may take place. 
 
 I. — The organic matter which lime thus causes to disappear is pre- 
 sented to it in one or other of five different forms : 
 
 P. In that of recent, often green, moist, and undecomposed roots, 
 leaves, and stems of plants. 
 
402 UPON THE DKCOMPOSITION OF ORGANIC MATTER. 
 
 2°. In that of dry, and still undecomposed, vegetable matter, such 
 as straw. 
 
 2'^. In a more or less decayed or decaying state, generally black or 
 brown in colour — and often in some degree soluble in wateV. 
 
 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 substance^ 
 — with the alumina for example, and with the lime or magnesia — al- 
 ready existing in the soil. 
 
 Upon these several varieties of organic matter lime acts with differ- 
 ent degrees of rapidity. 
 
 II. — The final result of the decomposition of these several forms of 
 organic matter, when they contain no nitrogen, is their conversion into 
 carbonic acid and water only (Lee. VIII., § 3). They pass, however, 
 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 decom- 
 position is effected. Thus the substance may decompose — 
 
 1°. Alone, in which case the changes that occur proceed slowly, and 
 arise solely from a new arrangement of its own particles. Tliis kind of 
 decomposition rarely occurs to any extent in the soil. 
 
 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 in- 
 flammable gases arise, water is the principal cause ofthe more rapid 
 decomposition. 
 
 3'^. In the presence of air only. — In nature organic matter is never 
 placed in this condition, the air of our atmosphere being always 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 uni- 
 versal condition of the organic matter in our fields and farm-yards. 
 The joint action of air and water, and the tendency ofthe elements of 
 the organic matter to enter into new combinations, cavise new chem- 
 ical changes to succeed each other Avith much rapidity. It will of 
 course be understood that moderate warmth is necessary to the pro- 
 duction of these effects.* 
 
 5°. In the presence of lime, or of some other alkaline substance (pot- 
 ash, 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 on its decomposition. A new chemical agency must then be 
 
 ' A familiar illustration of the conjoined efficacy of air and water in producing oxidation is 
 exhibited in their action upon iron. If a piece of polished iron be licpt in perfectly dry air 
 it will not rust. Or if it be completely covered over willi pure water in a well stoppered 
 bottle, from which air itJ excluded, it will remain brrght and untarnished. Cut if a polished 
 rod of iron he put into an open vessel half lull of water, so that one part of its lengih only 
 is under water — then tlie rod will begin very soon to rust at tlie surface of the water, and a 
 brown ochrey ring of oxide will form around it, exactly wlif-re (he air and water meet. 
 From this point ttie rust will gradually spread upwards and downwards. So it is with the 
 organic mattpr of the soil. Wherever the air and water meet, their decomposing action 
 upon it, in orilimiry temperatures, soon becomes perceptible. 
 
INFLUENCE OP ALKALINE SUBSTANCES. 403 
 
 introduced, by which the elements ofthe organic matter may again be 
 eet in motion. Lime is the agent which for this purpose is most large- 
 ly employed in practical agriculture. 
 
 § 25. General action of alkaline substances upon organic matter. 
 
 It is this action of alkaline matters upon the organic substances ofthe 
 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 acids, (Lee. XIIL, § 1,) with decaying vegetable fibre. 
 It tlien commences, at tlie 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 portion of carbonic — and, by the aid 
 of the hydrogen of the water which it decomposes, one or more of 
 the many compounds of carbon and hydrogen, wliich often rise up, 
 as the marsh-gas does, and escape into the air, (Lee. VIII., § 3.) 
 
 Thus tliere is a tendency towards the accumulation of acid substances 
 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 natural decay of the organic matter, and, on the other, to render 
 the soil unfavorable to the healthy growth of young or tender plants. 
 
 Tlie general effect of the presence of alkaline substances in the soil 
 is to counteract these two evils. They combine with and thus remove 
 the sourness of the acid bodies as they are formed. In consequence of 
 this the soil becomes svjeeter or more propitious to vegetation, while the 
 natural tendency ofthe vegetable matter to decay is no longer arrested. 
 
 It is thus clear that an immediate good effect upon the land must fol- 
 low either from the artificial application or from the natural presence of 
 alkaline matter in the soil — while at the same time it will cause the 
 vegetable matter to disappear more rapidly than would otherwise be 
 tile case. But the effect of such substances does not end here. They 
 actually dispose or provoke — pre-dispose, chemists call it. — the vegeta- 
 ble matter to continue forming 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 fjrward the exhaustion of the vegetable matter of the soil. 
 
 Such is the general action of all alkaline substances. This action 
 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 gradually converted 
 into another acid called the glucic. But in the 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 favor the decomposition. 
 
 But the nature of the alkaline matter which is present determines 
 also the rapidity with which such changes are produced. The most 
 powerful alkaline 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 of these, is far 
 from being Avithout an important influence. 
 
404 ACTION OF CAUSTIC LIME CPON ORGANIC MATTER 
 
 Hence one of the benefits which result from the use of wood-ashes il 
 containing carbonate of potash, when employed in small quantities 
 and along with vegetable and animal manures, as they are in this coun- 
 try ; but hence also the evil effects which are found to follow from the 1 
 application of them in too large doses. 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 tillaL"' 
 can be continued for a few years only. After one or two crops Ihc 
 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 of the alkalies in general. They are only less in de- 
 gree, or take place more slowly, than when soda or potash is em- 
 ployed. Hence, the greater adaptation of lime to the purposes of 
 practical agriculture. 
 
 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 color, but they may be preserved, it is 
 said, for years, without exhibiting any striking change of texture (Mr. 
 Garden.) If dry straw be so mixed Avith slaked lime, it will exhibit 
 still less alteration. In either case also the changes will be even lef^s 
 perceptible, if, instead of hydrate of lime, the carbonate (or viild 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 aiready reached an advanced stage of 
 decomposition, — an admixture of slaked lime produces certain percepti- 
 • ble changes immediately, and mild lime more slowly, but these changes 
 being completed, the tendency o^ lime cdone is to arrest rather than to 
 promote further rapid alterations. Hence, the following opinions of 
 experienced practical observers must be admitted to be theoretically 
 correct — in so far as they refer to the action of lime alone. 
 
 " If straAV of long dung be mixed with slaked lime, it will be pre- 
 served." (Morton, On Soils, 3d edition, p. 181.) 
 
 " Lime mixed in a mass of earth containing the live roots and seeds 
 of plants, will not destroy them." (Morton.) 
 
 " Sir H. Davy's theory, that lime dissolves vegetable matter, is 
 given up ; in fact, it hardens vegetable matter. (Mr. Pusey, Royal 
 Agricultural Journal, iii., p. 212. 
 
 These opinions, I have said, are probably correct in so far as re- 
 gards the unaided action of lime. They even express, with an ap- 
 proach to accuracy, what will take place in the interior of compost 
 heaps of a certain kind, or in some dry soils ; but that they cannot 
 apply to the ordinary action of lime upon the soil is proved by the 
 other result of universal observation, that lime, so far from preserv- 
 ing 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 lim-e on organic matter in the presence of air 
 and water. — In the presence of air and water, when assisted by a 
 
IN THE PRESENCE OP AIR AND WATER. 405 
 
 favoring temperature, vegetable matter, as w^e have already peen, 
 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 carbonic acid 
 and water. During its natural decay in a moist and open soil, organic 
 mattqr gives off' a portion of carbonic acid gas, which escapes, 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 
 absorbs carbonic acid from the air or unites with the carbonate already 
 formed, to produce the known compound of hydrate with carbonate 
 of lime, — (that compound, namely, which is produced when quick-lime 
 slakes spontaneously in tlie air — see p. 368.) — 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 Avait ; 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 
 substances — till finally the whole of the lime becomes combined either 
 with carbonic or with some other acid of organic origin. 
 
 Nor at thifs stage are the action and influence of lime observed to 
 cease. On the contrary, this result will, in most soils, be arrived at in 
 the course of one or two years, while the beneficial action of the lime 
 itselt'may be perceptible for 20 or 30 years. Hence there is much ap- 
 parent ground for the opinion of Lord Kames, '• that lime is as effica- 
 cious in its (so called) etiete as in its caustic state." Even the more 
 strongly expressed opinion of the same acute observer, '' that lime pro- 
 duces little effect upon vegetables till it becomes effete" — derives much 
 support from experience — 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 locali- 
 ties sufficient to deprive even slaked lime of all its caustic properties. 
 
 Of the saline compounds, (saline compounds or salts are always 
 formed when lime, magnesia, potash, soda, &c., combine with acids.) 
 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 permanently 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 
 tlipy 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 frequent- 
 ly 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 lim'^, therefore, depends upon its prolonged 
 o/iJer-action upon the vegetable matter of the soil. What is this ac- 
 tion, and in what consist the benefits to which it gives rise? 
 
406 ACTION OF CAKBONATE OF LIME UPON VEGETABLE MATTER. 
 
 In answering this question, it is of importance to observe that all 
 the effects produced by alkaline 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 witli 
 which they are united is retained by a comparatively feeble affinity, 
 and is displaced with greater or less ease by almost every other acid 
 compound which is produced in the soil. With this displacement is 
 connected an interesting series of beautiful reactions, wliich it is of 
 consequence to understand. 
 
 You will recollect that the great end which nature, so to speak, haa 
 in view, in all the changes to which she subjects organic matter in the 
 soil, is to convert it — with tiie exception of its nitrogen — into carbonic 
 acid and water. For this purpose it combines at one time, with the 
 oxygen of the air, while at another it decomposes water and unites witli 
 the oxygen or the hydrogen which are liberated, or with both, to ibrm 
 now chemical combinations. Each of these new combinations is either 
 immediately preliminary to or is attended by the conversion of a por- 
 tion to the elements of the organic matter into one or other of those 
 simpler forms of matter on which plants live. Now during these pre- 
 limi'iary or preparatory steps, aciil substances, as I have already ex- 
 plained, are among others constantly produced. With these acids, the 
 carbonate of lime, when present in the soil, is ever ready to combine. 
 But in so combining, it gives olf the carbonic acid with which it is al- 
 reaily 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 tlie various acid substances 
 which are th\is formed during the oxidation of the organic matter, and 
 v/hich successively unite with the lime, because the entire series of 
 interesting and highly important changes, which organic substances 
 undergo in tlie soil, has as yet been too little investigated, to permit 
 us to do more than speak in general terms of the nature of the che- 
 mical compounds wliich are most abundantly produced. Of two tacts, 
 however, in regard to them, we are certain — that they are simpler in 
 their constitution than the original organic matter itself from which 
 tl\ey are derived — and that they have a tendency to assume still 
 si.mpler forms, if they continue to be exposed to the same united action 
 of air, water, and alkaline substances. 
 
 Hence the coiiipounds which lime has tbrnied wilii the acid sub- 
 stances of the soil, themselves hasten forward to new decompositions, 
 — unite with more oxygen, liberate slowly portion after portion of 
 their ciirbon in the form of carbonic acid, and of their hydrogen in the 
 form of Avater, till at length the lime itself is left again in the state 
 of carbonate, or in union with carbonic acid only. This residual car- 
 bonate 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 neighborhood, while 
 this acid, by exposure to the due influences, vmdergoes new altera- 
 tions till it also is finally resolved into carbonic acid and water. 
 
 Two circumstances are deserving to be borne in mind in reference 
 to tliese successive decompositions— ;^r5t, that in the course of them 
 more soluble compounds of lime are now and then formed, some of 
 
SUMMARY OP THE CHANGES PRODCCED BY LIME. 407 
 
 which are washed out by the rains, and escape from the soil, wliile 
 others minister to the growth of plants ; — and second, that very much 
 carbonic acid is produced as their final result — 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 il- 
 lustration, I have supposed the carbonate of lime first tbrmed in the 
 soil to be subsequently combined with other acids, which gradually 
 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 one time employed in working up the acid 
 substances produced. But it is necessary that it should be univer- 
 sally diiTused through the soil in order that it may be everywhere 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 atone and the same time disappear (p. 380.) 
 
 The changes, tlierefore, which lime and organic matter, supposed 
 to be free from nitrogen, respectively undergo, and their mutual ac- 
 tion in the soil, may be summed up as follows: — 
 
 1°. The organic matter, under the influence of air and moisture, 
 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 
 imioM with them or Avith carbonic acid from the air, soon (compara- 
 rafively) loses its caustic state. 
 
 3 \ The production of acid substances by the oxidation of the organ- 
 ic matter — goes on more rapidly under the disposing influence of the 
 lime, whether caustic or carbonated. These acids combine with the 
 lime, liberating from it, Avhen in the state of carbonate, 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 decomposition, 
 at each of which it gives off water or carbonic acid, retaining 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. 
 
 During this series of progressive decompositions, certain more so- 
 luble compounds of lime are formed, by which plants are in part at 
 least supplied with this earth, and which Avith the aid of the rains 
 carry otl" both lime and organic matter from the soil. 
 
 And. again, the more rapid the production of the acid substances 
 
408 COMPARATIVE UTILITY OF BURNED AND UNBURNED LIME. 
 
 which result from the union of the organic matter with oxygen, the 
 more abundant in general also the production of those gaseous and 
 volatile compounds which they form by uniting Avith hydrogen, so 
 that, in promoting the formation of the one class of bodies, lime also 
 favors the evolution of tJie other in greater abundance, and thus in 
 a double measure contributes to the exhaustion of the soil. 
 
 The disposing action of lime to tliis twin form of decomposition, ^ew 
 varieties of organic matter can resist, — and hence arises the well 
 known efficacy of lime in resolving and rendering useful the appa- 
 rently inert vegetable substances that not unfrequently exist in the 
 soil. 
 
 § 28. Of the comparative utility of bm-ned and unburned lime. 
 
 Is there no advantage, then, you may ask, in using caustic or burned 
 rather than carbonated or unburned lime? If the ultimate effects of 
 both upon the land be the same, why be at the expense of burning? 
 Among other benefits may be enumerated the following : — 
 
 l'^. By burning and slaking, the lime is reduced to the state of an im- 
 palpable powder, finer than could be obtained by any available metliod 
 of crushing. It can in consequence be diffused more uniformly througli 
 the soil, and hence a smaller quantity Avill produce 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 particles of matter, and among solid sub- 
 stances the more rapidly, the finer the powder to which they can be re- 
 duced. Thus a mass of iron or lead slowly rvists 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 mechanical 
 division the apparent action of the oxygen of the air upon metals is aug- 
 mented and hastened in this extraordinary degree — and a similar re- 
 sult follows when lime in an impalpable state is brought into contact 
 with the vegetable matter vipon which it is intended to act. 
 
 2'. The effect of burned lime is more powerful and more immediate 
 than that of unburned hme in the form of chalk, marl, or shell sand. 
 Hence it sooner neutralizes the acids which exist in the soil, and 
 sooner causes the decomposition of vegetable matter of every kind to 
 commence, upon which its efficacy, in a greater degree, depends. 
 Hence, when it can easily be procured, it is better fitted lor sour grass 
 or arable lands, for such as contain an excess of vegetable matter, and 
 especially for such as abounds in that dead or inert form of organic mat- 
 ter wliich requires a stronger stimulus — the presence of more power- 
 ful chemical affinities, that is — to bring it into active decomposition. 
 In such cases, the lime has already done much good before it has been 
 brourht into the mild state — and remaining afterwards in this state in 
 the soil, it still serves, in a great measure, the same slower after-pur- 
 poses as tlie original addition of carbonate would have done. 
 
 3°. Besides, if any portion of it, after the lapse of two or three 
 years, still linger in the caustic state, (p. 368.) it will continue to pro- 
 voke more rapid changes among the organic substances in the soil, 
 than mild lime alone could have done. 
 
ORGANIC MATTER OF THE SOIL CONTAINS NITROGEN. 409 
 
 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 enabling 
 nearly twice the quantity to be conveyed from place to place at the 
 same cost of transport. This not only causes a direct saving of 
 money, — as when the burned chalk of Antrim is carried by sea to 
 the Ayr.shire coiusts — but an additional saving of labor also upon the 
 farm, — where the number of hands and horses is often barely suffici- 
 ent for the necessary work. 
 
 § 29. Action of lime on organic substances which contain nitrogen. 
 
 I have hitlierto, for the sake of simplicity, directed your attention 
 solely to the action, whether immediate or remote, which is exercised 
 by lime upon organic matter supposed to contain no nitrogen. 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 ni- 
 trogen. Even that which is most inert retains a sensible proportion of 
 it. It exists in dry peat to the amount of about 2 per cent, of its weight, 
 and still cUngs to the other elements of the organic matter, even after it 
 has undergone those prolonged changes by Avhich 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, 
 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 may contain, in whatever state of combina- 
 tion it may previously exist, will be given ofl'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 tlie hydrate 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 alkaline matters, in the so-called nitre beds, (Lee. 
 VIIL, § 5,) ammonia and nitric acid are both produced, the quantity of 
 nitrogen contained in the weight of these compounds extracted being 
 much greater than wasoriginally present in the animal and vegetable 
 matter employed (Dumas.) Under the influence of alkaline substances, 
 therefore, even when not in a caustic state, the decay of animal and ve- 
 getable matter in the presence of air and moisture causes some of the 
 nitrooren of the atmosphere to become fixed in the soil in the form of 
 18 
 
410 ANALOGOUS DECOMPOSITION OF ALL ORGANIC SUBSTANCES. 
 
 ammonia or of nitric acid. What takes place on the confined area of a 
 nitre bed, may take place to some extent also in the wider area of a 
 well-limed and Avell-manured field. 
 
 In the action of alkalies in the nitre bed, disposing to the produc- 
 tion of nitric acid, we observe the same kind of agency, which we 
 have already attributed to lime, in regard to the more abundant ele- 
 ments which exist in the vegetable matter of the soil. It gently per- 
 suades all the elements — nitrogen and carbon alike — to unite with 
 the oxygen of air and water, and thus ultimately to form acid com- 
 pounds with which it noay itself combine. 
 
 The action of lime upon such organic matters containing nitrogen 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 decomposition, the ge- 
 neral result of which is the production of ammonia, and of an acid 
 substance with which the ammonia may combine. This change is 
 precisely analogous to that which takes place in such substances as 
 starch and woody fibre, which contains no nitrogen. In each case, 
 one portion of the elements unites with oxygen to produce an acid, 
 the other with hydrogen to form a compound possessed of alkaline or 
 indifferent properties. Thus, — 
 
 With oxygen. — vegetable matter produces carbonic, ulmic, and other 
 acids. 
 " animal matter produces carbonic, nitric, ulmic, and 
 
 other acids. 
 With hydrogen, — vegetable matter produces marsh gas or other 
 carburetted hydrogens. 
 " animal matter produces ammonia. 
 
 If the ammonia happen to be produced in larger relative quantity 
 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 lite soil, the absorbent 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. 
 
 Wlien caustic (hydrate of) lime is added to a soil in which ammonia 
 exists in this state of combination with acid matter, it seizes upon the 
 acid and sets the ammonia free. This it does with comparative slow- 
 ness, however — for it does not at once come in contact 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 itself undergo a further change 
 by which its nitrogen may be rendered more fixed (p. 411.) 
 
 Carbonate of lime, on the other hand, still more slowly persuades 
 the ammonia to leave the acid substances (ulmic, nitric? &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 be- 
 come more immediately useful to vegetation. 
 
 2°. But in undergoing this spontaneous decay, even substances con- 
 taining nitrogen reach at length a point at which decomposition 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 
 
AMMONIA AND NITRIC ACID FORMED. 411 
 
 be capable of ministering to vegetable growth. Here caustic lime steps 
 in more quickly, and mild lime by slower degrees, to promote the fur- 
 ther 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 help- 
 ing 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 decay- 
 ing 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 nature 
 and upon the earth's surface the elements 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 surround- 
 ing oxygen and forming nitric acid (Lee. VIII.. § 5. note.) When no 
 other base is present, this nitric 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 present 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 oxidation 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 prodviction, 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 extensive applica- 
 tion, that when one elementary substance is vindergoing a direct cliemi- 
 cal union with a second in the presence of a third^ a tendency is impart- 
 ed to the third to unite'also with one or with both of the other two, al- 
 thougli in the same circumstances it would not unite with either, if pre- 
 sent alone. Thus, when the carbonaceous matter of the soil is under- 
 going oxidation in the air — that is, combining with the oxygen of the 
 atmosphere — it imparts a tendency to the nitrogen also to unite with 
 oxj^gen, which when mixed with that gas alone, (the atmosphere con- 
 sisting, as you will recollect, of nitrogen and oxygen — Lee. II., § 4,) — 
 it has no known disposition to do. The result of this is the production of 
 a small, and always a variable, proportion of nitric acid during the de- 
 composition in the soil, of organic matter even, which itself contains no 
 nitrogen. 
 
 Again, it is an equally remarkable chemical law, that elementary 
 bodies which refuse to combine, however long we may keep them to- 
 gether in a state of mixture, will yet unite readily when presented to 
 each other in what is called by chemists the nascent state^hat is, at 
 the moment when one or other of tliem is produced 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 tmitee with the greater part 
 of the oxygen and hydrogen which are set at liberty, and at the same 
 time Avith more or less of the oxygen of the atmosphere — but at the 
 
412 HOW THESE CHEMICAL CHANGES BENEFIT VEGETATION. 
 
 same instant the nitrogen of the atmosphere, which is everywhere 
 present, seizes a portion of the hydrogen and forms ammonia. Thus 
 a variable, and in any one Umited spot a minute, but over the entire 
 surface of the globe, a large quantity of ammonia is produced during 
 the oxidation even of the purely carbonaceous 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 propor- 
 tion does it promote the production of ammonia and nitric acid, at the 
 expense of the free nitrogen of the atmo.sphere, and this may be re- 
 garded as one of the valuable and constant purposes served by the 
 presence of calcareous matter in the soil. 
 
 § 30. How these cliemical changes directly benefit vegetation. 
 
 You will scarcely, I think, inquire how all these interesting chemical 
 changes which attend upon the presence of lime in the soil are di- 
 rectly 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 the decomposition of vegetable matter which 
 those acid substances arrest. The further decompositions which en- 
 sue are attended at every step by the production either of gaseous 
 compounds — such as carbonic acid and light carburetted hydrogen — 
 which are more or less abundantly absorbed by the roots and leaves 
 of plants, and thus help to feed them — or of acid and other compounds, 
 soluble in water, which, entering by the roots, bear into the circula- 
 tion of the plant not only organic food, but that supply of lime also 
 which healthy plants require. 
 
 2°. The changes it induces upon substances in which nitrogen i.g 
 present are still more obviously useful to vegetation. It eliminates am ■ 
 monia from the compounds in which it exists already formed, and pro- 
 motes its slow conversion into nitric acid, by which the nitrogen is 
 rendered more fixed in the soil. It disposes the nitrogen of more or 
 less inert organic matter to assume the form of ammonia and nitric 
 acid, in which state experience has long shown that this element is 
 directly favorable to the growth of plants. 
 
 3^. It influences in an unknown degree, the nitrogen of the atmos- 
 phere 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 oxidation which it brings 
 about in a given time, and by the kind of compounds 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 con- 
 dition as to drainage, and with the more or less liberal and skilful 
 manner in which it is farmed. 
 
 § 31. Why lime must he kept near the surface. 
 Nor will you fail to see tlie important reasons why lime ought to 
 be kept near the surface of tlie soil — since 
 
 1°. The action of lime upon organic matter is almost nothing m 
 
ACTION OF LIME UPON SALINE SUBSTANCES. 413 
 
 the absence of air and moisture. If the lime sink, therefore, beyond 
 the constant reach of fresh air, its efficacy is in a great degree lost. 
 
 2^. But the agency of the hght and heat of tlie sun, though I have 
 not hitherto 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 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 endeavor, if possible, to keep some of his lime 
 at least upon the very surface of his arable land. Perhaps this in- 
 fluence of hght might even be adduced as an argument in favor 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 es- 
 pecially 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 reason also 
 why a portion of the hme 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 injurious, or by the ac- 
 tion of lime may be rendered more wholesome to vegetation. 
 
 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 af- 
 forded 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 eflfects, 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. 
 
 Though the main general agency of lime is exerted, as we have 
 seen, upon the organic matter it meets with, yet it often also produces 
 direct chemical changes upon the mineral compounds existing in the 
 soil, which are of great importance to vegetation. Thus 
 
 1°. Lime, either in the mild or in the caustic state, possesses the 
 property of decomposing the sulphate of iron, which especially abounds 
 in peaty soils, and in many localities so saturates the subsoil as to 
 make it destructive to the roots of plants. Sprengel mentions a case 
 Avhere 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 ferruginous nature of the subsoil, which caused the death 
 of tiie plant as soon as the roots began to penetrate it. 
 
 When salts of iron exist in the soil, a dressing with lime will bring 
 the land into a wholesome state without other aid. The lime Avill 
 combine with the acid, and form gypsum, if it is the sulphate of iron 
 that is present, while the Jirst oxide of iron which is set free will, by 
 
414 LIME DECOMPOSES SULPHATES AND SILICATES, SETS FREE 
 
 exposure to the air, be converted into the spxond or red oxide, in 
 which state this metal is no longer hurtful to vegetation. 
 
 When these salts are to be decomposed and removed from the sub- 
 soil, lime must be aided by the subsoil plough and the drain. Unless 
 an outlet beneath be provided for the surface water, by which the 
 rains may be enabled to wash away slowly the noxious substances 
 from the subsoil, even the addition of a copious dose of lime will only 
 produce a temporary improvement. 
 
 2°. Lime decomposes also the sulphates of magnesia and of alumi- 
 na, both of which are occasionally found in the soil, and, being very so- 
 luble salts, are liable to be taken up by the roots in such quantity as to 
 be hurtful to the growing plants. When soils which contain any of 
 the three salts I have mentioned have once been limed or marled, it 
 is in vain to add gypsum in the hope of fivoring the clover crop, since 
 the lime, in decomposing the sulphates, has already formed an abun- 
 dant supply of this compound for all the purposes of vegetation. 
 
 3°. Among the earthy constituents of the soil, we have already seen 
 that there often exist fragments of felspar and of other minerals derived 
 from the granitic and trap rocks, which contain potash or soda in the 
 state o? silicates. These silicates we know to be slowly decomposed 
 by tile agency of the carbonic acid of the air, (Lee. X^ § 1.) and 
 their alkah set free in a soluble state. This decomposition is said to 
 be prompted by the presence of lime (p. 361.) 
 
 Again, the stalks of the grasses and the straw of the corn-bearing 
 plants contain much silica in combination witli potash and soda. In 
 farm-yard manure, therefore, much of these silicates is present, and 
 when mixed with the soil, there appears little reason to doubt that 
 they are of much benefit to the growing crops. On these silicates, 
 in the presence of carbonic acid and moisture, the lime acts as iidoes 
 upon the mineral silicates. It aids in the liberation of the potash and 
 soda, and thus promotes the performance of those important functions 
 which these alkalies are destined to exercise in reference to vegetable 
 growth (p. 328.) 
 
 AVhile the alkali is set free the lime itself combines with the silica, 
 and hence one source of the silicate of lime which, as I have already 
 mentioned to you, (p. 380.) usually exists in sensible quantity in our 
 cultivated soils. It has been stated by Sprengel (Lehre vom Diinger, 
 p. 310,) as one reason why the addition of lime mvist be repeated so 
 frequently upon some soils in which silica abounds, that an insoluble 
 silicate of lime is found, which is of no use to vegetation. But the 
 silicates of lime are slowly decomposed by the agency of the carbonic 
 acid of the air and of decaying vegetation, and to this cause in a pre- 
 vious lecture (Lee. XII., § 4,) I have ascribed much of the fertile 
 character of the trap and syenitic soils, and of their beneficial action 
 when laid on as a manure. 
 
 4°. Potash and soda exist to some extent in clay soils in combina- 
 tion with their alum.ina. The presence of lime has a similar influence 
 in setting the alkalies free from this state of combination also. 
 
 5°. Alumina has the property of com.bining readily with many vege- 
 table acids, and in the clay soils exercises a constant influence, similar 
 m kind to that of lime and other alkaline substances, in persuading the 
 
ALKALINE SUBSTANCES, AND DECOMPOSES COMMON SALT. 415 
 
 organic matter to those forms of decay in which acid compounds are 
 more abundautly produced. Hence, clay soils ahnost always contain a 
 portion of alumina in combination with organic matter. This organic 
 matter is readily given up to lime, and by the more energetic action of 
 this substance is sooner made available to the wants of new races of 
 plants. 
 
 6°. I shall bring under your notice only one other, but a highly im- 
 portant, decomposing action, which lime exercises 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 effect, even upon the sulphate of soda, and, ac- 
 cording to BerthoUet, (Dumas Traite tie Chemie, ii., p. 334,) incrus- 
 tations of carbonate of soda (of Trona or Natron, which is a sesqui 
 carbonate of soda,) 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 — that generally, along the same coasts, the application of 
 sulphates produces little sensible effect upon the crops, and that, there- 
 fore, in all probab-ility they abound in the soil, derived, it may be, from 
 tlie same sea spray — we may safely conclude, I think, that the decom- 
 position 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 formation, in which sea salt more especially 
 occurs. • 
 
 And if we further consider the important purposes which the carbo- 
 nate of soda thus produced may serve in reference to vegetation — that 
 it may dissolve vegetable matter and carry it into the roots — that it may 
 form soluble silicates, and thus supply the necessary 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 mat- 
 ter, provokes to the formation of nitrates, so wholesome to vegetable 
 life — we may regard the decomposing action of lime by which this car- 
 bonate is produced as among the most valuable of its properties to the 
 practical farmer, wherever circumstances are favorable for its exercise. 
 
 § 33. 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,* and to many insects injurious to the farmer, and to destroy 
 their eggs and larva;. In Scotland it has been found in some instances 
 to check the ravages of the fly. On the other hand, in the state of car- 
 bonate, it is propitious to the growth of the land snail and similar crea- 
 
 * When the wlient 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. 
 
416 LIME KILLS INSECTS AND &£ED3. 
 
 tures which bear shells. In highly limed land the former maybe seen 
 crowded at the roots of the hedges, from which they make frequent in- 
 cursions upon the young crops, and are, I believe, especially hurtful 
 to the turnips. 
 
 2°. It is found to prevent sviut in wheat. For this purpose the 
 seed is steeped in lime, and afterwards dried with slaked lime, or lime 
 Avater 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 ex- 
 tirpates certain of the coarser grasses from sour pastures and brings up 
 a tenderer herbage ; but practical men appear to ditfer in regard to its ef- 
 fects upon the roots and seeds of the more troublesome weeds. Accord- 
 ing to some, the addition oi" 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 (p. 405,) this is a mistake. 
 I believe the truth to be, that lime will lead to their destruction and 
 decay, if the circumstances are favorable or if proper pains be taken 
 to effect it. But air and moisture are necessary to insure this, as they 
 are to effect the rapid decay of dead organic matter. If the ingre- 
 dients of the compost be duly proportioned, or if the dose of lime 
 added to the land be sufficiently large, and if in each case the mix- 
 ture be frequently turned, the final destruction of roots and seeds may 
 in general be safely calculated upon. 
 
 § 34. Us^f silicate of lime. 
 
 There is one compound of lime which, though occurring occasionally 
 in all soils, has not hitherto been applied to the improvement of the land 
 even in localities where it most abounds. This compound is the silicate 
 of lime. I have already directed your attention to the presence of this 
 compound in the trap rocks, and to the fertile character which it imparts 
 to the soils which are fonned 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 employed in some dis- 
 tricts for mending the roads. It is not unworthy the attention of the 
 practical farmer — as an improver of his fields — especially where caus- 
 tic 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 im- 
 parts 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 attenlion to the most important topics connecteil witli (he use of 
 lime, so efficacious an iiistruni^nt in the hands of the sl<ilful and impiovinir farmer toranie- 
 lioratins the condition und incrpasins the prodnetivcnes.s of his land. If I have appeared 
 to dwell long upon this subject, it is because of (he value which I know to be attached by 
 pr.ictlcal men to a correct exposiiion 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 
 oiil to you the leading chemical principles upon which ils influence depends — if any thin^ 
 is still dark, it is because our knowledge is not yet complete. A few years more, and we 
 may hope to have the mists whicli hanz over this, as over many other branches of agricul- 
 tural chemistry, in a great mea.sure cleared away. 
 
LECTURE XVII. 
 
 Of organic manures — Vegetable and animal manures. — Green manuring ; ploughing in of 
 epurry, the white lupin, the vetch, buck-wheat, i-ap«, rye, borage. — Natural green manu- 
 rins- — Improvement of the soil by laying; down to grass and by planting. — Use of sea- 
 weed. — Dry vegptabli! manures: ilry straw, chaff, rape-dust, malt-dust, sawdust, colton 
 seeds, dry leaves. — Decayed vegetable niajter; use of peat, tanners' bark, and composts 
 of vegetable matier. — Charcoid powder, soot.— 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 applieti to the soil in three dif- 
 ferent forms — in the green, in the dry, and in the more or less natu- 
 rally decayed, fermented, or artificially decomposed state. 
 
 § I. Of g^reen 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. 
 
 1°. We have seen in the preceding lecture how important air and 
 water are to the decomposition of organic matter. Now green ve- 
 getable substances contain within themselves much water, undergo 
 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 compounds 
 containing nitrogen, which not only decompose very readily themselves, 
 but have the property of pensuading 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, the sap of 
 plants almost invariably undergoes more or less rapid decomposition 
 even when preserved from the contact of both air and water. When 
 this decomposition has once commenced in the sap it is gradually propa- 
 gated to the woody fibre and to the other substances of which the mass 
 of the stems and roots of plants is composed. Hence, recent vege- 
 table matter will undergo a comparatively rapid decomposition, 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 Avhere 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, it is gradually resolved more or less completely into car- 
 bonic acid, which escapes into the air and is so far lost. But when 
 buried beneath the surface, this formation of carbonic acid proceeds 
 less rapidly, and other compounds — preparatory to the final resolution 
 into carbonic acid and water— are produced in greater quantity and 
 18* 
 
418 GREEN VEGETABLES READILY DECAY, AND ENRICH THE SOIL. 
 
 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 tbod 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 ad- 
 vantages which are known to follow from green manuring and from the 
 employment of green vegetable matter in the preparation of composts. 
 
 § 2. Important practical results obtained by green manuring. 
 
 But this explanation of tiie principles on which the efficacy of gi^een 
 manuring depends, does not fully illustrate the important practical re- 
 sults by which, in many localities, it is uniformly followed. 
 
 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. Growing plants 
 bring up from beneath, as far as their roots extend, those substances 
 which are useful to vegetation — and retain them in their leaves and 
 stems. By 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 before 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 tecding stock, with a view to their con- 
 version into manure. In no other form can the same crop convey to 
 the soil an equal am-omit of enriching matter as in that of green 
 leaves and sterns. Where the first object, therefore, in the farmer's 
 practice, is so to use his crops as to enrich his land — he will soonest 
 effect it by plougliing them in in the green state. 
 
 3°. Another important result is, that the beneficial action is almost 
 immediate. Green vegetables decompose rapidly, and thus the first 
 crop which follows a green manuring is benefitted and increased by 
 ii. But partly for this reason also the green manuring — of corn crop- 
 ped land — if aided by no other manure, must generally be repeated 
 every second year. 
 
 4°. If is said that grain crops which succeed a green manuring are 
 never laid — and that the produce in grain is greater in proportion to 
 the straw, than when manured with fermented dung. 
 
 5°. But it is deserving of separate consideration, that green manu- 
 ring is especially adapted lor improving and enricliing soils which are 
 poor in vegetable matter. The principles on which living plants draw 
 a part — sometimes a large part — of their sustenance from the air, 
 
GREEN MANURE MOST USEFUL TO POOR AND SANDY SOIL. 419 
 
 have already been discussed, and I may presume that you sufficiently 
 understand the principles and admit the iact. Livang 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 from the air. 
 Plough in these living plants, and you necessarily add to the soil 
 more than was taken from it — in other words, yoii make it richer in 
 organic matter. Repeat the process with a second crop and it be- 
 comes 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 be- 
 yond the reach of this improving process 1 Those only are so on wliich 
 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 natu- 
 ral decay of the organic matter which the soils already contain. 
 
 But for those plants which grow naturally upon the soil, agricultural 
 skill may substitute others, which will increase more rapidly, and pro- 
 duce 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 pur- 
 pose of giving manuring — those being obviously the fittest which in the 
 given soil and climate grow most rapidly, or which produce the largest 
 quantity of vegetable tnatter in tlie shortest time and at the smallest cost. 
 
 § 3. Of the plants which in different soils and climates are employed 
 for gi^een manuring. 
 
 On this prmciple is founded the selection o^ 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. 
 
 P. Sparry (Spergula Arvensis.) — It is to poor dry sandy soils that 
 green manuring has been found most signally beneficial, and 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, and 
 ploughed in in spring preparatory to the annual crop, or it may be 
 used to replace the naked fallow, which is often hurtful 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 in to 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 Avinter corn. 
 
 Von Voght (Vortheile der griinen Bediingung) 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 abetter 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 
 epurry 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 qviality. 
 
420 USE OF THE VETCH, BUCKWHEAT. ETC. 
 
 2°. White Lupins. — In Italy, and in the south of France, the white 
 lupin is extensively cultivated as a green manure. In Germany, also, 
 it has been found to be one of those plants by which unfruitful sandy 
 soils may be most speedily brought into a productive state. The supe- 
 riority of this plant for the purpose of 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 at- 
 tacked 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 herb- 
 age. 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 opejis stiff clays by its strong stems and roots. 
 
 3^. T'he Vetch is inferior in many of its qualities to the white lu- 
 pin — yet in Southern Germany it is often sown on the stubble, 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 (British Husbandry, I., p. 407.) 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°. Brock- Wheat is also too uncertain a crop, and the high price of 
 its seed renders it inferior in value to spurry on sandy soils. It is su- 
 perior 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 xipon 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 verj' 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. 
 
 5°. 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. 
 
 6°. 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.* Potatoe tops also might be dug 
 or ploughed in with equal advantage. 
 
 7^. Borate has been strongly recommended in Germany, and es- 
 pecially 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 admirably fitted 
 for enriching the land on which it grows. 
 
 8°. Red Clover is often ploughed in as a manure. On the Rhine it 
 
 • "I find no better way of manuring for wheat after turnips, than ploughing in the fops 
 while iX\\\greertf as soon as the turnips arc taken off the land."— j>ir. Campbell^qf Craigic. 
 
GREEN MANURING SUITABLE FOR AFTER-CItOPS OF CORN. 421 
 
 IS sown for this purpose, being ploughed in before it begins 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 ma- 
 nure (Barclay's '• Agricultural Tour in the United States.") White 
 Clovc-r is not so valuable tor this purpose, tor neither is it so deep 
 rooted nor does it yield so large a crop of stems and leaves. 
 
 9^. Old Grass. — Perhaps the most common form of green manur- 
 ing practised in this country is that of ploughing up grass lands 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. 
 
 In regard to all these ibrms of green maimring it is to be observed 
 that they enrich the soil generally, and are therefore well fitted to 
 prepare it for after-crops of corn ; they will not fit it, however, lor a 
 special crop, such as turnips, which requires to be unnaturally forced 
 or pushed forward at a particular period of its growth. 
 
 § 4. Will green manuring alone prevent la ndfrom becom ing exhausted? 
 
 If by green manuring is meant the growing of vegetable matter upon 
 one field, and ploughing it in green into another, as is sometimes done, 
 it may be safely said that, when judiciously practised, land may by 
 this single process be secured for an indefinite period against ex- 
 haustion. But if we plough in only what the land itself produces, 
 and carry off occasional crops of corn, the time will ultimately come 
 when any soil thus treated will cease to yield remunerating crops. A 
 brief consideration of the subject will satisfy you of 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 or- 
 ganic matter, while the roots, more or less deep, bring up saline matters 
 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 surtace, 
 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 sahne substances which plants require. Hence, though by 
 skilful green manuring waste land may be brought to a remunerative 
 state of fertili ty, it will finally relapse again into a state of nature, if no 
 other methods are subsequently adopted for maintaining its productive- 
 ness. The process maybe a sIoav one, and practical men may be un- 
 willing to believe in the possibility of a result which does not exhibit it- 
 self within the currency of a single lease, or during a single hfe-time — 
 yet few things are more certain than that in general the soil must sooner 
 or later receive 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 has become an important branch of business, giving em- 
 ployment to many hands, and aflbrding an investment to much capital. 
 
 The following table, in addition to other particulars, exhibits the 
 
422 
 
 OF THE PRACTICE OF GREEN MANURING. 
 
 relative proportions of dry organic and saline matter, capable of be- 
 ing added to the surface soil by a few of those plants which are em- 
 ployed for the purposes of remanuring : — 
 
 Kind of Plant. 
 
 Avera^je 
 
 produce 
 
 per imp. 
 
 acre. 
 
 Spurry 
 
 White Lupin. 
 
 Vetch 
 
 Buck-wheat. 
 Rape 
 
 1000 lbs. coiitiiin 
 in the green stale 
 Organic Saline 
 Matter. Matter. 
 
 lbs 
 
 6,500 
 25,000 
 
 11,000 
 
 8,000 
 
 10,000 
 
 lbs. 
 
 11>9 
 
 188 
 
 233 
 170 
 214 
 
 Depth of 
 Roots. 
 
 lbs. 
 21 
 12 
 
 17 
 10 
 16 
 
 Crops 
 in a 
 year. 
 
 inches 
 
 12 to 152 or 3 
 
 24 to2Gl or l\ 
 
 15 to 20 2 
 12 to 15l 2 
 ■? llorU 
 
 Soil for which they are 
 fitted. 
 
 Dry, loose, sandy. 
 Any except marly or 
 
 calcareous. 
 Strong soil. 
 Dry, sandy, or moorish 
 Rich 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 becom- 
 ing a prey to weeds. 
 
 2^. That the plants ought to be mown or harrowed, 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 supposed especi- 
 ally to promote the growth of plants, it is desirable to retain as much 
 of it in the plant and soil as possible. Another reason is that, if al- 
 lowed to ripen, some of the seed may be shed and afterwards infest 
 the land with weeds. 
 
 3°. That they should be ploitghed 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. O/" natural manuring with recent vegetable matter. 
 
 Besides the method of ploughing in, which may be distinguished as 
 artificial green manuring, — there is another mode in which recent ve- 
 getable 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 surface may be mowed for hay, or 
 cropped by cattle, yet the roots remain and gradually add to the quantity 
 of vegetable matter beneath. The same is the case to a greater or less 
 extent with all the artificial corn, grass, and leguminous crops we grow. 
 They all leav^ their roots in the soil, and if the quantity of organic mat- 
 ter which these roots contain be greate r than that which the crop we car- 
 ry otr has derived from the soil, then, instead of exhausting, the growth 
 of this crop will actually enrich the soil in so far as the presence of or- 
 ganic 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 exhaust- 
 
WEIGHT OF ROOTS LEFT IN THE SOIL. 423 
 
 ing, to which are naturally attached the largest weight of roots. Hence, 
 the main reason why poor lands are so much benefitted by being laid 
 down to grass, and why an intermediate crop of clover is often as benefi- 
 cial to the after-crop of corn as if the land had lain in naked fallow. (If 
 the third crop be ploughed in, the land is actually enriched.-Schwertz.) 
 An interesting series of experiments on the relative Aveights of the 
 roots and of the green leaves and stems of various grasses, made by 
 Hlubek, (Erniihrung der Pflanzen, p. 466,) throws considerable light 
 upon their relative efficacy in enriching the soil by the vegetable mat- 
 ter they diffuse through it in the form of roots. The grasses were 
 grown in beds of equal size (180 square feet) in the agricultural gar- 
 den at Laybach, and mown on 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 follows : 
 
 Weight of 
 Produce in Profluce in Roots, dry Roots 
 
 Kind of Grass. , ^— — , , • v to 100 lbs. 
 
 Grass Itay Fresh. Dry. of Hay. 
 
 1. Festuca EhitioT—Tidl FexrMe-grass. . 124 lbs. 36 lbs. 56 lbs. 22 lbs. 6 libs. 
 
 2. Festuca Ovina — Sheep's Fescue-grass. 90 30 — 80 2()6 
 
 3. PMeumPiatense—Timolhygrass... 90 25 50 17 60 
 
 4. Dactylis Glomerata — Rough Cock's- 
 
 foot 202 67 — 22i 33 
 
 5. Lolium Perenne — Perennial Rye- 
 
 grass 50 17 — 50 300 
 
 6. Alopecurus VT&ltnsis— Meadow Fox- 
 
 tail 106 35 — 24 70 
 
 7. Triticum Ilepens — Creeping Cotich 
 
 or quukengrass 120 60 — 70 116 
 
 8. Poa Annua — Annual Meadow grass. — — — — 111 
 
 9. Bromus Mollis and Racemosus — 
 
 Soft and smooth Bromc-grass — — — — 105 
 
 10. Anthoxanthum Odoratum — Siveel- 
 
 scaitcd Verjidlr grass — — — — 93 
 
 A mixture of white clover, of ribwort, of hoary plantain, and of 
 couchrgrass, in an old pasture field, gave 400 lbs. of dry roots to 100 
 lbs. of hay — and 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 clo- 
 ver 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 quantity of 
 vegetable matter some of the grasses impart to tlie soil, and yet how un- 
 like the different grasses are in this respect. The sheep's-fescue and 
 the perennial rye-grass — besides the dead roots, which detach them- 
 selves 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 liay. If we take tlie 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 fonr-y ear-old gras<s field is plough- 
 ed up, will be equal to one-si.xth more than the weight of that yearns crop. 
 
 In an old pasture or meadoAv field again, when ploughed up, the 
 living roots left are epual to four times the weight of that yearns hay 
 
424 MANURING BY THE ROOTS OF CLOVER, AND BY 
 
 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 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 upwards of 
 one-half the weight of the whole hay which the clover has yielded. 
 Suppose there be three cuttings, yielding 4 tons of hay. then 2 toJis 
 of dry vegetable matter are added to the soil in the form of roots, 
 when the clover stubble is ploughed up. 
 
 Bvit the quantity of roots, like that of green produce, is dependent 
 upon a variety of circumstances. It will sometimes, therefore, be 
 greater and sometimes less than is above stated. It may be received 
 as a rule — not without exceptions 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 more difficult to 
 plough (Appendi.r, No. III.) 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 ameliorating 
 operations of nature which is always to some extent going on, where- 
 ever vegetation proceeds. It is one by which the practical man is 
 often benefitted unawares, and of which — too often without under- 
 standing the source from whence the advantage comes — he syste- 
 matically 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 permanent 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 Avhich are left in the soil enrich the surface 
 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 
 consequehce of the annual death of stems and roots, and of the soil being 
 more closely covered, but this increase is probably never in any one 
 after-year equal to that which takes place during the first. The quan- 
 tity of roots which is produced during the first year of the young plants' 
 growth 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 soil more in proportion to the 
 
LAYING DOWN TO GRASS. — PERMANENT PASTURE. 425 
 
 time e.Tpended, 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. Tliat which Hes 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 ar- 
 tificial 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 gi-eatest in proportion during the 
 first year. That farming, therefore, is most economical — where the 
 land will admit oi'it — which permits tl^e clover or grass seeds to occupy 
 the land for one year only. 
 
 But if, after the first year's hay is removed, the land be pastured for 
 two or three years more, it is possible that each succeeding 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 cir- 
 cumstance that the whole produce of the field remains upon it, ex- 
 cept what is carried off by the stock when removed — 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 tolerable 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 per- 
 manent 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 
 generally die and leave blank spaces, and these again are slowly 
 filled up by the sprouting of seeds of other species, which have either 
 lain long buried in the soil or have been brought thither 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 itself has 
 undergone during the few years that have elapsed since the grass 
 seeds v\'ere 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, lias reached its utmost point, the sward begins gradually 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 becomes. 
 
 But this is true only within certain limits. It may prove true for 
 the entire currency of a lease, or even for the lifetime of a single ob- 
 server 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. 
 
426 THE SOIL AND GRASSES CONTINUALLY CHANGE. 
 
 c. This, agairi; is owing to a new change which has come over the 
 soil. It has become, in some degree, exhausted of those substances 
 which are necessary to the growth of the more valuable grasses — 
 less nutritive species, therefore, and such as are less willingly eaten 
 by cattle, take their place. 
 
 Such is the almost universal process of change which old grass fields 
 undergo, whetlier they be regularly mown or constantly pastured only 
 — provided they are left entirely to themselves. If mown they begin 
 to lail the sooner, bat even when pastured they can be kept in a slate 
 of full productiveness only by repeated top-dressings, especially of sa- 
 line manure — that is, by adding to the soil those substances which are 
 necessary to the growth of the valup,ble grasses, and of which it suf- 
 fers 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 agriculture is to plough out the old and failing pas- 
 tures, 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 is a rich, brown, generally light and fria- 
 ble vegetable mould. Or when laid down it may have been a pale- 
 colored, red, or yellow sand or loam. In this case the surface soil 
 is still, when turned 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 down to grass principally re- 
 sults. In what does this change consist? and how is it effected ? 
 
 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 alumina than the soil which 
 formed the surface when the grass seeds were first sawn 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 alumina in the latter being originally small, the diffe- 
 rence 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 Avhich cultivated plants require, and 
 therefore more fertile in corn. But strong clay lands derive the fur- 
 ther important benefit of being rendered more loose and friable, and 
 thus more easily and more economically cultivated. 
 
 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, by increasing 
 the bulk of, the surfoce soil. The latter is thus converted into a mix- 
 ture of clay and decayed roots, which is of a dark colour, and is necessa- 
 rily more loose and friable than the original or subjacentunmixed clay. 
 
 2"^. But this admixture of roots effects 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 (Lee. 
 
AGENCY OF THE RAINS AND WINDS. 427 
 
 IX., § 1), which is gathered from beneath, wherever the roots pene- 
 trate, and is by them sent upwards to the surface. A ton oC hay con- 
 tains about 170 lbs. of this inorganic matter (Lee. X., § 3). Suppose 
 the roots to contain as much, and that the total annual produce of 
 grass and roots together amounts to four tons, then about 680 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 valua- 
 ble inorganic matter at the expense of the soil below. 
 
 3°. Nor are mechanical agencies wanting to increase this natural 
 difference between the surface and the under soils. The loosening 
 and opening of the clay lands by the roots of the grasses allow the 
 rains more easy access. The rains gradually wash out the fine par- 
 ticles of clay that are mixed with the roots, and carry them down- 
 wards, as they sink towards the subsoil. Hence the brown mould, as 
 it forms, is slowly robbed of a portion of its alumina, and is rendered 
 more open, while the under soil becomes even stiffer than before. 
 This sinking of the alumina is in a great measure arrested Avhen the 
 soil becomes 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 alumina. 
 
 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 particles and sifting 
 the air as it passes through them. Everywhere, even to remote dis- 
 tricts, and to great elevations, the winds bear a constant small burden 
 of earthy matter;* but there are few practical agriculturists who, du- 
 ring 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 constitution altered. 
 
 5^. Another important agency also must not be overlooked. In grass 
 lands insects, and 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 quantity 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,t and so striking has it appeared to some, that they have been in- 
 
 ' If. lias been observed tbat on spots purposely sheltered from the wind and rain on every 
 side, til'- qiiandly of <lii8t that is collected, vihcn pressed down, is in 3 years equal to one line, 
 or in 36 years to one inch in thickntsiS. — Sprengel, Lehre ram Diinger, p. 443. 
 
 t The permanence cf a fine carpeting of rich sweet grass upon a portion of his farm is 
 ascribed (by Mr. Purdie) to " the spewinss of worms, apparently immensely numerous, 
 which iiicessantlv act as a rich top dressing."— JV/ze Essays of the Highland Society, L 
 p. 191. 
 
428 WHY ARTIFICIAL PASTURES DETERIORATE. 
 
 dined to attribute to the slow but constant labour of these insects, the 
 entire formation of the fertile surlace soils over large tracts of country. 
 ('■ Geological Transactions.") 
 
 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 re- 
 marks : 
 
 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, Lee. XL, § 8). This is owing to 
 the fact that such soils naturally contain, and by their comparative 
 impermeability /-e-tain, a larger store of those inorganic substances on 
 which the valuable grasses live. When the surface soil becomes de- 
 ficient in any of these, the roots descend further into the subsoil and 
 bring up a fresh supply. But these grass lands are not on this account 
 exempt from the law above explained, in obedience to which all pas- 
 tured lands, when left to nature, must ultimately become exhausted. 
 They must eventually become poorer ; but in their case the deterio- 
 ration 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 es- 
 pecially upon clay lands when laid down to grass, explain why it is so 
 difficult to procure, by means of artifical grasses, a sward equal to that 
 which grows naturally upon old pasture lands. As the soil changes 
 upon our artificial pastures, it becomes better fitted to nourish other spe- 
 cies 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 under- 
 goes a further change, and new species again appear upon it. We can- 
 not tell how often different kinds of grass thus succeed each other upon 
 the soil, but we know that the final rich sward which covers a grass field 
 Avhen it has reached its most valuable condition, is the result of a long 
 series of natural changes which time only can bring about. 
 
 The soil of an old pasture field, which has been ploughed up, is made 
 to undergo an important change both in texture and in chemical con- 
 stitution, 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 unwillingness 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 nourishing sward is produced.* 
 
 ' For an exceUent article on the siipeiior feetlinj qualities of recent artificial erassf's 
 over m^ny old pasture Ian<Js, by Mr. Boswel], of Kingcaussie, see the Qtuirlerly Jouinal 
 of Agriculture, N., p. 783. 
 
IMPROVEMKNT OF THi; SOIL BY PLANTING OF TREES. 429 
 
 § 8. 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 forest, they 
 will produce a valuable herbage — or when cleared of trees they may 
 for some time be made to yield profitable crops of corn. 
 
 This fact has been observed in almostevery country of Europe, but 
 the most precise observations upon the subject with which I am ac- 
 quainted are those which have been made in the extensive plantations 
 of the late Duke of Athol. These plantations consist chiefly of white 
 larch (^Larix Eurupcsa.) and grow upon a poor hilly soil, resting on 
 gneiss, mica-slate, and clay-slate (Lee. XL, § 8.) In six or seven 
 years the lower brajiches spread out, become interlaced, and com- 
 pletely 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 lana- 
 tiis) spring up, and a fine sward is gradually produced. The giound, 
 whicli previously was worth only 9d. or Is. per acre as a sheep pas- 
 ture, at the end of 30 years becomes worth from 7s. to 10s. per acre. 
 The soil on this part of the Duke's estate is especiaUy propitious to 
 the larch — and. therefore, this tree both thrives best and in the great- 
 est degree improves the soil. Thus in oak copses, cut every 24 years, 
 the soil becomes worth only 53. or 6s. per acre, and this during the last 
 six years only. Under an ash plantation, the improvement 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. 
 (Mr. Stephens, in the Transactiotis of the Highland Society, xi., p. 
 189 ; also Loudon's Encylopaidia of Agriculture, p. 1346.) 
 
 The main cause of this improvement, as of that which is produced 
 by laying down to grass, is to be found in the natural manuring 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 lat- 
 ter enrich the soil both by their roots and by their leaves, the former 
 manure its surface only by the leaves which they shed. 
 
 The leave.« of trees, like those of grasses, contain much inorganic mat- 
 ter, 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 fol- 
 lowing trees, when dried in the air, contain respectively of inorganic 
 matter ((Sprengel, Chemiefur Landwirthe, ii., passim) : — 
 April. August. November. 
 
 Oak — 5 per cent. 4^ per cent. 
 
 Ash — 6i « — " 
 
 Beech — 7 « Qh " 
 
 Birch — 5 u _ « 
 
 Elm — llj " — " 
 
 Willow — 8i " — « 
 
 White Larch 6 J. per cent. — " — '^ 
 
 Scotch Fir — U " — " 
 
 In looking at the differences among these numbers — especially in 
 
430 RELATIVE EFFECTS OF DIFFERENT KINDS OF TREES. 
 
 the case of the elm and of the Scotch fir — one Avould naturally sup- 
 pose 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 mat- 
 ter which the leaves of these several trees contain. And to this 
 cause, no doubtj some effect is to be ascribed in localities 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 inorganic 
 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 luxu- 
 riantly, 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 great- 
 er proportion by plantations of the former tree. 
 
 Other special circumstances also will account for the relative de- 
 grees of improvement produced by the larch and by some of the 
 other trees — for example, the oak. In the oak copse the soil in IG 
 years become 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 al- 
 lowed to grow up into an oak forest, the permanent improvement of 
 the pasture, Qven 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 jporcer 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. 
 
 . The mode in which the lower branches of the larch spread out and 
 overshadow the surface is not without its influence upon the ultimate 
 improvement which the soil exhibits. All vegetation being prevented, 
 the land, besides receiving a yearly manure of vegetable mould, is 
 made to lie for upwards of 20 years in uninterrupted 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 pro- 
 tected from tlie wind, and to this protection Sprengcl attributes much 
 of that rapid improvement so generally experienced where lands are 
 
MANURING WITH SEA-WEED. 431 
 
 covered with wood. The winds bear along particles of earthy mat- 
 ter (see note, p. 427.) which they deposit again in the still forests ; and 
 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 evidently affords no explanation why, 
 m the same range of country, the soil which is covered by forests of 
 one kind should improve more rapidly than those which are sheltered 
 by trees of another species. 
 
 § 9. Of the use of sea-weed as a manure. 
 
 Among green manures of great value and extensive application 
 there remains to be noticed the sea-weed or sea-ware of our coasts. 
 The marine plants of which it consists differ from the green vege- 
 tables 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 com- 
 post or with quick-lime, they speedily crumble down into a black earth, 
 in which little or no trace of the plant can be perceived. 
 
 2°. By the greater proportion of saline or other inorganic matter 
 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 burn- 
 ed in the air. 
 
 We have seen (Lee. X., § 3,) that the quantity of ash left by 1000 
 lbs. of our more usually cultivated grasses, in the dry state, varies 
 from 5 to nearly 10 per cent., but the fucus vesicidosits, which is 
 reckoned the most valuable for the manufacture of kelp, gives up- 
 wards of 160 lbs. of ash from 100 lbs. of the dry plant. This ash, 
 according to Fageretrom, consists of — 
 
 Gypsum 63-4 lbs. 
 
 Carbonate of Lime 34-1 " 
 
 Iodide of Sodium 2-7 " 
 
 Other Salts of Soda 29-9 " 
 
 Silica, Oxide of Iron, and earthy Phosphates.31-1 " 
 
 161-2* 
 
 This ash contains less potash, but more soda and gypsum, than 
 those of the grasses, (Lee. X., § 3,) and hence, as you will readily 
 
 ' BerzeHus Arsberdttelse, 1824, p. 235. — If we compare the composition of Ibis ash with 
 that of the several varieties of kelp, given in page 356, i( will be seen to differ from them 
 very considerably. But kelp is always manufactured from a mixture of different plants 
 in varying proportions, and Itence one cause of the diversify of composition among differ- 
 ent samples of this substance. 
 
 Sprrngel slates (Lehre vom Dilnger, p. 277,) that the fuais vesicufosus contains only 16 
 per cent, of water. I do not know whether this is the result of experiments of his own, 
 but I have not introduced it into the text, because it appears to me inconsistent with the 
 remarkable manner in which seaweed shrivels up when dried, and with its lillle perma- 
 nence as a manure. " If an acre of land is completely covered with it, after a few days 
 of dry weather, the whole would not weigh 500 lbs. The fibrous parts reduced to mere 
 threads alone remain — so that it is like manuring land with cobicebs" (Dr. Walker.) This 
 would seem to imply the presence of a larger quantity of water in fresli sea weed than in 
 preen grass, and consequently a less efficacy as a manure when applied in equal weights. 
 According to Ilouisingaulf, the fjicus digitatus contains 40 per cent, of water, and the 
 fucus sacc/iarinua 76 per cent, when newly token from the sea, and 40 percent, afler being 
 dried in the air. 
 
432 MODE IN WHICH SEA-WEED IS APPLIED. 
 
 understand, may be expected to exercise a somewhat different influ- 
 ence upon vegetation. 
 
 It is of importance, however, to bear in mind that the saUne and 
 other inorganic matters which are contained in tlie sea-weed we lay 
 upon our fields, form a positive addition to the land. If we plough in a 
 green crop where it grew, we restore 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 supi>ly. It 
 brings back from the sea a portion of that which the rivers are con- 
 stantly carrying into it, and is tlms valuable in restoring, in some mea- 
 sure, 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 (British Husbandry, II., p. 418.) 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 value of the land from 25s. to 30s. an acre 
 (Kerr's Berimckshij^e, p. 377.) In the Western Isles it is extensively 
 collected and employed as a manure — (" sea-weeds constitute one- 
 half of Hebridean manures, and nine-tenths of those of the remoter 
 Islands," Macdonald's Agriculture of the Hebrides^ p. 401,) — and 
 on the north-east coast of Ireland, the farming fishermen go out in 
 their boats and hook it up from considerable depths in the sea (Mrs. 
 Hall's Ireland.) 
 
 It is appHed either immediately as a top-dressing, especially to grass 
 lands — or it is previously made into a compost with earth, with lime, 
 or with shell-sand. Thus mixed with lime, it has been used with ad- 
 vantage as a top-dressing for the young wheat crop, (British Hus- 
 bandry, II., p. 419;) and with shell-sand, it is the general manure for 
 the potatoe crop among the Western Islanders (Transactions of the 
 Highland Society, 1842-3, p. 766.) It may also T)e mixed with farm- 
 yard manure or even Avith peat moss, both of which it brings into a 
 more rapid fermentation. In some of the Western Isles, and in Jer- 
 se}'", 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. There 
 is no reason to doubt that 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 con- 
 sidered equal in immediate effect — upon the first crop, that is — to 2i 
 of fresh sea-Aveed, or to H after it 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 appli- 
 cation of sea-weed alone, for a long series of years (Macdonald's 
 Hebrides, p. 407.) 
 
 Conflicting opinions are given by different practical men, in regard 
 
USE OF STRAW AS A MANfRE. 433 
 
 lo the crops to which it is best suited. But the explanation of most 
 of these and similar discordances is to be found in the answers to the 
 three following questions — what substances does the crop specially 
 require ? — 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 maybe 
 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. 
 
 § 10. Of manuring with dry vegetable substances. 
 
 The main general difference between vegetable matter o/" z:^ sawie 
 kind, ami 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 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 advanced 
 age of the plant or have been exposed to the vicissitudes of the weather 
 while drying, it will no longer exhibit an equal efBcacy. 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 after- 
 wards formed — but, because, as the plant ripens, the stem restores to the 
 soil a portion of the saline, especially of the alkaline, matter it previous- 
 ly contained (Lee. X., § 5.) Alter 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 substance-s 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. 
 
 P. Dry straw. — It is in the form of straw that dry vegetable mat- 
 ter 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 produces a less sensi- 
 ble effect upon the succeeding crop ; it is usually fermented, there- 
 fore, more or less completely, by an admixture of animal manure in 
 the farm-yard before it is laid upon the land. During this fermenta- 
 tion a certain unavoidable loss of^ organic, and generally a large loss ot 
 saline matter, also takes place (see in the succeeding lecture the sec- 
 tion upon mixed animal and vegetable manures.) It is, therefore, the- 
 oretically true of dry, as it is of green, vegetable matter, that it will add 
 most to the soil, if it be ploughed in without 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 dis- 
 puted use of short and long dung becomes altogether 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 nature of straw, but it decomposes more 
 slowly when buried in the soil in the dry state. It is also difficult to 
 ]9 
 
434 ACTION OF HAPE-UUST ON WHEAT AND BEANS. 
 
 bring into a state of fermentation, even when mixed with the liquid 
 manure of the farm-yard. 
 
 3°. Rape-dust. — When rape seed is exhausted of its oil, it conies 
 from the press in tlae form of hard (rape) cakes, which, when crushed 
 to powder, form the rape-dust of late years so extensively employed as 
 a manure. It is occasionally mixed with farm-yard dung, and applied 
 to the turnip crop, but its principal employment has hitlierto been, I 
 believe, as a top-dressing for the wheat crop, either harrowed in with 
 the seed in October, or applied to tlie young corn in spring. 
 
 Rape-dust requires moisture to bring out its full fertilizing virtues; ; 
 hence it is chiefly adapted to clay soils or to such as rest upon a stifi' 
 subsoil. It is seldom applied, therefore, to the barley crop, and even 
 upon wheat it will fail to produce any decidedly good effect in a very 
 dry season. Several interesting circumstances have been experi- 
 mentally ascertained in regard 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 tur- 
 nips, potatoes, and other crops, while in the same circumstances the 
 effect of guano may be strikingly beneficial. Thus in one experi- 
 ment, made in 1S42, upon unmanured land sown with turnips — 
 
 16 cwt. of rape-dust gave 3J tons of bulbs per acre. 
 
 2 cwt. of guano gave 5 do. 
 Unmanured gave Sj do. 
 
 And in another, in the same season, upon unmanured land — 
 1 ton of rape-dust gave 14i tons of bulbs per acre. 
 
 3 cwt. of guano gave 23j do. 
 Unmanured gave 12i* do. 
 
 Again, upon potatoes, planted without other manure, in three ex- 
 periments the produce per acre, in tons, was as follows : — 
 
 Unmanured. 1 ion Kape-diist. 3 cwt. Guano. 4 cwt. Guano. 
 
 White Don Potatoes — 12i ISa — 
 
 Red Don Potatoes 6| 10 — 14^ 
 
 Connaught Cups 5| 13 — 13} 
 
 In none of the above experiments did the action of the large quan- 
 tity of rape-dust equal that of the comparatively small quantity of 
 guano — though, from being buried in the soil, the difference was less 
 striking in the case of the potatoe 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, m an experiment upon Oats, made at Lennox Love — 
 16 cwt. of rape-dust gave 45 bushels. 
 2 cwt. of guano gave 68 do. 
 Unmanured soil gave 49 do. 
 In this property of injuring the crop, when rain docs not happen to 
 fall, rape-dust resembles very much those saline sxibstances which, as 
 we have seen, may often be applied with much advantage to the land. 
 
 c. Yet it would appear to exercise less of this evil influence upon 
 wheat and beans, and in similar circumstances. Thus in the same 
 
 • See Appendi.\-, No. VIII. 
 
THE aUANTITV MUST NOT BE TOO GREAT. 435 
 
 season, 1S42, 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 4S do. 
 
 Unmanured gave 47i do. 
 
 And a crop of beans, with — 
 
 16 cwt. of rape-dust gave 38 bushels. 
 2 cwt. of guano gave 35i do. 
 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 quantity of guano. 
 It is deserving of investigation, therefore, whether rape-dust be more 
 especially adapted to wheat and beans. Even in favorable seasons 
 it may possibly prove more economical than guano as a manure for 
 these two crops (see Appendix, No. VIIT.) 
 
 (/. But even in favorable seasons, and to the Avheat crop, there is 
 reason to believe that rape-dust cannot be economical!)/ applied in more 
 than a certain, perhaps variable, quantitj'^ per acre. Thus four equal 
 plots of ground (nearly half an acre each.) sown with wheat, were top- 
 dressed with rape-dust in different proportions with the ibllowing results: 
 VVitli 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 i* 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 ivas put on. 
 
 e. It may be noticed as another curious fact, that the action of 
 rape- dust is dependent upon the presence or absence of certain other 
 fjubstances in the soil. Common salt and sulphate of soda, when 
 mixed with it under certain circumstances, lessen the effect which it 
 vrould produce alone, and tlie same will probably happen Avhen it is 
 applied, without admixture, to soils in Avhich these saline compounds 
 happen to be already present. Some remarks upon this interesting 
 point will be found in the Appendix, No. VIII. 
 
 4^. TJntsned, poppy-seed, cotton-seed, and cocoa-nut cakes. — The 
 cake which is luft 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 ns a manure in the Uuit(Ml States, though little known as yet. I 
 believe, in England. The cocoa-nut cake is employed in Southern In- 
 dia 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 ignorant 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 di- 
 
 ■ Brllish Iluabandry, I., p. 412. 
 
436 USE OP MALT-DUST, DRY LEAVES, AND PEAT, AS MANURES. 
 
 rectly 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. 
 
 5°. Malt-dust. — When barley is made to sprout by the malster, and 
 is afterwards dried, the small shoots and rootlets drop off, and form 
 the substance known by the name of malt-dust. One hundred 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 or dusted over the young grass in spring. 
 
 6°. Saw-dust is usually rejected by the agriculturist, in consequence 
 of the difficulty which is generally experienced in bringing it into a state 
 of fermentation. It decomposes slowly when ploughed into the soil in 
 its dry state, but it nevertheless gradually benefits 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 pre- 
 serves from sinking too rapidly when they are to be applied to porous, 
 sandy, or chalky soils, while these liquids again hasten the decomposi- 
 tion of the saw-dust and augment its immediate effect upon the land. In 
 localities favorable for the collection of sea-weed, it may also be more 
 rapidly fermented by an admixture with this substance. Saw-dust 
 forms an ingredient in some of the mixed manures which have re- 
 cently come into use (see Appendix, No. VIII., Exp. B.) 
 
 7°. Di-y leaves may either be dug into the land at once, or maybe 
 laid up in heaps, when they will gradually decay, and form, in most 
 cases, an enriching manure. They gradually improve the soil (as 
 we have already seen, p. 429,) on which they annually fall, but the 
 same quantity of leaves will do more good if collected and immedi- 
 ately 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 
 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, it is 
 clear that a judicious admixture of peat must prove advantageous, be- 
 cause it will supply some at least of those substances which are neces- 
 sary to the production of a higher degree of fertility. But peat decays 
 very slowly in the air, and hence its apparent effect Avhen mixed with 
 the soil is very small. It may gradually ameliorate its quality, espe- 
 cially 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 acknowledged fertilizing ma- 
 nure. Different methods have been successfully practised for bring- 
 ing it into this more rapid state of decay or fermentation. 
 
 a. The half-dried peat may be mixed with from one-fourth to one- 
 half of its weight of fermenting farm-yard manure — the whole heap 
 
FERMENTATION OF PEAT AND TANNER's BARK. 437 
 
 being carefully covered over with a layer of peat to prevent the es- 
 cape of fertilizing vapors. By this method — first introduced to pub- 
 lic notice by the late Lord Meadowbank — the entire mixture is gra- 
 dually brought into an equable state of heat and fermentation, 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 fer- 
 mentation will be more speedily etTected, and at a less expense of 
 common farm-yard dung. Or the half-dried peat may be used un- 
 mixed, as an absorbent fir the liquid of the farm-yard, by which, 
 without other aid, it will be brought into a state of fermentation with 
 comparative rapidity. 
 
 c. Or instead of the liquid manure, the ammoniacal liquor of the 
 gas-works may be employed, with less prominent benefit certainly, 
 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 gradually reduce 
 the entire heap into a fertilizing mass (British Husbandry, II., p. 417.) 
 
 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 before 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 con- 
 vert the whole into a uniform and rapidly decaying mass. 
 
 In shcrl, it is only necessary to mix half-dried peat with any sub- 
 stance 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 ministering to the growth 
 of cultivated plants. 
 
 2°. Tanner^s bark is still more difficult to reduce or to bring into a 
 rapid state of decomposition. Any of the methods above recommended 
 for peat, however. Avill to a certain extent succeed also with the spent 
 bark of the tan pits. But in the case of substances so solid and refrac- 
 tory as the lumps of bark are, the admixture of a quantity of lime and 
 earth, so as to form a compost heap, is perhaps the most advisable 
 mode of procedure. The way in which lime promotes the decay of 
 woody fibre in such heaps has already been explained (see p. 382.) 
 
 § 13. Use of charred vegetable matters as a manure. 
 
 Soot and charcoal are the principal substances of this class which 
 have been more or lees extensively employed for the purpose of in- 
 creasing the productiveness of the land. 
 
 1°. Soot is a complicated and variable mixture of substances pro- 
 duced during the combustion of coal. Its composition, and consequent- 
 ly 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 analyzed since the year 1826, when a variety ex 
 amuied by Braconnot was found by him to consist in a thousand parts of 
 
438 COMPOSITION OF SOOT — ITS EFFECTS UPON RYE-GHASS. 
 
 Ulmic acid ? (a substance resembling that portion of the 
 vegetable matter of the soil which is soluble in caustic 
 
 potash— (see Lee. XIII., § 1) 302-0 
 
 A reddish brown soluble substance, containing nitrogen, and 
 
 yielding ammonia when heated 200-0 
 
 A sbohne 5-0 
 
 Carbonate of lime, with a trace of magnesia (probably de- 
 rived in part from the sides of the chimney) 146-6 
 
 Acetate of lime 56-5 
 
 Sulphate of lime (gj-psum) 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 4l-'.5 
 
 Acetate of ammonia 2-0 
 
 Silica (sand) 9-5 
 
 Charcoal powder 38-5 
 
 Water 1250 
 
 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, therefore, 
 must be variable, being largest in quantity where the draught is strong- 
 est and where the earthy matter or ash in the coal is the greatest. The 
 quantity of gypsum present depends upon tlie sulphur contained in the 
 coal, — that which is freest from sulphur will give a soot containing the 
 least gj'psum. The ammonia and the soluble substances containing ni- 
 trogen Avill vary with the quantity 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 there- 
 fore very unequal. The consequence of this must be, that the results 
 obtained in one spot, or upon one crop, are not to be depended upon, as 
 indicative of 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 is more general, 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 
 Avill benefit the crop, soot also will be of use, and hence its successful 
 application to grass lands. From its containing gypsum it should also 
 especially benefit the clover crops. Yet Dr. Anderson 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 luxuri- 
 ant than in the places where no soot had been applied. But upon 
 rye-grass its eflTects are amazing, and increase in proportion to the 
 quantity so, flir as my trials have gone." (Dr. Anderson's Essays, 
 edit. 1800, ii., p. 304.) And his general conclusion is, that soot does 
 not affect the g-rowlh of clover in any way^ while it wonderfully promotes 
 
 ' Annates de Cftemie et de Physique, xxxi., p. 37. 
 
ACTION OF .SOOT UPON WIIKAT AND 0AT3. 439 
 
 tluit of rye-grass. Will any of you, by experiment, ascertain if such 
 be really the case with the soot of your own neighborhood ? 
 
 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 in- 
 teresting observation, " that the first plant Avhich appears afterwards 
 is conalantlif the common couch-grass (triiicum repens). (Dr. Ander- 
 son's Essays, edit. 1800, ii., p. 305.) 
 
 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 
 1S42, upon an 
 
 Unmanured part of the field was 29j bushels. 
 
 Dressed with 4 bushels of soot 28 bushels.* 
 
 It also diminished, in a small degree, the potatoe crop in the same 
 year in the experiments of Lord Blantyre, at Erskine (Appendix, No. 
 
 VVith manure alone, the produce was 11 tons 17 cwt. 
 
 With 30 bushels of soot sprinkled over the dung.ll tons 4 cwt. 
 
 Like rape-dust (p. 434) and saline substances, tl\erefore. 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 
 ill the same locahty (Erskine) was very benelicial. Thus the com- 
 parative produce of these crops, when undressed and when top-dress- 
 ed 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 — the 
 former weighing only 58, the latter 62 lbs. a bushel. In the oats there 
 was no difference. Are we to infer from these results that, even in 
 dry seasons, soot may be safely applied to croj^s of corn, while to pulse 
 and roots it is sure to do no good ? Further precise obsservations, no 
 doubt, are still necessary — and the more especially as the experiments 
 upon oats and wheat, made in the still drier locality of Lennox Love 
 (Appendix, No. VIII.), gave a decrease in the produce of grain — while 
 in Mr. Fleming's experiments upon turnips (Appendix, No. VIII.), 50 
 bushels of soot, applied alone, gave an increase of 4 tons in the crop. 
 
 e. An experiment of Lord Blantyre's (Appendix, No. IX.), enables 
 us to judge of the efficacy of soot in a dry season, compared with that 
 of nitrate of soda and of guano ui)on the produce of hay. Thus the 
 crop of hay, per imperial acre, from the 
 
 Cost, 
 tons. rvvf,?. £ a. d. 
 
 Undressed portion, weighed 1 8 
 
 Dressed with 40 bushels of soot 1 15 Oil 8 
 
 160 lbs. nitrate of soda 1 19 1 15 9 
 
 160 lbs. 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 obser- 
 
 ■ See Appendix, No. VIII. 
 
440 USE OP CHARCOAL-DUST, AND OF COAL-TAR. 
 
 vation — but it is an important one — made by Mr. Morton, when des- 
 cribing the management of a well conducted farm in Gloucestershire, 
 (that of Mr. Dimmery, described in the Journal of the Royal Agri- 
 cultural Society, I., p. 400.) " The quantity of soot used upon this 
 farm amounts to 3000 bushels a-year, one-half of which is applied to the 
 potatoe, 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 irom Gloucester, Bristol,* and Cheltenham. Soot no doubt 
 contains many things useful to vegetation, j'et 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 retain a perpetual fertihty. 
 The slow changes which theory indicates may altogether escajie tlie 
 observation of the practical man, who makes no record of the history 
 of his land, and yet may be ever slowly proceeding. 
 
 2'. Charcoal. — Wood-charcoal, from its porous nature, and its tend- 
 ency to absorb animal odors and other unpleasant efflnvia (Lee. I.. § 2), 
 has been found, when reduced to fine powder, to be an excellent admix- 
 ture for night soil, for liquid manure, and for other substances which 
 undergo putrescent decay. It is thereibre employed to a considerable 
 extent by the manufacturers of artificial manures. It is also applied 
 with advantage in some cases as a top-dressing to various cropsf — its 
 efficacy being probably due in part to its power of absorbing from the 
 air, or of retaining in the soil, those gaseous substances which plants rt- 
 quire, and in part to the slow decay which it is itself capable of \mder- 
 going. 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 simiiiar com- 
 posts, and it is one of the substances with which Mr. Daniel impreg- 
 nates his saAV-dust in the manvifacture of his patent manure. It is im- 
 possible to say how much of the good effect derived from the use of 
 such mixtures as that described in the Appendix. No. VIII., is due to 
 the coal-tar they contain, — and as no experiments have hitherto been 
 made from which the true action of coal-tar can be inferred, it may 
 still be considered as a matter of doubt whether it can at all add direct- 
 ly to the fertility of the soil. 
 
 ^ 14. Of the theoretical falue of different vegetable substances 
 as manures. 
 
 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 aod other French authorities, the re- 
 lative efficacy of all manures depends upon the proportions of nitrogen 
 
 ' At Bristol the price of soot is 9d. a bushel, at RIoucester only 6cl., yet the former is pre- 
 ferred even at the higher price. It is of belter quality, owing, it is said, to the greater length 
 of the chimnies — it may be also to the quality of the coal and to the way it is burned. 
 
 t See Mr. Fleming's experiment upon Swedes (Appendix No. VllI.), in which 50 bush- 
 els of charcoal powder increased the crop by three tons an acre. 
 
THEORETICAL VALUE OF VEGETABLE MANURES. 441 
 
 they severally contain^ (Annates de C/iemieet de Phys., 3d series, III., 
 p. 76. ) And taking farm-yard manure — consisting of the mixed drop- 
 pings and litter of cattle — as a standard, tliey arrange vegetable sub- 
 stances, as manures, in the following order of value: — 
 
 Equal effects are produced by 
 
 Farm-yard manure 1000 lbs. 
 
 Potatoe 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 1400 
 
 Barley straw 1750 
 
 Rye straw 1000 to 2400 
 
 Buck- wheat straAV 850 
 
 Wheat chaff 470 
 
 Fir saw-du^t 1700 to 2500 " 
 
 Oak do 750 « 
 
 Soot, from coal 300 « 
 
 Lint and rape-dust 80 " 
 
 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 tnan 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 pea, and probably 
 bean straw, far above the straws of wheat, oats, &c., in fertilizing 
 power, and in representing soot 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 sub- 
 stance as represented by the proportion of nitrogen it contains. 
 
 But if we bear in mind that plants, as we have frequently had occa- 
 sion to mention, require inorganic as well as organic /ood, it is quite 
 clear that the mere presence of nitrogen in a substance is not sufficient 
 to render it highly nutritive to growing plants. Otherwise the salts 
 of ammonia would be the richest manures of all, and would best nourish 
 and bring to perfection every crop and in all circumstances — which ex- 
 perience has proved to be by no means the case. Hence 
 
 2°. The value of vegetable substances as manures imist depend in 
 some degree upon the quantity and kind of inorganic matter they 
 contain. In reterence to the quantity of inorganic matter which they 
 respectively impart to the soil, their relative values are represented 
 by the following numbers : — 
 
 19* 
 
442 INFLUENCE OP THE CARBONACEOUS MATTER. 
 
 One ton contains of inorganic 
 matier about 
 
 Potato tope, green 26 lbs. 
 
 Turnip tops, do 4S " 
 
 Carrot tops, do 45 " 
 
 Rye-grass, do 30 " 
 
 Vetch, do 38 « 
 
 Green sea-weed, do 22 " 
 
 Hay 90 to ISO " 
 
 Pea straw 100 » 
 
 Bean straw 60 to 80 " 
 
 Wheat straw 70 to 360 « 
 
 Oatstraw 100 to ISO " 
 
 Barley straw 100 to 120 " 
 
 Rye straw 50 to 70 '• 
 
 Fir eaw-dust 6 " 
 
 Oak saw-dust 5 •' 
 
 Soot 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 respectively con- 
 tain. We knoiD tliat wood-ashes (p. 353), kelp, and the ashes of straw 
 (p. 356), do promote the fertility of the land, and therefore the abso- 
 lute as well as the relative efficacy of the above vegetable svibstances 
 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 in- 
 directly, a portion of the necessary food of plants. This has already 
 been shown in various parts of the preceding lectures. 
 " It is the property of substances whicli contain a larger proportion 
 of nitrogen, to undergo rapid decay in the presence of air and moisture, 
 and thus to produce a more immediate and sensible action upon grow- 
 ing plants. But the carbon changes more slowly, and the inorganic 
 matter also separates slowly from decaying vegetables in the soil — 
 and hence the apparent effects of these constituents are less striking. 
 7Vj?«s the immediate and visible effect of different vegetable substances, 
 in the same state, is measured by the relative quantities of nitrogen 
 they contain — their permanent effects by the relative quantities of in- 
 organic and of carbonaceous matters. In the case of rape-dust, for ex- 
 ample, the immediate effect is determined chiefly by its nitrogen — the 
 permanent effects, by the ash it leaves when burned, or when caused 
 to undergo complete decay in the air. 
 
LECTURE XVIIl. 
 
 Animal manures.— Flesh, blood, and skin. — Wool, woollen rags, hair, liorn, and bones.— On 
 what does the fertilizing action of bones depend?— Animal charcoal and the refuse ol the 
 sugar refineries. — Fish and fish-refuse, whale blubber and oil. — Relative fertilizing value 
 of the substances previously described. — Pigeon dung. — Dung of sea-fowl : guano. — 
 Liquid manures : the urine of varimis animals. — Mixed animal and vegetable manures. — 
 Night soil, the droppings of the horse, the cow, the pig. — Effects of digestion upon vege- 
 table food — Why equal weights of vegetable matter, and the droppings of animals fed 
 upon it, possess ditlerent fertilizing powers. — Farm-yard dung.— Weight of dung pro- 
 duced from a given weight of grass, straw, and other produce. — Loss undergone bf 
 farm-yard manure during fermentation.— Improvement of the soil by irrigation. 
 
 Animal f?ubstances have always been considered as more fertilizing 
 to the land than such as are of vegetable origin. Their action is in 
 general more immediate and apparent, and it takes place within such a 
 limited period of time that the farmer can calculate vipon its being ex- 
 ercised in benefitting the crop to which it is applied. The reason of this 
 more immediate action will presently appear. 
 
 § 1. Of flesh, blood, and skin. 
 
 1°. Flesh. — The flesh of animals is not only a rich manure m itself, 
 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 ap- 
 plied to the land as a manure. 
 
 The flesh of animals consists of a lean part, called the muscular fibre, 
 or by chemists fibrin, and ■& fatty part, intermixed witli the lean in 
 greater or less proportion, according to the condition of the animal. 
 Of these two it is the lean part which acts most immediately and most 
 energetically in the promotion of vegetation. Lean beef, in the recent 
 state, contains 77 per cent, of its weight of water, so that 100 lbs. consists 
 of 77 lbs. ol' water and 23 lbs. of dry animal matter. 
 
 2°. Blood. — The blood of animals is more extensively employed as 
 a manure. It is carried offin large quantities from the slaughter-houses 
 of the butchers, and makes rich and fertilizing composts. In some 
 parts of Europe it is dried, and in the state of dry powder is applied with 
 much effect as a top-dressing to many crops. 
 
 Liquid blood consists of fibrin — the substance of lean meat, of albu- 
 men— the same asthewhiteof eggs— of a red coloring matter, and of 
 certain saline substances dissolved in a considerable 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 colorless, 
 part called the serum. The clot contains most of the fibrin and color- 
 ing matter, and a portion of the albumen ; the serum, the greater part 
 oflhe albumen and of the soluble saline substances which are present 
 in the blood. 
 
 The relative composition of fresh muscular fibre and of liquid blood 
 i.5 thus represented in 100 parts : — 
 
444 COMPOSITION OF BLOOD, AND OF SKIN. 
 
 Water. Dry animnl matter 
 
 Muscular fibre 77 23 
 
 Blood 79 21* 
 
 It appears singular that the solid muscle of animals should contain 
 so nearly the same quantity of water as their liquid blood does. 
 
 But it is no less striking that the dry animal matter which remains, 
 when lean muscular fibre and when blood are fully dried, has nearly the 
 same apparent composition. Thus, according to the analyses of Play- 
 fair and Boeckman, dry flesh and dry blood consist respectively of— 
 
 Dry bee Dry nx blood. 
 
 Carbon 51-83 51-96 
 
 Hydrogen 7-57 7-25 
 
 Nitrogen 15-01 15-07 
 
 Oxygen 21-37 21-30 
 
 Ashes 4-23 4-42 
 
 100 lOOf 
 
 The organic -pari, therefore, of blood and of flesh is nearly identical 
 in ultimate composition, and the final result of equal weights of each, 
 ■when applied as manures, should be nearly the same. The ashes, how- 
 ever, or inorganic part, though present in each nearly in the same pro- 
 portion (4-23 and 4-42 per cent.), are somewhat different in composition, 
 and therefore the action of blood and flesh Avill be a little unlike in so 
 far as it depends upon the saline substances they are respectively capa- 
 ble of conveying to the roots of plants. 
 
 3^. Skin. — The skins of nearly all animals find their way ultimately 
 into the soil as manure, in a more or less changed state. 
 
 The refuse parings from the tan-yards, and from the curriers' shops, 
 though usually employed for the manvifacture 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 matter 
 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 its constitution from flesli 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 23-22 
 
 100 
 It contains, therefore, 3j 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 gelati- 
 nous substances, will consequently exhibit a greater efficacy than flesh 
 or blood. 
 
 ■ Thomson's AninuU Chemistry, pp. 285 and 367. 
 
 T Iiiebig's Organic C>iemistry applied to Physiology, p. 314. 
 
USE AND COMPOSITION OF WOOL. HAIR, AND HORN. 445 
 
 § 2. Wool, woollen rags, hair, horn, and bones. 
 
 1°. Wool, in the form of the waste of the spinning-mills, and espe- 
 cially in that of woollen rags, acts very efficaciously as a manure. 
 The rags are used with good effect upon light chalks and gravels, in 
 which they retain the water. They are sometimes ploughed in for 
 wheat along with the clover stubble, in the winter with the corn stub- 
 ble, when the land is intended for turnips, and are sometimes applied 
 as a top dressing to clover and grass lands (British Husbandry, I., p. 
 425.) They are used most extensively, however, in the hop-grounds, 
 being dug in round the roots, 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 £5 to £10 a ton. 
 
 2°. Hair also is fitted to produce effects similar to those which fol- 
 low 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^. Horn, in the form of horn shavings, parings, and turnings, is just- 
 ly considered as a very powerful manure. Even in the state of shav- 
 ings, however, it undergoes decay still more slowly than woollen rags ; 
 and, therefore, hke them, will always be most safely and economically 
 employed when previously rotted, by being made into a compost. 
 
 Wool, hair, and horn, differ from flesh, blood, and skin, by contain- 
 ing very much less water in their natural state, and by undergoing, 
 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, therefore, will bear this important distinction in 
 mind, in any opinion he may form as to the relative efficacy of these 
 several substances as general fertilizers of the land. 
 
 In chemical composition, these three substances are nearly identi- 
 cal, 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 : — 
 
 Wool leaves 2-0 per cent, of ash. 
 
 Hair 0-72 " " 
 
 Horn 0-7 " " 
 
 And the part which burns away — the organic part — consists of — 
 
 Wool. Hair. Horn. 
 
 Carbon 50-65 51-53 51-99 
 
 Hydrogen 7-03 6-69 6-72 
 
 Nitrogen 17-71 17-94 17-28 
 
 Oxygen and Sulphur 24-61 23-84 24-01 
 
 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 the same effects upon the young crops. They con- 
 tain 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 de- 
 pends upon this element, they ought to occupy an intermediate place 
 between these several substances. 
 
446 THE INORGANIC MATTER CONTAINED IN BONES. 
 
 § 3. Of the composition of bones. 
 
 Few substances have of late years done so much to increase the 
 agricultural produce of various parts ol' 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 upon its age. 
 According to Denis, tlie radius of a lemale, 
 
 Aged 3 years,' contained . ...33-3 per cent, water, Avith a little fat. 
 
 Aged 20 years, " 13-0 " " 
 
 Aged 78 years, " 15-4 •' " 
 
 The quantity of water thus present in bones performs an important 
 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 decomposition, and exercise, in conse- 
 quence, a more immediate and apparent, and therefore, as some may 
 think, a more poAverful and fertilizing action. 
 
 2^. But bones ditfer from the other animal substances already de- 
 scribed chiefly by containing a much larger proportion of inorganic 
 matter, or by leaving, when burned, a greater percentage of ash. 
 The quantity of inorganic matter, however, contained in bones is not 
 constant. It is less in the young than in the full-grown animal — less 
 in the spongy than in the compact or more solid bones — and less in 
 those of some animals than in those of others. Thus, when freed 
 from fat and perfectly dried — 
 
 Of iiiorcanic matter. 
 
 The lower jaw-bone of an adult left 68-0 per cent. 
 
 a child of 3 years. — 62-S " 
 
 A compact human bone — 58-7 " 
 
 A spongy human bone — 50-2 •• 
 
 The tibia of a sheep — 4S-03 '•' 
 
 The vertebra? of a haddock — 60-51 " 
 
 It is obvious that the relative efficacy of equal weights of bones 
 must be affected by such differences in the relative productions of 
 organic and inorganic matter Avhich they severally contain. 
 
 3"^. This inorganic matter or ash consists in great part of phosphate 
 of lime (Lee. IX., § 4.) but it contains also a considerable 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 carnivoroiis animals. 
 
 Thus, for every 100 parts of phosphate of lime there exists in — 
 
 Human bones about 20-7 carbonate of lime. 
 
 Bones of the sheep 24-1 " 
 
 Do. ox 13-5 « 
 
 Do. fowl 11-7 « 
 
 Do. haddock 6-2 « 
 
 Do. frog 5-8 " 
 
 Do. lion 2-6 
 
COMPOSITION OF BURNED B0NE9. 447 
 
 These proportions are not to be considered as constant, because it 
 varies 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. (Thomson's Animal Chemistry, p. 242.) But the existence of 
 such differences must render unlike the fertilizing action of the 
 bones of different animals — if, as many think, this action depends in 
 any great degree upon the quantity of phosphate of lime which they 
 respectively contain, 
 
 4^. Besides the phosphate and carbonate of lime, I have stated that 
 bones contain certain other inorganic substances, which are found in 
 email quantity in the ash. What these substances are will appear 
 in the following table, which represents the constitution of the bones 
 of some animals, as analysed by Dr. Thompson : 
 
 Ileum Ileum Vertebra, 
 
 of a sheep. of an ox. of a haililock. 
 
 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 
 
 Magne.sia 0-9 0-2 0-8 
 
 Soda 0-3 0-2 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 pho.sphate. An appreciable quantity of fluor- 
 ide of calcium, with traces of iron and magne.sia, are also generally 
 found in bones, in .addition to ihe substances indicated in the pre- 
 ceding analyses. 
 
 5^. VVhen bones are heated to redness in the open air the organic 
 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 cover- 
 ed with dilute muriatic acid, the earthy or inorganic part is slowly dis- 
 solved out, and tlie organic part — the cartilage or gelatine — will alone 
 remain, retaining also the form and size of the organic bone. In this 
 state it is flexible and somewhat soft, and by prolonged boiling may 
 be dissolved in water, and manufactured into glue. 
 
 This organic or combustible part of bones is identical in chemi- 
 cal composition with skin and glue, and is nearly the same as wool, 
 hair, and horn, of which the analysis has already been given. In 
 so far, therefore, as their eflicacy depends upon the organic consti- 
 tuent, dry bones must be greatly inferior to an equal weight of any 
 of the other animal substances above described, because of the much 
 greater proportion of earthy matter they contain. 
 
 § 4. On %i-hat does the fertilizing action of bones depend 7 
 
 Bones contain, as we have seen, a 1-arge proportion both of organic 
 and of inorganic matter; — on which of these two constituents does 
 their fertilizing action most depend ? Some regard the phosphate 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 suf- 
 ficiently impregnated with this phosphate, that Sprengel accovints for 
 
448 EFFECT OF BOILING UPON BONES. 
 
 the little success which has attended the use of bones in Mecklenburg 
 and North Germany. Others, again, attribute the whole of their in- 
 fluence to the organic part — the gelatine — which bones contain. 
 Neither of these views is strictly correct. Plants, as we have seen, 
 require a certain quantity of phosphoric acid, lime, and magnesia, 
 which are present in the inorganic part of bones, and so far, therefore, 
 are capable of deriving inorganic food from bone-dust. But the or- 
 ganic 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, therefore, 
 that a considerable part of the effect of bones upon all crops must be 
 due to the gelatine which they contain. 
 
 The principal focts, now known in regard to the action of bones, 
 may be thus stated : — 
 
 !■=. The organic matter of bones acts like tliatof skin, AvooUen rags, 
 horn shavings, &c., but as bone-dust contains only about one-third of 
 the organic matter which is present in an equal weight of cither of the 
 above substances, its total effect, in so far as it depends upon the or- 
 ganic matter, will be less in an equal proportion. 
 
 2°. But as the organic matter of bones contains more water than 
 horn or wool, (p. 446,) it will decay more rapidly than these substan- 
 ces when mixed Avith the soil, and will therefore be more immediate in 
 its action. Hence the reason why Avoollen rags and horn shavings must 
 be ploughed in in the preceding winter, if they are lo benefit the subse- 
 quent wheat or turnip crops, while bone-dust can be beneficially ap- 
 plied at the sowing of the seed. 
 
 3°. When bones are boiled the oil will be separated, and a portion of 
 the gelatine will at the same time be dissolved out.f The bones, 
 therefore, Avill be in reality rendered less rich as a manure. But as 
 they at the same time take up a considerable -qviantity of water, boiled 
 bones will decompose more rapidly when mixed with the soil, and 
 thus will 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, however, may occur in which the 
 
 ' The main (iifTfti'encp is in the quantity of sulphur cnntainpd in hair. An analy^:is of 
 liuman hair, by Van Labr (.Annalen der PhaTmacie, xiv , p. 16-!,) which has reached me 
 since the prereijing sheet went to (tress, shows the proportion of sulpliur more accurately 
 than that which is given at page 445. Ho found human liair of various colors to leave from 
 one-third to nearly two per cent, of ash when burned, and to consist besiiies of (Carbon, 
 50-65— Hydrogen, 6 36— Nitrogen, 1714-Oxygen, 20-85— Sulphur, 5 00- Total, lUO— and 
 nearly half a per cent, of Phosphorus, 
 
 t The prolonged boiling of bones, so as to dissolve a portion of the gelatini, is practised 
 to a considerable extent as a mode of manufacturing size or glue. In the large dyeing es- 
 tablishments in Manchester, the bones are boiled in open pans for 24 hours, the fat skim- 
 med off anil sold to the candle-makers, and the size afterwards boiled down in another 
 vessel till it is of sufficient strength for stiffening the thick goods for which it is intended. 
 The size liquor, when e.vhausted, or no longer of sufficient strength for stiffening, is applied 
 with much benefit as a manure to the adjacent pasture and artificial grass lands, and the 
 bones are readily bought up by the Lancashire and Cheshire farmers. The boiled bones 
 must evidently lose all the fertilizing virtue which the size liquor acquires. 
 
COMPOSITION OF LONG-BUKIED CON'ES, 449 
 
 skilful man will prefer to use boiled bones because they cire fitted to 
 produce more immediate effect where — as in the pushing forward of 
 the young turnip plant — such an effect is particularly required. 
 
 4°. When bones are btiried in a more or less entire state, as they oc- 
 casionally are about the roots of vines and fruit trees, they gradually 
 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 
 
 deep. shallow. Femur of a stag. 
 
 Animal matter 16-2 4-2 7-3 
 
 Phosphate of lime 56-0 62- 1 54-1 
 
 Carbonate of lime 13-1 13-3 19-3 
 
 Sulphate of lime 7-1 12-3 12-2 
 
 Phosphate of magnesia 0-3 0*5 2-1 
 
 Fluoride of calcium 2-0 2-1 2-1 
 
 Oxide of iron and manganese. 2-0 2-1 2-9 
 
 Soda M 1-3 — 
 
 Silica 2-2 2-1 — 
 
 100 mo 100 
 
 The most striking change undergone by these bones was the large 
 loss of organic or animal matter tliey had suffered. The relative 
 proportions of the phosphate and carbonate of lime had been com- 
 paratively little altered. The main effect, therefore, produced by 
 bones when buried at the roots of trees, and their first effect in all 
 cases, must be owing to the animal matter they contain — the ele- 
 ments of this animal matter, as it decomposes, being absorbed 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 advanced by Sprengel, and after him reiterated 
 by Liebig and his followers — that the principal efficacy of bones is, 
 in all cases, to be ascribed to their earthy ingredients, and especially 
 to the phosphate of lime. 
 
 This opinion of Sprengel rests mainly on two facts put forward by 
 himself (Lehre vom Diinger, p. 153.) Bones, he says, have failed to 
 produce 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, there- 
 fore, he concludes, be the animal matter of bones to which their benefi- 
 cial 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 tails even among ourselves. Let bones be tried for the turnip 
 crop — a crop still almost unknown in Northern Germany — and upon 
 well drained soils similar to those of our best turnip lands, and I ven- 
 ture to predict, in opposition to Sprengel's experience, that bones will 
 no longer fail even in Mecklenburg. 
 
 Again, having drawn his conclusion in regard to the inutility of the 
 animal matter, Sprengel states that the marl which is applied to the 
 land in Holstein and the neighboring provinces, contains phosphate 
 
450 CAUSE OF THE PROLONGED EFFECT OF BONF.S. 
 
 of lime (p. 371,) and hence the reason why the earthy matter of the 
 bones applied does not improve the land. In so far as the efficacy of 
 bones really depends upon tlieir earthy constituents, the use of a marl 
 containing phosphate of lime* will, no doubt, greatly supersede them ; 
 — but in so far as it depends upon the animal matter they contain, 
 bones Avill exhibit their natural fertilizing action, however rich the 
 soil may already be in those compounds of which their earthy or in- 
 combustible part consists. 
 
 5°. Yet there is reason to believe — nay, it may be assumed as cer- 
 tain — that the phosphate and carbonate of lime wiiich bones contain .<i) 
 largely, are not without effect in promoting vegetation. All our culti- 
 vated plants require and contain both phosphoric acid and Irme, (se(». 
 Lee. X.. § 3,) and from the vegetables on which they feed, all animai.s 
 derive the entire substance of their bones. This same phosphoric, 
 acid and lime, therefore, must exist in the soil on wliich the plants 
 grow, or they will neitlier thrive themselves nor be able properly to 
 nourish the animals they are destined to feed. If a soil, then, be de- 
 ficient in phosphate of lime or its constituents, it is clear that the ad- 
 dition of bones will benefit the after-crops not only by the animal, but 
 by the earthy matter also which they contain. And that such is the 
 case, in many instances, there is good reason for believing. But that 
 this can by no means account for the whole effect of bones, even sup- 
 posing the soil to which they are applied to be, in every instance, defi- 
 cient in phosphates, is clear from the fact (see Lee. X., § 4.) that 260 
 lbs. — less than 6 bushels — of bone-dust per acre are sufficient to sup- 
 ply all the phosphates contained in the crops which are reaped during 
 an entire fourshil't rotation of turnips, barley, clover, and wheat. Yet 
 the quantity of bones actually applied to the land is from three to five 
 times the above weight, repeated every time the turnip crop comes 
 round. 
 
 6^. Still, granting that the chief effect of bones upon the immedi- 
 ately succeeding crops is due to their organic part, upon what does 
 their proJonsred good effect depend ? Some lands remember a single 
 dressing of bones for 16 or 20 years, and some after the application 
 of 2 or 2 i tons of bones have yielded 10 to 15 successive crops of 
 oats, and have been sensibly benefitted for as many as sixty j'ears 
 after the bones were applied. (See Appendix, No. 1.. and British 
 Husbandry, I., p. 398.) 
 
 Tins prolonged effect is also due in part to both constituents. When 
 not crushed to powder, the organic matter of bones is always slow in 
 disappearing, and slower the deeper they are buried. In some soils, 
 also, the process is more slow than in others. The long-buried bones of 
 the bear and of the stag, of which the an;i,l}'sis is given above (p. 440. ) 
 had lain in the soil for an unknown period, and yet they still contained 
 a sensible proportion of animal matter. So it is with tbe bones used tor 
 manure, wiien they are not crushed too fine. They long retain a por- 
 tion of their organic matter, which they give out more slowly, and 
 
 * Most lime-slonps ami shell sands contain an appreciable quantity of this phos-phale. ami 
 will, therefore, to the same extent, supersede the use of the earthy matter of hones. Much 
 of the marl of Ilolstein consists of the <ielrltus of chalk rock.^, anciently broken up ami 
 carried ofT— by the waters of the sea with which that part of Europe was covered at no 
 very remote geological epoch. 
 
FERTILITY OF ANCIENT BATTLE-FIELDS. 451 
 
 in smaller quantity, every year that passes, yet still in such abun- 
 dance as to contribute sensibly to the nourishment, and in some de- 
 gree to promote the growth ot' the crops which the land is made to 
 bear.* So it would be with the horns and hoots ot^ cattle, if laid on in 
 equal quantity, for they also decay with exceeding slowness. 
 
 Still the inorganic part is not without its use. If the soil he defici- 
 ent in phosphates or in lime, the earthy matter of the bones will sup- 
 ply these substances. 1 only wish to guard you against the conclu- 
 sion, that because bones often act for so long a period, that therefore 
 the organic matter can have no share in the influence they exercise 
 after a limited period of years. 
 
 He who candidly weighs the considerations above presented will. I 
 think, conclude tJiat the whole effect of bones cannot in any case bo 
 ascribed exclusively either to the one or to the other of their principal 
 constituents. He will believe, indeed, that in the turnip husbandry the 
 organic part performs the most prominent and most immediately useful 
 office, but that the earthy part, nevertheless, affords a ready supply of 
 certain organic kinds of food, which in many soils the plants would 
 not otherwise easily obtain. He wall assign to each constituent its 
 separate and important function, being constrained, at tlie same time, 
 to confess that while in very many cases the earthy part of bones ap- 
 plied alone would fail to benefit the land, there are few cultivated 
 fields in which the organic part applied alone would not materially 
 promote the growth of most of our artificial crops. 
 
 § 5. Of the application of bone-dust to pasture lands. 
 
 If the soil be deficient in phosphate of lime, bone-earth alone, or the 
 mineral phosphate (Lee. IX., § 4,) may be advantageously applied to 
 increase its fertility. In a four-years' rotation of turnips, barley, clover, 
 and wheat, if bones be used for the turnip crop, the land will every ro- 
 tation become richer in bone-earth, (see preceding page,) and there- 
 fore the application of earthy phosphates cannot — after a few rota- 
 tions — be expected materially to affect its productiveness. But pas- 
 ture lands are treated differently, and it is not unlikely that in some 
 instances the earth of bones, even applied alone, may to such landa 
 be productive of 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 £10 per acre, it has increased 
 the value of old pastures from 10s. or 15s. to 30s. or 40s. per acre : 
 and after a lapse of 20 years, though sensibly becoming less valu- 
 able, land has remained still worth two or three times the rent it paid 
 before the bones were laid on. 
 
 It is this lengthened good effect of bone-dust that affords the strongest 
 ground for believing ihat the earthy phosphate has a large share in the 
 
 * This opinion derives a singularly Interesting confirmation from the fact that a portion 
 of the soil of an arable distrirt in Sweden, "which from time immemorial hal crown ex- 
 cellent wheat without manure," was found by Berzelius to contain minute fragmen's of 
 bone capable upon boiling with water of yielding a weak solution of gelatine. It was 
 concluded, therefore, that the spot had been an ancient battle-field, and that Its prolonged 
 fertility was due Co the bones of old time buried in it, and still to some extent undecom- 
 poicd (Marchand ) 
 
452 PHOSPHATE OF LIME YEARLY CARRIED OFF. 
 
 effect. I have already shown that this prolonged action is not conclu- 
 sive upon the point — isince the organic matter lingers long, even in buri- 
 ed bones — but a consideration of the necessary effect of long continu- 
 ed pasturage upon soils to which nothing is artificially added, lends a 
 singular support to the view that the bone-earth may act an important 
 and beneficial part upon old meadow and other grass lands. Take 
 the instance of a dairy farm in the neighborhood of a large town, — 
 
 1^. The milk is all carried off the farm, either directly or in the shape 
 of butter, cheese, &c.. and every 40 gallons of milk contain 1 lb. of 
 bone-earth, besides other phosphates. Estimate the average yield of a 
 good cow at oOOO quarts, or 750 gallons a-year, its milk will contain 19 
 lbs. of earthy phosphate — as much as is present in 30 lbs. of bone-dust. 
 
 2^. Again, the urine of a railk cow, taken at 700 gallons a-year, 
 contains about 11 lbs. of the same phosphate. (A coav, not in milk, 
 gives on an average about 1300 gallons of urine — see page 460.) 
 Suppose only a third of this to run to waste, and the flirm will lose for 
 every cow in this way about 4 lbs. — equal to about 6 lbs. of bone-dust. 
 
 3°. But for every cow an annua! calf is reared and sold off. Let this 
 calf contain but 20 lbs. of bone — then for every cow it maintains^ a dairy 
 farm will lose of earthy phosphates upon the whole as much as is 
 contained in 56 lbs. of bone-dust. Suppose a farm to be pastured 
 for centuries, as those of Cheshire have been, and the produce to be 
 carried off in the form of milk, butter, and veal — we may reasonably 
 suppose that it will at length begin to feel the want of those phos- 
 phates which year by year have been drawn from its surface. It is 
 reasonable also to suppose that the addition of these deficient phos- 
 phates would impart new vigor to the soil, would cause new grasses 
 to sprout, and a more milk-yiehling 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, while it failed materially to im- 
 prove those of other districts on which it had been tried. I still consider 
 it as by no means without its weight, though I cannot concur with the 
 extreme views which some have since adopted — that either in the case 
 of Cheshire, or in any other case with which I am acquainted, the benefi- 
 cial action of bone-dust is to be ascribed solely to its earthy constituents. 
 
 § 6. O/" animal charcoal, the refuse of the sugar refineries, and 
 animalized carbon. 
 
 1°. Animal charcoal, (bone black.) — When bones are charred or 
 distilled at a red heat in close vessels, they leave behind a coaly re- 
 siduum to which the name of animal charcoal is usually given. By 
 this calcination the animal matter is almost entirely decomposed. 
 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 obtained from the unma- 
 nured soil 12 tons 5 cwt. per acre ; but when manured with 10 cwt. 
 of animal charcoal, 21 tons 2 cwt. (see Appendix. No. VIII.) 
 
 2°. Refuse charcoal of the sugar refiners. — 'The animal charcoal 
 above described is chiefly employed for the purpose of removing the 
 
Repose charcoal of the sugar-refiners. 453 
 
 color 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 crys- 
 tallization. Hence the animal charcoal, the blood, the lime, and tlie 
 coloring and other matters separated from the sugar, become mixed 
 togetlier, 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 
 is in general — and especially in France, where it is extensively em- 
 ployed as a manure — considered from four to six times more power- 
 ful 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 thousaad 
 tons ("Boussingault, An. de Chim.et de Phys., 3d series, iii., p. 96.) 
 It sells at about five pounds a ton. 
 
 The value of this substance depends very much upon the propor- 
 tion of blood which it, contains, and as this is in some measure vari- 
 able, its fertilizing qualities must be variable also. In England 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.* This is probably one 
 reason why Mr. Fleming obtained from the use of it a somewhat 
 smaller crop of turnips than from an equal quantity of the unused 
 animal charcoal. Upon Swedish turnips 10 cwt. of unused animal 
 charcoal gave him 21 tons 2 cwt. ; while 10 cwt. of the refuse gave 
 10 tons 7 cwt. (Appendix, No. VIII.) 
 
 Still this result is sulRciently favorable to recommend the refuse or 
 exhausted animal charcoal to the practical agriculturist where more 
 economical manures cannot readily be obtained. 
 
 3'. Aninialized carbon. — The estimation in which the refuse char- 
 coal of the sugar works was held, has led to the manufacture of very 
 useful imitations of it under the name of animalized carbon. A cal- 
 careous soil, rich in vegetable matter, (an intimate mixture of peat 
 and marl or shell-sand would answer well,) is charred in close ves- 
 sels, and is then mixed at intervals witJh 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 adulteration and the uncertain- 
 ty to which, even when skilfully and conscientiously prepared, its 
 composition must be in some measure liable. 
 
 § 7. Of Jish, jish refuse., whale blubber, and oil. 
 
 P. Fish. — In some parts of the world, and occasionally on the shores 
 of En gland, fish are met with in such abundance that they can be econo- 
 mically employed as a manure for the land. They are either spread over 
 
 * Thp refining '■ consists In piitiins Ihe s\i!ar into a larse square coppercistern alons with 
 S"me lini'^ Wiilff a little bullocl<'s blood, anil from 5 to 20 per cent of bone black, ami in-, 
 jeclinj steam tlirongh the mixture Instead nf the blood many n fiM"r-i employ a mixtnre 
 of gelatinous alumina ami gypsum, called finings, prepared by addina lime water Jo a so- 
 lution of alum, and collecting the precipitate" (tire.) Hence Ihe reason why, in England 
 at least, the refuse charcoal of the sugar works Is not. always rich in blood. 
 
454 OF FISH, riSH refuse, and oil ; and the relative 
 
 it in a recent state, or — which is more economical, — are made into a com- 
 post chiefly with earth, which after a time proves rich and fertilizing. 
 
 The bones of fish are similar in composition to those of terrestrial 
 animals (p. 417), and their muscular parts are nearly identical in ele- 
 mentary constitution with the lean part of beef and the clot of blood. 
 As fertilizing agents, therefore, the parts of fishes will act nearly in 
 the same way as the blood and bodies of animals. 
 
 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, (fourteen barrels of herrings yield one of 
 refuse,) which is peculiarly valuable to the farmers in the neighbor- 
 hood of the principal fishing stations. 
 
 In the North, a compost prepared from this fish refuse, is generally 
 esteemed as a manure for barley and green crops, but when exten- 
 sivel}'^ used, " is said to render the soil unfit for the production of oats." 
 Such soil is said to be poisoned (Sinclair's Statistical Account of 
 Scotland, vii., p. 201, quoted in British Husbandry, I., p. 421.) 
 
 3^. WkaJe blubber. — When the oil is expressed from whale blub- 
 ber, a skinny or membraneous refuse remains, which has hitherto 
 been employed only as a manure. It is made into a compost Avith 
 earth, which is several times turned, and the mixture is most usefully 
 employed after it has lain not less than 9 or 12 months. It may be 
 applied either to grass or to arable land. 
 
 4°. 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 (see his Georgical Es- 
 says, vols. 1, 2, and 5.) Merely mixed with absorbent earth, and ap- 
 plied 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 
 23^ tons of turnips, while 40 bushels of bones gave him only 22 tons. 
 More recently, also, it has been found that the mixture of a few gallons 
 of oil with the usual quantity of bone-dust increased to a considerable 
 degree the turnip crop to which it Avas applied. In a theoretical point 
 of vicAV. it would be interesting to establish tlie f ict, that pure oil is 
 capable of promoting in a large degree the growth and produce of 
 our cultivated crops — though, as a resource, of Avhich farmers in gene- 
 ral can avail themselves AA'here other manure is scarce, its high price 
 will probably prevent it from ever becoming extensively useful. 
 
 § 8. Relative fertilizing value of the animal manures already 
 described. 
 
 No sufficit-ntly decisive experiments are yet upon record, from 
 Avhich the relative value of the several animal manures above des- 
 cribed can be satisfactorily deduced. That they difler in fertilizing 
 power every farmer is aAvare, but it is not yet decided by actual trial, 
 in Avhat proportion one of them exceeds the other. 
 
 I have already stated to you (p. 440) the theoretical opinion enter- 
 tained by many, that the efficacy of all vianures ?> in proportion to the 
 quantity of nitrogen they contain. Adopting this princij)le as true, it 
 IS easy to assign to eacli substance its proper place in an artificial table. 
 The last column in the foUoAving table shoAvs the quantity of each 
 
FERTILIZING VALUE OP VARIOUS ANIMAL MANURES. 433 
 
 substance in its ordinary state of dryness, vphich w^ill be necessary to 
 produce the same effect as 100 lbs. of common larm-yard manure, 
 supposing this effect to be determined by the nitrogen alone. 
 
 Equal effecls 
 Water per cent. Ash per cent. Nitrogen per cent, produced by 
 
 Farm-yard manure.. 80 ? i 100 lbs. 
 
 Flesh 77 1 3jt 14 " 
 
 Fish 80 2 2i 20 « 
 
 Blood ...79 to 83 1 3 16 « 
 
 Blood dried* 12 to 20 3i 12 to 13 8 " 
 
 Skin 58 i 8 12 " 
 
 Wool,hair,andhorn. 9 to 11 1 to 2 16 6 " 
 
 Bones 14 40 to 60 5 to 9 11 to 20 " 
 
 Refuse charcoal of 
 
 the Sugar-works. .48 'I 1 50 « 
 
 AnimaUzed carbon. .45 ? 1 50 " 
 
 I have already had occasion to remark, however, that this mode of 
 classifying manures is not altogether to be depended upon. Since — 
 
 P. It does not take into account the quantity of inorganic matter 
 they severally contain, Avhich as shewn in the third column is parti- 
 cularly large in bones, and is by some considered as the (most?) im- 
 portant and influential constituent of this manure. Nor is any effect 
 ascribed to such substances as the sulphur, whicli in hair and wool 
 forms nearly 5 per cent, ot" their whole weight, and which cannot be 
 wholly without influence upon the plants, by which, as tliey decay, 
 the elements of these manures may happen to be absorbed. 
 
 2^. It passes by the practical influence of the quantity of water 
 wliich the several substances contain. Flesh, fish, blood, and skin, in 
 their recent state, contain so much water that they begin almost im- 
 mediately to decompose, and thus expend most of their fertilizing 
 virtue upon the first crop to which they are applied. Hair and wool, on 
 the other hand, retain so little water that they decay with great slowness. 
 Hence, the true amount of the action of these latter substances cannot 
 be estimated in a single year, and must therefore be altogether a mat- 
 ter of theory xmtil a series of careful observations, made in consecu- 
 tive years, shall afibrd some decisive facts upon which to reason. 
 
 3°. This is confirmed by the statement of Boussingault and Payen, 
 (Annates de Chim. et de Phys., 3d series, iii., p. 94,) that the effect 
 of the animal charcoal of the sugar refiners and of the animalized 
 carbon is, by experience, five times greater than the proportion of ni- 
 trogen they contain would indicate; and — 
 
 4". Il" pure oil, which contains no nitrogen at all. will yet produce 
 an enriching manure by mere mixture with the soil (p. 454), 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 the impure or refuse whale oil used for composts may 
 contain some nitrogen, but we can scarcely suppose 250 or 300 lbs. 
 of such oil to hold so much of this element as to accoxint for all the 
 effects which the oil is said to have produced. 
 
 * As it is 8o!d for manure at Paris and elsewhere, p. 443. 
 
456 ^ or THE DROPPINGS OF BIRDS. 
 
 While, then, we put so much faith in theory as to behave that sub- 
 stances which contain mucli nitrogen are very hkeiy to prove valua- 
 ble manures, — we must not allow ourselves to be so carried away by 
 the simplicity of the principle as to believe either that their relative 
 effects upon our crops may be always estimated by the proportion of 
 nitrogen they contain, or that a substance may not largely increase 
 the produce of our fields in which no nitrogen is present at all. In- 
 deed, the effects of saline substances alone are sufficient to satisfy us 
 how untrue to nature this latter opinion would be. 
 
 § 9. Of the droppings of fowls — pigeons^ diing^ and guano. 
 
 The droppings of birds form one of the most powerful of known ma- 
 nures. This arises in part from the circumstances that in the econo- 
 my of birds there is no final separation between the liquid and sohd 
 excretions. Both escape mixed together from the same aperture. 
 
 1°. Pigeons' dung is much prized as a manure wherever it can be 
 obtained in any considerable quantity. In Belgium it is esteemed as 
 a top-dressing for the young flax, and the yearly produce of 100 
 pigeons is sold for about 20s. Its immediate effect depends upon the 
 quantity of soluble matter it contains, and this varies much accord- 
 ing to its age and the circumstances under which it has been pre- 
 served. Thus Davy ('Davy's Agricultural Chemistry, Lecture VI.,) 
 and Sprengel obtainea respectively of 
 
 Recent. Six months' olJ. After fprmentation. 
 
 (Davy.) (Sprengel ) (Divy.) 
 
 Soluble matter in ? oo 4. ic * a 
 
 pigeons' dung. . \ ^^ P^"" ^^"*- ^^ P^'' '^^"^- ^ P^'' <^«"*- 
 
 The soluble matter consists of uric acid in small quantity, of urate, 
 sulphate, and especially of carbonate of ammonia, common salt, and 
 sulphate of potash ; — the insoluble chiefly of phosphate of lime, with 
 a little phosphate of magnesia, and a variable admixture of sand and 
 other earthy matters (Sprengel's LeJire vom Diinger, p. 140.) When 
 exposed to moisture, the pigeons' dung, especially if recent, undergoes 
 fermentation, loses a portion of its ammoniacal salts, and thus be- 
 comes less valuable. When it is intended to be kept it sliould be 
 mixed with a dry vegetable soil, or made into 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 manu- 
 facture of the animaUzed carbon above described. 
 
 2'. Hens^ dung often accumulates, decomposes, and runs to waste 
 in poultry yards, when, with a little care, it might be collected in 
 considerable quantities. 
 
 3°. Goose dung is less rich than that of hens or pigeons, because 
 this bird feeds less upon grain, and derives a considerable portion of 
 its nourishment from the grass which it crops, when allowed to go at 
 liberty over the fields. Its known injurious effects upon the grass 
 upon which it falls arise from its being in too concentrated a state. 
 In moist weather, or where rain soon succeeds, it docs no injury, and 
 even when in dry weather it kills the blades on Avhich it drops, it 
 brings up the succeeding shoots with increased luxuriance. 
 
 4°. Books' dang unites with the leaves of the trees among which 
 they live, in enriching the pasture beneath thera. In old rookeries the 
 soil is observed also to be slowly elevated above the surrounding land. 
 
COMPOSITION OF GUANO. 457 
 
 This surface soil I have found to be especially rich in phosphate of lime, 
 which has gradually accumulated and remained in it while the volatile 
 and soluble part^ 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 isl- 
 ands that skirt tlie coast of South America, from the 13th to the 21pt 
 degree of south latitude. In that part of America, the climate being 
 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 cer- 
 tain places it is said even 60 (?) feet in thickness. In some places 
 the more ancient of these depositcs are covered bv layers of drift 
 sand, which tend further to preserve 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 birds most abound no considerable quantity 
 of guano can ever be expected to collect. 
 
 The solid part of the droppings of birds in general, when recent, con- 
 sists chiefl3-of uric acid, with a little urate of ammonia, and a variable 
 per-centage of phosphate of lime and other saUne compounds. The 
 liquid part, like the urine of other animals, contains much urea, with 
 some phosphates, sulphates, and chlorides. The uric acid and urea, 
 however, gradually undergo decomposition, and are changed into car- 
 bonate 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 tor a lengthened period of time, the salts of ammonia gradually 
 volatilize, and the efficacy of what remains becomes greatly dimin- 
 ished. Hence, the guano which is imported into this country is very 
 variable in quality, some samples being capable of yielding only 7 
 per cent, of ammonia, while others are said to give as much as 25 
 per cent. Of two portions taken by myself from the same box, the 
 one contained 8 per cent, and the other only \\ per cent, of sand, 
 while their other constituents were as follows : — 
 
 J- • percent! '^ • percpnt. 
 
 Water, salts of ammonia, I Ammonia 7-0 
 
 and organic matter ex- | Uric acid 0-8 
 
 pelled by a red heat 23-5 
 
 Sulphate of soda 1-8 
 
 Common salt, with a little 
 
 phosphate of soda 30-3 
 
 Phosphate of lime, with a lit- 
 tle phosphate of magnesia 
 and carbonate of lime. .. . 44-4 
 
 100 
 
 Water and carbonic and ox- 
 alic acids, &c., expelled 
 by a red heat 51-5 
 
 Common salt, with a little 
 sulphate and phosphate 
 of soda 11'4 
 
 Phosphate of lime, &c 29-3 
 
 100 
 
 On the other hand. Dr. Ure gives the following as the average re- 
 sult of his analyses of genuine guano : — 
 
 percent. 
 Organic matter containing nitrogen, including urate of ammo- 
 nia, and capable of affording from 8 to 17 per cent of am- 
 monia by slow decomposition in the soil 50 
 
 Water 11 
 
 20 
 
458 VALUE OF GUANO AS A MANURE. 
 
 per cent. 
 
 Phosphate of hmc 25 
 
 Ammonia, pliosphale of magnesia; phosphate of ammonia, & ox- 
 alate of ammonia, containing from 4 to 9 per cent, of ammonia. 13 
 Siliceous matter from tlie crops of the birds 1 
 
 100* 
 Others have found sand in much larger proportion than was pre- 
 sent in tlie samples examined by myself — while it may, I tliink, be 
 taken for granted that very little of what comes to this country is so 
 rich in soluble matter, containing ammonia or its elements, as is re- 
 presented by the analyses of Dr. Ure.f 
 
 Variable as its composition is, however, there is now no doubt that 
 any of the samples yet brought into the English market may be ad- 
 vantageously applied as a manure to almost any crop. From the 
 most remote period guano has been the chief manure applied to the 
 land on the parched shores of Peru — and at the present day it is not 
 only employed for the same purpose in the provinces 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" (Silliman's Journal, xliv., p. 10.) It has been 
 estimated that a hundred thousand quintals (the quintal is equal to 
 lOli lbs. avoirdupois) are, at the present day, annually sold in Peru. 
 There also the quantity and the price vary — the recent white guano 
 selling usually at 3s. 6d., the more recent red and grey varieties at 
 2s. 3d. per cwt. (Winterfeldt.)| In this country, the latter — the only 
 variety yet imported — sells at present (1843) at about 10s. a cwt. 
 
 In regard to the effects of guano upon various crops, many import- 
 ant experimental results, obtained in 1842, will be found in the Ap- 
 pendix. I here insert a few of the more important of these, along 
 with some others made in the more southern counties, which appear 
 to be highly deserving of consideration. 
 
 Swedish Turnips. 
 
 I'rodiice per acre. 
 Top-dressed with ions. cwt. Locality. 
 
 P. Farm-yard dung.20 tons. 18 ^1 ? Baroch-in near PaisW 
 Guano 3 cwt. 23 8 \ t^f^rocnan, near f aisley. 
 
 2°. Farm-yard dung.20 tons. 16 18 ^ 
 
 Guano§ 2k cwt. 17 4 > Parish of Wraxal. Somerset. 
 
 Bones 32 bush. 15 17 ) 
 
 * By way of comparison, I insert here the .Tpproximale composition of the solid part of 
 the excrements of four different varieties of eajile, as determined by Coindet : — 
 
 American American Grand Duke 
 
 Senesial Ragle. Hunting Eagle. Fishinc Eagle. of Virginia. 
 
 TTricacid 81)79 90-37 84-65 i»7l 
 
 Ammonia 7 S5 6-b7 9 20 8-55 
 
 Phosphate of liu'e 2-36 0-76 6 15 2-74 
 
 100 100 100 100(a) 
 
 (a) Ometin Ilandbuch dur Ckemie, II , p. 1450. 
 
 tThe presence of ammonia in guano is readily ascertained by mixing it with a lilile 
 slaked lime — wlien the odour of ammonia will be immediately perceived, and will be 
 strong in proportion lo the quantity contained in the guano. 
 
 } For further particular.^ rfgarding guano the reader is referred to a paper in the Juurnal 
 of the Royal AgricuUural Society, II., p. 301. 
 
 S Mixed with I cwt. of charcoal powder. 
 
ITS ACTION UPON TURNIPS, POTATOES, WHEAT. ETC. 
 
 459 
 
 YelloiD Turnips. 
 
 Produce per acre. 
 Top-dressed with !ons. cwl. Locality. 
 
 Guanot 5 cwt. 32 2^ 
 
 Rape-dust 15 cwt. 24 1 1 > Barochan, near Paisley. 
 
 Bone-dust 30 bush. 17 2 ) 
 
 Potatoes. 
 
 I''. Guano 3 cwt. 18 9") 
 
 Rape-dust 1 ton. 12 6 1 t? , t iwu 
 
 2°. Guano 4 cwt. 14 6 ^T''^^''''- ^" ""^^ ^^^''^ ""^^^^ 
 
 Rape-dust 1 ton. 10 ^^f ""^T^u '""T. P"* ? 
 
 Bone-dust 45 bu.=h. 9 15 f f.^*'"' ^'^^ th^ potatoe cut- 
 
 3\ Guano 4 cwt. 13 14 tings no other manure be- 
 
 Rape-dust 1 ton. 13 | '"^ afterwards added. 
 
 Bone-dust 45 bush. 13 14 J 
 
 As a top-dressing to the j^oung potatoe crop at Ersltine, in 1842, one 
 cwt. of guano per acre produced no important increase. This might, 
 however, be owing to the extreme dryness of the season f Appendix, 
 No. IX.) 
 
 Wheat. 
 
 Priidiice per acre. 
 Top-dressed with bush. Ih?;. Locality. 
 
 1°. Guano 1 cwt. 48 ^ Lennox Love, near Had- 
 
 Rape-dust 16 cwt. 51 > dington — 
 
 Undressed 47i ; drouglit very great. 
 
 2°. Guano 3 cwt. 30 40 > t, , 
 
 TT 1 1 o< -n ; Ijarocnan. 
 
 Undressed 24 oo (> 
 
 3°. Guano 2 cwt. 32 20 > ^ , . ,. - 
 
 Undressed: 31 31 S ^''^'^S^'^^^^ "ear Ayr. 
 
 4=. Guano 1 cwt. 46 15^ 
 
 Nitrate of Soda. . 1 cwt. 51 18 > Erskine. Renfrewshire.il 
 
 Undressed 44 4 ) 
 
 5°. Guano \\ cwt. 45 i 
 
 Nitrate of Soda.. H cwt. 41 > Sei.sdon, Worcestershire.§ 
 
 Undressed 39 0) 
 
 Barley. 
 
 Guano 3 cwt. 64 > r, , 
 
 TT J J /!-? ic > Barochan. 
 
 Undressed 47 15 ^ 
 
 Oats. 
 
 P. Guano 2 cwt. 70 i Lennox Love, near Had- 
 
 Undressed 52 ^ dington. 
 
 2=. Guano 1 cwt. 48 16^ 
 
 Nitrate of Soda. . 1 cwt. 50 > Erskine. Renfrewshire. 
 
 Undressed 49 ) 
 
 t Mixed with 2tl bushels of wooilashes. 
 
 } Tho undrpssed srain \va.« of siip'^rior qualify, yielding 70.^ per cent, of fine flour, while 
 that (Ires.sed with guano gave only 6-iJ per cent. 
 
 II The grain dressed with guano weighed half a pound per bushel less thati the others. 
 
 5 Thesiianogave4 cwt. more straw than the nitrate, and 11 cwt. more than the undressed. 
 The undressed grain also weighed half a pound less per bushel than either of the other two. 
 
4G0 SOLID MATTER Iff THE DRINE OF DIFFERENT ANIOTALSv 
 
 Beans. 
 
 Froduce per acre. 
 Top-dressed with bush. Localily. 
 
 Guano 2 cvvt. :J3n 
 
 Rape-dust 16 cwt. 35 (Lennox Love, near 
 
 Nitrate of soda. . 1 cwt. 33 \ Haddington. 
 
 Undressed 29| J 
 
 Hay. 
 
 tons. cwt. 
 
 1°. Guano li cwt. 1 18 ^ 
 
 Nitrate of Soda. . IJ cwt 2 10 > Barociian, near Paisley. 
 
 Undressed 1 S; 
 
 2°. Guano U cwt. 2 2 ^ 
 
 Nitrate of Soda. . Ij cwt. 1 17 > Erskine, Renfrewshire, 
 
 Undressed 1 10 ; 
 
 An inspection of the above result.s appears to indicate that guano 
 is more iimforinly successful with rwyt crops, than when appHed as a 
 top-dressing to corn and grass. Tlie unusual drought which pre- 
 vailed in 1842 no doubt materially dimini.shed its action, wlien used 
 as a top-dressing — and the results upon the corn crops in a more moist 
 season may probably prove naore generally favorable to its vise as an 
 economical manure. 
 
 Some experiments seem already to indicate that the favorable in- 
 fluence of guano does not cease with the first season. If the phos- 
 phate of lime which they contain operates in any way in prolonging 
 the fertilizing operation of' bones, the large, thouirh variable, quanti- 
 ty of tins phosphate contained in gxiano should render thi.s latter 
 substance also capable of permanently improving the soil. 
 
 By exposure to the air, guano gradually gives oif a portion of its 
 volatile constituents ; it ought, therefore, to be kept in covered ves- 
 sels or casks. It also- in our cHmate absorbs moisiure from the air. 
 and therefore should be purchased as soon as possible after importa- 
 tion. When applied as a top-dressing it may be conveniently mixed 
 with an equal weight of gypsum or wood ashes — with cliarcoal pow- 
 der, or with fine dry soil. 
 
 § 10. Of liquid animal manures — the urine of man, of the cow, 
 
 the horse, the sheep, and the pig. 
 The following table exhibits tlie average proportions of water, and 
 of the solid organic and inorganic, matters contained in the urine of 
 man and some other animrds in their healthy state — and the average 
 quantity voided by eacli in a day r — . 
 
 Water. Soliil mailer in 1001) parts. Averaee qiian- i 
 
 Urine in , ■ , lily vcidnd ia • 
 
 of a 1001 part.-!. Orairiiiv Icionanic. Tmal. 2t hiinrs. 
 
 Man 969* 23-4 7-6 31 3 lbs. 
 
 Horse ...940 27 33 60 3 "^ 
 
 Cow 930 50 20 70 40t « 
 
 Pig 926 56 18 74 ? 
 
 Sheep... 960 28 12 40 ? 
 
 ' Alfred Becquerel. See Thomson'.'! Animal Chemistry, p. 477 II is to be observed th.it 
 the proportions of water and of sdIIJ matier in urine vary with the food, and with a great 
 variety of circurastancef. 
 
 t A milk cow voids le.ss tlian this in a proportion which varies with the giiantily of millc 
 
COMPOSITION OF HUMAN tTRINE. 461 
 
 Of natural liquid manures, the most important and valuable, though 
 the most neglected and the most wasted afeo, consists of the urine of 
 man and of the animals he has domesticated. 
 
 Tiie efficacy of urine as a manure depends upon the quantity of 
 solid matter which it holds in solution, upon the nature of this solid 
 matter, and especially upon the rapid changes which the organic 
 part of it is known to vmdergo. 
 
 The numbers in the above table show that the urine of the cow, 
 estimated by tiie quantity of solid matter it contains, is more valu- 
 able than that of any oilier of our domestic animals, with the excep- 
 tion of the pig. Bui the qviantity voided by the cow must be so 
 much greater than by the pig, that in annual value the urine of one 
 cow must greatly exceed that of many pigs. 
 
 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 ex- 
 ceeds the urine voided by about one-tenth part only — while 
 
 Of wa(f r in 24 hourf. Of urine in 24 hoars. 
 
 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 ! 
 Tliat this should be very much greater indeed than in man, we are 
 prepared to expect from the greater extent of surface which the bo- 
 dies of these animals present. 
 
 Let us now examine more closely the composition of urine, the 
 changes which by decomposition it readily undergoes, and the effect 
 of these changes upon its value as a manure. 
 
 1=^. Hnman urine The exact composition of the urine of a healthy 
 
 individual in its usual state was found by Berzelius to be as follows :- 
 
 Phosphate of soda 2-9 
 
 Phosphate of ammonia. ... 1-6 
 
 Common salt 4-5 
 
 Sal-ammoniac 1"5 
 
 Phosphates of lime and mag- 
 nesia, with a trace of silica 
 
 and of fluoride of calcium, 1*1 
 
 Water 933-0 
 
 Urea 30-1 
 
 Uric acid 1-0 
 
 Free lactic acid, lactate of 
 
 ammonia, and animal 
 
 matter not separable... 17'1 
 Mucus of the bladder. . . . 0-3 
 
 Sulphate of potash 3-7 
 
 Sulphate of soda 3-2 , 1000 
 
 From what I have already had occasion to state in regard to the ac- 
 tion 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 marked action in promoting vegetation is chiefly to be ascribed. 
 This urea, which is a white salt-like substance, consists of — 
 
 she gives. Bniissinsantl found a milk cow to yield daily 18 lbs. of urine and 19 lbs. of 
 m\\V..—Ann. de C'kim.et de Phys., Ixjcl., pp. 123, 124. 
 
462 DRiNE or THE cow — rrs value. 
 
 Carbon 20-0 per cent. I Nitrog-en 46-7 per cent. 
 
 Hydrogen 6-6 " | Oxygen 26-7 " 
 
 100 
 
 It is, tlierefore, fitr riclier in nitrogen than flesh, blood, or any of 
 those other richly fertilizing substances, oi' which the main efficacy is 
 supposed to depend upon the large proportion of nitrogen they contain. 
 
 But urea possesses this furtlier remarkable property, that when 
 urine begins to ferment, — as it is known to do in a few days after it is 
 voided — it changes entirely intd carbonate of ammonia.* Of the aiw- 
 monia thus formed a portion soon begins to escape into the air. and 
 hence the strong ammoniac; tl odour of fermenting urine. This escape 
 of ammonia continues for a long period, the liquid becoming weaker 
 and weaker, and consequently less valuable as a manure every day 
 that passes. Experience has shown that recent urine exercises in gen- 
 eral an unfavorable action upon growing plants, and that it acts 
 most beneficially after fermentation has freely begun, but the longer 
 time we suffer to elapse after it has readied the 7^ipe slate, the greats 
 er the quantity of valuable manure we permit to go to waste. 
 
 2'^. The urine of the cow has been analysed in several states by 
 Sprengel, with the following results in 1000 parts : — 
 
 Altowed to ferment for four weeks 
 Fresh. in the open air. 
 
 A. B. 
 
 Water ... 926-2 954-4 934-8 
 
 Urea 40-0 10-0 6-0 
 
 Mucus 20 0-4 0-3 
 
 Hippuric and lactic acids... 6-1 7-5 6-2 
 
 Carbonic acid 2-1 1-7 15-3 
 
 Ammonia 2-1 4-9 16-2 
 
 Potash 6-6 6-6 6-6 
 
 Soda 5-5 5-5 5-6 
 
 Sulphuric acid 4-0 3-9 3-3 
 
 Phosphoric acid 0-7 0-3 1-5 
 
 Chlorine 2-7 2-7 2-7 
 
 Lime 6 trace trace 
 
 Magnesia 0-4 0-3 0-4 
 
 Alumina, oxide of iron, and 
 
 oxide of manganese 0-1 trace — 
 
 Silica 0-4 0.1 0-1 
 
 1000 998-2 999-Ot 
 
 The first variety of fermentivl urine (A.), had stood four weeks in 
 the air in its natural state of dilution ; the second (B.). had been mix- 
 ed while recent with an equal bulk of water — which is again deducted 
 
 ' This takes place by the decomposition at the same time of two atoms of the water in 
 which if is dissolved Thus nrea is ropr«>sented bv l.'a Hi N? Oa ; two of water by -211 O ; 
 and carbonate of ammonia by N Ih + C 0> ; and the r bange is tluis shown— 
 
 2 of L'of 
 
 Urea. Water. Carbonate of Ammonia. 
 
 Co Il4 No 02 + a H O = i (N H3 -}- C Oj) 
 tThe small quantify necessary to make up the \mO parts in (he two latter analyses con- 
 Bisled of a de|K>sit of carbonate and phosphate of lime and other earthy matters which 
 had gradually been formed, and of a trace of vinegar and of sulphuretted hydrogen.— Sea 
 Sprengel, Lelire row Diinger, pp. 107 to 110. 
 
CRINE OP THE HORSE, SHEEP. AND TIG. 463 
 
 from it in the analysis — Avith the view of ascertaining how far such 
 an admixture would tend to retain the volatile ammonia produced by 
 the natural decomposition of the urea. 
 
 An inspection of these tables shows three facts of importance to 
 the agriculturist — 
 
 1°. That the quantity of urea in the urine of the cow is considerably 
 greater tliaii in that of man; 2\ Tliat as the urine ferments, the quan- 
 tity of unra dimiiiishes, while that of ammonia increases — owing, as I 
 have already stated, to the gradual decomposition of the urea and its 
 conversion into carbonate of ammonia ; and 3^. That by dilution with 
 an equal bulk of water the loss of this carbonate of ammonia, which 
 would otherwise naturally take place, is in a considerable degree pre- 
 vented. The q}umiity of ammonia retained by the urine, after dilu- 
 tion, ivan in the same circurjislances nearly three time^^ as great a^ when 
 it was allowed to form e)it in the stat'-. in which it camefrovi the cow. 
 
 But even by this dilution the whole of the ammonia is not saved. 
 One hundred parts of urea form by their decomposition 56i parts of 
 ammonia, and as 36 parts of the urea in the urine B. had disappear- 
 ed, there ought to have been in its stead 19 parts of ammonia in ad- 
 dition to that which the urine contained in its recent state, or 21 parts 
 in all — whereas the table shows it to have contained only 16 parts. 
 Even when diluted with its own bulk of water, therefore, the urine 
 had lost by fermentation in the open air upwards of one-fourth of 
 the ammonia produced in it during that period. This .shows the ne- 
 cessity of causing our liquid manures to ferment in covered cisterns, 
 or of adopting some other means by v/hich the above serious loss of 
 the most valuable constituents may be prevented. 
 
 3^. The urine of the horse, sheep., and jjig, have not been so care- 
 fully analysed as that of the cow. They consist essentially of the 
 same constituents, and the specimens which have been examined 
 were found to contain the three most important of these in the follow- 
 ing proportions : 
 
 Ilorsp. Sfippp. Pi^. 
 
 Water 940 960 926 
 
 Urea 7? 28 56 
 
 Saline substances. . 53 12 18 
 
 1000 1000 1000 
 
 Some of the saline substances present in the urine, as above stated, 
 contain nitrogen. Tiiis is especially the case in the urine of the horse, 
 60 that the quantity of urea above given is not to be considered as re- 
 presenting the true ammonia-producingpower of the urine of this ani- 
 mal. The urine of the pig, if t!ie above analysis is to be relied upon as 
 any thing like an average result, is capable of producing more ammonia 
 from the same quantity than that of any other of our domestic animals. 
 
 § 11. Of the waste of liquid manure — of urate, and ofsulphated urine. 
 1°. WaJite of human urine. — The quantity of solid matter contain- 
 ed in the recent urine voided in a year by a man, ahorse, and a cow, 
 and the weight of ammonia they are respectively capable of yielding, 
 may be represented as follows : 
 
464 URATE, AND SULPHATED URINE. 
 
 Quanfitv of urine. Solid m;itter. Containing of urea. And yielding of ammonia. 
 
 Man 1000 lbs. 67 lbs. 30 lbs. 17 lbs. 
 
 Horse 1000 " 60 " ? ? 
 
 Cow 13000 " 900 " 400 " 230* " 
 
 How much of all this cniiching matter is permittetl to run to waste ? 
 The solid substances contained in urine, if all added to the land, would 
 be more fertilizing than guano. Avhich now sells at £10 a ton. If we 
 estimate the urine of each individual on an average at only 600 lbs., 
 then there are carried into the common sewers of a city of 15.000 in- 
 habitants, a yearly weight of 600,000 pounds, or 270 tons, of manure, 
 which, at the prcsentpriceof guano, is worth £2700, — which would no 
 doubt prove more fertilizing than its own weight of guano, and might be 
 expected to raise an increased produce of not less than 1000 qrs. of grain. 
 
 The saving of all this manure would be a great national benefit, 
 though it is not easy to see by what means it could be effectually ac- 
 complished. What is thus carried off by the sewers and conveyed 
 ultimately to the S(^a, 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 receives from the land ? 
 
 2°. Urate. — In order to prevent a portion of this waste, the practice 
 has been introduced into some large citiesof collecting the urine, add- 
 ing to it one-seventh of its weight of powdered gypsum, allowing 
 the whole to stand for some days, pouring ofl' the liquitl and drying 
 the powder. Under tJie name of urate this dry powder has been high- 
 ly extolled, but it can contain only a small portion of Avhat is really 
 valuable in urine. The liquid portion poured off must contain most 
 of the soluble ammoniacal and other salts, and even were the whole 
 evaporated to dryness, the gypsum does not act so rapidly in fixing 
 the ammonia as to prevent a considerable escape of this compound 
 as the fermentation of the urine proceeds. 
 
 3°. Si/Iphatpcl uriiie A method of more apparent promise is that 
 
 now practised by the Messrs. TurnbxiU of Glasgow, of adding diluted 
 sulphuric acid lo tlie urine as the ammonia is formed in it, and subse- 
 quently evaporating the whole to dryness. From the use of this sub- 
 stance very favorable results may be anticipated.! Still none of these 
 preparations will ever equal the urine itself part of the efficacy of 
 which depends upon the perfect state of solution in which all the sub- 
 stances it contains exist, and upon the readiness with which in this 
 state they make their way into the r<}ots of plants. 
 
 4°. Loss ofcow^s urine. — When left to ferment for five or six weeks 
 
 ■ Tiie numbers eiven above, ami in p. 46il, am calcwlatefl from the analysis of the urine 
 of tlie horse by FourcToy and I'tiuyuelin, and ofllial of llie cow by Sproiget. Boussingault, 
 however, obtained very diflerent results. Thus a cow and a horse, on which his experi- 
 ments were made, yielded a quantity of urine which in a year would have amounted tc, 
 and would liave contained, in pounds — 
 
 Containini; of Capable of yleld- 
 
 Quantily. Solid matter (total). Inorganic matter. Nitrosren. ing of ammonia. 
 
 Cow (".570 77.3 309 29 35 
 
 Horsft 1100 243 89 30 36 
 
 The cow yielded at the same time 19 lbs. of milk each ilay, which accounts for the 
 
 smaller proportion of urine voided, than is sriven in the text. It is remarkabte, however, 
 
 that the quantity of nitrogen contained in an equal weight of (he urine of the horse was in 
 
 this case so much greater than that of the cow— and in that the whole amount which would 
 
 have been yielded by that of a cow in a year should be so very much less tliun in the re- 
 
LOSS OF LiaUID MANURE IN THE FARM-YARD. 465 
 
 alone, and with the addition of an equal bulk of water, the urine of 
 the cow loses, as we have seen, a considerable proportion of volatile 
 matter, and in these several states will yield in a year — 
 
 Sul d matter. Yielfiins of ammonia. 
 
 Recent urine 900 lbs. 226 lbs. 
 
 Mixed with water, after 6 weeks. . 850 " 200 " 
 
 Unmixed, after 6 weeks 550 " 30 " 
 
 Those who scrupulously collect in tanks and preserve the liquid ma- 
 nure of their stables, cow-houses, and fold-yards, will see, from the 
 great loss which it undergoes by natural fermentation, the propriety 
 of occasionally washing out their cow-houses with water, and, by thus 
 diluting the liquid of their tanks, of preserving the immediately 
 operating constituents of their liquid manure from escaping into the 
 air. Even when thus diluted it is desirable to convey it on to the 
 land without much loss of time, since even in this state there is a con- 
 stant slow escape, by which its value is daily diminished. Gypsum, 
 sulphate of iron, and sulphuric acid, are, by some, added for the pur- 
 pose o[ Ji.ring the ammonia, but in addition to diluting it, an admix- 
 ture of rich vegetable soil, and especially of peat, will be much more 
 economical, and — except in so far as the gypsum or sulphuric acid 
 themselves act as manures — nearly as effectual. 
 
 But these remarks apply only to the liquid manure when collected. 
 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 manures are highly es- 
 teemed — at 40s. a year. It contains on an average, as we have seen, 
 900 lbs. of solid matter, and this estimated at the price of guano only, 
 is worth at present £i sterling. Multiply this by 8 millions, the num- 
 ber of cattle said to exist in the United Kingdom, and we have 32 mil- 
 lions of pounds sterling, as the value of the urine, supposing it to be 
 worth no more than the foreign guano. It is impossible to estimate 
 how much of this runs to waste, but 1-lOth of it will amount to nearly 
 as much as the whole income-tax recently laid upon the country. The 
 practical farmer who uses every effort to collect and preserve the ma- 
 nure which nature puts within his reach, is deserving of praise when 
 he expends his money in the purchase of manures brought from a dis- 
 tance, of whatever kind they may be ; but he, on the other hand, is 
 only open to censure who puts forward the purchase of foreign ma- 
 nures as an excuse for the neglect of those which are running to 
 Avaste around him. Let every stock farmer, with the help of the 
 facts above stated, make a fair calculation 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 to appreciate the importance of 
 taking some steps for preserving it in future. 
 
 suit obtained by Sprensel. The milk did not contain nitrogen sufficient to yield more than 
 45 lbs. of ammonia, and this, added to the 35 lbs. maizes only 80 lbs. in all — whereas 
 Sprensrel gives 2J0 lbs. as (lie qiantity which recent urine is capable of yielding. Thi.« re- 
 mark^bli^ diff.>rence mnst be ascribeil either to an actual loss of volatile mntter by the urine 
 analysed by Bouss niaiilt, or— which is more probable — to a difference in the quality of the 
 food on which the two animals were fed. 
 
 'Tlie Messr.a. Tiimbnll inform me that with (his su'phated urine, tinder the incorrect 
 name of sulphate nf ammonia, the experiments of Mr. Unmet were made (p. 362), as well 
 «8 those of Mr. Fleming and Mr. Alexander, detailed in the Appendix. 
 20* 
 
466 NIGHT SOfL READILY DECOMPOSES — ITS COMPOSITION. 
 
 § 12. 0/ solid animal manures — night soil, the dung of the cow, the 
 horse, the sheep, and the pig. 
 
 1°. Night soil is in general an exceedingly rich and valuable ma- 
 ntire, 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 powder ed charc oal or 
 with halt-charred peat, — a method which is adopted~iri"the manufacT- 
 ture of certain artificial manures. Q,uick-lime is in some places em- 
 ployed for the same purpose, but though the smell is thus got rid of^ 
 a large portion of the volatile ammonia produced during the decom- 
 position of the manure is at the same time driven off' by the lime. 
 
 In general, night soil contains about three-fourths ot' its weight of 
 water, and when exposed to the air undergoes a very rapid decompo- 
 sition, gives oti'much volatile matter — consisting of ammonia, of car- 
 bonic acid, and of sulphuretted and phosphuretted hydrogen gases — 
 and finally loses its smell. In the neighborhood of many large cities, the 
 collected night soil is allowed tlius naturally to ferment and lose its smell, 
 and is then dried and sold for manure, under the name of poudrette. 
 
 But by this fermentation a very large proportion of valuable rhaltef 
 is permitted to escape into the air. To retain this, g}q-)sum or dilute 
 sulphuric acid may be added to the night soil, but the more economi- 
 cal and generally practicable metiiod is to mix it with earth rich in ve- 
 getable matter, witli partially dried peat, with saw-dust, or with some 
 other readily accessible absorbent substance. In this way a rich and 
 fertilizing compost will be obtained, which will have little smell, and 
 yet will retain most of the virtues of the original manure. 
 
 In China the fresh night soil is mixed up with clay and formed into 
 cakes, which when dried arc sold under tiie name of Taffo, and form 
 an extensive article of commerce in the neighborhood of the larger cities. 
 
 The composition of night soil, and consequently its value as a ma- 
 nure, varies with the food, and wnth many other circumstances (p. 470). 
 The excrements of a healthy man were found by Berzelius to consist of: 
 
 Water 733 I Mucilage, fat, and other ani- 
 
 Albumen 9 mal matters 167 
 
 Bile 9 Undecomposed food 70 
 
 Saline matter 12 j TOOO 
 
 Of the excrement when freed from water 1000 parts left 132 ofash.viz. 
 
 Carbonate of soda. 8 1 Phosphate of lime and magne- 
 
 Sulphate of .soda, with a little | sia, and a trace of gypsum. . 100 
 
 sulphate of potash, and phos- Silica 16 
 
 phate of soda 8 | 232 
 
 2^^. Cow dung forms by far the largest proportion of the animal ma- 
 nure which in modern agriculture is at the disposal of the practical 
 farmer. It ferments more slowly than night soil, or than the dung of 
 the horse and the sheep. In fermenting it does not lieat much, and it 
 gives off little of an unpleasant or ammoniacal odour. Hence it acts 
 more slowly, though for a longer })eriod, when applied to the soil. 
 
 The slowness of tlie fermentation arises chiefly from the smaller 
 quantity of nitrogen, or of substances containing nitrogen, which are 
 present in cow dung, but in part also from the tbod swallowed by the 
 cow being less perfectly masticated than that of man or of the horse. It 
 
 ^^ 
 
HORSE DUNG SPEEDILY FERMnNTS, AND LOSES WEIGHT. 46? 
 
 is a consequence of this slower fermentation, that the same evolution 
 of aranioniacal vapours is not perceived from the droppings of the cow 
 as from night soil and from horse dung. Yet by exposure to the air, it 
 undergoes a sensible loss, which in 40 days has been found to amount 
 to 5 per cent, or nearly one-fifth of the whole solid matter which re- 
 cent cow dung contains.* (Gazzeri.) Although, therefore, the compa- 
 ratively slow fermentation as well as the soilness of cow dung fits it 
 better "for treading among the straw in the open farm-yard, yet the 
 serious loss which it ultimately undergoes will satisfy the economical 
 lurmer that the more etiectually he can keep it covered up, or the 
 sooner he can gather his mixed dung and straw into heaps, the great- 
 er proportion of this valuable manure will he retain for the future en- 
 riching of his fields. 
 
 3*^. Horse dung is of a Avarmer nature than that of the cow. It 
 heats sooner, and evolves much ammonia, not merely because it con- 
 tains less water than cow dung, but because it is generaUy also rich- 
 er in those organic compounds of which nitrogen forms a constituent 
 part. Even when fed upon the same Ibod the dung of the horse will 
 be richer than that of the cow, because of the greater proportion of 
 the ibod of the latter wliich is discharged in the large quantity of urine 
 it is in the habit of voiding (p. 470). 
 
 In the short period of 24 hours, horse dung heats and begins to suf- 
 fer loss by fermentation. If left in a heap for two or three weeks, scarce- 
 ly seven-tenths of its original weight will remain. Hence the propriety 
 of eai-ly removing it from the stable, and of mixing it as soon as possi- 
 ble with some other material by which the volatile substances given 
 off may be absorbed and arrested. 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 sub- 
 stance whicli can readily be obtained — or if a chemical agent be pre- 
 ferred, moistened gypsum maybe sprinkled among it, or diluted sulphu- 
 ric acid. There is undoubtedly great loss experienced from the general 
 neglect 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 hitherto been. 
 
 The warmth of horse dung fits it admirably for bringing other sub- 
 stances into fermentation. With peat or saw-dust it will form a rich 
 compost, and to soils which contain much inert vegetable matter it can 
 be applied with great advantage. Horse and cow dung, in the dry 
 state, have been subjected to ultimate analysis by Boussingaultf, 
 (Ann. de Chim., Ixv., pp. 122, 134,) with the following results: — 
 
 Dung of the Horse. Dung of a Milk Cow. 
 
 Carbon 38-7 42-8 
 
 Hydrogen 51 5-2 
 
 Oxygen 37-7 37-7 
 
 Nitrogen 2-2 2-3 
 
 Ashes 16-3 12-0 
 
 100 100 
 
 Water! 300 5 66 
 
 400 666 
 
 • Cow (iunz consisting of75 of water and 25 of dry solid matter, of which lattero disappear, 
 t Recent horse dung losing 75 per cent, of water bj' drying, of cow dung 75 per cent. 
 
468 THE DUNG OF THE PIG AND THE SHEEP. 
 
 The proportion of nitrof^en contained in the two njianures, according 
 to these results, is so nearly aliUe — being in reality greater in the cow 
 (Uing — that were we to consider the above numbers to represent the 
 aoei-age constitution of the droppings ol" the horse and cow, we should 
 be compelled to ascribe the difference in their qualities solely to the 
 different states in which the elements exist in the two, and to the pro- 
 portions of water they respectively contain. But the nature of the 
 food and other circumstances affect the quality of these manures so 
 much (p. 470), that we cannot as yet draw any general conclusion 
 from the results obtained in one special case. 
 
 4°. Pig^is dung is still colder and less fermentable than that of the 
 cow. It is characterized by an exceedingly unpleasant odour, which 
 when applied to the land alone 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 
 subsequently collected are unfit tor smoking [Sprengel, Lehre vom 
 Diinger, p. 38.] It is a good manvire ibr hemp and other crops not 
 intended for food, but is best employed in a state of mixture with the 
 other manures of the farm-yard. 
 
 5°. Sheep^s dung is a rich dry manure, which fermentsmore readi- 
 ly than that of the cow, but less so than that of the horse. A speci- 
 men examined by Zierl consisted of — 
 
 Water 68-0 per cent 
 
 Animal and vegetable matter 19-3 " 
 
 Saline matter, or ash 12-7 " 
 
 100 
 
 The food of the sheep is more finely masticated than that of the cow, 
 and its dung contains a little less water, and is probably richer in nitro- 
 gen ; hence its more rapid fermentation. When crops are eaten off 
 by sheep, their manvire 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 quan- 
 tity of vegetable matter is already present, are said to be most bene- 
 fitted by sheep's dung, because of the readiness with which they ab- 
 sorb the volatile matters it so soon begins to give off. 
 
 Sheep's dung is said to lengthen the straw of the corn crops, and 
 to produce a grain rich in gluten — and unfit therefore for seed, for the 
 manufacture of starch, or tor the purposes of the brewer and the dis- 
 tiller (Sprengel.) It may be doubted, however, whether 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. 
 
 § 13. Of the quantity of manure produced from tlie same kinds of 
 food by the horse, the cow, and the slieep. 
 
 The carefully conducted experiments of Block give the foIIowir>g 
 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. 
 
MANORE PRODUCED BY DIFFERENT ANIMALS. 469 
 
 Quanlily of manure in lbs., produced by 
 
 From lOtMbs. of the row. the horse. the sheep, the manure, 
 
 fresh, dried, fresh, dried, fre.sh. dried. per cent. 
 
 Rye — — '212 53 — — 75 
 
 Oats — — 204 51 — — 75 
 
 Rye a)id other straws(chopped)2r)8 43 168 42 117 40 C6 to 84 
 
 Hay 275 44 172 43 123 42 do. do. 
 
 Potatoes (containing 73 per ct. 
 
 of water) 87J14 — — 38 13 do. do. 
 
 Turnips (containing 75 per cent. 
 
 of w aier) 37.i 6 — — — — 84 
 
 Carrots (87 per cent, of water) 37i G — — — — 84 
 
 Green Clover (79 per ct. water) G5J 9j — — — — 86 
 
 Aftf-r 8 days. After 3 weeks. After 8 jveeka. 
 
 Rye Straw (used for bedding) 238 96 269 97 206 95 54 to 64 
 
 One important theoretical result is presented in this table — that 
 the nwnwe voided by an animal contains very much less solid ^natter 
 than the food it has consumed. We .shall presently see how thi.s fact 
 is to be explained (p. 472). and, at the same time, what light it throws 
 upon the quality o[ the manure produced. 
 The most valuable practical results from the above experiments are — 
 
 P. That tor 100 lbs. of dry fodder the horse or 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 rout crops, on an average, give about half their weight 
 of fresh or one-twelfth of dry manure — the potatoe giving more and 
 the turnip less. 
 
 3"^. That green crops give about half their Aveight of fresh or one- 
 eighth of dry manure. 
 § 14. Of the relative fertilizing values of different animal excretions. 
 
 1°. The theoretical value of different animal excretions calculated 
 solely from the quantity of nitrogen which the specimens examined 
 were found respectively to contain, is thus given by Payen and Bous- 
 singault. The numbers opposite to each substance indicate the weights 
 of that substance which ought to produce an equal elfect with 100 lbs. 
 of farm-yard manure in the recent and in the dry states : — 
 
 Equal efTects ought to be produced by 
 in the dry sifite. artificially dried. 
 
 Farm yard dung 100 lbs. 
 
 Cow 125 " 
 
 Do. urine 91 " 
 
 Horse 73 " 
 
 Mixed excrements of the — Pig 63 " 
 
 Horse 54 " 
 
 Sheep 36 '• 
 
 Pigeon 5 " 
 
 Poudrette lOj " 
 
 Another variety 26 " 
 Too much reliance is not in any case to be placed upon the princi- 
 ple of classifying manures solely by the proportion of nitrogen they 
 contain (pp.441 &454) — much less can we depend upon the order of 
 value it assigns to substances the composition of which is liable to 
 
 100 lbs. 
 
 84 
 
 (( 
 
 51 
 
 a 
 
 88 
 
 a 
 
 58 
 
 u 
 
 64 
 
 i( 
 
 65 
 
 a 
 
 22 
 
 a 
 
 44 
 
 a 
 
 73 
 
 a 
 
470 FERTILIZING VALUES OF AMIMAL EXCRETIONS. 
 
 constant change from the escape of those volatile compounds in which 
 the nitrogen principally exists. 
 
 2'^. A series of experiments made by Hermhstiidt upon the quantity 
 of grain of different kinds, raised in the same circumstances by equal 
 weights of different manures, gave the following results : 
 
 Number of seeds reaped from 
 Mannre applied. Wheat. liarley. Odta. Rye. 
 
 Oxblood 14 16 121 14 
 
 Night soil — 13 141 I3i 
 
 Sheep's dung 12 16 14' 13' 
 
 Human urine — 13i 13 13 
 
 Horse dung 10 13" 14 11 
 
 Pigeon dung — 10 12 9 
 
 Cow dung 7 11 16 9 
 
 Vegetable matter 3 7 13 6 
 
 Unmanured — 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 concern- 
 ed, 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 recommend the eating off 
 with sheep preparatory to either of the latter crops. 
 
 None of these kinds of manure, however, is constant in composition, 
 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 circwmstances on the auALiTV 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 niglit 
 soil is more valuable in those countries and districts in which much 
 flesh meat is consumed, than where vegetable food forms the principal 
 diet of the people. It is even said by Sprengel, that in the neighborhood 
 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 required to observe. (Lehre 
 vom, Danger, p. 142.) Every keeper of stock also knows that tJie ma- 
 nure in his farm-yard is richer wiien he is feeding his cattle upon oil- 
 cake, than when he gives them only the ordinary prodvice of his farm. — 
 [12 loads of the dung of animals fed (while fattening) chiefly upon oil- 
 cake was found to give a greater produce tlian 24 loads from store stock 
 fed in the straw yard. — Complete Grazier, 6th edit., p. 103.] 
 
 2°. By the quantity of urine voided by the animal. — Upon the unlike 
 quantities of urine they produce appears mainly to depend the unlike 
 richness of the dung of the horse and of the cow. The latter animal, 
 when full grown and not in milk, voids nearly 13 times as much urine 
 as the former (p. 460), and though an equal bulk of this urine is poorer 
 in solid matter, yet the whole quantity contains several times as much 
 
ANIMAL MANURES AFFECTED BY MANY CIRCUMSTANCES. 471 
 
 as is present in tiiat of the horse. But if the cow discharges more in 
 its urine it must void less in its soUd 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 amoiuit of exercise or labor to which the animal is sith' 
 jected. — The greater the fatigue to which an animal is subjected the 
 richer the urine is found to be in those compounds (xirea chiefly) which 
 yield ammonia by their decomposition (Prout). The food of two 
 animals, therefore, being the same — other things also being equal — 
 the solid excretions will be richer and more fertihzing 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. 
 
 4°. Bi/ 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 excretions. A young 
 animal, on the other hand, adds to and increases its bone and muscle 
 at the expense of its food. It rejects, therefore, a smaller proportion 
 of what it eats. Hence the manure in fold-yards, where young cattle 
 are kept, is always less rich than where full-grown animals are ied. 
 
 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 mate- 
 rials for increasing the size and strength of its muscles — with albu- 
 men, or fibrin, or other substances containing nitrogen. In such sub- 
 stances, therefore, or in nitrogen derived from them, the droppings 
 must be poorer, and as a manure, less valuable. 
 
 Is the animal to be fattened? Then its tbod mustsupply fatty mat- 
 ters, or their elements, of which nitrogen forms no part. All the ni- 
 trogen of the food, therefore, will pass off in the excretions, and hence 
 the richest manure yielded at any time by the same species of ani- 
 mal is that which is obtained when it is full-grown, and, being large- 
 ly 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 ihe farmer than that of a full-grown ani- 
 mal 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 mamire has been kept. — 
 In 24 hours, as we have seen, the dang of the horse begins to fer- 
 ment and to lessen in weight. All rich manures in like manner — the 
 dung of all animals especially — decompose more or less rapidly and 
 part witJi their volatile constituents. The value we assign to them 
 to-day, therefore, will not apply to them to-morrow, and hence the 
 droppings of tlie 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 permitted to ferment. 
 
 7^. Ijastly. By the way in which the manure has been preserved. — 
 The mixed dung of the farm-yard must necessarily be less valuable 
 where the liquid manure is allowed to run olf— or where it is permitted 
 
472 CHANGES PRODUCED UPON THE FOOD 
 
 to stand in pools and ferment. 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 liquid manure has been carefully collected 
 and returned upon the heaps — to hasten and complete their fermenta- 
 tion, and to saturate them with enriching matter. 
 
 Since, then, the quality or richness of the dung of the same animal is 
 Uable to be affected by so many circumstances — it is obvious that no 
 accurate general conclusions can be drawn iu regard to its precise 
 fertilizing virtue when applied to this or to that crop, or to 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 Hermbstiidt (p. 470), 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 ckanges 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 been called — 
 vegetable substances have been supposed to undergo some mysteri- 
 ous, 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. 469), that 
 the weight of dry wanure voided by an animal is always considerably 
 less than that of the dry food eaten by it. Upon the nature and 
 amount of this loss which the food undergoes depends the quality 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 Hquid excretions. We have already seen (Lee. VIII., § 3), 
 that the function of the lungs is to give off carbon in the form of car- 
 bonic acid, while they drink in oxygen from the air — and that the quan- 
 tity 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 proportion 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 ef- 
 fect 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 — 
 
BY PASSING THROUGH THE BODIES OF ANIMALS. 473 
 
 Carbon. Nitrogfin. Saline mitter. 
 
 In the potatoes 1716 grs. 47 grs. 196 gre. 
 
 In the bread 1004 " 34 " 22 " 
 
 In the beef 790 " 120 " 35 " 
 
 3510 grs. 201 grs. 253 grs. 
 
 And he has given off in respiration 2625 •• 
 
 Leaving to be rejected sooner or 
 
 later in the excretions 885 " 201 « 253 " 
 
 In this supposed case, therefore, the carbon, nitrogen, and saline 
 
 matter were to each other nearly as the numbers 
 
 Carbon. Nitrogen. Saline matter. 
 
 35 2 2i in the food, 
 
 and as 9 2 2i in the excretions : 
 
 Or^ in oiher words, the carbon being in great part sifted out of the 
 food by the lungs, the excretions are necessarily much richer in ni- 
 trogen and in saline matter, weight for weighty than the mixed vege- 
 table and animal matters on which the man has lived. 
 
 But the immediate and most sensible action of animal and vegetable 
 substances, as manures, depends upon the proportion of nitrogen and sa- 
 line matters they contain. This proportion, then, being greater in the ex- 
 cretions 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 svich an increase 
 of food — the carbon being removed by respiration — the proportion of 
 nitrogen and of saline matters in the excretions may be still further 
 increased, or as manures they may become still richer and more im- 
 mediafely fertilizing. 
 
 3°. Let me present to you the results of an actual experiment made 
 by Boussingault upon a horse fed with hay and oats — and of which 
 both the food and the excretions were carefully analysed. 
 
 In 24 hours the horse consumed — 
 
 Carbon. Nitrogen Saline matter. 
 
 Hay, 16 J lbs..t containing 45,500 grs. 1,500 grs. 8,960 grs. 
 
 Oats, 5 lbs..' 15,000 " 650 " 1,180 " 
 
 Total inthe food 60,500 " "2,150 " 10^140 ' " 
 
 And gave off from the lungs & skin 37,960 " 
 
 Leaving to be rejected in the ex- 
 cretions 22,540 " 2,150 « 10,140 " 
 
 While there was actually found in 
 the mixed dung 22,540 " 1,770 " 10,540 " 
 
 • I.iebig estimates the quantity of carbon which escapes from the lunjrs and skin of a 
 healthy man. taking moderate exercise, at 13 93 ounces (Hessian), or 15K ounces avoirdu- 
 pois, in 24 houis. 
 
 t Each containing about 14 per cent, of water. — Annalcs de Chim. et de Phys., Ixxi., p. \X. 
 
474 STATE IN WHICH FARM-YARD MANURE CAN BE 
 
 In this case, then, the carbon, nitrogen, and saline matter were con- 
 tained in the proportion of — 
 
 Carbon. Nitrogen. Saline matter. 
 
 28 1 5 in the food, 
 
 and of lOi 1 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 losing a large but variable proportion of its carbon, 
 
 c but parting with scarcely any of its nitrogen and saline matter — 
 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 pro- 
 portion of these two constituents (the nitrogen and the saline matter) 
 Avhich 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 excretions has 
 a material influence in rendering their action more immediate and 
 sensible than that of unchanged vegetable matter. It passes off for 
 the most part in the form of urea, which is 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, and of the stat.e in which it ought 
 to be applied to the land. 
 
 The manure of the farm-yard consists, for the most part, of cow- 
 dung and straw mixed and trodden together, in order that the latter 
 may be brought into a state of decomposition. In the improved hus- 
 bandry, where green crops are extensively grown and many cattle 
 are kept, the horse-dung forms only a small proportion of the whole 
 manure 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. 469). That is to say, for every 10 cwt. of dry fodder and bedding, 
 20 to 23 cwt. of fresh dung may be calculated upon. But if green 
 clover or turnips (every 100 lbs. of whioli 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 from 2 to 2| times the weight of the dry food and fodder only. 
 
 But the 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 onefotirth 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 com- 
 mon mixed farm-yard dung, therefore, obtained from 10 cwt. of dry food 
 and straw, at different periods, may be thus stated approximately — 
 
MOST ECONOMICALLY APPLIED TO THE LAND. 475 
 
 10 cwt. of dry food and straw yield of recent dung 23 to 25 cwt. 
 
 At the end of six weeks 21 cwt. 
 
 After eight weeks 20 cwt. 
 
 When half-rotten 15 to 17 cwt. 
 
 When fully-rotten 10 to 13 cwt.* 
 
 These quantities, you will observe, are supposed to be obtained in 
 the common open larm-yards, with the ordinary slow process of fer- 
 mentation. An improved, quicker, or more economical mode of fer- 
 menting 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. 
 
 P. The more recent the manure from a given quantity of food and 
 straw is ploughed in, the greater the quantity of organic matter Ave 
 add to the land. When the only object to be regarded, therefore, 
 is the general enriching of the soil, this is the most economical and 
 the most expedient form of employing farm-yard manure. 
 
 2°. But wliere the soil is already very light and open, the plough- 
 ing in of recent manure may make it still more so, and may thus ma- 
 terially injure its mechanical condition. In such a case the least of 
 two evils must be chosen. It may be better husbandry — that is, more 
 economical — 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 benefit 
 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 decom- ^ 
 position 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 pro- 
 ducts of decay does not take place so completely. 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 whicli when 
 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 necessarily takes place in the farm-yard. The practical man, 
 therefore, 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 and general opinion to hold 
 — one, however, which must not be maintained in regard to any par- 
 ticular tract of land in opposition to the results of enlightened expe- 
 rience — that recent farm-yard manure {long dung) is not suited to 
 very light soils, because it will render them still lighter, and because 
 m them the manure may suffer almost as much waste as in the farm- 
 
 ' In an pxcpllent little practical work printpd for private circulation, under the title of 
 " Notes on the Culture and Crnppivg of Arable. LMnd" by the late Dr. Coventry, of Edin- 
 burgh, llie reader will find a valuable section upon manures. The most complete work 
 now in existence np"n the general subject of apricullural statics, is that of Illubek, DieEr- 
 ndhrung der PJianzcn une die IStatik de» Landbatiea. 
 
476 AFIECTED BY THE PURPOSE IT IS TO SERVE. 
 
 yard ; — and, therefore, that into such soils it should be ploughed in 
 the compact state (short dung)^ and as short a time as possible be- 
 fore the powing of the crop which it is intended to benefit. 
 
 4°. But upon loamy and clay soils the contrary practice is recom- 
 mended. Such soils will not be injured, they may even be benefitted 
 by the opening tendency of the unfermented straw, while at the same 
 time the products of its decomposition will be more completely re- 
 tained — 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 greatly more influential upon the crops 
 of corn which followed it, either in winter or in spring, than a propor- 
 tional quantity of well lermented manure. By such treatment, in- 
 deed, the whole surface soil is converted into a layer of compost, in 
 which a slow fermentation proceeds, and which reaches its most fer- 
 tilizing 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 influ- 
 ence 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 enable it immediately 
 to benefit the rapidly growing plant. In this case, also, it may be 
 better to lose a portion by fermenting it in the farm-yard, than, by ap- • 
 plying his manure fresh, to allow his crop to reach nearly to maturity 
 before any benefit begins to be derived from it. 
 
 6°. So also the purpose for which he applies his manure will regu- 
 late his procedure. In manuring his turnips the farmer has two dis- 
 tinct objects in view. He wishes, first, to force the young plants for- 
 ward so rapidly that they may get into the second leaf soon enough 
 to preserve them from the ravages of the fly — and afterwards to fur- 
 nish 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 indispensable — 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 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 portion of the bones soon heats, fer- 
 ments, and gives oft' those substances by which the young plant is 
 benefitted — while the gelatine in the interior of the bone decays, lit- 
 tle by little, and during the entire season continues to feed the ma- 
 turing bulb. Rape-dust, when drilled in, acts in a similar manner, if 
 the soil be sufiiciently moist. It may be doubted, however, whether 
 its effects are 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 ques- 
 tions — Avhat is theoretically the best form in which farm-yard dung 
 can be applied in general ? — and what is theoretically and practical- 
 ly the best form in which it can be applied to this or to that crop, or 
 for this or for that special object ? 
 
TOP-DBESSING WITH FERMENTING MANURES. 477 
 
 § 18. Of top-dressing with ferm-enting manures. 
 
 If so large a waste occur in the farm-yard where the manure is 
 left long to ferment — can it be good husbandry to spread fermenting 
 manure as a permanent top-dressing over the surface of the fields 1 
 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 — 
 
 P. It is common in spring to apply such a top-dressing to old pas- 
 ture or meadow lands, and the increased produce of food in the form of 
 grass or hay is believed to be equal, at least, 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 applying the manure is consistent with good 
 husbandry. But if the quantity or market value of the food raised by 
 a ton of manure applied in this way is not equal to what it would 
 have raised in 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 mtcresting light upon this question. 
 
 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 dun^ contains all the elements which the growing grass re- 
 quires, Viut if spread on the surface of the field and then 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 fer- 
 mented state may be the most economical. 
 
 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 fermented 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. [Such 
 is the case upon some of the farms in the Vale of the Tame (Stafford- 
 shire.) where the turnips are raised with rape-dust, and wheat follows 
 the clover.] 
 
 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 ne- 
 cessary, as experience says, and why should farm-yard manure, which 
 is known to suffer waste, be applied as a top-dressing rather than 
 
478 EATING OFF COMPARED WITH GREEN MANURING. 
 
 rape-dust, which in ordinary seasons is not so likely to suffer loss ? 
 I oiler you the following explanation: — 
 
 Ifyou raise your turnip crop hy the aid of the bones or rape-dust alone 
 
 }Tou add to the soil what, in most oases, may be sufficient to supply near- 
 y all the wants of that crop, but you do not add all which the succeed- 
 ing 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 ma- 
 nure must be added — in which those necessary substances or kinds 
 of food are present which the bones and rape-dust cannot supply. 
 Farm-yard manure contains them all. This is within the reach of 
 every farmer. It is, in fact, his natural resource in every such diffi- 
 culty, lie has tried it upon his clover crop in the circumstances we 
 are considering, and has necessarily found it to answer. 
 
 Thus to explain the results at which he has arrived in this special 
 case, chemical theory only refers the practical man to the general prin- 
 ciple upon which all scientific manuring depends — that he must add to 
 the soil sufficient supplies of every th ing he carries off in h is crops — and, 
 therefore, without some such dressing as he actually applies to his 
 clover crop, he could not long continue 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. 
 
 § 19. Of eating off witn. sheep. 
 
 The practical advantages derived from eating off turnips and clover 
 crops with sheep are mainly of two kinds. Light lands are trodden 
 down and solidified, and they are at the same time equably and more 
 or less richly manured. With this latter effect, that of manuring, 
 some interesting practical facts and theoretical considerations are 
 connected. Thus — 
 
 P. In the preceding lecture (p. 410) I mentioned to you that in some 
 parts of Germany, spurry, among other plants, is extensively grown, 
 and with much profit, for ploughing in as a green manure. Now it is 
 mentioned that the crops of rye which follow a crop of spurry are some- 
 times quite as great when it has been eaten off with sheep or cattle as 
 when it has been ploughed in (Von Voght, Uber Manche Vortheile 
 der griiner dungung.) 
 
 2°. In accordance with this statement is the opinion of many skil- 
 ful practical men among ourselves, that a crop of clover or of tares 
 will cause a larger after-growth of corn, if it be eaten off with sheep, 
 than if it be ploughed in in the green state. 
 
 The correctness of these practical observations appears from a 
 brief consideration of one of those interesting theoretical questions 
 ■we have recently been discussing. 
 
 When a crop is eaten off by full-grown animals, it returns again to 
 the soil, deprived of a portion of its carbon only (p. 473.) The manure 
 contains all the nitrogen and saline matter of the green vegetables, and 
 in a state in which they are more immediately available to the uses of 
 the young plant. Thus f;ir, then, we can understand that in certain 
 
IMPROVEMENT OF THE SOIL BY IRRIGATION'. 479 
 
 cases a crop may appear to fertilize the land more after it has been eaten 
 and digested, than if it had been ploughed in green, and we can recog- 
 nize the correctness of the opinion atwhich practical men have arrived. 
 
 But theory does not forsake us here. As in all other cases in which 
 it furnishes a true explanation of known facts, it points to new facts also, 
 which more or less modify our received opinions, and define the limits 
 within which their truth can be rigorously maintained. Thus — 
 
 1°. Theory says that if the animals fed upon thp green crop be in a 
 growing state — if they be increasing in muscle or in bone — they will 
 not only dissipate through their lungs and skin a portion of its carbon, 
 but will retain also a part of its nitrogen and saline matter, and will 
 thus return to the soil, in their excretions, a smaller quantity of these 
 substances than the crop would have given to it if ploughed in green. 
 If. therefore, a maximum fertilizing effect is to be produced upon a 
 field by eating off a green crop, it is not altogether a matter of indif- 
 ference what kind of animals Ave employ as digesters. 
 
 2'. Again, the practice of green manuring is resorted to chiefly 
 upon soils which are poor in organic matter — to which the carbon of 
 the green crop is of consequence, as well as the nitrogen and saline 
 matter it contains. But when eaten off, much carbon is lost to the 
 soil, and thus the supply of organic matter which it ultimately gets is 
 considerably less than if the crop it bore had been ploughed in in the 
 green state. Such soils, then, cannot be equally enriched by the 
 former as by the latter method. 
 
 This case presents a very interesting illustration, and one which you 
 can readily appreciate, of the kind of useful information which theoreti- 
 cal chemistry is capable of imparting upon almost every branch of prac- 
 tical agriculture. It says to the farmer — yes, you may in some cases, 
 certainly, eat off the crop with advantage — but if you wish to do most 
 good to your land you must eat it off with fattening, not with growing 
 sheep — and you must do so upon soils which are not very poor in 
 vegetable matter. And that explains to mc also, says the practical 
 man, in reply, why I have always found sheep-folding to be most be- 
 neficial on soils which are rich in vegetable matter* (p. 468.) 
 
 § 20. Of the improvement of tlie soil by irrigation. 
 
 Irrigation, as it is practised in our climate, is only a more refined 
 method of manuring the soil. In warm climates, where 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 land almost solely that irrigation is applied 
 by British farmers, and the good effect it produces is to be explained 
 by a reference to various and natural causes. 
 
 1°. If the water be more or less muddy, bearing with it solid matter 
 which deposites itself in still places, the good effects which follow its 
 
 ' Sprengel explains lliis fdct by alleging that the hutnic acid of (he vegetable matter re- 
 tains more effV dually the ammonia of the decomposing dung. There may be something 
 in this, but more, in most cases, I think, in the fact that digestion separates much of the 
 carbon in which the soils abound, but returns the nitrogen and saline matter almost en- 
 tirely and lo a more active state. 
 
4S0 THE WATER SHOULD NOT BE STAGNANT. 
 
 diffusion over the soil may be ascribed to the layer of visible manure 
 which it leaves everywliere behind it. Thus the Nile and the Ganges 
 fertilize the lands over which their annual floods extend, and partly 
 in this way do some of our smaller streams improve the fields over 
 which they either naturally floAV or are artificially led. 
 
 2°. Or if the water hold in solution, as the liquid manures of the 
 farm-yard do, 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 which is prac- 
 tised in the neighborhood of our large towns, where the contents of 
 the common sewers are discharged into the waters which subsequent- 
 ly spread themselves over tlie fields. (For an interesting account of 
 the effects of such irrigation in the neighbofhood of Edinburgh, see 
 Stephens, On Irrigation and Draining, p. 75.) 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 im- 
 pregnated in this manner — so far may their beneficial action, when 
 employed for purposes of irrigation, be ascribed to the same cause. 
 
 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. Thus, in lime-stone districts, and especially 
 those of the mountain lime-stone formation (Lee. XL, § 8,) — in which 
 copious springs are not unfrequently met with — the water is generally 
 impregnated with much carbonate of lime, which it slowly deposites as 
 it flows away from its source. To irrigate with such water is, in a re- 
 fined 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. ( Some of the water 
 used in the well-known scientific irrigations at Closeburn Hall, in 
 Dumfries-shire, appears to have been impregnated with lime. See 
 Stephens, p. 43.) 
 
 In other districts, again, the springs contain gypsum and common 
 salt, and sulphate of soda and sulphate of magnesia, and thus are ca- 
 pable of imparting to plants many of those inorganic forms of matter, 
 without which, as we have seen, they cannot exhibit a healthy growth. 
 
 4°. Again, it is observed that the good effects of irrigation are pro- 
 duced only by running water — coarse grasses and marsh plants spring- 
 ing up when the water is allowed to stagnate (Low's Elements of 
 Agriculture, 3d edition, p. 472.) This is explained in part by the 
 fact that a given quantity of water will soon be deprived of that por- 
 tion 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 water, which makes it more 
 wholesome in the living plant. It comes upon the field charged with 
 gaseous matter, with oxygen and nitrogen and carbonic acid, in propor- 
 tions very different from those in which these gases are mixed together 
 in the air (Lee. II., § 6.) 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 matter. The carbonic acid is 
 
A Goon DH.viNAcr; NECcsyARV. 481 
 
 absorbed by and feeds the pliuit. Lt.-t the same water remain on the 
 same spot, and its supply of these gaseous substances is soon ex- 
 hausted. In its state of rest it re-absorbs new portions from the air 
 with comparative slowness. But let it flow along the surface of the 
 field, exposing every moment new particles to the moving air, and it 
 takes in the carbonic acid especially wnth much rapidity — and as it 
 takes it from the air, almost as readily again gives it up to the leaf or 
 root with which it first comes in contact. This is no doubt one of the 
 more important of the several purposes which we can understand 
 running water to serve when used for irrigation. 
 
 But further, if water be allowed to stagnate over the finer grasses, 
 they soon find themselves in circumstances in which it is not consist- 
 ent 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 Avith- 
 ont intermission for too long a period, will injure the pasture. This 
 is because a long immersion in water induces a decay of vegetable 
 matter in the soil which is unfavorable to the growth of the grasses — 
 producing chemical compounds which are not naturally formed in 
 those situations in which the grasses delight to grow, and which are 
 unwholesome to them. Although, therefore, the Avater continues to 
 support those various kinds of food by v.'hich the grasses are benefit- 
 ted, yet it becomes necessary to withdraw it for a time, in order that 
 other injurious consequences may be avoided. 
 
 6^. hasthj. — 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 .'=;ame benefits indeed flow from the 
 draining of irrigated as from that of arable lands. The soil and sub- 
 soil are at once washed free of any noxious substances they may 
 naturally contain, or may ha\'c derived from the crops they have 
 grown, and are manured and opened by the water which passes 
 tlirough them. As tlie Avater descends also, the air folloAvs it, to 
 ch.ange 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 account 
 for all the facts upon the subject with which I am acquainted. I 
 pass over the alleged beneficial action of water in keeping the tem- 
 perature of irrigated fields from sinking too low. As irrigation is 
 practised in our islands, little of the good done to Avatered meadoAVS 
 can be properly attributed to this cause. 
 
 1 have noAV draAvn your attention to the most important and readily 
 available means, mechanical and chemical, for improving the soil. 
 Let us next study the products of the soil — their composition, their 
 diflferences, and the purposes they are intended to serve in the feed- 
 ing and nourishment of animals. 
 
 21 
 
LECTURES 
 
 ON THE 
 
 APPLJCATIONS OF CHEMISTRY AND GEOLOGY 
 
 TO 
 
 AGRICULTURE. 
 
 ^rt urn. 
 
 ON THE PRODUCTS OF THE SOIL, AND THEIR 
 USE IN THE FEEDING OF ANIMALS. 
 
LECTURE XIX. 
 
 Of the produce of the soil. — Average produce of England and Scotland. — Circumstances by 
 which the produce of the land is affected. — Influence of climate, of season, of soil, of tha 
 kind and variety of crop, of the method of cullure, and of Uie 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, oats, barley, rye, and Indian corn.— In- 
 fluence of ciimale, soil, manure, variety ofseed, mode of culture, and time of cutting, upon 
 the composition of these grains. — Effect of baking upon bread. — Supposed relation between 
 the weight of bread and the proportion of gluten. — Effect of germination (malting) upon 
 birley. — Composiiion of peas, beans, and vetches. — Effects of soil, &c., upon the boiling 
 quality of pea.-? — Composition of the turnip, the carrot, the beet, and the potdtoe. — Effect 
 of soil, age, size, rapidity of growth, &c.,upon their coinposilion. — Relative proportions of 
 nutritive m -tter produced by iliffi^reut crops on the same e.vtent of ground. — Composition 
 of the grasses and clovers. — Effect of soils, manures, time of cutting, mode of drying, <kc., 
 upon their composition and nutritive value. 
 
 lI.wiNtx now con.sidered the most important of those means by which 
 the soil may be improved, it will be ])roper to direct our attention to that 
 which the land produces — 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, pota- 
 toes, hay, &c. 
 
 2°. Such as are tlie result of a kind of natural process of manufacture, 
 by which the direct produce of the soil is more economically convertctl 
 into the beef and mutton of the feeder of stock. 
 
 3°. Such as are the results of a further conversion at the hands of tlie 
 dairy farmer, and are sent to market in the form of butter and cheese. 
 
 Thus three distinct topics of consideration present themselves in con- 
 nection with the produce of tlie soil, — the nature of the immediate pro- 
 ducts themselves — the economy of the feeding of stock — and the prepara- 
 tion of butter and cheese. We shall study these several topics in their 
 natiu^al order. 
 
 § 1. Of the maximum or greatest possible, and tlie average or actual, 
 produce of the land. 
 
 There is a wide difference in most countries between the actual 
 amount of food produced by the land, and that wliich, in the most fa- 
 vourable circumstances, it would delight to yield. 
 
 An imperial acre of land in our island has been known to yield of 
 wheat 70 bushels,* barley 80 bu.shels, oats 100 bushels, potatoes 30 
 tons,t and turnips 60 tons.j 
 
 The average prodtice of the land, however, is far below the.se quanti- 
 : ics. It is not easy to arrive at a tolerable approximation even to the 
 
 • In the county of Middlese.x the produce of wheat varies from 12 to 68 bushels — of bar- 
 ley from 15 to 75— and of oats from o-i to 9G bushels. — Middleton's View of the Agricul- 
 ture of Middlesex. 1793. pp. 176, 1S3, and 188. 
 
 t See Mr. Fleming's experiments upon potatoes in Ibe Appendi.v. 
 
 X Perhaps this is not the viaximum.— ln\\ie Secovd Uepnrt of the Jioyal AgricvUural Im 
 provement Society of Ireland, p. 07, a crop of turnips is mentioned, which weighed 56 tons — 
 tops and bulbs amounting together to 76 tons. 
 
488 PRODUCE OF THE tAM) IN GREAT BRITAIH. 
 
 true average produce of the island. Mr. Macculloch estimates that of 
 wheat at 26 bushels an acre, barley at 32, and oats at 36. 
 
 Sir Charles Lemon gives for the average produce of all England, and 
 for the highest and lowest county averages, the following numbers — 
 Average for Highest 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 - - - - 35i 48 Lincolnshire. 20 Gloucester. 
 
 Potatoes - - - 241 360 Cheshire. 100 Durham. 
 
 "While in Scotland, according to Mr. Dudgeon, the average produce 
 of corn is — 
 
 Good land. Lighter land. 
 
 Wheat - - - - 30 to 32 bushels. 22 to 26 bushels. 
 Barley - - - - 40 to 44 do. 34 to 38 do. 
 
 Oats 46 to 50 do. 36 to 43 do. 
 
 If these numbers of Sir Charles liemon and of Mr. Dudgeon are to be 
 depended upon, the averages for the whole island cannot be far from 
 wheat 24 bushels, barley 34 bushels, oats 37 bushels, potatoes 6 tons, 
 and turnips 10 tons. 
 
 Though even these, especially in regard to the root crops, must be 
 considered as in a considerable degree hypothetical.* 
 
 What is the cause of the striking diflerences above exhibited between 
 the maximum produce of certain parts of the island and the average pro- 
 duce of the whole ? Are such diiferences necessary and unavoidable? 
 Can the less productive lands not be made to yield a larger return 1 
 Can the large crops of the richer districts not be further increased, and 
 their amount kept up for an indefinite succession of seasons ? 
 
 These interesting (]uestions lie at the foundation of all agricultural im- 
 proveinent — and skill and science answer that, though diflerences to 
 a certain amount are unavoidable, yet that means are already known 
 by which the fertility of the richer lands may be maintained, and the 
 crops of the less productive indefinitely enlarged. 
 
 § 2. Of (he circumstances by which the produce of food is affected- 
 climate, season, soil, Sj'c. 
 
 The quantity of food produced by a given extent of land is afiected 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, and by the ro- 
 tation or course of cropping tliat is adojited. 
 
 1°. Climate. — That the warmth of the climate, the length of the sum- 
 mer, and thecpiantity of rain that falls, inflxience in a remarkable degree 
 the amount of food which a district of country is fitted to raise, is fa- 
 miliar to every one. Tlie v.-armlh of the ecjuatorial regions maintains a 
 perpetual verdure, wliile the short northern .'summers afi^ord only a few 
 months of pasture to the stunted cattle. The difierence of latitude be- 
 tween the extreme ends of our island i)roduces a similar difference, though 
 in a less degree. The almost perennial verdure of the southern coiinties 
 
 ' In 1821, Mr. Wakefield estinialfd llie average produce of vvhear in sll RnglHrd at 17 
 bushels only — Devonshire producing an average ofSO, and the lands near the coast of Kent, 
 Norfolk, SulTolk, and Essex, 40 bushels peracic. 
 
INFLUENCE OF CtlMATK, SEASO^f, AND SOII,. 489 
 
 cannol be hoped for in the north of Scotland, and yet it is said that in 
 parts of Ross-shire the com and turnip crops are equal to those of the 
 most favoured districts of Britain. Is this to be regarded solely as the 
 triumpii of skill and industry over the difticulties 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 reaped again on 
 the next, because an unusual cold may arrest its growth. And 
 yet good husbandry will do much even here — since the higher the farm- 
 ing the fewer the number of failures which the intelligent man will 
 have occasion to lament. 
 
 3°. Soil. — Diversity of soil is held to be a sufficient reason for differ- 
 ence both in kind and in weight of 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 appears as yet to 
 have mucli to learn. Is there any method hitherto little tried by which 
 soils of known poverty may be compendiously and cheaply doctored, so 
 as tp produce a greatly larger return ? Science seems to say that there is, 
 and points to a wide field of experimental research, by the diligent cul- 
 ture of which we may hope that this great result will hereafter be at- 
 tained. The principles upon which tliis hope rests have been explained, 
 for the most part, in the preceding Lectures. 
 
 4°. Kind of crop. — The amount of food, either for man or beast, 
 which a given field mil produce, depends considerably upon the kind 
 of crop which is raised. Tlius 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 4400 lbs. of an agreeable, drjs and mealy food. Thus the 
 gross weight of food for man is in the one case three times what it is in 
 the other. So it is said, on the authority 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 pasture grass 
 of medium quality.* 
 
 5°. Variety of seed sown. — The variety of seed sown has also an im- 
 portant influence on the amount of produce reaped. I need not refer to 
 the well known necessity of changing the seed if the same laud is to 
 continue to yield good crops — but of strange seeds of the same species 
 two varieties 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 pr bush. Str.iw. Fine flour. Fine do. pr.ct. 
 
 White Downy - 48 bush. 62 lbs. 45.57 lbs. 2402 lbs. 80| lbs. 
 Jersey Dantzic - 43i bush. 63 Ib.s. 4681 lbs. 2161 lbs. 79|lbs. 
 while on a different soil and treated differently from the above, two other 
 varieties yielded — 
 
 Grain. Weight pr bush. Straw. Fine flour. Fine do. pr.ct 
 Whittrngton, - - - 33 bush. 61 lbs. 7786 lbs. 1464 lbs. 72|lbs. 
 Belle Vue Talavera, - 52 bush. 61 lbs. 5480 lbs. 2485 Ibs.f 78i lbs. 
 
 * Loudon's Encyclopadia of Agriculture, p. 910. 
 
 t Journal of the Royal Agricultural Sodety ofEnglatul, L, p. 123. 
 
490 INXLUKNtK or THK MKTHOD OF CULTURE, 
 
 III each of t]iese cases, thcrofijre, and especially in the last, a striking 
 tiifTeience presented itself both in the absolute and in the relative weights 
 of grain and of straw rcajied under precisely similar circumstances, by 
 the use of diHerent varletit^s of ilie same sjiccies of seed. Nor are the 
 above by any means extrcine cnsos. In the same field I have known 
 the Golden Kent and tlie Flanders Red vru-ieties, sown in the same 
 spring, to thrive so differently, that, while tiie former was an excellent 
 crop, the latter was almost a total failure. It will require a very refined 
 chemistry to explain the cause of sucli diversities as these. 
 
 § 3. lirfiuenc.c of the method of culture upon the produce of food. 
 
 In addition to tlie circumslanccs above alluded to, the ipiantity of food 
 that is raised depends very much upon the method of culture which is 
 adopted. Thus, in land of medium quallly, our opinion in regard to the 
 quantity of food it is likely to yield would be greatly atfected by the 
 answers we should obtain to the (bllowhig questions ; — 
 
 1°. Is the land in permanent jnisturc, or is it under the plough? — 
 "With the excc))tion of ricli pasture, it is said that land, mider clover or 
 turnips, will produce three times as much for cattle as when luider grass. 
 Ifsuchagreen crop tlien alternate with one of corn, the land would 
 every two years produce as iruicli food for stock as it would during three 
 years if lying in grass, besides tlie crop of corn ;is food for man, and 
 of straw for the production of manure. 
 
 This statement may ])ossibly bea littleexaggerated, or may represent tru- 
 ly 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. 
 
 2°. What kind and quality of manure is applied? — Every practical 
 man knows tlie importance of manuring his land, and ho\Y much the 
 abundance of every crop he sows depends both upon the quantity and upon 
 the kind of manure he is able to add to it. 
 
 3°. In ichat u-ajj is it applied ? — But much depends also upon the 
 manner in whicli the manure is exi)ended, or the kind of crop to which 
 it is applied. 
 
 I have already (}). 477) directed your attention to (he loss which must 
 necessarily be sustained by top-dressing with farm-yard manure, anrl 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, when applied as a top- 
 dressing to grass land for instance, and wlien Iniried with the turnip crop 
 in the usual manner, is ^■ery unlike. 
 
 Thus, suppose an acre of grass land, of such a ipiality as to produce 
 annually without manure 1| 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 beinnmired for turnips 
 with 20 tons of farm-vard manure at once. Then the grass land, by 
 the aid of the manure, would nol produce nioretb;ni double its natural 
 crop, or 2^ tons an acre, that is, 10 tons of hr.y in th(^ litin" years. This, I 
 believe, is making a large allowance for the effect of tlie manure. 
 
 But the arable land, in the four years, if of the same quality, may be 
 
A.N0 OF THE MOKE OF APfT^flNG TUE MANURE. 491 
 
 expected to produce — turnips 20 tons, barley 36 bushels, clover 2 J tons, 
 wheat 28 bushels ; besides upwards of 4 tons of straw. 
 
 In all these taken together tliere must be much more food than in the 
 ten tons of hay. 
 
 If we consider the money profit, however, to the farmer, the result 
 may be different. The cost oi^ raising the ten tons of hay, exclusive of 
 rent, may be reckoned at one-half tlie jiroduce, and of die several crops 
 in tlie four years' rotation at three-cjuarters of the produce: we thus 
 have for tlie clear return-r- 
 
 In the one case, half the produce — 5 tons of hay ; 
 In the other case, a fourth of the produce — 5 tons of turnips, 9 bushels 
 of barley, i ton of clover, 7 bushels of wheat, and 1 ton of straw. 
 
 Let the clover and the straw together equal in value only one ton of 
 llie hay, and the money value in the two cases will stand as follows ; — 
 Hay, 4 tons, at Xo, = <£20 
 
 Turnips, 5 tons, at 10s. = ^£2 10 
 Barley, 9 bush., at 4s. = I 16 
 Wheat, 7 bush., at 7s. — 2 9 
 
 6 15 
 
 Leaving a gain upon the grass land of <i£l3 5 
 Or, <£3. 6s, an acre every year. 
 
 Thus, though more food is raised by converting the land to arable 
 purposes, and more people may be sustained by it, yet more money 
 may be made by meadowing the land — where a ready market exists 
 for the hay, where it is allmccd to be sold off the farm, and where abun- 
 dance of manure can be obtained for the purpose of toj't-dressing the grass 
 every year. It is only in the neighbourhood of large towns, however, 
 that all these circumstances 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 solely to the raising of one or other 
 of these kinds of produce. 
 
 Of the two ways of employing his grass or green crops — in rearing 
 and fattening cattle, namely, and in the production of butter and cheese 
 — we shall hereafter see reason to believe that theoretically the latter 
 ought both to be the most profitable in money to the farmer, and at the 
 same time to produce the greatest amount of food for man. 
 
 3°. What roiatiou or course of cropjnng is adopted ? — If the land be 
 cropped with corn, year after year, the produce of food will not only be 
 less than ifan alternate husbandr^y were introduced — but the yearly return 
 of corn, even on tlic richest land, must sooner or later diminish, till at 
 length the crop will not be sufficient to defray the expense of cultivation. 
 The tillage of such land must then be abandoned, and it must be left to 
 a slow process of natural restoration. No arable land will 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, root, and leguminous crops be 
 made to succeed each otlier in a skilful alternation. 
 
 Upon the introduction of the alternate husbandry, it was found that 
 upon lands formerly in pasture, not only could one-third more stock be 
 
492 THEORT OF THE ROTATION OF CROPS. 
 
 kept continuously than before, buttliat 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 naked 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 cropinng influences, in 
 a great degree, tJie amount of food which tlie same piece of land is fitted 
 to produce. 
 
 § 4. Of the theory of the rotation of crops. 
 
 Upon what principles do the beneficial effects of this change of crop- 
 ping depend ? What is the true theory of a rotation of crops ? 
 
 It was supposed by Dccandolle — 
 
 1°. That the roots of all plants gave out or excreted certain substan- 
 ces peculiar to themselves — and, 
 
 2°. Tliat these substances were unfavourable to tlie growth of those 
 plants from the roots of which they came, but were capable of promo- 
 ting the growth of plants o? other species — that the excretions of one 
 species were poisonous to itself, but nutritive to other species. 
 
 Upon these suppositions he explained in a beautiful and apparently 
 simple and convincing manner the beneficial effects of a rotation or al- 
 ternation 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 second wheat crop could be safely 
 grown, it was because during the year of rest the poisonous matter had 
 time to decompose and become again fitted to feed the new crop. And 
 if, after beans or turni{»s, wheat grew well, it was because the excretions of 
 these 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 DecandoUe, this explanation obtained for 
 many years an almost universal reception. 
 
 But though there seems reason enough for believing (p. 82) tliat the 
 roots of plants really do give out certain substances into the soil — there is 
 no evidence that these excretions take place to the extent which the 
 theory of DecandoUe would imply — none of a satisfactory kind that 
 they are noxious to tlie plants from which they are excreted* — and none 
 that they are especially nutritive to phinis of other species. Being un- 
 supported by decisive facts and observations therefore, the liypotliesis of 
 DecandoUe 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. 
 
 Tlie true general reason why a second or third crop of the same kind 
 will not grow icell, is — not that the soil contains too much of any, but that 
 it contains too little of one or more kinds of matter. If, after 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 tliis new plant. If 
 clover thrive after this, it is because it naturally requires certain other 
 kinds of nourishment which neitlier of tlie former croj)s has exhausted. 
 If, again, luxuriant wheat succeeds, it is because the soil abounds still in 
 * Sec page 61, note. 
 
PRACTICAL RULES SUCiGESTEb BY THEORY. 493 
 
 all that the wheat crop needs — the failing vegetable and other matters of 
 the surface being increased and renewed by the enriching roots of the 
 preceding clover. And if now, turnips refuse again to give a fair re- 
 turn, 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 inorganic 
 constituents of plants, to observe that different species require very un- 
 like proportions of the several kinds of inorganic food which they derive 
 from the soil. Some require a kirge proportion of one kind, some of 
 another kind. If a soil, therel()re, abound especially in one of these va- 
 rieties of inorganic food, one kind of plant will especially flourish upon 
 it — while, if it be greatly deficient in another substance, a second plant 
 will remarkably languish upon it. If it abound in both substances, then 
 either crop will succeed which we may choose to sow, or they may be 
 alternately cultivated with a fair return from each. 
 
 Upon this principle the true general explanation of the benefit of a 
 rotation of cro|is appears to dej)end. There may be special cases in 
 which peculiar qualities of soil or climate may intervene and give rise 
 to appearances, or cause results to wliich this principle does not apply, 
 but for the general practice it seems to aflTord a satisfactory explanation. 
 
 It may be said that this explanation seems to imply that the same 
 kind of crop maybe reaj)ed from the same soil for an indefinite number of 
 years, bj^ simply adding to it what the crop carries off'. This is certain- 
 ly implied in the princii)le — and if we knew exactly what to add fur each 
 crop, 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 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 suffi- 
 ciently economical manner. 
 
 Two practical rules are suggested by the fact that diflTerent plants require 
 different substances to abound in a soil in wliich they shall be capable of 
 flourishing. 
 
 1'^. To grow alternately as many different classes or families of plants 
 as possible — repeatingeach class at the greatest convenient distance of time. 
 
 In this countiy 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 
 in alternate years. Every four, five, or six years, therefore, the culture 
 of the same class of i>lants comes round again, and a demand is made 
 upon the soil for the same kinds of food in the same proportion. 
 
 In otlier countries — tobacco — flax — rape, poppy or madia, cultivated 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 ])lant3 more distant. A perfect rotation would include all those 
 classes of plants which the soil, climate, and other circumstances allow 
 to be cultiva«;ed 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. 
 
491 WHY LAM) BKCOMtS CLOVER-SICK. 
 
 wheat, oats) usually grown, must be raiseO. But of the leguminous 
 crops we have the choice of beans, peas, vetches, and clover — of root 
 crops, turnips, carrots, beets, and ])otatoes — while of grasses, there is a 
 great variety. Instead, therefore, of a constant repetition of the turnip 
 every four years, theory says — make the carrot or the potatoe take its 
 place now and tlien, 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 fixxi which the 
 new crop will relish, than with sucli as the plant it has long fed before 
 continues to require. 
 
 It is for this reason that new species of crop, or new varieties, when 
 first introduced, succeed remarkably for a time, and give great and en- 
 couraging returns. But 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 in consequence to yield as before, and fall 
 into undeserved disrepute. Give then:i 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 growing in the 
 fields many different crops in succession, that gives the fertility of a gar- 
 den to parts of Italy, Flanders, and China.* 
 
 § 5. Why land becomes tired of clover {clover-sick). 
 
 What I have said of the general principle might be supposed to 
 explain fully wliy crops fail at one time and succeed at another — why 
 the soil will nourish one jjlant well, while it is unable adequately to sus- 
 tain another. But a brief reference to the case of tlie clover plant will 
 enable us to see how modes of culture, apparently skilful and generous, 
 may yet be of such a kind as to lead, sooner or later, to the inevitable 
 failure of a particular crop. 
 
 It is known that upon many well cidtivated fanns the lands beconfe 
 now and then tired or sick of clover, and this crop failing, the wheat 
 which succeeds it in a great measure fails also. It may be said that the 
 soil in such a case is in want of something, and so it is, — but how does 
 this deficiency of supply arise ? The land is skilfully managed and 
 has been well manured, and the failure of the clover crop is, therefore, a 
 matter of surprise. 
 
 If farm-yard manure be copiously applied i)revious to the root crop, 
 the land has received 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 rotation will require for food. When the clover comes 
 round, tlierefore, a supply of proper food is ready for it, as well as for 
 the wheat whicli is to follow. 
 
 But if the turnip crop be raised by means of bones only, the lime 
 
 A method of supersetling in some measure the necessity of a rotation of rrops is de- 
 scribed by Mr. .lames Wilson as lon<! practised in Shetland, in ttie neighbourhood of Ler- 
 wick. " It is linown that bear l)as been grown in the same patch fur perhaps 100 years suc- 
 cessively, and this they manaited by scarifyinfc other parts of the ground (the outfield por- 
 tion), and renovatinji 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 limini;, 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 Voyuge round the Coast of Scot!a7id, II., p. 26S. 
 
RESULT OK FREQUKNT MANDRING WITH B0>'E3. 495 
 
 and phosphoric acid which the earth of bones contains are almost the only 
 kinds of inorsjanic f )0.1 required by plants that are returned to the soil. 
 By the aid oftlie animal matter and the small suppl}^ of other substances 
 in the bones,* good crops — and especially the turnips and the 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 substance can replace fanii-yard manure for an in- 
 definite period, because it does not contain all the substances which the 
 entire rotation of crops requires. 
 
 If wood-ashes be used along with the bones, the bad effects I have des- 
 cribed will be mucli longer delayed — they may even be delayed indefi- 
 nitely, since wood-ashes are said to be especially favourable to the growth 
 of clover and other leguminous plants, (p. 353), and diis because they 
 contain those substances which the clovers require. 
 
 It thus appears, therefore, that while the failure, upon a given spot, of 
 a crop which formerly grew well there, is explained generally upon the 
 principle that the soil has become deficient in something which the crop 
 requires — the cause of this deficiency may not unfrequently be found in 
 the mode of culture, or in I lie species of manuring which the land has 
 received. The cause being discovered, the remedy is easy. Cease to 
 employ exdusivchj the manure with which your land has hitherto been 
 dressed. Mix 3'our bones or rape-dust with wood-ashes, with gypsum, 
 or with other portable manures in which the necessary food of your 
 crops is present — or employ farm-yard manure now and then in their 
 stead, and you wdl apply the most likely remedy. Unless this be done, 
 it will be of comparatively little service to vary tlie species, — to substi- 
 tute tares or beans for the clover, — since these also will refuse to grow 
 while the same incorrect sj'stem of manuring is persisted in. 
 
 I have already drawn your attention (p. 477) to the falling of the 
 clover crops in certain parts of Stafiordshire, where the turnips are 
 raised by means of rape-dust — and of the mode of improving them by a 
 top-dressing of farm-yard manure. Were this manure laid in with the 
 turnips, the after top-dressing would most probably not be required. 
 
 § 6. Of the theory of falloivs. 
 
 By fallowing, it has been known in all ages that the produce of the 
 land was capable of being increased. How is this increase to be ac- 
 counted for? We speak of leaving the land to rest, but it can never 
 really become wearied of bearing crops. It cannot, through fatigue, lie 
 in need of repose. In what, tJien, does the efficacy of naked fallowing 
 consist ? 
 
 1°. In strong clay lau'ls one great benefit derived from a naked fallow 
 is the opportunity it afibrds 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 have been kejjt so by other means they would not have been 
 adopted. Is it not the case on some farms that a neglect of other avail- 
 able metliods of extirpating weeds has rendered necessary the assistance 
 ' Foj- the composition of bones, see pajo 416. 
 
496 FALLOWS MAY RKPIACE DEEP P1,0UKH1>U AND DRAIMNG. 
 
 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 arc afterwards ploughed in, the land is 
 enriched by a green manuring of greater or less extent. If weeds abound, 
 tlie enriching is the greater — if they are more scanty, it is less — but in 
 almost every instance where land hes without an artificial crop during 
 the whole siunmer, a crop of natural herbage springs up, the burymgof 
 which in the soil must be productive of considerable good. 
 
 3°. When land is assiduously cropped, the surface in wldch the roots 
 chiefly extend tliemselves becomes especially exhausted. In indiffer- 
 ently 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 e(iualize the condition of the whole sur- 
 face soil— in so far as the soluble substances ii contains are concerned. 
 The water also, which in dry weather ascends from beneath, brings 
 with it saline and other soluble compounds, and imparts them to the up- 
 per layers of the soil. Thus, by lying fallow, the land, becomes equa- 
 bly furnished over its whole surface with all tliose substances reqiured 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 extent, make up for shallow -ploughing^ 
 and for insufficient working of the land. 
 
 4°. It is known that the subsoil in many places is of such a nature 
 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 sur- 
 face soil. To a less degree stiff clay lands acquire this noxious quality 
 during the ordinary course of cropping. Air and water do not find their 
 way through them in sufficient quantity to retain theiu in a healthy 
 condition, and thus they require an occasional fallow with rej)eated 
 ploughings, diat the air and the rains may have access )o their inner- 
 most parts. I do not detail the specific chemical changes which are in- 
 duced by this exposure to the air and rain ; it is sufficient that they eire 
 of a kind to render the soil more propitious to the growth of crops, to 
 satisfy us that, upon very stiff lands, one of the benefits of fallowing is to 
 be thus 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 permitted 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 ren- 
 dered wholesome by tlie frequent admission of new supplies of atmos- 
 pheric air. 
 
 It thus appears that in a certain sense draining and fallowing may 
 take the j)l<ice of each other — tliat where there is no drainage, fallowing 
 is more necessary and will partially supply its 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 exislence of organic 
 (animal and vegetable) matter in the soil, in a so-called inert state — a 
 state in which it undergoes decay very slowly, and thus only in a small 
 
THE SOIL IS JIANORED BY THE SEA AND THE AIR. 497 
 
 degree discharges those functions for wliich vegetable matter in the soil is 
 specially destined. In stilTclays also, the roots of plants, without actu- 
 ally attaining this inert state, yet decay with extreme slowness in conse- 
 quence of their being so completely sealed up from the access of the air. 
 In both cases the frequent and prolonged exposure which a naked fallow 
 occasions, induces 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 (p. 161) during this 
 prolonged exposure and more rapid decay of the organic matter of the 
 soil, nitric acid is one which appears to exercise a considerable in- 
 fluence upon the future fertility of the land. The favourable action of 
 the nitrates in promoting vegetable growth is now well known, and 
 the more rapid formation of these compounds, when the land lies na- 
 ked 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, (quartz) sand and lime of which it 
 chiefly consists, contains also fragments of mineral substances of a com- 
 poum] nature — of felspar, of mioa, of hornblende — of those minerals 
 which constitute or which occur in the granitic and trap rocks. These 
 slowly decompose in the soil — more rapidly also the more fi-eely they 
 are exjwseil to the air — and the substances (potash, soda, lime, magne- 
 sia, silica, &c.*) which they contain, are by this decomposition diffused 
 more equably and brought within the more easy reach of the roots of 
 plants. Wlien these minerals, therefore, exist in the soil, and when 
 their constituents are of such a kind as to favour the growth of any given 
 plant, tlie effect of a naked fallow being to produce an accumulation of 
 their constituent substances in the soil, it will be so far favourable in pre- 
 paring the land for an after-crop of that particular species of plant. 
 You are not to be misled, however, by any broad and unguarded state- 
 ments of scientiffc men, so as to imagine lor a moment that the benefi- 
 cial effects of fallowing in any case are to be solely ascribed to the oper- 
 ation of this one cause. f 
 
 7°. The rains bring down upon every soil periodical supplies of ail 
 tliose saline substances — common salt, gypsum, salts of lime, of mag- 
 nesia, and of potash in minute cpiantity — which exist in the sea, and of 
 nitrate of ammonia, produced or present in the air. If any soil be defi- 
 cient in these, tlien a year's rest from cropping, by allowing them to ac- 
 cumulate, may cause the succeeding herbage to cxhitjit a more luxuriant 
 growth. 
 
 8°. The same remark apjdies to soils into which springs from beneath 
 bring up variable quantities of lime and other substances which the wa- 
 terSjhold in solution. Such springs are, no doubt, of mucli benefit in 
 some districts, and when the sujiply they convey is scanty, a year's 
 accumulation may impart addirional fertility to the followed land. 
 
 9°. Besides that beneficial action of the air to which I have already 
 adverted (4° and S'^), and which is to be ascribed mainly to the influ- 
 
 ' For tlie constitulioii of these miiioral substances, see pp. 257 to 200. 
 t Fallow is the term applied to land left at rest fur further disintegration.— I.iebig's Organic 
 Chemistry applied to Agriculture, p. 149. 
 
498 OF GREEN OR FALLOW CROPS. 
 
 ence of the oxygen it contains — the exposure of the naked soil to the at- 
 mosphere for a length of time is said by some to be productive of another 
 good effect. Tbe atnio->i)here contains a small and variable portion of 
 ammonia (p. L5G). 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 sujiposed also to ha\e the power of 
 extracting this ammonia from the atmosphere and retaining it in their 
 pores. If so, the more the soil is exposeil, and lor the longer period 
 to the air, the more of this substance will it extract and absorb. If 
 turned over by trecjuent plougliing, it will be able to drink it in more 
 abundantly, from the greater surface it can ])rcsent to the passing winds; 
 and if, besides, it be kept naked tor an entire }'ear, a still larger accumu- 
 lation must take i)lace. And as this ammonia is known in many cases 
 to be favourable in a high degree to the growth of plants, it is not un- 
 reasonable to believe that if t}ius absorbed in quantity from the air, it should 
 be one source at least of the augmented fertility of fallowed land. 
 
 To one or other — or to all of these causes combined — the acknowledged 
 benefit of naked fallows is in a great degree to be ascribed. 
 
 Of green or fallow crops little need be Sciid in addition to what I have 
 already laid before you in reference to the rotation of crops. The green 
 crop demands a comparatively small supply only oi'those inorganic sub- 
 stances which the corn crops specially require. During its growtli, 
 therefore, these latter accumulate in the same way, thougli in a some- 
 what less degree than during a naked fallow. But the additional vege- 
 table matter and manure which the green crops introduce into tiie soil, 
 and the large supplies of inorganic matter which such of them as are 
 deep-rooted bring up from beneath, amply compensate for any diminu- 
 tion they may cause in the benefits which are usually derived from the 
 naked fallow. 
 
 § 7. Of wheat and icheaten flour. 
 
 The grain of wlieat in the hands of the miller is readily separated 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 11 or 16 percent, of 
 the whole weight* — though the quantity separated by the miller is 
 sometimes not more than ^th (or 11 per cent.) of the weight of the 
 wheat. In making the fine white flour of tiie metropolis and other 
 large towns, about |th of the whole is separated in the form of pollard 
 and bran. The j)roportion of the husk that can be sifted out at the mill 
 
 ' Boussingaiilt found as miicli as 38/t' per cenl. of husk on a winter wlieat grown in the 
 botanic garden of Paris. Tliree lots of good English wheat, ground at Mr. Rubson's mill in 
 Durham, gave per cent. respectively- 
 Fine lion r 74-2 751 779 
 
 Boxings 90 83 61 
 
 Sharps 5 8 6 6 5G 
 
 Bran 78 70 69 
 
 Waste 32 30 3-5 
 
 100 lOU 100 
 
RELATIVE WKIGIITS OF KLOUR A^•n BRAX. 499 
 
 depends considerably upon the hardness of the grain. From such as is 
 soft it peels oB'in flakes under the stones, wliereas, when the grain and 
 husk are flinty, much of the latter is crushed and ground — adding to the 
 weight of the flour, hut giving ita darker colour, and loweringits quality. 
 
 The country millers generally sej)aratc their whealen flour by sifting 
 into four parts only — fine flour, boxuigs, sharps or pollard, and bran. 
 In Loudon and Paris no less than six or seven qualities are manufac- 
 tured 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 bv simple inspection. 
 
 The experimental wheats of Mr. Burnet, of Gadgirt]i,f raised all from 
 the satne seed differently manured, gave respectively 54 j, 63', G5j, 
 ()6i, 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. 489) of difl^erent va- 
 rieties, grown under the same cirrumstances, gave from one field 8O3 
 and 79J lbs., and from another 72} and 78^ lbs. from 100 of wheat — so 
 that upon the variety of seed sown also, though in a less degree, the quan- 
 tity of fine flour is dependent. 
 
 § 8. Of the composition of wheaten Jlour. 
 
 1°. IVater. — When wheat is kept for ayear it loses a little water, be- 
 coming one or two pounds a bushel heavier than before. When put info 
 the mill and grotmd it becomes very hot, and gives off" so much watery 
 vapour, that the flour and bran, though together nearly twice as bulky, 
 are nearly 3 per cent, lighter tlian the grain beibre 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 temperalure not higher 
 than 220 tor several hours, it loses a (]uaniity of water, which, in up- 
 wards 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 as- 
 sumed, that English flour contains nearly a sixth part of its weight of 
 water — or ever^' six pounds of fine flour contain nearly one ])0und of 
 water. 
 
 2°. Gluten, albumen, caseine, starch, gum, and sugar. — When the 
 flour of wheat is made into dough, and is then washed carefully with 
 successive portions of water upon a fine gauze or hair sieve, as long as 
 the lifiuid passes througli milky, the flour is separated into two portions — 
 the starch, which subsides from the water, and the glut C7i, which remains 
 in the sieve (p. 116). If the water be poured off', after the starch has 
 subsided, and be lieated nearly loboiluig, it becomes troubled, and flakes 
 of vegetable albumen (p. 117) are seen to float in it. On setting aside to 
 
 * These are called respectively in London and Paris — 
 
 London. Paris. Called. 
 
 Fine flour. White flours, Ist quality, dc We. 
 
 Seconds. do. 2d du. delegruati. 
 
 Fine middiins^d. do. 3d do. de2egruau. 
 
 Coarse middlings. Brown meals, 4tli do. de 3e gniau. 
 
 Pollard. do. 5ih do. do 4e gruau. 
 
 Twentypcnny. Bran, fine and coarse. 
 
 Bran Waste, &.C., Reinuulage and Recoupc. 
 
 < Page 362, and Appendix, pp. 51 and 70. 
 
600 STARCH, SUGAR, GUM, ANt> OIL, IN WHEAT. 
 
 cool, the flaky powder falls to the bottom, and may lie collected, dried, 
 and weighed. If the water, after filtration, he evaporated to dryness on 
 the water bath, a residue will be obtained, ^\hich consists chiefly of solu- 
 ble sugar, gnm, and saline matter, with a Utile fatty matter, and sparingly 
 soluble caseine* (p. 117). 
 
 3°. Glutine and oil. — If, further, the crude gluten be boiled in alco- 
 hol, a solution is obtained which, on cooling, deposits a white flocky sub- 
 stance, having mtich resemblance to caseine. When the clear solution is 
 concentrated by evaporation, water separates from it an adhesive mass, 
 which consists of a substance to which tlie name of glutine is given, 
 mixed with a little oil. By digesting the mixed mass in ether the oil is 
 dissolved out from the glutine, and may be obtained in a pure state by 
 evaporating the ethereal solution. This oil possesses the general pro- 
 perties of the fatty oils, or of butter. As it is partly washed out, how- 
 ever, along with the starch, the whole of the fatty matter of the flour is 
 best obtained by boiling it in a considerable quantity of ether. 
 
 4°. Vegetahle Jibrine. — The crude gluten, after boiling in alcohol, has 
 much resemblance to the fibre of lean beef, and has therefore been named 
 vegetable fibrine. When burned, it leaves behind 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, f 
 
 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 
 vegetable fibrine, albumen, caseine, glutine, starch, sugar, gum, oil or 
 fat, besides the saline substances, chiefly phosphates, which remain in 
 the form of ash, when the flour is burned. All these substances Aary in 
 quantity in dirterent samples of flour, — their relative proportions appear- 
 ing 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-centageof oil, of glutine, or of caseine, 
 which the specimens examined have severally contained. In general, 
 the weight of the crude gluten only has been estimated, witliout extract- 
 ing from it either the oil or the glutine. 
 
 The following table exhibits the approximate composition of some 
 varieties of French and Odessa flour as determined many years ago by 
 VauquelinJ : — 
 
 * This caseine begins to form a pellicle on tlie surface, when the liquid is concentrated by 
 evaporation, and though it is generally present only in a small proportion (M to 1 per cent.), 
 yet the comparative quantiiies present in two samples of Jlour may be judged of by the 
 abundance in which the pellicle is formed. 
 
 t The saline and other inorganic matter of grain resi<Ies chiefly in the husk, as may be 
 Been by the relative quantities of ash left by the flour, bran, &c., of several samples of Eng- 
 lish and Foreign wheat as determined in niy laboratory— 
 
 ASH I.EPT PER CENT. BY DRY. 
 
 wbERE GROWN. Fine Flour. Boxings. Sharps. Bran. 
 
 1°. Sunderland Bridge, near ^ j.24 40 5.3 g.g 
 
 Durham ^ 
 
 2°. Kimblesworth, do 115 38 4-9 67 
 
 3°. Hougliall, do 0-96 30 5-6 7-1 
 
 4°. Plawsworth, do 093 2-7 55 7-6 
 
 5°. Sleltin 11 45 6-2 6-9 
 
 6°. Odessa 11 49 66 fiO 
 
 J Dumas' Traiie de Chimie, vi. p. 383. 
 
I 
 
 Oti THfi COMfOSttlO.^ OF WHEATEM FLOUR. 501 
 
 COMPOSITION 01^ THB FLoUR OF 
 
 French Wheat. Odessa Wheat. 
 
 !«' 2.1 ^l^^^^, Flinty ^i"/^ ^^^^l^' 
 
 quality. quaUty. ^oZ ^^'^«-'- qu'aUty. qu^ity. 
 
 Water 10 120 10 12 100 8 
 
 Gluten 110 73 101 14-6 120 120 
 
 Starch 715 72-0 728 56-5 620 70-3 
 
 Sugar 4-7 54 4 2 8 5 7 4 49 
 
 Gum 33 3-3 28 49 58 46 
 
 Bran _ _ _ 23 12 — 
 
 100-5 100 100 98-8 98-4 1003 
 
 § 9. Of Uie influence of soil and climate on the composition of 
 wheaten flour. 
 
 1°. The nature of the .soil has a sensible influence upon the composi- 
 tion of the grain that is reaped from it. The proportion of gluten, for 
 example, is gaid 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 has been observed in regard to the wheat grown in 
 the limestone districts ; and the millers of the midland counties of Eng- 
 land (on the new red sandstone) are accustomed to mix, with their native 
 corn, that of the chalk districts to tlie east and south, for the purpose of 
 giving additional strength to their flour. 
 
 Climate. — The wheat of warm climates also is supposed usually to 
 
 contain more gluten. Thus flour, prejjared from some Eastern wheats, 
 
 compared with that from others of French growth, was found to contain 
 
 water and dry gluten in the following proportions : 
 
 Water, Gluten, 
 
 per cent. per cent. 
 
 French, Saissette 15-1 12-7 
 
 Rochelle 12-9 11-2 
 
 Brie 13-5 10-7 
 
 Tuzelle 13-0 8-3 
 
 Odessa 13-0 15.0 
 
 Taganrog* . 12-6 22-7 
 
 The iiuautity of gluten contained in English flour has generally been 
 
 stated much too high. Thus, Sir Humphrey Davyf says that he ob- 
 tained from the flour of — 
 
 Gluten, Gluten, 
 
 per cent. per cent. 
 
 EngUsh winter wheat 19 Barbary wheat 23 
 
 English 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 sub- 
 stance assigned by previous experimenters has arisen from the water not 
 being sufficiently expelled from it by prolonged heating to 220° F. I 
 select the following from a greater number of determinations, carefully 
 made in my laboratory : — 
 
 • Tagaurog, at the head of the sea of Asoph, exports the produce of the bank.s of the 
 Don. 
 ' Agricultural Chemislrtj, Lecture III. 
 
602 I>Fl.UE?fCE OF CLIMATE, VARIKTI OF SEED, 
 
 Weight Water 
 
 per in Gluten. 
 
 KiNP OF WHEAT, busliel. Flour. where grown. 
 
 lbs. perct. perct. 
 Red English . . . 62^ 17-5 81 At Sunderland Bridge, near Durham. 
 
 " " .... 6>^ 16-4 95 At Kimblesworih, near Durham. 
 
 " " 6:j 150 8-5 At Houghall, near Durljam. 
 
 " " .... 02| li>S 99 Near North Deighloii, Yorkshire. 
 
 White " .... C3 155 75 At Plawswortti, near Durham. 
 
 " Scotch.. GIJ 1(5 3 9-4 .\t tiddjiirtli, near Ayr (Appendix, p. 59.) 
 
 Red Stettin 63 14 6 8 6 
 
 " Odessa.... 61 15-9 115 
 
 In all these cases tlie quantity of gluten falls far short of that assigned to 
 English flour by Davy ; yet we may safely, I tliink, conclude front them 
 that English flour seldoni contains looro than 10 per cent, ol'dry gluten. 
 The flour from North Deighton, which gave 9-9 per cent, was grown 
 upon a tliin limestone soil, and may j^crhaps owe its larger per-ccntage 
 to this circuinstance. 
 
 But these numbers do not indicate the exact quantity of nitrogen-hold- 
 ing food which these flours contained. For in the gluten there is al- 
 ways present a variable quantity of fatty matter which contains no nitrogen, 
 and wliich, if extracted, would lessen considerably the weight of the glu- 
 ten in some of the flours. On the other hand, however, the water em- 
 ployed in washing out the starch holds in solution some albumen and 
 ca.sein, which, having the same composition, might be added to the glu- 
 ten, 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 percent. 
 
 Making in all . . . 10-15 of substances which contain 
 nitrogen in nearly eciual proportions. 
 
 We probably, therefore, do not greatly err in general in estimating 
 the nutritive value of wheaten flour — in so far as it depends upon these 
 nitrogenous compounds — by the per centageof dry gluten which a care- 
 ful washing enables us to separate from il. Further researches, how- 
 ever, which are now in progress, will tlirow nuich additional light upon 
 this subject. 
 
 § 10. Influence of varielij of seed, of mode of culture, of time nf cutting, 
 and of special manures, on Oie composition of wheat. 
 1°. Variety of seed and mode of culture. — Tlie influence of these two 
 circumstances upon the relative proportions of bran and gluten are shown 
 by the following results of the examination I)V Boussingaultf of several 
 varieties of wheat grown in tlie Botanic Garden at Paris — 
 
 Husk or Bran Flonr Water Ginten, &c. 
 
 in the Grain, in tlie Grain, in llie Flour, in the Flour. 
 
 per cent. per cent per cent. per cent. 
 
 Cipewheaf 19 SI 70 20-6 
 
 Russian wheat IS !?2 C-4 24 S 
 
 Dinlzic wheat 24 76 73 tiSS 
 
 Red FoLt wlieat 18 5 815 9 3 261 
 
 Hanel wheat 22 78 8 8 27-7 
 
 Winter wheat 38 62 141 33 
 
 * No. 2. Appendix, p. 17 !■ 
 
 t Annates dc Ch:m. cl di Phys. Ixv., p. 311. 
 
TIME OF CUTTt.VG, AN'O SPECIAL MANL'KES. 503 
 
 In all the samples the hran and gluten are both ver\' hiijh, bnt they 
 vary much in the several varieties. 
 
 The gluten inrUules the albumen and easein nutl other substances con- 
 taining nitrosen, bnt even tliongh grown in t!)C rich soil of a liolanic gar- 
 den, I fear the sum of these has been estimated much too high.* Tlie 
 same variety of wheat grown in the open fields in Alsace ga\e 17*3 of 
 gluten, and in tlie Botanic Garden of Paris, '26-7 of gluten. 
 
 2°. 'ZV?e time ofcuffins^ aflf'cts tlie weight of produce, as well as the 
 relative proportions of flour, bran, and gluten. Thus from."? equal patch- 
 es of tlie 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 rijieness, and whiMi fully ripe, the produce w^as in grain — 
 20 days before. 10 days before. Fully ripe. 
 
 166 lbs. 220 lbs. 209 lbs. 
 
 and the per-centage of flt)tir, sharps, and bran, yielded by each, and of 
 water and gluten in the flour, was as follows : — 
 
 IN THE GliAIN PEK CENT. IN THE FI.OUR PER CENT. 
 WHEN CT-T. , " < , ^ 
 
 Flour. Sharps. Bran. Water. (-iliiten. 
 
 20 clays before it waa ripe 7-17 72 17-5 15 7 9-3 
 
 10 days before 79 1 5 5 l.'!-2 1.^-5 9 9 
 
 Fully ripe 72 2 110 160 15 9 96 
 
 When cut a fortnight before it is ripe, llierefore, the entire produce of 
 grain is greater, the ^deld of flour is larger, and of bran considerably less, 
 while the proportion of gluten contained in the flour ap]ie;u-s also lo be 
 in favour of that which was reaped before the corn was fully ripe.f 
 
 .3°. Special manures. — It is said that the employment of manures 
 wliich are ricli in nitrogen not only causes a larger crop, but also produ- 
 ces a grain wliicli is much richer in gluten. The experiments whicli 
 have hitherto been chiefly relied u))on in proof of this result are those of 
 Herrabstadt. On ten patches, each 100 s(]uare 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 wlieat — collected, 
 weighed, and analysed the produce. TJis results are represented in the 
 following table : — 
 
 — 3 
 
 - s 
 
 d^ Zg T.^ C-5 Ka E^ t-5 C'% > EPc 
 
 R.liirn HMJ 14 fold. IJ fold. I2fild. 12 fold. 10 fold. 9fold. 7 fold. 5 fold 3 fold. 
 
 W.Hier 4-3 4-2 4-2 4-3 4-2 4-3 4-3 42 4-2 4-2 
 
 Gluien 34-2 33-9 32-9 32-9 35-1 13-7 12-2 120 9-6 9-2 
 
 Albumen 10 1-3 r3 1-3 1-4 11 0-9 I'O 0-8 0-7 
 
 Siarrh.- 41-3 41-4 42-8 424 39-9 01 -6 632 62-3 65-9 66-6 
 
 Sugar 1-9 1-6 l-.-i 1-5 1-4 1-6 19 1-9 19 1-9 
 
 Gum 1-8 1-6 1-5 1-5 1-6 1-6 1-9 |-9 ] -6 l-S 
 
 FattyOil 0-9 IM TO 0-9 10 1 -0 09 !•;' 10 1-0 
 
 SotublePiiosphates.&c. 0-5 0-6 0-7 07 0-9 (i-b 0-5 5 05 0-3 
 
 Hu6l:andbran 139 14-0 13-3 14-2 11-2 U-0 14-0 14-9 140 14-0 
 
 99-S 99-7 99-7 93'7 997 99-6 99-8 99-7 99-8 997 
 The large per-centage of gluten obtained by the use of the first five 
 
 • In these flours the srhilen vvas; not iletermined by wa.'sliing out the starch, but by a in u-e 
 refined method of ultimnle analysi-s, as it is called, by which tlie per-orniase of nitrojen ia 
 determined, and the proportion of gluten, &c., calculated from lhi.«. When the per-centage 
 of nitrogen i.s small, as in wheaten flour, iliis method is open to many sources of error. 
 
 ■ See a paperby Mr. John Hannam, Quarterly Journal of Agriculture, Iviii , p. 173. 
 
604 EFFECTS OF GERMINATION AND BAKING 
 
 manures is very striking, if the determinations are really to be dependec 
 upon. They are certainly interesting in a theoretical point of view, ani 
 are deserving of careful repetition. In reference to their bearing upor 
 practical farming, however, it must not be t()rgotten, that the results ol 
 small experiments are never fully borne out when they are repeated oi 
 the large scale — that the relative value of different animal manures v. 
 materially affected by tlie kind of food on which the animal has lived— 
 that independent of manures, there are circinnstances not yet made ou 
 which materially affect the produce of single patches* — and that it wil 
 rarely be in the power of the practical farmer to apply at pleasure to hi; 
 fields the relative proportions of the several manures used by Hermb- 
 stiidt. Thus, if instead of 20 tons of farm-yard manure he wished It 
 try blood or urine alone, he must apply 24 tons of the former, and 7C 
 tons of the latter — quantities which it might be both difficult to procure 
 and inconvenient to apply. 
 
 The most practically useful results yet publislied in regard to the ac- 
 tion of the diff^erent manures upon the weight of the crop, the proportiori 
 of flour yielded by it, and of gluten in the flour, are those of Mr. Burnet, 
 to which I have already had occasion to draw your attention. f These 
 results were as follow : — 
 
 „,„„ „..,„„„ Produce Fine Flour Gluteo 
 
 KIND OP MANURE. per acre. fromlhe grain, intheilour. 
 
 Nothing 311 bshls. 76i lbs. 94 per cent 
 
 Sulphated urine and wood ashes. 40 " 66i " 10-5 " 
 
 Do. and sulphate of soda. 49 " G'ji " 97 " 
 
 Do. and common salt. . 4!) " 65j " 96 " 
 
 Do. and nitrate of soda. . 48^ " 54§ " 100 " 
 
 We perceive here a slight increase in the ])er-centage of gluten when 
 
 the manures were applied, bur nothing which at all resembles the great 
 
 differences given by Hermbsatdi, or which renders it probable tliat by 
 
 skilful management, as some have supposed, we may hereafter be 
 
 able to raise in our fields Avhole 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. 118), the very 
 beautiful change which takes place during the sj)routing of the seeds of 
 plants — how a jiortion 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. In an experiment made by De Saussurc, 100 parts of the 
 farina of wheat had by germinntion lost G parts of starch, and in their 
 stead had acquired 3^ of gum and 2i 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 contained 
 in the flour of wheat that renders it so much better fitted for the bakin? of 
 
 • See Appendix, pp. 59 and 79. I See p. 362 and Appendix pp. 49 and 71. 
 
UPO>I THE FLOUR OF WHEAT. 505 
 
 bread than the flour of any other 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 l)y the height to which, in 
 similar vessels, 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 gra- 
 dually changed inio gum {British gum, p. 113), and into a species of 
 sugar — becoming completely soluble in water. Such a change is pro- 
 duced 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. 
 
 Flour ... 68 .5 — 
 
 Bread . . . 53i 3^ 18 
 
 So that a very considerable portion of gum had been produced at the ex- 
 pense of the starch. 
 
 The yeast which is added to the dough in baking, acts in the same 
 wa}'^ 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 ihe oven. If too much water 
 have been added to the dough — or if it have not been sufficiently knead- 
 ed — or if the flour be too finely groimd — or if the paste be not sufficiently 
 tenacious in its nature, these minute bubbles will run into each other, 
 will form large air holes in the heart of the bread, and will give it that 
 open irregularly porous appearance so much disliked by the skilful 
 baker. Good bread should be full of .«mall pores and uniformly light. 
 Such bread is produced by a strong flour ; that is, one which will rise well, 
 will retain its bulk, and will bear the largest cjuantity of water. 
 
 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 assumed 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 prolonging 
 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 — 
 
 1°. \\Tiile 
 
 Brown* 
 2°. Brown 
 
 White 
 3°. White 
 
 • The brown breast is made from the whole grain of the wheat as it comes from the 
 miUstonee — notliing being separated by sifting. 
 
 )W long baked. 
 
 Water per cent. 
 
 24 hours. 
 
 43-3 
 
 24 do. 
 
 44-0 
 
 42 do. 
 
 44-1 
 
 36 do. 
 
 42-9 
 
 9 do. 
 
 44-1 
 
506 WATKn TAKKN UP BY FLOUR IN BAKING. 
 
 So that wheaten bread otic 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. 
 
 This proportion is almost exactly the same as that contained iu the 
 white bread of Paris. According to Dumas, the water in tht; common 
 white bread of Paris amounts to — 
 
 Hours bakeJ. Water per cetit. 
 
 2 45-7 
 
 4i 45-3 
 
 10 43-0 
 
 24 43-5 
 
 We may assume, therefore, 44 per cent, as very nearly the average 
 quantity of wate i*Jontained in good white bread both in England and in 
 France. Bread baked for public establishments contains 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 widi jiome- 
 made bread. Such is the ca-je witli the soldiers' bread of our own 
 country, and the barr.ack bread of Paris (pain de munition) which con- 
 tains about 51 per cent, of water. 
 
 We have already seen (p. 499) that 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- 
 
 G6J 
 
 Dry flour 56 
 
 Water in the flour (naturally) . lOi 
 
 Water added ])v the baker ' . . . " '. 33i 
 
 ino 
 
 Or, the flour, iti baking, takes up half its weigJil of water. A hundred 
 pounds of flour, therefore, as it comes from the mill, will give very 
 nearly 150 pounds of bread. Thus — 
 
 Flour contains Bread contains 
 
 Dry flour .... 84 84 
 
 Natural water . . . IG 16 
 
 Water added . . 50 
 
 100 
 
 Weight of bread 150 
 A sack of flour, therefore, or 280 lbs., ouglit to give about 420 lbs. of 
 well baked bread. Something must be deducted from this for the lo.s$ 
 by fermentation, and for the dryness of the crusts. Allowing 5 jjercent. 
 for these, a sack of flour shotdd give 400 lbs. of bread of the best quality,* 
 or 100 quartern loaves. The cost of fine white bread, therefore, com- 
 pared Avith that of corn and flour, ought to be very nearly as follows : — 
 
 Cost of Flour, Cost of Brea(), Market price of 
 
 per sack. per stone. per quartern loaf. (Jrain per qr.f 
 
 35s. Is. r>d. 4]d. 47s. 
 
 40s. 2s. Od. 4|d. 52s. 
 
 • Unmixed willi potatoes, wliicli are employeil by many bakers in considerable quantity 
 Mixed with the yeast they are said to make the bread lighter. 
 
 t This column bas been calculated for me, from ilie price of the flour, *iy my friend Mr. 
 John Robsnn, miller, in Uurham. The practical rule i.*, that 6 bushels ol corn should give 
 one sack of flour, and lliat the miller should have the offal for hia trouble. 
 
RELATIVE COST OF CORN, FLOUR, AND BREAD. 507 
 
 Cost of Flour, Cost of Bread, Market price of 
 
 per sack. per stone. per quartern loaf. Grain per qr. 
 
 45s. 2.S. 3d. 5|d. 60s. 
 
 50s. 2s. 6d. 6d. 67s. 
 
 55s. 2s. 9d. 6|d. 72s. 
 
 60s. 3s. Od. 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-cenlage of gluten in 
 Jlotir, 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 wliole 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 ])er- 
 centage of water, though the one sample contained upwards of twice as 
 much gluten as the other. Tlius — 
 
 Gluten per cent Water per cent, 
 
 in the Flour. in the Bread. 
 
 Flour of Brie . . . 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. 
 
 2°. The flour from Odessa wheat contains about Jth more gluten than 
 French flour in general, and yet it absorbs very little more water (Du- 
 mas). This Dumas accounts for by the fact that the starch of the 
 Odessa wheat fonus hard transparent horny particles, which take less 
 water to moisten them than the impalj>able powder yielded by the softer 
 French wheats — so lliat 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 wheats give the best biscuit flour — what the 
 baker calls the strongest, which rises best, and absorbs the most water.* 
 
 3°. Rice is said to contain very little gluten — not estimated by any to 
 amount to more than 6 or 7 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 ap- 
 parent 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 iiave a remarkable influence upon the 
 quantity of water which the flour will absorb. In some parts of Belgium 
 it appears to have been the practice to adulterate the bread with a small 
 quantity of sulphate of copper.J This salt is dissolved in water, and 
 
 * Thai sncli is the case also in foreign countries, see a letter from the British Consul at 
 Lisbon, in Oavy's Agricidlural Chemislry, Lecture III. 
 t Dumas' Tiaitc de Chimie, vi., p. 396. 
 t Blue vitriol — a violent poison. 
 22 
 
508 COMI'OSITION OI BARLKV. 
 
 the solution added lo llie water wiili whicli tlie dough i* to be made, in 
 the proportion of abont one grain to two pounds of flour. It gives the 
 bread a fairer colour, and thus permits i he use of inferior flour, and it causes 
 the bread to retain about six per cent, more water without ap|)earing nioist- 
 er. Even in the small pro])ortion of one grain of the sulphate to G, or 
 7 lbs. of flour, it j)roduces a very sensible etlect (Kuhlrnan). 
 
 Other adulterations also exercise a similar influence. Alum ituj)rovcs 
 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 tliat the addition of salt is a real gain 
 to the baker. 
 
 From all these facts, therefore, we may infer that, independent of tlie 
 relative proportions of gluten, very slight dilFerences in composition — 
 such as have not yet been sougiit tor or appreciated — may materially 
 affect the relative weights of bread obtained by the baker from difierent 
 samples of wheaten flour. 
 
 § 13. 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 in proportions somewhat different. These proportions, ho^v- 
 ever, are affected both by the kind of manure whh which the land is 
 dressed, and by the nature of the soil on which the seed is sown. 
 
 1°. Manure. — The effi;ct of manure a|jpears from the following table, 
 containing the results of Herinbstarlt, obtained in the same way as those 
 with wheat already described (p. 503) : — 
 
 KIND OP 
 
 •*; .at ^ .^ ^ y (TIC •"a:*' i^— - 
 
 MANURE. _ _ _ _ _ 
 
 OxBlood 10-4 13-6 57 04 59'9 46 44 04 0-4 16 
 
 Night-soil lfi-2 13-6 5S 0-5 59-6 4-5 43 0-5 0-6 13 
 
 Slieep's dnn?. .. 10-3 13-5 5-7 0-4 599 le 4-4 0-4 0-3 IG 
 
 Goat'sdung 10-4 13-5 5-7 0-4 599 4-6 4-5 0-4 0-3 15 
 
 Human urine... 10-3 136 5-9 Co 59-6 4-4 4-4 0-4 07 13^ 
 
 Horse duns 10-4 135 57 04 597 4-6 4o 0-4 04 13 
 
 Pigeons dung .. 104 13-5 5-6 0-4 59-S 4-6 45 0-4 0-4 10 
 
 Cow'sdung 10-8 13'6 33 0-2 61-9 4-S 4G 0-3 0-3 11 
 
 Veget. manure.. 10-8 136 29 0-2 62-2 4-9 48 02 0-1 7 
 
 No manure 10 8 13-6 2-9 0-1 62-5 5-0 47 O-l 0-1 4 
 
 In so far as reliance is to be placed upon the numbeis in the abo\'e 
 table, as indicative of the general efTect of the several manures men- 
 tioned, it would appear that the relative ])roportions of gluten, albumen, 
 and starch do not vary very much until we come to cow-dung, when the 
 former two substances sensibly diminish. Further exi)eriments, how- 
 ever, are required upon tliis subject (see page 514). 
 
 2°. Soil. — The effect of soil upon the barley crop is known (o all 
 practical farmers — so that the terms barley-land and wheat-land are the 
 usual designations for light and heavy soils adapted especially to the 
 growth of these several crops. On clay lands the iiroduce of barley is 
 greater, but it is of a coarser quality, and dors not malt so well-^)n 
 loams it is plump and full of meal — and on light chalk soils tJie crop is 
 light, but the grain is thin in the^kin, of a rich colour, and well adapted 
 
EFFKCT OF MALTING UPO.N BARLKV* 509 
 
 for malting.* The barley of the light lands in Norfolk is celebrated in the 
 Nortli of England for its inalthig properties — and the brewers refuse tlie 
 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 fat- 
 tening food for pigs and for some other kinds of stock. 
 
 § 14. Effect of inaUlng upon barley. 
 
 During the germination good barley increases in bulk one-half. Ill 
 order that il may do so, it must be uniformly ripe-^-a quality of great 
 value to the maltster. This maxiniuiw bulk is generally acquired in 24 
 hours after it lias been moistened and laid in heaps. In drying, how- 
 ever, the barley again diminishes in bulk, so that the dried malt raiT.ly 
 exceeds by more than f^.th or j-,th the bulk of the grain as it came from 
 the market. The well-dried malt, liowever, is lighter by ]th tnan 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 drjing the 
 barley itself before 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 fi)rni 
 the malt-dust {cummins), of which I have already spoken (p. 436) as 
 being a vaUiable manure, and of which 4 or 5 busliels 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 nurlt is obtained, which 
 gives a very white beer. A heat not rising aliove 180° gives an amber 
 coloured malt — while for brown malt the temperature may rise as higli 
 as 260° F. By mixing these varietiesbeer of any colour rnaj' be made. 
 But in the porter breweries it is usual to prepare a (piantiiy of malt of a 
 brownish black colour {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 converted into 
 diastase (p. 119), and about two-fifths "(40 per cent.) of its starch into 
 sugar or gum (dextrine). The quantity ol' diastase produced depends 
 upon the extent to which tlie germination has proceeded. It is greatest 
 at the moment when the gemmule is about to burst from the seed, and to 
 fonn the young shoot. 
 
 I have already ex[)lained 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 qtiantity of diastase is pro- 
 duced. It is sufficient if the gemmule, on holding up a grain of the 
 barley, be seen within the skin to have attained one-lialf or two-thirds of 
 the length of the seed. The diastase then jiroduccd is more than enough 
 to convert the whole of the starch of the grain into sugar (p. 120). 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 j)ossible supply of diastase may be contain- 
 ed in it. In this way also malt is prepared when it is to be employed 
 
 • "The barloy on the rom pact clays (in Hants) is of a coarser quality, tiut produce greater — 
 on the liirht chalk soils it i.s well calculatcil for malting — Ihe t^kiti is Ihin, and colour rich but 
 lislit— in fullness of meal and pUimpnesis of appearance it never equals ilie barleys grovsTi in 
 Slaffordshire, and upon loamy lands."— Mr. Gawler in Bntish Hitsburtdry, iii. p. 12. 
 
510 COMPOSITIOJT OF OATS A«D RYE. 
 
 in the manufacture of synip {glucose) from jiotatoe flour — a branch of in- 
 dustry which has become of some '.niportance in certain parts of France. 
 
 §15. Composition of oats, and effect of man ures in modifying that composition. 
 
 The relative proportions of husk and meal in the several varieties of 
 the oat differ in a greater degree, probably, than in any other grain. 
 Thus, the potatoe-oat is known to be richer in meal, the Tartar^'-oat in 
 husk. The round grain of the former is chiefly grown in Scotland, for 
 grinding info meal, The latter in England, for feeding horses. 
 
 But even the round potatoe-oat varies much in the produce of meal 
 whicli it gives. Many samples yield only half their weight of oatmeal, 
 others 9 stones out of IG, while some give as much as J 2 stones from the 
 same quantity, or threc-tijurtlif* of their weight. In one variety of oat 
 Vogel found 66 per cent, of meal and 34 of husk, which is equal to 10| 
 stones of meal from 16 of grain. He also extracted from the meal 2 per 
 cent, of oil, and 59 of starch, and observed it to lose by drying upwards 
 of 20 per cent, of water. 
 
 Soil, season, climate, variety of seed sown, and the kind and ([uantity 
 of manure appHed — all aflect the amount of produce and the cliemical 
 composition of the oats that are reaped. According to Hermbstadt, the 
 effect of diflTerent manures in modifying the composition of the produce 
 of the same seed are represented by the numbers in the following table : 
 
 si . d x: ^ -2 ,■■''" E'o 
 
 KIND OP aj J<! B a ~ '•' « P -Cobs' -^.-d 
 
 MANURE. ^ 3 =£5 rt I" 3 ■= -Si^oSi-g 
 
 > KU<3r7)!KUSi£ft< =.>8 as ^ n 
 
 Ox Blood 12 19-3 5-0 04 53-1 3-8 5\'. 0-3 04 12V 
 
 Niijhisoil 121 19-2 4-6 0-4 533 3-8 5-4 0-3 0-5 I4i 
 
 Sheep's duns... 12-6 133 4-0 0-5 54'0 52 5-5 03 04 14 
 
 Goai'sfliing. ...12-9 170 4-3 04 532 54 5-7 0;5 04 15 
 
 Human urine... 130 170 44 0'5 531 5-0 5-7 04 0-6 13 
 
 Horse (lung 13-1 160 40 Q-b 545 52 56 0'3 05 14 
 
 Pigeon's dung .. 123 lS-3 3-2 0-3 53-2 5-0 68 03 03 12 
 
 Cowdun<! 11-6 150 3-1 03 550 6-S 73 03 03 16 
 
 Veget. manure.. 10-S 130 2-0 0-2 .59-9 6-4 7-0 02 0-2 13 
 
 TJnmanured 10 8 120 1-9 02 600 6-4 7-0 0-3 01 5 
 
 The differences in this table are very striJdng [see p. 515]. 
 
 § 16. Composition of rye, and effect of different man ures upon its composition. 
 The grain of rye approaches nearest to that of wheat in the quantity 
 of gluten it contains, and in the consequent fitness of its flour for baking 
 into bread. It .sometimes also contains mucli sugar — recent rye-bread 
 having almost invariably a sweet taste — but the proportion of sugar ap- 
 pears to be by no means constant. Thus Einhof and Greif exliibit the 
 composition of a sample of rye-flour, examined by each of them, re- 
 spectively as follows : — 
 
 Einhof, per cent. Grief, per cent. 
 
 Husk ... 6-4 — ■ 
 
 Gluten (not dried) . 9-5 12-8 
 
 Albumen . . . 3-.3 3-0 
 
 Starch .... 61-1 58-8 
 
 Sugar .... 3 3 10-4 
 
 Gum . . . .11-1 7-2 
 
 Loss .... 5-3 7-8 
 
 100 100 
 
COMPOSITION OF RICE. 511 
 
 Perhaps no great degree of faith is to be placed in these analyses. If 
 they are to be depended upon, they show that very remarkable differ- 
 ences indeed may exist in the relative proportions of some of the consti- 
 tuents of rye flour. The flour of rye is said to be more absorbent of 
 moisture from the air than ihat of any other grain.* 
 
 Rye delights in a sandy soil, and is cultivated in general in such as 
 are poor in vegetable matter, and to which manure is not very abun- 
 dantly added. The experiments of Hermbstadt, whose results are ex- 
 hibi.ted in the following table, do not show any very striking difference 
 to have been produced upon the composuion of the grain by the use of 
 the different animal manures : — 
 
 ^ • = J= %: . -S • s" E"° • 
 
 KIND OP « J<: SicS-l «e --S- =-.•= 
 
 MANURE. S 3 .= =2; 2 3= ~'o-c.= "»^i;« 
 
 > S a <S IT. 5CC5 O 'CS^ ^^ (l^-Z'J2 
 
 OxBlood 10 1 10-4 120 3-6 52-2 36 6-2 10 OS 14 
 
 Niisht-soil 100 10-7 119 32 524 35 6-3 0-9 0-9 13| 
 
 Sheep's dung... 100 10-8 11-9 34 52 3 36 61 1-1 06 13 
 
 Goat'sdiing. ... 100 10-8 II 9 3-4 522 35 60 10 09 12i 
 
 Human urine... 101 10 S 120 3-5 50-2 33 46 1-1 42 13 
 
 Horse.iung 10 107 119 28 512 40 4-6 1-0 36 11 
 
 Pigeon's dung .. 10 1 105 11-6 37 .522 37 47 09 23 9 
 
 Cowduns! 100 104 108 20 &1-3 3-9 5-7 0-9 1-8 9 
 
 Ve£i!t. manure.. 10 10-7 8-8 2-6 551 4-8 5-2 0-9 17 6 
 
 Unminured 10 101 86 2-6 56-3 47 5-4 09 13 4 
 
 The above table exhibits a larger increase in the return or produce 
 from some of the animal manures than from others, but we do not see 
 any of those remarkable differences in the composition of the flour, whix;h 
 are observable in the results obtained by the application of different 
 manures to the wheat crop. 
 
 The substance extracted from rye, and called gluten by Hermbstadt, is 
 different from the gluten of wheat, and is more like xh& glutine extracted 
 from the latter grain. When dough made of rye flour is washed in 
 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. Like the gluten 
 of wheat, it is now insoluble in water, and is less cohesive than gluten. 
 Both of these forms of gluten are supposed to have the same composi- 
 tion as vegetable fibrin and albumen, and as the curd of milk. 
 
 § 17. Composition of rice, maize {Indian corn), and buck-wheat. 
 
 1°. Rice is usually supposed to differ from other kinds of grain by the 
 larger proportion of starch which it contain.s. 
 
 The large quantities of rice consumed by the native inhabitants of 
 India, and of other warm countries, has often appeared surprizing to 
 foreigners. Chemists have explained this alleged fact by .supposing the 
 small per-centage of gluten contained in rice, as shown by the following 
 analyses, to be insutiicient for the sustenance of the body — when no 
 other food is used — unless this grain be eaten in exceedingly large quan- 
 
 ' A samiile of rye meat, dried in my laboratory, lost only HH per cent, of water, and of 
 rye bread leavened 44, and yeasted 40 per ceM. This rye meal may possibly have been 
 mixed. 
 
filii OK MVIZK OK INDIAN CORN. 
 
 lities. It is probable, lJO^\■(•ver, that tlie nitrogenous constituents of rice 
 are stated too low in the analyses of Braconnot, and that it contains all)u- 
 men or casein, or some analogous substance, which has been passed over 
 by this chemist. A .-series of carefully repeated analyses of difierent 
 varieties of rice, if it did not modify, would at least fix our present opin- 
 ions in regard to its theoretical value as food for man.* 
 
 Two samj)les of rice examined by Braconnot, were found by him to 
 be composed of — 
 
 Carolina. Piedmont. 
 
 Water .... 50 7-0 
 
 Husk .... 4-8 4-8 
 
 Gluten .... 3-6 3-6 
 
 Starch .... 85-07 83-8 
 
 Sugar .... 0-3 0-05 
 
 Gum .... 0-7 0-1 
 
 Oil 0-13 0-25 , 
 
 Phosphates . . 0-4 0-4 
 
 100 100 
 
 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 rem_arkably fat- 
 tening qualities when given to poultry, pigs, and cattle. Buckwheat 
 is also a very nourishing grain. They consist respectively of — 
 
 Dry maize (Payen). Buckwtieat (Zenneck). 
 
 Husk .... 5-0 26-9 
 
 Gluten, Arc. . . . 1-2 10-7 
 
 Starch . . . • 7-1 52-3 
 
 Sugar and gum . . 0*5 8-3 
 
 Fatty matter . . . 8-9 0-4 
 
 Colouring matter . . 5-05 — 
 
 Salts .... 1-8 ? 
 
 24-53_f 98-6 
 
 The above analysis of maize must be incorrect, as it supposes the fatty 
 matter to amount to nearly 36 per cent, of the weight of the corn. 
 Dumas has lately stated it at 8"9^;er cent. — instead of 8-9 in 24-55 parts, 
 as found by Paj'en — and Liebig denies that Indian corn contains more 
 than 5 per cent, of fatty matter. New analyses, therefore, are required 
 of this grain also. Indeed it may be said in general of all the substances 
 used, especially in feeding animals, that we have not yet the requisite 
 knowledge to enable us to reason accurately in regard to the special ope- 
 ration of each in sustaining the body or in promoting tJie growth of fat. J 
 
 ' Five varieties of rice, as il is sold in the shops, examined in my laboratory, lost of water 
 and gave of ash per cent, re.^peclively — 
 
 Water. Ash. Water. Ash. 
 
 Madras rice .... 13 .5 CvS I Carolina rice . . . 130 033 
 
 lliiisal rice .... 13 1 4.5 Uo. Jlour . . 14-6 0-35 
 
 P.ilna rice .... 13-1 0'J6 | 
 
 The water in tliese samples is very much greater than in those examined by Braconnot. By 
 exposure to the air the rice in a few days n"-absorl>ed nearly all it had lost by drying. The 
 ash of rice contains more alkaline riiatipr tlian that of wheat, and is very ditficiilt to burn while. 
 
 t Dumas, Traile de CItimie, vi., p. 394. 
 
 t A sample of Indian corn examined in my laboratory, lost of water 136 per cent., and 
 left of while earthy ash 1-3 per cent. 
 
CK>KRAL KKKKCr OF MA.M'RIH. 513 
 
 § 18. On the alleged general effect of different mavures in modifying the 
 amount of gluten and albumen in wheat, barley, oats, and rye. 
 
 Among the general deductions in regard to the S])ecial influence of 
 manures upon the quality of the grain we reap, that which has heen re- 
 ceived with the greatest confidence is this — that the richer in nitrogen the 
 manure we apply, the richer in gluten, the grain, we reap. 
 
 The only e.\])erinK'nts, hasing any pretensions to ac(;uracy, hy whicli 
 this opinion has hitlierto been siijjported, arc tliose of Hermbstadt. The 
 results of these exi)eriments are contained in the four tables lo which I 
 have directed your attention under the heads of Avheat, barley, oats, and 
 rye. As the opinion founded upon them is one which, if correct, is of 
 great practical value, — it will be proper to examine the experiments them- 
 selves a little more narrowly. Are they really deserving of implicit 
 credit ? Do thev juslily the conclusion that has been drawn from them ? 
 
 Turn first to the experiments upon wheat, of which the results are 
 embodied in tlie following table, repeated from page 50;3 : — 
 
 CB 
 
 Htmin UlDld. 
 
 Water 4-3 
 
 Gluten 34-2 
 
 All)umen 10 
 
 Starch 41-3 
 
 Sugar 11) 
 
 Gum ]-8 
 
 Fatty Oil 0-9 
 
 SolublePliospliates,&c. 0-3 
 Husk and bnui I3'9 
 
 99-8 99-7 99-7 99-7 99-7 99G 99S 99-7 M'S 99-7 
 1°. Water present. — The water in each of these 10 3j)ecimens of grain 
 was nearly the same, about 4[ jier (•ent. 1 have already stated the quan- 
 tity of water in English flour to amount to about ..IG ])er cent, on an ave- 
 rage. Many samples of wheat also liave been dried in my laboratory. 
 FroTii tlie results I extract the to] lowing, showing the water lost b}' corn 
 grown in four diflcrent parts of ilie world : — 
 
 Englisl), Lammas red 15-1 per cent. 
 
 Scmiiioti' wheat 13-2 " 
 
 St. Petersburg 16-1 " 
 
 Burlelia wheat 13-1 
 
 This weight of water is lost when the grain, as it is sold in the market, 
 is crushed and tlien lieated to a temperature not exceeding 220° as long 
 as it loses weight. 
 
 The above quantities of water are very much greater than tliose founil 
 in the wheat-s of Hermbstadt. I cannot offer these results, however, as a 
 j)/-oo/ of inaccuracy on the part of tliis experimenter, as I have not had 
 access to his original memoir. It is only fair towards him, therefore, to 
 conclude that, before they were subjected to analysis, his wheats had been 
 artificially dried in a very considerable degree. 
 
 2°. oil in the different samples. — Again, it appears remarkable thai 
 the quantity of oil in all the samples of wheat in the above table is nearly 
 identical, and is also very small. I have examined the fine flour yielded 
 by several samples of the same wheat, grow n by INIr. Burnet, of Gad- 
 
 '■?. S 
 
 c . 
 
 4. = 
 
 U T3 
 
 
 c 5 
 tE-5 
 
 1^ 
 
 c .* 
 C-5 
 
 I'll 
 > E 
 
 11 
 
 11 fold. 
 
 l-'fold. 
 
 12fulcl. 
 
 12 r-jid. 
 
 lu fold. 
 
 9 fold. 
 
 7 fold. 
 
 5 fold. 
 
 3 fold. 
 
 4-2 
 
 4-2 
 
 4-3 
 
 4-2 
 
 4-3 
 
 4-3 
 
 4-2 
 
 4'2 
 
 4-2 
 
 33-9 
 
 32-9 
 
 32 -9 
 
 Sfrl 
 
 13-7 
 
 12-2 
 
 12-0 
 
 90 
 
 9-2 
 
 1-3 
 
 1-3 
 
 1-3 
 
 1-4 
 
 M 
 
 0-9 
 
 ro 
 
 0-8 
 
 0-7 
 
 41-4 
 
 4':>-s 
 
 42 '4 
 
 39'9 
 
 61-0 
 
 63-2 
 
 62-3 
 
 65-9 
 
 6C-6 
 
 10 
 
 ir, 
 
 1-5 
 
 1-4 
 
 10 
 
 1-9 
 
 1-9 
 
 1-9 
 
 1-9 
 
 l(i 
 
 1-5 
 
 1-5 
 
 10 
 
 1-0 
 
 1-9 
 
 1-9 
 
 10 
 
 1-8 
 
 11 
 
 10 
 
 0-9 
 
 1-0 
 
 10 
 
 O'.t 
 
 1-0 
 
 10 
 
 in 
 
 0-6 
 
 0-7 
 
 0-7 
 
 0-9 
 
 0-0 
 
 Oo 
 
 
 
 0-5 
 
 0-3 
 
 14 
 
 13 8 
 
 14-2 
 
 14-2 
 
 14-0 
 
 110 
 
 14-9 
 
 140 
 
 14 
 
514 OIL IN DIFfKREXT SAMPLES OF WHEAT. 
 
 girth, upon the same field, but dressed with different manures, [Appen- 
 dix, pp. 55 and 71,] and the proportions of oil which they yielded in 
 the state in which tliey came from the mill, were as follows : — 
 
 Per cent. 
 
 1°. From the undressed soil 1-4 
 
 2°. Dressed wlili guano and wood-ash 1*9 
 
 3°. With artificial guano and wood-ash 2-2 
 
 4°. Sulphated urine and wood-ash 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 
 
 The two facts — that the ([uantity of oil in nearly all the above sam- 
 ples is so much greater than was found by Hermbstadt in any of his 
 specimens, and that the proportion varied with the kind of manure with 
 which the wheat had been dressed — those two facts, I think, sIjow that 
 the analyses of Hermbstadt have not been made with such a degree of 
 accuracy as to justify us in relying with confidence upon the general de- 
 ductions to which tliey seem to lead. 
 
 3°. Relative effects of these manures upon differ evt crops. — If we com- 
 pare togetlier the relative proportions of gluten and albumen contained in 
 the several samples of wheat, bai'^ey, oats, and rye, examined bv 
 Hermbstadt, and exhibited in his tables, we shall find that the effects of 
 his manures were by no means unifo'm upon the several crops. Thus, 
 when manured with — 
 
 Tht gluten and albumen per cent, 
 taken together were in the 
 Kinil of Manure. Wticat. Harley. Oals. Rye. 
 
 Ox blood .... :i5-2 61 54 156 
 Night soil . . . . 35 2 6'3 5-0 151 
 Sheep's dung . . . 342 61 45 153 
 Human urine . . . Sti 5 64 4 9 155 
 Horse dang . . . 148 61 4 5 14 7 
 Pigeon's dung . . . 131 6 35 153 
 Cow dung .... 130 35 34 128 
 Nothing . . . . 9 9 3 21 112 
 
 Upon the numbers in this table I ofTer you the following remarks :— ■ 
 a. Upon the wheat, the eflfect of tlie horse and pigeoti's dung, in in- 
 creasing the amount of gluten and albumen, was little more than one- 
 fifth of that produced by the sheep's dung. Thus the wheat contained 
 of gluten and albumen, — 
 
 Per cent. Increase of gluten. 
 
 Undressed 9-9 — 
 
 With sheep's dung . . . 34'1 24-2 per cent. 
 
 With horse dung . . . . 14-7 4-8 
 
 With pigeon's dung . . . 13-1 3-2 
 
 But we have seen (p. 470) that in so far as the nitrogen is roncemed, 
 dry horse and sheep's dung ought to produce equal effects, while pigeon's 
 dung should have three times the effect of either.* Whatever be the 
 cause of the increasgd proportion of gluten in the experimental wheats 
 of Hermbstadt, it cannf)t, therefore, have been owing solely to the pro- 
 portion of nitrogen in the manures he applied. 
 
 * 22 of dry pigeon's dung are equal to 65 of sheep's, or 64 of horse's dung. 
 
DIFFERENT PROPORTIONS OF GLUTEN. 515 
 
 6. A_a;ain, upon the barley, oats, and rye, the sheep's dung produced 
 little more effect than the horse's dung. It niiglit be said that this was 
 because these two manures contain nearly the same proportions of nitro- 
 gen. But if so, why did they not produce like effects also upon the 
 wheat ? — and why did pigeon's dung impart less gluten than either, to 
 all these varieties of grain ? 
 
 c. The unsatisfactory nature of these experiments is still more clearly 
 seen when we compare the rehuive proportions of nitrogen, contained in 
 the several manures applied, with the proportions of the same element 
 contained in the several crops to wliich these manures had been added. 
 
 This comparison is made in the following table — ihe quantity of nitro- 
 gen in sheep's dung and in the crops manured with it being called 
 100 :— 
 
 Proporlions of Proportions of nitrogen added to the 
 Manure arplied. "^TAlllne. '^'°'' "' "'^■ '' "^^""^"•' 
 
 Wheat. Barley. Oala. Rye. 
 Sheep's dung ... 100 100 100 100 100 
 
 Horse dung ... 102 IG 75 100 66 
 
 Pigeon's dung . . 300 9 48 43 55 
 
 Cow dung ... 97 6 1 6G 22 
 
 The relation which exists among the numbers in the first of the above 
 columns, is totally unlike that which exists among those in any of the 
 others. In none of the crops does the quantity of nitrogen in the manure 
 bear a 'perceptible relation to that contained in the grain that was reaped. 
 The theocy, therefore, that the quantity of gluten in the crop is always 
 determined by that in the inaimre, and that the amount of gluten in the 
 grain we reap may at pleasure be increased by the use of manures 
 which are rich in nitrogen — this theory derives in reality no solid support 
 from the experiments of Herrnbstadt. The theory may indeed be correct, 
 but it is not sustained by any rigorous experiments iiitherto made — and 
 the prudent man will place little reliance upon it, until its correctness 
 shall have been proved by future and more rigorously conducted investi- 
 gations. 
 
 § 19. Composition of peas, beans, and vetches. 
 
 The seeds of leguminous plants in general contain a large quantity of 
 a substance — very analogous to the gluten of wheat — to which the name 
 of legu'nin has been given. 
 
 To extract this legumin, bruised beans, peas, or vetches, are steeped 
 in tepid water for some hours, then rubbed to a pulp in a mortar with 
 their own weight of warm water, and, after an hour, strained through 
 linen. The strained liquid deposits, at first, a quantity of starch, but is 
 obtained nearly clear by filtration. To the fihered .solution diluted 
 acetic acid (vinegar) or sulphuric acid is added in stnall quantity, when 
 the legumin coagulates and falls in the form of nearly insoluble flocks, 
 
 * These columns are calculated by multiplying together the Increase of crop and the in- 
 crease in the per centage of gluten and albumen. Thus in the case of wheat — 
 
 Increase of crop. Increase of gluten. Product. Proportions. 
 
 Siieep'sdung 9 fold X 24 3 per cent. = 218 7 = 100 
 
 Horse dung 7 fold X 4 9 per cent. = 34-3 = 16 
 
 Pigeon's dung 6 fold X 3-2 per cent. = 19 2 = 9 
 
 Cow dung 4 fold X 31 per cent. = 124 = 6 
 
 22* 
 
616 COMPOSITION OF PKAS, BEANS AND LENTILS. 
 
 which are easily collected on a filter. The addition of an excess of arid 
 will re-dissolve the coag\ilatetl leguuiin, which is again thrown down hy 
 a few drops of a solution of carbonate of soda or of ammonia; a slight 
 excess of either of the latter, however, will cause the precipitate a second 
 time to disappear. The legumin of the pea and bean, therefore, differs 
 from the gluten of wheat, in being soluble in water (Dumas), and in very 
 dilute acid or alcaline solutions. 
 
 The solution of legumin in water is coagulated when heated nearly to 
 boiling, in which respect it resembles albumen (white of egg), and it is also 
 coagulated by rennet, in which, and in its relations to acids and alcalies, 
 it resembles casein, the curd of milk. Legumin has, indeed, by Liebig, 
 been called vegetable casein, trom an impression that it is identical in 
 composition and properties with tlie ])ure curd of milk. 
 
 The semi-transparent soluiion of legumin in waier, obtained directly 
 from beans or peas, gradually becomes opaque, and slowly deposits the 
 legumin in an insoluble stare. Tliis is owing to the production of a 
 small quantity of acid by the decomposition of the sugar or other sub- 
 stances present in the licpiid. This acid slowly coagulates the legumin 
 in the same way a? when dilute acids are artificially adtled to the solu- 
 tion. It is proper to mention that other chemists consider legumin, like 
 casein, [see the following lecture,] to be nearly insoluble in water, and 
 that in the solutions from the bean and the pea it is rendered soluble by 
 the presence of a little potash, soda, or lime — the liquid beconiing turbid 
 as soon as a quantity of acid is formed to combine with these alcaline 
 substances. According to Dumas, pure legumin dried in vacuo at 284° 
 F. consists o(^ — 
 
 Fibrin 
 Legumin. c,( 
 
 Carbon 504 53'23 
 
 Hvdrogen .... G'J 701 
 
 Ni'irogen .... l8-2 lG-41 
 Oxygen, sulphur, & 
 
 phosph 245 2335 
 
 Albumen 
 
 Glutiiie 
 
 Ca.sein 
 
 of 
 
 of 
 
 of 
 
 Wheat. 
 
 Wheat. 
 
 Wheat. 
 
 53-74 
 
 53 05 
 
 53-46 
 
 711 
 
 7-17 
 
 713 
 
 15ti5 
 
 15 94 
 
 16-04 
 
 23-50 
 
 23-84 
 
 23 37 
 
 100 100 100 100 100 
 
 For the purpose of comparison, I have inserted th.e composition, ac- 
 cording to the same chemist, of the several nitrogenous compounds ex- 
 isting in wheat. . 
 
 If these analyses be correct, legumin contains more nitrogen than the 
 fibrin, the albumen, the glutine, or llie casein of wheat, and is almost 
 identical with the gelatine of bones. The important consequence deduced 
 from this fact, by Dumas, in reference to the feeding of animals, -we shall 
 consider in a sub.sequent lecture. 
 
 Above, I have given the composition of legumin, the nitrogenous 
 principles contained in peas and beans, as found by Dumas, Irom which 
 it would appear to contain more nitrogen than any of the other vegetable 
 principles hitherto found incultivaled grains. The legumin analysed by 
 Dumas was extracted from sweet almonds. 
 
 Since the preceding sheet was ])repared for press, a further analysis of 
 legumin, extracted from beans, has been published by Rochleder,* which 
 
 ' Annaien d'.r Cfiem. el Pharmacie, xlvj., p. 155. 
 
ANALYSIS OF LEOUMIN. 517 
 
 does not agree with that of Dumas, but represents this logumin as iden- 
 tical with casein, the curd of milk (see the following lecture), and as dif- 
 feruig in properties as well as in composition from that of the almond. 
 
 The legumin of beans and peas is isoluble in cold water, and the solu- 
 tion, upon evaporation, forms a skin on liie surface which is renewed as 
 often as it is removed. It is not coagulated by boiling, but is immediately 
 thrown down in fine flocks by acetic acid, which, when added in excess, 
 does not redissolve it (Liebig). 
 
 The legumin from sweet almonds is also soluble in cold water, but, 
 like albumen, falls in flocks when the solution is heated nearly to boil- 
 ing. It is precipitated also by diluted acetic acid, and is again dissolved 
 when an excess of this acid is added (Dumas). 
 
 The two substances, therefore, are different in their properties. Their 
 constitution is represented respectively by — 
 
 LEGUMIN PROM 
 
 Beans Sweet almonds 
 (Rochleder). (Dumas). 
 
 Carbon .... 54-5 50-4 
 
 Hydrogen .... 7'4 6-9 
 
 Nitrogen .... 14-8 18-2 
 
 Oxygen .... 23-3 . 24-5 
 
 100 100 
 
 When we come to consider the feeding of animals, we shall find that 
 this difference in the composition of the tv\o varieties will materially af- 
 fect the view we must take in regard ro the action of each in contributing 
 to the support of the various parts of the animal body. 
 
 The approximate composition of the entire peas and beans is thus 
 stated by Einhof. [Zierl Kncychpfsdie, ii., p. 52]. 
 
 Conipositiun o\ Ihe grain. Composition of llic 7ncal. 
 
 Wafer. Iluslt. Meal. Slarrh. Lejpimin. Gum,<fcc. 
 
 Peas 140 10 5 75 5 65 23 12 
 
 Field Beans . . • 15 5 16 2 68 3 690 19 12 
 
 A series o( rigorous analyses of the seeds oT leguminous plants is at 
 present mucli to be desired. According to those of Braconnot and Einhof, 
 certain species examined by them consisted of — 
 
 Kidney Field beans, Lentils, 
 Peas. beans. (Einhof.) dried' 
 
 (Einhof.) 
 
 Water • 12 5 230 156 
 
 Husk 8 3 70 10 187 
 
 Legumin, albumen, &c. . 264 236 117 385 
 
 .Starch 43-6 430 501 328 
 
 Sugur 2 2 „.o 31 
 
 Gum, &c 40 1-5 °- 6 
 
 Oilandfet 1-2 07 1 "? 
 
 Sahs and loss .... 20 l-Q 4-4 09 
 
 1000 1000 1000 lOOOt 
 
 These analyses agree in showing that the seeds of leguminous plants 
 
 • By dryinc, the lentils lost 14 per cent, of water. 
 
 1 Dumas Traite de Chimie, vi. p. 307, comparad witli Thomson's Vegetable Ch^/mstru, 
 p 884, Schubler's AgricuUnT Ckemie. ii., p. lQ4,andSpren£el's Chemie fiir Landwtrthe, U., 
 p. 368. 
 
618 EFFKCT OF SOILS AND MANURES UPON PEAS. 
 
 are especially rich in substances containing nitrogen (Icgurain and albu- 
 men), and arc therefore fitted to contribute much to the nfjurishment of 
 those animals which, in consequence of the state of their growth and 
 licalth, or tht; purposes for whicli they are reared and maintained, require 
 a large supply of this important element. 
 
 § 20. Effect of soils and manures upon the quality of peas and beans. 
 
 The quality of the seeds of leguminous plants is also 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 the husk 
 thinner than when tliat of hogs or oxen has been used." [British Hus- 
 bandry, ii., p. 217.] 
 
 2°. Effect of mineral manures. — The effect of gypsum and of other 
 sulphates upon leguminous plants is universally known (p. 482.) The 
 beneficial influence of a mixture of gypsum and common salt upon 
 sickly crops of beans and peas is very strikingly displayed in the inter- 
 esting experiments of Mr. Alexander, of Southbar, to the details of which 
 1 have already had occasion to draw vour attention. [See Appendix, p. 
 217.] ' L IP ,1 
 
 3°. Effect of lime.—'Dc. Anderson says, " that the pea cannot be 
 reared to perfection in any field which has not been either naturally 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 dnl)' prepared in other re- 
 spects." [Essa3's, ii., p. 302.] 
 
 4°. Boiling or melting quality of peas. — But the most singular cir- 
 cumstance in connection wiili this class of seeds, to which the asiricul- 
 tural chemist has hitherto been directed, is the property possessed by 
 peas and beans of boiling soft or mouldering 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 character. Thus — 
 
 a. Sprengel says *'that peas which are raised after liming or marling 
 boil sojt more easily, and are more agreeable to the taste than when raised 
 after manure." [Die Lehre vom Diinger, p. 297.] 
 
 6. A French authority, on the other hand, quoted by Loudon, [Ency- 
 clopaedia of Agriculture, p. 837,] says, that "stiff land or sandy land 
 that has been limed or marled, or to which gypsiun has been applied, 
 produces peas that tviil not melt in hoiling, no matter what the variety 
 uiay be. The satne effect is produced on the seeds antl pods of beans 
 and of all leguminous plants. To counteract this fault in the boiling, it 
 is only necessary to throw into the wafer a small quantity of the com- 
 mon soda of the shops." 
 
 c. The author of the British Husbandry, [ii., p. 217,] says, "that 
 sLcU marl or lime is found to forward this crop more than any other 
 mineral manure, though it is said to communicate a degree of hardness 
 to the grain which renders it unfit for boiling." 
 
SOME PEAS REFUSE TO BOIL SOFT. 519 
 
 InHeperiflently of all applications to the soil, I believe it is generally' 
 observed that good boilers are produced upon light, sandy, and gravelly 
 soils ; v,-hile heavy, wet, undrained (and newly broken uj) ?) land usually 
 produces bad boiling peas and beans. Thus melting peas {siddcr peas, 
 as ibey are locally called) for the Birmingham 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 produc- 
 ing in general pig* peas or beans only. It is on similar soils that melt- 
 ing 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. Tliat the boiling quality of the pea cro]> is not owing to the qual- 
 ity of the seed — since peas of both varieties have been raised from the 
 same seed.f 
 
 b. That it is not generally owing to the seasons, since some land pro- 
 duces hard peas every year. If the wetness of the soil indeed have any 
 influence, a rainy season may cause the pro-duclion of bad boilers upon 
 kind from which soft peas are usually reaped. 
 
 4°. Cuonicul difference bciicmeti the two varieties of pea. — Why does 
 one of these varieties of pea mt.It more readily than the other ? For 
 the same reason very nearly thai one potatoe boils mealy, and another 
 waxy, and that one sample of barley melts better in the mash-tub than 
 another. Melting peas and barley and mealy potatoes contain a larger 
 proportion of starch than samj)les whicii are possessed of an opposite 
 cjuality. 
 
 The pea, as we have seen, consists essentially of legumin and starch. 
 The former coagulates and contracts, or runs together into a mass by 
 boiling, — the latter, on the contrary, expands, becomes more bulky, tends 
 to burst the husk, and to separate into single grains. If the tendency to 
 contract and cohere be greater than the disposition to expand and sepa- 
 rate — in other words, if the legumin predominate — the pea does not melt, 
 while if the starch be abundant the pea boils well. It is possible that 
 the addition of a little soda may cause hard peas to melt, since legumin 
 is soluble in a solution of soda, but in waters impregnated with lime all 
 peas are said to boil soft much less readily than in such as are free from 
 that ingredient. [Dumas, Traite de Chimie, vi.] 
 
 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 ihey 
 are ascertained to be more nutritive, that they are preferred in this state. 
 When we come to consider the feeding of stock, we shall see that, ac- 
 cording to the present state of our knowledge, the opinion may rea- 
 sonably be entertained that insoluble peas are really better adapted for the 
 feeding and fattening pigs and other stock — the purpose for which they 
 are employed — than those which are possessed of the melting quality, 
 
 It is a ditlerence in the chemical composition of the seeds of legumi- 
 nous plants that makes them melt more or less easily — but by what 
 
 " Much used for the feeding of pigs. 
 
 t Some howevrr suppose it to depend upon the age of the seed, or the time of sowing. 
 —British Husbandry, ii., p. 217. 
 
4 
 
 620 COMPOSITION or potatoes. 
 
 quality in the soil or manure is this ditrerence in composition produced ? 
 In regard to lime the evidence is contradictorj'. Gypsum may render 
 them harder since legumin contains sulpliur, and a portion of die effect 
 of gypsum upon leguminous crops is supposed to arise from its yielding 
 sulphur to the growing plants, and thus promoting the ])roduction of le- 
 gumin. Wet and clay lands also favour the production of legumin 
 more than that of starch — but in what way, we are not yet in possession 
 of experimental results of sufficient accuracy to enable us to say. 
 
 § 21. Of the composition of potatoes, and the effect of circumstances in 
 modifying their compiosition. 
 
 1°. Comjwsition of potatoes. — Potatoes, in addition to much water, 
 consist of starch, gum, woody fibre, and albumen. The proportions of 
 these several constituents are very variable. Thus, according to 
 Einhof and Lampadius, the follow ing kinds of potatoe consisted in 100 
 parts of — 
 
 2°. Influence of the state of ripeness. — According to Korte the quan- 
 tity of dry solid matter contained in the potatoe depends very much upon 
 the stale of ripeness to which it has attained. The ripest leave 30 to 32 
 per cent, of dry matter, the least ri])e onl}' 24 per cent. The per 
 centage of starch varies from 8 to 16 per cent. The mean result of his 
 examination of 55 varieties of potatoe gave him for the solid matter 24'9, 
 and for the starch 11-85 per cent. [Schiibler, Agricultur Chemie, ii., p. 
 213.] 
 
 3°. Influence of variety. — Much appears also to depend upon the 
 variety of potatoe. Thus the following varieties of j-'otatoe grown at 
 Barroclian in Renfrewshire, in 1842, yielded respectively — 
 
 Connaught cups .... 21 per cent, of starch. 
 
 Irish blacks 16^ 
 
 White dons 13 " 
 
 Red dons 10? " 
 
 — wliile, according to a starch manufacturer in the neighbourhood, 11^ 
 per cent, has been the average cpiantity obtained from the common 
 rous^h red of good quality during the last four years. 
 
 The difference in the quantity of starch yielded by the above-named 
 varieties is tlie more striking when taken in connection whh 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. 
 
 Cups, with 4 cwt. of guano 135 tons 2-9 tons. 
 
 Tied Dons, witli 4 cwt. of guano 14{ " IS '■ 
 
 White Duiis, wiih 3 cwt. of guano ISJ" " 2 4" 
 
 So that, of these three crops, that of cups, which weighed the least, 
 gave the largest produce of starch. It yielded nearly twice as mucli as 
 the red dons, which were half a ton lieavier, and one-fifth more than 
 even the white dons, the crop of which was greater by five tons an acre. 
 Such differences as tliese, in the relative quantities of starch, which may 
 be obtained from an acre of the same land bj' the growth of different va- 
 rieties of potatoe are deserving of the attentive con.sideration of the prac- 
 tical man. 
 
 See ApptiuUx, p. 61. 
 
THE PROPORTIOjr OP STARCH VAftlES VERY MUCH. 521 
 
 V 
 
 Larger quantities of starch than any of those above stated have been 
 obtained from potatoes by some experimenters. Thus from the 
 
 Per cent, of starch. 
 Kidney potatoe, Dr. Pearson obtained . . . 28 to 32 
 
 Apple do. Sir H. Davy 18 to 20 
 
 Shaw do. VaurjueUn ..... 18"8 
 
 L'Orpheline do. . 24*4 
 
 The first and last of these proportions are probably very rare in out 
 climate. 
 
 4°. Effect of keeping. — Those potatoes are said to keep best in which 
 the starch is most abundant, but in general keeping has an effect — 
 
 a. On the proportion of starch. — By keeping till the spring, potatoes 
 lose from 4 to 7 per cent, of their weight, and the quantity of starch they 
 are capable of yielding suffers a considerable diminution. Thus, ac- 
 cording to Payen, the same variety of potatoe yielded of starch in 
 October, 17-2 per cent. January, 15-5 per cent. 
 
 November, 16-8 " February, 15-2 " 
 
 December, 15-G " March, " 15-0 
 
 April, 14-.5 
 
 This diminution is probably owing to the conversion of a portion of the 
 starch into sugar and gum. When potatoes are rendered unfit for food 
 by being frozen and sudilenly thawed, tlie quantity of starch which they 
 are capable of yielding is said to have undergone no diminution. 
 
 6. On the proportion of gluten. — The proportion of gluten also ap- 
 pears to become less when potatoes are kept. Thus, in new potatoes 
 Boussingault found the gluten amount to 2^ percent., but in old potatoes 
 to only li per cent, of their weight. To tliis natural diminution of the 
 l)roportion of starch and gUiten, is probably lo be ascribed llie smaller 
 value in the feeding of stock, whicli experience has shown \'ery old po- 
 tatoes to possess. 
 
 5''. Effect of soils and manures. — The potatoe thrives best on a light 
 loamy soil — neither too dry, nor too moist. The most agreeably flavour- 
 ed table potatoes are almost alwa^'s produced from newly broken up 
 pasture ground, not manured, or from any new soil. [Loudon's Ency- 
 clop-tcJia of Agriculture, p. 847.] When the soil is suitable, llie}' delight 
 in mucii rain, and hence the large crops of potatoes ol)tained in Ireland, 
 in Lancashire, and in the west of Scotland. No skill will enable 
 the farmer to produce crojrs of equal weight on the east coast where . 
 
 rains are less abundant. It has not been shown, however, that the rveigh^Ajr 
 of starch produced in the less rainy districts is defective in an equal de- ^ 
 gree. Warm clinuUes and dry s^^asons, 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, 
 liowever, the land in the neighbourhooil of some of our large towns, 
 where this crop is valuable, have been made to produce potatoes and 
 corn ever}- other year, for a very long period. 
 
 G". Influence of saline 7nanures. — I have alread)^ drawn vonr attention 
 to the remarkable inlluenne of certain saline substances in promoting the 
 growth of the potatoe crop in some localities. TJie most striking effects 
 of this kind hitherto observed in our island have been produced by mix- 
 
522 OCCASIONAL FAILURE OF SF.KD POTATOES. 
 
 tares of the nitrate of soda witli tlie suljihate of soda or with tlie sul])hat? 
 of magnesia.* The effet-t of such mixtures aHords a heautiful illustration 
 of the principle I have fre(|uently bel()re had occasion to press upon youi 
 attention — that plants reijuire for their healthy growth a constant supply 
 of a considerable number of dilForent organic and inorganic substances. 
 Thus upon a field of jiotatoes, the whole of which was manured alike 
 with 40 cart loads of dung, the addition of — 
 
 a. Nitrate of soda alone gave an increase of 3| tons. 
 Sulphate of soda alone gave ... " 
 While one half of each gave ... 5| " 
 
 h. Sulphate of ammonia alone gave . . 1^ 
 
 Sulphate of soda 
 
 But one half of each irave .... 6] 
 
 c. Nitrate of soda alone gave ... . 3r " 
 Sulphate of magnesia alone gave . . a " 
 And one half of each gave .... 9j " 
 
 These results are very interesting, and when confirmed by future re- 
 petitions of such experiments — and followed up by an examination of 
 the (juaUty and composition of the several samples of potatoes produced— 
 cannot fail to lead to very im])ortant j)ra('tical conclusions. 
 
 7°. Occasional failure of seed potatoes. — The seeds of all cultivated 
 plants are known at times to fiiil, and the necessity of an occasional 
 change of seed is recognised in almost every district. In the Lowlands 
 of Scotland potatoes brought from the Higlilands arc generally pre- 
 ferred for seed, and on the banks of the Tyne Scottish potatoes bring a 
 higher jirice for seed tlian those of native growth. This su])erior quality 
 is supposed by some to arise from the less perfect ripening of the up- land 
 potatoes, and in conformit}' with this view the extensive failures which 
 have taken place during flie present summer (1843) have been ascribed 
 to the unusual degree of ripeness attained by the potatoes during the 
 warm dry autumn of the past year. 
 
 This may in part be a true explanation of tlie fact, if — as is said — the 
 ripest potatoes always contain the largest jiroportion of starch — since 
 some very interesting observations of Mr. Stirrat, of Paisley, would 
 seem to indicate tliat whatever increases the j}i:r-centage of starch, in- 
 creases also the risk of failure in potatoes that are to be used for seed.'; 
 This subject is highly deserving of further investigation. 
 
 ' For the particulars of tlicse experiments see llie Appendix. 
 
 t I insert Mr. Sllrrat's letter upon ttiis subject, not only because his observations are in- 
 teresting in tliemselves, but because they are really deserving of ■the cartful attention of 
 practical men : — 
 
 ''SiH, — The fcillowinff experiment with potatoes was tried with the view of discovering the 
 :anse of so many failures in the crops of late years, from the seed not ve;;i'tatini;, and rotting 
 In tlie ground. I had an i<iea that the vegetative principle of the plant mi^ht l)ecome weaJc 
 in consequence of beins? grown on land th.it liad been a long time subjected to cropping, and 
 not allowed any l('ii2th of lime to lie at re.sf. 1, therefore, raised a few bolls on land thai haij, 
 lain le-i for 70 years (beins pari of my bleach green), and Ibuiid that these on being planted 
 again the following year were remarkably strong and lieallhy, and not a [)lant gave way, and 
 I have continued the same method for the last si.v years, and Ihe result has, in every instance, 
 been e(pially favourable. Four years ago, one boil of my seed potatoes was planted along 
 with some others In a field of about an acre, the other seed was grown on the farm, and the 
 seed all gave way excepting that got from me. They were all planted at the same time and 
 
KFFKCT OF SALINE SUESTAJ<CK3 523 
 
 8°. Effect of saline top-dressings on the quality of the seed. — It may 
 be doubted, however, whether the relative i)ro]iortioiis of btarcli are to be 
 considered as the cause of the relative values of dillerent sam[)]cs of seed 
 potatoes. This proportion may prove a \aluable test of the probable 
 success of two samples when ])lantc(l, without being itself the rea«in of 
 the greater or less amount of failures. Witli the increase of the starch 
 it is probable tiiat both the albumen and the saline matter of the potatoe 
 will in some degree diminish, and both of these are necessary to its fruit 
 fulness when used for seed. 
 
 The value of the saline matter is beautifully illustrated b}' the obser- 
 vation of Mr. Fleming, that the potatoes top-dressed with sulphate and 
 nitrate of soda in 1841, and used for seed in 1842, " presented a remark- 
 able contrast to the same variety of potatoe, ))lanted alongside of them, 
 but which had not been so top-dressed 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 
 (3J tons) an acre." This observation, made in 1842, is confirmed by the 
 ajjpearance of the croj)s now growing {July, 1843) upon Mr. P^leming's 
 experimental fields. The prosecution of the enquiry opened up by bis 
 experiments promises to lead to the most valuable practical results.* They 
 may teach us how to secure at all times a fruitful seed, and thus to dis- 
 pense with supplies of imported produce. 
 
 § 22. The composition of the turnip, the carrot, the beet, and tlie parsnip, 
 
 1°. Composition. — The potatoe is characterised by containing a large 
 proportion of starch in connection with a small quantity of albumen — the 
 turnip and carrot !)y containing, in place of the starch, a variable pro- 
 
 with the same mfiniire. From these circumstances, I am of opinion, that if farmers were 
 careful in raisiiij: their own seed potatoes from land that has lain lonj: in a stale of rest (o) — or 
 where thai cannot be had, the same object can lie obtained by bringinj: new soil to the sur- 
 face by trenching as nnich as is necessary, or by the use of the subsoil-plough — failures of 
 the potatoe crop from the seeil not being good, would become much less frequent 1 am 
 somewhat confirmed in this opinion by the fact, that it lias been found for the last dozen of 
 years that generally the best seed potatoes have been got from farms in the moors or high 
 lands of the country. The reason of this may be that these high lands have bi en but of late 
 brought under crops of any kinil, and many of then> but newly bi ought from a stale of nature, 
 and the superiority of seed polatnes from lliese high lands may not at all arise (as is gene- 
 rally siippos^ed) from a change of soil or climate. 
 
 '• Potatoes raised on new soil, or on ground that has been lone lying lea, are not so good 
 for the table as Ihe otiieis, being mostly very soft, and, by the following experiment, il would 
 appear that they contain a much less cpianlily of farina Ihaii those which are raised from 
 land that has hecn some lime under cro|i, and, perhaps, this is the reason why they arc better 
 for seed. From one peck of potatoes, grown on land near Paisley, which has been almost 
 constantly under crop for the last 30 years, 1 obtained near.y 7 lbs. of Hour or starch; and 
 from the other peck, grown on my bleach green, the cjuanlity oblauied was under 4 lbs., from 
 which It vvouM seem that as the vegetaiive principle of the plant is strengthened, the farina- 
 ceous principle is weakened, and rice versa. Jas. Stirhat." 
 
 Paisley, 22d November, 1S42. 
 
 (a) Mr. Finnie,of Swanslone, informs me that the growinH of potatoes intended forseed upon 
 new land, has long been practised by good farmers. Mr. I, iille, of C'arlesgill, near Langholm, 
 writes me that in Dumfrief:shire, they oblain the best change of potatoe seed from mossy 
 land — of oats and barley from the warmer and drier climate of Roxburghshire. The grains, 
 he adds, ileoenerAle by once sotehig, still looking plump when dry, but having a Ihicker husk, 
 and weighing two or lliree pounds less per bushel. The deteri<iraiion of seeds, in general, 
 is a c/;em/co physiological subject of great interest and importance, and will doubtles.s soon 
 be taken up and investigated. 
 
 • In the ApfifnfUx, p, 47, Ihe experiments are recorded, and in p. 66 I have more fully ad. 
 verted to the iulerestiiiK results likcl-y lo be derived Irom the continuance of such experitnenta. 
 
624 COMPOSITION OF TIIK Tt'RMP. CARROT, A.NU BKET. 
 
 portion of sugar, aiul of a j^elatinous guniniy-like sultsfance, to which 
 the name oi' jjcctin has been given. In the Swedish turnip and in beet- 
 root the sugar ])redominates, in the white turnip and in tlie carrot tlie 
 pectin is usually present in tlie larger (]naniily. 
 
 The composition of the turnip, the carrot, and the beet varies very much, 
 and is influenced by a great variety of circumstances. We are not in 
 possession of an}' recent detailed analyses of these roots. The following 
 table exhibits the component parts of several varieties, as they have been 
 given chiefly by Hermbstadt, [Schiibler, Ag. Chem., ii., p. "207] : — 
 
 Water . . . 
 Starch and fibre 
 Gum (^pectin ?) 
 Sugar . . . 
 Albumen . . 
 Salts .... 
 Loss .... 
 
 Vari 
 
 iety of Turnips. 
 
 Common 
 Cfurrot. 
 
 Sugar 
 
 beet 
 
 (Payen) 
 
 Parsnip 
 (Crome). 
 
 White. 
 
 Swedish. 
 
 Cabb.ige. 
 
 , 790 
 
 800 
 
 780 
 
 800 
 
 850 
 
 79-4 
 
 . 7-2 
 
 5:5 
 
 60 
 
 00 
 
 30 
 
 69 
 
 . 25 
 
 30 
 
 35 
 
 1-75 
 
 20 
 
 61 
 
 . 80 
 
 90 
 
 90 
 
 7-8 
 
 100 
 
 5-5 
 
 . 2-5 
 
 20 
 
 2 5 
 
 11 
 
 -? 
 
 21 
 
 . 05 
 
 0-5 
 
 0-5 
 
 — 
 
 1 
 
 1 
 
 . 0-3 
 
 0? 
 
 05 
 
 oil 35 
 
 ... 
 
 ... 
 
 100 100 100 100 100 100 
 These analyses are very defective, and apply with anv degree of cor- 
 rectness only to the specimens actually operated upon. Any reasonings, 
 therefore, Avhich are founded upon thcni can only lead to probable or ap- 
 proximate conclusions. 
 
 2°. The proportion of sugar contained in the sap of these roots is 
 greatest when they are young, and diminishes as they ripen. In the 
 beet, it lias been observed that the nitrates of potasli and ammonia are 
 present in considerable fjuantity, and that in the old beet these nitrates 
 become 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.* Tiie same may possibly be the case with the 
 coimuon cultivated turnips. It would not be without interest, both theo- 
 retically and practically, to ascertain by experiment, the relative com- 
 position of the same variety of turnip, grown on the same soil, by the 
 aid of rich farm-yard manure, and by the aid of bones or of rape-dust. 
 The one may produce more sugar, the other more albumen or nitrates. 
 Such diflerences may materially aflect the value of the crop, either in 
 the feeding of stock or in the production of an enriching manine. It is 
 in suggesting and carrying on enquiries of this kind tliat the joint labours 
 of the ])ractical farmer and of the theoretical chemist are likely, among 
 other ways, to promote the advancement of a rational and scientific agri- 
 culture. 
 
 3°. Effect of soils arid manures. — These roots delight in a rich, open, 
 and loam}' soil — and the weight of produce varies much wiih the kind 
 of manure tliat may have been applied to them. [See, for many in- 
 structive illustrations of this fact, the experimenls nj)on turnips, detailed 
 in tlie Appendix, pp. 43 el seq.] No experimenls, however, have yet 
 been made to determine the relative proportions of water and of their 
 other constituents which the .same turnips contain, when raided by the 
 
 ' According to Payen, tlie beet, when raised with street manure, contains 20 times as 
 much sallpcire ai wlien raised in the ordinary manner. 
 
WATER IN DIFFERENT VARIETIES OF TURNIP. 525 
 
 aid of tlifferent !n;inures, nor, consequently, the true etTect of these 
 manures upon the relative values of the several crops. 
 
 4^. Qaanlity of water in different varieties of turnip. — The same re- 
 mark may he made in regard to the several varieties of turnip. All 
 those examined by Hermb.stadt, as appears from tlie above tables, con- 
 tained 20 to 2-2 per cent, of solid matier (78 to 80 of water), while other 
 experimenters have found as little a^ from 3 to 15 of solid matter in tur- 
 nips, and generally less in tlie white and la-ge globe turnip than in the 
 yellow and more solid Swede. 
 
 Thus, four varieties of the above roots contain of water and solid mat- 
 ter, according to tliree different experimenters : — 
 
 WATER PER CENT. DRY MATTER PER CENT. 
 
 Einhof. Pltyfair. "^^™''- Einhof. Playfair. ^^^^f^ 
 White turaip 1)2 89 'lijl ' 8 11 21 ' 
 
 Swedish do. 87* 85 80 12.V 15 20 
 
 Cabbage do. 80 — 78 It — 22 
 
 Carrot . . 83 87 ' 80 11 13 20 
 
 The above differences are very great, especially when we look to the 
 relative proportions of dry matter in wliich the nutritive power resides. 
 They are of much importance, therefore, to the feeding of stock, and 
 the circumstances under which they occur, are deserving of a careful in- 
 vestigation. 
 
 5°. Relative nutritive properties of the potatoe and the turnip. — The 
 potatoe is usually considered more nutritive tfian the turnip, w;eight for 
 weight, and no doubt it generally is so. But if we compare together the 
 piantities of solid matter whicii the two roots may contain, we shall see 
 how very far wrong our estimate may be in any special case. Thus — 
 Tbe turnip contains of solid matter from 8 to 22 per cent. 
 
 The potatoe do. do. 24 to 32 " 
 
 — so that, wlule the driest turnips may contain four times as much solid 
 matter as the most watery potatoes, verj^ dry potatoes may contain 
 nearly as mucli as very juicy turnips. It is impossible, therefore, with- 
 out an actual examination of the samples, to pronounce Ujiun the relative 
 amount of food which is likely to be contained m any equal weights of 
 turni[)» and potatoes. Tlie very discordant estimates which diHerent 
 feeders of stock have formed in regard to tlio relative value of these 
 crops in the production of beef or mutton is paitly owing to this cause. 
 [Other causes for these discordant estimates will be stated in Lecture 
 XXI.] Until the effects of equal weights of tlie different kinds of food, 
 estimated in the dry state, are carefully ascertained, it will be impo.ssible 
 to obtain results of a general kind or upon which any real confidence 
 can be placed. 
 
 § 23. Of the composition of the sreen stems of peas, vetches, clover, spiirry, 
 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 at- 
 tained, to the rapidity of their growth, to the nature of the soil, tlie 
 season, and tbe mode of culture. They are generally supposed to be 
 richest in nutritive matter when tlie plant has just come into flower; 
 
526 COMPOSITION OF THK GREEN STEMS OF PEAS, ETC. 
 
 The following table exhibits the approximate composition of tha 
 green stems of some clovers and vetches, as they have been given by 
 Eiuhof and Crome : — 
 
 
 
 
 11 
 
 a 
 
 2 £ 
 
 3 
 
 S 
 
 3 
 a, 
 OS 
 
 m 
 
 t 3 
 
 CM 
 
 o 
 O 
 
 2 s3 
 
 •So 
 
 4) 
 
 = i 
 
 «o 
 
 Water 
 
 800 
 
 76 
 
 800 
 
 750 
 
 77-0 
 
 82-5 
 
 77-5 
 
 795 
 
 860 
 
 Starch 
 
 3-40 
 
 14 
 
 10 
 
 2-3 
 
 2-3 
 
 4-7 
 
 ■2^ 
 
 38 
 
 13 
 
 Woody fibre . 
 
 1031 
 
 139 
 
 11-5 
 
 143 
 
 120 
 
 100 
 
 10-4 
 
 115 
 
 70 
 
 Sugar 
 
 455 
 
 21 
 
 15 
 
 0-8 
 
 — 
 
 — 
 
 — 
 
 — 
 
 — 
 
 Albumen 
 
 090 
 
 20 
 
 15 
 
 19 
 
 2-3 
 
 02 
 
 1-9 
 
 0-7 
 
 1-8 
 
 Extractive matter and 
 
 
 
 
 
 
 
 
 
 
 £;um 
 
 0-65 
 
 35 
 
 3 4 
 
 44 
 
 52 
 
 26 
 
 76 
 
 3-6 
 
 2-9 
 
 Phosphate of lime . 
 
 019 
 
 10 
 
 0-8 
 
 0-8 
 
 0-8 
 
 '/ 
 
 — 
 
 — 
 
 — 
 
 Wax and Resin 
 
 — 
 
 01 
 
 02 
 
 0-6 
 
 -? 
 
 % 
 
 1 
 
 09 
 
 10 
 
 100 100 99-9 100 99-6 100 100 100 100 
 
 § 24. Of the composition of the grasses when made into hay. 
 
 1°. An elaborate examination of the grasses of this conntry, in the 
 dry state, with the view of determining their relative nutritive proper- 
 ties, was made by the late Mr. Sinclair, gardener to the Duke of Bed- 
 ford. His method was to boil in water equal weights of each species of 
 hay tilUevery thing soluble was taken up, and to evaporate the solution 
 to dryness. The weights of the dry matter thus obtained he considered 
 to represent the nutritive values of the grasses from which the several 
 samples of hay were inade. 
 
 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 clitnate, the season, the rapidity of 
 growtlj, the variety of seed sown, and with many other circumstances 
 which are susceptible of constant variation. 
 
 b. That animals have the power of digesting a greater or less propor- 
 tion of that i)art of their food which is insoluble in water. Even the 
 woody fibre of the hay is not entirely useless as an article of nourish- 
 inent — experiment having shown that the manure often contains less 
 of this insoluble matter than was present in tlie food consumed.* (Spren- 
 gel.) 
 
 c. That some of the substances which are of the greatest importance 
 in the nutrition of animals — such as vegetable fibrin, albumen, casein, 
 and legumin — are either wholly insoluble in water or are more or less 
 }»erfectly coagulated and rendered insoluble by boiling with water. Mr. 
 Sinclair, therefore, must have left behind, among the insoluble parts of 
 
 ' lliis will not appear surprising wh(>n it is recollertfHl that, by prolonged diseslion in 
 fliUili>(l sulphuric acid, insoluble woixiy fibre may he slowly chi<jii;ed into soluble gum or 
 sii^ar (see p. 112) The proportion oflhe woody fibre which will be thus worked up in (he 
 stomach of an animal will depend, among othi^r circumstancr-s, upon the constitution of the 
 animal itself, upon the abundance of food supplied to it, luiQ upon the more or less perfect 
 maistication to which the food is subjected. 
 
WOO07 FIBRE A>'D GLUTEN m THE GRASSES. 527 
 
 his hay, the greater proportion of these important substances. Hence, 
 the nature and weight of the dry extracts he obtained could not fairly re- 
 present either the kind or quantity of the nutritive matters which the 
 hay was likely to yield when introduced into the stomach of an animal. 
 
 For these reasons I do not think it necessary to dwell upon the results 
 of his experiments.* 
 
 2°. Woody jihrc in the grasses. — In the stems of the grasses (in hay 
 and straw), woody fibre is the predominating ingredient. They are not 
 destitute of starch, gum, and sugar, but they are distinguished from all 
 the other usual forms of animal food, by the large quantity of woody 
 fibre, and of saline or earthy matter which tliey contain. The propor- 
 tion of woody fibre in the more common grasses, in their usual state of 
 dryness when made into hay and straw, is thus given by Sprengel (see 
 p. 106) :— 
 
 Per cent. Per cent. 
 
 Wheat straw, ripe .... 52 
 
 Barley straw, do 50 
 
 Oat straw, do 40 
 
 Rye straw, do 48 
 
 Indian corn, do 24 
 
 Pea straw, ripe 30 
 
 Boan straw, do 51 
 
 Vetch hay, do 42 
 
 Red clover, do 28 
 
 Rye grass, do 35 
 
 The proportions of woody fibre here given, however, can be considered 
 only as approximations. The riper the straw or grass, the less soluble 
 matter does it contain, and every farmer knows how much soU, season, 
 and manure, affect the (jualit^' of his artificial grasses. One field will 
 grow a hard wiry rye-grass, while another will produce a soft and flexi- 
 ble plant, and a highly nutritious hay. 
 
 3^. Gluten in the grasses. — Boussingault, who considers the relative 
 nutritive value of the vegetable substances employed for fodder to be in- 
 dicated by the proportions of nitrogen they severally contain, has arranged 
 grass and clover hays and the straws of the corn plants, in their usual 
 state of dryness, in the following order : — 
 
 
 
 Or gluten, 
 
 
 Equal effects 
 
 
 NitroiPn 
 
 &c., 
 
 
 should be 
 
 
 per cent. 
 
 per cent. 
 
 
 produced by 
 
 Hay from mixed grasses 
 
 5 1 15 
 
 \' 104 
 
 154 
 
 71 
 6-4 
 
 
 100 lbs. 
 
 Do. afiermath . 
 
 9-3 
 
 75t" 
 
 Do. from clover in flower 15 
 
 93 
 
 
 75 " 
 
 Pea straw . 
 
 195 
 
 12-3 
 
 
 (Ax " 
 
 Lentil straw 
 
 101 
 
 64 
 
 
 114 " 
 
 Indian corn straw 
 
 054 
 
 3-4 
 
 
 240 " 
 
 Wlieat straw 
 
 — 
 
 — 
 
 
 520 " 
 
 Barley straw 
 
 — 
 
 — 
 
 
 520 " 
 
 Oat straw . 
 
 — 
 
 — 
 
 
 550 " 
 
 shall liave occasion to 
 
 compare 
 
 tlie abf 
 
 ve 
 
 theoretical 
 
 lalues 
 {equivalents) assigned to the several kinds of fodder, with the results of 
 
 ' They will be foun'l at lenjrth in the Appendix to D.»vy's Agricultural Chenv'stry, or in a 
 tabulated form in Schubler's Agricultur Chemie, ii., p. 208. 
 
 t It is usually supposed that the aftermath is not s« valuable as Ijie first produce. Schwartz, 
 however, considers it more nourishing by one-tenth part. 
 
 t "The value of all straw for fodder mu.«t depend on the mode in which it is harvested. 
 In Scotland, the order in which the farmer places his straw for fodder is — 1st, pea; 2n(I, 
 bean ; 3d, oat ; 4fh, wheat ; ,5th, barley. While in England, where the benn is quite withered 
 before it is cut, it stand.s last in the scale." — Mr. Hyelt, Jio\/al Ag> iciittural Juuinal, iv., p. 148. 
 
528 COMPOSITION OF HEMP AND LiNt SEEDS. 
 
 practical experience, when we come to direct our attention more parti- 
 cularly to the feeding of stock. 
 
 4°. Fatty matter in ike grasses. — -Besides woody fibre, starch, gum, 
 and gluten, dry hay and straw contain also a variable proportion of tatty 
 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 tal can be extracted from it. To this fVict we shall also re 
 turn when considering the methods of fattening stock. 
 
 5°. Inorganic matter in the grasses. — The proportion of saline and 
 earthy matter contained in the grasses is an important feature in their 
 composition. Tiiis, as I have already said, is much larger than in any 
 of tlie other kinds of food usually given to animals, being seldom less 
 than 5, and occasionally 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 stravv of the bean, pea, and vel,ch, and the ditierent kinds 
 of clover hay, contain little silica, its place in these plants being supi)lied 
 by a large quantity of lime and magnesia. 
 
 § 25. Of hemp, line, rape, and other oil-bearing seeds. 
 
 The oily seeds are important to the agriculturist from their long ac- 
 knowledged value in the feeding and fattening of cattle. Lintseed is ex- 
 jtensively used tijr ihe latter purpose, both in its entire state and in the 
 form oi' cake — when the greater part of the oil has already been expressed 
 from it. All these seeds, however, are not equally palatable to cattle. 
 Some varieties ihpy even refuse to eat. Among these is the rape-seed, 
 from which so much oil is expressed, and the cake left by whicii is now 
 so extensively employed as a manure. 
 
 These seeds are distinguished from those of the corn plants, by con- 
 taining, instead of starch or sugar, a predominating proportion of oil; and 
 instead of their gluten a substance soluble in water, which possesses many 
 of the properties of the curd of cheese (casein). 
 
 We are in possession of a somewhat imperfect analysis of hemp seed 
 and of the seed of the common lint, according lo which ihe varieties ex- 
 amined consisted in 100 parts of — 
 
 Hemp seed Lime seed 
 
 (Buctiolz). (Leo Meier) 
 
 Oil 19-1 11-3 
 
 Husk, dec 38-3 44-4 
 
 Woodv fibre and S'tarch . . 5-0 1'5 
 
 Sugar^ &c 1-6 10-8 
 
 Gum 9-0 7-1 
 
 Soluble albumen (Caseui ?) . 24-7 15-1 
 
 Insoluble do — 3*7 
 
 Wax and resin .... 1-6 3*1 
 
 Loss 0-7 3-0 
 
 100 100 
 
 These analyses show that, besides the oil, these seeds contain consi- 
 derable proportions of gimi and sugar and a large tpiantilv of a substance 
 Jjere called soluble albumen, of which nitrogen is a constituent part, but 
 
PROPORTION OF OIL IN DUVKRtNT SEEDS. 529 
 
 which differs in its properties from the gluten and albumen of tlie seeds 
 of the corn-bearing plants, and has much resemblance to the curd of 
 jnilk. Besides their fattening i)roperties, therefore — 'which these seeds 
 ])robably owe in a great measure to the oil they contain — tliis peculiar 
 albuminous matter ought to render tliem very nourishing also ; — capable 
 of promoting the growth of the growing, and of sustaining the strength 
 of the matured, animal. 
 
 The quantity of oil contained in different seeds of this class, and even 
 in the same species of seed when raised in different circumstances, 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. 
 
 Lijie seed 11 to 22 Sun-flower seed . . .1.5 
 
 Hemp seed 14 to 25 Walnut kernels . . . 40 to 70 
 
 Rape seed 40 to 70 Hazel-nut do. . . .60 
 
 Poppy seed . . . . 36 to 53 Beech-nut do. . . . 15 to 17 
 White mustard do. . . 36 to 38 Plum stone do. . . .33 
 Black do. do. . . 15 Sweet almond do. . . 40 to 54 
 
 Swedish turnip do. . . 34 Bitter do. do. . . 28 to 46 
 
 It seems to be a provision of nature, that the seeds of nearly all plants 
 sliould contain a greater or less jiroportion of oil, which is lodged lor the 
 most part in, or immediately beneath, the husk, and, among other pur- 
 poses, may be intended to aid in preserving the seed. We shall here- 
 after see that tliis oily constituent is of much importance also to the prac- 
 tical agriculturist. 
 
 § 26. General differences in cojupositlon among the different kinds of 
 vegetable food. 
 
 It may be useful shortly' to recapitulate the leading differences in 
 chemical constitution which exist among tlie different kinds of vegetable 
 food to whicli I have directed your attention in the present lecture. 
 
 We have seen that each of the varieties of food contains a greater or 
 less proportion of three different classes of cliemical substances — an 
 organic substance containing nitrogen, an organic substance containing 
 no nitrogen, and an in-organic substance. But it is interesting to mark 
 how in each class of those vegetable products wliich we gather from the 
 earth for our sustenance, theorgauic substances vary either in composition 
 or in chemical characters, while the inorganic matter alters also either in 
 kind or quantity. Thus — 
 
 1°. In the seeds of tlie corn plants — wheat, oats, &c. — the predonn- 
 nating ingredient is starch, in connection with a considerable proportion 
 of gluten, and a small quantity of saline matter consisting chiefly of the 
 phosphates of potash and of magnesia, and in the case of barley of a 
 considerable jjroportion of lime. 
 
 2°. In the seeds of leguminous plants — the pea, tlie bean, the vefch, 
 &c. — starch is still the predominating ingredient, but it is connected with 
 a large cpiantity of legumin, and with a greater proportion of inorganic 
 matter — in which phosjjliate of lime also is more abundant. 
 
 3°. In the oil-bearivg secds^ — those of hemj), lint, 6ic.~oil is often the 
 
630 SPECIAL DIFFERENCES AMONG SEEDS A>"D ROOTS. 
 
 predominadng ingredient, and it is connected with a large proportion of a 
 nitrogenous substance, resembling the curd of milk {casein), and with a 
 quantity of ash about equal to that in the pea, hut in which the phos- 
 phate of lime is said to be still more abundant. 
 
 4°. In the potatoe — starch is tlie greatly predominating ingredient, btit 
 it is united with albumen nearly in the same proportion as it is with 
 gluten in wheat. The inorganic matter is nearly in the same proportion 
 to the dry organic matter, as in the pea and the bean, but is much 
 more rich in potash and soda. Still it is more rich in the earthy phos- 
 phates than the ash left by wheat and oats, and is inferior in this respect 
 only to that of barley. 
 
 5°. //( the turnip — sugar and pectin take the place of the starch, and 
 these are associated with albumen, and with a proportion of inorganic 
 matter about ecpial to that of the potatoe, abounding like it in potash and 
 soda, but more rich in the phosphates of lime and of magnesia. 
 
 6°. In the stems of the grasses and clovers — icoody fibre becomes the 
 predominating ingretlient, associated apparently with albumen, and with 
 a larger proportion of inorganic matter than in any of tlie other crops. 
 In the straws and in some of the grasses which are cut for hay, silica 
 ibrms a large portion of this inorganic matter. In the clovers, lime and 
 magnesia take its place. 
 
 The natural dlfierences above described not only exercise an important 
 influence upon the mode of culture by which the different crops may be 
 most successfully and most abundantly raised, but also upon the way 
 in which they can be most skilfully and economically employed in the 
 feeding of stock. To this latter point we shall return hereafter. 
 
 § 27. Average composition and produce of nutritive matter per acre, by 
 each of the usually cultivated crops. 
 
 1°. Average composition. — The relative proportions of the several most 
 important constituents contained in our cultivated crops vary, as we have 
 seen, with a great number of circumstances. The following table exhi- 
 bits the average composition of 100 parts of the more common grains, 
 roots, and grasses, as nearly as the present stale of our knowledge upon 
 the subject enables us to represent it. (See table at top of next page.) 
 
 In drawing up this table, I have adopted the proportions of gluten, for 
 the most part, from Boussingault. Some of them, however, appear to 
 be very doubtful. The proportions of fatty matter are also very uncer- 
 tain. With a few exceptions, those above given have been taken from 
 Sprengel, and they are, in general, stated considerably too low. 
 
 It is an interesting fact, that the proj;oilion of fatty matter in and im- 
 mediately under the husk of the grains of corn, is generally much greater 
 than in the substance of the corn itself. Thus I have found the pollard 
 of wheat to yield more than twice as much oil as the fine flour obtained 
 from the same sample of grain ;* and Dumas states that the husk of oats 
 sometimes yields as much as 5 or G per cent, of oil. We shall perceive 
 the practical value of this fact when we come to consider the use of bran 
 and pollard in the fattening of pigs and other kinds of stock. 
 
 ' Thus the four portions separated by the miller from a stiperior sample of wheat grown 
 in the neigtibourhood of Durham, gave of oil respectively : — fine Hour, lo per cent. ; pollard, 
 2-4 ; boxings, 3 6; and bran, 3-3 per cent. 
 
AVERAGE COMPOSlTlOr< OF THE DIFFEREST CROPS. 
 
 631 
 
 
 
 Husk or 
 
 Starch, 
 
 Gluten, al- 
 
 
 
 
 Water. 
 
 woody 
 fibre. 
 
 gum, and 
 sugar. 
 
 bumen, le- 
 eumin,&c. 
 
 Fatty 
 matter. 
 
 Saline 
 matte c 
 
 Wheat . . 
 
 16 
 
 15 
 
 55 
 
 10tol5 
 
 2 to 4 J 
 
 20 
 
 Barley . . 
 
 15 
 
 15 
 
 60 
 
 121 
 
 2-5 J 
 
 20 
 
 Oats . . . 
 
 16 
 
 20 
 
 50 
 
 14 51 
 
 5-6 J 
 
 35 
 
 Rye . . . 
 
 13 
 
 10 
 
 60 
 
 14-5 
 
 30 
 
 10 
 
 Indian com . 
 
 14 
 
 151 
 
 50 
 
 120 
 
 5 to 9 D. 
 
 15 
 
 Buckwheat . 
 
 161 
 
 25 7 
 
 50 
 
 145 
 
 41 
 
 1-5 
 
 Beans . . . 
 
 16 
 
 10 
 
 40 
 
 280 
 
 2 + 
 
 30 
 
 Peas . . . 
 
 13 
 
 8 
 
 50 
 
 240 
 
 2-81 
 
 2-8 
 
 Potatoes . . 
 
 751 
 
 51 
 
 121 
 
 225 
 
 03 
 
 0-8 to 1 
 
 Turnips . . 
 
 85 
 
 3 
 
 10 
 
 1-2 
 
 1 
 
 0-8 to 1 
 
 Carrots . . 
 
 85 
 
 3 
 
 10 
 
 20 
 
 0'4 
 
 10 
 
 Meadow hay 
 
 14 
 
 30 
 
 40 
 
 71 
 
 2to5D, 
 
 5 to 10 
 
 Clover hay . 
 
 14 
 
 25 
 
 40 
 
 93 
 
 30 
 
 9 
 
 Pea straw 
 
 10tol5 
 
 25 
 
 45 
 
 123 
 
 1-5 
 
 5 
 
 Oat do. . . 
 
 12 
 
 45 
 
 35 
 
 13 
 
 0-8 
 
 6 
 
 Wheat do. . 
 
 12tol5 
 
 50 
 
 30 
 
 13 
 
 05 
 
 5 
 
 Barley do. 
 
 do. 
 
 50 
 
 30 
 
 13 
 
 0-8 
 
 5 
 
 Rye do. . . 
 
 do. 
 
 45 
 
 38 
 
 13 
 
 05 
 
 3 
 
 Indian com do. 
 
 12 
 
 25 
 
 52 
 
 30 
 
 1-7 
 
 4 
 
 2°. Gross produce per acre. — The gross produce, per acre, of the dif- 
 ferent crops varies as we have already seen (p. 487) 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 num- 
 bers in the following table : — 
 
 Wheat 
 Barley 
 Oats . 
 
 Rye 
 
 Indian corn 
 Buckwheat 
 Beans 
 
 Peas 
 
 Potatoes 
 
 Tiu-nips 
 
 
 
 Produce 
 
 Weight 
 
 Total weight 
 
 per acre. 
 
 per bushel. 
 
 in pounds. 
 
 . . . 25 bush. 60 lbs. 
 
 1500 
 
 
 
 30 " 
 
 
 1800 
 
 
 
 35 " 
 
 53 lbs. 
 
 1855 
 
 
 
 40 " 
 
 
 2120 
 
 
 
 40 " 
 
 42 lbs. 
 
 1680 
 
 
 
 50 » 
 
 
 2100 
 
 
 
 25 " 
 
 54 lbs. 
 
 1350 
 
 
 
 30 " 
 
 
 1620 
 
 
 
 30 " 
 
 60 lbs. 
 
 1800 
 
 
 
 30 " 
 
 46 lbs. 
 
 1380 
 
 
 
 25 " 
 
 64 lbs. 
 
 1600 
 
 
 
 30 " 
 
 
 1920 
 
 
 
 25 " 
 
 66 lbs. 
 
 1650 
 
 Weight of produce. 
 
 
 Weight of producek 
 
 . 6 tons. 
 
 Carrots . 
 
 . 25 tons. 
 
 12 tons. 
 
 Meadow hay 
 
 . 1^ tons. 
 
 . 20 tons. 
 
 Clover hay 
 
 . 2 tons. 
 
 
 3( 
 
 ) tons. 
 
 
 
 23 
 
532 
 
 PRODUCE PER ACRE. 
 
 
 Weight of produce. 
 
 
 Weigh! 
 
 of produce. 
 
 Wheat straw 
 
 . 3000 lbs. 
 3600 " 
 
 Rye straw 
 
 
 4000 lbs. 
 4800 " 
 
 Barley straw 
 
 . 2100 *' 
 
 Bean straw . 
 
 . 
 
 2700 "? 
 
 
 2500 " 
 
 
 
 3200 " 
 
 Oat straw 
 
 . 2700 " 
 3500 " 
 
 Pea straw 
 
 
 2700 " ? 
 
 3°. Average produce of nutritive matter per acre. — In the gross pro- 
 duce above given, there are contained, according to the first table, the fol- 
 lowing average proportions of nutritive matter of various kinds : — 
 
 AVERAGE PRODUCE OF NUTRITIVE MATTER OF DIFFERENT KINDS FROM 
 AN ACRE OF THE USUALI.,Y CULTIVATED CROPS. 
 
 
 
 Gross 
 
 produce. 
 
 MUSK, or 
 
 woody 
 
 fibre. 
 
 Starch, 
 sugar, &.C.. 
 
 Gluten, 
 A.C. 
 
 Oil or fut. 
 
 Saline 
 matter. 
 
 
 bush. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 IbB. 
 
 Wheat . 
 
 25 
 
 1,500 
 
 225 
 
 825 
 
 150 to 220 
 
 30 to 00 
 
 30 
 
 
 
 30 
 
 1,800 
 
 270 
 
 990 
 
 180 to 260 
 
 36 to 72 
 
 36 
 
 Barley 
 
 
 35 
 
 1,800 
 
 270 
 
 1080 
 
 216 
 
 45 + 
 
 36 
 
 
 
 40 
 
 2,100 
 
 315 
 
 1260 
 
 252 
 
 52 + 
 
 42' 
 
 Oats 
 
 
 40 
 
 1,700 
 
 340 
 
 850 
 
 2301 
 
 95 
 
 60 
 
 
 
 50 
 
 2,100 
 
 420 
 
 1050 
 
 2901 
 
 118 
 
 75 
 
 Rye . 
 
 
 25 
 
 1,300 
 
 130 
 
 780 
 
 190 
 
 40 
 
 13 
 
 
 
 30 
 
 1,600 
 
 160 
 
 960 
 
 230 
 
 48 
 
 16 
 
 Indian corr 
 
 i 30 
 
 1,800 
 
 270 
 
 900 
 
 216 
 
 90 to 170 
 
 27 
 
 Buck whea 
 
 t 30 
 
 1,300 
 
 3201 
 
 650 
 
 180 
 
 5 + 
 
 21 
 
 Beans . 
 
 25 
 
 1,600 
 
 160 
 
 640 
 
 450 
 
 32 + 
 
 48 
 
 
 30 
 
 1,900 
 
 190 
 
 760 
 
 530 
 
 36 + 
 
 57 
 
 Peas 
 
 25 
 
 1,600 
 
 130 
 
 800 
 
 380 
 
 45 
 
 45 
 
 Potatoes 
 
 tons. 
 6 
 
 13,.500 
 
 675 
 
 1620 
 
 300 
 
 45 
 
 120 
 
 
 13 
 
 27,000 
 
 1350 
 
 3240 
 
 600 
 
 90 
 
 240 
 
 Turnips 
 
 20 
 
 45,000 
 
 1350 
 
 4500 
 
 5401 
 
 7 
 
 400 
 
 
 . 30 
 
 67,000 
 
 2010 
 
 6700 
 
 8001 
 
 -? 
 
 600 
 
 Carrots 
 
 25 
 
 56,000 
 
 1680 
 
 5600 
 
 11201 
 
 2ob 
 
 560 
 
 Meadow h 
 
 ay IJ 
 
 3,400 
 
 1020 
 
 1360 
 
 240 
 
 70 to 170 
 
 220 
 
 Clover hay 
 
 ■ 2 
 
 4,500 
 
 1120 
 
 1800 
 
 420 
 
 135 to 225 
 
 400 
 
 Pea straw 
 
 — 
 
 2,700 
 
 675 
 
 1200 
 
 330 
 
 40 
 
 135 
 
 Wheat stra 
 
 w — 
 
 3,000 
 
 1500 
 
 900 
 
 40 
 
 15 
 
 150 
 
 
 — 
 
 3,600 
 
 1800 
 
 1080 
 
 48 
 
 18 
 
 180 
 
 Oat straw 
 
 — 
 
 2,700 
 
 1210 
 
 950 
 
 30 
 
 20 
 
 135 
 
 
 — 
 
 3,500 
 
 J.570 
 
 1200 
 
 48 
 
 28 
 
 175 
 
 Barley stra 
 
 w 
 
 2,100 
 
 1050 
 
 630 
 
 28 
 
 16 
 
 105 
 
 
 
 — 
 
 2,500 
 
 12.50 
 
 750 
 
 33 
 
 20 
 
 125 
 
 Rye straw 
 
 — 
 
 4,000 
 
 1800 
 
 1500 
 
 53 
 
 20 
 
 120 
 
 
 
 — 
 
 4,800 
 
 2200 
 
 1800 
 
 64 
 
 ai 
 
 114 
 
 The most uncertain column in this (able is that which re])resents the 
 quantity of oil or fat contained in tlie several kinds of produce. The 
 importance ot the whole table to the practical man will appear more 
 clearly when we come to treat of the feeding of stock. 
 
LECTURE XX. 
 
 Of milk and its products —Properties and composition of the milk of different animals.— 
 Circumstances which atr-ct ihe quality and quantity of milk— species, size, variety, age, 
 health, and constitution of the animal, time of milking, kind of food, &c. — iMode of sepa- 
 rdiingand estimating the several constituents of milk.^Sufrar of milk, and acid of milk 
 (Lactic acid), their composition and properlies. — Souring of milk, cause of. — Cream — 
 composition and variable proportions of — mode of estimating iis (piatitity — the guiactomrt- 
 ier. — Churning of milk and cream. — Composition of hulter. — liuiitrmilk. — The solid and 
 liquid fats contained in butler — margarin and butter oil — tIieirsp|iHrationand properties. — 
 Rancidity and preservation of butter — Composifion and properlirs of the cunt (casein). — 
 Curdling of milk, natural and artificial— by acids and by animal membranes. — Making and 
 action of rennet — how explained. — AIanufac;ure of cheese. — Varieties of cheese. — Aver- 
 age produce of butter and cheese. — Colouring of butter and cheese. — The whey. — Saline 
 matter in the whey. — Nature of the saline constituents of milk.— Fermentation of milk.— 
 Intoxicating liquor from milk. — Milk vinegar. — Purposes served by milk in tlje economy 
 of nature. 
 
 Of the indirect prodticls of agriculture, iriilk, and the butter and 
 cheese inanuf'actured from it, are ainono the most itn]}ortant. In our 
 large towns these substances ma}' almost be considered as necessaries of 
 life, and many extensive agricultural districts are entirely devoted to the 
 production of thein. The branch of dairy husbandry also presents many 
 curious and interesting questions to the scientific enquirer, and upon 
 these questions modern chemistry has thrown much light. To the con- 
 sideration of this subject, therefore, it is my intention to devote the pre- 
 sent lecture. 
 
 § 1. Of ihe properlies and composiUon of niilk. 
 1°. Properlies of milk. — The milk of most animals is a white opacjue 
 liquid, having a slight but ])eculiar odour — which becomes more di.stinct 
 when the milk is warmed — and an agreeable sweetish taste. It is 
 heavier than water — usually in the proportion of about 103 to 100.* 
 When newly taken from the anitnal, cow's milk is almost always 
 slightly alcaiine. It speedily loses this character, however, when ex- 
 posed to the air, and hence even new milk often exhibits a slight degree 
 of acidity. f 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 creain alone, be agitated in a proper 
 vessel (a churn), the temperature of tlie 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 vinega^or diluted muriatic acid, be add- 
 ed to milk warmed to about 100^ F., it immediately coagulates and se- 
 parates into a solid and a litjuid part — the curd and the whey. The 
 (Same effect is produced by the addhion of rennet or of sour milk — and 
 it takes place naturally when milk is left to itself until it becomes sour. 
 At a very low temperature, or when kept in a cool place, milk retnains 
 »weet for a considerable time. At the temperature of 60° F. it soon 
 
 * Or it has a specific gravity of 1020 in woman's milk, to lOtl in sheep's milk ; water being 
 
 loon. 
 
 1 It is said that if Ihe animal remain long uomilked, the milk will begin to sourtin tho 
 odder, and that hence it is sometimes slightly aciiTvvhen fresh drawn from the covr. 
 
634 pRorEuTiKS and composition ok milk. 
 
 turns or acquires a sour taste, and at 70° or 80° it sours with still greater 
 rapidity. If sour milk be gently warmed it undergoes fermentation, and 
 may be made to yield an intoxicating licjuor. By longer exposure to the 
 air it gradually begins to putrify, becomes disagreeable to the taste, 
 emits an impleasant odour, and ceases to be a wholesome article of 
 food. 
 
 The milk of each species of animal is distinguished by some charac- 
 ters 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 separated from 
 this milk with greater difficulty than from that of the cow. 
 
 Goafs milk generally possesses a characteristic unpleasant odour 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. Tlie 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 buuer is white and light, and soon becomes rancid. 
 It contains much sugar, and lience soon passes to the state of fermenta- 
 tion. 
 
 2°. Composition of inilk. — Milk, like the numerous vegetable products 
 we have had occasion to consider, consists, besides water, of organic sub- 
 stances destitute of nitrogen — sugar and butler ; of 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 slate, as found by Henry and 
 Chevallier : — 
 
 Woman. 
 
 Casein (cheese) . . l-5'2 
 
 Butter 3-55 
 
 Milk sugar . . . 650 
 
 Saline matter . . . 0*45 
 
 Water 87-98 
 
 Cow. 
 
 Ass. 
 
 Goat. 
 
 Ewe. 
 
 4-48 
 
 1.82 
 
 4-08 
 
 4-50 
 
 3- 13 
 
 0-11 
 
 3-32 
 
 4 20 
 
 4-77 
 
 6-03 
 
 5-23 
 
 5-00 
 
 0-GO 
 
 0-34 
 
 0-58 
 
 0-68 
 
 87-02 
 
 91-6.5 
 
 86-80 
 
 88-62 
 
 100 100 100 100 100 
 
 From the numbers in the above table, it appears that the milk of tlie 
 cow, the goat, and the ewe, contains much rriore cheesy matter than that 
 of the woman or the ass. It is ))rol)ably this similaritv of asses' milk to 
 that of the human species, together with its deficiency in butter, which, 
 from the most remote times, has recommended it to invalids, as a light 
 and easily digested drink. 
 
 § 2. Of the circumstances by which the composition or quality of the inilk 
 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 depar- 
 
INFLUENCE OF THE HEALTH OF THE ANIMAL. 535 
 
 ture 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 ordinary milk, coagulates by 
 heating, and contains an unusually large quantity of casein or cheesy 
 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 11-6 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 
 
 100 100 100 
 
 Tlie increase in the proportion of cheese is peculiarly great in the first 
 milk of the ass and the goat. 
 
 This state of the milk, however, does not long continue. It gradually 
 assumes its ordinary qualities. After ten or twelve days from the time 
 of calving, its peculiarities disappear, though in the celebrated dairy dis- 
 tricts of Italy it is considered that the milk does not reach perfection until 
 about eight months after calving. [Cataneo, 11 latte e i suui prodolti, p. 
 27.] 
 
 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 ten or twelve 
 years of age, and have had seven or eight calves, when they are 
 generally fattened for the butcher. 
 
 3°. Clvnale and season of the year. — Moist and temperate climates 
 are favourable to the production of milk in large quantity. In hot coun- 
 tries, and in dry seasons, the quantity is le.ss, but the average quality is 
 richer. Cool weatlier favours the production of cheese and sugar in the 
 milk, while hot weather increases the yield of butter, [Sprengel, Che- 
 mie fiir Landwirthe, ii., p. 620.] 
 
 In spring the milk is more abundant and of finer flavour. In autumn 
 and winter, uther things being equal, it yields less cheese, but a larger 
 return of butter.* Where cattle are fed upon pasture grass only, this 
 observed ditference may be derived from a natural 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 sensibly less ricW in cream also, 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 once 
 a day, the milk will yield a seventh ])art 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 abundant but still less 
 
 " British Ilugbandry, ii., p. 404. This opinion seems to contradict Dial of Sprengel in the 
 precedin:; paragraph. Does ihis iliffeiencc arise from the locality and other unlike circum- 
 stances in which the obser\ations of ihe two writers were seveially made — or are tiiere no 
 accurate experiments upon the subject from which a correct result can be drawn 7 
 
536 INFLUENCE OK THE BREED ON THE QUALITY OK MILK. 
 
 rich. It is also universally remarked, that the morning's milk is of bet- 
 ter quality than that obtained in the evening. 
 
 6°. Period al u-hkhit is takcv, Jxmng the milking. — The milk in the 
 udder of the cow is not uniform in quality. That which is first drawn 
 oflTis thin and poor, and gives little cream. That which is last drawn — 
 tlie stroakings, strip[)ings, or atterings — is rich in quality, and yields 
 much cream. Compared wiih the first milk, the same measure of the 
 last will give at least eight and often sixteen times as much cream (An- 
 derson). The qualliy of the cream also, and of the uiilk when skimmed, 
 is mucli better in the lafer than in the earlier drawn portions of ihe milk. 
 
 7°. Treat7ne7it and moral state of the animal. — A state of comparative 
 repose is favourable to the performance of all the important functions in 
 a healthy animal. Any thing which frets, disturbs, 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 lias 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 tlie hcuse after 
 the spring has arrived — v. hen 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 [lermanent kind. I 
 do not enquire at present into the physiological nature of tlie changes 
 which ensue — to I he dairy farmer it is of importance chiefly to be familiar 
 with the facts. 
 
 8°. Therace 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 snrall individiuils of the larger races, give the richest 
 milk from the same kind of food. Thus the small Higliland cow gives 
 a richer milk than tlie Aj'rshire. The small Alderneys give a richer 
 cream than any other breed in common use in this cormtry.* The small 
 Kerry cow is said to equal the Alderney in this respect, while the small 
 Shetlander has been found in the north of Scotland to give fn m the same 
 food a more profitable return of rich milk than an}' 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 sliort-horn and the 
 Holderness, is preferred by the London cow-keepers as gWmgxhe largest 
 quantity of milk, though poor in quality. 
 
 The long-horns are preferred in Cheshire and Lancashire because of 
 (heir producing a greater quantity of cheese. The Ayrshire kyloe, en 
 ordinary pasture, is said to be unrivalled for abundant produce (Avion) 
 — though the milk is not so rich as that of the small breeds. Various 
 crosses have been tried in dili'ercnt 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, tlie natural grasses, the prevailing 
 husbandry, or to the kind of dairy produce w hicli it is the interest of the 
 farmer to raise in his own peculiar neighbouili( od. 
 
 ' A very striking' illustration of fhp ilitP^rence in Dip qualify of tlie milk of two breeds, in 
 Ihe same circunisiances, is giieii by Mr Malcolm, in his Comnendium nf Modern Hus- 
 bandry. He liepl iin Alderney ai!fj a Siiff.ilk tow, the lattor tlie'hest he ever saw. Durififf 
 seven years, ihe milk and l-ulter bcina kept .separatp, it was found, ytar afttryear, that the 
 value of the Alderney exceeded that of Ihe Suffolk, lhou<rh the lutter gave more than 
 double the quantity of milk at a meal— BriVisA Huiba-ndry, \\., p. 397. 
 
EXPERIMKNTS WITH DIFFKRKNT KINDS OP FOOD. 537 
 
 In the South of Euroiie, the Swiss breeds are considered the best for 
 dairy purposes, and of these that of the Canton of Schweitz, whicli, 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 Suflulk cows it is less rich in butter and cheese. 
 
 The influence of breed alone upon ihe quality of the milk is well il- 
 lustrated by the result of a series of trials made at Bradley Hall, in 
 Derbyshire. During the heiglit of the season, and when fed upon the 
 same pasture, cows of four difi'erent breeds gave^er day — 
 
 Or 1 lb. of butter was 
 Breed. Milk. Butter. yielded by 
 
 Holderness . . 29 quarts, and 38^ oz. 12 quarts of milk. 
 
 Aldernev ... 19 " 25" " 12 
 
 Devon ' ... 17 " 28 " 93 " 
 
 Ayrshire ... 20 '*, 34 " 9^ 
 
 The Ayrshire cows gave the richest milk and a laiger quantity of both 
 milk and butter than the Alderneys or Devons, but the Holderness breed 
 surpassed them all. It gave | lb. more butter than the Ayrshire, and 
 nearly one-half more milk. It would appear, therefore, to be admirably 
 adapted to the purj)oses 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 production of cheese. 
 
 9°. The kind of food. — But the kind of food has probably more in- 
 fluence upon the quality of the milk than any oilier 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 slall. The taste of the wild onion and of the turnip, 
 when eaten by the cow, are often perceptible 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 upon one pasture a cow will yield more cheese, 
 upon another more butter. From this has arisen the practice more or 
 less ob.served in all dairy districis of a arying 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 tlie 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 districts, and where 
 different soils exist on the same farm, of turning them during the former 
 part of the da)^ into one field, and during the latter [lart into another. 
 
 Various sets of experiments have beAi made with the view of deter- 
 mining the relative quantities of butter and cheese produced by the same 
 animals, when fed upon different kinds of iboil. Much, however, re- 
 mains yet to be done both by the practical dairy farmer and by the ui- 
 alytical chemist, before this subject can be fully cleared up. According 
 to theorj^ as I sliall more fully explain in my next lecture, the legumi- 
 nous plants — clover, tares, &:c., and the cultivated seeds of such plants'^ 
 peas and beans, ought to jiromote the production of checae ; while oil- 
 cake, oats, and other kinds ol' food which contain much oily matter, 
 ought to favour the yield of butter. The most recent experiments we 
 possess, however, do not lend any decided confirtiiatiou to these theoreti- 
 
538 EXFERIME-NTS WITH DIFFERENT KINDS OF FOOD. 
 
 cal views. The most extensive series of^ trials lately published is tliat 
 of Boussingault, [Annales de C'liim. et de Phys., Ixxi., p. 79,] from 
 \vl]icli I select the following : — 
 
 FIRST SKRIES MADE ON A FRENCH COW. 
 
 T^ r, Quarts Composition of the milk per cent. 
 
 ^^1 nl Kind Of food. of , 
 
 •^^'''"S- Biiik. Casein. Butter. Sugar. Salts. Water. 
 
 200 Hay .... 5 30 45 47 0-1 877 
 
 207 Turnips ... 5^ 30 42 50 02 876 
 
 215 Beet .... 5 34 40 .5-3 02 871 
 
 229 Potatoes ... 4f 34 40 59 02 865 
 
 302 Hay and oil-cake 2^ 34 3 6 6 2 86-8 
 
 SECOND SERIES MADE ON A SWISS COW. 
 
 176 Potatoes and hay 8} 3 3 48 51 03 865 
 
 182 Hay and clover 7& 4 45 4 3 872 
 
 193 Clover ... 8f 40 22 47 03 888 
 
 204 Do. in flower . 6i 37 3-5 5 2 0-2 874 
 
 In the first series of experiments the proportion of dieesy matter and 
 of sugar was greatest when beets, potatoes, and oil-cake were given, 
 while the largest proportion of butter was obtained from the use of hay 
 and the least from oil- cake. 
 
 In the second series the proportion both of cheese and of butter de- 
 creased by the use of clover, while the quantity of milk was not per- 
 manently increased. 
 
 These two series of experiments may appear to be deserving of less 
 
 reliance because they were not made on successive days, but at varying 
 
 intervals of time. But some recent experiments, made in Lancashire 
 
 by Dr. Playfair, are little more satisfactory. These were made upon a 
 
 short-horned cow, which was fed one day in the field on after-grass, and 
 
 during the four succeeding days in the stall, upon weighed quantities of 
 
 different kinds of food. [Memoirs of the Chemical Society, i., p. 174.] 
 
 Composition of the milk. 
 
 Day's Food. Qts. , • — , 
 
 Casein. Butter. Sugar. SaJis. Water. 
 
 1° After <Ta«, 5 Evening's millc.. 4 5-4 3-7 ^-B 0-6 865 
 
 1 . Alter-grass ^Morning's do.. 4^ 39 56 30 0-5 87-0 
 
 2°. 28 lbs. Hay P Eveiiing-s do.. SJ 4-9 5-1 38 0-5 85-7 
 
 2A lbs. Oatmeal S Morning's do.. 4 5-4 39 4-8 0-5 85-4 
 
 3°. 28 lbs. nay .^Evening's do.. 4 - - - - - 
 
 8lbsVanFllt::^M--i'^ -!-• ^^ ^-^ 4-6 4-5 0-7 86-3 
 
 *°^1ih^-^H""°^^----^ Evening's do.. T, 39 67 46 0-6 W2 
 
 Q IK nVr,,;' ■( Morning's do.. 4 2-7 4-9 50 0-5 86-9 
 
 8 lbs. Bean Flour. . ) " 
 
 5°. 141bs.Hay ^Evening's do.. 5j 3-9 46 3-9 0-5 87-1 
 
 30 lbs. Potatoes... ^ Morning's do.. 4f 3-5 4-9 3-8 0-5 87-3 
 
 In these experiments there appears an increase in the proportion of but- 
 ter and sugar, and in the (juantity of milk on the fourth day, when the 
 potatoes, hay, and bean flour were given together. On the fifth, when 
 potatoes and hay only were given, the quantity of milk went on increas- 
 ing, but it was poorer in quality. Could we infer any thing, then, from 
 a single day's trial, it would be that the bean meal had aided in the pro- 
 duction of butter and sugar — instead of cheese, as theory would indicate 
 — while the steamed potatoes had added to the quantity of the milk. 
 But no sensible results can justly be expected in regard to the influence 
 
IJfFLUENCE OF THE STATE OF PREGNANCY. 539 
 
 of this or that food, except by a much more prolonged series of careful 
 observations. 
 
 If we compare the quantity of albumen and casein contained in the 
 food, with that yielded in the milk during the four days' experiments of 
 Dr. Playfair, we shall find no perceptible relation between the two quan- 
 tities. Thus, the cow on the — 
 
 Albumen Of Casein 
 
 2d day eat 2^ lbs., and yielded 0-93 lbs. 
 
 3d " 5 " " 1-0 " 
 
 4th " 4 " " 0-75 " 
 
 5th " 1-7 » '• 0-94 " 
 
 So that, whether, as on the third day double the quantity was eaten, or, 
 as on the fifth, little more than half as much as was consumed on the 
 second day, the produce of cheesy matter in the milk was sensibly the 
 same, on each of the three days. 
 
 We must not, however, from these experiments, infer that the kind of 
 food really has no influence upon the quality of the milk — for this con- 
 clusion is contradicted by general experience. We must wait rather for 
 renewed and more extended practical researches, by which both our 
 theory and practice may probably be amended, and by which the con- 
 clusions may be reconciled to which they respectively lead us. [See the 
 following Lecture " On the feeding of stock.''] 
 
 lO*'. State of pregnancy. — I have already stated (p. 535), that the 
 richness 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 become poorer in 
 every respect, or else considerably less in quantity (p. 541), as soon as the 
 cow is with calf, since a portion of tlie food which might otherwise have 
 been employed in tiie production of milk, must now be directed to the 
 nourishment of the young animal in the womb of the mother. In the 
 experiments to which I have just directed your attention in regard to the 
 effect of the kind of food upon the quality of the milk, the state of prccr- 
 nancy of the animal was not taken into consideration, though, as I have 
 already said, this must necessarily exercise an important influence upon 
 the quality of the milk, whatever be the kind of food upon which the 
 animal may have been fed.* To this the want of accordance between 
 theory and experiment is probably in part to be ascribed. 
 
 11°. Individual form and constitution of the animal. — But it is well 
 known that animals of tlie 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 tliin head, with a brisk but placid eye, — should be thin and 
 hollow in tlie neck, narrow in the breast and point of the shoulder, and 
 altogether light in the forequarter — but wide in the loins, with little dew- 
 lap, and neither too full fleshed along the chine, nor shewing in any part 
 an inclination to put on mucli 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 e(|uai distances and of tlie same size, and al- 
 
 * Both of the cows experimented upon by BoussinijauU were with calf, Dr. Piayrair does 
 not mention wliether his wa« so or not 
 •23* 
 
640 EFFECT OF i;>'DIVli)t'AL FORM AND C0>ST1TUT10.N. 
 
 though neither very large nor thick towards the udder, yet long and 
 tapering towards a point. A cow with a large liead, a high backbone, a 
 small udder and teats, and drawn up in the belly, will, beyond all doui)t, 
 be found a bad milker." [Youatt's Cattle, p. 244, quoted in British Hus- 
 bandry, ii., p. 397.] Thus, while much depends upon the breed, the 
 form of the individual also has much influence upon its value as a 
 milker. 
 
 But independent of form, the quality of the milk is greatly aflected by 
 the individual constitution of every cow we feed. Thus in a report of 
 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 regard to their forms — and which were 
 all fed upon the same pastures in Lanarkshire, the yield of milk and 
 butter by four of the cows in the same week is given as follows : — 
 Milk. Butler. 
 
 A yielded ... 84 quarts, which gave . . . . 3^ lbs. 
 
 F and R each . 86 " " " oi lbs. 
 
 G yielded ... 88 " " " 7 lbs.* 
 
 Showing 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 twice as rich. This result would have been still 
 more interesting had we known tlie relative quantities of grass consumed 
 by these two cows respectively. 
 
 I will not insist upon other causes by wViich the quality of the milk is 
 aiore or less materially affected. It is said that when stall fed the same 
 cow will yield more butter than when ])astured in the field — that the age 
 lof 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, probablj', few circumstances which are capable in any way 
 of alTecting the comfort of the animal which will not also modify the 
 quality of the milk it yields. 
 
 § 3. Of the circumstances which ajj'cct the quantity of the milk. 
 
 The c\ii\\\^t good-viillcer applied to a cow has very different significa- 
 tions in different di^lricfs and countries. Tims the experiments of 
 Boussingault upon the effect of different kinds of food on the quality of 
 the milk (p. 538) were made upon a French cow which was considered 
 a good milker, and yet when in best condition never gave more than 11 
 quarts a day. Two, or even two and a half, times that quantity is not 
 considered extraordinary in the height of the seaeon in many parts of our 
 island. 
 
 There are three circumstances which principally affect tlie quantity of 
 milk — namely, the breed, the Ivind of food or pasture, and the distance 
 from the lime of calving. 
 
 1°. The breed. — The smaller breeds of cattle yield, as is to be ex- 
 pected, a smaller daily ])ro(hire 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 
 
 ' Prize Essays of the Highland Society, New Series, ii., p. 25ii 
 
CIRCUMSTANCES AFFECT THE (QUANTITY OF HULK. 54^ 
 
 quarts a day. The coimty surveys state the a%erage daily produce of 
 dairy cows to be, in — 
 
 Devonshire ... 12 qts. I Lancashire . . . 8 to 9 qts. 
 
 Cheshire .... 8 " | Ayrshire 8 " 
 
 But the best Ayrshire kyloes will yield an average of 12i quarts dailyt 
 during 10 months of the year (Ayton). 
 The yearly produce of the best Ayrshire kyloes is stated by Mr. 
 
 Ayton at ' . 4000 qts 
 
 Of average Ayrshire stock ....... 2400 " 
 
 Good short-horns, grazed in summer, and fed on hay and tur- 
 nips in winter (Dickson) 4000 '• 
 
 Mixed breeds in Lancashire (Dickson) 3500 •' 
 
 Large dairy of inixed 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 i^ 
 known to be greatly influenced by the kind of food. This is best under- 
 stood in the neighbourhood of large towns where the profit of the dairy- 
 man is dependent upon the quantity* rather than upon the quality of his 
 milk. Hence the value of highly succulent foods — of the grass c»f irri- 
 gated meadows — of mashed and steamed food — of brewers' grains — ot 
 turnips, ])otatoes and beets — and of other similar vegetable productions 
 which contain much waler intimately mixed with nutriti\'e matter, and 
 thus tend both to aid in the production of milk and to increase its quan- 
 tity. 
 
 3°. Distance from the time of calvinsi- — It is a well-known fact that 
 cows in general after the first two montlis from the time of calving, 
 though fed upon the same f(X»d in equal (juantity, 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, tlie rate of this decrease is thus 
 represented by Mr. Ayton : — 
 
 First fifty davs, 24 qts. per Aay, — or in all, 1200 qts.' 
 ■ " " " ' " 1000 " 
 
 700 » 
 400 " 
 400 " 
 300 " 
 
 Some cows indeed do not run dry throughout the whole year, but these 
 may be considered as exceptions to the general rule. By feeding them 
 upon brewer's grains, mashes, and succulent grass, the milk-sellers near 
 our large towns occasionally ke(^j) the same cow in profitable milking 
 condition for three years and upwards. f Such cows are generally fat- 
 tened after they have become dry — indeed as they cease to give milk, 
 they generally lay on fat in its stead — and, as soon as they are consider- 
 ed ripe^ are sold off" to the butcher. 
 
 * It is quoted, even by foreijfn writers, as a fair joke against the dairy establishments of 
 our large towns, that among the advantages possessed by one which was advertised for sale, 
 much stress was laid upon a iiKverfailin^ ptimp. — Sec 11. latle e i suoi procUitti. p. 67. 
 
 t Even on shipboard I have heard of a cow being kept in milk during the whole of a three 
 years' cruise — t)\e fnod beiiifr principally a kind of pease soup. After the first year, how- 
 ever, the milk is said to become thinner and more watery. 
 
 Second 
 
 "do." 
 
 20 
 
 Tliird 
 
 do. 
 
 14 
 
 Fourth 
 
 do. 
 
 8 
 
 Fifth 
 
 do. 
 
 8 
 
 Sixth 
 
 do. 
 
 G 
 
542 MODE OF SKPARATING THE CONSTITUENTS OF HILK. 
 
 § 4. O/* tJie mode of separating and estimating the several constituents 
 
 of milk. 
 
 1°. If a weighed quantity of milk be allowed to stand for a sufficient 
 length of time, the cream will rise to the top, and may be easily skim- 
 med off. If this cream be gently heated the batter in an oily form will 
 collect upon the surfiice, and when cold may be separated from the 
 water beneftth, 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 collected in a 
 cloth, pressed, dried, and weighed. 
 
 3°. If a second etjual portion of the milk be weighed and then evap- 
 orated to dryness by a gentle heat and again weighed, tiie loss will be 
 the ciuantity of water which the n:iilk contained. 
 
 4^. If now the dried milk be burned in the air till all tlie combustible 
 matter disappears, and the residue be weighed, the quantity of inorganic 
 saline matter will be determined. 
 
 5°. Supposing those processes to be performed with tolerable accuracy, 
 the difference between the sum of the weight of the water, butter, curd, 
 and ash, and the weight of the milk employed, will nearly represent 
 that of the sugar contained in the given (juantity of milk. 
 
 For many purposes a rude examination of milk after this manner may 
 be sufficient, but where any thing like an accurate analysis is required, 
 more refined methods must be adf)pted. In such cases, the following 
 appears to be the best which has hitherto been recommended. [Haid- 
 len, Annal. der Chem. & Phar., xlv., p. 26'3.] 
 
 a. The butter. — The weighed quantity of milk is mixed with one- 
 sixth of its weight of common unburnt gypsum previously reduced to a 
 very fine powder. The whole is then evaporateil to dryness with fre- 
 quent 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 dissolved 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 estimated 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 evaporating this solution and 
 weighing the dry residue, the quantity of sugar is determined. Or, as 
 before, the powder itself may be dried and weighed and the sugar esti- 
 mated by the loss. If we wish to estimate tlie small quantity of inor- 
 ganic saline matter which has been taken up along with the sugar, if 
 may be done by burning the latter m the air, and weighing the residue. 
 
 c. The saline matter. — A second weighed portion of milk is now evap- 
 orated carefully to dryness and again weighed. The loss is tlie water. 
 The dried milk is then burned in the air. The weight of the incombus- 
 tible ash indicates the proportion of inorganic saline matter contained in 
 the milk. 
 
 d. The casein. — The weight of the butter, sugar, saline matter and 
 water being thus known and added together, the deficiency is the weight 
 of the casein. 
 
PROPERTIES OF THE SUGAR OF MILK. 543 
 
 § 5. Of the sugar of milk, and nf the acid of milk or lactic arid. 
 
 Before I'can hope to make you understand the nature of the changes 
 wliich take place during the souring, tlie churning, and the curdling of 
 milk, it will he necessary to make you acquainted with the sugar of 
 milk, and with lactic acid or the acid of milk. 
 
 1°. Sugar of milk. — Wlien the curd is separated from milk, the raw 
 whey afterwards boiled — with or without the addition of new and butter 
 milk — and the floating churd skimmed oflT or separated by straining 
 through a cloth, the whey is obtained nearly free from butter and cheese. 
 By mixing it while hot witli well beat white of egg, die 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 one 
 fi^urth of its bulk, then poured into an earthen dish, and set aside for a 
 i'ew 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 pre- 
 pared, which in many places is used as an article of food. Of the purer 
 variety large quantities are extracted 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 un.lergoes 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 be- 
 comes sour, lactic acid is formed, and the liquid begins to ferment. Car- 
 bonic acid is given off — as is the case during the fermentation of other 
 liquids — and alcohol is produced. In milk the two substances are na- 
 turally intermixed, and it is the presence of the cheesy matter, as we 
 shall hereafter see, which at favourable temperatures always causes milk 
 of every kind first to become sour and then to fenrienf. 
 
 The gluten of wheat and animal membranes of various kinds produce 
 a similar effect upon solutions of sugar of milk. A \nece 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 eflect of the calf's stomach, in the form of rennet, in the curdling of 
 milk. The eflect of such membranes is more speedy after they have 
 been some time taken from the body of the animal, a fact which also ac- 
 cords with the long experience of the dairy districts in the preparation of 
 rennet. 
 
 When a litde 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 undergoes a similar change 
 into the sugar of grapes. 
 
 Milk sugar has not hitherto been formed by art. It exists in the milk 
 of all niammiferous animals, and from this source alone have we hith- 
 erto 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 
 
644 THK ACID OF MILK, OR LACTIC ACID. , 
 
 intensit}' till at. length tlie whole begins to ferment. This sour taste is 
 owing to the procJuction of a peculiar acid, to which the name of acid 
 of milk or lactic acid has been given. The same acid is formed duriug 
 the fermentation of the juices of the beet, and of the turnip, in sour cab- 
 bage {sauer kraut), and sour malt, in brewers' grains which have become 
 sour, in the sour vegetable mixtures with which cattle are often fed, in 
 the waste liquor 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 become sour. 
 
 The acid, therefore, differs from the sugar of milk in so far that it can 
 readily be formed, and in any quantity', by artificial means. As it is 
 not employed for any economical purposes, I shall not trouble 3'ou with 
 the methods by which this acid is oljtaincd in a state of purity. 
 
 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. 
 
 § G. Of the mutual relations tvhich exist between lactic acid and the cane, 
 grape, atid milk sugars. 
 
 It is important, and I think it will prove interesting to you, to under- 
 stand the beaulifuUy simple relation which exists between the sugar of 
 milk and this lactic acid, which plays so important a part in nearly all 
 your daily operations. 
 
 Cane sugar, grape sugar, milk sugar, and lactic acid, as they exist in 
 solution in water or in milk, may all be represented as compounds of car- 
 bon ivith rvater — or of carbon with hydrogen and oxygen in the propor- 
 tions in which they exist in water. Thus they consist respectively of — 
 
 12 Carbon -1- 12 Watpr 
 
 Cane sugar . . . 12C -f ]'3H + 120 or 1-2C -f- 12HO* 
 
 12 Carbon -)- 14 Water 
 
 Grape sugar . . 12C -f 14H + 140 or 12C + 14HO 
 
 24 Carbon -f- 24 Water 
 Milk sugar . . . 24C + 24H + 240 or 24C -f 24HO 
 
 6 Carbon + 6 Water 
 
 Lactic acid ... 6C -f GH + 60 or 6C -f GHO 
 
 4 Carbon + 3 Water 
 
 Acetic acid (vinegar) 4C -f 3H + 30 or 4C + 3110 
 
 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 recol- 
 lect that starch, gum, and woody fibre, have also a similar relation to 
 the sugars — and that by certain ajjparently simple transtbrmations these 
 
 ■ 0, IT, and O, as in our former lectures, representing respectively carbon, hydrogen, and 
 oxygen, and HO water — a compound of hydrogen with oxygen. 
 
CHANGE OF MILK SUGAR INTO LACTIC ACID. 545 
 
 several substances are capable of being converted 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 woody fibre in favourable circumstances are transformed intc 
 sugar, (see Lecture VI., p. Ill) — the sugars, in favourable circum- 
 stajices, are further 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 tlie air, and ^Yithout the escape of any gas. 
 The above formulae show with what apparent simplicity tliis may be 
 accomplished. 
 
 In fact, cane sugar, milk sugar, and lactic acid, as above represent ed, 
 consist of the same elements united together in the same proportions. It 
 is easy to conceive therefore in what way the one may be transformed 
 into the other. 
 
 1°. Two of lactic acid are represented by 1'2C + 12H + 120, which 
 is the formula for cane sugar. Tiie transforming action of the animal 
 membrane, or of the casein in its state of incipient decay, is therefore 
 simply to cause the elements of the sugar to assume a new arrangement 
 — in which instead of cane sugar they form a substance having the very 
 ditTjrent properties of lactic acid. 
 
 2^. Again, milk sugar is represented by 24C + 24H. + 240, and 4 
 of lactic acid are also eijual to 24C + 24H + 240 ; the change which 
 takes place when milk becomes sour, therefore, is easily understood 
 Under the influence of the casein the elements 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, n:)t!iing is absorbed I'roni the air or given off into it. — but a simple 
 transposition of the elements of the sugar takes place, and the new acid 
 compound is produced. 
 
 These changes appear very simple, and yet how ditBcult it is to con- 
 ceive by wh U mysterious influence the more contact of this decaying 
 membrane or of the casein of the milk, can cause the elements of the 
 sugar to break up their old connexion, and to arrange themselves anev/ 
 in another prescribed order, so as to torm a compound endowed with 
 pro[)erties so very different as those of lactic acid. It is beautiful to sec 
 the simple means by which in nature so many important ends are ac- 
 complished — 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 adlliion to other rewards, which constantly 
 follow the study of nature, you will with me draw the conclusion — 
 which is ever pressing itself upon our attention — that it is the will and 
 intention of the Deity, that all his works shall be thoroughly studied and 
 investigited. But you will, I think, agree with me in drawing this con- 
 clusion, because of the further and higher moral effect also which such 
 investigations tend to produce upon the mind. Every fresh discovery, 
 as it opens up new (ields 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 whicli the several transforniaJ ions of starch intc 
 
546 SOURING AND PRE5KRVING OK MILK. 
 
 sugar, and of the latter into lactic aciJ, may be brought about, and seem 
 almost to understand how it is done, since it can be eHected by a sinijjle 
 transposition of their elements. But the after-thought occurs — by what 
 kind of power is this change effected ? The materials are certainly pre- 
 sent, but how are they made to shift their relative positions, and move 
 into their new places ? We have conipiered one intellectual difficulty 
 only to encounter another apparently still harder to overcome. 
 
 It was said first, I believe by Priestley, [Experiments and Obser- 
 vations, ii., p. ix., edition 1781,] " that the greater tlie 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 witli the sense 
 of their own want of knowledge. What a fine result this is of large 
 acquirements ! And how touchingly it was expressed by Sir Isaac New- 
 ton, wlien he likened his great discoveries to the gathering of a few peb- 
 bles along the sea-shore — the vast ocean of natural knowledge lying still 
 unexplored before him ! 
 
 § 7. Of the souring and preserving of milk. 
 
 The natural souringof 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 con- 
 nected with it to wliich it may be proper to advert. 
 
 1°. If milk be kept at a low temperature, it may be preserved for se- 
 veral days without becoming sensibly sour. This is effected in Switzer- 
 land 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. lu 
 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 be- 
 comes sour with great rapidity, and if afterwards raised to tlie boiling 
 point curdles immediately. An easy way of preserving milk or cream 
 sweet for a longer time, or of removing the sourness when it has already 
 come on, is to add to it a snnall (juantity of the common soda, pearl ash, 
 or magnesia of the sliops. 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 membrane, the curd of 
 milk, or any of those substances which possess tlie power of changing sugar 
 into lactic acid, loose that power if tlie 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 [)an 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 upwards of half a-year. 
 
 1 mentioned also that if the solution containing the sugar and cheesy 
 matter be again exposed to the air after boiling, it will gradually resume 
 the property of transforming the sugar into lactic arid. Hence, if milk 
 be boiled, it is preserved sweet fiir a longer period of time, but the 
 casein gradually resumes its transforming property, and at the end of a 
 
SEPARATION OF CREAM FROM THE MILK. 547 
 
 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 dryness 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 excel- 
 lent milk. It is known in Italy by the name of latteina. [II latte e i 
 suoi prodotti, p. 19.] 
 
 § 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 exists in 
 the cream, and which forms the butter, is merely mixed with and held in 
 suspension by the water of which the milk chiefly consists. In the 
 udder of the cow it is in some measure separated from, and floats on, the 
 surface of the milk, the later drawn portions 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 render- 
 ed slower, more difficult, and less comj)lete. 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 intimately together before it is set aside, the cream 
 will be considerably 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 ves- 
 sels, than when the whole milking is mixed together. When the collec- 
 tion of cream, therefore, is the principal object, economy suggests 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 collected. 
 
 Cream does not readily rise through any considerable depth of milk ; 
 it is usual, therefore, to set it aside in broad shallow vessels in which the 
 milk stands at a depth of not more than two or three inches. By this 
 means the cream can be more eflef:tually 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 sejiarated. Thus it is said that from the 
 same milk an equal quantity of cream may be extracted in a much 
 shorter time during warm than during cold weather — that, for example, 
 milk may be perfectly creamed in — 
 
 ."^6 hours, when the temperature of the air is 50° F. 
 
 24 " " " " 55° F. 
 
 18 to 20 hours " '• " 68° F. 
 
 10 to 12 " " " 77° F. 
 
 — while, at a temperature of .34° to 37" P\, milk may be kept for three 
 weeks, without throwing up any notable quantify 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 of the 
 milk so readily as it does when in a warm and perfectly fluid stale. 
 
- 548 COMPOSITION OF CKF.AM. 
 
 The above remarks ai)ply to milk of ordinary quality and consistency. 
 In very thin or {)Oor 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 tlie bulk of cream which rises to its 
 surface in a given time. For the purpose of testing this richness, a 
 simple instrument, dignified by the learned name of a galactometer 
 (milk-gauge), has been recommended and may often be useful. It con- 
 sists of a narrow cylindrical vessel or long tube of glass, divided or gra- 
 duated into 100 equal parts. This vessel is filled up to 100 witli the 
 milk to be tested, and at the end of 24 or 36 hours, the cpiantity 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 degrees 7 per cent, of cream. This instrument, hofv- 
 ever, will give a result which will be generally less than the truth, be- 
 cause tlie cream will always rise slowly through 5 or 6 inches of milk — 
 the smallest length which tlie instrument can conveniently be — and most 
 slowly in the richest and thickest milk. Unless considerable care be 
 taken, therefore, this milk-gauge may easily lead to erroneous con- 
 clusions 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 tat as they rise bring up witli 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 witli acid liquids or with acid fruits. 
 
 The proportion of cheesy matter present in c^ream depends upon 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 jiroportion of cheesy matter. The composition of 
 cream, therefore, is very variable — mucli 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 density 
 (specific gravity) of 1-0244, consisted of — 
 
 Batter, separated by agitation 4*5 per cent. 
 
 Cheesy matter., separated by coagulating the butter- 
 milk i ... 3-5 " 
 
 Whey 92-0 
 
 100 
 Some of the butter remained, as is usually the case, in the butter- 
 milk, and added a little to the weight of the curd which was afterwards 
 separated, but the result of this analysis is sufficient to show that cream 
 in general contains a very considerable proportion of cheesy matter^ 
 sometimes almost as much cheese as butter.* 
 
 * The cloiiteil cream of Dfvonshire and other Western counties, as well as the butter pre- 
 pared from it, probably contains an unusually liirge quantity of cheese. If is prepared by 
 strainina; the warm milk into large shallow pans into which a hllle water has previously been 
 put, allowing these to stand from 6 to VI huurs, and then carefully heating them over a slow 
 fire, or on a hot plate, till tlie milk approaches the boiling point. The milk, however, must 
 
CREAM-CHEKSE ANO MASCARPOM. 549 
 
 I would remark, however, lliat tliis cream examined by Berzeliua 
 must have been of an exceedingly poor quality — little richer, indeed, 
 than common milk, since 100 lbs, of it v/onld only have yielded 4^ lbs. 
 of butter. Cream of good ([uality in this country, when skilfully 
 churned, will yield about one-fourth of its weight of butter, or one wiue 
 gallon of cream, weighing 8} li)s., will give nearly 2 lbs of butier.* 
 
 4°. Cream-cheese. — You will now readily understand the nature of 
 what is called cream-cheese — how it dlHers from ordinary cheese and 
 from butter, and why it so soon becomes first sour, and then rancid. 
 
 In preparing this cheese the cream in this country is generally, I be- 
 lieve, eitiier tied up in a cioih 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, ac- 
 cording 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 rnolst curd, after a certain length of exposure to the 
 air, not only decomposes and becomes unpleasant of itself, but acquires 
 the property of changing the butter also and of imparting to it a dis- 
 agreeable 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 belter to 
 take 20 grains of Tartaric acid for each (piart of cream, to dissolve it in 
 a little water, and to add this, instead of the sour whey, to the hot cream. 
 The acid runs oiV in the whey of the cream, and the cheese is colour- 
 less and free from foreign flavour. The mascarponi, like the English 
 cream-cheeses, are covered with leaves or straw, are littled pressed or 
 handled, and must be eaten fresh. 
 
 § 9. Of the separation of butler by churniiig or otherwise. 
 
 Milk is a kind of natural emulsion in which the fatty matter exists in 
 the state of very minute globules, suspended in a solution of casein and 
 sugar. Cream is a similar emulsion, differing from milk chiefly in con- 
 taining a greater number of oily globules and a much smaller proportion 
 of water. In milk and cream tliese globules appear to be surrounded 
 with a thin white shell or covering, probably of casein, by which they 
 are i)revented 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 
 
 not actually boil, nor must the skin of the cream be broken. The dishes are now removed 
 into tlic dairy, and allmved to cool. la summer thi- cream should be churned on the: fol- 
 lowing day— ill winter it may stand over two dnya. Tiie quintity of cream obtained i.s said 
 to be oiiK-fourih {rreater by this nielhod, and the milk wtiich is left is proponionably iioor. 
 When milk on which no cre.ini floats is heated nearly to boilin;; in the air, a pellicle of 
 chee.sy mailer forms on its surface. Such a pellicle may form in a less dciiree in the scald- 
 dine process of Devonshire, and may thus increase the bulk of the cream. The Curstor- 
 phine cream of Mid-Lothian resembles the clouted cream very much, and is made in a very 
 Biinitar way. 
 
 • A series of analyses of cream, collected under different circumstances, might throw some 
 useful lijjhi upon the manufacture and preservation of butter. 
 
550 OF THE SEPARATION OF BUTTER. 
 
 their coverings, and unite into a film 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 atFord an explanation of the various methods which 
 are in different places adopted for tlie preparation of butter. 
 
 1°. By heating the cream. — When rich cream is heated nearly to boil- 
 ing, and is kept for some time at that temperature, the butter gradually 
 rises and collects on the surface in the form of a Quid oil. On cooling, this 
 oil becomes solid, and may be readily removed from the water and curd 
 beneath. The fatty matter of the milk is thus obtained in a purer form 
 than when butter is prepared in the usual way. It may, therefore, be 
 kept for a longer period without salt and without becoming rancid, but it 
 has neither 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 Eussia. In warm weather it has the consistence of a 
 thick oil, is used instead of oil for many culinary purposes, and is de- 
 noted, indeed, by (he same Russian word. It may be kept for a consi- 
 derable 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 several 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 tlie butter separates. This is collected into lumps, well beat and 
 squeezed free from the milk, and in some dairies is washed 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 squeezings and dryings with a clean 
 cloth. Both methods, no doubt, have tlieir 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 butter may 
 be obtained, but in most cases it requires more labour and longer time, 
 without, in the opinion of good judges, afli)rding in general a finer 
 quality of butter. In all cases the cream becomes sour during the agi- 
 tation and before the butter begins distinctly to form (see p. 5.54.) 
 
 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 
 
 ' It is said, that when melted butler is poured iuto very cold water, it acquires the coosis' 
 tency and appearance of common butter. 
 
CHURNING THE WHOLE MILK. 551 
 
 may be churned in 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 tliat the butter separates with very great ease. But 
 in this case the heating of the cream lias 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 com- 
 parative ease with which the churning is effected. I suppose there is 
 something peculiar in butter prepared in this way, as it is known in 
 other counties by the name of Bohemian butter. It is said to be very 
 agreeable in flavour, but it must contain more cheesy matter than the 
 butter from ordinary cream. 
 
 3^. Churning the lohole milk. — Butter m very many districts is pre- 
 pared from the wliole milk. This is a much more laborious method— 
 from the difficulty of keeping in motion such large quantities of fluid. 
 It has the advantage, however, it is said, of giving a larger quantity of 
 butter ; and in the neighbourhood of the towns in Scotland and Ireland 
 the ready sale obtained for the butter-milk is another inducement for the 
 continuance of the practice. 
 
 At Rennes, in Brittany, the milk of the previous evening is poured 
 into the churn along with tlie 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. [11 latte e i suoi prodotti, p. 112.] 
 
 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 ves- 
 sel, 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 stirt'6rai upon ihe surface ivhich has become uneven (Bal- 
 lantyne). Great care nmst be taken, however, to keep the brat and 
 curd unbroken until the milk is about to be churned, for if any of the 
 whe}'' be separated the air gains admission to it and to the curd, and 
 fermentation 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 allow- 
 ed to ri-;e to the surface at all, but the milk is stirred two or three tiiries a 
 day, till it gets sour, and so tliick that a wooden spoon will stand in it. 
 It is then put into the churn, and the working or the separation of the 
 buMer 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 
 ipiantity — which appears to be the opinion of those who practise it 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 
 ♦ In his Dairy Huabiindry, a work much praised, and which I regret that I have never seen. 
 
55*3 COMPOSITION OF BUTTER. 
 
 all the ingredients which exist in milk. It consists, however, essentially 
 of tlie fat of iniilc inlimately mixed with a more or less considi^ralilo 
 proportion of casein and ^^■ater, and with a small quantity of sujar of 
 milk. Fresh butter is said to contain about one-sixth of its weight (Ifi 
 per cent.) of these latter sul)stances, and five-sixths of ])ure fat (Clicv- 
 reul). How iimch of the IG per cent, usually consists of cheesy matter 
 lias not yet been determined.* 
 
 It is probable, however, that the pro])ortion 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 wa}' in wliich the cream is separated from the milk, 
 ■whether by clouting or otherwise — and the nature of the food and i)as- 
 ture, must all aff(3ct in a very considerable degi'ee the relative jjro- 
 portions of the fatty and cheesy matters of which our domestic butter 
 consists. 
 
 Besides the casein and sugar, butter also usually contains some colour- 
 ing substance derived from the plants on which the cow has fed, and 
 some aromatic or other similar ingredients to wliich 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 substance^-, 
 and obtained in a nearly pure state. Fresh newly-churned butter is 
 melted in a cylindrical jar at a temperature of 140° to 180° F., the 
 fluid oil poured oft' into water heated to the same temperature, and re- 
 peatedly shaken with fresh portions as long as any thing soUible is taken 
 up. When left at rest in a warm place, the melted fat rises to tiie sur- 
 face in the form of a nearly colourless transparent oil, which, on cooling, 
 hardens into a colourless mass. 
 
 1'his pure fat may be preserved for a much longer time without be- 
 coming rancid (Thenard). It is the various substances with which its 
 fatty matter is mixed that give to common butter its tendency to become 
 so speedily rancid and to acquire an unpleasant taste. To the nume- 
 rous precautions which have been adopted with the view of counteract- 
 ing this tendency, and of preserving the sweet taste of butter, I shall pre- 
 sently direct your attention. 
 
 § 11. Of the average quanlity of biiHer yielded by milk and cream, and 
 of the yearly produce of a cow. 
 
 J have already made you acquainted with some of those numerous 
 circumstances by which the (]uality of milk is affected. Tiiese same 
 circumstances will necessarily more or less affect the quantity of butter 
 also, which a given weiglii 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 but- 
 ter. 
 
 * Since the above was written, two samples of fresh bult.;r, from cream, examined in my 
 laboraio-^, have yieldoii only 0-5 and 7 per cent, respeclively of cheesy mailer. This is 
 certainly a mucli smaller quantity than I tiad expected. Does butter from l\)e trhole tnilk 
 contain more 1 A series of such examinations would prove not tuiinterosting. 
 
QUANTITY OF BUTTKR YIEIiDED BT iAllLK. 55S 
 
 Kerry cow, 12fi4 quarts, of which from 8 quarts to 6\ gave 1 lb. of 
 butter. 
 
 Showing, as I liave before stated, (p. 536), 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 average, 
 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 
 Roval Agricultural Society, I. p. 386.] 
 
 l^he 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 but- 
 ter : — 
 
 Milk. Cream. Butter. 
 
 18 to 21 lbs. I . , , W lbs. } , ,, 
 
 n t^ Ti . } Yield < o » * J- or 1 lb. 
 
 9 to 11 qts. ^ - ^2 qts.* \ 
 
 The cow, tlierefore, that yields 3000 quarts of milk should produce, 
 where butter is the principal object of the farmer, about 300 lbs. of but- 
 ter, or 1 lb. a day for 300 daj's 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 li^ four years continuously yielded nearly a pound and a 
 half of bulterf every day, are naturally 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 Holland, [Loudon's Encj^clopaedia,] a good cow will pro- 
 duce during the summer 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 poimd a day. 
 In Holstein and Lunenburg it is considered a fair return if a cow yields 
 100 lbs. of i)utter, and even in England, [British Husbandry, II., p. 
 404,] 160 to 180 lbs. is reckoned a fair annual produce for a cow, or from 
 8 to 9 ounces a day for ten months in the year. 
 
 § 12. Of the circumstances which affect the quality of butler. 
 It is known that the butter produced in one district of the country, dif- 
 fers often in quality from that produced in another, even though the same 
 method of manufacture be adopted. In different seasons also the same 
 farm will produce different qualities of butter — 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 
 spurrey (Sprengel) — that it is generally the hardest when the animal 
 lives upon dry tbod — and that autumn butter is best for long keeping. 
 
 ' The quarts spoken of in this lecture are old icine t|uarts, of which 5 make an iinperial 
 eallon. A wine gallon of milk or cream weiahs about 8 lbs. 4 oz., an imperial gallon about 
 10 lbs. 5 oz. About two imperial gallons, therefore, should yield a pound of butter. 
 
 t It gave in four years 2132 lbs. of butter from 23,669 quarts of milk, or 16 quarts a day, of 
 which 11 quarts gave a pound of butter. 
 
554 FIRST AND S>f,CO.ND MH.A AN;) tIRKAM. 
 
 These differences may all be ascribefl to varieties or natural differences 
 in the pasture or fodder upon wliich the cow is ted.* The constitution 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 but- 
 ter. 
 
 In all such cases as these, liowever, the quality of the butter is almost 
 entirely dependent upon that of the milk from which it is made, so that 
 whatever affects the (|uality of the milk nmst influence also that of the 
 butter prepared trom it. But as I have already considered the circum- 
 stances by which the quality of the milk is principally modified (p. 
 534), I shall not further advert to this subject at present. 
 
 But from the same milk, and even from the same cream, by different 
 modes of procedure, very difiierent qualities of butter may be obtained. 
 The mode of making or extracting butter, therefore, is highly worthy of 
 your attention. Let us consider a few of the more important circum- 
 stances under which different qualities of butler 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, we have already 
 seen (p. 536), that 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. Wliether. therefore, the butter be ex- 
 tracted directly from the whole milk, or from the cream, the butter ob- 
 tained from the three successive portions will differ in quality almost as 
 much as the several portions of milk themselves. 
 
 A practical application of this fact is made in some of the Highland 
 counties of Scotland, and in other districts, where the calves are allowed 
 to sucic, or are fed with, the first half of the milk as it comes from the 
 cow — the latter and richest half only being reserved for dairy purposes. 
 This second milk is found to afford an exquisite butter. 
 
 2'^. First and second cream. — In like manner the first cream that rises 
 upon any milk is always the richest, and gives the finest flavoured but- 
 ter. The after-creamings are not only poorer in butter, but yield it of a 
 whiter colour and of inferior quality. 
 
 This fact again is well understood, and has been long practically ap- 
 plied in the neighbourhood of Eppliig, which is celebrated for the excel- 
 leuce of its butter. The cream of the first 24 hours is set aside and 
 churned by itself. The second and third creams produce a pale, less 
 pleasant butter, which always sells for an inferior price. Any admix- 
 ture of the after-creamings causes a corresponding 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 tlie 
 surface, either naturally 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 rjnickly still when 
 the milk is heated, as in the preparation of clouted cream. The butter 
 
 ' The influence of the food given in the EtiiU and of the plants eaten In the pasture, upon 
 the colour and flavour of the butler, is familiar to all practic.il men. The turnipy taste of 
 the butter in winter— the garlic taste in summer, where the wiM onion grows in the pastures 
 — and the alleged effect of raw potatoes in winter, in giving a rich colour to the butler, are 
 eommon examples of this kind. 
 
TOO RAPID OR OVER-CIIl'RMNO. 655 
 
 {Bohemian butter) obtained from such cream — from cream thus rapidly 
 brought to the surface — may be expected to differ both in flavour, in con- 
 sistency, and in composition, from that yielded by tlie cream of the same 
 milk when allowed to rise in the usual manner. 
 
 4°. Sourness of the cream. — For the production of the best butter it is 
 necessary that the cream should be sufficiently sour before it is put into 
 the cluirn. Butter made from sweet cream (not clouted), is neither good 
 in quality nor large in ijuantity, and longer time is required in churning. 
 It is an unprofitable method (Ballantyne). 
 
 5°. Quickness in churning. — The more quickly iriilk or cream is 
 churned, the paler, the softer, and the less rich the butter. Cream, ac- 
 cording 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 inay 
 not be soft and white, and quicker in winter that the proper temperature 
 may be kept up. 
 
 Mr. Blacker has lately introduced into this country a barrel-churn in- 
 vented by a Mr. Valcourt, 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 Avater to the 
 milk, and churns ihe wlwle in ten or twelve mmutes. It is said also to 
 give a larger weight of butter from ttie same quantity of milk. 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 can not 
 be due to the mere rapidity of churning alone. 
 
 6°. Over-churning. — Wlien the process of churning is continued after 
 the full separation of the butter, it loses its tine yellowish, waxy ap- 
 pearance, and becomes soft and light coloured. Tlie weight of the butter, 
 however, is said to be considerably increased ; and hence that in Lan- 
 cashire over-churning is frequently practised in the manufacture of fresh 
 butter for immediate sale (Dr. Traill.) 
 
 7°. Tcmperalure of the milk or cream. — Much also depends upon 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 churneu,tne temperature should 
 be raised to 65° F., which is best done by pouring in hot water into the 
 churn wliile the ynilk is kept in motion.* 
 
 The importance of attending to the tem])erature and to the quickness 
 of churning, when the best quality of butter is required, is shown by the 
 two ffjUowing series of results obtained in the churning of cream at dif- 
 feretit temperatures and with different degrees of rapidity. 
 
 The first series was obtained in the August and September of 1823, by 
 Dr. Barclay and Mr. Allan. The quantity of cream churned in each 
 experiment was 15 wine gallons, weighing from 8 lbs. to S\ lbs. per gal- 
 lon. 
 
 • Uallantyne, Transactior,sr,f the Highland .Society, New Series, I., p. 24. Some objert to 
 thismetliod of addins; hot water, say ins that it renilersi the butter pale and leas valuable in the 
 market. Tliis is by no means universally llie rase, ami Ihe keepinp the milk in motion, 
 while the water is added, nisy possibly, in some cases, niak'' the dilTerence. lu other casea 
 may be owing to natural dilTerenccs in the quality of the milks operated upon. 
 
 24 
 

 Temperature. 
 
 «Jo. 
 
 1 
 
 50° 60° 
 
 2 
 
 55° 65° 
 
 3 
 
 58° 67° 
 
 4 
 
 60° 68° 
 
 5 
 
 66° 75° 
 
 556 TEMPtRATtttK OF THK AlILK OR CREAM. 
 
 Quantity of 
 Time in IJutler 
 
 „ , Churning, per gallon. Uuality of the Butter. 
 
 '^""- Hours. lb. oz. 
 
 4 1 15J Very best, rich, finn, well tasted. 
 
 bj 1 15^ Not sensibly superior to the former. 
 
 3 1 14 Good, but softer. 
 
 3 1 I2ij Soft and spongy. 
 
 2i 1 lOri Inferior in every respect. 
 
 The results of these experiments prescribe the temperature of 50 to 55* 
 F. for tlie cream when put into the churn, and from 3i to 4 hours as tlie 
 most eligible for producing butter, botli in the largest quantity and of the 
 finest quality. Something, liovvever, appears to depend upon the quality 
 of the cream ; since tlic indications of the next series of experiments dif- 
 fer considerably from the above, in so far at least as regards the length 
 of time expended in churning. 
 
 The following experiments were uKide in Edinburgh, by Mr. Ballan 
 tyne, between June and August, 1825. The quantity of cream he used 
 at each churning was 8 wine gallons — weighing 8 lbs. to the gallon, ex- 
 tcept hat of the fourth e.Kperiment, which weighed 4 ounces less. 
 Temperature. Tjme in Quantity of 
 
 Quality oVilie butter. 
 
 Inferior; white and softer than No. 2. 
 The flavour and quality of these two 
 
 butters could not be surpassed. 
 Soft, white, and milky. 
 Good — evidently injured by longchurn- 
 
 ing^.- 
 Most excellent. High in flavour and 
 
 colour, and solid as wax. 
 
 To obtain buffer from crcatn, tlierefore, both finest in quality and 
 largest in quantify, these two series of experiments prescribe the follow- 
 ing temperatures of the cream, and times in the churning — 
 Temperature. Time. 
 
 First ... 50° to 55° 3\ to 4 hours 
 
 Second . . 53|° U to 1?- " 
 
 In the temperature botli agree. It is probable ihat the nature ol" the 
 cream obtained at diflerent seasons or in different localities may render 
 a longer time necessary in tljc cluirning on some occasions 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 mitJ,:. — It is in connection with the tempera- 
 ture at which milk and cream may respectively be best and most eco- 
 nomically churned, that tlie chances of obtaining a butter of good quality 
 at every season of the year ai)pear to be greater when the whole milk is 
 used, than when the cream otdy is put into the chinii. 
 
 Cream, when the churning commences, should not be warmer than 
 SS" F. — luilk ought to be raised to 65° F. In winter, either of these tem- 
 peratures may be easily attained. In cold weather it is often necessary 
 
 ■ In sweet cream, when the butter is long in coming, the adiiition of a litllo vinegar, brandy, 
 ar whiskey, will hasten the churning. 
 
 Jo. 
 
 Of the When but- 
 
 Churn- 
 ing. 
 
 Buffer 
 per gallon. 
 
 
 cream, ter came. 
 
 Hours. 
 
 lbs. on. 
 
 1 
 
 56°F. 60°F. 
 
 U 
 
 2 1 
 
 2 
 
 52° 56° 
 
 2 
 
 2 Oi 
 
 3 
 
 52° 56 
 
 2 
 
 2 0\ 
 
 4 
 
 65° 67° 
 
 JL 
 
 1 15 
 
 5 
 
 50° 53a° 
 
 3' 
 
 1 15i 
 
 6 
 
 53J° 57i° 
 
 1} 
 
 2 Oj 
 
ADVANTAQK OF CtIURN!.\G THK WHOLK MtLK. 657 
 
 ti) aJil hot water to tlie cream to raise it even to 55°. But in summer, 
 and .'dj)ecially in hot weather, it is ditiicult, even in cool and well or- 
 dereii dairies, to keep the cream down to this comparatively low temper- 
 ature. Hence if the cream be then churned, a second rate butter, at best, 
 is all that can be obtained. 
 
 Milk, on the other hand, reipiires a temperature of G5° — ten degrees 
 liigber than cream — and therefore neither summer nor winter weather 
 materially alFecls th»i 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 — wliere the milk is kept in a well contrived 
 dairy — in which it will not be necessary to add more or less hot water in 
 order to raise the milk to G5° F. Thus, wliere the entire milk is churned, 
 the same regular method or system of churning can be carried on through- 
 out the wiiole year. No ditliculty is to be apprehended from tlie stale 
 of the weather, nor, so long as tlie ipiality 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 ahke firm, finely fla 
 voured, and rich in colour. 
 
 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 winter and 
 in summer. 
 
 />. A hundred gallons of entire milk will give in summer five per cent, 
 more butter than ihe cream from the same (juantity of milk will give 
 (Ballantyne). 
 
 c. Butter of the best quality can be obtained without difficulty both 
 in winter and in summer. 
 
 d. No S])ecial attention to circumstances or change of method is at 
 any time required. The churning in winter and summer is alike 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 (Ballantyne). 
 
 To these advantages it is set off, that except in the neighbourhood of 
 large towns, the butter-milk is of little value — while from the skimmed- 
 milk, a marketable cheese can always be manufactured. But this ought 
 to be no objection, where churning the whole milk would otherwise be 
 preferred, since it is Utile 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 solo bring under your notice the fact, that cream is remarkable 
 for the rapidity with which it absorbs and becomes tainted by any un- 
 pleasant odours. It is very necessary thai 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 can come. 
 
 § 13. Ofl}ie 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 temperature not ex- 
 
558 THE FATTY SfBSTANCKS ly EL'TTKK. 
 
 ceeding 180° F., aiKl be llion wa^lied sviih repeated portions of warm 
 water, a nearly colourless fluid oil is obtained, which, if not transpar- 
 ent, becomes so wlien filtered through paper, and when cool congeals into 
 a more or less pnre white solid fat. If this fat be put into a linen cloth 
 and be submitted to a strong pressure in a liydraulic or other press at the 
 temperature of GO" F., a slightly yellow, transparent oil will flow out, 
 and a solid white fat will remain behind in the linen cloth. The solid 
 fat is known to chemists by tlie name of margarine. The licpiid oil is 
 peculiar to butter, at least it lias not hitherto been found in any other sub- 
 stance ; it is therefore called the oleine of butter, or simply buUer-oil. 
 
 The pure fat of bntter consists almost entirely of these two substances, 
 there being generally present in it only a small quantity of certain faiiv 
 acids, which I shall presently introduce to your notice. Thus a speci- 
 men of butter made in the montli of May gave a fat which was found 
 by Bromeis to consist of about — 
 
 Margarine (18 per cent. 
 
 Butter oil 30 
 
 Butyric, caproic, and capric acids .... 2 " 
 
 100* 
 But the proportion of the solid and fluid fats in butler varies very much. 
 [t is familiar in every dairy that the butler is harder and firmer at 
 one time and with one mode of churning than with anoiher, — and this 
 greater firmness depends mainly upon the presence of the solid fat (mar- 
 garine) in larger proportion. According to Braconnot, summer butter 
 contains niucli more of the butter-oil tlian winter butter does; and he 
 states their relative projiortions in these two seasons, in the butter of the 
 Vosges, which he examined, to be as follows : — 
 
 Slimmer. Wiriier. 
 
 Margarine 40 65 
 
 Butter oil 60 35 
 
 100 100 
 
 Of course these projjortions are not to be considered as constant. In- 
 deed, the pro])ortion 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 aflected by climate, by sea- 
 son, by the race, the food, and the constitution of the animal; by the way 
 in which the butter is made, by the manner in which it is Uept, and by 
 other circumstances not hitherto in\ estigated. 
 
 2°. Margarine. — This solid fat, which exists so largely in butter, 13 
 also the solid ingredient in olive oil, and in goose and human fat. But- 
 ter, therefore, appears to be a most natural food forthe huirianrace, since 
 it contains so large a proportion of one of those substances which enter 
 directly into the constitution of tlie human frame. 
 
 Margarine is white, hard, and brittle, and melts at 118° F. In the 
 pure state it may be kept for a lengtli of lime without imdergoing any 
 sensible change, but in the slate of mixture in wliich it exists in milk and 
 butter it is apt to absorb oxygen from t!ie atmosphere, and to be ])artially 
 
 ' Annal. tltr Chein. und P/iar., \\n., p. 70. 
 
PROPERTIES OF THE SUGAR OF MILK. 559 
 
 changed into butter oil, and into one or other of those fatly acids which 
 are present in butter in smaller quantity. 
 
 3°. Margaric acid. — When this fat (Margarine) is introduced into a 
 hut 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 col- 
 lected, 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 Avith a sweet substance known by the name of glj'cerine, 
 or oil sugar.* 
 
 Margaric acid is represented by the formula 34 C + 34 H + 4 O, or 
 C34 H34 O4. To this formula it will be necessary in a few minutes to 
 revert. 
 
 Bullcr oil. — The liquid fat expressed from butter has the appearance 
 of an oil, sometimes colourless, but often tinged of a yellow colour. It 
 has the taste and smell of butter — mixes readily with alcohol, and be- 
 comes solid when cooled down to 32° F. — the freezing point of water. 
 It dissolves without ditiiculty in a solution of caustic potash, and forms 
 a soap. 
 
 Acid of butter-oil — oleic acid of bullcr. — When the solution of the oil 
 in caustic potash is diluted with much water, and decomposed by the ad- 
 dition of diluted sulphuric acid, an oily substance is separated, which is 
 dillerent from the original oil of butter, possesses acid properties, and is 
 known by the name of the oleic acid of butter. This fatty acid lias 
 never hilberto i)een obtained from any other substance than the oil of 
 butter, and the oil consists of the acid in combination with oil-sugar. 
 You will recollect that margarine consists of margaric acid in combination 
 with the same sugar (p. 558.) 
 
 * Such is the apparent composition of the two fatty svibslances, margarine and biitter-oil, 
 inasmuch as when they are dissolveU in a solulion of causiic potash, and their solulions 
 afterwards decomposed by an acid, they are resolved respectively — 
 Margarine — into margaric acid and oil-su^ar ; 
 Bulteroil—iulo butler oleic 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, consislina; of 3 atoms of carbon united to 2 o f 
 hydrogen — Cj IK', to wliich the name oUipyle is given. 
 
 2°. That this radical d H2 unites with an atom of oxygen, forming C?, 112 O, or oxide of 
 Upyle. 
 
 3°. That in neutral faify bodies, such as margarine, tliis oxide exists in combination 
 with a fatty acid. Thus, for example, that— 
 
 ,, . . . ,<i 1 of margaric acid = C3-) Il34 Ol 
 
 Mcrganiie consists of^j ^j- ^^^^^ ^f ^-^^^^ = C, Hs O 
 
 Formirig, together, 1 of margarine = C37 HSe 05 
 
 And . „ -, r S I of oleic acid of butler = Cs4 H.n OS 
 
 butter.oil of > ^ ^j. ^^ijg ^f ,i|,y,g = C3 H. O 
 
 Forniins, together, 1 of bulter-oil = C37 H33 Og 
 
 4°. And that when this oxide of lipyle is separated from its combination with the fatty 
 ftcids it unites with a (juantity of water, and forms glycerine or oil-susar. Thus — 
 
 2 ofoxidc oflipyle = Co H4 O-^ united to 
 
 3 of water = Its O3 give 
 
 1 of glycerine (oil-sugar) ..-....= Cr, H? O5 
 .'(°. The above Is the view 'if Berzeliu.', but Uedtenbaclier lias recently suggested, [Annal. 
 dcr Chem. und Phar., XI.VII., p. 141,] that a known substance called acrolein exists in the 
 
660 CHA.NOK or xMA^.(:AKI^E INTO OLKlt ACID. 
 
 When pure, this oily acid is colourless and transparent, and is re- 
 markable for the raphli y uilh which it absorbs ox 1/ gen from the atmos- 
 phere, and becomes conv ried into new chemical compounds. It is re- 
 presented by the foimula 34C + 31 H + 50, or C.i4 H31 O5. 
 Let us compare this formula with that of" the niarsaric acid : 
 
 Margaric acid = C34 H34 O4 
 
 Butler oleic acitl ,.,.=: C3! Ha O5 
 
 DitTerence +H3 — Oi 
 
 or, if 3 of hydrogen be taken from the margaric acid and 1 of oxvgen 
 added to it, it will be converte^l inUj tlie oleic acid. 
 
 Now this may be etietited by simply sup|)0sing one atom of margaric 
 acid to absorb four atoms of oxygen from the atmosphere. Thus — 
 
 1 of margaric acid = C34 H;i O4 
 
 4 of oxygen . . = Oi 
 
 1 of oleic acid -1- 3 of water. 
 
 €31 H34 08 , or C:?4 I-I31 O5 + 3HO. 
 
 So that either in the body of the animal, in the milk while it remains 
 in the udder, 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 jjortioii of the 
 margaric acid may absorb oxygen and become changed into the oleic 
 acid. It may also be that this change, this absorption of oxygen, is pro- 
 moted by warm and retarded by cold weather, and (hat thus the butter 
 is rendered generally softer in the summer and harder in the winter sea- 
 son. But these are as yet only conjectures ; for, after all, the relative pro- 
 portions of the soft and hard fat in butter at diflerent times of the year 
 may depend upon natural diflferences in the lierbasre at the several 
 seasons, or upon some other causes which have not as yet been in- 
 vestigated. 
 
 5°. Butyric, capric, and caproic acids. — These substances, as I have 
 already stated to you, exist in butter only in small cpiantity — to the 
 amount of 2 or 3 percent. To tliese acids, and especially to the capric 
 and caproic, butter owes its disagreeable smell when it liecomes rancid. 
 They do not exist, naturally, to any unpleasant extent in perfectly fresh 
 butter — they are gra<lually formed in it, however, when fresh butter 
 is exposed to the air. I do not enter into any detail of their proper- 
 ties, or of the mode of extracting them from butter, because these points 
 
 fats in combination with the fitly acit!. Tliis acrolein is represented by Ce H4 O?, which 
 is exucily the constitution of 2 of lipyle. So that according lo tliis view the solid fat of but- 
 ter would consist of— 
 
 2 of marsaric acid . . . . = res H53 03 
 
 1 of acrolein = Cs Hj O2 
 
 2 of margaric acid ....=: C7j Hn Olo 
 
 and, by a like substitution of acrolein for oxide of lipyle, may the constitution of butter-oil 
 be represented. 
 
 The principal known fact in favour of this view of Redlpub:icher is, that when alycerine I3 
 distil. ed with anhydrous phospiioric acid, acrolein i< produceil. He supposes that the acid 
 takes the elements of 3 atoms of water from glycerine, forming acrolein : since if from — 
 
 1 of glycerine =: Cs H? 05 wc lake 
 
 3 of water = lit O:) 
 
 Acroli'in remains =: Ci Hi Oj 
 
 Tlift conversion of acrolein into elycerine, when it is separated Cinm the frftty acids, is sup- 
 posed lo 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. 
 
PROPERTIKS or THr. CUKD 01' MILK. 561 
 
 fire of le > interest or importance lo you. It is necessary only, to a 
 clear understanding of the kind of cnangos which take place when butter 
 becomes rancid, that I should exhibit to you the formulae bv which these 
 n.:id bodies are severalh' rej)re.scuted : — 
 
 Butyric acid = C3 lis O4 
 
 Caproic acid = C12 II9 Oi 
 
 Capric acid = Cis H14 Oj 
 We sliall see how these sui)stances are produced from the solid and 
 fluid fats of butter, when we coaie to treat of tlu^ preservation of butter. 
 
 § 14. Of casein or the curd of null: and its properlics. 
 
 The casein or cheesy matter of milk may be obtained nearly pure by 
 the foUownig process : — Heat a quaulity of milk whifh has stood for 5 
 or (3 hours, as if you intended to prepare clouted cream (p. 548), let it 
 cool, and separate the cream completely. Add now to the milk a little 
 vinegar and heat it j^enlly. The whole will coagulate, and the curd will 
 separate. Pour otf the whey, and wash ihe curd well by kneading it 
 with repeated portions of water. Wlien pressed and dried, this will be 
 casein sulliciently pure tor ordinary purposes. It may be made still 
 more pure by dissolving it in a weak solution of carbonate of soda, al- 
 lowing the solution to stand for 12 hours in a shallow vessel, separating 
 any cream that may rise to the surfiice, again tlirowing down the curd 
 by vinegar, washing ir fretjuenlly, find occasionally boiling it with pure 
 wat^r. By repeating this process two or three times, it may be obtained 
 almost entirely free from tlie latty and saline matters of the milk. 
 
 Casein tlius prepared reddens vegetable blues, and is therefore a 
 slightly acid substance. It is very sparingly soluble in water — 400 lbs. 
 of cold'wnter dissolving only 1 lb. of pure casein (Rochleder). It dis- 
 solves readily, iiowcver, and in large quantity, in a weak solution of the 
 carbonate of potash or of so la, and to some extent even in lime-water. 
 These solutions are coagulated l)y tlic addition of an acid — of sulphuric 
 acid, of vinegar, or of lactic acid — and the curd readily separates on the 
 application ol"a gentle heat. If a large (juantity of acid be added, a por- 
 tion of the casein is re-dissolved. 'J^his property of dissolving in weak 
 alcaline (potasli or soda) solutions, satisfactorily explains what takes 
 place during the curdling of milk, as we shall hereafter sec (p. 567). 
 
 The casein of milk is identical in chemical constitution with the Hbnn 
 of wheat, the legumin of the pea and bean,* and tlie albumen of the 
 egg or of vegetal)Ie substances. Hence the ofiinion has naturally arisen 
 among chemists, that the cheesy matter contained in an animal's milk is 
 derived directly, and williout change, from the food on which it lives. 
 Tlie probability of this opinion will come naturally under our considera- 
 tion in the following lecture. (See next lecture, " On the feeding of 
 stock."') 
 
 Casein possesses still one property more remarkable than any of its 
 
 ■ In pigft 394 it is stated, on the antlmrity of Dumas, tliat tliplfgiimin of (lir^ pea and besm 
 differs in composition from fibrin and alliiinven Since ttiat sliPet was published, it appears, 
 from Ihe experiments of Rochleder (Annal. dpr Ctieni. iind Pharm., xlvi., p. 162), that the 
 leiiumin whicti Dumas exuacted from tlie almond, analysed, and supposed to be identical 
 with the legumin of the bean and pea, is not so, but Is in reality a different substance ; and 
 that the legumin of peas doen a!;ree in composition with the casein of milk. 
 
662 ACTIO^• OF casein upon sugar. 
 
 others, and exceedingly int(;resting to the practical agriculturist. Let 
 me explain this property a little more in detail. 
 
 § 15. Of the relations of casein to Lhe sugars and the fats. 
 
 1°. Relation to the sugars. — a. Production of lactic acid. — I have 
 already adverted (p. 543) to the romarkaljlc property which casein pos- 
 sesses of gradually converting milk or other sugars into lactic acid. If 
 a small quantity of this substance, either in tiie state of fresh curd or in 
 the purer form just described, be introduced inlcj a solution of cane-sugar, 
 or of sugar of milk, lactic acid begins very soon to be formed. Thus 
 the casein it contains is the cause of the souring of milk. In like man- 
 ner it is the casein contained in bean or pea-meal which makes it so 
 soon become sour when mixed with water. 
 
 h. Produrtion of hutyric acid. — But the transforming action of casein 
 doos not end when this change is {induced. After a longer time a 
 further alteration is cfiecfed by its means. A fermentation commences, 
 during which carbonic acid and pure hydrogen gases are given off", and 
 hutyric acid is produced (Peloiize and Gelis). Let us consider the 
 nature of this new change. 
 
 Butyric acid is represented by Cs Hg O4 ; and lactic acid, as we have 
 seen, by Ce Hg Oe ; therefore — 
 
 4 of lactic acid = C24 H2.1 O24 and 
 
 3 of butyric acid = C24 H24 O12 
 
 Difference Oio 
 
 That is to say, that 4 of lactic acid, in order to be converted into 3 of 
 but3'ric acid, must give off' 12 of oxygen. But during the fermentaticm 
 whicli accompanies the change no oxygen is given off". The gases 
 ■which escape are carl)onic acid and hydrogen. The oxygen given off" 
 by one portion of the lactic acid, therefore, must combine with the ele- 
 ments of another portion, and convert it into these gases. Thus to — 
 li of lactic acid . . = Cg H9 O9 
 Add 12 of oxygen . . = O12 
 
 9 of carho- , 6 of liy- , 3 of 
 nic acid "• drupen '* waier. 
 
 And we have . . . Cg Hg O21 = 9 C O2 -f 6H -f 3 HO ; 
 or, while 4 atoms of lactic acid are converted into 3 of b\ityric acid, l^ 
 of lactic acid are at the same time converted into 9 of carbonic acid gas, 
 6 of hydrogen gas, and 3 of water. The gases escape and cause the fer- 
 mentation, while the water remains ui the solution.* 
 
 ' I have taken in the text the smallest numbers by which the general change could be re- 
 presented In the simplest way. Accnnliii^ to Pelouze and Gtlis, however, the liydrogen 
 given off is sensibly one-tliird of llie bulk of the carbonic acid when the butyric fermenta- 
 tion is in its vigour. To satisfy this condition, llierefore, much higher numbers must be 
 taken ; such as the following : — 
 
 20 of lactic acid = C"i-o H150 O150 are converted into 
 
 15 of butyric acid = Civo Hr.o Oau 
 
 Giving off = Oeu 
 
 And these GO of oxygen decompose 6 of lactic acid, as above described. Thus to — 
 
 6 of lactic CssHaeOSB 
 
 Add 60 of o.vygen . . Oso 
 
 6 of carbonic acid -)- 12 hydrogen -f- 24 water. 
 
 And we have . . C36 H3C O90 = 36CO.: -|- i2II + uHO. 
 
 where the carbonic acid gas is exactly three times the bulk of the hydrogen gaj produced. 
 
OF THE RANCIDITr OF BUTTER. 563 
 
 The outyric aciJ thus produced is a colourless transparent volatile 
 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 batter, the rancidity of this important 
 dairy product is partly to be ascribed. 
 
 2°. Relation to the fatly bodies. — It is probable that in certain cir- 
 cumstances the casein of milk is capable of inducing chemical changes 
 in the fatty bodies as well as in t!ie sugars, but this conjecture has not, 
 as yet, been verified by rigorous experimental investigation. 
 
 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 i>roduction of lactic acid will re- 
 commence, and may continue till all the sugar is changed. If more 
 sugar be added by degrees, tlie 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 production of acid, and, at length, the acid will cease to 
 be formed, while b(3lh sugar and oil are present. The casein originally 
 added has now produced its full effect (Lehmann). 
 
 It appears, therefore, that in the presence of sugar, casein is capable 
 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 thase latter into which the butter-oil is convertible 
 may probably be reckoned the ca])ric and caproic 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- 
 
 § 16. Of the rancidity and 'preserration of butter. 
 
 We are now prepared, in some measure, to understand the changes 
 that take place when l)utter becomes rancid — and the way in which those 
 substances act which are usually employed for preserving it in a sweet 
 and natural state. 
 
 1°. When butter becomes rancid, there are two substances which 
 change — tlie 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 atmosphere. The quantity 
 of casein or cheesy matter which butter usually contains is very small, 
 but, as we have seen, it is the singular pro]2erty of this substance to in- 
 duce chemical changes of a very remarkable kind, upon other compound 
 bodies, even when mixed with them in very minute quantity. 
 
 2°. As it comes from the cow, this substance, casein, produces no 
 change on the sugar or on the fatty matters of the milk. But after a 
 
 Every chemist is aware, tiowcver, that in decompositions of this kinri, it is seldom 
 that one single prorluct is obtained alone. Ttinngh tlie above formula, therefore, represents 
 truly how butyric acid may be produced from lactic acid under the circumstances, yet 
 oilier substances are not unfrequenlly formed during tiie actual experiment, by which the 
 result is more or less compUcated. 
 
 24* 
 
664 INFLUENCE OK THE CUEESY MATTER. 
 
 short exposure to the air it alters in some degree, and acquires the power 
 of transforming milk sugar into lactic acitl. Hence, as we have seen, the 
 milk l)egins speedily to become sour. Further ciianges follow, and, 
 among other substances, bntyric acid is formed. 
 
 In butter the same changes take place. Tlie casein alters the sugar 
 and the fatty matters, producing the butyric and other acids, lo which its 
 rancid taste and smell are lo be ascribed. 
 
 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 oti" 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, liowever, it is care- 
 fully abstained from, in the case of butter which is to be salted for long 
 keeping. 
 
 There are two circuinsiances which, in the case of butter that is to be 
 kept for a length of time, may render it inexpedient to adopt the metliod 
 of washing. The water may not be of tlie purest kind, and thus may 
 be fitted to promote the future decomposition of the butter. S|)rengel 
 says that the water ought to contain as little lime as possible, because 
 the butter retains the lime and acqviires a bad taste from it. 
 
 But the water may also contain organic substances in solution — vege- 
 table or animal matters not visible ])crhaps, yet usually present even iu 
 spring water. These the butter is sure to extract, and" they may mate- 
 rially contribute to its after-decay, and to the dithculty of preserving it 
 from rancidity. 
 
 Again, the washing with water exposes the particles of the butter to 
 the action of the oxygen of the atmosphere much more than when the 
 butter is merely well squeezed. The effect of this oxygen, in altering 
 either the fatt}'' matters themselves or the small quantity of casein which 
 remains mixed with them, inay, no doubt, conmbute to render some but- 
 ters more susceptible of decay. 
 
 3°. But the casein, af'er it has l)een a still longer tinio or more fully 
 exposed to the air, inidergoes a second alteration, by which its tendency 
 to transform the substances with which it may be in contact, is consi- 
 derably increased. It ac([uires the property also of inducing chemical 
 changes of another kind, and it is not im]irol)al)le that tlie more un- 
 pleasant smelling capric and caproic acids may be jiroduced 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 if as com- 
 pletely 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, tlie better and 
 sweeter the butter is likely to remain. 
 
 4°. The action of tliis cheesy matter, and its tendency to decay, are 
 arrested or greatly retarded by the presence ol' saturated solutions of cer- 
 tain saline and other substances. Of this kind is common salt, which is 
 most usually employed for the purpose of preserving butter. Saltpetie, 
 also, possesses this jiroperty in a less degree, and is said to impart to the 
 butter an agreeable flavour. A syrup or strong soliuion of sugar will 
 likewise prevent both meat and butter from becoming rancid. Like salt- 
 
HOW TO PUniFY SALT FOR BUTTER. S^ 
 
 petre, however, it is seldom used alone, but it is not uncommon to em- 
 ploy a mixture uf common salt, saltpetre, and sugar, for the preservation 
 of butter. Where the butter lias been washed, this admixture of cane- 
 sugar may supply the place of the milk-sugar wliich the butter originally 
 contained, and may impart to it a sweeter taste. 
 
 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 otlier disagreeable taste. It is easy, however, to purify the 
 common salt of the shops from these impurities 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 tlirough a clean cloth. The v^^ater which runs through is a saturated 
 solution of salt, and contains all the impurities, but may be used for com- 
 mon 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 v\'iih tlie butter or with cheese. 
 
 The (piantity of salt usually employed is from :^'jth to /jjth part of the 
 weight of the bulter — with which it ought to be well and thoroughly in- 
 corporated. The first sensible efl'ect 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 wliich part of the salt also flows away. It 13 
 not known that the casein actually combines with the salt, nor, if it did, 
 considering the very small (juantity 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 
 remains in die butter shall be fuiL<j saturated ivith salt — that is to say, 
 shall have dissolved as much as it can possibly take up — and 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 sat- 
 urated solution of salt will not only preserve this cheesy matter from it- 
 self imdergoing decay, but will render it unable also to induce decay in 
 the su2:ar and fat which are in contact with it.* 
 
 It is really extraordinary that such rigid precautions should be neces- 
 sary to prevent the e\il influence of half a pound of cheesy matter, or less, 
 in a hundred pounds of butter (p. 551). 
 
 5°. Thougii 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 decomposition, and the presence 
 of which, therefore, shoitld be excluded as carefully as possible. 
 
 We liave seen that by the action of oxygen the solid margaric acid of 
 butter may be changed into the oleic or liquid acid of butter (p. 560.) 
 
 ' Mr. Ballantyne lliiis describes the melhod of saltii.s biHIer prarlised at his dairy farm of 
 30 cows, near Edinburjih : — " The butter Is drawn warm from the churn, and it is ati invari- 
 able rule never to waah it or dip it into walnr, jrlien inteinled to he salted. 'I'lie dairymaid 
 puis it into a clean tub, which is previously well rinsed with cold water, and Uien works it 
 wiih cool hands till alt the milk is thoroujhly sepjeezcd out. Half the allowed quantity of 
 salt is then added, and well mixed up with the bulter, and in this state it is allowed 10 stand 
 till next morning, when it is a2:iin wrou::lil up, any brine KqueP7.''d out. and the remainder 
 of the salt ad.ied. It is then packed into kits, whiih, 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 bulter." — 
 Journal of Agriculture., New Series, vol, /., p. 26. 
 
SS6 EVIL EFFEC 1" OF THE AIR UPON BUTTER. 
 
 This is the first stage in the decomposition, which, when once begun, 
 generally spreads or extends with increasing rapidity.* 
 
 Again, I have also statt'd that this fluid (oleic) acid of butter absorbs 
 oxygen with great rapidiiy from the air (p. 560), and changes rapidly into 
 other compounds. This is the second stage, and is succeeded by others, 
 which it is uiniecessary to enumerate. 
 
 To this action of the air is partly to be ascribed 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 knead- 
 ing together the butter in the cask or firkin — that no air holes or openings 
 for air be left — that the cask itself be not only water-tight but air-tight— 
 and that it should never be finally closed till the butter has shrunk in as 
 far as it is likely to do, and until the vacancies, which may have 
 arisen between the butter and the cask, have been carefully filled up 
 again. 
 
 § 17. Of the natural and artificial curdling of milk. 
 
 When milk is left to itself for a certain length of time it becomes sour 
 and curdles. The curd and whey, however, do not readily separate un- 
 less a gentle heat be applied, when the curd contracts in bulk, and either 
 squeezes out and floats upon the whey, or, when cut into pieces or j^laced 
 in a perforated cheese-vat, allows 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 at a slow fire, the buttery part will separate from the 
 cheese, and will float on the top in the form of a fluid o\\. 
 
 1°. Natural curdling. — The natural curdling of milk is produced by 
 the lactic acid, which, as we have seen (p. 5-14), 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°. ArLificial curdling. — But it is not usual in the manufacture of 
 cheese to allow tiie milk to snur and curdle of its own accord. The pro- 
 cess is generally hastened b}-^ the artificial addition of acid, or of some 
 substance, such as rennet, by which the natural production of acid is ac- 
 celerated. Almost any acid substance will have the efiect of curdling 
 milk. Muriatic acid (spirit of salt), diluted with water, is said to be ex- 
 tensively, though not universally, employed in Holland for this pur- 
 pose. In other countries vinegar, f tartaric acid, lemon juice, cream of 
 
 ' I do not know whetlier a converse change is ever obanrved in butter by long keeping in 
 contact witli brine — whether it ever becomes very sensibly harder. Tallow, as is well 
 known to candle-makers, and e.speclally to tlie manufacturers of stearin candles, becomes 
 harder by keeping, indeed somr-limes is unfit for use un!il it is a year oM — randies in a damp 
 place become iiarderby keeping — and in tallow iliat has lain long in a wet mine the oily part 
 has been found entirely chan^'e'd into the sulid fat of tallow (Beetz) A similar change, 
 therefore, is not impossible nor inexplicable in butter also — only if it over do take place, we 
 should expect the changed butter to be le.ss solid and dense than before. 
 
 t " To coagulate a coty'a of milk we ail I a cyiithus of sweet vineear" (t)ioscorides). Milk 
 is also curdled by ardent spirits, by the juice of the fj;;. and by a decoction of the {lowers of 
 the artichoke, of (he white and yellow bed-straw (galiiim), aiid of the crowfoot (t-aivinculua 
 Jlammula and Un^da). 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 gives a cheese of finer colour and less pungent tasle. 
 
I«ATURAI- AND ARTIFICIAL CURDLING OF I.IILK. 567 
 
 tartar, and salt cf sorrel have been occasionally used, and in Switzerland 
 — especially in the manufacture of the schabzieger cheese — it is cus- 
 tomary to add merely a little sour milk for the purpose of producing the 
 curd. 
 
 3°. Chemical action of ihe acid. — But how does the acid act in causing 
 tlie 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? 
 
 In regard to casein or the cheesy matter of milk, we ha%'e seen (p. 
 5C1)— 
 
 a. That though nearly insoluble in pure water, it dissolves readily in 
 water containing in solution a small (juantity of {)otash or soda, either in 
 the caustic or carbonated state. In other words the casein, which is an 
 acid substance, unites cheinically with the potash or tlie soda, and forms 
 a compound which is soluble in water. 
 
 h. That when an acid is added to this solution, it takes the potash or 
 soda from tlie casein and combines with it, leaving the curd again in its 
 original insoluble state, and cau.>ing it, therefore, to separate from the 
 water. 
 
 Now in milk, as it comes from the cow, the casein is in chemical 
 combination with a small quantity of soda, by which it is rendered so- 
 luble in the water of whicli the milk chiefly consists. When the milk 
 stands for a time in the air, the sugar of milk, as we have seen, is trans- 
 formed into lactic acid — this acid takes the soda from the casein, and 
 forms lactate of soda, and the chi^esy 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 scj)arate readily from the 
 whey. 
 
 If we add an acid artificially to nrilk, the effect is exactly the same. 
 Either muriatic acid, or tartaric acid, or vinegar, or sour milk, will, in the 
 same way, take the soda from the casein, and render it insoluble. And 
 that this is the true action is readily proved by adding a little soda to 
 curdled milk, when the curd will be re-dissolved, and the milk will be- 
 come sweet. Add acid to it now, or let it sour naturally a second time, 
 and the curd will again be se])arated. 
 
 The action of rennet is in some degree different, though no less simple 
 and beautiful. Let us first, however, consider what rennet is, and how 
 it is prepared. 
 
 § 18. Of the preparation of rennet. 
 
 Rennet is prepared from the salted stomach or intestines of the suck- 
 ling 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 if. 
 
 1°. Preparing the stomach. — The stomach of the newlv killed animal 
 contains a quantity of curd derived from the milk on which it has been 
 fed. In most districts (Switzerland, Gloucester, Cheshire) it is usual to 
 
 ' Dried pig's bludil^r is often employed inr.tcat! of the dried kid'3 stomach forcurjling the 
 goat's miik on Mom Dor. 
 
668 METHODS OF MAKING THE RENNET. 
 
 remove by a gentle washing the curd and slimy maUers which are pre- 
 sent in the stomach, as they are supposed to impart a strong taste to the 
 cheese. In Chesliire the curd is frequently salted 'separately for imme- 
 diate use. In Ayrshire and Limhurg, 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. 
 
 2°. Salting the stomach. — In the mode of salting the stomach similar 
 differences prevail. Some merely put a few liandfnls of salt into and 
 aroimd it, then roll it together, and hang it near the chimney to dry. 
 OLhers salt it 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 the following year. They 
 are then taken out, drained from the biine, 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. [Cattaneo, 
 II latte e i suoi prodotti, p. 204.] 
 
 In wliatever 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 rennet is thought in 
 Gloucestershire " to make the cheeses heave or swell, and become full 
 of eyes or holes." [British Husbandry, ii., p. 420.] 
 
 S'^. Making the rennet. — In making the rennet different customs also 
 prevail. In some districts, as in Cheshire, a bit of" the dried stomach is 
 ])ut into half a pint of lukewarm water with as much salt as will lie 
 upon a shilling, is allowed to stand over night, and in tlie morning the 
 infusion is poured into ;he milk. For a cheese of GOlbs. weight, a jiiece 
 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 stomach 
 {dried-mairs, veils, reeds, or yirning* they are often called), and to pour 
 upon them from one to three quarts oi' wafer for each stomach, and to 
 allow them to infuse for several days. If only one has been infused, and 
 the rennet is intended for immediate use, the infusion requires only to be 
 skimmed and strained. But if several via^v-skins be infused — or, as is 
 the custom in Cheshire, as many as have becTi provided for the whole 
 season — about two quarts of water are taken for each, and, after stand- 
 ing not more than two days, the infusion is poured off", and is completely 
 saturated with salt. During the summer it is constantly skimmed, and 
 fresh salt added from time to time. Or a strong brine may at once 
 
 ' In Northumberland the dried stomach is sometimes rolled the keslap, which ie evidently 
 the German kiiselab, cheese-rennet. Lvppert and lajipert, applied in Northumberland and 
 the West of Scoiland respectively to sour, curdled milk, is derived fi-om the same German 
 ialj, rennet, or latter, to coagulate. 
 
THEORY OF THE ACTION OF REN>fET. 569 
 
 be poured upon the skins, and the infusion, when the skins are taken 
 out, may be kept tor a length of time. Some even recommend that 
 the liquid rennet 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. 
 
 Ln 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 (juarts 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 tlirown 
 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 every reason to believe that they might be used with al- 
 most ei]ual 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 
 explain the mode in which rennet acts, you will see that the same slJin 
 may, wit'.i good reason, be expected to yield a good rennet, after being 
 salted again and again for an indefinite number of times. 
 
 In making rennet, 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 ailopted li)r the purpf)se of" making the rennet keep better, of lessen- 
 ing its unpleasant smell, of preventing any unpleasant taste it might 
 give to the curd, or finally of (lirectly improving the flavour of the cheese. 
 The acidity of the lemon will, no doubt, increase also the coagulating 
 power of any rennet to which it may be added. 
 
 4^. How the rennet is MSCf/.-r-The rennet thus prepared is poured into 
 thi^- milk previously raised to the temperature of 90° or 95° F., and is 
 intimately tnixed with it. The quantity wiilch it is necessary 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 necessary for the complete 
 tixiiig of the curd varies also from 15 minutes 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? Before 
 we can answer this (piestion it is necessary to enquire what rennet 
 really is. 
 
 § 19. 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 
 
 ' A tahle-spoonful of this rennet, acconlinz tn Mr. Alton, will roaaiilafe 30 gallon?? of milk, 
 and will curdle it in five or ten minutes, whereas the Ensjlish rennet requires from one to 
 three hours Tliis superiority he ascribes to the custom of leavini; the curdled milk in the 
 jtomach. He denies also that this milk gives any harsh taste to the cheese. 
 
570 THE SUBSTANCE OF THE STOMACH CHANGES 
 
 the custom both of preserving the natural contents of the stomach — and 
 of generally throwing away the bag atter being once salted, dried, and 
 extracted. The gastric juice which exudes fioni the interior surface of 
 tlie stomaclis of all animals is known to curdle milk readily, and, there- 
 fore, it was natural to ascribe the action of rennet to the presence of this 
 substance, and to infer that, oeing once extracted, it was in vain to ex- 
 pect much advantage from salting and infusing the membrane a second 
 time. But the three facts — 
 
 a. That in inost places it is customary to wash the interior of the 
 stomach before salting it, and thus to reinove the greater part of the gas- 
 tric juice it may contain ; 
 
 b. That besides, in many places, the lags are laid up in brine for 
 weeks and months, and are then drained out of this brine before they are 
 dried — by which any gastric juice remaining must be almost entirely re- 
 moved, — and 
 
 c. That after being dried and steeped once for the preparation of ren- 
 net, experience has proved that they may again be salted and used over 
 again ; 
 
 — these three facts, I think, sliew that the efficiicy of rennet does not de- 
 pend upon any thing originally contained in the stomach, hut upon 
 something dericed from the substance of the stomach itself. 
 
 Now when considering the jjroperties of milk-sugar and of lactic acid, 
 I have stated that if a piece of the fresh ineinl)rane of the stomach or in- 
 testine, or even of the bladder of an animal, be exposed to the air for a 
 few days, and be then immersed into a solution of milk-sugar, it will 
 gradually transform the sugar into lactic acid. In milk this membrane 
 would produce a similar effect, aiding and hastening the natural souring 
 and curdling etFect of the casein. By exposure to the air, tlie surface ol' 
 the membrane has undergone sucli a degree of change or decomposition, 
 as enables it to induce the elements of the sugar to alter their mutual 
 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 
 cl)ange of its surface will penetrate deejier, and it will become more ef- 
 fective in inducing the transformation of the sugar into lactic acid. But, 
 at the same time, a portion of its surface may run into a state of putre- 
 faction, and besides acquiring a disagreeable odour luay become cajiable 
 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 at- 
 tempt 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 pntrefaction 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 deef)er, if the salted membrane be subsequently dried slowly 
 in the air by a gentle lieat, and be afierwards kept lor a lencth 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 
 rennet, and it is an important practical observation that the membrane 
 
WHEN EXPOSED A SHORT TIME TO THE AIR. 571 
 
 should be kept at least 12 mouths, if it is to acquire very powerful 
 coagulatinii; properties. 
 
 It is necessary further to remind you that when malt is steeped in 
 water for a few minutes, a substance, named diastase, is extracted from 
 it, which possesses tlie remarkable property of changing starch into 
 sugar in a very short time, and in large quantity (p. 119). Now if this 
 diastase be exposed to the air lor a length of time, it undergoes a change 
 similar to that experienced by the surface of animal membranes, and 
 acquires the property of transforming sugar into lactic acid. After un- 
 dergoing 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 
 ivater, vvjiich possess the same power as slightly decayed but insoluble 
 animal membrane, of converting sugar into lactic acid. 
 
 During the protracted drying and deca}' of the salted stomach, the 
 chatige undergone at length by the surface of the membrane is such as to 
 proiluce a (juantity of matter capable of dissolving in water, and which 
 also possesses the property of quickly convening 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 tliis activity depends — 
 since as you already know any thing which will rapidly change sugar 
 into lactic acid, will also, if gently warmed, rapidly curdle milk (p. 
 567). 
 
 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 elTected 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 matter 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 pro- 
 duces acid near every particle of the cheesy matter. From this 
 cheesy matter the acid formed takes away the soda that holds it in solu- 
 tion, and thus renders it insoluble or curdles the milk. In milk, on the 
 rither 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. This change takes place more or less slowly, and chiefly 
 at the surface of the milk where it is in contact with the air. The sour- 
 ing, therefore, must also proceed slowly, and the curdling of which it is 
 the cause. 
 
 It is no objection to this explanation of the action of rennet, that neither 
 the milk nor the whey become sensibly sour during the separation of the 
 curd. The acid, as it is produced, combines directly with the soda pre- 
 viously united to the curd, and renders the latter insoluble — while, if 
 any excess of acid do haiipen to be formed, it is in great part taken up 
 and retained mechanically by the curd, and thus is not afterwards sen- 
 sibly perceived in the whey. 
 
572 USE or thk curd found in thk calf's stomach. 
 
 Using the same skin a second time. — If tliis then bo a true cxplanatiun 
 of the action of rennet — if tlie coHgiilating inii;redient in it be merely a 
 portion of the clianged membrane of the stomach itself — it is obvious lliat 
 the bag, after being once used, may be again salted and dried with ad- 
 vantage. The slow decay may, alter 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 
 whicli was first extracted from it. Bat ..nless it be inerely tlie inner 
 ineinbrane of the stomach and intestines which is capable of undergoing 
 that kind of change upon which the coagulating power depends, tliere is 
 no apparent reason, as I have alread}^ sta'ed to you, why tlie same 
 maw- skin may not be salted, dried, and steeped many times over. 
 
 Use of whey. — Again, iu the making of rennet there seems some i)ro- 
 priety 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 curdle 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 coag- 
 ulating power of the rennet obtained. 
 
 Use of the curdled milk contained in the stomach. — Docs the view we 
 have taken of the action of rennet throw any light upon the use of the 
 curdled inilk found in the stomach? Is it of any service, or ought it to 
 be rejected? 
 
 We are certain that it must be of service in coagulating mUk, since in 
 Cheshire, according to Dr. Holland, it is frequently taken out and salted 
 by itself for immediate use. But a slight consideration of the properties 
 of casein, as I have already stated them to yon (p. 562), 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, tlie property of converting sugar 
 into lactic acid (p. 56'2), and of curdling milk. Now the curdy matter 
 taken from the stomach of the calf, after being exposed to the air, ac- 
 quires this property as completely as a more pure curd will do. If salted 
 and kept, it will be changed still further, 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 wll 
 render it alike fit to be employed in the preparation of rennet. Nor is 
 it unlikely that fresh well-scpieezed cunl, if mixed with much salt and 
 kept in slightly covered jars for 10 or 12 months, might jdeld a rennet 
 possessed of good coagulating properties. 
 
 It thus appears that, so far as economy is concerned, tlie curdy matter 
 contained in the calfs stomach ought to i)e preserved and salted for use. 
 If in any district tills curd be suspected to impart an unpleasant flavour 
 to the cheese, this bad eff^ect may probably be remedied by taking it out 
 of the stomach, wasliing it well vvitli water — as is done in some dairy 
 districts — mixing it with salt, and then returning it into the stomach 
 again. 
 
 Another practical conclusion mav also be drawn from this ex])lanation 
 of the action of the stomach. Since it is the inembratu; alone that acts, 
 there can no loss accrue by carefully washing the stomach as well as 
 the curd it contains, On the contrarv, by so doing we mav remove 
 
CHEESE OF DIFFERENT qUALITIES HOW OBTAINED. G73 
 
 from its inner surface some substances which, if allowed to remain, might 
 afterwards act injuriously upon the flavour or upon tiie other qualities of 
 the cheese. 
 
 § 20. Of the circumstances by which the quality of cheese is affected. 
 
 All cheese consists essentially of the curd mixed with a certain jior- 
 tion of the fatty niMtter and of the sugar of milk. But dillereiices in the 
 quality of the milk, in the proportions in which the several constituents 
 of milk are mixed togetlier, or in the general mod(! of dairy manage- 
 ment, give rise to varieties of cheese almost without number. Nearly 
 every dairy district produces one or more qualities of cheese peculiar to 
 itself. It will not be without interest to attend briefly to some of these 
 causes of diversiiy. 
 
 1^. Natural dijf'erenccs in the milk. — It is o!)vionsthat whatever gives 
 rise to natural ditferences in the quality of the milk must aiiJ^ct also that 
 of the cheese prepared from it. If the imlk he poor in butter, so uuist 
 the cheese be. If the pasture he such as to give a milk rich in cream, 
 the cheese will partake of the same cpiality. If the herbage or other food 
 atfect the taste of the milk or cream, it will also tnodifythe flavour of the 
 cheese. 
 
 2^. Alilk of different animals. — So the milk of difTerent animals 
 will give cheese of unlike qualities. The ewe-milk cheeses of Tuscany, 
 Naples, and Langnedoc, and those of goat's milk made on Mont Dor 
 and elsewhere, are celebrated for qualities which are not possessed by 
 clieeses prepared from cow's milk in a similar way. Bufljilo milk also 
 gives a cheese of peculiar (]ualities, which is manufactured in some parts 
 of the Neapolitan territory''. 
 
 Other kin Is of cheese agam are made from mixtures of the milk of dif- 
 ferent animals. Thus the strong tasted cheese of Lecca and t!ie cele- 
 brated Roquefort cheese are prepared from mixtures of goat wilh ewe- 
 milk, and the cheese of .Mont Cenis* from botli of tliese mixed with the 
 milk of the cow.j 
 
 3°. Creamoxl or uncreamcd milk. — Still further differences are pro- 
 duced according to the proportion of cream which is left in or is added to 
 the milk. Thus if cream only be emplo^'cd, we have the rich cream- 
 cheese wliich must be eaten in a comparatively recent state. Or, if the 
 cream of the previous night's milking be added to the new milk of the 
 morning, we m'ly have such cheese as the Stilton of England, or tlje 
 smal). soft, and rich Brie cheeses, so much esteemed in France. If the 
 entire milk only be used, we have sucli cheeses as the Cheshire, the 
 Drtuhle Gloucester, the Cheddar, the Wiltshire, and the Dunlop cheeses 
 of Britain, the Kinnegad cheese, I believe, of Ireland, and the Gouda and 
 Edam cheeses of Holland. Even here, however, it makes a dilTcrence 
 whether the warm milk from the cow is curdled alone, as at Gouda and 
 Edam, or whether it is mixe<l witJi t!ie milk of the evening before, as is 
 generally done in Cheshire and Ayrshire. Many persons are of opin- 
 ion that cream, which has once been separated, can never be so well 
 
 • I.ct-ra i- a provinre in the E istern pari of the Neapolitan territory ; Rnquefort, a town 
 in the pastoral departmi'iii of Aveifoii, in the South of France, faniej for its sheep; and 
 Mont Ceuis, a mountain in Savoy. 
 
 f The milk of 2 goats is mixed with that of 20 sheep and 5 cows. 
 
574 BUTTKR-MILK, WHEY, AND VEGETABLE CIIKESES. 
 
 mixed again with the milk, that a portinn of the fatty matter shall no*' 
 flow out witli the whey and render tiie cheese less rich. 
 
 If, again, the cream of tlie evening's milk be removed, and the skim- 
 med milk adrled to the new milk of the next morning, such cheeses as 
 the Sirigle 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 Friesland and Groningen. If skinmied 
 for tlnee or four days in succession, 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 (juality 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 witliout the use of rennet, 
 butter-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 mixing more or 
 less sweet milk with the butter-milk before it is warmed, several other 
 qualities of mixed butter and sweet ndlk cheese may readily be manu- 
 factured. 
 
 If, as is stated by Mr. Ballantync, the churning of the whole milk 
 gives butter in larger quantity, of better quality, and more unitbrmly 
 throughout the whole year (p. 553), the manufacture of these butter-milk 
 cheeses is deserving of the attention of dairy farmers, 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 unfrecjuently a considerable quantity of butter 
 also. When the whey is heated, the curd and butter rise to the surface, 
 and are readily skimmed oti'. This curd alone will often yield a cheese 
 of excellent quality, and so rich in butter, that a very good imitation of 
 Stilton cheeee may sometimes be made with alternate layers of new 
 milk-curd and this curd of wdiey. 
 
 6°. Mixtures of vegetable substances with the milk- — New varieties 
 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 ; eome even mix 
 up the entire leaves with the currl. The celebrated Schabzieger cheese 
 of Switzerland is made by crushing the skim-milk cheese alier it is se- 
 veral months old to Hne powder in a mUl, mixing it then witli one-tenth 
 of its weight of fine salt and one-twentietli of the powdered leaves of the 
 melldot trefoil {trifolium mclilotvs ccrulea), 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 
 
TEMPERATURE AND HEATI.VQ OF THE MILK. 575 
 
 pound of sour milk is mixed with five pounds of boiled potatoes 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 dried boiled potatoes with two of fresh curd, or equal 
 weights, or more curd than potato according to the cjuality required. 
 Such cheeses are made in Thurhigia, in Saxony, and in other parts of 
 Germany. In Savoy, an excellent cheese is made by mixing one of the 
 pulp of potatoes with three of ewe milk curd, and in Westphalia a ]io- 
 tato cheese is made with skimmed milk. This Westphalian cheese, 
 while in the pasty state, is allowed to undergo a certain extent of fer- 
 mentation 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. 
 
 § 21. Circumstances under lohicli cheese of different qualities may be 
 obtained from the same milk. 
 
 But from the same milk, in the same state, dilferent kinds or qualities 
 of cheese may be pre[)ared 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 ivhich the milk is heated. — The temperature of new 
 or entire milk, when the rennet 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 ob- 
 tain free from the whey. When the former happens to be the case, a 
 portion of the first whey that sepaiates 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 contain- 
 ing hot water may be put into it before the curdling commences — or tlie 
 first portion of whey that separates may be heate;! and poured again 
 upon the cunl. Tlie 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 ba attained as nearly as possible, before the rennet is added. 
 
 2^. jMode ia which the milk is warmed. — If, as is the case in some 
 dairies, tlie milk be warmed in an iron pot upon the naked fire, great care 
 must be taken tliat it is not singed or firc-fanoed. A very slight inat- 
 tention may cause this to he the case, and the taste of the cheese is sure 
 to be myre or less atlected by it. In Cheshire the milk is put into a large 
 tin pail, wliich is plunged into a boiler of hot water, and frequently stir- 
 red till it is raised to the proper temperature. In large dairy establish- 
 ments, however, the safest method is to have a pot with a double bottom, 
 consisting of one pot within anoiiier — after the manner of a glue-pot — the 
 space between tjie two being filled with water. The fire applied be- 
 neiith thus acts only upon the water, and can never, bv any ordinary 
 neglect, do injury to the milk. It is desiral)!e in this heating, not to raise 
 the temperature hisher than is necessary, as a grt-at 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 
 shot. Id be broken up as soon as tlie milk is fully coagulated. The longer 
 it stands after this the harder and tougher it will become. 
 
676 QUALITV AND QUANTITY OF THE RENJSET. 
 
 4°. The qtiaUty of the rennet is of much importance not only in regard 
 to tlie certainty ot the coagulation, but also to the flavour of the cheese. 
 In some parts of Cheshire, as wa have seen, it is usual to take a piece 
 of the dried membrane and steep it overnight 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 j)reservation. But where it is customary to steep 
 several skins at a time, and to bottle tlie 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 rennet is said to be frequently kept 
 in bottles till it is almost putrid, and in this state is still put into the milk. 
 Such rennet may not only impart a bad taste to the cheese, but is likely 
 also to render it more ditfiL'uU to cure and to bring on putrefaction after- 
 wards and a premature decay. 
 
 5°. The quantity of rennet added ouglit to be regulated as carefully 
 as the temi)erature of the milk. Too much renders tlie curd tough ; too 
 little causes the loss of much titne, and may piermit a larger [wrtion of 
 the butter to separate itself from tlie 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 fermentation. It is probable also that it will atfect the 
 flavour which the cheese acquires by keeping. Thus it may be that the 
 agreeable or unpleasant taste of the cheeses of certain districts or dairies 
 may be less due to the qualify of the ])astures or of the milk itself, than 
 to the quantity of rennet with which it has there been customary to co- 
 agulate tlie milk. 
 
 6^. The way in which the rennet is made, no less than its state of pre- 
 servation and tlie quantity emi)loyed, may also intluence the flavour or 
 other qualities of the cheese. For instance, in the manufacture of a 
 celebrateil French cheese — that of Epoisse — the rennet is prepared as fol- 
 lows : — Four fresh calf-skins, witli the curd they contain, are well 
 washed in water, chopped into small jneces, and digested in a mixture 
 of 5 quarts of brandy with 15 of water, adding at the same time 22 lbs. 
 of salt, half an ounce of black pepper, and a tjuarter of an ounce each 
 of cloves and fennel seeds. At the end of six weeks the liquor is filtered 
 and preserved in well corked bottles, M'hile the membrane is i)ut into salt- 
 water to form a new portion of rennet. For makuig rich cheeses, the 
 rennet should always be filtered clear. [II lalte e i siioi prodofti, p. 274.] 
 
 Again, on Mont Dur, the rennet is made with white wine and vinegar. 
 An ounce of common salt is dissolved in a mixture of half a [liiit of 
 vinegar with 2i pints (jf white wine, and in this solution a jirepared 
 goat's stomach or a piece of dried pii^'s bladder is steejjfd t()r a length of 
 tune. A single sjwonful of this rennet is said to be suHicient for 45 or 
 50 quarts of milk. No doubt the acid of the vinegar and of the wine aid 
 the coagulating ])ower derived from the membrane. 
 
 Rennets prepared in the above ways must atTect the flavour of the 
 cheese difierently from such as are obtainef! l)y the several more or less 
 careful methods usually adopted in this coimti-y. 
 
 7^. IVlien acids are used, alone — as vinegar, tartaric; acid, and muria- 
 tic acid sometimes arc — for coagulating the milk, the flavour of the 
 
now THE WUEV IS SKPARATED. 577 
 
 cheese can scarcely fail to be in some measure difierent from that which 
 is prepared with ordinary rennet. 
 
 8°. The ivay in ivhich the curd is treated. — It is usual in our best 
 cheese districts carefully and slowly to separate llie curd from the whey — 
 not to hasten the separation, lest a larger portion of the fatty matter should 
 be squeezed out of the curd and the cheese sliould thus be rendered poorer 
 than usual. But in some places the practice prevails of washing the 
 curd with hot water after tlie 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 re- 
 main 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 cacciu-cavallo cheeses and 
 the round palloni cheeses of Gravina, in the Neapolitan territory, are 
 made from curd, which, after being scalded with boiling whey, is cut into 
 slices, kneaded in boiling water, worked witli the hand till it is perfectly 
 tenacious and elastic, and then made into shapes. The water in which 
 the curd is washed, after standing 24 hours, throws up much oily mat- 
 ter, which is skimmed oti' and made into butter. 
 
 The varieties of cheese prepared by tiiese methods no doubt derive the 
 peculiar characters upon which their reputation depends from the treat- 
 ment to which the curd is subjected — but it is obvious tliat none of them 
 can be soricli 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 extraction of the whey 
 than in almost any other district. Indeed, when it is considered that the 
 whey contains sugar and lactic acid, whicli may undergo decomposition, 
 and a quantity of rennet which may bring on fermentation — by both of 
 which processes the flavour of the cheeses must be considerably affected 
 — it will appear of great importance that the whey should be as com- 
 oletely removed from the cunl 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 the large English dairies, and a very ingenious, and I 
 believe effectual, pneumatic cheese-press for sucking out the whey was 
 invented by the late Sir John Robinson, of Edinburgh. [Transactions 
 and Prize Essays of the Highland Society, vol. x., p. 204.] 
 
 But tlie way in which die whey is separated is not a matter of indif- 
 ference, 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 tlie help of her 
 wooden ladle breaks up minutely and intimately mixes the curd with tlie 
 whey. This slie does for 10 or 15 minutes, after which the curd is al- 
 lowed to subside, and the whey is drawn off". By this agitation 
 the whey must carry olF 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 tlie oily matter is retcuned. On the same principle, in mxiking 
 the Stilton cheese, the curd is not cut or broken at all, but is preesed 
 
678 Rl.ND OF SALT, AND HOW IT IS APPLIKD. 
 
 gently and with care till the whey gradually drains out. Thus the butter 
 and the curd remain intermixed, and the rich cheese of Siilton is the result. 
 
 Thus you will sec that while it is of importance ihat nil the whey 
 sliould he extracted from the curd, yet that the (|uicUcst way ma^' not he 
 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 de- 
 ficiencies in the richness or other qualities of our cheese, which are 
 in reality due to slight but material differences in our mode of manufac- 
 turing it. 
 
 10^. The kind of sail used is considered by many to have some effect 
 upon the taste of the cheese. Thus the cheese of Gerome, in the Vos- 
 ges, is supposed to derive a peculiar taste from the Lorena salt with 
 which it is cured. In Holland, also, tlie efficacy of one kind of salt 
 over another for the curing of cheese is generally acknowledged, [British 
 Husbandry, ii., p. 424.] It is indeed not unlikely that the more or less 
 impure salts of diirerent localities may affect tlie 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 process of purification, 
 which I have already described to you (p. .565.) 
 
 11°. The mode in which Ike 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 ecpial portions. One of these is 
 mingled with double the quanthy 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-stdting on the surface is sure to penetrate 
 deep enough to cure efiectually 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 iu these counties, but were it adopted for the large cheeses 
 of Cheshire and Dunlop, or even for the pine-ajiple cheeses of Wiltshire, 
 there can be no doubt that their quality would Imiuently be injured. It 
 may not be impossible to cause salt to penetrate into the very heart of a 
 large cheese, but it canuot be easy in this way to salt the whole cheese 
 etjually, while the care and attention required must be greatly increased. 
 
 12°. Addition of cream or butter to tJ/c curd. — Another mode of im- 
 proving the quality of cheese is by the addition of cream or butter to the 
 dried and crumbled curd. Much diligence, however, is required fully 
 to incorporate these, so that the cheese may be uniform throughout. Still 
 this practice gives a peculiar character to the cheeses of certain districts. 
 In Italy they make a cheese after tlie manner of the English, [II latte e i 
 suoi prodotti, p. 277], into which a considerable quantity of butter is 
 worked; and the Rerkeni cheese of Belgium is made by adding half an 
 ounce of butter and the yoke of an egg to every pound of pressed curd. 
 
 13°. Tlie colouring matter added to the cheese is thought by many to 
 affect its qualify. In foreign countries saffron is very generally used to 
 give a colour to the milk before it is coagulated. In Holland and in 
 Cheshire annatto is most commonly employed, while in other dis- 
 tricts the marigold or the carrot, boiled in milk, are the usual colouring 
 matters. 
 
MODE OF CURING THE CHEESE. 679 
 
 The quantity of annatto employed is comparatively small — less than 
 naif an ounce to a cheese of 60 lbs. — but even this quantity is considered 
 by many to be an injurious admixture. Hence a native of Cheshire 
 prefers the uncolouretl cheese, the annatto being added to such only as 
 are intended tor iha 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 degree different. 
 Hence, without supposing any inferiority, either in the milk or in the ge- 
 neral mole of treatment, the size usually adopted for liie cheeses of a 
 particular district or dairy, may be the cause of a recognized inferiority 
 in som3 quality which it is desirable that they should possess in a high 
 degree. 
 
 l.S''. The method of curlnsr lias very niucli influence upon the after- 
 qualities of the cheese. The care with which tliey are salted — the 
 warmth of the place in which they are kept during the first two or three 
 weeks — the temparature and closeness of tlie clieese-room in wliich 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 tlie high reputation of a particular dairy district or 
 dairy farm is derived from some special attention to one or other or to all 
 of the apparently minor points to which I have just a(]verted. 
 
 In Tuscany, the cheeses, after being hung u]! 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 Roquefort are supposed to 
 owe much of the peculiar estimation in which they are held, to the cnol 
 and uniform temperature of the subterranean caverns in which tlie 
 inhabitants of the village have long been accustomed to preserve them. 
 
 In Rosshire it is said to be the custom with some proprietors to bury 
 their cheeses im ler 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'. A^nmoniacal cheese. — The influence of the mole of curing upon 
 the quality is sliown very strikingly in the small ammoniacal cheeses of 
 Brie, which are very fnuch esteemed in Paris. They are soft unpressed 
 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 tlie putrefac- 
 tive fermentation and emit an ammoniacal odour. They are ge- 
 nerally 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 niay 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 shoulil be made to resemble. Of course 
 this can apply only to cheeses otherwise of etpial richness, for we could 
 scarcely expect to give a single Gloucester the flavour of a Stilton, 
 25 
 
580 AVERAGE QUANTITY OF CHEKSK YIELDED. 
 
 by merely putting into it a small portion of a rich and esteemed Stilton 
 cheese. 
 
 § 22. Of the average quantity of cheese yielded by different varieties of 
 milk, and of the produce of a single coiv. 
 There appear to be very great differences in the proportions of cheese 
 yielded by milU at different seasons and in different localities. 
 
 Tnmilk, of an average quality, there are contained from 4 to 5 percent, 
 of casein or dry cheesy matter (p. 534), which, if all ex traded, would give — 
 6 lbs. to 7 lbs. of shimmed milk cheese, or ? from 100 lbs. of 
 9 lbs. to 10 lbs. of entire milk cheese, \ milk. 
 
 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 } gave 1 lb. of whole milk 
 1 imjierial gallon, ^ cheese ; 
 
 or 136 wine quarts gave 1271 lbs. of cheese three months old.* 
 
 In Gloucester — 7 lbs. of milk, or / gave 1 lb. of double 
 3J wine quarts, ^ Gloucester ; 
 
 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— 
 
 Neiv 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 piuch water 
 was present in the ne^o cheese. Indeed, most of the statements on record 
 are deficient in this respect, that the dryness of the cheese is not accu- 
 rately expressed. 
 
 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. 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 j^roportion of cheese varies very 
 much with the season of the year and icith 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 s-^asons 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 skiiiimed milk cheese, and 4 to 7 lbs. of butter. Of whole milk 
 cheese some expect as 7uuch as 3 or 4 lbs. a day. 
 
 ' Mr. Alexander, of Soutlibar, informs me thai the result of his experience with a dairy 
 of 40 cows ill the higher part of Ayrshire, near Muirkirk, is, thai — 
 
 90 imperial quarts of sweet milk grive an Ayrshire stone of 24 lbs. of full milk cheese, 
 while tlie same quantity of skim milk gives only 15 lbs. of skimmed milk cheese. That is 
 veiT nearly— 
 
 9 lbs. of new milk give 1 lb. of full milk cheese. 
 
 H lbs. of skim-milk give 1 lb. of skim- milk cheese (see p. 585). 
 
MILK SPIRIT AND MILIC VINEGAR. 581 
 
 In Switzerland, generally, a cow, giving 12 ([uarts of milk a clay will, 
 during tlie 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. 
 
 In the high pastures of Scaria, again, in the same country, one cow- 
 will give for the 90 days of summer about GO 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. 
 
 § "23. Of the fermented liquor from milk, and of milk vinegar. ( 
 
 Milk is capable of undergoing what is called the vinous fermentatior^ 
 and of yielding an intoxicating liquor. The Tartars prepare su"h a 
 liquor from mare's milk, to which the name 6[ kou/niss is given. Wheii 
 made from cow's milk it is called airen, and is less esteemed because 
 generally of a weaker quality. Tiie Arabians and Turks prepare a si4 
 milar liquor, which the former call leban, and the latter yaourt. In the 
 Orkney Islands, and in some parts of tlie north of Scotland and Ireland,, 
 butter-milk is sometimes kept till it undergoes the vinous fermentation,' 
 and ac(|tures iBtoxicating qualities. 
 
 It is the sugar contained in milk whicli, by the fermentation, is changed 
 into alcohol. As mare's milk, like that of the ass, contains more sugar 
 (p. 531) than that of the cow, it gives a stronger liijuor, and is therefore 
 naturally preferred by the Tartars. By distillation ardent spirits are ob- 
 tained from koumiss, and when carefully ntade in close vessels, a pint of 
 the li(]uor will yield half an ounce of spirit. The koumiss is prepared in 
 the following maiiner : 
 
 To the new milk, dilnted with a sixth of its bulk of water, a quantity 
 of rennet, or what is better, of sour koumiss, is added, and tite whole is 
 covered up in a warrei place fur 24 hours. It is then stirred or cliurned 
 together till the curd and whey are intimately mixed, and is again left 
 at rest for 24 hours. At tlie end of this lime it is put iiuo a tall vessel, 
 and agitated till it becomes perfectly homogeneous. It has now an agree- 
 able sourish taste, and in a ceol place uiay bs preserved for several 
 months in close vesse'ls. It is alwavs 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 in- 
 toxicating liquors. It is even recomniended 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 dis- 
 .appears and vinegar is formed. In some jiarts ef Italy a milk vinegar 
 of pleasant quality is prepared by adding honey, sugar, spirit, and a lit- 
 tle yeast to the boiled whey, and setting the mixture aside to ferment in 
 a warm place. [II latte e i suoi prodotti, pp. 415 and 450.] 
 
 § 24. Of the composition of the saline constituents of milk 
 
 When milk is boiled down to dryness, and the dr^' residue bsirned, a 
 
 small (piantity of ash remains behind. The proportion which the 
 
 weight of tliis ash bears to that of. the whole milk is variable — as the 
 
 qualities of the milk itself are — so that 1000 lbs. will leave sometimea 
 
582 USE OF MILK IN THE AMMAI< ECONOMY. 
 
 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. 188), with the 
 ]>hosphates of lime, magnesia, and iron. The relative proportif)ns of 
 these several substances yielded by 1000 lbs. of the milk of two dif- 
 ferent cows, were as follows [Haidlen, Annal. der Chem. und Phar., 
 xiv., p, 273] : 
 
 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 " 1-83 " 
 
 Chloride of sodium 0-24 •' 0-34 " 
 
 Free soda 0-42 " 0-45 " 
 
 4-90 " 6-77 '* 
 
 It is probable that the phosphates and chlorides existed as such in the 
 milk as ii came from the cow, the free soda is believed to have been in 
 combination with the casein, and to have held it in solution in the milk. 
 You will recollect that the explanation I have given of the cvirdling of 
 milk is, that the acid produced in, or added to, the milk, takes this soda 
 from the casein, and renders it insoluble in water, and that in conse- 
 quence it separates in the form of curd (see p. 566). 
 
 § 25. 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 constitution 
 with the lean part or fibrin of the muscles serves to promote the growth 
 of the flesh of the animal. 
 
 2°. 'Jlie fat or butter, which is mainly expended in supplying fat to 
 those parts of the body in which fat is usually (ieposited. 
 
 3°. The sugar, which is probably consumed by the lungs during re- 
 spiration. 
 
 4°. The saline mailer, 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 again under our 
 consideration in the following lecture. 
 
 NOTES. 
 1°. On the churning of butler in the French churn. 
 Mr. Burnett, of Gadgirtli, has favoured me with the following infor- 
 mation regarding the merits of the French churn mentioned in page 
 555 :— 
 
 "I see you make mention, in page 555 of your Lectures, of a churn 
 lately introduced by Mr. BlacKer from France. I got one of these from 
 Mr. Blacker about two years ago, and'have proved its merits to be very 
 great. I use none else, and have been the means of distributing it over 
 
CHURNING IN THE FRENCH CHURN. 583 
 
 different parts of England anJ Scotland. It is made of tin, of a barrel 
 shape, and is placed in a trough of water, heated or otherwise, to convey 
 the proper teniperature to the cream. I have tried many experi- 
 ments to ascertain the proper temi)erature for churning cream in 
 tliis churn, and have found that 58° F. produces the best quality of but- 
 ter in the shortest time — the time occupied being from ten to twenty 
 minutes. At G0° it was often done in five to seven minutes, and although 
 a little soft at first, produced butter of a good colour and quality — on no 
 occasion was it ever white. I also tried 56° F. It took generally one 
 hour, was harder, but no better in quality than that of 58°. 
 
 ♦' With regard to the quantity of butter from a given quantity oC cream, 
 I found that in July, when the cows were on good pasture, and occasion- 
 ally house-fed on clover — 
 
 16 quarts of cream produced . 12 lbs. 8 oz. 
 
 24 do. do. do. . 16 lbs. 12 oz. 
 
 30 do. do. do. . 20 lbs. 8 oz. 
 
 Or, 70 quarts produced 49 lbs. 12 oz. 
 
 When fed on cabbage — 
 
 50 quarts of cream produced . . 32 lbs. 
 Again — 
 
 50 quarts of cream produced . . 32 lbs. 4 oz. 
 60 do. do. do. . . 40 lbs. 
 
 Or the whole six quarts of cream in July gave 4 lbs. of butter. 
 
 " On churning the whole milk in this churn, 100 quarts of milk at 60° 
 produced 8 lbs. of butter of excellent quality in one hour and a half — 8 
 quarts of hot water were put i?ito the churn according to the old system. 
 
 " 100 quarts of milk from the same cows at 64° produced only 7 lbs. 
 of butter of a soft and inferior quality, and took two hours to churn, 16 
 quarts of hot water being put into the churn on this occasion. 
 
 " Tlie whole milk was sometimes churned in less than one hour, but 
 from that to one hour and a half was the general time occupied, whereas 
 three to four hours is the time occupied in churning in {hecoinmon churn. 
 
 " To ascertain whether the whole milk or the cream produced the 
 greatest quantity of butter in this churn, I took the milk of five cows 
 (Ayrshire breed) for one week in July last, amounting to 508 quarts — 
 the yield of butter was 36 lbs. 11 oz. I then took the same quantity of 
 milk from the same cows for the same period of lime, and let it stand for 
 cream — the butter produced was 37 lbs. 4 oz. The food and other cir- 
 cumstances were quite the same. 
 
 " To test the quality of my butter, I sent it last summer to a show at 
 Ayr, and obtained the seconcl premium both for fresh and salt ; the heat 
 at which it was churned was 58°, and the time not exceeding half an 
 hour." 
 
 On these obser^'ations of Mr. Burnett, I must in fairness remark, that 
 several other persons who have used this churn, have not reported by any 
 means so favourably of its merits. Perhaps they have not known how 
 to manage it so skilfully. 
 
 2°. ^antily of milk and butter yielded by Ayrshire cows. 
 Mr. Alexander, of Southbar, has furnished me with the following pro- 
 
564 COMPARATIVE PROFIT OF 
 
 portions of cream and butter yielded by his dairy of 38 cows, at Well- 
 wood, in the higher part oF Ayrsliire, near Muirkirk, during six several 
 days in November and December, 1843 : — 
 
 Cream Butter 
 
 Date. in imp. jralls. in pounds. 
 
 November 1 ••..-. 16 43i 
 
 7 19^ 47A 
 
 14 Wi 43 
 
 21 21>- 47 
 
 29 18 39 
 
 December 7 19 43J 
 
 In all 112^ galls, gave 263^ 
 
 or, seven quarts of cream in November gave four potmds of butter. 
 
 The cream appears from the table toliave become gradually less rioli, 
 though the whole quantify did not diminish. 
 
 Mr. Alexander remarks, that " the proportion oC cream varies in his 
 dairy from |th to y'^th of tlie bulk of the inilk, and that the Guernsey or 
 Highland, or awf Mack or blacJc-marked cotv, 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 ob- 
 servation 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 an-y thing of this kintl has been observed in the 
 Durham breed — ^as white animals, of pure blood, are often great favour- 
 ites with the breeders of Tees-Water stock. 
 
 3°. Profit of making hitler and cheese compared with that of 
 selling the milk. 
 
 For the following particulars I am also indebted to Mr. Alexander. 
 The produce of cheese and butter is the average of his experience at 
 Welhvood, in Ayrshire. 
 
 There are three ways in which the milk is usually disposed of. It is 
 sold in the state of new m^ilk, or it is made into full milk cheese, and the 
 whey given to pigs — or it is niade into butter, and ti)e skiimnilk 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 : — 
 
 s. d. 
 a. — 90 quarts of new milk, at 2d. a quart, are sold for . 15 
 
 h. — 90 quarts of new milk give 24 lbs. of full milk cheese, 
 
 which, at 4^d., per lb. are sold for . . . .90 
 
 The whey is worth, at least . . . . . .06 
 
 9 6 
 
 c. — 90 quarts of milk, churned altogether, give 9 lbs. of butter, 
 
 at 9d. 6 9 
 
 90 (parts of butter-milk, at Id. per quart . . . .39 
 
 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. 
 
MAKING BUTTER AND CHEKSE. 585 
 
 $. d. 
 
 d. 90 quarts of new milk give 18 quarts of cream, yielding 
 
 9 lbs. of butter at 9d., as before . . . . .69 
 
 18 quarts of butter-milk, at ^d 9 
 
 70 quarts of skim-milk, at ^d. . . . . . 2 11 
 
 10 5 
 
 When the skim-milk cannot be sold, it may be given to the pigs, 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 . . • . .76 
 70 quarts of skim-milk give 16 lbs. of cheese, which, at 3d. 
 
 per lb 4 
 
 11 6 
 
 Thus we liave 90 quarts of milk — 
 
 s. d. 
 a — sold as new milk, worth . . . . 15 
 
 b — made into full-milk cheese .... 96 
 
 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 . . 11 6 
 In the country, thereftire, according to these calculations, the most pro- 
 fitable way is to make butter and skim-milk cheese- The farmer is thus 
 in a great mea'^ure independent of an adjoining population. The small 
 quantity of butter-milk he thus obtains he will easily be able to dispose 
 of, or otherwise to employ to advantage. 
 
 According to Mr. Ayton, it is still more profitable to feed calves with 
 the milk, but I find many people dilFer from him on this point. At all 
 events, a good and ready market is required for the veal. 
 
LECTURE XXI. 
 
 Of the feeiling of animals, and (he purposes serped by their food. — Substances of which tlie 
 parts of animal bodies consist. — Whence, tlo tlie animals derive these substancen- are 
 they all present in the food 7 — Use of the starch, gum. and su(;ar contained in vegetable 
 food.— Functions of a full-grown animal. — Of the respiration of animals.— General ori>;in 
 and purposes served by the fat in carnivorous and herbivorous animals.— Of ihe diges'ive 
 process in animals. — Purposes served by food and digestion. — The food sustains the full- 
 grown aniinril. — Necessity of a mixed food. — It sustains and increises the fattening ani- 
 mal. — Ilelalive {Men'm^i powers of ditferent kinds of food. — How circumstances affect thi.s 
 fattening property. — Purposes serveil by food in the prej^nant — in the yoimg and growing 
 animals, such as the calf — and in llie milk cow. — Eif.ctof different kinds of food on the 
 quality of Ihe milk. — Fattening of the cow as the milk lessens in quantity — Experimental, 
 economical, and theoretical value of different kinds of food for tliese several i)urposes — 
 Circumstances which affect these values. — Soil, manure, form in which the food is given, 
 ventilation, light, warmth, cxeici^e, activity, salt and other condiments. 
 
 Having in the preceding lectures coii.sidered llie composition of the 
 direct products of the soil — grtiins, roots, and gnisses — and of the most 
 important indirect prodticrs — inilU, butter, and cheese — llie only part of 
 our subject which now remains to be discussed is the relative values of 
 these several products in the feetling 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 ani- 
 mal — by the purposes for which it is fed — and by the circumstances 
 under which it is placed while the food is administered to it. 
 
 § 1. Of tlie substance of winch 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. 
 
 a. The muscles, in their natural state, as I have already had occasion 
 to mention (p. 444), consist in 100 ])arts of about — 
 
 Dry matter 23 
 
 Water 77 
 
 100 
 so that, to add 100 lbs. to tde 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 disappear, and 
 the muscle becomes periectly white. In this state, with the exception 
 of some fatty and other matters which still remain intermixed with it, the 
 white mass forms what is known to chemists by the name o{ fibrin. 
 This naiue is given to it because it forms the fibres whicli run along the 
 muscles and constitute the greater portion of their substance. 
 
 The following table exhibits the relative proportions of muscular fibre 
 and otjier substances contained in the flesh of several ditfercnt animals in 
 its natural state, [Schlossberger, Annalen der Pharmacie, December, 
 1842, p. 344] :— 
 
COMPOSITIOK OF RECKNT MUSCLE. 587 
 
 e 
 Calf . ° I Q. a 
 
 O X°. 2°. 0^ Pi P, 5 O H 
 
 Muscular fibre, vessels. nerves 
 
 and cellular substance . . 17-5 150 1G2 16-8 18-0 170 165 12 IM 
 
 Soluble albumen and colour- 
 ing maiur of blood Uiejiia- 
 (vsin) 2-2 3-2 26 24 2-3 45 3-0 5 2 4-4 
 
 AlcolioUcextract,conlaining< ^.^ ^.^ ^.^ j ~ ■ , ^.q ^^ j.q ^.g 
 saline matter S > " 4 ) 
 
 Watery extract, containing K.3 ^.^ ^.^ ^^.g ( " J^^ ^.3 ^.^ Q.g 
 saline niaiter ) ■' ^ 
 
 Phosphate of lime, with a lit- 
 tle albumen* .._... trace 01 trace trace 04 — 06 — 22 
 
 Water and loss 775 797 782 78 3 76-9 760 773 80-1 805 
 
 100 100 100 100 100 100 100 100 100 
 
 The proportions in the above table are not to be regarded as constant ; 
 they seem, however, to shew what we should otherwise expect, that the 
 muscular part of fishes contains a less proportion of fibrin than that of 
 land animals in general. 
 
 When dried beef is burned it leaves about 4.V per cent, of incombus- 
 tible 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 tills 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 incorporated with its substance 
 about — 
 
 Water 77 lbs. 
 
 Fibrin, with a little fat . . 22 »' 
 
 Phosphate of lime ... | " 
 
 Other saline matters . . A " 
 
 100 
 
 6. The fat of animals consists, like tlie 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 oleine, 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 of the oils of many other fruits. It exists in larger quantity in the 
 fat of tlie 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 United 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 fusible candle. The 
 fluid oil of animal fats, however, is known to differ from the li(]uid part 
 of butter (butter-oil) described in the preceding Lecture (p. 559), and 
 from the fluid part of linseed and other similar oils which dry, and form 
 
 ■ This phosphate of lime is over anc| above (hat which exists naturally in, and is insepar- 
 able from, the muscular fibre ilseif a'ld Irom tlie iilbumen. 
 
 25* 
 
688 OP FAT, ANr> OF WHAT BONES CONSIST. 
 
 a kind of vaniisb when exposed to th« air. These latter facts are not 
 without their importance, as we shall hereafter see. 
 
 The »olid part of the fat of animals is lu:ovvn to vary to a certain ex- 
 tent among difierenl races. Tlins tlie solid fat of man is the same with 
 that of the g(x>se, and with tliat which exists in olive oil and in butter- 
 To this the name o^' mar gar me \9 grveii. But the so'lid fat of the cow, 
 the sheep, the horse, and the pig, differs from that oi man, and is 
 known by the name of »tearine. 
 
 The solid aixl fluid parts are mixed together in different proportions iu 
 the felt, not only of ditierent animals, but of the same animal at differ- 
 ent periods, and in ditierent parts of its body- Hence the greater hard- 
 ness oljserved in the suet than irj other portions of the fat of beef and mut- 
 ton, and hence also tlie diflerent qnality aixl appearance of the fat of an 
 ox according to the kind of food u[)on which it ha-s been fed or fattened. 
 
 c. The bones, like the muscles, consist of a combuslible and an incom- 
 bustible portion, but in the bones the inorganic or incombustible part is 
 by much the greater. To the organic n^atter of bones the name of gel- 
 atine or glue is given, and it can be partly extracted from them by boil- 
 ing. The proportion of gelatine wliich exists in l>ones varies with the 
 kind of animal — with ihe part of the body from which the bone is taken 
 — and very often with the age and state of health of tlie anim^al, and with 
 the way in which it has been accustomed tobe feu- If is greater in spongy 
 bones, in the bones of yonng animals, and probably also in the bones of 
 such as are in higli condition. In perfectly dry bone it rarely exceeds 
 from 35 to 40 per cent, of the whole weight. 
 
 Tlfe incombustible portion consists for the most pnirt of phosphate and 
 carbonate of lime. The relative proportions of these two earthy com- 
 pounds also vary with the kind of animal, wiih 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 ahont — 
 35 pounds of gelatine, 
 55 pounds of phosphate of lime, 
 4 pounds of carbonate of lime, 
 3 pounds of phosphate ol^ magnesia, 
 3 pounds of soda, potash, and con^mon 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 sul- 
 phur which they contain- They corrsist of a substance which in other 
 respects closely resembles gluten and gelatine in its chemical composi- 
 tion (page 445). 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 0-39 
 
 Phosphate and sulphate of lime, phosphate of magnesia and silica . 020 
 
 1-10 
 The inorganic matter contained in hair is therefore, generally speak- 
 
OF HAIR, HORN, AND WOOL, AND OF BLOOD. 689 
 
 ing, the same in kind as that which exists in the muscular fibre and in 
 the bone. It contains the same phosphate of lime and magnesia — the 
 same sulphates and the same chlorides, among wliich latter common salt 
 is the most abundant. The absolute (juantity 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 sub- 
 stances themselves of whicli the inorganic matter is composed are nearly 
 the same, whether they be obtained from the bones, from the muscles, or 
 from the hair. 
 
 2°. Of the fluid parts of the body, the blood is the most important, 
 and by far the most abundant. The body of a full grown man, of mo- 
 derate dimensions, contains about 12 lbs. of blood, [Lehmann, Physi- 
 ologische Chemie, I., pp. 113 and 338,] 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 1 , 
 
 100 
 
 The organic matter consists chiefly of fibrin, whifh, when the blood 
 coagulates, forms the greater part of the clot — and of albumen, which re- 
 )nains dissolved in the serum or fluid part of clf)tted blood, but which, 
 like the white of egg, runs together inio insoluble clots when the serum 
 is heated. 
 
 The saline matter remains dissolved in the serum after the albumen 
 has been separated by heating, and consists chiefly of phosphates, sul- 
 phates, 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 por- 
 tion 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 .... 1*8 per cent. ? /t> -i- ■. 
 Fibrin of human blood .... 0-7 per cent. ^^ '' 
 
 This the same saline and earthy compounds, which form so large a 
 portion of the bones, are distributed every where in sensible proportions 
 throughout all the more important solids and fluids of the body 
 
 § 2. Whence does the body obtain these substances ? Are they contained 
 in the food 1 
 
 Whence does the body derive all the substances of which its several 
 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 con- 
 sidered, a reply to it is not so readily given. 
 
 It is true, indeed, that tlie organic part of the food contains carbon, 
 hydrogen, oxygen, and nitrogen — the elements of which the organic parts 
 of the body are comiwsed. The m-organic matter also which exists in 
 
^dfl WnE:5CE THE FAT AND BONES OF AN'IMALS. 
 
 the food contains the lime, tlie magnesia, the potash, the soda, the sul- 
 phur, the phosphorus, and the iron, which exist in the inorganic parts of 
 the animal hody — so that the (juestion seems already resolved. The 
 body obtains from llic food all the elements of whicli it consists, and 
 if these be not present in the food, the body of the animal cannot be 
 properly built up and supporteii. 
 
 But to the chemist and physiologist the more important part of the 
 question still remains. In what slate do these demenls enter into the 
 body ? Are the substances of which the food C(jnsists decomposed after 
 they are taken intotfie stomach ? Are their parts first torn asunder, and 
 then re-united in a ditTerent way, so as to form the chemical compounds 
 of which the muscles, bones, and blood consist? Are the vitcd 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 tlie body is comi)osed — or do they obtain these sub- 
 stances ready prepared from the vegetable food on which animals, in 
 general, are fed ? The answer wiiich 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 Hour of wheat and of our other cultivated 
 grains consists in part of gluten, of albumen, or of casein. These sub- 
 stances all contain nitrogen, and are identical in constitution with each 
 other, and with the fibrin of which the muscles of animals chiefly con- 
 sist.* The substance of the muscles exists ready formed, therefore, in the 
 food which the animal eats. The labour of the ston>ach is in conse- 
 quence restricted to that of merely selecting these substances from the 
 food and dispatching them to the several parts of the boily, where tiiey 
 are required. The plant compounds and prepares llie 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 
 liappen 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 wliich exist in the bo lies 
 of animals. In regard to this portion, therefore, of the body, the vege- 
 table performs also the larger part of the labour. It builds up fatty sub- 
 stances out of their elements — carbon, hydrogen, and nitrogen. These 
 substances the stomacli extracts 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 na- 
 tural — and probably, where a sutficient supply exists, the only one had 
 recourse to by the healthy animal — is the fat which is found, rcidy 
 formed, in the vegetable food it eats. 
 
 3°. Further, the bones, the muscles, and the blood, contain phosphate 
 
 ' The chemical reader, who is aware of the exact stale of onr knowledge upon this sub- 
 ject, will perceive that I speak here of the iilentlty of these snbslanrrs only in so far a-i tlie 
 proportions of carbon, hy(lro!£en,oxy{;eti, and nitrogen are concerned 1' is unnecessa y to 
 allude in this place to the different proportions of sulphur and plio.-iphorus they are kn ■wi: 
 to contain — as the more popular nature of this work will not permit ine to discuss the re- 
 fined, Chough singularly beautiful, physiological questions with which these diflferences are 
 connected. 
 
THE ru.NCTlON Of RESPlRATlOJf . 591 
 
 of lime, |)hosj)liate of magnesia, common salt, and other saline com- 
 pounds. These same compounds exist, ready formed, in the vegetahle 
 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 inorganic saline substances which are 
 found in llie 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 whicli the animal is to live. 
 
 Not only, therefore, do tlie mere elements of which the parts of the 
 bodies of animals are formed, exist in the food — but tliey occur in it, put 
 together and combined, nearly in the state in wliich they are wanted, in 
 order to tbrm the several solids ami fluids of the body. The plant, in 
 short, is the compounder of the raw materials of living bodies. The ani- 
 mal uses up these raw materials — cutting them into shape when neces- 
 sary, 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 tlie 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, wliich supplies the mate- 
 rials from which the muscular parts of animals are formed, the oil which 
 is converted into the fat of animals, and the saline and earthy matters 
 of plants w'hich 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 w hich consist of carbon and the elements of 
 water only (p. 111). What purpose is served by this part of the food? 
 Is it merely taken into the stomach and again rejected, or is it decom- 
 posed 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 miglit infer that they were destined to 
 .serve some important purpose in the animal economy. To the herbiv- 
 orous 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 produced by it, and 
 the purposes it is sup|)osed to serve in the animal economy. 
 
 1°. Of the function of respiration. — All animals possessed of lungs al- 
 ternately inhale and exhale the atmospheric air. They breathe, that is, 
 or respire. The air ihey draw into their lungs, supposing it to be dry, 
 consists by volume (pp. 32 and 148) very nearly of — 
 
 Nitrogen . 79-16 
 
 Oxygen 20-80 
 
 Carbonic acid 6-04 
 
 100 
 
592 FAT SUPPORTS RESPIRATION IN SOME, 
 
 — 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 
 
 100 
 »— the proportion of oxygen being considerably less, that of carbonic acid 
 very much greater, tlian before. On an average the natural proportion 
 of carbonic acid in the air is found to be increased 100 times after it ia 
 expelled by breathing from the lungs. 
 
 Now carbonic acid consists, as we have previously seen, of carbon and 
 oxygen. In breathing, therefore, the animal throws off into the air a 
 quantity of carbon — in the form of carbonic acid — which varies at dif- 
 ferent times, in different species of animals, and in diflerent 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. AH this carbon must be derived from the food. 
 The animal eats, therefore, not merely' to support or to add weight to its 
 body, but to supply the carbon also which is wasted by respiration. 
 
 2°. How the respiration is fed. — What part of the food sujjplies the 
 waste caused by respiration ? How is the respiration fed ? 
 
 In animals which live upon flesh — carnivorous animals — it is the fat 
 of their food from which the carbon given ofl' by their lungs is derived. 
 It is only when the fat fails in quantity that the lean or muscular part 
 of the flesh they eat is deconii)osed for the purpose of supplj'ing carbon 
 to their lungs. 
 
 In an animal to which no food is given for a time, the lungs are fed, 
 so to speali, 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 ad- 
 ministered, but the carbon given off' is derived from the substance of the 
 body itself. The fat first disappears — escapes with the breath — and af- 
 terwards the musculai- part is attacked. Hence the emaciation which 
 follows a prolonged abstinence from food. 
 
 In animals which live upon vegetable food again — herbi^'orous ani- 
 mals — it is the starch, gum, and sugar, of the food which supply the 
 carbon for respiration. It is only when the food does not contain a suf- 
 ficient supply of these compounds tliat the oil first, and then the gluten, 
 are decomposed, and made to yield their carbon to the lungs. 
 
 In man, who lives on both kinds of food, and in the domestic dog, and 
 the pig, which also cat indifferently both animal and vegetable (bod, the 
 carbon of respiration may be derived in j)art from the fat, and in part 
 from the starch and sugar which they eat — according as they are chiefly 
 supported by the one cr by the other kind of food. 
 
 It may be asked how we know that such are the parts of the food, to 
 which the duty of supplying the demands of the lungs is especially com- 
 mitted. There are several considerations which lend force to this opin- 
 ion. Of these I will draw your attention to one or two. 
 
 a. Why is the fat rather than the lean part of the food oi carnivorous 
 
STARCH AND SUGAR IN OTHER RACES. 593 
 
 animals devoted to the service of the lungs, and why do starving ani- 
 mals lose tlieir fat first 7 Because the chemical decomposition by which 
 carbon can be derived from the fat is simpler and more easily effected 
 than that by which it can be ob ained from muscular fibre. By combi- 
 nation with oxygen, fat can be converted into carbonic acid and water 
 only, of whicli the former will pass off'by tlie lungs and the latter in the 
 xirine. The muscular fibre, on the other hand, contains much niirogen 
 (p. 444), and, if deprived of its carbon for the uses of res![»iration, must 
 undergo very complicated decompositions, and form a series of com- 
 pounds, the use of which, in the animal economy, it is not easy to perceive. 
 
 Besides, in producing the carbonic acid of the l:ings 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, hydrogen, and oxygen. 
 Thuse all disappear entirely in the form of carbonic acid and water — both 
 of which are used up. Muscle, on the other hand, besides nitrogen, con- 
 tains 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 sulphate and phosphorus 
 also, would go to waste, and would pass off in the urine. In nature, 
 however, such waste is rarely seen to lake place ; and, therefore, as a 
 general rule, the respiration will be supported by the muscrilar fibre only 
 when other kinds of food are deficient. 
 
 b. But in the stomachs oi herbivornus animals, why are the starch and 
 sugar especially appropriated to the use of the lungs ? The food of ani- 
 m ds which live upon vegetable substances contains fat as well as starch 
 — why then is the starch in this case dissipated by the process of respira- 
 tion, while the fat is applied as it is supposed to another use ? The 
 answer to this question is both beautiful and satisfactory. 
 
 Starch, gum, and sugar, consist of carbon and water only, and we can 
 cjuceive them in their ])assage through the body to be actually separated 
 into these two substances — in which case the carbon has only to combine 
 with oxygen and form carbonic acid, to be ready to pass off by the lungs. 
 H "-re, theref(>re, only one chemical combination is required — the union 
 of carbon with oxygen. It is the simplest way in which we can con- 
 ceive carbon to be supplied for the use, or for the purposes of the lungs.* 
 
 But it is otherwise with fat. Though nearly all kinds of fot consist en- 
 tirely of carbon, hydrogen, and oxygen— yet they cannot be supposed to 
 consist only of carbon and water. Theycontain much more hydrogen than 
 is necessary to form water with the oxygen which is present in tliem. If, 
 then, the carbon of these fats be separated, this excess of hydrogen will 
 also be set free, and if the farmer be made to combine with oxygen to 
 fjrm carb inic acid, the latter nrust also coiiibine with hvdrogen 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 system than when the carbon alone is to be combined with oxygen. 
 It is natural, therefore, that where both starch and oil are present to- 
 gether, 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. 
 
 ' Th*? chemical reader will iinderslanfl that I am here only giving a popular view of the 
 finai result of the several chances through which the carbon no doubt passes before it 
 escapes in the form of carbonic acid. 
 
594 PURPOSES SKRVED BT RKSPIRATIOI*. 
 
 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 tlie more abundant varieties of vegetable food contains. In obtaining 
 carbon from thess, the least possible labour, so to speak, is imposed upon 
 the digestiv^e organs of the herbivorous races. The starch and sugar 
 abound because much carbon is reipiired, while fatty matter or oil is 
 present in smaller ([uantity, because comparatively little of this is neces- 
 sary to the performance of the usual healthy functions of the animal 
 body. Aad it is another adaptation of the living body to the circum- 
 stances in which it may be placed, that when starch or sugar cannot be 
 obtained, the oil of the food is consumed for the supply of carbon lo the 
 lungs — and failing this also, the gluten and albumen of tlie vegetable food 
 or the muscular fibre of the animal food, or even of the living animal it- 
 self. 
 
 3°. Purposes served by respiration. — But for what purpose essential to 
 life do animals respire ? If the starch and sugar be so necessary Xo 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, 
 liowever, that carbon is consumed or given off from the lungs for the pur- 
 pose 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 conversion of starcli and sugar into 
 carbonic acid an 1 water — taking place, heat must in like manner be ])ro- 
 duced. A slow combustion, in short, is supposed to be going on in the 
 interior of the animal — the heal of the body being greater, in proportion 
 to the quantity of carbonic acid given otV 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 satis- 
 factorily removed. 
 
 Were we to adopt this o))inion in regard to the main purpose served by 
 respiration as the true one, it would ati()rd a very distinct reason for the 
 large amount of starch existing in all our cultivated 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. The life and labfiurs of the plant again minister to 
 the life and labours of the animal. 
 
 § 4. Of the origin and the purposes served hy the fat of animals. 
 
 1*^. The immediate ori nin or source of the fat of animals depends upon 
 the kind of food with which the animal is fed. Carnivorous 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 herbage, 
 on which cattle are fed, contain a sufficient (juantity of oily matter ready 
 formed tosujjply all the fat which accumulates in their bodies — or which, 
 by the milk cow, is yielded in the form of butter. Before the ditlerent 
 kinds of food had been analyzed, with the view of determining the quan- 
 tity of oil and fat they severally contain, it was suj) posed that the fat of 
 animals wa? derived almost solely from the starch and sugar or gum, of 
 
ORIGI.N OF THE FAT OF AMMALS. 595 
 
 which so large a i)roportion of vegetable food consists. This opiuioa, 
 however, has given way before the advance of analytical researcli. 
 Animals Kitten ciuickest upon Indian corn, or oil cake, or oil mixed with 
 chopped straw, or upon oily seeds and nuts — or, as in the case of ponltrv, 
 on a mixture of meal or suet — because these kinds of food contain a large 
 jjropnrtion of fatty matter ready formed which the animal can easily ex- 
 tract, and after a slight chemical change can convert into a portion of its 
 own substance. 
 
 The conversion of starcli or sugar into fat in the animal body implies 
 a chemical change of a less sim[)le nature — one which seems to impose 
 upon the \ital 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, tlicre be in the ihod as mucli fat as is necessary to supply all that 
 the animal approjiriates to itself, and if it is observed to lay on or appro- 
 I)riate more when the food is richer in latty 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 
 animal and lessens its labour by preparing beforehand the materials 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 animal can 
 procure does not contain a sutiicient proportion of fat to supply all the 
 wants of its body — or to enable it to perform the several natural functions 
 it is destined to fulfil. Thus wax is a kind of fat, and it has been shown 
 (Milne Edwards) that, when fed upon pure sugar, the bee is capable of 
 forming wax from its food. When fed upon such sugar, it not (jidy lays 
 tip a store of honey, but 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 njan and of other animals. That power which the bee 
 possesses they also may in cases of emergency be able to exercise. 
 Where a sutiicient supply of oil for the necessary uses of the animal is 
 not contained in the food it eats, it may form 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 proposition. 
 
 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 ujran 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 functions of its 
 body, it has the power to form an additional quantity from the starch or 
 sugar it eats — but that it wdl not readily fatten or lay on large adilitions 
 of fat upon its body when fed upon farinaceous, saccharine, or other food 
 in v.duch oil is not naturally contained.* 
 
 ■ For tlie sake of tlie chemical reader I may be permitted here to show by what kind of 
 chemiCHl cfianges — 1°, ihe fat ofanjinala in geneml may be derived from tlie starch or sugar 
 of their fo^ul ; and 2"^, how the pt>culiar kinds of fai contained in (lie body of any given ani- 
 mal may be formed from the pecnhar krnda of fat contained in ils lood. 
 
 1°. How fat may be formed from, stiirch or sugar. — These iwo substances, as we have 
 already seen, may be represented by carbon and water only — 
 
CHANGES OF OX FAT INTO HUMAN FAT. 596 
 
 2°. The purposes served by the fat. — In all healthy animals which 
 take a sufficient quantity of exercise to maintain them in a healthy con- 
 carbon. Water. 
 
 Starch, consistin? of 12 + 10, represented by Ci2 Hio Oio 
 
 Cane sug-ar, consisting ot" 12 -j- 11, represented by Ci2 Hn On 
 Fct, again, margarine for example, the solid fat of the humm body, is represented (p. 
 559, note,) by Cm IIig Os Compare this with 4 of starch, and wo have— 
 4 of starch = Cid Hio 043 
 
 1 of margarine = CiV Has Oj. 
 
 Difference = Cii Uj O35 
 
 This difference is equal to, or may be represented by, 
 
 U of carbonic acid + 4 of water + 9 of o.xygen 
 11 COi + 4PIO + 90 
 
 Si) that by the sepan-.tion of carbonic acid, whicli may be given off from the lungs — of 
 water, which may or may not remain in the system, — and of a portion of o.tygen, which 
 may be used up in various ways in the blood, the starch or sugar of the food may be con- 
 verted into fat. 
 
 Tliat in some sucli 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 fa: is really formed in tlie 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 ne- 
 cessity for the constant production or formation of fat in the body itself, therefore, is not now 
 so apparent, and the soundest opinion, according to our present knowledge, seems to be 
 that, while the vegetable food usiiaJly supplies all the fat ready formed which the animal re- 
 quires, yet that a conversion of a certain part of the starch, gum, sugar, and even of the cel- 
 lular fibre of the food, into fat, may take place, when all the wants of the body are not sup- 
 plied 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 con- 
 stant 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 fal. 
 
 2^. How the peculiar kinds of fat in the body may be derived from the peculiar kinds of fat 
 in the food. 
 
 a. We have already seen (p. 553) that the solid part of butler, of olive oil, and of the goose, 
 is identical with the solid fat of the human body. When eaten by man, therefore, these se- 
 veral 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 foo 1 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 = C74 Il72 Oio 
 
 1 of stearine = C?) Ho9 O7 
 
 Difference = C3 113 O3 
 
 If we double this difference, we have Cs 115 Oj ; 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 nwy po.sBibly be llie evolution 01 the 3 of carbon (C3 ) 
 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. Tlie stearine of the anim.-il in this case may be formed from the mar- 
 garine of the butter, being exactly the converse of the previous case, while the butter oil may 
 be changed into the liquid fat of the tallow. 
 
 This latter is more difficult to explain, since the composition of elaine — the liquid fat of 
 the ox, calf, and sheep— compared with Oiat of butter oil, presents a considerable difference. 
 Thus— 
 
 Elaine = C47 H12 Og 
 
 Butter oil = C37 II33 Ou 
 
 Difference . . . . = Cio H9 
 
 What becomes of this difference, Cio H9, we are unable as yet precisely to explain. By 
 the intervention of a little oxygen it might readily give rise to a little more fat. 
 
 d. The cow and calf together, however, illustrate very clearly the existence of this trans- 
 forming power of the animal body. We are unacquainted, as jet, with the composition of 
 the several kinds of fat which occur in vegetables — but we know that out of these the cow 
 can form the two kinds of fat — the stearine and the elaine — which exist in its own tallow, 
 and at the same time the two kinds of fat — margarine and butler-oil — which are found in its 
 milk. The calf, again, can change these two latter fats into those which its own body, aa 
 
PURPOSES SERVED BV THE KAT. 597 
 
 dition, 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 liair and skin soft and flexible, — and, by filling up hollovvs, 
 contributes to the roundness and plumpness of the parts, and defends tlic 
 extremities uf 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 
 removed, 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, recjuire a cerlain supjdy to be daily 
 given to them in their food. 
 
 The accumulation of fat in animals seems to be an effort of nature 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 por- 
 tion 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 tliey cat — and that the lean- 
 ness which attends upon starvation is owing to the fat of the living body 
 beingconsumed in supplying thecarbon 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 demand 
 which the food may not be able wlioUy to supply. 
 
 § 5. Of the natural loasle of the parts of the body in a full grown animal. 
 
 We have sein that, if the food of the animal be unable to stipply the 
 carbon given otl'from the lungs, and the fat which the movements of the 
 limbs require, th6 parts of the body themselves are laid under contribu- 
 tion 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, liowever, do undergo a con- 
 stant and natural waste, to make up for which is one of the main pur- 
 poses 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 out- 
 wards. But the muscles and even the bones are by little and little re- 
 well as thar of ifs mother, rerjuires. And, lastly, man by eating the fat of the calf can re- 
 convert it into margarine ami those other fatty substances which are found in the various 
 parts of hi* bo<ly. Substances which can thus so frequently and so readily be changed, the 
 one into the oiher, must be very closely connocted, and the mode in which their mutual 
 transformations are effected will, no doubt, prove to be simple when these are rightly un- 
 derstood. 
 
 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 fatly 
 acids only which they are known to contain. 
 
 The reader will con.siiU with much advantage and sHlisfaction upon this subject, a work 
 upon Chemicrtl Physiology, by Professor Mulder, of Utrechi (Prone eener Algemeene Phy- 
 Slolo gische S'chei/eunde, p. 260, el seq.) of which I am happy to say that a translation from 
 thi> Dutch is now in progress by my assistant, Mr. Fromberg, and will speedily be published 
 by the Messrs. Blackwood. 
 
698 FOOD RKQUISITE FOR THE NATURAL VVASTK. 
 
 moved itnvanlly and rejected in the excretions — tlie place of that which 
 IS removed being sup[)Ued by zievv portions of matter derived from the 
 food. 
 
 This removal, though unfelt by us, goes on so rapidly that in a space 
 of time, which varies Jrom one to five years, the whole body of the ani- 
 mal is renewed. There doe<> 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 ofthe corner of a house, and put in a new one — ihe form and 
 dimensions ofthe 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 ra- 
 pidly than others — the muscles, for example, more frequently aird rapidly 
 than the bones and the brain. In young animals, again, the whole body 
 is oftener renewed than in such as are advanced 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 which the food contains — tlie fat from its oil — 
 and the earthy matter of the bones and the salts of the blood, from the 
 phosphates and saline substances which are naturally present in it. On 
 the other hand, those parts which are extracted from the muscles and 
 bones, and carried off in the excretions, are decomposed during their re- 
 moval. New chemical compounds are produced from them, wliich are 
 found in the urine and dung of the animal, and which give to these ex- 
 cretions their richness and value in the manuring ofthe soil. 
 
 § 6. Ofthe Mud and quantity of food necessary to make up for the natural 
 tvasle in the body of a full groicn animal. 
 
 The substances which constantly disappear from tile body in conse- 
 quence of the natural waste above described, are of three kinds — ihe fibrin 
 and other analogous organic compounds, which form the muscles and the 
 cartilage of the hones — the earthy phosphates (of lime and magnesia), 
 which form so large a proportion of the bones, and exist in small quan- 
 tity in the muscles also — and the soluble saline substances, which abound 
 in the blood and in the other fluids of the living animal. In tlie solid and 
 liquid excretions, a larger quantity of each of these three classes of com- 
 pounds is carried out of the body. How much of each must be contained 
 in the daily food of a full-grown animal in order tliat 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. — Tlie most accurate experi- 
 ments that have yet been made^upon this subject (Lccanu) apjiear to 
 show tliat a full grown man rejects in his urine alone about half an ounce 
 of nitrogen (230 grs.) every 24 hours. This (|uantity of nitrogen is con- 
 tained in about three ounces of dry muscular fibre, which must, therefore, 
 every day be decomposed or removed in order to yield it. 
 
 But if the body is kept in condition, this quantity of fibrin must be 
 daily restored again by the food. Now, to supply tliree ounces of dry 
 fibrin, there must be eaten about — 
 
IN THE BODY OF A FULL-GROWN ANIMAL. 599 
 
 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 
 4 " of cheese ;* 
 Or, if we live wholly upon potatoes or milk, we must eat no less than 
 six or seven pounds of the former daily, or drink three or four imperial 
 pints of tlie latter — if we would restore to the body as much of the sub- 
 stance of its muscles and cartilage as is daily removed from it by the 
 urine. 
 
 But the urine is not the only cliannel tlirough which nitrogen is given 
 o3' from the animal body. A considerable, though, of course, a variable 
 proportion is found in the solid excretions or dung, which has also been 
 derived from the substance of the body itself. A small quantity of ni- 
 trogen is believed to be given olf from the lungs also in breathing, and 
 from the skin in the perspiration, whicli nitrogen must have been either 
 directly 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 nourishment 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 (piantity 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 wiiich 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 oeen published from which we can de- 
 termine the average quantity of nitrogen rejected in the excretions 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, compared with that of a full grown man — or 
 five times greater than in a man — 'then tlie 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 
 mentioned : — 
 
 120 lbs. of turnips. 17 lbs. of clover hay. 
 
 115 " of wheat straw. 12 " of pea straw. 
 
 75 " of carrots. 12 " of barley. 
 
 67 " of potatoes. 10 " of oats. 
 
 20 " of meadow hay. 5 " of beans. f 
 
 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 the animal will pro- 
 
 ' Supposinc the wheaten flour to i!ni\tain 10 per cent, of gluten, and the cheese one half 
 Its \veii;ht of dry curd (see also pp. 506 and 531.) 
 T These numbers are calculated from the (able given in p. 631. 
 
600 A MIXED FOOD NKCESSARY TO ANIMALS. 
 
 bably be found to thrive better on the mixture than if fed upon any one 
 of tliese kinds of food alone. 
 
 2°. Quantity of fixed saline matter and of earthy phosphates which 
 the food ought to contain. — A fuil 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 jt by 
 the daily food. Thus whatever (]uantity of saline and earthy matter is 
 present in the food, an equal quantify is found in the excretions of the 
 living animal. 
 
 But how much of that which is found in the excreiions has actually 
 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 J'uU 
 grown animal, in order to sup{)ly it with the necessary daily proportion 
 of saline and earthy substances. 
 
 The benefits so often derived frora the use of salt in the feeding of 
 stock show how a judicious admixture of saline matter with the food 
 may render its other constituents more available than they would other- 
 wise be, to the support and increase of the animal body. 
 
 § 7. The health of the animal can be sustained only by a mixed food. 
 
 Fro!n what I have already stated, you see that the vegetable 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 ofi" in respiration. 
 
 2°. Fat or fatty oil, to supply the fatty matter which exists more or 
 less abundantly in the bodies of all animals. 
 
 3°. Gluten or fibrin, to make up for the natural waste of the muscles 
 and cartilage. 
 
 4°. jEar</?j/^;/iosp/(fl<es, to supply what is removed from the bon&s of 
 the full grown animal by the daily waste ; and — 
 
 5°. Saline substances — sulphates and chlorides — to replace what is 
 daily rejected in the excretions. 
 
 Hence the food iipon which any animal can be fed with the hope of 
 maintaining it in a healthy state tnust be a mixed food. Starch, or sugar 
 alone, or pure fibrin or gelatine alone, will not sustain the ainmal body, 
 because these substances do not contain what is neccssar\- to build up all 
 its parts, or to supply what is daily given olf during respiration and in 
 the excretions. The skilful feeder, therefore, will not attempt to main- 
 tain his stock on any kind of food which does not contain a sufficient 
 supply of every one of the kinds of matter which tlie body requires. 
 
 Two other points he will also attend to. First, he will occasionally 
 change the kind of food, or will vary the proportions in which he gives 
 the diffi^rent kinds of fodder to his feeding stock. This practice is founded 
 on the fact tliat, although every crop he raises contains a certain jiropor- 
 tion of all the substances which the animal requires, yet some contain 
 one of these in larger quantity than others do, and by an occasional 
 
ADDITIONAL FOOD REqUIRED FOR FATTENING. 601 
 
 change or variarion 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 differ- 
 ent proportions, according to its age and to the special purpose for which 
 it is fed. Let me direct your attention to this lattei- fact a littler more 
 at length. 
 
 § 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 increase the 
 body. To increase the body, an additional quantity of food must be con- 
 sumed, but the kind or nature of this additional food will depend upon 
 the kind of increase which the animal is inaking or is intended to make. 
 
 One of the important objects of llie stock farmer is to make liis full 
 grown animals lay on fat, so that they may as quickly as possible, 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 ob- 
 ject he wishes to attain. 
 
 We have already seen reason to believe, that tlie natural and imme- 
 diate source of the fat of animals is in the oily matter which die food 
 contains. If we wish only, or chiefly, to lay on fat, therefore, we 
 ought to give some kind of food which contains a larger proportion of 
 fatty matter than that upon whicJi the animal has been accustomed to 
 live. This is what the practical man has actually learned to do. To 
 his sheep and oxen he gives oil-cake or linseed oil mixed with chopped 
 straw, to his dogs cracklings,* to his geese and turkeys Indian corn, 
 which contains much oil, and to his poultry beef or mutton suet. 
 
 Many experiments are yet wanting to determine with accuracy the 
 proportion of fat contained in all the different kinds of food usually con- 
 sumed by animals. Nearly all we yet know upon this subject is ex- 
 hibited in the tabular view of their composition to which I have already 
 directed your attention (p. 531.) 
 
 One thing, however, of considerable practical value has been recently 
 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 the examination of two 
 varieties of this gcain, one grown near Durham, the other in France. 
 The result as to the French grain is given by Dumas : — 
 
 PER CENTAaS OP PATTY OIL. 
 
 Snglrsh. French. 
 
 Fine flour ... 1-5 1'4 
 
 Pollard .... 2-4 4-8 
 
 Boxings .... 3*6 — 
 
 Bran 3-3 5-2 
 
 " Cracklines are the skinny parts of the suet from which the tallow has been for the most 
 part sqiieezeii out by the tallow chandlere. Miiiht cattle not be fattened upon cracklings 
 cnisheJ and mixed with their otlier food 7 Might not some cAec;) varieties of oU also bs 
 mixed with Iheir food for the purpose of fattening. 
 
602 FATTV HATTKR IN THE HI'SKS OK SEEDS. 
 
 This fact of the existence of more fat in the husk than in the inner 
 part of the grain, explains what often seejns inexplicable to the practical 
 man — why bran, namely, wliich appears to contani little or no nourish- 
 ing substance, should yet fatten pigs anil other full grown animals, when 
 given to them in sufficient (piantity along with their other fooil. It also 
 explains why rice dust, should be found to fatten stock,* though the 
 cleaned and prepared rice contains but little oil, and is believed, there- 
 fore, to be unfitted for laying on fat upon anunals 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. Ki7id 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 in- 
 crease rapidly in size when the food is of a proper kind. This food, 
 therefore, should contain a large supply of the phosphates, from which 
 bone is formed, and of gluten or fibrin, by which the muscles are en- 
 larged. Some kinds of fodder contain a larger proportion of these phos- 
 phates. Such are corn seeds in general, and the red clover among grass- 
 es. Some again contain more of the materials of muscles. Such are 
 beans and peas among our usually cultivated seeds, and tares and other 
 leguminous plants among our green crops. 
 
 Hence the skilful feeder or rearer of stock can often select with judg- 
 ment that kind of food which will specially supply that which the ani- 
 mal, on account of its age or rapid growth, specially requires— or which, 
 with a viewto some special object, he wishes his animal special!}' to lay 
 on. Do;>3 he admire the fine bone of the Ayrshire breed? — he will try 
 to stint it while young of that kind of food in which the phosphates 
 abound. Does he wish to strengthen liis stock, and to enlarge their 
 bones ? — he will supply the 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 sto<!k, to be sold to the butcher at two or three years old, 
 they are well feil with good and abundant food from the first, that they 
 may grow rapidly, attain a great size, and carry much fiesh. 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 husbanlry. To the man who has a calf and a milk cow, 
 the principal qu:?stion 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 
 iny calf a little of the milk, and sell the remainder in the form of new 
 
 * Rice dust is very good food for fattening pigs, makes excellent pork, and i8 ver/ profit- 
 able when given along with whey. 
 
rKCDI>-G OF TOUNG CAL\'KS. 603 
 
 milk — or bad I better make butter and give the skimmed milk to my 
 calves — or will the veal, if I give m^' calf all the milk, pay me a bet- 
 ter price in the end ? The result of many trials has shown, that in some 
 districts the liigh price obtained for well fed veal gives a greater profit 
 than can be derived from the milk in any other way. 
 
 While tlie calf is very young — during the first two or three weeks- 
 its bones and nmscles chiefly grow. It requires the materials of tJiese, 
 therefore, more than fat, and lience 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 cos- 
 tive effect of the bean meal must be guarded against by occasional me- 
 dicine, if required. 
 
 In tne next stage, more fat is necessary, and in the third week at 
 latest, full milk, with all its cream, sliould be given, and more luilk iJian 
 the motlier 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 lin- 
 seed meal, may supply at a cheap rate tlie 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 afterivgs of several cows may be given to the calf along 
 with its food. For the expensive cream there might no doubt be sub- 
 stituted many cheaper kinds of fat whicli the young animal miglit be 
 expected to ap[)ropriate as readilv as it does the fat of the milk. Lin- 
 seed 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 whicli would increase his weight at an equally low cost ? 
 A fat pease-sou [) 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 wtiich will specially increase the size 
 of tiie bones in the growing animal, by supplying a large quantity 
 of the ]»hosphates, is at present limited in a considerable degree. The 
 grain of wheat, barley, and oats is the source from which these phos- 
 phates are most certainly and most abundantly supplied to the animals 
 that feed upon them. But in many cases corn is too expensive a food, 
 and those kinds of corn which contain the largest proportion of the phos- 
 phates sup[)ly only a comparatively small quantity in a given time to the 
 growing animal. Why should not bone-dust or hone-meal be introduced 
 as an article of general food for growing animals '.' 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 lo 
 minister directly to the weak lim!)s<)f our growing stock, and at pleasure 
 to provide the spare-boned animal with the materials out of which a 
 limb of great strength might be built up. 
 
 Chemical analvsis 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 
 86 
 
604 FOOD REQUIRED DURING PREGWANCT. 
 
 of tne animal body. Thus in regard to the same growth of bone, it ap- 
 pears that, while linseed and other oil cakes are mainly 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 m}^ laboratory, contained respectively of earthy 
 phosphates and of otiier inorganic matter in 100 lbs. the following quan- 
 tities : — 
 
 PEH CENTAGB OP 
 
 Eartfit/ phosphates. Other inorganic malter, 
 
 British linseed cake . . 2-86 2*86 
 
 Dutch do. . . 2-70 2-54 
 
 Poppy cake .... 5-22 1-24 
 
 Dodder 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 tlie 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 tlieir increasing bones. 
 
 § 10. Kind and quantity of additional food required by a 
 inegnant 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 unborn young. 
 The quantity of food which is necessary to sustain the mother.^ — if herself 
 full-grown, whicli 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 one-fifth of its weight 
 of turnips in a day, or one-fiftieth of dry food, such as liay and straw. 
 With this allowance of food the animal would probably increase in 
 weight in some degree, — but according to Riedesel one-sixtieth of its 
 weight of dry hay is necessary merely to sustain it. From what we 
 have already seen of the composition of the different grasses, it is obvi- 
 ous that the quantity required vv'ili be much affected by the kind of hay 
 with which the animal is fed. 
 
 To nourish tlie young calf in the womb of its mother, an additional 
 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 materials of the growing 
 bones and muscles of the fostus, yet it must contain also a larger quan- 
 tity of starch or sugar also than the mother in her ordinary state would 
 require. This is owing to the circumstance that the mother must now 
 breathe 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 
 of farinaceous or saccharine food must be eaten from the time when 
 pregnancy 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 expeiiments have been made vAxh the view of spe- 
 cially affecting the condition of the future calf by the kind of food given 
 to tlie mother. A certain proportion of bone and muscle no doubt must 
 
FOOD REQUIRED BY A COW I.V MILK. 605 
 
 be supplied to the young animal by the food given to the mother, or the 
 bones and muscles of the mother herself will he laid under contribution to 
 supply it — but it does not appear impossible to affect the size of the bone 
 by the quantity of phosphates which are given in the food, or the growth 
 and development of the muscles by that of the gluten, fibrin, 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-mdk 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 niother 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 be- 
 come greater. At this period, therefore, the cow must obtain larger sup- 
 plies of food to sustain herself and to produce a sufficient quantity of 
 milk for her calf than at any other period. 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 consequence 
 relieved of a part of her burden — her udders are less drawn upon — the 
 quantity of milk secreted becomes less — slie begins again to lay muscle 
 and fat upon herself — her udders at length become dr}', 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 ofT 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 affect the bodily character of the future 
 calf, applies equally to the means of more or less efTectually promoting 
 the growth of the young aniinul 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 phosjjhates and of otlier saline substances, and 
 there is little reason to doubt that if an uinjsual quantity' of these be given 
 in the fjod of the mother, an unusual quantity will be found also in the 
 milk she ])roduces. 
 
 For the production of milk the mother requires an adequate additional 
 supply of all the substances which we have seen to be necessary to the 
 support of the unborn fajtu^ — of the starch as well as of the gluten and 
 saline substances of the food. But it is interesting to mark the very dif- 
 ferent 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 lespiration. She breathes, as 
 I have already said, for her young and for herself, and therefore gives 
 off more carbon from her lungs. 
 
606 USES OF MIIyK IN THK KCONOitlY OF NATURE- 
 
 But when the young animal is born it breatlies for itself. It must, 
 therefore, be sujiplied with that kind of food which seems specially in- 
 tended to meet the wants of respiration. 
 
 Th^ 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 tliis sugar is to supply the carbon which the 
 young animal gives ofi' when it begins to breathe for itself. 
 
 It is not difficult to understand the kind of j)rocess by which the 
 starch of the mother's food is converted into the sugar of her milk. If to 
 
 2 of starch = 24C + 20H + 20O, 
 we add 4 of water = 4H + 40, 
 
 we have 24C -j- 24H -\- 240, which is the formula for 
 
 7Tiilk sugar. In passing through the digestive organs of the cow, ihere- 
 tbre, 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 nailk. 
 
 But though it is not difficult to understand in what way this change 
 may be eifected, yet it is exceedingly interesting to find that such a 
 chemical change as this should be made to commence al a certain special 
 epoch ivitJi 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 phos- 
 phates which are to build up the bones, and the sugar which is to feed 
 the respiration. Notliing is wanting in it. The mother selects all the 
 ingredients of this perfect food from among the useless substances which 
 are mingled in her own stomach with tlie food she eats — she changes 
 these ingredients chemically in such a degree 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 lo do at a 
 given and appointed moment of time. How beautiful, how wonderful, 
 how kindly provident is all this ! 
 
 But apart from its natural use in the economy of nature, milk may be 
 regarded as an article of manufacture — an important article of agricul- 
 tural husbandry. As a mere producer of milk for other purposes than 
 the feeding of calves, the cow will be differently fed according to the pur- 
 pose f )r which her milk is intended to be emi'loyed, or the form in which 
 it is to be carried to market. 
 
 a. The town dairyman, who sells his new milk to daily customers, 
 requires quantity rather than quality. He gives his cattle, therefore, 
 succulent fiwd in which water abounds — green grass — forced rapidly for- 
 ward by irrigation or otlierwise — green clover, young rye, brewers' 
 grains, or hay tea.* In this way, whhout tlie actual addition of water, 
 he can make his milk thin, and increase its bulk. 
 
 b. Those, again, who desire much rich cream, or who groio milk for 
 
 A mixed hay lea ami pease soup, which is excellent for makin;T cows give milk, is pre- 
 pared by putting liay iiiio a pot in al'ernute layers, sprinkJins; between each a hmidful of 
 pease-meal, adding water and bringing to a boil. 
 
TO PRODUCE MILK KOR CHEKdE OR BUTTER. 607 
 
 the manufacture of butter, pay less attention to the bulk of the milk 
 itself than to that ot' the cream they can coUect from its surface. The 
 proportion of butter is increased by the use of food which contains much 
 fatty matter — of any of those kiuds of food, indeed, by which an ox can 
 be made rapidly to lay on far. Oil-cake has by some been objected to 
 as likely to give a taste to the milk, but it may be safely used in small 
 (juantity, and gives an abundant and good flavoured cream. 
 
 c. In cheese countries, again, it is the curd that is "chiefly in request. 
 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 mainly 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 
 casein or vegetable curd, 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 advantage be employed to pro- 
 duce the same effect. As every thing which tends to lay on fat on the 
 animal is likely also to increase the proportion of butter in its milk, so 
 every thing which promotes the growth of muscle will also add to the 
 richness of the milk in curd or cheese. 
 
 § 12. Influence of size, condition, warmth, exercise, 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 require is 
 affected by many circumstances. Thus — 
 
 1°. IVie size and condition of the animal will regulate very much the 
 quantity of food wliich is necessary to sustain it. The larger the mus- 
 cles and bones the greater will be the daily waste, and the greater the 
 (juantity, therefore, of the food necessary to replace it. If an animal re- 
 quire a 50th or a 60th of its weight of dry food daily, of course his size 
 and weight will regulate almost entirely the quantity of food he 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 condition- 
 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 tiling 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 sus- 
 tain its body, or converts one stone wholly into dung. Whatever it eats 
 beyond this quantity, therefore, will go to the production of increased 
 beef and bone. Hence, if I have a given quantity of vegetable produce, 
 [ ouoht to be able to manufacture more beef from it by the use of small 
 cattle than of large, provided my large and small stock are equally pure 
 in breed, are equally quiet, and are as kindly feeders. 
 
608 INFiiUEXCE OK EXERCISK AND WARMTH. 
 
 The same reasoning applies to dairy cows of different breeds. If I 
 give two stones of hay to a sniail Shetland cow, she may not convert 
 more than one of tlieni into dung, the other she may consume for the 
 production of milk. But if 1 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 observed, 
 that small breeds of cattle give the richest milk, and that such as the 
 small Orkney breed yield the largest produce of butter 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 ofl'frora its lungs, the more starch or sugar con- 
 sequently its lixxl n:iu.st 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 bfxly are subjected. Take more exercise, therefore, 
 move one or more limbs oftener than usual, and a larger part of the sub- 
 stance of these limbs will be decomposed, removed, and rejected in the 
 excretions. Hence tlie reason why hard work recjuires 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 uourishing 
 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 tem- 
 perature of the atmosphere in which it lives, aHects also tlie quantity of 
 food which the animal requires to eat. The heat of the animal is inse- 
 parably connected with its respiration. The more frequently it breathes, 
 the warmer it becomes, and the more carbon it throws oti' from its lungs. 
 It is believed, indeed, by many, that the main purpose of respiration is to 
 keep up the heat of the body, and that this heat is produced very much 
 in the same way as in a common fire, by a slow combustion of that car- 
 bon 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 himsell". He will probably take exercise, and by this 
 means cause himself to breathe quicker. But to do this lor 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 exercise he takes causes a greater 
 natural waste also of the substance of his body- 
 So it is with all animals. The greater the difierence between the tem- 
 perature of the body and that of the atmosphere in which they live, the 
 more food they re(iuire to *' feed the lamp of life" — to keep them warm, 
 that is, and to supply the natural waste. Hence the importance of plan- 
 tations 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 
 
EFFKCT OF ABSENCE OF LIliHT. G09 
 
 closer covering to nuiet and gentle breeds of cattle or sheep, which feed 
 without restlessness and quickly fatten. 
 
 A proper attention to tho warinlh of iiis cattle or sheep, therefore, is of 
 great practical consequence to the feeder of stock. By keeping theni 
 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, which contirm the 
 opinions above deduced from theoretical considerations. Of these I shall 
 only mention one by Mr. Childers, in which 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 tliree months — January, February, 
 and Marcli — upon turnips, as many as they chose to eat, half a pound 
 of linseed cake, and half a pint ot" barley each sheep jjer day, with a 
 little hay and salt. The sheep in the field consumed tlie 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 3G 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 turnips each less in t!ie day, and in the 
 ninth week, again 2 lbs. less, or only 15 lbs. a day. Of the linseed-cake 
 they also eat about one-third less tiian the other lot, and yet they in- 
 creased 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 rnore 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 ? Because the stomach of an animal will not do more than a 
 certain limited amount of work in the way of diijesting, after the wants 
 of the body are fully supplied. When circumstances cause the sustain- 
 ing quantUi/ 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 condition. If the sustaining portion be lessened, by placing 
 the animal 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 quan- 
 tity 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 con- 
 sume less food. 
 
 4°. The absence of light has also a material influence upon the efTects 
 of food in increasing the size of animals. Whatever excites attention in 
 an animal, awakens, disturbs, or makes it restless, appears to increase 
 the natural waste, and to diminish the eflect 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 sew- 
 ing up the eyelids of the wild hog-deer, the s])otted deer, and other wild 
 
 * It is astonishing with what rapiMity fowls (dorkings) increase when well fed, Itept in con- 
 fined cribs, and in a darkened room. Fed on a mixture of 4 lbs. of oatmeal, 1 lb. of suet, 
 and i lb. of sugar, with milk for drink five or six^imes 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 
 .OS. a week, under the same treatment 
 
610 
 
 VENTILATION AND CLKANMNKSS. 
 
 animals when netted in the jancjlc-;, with the view of taming and speedily 
 fattening them. The alisence of li<j;ht indeed, however ])rodiiced, seems 
 to soothe and quiet all animals, to dispose them to rest, to make less ftxrl 
 necessary, and to induce them to store up more of wliat they eat in the 
 form of fat and mus;ie. 
 
 An experiment m.ide hy Mr. Morton, on the feeding of slieep, shows 
 the effect at once of shelter, of (|uier, and of the absence of light upon 
 the (|nantiry of f>.)l eaten and of mutton produced from it. 
 
 Five sheep, of nearly ecpial weights, were fed each with a pound of 
 oats a-day and as miK-h turnips as tliey chose to eat. One was fed in 
 the open air, two in an ofien sheJ — one of l hem being conlined in a crib — 
 two more were fed in a close shed in the dark — antl one of these also was 
 confined in a crib, so as to lessen as mucli as possible the quantity of ex- 
 ercise it should take. The increase of live weight in each of the five, 
 and the quantity of turnips they respectively consumed, appear in the 
 following table : — 
 
 
 
 
 
 Increase 
 
 t.lVB WBISHT. 
 
 
 
 for eacll 
 
 
 
 Increase. 
 
 Turnips 
 eaten. 
 
 lOOlbs. of 
 turnips. 
 
 Nov. 13. 
 
 Mdrcli 9. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 108 
 
 131-7 
 
 23 7 
 
 1912 
 
 1-2 
 
 102 
 
 130-8 
 
 27-8 
 
 1394 
 
 2-0 
 
 108 
 
 i:?o-2 
 
 222 
 
 1238 
 
 1-8 
 
 101 
 
 1.3-24 
 
 28-4 
 
 886 
 
 31 
 
 111 
 
 131-3 
 
 20-3 
 
 886 
 
 2-4 
 
 Unsheltered 
 
 Ill open sheds .... 
 Do., but confined in cribs 
 In a close shed in the dark 
 Do., but confined in cribs 
 
 From this table it appears, as we should have expected — 
 
 a. That much less — 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 jjonnds 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 animal, in 
 fact, was fretful and restless in confinement, and whatever produces this 
 effect upon an animal prevents or retards its fattening. 
 
 d. That the most profitable return of mutton from the food consumed, 
 is when the anim-al is kept under shelter and in the dark. 
 
 Such a mode of keeping animals, however, must not be entered upon 
 hastily or without due consideration. The habits of the breed must be 
 taken into account, the effect of the confinement upon their health must 
 be frequently attended to, and, above all, the ready admission of fresh air 
 and a good ventilation must not be forgotten. By a neglect of tlie ])ro- 
 per precautions, unfortunate results have frequently been obtained and a 
 sound practice brought info disrepute. 
 
 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. 
 
EFFECT OF THE SOURING OF FOOD. 611 
 
 § 13. Influence of the form or slate in which the food is given on the 
 quantity required by an animal. 
 The state in which the food is giveu 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 econo- 
 mical. Arthur Young details several series of experiments on the fat- 
 tening of pigs, in which bean meat 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 quantity, the price obtained for the pork 
 v/as less than iliat which was paid for the meal. 
 
 Upon sour food, indeed, pigs arc universally observed to fatten best. 
 In Hulstein, 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 l)e owing the profitable use of sour whey in feeding this 
 kind of stock in cheese-making districts. 
 
 I have been told bv some cow-feeders who use brewers' grains, that 
 the dry cows, when "fattening oB', 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 recommended. 
 
 2°. The boiling or steaming of dry food, and even of potatoes and tur- 
 nips, is recommended by many as an economical practice. I beUeve 
 that the general result of tlie numerous experiments which have been 
 made upon this subject in various parts of tJie 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. [Stephens' Book of the Farm.] 
 
 3°. 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 nourishment of animals. Thus new oats are not con- 
 sidered 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 whicli 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 inio flower, add much less than before to tlie 
 weight of his fattening stock. 
 26* 
 
^ig INFIiUKNCE OF SOIL AND CULTURE ON THE 
 
 ^ 14. Influence of soil and culture on the nutritive value of agricultural 
 
 produce. 
 
 I have on several former occasions, (pages 500 to 528), direcled your 
 attention to the remarkable inlJuence which soil, culture, and climate 
 have upon the chemical composition of the diflerent corn and green crops 
 usually raised for food. Every such change of composition alters also 
 the nutritive value of any given crop. If the wheat or barley be richer 
 in gluten, it will build up more muscle — if it abound more in starch, a 
 smaller weight of it will supply ihe carbon of respiration — if it be richer 
 in fatty matter, it will round olfthe edges of tlie bones, and fill up the in- 
 equalities in an animal's body more ([uickly with fat. Such differences 
 as these I have already shown you do really exist aiTiong samples of the 
 same kind of grain grown upon soils either of different quality, or of the 
 same quality when ditFerently cultivated or manured. 
 
 But this different culture or manuring affects the relative proportions 
 of the several kinds of inorganic matter also — the phosphates and other 
 saline substances — which are known to exist necessarily in all vegetable 
 productions. In illustration of this, I would direct your attention to the 
 following analyses — made in my laboratory by Mr. Fromberg — of the 
 ash of two samples of the same kind of turnip (red topped yellow) 
 raised by Lord Blantyre, on the same field, the one with guano alone, 
 the other with farm-yard dung alone. The (juantity of ash left by the 
 two varieties of turnip was 0-66 and 0-7 per cent, respectively, and thi:* 
 ash was com posed as follows : — 
 
 Composition of the ash, of turnips raised with guano, and with farm-yard dung. 
 
 Chloride of Potassium . 
 Sulphate of Potash . , 
 Carbonate of Potash . . 
 Phosphate of Potash . . 
 
 Lime . , 
 
 Magnesia . 
 
 Alumina . 
 
 Carbonate of Lime . . 
 
 Alumina 
 
 Oxide of Manganese . . 
 Silica 
 
 OUANO. 
 
 1 
 
 DCTNO. 
 
 Interior. 
 
 Esterior. 
 
 Interior. 
 
 Exterior. 
 
 556 
 
 503 
 
 540 
 
 10-71 
 
 30H5 
 
 37 04 
 
 3120 
 
 35-47 
 
 11 -38 
 
 903 
 
 36 74 
 
 17-63 
 
 20 93 
 
 1017 
 
 551 
 
 3-65 
 
 4-55 
 
 • 449 
 
 1-58 
 
 202 
 
 034 
 
 1-62 
 
 2-63 
 
 313 
 
 4-87 
 
 9.94 
 
 0-92 
 
 2-76 
 
 9-52 
 
 973 
 
 1156 
 
 14-82 
 
 509 
 
 2-79 
 
 094 
 
 0-46 
 
 321 
 
 5 90 
 
 260 
 
 5.33 
 
 1 65 
 
 343 
 
 — 
 
 304 
 
 97-95 9910 9908 99-02 
 
 The most striking difference between the two varieties of ash is in the 
 proportion of phosphates they respectively contain. The ash of the 
 guano turnips contained from 25 to 30 per cent, of pliosphates, that of 
 the dung turnips only from 9 to 11 per cent. Tliis could not fail to 
 make an important difference in their relative values for the feeding of 
 stock whose bones are growing, and whicti require, therefore, a larger 
 sujiply of phospliates in their food. 
 
 The phosphates of lime and magnesia form, as we know, one of the 
 valuable constituents of guano, but we could scarcely have inferred that 
 this manure would have caused so much larger a proportion of these 
 phosphates to enter into the constituents of the turnips raised with tliem- 
 
NUTRITIVE VALUE OF AGRICULTURAL PRODUCE. 613 
 
 It is not unlikely that turnips, raised from bones, will also abound more 
 largely in plio.sphates than turnips raised from dung or rape dust, and 
 m?.y therefore be better fitted for growing stock. 
 
 § 15. Can we correctly estimate the relative feeding properties of different 
 kinds of produce under all circumstances. 
 
 Since the several nutritive effects of different kinds of food are de- 
 peudent upon so many circumstances — upon the state of the animal 
 itself — the purpose for which it is fed — the mode in which it is housed 
 and protected — the forin and period at which it is given^-can it be pos- 
 sible to classify them in an order which will indicate their relative feed- 
 ing values in all cases and for all purposes ? This is obviously impos- 
 sible. We may easily 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 shew in as many different tables the order of their relative 
 values in laying on fat — in mcreasing the muscles — or in promoting the 
 growth of bone ; but we cannot arrange theoretically, nor can experi- 
 ment ever practically classify, all our c(jmmon 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 
 attempred to do. Making their experinieiits in diflerent circumstances, 
 with different varieties of the same produce, upon different kinds of 
 stock, or upon animals fed for different purposes, they have obtained re- 
 sults of the most diversified kind, and have classified the several kinds of 
 fodder in the most unlike order. I se'ecl a few of these results 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 — according to the several authors whose names are 
 given. 
 
 Experimental quantities of fodder which must be used to produce an 
 equal nutritive effect, according to — 
 
 Schwertz. Block. Petri. Thacr. Pabst. Meyer. Middleton. 
 
 Meadow hay . . 
 
 10 
 
 10 
 
 10 
 
 10 
 
 10 
 
 10 
 
 10 
 
 Aftermath hay 
 
 11 
 
 — 
 
 10 
 
 — 
 
 — 
 
 — 
 
 __ 
 
 Clover hay . . . 
 
 10 
 
 10 
 
 9 
 
 9 
 
 10 
 
 — 
 
 
 
 Green clover in flow- 
 
 
 
 
 
 
 
 
 er and lucerne . 
 
 — 
 
 43 
 
 — 
 
 45 
 
 42 
 
 — 
 
 
 
 Lucerne hay . . 
 
 9 
 
 — 
 
 9 
 
 9 
 
 10 
 
 
 
 __ 
 
 Wheat straw . . 
 
 — 
 
 20 
 
 36 
 
 45 
 
 30 
 
 15 
 
 
 
 Bailey straw . . 
 
 40 
 
 19 
 
 18 
 
 40 
 
 20 
 
 15 
 
 _ 
 
 Oat straw . . . 
 
 40 
 
 20 
 
 20 
 
 40 
 
 20 
 
 15 
 
 _ 
 
 Pea straw . . . 
 
 — 
 
 16 
 
 20 
 
 13 
 
 15 
 
 15 
 
 
 
 Potatoes . . , 
 
 20 
 
 22 
 
 20 
 
 20 
 
 30 
 
 15 
 
 __ 
 
 Old potatoes . . 
 
 — 
 
 40 
 
 — 
 
 — 
 
 — 
 
 — 
 
 — 
 
 Carrots .... 
 
 27 
 
 37 
 
 25 
 
 30 
 
 25 
 
 23 
 
 34 
 
 Turnips .... 
 
 45 
 
 53 
 
 60 
 
 52 
 
 45 
 
 29 
 
 80 
 
 Wheat .... 
 
 4 
 
 3 
 
 5 
 
 6 
 
 
 
 
 
 — . 
 
 Barley .... 
 
 — 
 
 3 
 
 6 
 
 — 
 
 5 
 
 5 
 
 — 
 
 Oats 
 
 — 
 
 4 
 
 7 
 
 — 
 
 G 
 
 — 
 
 — 
 
 From an inspection of this table, we should naturally conclude eitner 
 
614 Theorktical >utritive valces. 
 
 that the clifTerent kinds of forltler vary very much in quality, or that those 
 who determined their relative values by experiment must have tried 
 their effects upon very ditierent kinds of stock, fed probably also for dif- 
 ferent purj)oses. Botli 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 tiiat dillierent samples of the same kind of 
 turnip arc so unlike each other that 29 lbs. of the one will go as far in 
 feeding the same animal a.s 80 lbs. of another. These great diirerences 
 in the table, therefore, seem to show that different kinds or varielies of 
 fodder have been used, or under ditferent 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 of 
 potatoes and 30 of carrots appear to be equal in nutritive value to 10 of 
 hay. It must be confessed, however, that this sul)ject of the cxpenmentaL 
 value of different kinds of farm produce in feeding stock of the same 
 kind for the same lytirposes 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 inquiry ? 
 
 2°. Theoretical values. — But the theoretical values of different kinds 
 of fooil in reference to a particular object, can be determined by analyti- 
 cal investigations made in the laboratory. This has been done in a 
 very able manner by Boussingault, in reference to the value of different 
 Tcinds 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 quantifies of different kinds of vegetable produce which will 
 "produce equal effects in the growth of muscle {Boussingault) . 
 
 Hay 10 
 
 Clover hay, cut in flower . . 8 
 
 Lucerne do 8 
 
 Aftermath do 8 
 
 Green clover, in flower ... ,34 
 
 Green lucerne 35 
 
 Wheat straw 52 
 
 Rye straw 61 
 
 Barley straw 52 
 
 Oat straw 55 
 
 Pea straw 6 
 
 Vetch straw 7 
 
 Potato leaves 36 
 
 Carrot leaves 13 
 
 Oak leaves 13 
 
 This table possesses much value. 
 
 Potatoes 28 
 
 Old potatoes 41 
 
 Carrots .35 
 
 Turnips 61 
 
 While cabbage 37 
 
 Vetches 2 
 
 Peas 3 
 
 Indian corn 6 
 
 Wheat 5 
 
 Rye 5 
 
 Barley 6 
 
 Oats 5 
 
 Bran 9 
 
 Oil-cake 2 
 
 It cannot, however, be relied upon 
 
 as a safe guide in all cases by the feeder, because of the differences in 
 the composition of our crops, which arise from the mode of culture and 
 the kind of manure employed. It ])ossesses, however, a higher 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 l>e adopted 
 as the order also of their relative values in sustaining animals and keep- 
 ing them in ordinary condition. The same remark, iiowever, will not 
 
EFFECT OF MODE OF FEEDING ON THE MANURE. 615 
 
 apply to animal food, since we may have a kind of animal food, such as 
 gelatine, which would greatly promote tlie growth of muscle, but whicli, 
 from its composition, is capable of ministering so little to the wants of 
 the odier parts of the body tliat it will not even support life for any length 
 of time. 
 
 § 16. 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 eciual importance with the production of milk or the fattening of 
 stock. What influence has the mode ol' feeding or the purpose for 
 which the animal is fed, upon the quantity and (luality of the manure 
 obtained ? 
 
 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 carbonic 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, with 
 the coldness 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 purjiose but to manufacture manure — by 
 giving them an unlimited supply of food, using means to persuade them 
 to eat it, and causing 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 al- 
 most entirely upon the kind of food given to an animal, and upon the 
 purpose tor which it is fed. 
 
 a. The full- grown animal, wliich 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. 472), 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 
 neailv the same quantities of botli or of their elements. 
 
 b. The case of the fattening animal again is ditTerent. 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 alfected by it. It will be httle 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 cpiantity of this additional 
 food which is given. Thus if oil-cake be given for the purpose of laying 
 on fat — the usual sustaining fcKxl at the same time being supplied — the 
 
616 WHY OLD PASTURES CONTINUE RICH. 
 
 dung will be enriched by all those other fertilizing 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 manure were it put 
 into the soil at once; it is not surprising, therefore, that after it lias 
 parted with a portion of its oil it should still add much to the richness of 
 common dung. 
 
 A knowledge of t!ie kind of material, so to speak, which the animal 
 requires to fatten it, explains in a considerable degree another 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 un- 
 necessary, if the produce be eaten off by stock — that the droppings of 
 the animals which are fed upon the land are alone sufficient 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 alreaily 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 are 
 indebted to, and carry off the land, little more than the fat in which 
 they are observed daily, to increase. 
 
 But as the materials of the fat inay be, and no doubt originally are, 
 derived wholly — perhaps indirectly, yet wholly — from the atmosphere, 
 the land is robbed of nothing in order to snpply it, and thus may con- 
 tinue for many generations to exhibit an equal degree 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 circwmaiances of the spot, or of the district in which such 
 rich old pastures exist. 
 
 c. The growing animal, again, does not return to the soil all it re- 
 ceives. 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, tlierefore, will not be so 
 rich as that of the full-grown animal fed ^^\^^>n the same kind and quan- 
 tity 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 further the f(X)d it eats. In the leau 
 
THE OROWINO AMMAL AIND THE MILK COW. 617 
 
 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 hus- 
 bandman in her dung. Tlie 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 u^ilk, but this bulk is 
 made up chiefly of the indigestible woody fibre and other comparatively 
 useless substances which her bulky food contains. The ingiedients 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 f(X)d they consume, than the well-known and remarkable dif- 
 ference in (|uality which exists between distillery dung, obtained from 
 fattening cattle fed upon the refuse of the distilleries, and cow-feeders' 
 dung, voided by milk cows fed upon nearly the same kind of food— 
 namely, the refuse of the breweries. 
 
 § 17. Summary of the views illustrated in the present Lecture. 
 
 The topics discussed in this Lecture are of so interesting a kind, and so 
 beautifully connected together, tiiat you will permit me, I am sure, 
 briefly to draw your attention again to the most important and leading 
 points. 
 
 1°. It appears that all vegetables contain ready formed — that is, 
 form during their growth from the food on which they live — those sub- 
 stances of which the parts of animals are composed. 
 
 2^. That from the vegetable food it eats, the animal draws directly 
 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 oz. — a cow or horse ti\'e times as much — of 
 carbon every 24 hours; and that the main office of the starch, gum, and 
 sugar of vegetable food is to supply this carbon. In carnivorous animals 
 it is supplic.l by the fat of tlieir food — in starving animals, by tlie fat of 
 their own bodies — and in young animals, which live upon milk, by the 
 niilk sugar it contains. 
 
 4°. That muscles, bone, skin, and hair undergo a certain necessary 
 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 substances in the (ijod of the full 
 grown animal, Is to replace the portions of the body which are thus re- 
 moved, and to sustain its original condition. Exercise Increases this na- 
 tural waste and accelerates the breathing also, so as to render necessary 
 
618 SUMMART OF THE VIEWS ILLUSTRATED. 
 
 a larger sustaining supply of food — a larger daily quantify to keep the 
 animal in condition. 
 
 5°. That the fat of the body is generally derived from the fat of the 
 vegetable food — wliich fat undergoes during digestion a change or trans- 
 formation by whicli it is converted into the peculiar kinds of fat whicli 
 are specially fitted to the body of the animal that eats it. In carnivor- 
 ous animals, the fiit 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, 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 pro- 
 portion of oil or fat. To the growing animal, on the other hand, it must 
 supply also an additional quantity of gluten fortlie muscles, and of phos- 
 phates for the bones. If to each of a number of animals, ecjual 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 con 
 vert 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 ex- 
 pended in the production of milk, and tiie 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— wliile they de- 
 pend 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 atlected by ilie 
 jjurpose for which the animal is fed. If it be full-grown and merelj'^ 
 kept in condition, the dung contains all that was present in the food, ex- 
 cept the carbon that has escaped from the lungs. If it be a growing 
 animal, then a portion of the phosjihates and gluten of the I'ood are re- 
 tained 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 comparatively 
 little in sustaining her own body, but exhausts all the food that passes 
 through her digestive organs, for the production of the milk whicli is to 
 feed her young. 
 
 The reverse takes place with the fattening 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 constituents 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 — tliey involve so many interesting considerations, both of a 
 
co>CLur)i>G sr.cTio.N. 619 
 
 theoretical and of a practical kind, that had my limits permitted I could 
 have wished to dwell upon them at still greater length. 
 
 § 18. Cu7tcluding Section. 
 
 T have now brought the subject of these Lectures to a close. I have 
 gone over the whole ground which in the outset 1 proposed to tread. It 
 is the first time, I believe, that much of it has been trodden 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 jjractical bearing or was likely to be suscepti- 
 ble hereafter of a practical apjilication. 
 
 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 tbod plants live — anil by what chemical ciianges the peculiar 
 organic compounds of which they consist are formed out of the organic 
 tood on which they live. 
 
 In the second Fart, I explained in a similar way the nature, composi- 
 tion, and origin of the inorganic portion of plants. I dwelt, also, upon 
 the nature, 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 fitted to throw upon the means of prac- 
 tically improving the soil. 
 
 In the third Part, I dwelt upon the various means which may te 
 adopted for increasing the general productiveness of the land — whether 
 these means be of a mechanical or chemical nature. The whole doc- 
 trine of manures was here discussed and many suggestions offered to 
 your notice, which have already led to interesting practical results. 
 
 In the fourth Part, 1 have explained the chemical composition of the 
 several kinds of vegetable produce which are usually raised for food— ^ 
 showed upon what constituents their nutritive values de])end — 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 ([ualities depend — and, lastly, the 
 way in which food acts upon and supports die animal body, and how the 
 value of the manures they make is dependent 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 consi- 
 deration, and I feel it to have been one of the greatest advantages which 
 have attended the periodical form in which these Lectures have been 
 brought before the public, tliat it has allowed me leisure to think, to in- 
 quire, and to make experiments in regard to points upon which it wa3 
 ditticult at first to throw any satisfactory light. It is gratifying to me to 
 know that the general diff'iision which these Lectures have obtained, has 
 already done some service to the agriculture of the country. 
 
APPENDIX: 
 
 CONTAINING 
 
 SUGGESTIONS FOR EXPERIMENTS IN PRACTICAL AGRI- 
 CULTURE, WITH RESULTS OF EXPERIMENTS 
 MADE IN 1841, 1842, AND 1843. 
 
APPENDIX. 
 
 No. I. 
 
 nr&OESTIOXS FOR EXPERIMENTS IN PRACTICAL AGRICVLTURH 
 DURING THE ENSUING SPRING AND SUMMER. 
 
 On'e of the most important objects which chemistiy is at present desirous of 
 attaining for the improvement of practical agriculture, is the discovery and ap- 
 plication of specific or special manures. 
 
 We know that certain substances, such as fold-yard manure, are capable of 
 fertilizing to a considerable extent almost any land, and of causing it to yield 
 a better return of almost any crop. But we know also that manures or fertili- 
 zers of nearly every kind are more efficacious on one soil than on another, and 
 that some answer better also for one species of crop than for another. The 
 case of gypsum will serve to illustrate both these positions. 
 
 The effects of gj'psum in the United States, in Prussia, and other parts of 
 Germany, and in some districts of England, arc said to be absolutely astonish- 
 ing ; while in many other parts of our Island, of Germany, and even of the 
 United Slates, the benefit derived from it has not repaid the trouble and expense 
 incurred in applying it. Gypsum, therefore, is especially adapted for use in cer- 
 .tain soils only. 
 
 Again, the remarkable effects of gypsum have been observed most distinctly 
 on clover* and certain kinds of grass. The same benefits have not followed, 
 to any thing like an equal extent, from its use on barley, oats, wheat, or other 
 kind of grain. Therefore, while specially adapted to certain soils, it is also 
 specially adapted to certain crops. It is a kind of specific manure for clover 
 and some of the grasses. 
 
 Now, neither of these subjects which it is so important to investigate, — 
 neither that of the manures which are especially fitted for each soil, nor of those 
 which are specially fitted for each crop,— can be determined either from theory 
 or from experiments devised and executed in the laboratory of a chemist. The 
 aid of the practical farmer, of many practical farmers, must be called in. Nu- 
 merous experiments, or trials, must be made in various localities, and by differ- 
 ent individuals, — all, however, according to the same rigorous and accurate 
 method, — in order that, from the comparison of many results, something like a 
 general principle may be deduced. 
 
 It is partly with a view to determine the mode of action of certain fertilizers, 
 and partly in the hope of obtaining some additional light on the subject of 
 manures specifically adapted to particular crops, that I venture to suggest to you 
 the propriety of making one or more of the following sets of experiments, 
 during the spring and summer of the present year. I could have much enlarged 
 
 ' In regard to its use in Germany, Lampaiilus says, — " It may with certainty, he stated, 
 th;it by the use of gypsum the produce of clover and the consequent amount of live stock 
 have boen increased at leaal one-third."— V>\ii Lehbe von den Mineralischen Dunojiit- 
 
 TKLN, p. 34. 
 
2 or GRASS AND CLOVER. [Appendix, 
 
 the list of suggestions, but I neither wish to fatigue your attention, nor to place 
 before you more work of the kind than can be readily accomplished, with liUk 
 expense of time, labour, or money. Another season will, I hope, afford us an 
 opportunity of interrogating nature by further, and perhaps more refined, modes 
 of experimenting. 
 
 1. OF GRASS AND CLOVER. 
 
 1°. It is beyond dispute, that on certain soils, gypsum causes a largely in- 
 creased gi-owth of grass and clover, but experiment alone appears capable of 
 determining on ^ckat soils it is likely to be thus beneficial, fcsuch experiments, 
 therefore, ought to be made on every farm, on a small scale at first, and at little 
 cost,* but made with care and accuracy, and with a minute attention to weights 
 and measures. 
 
 2°. The action of gypsum appears to be entirely cliemical, but the only ex- 
 planation of this action yet attempted is far from being satisfactory. It is desi- 
 rable therefore, that experiments with other substances should be made, wliich 
 are likely to throw light an the theory. Important practical results may at the 
 same time be obtained — they are sure, indeed, to tbllow from a right under- 
 standing of the theory. 
 
 In the neighbourhood of Lyons, it has been found that very dilute sulphuric 
 acid^ (oil of vitrol) exhibits the same beneficial effect upon clover, that has else- 
 where attended the use of gypsum. It is desirable, therefore, that a compara- 
 tive experiment should be made with this acid on a portioji of the same field to 
 which the gypsum is applied. Where the one fails the other may act. 
 
 3'^. It was observed by Dr. Home, of Edinburgh, so early as the year 175G, 
 that sulphate of soda; had a remarkable effect in promoting the growth of plants 
 — its action being nearly equal to that of saltpetre or nitrate of soda. This fact, 
 though mentioned by Lord Dundonald, has been lost sight of by practical men, 
 the sulphate of soda being generally represented as too high in price to be avail- 
 able as a fertilizer.! The use of saltpetre, however, and of nitrate of soda, both 
 of which are more than double the price of sulphate of soda, show that the cost 
 of this latter article should not stand in the way of an accurate trial of its value 
 as a fertilizer on various crops. Dry sulphate of soda can be readily obtained 
 from any of the alkali works on the Tyne,ll and being an article of domestic 
 manufacture, it is proper that its merits should be ascertained, and, if it can be 
 available, that its use should be encouraged. 
 
 From the circumstance of its containing sulphuric acid, therefore, I would 
 recommend that it should be tried on clover and grass, in comparison with 
 gypsum and sulphuric acid, and on a portion of the same field. It may suc- 
 ceed where the others fail. 
 
 4°. Nitrate of soda also, as a top-dressing on grass land, has been often used 
 with great benefit. I have seen grassland in Dumfriesshire, which, after being 
 long let for pasture at 39s. an acre, had been sprinkled with an annual top- 
 dressing of nitrate of soda at the rate of 20s. an acre, and had since readily let 
 at £4 an acre, yielding thus an annual profit of 39s. an acre to the landlord. 
 
 In other districts, again, it has been found to answer better for corn. Thus, 
 after a discussion on this subject in the Gloucester Farmers' Club, it was agreed, 
 that nitrate of soda "was a very valuable manure for white straw crops, but 
 
 ' The price of gypsum in London is about 23. 6d. per c\v!. ; in Newcastle, 3s. 
 
 1 Gypsum consists of sutp/iuric acid and li7ne. 
 
 1 Olauher sails — consisting of sulphuric acid and soda. 
 
 § Lord Dundonald says — " From experiments it has been proved to promote vegetation In 
 a very \n»\\ degree. The high price at present of this article precludes the use of it, but 
 could it be made and sold at a cheap rale, it would prove a mo.sit valuable acquisition to agri- 
 culture." Since the time of Lord Dundonald some trials made in Germany have shown il 
 to have a beneficial action on rye, potatoes, and fruit tree.s. 
 
 I Messrs. Allan & Co., of the Hewonh Alkali Works, deliver it in Newcastle and the neigh- 
 bouring towns, at 9s. or 10?. per cwl. 
 
JVa 7.] OP GRASS AND CLOVER. 3 
 
 when applied to green crops the beneiii was not sufficiently great to counter-bal- 
 ance the expense." In Northumberland, whore it has been tried in a skilful 
 manner by Mr. Gray, of Dilston, it was found to yield a most profitable return 
 on both hay and barley. 
 
 These results show the necessity of further trials, not only for the purpose of 
 illustrating the cause of the beneficial action of this saline substance, but also 
 with the view of arriving at some general rule by which the practical man may 
 be guided in determining on what fields, and for what crops on those fields, the 
 nitrate of soda may be beneficially applied 
 
 This experiment, like the others above-mentioned, will be much more valua- 
 ble, if made in such a way that the result can be compared with that obtained 
 by the use of other chemical agents. I would, therefore, propose that in the 
 same field of grass or clover, a portion should be measured off, to be top- 
 dressed with nitrate of soda, that tlius not only the absolute, but also the cam- 
 para/ive, weight of the produce may at the same time be ascertained. 
 
 5°. There are other trials also, from which this general subject is capable of 
 receiving illustration. The fertilizing power of gypsum has been explained by 
 its supposed action on the ammonia wliich is presumed to exist in the atmos- 
 phere. If this be the true explanation, a substance containing ammonia should 
 act at least as energetically. At all events, the action of fold-yard manure and 
 of putrid urine is supposed to depend chiefly on the ammonia they contain or 
 give off. Now, among the substances containing ammonia in large quantity, 
 which in most towns are allowed to run to waste, the ammoniacal liquor of 
 the gas works is one which can easily be obtained, and can be applied in a li- 
 quid state at very little cost. It must be previously diluted with water till its 
 taste and smell become scarcely perceptible. 
 
 I would propose, therefore, as a further e.Kperiraent, that along with one or 
 more of the substances above-mentioned, the ammoniacal liquor of the gas 
 works should be also tried, on a measured portion of ground, and, if possible, 
 in the same field. 
 
 0°. Soot, as a manure, is supposed to act partly, if not chiefly, in conse- 
 quence of the ammonia it contains. In Gloucestershire it is applied to pota- 
 toes and to wheat, chiefly to the latter, and with great success. In the Wolds 
 of Yorkshire it is also applied largely to the wheat crop, at the rate of about 24 
 bushels to the acre.* In this county it is frequently used on grass land, to the 
 amount of 20 bushels an acre, and though 1 am not aware that it is extensively 
 employed upon clover, I am inclined to anticipate that the sulphur it contains, t 
 in addition to the ammonia, would render it useful to this plant. At all events, 
 comparative experiments in the same field with the gypsum and the ammonia- 
 cal liquor, are likely to lead to interesting results. 
 
 7^. Common salt, highly recommended as a manure by some, has been as 
 much depreciated by others, and hence, when directly applied, is considered as 
 a doubtful fertilizer by ahiiost all. The obscurity in regard to its use^ however, 
 rests chiefly on the quantity which ought to be employed. The result of com- 
 parative experiments made in Germany, showed that a yery few pounds per 
 acre were sufficient to produce a largely increased return of grass — while in 
 England it has been beneficially applied within the wide limits of from five to 
 twenty bushels per acre, and, when used for cleaning the land for autumn, of 
 thirty bushels an acre. 
 
 Among the comparative experiments upon grass and clover here suggested, 
 the effect of salt might also be tried with the prospect of practical benefit. It 
 would give an additional interest to the experiments and supply an additional 
 term of comparison. 
 
 ' The price is from 6tl. to Is. a bushel. In this county the soot is said to be often of an 
 inferior quality, and brings therefore a less price. 
 
 t The gypsum. I might also say, for much of our soot contain.s gypsum, the lime being 
 derived chiefly from the sides of the flue. 
 
OF GRASS AND CLOVER. 
 
 [Appendix, 
 
 The entire series of experiments, therefore, which I would recommend, would 
 occupy eight patches on a clover or grass field, one of which would be left un- 
 dressed for the purpose of comparison. Thus, each plot being half an acre- 
 
 Gypsum. 
 
 Suljiliate of 
 Soda. 
 
 Ammoniacal , 
 Liquor. 1 
 
 Sulphuric 
 Aciit. 
 
 Nifrafe of 
 Soda. 
 
 ^°S^1I?°" ^°°^ 
 
 The ammoniacal liquor and the soot are placed as far as possible from the 
 
 fypsuin and sulphuric acid, that they may not interfere with each other's action, 
 n a large field they might be placed still farther apart, and otiier trials might be 
 made in one or two of the vacant places. 
 
 The appearance of each patch should be entered, with the date, in an experi- 
 ment book, at weekly intervals, and the final produce both of hay and of after- 
 math carefully noted, both as to vxight and <pialilij. 
 
 Nor will the experiment be completed when the crop for the year is gathered 
 in ; but, where it is possible, two further points should be ascertained, — 
 
 1°. The relative feeding or nourishing properties of the produce. To tliose 
 who rear and fatten cattle, this is a matter of great importance, and it is one 
 which they could easily determine, at least very approximately. 
 
 2^. What has been the permanent effect of the several substances on the soil, 
 as indicated by the comparative quantity and quality of the crop obtained from 
 each half acre, on the surxcedlng or during the tii^o following years. The result of 
 these further observations may materially modify the conclusion we should draw 
 from the comparative weight and quality of the produce of the first year. 
 
 I shall only observe, in conclusion, on this head, that the result of a simulta- 
 neous trial of all these substances in the same field would not only throw much 
 light on the specific action of each on the grass or clover in general, but would 
 be of permanent utility to that farm or locality in which the experiments were 
 made. It would indicate the kind of fertilizer which was best adapted to the 
 farm or neighbourhood, in the existing condition of its general culture. It would 
 form a local record, useful not only to the tenant who made the experiment (if 
 well made) and by whom the farm at the time was tenanted, but more useful 
 by far, and more permanently so, to the owner of the land, whose interest in it 
 is supposed to be not only greater, but much more lasting. 
 
 In regard to the quantities of the several substances above-mentioned, which 
 are to be applied to eacli acre, they may probably be varied according to cir- 
 cumstances, but the following may be i-ecommended in the comparative experi- 
 ments: 
 
 1°. Gypsum 2 to 3 cwt. per acre. 
 
 2°. Sulphate of Soda 1 cwt. per acre. 
 
 3°. Nitrate of Soda 1 cwt. per acre. 
 
 4°. Soot 20 bushels per acre — this in different districts may be varied accord- 
 ing to the known quality of the soot. 
 
 5°. Of Sulplmric Acid from 30 to 40 lbs. per acre, applied at three or four 
 several intervals — and diluted with at least 200 times its weight of water. Or 
 so much water may be added as to make it perfectly tasteless, or so weak as 
 not sensibly to injure the texture of a plant left in it during the previous night.* 
 
 6°. Of Ammoniacal Liquor 100 to 200 gallons per acre, according to its 
 strength, for this is constantly vaiying. It must also be diluted with so large a 
 quantity of water as will render it periecily tasteless, and is likely to prove most 
 beneficial if laid on at several successive periods. 
 
 ' The rjuanlily above Dienlioiicd amounts to about two sa'.ion.s of the acid of the shops, and 
 it should be dihited wiih three or four hundred gallons of water. 
 
No. I.] OF WHEAT, BARLEY, AND OATS. 5 
 
 7°. Of common salt it will be safer to apply not more than four to six bushels 
 an acre; though, where time and circumstances permit, comparative trials might 
 also be made on the efficacy of salt when applied in different proportions, to the 
 su/iu: land on which the otlier experiments are made. 
 
 As to the lime wlien these several dressings ought to be applied, some varia- 
 tion may be made according to the state of the young crop. They need not, in 
 general, be used before the lOlh of April, and they should rai-ely be later 
 than the middle of JMay. 
 
 It will be desirable that in the detail of every set of experiments, the kind and 
 quality of the soil (and subsoil) should be staled — with its drainage and expo- 
 sure — and the kind of grass or clover which had been sown upon it. 
 
 II. OP WHEAT, BARI-EY, .4ND OATS. 
 
 It is known that saltpetre and nitrate of soda produce highly beneficial effects 
 on all these varieties of grain. There remains much to be done, however, be- 
 fore the principle of their operation, or the circumstances on which their most 
 useful application dei)ends, can be clearly understood. Their relative effects on 
 the same kind of gram must be made the subject of more frequent, more precise, 
 and more carefully conducted experimenis — and these effects must be compared, 
 with those of other fertilizing substances, in order that we may arrive ultimate- 
 ly at some comparative estimate of the practical value of each, in increasing the 
 growth and produce of those crops which are the staples of animal food. 
 
 A.—OfWhfiat. 
 
 It is confidendy stated by some, as a general rule, that saltpetre is more ad- 
 vantageous than nitrate of soda, when applied to wheat. On the other hand, it 
 is beyond question that the application of nitrate of soda to wheat has been 
 found productive of remarkable benefit. 
 
 Is saltpetre eapecuiVij adapted for wheat oi all varielie^, on (dl soils, and under 
 every vaneti/ of manngcment, and is nitrate of soda, in like manner, especially 
 fitted for barley and oats 1 
 
 These are questions to which the experiments hitherto made do not enable us 
 to give a reply. New data must be obtained before we can have the means of 
 reasoninii usefully in regard to any of them. I would propose, therefore, — 
 
 1°. That v.here two varieties of wheat are sown on the same field, or on dif- 
 ferent fields of precisely the same kind of land and in the same condition, that 
 two half acres of each variefy should be measm'ed off, and that one half acre of 
 each should be dressed *vith saltpetre, and the other with nitrate of soda, at the 
 rate of 1 cwt. per .t: re. If three varieties could be so treated, the experiment 
 would be the more valuable. 
 
 It would thus be determined how far the effect of each of these nitrates was 
 dependent upon the vancti/ of wheat sown — and wliat was the relative action of 
 each nitrate upon any of the varieties. 
 
 2^. Ihat when the same varieties of wheat are sown upon two or more dif- 
 ferent soils — in different parts ofa farm — that one portion of the wheat on every 
 different soil should be dressed with nitrate of soda, and another with nitrate ot 
 potash (saltpetre). By this experiment, it would be shown how far the effect 
 of these substances is dependenton the nature of the soil, arid how farthe action 
 of the one, compared with that ot the other, is modified by diversity of soil. 
 
 In these different experiments, the management is presumed to be the same. 
 If the experiments be repeated by several persons in different parts of the cnun- 
 tiy, the effects of difference of management will, in a great measure, be shown 
 in the diversity of the results. 
 
 3^. With the view of ascertaining the comparative effect of the f^ulphate of 
 soda on this crop, I would .^suggest that in each case above specified, an equal 
 ai-ea should be set aside to be dressed with this salt, in the proportion of 1 cwt. 
 per acre. 
 
 Of each variety of wheat, therefore, and on each variety of soil, four patches 
 
6 
 
 OF WHEAT, BARLEY, AND OATS. 
 
 [Appendix, 
 
 Nitrate of 
 Soda. 
 
 Saltpetre. 
 
 1 
 
 
 Sulphate of 
 fc>oda. 
 
 of equal area, say half an acre, should be measured off — one of which should be 
 undressed for the purpose of comparison : thus — 
 
 As before, the nature of the soil and the kind of 
 grain must be recorded — the appearance of each patch 
 noted week by week — with the time of ripening and 
 reaping — and the respective qualities and weiglits of 
 the grain and straw collected from each half acre. 
 
 The quantity of gluten contained in the wheat 
 should also be determined, or a sarnple of the flour 
 transmitted for tlie purpose to the writer of these sug- 
 gestions, accompanied by a detail of the experiments they are intended to 
 illustrate. 
 
 B. — Of Barley and Oats. 
 To barley and oats the above remarks all apply, with this difference, that to 
 these crops saltpetre is .said to be less beneficial than the nitrate of soda. In 
 connection with these crops, however, I would make the following additional 
 observation. 
 
 According to any theory of the action of the nitrates of potash and soda 
 which readily presents itself, their effect on any crop which they are equally 
 capable of benefitting ought to be nearly equal, weight for weight. The nitrate 
 of soda ought to have a decidedly rr.ove powerful action, were it not that the 
 state of moisture in which it is generally sold, increases its weight so much as 
 in a great measure to deprive it, in equal weights, of this superiority. 
 
 But while 1 cwt. of salt})etre (nitrate of potash) is recommended as a suffi- 
 cient dressing for an acre, IJ to IJ cwt. of nitrate of soda is recommended for 
 an equal area It would, therefore, be desirable where nitrate of soda is applied 
 to any large extent of land, either with oats or barley, to make a comparative 
 trial on three equal portions of the same field, with 1, U, and IJ cwt. per acre, 
 respectively. 
 
 In addition, therefore, to the experiments suggested in regard to wheat, with 
 the view of determining — 
 
 1°. The absolute and relative efficacy of saltpetre and nitrate of soda on dif- 
 ferent varieties of the grain ; 
 
 2°. The same on different varieties of soil ; 
 
 3°. And under dirersities of management, — as in llie previous treatment of 
 the land, &:c. ; 
 
 There may be added, in regard to oats and barley, another series of trial to 
 determine — 
 
 4°. The relative effects of the different proportions of the nitrate of soda, 
 which is at present supposed to be specially beneficial to these kinds of gi-ain. 
 If any one be desirous of uniting this latter series with the fonuer, it may be 
 done thus — 
 
 The vacant half-acre being as before left 
 for the purpose of comparison. Such an 
 entire series might be made at the same 
 time on a field of Tartary and of potatoe 
 oats, and on two or more varieties of bar- 
 ley. 
 
 These top-dressings may all be sown 
 broad-cast — on the wheat most convenient- 
 ly when the seeds are sown in April or May, and on the barley and oats when 
 the fields have become distinctly green. 
 
 I may be permitted to add, as inducements to practical men, to try one or 
 more of these experiments in the accurate manner above described: 
 
 1°. That the result will be directly available and of immediate practical value 
 on his own farm, to the person by whom they are carefully made. That they 
 
 Sulphate of 
 isoda. 
 
 Nitrate of 
 
 Soda, 1 cwt. 
 
 per acre. 
 
 Saltpetre. 
 
 Nitrate of 
 Soda, 
 l\ cwt. 
 
 
 Nitrate of 
 Soda, 
 IJ cwt. 
 
No. I.] OF TCRVIPS. 7 
 
 will be permanently useful to his landlord (if carefully recorded), ought to be 
 an inducement to the latter to give every facility and encouragement to his ten- 
 ant in making theai. 
 
 2'. 'I'hat, mst< ad of involving expense and outlay, which in many instances 
 may ill be spared, t/uy arc sum in aLiwst every case to do inorc than repay the cost 
 of nialnng ihcrn, by the increased quantity or value of the produce obtained. 
 Any of the series of experiments, on the scale suggested, may be made for five 
 pounds, so that were the outlay all to be lost, the accurate kno\vledL;e obtained 
 in reference to the general tillage of his land, would be worth more money to 
 the holder of a farm of a iuindred acres. 
 
 3^. 1 need scarcely add, as a further inducement, the additional interest which 
 such experiments give to the practice of fiirming — and the means they afford 
 of calling forth die intelligence of the agricultural population. The moment a 
 man begins to make experiments under the guidance of an understood principle, 
 from tliat moment he begins to think. 'I'o obtain materials tor thought he wilt 
 have recourse to books — and thus every new experiment he makes, will further 
 stimulate and awaken his intellect, and lead him to the acquisition of further 
 knowledge. Does it require anything more than this general awakening of the 
 minds of the agricultural class, to advance the science of agriculture as surely 
 and as rapidly as any of the other sciences, the practical application of which 
 have led to those extraordinary developments of natural resources which are 
 the characteristic and the pride of our time ] 
 
 in. OF TJRNIPS. 
 
 The raising of turnips is of such vast importanee in the prevailing system 
 of husbandry', that any improvement in the mode of culture must be of exten- 
 sive and immediate benefit. Experiments so numerous and so varied have been 
 made with this view, that it may almost seem superflu.ius in me now to make 
 any further suggestions on the subject. But wlien experiments have been 
 made with a view to one subject only, it often happens in ail departments ol' na- 
 tural science, that as new views are advanced or more precise methods pointed 
 out, it becomes nc;essary to repeat all our former experiments, — either lor the 
 purpose of testing the results they gave us, or of observing new phenomena to 
 which our attention had not previously been directed. 
 
 I. Num'jrous experiments, for ex.'imple, have been made upon the use of bones 
 in the raising of turnips, but they have been chieftj'^ directed lo economical ends 
 and so far with the most satisfactory results. But among fifty intelligent and 
 thinking jiractical men, and who all agree in regard to die profit to be derived 
 from the use of bones with the turnip crop, hov/ many will agree in regard to 
 the mode in which they act — how few will be able to give a satistactory reason 
 for the opinion they entertain! The same is true of theoretical cheiuists, some 
 attributing their effect more especially to the earthy matter, others to the gelatine 
 they contain. Dry bones contain about two-thiids of their Vv'eight of eartliy- 
 matter, the other third consisting chiedy of animal matter resembling glue. Of 
 the earthy matter five-sixths consist of phosphate of lime and magnesia, and 
 the rest chiefly of carbonate of lime. Thus a ton of bone dust will contain — 
 
 Animal matter 74i) lbs. 
 
 Phospate of lime, &c 124,'5 
 
 Carbonate of lime, &c 219 
 
 2240 
 
 On which of these constituents does the efiicacy of bones chiefly depend 1 
 Does it depend upon the animal matter 1 This opinion is in accordance with the 
 follovving facts : — 
 
 1°. That in the Doncaster report it is said to be most effectual on calcareous 
 soils, — for in the presence of lime all organic matter more rapidly decomposes. 
 
B OF TURNIPS. [Api^ndix- 
 
 2°. That horn shavings are a more powerful manure than bones, — since 
 horn contains only one or two per cent, of earthy matter.* 
 
 3°. That before tlie introduction of cruslied bones, the ashes of burned bones 
 had been long employed to a small extent in agriculture, but have since fallen 
 almost entirely into disuse. 
 
 4°. I'hat old sheep skins cut up and laid in the drills, have been found to 
 yield as good a crop of turnips and after-crop of corn, as the remainder of the 
 field wliich was manured with bones. 
 
 5°. That "4U lbs. of bone dust are sufficient to supply three crops of wheat, 
 clover, potatoes, turnips, iLc , with phosphates, "t while one to two-thirds of a 
 ton of bones, containing from 400 to 800 lbs. of phosphates, is the quantity usU' 
 ally applied to the land. 
 
 Un the other hand, the quantity of animal matter present in a ton of bones 
 (74t) lbs ) is so small, and its decomposition so rapid during the growth of the 
 turnips — while at the same time the effects of the bones are so lasting and so 
 beneficial to the afier-crop of corn — that many persons hesitate in considering 
 the great excess of phosphates applied to the land, as really without any share 
 of induence in tlie production of the crops. 
 
 Thus Sprengel, an avrthority of the very highest character, both in theoretical 
 and practical agriculture, is persuaded that the phosjihates are the sole fertilizing 
 ingredients in bones, and he explains the want of success from the use of crush- 
 ed bones in Mechltnburg and North Germany, on the supposition that the 
 soils in those countries already contain a sufficient supply of phosphates, while 
 in England generally they are deficient in these compounds. 
 
 P'urther, if the animal matter be the fertilizing agent in bones, why are not 
 they of equal efficacy on grass land as upon turnips 1 
 
 With the view, therefore, of leading to some rational explanation of the rela- 
 tive effects of the several constituents of bones, it would be dc-sirable to institute 
 comparative experiments of the following kind — 
 
 1°. With half a ton of bones per acre. 
 
 2°. "With three or four ewl. of horn shavings or ghic per acre. 
 
 3°. With two cwt. of burned bones per acre. 
 
 4°. With six or seven cwt. of burned bot\es per acre. 
 
 The quantity of burned bones in No. 4 is that which is yielded by a ton of 
 fresh bones; that in No. 3 is upwards of five times what should be taken up by 
 the crops — as great part of what is added must be supposed to remain in the 
 soil, while sarne must be dissolved anil carried off by tke rui-ns. 
 
 The result of such experiments as these, if made accurately on different soils, 
 will lead us sooner to the truth than whole volumes of theoretical discussion. 
 
 II. .Nitrate of soda has also bpen applied with great benefit in the culture of 
 turnips. Some experiments, exceedingly favourable in an economical point of 
 view, have been made by JVlr. Barclny, of Eastwick Park, Surrey,! who found 
 that one cwt. per acre, drilled in with the seed, gave as great a return of Swedes 
 as 1.5 bushels of bones with 15 of wood ashes per acre, and when the nitrate of 
 soda was sown broadcast, from 20 to 25 per cent. more. In every pan of the 
 country, therefore, this substance ought to be tried. And as this nitrate is very 
 soluble in water, and may therefore be n^adily carried off by the rain, and as 
 that only which is within reach of the plant is of any avail, I would suggest 
 that not more tlian one-fourth of the whole should be drilled in with the seed, 
 for the purpose of hrivgivg axcaif the plant ; and that after thu tliinning by the 
 hoe, the rest should be strewed along the rows by the hand or by the drill. In 
 
 * This, I bplieve, is ralber a mnltcr of opinion timn tlie result of a siifScient number of ac- 
 tual trials. Some trials mafle hy Mr. Hawilen (British IlusbamJry, I. p. 3SG) gave results 
 very unfavouiahle to born shaviti^s. 
 
 t Liebig^ p 84. Tlio acre liere spoken of is the Hessian, about three fifths of the English 
 acre. The English, therefore, will require 66 lbs. 
 
 I Journal of the English .\gricultural Society, I. p. 428. 
 
^■o. I.] 
 
 or TURNIPS. 
 
 this way the \Yhole energy of the salt being expended where it is required, the 
 greatest possible effect will be produced. 
 
 III. I liave already stated the reasons which lead me to anticipate highly be- 
 neficial effects to vegetation from the use of sulphate of soda ; I would suggest, 
 therefore, a trial of this salt on the turnips also, at the same rate of 1 cwt. per 
 acre, and applied in the way above recommended for the nitrate of soda. Of 
 course ths intelligent farmer will vaiy the proportions and mode of application 
 of tiiese substances, as his leisure or convenience permit, or as his better judg- 
 ment may suggest to him. 
 
 The entire series of experiments on turnips, above suggested, may be repre- 
 sented as follows, adding two plots for different proportions of the nitrate and 
 sulphate of soda : — 
 
 Burned Bones, 
 2 cwt. per acre. 
 
 Nitrate of Soda, 
 li cwt. per acre. 
 
 Bone Dust, or 
 
 Crushed Bones, 
 
 1 ton per acre. 
 
 Burned Bones, 
 
 6 or 7 cwl. per 
 
 acre. 
 
 Sulphate of 
 
 Soda, 
 
 1 cwt. per acre. 
 
 Horn Shavin;is, 
 or Glue, 7 or 8 
 cwt. per acre. 
 
 Uninanured. 
 
 Siil()hate of 
 
 Soda. 
 
 IJ cwt. per acre. 
 
 Nitrate of 
 
 Soda, 
 
 J cwt. per acre. 
 
 Some of these experiments most of you may easily try. Those with the 
 burned bones and horn shavings, which in this parL of the country are less easy 
 to be obtained, it is not to be expected that many of you will think of imdertak- 
 ing. I hope, however, that they will not be lost sight of by those who possess fa- 
 cilities for obtaining them in sufficient quantity to make a satisfactory experiment. 
 
 In many parts of the United States, gypsum is the universal fertilizer for 
 every crop, and among the rest it is said to benefit turnips. The same opinion 
 is entertained in Germany. I am not aware how far, in what way, or with 
 what results, it has been applied to the turnip crop in this country. A simple 
 mode of testing its efficacy, however, would be to strew it over the plants when 
 in the rough leaf, on part of a field, the whole of which had been already ma- 
 nured in the ordinary way with fold-yard manure. The difference of produce 
 would thus show its efficacy, in the given circumstances; and the experiment 
 could be made effectually at the cost of a single cwt. of gypsum. 
 
 I have not included rape du.sl among the trials above suggested, though it is 
 undoubtedly, under certain modes of management, a beneficial manure both to 
 com and turnip crops. There is also a diversity of opiniiMi as to the cause of 
 its fertilizing action, as well as a manifest difference in the effect of different 
 sainfiles of the dust on the same soil. Though, therefore, certain experiments 
 whicli I may on a future occasion suggest, would undoubtedly throw light on 
 the cause of the good qualities of this manure, yet as its action (taking different 
 samples) is not rons'anl on the same soil, results obtained with it cannot pos- 
 sess the same importance, either theoretical or practical, as those which are ob- 
 served to follow from the use of bones and of saline substances, the composi- 
 tion of which is iiearly invariable. 
 
 Many farmers, however, are in the habit of constantly using rape dust. If 
 any of these could conveniently make experiments on theeffecrof differentsam- 
 ples of the cake, from different kinds of seed, and from different oil mills, and 
 would accurately note the results, they would perform an important ser\'ice in 
 preparing the way for that clear explanation of the cause of its fertilizing action, 
 which is at present wanted,* and which experiment alone can discover to us. 
 
 ■ Its snod effects are generally attributed to the oil which is Ipft in the seed, and its vary- 
 ine action to the different quantities of oil left in it by different crushers. I doubt, however, 
 if the oil ought to be considered as more than a secondary cause of its beneficial action. 
 
10 OF POTATOES. [Aj^mdix, 
 
 IV. OF POTATOES. 
 
 1°. Nilrate of so:5a has been applied widi great benefit to potatoes also. Af- 
 ter the potatoes have been harrowed down and (hand) hoed, and the plants are 
 four to six inches above the ground, it is applied by the hand round the stem 
 of the plants, and the earth then set up by the plough. Mr. Tunibull, in Dum- 
 bartonshire, last year used it in this way at the rate of li to 2 cwt. per ycotch 
 acre, (1^ English acres.) and the produce exceeded that of the land to which no 
 nitrate was applied, by 20 Scotch bolls to the Scotch acre. 
 
 2°. Applied in the same way there is c^eiy reason to believe that tlie sul- 
 phate of soda would have a highly beneficial effect also I repeat my recom- 
 mendation that this substance should be fairly tried with eveiy crop, because it 
 is a product of our own manufactories, which can be supplied m uidimited 
 quantity, and without the chance of any material increase of cost: wliile the 
 nitrate of soda is already in the hands of speculators, and within a short periocj 
 lias risen in the market to the extent of nearly one-third of its tbrmer price. 
 
 In plasUring their potatoes, the Americans generally put in a spoonful of 
 gypsum with every cutting — a similar method, if preferred, might be adopted 
 wiih the nitrate and sulphate of soda, though tiie chance of loss by percolation 
 through the soil, would, by this method, be in some degree increased. In Flan- 
 ders, wood ashes and rape dust are frequently thrown in by the hand, when each 
 cutting is introduced. 
 
 3°. 1 shall have occasion hereafter to recommend to the attejition of the prac- 
 tical farmer, many waste materials of various kinds, thrown out from our manu- 
 factories, the application of which to useful purposes would be a great national 
 benefit. In reference to the culture of potatoes, I will here bring under yonr no- 
 tice the chloride of calcium, which is said to have been beneficially applied to 
 various crops, but to jxitatoes especially, with surprising effect. Under the in- 
 fluence of this substance the sunflower and maize have grown to the height of 
 14 to IS feet, and potatoes have attained the weight of 2 to 3 lbs.* In Germany, 
 Sprengel also found it useful to potatoes. — (C/tcmic fUr Landwirlhe, I. p.G'Sb.) 
 
 Thousands of tons of chloride of calcium may eveiy year be prepared from tjie 
 waste materials which flow into the river Tyne, from the alkali works upon its 
 banks. Thousands of gallons of the solution of this substance j'early run of! 
 from the works of Messrs. Allan & Co at Heworth, and might be procured for 
 little more than the expense of collecting. It is also contained largely, though 
 mixed with other substances, in the mother liquor of die salt pans; and from the 
 numerous salt works on the coast might readily be obtained for trial. When 
 prepared in the dry state, this substance rapidly deliquesces and runs into a liquid. 
 The most convenient way of ap]ilyiiig il, therefore, would be in the state of so- 
 lution — so largely diluted as to have only a slight taste — and by means of a wa- 
 tering cart so contrived as to allow it to flow on the tops of the ridges and young 
 plants, by which unnecessary waste would be prevented. 
 
 Without knowing the strength of the solution likely to be olitained from the 
 works, it is impossible to give any idea of the quantity of the chloride of calcium 
 which ought to be employed; but .'iOO gallons jier acre may safely be used, if 
 the solution be so far diluted as to have only a decided taste of the substance. 
 
 The experiments here suggested, therefore, require four patches, as follows: — 
 
 ; j T These experiments are supposed to be made in ground 
 
 Sulphate of already prepared for the potaloe crop, by the usual quan- 
 
 r^oda, Itoljij tity of manure. I think it not unlikely, however, that 
 
 cwt. pracre. | ]jy pi^,„tin^. jijg potaloe in the midst of nitrate or sul- 
 
 I pliate (sprinkled over with diy soil) at the rale of A cwt. 
 
 Manure \ per acre, and afterwards applying I cwt. per acre, when 
 
 only- i the plants are hoed, a crop might be olnained without 
 
 the use of manure. Of course, such an fxjieriment as 
 
 Nitrate of 
 ;So(la, Itol,'^ 
 jcwt. pr acre. 
 
 Chloritle of 
 Calcium, ijOO 
 gals, pr acre 
 
 * The Rohan, a French variety of potafoe lately intrndiiced info the United States — by the 
 ordinary mode of culture— yields lubers, very many of which weigh 3 lbs. and many attain to 
 
Xo. /.] or MIXED MANURES. H 
 
 this, though important to be made, should be tried cautiously, and on such a 
 scale as to secure the experimenter fiom any serious loss. 
 
 In the above suggestions I liave introduced nothing in regard to mixed ma- 
 nures — though where plants require for the supply of all their wants nine or 
 ten different ingredients, of which the soil they grow in can perhaps yield in 
 sufficient quantity only three or four, it is obvious that the very best conse- 
 quences may follow from the employment of mixed manures. To this class 
 belong common night-soil, urine, animalised carbon, pOTia'/t/fc (night-soil mixed 
 with lime and gypsum), the -powlre vgetaiif (a mixture of soot and saltpetre), 
 die urate (now manufactured in London), and many otliers. 
 
 The mode of preparing, and tiic special uses of these and other mixed ma- 
 nures, will be explained in the third part of these lectures, which will be devoted 
 to the consideration of the nature and uses, and to the theory of the action of 
 natural and artificial fertilizers. In the mean time it is desirable, in the first 
 place, to obtain results from which the special action of each, when used almie, 
 can be fairly deduced. 
 
 That these experiments may have their full value, it is indispensable that a 
 measured portion of each field should be left without manure or dressing of any 
 kind, in order that a true idea may be formed of the exact effect of each sub- 
 stance employed. Experiments are valuable to the practical man if they mere- 
 ly show the superiority of one species of manure over anotlier, but they are in- 
 sufficient to show how much each of them tt'nds to increase the produce — or to 
 enable us to arrive at a satisfacttny explanation of tlie mode in which they 
 severally act in promoting vegetation. 
 
 Among other important experiments lately published, to which the above ob- 
 servation is applicable, may be mentioned those of Mr. T. Waite of Doncaster. 
 The effects of nitrate of soda on his land were veiy striking, showing a remarkable 
 increase of produce over bone dust, rape-dust, or rotten fold-yard manure — but 
 he does not seem to have deteniiined the produce of the same land during the 
 same season and vi/fiout jnannre. We have, therefore, no term of comparison, 
 by means of which we can ascertain the absolute or even tlie exact comparative 
 effect of the different substances employed. 
 
 It has been well observed by Sir [Humphry Davy, "that nothing is more 
 wanting in agriculture than experiments in which all the drcuniSian.es are mi- 
 nutely and scientifically detailed, and that this art will advance in proportion as 
 it becomes exact in its methods."* The above suggestions are submitted to 
 practical men in the hope that they may assist in introducing such exact meth- 
 ods into our agricultural operations, and at the same time promote the theoreti- 
 cal advancement of the most important art of life. 
 
 Exact methods lead to theoretical discoveries, while these are no less certain- 
 ly followed by important practical improvements. 
 
 No. II. 
 
 {See Lecture II., p. 37.) 
 
 In illustration of the effect of sudden alternations of temperature on vegetable 
 substances, explained in a note subjoined to page 37, I quote with pleasure the 
 
 the weigtit of 51bs. When perfectly ripe, it issaiil to be an excellent table polatoe, and to be 
 best in the spring. — Albany Cultivator, for March, 1841. 
 * Agricultural Chemistry, Lecture I. 
 
12 ON SUDDEN ALTERNATIONS OF TEMPERATURE. [AppendLt, 
 
 following instructive letter from an ably conducted monthly journal published 
 at Albany, in tlie State of JNcu'-Yoik, under the title of the Cultivatur. It is 
 extracted from the Number for March last : — 
 
 " In regard to Irish potatoes, a still thinner coverins; of earth than the one 
 just mentioned suffices with us to preserve them from rottins:- Indeed, it would 
 seem as if they could freeze and thaw several times, during winter, without 
 being destroyed, provided they f.re covered with earth all the lime ; for we often 
 find them near the surface and perfectly sound, in the spring, when spading up 
 the g^-ound in which the crop had grown during the previous season. There 
 they must have undergone freezing and thawing wlienever the earth was in 
 either state, as it often is to a much greater depth than the potatoe roots ever 
 extend. Why should those roots always be destroyed when they freeze above 
 ground, and not suffer equally when frozen under ground 7 
 
 "The reason why potatoes, apples, &;c. become soft, and rot when frozen 
 and then thawed suddenly, uncovered and in open air, is the sudden thawing. 
 You may put a heap of apples on tlie floor of a room, or otiier dry place, where 
 they will freeze perfectly hard, and if covered close with any thing that will ex- 
 clude the air, when the weather becomes warm enough to thaw, the apples will 
 remain sound and uninjured, after they are thus closely thawed. The cover 
 may be of the coarse tow of flax, or any article that will cover them close and 
 exclude the air. So apples may be packed in a tight barrel, if full and beaded 
 up so as to exclude the air. They may be sufTered to remain so in a garret, or 
 any dry place wliere it freezes hard, and they will be found sound and free from 
 injury, if the bairel remains tight till they are thoroughly thawed. It is the sud- 
 den thawing that causes the apples or other vegetables to become soft and rot. 
 
 " So if the fingers on your hand be frozen, and you expose them to sudden 
 heat by warming them at the fire and they suddenly thaw, the flesh will morti- 
 fy and slough off". But, if you freeze your fingers or other limbs, and put them 
 in snow, and rub gently till tliey thaw, — or if put into a pail of water just drawn 
 from the well, which will be less cold than your frozen fin'^ers, — they will thaw 
 slowly, and suflfer but little injury. 
 
 " So during the early autumnal frosts in September, if the morning after the 
 frost is cloudy, the frost will be slowly drawn t'rom the frozen vegetables, and 
 they v/ill he uninjured ; but if they receive the rays of the early and clear sun, 
 they thaw so suddenly, that they will hang their heads and perish. If wet with 
 water from the well, long enough to extract the frost before the sun shines on 
 them, they do not suffer. 
 
 " Onions are a difficult root to keep in winter. If they are put in a cellar 
 warm enough to save them from frost, they will vegetate and be deteriorated. I 
 put them in the warehouse, where they freeze as hard as if out of doors. If in 
 a heap, I cover them close with some old clothes, or anything that covers close, 
 to exclude the air. The same if in boxes or casks. They freeze hard, but it 
 does not appear to injure them for present use, if tliawed by putting them into 
 a pail of fresh-drawn water, to draw out the frost just before cooking them. 
 Onions, thus kept, will be in good condition in the spring, after thawing under 
 cover from the air. 
 
 " I put parsncps, carrots, beets, &c., in boxes or casks, and then cover them 
 with potatoes, which preserves them from drying." 
 
 In further illustration of this subject I need only recall to the recollection of 
 the gardener the well known fact, that, when the wiiUer frosts begin to set in, 
 and his finest flowers to be nipped, those continue to blow the longest, on which 
 the sun's rays fall latest in tlie day. Dahlias protected in litis way, will bloom 
 occasionally for weeks, after those whicii regard the eastern sky are completely 
 withered. 
 
 Professor Lindley has published a series of valuable obsen'ations on the effects 
 of extreme cold upon plants. The general results of these observations are 
 stated in his "Theory of HorLiculturc" p. 88. But the conclusions at which 
 
No. II.] OK SUDDEN AI,TEa\ATIONS OP TEMTERATrRE. tS 
 
 he has arrived are deduced from the appearance presented by the plant after it 
 was thawed. He found the tissue more or less lacerated, the contents of the air 
 and sap vessels intermingled, and the colouring matter and other secretions de- 
 composed. He attributes the laceration to the freezing and consequent expan- 
 sion of the juices, but tins cannot be the necessary consequence of that freezing, 
 since it does not appear, if the whole tuber or leaf be slowly thawed. I would 
 explain the phiMioniena as follows: — 
 
 1°. When the leaf, fruit, or tuber freezes, the fluid portions slightly expand 
 in becoming solid, but the air in the air vessels contracts in at least an equal de- 
 gree, and thus allows a lateral expansion of tiie sap vessels sufHcieut to prevent 
 lesion. When the temperature is slightly raised, the air expands but slightly, 
 and ice is melted long beRirc the gaseous substances reach their original bulk. 
 
 '2°. But if tlie rays of the sun strike suddenly upon the leaf or fruit, the sur- 
 face may at once be raised in temperature 30° or 40° F, The air will conse- 
 quently expand suddenly, and before tlie sap is thawed may have distended and 
 torn the vessels, and caused sap and air to ne mutually intermingled. 
 
 3°. But the moment the sun's rays strike upon the green leaf, its chemical 
 functions commence. It begins to absorb and decompose carbonic acid : and 
 as in the frozen part of the leaf the circulation is not, and in consequence of the 
 lesion cannot be, established, the chemical action of the sun's rays must be ex- 
 pended upon the stagnant sap; and hence those changes not only in the sap 
 Itself, but even in the solid parts, which are seen to take place in the withered 
 leaf 
 
 4^. Tl\ougli not in a state of growth, the tuber of the potatoe contains the 
 living principle, and there must be such a circulation going on in its interior as 
 to manitain an approximate equilibrium of temperature throughout iis sub- 
 stance. A sudden thawing of the exterior, will, as in the leaf, expand the air 
 before the circulation can be established throughout the frozen mass. The solid, 
 fluid, and aeriform substances which nature has separated and set apart from 
 each other, will thus ail be intermingled, and from their mutual action, those 
 chemical changes of which we know the starch of the potatoe to be susceptible, 
 will speedily ensue ; — in other words, the potatoe will rot. 
 
 The practical applications of these views are numerous. If a sudden frost 
 come on, — protect your delicate flowers in die early morning from the rays of 
 the approaching sun, and cover with straw or earth the potatoes which have 
 been left overnight in the field. 
 
 No. III. 
 
 RESULTS OF EXPEKIMENTS ON PRACTICAL AGBICtTLTURE DUBINO 
 THE SPRING AND SUMMER OF 1841. 
 
 (See Appendi.i\ No. 1., and Lectures VIII. and ZX) 
 
 In a previous article inserted in this Appendix, and which was published 
 early in the present spring (April, 18-41,) I ventured to offer to the practical ag- 
 riculturist some suggestions in regard to the cxprrimcntal use of certain un- 
 mixed manures. From the results of these experiments, which I was quite sure 
 some of the many zealous agriculturists of the day would be induced to under- 
 tfUce after the maimer, and with the precautions, I had pointed out, I anticipated 
 
 27* 
 
14 
 
 HESULT3 OF KXPERlMENTa ON TRACTICAL AGUICULTfRE. [Ajfpendix, 
 
 a two-fold advantage. In the first place, that important practical benefits to 
 the agriculture of certain districts would be derived from tlieni, and secondly, 
 that interesting and important light would be thrown by them on many parts 
 of agricultural theory. It is by exj)eriineni that all ilic remarkable results — 
 theoretical as well as jiractical — of modern chemistry have been arrived at ; 
 but by experiments cautiously made, frequently repeated, and logically reason- 
 ed from. I'he proceedings of the jnactical farmer are a continued course of ex- 
 perimental trials, aiid to convert him into an experimental philosopher, and to 
 lead him to philosophical resalts, il is necessary only that his experiments 
 should be made wilh a amstnid rcjbrcit.cc to wcigid and measure, and should be 
 repeated lender varied and carefully i>oled conditions — and that he should be 
 taught to draw from them no conclusions more general than they really 
 justify. 
 
 The following results of experiments nuide during the past summer confirm 
 all my anticipations. Thovigii necessarily somewhat limited, and local in their 
 nature, they, nevertheless, present on the whole a beautiful illustration of v/hat 
 we have yet to expect from a continuation of such experimental researches, con- 
 ducted in so skilful a manner. 1 need not especially commend the experiments 
 of Mr. Fleming : for 1 can scarcely, 1 think, render a better service to practical 
 agriculture than by placing all of them in the hands of practical men, and ear- 
 nestly commending them to their careful consideration and imitation. 
 
 I. Experiments made near Aske Hall, on the property of the Earl of Zet- 
 land, on lots of half an acre each. 
 
 1. Soot — p^tt 071 May 24 — 10 bvshels cost 6s. Gd. 
 Weight of glass when mown, 3 tons 16 cwt. 
 Weight when made into hay, 1 " 15 " 
 
 3. No Mamire. 
 
 Weight of grass when mown, 3 tons 12 cwt. 
 
 Weight when made into hay, 1 " " 
 
 4. Nitrate of Soda — -jntl on May 24 — 4 stones 
 
 cost 1 Is. 
 
 Weight of grass when mown, 4 tons 10 cwt. 
 Weight when made into hay, 1 " 12 " 
 
 2. Salt — put on May 24 — 3 bushels cost 6s. 6d. 
 Weight of grass when mown, 3 tons 19 cwt, 
 Weight when made into hav, 1 " 16 " 
 
 Sulphate of Soda (in crystak) — pni on May 
 24 — 4 stones cost lOs. 
 Weight of grass when mown, 3 tons 3 cwt. 
 Weight when made into hay, 1 " !) " 
 
 6. Sulphuric Acid— i put on May 26, * fnd on 
 
 June 7, 5 put on Jane 1 1 — \blbs. cost 5s. 
 Weight of grass when mown, '.i tons 4 cwt. 
 Weight when made into hay, 1 " 6 '" 
 
 <u 
 
 t O 00 0> «5 O 1 
 
 ^ >% 
 
 £ rt-^ 
 
 
 
 
 
 cS 
 
 1— OOOO 1 
 
 B 
 
 
 
 
 XrH 
 
 (M CO o tc o ys 
 
 is tn cc ■^ •«*< P5 
 
 
 
 
 
 ~ 
 
 
 0-^ . 
 
 r Cl O ri< 00 (N (M 
 
 
 
 
 
 •dz 
 
 
 e c 
 
 te 
 
 e,"" 
 
 gcoccec «(N (M 
 
 r 00 C-t C W X Tt 
 
 : l^ t^ ci o «a t^ 
 
 CO EO K CO Cfl 
 
 c: M fN c o 
 — i-H(M01 I 
 
 _2 — - - 
 
 C: O C) O O 
 
 &Q 
 
 c/.. 
 
 o 5 
 
 C C 0) -^ . 
 
 2 • o c8 5 J5 
 p -e £ c_ cJ^ 
 5 g ; - ■= -5 o 
 O X j!^ o; cc a 
 
 K. B. The cost of the manure doss not include the expense of laying it on. 
 
No. III.] RESULTS OF EXPERIMENTS ON PRACTICAL AGRICULTURE. 15 
 
 Mr. Turner, his lordship's agent, tlius writes: — 
 
 " The pln;i I followed in putting on the dilTerent manures, and the quantities 
 used, accorded as nearly as 1 could manage it, with the directions given in your 
 published lectures. 
 
 " The field on which the experiments were tried is situate in a higli, bleak 
 climate, and consists of a thin light soil, upon a bad subsoil of barren clay 
 resting upon limestone. It had been completely exhausted by a succession of 
 white crops, and was full of weeds and quickens. I had it well ploughed, and 
 took a crop of drilled turnips fairlj^ but not extravagantly, manured. The crop 
 was a poor one. I ploughed the land as soon as the turnips could be got off. 
 Drained it ; and in the spring worked it very fine. The following August I 
 sowed it away with grass seeds without a crop. The seeds came up beautiful- 
 ly, and were the admiration of all who saw them, keeping a deep green through 
 the winter, and beginning to grow early in the spring; and it was on this crop 
 that the experiment was tried early in the succeeding summer. 
 
 " I need Scarcely remark, that the crop of grass for such land was enormous, 
 and has fully repaid the money expended upon it, with the exception of drain- 
 ing, and in two or three years I have no doubt but it will repay this also." 
 
 Re.m.irks. — On comparing the effect of these several top-dressings as indi- 
 cated by the results above stated, the reader will be struck with tlie extraordi- 
 naiy increase caused by the addition of common salt. 1 have in the text 
 (Lecture IX., p. I'.IO,) indicated a principle which may serve to explain in sorie 
 measure both the localities in which the use of common salt may be expected 
 to be beneficial, and the reason why in many parts of our island the employ- 
 ment of this substance has not been attended by any large measure of success. 
 The position of the land experimented upon by Mr. Turner, is such as to lead 
 us to expect it to be improved by common salt, according to the views there 
 stated. 
 
 The nitrate of soda produced less effect than either the common salt or the 
 soot, but it gave an increase which was double of that yielded by the sulphate 
 of soda. The latter salt, however, was applied in the state of crystals, which 
 contain 55 per cent, of water, so that less than one half of that weight of dry 
 salt was used, which was recommended in tlie suggestions 1 offered for the 
 employment of this substance in practical agriculture. At the same time, the 
 price paid by Mr. Turner for this salt was four tiv^a; as great as it ought to 
 have been. Any quantity of the chy sulpliate of soda may be procured at lOs. 
 a cwt., at which price it is forwarded in casks to all parts of the country by 
 Messrs. Allan <.^: Co., Heworth Alkali Works, Newcfustle. 
 
 The most valuable practical suggestion to be derived from these experiments 
 is certainly this — that a liberal use of common salt is likely to increase in a great 
 degree the produce of grass in the locality where they were made, and on the 
 same kind of soil. This valuable discove'ry will far more than repay the ex- 
 pense and troubJc of the entire series of experiments. No application can be 
 so cheap as this, so long as it svcccais. At the same time a mixture of the other 
 substances— the nitrate and the sulphate, which were partially successful — might 
 possibly prove still more efficacious on the grass, and might be expected even 
 to ameliorate the condition of the land for the further production of\yhite crops. 
 In a future part of this Appendix I intend to offer some suggestions in regard to 
 the kind and qvaniUy of the ingredients which may, with probable advantage, 
 enter into the constitution of these 'niix-ed manures. 
 
 I have calculated and introduced into Mr. Turner's table an additional col- 
 umn, exhibiting the weight of hay yielded by 100 lbs. of grass, with the view 
 of showing the relative succulence of the several crops when cut. As a gen- 
 eral rule, the weight of dry hay does not exceed one-fourth of the weight of the 
 grass when cut. In the experiments of Mr. Turner, however, the weight of 
 hay in every case was much beyond this quantity — tlie most succulent crop, 
 that to which no dressing was applied, yielding 36 per cent, of hay. This gen- 
 
16 RESULTS OP r.xPi.ntMKNTS ON puACTiCAi, AcnicvLTtTRE. [Appendix, 
 
 eral result may have been partly due to the state of ripeness in which all the 
 grasses were cut, while tlie gre;Uf:r produce of hay from the ilressed portions 
 may indicate the rehitive ripeness, and therefore dryness, of each when cut down. 
 
 It is evident, therefore, that liie relative values of crops of grass or clover are 
 not to be judged of by the several weiglits when green, but by the weights of 
 the di*y hay. This is further confirmed by the results of an experiment witii 
 nitrate of soda, communicated to me by Mr. Canxuhers, of Warmonbie, near 
 Annan, in which the relative weights of hay obtained were miKk marc in favour 
 of the use of the nitrate than the several weights of gi-ass yielded by the dressed 
 and undressed portions of the field. On the contrary, from a field on Oliver 
 Farm, near Richmond, Air. Sivers informs me, that the weight of liay v/as inuck 
 less in favour* of the us2 of the nitrate of soda than the relative weights of 
 grass. In all cases, therefore, the weight of the dry crops obtained by different 
 methods should be com[)ared with each other, as the safest lest of the relative 
 merits of the several modes of procedure by which they have respectively been 
 raised. 
 
 II. Experiments made at Erskine, on the property of Lord Blantyre. 
 
 1 insert the clear and well-digested statement of his Lordship's agent without 
 alteration : — 
 
 " Freehnul, Ersliiie, by Old Kilpsi!-rid-, Glasgov.', 'JfJ'h Jitly, iBil. 
 
 " Sir — Agreeably to Lord Blantyre's instructions I send you a copy of the re- 
 sults of some experiments with nmnures on young grass for hay, undertaken 
 on two separate pieces of land — the one a very good light soil (subsoil gravel); 
 the other stiff clay soil with a clay subsoil. The manures were applied on 1st 
 May, the hay cut on tlie Isl and weighed on the 19ih .Tuly current; the extent 
 of each plot one-twentieth of an miperial acre. From the small extent of each plot 
 it will be evident that the results cannot be exactly depended on, farther than as 
 a general result ; because in so small a portion of land the least variation in the 
 soil or crop naturally will affect the results very materially ; still, on the whole, 
 I am of opinion that the experiment gives the comparative view of the value of 
 the diffei'ent manures used pretty nearly. 
 
 " One thing has astonished us with regard to soda (nitrate). On all the fields 
 I have observed it sown on, the part dressed has a much greater vigour of after- 
 math than where no nitrate of soda was given: showing that this maiiure is not 
 so evanescent as was generally supfiosed. 
 
 " I am, Sn*, your most obedient servant, 
 
 " J.4S. WlI-SON." 
 
 Experiments with Manures as a lop-draslns for Hay, at Erskine, 1841. 
 
 Remarks — It will be observed in these experiments, that the saltpetre and 
 nitrate of soda produced ne<irUj an equal increase on both kinds of soil, the ni- 
 trate of soda having the greater effect on the light, the nitrate of potash on the 
 heavy soil. Next to these on the light soil are the common salt and sulphate of 
 soda, though on the heavy soil the common salt had the better effect of the two. 
 It is to be observed, however, that in this case the sulphate was used in crystals, 
 and therefore only in half the quantity recommended. Had twice the quantity 
 been employed upon the light soil the produce might have equalled that from the 
 nitrates. 
 
 It is a singular illustration, however, of the necessity of applying different 
 substances to different soils — that so far as this experiment is to be depended 
 upon, the sulphate of .soda almost entirely failed on the heavy land. 
 
 The most valuable practical deduction from diese experiments also, is, that 
 on both the soils in question, the grass land, m its present condition, may he salted 
 to advantage. At the same time, it appears probable that on the light soil the 
 increased produce would amply repay the cost of applying either nitrate or sul- 
 
 * In Mr. Sivers' experiments, 100 square yards, nitrcted, gave 68 stones oThay, unnitrateJ 
 62 stones, but when dry thev were reduced to 12 stones each. How very much more suc- 
 culent these grasses were tlian those of Mr. Turner 1 
 
N>. lit] 
 
 ON MANURE AS A TOP-DHESSlNa fOR lUT. 
 
 It 
 
 phate of soda at the rate of 120 lbs. per acre — the latter being in its dry or uil- 
 crystaliized state. 
 
 The effect, generally, of all the dressings is strikingly greater on the light 
 soil — a fact which speaks strongly in favour of the adoijuoii of any of those 
 methods by which the openness and friability of the land has been found to be 
 permanenuy promoted. On tiie stiff soil, even the ammonia, by some deemed 
 so vitally necessary to vegetation, appears to have produced no sensible alter- 
 ation. 
 
 ^ 
 
 Manures tisi'd, and quantities applied, to 
 
 
 u 
 
 Total produce 
 
 Total additional 
 
 c 
 
 each plot of l-20tli ot an acre. 
 
 x£ 
 
 ^ ■^ 
 
 
 I' 
 
 -r 
 
 weight per 
 
 B. 
 
 
 ^.s 
 
 ^& 
 
 Imperi 
 
 ,1 Acre. 
 
 Iiuperiai Acre. 
 
 
 E.rp. J. Good light soil, sidsoil gravel. 
 
 
 __ 
 
 
 
 
 
 
 
 1 
 
 1 lb. sulpliuric acid, diluted in 47 \ 
 galls, water . . . ) 
 
 271 
 
 44 
 
 Is. 
 2 
 
 cwt. 
 8 
 
 qrs. lbs. 
 1 16 
 
 ts. 
 
 cwt. 
 
 7 
 
 qrs. lbs. 
 3 12 
 
 2 
 
 Gibs, saltpetre (nitrate of potash) 
 
 322 
 
 95 
 
 2 
 
 17 
 
 2 
 
 - 
 
 16 
 
 3 24 
 
 3 
 
 6 lbs. nitrate of soda . 
 
 339 
 
 112 
 
 3 
 
 
 
 2 4 
 
 1 
 
 
 
 
 
 4 
 
 G lbs. sulphate of soda (in crystals) 
 
 •292 
 
 65 
 
 2 
 
 12 
 
 16 
 
 - 
 
 11 
 
 2 12 
 
 5 
 
 17 lbs. gypsum .... 
 
 254 
 
 27 
 
 2 
 
 5 
 
 1 12 
 
 - 
 
 4 
 
 3 8 
 
 (i 
 
 1 bush, wood charcoal (pounded) 
 
 277 
 
 50 
 
 2 
 
 9 
 
 1 24 
 
 - 
 
 8 
 
 3 20 
 
 T 
 
 ^ bush, common salt, 25 galls, water 
 
 294 
 
 G7 
 
 2 
 
 12 
 
 2 
 
 _ 
 
 11 
 
 3 24 
 
 8 
 
 1 gahammoniacal liquor, 47 gls. water 
 
 277 
 
 50 
 
 2 
 
 9 
 
 I 24 
 
 _ 
 
 8 
 
 3 20 
 
 9 
 
 No application .... 
 Exp. II. Clay soil, subsoil chiy. 
 
 227 
 
 
 2 
 
 
 
 2 4 
 
 
 
 
 1 
 
 1 lb. sulphuric acid, diluted in 47 \ 
 galls, water . . . \ 
 
 256 
 
 2G 
 
 2 
 
 5 
 
 2 24 
 
 - 
 
 4 
 
 2 16 
 
 2 
 
 Gibs, saltpetre (nitrate of potash) 
 
 286 
 
 56 
 
 2 
 
 11 
 
 8. 
 
 _ 
 
 10 
 
 
 
 3 
 
 Gibs, nitrate of soda . 
 
 2H2 
 
 52 
 
 1 
 
 10 
 
 1 12 
 
 - 
 
 9 
 
 1 4 
 
 4 
 
 G lbs. sulphate of soda (in crystals) 
 
 232 
 
 2 
 
 2 
 
 1 
 
 1 20 
 
 _ 
 
 
 
 1 12 
 
 5 
 
 17 ll)s. gypsum .... 
 
 240 
 
 10 
 
 2 
 
 2 
 
 3 12 
 
 _ 
 
 1 
 
 3 4 
 
 6 
 
 1 bush, wood charcoal (pounded) 
 
 257 
 
 27 
 
 2 
 
 5 
 
 3 IG 
 
 _ 
 
 4 
 
 3 8 
 
 
 \ bush, common salt, 25 galls, water 
 
 2G9 
 
 39 
 
 2 
 
 8 
 
 4 
 
 - 
 
 6 
 
 3 24 
 
 1 8 
 
 1 gal. ainmoniacal hquor, 47 gls. water 
 
 201 
 
 — 
 
 1 
 
 15 
 
 3 IG 
 
 - 
 
 - 
 
 - _ 
 
 1 9 
 
 No application .... 
 
 230 
 
 — 
 
 2 
 
 1 
 
 8 
 
 J2_ 
 
 - 
 
 - - 
 
 The Dressings were applied 1st May, the Grass cut 1st July, and the Hay 
 weighed 19th July. 
 
 III. Experiments made under the immediate superintendence of W. Fleming, 
 Esq., of Barochan, near Paisley, and on his own property. The statement is 
 drawn up by Mr. Fleming himself 
 
 1. — Experiments on Hay with Nitrate ami Sulphate of Soda, and with Gypsum, 
 
 
 
 Description of 
 
 Rate per 
 
 Weight per 
 
 Weijiht 1 
 
 No. 
 
 Field. 
 
 Dressing. 
 
 imp. liooil 
 
 Rood, green. 
 
 when stack'd 
 
 1 
 
 Covenlea. 
 
 Nothing. 
 
 
 
 3361 lbs. 
 
 1120 lbs. 
 
 2 
 
 Do. 
 
 Nitrate of Soda. 
 
 40 lbs. 
 
 4907 " 
 
 1636 " 
 
 3 
 
 Do. 
 
 .Sulphate of Soda. 
 
 40 lbs. 
 
 3966 " 
 
 1322 " 
 
 4 
 
 Do. 
 
 Gypsum. 
 
 10 lbs. 
 
 3831 « 
 
 1277 " 
 
 1 
 
 Crook's High 
 
 Nothing. 
 
 — 
 
 4436 " 
 
 1478 " 
 
 2 
 
 Do. 
 
 Nitrate of ^oda. 
 
 40 lbs. 
 
 4999 " 
 
 1666 " 
 
 I 
 
 Crook's Low. 
 
 Nothing. 
 
 
 
 2185 " 
 
 728 " 
 
 2 
 
 Do. 
 
 Nitrate of Soda. 
 
 40 lbs. 
 
 37G4 " 
 
 1254 " 
 
 3 
 
 Do. 
 
 Gypsum. 
 
 80 lbs. 
 
 3110 " 
 
 1036 " 
 
18 
 
 EXPERIMENTS ON WINTER RYE. 
 
 [Appendix, 
 
 Character of the Soil — Nos. 1, 2, 3, and 4 were good shai-p soil, on rotten 
 rock, (decayed trap,) all as near as ])03sible the same description of land, 
 drained, and lying together. Nos. 1 and 2, Crook's High, stiff clay, drained; 
 the hay was after wheat. Nos. 1,2,' and 3, Crook's Low, light clay-loam, 
 drained ; the liay was aT(er barley. 
 
 On Covenlea the dressings were applied on the 22nd of April, and the hay cut 
 on the 2nd of July ; on the other fields the nitrate and gypsum were applied on 
 the r2th of April, and the hay cut on the 9tli of July. 
 
 N. B. The above is the average of trials in three parts of the Covenlea field; 
 a small portion of moss was also sown wiih nitrate of soda, in the low part of 
 the siiine field, but no benefit was observable, beyond the usual dark green 
 colour which appeared about ten days after the application. The sulphtue of 
 soda, although evidently beneficial, does not produce the dark green colour. Jn 
 the Crook's fields the effect of nitrate of soda in producing the dark green colour 
 was as remarkable as in the Covenlea field. The gypsum on both fields seems 
 to have had a good effect, particularly on the aftermath clover. 
 
 Rrmari^s. — In these experiments also the sulphate of soda was used in only 
 half the quantity recommended. By referring to the prices paid by Ml. Fleming, 
 it will appear that the use of sulphate of soda gave an increase of 200 lbs. of 
 hay for Is 9d. (or 500 lbs. for 4s. 5d.), while the nitrate of soda gave an increase 
 of 516 lbs. for 7s. lOd. ; so that, though the actual increase of hay per rood was 
 considerably less by the use of the sulphate, yet that increase was obtained at 
 little more than half the cost of the same weight of increase derived from the ni- 
 trate. A similar remark applies to the gypsum, so that these experiments give 
 ample encouragement for the application of both these substances in somewhat 
 large quantity to succeeding crops, on the same land. 
 
 2. — Experiments on Winter Rye, dressed with Nitrate of Soda, Lime loiih Potash, 
 Sulphate of Soda, and Muriate of Ammorda\Sal Amvwniac.') 
 
 No. 
 
 Field. 
 
 Df-.^cription of 
 Dressing. 
 
 [Garden Plot. 
 Do. 
 Do. 
 Do. 
 Do. 
 
 Nothing. 
 Nitrate of Soda. 
 Lime and Potash. 
 Sulphate of Soda. 
 Mur. of Ammonia 
 
 R ite per 
 
 rood 
 imperial 
 
 Wei;!;ht of 
 
 Grain, 
 per rood. 
 
 Weisht of 
 
 ^^!ra^v 
 per rood. 
 
 40 lbs. 
 40 " 
 40 " 
 5 " 
 
 160 
 336 
 272 
 224 
 232 
 
 bs. 
 
 1024 lbs. 
 1664 " 
 1344 " 
 1152 " 
 1216 " 
 
 Bushels 
 per 
 rood 
 
 3i 
 5i 
 41 
 
 Character of the Soil. — Tilly clay, which liad been trenched, and in potatoes 
 the year before. The Rye was sown on their being lifted in October, 1840. 
 
 The applications were made on the 14th of April, the grain was cut on the 
 9th of August, and thrashed on the 25th. 
 
 N. B. As early as the end of April the eff.;cls of the nitrate of soda were very 
 apparent from the dark green colour produced, and broad leaves, and after it was 
 ripe the heads were longer than any of the others ; but it was so strong that it 
 was laid a month before it was cut; none of the others were laid. Every ap- 
 plication seems to have done good, by increasing the produce. The potash and 
 lime was made by slaking quick-lime and sand with a solution of potash, and 
 allowing them to lie together for a month. As much was used as contained 1 
 lb. of carbonate of potash to the pole. 
 
 Re.marks. — From these experiments, it appears that, besides the proportionate 
 increase of straw, that of grain was 
 
 From nitrate of soda, 12 bushels for 31s. Od., or 2s. 9d. per bush. ; 
 " lime and potash, 7 " for 33s. Gd, or 4s. 9d. " 
 " sulphate of soda, 3 " for 7s. Od., or 2s. 4d. " 
 " sal-ammoniac, 5 " for lOs. 9d., or 2s. 2d. " 
 
Ab. ///] 
 
 EXPERIMENTS ON WHEAT FIELD. 
 
 19 
 
 Although, therefore, iJie total increase by the employment of sulphate of soda 
 and muriate of ammonia, in the proportions actually put on, was not so gi-eat as 
 by the use of the other two dressings, yet this increase was obtained at a con- 
 siderably less cost per bushel. The lime and potash, though producing an im- 
 portant effect, will probably not yield a remunerating return with this crop on 
 tkis t,oiJ, while the results hold out a fair inducement for the trial of the last two 
 dressings in larger and varied proportions. 
 
 The five samples weighed respectively, — 45 3-5, 51 3-4, 51 4-5, 52 3-5, and 
 48 4-5 lbs. per bushel, so that, while on all the dressed plots the gredn was 
 heavier than on the undressed, that which was dressed with sulphate of soda 
 was considerably the heaviest. 
 
 3 — Experimciils on Wheat fidJ, Crook's {crop, 1841.) 
 
 
 
 
 Weiiil.t. of 
 
 WeiytTt 
 
 VVelglit of to- 
 
 
 Description 
 
 Rate per 
 
 produce nl 
 
 of 
 
 tal produce, 
 
 No. 
 
 of Top-dressing. 
 
 .Scotcli acre. 
 
 Grain of 
 
 Grain 
 
 when cut, of 
 
 
 
 
 Jsth acre. 
 
 pr. batiU 
 
 ieth an acre. 
 
 I 
 
 Nitrate of Soda. 
 
 IGO lbs. 
 
 209 lbs. 
 
 G3 lbs. 
 
 9,500 lbs. 
 
 2 
 
 Potash 
 and Lime. 
 
 IfiOlbs. \ 
 40 bush. 1 
 
 210 " 
 
 62 '= 
 
 8,930 " 
 
 3 
 
 Common Salt. 
 
 iGO lbs. 
 
 249 " 
 
 62 " 
 
 12,540 " 
 
 4 
 
 Mur. Ammonia. 
 
 20 lbs. 
 
 208 " 
 
 G2 " 
 
 8,360 " 
 
 5 
 
 Nitrate of Soda 
 and Gypsum. 
 
 W lbs. { 
 IGO bush. \ 
 
 214 " 
 
 62 " 
 
 8,620 " 
 
 6 
 
 Nitrate of Soda 
 and Rape-dust. 
 
 80 lbs. ) 
 5 cwt. \ 
 
 240 " 
 
 62i" 
 
 11,970 " 
 
 7 
 
 Mur. Ammonia 
 and Lime. 
 
 20 lbs. \ 
 40 bush. ^ 
 
 230 " 
 
 63 " 
 
 9,500 " 
 
 8 
 
 Common Salt 
 and Lime. 
 
 28 lbs. \ 
 80 bush. S 
 
 200 " 
 
 63*" 
 
 8,740 " 
 
 9 
 
 Nothing. 
 
 — 
 
 190 " 
 
 61 " 
 
 8,050 " 
 
 Character of tlie Soil. — The land was a heavy loam, and of as nearly as pos- 
 sible the same quality. It had been in potatoes, and the wheat was sown when 
 tliey were lifted in October, 1840. 
 
 The applications were all made on the I3th of April, and the crop was reaped 
 on the 2d of September. 
 
 The produce of Jtli of a Scotch acre, thrashed and weighed and well cleaned, 
 gave an average of from 32 to 33 bushels of 61 lbs. each per Scotch acre of grain. 
 
 Rbmarks. — This table presents us with two remarkable results, — that ob- 
 tained by the use of common salt, and that from a mixture of soda and rape- 
 dust. Thu.s, exclusive of the straw, — 
 
 Nitrate of soda alone gave 1.52 lbs. of wheat for 31 s., or I2s. 2d. per bushel ; 
 
 Nitrate with rape-dust gave 400 lbs. of wheat for 43s. (kI., or 6s. 9d. per bushel ; 
 
 Common salt gave 472 lbs. of wheat for 3s. 6d., or 6d. per bushel. 
 
 The increased produce, by the use of common salt, is by far the most valua- 
 ble result to Mr. Fleming in an economical point of view, and plainly indicates 
 the kind of application he can most profitably make — to his wheat crops at least — 
 on land similar to the above, and in the district where he resides. 
 
 Neither the nitrate of soda nor the mixture of this salt with rape-dust, gave 
 such an increase as to repay their ovvn cost, unless wlien corn is very high. It 
 is interesting, however, to observe that the mixture with rape-dust gave so large 
 an increase, though the value of this particular experiment is lessened by the ab- 
 sence of any trial with rape-dust alone, by which the effect of each of the ingre- 
 dients ought to be judged of I have reckoned the rape-dust at £7 a ton, so that 
 5 cwt. would cost '23s., and we know that a top-drpssingof this substance alone, 
 in a somewhat larger quantity, gives a remunerating return in many ofourM'heat 
 huids. 
 
%h EXPERIMENTS ON EARLY POTATOES. [Appendix, 
 
 Mr. Oiuhwaite, of Banesse, in the North Riding of Yorkshire, a skilful and 
 enterprising practical farmer, who has for some years been using rape-dust over 
 a great breadth of his wheat crop, han favoured me with the result of one of his 
 more accurate trials on spring wheat, made during the pa.st season. The wheat 
 was sown after turnips taken off in April, and part of the field was dressed with 
 rape-dust at the rate of 5| cwt. (or at £l a ton, of 40s.) per acre. The produce 
 of the dusted portion Was 39 bushels, and of the undusted ^O bushels per acre, 
 and the increase of straw was one-fiftii of the whole. Both samples were of 
 equal weight, and sold at the same price, — 8s. 3d. per bushel. In this experi- 
 ment the increased 10 bushels cost 40s., or 4s. per busliel, giving, on a large 
 breadth of land, a handsome remuneration. 
 
 Tiiese results will, I trust, encourage others to make trials similar to tho.se of 
 Mr. Fleming and Mr. Outhwaite ; while these gentlemen will, doubtless, be in- 
 duced each to try that application which has succeeded so well in the other's 
 hands. It might be useful as well as interesting to compare the produce of four 
 plots arranged and dressed as follows : — 
 
 Common Salt. 
 
 Rape- dust. 
 
 Common Salt 
 and Rape-dust. 
 
 Nothins 
 
 4. — Experiments on Early Pola'oes, 1841. 
 All were dunged in the usual manner with farm-yard manure, at the rate of 
 about 30 cubic yards per acre. The potatoes were all planted on the 25th of 
 March, on the same lieavij black soil. The several dressings were applied on 
 the 20111 of May, and the potatoes were all lifted on the '28th of September. 
 
 Description 
 
 of 
 Top-dressing. 
 
 Rate 
 per imp. 
 
 Nothing. 
 Nitrate of .Soda. 160 lbs. 
 aiSulphateofSoda. |2:>0 " 
 4!Do.(teNitr.of Soda 200 " 
 
 Produce 
 per imp. 
 
 VVeiahl of 
 Priifiuce of 
 18 yards drill. 
 
 Gf) bolls. 
 80 " 
 73 " I 
 107 " I 
 
 lbs. 
 
 1)3 
 
 8(5 
 124 
 
 [)eck is 35 lbs. 
 weiij-ht, and IG 
 make a boll 
 or 5 cwt. 
 
 This break of ground consists of a piece of poor clay mixed with moss, about 
 9 inches deep ; subsoil a very stiff blue till. The dung was old from the farm-yard, 
 about the ordinaiy quantity (30 cubic yards per acre) spread upon the land, and 
 dug in. Tiie potatoes were drilled in with the hoe; as the ground was wet the 
 plants came up but weak. The nitrate of soda was sown before the other top- 
 dressings, and had remarkably quirk effect, as it showed the third night after 
 being sown. The sulphate of soda does not occasion the dark green colour 
 which is seen upon the potatoes after the dressing of the nitrate, but there is not 
 the smallest doubt of its benelicial elTects, although not in so great a degree as 
 the nitrate. The mixture, which is comijosed of fds of sulphate of soda and^d 
 of nitrate, has a wonderful effect in strengthening the growth (which it keeps 
 longer than with nitrate alone), and the mixture has the same effect in producing 
 the dark green colour as the nitrate alone. 
 
 Rrmauks. — That a wixlvre of substances is likely to be more eflicncious asa 
 dressing, than the application of one substance alone, except in peculiar circum- 
 stances, is consistent not only with long practical experience — for how many 
 substances are mixed together in farm-yard manure 1 — but also with the theore- 
 tical principles laid down in the text. [See Lectures IX. and X.] These experi- 
 ments upon potatoes show that this crop upon Mr. Fleming's land was benefitted 
 by both nitrate and sulphate of soila, but in a vastly greater degree by a mixture 
 of the two. A.nd I might consider my suggestion in regard to the employment 
 of sulphate of soda as a manure, to have been of no mean use in practical agri- 
 culture, had it led to nothing else than to this happy mixture of Mr. Fleming. 
 
 I have received also from Mr. Fleming's gardener (Mr. Alexander Gardiner) 
 
S'O. Ill] EXPERIMENTS ON EARLY POTATOES. 21 
 
 a very well digested nnd well drawn up paper, detailing numerous experiments 
 made by himself during the past summer. Among these is one unonthe use of 
 this same mixture upon thepotatoe crop, wjiich I shall quote in his own words: 
 
 "April 2t)ih. — Planted potatoes of the red Don variety, soil a mellow loam, 
 two feet deep, subsoil yellow till. Farm-yard dung was trenched in some days 
 before planting, at tin: rate of 40 cubic yards per acre ; sets drilled in with the 
 hoe. Plants eame up veiy regular, and were top-dressed with a mixture of ' 
 sulphate and J nitrate of soda on Juiie 2nd, at the rate of '2 cwt. per acre. They 
 grew v?ry strong aft'^r this application. S-'ems six or scvrn feet in Length, dark 
 green, and the prodii.^e, when liftei in October, was IG Renfrewshire pecks of 35 
 lbs. each per Scotch fall of potatoes fit ff)r market." 
 
 Tills produce is equal, i believe, to about -16 tons ]ier Scotch, or 21 tons per 
 imperial acre, about equal to that of Mr. Fleming with the same mixture. And 
 what an amazing luxuriance of vegetation, to yield at once stems seven feet iu 
 length and upwards of 20 tons of tul)ers per acre ! 
 
 Those who are the most sceptical in regard to the benefits to be derived from 
 agricultural experiments, when well conducted, will scarcely question the impor- 
 tance of this result — the most backward in making experiments will be anxious 
 to repeat this upon his ovn potatoes. The cost of the mixture to be applied in 
 the quantity used by Mr. Fleming is as follows: — 
 
 s. d. 
 oil, re J S 7.5 lbs. ^/r?/ at lOs. per cwt. or ) ^ „ 
 Su phate of Soda <,rrtiu • . i .r i " 9 
 
 ^ ^150 lbs. in crystals at 5s. . \ 
 
 Nitrate of Soda . . 75 lbs. at 22s 14 9 
 
 21 6 
 
 The return for this 21s. 6d. was in each of the above cases upwards of 8 tons 
 of potatoes. 
 
 I may here mention also two other interesting experiments of Mr. Gardiner, 
 in which he tried the effect of sal-ammoniac upon his potatoe crop, — 
 
 1°. In the one he mixed sal-ammoniac, previously dissolved in water, in the 
 proportion of I lb. to each cubic yard of a compost formed from the refuse of the 
 garden, and planted early potatoes with it at the rate of 35 cubic yards per acre. 
 The produce was one-sixth more than wlien no ammonia was used. The va- 
 riety of potatoe was Taylor's forty-fold, the soil moss and clay. The cost of 
 this application was 19s. per acre. 
 
 2^. Sal-ammoniac, dissolved in water, was sprinkli^d on moss or peat earth, 
 at the rate of 20 lbs. to a ton of earth, and, after strewing a little lime at the bot- 
 tom of the drills, this mixture was put in at the rate of 2 tons peracre. Thepo- 
 latoes were 14 days later in coming through the ground than the same variety 
 planted witli farm-yard manure. They were strong in the stem, of a dark green 
 colour, and equal, in point of produce, to the others. The variety of potatoe 
 was the Irish apple, tlie soil a very light brown loam, of that description locally 
 named deaf 
 
 I may observe on this latter experiment, that the application is not so simple 
 as it appears. The lime would decompose the sal-ammoniac, and form chloride 
 of oilciu.n, while ammonia would be liberated. The etTect, therefore, may be 
 partially due to both. It will be recollected that in a previous part of this A p- 
 pendix I suggested the trial of this chloride of calcium as a top-dressing for va- 
 rious crops. 
 
 5. — t>].rperimc7its on Mosx Oats, soii-n about 1st May, 1841, toji-dressfd 'Hoth Jnne. 
 "These top-dressings vveie ap])lied on the 5th of June, and by the 24tli there 
 was a striking improvement, especially on No. 2 and No. 7. It was quite visi- 
 ble in greater strength and evenness of crop. One or two of the others also 
 showed improveiuent, but not so visibly as to merit particular notice. I exam- 
 ined them from time to time, and at different dates; the appearances much the 
 same as noticed upon June 34th. I again examined them a few days before 
 
S3 
 
 EXPEKIMENTS ON OATS. 
 
 [Appaidix, 
 
 they were cut, when. I was much satisfied with No. 2; t!ie straw appeared to me 
 as stiff and shining, and the ear as well filled, as if it had been grown upon stiff 
 loam, and 1 consider the same dressing, applied to grain crops upon macs, ivdl in- 
 sure a good crop of well-fiUed o.i.'s. INo. 7 was nearly as good, but the want of the 
 bones being dissolved was a drawback. However, I consider ths two merit 
 tiie expense of another trial.'' 
 
 No. T'lp-dre-ssirifj per pole (inipetial). 
 
 Nothing. 
 
 Bon3s dissolved in sulphuric acid and nitrate of soda } lb 
 
 Sulpliate of soda J lb., bone dust i peck. 
 
 Potash I lb., lime and bone dust J peck. 
 
 Chloride of calcium 1 lb., bones J peck. 
 
 Lime, pota->h, and chloride of calcium, I lb. each. 
 
 Potasii and lime, nitrate, and bones, ^ lb. each. 
 
 Character of the Soil. — Moss 4 feet to clay. No. 2 the best crop and heaviest 
 grain (not thrashed). Nos. 3, 4, and 5 not so good as No. '2, but all much 
 better than Nos. 1 or G. No. 6 the worst — not better than No. 1. No. 7 very 
 good — next to No. 2. 
 
 Rem.vuks. — These experiments of Mr. Fleming on moss oats may be con- 
 sidered as affording another illustration of the benefits which are yet to accrue 
 to practical agriculture from the suggestions of natural science. It is well known 
 to those who have directed their attention to the reclaiming of peat lands, that 
 the crops of oats raised on such land yield abundance of straw, but that the ear 
 is small and badly filled. It is also well known ihal ckiying such lands is an al- 
 mo.5t unfiiling remedy for tliis defect in the ear, as well as for the less important 
 one wliich is also observed in tlie straw. My friend, Mr. Alexander, of !South 
 Bar, a neighbour of Mr. Fleming, and, like him, extensively engaged in the im- 
 provement of peat lands, finding, as most other persons have, that in some lo- 
 calities the claying of his land was very expensive,* conceived the idea that 
 some chemical application might be made to this soil, wliich woidd supply 
 what the defective oat plants required, and thus supersede the necessity of 
 cl-ayiiig He was pleased to conmiunicate this opinion to me — stating the de- 
 fect in the crop, and asking a chemical remedy. Looking cliiefly to what was 
 evidently required by the ear, [ suggested a trial of various mi.xtures, in all of 
 which, — from an idea that jiiiosphutes, among other substances, might be ne- 
 cessary to coKipleLc the ear, — bone-dust formed a necessary part. The result of 
 these suggestions is seen in the above experiments of Mr. Fleming. They have 
 been varied and improved upon, as Mr. Fleming's united chemical knowledge 
 and practical skill enabled lum to do, and as first results on a new field of re- 
 search, Nos. 2 and 7 may be considered as highly encouraging, if not, indeed, 
 eminently successful. Too much confidence, however, must not be placed on 
 the effects observed in one or two instances; yet I hope those above stated are 
 such as will induce otiiers to repeat the experiments with equal care, in order 
 that another year, affording us more numerous results, may enable us to base 
 our conclusions upon a larger experience. 
 
 6. — Experiments upon Oats top-dressed with Sulphate and Nitrate of Soda (lower 
 end of Bnrn ParL) 
 "Ths first was sown on the 11th May, viz., 3 ridges with sulphate of soda, 
 at the rate of 1 J cwt. per acre. This was examined from time to time, but there 
 
 ' Mr. Gardpn, of nienae Ilou.'se, nearRiimfries, a gentleman to wtiom.lhnnph personally 
 unkriinvii. 1 am inilebtcd for many valuable communications, infirms me thai, in improving 
 liis pornns peat l.imis, lie lias foiiiul it necfs.sary to lay on a coaling of clay six inciins thick, 
 at an txpeiisii of X15 an acre. A coating of two or three inches on their peat, he says, sinks 
 down, anil in a few years descends beyond the reach of the plough, and hence it. is more 
 ttconoiuical to lay on at once an entire soil of six inches. 
 
A'o. ///.] EFFKCTS OF SULPnATF, AMD .VITRATE OF SODA. 23 
 
 appeared to be little, if any, difference from the general crop (it lias not yet been 
 thrashed.) Next, 3 ridi^es were sown witl) nitrate ol'soJa, at the rate oi'SO lbs. 
 per acre. This made a little alteration both in colour and strength, but it was 
 too little to make a very decided difference. Also, alongside of ihe last -men- 
 tioned, a piece was dressed with a nii.xture of suiphate and nitrate of soda, in the 
 proportion of j-rds of the fornT^r to Jrd of the latter. This immediately took the 
 lead of the others both in colour and strengtli, so much so, that by May 21th it 
 could be seen from a distance. iVIany e.xaminations were made of thena all 
 during tiie season, and this always appeared the best. A few days before it was 
 cut, it showed the largest and best filled ear. There was a piece of yellow-col- 
 oured earth at the bouom of the fijld, showing the presence ;>f iron, upon which 
 was sown potash and lime. The plant was yellow and sickly looking, but im- 
 mediately after the application it acquired a dark green colour, and became vi- 
 gorous, and yielded a crop at least equid to any in the field. There were some 
 other dressings put on other ridges of this fidd, but it was dry weather directly 
 after they were sown, and the crop was too far forward before they began to take 
 effect to siiy any thing decided about them. By mista':e lUt^n were two varie- 
 ties of oats sown upon the field, which prevented the experiments being so de- 
 cided, as the dressings were put on indiscriminately upon the land before it was 
 known." 
 
 RKNTAitifs. — The only remark I need mtike upon these experinieiU.s is, to sug- 
 gest to my readers that, by repeating the above trials upon oats with "vlr. Flem- 
 ing's ■nvxlu.res, they may not only benefit their own crops, luit may also aid 
 materially iu the advancement of practical agricultural knowledge. 
 
 7. — Oil Ihe effect of Sulphate ofS'fda applied ns a f.op-dressi}ig to B':ans and Peas. 
 
 '• The first dressins: was applied the 4th of May, on .-iome beans on a border 
 in the garden; the drills tliat were dressed quickly took the lead of the others. - 
 There was no alteration of colour, but greater strength, and it tlUered, voiider- \J 
 fulhj. There were five or six stems from every seed sown, and the pods were 
 larger and more numerous, and the beans in the pods a great deal larger than 
 the same variety undressed. It was also put upon some of tlie ridges of the 
 beans in the field, and witli the same effect, and gave a very large crop (not yet 
 thraslied.) 
 
 " Upon peas in the garden it appeared to add little., if any thing, to the strength 
 of straw, but those that were dressed had a far greater number of pods, and those 
 better filled, and the peas of a better flavour, and ii srnn.s a ruluable dressing for 
 aU. Lgumittoiu; crops. When sown in the drills along with the peas, it nearly 
 killed every one of thein, while the same quantity, put on as a top-dressing to 
 some drills next to them (where the peas were two inches high,) did no injury. 
 
 Kk.mauks — The testimony of Mr. Fleming to the value of sulphate of soda 
 as a dressing for leguminous crops, is veiy valuable and satisfactory. We may 
 hope that next year will furnish us with experiments, all the results of which 
 shall have been so carofuliy ascertained, as to enable us to decide upon the eco- 
 nomical value of this sulphate as a manure, by a comparison of the amount of 
 increase in the crop, with the cost of the application. 
 
 / 8. — On Nitrate of Sola as n top-dressing to Gooseberry and Currant bushes. 
 
 " It was applied April llth. at about the rate of h cwt. per acre, or } lb. per 
 bush. It had ilie effect, in tiie course of a week, of produchig on the bushes a 
 dark green colour and broader leaves, and the fruit set better and more plentiful- 
 ly, especially on some red currants that had borne little for two years. These 
 set their fruit well, and yielded double their former produce. The dressed bushes 
 kept the. lead in strength and vigour all the season, and now, when the undressed 
 bu lies have lost their leaves, the others are quite green." 
 
 9. — "Many experiments were tried in the garden on tni'nips, by top-dressing 
 with nitrate of soda, but with no perceptible effect. However, the Swedish, and 
 
24 ON EXPEBiMENTs WITH GLANo. [Appendix 
 
 red-top yellow, in a field of rather stiff soil, were benefitted, the former yielding 
 i more produce in weight, and the latter j more weight. Wm. Fi.f.ming. 
 
 "Barochan, 2Glk Odober, 1841." 
 
 Note. — Thn prices |)ai(i by Mr. Fletninffwere as follow :— Bone tliist(fine) Is. 9d. per bushel; 
 sulphate of ammonia (in crystals)283. per cwt. ; polasli(very impi)re)24s. percwt. ; sulphate 
 of soda (in crystals) 5i. per cwt. ; nitrate of soda 2Js. ; and sal-ammoniac 60s. per cwt. 
 
 No. IV. 
 
 SUGGESTIONS FOIl COMPAR.^TIVE EXPKKIMEXTS WITH GUANO 
 AND OTHER M.\NURES. 
 
 Giiatio is the name given in South America to the dung of the sea fowl which 
 hover in countless flocks along the shores of the Pacific, and which, from time 
 immemorial, have deposited their droppings on the rocks and the islands which 
 are met with along the coast o. Peru. 
 
 Besides the fresli white guano which is deposited year by year in these locali- 
 ties, there exist, in some spots, large accumulations more or less buried beneath 
 a covering of drifted sand, which hava been thus buried and partially preserved 
 from an unknown antiquity. Tiiis ancient guano is of a brown colour, more or 
 less dark, and forms layers or heaps of limited extent, but which are said some- 
 times to exceed even (>0 feet in thickness. 
 
 In the time of the Incas tiiis substance was known and highly valued as a ma- 
 nure, — the country along the coast for a length of "200 leagues was entirely ma- 
 nured by it, — the islands on which it was formed were carefully watched and 
 preserved, — and it was declared to be a capital oftence to kill any of the sea fowl 
 by which it was deposited. Ever since tluit time it has been more or less em- 
 ployed for the same purpose, and much of the culture now practised on this 
 thinly-peopled coast is entirely dependent for its success, if not for its existence, 
 on the stores of manure which the sea fowl thus place within reach of those parts 
 of the country whicii are susceptible of cultivation. 
 
 In modern times, however, the access of foreign shipping, and the want of 
 careful protection, have driven away many of the sea fowl, and lessened toa very 
 great degree the production of the recent guano. Thus the country is more de- 
 pendent than in former times on the more ancient deposits, which are now assi- 
 duously sougiit for, and when discovered beneath the sand, are carefully exca- 
 vated and transported to the sea-ports for sale. 
 
 The dung of birds of all kinds, when exposed to the air, gradually undergoes 
 decomposition, gives off ammonia, and acquires a brown colour. As this am- 
 monia is one of the most fertilizing substances it contains, it will be rendily un- 
 derstood that the old brown guano is much less valuable as a manure than that 
 which is recent and white ; hence the care of the ancient Peruvians in collect- 
 ing the fresh, and their comparative neglect of the ancient guano. 
 
 Wiien the brown guano is put into water, a large quantity of it — sometimes 
 70 per cent, of the whole — is dissolved. Hence, it is, because the climate of 
 Peru is so dry and arid that in the plains rain scarcely ever tails, that the guano 
 can accumulate as it is found to do. Psorth and south of this line of coast, 
 where rains are less unfrequent, such accumulations are nut met with, though 
 the birds appear equally plentiful, and it may be safely stated that, ha<l the cli- 
 mate of Peru been like that of Kngtand, the rains w(ndd have washed the guano 
 from the rocks almost as rapidly as it was deposited. 
 
 Of the brown guano several cargoes have lately been brought to England by 
 
No. IV.] ON EXPERIMENTS WITH GUANO. 25 
 
 an enterprising merchant in Liverpool, and it lias been deservedly recommend- 
 ed to ilie alUnlioii of British agrieulturists. It has already been tried upon va- 
 rious crops, bolli of h »y and corn, upon turnips also, and upon hops, and there 
 can be no doubt whatever that in our climate, as well as in that of Peru, it is 
 fitted to promote vegi^iaiion to a very remarkable degree. 
 
 This brown guano varies much ui quality, according probably to the degree 
 of exposure to the air to which it has been subjected, or to its position in the de- 
 posit from which it has been dug. Two different portions, taken at random 
 from the same box, gave me the following very different results : — 
 1°. — Water, salts of ammonia, and organic matter, expelled 
 
 by a red heat, 23 5 per ct. 
 
 Sulphate of soda, 18 " 
 
 Common salt, with a little phosphate of soda, . . 30'3 " 
 Phosphate of lime, with a little phosphate of magnesia 
 
 and carbonate of lime, 44 4 " 
 
 100* 
 
 2='.— Ammonia, = 70 ^ 
 
 Uric acid, . . . . . . =08 Ly.Spgrct 
 
 Water, carbonic and oxalic acids, &c., expelled f '^ 
 
 by a red iieat, =51-5 J 
 
 Common salt, with a little sulpliate & phosphate of soda, 11-4 " 
 Phosphate of lime, (fee 29 3 " 
 
 100 
 According to M. Winterfeldt, this brown guano is sold at the ports near 
 which it is obtained at about 33. a cwt. It might, therefore, if this be correct, 
 oe imported inio the country, and sold at less than lOs. per cwt. The price at 
 present asked, however, is 25s. per cwt., a cost at which it is doubtful if the 
 English agricuUurisi can afford to use it. 
 
 In any case it seems improbable that the guano can continue to be imported 
 into this country for any length of time. It is absolutely necessary to the cul- 
 tivation of the land in Peru,— and it is also diminishing in quantity, — the first 
 settled government, therefore, which is formed in that country, must prohibit 
 t!ie further exportation of a substance so important to ilie national interests. It 
 is a matter not unworthy of the attention of chejnists, therefore, to consider 
 whether a mixture similar to the guano, and of equal etlicacy, cannot be form- 
 ed bv art — not only at a cost so reasonable as at once to make the British 
 farmer independent of the importer, — liut also in such abundance as at the same 
 time to place so valuable a manure witliin the reach of all. 
 
 The fttllowing mixture contains the several ingredients found in guano in 
 nearly the average proportions ; and I believe it is likely to be at least as effica- 
 cious as the natural guano, for all the crops to which tiie latter has hitherto been 
 applied in this country: — 
 
 315 lbs. [7 bushels] of bone dust at 9s. 9d. per bushel 
 100 lbs. of sulphate of ammonia, + containing 35 lbs. of ammo- 
 nia at 20s. a cwt 
 
 5 lbs. of pearl-ash . . .... 
 
 100 lbs. of common salt . ..... 
 
 11 lbs. of dry sulphate of soda .... 
 
 531 \hs. of art ijicial guano cost . .... 2 1 
 
 • Tlie fir.st contained also 8 per cpnt. and the seron<l It per cent, of sand, wliicli has been 
 lefl (lilt of ilic true composition of the guano considerpd as free from sand. 
 
 t Sulpliate of ammonia is now manufaciiired largely at Glasgow, and may be had for less 
 than 20s. a cwt. 
 
 £. 
 
 ,<:. 
 
 d. 
 
 
 
 19 
 
 
 
 
 
 18 
 
 
 
 
 
 1 
 
 
 
 
 
 2 
 
 
 
 
 
 1 
 
 
 
26 
 
 ON EXPKRIMKXTS WITH GUANO. 
 
 [Ajyp-mdix, 
 
 The quantity here indicated may be intimately mixed with 100 lbs. of chalk, 
 and will be fully equal in efficacy, I believe, to 4 cwt. of guano, now selling 
 at £5. 
 
 At the same time it is desirable that the relative efficacy both of this mi.xture 
 (artificial guano), and of the American guano, should be tried by actual experi- 
 ment in comparison wiili other substances of known value, and which are 
 supposed to act in a way somewhat similar. The substances with whicli I 
 would suggest that such comparative experiments should, in ti\e first place, be 
 made, are farm-yard manure, bone dust, and rape dust, and the following 
 scheme exhibits the proportions in which they may be added to the different 
 plots of land on wliich the experiments are intended to be made : — 
 
 on tnnc nf 20 busliels of 6 cwt. of guano, 
 
 6 cwt. of 
 artificial guano. 
 
 10 tons dn. on „ , r 
 
 Ill Ions of farm- 
 yard manure with 
 3 cwt. of guano. 
 
 10 lonsof firm-yard 
 ni;uiuri' Willi 3 cwt. 
 of artificial guano. 
 
 lOfonsilo. lOpwt. of 
 
 wtlh 10 cwt. of rape with 3 cwt. 
 
 rape dust. ofgnano. 
 
 10 tons do. Willi 
 2 cwt. of guano. 
 
 10 Inns i!o. with 2 
 
 cwt. of arlificial 
 
 guano. 
 
 The practical farmer need not be deterred by the formidable array of experi- 
 ments above suggested. He may try any tv/o or tliree of them, and his results 
 will be valuable in proportion to the accuracy with which his land is measured 
 and his manures and crops weighed, i have taken 20 tons of farm-j'ard manure 
 as a standard, thou2:h in many highly farmed parts of tlie country no more than 
 15 tons are usually applied. Twenty bushels of bones are recommended by the 
 Doncaster report, and I have lately found (hat in tiie Lothians 1 cwt. of rape 
 dust is considered to replace 1 ton of farm-yard manure. This proportion of 
 course will vary with the quality of the latter manure; but whatever quantity 
 of this latter we take as the standard of comparison, it is easy to adjust the 
 proportions of the other substances accordingly. I have not recommended any 
 trial to be made with more than G cwt. of guano, because, where farm-yard 
 manure is valued only at Gs. or 7s. per ton, 5 cwt. of the foriner would cost as 
 much as 20 tons of the latter " 
 
 The above experiments are intended to be made with the green crop, and to 
 be continued during an entire rotation :+ any pair of them, however, may be 
 tried on single crops, whetiicr of corn or of turnips and potatoes. In this way 
 guano ought also to be tried against nitrate of soda and against bones, upon 
 seeds and upon old grass- lands. The mode in which such experiments may 
 be made Avlll speedily suggest themselves to the intelligent farmer. In oil 
 cases tke results should be accnralely recorded, and, if possMe, piihlisk-cd. 
 
 ' Whr-n thi.-; parasraph was written, the price of guano was Sua. a cwt. ; it is now (May. 
 1842) rrduced to 15.?. < 6 . ^ /, 
 
 t By this I mean that the effect of these several manures, applied once/or all to the green 
 crop at the commencementofihe rotation, should be traced on each successive crop through 
 the entire course of cropping. 
 
No. F.] OP THK PHYSICAL PROPERTIES OP THE SOII.. 27 
 
 No. V. 
 
 OF THE EXAMINATION AND ANALYSIS OF SOILS. 
 
 l". Sdsdion of spenmensof SoUr. — Iii tlia same field different varieties of soil 
 often occur, aad some recommend that in collecting a specimen for analysis, 
 
 Eortions slaould be taken from different parts of tho field and mixed together, 
 y which an average, quality of soil would be obtained. But this is bad advice, 
 when the soils in different pans of the fisl] are really unlike. Suppose one 
 part of a field to be clay, and another sandy, as is often the case in this county, 
 and that an average mixture of theai 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 specim^'n of soil, therefore, one or 
 two pounds should be taken from each of four or five parts of the field v/here 
 tlie soil appears nearly alike, these should be WiU-mixed together and dried in 
 the opiii air or before the fire. Two separate pounds should then be taken 
 from the whole for the puqDOse 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 en- 
 closed in clean well-corked bottles. 
 
 I. — OF THE PHYSICAL PROPERTIES OF THE SOIL. 
 
 •2\ Del cr ruination of the doisity of the soil. — In order to determine the den- 
 sity of the soil, a portion of it must be dried at the temperature of boiling 
 water (•212^), till it ceases to ]'is3 weight, or upon a piece of while paper in an 
 oven at a heat not great enough to render the paper brown. A common phial 
 or other small battle perfectly clean and dry may then be taken and filled up 
 to a mark nia le with a file on tin neck, with distilled or pure rain water, and 
 then carefully weighed. Part of the water may then be poured out of the 
 bottle, and 100^ grains of the dry sod 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 tlis neck, and again weighed. The weight 
 of the soil, divided by the difference between the weight of the bottle with soil 
 ani water and th^ sum of the weights of the soil and the bottle of water to- 
 gether, gives the specific gravity. 
 
 Thus, let tin botde with water weigh 2000 grains, and with water and soil 
 ^BOO, then- 
 Grains. 
 
 The weight of the bottle with water alone = 2000 
 
 The weight of the dry soil 1000 
 
 Sum, being the weight which the botde with the soil and water ) 
 
 woul i, kave had could the soil have been introduced without > 3000 
 displacing any of the water ) 
 
 But the weight of the bottle with soil and water was .... 2600 
 
 Difference, being the weight of water taken out to admit 1000) ^qq 
 grains of dry soil S 
 
 Therefore, 1090 grains of soil have the same b^ilk as 400 grains of water, or 
 the soil is 24 times heavier than water, since 1000-r 400 = 2-5 its specific 
 gravity. 
 
 3°. Dst'ermlnalioii of the alsolidc weight. — The absolute weight of a cubic 
 foot of solid rock is obtained in pounds by multiplying its specific gravity by 
 (\'i\ — the weight in pounds of a cubic foot of water. But soils are porous, and 
 contain more or less air in their interstices according as their particles are more 
 or k'ss 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 aa 
 exact imperial half pint of the soil in any state of dryness, when this weight 
 
28 or THE PHYSICAL PROPERTIES OF THE SOU-. [Appendix, 
 
 multiplied by 150, will give very nearly the weight of a cubic foot of the soil in 
 that state. 
 
 4^. Dderminatian of the relative proporlions of gravel, mnd, mid clay. — Five 
 hundred grains of the dry soil niayba boiled in a flask half full of water till the 
 particles arc 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 ap- 
 pears that nothing but sand or gravel remains. This sand and gravel is then 
 to be washed completely out of the flask, dried, and weighed. Suppose the 
 weight to be 300 grains, then GO per cent.* of the soil is sand and gravel. The 
 sand and gravel are now to be sifted through a gau/.e sieve more or less fine, 
 when the gravel and coarse sand are separated, and may be weighed anl 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 the view of 
 ascertaining if thjy are wlmlly sihcious, or if tliey contain also fragments of 
 different kinds of rock — sand-stones, slates, granites, traps, lime-stones, or iron- 
 stones. A frfw drops of strong muriatic acid (spirit of salt) should also be 
 added — when the presence of lime-stone is show/i more distinctly by an effer- 
 vescence, which can be readily perceived by the aid of the glass, — of per-oxide 
 of iron by the brown colour which the acid speedilj' assumes, — and of black 
 oxide of manganese by a distinct smell of chlorine which is easily recognised. 
 In tlie subsequent description of the soil, tiiese points should be carefully noted. 
 
 Suppose the san I and gravel to contain half its v/eight of fine sand, then 
 our soil would consist of coarse sand and small stones 30 per cent., fine sand 
 30 percent., clay and other lighter matters 40 per cent. 
 
 5^. Ahsorbiiiu; power of the soil. — A thousand grains of the perfectly dn/ soil, 
 crushed to powder, should be spread over a sheet of paper and exposed to the 
 air for twelve or twenty-tour 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. 
 
 G^. lis power of hot-ling VJiit'r. — This same portion of soil may now be put 
 into a funnel upon a doioblei filter and cold water pour.^d 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 then 
 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 adliere 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. Su[ipose the original thousand grains now to weigh 1400, then 
 the soil is capable of holding 40 per cent, of water.! 
 
 7°. Rapi'/itv vvth which, the Mil 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 au'l moisture, for 4, 12, or "34 hours, and 
 the loss of weight then ascertained. This will indicate the comparative ra- 
 pidity 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 of sand saturated with water, in 4 hours, as 
 fron an equal weight of pure clay in 11, and of peat in 17 hours — when placed 
 in the same circumstances. 
 
 8\ Power of ahsorbinfx heat from the sun. — In the preceding experiment a por- 
 tion of pure quartz sand or of pipe clay may be employed for the purpose of 
 
 • A.s 500 : 300 : : 100 to 60 per cent, 
 t That is, one filter within another, 
 t ItWO : 400, tliB increase of weight as 100 : 40. 
 
No. v.] OP THE PHYSICiL PROPERTIES OF THE SOIL. 89 
 
 obtaining a coivparaUvs result as to the rapidity of drying. The same method 
 may be adopted in regard to the power of the soil to become waiTn under the 
 influence ot' 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 thty severally acquire 
 determined by a ilieraiometer, bvniej alioui a quarter of an inch beneath the 
 surface, broils are not found to differ so much m 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 re- 
 lative d\i:ree 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 experimenter, be dispensed with. 
 
 11. — OF THE ORGANIC MATTER PRESENT IN THE SOIL. 
 
 9". Dctcrm illation of the pcr-ccvlage of organic matter — The soil must be 
 thoroughly dried in an oven or otherwise, at a temperature not higher than be- 
 tween 'ibCf^ to 300° F. Humic and ulniic acids will bear this latter tempera- 
 ture without change. A n accurately weiglied portion ( 100 to 210 grains) must 
 tiien be burned in the open air, till all the blackness disappears. This is best 
 done in a small platinum capsule over an argand S[iirit or gas lamp. The loss 
 indicates the total weiirht of organic matter present. It is scarcely ever pos- 
 sible, however, to render soils absolutely dry without raising them to a tem- 
 {>erature so high as to eliar the organic mailer prfsent, and hence its weight, as 
 above determined, will always somewhat exceed, the truth, the remaining water 
 being driven olf along witli the organic matter when the soil is heated to red- 
 ness. This excess, a so, 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. 
 
 10'^. Determination of llic huviic a-'id. — Thisacid, whether merelymixed with 
 the soil, or combined with some of the lime and alumina itcontains, is extracted by 
 boiling with a solution of the common sodaof thesliops. Into about two ounces 
 by measure of a saturated solution of this salt, contained in a flask, 200 or 300 
 grains of soil, previously reduced to roars2 powder, are introduced, an equal 
 bulk of water added, and tlie whole boiled or digested on the sand bath with 
 occasional shaking for an hour. The flask is then removed from the fire, filled up 
 with water, well siiaken, and die particles of soil at'ierwards allowed to subside. 
 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 repeated once or twice 
 with fresh portions of tiie soda solution, till the whole of the soluble organic 
 matter appears by the pale coloitr of the solution to be taken up. These coloured 
 solutions are then to be mixed and filtered. 1 he filtering generally occupies 
 considerable time, the humic and ulmic acids clogging up tlie pores of the filter 
 in a remarkable manner, and permitting the liquid to pass through sometimes 
 with extreme slowness. 
 
 When filtered, muriatic acid is to be slowly added to the coloured liquid — 
 which should be kept in motion by a glass rod — till effervescence ceases, and 
 the whole has become diclinctly 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 througli it, and the humic acid thus collected. It must be washed in the 
 filter with pure water — rendered slightly sour by muriatic acidt — till all the soda is 
 
 ■ Tliis !<! hp.«t elTt'Cled by piillirij the filter info a covrieil porcelain crucible of known 
 wciulil, anil bcHiitiL' it f'>r t( n tnimiies over a lamp or otlierwise, at a tempfrHliire which 
 just lioi's not liisci.Iour the paper, allowliiit then the crnciblp to cool under C'>vpr, anl wlien 
 colli weigliin;; it. The iiicrease above the known weifrht of the crucible is that of the filter, 
 which, besides being recordpcl in (he rxpr-ridiont book, shovilil also be marked in several 
 places on the edge of the ijlter with a black lead pencil. 
 
 t This is to prevent in some measure ihe humic acid from passing through the filter, 
 which it 13 very apt to do, when the saline matter is nearly washed out of it. 
 
 28 
 
30 OF THE OrtGAXIC MATTER PRE.vEN'T IV THE SOIL. [AppendtX, 
 
 separated from it,* when it is to be dried at 250° F., till it ceases to lose ■weight. 
 The final weight, minus that of the filter, gives the quantity of humic acid con- 
 tained in the portion of soil submitted to examination. As it is rarely possible to 
 wash the hmnicacid perfectly upon the filter, rigorous aecuracy requires that the 
 filter and acid should be burned <»fter being weighed, and the weight of ash left, 
 minus the known weight of ash left by the filter,! deducted from that of the 
 acid as previously determined. It is to be observed here that by this, which 
 is really the only available method we possess of estimating tlie liumic acid, a 
 certain amount of loss arises from its not being wholly msoluble, the acid 
 liquid which passes through the filter being always more or less of a brown 
 colour.! 
 
 11'"'. Dicnninn.linn, of the insoluble kumus.—M.AnY aoWs after this treatment 
 with carbonate of soda are still more or less of a brown colour, evidently duo 
 to the presence of other organic matter. I'o separate this, Sprcngel recom- 
 mends to boil the soil, which has been treated with carbonate of soda, and 
 which we suppose still to remain in the flask, witli a solution of caustic potash, 
 repeated, if necessary, as in the case of the soda solution. By this boiling, 
 the vegetable mattet, 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. 
 
 In some soils, also, distinct portions of vegetable fibre, such as portions of 
 roots, &c., are present, and may be separated, mechanically dried, and weighed. 
 
 12"^. Of other orannic substaiica present in tJie .soil. — The sum of the weights 
 of the above substances deducted froin tiie whole weight of organic matter, as 
 determined by burning, jjives that of oUfr organic substances present in the 
 soil. The quantity of these is in general comparatively small, and, unless they 
 are soluble in water, there is no easy method of separating them, and determin- 
 ing their weigl'.t. The following two methods, however, may be resorted to: — 
 
 1°. 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 tlms boiled with water, the fine particles do not readily subside. 
 Sometimes, after stnndingfor several days, tiic water is still muddy, and passes 
 muddy through the filter, but, after being evaporated, as above recommenaed, to 
 a small bulk, most of tlie fine clayey matter remains on the ])aper when it is 
 again filtered. As soon as it ha.'; thus passed through clear, the liquid may be 
 evaporated to perfect dryness at 230'^ F., and weighed. Being now treated 
 with Avater — a portion will be dissolved — this must be poured oif, and the inso- 
 luble 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 ag.nn weighing. This loss may be 
 considered as huinic acid rendered insoluble by drying.§ It does not require to 
 be added to the weight of humic acid already determined (10"), because in 
 that experiment a portion of soil was employed which had not been boiled in 
 wiUer, and from which therefore the carbonate of sod.i would at once extract 
 all the humic acid. The present experiment need only be made when it is de- 
 
 * This isascortaineri by collectiiif; a few Orops of what i,^ pa.«.«in5 tlirougli upon a piece of 
 clean glass or platinum, and dryins; tlieni o» or the lamp, wlien, ifa perce|)lihle stain orspotia 
 Jcft, the substance is not snflir.lently waslied. 
 
 t Ttie asli left by Ihe paper employ eti for filters should aUvay« be known. This is ascer- 
 tained, once for all, by drying a quantity of it in the way described in the previous 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. 
 
 t The portion which thu.'j remains in tlie 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 mailer, and after being collected on a filter, washed, and dried, 
 the weight of organic matter in the precipitate may be determined approximately as des- 
 cribed under 12° (2°). 
 
 i See Lecture xiii., S 1. 
 
No. v.] OF THE ORr.ANIC MATTKU HRESKM' IN TltK SOIL. 31 
 
 sirable 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 chemists consider this quantity to be very considerable, and to exercise 
 an important influence upon vegetation. 
 
 Tliat 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 Imo 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 coiupounds of which, with lime, 
 alumina, and proi-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 indication of the presence of nitric acid — in the form of ni- 
 trate of potash, soda, or lime. In this case the loss by burning will slightly ex- 
 ceed" the true amount of organic matter present, owing to the decomposition and 
 escape of the nitric acid also. The mode of estimating the quantity of this acid, 
 when it is present in any sensible proportion, will be hereafier described. 
 
 2°. The caustic potash employed to dissolve the insoluble humus (ll*^') takes 
 up also any alumina which may have been in comliination with the humic 
 acid or may still remain united to the mudesous'^ 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 distinctly sour taste, this alumina, and the acids with 
 which it is in combination, 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 whicli 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 IJOO'-' F., weighed and heated 
 for some time in a close crucible over the lamp, at a temperature which begins 
 to discolour it, and again weighed. Bfing now burned in the air till it is quite 
 white, and weighed, the last loss may be considered as mudesous or some simi- 
 lar acid. 
 
 The reason why this second method of drying over the lamp is here re- 
 commended, is, that alumina and nearly all its compounds part with their 
 water with great difiiculty, and even with the precautions above indicated, it is 
 not unlikely that a larger per-centage of organic matter 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 
 liumic acid, the insoluble humus, the vegetable fibre, and of the crenic and mu- 
 desous acids, if pres:'nt, 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 s^en to bp in most cases greater than the truth, 
 D3cause any remaining water or any nitric acid the soil maj' contain, are at the 
 same time driven oflT. 
 
 I may further remr.rk 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 wliich 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. — OP THE SOLUBLE S.\LIN'E MATI'ER IN THE SOIL. 
 
 13". With a view to determine the nature of the soluble saline matter in the 
 soil, a preliminary experiment must be made. An unweighed portion must be 
 introduced into five or six ounces of boiling distilled water in a flask, and kept 
 at a boiling temperature, with occasional shakiiig tor 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 
 
 ■ Except where gypsum is present in tlie insoluble portion, which is not unfreqiiently the 
 casp, when the loss will be partly wnter — since gypsum, after being dried at 250°, loses still 
 abuiit 'JO 3 per cent, of water when heated to redness. 
 
32 OF THE SOLUBLE S/4LINE MATTER IN THE SOIL. [Appendix, 
 
 separate portions are to be put into so many clean wine glasses, and the effect 
 produced upon these by different chemical substances careluUy noted. 
 
 If with a few drops of — 
 
 o. Nitrate of Barijta, it gives a white powdery precipitate, which does not 
 disappear on the addition of nitric or muriatic acid, tlie solution contains sidphu- 
 Tie acid. If the precipitate does appear, it contains carbonic acid. In this lat- 
 ter case, tlie liquid will also effervesce on the addition of either of the acids 
 above mentioned. 
 
 b. If with oxalate 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. 
 
 c. If with nitrate of silver, it gives a white curdy precipitate, insoluble in pure 
 nitric acid, and speedily becoming purple in the sun, it may be presumed to 
 contain chlorine. 
 
 d. If with caustic am.rnoiua, it gives a pure white gelatinous precipitate, it 
 contains either alumina, or via.gncsia, 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 reappears undiminished 
 in quantity, it contains aluvtina only. If it be distinctly I ss 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 be present, 
 it may be necessaiy to re-dissolve and acidify the solution a second tune be- 
 fore, on the re-addition of ammonia, the precipitate would entirely disappear. 
 
 If the precipitate, by ammonia, have more cr less of a brown colour, the pre- 
 sence of iron, and perhaps mangancs:, may be inferred. If, on tiie second 
 addition of ammonia, the colour of the precipitate has disappeared, it hao been 
 due to the manganese only— if it still continue brown, it is owing chiefly or 
 altogether to the presence of oxide of iron. If the colour of the precipitate, by 
 ammonia, be very dark, it consists almost entirely of oxide of iron, and may 
 contain little or no aluninia, — when it is only more or less brown, the presence 
 of both alumina and oxide of iron may with certainty be inferred. 
 
 e. 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, 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 remain,t it is probable that folasii or soria, or 
 both, are present. If, on dissolving this residue in a little water, the addition of 
 a few drops of a solution of tartaric acid to it produce a deposite of small 
 colourless crystals (of cream of tartar), or if a drop of a solution of bi-chlo- 
 ride of platinum produce in a short time a yellow powdery precipitate, it con- 
 tains ■potash. If no precipitate is produced by either of these — re-agents as tliey 
 are called — the presence of soda may be inferred. If the yellow precipitate, 
 containing potash and platinum, be separated by the filter, and the solution, after 
 being treated with sulphuretted iiydrogen and filtered to separate the excess of 
 bi-chloride of platinum, be evaporated to dryness — if, then, a soluble saline 
 residue still remain, the solution contains soda as well as potash. 
 
 It is to be observed that some magnesia, if present, may accompany the pot- 
 ash 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 interfere with this preliminary examination as to prevent the 
 experimenter from arriving at correct results (see p. 35, /). 
 
 * Tlie learned rradrr will undprslanii why, for the sake of .sjinplicily, I lake nn nitice of 
 subslancp.s not likely to he present in the i^oil — as, for example, l)aryta, which woiilil here be 
 thrown down alon" with the lime, or of ox die acid, which, etjually with the sulphuric or car- 
 bonic (a), would sive a white precipitate with nitrate of baryta. 
 
 t Not precipitated from its solution by ammonia, for if precipitated it is partly at least 
 chloride of magnesium. 
 
No. v.] OP THE SOLUBLE SALINE MATTER I.V THE SOIL. 33 
 
 /. If the addition of bi-chloride of platinum to the solution directly filtered 
 f/om the soil give a yellow precipitate, it contains either /7o/r/.s/4 or aiumoyiia. 
 If, when collected on the filter, dried, and heatfd to bright redness in the air, 
 white fumes are given olf by this yellow precipitate, and only a spong\' mass 
 of metallic platinum remains behind, the solution contains aiiUiio7iia only. If, 
 with ihi^ platinum, be mixed a portion of a soluble substance having a taste 
 like tlml of common salt, and giving again a yellow precipitate with bi-chloride 
 ofplaiinum, it contains po'a^/i — and if ihc sjjongy platinum contained in the 
 burned mass, after prolonged heating, amount to more than .57 per cent, of 
 its weight, or if it be to the soluble matter in a higher proportion than that of 
 4 to :j, the solution contains both po.'as.'i. and ainmoaw. 
 
 The presence of //.mmonia in the saline substance, or in the concentrated solu- 
 tion, is more readily detected by adding a few drops of a solution of caustic 
 potash, when the smell of ammonia becomes perceptible, or if in too small 
 quantity to be delected by the smell, it will, if present, restore the blue colour 
 to reddened litmus paper. This experiment is best made in a small tube. 
 
 g. If, when the solution, obtained directly from the soil, is evaporated to dry- 
 ness, and the residue heated to redness in the air, a deflagration or burning like 
 match-paper he obs.rved, nitric acid is present. Or, if the dry mass, when put 
 into a test tube with a little mui iatic acid, evolves distinct red fumes on bemg 
 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 cer- 
 tainty be infeiTcd. It will be only on rare occasions, however, that salts, so 
 soluble as the nitrates, will be found in sensible quantity in the small portion 
 of a soil likely to be employed in these preliminary experiments. 
 
 h. If ammonia throw down nothing (see under ^./) from the solution, and if 
 no precipitate appear when chloride of calcium or magnesium is afterwards 
 added, the solution contains no phospkui'tc add. But if ammonia cause a pre- 
 cipitate, and after this is separated by the filter, nothing further falls on adding 
 either of the above chlorides, the phosphoric acid, if any is present, will be con- 
 tained in the precipitate which is upon the filter. Let this, after being well 
 washed with distilled water, be dissolved off with a little pure nitric acid 
 diluted with water, and then neutralized as exactly as possible with ammonia. 
 If a solution of acetate (sugar) of lead now throw down a white precipitate, phos- 
 phoric acid is present. The phosphate of lead — the white precipitate which 
 falls — melts readil}^ before the blow-pipe, and, on cooling, crystallizes into a bead 
 with beautiful crystalline facets. 
 
 Or — if the precipitate thrown down by ammonia be wholly or in part insolu- 
 ble in pure acetic acid (vinegar), that which is undissolved contains phosphoric 
 acid. If acetic acid dissolve the whole, it may be inferred that no phosphoric 
 acid is present in the soil. 
 
 But if no precipitate be thro\vn down by ammonia, instead of the chloride of 
 calcium above recommended, a few drops of a dilute solution of alum may ba 
 mixed with the solution, after adding the ammonia, and the whole well shaken. 
 If the white preci])itate, which now falls, dissolve wholly in acetic acid, no phos- 
 phoric acid is present, and vice versa. 
 
 These preliminary trials being made, notes should be kept of all the appear- 
 ances 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. 
 
 14°. Drtcrminntion of the quant.itks of the several conslituents of the soluble 
 saline mailer. — The quantity of soluble saline matter extracted from a mode- 
 rate quantity of any of our soils is rarely so great as to admit of a rigorous 
 analysis, and the preceding determination of the ki7id of substances it contains 
 will be in most cases sufficient. Cases may occur, however, in which much 
 
34 
 
 or THE sai.uBi.f: SALr.vE matter in the soil. 
 
 [Appendix, 
 
 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 ac- 
 curately detenniiied. 
 
 a. Esiiinaiwii of the S-dphnric Acid. — The solution being gently warmed, a 
 few drops oi' nitric acid are to be added until the solution is slightly acid, and 
 any carbonic acid that may be present is expelled, after which nitrate of baryta 
 is to be added to the solution as long as any thing falls. 'J he white precipi- 
 tate (sulphate of baryta) is then to be collected on a weighed filter, well washed 
 with distilled water, dried over boiling water as long as it loses weight, and 
 then weighed. 'I'he v/eight of the filter being deducted, t every 100 grains of 
 the dry powder are equal to 34-37 grains of siilpliuric acid. 
 
 b. Eslimation i>f Itu: Cktorin". — 'I'he solution of nitrate of silver must be add- 
 ed as long as any precipitate falls, the precipitate then washed, dried at 212° F., 
 and weighed as before. Eveiy 100 grs. of chloriJe of silver indicate 24-67 grs. 
 of chlorine, or 40-88 gi-s. of common sdt. 
 
 c. Esdfiialion of the Liime. — 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 operations, and the precipitates separated by fil- 
 tration — caustic ammonia is to bepotu-ed in, till the solution is distinctly alcaline. 
 
 " This is the case with the rich soils of India aod Kirypf, anil of other warm climate.-^. 
 This will appear fioni ilie fullowinj; analyses of sdme ImJiaii soils, inaje on tlie spot by Air. 
 Fleming, of Bdroclinn, during the hours of leisure left him by his more imi)ortant duties : — 
 
 A)UJ-lys!.s af soils ia Nortli aii,d South Bchar, Bengal Presidency — {200 grains of 
 each being analysed.) 
 
 J. 
 
 - 
 
 
 
 
 c 
 
 .Q 
 
 0) 
 
 ■' 
 
 
 ■s^ 
 
 r; 
 
 fa' 
 
 ■- 
 
 ^^ 
 
 ■; 
 
 3 
 
 -i 
 
 4J 
 
 -2 
 
 IS 
 
 1,. 
 
 u 
 
 .- £ 
 
 •r 
 
 
 
 
 
 
 
 
 
 
 
 
 \>~ 
 
 5 
 
 J3 -a 
 
 c 
 
 
 " .c 
 
 ■3 
 
 
 < 
 
 ■22 
 
 4 
 
 15 
 
 712 
 
 9 
 
 1 
 
 20 
 
 14 
 
 10 
 
 8 13 
 
 14 
 
 ■20 
 
 6 
 
 11 
 
 4 
 
 20 
 
 •20 
 
 19 
 
 9 
 
 9 
 
 1 
 
 2 
 
 10 
 
 !■? 
 
 7 
 
 8 
 
 2 
 
 1 
 
 1-2 
 
 12 
 
 3 
 
 4 
 
 
 1 
 
 6 
 
 
 m''Z=.\ -J 
 
 130 
 
 140 
 
 9^ 
 
 1°. Near Gya, South Bohar. — Ofa dark colour, soapy 
 to the touch when moist, hard and cracks when dry ; 
 yielilsa crop of rice and one of wheat every year. Ne- 
 ver lie.-" fallow, but is covered with water durinj; part of 
 the rainy season, and is productive — from 30 to 50 
 bushels of wheat per acre. 
 
 2°. Soil from the same district. — Also soapy when 
 moisi and cracks when dry — rather more productive 
 than No. 1. 
 
 3*^. From the same district. — Heavy red clay soil, 
 
 , producing wheat, pease, cnllon. or poppy in the dry 
 
 3 6-1 se.HSon, and Indian corn and millet i)i ihe wet season ; 
 
 not inundated in Ihe rains, and sometimes manured 
 
 with ashes of wood and cow dun';. 
 
 4°. Soil from North Behar, Tirlioot. — A deep loam, 
 yieldinH two crops yearly; not inundated, producing 
 wheat, barley, Indian corn, indjg:\ poppy, &c. From 
 25 to 35 bushels of wheat per acre ; is not u.sually 
 mnnured. 
 
 5°. Tirlioot. — Soil lii;ht coloured ; producing nearly 
 the same crops, but not so productive aa No 4. Saline 
 [ efflorescence in patches. 
 
 f 13^. Tirlioot.— Not so productive as No. 5, and some 
 patches nearly sterile from Ihe saline efflorescence, 
 e.xcept in the rainy sea.^nn. when it produces good 
 crops of" Indian corn. Soillight coloured. 
 
 1 have already alluded (Lecture VIII., p. 159) to the influence which this large proportion 
 of saline matter exercises upon the luxuriance of the vegetation. 
 
 t Or the wliole may he 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 dua 
 proportion deducted from the weiglit of the sulphate. 
 
Xo. v.] or TtlE SOLUBLE .SAf.IM: .MATTF.ll IX T.'IK 3011.. 3,'> 
 
 If no precipitate fill, oxalate of ammonia is to be added as lon;^ as any wliite 
 powder appears to he profluced. T!ie solution must then be let't to stand over 
 niijht — thai the wliole of the lime may separate, — the white powder afterwards 
 collected on a filter, washed, drieJ, and burned withthe filter, at a low red heat. 
 The grey powder obtained is carbonate of lime, every lUO grs. of which con- 
 tain A'i'll grs. of liaie. 
 
 d. EsUmoJhtti. of Ike O.ri'lc of Iron o.nd of the Aluiiiriia. — But if a precipitate 
 fall on the addition of ammonia, as above prescribed — the solution may con- 
 tain magnesia, alumina, and the oxides of iron, and manganese. la this case 
 the precipitate is to ber.^-dissolvcd by the addition of muriatic acid till it is dis- 
 tinctly acid, and amaionia again adde.l in slight excess. If any precipitate now 
 fall, it will consist only of alumina and oxide of iron, unless magnesia and 
 oxide of inanganes-^ be present in large proportion, when a minute quantity of 
 each may tall at the same time. 
 
 The precipitate is to be collected on th ^ tilter as quickly as possible, — the fun- 
 nel being at the same time covered with a plate of glass to prevent as much as 
 possible the ai-cess of the air, — w.ishei with distilled water, and then re-dissolved 
 in muriatic acid. This is best eflecied by spreading out the filter in a small 
 porcelain di,sh, adding dilate acid till all is dissolved, and then washing the pa- 
 per well with distilled water. A few drops of nitric acid are. then to be added, 
 snd the solution heated, to peroxidize the iron. A solution of caustic potash 
 added in excess, will at first tlrrow down both the oxide of iron and alumina, but 
 will afterwards re-dissolve the alumina, and leave only the oxide of iron. This 
 is to be collected on a filter, washed, dried, heated to redness, and weighed. 
 Every 100 grains of this peroxide of iron are equal to H!)-78 grains of protoxide, 
 in which state it had most probably existed in the original solution. 
 
 To the potash solution muriatic acid is added till the alkali is saturated, or till 
 the solution reddens Htmvs papar,* when the addition of a.nmonia precipitates 
 the alumina. As it is difficult to wash this precipitate perfectly free from potash, it 
 is better to dissolve it again in nmriatic acid, 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. 
 
 r. Estlmafion of the Maii^iinenr. — To the ammoniacal solutions from which 
 the oxalate of lime has been precipitated (-), a solution of hydro-sulphuret of 
 ammonia is to be added. The manganese will fall in the form of a flesh red 
 snl|3huret. When this precipitate has fully subsided, it must be collected on the 
 filter ;>nd washed with water containing a very little hydro-sulphuret of ammo- 
 nia. The filter is then jiut into a glass or porcelain basin, the precipitate dis- 
 solved off by dilute muriatic acid, and the solution filtered, if necessaiy. A so- 
 lution of carbonate of potash then t'arows down carbonate of manganese, which 
 is collected, dried, and heated to redness in the air. Of the brown powder ob- 
 tained 100 grains indicate the presence of 93-34 grains of protoxide of manganese 
 in the salt or solution under examination. 
 
 f. Estimation oftlie 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 hydro-sulphuret of ammonia previously added. The 
 solution is then evaporated to dryness, and the dry mass heated to redness to 
 drive off all the amtnoniacal salts' previously added. A few drops of diluted sul- 
 phuric acid are added to what remains, to change the whole of the magnesia 
 mlo sulphate, the mass again heated to redness and weighed. One hundred 
 grains of this sulphate indicate the presence of 3401 grs. of pure magnesia. 
 
 But if potash or soda be present — the weight of which it is desirable to deter- 
 mine— the simplest methoa is to take afresh portion, 15 to 20 grains, of the 
 
 * Litmus paper is paper siaineii by lilpping it into a solution of litmus, a vegetable blue co 
 lour, prepared and sold for the purpose of detecting the presence oi free acids, by which it 
 is reddened. 
 
36 OF THE SOLUBLE EALIN'E MATTER IN THE SOIL. {App37l^tX, 
 
 saline matter under examination. If any sulphuric acid be present in it add n'- 
 tratc of baryta drop by drop to the solution till tlie whole of the acid is exactly 
 thrown down — if possible, no excess of baiyta being left in the solution — then 
 precipitate the alumina an 1 oxides of iron and manganese, and the lime, if any 
 of these be present, and, finally evaporate to dryness, and heat to redness as be- 
 fore. The di-y mass is now to be dissolved in water, adding, if necessary to 
 comp'eL-: the solidvm, a few drops of muriatic acid. A quatuity of red oxide of 
 mercury i,s then to be added to tlie concentrated solution, and the whole boiled 
 down to dryness. Water now dissolves out the potash and soda only, and 
 leaves the magnesia mixed with oxide of mercury. This is to be collected on 
 a filter, washed — not with too much water — and heated to redness, when the 
 magnesia remains pure, and may be weighed. 
 
 g. EsiimUlowiif tfie Piitisiaiil Si Ui. — Tiia solution containing the potash 
 and soda, is to bs evaporated to dryness, and heated to redness to drive off any 
 mercury it may contain. The weight of the mass which consists of a mixture 
 of chloride of potassium with chloride of sodium (common salt) is accurately 
 determined, it is then dissolved in a small quantity of water, arui a solution of 
 bi-chloride of platinum added to it in sufficient quantity. Being evaporated by 
 a very g ntle heal nearly to dryness, weak alcohol is added, wliich dissolves the 
 chloride of S'idium and any excess of .salt of platinum which may be present. 
 The yellow powder is collected on a weighed filter, washed well v/ilh spirits, 
 dried by a gentle heat and weighed on the filter. Every 100 grains indicate 
 the presence of 19H3 grains of potash, or 3056 grains of chloride of potassium. 
 The quantity of chloride of sodium is estimated from the loss. I'he weight 
 of the chloride of potassium above found, is deducted from that of the mixed 
 chlorides previously ascertained, the remainder is the weight of the chloride of 
 sodium. Every 100 grains of chloride of sodium (common salt) are equiva- 
 lent to i33'21) of soda. 
 
 A. Es'iinatian nf the Ammojna.—lf ammonia be present in tlie solution along 
 with potash and other substances, die method by which it can be most easily 
 estimated is to introduce the solution into a large tubulated retort, to add water 
 until the solution amounts to nearly an English pint — then to introduce a quan- 
 tity of caustic potash or caustic baryta, and to distil by 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 is evaporated ncarlij to dryness by a veiy 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 spirit, dried by a very gentle heat, 
 and weighed. One hundred grains indicate the presence of 1-&3 grains of 
 ammonia. 
 
 Or the yellow powder, without being so carefully dried, may be heated to red- 
 ness, when only metallic platinum will remain. One hundred grains of this 
 metallic platinum indicate the presence of 17 39 grains of ammonia. 
 
 i. EslimaJion of the Phosphoric. Add. — If phosphoric acid be j^resent in the 
 solution, it will be contained in the precipitate thrown down by ammonia (^/). 
 As it will never be found but in very small quantity, the rigorous determination 
 of its amount is a matter of considerable ditSculty. The following method 
 already described (13'', /(,) may be adopted. The precipitated alumina, oxide 
 of iron, &c., thrown down by ammonia, after being dried, are to be mixed with 
 three times their weight of pure diy carbonate of soda, and fused together in a 
 platinum crucible. l"he fused mass is then to be treated with cold distilled 
 water till every thing soluble is taken up. The filtered solution is next to be 
 gently heated and exactly neutralized with nitric acid, when a solution of ni- 
 trate of silver will throw down a ii'hiie 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. 
 
A'O. I'.] OF Tlin SOLVBLF. SALINE MATTEH IN THE SOIL. 37 
 
 Or thp filtered solution raay be treated with muriatic acid, ammonia added in 
 excess, and tlien a solution of chlondvj of calcium. Bon-c earth will fall, which 
 is to be collected, washed, heated to redness, and weighed. One hundred 
 grains of it contain 48-45 of phosphoric 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 solu- 
 tion ((■), from which the lime is not yet thrown down, as when little alumina 
 and oxide of iron are pre.sent, a small portion of lime and magnesia, if con- 
 tained in tiie salt under examinauon, may have fallen along with them in com- 
 bination with phosphoric acid. 
 
 The alumina and oxide of iron which rest on the filter are to be separated 
 and estimated as already described {a). 
 
 k. Estimation of Ike Carbonic Aid. — The lime and magnesia dissolved by 
 cold diluted muriatic acid are partly in combination with carbonic acid and 
 partly with the hu.nic, ulmic, and other vegetable acids. To determine the 
 carbonic acid, 100 grains of the soil dried at •J12-', ;ire to be introduced into a 
 small weighed flask, and then just covered by a weighed quantity of cold di- 
 luted 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 tiie 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 would be more rigorously ascertained 
 by fitting into the mouth of the flask a lube containing chloride of calcium, 
 and then heating the solution to expel the carbonic acid. 
 
 Kvery hundred grains of carbonic acid indicate the presence of 77 24 grains 
 of lime in the state of carbonate. The weight of lime in this state, deducted 
 frowi the whole weight obtained as above (c), gives the quantity which is ii 
 combination with oihex vrganic acids. 
 
 IV. OP TIIK INSOLUBLE EARTHY MATTEK OF THE SOX. 
 
 15^. "When the soil has been washed with distilled water as above directed — 
 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 jihosphates of lime, and alumina, are dissolved — 
 with any lime, magnesia, oxide of iron, or alunnna, which may have been in 
 co:nbination 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. 
 
 16". I'he undissolved portion may now be treated with hot concentrated 
 muriatic, 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 subsequendy 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, potasli, 
 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. 
 
 17°. 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 till the sulphuric acid is nearly all driven oflT. 
 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 sulphuric acid must be repeat- 
 
 28* 
 
OF Tin; SOLUBLE SALINE MATTER IN THE SOIL. 
 
 [Appendix, 
 
 (j fliil r 
 
 C JS 
 
 _o 
 
 M 
 
 
 CC 
 
 
 
 s 
 
 o 
 
 o 
 
 p. 
 
 «J 
 
 
 
 
 <t> 
 
 <u 
 
 
 Ul 
 
 
 
 
 Xf 
 
 
 
 t« 
 
 S 
 
 g cj c-1 d 
 
 2 'T3 rS , 
 
 -5 S 
 
 2 s :h.2 -S 
 
 \% 
 
 ,,_, 
 
 c 
 
 a 
 
 .1 
 
 C5 
 
 •c 
 
 'O 
 
 G 
 
 < 
 
 
 
 
 
 5i 
 
 
 To 
 
 
 
 c;; o 
 
 b.Og d. 
 
 0.2 o 
 
 J-^ L 
 
 E^.,^ 
 
 .c i .= "o? ^ 
 
 .= E 'S ■=. 
 
 S " ■- " 
 
 r 1^ s: «) M 
 
 « K 0. _ 1> 
 
 o= !: t c 
 
 
 = 'g « c S y: " .i -c ■= ■ 
 
 ■< K •- •- E ^ .S 5 S £ , 
 
 
 !2 = 
 
 ■f-l a.' <« rS -5 ? '§ -S " 
 
 
 i — « C Cf .C 
 
 ■'c i '""a . 
 
 ■^ c-E-S.'" 
 
 o 
 
 '.:: ™ V « « 
 
 — _ g _ X CJ= 
 
 3 ■? ~ ?' s o 
 
 
 , .^ e e ,.^-3 
 
 *""C 
 
 ,. JS O 
 
 r-|.||g 
 
 
 .= •= 
 
 .S a 
 
 eg 
 
 2; ~ !^" -' ^ 
 
 
 
 1' c^c — 
 
 etf-5 
 
 O.J3 
 
 .— 0^ - "* C 
 
 
 'o ^ 
 
 I.T3'— " 
 
 ^ '^ 
 
 III 
 
 0. = -r; c w 
 
 J -5 ts t jj 
 
 1° 
 is 
 
 e-— _ >,<i. 9 
 
 
 *-* W QJ 
 
 ^. >2 .= .c .c S 
 
 <- « g 
 
 . &.C 
 
 
 
 to 
 
 
 
 
 c-n c i^ a; 1) 
 
 -'. W t£1? A 
 
 " - r j: > a" b = 
 
 ■SiilsSE-'* 
 
 = g^.= fc "2 = = a; 
 
 ^ = - > t3J= 
 
 Z— c l- O 
 
 ^ " = S ■§ ; 
 ■E§N|f 
 
 = C = C 4) 
 
 ;= « 2 o j: ^ 
 
 
 
 
 
 c St — •/. ,2 -■ 
 
 — C „ ,, K O 
 
 Ol 1 . i' I. C — 
 
 ^o££.Eta 
 
 — ■- •- i OJ B. 
 
 l2 
 
 lO 
 
 1^ 
 
No. v.] or TRK SOLUCr.E SAI.ING MATTER I\ TIIH SJIL. 39 
 
 ed, till on treating with water and ammonia, as before, no more alumina ap- 
 pears. 
 
 h. Or that portion of the soil on which hot iruriatic 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 coinnletcdy fus;d. The mass is then to be treated with 
 diluted muriatic acid till every thing soKible is taken up, the fikered solution 
 evaporated to dryness, the diy mass moistened with muriatic acid, and again 
 treated With wat^T. If any thing is left undissolved it will be silica, and if any 
 alumina be contained in the solution, it will be precipitated by ammonia, and 
 may be collected, waslied, dried, and weighed, as already described. The so- 
 lution may also bj tested for magnasia, and if any be present it may be sepa- 
 rated by tiie process already explained. 
 
 The former of the.se two methods is to be preferred as the simpler, though it 
 will also require considerable caie and attention. 'I'hat which the sulphuric acid 
 leaves behind must be washed, dried, heated to redness, and weighed. It will be 
 found to consist chiefly of quaitz sand, and fin?ly divided siliceous matter. 
 
 The accuracy and c:Are with which the whole of these processes have been 
 conducted is tested by addhig 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 
 likely to err, is in the washing of the several precipitates lie 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. 1'he precipitates 
 should always be washed with distilled water, and the washing continued until 
 a drop of what passes through leaves no stain when dried upon a bit of glass. 
 
 No. VI. 
 
 ACTION OF GYPSUM. — {See pages 21^2-21.) 
 
 In the text I have stated what appear to me the most probable effects which 
 gypsum is fitted to produce upon the soil. Some of the numerous opinions that 
 have been entertained upon this point are thus summed up by Illubeck: — 
 
 " According to /ui/Z/iT, the action of gypsum depends upon the power pos- 
 sessed by lime to form witli the oxygen and carbon of the atmosphere compounds 
 which are favourable to vegetation ; according to RKckcrt, it acts like any other 
 food ; according to Ma.y:r and Bivnui, it merely improves the physical proper- 
 ties of the soil ; while, according to fi-il, it is an essential constituent of the plant. 
 /fc.///,v> called gypsum the saliva and gastric juice of plants ; UumboldL , Gir- 
 tan:r, and AVjcrt T.'u/cr considered it as a stiinulant by which the circulation 
 of plants is promo:,ed ; and C/iap'al ascribed its action to a supposed power of 
 supplying water and carbonic acid to plants. Davi/ regarded it as an essential 
 constituent of plants, because it acts only where gypsum is wanting in the soil, 
 while other English agriculturists have supposed it to promote fermentation in 
 the soil. According to Laichcnkr, it acts as an exciting power without mixing 
 itself with the sap of the plant; according to LiehU';, it fixes the ammonia of the 
 atmosphere; and, according to J?m77M?w/ and Sprens^d, it supplies sulphur 
 for the formation of the legumin of the leguminous plants (the most pro' V 
 view)." — Erndkrung der Pjlunzcn, p. 70, note. 
 
 To the above extract I may add, tliat Mr. Cuthbert Johnson, so lor 
 for his many valuable writings upon agriculture, in following out the 
 of Reil and Davy in a recent paper on the use of gypsum (Jour. 
 
40 ACTION OF GVPsuM, [Appendvt, 
 
 Agr. Society, ii., p. 108,) has stated that a crop of clover or sainfoin contains IJ 
 to i! cwt. of gypsum per acre, exactly tiie quatuity whicli tlie f.iriners of Kent and 
 Hampshire find it useful to apply to their grass lands eveiy year. 'I'his state- 
 ment affords a very simple explanation of the use of gypsum, and one which 
 at first sight leaves nothing to be desired. But it proves too much, for it 
 supposes the whole of the gypsum waic'n is laid upon the grass or clover 
 field to be removed year by year in the crop, and makes no allowance either for 
 the quantity which must necessarily be carried off by the rains, or for tiiat 
 whicii must be sometimes at least laid on in the form of farm-yard or other 
 similar manure. Nor does the result >'f analysis confirm the above statement 
 as to the quantity of gypsum contained in the crop of clover or sainfoin. By 
 referring to page 2-2'J, it will be seen that 1000 lbs. of dry hay do not con- 
 tain, on on average, more than 4 lbs. of sulphuric acid — equal, supposing it all 
 to be in combination with lime, to 8j lbs. of gypsum. Or a ci-op of 1 J tons of 
 hay contains the elements of about 30 lbs. of gypsum — only about a sixth 
 part of what is usually added as a top-dressing to the land. 
 
 No. VII. 
 
 SUGGESTIONS FOR KXPERIMENTS WITH THE SOLUBLE SILICATES 
 OF POTASH AND SODA. 
 
 In the text (pp. 207 and 319,) 1 have had frequent occasions to refer to the pre- 
 sence in the soil of the silicates of potasli and soda, and to their supposed action 
 in supplying silica to the stems of the grasses and of the corn-bearing plants. 
 It would be interesting in a theoretical point of view, to ascertain, by experi- 
 ment, more fully than lias hitherto been done, how far thf^ application of these 
 substances to the growing crops would, as a general rule, improve or otherwise 
 affect their growth. Bui as those experiments whicii have already been made 
 (page 34'J), afford a strong presumption in favour of their economical value, 
 it becomes a matter of practical interest also to investigate their apparent effects 
 upon each of our cultivated crops. 
 
 These experiments are placed within the reach of the practical farmer during 
 the ensuing season, by the introduction of the above compounds into the 
 market at a reasonable rate (page 3(53). I tlierefore subjoin a few sugges- 
 tions for experiments with these silicates, in the hope that some of the many 
 zealous and intelligent practical men, wiio are now directing their attention to 
 the applications of chemical science to agriculture, may be induced to enter 
 upon this field of inquiry during the ensuing spring. 
 
 1°. In order to convey silica into the plant, it appears to be chemicallj- indif- 
 ferent whether the silicate, of potash or that of soda be placed within reach of 
 its roots. But as the silicai(> of soda can be manuflictured very much cheaper 
 than that of potash, it is desirable above all to try the effects of this compound 
 — upon the grasses and corn-bearing plants especially. 
 
 2^. But as in the ashes of most p\ants potash is found in larger quantity than 
 soda, it is possiMc that the effect of th(, silicate of potash upon some soils may 
 be so much greater than that of the salt of soda as to counterbalance the dif- 
 ference of expense. Hence the propriety of extended trials with this com- 
 pound also. 
 
 3=. But as in the ashes of all our cultivated plants both potash and soda are 
 found, it may be that a mixture of the two silicates may act better than either 
 alone. It will be proper, therefore, to apply such a mixture in different pro- 
 portions, and to compare it effects wi^ those of each of the silicates laid 
 on singly. 
 
No. VIII.] OP THE SOLUBLE SILICATES OF POTASH AND SODA. 
 
 43. 
 
 The first seriss of comparative experiments, therefore, would be as follows : 
 
 The application may be from 1 cwt. to 1 J 
 cwt. per acre, laid on as a top-dressing in 
 moist weather early in the spring. Or it 
 may be mixed with a large quantity of wa- 
 ter, and applied with a water-cart. Jn either 
 
 Silicate of 
 Soda. 
 
 Silicate of 
 Potash. 
 
 ,'3 Silicate of 
 I'ljrash, 
 
 .^ Silicate of 
 Soila. 
 
 'j Silicate o 
 Potasli, 
 
 '4 Silicate of 
 Soda. 
 
 case it ought to be in the state i jf a fine powder. 
 
 But altnough the above application.s produce a bene- 
 ficial eflfect upon the crops, it will not necessarily follow 
 that the silica, which the silicates contain, has had any 
 share in bringing about the good result. By mere expo- 
 sure to the air for a length of time the potash or soda of those silicates will absorb 
 carbonic acid from the atmosphere, and be converted into carbonates. 'I'he 
 same will take phice more rapidly still in the soil, where carbonic ac;d abounds 
 'ihis coiiversioii of the alkali into carbonate wiil set free a large part of the 
 silica — in a state it is true in which it is in some degree soluble m water (page 
 20t),) — but in whicn, nevertheless, it will find its way into the plant with 
 much more difficulty than if it had remained in the state of a soluble silicate. 
 
 Now as the caihomUcs of potash and soda are known to promote vegetation 
 (page 3-.i8), — though even with these, sutiicient trials have not yet been made 
 — it is possible, as 1 have remarked above, that a good efFect may follow the 
 application of the silicates, and yet it may be altogetlier due to the action of the 
 carbonates which are formed by their decomposition. It is of consequence to 
 ascertain if this really be the case, because the quantity of carbonates which 
 would be formed by the decomposition of the silicates could be laid on directly 
 at one half of the price at which the silicates can as yet be sold. 
 
 I'he second sr-ries of comparative experiments, there.Core, which it would be 
 interesting to try, would be such as the following: — 
 
 The quantities here indicated are by the acre— that 
 of carbonate of soda is given so great, Ijecause this salt 
 contains upv."ards of three-fifths its weight of water (see 
 p. 215.) 
 
 Another consideration o\ight not here to be omitted. 
 Nature, as has been frequently illustrated in the text, 
 feeds her plants with a mixture of many diiferent sub- 
 stances, and by the aid of such mixtures they always 
 thrive the best. 'J'he full benefit of the silicates, when 
 applied alone, will be experienced only when every oth- 
 er ingredient which the plant requires is already present in the soil, and in suf- 
 ficient abunilance. But this can rarely be the case. Its success will be mors 
 sure, therefore, if it be applied in a slate of mixture with other saline substances 
 which are known to be more or less useful to vegetation, and which will not, 
 upon admixture, decompose these silicates. Such are common salt and the 
 sulphate and nitrate of soda. 
 
 A third series of comparative experiments, therefore, might be made, in which 
 from 1 to IV cwt. per acre of the following mixtures might be applied: — 1 '-'. 
 Equal weights of common salt, of thij sulphate of soda, of nitrate of so'lc, and 
 of silicate of /^c.i.'c?.s-/i; 2". Equrd weights of the same substances, omitting the 
 silicate of potash ; 3'^. Equal weights of common salt, ot' iJnj sulphate of soda, 
 of nitrate of potash, and of silicate of so/la ; and 4'-\ Equal weights of the same 
 substances, omitting the silicate of soda, or substituting carbonate of soda in 
 its stead. 
 
 The sulphate of magnesia (Epsom salts) or of lime (gypsum) can not be 
 safely used along with the silicates, as the magnesia or lime they contain may 
 decompose the silicates— forming sulphate of potash or soda and silicate of 
 magnesia or lime, in which the silica is insoluble, and could not, therefore, until 
 a further chemical change took place, find its way into the roots of the plant. 
 
 Silicate of 
 Potash, 
 1 cwt. 
 
 Silicate of 
 Soda, 
 1 cwt. 
 
 Crude 
 Potash or 
 PeaiUi.-^h, 
 
 7.5 lbs. 
 
 Crystallized 
 
 Carbonate 
 
 of Soda, 
 
 100 lbs. 
 
EXPERIMENTS ON TURNIPS. 
 
 [Appendix, 
 
 No. VII [. 
 
 RESULTS OF EXPERIMENTS IS PRACTICAL AGRICULTURE, 
 MADE IN 184'2. 
 
 I have much gratification in laying before my readers the results of a second 
 year's series of experiments undertaken in consequence of suggestions thrown 
 out in previous parts of this Appendix, or of opinions expressed in tiie body of 
 the work. It is one of the numerous good results which have followed from the 
 issue of these Lectures in a jieriodical form that I have the pleasure of incoipo- 
 rating in the same volume the results of experiments made during two succes- 
 sive years. No one who studies with care the experiments which follow, and 
 the few remarks I have appended to them, will hesitate in pronouncing them to 
 be as a whole the most valuable contributions to accurate experimental agricul- 
 ture ever hitherto published. The results are not all equally important, nor all 
 equally instructive, but they are the first fruits of a new line of research, which 
 will lead us hereafter to the discovery of important general truths. They show 
 that practical men are now on the right road, and — spreading as scientific know- 
 ledge now is among tiie agricultural body — 1 trust there is no fear of their here- 
 after being prevented from pursuing it. 
 
 A.— EXPERIMENTS ON TURNIPS. 
 I. The first series of experiments was made with the view of obtaining an- 
 swers to these two questions : 
 1°. IVAiil. are the rclativ:: rffccls of different, saline suhstances upon the tvrnip crop 
 
 under the same circmri stances ? and 
 2°. How far may these subslances be employed alone to supersede farm-yard manure 
 in the cnUurc of turnips? 
 
 Turnips srowii in Salter's Bog. — Field fiirrow-draiiicd and subsoil ploiijjhed. Manures ap- 
 plied partly in drills before sowinji on 1st June, and partly as topdrc-sins on 28th July, 
 1842. The salt and nitrate of soda last applied were dissolved in water ; the others applied 
 dry. The quantity of land in each plot leas one-thirteenth of an acre. 
 
 No. 
 
 Descri[ilion of 
 Uressins. 
 
 Nothing 
 
 Common Salt. ... 
 Ciimmon Salt.. . . 
 
 Rape-dust 
 
 Nitrate of Soda. 
 Nitrate of Soda.. 
 
 Rape-dust . 
 
 Nitrale of Soda.. 
 Sulphate of Soda. 
 Sidpliate of Soda. 
 Sulphate of Soda. 
 
 Rape-dust 
 
 Rape-dust 
 
 Guano 
 
 Manure applied. 
 
 1st June. SSthJuly Total 
 
 lbs 
 2 
 
 67 
 2 
 
 67 
 ; 2 
 ' 2 
 
 67 
 
 67 
 
 8 
 
 bush. 
 
 a 
 
 lbs 
 
 67 
 
 9 
 
 bush. 
 
 1 
 
 Produce 
 weight 
 of bulbs. 
 
 lbs. 
 
 sts. 
 
 lbs 
 
 _ 
 
 4:^ 
 
 11 
 
 8 
 
 23 
 
 
 
 r.^( 
 
 68 
 
 10 
 
 8 
 
 ■M 
 
 6 
 
 67 ( 
 
 45 
 
 8 
 
 st^ 
 
 35 
 
 12 
 
 ^ 8 
 
 29 
 
 7 
 
 ^ti 
 
 39 
 
 12 
 
 134 
 
 4R 
 
 3 
 
 17 
 
 61 
 
 6 
 
 2i 
 
 9 
 
 9 
 
 Remarks. 
 The rest of the field, 
 grown with farmyard 
 manure, was a fair ave 
 rage crop. Those expe- 
 rimenttMl upon were 
 complete failure, owing 
 partly, no doubi, to the 
 severe drought of the sea 
 son, bur chiefly to the 
 want of farmyard dung. 
 The seeds brairded bad- 
 ly, and the drills were 
 tilanky throughout. Few 
 of the plants reached any 
 size, and thebestof therii 
 were inferior to the plants 
 immediately adjoining 
 sown at the same time. <& 
 similarly treated, except 
 as respertsthe manuring 
 
 The foregoing experiments were made at the suggestion of Lord Blantyre on 
 the home farm, at Lennox Love, near Haddington, and have been reported to 
 me, at his Lordship's request, by Mr. William Goodlet, under whose immedi- 
 diate superintendence the whole were conducted. 
 
 The reader will not suppose, because they proved what are commonly called 
 
No. VIII.] EXPERtMENTS ON' TURNIPS. 43 
 
 failnrrs, that therefore they are of no value. On the contrary, they so far satis- 
 factorily answer the questions they were intended to solve. They show 
 
 1°. That s:\line manures in that locality cannot economically take the place 
 of farm-yard manure, even for a single season. 
 
 •2°. That saline manures are even hurtful in the present condition of the land, 
 when employed alone — producing a smaller crop than if no manure had been 
 applied at all, and some of them in a remarkable degree. This appears to be 
 especially the case with common salt, which at the rate of 1 cv.'t. an acre reduced 
 the crop of bulbs nearly to one-half of what was yielded by the unmanured por- 
 tion of the field. It is still more striking that nitrate of soda applied at the same 
 rate should diminish the crop though in a less degree than connnon salt — and 
 that soot should afmost kill it entir.'ly, and that 15 cwt. of rape-dust per acre 
 should produce scarcely any effect. In regard to guano, it was applied in too 
 small quantity to do all the good of which it was capable had it been laid on 
 more largely. If (3 or 8 cwt. instead of li cwt per acre had been used, the crop 
 would probably have equalled that obtained by the use of farm-yard manure. 
 
 There is no doubt that to the CKtrems drought of tlie season, as Mr. Goodlet 
 observes, must be ascribed the injury or actual lessening of the crop, in this case, 
 by the use of saline manures. The drought brings up the saline matters to the 
 surface, and thus enables it to encrust, and weaken, or entirely kill, the growing 
 plants. The want of rain in 1813 was much more fell in the Eastern part of 
 Scotland than in the West, where the greater part of the succeeding expeii- 
 ments were made, and where occasional showers refreshed the land. 
 
 One other observation I may make. Had the saline matters beer\ mixed 
 with a fair projjortion of farm-yard n)anure, it is probable that even on this field 
 the effects would have been very ditTerent. One reason fir tiiis expectation is, 
 that the plants being kept in a rapidly growing state — partly use up, and even 
 eagerly a[)propriatc, a large portion of the saline matter as it rises to the surface 
 — and by their strength are enabled to resist the injurious action of any excess, 
 which in ordinary circu)nstances is likely to remain. The reader, however, 
 will not ask why the experiments were not so made — for he has already seen 
 that their object was to ascertain the effect of saline manures applied al^ne. 
 From their results, however, he will draw for himself the important practical 
 rule, that hiorJinani circumstances it is unsafe to Inist his turnip crop to saline 
 manures aloni: — that they may assist the action of farm-yard or other similar 
 mixed manures, but cannot supply their place. But upon this point the suc- 
 ceeding series of experiments throw much further light. 
 
 II. The special object of the follosving four series of experiments was to as- 
 certain — 
 
 P. Tkc reWivc effects ckiejly of various rtiixcd 'manures upon several varieties 
 of turnips ; and 
 
 2°. Whether anti of these mixtures could alone be cconovjicalhj used to supersede 
 farm-yard vianurc. 
 
 They were ma le at the home-farm at Barochan, near Paisley, under the 
 direction and superintendence of Mr. Fleming, whose excellent experiments, 
 made in 1841, are recorded in a previous part of this Appendix (pp. 17 to 24). 
 Mr. Fleming describes himself as much indebted to his overseer, Mr. Gardiner, 
 without the aid of whose zeal, intelligence, and careful superintendence, so 
 numerous a body of experiments could neither have been made, nor the results 
 accurately ascertained. 
 
 1°. Comiurativp E.\perim«nls with various suhstanncs iiserl as manures, for growing 
 Sired,'sh Tarnijis : seed sown Gth June, bulbs lifted 25lh Nov., 184'2. 
 Remarks. — The land is a light loam, loose in texture, and of a light brown colour. Sub- 
 soil h^id, ajid full of small stoiiPs : if is of as nearly as po.ssihle the same quality. The fur- 
 nip set'd Wis all sown upon tlio same day. Rain came on the iiijiht after sowinjr, and in 
 conpeqiieiice \hf crops brairded well, and came away sironj. Those wliich .show fhe great- 
 est weiirht in Ihe Table kepf the lead of the others all the season. The numbers of the 
 plots io the Table are placed in the order in which they followed each other on the ground. 
 The crop would probably have been larger had there been more rain. 
 
44 
 
 EXPERIMENTS ON TLKKirS. 
 
 [Appendix, 
 
 No. 
 
 ORCHARD FIELD. 
 
 Description of Manures u.seil. 
 
 Uu.iiiiiiy 
 ai'piied 
 
 per 
 
 imperial 
 
 Acre. 
 
 Produce 
 of IJulb.-i, 
 topped <V 
 tailed, |)ei 
 imp Acre. 
 
 Pi.Hlu.e oi 
 
 Itulbs, loppei 
 
 and tailed, pei 
 
 imperial 
 
 acre. 
 
 Contol Mailwn 
 per imperial 
 
 Acre,iiicluilinj; 
 carnage and 
 putting on. 
 
 I 
 2 
 
 3j 
 
 4 
 
 5 
 
 6 
 
 7 
 
 8 
 
 9 
 
 10 1 
 11 
 12 
 13 
 
 15 
 
 16), 
 
 17 
 IS 
 19 
 20 
 21 
 22 
 •23 [ 
 
 Peat and Nightsoil, mixed. . . . 
 
 20 tons. 
 
 5 cwt. 
 20 bush. 
 
 1 cwt. 
 20 bush. 
 aO bush. 
 
 6 lbs. 
 50 hush. 
 50 bu.<h. 
 10 cwt. 
 10 cwt. 
 50 bush. 
 10 cwt. 
 
 3 cwt. 
 3 cwt. 
 3 cwt. 
 
 50 bush. 
 
 50 bush. 
 
 50 bush. 
 
 50 bush. 
 50 bush. 
 40 bush. 
 
 1 ton. 
 
 1 ton. 
 20 ions. 
 
 lbs. 
 4800 
 4OS0 
 4640 
 
 i 4.320 
 
 3980 
 44(i0 
 
 4240 
 59J0 
 5560 
 4800 
 5-JOO 
 49(30 
 4OH0 
 65(30 
 
 4240 
 
 4480 
 
 4403 
 
 3200 
 
 36U0 
 4lf:o 
 4000 
 39iO 
 5200 
 3440 
 
 tons 
 17 
 14 
 16 
 
 15 
 
 14 
 15 
 15 
 21 
 19 
 17 
 IS 
 17 
 14 
 23 
 
 15 
 
 16 
 
 15 
 
 11 
 12 
 14 
 14 
 14 
 IS 
 12 
 
 cwt 
 2 
 11 
 U 
 
 8 
 
 13 
 
 14 
 2 
 2 
 
 17 
 o 
 
 11 
 
 14 
 11 
 
 8 
 
 2 
 
 14 
 
 8 
 17 
 17 
 
 5 
 
 
 11 
 
 5 
 
 T 
 
 2 
 2 
 
 o 
 
 1 
 
 1 
 3 
 3 
 1 
 3 
 
 1 
 2 
 2 
 
 3 
 
 
 
 1 
 
 2 
 1 
 1 
 3 
 
 2 
 3 
 
 £. 
 6 
 
 
 
 
 1 
 
 
 
 2 
 
 2 
 2 
 2 
 3 
 
 1 
 1 
 3 
 
 
 
 1 
 1 
 
 
 
 1 
 
 5 
 8 
 9 
 10 
 
 s. 
 12 
 12 
 
 12 
 
 2 
 ir, 
 10 
 10 
 
 
 10 
 
 
 10 
 
 4 
 15 
 
 15 
 
 
 
 17 
 
 9 
 b 
 10 
 10 
 9 
 10 
 
 d. 
 
 6 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 9 
 
 
 
 C 
 
 9 
 
 10 
 
 
 
 
 
 
 
 
 
 [miration of Daniel's mixture. 
 
 Wood CharcOMl Powder 
 
 Fresh Animal Charcoal 
 
 Exhausted Animal Charcoal. . . 
 
 Bones diss, in Muriatic Acid... 
 
 Biiochan Artificial Guano 
 
 Turnbull's do. do 
 
 Salt and Quicklime, mixed, > 
 
 3 nionllis old \ 
 
 Soot 
 
 Potash and Lime mixed, 14 f 
 
 
 
 
 Ripe.lu^f 
 
 Woollen Ra;;s 
 
 Xotliins 
 
 2°. Results of Experiments with various Substances used as manures for crowin" .Eflr/y 
 Liverpool Yel/uw Turnips, sown 9ih .lunr, and lifted 2d December, 1^42. The quantitjj of 
 land in each plot was one eighth of an imperial acre. 
 
 No. 
 
 BERRIE KNOWES FIELD. 
 
 Description of Manures used. 
 
 Quantify of 
 Manure ap- 
 plied per im- 
 (lerial Acre. 
 
 Cost per 
 
 includ 
 
 carriage 
 
 pulling 
 
 Acre, 
 ind 
 and 
 on. 
 
 Produce of 
 
 Bulbs, topped 
 and tailpd, per 
 imperial Acre. 
 
 'S 
 
 2J 
 3 
 
 :! 
 
 6 
 
 7 
 
 8 
 
 9 
 10 
 11 
 12 
 
 ■ 3 J 
 
 14? 
 
 :} 
 
 17 
 18 
 
 Natural Guano at 25s 
 
 5 cwt. 
 20 bush. 
 
 5 cwr, 
 20 bush. 
 15 cwt. 
 
 5 cwt. 
 20 bush. 
 
 50 bush. 
 30 t>ush. 
 .50 hush. 
 50 hush. 
 
 1 cwt. 
 
 1 cwt. 
 
 1 cwt. 
 56 lbs. 
 40 hush. 
 56 lbs. 
 28 lbs. 
 40 hush. 
 84 lbs. 
 40 lbs 
 20 bush. 
 
 5 cwt. 
 
 5 cwt. 
 
 JE. 
 ti 
 
 2 
 
 6 
 2 
 
 " 
 
 2 
 4 
 1 
 1 
 
 
 } 
 
 
 
 1 
 
 
 
 
 1 
 
 
 
 
 2 
 2 
 
 s. 
 
 5 
 10 
 10 
 10 
 10 
 
 1 
 10 
 
 11 
 
 3 
 
 17 
 
 
 
 8 
 
 1 
 
 5 
 U 
 
 
 12 
 
 2 
 
 
 16 
 
 3 
 
 8 
 
 1 
 10 
 
 d. 
 OS 
 
 o,* 
 
 l\ 
 
 6 
 6 
 6 
 
 
 
 
 
 Si 
 
 0^ 
 
 6 
 
 
 tons. cwt. 
 32 2 
 
 21 2 
 24 11 
 18 5 
 
 11 8 
 
 13 14 
 17 2 
 
 14 5 
 
 15 17 
 14 17 
 24 11 
 27 2 
 
 20 17 
 
 11 11 
 
 16 14 
 
 21 4 
 24 2 
 
 12 17 
 
 qrs. 
 2 
 
 3 
 2 
 3 
 
 2 
 1 
 3 
 3 
 1 
 1 
 2 
 3 
 2 
 
 2 
 
 1 
 
 1 
 1 
 1 
 
 Wooilashes. ... . . 
 
 
 
 Rape dust 
 
 
 
 Soil simple 
 
 
 
 Potash & Lime mixed, 14 mos. old. . . 
 Salt & Lime mixed, 3 mos. old 
 
 
 Nitrate of Soda 
 
 
 Wooil-ashes 
 
 Nitrate of Soda 
 
 
 Wonilashes 
 
 
 
 Lime and Potash 
 
 Turnbull's Arlifi.ial Uuaiio 
 
 Barochan Artificial Guano 
 
 Soil simple 
 
No. riH] 
 
 EXPERIMEN'TS ON TURNIPS. 
 
 45 
 
 Kemarks.— The rot! is a li^ht liaze) Kim incumbent upon sandstone rock. It was 
 Irciiclied with Ihe spaile. in llie spring ol 184:i, out ol jia.slure jjiiiss^ Ui ihe lieptli of 16 inclies, 
 and ihe roik qiiairied out when it came nearer Ihe suilnce Ihun lliat dc -plti, il wa.s a^am 
 pointed over before sowinu. alier winch ilie drills were made npun llie flat surface wilh (tie 
 hoe, at ttie distance of '<.7 inches between llicm, Ihe manure t:i/:in m by the hand, and co- 
 vered up, the seed sown and rolled in. Ttie weather was very dry at llie timn they were 
 sown, and continued so till ahout the 2UIIi June, accornpHnied wiili east winds and bright 
 sunshine. They brairded modc-rately well, and most of iliem came a«ay sirong and 
 healthy. In ex.iniiiiin>; them, arxl in the woiking llieni, wiiii :h was ilone by the haiid-lioe, 
 many of Ihein showed a remaik-.diU- diflVience Ironi the others ; parlicularly No. 1 was pie- 
 eminent abuce Ihe others fui size a/ Imlbs and stnngth of fo'iage jMany of Ihe bulbs were 
 11 \b<.. in \veif;ht; iho.se wilh Ihe saline and alk.time numuies, such as Nos. 8, y, iO, and 12, 
 were much smaller in bulbs and leaves than No. \, liut were remarkable for fir iiniess and 
 suiiditij uf bulbs. No. 11 was lap ser in size boih of bulbs and leaves, biit suit and lighi in 
 Weight. No. 7 had very hrui solid bulbs, as had also Nos. 2 and 4. The numbers of the 
 plots f;iven in the Table nidicaie the order in which they were grown in ttie field. 
 The Baruihan Artificial Guano consisted of 
 
 Bones dissolved in Murialic Acid 2 cwt. i Nitrate of Soria .28 lbs. 
 
 Charcoal powiler 2 cwt. | Sulphate of Soda and / , iniha 
 
 Sulphate of Ammonia 1 cwi. i fJulphate of Magnesia ^ '^^^" ° 
 
 Common Salt and Gypsum, each 1 cwt | 
 
 Wood ashes 5 cwt. | 12 cwt. 1 qr. 20 lbs. 
 
 See note to page 47. 
 
 3°. Experiments with various Manures on nine Acres of Turnips on Ihe Farm 
 at Crooks, 1842. 
 
 
 
 Qu 
 
 Fintiiy 
 
 
 Produce 
 
 Kinds 
 
 of 
 
 Turnip. 
 
 Va 
 
 ue 
 
 
 Date of 
 
 of Laud 
 
 Manures, and quantities applied to 
 
 in Tons 
 
 ol ma- 
 
 c 
 Z 
 
 Sowing. 
 
 per Scotch 
 acre. 
 
 the land sown, per Scotch acre. 
 
 per Scotch 
 
 acre. 
 
 nures 
 applied. 
 
 
 
 A. 
 
 R. 
 
 
 
 
 £■ 
 
 s. 1 
 
 1 May 28. 
 
 1 
 
 1 
 
 Rape-dusl 5 cwt., Ilumiis 25 bushels. 
 Bone-dust 12 bushels. Peat ashes 5 
 
 
 
 
 
 2,May 30. 
 
 1 
 
 
 
 
 22 
 
 Swedes. 
 
 4 
 
 15 
 
 Rape dust 5 CWI., Bones lU bushels, 
 
 j 
 
 
 
 llnnius 25 bu.<h., Ashes 5 carts.. . . 
 
 20 
 
 Do. 
 
 4 
 
 10 
 
 3 June 6. 
 
 1 
 
 2 
 
 Johnstone lowu dnns 30 tons at 6s., 
 
 
 
 
 
 1 
 4,Junell. 
 
 
 
 3 
 
 
 24 
 
 Yellow. 
 
 10 
 
 15 
 
 Fai m-yard dun^ 25 tons at 7s., Bone:- 
 
 1 
 
 
 
 10 hii.*h. at s. 6d 
 
 19 
 
 Do. 
 
 10 
 
 
 
 5 June 15. 
 
 1 
 
 
 
 Anifirial Giiano (No. 1., p. 50)2 cwl.. 
 
 
 
 
 
 j 
 
 
 
 Hiimus4Ubush., Peat ashes 5 carls. 
 
 20 
 
 Do. 
 
 3 
 
 5 
 
 6 June 17. 
 
 1 
 
 1 
 
 Natural Guano 1 cwl , Humus 40 
 
 
 
 
 
 1 
 
 
 
 bushels ^ 
 
 13 
 
 Do. 
 
 2 
 
 15 
 
 7 June 28, 
 
 1 
 
 1 
 
 Humus 57 bush.. Bones 10 bush 
 
 14 
 
 Do. 
 
 4 
 
 2 
 
 8 
 
 Inly 4. 
 
 1 
 
 1 
 
 ArilfiriHl Guano mix., (No. 11.. p. .':0.) 
 
 121 
 
 White. 
 
 5 
 
 12 
 
 Remarks.— No. 1 Soil a siiflT loam, moist, and in good order ; when the seed vras sown 
 It brairded well, and came awav at once. 
 
 No. 2. Soil raiher lighter ihan Ihe fornier; seed bndrded well, and came away at once. 
 
 No. 3. Soil the same as above ; brairded quickly in consequeme of a shower of rain. 
 
 No. 4. Soil lighter than No. 3; a bail braird, and' liirnips Ions of springing lor want of rain 
 
 No. 5 Soil as above; long i>f brairding in consequence of want of rain 
 
 No. G. Soil as above ; and like No 5, still very dry lor want of rain ; a late braird. 
 
 No. 7 Soil li^hier, mixed wilh pea! ; no rain — bad braird. 
 
 No. 8. Soil heavy clay loiini ; no rain, and a bail braird. 
 
 The two laitcr, from droii^l.t and laie sowing, di.l not prow much till the end of Sep- 
 tember; aniK when checked by frost in the beginning of November, were- still growing 
 vigorously. 
 
 N. B —The land was of difTereut qualities, the seed also sown at different time."!, and in 
 very ililTereiil stales of Ihe aimosiihere, wilh respect to moi.viure, yel the average produce 
 was good ; and although ii is not easy to say which of the artificial manures, under such 
 circumstances, was aciually the best, the general result shows thai any of these used will 
 produce on my land a gonil aveia;:c crop of turnips, and at a less expense than farm-yard 
 manure, and tends to confirm the correctness <if various experiments Irieil by me on a 
 ■ma'lerscale. The measurements tiaving been made by the Scotch chain, I have not al- 
 tered them. No. 8 would probably have been the best turnips, had they been sown earlier, 
 end been assisted by a fall of rain. 
 
•lb 
 
 EXPERIMENTS ON TDHNII'.?. 
 
 [Appendix, 
 
 4°. Reaults of Experiments with ditfu-rent mixed manures, in growing Whi>e Globe Tur- 
 nips, on new treiicliedland, Bucklatliijr Field. Sown 13th July, uiid lilted Ibih December, 
 1U12. 
 
 c 
 
 Description of Manure used. 
 
 Quantity 
 
 per 
 
 imperial 
 
 Acre. 
 
 Price of 
 
 Manure 
 
 per 
 
 Acre. 
 
 Weight in 
 imperial 
 pounds pr. 
 3a til Acre 
 
 Wfiglit in: 
 Tonn, &c. 
 per impe- , 
 rial Acre. 1 
 
 1 
 
 3 
 
 4 
 
 
 60 bush. 
 6 cwt. 
 5 cwt. 
 5 cwt. 
 
 £. s. d. 
 3 (1 
 
 1 10 
 
 2 10 
 6 5 
 
 Ihs. 
 f.9i0 
 490,1 
 
 t;.«)0 
 
 9170 
 
 ions. cwt. 
 21 5 • 
 
 TunibuU's improved Bones 
 
 17 10 
 
 22 10 1 
 
 iValural Guano 
 
 39 15 1 
 
 The Natural Guano was purchased December, 1841, when the price was JE25 per ton. It 
 can now be had for jE12. 
 
 Remarks — The land was trenched IS inches deep, and completely drained at the dis- 
 tance of IS leer, with tile drains laid 30 inclies deep, in Feb. 1842. Previous to this it was in 
 a wet, sour state. I' was agun pointed over with the spade, and the drills madi; for the 
 manures with the hoe upon the level surface. The manures weie then sown in the bottom 
 of the (hills with the liand, and a lillle earth beins; put over them, ihe seed was sown, 
 covered, and rolled. The weather had been dry for some time before sowinc, hut rain 
 came on that day , they brairded quickly, and continued to jirow till lified — the field being 
 well sheltered. The tops of Nos. 2, 3, and 4 were of a dark green colour, and remarkably 
 luxuriant, many of the bulbs weiiihiiig from 5 lo fllbs. No. 1 was of a hchter green, but 
 strong and he.ilthy, and many of the bulbs of this lot were 5 and 6 lbs. The bulbs of all of 
 them were finely shaped. 
 
 III. The olijrct of the two following scries of e.xperiiuenls was the same as in 
 those of Mr. T'leniing. 
 
 1°. Results of comparative experiments upon Sh'j'edes and oiker Turnips made 
 on the home farm of Mr. Alexander, of Southbar, near Paisley, in 1842. 
 
 The soil of the field was a deep loam, with a slight admixture of peat — the 
 subsoil was partly a hght clay and partly a sandy gravel. It was thoroughly 
 tile-drained and subsoilcd to the depth of fourteen inches. 
 
 Kind of Manures. 
 
 Quantity V. . 
 
 per 
 nper 
 Acre. 
 
 -p--> 1'"^;;;:;;^" 
 
 Swedes, soicii Sth May. 
 
 Bone-dust i32 bush. 
 
 Bones 16 bush. 
 
 Ash-duntt 112 Ions. 
 
 Farm-yard dun;; 32 tons. 
 
 Mixture of Yellow Sc Ti'^iVe, sown 20?A Juhj. I 
 
 Guano ! 3J cwt. 
 
 Guano ! 2 cwt. 
 
 Farm-yard manure ' 8 tons. 
 
 £. 8. 
 
 4 8 
 
 ^ 5 S 
 
 n 4 
 
 Produce 
 
 in bulbs 
 
 per imp. 
 
 Acre. 
 
 24 tons. 
 28 tons. 
 30i tons. 
 
 3 10 actons. 
 I 4 16 '24 tons. 
 
 Mr. Alexander adds, I must here notice particularly the result of the last two experi- 
 ments. Tiie seed sown was a mixture of yellow and white, anc' the period of sowing as 
 late as Ihe lOlh July. The weather at the lime bein^ favourable, they brairded quickly, 
 grew with great visour, and when all Ihe oilier lurnips in the field heranie affected with 
 mildew they stood as preen as ever. This (viz , the non-inildewins) I attribute preally lo 
 the guano, as well as to the lale sowing, never before having seen such a weight of lurnips 
 produced, sown so lale in the season. I applied other arlificial manures on bot)i of these 
 fields with a due proportion of dung, varying ihe quantities and modes of application, as ap- 
 peared to me best 111 test their qualities, but as the comparative effect is so difli.iili lo decide 
 upon, 1 can only here ob.serve, with any cert.iinly, that ihoiigh ttie turnips brairded quicker 
 when tlie dung was assisted with these manures, particularly uhcre TurnbuU's humus uus 
 applied, the crops afterwards did not appear to me lo be materially aided. 
 
 2". Result of experiments upon Yellow Ttirmps made by Mr. Alexander, of 
 Southbar, at Wellwood Farm, Muirkirk, Ayrshire, 1842. 
 
 The nature of the soil on which the experiments were made was reclaimed moss 
 Tthen about 2 fret deep), having a clayey subsoil, but which had been thoroughly 
 orained with tiles at fifteen feet apart. The field had produced white and hay 
 
^•o. VII I] 
 
 EXPERI.\^ENT^ ON TURNIPS. 
 
 47 
 
 crops, but, as for as known, had never been previously green-cropped. The whole 
 of it receivi d the same labour, preparatory to sowing, and the weather during the 
 opi^ration (-wliich lasted four days) was the same, thus giving to each experiment 
 an equal chance. 1 he peiiod of sowing was from tlie 15ili to I'JtIi of May; the 
 turnip seed used was Skirving's improved )3urple-;opped yellow; the dung used 
 was the produce of the farm, and, with the exception of the foreign gviano, all the 
 other manures applied were those manufactured and sold by iVJr. Tumbull, of 
 Glasgow. 'J'/tc extent of ground for each experiment vms one u're, Scotch measure. 
 
 Farm-yard Dung. . . .i 12 tons. 
 Ftuniii!! I 2 cwl. 
 
 Kind of Manure. 
 
 Quantity I Cos! of Proriiico 
 
 per I Manure | in Bulhs 
 
 imperial Iptr impe- perimpe- 
 
 Acre. irial Acre.; rial Acre. 
 
 Fariii-yard l)ini| 
 
 Humus' 
 
 Artiliciai Guano.. . . 
 Farmyard Duns. . . 
 Prepared II' iics".. . 
 Farm yard Dung. . . 
 
 Flumus 
 
 Improved Bones.. . 
 Artificial Guano.. . . 
 Ammoniacal Salts.. 
 Artificial Guano.. . . 
 Guano 
 
 13 Inns. 
 14 cwl. 
 
 12 tons. 
 
 2A cwt. 
 12'ton8. 
 9U Itis. 
 9(1 " 
 90 " 
 45 " 
 
 34- cwt. 
 
 3| " 
 
 £■ 
 
 s. 
 
 d. 
 
 4 
 
 4 
 
 0^ 
 
 (1 
 
 K 
 
 <M 
 
 4 
 
 4 
 
 o) 
 
 
 
 7 
 
 ^\ 
 
 
 
 6 
 
 <n 
 
 4 
 
 4 
 
 "(> 
 
 
 
 15 
 
 OS 
 
 4 
 
 4 
 
 SI 
 
 
 
 3 
 
 
 
 4 
 
 10 \ 
 
 
 
 5 
 
 6 
 
 
 
 8 
 
 
 
 1 
 
 3 
 
 
 
 3 
 
 5 
 
 
 
 28 ton.s 
 
 Co.st for 
 Manure 
 per ton. 
 
 3i 
 
 n 
 
 lU 
 
 n 
 
 IV. E['ecL of Gypsum on the Turnip Crop. 
 
 In 1841, Mr. Burnet of Gadgirth, near Ayr, applied a top-dressing of gypsum 
 to part of a field of turnips, and found that it nearly doubled the crop. 
 
 In 1842, Mr. Campbell, ofCraigie, in the same neighbourhood, "dressed a 
 six acre field, with the exception of a few rows, with two cwt. of unburncd 
 gypsum per acre. The croji over the whole was excellent, but there was no 
 perceptible diffei-encc between the dressed and the undressed part." 
 
 How are these discordant results to be reconciled 1 The following questions 
 suggest themselves as worthy of investigation — 
 
 1°. Is ^'vpsurii realhi propicious to the turnip crop^ — and to every variety aide? 
 
 2°. Are the unlike results above obtained to be ascribed to the abundant pre- 
 sence, in the one case, of gypsum in the soil, or in the manure ploughed in, 
 and its absence in the other — or to the variety of turnip cultivated 1 — or 
 
 3°. Can the sea-spray supply gypsum to Mr. Campbell's estate, which is 
 within two miles of the coast, while it is less bountiful to that of Mr. Burnet, 
 which is six miles inland 1 
 
 B.— EXPERIMENTS ON POTATOES. 
 
 I. Results obtained by Mr. Campbell, ofCraigie. 
 
 Four equal drills of potatoes were treated as follows: — 
 
 P. Guano, 3 cwt. per acre produce 5 pecks. 
 
 2°. Farm-yard dung, 40 cubic yards per acre . . . produced do. 
 3°. Do., top-dressed afterwards with HO lbs. of nitrate of soda, produce 6 do. 
 4°. Do., top-dressed with 160 lbs. sulphate and nitrate, mixed, produce 6 do. 
 
 " TurnbutVs Humus is formed from urine and night-soil mixed with gypsum and char- 
 coal and then dried. 
 
 Tumbull's prepared liurifs are bones and flesh dissolved in murialic acid, and mixed 
 with ahotitan erpial qii.inlity of charcoal in powder. 
 
 TunibuWs Artificial Guano is, I believe, prepared bones, with a Uule salt and sulphate of 
 ammoQta prepared from urine, and dried with a stove-beat. 
 
4b fc EXPi:niME\Ts os turn'ips. [Appendvc, 
 
 The above result is favourable to guano, considering that it was applied in 
 such small quantity; but why did the saline munures produce no effect — was 
 it because of ilie drought of ilie season, or was it because iVlr. Campbell's land 
 is already amply supplied with salts of soda from its vicinity to the seal (see 
 Lectures, pp. 344 and 34(5). These experiments are not unworthy of repetition 
 on a larger scale. 
 
 TI. Some very striking results, obtained by top-dressing potatoes with saline 
 manures on a small scale, were described by Mr. Fleming, of Barochan, in 
 1841, and are recorded in the preceding part of this Appendix (p. 20). The 
 following three series of experiments, made under the direction and superin- 
 tendence of the same gentleman, have been made upon a larger scale, and with 
 the view of throwing light upon a greater number of interesting points — 
 
 The object of the first series was to ascertain the effect — 
 
 1°. Of di]]erent, mixed manures, when applied alone to the potato crop. 
 
 2°. VYieir relative effects on different varieties of potato. 
 
 'tCiy t^ f^rc — .-^- — _H->— — H- — 
 
 o — « 
 
 K,. c - p c e>M . 
 
 ^ ■ S 3 5 = ^^■. 
 
 •=■■ ^\- ^^-l: ; 
 •r =; • • 1^- ^i : 
 
 - . . . O O . p ■ . 
 
 : : : i- i : " ■ : 
 
 S !S; S^ ^= "^"^ f^Si? = 
 
 ss?. m 
 
 5^ 
 
 ■3 V 
 
 £ 3 : 
 
 CO COCO" : 
 
 - -S ° 
 
 •HJO 
 
 3~ 2 
 
 03*»co oooc■oocoiSooooo^ooowoS3l — w 
 
 OOtOOO OOOCOCOOtCOCOOOOCOCSKiCO 5i 5 
 
 = 2 s a 
 "^ 5 S 
 
 oi o tf* --I cji en o o CI v o o en .*- :ji on o CT ci ~ ;;i -.c oi >£»■ ci 00 c 
 oo — c-o o = o o oc oo — oo = 001(00 CO — ^^ ^3 "9 
 
 
 ^ f^: 
 
 (o enoi oitot-'Otci<0 3)>-'H-ro^-os«icn»- 
 cv c ooocnoCT>ooa:cnooo>co 
 
 03>-O 3) hS 
 
 ^ I "H 5 s- = 
 
 _. o 
 
 -4 ife. X to ^ ?■ 
 
 o c oo c Q. 
 
 
 3'< S 
 
 •^ CO 
 
 s _S 
 
 s to 
 
 l?l 
 
 2.0 s, 
 
 ;? * 
 
 8 -, 
 
 =■■ =' 2 S 
 
Ne. VJII] 
 
 EXPERIMENTS ON POTATOES. 
 
 4S 
 
 2°. The object of the two following series of experiments was to ascertain — 
 1°. The relative effect of different salnic substanas applied a'ong icith fanu-yald 
 manure; and — 2-'. Whether die effects were gredXcx \/\\e.n mixed with the ma- 
 nure at the tiiTie of planting, or wheri subsequently applied, as a top-dressing, to 
 the growing plants. 
 
 1 °. Result of Experiments with, saline substances in top-dressing Early American 
 Potatoes. Planted 18th April, top-dressed 1st June, and lifted 28th Sep- 
 tember, 1842. Low Field, Barochan. T/ie quantity of land in each plot 
 ivas on^-eighth of an imperial acre. 
 
 Description of 
 Top-dressing. 
 
 Quantity Produce 
 of dressing in pecks 
 applied j of 35 
 per ' pounds 
 imp. acre. each. 
 
 Produce in 
 
 bolls of 5 
 
 c\vt. each 
 
 per imperial 
 
 acre. 
 
 Produce in 
 
 tons, i-c, 
 
 per imperial 
 
 acre. 
 
 Cost of 
 
 dressings pr. 
 
 imp acre, 
 
 including 
 
 carriage and 
 
 putting on. 
 
 Nitrate of Soda 
 
 Sulphate nf Ammonia 
 Sulphate of Ma;;iiesia 
 
 Nitrate of Potash , 
 
 Nulhina but Ouiig 
 
 Sulphate of Soda , 
 
 Nitrate of Soda. ., 
 Siilphiite of Soda. 
 
 o5 Sulphate of Soda 
 
 ( Sulphate of Ammonia 
 
 q^ Sulphate of Magnesia. 
 
 } Nitrate of Scdn 
 
 cwt. 
 li 
 \l 
 
 \l 
 
 40 cubic yds. 
 
 ?! 
 
 pecks. 
 128 
 116 
 106 
 143 
 98 
 
 144 
 
 90 
 
 151 
 
 180 
 
 bolls. 
 64 
 58 
 53 
 74 
 49 
 72 
 49 
 
 90 
 
 Ins. cwt. qrs. 
 16 — — 
 14 10 — 
 13 5 — 
 18 10 — 
 12 15 — 
 
 18 — 
 
 12 15 
 
 18 17 
 
 22 10 
 
 e. s. d. 
 
 1 11 
 
 1 11 
 12 6 
 
 2 3 
 
 
 1 4 9 
 
 15 
 
 1 4 9 
 
 1 9 
 
 Kbmarks. — The soil is a lii;hl loam of good quality, subsoil hard,sti)ney till, and retentive 
 of water. The potatoes were piHnle.d witii the spade at the distance of 26 inches between 
 drills. The manure, farm-yard dung at the rate of 40 cubic yards per acre, spread in the 
 bottom of the drills— cut sets laid on thi.s and covered up. (The cut tubers planted were 
 the produce of tliose top-drossed last season (see Appendix, page 20). Game away strong 
 and hialthy, nf a dark green colour, and were very remarkable from the contrast which 
 they presenteii to the same vanity of Pocato — planted alongside this experimental ufound 
 — that had not beoti dressed last sea^-on. Ttiese last came away wenk, and of a yellowish 
 preen oolmtr, and, under the same treatment in every respect, did not proiluce so good a 
 crop by 15 bolN per acre). Nos. 1, 2, 4, 0, S, and 9, had all the same effi-ft iji altering the 
 colour of the stems and leaves to a darker green. Nos 3 and 7 had not that pflTect, hnl No. 
 Sadiled ureatly to the produce. No. 7 made no visible n\\>irzilwn, but burned the tups se- 
 verely at the time nf dressing, as did most of the others this dry season ; this burning wa.s in 
 most cases only temporary. 
 
 2''. Results of Experiments witJi different saline stiis'.anccs, mixed vnthfarr/i- 
 V'fd dung at (he tirae of planfing, in growing Early American Potatoes. 
 Planted 29th April, and lifted 31st August, 1842. The qiuadily of land in 
 each plot was one-eighth of an imperial acre. 
 
 
 
 1 
 
 
 
 
 Cost of Salts 
 
 
 
 Quantity 
 
 Produce 
 
 Produce 
 
 Produce 
 
 used, per 
 
 
 Descriotion 
 
 applied per 
 
 in pecks 
 
 in bolls, of 
 
 in tons, 
 
 acre, im-lu- 
 
 No. of Manure and Salts. 
 
 imperial 
 
 of .35 lbs. 
 
 5 cwt. 
 
 &c., per 
 
 ding pntting 
 
 
 acre. 
 
 each. 
 
 each, per 
 acre. 
 
 acre. 
 
 on, exclusive 
 of Dung." 
 
 1 
 
 
 Perks. 
 
 Bolls. 
 
 Ins. cwt. qra. 
 
 £. s. d. 
 
 1 F.^rmvard Dung alone. . 
 
 35 cubic yds. 
 
 71 
 
 35i 
 
 8 17 2 
 
 
 2 Com Salt, added to Dung 
 
 2 cwt. 
 
 711 
 
 3b 
 
 8 15 
 
 4 
 
 3 Nitrate of Soda, do. 
 
 H " 
 
 99 
 
 m 
 
 12 7 2 
 
 1 12 
 
 4 Sidph. of Maiiiieeia, do. 
 
 2 " 
 
 91 
 
 45| 
 
 II 7 2 
 
 17 
 
 5 Sulph. of Ammonia, do. 
 
 H " 
 
 107 
 
 53| 
 
 13 7 2 
 
 I 12 
 
 6 Sul|)h. of Soda, do. 
 
 2 » 
 
 64 
 
 32 
 
 8 
 
 17 
 
 7 
 
 Silicate of Potasht do. 
 
 1 " 
 
 120 
 
 60 
 
 15 d 
 
 
 ■ Dund 5s. 6il per ruhic yard, exclusive of cartasie and spreading. 
 
 t The silicate of potash or soluble glass was directly prepared from caustic potash and 
 sand or silex fused together. 
 
50 
 
 EXPERIMENTS ON POTATOES. 
 
 [Appendix, 
 
 Remarks. — The soil upon which the above were grown was a subsoil, the unppr soil 
 haviii(! been taken off at (UlTerpnt times. It was trenched two feet deep in the Spring it( 
 1841, and which had to he done witli tlie mattock, it beini; loo hard fur the spade alone, it 
 was cropped that season wilh potatoes, manured with 40 cubic yards of compot^t of weeds, 
 cut tfras.s, anil half-rotteti leaves. It was aj^ain trenched to the sume depth alter the crop of 
 potatoes was lifted ; and was ajiain planted in the Sprino; of 1842 with putaioei-', manureil 
 with 35 cubic yards of lai'm-yard duns, mixed in the proportions stated witli the above salts. 
 The potatoes were planted will) the spadi^-, at the distance of two leet between llie drills, '.lie 
 manure being put in tlie botlotii of the drills, the salts sown liy the hand above it, ami then 
 all mi.xed '.oaelher with a diuig fork. The rut sets were laid upon the mixture, and covered 
 up. As icas reTTujr/cr.d in 1S41. the potatoes wilh No. 3 icere eif;ht to ten days brairded before 
 the others ; also Nas. 5 and 7 mere earlier than the others, those three bei?ig allj'uirly up iit 
 drilk before the ot/uirs made their appearance through the gronirui. Nos. 2, 4, and 6 wert la- 
 tost, and very inegular in comma up, and upon examining tlie drills a few of the sets ap- 
 peared to have been burned. Tliere was a marked dissimilaiily in the stems and leaves of 
 these potatoes through the summer. Nos. 3, .^i, and 7, were all of a darker frreeti colour and 
 stronger than the others. No. 7 vrns rcmarkafile for intenseness of colour mid length of 
 stems, so much so that it appe.ared to be a dilferent variety of potato. JSo. 4 wa.s fuily bet» 
 ler in appearance thun Nos. 2 and 6, which were of a yellowish green colour and hail a 
 Btunted appearance all the season. — Wlien this ground was first broken up, a pound of it 
 was boiled in pure raio water and filtered, which was tlien evaporated, the residue weigheil 
 4^ grains, mostly soluble salts, but hardly a trace of common salt. 
 
 o°. The following experiments were made with the view of'determining hoiv 
 far e:onamicnl mixtures might de made t^o supersede farm-yard maiuurc in the 
 groioth (if potatoes : — 
 
 1°. Account of an Experiment in growing Potatoes (Irish Piuk Eyes) witli the following 
 mixture of substances, instead of farm yard dung, planted 20th April, 1842. 
 
 No. 
 
 Ingredients. 
 
 Quantity in- 
 tended to ma- 
 nure four 
 acres. 
 
 Cost of 
 f-ubstances 
 
 for 
 four acres. 
 
 1 
 
 3 
 
 4 
 
 6 
 7 
 
 s. 
 
 9 
 10 
 
 Rape-dust 
 
 Bones dissolverl in Muriatic Acid. 
 
 cwts. qrs. lbs. 
 
 5 
 2 
 2 24 
 2 
 
 2 
 
 1 2 
 1 2 
 2 
 2 
 
 6 2 
 
 £. s. d. 
 1 10 
 12 
 
 1 C 
 10 
 2 3 
 9 
 10 
 1 
 
 
 NitJ Hte of Soda 
 
 ."^ulphale of Soda 
 
 Sulpliate of Ammonia 
 
 
 Dry Moss-Earth 
 
 
 20 --^5 
 
 4 1 9 
 
 Remarks. — Tliealiove mixture was sown in the drills at the r^ne ofahou; 5 cwts. per im- 
 perial acre, at a cost of little more tlian JEI. sterling, snd produced a fair crop of poliitoep of 
 a rematkably fine quality, 43 bolls per acre of imperial Ilcnfrewshlre measure, weighing 5 
 cwt. each, upon a poor ami light, although new soil, but not worth n.ore than 25s. per acre. 
 Great caution is required ifi using this mixture, as it is very apt to burn the cut seta if laid 
 directly upon them. .V little earth should be put between the cut potato and the n;annre. 
 
 2°. The follovving mixture was made, and lay together for five weeks, whrn it was sown in 
 the bottoms of potato drills upon a poor tilly soil, and White Don Potatoes plautp.d with it 
 30lll April, 1842. 
 
 Ingredients 
 
 Quantity mixed 
 I to manure one 
 I acre. 
 
 Sawdust, mosOy from Alder. 
 Potash «t Lime mixed, 14 mos old 
 
 Common Suit 
 
 SnlDhale of .\mmonia 
 
 Sulphate of Soda 
 
 Sulphate of Magnesia 
 
 Coal Tar, 20 gallons, say 
 
 jcwts. qrs 
 
 1 
 
 o 
 
 1 
 
 
 
 
 
 2 
 
 
 
 2 
 
 bush 
 40 
 10 
 
 50 
 
 Cost of Siib- 
 st.inros for 
 one acre. 
 
K 
 
 No. VIII.] EXPERIMENTS ON POTATOES, 51 
 
 Remarks. — The pofatoes planted with the above mixture came quickly fhrotijh the 
 (^ouikI, aiiij were very luxiirianl in foliaae. They were lifted 15th October, after being cut 
 down by frost whilst still unripe and powing. On being taken up, they were found to yield 
 a produce 01 56 bolls of Renfrewshire measure, weighing 5 cwts. each, per acre, of very 
 fine potatop.*, many of which weighed from 24 to '30 oz. euch. 
 
 N. B — This niixmrc, after being put together, fermented, and was frequently turned, but 
 kept dry. 
 
 The several series of experiments made upon potatoes by Mr. Flemins; are 
 deserving of careful consideration, and many of them of judicious repetition. 
 They are all well contrived or devised, and each scries skilfully arranged. 
 
 In agricultural experiments it is of the greatest possible consequence that the 
 ractical man should have a clear and definite object distinctly in view. If so, 
 is experiments may be signally successful in h;s own estimation, while, eco- 
 nomically considered, they may be total failures. This, as we have seen, was, 
 to a certain extent, the case with the first series of ex]3erinients made upon Lord 
 Blantyrc's farm, as above detailed (p. 4'2). The applications in some instances 
 lessened the crop, but the result, nevertheless, threw considerable light upon tjie 
 questions which the trials were intended to solve. 
 
 In making an experiment, the practical farmer aslis a qtiestmi of nature; —in 
 arranging the form and details of his experiment, he is putting together the 
 words by which his question is to be expressed. If his question be clearly put, 
 nature will give him, sooner or later, a clear and distinct answer — if he have 
 skill enough in nature's langua^-e to understand what she has said to him. I 
 say, sooner or later, for it m.iy be sometimes necessary to repeat the question, 
 either because sometliing has intervened to prevent nature, so to speak, from 
 hearing his question, — because it has not been accurately expressed — or because 
 something in the seasons, or otherwise, has prevented her answer from being 
 clearly understood — perhaps from being heard or read at all. Circumstances 
 may even prevent the answer from being given until a second summer come 
 round, when, if we are not on the alert, it may never be received at all. 
 
 The above experiments, as well as those which follow, form a.n excellent 
 study for the practical farmer in reference to this matter. Eveiy series is plan- 
 ned with a view to a given end, the circumstances are carefully noted before, 
 during, and at the close of each of the several trials, and the answers are re- 
 corded with a very praiseworthy degree of accuracy. I shall place together, in 
 one view, the most important of the deductions to which the experiments of 
 184*2 appear to have led, when I shall have laid before the reader the v/hole of 
 the tables which have as yet been placed in my hands. 
 
 C— EXPERIMENTS UPON BARLEY. 
 
 The object of the following experiments, also made by Mr. Fleming, was to 
 ascertain the Tehttivc. effect of different mime fuHtmu'cs, when applied, as top- 
 dressings, to a crop ofivhite darky. 
 
 The results, as shown in the last column, are sufficiendy interesting. 
 
 Results of Experiments with various substances used as top-dressings upon 
 Barley (common white"). The Barley sown I4th April, top-dres.sed 6th 
 May, and cut down 25th August, tlivashed, cleaned, measured, and weighed 
 5th October, 1842. The quantity of land in each pl-ot was one-eighth of an 
 imperial acre. 
 
 Remarks. — The soil of this field is a light lo■^m, as nearly as posjsible uniform in qnality, 
 and had l;iin about ten years in pasture previous to the spring of 1^2, when it was all 
 trenched with the sp.-.de twf Ire inches deep. It had been thoroiiuh-drained wiih tiles some 
 years before breakinc up. After beine trenched, it was dressed over, except where the ex- 
 periments were, wilh two chaldrons nf lime per acre, -slaked with water, in which common 
 Fait had been iii.-?solvci), and bpforp sowing the barley, with thf exception of the experiment 
 Rroimd, it v.rxs top dressed over with two and a half cwts. of Tiirnbnll's artificial guano per 
 acre, hnrrowed in. as was also the topdressins^ No 3 in the table of oxpennient.=!. The bar- 
 ley was .sown broadcast, 2i bushels per acrel Owing to the extraordinary drought at lime 
 of sowing, it did not braird well till rain came ; after which it made rapid progress. Advan- 
 tage was taken of heavy rains to put on the top-dressings, all of which were sown at the 
 time above etated, vii , 6lh M»y, except No. 4, which was not sown till the I7th, at which 
 
53 
 
 EXPERIMENTS UPON BARLET. 
 
 [Appeitdix 
 
 RoDEN Hill Field. 
 
 Depcription 
 of Tu[)-Dressing3. 
 
 Nitrate of Soda 
 
 Common Stlt 
 
 Sulphate of Soda 
 
 Sulphate of Mai;iicsia 
 
 Natural Guano, at 25s 
 
 Nilratfof Potash 
 
 Common Salt 
 
 iS'otliiiig 
 
 Turiibull's Arliticial Guano. 
 
 ex:-. . " K 
 — = m c D. t 
 
 lbs. 
 1821 
 
 1633 
 2192 
 
 mm 
 
 1735 
 1620 
 1925 
 
 lbs. 
 364 
 
 378 
 
 432 
 255 
 378 
 '325 
 334 
 
 
 * b 
 
 lbs. 
 
 500 
 
 491 
 
 5S9 
 .590 
 495 
 425 
 480 
 
 lbs. 
 56 
 
 55 
 
 54 
 54 
 57 
 55 
 54 
 
 
 2i' 
 
 1 6 , 
 5} I 
 9 7 
 
 3 6 
 
 Hi 
 
 3 
 
 bush. lbs. 
 
 62 
 
 54 54 
 
 64 
 
 37 42 
 
 53 3 
 
 47 15 
 
 49 26 
 
 time there was little rain, and, in ccMserjuence,it burnnd the plants, of which they did not re- 
 cover all the seasun, and the ground got full of weeds No. 5 l-nrned the planis also, bnt 
 they recovered quickly, and ^ave a good relurn. Aswas remaikf-.d before, ^cherevcr common 
 suit was put on as a top dressing on grain crops, either (f wheat, barley, or oats, and on what- 
 ever dtscription of soil upon this estate, the groin was mvariat-ly h-avier per bushel, and had 
 fewer weu/<s or tails in vropurti(m to the quantity of grain per acre, than any of the other 
 dressings apjilied here, f'rom Ihe frequent mention of spade culture in these experiments, 
 many may consider tliat they were upon a very small scale, which is not the case, Ihe 
 greater proportion of them beini; very extensive. Mr. Fleming, to tive employment lo Ihe 
 destitute labourers, having ilug and trenched about thirty acres of land instead of plou!;lung 
 it, which accounts for the frequent mention of spade culture, which, when it can be got ex- 
 ecuted at a moderate rate (particularly trenching at X4. per acre), is very advantageous, 
 and seems superior lo trench ploughing. A. F. Gardiner. 
 
 D.— EXPERIMENTS UPON OATS. 
 
 The first of the following series of experiments was made at Lennox-Love, 
 
 at the request of Lord Blantyre, tlie second at Barochan, under the direction 
 
 of Mr. Fleming. The general object of botli was the same — to ascertain the. 
 
 relative effr.cl of tlijfcrent saline stiliflwiiccs a}rplied as top-dreisings vpon young 
 
 oats; but those of Mr. Fleming have, besides, t/ie special object of ascertaimng the 
 
 effect of certain mixtures upon oats xohcn grown vpo7i mossy land. 
 
 1°. Oats, second crop, after old lea. Soil sharp loam ; subsoil clay reeling on sand stone 
 
 rock. Oats sown 14th March; lop-dres^iniis applied 13lh May ; crop cut 27th Aug. ; and 
 
 thrashed 9th Sept., 1842. The quantity of la.ndincaehplotwasoneeighlhof animperialacre. 
 
 No. 
 
 Quarry Park, 
 
 Lennux-Love. 
 
 Description of 
 Dressing. 
 
 MANURES. 
 
 Nothing.. 
 
 Common Salt 
 
 Common Salt 
 
 Rape-dust 
 
 Nitrate of Soda 
 
 Nitraleof Soda 
 
 Rape-dust 
 
 Nitrate of Soda. . . 
 Sulphate of Soda. . . 
 Sulphate of Soda. . . 
 Sulphate of Soda . . 
 
 Ftape-rtust 
 
 Rape-dust 
 
 Guano 
 
 Soot 
 
 Waste water from gas ) 
 work diluted with 4j > 
 llimes jtsbuLk of water, ) 
 
 14 
 
 „if 
 
 14 
 ]I2( 
 
 ?i 
 
 14 
 
 „;; 
 
 ?i4 
 
 28 
 
 hush 
 
 6ga]ls. 
 
 Weigfil taken iiomi'i; . 
 Thrashing Mill of "S .S 
 
 
 4 
 
 7 O' 
 3l' 
 
 8 7 
 
 2 
 
 1 
 
 7 
 
 14 
 5 
 4 
 
 lbs. 
 672 
 
 D88 
 
 644 
 
 588 
 616 
 
 504 
 
 504 
 
 672 
 
 616 
 938 
 532 
 
 17 296 
 
 00 273 15 3'JO 22 39^ 7 00 
 
 
 . 
 
 d^ 
 
 bushs. 
 6-75 
 600 
 
 5 95 
 
 5 19 
 
 556 
 
 4-81 
 
 4 82 
 
 40.M 5-62 
 40l 8 75 
 ■373 512 
 
 = « 
 
 r 3 >- I 4J 3 u 
 .= -c O C -6 O 
 
 bush. 
 
 •75 
 
 80 
 
 1-56 
 
 119 
 
 1-94 
 
 1-9.3 
 
 ■19 
 
 1 13 
 
 163 
 
No. VIII. ] 
 
 EXPERIMENTS UPON OATS. 
 
 53 
 
 2°. Resalts of Experiments tm'th various ntbstances used as top dressings upon Oats (Sandy 
 Oats), sown I61I1 April, upun drained peat moss Nos. 2, 3, and 5 top-dressed on the same 
 flay ; No. 1 dressed 6lh May, cut clown Ulh September, and thrashed, cleaned, and 
 weigheii Glh Oct,. 1S42 The (/uanti/t/ iifland in cackplot trns ime-eif^hlh of an imperial ture. 
 
 I No. 
 
 JEBAW PARK FIEU), BAROCBAN 
 
 Description of Dressing. 
 
 or 
 
 Sulphate of Ammonia ilSJ lbs. 
 
 Water 20 (falls. 
 
 Sulphate of Soda 21 lbs. 
 
 Nilrateof Soda 9i lbs. 
 
 Bones disaolved in Muriatic 
 
 Acid ]421bs. 
 
 Nothing ., I 
 
 Sulphate of Ammunia I 7 lbs. 
 
 f^llrcate of Potash ..14 lbs. 
 
 Sulphate of Soda . !l4 lbs. 
 
 Bones dissolved in Muriaticl 
 
 .\cid 114 lbs. 
 
 0.3 
 
 — -3 
 
 — c 
 
 Si v' ■-" I -s 
 
 •- — ^ |C 2 
 
 ^ — •^ r^.£ 
 
 ^1 75'^.55^| 
 
 lbs 
 I 1105 
 
 1340 
 
 900 
 
 lbs. 
 270 
 
 320 
 210 
 
 Jbs. 
 420 
 
 450 
 
 4=50 
 320 
 
 M2 
 
 ■J at*: 
 
 lb.s. 
 41 
 
 s. d. 
 2 6 
 
 ■S'£ = 
 
 /5 '^ 
 
 .« 
 
 bush. lbs 
 52 18 
 
 60 40 
 43 3 
 
 Remarks. — The soil upon which the above were grown is mo^s, rather deeper in some 
 parts than others, incumbent u|ion gravel of a stitf retentive rjnality. It had been partly 
 drained some yars ai;o, but nwins to the nature of the soil t!ie drains did not act well. In 
 the s|)rin!j of l'^4J, it was again drained with tiles, and trenrhed over with the spade to the 
 depth of 16 inches, ami some of the gravel subsoil brought up among tlie moss. The ground 
 being divided into lots for the purpose, the topdressings Nos. 2, 3, and 5 were sown on the 
 16th .\pril, and slightly harrowed in ; the oats were then sown and harrowed in- No. I was 
 made front 100 lbs. sulphate of ammonia dissolved in 100 galls, of water (proportions for an 
 imperial acre), and sprinkled upon the oats during the lime of rain on Otii May. No. 5 was 
 sown upon a lot where the moss was fully the ileepest. They all brairded well; Nos. 2 and 
 5 coming rather earlier than ttie other.s, and of a darker colour, particularly No. 2. No. 1, 
 after being watered with the solution, became also of a darker green, but neither Nos. 1 nor 
 2 were so strong iti the straw as Nos. 3 nfid 5, //olh of ithich were mmarkahle for strength and 
 luxuriance, especially No. 5, which kept the lead of the otlieis all the season. 
 
 E.— EXPEPJMENTS UPON WHEAT. 
 The following three E.xperimeiits upon wiieat e.thibit very interesting results : 
 1°. The first series was made on ihe home farm of Loril Blantyre at Lennox 
 Love, and was intended to ascertain the rdalivs effects in that locality of dijfer- 
 ent, chiejly saline, vianures applied as lop-dressiiigs to spring wheat. 
 
 
 
 MANURES. 
 
 <o <u 
 
 Weight tak( n from 
 
 ■3 
 
 M 
 
 lA- f 
 
 
 
 
 
 = — 
 
 Thrashing Mill of 
 
 ■y - 
 
 2 
 
 el's 
 
 
 
 LbnnoxLove. 
 
 
 ^ 
 
 5S 
 
 c 
 
 
 
 
 ^^ 
 
 « 
 
 
 
 No. 
 
 
 
 J; 
 
 — ■" 
 
 e> 
 
 
 
 J'j 
 
 Q-O 
 
 
 
 -0 
 
 
 
 Des!-.ription of 
 Dressing. 
 
 
 S 
 
 "^ 5 — : 
 
 5 
 •& 
 
 
 >-.-r 
 
 S 
 
 s 1 
 
 H^ ^ 
 
 50 
 
 u ■« 
 
 
 
 
 Of =1 
 
 
 
 ?2« 
 
 a 
 
 ;; z 
 
 55 
 
 '-> z 
 
 5 c 
 
 of^- 
 
 aia 
 
 c-aa 
 
 1 
 
 
 lbs. 
 
 s. d 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 Ih^ 
 
 lb.--. 
 
 lbs. 
 
 bu.shs. 
 
 bush. 
 
 bush. 
 
 1 
 
 Nothing 
 
 — 
 
 — 
 
 10.36 365 
 
 10 
 
 .^1)7 
 
 1.54 
 
 6I| 
 
 5-9%6 
 
 — 
 
 
 
 
 (Joramon Salt 
 
 14 
 
 4 
 
 1003 349 
 
 20 
 
 54: 
 
 92 
 
 6U 
 
 5-750 
 
 — 
 
 •206 
 
 ■■^) 
 
 Common S.ilt 
 
 „i( 
 
 7 
 
 114^ 366 
 
 17* 
 
 610 
 
 134^ 
 
 61i 
 
 6 250 
 
 •29 
 
 — 
 
 4 
 
 Nitrate of Soda 
 
 14 
 
 3 1 
 
 1120 363.1 
 
 20-i 
 
 ,'-,9^ 
 
 i:«f 
 
 fiOf 
 
 5 970 
 
 •014 
 
 
 
 I5) 
 
 Nitrate of Soda 
 
 flape-dust 
 
 112^ 
 
 87 
 
 1176 394 
 
 17| 
 
 64R 
 
 116}- 
 
 61i 
 
 6 375 
 
 419 
 
 — 
 
 A 
 
 Nitrate of Soda. ... 
 Sulphate of Soda.. .. 
 
 7 > 
 7<, 
 
 2 
 
 1078 364 
 
 12 
 
 595 
 
 107 
 
 60| 
 
 6 000 
 
 •044 
 
 — 
 
 7 
 
 Sulphate of Soda 
 
 14 
 
 1 
 
 896 2^6i 
 
 11 
 
 4R1 
 
 1151 
 
 60 
 
 4-750 
 
 
 
 1206 
 
 '\ 
 
 Sulphate of Soda . .. 
 
 Rape-dust 
 
 Rape-dust 
 
 uii 
 
 7 i". 
 
 9^0 3391 
 
 UV, 
 
 514 
 
 II6i 
 
 61 
 
 5-562 
 
 — 
 
 •394 
 
 9^ 
 
 '>24 
 
 14 
 
 1100 399 
 
 14 
 
 57.'-. 
 
 no 
 
 62} 
 
 6-381 
 
 •425 
 
 
 
 10 
 U 
 
 
 28 
 4 bush. 
 
 5 
 4 
 
 1092 .Mfi7 
 
 14 
 14 
 
 .504 
 
 145 
 97 
 
 60| 
 
 6 0' 10 
 5-939 
 
 •044 
 
 
 Soot 
 
 1036 
 
 361 
 
 -017 
 
 29 
 
54 
 
 KXPERIMKNTS tPON WHEAT. 
 
 [Appendix 
 
 Remarks.— Spring Wheat after Turnips, South-Lawn. Soil loamy clay ; subsoil clay 
 Drained every fiinow before breakin? up from okl grass in the autumn of \^^; ploughtd 
 deep and subsuiled m &\mi\g of \?A\. Wheat sown 5th February, 1842; manures applied 13th 
 May; crop cut 24th August; and thrashed lOih September, 1842. The quantity of land in 
 eachplot was oneeighlh iif an imperial acre. 
 
 2°. The object of the second series, made at Barochan, was to ascertain the 
 relative effect of certain mixeil, chicjkj saline, vumuir.s applied as top-dressings to 
 roinler vhcat. 
 
 Results of Experiments with various subslances used as top dressings, upon Winter Wheat. 
 Dressed 9th May, and cut 7th September, 1842. Tlie quantity of land in ca£h plot tros one- 
 sixteenth of an imperial acre. 
 
 No. 
 
 crook's farm, 
 barochan. 
 
 
 
 
 5 .5 
 
 = 1 
 
 
 II ■ 
 
 ■a 75 
 c o. 
 
 ■£■§ 
 
 
 Description of 
 
 >-.— 
 
 
 Zo£ 
 
 "- ri 
 
 - s 
 
 <z 
 
 
 ■^ &, 
 
 
 Top Dressings. 
 
 C?.S 
 
 II 
 
 Ml 
 
 lbs. 
 
 it: 2 
 
 lh<!. 
 
 o 
 
 o 
 
 '" = oi 
 
 |£S 
 
 
 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 s. d. 
 
 bush. lbs. 
 
 Ibs^ 
 
 I 
 
 Nothinc 
 
 21 
 
 400 
 
 95 
 
 1(50 
 230 
 
 61 
 60 
 
 
 4 4i 
 
 24 ^ 
 30 40 
 
 2560 
 
 36eo 
 
 Natural Guano 
 
 540: 115 
 
 2 
 
 TurnbuU's Artificial 
 
 
 
 
 
 
 
 
 
 3 
 
 
 21 
 21 
 
 420 
 360 
 
 95 
 80 
 
 175 
 150 
 
 61i 
 G2« 
 
 1 8 
 4 
 
 24 r.6 
 21 27 
 
 2800 
 2400 
 
 Common Salt 
 
 «s 
 
 Sulphate of Soda. . . . 
 Nitrate of Soda 
 
 10*; 
 
 6j- 
 
 480 
 
 101 
 
 190 
 
 CI 
 
 50 8; 
 
 1 
 
 26 30 
 
 3040 
 
 5^ 
 
 Common Salt 
 
 Dissolved Bones 
 
 21 ■( 
 7 S 
 
 4C0 
 
 90 
 
 iro 
 
 63 
 
 <,o 4; 
 
 >0 7^ 
 
 22 54 
 
 2720 
 
 6 5 
 
 Rape-dust 
 
 a."-! I 
 
 'Sin 
 
 110 
 
 200 
 
 r,') 
 
 2 7^ 
 
 28 24 
 
 32C0 
 
 
 Sulphate of Magnesial 
 
 Sis 
 
 
 
 
 
 
 Remarks. — The soil is a heavy loam, incumbent upon a deep clay. The wheat was sown 
 at the end of November, 1841, after a crop of yellow turnips. The turnips were manured 
 with 20 tons of town dung per acre. Owing to the severity of the winter of 1S41 and spring 
 of 1842, the plants were very thin upon the grounrl. In April. 1S42, it was sown down with 
 grass seeds, harrowed and rolled, after which it tillered and gradually recovered. At the 
 time the dressings were put on there was rain, but in general it vras dry ircniher after, arid 
 in consequence tlie top-dressings did not produce such great results as they did in 18-11. The 
 field was examined from time to time, and the appearance of earh experimeni as noted 
 down is fully borne out by the results given in the ta"ble, viz. :— No. 1 was taller in the straw, 
 longer in the ear, and of a darker green colour than any of the others ; No. was nevt, and 
 Nor4 was third. In point of appearance lliere was in the others no perceptible ditTerence 
 from the general crop, except No. 3, whicli appeared to have checked Ihe growlli of the 
 plants, and from this check Ihey scarcely recovered all the season. It is however remarka- 
 ble that wherever common spit was applied the grain was heavier per bushel. // mill be 
 observed, with reference to the experiment upon wheat grown on this land last year, that the 
 application of common salt had a very great effect, and would probably have also benefited the 
 general crop tliis year, had it not been fur the extraordinary drouglit of tlie season (see Appen- 
 dix, p. 17.) 
 
 3°. The object of the third series, rnade by Mr. Burnet, of Cadgirtli, nea 
 Ayr, was the saine as those of Mr. Fleming. The mixtures employed, how- 
 ever, were different, and the tabulated results are at least equally interesting, 
 and satisfactory. 
 
 Results of Experiments wish mi.\cd INInnurcs used as top-dressings upon Winter Whca 
 (Eclipse variety), sown 29th October, 1S41, and reaped 15th August, 1^42. 7'he quantity 
 of land in each pilot teas one fourth of an imperial acre. 
 The soil a loam, with subsoil of clay ; tile-drained and trench-ploughed. Had been in 
 
 beans the year previous, and had no manure with that crop nor with the wluat, except tha 
 
 above applications, harrowed in in spring. No. 6, at a cost of £2. 4s., has produced an iiv 
 
 crease over No. 1 of JE6. 193. 3d. beinj; a^«in of £i. 15s. 3d. 
 
No. VIII.] 
 
 EXPERIMENTS UPON WHEAT. 
 
 55 
 
 
 GADGIRTH, 
 NKAR AYR. 
 
 1 
 
 
 1 
 
 C3 
 
 3 
 
 c 
 
 t« 
 
 
 .TJ 
 
 3 
 
 > 
 
 5 
 
 'a. 
 
 C J, 
 'to S 
 
 
 Manures applied 
 
 o 
 
 "o 
 
 = "3 
 
 a. 
 
 O 
 
 a. . 
 
 
 •a 
 
 ■a 
 
 S'oJ 
 
 5^- 
 
 d 
 
 16th April. 
 
 
 1 
 
 ■5, -5 
 
 '5 c 
 ^2 
 
 _ti) 
 
 1 
 
 "5, 
 
 3 
 
 3 t- 
 CL,- 
 
 II 
 
 cO 
 
 
 O .-0 
 
 -Ii 
 CO S 
 
 2i-§: 
 
 
 cwt qrs IbB 
 
 cwl qrs lbs 
 
 cwt qrs lbs 
 
 lbs. 
 
 lbs 
 
 bslil. lbs 
 
 L. s. 
 
 L. 8. 
 
 8. d. 
 
 L. s 
 
 1d7 
 
 1 
 
 No application. . 
 
 7 1 18i 
 
 4 a 23i 
 
 4 16 
 
 6U 
 
 9 
 
 31 38 
 
 11 1 
 
 — 
 
 
 
 — 
 
 9£ 1 
 
 2 
 
 Guano J cwL & 
 
 
 
 
 
 
 
 
 
 
 
 i 
 
 
 \Vi)0(l-asties 
 
 7 2 18 
 
 5 24 
 
 4 1 9 
 
 6U 
 
 10 
 
 32 20 
 
 11 6 
 
 5 
 
 
 
 2 
 
 88 i 
 
 3 
 
 .\rufifial Guano 
 I cwl. & Wood 
 
 
 
 
 
 
 
 
 
 
 
 1 
 1 
 
 
 •ishes 1 cwt . . . . 
 
 6 3 25 
 
 5 17 
 
 4 1 10 
 
 59i 
 
 9 
 
 32 24 
 
 11 6 
 
 5 
 
 
 
 I 12 
 
 88 
 
 4 
 
 Sulpti. ofAmmii- 
 uia J cwl., Wood- 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ashes 1 cwt 
 
 8 3 21 
 
 6 2 7 
 
 5 1 lOi 
 
 60 
 
 17 
 
 39 54 
 
 14 
 
 2 19 
 
 63 
 
 2 
 
 85 
 
 5 
 
 Siilph. of Ammo- 
 nia A cwt .Sulph 
 lif Soda J cwt., 
 &; Wood-ashes 1 
 
 
 
 
 
 
 
 
 
 
 
 
 C 
 
 cwt 
 
 11 18i 
 
 7 9i 
 
 6 2 Si 
 
 60 
 
 13 
 
 49 6 
 
 17 4 
 
 6 3 
 
 16 9 
 
 2 16 
 
 81 
 
 Sulpti. of Ammo- 
 
 
 nia J cwt., Com- 
 
 
 
 
 
 
 
 
 
 
 
 
 
 mon Salt i cwt , 
 
 
 
 
 
 
 
 
 
 
 
 
 
 & Wood-ashes 1 
 
 
 
 
 
 
 
 
 
 
 
 
 
 cwt 
 
 U 1 4 
 
 7 1 24 
 
 6 2 6i 
 
 60 
 
 9 
 
 49 
 
 17 3 
 
 6 2 
 
 17 3 
 
 2 4 
 
 84 
 
 
 Siilph. of Ammo- 
 nia ^cwl.. Nitrate 
 of Soda i cwt , 
 * Wood-ashes 1 
 
 
 
 
 
 
 
 
 
 
 
 1 
 
 8 
 
 cwt 
 
 U 5 
 
 7 23 
 
 6 1 25 
 
 59 
 
 11 
 
 48 20 
 
 i6 IS 
 
 5 17 
 
 16 li 
 
 3 4 
 
 70 
 
 TurnbuU's Gua 
 
 
 
 nn 1 rwt., Sulph. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 )f Lime 1 cwt., 
 
 
 
 
 
 
 
 
 
 
 
 
 & Wood-ashes 1 
 
 
 
 
 
 
 
 
 
 
 
 
 cwt 
 
 8 6 
 
 5 2 8 4 2 2 1 60 
 
 23 
 
 33 44 11 Ifi 
 
 15 
 
 2 3 
 
 I 16 
 
 Rl 
 
 
 p.— EXPERIMENTS UPON PASTURE AND OTHER GRASSES. 
 
 I. Experiments made by Mr. Alexander, at Wellwood, in 1842. 
 
 A. On crops of meadow and rye grass hay. 
 
 1°. One Scots ocre of well-drained mossy meadow, and full of timothy grass, 
 was top-dressed during the last week of April, with 1 cwt. improved bones, \ 
 cwt. gkiuber salts, J cwt of charcoal, all well mixed with ashes. Result. — 
 Crop much improved, and came to 180 Ayrshire stones (of 24 lbs.) per acre. 
 I may mention that this meadow suft'ered generally much from the severe 
 drought; the above kept its growth best. 
 
 2^. One Scots acre of well-drained mossy meadow, full of tiiTiothy grass, was 
 top-dressed during the last week of April, with 1 cwt. of artificial guano, 12 
 bushels of humus, well mixed with a quantity of ashes. Rksult. — Not so 
 good; more affected by drougiit; crop IGU stones per acre ; the rest of the un- 
 di-essed meadow land, on an average, 140 stones per acre. 
 
 3^. Three acres of rye grass hay, upon « i-'ery light sharp soil, was top-dressed 
 during the last week of April, with 3 cwt. of artificial guano, 2* cwt. of improved 
 bones, 1 cwt. of charcoal, all mixed with a quaiility of ashes. Result. — I can- 
 not pronounce that the hay on the three acres was increased in bulk ; the crop 
 was a light one on the whole field, owing to the severe drought, and the very 
 dry nature of the soil this season, therefore, gave this experiment no fair trial, 
 I would say, however, that I have rarely seen such an appearance of white 
 clover since the hay was cut, and particularly on the dressed land. 
 
66 
 
 EXPEHiMENTS UPON PASTURE GRASS. 
 
 [Appendiz, 
 
 B. On pashcre grass. 
 
 Three years' old lea. The extent 2 acres 3 roods Scots measure, divided into 
 three equal parts, and the manures applied during the last week of April, 
 
 No. 1. Dressed with i cwt. of ammoniacal salts, 1 cwt. of sulphate of soda 
 (glauber salts). 
 
 No. 2. Dressed with \ cwt of ammoniacal salts, J cwt. of glauber salts, I cwt. 
 of common salt. 
 
 No. 3. Dressed with \ cwt. of ammoniacal salts, | cwt. of glauber salts, J cwt. 
 of nitrate of soda. 
 
 Rksui.ts. — Nos. 1, 2, and 3 were much alike ; in all the three cases the vege- 
 tation was quickened and improved; but, as is always the case with experi- 
 ments on pasture, unless the cattle were kept off for the whole season, and the 
 produce cut, it is not easy to say how far the above application went to improve 
 the grass ; but certainly the small field did wonders — for it pastured fifteen early 
 calves nearly all the season. 
 
 II. The following carefully conducted series of experiments were made by 
 Mr. Fleming, of Barochan, with the view of determining the relative effect of 
 saline substances upon the vjeight of the hay crop, on the field where the experi- 
 mental wheat of 1841 was grown: — 
 
 Result of Experiments tried upon sown Grass, cut for Ilay on 30th June, 1842, Crook's 
 Farm, where the Wheat grew in 1841. (See prececiiiig part of this Appendi-t, p. 19.; 
 The quantity of land in each plot was one-sixieenth of an imperial acre. 
 
 crook's FAIIM, BAROCHAN. 
 
 Description of Dressing, 
 
 Nothing , 
 
 Sulphate of Soda 
 
 Common Salt 
 
 Nitrate of Soda 
 
 Sulphate of Soda. 
 
 Nitrate of Soda, mixed. . . . 
 
 Natural Guano 
 
 Silicate of Potash 
 
 Gypsum. . . 
 
 Sulphate of Ammonia 
 
 Turnbull's Guano 
 
 Common Salt 
 
 Snot 
 
 Hay of Barley Land, ma- 
 nured with Bone-dust, 1841. 
 
 lbs. 
 
 21 
 
 21 
 lOJ 
 
 3i 
 lOJ 
 
 21 ' 
 7 
 14 
 
 14 , 
 1 bushel ' 
 
 i •= 
 
 ■^ z 
 
 
 u B. 
 
 
 65t 
 
 
 
 
 
 o ^ 
 
 -.c"^ 
 
 •a 
 
 ^# t 
 
 
 
 £■= 5 
 
 ^'ih 
 
 lbs. 
 
 lbs. 
 
 710 
 
 11,360 
 
 484 
 
 7,740 
 
 6721 
 
 10,960 
 
 1125 
 
 18,100 
 
 515 
 
 8,240 
 
 93-4 
 
 14,920 
 
 7571 
 
 12,120 
 
 820 
 
 13.120 
 
 595 
 
 9,520 
 
 795 
 
 12,720 
 
 940 
 
 15,840 
 
 
 
 lbs. lbs 
 
 — il95 
 
 — 1163 
 
 — 1176 
 6640 351 
 
 jl86 
 
 3560 2561 
 
 760 198 
 
 1760 '225 
 
 |1H6 
 
 1360 228 
 
 lbs. 
 275 
 337 
 262 
 312 
 
 275 
 262 
 
 : '^3 
 
 c 
 
 3 jj- 
 
 
 
 
 
 
 
 
 
 
 
 
 tns.cwt 
 
 qrs 
 
 5 
 
 I 
 
 2 
 
 3 
 
 9 
 
 
 
 4 
 
 17 
 
 3 
 
 8 
 
 
 
 3 
 
 6 14 1 
 
 Remarks,— Nos. ] , 2, 3, 4, 5, and 8, were all -Iressed on the 9th of April, the weather be- 
 ing very dry at the time, and their effects were hardly perceptible ; but iti the last week of 
 April Nos. 3 and 4 showed an improvement over the others. We liad heavy rains the firsf 
 week of May, and by the 7th of May the nitrate of sod.i (No. 3) could be seen at a distance by 
 the alteration of the colour to dark sreen, and its height above the others; upon that day 
 Nos. 1 and 2 showed no visible alteration from the undressed. No. 3 was the best of any : 
 taller, and ofa dark ereen colour, and thicker swarded. No. 4 showed little or no alteration 
 in colour, hut was fully longer than t/ic gemral crjp, unci presented the remarkable apjjearance, 
 as did No 1. in being 7tearly all Fe.sluca Rubra, with hardly any rye grass, although of this 
 grass, viz. (Festuca Rubra), none was sown ; the field having been sown with rye grass, tim- 
 othy, and red clover. No. 5 darker than No. 4 in'the colour, and good ; but No. 8 hardly im- 
 proved. Nos. 6, 7, 9, anil 10, were dressed upon the 7th of May. The men in ploughing up 
 the stubble of 1841 found that the ridges which were lop dressed that season with ni'rate of 
 soda, were more difficult to plough, from the strength and depth of the grass roots, than the 
 ridges undressed, each alternate ridj;e only having been dressed. 
 
 Prtces (i/">/an«res.— Sulphate of soda, 7s. per cwl. ; Nitrate of soda, jEl. per cwt. ; N:du- 
 ral Guano, 25s. per cwt. ; Artificial Guano, Ss. per cwt. ; Silicate of Potash or Soluble Glass, 
 I63. per cwt. ; Sulphate of Ammonia, XI. per cwt. 
 
No. VJII.] KXPERIMENTS UPOM MIXED CROPS. 57 
 
 G.— EXPERLMENTS UPON MIXED CROPS. 
 
 The following interesting experiment was made by Mr. Alexander, for the 
 purpose of ascertaining the effect of a viixture of iiypsuia and common salt upon a 
 viixfd crop of oals, beam, and peas : — 
 
 Result of an experiment upon the effect of gypsum and common salt, applied 
 as a top-dressing at Weilwood, Muirkirk, 1812. 
 
 Four Scotch acres of strong soil, bordering on clay, broken up from two-year- 
 old pasture, w-'re sown with oats, beans, and peas (which is called in Scotland 
 mnsUem, and is a first-rate fodder for dairy stock). 'They all came well up, but 
 worming and other causes injured the crop so much that I had serious intention 
 of ploughing it up, and sowing turnips. Instead of doing so, I top-dressed the 
 whole four acres with the following substances, well-pounded and mixed to- 
 gether, and this bein^ done immediately before copious rains, the mixture was 
 washed into the soil : — 12 cwt. gypsum (from Turnbull), which, with carriage, 
 cost 8s. ; 4 cwt. common salt, which, with carriage, cost 8s. ; — this and the 
 gypsum, 16s. Cost of top-dressing, 4s. per acre. 
 
 The effect was like magic ; the plants immediately assumed a deeper green 
 colour, and grew wondertully, and this field took the lead of all my other oats, 
 and when reaped the field generally was the best I had. Oats, beans, and peas 
 ■were all particuleirly well filled. I may state further, that after the dressing it 
 stood the severe drought better than any of my other crops. Weilwood is 23 
 miles from the sea, and 550 feet above it. 
 
 From other experiments which I had before made, but which I shall not fur- 
 ther enter on here, I am convinced that common salt is a great auxiliary in that 
 locality (if not to most others distant from the sea), and it ought to be far more 
 extensively used. 
 
 H.— EXPERIMENTS UPON BEANS. 
 
 The following experiments were made by Mr. Alexander, of Southbar, at his 
 farm of Weilwood, in Ayrshire, with the view of ascertaining the relative appa- 
 rent effects of different saline top-dressings upon beans at different periods oj 
 their growth : — 
 
 Experiments made at Weilwood upon a crop of beans (1842). 
 
 The ground was manured, previous to sowing, with 15 tons of farm-yard 
 dung per Scotch acre, and the other manures applied when the beans were about 
 two inches high (they were sown in broad-cast). The extent of ground was Sj 
 acres Scots measure, divided into four equal proportions. 
 
 No. 1. Dressed with § cwt. of sulphate of soda, J cwt. of nitrate of soda. 
 Result. — The effect of the dressing was seen soon after application, by deep- 
 ening the colour of the plants. The beans were deficient in straw, but remark- 
 ably well podded and filled. . . 
 
 No. 3. Dressed with i cwt. of sulphate of soda, 1 cwt. of gypsum. Result.'./ 1^ 
 — More straw than the foregoing, and rather better crop. t ' 
 
 No. 3. Dressed with \ cwt. improved bones, \ cwt. artificial guano, 3 bushels 
 TurnbuU's humus. Resllt. — About the same as No. 1. 
 
 No. 4. At first not dressed; but, in consequence of being weakly, was after- 
 wards top-dressed with 3 cwt. of gypsum, and 1 cwt. of common salt, done in 
 consequence of the highly beneficial effect produced on the four acres of mashlam 
 crop above alluded to. Result. — Tliongh done so late that the beans were already 
 coming into fioiar, it helped them mwh, and they ended as -well as any of the 
 above. It may here be remarked, that all the beans were, particularly for that 
 high district, heavy, being on trial soon after mowing C5 to 66 lbs. per bushel. 
 
 I. Observations upon the effect of the top-dressings applied iw 1841 upon the crop 
 of IS 12. 
 The following remarks are quite as interesting as any thing contained in the 
 numerous experiments made this year at Barochan by Mr. Fleming's skilful 
 
 ^ 
 
68 r.xPK.niMnNT.s upon mixkd crops. [Appendia:, 
 
 overseer. Tliey are, I believe, the first syslemntic scries of observations of the 
 Kind yet pubhshed. They are valuable, therefore, as the first s;eps in the line 
 o^ prolongcil observations upon tlie same land made during succesj^ive seasons, 
 by which prolonged observations only can we hope to eliminate the effect of 
 our variable seasons, and to arrive at true deductions in regard to the kind and 
 amount of effect which this or that manure is fitted to produce. 
 
 I do hope that Mr. Gardiner, who is capable of observing so well, and of 
 experimenting so accurately, will not lose the opportunity which, the prese.it 
 year will af!brd him of continuing d\ese important observations: — 
 
 1°. Top-dressings upon hay, C-'ovcnlea field (see Appendix, p. 17). On 
 looking over this field at different times, and parUcularly early last spring, the 
 square on which nitrate of soda and bones mixed had been sown was earlier, 
 and of a darker green colour, than any of the rest of the field, and when stocked 
 with cattle, the portion top-dressed was more relished, and consequently always 
 eaten quite bare. 
 
 '2,°. Upon part of the pleasure-ground — soil a very stiflfblue clay — nitrate of 
 soda was sown at the rate oflGOlbs. per acre. After this application white 
 clover came up very thick and strong, and it was cut three different times with 
 the scythe, and each time it came up stronger and thicker than the surrounding 
 grass, whilst, before dressing, it was the weakest, and this season, 1842, it is 
 better, and the portion dressed still easily distinguished. 
 
 3°. The field at Crook's farm (see Appendix, p. 17), which had been top- 
 dressed with nitrate of soda applied on each alternate ridge, on being ploughed up 
 from hay stubble was found tougher upon the dressed ridges, the grass roots 
 being stronger and deeper in the soil of those ridges which had been dressed. 
 
 4°. At p. 21 of this Appendix an experiment upon moss-oats is recorded. 
 This was sown down with a mixture of grass and clover seeds, and cut for hay 
 this season, 1842. In examining the hay crop some of the dressings on the oats 
 of last year seemed to have had a good effect on the hay crop of this year. ISos. 
 ] and 3 were the worst of any ; No. 3 very little better, rather more clover ; No. 
 4 excellent, very thick of red and white clovers and rye-grass, and the hay was 
 of a good quality ; No. 5 a little better than No. 3, but far from being equal to 
 No. 4 ; No. 6 the best of any, full of red and white clovers and rye-grass, and 
 had three-fourths more hay upon it than all the others, except No. 4 ; No. 7 not 
 better than the undressed ; Nos. C and 4 presented a most remarkable appearance 
 compared with the others, and any person seeing them, and not knowing the 
 circumstances of the case, would have said that these two portions only had 
 been cultivated, whilst the rest had been left in a state of nature. After being 
 cutfijrhay, the aftermath of these two portions still presented the same difference 
 of appearance in the sward, and they continue of a better colour. 
 
 A. F. GAUDiNEn. 
 
 GENERAL KEMARKS ON THE ABOVE EXPERIMENTS OF 1842. 
 
 However valuable the above experiments may be, and however interesting 
 the results to which some of them may appear to lead, it is of importance to 
 bear in mind — 
 
 1°. That they are the results only of a single season, and tliat a remarkably 
 dry one. 
 
 2°. That they show the effect of the substances employed in certain localities 
 only — the localities differing in the nature of their soil — in their distance from, 
 and height above, the sea — and in the average fall of rain to whieh they are 
 subject. 
 
 3°. That the results are obtained by trials upon certain varieties of each crop 
 only, and may not be obtained even on the same spots with other varieties — of 
 turnips for example, of potatoes, oats, wheat, or barley. 
 
 4°. And that other causes, not yet noted, may have existed of sufficient in- 
 
No. VIII.] EXPERIMKNTS UPON' TLRNTPS. f>9 
 
 flucnce to prevent the exact results from being obtained upon a repetition of the 
 experiment. 
 
 5°. Above nil, it must be borne in mind that w^e are yet in the first infancy of 
 accurate experimental agriculture — that it will take many careful repetitions of 
 our experiments before we can elin)inate the effects of the seasons — of the alti- 
 tude of our farms, their distance iVom the sea, the falls of rain to which they 
 are subject, and the kind of soil of which they consist. In tl>e mean time our 
 most careful deductions must be considered as partir/l only, and as open to douLt 
 — as fiicis by the combination and comparison of which we are hereafter to ai- 
 rive at more general truths. 
 
 With those preliminary observations, I turn to the experiments themselves — 
 
 A. — Tki c.ipcrhmnts vpon turnips. 
 
 The first series, those of Lord Blantyre — except the general answer that soliw: 
 suhstaiir-cs cannot replace farm-vard 'nuiiniix — afford no very satisfactory results. 
 They exhibit, indeed, some striking circumstances — such as 
 
 l'^. Tliai 100 lbs. of salt per acre may, in a diy season, reduce the natural or 
 unaided produce of turnips one-haif— and that the some weight of nitrate of soda 
 may reduce it one-fourth. 
 
 2^. That in such a season as much as 16 cwt. of rape-dust per acre may be 
 applied, one-half drilled in, and one half as a top-dressing, tcitlwut producing any 
 sensilAe benefit. 
 
 3^. That the same may be the case, if eight cwt. of rape-dust be drilled in, 
 and half a cwt. of nitrate of soda be afterwards applied as a top-dressing — 
 while if the same weight of common salt be used as a top-dressing instead, 
 the crop will be increased one-lialf. 
 
 These results are too anomalous to be considered for the present as more than 
 accidental. They may possibly be explained either by the different degrees of 
 moisture of the several parts of the field in which the mixtures were applied — 
 or on the supposition, which is very probable, that in the concentrated state 
 some of these saline siilstnnces are more liurljid to the growiiif plant than others. 
 It is to be regretted that the season was so uiipropitious to this series of experi- 
 ments, for though the following experiments rf Mr. i-'leming afToid some valuable 
 information, further knov^ledge still is wanted in regard to the rdntive effects of 
 different saline siibstancts upon the grov:th of titrni-ps, where no fermentible ma- 
 nure is applied. 
 
 4-^. In these experiments, a striking contrast is presented between the effects 
 of rape-dust and those of guano. IG cwt. per acre of the tbrmer gave only Sf 
 tons of turnip bulbs, while 2 cwt. per acre of the latter gave 5 tons. It appears, 
 therefore, that rape-dvst requires moist weather or occasional rain, u-hile guano, 
 even in very dry seasons, u-iU prod.iue a considerable effect. This is consistent with 
 what we know of the eniploymerit of the latter substance as a manure on the 
 arid plains of Peru. 
 
 II. The next four series of experiments, those of Mi-. Fleming, are rich in re- 
 sults and suggestions. 
 
 1°. Limits of error. — The first observation which a careful examination of 
 them will lead the reader to make — and it appears to me to be a very important 
 one in reference to all future experiments of this kind — is suggested by the se- 
 cond series — those upon early ydlmr turnips, p. 44. 
 
 In this series there are included two plots (Nos. 5 and 18), upon which no 
 manure was used. Upon one of these the produce amounted to 12 tons 17 cwt., 
 upon the other to 11 tons 8 cwt. only — being a difference of U tons, or one- 
 eighth of the whole. This difference between two equal portions of the same 
 field, ap])arently similar in soil, could scarcely, 1 think, have been anticipated, 
 and it shews that — where the produce ol/lained by the application of two unlike 
 manures, to this turnip ciop, does not differ mare than IJ tons per acre, the effects 
 
(/ 
 
 , €0 EXPERiiENTs UPON TURNIPS. [Appendix, 
 
 rfihe lieo mnimrcs may be considered as pracUcally e<i'tifd — since this amount of 
 difference may have arisen tVom the unlike qualities of the two plots of land, to 
 which the manures were respectively applied. 
 
 This is an important practical rule for enabling us to judge accurately in 
 regard to the true effect of the several manures employed in the series of experi- 
 ments (p. 41) referred to, but the fact itself suggests also an important modifi- 
 cation in the mode of conducting all similar comparative experiments in future. 
 
 In my previously ])ublished Suggestions, I have recommended the setting 
 apart oi one undressed portion only of the field on which the trials were made — 
 considering tiiat the produce of this portion would represent the average fertility 
 of the whole undressed part of the field But these experiments of Wr. Flem- 
 ing seem to shew that this opinion cannot safely be entertained. It appears to 
 be necessary, therefore, in all future experiments from which accurate deduc- 
 tions are intended to be drawn — that two vndresscd plots, at least, should, in cu.'ii 
 cdsc, be measured, out, and their relative proliicc asrertained, in order to afford a 
 trust-worthy average of the unaided fertility of the land. 
 
 Suggestion I. — For the clearing up of this point, however, it wouli be very 
 desirable to institute a series of weighings of the produce of equal portions of 
 land, in several different parts of the same field, the w-hole of which nas been 
 tilled and manured in the same way. This would throw some certain and sat- 
 isfactory light upon the amount of variation which, from natural causes, may 
 take place in the same crop, grown upon different parts of the same field, and 
 under the same circumstances. We should thus be enabled to allow for the 
 influence of natural causes upon the results of such experiments as are made, 
 with the view of determining the true action of the different manures we apply. 
 
 Siiiigestioii II. — Butif soine slight difference in the soil, which the eye cannot 
 detect, be capable of materially affecting the natural produce of the unmanured 
 parts of a field, it may also be sufficient to modify — t'.iat is, to increase or to 
 lessen — the effects produced by the saline and other manures we apply to the 
 different parts of the same field. It suggests itself, therefore, as the more pru- 
 dent and wary course of experiment to dress two plots at least with each of tha 
 manures whose relative virtues v/e are desirous of testing, and these in different 
 parts of the piece of land upon which our trials are made. The mean produce 
 of the two or more plots we thus dress, compared with the mean produce of 
 those to which no dressing has been given, M'ill indicate more nearly the aver- 
 age effect of the manure we have been trying, upon the given soil and crop. 
 
 The reader will perceive in the new precautions thus indicated, one of those 
 practical results which year by year will necessarily flow from the continuation 
 of the train of inductive experimental research, now, I hope, fairly entered upon 
 by the practical agriculture of our country. 
 
 2°. Giianei. — Among the other experiments upon turnips here stated, those 
 upon guano are the most practically successful. Thus, per acre, without any 
 farm-yard manure 
 3 cwt. of guano alone gave 23 tons 8 cvii. oi Swedes . . (p. 41)' 
 
 5 CWl. of guano with ) nn . n . r t-. j ^7- ?» r At\ 
 
 20 bushels"ofwood-a.shes5 ^^ tons 2 cm. oi Early Yelhw . (p. 44). 
 
 5 cwt. of guano alone 32 tons 15 cwt. of White Globes . (p. 46\ 
 
 3i cwt. do. 20 tons cwt. of Yellow i^- White mixed (p. AC-e). 
 
 3} cwt. do. 28 tons cwt. oi Purple-topped Yellow (p 47). 
 
 These results are very gratifying, since they seem to shew that for the turnip 
 crop this light and portable manure may be substituted with safety tor farm- 
 yard dung. But they are more gratifying in connection with the large reduction 
 which has lately taken place in the price of this substance. In none of the 
 cases above mentioned did the quantity applied exceed 5 tons per acre. This 
 quantity may now be purchased for three guineas, though when these experi- 
 ments were undertaken it cost X6 5s. 
 
 It is no small matter of congratulation, that this important reduction has been 
 
No- VIII.] EXPERIMENTS UPON TURNIPS. M 
 
 mainly brought about by the expression of scientific opinion, and by the readi- 
 ness with which various persons, manure-manufacturers and others, have put 
 in practice the su2;gestions contained in the precedina; part of this Appendix 
 (p. 2f)), for the formation of an artificial mixture in imitation of the natural 
 guano The fear of competition produced its natural effect upon the market, 
 and led the importers of this substance to content themselves with a smaller 
 profit. It is to be hoped that the more extended sale which has followed the 
 reduction, will leave the spirited merchants who first brought it into the country 
 no reason to regret the diminution in price. The benefits which the practical 
 agriculturist derives from one such reduction as this are not all at first 
 sight perceptible. The demand for guano has so greatly lessened the call for 
 rape-dust, that it has also fallen in price from £8 to £5 10s. per ton. Thus 
 ramified and extended are the results of a single chemical investigation — or the 
 publication of a single well-founded scientific opinion. 
 
 3°. Artificial Guano. — In connection with this subject it is important to as- 
 certain to what extent the attempts to manufacture a substitute for the natural 
 guano have been attended with success — in soferas the turnip crop is concem- 
 ed. The only comparative results which the above experiments present, are the 
 following — those upon Swedes being obtained by the use of 3 cwt. of each 
 mixture, those upon the yellow and white turnips by the use of 5 cwt. of each: — 
 
 Swede.'. Early Yellow. White Globe. 
 
 1°. Nothing . . . 12 tons 5 cwt. 12 tons 17 cwt. — tons — cwt. 
 
 2°. Natural guano . . 2^ " 8 » 32 " 2 " 32 " 15 " 
 3°. Barochan artificial guano 17 " 14 " 21 " 2 " 22 " 10 " 
 4°. Turnbull's artificial guano 14 "11 " 21 " 4 " — " — " 
 
 These results show that, when equal quantities are employed, equal results 
 are not obtained from the natural guano and from the artificial mixtures. 
 It also appears that Mr. Fleming's mixture is much more efficacious than that 
 of Mr. Turnbull. They are made up, with some modifications, after the recipe 
 given in the preceding part of tliis .'\ppendix (p. 25), 6ut are, no doubt, suscep- 
 tible of improvement. It is, indeed, one of the indirect benefits which will re- 
 sult fiom the introduction of this foreign manure, that it will stimulate to expe- 
 riments, by which we shall, no doubt, at last successfully imitate it — and will 
 lead, at the same time, to a more general and thorough understanding of the 
 principles upon which mixed manures ought to be compounded, and of the 
 mode of preparing them with the greatest possible economy. Many crude mix- 
 tures may be made at first, by dealers in manure and others, and many instan- 
 ces of want of success may occur, but now that we have adopted the system of 
 recordivs rrsnlts, whether apparently successful or the contrary, there is little fear 
 of our arriving at .satisfactory and economical truths at last. 
 
 Sugsestion III. — In experiments made for the purpose of aiding the real ad- 
 vance of scientific agriculture, I would suggest that no mixture should be used of 
 which, the composition is not exactly known — which, therefore, has not been either 
 made by the experimenter himself or by some dealer upon v/hose honor perfect 
 reliance is to be placed. The use of the random mixtures now sold under so 
 many different names, however successful they may be in this or that case, can 
 never lead to the discovery of useful agricultural principles, and, therefore, are 
 unworthy of the attention of the cultivator of inductive experimental agriculture. 
 
 4°. Sulphate of avimonin. — These remarks lead me to notice the effect ascrib- 
 ed in Mr. Fleming's second table (p. 44), to sulphate of ammonia — one cwt. 
 of which nearly doubled the crop. Thus — 
 
 The unmanured soil gave . . 12 tons 17 cwt. 
 With 1 cwt. of sulphate of ammonia 24 " 11 " 
 
 This is exactly equal to the effect produced by 15 cwt. of rape-dust ata cost of 
 XG 10s. But the sulphate of ammonia here employed was that prepared by 
 the Messrs. Turnbull, of Glasgow — which is not merely sulphate of ammonia, 
 but a variable and undetermhied mixture. It is prepared from virine, and I be- 
 
 29* 
 
63 EXPERIMENTS UPON TURNIPS. [Appendix, 
 
 lieve is contaminated also with a considerable proportion of saline substances 
 
 artificially :vlded to it. That it contains many substances useful to plants there 
 can be no doubt, and that it may prove a valuable manure is exceedingly pro- 
 bable, but under Us present name it can only lead to false deductions in expe- 
 rimental agriculture — and the use of it, therefore, iji comparative tiials such as 
 these we are now discussing, ought to be avoided. It is only, as I have already 
 said, from the use of pure substances mixed in known proportions, lliat valua- 
 ble, because undoubted, conclusions can be drawn. It is in vain co attempt to 
 eliminate the effects of diversity of soil and climate, if new causes of divei-sity 
 are introduced by die very substances with which our experiments are made. 
 
 5°. Bones dissolved in 'muriatic acid. — The action of bones is not in general 
 exhausted in a single season. If they are in the state of fine dust, tliey decom- 
 pose more quickly and cease to act in a shorter space of time. Ey dividing 
 them still more minutely, or by solution in an acid, it has been thought that 
 their apparent efficacy might be increased. Mr. Fleming, in 1841, made some 
 experiments which seemed to justify this conclusion. In the present tables 
 other results are exhibited, which favour the same opinion. I place together 
 here the results upon potatoes, as well as upon turnips, for the purpose of 
 comparison: — 
 
 Bone-dust. Bones in muriatic add,. 
 
 16CWT. 18 CTV"T. 3 CWT. 10 CWT. 
 
 tons. cwt. tons. cwt. tons. cwt. tons. cwl. 
 Swede Turnips . . . 14 17 . — — — — 18 11 
 
 White Don Potatoes . . — — 9 15 12 15 — — 
 
 These results, the only ones contained in our tables which can be compared 
 together, are both greatly in favour of the dissolved bones, in so far as the action 
 upon the fiist crop is concerned. It will require longer obser\'ation to deter- 
 mine in whirh form the same weight of bones will produce the more lasting 
 eflfects — and will be the more economical on the wliole. 
 
 6°. Ni'ratc of soda. — The effect of 1 cwt. of this salt per acre upon the early 
 yellow turnip is very remarkable (p. 44), having given upwards of 27 tons of 
 bulbs, at a cost of 25s. It is to be regretted that no similar experimpnt is re- 
 corded upon the other varieties of turnip, either by Mr. Heming or by Mr. Al- 
 exander. In the text (Lecture XV., p. 3^5 to p. 342) an abstract of all the pub- 
 lished results hitherto obtained by the use of nitrate of soda will be found in a 
 tabulated form. 
 
 1°. Lime. — An interesting result in Mr. Fleming's first table may hereafter 
 lead to some satisfactoi-y eiyerimcnial determinations of the points considered 
 still doubtful in regard to the form in which, and the time when, lime may 
 be most efficaciously applied, in reference to the culture of particular crops. He 
 caused carbonate of lime and caustic (newly slaked?) lime to be sown in the 
 drills without manure, and the effect upon the crop of Swedes was as follows: 
 
 Soil unmanured 12 tons 5 cwt. 
 
 Carbonate of lime, 20 bushels . . IG " 11 " 
 
 Caustic lime, 5t) bushels . . 11 " 8 " 
 
 The immediate effects of lime applied in these two forms was veiy different — 
 the caustic lime les.sened the turnip crop, while the cu-bonate increased it by 
 4? tons. This effect most probably arose from the lime, in its caustic state, 
 taking from the soil the carbonic and other organic acids from which the roots 
 in the early infancy of the plant would have derived a portion of their nourish- 
 ment, and thus retarding and stunting their growth. At all events the experi- 
 ment seems to indicate that lime ought to be in the state of carbonate — die mild 
 state — more or less entirely, if it is intended to benefit the crop to which it is 
 immediately applied. When mixed with manure, however, where vegetable 
 matter abounds in the soil, or where the lime is nrerely harrowed into the sur- 
 face — in all which cases it will readily become, in a great measure, saturated 
 with carbonic acid — the skilful farmer will understand that the deduction drawn 
 from the preceding experiment will not apply. 
 
No, VIII.] EXPERIMEN'TS I'PO-V TURNIPS. 63 
 
 8°. RiTpc-(hnf. — The results exhibited in this year's experiments, generally, 
 are not so favourable to the employment of this substance as was to be expect- 
 ed The reason, however, is, probably, that which has already been suggested 
 in discussing the results obtained at Lennox Love — that rape-dust requires a 
 vioist soil or O'y-tts'onal showers. But this itself is an impoitant probable deduction. 
 The reader will find a comparative view of the whole of the results with this 
 substance in ths text (see Lecture XVII ) 
 
 9^. Animal Ciarcoal. — Tiie effect of animal charcoal upon Swedes in Mr. 
 Fleming's experiments is only inferior to that of guano. It is certainly deserv- 
 ing of fuither trials, and especially in comparison with what is called exhausted 
 arumal charcoal — that which has already been used in the refining of sugar. 
 In France, the latter is said to be preferred to the former, and to be sold by the 
 sugar refiners at a higher price than they pay for it in tiie recenUy prepared 
 state. 
 
 10"^. 0!ker mixed manures. — In regard to other mixed manures, the reader 
 will find much practical information by the study especially of No. 3 of Mr. 
 Fleming's tables, p. 45; and of Nos. 1 and 2 of those of Mr. Alexander, p. 46. 
 These are the more worthy of the attention of the practical man, since Mr. Flem- 
 ing considers himself justified in remarking as the general result of the experi- 
 ments in p. 45, that any of the mi.r.tur-:s used will in his Inid prodMce an ave- 
 ri'se crop of tnrn'ps a! a less expense than farm-yard vumvrrT. This is the kind 
 of ro!sult which it ought to be the ambition of every practical man to work out 
 for himself upon his own land. 
 
 11°. Si.e and weight of huUts. — There remains only one other topic in con- 
 nection witii thesj experiments to wluch space will permit me at present to ad- 
 vert. In the remarks upon the table inserted in p. 41, it is stated that the tur- 
 nips on the plots dressed with — 
 
 (3ruano and wood-ashes — were pre-eminent for size of M.bs. 
 
 Sulphate of ammonia — larg;e in bulb, but soft, and light in we'ghl. 
 
 Potash and lime, salt and lime, sulphate of magnesia, nitrate of soda— swiaM 
 in bulb, but firm an/l solid. 
 
 Bone-dust and the artificial guanos — both containing bones — Ike bvXhs firm 
 ani sola, but not remark-Me in siz".. 
 
 Now upon the solidity of tlie bulb — other things being equal — it may be pre- 
 sumed that the relative nourisliing properties of different species of turnip will 
 materially depend. The quantity of water which diflerent specimens of the 
 same variety of turnip contain varies from 79 to'91 per cent. — that is, some tur- 
 nips of the sane speciis contain nnlij four-fifths, while others c-ontain upwards of 
 nine-tenths of their iv.:ight of -lo-i'rr. In other words, the same variety of turnip 
 may contain such unlike quantities of water, that '2 tons grown on one spot 
 may not contain more than 1 ton grown inanotiier. The weight of buUjs, there- 
 fore, is no safe criterion of the quantity of fjod raised on different parts of the 
 same field — where tlie general treatment, or the substances applied to aid the 
 growth, have been different. 
 
 Now in the above experiments the guano gave 32 tons of veri/ large, the sul- 
 
 fhate of ammonia 21 of soft, and the nitrate of soda 21 oi smaU and solid, bulbs, 
 t is probable, therefore, that the actual quantity of food raised by the aid of the 
 nitrate of soda was much greater than even by the natural guano. It may also 
 have been that the lli tons of solid bulbs given by the svUphate of magnesia, 
 or the 12§ raised from the land without manure at all, may have contained as 
 mucli nutriment as the 21 tons of so ft bulbs raised by the sulphate of ammonieu 
 Snggcstion IV. — The bare possibility of sucji a circumstance as the last, 
 shows how little absolute confidence we can place in the numerical results as 
 yet obtained, considered as evidences of tke greater or less a'/)wunt of food, which 
 the use of this or that kind of manure will enable us to raise from a given ex- 
 tent of land. It suggests, also, the necessity of a further determination of the 
 relative quantity of water contained in our experimental turnip crops. This 
 will, without diflSculfy, be effected by selecting three or four turnips of different 
 
64 EXPERIMENTS UPON POTATOES. [Appendix, 
 
 sizes from each sample — cutting a slice from either side, and one from the mid- 
 dle of each turnip — wei^liing the whole — drying them then, first in the air, 
 aftei-wards before a gentle fire, and lastly in an oven so hot as not to brown white 
 paper or dry flour, and then weighing. The loss being the weight of the water 
 in the turnips, will enable the experimenter to determine the relative quantities 
 of food raised upon his differont plots, and tlierefore the relative value of his 
 different applications or methods of culture. 
 
 In this suggestion the reader will perceive another of those precautions which 
 the prosecution of our experimental inquiries renders necessary — future years 
 will suggest others — but the increase of trouble will not deter the zealous la- 
 bourer in this important field — for the more precautions and difficulties multiply, 
 the greater the honour will be to those who by perseverance shall successfully 
 overcome them. 
 
 B. — The E.cperimcnls upon Potatoes. 
 
 Nearly all the experiments in the first table of results (p. 48) were made with 
 mixed manures. 
 
 1°' G-uaiio and rapc-diist. — Among these the effect of guano is again sticking, 
 and upon two of the varieties greatly exceeds that of rape-dust. Thus, the pro- 
 duce of the three varieties tried was — 
 
 While Don. Red Don. Connaught Cups. 
 
 Unaided soil . . .1 tons '\ cwt. 6 tons 15 cwt. 5 tons 15 cwt. 
 With 3 cwt. guano . . 18 " 9 " — " — " — " — " 
 With 4 cwt. guano . .- " — " 14 " G " 13 " 14 " 
 With 1 ton of rape-dust . 12 " 6 " 10 '= " 13 " " 
 
 We are not enabled, by the experiments before us, to compare its effect with 
 that of farm-yard manure. 
 
 A curious question suggests itself upon the inspection of the above numbers 
 — one which could scarcely have arisen in our minds, had not differences such 
 as the above presented tliemselves among the results of our experiments. 
 Nothing is more common than to ask which of several varieties of potato is the 
 more prolific — and a practical man who lias made the trial has no difficulty in 
 giving an immediate answer to the question. But the experiments of Mr. Flem- 
 ing seem to say that the rdatwe weight of crop yielded by each of two or more xa- 
 rieties of potato, drpcnds vpon the way in wMch ijou treat or manure them. Willi 
 one treatment a variety (A), with another a variety (B), will give the heaviest 
 crop. Thus, oui" three varieties gave with — 
 
 Wliile Don. Red Don. Connauclit Cnpg. 
 
 Natural guano . 18 tons 9 cwt. 14 tons 6 cwt. 13 tons 14 cwt. 
 
 Rape-dust . . 12 " 6 " 10 " " 13 " " 
 
 Both substances agree in saying that the white is considerably more prolific 
 than the red Don. But while the guano adds that both Dons are more prolific 
 than the C«p5, the rape-dust pronounces the latter variety to be superior to either 
 of Uie former. Now it may have happened tliat in the last case of the three, the 
 rape-dust, from some circumstance not noticed, may have acted better than in 
 the other two cases, and that in this way the discordance may have arisen. Un- 
 fortunately, however, there are upon record no other experiments made upon 
 any two of the varieties of potato with otlier substances used in hke proponion 
 — by which this question might have been in some measure solved. But the 
 interesting, and as it may hereafter prove, important inquiry suggests itself — 
 what is the order of relative productive ncss of the several varieties of the same atlli- 
 cated plant, when they are srverallij dressed or mam/red with this or with that sub- 
 stenu-c? This question will, no doubt, hereafter lead to extended series of very 
 refined experimental inquiries, from which not only much knowledge but much 
 practical benefit may be derived. 
 
 Suggestion V. — It may be, for instance, that a given variety of potato, turnip, 
 oat, barley, &c., is more valuable as food, more agreeable to the taste, or brings 
 
So. VJII] EXPERIMENTS CPON POTATOES. 65 
 
 a better price in tlie market — but by the ordinary modes of culture is the least 
 productive of those generally cultivated. It would then be not only an interest- 
 ing, but an important economical question to ask — could this variety be render- 
 ed more productive by a different mode of treatment — one especially adapted to 
 its own nature 1 Would the practical man not rejoice to think that such a result 
 could be brouoht about by the aid and suggestions of science"? Yet this is the 
 result to which the refined series of experiments suggested by the question 
 above proposed may possibly lead. 
 
 ]\Iay I venture to hope that some of my more zealous readers will be induced, ' 
 during the present or succeeding summer, to make trials of the relative effects 
 of the same saline or other known substances and mixtures, upon different varie- 
 ties of the same crop — of potatoes, turnips, wheat, &;c., in circumstances other- 
 wise equal, in some such form as the following : 
 
 Variety A. Variety B. Vaiiety C. Variety D. Variety E. 
 
 Substances. Substances. Substances. Substances. Substances. 
 
 A. I B. I C. •*• I B. I C. A. I B. I C. A. I B. I C. A. ] B. | C. 
 
 The results if carefully ascertained are sure to lead to good, if they should 
 not be successful at once in solving the problem above proposed. 
 
 3°. Solidity and size nf the potatoes. — Nothing is said in the observation of 
 Mr. Fleming, or his overseer, in regard to the size or solidity of the different 
 varieties of potato, or of the different samples of the same variety on which the 
 experiments were made. Yet in connection with the remarks I have already 
 offered upon these qualities of the turnip, it is proper to add that the potato is 
 subject to similar variations in the proportion of water it contains — and, there- 
 fore, in the relative amount of nourishment capable of being afforded by equal 
 weights of its different varieties. 
 
 Some potatoes contain less than 70, otbprs upwards of 80 per cent, of water, 
 so that while 100 tons of one sample will give only 20 tons of nourishment, the 
 same weight of another will give 30 tons, or one half more. In general, such 
 as grow on heavy or clay soils, or such as are less ripe, contain the most, while 
 those which have been planted upon sandy spots, or are fully line, contain the 
 least water. But the effect produced by different soils we begin now to 
 see may be produced by different meiliods of dressing or medicating our crops 
 also. 
 
 Siigi(rsli(m VI. —It would be interesting to determine, therefore, by actual 
 experiment, the relative proportions of water contained in die produce of the 
 several experimental patches of potato ground upon the same field, when 
 equally ripe, or when dug up on the same day. This would afford us the 
 means of approximating still more closely to the true economical action of our 
 different manures upon the potato crop. It may turn out that in certain cases 
 the increase of produce, as indicated by a greater weight, is only apparent, 
 while the increased amount of food raised may in other cases be considerable, 
 though the balance indicates no increase of weight. 
 
 Did we know the relative proportions of water in the several samples of the 
 three varieties of potato raised by Mr. Fleming by the aid of guano, and of 
 rape-dust, already compared together, our conclusion in regard to their relative 
 productiveness, when treated by either substance, might be materially altered. 
 I hope, therefore, that this point also will hereafter arrest the attention of some 
 of our experimentalists. 
 
 4°. Permo.nnit effects of salins manures on the futvre productiveness of the 
 seed. — Recommending to my practical readers a careful consideration of tlie 
 effects of an admixture of wood ashes with the several dressings applied to the 
 turnip and potato crop, I pass on to the two following series of experiments 
 with saline manures upon the potato crop, as given on p. 49. These two series 
 are well conceived, and the results very instructive. Of these results the one 
 which seems to me most deserving of the attention of the practical man is con- 
 
66 EXPERIMENTS UPON POTATOES. [Appendix, 
 
 tained in a few words, thrast in as it were, amons; the remarks appended to tlie 
 table (1°, p. 4y.) In the later printed copies I have caused them to be put m 
 italics, with tlie view of bringing them into notice. If the reader will turn to p. 
 20 of this Appendix, he will find a remarkable experiment recorded, in ■•vhich, 
 by top-dressing well-manured potatoes, with a mixture of \ of nitrate and | of 
 sulphate of soda, the enormous crop of liO tons an acre was obtained from the 
 small plot experimented upon. Some of these potatoes were kept for seed, and 
 planted alongside of others of the same variety, which had not been so dressed, 
 arkd tlie result is stated in tlie few words above referred to — " These last, under 
 the same /■rcatmenl in every respect, did not produce so good a crop by lb bolls (3| 
 to9is) per acre." 
 
 In so far, therefore, as this experiment is to be relied upon — for we must not 
 be hasty in drawing general conclusions — it appears that the benefit to be de- 
 rived from a skilful treatment of the potato plant does riOt terminate with the 
 greater immediate crop we reap, but extends also into future years, improving 
 the seed and rendering its after-culture more productive. 
 
 Siigffestio-n VII. — I'his idea is worth pursuing, were it only for the purpose 
 of making out the possible existence of so important a physiological law — how 
 much more when it appears so pregnant with important practical results. But 
 thus it is in all cases, that the prosecution of experimental research, witli im- 
 mediate reference eitlier to purely scientific or to purely practical results, ends 
 in improving and benefitting both abstract science and economical practice. 
 
 I am unwilling to follow out or to reason upon this possible law, as if it 
 were really established; but the possibility of its tmtlt appears to throw light 
 upon such questions as this — why the seed must occasionally be changed if 
 large crops are to be continually reaped. One soil may be adapted to give the 
 plant a large supply of this or that substance in which the other soil is com- 
 paratively deficient ; and it may be possible to medicate our seed-corn, while 
 growing, so as to give it the qualities which at present it can acquire only by a 
 change of soil. 
 
 All this, however, can be only determined by experiment, and the intelligent 
 reader will net fail to be struck with the remarkable richness of these first trials, 
 in suggestions for future carefully conducted experimental researches. 
 
 5°. IIow shouM saline vianvrcs be applied to the pnlalo crop? — Ought they to 
 be mixed with the manure, or to be applied as a top-dressing ? Mr. Fleming's 
 experiments do not fully solve this question ; because the soil on his two fields 
 was very unlike in quality. Thus with manure alone the one field produced 
 12 tons 15 cwt., the other only 8 tons 17 cwt per acre. A perfectly satisfactory 
 solution of the question can be obtained only by experiments with the same sub- 
 stances, upon the same soil, and with the same variety of potato. Yet the experi- 
 ments now before us add considerably to our knowledge upon this point, and 
 such of them as are capable of being compared together are much in favovr 
 of mixing the saline substances 7cith the manure. Thus applied in nearly 
 equal proportions by both methods, nitrate of soda, sulphate of magnesia, and 
 sulphate of ainmonia, gave the following results : — 
 
 FIRST FIELD. 
 
 Topdi 
 tons. 
 
 Manure alone 12 
 
 Nitrate of soda It! 
 
 Sulphate of magnesia .... 13 
 
 Sulphate of ammonia .... 14 
 The proportionate increase, therefore, in these three cases, is g^-eatly in favour 
 of mixing with the manure, but something may depend upon die soil and 
 season ; and, therefore, other experiments are necessaiy before we can draw a 
 general conclusion. It may prove that some act better when applied in the one 
 way, and some in tlie other. 
 
 C°. Shdphate of soda. — With this substance applied in either way, the singu« 
 
 ELD. 
 
 SECO.VD FIELD. 
 
 sefi. 
 
 Mixed with manure. 
 
 •wt. 
 
 tons. cwl. 
 
 15 
 
 8 17 
 
 
 
 12 7 
 
 5 
 
 11 7 
 
 10 
 
 13 7 
 
No. VIII] F.XPEHIMENTS UPON' POTATOES, BARLEY AND OATS. 67 
 
 lar and consistent result was obtained that 2 cwt. per acre caused no alteration 
 vvliatever in the weigkt of the produce upon either of the two on Which tlie tiials 
 were made. Of tl>e respective qualities of the crops nothing is stated. 
 
 7°. Siilp-hate with nitrate of soda. — Tlie above result with sulphate of soda 
 alone, is the mora remarkable from the known effect produced by this and other 
 sulphates when mixed with nitrate of soda. Tlus yeai", also, the mixture of 
 nitrate with sulphate of soda added one-half (G tons per acre) to the crop, a 
 gre;it°r proportionate increase even than in the experiment of 1841, which gave 
 an increase of 8 tons out of a total produce of 30 tons per acre. But this 
 season Mr. Fleming has tried, with still greater success, a mixture of 1 cwt. 
 each of sulphate of magnesia and nitrate of soda, the pi-oduce rising by- the use 
 of this top-dressing to •2-2k tons. The relative effects of the two sulphates 
 would have been more clearly proved, had die proportions of nitrate of soda 
 applied per acre in the two mixtures been the same. 
 
 8°. Nitrates of soda and potash. — Another interesting fact to add to those 
 alrerdy registered upon the relative efficiency of these two saline substances, is 
 presented in page 49. One hundred weight and a half of — 
 
 Nitrate of soda gave Hi tons. 
 
 Nitrate of potash gave 18 J tons. 
 
 This difference may have been due to accidental causes — or the 18^ tons of 
 the one result may have contained no more food than the 16 tons of the other; 
 but the multiplication of accurate experiments will eventually lead us to the 
 truth. Apparent failures and discordant results must not discourage the prac- 
 tical man. By recording all trust-worthy results, the light will almost sponta- 
 neously spring up at last. 
 
 9^. SiliraJe of potash. — The results obtained by the use of this substance, and 
 the remarks appended to them (p. 50), are deserving of much attention. In re- 
 ference to this compound, and to the silicate of soda, I beg the reader to turn to 
 the suggestions contained in diis Appendix, p. 40. 
 
 10°, jM'.red 'inanurcs. — The mixtures in i:>age 50 will no doubt be imitated, 
 and by those who can obtain them oiknoim composition, comparative exjieri- 
 ments may be tried with advantage both to theory and to practice. 
 
 C. — The Erperinien/s vpon Barky. 
 
 The true practical value of the experiments upon barley will be shown by 
 placing them in the following form : — 
 
 Incroase. £ s d Cost per bush. 
 
 Nitrate of soda with common salt, gave 5 bush, for 17 6 — 3s. 8d. 
 
 Sulphate of soda with sulphate of magnesia, 7i bush, for 15 6 — 2s. Id. 
 Guano (at 2:)s.), .... 17 bush for 3 180 — 4s. 7d. 
 
 Common salt, 6 bush, for 4 6 — Os. 9d. 
 
 Tiu-nbuU's artificial guano, . . 2 bush, for 14 — 12s. Od. 
 
 The cheapest application, without doubt, upon this soil, is common salt. 
 At half the above price guano would produce the barley at 2s. 3d. per bushel, 
 and the larger quantity reaped, together with the value of the straw in the pre- 
 paration of manure, may satisfy many that either guano or the mixture of sul- 
 phates may be used with profit. It is a further recommendation of the common 
 salt, however, that it produced the heaviest, while guano produced the lightest 
 grain. 
 
 From tlie experiment with nitrate of potash no result can fairly be drawn, in 
 consequc;nce of the great drought of the season (see Mr. Gardiner's remarks). 
 
 D. — The Experiments vpon O.xts, 
 1°. Negative effect of saline manures. — The first of the two series of experi- 
 ments above recorded being made at Lennox Love — like those made at the same 
 place upon turnips — derive their principal interest from the illustration they 
 afford of the negativz effect of saline manures upon the cat crop, under the in- 
 
68 EXPERIMENTS UPON OATS AND WHEAT. [AppendtX, 
 
 fluence of great heat and drought. I select the more simple and striking cases 
 of diminution. The undressed part of the field produced 54 bushels per acre. 
 Common salt diminished this produce by G bushels. 
 
 Nitrate of soda 12* " 
 
 Sulphate of soda 15^ " 
 
 Rape-dust 9 " 
 
 Soot . . 12§ " 
 
 while 2 cwt. of guano raised the produce to 70 bushels, being an increase of 16 
 bushels. 
 
 These results not only confirm the deductions which we have already drawn 
 from the preceding experiments upon potatoes and turnips — that guano will act 
 even in our driest seasons, while rape-dust requires at least occasional rain — but 
 they go further in showing that, like the saline substances, ?v/;)r-('/!/s/, and even soof, 
 will iiiaterially diminish ihe oat crop, if the season be disttnguiskcd, by remarkable 
 drought. 
 
 2°. Moss oats. — The experiments upon moss oats (p. 53) are a continuation 
 and extension of those of 1841 with gi-eater attention to accuracy in the determi- 
 nation of the produce. The last column in the table speeiks for itself The 
 general produce of the field being 43 bushels per acre. 
 
 Increase. Cost per bush. 
 
 Sulphate of ammonia gave ... 9 bushels 2s. 3d. 
 
 Sulphate of soda with nitrate of soda gave 18 bushels Is. 7d. 
 
 Bones in muriatic acid gave . . . 18 bushels Is. 6d. 
 
 Silicate of potash, mixed with the above, gave 22 bushels 2s. Od. 
 
 In the last two cases the straw, which is usually imperfect in oats grown upon 
 moss land, was strong and healthy- It is obvious, therefore, that all these exper- 
 iments deserve repetition, though, as here set forth, the increase of grain by Nos. 
 2 and 3 was obtained at the least cost, and, therefore, to the economist will ap- 
 pear most important. 
 
 E. — The Experiments upon Wheat. 
 I. Effect of drnvght. — The first series, those made at Lennox Love, afford in- 
 teresting illustrations of the effect of gi-eat drought in modifying the action of sa- 
 line manures and of rape dust, upon the wheat crop. The more prominent 
 results are distinctly brouglit out when thrown into the following form. The 
 produce of the undressed part of the field being 47i bushels an acre, this produce 
 was affected by the several substances employed in the fuUowing manner : — 
 
 Decrease per acre. Increase peracie. 
 
 Common salt, 1 cwt li bush. — 
 
 Sulphate of soda, 1 cwt. . . . 9i bush. — 
 
 Soot, 32 bush slight. — 
 
 Nitrate of soda, 1 cwt. ... — slight. 
 
 Rape-dust, 16 cwt — 3* bush. 
 
 Guano, 2 cwt. ..... — s bush. 
 
 Thus, the nitrate of soda and the soot did no harm, though the drought did 
 not permit them 'o do any good. Conmion salt slightly, and sulphate of soda 
 largely diminished the crop ofgrain— while of these four substances the sulphate 
 was the only one which diminished the yield ofsti'aw. Nitrate of soda and 
 soot largely increased it. 
 
 On the other hand, guano slightly increased the yield of gi-ain, and rape-dust 
 added 3j bushels to the natural produce, both also augmenting the weight of 
 the straw by about one-tenth of tJie whole. 
 
 In this case, then, tlie rape-dust surpassed in beneficial effect the natural 
 guano, though, as we have already seen, it proved greatly inferior to the latter 
 when applied in similar proportions to oats, potatoes, and turnips. 
 
 2°. Suggestion VIII. — This fact suggests an interesting inquiry. It is known 
 that one of the most lucrative modes in wltich rape-dust has been hitherto 
 
No. VJIJ.] EXPERIMENTS UPON OATS AND WHEAT. 69 
 
 employed as a manure has been in top-dressing the wheat crap (see the prece- 
 ding part of this Appendix, p. 19). Has it.therefore, some x/wrm/ adaptation to 
 the wheat crop — which will account at once for its comparative failure upon oats, 
 turnijis, and potatoes, and for its superior efficacy to guano upon the wheat crop 
 — in the proportions stat.-d, and even in a very dry summer'? 'Ihe comparative 
 efficacy of the two substances applied in various proportions is certainly deserv- 
 ing of further investigation. It will be a gain not only to practical but to theo- 
 retical agriculture, should it be establislied that rape-dust can be profitably 
 applied to the wheat crop, in circumstances when it would be thrown away upon 
 oats or turnips. By turning to the next series, that of Mr. Fleming (p. 54), it 
 will be seen that the last result diere stated is also favourable to the action of 
 rape-dust upon tlie wheat crop.* 
 
 3°. MiduaUy counteriu-ting influence of different manures. — But another curi- 
 ous observation presents itself in the table of Lord Blantyre's results. It is in 
 the appaient struggle between the good and evil influences of the rape-dnst on 
 the onehanl, and of the saline substances on the other, when they were applied 
 together to the same plot of wheat (see Appendix, p. 19). Thus, when applied 
 in the proportions above stated — 
 
 Increase. Decrease. 
 
 Common salt gave .... — 1 J bush. 
 
 Rape-dust gave 3i bush. — 
 
 One-half of each gave . . . 2j bush. — 
 
 Or the natural effect of the rape-dust was lessened one-third when mixed with 
 the given weight of common salt. So, also — 
 
 Increase. Decrea.se. 
 
 Sulphate of soda gave ... — 9j bush. 
 
 Rape-dust gave ..... 3j bush. — 
 
 One-half of each gave ... — 3 bush. 
 
 Or the ivfluence of 1 cwt. of svlphate of soda for evil was one-third greater than 
 that of \G cwt. of rape-dust for good — in the given circumstances of soil, climate, 
 and crop. This result, which at present seems only curious, may hereafter lead 
 to the establishment of interesting truths capable of practical application. 
 
 Suppose, for instance, that upon two fields rape-dust were applied to the 
 wheat crop at the rate of Hi cwt. per acre, and that the one field contained na- 
 turally in its surface soil tlie proportion of sulphate of soda employed in Lord 
 Blantj're's experiment, while the other contained none — then iti the one case 
 the rape-dust would not only expend all its influence in overcoming the tenden- 
 cy of the sulphate to lessen the crop. — but would even seem to do harm if the 
 produce were compared with that of another field, of apparently similar soil, 
 near the surface of which this abundance of sulphate did not exist ; while, in the 
 other case, the rape-dust, having no counteracting influence to overcome, would 
 spend itself entirely in increasing the growth of the plant and the final yield of 
 grain. 
 
 Or suppose an artificial guano or other mi.xed manure artificially prepared, 
 to contain two or more substances which, in the soil they are applied to, have 
 a tendency to produce opposite effects — the one to increase, the other to 
 diminish, the amount of produce — the effect of this conflicting action of its 
 component substances would be such as to render the mixture of less efficacy, 
 perhaps of no efficacy at all — it mis:lit be even injunous to the crops, — although 
 it contained substances which, if applied alone, would have exhibited a power- 
 ful fertilizing action. 
 
 These two illustrations are sufficient to show the kind of light which obser- 
 vations, such as the one above adverted to, may hereafter throw upon practical 
 agriculture. 
 
 II. The substance of Mr. Fleming's table (p. 54), may be thus presented. 
 
 ■ See also the subsequent observations on the experiments upon beam. 
 
70 EXPERIMENTS UPON wiiKAT. [Appendix, 
 
 The unaided produce of tlie soil was 25 bushels an acre, and tlie eftVct of the 
 dressings as follows: — 
 
 Increase. Decrease. 
 
 Guano, 3 cwt ti bush. — 
 
 Rape-dust, 5 cwt., sulphate of magnesia, | cwt. . 3j bush. — 
 
 Sulphate of soda, li cwt., nitrate of soda, J cwt. \h bush. 
 
 Common salt, 3 cwt. ...... — Sj bush. 
 
 Common salt, 3 cwt,, dissolved bones, 1 cwt. . — 3 bush. 
 
 TurnbulTs artificial guano produced no sensible effect. 
 
 Under the circumstances, besides being favourable to guano, the above re- 
 sult is also in favour of the mixed sulphate and nitrate of soda, which we have 
 seen to operate beneficially upon so many other cultivated plants. The entire 
 crop appears to have been injured, not only by the summer's drought, but by 
 the severity of the preceding winter. 
 
 /n regard to common salt, it is worthy of remark, that the grain dressed by 
 it, whether oats, barley, or wheat, in Mr. Fleming's experiments of this year, 
 has been always heavier per bushel than any of the other samples tried. This 
 accords with tiie previous resulis of some other experimenters; but it does not 
 agree with Mr. Fleming's observations upon the wheat of IHil, nor with those 
 of JVIr. Burnet for lS'12, and therefore cannot yet be considered as a universal 
 consequence of thr; appUcation of this substance as a top-dressing. 
 
 III. The experinaents of Mr. Burnet, of Gadgirth, have already been paitially 
 detailed in the text {Lecture XVI., p. 362), and their value explained. They 
 are important, chiefly, as showing — ■ 
 
 1°. Ecotwinical viixtnrcs. — That mixtures can be prepared which, upon some 
 soils, surpass guano in efiicacy and in economical value, at its former price. 
 The price being now reduced, other experiments are required, yet still the less 
 effect of guano upon the wheat crop is in accordance with the results of Lord 
 Elantyrc. A wet season, however, may alter the numerical relation which 
 these result!5 exhibit. It will be observed that here also TurnbuU's guano pro- 
 duced no sensible effect. 
 
 2°. Effect of soda. — The efficacy of the salts of soda, whether the sulphate, 
 the nitrate, or common salt, upon Mr. Burnet's land, are aJ.so veiy striking — 
 half a hundred weight per acre of either producing an additional increase of 
 about 10 bushels of grain. 
 
 3'^. Yield of jlour. — Into his tabulated results, Mr. Burnet has introduced a 
 new element, and, as it seems to me, an important one in an economical point 
 of view, namely, the qvaiility of fiiie flour yielded Inj equal weights of the several 
 samples of grain. The differences presented in this column are veiy stiiking. 
 Thus 100 lbs. of the grain reaped from the plot which was — 
 
 Undressed, gave 76^ lbs. of fine flour. 
 
 Dx'essed with guano 68j lbs. " 
 
 With sulphate of ammonia 66j lbs. " 
 
 With sulphate of ammonia and nitrate of soda . . . 54| lbs. " 
 
 It would be interesting to learn from an experienced miller to what extent 
 such differences affect tlie money value of the grain to the manufacturer of 
 flour. 
 
 4°. Amount of gluten. — Through the anxiety of Mr. Burnet to draw as much 
 information as pos.sible from his excellent experiments, I am able to present 
 another feature in regard to the action of these saline and other substances upon 
 tlie qtiaUlij of (he prodiKX. 
 
 It is known that the quantity of gluten contained in different samples of 
 flour is very unlike, and that the nutritive property of the flour depends, to a cer- 
 tain extent, upon this quantity of gluten. It has also been stated, as the result 
 of experiment, that the grain which is raised by means of manure containhig 
 the largest quantity of nitrogen, is also the richest in gluten. With a view to 
 these questions, Mr. Burnet transmitted to me a pound of each of the samples 
 
No. VIII.] EXPERIMENTS UPON WHEAT. 71 
 
 of flour (see Appendix, p. 5), and upon examination I found them to contain 
 the following proportions of gluten : — 
 
 Water per cent. Gluten per cent. 
 No. 1. No apphcation 16-3 9-4 
 
 2. Guano and wood-ashes 16' 15 9-3 
 
 3. Artificial guano and do 16-8 96 
 
 4. Sulphate of ammonia and do 16'4 l()-5 
 
 5. Do., do., and sulphate of soda 15 7 97 
 
 6. Do., do., and common salt 15'7 9'6 
 
 7. Do., do., and nitrate of soda lf)-4 lO'O 
 
 8. TurnbulFs guano, gypsum, and wood-ashes . 15-2 9-1 
 These results are not without their interest, for though they do not show any 
 
 slrikinsd\ff>irence in the per-centage of gluten, yet upon the whole the result is 
 in favour of those samples to which the sulphate of ammonia* had been ap- 
 plied. One of these. No. 4, exceeded the undressed grain by about one per 
 cent., or one-ninth of the whole gluten it contained. Were the amount of this 
 gluten alone thei-efore to determine the feeding quality of the grain, (bis sample 
 might be considered as considerably the most nutritious. But besides the re- 
 lative proportions of fine tlour which tliey severally yielded, there are other im- 
 portant considerations which bear upon this question, and must influence our 
 judgment. These considerations it would be out of place to present among the 
 present observations. They will be found stated in the text of the Lectures, 
 (XIX., p. 498 et seq.) where we treat of the composition of wheat and other 
 varieties of grain — and of their respective values in the feeding of man and other 
 animals. 
 
 F. — The Experiments upon Grass. 
 
 I. The experiments of Mr. Alexander are not very remarkable or conclusive. 
 The meadow, which was drained moss full of timC)thy grass, gave naturally 1 
 ton 4 cwt. of hay, whereas the one dressing raised the produce to 1 ton 8 cwt., 
 the other to I ton 11 cwt., per imperial acre. The cost is not stated. 
 
 II. But those of Mr. Fleming are very interesting. By referring to page 17 
 of this Appendix, it will be seen that in 1S41 Mr. Fleming obtained a greatly 
 increased produce of hay by the use of nitrate of soda. He informs nie that 
 in making the present experiments he was desirous of again testing the efficacy 
 of this salt upon grass, on the same kind of laud, and of comparing it with that 
 produced by other saline substances. He selected also a portion of the same 
 field, on another part of which the trials upon wheat had been made in 1841 
 (see Appendix, p. 19), with the view of ascertaining if any analogy could be 
 traced or difference detected, between their action in 1841 iipn7i iv/ieat, and their 
 effect in 1842 on sovjn grasses — rye-grass, timothy, and red clover. Both objects 
 have been in some measure attained. I shall first present a summary of tiie 
 results. 
 
 OP HAV. INCREASE. DECREASE. 
 
 tons cwt. tons cwt. tons cwt. 
 
 The undressed soil produced ..18 5 
 
 Sulphate of soda, 3 cwt. ... 1 3 
 
 Nurate of soda, IJ cwt 2 10 12 
 
 Sulphate of soda, 1 cwt i . ~ „ 
 
 Nitrate of soda, i cwt S ^ i 
 
 Common salt, 3 cwt 1 6 2 
 
 Common salt, 2 cwt ^ i lo n a 
 
 Soot, IG bushels ^ i i^ u 4 
 
 Sulphate of ammonia, 1 cwt. . . 1 13 5 
 
 Guano, U cwt 1 18 10 
 
 * It will be borne In minrl that this is TiirnbuU's sulphate of ammonia, already adverted 
 to in pa^e 61 of this Appendix. 
 
72 EXPERIMENTS UPON GRASS. [Appendix, 
 
 A mixture of silicate of potash witli gypsum produced no sensible effect, 
 neither did Turnbuli's artificial guano. 
 
 \°. In this repetition of his experiment, therefore, the nitrate of soda on si- 
 milar land again increased greatly the produce of hay — giving, at the first cut- 
 ting, an excess of upwards of 1 ton, at a cost of 30s. 
 
 2°. But on comparing this action of the nitrate upon grass with its action in 
 the same field the previous year upon wheat — we find that though it considera- 
 bly increased the crop of wheat, yet every additional bushel raised cost I2s. tid. 
 as the price of the nitrate added to the land (Appendix, p. ID). It appears, 
 therefore, that upon soils where ike nilrale will not pay wken applied to wlieat, it 
 m/iy yel pay well wken applied to grass. 
 
 3°. Again, we find above that 3 cwt. of common salt lessened in a slight de- 
 gree the crop of hay, while, in 1841, IJ cwt. increased considerably the produce 
 of wheat in the same field — the additional grain reaped from the salted portion cost- 
 ing only 6d. a bushel (p. 19). It would appear, therefore, that on soils where 
 common sail can be projllnhly used upon wheat it may do injury upon hay. The 
 only circumstance that renders this deduction less safe is that 3 cwt. of salt per 
 acre were applied to the grass, which may have been too much considering the 
 dryness of the season. 
 
 4°. The latter remark applies also to the sulphate of soda which was laid on 
 at the rate of 3 cwt. per acre. A less addition might possibly have aided the 
 crop. Yet the negative influence of this salt seems great, since 1 i cwt. of nitrate 
 — Itself tending to increase the crop — was unable entirely to overcome the dimin- 
 ishing influence of 1 cwt. of sulphate. 
 
 But the reason of this apparent inefficiency of the nitrate, when mixed with the 
 sulphate, is in some measure explained by the remarkable fact, that on both of the 
 patches to vihick the sulphate of soda ivas applied, the grass that cavie up consisted 
 almost entirely of red fescue (Festuca Rubra), though rye grass, timothy, and red 
 clover ivere the only grasses smvn. The sulphate, therefore, must first have checked 
 or entirely destroyed the grasses which had already sprung up, and then have 
 incited the dormant seeds of fescue to germinate, before the fertilizing agency of 
 the nitrate could come into play. 
 
 This effect of the sulphate, should it be confirmed by later experiments, will 
 establish the important theoretical principle, that those substances which, when 
 present in the soil, will destroy some of our cultivated grasses, will encoiu'age the 
 growth of others; and the no less important practical truth, that saline substan- 
 ces exercise such a special action on the several crops we grow that we may 
 hope to discover the means of aiding the growth of the one or the other at plea- 
 sure, and it may be at little cost. 
 
 Suggestion IX. — It is to be recollected that in the case of Mr. Fleming's 
 field it may have accidentally happened that the seeds of the fescue particularly 
 abounded in those plots to which the sulphate was applied. With every dis- 
 position, therefore, to advance as rapidly as we possibly can, I think it better 
 to suspend our judgment upon this point — until the following two series of ex- 
 periments shall have been made in two or three different localities : — 
 
 a. By top-dressing any of the ordinary grasses sown — excluding the fescues 
 — on four or more plots, with J cwt., 1 cwt., 2 cwt , and 3 cwt. of sulphate 
 of soda respectively, and marking the kind of grasses that most abundantly 
 spring. 
 
 b. By sowing half an acre of one or more of the fescues, and especially the 
 Rubra, and noting the effect of the sulphate applied in similar proportions upon 
 as many patches as before. 
 
 These experiments, it is obvious, would be rendered more interesting were 
 nitrate of soda, alone and mixed with the sulphate, tried on other plots, and on 
 both varieties of grass. I trust Mr. Fleming, whose educated eye enabled him 
 to detect the interesting fact in question, may be induced himself to prosecute 
 the subject by further experiments. 
 
 5°. Shiggestion X. — We have already seen in the above joint action of ihe 
 
So. VIII.] EXPERIMENTS UPON GRASS AND MIXED CROPS. 73 
 
 nitrate and sulphate, another illustration of the kind of struggle we may suppose 
 to go on between substances tending respectively, the one to increase, the other 
 to diminish, the produce. In the joint action of the common salt and the soot, 
 when applied together, we have a further instance of the same kind — an increase 
 of 4 cwt. only being caused by the application of IG bushels of soot, when coun- 
 teracted by an admixture of 2 cwt. of common salt. Applied alone, the increase 
 of produce would probably have been greater. Will any one undertake exper- 
 iments with the view of further bringing out this interesting mutually-counter- 
 acting influence of different applications'? 
 
 6°. I can only call attention to the large yield of hay naturally obtained from 
 that part of the field on whicli barley dressed with bone-dust in 1841 had previ- 
 ously grown : Air. Fleming informs me that no sensible difference in the produce 
 of hay was ooserved between the undressed part of the field and that upon which 
 the 'tressed wheat had grown in 1841, though the crop was not set apart or 
 weighed, as we might wis'i it to have been. 
 
 111. Since the preceding experiments went to press I have received the fol- 
 lowing short notice of trials upon hay made by Mr. Campbell, of Islay : — 
 
 " It is very difficult to get tlie tenants in our wild part of the world to e.xpend 
 money in the purchase of foreign substances, however beneficial ; and for thia 
 reason I have been induced to tiy the substances mentioned below, because, 
 with the exception of sulphuric acid, the others are to be got in abundance 
 in the island — the pigeons' dung may be got in large quantities in the caves, 
 sea-ware on tlie shore, and lime is abundant and excellent in quality. The ex- 
 periment was made thus — 
 
 WEIGHT IN POUNDS. 
 
 Fresh cut. Dry. 
 
 1. iNothing 240 199 
 
 2. Pigeon Dung 318 275 
 
 3. Sea-ware, Lime, and Sulphuric Acid . . . 306 269 
 
 4. Lime and Sulpimric Acid 293 256 
 
 1. A field of about ten acres, lately improved from heather, was chosen ; the 
 field was well drained and deep ploughed, so as to raise the subsoil (red loam) 
 with the moss. On its surface the grass was sown down with oats — 8 cwt. of 
 each substance was used to the acre. Eight yards square carefully measured 
 from the centre of each variety, and weighed the day they were cut, and again 
 on the day they were put into stack. 1 lie hay was fully ripe when cut. 
 
 2. The pigeon dung, which looks like peat-dust, was laid on exactly as it 
 was taken from the cave. 
 
 3 One ton of lime-shells was mi.xed with 12 tons fresh sea-ware; after being 
 twice turned, the whole of the sea-ware was consumed, leaving only small black 
 panicles mixed with the lime: the bulk was reduced to five large carts (not 
 weighed); 4 galls, sulpimric acid, mixed with 400 galls, of water, were added to 
 the powder — a violent fermentation took place, and the bulk was further re- 
 duced about an eightli. 
 
 4. A ton of lime-shells was prepared according to your recommendation 
 slaking the lime with the dilute acid. 
 
 N. B. One measure of this lime in shells gives three and a half in powder." 
 
 G. — T'he Experiments upon Mixed Crops. 
 Mr. Alexander's experiment upon a field of mixed oats, beans, and peas, is 
 very deserving of notice, and will, I have no doubt, be repeated. Not only did 
 the mixture of gypsum and common salt iiicrcusc the ultimate produce — but, as 
 Mr. Alexander says, it acted like magic — imparting life and vigour to an appa- 
 rently dying and worthless crop. 
 
 H. — The Experiments upon Beans. 
 I. The principal fact of importance in the experiments of Mr. Alexander is 
 the effect he found his mixture of gypsum and common salt to produce upon the 
 
74 
 
 EXPKRIMENTS UPON BK.WS. 
 
 [Appendix, 
 
 beans a-ot tchen already in flower. This is another of those new and practical- 
 ly valuable obsei-vations which, year by year, are sure to present themselves to 
 our observing experimenters as their inductive researches are continued. 
 
 II. I am happy in being able to introduce here, though it reached me too late for 
 insertion among the other tables, the following digest of results upon beans, ob- 
 tained upon Lord Blantyre's farm at Lennox Love. The object of them was 
 to ascertain the relatwc cjfed of certain saline manures, and of rajie-dnsi, and 
 guano, upon beans, after a crop of oats. 
 
 Experiments upon Beans, after a crop of Oats. The quantity of land in each 
 plot was one-eighth of an imperial acre. Seeds sown 25th February ; manures 
 applied l3th May ; crop cut Sth August; stacked 1st September, 1842; and 
 thrashed 6th February, 1843. 
 
 
 MANURES. 1-- 
 
 Weight taken from 
 
 M 
 
 S 
 
 
 
 
 1 O 
 
 Thrashing Mill of 
 
 § 
 
 <d 
 
 Increase 
 
 De- 
 
 
 FORDHILL 
 
 hi 
 
 
 
 
 
 
 .a 
 
 £i 
 
 of 
 
 crease of 
 
 
 FIELD, 
 
 •3 1« 
 
 
 
 
 
 
 w. • 
 
 c % 
 
 produce 
 
 produce 
 
 No. 
 
 LENNOX LOVE. 
 
 1^6 
 
 
 
 
 
 
 o-Z 
 
 i"^ 
 
 in grain. 
 
 in grain. 
 
 Description of 
 
 •2 
 
 •s 1 
 
 c 
 
 
 _: 
 
 ^ 
 
 axi 
 
 si 
 
 c 
 
 . 
 
 c 
 
 
 
 Dressing. 
 
 i5 
 
 
 £ ° 
 
 n 
 
 III 
 
 J_ 
 
 g 
 
 5 S 
 
 lbs. 
 
 
 
 a. 
 
 a! 
 
 a 
 
 I 
 
 
 
 H)s. 
 
 s. d. 
 
 lbs. 
 
 lbs 
 
 lbs. 
 
 lbs. 
 
 lbs 
 
 lbs. 
 
 biislis. 
 
 bsh. 
 
 lbs. 
 
 bsh. 
 
 lbs. 
 
 1 
 
 Common Salt. 
 
 14 
 
 4 
 
 588 
 
 231 
 
 54 
 
 285 
 
 225 
 
 78 
 
 651 
 
 3-538 
 
 
 — 
 
 ■182 
 
 31 
 
 '\ 
 
 Common Salt. 
 Rape-dust .... 
 
 
 7 
 
 630 
 
 260 
 
 53 
 
 318 
 
 230 
 
 82 
 
 66i 
 
 4-000 
 
 •2S2 
 
 - 
 
 - 
 
 32 
 
 3 
 
 Nitrate of Soda 
 
 14 
 
 3 1 
 
 G72 
 
 276 
 
 63 
 
 339 
 
 254 
 
 79 
 
 66f 
 
 4 134 
 
 -414 
 
 — 
 
 — 
 
 •22 
 
 4^ 
 
 Nitrate of Soda 
 Rape-dust .... 
 
 112^ 
 
 8 7 
 
 044 
 
 2iO 
 
 59 
 
 339 
 
 253 
 
 52 
 
 6Gi 
 
 4210 
 
 •490 
 
 - 
 
 - 
 
 26 
 
 h\ 
 
 Nitrate of Soda 
 Sulpli. of Soda 
 Sulpli. of Soda 
 
 14 
 
 2 
 
 686 
 
 282 
 
 60 
 
 342 
 
 258 
 
 86 
 
 661 
 
 4 256 
 
 -536 
 
 — 
 
 — 
 
 25 
 
 6 
 
 1 
 
 700 
 
 282 
 
 73 
 
 355 
 
 261 
 
 84 
 
 66* 
 
 4-240 
 
 -52(1 
 
 — 
 
 — 
 
 12 
 
 ^\ 
 
 Siilpli. of Soda 
 Rape-dust ... 
 
 7} 
 Wis 
 
 7 r. 
 
 700 
 
 289 
 
 65 
 
 354 
 
 261 
 
 85 
 
 6; 
 
 4 313 
 
 693 
 
 - 
 
 - 
 
 20 
 
 8 
 
 Rape-dust .... 
 
 224 
 
 14 [■■ 
 
 700 
 
 292 
 
 61 
 
 353 
 
 260 
 
 87 
 
 66,= 
 
 4-374 
 
 654 
 
 — 
 
 — 
 
 24 
 
 9 
 
 Guano 
 
 28 
 
 5 (' 
 
 728 
 
 2=0 
 
 68 
 
 348 
 
 263 
 
 117 
 
 66i 
 
 4-210 
 
 •490 
 
 — 
 
 — 
 
 17 
 
 10 
 
 Nothing 
 
 
 — 
 
 672 
 
 248 
 
 85 
 
 333 
 
 265 
 
 74 
 
 66| 3-720 
 
 — 
 
 — 
 
 — 
 
 — 
 
 U 
 
 Soot 
 
 4 hsli 
 
 4 Oj (&) 
 
 234 
 
 87 
 
 321 
 
 261 
 
 84 
 
 66 3 545 
 
 — 
 
 2 
 
 •175 
 
 — 
 
 Remarks. — The soil of Fordhill. on -which they arew, is light and of inferior quality — the 
 subsoil is of indurated clay, intersperised with boulders and small stones, and occasionally 
 beds of gravel. The field was drained every furrow previous to its being broken up from 
 old lea in the winter of 1840— ploughed deep and subsoiled in the autumn of 1S41, and ma- 
 nured with farmyard dung in the drill before sowing the bean.^ in llie spring of 1S42. Owing 
 to the dryness of the season, tlie beans were rather short in the straw; the specific manures 
 were applied after (he plants had attained some inches in height. 'JVie siilp/ialp of soda (dry , 
 not in cnjslals) lilackened and destroyed t/ie nnrler leai'es, ir/ierever il came m contact tcit/t 
 them, but fresh shoots soon appeared, and it did not seem permanently to injure or retard the 
 growth of' t lie plants. They did not, after the application, sliewany marked change of colour; 
 and at no period did they seem to dilTer much from the rest of the field. A few peas were 
 sown among the beans ; and in dressing the grain, an attempt, partially successful, was made 
 to sefiarate lliem — each e.-<perimerit underwent tlie same process in the dressing. Grain 
 column 1st represents the produce in beans — grain column 2nd represents ll.at in peas. 
 The separation, however, not being completely eflected, there were left peas among the beans, 
 and some of the smaller and inferior beans among the peas. I thought a distinction of this 
 kind worth making in the Tables, as 1 observed that some of the lots contained much more 
 peas than others, and conceived that the relative value of the manure, as applied to either, 
 might thereby in soiie measure be shown, as well as their effects on the beans alone more 
 truly e.xliibited. The gross weights were taken, as those of the other experiments, at the 
 town of Haddington's weighing machine, before thrashing — the detailed weights and mea- 
 surements by niyself. Wm. GooDLEr. 
 
 The produce of the undressed part amounted in the above experiment to 29 J 
 bushels, and it is remarkable — 
 
 1^. That the soot alone caused a sensible diminution of the gross produce, 
 and alone did not lessen the proportion of peas. 
 
 2"^. Although the season was so dry the sulphate of soda gave a larger increase 
 than was obtained by tlie addition of twice its own weiglu of guano. '■ 
 
 3°. That an admixture of half its weight of nitrate with the sulphate of soda 
 
Ao. VIII.] EXPERIMENTS UPON BEANS. 75 
 
 did not increase the produce beyond that of an equal weight of sulpliate alone. 
 This is different from the action of the latter salt in the case of the other grain 
 crops and of potatoes. 
 
 4° . That 1 cwt. of sulphate of soda produce as great an effect as 16 cwt. of rape- 
 dust — tlie quantity of grain reaped from both applications being very nearly the 
 same. 
 
 Sugs'es/ion. XI. — These striking effects of the sulphate ultimately took place, 
 although when first applied to the young plants it burned and blackened their 
 leaves. I trust that these results will also be tested by repetitions in other years 
 — '.ess droughty, it is to be hoped — and in other parts of the country. For the 
 sulphate of soda, Mr. Ale.xander's experiment seems to saytlial gypsum, which 
 is still cheaper, may be economically substituted. 
 
 5°. It will be seen ihat guano upon this crop, as upon the wheat already noticed 
 (p. 68), was less successful than some of the other sub.stances employed. 
 
 Condunon. — Upon the observations of Mr. Gardiner in regard to the effect 
 of the dressings of 18^1 upon the crop of 184-3, I have nothing to add to the re- 
 marks I have already made (p. 57) upon their importance, and upon the good 
 that must follow from continumg them. But in concluding these observations, 
 the reader will please to recollect that I have adverted to those points only, in the 
 above tables of results, which appeared to myself most important. Tiiere are 
 many other points to which by a careful study of the tables his attention will 
 naturally be drawn. He will consider the observations themselves also, as 
 only so many gropings after truth. Tiie present state of our experimental inqui- 
 ries can scarcely be supposed as yet to give us more than a glimpse here and 
 tliere of the true light. Like a man who finds himself in a dark dungeon, we 
 are peering through the comparative gloom of our prison-house, in the hope of 
 finding some mode of escape into the upper day. Like him we may be long in 
 discovering the true outlet, and the passage upwards may be narrow and in- 
 tricate; — but the same conviction which will give him safety, will ultimately 
 lead us also to the light — that he who persists in trying — marking and recollect- 
 ing every turning he has explored — mo,y at length escape; but that he who sits 
 still, in indifference, or gives up his quest in despair, is sure to die in daikness. 
 
 No. IX. 
 
 ADDITIONAL EXPERIMENTS IN PRACTICAL AGRICULTURE, 
 MADE IN 1842. 
 
 The following experiments were made at Erskine, in Renfrewshire, upon the 
 Home Farm of Lord Blantyre: — 
 
 Experiment I. — Potato Oats, after old Grass. 
 
 The soil was variable, chiefly good loam, resting on a subsoil partly gravel 
 and partly sand. The field, having been long in pasture, in many places very 
 wet, was drained in November and December, 1811 ; ploughed soon after, and 
 sown with oats on the 8th of April. The manures were applied on the 15th 
 of April, and harrowed in with a single stroke of the harrows. One-fourth of 
 an hnpcrial acre being previovsly measured off for each plot. 
 
 According to notes taken of the appearance of the crop from time to time — 
 
 May 23. — The nitrate of soda (No. I ) looking darker in colour than any of 
 tlie other plots; next to it, in point of colour, the foreign guano (No. 5) seems 
 best; then the soot (No. 9); then the sulphate of ammonia (No. 2); cannot, 
 however, discern any very decided difference in the appearance of the others. 
 
76 
 
 EXPERIMENTS UPON OATS AND GRASS. 
 
 [Appendix, 
 
 May 30. — There appears a slight difference in favour of all the applications 
 in the order above stated, the sulphate of soda (No. 3) pale in colour. 
 
 June 28. — Appearance same as on 3(!th May. 
 
 The crop was cut 19th and 20ih of August, and thrashed fiom the stock on 
 the 7th of September; the results carefully ascertained, the grain by weight and 
 measure; the straw by weight, as it came from the thrashing-machine; no ac- 
 count taken of the chaff. 
 
 KESULTS OF EXPERIMENT I. OATS. 
 
 Applications. 
 
 Nitrate of Soda, 28 lb.s 
 
 Sulphate of Ammonia, 28 lbs... 
 
 Sulphate of Soda, 06 lbs 
 
 Nothing 
 
 Foreign Guano. 28 lbs 
 
 Turnhull's BrilishGuano.56 Ihs. 
 Turnbull's Impr'd Bones, .50 lbs. 
 
 Turiibiill's jiumus, lU bush 
 
 Soot, 10 busi, 
 
 z-^ ^ 
 
 
 PRl 
 
 DUCE. 
 
 
 
 
 :^ c i- 
 
 Good grain. 
 
 Lifc'ht grain. 
 
 
 Increase + 
 
 
 
 -^ j: 
 
 
 - j: 
 
 
 or 
 
 M« 
 
 
 .MIJ= 
 
 
 .2.'J= 
 
 ^ 
 
 Decrease — . 
 
 
 
 
 
 
 
 
 3«c 
 
 
 ^a 
 
 
 :S^ 
 
 ID 
 
 Grain. 
 
 Straw. 
 
 s. d. 
 
 bsh. lbs. 
 
 Ib.^ 
 
 lbs. 
 
 lbs 
 
 lbs. 
 
 lbs. 
 
 lbs. 
 
 6 3 
 
 12 21 
 
 42i 
 
 8 
 
 29i 
 
 908 
 
 +26* 
 
 +191 
 
 5 
 
 12 22 
 
 411 
 
 10 
 
 
 7iO 
 
 
 
 + 53 
 
 3 
 
 12 — 
 
 40 
 
 14i 
 
 — 
 
 762 
 
 -18 
 
 + 45 
 
 
 12 10 
 
 41 
 
 10^ 
 
 
 
 717 
 
 
 
 
 r> 3 
 
 12 4 
 
 41i 
 
 6i 
 
 — 
 
 768 
 
 4-6 
 +14 
 
 + SI 
 
 4 
 
 12 17A 
 
 4U 
 
 101 
 
 — 
 
 788 
 
 + 71 
 
 3 n 
 
 11 2 
 
 41 
 
 lOi 
 
 — 
 
 67.5 
 
 -^9 
 
 -42 
 
 10 
 
 11 W 
 
 41 
 
 iii 
 
 — 
 
 644 
 
 +41 
 
 - 73 
 
 2 11 
 
 13 30i 
 
 41 
 
 H 
 
 — 
 
 8S(J 
 
 —60 
 
 +163 
 
 Experiment II. — On Old Pasture Grass to be cut for Hay. 
 
 The soil was of medium quality, on stony clay subsoil. The part of the 
 field experimented on was originally very wet, producing scarcely any better 
 herbage than rushes and other semi-aquatic plants, was drained in 1835, has 
 been three years pastured after a crop of hay from young grass in 1838; the 
 soil is of a blackish friable texture, the subsoil very retentive. The specific 
 manures were applied on 15th April, with the exception of the soot, which was 
 sown on the plot in the experiment at the same time that the other parts of the 
 field were dressed with soot, being about the middle of March, and by the 
 15th of April were shewing a greener shade than the portion left for experiment. 
 
 April 25. — Observed the ridge or plot No. 5 (sulphate of anmionia) looking 
 dark in the shade, and that the salt has burned the leaves of daisies and other 
 broad-leaved plants ; the moss or fog seems also to be burned, it looks black 
 and unhealthy. 
 
 May 7. — I'he ridges or plots Nos. 2, 5, and 7, look decidedly better than the 
 rest ; No. 3 also seems farther advanced than where no applications were made. 
 
 May 23 — No. 2 getting on very fast, and now looks as well as No. 1, which 
 has always had the advantage (to appearance) of the other plots. The grass 
 on No. 3 pale in colour, but taller than where no manure was applied. 
 
 The hay was cut on the 3d of July, and the grass weighed soon, i. e., in a 
 few hours after being cut down, but being very sunny weather it was somewhat 
 faded when weighed. The made hay weighed and put into stack on . 
 
 Each plot co7mstcd of one-fourth of an imperial acre. 
 
 RESULTS OF EXPERIMENT II. — HAY. 
 
 No. 
 
 Applications. 
 
 Cost of 
 applica- 
 tion. 
 
 PRODUCE. 
 
 Increase 
 in Hay. 
 
 Grass. 
 
 Hay. 
 
 1 
 2 
 3 
 4 
 5 
 6 
 7 
 
 Snot, 10 bushels 
 
 Nitrate of Soda, 40 lbs... .' 
 
 s. d. 
 2 11 
 8 \\\ 
 
 4 Z\ 
 
 ~n 
 
 5 lljt 
 
 5 8i 
 
 lbs. 
 2331 
 2536§ 
 19.36 
 1760 
 25 16 J 
 2;}74 
 3(124 
 2841 
 
 lbs. 
 970 
 10261 
 841" 
 726 
 935 
 838 
 1190 
 1044 
 
 lbs. 
 
 188 
 244J 
 59i 
 
 153 
 
 408 
 262 , 
 
 Sulphate of Soda, 80 lbs 
 
 Sulphate of Ammonia, 40 lbs.. .. 
 Nothing 
 
 8 
 
 Turnbull's Britisii (Juano. 80 lbs 
 
No. IX] 
 
 EXPERIMENTS UPON WHEAT AND POTATOES. 
 
 77 
 
 N. B. — I take the average of the two plots which had no manure, as the sum 
 to deduct for finding the increased produce. The second column from the 
 right is made hay, the third is green grass, weighed soon after being cut. 
 
 Experiment III. — Upon Wkeat. 
 
 Soil, a good strong loam, resting on a heavy subsoil composed of clay and 
 small stones, called till. The wheat was sown in November, 1841, after a crop 
 of potatoes. The field had been long in grass previous to 1840 — when it was 
 drained, and plou:ihed for oats in the spring of 1840 — was well dunged with 
 good farm-yard manure, and was also limed for the potato crop of 1841, so that 
 the field was in very good condition for wheat. 
 
 The manures were applied 14th April, 1842, and haiTowed in with a stroke 
 of the harrows. 
 
 iVlay 10. — The portion No. 1 seems darker in shade than No. 9 and No. 8. 
 
 June 23. — A calm day, with gentle rain — many of the lots much bent down, 
 as follows: — No. 1 much bent down. No. 2 partly swirled and bent at the 
 end next a planting. No. 1 swayed at east end next the planting, not so bad as 
 No. 2. No. 4 less bent down than No. 3. No. 5 much bent down and swirled. 
 Nos. G and 7 all standing. No 8 partly laid down. No. 9 very much swirled 
 and laid. All the laid wheat came up again in a few days after the rain. 
 
 The wheat was reaped with the sickle, and in due course stacked, in good 
 condition. It was thrashed on the 8th February, 1843. 
 
 RKSL'LTS OF EXPERIMENT III. — WHEAT. 
 
 Applications. 
 
 Total Increase + 
 qnan- I or 
 
 I (itv. [Decrease — . 
 
 1 Soot, 10 bushels 
 
 2 TMrnt)iill's Ilnmu!:, 10 bushels. . 
 
 3 ImprovBi! B^nes 
 
 4 Tiiriibull's British Guano 
 
 5 Fireiiiii Guano 
 
 C Nothinj 
 
 7 Sulpliale of Soila , 
 
 8 |S:il|)hale of Ammonia 
 
 9 Nitrate of Sod.i 
 
 Ih.s. 
 1213 
 105.5 
 973 
 1193 
 1049 
 100,S 
 1073 
 1I3S 
 11.59 
 
 lbs. 
 + 205 
 + 47 
 — 35 
 + 18o 
 + 41 
 
 -Tgo 
 + 1 30 
 + 151 
 
 bush. lbs. 
 
 13 3-5 
 
 12 48 
 11 53 
 
 14 43 
 
 u 341 
 
 11 r 
 
 13 7 
 13 38 
 13 38 
 
 Wei-lil 
 
 Ib.s. 
 
 5S 
 
 60 
 
 62 
 
 61 
 
 61* 
 
 62" 
 
 62 
 
 62 
 
 62 
 
 Increase. 
 
 bush. lbs. 
 2 32 
 
 47 
 57 
 42- 
 33.i 
 
 6 
 
 37 
 37 
 
 Experiment IV. — On Potatoes. 
 
 Soil, a mediuiTi loam, resting on gravel and sand. The field was ploughed 
 from oil grass, and sown with oats in 1841 ; was drained (where wet) and deep 
 ploughed in the autumn of 1841 ; prepared for potato^^s in the spring of 1842, 
 and well dunged at the rate of about 45 tons of very good dung from Glasgow, 
 per acre. The manures were applied in addition to the dung, by being fpnnkkd 
 above Itc duns in the (/rills before placing the sets, then covered by reversing the 
 drills, on the 2lst and 22d ofApriK 1842. 
 
 During the season could discover little or no difference in the appearance of 
 ths portions dressed with the specific manures, from where no applications 
 were made; the crop was a very equal good one over all the field. One-fourth 
 of un imperial acre in cadi plot, 
 
 I ran ill reconcile the srcat produce iVnm No. 4 with the appearancps when "rowini;, 
 ami hiive been suspicious, that noiwitlistandnij every precaution being taken to avoid mix- 
 ing, some .sheaves of No. 5 plot, have been taken to No. 4, while the i:rop was in stonk, as it 
 was sonii.titues necessary (during tlie time the slooks were in the field) to have them re- 
 paired, ihey bein^ blown down once or twice. 
 
 Tlie cost of the applications, as also the quao'llies applied, of the different materials, were 
 (lie .same as in Experiment No. I , on O its. The liaht grain is not hero taken into account, 
 as it was loo trifling in quantity and quality to be of any importance, and nearly the same in 
 every case. 
 
m 
 
 EXPERIMENTS UPON POTATOES. 
 
 [Appertdtz, 
 
 RESULTS OF EXPERIMENT IV. ON POTATOES. 
 
 Manures. 
 
 Cost. 
 
 Nitrate of Soda 
 
 .14 lbs. ) 
 
 
 .28 lbs. \ 
 
 Sulphate of Soda 
 
 28 lbs. ) 
 
 Sulphate of Ammonia. . . . 
 
 14 lbs. S 
 ...'28 lbs. 
 
 Tiirnbull's British Guano. 
 Soot, 7i bushels 
 
 ...56 lbs. 
 
 Improved Bones, Turnbul 
 Gypsum, 1 bushel 
 
 's, 56 lbs. 
 
 Nothing 
 
 s. 
 
 d. 
 
 4 
 
 7J 
 
 4 
 
 
 
 6 
 
 3 
 
 4 
 
 
 
 2 
 
 6i 
 
 3 
 
 
 
 tons. cwt. qrs. lbs 
 3 1 aij 
 
 2 19 
 
 24J 
 
 
 
 2 21 
 
 3 21 
 2 21 
 
 1 21 
 7 
 
 Increase + of 
 Decrease — . 
 
 cwt. qrs. lbs 
 
 + 1 I in 
 
 + Vi 
 + 3 21 
 
 + 
 
 — 3 
 + 
 
 - 
 
 The gypsum used turned out to be genuine on analysis.* 
 
 REMARKS UPON THE PRECEDING EXPERIMENTS. 
 
 1°. Effect of the drought. — It is to be observed, in the first place, that the 
 great drought of the season exercised an unfavourable influence upon the re- 
 sults of these experiments also, it is necessary, therefore, to suspend our judg- 
 ment in some measure regarding them — until future experiments in other sea- 
 sons shall confirm or modify them. 
 
 2"^. Inferences to be drawn fro'iii the colour of the crop. — A new feature in- 
 troduced by Mr. Wilson in the account of these experiments, is the appearance 
 presented by the several crops at different specified periods after the dressings 
 were applied. 
 
 It is a common thing for practical men to estimate the relative pi-oduce of 
 different fields or parts of the same field by their appearance, and especially by 
 the colour of the growing crops. Yet that this is not to be depended upon in 
 a corn crop, is proved by the observation that up to the end of June appearances 
 in the oat field were most in favour of the nitrate of soda, the guano being se- 
 cond, and the soot third in order. Yet, when reaped, the — 
 
 Nitrate gave an increase of only 2* bushels per acre. 
 
 Guano 2^1 lbs. per acre. 
 
 Soot () bushels per acre. 
 
 The nitrate did give a little more straw than either of the other two, but that 
 the colour is not an unfailing criterion even as to the produce of straw or of 
 hay is shewn by the experiments upon oats and upon hay. In both of these 
 
 * List of prices paid for the manures used in the foregoing experiments :— 
 
 1. Foreign Guano 253. per cwt. 
 
 2. Turnbull's Guano 8s. " 
 
 3. Turnbull's Improved Bones 63. " 
 
 4. Turnbull's Humus Is. per bushel 
 
 5. Nitrate of Soda 2.'>s. per cwt. 
 
 6. Sulphate of Soda (dry) 6s. " 
 
 7. Sulphate of Ammonia 20s. " 
 
 8 Sont 3^il. perbushel. 
 
 Nos. 2, 3, 4, and 7, wnre manufactured and furnished by Turnbull and Company, Chem- 
 ists, Glasgow. The Rritish (Guano No. 2) is said to be made up as follows : — 
 2 cwt. of Sulphate of Soda. 
 2 cwt. of Sulphate of Ammonia. 
 1 cwt. of Common Carbonate of Soda. 
 15 cwt. of Improved Bones, manufactured by Turnbull & Co. 
 
 20 cwt.. or 1 Ion. 
 
 The Improved Bones are said to be half dissolved bones and half wood-charcoal. I be- 
 lieve the bones include animal matter, as 1 am informed the carcases of old horses, &c., 
 are all used in the manufacture. JiJiES Wilson. 
 
 FreeloMd, Erakine, 20/A Fetmiary, 1843. 
 
No. IX.] REMARKS UPON PRECEDING KXPEE1MENT8. 79 
 
 crops the portions dressed with sulphate of soda are described as pale in colour, 
 and yet the excess of produce over the undressed parts was as follows : — 
 
 In the oats . . IJ cwt. straw. Uyhere the sulphate was applied. 
 In the hay . . 2 cwt. per acre. ^ ' ^' 
 
 The increase in neither case would hi deserving of much attention — except 
 as showing satisfactorily that wrong conclusions may be drawn in regard to 
 the efficacy of manures and top-dressings by those who judge only by the eye 
 — and that safi: reliance can be placed on those comfaralivc results only which have 
 been tested bi/wei^'ht and measure. I know, indeed, that practical farmers who 
 have applied nitrate of soda to grass land, and have been delighted by the beauti- 
 ful green colour which followed, have occasionally been disappointed by find- 
 ing that after all this promise the weight of hay obtained was no greater than 
 upon the undressed parts of their fields. As to the feeding qualities of the two 
 kinds of hay no experiments have yet been made, though it is known that cat- 
 tle prefer that which has been dressed. 
 
 Suggestion XI. — I put down, therefore, as a distinct suggestion for the pur- 
 pose of drawing attention to the subject, that this plan of specially noting the 
 appearance of the crops at staled, say monthly periods, should be adopted in all 
 future experiments. This will serve, not merely to show us more clearly what 
 kind of appearances are to be trusted, and how far, as indications of an increase 
 of crop — but may hereafter prove of further importance when experiments shall 
 begin to be instituted upon the feeding properties of crops reaped vmder dif- 
 ferent circumstances, and raised under different kinds of management. 
 
 3°. Iinpm-Lancc of having two or more experimental "plots similarly treated. — 
 The experiments upon hay above-mentioned exhibit another illustration of the 
 fact adverted to in page 59 of this Appendix under the head of livdts of error. 
 I there drew the attention of experimenters to the difference in the produce ob- 
 tained on two equal patches of the same field of turnips, to neither of which 
 any dressing had been applied. At Erskine two equal plots of grass in the 
 same field gave a similar difference of produce. 1 present both results here for 
 the sake of clearness. The produce per imperial acre was — 
 
 Hay at Erskine. Turnips at Barochan. 
 
 tons. cwt. tons, cwt 
 
 1st plot 4 5 ]2 17 
 
 2d plot 3 3 118 
 
 Difference 12 19 
 
 In my remarks upon the difference between the two plots of turnips (Appen- 
 di.x, p. 59), I expressed an opinion that differences equally great, depending not 
 at all upon the substance applied, might be expected on equal portions of those 
 fields upon which our different saliin; manures may have been applied; — and 
 that very erroneous conclusions might thence be drawn in I'egard to the abso- 
 lute and comparative effects of the substances with which our experiments are 
 made upon the crops to which thej' are applied. 
 
 I have .since met with a confirmation of this view in a record of two pairs of 
 experiments made with equal quantities of rape cake upon equal plots of red 
 wheat, in the same season, and upon adjoining parts of the same field, (British 
 Husbandry, I., p. 11'2.) The results of two experiments with different quan- 
 tities of rape dust were as follows: — 
 
 Produce of Light 
 
 Rape dust applied, market com. Weight per bushel. corn. 
 
 stones, bush. lbs. oz. lbs. 
 
 1st plot 59A ... 26 ... 52 10 ... 46 
 
 2nd plot 59i ... 21 ... 50 8 ... 67 
 
 1st plot 86 ... 28 ... 53 4 ... 35 
 
 2nd plot 86 ... 22 ... 51 2 ... 91 
 
 The differences both in the quantity and in the weight of the grain reaped, ip 
 
8Br REMARKS UPON PRECEDING EXPERIMENTS. [Appendix, 
 
 each of these pairs of experiments, are so great that had they been obtained from 
 plots of ground dresssd with different manures we should readily have ascribed 
 them to the unlike action of the substances we had applied. Doubts may natu- 
 rally arise, therefore, when we look at the s?veral tables of results contained in 
 this Appendix, how far the differences presented in them are really due to the un- 
 like action of the manures employed, and how far to natural causes not hitherto 
 investigated. Can all the experiments made during these List two year:, wiili so 
 mucli care really be vitiated by this source of error] The point must be eluci- 
 dated by further experiment. Should it prove that we have here a general 
 source of error, it is satisfactory at least that we have discovered it at the thresliold 
 as it were of our accurate experimental inquiries, and that we can devise means 
 of avoiding it in future. 
 
 I therefore repeat the Suggestions I. and IF., which I ventured to offer in page 
 (JO (Appendix), that some of my readers, of whom I believe many are interested 
 in this subject, would in the ensuing season ascertain accurately the produce of 
 equal measured quantities of the same field, under whatever crop it may be, 
 and publish or transmit the result to me — and that in all future experiments 
 made with the viewof ascertaining the effectof different manures upon any crop. 
 two plats af least, and not ad joining to each other .^ should be treated alike in each 
 field, and the mean of the several results obtained with each substance taken as 
 the average produce from which their comparative effects are to be estimated. 
 
 These pomts appear to me to be of primary importance, and to lie at the 
 foundation of the structure 1 hope we are now beginning to rear with the results 
 of inductive experimental agriculture. 
 
 4. Action of soot. — In these experiments a top-dressing of soot increased con- 
 siderably the produce of oats and wheat, while it diminished the produce of po- 
 tatoes ?yA??j. ?»i.re(i wi/A ^Ae mareiire. Thus the produce per acre on the dressed 
 and undressed parts was — 
 
 Oats. Wheat. Potatoes. 
 
 Undressed . . 49 bush. . . 44 bush. . . 11 tons I(> cvvt. 
 Dressed ... 55 bush. . . 54 bush. . . 11 tons 3 cwt. 
 The unfavourable effect upon the potato crop may probably be due to the 
 mode in which it was applied, as in other districts it is very useful to potatoes, 
 and gave, as we have seen, when applied alone to turnips, an increase of4tons 
 per acre. (See Mr. Fleming's Experiments, Appendix, p. 43; also, Lecture 
 XVII. p. 438). 
 
 5. Comparative action of soot and of nitrate of soda. — The immediate effect 
 of both these substances is to darken the colour and to increase the growth 
 of hay and straw. In this respect the advantage is rather on the side of the ni- 
 trate, while the soot in some cases gives a little more grain Thus the increase 
 of produce per imperial acre of the three crops of hay, wheat, and oats, dressed 
 with each of the three, was nearly as follows: — 
 
 Hay. Wlieat. Oats. 
 
 Grain. Siraw. 
 
 Soot .... 7 cwt. . . 10 bush. . . 6 bush. G cwt. 
 Niirate of soda . 9 cwt. . . lOi bush. . . 6i bush. 7 cwt. 
 In both cases, however, the sooted grass was lighter per bushel. Thus their 
 comparative weights were — 
 
 Wheat. Oals. 
 
 Sooted ... 58 lbs. . . 41 lbs. 
 Nitrated ... 63 lbs. . . 42* lbs. 
 Nevertheless, the advantage to the practical man is decidedly on the side of 
 the soot, since the cost of 40 bushels of soot per acre was only I2s., while that 
 of 1 cwt. of nitrate of soda was 25s. It is only to be regretted that soot is so 
 variable in its constitution that firm reliance cannot be placed upon the uniform- 
 ity of its effects. 
 
 6°. Action of guano. — In the text, p. 460, 1 have stated the apparent conclusion 
 to which the Erskine experiments, taken in connection with all the others I have 
 
No. IX.] KEMARKS UPON PRECEDING EXPERIMENTS. 81 
 
 yet met with, seem to point — that il is more ■uniformly successful when applied to 
 Tool- than to ^rain crops. The increase of oats in the present experiment did not 
 exceed half a busiiel per acre — though that of hay amounted to 14i cwt. 
 
 7^. Adioii of sidpkale of soJa. — I have ah-eady noticed the effect which this 
 salt has in paling the colour of the crop, even when the produce of grass or 
 straw is increased. In regard to the grain, we see in the experiment upon oats 
 that it reduced the crop, 1| bushels per acre — while the wheat crop was increased 
 10 bushels by a similar application. 
 
 Is this difference in its effects due to the nature of the soil, or to the special 
 action of the sulphate upon the two crops 1 
 
 We have seen in the experiments made in 1842 at Lennox Love (p. 52), that the 
 sulphate of soda diminished the oat crop 15J bushels per acre — an effect, how- 
 ever, which may be mainly ascribed to the great drought in that locality, since 
 even nitrate of soda caused a diminution of ,2h bushels. But it also diminished 
 the wheat crop at the same place to the extent of 9i bushels per acre, but upon 
 this crop also the drought appeared to interfere with the natural action of the sev- 
 eral top-dressings which were applied, so that no trust-worthy conclusion can 
 be drawn from the apparent results of their action. 
 
 Suggestion XII. — 1 have already suggested (p. 72) an interesting experiment 
 with sulphate of soda, in order to test the very curious observation of Mr. Flem- 
 ing, that when applied to land sown with artificial grasses, it brought up a crop 
 consisting almost entirely of fescue grasses, though none of these had been 
 sown. I would here suggest further that the marked difference observed at 
 Erskine between the action of this sulphate upon wheat and oats should be 
 further investigated — with the view of obtaining a satisfactory answer to this 
 question — Does sulphate of soda act less favourable upon wheat than upon 
 oats in the same soill Or does an unlike action manifest itself only when the 
 soils are different 1 I fear the suggestion comes too late for the present year, 
 unless, as I hope, there are experiments already in progress which will throw 
 light upon the question. But the suggestion will not, [ believe, be overlooked 
 when another year comes round. 
 
 It is further worthy of remark, in regard to the action of the sulphate of soda 
 upon the wheat crop, that the straw was stronger and less laid than where any 
 of the other dressings were applied. 
 
 8^. Action of sulphate of ammonia. — The substance employed under the name 
 of sulphate of ammonia, as I stated in a previous part of this Appendix (p. 61,) 
 is not what its name implies. The makers, the Messrs. TurnbuJl, of Glasgow, 
 inform me that it is prepared by adding sulphuric acid to fermenting urine, and 
 evaporating to dryness*. Though such a substance must vary in composition 
 with the urine from which it is prepared, and must contain more or less am- 
 monia according to the degree of fermentation which the urine has undergone, 
 yet good effects may fairly be expected from it. I here exhibit the effect of 1 to 
 IJ cwt. per acre applied to different crops — 
 
 Undressed. Dressed. Made at 
 
 Wheat 44 bush. 54i bush. Erskine. 
 
 Do 31* bush. 40 bush. Gadgirth. 
 
 Oats 49 bush. 50 bush. Erskine. ' 
 
 Turnips 12? tons. 24^ tons. Barochan. 
 
 Potatoes 12? tons. I4i tons. do. 
 
 Do si tons. 13* tons. do. 
 
 These results not only recommend this substance to the practical farmer, but 
 they also enforce the remarks I have made in the text upon (he value of urine 
 in general, upon the large waste of manure annually incurred by the neglect of 
 it, and upon the virtual money-tii<is which is suffered by those who allow it to 
 escape from their farm-yards. [See Lecture XVIII., p. 46o.] 
 
 9°. Action of Turnbull's humus. — This humus, as it is called, is night-soil 
 
 ' In the test I have described it under the name of aulphated urine.— Seep. 451. 
 
8f REMARKS UPON PRECEDING EXPERIMENTS. [Appendix, 
 
 and urine mixed with charcoal and gypsum, and dried by a gentle heat. Its ef- 
 fects upon the wheat crop are, in the present experiments, more favourable than 
 any of those I have yet placed upon record. 'I'he following experimental re- 
 sults exhibit the nature of its action in two localities, both in the same neigh- 
 bourhood: — 
 
 Undressed. Dressed. Eicperiments made at 
 
 Wheat ... 41 bush. 51 bush. Erskine. 
 
 Oats .... 49 bush. 45 bush. do. 
 
 Turnips . . . 12| tons. l3j tons. Barochan. 
 
 Do. ... 12 tons. 17 tons. do. 
 
 Potatoes ... 5| tons. lOf tons. do. 
 
 These results, especially tliose upon the corn crops, are not so beneficial as 
 might well be expected from a prepared night-soil, and they aiford room for the 
 suspicion that the mode of manufacture has been such as to dissipate some of 
 the more valuable constituents. 
 
 10°. Expcrimcnls upon potatoes. — In the experiments upon potatoes the wholi 
 crop averaged 12 tons per acre, and the parts of the field to which the artificial 
 manures were added exhibited no marked increase above this general average. 
 Even the mixture of nitrate with sulphate of soda, which in so many other 
 cases has proved beneficial to the potato crop, in this instance produced only 1 
 cwt. of increase. 
 
 It may be that the manure which was added at the rate of 45 tons per acre 
 contained a sufficient supply of all those kinds of food which were added after- 
 wards in the saline and other substances. If so, a larger crop could only have 
 been obtained by the addition of some other substance not tried, for a loam of 
 moderate quality ought to be able to produce more than 12 tons of potatoes per 
 acre. 
 
 Or it may be that these same artificial manures would have produced a larger 
 increase had they been put on as a top-diessing after the crop had come up, in- 
 stead of being spread upon the manure before the potatoes were planted upon 
 it. In the experiments of Mr. Fleming made with especial reference to this 
 point, [Appendix, pp. 49 and (iO,] it was found that a larga- proportionate 
 increase was obtained from the same saline substances applied in equal quanti- 
 ties to the potato crop when thcij v-cre spread upon the manvre, than vhcn Ihry 
 were applied as a top-dressing after the crop had come vp. Still the experiments 
 in his case being made in different fields, I stated that the point was not to ba 
 considered as established, but was deserving of further investigation. This 
 opinion is strengthened by the results of these experiments of Lord Blantyre : 
 I would therefore beg to offer as — 
 
 Suc^grMion XIII. — That the application of saline manures to the potato 
 crop— either when the trial is made for the purpose of obtaining practical infor- 
 mation, which may, hereafter, be valuable as a guide to the operations of the 
 farmer, on the land where his experiments are made, or for that of arriving at 
 results which may be theoretically useful — that the same proportions should be 
 applied to two or more plots buried with the manure, and to two or more dusted 
 on as a top-dressing. From an accumulation of results obtained in both ways, 
 we shall be able to extract something like a principle by which practical men 
 may be easily guided in that direction wliich is likely in the greatest number 
 of cases to lead to the greatest amount of profit. 
 
 11°. Water in the polatois. — 1 will here add one other observation upon the 
 potato experiments. There was, as we have already remarked, no notable dif- 
 ference in the ircighl of crop raised upon the several patches. But the oiiality of 
 the crop — the weight of dry food raised upon the several patches— might really 
 be different notwithstanding. In my remarks, [Appendix, p. ti.^i], upon the Baro- 
 chan experiments upon potatoes, made in 1H42, I have drawn attention to the 
 fact that potatoes sometimes contain as much as 30 per cent, of dry food, and at 
 other times as little as 20 per cent., and therefore that a ton of potatoes of one 
 kind may contain 6 cwt., while the same weight of another contains only 4 
 
Nu. IX] REMARKS UPON PRECEDIN-Q EXPERIMENTS. 83 
 
 cwt. of dry noufishment. It may be, therefore, that as by growing in unlike 
 soils or with unequal decrees of rapidity our potatoes may contain different pro- 
 portions of water, so by different kinds of dressings which act in the same way 
 as natural differences of soil, and cause the plants to develope themselves with 
 greater or less rapidity, the same effects may be produced. One kind of saline 
 substance, such as nitrate of soda, by hastening the growth, may give us a crop 
 of potatoes containing much water, while another, such as sulphate of soda, by 
 retarding the growth, may give a crop containing less water — and thus, though 
 tnere may be no difference in the weight of the two crops, they may be vei-y 
 unlike in the relative proportions of food they contain. 
 
 If such be the case it is of great practical importance to determine the quantity 
 of water which our several experimental potato crops contain, since without 
 this we may draw very incorrect conclusions as to the value of our experimental 
 manures — placing the highest value upon that which gives the greatest weigiU 
 of raw material, and esteeming least, perhaps, that which produces the greatest 
 weight of dry food. 
 
 I would again, therefore, draw the attention of my readers to the subject of 
 Suggestions IV. and VI., [Appendix, pp. G3 and 65,] in reference to the deter- 
 mination of the quantity of water in tiieir experimental root crops. The 
 method of doing this is very simple, and has already been described, [Appendix, 
 p. «4] 
 
 Each new series of experimental results we are called upon to examine and 
 analyse, will, I hope, more and more satisfy my readers, as thsy do myself, 
 that this is the true line of procedure, and that thougli there may be much in 
 our results at first which may appear contradictory and discouraging, yet that 
 out of these crude results, when combined, compared, and freq\iently repeated, 
 the real substance of a rational agriculture will, slowly it may be and with dif- 
 ficulty, yet siU'ely at last, be extracted. 
 
 No. X. 
 
 RESULTS OF EXPERIMENTS IN PRACTICAL AGRICU! TUBE, MADE 
 AT B.\ROCHAN IN 1843. 
 
 Experiment I. — Upon. Potatoes. 
 
 Comparative effects of guano, farm-yard manure, gypsum, &c., by them- 
 selves and in mixture, upon Potatoes of different varieties, planted 2.5th, 26th, 
 and 27th April; lifted, measured, and weighed from I2lh to 14th October, 
 1843. On one-rAshth of an imperial acre. 
 
 The portion of the field upon which tli^se potatoes v.-ere grown contams 
 about five acres ; soil — loam of medium texture, super-incumbent u])on trap 
 rock. It was trenched with the spade out of seven years old lea in the winter 
 of 1812 and 1S13 to the depth of 16 inches, the sward being turn-spaded into 
 the bottom of the trench, and the subsoil a stiff yellow till brought up to the 
 top, wliicii muuldered down to a fine mould during the winter. The drills were 
 fortned for the potato cms with tlio double-moulded plough, and by the 7th 
 June the plants were all brau-ded in the rows, and were worked in the usual 
 manner with t!ie plougli, drill, grubber, and hand-hocs. After the drills were 
 formed, where the guano was used, it was sown in the drills by the hand, on 
 the bottom and sides of the drills, the farm-yard manure being then put in and 
 
M 
 
 EXPERIMENTS UPON POTATOES. 
 
 [Appendix, 
 
 No. 
 
 Manures. 
 
 Giiano 
 
 Farmyard manure.. 
 
 Guano 
 
 Fariii-yard manure.. 
 FarmyarJ manure.. 
 
 Guano 
 
 Farm-yard manure.. 
 
 Guano 
 
 Farm-yard manure.. 
 
 Gypsum 
 
 F.innyard manure.. 
 Gypsum, powdered on 
 
 i sets 
 
 [Farmyard manure 
 
 i Farm yard manure 
 
 [and top-dressed 7lli July 
 
 with Guano 
 
 iGuano 
 
 JFrtrm yard manure 
 
 IGuano 
 
 Guarin 
 
 Farmyard manure..... 
 Farmyard manure... 
 Guano 
 
 
 o — 
 
 > S £ 
 
 154 19 
 
 Ins. cwt. £. s. 
 
 oo in Perths 
 r*' '°IReds. 
 
 136 |l7 134 o\^l'^^f 
 
 US 114 15 j29 10 
 
 123 16 33 
 
 IS 36 
 
 15 5 i30 10 
 
 112 il4 128 
 
 29 
 32 10 
 
 30 
 
 122 
 
 116 
 
 11 
 
 10 
 
 130 
 
 16 
 
 5 
 
 120 
 
 15 
 
 
 
 105 
 
 13 
 
 5 
 
 93 
 S6 
 
 12 
 10 
 
 
 15 
 
 Do. 
 
 Cups. 
 
 Do. 
 
 Do. 
 Do. 
 Do. 
 
 I Buffs. 
 
 Do. 
 
 -^ ^°| Blues. 
 24 Do. 
 21 lOl Do. 
 
 pread upon the top of it. Cut .sets were then laid on and covered up with 
 kbout three inches of soil. Particular atieiUion should be paid when- guano is 
 us;d, that it bn vieli mixed jvilh the soil, as this is of the greatest importance to the 
 hccdlh of till ptojits and the bulk of the crop, especially in the case of potatoes and 
 turnips. This conclusion has been arrived at after three years' extensive ex- 
 perience in the use of guano as a manure; as it has been found here that the 
 more minutely it is spread and worlved into the soil the crop is the heavier and 
 the better matured. When it has been used in a body immediately under the 
 plant, it has always been found to induce a strong vigorous growth of stems 
 and leaves, and, in general, to ripen the plant prematurely, and both the potatoes 
 and turnips were in consequence deficient in tubers and bulbs. From these 
 circumstances it may be inferred — what is indeed known to be the case — that 
 the guano does not contain all the. ingredients which are required by the plants, 
 and that the large proportion of ammoniacal salts it contains — when it is laid 
 in a mass in immediate contact with the roots of the plants — pushes on the 
 growth too quickly with small stems and delicate leaves. Numerous small 
 bulbs are the conseqncnr?, and the cultivator being disappointed is led to pro- 
 nounce the guano wort'iless, whilst his inferior crop may be in a great measure 
 owing to bad management. Whatever may be the reason, however, it has 
 been found in using it here that when son- abroad -east the cropsof every descrip- 
 tion have been benefitted, while, on the other hand, v:hcn laid in a lodij near 
 the roots the reverse has been the case. In cutting the potato for seed, gypsum 
 in powder was strewed upon the sets when newly cut, and it will be seen from 
 No. (iof the table, with good effects in adding to the produce, as where the cuts 
 were so powdered, as in No. (!, their sup"riorily over No. 7 (which was not 
 done so) in point of strength and vigour was most remarkable, and when lifted 
 the produce was 1 ton 5 cwt. per acre more than No. 7. It may also in a certain 
 measure be a means of preventing failure in the potato, as there was no failure 
 in this field where the gypsum was so used on the cuts, while the same seed 
 potatoes failed upon another field which was planted at the same time, but 
 
No. X.] 
 
 EXPERIMENTS UPON POTATOES AND HAY. 
 
 85 
 
 v)herc iw gypsum v;as poiodered on Ihe nets. At all events, it is worthy of a more 
 extensive trial as a preventative, and it will in all soils, where it is deficient, 
 add to the produce. It has, at the same time, the merit of being a cheap ajipli- 
 cation. 
 
 There was no great alteration in point of strength or forwardness till the 1st 
 of July, when all thos? patches upon which the guano had been used began to 
 take tiie lead of those planted with iarrn-yard manure alone. The guano produced 
 a dark green colour and very strong stems and leaves, so much so, that it was 
 found wlien too late that they had been too near planted, ?. c, 3'2 inches between 
 tiie drills, and 12 inches between plant and plant. There would have b<-en a 
 far heavier crop if there had been more space, as the strong growing varieties, 
 such as the cups and blues, were nearly choked for want of air. It will be 
 seen from the tables that a mixture of guano and farm-yard manure gave a 
 greater crop than where either of them was used alone. The portion, iSo. 8, 
 was tofvdressed with guano when the |;otaioes were set up for the last time. 
 It was sown Lroad cast between the drills, after which the drill harrow was put 
 through tliem and the plough followed, it acted immediately by altering the 
 colour to a dark green, the plants putting out, at the same time, new stems and 
 leaves, but owing to its being applied so late in tlie season, there was a larger 
 proportion of small potatoes than at the others when lifted. After many trials 
 it has been found that '/(? best and most economical VMij of using ouuno for Ike 
 •potato crop is lij adding 2 or 3 cu't. per acre to half the ti'siial quantify of farm- 
 yard dung, which wilt tjc found lo give, at least, as good a crop as double the quan- 
 tity of dung alone, whilst it is much cheaper in the first cost, and saves much 
 cartage, which is of the greatest moment to the farmer in spring. From its 
 effects upon the oat crop of this season, where it v/as used as a manure for the 
 turnip crop of 184'2, at the rate of 3 cwt. per acre, it seems permanent — as the 
 oats will bear a comparison with those which grew where the land was manured 
 with 40 cubic yards of farm-yard dung, and the hay crop, at this time, looks 
 as strong and forward as any in the same field. Potatoes manured with guano, 
 or dressed with sulphate and nitrate of soda, appear also to be improved in health, 
 and the tubers so grown are less apt to fail when cut and planted the following 
 season. 
 
 Experiment II. — On Hay. 
 
 Efifect of top-dressings of various substances upon three years old Grass, 
 mostly Timothy, cut for hay in 1843; top-dressed on the 3d of June ; cut on 
 the 5th of August ; weighed when cut, and again v/eighed when stacked on the 
 28th ot August, duantity of ground under each dressing — One-eighth of an 
 imperial aax. 
 
 
 
 ON ONE-EIGHTH 
 
 OP AN IMPERIAI. ACRE. 
 
 PEK. IMP. ACRE. 
 
 
 -6 
 
 
 - 
 
 - 
 
 9 .-; -"^ 
 
 >-. 
 
 .-:) rt 
 
 
 
 
 S 
 
 
 
 s c S - 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 >>x: 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 c 
 
 c; 
 
 j: 
 
 r^ 
 
 O.S 
 
 -, 
 
 g 
 
 •^ s 
 
 — t- 
 
 No. 
 
 Dressings. 
 
 
 ■a 
 
 ■s 
 
 s 
 
 -is,. 
 
 
 
 
 
 
 >% 
 
 ._ 
 
 w 
 
 % 
 
 "'' r- 
 
 
 ^ 
 
 
 ^ 
 
 
 
 
 
 
 
 
 
 3 ==- 
 
 
 
 
 
 c 
 5 
 
 o 
 
 
 3 Oj 
 
 ■3 ^ S^S 
 
 
 ,a— ■ 
 
 l> ri- '.1 
 
 
 
 
 qrs. lbs. 
 
 s. d. 
 
 lbs. 
 
 ib-s. 
 
 St. lbs. St. lbs. 
 
 St. 
 
 £. s. tl. 
 
 lbs. 
 
 1 
 2 
 
 
 1 14 
 5 bush. 
 
 3 10 
 2 6 
 
 1314 
 4560 
 
 45C0 
 
 3316 
 3156 
 
 52 11 
 
 9! 7 3S 10 
 
 96 (! 43 9 
 
 416 
 752 
 
 761 
 
 6 18 S 
 i2 10 8 
 
 12 13 8 
 
 3bO 
 
 275 
 
 300 
 
 
 Compost of Siw- ) 
 (lust and coal tar. \ 
 
 4^ 
 
 Muriate of ammonia. 
 
 20 
 
 3 
 
 3700 
 
 2356 
 
 70 17 3 
 
 560 
 
 9 6 8 
 
 266 
 
 '7 
 
 Sulphate of urine, ) 
 'riirnbuU'.s \ 
 
 20 
 
 3 
 
 3780 
 
 2136 
 
 84 0.32 
 
 672 
 
 a 4 
 
 312 
 
 Nitrate of soHa 
 
 20 
 
 9 
 
 2840 
 
 1496 
 
 53 I 
 
 424 
 
 7 1 4 
 
 265 
 
 '! 
 
 Muriate of ammonia. 
 v,"ommon salt 
 
 15 
 
 1 
 
 ■IK, ) 
 44^ 
 
 3760 
 
 2416 
 
 93 8 41 
 
 744 
 
 12 S 
 
 375 
 
 =! 
 
 Nitrate of soda 
 
 Common salt 
 
 15 
 
 1 
 
 2 4 ; 
 4J 
 
 3460^2116 
 
 87 0J35 
 
 696 
 
 U 12 
 
 350 
 
86 
 
 EXPERIMENTS UPON HAY AND OATS. 
 
 [Appendix f 
 
 The part of the fisld where the above dressings were put is a stiff clay loam 
 lying quite level upon a sandstone rock, and has a south exposure. The 
 dressings were late of l)ping put on, and it was intended for green cutting for 
 soiling, but owing to the abundunce of other feeding, the parts dressed were 
 saved for hay. All the dressings excci.t No. 3 had the eflect of altering the 
 colour to a dark green in the course of a week, and they all came away very 
 strong and vigorous. No. 3 (tlie compost, see note 1^, p. 8b,) had the effect of al- 
 tering the colour in about three weeks afier being applied, and came away so 
 rapidly tint it soon gainsd upon the others in point of strength and luxuriance 
 of stems and le;ives It will be seen from the tables that Jxos. 4 and gave 
 less bay from lOOU lbs. green cut, when used alone, than any of the others ; but 
 with the addition of common salt 1000 lbs. gave more than any of the other 
 dressed portions. Sulpliated urine may be considered a salt of ammonia, all 
 of which salts have been found to give greater bulk than almost any other ap- 
 plication of salts applied to green produce, but they have invariably been fiiuiid 
 here to g ve less dry hay when used by tlumselves. The extra produce from 
 the sulphatei urine is probably owing to its compound nature. It appears from 
 the above, therefore, that the most profitable way of using these salts is by 
 mixing Ihcrn luUk others, an I Iha'. the more compound the 'mixture is tkc better will 
 be the crap.* 
 
 Experiment III. — On Oats. 
 
 Effects of guano upon Oats (potato), sown on the I7th of April ; cut and 
 weighed on the 15th of September. Thrashed, cleaned, and weighed on the 
 24th of October. 
 
 
 
 3 c 
 
 5 iC 
 
 S 
 
 s 
 
 
 c 
 
 
 V c 
 
 .^ i 
 
 S^ 
 
 2 " 
 
 fl 
 
 
 2 
 
 
 
 "3. m 
 
 « ?v; 
 
 at,M-3 
 
 ^ .c 
 
 tD 
 
 <U 
 
 » 
 
 No. 
 
 Dressing. 
 
 ^ .-^ 
 
 = 1 
 
 nu 
 
 'o £ 
 
 = 1 
 
 11 
 
 
 
 
 
 'z: 
 
 - 
 
 
 
 ^ — 
 
 .n — 
 
 
 
 
 
 
 o 
 U 
 
 &il 
 
 
 ■5^ 
 
 > 5 
 
 
 c 
 
 
 
 qrs. 
 
 s. d. 
 
 lh.s. 
 
 Ihs. 
 
 Itis. 
 
 Ib.s. 
 
 bush. lbs. 
 
 bush. lbs. 
 
 1 
 
 Guano 
 
 3 
 
 7 i; 
 
 3300 
 
 b53 
 
 1015 
 
 40 
 
 10 13 
 
 3 20 
 
 2 
 
 Nothing 
 
 — 
 
 — 
 
 2120 
 
 539 
 
 749 
 
 4-2 
 
 li 35 
 
 
 
 Note. — The above quantities were applied to and reaped from oTie-fourlh of 
 an impjr/.al ozre. 
 
 The portion of the field upon which ihe above oats were grown is a deep 
 stiff yellow clay, supf-r-incumbent upon sandstone rock. It has been thoroughly 
 drained for a number of years. It had been sown with wheat on the "JOth of 
 January, 1843, top lires-sed with gnano at the same time, which was harrowed 
 in, but owing to the dampness and constant change from frost and thaw, the 
 greatest part of the wheat failed, and was ploughetl up on tlie loth of April, and 
 potato oats sown upon it on the 17th of that month. The oats brairded all 
 alike, showing no difference in point of earliness ; but by the Dth of June a 
 most romarlcable alteration had taken place, the portion which had been dressed 
 with guano for the wheat taking the lead of the undressed portion, and being 
 of adiirk green colour with broad leaves, and covering the ground well; whilst 
 that which had no dressing was brown and stinted in comparison, and the 
 ground not half covered. The two poruons continued throughout the season to 
 prcFsnt the same difference in their appearance, and at the time of cutting there 
 was more than a foot in length of straw in favour of the dressed portion. It 
 will be seen from the table, however, that although the guano had the effect of 
 giving more bushels per acre, the bushels were lighter in weight by 2 lbs. than 
 the grain from the undressed. It may be remarked, however, that had common 
 
 ■ See on this subject of mixtures tlie Author's Elemtnta of Agricullural Chemistry emd 
 Geologij, p. 149. 
 
EXPERIMENTS UPON OATS AND TURNIPS. 
 
 87 
 
 No. X.] 
 
 salt been mixed with tlie guano, there is reason to believe, from other trials, 
 tliat the grain would not have been deficient in weight per bushel. Ainmonia- 
 cal salts should at no time be dressed upon grain crops, without, at the same 
 time, adding, according lo the composition ot' the soil upon which such crops 
 are grown, such other morganic ingredients as may be required. Few soils, at 
 least in this part of tlie countiy, appear able to supply these in sufficiency to the 
 plants — particularly the phosphates, which seem always deficient. At least the 
 addition of bone-dust or animal charcoal seems always to improve the crops to 
 which they are applied. 
 
 Experiment IV. — On Turnips. 
 Comparative effects of guano, farm-yard manure, bone-dust, and animal char- 
 coal, by themselves and in mixtures,' on Turnips of different varieties; lifted, 
 topped, tailed, and weighed, in Nov., 1843. 
 
 ON AN EIGHTH OP AN IMPERIAL ACRE. 
 
 ON ANIMP.ACRE. 
 
 No. 
 
 Variety of turiiijisi an'-'lTjrne oi 
 kiiiU ot maiiuies. Isowing. 
 
 1 Cost, of 
 Quantity oi'j ni.'tniire.'j, 
 manure le.xclusive of 
 applied. I cartage. 
 
 Pro- 
 luce. 
 
 1 Value of 
 
 produce 
 
 at 15s. 
 
 per ton. 
 
 1^ 
 
 SWEDISH. 
 
 Farmyard manure.... 
 
 Uuaiiu 
 
 Aiiiniai cliarcual'... 
 { Farm yard manure 
 
 2]|Guano. 
 
 ( ilalf-uicli bones. . . . 
 
 3 iKarm-yard manure. 
 
 4 Uuanu 
 
 5 lUalf-inch bones. . . . 
 
 June 
 
 5 to 7 
 
 Pt;RPLE-T0P VGLLOW 
 
 Ciuauo 
 
 Uun- 
 
 Bones 
 
 I'arm-yard manure... 
 
 Guano 
 
 l-'aiiu yard manure 
 
 UoneUu:»t ....... . 
 
 Farm yard manure 
 
 Guano 
 
 Animal charcoal. . , 
 
 S-1 
 
 JONES' YELLOW TOP. 
 
 Farm-yard manure .... 
 
 Animal cliarcoal 
 
 Farm yard manure 
 
 Bone-dust 
 
 Farm-yard manure 
 
 Sulphate of Soda, as a 
 
 top dressing 
 
 Farm-yard manure 
 
 Guano 
 
 Farm-yard manure. 
 
 Guanot 
 
 Animal ciiarcoal. . . 
 Compost of coal lar 
 
 and saw-dust. . . . 
 
 2h cub. yds. 
 42 It)3. 
 70 lbs. 
 2^ cub. yds. 
 42 lbs. 
 2^ bushels. 
 5 cub yds. 
 70 lbs. 
 5 bushels. 
 
 .56 lbs. 
 4i cub. yds. 
 4j bushels. 
 2l cub. yds. 
 2^ lbs. 
 2i cub. yds. 
 ll bushels. 
 2i yds. 
 28 lbs. 
 42 lbs. 
 
 3| yds. 
 7U lbs. 
 .3f yd^. 
 li bushels 
 
 3f yds. 
 2U lbs. 
 
 3i yds. 
 70 lbs. 
 2:V yds. 
 42 lbs. 
 1-J- cwt. 
 
 3 bushels. 
 
 ts. cts. qrs. 
 6 Oi 
 
 4 19 
 
 ts. cts. £. s. d. 
 42 9.31 7 
 
 39 1229 19 3 
 
 5 
 
 1 2 6 
 9 
 12 6, 
 2 61 
 12 6, 
 3 0< 
 12 6 
 
 3 10 
 7 
 
 
 4 10 
 
 33 17 
 32 
 25 14 
 
 25 7 II 
 
 6 
 
 S24 
 
 4 18 3 
 
 25 5 14 2 6 
 
 26 1613 3 
 
 24 0jl2 
 
 36 018 
 
 25 10112 15 
 
 3) 1019 15 
 
 3 10 
 
 4 
 
 2 
 
 3i 
 
 2 
 
 13 
 
 li 
 
 3 
 
 12 
 
 3i 
 
 16 
 12 4 6 
 
 14 
 
 
 
 
 
 1 
 
 17 
 
 10 13 6 
 
 14 11 
 
 The field upon which the above turnips were grown is a light gravelly loam, 
 super-incumbent upon a deep gravelly till. The greater part of the field was 
 trenched with the spade, and all drained with tiles and soles 30 inches deep and 
 20 feet apart, in the winter of 1841 and 1842, and in the preparation for the tur- 
 
 ' The animal charcoal here used is the refuse of the sugar refiners, and contains about 
 {lb. of its weight o( bone-earth. 
 t This paj-t of ibe field was treacbed. 
 
88 EXPERi.MENTs UPON TLRNiFS. [Appendix, 
 
 nip crop in 1842 and 1843, wliat liad not been Irenched was subsoilecl. The 
 turnip crop was sown at different times, as noticed in the tables. All the parts 
 brairded well and healthy, and continued to grow without intermission through 
 the season. The field contains about 11 acres imperial, and the crop was most 
 luxuriant, so much so, that the lightest turnips in any part of the field would 
 have been reckoned good. The iield was drilled for the crop with the double 
 mould plough at 30 inches apart, for sivedcs and -purple top-ijdloir, and 2t!aiid 28 
 inches for Janes' ydknc, v/hich variety is remarkable for very small tops, and, in 
 consequence, may be drilled nearer. The difference in the appearance of the 
 turnips, where the various manures and mixtures had been applied, was very 
 marked. Wherever guano had been applied, the tops were larger Uian any of 
 the others, except No. 3 of f he table {Jones' yellow), upon which sulphate of soda 
 was top-dressed, after the plants were thinned. The crop upon this portion was 
 remarkable for luxuriance of tops and large bulbs, and gave a veiy good crop.* 
 No. G of the table (Jones' yellow), was upon spade-trenched land, and 
 is the only lot where a comparison can be made between trenching and subsoil- 
 ing. Where bone dust was used ths tops were not so large, and where //i;e«/ii- 
 -Kinl ckarcoal had been added the tops wei'e least of all and the bulbs largest. Upon 
 a'l the varieties of soils in this farm, the application of animal charcoal or bone 
 dust has been of great benefit to all crops — to wiieat, barley, oats, hay, and grass 
 — the crops being bulkier and of superior quality, especially upon soils superin- 
 cumbent on trap rock, giving an evidence that all such soils upon this estate are 
 in want of phosphates. This has also been proved by the analysis of several — 
 none of them giving more than a trace of phosphates, and some of them none at 
 all. Upon all these soils animal charcoal or bones seem to be indispensable, 
 because the grain crops cannot be matured without phosphates of lime and 
 magnesia. It appears from the many experiments that have been made here, 
 that guano does not contain a sufficiency of the phosphates to supply the crops 
 to wiiich it is usually applied, and which, from the greater luxuriance of growth 
 its application at all times induces, would be required in gi eater quantity accord- 
 ing to the bulk of crop. A jiortion of the animal cliarcoal of tiie sugar refiners 
 b^ing mixed with it at the time of sowing, will supply the deficiency, and at all 
 places inland from the sea, common salt will be found a valuable addition. The 
 cultivator who is obliged from deficiency of farm-yard manure to use guano will 
 find that by taking one-half of his usual quantity of farm-yard manure per acre, 
 and making up for the other half by the addition of 2 to 4 cwts. of guano, his 
 crops will be, at least, as bulky, and his after-crops as good, as if he had used 
 40 cubic yards of good dung. Guano, however, should not be used by itself 
 upon soils that do not contain a certain amount ofvegelable matter ((.e. on poor 
 sharp soils), but it will in all cases be found an invaluable manure for thorough- 
 drained moss soils. 
 
 Notes. — 1^. The compost of coal-rar and saw-du.st used in the preceding experimcnls is 
 composed of saw-dii3t or moss 40 biishel.s, coal-tar 20 jrallons, bone-dust 7 bushels, siilpliale 
 of soda I cwt., sulphate of mafinesia li owl., and common salt li cwt.. put together in a 
 heap, with 20 bushels of quicklime, and allowed to ferment and heat for three weeks, when 
 it is turned, and again allowed to ferment, and is then fit for use. 
 
 2°. In usins the nitrate of soda for the last four years in the garden, it has been found 
 that top-dressing the leeks- irrthe month of August or September enabled Ihem to resist the 
 effects of winter, whilst those that were not so dressed have invariably failed, and gone to 
 decay early in the season ; at the same time, it increases their bulk in a remarkable man- 
 ner. Knowing this effect upon leeks,— a crop that if ftrown to a large size has a fireat 
 tendency to rot and fail in winter, — might it not have the same effect upon autumn sown 
 wheals if dresse<l wiih it after Iliey are brairded 1 This hint is merely thrown out as worthy 
 of trial, as the salt appears to have the power of tougheninjj the fibre or o'.'ierwise enat>ling 
 the plants to withstand the rigours of winter, and in this way might, peihajis, prevent ttie 
 wheat crop from failing in winter, which i.>< often the case, to the great loss and disappoint- 
 ment of the farmer 
 
 W.M. Fleming. 
 
 Barochan, Feb., 1844. 
 
 * Sulphuric acid and the sulphates appear to exercise a marked actton on the turnip crop.-^J. 
 
No. A'.] REMARKS UPON PRECEDING EXPERIMENTS, 89 
 
 REMARKS. 
 
 I submit these experiments to tlie reader without any lengthened comment. 
 The experiments with guano are very seasonable, and will be of much service 
 to the thousands of practical men who are now likely to try this valuable 
 manure. 
 
 There are three interesting geneml observations of Mr. Fleming, to which 
 alone I would direct especial attention — 
 
 1°. That tlie potato sets did not fail when powdered with gypsum, and that 
 the more extensive trials of this substance which he recommends ought cer- 
 lainly to be encouraged. 
 
 2°. That potatoes dressed with guano, or with nitrate and sulphate of soda, 
 appear to be improved in health, and are less apt to fail when cut and planted 
 the following year. 
 
 3^. That his trap soils are supposed to be -specially deficient in phosphates, 
 and that the use of bones, in any form, alwe^ s improved his crops upon these 
 soils. 
 
 These three observations are very interesting, and a careful study of the 
 tables of results will lead the reader to make other interesting observations and 
 deductions for himself 
 
 It is very satisfactory to me to have been able in this Appendix to incorporate 
 the results of experiments performed on three successive years by one so skilful 
 and zealous as Mr. Fleming, — conducted every year also with more care, and 
 more likely, therefore, to lead to important conclusions. 
 
 The subject of agricultural experiments has now been taken up so warmly 
 and so successfully in almost every part of the country, that we may look for- 
 ward with confidence to the gradual accumulation of a body of facts, out of 
 which correct and practically useful principles may gradually be elicited. The 
 large body of experimental results, which the prize offered last year by the 
 Highland Society has brought before the public, showa h7W eagerly the en- 
 lightened practical farmers of the present day will follow ;iS» /Guidance of such 
 as are willing to show them how tne art by which they lxf» iv* be really and 
 permanently improved. 
 
 Jamrr r. Wright Printer, 
 
 12J Fulton strpet. 
 
^'K 826®