E I. E M B N T S AaEICULTURAL CHEMISTRY AND GEOLOGY. BY JAxMES F. IV/ JOHNSTON, M.A,, F.RSS. L. & E. Honorary Member of the Royal Agricultural Society of England, and Author of " Lectures on Agricultural Chemistry and Geology." WITH A COMPLETE INDEX, AMERICAN PREFACE: BY SIMON BROWN, ^ ^. . . . , FDITOR OF THF NEW ENGLAND FARMER. >_^. A NEW YORK: "" : ^,,! --" C. 31. S AXTOIT, AGRICULTURAL BOOK PUBLISHER. 1853. Enlered according to Act of Congress, in the j-ear 1S53, hy C. M. SAXTOX, in the Clerk's Office of the District Court of the United States for Iho South- ern District of New York. S. W. BENEDICT, Sterkotyper and Printer, 16 Spruce slrenl, N. Y. PREFACE TO THE AMERICAN EDITION. In England, and on the continent of Europe, it has been long understood among the class who own the soil, and culti^ vate it by the sweat of the brow of other men, and not their personal labor, that success in husbandry must depend upon giving to the soil, in some form, what is annually taken away in cultivated crops. In America, in the older States, the same truth is at length reluctantly admitted. The census tables have shown that the wheat crop of New York, in some counties, has fallen in its average product so low as eight bushels to the acre, where for- merly from thirty to forty were produced. Lands deemed inex- haustible have been cropped almost to barrenness. Large sec- tions of territory in Virginia, formerly very productive, by a course of culture not guided by a correct knowledge of the science of Husbandry, have become utterly unproductive, and been abandoned by the original cultivators. A succession of tobacco crops raised by shoal plowing without artificial manur- ing, or a proper rotation with other products, exhausted the surface soil, and compelled^^ the proprietors to seek fresh fields. Recently a more thorough and intelligent system, by men who are both owners of the land and laborers upon it, has shown that it was only with mireasonahle demands upon her resources PREFACE. that a generous mother Earth had refused to comply; for the same lands, by deep plowing and judicious rotation, are yielding already a rich return for labor and capital to their owners.. In both countries it is now regarded by well-informed men as settled, that only labor directed by scientific knowledge can yield a fair return upon any but new lands, where, as in our Western States, Nature's storehouses of fertilizers are yet unex- hausted. In England the soil is owned by a few, and those mostly educated men, and they, directly or indirectly, insist upon systematic and thorough tillage, as the only means of deriving profit from their capital. In America, in the free States, the land owner labors with his own hands, and a' knowledge of the principles of husbandry must be generally diffused, that each for himself may apply them in his own practice. Indeed, it seems peculiarly fitting that the owner of the soil, who himself performs the labor upon it, should have constantly in view the reason for the various processes he performs in bringing his crops to maturity. No writer, perhaps, of the present day, has succeeded so well as Mr. Johnston, in adapting to the apprehension of the general reader his teachingsHipon the Science of Agriculture, — ■ in combining with instructions necessarily abstruse, the practi- cal ideas which make his theories of manifest present value to the farmer. His style has the simplicity and directness only acquired by those accustomed to speak to practical men. He announces at once his object, — the advantages to be gained ; and then tells us in the plainest language how to attain it. More advancement has been made in Agricultural Chemistry in the last ten years, than in any other branch of Science, and no mind is better qualified than Mr. Johnston's, to seize upon INTRODTJCTIOlSr. The scientific principles iipon which the art of culture depends, have not hitherto been sufficiently understood or appreciated by practical men. Into the causes of this I shall not here in- quire. I may remark, however, that if Agriculture is ever to be Ijrought to that comparative state of perfection to which many other arts have already attained, it will only be by avail- ing itself, as they have done, of the many aids which science offers to it. And if the practical man is ever to realise upon his farm all the advantages which science is capable of placing within his reach, he must become so far acquainted with the connection that exists between the art by which he lives and the sciences, especially of Chemistry, Greology, and Chemical Pliysiology, as to be prepared to listen with candor to the suggestions they are ready to make to him, and to attach their proper value to the explanations of his various processes which they are capable of affording. The following little Treatise is intended to present a familiar outline of the subjects treated of more at large in my published Vin INTRODUCTION. Lectures on Agricultural Chemistry and Geology. What, in tliis work, has necessarily been taken for granted, or briefly noticed, is in the Lectures, examined, discussed, or more fully detailed. Those who wish to put into the hands of the young a still more condensed view of the principles of scientific agriculture, will find it in my Catechism of Agricultural Chemistry and Geology. To most persons, indeed, it will prove advantageous to read the Catechism first, and to pi'oceed from it to the Ele- ments, and then to the Lectures. Durham, November 1852. PREFACE. V every new theory mid fact, and to coniljinc tiiem all into a har- monious whole. The present volume pretends.. to no great recent discoveries in Agriculture, but it is believed that in no other work have the results of experience and theories been more carefully com- pared. The writer, in addition to a complete treatise upon the Elements of Agricultural Chemistry, suggests modes of thought calculated to lead the reader constantly to reflection. What each crop and each rotation of crops takes fp^m the soil, is carefully shown, that so the farmer may be led to inciuire how he can return the elements thus exhausted. Exact analyses are given of the various substances used as manure, thus giving aid to answer such inquiries. The structure of the various parts of plants, the stem, root, and leaves, and their various functions, are also carefully considered, with a view of ascertaining both how their grow^th may be promoted, and to what useful pur- poses they may be applied as manure, when their other uses are exhausted. The structure of the earth, of its various rock formations, which are the foundation of all soils, is lucidly discussed, giving an insight into the value of geology as a practical helper in husbandry — ^giving us'at the same time direct instruction in the best mechanical treatment of the farm, in plowing, subsoiling, liud thorough draining. The reader will find practical advantage in the suggestions of the author as to aduUerations of the various fertilizers now ex- tensively used in this country, especially of guano. It is believed that gross impositions are already practiced upon the agricultu- ral community, in the sale of various articles of little value. It is only by the aid of scieutitic men, like our author, that these VI PREFACE. frauds can be detected, and the community be jirotected from imposition, while they reap the full advantage to be derived from the use of those articles when honestly supplied to them in a pure form. The work is offered to the public, not to su- persede the truly-scientific and more technical treatise of Stock- hardt in the schools and colleges, not indeed to take the place of any existing work, even in our libraries, ])ut as containing the matured results of a carefully-trained mind, which has long compared the practical notions of the farmer with the theoreti- cal ideas of the chemist and geologist, and so wrouglit out a fund of valuable knowledge ioY ]p radical men, such as, it is be- lieved, no other book supplies. Another feature of great value to the work is that it has a thoroughly-digested analytical and alphabetical index, so that the editor, or student, in discussing any particular subject here- in treated, may turn directly to it ; or the farmer, when in doubt as to the treatment or composition of certain soils, the compost- ing or application of manures, or the fertilizing properties of the rocks upon his farm, by the -aid of the index is directly referred to the sul)ject in question, where he will usually find such plain and practical suggestions as will enable him to derive important aid in his operations. Simon Brown. Boston, 185o. ELEMENTS OP AGEICULTUEAL CHEMISTRY ETC. CHAPTER I. Object of the farmer. — What chemistry, geology, and chemical physiology may do for agriculture. — Distinctiou between organic and inorganic sub- stances. — The ash of plants and animals. — Simple and compomid bo- dies. — What elementary bodies are contained in the organic part of soils, plants, and animals. — Properties of carbon, sulphur, phosphorus, hydrogen, oxygen, and nitrogen. — Relative proportions of these elemen- tary bodies contained in plants and animals. — Meaning of chemical com- bination and chemical decomposition. The object of the practical farmer is to raise from a given extent of land the largest qaantitj of the most valuable pro- duce at the least cost, in the shortest period of time, and with the least permanent injury to the soil. Chemistry, Geology, and Chemical Physiology throw light on every step he takes, or ought to take, in order to effect this main object. SECTION I. WHAT CHEMISTRY, GEOLOGY, AND CHEMICAL PHYSIO- LOGY MAY HOPE TO DO FOR AGRICULTURE. But there are certain definite objects which, in their connec- tion with agriculture, these sciences hope to attain. Thus, without distinguishing the special province of each, they pro- pose generally : — 1 Z WHAT CHEMISTRY AND GEOLOGY . 1°. To colled, to investiga/c, and, if possible, to explain- all known facts in practical husbandry. — This is their first duty — a laborious, difficult, but important one. Many things which are received as facts in agriculture, prove to be more or less untrue when investigated and tested by experiment. Many ascertained facts appear inexplicable to the uninstructed — many even oppo- site and contradictory, whieh known principles clear up and reconcile — yet there are many more which only prolonged re- search can enable us to explain ! 2°. From observations and experiments made in the field or in the laboratory, to deduce principles which may be more or less appli- cable in all circumstances. — Such principles will explain useful practices, and confirm their propriety. They will also account for contradictory results, and will point out the circumstances under which this or that practice may most prudently and most economically be adopted. Armed with the knowledge of sucli principles, the instructed farmer will go into his fields as the physician goes to the bed- side of his patient, — prepared to understand symptoms and appearances he has never before seen, and to adapt his prac- tice to circumstances vrhich have never before fallen under his observation. To deduce principles from collections of facts is attended with mucli difficulty in all departments of knowledge. In agri- culture it is at present an unusaally difficult task. Observations and experiments in the field have hitherto been generally made with too little care, or recorded with too little accuracy, to justify the scientific man in confidently adopting them as the basis of his reasonings. A new race, however, of more careful observers, and more accurate experimenters, is now springing up. By their aid, the advance of sound agricultural know- ledge cannot fail to be greatly promoted. 3°. To suggest improved, and, perhaps, previously unthought-of methods of fertilising the soil. — A true explanation of twenty known facts or results, or useful practices, should suggest nearly MAY HOrE TO DO FOR AGRICULTURE. 3 as many more. Thus the explanation of old errors will not only guard the practical man from falling into new ones, but will suggest direct improvements he would not otherwise have thought of. So, also, the true explanation of one useful prac- tice will point out other new practices, which may safely and with advantage be adopted, 4°. To analyse soils, mamircs, and vegetable products. — This is a most laborious department of the duties which agriculture expects chemistry to undertake in her behalf. a. Soils. — The kind and amount of benefit to be derived from the analyses of soils, are becoming every day more apparent. We cannot, indeed, from the results of an analysis, prescribe in every case the kind of treatment by which a soil may at once be rendered most productive. In many cases, however, certain wants of the soil are directly pointed out by analysis ; in many others, modes of treatment are suggested, by which a greater fertility is likely to be produced, — and, as our knowledge of the subject extends, we may hope to obtain, in every case, some useful directions for the improvement or more profitable culture of the land. b. Manures. — Of the manures we employ, too much cannot be known. An accurate knowledge of these will guard the practical man against an improvident waste of any of those natural manures which are produced upon his farm — thus les- sening the necessity for forei"gn manures, by introducing a greater economy of those he already possesses. It will also protect him against the ignorance or knavery of the manure manufacturer. The establishment of such manufactories, con- ducted by skilful and honorable men, is one of the most impor- tant practical results to which the progress of scientific agricul- ture is likely to lead. And if it cannot prevent unsorupulous adulterators from engaging in this new traflQc, chemistry can at least detect and expose their frauds. c. Vegetable Products. — In regard, again, to the products of the soil, few things are now more necessary than a rigorous 4 WHAT CHEMISTRY AND GEOLOGY MAY HOPE TO DO, &C. analysis of all their parts. If we know what a plant contains, we know what elementary bodies it takes from the soil, and, consequently, what the soil must contain, if the plant is to grow upon it in a healthy manner, — that is, we shall knov,^, to a cer- tain extent, how to manure it. On the other hand, in applying vegetable substances to the feeding of stock, it is of equal importance to know what they severally contain, in order that a skilful selection may be made of such kinds of food as may best suit the purposes we intend them to serve: 5°. To explain how plants groio and are nourished, and how animals are supported and most cheaply fed.- — What food plants require, and at different periods of their growth, whence they obtain it, how they take it in, and in what forms of chemical combination ? Also, what kind and quantity of food the animal requires, what purposes different kinds of food serve iu the animal economy, and how a given quantity of any variety of food may be turned to the best account ? What questions ought more to interest the practical farmer than these ? Then there are certain peculiarities of soil, both physical and chemical, which are best fitted to promote the growth of each of our most valuable crops. There are also certain ways of cultivating and manuring, and certain kinds of manure which are specially favorable to each, and these again vary with every important modification of climate. Thus chemical physiology has much both to learn and to teach in regard to the raising of crops. So, different kinds and breeds of domestic animals thrive best upon different kinds of food, or require different proportions of each, or to have it prepared in different ways, or given at differ- ent time«. Among animals of the same species also, the grow- ing, the full-grown, the fattening, and the milking animal, re- spectively require a peculiar adjustment of food in kind, quan- tity, or form. All such adjustments the researches of chemistry and physiology alone enable us accurately to make. ORGANIC AND INORGANIC PARTS OF PLANTS, &C, 5 6°. To test the opinions of theoretical men. — Erroneous opinions lead to grave errors in practice. Such incorrect opinions are not unfrequently entertained and promulgatetl even by eminent scientific men. They are in this case most dangerous and most difficult to overturn ; so that against these unfounded theories the farmer requires protection, no less than against the quack- ery of manufactured manures. It is only on a basis of often repeated, skilfully conducted, and faithfully recorded experi- ments, made by instructed persons, that true theories can ever be successfully built up. Hence the importance of experiments in practical agriculture. Such are the principal objects which chemistry, aided by geo- logy and physiology, either promises or hopes to attain. In no district, however, will the benefits she is capable of conferring upon agriculture be fully realised, unless her aid be really sought for, her ability rightly estimated, and her interference earnestly requested. In other words, what we already know, as well as what we are every day learning, must be adequately diffused among the agricultural body, and in every district means must be adopted for promoting this diffusion. It is in vain for che- mistry and the other sciences to discover or suggest, unless her discoveries and suggestions be fully made known to those whose benefit they are most likely to promote. SECTION II. OF ORGANIC AND INORGANIC MATTER, AND OF THE OR- GANIC AND INORGANIC PARTS OF ANIMALS, PLANTS, AND SOILS. In the prosecution of his art, two distinct classes of substances engage the attention of the practical farmer — the living animals and crops he raises, and the dead soils from which the latter are gathered. If he examine any fragment of an animal or vegetable, either living or dead, — a piece of flesh or wood, for example, — he will observe that it exhibits pores of various kinds arranged in a certain order ; that it has a species of inter- nal structure ; that it has various parts or organs ; in short, 6 ORGANIC AND INORGANIC PARTS OF PLANTS, &C. that it is what physiologists term organised. If he examine, in like manner, a lump of earth or rock, he will perceive no such structure. To mark this distinction, the parts of animals and vegetables, either living or dead — whether entire or in a state of decay — are called organic bodies, while earthy and stony sub- stances are called inorganic bodies. Organic substances are more or less readily burned away and dissipated by heat in the open air ; inorganic substances are generally fixed and permanent in the fire. Now the crops which grow upon the land, as well as the soil in which they are rooted, contain a portion of both of these classes of substances. In all fertile soils there exists from 3 to 10 per cent, of vegetable or other matter, of organic origin. If we heat a portion of such a soil to redness in the open air, as in the annexed, (fig. 1,) this organic matter will burn away, leaving the inorganic or mineral matter behind. By this burn- ing, most soils are changed in color, but, if previously dried, Pig. 1. are not materially diminished in bulk. The inorganic matter forms by far their largest part. All vegetables, again, as they are collected for food, leave, when burned, a sensible quantity of inorganic ash ; but of them it forms only a small part. Wood leaves about a J per cent, grain 2 or 3 per cent, straw about 5 per cent ; and only in rare cases does the ash left amount to 15 or 20 per cent of the weight of a vegetable substance. Hence, when a handful of wheat, wheat straw, hay, &c., is burned in the air, a compara- tively small weight of matter only remains behind. Every one r SIMPLE AND COMPOUND BODIES. T m familiar with tliis fact who has seen the small bulk of ash that is left when weeds, or thorn-bushes, or trees, are burned in tlie field, or when a hay or corn stack is accidentally consumed. Yet this ash is ver/ important to the plant, and the study of its true nature throws much light, as we shall hereafter see, on the practical management of the land on which any given crop is to be made to grow. It strikes us also as being important in quantity, when we consider how much may be contained in an entire crop. Thus the quantity of ash left by a ton of wheat straw is sometimes as much as 360 lb., and by a ton of oat straw as much as 200 lb, A ton of the grain of wheat leaves on an average about 45 lb., of the grain of oats about 9 lb., and of oak wood only 4 or 5 lb. Animal substances also leave a proportion of ash when burned in the air. Dry flesh and hair leave about 5 per cent of their weight of inorganic ash ; dry bones more than half their weight. Generally, therefore, the soil contains little organic and much inorganic or mineral matter — the plant much organic and little mineral — the animal, in its soft parts, little, in" its hard or solid parts, much mineral matter. SECTION III. OF SIMPLE OR ELEMENTARY AND COMPOUND BODIES. The various kinds of organic and inorganic matter of which soils, plants, and animals consist, are distinguished by chemists into two groups. Those which, by the agency of heat, or by any chemical or other means, can be separated into two or more unlike kinds of matter, are called compound bodies — those which cannot be so separated, are called simple or elementary bodies. Gold, iron, sulphur, and pure charcoal are simple substances. They cannot by any known means be separated or resolved into more than one substance. Wood, flesh, limestone, sand, &c., are CGmpound substances. We are acquainted with methods by which they can each be split up into two or more substances different from each other, 8 PROPERTIES OF CARBON and from the wood or flesh, &c., from which they are ob- tained. Of simple or elementary bodies sixty-four are at present known to chemists. All the other forms of matter which occur in the animal, vegetable, or mineral kingdoms are compound. SECTION IV. OF THE ELEMENTARY SUBSTANCES OF WHICH THE ORGANIC PART OF SOILS, PLANTS, AND ANIMALS CONSISTS. The organic or combustible part of soils, plants, and animals is composed almost exclusively of four elementary substances, known to chemists by the names of carbon, hydrogen, oxygen, and nitrogen. It usually contains also a minute proportion of sulphur and phosphorus. Of these, carbon, sulphur, and phosphorus are solid substances ; while hydrogen, oxygen, and nitrogen are gases, or peculiar kinds of air. Their properties are as follows : — 1. Carbon. — When wood is burned in a covered heap, as is done by the charcoal burners, — or is distilled in iron retorts, as in making wood-vinegar, — ^it is charred, and is converted into common wood charcoal. This charcoal is the most usual and best known variety of carbon. It is black, soils the fingers, and is more or less porous, according to the kind of wood from which it has been formed. Coke obtained by charring or distilling coal is another variety. It is generally denser or heavier than charcoal, though usually less pure. Black lead is a third va- riety, still heavier and more impure. The diamond is the only form in which carbon occurs in nature in a state of perfect purity. This latter fact, that the diamond is pure carl3on — that it is essentially the same substance* with the finest and purest lamp- black — is very remarkable ; but it is only one of the numerous striking circumstances that every now and then present them- selves before the inquiring chemist. Charcoal, the diamond, lamp-black, and all the other foriiis PROPERTIES OF HYDROGEN. 9 of carbon, burn away more or less slowly wlien heated to red- ness in the ah* or in oxygen gas, and are converted into a kind of gas known by the name of carhonic acid gas. The impm^e varieties, when burned, leave behind them a greater or less pro- portion of ash. 2. Sulphur is a well known solid substance of a light yellow color, and faint peculiar odor. It burns with a pale-blue flame, and in burning gives off fumes possessed of a strong pun- gent characteristic smell. 3. Phosphorus is a yellowish waxy substance of a peculiar smell, which smokes in the air, shines in the dark, takes fire by mere rubbing, and burns with a large bright flume and much white smoke. Like sulphur, it exists in all plants and animals, though in comparatively small quantity. Like sulphur, also, it is employed largely in the arts, especially in the manufacture of lucifer matches. 4. Hydrogen. — If oil of vitriol (sulphuric acid) be mixed Eig. 2. with twice its bulk of water, and be then poured upon iron filings, or upon small pieces of zinc, the mixture will speedily begin to boil up, and bubbles of gas will rise to the surface of the liquid in great abundance. These are bubbles of hydrogen gas. 1* ; ( 10 PROPERTIES OF OXYGEN. If the experiment be performed in a bottle, the hydrogen which is produced will gradually drive out the atmospheric air it contained, and will itself take its place. If a taper be tied to the end of a wire, and, when lighted, be introduced into the bottle, (fig. 2,) it will be instantly extinguished ; while the hydrogen will take fire, and burn at the mouth of the bottle with a pale yellow flame. If the taper be inserted before the common air is all expelled, the mixture of hydrogen and com- mon air will burn with an explosion more or less violent, and may even shatter the bottle and produce serious accidents. This experiment, therefore, ought to be made with caution. It may be more safely performed in a common tumbler, (fig. 3,) Fiff. 3. covered closely by a plate, till a sufficient quantity of hydrogen is collected, when, on the introduction of the taper, the light will be extinguished, and the hydrogen will burn with a less violent explosion. Or the gas may be prepared in a retort, and collected over water, as shown in fig. 4. This gas is the lightest of all known substances, rising through common air as wood does through water. Hence, when con- fined in a bag made of silk, or other light tissue, it is capable of sustaining heavy substances in the air, and even of carrying them up to great heights. For this reason it is employed for filling and elevating balloons. Hydrogen gas is not known to occur any where in nature in any sensible quantity in a free state. It is very abundant in water, and in many other substances, in what by chemists is called a state of combination. (See pages 15 and 24.) 5. Oxygen. — When strong oil of vitriol is poured upon black PROPERTIES OF OXYGEN, 11 oxide of manganese, and heated in a glass retort, (fig. 4,) or when a mixture of chlorate of potash with an equal weight of Fio-. 4. oxide of manganese, or when chlorate of potash alone, or red oxide of mercury alone, is so heated — or when saltpetre, or the black oxide of manganese, is heated alone in an iron bottle, — in all these cases a kind of air is given off, to which the name of oxygen gas is given. It is obtained with the greatest ease, rapidity, and purity, from the mixture of chlorate of potash and oxide of manganes^e. A very elegant method of preparing the gas is to put a few Fig. 5. grains of rtd oxide of mercury into a tube, and apply the heat of a lamp as in fig. 5. Oxygen gas will be given off' while minute globules of metallic mercury will condense on the cool part of the tube. The presence of oxygen in the tube is shown by in- 12 PREPARATION OF NITROGEN. troducing iiito one end of it a half-kindled match, when it will be seen to burn up brilliantly. It is the characteristic property of this gas, that a taper, when introduced into it, burns with great rapidity, and with ex- ceeding brilliancy, and continues to burn till cither the whole of the gas disappears or the taper is entirely consumed. In this respect it differs both from hydrogen and from common air. If a living animal is introduced into this gas, its circulation and its breathing become quicker — it is speedily thrown into a fever ■ — it lives as fast as the taper burned^and, after a few hours, dies from excitement and exhaustion. This gas is not lighter, as hydrogen is, but is about one-ninth part heavier than com- mon air. In the atmosphere, oxygen exists in the state of gas. It forms about one-fifth of the bulk of the air we breathe, and i« the substance which, in the air, supports all animal life, and the combustion of all burning bodies. It is necessary also to the growth of plants, so that were it by any cause suddenly re- moved from the atmosphere of our globe, every living thing would perish, and all combustion would become impossible. 6. N'lTROGEN. — This gas is very easily prepared. Dissolve a little green copperas in water, and pour the solution into a flask, or crystal bottle, provided with a good cork. Add a little of the hartshorn of the shops (liquid ammonia) till it is quite muddy, put in the cork tight, and shake the bottle well for five minutes. Loosen the cork well without removing it, so as to allow air to enter the bottle. Cork tight again and shake as before. Re- peat this as often as the loosening of the cork appears to admit any air, and after finally shaking it, allow it to stand for a few minutes. The air now in the bottle is nearly pure nitrogen gas. If a lighted taper be introduced into the bottle it will be extinguished by this gas, but no other effect will follow. The gas itself does not take fire as hydrogen does. Or if a living animal be introduced into it, breathing will instantly cease, and it will drop without signs of life. COMPOSITION OF THE ORGANIC PART OF PLANTS. 13 This gas possesses no other remarkable property. It is a very little lighter than common air, (as 9^1 to 100,) and exists in large quantity in an uncombined state in the atmosphere only. Of the air we breathe it forms nearly four-fifths of the entire bulk— the remainder behig oxygen. In the process above described for preparing the gas, the oxygen is absorbed by the iron, and the nitrogen left behind. These three gases are incapable of being distinguished from common air, or from each other by the ordinary senses ; but by the aid of the taper they are readily recognised. Hydrogen extinguishes the taper, but itself takes fire ; nitrogen simply extinguishes it ; while in oxygen the taper burns rapidly and with extraordinary brilliancy. SECTION V. PROPORTIONS OF THESE ELEMENTARY SUBSTANCES CONTAINED IN THE ORGANIC PART OF PLANTS AND ANIMALS. Of the one solid substance, carljon, and the three gases, hy- drogen, oxygen, and nitrogen, above described, the organic part of all vegetable and animal l)odies is essentially" made up. In fhose organic sul)stances which contain nitrogen, sulphur and phosphorus also are present, but generally in minute pro- portion. But the organic part of plants contains these four substan- ces in very different proportions. Tims, of all the vegetable productions which are gathered as feod by man or beast, in their dry state, the Carbon forms nearly one-half by weight, Oxygen rather more than one-third, Hydrogen little more than 5 fer cent, Nitrogen from \ to 4 ■per cent, Sulphur 1 to 5 per cent, Phosphorus about a thousandth part. This is shown in part by the folloAving table, which exhibits 14 COMPOSITION OF THE ORGANIC PART OF PLANTS. the actual composition of 1000 lb. of some yarieties of the more common crops, wlien made ])erfe.ctly dry : — Carlson. Hydrogen. Oxygen. Nitroffon. Ash. Hay, . 458 lb, 50 lb. 387 lb. 15 lb. 90 1b. Red Cloyer Hay, 474 50 378 21 77 Potatoes, . 440 58 447 15 40 Wheat, . 461 58 434 23 24 Wheat Straw 484 53 389J H 70 Oats, . 507 64 367 22 40 Oat Straw, 501 54 390 4 51 It is to be obseryed, lioweyer, that in drying by a gentle heat, 1000 lb. of common hay from the stack lost 158 lb. of water; of clover hay, 210 lb.; of potatoes wiped dry externally, 159 lb. f of wheat, 145 lb. ; of wheat straw, 260 lb. ; of oats, 151 lb. ; and of oat straw, 28 1 lb. The aboye table represents their composition when thus made perfectly dry. The bodies of animals contain also a large proportion of water ; but the dry matter of their bodies, as a whole, is dis- tinguished from that of plants, by containing a larger proportion of nitrogen, sulphur, and phosphorus. Some parts of the bodies of animals are particularly rich in these ingredients. Thus— • Dry lean muscle contains 12 to 14 per cent of nitrogen, Dry hair or wool about 5 per cent of sulphur ; and Dry hone about 6 per cent of phosphorus. But in animals, as in plants, the chief constituents are carbon and oxygen. Thus, lean beef, blood, white of &^g, and the curd of milk, when- quite dry, consist in 100 parts of about — Per cent. Carbon, . . . . . 55 Hydrogen, ..... t Nitrogen, . . . . . 16 Oxogen, with a little sulphur and phosphorus, 22 100 * Potatoes contain about foiir-fifrhs of their weight of water, or five tons of roots contain nearly four tons of water. Turnips contain sometimes up- wards of nine-tentlis of their weight of water. CHEMICAL COMBINATION AND DEGOMrOSITION. 15 SECTION VI. OF CHEMICAL COMBINATION AND CHEMICAL DECOM- POSITION. 1°. If the three kmcls of air above spoken of be mixed to- gether in a bottle, no change will take place ; and if charcoal in fine powder be added to them, still no new substance will be produced. Or if we take the ash left by a known weight of hay or of wheat straw, and mix it with the proper quantities of the four elementary substances — carbon, hydrogen, oxygen, and nitrogen — as shown in the above table, we shall be unable by this means to form either hay or wheat straw. The elements of which vegetable substances consist, therefore, are not merely mixed together, they are united in some closer and more inti- mate manner. To this more intimate state of union the term chemical comhinaticn is applied — the elements are said to be chemically combined. Thus, when charcoal is burned in the air, it slowly disappears, and forms, as already stated, (p. 9,) a kind of air known by the name of carbonic acid gas, which rises into the atmosphere and diffuses itself through it. Now this carbonic acid is formed by the union of the carbon (charcoal) while burning, with the oxygen of the atmosphere, and in this new air the two elements, carbon and oxygen, are chemically combined. Again, if hydrogen be burned in the air by means of a com- mon gas jet, (see p. 24,) water is formed, and the hydrogen, and a portion of the oxygen of the atmosphere, disappear to- gether. The two gases have combined chemically with each other, and formed water, 2°. On the other hand, if a piece of wood, or bit of straw, in which the elements are already chemically combined, be burned in the air, these elements are separated, and made to assume new states of combination, in v/hicli new states they escape into the air and become invisible. When a substance is thus changed, and converted or separated into other substances by the action of heat, or in any other way, it is said to be de- 16 CHEMICAL COMBINATION AND DECOMPOSITION. composed. If it more gradually decay and perish, as animal and vegetable substances do, by- exposure to the air and moisture, it is said to undergo slow decomposition. When, therefore, two or more substances unite together, so as to form a third, possessing properties different from both, they enter into chemical union — they form a chemical combinatio^f, or chemical compound. And when, on the other hand, a compound body is so changed as to be converted into two or more sub- stances different from itself, it is decomposed. Thus carbon, hydrogen, and oxygen undergo a chemical combination in the interior of the plant during the formation of wood — while wood, again, is decomposed, when in the retort of the vinegar-maker it is converted among other substances into charcoal and wood- vinegar. So the flour of grain is decomposed when the brewer or distiller converts it into ardent spirits ; and so in the experi- ment described in section iv, for preparing oxygen gas from red oxide of mercury, the oxide is decomposed by the heat, and is resolved into its two constituent elements, oxygen and metallic mercmy. CHAPTER II. rorms iu which the organic elements, carbon, hydrogen, oxygen, nitrogen, sulphur, and phosjohorus, enter into plants. — Properties of the carbonic, humic, ulmic, geic, and crenic acids, and of humine and ulmine. — Of water, and its relations to vegetable life. — Of ammonia, its properties and pro- duction in nature. — Of other organic alkalies containing nitrogen. — Of nitric acid, and its production in the air and in the soil. — Composition of the atmosphere. — Of sulphuric 9,nd phosphoric acids. SECTION I. FORMS IN WHICH THE ORGANIC ELEMENTS, CARBON, HYDROGEN, OXYGEN, NITROGEN, &C.,, ENTER INTO PLANTS. It is from their food that plants derive the carbon, hydrogen, oxygen, and nitrogen, as well as the sulphur and phosphorus, of which their organic part consists. This food enters partly by the minute pores of their roots, and partly by those which exist in the green parts of the leaf and of the young twig. The roots bring up food from the soil, the leaves take it in directly from the air. Now, as the pores in the roots and leaves are very minute, carbon (charcoal) cannot enter them in a solid state ; and as it does not dissolve in water, it cannot, in the state of simple car- bon, be any part of the food of plants. The same is true of sulphur and phosphorus. Again, hydrogen gas neither exists in the air nor usually in the soil ; so that, although hydrogen is always found in the substance of plants, it does not enter them in the state of gas. Oxygen, on the other hand, exists in the air, and is directly absorbed both by the leaves and by the roots of plants ; while nitrogen, though it forms a large part of the atmosphere, is not known to enter directly into plants in any considerable quantity. The whole of the carbon and hydrogen, therefore, and the 18 PROPERTIES OF CARBONIC ACID. greater part of the oxygen and nitrogen also, enter into plants in a state of chemical combination with other substances. The carbon is taken up chiefly in the state of carbonic acid, and of certain other soluble compounds which exist in the soil; the hydrogen and oxygen in the form of water-; the nitrogen chiefly, it is supposed, in those of ammonia, of certain other soluble sub- stances containing nitrogen, and of nitric acid ; and the sulphur and phosphorus in those of sulphuric and phosphoric acids. It will be necessary, therefore, briefly to describe these several compounds. SECTION II. OF THE CARBONIC, HUMIC, ULMIC, GEIC, AND CRENIC ACIDS. 1. Carbonic Aqid. — If a few pieces of chalk or lime-stone, Kg. 6. or of common soda, be put into the bottom of a tumbler, and a little spirit of salt (muriatic acid) be poured upon them, a boil- ing up or effervescence will take place, and a gas will be given off, which will gradually collect and fill the tumbler; and when pro- duced very rapidly, may even be seen to run over its edges. PROPERTIES OF CARBONIC ACID. 19 This gas is carbonic acid. It cannot be distinguished from common air by the eye ; but if a lighted taper be plunged into it, the flame will immediately be extinguished, while the gas Fiff. T. will remain unchanged. This kind of air is so heavy, that it may be poured from one vessel into another, and its presence in the second vessel recognised as before by the use of the taper. Or it may be poured upon a lighted candle, which it will in- stantly extinguish, (fig. 6.) This gas has also a peculiar odor, and is exceedingly suffocating, so that if a living animal be in- troduced into it, life immediately ceases. It is absorbed by water — a pint of water absorbing or dissolving a pint of the gas, and acquiring a faintly acid taste. This gas derives its name of acid from this taste, which it imparts to water, and from its property of reddening vegetable blue colors, and of combining with alkaline* substances to form carbonates. The former property may be shown by passing a stream of the gas through a decoction of red cabbage — as in * Acids have generally a sour taste like vinegar, and redden vegetable blues. Alkalincs, again, have a peculiar taste called alkaline, of which the taste of common soda or of hartshorn are examples ; they restore the blue color to vegetable blues which have been reddened by an acid, and they unite with acids to form chemical combinations, known by the name of salts or sahue combinations. 20 PROPERTIES OF CARBONIC ACID. 8 when tlie liquid will gradually become red; the latter, by putting lime water into the glass instead of the decoction of red cabbage, when the stream of gas will render it milky, forming carbonate of lime. . Fig. 8. Carbonic acid gas exists in the atmosphere ; it is given off from the lungs of all living animals while they breathe ; it is also produced largely during the burning of wood, of coal, and of all other combustible bodies, so that an unceasing supply of it is perpetually being poured into the air. Decaying animal and vegetable substances also give off this gas, and hence it is always present in greater or less abundance in the soil, and es- pecially in such soils as are rich in vegetable matter. It is pro- duced during the fermentation of malt liquors, or of the ex- pressed juices of different fruits, such as the apple, the pear, the grape, or the gooseberry — and the briskness of such fermented liquors is due to the escape of carbonic acid gas. From fer- menting dung and compost heaps it is also given off ; and when put into the ground, farm-yard manure imparts much carbonic acid to the soil and to the roots of plants. Carbonic acid consists of carbon and oxygen only, combined together in the proportion of 28 of the former to 12 of the lat- ter. Or 100 lb. of carbonic acid contain 28 lb. of carbon and 1 2 lb. of oxygen. It combines with potash, soda, lime, magnssia, ammonia, &c., forming carbonates of these bases. HUMIC AND ULMIC ACIDS. ' 21 2. HuMic AND Ulmic Acids. — The soil always contains a portion of decaying vegetable matter, (called humus by some writers,) and such matter is always added to it when it is ma- nured from the farm-yard or the compost heap. During the de- cay of this vegetable matter, carbonic acid, as above stated, is given off in large quantity, but other substances are also formed at the same time. Among these are the two to which the names of humic and ulmic acids are respectively given. Both of these acids contain much carbon, — they are both capable of en- tering the roots of plants, and both, in favorable circumstances, help to feed the plant. In peat bogs two distinct kinds of turf are frequently recog- nised — a light, porous, brown-colored, and a dense, compact, black variety. The former abounds in reddish-brown ulmic, the latter in brownish-black kmnic 2iC.\di. These acids may readily be extracted from the peat by means of potash, soda, or ammo- nia, in solutions of which they easily dissolve. Thus if the common soda of the shops be dissolved in water, and a portion of a rich vegetable soil, or a bit of peat, be put into this solution, and the whole then boiled, a brown liquid is obtained. If to this brown liquid, spirit of salt (muriatic acid) or vinegar be added till it is sour to the taste, a brown fiocky tasteless powder falls to the bottom. This brown substance is humic or ulmic or geic acid, or a mixture of all the three. In our cultivated soils, the humic is more abundant than the ulmic acid. The quantity of these mixed acids, extracted in this way from three rich soils, was respectively 4 J, 5 J, and 8| per cent. In most of our arable soils, however, the proportion present is con- siderably less. 3. Geic Acid. — The geic acid resembles the above acids in appearance, but contains more oxygen. Like them it exists in tlie soil in variable quantity, and may be extracted from it by solutions of potash, soda, or ammonia, and is thrown down from these solutions by the addition of an acid. 22 PROPERTIES OF CREXIC AND APOCRENIC ACIDS. These three acids have so strong a tendency to coml)ine with ammonia, that it is ahnost impossible to ol)tain them free from this substance. In the soil they absorb it whenever it is pre- sent, and if exposed to the air m a moist state, they drink it in from the atmosphere, if any happen to be floating in their neigh- borhood. Hence the utility of partially dried peat for absorb- ing liquid manure, or for mixing with or covering fermenting compost heaps. All the three acids above named are sparingly soluble in wa- ter, and, therefore, in their uncombined state can afford little direct nourishment to plants. They form compounds with lime, magnesia, and oxide of iron, which are also very sparingly solu- ble, and enter little into the roots of plants. They all dissolve readily, however, when they are coml^ined with potash, soda, or ammonia. And as the latter substance especially is produced, and is always present in the soil, and as these acids attract it very strongly, there is good reason for believing that they are frequently rendered soluble by it, and that in this way ulmic, humic, and geic acids Contribute directly to the nourishment of our cultivated crops." 4. Crenic and Apocrenic Acids. — By these names are dis- tinguished two other acid substances which exist in the soil, and in a greater degree, perhaps, and more directly, promote the growth of plants. They exist in the water of all bogs and mo- rasses, and are often met with in considerable quantity in the water of springs, especially in such as form an ochrey deposit when exposed to the air. They are produced from the humic and ulmic acids by the absorption of more oxygen from the at- mosphere, and, like them, eagerly combine with ammonia ; but they are lighter in color, and much more soluble in water. AVhen rich soil is boiled in carbonate of soda, as above de- scril)ed, and the humic, ulmic, and geic acids are thrown down by the addition of muriatic acid, the crenic and apocrenic acids remain still in the solution, and may be separated by further processes which it is unnecessary here to describe. GENERAL OBSERVATIONS. 23 All the al;ove acids, and especially the two latter, exist in greater or less quantity in the rich brown liquor of the farm- yard, whicli is so often allowed to run to waste. They are pro- duced, also, during the decay of the mixed animal and vegeta- ble manure we add to the soil, and yield to the plant a portion of that Supply of organic food Avhich it must necessarily receive from the soil. 5. HuMiNE AND TJlmine arc the names given to certain inso- luble black substances formed in the soil along with the humic and other acids during the decay of vegetable matter. One of the ways in which lime acts beneficially upon the soil is supposed to be by disposmg these insoluble matters to enter into new states of combination, in which they may become solul)le, and thus capable of entering into the roots of plants.* Of the important substances above described, I may further remark — a. That the ulmic acid is the first formed from the decay of vegetable matter. Hence, in peat bogs the red turf is usually found nearest to the surface. b. That the humid acid is formed from the ulmic by the ab- sorption of more oxygen from the atmospliere. It consists of carbon and water only. (See page 50.) c. That the gcic contains more oxygen than the humic acid, and is formed from it by the absorption of a further quantity of oxygen from the air, or from the water with which it is in con- tact. d. That the crenic and apocrenic acids contain still more oxy- gen, and, along with other substances produced in the soil, are formed by the union of the geic acid with another proportion of oxygen. Thus decaying vegetable matter appears first to form the ul- mic, next the humic, than the geic, after that the crenic and apocrenic acids. We do not know how many other compounds * See in the Chapter " On the Use of Lime, " the sections which treat of the chemical action of Umo when appHcd to the soil. 24 COMPOSITION OF "WATER. may succeed to these by the union of their elements with more and more oxygen, before they are entirely resolved into car- bonic acid, — the final state to which all these changes ultimately lead. These excessive absorptions of oxygen by the decaying veg- etable matter, promote the production of ammonia in the soil, as well as of nitric acid. This fact will be more clearly ex- plained in section vi. SECTION III. OF WATER, ITS COMPOSITION, AND ITS RELATIONS TO VEGETABLE LIFE. If hydrogen be prepared in a bottle in the way already de- scribed, (p. 9,) and a gas-burner be fixed into its mouth, the Fig. 9. hydrogen may be lighted, and will burn as it escapes into the air, (fig. 9.) Held over this flame, a cold tumbler will become covered with dew, or with little drops of water. This water is produced during the burning of the hydrogen ; and as its pro- duction takes place in pure oxygen gas as well as in the open SOLVENT POWER OF WATER. 25 air, which contains oxygen — a portion of the oxygen and hydro- gen alone disappearing — the water formed must contain the hydrogen and oxygen which disappear, or must consist of hydro- gen and oxygen only. This is a very interesting fact ; and were it not that chemists are now familiar with many such, it could not fail to appear truly wonderful that the two gases, oxygen and hydrogen, by uniting together,' should form water — a substance so very dif- ferent in its properties from either. Water consists of 1 of hydrogen united to 8 of oxygen by weight ; or every 9 lb. of water contain 8 lb. of oxygen and 1 lb. of hydrogen. Water is so familiar a substance that it is unnecessary to dwell upon its properties. When pure, it has neither color, taste, nor smell. At 32'^ of Fahrenheit's scale, (the freezing point,) it solidifies into ice ; and at 212® it boils, and is con- verted into steam. It possesses two other properties, which are especially interesting in connection with the growth of plants. \st. If sugar or salt be put into water, they disappear, or are dissolved. Water has the power of thus dissolving numerous other substances in greater or less quantity. Hence, when the rain falls and sinks into the soil, it dissolves a portion of the soluble substances it meets with in its way, both through the air and through the soil, and rarely reaches the roots of plants in a pure state. So waters that rise up in springs are rarely pure. They always contain earthy and saline substances in solution, and these they carry with them when they are sucked in by the roots of plants. It has been above stated, that water absorbs (dissolves) its own bulk of carbonic acid ; it dissolves also smaller quantities of the oxygen and nitrogen of the atmosphere ; and hence, when it meets any of these gases in the soil, it becomes im- pregnated with them, and conveys them into the plant, there to serve as a portion as its food. In nature, water never occurs in a pure state. It generally contains both gaseous ^nd saline substances in a state of solu- 26 PROPERTIES OF AMMONIA. tion ; and this, no doulDt, is a wise provision by which the food of phints is constantly renewed and brought within their reach. 2sphorus be kindled in the air, it burns with a brilliant flame, and gives off dense white fumes. These white fumes are phosphoric acid. They are produced by the union of the burning phosphorus with the oxygen of the atmosphere. A 100 lb. of phosphorus, when burned, form 227^ lb. of phosphoric acid. Yiq;. 10. ■ If the experiment be performed under a glass, as in the annexed figure, the white fumes of acid will condense on the cool inside of the vessel in the form of a white powder, which speedily absorbs moisture from the air, and runs to a liquid. This acid is very sour and -corrosive. It combines with potash, lime, &c., and forms phosphates, and in these states of combina- tion it exists in soils and manures, and enters into plants. The bones of animals contain a large proportion of this acid, chiefly in combination with lime and magnesia, Lucifer matches are tipped with a morsel of phosphorus, which, wlien rubbed, takes fire and kindles the sulphur. The white smoke given off by such a match, when first kindled, con- sists of phosphoric acid. CHAPTER III. Structure of the stem, root, and leaves of plants. — Functions of the root, the leaves, and the stem. — How plants draw their nourishment from the soil and the air. — Of the substance of plants, and the structure of the seed or grain. — Of cellulose, starch, sugar, gum, mucilage, and pectose, or pectic acid. — Of the oil or fat, wax, resin, and turpentine of plants. — Of gluten, albumen, and casein. — Germination of seeds and growth of plants. — Mutual transformations of starch, sugar, and cellulose. — Production of cellular fibre from tlie organic food of plants. — Necessity of nitrogen, or substances containing it, to the growth of plants. — Forms in which nitro- gen may enter into plants. From the compound substances described in the preceding chapter, plants derive the greater portion of the carbon, hydro- gen, oxygen, and nitrogen, with the sulphur and phosphorus of which their organic part consists. The living plant possesses the power of absorbing these compound bodies, of decom'posing them in the interior of its several vessels, and of re-cojnpounding their elements in a different way, so as to produce new sub- stances, — the ordinary products of vegetable life. Before describing the nature of these new substances, I shall briefly consider the general structure of plants, and their mode of growth. SECTION I. OF THE STRUCTURE OF THE STEM, ROOT, AND LEAVES . OF PLANTS. A perfect plant consists of three several parts: — a root which throws out arms and fibres in all directions into the soil ; a trunk which branches into the atmosphere on every side ; and leaves which, from the ends of the branches and twigs, spread out a more or less extended surface into the surrounding air. 36 STRUCTURE OF THE STEM AND ROOT OF PLANTS. Each of these parts has a i3eculiar structure, and special func- tions assigned to it. 1°. The stem of any of our common trees consists of three parts — the pith in the centre, the wood surrounding the pith, and the bark which covers the whole. The pith consists of a collection of minute cells, supposed to communicate horizontally with the external air through the medullary rays and the outer bark ; while the wood and inner bark are composed of long tubes bound together in a vertical position, so as to be capable of carrying liquids up and down between the roots and the leaves. When a, piece of wood is sawn across, the ends of these tubes may be distinctly seen. The branch is only a pro- longation of the stem, and has a similar structure. 2°. Tlie root, immediately on leaving the trunk or stem, has also a similar structure. But as the root tapers away, the pith disappears — in some, as in the walnut and horse-chestnut, grad- ually — in others immediately. The.bark also thins out, and the wood softens, till the white tendrils, of which its extremities arc composed, consist only of a colorless spongy mass, full of pores, and in which no distinction of parts can be perceived. In this spongy mass the vessels or tubes which descend through the stem and root lose themselves, and by these tubes the spongy extremities in the soil are connected with the leaves in the air. 3°. The leaf is an expansion of the twig. The fibres, which are seen to branch out from the base through the interior of the leaf, are prolongations of the vessels of the wood, and are con- nected with similar prolongations of the inner bark, which usu- ally lie beneath them. The green exterior portion of the leaf is, in like manner, a continuation of the outer or cellular tissue of the bark, in a very thin and porous form. The pores, or mouths, {stomata) contained in the green part, are an essential feature in the structure of the leaves, and are very numerous. The leaf of the common lilac contains as many as 120,000 of them on a square inch of surface. They are generally most numerous on the under part of the leaf, but in the case of leaves which float upon water, they are chiefly confined to the upper part. I'UNCTIONS OF THE ROOT. 3t The annexed woodcut shows the appearance of the oval pores j9 on the leaf of the garden balsam.' Connected with these pores, the green part of the leaf consists of or contains a collec- tion of tubes or vessels which stretch along the surface of the leaf, and communicate, as we have said, with those of the inner bark. SECTION II. FUNCTIOXS OF THE ROOT, THE LEAVES, AXD THE STEM. COURSE AND MOTION OF THE SAP. Each of these principal parts of the plant performs its pecu- liar functions. 1°. Functions of the root. — The root sends out fibres in every direction through the soil in search of water and of liquid food, which its spongy extremities suck in, and send forward with the sap to the upper parts of the tree. It is to aid the roots in procuring the food more rapidly that in the art of culture such substances are mixed with the soil as experience has shown to be favorable to the growth of the plants we wish to raise. What chemical changes the food is made to undergo in en- tering or passing along the roots is not yet understood. 2°. Functions of the leaf. — It is not so obvious to the common observer that the leaves spread out their broad surfaces into the air for the same purpose precisely as that for which the roots diffuse their fibres through the soil ; the only difference is, that while the roots suck in chiefly liquid, the leaves inhale alinost 38 FUNCTIONS OF THE LEAF. solely gaseous food. In the daytime, whether in the sunshine or in the shade, the green leaves are continually absorbing carbonic acid from the air, aiid giving off oxygen gas. That is to say, tliey are continually appropriating carbon from the air.* When night comes, this process is reversed, and they begin to absorb oxygen and to give off carbonic acid. But the latter process does not go on so rapidly as the former ; so that, on the whole, plants, when growing, gain a large portion of carbon from the air. The actual quantity, however, varies with the season, with the climate, and with the kind of plant. The proportion of its carbon, which has been derived from the air, is greatly modified, also, by the quality of the soil in which the plant grows, and by the comparative abundance of liquid food which happens to be within reach of its roots. It has been ascertained, however, that in our climate, on an average, not less than from one-third to four-fifths of the entire quantity of carbon contained in the crops we reap from land of average fertility, is really obtained from the air. We see then why, in arctic climates, where the sun, once risen, never sets again during the entire summer, vegetation should almost rush up from the frozen soil ; the green leaf is ever gaining from the air and never losing, ever taking in and never- giving off carbonic acid, since no darkness ever interrupts or suspends its labors. How beautiful, too, does the contrivance of the expanded leaf appear ! The air contains only one gallon of carbonic acid in 2500, and this proportion has been adjusted to the health and comfort of animals to whom this gas is hurtful. But to catch this minute quantity, the tree hangs out thousands of square feet of leaf — in perpetual motion, through an ever-moving air ; and thus, by the conjoined lal)ors of millions of pores, the substance of whole forests of solid wood is slowly extracted from the fleeting winds. I have already mentioned the number of * Since carbonic acid, as shown in the previous chapter, (p. 20,) consists only of carbon and oxygen. Of these the leaves retain the carbon and re- ject the oxygen. SUBSTANCE OF PLANTS. 39 pores which have been observed on a square mch of leaf ; and when I add that on a single oak tree seven millions of leaves have been counted, the multitude of absorbing mouths in a for- est — like those of the coralline animals in a reef — will appear equal to the most gigantic eifects. The green stem of the young shoot, and the green stalks of the grasses, also abound in pores, and consequently absorb car- bonic acid, and give off oxygen, as the green leaf does ; and thus a larger supply of food is afforded when the growth is most rapid, or when the short life of the annual plant demands much nourishment within a limited time. The yellow and red leaves and parts of plants give off no oxygen, (Senebier.) 3°. Functions of the stem. — From the spongy part of the root the sap ascends through the vessels of the woody stem till it is diffused over the interior of the leaf by the woody fibres which the leaf contains. During this passage the substances which the . sap contains undergo certain chemical changes, which are as yet not well understood. From the woody fibre, of the leaf — along the vessels which lie beneath these fibres, and are covered by the green part of the leaf — and after it has absorbed or given off the gases which the pores transmit, the sap is returned towards the outer part of the stem, and through the vessels of the inner bark descends again to the root. 4°. ^oiirse and inoticn of the saj). — In the living plant, at least till it has passed maturity, most of the vessels are full of sap, and this sap is in continual motion upwards within the stem, and downwards along its surface within the inner bark. In spring and autumn the motion is more rapid. In winter it is some- times scarcely, perceptible ; yet the sap, except when frozen, is supposed to be rarely quite stationary in any part of the tree. SECTION III. OF THE SUBSTANCES OF WHICH PLANTS CHIEFLY CONSIST, AND OF THE STRUCTURE OF THEIR SEEDS. In the way above described, the perfect plant derives from the 40 SUBSTANCE OF PLANTS. soil and from the air the food by which it is sustained and ena- bled to grow. In the substance or stem of plants thus formed, and in their seeds, various chemical compounds exist, but they may all be included in three main groups or classes. When the grain of wheat, barley, oats, rye, Indian corn, &c., is sent to the mill to be ground, two products are obtained — the bran or husk, and the flour. When washed free from flour, the bran or husk is tasteless, insoluble in water, and woody. It is the same thing, indeed, for the most part, as the cellular and fibrous part of wood or straw. Again, when a portion of the flour is made into dough, and Fig. 12. this dough is kneaded with the hand under a stream of water upon a piece of muslin, or on a fine sieve, as long as the water passes through milky — there will remain on the sieve a glutinous sticky substance resembling bird-lime, while the milky water will gradually deposit a pure white powder. This white powder is starch, the adhesive substance which remains on the sieve is glu- ten. Both of these substances exist, therefore, in the flour ; they both also exist in the grain. Further, when bruised wheat, oats, Indian corn, linseed, or even chopped hay and straw, are boiled in alcohol or ether, a portion of oil or fat, of wax and of resin, is extracted, and is ob- THE STARCH GROUP. 41 tained separately by allowing the solution to evaporate to dry- ness in the air. Thus, from the seed or grain we have obtained four different substances — the woody part which covers it, starch, gluten, and fat. The annexed woodcut shows the position and relative quantities of the last three substances in the seeds of wheat, bar- Indian Barley. ley, and Indian corn. Thus, a shows the position of the oil in the outer part of the seed. It exists in minute drops, enclosed in six-sided cells, which consist chiefly of gluten, h the posi- tion and comparative quantity of the starch, which in the heart of the seed is mixed with only a small proportion of gluten, c the germ or chit which contains much gluten. These substances represent the three great classes of organic bodies of which the bulk of all plants is made up. The woody matter and the starch represent what is called the starch group. The gluten represents the gluten or albumen group. The oil or resin represents the fatty group. I shall briefly describe these several groups or classes of sub- stances. SECTION IV. OF THE STARCH GROUP WOODY FIBRE, STARCH, GUM, MUCILAGE, SUGAR, AND PECTOSE, OR PECTIC ACID. The starch group comprehends a great number of different substances, possessing different properties, but all characterised by this similarity in composition, that they consist of carbon and water only. 42 CELLULOSE, STARCHES, GUMS AND MUCILAGES. The following are the principal substances belonging to this class : — 1°. Cellulose or woody fibre. — This forms the walls of the cells of plants, the fibres of cotton and linen, the woody part of the husk or covering of the seed, and a large portion of the sub- stance of wood, hay, straw, &c. It is insoluble in water, both in the fresh and dry states, but, as it exists in fodder, appears, after due mastication, to be in some degree soluble in the stom- achs of animals. It consists of 36 parts by weight of carbon, and 45 of water. 2°. The starches. — There are several varieties of starch besides that which occurs in the flour of wheat, oats, barley, the pota- to, &c. These are all insoluble in cold water, but give a jelly with boiling water. The Iceland moss, and some other lichens, contain a starch which gives a jelly with boiling water, but which is somewhat different from that of common starch ; while the roots of the dahlia and the dandelion give a starch which dissolves in boiling water, but does not form a jelly, and fails again in a powdery state as the solution cools. Common starch, and that of the dandelion and the hchen, consist, like woody fibre, of 36 parts of carbon by weight, and 45 of water; that of the dahlia contains a very little more water. 3°. The gums. — When common starch is heated in an oven to 300° F., or when it is mixed with water containing a little sulphuric acid and gently heated, it is changed into a soluble gummy adhesive substance, to which the name of dextrin is given. In this soluble state, starch is supposed to exist abun- dantly in the sap of plants. The name arabine is given to gum arable, which is soluble in cold water, and ceracine to cherry tree gum, which is insoluble in cold, but dissolves i;^adily in boiling water. All these three varieties of gum consist, like common starch and woody fibre, of 36 parts by weight of car- bon, united to 45 parts of water. 4°. The mucilages. — The name of mucilage is given to gum CANE AND GRAPE SUGARS. 43 tragacanth, wliicli does not dissolve, but swells out into a jelly when placed in water — to the adhesive matter which v/ater ex- tracts from linseed and other oily seeds, and to the jelly which is obtained from the roots of the orchis, (Salop,) the mallow, &c. It consists of 48 parts by weight of carbon, and 51 of water. 5°. The, sugars. — In the sap of plants several kinds of sugar occur; but those called cane and grape sugars are the most abundant. Cane sugar exists in the sugar cane, the maple, tlie beet, the stalks of corn, and in many other plants. In the ordinary states of loaf sugar, crystallised sugar, sugar-candy, &c., it consists of 48 parts of carbon by weight, and 66 of water. Grape sugar exists naturally in the grape, in fruits in general, and in honey. It is formed artificially when cellulose or starch is boiled for a length of time in water made slightly sour by means of sulphuric acid, (oil of vitriol.) It is less sweet than cane sugar, and in its crystallised state consists of 48 of carbon by weight, and 84 of water. The following table exhibits the relative composition of these several substances in a hundred parts, as nearly as it can be expressed in whole numbers : — • Carbon. Water. Cellulose or woody fibre, 44 56 Starch, .... 44 56 Gum, ..... 44 56 Mucilage, .... 46 54 Sugar of the cane, 42 58 Sugar of the grape, . » 36 64 In stating that these substances consist of carbon and water only, I have adopted, for the sake of clearness and simplicity, a mode of expression which has not yet been shown to be quite correct. It is not certain that these substances contain water in the proportions above stated, but they contain hydrogen and oxygen in the proportions (1 to 8) in which they form water. For simplicity, therefore, we may suppose these two elementary 44 FATTY SUBSTANCES OF PLANTS. bodies actually to exist in the vegetable substances above de- scribed in the form of water. 6°. Pedose and jpedic acid. — The reader will not fail to be struck with the remarkable circumstance, that substances so different as woody fibre, starch, and gum, should yet consist of the same elements — charcoal and water united together in the same proportions. In some vegetable substances, however, which otherwise resemble starch and gum, and may be classed along with them, the hydrogen and oxygen do not exist exactly in this proportion. In fleshy fruits, such as the plum, peach, apricot, apple, pear, &c., and in the bulbs or roots of the turnip, the carrot, the parsnip, &c., there exists no starch, but in its stead a substance to which the name of pectose and sometimes of fedic acid is given. This substance is nearly as nutricious as search, and serves the same purposes when eaten. It contains, however, less hydrogen and more oxygen than starch does, and changes also more readily into other substances both in the plant and in the stomach. SECTION V. OF THE FATTY SUBSTANCES OF PLANTS. The fatty substances which occur in plants are of three kinds — the true fats and oils, the waxes, and the turpentines and resins. They all agree in containing less oxygen than would be required to convert their hydrogen into water — less than 8 to 1 by weight. 1°. The true fats which have as yet been found in plants are divided into two classes — the soUd and the liquid fats. ' a. Solid fats. — When almond, olive, or linseed oil is exposed to a very low temperature, a portion of it freezes or becomes solid. This portion may be separated, and by pressure may be, in great measure, freed from the liquid portion. The solid part thus obtained from most vegetable oils is called margarine, and is identical with the solid part of butter, and of the fat of man, of the horse, and of some other animals. Some SUBSTANCES CONTAINING NITROGEN. 45 plants yield a solid fat called steariiie, which is the same thing as the solid fat of the cow, the sheep, the pig, the goat, and many other animals. h. To the liquid fats the name of elaine is given. That obtained from the oils of almonds, olives, &c., which are called fat oils, is somewhat different from that of which linseed, wal- nut, and other drying oils chiefly consist. The liquid oil ex- pressed from the fat of animals consists chiefly of the former variety of elaine. 2°. The waxes. — Many plants produce wax. It coats the flowers and leaves of many trees and shrubs, and forms the beautiful bloom which covers the grape and other fruits. From these the bees collect it; and though the different varie- ties of wax differ somewhat in properties, they all agree with bees-wax in being insoluble in water, partially soluble in alcohol, nearly without taste and very combustible. 3°. The turpentines and resins abound in trees of the pine tribe. They are all insoluble in water, but readily soluble in alcohol; are more combustible than either true fat or wax, and contain less oxygen than either. Nothing resembling either wax or resin is found in the bodies of animals. SECTION VI. OF VEGETABLE SUBSTANCES CONTAINING NITROGEN THE GLUTEN OR ALBUMEN GROUP. In washing the dough of wheaten flour, we have seen (p. 40) that a portion remains on the sieve or muslin, to which the name of gluten is given. This substance contains nitrogen in addition to the carbon, hydrogen, and oxygen which are present in the bodies described in the preceding sections, and is the re- presentative of an entire class of important substances into Avhich nitrogen enters as a constituent. I shall briefly mention the most important of these substances. 1°. Gluten. — This is obtained from the dough of wheaten 46 ALBUMEN AND CASEIN. flour, in tlie way already described. It is insoluble in water, partly soluble in alcohol, which extracts from it a fatty oil, and entirely and easily soluble in vinegar, (acetic acid,) or in solu- tions of caustic potash or soda. Besides the fatty oil which it contains, the crude gluten, as it is washed from wheaten flour, consists of at least two substances, — one soluble in alco- hol, {gliitin,) the other insoluble in this liquid, (gluten,) and which appears closely to resemble coagulated albumen. When moist, gluten is nearly colorless, and is tenacious and adhesive like bird-lime ; but when perfectly dry, it is hard, brittle, and of a grey or brownish color. 2°. Alhumcn. — The white part of eggs is called albumen by chemists. In the natural state it is a glairy thick liquid, which can be diffused through or dissolved in v.- ater, but Avhich coagu- lates, or becomes solid and opaque, when heated to about 180° of Fahrenheit, or nearly to the temperature of boiling water. In this coagulated state it is insoluble in water, or in alcohol, but dissolves in vinegar, or in solutions of caustic potash or soda. When dried it becomes hard, brittle, semi-transparent, and of a brownish color. When the expressed juice or sap of plants is heated, a solid substance coagulates, and separates from it in opaque white flocks. This substancfe possesses nearly all the properties of the albumen of the q^^, and is therefore called vegetable albumen. Albumen exists in plants not only in the liquid state, as in the sap of plants, but also in the coagulated state. In the husks and envelopes of many seeds — the bran of corn for exam- ple — and in the solid parts of woody and herbaceous plants, it is found in this state in greater or less proportion. 3°. Casein. — ^When rennet, vinegar, or diluted muriatic acid is added to milk, it coagulates or ci^i'dles, and a white curd separates from the whey. Alcohol or ether extracts the fat or butter from the coagulated mass, and leaves pure curd behind. To this curd chemists give the name of casein. When cold water is shaken up with oatmeal for half an hour, GERMIXATION OF SEEDS. 4T and is then allowed to subside, the clear liquid becomes troubled on the addition of a little acid, and a white powder falls, pos- sessing nearly all the properties of the casein of milk. The sap of nearly all plants — the expressed juice of the po- tato, the turnip, and other roots, after being heated to coagu- late the albumen — and the solution obtained when the meal of the bean, the pea, and other legumes, is treated with warm water — yield, on the addition of an acid, precipitates of this substance differing but httle from one another. Vegetable casein, therefore, is a constant constituent of our best known and cultivated plants. To the variety obtained from the oat the name of avenin has been given, and to that yielded by the bean, the pea, and the vetch, the name of Icguviin. All these substances arc combinations of a body called protein, and are therefore frequently spoken of under the general desig- nation of prGtein compounds/'^ They occur mixed in variable proportions in the different kinds of grain and roots which are used for food. In addition to carbon, oxygen, and hydrogen, they all contain, when quite dry, about 1 6 per cent of nitrogen, with 1 or 2 per cent of sulphur, and most of them also a small per-ceutage of phosphorus. SECTION VII. OF THE GERMINATION OF SEEDS AND THE GROWTH OF PLANTS. When a seed is committed to the earth, if the warmth and moisture are favorable, it begins to sprout. It pushes a shoot upwards, it thrusts a root downwards, but, until the leaf expands and the root has fairly entered the soil, the young plant derives no nourishment other than water, either from the earth or from the air. It lives on the starch and gluten contained in the seed. But these sub'stances, though capable of *being sepa- rated from each other by means of water, as described in a * For an account of protein and its compounds, see my Lectures on Acjri- cultural Chemistry^ 2d edition, p. 5. 48 CHANGE OF STARCH INTO SUGAR. previous section, (p. 40,) are neither of tliem soluble in water. Hence they cannot, without undergoing a previous chemical change, be taken up into the sap and conveyed along the ves- sels of the young shoot they are destined to feed. But it is so arranged in nature that, when the seed first sprouts, there is produced at the base of the germ, from a portion of the gluten, a small quantity of a white soluble substance called diastase. This substance exer,cises so powerful an effect upon the starch as almost immediately to render it soluble in the sap, which is thus enabled to take it up and convey it by degrees, just as it is wanted, to the shoot or to the root.* The starch, when thus changed and rendered soluble, becomes the substance called dextrin, which we have already described, (p. 42.) In the oily seeds which contain no starch, the mucilage and the oil take the place of starch in nourishing the young sprout. As the sap ascends it becomes sweet — the dextrin formed from the starch is further changed into sugar. When the shoot first becomes tipped with green, this sugar again is changed into cellulose or woody fibre, of which the stem of perfect plants chiefly consists. By the time that the food contained in the seed is exhausted — often long before — the plant is able to live by its own exertions, at the expense of the air and the soil. This change of the sugar of the sap into cellular or woody fibre is observable more or less in all plants. When they are shooting fastest the sugar is most abundant — not, however, in those parts which are actually shooting up, but in those which convey the sap to the growing parts. Thus the sugar of the * In malting barley, it is made to sprout a certain length, and the growth is then arrested by heating and drying it. Mashed barley, before sprout- ing, will not dissolve in water; but when sprouted, the whole of the starch (the flour) it contains dissolves readily by a gentle heat, and is changed into soluble dextrin. The diastase formed during the germination effects this. By further heating in the brewer's wort, this dextrin is converted into sugar by the agency of the same diastase, as it is also in the growing plant. Wo can thus imitate by art ; and, in brewing, we do imitate what takes place naturally m the living vegetable. FORMATION OF CELLULAR FIBRE. 49 ascending sap of the maple and the alder disappears in the leaf and in the extremities of the twig. Thus the sugar-cane sweet- ens only a certain distance above the ground, up to where the new growth is proceeding ; and thus also the young beet and turnip abound most in sugar — while in all these plants the sweet principle diminishes as the year's growth draws nearer to a close. In the ripening of the ear, also, the sweet taste at first so perceptible in young grain gradually diminishes, and finally dis- appears. The sugar of the sap is here changed into the sfarck of the grain, which, as above described, is afterwards destined, when the grain begins to sprout, to be reconverted into sugar for the nourishment of the rising germ. In the ripening of fruits a different series of changes presents itself. The fruit is at first tasteless, then becomes sour, and at last sweet. In this case, either the acid of the unripe is changed into the sugar of the ripened fruit, or a portion of the other constituents of the fruit — its cellulose and pectose — are con- verted into sugar, and disguise the acid. SECTION VIII. HOW THE CELLULAR OR WOODY MATTER OF PLANTS IS FORMED FROM THEIR ORGANIC FOOD, The substance of plants — their solid parts, that is — consists chiefly, as we have already stated, of cellular- fibre, the name given to the fibrous substance of which wood evidently consists. It is interesting to inquire how this substance can be formed from the compounds — water and carbonic, humic, ulmic, and other acids — of which the organic food of plants in a great measure consists. Nor is it difficult to find an ansv/er. 1°. It will be recollected that the leaf drinks in carbonic acid from the air, and delivers back its oxygen, retaining only its carbon, (p. 38.) It is also known that water abounds iu the sap. Hence carbon and water are abundantly present iu the pores or vessels of the green and living leaf. Now, as cel- 3 50 FORMATION OF CELLULAR FIBRE, lulose or woody fibre consists ctily of carlcn and water chemically combined together, it is easy to see how, when the carlion and water meet in the leaf, cellular fibre may be produced by their mutual combination. 2°. If, again, we inquire how this important constituent of plants may be formed from the other substances, which enter jjy their roots — from the humic acid (p. 21) for example — the answer is equally ready. This acid also consists of carbon and water only — 50 lb. of carbon with 37J of water forming 8tJ of humic acid — so that, when it is conveyed by the roots into the sap of the plant, all the materials are present from which the cellular fibre may be produced. 3°. Nor is it more difficult to understand how the starch of the seed may be converted into sugar, and this again into cel- lular, fibre ; or how, conversely, sugar may be changed into starch in the ear of corn, or cellular fibre into sugar during the ripening of the winter pear after its removal from the tree. Any one of these substances may he represented by carbon and water only. In the interior of the plant, therefore, it is obvious that if any one of them is present in the sap, the elements are at hand out of which any of the others may be produced. In what way they really are produced, the one from the other, and by what circumstances these transformations are favored, it would lead into too great detail to attempt here to explain.* We cannot help admiring the varied purposes to which in nature the same elements are applied, — ^and from how small a number of materials, substances the most varied in their pro- perties are in the living vegetable daily produced. * For fuller and more precise explanations ou tliese interesting topics, see the Author's Lectures on Agricultural Chemistry aiid Geology, 2d edition, Part I. NECESSITY OF NITROGEX TO THE GROWTH OF PLANTS. 51 SECTION IX. OF THE NECESSITY OF NITROGEX, OR OF SUBSTANCES CONTAINING IT, TO THE GROWTH OF THE PLANT, AND OF THE FORMS IN WHICH IT MAY ENTER THE ROOTS. But a substance containing nitrogen is necessary to the pro- duction of those beautiful and varied changes which take place in the sap of the plant at the different stages of its growth. We have seen that, during germination, the insoluble gluten of the seed is partly changed into a soluble substance — diastase — by which the first alteration of the insoluble starch into solu- ble dextrin is effected. The remainder of the gluten ascends or descends by degrees with the sap, in some soluble form which is not yet clearly understood, and, if not actually the cause of the successive changes which the starch, sugar, and gum of the sap undergo, it is at least always present when they are produced. At every point in the growings shoot and root some compound of nitrogen must be present, if it is to increase in size, — since in the interior of every new cell the presence of such a com- pound in minute quantity can be distinctly recognised. In the young radicles of the sprouting barley there are 32 per cent, of a substance containing nitrogen, while the grain itself contains only 14. This substance seems to preside over the change of the soluble substances contained in the sap, into the insoluble fibre of the cell. The change of the sugar and gum of the sap into the starch of the ear always takes place also in the presence of a substance containing nitrogen. In the young seed it is present in much larger proportion than when the seed is matured. In the pea, when beginning to form in the shell, it constitutes 48 per cent, of the whole weight, (Payen,) while in the ripe pea it does not exceed one-half the quantity. When the starch or sugar undergoes a change, the nitrogen- ous compound undergoes a simultaneous change ; and as the . transfoi-mation of the starch of the seed into the sugar of the 52 FORMS IN WHICH NITROGEN ENTERS INTO PLANTS. sap is attended by the change of its gluten into diastase and other soluble compounds, so the converse change of the sugar of the sap into the starch of the ear is attended by a converse production of the insoluble gluten of the ripening grain. It has also been ascertained that the leaves of growing plants are in the sunshine always giving off nitrogen, in quantity which varies with the kind, and probably the age, of the plant, and with the time during which it has been exposed to the sun's rays. This nitrogen appears to be derived from gluten and other nitrogenous (protein) compounds, which are continually undergoing changes in the sap, and which arc necessary to the ordinary processes of vegetable grow^th. The necessity of nitrogen to the growth of the plant in all its stages is thus fully established ; and hence the utility, estab- lished by long practical experience, of applying manures in which nitrogen is contained. It has not yet been proved in what form of combination nitrogen is most fitted to promote the growth of our cultivated crops. It usually jBnds its way into the roots of plants in the form of nitric acid, of amntonia, of other organic alkalies con- taining nitrogen, (p. 30.) or of the compounds of these alkalies with the humic and ulmic acids, which are so extensively pro- duced in the soil itself. Animal manures may owe part of their peculiar beneficial action to their supplying other compounds of nitrogen — protein compounds, perhaps, in a soluble form — which the plant, with still less trouble to itself, can convert into por- tions of its own substance. The plant grows rapidly by the aid of the ready-formed gluten of the seed, — why should it not thrive well also by the aid of similar compounds placed within its reach in the soil and absorbed by its roots ? There seems, indeed, very little solid foundation for the opinion held by some, that the plants in our cultivated fields derive the ichoh of their nitrogen from ammonia and nitric acid together — still less that they obtain it from ammonia alone. FORMS IN WHICH NITROGEN MAY ENTER ROOTS. 53 The plant that grows on the surface of common vinegar, and makes it thick and glairy, is formed from the vinegar* itself, and from a nitrogenous substance resembling gluten, which the liquid vinegar holds in solution. So the mould which grows on flour paste is formed from the starch and the gluten of the flour, and the minute j^lant which forms the yeast in the brewer's vat is produced from the sugar of the wort and the changed gluten of the barley.' In all these cases the substance of the plant is formed by the direct appropriation of compounds, which bear a close analogy to those of which its own parts consist ; and though the mould plants above mentioned are very different in kind from those we raise for food, yet the mode in which they are built up is very similar to that by which the solid parts of larger plants are really produced from the substances contained in the sap. If, then, those substances from which their growing parts are thus known to be built up can be conveyed directly into the circula- tion of our cultivated plants by their roots, it is reasonable to suppose that their growth may be promoted by them at least as well as if the roots took up only carbonic acid to supply the car- bon, and ammonia to supply the nitrogen. In other words, the probabihties are, I think, in favor of the view that animal or vegetable substances containing nitrogen, when brought into a soluble state by fermentation, may enter directly into the roots, and feed our crops, without being first decomposed either into ammonia or into nitric acid. The subject is deserving, therefore, of being made matter of direct experi- ment in the field or garden. * Pure vinegar, like starch and cellular fibre, consists of carbon and water alone, 50 of carbon and 56 of water forming 106 of vinegar. CHAPTEK TV. Of the iDorganic constituents of plants. — Potash, soda, Hme, magnesia, sihca, alumina, oxide of iron, oxide of manganese, sulphur, sulphuric acid, phos- phorus, phosphoric acid, chlorine, iodine, fluorine. — Immediate source of these constituents of plants. — The quantity contained in plants, and iu parts of plants, varies with many circumstances. — The composition or quality of the inorganic constituents in plants. — It varies also with many circumstances. — Average quantity of each constituent in certain common crops, and in a series of crops. — Practical deductions from a knowledge of the inorganic constituents of plants, SECTION I. SOURCE OF THE EARTHY MATTER OF PLANTS, AND SUBSTANCES OF WHICH IT CONSISTS. When plants are burned, they always leave more or less of ash behind. This ash varies in quantity in different plants, in different parts of the same plant, in different specimens even of the same kind, and of the same part of a plant, especially if grown upon different soils ; yet it is never wholly absent.* It is as necessary to theii' existence in a state of perfect health, as any of the elements which constitute the organic or combustible part of their substance. They must obtain it, therefore, along with the food on which they live. It is, in fact, a part of their natural food, since without it they become unhealthy. We shall speak of it, therefore, as the inorganic food of plants. We have seen that all the elements which are necessary to the production of the cellular fibre, and of the other organic parts of the plant, may be derived either from the air, from the carbonic acid and watery vapor taken in by the leaves, or from * The only known exceptions occur in the mould plants — as in the myco- derma vini, which grows on pure vinegar, that which groves on solutions of milk sugar, &c. By these no trace of ash is left. INORGANIC OR EARTHY MATTER OF PLANTS. 55 the soil tlirougli the medium of the roots. In the air, however, only rare particles of inorganic or earthy matter are known to float, and these are in a solid form, and therefore unable to en- ter tlie minute pores of the leaves. Hence the earthy matter which constitutes the asli of plants must all be derived from the soil. The earthy part of the soil, therefore, serves a double use. It is not, as some have supposed; a mere substratum, in which the plant may so fix and root itself as to be able to maintain its up- right position against tlie force of winds and tempests ; b-ut it is a storehouse of food also, from which the roots of the plant may select such eartliy substances as are necessary to, or are fitted to promote, its growth. The ash of plants consists of a mixture of several, sometimes of as many as fourteen, different substances.. These substances are the following : — 1. Potash. — The common pearl-ash of the sliops is a com- pound of potash with carbonic acid, or it is a carhoiiate of j)otash. By dissolving the pearl-ash in water, and ]joiHng it with quick- lime, the carbonic acid is separated, and potash alone, or caus- tic potash, as it is often called, is obtained. 2. Soda. — Tlie common soda of the sho})S is a carlciiate of soda. By l.oiling it with quick-lime, the carbonic acid is sepa- rated, as in the case of peai'1-ash, and pure or caustic soda re- mains. The proportions to lie used are 1 li). of the carbonate to a I lb. of lime and 10 lb. of water. 3. Lime. — This is familiar to every one as the Ume-shdls, or unslaked lime of the lime-kilns. The unburned lime-stone is a carbonate of lime, the carbonic acid in tliis case being separated from the lime by tlie roasting in the kiln. 4. Magnesia. — This is the calcined magnesia of the shops. The uncalcined is a carbonate of magnesia, from which heat drives off the carbonic acid. 5. Silica. — This is the name given by chemists to the sub- stance of flint, of quartz, of rock crystal, and of siliceous sands 66 OXIDES OF IRON, MANGANESE, &C. and sandstones. It is particularly abundant in the straws and grasses, and in the glaze of the bamboo and other canes. 6. Alumina is the pure earth of alum, obtained by dissolving alum in water, and adding liquid ammonia (hartshorn) to the solution. It forms about two-fifths of the weight of porcelain and pipe-clays, and of some other very stiff kinds of clay. It exists abundantly in most soils, but as an essential constituent of plants it has hitherto been met with only in the ash of the club mosses. 1. Oxide of iron. — The most familiar form of this substance is the rust that forms on metallic iron in damp places. It is a compound of iron with oxygen, hence the name oxide. There are, however, two oxides of iron. The red, which gives its color to rust and to our red soils. This oxide is insoluble in water, and has the property of absorbing ammonia to a certain extent. The Hack oxide gives their color to many blue clays. It is so- luble in weak acids, is produced from the red oxide by the ac- tion of organic matter in the soil, and is believed, when so pro- duced, to be very noxious to the roots of plants. 8. Oxide of manganese is a dark brown powder, which con- sists of oxygen in-combination with a metal resembling iron, to which the name of manganese is given. It usually exists in plants and soils in very small quantity only. 9. Sulphur.- — This substance is well known. It is present in nearly all the parts of plants and animals. It exists largely in mustard seed, is a necessary constituent of the gluten of wheat, of the white of the egg, of the fibre of beef, and of the curd of milk, and forms one-twentieth part of the weight of hair and wool. When sown along with turnip seed, it is said to prevent the attack of the fly. Sulphuric Acid, or oil of vitriol, has been already described. It forms, with potash, sulphate of potash ; with soda, sulphate of soda, or Glauber's salts; with ammomsi, sulphate of ammo7iia ; with lime, sulphate of lime, or gypsum 5 with magnesia, sulphate PHOSPHORUS AND CHLORINE. 5t of magnesia, or Epsom salts ; with alumina, sulphate of alumina, which exists in alum ; and with oxide of iron, sulphate of iron, or green vitriol. When the sulphate of potash is combined with sulphate of alumina, it forms common alum. 10. Phosphorus and phosphoric acid have been already de- scribed, (pp. 9 and 33.) Phosphoric acid forms phosphates with potash, soda, ammonia, lime, and magnesia. When bones are burned, a large quantity of a white earth remains, (bone earth,) which is chiefly a phos- phate of lime, consisting of lime and phosphoric acid, in the proportion of 48-| of phosphoric acid to 51| of lime. Phosphate of lime is present in the ash of plants generally. Phosphate of magnesia is contained most abundantly in the ash of wheat, barley, and other varieties of grain. It exists also in beer, to the amount sometimes of 100 grains in a gallon. 11. Chlorine. — This is a very suffocating gas, of a pale, yellow- Fisr. 14. ish green color, which gives its peculiar smell to chloride of lime, and is used for bleaching and disinfecting purposes. It is readily obtained by pouring muriatic acid (spirit of salt) upon the black oxide of manganese of the shops, contained in a flask, and applying a gentle heat, as in the annexed figure. If the flask be of colorless glass, the color of the gas will immedi- 3* 68 IODINE AND BROMINE. ately become perceptible, and its smell will diffuse itself through the room. This gas is 2 J times heavier than common air, and a burning taper plunged into it is speedily extinguished. In combination with the metallic bases of potash, soda, lime, and magnesia, it forms the chlorides of potassium, sodium,) common salt), calcium, and magnesium ;* and in one or other of these states it generally enters into the roots of plants, and exists in their ash. Iodine is a solid substance of a grey color and metallic lus- tre, very much resembling filings of lead. It has a peculiar odor, not unlike that of chlorine, an acrid taste, and stains the fingers of a brown color. It is distinguished by two proper- ties — by being changed into a beautiful violet vapor when heated, and by giving with starch a beautiful blue compound. It occurs in small quantities in sea water, and in marine and many fresh-water plants. In still smaller proportion, it has been recently detected in wood ashes and in those of land plants, and it probably forms a constant though very minute constitu- ent of all the plants we raise for food. Like their chlorine, they will obtain it generally from the soil through their roots, though, as it has been detected in the atmosphere, they may derive some of this element from the rain water that falls on their leaves. Bromine is a dark brownish red heavy liquid, possessed of a strong odor, giving a yellowish red vapor, and coloring starch yellow. It also exists in sea water, in certain salt springs, and has been detected in the ashes of certain plants. It probably accompanies chlorine and iodine into all plants, though the proportion, which is still less than that of iodine, has hitherto prevented its presence from being detected. * Potash, soda, lime, and magnesia, are compoands of the metals hero named with oxygen. It is a very striking fact, that the suffocating gas chlorine, wlien combined with sodium, a metal which takes fire when placed upon hot water, should form the agreeable and necessary condiment common salt. VARIATION IN THE QUANTITY OF ASH IN PLANTS. 59 As chlorine forms chlorides, so iodi7ie forms iodides, and bromine forms bromides with the metals ah'eady mxeutioned. The chlo- rine is the only one of these three, the presence of which in plants is at present believed to be of any importance in a prac- tical point of view. Fluorine is a very corrosive gas, of which little is yet known. It exists in small quantity in the teeth and bones, and in the blood and milk,' of animals. Traces of it also have been detect- ed in the ashes of some plants ; so that it is probably necessary to the growth of both animals and vegetables. With metals, it forms fluorides.; and fluoride of calcium, or fluor spar, is the best known and most common of its combinations. Such are the inorganic substances usually found mixed or combined together in the ash of plants. It has already been observed, that the quantity of ash left by a given weight of vegetable matter varies with a great many conditions. This fact deserves a more attentive consideration. SECTION II. OF THE DIFFERENCES IN THE QUANTITY OF ASH LEFT BY PLANTS, AND BY THEIR SEVERAL PARTS. 1. The quantity of ash yielded by different jplants is unlike. Thus 1000 lb. of the following vegetable substances, in their ordinary state of dryness, leave of ash, on an average, Wheat, about 20 lb. Wheat straw, 50 lb. Barley, - 30 Barley straw, 50 Oats, - 40 Oat straw, 60 Eye, - 20 ' Rye straw, 40 Indian corn, 15 Indian corn do. 50 Beans, - 30 Pea straw, 50 Peas, . 30 Meadow hay, - 50 to 100 lb. Clover h'ay, . 90 Rye-grass hay, - 95 Potatoes, 8 to 15 Turnips, 5 to 8 Carrots, - 15 to 20* * See Lectures on Agricultural Chemistry and Geology. 60 VARIATION IN THE QUANTITY OF INORGANIC MATTER, &C. So that the quantity of inorganic food required by different vegetables is greater or less according to their nature : and if a soil be of such a kind that it can yield only a small quantity of this inorganic food, then those jilants only will grow well upon it to which this small supply will prove suiTiflent. Hence trees may grow where arable crops fail to thrive, because many of the former require and contain comparatively little inorganic matter. Thus the weight of ash left by 1000 lb. of Elm wood is 19 lb. Birch wood is 3), lb. Poplar, - 20 Pine, - 1^ to 3 Willow, - 4 J Oak, - 2 Beech, - l^o 6 Ash, - 1 to G The elm and the poplar contain about as much inorganic matter as the grain of wheat, but very much less than any of the straws or grasses. How much less also does the oak con- tain than either the elm or the poplar ! 2. The quantity of inorganic matter varies in different parts of the same pkmt. This is shown clearly by the different pro- portions of ash left by the grain and by the straw of our culti- vated crops, as given in the preceding table. It appears, also, by the following comparison of the quantities left by 1000 lb. of the different parts of some of our cultivated plants in their dry state. Thus — R 30ts or tuber. Grain or seed. Straw or stalks. Leaves. Turnip, 80 1b. 25 1b — lb. 130 lb. Potato, 40 " — 180 " Wheat, — 20 " 50 '•' Pea, . . — 30 " 50 " 130 " Tobacco, . *f0 " 40 " 100 " 230 " In trees, also, the leaves contain a much larger proportion of inorganic matter than the wood. Thus, 1000 lb. of the dry wood and leaves of the following trees left of ash respectively — Seed. WiUow, Beech, . Wood. . 4i lb. . 4 " Leaves. 82 1b. 42 " Birch, . Pine, . Elm, . . 3 " . 19 " 50 " 20 to 30 120 50 1b. IT VARIES ALSO WITH THE SOIL. 61 It appears, therefore, that by far the largest proportion of the inorganic matter which is withdrawn from the soil by a crop of corn is returned to it again, by the skilful husbandman, in the fermented straw. In the same way also nature, in causing the trees periodically to shed their leaves, returns with them to the soil a very large portion of the soluble inorganic substances which had been drawn from it by their roots during the season of growth. Thus an annual top-dressing is naturally given to the land where forests grow; and that which the roots from spring to autumn are continually sucking up, and carefully collecting from considerable depths, winter strews again on the surface in the f j-m of decaying leaves, so as, in the lapse of time, to form a ricn and fertile soil. Such a soil must be propitious to vegeta- ble growth, since it contains or is made up of those very mate- rials of which the inorganic substance of former races of vege- tables had been almost entirely composed. 3. It varies in quantity in different portions of the same part of the plant. Thus, if a tall stalk of wheat, oats, or barley straw be cut into four equal parts, and these be burned sepa- rately, the lowest portion will generally leave the smallest, the highest portion the greatest per centage of ash. If the bottom of the stalk, for example, leave 3| or 4 per cent., the next por- tion will leave 5 or 6, the third 6 or t, and the highest perhaps 8 or 9. This is a very interesting and curious fact, not hitherto noticed by experimenters, though evidently of great interest hi connection with the inorganic food of plants. In some cases this difference is not observed, while in others the largest proportion of ash is left by the bottom part of the straw. These exceptions, however, occur generally in stunted grain, which has grown upon an unfavorable soil, or has been injured by the season. 4. The quantity of inorganic matter often differs in different speciinens and varieties of the same plant. Thus 1000 lb. of wheat straw, grown at different places, gave to four different experi- 62 DIFFERS WITH VARIETY AND SOIL. menters 43, 44, 35, and 155 lb. of ash respectively. Wheat straw, therefore, does not always leave the same quantity of ash. The same is true also of other kinds of vegetable pro- duce. This fact, as well as the variation of the quantity of ash with the part of the plant, is shown by the following table of the proportions of ash left by the several parts of two different varieties of oats grown on different soils, (Norton) — Hopeton oat. Potato oat. 2.14 2.22 6.47 6.99 4.98 8.62 Grain, Husk, Straw, Leaf, Chafe, 8.44 14.59 16.53 18.59 Here not only do the different parts of the same plant, but similar parts also of different plants of the same species, leave very different proportions of ash. To what is this difference owing ? Is it to the nature of the soil, or does it depend upon the variety of wheat, oats, or other produce experimented upon ? It seems to depend partly upon both. a. Variety. — Thus on the same field, in Ravensworth Dale, Yorltshire, on a rich clay soil abounding in lime, the Golden Kent and Flanders Bed wheats were sov/n in the spring of 1841. The former gave an excellent crop, while the latter was a total failure, the ear containing 20 or 30 grains only of poor wheat. The straw of the former left 165 lb. of ash from 1000 lb., that of the latter only 120 lb. Something, therefore, dejpends upon the variety. b. Soil. — Again, 1000 lb. of the straw of the same variety of oat, grown by the Messrs. Drummond of Stirling in 1841, upon Aberdeen granite, left 96 lb. of ash. On clay-slate, 18 On greenstone, 79 On limestone, 102 On gypsum, 58 On silicious S9.nd, 64 On light loamy soil. 88 GENERAL CONCLUSION, 63 The quantity of ash, therefore, depends in some measure also upon the nature of the soil. 5. But the degree of ripeness which a plant has attained has also an influence on the i)roportion of ash which it leaves. Thus the straw of the same wheat grown on the same limestone soil near Wetherby, in Yorkshire, gave me, when cut five weeks before it was ripe, 40 lb., and when fully ripe, 55 lb., from 1000 lb. of dry straw.' To compare the ash, therefore, of any two samples of straw, they ought to be gathered in the same state of ripeness. A similar observation also has been made in regard to the wood of trees. The quantity of ash they leave varies both with their age and with the season of the year at which they are burned. On the whole, the truth, so far as it can as yet be made out, seems to be this — that every plant must have a certain quantity of inorganic matter to make it grow in the 7uost healthy manner • — that it is capable of living, growing, and even ripening seed with much less, and probably with much more, than this quan- tity — ^but that those soils will produce the most perfect plants wdiich can best supply all their wants; and that the best seed will be raised in those districts wdiere the soil, without being too rich or rank, yet can yield both organic and inorganic food in such proportions as to maintain the corn plants in their most healthy condition. This latter observation, in regard to the quality of seed, is of great practical importance, and must be borne in mind w^hen we come hereafter to inquire wdiether seeds can be so prepared or doctored, by steeping or otherwise, as to grow quicker, with more certainty, and with greater luxuriance, and to yield larger returns of grain. 64 THE QUALITY OF THE ASH OF FLANTS. SECTION III. OF THE COMPOSITION OR QUALITY OF THE ASH OF PLANTS, AND THE CIRCUMSTANCES BY WHICH IT IS MODIFIED. But much also depends upon the quality as well as upon the quantity of the ash. Plants may leave the same weight of ash when burned, and yet the nature of the specimens of ash — the kind of matter of which they respectively consist — may be very different. The ash of one may contain much lime, of another much potash, of a third much soda, while in a fourth much sili- ca may be present. Thus 100 lb. of the ash of hean straw have been found to contain 53 lb. of potash, while that of barley con- tained only 9 lb. in the hundred. On the other hand, 100 lb. of the ash of barley straw contain 68 lb. of silica, while in that of bean straw there are only *T 11). The quality of the ash seems to vary with the same conditions by which its quantity is affected. Thus — 1. It varies with the kind of -plant. — 1000 lb. of the ash of the grain of wheat, barley, oats, beans, and linseed — of the potato tuber and the turnip bulb, for example — contain respectively — Potash, - Soda, Lime, Magnesia, Oxide of iron, - Phosphoric acid, Sulphuric acid. Silica, - Chlorine, - a O 6 .2 ^ G 0) r3 c p. 5 H 237 91 28 120 1 500 3 12 136 81 26 15 15 390 1 2t3 trace. 262 60 100 4 438 105 27 3 220 116 49 103 13 495 9 4 |-325 j 14 162 3 449 28 14 2 336 106 58 80 6 380 10 12 7 245 34 147 99 19 381 9 57 3 557 19 20 53 5 126 136 42 42 419 51 136 53 13 76 136 79 36 998 997 999 1009 997 995 994 1000 999 A comparison of the numbers in the first four columns shows how unlike the quantities of the different substances are which THE ASH OF GRAINS AND BULB. 65 are contaiued in an equal weight of the ash of the four varieties of grain. It is to be remarked, however, that the great differ- ence in the case of barley arises from the thick husk with which it is covered, and from which the large per centage of silica is derived. The sample of oats was taken without the husk. Beans contain more sulphuric acid, also, than any of the other grains in the above table, while they are deficient in phosphoric acid when compared with wheat, barley, or oats. But the most striking differences appear between the several kinds of grain and the potato and turnip. In these last the alkaline matter is very much greater, while the phosphoric acid is much dimin- ished. It is thus evident that a crop of wheat will carry off from the soil — even suppose the whole quantity of ash left by each to be the same in weight — very different quantities of potash, soda, lime, phosphoric acid, &c., from what would be carried off by a crop of beans or of potatoes. It will, therefore, exhaust the soil more of some, as beans and potatoes will of other substances. Hence one reason why a piece of land may suit one crop and not suit another. Hence, also, two successive crops of different kinds may grow well where it would greatly injure the soil to take two in succession of the same kind, especially of either wheat or barley ; and hence we likewise deduce one natural rea- son for a rotation of crops. The surface-soil may be so far ex- hausted of one inorganic substance that it cannot afford it in sufficient quantity to bring a given crop to healthy maturity ; and yet this substance may, by natural processes, be so far re- stored again, during the intermediate growth of certain other crops, as to be prepared in a future season fully to supply all the wants of the same crop, and to yield a plentiful harvest. 2. The kind of inorganic matter varies with the 'part of the plant. — Thus the grain and the straw of the corn-plants contain very unlike quantities of the several inorganic constituents, as will appear by comparing the several columns in the following with those of the preceding table. 66 ASH OF STRAW. 1000 lb. of the ash of the straio of wheat, barley, oats, rye, and Indian corn, have been found to contain respectively of — Potash, - - - Wheat. Barley. Oats. Eye. Indian corn. 125 92 191 173 96 Soda, - - - 2 3 97 3 286 Lime, - - - 67 85 81 90 83 Magnesia, - - .^9 50 38 24 66 Oxide of iron, - 13 10 IS 14 8 Phosphoric acid, 31 31 26 38 171 Sulphuric acid,- 58 10 33 8 7 Chlorine, - - 11 6 32 5 15 Silica, - - - 654 676 484 645 270 1000 963 1000 1000 1012 The quantities of the several inorganic substances contained in the above kinds of straw are very different from those con- tained in the corresponding kinds of grain. In this difference we see one reason why the same soil which may be favorable to the growth of the straw of the corn plant may not be equally propitious to the growth of the ear. The straw contains com- paratively little of some of the ingredieuts found in the ear, es- pecially of the lime, magnesia, and phosplioric acid, while the grain contains a large proportion of these substances. On the other hand, the straw is rich, and the grain very poor in silica. It is clear, therefore, that the roots may, in certain plants and in certain soils, succeed in fully nourishing the straw, while they cannot fully ripen the ear ; or contrariwise, where they feed but a scanty straw, may yet he ahle to give ample sustenance to the filling ear.* That similar differences prevail in other orders of plants also, and that their several parts require, therefore, different propor- * And occasionally do give ; for a plump grain, and even a ■well-filled ear, are not uu frequently found where tlie straw is unusually deficient. ASH OF THE APPLE TREE AND FRUIT. 6t them to tions of the several kinds of inorgauic food to brin^ perfection, is shown by the following table. 1000 lb. of the ash of the stem, leaves, and fruit of the apple tree, {Pyrus sjpectahilis — Chinese crab,) have been found to contain respectively, (Vogel,) Carbonates of potash and soda, Phosphates of do., - CaFbonate of lime, - Carbonate of mao-nesia, - Phosphates of hme and magnesia, Silica, Stem. Leaves Fruit. 4G 822 49 88 68 trace. 729 98 105 190 141 370 55 186 37 1005 1000 979 Thus potash and phosphoric acid abound most in the fruit of the apple tree, as they do in the ear of our corn plants, and are therefore as necessary to their healthy grov/th and complete maturity. 3. The quality of the. ash varies also with the hind of soil in which the plant is made to grow. — This will be understood from what has been stated above. Where the soil is favorable, the roots can send up into the straw everything which the plant re- quires for its healthy grow^th, and in the right proportions. When it is either too poorly or too richly supplied with one or more of those inorganic constituents which the plant desires, life may indeed be prolonged, but a stunted or unhealthy crop will be raised, and the kind, and perhaps the quantity, of ash left on burning it, will necessarily be different from that left by the same species of plant grown under more favoring circum- stances. Of this fact there can be no doubt, though the extent to which such variations may take place without absolutely kill- ing the plant has not yet been made out. That it is considera- ble is shown by the following table, which exhibits the compo- 68 INFLUENCE OF SOILAGE AND SEASON. sition of 1000 lb. of the ash of three samples of wheat grown in different localities : — Dutch. German. White. Red. Potash, .... 64 219 338 Soda, .... 278 157 Lime, .... 39 19 31 Magnesia, 130 96 136 Oxide of iron, 5 14 3 Sulphuric acid. 3 2 Pliosphoric acid. 461 493 492 Silica, .... 3 •• 983 1000 1000 In the first of these we find little potash, in the last no soda, while in all nearly half the weight consists of phosphoric acid. 4. It varies also with the period of the planfs growth, or the season at which it is reaped — Thus, in the young leaf of the turnip and potato, a greater proportion of the inorganic matter consists of potash than in the old leaf. The same is true of the stalk of wheat; and similar differences prevail in almost every kind of plant at different stages of its growth. The enlightened agriculturist will perceive that all the facts above stated have a more or less obvious connection with the ordinary processes of practical agriculture, and tend to throw considerable light on some of the principles by which these pro- cesses ought to be regulated. One illustration of this is exhib- ited in the following section. SECTION IV. AVERAGE QUANTITY OF INORGANIC MATTER CONTAINED IN AN ORDINARY CROP, OR SERIES OF CROPS. The importance of the inorganic matter contained in living vegetables, or in vegetable substances when reaped and dry, WHAT A WHOLE CROP CARRIES OFF. 69 will appear more distinctly if we consider the actual quantity carried off from the soil in the series of crops. In a four years' course of cropping, in which the crops gathered amounted per acre to — 1st year, Turnips^ 20 tons of bulbs and 63- tons of tops. 2d year, Barley^ 40 bushels of 63 lb. each, and 1 ton of straw. 3d year, Clover and Rye-Grass^ \h ton of each in hay. 4th year, Wlieat, 25 bushels of GO lb., and 1| tons of straw. 1°. The quantity of inorganic matter carried off in the four crops, supposing none of them to be eaten on the land, amounts to about — Potash, 311 lb. Sulphuric acid, . 108 lb. Soda, 54 " Phosphoric acid 116 " Lime, . 193 " Chlorine, . TO " Magnesia, , 55 " Oxide of iron, 15 " Silica, 356 " Total, 1284 • or in all about 11 cwt.; of which gross weight the different sub- stances form unlike proportions. 2°. A still clearer view of these quantities will be obtained by a consideration of the fact, that if we carry off the entire pro- duce, and add none of it again in the shape of manure, we must or ought, in its stead, if the land is to be restored to its original condition, to add to each acre every four years — Dry pearl-ash, 465 lb Common bone dust. 552 » Epsom salts. 326 " Common-salt, 116 " Quick-lime, . . . • 70 " Total, 1529 Several observations suggest themselves from a consideration of the above statements. First, That if this inorganic matter be really necessary to the plant, the gradual and constant removal of it from the land ought, by and by, to make the soil poorer in this part of the food of plants. 70 ' GENERAL CONSIDERATIONS. Second, That the more of the crops which grows upon the land we return to it again in the form of manure, the less will this deterioration be perceptible. Third, That as many of these inorganic substances — the potash, soda, &c., — are readily soluble in water, the Hquid ma- nure of the farmyard, so often allowed to run to waste, must carry with it to the rivers much of the saline matter that ought to be returned to the land. Fourth, If the rains also are allowed to run over and vmsk the surface of the soil, they will gradually deprive^t of those soluble saline substances which appear to be so necessary to the growth of plants. Hence one important benefit of a system of drainage so perfect as to allow the rains to sink into the soil where they fall, and thus to carry down, instead of away, what they naturally dissolve. And, lastly. That the utility, and often indispensable necessity, of certain artificial manures — though, in some districts, perhaps arising from the natural poverty of the land in some of the mineral substances which plants require — ^is most frequently owing to a want of acquaintance with the facts above stated, and to the long-continued neglect and waste which has been the natural consequence. In certain districts, the soil and subsoi] contain within them- selves an almost unfailing supply of some of these inorganic or mineral substances, so that the waste of them is long in being felt; in others, again, the land contains less, and therefore becomes sooner exhausted. This latter class of soils requires a more careful, and usually a more expensive mode of cultivation than the first; but both will become at length alike unproductive, if that which is yearly taken from the soil is not in some form or other restored to it. One thing is of essential importance to be remembered by the practical farmer — that the deterioration of land is often an ex- ceedingly slow process. In the hands of successive generations, a field may so imperceptibly become less valuable, that a cen- ARTIFICIAL MANURES, WHY NECESSARY. 11 tury even may elapse before the change prove such as to make a sensible dhuinution in the valued rental. Such slow changes, however, have been seldom recorded; and hence the practical man is occasionally led to despise the clearest theoretical prin- ciples, because he has not happened to see them verified in his own limited experience; and to neglect, therefore, the sug- gestions and the wise precautions which these principles lay before him. The special agricultural history of known tracts of land of different qualities, showing how they had been cropped and tilled, and the average produce in grain, hay, and stock every five years, during an entire century, would aftbrd invaluable mate- rials both to theoretical and to practical agriculture. General illustrations of this sure though slow decay may be met with in the agricultural history of almost every country. In none, perhaps, are they more striking than in the older slave states of North America. Maryland, Yirginia, and North Ca- rolina — once rich and fertile — by a long-continued system of forced and exhausting culture, have become unproductive in many places, and vast tracts have been abandoned to appa- rently hopeless sterility. Such lands it is possible to reclaim, but at v»^hat an expense of time, labor, manvn-e, and skilful management ! It is to be hoped that the newer states will not thus sacrifice their future power and prospects to present and temporary wealth — that the fine lands of Ohio, Kentucky, and the Prairie states, which now yield Indian corn and wheat, crop after crop, without intermission and without manure, will not be so cropped till their strength and substance is gone, but that a better conducted and more skilful husbandry will con- tinue, without diminishing the 'present crops, to secure a per- manent fertility to that naturally rich and productive country. SECTION Y. PRACTICAL DEDUCTIONS TO BE DRAWN FROM A KNOW- LEDGE OF THE INORGANIC CONSTITUENTS OF PLANTS. Several important practical deductions are to be draT^^l from T2 PRACTICAL DEDUCTIONS. what lias been stated in regard to the inorganic constituents of plants. 1"^. Why one crop may grow well where another fails. — Sup- pose, for example, a crop to require a peculiarly large supply of potash — it may grow well if the soil abound in potash ; but if the soil be deficient in potash and abound in lime, then this crop may scarcely grow at all upon it, while another crop to which lime is especially necessary may grow luxuriantly. 2°. Why 7nixed crops groio tvell together. — If two crops of unlike kinds be sown together, their roots suck in the inorganic substances in different proportions — the one more potash and phosphoric acid perhaps — the other more lime, magnesia, or silica. They thus interfere less with each other than plants of the same kind do — which require the same kinds of food in nearly the same proportions. Or the two kinds of crop grow with different degrees of rapidity, or at different periods of the year ; and thus, while the roots of the one are busy drawing in supplies of inorganic nourishment, those of the other are comparatively idle ; and thus the soil is able abundantly to supply the wants of each as its time of need arrives. 3°. Why tJiesame crop grows letter on the same soil after long i7itervals. — If each crop demands special substances, or these substances in quantities peculiar to itself, or in some peculiar state of combination, the chances that the soil will be able to supply them are greater, the more distant the intervals at which the same crop is grown upon it. Other crops do not demand the same substances, or in the same proportions ; and thus they may gradually accumulate on the soil till it becomes especially favorable to the particular crop we wish to grow. 4°. Why a rotation of crops is necessary. — Suppose the soil to contain a certain average supply of all "those inorganic sub- stances which plants require, and that the same corn crop is grown upon it for a long series of years — this crop will carry off some of these substances in larger proportion than others, ROTATION OF CROPS : EXHAUSTION. 73 SO that year by year the quantity of those which are thus chiefly carried off will become relatively less. Thus at length the soil, for want of these special substances, will become unable to bear a corn crop at all, though it may still contain a large store of the other inorganic substances which the corn crop does not specially exhaust. Suppose bean or turnip crops raised in like manner for a succession of years, they would exhaust the soil "of a different set of substances till it became unable to grow them profitably, though still rich perhaps iu those things which the corn crop especially demands. But grow these crops alternately, then the one crop will draw especially upon one class of substances, the other crop upon another ; and thus much larger crops of each will be reaped from the same soil, and for a much longer period of time. On this principle the benefit of a rotation of crops in au important degree depends.* 5°. What is meant by exhaustion. — Thus, exhaustion may either be general, arising from the gradual carrying off of all the kinds of food on which plants live — or special, arising from the want of one or more pf those substances which the crops that have been long grown upon it have specially required. To repair the former kind of exhaustion, an addition of many things to the soil may be necessary ; — to repair the latter, it may be sufficient to add a needful supply of one or more things only. In showing how this may be most efficiently and most economically done, chemistry will be of the most essential service to >the practical man. Before en- tering further upon this point, however, it will be necessary to study also the nature of the soil in which plants grow. * In showing, in the above remarks, how the doctrine of the inorganic part of plants throws hght, among other things, upon the use of a rotation of crops, the reader will bear in mind that a knowledge of the organic por- tion of the plant, and of the living functions of each part in each species, is no less necessary to the full understanding of this intricate subject. 4 C H A P T E R V . Of soils. — Their organic and inorganic portions. — Saline or soluble, and earthy or insoluble, matter in soils. — Examination and classification of soils. — Determination of the per-centage of sand, clay, vegetable matter, and lime. — Diversities of soils and subsoils. Soils consist of two -parts ; of an organic part, which can readily be burned away when the soil is heated to redness ; and of an inorganic part, which is fixed in the fire, and which con- sists entirely of earthy and saline substances. SECTION I. or THE ORGANIC TART OF SOILS. The organic part of soils is derived chiefly from the remains of vegetables and animals which have lived and died in or upon the soil, which have been spread over it by rivers and rains ; or which have been added by the hands of man, for the purpose of increasing its natural fertility. This organic part varies very much in quantity in different soils. In some, as in peaty soils, it forms from 50 to 70 per cent of their whole weight ; and even in rich long-cultivated soils it has been found, in a few rare cases, to amount to as much as 25 per cent. In general, however, it is present in much smaller proportion, even in our best arable lands. Oats and rye will grow upon a soil containing only 1 J per cent, barley when 2 to 3 per cent are present, while good wheat soils gene- rally contain from 4 to 8 per cent. The rich alluvial soil of the valley of the Nile contains only 5 per cent of dry organic mat- ter. In stiff and very clayey soils, 10 to 12 per cent is some- times found. In very old ])asture-lands, and in gardens, vegeta- ble matter occasionally accumulates so as to overload the upper soil. ORGANIC AND INORGANIC PARTS OF THE SOIL. T5 To this organic matter in the soil the name of humus has been given by some writers. It contains, or yields to the plant, the ulmic, humic, and other acids already described, (see Chap- ter II.) It supplies also, by its decay in contact with the air which penetrates the soil, much carbonic acid, which is supposed to enter the roots, and thus to assist the growth of living vege- tables. During the same decay, ammonia, as we have already stated, is likewise produced, and this in larger quantity if ani- mal matter be present in considerable abundance. Other sub- stances, more or less nutritious, are also formed from the organic matter in the soil. These enter by the roots, and contribute to nourish the growing plant, though the extent to which it is fed from this source is dependent, both upon the abundance with which these substances are supplied, and upon the nature of the plant itself, and of the climate in which it grows. Another influence of this organic portion of the soil, whether naturally formed in it or added to it as manure, is not to be neglected. It contains — as all vegetal)le substances do — a con- siderable quantity of inorganic, that is, of saline and earthy matter, Avhich is liberated as the organic part decays. Thus living plants derive from the remains of former races, Ijuried beneath the surface, a portion of that inorganic food which can only be obtained from the soil, and which, if not thus directly supplied, must be sought for by the slow extension of their roots through a greater depth and breadth of the earth in which they grow. The addition of manure to the soil, therefore, j^laces within the easy reach of the roots not only organic but also inor- ganic food. SECTION II. OF THE INORGANIC PART OF SOILS. The inorganic part of soils — that which remains behind, when everything combustible is burned away by heating it to redness in the open air — consists of two portions, one of which is sduhle in water, the other insoluble. Tlie soluble consists of saline sub- stances, the insoluble of carl/iy substances. 76 SALINE OR SOLUBLE PART. 1. The saline or soluble portion. — In this country, the surface- soil of our fields, in general, contains very little soluble matter. If a quantity of soil be dried in an oven, a pound weight of it taken, and a pint and a-half of pure boiling rain water poured over it, and the whole well stirred and allowed to settle, the clear liquid, when poured off and boiled to dryness, may leave from 30 to 100 grains of saline mixed with a variable quantity of organic matter. This saline matter will consist of common salt, gypsum, sulphate of soda, (Glauber's salts,) sulphate of magnesia, (Epsom salts,) with traces of the chlorides of calcium, magnesium, and potassium, and of potash, soda, lime, and mag- nesia, in combination with nitric and phosphoric, and with the humic and other organic acids. It is from these soluble sub- stances that the plants derive the greater portion of the saline ingredients contained in the ash they leave when burned. Xor must the quantity thus obtained from a soil be considered too small to yield the whole supply which a crop requires. A single grain of saline matter in even/ pound of a soil a foot deep, is equal to 500 lb. in an acre. This is more than is carried off from the soil in ten rotations, (forty years,) where only the wheat and barley are sent to market, and the straw and green crops are regularly, and without loss, returned to the land in the manure."^ In some countries — indeed, in some districts of our own coun- try — the quantity of saline matter in the soil is so great as in hot seasons to form a white incrustation on tlie surface. It may often be seen in the neighborhood of Durham ; and is more especially to be looked for in districts where the subsoil is sandy and porous, and more or less full of water. In hot weather, the evaporation on the surface causes the water to ascend from the porous subsoil ; and as this water always brings with it a quantity of saline matter, which it leaves behind when it rises * A furllier portion, it will be recollected, is carried off in the cattle tliat {ire sent to market, or is lost in the liquid manure that is wasted, or is washed out by the rains from the soil or from the manure ; all these are here neglected. SALINE INCRUSTATIONS UPON THE SOIL. 71 in vapor, it is evident that, the longer the dry weather and conseqnent evaporation from the surface continue, the thicker the incrustations will be, or the greater the accumulations of sahne matter on the surface. Hence, where such a moist and porous subsoil exists in countries rarely visited by rain, as in the plains of Peru, of Egypt, or of India, the country is whitened over in the dry season with an unbroken snowy covering of the different sahne substances above mentioned. When rain falls, the saline matter is dissolved, and descends again to the subsoil. In dry weather it re-ascends. Hence the surface-soil of any field will contain a larger proportion of solu- ble inorganic matter in the micldle of a hot dry season than in one of even ordinary rain. Hence, also, the fine dry weather which, in early summer, hastens the growth of corn, and later in the season favors its ripening, does so probably, among its other modes of action, by bringing up to the roots from beneath a more ready supply of those saline compounds which the crop requires for its healthful growth. In some countries, however, this saline matter ascends in such quantity as to render the soil unfit to grow the more tender crops. Thus, on the plains of Attica, when the rainy season ends, saline substances begin to rise to the surface in such abundance as by degrees entirely to burn up or prevent the growth of grass, though abundant wheat crops are yearly ripened. 2. T'he earthy or insoluble 'portion. — The earthy or insoluble portion of soils rarely constitutes less- than 95 lb. in a hundred of their whole weight. It consists chiefly of silica in the form of sand- — of alumina mixed or combined with silica in the form of clay — and of lime in the form of carhonate of lime. It is rarely free, however, from two or three per cent of oxide of iron ; and where the soil is of a red color, this oxide is often present in still larger proportion. A trace of magnesia also may be almost always detected, and a minute quantity of phos- phate of lime. The principal ingredients, however, of the earthy part of all soils are sand, clay, and lime ; and soils are 78 SEPARATION OF SAND AND CLAY. named or classified according to the quantity of each of these three they may happen to contain. a. If an ounce of soil be intimately mixed with a pint of water till it is perfectly softened and diffused through it, and if, after shaking, the heavy parts be allowed to settle for a few minutes, the sand will subside, while the clay, which is in finer particles, and is less heavy — will still remain floating. If the water and fine floating clay be now poured into another vessel, and be allowed to stand till the water has become clear, the sandy part of the soil will be found on the bottom of the first vessel, and the clayey part on that of the second, and they may be dried and weighed separately. h. If 100 grains of dry soil, not peaty or unusually rich in vegetable matter, leave no more than 10 of clay when treated in this manner, it is called a sandy soil ; if from 10 to 40, a sandy loam ; if from 40 to tO, a loaTiiy soil ; if from 10 to 85, a clay loam ; from 85 to 95, a strong clay soil ; and when no sand is separated at all by this process, it is a pure agricultural clay. c. The strong clay soils are such as are used for making tiles and bricks ; the pure agricultural clay is such as is commonly employed for the manufacture of pipes, (pipe-clay.) This pure clay is a chemical compound of silica and alumina, in the pro- portion of about 60 of the former to 40 of the latter. Soils of pure clay rarely occur — it being well known to all practical men that the strong clays, (tile clays,) which contain from 5 to 15 per cent of sand, • are brought into arable cultivation with the greatest possible difficulty. It will rarely, almost never, happen, therefore, that arable land will contain more than 30 to 35 per cent of alumina. d. If a soil contain more than 5 per cent of carbonate of lime, it is called a marl ; if more than 20 per cent, it is a cal- careous soil. Peaty soils, of course, are those in which the vegetable matter predominates very much. e. The quantity of vegetable or other organic matter is de- termined by drying the soil well upon paper in an oven, until it J DIVERSITIES OF SOILS AND SUBSOILS. 79 ceases to lose weight — taking care that tlie heat is not so great as to char the paper — and then burning in the open air a weighed quantity of the dried soil : the loss by burning is nearly all organic matter. In stiff clays this loss will include also a portion of water, which is not wholly driven off from such soils by drying upon paper in the way described. /. To estimate the lime, a quantity of the soil should be heated in the air till the organic matter is burned away. A weighed portion, (200 or 300 grains,) should then be diffused through half a pint of cold water mixed with lialf a wine- glassful of spirit of salt, (muriatic acid,) and allowed to stand for a few hours, with occasional stirring. When minute bub- bles of gas cease to rise from the soil, the water is poured off, the soil dried, heated to redness as before, and weighed : the loss is nearly all lime. SECTIOX III. OF THE DIVERSITIES OF SOILS AND SUBSOILS. 1st. Soils. — Though the substances of which soils chiefly con- sist are so few in number, yet every practical man knov/s how very diversified they are in character — how very different in agricultural value. Thus, in some of our southern counties, we have a white soil, consisting apparently of nothing else but chalk ; in the centre of England a wide plain of dark-red land ; in the border counties of Wales, and on many of our coal-fields, tracts of country almost perfectly black ; while yellow, white, and brown sands and clays give the prevailing character to the soils of other districts. Such differences as these arise from the different proportions in which the sand, lime, clay, a,nd the oxide of iron and organic matter which color the soils, have been mixed together. But how have they been so mixed — differently in different parts of the country ? By what natural agency ? For what end? 2d. Subsoil. — Again, the surface-soil rests on what is usually denominated the subsoil. This is also very variable in its cha- 80 IMPORTANCE OF THE SUBSOIL. racter and quality. Sometimes it is a porous sand or gravel, through which water readily ascends from beneath, or sinks in from above ; sometimes it is light and loamy, like the soil that rests upon it ; sometimes stiff, and more or less impervious to water. The most ignorant farmer knows how much the value of a piece of land depends upon the character of the surface-soil, — the intelhgent improver understands best the importance of a favorable subsoil. "When I came to look at this farm," said an excellent agriculturist to me, " it was spring, and damp, growing weather : the grass was beautifully green, the clover shooting up strong and healthy, and the whole farm had the appearance of being very good land. Had I come in June, when the heat had drunk up nearly all the moisture which the sandy subsoil had left on the surface, I should not have offered so much rent for it by ten shillings an acre." He might have said also, " Had I taken a spade, and dug down 18 inches in various parts of the farm, I should have known what to expect in seasons of drought." But how come subsoils thus to differ — one from the other — and from the surface-soil that rests upon them ? Are there any principles by which such differences can be accounted for — by which they can be foreseen — by the aid of which we can tell what kind of soil may be expected in this or that district, even without visiting the spot, and on what kind of subsoil it is likely to rest ? Geology explains the cause of many of these differences, and supplies us with principles by which we can predict the general quality of both soils and subsoils in the several parts of entire kingdoms ; and where the soil is of inferior quality, and yet susceptible of improvement, the same principles indi- cate whether the means of improving it are likely to exist in any given locality, or to be attainable at a reasonable cost. It will be proper shortly to illustrate these direct relations of geology to agriculture. CHAPTER YT. Direct relations of geology to agriculture. — Origin of soils. — Causes of their diversity. — Relation of soils to the rocks on which they rest. — Constancy in the relative position and character of the stratified rocks. — Relation ot this fact to practical agriculture. — Of primary, secondary, tertiary, and post-tertiary rocks. — Different soils observed upon each of these divisions along the Atlantic sea-hoard of North America. Geology is that branch of knowledge which embodies all ascertained facts in regard to the nature and internal structure, both physical and chemical, of the solid parts of our globe. This science has many close relations with practical agriculture. It especially throws much light on the na.ture and origin of soils — on the causes of their diversity — on the agricultural capa- bilities, absolute and comparative; of different farming districts and countries — on the unlike effects produced by the same manure on different soils — on the kind of materials, by admix- ture with which they may be permanently improved — and on the sources from which these materials may be derived. It tells beforehand, also, and by a mere inspection of the may, what is the general character of the land in this or that district of a country — where good land is to be expected — where improvements are likely to be effected — of what kind of im- provements this or that district will be susceptible — and where the intending purchaser may hope to lay out his money to the greatest advantage. SECTION I. OF THE CRUMBLIXG OF ROCKS AND THE ORIGIX OF SOILS. If we dig down through the soil and subsoil to a sufficient depth, we always come sooner or later to the solid rock. In many places the rock actually reaches the surface, or rises in 4* 82 GENERAL COMPOSITION OF ROCKS. cliffs, hills, or ridges, far above it. The surface (or crust) of our globe, therefore, consists everywhere of a more or less solid mass of rock, overlaid by a covering, generally thin, of loose materials. The upper or outer part of these loose materials forms the soil. The geologist has travelled over great part of the earth's surface, has examined the nature of the rocks which everywhere repose beneath the soil, and has found them to be very unlike in appearance, in hardness, and in composition — in different coun- tries and districts. In some places he has met with a sandstone, in other places a limestone, in others a slate or hardened rock of clay. But a careful comparison of all the kinds of rock he has observed has led him to the general conclusion that they are all either sandstones, limestones, or clays of different degrees of hardness, or a mixture in different proportio7is of two or more of these kinds of matter. When the loose covering of earth is removed from the sur- face of any of these rocks, and this surface is left exposed, sum- mer and winter, to the action of the winds and rains and frosts, it may be seen gradually to crumble away. Such is the case even with many of those which, on account of their greater hardness, are employed as building-stones, and which, in the walls of houses, are kept generally dry ; how much more with such as are less hard, or lie beneath a covering of moist earth, and are continually exposed to the action of water. The natural crumbling of a naked rock thus gradually covers it with loose materials, in which seeds fix themselves and vegetate, and which eventually form a soil. The soil thus produced partakes neces- sarily of the chemical character and composition of the rock on which it rests, and to the crumbling of which it owes its origin. If the rock be a sandstone, the soil is sandy — if a claystone, it is a more or less stiff clay- -if a limestone, it is more or less calcareous — and if the rock consist of any peculiar' mixture of those three substances, a similar mixture is observed in the earthy matter into which it has crumbled. RELATIOXS OF SOILS TO ROCKS. 83 Led by this observation, the geologist, after comparing the rocks of different countries with one another compared next the soils of various districts with the rocks on which they immedi- ately rest. The a-cmral result of this comparison has been, that in almost every country the soils* as a whole, have a resemblance to the rocks beneath them, similar to that which the loose earth derived from the crumbling of a rock before our eyes bears to the rock of which it lately formed a part. The conclusion, therefore, is irresistible, that soils, generally speaking have been formed by the crumbling or decay of the solid rocks — that there was a time vv hen these rocks were naked and without any cover- ing of loose materials — and that the accumulation of soil has been the slow result of the natural degradation or wearino; away of the solid crust of the globe. 'O' SECTION II. CAUSE OF THE DIVERSITY OF THE SOILS. The cause of the diversity of soils in different districts, there- fore, is no longer obscure. If the subjacent rocks in two local- ities differ, the soils met with there are likely to differ also, and in an equal degree. But why, it may be asked, do we find the soil in some coun- tries uniform in mineral'^ character and general fertility over hundreds or thousands of square miles, while in others it varies from field to field — the same farm often presenting many well- inarked differences both in mineral character and in agricultural value ? A chief cause of this is to be found in Ihe mode in which the different rocks are observed to lie — upon or by the side of each other.f 1. Geologists distinguish rocks into two classes, the stratified and the unst ratified. The former are found lying over each other in separate beds or strata, like the leaves of a book when * That is, containing the same general proportions of sand, clay, lime,' &c , or colored red by similar quantities of oxide of iron. •j- For another important cause, see Section II. of Chapter YIII. 84 STRATIFIED AND UXSTHATIFIED ROCKS. kid on its side, or like the layers of stones in the wall of a building. The latter — the unstratified rocks — form hills, moun- tains, or sometimes ridges of mountains, consisting of one more or less solid mass of the same material, in which no layers or strata are usually anywhere or distinctly perceptible. Thus, in the following diagram, (No. 1,) A and B represent unstratified masses, in connection with a series of stratified deposits, 12 3, lying over each other in a horizontal position. On A one kind of soil will be formed, on C another, on B a third, and on D a fourth — the rocks being all different from each other. No. 1. !5 If from A to D be a wide valley of many miles in extent, the undulating plain at the bottom of the valley, resting in great part on the same rock, (2,) will be covered by a similar soil. On B the soil will be different for a short space ; and again it will differ at the bottom of the valley C, and on the first ascent to A, at both of which places the rock (3) rises to the surface. In this case the stratified rocks lie horizontally ; and it is the undulating nature of the country which, bringing different kinds of rock to the surface, causes a necessary diversity of soil. 2. But the degree of inclination which the beds possess is a more frequent cause of variation in the characters of the soil in the same district, and even at very short distances. This is shown in^the annexed diagram, (No. 2,) where ABODE represent the mode in which the stratified rocks of a district of country not unfrequently occur in connection with each other. No. 2. Proceeding from E in the plain, the soil would change when ORDER OF SUCCESSION CONSTANT. 85 we came upon tlie rock D, but would continue pretty uniform in quality till we reached the layer C, Each of these layers may stretch over a comparatively level tract of perhaps hun- dreds of miles in extent. Again, on climbing the hill-side, another soil would present itself, which would not change till we arrived at B. Then, however, we begin to walk over the edges of a series of beds, and the soil may vary with every new stratum or bed we pass over, till we gain the ascent to A, where the beds are much thinner, and where, therefore, still more frequent variations may present themselves. Everywhere over the British islands valleys are hollowed out, as in the former of these diagrams, (No. 1,) by which the different rocks beneath are in different places exposed and dif- ferences of soil produced ; or the beds are more or less inclined, as in the latter diagram, (No. 2,) causing still more frequent variations of the land to appear. By a reference to these facts, therefore, many of the greater diversities which the soils of the country present may be satisfactorily accounted for. SECTION III. OF THE CONSTANCY IN MINERAL CHARACTER, AND ORDER OF SUCCESSION, WHICH EXISTS AMONG TPIE STRATIFIED ROCKS. Another fact, alike important to agriculture and to geology, is the natural order or mode of arrangement in which the stra- tified rocks are observed to occur in the crust of the globe. Thus, if 1 2 3 in diagram No. 1 represent three different kinds of rock — a limestone, for example, a sandstone, and a hard clay rock (a shale or slate) lying over each other in the order here represented — then, in whatever part of the country, nay, in whatever part of the v/orld these same rocks are met with, they will always be found in the same position. The bed 2 or 3 will never he observed to lie over the bed 1. This fact is important to geology, because it enables this science to arrange all the stratified rocks in a certain invariable 86 DEDUCTIONS FROM THIS. order — wliicli order indicates their relative age or antiquity — since that rock which is lowest, like the lowest layer of stones in the wall of a building, must generally have been the first deposited, or must be the oldest. It also enables the geologist on observing the kind of rock which forms the surface in any country, to predict at once whether certain other rocks are likely to be met with in that country or not. Thus at C, (diagram No. 1,) where the rock 3 comes to the surface, he knows it would be in vain, either by sinking or otherwise, to seek for the rock 1, the natural place of which is far above it ; while, at D, he knows that by sinking he is likely to find either 2 or 3, if it be worth his while to seek for them. To the agriculturist this fact is important, among other reasons, — 1. Because it enables him to predict whether certain kinds of rock, which may be used with advantage in improving his soil, are likely to be met with within a reasonable distance or at an accessible depth. Thus, if the bed D (diagram No. 2) be a limestone, the instructed farmer at E knows that it is not to be found by sinking into his own land, and therefore brings it from D ; while to the farmer upon C it may be less expen- sive to dig down to the bed D in one of his own fields, than to cart it from a distant spot, where it occurs on the surface. Or, if the farmer requires clay, or marl, or sand, to ameliorate his soil, this knowledge of the constant relative position of beds enables him to say where these materials are to be got, or where they are to be looked for, and whether the advantage to be derived is likely to repay the cost of procuring them. 2. It is observed that, when the soil on the sur^ce of eadi of a series of rocks, such as C or D or E, (diagram No. 2,) is uniformly bad, it is almost umformly of letter quality at the point where the tioo rocks meet. Thus C may be dry, sandy, and barren ; D may be a cold unproductive clay ; and E a more or less unfruitful limestone soil ; yet at either extremity of the tract D, where the soil is made up of an admixture of the PRACTICAL YALUE OF GEOLOGICAL KNOWLEDGE. 81 decayed portions of the two adjacent rocks, the land may be of average fertility — the sand of C may adapt the adjacent clay to the growth of turnips, while the lime of E may cause it to yield large returns of wheat.* Thus, to the tenant in look- ing out for a farm, or to the capitalist in seeking an eligible investment, a knowledge of the mutual relations of geology and agriculture will often prove of the greatest assistance. But how little is such really useful knowledge diffused among either class of men — how little have either tenants or proprie- tors been hitherto guided by it in their choice of the local- ities in which they desire to live ! 3. The further fact that the several stratified rocks are re- markably constant in their general mineral character, renders this knowledge of the order of relative superposition still more valuable to the agriculturist. Thousands of different beds are known to geologists to occur on various parts of the earth's surface — each occupying its own unvarying place in the series. Most of these beds also, when they crumble or are worn down, produce soils possessed of some peculiarity by which their general agricultural capabilities are more or less affected, — and* these peculiarities may gcnercdly be observed in soils formed from rocks of the same age — that is, occupying the same place in the series — in whatever part of the world we find them. Hence, if the agricultural geologist be informed that his friend has bought, or is in treaty for a farm or an estate, and that it is situated upon such and such a rock, or geological formation, or is in the immediate neighborhood of such another,- — he can immediately give a very probable opinion in regard to the agricultural value of the soil, whether the property be in Eng- land, Australia, or in New Zealand. If he knows the nature of the climate also, he will be able to estimate with tolerable correctness how far the soil is likely to repay the labors of the practical farmer — nay, even whether it is likely to suit better for arable land or for pasture ; and if for arable, what * See p. 84. 88 AGRICULTURAL VALUE OF GEOLOGY. species of grain and root crops may be expected to produce most abundantly. These facts are so very curious, and illustrate so beautifully the value of geological knowledge — if not to A and B, the holders and proprietors of this and that small farm, yet to enlightened agriculturists, to scientific agriculture in general — that I shall explain this part of the subject more fully in a separate section. To those who are now embarking in such numbers in quest of new homes in our numerous colonies — who hope to find, if not a more willing, at least a more attainable soil in new countries — no kind of agricultural knowledge can at the outset, — I may say, even through life — be so valuable as that to v.-hich the rudi- ments of geology will lead them. Those who prepare themselves the best for becoming farmers or proprietors in Canada, in New Zealand, or in wide Australia, leave their native land in general without a particle of that preliminary practical know- ledge which would qualiTy them to say, when they reach the land of their adoption, " on this spot rather than oh that — in this district, rather than that, — will I purchase my allotment, because though both appear equally inviting, yet I know, from the geological structure of the country, that here I shall have the more permanently productive soil ; here I am more within reach of the means of agricultural im- provement; h'fere, in addition to the riches of the surface, my descendants may hope to derive the means of wealth from mine- ral riches beneath." And this oversight has arisen chiefly from the value of such knowledge not being understood — often from the very nature of it being unknown, even to otherwise well- instructed practical men. It is not to men well skilled merely in the details of local farming, and who are therefore deservedly considered as authorities, and good teachers in regard to local or district practice, that we are to look for an exposition, often not even for a correct appreciation of those general principles on which a universal system of agriculture must be based — without which, indeed, it must ever remain a mere collection of SUBDIVISIONS jOF STRATIFIED ROCKS. 89 empirical rules, to be studied and laboriously mastered in every new district we go to — as the traveller in foreign lands must acquire a new language every successive frontier he passes. England, the mistress of so many wide and unpeopled lands, over which the dwellings of her adventurous sons are hereafter to be scattered, on which their toil is to be expended, and the glory of their motherland by their exertions to be perpetuated — England should especially encourage all such learning, and the sons of English farmers should willingly avail themselves of every opportunity of acquiring it. • SECTION IV. OF THE SUBDIVISIONS OF THE STRATIFIED ROCKS, AND OF OBSERVED DIFFERENCES AMONG THE SOILS THAT RESt UPON THEil. The thousands of beds or strata of which I have spoken as lying one over the other in the crust of the globe, have — partly for convenience, and partly in consequence of certain remarkably distinctive characters observed among them — been separated by geologists into thre« great divisions. The primary are the lowest and the oldest ; the secondary lie over these ; and the terti- ary are the uppermost, and have been most recently formed. The sands, gravels, clays, and alluvial deposits, which in many places overlie the solid rocks and the beds of soft limestone, in many places formed by calcareous springs, are often spoken of as post- tertiary. In some countries, on the surface of which these several divisions of the strata are seen to succeed each other very closely, the character of the surface soil and its agricultural capability are also seen to vary as we pass from the rocks of the one epoch to those of the other. This is the case, for example, in the more southernly of the United States of America which lie along the Atlantic border. As we walk inland from the sea-shore, we pass over low and swampy, but rich muddy flats, which yield large returns of sea-island cotton and rice. As we proceed, the 90 DIFFERENT ROCKS OF THE ground gradually rises above the sea-level — becomes firmer and drier — and instead of the swamp willow and cypress, bears the hickory and the oak. Tobacco and sugar are the marketable crops on this drier land, and Indian corn tlie staple food of the colored population. After twenty miles or so, the edge of this drier alluvial plain is reached, and we ascend a low escarpment or terrace of yellow sand. Here we find ourselves amid thin forests of unmixed natural pine, growing upon a poor sandy soil ; and till v/e cross this belt and reach a second terrace, few corn-fields, or attempts at clearing for the purposes of cultiva- tion meet the eye. The new terrace presents the remarkable contrast of an open prairie, void of trees, covered with a thin Soil waving with grass, and resting, like our English downs, on chalk rocks beneath. This tract is dry and deficient in water; but the thin soil, when turned over, yields crops of corn, and bears, among others, a variety of hard wheat, known in the market by the name of Georgian wheat. Still farther on this prairie is passed, and we ascend hilly slopes, upon wiiich clays and loams of various qualities and capabilities occur at intervals intermingled, and broad-leaved trees of various kinds ornament the landscape. It is a country fitted for general husbandry, propitious to skill and industry, and, by its climate, adapted to the constitution of settlers of European blood. These changes in agricultural character and capability are coincident with changes in the geological age of the beds which form its surface. This I have shown in the following section of the coast-line in question, from the sea to the mountains. The letterpress below the section indicates the geological formiations ; that placed above it indicates, first, the natural vegetation, and then the kind of husbandry and of labor v/hich are best adapted to each. AMERICAN ATLANTIC BORDER. 91 Broad-loaved forests. General husbandry. No. 3. Oak Swamp and willow, hickory. Dry chalk downs. "White labor. Rice Sugar Pine forests. Treeless prairies. * and and Sandy barrens. ■ cotton, tobacco. Georgian wheat Little cultivation. Colored labor Sea. Post-tertiary, and alluvial. Tertiary sands. Secondary Primary metamorphic* chalk marks. rocks and granite. In this section the reader will observe a close general relation between the changes in geological and agricultural character which appear on the several successive terraces or flats of laud which intervene between the shores of the Atlantic and the slopes of the Alleghany Mountains. Where the most recent or alluvial loams and rich clays end, there the tobacco, Indian corn, and even wheat culture, for the time, end also. The tertiary sands be- long to a more ancient epoch, and to them are limited, by a strictly defined boundary on each side, the dark pine forests which are so striking a feature of the country. On the still older chalk, again, the treeless prairie and flinty wheat country is as distinctly limited by the formations on either hand; and beyond this, again, the changed forests and cultivation of the higher country are determined by the change in nature and in age which the rocks of this region exhibit. * The word metamorphic here used means changed or altered — ^as clay, for example, is changed when it is baked into tiles or bricks. CHAPTER YII. Subdivisions of the tertiary, secondary, and primary groups of rocks. — Agricultural relations of the crag and London clay. — Fossil phosphates of the crag; quantity and value of these. — Soils of the London and plastic clays. — Of the chalk and green-sand. — Ware malt. — Clays of the "Weald and Lias. — Rich soils of the new red sandstone. — Contrast between those of the millstone grit and mountain limestone. — Soils of the Silurian, Cambrian, and Mica slate rocks. General conclusions as to the relations of geology to agriculture. But tlie several great groups of strata, of which we h'ave spoken under the names of primary, secondary, &c., are them- selves broken up or subdivided by geologists into a variety of subdivisions called systems and formations, each of which pos- sesses its peculiar mineral characters and special agricultural relations. These, in so far as relates to the geology of our own country, it will be proper briefly to indicate. SECTION I. THE TERTIARY STRATA. The tertiary strata, as they occur in England, consist chiefly of the crag, which lies above, and the Loudon and plastic clays, which follow each other underneath. 1. The Crag consists of a mass of rolled pebbles mixed with marine shells and corals, and resting upon beds of sand and marl. It is in places as much as 50 feet in thickness, though generally of less depth, and forms a strip of flat land, a few miles in width, along the eastern shores of Norfolk and Suffolk. The soil is generally fertile, but varies in value from 5s. to 25s. an acre of rent. This crag Ls chiefly interesting to the agriculturist from its NODULES OF PHOSPHATE OF LIME. 93 containing hard, rounded, flinty nodules — often spoken of as coprolitcs — in which as much as 50 per cent of phosphate of lime (bone-earth) is frequently found. These nodules are scattered through the body of the marls, and through the subsoils of the fields far inland, and are collected for sale to the manufacturers of super-phosphate of lime and other artificial manures. Some parties are said to have dug up as much as 60 or tO tons a-week.* 2. The London and j)lastic clays, from 500 to 900 feet thick, consist of stiff, almost impervious, dark-colored clays — the soils formed from which are still chiefly in pasture. The lower beds — the plastic clay — are mixed with sand, and produce an arable soil ; but extensive heaths and wastes rest upon them in Berk- shire, Hampshire, and Dorset. The crops of corn and roots yielded by the stiff clay soils of these strata have hitherto, in many districts, been found insufficieilt to pay the cost of raising them. The drain and the subsoil plough, with lime or chalk — ■ in which these clays are very deficient, and for the addition ol which they are very grateful — would render them more produc- tive and more profitable to the farmer. SECTION II. THE SECONDARY STRATA. 3. The Chalk, about 600 feet in thickness, lies below the Lon- don and plastic clays above described. It consists — as shown in the section No. 4 — in the upper part, of a purer chalk with * The cost of digging up, screening, cleaning, &c., of these nodules, is about 5s. a ton, and they are delivered on board the vessel at 30s. to 45s. The quantity of the fossils which is scattered over this part of the county, and the treasure they are now proving to the owners of the land, may be judged of from two facts stated by Mr. Herapath, {Jour. Royal Agric. Soc, xii. p. 93,) "that £60, £70, and £80, have been repeatedly given for leave to dig over a two-acre field;" and "that the land itself is actually improved by the course of treatment to which it is subjected when excavating for the fossils. 94 THE CHALK AXD GREEN-SAND. Suffolk. No. 4. Mouth of the Thames. Kent. 1. London clay. 2. Plastic clay. 3. Upper chalk, with flints. 4. Under chalk, without flints. layers of flint, (3) ; in the lower, of a marly chalk without flints, (4.) The soil of the upper chalk is chiefly in sheep- walks ; that of the lower chalk is very productive of corn. In some localities, (Croydon,) the arable soils of the upper chalk have lately been rendered much more productive in corn and beans by deep ploughing, and thus mixing with the upper soil as much as 6 or 8 inches of the inferior chalk. Excellent crops of carrots also have been obtained by deep-forking such land. The general and comparative agricultural value of the soils upon the chalk may, to a certant extent, be judged of by the fact, that, in the lowest-rented counties in England, chalk is the prevailing rock. 4. The Green-sand, 500 feet thick, consists of 150 feet of clay, with about 100 feet of a greenish, more or less indurated, sand above, and 250 feet of sand or sandstone below it. The upper sand forms a very productive arable soil ; but the clay forms impervious wet and cold lands, chiefly in pasture. The lower sand is generally unproductive. In the green-sand, both upper and lower, but especially in the upper, beds of marl occur, in which are found layers of so-called coprolites and other organic remains, rich in phosphate of lime. To the presence of these beds is ascribed the fertility of the soil of the upper green-sand, which in some localities is very remarkable, and, as at Farnham in Surrey, is found to be espe- cially favorable to the growth of hops. The organic remains are in some places so abundant, that, as in the crag, they are sought FERTILITY OF MIXED SOILS. 95 for and dug up, as a natural source of the phosphate of lime, usually supplied to the soil directly in the form of bones. It is an important agricultural remark, that where the plastic clay comes in contact with the top of the chalk, an improved soil is produced ; and that where the chalk and the green-sand mix, extremely fertile patches of country present themselves. The following imaginary section shows the relative positions of these two fertile strips of country, above and below the chalk. At the contact with the plastic clay it is particularly adapted for the growth of barley, which, for quality and malting proper- ties, is not excelled by any in the kingdom. In Essex, barley grown on this soil is principally sold to maltsters at Stortford, &c. ; and when malted, is sold again in London under the name of Ware malt. This name is derived from Ware in Hertford- shire, a market town standing on a similar soil. No. 5. "Wheat and hop land. Barley soils. .plastic Clay: Green- Sand. "'•--^^ Chalk. The soils at the contact of the chalk and upper green-sand are celebrated for their crops of wheat, in producing which the phosphates in the marls of the upper green-sand are supposed to have some infxuence, 5. The Weolden formation, which succeeds the green-sand, is nearly 1000 feet thick, and consists of 400 feet of sand, covered by 300 of clay, resting upon 250 of marls and limestones. The clay forms the poor, wet, but improvable pastures of Sus- sex and Kent. These clays, in many places, harden like a brick when dried in the air ; and clods which have lain long in the sun, ring, when struck, like a piece of pottery. By drain- ing alone, their produce has been raised from 16 to 40 bushels of wheat an acre. On the sands below the clay rest heaths and brushwood ; but where the marls and limestones come to 96 THE WEALDEN AND OXFORD CLAYS. the surface, the land is of better quality, and is susceptible of profitable arable culture. 6. In the U^per oolite, of 600 feet in thickness, we have a bed of clay (Kimmeridge clay) 50D feet thick, covered by 100 feet of sandy limestones. The clay lands of this formation are difficult and expensive to vrork, and are therefore chiefly in old pasture. The sandy limestone soils above the clay are also poor ; but where they rest immediately upon, and are inter- mixed with, the clay, excellent arable land is produced. 7. The Middle oolite, of 500 feet, consists also of a clay, (Oxford clay,) dark blue, adhesive, often rich in lime, and nearly 400 feet thick, covered by 100 feet of limestones and sandstones. These latter produce good arable land where the lime happens to abound, but the clays, especially while un- , drained, form close heavy compact soils, most difiBcult and ex- pensive to work. In wet weather they are often adhesive like bird-lime, and in dry summers become hard like stone, so as to require a pick-axe to break them. They have therefore hitherto . been very partially brought into arable culture. . The extensive pasture-lands of Bedford, Huntingdon, Northampton, liincoln, Wilts, Oxford, and Gloucester, rest chiefly upon this clay ; as do also the fenny tracts of Lincoln and Cambridge. ^The use of burned clay upon the arable land has, in some parts of this clay district, been of much advantage, 8. The Lower or Bath oolite, of 500 feet in thickness, con- sists of many beds of limestone and sandstone, with about 200 feet of clay in the centre of the formation. The soils are very various in quality, according as the sandstone or limestone pre- dominates in each locality. The clays are chiefly in pasture : the rest is more or less productive, easily worked, arable land. In Gloucester, Northampton, Oxford, the east of Leicester, and in Yorkshire, this formation is found to lie immediately beneath the surface, and a little patch of it occurs also on the south-eastern coast of Sutherland. 9. The Lias is an immense deposit of blue clay, from 500 to THE COAL MEASURES. 97 1000 feet in thickness, wliicli produces cold, blue, unproductive clay soils. It forms a long stripe of land, of varying breadth, which extends, in a south-western direction, from the mouth of the Tees, in Yorkshire, to Lyme Regis, in Dorset. It is chiefly in old, and often very valuable pasture. An efficient system of drainage will by-and-by convert much of this clay into most productive wheat land. 10. The New red sandstone, though only 500 feet in thickness, forms the surface of nearly the whole central plain of Eng- land, and stretches northwards through Cheshire to Carlisle and. Dumfries. It consists of red sandstones and red marls, the soils produced from which are easily and cheaply worked, and form some of the richest and most productive arable lands in the island. This is in some degree indicated by the fact that the three highest-rented counties in England rest chiefly upon this rock. In whatever part of the world the red soils of this formation have been met with, they have been found to possess in general the same valuable agricultural capabilities, 11. The Mag7iesian limestone, from 100 to 500 feet in thick- ness, is covered by a stripe of generally poor thin soil, extend- ing from Durham to Nottingham, capable of improvement as arable land by high farming, but bearing naturally a poor pas- ture, intermingled with sometimes magnificent furze. 12. The Coal measures, from 300 to 3000 feet thick, consist of beds of grey safndstone, and of dark blue shale, or har- dened clay, intermingled {inter-stratified) with beds of coal. Where the sandstones come to the surface, the soil is thin, poor, hungry, sometimes almost worthless. The shales, on the other hand, produce stiff, wet, almost unmanageable Mays — not un- workable, yet expensive to work, and requiring draining, lime, skill, capital, and a zeal for improvement to be applied to them, before they can be made to yield the remunerating crops of corn they are capable of producing. The blaes or shales of this formation, when dug out of cliffs or brought from coal- mines, may be laid with advantage on loose sandy soils, and 5 98 MILLSTONE GRIT. 600 feet or upwards in thick- It lies below the coal, but is sandstones and shales of the even, it is said, on the stiff whitish clays almost destitute of vegetable matter, which, as in Lanarkshire, occasionally occur on the surface of our coal-fields. 13. To the Millstone grit, of ness, the same remarks apply, often only a repetition of the coal measures, and forms in many cases soils still more worth- less. Where the sandstones prevail, large tracts lie naked, or bear a thin and stunted heath. Where the shales abound, the naturally difficult ^soils of the coal shales again recur. The rocks of this formation generally approach the surface, around the outskirts of our coal-fields. This arises from the circumstance that our coal measures often lie in basin-shaped deposits, from beneath each edge of which, the millstone grit and mountain limestone rocks rise up to the surface. This is illustrated by the annexed section, (No. 6,) across a part of Lancashire, in which 1 represents the coal measures ; 2 the coarse sandstones, &c. of the millstone grit ; 3 a thick shale-bed, which often overlies the thick masses of mountain limestone represented by 4. Boulsworth hill. 1689. The traveller passes off the poor, often cold and wet, clay soils of the coal measures, on to the equally poor lands of the millstone grit, and over its top, as at Pendle hill, descends upon the sweet herbage and rich dairy pastures of the moun- tain limestone at 4. The section shows also how in this country the millstone grit OLD RED SANDSTONE SOILS. 99 often rises into high hills. These are then covered with poor heaths and worthless moors, while limestone hills of equal height bear green herbage to the very top. 14. The Mountain limestone, 800 to 1000 feet thick, is a hard blue limestone rock, separated here and there into distinct beds by layers of sandstones, of s"andy slates, or of bluish-])lack shales like those of the coal measures. The soil upon the limestone is generally thin, but produces a naturally sweet herbage, everywhere superior in value to that which grows on the sandier soils of the millstone grit. When the limestone and clay (shale) adjoin each other, as where 3 and 4 in the section meet, arable land occurs, which is naturally productive of oats, and where the climate is favourable, may, by skilful treatment, be converted into good wheat land. In the north of England — in Derbyshire, for example, and among the York- shire dales — a considerable tract of country is covered by these rocks ; but in Ireland they form nearly the whole of the interior of the island. 15. The Old red sandstone varies in thickness from 500 to 10,000 feet. It possesses many of the valuable agricultural qualities of the new red,, (No. 10,) consisting, like it, of red sandstones and red marls, which -crumble down into rich red soils. Such are the soils of Brecknock, Hereford, and part of Monmouth ; of part of Berwick and Roxburgh ; of Hadding- ton and Lanark ; of southern Perth ; of either shore of the Moray Firth ; and of part of Sutherland, Caithness, and the Orkney islands. In Ireland, also, these rocks abound in Tyrone, Fermanah, and Monahan ; in Waterford, in Mayo, and in Tipperary. In all these, places the soils they form are generally the best in their several neighborhoods. Here and there, however, where the sandstones are harder, more silicious and impervious to water, tracts, sometimes extensive, of heath and bog occur ; while in others the rocks have crumbled into hun- gry sands, which swallow up the manure, and are expensive to maintain in arable culture. 100 THE PRIMARY STRATA SECTION III. THE PRIMARY STRATA. The primary stratified rocks, which lie underneath all those already described, are separable into three natural divisions ; the Silurian'^ above, which contain the remains of animals in a fossil state ; the Cambrian^ below, in which no animal remains have yet been discovered ; and, lowest of all, the mica slate and gneiss rocks, which exhibit marks of change or alteration by tlie agency of heat. Hence these last are ofteu spoken of as metamoi-'phic, or changed rocks. 16. The Upper Silurian system is nearly 4000 feet m thick- ness, and forms the soils which cover the lower border counties of Wales. It consists of sandstones and shales, with occasional limestones ; but the soils formed from these beds take their character from the general abundance of the clay. They are cold — ^^usually unmanageable muddy clays ; with the remarkably inferior agricultural value of which the traveller is immediately struck, as he passes westward from the red sandstones of Hereford to the Upper Silurian rocks of the county of Radnor. It. The Loiver Silurian rocks are many thousand feet in thickness, and in Wales lie to the west and north of the Upper Silurian rocks. They consist, on the upper part, of about 25,000 feet of sandstone, on which, when the surface is not naked, barren heaths alone rest. Beneath these sandstones lie 1200 feet of sandy and earthy limestones, from the decay of which, as may be seen on the soutliern edge of Caermarthen, fertile arable lands are produced. The high land, which stretches across the whole of southern Scotland, from St. Abb's head to Portpatrick, including the Lammermuir hills, so far as they have yet been examined, con- sists of strata belonging to the upper part of the Lower Silu- rian, and the lower part of the Upper Silurian. The soils in * Or older Falaiozoic, as containing evidences of most ancient life. f Or Azoic, from containing no traces of life. CAMBRIAN SYSTEM, MICA SLATE, AND GNEISS. 101 general are of inferior quality, the slaty rocks crumbling with difficulty, and being poor in lime. Cold and infertile farms cover the higher grounds, and wide heathy moors and bogs. 18. The Cambrian system — meaning by this term unaltered rocks, containing no fossils — is at present a subject of dispute among geologists, and its limits even in our own island are not well defined. It is probably many thousand feet in thickness — lies beneath the Lower Silurian — and in its agricultural re- lations has much resemblance to these rocks. It consists in great part of slaty rocks, more or less hard, which often crum- ble very slowly, and almost always produce either poor and thin soils — or cold, difficultly manageable clays, expensive to work, and requiring high farming to bring them into profitable arable cultivation. In Cornwall, western Wales, the mountains of Cumberland ; in the mountains of Tippejary, in the extreme south of Ireland, on its east coast, and far inland from the bay of Dundalk, such slaty rocks occur, though the limits of the two formations have not been everywhere defined. Patches of rich, well-cultivated land occur here and there in these districts, with much also that is improvable ; but the greater part is usurped by worthless heaths and extensive bogs. On the dif- ficult soils of those formations — thinly peopled, inhabited by small farmers with little capital^ and therefore hitherto neglected • — much improvement is now here and there appearing ; and the introduction of the drain promises to make much corn grow, where little food, either for man or beast, was previously produced. These rocks in general contain little lime, and therefore, after the drain, the addition of lime is usually one of the most certain means of increasing the productiveness of the soils formed from them. 19. The Mica • slate and Gneiss systems are of unknown thickness, and consist chiefly of hard and slaty rocks, crumb- ling slowly, forming poor, thin soils, which rest on an imper- vious rock, and which, from the height to which this formation generally rises above the level of the sea, are rendered more 102 GENERAL CONCLUSIONS. unproductive by an unpropitious climate. They form extensive heathy tracts in Perth and Argyle, and on the north and west of Ireland. Here and there only — in the valleys or sheltered slopes, and by the margins of the lakes — spots of bright green meet the eye, and patches of a willing soil, fertile in corn. SECTION IV. GENERAL CONCLUSIONS AS TO THE RELATIONS OF GEOLOGY TO AGRICULTURE. A careful perusal of the preceding sketch of the general agricultural capabiUties of the soils formed from the several classes of stratified rocks, will have presented to the reader many illustrations of the facts stated in the previous chapter. He will have drawn for himself — to specify a few examples — the following among other conclusions : — 1. That some formations, like the new red sandstone, yield a soil almost always productive ; others, as the coal measures and millstone grits, a soil almost always naturally itnproduct- ive ; and others, again, like the mountain limestones, a short sweet herbage, grateful to cattle, and productive of butter and cheese. 2. That good — or better land, at least, than generally pre- vails in a district — may be expected where +wo formations, or two different kinds of rock, meet. As when a limestone and a clay mingle their mutual ruins for the formation of a com- mon soil.* 3. That in almost every country extensive tracts of land, on certain formations, will be found laid down to natural grass, in consequence of the original difficulty and expense of working. Such are the Lias, the Oxford, the Weald, the Kimmeridge, and the London clays. In raising corn, it is natural that the lands which are easiest and cheapest worked should be first sub- jected to the plough. It is not till implements are improved, skill increased, capital accumulated, and population presses, that * See diagram No. 5, p. 95. ROTATIONS OFTEN PRESCRIBED BY THE SOIL. 103 the heavier lands in a country are rescued from perennial grass, and made to produce that greatly increased amount of food for both man and beast, which they are easily capable of yielding. 4. That the rotations adopted in a district, though faulty, and, in the eyes of improved agriculture, deserving of condem- nation, are often not only determined, but rendered necessary by the natm'al structure of the country. When cold clays re- fuse to bear even average crops of any other kinds than wheat and beans, the old European rotation of wheat, beans, fallow — which in this country has prevailed, in many places, since the times of the ancient Britons — becomes almost a necessity to the farmer. It is unfair to blame his rotations, or accuse him of prejudice and ignoranc.e in clinging to them, till the natural condition of the land has been altered by art, so as to fit it for the profitable growth of other crops. The turnip and barley soils of Great Britain are in many dis- tricts, it may be, but indifferently farmed; and the State has reason to complain of much individual neglect* of known and certain methods of increasing their productiveness. But the great achievement which British agriculture has now to effect, is to subdue the stuhhorn clays, and to convert them into, what many of them are yet destined to become, the richest corn and grecn-crojp bear- ing lands in the kingdom. 5. That there are larger tracts of country still — such as rest on the slates of the Lower Silurian and Cambrian systems, for example — from which the efforts of the enlightened agriculturist have hitherto been withheld, in consequence of the apparent hopelessness of ever bringing them into profitable culture. Over these tracts, however, there are large portions which will pay well for skilful improvement. Make roads and drains, bring in lime, and manure well. You will thus improve the soil, gradu- ally ameliorate the climate, make modern skill and improvements available, obtain a remunerating return for labor economically expended, and for capital judiciously invested, and you will at the same time increase the power and the resources of the country. CHAPTER YIII. Poor soils of the granites and fertile soils of the trap rocks, and of the modem lavas. — Composition of felspar and hornblende. — Accumulations of trans- ported sands, gravels, and clays. — Their influence on agricultural capa- bility. — Illustration from the neighborhood of Durham. — Importance of surface or drift geology to agriculture. — General uniformity in the agri- cultural character of the rocks and soils on geological formations of the same age. — Exceptions among the Silurian rocks. — Use of geological maps in reference to agriculture. It was stated in a preceding chapter that rocks are divided by geologists into the stratified and the unstratijied.^ The stra- tified rocks cover by far the largest portion of the globe, and form the great fariety of soils, of which a general description has just been given. The nnstratified rocks are of two kinds — • the granites and the trap rocks ; and as a considerable portion of the area, especially of the northern half, of our island is covered by them, it will be proper shortly to consider the peculiar char- acters of each, and the diiferences of the soils produced from them. SECTION I. POOR SOILS OF THE GRANITES, AND FERTILE SOILS OF THE TRAP ROCKS AND MODERN LAVAS. 1. The Ch-anites consist of a mixture, in different proportions, of three minerals, known by the names of quartz, felspar, and mica. The latter, however, is generally present in such small quantity, that in our general description it may be safely left * The nnstratified are often called crystalline rocks, because they fre- quently have a glassy appearance, or contain regular crystals of certain mineral substances ; often also igneoiis rocks, because they appear all to have been originally in a melted state, or to have been produced by fire. POOR GRANITE SOILS. 105 out of view. Granites, therefore, consist chiefly of quartz and felspar, in proportions which vary very much; but the former, on an average, constitutes perhaps from one-third to one-half of the whole. Quartz has already been described as being the same sub- stance as flint, or the silica of the chemist. When the granite decays, this portion of it forms a more or less coarse silicious sand. Fdsjpar is a white, greenish, or flesh-colored mineral, often more or less earthy in its appearance, but generally hard and brittle, and sometimes glassy. It is scratched by quartz, and thus is readily distinguished from it. When felspar decays, it forms an exceedingly fine tenacious clay, (pipe-clay.) Granite generally forms hills, and sometimes entire ridges of mountains. When it decays, the rains and streams wash out the fine felspar clay, and carry it down into the valleys, leaving the quartz sand on the sides of the hills. Hence the soil in the bottoms and flats of granite countries consists of a cold, stiff, wet, more or less impervious clay, which, though capable of much improvement by draining, often" bears only heath, bog, or a poor and un-nutritive pasture. The hill sides are either bare, or are covered with a thin, sandy, and ungrateful soil, of which little can be made without the application of much skill and industry. Yet the opposite sides of the same mountains often present a remarkable difference in this respect; those which are most beaten by the rains having the light clay most thoroughly washed from their surfaces, and being therefore the most sandy and barren. 2. The T'rajp rocks, comprising the green-stones and basalts — both sometimes called whin-?>iowQ& — consist essentially* of felspar and hornblende or augite. In contrasting the trap rocks with the granites, it may be stated generally, that while the granites * The reader is referred for more precise information to the Author's "Lectures," 2d edition. 5* 106 COMPOSITION OF FELSPAR AND HORNBLENDE. consist of felspar and quartz, the traps consist of felspar and hornblende (or augite.) In the traps, both the felspar and the hornblende are reduced, by the action of the weather, to a more or less fine powder, affording materials for a soil ; in the granites, the felspar is the principal source of the fine earthy matter they are capable of yielding. If we compare together, therefore, the chemical composition of the two minerals, (hornblende and fel- spar,) we shall see in what respect these two varieties of soil ought principally to differ. Thus they consist respectively of — Felspar. Hornblende. Silica, 65 42 Alumina, 18 14 Potash and soda, 1*7 trace. Lime, ... trace. 12 Magnesia, do. 14 Oxide of iron, do. 14i Oxide of manganese, do. k 100 91 A remarkable difference appears thus to exist, in chemical composition, between these two minerals — a difference which must affect also the soils produced from them. A granite soil, in addition to the silicious sand, will consist chiefly of silica, alu- mina, and potash, derived from the felspar, A trap soil, in addi- tion to the silica, alumina, and potash from its felsj)ar, will generally contain also much lime, magnesia, and oxide of iron, derived from its hornblende. If the variety of trap consist chiefly of hornblende, as is sometimes the case, the soil formed from it will derive nearly 2i- cwt. each of lime, magnesia, and oxide of iron, from every ton of decayed rock. A hornblende soil, therefore, contains a greater number of those inorganic substances which plants require for their healthy sustenance, and, therefore, will prove more generally productive than a soil of decayed felspar. But when the two minerals, hornblende and felspar, are mixed together, as they are in the variety of trap called green-stone, the soil formed from them must be still more FERTILITY OF TRAP AND GREEN-STONE SOILS. 107 favorable to vegetable life. The potash and soda, of which the horubleiide is nearly destitute, is abundantly supplied by the fel- spar ; while the hornl)lende yields lime and magnesia, which are known to exercise a remarkable influence on the progress of vegetation. This chemical knowledge of the nature and differences of .the rocks from which, the granite and trap soils are derived, explains several interesting practical observations. Thus it shows — a. That while granite soils, in their natural state, may be eminently unfruitful, trap soils may be eminently fertile ; and such is actually the result of observation and experience in every part of the globe. Unproductive granite soils cover nearly the whole of Scotland, north of the Grampians, as well as large tracts of land in Devon and Cornwall, and on the east and west of Ireland. On the other hand, fertile trap soils extend over thousands of square miles in the lowlands of Scotland, and in the north of Ireland ; and where in Cornwall they occasionally mix with the granite soils, they are found to redeem the latter from their natural barrenness. But while such is the general rule in regard to these two classes of soils, it happens on some spots that the presence of other minerals in the granites, or of hornblende or mica in larger quantity than usual, gives rise to a granitic soil of average " fertility, as is the case in the Scilly Isles. In like manner, the trap rocks are sometimes, as in parts of the Isle of Skye, so- peculiar in their composition as to condemn the land to almost hopeless infertility. h. Why in some districts the decayed traps, under the local names of Rotten rock, Marl, kc, are dug up, and applied with advantage, as a top-dressing, to other kinds of land. They afford supplies of lime, magnesia, &c., of which the soils they are found to benefit may be naturally deficient. And as, by admixture with the decayed trap, the granitic soils of Cornwall are known to be improved in quality, so an admixture of decayed 108 LIMING OF TRAP SOILS. granite with many trap soils, were it readily accessible, might add to the fertility of the latter also. c. Why the application of lime in certain trap districts adds nothing to the fertility of the land. The late Mr. Oliver of Lochend informed me that he had never known a case in which the application of lime within five miles of Edinburgh had done any good. This he accounted for from the vast number of oyster shells which are mixed with the town dung laid on by the Edinburgh farmers. Another important reason, however, is the abundance of lime contained in the trap rocks from which the soils are formed, and of which they contain so many fragments. A piece of decaying trap I lately picked up on the north side of the Pentland hills, on the farm of Swanstone, was found in my laboratory to contain as much as 16 per cent of carbonate of lime. d. Why, as in many parts of the counties of Ayr and Eife, the application of lime is found to be useful when the trap soils are first broken up or reclaimed, but to produce little sensible benefit for twenty or thirty years afterwards, however frequently applied. In these cases the lime has been washed out of .the surface soil, and from the thoroughly decayed parts of the trap, so that, when first broken up, lime is necessary to supply the deficiency. But the constant turning up of the soil by the after- cultivation exposes fresh portions of trap to the air, the decay of which annually supplies a quantity of lime to the soil from the rocky fragments themselves, and renders further artificial appli- cations less necessary. I have picked up a piece of decaying trap, of which the outer portion contained scarcely any lime, while the central kernel contained a large proportion. The plough and harrow break up such decaying masses, and expose the undecomposed kernels to the weathering action of the atmo- sphere, and to the roots of the growing crops. 3. The Lavas which often cover large tracts of country, where active or extinct volcanoes exist, are composed essentially of the same mineral substances as the trap rocks. These latter, indeed, APPARENT DIFFICULTIES. 109 are in general only lavas of a more ancient date. Like the traps, the lavas not unfrequently abound in hornblende or augite, and consequently in lime. They also crumble, with various degrees of rapidity, when exposed to the air, and in Italy and Sicily often form soils of the most fertile description. Like the traps also, when in a decayed state, they may be advantageously employed for the improvement of less fruitful soils. In St. Michael's, one of the Azores, the natives pound the volcanic matter and spread it on the ground, w^here it speedily becomes a rich mould, capable of bearing luxuriant crops. SECTION II. OF THE SUPERFICIAL ACCUMULATIONS OF TRANSPORTED MATERIALS ON DIFFERENT PARTS OF THE EARTH's SURFACE, AND THEIR RELATIONS TO THE SOIL. It is necessary to guard the reader against disappointment when he proceeds to examine the relations which exist between the soils and the rocks on which they lie, or to infer the quality of the soil from the known nature of the rock on which it rests — ^in conforpiity with what has been above laid down — by ex- plaining another class of geological appearances, which present themselves not only in our own country, but in almost every other part of the globe. The unlearned reader of the preceding section and chapter may say — I know excellent land resting upon the granites, fine turnip soils on the Oxford or London clays, tracts of fertile fields on the coal measures, and poor gravelly farms on the boasted new red sandstone : I have no faith in theory — I can have none in theories which are so obviously contradicted by natural ap- pearances. Such, it is to be feared, is the hasty mode of rea- soning among too many locally* excellent practical men — * By locally excellent, I mean those who are the best possible farmers on their own districts and after their own way, but who would fail in other districts requiring other methods. To the possessor of agricultural princi- ples, the modifications required by difference of crop, soil, and cUmate, 110 ' LOOSE, TRANSPORTED MATERIALS. familiar, it may be, with many useful and important facts, but untaught to look through and beyond isolated facts to the principles on which they depend. Every one who has lived long on the more exposed shores of our island, has seen that, when the weather is dry, and the sea- winds blow strong, the sands of the beach are carried inland and spread over the soil, sometimes to a considerable distance from the coast. In some countries this sand-drift takes place to a very great extent, travels over a great stretch of country, and gradually swallows up large tracts of fertile land, and converts them into sandy deserts. Again, most people are familiar with the fact, that during periods of long continued rain, when the rivers are flooded and overflow their banks, they not unfrequently bear with them loads of sand and gravel, which they carry far and wide, and strew at intervals over the surface soil. So the annual overflowings of the Nile, the Ganges, the Mis- sissippi, and the river of the Amazons, gradually deposit accu- mulations of soil over surfaces of great extent ; — and so also the bottoms of most lakes are covered with thick beds of sand, gravel and clay, which have been conveyed into them from the higher grounds by the rivers which flow into them. Over the bottom of the sea also, the ruins of the land are spread. Torn by the waves from the crumbling shore, or carried down from great distances by the rivers which lose themselves in the sea, they form beds of mud, or banks of sand and gravel of great extent, which cover and conceal the rocks on which they lie. To these and similar agencies, a large portion of the existing dry land of the globe has been, and is still, exposed. Hence, in many places, the rocks and the soils naturally derived from them are buried beneath accumulated heaps of layers of sand, gravel, and clay, which have been brought from a greater or less distance, and which have not unfrequently been derived readily suggest themselves, where the mere practical man is bewildered, disheartened, and in despair. CIRCUMSTANCES TO BE CONSIDERED. Ill from rocks of a totally different kind from those of the districts in which they are now found. On these accumulations of trans- ;ported materials, a soil is produced which often has no relation in its characters to the rocks v.hich cover the country, and the nature of which soils, therefore, a familiar acquaintance with the rocks on which they immediately rest would not enable us to predict. To this cause is due that discordance between the first indi- cations of geology, as to the origin of soils from the rocks on which they rest, and the actually observed characters of those soils in certain districts — of which discordance mention has been made as likely to awaken doubt and distrust in the mind of the less instructed student, in regard to the predictions of agricul- tural geology. There are several circumstances, however, by which the careful observer is materially aided in endeavoring to understand what the nature of the soils is likely to be in any given district, and how they ought to be treated even when the subjacent rocks are thus overlaid by masses of drifted materials. Thus— 1. It not unfrequently happens that the materials brought from a distance are more or less mixed up with the fragments and decayed matter of the rocks which are native to the spot, — so that, though modified in quality, the soil nevertheless retains the general characters of that which is formed in other places from the decay of these rocks alone. 2. Where the formation is extensive, or covers a large area, — as the new red sandstones and coal measures do in this coun- try, the mountain limestones in Ireland, and the granites in the north of Scotland, — the transported sand, gravel, or clay, strewed over one part of the formation, has not unfrequently been derived from the rocks of another part of the savie for- mation ; so that, after all, the soils may be said to be produced from the rocks on which they rest, and may be judged of from the known composition of these rocks. 3. Or if not from the rocks of the same formation, they 112 SOILS OVERLAP THEIR NATURAL LIMITS. have most frequently been derived from those of a neighboring formation — from rocks which are to be found at no great distance, geologically, and generally on higher ground. Thus the ruins of the millstone-grit rocks are in this country often spread over the surface of the coal measures — of these, again, over the magnesian limestone — of the latter over the new red sand- stone, and so on. The effect of this kind of transport of the loose materials upon the character of the soils is merely to overlap, as it were, the edges of one formation with the proper soils of the formations that adjoin it, in the particular direction from which the drifted materials are known to have come. It appears, therefore, that the occurrence on certain spots, or tracts of country, of soils that have no apparent relation to the rocks on which they immediately rest, tends in no way to throw doubt upon, to discredit or to disprove, the conclusions drawn from the more general facts and principles of geology. It is still generally true that soils are derived from the rocks on which they rest. The exceptions are local, and the difficulties which these local exceptions present, require only from agricul- tural geologists a more careful study of the structure of eacji district — of the direction of the highlands — the nature of the slopes — the course and width of the valleys — and the extent of the plains, — before they pronounce a decided opinion as to the degree of fertility which the soil either naturally possesses, or by skilful cultivation may be made to attain. ^ It is not to be denied, however, that the practical importance of these local exceptions is becoming every day more manifest, and the necessity more apparent for a careful recording and mapping of them in the interests of agriculture. Riding over the country, for example, due north from the city of Durham, a distance of about three miles, till we are stopped by a bend of the river Wear, the superficial covering, so far as it can be seen, is represented by the subjoined section. DRIFT COVERING NEAR DURHAM. 113 No. 7. Red Hills Bishop's Grange. 1. Yellow unstratiSed hard clay with small stones and boulders, forming cold impervious clay soils, 3 to 40 feet. 2. Yellow sand, loose, with fragments of drifted coal and sandstone gravel and boulders, forming potato, barley, and light turnip soils, 10 to 100 feet. 3. Blue unstratified clay, with boulders — often wanting — 10 to 30 feet. 4. The coal measures lying beneath. All the country being covered, as this section represents, with from 30 to 120 feet of superficial sands and clays, it is obvious that it can be of comparatively little use to me to know that the sandstones and shales of the coal measures lie far below ; and though I know that the sands and clays are all derived from the crumbled beds of the coal measures, yet they give me no information respecting the sandy nature of the soils near Kimblesworth, or that they are cold and clayey about Bishop's Grange. The nature of the soil in each portion of the district — and the same is true of a large portion of the county of Durham — depends upon whether the clay or the sand comes to the surface. This can only be shown upon special maps, rig- orously prepared for the purpose ; and these the progress of scientific agriculture will soon render indispensable. SECTION III. GENERAL UNIFORMITY IN THE AGRICULTURAL CHAR- ACTER OF THE ROCKS AND SOILS ON GEOLOGICAL FORMATIONS OF THE SAME AGE. And yet there is a wonderful degree of general uniformity in 114 UNIFORMITY IN THE AGRICULTURAL CHARACTER the mineral character and agricultural capabilities of the same geological formation in different countries, even when they lie at great distances from each other. I have already alluded, for example, in a preceding chapter,* to the natural dryness of the belt of chalk which runs along the Atlantic border of the United States. The scarcity of water experienced by those who reside upon it is often great. Every one knows that the same is true of our own chalk region in England, and that this very materially affects its agricultural capabilities. It is famil- iar to every one also, that in very many places wells are sunk through it with the view of reaching water, and that in London great depths are gone to, and at a vast expense, through the London clay and the chalk, before water can be obtained. In the Paris basin the chalk is equally dry ; and there are very few who have not read of the remarkably deep w^ell at Grenelle in the neighborhood of Paris, which, like the less profound London wells, has been sunk to the sands below the chalks, and with similar success. So, in the remote State of Alabama, on this formation, water is only to be obtained by sinking through the chalk ; and there also this circumstance modifies in a wonderful degree the gene- ral dispositions of rural economy. Three years ago there were already about 500 wells in that State, sunk to a depth of from 400 to 600 feet, there being one generally upon each i^lantatiou. And thus, while the climate there, as elsewhere, determines the general character of the vegetable produce, and what kind of plants under the meteorological conditions can arrive at perfec- tion, yet the geological structure determines, and enables us to judge beforehand, to a certain extent, whether or not any crops shall be able to grow at all, and of the kind of plants suitable to the climate, which can be profitably cultivated, under the circumstances of soil and dryness, which that geological structure implies. * See the diagram in p. 91. OF SOILS OF THE SAME FORMATION. 115 I may here remark, that, in this case of Alabama, the geo- logical structure determines more. In such a climate, and with a soil so naturally arid, abundant water is indispensable ; but this can only be obtained by deep boring, performed at a great expense. The geological conditions, therefore, confine the pos- sibility of cultivation to men of large means, and, in present circumstances at least, necessarily exclude all petty farming and the subdivision of the land into small holdings. They deter- mine, in other words, the social condition of the people. This single illustration is enough of itself to satisfy any impartial person of the close general relation which exists between the geological character and the agricultural capability of a coun- try, and of the broad general deductions in regard to its possible future prosperity — in a rural sense — which may be drawn from a knowledge of its geology. I believe it is partly under the influence of this conviction that the Senate and Congress of the United States have so often and so cordially voted large sums of money for the purpose of investigating and mapping the main geological features of the new States and territories which from time to time have been admitted into the Union. Geological majps, such as those now referred to, indicate with more or less precision the extent of country over which the chalk, the red sandstone, the granites, &c., are found immedi- ately beneath the loose materials on the surface. Such maps, therefore, are of great value in indicating also the general qual- ity of the soils over the same districts. It may be true, as I have above explained, that here and there the natural soils are masked or buried by transported materials — yet the 'political economist may, nevertheless, with safety estimate the general agricultural capabilities and resources of a country by the study of its geological structure — the capitalist judge in what part of it he is likely to meet with an agreeable or profitable investment — and the practical farmer in what country he may expect to find land that will best reward his labors, that will admit of the kind of culture to which he is most accustomed, or, by the 116 GEOLOGY NOT PERFECT. application of better methods, will manifest the greatest agri- cultural improvement. There are many cases also in which geology, leaving the hum- bler task of explaining why certain regions exhibit, or are capa- ble of exhibiting, singular natural fertility, or the reverse, advances to the higher gift of prediction. United theory and observation enable it not only to point out where rich and desirable lands are sure to be found — to inform the statesman as to the true value of regions still wild and neglected — to direct the agricultural emigrant in the choice of new homes — but looking far into the future, to specify also the kind of popu- lation and the processes of industry which will hereafter prevail upon it — the comparative comfort, wealth, numbers, and even morality, of its future people. That there are certain cases in which geology finds herself at fault, or her general deductions unsupported by the reality, is only a proof that it is a part of human science, rapidly pro- gressive, but still full of imperfections. CHAPTER IX. Of the physical, chemical, and botanical relations of soils. — Physical proper- ties. — Density, absorbent, and evaporative powers, capillary action, shrinkage, absorption of moisture from the air, and of heat from the sun. — Functions of soils in reference to vegetation. — Chemical composition and analysis of soils. — Comparative composition of certain fertile and barren soUs. — Importance of certain forms of organic matter to the fertility of a soil. — The black earth of central Russia. — Direct relation between the character of the soil and the kind of plants that naturally grow upon it. Soils formed, as we have described, from the ruins of crumb- led rocks, more or less sorted and drifted by water, possess three classes of properties, intimately related to each other, and to their special agricultural value. These are their phy- sical, chemical, and botanical properties. A brief consideration of these will form the subject of the present chapter. SECTION I. OF THE PHYSICAL PROPERTIES OF SOILS. 1°. Density. — Some soils are heavier and denser than others, sands and marls weighing most and dry peaty soils the least. This density is of so much practical importance, that treading with sheep and other stock is resorted to in many districts, with the view of rendering the land more solid ; or heavy rollers are passed over it, to prepare a firm seed-bed for the corn. Also, in reclaiming peaty soils, it is found highly bene- ficial to increase their density by a covering of clay or sand, or, 'as in Ireland, of limestone gravel. 2°. Absorption of water. — Again, some soils absorb the rains that fall, and retain them in larger quantity and for a longer period than others. Strong clays absorb and retain nearly three times as much water as sandy soils do, while peaty 118 PHYSICAL PROPERTIES OF SOILS. soils absorb a still larger proportion. Hence the more fre- quent necessity for draining clayey than sandy soils ; and hence also the reason why, in peaty land, the drains must be kept carefully open, in order that the access of springs and of other water from beneath may be as much as possible prevented. 3°. The ca/pillary action of soils also differs. Some, when immersed in water, will become moist, or attract the water upwards for 10 or 12 inches, some as many as 16 or 18 inches, above the surface of the water. This property is of great importance in reference to the growth of plants — to the rising of water to the surface of land which rests upon a wet subsoil — to the necessity for thorough drainage — to the general warmth of the soil, and so on. 4°. Evaporative jtoioer. — When dry weather comes, soils lose water by evaporation with different degrees of rapidity. In this way a silicious sand will give off the same weight of water, in the form of vapor, in one-third of the time necessary to evaporate it from a stiff clay, a peat, or a rich garden mould, when all are equally exposed to the air. Hence the reason why plants are so soon burned up in a sandy soil. Not only do such soils retain less of the rain that falls, but that which is retained is also more speedily dissipated by evaporation. When rains abound, however, or in very moist seasons, these same properties of sandy soils enable them to dry quickly, and thus to sustain a luxuriant vegetation at a time when plants will perish on clay lands from excess of moisture. 5°. Shrinkage. — In drying under the influence of the sun, soils shrink in, and thus diminish in bulk, in proportion to the quantity of .clay or of peaty matter they contain. Sand scarcely diminishes at all in bulk by drying, but peat shrinks one-fifth in bulk, and strong agricultural clay nearly as much. The roots are thus compressed and the air excluded from them, especially in the hardened clays, in very dry weather, and thus the plant is placed in a condition unfavorable to its growth. Hence the value of proper admixtures of sand and clay. By TEMPERATURE OF A SOIL. 119 the latter (the clay) a sufficient quantity of moisture is re- tained, and for a sufficient length of time ; while by the former the roots are preserved from compression, and a free access of the air is permitted. 6°. Ahsorjption of moisture from the air, — In the hottest and- most drying weather, the soil has seasons of respite from the scorching influence of the sun. During the cooler season of the night, even when no perceptible dew falls, it has the power of again extracting from the air a portion of the moisture it had lost during the day. Perfectly pure sand possesses this power in the least degree ; it absorbs little or no moisture from the air. A stiff day, on the other hand, ivill, in a single night, absorb sometimes a ZOth part of its own weight, and a dry peat as much as a 12th of its weight ; and, generally, the quan- tity thus drunk in, by soils of various qualities, is dependent upon the proportions of clay and vegetable m.atter they seve- rally contain. We cannot fail to perceive from these facts, how much the productive capabilities of a soil are dependent upon the proportions in which its different earthy and vegetable constituents are mixed together. ^^. The temperature of a soil, or tlie degree of warmth it is capable of attaining under the influence of the sun's rays, materially afi*ects the progress of vegetation. Every gardener knows how much bottom heat forces the growth, especially of young plants ; and wherever a natural warmth exists in the soil, independent of the sun, as in the neighborhood of vol- canoes, there it exhibits the most exuberant fertility. One main influence of the sun in spring and summer is dependent upon its power of thus warming the soil around the young roots, and rendering it propitious to their rapid growth. But the sun does not warm all soils alike — some become much hotter than others, though exposed to the same sunshine. When the temperature of the air in the shade is no higher than 60°, or 70°, a dry soil may become so warm as to raise the thermometer to 90° or 100°. Mrs. Ellis states, that among 120 INFLUENCE OF THE SUN. the Pyrenees the rocks actnally smoke after rain, under the influence of the summer sun, and become so hot that you can- not sit down upon them. In Central Australia, where the thermometer is sometimes as high as 132° F. in the shade, and 15*1° in the sunshine, the ground becomes so hot that it kindles matches that fall on it, and burns the skin off the dogs' feet. In wet soils the temperature rises more slowly, and rarely attains the same height as in a dry soil by 10° or 15°. Hence it is strictly correct to say, that wet soils are cold ; and it is easy to understand how this coldness is removed by perfect drainage.* Dry sands and clays, and blackish garden mould, become warmed to nearly an equal degree under the same sun ; brownish-red soils are heated somewhat more, and dark-colored peaty soils the most of all. It is probable, therefore, that the presence of dark-colored vegetable matter renders the soil more absorbent of heat from the sun, and that the color of the dark-red marls of the new and old red sandstones may, in some degree, aid the other causes of fertility in the soils which they produce. * In reading the above observations, the practical reader can hardly fail to have been struck with the remarkable similarity in physical properties between stiff clay and peaty ^oils. Both retain inuch of the water that falls in rain, and both part with it slowly by evaporation. Both contract much in drying, and both absorb moisture readily from the air, in the absence of the sun. In this similarity of properties we see not only why the first steps in improving both kinds of soil must be very nearly the same, but why, also, a mixture either of clay or of vegetable matter will equally impart to a sandy soil many of those elements of fertility — of which they are alike possessed. * See the succeeding Chapter. CHEMICAL COMPOSITION AND ANALYSIS OF SOILS. 121 SECTION II. OF THE CHEMICAL COMPOSITION AND ANALYSIS OF SOILS. Soils perform at least three functions in reference to vege- tation. They serve as a basis in which plants may fix their roots and sustain themselves in their erect position — they supply food to vegetables at every period of their growth — and they are the medium in which many chemical changes take place, that are essential to a right preparation of the various kinds of food which the soil is destined to yield to the growing plant. We have spoken of soils as consisting chiefly of sand, lime, and clay, with certain saline and organic substances in smaller and variable proportions. But the study of the ash of plants (see chap, iv.) shows us that a fertile soil, besides its organic matter, must of necessity contain an appreciable quantity of twelve or fourteen different mineral substances, which, in most cases, exist in greater or less relative abundance in the ash both of wild and of cultivated plants. Two well-known geological facts lead to precisely the same conclusion. We have seen that the soils formed from the un- stratified rocks — the granites and the- traps — while they each contain certain earthy substances in proportions peculiar to themselves, yet contain also in general, especially the trap soils, a trace, of most of the other kinds of matter which are found in the ash of plants. Again, it is equally certain that the stratified rocks are only the more or less slowly accumu- lated fragments and ruins of more ancient stratified or unstra- tified masses, which, under various agencies, have gradually crumbled to dust, been strewed over the surface in alternate layers, and have afterwards again consolidated. The reader will readily grant, therefore, that in all rocks, and consequently in all soils, traas of every one of these substances may gene-* rally be presumed to exist. 6 122 GENERAL COMPOSITION OF SOILS. Actual cJmnical analysis confirms these deductions in regard to the composition of soils. It shows that, in most soils, the presence of all the constituents of the ash of plants may be de- tected, though in very variable and sometimes in very minute proportions ; and, following up its investigations in regard to the effect of this difference in their proportions, it establishes certain other points of the greatest possible importance to agri- cultural practice. Tims, it has found, for example — 1. That as a proper adjustment of the proportions of clay, sand, and vegetable matter, is necessary in order that a soil may possess the most favorable ^physical properties, so the mere presence of the various kinds of food, organic and inor- ganic, in a soil, is not sufficient to make it productive of a given crop, but that they must be present in such quantity that the plant shall be able readily — at the proper season, and within tlie time usually allotted to its growth — to obtain an adequate supply of each. Thus a soil may contain, on the whole, far more of a given ingredient, such as potash, soda, and lime, than the crop we have sown may require, and yet, being diffused through a large quantity of earth, the roots may be unable to collect this sub- stance fast enough to supply the wants of a rapidly growing plant. To such a soil it will be necessary tc add a further por- tion of what the crop requires. Again, a crop of winter wheat, which remains nine or ten months in the field, has much more leisure to collect from the soils those substances which are necessary to its growth than a crop of barley, which in cold climates like that of Sweden is only from 6 to 7| weeks in the soil, and which in warm countries like Sicily may be reaped twice in the year. Thus a soil which refuses to yield a good crop of the quick-growing barley may readily nourish a crop of slow-growing wheat. 2. That when a soil is particularly poor in certain of these substances, the valuable cultivated corn crops, grasses, and USE OF CHEMICAL ANALYSIS TO AGRICULTURE. 123 trees, refuse to grow upon them in a healthy manner, and to yield remunerating returns. And, 3. That when certain other substances are present in too great abundance, the soil is rendered equally unpropitious to the most important crops. In these facts the intelligent reader will perceive the founda- tion of the varied applications to the soil which are everywhere made under the direction of a skilful practice — and of the diffi- culties which, in many localities, lie in the way of bringing the land into such a state as shall fit it readily to supply all the wants of those kinds of vegetables which it is the special ob- ject of artificial culture easily and abundantly to raise. Chemical analysis is a difficult art — one which demands much chemical knowledge, as well as skill in chemical practice; (manipulation, as it is called,) and calls for both time and per- severance — if valuable, trustworthy, and minutely correct results are to be obtained. I believe it is only by aiming after such minutely correct results that chemical analysis is likely to throw light on the peculiar properties of those soils which, while they possess much general similarity in composition and physical pro- perties, are yet found in practice to possess very difierent agri- cultural capabilities. Many such cases occur in every country, and they present the kind of difficulties in regard to which agriculture has a right to say to chemistry — "These are mat- ters which I hope and expect you will satisfactorily clear up." But while agriculture has a right to use such language, she has herself preliminary duties to perform. She has no right in one breath to deny the value of chemical theory to agricultural practice, and in another to ask the sacrifice of time and labor in doing "her chemical work. Chemistry is a wide field, and many zealous lives are now being spent in the prosecution of it, without at all entering upon the domain of practical agriculture. It may be that here and there it may fall in with the humor or natural bias of some one chemist to apply his knowledge to this most important art; but hitherto the appreciation of such efforts 124: CLAY AND SAND IN SOILS. has, except by a limited few, been so small — the reception of scientific results and suggestions by the agricultural body gene- rally so ungracious — that little wonder can exist that so many chemists have quitted the field in disgust — that the majority of capable men should studiously avoid it. SECTION III. COMPARATIVE COMPOSITION OF FERTILE AND BARREN SOILS. With the view of illustrating the deductions which, as above stated, may be drawn from an accurate chemical analysis, I shall exhibit the composition of three different soils, as deter- mined by Sprengel, a German agricultural chemist. , No. 1 is a very fertile alluvial soil from East Friesland, for- merly overflowed by the sea, but for sixty years cultivated with corn and pulse crops, without manure. No. 2 is a fertile soil near Gottingen, which produces excel- lent crops of clover, pulse, rape, potatoes, and turnips, the two last more especially when manured with gypsum. No. 3 is a very barren soil from Luneberg. When washed with water in the manner described in page Y6, they give respectively, from 1000 parts of soil — No. 1. No. 2. No. 3. Soluble saline matter, Fine clay and organic matter, Silicious sand, 18 . 937 45 1 839 IGO 1 599 400 1000 1000 1000 The most striking distinction presented by these numbers is the large quantity of saline matter in No. 1. This soluble mat- ter consisted of common salt, chloride of potassium, sulphate of potash, and- sulphate of lime, (gypsum,) with traces of sulphate of magnesia, sulphate of iron, and phosphate of soda. The presence of this comparatively large quantity of these different saline substances — originally derived, no doubt, in great part COMPOSITION OF CERTAIN SOILS BY ANALYSIS. 125 from the sea — was prol3ably oiie reason why it could be so long cropped Avithout manure. The unfruitful soil is much the lightest (in the agricultural sense) of the three, containing 40 per cent of sand; but this is not enough to account for its barrenness, many light soils con- taining a larger proportion of sand, and yet being sufficiently fertile. The finer portions, separated from the sand and soluble mat- ter, consisted, in 1000 parts, of — Organic matter, Silica, Alumina, . Lime, Magnesia, . Oxide of iron, . Oxide of manganese. Potash, Soda, Ammonia, Chlorine, . Sulphuric acid, . Phosphoric acid, Carbonic acid, . Loss, . No. 1. No. 2. No. 3, 97 50 40 648 833 778 57 51 91 59 18 4 8i 8 1 61 30 81 1 3 i 2 trace. trace. 4 do. do. trace. do. do. 2 do. do. 2 4 do. H 11 do. 40 U do. 14 U 1000 1000 1000 1 . The composition of 'No. 1 illustrates the first of the general deductions stated in the preceding section — that a considerable supply, namely, of all the species of inorganic food is necessary to render a soil eminently fertile. Kot only does this soil contain a comparatively large quantity of soluble saline matter, but it contains also nearly 10 per cent of organic matter, and what, in connection with this, is of great importance, nearly 6 per cent of lime. The potash and soda, and the several acids, are also present in sufficient abundance. 2. In the second — a fertile soil, but one which cannot disjpense with manure — there is little soluble saline matter, and in the insoluble portion we see that there are mere traas only of 126 PRACTICAL DEDUCTIONS. potash, soda, and the important acids. It contains also only 5 per cent of organic matter, and less than 2 per cent of lime; which smaller proportions, together with the deficiencies above stated, remove this soil from the most naturally fertile class to that class which is susceptible, in hands of ordinary skill, of being hrought to^ and kejpt in, a very productive condition. 3. In the fine part of the third soil, we observe that there are many more substances deficient than in No. 2. The organic matter amounts apparently to 4 per cent, and there seems to be nearly half a per cent of lime. But it will be recollected that this soil contains 40 per cent of sand, (p. 125;) or that in every hundred of soil there are only 60 of the fine matter, of which the composition is presented in the table; — or 100 lb. of the native soil contain only 2| lb. of organic matter and \ lb. of lime. But all these wants would not alone condemn the soil to hopeless barrenness, because, in favorable circumstances, they might all be supplied by art. But the oxide of iron amounts to 8 per cent of this fine part of the soil ; a proportion of this sub- stance which, in a soil containing so little lime and organic mat- ter, appears, from practical experience, to be incompatible with the healthy growth of cultivated crops. This soil, therefore, requires, not only those substances of which it is destitute, but such other substances also, or such a form of treatment, as shall prevent the injurious effects of the large portion of oxide of iron it contains. In these three soils, therefore, we have examples, fitst, of one which contains within itself all the elements of fertility ; second, of a soil which is destitute, or nearly so, of certain substances required by plants, which, however, can be readily added by the ordinary manures in general use, and to which the elements of gypsum are especially useful, in aiding it to feed the potato and the turnip; and third, of a soil not only poor in many of the necessary species of the inorganic food of plants, but too rich THE BLACK EARTH OF RUSSIA. 12t in one (oxide of iron) which, when present in excess, is usually prejudicial to vegetable life. This illustration, therefore, will aid the general reader in comprehending how far rigid chemical analysis is fitted to throw light upon the capabilities of soils, and to direct agricul- tural practice. SECTIOX IV. IMPORTANCE OF CERTAIN FORMS AND QUANTITIES OF ORGANIC MATTER TO THE FERTILITY OF A SOIL. The hlack earth of Russia. — The Tchornoi Zem, or black earth of Central Russia, illustrates, in a very striking manner, the fact, that the kind and quantity of the organic matter which a soil contains are scarcely less influential upon its fertihty than the mineral constituents to which, in the last section, I prin- cipally adverted. This remarkable black soil, ''the finest in Russia, whether for the production of wheat or grass," covers an area of upwards of 60,000 square geographical miles, and is said to be everywhere of extreme and of nearly uniform fer- tility. It nourishes a population of more than twenty millions of souls, and yet annually exports upwards of fifty millions of bushels of corn. This black earth stretches into Hungary, and forms the largest extent of fertile soil possessing common and uniform qualities which is anywhere known to exist. Its origin and chemical composition, therefore, have naturally engaged the attention both of scientific and of practical observers. Its depth varies from 1 or 2 to 20 feet ; when moist, it is jet black, and when dry, of a dark brown. This dark color, from which it derives its name, is due to the presence of or- ganic, chiefly vegetable matter, in a peculiar decomposed state, minutely divided and intimately mixed with mineral matter. Of the weight of the dry soil, it forms, in different samples, from 6 to 18 per cent. This vegetable matter is distinguished by two circumstances. 1. That it is in an exceedingly minute state of division, and 128 ANALYSIS OF THE BLACK EARTH, is intimately mixed with finely-divided mineral matter. The black earth, therefore, forms a comparatively free and open soil, into which the air penetrates and the roots of plants descend freely. 2. It contains in a state of combination a considerable pro- portion of nitrogen. In different samples this constituent has been found to vary from 21 (Payen) to eight per cent (Schmidt) of the weight of the organic matter. Through the action of the air, this nitrogen will favor the production in the soil of nitric acid, ammonia, and other soluble compounds containing nitrogen, which I have already described as propitious to the growth of plants. But in this black earth the composition of the mineral or inorganic part is also such as to promote fertility. In one of the richest varieties, in which the organic matter amounted to 18 per cent, the mineral matter was found to consist of — Per cent. Potash, 5.81 Soda, • 2.31 Lime, 2.60 Magnesia., 0.95 Alumina and oxide of iron, with traces of phosphoric acid, .... . 17.32 Silica, of which 1 or 8 per cent were soluble, T 0.94 99.93 We see in this analysis an abundant supply of those mineral substances which appear to be so necessary to the healthy growth of plants. The general results of our analytical examination of soils, therefore, are chiefly these — a. That a due admixture of organic matter is favorable to the fertility of a soil. h. That this organic matter will prove the more valuable in proportion to the quantity of nitrogen it holds in combination. c. That the mineral part of the soil must contain all those substances which are met with in the ash of the plant, and in AND CAUSES OF ITS FERTILITY. 120 such a state of chemical combination that the roots of plants can readily take them up in the requisite proportion. It is to the long accumulation of the remains of forests, or other abundant aucient vegetation, that the color of the Black earth, and its richness in organic matter, is, with the greatest probability, ascribed. SECTION V. — OF THE DIRECT RELATION THAT EXISTS BETWEEN THE CHARACTER OF THE SOIL AND THE KIND OF PLANTS THAT NATU- RALLY GROW UPON IT. The importance of a minute study of the chemical composi- tion of soils will, perhaps, be most readily appreciated by a glance at the very different kinds of vegetables which, under the same circumstances, different soils naturally produce ; in other words, by a glance at their botanical relations. There are none so little skilled in regard to the capabilities of the soil, as not to be aware that some lands naturally produce abundant herbage or rich crops, while others refuse to yield a nourishing pasture, and are deaf to the often-repeated solicita- tions of the diligent husbandman. There exists, therefore, a universally understood connection between the kind of soil and the kind of plants that naturally grow upon it. It is interest- ing to observe how close this relation in many cases is. 1. The sands of the sea-shore, the margins of salt lakes and the surfaces of salt plains, like the Russian steppes, are distin- guished by their peculiar tribes of salt-loving plants — by varie- ties of salsola, salicornia, &c. The Triticum junceum (sea wheat) grows on the seaward slopes of the downs at no great distance from the sea. The drifted sands more removed from the beach produce their own long, waving, coarser grass, — the Arundo arenaria, (sea bent,) the Elymus arenarius, (sea lime grass,) and the Carex arenarius, (sand sedge,) the roots of which plants bind the shifting sands together The beautiful 6* 130 PLANTS SELECT THE SOILS sea pmk spreads itself over the loose downs — while further inland, and as the soil changes, new vegetable races appear. 2. The peaty hills and flats of our island naturally clothe themselves with the common ling, ( Calluna vulgaris^ ) the fine- leaved heath, {Erica cinerea,) and with the cross-leaved heath, {Erica tetralix.) When drained and laid down to grass, or when they exist as natural meadows, they produce one soft woolly grass almost exclusively — the Holms lanatus. After they are limed, these same soils become propitious to greeu crops and produce much straw, but refuse to fill the ear. The grain is thick-skinned, and therefore light in flour. There is a greater tendency to produce cellular fibre, and the insoluble matter associated with it, than the more useful substances starch and gluten. 3. On the margins of water-courses in which silica abounds, the mare's tail {Equisetum) springs up in abundance : while, if the stream contain much carbonate of lime, the water-cress appears and Hues the sides and bottom of its shallow bed, some- times for many miles from its source. 4. The Cornish heath (Erica vagans) shows itself rarely above any other than the serpentine rocks ; the red broom- rape, (Orohanche rubra,) only on trap or basaltic rocks ; the Anemone pulsatilla on the dry banks of chalky mounds, as in the neighborhood of Newmarket ; the lady's slipper on calca- reous formations only ; the Medicago lupulina on soils which abound in marl ; while the red clover and the vetch delight in the presence of gypsum, and the white clover in that of alka- line matter in the soil. So the red and white fire-weeds, Epilobium coloratum, and Erichtites hierecif alius, cover with their bright blossoms every open space in the jN'orth American woods, over which the fires, so frequent there, have run during the previous year. The ashes of the burned trees and underwood are specially grateful to the seeds of these plants, which in vast quantities lie dor- mant in the soils. ON WHICH THEY TREFER TO GROAV. 131 5. The clays, too, have their likings. The Rest harrow, (Ononis arvensis,) delights in the weald, the gault, and the plastic clays, but passes by the green-sand and chalk soils, by which these chxys are separated from each other. The oak, in like manner, characterises the clays of the weald ; while the elm flomnshes, in preference, on the neighboring soils of the green-sand formation. 6. Then, again, plants seem to alternate with each other on the same soil. Burn down a forest of pines in Sweden, and one of birch takes its place for a while. The pines after a time again spring up, and ultimately supersede the birch. The same takes place naturally. On the shores of the Rhine are seen ancient forests of oak from two to four centuries old, gra- dually giving place at present to a natural growth of beech, and others where the pine is succeeding to both. In the Pala- tinate, the ancient oak-woods are followed by natural pines; and in the Jura, the Tyrol, and Bohemia, the pine alternates with the beech. These and other similar difterences are believed to depend in great part upon the chemical composition of the soil. The slug may live well upon, and therefore infest, a field almost deficient in lime ; the common land snail will abound at the roots of the hedges only v/here lime is plentiful, and can easily be obtained for the construction of its shell. So it is with plants. Each grows spontaneously where its wants can be most fully and most easily supplied. If they cannot move from place to place like the living animal, yet their seeds can lie dormant, until either the hand of man or the operation of natural causes pro- duces such a change in their position, in reference to light, heat, &c., as to give them an opportunity of growing — or in the composition and physical qualities of the soil itself, as to fit it for ministering to their most important wants. And such changes do naturally come over the soil. The oak, after thriving for long generations on a particular spot, gradu- ally sickens ; its entire race dies out, and other races succeed it. 132 PLANTS SICKEN ON SOME SOILS. Has the operation of natural causes gradually removed from the soil that which favored the oak, and introduced or given the predominance to those substances which favor the beech or the pine ? On the light soils of the state of New Jersey tlie peach tree used to thrive better than anything else, and large sums of money were made from the peach grounds in that state. But of late years they have almost entirely failed. In Scotland, the Scotch fir has been known at once to die out over an area of 500 or GOO acres — and the forests of larch are now in many localities exhibiting a similar decay. This decay is often, I believe, owing to the presence of noxious matters in the subsoil, but it is due in some cases also to a natural change in the composition and character of the several soils, which has taken place since the peach, the fir, and the larch trees were first planted upon them. In the hands of the farmer, the land grows sick of this crop — it becomes tired of that. These facts may be regarded as indications of a change in the chemical composition of the soil. This alteration may proceed slowly and for many years; and the same crops may still grow upon it for a succession of rota- tions. But at length the change is too great for the plant to bear ; it sickens, yields an unhealthy crop, and ultimately refuses altogether to grow. The plants we raise for food have similar likes and dislikes with those that are naturally produced. On some kinds of food they thrive: fed with others, they sicken or die. The soil must therefore be prepared for their special growth. In an artificial rotation of crops we only follov/ nature. One kind of crop extracts from the soil a certain quantity of all the inorganic constituents of plants, but some of these in much larger proportions than others. A second kind of crop carries oif, in preference, a large quantity of those substances of which the former had taken little; and thus it is clearly seen, both why an abundant manuring may so alter the composition of the soil as to enable it to grow almost any crop; and why, at the AGRICULTURE A CHEMICAL ART. 133 same time, this soil may, in succession, yield more abundant crops, and in greater number, if the kind of plants sown and reaped be so varied as to extract from the soil, one after the other, the several different substances which the manure we have originally added is known to contain. So with regard to the organic matter which soils contain. That form of organic food which suits one, may not equally favor another species of plant, and thus, at different times, different species may be most suited to the chemical condition of the same field. The management and tilUng of the soil, in fact, is a branch of practical chemistry which, like the art of dyeing, of lead- smelting, or of glass-making, may advance to a certain degree of perfection without the aid of pure science,- but which can only have its processes explained, and be led on to shorter, more simple, more economical, and more perfect processes, by the aid of scientific principles. CHAPTER X. Of the general iraprovement of the soil, and how the prudent man will commence such improvement. — Mechanical methods of improving the soil. — Draining, cause of the benefits produced by it. — Draining of appa- rently dry land. — Summary of the economical advantages of draining. — Depth to which drains ought to be dug. — Effects produced by the rains as they descend through the soil. The soil, in its natural condition, is possessed of certain ex- isting and obvious qualities, and of certain other dormant capa- bilities. How are the existing qualities to be improved, — the dormant capabilities to be awakened ? SECTION I. OF THE GENERAL IMPROVEMENT OF THE SOIL, AND HOW THE PRUDENT MAN WILL COMMENCE SUCH IMPROVEMENT. There are few soils to which something may not still be done in the way of improvement, while by far the greatest breadth of the land, in almost every country, is still susceptible of ex- tensive amelioration. In its present condition, the art of culti- vating the land in England generally, differs from nearly all other arts practised among us in this — that he who undertakes it later in life, who brings to it a mind already matured, a good ordinary education, a sound judgment, and a fair share of pru- dence, who turns to it as a new pursuit, is often seen to take the lead among the agriculturists of the district in which he settles. He comes to the occupation free from the trammels of old customs, old methods, and old prejudices, and hence, is free to adopt a sounder practice and more rational methods of cul- tivation. Such men, from lack of prudence or other causes, have not always prospered in their worldly affairs, but they GENERAL IMPROVEMENT OF SOILS. 135 have in very many districts been the beginners of agricultural improvements, the introducers of better systems of culture, and consequently public benefactors to the country. What ought to be the course of such a man in embarking any serious amount of capital in this new pursuit ? What that of an intelligent practical farmer on establishing himself in a new district ? Suppose them to be equally well read in the theory and in the general practice of agriculture, they will — 1. Examine the quality of the land, its soil and its subsoil, the exposure and the climate, the access to markets and to ma- nures ; and generally, they will inquire what, in that district, are the more common sources of disappointment to the indus- trious farmer. 2. Consider what, in the abstract, theory would indicate as the most proper treatment for such land so situated, and the amount of produce it ought to yield. 3. Inquire what is the actual produce of the land, what the actual practice in the district, and especially the cause or rea- son of any local peculiarities in the practice which may be found to prevail. There are often good reasons for local pecu- harities which new settlers injure themselves by overlooking, and find out too late for their own interest. The prudent man may look with suspicion upon such local customs, but he will be satisfied that there is no sufiicieut reason for their adoption, before he finally reject them to follow the indications of theory alone. In illustration of this I may mention, that a friend of mine in Ayrshire, in agreeing to become the tenant'of a farm which appeared to have been exhausted by the previous occupant, founded his hopes of success on ploughing deeper, and thus bringing a new soil to the surface, and his anticipations have not been disappointed by the result. On the other hand, I know of an instance in Berkshire, where, under the direction of a new agent, deeper ploughing was introduced, and the crops 136 IMPROYEMEXT BY DRAINING. proved in consequence almost an entire failure. In this case sound theory indicated a deeper ploughing, but local experience had proved that shallow ploughing alone could preserve the crops from the fatal ravages of insect tribes. The local custom here, therefore, was founded upon a good reason, one sufficient to deter the prudent man from hasty or extensive experiments, though not enough to prevent him from seeking out some method of so extirpating the insect destroyers from his land, as to enable him afterwards to avail himself of its greater depth of soil. Suppose it now to be determined that the land is capable of being made to yield a larger produce, the questions recur — what is the kind of improvement for which this land will give the best return ? how is this improvement to be best, most fully, and at the same time most economically brought about ? All soils may be arranged into one or other of two classes. 1. Those which, hke No. 1, (p. 125) contain in themselves an abundant supply of all those things which plants require, and are therefore fitted chemically to grow any crop. 2. Those which, like Nos. 2 and 3, (p. 126) are deficient in some of those substances on which plants live, and are there- fore not fitted to grow, perhaps, any one crop with luxuriance. Both of these classes of soils, as they are naturally met with, are susceptible of improvement, the former by mechanical methods chiefly, the latter by mechanical partly, but chiefly by chemical methods. In the present chapter we shall consider the mechanical methods of improving the soil. SECTION II. OF IMPROVING THE SOIL BY DRAINING, AND THE CAUSES OF THE BENEFITS PRODUCED BY IT. The first step to be taken in order to increase the fertility of nearly all the improvable lands of Great Britain, is to drain them. The advantages that result from draining are manifold. 1°. The presence of too much water in the soil keeps it con- stantly cold. The heat of the sun's rays, which is intended by EFFECTS OF DRAINING. 13*1 nature to warm the land, is expended in evaporating the water from its surface ; and thus the plants never experience that genial warmth about their roots which so much favors their rapid growth. The temperature which a dry soil will attain in the summer time is often very great. Sir John Herschel observed, that at the Cape of Good Hope the soil attained a temperature of 150° Fahrenheit, when that of the air was only 120^ ; and Hum- boldt says, that the warmth of the soil between the tropics often rises to from 124° to 136°, (see p. 119.) When the land is full of water, it is only after long droughts, and when it has been thoroughly baked by the sun, that it be- gins to attain the temperature which dry land under the same sun may have reached, day after day, probably for weeks before. 2°. Where too much water is present in the soil, also, that portion of the food of the plant which the soil supplies is so much diluted, that either a much greater quantity of fluid must be taken in by the roots — much more work done by them, that is — or the plant will be scantily nourished. The presence of so much water in the stem and leaves keeps down their tem- perature also, when the sunshine appears — an increased evapo- ration takes place from their surfaces — a lov/er natural heat, in consequence, prevails in the interior of the plant, and the chemical changes, on which its growth depends, proceed with less rapidity. 3°. By the removal of the water, the physical properties of the soil, also, are in a remarkable degree improved. Dry pipe- clay can be easily reduced to a fine powder, but it naturally, and of its own accord, runs together when water is poured upon it. So it is with clays in the field. When wet, they are close, compact, and adhesive, and exclude the air from the roots of the growing plant. But remove the water and they gradually contract, crack in every direction, become thus open, friable, and mellow, more easily and cheaply worked, and per- vious to the air in every direction. 138 DRAINING OF LIGHT SOILS. 4^. The access of this air is essential to the fertility of the soil, and to the healthy growth of most of our cultivated crops. The insertion of drains not only makes room for the air to enter by removing the water, but actually compels the air to penetrate into the under parts of the soil, and renews it at every successive fall of rain. Open such outlets for the water below, and as this water sinks and trickles away, it will suck the air after it, and draw it into the pores of the soil wherever itself has been. Vegetable matter becomes of double value in a soil thus dried and filled with atmospheric air. When drenched with water, this vegetable matter either decomposes very slowly, or produces acid compounds more or less unwholesome to the plant, and even exerts injurious chemical reactions upon the earthy and saline constituents of the soil. In the presence of air, on the contrary, this vegetable matter decomposes rapidly, produces carbonic acid in large quantity, as well as other com- pounds on which the plant can live, and even renders the inor- ganic constituents of the soil more fitted to enter the roots, and thus to supply more rapidly what the several parts of the plant require. Hence, on dry land, manures containing organic matter, (farmyard manure, &c.,) go farther or are more profit- able to the farmer. 5°. Nor is it only stiff and clayey soils to which draining can with advantage be applied. It will be obvious to every one, that when springs rise to the surface in sandy soils, a drain must be made to carry off the water ; it will also readily occur, that where a sandy soil rests upon a hard or clayey bottom, drains may likewise be necessary ; but it is not un- frequently supposed, that where the subsoil is sand or gravel, thorough draining can seldom be required. Every one, however, is familiar with the fact, that when water is applied to the bottom of a flower-pot full of soil, it will gradually find its way towards the surface, however light the soil may be. So it is in sandy soils or subsoils in the open SOIL LIABLE TO BE BURNGD UP. 139 field — all possess a certain power of sucking up water from beneath, (p. 118.) If water abound at the depth of a few feet, or if it so abound at certain seasons of the year, that water will rise towards the surface ; and as the sun's heat dries it off by evaporation, more water will follow to supply its place. This attraction from beneath will always go on when the air is dry and warm, and thus a double evil will ensue — the soil will be kept moist and cold, and instead of a constant circulation of air doumicards, there will be a constant current of water upwards. Thus will the roots, the under soil, and the organic matter it contains, be all deprived of the benefits which the access of the air is fitted to confer, and both the crops and the farmer will suffer in consequence.* The remedy for these evils is to be found in an efficient system of drainage. 6°. It is a curious and apparently a paradoxical observation, that draining often improves soils on which the crops are liable to be burned up in seasons of drought. Yet, upon a little consideration, the fact becomes very intelligible. Let , a b he the surface of the soil, and c d the level at which the water stagnates, or below which there is no outlet by drains or natural ^ J openings. The roots will readily penetrate to c d ; but they will in general refuse to descend farther, because of the unwholesome substances which usually collect in water that is stagnant. Let a dry season come, and^ their roots having little depth, the plants will be more or less speed- ily burnt up. And if water ascend from beneath the line c d, to moisten the upper soil, it will bring with it those noxious substances into which the roots have already refused to pen- etrate, and will cause the crop to droop and wither. But put * A few miles south of the town of Elgin in Moraysliire, I was shown a tract of land on which the crops were usually three weeks later than ou another tract, separated from it by a small stream. Beneath the former was a pan at the depth of 3 feet, which prevented the surtace-water from sinking beyond that level, and thus retarded the growth of the crop. 140 REMOVAL OF OCHREY MATTER in a drain, and lower the level of the water to e f, and the rains will wash out the noxious water from the subsoil, and the roots will descend deep into it ; so that if a drought again come, it may parch the soil above c d, as before, without in- juring the plants, since now they are watered and fed by the soil beneath, into which the roots have descended. ^o. In many parts of the country, and especially in the red- sandstone districts, the oxide or rust of iron abounds so much in the soil, or in the springs which ascend into it, as gradually to collect in the subsoil, and form a more or less impervious layer or pan, into which the roots cannot penetrate, and through which the surface-water refuses to pass. Such soils are benefited, for a time, by breaking up the pan where the. plough can reach it ; but the pan gradually forms again at a greater depth, and the evils again recur. In such cases, the insertion of drains below the level of the pan is the most cer- tain mode of permanently improving the soil. If the pan be now broken up, the rains sink through into the drains, and gradually wash out of the soil the iron which would otherwise have only sunk to a lower level, and have again formed itself into a solid cake. 8°. It is not less common, even in rich and fertile districts, to see crops of beans, or oats, or barley, come up strong and healthy, and shoot up even to the time of flowering, and then begin k) droop and wither, till at last they more or less com- pletely die away. So it is rare in many places to see a second year's clover crop come up strong and healthy. These facts indicate, in general, the presence of noxious matters in the subsoil, which are reached by the roots at an advanced stage of their growth, but into which they cannot penetrate without injury to the plant. The drain calls in the aid of the rains of heaven to wash away these noxious substances from the soil, and of the air to change their nature, and this is the most likely, as well as the cheapest, means by which these evils can be prevented. AND OF SALINE INCRUSTATIONS. 141 9°. Another evil in some countries presents itself to the prac- tical farmer. Saline substances are in certain quantity bene- ficial, nay, even necessary to the growth of plants. In excess, however, they are injurious, and kill many valuable crops. I have already adverted to the existence of such saline substances in the soil, and to the fact of their rising in incrustations to the surface (p. t6) when droughts prevail. In some countries, as in the plains of Athens, and near the city of Mexico, they come to the surface in such quantity as actually to kill the more tender herbage, and to permit only the stronger plants to grow. In the plains of Athens, when the rainy season ends, a rapid evaporation of water from the surface begins. The water, as it rises from beneath, brings much saline matter with it. This it leaves behind as it ascends in vapor, and thus at length so overloads the surface-soil that tender grass refuses to grow, though the stronger wheat plant thrives well and comes to maturity. This result could scarcely happen if an outlet beneath were pronded for the waters which fall during the rainy season. These would wash out and carry away the excess of saline mat- ter which exists in the under soil, and would thus, when the dry weather comes, prevent it from ascending in such quantities as to injure the more tender herbage. It may be objected to this suggestion, that drains in such countries would render more dry a soil already too much parched by the hot suns of summer. It is doubtful, however, if this would really be the case. Deep drains, as in the case above explained, (6°,) would enable the roots to penetrate deeper, and would thus render them more independent of the moisture of the surface-soil. 10°. On this subject I shall add one important practical re- mark, which will readily suggest itself to the geologist who has studied the action of air and water on the various clay-beds that occur here and there, as members of the series of stratified rocks. There are no clays ivhich do not gradually soften under 142 DEPTH OF DRAIN'S. the united influence of air, of frost, and of running vmter. It is false economy, therefore, to lay down tiles of the common horse- shoe form without soles, however hard and stiff the clay subsoil may appear to be. In the course of ten or fifteen years, the stillest clays will generally soften so much as to allow the tile to sink to some extent — and many very much sooner. The passage for the water is thus gradually narrowed; and when the tile has sunk a couple of inches, the whole may have to be taken up. Thousands of miles of drains have been thus laid down, both in the low country of Scotland and in the southern counties of England, which have now become nearly useless. The extend- ing use of the pipe-tile will, it is to be hoped, gradually lessen the chances of pecuniary loss, which the above practice involves. SECTION III. SUMMARY OF THE ECONOMICAL ADVANTAGES OF DRAINING. The economical advantages of draining in such soils as we possess are chiefly these : — 1. Stiff soils are more easily and more cheaply worked. 2. Lime and manures have more effect, and go farther. 3. Seed-time and harvest are earlier and more sure. 4. Larger crops are reaped, and of better quality. 5. Valuable crops of wheat and turnips are made to grow where scanty crops of oats were formerly the chief return. 6. Naked fallows are rendered less necessary, and more pro- fitable rotations can be introduced. 7. The climate is improved, and rendered not only more suited to the growth of crops, but more favorable to the health of man and other animals. SECTION IV. OF THE DEPTH TO WHICH DRAINS OUGHT TO BE DUG. Much has lately been written in regard to the depth to which drains ought to be dug in a system of thorough drainage. It is ADVANTAGES OF DRAINING. 143 diflBcult, perhaps impossible, to establish any empirical or gene- ral rule upon this subject; but there are certain indisputable points which will serve to guide the intelligent farmer in most cases which are likely to occur. 1°. It is acknowledged, as a general rule, to be of great im- portance, that the soil should be deepened — that it should be opened up, for the descent of the roots, to the greatest depth to which it can be economically done. Now, by the use of the sub- soil plough or the fork, the soil can be stirred to a depth of from 22 to 24 inches. The tile — or the top of the drain, if made of stones — should be at least three inches clear of this disturb- ance of the upper soil; and as most tiles will occupy at least 3 inches, we reach 30 inches as the minimum depth of a tile drain, and about 3 feet as the minimum depth of a stone drain, in which the layer of stones has a depth of not more than 9 inches. 2^. Where the outfall is bad, and a depth of 30 or 36 inches cannot be obtained, the drains should be made as deep as they can be made to run and deliver water. 3°. The roots of our corn and otlier crops will, in favorable circumstances, descend to a depth of 4 or 5 feet. They do so in quest of food, and the crop above ground is usually the more luxuriant the deeper the roots are enabled to penetrate. It is, therefore, theoretically desirable to dry the soil to a greater depth even than 3 feet, where it can be done without too great an outlay of money. 4°. The question of economy, therefore, is one of great im- portance in this inquiry. In some places it costs as much to dig out the fourth or lowest foot as is paid for the upper three ; and this additional cost is, in many localities, a valid reason for limiting the depth to 30 inches, or 3 feet. 5°. But the question of economy ought to be disregarded, and deeper drains dug where springs occur beneath, or where, by going a foot deeper, a bed or layer is reached in which much water is present. The reason of this is — that though water may not rise from this wet layer in such quantity as actually to 144 RAINS WARM THE SOIL. run along the drains, yet it may do so in sufficient abundance to keep the subsoil moist and cold, and thus to retard the develop- ment of the crops that grow on its surface. The above circumstances appear sufficient to guide the prac- tical man in most cases that will present themselves to him. No uniform depth can be fixed upon; it must be modified by local circumstances. In regard to the distance apart at which drains should be placed, experience appears to be the only satisfactory guide. This says, as yet, that 18 to 21 feet are safe distances, and that drains placed at greater distances are doubtful, and may fail to dry the land. SECTION V. EFFECTS PRODUCED BY THE RAINS AS THEY DESCEND THROUGH THE SOIL. The most important immediate effect of thorough-drainage is, that it enables the rain or other surface water to descend more deeply and escape more rapidly from the soil. It maybe interesting to specify briefly the benefits which are known to follow from this descent of the rain through the soil. 1°. It causes the air to he renewed. — It is believed that the admission of frequently renewed supplies of air into the soil is favorable to its fertility. This the descent of the rain pro- motes. When it falls upon the soil it makes its way into the pores and fissures, expelling of course the air which previously filled them. When the rain ceases, the water runs off by the drains ; and as it leaves the pores of the soil empty above it, the air follows, and fills with a renewed supply the numerous cavities from which the descent of the rain had driven it. Where land remains full of water, no such renewal of air can take place. 2°. It warms the under soil, — As the rain falls through the air it acquires the temperature of the atmosphere. If this be higher than that of the surface soil, the latter is warmed byitj RAINS WASH OUT NOXIOUS MATTER. 145 and if the rains be copious, and sink easily into the subsoil, they will carry this warmth with them to the depth of the drains. Thus the under soil in well drained land is not only warmer, because the evaporation is less, but because the rains in the summer season actually bring down warmth from the heavens to add to their natural heat. 3°. It equcJises the temperature of the soil during the season of growth. — The suii beats upon the surface of the soil, and gra- dually warms it. Yet, even in summer, this direct heat descends only a few inches beneath the surface. But when rain falls upon the warm surface, and finds an easy descent, as it docs in open soils," it becomes itself warmer, and carries its heat down to the under soil. Then the roots of plants are warmed, and general growth is stimulated. It has been proved, by experiments with the thermometer, that the under as well as the upper soil is warmer in drained than in undrained land, and the above are some of the ways by which heat seems to be actually added to soils that have been thoroughly drained. 4°. It carries down sohMe substances to the roots of plants. — "When rain falls upon heavy undrained land, or upon any land into which it does not readily sink, it runs over the surface, dis- solves soluble matter, and carries it into the nearest ditch or brook. Rain thus robs and impoverishes such land. But let it sink where it falls — then whatever it dissolves it will carry downwards to the roots — ^it will distribute uniformly the saline matters which have a natural tendency to rise to the surface, and it will thus promote growth by bringing food every- where within the reach of plants. 5°. It washes noxious 7natters from the under soil. — In the sub- soil, beyond the reach of the air, substances are apt to collect, especially in red-colored soils, which are injurious to the roots of plants. These the descent of the rains alters in part and laakes wholesome, and in part washes out. The plough may then safely be trusted deeper, and the roots of plants may 7 146 PROPORTION OF RAIN EVAPORATED. descend in search of food where they wouhl previously have been destroyed. It is true that, when heavy rains fall, they will also wash out of the soil and carry into the drains substances which it would be useful to retain. Upon this fact some have laid unnecessary stress, and have adduced it as an argument against thorough- drainage. But if we balance the constant benefit against the occasional evil, I am satisfied, as experience indeed has shown, that-the former will greatly preponderate. 6*^. It hrmgs down fertilising substances from the air. — Besides, the rains never descend empty-handed. They constantly bear with them gifts, not only of moisture to the parched herbage, but of organic and saline food, by which its growth is promoted. Ammonia and nitric acid, (p. 33,) together with the many exhalations which are daily rising from the earth's surface, come down in the rains. ; common salt, gypsum, and other saline substances derived from the sea, are rarely wanting ; and thus, the constant descent from the heavens may well be supposed to counterbalance the occasional washings from the earth. I*^. Mitch of the rain is evaporated. — And lastly, in answer to this objection, it is of importance to state, that in our climate a very large proportion of the rain that falls does not sink through the soil, even where there are drains beneath, but rises again into the air in the form of watery vapor. Experiments in Man- chester have shown, tliat of 31 inches of rain which fall there in a year, 24 are evaporated ; while in Yorkshire, of 24| inches of rain which fall, only 5 inches run off through pipes laid at «i depth of 2 feet 9 inches, the rest being evaporated. There is little cause, therefore, for the fear expressed by some, that the draining of the land will cause the fertility in any perceptible degree to diminish in consequence of the washing of the descend- ing rains. They may, as I have said, improve the subsoil by washing hurtful substances out of it ; but, in general, the soil will have extracted from tlie vvater which filters through it all the valuable matter it holds in solution before it has reached the depth of a 3-feet drain. CHAPTER XL Mechanical methods continued. — The subsoil-plough and the fork. — How they act in improving the soil. — Experunents on tJie profit of subsoihng. — How deep ploughing and trenching improve the soil. — Chemical and other effects of common ploughing. — Improvement of the soil by mixing. After the land has been laid dry by drains, other mechanical modes of improvement can be employed with advantage. Even the ordinary methods of mechanical culture become more useful, and the benefits which in favorable circumstances are derived from turning up the soil are greater and more manifest. These facts will appear by a brief consideration of tlie eflects produced by ploughing to various depths, and the causes from which they arise. SECTION I. USE OF THE SUBSOIL-PLOUGH. HOW IT ACTS IN IMPROV- ING THE SOIL. The subsoil-plough is an auxiliary to the drain — it stirs and opens the under soil without mixing it with the upper or imme- diately active soil. Though there are few subsoils through which the water will not at length make its way, yet there are some so stiif, either naturally or from long consolidation, that the good effect of a well-arranged line of drains is lessened by the slowness with which they allow the superfluous water to pass through them. In such cases, the use of the subsoil-plough is most advantageous in loosening the under layers of soil, and in allow- ing the water to find a ready escape downwards to either side, until it reaches the drains.* * For a fuller discussion of the benetits of drainage, sec the Author s Lectures. 148 HOW THE SUBSOIL-PLOUGH ACTS. It is well known that if a piece of stiff clay be cut into the shape of a brick, and then allow^ed to dry, it will contract and harden — it will form an air-dried brick, almost impervious to any kind of air. Wet it again, it will swell and become still more impervious. Cut up while wet, it will only be divided into so many pieces, each of which will harden when dry, or the whole of which will again attach themselves and stick together if exposed to pressure while they are still wet. But tear it asunder when dry and it will fall into many pieces, will more or less crumble, and. will readily admit the air into its inner parts. So it is with a clay subsoil. After the land is provided with drains, the subsoil being very retentive, the subsoil-plough is used to open it up — to let out the water and let in the air. If this is not done, the stiff under clay will contract and bake as it dries, but it will neither suffi- ciently admit the air, nor open so free a passage for the roots. Let this operation, however, be performed when the clay is still too wet, a good effect will follow in the first instance ; but after a while the cut clay will again cohere, and the farmer will pro- nounce subsoiling to be a useless expense o7i his land. Defer the use of the subsoil-plough till the clay is dry — it will then tear and break instead of cutting it, and its openness will remain. Once give the air free access, and, after a time, it so modifies the drained clay that it no longer has an equal tendency to cohere. Mr. Smith of Deanston very judiciously recommended that the subsoil-plough should never be used till at least a year after the land has been thoroughly drained. This in many cases will be a sufficient safeguard — will allow a sufficient time for the clay to dry : in other cases, two years may not be too much. But this precaution has by some been neglected; and, subsoil- ing being with them a failure, they have sought, in some sup- posed chemical or other quality of their soil, for the cause of a want of success which is to be found in their own neglect of a most necessary precaution. Let not the practical man be too RESULTS OF EXPERIMENTS. 149 hasty in desiring to attain those benefits which attend the adop- tion of improved modes of culture ; let him give every method a fair trial; and above all, lei him male his trial in the way and with the precaution recommended by the author of the method, before he pronounces its condemnation. SECTION II.- -EXPERIMENT ON THE PROFITS OF SUBSOILING. USE OF THE FORK. The benefits of subsoil ploughing having been sometimes called in question, and there being even some cases on record in which positive injury has been said to follow from the prac- tice, I introduce the following numerical results observed on two farms in the neighborhood of Penicuik, a few miles from Edinburgh. 1°. Mr. Wilson of Eastfield, Penicuik, made an experiment, after thorough drainage, upon two portions of land under each of three crops, and found the effects in the first year after sub- soil ploughing, compared with ordinary ploughing, to be as follows : Ploughed to 8 inches, - Subsoiled to 15 inches, Difference, TURXIPS. Bar Grain. LEY. Straw. Potatoes. tons. cwt. 20 7 26 17 qrs. 3 cwt. 28 36i tons. cwt. 6 14i 7 9,^ 6 10 i 8^ Voi 1 From this table, the effects of subsoiling to a depth of 15, above that of ploughing to a depth of 8 inches, appears to have been to increase the turnip crop by 6J tons, the potatoes by 15 cwt., and the barley by 7 bushels of grain and 8 cwt.. of straw. 2°. Mr. Maclean of Braid wood, near Penicuik, made a sim- 150 USE OF DEEP PLOUGHING. ilar experiment with turnips and barley, with the following results : — Ploughed 8 inches deep, - - Suhsoiled to 15 inches, - - Difference, - - Turnips. Barley. Grain. Straw. tons. cwt. 19 15 23 11 qrs. 61 stones, 168i 206^ 4 2 1 38 The turnip crop, in this experiment, was increased 4 tons ; and the barley crop by 6 bushels of grain and 38 stones of straw. It has been observed, also, that the effects of the subsoiling do not cease with the first crop. In one case, in which an accurate account of the produce was kept, the profit was estimated at 6s. an acre, for Jive successive years after the operation. There is reason, therefore, to anticipate general good from the careful introduction of this practice ; though it is exceedingly desirable, at the same time, that the causes of its failure, wherever it is found to fail, should be rigorously investigated. The use of the fork, instead of the subsoil-plough, has lately been recommended as a more efficient, and even a more econom- ical method of opening up the under soil. The upper soil of 9 to 12 inches is thrown forward with a spade, and the under soil, to a depth of 15 inches further, is stirred and turned over with a three-pronged fork. I have seen it in operation ; and it cer- tainly does appear to loosen and open up the under soil more effectually than the subsoil plough can do, and to a depth which few subsoil-ploughs are yet able to reach. SECTION III. HOW DEEP PLOUGHING AND TRENCHING IMPROVE THE SOIL. 1°. Deep ploughing, like subsoiling, aids the effect of the I LIME AND CLAY SINK. 151 drains, and so far — where it goes nearly as deep — even more completely effects the same object. But, independently of this, it has other uses and merits, and, where it has been successfully applied, has im})roved the land by the operation of other causes. Subsoiling only lets out the water, and allows access to the air and rains, and a free passage to the roots. Deep ploughing, in addition to these, brings new earth to the surface, forms thus a deeper active soil, and more or less alters both its physical qualities and its chemical composition. If the plough be made to bring up 2 inches of clay or sand, it will stiffen or loosen the soil, as the case may be ; or it may affect its color or density. It is clear and simple enough, there- fore, that by deep ploughing, the physical properties of the soil may be altered. But there are certain substances contained in every soil, whether in pasture or under the plough, which gradually make their way down towards the subsoil. They sink till they reach at last that point beyond which the plough does not usually pen- etrate. Every farmer knows that lime thus sinks. In peaty soils top-dressed with clay, as is done in Lincolnshii*e, the clay thus sinks. In sandy, soils, also, which have been clayed, the clay sinks : and in all these cases, I beheve, the sinking takes place more rapidly when the land is laid down to grass. Where soils are marled, the marl sinks ; and the rains, in like manner, gradually wash out that which gives their fertilising virtue to the large doses of chalk which in some districts, are spread upon the land, and render necessary a new application to renovate its productive powers. If this be the case with earthy substances such as those now mentioned, which are, for the most part, insoluble in water, it will be readily believed that those saline ingredients of the soil which are easily soluble, will be still sooner washed out of the upper and conveyed to the under soil.' Thus the subsoil may gradually become rich in those substances of which the surface soil has been robbed by the rains. Bring up va portion of this 152 BKIXGIXG UP THE SUBSOIL. subsoil by deop-plougliiug, and yon restore to the surface soil a part of what it lias beeu gradually losing — you bring up what may probably render it more fruitful than before. Such is an outline of the reasons in favor of deep ploughing. In Germany, theory has pointed out the growing of an occa- sional deep-rooted crop in light soils to efiect the same end. The deep roots bring up again to the sui'face the substances which had naturally sunk. But suppose the land to have originally contained something noxious to vegetation, which in process of time has been wash- ed down into the subsoil, then to bring this again to the sm*- face would be materially to injure the land. This also is true, and a sound discretion must be employed, in judging when and where such evil effects are likely to follow. Such cases, however, are more rare than many suppose. There are few subsoils which after a year's draining, a full and fair exposure to the winter's frost will not in a great degree de- prive of all their noxious qualities, and render fit to ameliorate the general surface of the poorer lands. If the reader doubt this fact, let him visit Tester, and give a calm consideration to the effects produced by deep ploughing on the home farm of the Marquis of Tweeddale. Let him also study the practice of deep ploughing, as it is followed by the Jersey farmers, and ho will be still further persuaded of the value of deep-ploughing, in some localities at least. In many cases the farmer fears, as he does in some parts of the county of Durham, to bring up a single inch of the yellow clay that lies beneath his surface soil. In the first inch lodges, among other substances, the iron worn from his plough, which, in some soils, and after a lapse of years, amounts to a conside- rable quantity. Till it is exposed to the air, this iron is hurt- fid to vegetation ; and one of the benefits of a winter's expo- sure of such subsoils to the air arises from the effect produced upon the iron they contain. It is the want of drainage, however, and of the free access COMMON PLOl-GIIIXG. 153 of air, that most frequently renders snbsoils for a time injurious to vegetation. Let the lands be well drained — let the subsoils be washed for a few years by the rain water passing through them — and there are few of tliose which are clayey in their na- ture that may not ultimately be brought to the surface, not only with safety, but with advantage to the upper soil. 2°. Trenching with the spade more fully and effectually per- forms what the trench-plough is intended to do. The spade more completely turns over the soil than the plough does; and, in the hands of an industrious laborer, many think it the more economical instrument of the two. SECTION IV. CHEMICAL AND OTHER EFFECTS OF COMMON PLOUGHING. Other benefits, again, attend upon the ordinary ploughings, hoeings, and working of the land. Its parts are more mi- nutely divided — the air gets access to every particle — it is ren- dered lighter, more open, and more permealjle to the roots. The vegetable matter it contains decomposes more rapidly by a constant turning of the soil, so that wherever the fibres of the roots penetrate, they find organic food provided for them, and an abundant supply of the oxygen of the atmosphere to aid in preparing it. The production of ammonia and of nitric acid also, (see pages 26 to 32,) and the absorption of these and of watery vapor from the air, take place to a greater extent the finer the soil is pulverised, and the more it has been exposed to the action of the atmosphere. All soils contain, likewise, an admixture of fragments of those minerals of which the granitic and trap rocks are composed, which, by their decay, yield new supplies of inorganic food to the growing plant. The more frequently they are exposed to the air, the more rapidly do these fragments crumble away and decompose. The general advantage, indeed, to be derived from tlie constant working of the soil, may be inferred from the fact, that Tull reaped twelve successive crops of wheat from the same land by the 154 MIXING THE SOIL repeated use of the plough and the horse-hoe. There are few soils so stubborn as not to show themselves grateful hi pro- portion to the amount of this kind of labor that may be be- stowed upon them. It is chiefly because the spade or the fork divides and separates the soil more completely, or to a greater depth, that larger crops have been obtained in many districts by the in- troduction of spade husbandry than by the ordinary mode of culture with the plough. But all these benefits, which a thorough working of the soil is fitted to confer, are only fully realised where the land is naturally dry, or by artificial drain- age has been freed from superfluous water. SECTION V. OF THE IMPROVEMENT OF THE SOIL BY MIXING. It has been already shown that the physical properties of the soil have an important influence upon its average fertility. The admixture of pure sand with clay soils produces an alter- ation which is often beneficial, and which is almost wholly physical. The sand opens the pores of the clay, and makes it more permeable to the air. The admixture of clay with sandy or peaty soils, however, produces both a physical and a chemical altsiation. . The clay not only consolidates and gives body to the sand or peat, but it also mixes with them certain earthy and saline substances, useful or necessary to the plant, which neither the sand nor peat might originally contain in sufficient abundance. It thus alters its chemical composition and fits it for nourishing new races of plants. Such is the case also with admixtures of marl, of shell-sand, and of lime. They slightly consolidate the sands and oi>en the clays, and thus improve the mechanical texture of both kinds of soil ; but their main operation is chemical ; and the almost universal benefit they produce depends mainly upon the new chemical element they introduce into the soil. WITH CLAY, SAND, &C. ] 55 It is a matter of almost universal remark, that in our cli- mate, soils are fertile — clayey or loamy soils, that is — only when they contain an appreciable quantity of lime. In what- ever way it acts, therefore, the mixing of lime in any of the forms above mentioned, with a soil in which little or no lime exists, is one of the surest practical methods of bringing it nearer in composition to those soils from which the largest returns of agricultural produce are usually obtained. Some of the chemical effects of lime upon the soil will be explained in a subsequent chapter. CHAPTER XII. Improvement of the soil by planting and the growth of wood. — Influence of the Scotch fir and the larch on tlie value of pasture. — Causes of such influence of growing trees. — Improvement by laying down to grass. — Ob- served flicts. — Forms which the improvement assumes. — In what way pastures generally increase in value by age. — Agency of roots, of insects, and of winds. — Why rich pasture, wlien ploughed up, is difficult to restore. There are certain modes of improving tlie soil, which, tliougli involving only simple mechanical operations on the part of the improver, produce their effects through the agency of refined scientific causes. Such are the improvements produced by planting and laying down to grass. These, therefore, I shall briefly consider in the present chapter. SECTION I. IMPROVEMENT OF THE SOIL BY PLANTING, AND HOW IT IS EFFECTED. It has been observed that lands which are unfit for arable culture, and which yield only a trifling rent as natural pasture, are yet in many cases capable of growing profitable plantations, and of being greatly increased in permanent value by the pro- longed growth of wood. Not only, however, do all trees not thrive alike on the same soil, but all do not improve the soil on which they grow in an equal degree. Under the Scotch fir, for example, the pasture which springs up after a lapse of years is not worth 6d. more per acre than before the land was planted; — under the beech and spruce, it is worth even less than before, though the spruce affords excellent shelter; — under the ash, it gradually acquires an increased value IMPROVEMENT BY PLANTING. 15 1 of 2s. or 3s. per acre. In oak copses, it becomes worth 5s. or 6s., but only during the last eight years (of the twenty-four) before the oak copse is cut down. But under the larch, after the first thirty years, when the thinnings are all cut, land not worth originally more than Is. per acre becomes worth 8s. to 10s. per acre for permanent pasture.* 1. The main cause of this improvement is to be found in the nature of the soil, which gradually accumulates beneath the trees by the shedding of their leaves. The shelter from the sun and rain which the foliage affords, prevents the vegetable mat- ter which falls from being so speedily decomposed, or from being so much washed away, and thus permits it to collect in larger quantities in a given time than where no such cover ex- ists. The more complete the shelter, therefore, the more raj)id will the accumulation of soil be, in so far as it depends upon this cause. 2. But the quantity of leaves which annually fall, as well as the degree of rapidity with which, under ordinary circumstances, they undergo decay, have also much influence upon the extent to which the soil is capable of being improved by any given species of tree. The broad leaves of the beech and oak decay more quickly than the needle-shaped leaves of the pine tribes, and this circumstance may assist in rendering the larch more valuable as a permanent improver. 3. We should expect, likewise, that the quantity and quality of the inorganic matter contained in the leaves (p. 60) — brought up year by year from the roots, and strewed afterwards uni- formly over the surface where the leaves are shed — would ma- terially affect the value of the soil they form. The dry leaves of the oak, for example, contain about 5 per cent of saline and earthy matter, while those of the Scotch fir contain less than 2 per cent; so that, supposing the actual weight of leaves which falls from each kiiul of tree to be equal, we should expect a * The result of trinls made on the mica slate and gneiss soils (see page 101) of the Duke of Atholl. 158 HOW FALLEN LEAVES FERTILIZE. greater depth of soil to be formed in the same time by the oak than by the Scotch fir. The leaves of the larch in the dry state contain from 5 to 6 per cent of saline matter, so that they may enrich the surface on which they fall in at least an equal degree with those of the oak. Much, however, depends upon the annual weight of leaves shed by each kind of tree, in regard to which we possess no precise information. The improvement of the land, therefore, by the planting of trees, depends in part upon the quantity of organic food which the trees can extract from the air, and afterwards drop in the form of leaves upon the soil, and in part upon the kind and quantity of inorganic matter which the roots can bring up from beneath, and in like manner strew upon the surface. The quan- tity and quality of the latter will, in a great measure, determine the kind of grasses which will spring up, and the consequent value of the pasture in the feeding of stock. In the larch forests of the Duke of Atholl, the most abundant grasses that spring up are said to be the Holcus mollis, and the Holcus lanatus (the creeping and the meadow soft grasses.) The action of a tree, therefore, in improving the soil, is two- fold. 1°. It causes vegetable matter to accumulate on the surface; and, 2°. It brings up from beneath certain substances which are of vital importance to the growth of plants, but of which the upper soil may have been deficient. In a previous chapter I have described the black earth of Central Russia, which presents probably the most remarkable example now existing of the fertilising effect of a long-con- tinued growth of trees. The cotton soil of Central and South- ern Hindostan owes its richness to a similar cause. LAYING DOWN TO GRASS. 159 SECTION II. IMPROVEMENT OF THE SOIL BY LAYING DOWN TO GRASS, FACTS WHICH HAVE BEEN ASCERTAINED. On this subject, two facts seem to be pretty generally acknowledged. First, That land laid down to artificial grasses for one, two, three, or more years, is in some degree rested or recruited, and is fitted for the better production of after crops of corn. Letting it lie a year or two longer in grass, therefore, is one of the received modes of bringing back to a sound condition a soil that has been exhausted by injudicious cropping. Second, That land thus laid down with artificial grasses diminishes in value again after two, three, or five years — more or less — and only by slow degrees acquires a thick sward of rich, nourishing natural herbage. Hence the opinion that grass land improves in quality the longer it is permitted to lie — the unwillingness to plough up old pasture — and the comparatively high rents which, in some parts of the country, old grass land is known to yield. Granting that grass land does thus generally increase in value, three important facts must be borne in mind before we attempt to assign the cause of this improvement, or the circumstances under which it is likely to take place for the longest time and to the greatest extent. 1. The value of the grass in any given spot may increase for au indefinite period, but it will never improve beyond a certain extent — it will necessarily be limited, as all other crops are, by the quality of the land. Hence the mere laying down to grass will not make all land good, however long it may lie. The ex- tensive commons, heaths, and wastes, which have been in grass from the most remote times, are evidence of this. They have, in most cases, yielded so poor a natural herbage as to have been considered unworthy of being enclosed as permanent pas- ture. 160 NATURE OF THE IMPROVEMENT. 2. Some grass-lands will retain the good condition they thus slowly acquire for a very long period, and without manuring — in the same way, and upon nearly the same principle, that some rich corn-lands have yielded successive crops for 100 years without manure. The rich grass-lands of England, and especially of Ireland, many of which have been in pasture from time imme- morial, without receiving any known return for all they have yielded, are illustrations of this fact. 3. But others, if grazed, cropped with sheep, or cut for hay, will gradually deteriorate, unless some proper supply of manure be given to them — which required supply must vary with the nature of the soil, with the kind of stock fed upon it, and with the kind of treatment to which it has been subjected. SECTION III. FORM WHICH THE IMPROVEMENT ASSUMES, AND HOW IT IS BROUGHT ABOUT. In regard to the acknowledged benefit of laying down to grass, then, two points require consideration. 1°. What form does it assume — and how is it effected ? The improvement takes place by the gradual accmnulation of a dark-brown soil rich in vegetable matter, which soil thick- ens or deepens in proportion to the time during which it is allowed to lie in grass. It is a law of nature, that this accu- mulation takes place more rapidly in the temperate than in tropical climates, and it would appear as if the consequent darkening of the soil were intended, among other purposes, to enable it to absorb more of the sun's warmth, and thus more speedily to bring forward vegetation where the average tempe- rature is low and the summers comparatively short. If the soil be very light and sandy, the thickening of the vegetable matter is sooner arrested ; if it be moderately heavy laud, the improvement continues for a longer period; and some of the heaviest clays in England are known to bear the richest permanent pastures. HOW IT IS BROUGHT ABOUT. 161 The soils formed on the surface of all our rich old pasture lands thus come to possess a remarkable degree of uniformity • — both in physical character and in chemical composition. This uniformity they gradually acquire, even upon the stiff clays of the lias and Oxford clay, which originally, no doubt, have been left to natural pasture — as many clay lands still are — from the difficulty and expense of submitting them to arable culture. 2°. How do they acquire this new character, and why is it the work of so much time ? a. When the young grass throws up its leaves into the air, from which it derives so much of its nourishment, it throws down its roots into the soil in quest of food of another kind. The leaves may be mown or cropped by animals, and carried off the field ; but the roots remain in the soil, and, as they die, gradually fill its upper part with vegetable matter. On an average, the annual production of roots on old grass-land is equal to one-third or one-fourth of the weight of hay carried off* — though no doubt it varies much, both with the kind of grass and with the kind of soil. When wheat is cut down, the quantity of straw left in the field, in the form of stubble and roots, is sometimes greater than the quantity candied off in the sheaf. Upon a grass field two or three tons of hay may be reaped from an acre, and therefore, from half a ton to a ton of dry roots is annually produced and left in the soil. If anything like this weight of roots die every year, in land kept in pasture, we can readily understand how the vegetable matter in the soil should gradually accumulate. In arable land this accumulation is prevented by the constant turning up of the soil, by which the fibrous roots, being exposed to the free access of air and moisture, are made to undergo a more rapid decomposition. h. But the roots and leaves of the grasses contain earthy and saline matters also. Dry hay leaves from an eighth to a * See the Autlior's Lectures on Agricultural Chemistry and Geology, 2d edition. 162 CIRCUMSTANCES BY WHICH IT IS PROMOTED. tenth part of its weight of ash when burned. Along with the dead vegetable matter of the soil, this inorganic matter also accumulates in the form of an exceedingly fine earthy povrder; hence one cause of the universal fineness of the surface-mould of old grass-fields. The earthy portion of this inorganic mat- ter consists chiefly of silica, hme, and magnesia, with scarcely a trace of alumina ; so that, even on the stiffest clays, a sur- face soil may be ultimately formed, in which the quantity of alumina — the substance of clay — is comparatively small. c. There are still other agencies at work, by which the sur- face of stiff soils is made to undergo a change. As the roots of the grasses penetrate into the clay, they more or less open up a way into it for the rains. Now, the rains in nearly all lands, when they have a passage downwards, have a tendency to carry down the clay along with them. They do so, it has been ob- served, on sandy and peaty soils, and more quickly when these soils are laid down to grass. Hence the mechanical action of the rains — slowly in many localities, yet surely — has a tendency to lighten the surface soil, by removing a portion of its clay. They constitute one of those natural agencies by which, as elsewhere explained, important differences are ultimately estab- lished, almost everywhere, between the surface crop-bearing soil and the subsoil on which it rests. d. But further, the heats of summer and the frosts of winter aid this slow alteration. In the extremes of heat and of cold, the soil contracts more than the roots of the grasses do ; and similar, though less visible, differences lake place during the striking changes of temperature which are experienced in our climate in the different parts of almost every day. When the rain falls, also, on the parched field, or when a thaw comes on in winter, the earth expands, while the roots of the grasses re- main nearly fixed ; hence the soil rises up among the leaves, mixes with the vegetable matter, and thus assists in the slow accumulation of a rich vegetable mould. The reader may have witnessed in winter hoAv, on a field or EFFECT OF EARTH-WORMS AND WINDS. 163 by a way-side, the earth rises above the stones, and appears in- clined to cover them ; he may even have seen, in a deserted and undisturbed highway, the stones gradually sinking and dis- appearing altogether, when the repetition of this altei'nate contraction and expansion of the soil for a succession of winters has increased, in a great degree, the effects which follow from a single accession of frosty weather. So it is in the fields. And if a person skilled in the soils of a given district can make a guess at the time when a given field was laid down to grass, by the depth at which the stones are found beneath the surface, it is partly because this loosen- ing and expansion of the soil, while the stones remain fixed, tends to throw the latter down by an almost imperceptible quantity every year that passes. e. Such movements as these act in opening up the surface soil, in mixing it with the decaying vegetable matter, and in allowing the slow action of the rains gradually to give its earthy portion a lighter character. But with these, among other causes, conspires also the action of living animals. Few persons have followed the plough without occasionally observ- ing the vast quantities of earth-worms with which some fields seem to be filled. On a close-shaven lawn, many have noticed the frequent little heaps of earth which these worms during the night have thrown out upon the grass. These and other minute animals are continually at work, especially beneath an undisturbed and grassy sward — and they nightly bring up from a considerable depth, and discharge on the surface, their bur- den of fine fertilising loamy earth. Each of these burdens is an actual gain to the rich surface soil; and who can doubt that, in the lapse of years, the unseen and unappreciated labors of these insect tribes must both materially improve its quality and increase its depth ? * * In the Prize Essays of the Highland Society, (vol. 1. p. 191,) the reader will find the testimony of a practical man that such was in reality the case, as observed by himself on part of his own farm in Koxburgshire. 164 FOREST TREES ENRICH THE SOIL. /. In most localities, also, the winds may be mentioned among the natural agencies by which the soil on grass lands is slowly imi^roved. They seldom sweep over any considerable extent of arable land without bearing with them particles of dust and sand, which they drop in sheltered places, or leave behind them when sifted by the blades of grass, or by the leaves of an ex- tensive forest. In hot summers, in dry springs, and even in winter, when the snow is drifting, the ploughed lands and dusty roads are more or less bared of their lighter particles of soil, which are strewed by the winds as a natural top-dressing over the neighboring untilled fields. In some countries the agency of the winds is more conspicuous than among ourselves. Thus on the banks of the Kuruman and Orange rivers in South Africa, the winds blow during the spring months — August to November in that climate — from the Kula- gare desert, bearing with them light particles of dust, which make the air seem as if dense with smoke, and which are so ex- quisitely fine as to penetrate through seams and cracks which are almost impervious to water.* Forest trees and waving grass sift this thick air and enrich the soils on which they grow by the earthy particles they arrest. In countries where active volcanoes exist, these also exercise an appreciable influence of a similar kind upon the surface soil. Showers of dust and ashes are sprinkled widely over the land, by which its natural agricultural capabilities are materially in- terfered with. Vesuvius is said, in this way, to scatter its ashes over the adjoining country, so as, on an average, to destroy the crop every eighth year. But to this circumstance the remarka- I have lately seen a notice from the Carlisle Journal of a bowhng-green at Penrith, (45 yards by 32,) from which, after watering with a solution of corrosive sublimate, eleven stones of worms were this year gathered, and four years ago ticenty stones. The labors of such a number of animals must produce in time a very sensible effect. * Mojfafs Missionary Labors, p. 333. ALL LAND REQUIRES ADDITIONS. 165 ble general richness of the soil is ascribed — (Moiil.) So does good arise from seeming evil. There are natural causes, then, which we knoio to be at work, that are sufficient to account for nearly all the facts that have been observed in regard to the effect of laying land down to grass. Stiff clays will gradually become lighter on the surface, and, if the subsoil be rich in all the kinds of inorganic food which the grasses- require, will go on improving for an indefinite period without the aid of manure. Let them, however, be de- ficient in, or let them gradually become exhausted of any one kind of this food, and the grass lands will either gradually-dete- riorate after they have reached a certain degree of excellence, or they must be supplied with that one ingredient, that one kind of manure of which they stand in need. It is doubtful if any pasture lands are so naturally rich as to bear to be cropped for centuries without the addition of manure, and at the same time without deterioration. Where they appear to be so, they pro- bably receive from springs, from sea-drift, or from some other unobserved source, those perennial supplies which reason pro- nounces to be indispensable. On soils that are light, again — which naturally contain little clay — the grasses will thrive more rapidly, and a thick sward will be sooner formed, but the tendency of rains to wash out the clay may prevent them from ever attaining that luxuriance which is observed upon the old pastures of the clay lands. On undrained heaths and commons, and generally on any soil which is deficient in some fertilising element, neither abundant herbage, nor good crops of any other kind, can be expected to flourish. Laying such lands down, or permitting them to remain in grass, may prepare them for by-and-by yielding one or two average crops of corn, but cannot be expected alone to convert them into valuable pasture. Finally, plough up the old pastures on the surface of which this light and most favorable soil has been long accumulating, and the heavy soil from beneath will be again mixed up with it, 166 NATURAL GRASSES CHANGE. the vegetable matter will disappear rapidly by exposure to the air during the frequent ploughings; and, if again laid down to grass, the slow changes of many years must again be begun through the agency of the same natural causes, before it become capable a second time of bearing the same rich herbage it was known to nourish while it lay undisturbed. Many have supposed that, by sowing down with the natural grasses, a thick and permanent sward may at once be obtained; and on light loamy land, rich in vegetable matters, this method may, to a certain extent, succeed ; but, on heavy land, in which stiff -clay abounds and vegetable matter is defective, disappoint- ment will often fallow the sowing of the most carefully selected seeds. By the agency, among other causes, of those above adverted to, the soil gradually changes, so that it is unfit, when first laid down, to bear those grasses which, ten or twenty years afterwards, will spontaneously and luxuriantly grow upon it. Nature is not regulated by one principle in the growth of corn and by another in growing grass ; the apparent difference in her procedure arises from real differences in our j^ractice. CHAPTER XIII. Chemical methods of improving the soil. — Use of manures. — Objects of the farmer. — Vegetable manures. — Green manuring. — Use of sea- weed. — Dry- vegetable substances. — Straw. — Sawdust. — Bran. — Brewers' grains. — Malt-dust. — Rape-dust. — Hemp, poppy, cotton, and cocoa-nut cakes. — Use of peat. — Peat composts and tanners' bark. — Use of vegetable substances decomposed by art. — Charred peat, wood charcoal, soot, coal-dust, and coal-tar. — Relative fertilising and money values of different vegetable manures. KoNE of the methods of improving the soil which have been described in the preceding chapter are purely mechanical. They all involve, as I have shown, some chemical alterations also, which are to be explained only by a knowledge of chemical principles. But the manuring of the land is more strictly a chemical operation, and may therefore with propriety be sepa- rated from those methods of improvement which involve at the same time important and expensive mechanical operations. In commencing the tillage of a piece of land, the conscien- tious farmer may have three objects in view in regard to it. 1. He may wish to reclaim a waste, or to restore a neglected farm to an average condition of fertility. 2. Finding the land in this average state, his utmost ambition may be to keep it in its present condition; or, 3. By high farming he may wish to develop all its capabili- ties, and to increase its permanent productiveness in the great- est possible degree. The man who aims at the last of these objects is not only the best tenant and the best citizen, but he is also his own best 168 "WHAT IS A MANURE. friend. The highest farming, skilfully and prudently conduct- ed, is also the most remunerntinp:.* But whichever of these throe ends he aims at, he will be un- able to attain it without a due knowledge of the various manures it may be in his power to apply to his land — what these manures are, or of what they consist — the general and special purposes they are. each fitted or intended to serve — wiiich are the most effective for this or that crop, and why they are so — how they are to be obtained in the greatest abundance, and at the least cost^how their strength may be economised — and in what state and at what season of the year they may be most beneficially applied to the land. Such are a few of the questions which the skilful farmer should be ready to ask himself, and should be able to answer. By a manure is to be understood whatever is capable of feeding or of supplying food to the plant. And as plants re- quire earthy and saline as well as vegetable food, gypsum and nitrate of soda are as properly called manures as farmyard dung, bone-dust, or nightsoil. Manures naturally divide themselves into such as are of vege- tahle, of animal, and of mineral origin. I shall consider these different kinds of manure in successive chapters. SECTION I. OF THE USE OF VEGETABLE MANURES. There are two purposes which vegetable manure is generally * A singular illustration of this fact is mentioned as observed in Hol- stein, where marl is extensively applied to the land. Those fields which nre marled yield a much larger produce than before, while the adjoining fields, which are left unmarled, give a less return than when all were un- maiied ; so that the holder of the latter is compelled to improve by marl- ing his fields also. — Sprengel. It is also a curious but important observation, that when light lauds, poor in vegetable matter, are reclaimed from a state of waste, they pay better for the manure added to them every succeeding year ; that is, the richer in organic matter they become. — Yon Vogiit. VEGETABLE MANURES. 169 supposed to serve when added to the soil — it loosens the land, opens its pores, and makes it lighter ; and it also supplies organic food to the roots of the growing plant. It serves, how- ever, a third purpose. It yields to the roots those saline and earthy matters, which it is their duty to find in the soil, and which exist in decaying plants in a state more peculiarly fitted to enter readily into the circulating system of new races. Decayed vegetable matters, therefore, are in reality mixed manures, and their value in enriching the land must vary con- siderably with the kind of plants, and with the parts of those plants of which they are chiefly made up. This depends upon the remarkable difference which exists in the quantity arid kind of the inorganic matter contained in different vegetable sub- stances, as indicated by the ash they leave, (see pages 59 to 69.) Thus if 1000 lb. of the sawdust of the willow be fer- mented and added to the soil, they will enrich it by the addi- tion of only 4| lb. of saline and earthy matter, while 1000 lb. of the dry leaves of the same tree, fermented and laid on, will add 82 lb. of inorganic matter. Thus, independent of the effect of the organic matter in each, the one will produce a very much greater effect upon the soil than the other.* There are several states in which vegetable matter is collect- ed by the husbandman for the purpose of being applied to the land — such as the green state, the dry state, that state of im- perfect natural decay in which it forms ;peat, and the decom- posed state of charcoal, &c., to which it has been reduced by art. SECTION II. OF GREEN MANURING, AND OF THE USE OF SEA-WEED. When grass is mown in the field, and laid in heaps, it speed- * It is owing, in part, to this large quantity of saline and other inorganic matters which they contain, that fermented leaves alone form too strong a dressing for flower borders, and that gardeners therefore generally mix them up into a compost. 8 1^0 GREEN MANURING. ily heats, ferments, and rots. But, if turned over frequently and dried into hay, it may be kept for a great length of time without undergoing any material alteration. The same is true of all other vegetable substances — they all rot more readily in the green state. The reason of this is, that the sap or juice of the goeen plant begins very soon to ferment in the interior of the stem and leaves, and speedily communicates the same condition to the moist fibre of the plant itself. When once it has been dried, the vegetable matter of the sap loses this easy tendency to decay, and thus admits of long preservation. The same rapid decay of green vegetable matter takes place when it is buried in the soil. Hence the cleanings and scour- ings of the ditches and hedge-sides form a compost of mixed earth and fresh vegetable matter, wdiich soon becomes capable of enriching the ground. When a green crop is ploughed into a field, the whole of its surface is converted into such a compost — the vegetable matter in a short time decays into a light, black mould, and enriches in a remarkable degree, and fertilises the soil. This is one reason why the success of wheat after clover, or of oats after lea, depends so much on the ground being w^ell covered when first ploughed up. 1°. Green manuring. — Hence the practice of green manuring has been in use from very early periods. The second or third crop of lucerne vv^as ploughed in by the ancient Romans — as it still is by the modern Italians. In Tuscany, the ichite lupm is i;)loughed in — in parts of France, the bean and the vetch — in Germany, borage — and upon sandy soils in Holstein, slurry. The Madia sativa has lately been tried as a green manure in Silesia. It is sown in June, and is ploughed in, when two feet high, in October. Sheep do not eat it ; so that if a flock of sheep be turned in, they eat up the weeds and trample down the madia, after which it is easily ploughed in. In a month it is rotten, and the land may be cross-ploughed, and the winter corn sown. TURNIP LEAVES AND POTATO TOPS READILY DECAY. Ill In French Flanders, two crops of clover are cut, and the third is ploughed in. In some parts of the United States, the clover is never cut, but is ploughed in as the only manure ; in other parts, the first crop is cut and the second ploughed in. In some of the northern States, Indian corn is sown upon poor lands, at the rate of 4 to 6 bushels an acre, and two or sometimes three such crops are turned in during the summer. In north-eastern China, a species of coronilla and a trefoil are specially sown and grown in ridges, as a manure for the rice crop. They are ploughed and harrowed in before the young rice plants are put into the flooded land. In Sussex, and in parts of Scotland, hirmp seed has been sown at the end of harvest, and after two months again ploughed in, with great benefit to the land. Wild mustard, also, which grows so abundantly as a weed on many of our corn-fields, is not unfrequently raised for ploughing in green. White mustard is sown in Norfolk, and ploughed in as a preparation for wheat ; sometimes, also, on the stubble, as a preparation for turnips. It is said to destroy the wire-worm. Turnip leaves and potato tops decay more readily and more perfectly, and are more enriching when buried in the green state. It is a prudent economy, there- fore, where circumstances admit of it, to bury the potato tops on the spot from which the potatoes are raised.* Since the time of the Romans, it has been the custom to bury the cut- tings of the vine stocks at the roots of the vines themselves ; and many vineyards flourish for a succession of years without any other manuring. In the Weald of Kent the prunings of the hop-vine, chopped and dug in, or made into a compost and applied to the roots of the hop, give a larger crop, and with half the manure, than when they are burned or thrown away, as is usually done. * By taking- off the blossoms of potatoes — besides the usual increase of crop — the tops keep green till the potatoes are lifted. Thus much green matter is obtained : and if this be made mto manure, and applied to the next potato crop, it is said to raise the largest xnoduce of tubers. Its USE OF SEA-WEED. Buckwheat, rye, winter tares, clover, and rape, are all occa- sionally sown in tliis country for the purpose of being ploughed in. This should be done when thefiower has just begun to open, and, if possible, at a season when the warmth of the air and the dryness of the soil are such as to facilitate decomposition. That the soil should be richer in vegetable matter after this burial of a crop than it was before the seed of that crop was sown, and should also be otherwise benefited, will be understood by recollecting (see page 36) that perhaps three-fourths of the whole organic matter we bury has been derived from the air — that by this process of ploughing in, the vegetable matter is more equally diffused through the whole soil, than it could ever be by any merely mechanical means — and that by the natural decay of this vegetable matter, ammonia and nitric acid are, to a greater extent, (page 26 and 29,) produced in the soil, and its agricultural capabilities in consequence materially increased. Indeed, a green crop ploughed in is believed, by some practical men, to enrich the soil as much as the droppings of cattle from a quantity of green food three times as great. These considerations, while they explain the effect and illus- trate the value of green manuring, will also satisfy the intelligent agriculturist that there exist methods of improving his land without the aid either of town or of foreign manures — and that he overlooks an important natural means of wealth who neglects the green sods and the crops of weeds that flourish by his hedge- rows and ditches. Left to themselves, they will ripen their seeds, and sow them annually in his fields ; collected in compost heaps, they will materially add to his yearly crops of corn. 2°. Use of sea-weed. — Among green manures, the use of fresh sea-ware deserves especial mention, from the remarkably fertilis- ing properties it is known to possess, as well as from the great extent to which it is employed on all our coasts. The agricul- tural produce of the Isle of Thanet, in Kent, is said to have been doubled or tripled by the use of this manure; the farms on the Lothian coasts let for 20s. or oOs. more rent per acre when SPECIAL ACTION OF SEA-WEED. 173 they have a right of way to the sea, where the weed is thrown ashore;* and in the Western Isles the sea-ware, the shell-marl, and the peat-ash, are the three great natural fertilisers, to which the "agriculture of this remote region is indebted for the com- parative prosperity to which it has in some of the islands already attained. The common red tangle, which grows farther out at sea, is in some districts preferred as a manure to the other varieties of sea-weed, when applied green or made into compost. At Oban, on the west coast of Scotland, the fishermen bring it in their boats and sell it on the shore at a shilling a cart. One cart is there reckoned equal to two of farmyard dung for raising pota- toes. Used alone for this crop, it gives a good return, but gen- erally of inferior quality.f On the south-east coast of Fife, where the sea-weed is laid on the stubble at the rate of 20 carts an imperial acre, ploughed in, and the turnips afterwards raised with half dung, the clover is said never to fail. Laid on bean- stubble, and ploughed in, 2t cart-loads gave in Suffolk, (1819,) three times as much wheat as 5 bushels of salt and 15 loads of farmyard manure per acre. Sea-weeds decompose with great ease when collected in heaps or spread upon the land. During their decay they yield not only organic food to the plant, but saline matters also, to which much of their efficacy both on the grass and the corn crops is no doubt to be ascribed. Especially to this saline matter may be ascribed the benefi- cial influence of sea-weed on garden asparagus, originally a sea- side plant, and upon fruits like raspberries, which contain much alkaline matter. * In this locality 16 loads of sea-weed are reckoned equal to 20 tons of farmyard manure. In the Island of Lewis 20 tons of sea- ware, which would yield half a ton of Icelp, are considered to be ample manure (or a Scotch acre. f The potatoes are said to be of better quality when the sea-weed is put into the soil and covered with a layer of eartli, upon which the potatoes are to be planted. 174 DRY VEGETABLE MATTER FOR MANURING. The value of sea-weed as a manure may be understood from the fact that the fticus saccharimis leaves, when dry, 28-6 per cent of ash, and contains 19 '2 6 — say 20 per cent — of protein compounds. In its recent state it contains 1 6 per cent of water, (Payen.) section iii. of manuring with dry vegetable matter. 1. Straw, — Almost every one knows that the sawdust of most common woods decays very slowly — so slowly, that it is rare to meet with a practical farmer who considers it worth the trouble to mix sawdust with his composts. This property of slow decay is possessed in a certain degree by all dry vegetable matter. Heaps of dry straw when alone, or even when mixed with earth, will ferment with comparative difficulty, and with great slowness. It is necessary, therefore, to mix it, as is usually done, with some substance that ferments more readily, and which will impart its own fermenting state to the straw. Ani- mal matters of any kind, such as the urine and droppings of cattle, are of this character ; and it is by admixture with these that the straw which is trodden down in the farmyard is m.ade to undergo a more or less rapid fermentation. The object of this fermentation is twofold — first, to reduce the particles of the straw to such a minute state of division, that they may admit of being diffused through the soil ; and second, that the dry vegetable matter may be so changed by exposure to the air and other agencies, as to be fitted to yield without difficulty both organic and inorganic food to the roots of the plants it is intended to nourish. Differences of opinion have prevailed, and discussions have taken place, as to the relative efficacy of long and short, or of half fermented and of fully rotten dung. But if it be added soldy for the purpose of yielding food to the plant, or of prepar- ing food for it, the case is very simple. The more complete the state of fermentation, if not carried too far, the more immediate LOSS OF WEIGHT BY FERMENTATION. 1T5 will be the agency of the manure — hence the propriety of the application of short dung to turnips and other plants it is desir- able to bring rapidly forward ; but if the manure be only half decayed, it will require time in the soil to complete the decom- position, so that its action will be more gradual and prolonged. Though in the latter case the immediate action is not so per- ceptible, yet the ultimate benefit to the soil, and to the crops, may be even greater, supposing them to be such as require no special forcing at one period of the year. This is easily under- stood. While it is undergoing fermentation in the farmyard, the straw loses part of its substance — either in the state of gaseous matter, which escapes into the air — or of saline matter, which is washed out in the liquid form. Thus, after complete fermentation, the quantity of matter present is really less, and consequently, when added to the soil, though the immediate effect upon the crop be greater, the whole effect may also bo very considerably less. This will appear more clearly when it is considered that the quantity of recent dung — mixed straw and cow dung — is by experiment equal on an average to 2 or 2^ times that of the dry food and fodder taken together, while, when fully rotten, the weight of the dung may be no greater than that of the dry food and fodder consumed by the cattle. Thus it has been found that one ton (20 cwt.) of dry food and straw gives a quantity of farmyard dung which weighs, "When recent, 46 to 50 cwt. After 6 weeks, 40 to 44 . . After 8 weeksj 38 to 40 . . When lialf rotten, 30 to 35 . . When fully rotten. 20 to 25 .. A part of this loss may, no doubt, be ascribed to the evapora,- tion of a portion of the water of the recent dung ; but the larger part is due to an actual escape of the substance of the manure itself. The farmer, therefore, who applies the manure from a given weight of food and straw, in a fresh state, adds 116 SAWDUST AND BRAN. more to his land than if he first allows it to become perfectly fermented. Were he to chop his straw, and put it in as it comes fresh from the field, he would add still more ; but its ac- tion as a manure would be slower, and while it would benefi- cially open stiff and heavy soils, it would injure others, by rendering them too light and porous, 2. Sawdust. — With a view to this slow amelioration, dry vegetable matter of any kind may, if in a sufficient state of di- vision, be added with benefit to the soil. Even sawdust, applied largely to the land, has been found to improve it, — little at first, more during the second year after it was applied, still more during the third, and most of all in the fourth season after it was mixed with the soil. That any dry vegetable mat- ter, therefore, does not produce an immediate effect, ought not to induce the practical farmer to despise the application to his land — either alone or in the form of a compost — of everything of the kind he can readily obtain. If his fields are not already very rich in vegetable matter, both he and they will be ulti- mately benefited by such^ additions to the soil. Saturated with ammoniacal liquor, or with hquid manure, sawdust has been profitably used, and without further addition, in the raising of turnips. It may also be charred either by burning, or by alternate layers of quick-lime, and thus benefi- cially applied. 3. Bran. — The bran and pollard of wheat are highly recom- mended as manures. Drilled in with the turnip seed at the rate of 5 or 6 cwt. an acre, at a- cost of £1 2s. 6d., it brought the young plants rapidly forward, and gave one-third more in weight of bulbs than the other parts of the field, which had been treated in the same way in every respect, except that no addition of bran had been made to them. If moistened with urine and slightly fermented, the action of bran would no doubt be hastened and rendered more powerful. The husk of the oat, hitherto wast(M at many of the oatmeal MALT AND RAPE DUST. 17t mills in the north, might also be beneficially fennented and em- ployed as a manure. 4. Brewers' grains, though usually given as food to fattening cattle or to milch cows, are by some of the farmers in Norfolk employed as a manure. They are supposed to pay best when mixed with farmyard manure. 5. Malt-dust — cummins, or combings — consists of the dried sprouts of barley, which, when the sprouted seed is dried in the process of malting, break off and form a coarse powder. This is found to be almost equal to rape-dust in fertilising power. One hundred bushels of barley yield 105 to 110 of malt and 4 to 5 of dust. In this neighborhood (Durham) it is sold at one shilling a bushel. Applied in the dry state, malt-dust decomposes slowly, and from its extreme lightness is applied with difficulty, as a top- dressing. If it be moistened with liquid manure and laid in heaps for a few days till it heat and begin to ferment, it may be used either as a top-dressing for grass, clover, and young corn, or it may be drilled in with the seed. It may also in this state be employed with advantage without any other manure for the turnip or potato crop ; but the turnip-seed should not be brought into immediate contact with it in the drills. Malt-dust leaves, when dry, 8 per cent of ash, and contains 23 per cent of protein compounds, (Payen.) This composition explains both its fertilising action when applied to the soil, and its nourishing effects when given to cattle or sheep along with turnips. 6. Rape-diist. — It is from the straw of the corn-bearing plants, or from the stems and leaves of the grasses, that the largest portion of the strictly vegetable manures applied to the soil is generally obtained or prepared. But the seeds of all plants are much more enriching than the substance of their leaves and stems. These seeds, however, are in general too va'uable for food to admit of their application as a manure. Still the re- fuse of some — as that of different kinds of rape-seed after the 8* 118 HEMP, POPPY, AND COTTON CAKES. oil is expressed, and which is unpalatable to cattle — ^is applied with great benefit to the land. Drilled in with the winter or spring wheat, or scattered as a top-dressing in spring at the rate of 5 cwt. an acre, it gives a largely increased and remune- rating return. Applied at a cost of 40s. per acre to wheat, it has been known to increase the produce 10 bushels an acre (from 29 to 39 bushels) and to give one-fifth more straw. Nor is the practice recent, for the application of it in this way, and at a cost of 40s to 42s. an acre, was common in Norfolk in the time of Arthur Young, (1170,) eighty years ago. In some districts it is used largely, and without admixture, for the raising of turnips. It is applied with equal success to the cultivation of potatoes, if it be put in the place of a part only of the manure. If used alone it is apt to give very large and luxuriant tops, with only an inferior weight of tubers. It is safer, therefore, to mix it with other manure ; and generally it may be substituted for it at the rate of about 1 cwt. of rape- dust for each ton of farmyard manure. 7. Ilemjp, ;pojppy, and cotton cakes — the refuse of crushed hemp, poppy, or cotton seed — may be used for similar purposes, and in the same way, as rape-cake. 8. Cocoa-nut cake, left by the expressed cocoa-nut, is also a valuable manure, and has alone been found to produce large crops of potatoes. These different kinds of cake all contain a large per-centage of nitrogen, (4 to 4i per cent,) or, in other words, of protein compounds. These ferment very easily, promote growth ra- pidly, and give to the manures that contain them peculiar fertilising virtues. SECTION IV. OF THE USE OF PEAT, PEAT COMPOST, AND TANNER's BARK. 1. Natural jpeat. — In many parts of the world — and in none more abundantly, perhaps, than in some parts of our own islands PEAT, NATURAL AND FERMENTED. 179 — vegetable matter continually accumulates in the form of peat. This peat ought to supply an inexhaustible store of organic matter for the amelioration of the adjacent soils. We know that by draining off the sour and unwholesome water, and afterwards applying lime and clay, the surface of peat bogs may be gradually converted into rich corn-bearing lands. It must, therefore, be possible to convert peat itself by a similar process into a compost fitted to improve the condition of other soils. 2. Fermented feat. — The late Lord Meadowbank, who made many experiments on this subject, found, that after being par- tially dried by exposure to the air, peat might be readily fer- mented, and brought into the state of a rich fertilising compost, by the same means which are adopted in the ordinary ferment- ing of straw. He mixed with it a portion of animal matter, which soon communicated its own fermenting quality to the sur- rounding peat, and brought it readily into a proper heat. He found that one ton of hot fermenting manure, mixed in alternate layers with two of half-dried peat, and covered by a layer of the same peat, was sufficient to ferment the whole. He observed afterwards, also, that the vapors which rise from naturally fermenting farmyard manure or animal matters, would alone produce the same effect upon peat, placed so as readily to receive and absorb them. As ammonia is one of the compounds specially given off by putrefying animal substances, it is not unlikely that a watering with ammioniacal liquor would materially prepare the peat for undergoing fermentation. At all events, it seems possible to prepare any quantity of valuable peat compost by mixing the peat with a little soil, and with a still smaller quantity of fer- mented manure than was employed by Lord Meadowbank, pro- vided the liquid manure of the farmyard be collected into a cistern, and be thrown at intervals, by means of a pump, over the prepared heaps. After being partially dried, natural peat may be very benefi- 180 PEAT COMPOST : CILUIRED PEAT. cially employed in absorbing the liquid manure of tlie farmyard, or in mixing with the contents of the tanks. 3. Mr. FUming^s peat compost. — Many other ways of working up peat have been suggested, such as adding lime, salt, and other substances, to aid the fermentation. The most successful of these mixtures with which I am acquainted is one which has been used with much advantage on the home farm of Mr. Flem- ing of Barochan. This compost consists of — Sawdust, or dry earthy peat, - - 40 bushels. Coal-tar, - - - - - 20 gallons. Bone-dust, .... 7 bushels. Sulphate of soda, - - ... 1 cwt. Sulphate of magnesia, - - - IJ " Common salt, - - - - I2 " Quick-lime, - - - - 20 bushels. These materials are mixed together and put into a heap, and allowed to heat and ferment for three weeks, then turned, and allowed again to ferment, when the compost is ready for use. Compared with farmyard manure and guano, this mixture gave on hay and turnips — 1°. On hay per imperial acre. Produce. Cost. Nothing, - - 416 stones. Guano, 3 cwt. - - *?52 ... $7 50 Compost, 40 bushels, 761 ... 5 00 2°. On turnips, (Jones' yellow top.) Produce. Cost. Farmyard manure, 28 yards, 26 tons. Guano, 5 cwt. . . 18 .. $12 50 Compost, 64 bushels, . 29 . . 7 75 According to these results, this compost is superior even to guano. The experiments, however, require repetition, and the results will no doubt vary with the kind of soil and of crop to which the compost is apphed. 4. Charred peat. — By being built up and charred or half burned in covered heaps, peat may be obtained in a state in USE OF CHARCOAL POWDER. 181 wliich it is easily reduced to powder. In this powdery state, it lias been used alone for turnips, at the rate of 50 bushels an acre, and was found to give as good a crop as 50 carts of farm- yard dung. Something of this action, however, may have de- pended upon the nature of the soil, and upon the kind of peat. Charred peat forms, hkewise, an excellent absorbent for the liquids of the farmyard and the stable, and for drying up dis- solved bones. 5. Tanners'' hark. — I may here advert also to the use of tan- ners' bark, a form of vegetable matter which, like sawdust and peat, is difficult to work up, and is therefore often permitted largely to go to waste. Like peat it may be dried and burned for the ash, which is light, portable, and forms a valuable top- dressing. But the economist will prefer to ferment it in a compost, in the way above described for peat. An occasional watering of the compost with the liquid manure of the farm- yard will bring it into a heat, and when the ammoniacal liquor of the gas-works can be procured at a cheap rate, it may be employed for a similar purpose. The hard thick fragments of bark, however, cannot be so soon decomposed as the already finely divided peat, and must be expected therefore to demand more time. With lime it may, like sawdust or peat, be reduced and charred. SECTION V. MANURING WITH ARTIFICIALLY DECOMPOSED VEGETABLE SUBSTANCES CHARCOAL, SOOT, COAL-TAR, &C. When wood and other vegetable substances are heated in close vessels they are converted into charcoal. Coal, which is of vegetable origin, deposits in our chimneys, when burned, large quantities of soot ; and when distilled in gas-retorts it yields, besides gas, a quantity of coal-tar and other products. All these substances have been tried and recommended as ma- nures. 1°. Charcoal powder possesses the remarkable properties of 182 EXPERIMENTS WITH SOOT. absolving noxious vapors from the air and from the soil, and of extracting unpleasant impurities as well as saline substances from water, and of decomposing many saline compounds. It also sucks into its pores much oxygen and other gases, from the air. Owing to these and other properties, it forms a valuable mixture with liquid manure, nightsoil, farmyard manure, ammo- niacal liquor, or other rich applications to the soil. It is even capable itself of yielding slow supplies of nourishment to living plants ; and it is said in many cases, even when unmixed, to be used with advantage as a top-dressing in practical agriculture.* In moist charcoal the seeds of the gardener are found to sprout with remarkable quickness and certainty ; but after they have sprouted, they do not continue to grow well in charcoal alone. Drilled in with the seed, charcoal powder is said greatly to promote the growth of wheat. 2°. Soot, whether from the burning of wood or of coal, con- sists chiefly of a finely divided charcoal, possessing the proper- ties above mentioned. It contains, however, ammonia, gypsum, nitric acid, and certain other substances in considerable quan- tity, to which its well-known effects upon vegetation are chiefly to be ascribed. In many localities it increases the growth of the grass in a remarkable degree, and as a top-dressing to wheat and oats, it sometimes produces effects equal to those which follow the use of the nitrates of potash or soda.f Thus wheat and oats dressed with soot, in comparison with undressed, gave the following return of grain — Wheat. Oats. Undressed, 44 bushels. 49 bushels. Dressed^ 54 55 .. Increase, .10 6 * This may no doubt be in part owing to its aiding the production, as all porous substances do, of ammonia in its interior, and hence of apocrenate of ammonia (p. 23) in the soil, but in part also to its power of decomposing other substances. f Journal of the Boy al Agricultural Society of England, ii. p. 259. COAL DUST AND COAL TAR. 183 It acts also upon root crops — 56 bushels of soot mixed with 6 of common salt having produced larger crops of carrots than 24 tons of farmyard manure, with 24 bushels of bones.* I have lately examined several varieties of soot, and find that it contains from 18 to 48 per cent of mineral matter, con- sistiug of earthy substances from the coal carried up into the chimney by the draught, and of gypsum and sulphate of mag- nesia derived from the lime of the flue and the sulphur of the coal. It contains besides from 1 to 2 per cent of ammonia, chiefly in the state of sulphate. These proportions of ammonia, calculated in the state of sulphate of ammonia, are equal to from 5 J to 12 per cent of the whole weight of the soot. It is cot wonderful, therefore, that its ejffects should resemble, and even rival, those of the nitrate of soda and of the sulphate of ammonia. When applied to grass in spring it is said to give a peculiar bitterness to the pasture, and even to impart a taste to the milk. Hence, in large towns, the cow-feeders of the milk- dairies are unwilling to purchase early grass which has been manured with soot. 3°. Coal-dust. — In the county of Durham the dust of com- mon coal, such as is sifted out at the mines as too small for burning, has been spread upon poor, cold, arable land, and as a top-dressing upon old pastures, wdth manifest advantage. Something will, no doubt, depend both upon the quality of the coal and upon the kind of land to which it is applied. 4°. Coal-tar applied to the wheat-stubble with a water-cart, at the rate of 180 gallons to the imperial acre, and allowed to remain two or three months before it is ploughed in, is said greatly to benefit the after crop of roots. It has been tried on a sandy loam, and on a deep clay. It has also been used in the form of compost. * Journal of the Royal Agricultural Society of England, iv. p. 270. 184 DIFFERENT VEGETABLE MANURES. SECTION VI. RELATIVE FERTILISING AND MONEY VALUES OF DIFFERENT VEGETABLE MANURES. There are two principles on which the relative values of dif- ferent vegetable substances, as manures, may be estimated ; — first^ by the relative quantity and kind of inorganic matter they respectively contain ; and second, by the relative proportions of nitrogen present in each. 1. Yalued according to the quantity oi inorganic matter they contain, the worth of the several kinds of straw, hay, &c., would be represented by the following numbers : A ton loeight of each substance, when made into manure — provided nothing is washed out by the rains — will return to the soil the following quantities of inorganic matter in pounds :- Wheat-straw, . . . . •70 to 3.60 Oat-straw, .... 100 to 180 Hay, .... 100 to 200 Barley-straw, 100 to 120 Pea-straw, . . . " . 100 to 110 Bean-straw, 100 to 130 Rye-straw, .... 50 to 100 Dry potato-tops. 400 Dry turnip-tops, 370 Rape, and other cakes, 120 Malt-dust, .... 180 Dried sea-weed. 560 Generally, perhaps, these numbers will give the reader a tolero,- bly correct idea of the relative permanent eifects of the above different kinds of vegetable matter, when laid upon the soil. But a reference to the facts stated in pp. 64 to 13, in regard to the quality of the inorganic matter contained in plants, will sat- isfy him that the effect of these manures on particular crops is not to be judged of solely by the absolute quantity of earthy and saline matter they contain. What the turnip-top, for example, or the bean-stalk, returns to the soil, may not be exactly what will best promote the growth of wheat. EFFECTS OF THEIR NITROGEN ON THEIR VALUE. 185 2. On the other hand, if the fertilising value of vegetable substances is to be calculated from the relative quantities of ni- trogen they severally contain, we should place them in the fol- lowing order ; — the number opposite to each suljstance repre- senting that weight of it in pounds which would produce the same effect as 100 pounds of farmyard mamlre, consisting of the mixed droppings and litter of cattle. (Boussingault.) ' Equivalent quantities in pounds. Farmyard manure, . . . . 100 "Wheat-straw, 80 to 170 Oat-straw, . 150 Barley-straw, 180 Buckwheat-straw, . 85 Pea-straw, . 45 Wheat-chaff, 50 Green grass, 80 Potato-tops, •75 Fresh sea-weed, 80 Dried sea-weed, 20 Bran of wheat or Indian coi 'Qj 26 Malt-dust, . 13 Eape, and other cakes, 8 Pir sawdust, 250 Oak sawdust, 180 Coal-soot, 20 to 30 This table again presents the same substances in a somewhat different order of value ; showing, for example, not only that such substances as rape-dust, malt-dust, and soot, should pro- duce a much more remarkable effect upon vegetation than the same weight even of farmyard manure, but also that certain dry vegetables, such as bran, chaff, and pea-straw, will yield, when not unduly fermented, a more enriching manure than the straw of barley, oats, or wheat. It agrees also with the known effect of green manuring upon the land, since 80 'pounds of meadow grass ploughed in should, according to the table, be equal in virtue ^o 100 of farmyard manure. Some writers ascribe the entire action of these manures to the 186 GENERAL CONCLUSIONS. nitrogen they contain. This, however, is taking a one-sided view of their real natural operation. The nitrogen, during their decay, is liberated chiefly in the form of ammonia, — a compar- atively evauescent substance, producing an immediate effect in hastening or carrying farther forward the growth of the plant, but not remaining permanently in the soil. The reader, there- fore, will form an opinion consistent alike with theory and with practice, if he concludes — 1. That the immediate effect of vegetable manures in hasten- ing the growth of plants is dependent, in a great degree, upon the quantity of nitrogen they contain and give off during their decay in the soil ; but — 2. That their jpeiinanrnt effect and value is to be estimated chiefly by the quantity and quality of the inorganic matter they contain — of the ash they leave when burned. The effect of the nitrogen may be nearly expended in a sin- gle season; that of the earthy and saline matters may not be exhausted for several years. Kor is the carbon of vegetable substances without its im- portant uses to vegetation. From the statements contained in the earlier chapters of the present work — especially in reference to the production of ammonia and nitric acid in the soil, through the agency of decaying carbonaceous matter — it may be inferred that, however much influence we may allow to the nitrogen and to the earthy matter of plants in aiding the growth of future races, the soundest view is that which con- siders each of the elements present in decayed or decaying plants to he capable either of ministering to, or of p/reparing food for, such as are still alive. We may not be able as yet to estimate the precise importance of each element to any particular kind of crop or soil, or so to adjust the quantities of each in our manures, as to promote the growth of that crop upon that soil, in the greatest possible degree, yet the principle itself is a sound one, and will hereafter guide us to safe and correct results. CHAPTER XIY. Animal manures. — Flesh, fish, shell-fish. — Insects. — Blood. — Animalised charcoal. — Skin, horn, hair, wool. — Woollen rags. — Shoddy. — Horn-saw- dust, and hoof parings. — Cause of the fertilising influence of these ma- nures. — Composition and use of bones and horn-flints. — Preparation of dissolved bones. — Comparative experiments with crushed and dissolved bones. — Why solution in acid makes bones more active. — Comparative action of flesh, blood, horn, woollen rags and bones. — Use of the liquid excretions of animals. — Urine of man, the cow, the horse, and the pig. — Construction of liquid-manure tanks. — Urate. — Sulphated urine. The animal substances employed as manures consist chiefly of the flesh, blood, bones, horns, and hair of sea and land ani- mals, and of the solid and liquid excrements of land animals and birds. SECTION I. OF FLESH, FISH, BLOOD, AND SKIN, AND OF THEIR USE AS MANURES. Animal substances, in general, act more powerfully as ma- nures than vegetable substances; it is only the seeds of plants which can be at all compared with them in efficacy. 1. The flesh of animals is rarely used as a manure, except in the case of dead horses or cattle which cannot be used for food, 2. Fish are, in this country, chiefly applied in the form of the refuse of the herring and pilchard fisheries, though occa- sionally such shoals of sprats, herrings, dog-fish, and even mackerel, have been caught on our shores, as to make it neces- sary to employ them as manure. These recent animal sub- stances are found to be, for the most part, too strong when applied directly to the land; they are usually, therefore, made 188 FISH AS A MANURE. into a compost, with a large quantity of soil. Five barrels of fish, or fish refuse, made into twenty loads of compost, will be sufficient for an acre. On the coast of Norfolk, large quantities of sprats are used as a manure for the turnip crop. They are sold for about 8d. a bushel. A ton and a half, mixed with twelve to fifteen cwt. of mould taken from the head of the field, makes a compost which is suffi- cient for an imperial acre, and is said never to fail. On the shores of Aberdeenshire, dog-fish are caught and applied as a manure. In Rhode Island and the adjoining States, considerable quan- tities of manure are made by mixing the fish called menhaden, of which large numbers are taken in the bays, with peat or swamp mud, in the proportion of one load of fish to ten of peat or mud. As many as 150 tons of this fish have been taken at a single haul, and sold to the farmers at about 2s. 6d. the thou- sand fish, or waggonload.* On the coasts of Connecticut large quantities of fish, called white fish, are caught and sold for manure, at the rate of about a dollar (4s.) a thousand, weigh- ing 15 or 20 cwt. They are either laid on the land and ploughed in, or are made into a compost. In the north of China, prawns and other kinds of fish are collected and employed for manuring purposes. The refuse of the fish oils, of the fat of animals that has been malted for the extraction of the tallow, of skins that have been boiled for the manufacture of glue — as also horns, hair, wool, woollen rags, and all similar substances, when made into com- posts — exercise, in proportion to their weight, a much greater Influence upon vegetation than any of the more abundant forms of vegetable matter. 3. Shell-fish, when they abound on our coasts, have been found to be capable of economical application to the land, even for raising turnips and potatoes. They are mixed with a little * See the Author's Notes on North America, vol. ii. p. 231. INSECTS AND BLOOD. 189 eartli into a ricli compost, and allowed slightly to ferment. If the means of crushing them be at hand, their value is by this process considerably increased. On the northern shores of the Solway, near Annan, the common mussel is found in such quan- tities in some places, that, when the tide recedes, a cart-load can be raked out of the sand in so short a time as to make it a very economical manure. The Rev. Mr. Gillespie of Cum- mertrees informs " me, that 700 cart-loads were collected and applied to the raising of turnips during the year 1844. They are used without other manure, at the rate of about 50 bushels to the Scotch acre. On the coasts of Lincolnshire, also, they are met with in some places in large quantities, and collected for use as a manure. 4. Even the bodies of insects in many parts of the world form important manures. In warm climates, a handful of soil some- times seems almost half made up of the wings and skeletons of dead insects : in Hungary and Carinthia the peasant occasionally collects as many as 30 cart-loads of dead marsh-flies in a single year ; and in the richer soils of France and England, where worms and other insects abound, the presence of their remains in the soil must aid its natural productiveness. 5. Blood is in this country very seldom, applied to the land directly. Like the other parts of animals, however, it makes an excellent compost. In Northamptonshire, such a compost is made by mixing about 50 gallons of blood with 8 bushels of peat-ashes and charcoal powder, and allowing the mixture to stand for a year or two. On light soils, this compost raises excellent turnips when applied olone, at the rate of 6 quarters (48 bushels) per imperial acre — or of 2 quarters with 12 tons of farmyard dung. As a top-dressing to young wheat, 20 or 30 bushels an acre greatly increase the crop. On heavy and wet lands, its effects are less perceptible. In that part of England the blood is contracted for at the rate of 3d. a gallon. In some countries the blood is dried, and in the state of powder is applied as a top-dressing to the growing crops. In this state it is sold 190 WOOLLEN RAGS AND SHODDY. in Paris at about 8s. a cwt. — a moderate price, if it be tolera- bly dry. Samples prepared in London, and containing still 22 per cent of water, have also been valued at £S or .£9 a ton. But this mode of using blood is not very widely adopted. 6. Animalised charcoal. — As blood comes from the sugar re- fineries, however — in which, with lime-water and animal char- coal, it is employed for the refining of sugar — it has obtained a very extensive employment, especially in the south of France. This animal black, or animalised charcoal, as it is sometimes called, contains about 20 per cent of blood, and has risen to such a price in France that the sugar refiners actually sell it for more than the unmixed blood and animal charcoal originally cost them. This has given rise to the manufacture of artificial mixtures of charcoal, fecal matters, and blood, which are also sold under the name of animalised charcoal. A great disad- vantage attending the use of these artificial preparations is, that they are liable to be adulterated, or, for cheapness, pre- pared in a less efficient manner. Y. Skin. — Fragments of skin are sometimes used as a ma- nure. The parings of skins from the tan-works are Boiled by the glue-makers, and the insoluble refuse is sold as a manure. This refuse, in the form of compost, ought to nourish the crops very much. When used alone for potatoes, it is said to make them waxy on soils where, with other manures, they grow mealy and dry. SECTION IL OF HAIR, WOOL, WOOLLEN RAGS, SHODDY, HORN-SAW- DUST, AND HOOF-PARINGS. 1. Horn, hair, and loool, depend for their efficacy precisely ou the same principles as the blood and flesh of animals. They differ chiefly in this, that they are dry, while blood, flesh, and fish contain about 80 per cent of their weight of water. Hence, one ton of horn-shavings, of hair,* or of dry woollen * In China, the hair, which every ten days is shaven from the heads of the entii'e population, is collected and sold for manure throughout the empire. NITROGEN IN ANIMAL MANURES. 191 rags, ought to enrich the soil as much as 4 to 5 tons of blood. In consequence, however, of their dryness, the horn and wool decompose much more slowly than the blood. Hence the effect of soft animal matters is more immediate and apparent, while that of hard and dry substances is less visible, but continues for a much longer period of time. 2. Woollen rags, when made into a compost and fermented, form an excellent manure for potatoes or turnips. In the hop countries, they are buried at the roots of the hop plants with great advantage. They sell at about £5 a ton. On the sandy land in Wiltshire, they are frequently used as a manure for turnips. 3. Shoddy, or mill-waste — the waste of the woollen and cloth mills of Yorkshire — is nearly the same thing as hair and woollen rags. It sells at about £2 a ton, and is extensively used by the farmers of Kent and Northampton. 4. Horn-saiodiist and hoof-parings. — The small dust, parings, turnings, and siftings of horn from the shops of the comb-makers, as well as the hoofs of cattle, are now sold to the prussiate of potash manufacturers at the rate of about £2 a ton. If they were free from admixture, they should be worth to the farmer about the same price as woollen rags. They are usually mixed with much sand and dust — amounting sometimes to 50 or 60 per cent of their whole weight. In this state they are not worth more than two-fifths of the price of dry hair or woollen rags. They may be used instead of bones for the turnip or potato crop, but should be made into a fermented compost before they are employed as a top-dressing. SECTION II. CAUSE OF THE FERTILISING INFLUENCE OF THE ABOVE ANIMAL MANURES. The fertilising influence of the parts of animal bodies, described in the preceding sections, depends mainly upon their consisting, for the greater part, of substances very rich in nitrogen. Thus — 192 HORN AND BONES. Percentage of nitrogen. Dry blood, flesh, and fish contain about . . 15| Dry skin, hair, wool, horns, and hoofs, . . 16 to 17^ But these two classes of substances differ much in the quan- tity of water they contain — Percentage of water. Blood, fish, and flesh, contain . . . 78 to 82 Hair, wool, and. horn, . . . . 10 to 15 Skin and hoofs vary much in dryness, and therefore the aver- age proportion of water in them cannot be estimated. The special differences of the above substances as manures depend mainly upon those differences in the proportion of water. Blood, fish, and flesh decompose rapidly, act quickly," and pro- mote growth speedily. Wool, hair, and horn take a long time to rot, are not so well adapted, therefore, for promoting speedy growth, but by their gradual decay are better fitted to afford prolonged nourishment to a crop which continues long in the ground, or permanently to enrich a soil which has been exhausted by too severe cropping. The mineral matter contained in these substances is small in quantity, and therefore of comparatively little influence upon their manuring value. Dry blood and flesh leave about 4 per cent of ash, while wool, hair, and horn leave only 1 or 2 per cent. The ash of flesh and fish consists almost entirely of phos- phates, and that of blood in great part of common salt. This may influence their respective action upon plants — as the fact that hair contains 5 per cent of sulphur may also modify the action of this substance as a manure. (See p. 000.) SECTION IV. COMPOSITION OF BONES AND THE PITH OF HORNS, AND THEIR VALUE AS MANURES. 1. Bones, while they resemble hair and horn in being dry, HORN, FLINT OR PITH. 193 diflfer from them in containiug a large quantity of earthy matter, and hence they introduce a new agent to aid their effect upon the soil. Thus, the bones of the cow consist in 100 lb. of — Phosphate of lime, , 55J Phosphate of magnesia, 2 Soda and common salt, 2i Carbonate of lime, . . . . 31 Fluoride of calcium. 3 Gelatine (the substance of horn,) . 33i 100. While 100 lb. of dry bone-dust, therefore, add to the soil as much organic animal matter as 33 lb. of horn, or as 300 to 400 lb. of blood or flesh, they add at the same time two-thirds of their weight of inorganic matter, consisting of lime, magnesia, soda, common salt, and phosphoric acid (in the phosphates) — all of which, as we have seen, must be present in a fertile soil, since the plants require a certain supply of them all at every period of their growth. These substances, like the inorganic matter of plants, may remain in the soil, and may exert a be- neficial action upon vegetation after all the organic or gelati- nous matter has decayed and disappeared. 2. Horn Jlints, or piths, resemble bone very much in compo- sition. They contain a little more animal matter, and from their softness and porosity are more difiicult to crush in the mill. For the same reason, however, they decay more rapidly in the soil, and act more immediately than bones. They boil down, however, more readily than bones, and are therefore largely used for making the size used in stiffening calicoes. For this purpose they are sold by the comb-makers at about £4 a ton. When they are not in demand for this purpose they may be very usefully employed as a manure. A sample of the pith, as it is sold in tlie market, gave to Professor Norton in my laboratory — 9 194 PREPARATION OF DISSOLVED BONES. Water, (lost at 212",) . . . 10.31 • Phosphates of lime and magnesia, . 46.14 Carbonate of lime, . . . . "/.Tl Gelatine, (organic matter,) . . . 35.84 100. SECTION V. PREPARATION OF DISSOLVED BONES. COMPARATIVE EX- PERIMENTS WITH CRUSHED AND DISSOLVED BONES, WHY THIS SOLUTION MAKES BONES MORE ACTIVE. For the purpose of bringing bones into a state in which the substances they contain can be more readily taken up by the roots of plants, and at the same time more uniformly distri- buted through the soil, the method has been adopted of dis- solving them in sulphuric acid. For this purpose, the bone-dust is mixed with one-half its weight, and sometimes with its own weight of sulphuric acid (the oil of vitriol of the shops,) previously diluted with from one to three times its bulk of water. Considerable effervescence takes place at first, from the action of the acid upon the carbonate of lime in the bones; but, after two or three days, with occasional stirring, the bones are entirely dissolved or reduced. The solution or paste may now be dried up with charcoal powder, with dried or charred peat, with sawdust, or with fine vegetable soil, and applied with the hand or with the drill to the turnip crop ; or it may be diluted with 50 times its bulk of water, and let off into the drills with a water-cart. Applied either way, the effect is much more striking than when the same weight of bone-dust is applied in the ordinary form. Thus — a. At Gordon Castle (Mr. Bell) the following results were obtained : — Manure per Imperial Acre. Cost. -p. , , Hvbrid ' 3 cwt. guano, 1 17 ( 9.2C) 11-2 .. 16 bushels bones, 1 16 ( 9.00) 11 EXPERIMENTS WITH DISSOLVED BONES. 195 Manure per Imperial Acre. Cost. ■^^°^"''®x?^?"i^^' Dale s Hybrid. 2 bushels bones, ) 83 lb. sulphuric acid, I £0 11 6 ($2.88) 12-2 .. 400 gallons water, \ 8 bushels bones, j 83 1b. sulphuric acid — I 1 5 ( 6.25) 11 sown with the hand. ) The largest produce was here obtained, when the dissolved bones were applied with a water-cart, and at a cost of eleven shillings per acre. b. Again, on the farm of Sherriffstoun in Morayshire, (Mr. M' William,) the following comparative results were obtained in 1843 :— 1. Swedish Turnips. Manures. Cost per Produce in Bulbs per Acre. Imperial Acre. •75 lb. (1-6 bushels) bones, ' £0 9 3 ($2.31) 46 lb. acid, IT -5 tons. 400 gallons water, The same with 200 gallons water. 9 3 ( 2.31) 18-5 .. 440 lb. (9-5 bushels) bones, 28 lb. of acid, I 1 4 9 ( 6.19) IT 2. Common Turnips. 170 lb. (3-2 bushels) bones, " ) 92 lb. acid, [■ £0 1*7 6 ($4.38) 16 tons. 400 gallons water, ' \ 16 bushels bones, . ) 46 lb. acid, - 2 2 ( 5.50) 13-5 . . 10 gallons water, j 1 In all these cases the smaller quantity of bones, when dis- solved in acid and applied in a liquid state, gave a heavier return of bulbs than the larger quantity when drilled in dry. Even the watering of the large quantity of bones with a portion of acid, did not make their effect on the crop equal to that of the small quantity of dissolved bones. 196 INFLUENCE OF THE SULPHURIC ACID. Mr. Hannam obtained, by the use of crushed and dissolved bones upon turnips, the following results : — Tons. cwts. 10 3 per imperial 9 12 11 15 12 11 14 6 14 11 13 15 15 2 16 1 Bones. 16 bushels, crushed, gave 2 . . dissolved, 2 4 4 4 We can explain this superior action of dissolved bones by the fact, that the dissolving separates their particles completely from each other, diffuses them more completely through the soil, and presents them to a larger surface of the turnip roots, and in a state in which they can be more readily absorbed. The sul- phuric acid also may have some effect, since we know that sul- phur, in some form, is necessary to the growth of all our crops. I have indeed been informed of a case at Balcarras, in Fifeshire, where diluted sulphuric acid applied alone to the drills produced an excellent crop of turnips ; and of another in Dumfriesshire, where steeping the seed-corn in diluted sulphuric acid added many bushels to the crop of barley. Though the immediate effect of a small quantity of bones on the first crop is made so much greater by this mode of applying them, it is not to be expected that the effect upon the after crops should be as beneficial as when a larger quantity of bones is applied in the ordinary method. SECTION VI. COMPARATIVE ACTION OF FLESH, BLOOD, HORN, WOOLLEN RAGS, AND BONES. From what has been stated in the preceding sections the reader will gather these general conclusions — ] . That animal substances which, like flesh and blood, con- GENERAL CONCLUSIONS. l^t tain much water, decay rapidly, and are fitted to operate imme- diately and powerfully upon vegetation, but are only temporary or evanescent in their action. (P. 192.) 2. That when dry, as in horn, hair, and wool, they decom- pose — and consequently act — more slowly, and continue to ma- nifest an influence, it may be, for several seasons. 3. That bones and horn flints act like horn, in so far as their animal matter is concerned, and, like it, for a longer or shorter time, according as they have been more or Tess finely crushed; but that they ameliorate the soil by their earthy matter for a still longer period — permanently improving the condition, and adding to the natural capabilities of the land. 4. That the action of bones may be rendered more imme- diate and striking by bringing them into a minute state of di- vision, — as by dissolving them in diluted sulphuric acid, or by fermenting them in a mixture of moist sand or soil — but that, like flesh and blood, their effect, by that means, is likely to be rendered less permanent. SECTION VII. OF THE URINE OF ANIMALS, AND THE MEANS OP PRESERVING AND APPLYING IT. URATE. SULPHATED URINE, &C. Practical men have long been of opinion that the digestion of food, either animal or vegetable, — its passage through the bodies of animals — enriches its fertilising power, weight for weight, when added to the land. Hence in causing animals to eat up as much of the vegetable productions of the farm as possible — of the straw and turnip-tops, for example, as well as of the grain and bulbs — it is supposed that not only is so much food saved, but that the value of the remainder in fertilising the land is greatly increased. In a subsequent section we shall see how far theory serves to throw light upon these opinions. The digested animal substances usually employed as manures are — the urine of man, of the cow, and of the sheep; the solid excrements of man (nightsoil,) of the horse, the cow, the 198 THE URINE OF MAN. sheep, and the pig, and the droppings of pigeons and other birds. The liquid manures act chiefly through the saline sub- stances which they hold in solution, while the solid manures contain also insoluble matters which decay slowly in the soil, and there become useful only after a time. The former, there- fore, will influence vegetation more powerfully at first ; the action of the latter will be less evident, but will continue to be sensible for a much longer period of time. 1. Tht urim of man. — Human urine consists, in 1000 parts of— Water, 932 Urea, and other organic matters containing nitrogen, 49 Phosphates of ammonia, soda, lime, and magnesia, . 6 Sulphates of soda and ammonia, .... 7 Sal-ammoniac, and common salt, .... 6 1000 1000 lb. of urine, therefore, contain 68 lb. of dry fertilising matter of the richest quality, worth, at the present rate of sell- ing artificial manures in this country, at least 10s. a cwt. As each full-grown man voids about 1000 lb. of urine in a year, the national waste incurred in this form amounts, at the above va- luation, to 6s. a head. And if 5 tons of farmyard manure per acre, added year by year, will keep a farm in good heart, 4 cwt. of the solid matter of urine would probably have an equal effect ; or the urine alone discharged into the rivers by a popu- lation of 10,000 inhabitants would supply manure to a farm of 1500 acres, and would yield a return of 4500 quarters of corn, or an equivalent produce of other crops. Mr, Smith of Deans- ton considered the urine of two men to be a suSicient manuring for an acre of land, and that when mixed with ashes, it would produce a fair crop of turnips,* An important chemical distinction exists between the urine of man and that of the cow, the horse, and the sheep. It con- tains, as is shown in the previous page, about 6 per cent of * Report of Committee on Metropolitan Sewerage. URINE OF THE COW. 199 phosphates, while these compounds are entirely absent from the urine of the other animals. The presence of the phosphoric acid contained in these phosphates, adds very much to the ma- nuring value of human urine. If milk or lime be mixed with fermenting human urine, this phosphoric acid is precipitated with a portion of the animal matter. Dr. Stenhouse found a precipitate of this kind, when dried at 212°. F.-, to contain 40 per cent of phosphoric acid and of organic matter, including about 1 per cent of ammonia. By the use of this method, an important part of the fertilising ingredients of human urine may be separated in a solid state. It has recently been adopted with some success for the purpose of separating the fertilising matters contained in sewage water. 2. Pig^s urine. — The urine of the pig resembles that of man, in containing a considerable proportion of phosphoric acid. In this respect it is more valuable as a manure than those of the horse, the cow, and the sheep. 3. The urine of the coia is said to contain less water than that of man, though of course much must depend upon the kind of food with which it it is fed. Considering, then, the large quantity of liquid manure that is yielded by the cow (1200 or 1500 gallons a-year,) we may safely estimate the solid matter given off by a healthy animal in the form of urine in twelve months, at about 1000 lb. in weight — worth, if it icere in the dry state, from £i to £5 sterling. In the liquid state, the urine of one cow, collected and preserved as it is in Flanders, is valued in that country at about £2 a-year. Any practical farmer may calculate for himself, therefore, how much real wealth, taking it even at the Flemish value, is lost in his own farmyard — how much of the natural means of reproduc- tive industry passes into his drains, or evaporates into the air. This liquid manure is very valuable, when collected in tanks, for watering the manure and compost heaps, and thus hasten- 200 CONSTRUCTION OF LIQUID-MANURE TANKS.' ing their decomposition. It may also be sprinkled directly upon the fields of grass or of clover, and upon the young corn, — or the young green crop (turnips, &c.) may be watered with it, with the best effects. It must, however, be permitted to stand till fermentation commences, and must afterwards be diluted with a considerable quantity of water, before it will be in the best condition for laying upon the land. This dilution, indeed, where the receiving tanks are large enough, should be made at an earlier period, for it has been found that, when un- mixed with water, cows' urine, which is six weeks old, contains only one-sixth part of the ammonia retained by the same urine when.it has been previously diluted with an equal bulk of water. Sulphuric acid may also be added to fix the ammonia.* 4. Of the construction of liquid-manure tanks. — There are four practical points which are worthy of attention in the construc- tion of tanks for liquid manure. a. They ought to be well puddled with clay behind the stone or brick work, to prevent any loss or escape of the liquid. h. They ought to be covered over, and the closer the better. In Germany they are usually vaulted. From close tanks the sun, rain, and air, are in a great measure excluded, and the fer- mentation is slower, and the loss of ammonia in consequence considerably less. c. They should be divided by a wall, into at least two com- partments, capable of holding each a two or three months' sup- ply. When the first of these is full, the stream is turned into the second, and by the time it is also full, the contents of the first are ripe, or in a fit state for putting upon the land. The * To saturate and fix the whole of the ammonia capaUe of being formed iu the urine of a single cow of average size, would require about V 00 lb. of the common strong sulphuric acid of the shops, or nearly 60 lb. a month, costing 9s. One-third or one-fourth of this quantity, however, added to tho liquid-manure tank, would be sufficient to prevent any very sensible loss. Mr. Kinninmonth found 750 gallons of cows' urine so treated, with about 15 lb. of acid, equal in increasing the produce of hay to 2^ cwt. of guano, or 1 cwt. of nitrate of soda. , URATE AND SULPIIATED URINE. 201 liquid ought always to be in a state of fermentation before it is applied either to grass or to any other crop. This double tank also enables the farmer to collect and preserve his liquid during the three mouths of winter, when it cannot be applied, and to have a large supply in a fit state for putting on when the young grass or corn begins to shoot. The liquid as it comes from the cattle ought to be mixed in the tank with at least its own bulk of water. By this means a considerable loss of ammonia is prevented which would other- wise escape from the urine during fermentation ; and it is pre- vented from burning the grass, which in very dry seasons it is apt to do when put on without dilution. This necessarily involves larger cisterns, and more labor in carrying out the liquid ; but experience seems to say that the additional profit exceeds considerably the additional expense. 5. Urate. — Among other methods of obtaining the virtues of animal urine in a concentrated form, burnt gypsum is mixed with it in the state of powder in the proportion of 10 lb. to every t gallons, allowing the mixture^ occasionally stirred, to stand some time, pouring off the liquid, and drying the gypsum. This is sold by manure manufacturers under the name of urate. It never can possess, however, the virtues of the urine, since it does not contain the soluble saline substances, which the gypsum does not carry down with it. Except the gypsum, indeed, 100 lb. of urate contain no greater weight of saline and organic matter than ten gallons of urine. If it be true, then, as the manufacturers state, that 3 or 4 cwt. of urate are sufiicient manure for an acre, the practical farmer will, I hope, draw the conclusion, — not that it is well worth while to venture his money in buying this urate, and trying it upon his land, but that a far more promising adventure will be to go to some expense in sav- ing his own liquid manure, and after mixing it, if he think proper, with the burned gypsum, to lay it abundantly upon all his fields. 6. Sulphated urine. — A better method than that of using 9* 202 AJIMONIACO-MAGNESIAN PHOSPHATE. , gypsum has been lately adopted by several manure manufac- turers. They -mix as much sulphuric acid with the urine as is sufficient to combine with and fix the whole of the ammonia which may be produced during the decomposition of the urine. The mixture is then evaporated to dryness, and is sold and applied to the land in the state of a dry powder. This sulphated urine, containing as it does all the saline sub- stance of the liquid urine, with the addition of sulphuric acid, ought to prove a most valuable manure. If prepared from human urine, it will promote the growth of nearly all crops ; but, from the sulphuric acid it contains, it may exercise a special influence on beans, peas, and clovers. As a top-dressing it may be applied alone ; but when used for root-crops, it ought to be mixed with and to take the place of not more than one-half of the farmyard manure usually applied. Used in this way, at a cost of £2 an acre, Mr. Finnie of Swanston obtained, in 1843, four tons of turnips per imperial acre more than from an equal cost of guano. As a top-dressing for wheat, and probably also for other corn crops, this sulphated urine may be advantageously mixed with an equal weight of sulphate of soda or of common salt, with at least as much wood ashes, if they can be had, and with half its weight of dissolved bones. The soda salts are especially desir- able where the land lies remote from the sea. 1. Ammonia co-ma gnesian pkosp/iaie.- — Boussingault fixes the ammonia and phosphoric acid of human urine by adding to it, after it has acquired an ammoniacal odor, a solution of sul- phate or muriate of magnesia, when the double phosphate of magnesia and ammonia falls to the bottom of the liquid. About T lb. of this salt are obtained from 100 lb. of urine ; and it has been ascertained to possess powerful fertilising pro- perties.* * In reference to liquid manures, I strongly recommend to my readers, the "Minutes of Information collected on the Practical Application of Sewer "Water, and Town Manures, to Agricultural Purposes," published by- the General Board of Health. CPIAPTER XY. Animal manures continued. — Solid excretions or droppings of animals. — Nightsoil. — Poudr-ette. — Tafl'o. — Cow, horse, and pigs' dung. — Droppings ^ of birds, — Pigeons' dung. — Guano. — African and -American varieties. — Their composition, and fertilising values. — Their durability. — Adultera- tion ofj how to test or select a good sample, quantity imported, and va- lue to the nation. The solid excretions of animals are not less valuable as ma- nures than their urines, and in almost every country are much more generally employed. SECTION I. OF NIGHTSOIL, POUDRETTE, AND TAFFO ; AND OF COW, HORSE, AND PIGs' DUNG. 1. Nightsoil is probably the most valuable of all the solid animal manures. It varies in richness with the food of the in- habitants of each district,* — chiefly with the quantity of ani- mal food they consume, — but when dry, few other solid manures, weight for weight, can be compared with it in general efficacy. It contains much soluble and saline matter, and as it is made up from the constituents of the food we eat, of course it con- tains most of those elementary substances which are necessary to the growth of the plants on which we principally live. 2. Poudrette. — Attempts have been made to dry nightsoil so * This is said to be so well known in some of the towns in the centre of Europe, where a mixed population of Protestants and Roman Catholics live together, that the neighboring farmers give a larger price for the house- dung of the Protestant families. In Persia, the nightsoil of the Russian families is, for a similar reason, preferred to that of the less flesh-eating Mahometans. ^04 cow, HORSE AND PIGs' DUNG. as to render it more portable, — to destroy its unpleasant smell, so as to reconcile practical men to a more general use of it, — and, by certain cliemical additions, to prevent the waste of am- monia and other volatile substances, which are apt to escape and be lost when this and other powerful animal manures begin to putrefy. In Paris, Berlin, and other large cities, the night- soil, dried first in the air with or without a mixture of gypsum or lime, then upon drying-plates, and finally in stoves, is sold under the name of poudrette, and is extensively exported in (^ casks to various parts of the country. It is said to be equal in efiicacy to 30 times its bulk of horse or street manure, and is applied at the rate of from 15 to 35 bushels an acre. In London, also, nightsoil is dried with various admixtures; and in some of our other large towns an animalised charcoal is prepared by mixing and drying nightsoil with gypsum and or- dinary wood charcoal, in fine powder. Charred peat would answer well for such a purpose. Few simple and easily attainable substances would make a better compost with nightsoil, and more thoroughly preserve its virtues, than half-dried peat, saw-dust, or rich vegetable soil, mixed with more or less marl or gypsum. It is impossible to estimate the proportion of waste which this valuable manure undergoes b^ being allow^ed to ferment, without mixture, in the open air, 3. Taffo. — In China nightsoil is kneaded into cakes with clay, which are dried in the air, and, under the name of taffo, form an important article of export from all the large cities of the empire. In Persia it is dried in the sun and powdered. Mixed with twice its bulk of dry soil, it is then used for raising the finest melons. 4. Cow, horse, and pigs' dung. So much of the saline and soluble organic matters in the excretions of the cow pass off in the liquid form, that its dung is correctly called cold, since it does not readily heat and run into fermentation. Mixed with other manures, however, or well diffused througn the soil, it DROPPIXGS OF BIRDS. 205 aids materially in promoting vegetation. The horse being fed generally on less liquid food, and discharging less urine, yields a hotter and richer dung, which is admirably fitted for bringing substances into a state of fermentation, but answers best for the land when mixed with other varieties of manure. The dung of the pig is soft and cold like that of the cow, contain- ing, like it, at least t5 per cent of water. As this animal lives on moro^ varied food than any other which is reared for the use of man, the manure obtained from it is also very variable in quality. Applied alone, as a manure to roots, it is said to give them an unpleasant taste, and to injure the flavor even of the tobacco plant. It answers well for hemp and for hops ; but when mixed with other manures, it may be applied to any crop. In some districts pigs' dung is considered one of the richest and most valuable that can be applied to the land. But the most generally useful manure is obtained by mixing all these varieties together, as is usually done in the manure -heaps of our larger farmers. SECTION II. DROPPINGS OF BIRDS. PIGEONS' DUNG AND GUANO. AFRICAN AND AMERICAN VARIETIES THEIR COMPOSITION AND FER- TILISING EFFECTS. 1. Pigeons'' dung. — The dung of nearly all birds is distin- guished by eminent fertilising properties. Some varieties are stronger than others, or more immediate in their action, and all are improved for the use of the farmer by being some time kept, either alone or in compost. In Flanders the manure of one hundred pigeons is considered to be worth 20s. a-year for agricultural purposes. In Catalonia, Arragon, and some other parts of Spain, pigeons' dung is sold as high as 4d. a pound, for applying, when mixed with water, to flower-roots, melons, tomatos, and other plants.* * The estimation in which it was held in ancient Palestine may be in- ferred from the statement, that, during a siege of Samaria, the fourth part 206 GUANO AND FARMYARD DUNG. The dung of birds possesses tlie united virtues of both the liquid and solid excretions of other animals. It contains every part of the food of the bird, with the exception of what is abso- lutely necessary for the support and for the right discharge of the functions of its own body. It is thus fitted to return to the plant a greater number of those substances on which plants live, than either the solid or the fluid excrements of other animals ; in other words, to be more propitious to vegetable growth. 2. Guano is the name given by the natives of Peru to the dung of sea-fowl, which in former periods used to be deposited in vast quantities on the rocky shores and isles of the Peruvian coast. The numerous shipping of modern times has disturbed and driven away many of the sea-fowl, so that much less of their recent droppings is now preserved or collected. Ancient heaps of it, however, mixed with feathers and fragments of bone, still exist in many places, more or less covered up with drifted sand, and also more or less decomposed. These are now largely excavated, especially on the Chincha islands, for expor- tation, not only to different parts of the coast of Peru, — as seems to have been the case from the most remote periods, — but also to Europe, and especially to England. It is at present sold in this country at a price which varies from £8 to ^11 a ton. Guano was also imported, for a few years, (1843 to 1841,) in large quantities from the island of Ichaboe, and from other places on the west coast of Africa. The quality of the African was not equal, however, to that of the guano brought from Peru. It contained more water, and was in a more advanced stage of decomposition. The known sources of supply from this quarter are now nearly exhausted ; and with the exception per- haps of a little from Saldanha Bay, there is none of it now in of a cab of doves' dung was sold for 5 pieces of silver. — 2' Kings vi. 25. I may state, however, that what is here translated doves' dung, was con- sidered by Linneeus to mean the bulbous root of the Ornithogallum umhel- latum, still eaten in Palestine, and forming part of the food of some of the tribes of Hottentots at the Cape of Good Hope. FERTILISING EFFECT OF GUANO. 20t the market. Its price varied with the quality, from £3 to £S a ton. Guano is capable of entirely replacing farmyard dung, — that is to say, turnips and potatoes may be manured successfully with guano alone. It may be used either as a top-dressing to the young corn and grass ; or it may be put in with the turnip-seed, or with the potato cuttings, being previously mixed with a quan- tity of fine dry soil, charcoal powder or gypsum. It may also be mixed with water, and used as a liquid manure. It is applied in various proportions, from one to three, four, or live hundred weights per acre. Three cwt. of guano, without other manure, gave Mr. Fleming of Barochan 18| tons of potatoes per acre ; and 5 cwt., with 20 bushels of wood ashes, gave him 32 tons of yellow turnips. The application of guano to the sugar cane has largely increased the produce of sugar, both in the British West India Islands and in the Mauritius. When applied in too large a quantity, the effect both upou the turnip and upon the after corn-crop is of a very hurtful kind. This is very strikingly shown ])y the following results of an experiment made in Ross-shire (in 1843 and 1844) with 4, 8, and 1 6 cwt. respectively to the Scotch acre : — Quantity of Guano. Effect on the Turnip Crop On the after crop of Wheat. 4 cwt. 8 .. '•■1 Good turnips, 18 tons. Very indifferent, 14 tons. Grew up wonderfully, looked beautiful, but there was little bulb. Produce 10 tons. Good Wheat. Inferior. Stubble black, grain -/ dark, and not larger than small rice. 3. The fertilising effects of guano depend mainly upou the quantity of ammonia which already exists in it, or which may be formed in it by its further decomposition, and upon the pro- 208 COMPOSITION OF GUANOS. portion of phosphates which are present in it. Of these the former is the more valuable ingredient of the two — that is to say, it would cost the farmer most money to buy it in ^a sepa- rate state, at its present price. The phosphates, in like man- ner, would cost more to buy in the shape of bones or of sugar- refiners' refuse, (animal charcoal,) than any of the other ingredients which the guano contains — the ammoniacal matter excepted. 4. Composition. — The following table exhibits the composi- tion of four samples of guano, two from the South American and two from the African coast. These analyses do not enter much into details, but they are sufficient for ordinary purposes — as guides, that is, to the practical man. Water, - Organic matter con- taining ammonia. Common salt and [ sulphate of soda, [ Carbonate of lime, Phosphates of lime ) and magnesia, ) Silicious matter or ) sand, j" South Amkrica.n. African. Peruvian. Bolivian. Ichaboe. Saldanha Bay. 13.09 53.17 4.63 4.18 23.54 1.39 6.91 55.52 6.31 3.87 25.68 1.71 16.71 46.61 12.92 0.27 22.4t0 0.52 18.35 22.14 5.78 1.49 50.22 2.02 100. 100. 99.43 100. These analyses are not to be considered as doing more than generally rejprescnting the difference between the African and American guanos. The several cargoes, both of African and of American, which used to arrive in this country, differed much among themselves. As I have already stated, the importation of African guano has now almost entirely ceased. PERMANENCE OF THEIR ACTION. 209 It is one of the valuable qualities of guano, that it contains a mixture of so many of these substances on which plants live. The only ingredient in which it is manifestly defective is potash — of which it usually contains less than 1 per cent ; and hence an admixture of wood ashes, and especially of leached or washed wood ashes, would be likely to improve its action upon the crops, in such soils as do not naturally abound in potash. 5. Lolos Islands guano, which is at this moment attracting so much of the attention of politicians, is said to be the pro- duce of the seal or sea-wolf, and to be from 25 to 33 per cent less valuable than the guano of the Chincha islands. 6. British guano. — The successful employment of foreign guano has caused the droppings of pigeons, sea-fowls, and bats, to be sought for in the caves along our east and west coasts, and in our western islands. I have examined several samples from both coasts ; but though they may prove valuable manures in the immediate neighborhood where they are found, they are not rich enough to pay the cost of collection and transport to any considerable distance. t. Is guano permanent in its action ? — This is a question which the practical man naturally asks when he is about to employ it to a large extent. Experience seems to show that its beneficial action extends to at least two crops, when it is applied in proper quantity. Theory also indicates, that though the action of the ammoniacal salts may be more or less exhausted in a single sea- son, yet that the effect of the phosphates and other saline sub- stances it contains — which is very important — will continue beyond one year. But the kind and quality of the guano will materially affect the length of its action. In general, however, it may be said, that as guano resembles bones very much in its composition, and as bones are known to benefit the crops in an entire rotation, so ought guano also. The chief difference between bones and guano is this — that the guano contains ammonia ready formed, or forming, so to speak — while the bones contain gelatine, which forms ammonia only 210 ADULTERATION OF GUANO. after it has fermented. The ammoniacal part of the one, there- fore, will act early, of the other after a longer period — while the permanent effects of the remaining ingredients of both will be very much alike if they are laid on in nearly the same proportions. SECTION III. ADULTERATIONS OF GUANO HOW TO SELECT A SAM- PLE OF GOOD QUALITY NATIONAL VALUE OF THIS MANURE. 1. Adulterations of guano. — In consequence of the high price of guano, the great demand for it, and the ease with which the unwary farmer may be imposed upon, guano is adulterated with various substances, and to a great extent. Impositions even have been practised by selling as genuine guano artificial mix- tures, made to look so like guano that the practical man in remote districts is unable to detect it. A sample of such pre- tended guano, which had been sold in the neighborhood of Wig- town, and had been found to produce no effect upon the crops, when examined in my laboratory, was found to contain, in the state in which it was sold, more than half its weight of gypsum — the rest being peat or coal ashes, with a little common salt, sul- phate of ammonia, and either dried urine or the refuse of the glue manufactories, to give it a smell. I could not satisfy myself that it contained a particle of real guano. Burnt earth and brick-dust are now prepared of various shades, and in fine powder, in special manufactories, for the purpose of mixing with guano and with artificial manures. These facts show how important it is that the farmer should possess some means of readily, and at a cheap rate, testing the costly manures he employs.* * "Four vessels recently sailed hence for guano stations ballasted with gypsum, or plaster of Paris. This substance is intended for admixture with guano ; and will enable the parties to deliver from the vessel a nice-looking and light-colored article. Parties purchasing guano are very desirous of havhig it delivered from the vessel, as they believe they obtain it pure. The HOW TO SELECT A GOOD GUANO. 211 2, In selecting a good guano, the following simple observations will aid the practical man. a. The drier the better — there is less water to pay for and to transport. h. The lighter the color, the better also. It is the less com- pletely decomposed. c. If it has not a strong ammoniacal smell, it ought to give off such a smell when a spoonful of it is mixed with a spoonful of slaked lime in a wine glass. d. When put into a tumbler with water, stirred well about, and the water and fine matter poured off, it ought to leave little sand or stones. e. When heated to redness in the air till all the animal mat- ter is burned away, the ash should nearly all dissolve in dilute muriatic acid. The insoluble matter is useless sand or earthy adulterations. /. In looking at the numbers in a published analysis of a Peruvian guano, those representing the water should be small ; the organic matter containing ammonia should approach to 50 or 60 per cent ; the phosphates should not much exceed 20 per cent ; and the common salt and sulphate of soda ought not to form much more than 5 or 6 per cent of the weight of the guano. in Saldanha Bay guano the proportion of phosphates was much greater, and of organic matter less. 3. The national value of guano, and the consequent import- ance of preventing adulteration as far as possible, may be judged of from three important facts. a. From the amount of the importation of it into this coun* try, which, during the last ten years, has been as follows : — favorite material for the adulteration of guano, at the present moment, is umber, which is brought from Angiesea in large quantities. The rate of admixture, we are informed, is about 15 cwt. of umber to about 5 cwt. of Peruvian guano, from which an excellent-looking article, called African guano, is manufactured." — Liverpool paper. 212 YEARLY IMPORTATION OF GUANO. Years. Tons. Years. Tons. 1841, 2,881 1847, 82,000 1842, 20,398 1848, n,414 1843, 3.002 1849, 83,438 1844, 104,351 1850, 116,925 1845, 283,300 1851, . 245,016 1846, 89,203 h. That the quantity huported in 1851 would sell for upwards of two millions sterling, and with good management ought to produce two or three times its own value in grain or other vege- table food. In other words, such a yearly supply of guano is equal to the importation of foreign grain and other produce to the value of from four to six millions sterling. c. It also serves as a stimulus, while it supplies one of the requisites, to the general introduction of improved methods of agricultural practice. CHAPTER XYI. Eelative theoretical values of different animal manures. — Chemical distinc- tion or difference between animal and vegetable manures. — Cause of this difference. — Effects of respiration. — Coldness of the droppings of the cow, and poorness of the manure from growing stock. — Improvement of the land by eating off' with sheep. SECTION I, OF THE RELATIVE THEORETICAL VALUES OF THE DIFFER- ENT ANIMAL MANURES. The fertilising power of animal manures, in general, is de- pendent, like that of the soil itself, upon the happy admixture they contain of a great number of those substances which are required by all plants in the universal vegetation of the globe. Nothing they contain, therefore, is without its share of influ- ence upon their general effects ; yet the amount of nitrogen present in each affords one of the readiest and most simple tests l)y which their relative agricultural values, compared with those of vegetable matters, and with each other, can be pretty nearly estimated. In reference to their relative quantities of nitrogen, there- fore, they have been arranged in the following order — the num- ber opposite to each representing the weight in pounds, which is equivalent to, or would produce the same sensible effect upon the soil as 100 lb. of farmyard manure: — Farmyard manure, Solid excrements of the cow, horse, Liquid excrements of the cow, horse. Mixed excrements of the cow, , horse, '■ sheep, pig, 100 125 73 91 16 98 54 36 64 214 RELATIVE VALUES OF ANIMAL MANURES. Dry flesh, . . _ ' . 3 Pigeons' dung, .... 5 Plemish liquid manure, . . 200^ Liquid blood, . . . . 15 Dry blood, . * . . . 4 Featliers, . . . . 3 Cow hair, .... 3 Horn shavings .... 3 Dry woollen rags, . . . 21 It is probable that the numbers iu this table do not err very widely from the true relative values of these different manures, in so far as the organic matter they severally contain is con- cerned. The reader will bear in mind, however — 1. That the most powerful substances in this table, woollen rags for example — 2 J lb. of which are equal in virtue to 100 lb. of farmyard manure — may yet show less immediate and sen- sible effect upon the crop than an equal weight of sheep's dung, or even of urine. Such dry substances, as I have said, are long in dissolving and decomposing, and continue to evolve fertilising matter, after the softer and more fluid manures have spent their force. Thus, while farmyard manure or rape-dust will immediately hasten the growth of turnips, woollen rags will come into operation at a later period, and will prolong their growth into the autumn. 2. That besides their general relative value, as represented in the above table, each of these substances has a further spe- cial value not here exhibited, dependent upon the kind and quantity of the saline and other inorganic matters which they severally contain. Thus three of dry flesh are equal to five of pigeons' dung, in so far as the organic part is concerned ; but the latter contains also a considerable quantity of bone earth and of saline matter which is present only in minute quantity in the former. Hence pigeons' dung will benefit ve- getation in circumstances where dry flesh would in some degree fail. So the liquid excretions contain much important saline matter not present iu tlic solid excretions^ — not present cither in such substances as horn, wool, and hair — and, therefore, DIFFERENCE IN ANDIAL AND VEGETABLE MANURES. 215 each must be capable of exercising an influence upon vegeta- tion peculiar to itself. Hence the practical farmer sees the reason why no one simj^k manure, such as hair or flesh, can long answer on the same land ; and why, in all ages and countries, the habit of employing mixed manures and artificial composts has been universally diffused. When mixed manures are not employed, the kind of manure which has been used must, after a time, be changed. A species of rotation of manures must, in fact, be introduced, in order that a second or third species of manure may give to the land those substances with which the first was unable to supply it. SECTION II. CHEMICAL DISTINCTION OR DIFFERENCE BETWEEN ANIMAL AND VEGETABLE MANURES. In what do animal manures differ from vegetable manures ? What is the cause of this difference ? How does the digestion of vegetable matter improve its value as a manure ? 1. The characteristic distmctio7i hGUveen animal and vegetable manures is this — that the former contain a much larger proportion of nitrogen than the latter. This will be seen at once, by comparing together the tables given in the preceding pages, (184 and 212,) in which the numbers given represent the relative agricultural values of different vegetable and animal substances compared with that of farmyard manure. The lowest numbers represent the highest value, and the largest amount of nitrogen, and these low numbers are always opposite to the purest animal substances. 2. In consequence of their containing so much nitrogen, animal substances are further distinguished by the rapidity with which, when moist, they putrefy or run to decay. During this decay, the nitrogen they contain gradually assumes the form of ammonia, which is perceptible by its smell, and which, when proper precautions arc not taken, is apt, in great part, to escape into the air. Hence the loss which occurs when manure is 216 CAUSE OF DIFFERENCE BETWEEN THE MANURES. fermented too completely, or without proper precautions to prevent the escape of volatile substances. And as animal manure, when thus over-fermented, or permitted to give off its ammonia into the air, is, found to be less active upon vegetation than before, it is reasonably concluded that to this ammonia, and the compounds formed along with it, or to the substances from which they are produced, the ^peculiar virtue of animal manures, when rightly prepared, is in a great measure to be ascribed, Yegetable substances in general do not decay so rapidly, and emit little odor of ammonia when fermenting. When prepared in the most careful way, also, vegetable manure does not exhibit the same immediate and remarkable action upon vegetable growth as is displayed by almost every substance of animal origin. There are exceptions, indeed, to this general rule, since the crushed seeds of plants — rape-dust for example — produce an effect on many crops little inferior to that of animal manures. They, in fact, resemble animal substances very closely in their chemical composition. SECTION III.' CAUSE OF THE DIFFERENCE BETWEEN ANIMAL AND VEGETABLE MANURES. EFFECTS OF RESPIRATION. Whence do animal substances derive all this nitrogen ? Ani- mals live only upon vegetable productions containing little nitrogen ; can they then procure all they require from this source alone? Again, does the act of digestion produce any chemical alteration upon the food of animals so as to render their excretions a better manure, richer in nitrogen than the substances on which they feed ? Does theory throw any light upon the opinion generally entertained among practical men upon this point ? These two apparently distinct questions will be explained by a brief reference to one common natural principle. 1. Animals have two necessary vital functions to perform — to EFFECTS OF ANIMAL DIGESTION. 21 1 breathe and to digest. Both are of equal importance to the health and general welfare of the animal. The digester (the stomach) receives the food, melts it down, extracts from it those substances which are best suited to supply the wants of the bodj, and sends them forward into the blood. The breathers (the lungs) sift the blood thus mixed up with the newly-digested food, combine oxygen with it, and extract carbon — which car- bon, in the form of carbonic acid, they discharge by the mouth and nostrils into the air. Such is a general description of these two great processes ; their effect upon the food that remains in the body, and has to be rejected from it, is not difficult to perceive. Suppose an animal to be full grown. Take a full-grown man. All that he eats as food is intended merely to renovate or replenish his system, to restore that which is daily removed from every part of his body by natural causes. In the full-grown state, everything that enters the lody must come out of the body in one form or another. The first part of the food that escapes is that portion of its carbon that passes off from the lungs during respiration. This portion varies in weight in different individuals — chiefly according to the quantity of exercise they take. From 6 to 9 ounces a-day is the average quantity given off from the lungs of a fulhgrown man, though in periods of violent bodily exertion, 13 to 15 ounces of carbon are breathed out in the form of carbonic acid. Suppose a full-grown man to eat a pound and a half of bread, and a pound of beef in 24 hours, and that he gives off by respi- ration 8 ounces of carbon (3500 grains) during the same time. Then he has Carbon. Nitrogen. Taken in his food, about 4500 grains, and 500 grains, while He has given off in res- \ piration, . . [ 3500 and little or no nitrogen. Leaving to be converted \ into his own substance, >- 1000 grains and 500 grains. or to be re-jected, . ) 10 218 VALUE OF THE DUNG. Our two conclusions, therefore, are clear. The vegetable food, by respiration, is freed from a large portion of its carbon, which is discharged into the air, while nearly the whole of the nitrogen remains behind. In the food consumed, the carbon was to the nitrogen as 9 to 1 ; in that which remains in the body after respiration has done its work, the carbon is to the nitrogen in the proportion of only 2 to 1. It is out of this residue, rich m nitrogen, that the several parts of animal bodies are built up. Hence the reason why they can be formed from food poor in nitrogen, and yet be them- selves rich in the same element. It is this same residue also, which, after it has performed its functions within the body, is discliarged again in the form of solid and liquid excretions. Hence the greater richness in ni- trogen — in other Avords, the greater fertilising power possessed by the dung of animals than by the food on which they live. 2. It must also be borne in mind, that the digested food con- tains all the saline matter, as well as nearly all the nitrogen, which had entered the stomach of the animal. Weight for weight, therefore, the dung must be richer also in saline matter than the vegetable food, and therefore i\iust be more fertilising in its effects upon the land. In an experiment made on the food and dung of the horse, it was found that while in the dry food the carbon was to the saline matter as 6 to 1, it was in the dry dung only as 2 to 1. 3. Two other remarks I may here add, because of their interest to the practical man. a. The manure of the cow, taking it mixed, is not so rich in nitrogen as that of man. It is true that the cow, owing to its larger bulk and larger lungs, gives off perhaps eight or nine times as much carbon by respiration as an active full-grown man. But the weight of its daily food still farther exceeds that of a healthy man. Suppose the daily food of a cow to weigh ten times as much as the food we have supposed a man to eat, and to contain carbon and nitrogen in nearly the same propor- DUNG OF FULL-GROWN ANIMALS, 219 tions — and that it gives off 60 ounces of carbon each day from its lungs — then we have Carbon. Kitrogen. In the food, . . 45,000 grains. 5000 grains. Given off by the lungs . 26,000 " . . " To be ultimately rejected, 19,000 " . 5000 " In the mixed manure rejected by such a cow, therefore, the carbon would be to the nitrogen in the proportion of about 4 to 1 ; while in nightsoil it was, according to our former suppo- sition, as 2 to 1. Thus the mixed dung and urine of the cow is less rich as an immediately acting manure than the mixed nightsoil and urine of man. And since much of the nitrogen, as well as of the saline matter of the food, is contained in the urine of the cow, if this urine be allowed to escape, the solid cow-dung will be still colder and less fertilising. The dry mixed manure of the cow is richer in nitrogen than the dry food, weight for weight, but not so much so as if the cow gave off from her lungs a larger proportion of the carbon contained in her food. b. Since the parts of animals — their blood, muscles, tendons, and the gelatinous portion of their bones — contain much nitro- gen, young beasts which are growing must appropriate to their own use, and work up into flesh and bone, a portion of the ni- trogen contained in the non-respired part of their food. But the more they thus appropriate, the less w^ill pass off into the fold- yard ; and hence it is natural to suppose that the manure, either liquid or solid, which is prepared where many growing cattle are fed^ the food being the same, will not be so rich as that which is yielded by full-grown animals. This deterioration has actually been observed in practice, and it may with some degree of cer- tainty be expected in all cases to take place, unless, by giving a richer food to the young cattle, the difference to the farmyard is made up.* * Though I have dwelt as long upon these interesting, and, I believe, 220 EATING OFF WITH SHEEP. SECTION lY. IMPROVEMENT OF THE LAND BY EATING OFF WITH SHEEP. The eating off with sheep is a practice on which some light is thrown by the considerations presented in the preceding sec- tion. This 'practice is adopted in different places with a view to very different objects. 1. On sandy soils, as in Norfolk, the whole or part of the tnrnip crop is eaten off with sheep, for the purpose chiefly of treading down and consolidating the soil, and thus fitting it for the better growth of the succeeding crop of barley. The production of a mechanical effect upon the soil is here the chief tiling sought for, 2. When the soil is not so light, the turnips are often eaten off with sheep for the sake of the regular and even manuring which the land is sure to obtain. The effect sought for here is also chiefly mechanical. The turnips could be drawn, and the dung collected, but it would afterwards have to be spread — and it could not by hand be so easily spread, or laid on the land so completely without loss. 3. Independent of the above considerations, the general be- nefit to the land of eating off with sheep arises from the con- version of the vegetable produce into a manure richer, weight for weight, in nitrogen and saline matter, and, tlierefore, having a more immediate and powerful effect upon the after crops. In the case of land which is otherwise in good heart or condition, perhaps no better or more profitable husbandry than this, for rural districts, could readily be recommended. 4. But the manure is richer, as we have seen, because the respiration of the animal separates a large proportion of the novel considerations, as the limits of this little work will permit, yet for fuller details, and for perhaps a clearer exposition of the principles above advanced, I must refer the reader to my Lectures on Agricultural Chemistry and Geology, 2d edition. EATING OFF AGAINST PLOUGHING IN. 221 carbon which, the food contains. This fact throws light upon a question which the improving farmer has frequently asked him- self in reference .to poor or worn-out arable land, or to land he wishes to reclaim. If I sow a green crop — rape, or buckwheat, or rye, or tares-^had I better eat it off with sheep, or plough it in ? I am in doubt about the elfect of ploughing in, but I am sure that by eating off I shall give the land a good ma- nuring. Now theory answers this question distinctly. If the only object be to enrich the ground, plough in green. By this means the carbon is saved which would otherwise be dissipated by the lungs of the animal, — and this carbonaceous matter is of great value in improving poor, thin, or sandy soils, in which organic matter is deficient. But if enriching the soil be not the sole object— if some mut- ton also be desired — then it is good husbandry to eat off, with full-grown and fattening stock. The land will improve less rapidly in this way than by ploughing in, and it will be longer before you can safely crop it with corn, but it icill gradually improve under such treatment. Why fattening and not growing stock is to be kept on such land will appear from the considerations to be presented in the concluding chapter — on the feeding of animals. CHAPTER XV 11. Saline and mineral manures. — The salts of ammonia as manures. — Ammo- niacal liquor, sal-ammoniac, and sulphate of ammonia. — Results of expe- riments with these salts. — Quantity of nitrogen required by the wheat crop. — Carbonates, nitrates, a)id silicates of potash and soda. — Sulphates of potash and soda. — Common salt. — Sulphate of magnesia. — Sulphate of iron. — Gypsum. — Use of the phosphate and super- phosphate of lime, and cause of tiieir beneficial action. — Use of kelp, and of the ashes of wood, straw, the husk of oats, barle}'-, and rye, and of the sugar-cane. — Compo- sition and use of peat or Dutch ashes. — Coal ashes. The general nature and mode of operation of sucli saline and mineral substances as are capable of acting as manures, will be in some measure understood from what lias already been stated as to the necessity of nitrogen and of inorganic food to living plants, and as to the kind of inorganic food which they espe- cially require. It will be necessary, however, to advert briefly to the more important of these manures, — their use, their mode of action, and the theory of their observed effects. SECTION I. THE SALTS OF AMMONIA AS MANURES. The value of ammonia as a manure has been already spoken of (pages 27 and 52.) It exists in all fermenting animal ma- nures, and thus is constantly applied to the land even in the least advanced districts. There are several states, however, in which it has lately begun to be used, unmixed with other substances, and with manifest advantages to the crops. 1. Ammoniacal Liquor. — This is water rich in ammonia, which is distilled from coal during the manufacture of coal gas. It is of various degrees of strength, and therefore, if applied to the land alone, it must be diluted with a variable proportion of CARBONATE OF AMMONIA. 223 water. It often contains ammonia enough to yield, when satu- rated with spirit of salt, as much as a pound and a half of sal- ammoniac from a single gallon. That of the London gas- works is said to yield, when saturated with sulphuric acid, about 14 ounces of sulphate of ammonia from the gallon. To grass land this ammoniacal liquor may be appUed with great advantage, by means of a water-cart — being previously diluted with from three to five times its bulk of water. If too strong it will burn up the grass at first, especially if the wea- ther be dry; but, on the return of rain, the herbage will again spring up with increased luxuriance. On arable land it may be applied with profit to the young wheat or other corn by the water-cart, or it may be dried up by any porous material, and thus put into the turnip or potato drills. A friend in Northamptonshire writes me that the 200 gallons of ammoniacal liquor per imperial acre, drunk up by sawdust and put into the drills, has alone given him an excel- lent crop of turnips. This manuring, however, cannot be ex- pected to keep the land in heart. A certain proportion of bone-dust should be mixed with this ammoniated sawdust, or else the corn crops should afterwards be top-dressed with rape- dust, guano, or bones. If, indeed, the land be already bom- sick, the saturated sawdust may be used alone, or Avith a mix- ture of wood or peat ashes for one rotation. The ammoniacal liquor may also be used advantageously to promote the fermentation of peat, sawdust, and other com- posts, — or it may be added to the ordinary dunghill, or to the liquid manure of the farmyard, and applied along with it to the laud. It is said to extirpate moss from old grass land more perma- nently than lime. 2. Carbonate of ammonia is the common smelling salts of the shops. It exists in the ammoniacal liquor above described, and is very useful, in a diluted state, in promoting vegetation. It is too expensive, however, in the form in which it is at present 224 STEEPING SEEDS IN SALTS OF AMMONIA. sold, to be of much use to the practical farmer. An oimce of it, dissolved in a gallon of water, gives a solution which destroys insects on rose-trees and other plants, and adds to their luxuriance at the same time. A few pieces laid on a plate and allowed to evaporate slowly into the atmosphere of a conserva- tory, are said to add greatly to the green and healthy appear- ance of the plants. 3, Sal-ammoniac. — The same may be said of muriate of ammo- nia, the sal-ammoniac of the shops. Though experiment has shown that this substance exercises a very beneficial influence on the growth of our cultivated crops, yet the pure salt is too high in price to admit of its being economically used in ordinary husbandry. An impure variety, however, is prepared from gas liquor, which is sold at about 15s. a cwt, 4, Sulphate of ammonia is now manufactured at a compara- tively cheap rate, and is sold at £16 a ton. This salt may be applied with advantage, especially to soils which are locally called deaf — which contain, that is, much inert vegetable matter, and to such as are naturally rich in phosphates. It may also be mixed with bones, rape-dust or wood-ashes, and put into the turnip or potato drills, or it may be used as a top-dressing in spring to sickly crops of corn. A case is mentioned of a field being manured for wheat, in part with ordinary farmyard manure, and in part with IJ cwt. per imperial acre (cost J£l*2s.) of sulphate of ammonia — when the produce of the former was 24, and of the latter 33 bushels per imperial acre. In other cases, also, it has been found a profitable application, both to young corn and to meadow hay. Faded flowers, when introduced into a solution of sulphate of ammonia, are said to be perfectly restored and revivified. 5, Steeping of seeds in the salts of ammonia. — The salts of ammonia, especially sal-ammoniac and the sulphate of ammonia, have been strongly recommended as steeps for seed-corn. They have in many cases been found very advantageous in hastening germination, and in increasing the after luxuriance of the cKjp, EXPERIMENTS UPON WHEAT. 225 Thus, in one experiment, seeds of wbeat, steeped in the sulphate of ammonia on the 5th of July, had by the 10th of August tillered into nine, ten, and eleven stems of nearly equal vigor, while unprepared seed had not tillered into more than two, three, or four stems. Sal-ammoniac has a similar effect. In Upper India it is pre- pared by heating together cAmel's dung and sea salt, and is used in the plains, among other purposes, for the steeping of seeds. It is to be observed, however, that neither when applied directly as a manure to the growing crops, nor when used as a steep for the seed, can the salts of ammonia alone bring a plant to maturity. .They tend to hasten its growth, if all its other wants can he readily supplied by the soil ; but if this is not the case, a quick decay will succeed to a short-lived luxuriance. SECTION II. RESULTS OF EXPERIMENTS WITH THE SALTS OF AMMONIA. NITROGEN NECESSARY TO THE WHEAT CROP. The last mentioned fact, as well as the general value of the salts of ammonia, is illustrated by the results of some experi- ments made by Mr. Lawes at Rothampstead in Hertfordshire. He sowed wheat for three successive years on the same piece of ground, applying only mineral manures the first year, and only ammoniacal manures the second and third years. The following were the results : — . ,. ,. . . , Produce. Application per imperial acre. ^^^^^^ g^^^^_ 1844. Superphosphate of lime, 560 1b.) ^^ ^ j ^^^2 lb. Silicate of potash, - 220 ) 1845. Sulphate of ammonia, ) ^^^^ ^, ^^,^_ 3^i _ ^266 .. Muriate of do. J 1846. Sulphate of ammonia, 2 .. 27 .. 2244.. Thus upon a soil already rich in mineral manure, the applica- cation of salts of ammonia nearly doubled the crop of grain in 1845, and quadrupled that of straw ; and, in 1846, added 10* Z2f) NITRATES OF POTASH AND SODA. agam one-half to the grain above 1844, and doubled the straw. In each case, however, some allowance must probably be made for the influence of natural varieties in the seasons. As to the necessity of nitrogen to the wheat crop, Mr. Lawes concludes, from numerous experiments, that, ujpon his soil and in his locality, five pounds of ammonia — or four of ni- trogen, in some other available form — are '' required for the production of every bushel of wheat beyond the natural yield of the soil and the season."* But as a bushel of wheat con- tains only about 1 lb, .of nitrogen, (equal to 1^ lb. of ammonia,) it is obvious that, if this estimate be correct, the greater part of the nitrogen is lost to the farmer. The subject, therefore, is open to further investigation. SECTION III. SALTS OF POTASH, SODA, MAGNESIA, AND IRON. 1°. Carbonate of fotash and soda.—^\\^ common pearl-ash, and the common soda of the shops, have not in this state been much employed in agriculture. Both, however, greatly pro- mote the growth of strawberries in the garden,- — and the latter is now cheap enough (10s. a cwt.) to admit of its being tried as a top-dressing on clovers and grass lands, on such as are old and mossy especially, with every prospect of advantage. It should be dissolved in much water, and put on with a water- cart, or thoroughly mixed with earth, and applied as a top- dressing. Mixed at the rate of one cwt. an acre, with bone or rape dust, or even with guano, it may be expected to improve both the turnip and the potato crops. Carbonate of soda, in the form of soda ash, has been applied with success to kill or to remove the effects of the wire-worm. It may either be sown with the wheat in winter, or applied as a top-dressing in the spring, to the affected wheat or oats. 2°. Nitrates of j>otash and soda. — Saltpetre and nitrate of * Journal of Royal Agricultural Society of England, viii. 246. COMMON SALT. 22 1 soda have been deservedly commended for tlieir beneficial ac- tion, especially upon youmg vegetation. They are distinguished, Hke the salts of ammonia, for imparting to the leaves a beautiful dark green color, and are applied with advantage to grass and young corn of any kind, at the rate of 1 cwt. to 1^ cwt. per acre. They are said even to benefit young fir-trees. Applied to young sugar-canes they have been found largely to increase the crop, and even, in the second year after their application, to add much to the luxuriance of the cane fields. The nitric acid they contain yields nitrogen to the plant, while potash and soda are also put within reach of its roots, and no doubt serve many beneficial purposes. Upon land rich in phosphates, ni- trate of soda is a profitable application to wheat, being found, in Norfolk, to return an Increase of from 4 to 1 bushels of grain for every cwt. applied to the corn in spring.* It is especially recommended for wheat, on hght, gravelly, and sandy soils, and on cold undrained clays. 3°. Sulphate of potash is likely to be useful, especially to root and leguminous crops. Its price, however, is usually high, varying from £\% to £20 a ton. 4°. Common salt has, in many districts, a fertilising influence upon the soil. It destroys small weeds; improves the quality of pastures, and renders them more palatable ; strengthens and brightens the straw, and makes the grain heavier per bushel, both of wheat and oats. It has been observed, also, to pro- duce specially good effects upon mangold-wnrtzel. A small quantity of salt is absolutely necessary to the healthy growth of all our cultivated crops, but it is in inland and shel- tered situations, and on high lands often washed by the rains, that its effect is likely to be most appreciable. The spray of the sea, borne to great distances by the winds, is in many dis- tricts, where prevailing sea winds are known, sutficient to sup- ply an ample annual dressing of common salt to the land.f * See the Author's Lectures on Agricultural Chemistry, 2d edition. f At Penicuik, near Edinburgh, the rain that falls contains so much com- mon salt as alone to convey 640 lb. to every acre in a year. — (Dr. Madden-") 228 SULPHATES OF MAGNESIA AND IRON. It has sometimes been found to be of still more advantage, in strengthening the straw, to apply a mixture of quicklime with a fourth or a fifth part of its weight of dry salt; or the salt may be dissolved in water, and the lime heap slaked with the solution — or sea water may be at once employed to slake the lime. 5°. Sulphate of soda, or Glauber's salt, has lately been re- commendetl in this country for clovers, grasses, and green crops. Mixed with nitrate of soda it produces on some soils remarka- ble crops of potatoes, and in some localities, when used alone, it has greatly benefited the turnip crop. Mr. Girdwood found that li cwt. of this sulphate per acre, sprinkled upon the other manure in the drills, added 16 bushels an acre to his crop of beans. It is on rich land only, however, that the addition of a single saline substance can be expected to produce results so favorable as this. 6°. Silicates of jpotash and soda. — When potash and soda are melted together with silicious sand, they form a kind of glass which is soluble in water. This has produced remarkable effects upon the potato crop, and, like other silicates, is recom- mended as a strengthener of the straw of our corn crops. ^°. Sulphate of magnesia, or Epsom salts, is also beneficially applied in agriculture to clovers and corn crops. It can be had in pure crystals at 10s. a cwt., and in an impure state at from 3s. to 6s. a cwt. It has been found of advantage as a top- dressing for the young wheat, and as an application to the potato. Where the soil is deficient in magnesia, it may always be expected to improve the crops of corn. 8°. Sulphate of iron. — Common green vitriol, applied in the form of a weak solution, has been observed to strengthen feeble plants, and to give them a brighter green. It has also been used as a top-dressing for grass, and as an application to dis- eased fruit trees. It deserves a further trial GYPSUM AND OTHER SULPHATES. 229 SECTION IV. USE OF THE SULPHATE AND PHOSPHATES OF LIME, AND CAUSE OF THEIR BENEFICIAL ACTION. 1°. Sulphate of liiiie, or gypsum, is in Germany applied to grass land with great success, and over large tracts of country. In the south of England it has been applied to some grass lands with benefit for thirty-five years in succession, at the rate of 2 J cwt. per acre. It supplies the lime and sulphuric acid annually, which are annually removed by the crop. In the United States it is used for every kind of crop ; and I have there seen it pro- duce very striking effects on Indian corn. It is especially adapted to the pea, the bean, and the clover crops. It is more sensibly efficacious when applied in the natural state than after it is burned. The sulphates all afford sulphur to the growing plant, while the lime, soda, magnesia, &c., which they contain, are themselves in part directly appropriated by it, and in part employed in pre- paring other kinds of food, and in conveying them into the ascending sap. Though there can be no question that these sulphates, and other similar substances, are really useful to vegetation, yet the intelligent reader will not be surprised to find, or to hear, that this or that mineral substance has not succeeded in benefiting the land in this or that district. If the builder has already bricks enough at hand, he needs mortar only, to enable him to go on with his work : so, if the soil contain gypsum or sulphate of magnesia in sufficient natural abundance, it is at once a need- less and a foolish waste to attempt to improve the land by add- ing more ; it is still more foolish to conclude, because of their failure in one spot, that these same saline compounds are unlikely to reward the patient experimenter in other localities. 2°. Phosphates of lime. — a. Burned bone. — When bones are burned in an open fire, they diminish in weight about one-half, and leave behind a white earthy matter long known by the name 230 ACID OR SULPHATE OF LIME. of hone earth. This bone earth consists chiefly of j)hosjphafe of lime (page 193.) Bones are known to be an excellent manure, and as our cul- tivated crops, and especially our corn crops, contain much phos- phoric acid, it has been justly concluded that part of their eifect is due to the bone earth they contain. Hence the use of burned bones as a manure has been warmly recommended. In soils which are poor in phosphate of lime, there is no doubt but burned bones will be likely to benefit the crops of corn ; but there are few soils, I think, in which a ton of bone-dust would not produce a better effect than the ash left by an equal weight of bones. h. Native jihosjphate of lime. — Phosphate of lime is found as a native mineral in many countries, and has been applied with advantage to the soil. It has lately been met with in the States of New York and New Jersey in sufficient quantity to make it likely to prove a profitable article of import into this country. It has also been discovered in considerable quantity in the marls of the crag and green-sand formations (see p. 94,) of England, and is now dug up in large quantities for agricultural purposes.* In our ordinary limestones it also exists in variable quantity. In a burned lime from Carluke, which is full of fossils, I have found it to the extent of 2| per cent ; so that every ton of such lime conveys to the land as much phosphate of lime as two bushels of bones. This must modify in a favorable manner the effect of such lime when applied to the land. c. Acid or sujper-jphosjphate of lime. — When burned bones are digested with sulphuric acid diluted with three times its bulk of water, gypsum (sulphate of lime) is produced, and falls to the bottom of the solution, while the phosphoric acid, and a portioii of the lime, remain in the sour liquid above it. When this liquid is boiled down or evaporated to dryness, it leaves a white powder, which is known by the name of acid or super-phosphate * Journal of the Royal Agricultural Society, vol. ix. p. 56, and vol. xii. p. 93. ASHES OF SEA-WEED, WOOD AND STRAW. 231 of lime. Under the latter name it has been introduced into the manure market. It is extensively manufactured in this country, by grinding the mineral phosphate obtained from the crag of Norfolk and Suffolk, (p. 93,) mixing it with about an equal weight of strong suli)huric acid, and then drying the whole. Some manufacturers mix a portion of bone dust with the mine- ral powder, and thus produce a manure containing some animal matter, and therefore of more general utility. As the ordinary burned bones are difficult to dissolve in the soil, and as the acid phosphate is more easy of solution, it is likely to be taken up more readily by the roots, and thus more rapidly to aid the growth of plants. These super-phosphates are sold at present at about £7 a ton. Numerous experiments have been made with the super-phos- phate, and very remarkable results have been obtained by its use, chiefly as a manure for the turnip crop, but also as a top- dressing for grass, and for wheat, and other kinds of corn. What is sold as super-phosphate by the manufacturers, is very variable in its composition, and is often largely adulterated. SECTION v.— OF THE ASHES OF SEA-WEED, WOOD, STRAW, THE HUSK OF OATS, BARLEY, AND RICE, AND OF THE SUGAR-CANE. 1. Kdj> is the ash left by the burning of sea-weed. It con- tains potash, soda, lime, silica, sulphur, chlorine, iodine, and several other of the inorganic constituents of plants which are required by them for food. It is nearly the same also— with the exception of the organic matter which is burned away— with the sea-weed which produces such remarkably beneficial effects upon the soil. In the Western Isles a method is prac- tised of half-burning or charring sea-weed, by which it is pre- vented from melting together, and is readily obtained in the form of a fine black powder. The use of this variety ought to combine the beneficial action of the ordinary saline constituents of kelp, in feeding or preparing food for the plant, with the 232 LIXIVIATED WOOD AND STRAW ASHES. remarkable properties observed in animal and vegetable char- coal. In Jersey, the sea-weed is dried and burned in the kitchen grates, and the ash is considered to be efficacious in destroying grubs. In the Orkneys, potatoes are ^ raised by means of a mixture of peat ashes and kelp, applied at the rate of fifty bushels to the Scotch acre. 2. Wood ask contains, among other substances, a portion of common pearl ash in an impure form, mixed with sulphate and silicate of potash. These substances are all valuable in feeding and in preparing the food of plants, and hence the extensive use of wood ash as a manure in every country where it can readily be procured. Wood ash, applied alone, is especially beneficial to clovers, beans, and other leguminous plants. Mixed with bones in nearly equal bulk, it is extensively employed in this country as a manure for turnips. In some soils it has been found, without any admixture, to raise large crops of potatoes. In Persia, seed wheat and melon seeds are always steeped, for 24 hours before sowing, in a ley of wood ashes. In Lower Canada, 40 bushels of wood ashes applied alone, give a crop of 200 to 250 bushels of potatoes. 3. Lixiviated tvood ash. — When the common wood ash is washed with water as long as any thing dissolves, and the solu- tion is then boiled to dryness, the common potash of commerce is obtained. But a large portion of the ash remains behind un- dissolved, and in countries where much wood is burned for the manufacture of potash, this lixiviated or washed refuse accumu- lates. It consists of silicate of potash mixed with silicate, phosphate, and carbonate of lime, and when applied to the land is remarkably favorable to oats. It suits better for clay lands, and when laid on in considerable quantity, (1 or 2 tons to the acre,) its effects have been observed to continue for 15 or 20 years. (Sprengel.) 4. Straw ashes. — In this country straw is seldom burned for the ash. In Germany, rye-straw is not unfrequcntly burned, and the ash employed as a top-dressing. The dry straw is ASHES OF OATS, BARLEY, RICE AND CANE HUSKS. 233 strewed over the field, tlien burned, and the ash ploughed in on the spot. In many countries — among others, in some parts of the United States — the straw is often burned, and the ash scattered to the wind. When it is too much trouble to ferment the straw in the farmyard, labor might surely be spared to strew the £tsh upon the fields from which the crop was taken. The soil would not fail to give a grateful return. 5. Ash of the- husk of oats, harley, and rice. — The hush, seeds, or shellings of oats or barley, being supposed to contain no nourishment, are often burned for the purpose of heating the kiln on which the grain is dried. When thus burned, these husks leave a considerable quantity of a white or. grey ash. The oat husk I find to leave about 5 J per cent of its weight. This ash has hitherto been neglected by the millers, being ge- nerally thrown into the stream by which their mills are worked. It should, however, be carefully preserved. It may be ex- pected to prove a valuable top-dressing to meadow land, to young corn crops, and especially to bog oats. One miller in the north of Scotland informs me that he makes about two bushels a day of ash from the husk of the oats he grinds. The waste of this ash, long persevered in, can scarcely have failed slowly to impoverish the adjoining land. In China, India, and other countries where rice is grown, the husk of this grain also is burned; but the ash is rarely afterwards returned to the soil. In China, it is said to be em- ployed in the making of certain articles of manufacture. 6. Cane ash. — The sugar-cane when brought from the mill in the state of trash, is burned for the purpose of boiling down the syrup. The ash left by it is rich in those saline substances, without which the cane cannot thrive. Without having per- sonally examined any of our West India plantations, I may safely hazard the opinion that some, at least, of the exhaustion complained of by the planters is owing to the neglect of this valuable ash — and that the large importation of foreign ma- nures, now -had recourse to, might by and by be in some mea- 234 PEAT ASHES FROM PAISLEY. sure dispensed with, by carefully collecting, grinding, and returning it to tlie soil. SECTION VI. COMPOSITION AND USE OF PEAT OR DUTCH ASHES. COAL ASHES. Peat or Dutcli ashes are the ashes of peat burned for the purpose of being applied to the land. They vary in composi- tion with the kind of peat from which they have been prepared. They often contain traces of potash and soda, and generally a quantity of gypsum and carbonate of lime, a trace of phos- phate of hme, and much silicious matter. In almost every country where peat abounds, the value of peat ashes as a ma- nure has been more or less generally recognised. The following analyses of two samples of such ashes from the Paisley moss, and of two from the island of Lewis, all examined in my labo- ratory, show how valuable, and, at the same time, how very different in quality, such ashes may be, even when they are ob- tained from the same locality. a. Ashes from the Paisley moss. White Peat Black Peat Ashes. Aslies. Charcoal, - - 54.12 3.02 Sulphates and carbonates of potasli, soda, and magnesia, - - 6.5Y 5.16 Alumina, - - 2.99 2.48 Oxide of iron, - - 4.61 18.66 Sulphate of lime, - - - 10.49 21.23 Carbonate of ditto. - - 8.54 3.50 Phosphate of ditto, - - 0.90 0.40 Silicious matter, - - 10.88 43.91 99.10 98.3G It will be observed that the first of tliese contained more than half its weight of unburncd charcoal, and still was richer than the other, weight for weight, both in soluble salts and in phosphate of lime — two of their most valuable ingredients. PEAT ASHES FROM LEWIS. 235 The reason of this is, that the white peat, being nearer the surface, consists of vegetable matter less decomposed. The ashes of the upper layers of peat, therefore, will generally be more valuable than those of the under layers. _ h. Ashes from the island of Lewis. 0.29 6.51 Chloride of sodium, (common salt,) 0.41 Phosphate of lime, - - - 2.46 Sulphate of iime, (gypsum,) - - 28.66 16.85 Sulphate of magnesia, - - 1.68 2.01 Magnesia ) in state of silicate ( ^.f^ ^^^ , Potash. .d soda, J ,,, ,,rhonate, | ,f,^^ \f. Oxide of iron, - - - 9.18 6.58 Silica, soluble in caustic potash, - 15.55 28.58 Insoluble silicious matter and sand, - 7.94 14.20 Carbonic acid, charcoal, and loss, - 10.85 7.99 100. 100. These samples, again, present other differences. They con- tain, in addition to the alkaline matter and the gypsum, a more considerable proportion of phosphate of lime than the others. In the one, the phosphate amounts to 6| per cent, and must contribute materially to its fertilising value. The soluble silica is also deserving of notice, as likely to be useful — especially to grass land and to crops of corn. Peat ashes are not unfrequently used alone, and with success, for the raising of turnips. Much of their success, however, will depend on the peculiar composition of the ashes employed. In Lancashire, peat only half burned is considered preferable to double the quantity burned to a perfect ash. Coal ashes consist in general of alumina and silica mixed with a variable proportion of gypsum, carbonate of lime, phos- phate of lime, and oxide of iron, mixed with half-burned coal. They vary, however, with almost every different kind of coal that is burned. CHAPTER XYIII. Why saline manures are required by the soil. — Mode of determining their local value. — Circumstances necessary to insure the successful application of saline manures. — Of saline manures which exercise a special or specific action upon plants. — Results of experiments with mixed saline maniires, made with the view of increasing the crop or of affecting its quality. — Artificial mixtures in imitation of valuable natural manures. — Recipe for artificial g^uano. SECTION I. WHY SALINE MANURES ARE REQUIRED BY THE SOIL. The use of saline substances as manures is of comparatively recent introduction. In many districts, however, they are indis- pensable, , if we wish to maintain the present condition, or to restore the ancient fertility of the land. This will appear from the following considerations : 1. These saline substances exist in all plants, and must there- fore abound, to a certain extent, in all soils in which plants can be made to grow. 2. The rains gradually wash out from the surface — especially of undrained arable soils, and in inland districts — a portion of the saline matter they contain. If the surface soil is to be retained in its present condition, this natural waste must, by some means or other, be supplied. 3. The crops we carry off the land remove also a portion of this saline matter from the soil, and thus gradually impoverish it, if the saline substances be not again brought back. 4. And though we return to the soil, in the form of farmyard manure, all the straw of our corn crops and the dung of our cattle, land still loses all that we carry to market, and all that escapes from our farmyards and dung-heaps in the form of liquid LOCAL VALUE OF SALINE MANURES. 23t manure. Even where tanks for liquid manure are erected, the farmer can never return to the land all the saline substances contained naturally even in his straw. The rains that fall, were there no other cause of waste, would wash away some portion of what he would desire to carry back into his field. The necessary waste of saline matter, arising from the above causes, must be supplied from some source or other. When, for a long period of time, the land has maintained its fertility with- out receiving any artificial supply, it must contain within itself naturally a very large proportion of these substances — must derive from springs a continued accession of such matter, or from waters that flow down from a higher level and bring with them the washings of the upper soils — or it must obtain from abundant sea-spray a sufficiency to supply the wants of the plants that grow upon it. The practical man will readily acknowledge that, when a suffi- ciency of saline matter is not conveyed to his land from these or similar sources, he must necessarily supply it by art. He will understand, also, that the saline manures he adds to' the soil operate by yielding to the plant what it could not otherwise so readily obtain ; and that a saline substance which has been found to benefit his neighbor's land, may happen, when applied, to do no good to his own — because his own may already con- tain a sufficient supply of that substance. SECTION II. MODE OF DETERMINING THE LOCAL VALUE OF SALINE MANURES. In order, therefore, to determine whether his land will rea- dily be benefited by the application of those saline substances from which, in other districts, or upon other soils, much benefit has been derived, the intelligent farmer will commence a series of preliminary trials or small experiments. That many of the saline substances described in the preced- ing Sections maybe projitahly applied to most soils by the prac- 238 VALUE OF SALINE MANURES. tical farmer, can no longer be doubted. At the same time, no prudent man will at once expend any large sum upon them, until either he himself, or some of his immediate neighbors who cultivate a similar soil, have previously proved their efficacy on a smaller scale. It is no doubt the duty of every practical farmer — a duty he owes not only to his country but to himself — to be alive to the benefits which are to be derived from every improved method of culture that may be introduced ; but it is no less his duty to avoid every reasonable risk of pecuniary loss which might be injurious to himself. Suppose, therefore, I were to enter upon a farm which I was desirous of rendering as productive as possible, by the applica- tion of every new manure, or every new method of culture that might prove to be suited to the kind of soil I possessed, I would begin by trying the effect of each manure or method upon a single acre, and I would extend my trials or alter my methods according to the success I met with. Among saline manures, for example, I would try nitrate of soda, or carbonate of soda, or wood ashes, or sulphate of soda, or common salt, or silicate of soda, or gypsum, or sulphated urine, or guano, or the ammoniacal salts, or the soluble phosphates, or a mixture of two or more of these substances, on a single acre or half acre of my various crops — never expending in this way, during any one year, more than I could easily afford to lose if my trials should fail ; and I would not begin to use any of these sub- stances largely till I was satisfied that there was a reasonable prospect of remuneration. And having once begun upon this assurance, I would cease applying them for a while as soon as the crops no longer gave me a fair return for my outlay — the probability then being, that the soil for the present had ob- tained enough of the peculiar substance I had been employing, and stood more in need of some other. Thus if, as happened to a friend of mine, a dressing of salt was followed by a produce of 35 bushels from the first wheat crop, and yet, when applied to the next crop of the same grain CIRCUMSTANCES NECESSARY TO SUCCESS. 239 on the same field, the yield was only 20 bushels, I should con- clude that, for the present, my land was sufficiently salted, and that I had better apply something else. I would therefore begin my experiments anew upon my salted land. I would try some of the other substances above named, employing always the same caution and economy as before, and carefully keeping an account of my procedure, and of my profit and loss from each experiment. Such facts, also, as that in the State of Xew York, after a long-continued use of gypsum, the employment of leached or ex- hausted wood ashes (p. 233) was found to be more beneficial, woTild incline me to make many trials of such variations or ro- tations of manures. I should thus have always several experimental patches upon my farm ; and I should not only avoid the risk of serious disap- pointment and pecuniary loss, but I should enliven my ordinary farm routine by the interest I should necessarily feel in watch- ing the results of my different experiments — I should gradually acquire habits of reflection, and of careful observation also, which would be of the greatest possible service to me in all my future operations.* SECTION III. OF THE CIRCUMSTANCES WHICH ARE NECESSARY TO INSURE THE SUCCESSFUL APPLICATION OF SALINE MANURES. The application of saline substances to the soil is not always attended with sensible benefit to the crop. Th§ same substance which, in one district, or in one season, has produced an increased return, may fail in another district or in a different season. The circumstances which are necessary to insure success in the appli- cation of saline manures are chiefly the following : — 1°. They must contain one or more of those substances which * For numerous suggestions as to such experiments, I would refer the reader to my pubUshed ExpeTimcntal Agriculture — a work entirely devoted to the subject of rural experiments. 240 SUBSTANCES EXERCISE A SPECIAL ACTION are necessary to the growth of the plant, and in a condition or state of combination in which the plant can take them up. 2°. The soil must be more or less deficient in these substances. 3°. The weather and soil must be moist enough to admit of their being readily dissolved and conveyed to the roots, or the land must be artificially irrigated. 4°. They must not be applied in too large a quantity, or allowed to come in contact with the young shoots in too con- centrated a form. The water th-at 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 penetrate 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 much importance. A re- tentive subsoil will prevent the total escape of that which readily passes through a sandy or gravelly soil ; ivhile a very open subsoil, again, may retain little or nothing of what has once made its way through the surface. 6°. I may add, lastly, that it is in poor or worn-out soils that all such applications may be expected to produce the most marked and characteristic effects. SECTION IV. OF SALINE MANURES WHICH EXERCISE A SPECIAL OR SPECIFIC ACTION UPON PLANTS. An interesting branch of the present part of our subject is the use of what are called special manures. Certain substances have been observed to exercise a special action. 1. Ujpon all 'plants. — ^Thus, the salts of ammonia promote the growth, or prolong the green and growing state of most plants. Nitrate of soda has a similar effect — while the addition of lime to the soil, especially in well-drained and high lands, almost uniformly hastens the ripening of the seed, and produces an earlier harvest. ON DIFFERENT KINDS AND PARTS OF PLANTS. 241 2. On particular parts of plants ; — as when the gardener improves his roses by mixing manganese with the soil, reddens his ornamental hyacinths by putting carbonate of soda into the water in which they grow — or by other substances, as by the acid or 5Wj?e/--phospliate of soda, attempts to vary the hue or bloom of his cultivated flowers. This principle is attended to in practical agriculture, when substances are mixed with the manure, which are believed to be specially required by the stalk of corn, where a field produces a defective straw — or by the ear, where the grain refuses to fill. The application of silicate of potash, of soda, or of lime, to the soil may add strength to the straw, while the phosphates fill the ear, or bring it to ear- lier maturity — as carbonate of potash, according to Wolff, pro- motes the growth of the leaves and stems of the vine, while the phosphates develop the fruit. 3. On particular kinds of plants. — Farmyard manure rarely comes amiss to any soil or any crop; but gypsum exercises a peculiar action upon red clover; while wood-ashes, lime, and other alkaline manures, cause white clover to spring up sponta- neously, where it had before refused to grow even when sown. So lixiviated wood ashes are favorable to oats; ammonia, or the nitrates, are by some regarded as the peculiar manures for wheat; phosphate of magnesia has been extolled as a specific for potatoes ; and superphosphate of lime for our British turnip crops. All such facts as these are exceedingly valuable. Many of the alleged specifics, however, are only locally so. Thus bones, which produce such wonderful effects in Great Britain, espe- cially upon turnips and upon some old grass lands, as those of Cheshire, are much less conspicuously effective in some parts of Germany, and even of our own island ;* while gypsum, so much and so generally prized by the German and American farmer, is more rarely found to answer the expectations of the English agriculturist. * On some of the soils of the green-sand, for example. 11 242 RESULTS OF EXPERIMENTS The truth is, that if the crop we wish to raise specially re- quires any one substance which is not present in sufficient quan- tity in the soil, that substance will there prove a specific for that crop ; while, in another soil in which it is already abun- dantly present, this substance will produce little beneficial ef- fect. Failures, therefore, may every now and then be expect- ed in the use of so-called specific manures, the evil of which is not limited to the immediate loss experienced by the incau- tious experimenter. They serve also to dishearten those who, through their much faith, have been disappointed in their ex- pectations, and thus to retard the progress of a truly rational experimental agriculture. SECTION V, RESULTS OF EXPERIMENTS WITH MIXED SALINE MA- NURES, MADE WITH THE VIEW OF INCREASING THE QUANTITY OF THE CROP. The same remark applies also to artificial mixed manures, when held forth as specifics for any or for all crops on every soil. The animal and vegetable manures which occur in na- ture, are all mixtures of a considerable number of different substances, organic and inorganic. We are imitating na- ture therefore, and are in reality so far on the right road, when we compound our artificial mixtures. The soil may be deficient in two, three or more substances ; and to render it fertile, it may be necessary to add all these ; while, if it be de- fective in one only, we are more likely to administer the right one, if we add a mixture of several at the same time. It is safer and surer, therefore, to add a mixture of several saline substances to our soils. There are only two ways, however, in which we can safely make up mixtures .that are likely to be useful — either by actual experiment upon the kind of land we wish to improve, or by an exact imitation of the procedure, and })y attention to the re- quirements, of nature. WITH MIXED SALINE MANURES. 24S 1. Mixture of nitrate u-ith sid'phate of soda. — In 1840 I re- commended the trial of sulphate of soda (Glauber's salts) as a manure, and in 1841, Mr. Fleming of Barochan, besides mak- ing an experiment with the sulphate alone, tried a mixture of it with nitrate of soda in equal weights — adding 1| cwt. of the mixture to the acre. The effect of this mixture as a top-dress- ing upon potatoes was extraordinary. T/ie stems were six and seven feet in length, and the 'produce upward of 30 tons per impe- rial acre. In 1842, tried on a larger scale, the produce was not so extraordinary ; but, though a very dry season, the pro- duce was 18 tons per acre of early American potatoes ; while the dung alone, 40 cubic yards per acre, gave less than 13 tons. These results are sufficiently striking to justify the reader in trying this mixture on any soil. If his fields be like the land of Mr. Fleming, the trial may prove eminently successful ; if different in physical character or chemical composition, or if the season be unpropitious, the result may be less favorable. A mixture, though it succeed in the hands of fifty experiment- ers, will still not be entitled to be considered as a specific. It must first be found never to fail. The cost of this mixture, as applied per acre, was at that time as follows : — •75 lb. nitrate of soda, at 22s. per cwt. . . . £0 14 9 75 lb. dry (uncrystallised) sulphate of soda, at 9s., 6 3 [about $5 25] 1 1 The increased produce from this application — strewed about the young plants when they came above ground — was 8 tons per acre in 1841, and 5 tons per acre in 1842. 2. The superior effect of mixtures above that of the substances they contain when employed singly, is shown in an interesting manner by the following results, obtained by the same experi- menter : — An entire field was manured for potatoes with 40 cubic yards 244 MIXED SULPHATES AND NITRATES. of dung, and when the potatoes — early Americans — were a few inches above the ground, different measured portions of the field were top-dressed with different saline substances, with the following results per imperial acre : — Tons. Dung alone gave . . . . 12| - . . with 2 cwt. sulphate of soda, . . 12| 1 5 cwt. nitrate of soda, . . 16 1 4 cwt. sulphate, ) _• ^j to T , ..^ . ' y mixed, . lo I cwt. nitrate, J ' Here, though the sulphate alone produced no increase, it materially augmented the effect of the nitrate when the two were applied together. 3. Sulphate of soda with sulphate of ammonia. — Again, on the same field on which sulphate of soda, applied alone, gave no increase, Tons. 1^ cwt. sulphate of ammonia alone gave only . lij While n cwt sulphate of soda, and ) ^. ^g^ I cwt. sulphate of ammonia, ) ' ^ Being an increase of 6 tons an acre above sulphate of soda, and 4 tons above sulphate of ammonia applied alone. 4. Nitrate of soda with sulphate of magnesia. — Also on the same field, while Tons. I5 cwt. of nitrate of soda gave, as above, onlj . 16 And 1 2 cwt. of sulphate of magnesia, only . . 134 1 cwt. of each, mixed together, gave . . 22 J Thus experiment, as well as theory, indicates that the appli- cation of several saline substances mixed together, is more likely to increase the produce of the soil than a larger addition of either applied alone. 5. Phosphate of 7nagnesia with phosphate of ammonia.- — I have said that attention to the requirements of nature will indicate EXPERIMENTS WITH MIXED PHOSPHATES. 245 what mixtures m^ be tried wifh the hope of success, and even what mixtures may be likely to prove specific manures. Thus it is known from analysis that the seeds of plants — the grain of our corn crops for example — contain much nitrogen in their gluten, and that the ash of grain is rich in phosphoric acid and magnesia. It was natural to suppose, therefore, that the appli- cation to growing corn of a mixture capable of specially sup- plying these three substances would specially act in filling the ear. A saline compound known by the name of phosphate of magnesia and ammonia, containing the two phosphates united,* is fitted for this purpose, and was consequently recommended for trial. Experiments, recently made, show that it exercises a power- ful influence, especially upon Indian corn. Applied at the rate of 130 to 260 lb. per acre, it had also a very favorable, though less marked, influence upon wheat. Upon Indian corn, at the rate of 3 cwt. per acre, it increased the crop of grain six times, and of straw three times. A constant effect is to increase the weight of the grain per bushel as common salt does; and, like many other substances, it produces most marked effects upon poor and worn-out soils. This compound, therefore, is deserving of further trial ; and it is desirable that attempts should be made to manufacture it for the manure-market at a moderate price. f SECTION VI. RESULTS OF EXPERIMENTS WITH MIXED SALINE MA- NURES MADE WITH THE VIEW OF AFFECTING THE CHARACTER OR QUALITY OF THE CROP. The above are illustrations of the kind of mixtures which, on * It is prepared by pouring mixed solutions of sulphate of magnesia and sulphate of ammonia into a solution of the common phosphate of soda of the shops. \ See the Author's Experimental Chemistry^ p. 216. Also the Annales de Chemie for September 1852, p. 46. 246 MIXTURES PROMOTING GROWTH the faith of results obtained by actual trial, may be recom- mended to the practical man as likely to increase the quantity of the crop. But mixtures may, by the reflecting farmer, be applied for other purposes. 1. As when he mixes together Nitrate of Soda, 3 cwt. Gypsum, . . . , , . 5 " }• 28 cwt. Wood ashes, 20 ' )wt. ) and applies this mixture at the rate of 5 or 6 cwt. an imperial acre as a cure for clover-sick land — as recommended by Mr. Prideaux. 2. Or when two good effects on the growth are sought for at the same time by the simultaneous application of two sub- stances to the crop. Or when an evil effect, considered likely to follow from the use of one substance alone, is to be pre- vented or counteracted by the use of another substance along with it. Thus, nitrate of soda applied to corn crops gives increased luxuriance, and greatly promotes the growth of straw, while it also increases the size of tiie ear But this rapid growth makes wheat, in some localities, liable to mildew. It is apt also to give a feebleness to the straw, which makes the crop more liable to be laid by the wind and rains ; so that if stormy wea- ther come when harvest approaches, the corn may be seriously damaged. On the other hand, common salt, while it usually strengthens and brightens the straw, makes mildew more rare, and adds, besides, to the weight of the grain per bushel. By using the two substances together, therefore, the increased growth caused by the nitrate will be secured, and mildew pro- bably prevented ; while the common salt will give the straw strength to stand. With this view experiments have been made with such a mixture by various persons, with the best results. I quote only two results, obtained at Holkbam by Mr. Keary, from applications to his wheat crops in 1850 and 1851. AND PREVENTING MILDEW. 24 T Application Produce, per imperial acre. Grain. Straw. 1850. No application, ... 37 busk 26 cwt. Nitrate of soda, 1 cwt. . . 40 . . 32 . . Nitrate of soda, 1 • • [ aq oa Comiiiou salt, 2 . . f ' In this case the addition of salt produced no increase above the nitrate alone, except in augmenting by 2 cwt. the weight of the straw. 1851. No application, . . . SYi bush. 27 cwt Nitrate of soda, 1 cwt. . . 431 . . 37 . . Nitrate of soda, 1 . . [ Common salt, 2 . . J * 45^ .. 36* In this experiment the grain was increased nearly 2 bushels by the salt, while the straw was lessened by 1 cwt. These differences are of little pecuniary consequence. The chief ad- vantage to be looked for from the use of the salt is, as I have said, in its making more sure the gain which nitrate of soda, on all poor soils, and especially upon sickly crops, may be expected to produce. SECTION VII. ^USE OF ARTIFICIAL MIXED MANURES, COMPOUNDED IN IMITATION OF NATURAL MANURES ARTIFICIAL GUANOS. The above experiments illustrate how saline mixtures may be made and used for a definite and known purpose, other than that of simply adding to the natural produce of the land. But mixtures may also be made, with the view of imitating nature, and of compounding by art those valuable manures which she furnishes in such variety, where we can do it effectually, and at a reasonable cost. Thus guano is a highly fertilising substance; and as the sup- ply brought to this country is limited, and the price at which it was sold, when first introduced into this country, was a great * Journal of the Rotjal Agricultural Society, vol. xiii. p. 210. See also for similar experiments by Mr. Pusey, vol. xii. p. 202. £0 19 0. [$4 Y5 14 6 3 63 4 1 00 16 37 2 50 5 1 25 1 6 38 248 ARTIFICIAL GUANOS. bar to its extensive employment, I was induced at the time to recommend the following, or some similar mixture — as likely to resemble it in fertilising virtue, because it contains the same in- gredients, as determined by analysis — to be inexhaustible in supply, because prepared chiefly from the produce of our own manufactories — and to be at least as cheap as the best import- ed guano. 315 lb. (7 bushels) of bone dust at 2s. 9d. a bushel, £0 19 0, 100 " sulphate of ammonia, 20 " of pearl ash, or 80 lb. of wood ashes, 80 " of common salt, .... 20 " of dry sulphate of soda, . 25 " of nitrate of soda, .... 50 " of crude sulphate of magnesia, . 610 £2 7 6 $11 88 This quantity should be equal in efficacy to 4 or 5 cwt. of guano, and may by many be made at a cheaper rate. This recipe has formed the basis of numerous varieties of ar- tificial guano which have been manufactured in different parts of the country, and sold under different names, and at various prices — some of them sufficiently low to indicate that either the mixtures are not good, or that they are not made of valuable materials. They have, therefore, been applied to the land with, as might be expected, very discordant results. Though we should never be able to manufacture an artificial guano equal to the native, this good effect to the practical man arose at once from the publication of the above recipe, and from the manufacture and sale of artificial guano — that natural guano fell remarkably in price, and with it rape-dust, bone-dust, and other costly manures of a similar kind. Thus chemistry pos- sesses an intelligible money value even to the working farmer. This question of cheapness is second only to that of eflQciency in a manure. To make these manures cheap is the next point after making them well. With many manufacturers — and un- fortunately with many purchasers too — cheapness is made the CHEAPNESS SECOND ONLY TO EFFICIENCY. 249 first consideration; and hence mixtures are brought into the market at a low price, which are of comparatively little value, and can produce a sensibly profitable result in a few cases only, and upon peculiar soils. To make the manure cheap, the ingredients employed must be so. The refuse of manufactories has been looked to as a source of such cheap materials, and not without the prospect of ultimate advantage to the country. The use of such refuse, liowever, has, in the first instance, led to much imposition. The exact nature of the refuse must be known, and its uniformity and constancy of composition ascertained, before it can be safe- ly employed in the manufacture of any mixed manure. It is a great objection to the numerous artificial guanos and mixed manures now offered for sale, that the public have no guarantee, either of the competency of the parties who make them to devise a mixture which shall be universally advanta- geous — of their ability to select materials which shall render it of that uniform composition which is essential to its success — or of their good faith in endeavoring to secure such a compo- sition.* *For numerous recipes for particular crops, the reader is referred to the author's Lectures, 2d edition, p. 639-646. CHAPTER XIX. Use of lime in Agriculture. — Composition of limestones, chalks, corals, shell-sands, and marls. — Burning and slaking of lime, hydrate of lime, spontaneously slaked lime. — Effects of exposure to the air upon quick- lime. — Advantages of burning lime partly mechanical and partly chemi- cal. — Silicate of lime produced by burning. — Quantity of lime usually apphed to the land. — Visible improvements produced by Ume. — Why liming must be repeated. — How lime is gradually removed from the land. — Circumstances which modify the effects of lime upon the land. — Che- mical effects of caustic and of mild lime upon the soil. — What is meant by overliming. — Proportion of lime in overlimed land. — How overliming is to be remedied. — Exhausting effects of lime. — Is lime necessarily ex- hausting. The use of lime is of the greatest importance in practical agriculture. It has been employed in the forms of marl, shell, shell-sand, coral, chalk, limestone, limestone gravel, quick-lime, &c., in almost every country, and from the most remote period. SECTION I. COMPOSITION OF LIMESTONES AND CHALKS. When diluted muriatic acid, or strong vinegar, is poured upon pieces of lime- stone, chalk, common soda, or common pearl ash, effervescence takes place, and carbonic acid gas is given off, (p. 18.) If a current of this gas be made to pass through lime water, (see figure,) the liquid becomes milky, and a white pow- der falls, which is pure carbonate of lime. It consists of COMPOSITION OF LIMESTONES. 251 Per cent Carbonic acid, 43-7 Lime. 56-3 100 One ton of pure dry carbonate of lime contains, of Cwtau Carbonic acid, 8| Lime, Hi 20 Limestone and chalk consist, for the most part, of carbonate of lime. In soft chalk, the particles are held more loosely to- gether; in the hard chalks and in limestones, the minute grains have been pressed or otherwise brought more closely together, so as to form a more solid and compact mass. In regard to limestones and chalks, there are several circum- stances which it is of importance for the practical man to know. For example — a. That they are not composed entirely of mineral or inor- ganic particles, such as are formed by the passage of a current of carbonic acid through lime-water. They consist in great part, sometimes almost entirely, of minute microscopic shells, of the fragments of shells of larger size, or of solidified masses of corals, which formed coral reefs in ancient seas which once covered the surface where the limestones are now met with. The blue mountain limestones contain many of these coral reefs, while in our chalk rocks vast quantities of microscopic shells and fragments of shells appear. h. Being thus formed at the bottom of masses of moving wa- ter, the chalks and limestones are seldom free from a sensible admixture of sand and earthy matter. Hence, when they are treated with diluted acid, though the greater part dissolves and disappears, yet a variable proportion of earthy matter al- ways remains behind in an insoluble state. This earthy matter 252 PHOSPHATE OF LDIE IX LIMESTONE. is sometimes less than half a per cent of the whole weight, though sometimes it amounts to as much as 30 or 40 per cent. c. Ail animals hitherto examined contain in the parts of their bodies traces more or less distinct of phosphoric acid, generally in combination with lime, forming phosphate of lime. This phos- phate of lime their remains, when dead, retain in whole or in part. It thus happens that limestones almost invariably con- tain phosphoric acid, and that the proportion of it usually in- creases with that of the visible remains of animals, shells, co- rals, &c., which occur in it. In the magnesian limestones of the county of Durham, I have found the proportion of phosphate of lime to be as small as 0.07 to 0.15 per cent ; while in a lime- stone from Lanarkshire (Carluke,) analysed in my laboratory, it amounted to IJ per cent ; or one hundred pounds of the burned lime contained as much as 21 pounds of phosphate of lime. d. The parts of animals also contain sulphur, and this has given rise to the presence of sulphuric acid in chalks and lime- stones. This acid exists in them in combination with lime — in the state of gypsum. The proportion of this gjq^sum which I have hitherto found in native chalks and limestones is small, varying from one-third to four-fifths of a per cent. e. Carbonate of magnesia, the common magnesia of the shops, is also present, almost invariably, in all our limestone and chalk rocks. In the purest it forms 1 or 2 per cent, in the most im- pure from 40 to 45 per cent of the whole weight. The rocks called dolomites or magnesian limestones, (p. 9t,) are charac- terised by the presence of a large proportion of carbonate of magnesia. In the old red sandstone formation also, beds of limestone occur which are rich in magnesia. Such limestones are usually considered less valuable for agricultural purposes. They can be applied less freely and abundantly to the land, and possess what practical men call a burning or a scorching quali- ty. They are, however, preferred to purer limes in some dis CORALS, SHELL SANDS, AND MARLS. 253 tricts, as in the high lands of Galloway, for application to hill pastures. ^ SECTION II. COMPOSITION OF CORALS, SHELL-SANDS, AND MARLS. 1°. Corah, as they are gathered fresh from the sea on the Irish (Bantry Bay) and other coasts, contain, besides carbonate of lime, a small percentage of phosphate of lime, and sometimes not less than 14 per cent of animal matter — (Jackson.) This animal matter adds considerably to the fertilising value of coral sand, when laid upon the land in a recent state, or when made into compost. 2°. Shell-sand consists of the fragments of broken shells of various sizes, mixed with a variable proportion of sea sand. It contains less animal matter than the recent corals, and its value is diminshed by the admixture of sand, which varies from 20 to to per cent of the whole weight. On the shores of many of the Western Islands, shell-sand is found in large quantities, and is extensively and beneficially applied, especially to the hill-side pastures, and to peaty soils. 3°. Marls consist of carbonate of lime — generally the frag- ments of shells — mixed with sand, clay or peat in various pro- portions. They contain from 5 to as much as 80 or 90 per cent of carbonate of lime, and are considered more or less rich and valuable for agricultural purposes as the proportion of lime in- creases. They are formed, for the most part, from accumula- tions of shells at the bottom of fresh-water lakes which have gradually been filled up by clay or sand, or by the growth of peat. SECTION III. OF THE BURNING AND SLAKING OF LIME. 1°. Burning. — Limestones, when of a pure variety, consist almost entirely of carbonate of lime. This carbonate of lime, as we have seen, contains about 56 per cent of lime, or 11 J cwt. to the ton. 254: BURNING AND SLAKING OF LIME. When this h'mestone is put into a kiln, with so much coal as, when set on fire, will raise it to a sufficiently high temperature, the carbonic acid is driven oif in the form of gas, leaving the pure lime behind. In this state it is known as burned lime, lime-shells, caustic lime, and quick lime, and possesses properties very different from those of the unburned limestone. It has a hot alkaline taste, absorbs water with great rapidity, falls to powder or slakes, and finally dissolves in t32 times its weight of cold water. This solution is known by the name of lime-water. 2°. Slaking. — Its tendency to combine chemically with water is shown in the process of slaking. Almost every one is fami- liar with the fact that, when water is poured upon quick-lime, it heats, emits steam, swells, cracks, and at last falls to a fine, usually white, powder, which is two or three times as bulky as the lime in its unslaked state. When thus fully slaked and cool, the fine powder consists of — Lime, t6 per cent. Water, . ... 24 . 100 Or 20 cwt. of pure burned lime absorb and retain in the solid state 6J cwt. of water, forming 26J cwt. of slaked lime, called hydrate of lime by chemists. When quick-lime is left exposed to the air, even in dry weather, it gradually absorbs moisture from the atmosphere, and falls to powder without the artificial addition of water. In this case, however, it does not become sensibly hot as it does when it is slaked rapidly by immersion, or by pouring water upon it. SPONTANEOUS SLAKING. 255 SECTION IV. OF THE CHANGES WHICH SLAKED LIME UNDERGOES BY EXPOSURE TO THE AIR, AND OF THE BENEFITS OF BURNING LIMESTONES. 1°. Effects of ex'posure to the air. — When lime from the kiln is slaked by means, of water, it still retains its quick or caustic quality. But if, after it lias fallen to powder, it be left un- covered in the open air, it gradually absorbs carbonic acid from the atmosphere, gives off its water, and becomes reconverted into dry carbonate of lime. When lime is allowed to slake spontaneously in the air, it first absorbs water, and slakes, and falls to powder, and then absorbs carbonic acid and is changed into carbonate. But as soon as a portion of the lime slakes, it begins to absorb carbonic acid, probably long before the whole is slaked. Thus the two processes go on together, so that, in lime left to slake sponta- neously, as it is often on our fields and headlands, the powder into which it falls consists in part of caustic hydrate and in part of mild carbonate of lime. Its composition is nearly as follows: — Per cent. Carbonate of lime, 57.4 Hydrate ofltae. \^^^,;,f,^^\ ■ . . 42.6 100 When it reaches this stage or composition, the remainder of the hydrate absorbs carbonic acid much more .slowly, so that when spread upon or mixed with the soil, it takes a much longer time to convert it into carbonate. At last, however, after a longer or shorter period of time, the whole of the lime becomes saturated with carbonic acid, and is brought back to the same state of mild ?<,?z-caustic carbonate in which it existed in the na- tive chalk or limestone before it was put into the kiln. 256 ADVANTAGES OF BURNING. 2°. Advantages of burning lime. — If the lime return to the same chemical state of carbonate in which it existed in the state of chalk or limestone, — what is the benefit of burning it ? The benefits are partly mechanical and partly chemical. a. We have seen that, on slaking, the burned lime falls to an exceedingly fine bulky powder. When it afterwards becomes converted into carbonate, it still retains this exceedingly mi- nute state of division ; and thus, whether as caustic hydrate or as mild carbonate, can be spread over a large surface, and be intimately mixed with the soil. No available mechanical means could be economically employed to reduce our limestones, or even our softer chalks, to a powder of equal fineness. b. By burning, the lime is brought into a caustic state, which it retains, as we have seen, for a longer or shorter jDcriod, till it again absorbs carbonic acid from the air or from the soil. In this caustic state, its action upon the soil and upon organic matter is more energetic than in the state of mild lime ; and thus it is fitted to produce effects which mere powdered lime- stone or chalk could not bring about at all, or to produce them more effectually, and in a shorter period of time. c. Limestones often contain sulphur in combination with iron, (iron pyrites.) The coal or peat, with which it is burned, also contains sulphur. During the burning, a portion of this sulphur unites with the lime to form gypsum, by this means adding to the proportion of this substance, which naturally exists in the limestone. d. Earthy and silicious matters are sometimes present in considerable quantity in our limestone rocks. When burned in the kiln, th« silica of this earthy matter unites with lime to form silicate of lime. This silicate of lime, being diffused through the burned and slaked lime, and afterwards spread, in a mi- nute state of division, through the soil, is in a condition in which it may yield silica to the growing plant. Thus the benefits of burning are, as I have said, partly me- chanical and partly chemical. They are mechanical, inasmuch QUANTITY OF LIME REQUIRED. 257 as, by slaking, the burned lime can be reduced to a much finer and more bulky powder than the limestone could be by any me- chanical means ; and they are chemical, inasmuch as, by burn- ing, the lime is brought into a more active and caustic state, and is, at the same time, mixed with variable proportions of sulphate and of silicate of lime — which may render it more useful to the growing crops. SECTION V. QUANTITY OF LIME USUALLY APPLIED TO THE LAND. The quantity of quick-lime laid on at a single dressing, and the frequency with which it may be repeated, depend upon the kind of land, upon the depth of the soil, upon the quantity and kind of vegetable matter which the soil contains, and upon the species of culture to which it is subjected. If the land be wet, or badly drained, a larger application is necessary to pro- duce the same effect, and it must be more frequently repeated. But when the soil is thin, a smaller addition will thoroughly impregnate the whole, than where the plough usually descends to the depth of 8 or 10 inches. On old pasture lands, where the tender grasses live in 2 or 3 inches of soil only, a feeble dressing, more frequently repeated, appears to be the more rea- sonable practice ; though in reclaiming and in laying down land to grass, a heavy first liming is often indispensable. In arable culture, larger and less frequent doses are admissi- ble, both because the soil through which the roots penetrate must necessarily be deeper, and because the tendency to sink beyond the reach of the roots is generally counteracted by the frequent turning up of the earth by the plough. Where vege- table matter abounds, much lime may be usefully added ; and on stiff clay lands, after draining, its good effects are very re- markable. On light land, chiefly because there is neither moist- ure nor vegetable matter present in sufficient quantity; very large applications of lime are not so usual, and it is generally preferable to add it to such land in the state of compost only. 268 WHY LIME MUST BE REPEATED. The largest doses, however, which are applied in practice, alter in a very immaterial degree the chemical composition of the soil. The best soils generally contain a natural proportion of lime, not fixed in quantity, yet scarcely ever wholly wanting. But an ordinary liming,' when well mixed up with a deep soil, will rarely amount to one per cent of its entire weight. It re- quires about 400 bushels (12 to 15 tons) of burned lime per acre to add one per cent of lime to a soil of twelve inches in depth. If only mixed to a depth of six inches, this quantity would add about two per cent to the soil. Though the form in which lime is applied, the dose laid on, and the interval between the doses varies, yet in Great Britain, at least in those places where lime can be obtained at a reasonable rate, the quantity applied amounts, on an average, to from *I to 10 bushels a-year. SECTION VI. VISIBLE IMPROVEMENTS PRODUCED BY LIME, AND WHY LIMING MUST BE REPEATED. The most remarkable visible alterations produced by lime are — upon pastures, a greater fineness, sweetness, closeness, and nutritive character of the grasses — on arable lands, the im- provement in the texture and mellowness of stiff clays, the more productive crops, their better quality, and the earlier period at which they ripen, comp^fred with those grown upon soils to which no lime has ever been added. This influence of lime is well seen when limed is compared with unlimed land, or when soils, which are naturally rich in lime, are compared with such as contain but little. Barley grown on the former is of better malting quality. The turnips of well-limed land are more feeding for both cattle and sheep. And the hill pastures on limestone soils, like those of Derby- shire, continue longer green in autumn, and yield a greater year- ly return of milk and cheese, than the soils which are produced from sandstone rocks. CROPS AND RAINS CARRY AWAY LIME. 259 But this superiority gradually diminishes year by year, iii land artificially limed, till it returns again nearly to its original con- dition. On analysing the soil when it has reached this state, the lime which had been added is found to be in a great measure gone. In this condition the land must either be limed again, or must be left to produce sickly and unremunerating crops. This removal of the lime arises from several causes. 1. The. lime naturally sinks, — more slowly perhaps in arable than in pasture or meadow land, because the plough is continu- ally bringing it to the surface again. But even in arable land, it gets at last beyond the reach of the plough, so that either a new dose must be added to the upper soil, or a deeper plough- ing must bring it again to the surface. 2. The crops carry away a portion of lime from the soil. — Thus the following crops, including grain and straw, or tops and bulbs, carry off respectively — Of lime. 25 bushels, wheat, about . 13 lb. 40 .... barley, . . l? " 50 .... oats, . . 22 " 20 tons of turnips, about . 118 " 8 ... potatoes, . . 40 " 2 ... red clover, , . 17 " 2 ... rye grass, . . 30 " The above quantities are not constant, and much of the lime is no doubt returned to the land in the straw, the tops, and the manure ; yet still the land cannot fail to suffer a certain annual loss of lime from this cause. 3. The rains wash out lime from the land. — The rain-water that descends upon the land holds in solution carbonic acid which it has absorbed from the air. But water charged with carbonic acid is capable of dissolving carbonate of lime ; and thus year after year the rains, as they sink to the drains, or run over the surface, slowly remove a portion of the lime which the soil contains. Acid substances are also formed naturally by the decay of vegetable matter in the land, by which another 260 CHEMICAL EFFECTS OF LIME UPON THE SOIL. portion of the lime is rendered easily soluble in water, and therefore readily removable by every shower that falls. It is a necessary consequence of this action of the rains, that lime must be added more frequently, or in larger doses, where much rain falls than where the climate is comparatively dry. SECTION VII. CIRCUMSTANCES WHICH MODIFY THE EFFECTS OF LIME UPON THE SOIL. There are four circumstances of great practical importance in regard to the action of lime, which cannot be too carefully borne in mind. These are — 1. That hme has little or no marked effect upon soils in which organic — that is animal or vegetable — matter is greatly de- ficient. 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, as this organic matter becomes less in quantity, fresh ad- ditions of lime produce a less sensible effect. SECTION VIII. CHEMICAL EFFECTS OF CAUSTIC LIME UPON THE SOIL. The chemical effects of lime upon the soil in the caustic and mild states are chiefly the following : — a. When laid upon the land in the caustic state, the first ac- tion of lime is to combine immediately with every portion of free acid matter it may contain, and thus to sweeten the soil. Some of the compounds it thus forms being soluble in water, enter into the roots and feed the plant, or are washed out by CHEMICAL EFFECTS OF CAUSTIC LIME. 261 the springs and rains ; while other compounds which are insol- uble remain more permanently in the soil. l. Another portion decomposes certain saline compounds of iron, manganese, and alumina which naturally form them- selves in the soil, and thus renders them unhurtful to vegetation. A similar action is exerted upon some of the compounds of potash, soda, and ammonia — if any such are present — by which these substances are set at liberty, and placed within the reach of the plant. c. Its presence in the caustic state further disposes the organ- ic matter of the soil to undergo more rapid decomposition — it being observed that, where Ume is present in readiness to com- bine with the substances produced during the decay of organic matter, this decay, if other circumstances be favourable, will proceed with much greater rapidity. The reader will not fail to recollect that, during the decomposition of organic substances in the soil, many compounds are formed which are of importance ill promoting vegetation. d. It is known that a portion at least of the nitrogen which naturally exists in the decaying vegetable matter of the soil is in a state in which it is very sparingly soluble, and therefore becomes directly available to plants with extreme slowness. But when heated with slaked lime in our laboratories, such compounds readily give off their nitrogen in the form of ammo- nia. It is not unlikely, therefore, that hot lime produces a similar change in the soil, though more slowly — hastening, as above stated, the general decomposition of the whole organic matter, but specially separating the nitrogen, and causing or en- abling it to assume the form, first of ammonia, and afterwards of nitric acid, both of which compounds the roots of plants can readily absorb. e. Further, quick-lime has the advantage of being soluble to a considerable extent in cold water, forming lime-water. Thus the complete diffusion of lime through the soil is aided by the power of water to carry it in solution in every direction. 26^ CHEMICAL EFFECTS OF MILD LIME. SECTION IX. CHEMICAL EFFECTS OF MILD LIME WHEN APPLIED TO THE SOIL. When it has absorbed carbonic acid, and become reconverted into carbonate, the original caustic lime has no chemical virtue over chalk or crushed limestone, rich shell-sand, or marl. It has, however, the important mechanical advantage of being in the form of a far finer powder than any to which we can reduce the limestone by art — in consequence of which it can be more uniformly diffused through the soil, and placed within the reach of every root, and of almost every particle of vegetable matter that is undergoing decay. I shall mention only three of the important purposes which, in this state of carhonate, lime serves upon the land. a. It directly affords food to the plant, which, as we have seen, languishes where lime is not attainable. It serves also to convey other food to the roots in a state in which it can be made available to vegetable growth. h. It neutralises (removes the sourness) of all acid substances as they are formed in the soil, and thus keeps the land in a condition to nourish the tenderest plants. This is one of the important agencies of shell-sand, when laid on undrained grass or boggy lands ; and this effect it produces in common with wood ashes and many similar substances. c. During the decay of organic matter in the soil, it aids and promotes the slow natural production of nitric acid. With this acid it combines and forms nitrate of lime — a substance very sol- uble in water — entering readily, therefore, into the roots of plants, and producing effects upon their growth which are very similar to those oflhe now well-known 7zz7r«^e of soda. The success of frequent ploughings, harrowings, hoeings and other modes of stirring the land, is partly owing to the facilities which these operations afford for the production of this and other natural nitrates. OYER-LIMED SOILS. 263 SECTION X. WHAT IS MEANT BY OVER-LIMING ? PROPORTION OF LIME IN OVER-LIMED LAND. HOW OVER-LIMING IS TO BE REM- EDIED. It is known that the frequent addition of lime, even to com- paratively stiff soils long kept in arable culture, will at length so open them that the wheat crop becomes uncertain, and is especially liable' to be thrown out in winter. To lighter soils, again, and especially to such as are reclaim- ed from a state of heath, and contain much vegetable matter, the addition of a large dose of lime opens and loosens them, often to such a degree that they sound hollow, and sink under the foot. This effect is usually ascribed to an over-dose of lime, and the land is commonly said to be over-limed. In this state it refuses to grow oats and clover, though turnips and barley thrive well upon it. Being desirous of ascertaining the proportion of lime re- ally present in land which has been brought by lime into such a condition, I obtained from Sir George Macpherson Grant a number of soils from different fields upon his estate of Ballin- dalloch, and caused them to be analysed in my laboratory. The results of the analyses were as follows : — a ^ ■^^ -a -S^ o . ni G . % 1 '^-< S Cr4 c Ph a — Ph ei^ S'i^ sig >.-:z ® tJ-'i Organic matter, r^ 03 |1" Suth( Par soil sub 10.29 9.54 5.65 5.73 5.23 Salts soluble in water, 0.45 0.15 0.50 0.15 0.44 Oxide of iron, 2.49 3.68 0.50 0.96 2.04 Alumina, .... 1.71 2.54 1.11 1.48 1.15 Carbonate of lime, . 1.40 0.69 1.10 0.98 0.67 Oxide of manganese, trace. 0.72 trace. trace. 0.22 Carbonate of magnesia, . do. trace. do. do. trace. Insoluble matter, chiefly sand, , 81.7t 82.79 91.20 90.34 89.60 98.11 100.11 100.06 99.64 99.35 264 HOW TO TREAT SUCH SOILS. In all these soils the quantity of carbonate of lime was much less than is usually found in fertile soils. I inferred, therefore, that the effects ascribed to the lime were not due to its presence in too large a proportion, compared with other soils. Two other facts aided me in arriving at a correct conclusion upon the subject. 1. That these same soils were known to produce good oats when they had been some years in pasture, or when turnips had been eaten off them with sheep, and the ground thus trodden and consolidated by their feet. 2. -That oats and clover prefer a stiffer, stronger soil in which to fix their roots, while turnips and barley delight in a light and open soil. It was therefore the mechanical, and not the chemical con- dition of the soils, wiiich caused the failure of the turnip and clover crops. Consolidate them by any means,* and these crops would become more certain. The remedies, therefore, were — a. To eat off the turnips always with sheep ; — or h. To consolidate the loose and open soil by the use of a heavy roller, a clod-crusher or peg-roller, or other similar me- chanical means; — or c. To use the cultivator as much as possible instead of the plough, and thus to avoid the artificial loosening of the soil which is caused by frequent ploughing. Still the questions were unsolved, — In what way does the lime produce, or aid the plough in producing, this opening of the soil ? — and how are these effects to be prevented in fu- ture ? I offer the following considerations, as affording a conjectu- ral explanation of this matter : — 1. The lime, in whatever state it is added to the land, as- sumes in a short time the state of carbonate. 2. In soils which are rich in decaying vegetables much acid EXHAUSTING EFFECTS OF LIME. 265 matter is gradually produced by the action of the air. The acids thus produced decompose the carbonate of lime, and libe- rate its carbonic acid more or less copiously. 3. The effect of this liberation of the carbonic acid gas may be to heave up the land, to loosen it and lighten it under the foot. In heavy lands this may be less perceived, both because they are naturally denser and more difficult to heave up, and because they contain less vegetable matter, and consequently produce less of these acid substances in the soil. In light peaty or thin moorish soils, however, which are rich in decay- ing plants, the particles of soil are more readily lifted up and separated from one another. Will this supposed action never cease ? It is doubtful if it will, until the nature of the soil is altered — by the gradual re- moval of the lime — by a diminution of the quantity, and a change in the nature of the decaying vegetable matter — or by a permanent solidifying of the land. This last change maybe effected either by a top-dressing of clay, sand, limestone-gravel, or other heavy matter, or by bringing up a heavier subsoil from below. Where the temporary solidifica- tion produced by eating off with sheep and the use of a roller is not approved of, the improvement of over-limed land is to be sought for in draining, subsoiling so as to admit the air into the under-soil, and, after a time, in bringing up and mixing with the surface a sufficient portion of this under-soil. SECTION XI. EXHAUSTING EFFECTS OF LIME. IS LIME NECESSARILY EXHAUSTING ? The exhausting effects of lime have been remarked from the earliest times. It causes larger crops to grow for a certain number of years, after which the produce diminishes, till at length it becomes less than before lime was applied to it. Hence the origin of the proverb that " Lime enriches the fathers and im- poverishes the sons." 12 266 ORGANIC MATTER DIMINISHES IN THE SOIL. Two interesting questions, therefore, suggest tliemselves in connection witli this circumstance. How is this exhaustion pro- duced ? Is it a necessary consequence of the addition of lime, or can it be prevented ? It has already been stated that lime promotes those chemical changes of the organic part of the soil by which it is rendered more serviceable to the growth of plants. But in consequence of this action, the proportion of organic matter in the soil grad- ually diminishes under the prolonged action of lime, and thus the soil becomes less rich in those substances of organic origin on which its fertility in some degree depends. Again, lime acts also on the mineral matter of the soil, and prepares it for more abundantly feeding the plant. Now, as the crops we reap carry off not only organic but min- eral matter also from the soil, anything which prepares that mineral matter more abundantly for the use of the plant must cause also a more rapid diminution of those mineral substances on which, as well as upon its organic matter, the fruitfulness of the soil is dependent. By this mode of action, therefore, arises the exhaustion which universal experience has ascribed to the use of lime. But without reference to the chemical processes by which it is brought about, a common-sense view of the question sufficient- ly explains how the exhaustion arises. It is conceded that the crops we grow rob the soil both of organic and inorganic matter. A double crop will take twice as much, a triple crop three times as much, and so on. And the more we take out in one year, the more rapidly will the land be exhausted. Now, if lime, by its mode of action, enables us in the same time to extract three or four times as much matter from the soil in the form of increased crops, it must so much the more rapidly exhaust the soil, in the same way as we should drain a well sooner by taking out fifty than by remov- ing only five gallons a-day. But we can restore to the soil what crops carry off. By THE SOIL CAN BE RESTORED feY MANURE, &C. 20*1 farmyard manure, and by saline applications, we can return everything which the lime enables us thus to extract, and we can thus preserve its fertility unimpaired. Manure, therefore, in proportion to the crops taken off, and lime, will cease to be exhausting. There is much wisdom in the rhyme, "Lime and lime loWiout manivre .Will make both land and farmer poor." CHAPTER XX. Improvement of the soil by paring and burning. — Use and properties of burned earth and burned clay as improvers. — Effects of buriJing upon clay. — Smother-burning and over-burning. — How they improve the soil. — Improvement by means of irrigation. — Irrigation a kind of manuring. — How waters manure the land. — Composition of the water of the Hamp- stead water-works. — Different virtues of natural streams. There remain still a few important modes of improving the soil by forms of mineral and organic manuring, which it is ne- cessary briefly to notice. SECTION I. IMPROVEMENT OF THE SOIL BY PARING AND BURNING. A mode of improvement often resorted to on poor lands is the paring and burning of the surface. The effect of this treatment is easily understood. The matted sods consist of a mixture of much vegetable with a comparatively small quantity of earthy matter. When these are burned, the ash only of the plants is left, intimately mixed with the calcined earth. To strew this mixture over the soil is much the same as to dress it with peat or wood ashes, the beneficial effects of which are almost universally recognised. And the beneficial influence of the ash itself is chiefly due to the ready supply of inorganic food it yields to the seed, and to the effect which the potash and soda, &c., which it contains exercise either in prepar- ing organic food in the soil, or in assisting its assimilation in the interior of the plant. Another part of this process is, that the roots of the weeds and poorer grasses are materially injured by the paring, and that the subsequent dressing of ashes is unfavorable to their further growth. BURNED EARTH AND CLAY. 269 It is besides alleged, and I believe with truth, that poor old grass land, when ploughed up, is sometimes so full of insects that the success of any corn or green crop put into it becomes very doubtful. When pared, these insects collect in the sod, and are destroyed by the subsequent burning. Paring and burning is a quick method of bringing land into tillage, and will secure one or two good crops. But it is exhausting, and the prudent man will rarely have recourse to it for the purpose of reclaiming land which is to be kept in constant tillage. It is very much less practised now than it was twenty or thirty years ago. Another evil also follows the practice of paring and burning. Where the land has little fall for drainage — is raised, that is, only a few feet above the level of the nearest brook — this paring and burning gradually lowers the level, and makes it impossible at last to drain it. In Northamptonshire I have been told of pieces of land, a few years ago two feet above the water level, which are now brought down to that level by the repetition of this hurtful practice. This is certainly enriching the farmers and impoverishing the sons. SECTION II. ON THE USE AND PROPERTIES OF BURNED EARTH AND CLAY AS IMPROVERS. 1^, Burned earth and clay have long been recognised by the farmer as useful applications, in certain circumstances, to his land. Mixed with much vegetable matter of any kind, and burned slowly and without free access of air, stiff soils of all sorts will give blackened heaps, which may be spread with ad- vantage as a top-dressing, or employed, as in China, to cover the seed after it has been committed to the earth. To the light porosity of the earth, and to the action of the vegetable ashes which are mixed with it, the beneficial influence of such burned mixtures is distinctly to be ascribed. 2°. Burned day^ in which little organic matter exists, and 2*10 CAUSE OF THEIR USEFUL ACTION. with which little is mixed during the burning, must owe any fertilising properties it possesses to a different cause. Such clay, properly prepared, has in numerous instances been found beneficial when applied to the land. It is usually laid on in large doses, and acts both mechanically and chemically. a. Mechanically, in rendering the soil more friable, so that it can be worked with less labor, and in esjDCcially aiding the cul- ture of green crops. I. Chemically, in considerably increasing the produce. Thus Mr. Pusey found a dressing of burned Oxford clay to increase his wheat crop from 3*1 J to 45 J bushels per imperial acre. And Mr. Danger, who farms on the new red sandstone, near Bridge water, says, that a soil which he found '* quite sterile, has, by the application of burned clay, become totally changed."* It is equally true, however, that burned clay has often failed to do any good — that the practice of burning clay, which is common in some districts, is for this reason never adopted in others — and that clay from the same locality may or may not do good according to the method of burning. All this is easily explained when the true cause of the chemical action of burned clay is understood. 3°. Cause of its useful chemical action. — All clays contain sensible quantities of most of the mineral substances — potash, soda, lime, magnesia, phosphoric acid, &c. — which plants re- quire for their healthy growth. They are, however, in a com- paratively insoluble condition, which circum.stance, united to the stiffness of the clay, prevents the roots of plants from readily taking them up. When the clays are burned by a gen- tle heat, however, the chemical condition of the constituents of the clay is altered, and the substances which plants require are rendered more soluble. After the burning, both water and acids will dissolve out more from the same weight of dry clay, * Boyal Agricultural Journal, vi. 411, and xii. 509. OVER-BURNED CLAY. 211 and the matter thus dissolved contains a large proportion of those mineral ingredients which all plants contain. In one ex- periment, I found that a ton of clay which, in the natural state, gave to water only 11 lb. of mineral matter, yielded readily 36 lb. after being burned. Besides, the clay is rendered more porous by the burning, so that water and the roots of plants can penetrate more easily to take up the soluble matter. Again, of burned clay, 50 to 100 tons an acre is not an un- usual application. Now, at 36 lb. to the ton, the largest dose would yield to water not less than 3600* lb. of soluble mine- ral matter ; while the whole quantity of such matter carried off in a four years' rotation, from our best farms, (p. 69,) is only 1300 lb. It is not surprising, therefore, knowing, as we do, how applications of saline matter increase the crops, that so great and ready a supply of such matter in the burned clay should produce a marked effect upon the fertility of the laud upon which it is spread. But, further, all clays have not the same composition. Some contain more lime, others more magnesia, others more potash or fioda, and others more phosphoric acid ; while some, again, con- tain so little of any of these substances as to produce no sensible effect when burned and laid upon the land. Thus the chemical composition of a clay determines whether or not it can be burned and applied to advantage. Those clays ar6 likely to suit well which contain most alkaline matter, (potash and soda ;) next those which contain a cousid- erablij percentage of lime or magnesia, or phosphoric acid ; and, best of all, those which with the alkaline contain also the cal- careous matter. Hence it is that to clays which contain little lime it is a judicious recommendation that a quantity of slaked lime should be sprinkled upon the clay during its preparation for burning. In the fourth place, it is remarkable that, by too complete and prolonged a Imrning, the clay is again rendered less solu- * Expei'imentaL AgricuUiore, p. 261. 212 IMPROVEMENT OF ble in water and in acids than before. Hence tlie evil of over- hurning, as it is called, and the reason why the same clay pre- pared in different ways does not produce the same good effects. The method of slow smothcr-hmmn^ — the heat being kept low, and free access of air prevented — is that which gives the most constant good results. Lastly, I notice, as a beneficial consequence of burning, that the burned clay, being generally porous, absorbs ammoniacal and other vapors from the air and from the soil more readily and abundantly than before, and fixes them for the use of plants. In the black smother-burned clay, which contains much iron, this metal, in absorbing oxygen from the air, may even give rise to the formation of ammonia, and thus, in another chemical manner, act favorably upon the soil. Advantage is taken of this porous quality of burned clay by some English farmers — as by Mr. Randall, of Chadbury, near Evesham — to absorb and preserve the droppings of sheep. Under house-fed sheep, kept upon boards or otherwise, a layer of burned clay is spread, upon which the droppings fall : from time to time fresh layers are added to the surface, till it be- comes necessary to remove the whole. In this way, the smell of the dung never becomes excessive, and the clay is rendered so rich that 10 tons of it are found equal, in the raising of turnips, to 4 cwt. of guano. SECTION III.- -ON THE IMPROVEMENT OF THE LAND BY IRRIGATION. The irrigation of the land is, in general, only a more refined method of manuring it. The nature of the process itself, how- ever, is different in different countries, as are also the kind and degree of eifect it produces, and the theory by Vvdiich these effects are to be explained, 1. In dry and arid climates, where rain rarely falls, the soil may contain all the elements of fertility, and require only water to call them into operation. In such cases — as in the irriga- THE LAND BY IRRIGATION. 2t3 tions practised so extensively in Eastern countries, and without which whole provinces in Africa and Southern America would lie waste — it is unnecessary to suppose any other virtue in irrigation than the mere supply of water it affords to the parch- ed and cracking soil. But in climates such as our own, there are several other be- neficial purposes in reference to the soil, which irrigation may, and some of which, ajt least, it always does serve — thus, 2. The occasional flow oi jpure water over the surface, as in our irrigated meadows, and its descent into the drains, where the drainage is perfect, washes out acid and other noxious sub- stances naturally generated in the soil, and thus purifies and sweetens it. The beneficial effect of such washing will be rea- dily understood in the case of peat-lands laid down to water- meadow, since, as every one knows, peaty soils abound in matters unfavorable to general vegetation. These substances are usually in part drawn off by drainage, and in part destroy- ed by lime and by exposure to the air, before boggy lands can be brought into profitable cultivation. 3. But it seldom happens that perfectly |?i<,re water is employ- ed for the purposes of irrigation. The waters of rivers, as they are diverted from their course for this purpose, are more or less loaded with mud and other fine particles of matter, which are either gradually filtered from them as they pass over and through the soil, or, in the case of floods, subside naturally when the waters come to rest. Or, in less frequent cases, the drainings of towns and the water from common sewers, or from the little streams enriched by them, are turned with benefit upon the fa- voured fields. These are evidently cases of gradual and uniform manuring. 4. Even where the water employed is clear and apparently undisturbed by mud, it almost always contains ammonia, nitric acid, and other organic and saline substances grateful to the plant in its search for food, and which plants always contrive to extract, more or less copiously, as the water passes over their 12* 214 COMPOSITION OF THE HAMPSTEAD WATER. leaves or along their roots. The purest spring waters and mountain streams are never entirely free from impregnations of mineral and vegetable or animal matter. Every fresh access of water, therefore, affords the grass in reality another liquid manuring. 5. In illustration of this, I insert the following analyses of the water supplied by the Hampstead Water-works, for the use of the city of London, as given by Mr. Mitchell. It contains in all 40 grains of dry matter to the imperial gallon, which consists of— Carbonate of lime, 3.83 gr ail Carbonate of magnesia, . 3.41 ... Phosphate of hme. 0.28 ... Sulphate of lime, 4.42 ... Sulphate of potash, 3.28 ... Sulphate of soda. 4.81 Chloride of sodimn (common salt,) 17.76 ... Silica (soluble,) . 0.28 ... Crenic acid, . 0.17 ... Aprocrenic acid. , , 0.08 ... Other organic matters, . 1.72 Oxides of iron and manganese, traces ... 40.04 In this list of substances, we recognise nearly 'every mineral ingredient which is found in the ash of plants. But, in addition to these ingredients, nearly all river and spring waters contain appreciable quantities of ammonia and of nitric acid, which are not mentioned, and were probably not sought for by Mr. Mitchell. It is not surprising, therefore, that waters containing such sub- stances, in an available form, should promote vegetation when used for the purpose of irrigation. 6. The kind of saline substances which spring water or that of brooks contains, depends upon. the nature of the rocks or soils from which it issues or over which it runs. In countries where granite or mica-slate abounds, potash and soda, and even mag- nesia, may be expected in notable quantities, while in limestone districts the waters are generally charged with lime. When WATERS DIFFER IX NATURAL VIRTUE. 2t5 spread over the fields, these latter waters supply lime to the growing plants, and so affect the general fertility of the soil as to render almost unnecessary the direct application of lime to the land. The value of the mountain streams for the purpose of irrigation in limestone districts is so well known, that some have been inclined to undervalue all the constituents of natural waters, and to ascribe little worth as irrigators to the clear waters of brooks and springs which are not rich in lime. This opinion, however, is not in accordance with the-resultsof the an- alyses made in my laboratory, of waters which have been pro- fitably employed for irrigation. 7. Flowing water also drinks in from the air, as it passes along, a portion of the oxygen and carbonic acid of which the atmosphere in part consists. These gaseous substances it brings in contact with the leaves at every moment, or it carries them down to the roots in a form in which they can be readily absorbed by the parts of the plant. It is not unlikely that, in consequence of this mode of action, even absolutely pure water would act beneficially if employed in irrigating the soil. 8. Further, the constant presence of water keeps all the parts of the plant in a moist state, allows the pores of the leaves and stems to remain open, retards the formation of hard woody fibre, and thus enables the growing vegetable, in the same space of time, to extract a larger supply of food, espe- cially from the air. In other words, it promotes and enlarges its growth. In the refreshment continually afforded to the plant by a plentiful supply of water — in the removal of noxious substances from the soil — in the frequent additions of enriching food, saline, organic, or gaseous, to the land — in the soft and porous state in which it retains the parts of the plant, the efficiency of irrigation seems almost entirely to consist. 9. To one other interesting point I must advert. It is known that waters which have passed over the surface of a field become sensibly less fertilising. This is easily explained, 276 SPRING WATEK3 IN THE YOSGES. by tlie reasonable supposition that the plants among which they have flowed have deprived them of a portion of their en- riching matter. But, in the same neighborhood, it has been often observed that waters fropi natural springs which are perfectly alike in appearance, yet differ remarkably in their value for irrigation. Such is the case among the mountains of the Vosges, where ir- rigation is much attended to. The same quantity of water, from two neighboring springs, for example, employed on two adjoining meadows of similar quality, in 1848, gave of hay per acre — 1st Cutting. 2d Cutting. Total. Good spring, . 58 cwt. 24 cwt. 82 cwt. Bad spring, 14 .. H-. 21^.. Or the good spring produced nearly four times as much hay as the bad one. A chemical examination of the waters of the two springs satisfied the experimenters (Chevandier and Salvetat) that this difference was not due, either, a. To the quantity or kind of the gases which the two waters held in solution ; nor h. To the quantity or kind of the mineral matters in which both were nearly equally rich ; nor c. To the quantity of organic matter, of which the bad water in reahty contained the most ; nor d. To the absolute quantity of nitrogen contained in this or- ganic matter — for the bad water actually spread the larger quantity over the soil ; but e. To the circumstance that the organic matter, though smaller in quantity, was richer in nitrogen. It contained six per cent of this constituent, while that of the poor water con- tained only two per cent. This result is in entire consistency with all I have stated on the subject of manures — of the necessity of nitrogen to the growth of plants (p. 51,; — of the tendency of such as are ENGLISH AND INDIAN RIVERS. 27 1 rich in nitrogen especially to promote growth — and of the in- fluence of organic matters, rich in nitrogen, in enabling plants to work up the mineral and other ingredients in a mixed ma- nure*or in the soil, (p. 129,) which may happen to be within their reach.* * The following extracts in connection with waters good and lad for irri- gating, will interest .the reader: — " There are two brooks on this estate, Delamere, (the property of G. Wilbraham, Esq.,) — one a clear white water, the other brown — both of which abound in trout, and on each there are irrigated meadows. In the former stream the trout are large ; in the latter small, and never grow be- yond a certain size. The meadows watered by the former are green, lux- uriant, and productive ; those of the latter comparatively barren. It is supposed that the pernicious effects of the brown stream are occasioned by passing through peat or some mineral substance ; but the cause has never been satisfactorily demonstrated."' — Mr. Palin, " Ou the Agriculture of Cheshire," in Royal Agricultural Journal, of the Royal Agricultural Soci- ety, vol. V. p. 105. " On the property of the Earl of Caernarvon, near Exmoor, there are four streams : — the Hudson, containing excellent trout, and making su- perior water-meadows ; the Exe, inferior in the quality of the fish, and less beneficial to grass ; the Barle, worse again in each respect ; and lastly, the Danes' brook, containing no fish at all, and itself) as I am informed, poison- ous to grass land. The variation of their color confirms Mr. Paiin's opinion that these differences are owing to the presence of peat." — Ph. Pusey, ibid. Note. As a pendent to these home cases, I add the following regarding a. foreign river in different parts of its course : — " I ought to mention of the Tochee, that so long as it remains in Bunnoo, its waters are used both for irrigatioii and household purposes, and I never heard any complaint of it in either of these departments. But, changing its qualities with its name, in Merwiat, the Goombeeluh, as it is now called, is deemed useless for agriculture ; and though habit enables the natives to drink it with impunity, it is yexy injurious to strangers, producing, after a few days, and sometimes hours, great pain and inflammation." — A Year on the Punjab Frontier in 1848-49, by Major Herbert B. Edwards. Vol. i, p. 68. CHAPTER XXI. The products of vegetation. — Influence of different manures on the quan- tity of a corn crop. — Average composition of the grain of wheat, and influence of climate upon that composition. — Influence of manure on the proportion of gluten and yield of flour, — Experiments of Mr. Burnet. — Composition of the oat, and influence of variety on its composition and nutritive quality. — Composition of barley, and influence of circumstances on its sprouting, melting, and feeding properties. — Composition of rice, maize (Indian corn), and buckwheat. — Composition of the bean, the pea, and other leguminous seeds. — Composition of oily seeds, and nuts, and of the acorn. — Relation of the quality of the soil to the quality of our corn crops. The first object of the practical farmer is, to reap from his land the largest possible return of the most valuable crops, without permanently injuring or exhausting the soil. With, this view he adopts one or other of the methods of treatment above adverted to, by which either the physical condition or the chemical composition of the soil is altered for the better It may be useful to show how very much both the quantity and the quality of a crop is dependent upon the mode in which it is cultivated and reaped, and how much control, therefore, the skilful agriculturist really possesses over the ordinary pro- ductions of nature. SECTION I. OF THE INFLUENCE OF MANURE ON THE QUANTITY OF THE WHEAT AND OTHER CORN CROPS. Every one knows that some soils naturally produce much larger returns of wheat, oats, and barley than others do, and that the same soil will produce more or less according to the mode in which the land has been prepared — by manure or INFLUENCE OF MANURE. ■ 219 otherwise — for the reception of the seed. The following table shows the effect produced upon the quantity of the crop by equal quantities of different manures applied to the same soil, sown with an equal quantity of the same seed : — Return in bushels from each bushel of seed. Manure applied. Wheat. Barley. Oats. Rye. Blood, . . 14 16 121 14 Nightsoil, ■ . — 13 14^ 13^ Sheep's dung, 12 • 16 14 13 Horses' dung, 10 13 14 11 Pigeons' dung, — 10 12 9 Cows' dung, 7 11 16 9 Vegetable manure, . 3 7 13 6 Without manure. — 4 5 4 It is probable that on different soils the returns obtained by the use of these several manures may not be uniformly in the same order, yet it will always be found that blood, nightsoil, and sheep, horse, and pigeons' dung, are among the most enriching manures that can be employed. (See table in pp. 213, 214.) It is a practical fact, bearing upon this point, that in some parts of Bedfordsliire, high-farming causes barley to run to straw, to the injury of the corn ; while, on the contrary, the wheat in- creases in yield with higher cultivation.* Two facts will particularly strike the practical man on look- ing at the above table. 1. That exclusive of blood, sheep's dung, in these experiments, gave the greatest increase in the barley crop. The favorite Norfolk system of eating off turnips with sheep previous to barley, besides other benefits ^yhich are known to attend the practice, may possibly owe part of its acknowledged utility to this powerful action of sheep's dung upon the barley crop. Still, too much reliance is not to be placed on such special results till the experiments have been carefully repeated. 2. The action of cows' dung upon oats is equally striking, and the large return of this crop (thirteen-fold) obtained by the use * Caird's EnglisJi Agriculture, p. 451. 280 AVERAGE COMPOSITION OF THE GRAIN OF WHEAT. of vegetable manure alone, may perhaps explain why, in poorly farmed districts, oats should be a favorite and comparatively profitable crop, and why they may be cultivated with a certain degree of success on land to which rich manure is rarely added. It is possible, I repeat, that results different from those re- corded in the above table may be obtained by a careful repeti- tion of the same experiments on soils of different kinds and in different circumstances. It is very desirable, therefore, that such experiments should be undertaken, accurately conducted, and carefully recorded. SECTION II. AVERAGE COMPOSITION OF THE GRAIN OF WHEAT, AND INFLUENCE OF CLIMATE ON THAT COMPOSITION. The grain of wheat consists, on an average, of Water, 14.0 ratt}"- matter, .... 1.2 Protein compounds, Gluten and albumen, ) 14. fi . it.o Starch and dextrin, 66.9 Cellular fibre, 1.7 Mineral matter, . • 1.6 100 This average composition does not truly represent the composi- tion of our British and European varieties of wheat. It makes the proportion of protein compounds rather too large. Climate and season are believed to influence the proportion of gluten, so that the grain of warm climates and hot seasons is generally richer in this ingredient. Thus four varieties gave to Peligot : — PECULIAR QUALITIES OF IMPORTED WHEAT, 281 Flemish. French. Pohsh. Egyptian Grown, in France. Water, 14.6 14.6 13.2 13.5 Fat, . . 1.0 1.3 1.5 1.1 Protein compounds. 10.7 9.9 21.5 20.6 Starch, &c. 11.9 74.2 61.9 64.8 Cellulose, 1.8 ? ? ? Mineral Matter, ? ? 1.9 ? 100 100 100 100 The increased proportion of protein compounds in the samples of Polish and Egyptian wheat is very remarkable ; and it is not less interesting that they had been grown in France from the foreign seed. This latter fact illustrates — what every practical farmer is familiar with- -that imported seed always retains for some seasons the peculiar qualities which distinguish it in the country from which it is brought. It is not to be supposed that all varieties of wheat from Poland or Egypt contain the large proportion of gluten found by Peligot in the above varieties, which must, I believe, be regarded as very rare and extreme cases. An increase of 2 or 3 per cent in the protein compounds is the most that can reasonably be expected in Eastern com- pared with British wheat ; and even this is by no means con- stant, as it is modified by season, by modes of culture, and by other causes. SECTION III. INFLUENCE OF THE KIND OF MANURE ON THE PROPORTION OF GLUTEN IN WHEAT, AND ON THE YIELD OF FLOUR. Among these other modifying causes may be mentioned the kind of manure by which its growth is assisted. That this is really ca- pable of altering the proportion of gluten contained in the grain is very probable ; though it has not as yet been experimentally established that it is capable of doing so in a very great degree. . Another influence of manure upon the grain of wheat appears less uncertain — that is, the proportion of fine flour which the per acre. from the grain. the flour. In bush. Per cent. Per cent. 31i 16 9^ 40 66 10^ 49 63 9^ 49 65 9^ 48 54 10 282 COMPOSITION OF THE OAT. grain will yield when sent to the mill. This is somewhat striking- ly illustrated by the following experiment : — The same variety of wheat, top-dressed with the same rich manure — suljphated urine, (jd. 201,) mixed with different saline, substances — and grown in the same season on the same fields, gave Mr. Burnett of Gadgirth — Manure. Produce Fine Flour Gluten iu No manure, .... Sulphated urine and -wood-ashes. Do. and sulphate of soda, . Do. and common salt, Do. and nitrate of soda, . In these results we see, first, that the produce of fine flour from the grain is very different in the different samples ; and second, that the rich top-dressings did not very largely increase the proportion of gluten in the flour. The whole produce of gluten in the crop was increased, be- cause the crop was increased in quantity ; but in none of the ex- periments was the percentage of gluten largely augmented. A flour peculiarly rich in gluten is required— such at least is the prevailing oj^inion — for the manufacture of macaroni and vermi- celli : and such is said to be the quality of the grain naturally produced in tiouthern Italy. Further experiments are required to show how far, by what means, and in what circumstances, the percentage of protein compounds can in this country be econo- mically increased by the management of the cultivator.* SECTION IV. COMPOSITION OF THE OAT, AND INFLUENCE OF VARI- ETY ON ITS COMPOSITION AND NUTRITIVE QUALITIES. The following analyses of two samples of Scotch oats, made * In the neighborhood of Kirkcaldy wheat is said to be poorer after early- lifted than after ripe potatoes. Is this the case ? — and if so, how is it to be explained ? COMPOSITION OF OATS. 283 in my laboratory by Professor Norton, will show the relative proportions iu which the several constituents exist in this kind of grain, and the amount of variation which these relative pro- portions are liable to undergo in this country in different vari- eties : — Composition of Oats, dried at 212 Fah.* Starch, Gum, Sugar, OD, Avenin,* Albumen,^ Grluten, Husk, Ash, Potato Hopetoun Oats. Oats. 65.60 64.80 2.28 2.41 0.80 2.58 •7.38 6.97 16.29 16.26 2.17 1.29 1.45 1.46 2.28 2.39 2.60 2.32 100.85 100.48 The united percentage of the three varieties of 'protein compounds (within the bracket) in the oat" is very large ; and hence the very nutritive quality of this grain. But the quality of the oat, like that of wheat, varies with the soil, the climate, the manure, and the variety. As an instance of the latter, I may mention that the hinds in many parts of Scotland live only on oatmeal, of which they are allowed two pecks each a-week. If made from potato oats, the two pecks are often insufficient ; but when made from the common Angus oat, this quantity is frequently more than the hind can consume. SECTION V. INFLUENCE OF VARIETY ON THE QUANTITY OF PRODUCE, AND ON THE PROPORTION OF MEAL YIELDED BY THE OAT. The quantity, as well as the quality, of the grain of the oat yielded by the same soil is much affected by the variety of oat which is sown. The proportion of meal yielded by an equal * See page 47. 284 COMPOSITION OF BARLEY. weight of the grain is also materially aifected by the variety. This is shown by the following table of the results obtained by Mr. Hay from eight different varieties of oats well known in Scotland. The experiment was made in the year 1850, upon a thorough drained field of stiff cold clay with a relentive subsoil. All the varieties were sown on the 26th and 2tth of March, all reaped between the 20th and 26th August, and the extent of each experimental plot was three quarters of an imperial acre. Variety. Produce. Meal yielded by 100 lb. of grain. Grain. straw. Potato oat, .... Sheriflf Berlie Hopetoun Blainslie Sandy Early Angus Barbachla 1 bush. 69 651 55^ 56i 52i 47 48i 45 cwt. 621 55^- 55* 56| 601 481 451 49 lb. 60^ 52i 58 60^ 5U . 60 551 601 The differences in each of these three columns are very striking, and will suggest to the reader many interesting con- siderations, to which space does not permit me to advert. I only add, that in all the different grains we cultivate vari- ety is found to affect in a similar manner the quantities of pro- duce reaped. SECTION VI. OF THE AVERAGE COMPOSITION OF BARLEY. The Scotch oat is the most nutritious of our homegrown grains. Among the ancients, barley was highly esteem.ed for its feeding qualities The Greeks, Egyptians, and Hebrews made much use of it, and the wrestlers and gladiators ate only barley bread ; hence they were called hordearii* It is still re- cognised in this country as possessed of great feeding power, * Pliny, Book xviii. MALTING QUALITIES OF BARLEY. 285 though the higher price obtained for samples which malt well has thrown somewhat into the shade its purely nutritive qual- ities. The average composition of fine barley meal is nearly as follows : — Water, .... 14 Protein compounds, . 14 Starch, &c.. 68 Fatty matter. 2 Mineral matter, 2 100 The above is exclusive of the bran separated by the miller, which forms from 10 to 18 per cent of the weight of the grain. It shows the flour to be very nutritious, containing 14 per cent of the protein or flesh-forming constituent, while fine wheaten flour rarely contains more than 10 per cent. SECTION VIII. INFLUENCE OF CIRCUMSTANCES ON THE SPROUTING, MALTING, AND FEEDING QUALITIES OF BARLEY. 1°. Malting qualities. — The malting of barley is known to be affected by various circumstances. Unless the grain be dry, it does not sprout readily, and hence it is customary for maltsters to sweat their barley on the kiln before malting it. The grain should also be so uniform in ripeness as to sprout uniformly, so that no part of it may be beginning to shoot when the rest has already germinated sufficiently for the maltster's purpose. On this perfect and uniform sprouting of the whole depends in some degree the swelling of the malt, which is of considerable conse- quence to the manufacturer. The uniformity of sprouting depends sometimes on the mode of husbandry practised where it is grown. Thus when barley is taken after turnips, if the land be merely cross-ploughed, the ma- nure which had been laid in the turnip drills will remain in lines along the field where the turnips had grown, and the barley along 286 FEEDING QUALITIES OF BARLEY. those lines will ripen first. But if the land be ploughed diago'iv- ally, the manure will be equally spread and the barley nourished and ripened equally, and thus it will be likely to sprout uniform- ly also. But the malting quality of the grain, which is of more con- sequence to the brewer and distiller, is understood to be modi- fied chiefly by the proportion of gluten which the barley contains. That which contains the least gluten, and, therefore, the most starch, is supposed to malt the most easily and the most completely and to yield the strongest beer or spirit from the same quantity of grain. Hence the preference given by the brewer to the malt of particular districts, even where the sample appears otherwise inferior. Thus the brewers on the sea-coast of the county of Durham will not purchase the barley of their own neighbor- hood, if Norfolk grain can be had at a moderate increase of price. But that which refuses to malt well in* the hands of the brewer, will cause pigs and other stock to thrive well in the hands of the feeder, and this is the chief outlet for the barley which the brew- er and distiller reject, 2°. Feeding qualities. — So far as a practical deduction can be drawn from the experiments hitherto made in regard to the effects of different manures upon the proportion of gluten in barley, it would appear that the larger the quantity of cows' dung contained in the manure applied to barley land — in otlier words, the greater the number of stock folded about the farmyard, the more likely is the barley to be such as will bring a high price fro7n the brewer. The folding of sheejp appears to produce a larger return from the barley crop, and the folding of cattle to give grain of a better quality. These points also, however, require to be elucidated by more careful experiment. Such statements stand in our books at present rather as guesses at the truth, than as deduc- tions from rigorously made observations. COMPOSITION OF BEAN, PEA, &C. 287 SECTION VIII. COMPOSITION OF RYE, RICE, MAIZE (^INDIAN CORN}, AND BUCKWHEAT. These four species of grain contain respectively, when dried at 212° Fahr., of— Starch, &c., Protein compounds, . . Fatty matter, .... Husk, ) Mineral matter, . . ) Rye. Rice. Maize. | Buckwheat. 1 78.0 12.5 3.5 6.0 87.4 7.5 0.8 3.4 0.9 71.6 12.3 9.0 5.9 1.2 60.6 10.7 0.4 26.0 2.3 100 100 100 100 These numbers, it will be understood, are liable to variation in different samples ; especially the quantity of protein compounds in rye varies, and that of the fatty matter or oil contained in Indian corn. In some varieties of the latter grain this oil is only 2 to 3, in others as much as 9, per cent of the dry cone. In their natural undried state they alt contain 14 to 15 per cent of water. It will be seen that, in so far as that the protein or muscle-forming ingredients are concerned, rice is the least, and rye and maize the most nutritious of these four varieties of grain. SECTION IX. COMPOSITION OF THE BEAN, THE PEA, AND OTHER LEGUMINOUS SEEDS. The bean, pea, lentil, vetch, &c., are distinguished from white corn by the large proportion of protein compounds they contain, and their consequently greater nutritive power.* They resemble each other very much in composition ; and in the state of dry- ness in which they are generally brought to market, as field crops, they consist of about 288 COMPOSITION OF OILY SEEDS AND NUTS. Water, . . * . 14 Starch and sugar, 48 Protein compounds, (legumin,) 24 Fatty matter, 2 Husk, ' . . . . 10 Mineral matter . . . . 2 100 The proportion of husk varies ; the pea, which contains 10 per cent, having generally a thinner, and the bean a thicker skin. The proportion of protein compounds varies from 20 to as high as 30 per cent ; and according to experiment, the kind of ma- nure employed materially influences this proportion. Manures rich in nitrogen cause it to increase. It is also an interesting fact that the young legumes, when just beginning to form in the shell, are exeedingly rich in protein compounds. The very young pea, for example, contains as much as 48 per cent ; while, as the above table shows, the ripe pea rarely contains more than 24 per cent (p. 51.) The kind of protein compound which exists in these grains possesses peculiar chemical properties, and has been called le- gumin, (p. 47 ;) but its nutritive quahties are believed to be very much the same as those of gluten and albumen. SECTION X. COMPOSITION OF THE OILY SEEDS AND NUTS, AND OF THE ACORN. Many seeds, like those of flax and rape, contain a much larger quantity of oil than the kinds of corn which are usually em- ployed as food for man. The same is the case with nuts. From the kernels of the walnut, for example, and from those of the sweet almond, upwards of half their weight of oil can often be extracted. 1. Linseed and linseed cake. — Linseed contains from 20 to 30 per cent of oil. -A large proportion of this is squeezed out in the oil mills, and sold under the name of linseed oil. The cake or residue which remains, still contains a considerable proportion of oir; and, as it is very nutritive, is extensively employed in COMPOSITION OF THE ACORN. the feeding of cattle. The relative values of the seed and the cake for feeding purposes, and the value of both compared with other kinds of food, is shown very nearly by the following table : — Composition of Linseed. Linseed cake. "Water, .... 9 10 Protein compounds, . 19 22 Starch, &c., 34 39 OU, ... 25 12 Husk, 8 9 Saline mineral matter, 5 8 100 100 Both seed and cake, therefore, are very nutritious ; and even the pressed cake still contains more fatty matter than Indian corn, some varieties of which contain as much as 9 per cent. What is called starch in the above analyses is, in reality, a kind of mucilage or gum, which dissolves readily in water, but serves the same purposes as starch in the feeding of animals. 2. Rape cakt is about of equal nutritive value with linseed cake, but is often refused by cattle on account of its hot and acrid taste : this repugnance, however, may be overcome by mixing the crushed cake with a small quantity of molasses, or, by boiling it into a jelly with one-third of bean-meal, and making this into a mess with cut straw or hay. Sheep eat it readily when fed upon cabbage, and if kept upon other green food they soon become accustomed to it, if copiously supplied with water. The lower market price of rape cake makes a knowledge of these circumstances of money value to the practical feeder. 3. Nuts resemble the oily seeds in their composition ; and hence nut-cakes approach linseed cake in value as a food for cattle. 4. The acorn is also very nutritious, though it does not con- tain much fatty matter. As it falls ripe from the tree it consists of— 13 290 INFLUENCE OF THE SOIL ON OUR CORN CROPS Water, .... 32 Protein compounds, 15 Starch and sugar, 47 Fatty matter, 3 Cellular iibre, 2 Mineral matter, . 1 100 Were the acorn made as dry as the bean is usually sold, it would, weight for weight, be nearly as nutritive. Hence the fattening of pigs when turned into oak forests, the use of the common acorn in periods of famine in many countries, and the constant u^e of the sweet acorn, (that of the Quercus gramuntia of Linnaeus,) in parts of Spain and Sardinia, as a common food of the people. A sweet acorn is also regularly found in the North African markets of Constantine, Bona, and Algiers. The acorn is remarkable for containing as much as 1 per cent of sugar, of which a small portion is sugar of milk. Could the bitter astringent substance, which gives our common acorns their unpleasant taste, be readily extracted, it might become an ac- ceptable article of food in every country. SECTION XI. INFLUENCE OF THE CONDITION AND QUALITY OF THE SOIL ON THE QUALITY OF OUR CORN CROPS. We have already shown that the quantity of the crop is ma- terially affected by the character of the soil, but the quality of the x^roduce is no less affected by the same cause. Thus — 1. Barley. — The varying quality of this grain raised in different localities is familiar to every farmer. On stiff clays, barley may yield a greater produce, (North Hampshire,) but it is of a coarser quaUty. On light chalky soils it is thin-skinned, rich in color, and, though light in weight, well adapted for malting; while on loamy lands and on sandy marls it assumes a greater plumpness, yet still retains its malting quality.* * See p. 95, on the growth of the Ware malt PECULIARITIES OF THE PEA AND BEAN. 291 2. T^lieat. — Similar differences affect the same variet}^ of wheat when grown upon different soils. In a previous section it was stated that the quantity of gluten contained in wheat is believed to vary with the climate, and in some degree also with the ma- nure applied to the land ; but a similar variation occurs on unlike soils, when manured, or otherwise treated in every respect alike. The miller knows by experience the relative qualities of the wheat grown on the several farms in the neighborhood of his mill, so that even when his eye can detect no difference of quality be- tween two samples, a knowledge of the places where they were grown enables him to decide which of the two it will be most for his interest to buy. 3. The oaf varies in quality likewise with the soil on which it is grown. The meal made from oats grown upon clay land is the best in quality, is the thriftiest, keeps the longest, and gen- erally brings the highest price. I lately visited a farm in Forfarshire, part of which consisted of a sharp gravelly soil on a slope, and part of flat boggy land, resting on marl. Oats were usually grown on both soils, and I asked what difference the tenant observed in the quality of the grain he obtained from each. " In appearance," he answered, " there is no difference ; I could take the samples to market, and get the same price for each. If I wanted them for seed, I would buy either of them indifferently at the same price ; but for meal for my own eating, I would give two shillings a boll more for the oats of the sharp land. The sharp land meal," he added, " gives a dry knotty brose and a short oat cake ; that from the bog land may do for porridge, but it makes bad soft brose and a tough cake." 4. Rye also flourishes upon light and sandy soils in general, but when grown upon sandy marls it is found (in Germany) to yield much brandy. 5. The pea and the bean are distinguished by similar peculiarities, when grown in light and in heavy soils. There are certain spots in the neighborhood of all large towns, which are known to 292 BOILING AND PIG PEAS. produce tlie best boiling peas, — such as boil soft and mealy. Thus the gravelly slope of Hopwas Hill, near Tamworth, on the Lichfield road, grows the best sidder or boiling green peas for the Birmingham market ; the Yale of Tamworth in general growing only jpig peas — hard boilers used only for feeding. Lime and gypsum are said by some to impart the boiling quality, while by others exactly the reverse is stated. No doubt the different results are owing to differences in the soils upon which the seve- ral experiments were made. It is a remarkable circumstance, that on the London corn exchange, the dealers seldom buy British peas without first sending a sample to be boiled, — while foreign peas are gene- rally bought without any trial. They are almost invariably boilers. For split peas, used in making soups and pease-meal, it is obvious that this boiling quality is of great importance. The explanation of all these differences is, to a certain extent, simple. The relative proportions of gluten and starch in all vegetable juices, and seeds, is variable. The plant is fitted to flourish, to live in a comparatively healthy manner, and to per- form all its natural functions, although the supply of those kinds of food out of which its gluten is formed be greater or less within certain limits ; but the boiling, feeding, malting, or distilling quaUties of its stems, seeds, or roots will be materially affected by variations in this supply. Again, the proportion of gluten seems to be dependent upon the quality of the soil, not only because the nitrogen it con- tains is chiefly imbibed by the roots of the plant, but because this gluten is always associated with a certain small quantity of sulphur, phosphorus, and earthy matter, which can only be derived from the soil. Where these elements abound in the neighborhood of the roots, the plant may produce much glu- ten ; where they are absent, it may not ; so that the feeding and other important qualities of the plant depend no less upon the presence of sulphur and phosphorus in the soil, than UMcn CAUSE OF THESE DIFFERENCES. 293 that of any of the so-called organic elements of which its se- veral parts are principally made up. Still it must be borne in mind, that these explanations of the differences observed on the corn exchange, and by the miller, are as yet hypothetical. The causes stated may produce the effects actually observed, but it has not been proved, by ana- lytical and other experiments, that they really do produce them. Mere age induces changes in the qualities of grain, such as I have described, which the miller values and is willing to pay for. CHAPTER XXII. Average composition of the potato, turnip, mangold- wurtzel, and carrot. — Influence of soil, variety, manure, &c., on the quality of the potato and the quantity of starch it contains. — Influence of soil, season, variety, and manure on the composition and feeding properties of the turnip. — Com- position of the cabbage, cauliflower, mushroom, turnip-top, and of hay, straw, and the leaves of trees. — Composition of fruits, and the effect of soil upon their quality and flavor. — Relative quantities of starch and gluten contained in our usually cultivated crops. — Quantity of oil or fat in grain, root, and hay crops. — Absolute quantity of food yielded by an acre of land under different crops. SECTION I. AVERAGE COMPOSITION OF THE POTATO, TURNIP, MAN- GOLD-WURTZEL, AND CARROT. 1. The turnip tribe differs from the potato in two principal points. a. In the quantity of water they respectively contain. In the potato this forms three-fourths, but in the turnip nine-tenths, of the whole weight, when taken from the ground : or they consist of — Potato. Turnip. Water, .... 75 91 Dry nutritive matter, . .25 -9 100 100 h. In the presence of starch in the potato, while the turnip contains in its stead a substance — pectose or pectic ^cid — whic^ contains more oxygen than starch, but serves the same pur- poses in the nutrition of animals, (p. 44.) 2. The dry nutritive matter of the potato and turnip con- tains, on an average, about — IMPORTANCE OF THE POTATO. 295 Potato. Turnip. Starch or pectose, 62 15 Sugar and gum, 15 56 Protein compounds, 9 15 Fatty matter, 1 2 CeUular fibre, 9 7 Mineral matter, 4 5 100 100 This table shows also that the turnip contains more sugar than the potato, and is richer also in protein compounds. Hence the advantage derived from, and the preference generally given to it, in the feeding of stock. 3. The dry matter of the mangold-wurtzel and the carrot resembles in composition that of the turnip. Some varieties of these roots contain still more sugar. They likewise surpass the turnip in their per-centage of dry nutritive matter. This, in the three roots, is nearly as follows : — Turnip. Mangold. Carrot. Dry nutritive matter, 8 to 12 15 14 to 20 "Water, . . 92 to 88 85 86 to 80 100 100 100 Hence the generally more nutritive quality of the two latter roots, weight for weight. SECTION II. INFLUENCE OF SOIL, VARIETY, DEGREE OF RIPENESS, KIND OF MANURE, AND OTHER CIRCUMSTANCES, ON THE QUALITY OF THE POTATO, AND THE QUAJ^TITY OF STARCH IT CONTAINS. The potato is a crop of so much importance in this country, that it may be interesting to introduce a few more detailed re- ijiarks in regard to the variations which the quality, and especi- ally the proportion of starch contained in it, has been found to undergo. 1. Influence of soil. — It is familiarly known to the potato grow- er, that clay soils produce waxy, and sandy soils mealy potatoes. 296 INFLUENCE OF VARIETY But the condition of the land also exercises a material in- fluence both upon their growth and quality. When, for example, potatoes are planted in rich newly broken-up land, they run up greatly to shaws or tops, produce generally few or small tubers, and of bad eating quality, because they seldom ripen before the frost sets in. Thus in one case it was remarked by Mr. Thompson, of Kirby Hall, York, that Hack kidneys planted on such a soil seemed quite to have changed their character. Instead of the fine mealiness for which they are usually remarkable, they bore much more resemblance to a piece of yellow soap. They, how^ ever, proved excellent seed, and in the wet summer of 1843 showed no failures, and gave a capital crop. They were certain- ly not ripe, and to this circumstance Mr. Thompson ascribed their badness for eating and their goodness for seed. Again, it has been observed that the quantity of starch is larger in potatoes which are grown upon land long in arable culture than upon such as is newly brought into cultivation or broken up from grass. Thus Mr. Stirrat states, that from one peck of potatoes grown upon land near Paisley, which had been almost constantly under crop for the last thirty years, he obtain- ed t lb. of starch, while another peck grown on his bleach-green, newly broken up, gave him only 4 lb.* 2. Influence of variety. — On the same soil, different varieties produce different proportions of starch. Thus, in 1842, Mr. Flem- ing, of Barochan, obtained from four varieties of potato grown on his farm, the following percentage of starch : — Connaught Cups, . . . 21 per cent. Irish blacks, . . . , 164 White Dons, . . . . 13 ... Red Dons, .... 10| These differences in the per-centage of starch become very striking when we calculate the relative quantities per acre yielded * See the Author's Lectures on Agricultural Cliemistry and Geology, 2d edit. p. 901. EFFECT OF MANURES. 2ftt by these varieties. Thus under similar treatment they gave re- spectively — Produce per acre. Of potatoes. Of starch. Cups, . . . I'dk tons. 2.9 tons. Rod Dons, . . lU 1.5 White Dous, . . 18^ 2.4 So that the lightest crop gave the most starch. Though Jive ton an acre heavier, the crop of white Dons gave half a ton less starch than the Connaught Cups. 3. Effect of manures. — I have already mentioned the alleged influence of sea-weed, (p. 169,) and of skin parings, (p. 162,) in making potatoes waxy. It is not so surprising, therefore, that the kind of manure employed should affect in a sensible degree the proportion of starch yielded by the potato. Thus Mr. Flem- ing found his potatoes, raised with different manures in 1843, to give the following per-centage of starch : — Per cent. 1. Cups with dung alone, gave - 14.5 of starch. and guano, - 14*4 2. White Dons with guano alone, - 9.0 and dung, - 10.2 3. Rough reds with guano alone, - 15.7 and dung, - 17.1 4. Perth reds with guano alone, - 15.3 and dung - 15.5 These experiments show, first, that in so far as the proportion of starch is concerned, either dung alone, or half guano and half dung, may be used with equal advantage. The experiment upon the Cups shows this. Second, that a mixture of dung and guano is in this respect better than guano alone.* All the other trials * This arises from the tendency of the potato to rush up to stalk when manured with guano alone, — the eftect of the guano being more or less exhausted before the plant reaches maturity, or has time to form its tubers. When mixed with dung, the latter carries on the growth which the former may have left unfinished. 13* 298 INFLUENCE OF SOIL. show this, — ^while they show further, also, how much the propor- tion of starch depends upon the variety of potato we grow. These varying proportions of starch are of much moment to the practical farmer at the present time, when potato failures are so common, — inasmuch as the certainty of the growth of the potato, when used as seed, appears to he the greater, the smaller the per-centage of starch. 4. Effect of other circumstances. — I advert briefly to three other circumstances which affect the quantity of starch con- tained in the potato. a. The effect of keeping is to diminish the quantity of starch. Potatoes which in October yielded readily 17 per cent of starch, gave in the following April only 14| per cent. In connection with the keeping of the potato, it is a very interesting fact, that the epidermis or outer covering of the skin consists of a thin layer of cork, without visible pores, and through which v/ater passes with extreme slowness. Hence the potato can be kept for months at a temperature of 86° Fahrenheit, without losing more than three per cent of its Aveight. h. The effect of frost is also to lessen the starch. It acts chiefly upon the vascular and albuminous part, but it also converts a portion of the starch into sugar, hence the sweetish taste of frosted potatoes. c. The heel end of the potato contains more starch than the rose end, and both more than th^ central part. Thus, a variety of red potato which yielded 21 per cent of starch from the heel end, gave me only 16 J from the rose end, and 14 per cent from the central part. SECTION III. INFLUENCE OF SOIL, SEASON, VARIETY, AND MANURE, ON THE COMPOSITION AND FEEDING PROPERTIES OF THE TURNIP. 1. Soil. — That the soil has an influence on the composition of the turnip crop, has long been believed by the practical man, IXFLUENCE OF MANURE. 299 because of the difference in the taste and feeding properties of the same kinds of turnip grown on different fields and farms. The chemical nature of this difference has lately been inves- tigated by Dr. Anderson. Ilis analyses of turnips, grown in the same season and circumstances, upon a. The heavy alluvial clay of the Carse of Gowrie ; h. The black land which separates the clay from the hill, and there, as in- Lincolnshire, skirts the slopes ; c. The hill land, which is a light loam — showed that the proportion of nitrogen or of protein compounds was almost always greater on the hill laud than on either of the other soils — sometimes twice as great. The turnips of the black land were also slightly superior in this respect to those of the clay. This result of analyses fully supports that of prac- tical experience in the feeding of stock. 2. Season. — The same analyses have confirmed another opin- ion of practical men, that the turnips of different seasons differ in their nutritive properties. Thus, in 1850, the turnips, from all the varieties of soil above mentioned, contained a smaller per-centage of protein compounds than in 1849, and the dif- ferences among them were less. The proportion of phosphates was also considerably less in the turnips of 1850. 3. Variety. — The influence of variety is more striking, per- haps, on the turnip than upon any other of our more largely cultivated crops. The swede not only keeps better and longer, but is also sweeter and more nourishing than the white globe or yellow turnip. Hence in our large towns, when swedes, as they sometimes do, sell for 30s. a ton, the yellow will bring only 25s., and the globe turnip 18s. 4. Manure. — The kind of manure afi'ects the quality and feeding properties of the turnip. According to the experiments of Mr. Lawes,* it appears that where a field is in a condition to produce an average crop of turnips, the proportion of ni- * Journal of the Royal Agricultural Society of England, viii. 494. 300 COMPOSITION OF THE CABBAGE. trogen in the crop — that is of albumen and other protein com- pounds, which are very nutritive — may be increased by the ap- plication of animal or other manures containing iiitrogen — such as pigeons' dung, guano, woolen rags, rape cake, the salts of ammonia, nitrate of soda, &c. Mr. Lawes states, that by the use of such manures the proportion of this valuable ingredient, compared with what is contained in turnips raised by farm- yard manure, may be doubled. This result has, to a certain extent, been confirmed by the more recent analyses of Scotch turnips published by Dr. Anderson.* It is desirable, however, that the results of experiments in the laboratory, as to the composition of the crop, should be tested by after experiments with the same turnips in the actual feeding of cattle. Such experiments are difficult of execution, and require much care, but they are necessary to the attain- ment of results on which the practical man can be requested confidently to rely. SECTION IV. COMPOSITION OF THE CABBAGE, CAULIFLOWER, MUSH- ROOM, TURNIP-TOP, HAY, STRAW, AND THE LEAVES OF TREES. 1. The Callage is one of the most nutritious crops we grow. Like the turnip, it contains a large proportion of water — about 89 per cent ; but the dry matter of the cabbage is much more rich in protein or tissue-forming compounds than that of the turnip. It consists very nearly of — Starch, sugar, &c., 46 Protein compounds, (albumen, &c.) . . 30 to 35 Oil or fat, 3 Cellular fibre, 9 Saline or mineral matter, . . . . 12 to 18 100 The value of the cabbage in feeding — especially for milch * Quarterly Journal of Agriculture for January 1852, pp. 221-233. HAY, STRAW, AND LEAVES OF TREES. 301 COWS — and its exhausting effect upon the soil, are not therefore to be wondered at. 2. The Caulijlower is still more nutritious than the cabbage leaf. It contains about 64 per cent of protein compounds. In this respect it approaches nearer to animal food than any ve- getable we grow, of which the composition has yet been ex- amined. 3. The Mushroom comes nearest to the cauliflower in this respect. It contains about 56 per cent of protein compounds ; and though by some found to be indigestible, its nutritive qua- lities are very generally admitted. 4. The Turnip-top, though apt to scour cattle if given too freely, is generally as nutritive as the bulb. It contains as large a per-centage both of protein compounds and of phos- phates, especially when young. The young sprouts which tur- nips, left in the field, throw out in spring, resemble cabbage very much, and are very nutritious. Hence the reason why turnips which have thrown out large leaves in spring are gene- rally found less valuable in feeding. The composition of the turnip-top indicates the cause both of its great value as a manure when left upon the land, and why it forms a very appropriate food for the milch cow and the growing calf. 5. Hay and Straio are distinguished by the large proportion of cellular or woody fibre, in an indigestible state, which they contain. Good hay, however, contains also from 6 to 9 per cent of protein compounds, and clover hay even as much as 12 per cent ; so that, in muscle-forming matter, hay is nearly as -•rich as our English wheat. The straw of our white-corn plants contains only 3 or 4 per cent of these compounds. Pea and bean straw are more nutritious — good pea straw approaching in this respect to the best clover hay. 6. The Leaves of Trees are often very nutritious ; and did they not frequently contain substances which render them un- palatable or unwholesome when eaten, they might be very ex- 302 COMPOSITION OF FRUITS. tensively employed as food for cattle. The dry tea-leaf con- tains about 25 per cent of protein compounds, chiefly albumen, and would prove as nutritious in this respect as an equal weight of beans or peas, were it the fashion in Europe to eat it. The tobacco leaf contains about 23 per cent. The elephant — the largest of existing quadrupeds — lives much upon leaves in its native forests ; and in some Alpine countries, the annual har- vest of dried leaves forms an important part of the winter's provision for the domesticated cattle.* (See p. 316.) It is not surprising, therefore, that leaves should form a valu- able manure, or that poor land should be permanently improved by planting it with trees. (P. 158.) SECTION v. OF THE COMPOSITION OF FRUITS, AND THE EFFECT OF SOIL UPON THEIR QUALITY AND FLAVOR. To fruits it is necessary to do little more than allude in the present work.f They contain from tO to 90 per cent of water — the quantity diminishing as the fruit ripens. In the fleshy fruits — plums, peaches, &c. — when ripe, the water forms about *I5 per cent ; in apples, pears, and gooseberries, a little more than 80 per cent of the whole weight. The dry matter con- tains chiefly sugar and pectic acid, with a considerable propor- tion of protein compounds and of soluble phosphates. Fruits are therefore fitted to nourish as well as to refresh. The dried gooseberry contains about 9 per cent of protein compounds. The acidity of our usually cultivated fruits is due to the pre- sence of variable quantities of malic and citric acids. In cider, perry, and wine countries, the nutritive qualities of * " For several mileS, when crossing the high Alps of Savoy, we ob- served the peasants stripping the mountain ash trees of all their leaves, for their cattle during the winter." — Weld's Tour in Auvercjne and Piedmont. — [Were these leaves gathered for food or for litter ?] f For fuller information, see the Author's pubhshed Lectures. INFLUENCE OF TIME OF CUTTING. 303 the apple, pear, and grape are seen in the use of the refuse of the mills in feeding pigs or other animals ; or where it is not used up in this way, these qualities are equally shown by the profitable employment of the refuse as a manure. Fruits of all kinds, like our corn and root crops, arc affected in flavor and quality by the soil on which they grow. In the Norman orchard, the gout de terrain is a recognised quality both in the apple and in the cider. The extended apple and peach culture of North America has led to similar observations ; and the peculiar qualities possessed by the wines of neighboring vineyards are familiar everywhere. There are only three farms situated on the side of a hill which produce the famous Con- stantia wine. The same grape has been tried in various parts of the Cape colony without success. Even a mile from the hill the wine is of a very inferior description. In Europe, on the banks of the Rhine, the Johannisberg is equally well known for the unique qualities of its celebrated wine. SECTION VI. INFLUENCE OF THE TIME OF CUTTING ON THE QUANTITY AND QUALITY OF THE PRODUCE OF HAY AND CORN. 1. Hay. — The period at which hay is cut, or corn reaped, materially affects the quantity (by weight) and the quality of the produce. It is commonly known that when radishes are left too long in the ground they become hard and woody — that the soft turnipy stem of the young cabbage undergoes a similar change as the plant grows old — and that the artichoke becomes tough and uneatable if left too long uncut. The same natural change goes on in the grasses which are cut for hay. In the blades and stems of the young grasses there is much sugar and starch, which, as they grow up, are gradually changed into woody or cellular fibre, (p. 42.) The more com- pletely the latter change is effected — that is, the riper the stem of the plant becomes — the less sugar and starch, both readily soluble substances, its various parts contain. And 304 CUTTING STRAW AND GRAIN. though it has been ascertained that cellular fibre is not wholly indigestible, but that the cow, for example, can appropriate a portion of it for food as it passes through her stomach — yet the reader will readily imagine that those parts of the food which dissolve most easily, are also likely, other things being equal, to be most nourishing to the animal. It is ascertained, also, that the weight of the hay or of the straw we reap, is actually less when it is allowed to become fully ripe ; and therefore, by cutting soon after the plant has attained its greatest height, a larger quantity, as well as a bet- ter quahty of hay, will be obtained, while che land also will be less exhausted. 2. Straw. — The same remarks apply to crops of corn — both to the straw and to the grain they yield. The rawer the crop is cut, the heavier and more nourishing the straw. Within three weeks of being fully ripe, the straw begins to diminish in weight ; and the longer it remains uncut after that time, the lighter it becomes, and the less nourishing, 3. Grain. — On the other hand, the ear, which is sweet and milky a month before it is ripe, gradually consolidates — the sugar changing into starch, and the milk thickening into the gluten and albumen of the flour. As soon as this change is nearly completed, or about a fortnight before it is ripe, the ^rain of wheat contains the largest proportion of starch and gluten. If reaped at this time, the bushel will weigh most, and will yield the largest quantity of fine flour and the least bran. At this period the grain has a thin skin, and hence the small quantity of bran. But if the crop be still left uncut, the next natural step in the ripening process is, to cover the grain with a better protection — a thicker skin. A portion of the starch of the grain is changed into woody fibre — precisely as in the ripening of hay, of the soft shoots of the dog-rose, and of the roots of the common radish. By this change, therefore, the quantity of starch is lessened and the weight of husk increased j WHEN OATS SHOULD BE CUT. 305 hence the diminished yield of flour, and the increased produce of bran. Theory and experience, therefore, indicate about a fortnight before it is fully ripe as the most proper time for cutting wheat. The skin is then thinner and whiter, the grain fuller, the bushel heavier, the yield of flour greater, its color fairer, and the quantity of bran less ; while, at the same time, the straw is heavier, and contains more soluble matter than when it is left uncut until it is considered to be fully ripe. In regard to oats, it is said that the superiority of Ayrshire oatmeal is partly owing to the grain being cut rather glazy, (that is, with a shade of green upon it,) and the straw is con- fessedly less nourishing for cattle when the crop is allowed to stand till it is dead ripe. Early cut oats, also, are heavier per bushel, fairer to the eye, and usually sell for more money. A week before full ripeness, however, is the utmost that is re- commended in the case of oats, the distance of the top and bottom grains upon the stalk preventing the whole from becom- ing so uniformly ripe as in the ear of wheat. Barley cut in the striped state is also thinner in the skin, sprouts quicker and more vigorously, and is therefore preferred by the maltsters. It is also fairer to the eye, and generally brings a higher price in the market. SECTION VII. OF THE RELATIVE QUANTITIES OF STARCH AND GLUTEN IN OUR USUALLY CULTIVATED CROPS. In addition to the details already given in regard to the composition of the several kinds of grain and roots usually cul- tivated in this country, it may be useful to exhibit, in a tabular form, the relative proportions of starch and gluten contained in each. The following numbers cannot be considered as precisely accurate, yet they represent pretty nearly the average quanti- ties of these two substances contained in 100 lb. of our common 306 PROPORTIONS OF STARCH, GLUTEN, crops in the state of dryness, &c., in which they are usually sent to market : — Starch, gum, Gluten, albu- and sugar. men, &c. Wheat, (flour,) .... 55 10 to 19 Bran of wheat, . . . — 16 Barley, 60 12 to 15 Oats, (without husk,) 60 14 to 19 Rye, 60 10 to 15 Indian corn (maize,) •70 12 Bran of do — 13 Rice, 1o 1 Beans, peas, vetches, and lentils, 40 to 50 24 to 28 Linseed, 40 24 Potatoes, 18 2 Do. sliced and dried, 72 8 Turnips, carrots, and mangold- wurtzel, 9 to 11 l^to 2 Do. sliced and dried, . 90 12 to 16 Cabbage, . . . , . — 30 to 35 These numbers are somewhat open to correction. Indeed, if the reader recollects what has been stated in the previous sec- tions, in regard to the variable quality of the different crops we raise, he will understand that the numbers contained in all tables such as this are to be regarded only as approximations to the truth. SECTION VIII. OF THE QUANTITY OF OIL OR FAT IN GRAIN, ROOT, AND HAY CROPS. It is generally known that linseed, rape-seed, turnip-seed, hemp-seed, poppy-seed, and the seeds of many other plants, abound so much in oil, that it can be squeezed out by strong pressure, as is done in the mills of the oil manufacturers. The kernels of some nuts also, as those of the walnut, the hazel, and the beech, contain much oil ; and even some trees, as certain species of the palm, yield it in large quantities. It has only recently been discovered, however, that all our cultivated grains contain an appreciable quantit}' of oil or fatty AND OIL IN DIFFERENT CROPS. 307 matter — that it is present also in our root crops, and that even in straw and hay it exists in sensible proportion. Soil, climate, mode of culture, manure, and the variety of the plant we grow, all affect the proportion of oil which its seeds, stems, or roots contain. To extract this oil we have only to reduce the part of the plant into minute fragments, to boil these in ether, filter the solution, and afterwards distil off the ether, when the oil or fat will remain behind. It is usually more or less of a yellow color, and when heated, not unfre- quently emits an odor peculiar to the plant. Thus the oil from the oat emits, when heated, the well-known odor of burned oatmeal. The proportion of oil contained in 100 lb. of some of our more commonly cultivated plants is as follows : — Wheat flour (fine), 2 to 4 lb Bran of wheat, 3 to 5 lb. Barley, 2 to 3 lb. Oats, 5 to 8 lb. Indian corn, 5 to 9 lb Linseed, 30 to 35 lb. Eape and turnip seeds, 40 1b. Potatoes, turnips, and cabbage, . 1-5 lb. Wheat straw. . 2 to 3^ lb. Oat straw, . 4 1b. Meadow hay, , 2 to 5 lb Clover hay. . 3 to 5 lb. The quantity of fat varies, as this table shows, in the same kind of food. These variations are caused by differences in the soil, manure, climate, season, &c. In most seeds, however, the largest proportion of fat resides in the exterior part, near to or actually in the husk or bran. Hence the bran of wheat generally contains much more oily matter than the fine flour. Thus in two varieties of wheat, the fine flour from which con- tained only li, the bran contained from 3 J to 5 per cent of fat. To this large quantity of oil, bran owes part of its value in feeding pigs, as we shall see more clearly when, in a subsequent chapter, we come to consider the important part which this 308 FOOD YIELDED BY AN ACRE fatty matter performs in the artificial rearing and fattening of stock. SECTION IX. ON THE ABSOLUTE QUANTITY OF FOOD YIELDED BY AN ACRE OF LAND UNDER DIFFERENT CROPS. The quantity of food capable of yielding nourishment to man, which can be obtained from an acre of land of average quality, depends very much upon the kind of crop we raise. In the seeds of corn, when fully ripe, little sugar or gum is generally present ; and it is chiefly by the amount of starch and gluten* they contain, that their nutritive power is to be estimated. In bulbs, such as the turnip and potato, sugar and gum are almost always present in considerable quantity in the state in which these roots are consumed, and this is especially the case with the turnip. These substances, therefore, must be included among the nutritive ingredients of such kinds of food. If we suppose an acre of land to yield the following quan- tities of the usually cultivated crops, namely — Of wheat, Of barley, Of oats, ■ Of pease, Of beans. Of Indian corn. Of potatoes, Of turnips, Of wheat straw, Of meadow hay. Of clover hay, ■■ Of cabbage. 25 bushels or 1,500 lb. 35 .. or 1,800 . , 50 or 2,100 .. 25 .. or 1,600.. 25 or 1,600 .. 30 .. or 1,800 . . 12 tons, or 27,000 .. 30 .. or 67,000 .. u .. or 3,000 . . n .. or 3,400 . . 2 .. or 4,500 .. 20 or 45,000 . . The weight of dry starch, sugar, and gum — of gluten, albumen, casein, &c. — of oil or fat — and of saline matter, reaped in each * Including under gluten the albumen, avenin, legumin, and casein — all the varieties of the protein compounds, in short, which arc contained in gram. (See page 47.) OF DIFFERENT CROPS. 309 crop, will be represented very nearly by the following num- l)ers : — Husk or Starch, Gluten, al- Oil or Saline woody fibre. sugar, &;c. bumen, &c. fat. matter Wheat, 225 825 lb. 180 lb. 45 30 Barley, 270 1080 230 50 50 Oats, 420 1050 300 100 •75 Pease, 130 800 380 34 48 Beans, 160 640 420 40 50 Indian corn, 100 1260 220 130 30 Potatoes, 1080 4800 540 45 240 Turnips, 1340 6000 1000 200 450 Wheat straw, 1500 900 40 80 150 Meadow hay. 1020 1360 240 120 220 Clover hay. 1120 1800 420 200 400 Cabbage, 430 2300 1300 130 600 1. If it be granted that the quantities above stated are fair average returns of the different kinds of produce from the same quality of land — that the acre, for example, which, in our cli- mate, produces 25 bushels of wheat, or 30 of Indian corn, will also produce 50 bushels of oats, or 12 tons of potatoes, or 30 of turnips, and so on * — then it appears that the land which, by cropping with wheat, would yield a given weight of starch, gum, and sugar, would, when cropped with barley or oats, yield one-fourth more of these substances — with potatoes about four times as much — and with turnips eight times the same quantity. In other words, the piece of ground which, when sown with wheat, will maintain one man, would support one and a quarter if sown with barley or oats, four with potatoes, and eight with turnips — in so far as the nutritive power of these crops depends upon the starch, sugar, and gum they contain. * These are not by any means to be regarded as universally equivalent crops. Even m our country, local climate modifies very much the relative quantities of the same crops obtained in difierent localities. Thus, in the southern part of Wigtonshire, 30 tons of Swedes, 20 tons of mangold, and 20 tons of white carrots per acre are equivalent crops, while in Berkshire it is as easy to grow 30 tons of mangold as 20 tons of Swedes per acre. See Journal of the Royal Agricultural Society ^ vol. xiii. part i. 310 RELATIVE NUTRITIVE VALUES 2. Again, if we compare the relative quantities of gluten, &c., in the several crops, we see that wheat, barley, and Indian corn yield, from the same breadth of land, nearly equal quan- tities of this kind of nourishment — oats one-half more, peas and beans upwards of twice, potatoes upwards of thrice, turnips upwards of four times, and cabbage six times as much as wheat or Indian corn. On whichever of these two substances, then — the starch or the gluten — we consider the nutritive property of the above kinds of food to depend, it appears that the turnip is, on the whole, the most nutritive crop we can raise. It is by no means the most nutritive, weight for weight; but the largeness of the crop — here taken at 30 tons — affords, us from the same field a much greater weight of food than can be reaped in the form of any of the other crops above mentioned. If, again, we look to th% gluten alone, none of our crops can compete with the cabbage, even supposing the crop not to ex- ceed 20 tons an acre. 3. Further, the oil or fat they contain is not without its value in relation to the nutritive, and especially to the fattening properties of the different crops. In this respect also the tur- nip would appear to be superior to most of the other usual forms of vegetable produce. Clover hay and Indian corn can alone be compared with it. In these two facts the practical farmer will see the peculiar adaptation of the turnip husbandry to the rearing and fatten- ing of stock. Could the turnip be rendered an agreeable article of general human consumption, the produce of the land might be made to sustain a much larger population than under any of the other kinds of cropping above oJluded to. At- tempts have been made to grind them, and convert them into meal, as is done with the potato; but the cost of manufactur- ing, and the disagreeable taste of the meal, have hitherto stood in the way of a successful prosecution of this branch of rural industry. OF DIFFERENT VEGETABLE SUBSTANCES. 311 The relative nourishing powers of different vegetable sub- stances, or their value for food, is supposed by some to depend entirely upon the relative proportions of gluten, &c., they con- tain. According to this view, the pea and the bean are much more nourishing, weight for weight, than wheat, or any other grain, since 100 lb. of beans would afford as much gluten to an animal as 230 lb. of wheaten flour or Indian corn, or as 130 lb. of oats or 200 lb. of rye ; and, in like manner, an acre of cab- bage would support both more people and more stock even than an acre of turnips. This opinion, however, is not alto- gether correct. But we shall be able to form a better judgment in regard to the relative value of the starch and gluten, as well as to under- stand the importance of the salim matter of the food, when we come in a succeeding chapter to consider the several purposes which the food is destined to serve in the animal economy — what different substances the animal must derive from its food in order to nourish its growing body, to maintain its existing condition when full grown, or to admit of a healthy Increase in its bulk. CHAPTER XXIII. Of milk and its products. — The properties and composition of mQk. — Influ- ence of breed, constitution, food, soil, &c., on its quantity and quality. — Adulteration of milk. — Composition of cream. — Churning. — Quality, composition, preservation, and coloring of butter. — Theory of the action of rennet. — Manufacture, quality, and varieties of cheese. Of, the indirect products of agriculture, milk, butter and cheese are among the most important. They are in reality ne- cessaries of life in all civilised countries, and are almost the sole productions of many agricultural districts. The various branches of dairy husbandry present also many interesting sub- jects of inquiry, on which modern chemistry throws much light. SECTION I. OF THE PROPERTIES AND COMPOSITION OF MILK. Milk is a white opaque liquid, possessed of a slight but pecu- liar odor. It is heavier than water, usuall}? in the proportion of 103 to 100. When left at rest for a number of hours it se- parates into two portions — the cream, which rises to the sur- face, and the thinner creamless milk on which it floats. When the whole milk or the cream alone is agitated in a churn, the fatty part of the milk separates in the form of butter, while the milk itself, butter-milk, becomes shghtly sour. If left to itself for several days, milk sours and curdles ; and if in this state it be placed upon a linen cloth, the liquid part, or whey, will pass through, while the curd or cheesy part will remain on the cloth. The same effect is produced more rapidly by adding vinegar to the milk, lemon juice, muriatic acid (spirit of salt), or rennet. In Holland the milk is sometimes curdled COMPOSITION OF MILK. 313 for the manufacture of cheese by the addition of muriatic acid; but in most countries rennet is employed for this purpose. It is coagulated also by alcohol or any strong spirit, and hence, probably, the practice of adding a quantity of. whisky or brandy to the rennet — as is done in many dairy districts. When exposed to the air for a length of time, milks begins to putrefy and to ferment. It becomes disagreeable to the taste, emits an offensive smell, and ceases to be a wholesome article of food. The milk of nearly all animals contains the same ingredients — cheesy matter or casein, butter, milk-sugar, and saline mat- ter, but in different proportions. The best known varieties of milk consist nearly of Woman. Cow. Ass. Goat. Ewe. Casein, (or curd,) 1.5 - 4.5 • ■ 1.8 - 4.1 . • 4.5 Butter, 3.6 - 3.1 ■ • 0.1 - 3.3 • • 4.2 Milk-sugar, 6.5 - 4.8 • ■ 6.1 - 5.3 • • 5.0 Saline matter, 0.5 - 0.6 . . 0.3 - 0.6 • 0.7 Water, 87.9 - 87.0 . • 91.7 - 86.7 • . 85.6 100 100 100 100 100 The milk of the ass appears from the above table to resem- ble woman's milk, in containing little cheesy matter and much sugar. It contains also much less butter than any of the other varieties above mentioned, and hence, probably, its peculiar fitness for invalids. SECTION II. INFLUENCE OF BREED, CONSTITUTION, FOOD, SOIL, &C., ON THE QUANTITY AND QUALITY OF THE MILK. Both the quantity and the quality of the milk are affected by a great variety of circumstances. Every dairy farmer knows that his cows give more milk at one season of the year than at another, and that the quality of the milk also — its richness in butter or in cheese — depends, among other condi- tions, upon the kind of food with which his cows are fed. It 14 814 INFLUENCE OF CIRCUMSTANCES will be proper to advert to these circumstances a little in detail. 1. The quantity and quality of the milk are affected by the breed. — Small breeds generally give less milk, but of a richer quality. Good ordinary cows in this country yield an average produce of from 8 to 12 quarts a-day. Thus the dairy cows of Devonshire give 12 quarts a-day, Lancashire - 8 to 9 quarts a-day, Cheshire and ) o ^ j Ayrshire, [ ^ ^"^^^^ ^ ^^^' 19 25 oz. 17 .. 28 oz. 20 34 oz. during ten months of the year ; but crossed breeds are, in many districts, found more productive of milk than the pure stock of any of the native races. The influence of breed ])oth on the quantity and on the qua- lity of the milk appears from the following comparative pro- duce of milk and butter of one cow of each of four different breeds, in the height of the season, and when fed on the same pasture. The Milk. Butter. Holderness gave 29 quarts and 883 oz. Alder ney^ Devon^ Ayrshire^ Not only was the quantity of milk very di^rent in the four cows, but the produce of butter also — the Holderness, in the quantity both of milk and of butter, being greatly superior to all the other breeds. The milk of the Holderness and of the Alderney breeds was equally rich in butter, as was the case also with that of the Devon and the Ayrshire, since 1 lb. of butter was yielded by 12 quarts of milk from the Holderness cow, 2 . . , . Alderney cow, 9| . . . . Devon cow, 9|- . . . . Ayrshire cow. Some stocks of Jersey cows produce 1 lb. of butter from 8 J ON THE QUANTITY AND QUALITY OF MILK. 315 quarts of new milk, the year round, and at the same time con- sume less food than others. The butter of the milk is often in great part derived directly from the fat of the food. Hence the value of food which, like Indian corn and linseed cake, is rich in oil. Hence, also, those animals which lay the smallest proportion of this fat upon their own bodies will be likely to give the largest proportion in their milk. Thus the ■ Ayrshires and Alderneys, which are good milkers, are narrow across the shoulders, and wiry and muscu- lar about the flanks. They give a rich milk, but rarely fatten well. The short-horns, on the contrary, are celebrated for their fattening tendency. They deposit more of the fat under their skin, and impart less of it to their milk. In both breeds, how- ever, there are striking exceptions, because — 2. The individual form and constitution of the coiv causes both the yield and the richness to vary much among animals of the same breed. Every dairy farmer knows that some Ayrshire, or Holderness, or Devon cows are better milkers than others. And even when they yield nearly the same quantity of milk, the richness or produce in butter may be very unlike. Thus, four cows of the Ayrshire breed, fed on the same pasture, gave in the same week — the Milk. Butter. First, ... 84 quarts which yielded 82 lb. Second and third, each, 86 . . . . 63 " Fourth, ... 88 .. . . 7 " SO that the fourth, though it produced only four quarts more milk, gave twice as much butter as the first. Individual cases of extraordinary productiveness occur now and then. Thus a Durham cow belonging to Mr. Hewer of Charleton, Northampton, gave in the height of the season 8 imperial gallons of milk in a day, yielding 3 lb. of butter. A cow upon ordinary keep has been known also to produce as much as 350 lb. of butter in a year. The tendency to yield 316 CONSTITUTION AND FOOD. butter is no doubt constitutional, like the tendency to lay on fat. 3. The kind of food also exercises, as all cowfeeders know, much influence upon the quantity and upon the richness of the milk.* The Swedish turnip and the cabbage give a richer milk, the white globe turnip a larger quantity, while both vari- eties of turnips are said to cause a greater yield of milk when tops and bulbs are given together. Culpepper recommends the leaves of the black alder as a fodder for causing cattle to give much milk. (See p. 302.) Spurry is said to have a similar effect. When fed on grass and brewers' grains, the cow yields a larger quantity of milk; and when fed on malt dust, she drinks much and milks well. It is believed also, that cabbage and the leguminous plants, such as clover, tares, &c. — as well as the cultivated seeds of such plants, beans, peas, &c. — promote the production of cheese ; while oilcake, oats, Indian corn, and other kinds of food, which contain much oily matter, favor the yield of butter. The cakes left by oily seeds, linseed, poppy seed, dodder, sesa- min, give a milk which contains more solid matter, and is richer both in butter and cheese. If the cake be not old or rancid, it does not impair when given in moderate quantities, but rather increases the flavor and pleasantness of the butter. If the food contain little fat, the animal still produces butter It has the power of changing the starch and sugar of its food into fat during the process of digestion. It even robs its own body of fat, becomes leaner, and thus yields more fat in the form of butter than it has eaten in its food. Where only part of a dairy of cows is kept for tloeir butter, and the rest for cheese, the butter-milk from the former may be given to the latter, and thus the produce of cheese increased. In the State of New York, cows are said to yield 100 lb. more cheese in a year * Hence the Ayrshire adage, " The coio gives the milk by the inou.^^ INFLUENCE OF THE SOIL. 317 when the whey from their own milk is added to their daily food. 4. The nature of the soil also in which plants grow, and the manure by which they are raised, affects their influence upon the milk. It has been known from the most remote times, that when fed upon one pasture the cow will yield more butter, upon another more cheese. This difference must depend upon the soil. Again, it has been found by experiment, that vetches grown upon well-limed or marled land promote the production of cheese, while, after a manuring with wood-ashes, they in- crease the quantity of milk and of cream, (Sprengel.) In Cheshire the addition of bones has greatly increased the value of the grass, and the produce of milk and cheese ; while, as to the quality, it has been found in Leicester that the manuring of old pasture with good farm-yard manure, rendered the cheese for three years nearly unsaleable. On this curious subject numerous experimental researches are still required. 5. The milk is affected also by a variety of other circum- stances. Its quantity depends very much upon the distance from the time of calving, diminishing as the calf in the womb gets older. This is no doubt a natural adaptation to the wants of the calf, which, in a state of nature, gradually ceases to re- quire support from its mother. A cow which, during the first fifty days after calving, yields 24 quarts of milk a-day, may yield no more than 6 quarts a-day after six months have elapsed. The quality of the milk is better from cows that are in good condition and have already been two or three times in calf — it is richer in warm climates, in dry seasons, and when the cow is not too frequently milked. It is said to be richer when cows are kept constantly in the house and regularly fed — those which go at large in the pasture yielding more cheese. When a cow is allowed to go dry for two or three months before calving, it is believed to o:ive more milk the following season. In autumn 318 ADULTERATION OF MILK. it is richer upon the whole, giving a less proportion of butter, but a greater of cheese ( Aiton, ) while it becomes poorer in both when the cow is in calf. The first milk which comes from the udder is also poorer than that which is last drawn, the strijp- pings or stroakings — and, lastly, the quality of the milk is very much affected by the treatment and moral state of the animal. Gentle treatment and a state of repose are favorable to the richness of the milk ; while anything that frets, irritates or ha- rasses the animal, injures its quality. I need scarcely add that cleanliness and good ventilation in the cow and milk houses are essential to the good flavor of milk. SECTION III. OF THE ADULTERATION OF MILK. Milk is almost everywhere more or less adulterated with wa- ter. In Paris and the neighborhood, the cream is taken off, and the skimmed milk thickened with sugar aud an emulsion of sweet almonds and hemp-seed, (Raspail.) Skim milk may also be thickened with magnesia, and by this means the thick- ness of cream may be given to new milk, while it will also be kept longer sweet. Common soda or pearl ash is sometimes added to milk which has turned, to restore its sweet taste. But the most singular adulteration of which I have heard is that of mixing up the skim milk with calf's and sheep's brains. This mixture renders it thick and rich, and causes a coating, apparently of cream, to rise to the surface, which it requires a nice chemical examination to distinguish from genuine cream.* * The method of examuiation is to treat the creamy matter with ether, and to boil what the ether takes up with water containing a little sulphuric acid. If the cream is not genuine, the acid solution will then give with lime or baryta traces of phosphoric acid. THE CHURNING OF CREAM, 319 SECTION IV. OF THE COMPOSTTION OF CREAM AND THE CHURNING OF BUTTER. 1. Cream. — When milk is left at rest for a length of time, the fatty matter which floats in it in the form of minute globules, rises to the surface in the form of cream. The rapi- dity with which.it thus rises to the surface depends upon the temperature to which it is exposed — being quicker in warm than in cold weather. Thus, for example, when milk is set aside it may be perfectly creamed in Hours. Degrees, F. 36 when the temperature of the air is 50 24 .. .. 55 18 to 20 . . . . 68 10 to 12 .. .. ^7 while at the temperature of 34° to 3t° F.,— a little higher than the freezing point of water, — milk may be kept for three weeks without throwing up any notable quantity of cream. If the milk when new is placed in a hot basin, and covered over with another, the cream is thrown up more quickly, and a larger quantity of butter is obtained. Of course, the skimmed milk will be so much the poorer. The cream thus thrown up contains the greater part of the fatty matter of the milk, mixed with a small proportion of the curd and much water. Cream of good quality in this country, when skilfully churned, will yield about one-fourth of its weight of butter; or, one wine gallon of cream weighing 8 J lb, will give nearly 2 lb. of butter, 2. Chioniing. — When milk or cream is agitated for a length of time, the fatty matter gradually separates from the milk, and collects in lumps of butter. There are several circum- stances in connection with the churning to which it is of inte- rest to attend. a. In the churning of crea7?i it is usual to allow the cream to 8^0 TEMPEKATURE FOR CREAM. stand in cool weather for several days, until it becomes dis- tinctly sour. In this state the butter comes sooner, and more freely. The butter, when collected in lumps, is well beat and squeezed from the milk. In some places it is usual also to wash it in cold water as long as it renders the water milky; in other places the remaining milk is separated by repeated squeezings, and by drying with a clean cloth. h. Clouted cream may be churned with advantage in the sweet state — the butter separating from it with great ease. Colonel le Couteur states that, in Jersey, it is usual to make ten pounds of hitter in five minutes from the clouted cream of the Jersey or Alderney cow. Clouted cream is obtained^ by gra- dually heating the milk in deep pans, almost to boiling, but so as never to break the skin or clout that forms on the surface. The cream is said to be more completely separated by this pro- cess than by any other, and a larger quantity of butter to be obtained from the milk. c. The tvhole milk may also be churned, after being allowed to stand till it has attained the proper degree of sourness, which is indicated by the formation of a stiff brat on the surface, ickich has become uneven. This method is more laborious, re- quiring more time than when the cream only is used ; but it has the advantage, as many practical men have found, of yielding five per cent more butter from the same quantity of milk, and of a quality which never varies in winter or in summer. It also requires no greater precautions or more trouble to be taken in warm than in cold weather. d. Temperature. — This latter advantage is derived from the circumstance, that the temperature at which the whole milk ought to be churned is higher than that of the air in our cli- mate, throughout nearly the whole course of the year. The temperature at which milk can be churned most economi- cally is about 65° F., a degree of heat which the air seldom attains in our warmest summer mornings. The dairy-maid has simply to add hot water enough to the milk to raise it to 65° TIME REQUIRED FOR CHURNING. 321 F., and to repeat this every morning of the year, if she churns so often. On the other hand, the temperature of cream, when churned, should not be higher than from 53° to 55° F., a tem- perature beyond which the air often rises. It becomes neces- sary, therefore, in summer, to cool the railk-room in which the cream is churned, and, by churning early in the morning, to en- deavor to keep the cream down to the proper temperature. Thus, in churning cream, the task of the dairy-maid is a more difficult one. In winter, she must add hot water to bring the temperature up to 55°, and in summer must apply cold, to keep it down. In this she sometimes fails, and on these occa- sions the quality of the butter suffers. e. The time required for churning the whole milk in the ordi- nary churn is from three to four hours, while the cream alone can be churned in about an hour and a half. A churn, how- ever, has lately been introduced which churns both milk and cream in a much shorter period of time. It is made of tin, is of a barrel shape, and is placed in a trough of water, which is heated to the temperature the milk or cream ought to be brought to. In this churn the butter was extracted from cream, at the temperature of 5G- F. in 60 minutes, . . .\ Butter was harder but no ' ( better than the lollowing. 58° F. in 10 to 20 minutes, . Butter excellent. 60< F. in 5 to 7 minutes, . \ ^^^\^^ fi''f'^ "f^ °^ ^^^^^ ' ( color and quality. The whole milk in this churn gave the butter in one hour to one hour and a half. Mr. Burnett of Gadgirth informs me, that he obtains in this churn a larger quantity of butter from the cream than from the whole milk. Thus, from 508 quarts of milk — the produce of five cows in one week of July (1843) — he obtained, on churning the whole milk, 36 lb. 11 oz. The cream, on the other hand, yielded by an equal quantity of milk drawn from the same cows during another week, gave him 3t lb. 4 oz., being a difference of 9 ounces, or about 3 per cent in SMALL BREEDS GIVE MOST BUTTER. favor of the cream, which is contrary to general experience with the ordinary churn, as stated in the previous page. Other persons who have tried this churn have not been so successful in the use of it as Mr. Burnett. Where they have obtained the butter much sooner than usual, they have found reason to complain of its quality. Perhaps in these cases the churn has not been skilfully used, or something may depend upon the quality of the milk — since the cream from the milk of some cows is said in the ordinary churn always to come to but- ter in ten minutes or less. The air ckurn — a still more recent invention — which agitates the milk, by forcing a current of air through it, is said to bring the butter in the still shorter period of four minutes. /. The largest quantity of butter from a given weight of the same food, and the richest milk, is yielded by the milk of the smaller races. The small Alderney, or Jersey, West Highland, and Kerry cows, give a richer milk even than the small Ayr- shire. But the small Shetlander is said to surpass them all. These breeds are all hardy, and will pick up a subsistence from pastures on which other breeds would starve. The quantity of butter yielded by different cows in the same yard, and eating the same food, is sometimes very different. Some will yield only 3 or 4 lb. a week, while more will give 8 or 9 lb., and a few 15 lb. a-week. As a rare instance, I may mention that a cow has been known in Lancashire to yield up- wards of 22 lb. in seven days. SECTION V. — OF THE QUALITY, COMPOSITION, PRESERVATION, AND COLORING OF BUTTER. 1. The quality of butter varies with numerous circumstances. The kind of natural pasture, or of artificial food, upon which the cow is fed, the season of the year, the breed, the individual constitution and state of health of the animal, the mode of 14* QUALITY OF IJUTTER VARIES. 323 churning, the cleanliness of the cow and milk houses, &c., all more or less affect the quality of the butter. But from the same cow, fed on the same food, and in the same circumstances, a richer l)utter, and of a finer and higher flavor, will be obtained by churning the last drawn portions of the milk. So the first cream that rises gives the finest flavored butter, — while any cream or milk will give a butter of better quality if it be- properly soured before it is churned, and be then churned slowly and at a low temperature. 2. Tht composition of butter. — Butter, as it is usually brought to the market, contains more or less of all the ingredients of milk. It consists, however, essentially of the fat of milk, inti- mately mixed with about one-eighth of its weight of water, and a small quantity of casein or curd, of saline.matter, alld of the sugar of milk. The quantity of casein (cheesy matter or curd) seldom amounts to one per cent of the whole weight of the butter. If the butter be melted in hot water several times, shaken, with renewed portions of water as long as they become milky, and left then to repose, it will collect on the surface in the form of a fluid yellow oil, which will concrete or harden as it cools. If when cold it be put into a linen bag, and be sub- mitted to strong pressure in a hydraulic or other press, at tho temperature of 60° F,, a slightly yellow transparent oil will flow out, and a solid white fat will remain behind in a linen cloth. The solid fat is known by the name of margerine, and is identical with the solid fat of the human body, with that of the goose, and with that which causes the thickness of olive oil when exposed to the cold. It is very similar also to the solid fat of palm oil. The liquid or butter oil is a peculiar kind of fat not hitherto discovered in any other substance. The proportion of these two kinds of fat in butter varies con- siderably, and hence the different degrees of hardness which different samples of butter present. The solid fat is said to abound more in winter, the liquid fat in summer. Winter and 324 SOLID AND LIQUID FATS IN BUTTER. summer samples of butter manufactured in the Vosges were found to contain per cent respectively of Summer. "Winter. Solid (at or margerine, . . 40 65 Liquid fat or butter oil, . . 60 35 100 100 These proportions, however, will be found to vary more or less in almost every sample of butter we examine. In Jersey, the drainings of the curd in rich-cheese making give a butter which is inferior for eating with bread, but very superior for pastry. It is peculiarly hard, and fitted for such use in hot weather. It probably contains more of the solid fat of butter. 3. The preservation of butter. — Fresh butter cannot be kept for any length of time in our climate without becoming rancid. The fats themselves undergo a change ; and the same is the case with the small quantity of milk sugar which the butter contains. The main cause of this change is the casein or curd which is usually left in the butter. The proportion of this cheesy matter I have found in two samples of fresh butter to vary from one-half to three-fourths of a per cent, — or from half a pound to three-quarters of a pound in 100 pounds of butter; and yet this small quantity is sufincient, if the ])utter be expos- ed to the air, to induce those chemical decompositions to which the disagreeable smell and taste of rancid butter are owing. The butter made in the pure air of the Alpine valleys of Pied- mont and Switzerland, after a complete expression of the milk, is said to be " preserved sweet, or at least fit for use, through the whole season, without any admixture of salt.-' By melting and skimming the butter also, and then pouring it hot into a jar, it is in Switzerland preserved without salt. In this latter state it is called boiled butter, {huerre cuit,) and is chiefly used for cookery.* * Fhysician's Holiday, by Dr. Egrbes, p. 336. HOA? BUTTER BECOMES RANCID. 325 I do not enter here into the theory of the action of this casein, nor into an explanation of the nature of the chemical eha-nges themselves.* It is sufficient to state, that this evil action of the cheesy matter may be entirely prevented. a. By salting immediately after the butter is made, and be- fore the cheesy matter has had time to become altered by ex- posure to the air. h. By taking- care that any water which may remain in or around the butter be always kept perfectly saturated with salt. c. By carefully excluding the air from the casks or other ves- sels in which the butter is packed. So long as the cheesy matter is kept from the air, and in a saturated solution of salt, it will neither undergo any rapid alteration itself, nor will it soon induce any offensive alteration in the butter. About half a pound of salt is used to 12 or 14 lb. of butter ; but when salted for exportation, or for the use of the navy, one pound of salt is added to 10 or 12 of butter. Though many wash their butter, it is a rule with others never to wash it or dip it into loater when intended to he salted, but to work it with cool hands till the butter milk is thoroughly squeezed out, and then- to proceed with the salting. Theoretically, I should consider this latter the better plan, since it exposes the cheesy matter less to the air, and consequently to less risk of incipient decom- position. Some fancy they cure their butter better by dissolving the salt in the cream before churning, while many consider its pre- servation and good quality to depend much upon the quality of the salt that is employed. Some prefer, instead of salt alone, to make use of a mixture of one part of sugar, one of nitre, and two of salt ; and some who use an impure salt, consider the butter to be improved by washing it in a saturated solution of salt. * The reader will find these fully explamed in the Author's published Lectures on Agricultural Chemistry and Geology^ 2d edit., p. 976. 326 SOURING OF MILK. It is said that rancid butter maybe rendered sweet by churn- ing it with fresh sweet milk, in the proportion of six pounds of butter to the gallon. 4. Coloring butter. — Butter is sometimes colored, and the juice of scraped carrots is not unfrequently employed for the purpose. BECTION VI. OF THE SOURINU OF MILK, OF MILK-SUGAR, AND OF THE ACID OF MILK. 1. When milk is left to itself for a sufiicient length of time, it becomes sour and curdles. This takes place sooner in warm weather, and in vessels which have not been cleaned with suffi- cient care. Why does milk thus become sour ? a. Sugar of Milk. — I have already stated that milk contains a quantity of a peculiar kind of sugar, found only in milk, to which, therefore, the name of milk-sugar is given. It differs from common cane sugar in being harder, less sweet, and much less soluble in water. Of this sugar, miUc contains generally a- larger jproportion than it does of either fat or curdy (p. 313). A gallon of milk, therefore, would yield a greater weight of sugar than it does of either butter or cheese. In this country, the sugar is usually neglected. In our cheese districts, it is given to the pigs, and sometimes to the cows in the whey with which they are fed. In Switzerland and elsewhere, it is extracted as a profitable article of commerce, h. Acid of milk, — When milk becomes sour, a peculiar acid is formed in it, to which, from its having been first observed in milk, the name of lactic acid, or acid of milk, has been given. To this acid the sourness of milk is owing. The same acid is produced when crushed wheat — as in the manufacture of starch from wheat — wheaten flour, oat-meal, pease-meal, &c., or when cabbage and other green vegetables are mixed with water, aud SUGAR AND ACID OF MILK. 32 1 allowed to become sour. It exists also in small quantity in the acorn, (p. 289.) c. But how is iha add produced ? — As the acid of milk in- creases in quantity, the sugar of milk diminishes. The acid, therefore, is formed from or at the expense of the sugar. There is no fermentation, and therefore no loss of matter : the sugar is merely transformed into the acid, and by a process the out- line of which it is very easy to understand. Like cane sugar, grape sugar, and gum, (p. 43,) both may be represented by, or may be supposed to consist of, carbon and water, and in the same proportions. Thus. — Carbon. Water. Sugar of milk consists of . .6 and 6 Acid of milk, {lactic acid,) . . 6 and 6 The same particles of matter, therefore, which compose the sugar, are made to assume a new arrangement, and, instead of a sweet sugar, to form a sour acid. In the interior of the milk, nature takes down and builds up its materials at her pleasure, — using the same molecules to form now this and now that kind of substance — as the child plays with its wooden bricks, erect- ing a hut or a temple with the materials of a ruined palace or a fallen bridge. So nature seems to play with her materials, — working up all, wasting none, — yet so skilful in all her opera- tions as to excite our wonder, so secret as not unfrequentl^ to escape our observation, and so quick as often to show that she has been working, only by the striking effects she has produced. To the simple peasant and to the instructed philosopher, it is equally a matter of wonder, and almost equally unintelligible, that the same number of material particles arranged in one way should affect the organs of taste with the sweetness of sugar, in another with the sourness of lactic acid. 328 WONDERFUL CHANGES OF FORM. SECTION VII. OF THE CURDLING OF MILK, OF CASEIN, AND OF THE ACTION OF RENNET. As milk becomes sour, it also thickens or curdles. If it he then slightly heated, the curd runs together more or less, and separates from the whey. If the whole be now thrown upon a linen cloth and gently pressed, the clear whey will run through and the curd will remain on the cloth. This curd, when salted, pressed, and dried, forms the cheese which we consume so ex- tensively as an article of food. In consequence of what chemical change does this separation of the curd take place ? 1. It is to be borne in mind, that this curdling does not take place naturally till the milk has become sour. The acid of the milk, therefore — the lactic acid — has some connection with the separation of the curd. It is, in fact, the cause of the curd- ling. 2. But, in order to understand how this is, we must turn for a moment to the properties of the curd itself. Chemically pure curd or casein is a protein compound, which contains less sul- phur than albumen does, and no phosphorus, (p. 46.) a. When the curd of milk is separated carefully from the whey, it may be washed or even boiled in water, without being sensjbly lessened in quantity. Pure curd is nearly insoluble in jpure water. b. But if a little soda be added to the water in which the curd is heated, it will dissolve and disappear. Pure curd is soluble in a solution of soda. c. If to the solution of the curd in soda and water a quanti- ty of the acid of milk be added, this acid will combine with the whole of the soda — will take it from the curd, which will thus be again separated in an insoluble state. The curd is insoluble in water, rendered sour by the acid of milk. These facts explain very clearly the curdling of milk. As it WHY THE CURD SEPARATES. 329 comes from the cow, milk contains a quantity of soda not com- hiimi loith a7iy add, by which soda the curd is believed to be held in solution. As the milk becomes sour, this soda combines with the lactic acid produced, and thus the curd becoming in- soluble separates from the whey — or the milk thickens and curdles. Now, the effect which is thus produced by the natural for- mation of lactic acid in the milk, may be brought about by the addition of any other acid to it — such as vinegar or spirit of salt. And, in fact, vinegar is used now, in some countries, and in ancient times was used more extensively, for curdling milk ; while in some of the cheese districts of Holland, spirit of salt (muriatic acid) is said to be employed for the same purpose. Sulphuric acid has been also recommended, but has been found to give the cheese an unpleasant taste. 3. But in most dairy countries rennet is the substance used for the curdling of milk. What is rennet ? and how does it act? a. The stomach of the calf, of the kid, of the lamb, of the young pig, and even of the hare,* when covered with salt, or steeped for some time in water perfectly saturated with salt and then dried, forms the dried maw-skin or bag which is used for the prepara- tion of rennet. If the dried skin of nine or ten months old be steeped in salt and water, a portion of its substance dissolves, and imparts to the water the property of coagulating milk. The water thus impregnated forms the rennet or yirning of the dairy-maid. In some districts it is usual to steep several skins at once, and to bottle the solution for after use — mixed with more or less brandy, whisky, or other spirit. In others, a por- tion of the dry skin, sufficient to make the quantity of rennet required, is cut off the night before, and steeped in water till the milk is ready in the morning. To this solution many dairy- * Three hares' stomachs are considered equal to one calf's. 330 HOW RENNET ACTS. maids add a quantity of strong spirit before putting it into the milk, which probably increases its coagulating power. h. The rennet thus prepared coagulates more or less readily, according to its strength. On what priiiciple does it act ? If a piece of the fresh membrane of the calf's stomach or intestine, or even if a piece of fresh bladder, be exposed to the air for a short time, and be then immersed into a solution of milk-sugar, it gradually causes the sugar to disappear, and to change into lactic acid — the acid of milk. If the salted and dried memt)rane be employed instead, it will produce the same effect, only with greater rapidity. But, by long exposure to the air in drying the surface, the salted membrane undergoes such a change, that a portion of it becomes soluble in water, yet still retains or acquires, even in a higher degree, the -property of changing milk-sugar into the acid of milk. It is this soluble portion which exists in the liquid rennet. Now, the same effects which the membrane produces upon the sugar of milk alone, it produces also upon the sugar as it is contained naturally in the milk — in other words, the rennet, when added to the warm milk, changes the sugar into the acid of milk. This it effects more or less rapidly according to circum- stances, and hence the different length of time which elapses in different dairies before the milk is fully thickened. c. The addition of rennet, therefore, is only a more rapid way of making the milk sour, or of converting its sugar into lactic acid. The acid produced, as in the natural souring of milk, combines with the free soda, and renders the cheesy matter in- soluble, which, in consequence, separates ; — in other words, the milk curdles. The milk, it is true, does not become sensibly sour, because the production of acid in a great measure ceases as soon as the soda of the milk is fully saturated with the acid ; and if any excess of acid be produced, it is taken up and ab- sorbed or separated in and by the curd, so as to leave the whey comparatively sweet. Even the rennet that is added is carried MANUFACTURE OF CHEESE. 331 off by the curd, which is thus often injured in quality if too much rennet have been added, or if its smell or taste have been unpleasant. The sugar that remains in the whey is thus ena- bled to retain its sweetness — that is, to remain unchanged into acid — longer than it could have done had any excess of rennet remained in it after the separation of the curd. The chemical change produced by rennet in curdling milk, therefore, is precisely the same as that which takes place when milk sours naturally. In both cases the lactic acid which is formed causes the milk to curdle. SECTION VIII. OF THE MANUFACTURE AND THE QUALITY OP CHEESE. 1. TJie. manufacture of cheese is, generally speaking, con- ducted in the same manner in all countries. The milk is curdled by the addition of rennet, vinegar, muriatic acid (spirit of salt,) lemon juice, tartaric acid, cream of tartar, salt of sorrel, — by sour milk even, as in some parts of Switzer- land,* or by the decoction of certain plants or flowers, as of those of the wild thistle, employed for the ewe cheeses of Tuscany. The curd is then more or less carefully separated from the whey, tied up in a cloth, and exposed to gentle pressure. In general, the curd at this stage is broken small, and mixed with a due proportion of salt before it is allowed to consolidate and dry. For the thin cheeses of Gloucester and Somerset, how- ever, this mode of salting is not adopted, the whole of the salt that is necessary being afterwards rubbed in and made to penetrate through the exterior of the cheese. After it is removed from the press, the cheese is rubbed over * It is stated bj old cheese-makers in Nottinghamshire, that churned milk added to cheese milk in the usual way, very much unproves both the quality and taste of the cheese, and prevents it from rising after it is made. 332 THE QUALITY OF THE CHEESE with salt, or is covered with a layer of it — at a later period is more or less frequently anointed with butter, is kept for a week or two in a rather warmish place, and is frequently turned. There are minute details to be attended to, where cheese of good quality is desired, with which the skilful and experienced dairy-maid is familiar, but upon which it is unne- cessary here to dwell. 2. The quality of the cheese varies with a great variety of circumstances, partly natural and unavoidable, but partly also to be controlled by art. a. Thus there are natural differences in the milk, arising from the kind of grass or other food on which the cows are fed, which necessarily occasion corresponding differences in the quality of the cheese made from it. The milk of different animals also gives cheese of unlike qualities. The ewe-milk cheeses of our own country, of Italy, and of France, and those of goat's milk made on Mount d'Or and elsewhere, are dis- tinguished by qualities not possessed by cow's milk cheeses pre- pared exactly in the same way. The milk of the buffalo like- wise gives a cheese of peculiar qualities, arising, as in the cases of the ewe and the goat, from some natural peculiarity in the composition of the milk itself. h. But every dairy farmer knows that, from the same milk, cheeses of very different flavors, and of very unlike values in the market, may be made — that the mode of management has not much less to do with the peculiar quality of his dairy pro- duce than the breed of cattle he uses, or the pasture on which his cows are fed. Yery slight circumstances, indeed, affect the richness, flavor, and other valuable properties of his cheese. Thus if the new milk, when the rennet is added, be warmer than 95° F., the curd is rendered hard and tough ; if colder, it is soft, and difficult to free from the whey. If heated on the naked fire, as is often done, in an iron pot, the milk may, by a very slight inattention, become fir e-fanged, and thus impart an unpleasant flavor to the cheese. If the curd stand long un- IS AFFECTED BY MANY CIRCUMSTANCES. 333 broken after the milk is fairly coagulated, it becomes bard and tough. If the rennet have an unpleasant flavor, or if too much be added, the flavor and keeping qualities of the cheese are affected. If acids are used instead of rennet, the properties of the cheese are altered. It is less rich if the whey be hastily and with much pressure squeezed out of the curd ; or if the curd be minutely broken up and thoroughly mixed and stirred up with the whey, or washed by it, as is the custom in Norfolk • — instead of being cut with a knife, so that the whey may flow slowly and gently out of it, as is done in Cheshire or Ayr- shire — or instead of being placed unbroken upon the cloth, as in making Stilton cheese, so that the whey may drain and trickle out spontaneously, and may carry little of the fatty mat- ter along with it. Some of the Cheshire dairy-maids give their cheese a tendency to green mould, by setting or curdling their milk at a low temperature ; and the inferiority of Dutch cheese is ascribed by some to the custom of soiling or feeding in the house, which affects the flavor of the cheese without injuring the health of the animal. c. The kind of salt also which is used,* the way in which the cheese is salted, the size of the cheese itself, and, above all, the mode in which it is cured, have very much influence upon its after qualities. Hence a fair share of natural ability, as well as long ex- perience, are necessary in the superintendent of a large dairy establishment, when the best quality of cheese which the milk can yield is to be manufactured uniformly, and at every season of the year. SECTION IX. OF THE VARIETIES OF CHEESE. The varieties of cheese which are manufactured are very * The kind of salt preferred in the dairy districts of the west of Scotland is an impure variety from Saltcoats, which contains a notable quantity ol the deliquescent salts, (chlorides of lime and magnesium.) These salts seem to keep the skin of the cheese moist, and to assist its stoning. 334 VARIETIES OF CHEESE. numerous, but the greater proportion of these varieties owe their peculiar qualities to the mode of management which is fol- lowed in the districts or dairies from which they come. IS'atural varieties, however, arise under the same general management, and from the same milk, according to the state in which the milk is used. Thus we have — a. Cream cheeses, which are made from cream alone, put into a cheese-vat, and allowed to curdle and drain of its own accord, and without pressure ; or as in Italy, by heating the cream, and curdling with sour whey or with tartaric acid. These cheeses are too rich to be kept for any length of time. h. Cream and milk cheeses, when the cream of the previous night's milking is mixed with the new milk of the morning, be- fore the rennet is added. The English Stilton cheeses and the small soft Brie cheeses, so much esteemed in France, are made in this way. c. Whole or full milk cheeses, which, like those of Gloucester, Wiltshire, Cheshire, Cheddar, and Dunlop, are made from the uncreamed milk. These cheeses, like the preceding, however, will be more or less rich according to the way in which the curd is treated, and according as the milk is curdled while naturally warm, as in the best Ayrshire dairies, and in some parts of Holland — or is mixed, as in Cheshire and in some Ayr- shire dairies, with the milk and cream of the previous evening. The large 60 to 120 lb. cheeses of Cheshire will not stand, will break and fall asunder, if all the cream is left in the milk. About one-tenth of the cream, therefore, is skimmed off and made into butter. About 20 lb. of butter a-week are thus made in a cheese dairy of 100 cows. d. Half-^ilk cheeses, such as the single Gloucester, are made from the new milk of the morning, mixed with the skimmed milk of the evening before. g. Skimmed-milk cheeses — which may either be made from the milk once skimmed, like the Dutch cheeses of Ley den, twice skimmed, like those of Friesland and Groningen, or skimmed WHEY AND BUTTER-MILK CHEESES. 335 for three or four days in succession, like the horny cheeses of Essex and Sussex, which often require the axe to break them, and are sometimes used for certain purposes in the arts,* /. Whey cheeses made from the curd which is skimmed off the whey when it is heated over the fire. This is by no means a poor kind of cheese ; and good imitations of Stilton are said to be sometimes made by mixture of this curd with that of the whole milk. g. Biitter-^iilk cheeses, made by simply straining the butter- milk through a cloth, and then either gently heating the butter- milk, which causes the curd to separate, or, as is sometimes done, by the addition of rennet. This kind of cheese is not unworthy of attention, as it is often richer than that made from milk only once skimmed. Though it cannot, of course, have the richness, it is said to possess some of the other cha- racteristic qualities of good Stilton cheese. h. Vegetable cheeses are made by mixing vegetable substances with the curd. The green Wiltshire is colored by a decoction of sage leaves, marigold, and parsley. I do not know if it is to this practice, or to one of actually mixing the sage leaves with the curd, that Gay alludes in the line — " Marbled with sage, the hardening cheese she pressed." The Schabzieger cheese of Switzerland is a mixture of the curd obtained from the whey of skimmed milk, with one-twentieth of its weight of the dried leaves of the mellilot trefoil. f i. The Potato cheeses of Saxony and Savoy consist of dry boiled potatoes mixed with a half or a third of their w^eight, or with any other proportion of the fresh curd, or simply with sour or with skimmed milk. The mixture is allowed to undergo a * Suffolk cheese, which is locally known by the name of " Suffolk Bank," is so hard that " pigs grunt at it, dogs bark at it, but neither of them dare bite it." f Zkger is the curd separated from whey either by a fresh addition of acid or in some other way. 336 POTATO CHEESE. species of slight fermentation before it is made up into shapes. Such cheeses, when well cured, are said to form a very agree- able article of diet, and to be capable of being kept for a long period of time.* * For farther details in regard to milk and its products, the reader is re- ferred to the Author's Lectures on Agricultural Chemistry and Geology, 2d edition, pp. 928 to 1008. CHAPTER XXlV. On the feeding of animals. — Main visible functions of the living animal. — The food must supply the wants of resph-ation. — Nature, wants, and pur- poses of this function. — The daily waste of the muscular parts and tissues of the body. — Food necessary to repair it. — Saline and earthy matters contained in its several parts, and daily rejected by the body. — Waste or increase of fat supplied by the food. — Special waste in the perspiration. — Forms in which the solid matter of the tissues escapes in the urine of animals. — G-eneral balance of food and excretions. — Kind of food re- quired, as indicated by the composition of the blood. — Importance of a mixed food. The food of plants we have seen to consist essentially of two kinds, the organic and the inorganic, both of which are equally necessary to the living vegetable — equally indispensable to its healthy growth. A glance at the purposes served by plants in the feeding of animals, not only confirms this view, but throws also additional light upon the kind of inorganic food which plants must be able to procure, in order that they may be fitted to fulfil their assigned purpose in the economy of nature. SECTION I. MAIN VISIBLE FUNCTIONS OF LIVING ANIMALS. Man, and all domestic animals, may be supported, may even be fattened, upon vegetable food alone. Vegetables, therefore, must contain all the substances which are necessary to build up the several parts of animal bodies, and to supply the waste at- tendant upon the performance of the necessary functions of ani- mal life. All living animpJs perform three main or leading functions necessary to the continuance of healthy life. 15 338 FUNCTIONS OF THE LIVING ANIMAL. 1°. They breathe, alternately inhaling and exhaling air by means of the lungs. 2°. They digest, dissolving the food in the stomach, and se- lecting from it the materials necessary to form blood. 30. They excrete, rejecting in the solid excretions and the urine, or giving off from the skin and the lungs — a. That part of the food which cannot be dissolved and made use of as it passes through the alimentary canal. h. The materials derived from the decomposed tissues or parts of the body vrhich are undergoing a constant waste. To the wants of an animal performing these visible functions in a healthy and regular manner, the food must be adapted in kind and quantity. I shall briefly illustrate what these wants demand. To the numerous minor and invisible functions performed within the' several parts of the living body, it is unnecessary to advert in detail. I may have occasion incidentally to advert to one or two of the more interesting of these ; l)ut as a healthy blood contains all that is necessary to the discharge of these functions, it would only complicate our present inquiry to consider their several direct relations to the undigested food as it is introduced into the stomach. SECTION II.-THE FOOD MUST SUPPLY THE WANTS OF KESPIRATION. NATURE, WANTS, AND PURPOSES OF THIS FUNCTION. While an animal lives it breathes. It alternately draws in and throws out atmospheric air by means of its lungs. 1. When this air enters, it contains about two gallons of carbonic acid in every 5000 ; when it escapes from the lungs it contains 2 gallons or upwards in every 100. The proportion is increased from 50 to 100 times. Much carbonic acid, there- fore, is given off from the lungs of animals during breathing. In other words, living animals are continually throwing off car- CARBON GIVEN OFF BY THE LUNGS. 339 bon into the air, since carbonic acid contains about two-sevenths of its weight of solid carbon, (p. 20.) A man of sedentary habits, or whose occupation requires lit- tle bodily exertion, may throw off in this way about five ounces of carbon in twenty-four hours — one who takes moderate exer- cise, about 8 ounces — and one who has to undergo violent bodily exertion, from 12 to 15 ounces. In our climate about one-fifth more is given off in summer than in winter. If we take the mean quantity respired at 8 ounces, then, to supply this carbon alone, a man must eat 18 ounces of starch and sugar every day.* If he take it in the form of wheaten bread, he will require 1| lb. of bread ; if in the form of pota- toes, about 7 J lb. of raw potatoes to supply the carbon which escapes through his respiratory organs alone. When the habits are sedentary, 5 lb. of potatoes may be sufficient ; when violent and continued exercise is taken, 12 to 15 lb. may be too little. At the same time, it must be observed that when the supply is less, either the quantity of carbon gi- ven off will be less also, or the deficiency will be supplied at the expense of the body itself, especially its fatty part. In either case the strength will be impaired, and increased supplies of nourishing food will be required to recruit the exhausted frame. 'Other animals give off from their lungs quantities of carbon proportioned to their weights. A cow or a "liorse, eight or ten times the weight of a man, will give off 4 to 5 lb. of carbon. The quantity of food required to supply this carbon will be pro- portionably greater. I have in the above calculations supposed that the vfhole of the carbon given off from the lungs is derived from the starch, sugar, or gum of the food. This view is the simplest, and most easily intellegible. It only requires us to suppose that in the system the starch is separated into carbon and water, of whicli, * Since 12 lb. of starch contain about 5 lb. of carbon, (see p. 43.) 340 THE BODY FED BY OXYGEN. as we have seen, (p. 43,) it may be represented to consist ; and that the former is given or burned off from the lungs in the form of carbonic acid. But many physiologists do not regard the process as being really so very simple. They consider that the carbon given off is partly derived from the gluten or flesh of the food, as well as from the starch or fat — in which case the quantity of starch or sugar in the food, as I have calculated it, need not be so large ; and it is certain that where animals live on food which contains no starch or sugar, and but little fat, the gluten or fleshy fibre it contains must yield the carbon which is given off by the lungs. 2. But when the air escapes from the mouth of a breathing animal, it contains much moisture also. It enters comparatively dry, it comes out so moist as readily to deposit dew upon any cold surface, or to form a white mist in a wintry atmosphere. This water is given off by the lungs, along with the carbonic acid, and, like it, is derived from the food, solid or liquid, which has been introduced into the stomach. It may either be part of the water which has been swallowed as such, or the water which may be supposed to exist in the starch and sugar of the food. Or it may be water formed by the union of the hj^dro gen of the other kinds of food with the oxygen inhaled by the lungs. It is probably derived in part from each of these sour- ces, in proportions which must vary with many circumstances.* 3. But the lungs actually feed the body. The air which en- ters contains more oxygen than when it returns again from the lungs. The oxygen which disappears equals in bulk very near- ly that of the carbonic acid which is evolved. This oxygen enters the lungs, through them into the blood, and with the blood flows on and circulates through the body. It also en- ters partly into the composition of the tissues, so that it is a real food, and is as necessary to the construction of the human body as the other forms of food which are usually introduced into the stomach. The weight of oxygen taken up by the DAILY WASTE OF TISSUES. 341 lungs exceeds considerably that of all the dry solid food which is introduced into the stomach of a healthy man. (See p. 38t.) 4. The purposes served by the oxygen thus introduced into the S3^stem are very difficult and complicated. But an inciden- tal circumstance, which accompanies all its operations in the system, is the evolution of heat. From the time the solid di- gestible food enters the blood till it escapes from the lungs, or in the other excretions, it is continually uniting with oxygen into new forms of combination, and at each change heat is produced or given off. Thus the animal heat is kept up, and thus it is, in a certain sense, correct to say that oxygen is taken in by the lungs for the purpose of giving warmth to the body, — or, more poetically, that the body is a lamp fed with oil from the stomach, and with air from the lungs, w^hich burns with a slow and invisible flame, but which ever does burn while life lasts, and maintains a gentle warmth through all its parts. SECTION III. — THE FOOD MUST REPAIR THE DAILY WASTE OF THE MUSCULAR PARTS AND TISSUES OF THE BODY. From every part of the growing as well as of the full-grown body, a portion is daily abstracted by natural processes, and re- jected either throtigh the lungs and skin, or in the solid and fluid excretions. This proportion is so great that in summer the body loses one-fourteenth, and in winter one-twelfth of its weight daily, when no food is taken. And if food be continu- ously withheld, the mean duration of life is only fourteen days, and the weight diminishes two-fifths. But the waste or change of material proceeds more rapidly when the animal is well fed, so that the opinion now prevails among physiologists that every twenty or thirty days the greater part of the matter of the hu- man body, when adequately fed, is constantly renewed. This waste of the tissues is more rapid in women than in children, in men than in women, and most of all in men between the ages, of 30 and 40. The amount of waste is the measure of life. 342 coMPOsmo!T op fibrin. The materials for this change must be supplied by the food And the quantities required must be adapted to the nature, age, and sex of the animal. The muscles of animals, of which lean beef and mutton are ex- amples, are generally colored by blood ; but when washed with water for a length of time, they become quite white, and, with the exception of a little fat, are found to consist of a white fibrous substance, to which the name oi fibrin has been given by chem- ists. The clot of the blood consists chiefly of the same sub- stance ; while skin, hair, horn, and the organic part of the bones, are composed of varieties of gelatim. This latter sub- stance is familiarly known in the form of glue, and though it differs in its sensible properties, it is remarkably similar to fihrin in its elementary composition, as well as to the white of the tgg, {albumen,) to the curd of milk, (casein,) and to the gluten of flour. They all contain nitrogen, and the three latter con- sist of the four organic elementary bodies very nearly in the following proportions : Carbon, ...... 55 Hydrogen, ...... 7 Nitrogen, . . . • , . .16 Oxygen, with a little sulphur and phosphorus, . 22 100 Gelatine or dry glue contains about 2 per cent more nitrogen. The quantity of one or other of these substances removed from the body in 24 hours, either in the perspiration, (p. 369,) or in the excretions, amounts to about five ounces, containing 350 grains of nitrogen ; and this waste at least must be made up by the gluten, fibrin, or other protein compounds of the food. In the 1| lb. of wheaten bread, supposed in the previpus section to be eaten to supply the carbon given off by the lungs, there will be contained also about 3 ounces of gluten — a sub- FOOD CONSUMED, 343 stance nearly identical with fibrin^ and capable of taking its place in the animal body. Let the other two ounces which are necessary to supply tlie daily wj^ste of muscle, &c., l)e made up in beef, of which half a pound contains 2 ounces of dry fibrin, and we have- — For For waste respiration. of muscle, &c. 1| lb. of bread yielding 18 oz. starch and 3 oz. of gluten. 8 oz. of beef yielding . . 2 oz of fibrin. Total consumed by I ( gluten or respiration and the >• 18 oz. starch and 5 oz.- -j ^'^j^j-j^^ ordinary waste, ) If, again, the 1\ lb. of potatoes be eaten, then in these are contained about 2^ ounces of ghiten or albumen, so that there remain 2^ ounces to be supplied by beef, eggs, milk, or cheese. The reader, therefore, will understand why a diet, which will keep up the human strength, is easiest compounded of a mix- ture of vegetable and animal food. It is not merely that such a mixture is more agreeable to the palate, or even that it is ab- solutely necessary — for, as already observed, the strength may be fully maintained by vegetable food alone ; — it is because, without animal food in one form or another, so large a bulk of the more common varieties of vegetable food requires to be consumed in order to supply the requisite quantity of nitrogen in the form of gluten, albumen, &c. Of ordinary wheateu bread alone, about 3 lb. daily must be eaten to supply the ni- trogen,* and there would then be a considerable waste of car- bon in the form of starch, by which the stomach would be over- loaded, and which, not being worked up by respiration, would pass off in the excretions. The wants of the body would be * The dry flour being supposed to contain 15 per cent of dry gluten, (a large proportion,) on which supposition all the above calculations arc made. 344 SALINE MATTER OF FLESH AND BLOOD. equally supplied, and with more ease, by 1| lb. of bread, and 4 ounces of cheese. Oatmeal, again, contains at least one-half more nitrogen than the wheaten flour of our climate (p. 283,) and hence 21b. of it will usually go as far in supplying this portion of the na- tural waste as 3 lb. of wheaten flour, and the stomach will be less oppressed. This fact throws much light on the use and value of what has been called the natural food of Scotland. The stomach and other digestive apparatus of our domestic animals are of larger dimensions, and they are able, therefore, to contain with ease as much vegetable food, of almost any wholesome variety, as will supply them with the quantity of ni- trogen they may require. Yet every feeder of stock knows that the addition of a small portion of oil-cake, or of bean- meal, substances rich in nitrogen, will not only fatten an ani- mal more speedily,, but will also sa,ve a large hulk of other kinds of food. SECTION IV. THE FOOD MUST SUPPLY THE SALINE AND EARTHY MATTERS CONTAINED IN AND DAILY REJECTED BY THE BODY. The full-grown animal daily rejects a quantity of saline and earthy matter withdrawn from its wasting tissues ; while the growing animal appropriates also every day an additional por- tion in the formation of its increasing parts. The food must yield all this, or the functions will be imperfectly performed. 1. Thejiesh, the hlood, and the other ftuids of the body con- tain much saline matter of various kinds — sulphates, muriates, phosphates, and other saline compounds of potash, soda, Hme, and magnesia. The dry muscle and blood of the ox leave, when burned, about 41 per cent of saline matter or ash. The composition of this saline matter is represented in the follow- ing table of Enderlin : — MINERAL MATTERS IN THE BODY. 345 Phosphate of soda, (tribasic,) . Chloride of sodium, (common salt,) Chloride of potassium, . Sulphate of soda, Phosphate of magnesia, Oxide, with a little phosphate of iron, Sulphate of lime, gypsum, and loss, Blood. Flesh. 16.77 45.10 59.34 ) 6.12 ■ 45.94 3.85 trace. 4.19) 8.28 • 6.84 1.45) 100 97.88 All these saline substances have their special functions to perform in the animal economy, and of each of them an unde- termined quantity daily escapes from the body in the perspira- tion, in the -urine, or in the solid excretions^ This quantity, therefore, must be daily restored by the food. 2. It is interesting to remark how the mineral matter differs in kind in the different parts of the body. Thus, blood con- tains much soda and little potash — the former in the serum, the latter in the globules — the cartilages much soda and no potash, and the muscles much potash and little soda. So T^hosphate of lime is the earth of bones, and phosphate of magnesia the earth of the muscles. So also the presence of fluo- rine characterises the bones and teeth, and that of silica, the horny parts, hair and feathers of animals — while an abundance of iron distinguishes the blood and the hair. The distinction now noticed between the blood and the mus- cle is not brought clearly out by the analysis above given of the comparative composition of the saline matter of each. It is seen more clearly in the following comparison : — The mineral matter or ash Common salt, Chloride of potassium, Potash, Soda, Phosphoric acid, Oxide of ii'on, 15* of ox blood of ox flesh contains, contains, per cent. per cent. 47 to 51 — 10 7-8 36 12 - 14 — 3 - 7 35 7 - 10 1 346 MINERAL MATTERS IN THE BODY. From the blood, therefore, as a common storehouse, each part obtains, by a kind of selection, the mineral matter which it specially requires. It has not yet been accurately determined by experiment how much saline matter must necessarily be excreted every day from the body of a healthy man, or in what proportions the different inorganic su])stances are present in what is ex- creted ; but it is satisfactorily ascertained, that without a cer- tain sufficient supply of all of them, the animal will languish and decay, even though carbon and nitrogen, in the form of starch and gluten, be abundantly given to it. It is a wise and beautiful provision of nature, therefore, that plants are so or- ganised as to refuse to grow in a soil from which they cannot readily obtain an adequate supply of soluble inorganic food, — since that saline matter, which ministers first to their own wants, is afterwards surrendered by them to the animals they are destined to feed. Thus, the dead earth and the living animal are but parts of the same system, — links in the same endless chain of natural ex- istences. The plant is the connecting bond by which they arc tied together on the one hand, — the decaying animal matter, which returns to the soil, connects them on the other. 3. The bones of the animal are supplied with their mineral matter from the same original source, — the vegetable food on which they live. The dried bones of the cow contain 55 per cent of phosphate of lime with a little phosphate of magnesia, those of the sheep 10, of the horse 61, of the calf 54, and of the pig 52 lb. of these phosphates in every hundred of dry bone. All this must come from the vegetable food. Of this bone- earth, also, a portion — varying in quantity with the health, the food, and the age of the animal — is every day rejected. The food, therefore, must contain a daily supply, or that which passes off will be taken from the substance of the living bones, and the animal will become feeble. The importance of this bone-earth will be more apparent if THE FOOD SUPPLIES THE INCREASE. 34*1 we consider, — First, that in animals the bones form not only a very important l)ut a very large part of their bodies. The body of a full-grown man contains 9 to 12 lb. of clean dry bone, yielding from 6 to 8 lb. of bone-earth. In the horse and sheep the fresh moist bone has been estimated at one-eighth of the live, or in the sheep to one-fifth of the dead weight, and to one-third of the weight of the flesh. Second, that in a growing sheep the increase of bone-earth amounts to about 3 per cent of the whole increase in the live weight. And — Third, that every hundred pounds weight of live weight indi- cates 5 or 6 of phosphate of lime. It is kindly provided by nature, therefore, that a certain pro- portion of this ingredient of bones is always associated with the gluten of plants in its various forms, — with the fibrin of animal muscle and with the curd of milk. Hence man, from his mixed food, and animals, from the vegetables on which they live, are enabled, along with the nitrogen they require, to ex- tract also a sufficiency of bone-earth to maintain their bodies in a healthy condition. SECTION V. THE FOOD MUST SUPPLY THE WASTE OR INCREASE OF FAT IN ANIMALS. Every one knows that in some animals there is much more fat than in others, but in all a certain portion exists, more or less intermingled with the muscular and other parts of the body.* This fat is subject to waste, as the muscles are, and therefore must be restored by the food. All the vegetable sub- stances usually cultivated on our farms contain, as we have seen, (p. 306,) a notable quantity of fatty matter, which seems to be intended by nature to replace that which disappears na- turally from the body. * At Port Philip, in the boiling-houses, a Merino sheep of 55 lb. gives 20 lb. of tallow, and of all weight above 55 lb. four-fifths are tallow. 348 WASTE OF THE FAT. A full-grown animal, in which the fat may be regarded as in a stationary condition, requires no more fat in its food than is necessary to restore the natural loss. In such an animal the quantity of fatty matter found in the excretions is sensibly equal to that whiqh is contained in the food. But to a growing animal, and especially to one which is fat- tening, the supply of fatty matter in the food must be greater than to one in which no increase of fat takes place. It is in- deed held, that, in the absence of oil in the food, an animal may convert a portion of the starch of its food into fat, — may become fat while living upon vegetable food in which no large proportion of fatty matter is known to exist. And it can hardly be doubted, I think, that the organs of the living ani- mal are endowed with this power of forming in a case of emer- gency — that is, when it does not exist ready formed in the food — as much fatty matter as is necessary to oil the machinery, so to speak, of its body. But the natural source of the fat is the oil contained in the food it eats, and an animal, if inclined to fatten at all, will always do so most readily when it lives upon food in which oil or fat abounds. It does not however follow, because fat abounds in the food, that the animal should become fatter,— since if starch be defi- cient in the food, the fat containing no nitrogen, may be decom- posed and worked up for what may be called the purposes of respiration. This working up of the fat, already existing in the body, is one cause of the rapid emaciation and falling away of fat animals when the usual supply of food is lessened, or for a time altogether withheld. The fat is indeed considered by some as nothing more than a store laid up by nature in a time of plenty to meet the wants of respiration when a season of scarcity arrives, — that a fat animal is like a steam-frigate heavily laden with fuel, which it burns away during its voyage for the purpose of keeping up the steam. It is by reference to this supposed purpose of the fat of the body, and to the possibility of using it up for the purposes of PURPOSES SERVED BY THE FAT. 349 respiration, that the benefits of repose, of shelter, of moderate warmth, of the absence of light, and even of a state of torpor, in conducing to the more speedy fattening of cattle and sheep, are explained. Exercise causes more frequent respirations, and hence a greater waste of that part of the food which should be laid on in the form of fat. Cold also has the same effect, since more heat must be produced in the interior of the animal — in other words, more frequent respiration must take place, in order to make up for the greater loss of heat by exposure to the extenial air. Thus, as was stated at the commencement of the present chapter, a study of the nature and functions of the food of ani- mals throws additional light upon the nature also and final uses of the food of plants. It even teaches us what to look for iu the soil — what a fertile soil must contain that it may grow nou- rishing food — what we must add to the soil when chemical analysis fails to detect its actual presence, or when the food it produces is unable to supply all that the animal requires. SECTION VI. SPECIAL WASTE IN THE PERSPIRATION OF ANIMALS, AND IMPORTANCE OF THIS FUNCTION. Animals perspire that they may live, and this function is as necessary to a healthy life as either breathing or digestion. The skin, like the lungs, gives off carbonic acid and absorbs oxygen. But it differs from the lungs in giving off a much larger bulk of the former gas than it absorbs of the latter. The quantity of carbonic acid which escapes varies with cir- cumstances. It is sometimes equal to a thirtieth, and some- times amounts only to a ninetieth part of that which is thrown off from the lungs. But exercise and hard labor increase the evolution of carbon from the skin, as it does from the lungs. In motion, the human body gives off nearly three times as much as when it is at rest ; while from a horse, when put to the 350 CARBONIC ACID AND NITROGEN FROM THE SKIN. trot, the^ carbonic acid of the skin augments as mucli as an hundred and seventy times. (Gerlach.) Water is also given off from the skin as from the lungs, and every one knows that fat exudes from its pores and lubricates the surface of the body. The salt taste of the perspiration is an equally familiar proof that a portion, at least, of the saline matter derived from the waste and change of materials in the body escapes through this channel. Nitrogen also escapes from the skin. The quantity of nitro- gen in the food is a third or a fourth greater than that contained in the solid and liquid excretions. (Barral.) This third or fourth, therefore, is supposed to be given off by the organs of perspiration, the lungs and the skin. A cow or a horse is reck- oned to exhale by the skin and lungs about 400 grains of nitro- gen daily ; a man, perhaps, 100 ; and a sheep or pig 80 grains. (BOUSSINGAULT.) The functions of the skin, therefore, are very important ; and thus, in the practical feeding of animals, a healthy and clean condition of the skin must contribute not only to healthy growth, but to a profitable employment of vegetable produce in rearing, maintaining, and fattening them.* SECTION VII. FORMS IN WHICH THE SOLID MATTERS OF THE TISSUES ESCAPE IN THE URINE. The lungs throw off, in the form of gas or vapor, a large pro- portion of the matters which, after being taken into the stomach, have already served their purpose in the body. The kidneys remove the greater part of that which is derived from the destruction of the tissues. The solid excretions in man amount * Six pigs were put up together for seven weeks. Three were curry- comlaed and eared for — the other three left to themselves; the former three consumed five bushels of pease less, and had gained 2 stones 4 pounds more, than the uncurried three. The skins of pigs fed in the forest, in the season of the acorns, are white and shininjr. SALTS AND NITROGEl^ IN THE URINE. 351 only to a fourteenth or an eighteenth of the whole food con- suraetl. In a state of health, the saline substances of the food escape for the most part in the urine. The mineral matter contained in that part of the solid excretions which has undergone diges- tion, consists chiefly of earthy salts and of iron. In man, and in our domestic animals, the nitrogen of the food and tissues is also separated from the blood by the kidneys, and is found in the urine. It is chiefly in the form of a sub- stance to which the name of urea is given. In birds, serpents, and insects, it is separated in the form of uric acid. The urine Toided by a healthy man in 24 hours, averages about 40 ounces, and contains about 150 grains of solid matter, which has served its purpose in the system. Of this solid matter, about 2t0 grains consist of urea, 8 of uric acid, and 110 of mineral or saline matter. The -urine of the horse is richer in urea than that of the cow, and that of the cow than the urine of man. It is this urea which, during the fermentation or ripening of urine, becomes changed into ammonia. The urea and uric acid discharged daily in the urine of a healthy man, contains about half an ounce of nitrogen — to fur- nish which requires 3 ounces of dry gluten, albumen, or flesh. If so large a proportion of that which is most valuable in food, and which has been derived from the decay of the tis- sues of the body, is contained in the urine, it ought to be an important object to the farmer to contrive some method of re- turning it without loss to the soil, that it may aid again in rais- ing new vegetables as food for other animals. SECTION VIII. GENERAL BALANCE OF FOOD AND EXCRETIONS IN MAN. The general balance of the food taken into the human body and of the excretions of various kinds, has been thus represent- ed by M. Barral : 352 BALANCE OF FOOD AND EXCRETIONS. Evenj 100 parts taken in, consist of— Food, solid and liquid, containing in all '75 per cent of water . 14.4 Oxygen taken in by the lungs, 25. G 100 And are given off as — "Water perspired by the lungs and skin, . . . . 34.8 Carbonic acid, do. do., 30.2 Evacuations, solid and liquid, 34,5 Other losses, 0.5 100 In general, the substances perspired are to the evacuations as 2 to 1. Of course, in an estimate of this kind, it is impossible accu- rately to put down the several quantities given off in the form of hair, nails, surface skin — both of the outer and inner parts of the body — &c., &c., all of which are constantly shed or cut, and as constantly renewed. It is useful, however, in show- ing generally the relation which the oxygen inspired bears to the other food which the stomach receives, and the proportion of the work of excretion performed respectively by the per- spiring organs, and by the organs of evacuation. SECTION IX. KIND OF FOOD REQUIRED BY ANIMALS AS INDICATED BY THE COMPOSITION OF THE BLOOD. A knowledge of the kind of food required by animals may be gathered, as we have seen, from the composition of tlie several parts of the animal body, and a study of the functions they perform. The muscles must be sustained ; therefore glu- ten, albumen, &c. — often popularly called muscular matter, must be eaten. The fat of the body must be renewed, and hence fat should be present in the food. And, as much carbon escapes from the lungs and skin, it seems natural, if not abso- lutely necessary, that starch or sugar should be introduced into the stomach with the view of supplying it. The mineral mat- WHAT THE BLOOD TEACHES. 353 ter of the flesh, blood, and bones, must in like manner be pro- vided. Tlie study of the excretions indicates, besides, the quantity of food of each kind which ought to be consumed. The quantity of carbon evolved in the form of carbonic acid, of nitrogen in the forms of urea and uric acid, and of saline matters in the urine and solid excretions of a healthy man, afford a means of ap- proximating very nearly to the quantity of each which a suffi- cient food ought to contain ; but the excretions do not alone tell us in what forms the carbon, nitrogen, and saline matters are best suited to the wants of the animal. An examination of the blood gives us this latter information very clearly. The blood consists essentially, besides the water, of albumen, sugar, fat, and saline matter. The main purpose or object of the process of digestion is to form blood ; for out of the blood are drawn the materials necessary to the wants of the bones, and of the various tissues and fluids of the body. Those forms of vegetable or animal matter, therefore, must be best adapted for food, which most resemble the ingredients^ of the blood which is to be produced from them. These will give the digestive organs least trouble, or will be most easily digested. Thus we arrive again at the conclusion that a healthy, nourishing, and easily digestible food ought to contain gluten or albumen, sugar or starch — which, in the stomach, readily changes into sugar — fat either of animal or vegetable origin, and saline or mineral matters of various kinds. Of course, if the stomach of the animal be in an unhealthy condi- tion, the quality of the food may require to be adapted to its unnatural condition ; but this does not affect our general con- clusion. SECTION X. IMPORTANCE OF A MIXED FOOD. All these different modes of examining the question, there- fore, indicate not only the advantage but the necessity of a 354 IMPORTANCE OF A MIXED FOOD. mixed food to the healthy sustenance of the animal body. Hence the value of any vegetable production, considered as the sole food of an animal, cannot be accurately determined by the amount it may contain of any one of those substances, all of which together are necessary to build up the growing body of the young animal, and to repair the natural waste of such as have attained to their fullest size. Hence the failure of the attempts that have been made to support the lives of animals by feeding them upon pure starch or sugar alone. These substances would supply the carbon perspired by the lungs and the skin ; but all the natural waste of nitrogen, of saline matter, of earthy phosphates, and probably also of fat, must have been withdrawn from the existing solids and fluids of their living bodies. The animals, in consequence, pined away, became meagre, and sooner or later died. So some have expressed surprise that animals have refused to thrive — have ultimately died, when fed upon animal jelly or gelatine alone, nourishing though that substance, as jpart of the food, undoubtedly is. When given in sufficient quantity, gela- tine might indeed supply carbon enough for respiration, with a great waste of nitrogen, but it is deficient in the saline in- gredients which a naturally nourishing food contains. Even on the natural mixture of starch and gluten which ex- ists in fine wheaten bread, dogs have been unable to live be- yond 50 days, though others fed on household bread, contain- ing a portion of the bran — in which earthy matter more largely resides — continued to thrive long after. It is immaterial whe- ther the general quantity of the whole food be reduced too low, or whether one of its necessary ingredients only be too much diminished or entirely withdrawn. In either case the effect will be the same — the animal will become weak, will dwindle away, and will sooner or later die. The skill of the feeder may often be applied with important economical effects to the proper selection and mixture of the VALUE OF OILY FOOD IN FATTENING. 355 food he gives his animals generally, and at various stages of their growth. It has been found by experiment, for example, that food which, when given alone, does not fatten, acquires that pro- perty in a high degree when mixed with some fatty substance, and that those which are the richest in the muscle-forming in- gredients produce a comparatively small effect, unless they con- tain also, or are mixed with, a considerable proportion of fatty matter. Hence the reason why a stone of linseed has been found by some to go as far as two stones of linseed cake, and why the Rutlandshire farmers find a sprinkling of linseed oil upon the hay to be a cheap, wholesome, and fattening addition to the food of their cattle and horses. A Merino sheep of 55 lb. contains about 20 lb. of fat, but four-fifths of any subsequent addition consists of tallow, (p. 34 1 note ;) hence w^e may infer that oily food should be profit- able in fattening sheep. To pigs the same remark appUes ; and, in practice, fat of any kind, animal or vegetable, is found to be a profitable addition to the food of these animals when they are to be fattened off. CHAPTER XXY. Feeding of animals continued. — Kind and quantity of food necessary to maintain a healthy man. — Prison dietaries. — Food required by other animals. — Practical value of the constituents of milk in feeding the growing calf — Effect of long-continued dairy husbandry upon the quality and produce of the soil. — On the growing of wool, and its effect upon the soil. — Of the practical and theoretical values of different kinds of food. — Relative proportions of food for man yielded by the same herbage in the forms of beef and milk. — Influence of circumstances in modifying the practical values of animal and vegetable food. — Concluding observa- tions. Practical experience sustains and confirms all the theoretical views, and the deductions, chemical and physiological, which have been advanced in the preceding chapter. To a few of these practical confirmations I shall briefly advert. SECTION I. KIND AND QUANTITY OF FOOD NECESSARY TO MAINTAIN A HEALTHY MAN. PRISON DIETARIES. — FOOD REQUIRED BY SHEEP AND CATTLE. The dietaries of prisons, and their effects on the bodily health and weight of the" prisoners, afford one of the simplest methods of testing the influence of kind and quantity upon the nourishing power of food. In such establishments — though open to the objection that the prisoners are in a state of un- usual restraint — experiments can be performed so much more accurately, and on so much larger a scale than elsewhere, as to make them worthy of a very considera^ble amount of confi- dence. An inquiry lately made into the comparative health and food SCOTCH PRISON DIETARIES. 357 of the inmates of the Scotch prisons, has aiforded very inter- esting materials for proving the necessity of a mixed food, and of a certain minimum proportion of that kind of food which is supposed especially to sustain the muscular and other tissues. In the course of the preceding chapter we have stated : 1°. That a healthy man in ordinary circumstances voids daily about half an ounce of nitrogen in his urine alone, (p. 351.) To supply this he would require to consume three ounces of dry gluten, albumen, or flesh. 2°. That altogether he gives off from the lungs, skin, and kidneys, about 350 grains, or five-sevenths of an ounce, to supply which he must consume about five ounces of the same rdaterials, (p. 342.) But in a state of temporary confinement, when not subjected to hard labor, this quantity may be safely diminished. Yet even here there is a limit below which it is unsafe to go. In the Scotch prisons the weight of food is given to prisoners con- fined for not more than two months, and not subjected to hard labor, is uniformly about 1 1 ounces, and the proportion of glu- ten or nitrogenous food contained in this is about four ounces. Where this proportion is maintained, the average general health and weight of the prisoners improves during their confinement. Where the contrary is the case, the weight diminishes, -and the health declines. This is shown in the following tabular view of the kinds and weight of food given in five of the Scotch prisons, and its effects upon the weight of the prisoners : — Jail. Food givex. Per-centage of pri- soners who lost weight. Nitrogenous. Carbonaceous. Total. Edinburgh, Glasgow, Aberdeen, Stirling, Dundee, 4 oz. 4.06 3.98 4.27 2.75 13 oz. 12.58 13.03 13.4 14 17 oz. 16.84 17 17.67 10.75 18 lost IJ lb. each 32.66 4 V 32 4.2 " 50 4.35 " 358 THEIR RESULTS. This table shows that, with the Edinburgh dietary and man- agement, 12 per cent of the prisoners either maintained or in- creased their weight, while only 18 per cent diminished in weight, and that only to the small extent of IJ lb. each. In Glasgow the result was less favorable, though even there, out of nearly 500 prisoners, only one-third diminished in weight. The same was the case at Aberdeen and Stirling ; so that in these three places the diet may be regarded as, on the whole, sufiicient. But in Dundee, one-half of the prisoners (50 per cent) lost weight during their short confinement ; and the cause is obvious, in the diminished proportion of mascle-forming food, which in this case was reduced to 2j, in place of four ounces. And it is an interesting fact, as marking the close connection between science and practice, that this deterioration in the quality of the diet was caused by the substitution of molasses for the milk, which had been previously distributed to the pri- soners along with their porridge of oatmeal. Milk is rich in nitrogenous food, while molasses contains none ; and the sub- stitution was immediately followed by a perceptible falling off in the health and weight of the prisoners. So general are the evils which may arise from ignorance or disregard of scientific principles in a single director or directing 'body. The appa- rently trivial substitution of molasses for milk brought weakness and want of health on the inmates of an entire prison. In the feeding of other animals, similar results follow from similar inattention to the requirements of animal nature. Of dry hay it has been found, in practice, that cattle and sheep require for their daily food — An ox at rest, 2 per cent of his live weight. . . at work, 2\ . . . . fatting, 5 at first. .. half fat, 4^ .. when fat, 4 Milch cow, 3 Sheep, full grown, 3 J . . FOOD REQUIRED BY ANIMALS. 359 In the case of the ox tlie daily waste or loss of muscle and tissue requires that he should consume 20 to 24 ounces of glu- ten or albumen, which, as may be calculated from the table given in a subsequent section, (p. 364,) will be supplied by any of the following weights of vegetable food^ : — Meadow hay, . . 20 lb. Turnips, 120 lb. Clover hay, 16 " Cabbage, 70 " Oat straw, . 110" Wheat or other white grain, 11 " Pea straw, 12 " Beans or pease, 6 " Potatoes, 60" Oil-cake, 4 " Carrots, . . *70" Or instead of any one of these, a mixture of several may be given, with the best results. But if the due proportion of ni- trogenous food be not given, the ox will lose his muscular strength, and will generally fail. So with growing and fatting stock of every kind, the proportion of each of the kinds of food required by the animal must in practice be adjusted to the purpose for which it is fed, as theory indicates, or actual money loss will ensue to the feeder. SECTION II. PRACTICAL VALUE OF SALINE AND OTHER INGREDIENTS OF MILK IN FEEDING THE GROWING CALF. In the course of the preceding section I have incidentally remarked, that the substitution of molasses for milk lowered the proportion of nitrogenous food in the Dundee prison diet, and rendered it insufficient for the healthy maintenance of the prisoners. The reason of this appears in the composition of milk, already given in a previous chapter. The consideration of milk as a natural food supplies us with another beautiful practical illustration of our theoretical principles, to which I shall briefly advert ; and I do so, not merely because of the light it throws upon the supply of nitrogen which a milk diet is fitted to yield, but because it so clearly illustrates another of the positions laid down in the preceding chapter, that the food 860 MILK A TRUE FOOD. must supply, in kind and quantity, all the saline and earthy substances contained in the body. Milk is a true food. It contains sugar, casein, saline mat- ter, and fat — a portion of each of those classes of substances on which the herbivorous races live in the most healthy man ner. But the provision is very beautiful by which the young animal — the muscle and bones of which are rapidly growing — is supplied, not only with a large proportion of nitrogenous food, but also of bone-earth, than would be necessary to main- tain the healthy condition of a full-grown animal of fiqual size. The milk of the mother is the natural food from which its sup- plies are drawn. The sugar of the milk supplies the compara- tively small quantity of carbon necessary for the respiration of the young animal. As it gets older, the calf or young lamb crops green food for itself, to supply an additional portion. The curd of the milk (casein) yields the materials of the grow- ing muscles and of the organic part of the bones ; while along with the curd, and dissolved in the liquid milk, is the phosphate of lime, of which the earthy part of the bones is to be built up. A glance at the composition of milk will show how copi- ous the supply of all these substances is, — how beautifully the composition of the mother's milk is adapted to the wants of her infant offspring. Cow's milk consists in 1000 parts by weight of about — Butter, 21 Cheesy matter, (casein,) 45 Milk-sugar, 36 Chloride of potassium^ and a little common salt, . 14 Fhosjyhates, chiefly of Ume^ 24 Other saline substances, 6 Water, 882^ 1000 The quality of the milk, and consequently the proportions of the several constituents above mentioned, vary, as I have ex- plained in a preceding chapter, with the breed of the cow — DAIRY HUSBANDRY AFFECTS THE SOIL 361 with the food on which it is supported — with the time that has elapsed since the period of calving — with its age, its state of health, and with the warmth of the weather;* but in all cases this fluid contains the same substances, though in different quantities and proportions. Milk of the quality above analysed contains, in every 10 gal- lons, 4| lb. of casein, equal to the formation of 18 lb. of ordi- nary muscle, — and 3 J ounces of phosphate of lime, (bone- earth,) equal to the production of t ounces of dry bone. But from the casein have to be formed the skin, the hair, the horn, the hoof, &c., as well as the muscle ; and in all these is con- tained also a minute quantity of the bone-earth. A portion of all the ingredients of the milk likewise passes off in the ordi- nary excretions, and yet every one knows how rapidly young animals thrive, when allowed to consume the whole of the milk which nature has provided as their most suitable nourish- ment. SECTION III. — EFFECT OF LONG-CONTINUED DAIRY HUSBANDRY UPON THE QUALITY AND PRODUCE OF THE SOIL. And whence does the mother derive all this gluten and bone- earth, by which she can not only repair the natural waste of her own full-grown body, but from which she can spare enough also to yield so large a supply of nourishing milk ? She must extract them from the vegetables on which she lives, and these again from the soil. The quantity of solid matter thus yielded by the cow in her milk is really very large, if we look at the produce of an entire year. If the average yield of milk be 3000 quarts, or 750 gallons, in a year, (every 10 gallons of which contain bone- earth enough to form about 7 ounces of dry bone, ) then by the * In warm weather the milk contains more butter, in cold weather more cheese and suocar. 363 BY REMOVING BONE-EARTH. milking of tlie cow alone we draw from her the earthy ingre- dients of 33 lb. of dry bone in a year. These are equal to 40 lb. of (Common bone-dust,, or 3J lb. in a month. And these she draws necessarily from the soil. If this milk be consumed on the spot, then all returns again to the soil on the annual manuring of the land. Let it be carried for sale to a distance, or let it be converted into cheese and butter, and in this form exported — there will then be yearly drawn from the land from this cause alone a quantity of the materials of bones which can only be restored by the ad- dition of 40 lb. of bone-dust to the land. If to this loss from the milk we add only 10 lb. for the bone carried off by the yearly calf,* the land will lose by the practice of dairy hus- bandry as much bone-earth as is contained in 50 lb. of bone- dust — or in 45 years every imperial acre of land will lose what is equivalent to a ton of bones. After the lapse of centuries, therefore, we can easily under- stand how old pasture lands, in cheese and dairy countries, should become poor in the materials of bones — and how in such dis- tricts, as is now found to be the case in Cheshire, the applica- tion of bone-dust should entirely alter the character of the grasses, and renovate the old pastures. SECTION IV. — OF THE GROWING OF WOOL, AND ITS EFFECTS UPON THE SOIL. The rearing of wool affords another beautiful practical illus- tration, both of the kind of food which animals require i'or par- * It has been estimated that the proportion of bone in the — Horse, . . . . = .125of thehve weight. Sheep, old, (Merino,) . . == .125 of live, 20 of dead diO. = .33 nearly, of flesh and fat Pig, unfatted, . . . ^ = .1'? of live, .20 of dead do. And generally, that 100 hve weight indicate 2 to 3 of phosphoric acid ; but these proportions are, no doubt, subject to great variation. LONG GROWTH OF WOOL ON THE LAND. 363 ticular purposes, and of the effect which a peculiar husbandry must slowly produce upon the soil. Wool and hair are distinguished from the fleshy parts of the animal by the large proportion of sulphur they contain. Per- fectly clean and dry wool contains about 6 per cent of sulphur, or every 100 lb. contains 5 lb. The quantity as well as the quality of the wool yielded by a single sheep varies much with the breed, the climate, the con- stitution, the food, and consequently with the soil on which the food is grown. The Hereford sheep, which are kept lean, and give the finest wool, yield only 1^ lb. ; but a Merino often gives a fleece weighing 10 or 11 lb., and sometimes as much as 12 lb. The number of sheep in Great Britain and Ireland amounts to 30 millions, and their yield of wool to 111 millions of pounds, or about 4 lb. to the fleece. This quantity of wool contains 5 millions of pounds of sulphur, which is of course all extracted from the soil. If we suppose this sulphur to exist in, and to be extracted from, the soil in the form of gypsum, then the plants which the sheep live upon, must take out from the soil, to produce the wool alone, 30 millions of pounds, or 13,000 tons of gypsum. Now, though the proportion of this gypsum lost by any one sheep farm in a year is comparatively small, yet it is reasonable to beUeve that, by the long growth of wool on hilly land, to which nothing is ever added, either by art or from natural sources, those grasses must gradually cease to grow in which sulphur most largely abounds, and which favor, therefore, the growth of wool. In other words, the produce of wool is likely to diminish, by lapse of time, where it has for centuries been yearly carried off the land; and, again, this produce is likely to be increased in amount when such land is dressed with gypsum, or with other manure in which sulphur naturally ex- ists. Of course, this general conclusion will not apply to lo- 364 PRACTICAL AND THEORETICAL VALUES calities whicli derive from springs or other natural sources a supply of sulphur equal to that which is yearly removed. SECTION V.- -OF THE PRACTICAL AND THEORETICAL VALUES OF DIF- FERENT KINDS OF FOOD. From what has been stated in the preceding sections, it ap- pears, as the result both of theory and of practice, that dif- ferent kinds of food are not equally nourishing. This fact is of great importance, not only in the preparation of human food, but also in the rearing and fattening of stock. It has, there- fore, been made the subject of experiment by many practical agriculturists, with the following general results : 1. If common hay be taken as the standard of comparison, then, to yield. the same amount of nourishment as 14 lb. of hay, experiments on feeding made by different persons, and in dif- ferent countries, say that a weight of the other kinds of food must be given, which is represented by the number opposite to each in the following table : — Hay, 10 Carrots, (white,) 45 Clover hay, 8 to 10 Mangold-wurtzel, . 35 Green clover, 45 " 50 Turnips, 50 Wheat straw, 40 " 50 Cabbage, 20 " 30 Barley straw, ■ 20 " 40 Pease and beans. 3 " 5 Oat straw, 20 " 40 Wheat, . 5 " 6 Pea straw, 10 " 15 Barley, . 5 " 6 Potatoes, 20 Oats, . 4 " 1 Old potatoes 40 ? Indian corn, . 5 Carrots, (red) 25 " 30 On-cake, 2 " 4 It is found in practice, as the above table shows, that twenty stones of potatoes, or three of oil-cake, will nourish an animal as much as ten stones of hay will, and 5 stones of oats as much as either. Something, however, will depend upon the quality of the sample of each kind of food used — which we know varies very much, and with numerous circumstances; and something also upon the age and constitution of the animal, OF DIFFERENT KINDS OF FOOD. 365 and upon the way and form in which the food is administered. The skilful rearer, feeder, and fattener of stock knows also the value of a change of food, or of a mixture of the different kinds of vegetable food he may have at his command — a sub- ject we have considered in a previous section, 2. The generally nutritive value of different kinds of food has also been represented theoretically, by supposing it to be very nearly in . proportion to the quantity of nitrogen, or of gluten, which vegetables contain. Though this cannot be con- sidered as a correct principle, yet as the ordinary kinds of food on which stock is fed contain in general an ample supply of carbon for respiration, with a comparatively small proportion of nitrogen, these theoretical determinations are by no means without their value, and they approach, in many cases, very closely to the practical values above given, as deduced from actual trial. Thus assuming that 10 lb. of hay yield a certain amount of nourishment, then of the other vegetable substances it will be necessary, according to theory, to give the following quantities, in order to produce the same general effect in feeding Hay, . . Clover hay,* Vetch hay, "Wheat straw, Barley straw, Oat straw, Pea straw. Potatoes, Old potatoes, Turnips, Mangold- wurtzel, 10 8 4 52 52 55 6 28 40 60 50 Carrots, (red,). . Cabbage, . Pease and beans. 35 30 to 40 2 to 3 Wheat, Barley, Oats, 5 6 5 Rye, Indian com, 5 6 Bran, Oil-cake, : 5 2 If the feeder be careful to supply his stock with a mixture or occasional change of food — and especially, where necessary, with a proper proportion of fatty matter — he may very safely regulate, by the numbers in the above tables, the quantity of * Both cut in flower. 366 ON WHAT TUE FATTENING PROPERTY any one which he ought to substitute for a given weight of any of the others — since the theoretical and practical results do not in general very greatly differ. 3. As has been already stated, however, it is not strictly cor- rect that this or that kind of vegetable is more fitted to sustain animal life, simply because of the large proportion of nitrogen or gluten it contains; but it is wisely provided that, along with this nitrogen, all plants contain a certain proportion of starch or sugar, and of saline and earthy matter — all of which, as we have seen, are required in a mixture which will most easily sus- tain an animal in a healthy condition; so that the proportion of nitrogen in a substance may be considered as a rough jprao Heal index of the proportion of the more important saline and earthy ingredients also. 4. It is very doubtful, however, how far this proportion of nitrogen can be regarded as any index of the fattening pro- perty of vegetable substances. If the fat in the body be pro- duced from the oil in the food, it is certain that the proportion of this oil in vegetable substances is by no means regulated by that of the gluten or other analogous substances containing ni- trogen. The stock farmer who wishes to lay on fat only upon his animals, must therefore be regulated by another principle. He must select those kinds of food, such as linseed and oil- cake, in which fatty matters appear to abound, or mix, as I have already said, (p. 354,) a due proportion of fat or oil with the other kinds of food he employs. But large quantities of fat accumulate in the bodies of most animals, only when they are in an unnatural, and, perhaps in some measure, an unhealthy condition. In a state of nature there are comparatively few animals upon which large accumu- lations of fat take place. A certain portion, as we have seen, is necessary to the healthy animal ; but it is an interesting fact, that as much as is necessary to supply this is present in most kinds of vegetable food. In wheaten flour it is asso- ciated with the gluten, and niny be extracted from it after the OF FOOD DEPENDS. 36T starch of the flour has been separated from the gluten by washmg with water, as akeady described (pp. 40 and 45.) In so far, therefore, as this comparatively small necessary quantity of fatty matter is concerned, the proportion of nitrogen may a^so be taken, without the risk of any serious error, as a prac- tical indication of the ability of the food to supply the natural waste of fat in an animal which is either growing in general size only, or is only to be maintained in its existing condition. While, therefore, it appears from the study of the principles upon which the feeding of animals depends, that a mixture of various principles is necessary in a nutritive food, it is interest- ing to find that all the kinds of vegetable food which are raised, either by art or by natural growth, are in reality such mixtures of these several substances — more or less adapted to fulfil all the conditions required from a nutritious diet, accord- ing to the state of health and growth in which the animal to be fed may happen to be. An important practical lesson on this subject, therefore, is taught us by the study of the wise provisions of nature. Not only does the milk of the mother contain all the elements of a nutritive food mixed up together — as the egg does also for the unhatched bird — but in rich natural pastures the same mixture uniformly occurs. Hence, in cropping the mixed herbage, the animal introduces into its stomach portions of various plants — some abounding more in starch or sugar, some more in gluten or albumen — some more in fatty matter — while some are natu- rally richer in saline, others in earthy constituents ; and out of these varied materials the digestive organs select a due propor- tion of each and reject the rest. Wherever a pasture becomes usurped by one or two grasses — either animals cease to thrive upon it, or they must crop a much larger quantity of food to supply from this one grass the natural waste of all the parts of their bodies. It may indeed be assumed as almost a general principle, that whenever animals are fed on one kind of vegetable only, there 368 COMPARATIVE PRODUCE OF BEEF AND MILK. is a waste of one or other of the necessary elements of animal foodj and that the great lesson on this subject taught us by na- ture is, that by a judicious admixture, not only is food economis- ed, hut the labor imjposed ujpon the digestive organs is also materi- ally diminished. • SECTION VI. RELATIVE PROPORTIONS OF FOOD FOR MAN YIELDED BY THE SAME HERBAGE IN THE FORMS OF BEEF AND MILK. A curious economical question, in connection with the value of vegetable produce in feeding cattle, presents itself to us when we come to compare the proportions of human food which may be obtained from the same weight of herbage when cattle are fed with it for different immediate purposes. A ton of hay may be given to a bullock to be converted into beef. Another ton of the same hay may be . given to a cow to be converted iiito milk. Would the beef or the milk produced contain the larger supply of food for man ? We have rather imperfect data to rely upon in answerisg this question, but they lead us to very interesting results. 1. According to Sir John Sinclair, the same herbage which will add 112 lb. to the weight of an ox, will enable a cow to yield 450 wine gallons, or 3600 lb. of milk. This milk will contain 160 lb. of dry curd, 160 lb. of butter, 180 lb. of sugar, and 18 lb. of saline matter, while the 112 lb. of beef will not contain more than 25 lb. or 30 lb. of dry muscle, fat, and sa- line matter together ; that is to say, the same weight of herb- age which will produce less than 30 lb. of dry human food in the form of beef, will yield 500 lb. in the form of milk. 2. But this statement of Sir John Sinclair's is, I fear, not to be relied upon. We have another, however, something differ- ent, from Riedesel, a Continental authority. He says that the same quantity of hay will produce either 100 lb. of beef, or 100 imperial gallons (1000 lb.) of milk. This quantity of CIRCUMSTANCES MODIFY 369 milk contains only 150 lb. of dry food, but it is still five times as much as is contained in the beef. This statement of Riedesel is also to be received with hesita- tion ; but the subject is interesting and important, as well as curious, and is deserving of further investigation. Should the population of the country ever become so dense as to render a rigorous economy of food a national question, butcher-meat, if the al)ove data deserve any reliance — will be banished from our tables, and a milk diet will be the daily sustenance of al- most all classes of society. SECTION. VII. INFLUENCE OF CIRCUMSTANCES IN MODIFYING THE PRACTICAL VALUES OF ANIMAL AND VEGETABLE FOOD. The indications of theory, and the results of general prac- tice, in regard to the nutritive power of different vegetable substances, are modified by many circumstances which ought to be borne in mind. Whether fed for work, or for the produc- tion of flesh or milk, the eflfect of the food given to animals will depend partly on the kind, breed, and constitution of the ani- mal itself — on the general treatment to which it is subjected, and the place in which it is kept — on its size and state of health — and on the form in which the food itself is given. 1. The breed or constitution, every feeder knows, has a great influence on the apparent value of food. Some breeds, like the improved short-horn, have a natural tendency to fatten, which makes them increase in weight more rapidly than other breeds, when fed upon the same food. And even in the same breed, the rapidity with which one animal lays on flesh will sometimes make it two or three times more profitable to the farmer than others which are fed along with it. 2. Warmth and shelter cause the same amount of food to go farther, as do also gentle treatment and the absence of glaring light. Sheep have produced double the weight of mutton from the same weight of vegetable food, when fed under shel- 3 to THE PRACTICAL VALUE OF FOOD. ter, and kept undisturbed and in the dark. It is probably from this beneficial influence of warmth that, in the North American states, a difference of 25 per cent is observed in favor of the spring and summer over the winter feeding of the pigs upon similar food. 3. The form in which the food is given is of no less importance- Grass newly cut goes farther than after it is made into hay; and the opinion is now becoming very generally prevalent, that steamed, boiled, or otherwise prepared food, is more whole- some for .cattle, and more economical to the feeder, than the same food given in a dry state. In the case of horses, the difference between the practice of giving all the food dry and uncut, and that of giving all the hay cut with the oats and beans crushed, and an evening meal of steamed food, is such as to effect a saving of nearly one- third. Thus, the same waggon horses which consumed 8J bushels of oats per week, and 14 stones of hay, when given uncut, uncrushed, and uncooked, were kept in good condition by 2J bushels of oats, 8 stones of hay, and *I lb. of linseed when the grain was crushed, the hay cut into half-inch chaff, and the linseed with a little bean-meal and cut hay made into a steamed meal-feed ii^the evening.* 4. The malting and sproibting of harky is by many practical men considered to increase its nutritive qualities. It is certain that, when mixed with boiled potatoes to the extent of three or four per cent, and kept warm for a few hours, bruised malt produces a prepared food which is much relished by milch cows, and is profitable to the dairy-man. There is reason to believe that similar mixtures with other kinds of food would produce similar beneficial effects. Mr. Hudson, of Castle Acre, feeds his farm-horses on 12 lb. of sprouted barley a-day, besides their fodder ; and this, on his * The dry feeding being — hay 12 lb., with oats and beans 14 lb. ; the steamed feed — hay 3 lb., beans 3 lb., linseed 1 lb. — Caird's English Agri- culture, p. 346. CONCLUDING REMARKS. 311 light land, keeps them in good condition. It is prepared by steeping the barley for 24 honrs, and then putting it into a heap and turning it over for five days.* 5. The souring of food of all kinds has, by almost universal consent, been found to make it more jn'ofitable in the feeding and fattening of pigs. It makes them fatten faster, and gives a firmer and whiter flesh. Many other circumstances also modify the real practical value of food, and cause it to produce results different from those indicated by its chemical composition. But to those, want of space does not permit me here to advert. SECTION VIII. CONCLUDING REMARKS. In the little work now brought to a close, I have presented the reader with a brief, but I hope plain and familiar sketch of the various topics connected with Practical Agriculture, on which the sciences of Chemistry, Geology, and Chemical Phy- siology are fitted to throw the greatest light. We have studied the general characters of the organic and inorganic elements of which the parts of plants are made up, and the several compounds of these elements Avhich are of the greatest importance in the vegetable kingdom. We have exa- mined the nature of the seed — seen by what beautiful pro- vision it is fed during its early germination — in what forms the elements by which it is nourished are introduced into the cir- culation of the young plant when the functions of the seed are discharged— and how earth, air, and water, are all made to minister to its after-growth. We have considered the various chemical changes which take place within the growing plant during the formation of its woody stem, the blossoming of its flower, and the ripening of its seed or fruit, — and have traced the further changes it undergoes, when, the functions of its, * Oaird's English Agriculture, p. 168. 312 CONCLUDING REMARKS. short life being discharged, it hastens to serve other purposes, by minghng with the soil, and supplying food to new races. The soils themselves in which plants grow, their nature, their origin, the causes of their diversity in mineral character, and in natural productiveness, have each occupied a share of our attention — while the various means of improving their agricul- tural value by mechanical means, by manuring or otherwise, have been practically considered, and theoretically explained. Lastly, we have glanced at the comparative worth of the va- rious products of the land as food for man or other animals, lind have briefly illustrated the principles upon which the feed- ing of animals, and the relative nutritive powers of the vegeta- bles on which they live, and of the parts of animal bodies themselves, are known to depend. In this short and familiar treatise I have not sought so much to satisfy the demands of the philosophical agriculturist, as to awaken the curiosity of my less instructed reader, to show him how much interesting as well as practically useful informa- tion Chemistry and Geology are able and willing to impart to him, and thus to allure him in quest of further knowledge and more accurate details to my larger work,'^ of which the present 'exhibits only a brief outline. * Lectures on Agricultural Cliemistry and Geology. THE END. ALPHABETICAL AND ANALYTIOAL INDEX A. Analysis of organic parts of plants. 14 Acm, Carbonic, . . 18, 32 " of barley, wheat, oats. " Humic, 21^ beans, rye, corn, " Geic, .... 21 linseed, potato, and " Crenic, 22 turnip. 64 " Apo-Crenic, . . 22 " of guano, , 208 " Nitric, 29 " of experiments with " Sulphuric, 33 salts of ammonia, 225 " Pliosplioric, 34 " of carbon and nitro- " Pectose, pectic. 44 gen taken in food " of milk, how produced. 327 and respired, 21'? Acorn, composition of, 289 " of soils. 263 Agriculture, a .chemical art, 133 " of water, 274 Albumen, . . .46 342 Aquafortis, (nitric acid,) 29 Alumina, .... 56 Ash , of wood and grain. 6 Ammonia, its properties, . 26 (( of wheat and oat straw. " nitrate of. 30 wheat leaves, oats, oak " salts of, as manures. 222 wood, animal substan- " carbonate ofj 223 ces, and bones. •7 " sulphate of; 224 li quantity of left by plants. 59 *' salts of, experiments u " of in different plants, 59 with, 225 11 quality of. 64 Animals, organic parts of. 14 u of grains, table of, 64 " main visible functions a quantity of depends on the- of; . . . 337 soil, ... 63 , 67 " respiration of. 338 u of straw, table of. 68 " carbon given oflT by. 339 u of crab apple tree. 67 " bones of. 346 " of wheat, table of, 68 kind of food required by, 3 5 9 of wood and straw. 232 3U INDEX. Ash, of bushels of oats, barley, and rice, . . 233 " of peat and coal, . 234 Atmosphere, composition of, .82 B. Barley, composition of, . 284 " malting quahties of, . 285 " feeding qualities of, 286 " varying qualities of, 290 " oil in 100 lbs. of; . 307 Bean, composition ofj . .288 Beef, and milk, ... 368 Blood, kind of food required, as indicated by the, . 352 " what it teaches, . 353 Body, muscular parts of the, . 341 *' mineral matter in the, 345 Bran, value of, . . .176 Bromides, ... 59 Bromine, ... .58 Bones, dry, 6 per cent, phospho- rus, ... 14 " composition of and value as manure, . . 192 " to dissolve with acid, 194 " experiments with, . 195 Buckwlieat, composition of, 287 Butter, quality of varies, . 322 " composition of, . 323 '' preservation of, . 324 " why it becomes rancid, 325 " coloring of, . . 326 0. Cabbage, composition of, . 300 Carbon, . . . . 218 Carbonate of potash and soda, 226 " of magnesia in lime- stone, . . 252 Casein, . . . .46, 342 Cauliflower, qualities of, . 301 Chalk, iu Alabama, . .114 Charcoal, uses of, . . 181 Cheese, manufacture of, . 331 " quality of, . .332 " varieties of, . . 333 " .cream, cream and milk, whole or full milk, half milk, skimmed milk, . . 334 " whey, butter-milk, veg- etable and potato, 325 Chemistry, what it will do for agriculture, . 1 Chlorides, how formed, . 58 Chlorine, . . . .57 Churning, . . . 319 Clay, influence of air, frost, and water on, . . 142 " sinks in the soil, . 151 " and earth burned, . 269 " cause of the mechanical and chemical action of, 270 Clover, red and white, what soils they like, . . 130 " hay, oil in 100 lbs. of 307 Coal dust and coal tar, . 183 Cocoanut cake, . . .178 Corals, shell-sand, marls, . 253 Corn, Indian, composition of, 287 " oil in 100 lbs. of . 307 Cream, composition of, . .319 Crops, why one may grow well where another fiiils, . t2 " rotation of necessary, 72,132 Curd, why it separates, . 329 Dairy husbandry, effects of on the soil, . . .361 Digestion, effects of animal, 217 Draining, benefits produced by, 137 " of light soils, , 138 " summaryof advantages of; . . . 142 " depth of; . . . 142 Dung, value of, . . . 218 ' ' of full-grown animals, 219 INDEX. 3t5 E. Experiments, importance of, Farmer, object of the practical, 1 Fat, waste of in animals, . 347 " pur^joses served by, . 349 Fermentation, of dry vegetable matter, . 174 " loss of weight by, 175 Fibrin, composition of, . 342 Fluorine, . . . . 59 Food., quantity yielded by an acre, ... 308 " must repair daily waste in animals, . . 341 " must supply saline and earthy matters. . 344 " importance of a mixed, 353 " vakie of oily, in fatting, 355 " kind and quantity neces- sary to maintain a heal- tliy man, , . 356 " given prisoners, . . 357 " required by sheep and cattle, . . . 358 " practical and theoretical value of, . . 364 " on what its fattening prop- erties depends, . 366 " animal and vegetable, 369 " practical value of, . . 370 " form in which it is given, 370 " the souring of, . .371 Fork, use of in loosening subsoil, 150 Fruits, composition of, . 302 " effects of soil on their quality and flavor, 303 G. Gas, Hydrogen, " Oxygen, " Nitrogen, Geology, what it will do for agri- culture, . . 1 " its relations to agricul- ture, . . 8, 102 " value of to the farmer, 88 Gelatine, ... 34, 342 Gluten, .... 342 Grass, laying down land to, 159 " how land is improved by laying down to, . 160 " roots of remaining in the soil, . . . 161 " natural changes, . . 166 Guano, varieties of, . . 205 " fertilizing effects o^ 206 " composition of, . 208 " permanence of action of, 209 " adulteration of, . 210 " how to select good, 211 " national value of, . 212 " artificial, how to pre- pare, . . 248 Gypsum, taken from the soil by wool-growing, . 363 H. Hay and straw, . . 309 " time of GUI ting affects quan- tity and quality ot; . 303 " clover, oil inlOO lbs.' of, 307 " meadow, oil in 100 lbs. of, 307 Hemp, poppy and cotton cakes, 178 Horn and hoof parings as ma- nure, . . . 119 Hydrogen, ... 9 Illustrations — Burning the soil, . . 6 procuring hydrogen gas, 9, 10 " oxygen gas, 11 » carbonic acid, 18, 19, 20 burning hydrogen gas, . 24 procuring phosphoric acid, 34 pores on the leaf of garden balsam, . . .37 376 Illustrations — procuring starch, 40 starch, ghiten and fat in grain, 41 procuring chlorine, . 57 stratified and unstratified rocks, ... 84 section of coast Hnc, . 91 of different soils, . 94,95,98 of drifts, . . .113 Inorganic bodies, . . 6 " matter carried off in crops, 69 Insects, as a manure, . . 189 Iodine, .... 58 Iodides, .... 59 Iron, oxide or rust of, . 140 Irrigation, . . .272 Land, improvement of by feed- ^on ing sheep. Leaves, how they fertilize . 158 " of turnips, potatoes, &c., 171 " of trees, nutrition of, 301 Lime, . . . .55, 155 " Nitrate of, . . . 30 " sinlvs in the soil, 150, 259 " phosphate ofj in animals, 252 " burning and slaking of, 254 " effects of exposure of, to the air, . . . 255 " effects of burning, . 256 " quantity usually applied, 257 " visible improvements by, 258 " why it must be repeated, 258 " crops and rains carry it away, . . . 259 " chemical effects of, . 260 " exhausting eftects of, 265 Limestones and chalks, composi- tion of; . . 2^0 " benefits of burning, 255 Xinsoed, and linseed cake, . 287 " oil in 100 lbs. of, . 307 Lungs, carbon given off by, 339 " the, actually feed the body, . . .340 M. Magnesia, . . . .55 " nitrate of, . . 30 " carbonate of, in lime- stone and chalk, 252 Maize, (Indian corn), composi- tion of, . . . 287 Malt-dust, . . . .177 Manure, accurate knowledge of, . . . 3 " artificial, why necessary, 71 " what is a, . . 168 " use of vegetable, . .168 " relative fertilizing and money values of dif- ferent vegetable, 184 " sea-weed, uses of, as a, 169 " saw-dust and bran, as a, 176 " brewers' grains, malt and rape dust, . 177 " hemp, poppy, and cotton cakes, . . . 178 " peat, peat compost, and tanners' bark, . 178 " fermented and charred peat, . . 179, 180 " charcoal, soot, and coal- tar, ... 181 *' immediate and perma- nent effects of vege- table manures, . 186 " animal, fish, . . 187 " blood as a, . . 189 " skin, bone, hair, wool, 190 " nitrogen in animal, 191 " cow, liorse, and pig, 204 " droppings of birds, 205 " relative values of dif- ferent animal, . 213 " difference in animal and vegetable, . .215 " causes of difference be- tween animal and ve- getablej . . 216 " saline, whj'- required by the soil, . . 236 " how to determine the value of sahne, . 237 INDEX. 3tt Manure, saline, circumstances under wliieh they are to be used, . 238 " saline, specific action of on plants, . . 240 " saline, action of on par- ticular parts and kinds of plants, " sulphates and nitrates, mixed, " mixed, promote growth, and prevent mil- dew, . . 24G, 247 " soil can be restored , by, . . . '* influence of, on wheat and other corn crops, Manuring, green, " with dry vegetable matter, Matter, organic diminishes in the soil. Milk, properties and composition 241 243 267 278 171 174 266 of, . . . 312, 360 " influence of breed on, 314 *' of form and constitution on, ... 315 " of kind of food on, 316 " of soil on, 317 " adulteration of. 318 " the whole may be churn- ed, ... 320 " time required for churn- ing, 321 " why it becomes sour, 326 " sugar of, acid of, . 326 " acid of, how produced. 327 " curdling of; and casein, 328 *' rich in nitrogenous food, 358 " value of saline ingredients in, . 359 " a true food, . 360 " removes bone-earth from the soil, . 362 " proportions of food yielded by, .. . . 368 uahroom, .... 301 N. Night-soil, and poudrette, . 203 Nitrogen, . . . 12, 218 " necessity of, to the plant, 15 *' forms in which it enters the roots, . . 52 " in animal manures, 191 " necessary to the wlieat . crop, . . . 225 " exhaled by the skin and lungs, . . 350 0. Oats, composition of, . . 282 " when tb cut, . . 305 " and straw, oil in, . .307 Oil, in grain, hay and root crops, . . . 306 Organic bodies, ... 6 Oxygen, . . . . 9, 32 " ' the body fed by, . 340 Paring and burning, . . , 268 Pea, composition of, . . 288 " and bean, varying quaU- ties ot; . . . 291 Peat, use of, . . . - 178 " fermented, . . . 179 " charred, as an absorbent, 180 " ashes, composition of. 235 Perspiration, waste in animal, 349 Phosphate, how formed, 34, 57 " ammoniaco-magne- sian, . . 202 " of lime (and na- tive,) . 229, 230 " experiments with mixed, . . 245 " of lime in limestone, 252 Phosphorus, .... 9 Physiology, what it will do for agriculture, . 1 378 INDEX. Plants, organic parts of, . 13, 14 " structure of stem, root and leaf of; . . 36 " functions of roots of, 37 " " of tlie leaf of, 37 " " of the stem of, 39 " substances of which they consist, . , 39 " structure of their seeds 41 ^* fatty substance of, . 44 " waxes and resius of, 45 " growtli of; . . . 4V " woody matter of, . 49 " source of earthy matter of 54 " select the soils On which tliey prefer to grow, 130 " sicken on some soils, 132 Plow, subsoil, how it acts in improving the soil, 147 " results of experiments witli, . . 149, 150 Plowing, deep, how it im- proves tlie soil, 158 " chemical eflects o^ 153 Potash, . . . .55 " nitrate of, . . 30 Potato, average composition of, . . 294, 295 " influence of variety on, 29G " effect of manures on, 297 " effects of keeping, and frost on, . . 298 Poudrette, . . . .203 R. Rags, woollen, as manure, 191, 214 Rain, efiects of on the soil, 144 " causes the air to be re- newed, . . . 144 " warms the under soil, 144 " equalizes the temperature, 145 " carries down soluble sub- stances, . . , 145 " washes out noxious mat- ters, . . . .145 " brings down fertilizing substances, . . 146 Rain, mechanical action of, 162 Rape-dust, as manure, . 177 " cake value of, . 289 Rennet, action of, . . 329 Respiration, effects of, . .216 Rice, composition of, . . 287 Rivers, English and Indian, 277 Rocks, crumbling of; . . 82 ^' constancy in mineral character among the stratified, . . 85 " the crag, ... 92 " the plastic clays and chalks, . . 93 " the green sand, . . 94 " the wealden formation, 95 " the upper, middle, and lower oolite and the leas, . . .96 " the new red sand-stone, the magnesian lime- stone, and the coal measures, . . 97 " the mill-stone grit, the mountain limestone, and old red sandstone, 98, 99 " the upper and lower Sil- urian system, . 100 " the Cambrian, mica slate and gneiss systems, . 101 " granite, composition of, 104 " quartz, felspar, trap and hornblende composi- tion of, . . 105, 106 " rotten rock, marl, . 107 Rye, composition of; . . 287 " varying quality of, . 291 Sal-ammoniac, . 224 Salt, common. 227 Salts, Glauber's, . . 228 " Epsom, 228 Sap, cause and motion of, . 39 " changes as it ascends, . 48 Saw-dust, value of, . 176 INDEX. 379 Science and practice, close con- nection between, . . 358 Sea-weed and straw, ashes of, 321 Seeds, structure of, . • 41 " germination of, . . 4T " steeping of in salts of ammonia, • . 224 Sheep, sulphur in their wool, 3G3 Silica, 55 Silicate of potaeh and soda, 228 Skin, carbonic acid and nitrogen from, . • • 350 Soda, .... 55 " nitrate of, . . • ^^ " and potash, carbonate of, 226 " sulphate of (Glauber's salts), 328 " sulphate and nitrate of, mixed, . . .543 Soils, benefit from analysis 'of, . . 3,122,123 " organic part of, . . "^^ " inorganic part of, . _ . ^^ " saline or soluble portion of, 16 " earthy or insoluble portion of, .... '^^ " sandy, loamy, and peaty, 18 " diversities of, and subsoil, 19 " origin of, . • • ^2 " caiise of the diversity of, 82 " diflerences of, on stratified roclvs, ... 89 " density, and absorbent power of, . . Ill " evaporative power and shrinkage of, . • 118 " absorption of moisture of the air by, and tempera- ture of, ... 119 " chemical composition of 121 " fertile and barren com- pared, . . . 124 «' causes of the fertility of black, . . .129 " connection between and plants, . . • -'•^^ " general improvement of, 135 " two classes of, . .136 " liable to be burned up, 139 Soils, improvement of by mixing, 154 »' " by planting, 156 u " by laying down to grass, 152 Soot, uses of, . . • • 189 Starch and gluten, quantities of in crops, . 305 Straw, ashes of, . . • 231 " and hay, . . .301 " atfected by the time of cutting, . . 304 Subsoil, importance of, . . 80 " effects of bringing it up, 152 Sulphate, how formed, . 34, 56 " of ammonia, . .224 » of potash, . . 221 » of soda, (Glauber's salts,) . . 228 " of magnesia, (Epsom salts,) . . 228 " of iron, (green vitrei,) 228 " of hrae, (gypsum,) 229 " of soda with nitrates, 243 Sulphur, . . . 9, 56, 363 Sulphuric acid, ... 33 " influence of on crops, 196 Super-phosphate of lime, 34, 230 Table — " of sugars, ... 43 " of the ash of plants, 59,60 " of hornblende and felspar, 106 " of soils, . . 125, 128 " of experiments with tur- nips, barley, and po- tatoes, . . 149, 150 " of dry food and farm-yard dung, . . . 115 " of peat compost, . . 180 " of farm-yard manure and guano, . . . 180 " of wheat dressed wath soot, 182 " of the relative fertilizing and money values of diflerent vegetable ma- nures, . . 184,185 380 INDEX. Table of horn and bones, . 192 " of experiments with gu- ano, " of comparison of man- nures, . . 213, " of carbon and nitrogen taken in the food and respired, " of experiments with sahs of ammonia, . " of composition of peat ashes, " of mixed sulphates and - nitrates, " of mixtures promoting growth, . ^' and preventing mildew, " of artiiicial guano, " of composition of lime- stone, " of lime carried away by crops, " of the effect of equal quan- tities of mo.nures. . " of composition of wheat, 280-1 " of composition of the oat, . . 282 " of composition of bar- ley, . . 284 " of composition of rye. 207 214 2n 225 235 244 246 247 248 251 259 279 283 285 287 287 287 287 of " rice, of " corn, . of " buckwheat of " tne bean and pea, of " linseed and cake, . of " the acorn, of " the turnip, of " the potato, of " the cabbage of '* the cauliflower, 301 of " hay, straw, leaves, 301 of ' fruits, . 302 of relative quantities of starch and gluten in cultivated crops, . 305 288 289 290 294 294 300 Table of proportion of oil in plants, . . . 307 " of quantity of food yield- ed by an acre of land, 308 " of composition of that food, . . . 309 " of composition of milk, 313 319 322 " 01 cream, " of " butter, " of " fibrin, or muscle, 342 " of " saline matter in the body, 344 "of " mineral mat- ter, . 345 " of " food given in Scotch pris- ons, . 357 " of food required daily by animals, . . 358 " of composition of cow's milk, . . . 360 " of value of different kinds of food, ... 364 Taffo, Chinese, night-soil, . 204 Tanks, for liquids, construction of, ... 200 " Tanners' bark, . .178 Trees, why different kinds suc- ceed each other. . 131 " the peach in New Jersey, 131 " effects of the Scotch fir and beech on pasture land, . . . 156 " action of, iii improving the soil, ... 158 Trenching, how it improves the soil, . 150, 153 Tull, Jethro, experiments of, 153 Turnip, composition of, 294, 295 U. Urine, means of preserving and applying it, . . 1 9t " of man, . . .198 " of the pig and cow, 199 /j » -i-'- INDEX. 381 Urine, sulphated, . . 201 " solid matters escape from, the, . . . .350 " salts and nitrogen in, 351 Urate, how to form a, . 201 V. Vegetable products, analyses of, 3 Vitriol, oil of, • . . . 9 " green, sulphate of iron, 2'28 W. Water, composition of, . 25 " its relations to vegetable life, ... 26 " differs in natural virtue, 275 " effects of difierent springs of, . . . 276 Weeds, fire, what soils they like, 130 Weeds sea, uses of, 172 " special action of, 173 " sea, ashes of and straw. 231 Wells, in Alabama, 114 Wheat, average composition of. 280 " influence of climate on, 280 " influence of the kinds of manure on, 281 " varying quality of, 291 " when to cut it. 304 " flour, oil in, 307 Winds, effects of in improving the soil, 164 Wool, growing, its effects on the soil, 362 " varied by climate and food, 363 " and hair, 5 per cent, sul- phur, . 14 Worms, earth, effect of as labor- ers, . 163 " quantity of, 164 MAP m LIBRARY OF CONGRESS DD0Eb71fl'^34