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Wiley ^ Putnam's New Publications, 
 L E C T U R«E S 
 
 ON 
 
 AGRICULTURAL 
 
 CHEMISTRY AND GEOLOGY; 
 
 TO WHICH ARE ADDED, 
 
 SUGGESTIONS FOR EXPERIMENTS IN 
 PRACTICAL AGRICULTURE. 
 
 BY 
 
 JAS. F. W. JOHNSTON, M.A.,F.R,SS.L.&E. 
 
 Fellow of the Geological Society, Honorary Member of the Royal 
 
 Agricultural Society, &c. <fec. ; Reader in Chemistry and 
 
 Mineralogy in the University of Durham, &c. 
 
 These Lectures will be divided into four Parts, of which 
 the First is now ready ; the others are in course of publi- 
 cation, and the whole will be completed in two volumes. 
 
 Outline of Part I. — ^' On tJie Organic Constituents of 
 Plants." — Lecture I. Elementaiy substances of which 
 plants subsist. II. and III. Compound substances which 
 minister to the growth of plants. IV. Sources from which 
 plants immediately derive their elementary constituents. 
 V. How the food enters into the circulation of plants — 
 general structure of plants, VI. Into what substances the 
 food is changed in the interior of plants — substances of 
 which plants chiefly consist. VII. Chemical changes by 
 which the substances of which plants chiefly consist are 
 formed from those on which they live. VIII. How the 
 supply of food for plants is kept up in the general vegeta- 
 tion of the globe. 
 
 Outline op Part II. — " On the Inorganic Constituents 
 of Plants — the Origin, Classification, and Chemical Consti- 
 tution of Soils — General and Specifd Relations of Geology to 
 Agriculture — Origin, Constitution, Analyses, and MetJwds of 
 Improving Soils in different Districts and under unlike con- 
 ditions" — Lecture IX. Kind and proportion of inorganic 
 1 
 
Wiley 4* Putnam's New Publications, 
 
 matter contained in plants. X. Properties of the inorganic 
 compounds which exist in vegetable substances, or which 
 promote their growth. XL Of the nature, origin, and classifi^ 
 cation of soils — Structure of the earth's crust — Classification 
 and general characters of the stratified rocks — Agricultural 
 capabilities of the soils derived from them. XII. Granite 
 and trap rocks, and the soils derived from them — Superficial 
 accumulations. XIII. On the exact chemical constitution, 
 the analysis, and the physical properties of soils. 
 
 Part III. — Methods of improving the soil by mechanical 
 and by chemical means — Manures, their nature, composition, 
 and mode of action — theory of their application in different 
 localities. 
 
 Part IV. — The results of vegetation — the nature, consti- 
 tution, and nutritive properties of different kinds of produce, 
 and by difterent modes of cultivation — the feeding of cattle, 
 the making of cheese, &c. &c. The constitution and difier- 
 ences of vai-ious kinds of wood, and the circumstances which 
 favour their growth. 
 
 CRITZC/LIi iroTiciss. 
 
 "A valuable and interesting course of lectures." — Quar- 
 terly Review. 
 
 " But it is unnecessary to make large extracts from a book 
 which we hope and trust will soon be in the hands of nearly 
 all our readers. Considering it as unquestionably the most 
 important contribution tliat has recently been made to popu- 
 lar science, and as destined to exert an extensively beneficial 
 influence in this country, we shall not fail to notice the forth- 
 coming portions as soon as they appear from the press." — 
 SiUmum's American Jounial of Science. Notice of Part I. of 
 the American reprint. 
 
 " We think it no compliment to' Professor Johnston to say, 
 that among our own writers of the present day who have re- 
 cently been endeavouring to improve our agriculture by the 
 aid of science, there is probably no other who has been more 
 eminently successful, or whose efforts have been more highly 
 appreciated." — County Herald. 
 
 " Prof Johnston is one who has himself done so much al- 
 ready for English agriculture, that to behold him still in hot 
 pursuit of the inquiry into what can be done, supplies of itself 
 a stimulus to further exertion on the part of others." — Ber- 
 wick Warder. 
 
ELEMENTS 
 
 OF 
 
 AGRICULTUKAL CHEMISTRY, &c. 
 
ELEMENTS 
 
 OF 
 
 AGRICULTURAL 
 
 CHEMISTRY AND GEOLOGY. 
 
 / 
 
 BT 
 
 JAS. F. W. JOHNSTON, M.A., F.R.S., 
 
 HONORARY MEMBER OP THE ROYAL ENGLISH AGRICULTURAL 
 SOCIETY, AND AUTHOR OF " LECTURES ON AGRI- 
 CULTURAL CHEMISTRY AND GEOLOGY." 
 
 NEW-YORK: 
 WILEY AND PUTNAM. 
 
 MDCCCXLII. 
 
 ^^ WASHfllfil 
 

 J. p. Wright, Printer, 
 18 New Street, N. Y. 
 
INTRODUCTION. 
 
 The scientific principles upon which the art 
 of culture depends, have not hitherto been suf- 
 ficiently understood or appreciated by practi- 
 cal men. Into the causes of this I shall not 
 here inquire. I may remark, however, that if 
 Agriculture is ever to be brought to that 
 comparative state of perfection to which many 
 other arts have already attained, it will only 
 be by availing itself, as they have done, of the 
 many aids which Science offers to it; and 
 that, if the practical man is ever to realize 
 upon his farm all the advantages which Sci- 
 ence is capable of placing within his reach, it 
 will only be when he has become so far ac- 
 quainted with the connection that exists be- 
 
;yill INTRODUCTION. ' ^ 
 
 tween the art by which he Hves and the sci- 
 ences, especially of Chemistry and Geology, 
 as to be prepared to listen with candour to 
 the suggestions they are ready to make to him, 
 and to attach their proper value to the expla- 
 nations of his various processes which they 
 are capable of affording. 
 
 The following little Treatise is intended to 
 present a familiar outline of the subjects of 
 Agricultural Chemistry and Geology, as treat- 
 ed of more at large in my Lectures, of which 
 the first Part is now before the public. 
 What in this work has necessarily been taken 
 for granted, or briefly noticed, is in the Lec- 
 tures examined, discussed, or more fully de- 
 tailed. 
 
 Durham, Sth April, 1842. 
 
CONTENTS. 
 
 CHAPTER L 
 
 PAGE 
 
 Distinction between Organic and Inorganic Substances 
 — The Ash of Plants — Constitution of the Organic 
 Parts of Plants — Preparation and Properties of Car- 
 bon, Oxygen, Hydrogen, and Nitrogen — Meaning of 
 Chemical Combination .13 
 
 CHAPTER IL 
 
 Form in which these different Substances enter into 
 Plants — Properties of the Carbonic, Humic, and Ul- 
 mic Acids ; of Water, of Ammonia, and of Nitric 
 Acid — Constitution of the Atmosphere. . . .25 
 
 CHAPTER III. 
 
 Structure of Plants — Mode in which their Nourishment 
 is obtained — Growth and Substance of Plants — Pro- 
 duction of their Substance from the Food they imbibe 
 — Mutual Transformations of Starch, Sugar, and 
 Woody Fibre 38 
 
X CONTENTS. 
 
 CHAPTER IV. 
 
 PAaB 
 
 Of the Inorganic Constituents of Plants — Their imme- 
 diate Source — Their Nature — Cluantity of each in 
 certain common Crops .49 
 
 CHAPTER V. 
 
 Of Soils — Their Organic and Inorganic Portions — 
 Saline Matter in Soils — Examination and Classifica- 
 tion of Soils — Diversities of Soils and Subsoils. . 67 
 
 CHAPTER VI. 
 
 Direct Relations of Geology to Agriculture — Origin of 
 Soils — Causes of their Diversity — Relation to the 
 Rocks on which they rest — Constancy in the Relative 
 Position and Character of the Stratified Rocks — 
 Relation of this Fact to Practical Agriculture — Gen- 
 eral Characters of the Soils upon these Rocks. . , 78 
 
 CHAPTER VII. 
 
 Soils of the Granitic and Trap Rocks — Accumulations 
 of Transported Sands, Gravels, and Clays — Use of 
 Geological Maps in reference to Agiiculture — Phy- 
 sical Characters and Chemical Constitution of Soils 
 — Relation between the Nature of the Soil and the 
 Kind of Plants that naturally grow upoo it- . . 103 
 
CONTENTS. XI 
 
 CHAPTER VIII. 
 
 PAGE 
 
 Of the Improvement of the Soil — Mechanical and Che- 
 mical Methods — Draining — Subsoiling — Ploughing, 
 and Mixing of Soils — Use of Lime, Marl, and Shell- 
 sand — Manures — Vegetable, Animal, and Mineral 
 Manures 133 
 
 CHAPTER IX. 
 
 Animal Manures — Their Relative Value and Mode of 
 A ction — Difference between Animal and Vegetable 
 Manures — Cause of this Difference — Mineral Man- 
 ures — Nitrates of Potash and Soda — Sulphate of So- 
 da, Gypsum, Chalk, and Gluicklime — Chemical Ac- 
 tion of these Manures — Artificial Manures — Burning 
 and Irrigation of the Soil — Planting and Laying 
 Down to Grass. 165 
 
 CHAPTER X. 
 
 The Products of Vegetation — Importance of Chemical 
 quality as well as quantity of Produce — Influence of 
 different Manures on the quantity and quality of the 
 Crop — Influence of the Time of Cutting — Absolute 
 quantity of Food yielded by different Crops — Princi- 
 ples on which the Feeding of Animals depends — 
 Theoretical and Experimental Value of different 
 kinds of Food for Feeding Stock — Concluding Ob- 
 servations. 216 
 
ELEMENTS 
 
 or 
 
 AGRICULTURAL CHEMISTRY, &c 
 
 CHAPTER I. 
 
 Distinction between Organic and Inorganic Substances.—^ 
 The Ash of Plants — Constitution of the Organic Parts of 
 Plants. — Preparation and Properties of Carbon, Hydro- 
 gen, and Nitrogen. — Meaning of Chemical Combination. 
 
 The object of the practical farmer is to raise 
 iVom a given extent of land the largest quantity 
 of the most valuable produce at the least cost, and 
 witYi the least permanent injury to the soil. The 
 sciences either of chemistry or geology throw light 
 on every step he takes or ought to take, in order to 
 effect this main object. 
 
 2* ^ 
 
14 ORGANIC AND INORGANIC BODIES. 
 
 SECTION I. OF THE VEGETABLE AND EARTHY OR THE 
 
 ORGANIC AND INORGANIC PARTS OF PLANTS. 
 
 In the prosecution of his art, two distinct classes 
 of substances engage his attention — the living crops 
 he raises, and the dead earth from which they are 
 gathered. If he examine any fragment of an ani- 
 mal or vegetable, either living or dead, he will ob- 
 serve that it exhibits pores of various kinds ar- 
 ranged in a certain order — that it has a species of 
 internal structure — that it has various parts or or- 
 gans — in short, that it is what physiologists term 
 organized. If he examine, in like manner, a lump 
 of earth or rock, he will perceive no such struc- 
 ture. To mark this distinction, the parts of ani- 
 mals and vegetables, either living or dead — whe- 
 ther entire or in a state of decay, are called or- 
 ganic bodies, while earthy and stony substances 
 are called inoj'ganic bodies. 
 
 Organic substances are also more or less readily 
 burned and dissipated by heat in the open air ; in- 
 organic substances are generally fixed and perma- 
 nent in the fire. 
 
 But the crops which grow upon it, and the soil 
 in which they are rooted, contain a portion of 
 both of these classes of substances. In all fer- 
 
ASH OF PLANTS. 15 
 
 tile soils, there exists from 3 to 10 per cent, of ve- 
 getable or other matter of organic origin ; while, 
 on the other hand, all vegetables, as they are col- 
 lected for food, leave, when burned, from one-half 
 to twenty per cent, of inorganic ash. 
 
 If we heat a portion of soil to redness in the 
 open air, the organic matter will burn away, and, 
 in general, the soil, if previously dry, will not be 
 materially diminished in bulk. But if a handful 
 of wheat, or of wheat straw, or of hay, be burned 
 in the same manner, the proportion that disap- 
 pears is so great, that in most cases a compa- 
 ratively minute quantity only remains behind. 
 Every one is famihar with this fact who has seen 
 the small bulk of ash that is left when weeds, or 
 thorns, or trees, are burned in the field, or when 
 a hay or corn-stack is accidentally consumed. Yet 
 the ash thus left is a very appreciable quantity, 
 and the study of its true nature throws much light, 
 as we shall hereafter see, on the practical manage- 
 ment of the land on which any given crop is to be 
 made to grow. 
 
 Thus the quantity of ash left by a ton of wheat 
 straw is sometimes as much as 360 lbs.; by a ton 
 of oat straw as much as 200 lbs.; while a ton of 
 the grain of wheat leaves only about 40 lbs.; of the 
 grain of oats about 90 lbs.; and of oak wood only 
 
 f 
 
1& PROPERTIES OF CARFOJT. 
 
 4 or 5 lbs. The quantities of inorganic matter, 
 therefore, though comparatively small, yet, in some 
 cases, amount to a considerable weight in an entire 
 crop. The nature, source and uses of this earthy 
 matter will be explained in a subsequent chapter* 
 
 SECTION II. CONSTITUTION OF THE ORGANIC PART OF 
 
 PLANTS AND ANIMALS. 
 
 The organic part of plants, when in a perfectly 
 dry state, constitutes therefore from 85 to 99 per 
 cent, of their whole weight. Of those parts of 
 plants which are cultivated for food, it is only hay 
 and straw, and a very few others, that contain as 
 much as 1 per cent, of inorganic matter. 
 
 This organic part consists of four substances, 
 known to chemists by the names of carbon, hydro- 
 gen, oxygen, and nitrogen. The first of these, 
 carbon, is a solid substance, the other three are 
 gases or peculiar kinds of air. 
 
 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 converted into com- 
 mon 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 
 
PREPARATIO]V OF HYDROGEN GAS. 17 
 
 according to the kind of wood from which it has 
 been formed. Coke obtained by charring or dis- 
 tilHng coal is another variety. It is generally 
 denser or heavier than the former, though less 
 pure. Black lead is a third variety, still heavier 
 and more impure. The diamond is the only form 
 in which carbon occurs in nature in a state of per- 
 fect purity. 
 
 This latter fact, that the diamond is pure car- 
 bon — that it is essentially the same substance with 
 the finest and purest lamp-black — is very remark- 
 able ; but it is only one of many striking circum- 
 stances that every now and then present themselves 
 before the inquiring chemist. 
 
 Charcoal, the diamond, lamp-black, and all the 
 other forms of carbon, burn away more or less 
 slowly when heated in the air, and are converted 
 into a kind of gas known by the name of carbonic 
 acid. The impure varieties leave behind them a 
 greater or less proportion of ash. 
 
 2. Hydrogen. — If oil of vitriol (sulphuric 
 acid) be mixed with twice its bulk of water, and 
 then poured upon iron fiUngs, 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. 
 
 If the experiment be performed in a bottle, the 
 2* 
 
18 PROPERTIES OF HYDROGEN. 
 
 hydrogen which is produced will gradually drive 
 out the atmospheric air it contained, and will itself 
 take its place. If a bit of wax taper be tied to the 
 end of a wire, and when lighted be introduced into 
 the bottle, 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 common air will burn 
 with an explosion more or less violent, and may 
 even shatter the bottle and produce serious acci- 
 dents. This experiment, therefore, ought to be 
 made with care. It may be safely made in an open 
 tumbler, covered by a plate or a piece of paper, 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. 
 
 This gas is also an exceedingly light substance, 
 rising through common air as wood does through 
 water. Hence, when confined in a bag made of 
 silk, or other light tissue, it is capable of sustaining 
 heavy substances in the air, and even of transport- 
 ing them to great heights. For this reason it is 
 employed for filling and elevating balloons. 
 
 Hydrogen gas is not known to occur anywhere 
 in nature in any sensible quantity. It is very abun- 
 
PROPERTIES OF OXYGEX. 19 
 
 dant, as we shall hereafter see, in what by chemists 
 is called a state of combination, 
 
 3. Oxygen. — When strong oil of vitriol is poured 
 upon black oxide of manganese, and heated in a 
 glass retort : or when red oxide of mercury, or 
 chlorate of potash, is so heated alone ; or when salt- 
 petre, or the same oxide of manganese, is heated 
 alone in an iron bottle ; — in all these cases a kind 
 of air is given off, which, when collected and ex- 
 amined by plunging a taper into it, is found to be 
 neither common air nor hydrogen gas. The taper, 
 when introduced, burns with great rapidity, and 
 with exceeding brilliancy, and continues to burn 
 till either the whole of the gas disappears, or the 
 taper is entirely consumed. If a living animal is 
 introduced, its circulation and its breathing be- 
 come 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 light like hydrogen, but is about one- 
 ninth part heavier than common 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 is the substance which, in the air, 
 supports all animal life and the combustion of all 
 burning bodies. Were it by any cause suddenly 
 removed from the atmosphere of our globe, every 
 
20 PROPERTIES OF NITROGEN. 
 
 living thing would perish, and all combustion 
 would become impossible. 
 
 4. Nitrogen. — If a saucer be half filled with 
 milk of lime, formed by mixing slaked quicklime 
 with water, a very small tea-cup containing a little 
 burning sulphur then placed in the middle, and a 
 common large tumbler inverted over the whole, 
 the sulphur will burn for a while, and will then 
 gradually die out. On allowing the whole to re- 
 main for some time, the fumes of the sulphur will 
 be absorbed by the milk of lime, which will rise a 
 certain way into the tumbler. When the absorp- 
 tion has ceased, a quantity of air will remain in the 
 upper part of the tumbler. This air is nitrogen 
 gas. 
 
 If the whole be now introduced into a large 
 basin of water, the tumbler being held in the left 
 hand, the cup and saucer may be removed from 
 beneath. The saucer may then be inverted and 
 introduced with its under side into the mouth of 
 the tumbler, which may thus be lifted out of the 
 water and restored to its upright position, the 
 saucer serving the purpose of a cover. By carefully 
 removing this cover with the one hand, a lighted 
 taper may be introduced by the other. It will 
 then be seen that the taper is extinguished by this 
 air, and that no other effect follows. Or if a living 
 
COMPOSITION OF HAY AND OATS. 21 
 
 animal be introduced into it, breathing will in- 
 stantly cease, and it will drop without signs of 
 life. 
 
 This gas possesses no other remarkable property. 
 It is a very little lighter than common air, and is 
 known to exist in large quantity in the atmosphere 
 only. Of the air we breathe it forms nearly four- 
 fifths of the entire bulk. 
 
 These three gases are incapable of being distin- 
 guished from common air, or from each other, by 
 the ordinary senses ; but by the aid of the taper 
 they are readily recognised. Hydrogen extin- 
 guishes the taper, but itself takes fire ; nitrogen 
 simply extinguishes it ; while in oxygen the taper 
 burns with extraordinary brilliancy and rapidity. 
 
 Of this one solid substance, carbon, and these 
 three gases, hydrogen, oxygen, and nitrogen, all 
 the organic part of vegetable and animal substances 
 is made up. 
 
 Into these substances, however, they enter in 
 very different proportions. Nearly one half the 
 weight of all vegetable productions which are 
 gathered as food for man or beast — in their dry 
 state — consists of carbon ; the oxygen amounts to 
 rather more than one third, the hydrogen to little 
 more than five per cent., >vhile the nitrogen rarely 
 
22 CHEMICAL COMBINATION. 
 
 exceeds two and a half or three per cent, of their 
 weight. 
 
 This will appear from the following table, which 
 exhibits the actual constitution by analysis of some 
 varieties of the more common crops when perfectly 
 dry. 
 
 Carbon. Hydrogen. Oxygen. Nitrogen. Ash. 
 
 Hay, . . . . 
 
 458 
 
 50 
 
 387 
 
 15 
 
 90 
 
 Potatoes, . . 
 
 441 
 
 58 
 
 439 
 
 12 
 
 50 
 
 Wheat Straw, . 
 
 485 
 
 52 
 
 3891 
 
 3^ 
 
 70 
 
 Oats, . . . . 
 
 507 
 
 64 
 
 367 
 
 22 
 
 40 
 
 These numbers represent the weights of each 
 element in pounds, contained in 1000 lbs. of the 
 dry hay, potatoes, dec. ; but in drying by a gentle 
 heat, 1000 lbs. of hay from the stack, lost 158 lbs. 
 of water, of potatoes wiped dry externally 722 lbs.,* 
 wheat straw 260 lbs., and oats 151 lbs. 
 
 SECTION III. — OF THE MEANING OF CHEMICAL 
 COMBINATION. 
 
 If the three kinds of air above spoken of be 
 mixed together in a bottle, no change will take 
 place, and if charcoal in fine powder be added to 
 
 * Both potatoes and turnips contain about four-fifths of 
 their weight of water, or five tons of either of these roots 
 contain nearly four tons of water. 
 
WOOD, ETC. ARE CHEMICAL COMPOUNDS. 23 
 
 them, still no new substance will be produced. If 
 we take the ash left by a known weight of hay or 
 wheat straw, and mix it with the proper quantities 
 of the four elementary substances, carbon, hydro- 
 gen, &;c., as shewn 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 intimate 
 manner. To this more intimate state of union, 
 the term chemical combination is applied — the ele- 
 ments are said to be chemically combined. 
 
 Thus, when charcoal is burned in the air, it 
 slowly disappears, and forms, as already stated, a 
 kind of air known by the name of carbonic acid 
 gas, which rises into the atmosphere and disappears. 
 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 a piece of wood or a 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 
 which new states they escape into the air and be- 
 come invisible. When a substance is thus changed 
 
24 CHEMICAL DECOMPOSITION. 
 
 by the action of heat, it is said to be decomposed^ 
 or if it gradually decay and perish by exposure to 
 the air and moisture, it undergoes slow decompo- 
 sition. 
 
 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 combination or chemical 
 compound. When, on the other hand, one com- 
 pound body is so changed as to be converted into 
 two or more substances different from itself, it is 
 decomposed. Carbon, hydrogen, &;c., are chemical- 
 ly combined in the interior of the plant during the 
 formation of wood : wood, again, is decomposed 
 when by the vinegar-maker it is converted among 
 other substances into charcoal and wood-vinegar, 
 and the flour of grain when the brewer or distiller 
 converts it into ardent spirits. 
 
CHAPTER II. 
 
 Form in which these different substances enter into Plants. 
 Properties of the Carbonic,' Humic, and Ulmic Acids — of 
 Water, of Ammonia, and of Nitric Acid. Constitution 
 of the Atmosphere. 
 
 SECTION I. FORM IN WHICH THE CARBON, ETC. ENTER 
 INTO PLANTS. 
 
 It is from their food that plants derive the car- 
 bon, hydrogen, oxygen, and nitrogen, 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 part 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 into 
 either in a solid state ; and as it does not dissolve 
 3* 
 
26 HOW CARBON, ETC. ENTER INTO PLANTS. 
 
 in water, it cannot, in the state of simple carbon, 
 be any part of the food of plants. Again, hydro- 
 gen 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 the gas above described. Oxygen 
 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 supposed to enter directly into plants in any 
 considerable quantity. 
 
 The whole of the carbon and hydrogen, and the 
 greater part of the oxygen and nitrogen also, enter 
 into plants in a state of chemical comhination with 
 other substances ; the carbon chiefly in the state of 
 carbonic acid, and of certain other soluble com- 
 pounds which exist in the soil ; the hydrogen and 
 oxygen in the form of water : and the nitrogen in 
 those of ammonia or nitric acid. It will be neces- 
 sary therefore briefly to describe these several com- 
 pounds. 
 
 SECTION n. OF THE CARBONIC, HUMIC, AND ULMIC ACIDS. 
 
 1. Carbonic Acid. — If a few pieces of chalk or 
 limestone be put into the bottom of a tumbler, and 
 a little spirit of salt (muriatic acid) be poured upon 
 
PROPERTIES OF CARBONIC ACID. 27 
 
 them, a boiling up or effervescence will take place, 
 and a gas will be given off, which will gradually 
 collect and fill the tumbler ; and when produced 
 very rapidly, may even be seen to run over its 
 edges. This gas is carbonic acid. It cannot be 
 distinguished from common air by the eye ; but if 
 a taper be plunged into it, the flame will imme- 
 diately be extinguished, while the gas remains un- 
 changed. This kind of air is so heavy, that it may 
 be poured from one vessel into another, and its 
 presence recognised by the taper. It has also a 
 peculiar odour, and is exceedingly suffocating, so 
 that if a livins: animal be introduced into it, life 
 immediately ceases. It is absorbed by water, a 
 pint of water absorbing or dissolving a pint of the 
 gas. 
 
 Carbonic acid 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, coal, and all other combustible 
 bodies, so that an unceasing supply of this gas is 
 poured into the air. Decaying animal and vege- 
 table substances also give off this gas, and hence 
 it is always present in greater or less abundance in 
 the soil, and especially in such soils as are rich in 
 vegetable matter. During the fermentation of malt 
 liquors, or of the expressed juices of different fruits, 
 
28 HUMIC AND ULMIC ACIDS. 
 
 — the apple, the pear, the grape, the gooseberry — 
 it is produced, and the briskness of such fermented 
 liquors is due to the escape of this gas. From the 
 dung and compost heap it is also given off; and 
 when put into the ground in a fermenting state, 
 farm-yard manure affords a rich supply of carbonic 
 acid to the young plant. 
 
 Carbonic acid consists of carbon and oxygen 
 only, combined together in the proportion of 28 of 
 the former to 72 of the latter, or 100 lbs. of car- 
 bonic acid contain 28 lbs. of carbon and 72 lbs of 
 oxygen. 
 
 2. HuMic AND Ulmic Acids. — The soil always 
 contains a portion of vegetable matter (called ^m- 
 mus by some writers), and such matter is always 
 added to it when it is manured from the farm- 
 yard or the compost heap. During the decay 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. 
 They both contain much carbon, are both capable 
 of entering the roots of plants, and both, no doubt, 
 in favourable circumstances, help to feed the plant. 
 
 If the common soda of the shops be dissolved in 
 water, and a portion of a rich vegetable soil, or a 
 
EXIST IN FARM-YARD MANURE. 29 
 
 bit of peat, be put into this solution, and the whole 
 boiled, a brown liquid is obtained. If to this brown 
 liquid, spirit of salt (muriatic acid) be added till it 
 is sour to the taste, a brown flocky powder falls to 
 the bottom. This brown substance is humic acid. 
 But if in this process we use spirit of hartshorn 
 (liquid ammonia), instead of the soda, uhnic acid 
 is obtained. 
 
 These acids exist along with other substances in 
 the rich brown liquor of the farm-yard, which is 
 so often allowed to run to waste ; they are also 
 produced in greater or less quantity during the de- 
 cay of the manure after it is mixed with the soil, 
 and no doubt yield to the plant a portion of that 
 supply of food which it must necessarily receive 
 from the soil. 
 
 SECTION III. OF WATER, AMMONIA, AND NITRIC ACID. 
 
 1. Water. — If hydrogen be prepared in a bot- 
 tle, in the way already described, and a gas-burner 
 be fixed into its mouth, the hydrogen may be 
 lighted, and will burn as it escapes into the air. 
 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 it takes place in pure oxygen 
 3* 
 
30 COMPOSITION OF WATER. 
 
 gas as well as in the open air, this water must corf" 
 tain the hydrogen and oxygen which disappear, or 
 must consist of hydrogen 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 their union, 
 should form so very different a substance as water 
 is from either. It consists of 1 of hydrogen to 8 
 of oxygen, or every 9 lbs. of water contain 8 lbs, 
 of oxygen and 1 lb. of hydrogen. 
 
 Water is so familiar a substance, that it is unne* 
 cessary to dwell upon its properties. When pure, 
 it has neither colour, taste, nor smell. At 32° of 
 Fahrenheit's* scale (the freezing point), it solidifies 
 into ice, and at 212° it boils, and is converted into 
 steam. There are two others of its properties which 
 are especially interesting in connection with the 
 growth of plants. 
 
 1st, If sugar or salt be put into water, they disap- 
 pear 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 some of the soluble sub- 
 
 * This is the scale of the common thermometer used in 
 this countiy. 
 
PROPERTIES OF WATER. 31 
 
 stances it meets in its way, and rarely reaches the 
 roots of plants in a pure state. So waters that rise 
 up in springs are rarely pure. They always con- 
 tain earthy and saline substances in solution, and 
 these they carry with them, when they are sucked 
 m by the roots of plants. 
 
 It has been above stated, that water absorbs 
 (dissolves) its own bulk of carbonic acid ; it dis- 
 solves 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 
 impregnated with them, and conveys them into 
 the plant, there to serve as a portion of its food. 
 
 "Zd, Water is composed of oxygen and hydrogen ; 
 S)y certain chemical processes it can readily be re- 
 ?solved or decomposed artificially into these two 
 ^gases. The same thing takes place naturally in the 
 interior of the living plant. The roots absorb the 
 wat^, but if in any part of the plant hydrogen be 
 required, to make up the substance which it is the 
 function of that part to produce, a portion of the 
 water is decomposed and worked up, while the oxy- 
 gen is set free, or converted to some other use. So, 
 also, in any case where oxygen is required water is 
 decomposed, the oxygen made use of, and the hy- 
 drogen liberated. Water, therefore, which abounds 
 in the vessels of all growing plants, if not directly 
 
32 PROPERTIES OF AMMONIA. 
 
 converted into the substance of the plant, is yet a 
 ready and ample source from which a supply of 
 either of the elements of which it consists may at 
 any time be obtained. 
 
 It is a beautiful adaptation of the properties of 
 this all-pervading compound (water), that its ele- 
 ments should be so fixedly bound together as rare- 
 ly to separate in external nature, and yet to be at 
 the command and easy disposal of the vital powers 
 of the humblest order of living plants. 
 
 2. Am3ionia. — If the sal-ammoniac of the shops 
 be mixed with quicklime, a powerful odour is im- 
 mediately perceived, and an invisible gas is given 
 off which strongly affects the eyes. This gas is 
 ammonia. Water dissolves or absorbs it in very 
 large quantity, and this solution forms the com- 
 mon hartshorn of the shops. The white solid 
 smelling-salts of the shops are a compound of am- 
 monia with carbonic acid, — a solid formed by the 
 union of two gases. 
 
 The gaseous ammonia consists of nitrogen and 
 hydrogen only, in the proportion of 14 of the for- 
 mer to 3 of the latter, or 17 lbs. of ammonia contain 
 3 lbs. of hydrogen. 
 
 The chief natural source of this compound is, in 
 the decay of animal substances. During the pu- 
 trefaction of dead animal bodies ammonia is inva- 
 riably given off. From the animal substances of the 
 
NATURAL AND ARTIFICIAL PRODUCTION OF. 33 
 
 farm-yard it is evolved, and from all solid and li- 
 quid manures of animal origin. It is also formed 
 in lesser quantity during the decay of vegetable 
 substances in the soil ; and in volcanic countries, it 
 escapes from many of the hot lavas, and from the 
 crevices in the heated rocks. 
 
 It is produced artificially by the distillation of 
 animal substances (hoofs, horns, &;c.), or of coal. 
 Thousands of tons of the ammonia present in the 
 ammoniacal liquors of the gas-works, which might 
 be beneficially applied as a manure, are annually 
 carried down by the rivers, and lost in the sea. 
 
 The ammonia which is given off during the pu- 
 trefaction of animal substances rises partially into 
 the air, and floats in the atmosphere, till it is either 
 decomposed by natural causes, or is washed down 
 by the rains. In our climate, cultivated plants 
 derive a considerable portion of their nitrogen 
 from ammonia. It is supposed to be one of the 
 most valuable fertilizing substances contained in 
 farm-yard manure ; and as it is present in greater 
 proportion by far in the liquid than in the solid 
 contents of the farm-yard, there can be no doubt 
 that much real wealth is lost, and the means of 
 raising increased crops thrown away in the quan- 
 tities of liquid manure which are almost every- 
 where permitted to run to waste. 
 
S4 PROPERTIES OF NITRIC AClD* 
 
 3. Nitric Acid — is a powerfully corrosive li- 
 quid known in the shops by the familiar name of 
 aquafortis. It is prepared by pouring oil of vitriol 
 (sulphuric acid) upon saltpetre, and distilling the 
 mixture. The aquafortis of the shops is a mixture 
 of the pure acid with water. 
 
 Pure nitric acid consists of nitrogen and oxygen 
 only ; the union of these two gases, so harmless in 
 the air, producing the burning and corrosive com- 
 pound which this is known to be. 
 
 It never reaches the roots of plants in this free 
 and corrosive state. It exists in many soils, and 
 is naturally formed in compost heaps, and in most 
 situations where vegetable matter is undergoing 
 decay in contact with the air ; but it is always in 
 a state of chemical combination in these cases. 
 With potash, it forms nitrate of potash (saltpetre) ; 
 with soda, nitrate of soda; and with lime, nitrate 
 of lime ; and it is generally in one or other of these 
 states of combination that it reaches the roots of 
 plants. 
 
 Nitric acid is also naturally formed, and in some 
 countries probably in large quantities, by the pas- 
 sage of electricity through the atmosphere. The 
 air, as has been already stated, contains much oxy- 
 gen and nitrogen mixed together, but when an 
 electric spark is passed through a quantity of air, 
 
PRODUCTION OF IN THE AIK. 35 
 
 a certain quantity of the two unite together che- 
 mically, so that every spark that passes forms a 
 small portion of nitric acid. A flash of lightning 
 is only a large electric spark ; and hence every 
 flash that crosses the air produces along its path a 
 quantity of this acid. Where thunder-storms are 
 frequent, much nitric acid must be produced in 
 this way in the air. It is washed down by the 
 rains, in which it has frequently been detected, and 
 thus reaches the soil, where it produces one or 
 other of the nitrates above mentioned. 
 
 It has been long observed that those parts of 
 India are the most fertile in which saltpetre exists 
 in the soil in the greatest abundance. Nitrate of 
 soda, also, in this country, has been found wonder- 
 fully to promote vegetation in many localities ; 
 and it is a matter of frequent remark, that vege- 
 tation seems to be refreshed and invigorated by 
 the fall of a thunder-shower. There is, therefore, 
 no reason to doubt that nitric acid is really bene- 
 ficial to the general vegetation of the globe. And 
 since vegetation is most luxuriant in those parts of 
 the globe where thunder or lightning are most 
 abundant, it would appear as if the natural pro- 
 duction of this compound body in the air, to be 
 afterwards brought to the earth by the rains, were 
 a wise and beneficent contrivance by which the 
 
36 THE CONSTITUTION OP THE ATMOSPHERE 
 
 health and vigour of universal vegetation is in- 
 tended to be promoted. 
 
 It is from this nitric acid, thus universally pro- 
 duced and existing, that plants appear to derive a 
 large — probably, taking vegetation in general, the 
 largest — portion of their nitrogen. In all climates 
 they also derive a portion of this element from 
 ammonia ; but less from this source in tropical 
 than in temperate climates.* 
 
 SECTION IV. OP THE CONSTITUTION OF THE ATMOSPHEKE. 
 
 The air we breathe, and from which plants also 
 derive a portion of their nourishment, consists of 
 a mixture of oxygen and nitrogen gases, with a 
 minute quantity of carbonic acid, and a variable 
 proportion of watery vapour. Every hundred gal- 
 lons of dry air contain about 21 gallons of oxygen 
 and 79 of nitrogen. The carbonic acid amounts 
 only to one gallon in 2500, while the watery va- 
 pour in the atmosphere varies from 1 to 2^ gal- 
 lons (of steam) in 100 gallons of common air. 
 
 The oxygen in the air is necessary to the respi- 
 ration of animals, and to the support of combus- 
 tion (burning of bodies). The nitrogen serves 
 
 * For fuller mfoniiation on this point, see the Author's 
 " Lectures on Agricultural Chemistry and Geology" Part L 
 
ADJUSTED TO ANIMAL AND VEGETABLE LIFE. 37 
 
 principally to dilute the strength, so to speak, of 
 the pure oxygen, in which gas, if unmixed, animals 
 would live and combustibles burn with too great 
 rapidity. The small quantity of carbonic acid af- 
 fords an important part of their food to plants, 
 and the watery vapour in the air aids in keeping 
 the surfaces of animals and plants in a moist and 
 pliant state ; while, in due season, it descends also 
 in refreshing showers, or studs the evening leaf 
 with sparkling dew. 
 
 There is a beautiful adjustment in the constitu- 
 tion of the atmosphere to the nature and necessi- 
 ties of living beings. The energy of the pure oxy- 
 gen is tempered, yet not too much weakened, by 
 the admixture of nitrogen. The carbonic acid, 
 which alone is noxious to life, is mixed in so mi- 
 nute a proportion as to be harmless to animals, 
 while it is still beneficial to plants ; and when the 
 air is overloaded with watery vapour, it is provided 
 that it shall descend in rain. These rains at the 
 same time serve another purpose. From the sur- 
 face of the earth there are continually ascending 
 vapours and exhalations of a more or less noxious 
 kind ; these the rains wash out from the air, and 
 bring back to the soil, at once purifying the at- 
 mosphere through which they descend, and re- 
 freshing and fertilizing the land on which they fall. 
 4 
 
CHAPTER III. 
 
 Structure of plants — Mode in which their nourishment is ob- 
 tained — Growth and substance of plants — Production of 
 their substance from the food they imbibe — Mutual trans- 
 formations of starch, sugar, and woody fibre. 
 
 From the compound substances, described in the 
 preceding chapter, plants derive the greater por- 
 tion of the carbon, hydrogen, oxygen, and nitrogen, 
 of which their organic part consists. The living 
 plant possesses the power of absorbing these com- 
 pound bodies, of decomposing them in the interior 
 of its several vessels, and of recompounding their 
 elements in a different way, so as to produce new 
 substances, — the ordinary products of vegetable 
 life. Let us briefly consider the general structure 
 of plants, and their mode of growth. 
 
STRUCTURE OF THE STEM AND ROOT OF PLANTS. 39 
 
 SECTION I. OF THE STRUCTURE OF PLANTS, AND THE MODE 
 
 IN WHICH THEIR NOURISHMENT IS OBTAINED. 
 
 A perfect plant consists of three several parts, — 
 a root which throws out arms and fibres in every 
 direction into the soil, — a trunk which branches 
 into the air on every side, — and leaves which, from 
 the ends of the branches and twigs, spread out a 
 more or less extended surface into the surround- 
 ing air. Each of these parts has a peculiar struc- 
 ture and a special function assigned to it. 
 
 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 bundles of mi- 
 nute hollow tubes, laid horizontally one over the 
 other ; the wood and inner bark, 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 dis- 
 tinctly seen. The branch is only a prolongation 
 of the stem, and has a similar structure. 
 
 The root,, immediately on leaving the trunk or 
 stem, has also a similar structure ; but as the root 
 tapers away, the pith gradually disappears, the 
 
40 STRUCTURE OF THE LEAF. 
 
 bark also thins out, the wood softens, till the 
 white tendrils, of which its extremities are com- 
 posed, consist only of a colourless spongy mass, 
 full of pores, but 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 them these spongy extre- 
 mities are connected with the leaves. 
 
 The leaf is an expansion of the twig. The fibres 
 which are seen to branch out from the base over 
 the inner surface of the leaf are prolongations of 
 the vessels of the wood. The green exterior por- 
 tion of the leaf is, in like manner, a continuation 
 of the bark in a very thin and porous form. The 
 green of the leaf, though full of pores, especially 
 on the under part, yet also consists of, or contains, 
 a collection of tubes or vessels, which stretch along 
 its surface, and communicate with those of the 
 bark. 
 
 Most of these vessels in the living plant are full 
 of sap, and this sap is in almost continual motion. 
 In spring and autumn the motion is more rapid, 
 and in winter it is sometimes scarcely perceptible ; 
 yet the sap is supposed to be rarely quite station- 
 ary in every part of the tree. 
 
 From the spongy part of the root the sap ascends 
 through the vessels of the wood, till it is diffused 
 
FUNCTIONS OF THE LEAF. 41 
 
 over the inner surface of the leaf by the fibres 
 which the wood contains. Hence, by the vessels 
 in the green of the leaf, it is returned to the bark, 
 and through the vessels of the inner bark it de- 
 scends to the root. 
 
 Every one understands why the roots send out 
 fibres in every direction through the soil, — it is in 
 search of water and oHiquicl food, which the spongy 
 fibres suck in and send forward with the sap to the 
 upper parts of the tree. It is to aid these roots in 
 procuring food that, in the art of culture, such sub- 
 stances are mixed with the soil where these roots 
 are, as are supposed to be necessary, or at least fa- 
 vourable, to the growth of the plant. 
 
 It is not so obvious that the leaves spread out 
 their broad surfaces into the air for the same pur- 
 pose 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 almost solely gaseous food. In the 
 sunshine, the leaves are continually ahsorhing car- 
 bonic acid from the air and giving off oxygen gas. 
 That is to say, they are continually appropriating 
 carbon from the air.* When night comes, this pro- 
 cess ceases, and they begin to absorb oxygen and to 
 
 * Since carbonic acid, as shewn in the previous chapter, 
 
 consists only of carbon and oxygen, they retain the carbon 
 
 and reject the oxygen. 
 4* 
 
42 THEY ABSOEB CAEBON FROM THE AIB. 
 
 give off carbonic acid. But this 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, how- 
 ever, varies with the season, with the climate, and 
 with the kind of tree. The proportion of the whole 
 carbon contained by a plant, which has been de- 
 rived from the air, is greatly modified also by the 
 quality of the soil in which it grows, and by the 
 comparative abundance of liquid food which hap- 
 pens 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 three- 
 fourths of the entire quantity of carbon contained 
 in the crops we reap from land of average fertili- 
 ty, 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 dark- 
 ness ever interrupts or suspends its labours. 
 
 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 
 
SUBSTANCE OF PLANTS. 43 
 
 comfort of animals to whom this gas is hiirtfal. 
 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 labours of millions of pores, the 
 substance of whole forests of solid wood is slowly 
 extracted from the fleeting winds. The green 
 stem of the young shoot, and the green stalks of 
 the grasses, also absorb carbonic acid as the green 
 of the leaf does, and thus a larger supply is af- 
 forded when the growth is most rapid, or when 
 the short life of the annual plant demands much 
 nourishment within a limited time. 
 
 SECTION II. OF THE GROWTH AND SUBSTANCE OF PLANTS. 
 
 In this way the perfect plant derives its food 
 from the soil and from the air ; but perfect 
 plants arise from seeds ; and the study of the en- 
 tire life— the career, so to speak — of a plant, pre- 
 sents many interesting and instructive subjects of 
 consideration. 
 
 When a portion of flour is made into dough, 
 and this dough is kneaded with the hand under a 
 stream of water upon a fine sieve, as long as the 
 water passes through milky, there will remain on 
 the sieve a glutinous sticky substance resembhng 
 
44 STARCH AND GLUTEN IN THE SEED. 
 
 birdlime, while the milky water will gradually de- 
 posit a pure white powder. This powder is starch, 
 that which remains on the sieve is gluten. Both of 
 these substances exist, therefore, in the flour ; they 
 both also exist in the grain. The starch consists 
 of carbon, hydrogen, and oxygen only ; the gluten, 
 in addition to these, contains also nitrogen. 
 
 When ground into flour, these substances serve 
 for food to man ; in the unbruised grain they are 
 intended to feed the future plant in its earliest in- 
 fancy. 
 
 When a seed is committed to the earth, if the 
 warmth and moisture are favourable, it begins to 
 sprout. It pushes a shoot upwards, it thrusts a 
 root downwards, but, until the leaf expand, 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 
 substances, though capable of being separated from 
 each other by means of water, as above stated, yet 
 are neither of them soluble in water. Hence, they 
 cannot, without undergoing a previous change, be 
 taken up by the sap, and conveyed along the 
 pores of the young shoot they are destined to feed. 
 But it is so arranged that, when the seed first 
 shoots, there is produced at the base of the germ, 
 
STARCH CHANGED INTO SUGAR. 45 
 
 from a portion of the gluten, a small quantity of 
 a substance (diastase) which has so powerful an 
 effect upon the starch as 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.* As the sap ascends, it 
 becomes sweet, — the starch thus dissolved changes 
 into sugar. When the shoot first becomes tipped 
 with green, the sugar is again changed into the 
 woody fibre, of which the stem of perfect plants 
 chiefly consists. By the time that the food con- 
 tained in the seed is exhausted, — often, as in the 
 potato, 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 woody 
 fibre is observable more or less in all plants. When 
 they are shooting fastest the sugar is most abun- 
 dant ; not, however, in those parts which are grow- 
 
 * 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 sprouting, will not dissolve in water, 
 but when sprouted, the whole of the starch (the flour) it con- 
 tains dissolves readily by a gentle heat. The diastase formed 
 during the germination eifects this. By further heating in the 
 brewer's wort, this starch is converted into sugar as it is in 
 the growing plant. 
 
46 SUGAR CHANGED INTO WOODY FIBRE. 
 
 ing, but in those which convey the sap to the grow- 
 ing parts. Thus the sugar of the ascending sap of 
 the maple and the alder disappears in the leaf and 
 in the extremities of the twig ; thus the sugar-cane 
 sweetens 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 prin- 
 ciple 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, gradually diminishes and finally 
 disappears ; the sugar of the sap is here changed 
 into the starch of the grain, which, as above de- 
 scribed, is afterwards destined, when the grain be- 
 gins 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 first taste- 
 less, then becomes sour, and at last sweet. In this 
 case the acid of the unripe is changed into the su- 
 gar of the ripened fruit. 
 
 The substance of plants, — their solid parts that 
 is — consist chiefly of woody fibre, the name given 
 to the fibrous substance, of which wood evidently 
 consists. It is interesting to inquire how this sub, 
 gtance can be formed from the compounds, car. 
 
Woody fibre formed from the food. 47 
 
 bonic acid and water, of which the food of plants 
 in great measure consists. Nor is it difficult to 
 find an answer. 
 
 It will be recollected that the leaf drinks in cai'- 
 bonic acid from the air, and delivers back its oxy- 
 gen, retaining only its carbon. It is also known 
 that water abounds in the sap. Hence carbon and 
 water are thus abundantly present in the pores or 
 vessels of the green leaf. Now, woody fibre con- 
 sists only of carbon and water chemically combined 
 together, — 100 lbs. of dry woody fibre consisting of 
 50 lbs. of carbon and 50 lbs. of water. It is easy, 
 therefore, to see how, when the carbon and water 
 meet in the leaf, woody fibre may be produced by 
 their mutual combination. 
 
 If, again, we inquire how this important prin- 
 ciple of plants may be formed from the other sub^ 
 stances, which enter by their roots, from the ul- 
 mic acid, for example, the answer is equally ready. 
 This acid also consists of carbon and water only^ 
 60 lbs. of carbon with 37| of water forming ulmic 
 acid, so that when it is introduced into the sap of 
 the plant, all the materials are present from whicb 
 the woody fibre may be produced. 
 
 Nor is it more difficult to see how starch may 
 be converted into sugar, and this again into woody 
 fibre ; or how, again, sugar may be converted into 
 
48 CONSTITUTION OP SUGAR, STARCH, ETC. 
 
 starch in the ear of corn, or woody fibre into sugar 
 during the ripening of the winter pear after its re- 
 moval from the tree. Any one of these substances 
 may he represented by carbon and water only. 
 Thus,— . 
 
 50 lbs. of carbon with 50 of water, make 100 of woody fibre. 
 50 lbs 37^ 87j of ulmic acid. 
 
 C of cane sugar, 
 
 50 lbs 72i 122i } of starch, or 
 
 / of gum. 
 
 50 lbs 56 ; 106 of vinegar. 
 
 In the interior of the plant, therefore, it is obvi- 
 ous that, whichever of these substances be 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 favoured, it would lead into too great detail to 
 attempt here to explain.* 
 
 We cannot help admiring to what varied pur- 
 poses in nature the same elements are applied, and 
 from how few and simple materials, substances, the 
 most varied in their properties, are in the living 
 vegetable daily produced. 
 
 * For fuller and more precise explanations on these in- 
 teresting topics, see the Author's Lectures on Agricultural 
 Chemist/ry and Geology, Part I. 
 
CHAPTER IV. 
 
 Of the Inorganic Constitution of Plants — Their immediate 
 Source — Their Nature — Gluantity of each in certain com- 
 mon Crops. 
 
 SECTION I. — ^SOURCE OF THE EARTHY MATTER OP PLANTS 
 —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, and sometimes in different speci- 
 mens of the same kind of plant, especially if grown 
 upon different soils ; yet it is never wholly absent. 
 It seems as necessary to their existence in a state 
 of perfect health as any of the elements which con- 
 stitute 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 
 
50 USES OF THE SOIL. 
 
 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 woody fibre, 
 and of the other organic parts of the plant, may 
 be derived either from the air, from the carbonic 
 acid and watery vapour taken in by the leaves, or 
 from the soil, through the medium of the roots. 
 In the air, however, only rare particles of inor- 
 ganic or earthy matter are known to float, and 
 these in a solid form, so as to be unable to enter 
 by the leaves ; the earthy matter which constitutes 
 the ash, therefore, must be all derived from the 
 soil. 
 
 The earthy part of the soil, therefore, serves a 
 double use. It is not merely, as some have sup- 
 posed, a substratum in which the plant may so fix 
 ind root itself, as to be able to maintain its upright 
 position against the force of winds and tempests ; 
 but it is a storehouse of food also, from which the 
 roots of the plant may select such earthy sub- 
 stances as are necessary to, or are fitted to pro- 
 mote, its growth. 
 
 The ash of plants consists of a mixture of seve- 
 ral, sometimes of as many as eleven, different earthy 
 substances. These substances are the following : — 
 
POTASH, SODA, LIME, ETC. 51 
 
 1. Potash. — The common pearl-ash of the shops 
 is a compound of potash with carbonic acid ; it is 
 a carbonate of potash. By dissolving the pearl- 
 ash in water, and boiling it with quicklime, the 
 carbonic acid is separated, and potash alone, or 
 caustic potash, as it is often called, is obtained. 
 
 2. Soda. — The common soda of the shops is a 
 carbonate of soda, and by boihng it with quick- 
 lime, the carbonic acid is separated, as in the case 
 of pearl-ash. 
 
 3. Lime. — This is familiar to every one as the 
 lime-shells, or unslaked lime of the limekilns. The 
 unburned limestone is a ca?'bonate of lime ; the car- 
 bonic acid in this case being separated by the 
 roasting in the kiln. 
 
 4. Magnesia. — This is the calcined magnesia of 
 the shops. The uncalcined is a carbonate of mag- 
 nesia, from which heat drives off the carbonic acid. 
 
 5. Silica. — This is the name given by chemists 
 to the substance of flint, quartz, and of siliceous 
 sands and sandstones. 
 
 6. Alumina is the pure earth of alum, ob- 
 tained 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. 
 
52 SULPHUR AND SULPHURIC ACID. 
 
 7. Oxide of Iron. — The most familiar form of 
 this substance is the rust that forms on metalHc 
 iron in damp places. It is a compound of iron 
 with oxygen, hence the name oxide. 
 
 8. Oxide of Manganese is a brown powder, 
 which consists of oxygen in combination with a 
 metal resembling iron, to which the name of man- 
 ganese is given. It exists in plants, and in soils 
 only in very small quantity. 
 
 9. Sulphur. — This substance is well known. It 
 generally exists in the ash in the state of sulphuric 
 acid (oil of vitriol), which is a compound of sul- 
 phur with oxygen. It does not always exist in 
 living plants, however, in this state. 
 
 Sulphuric acid forms with potash a sulphate of 
 potash, — with soda, sidphate of soda (or Glauber's 
 salts), — with lime, sulphate of lime (gypsum), — with 
 magnesia, sulphate of magnesia (Epsom salts), — 
 with alumina, sulphate of alumina, — 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 is a soft pale yellow substance 
 which readily takes fire in the air, and gives off, 
 while burning, a dense white smoke. The white 
 fumes which form this smoke are a compound of 
 phosphorus with oxygen obtained from the air, 
 
PHOSPHORIC ACID AND SULPHUR. 53 
 
 and are called pJiosjjhoric acid. In the ash of 
 plants the phosphorus is found in the state of phos- 
 phoric acid, though it probably does not all exist 
 in the living plant in tiiat state. 
 
 Phosphoric acid forms jihosphales with potash, 
 soda, lime, and magnesia. When bones are burned, 
 a large quantity of a white earth remains (bone 
 earth), which is a phosphate of lime, consisting of 
 lime and phosphoric acid. Phosphate of lime is 
 generally present in the ash of plants ; phosphate 
 of magnesia is contained most abundantly in the 
 ash of wheat and other varieties of grain. 
 
 11. Chlorine, — This is a very suffocating gas, 
 which gives its peculiar smell to chloride of lime, 
 and is used for bleaching and disinfecting. It is 
 readily obtained by pouring muriatic acid (spirit 
 of salt) on the black oxide of manganese of the 
 shops. 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. 
 
 * Potash, soda, lime, and magnesia, are compounds of die 
 metals here named with oxygen. It is a veiy striking fact, 
 that the suffocating gas chlorine, when combined with sodi- 
 um, a metal which takes fire when placed upon water, should 
 form the agreeable and necessary condiment, comvion salt. 
 5* 
 
54 THE QUANTITY OF ASH VARIES 
 
 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 DIFFERENCE IN THE QUANTITY OP 
 ASH. 
 
 1. The quantity of ash yielded by different 
 plants is unlike. Thus 1000 lbs. of 
 
 Wheat leave 12 lbs. Barley leave 25 lbs. 
 
 Oats ... 26 lbs. Potatoes ... 8 lbs. 
 
 Turnips ... 8 lbs. Carrots ... 7 lbs. 
 
 Red Clover ... 16 lbs. White Clover ... 17 lbs. 
 Rye Grass ... 17 lbs. 
 
 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 in- 
 organic food, then only those plants will grow 
 well upon it which require the least. Hence, 
 trees may often grow where arable crops fail to 
 thrive, because many of them require and contain 
 very little inorganic matter. Thus while 1000 lbs. 
 of elm wood leave 19 lbs. and of poplar 20 lbs. of 
 
WITH THE SPECIES AND THE PART. 55 
 
 ash, the same weight of the willow leaves only 4^ 
 lbs., of the beech 4 lbs., of the birch S^ lbs., of dif- 
 ferent pines less than 3 lbs., and of the oak only 
 2 lbs. of ash when burned. 
 
 2. The quantity of inorganic matter varies in 
 different parts of the same 'plant. Thus while 
 1000 lbs. of the turnip root sliced and dried in 
 the air leave 70 lbs. of ash, the dried leaves give 
 130 lbs. ; and while the grain of wheat yields only 
 12 lbs. wheat straw will yield 60 lbs. of earthy 
 matter. So, though the willow and other woods 
 leave little ash, as above stated, yet the willow 
 leaf leaves 82 lbs., the beech leaf 42 lbs., the birch 
 50 lbs., the different pine leaves 20 lbs. to 30 lbs., 
 and the leaves of the elm as much as 120 lbs. of 
 incombustible matter when burned in the air. 
 
 Most of the inorganic matter, therefore, which 
 is withdrawn from l^e soil in a^jpop of corn is re- 
 turned to it again, by the skilful husbandman, in 
 the fermented straw, — in the same way as 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 the roots during the 
 season of growth. 
 
 Thus an annual top-dressing is given to the 
 land where forests grow ; and that which the roots 
 
56 AND WITH THE VARIETY OF THE PLANT. 
 
 from spring to autumn are continually sucking 
 up, and carefully collecting from considerable 
 depths, winter strews again on the surface, so as, 
 in the lapse of time, to form a soil which cannot 
 fail to prove fertile, — because it is made up of those 
 very materials of which the inorganic substance of 
 former races of vegetables has been entirely com- 
 posed. 
 
 2. The quantity of inorganic matter often differs 
 in different specimens of the same plant. Thus, 
 1000 lbs. of wheat straw, grown at different places, 
 gave to four different experimenters 43, 44, 35, 
 and 155 lbs. of ash respectively. Wheat straw, 
 therefore, does not always leave the same quantity 
 of ash. 
 
 To what is this difference owing ? Is it to the 
 nature of the soil, or does it depend upon the va- 
 riety of wheat experimented upon 1 It seems to 
 depend partly upon both. Thus, on the same field, 
 in Ravensworth dale, Yorkshire, on a rich clay soil 
 abounding in lime, the Golden Kent and Flanders 
 Red wheats were sown 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 lbs. of ash from 1000 lbs., that of the latter only 
 120 lbs. Something, therefore, depends upon the 
 
WHENCE THESE DIFFERENCES ? 57 
 
 variety. But as from the straw of a good wheat 
 crop grown near Durham this last summer on a 
 clay loam I obtained only 66 lbs. of ash, I am per- 
 suaded that the very wide variations in the quanti- 
 ty of ash left, by different wheat straws, must be de- 
 pendent in some considerable degree upon the soil. 
 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 most healthy manner ; — that it is capa- 
 ble of living, growing, and even ripening seed 
 with very much less than this quantity ; — but that 
 those soils will produce the most perfect plants 
 which can best supply all their wants, — and that 
 the best seed will be raised in those districts where 
 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. 
 
 SECTION III. — OP THE QUALITY OF THE ASH OF PLANTS. 
 
 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 two specimens of ash, the kind of 
 matter of which they respectively consist, may be 
 
58 
 
 QUALITY OF THE ASH VARIES. 
 
 very different. The ash of one may contain much 
 lime, of another much potash, of a third much 
 soda, while in a fourth much silica may be pre- 
 sent. Thus 100 lbs. of the ash of hean straw con- 
 tain 53i lbs. of potash, while that of barley straw 
 contains only 3^ lbs. in the hundred ; and, on the 
 other hand, the same weight of the ash of the lat- 
 ter contains 73i lbs. of silica, while in that of the 
 former there are only 1\ lbs. 
 
 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. 100 lbs. of 
 the ash of wheat, barley, and oats, for example, 
 contain, respectively, 
 
 
 
 Wheat. 
 
 Barley. 
 
 Oats. 
 
 Potash, . 
 
 
 19 
 
 12 
 
 6 
 
 Soda, 
 
 
 . 20i 
 
 12 
 
 5 
 
 Lime, 
 
 
 8 
 
 4i 
 
 3 
 
 Magnesia, 
 
 
 8 
 
 8 
 
 2^ 
 
 Alumina, 
 
 
 2 
 
 1 
 
 i 
 
 Oxide of Ii 
 
 on. 
 
 
 
 trace. 
 
 U 
 
 Silica, 
 
 , . 
 
 . 34 
 
 50 
 
 76i 
 
 Sulphuric 
 
 acid. 
 
 4 
 
 21 
 
 U 
 
 Phosphoric acid, 
 
 3i 
 
 9 
 
 3 
 
 Chlorine, 
 
 . 
 
 1 
 
 1 
 
 h 
 
 100 
 
 100 
 
 100 
 
 A comparison of the several numbers opposite 
 to each other in these three columns, shews how 
 
MORE POTASH AND SODA IN WHEAT. 59 
 
 unlike the quantities of the different substances 
 are, which are contained in an equal weight of the 
 ash of these three varieties of grain. The ash of 
 wheat contains 19 lbs. of potash in the 100 lbs., 
 while that of oats contains only 6 lbs. In wheat 
 are 20 J per cent, of soda, in oats only 5 per cent. 
 Wheat also contains more sulphuric acid than 
 either of the other grains, while barley contains a 
 still greater predominance of phosphoric acid. 
 
 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 the same in weight — very dif- 
 ferent quantities of potash, soda, &c. from a crop 
 of oats. It will take more of these, of sulphuric 
 acid, and of certain other substances, from the soil. 
 It will, therefore, exhaust the soil more of these 
 substances — as barley and oats will of others — 
 hence one reason why a piece of land may suit one 
 of these crops and not suit the others. That which 
 cannot grow wheat may yet grow oats. Hence, 
 also, two successive crops oi different kinds of grain 
 may grow 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 reason for a rotation of crops. 
 The surface soil may be so far exhausted of one 
 inorganic substance, that it cannot afford it in 
 
60 THE ASH OF WHEAT AND OTHER STRAWS 
 
 sufficient quantity during the present season to 
 bring a given crop to healthy maturity, and yet 
 may, by natural processes, be so far supplied 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 ap- 
 pear by comparing the following with the preced- 
 ing table :— ^ 
 
 Wheat Straw. Barley Straw. Oat Straw 
 
 Potash, 
 
 h 
 
 3i 
 
 15 
 
 Soda, 
 
 1 
 
 1 
 
 trace. 
 
 Lime, 
 
 . 7 
 
 lOi 
 
 21 
 
 Magnesia, 
 
 1 
 
 li 
 
 i 
 
 Alumina, . 
 
 • 21 
 
 3 
 
 trace. 
 
 Oxide of Iron, . 
 Oxide of manganese, 
 
 V 
 
 i 
 
 trace. 
 
 Silica, 
 
 81 
 
 73i 
 
 80 
 
 Sulphuric acid. 
 
 1 
 
 2 
 
 li 
 
 Phosphoric acid, 
 
 . 5 
 
 3 
 
 i 
 
 Chlorine, . 
 
 . 1 
 
 n 
 
 trace. 
 
 100 
 
 100 
 
 100 
 
 Not only are the quantities of the several in- 
 organic substances contained in these different 
 
VARIES IN QUALITY WITH THE SOIL, 61 
 
 kinds of straw very unlike — especially the pro- 
 portions of potash, lime, and phosphoric acid in 
 each — but these quantities are also very different 
 from those exhibited by the numbers in the pre- 
 ceding table as contained in the three varieties of 
 grain. In this difference we see, further, one rea- 
 son why the same soil which may be favourable to 
 the growth of straw may not be equally propitious 
 to the growth of the ear. Wheat straw contains 
 little either of potash or of soda ; the ash of the 
 grain contains a large proportion ; while the ash of 
 the oat-straw, on the other hand, contains a 
 much larger proportion of potash than that of its 
 own ear does. 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 be able to give 
 ample sustenance to the filling ear.* 
 
 3. The quality of the ash varies also with the 
 soil in which it grows. This will be understood 
 from what is stated above. Where the soil is 
 favourable, the roots can send up into the straw 
 
 * And occasionally do give ; for a plump grain, and even 
 a well-filled ear, are not unfrequently found where the straw 
 is unusually deficient. 
 6 
 
62 AND WITH THE AGE OF THE PLANT. 
 
 every thing which the healthy plant requires ; 
 when it is poorly supplied with some of those in- 
 organic constituents which the plant desires, Hfe 
 may be prolonged, a stunted or unhealthy crop 
 may be raised, in which the kind, and perhaps the 
 quantity, of ash left in burning will necessarily be 
 different from that left by the same species of 
 plant grown under more favouring circumstances. 
 Of this fact there can be no doubt, though the 
 extent to which such variations may take place 
 without absolutely kiUing the plant, has not yet 
 been by any means made out. 
 
 4. It varies also with the period of a plant's 
 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 they contain con- 
 sists 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 perceptible con- 
 nection with the ordinary processes of practical 
 agriculture, and tend to throw considerable light 
 on some of the principles by which they ought to 
 be regulated. One illustration of this is exhibited 
 in the following section. 
 
ASH IN A SERIES OF CROPS. 63 
 
 SECTION IV. QUANTITY OF INORGANIC MATTER CONTAINED 
 
 IN AN ORDINARY CROP OR SERIES OF CROPS. 
 
 The importance of the inorganic matter con- 
 tained in living vegetables, or in vegetable sub- 
 stances when reaped and dry, will appear more 
 distinctly if we consider the actual quantity car- 
 ried off from the soil in a series of crops. 
 
 In a four-years' course of cropping, in which the 
 crops gathered amount per acre to — 
 
 1st year, Turnips, 25 tons of bulbs, and 7 tons of tops. 
 
 2d year. Barley, 38 bushels of 63 lbs. each, and 1 ton of 
 straw. 
 
 3d year, Clover and Rye- Grass, 1 ton of each in hay. 
 
 4th year. Wheat, 25 bushels of 60 lbs. , and 1 f tons of straw. 
 
 The quantity of inorganic matter carried off 
 
 in the four crops, supposing none of them to be 
 
 eaten on the land, amounts to — 
 
 Silica, . . . 318 lbs. 
 Sulphuric acid, 111 " 
 Phosphoric acid, 61 " 
 Chlorine, . 39 " 
 
 Potash, . . 
 
 . 281 lbs, 
 
 Soda, . . , 
 
 . . 130 " 
 
 Lime, . . 
 
 . 242 " 
 
 Magnesia, 
 
 42 " 
 
 Alumina, 
 
 . 11 " 
 
 Total, 1240 
 
 or, in all, about 11 cwt. — of which gross weight 
 the different substances form very unlike pro- 
 portions. 
 
 A still clearer idea of these quantities will be 
 
64 
 
 HOW TO BE REPLACED. 
 
 obtained by a consideration of the fact, that if we 
 carry off the entire produce, and return 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, add to each acre every four 
 years : — 
 
 Pearl or Pot-ash, . , 390 lbs. at a cost of Z.3 10 
 
 Ciystallized carbonate of soda, 440 ... 25 
 
 Common salt, . 
 
 duick (burned) lime, 
 
 Epsom salts. 
 
 Alum, 
 
 Bone dust. 
 
 Total, 
 
 65 
 240 
 250 
 
 84 
 260 
 
 1729 
 
 2 
 
 1 
 
 1 5 
 8 
 16 
 
 Z.8 7 
 
 Several observations suggest themselves from 
 a consideration of the above statements ijirstt 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 impoverish the soil 
 of this inorganic food ; second, that the more of 
 what grows upon the land we can again return 
 to it in manure, the less will this deterioration be 
 perceptible ; third, that as many of these inorganic 
 substances are readily soluble in water, the liquid 
 manure of the farm-yard, so often allowed to 
 run to waste, carries with it to the rivers much of 
 the saline matter that ought to be returned to the 
 
DETERIORATION OF LAND OFTEN SLOW. 65 
 
 land ; and, lastly, that the utility and often indis- 
 pensable necessity of certain artificial manures is 
 owing, it may be, in some districts, to the natu- 
 ral poverty of the land in certain inorganic substan- 
 ces, — but more frequently to a want of acquaint- 
 ance with the facts above stated, among practical 
 men, and to the long continued neglect and waste 
 which has been the natural consequence. 
 
 In certain districts, the soil and subsoil contain 
 within themselves an almost unfailing supply of 
 some of these inorganic substances, so that the 
 waste is long in being felt ; in others they become 
 sooner exhausted, and hence call for more care, 
 and, when exhausted, for a more expensive culti- 
 vation, in order to replace them. 
 
 One thing is of essential importance to be re- 
 membered by the practical farmer — that the dete- 
 rioration of land is often an exceedingly slow 
 process. In the hands of successive generations 
 a field may so imperceptibly become less valuable, 
 that a century even may elapse before the change 
 prove such as to make a sensible diminution in 
 the valued rental. Such slow changes, however, 
 have been seldom recorded ; and hence the prac- 
 tical man is occasionally led to despise the clear- 
 est theoretical principles, because he has not hap- 
 pened to see them verified in his own limited ex- 
 6* 
 
66 VALUE OF A HISTORY OF TILLAGE. 
 
 perience, and to neglect therefore the suggestions 
 and the wise precautions which these principles 
 lay before him. 
 
 The agricultural history of tracts of land of 
 different qualities, shewing how they had been 
 cropped and tilled, and the average produce in 
 grain, hay, straw, and other crops, every five years, 
 during an entire century, would be invaluable ma- 
 terials both to theoretical and to practical agri- 
 culture. 
 
CHAPTER V. 
 
 Of Soils — their Organic and Inorganic Portions — Saline 
 Matter in Soils — Examination and Classification of Soils 
 — Diversities of Soils and Subsoils. 
 
 Soils consist of two parts, — of an organic part, 
 which can readily be burnt away when the soil 
 is heated to redness ; and of an inorganic part, 
 which is fixed in the fire, and which consists en- 
 tirely of earthy and saline substances. 
 
 SECTION I. — OF THE ORGANIC PART 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 
 
68 THE ORGAIVIC PART OF SOILS VARIES. 
 
 have been added by the hand of man for the pur- 
 pose of increasing its natural fertihty. 
 
 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 some rich long cultivated lands 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~ per cent., barley when 
 2 to 3 are present, while good wheat soils gene- 
 rally contain from 4 to 8 per cent. In stiff and 
 very clayey soils 10 to 12 per cent, may occasion- 
 ally be detected. In very old pasture lands and 
 in gardens, vegetable matter occasionally accumu- 
 lates, so as to overload the upper soil. 
 
 To this organic matter in the soil the name of 
 humus has been given by some writers. It con- 
 tains or yields to the plant the ulmic and humic 
 acids described in a previous chapter. 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 minister to the 
 growth of living vegetables. During the same de- 
 cay ammonia is likewise produced, — and in larger 
 quantity, if animal matter be present in consider- 
 
INFLUENCE OF THE ORGANIC PART. 69 
 
 able abundance, — which ammonia is found to pro- 
 mote vegetation in a remarkable manner. Other 
 substances, more or less nutritious, are also formed 
 from it 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 we have seen that all vegetable substances 
 do, — a considerable quantity of inorganic, that is, 
 of saline and earthy matter, which is liberated 
 as the organic part decays. Thus living plants 
 derive from the remains of former races buried 
 beneath the surface, a portion of that inorganic 
 food which can only be obtained in the soil, — and 
 which, if not thus directly suppHed, 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, places within the easy reach of the roots 
 not only organic but inorganic food also. 
 
70 SALINE INGREDIENTS OF SOILS. 
 
 SECTION II. OF THE INORGANIC PART OF SOILS. 
 
 The inorganic part of soils, — that which remains 
 behind, when every thing combustible is burned 
 away by heating it to redness in the open air, — 
 consists of two portions, one of which is soluble in 
 water, the other insoluble. The soluble consists 
 of saline substances, the insoluble of earthy sub- 
 stances. 
 
 1. The saline or soluble portion. — In this coun- 
 try the surface soil of our fields, in general, con- 
 tains 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, the whole well stirred and allowed 
 to settle, — the clear liquid, when poured off and 
 boiled to dryness, may leave from 2 to 20 grains 
 of saline matter. This saline matter will con- 
 sist of common salt, gypsum, sulphate of soda 
 (Glauber's salts), sulphate of magnesia (Epsom 
 salts), with traces of the chlorides of calcium, mag- 
 nesium, and potassium, and of the nitrates of pot- 
 ash, soda, and lime.* It is from these soluble sub- 
 stances that the plants derive the greater portion 
 
 ♦ See pages 51 and 52, where these substances are described. 
 
SALINE INCRUSTATIONS. 71 
 
 of the saline ingredients contained in the ash they 
 leave when burned. 
 
 Nor 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 every pound of a soil a foot deep, is 
 equal to 500 lbs. in an acre, which is more than is 
 carried off from the soil in 10 rotations (40 years), 
 where only the wheat and barley are sent to mar- 
 ket, and the straw and green crops are regularly 
 returned to the land in the manure.* 
 
 In some countries, indeed in some districts of 
 our own country, the quantity of saline matter in 
 the soil is so great, as in hot seasons to form a dis- 
 tinct incrustation on the surface. This may often 
 be seen in the neighbourhood 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 in vapour, — it is evident that 
 the longer the dry weather and the consequent 
 
 ♦ A further portion, it will be recollected, is carried off 
 in the cattle that are sent to market, — this is here ne- 
 glected. 
 
72 EFFECT OF RAIN AND DROUGHTS. 
 
 evaporation from the surface continue, the thicker 
 the incrustations will be, or the greater the accu- 
 mulation of saline 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 
 covering of the different saline substances above 
 mentioned. 
 
 When rain falls, the saline matter is dissolved, 
 and descends again to the subsoil, — in dry weather 
 it reascends. Thus the surface soil of any field 
 will contain a larger proportion of soluble inor- 
 ganic matter in the middle of a hot season than 
 in one of even ordinary rain ; and hence the fine 
 dry weather which, in early summer, hastens the 
 growth of corn, and later in the season favours its 
 ripening, does so, among its other modes of ac- 
 tion, by bringing up to the roots from beneath a 
 more ready supply of those saline compounds 
 which the crop requires for its healthful growth. 
 
 2. The earthy or insoluble portion. — The earthy 
 or insoluble portion of soils rarely constitutes 
 less than 95 lbs. in a hundred of their whole 
 weight. It consists chiefly of silica in the form 
 of sand, of alumina in the form of c7«?/, and of 
 lime in the form of carbonate of lime. It is rarely 
 
CLASSIFICATION OF SOILS. 73 
 
 free, however, from one or two per cent, of oxide 
 of iron ; and where the soil is of a red colour, this 
 oxide is present in a still larger quantity. A trace 
 of magnesia also may be almost always detected, 
 and a minute quantity of phosphate of lime. The 
 principal ingredients, however, of the earthy part 
 of all soils are sand, clay, and lime ; and soils are 
 named or classified according to the quantities of 
 each of these three they may happen to contain. 
 
 If an ounce of soil be boiled in a pint of water 
 till it is perfectly softened and diffused through 
 it, and, 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 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 on the bot- 
 tom of the one vessel, the clayey part on that of 
 the other, and they may be dried and weighed se- 
 parately. 
 
 If 100 grains of dry soil leave no more than 10 
 of clay, it is called a sandy soil ; if from 10 to 40, 
 a sandy loam ; if from 40 to 70, a loamy soil ; if 
 from 70 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, 
 7 
 
^i HOW to ESTIMATE THE LIME. 
 
 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 ma- 
 nufacture of pipes (pipe clay). 
 
 Soils consist of these three substances mixed to- 
 gether. The pure clay is a chemical compound of 
 silica and alumina, in the proportion of about 60 of 
 the former to 40 of the latter. Pure clay soils 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 happen, therefore, that arable land 
 will contain more than 30 to 35 of alumina. 
 
 If a soil contain more than 5 per cent, of carbo- 
 nate of lime, it is called a rnarl ; if more than 20 
 per cent., it is a calcareous soil. Peaty soils, of 
 course, are those in which the vegetable matter 
 predominates very much. 
 
 To estimate the lime, a quantity of the soil 
 should be burned in the air, and a weighed por- 
 tion, 100 or 200 grains, diffused through half a 
 pint of cold water mixed with half a wine glass- 
 ful of spirit of salt (muriatic acid), and allowed 
 to stand for a couple of hours, with occasional 
 stirring. The water is then poured off, the soil 
 
DIVERSITIES OF SOILS. 75 
 
 dried, heated to redness as before, and weighed : 
 the loss is nearly all lime.* 
 
 The quantity of vegetable or other organic mat- 
 ter is determined by drying the soil well upon 
 paper in an oven, and then burning a weighed 
 quantity in the air : the loss is nearly all organic 
 matter. In stiff clays this loss will comprise a 
 portion of water, which is not wholly driven off 
 from such soils by drying upon paper in the way 
 described. 
 
 SECTION III. OP THE DIVERSITIES OF SOILS AND 
 
 SUBSOILS. 
 
 Though the substances of which soils chiejly 
 consist are so few in number, yet every practical 
 man knows how very diversified they are in cha- 
 racter — 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 give the prevailing character to the 
 
 * Unless the soil happen to contain a large quantity of 
 magnesia, which is rarely the pase. 
 
76 KNOWLEDGE OF SUBSOILS IMPORTANT. 
 
 soils of other districts. Such differences as these 
 arise from the different proportions in which the 
 sand, lime, clay, and the oxide of iron which co- 
 lours 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 ? 
 
 Again, the soil on the surface rests on what is 
 usually denominated the subsoil. This, also, is 
 very various in its character and quality. Some- 
 times 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 
 impervious to water. 
 
 The most ignorant farmer knows how much the 
 value of a piece of land depends upon the cha- 
 racters of the surface soil, — the intelligent im- 
 prover understands best the importance of a fa- 
 vourable 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 
 
HOW SUBSOILS COME TO DIFFER. 77 
 
 all the moisture which the sandy subsoil had left 
 in 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 all such differ- 
 ences, and supplies us with principles by which 
 we can predict the general quality of the soil and 
 subsoil in the several parts of entire kingdoms ; — 
 and where the soil is of inferior quality and yet 
 susceptible of improvement, the same principles 
 indicate whether the means of improving it are 
 likely, in any given locality, to be attainable at a 
 reasonable cost. 
 
 It will be proper shortly to illustrate these di- 
 rect relations of geology to agriculture. 
 
CHAPTER VI. 
 
 Direct relations of Geology to Agriculture — Origin of Soils — 
 Causes of their Diversity — Relation to the Rocks on which 
 they rest — Constancy in the relative Position and Charac- 
 ter of the Stratified Rocks — Relation of this fact to Prac- 
 tical Agriculture — General Character of the Soils upon 
 these Rocks. 
 
 Geology is that branch of knowledge which em- 
 bodies all ascertained facts in regard to the nature 
 and internal structure, both physical and chemi- 
 cal, of the solid parts of our globe. This science 
 has many close relations with practical agricul- 
 ture, and especially throws much light on the na- 
 ture and origin of soils, — on the cause of their di- 
 versity, — on the kind of materials by the admix- 
 ture of which they may be permanently improved, 
 — and on the sources from which these materials 
 may be derived. 
 
GENERAL COMPOSITION OF ROCKS. 79 
 
 SECTION I. — OF THE ORIGIN 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 ac- 
 tually reaches the surface, or rises in cliffs, hills, 
 or ridges, far above it. The surface (or crust) of 
 our globe, therefore, consists everywhere of a solid 
 mass of rock, overlaid with 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 
 character, in composition, and in hardness — in dif- 
 ferent countries and districts. In some places he 
 has met with a sandstone, in other places a lime- 
 stone, 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 conclu- 
 sion, that they are all either sandstones^ limestones, 
 or clays of different degrees of hardness, or a mix- 
 ture in different proportions of two or more of these 
 kinds of matter. 
 
 When the loose covering of earth is removed 
 
80 THE CEUMBLING OF ROCKS 
 
 from the surface of any of these rocks, and it is 
 left exposed, summer and winter, to the action of 
 the winds and r ins 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 are kept generally dry ; how much more with 
 such as are less hard, and, beneath a covering of 
 moist earth, 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 forms a soil. The soil thus produced 
 partakes necessarily of the character 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 calca- 
 reous ; and if the rock consist of any peculiar mix- 
 ture of those three substances, a similar mixture 
 is observed in the earthy matter into which it has 
 crumbled. 
 
 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 immediate- 
 ly rest. The general result of this comparison has 
 
GIVES RISE TO SOILS, 81 
 
 been, that in almost every country the soils have 
 as close a resemblance to the rocks beneath them — 
 as 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 so- 
 lid rocks, — that there was a time when these rocks 
 were uncovered by any loose materials, — and that 
 the accumulation of soil has been the slow result 
 of the natural degradation (wearing away) of the 
 solid crust of the globe. 
 
 SECTION II. CAUSE OF THE DIVERSITY OF SOILS. 
 
 The cause of the diversity of soils in different 
 districts, therefore, is no longer obscure. If the 
 subjacent rocks in two localities differ, the soils 
 met with there must differ also, and in an equal 
 degree. 
 
 But why, it may be asked, do we find the soil in 
 some countries uniform, in mineral* character and 
 general fertility, over hundreds or thousands of 
 square miles, while in others it varies from field 
 
 * That is, containing the same general proportions of 
 sand, clay, lime, &c., or coloured red by similar quantities of 
 oxide of iron. 
 
l82 STRATIFIED AND UNSTRATIFIED EOCKS. 
 
 to field, — the same farm often presenting many 
 well marked differences both in mineral character 
 and in agricultural value ? The cause of this is to 
 be found in the mode in which the different rocks 
 are observed to lie, one upon or by the side of 
 the other. 
 
 Geologists distinguish rocks into two classes, 
 the stratified and the unstratified. The former are 
 found lying over each other in separate beds or 
 strata^ like the leaves of a book, when laid on its 
 side, or Hke the layers of stones in the wall of a 
 building ; the latter form hills, mountains, or 
 sometimes ridges of mountains, consisting of one 
 more or less solid mass of the same material, in 
 which no layers or strata are any where distinctly 
 perceptible. Thus, in the following diagram, 
 (No. 1,) A and B represent unstratified masses, 
 in connection with a series of stratified deposits, 
 1, 2, 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. 
 
 If from A to D be a wide valley of many miles in 
 
iNCLINATlOJir OF STRATA. 8^ 
 
 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 at 
 C, and on the first ascent to A, where 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. 
 
 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 shorter distances. This is shewn in the 
 annexed diagram (No. 2), where A, B, C, D, E, re* 
 present the mode in which the stratified rocks of a 
 district of country not unfrequently occur in con- 
 nection with each other. 
 
 No. 2. 
 
 Proceeding from E in the plain, the soil would 
 change when we came upon the rock D, but would 
 then continue uniform till we reached the layer C. 
 Each of these layers may stretch over a compara- 
 
84 ORDER OF SUCCESSION 
 
 tively level tract of perhaps hundreds 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 the beds, and the soil may 
 vary with every new stratum (or bed) we pass 
 over, till we gaiii 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 rocks beneath are exposed, 
 and differences 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, 
 nearly all the great diversities which the soils of 
 the country present may be satisfactorily account- 
 ed for. 
 
 SECTION III. OF THE CONSTANCY IN THE CHARACTER AND 
 
 ORDER OF SUCCESSION OF THE STRATIFIED ROCKS. 
 
 Another fact alike important to agriculture and 
 to geology, is the natural order or mode of ar* 
 rangement in which the stratified rocks are ob- 
 served to occur in the crust of the globe. Thus, 
 
OF THE STRATIFIED ROCKS. 85 
 
 if 1, 2, 3, in diagram No. 1 represent three dif- 
 ferent 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 repre- 
 sented ; then, in whatever part of the country 
 nay, in whatever part of the world, these same 
 rocks are met with, they will always be found in 
 the same relative position. The bed 2 or 3 will 
 never be observed to lie over the bed 1. 
 
 This fact is important to geology, because it en- 
 ables this science to arrange all the stratified rocks 
 in a certain invariable order, — which order in- 
 dicates their relative age or antiquity, — since that 
 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 oi 
 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. 
 
 8 
 
86 DEDUCTIONS FROM THE ' 
 
 To the agriculturist this fact is important, 
 among other reasons, — 
 
 1. Because it enables him to predict whether 
 certain kinds of rock, which might be used with 
 advantage in improving his soil, are likely to be met 
 with within a reasonable distance or at an acces- 
 sible 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 expensive 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- 
 face of each of a series of rocks, such as C, or D, 
 or E, in the same diagram, is uniformly bad, it is 
 almost invariably of better quality at the point 
 where the two rocks meet. Thus C may be dry, 
 sandy, and barren ; D may be cold, unproductive 
 clay ; and E a more or less unfruitful limestone 
 
KNOWLEDGE OF THIS ORDER. 87 
 
 soil : yet at either extremity of the tract D, where 
 the soil is made up of an admixture of the 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 looking 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. Yet how little is such really 
 useful knowledge diffused among either class of 
 men — how little are either tenants or proprietors 
 guided by it in their choice of the localities in 
 which they desire to live ! 
 
 And yet here and there the agricultural practice 
 of more or less extended districts, if not really 
 founded upon or directed by, is yet to be explained 
 only by principles such as those I have above illus- 
 trated. I shall mention only one example. The 
 chalk in Yorkshire, in Suffolk, and in other 
 southern counties, consists of a vast number of 
 beds, which, taken all together, form a deposit of 
 very great thickness. Now, the upper beds of 
 the chalk form poor, thin, dry soils, producing a 
 scanty herbage, and only under the most skilful 
 
 * See page 94. 
 
88 
 
 CHALKING THE SOIL. 
 
 culture yielding profitable crops of corn. The 
 lower beds, on the contrary, are marly ; produce 
 a more stiff, tenacious, and even fertile soil ; and 
 are found in a remarkable degree to enrich the 
 soils of the upper chalk, when laid on as a top- 
 dressing in autumn, and allowed to crumble under 
 the action of the winter's frost. Hence in York-, 
 shire, Wiltshire, Hampshire, and Kent, where the 
 lower chalk covers the surface, or is found at no 
 great depth beneath it, it is dug out of the sides 
 of the hills, or pits are sunk for it, and it is imme-. 
 diately laid upon the land with great benefit to 
 the soil. But in parts of Suffolk, where the soil 
 equally rests upon the upper chalk, there is no 
 other chalk in the neighbourhood, or to be met 
 with at any reasonable depth, which will materi. 
 ally improve the land. The farmers find it, from 
 long experience, to be more economical to bring 
 chalk by sea from Kent to lay on their lands in 
 Suffolk, than to cover them with any portion of 
 the same material from their own farms. The 
 following imaginary section will fully explain the 
 fact here mentioned :— 
 
 Suffolk. 
 
 No. 3. 
 Mouth of the Thames. 
 
 Kent. 
 
CONSTANT MINERAL CHARACTER. 89 
 
 In this diagram 1 represents the London clay ; 
 2, the plastic clay which is below it ; 3, the upper 
 chalk with flints, rising to the surface in Suffolk ; 
 and 4, the lower chalk, without flinls, which is 
 too deep to be reached in Suffolk, but which rises 
 to the surface in Kent, — where it is abundant, is 
 easily accessible, and whence it is transmitted 
 across the estuary of the Thames into Suffolk. 
 
 3. The further fact that the several stratified 
 rocks are remarkably constant in their 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 un- 
 varying place in the series. Most of these beds 
 also, when they crumble or are worn down, pro- 
 duce soils possessed of some peculiarity by which 
 their general agricultural capabihties are more or 
 less affected, — and these peculiarities may gener- 
 ally 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 situ- 
 ated upon such and such a rock, or geological for- 
 8* 
 
90 OF BEDS OF THE SAME AGE. 
 
 mation, he can immediately give a very probable 
 opinion in regard to the agricultural value of the 
 soil, whether the property be in England, in Aus- 
 tralia, 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 labours of the practical farmer, — nay, 
 €ven whether it is likely to suit better for arable 
 land or for pasture, and if for arable, what species 
 of white crops it 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 or proprietors of 
 this and that small farm, yet to enlightened agri- 
 culturists, — 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 colonics, 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 which the rudiments of 
 geology will lead them. Those who prepare them- 
 selves the best for becoming farmers or proprie- 
 tors in Canada, in New Zealand, or in wide 
 
PRACTICAL VALUE OF GEOLOGY. 91 
 
 Australia, yet leave their native land in general 
 without a particle of that preliminary practical 
 knowledge, which would qualify them to say, 
 when they reach the land of their adoption, " On 
 this spot, rather than 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 produc- 
 tive soil ; here I am more within reach of the 
 means of agricultural improvement ; here, in addi- 
 tion to the riches of the surface, my descendants 
 may hope to derive the means of wealth from 
 mineral 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 ^o otherwise well in- 
 structed practical men. It is not to men well 
 skilled merely in the details of local farming, and 
 who are therefore deservedly considered as autho- 
 rities and good teachers in regard to local or dis- 
 trict practice, that we are to look for an exposi- 
 tion, often not even for a correct appreciation, of 
 those general principles on which a universal sys- 
 tem of agriculture must be based — without which 
 principles, indeed, it must ever remain a mere col- 
 lection of empirical rules, to be studied and labori- 
 
92 TO EMIGRATING AGRICULTURISTS. 
 
 ously mastered in every new district we go to — as 
 the traveller in foreign lands must acquire a new 
 language every successive frontier he passes. Eng- 
 land, the mistress of so many wide and unpeopled 
 lands, over which the dwellings of her adventur- 
 ous 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 willingly 
 avail themselves of every opportunity of acquir- 
 ing it. 
 
 SECTION IV. OP GEOLOGICAL FORMATIONS, AND THE 
 
 GENERAL CHARACTERS OF THE SOILS THAT REST 
 UPON THEM. 
 
 The thousands of beds or strata of which I have 
 spoken as lying one over the other in the crust ol 
 the globe, have, partly for convenience, and partly 
 in consequence of certain remarkably distinctive 
 characters observed among them, been separated 
 by geologists into three great divisions — the pri- 
 mary, which are the lowest and the oldest ; the 
 secondary, which lie over them ; and the tertiary, 
 which are uppermost, and have been most recently 
 formed. The strata, in these several divisions, 
 
THE LONDON CLAY AND THE CHALK. 93 
 
 have again been subdivided into groups, called 
 formations. The following table exhibits the 
 names and thicknesses of these formations, and 
 the mineralogical characters of the rocks of which 
 they severally consist, 
 
 I. TERTIARY STRATA. 
 
 1. The London and Plastic clays, 500 to 900 
 feet thick, consist of stiff, almost impervious, dark 
 coloured clays, — chiefly in pasture. The lower 
 beds are mixed with sand, and produce an arable 
 soil, but extensive heaths and wastes rest upon 
 them in Berkshire, Hampshire, and Dorset. 
 
 II. SECONDARY STRATA. 
 
 2. The Chalk, about 600 feet in thickness, con- 
 sists in the upper part (see diagram. No. 3, p. 88) 
 of a purer chalk with layers of flint ; in the lower, 
 of a marly chalk without flints. The soil of the 
 upper chalk is chiefly in sheep-walks, that of the 
 lower chalk is very productive of corn. 
 
 3. The Green Sand, 500 feet thick, consists of 
 150 feet of clay, with about 100 feet of sand above, 
 and 250 feet below it. The upper sand forms a 
 very productive arable soil, and the clay imper- 
 
94 THE WEALD CLAY AND THE OOLITE. 
 
 vious, wet and cold lands chiefly in pasture. The 
 lower sand is generally unproductive. 
 
 It is an important agricultural remark, that 
 where the clay (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 them- 
 selves, (See pages 86 and 87.) 
 
 4. The Wealden formation, nearly 1000 feet thick, 
 consists of 400 feet of sand, covered by 300 of 
 clay, and resting upon 250 of marls and lime- 
 stones. The clay forms the poor wet pastures of 
 Sussex and Kent. On the sands below the clay 
 rest heaths and brushwood ; but where the marls 
 and limestones come to the surface, the land is of 
 better quality, and is susceptible of profitable ara- 
 ble culture. 
 
 5. In the Upper Oolite^ of 600 feet in thickness, 
 we have a bed of clay (Kimmeridge clay) 500 feet 
 thick, covered by 100 feet of sandy limestones. 
 The clay lands are difficult and expensive to work, 
 and are chiefly in old pasture. The sandy lime- 
 stone soils above the clay are also poor, but where 
 they rest immediately upon, and are intermixed 
 with the clay, excellent arable land is produced. 
 
 6. The Middle Oolite of 500 feet consists also of 
 
THE BATH OOLITE AND THE LIAS. 95 
 
 a clay (Oxford clay) dark-blue, adhesive, and 
 nearly 1000 feet thick, covered by 100 feet of 
 limestones and sandstones. These latter pro- 
 duce good arable land where the lime happens to 
 abound ; the clays form close heavy compact soils, 
 most difficult and expensive to work. The exten- 
 sive pasture lands of Bedford, Huntingdon, Nor- 
 thampton, Lincoln, Wilts, Oxford, and Glouces- 
 ter, rest chiefly upon this clay, as do also the fen- 
 ny tracts of Lincoln and Cambridge. 
 
 7. The Lower or Bath Oolite, of 500 feet in 
 thickness, consists of many beds of limestone and 
 sandstone, with about 200 feet of clay in the 
 centre of the formation. The soils are very vari- 
 ous in quality, according as the sandstone or lime- 
 stone predominates. The clays are chiefly in pas- 
 ture, — the rest is more or less productive, easily 
 worked, arable land. In Gloucester, Northamp- 
 ton, 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. 
 
 6. The Lias is an immense deposit of blue clay 
 from 500 to 1000 feet in thickness, which pro- 
 duces cold, blue, unproductive, clay soils. It forms 
 a long stripe of land from the mouth of the Tees, 
 
96 RICH SOILS OF THE NEW RED SANDSTONE. 
 
 in Yorkshire, to Lyme Regis in Dorset. It is 
 chiefly in old, and often very valuable pasture. 
 
 9. The New Red Sandstone^ though only 500 
 feet in thickness, forms the surface of nearly the 
 vi^hole central plain of England, and stretches 
 north through Cheshire to Carlisle and Dumfries. 
 It consists of red sandstones and marls, — the soils 
 on which are easily and cheaply worked, and form 
 some of the richest and most productive arable 
 lands in the island. In whatever part of the 
 world the red soils of this formation have been 
 met with, they have been found to possess in ge- 
 neral the same agricultural capabilities. 
 
 10. The Magnesian Limestone, from 100 to 500 
 feet in thickness, forms a stripe of generally poor 
 thin soil from Durham to Nottingham, capable of 
 improvement as arable land by high farming, but 
 bearing naturally a poor pasture, intermingled 
 with sometimes magnificent furze. 
 
 11. The Coal Measures, from 300 to 3000 feet 
 thick, consist of beds of sandstones and dark blue 
 shales (hard clays), intermingled (interstrati- 
 Jied) with beds of coal. Where the sands come 
 to the surface, the soil is thin, poor, hungry, 
 sometimes almost worthless. The shales, on the 
 other hand, produce stiff, wet, almost unmanage- 
 able clays ; — not unworkable, yet expensive to 
 
MILLSTONE GRIT AND MOUNTAIN LIMESTONE. 97 
 
 work, and requiring draining, lime, skill, capi- 
 tal, and a zeal for improvement, to be applied to 
 them, before they can be made to yield the re- 
 munerating crops of corn they are capable of pro- 
 ducing. 
 
 12. To the Millstone Grits of 600 feet or up- 
 wards in thickness the same remarks apply. They 
 are often only a repetition of the sandstones and 
 shales of the coal measures, forming in many cases 
 soils still more worthless. When the sandstones 
 prevail, large tracts lie naked, or bear a thin and 
 stunted heath ; where the shales abound, the na- 
 turally difficult soils of the coal shales again recur. 
 These rocks are generally found on the outskirts 
 of our coal-fields. 
 
 13. The Mountain Limestone, 800 to 1000 feet 
 thick, is a hard blue limestone rock, separated here 
 and there into distinct beds by layers of sand- 
 stones, of sandy slates, or of blue shales like those 
 of the coal measures. The soil upon the limestone 
 is generally thin, but produces a naturally sweet 
 herbage. When the limestone and clay (shale) 
 adjoin each other, arable land occurs, which is 
 naturally productive of oats, yet, when the climate 
 is favourable, capable of being converted into 
 good wheat land. In the north of England a 
 considerable tract of country is covered by these 
 
 9 
 
98 OLD RED SANDSTONE SOILS. 
 
 rocks, but in Ireland they form nearly the whole 
 of the interior of the island. 
 
 14. 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, 
 consisting, like it, of red sandstones and 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 Haddington and Lanark ; of southern Perth ; 
 of either shore of the Moray Firth ; and of the 
 county of Sutherland. In Ireland, also, these 
 rocks abound in Tyrone, Fermanagh, and Mona- 
 ghan ; in Waterford, in Mayo, and in Tipperary. 
 In all these places, the soils they form are gene- 
 rally the best in their several neighbourhoods, 
 though here and there, — where the sandstones are 
 harder, more siliceous and impervious to water, — 
 tracts, sometimes extensive, of heath and bog 
 occur. 
 
 HI. PRIMARY STRATA, 
 
 15. The Upper Silurian system is nearly 4000 
 feet in thickness, and forms the soils over the 
 lower border counties of Wales. It consists of 
 sandstones and shales, with occasional limestones ; 
 
SILURIAN AND CAMBRIAN ROCKS. 99 
 
 but the soils formed from these beds take their cha- 
 racter from the general abundance of 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 off the red sandstones of Hereford on to 
 the upper silurian rocks of Radnor. 
 y, 16. The Lower Silurian rocks are also nearly 
 4000 feet in thickness, and in Wales lie to the 
 west of the upper silurian rocks. They consist 
 of about 2500 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 southern edge of Caermar- 
 then, fertile arable lands are produced. 
 
 17. The Cambrian System^ of many thousand 
 yards in thickness, consists in great part of clay 
 slates, more or less hard, which often weather 
 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 cul- 
 tivation. Cornwall, western Wales, and the moun- 
 tains of Cumberland, in England ; the high coun- 
 try which stretches from the Lammermuir hills 
 to Portpatrick, in Scotland ; the mountains of 
 
100 MICA SLATE AND GNEISS SOILS. 
 
 Tipperary, and a large tract on the extreme south 
 of Ireland, — on its east coast, and far inland from 
 the bay of Dundalk, — are covered by these slate 
 rocks. Patches of rich, well cultivated land occur 
 here and there on this formation, with much also 
 that is improvable ; but the greater part of it is 
 usurped by worthless heath and extensive bogs. 
 
 18. The Mica Slate and Gneiss systems are of 
 unknown thickness, and consist chiefly of hard and 
 slaty rocks, crumbling slowly, forming poor, thin 
 soils, which rest on an impervious rock, and which, 
 from the height to which this formation gene- 
 rally rises, are rendered more 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. 
 
 A careful perusal of the preceding sketch of 
 the general agricultural capabilities of the soils 
 formed from the several classes of stratified rocks, 
 will have presented to the reader many illustra- 
 tions of the facts stated in the preceding section ; 
 he will have drawn for himself — to specify a few 
 examples — the following among other conclusions. 
 
GENERAL DEDUCTIONS. 101 
 
 1. That some formations, like the new red sand- 
 stone, yield a soil almost always productive ; others, 
 as the coal measures and millstone grits, a soil 
 almost always naturally unproductive. 
 
 2. That good, or better land at least, than 
 generally prevails in a district, may be expected 
 where two formations or two different kinds of rock 
 meet, — as when a limestone and a clay mingle their 
 mutual ruins for the formation of a common 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 Kimmeridge, and the London 
 clays. In raising corn, it is natural that the lands 
 which are easiest and cheapest worked should be 
 first subjected to the plough ; it is not till im- 
 plements are improved, skill increased, capital 
 accumulated, and population presses, that the 
 heavier lands will be 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. 
 
 The turnip soils of Great Britain are in many 
 districts, it may be, but indifferently farmed ; 
 and the state has reason to complain of much in- 
 dividual neglect of known and certain methods 
 9* 
 
102 PLOUGHING Ur THE STIFF CLAYS. 
 
 of increasing their productiveness ; but the next 
 great achievement which British agriculture has 
 to effect, is to subdue the stubborn clays, and to 
 convert them into what many of them are yet 
 destined to become, the richest corn-bearing lands 
 in the kingdom. 
 
CHAPTER VII. 
 
 Soils of the Granitic and Trap Rocks — Accumulations of 
 transported Sands, Gravels, and Clays. — Use of Geologi- 
 cal Maps in reference to Agriculture, — Physical charac- 
 ters and Chemical constitution of Soils. — Relation be- 
 tween the nature of the Soil and the kind of Plants that 
 naturally grow upon it. 
 
 It was stated, in the preceding lecture, (see 
 p. 82,) that rocks are divided by geologists into the 
 stratified and the unstratified.* The stratified rocks 
 cover by far the largest portion of the globe, and 
 thus form a variety of soils, of which a general 
 description has just been given. The unstratified 
 rocks are of two kinds — the granites and the trap 
 
 * The unstratified are often called crystalline rocks, be- 
 cause they frequently have a glassy appearance, or contain 
 regular crystals of certain mineral substances ; often also 
 igneous rocks, because they appear all to have been original- 
 ly in a melted state, or to have been produced by fire.. 
 
 I 
 
104 GRANITES, QUAKTZ, AND MICA. 
 
 rocks ; and as a considerable portion of the area 
 of our island is covered by them, it will be proper 
 shortly to consider the peculiar characters of each, 
 and the differences of the soils produced from them. 
 
 SECTION I. SOILS OF THE GRANITES AND TRAP ROCKS. 
 
 1. The granites 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 quan- 
 tity, that in our general description it may be 
 safely left out of view. Granites, therefore, con- 
 sist chiefly of quartz and felspar, in proportions 
 which vary very much, but the former, on an ave- 
 rage, constitutes perhaps from one-third to one- 
 half of the whole. 
 
 Quartz has already been described — (see p. 51) 
 — as the substance of flint, the silica of the che- 
 mist. When the granite decays, this portion of 
 it forms a more or less coarse siliceous sand. 
 
 Felspar is a white, greenish, or flesh-coloured 
 mineral, often more or less earthy in its appear- 
 ance, but generally hard and brittle, and some- 
 times glassy. It is scratched by, and thus is rea- 
 dily distinguished from, quartz. When it decays, 
 it forms an exceedingly fine clay. 
 
TEMPERATURE OF SOILS. 105 
 
 how much hotiom heat forces the growth, espe- 
 cially of young plants ; and wherever a natural 
 warmth exists in the soil, independent of the sun, 
 as in the neighbourhood of volcanoes, there it ex- 
 hibits the most exuberant fertility. One main in- 
 fluence of the sun in spring and summer is de- 
 pendent upon its power of thus warming the soil 
 around the young roots, and thus 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 hig'icr than 60° to 70°, a dry soil may 
 become so warm as to raise the thermometer to 
 90° or 100°. Mrs. Ellis states, that among the Py- 
 renees the rocks actually smoke after rain under 
 the influence of the summer sun, and become so 
 hot, that you cannot sit down upon them. In wet 
 soils the temperature rises more slowly, and never 
 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, be- 
 come warmed to nearly an equal degree under 
 the same sun ; brownish red soils are heated some- 
 what more, and dark-coloured peat the most of 
 
' 4 
 
 106 COMPOSITION OF HORNBLENDE AND FELSPAE. 
 
 weather, to a more or less fine powder, affording 
 materials for a soil ; in the granites the felspar is 
 the principal source of all the earthy matter they 
 are capable of yielding. If we compare together, 
 therefore, the chemical composition of the two 
 minerals (hornblende and felspar), we shall see 
 in what respect these two varieties of soil ought 
 to differ. Thus they consist of 
 
 
 Felspar. 
 
 Hornblende 
 
 Silica, 
 
 65 
 
 42 
 
 Alumina, . 
 
 18 
 
 14 
 
 Potash and soda, 
 
 17 
 
 trace. 
 
 Lime, 
 
 trace 
 
 12 
 
 Magnesia, 
 
 , do. 
 
 14 
 
 Oxide of iron, 
 
 . do. 
 
 14i 
 
 Oxide of manganese, 
 
 . do. 
 
 h 
 
 100 
 
 97 
 
 A remarkable difference appears thus to exist, 
 in chemical constitution, between these two mine- 
 rals — a difference which must affect also the soils 
 produced from them. A granite soil, in addition 
 to the siliceous sand, will consist chiefly of silica, 
 alumina, and potash ; a hornblende soil, in addi- 
 tion to silica and alumina, of much lime, magnesia, 
 and oxide of iron — of nearly 2^ cwt. of each of 
 these latter for every ton of decayed rock. A 
 hornblende soil, therefore, contains more of those 
 
GREENSTONE AND OTHER TRAP SOILS. 107 
 
 inorganic constituents which the plants require 
 for their healthy sustenance, and therefore will 
 prove more generally productive than a soil of 
 decayed felspar. But when the two are mixed, 
 as in the greenstones, the soil must be still more 
 favourable to vegetable Hfe. The potash and 
 soda, of which the hornblende is nearly destitute, 
 the felspar is able abundantly to supply ; while, 
 by the hornblende are yielded lime and magnesia, 
 which are known to exercise a remarkable influ- 
 ence on the progress of vegetation. 
 
 Thus theory shews, that while granite soils may 
 be eminently unfruitful, trap soils may be emi- 
 nently 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, 
 and large tracts of land in Devon and Cornwall, 
 and on the east and west of Ireland ; while 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 occasion- 
 ally mix with the granite soils, they are found to 
 redeem them from their natural barrenness. 
 
 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, 
 
108 DECAYED TRAP AS A MANURE. 
 
 or of hornblende or mica in larger quantity than 
 usual, give rise to a granitic soil of average fertil- 
 ity, as is the case in the Scilly isles ; while, in 
 like manner, the trap rocks are sometimes, as in 
 parts of the isle of Skye, so peculiar in constitu- 
 tion as to condemn the land to almost hopeless 
 infertiHty, 
 
 In some districts the decayed traps are dug up, 
 and applied with advantage, as a top-dressing, to 
 other kinds of land ; and as by admixture with 
 the decayed trap, the granitic soils are known to 
 be improved in quality, so an admixture of decayed 
 granite with many trap soils, were it readily acces- 
 sible, might add to their fertility also. 
 
 SECTION II. OF THE SUPERFICIAL ACCUMULATIONS OF TRANS- 
 PORTED MATERIALS ON DIFFERENT PARTS OF THE EARTh's 
 SURFAC E 
 
 It is necessary to guard the reader against dis- 
 appointment, when he proceeds to examine the 
 existing relation 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 in con- 
 formity with what has been above laid down, — by 
 explaining another class of geological appearances 
 which present themselves not only in our own 
 
SOIL FORMED FROM DRIFTED MATERIALS. 109 
 
 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 appear- 
 ances. Such, it is to be feared, is the hasty mode 
 of reasoning among too many locally* excellent 
 practical men, familiar, it may be, with many 
 useful and important facts, but untaught to look 
 through and beyond isolated facts to the princi- 
 ples 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 
 
 * By locally excellent, I mean those who are the best pos- 
 sible farmers of their own district and after their own way, 
 but who would fail in other districts requiring other methods. 
 To the possessor of agricultural principles the modifications 
 required by difference of crop, soil, and climate, readily sug- 
 gest themselves, where the mere practical man is bewildered, 
 
 disheartened, and in despair. 
 10 
 
110 HOW SANDS AND CLAYS ARE DRIFTED. 
 
 distance from the coast. In some countries this 
 sand-drift takes place to a very great extent, and 
 gradually swallows up large tracts of fertile land. 
 
 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, and the river of Amazons, gradually de- 
 posit accumulations 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 through which they 
 are fed. 
 
 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 or layers 
 of sand, gravel, and clay, which have been brought 
 from a greater or less distance, and which have 
 not unfrequently been derived from rocks of a 
 totally different kind from those of the district 
 in which they are now found. On these accumu- 
 
DIFFICULTIES RESULTING FROM THIS DRIFT. Ill 
 
 lations of transported materials, a soil is produced 
 which often has no relation in its characters 
 to the rocks which cover the country, and the 
 nature of which a familiar acquaintance with 
 these rocks would not enable us to predict. 
 
 To this cause is due that discordance between 
 the first indications of geology, as to the origin 
 of soils from the rocks on which they rest, and 
 the actually observed character of those soils in 
 certain districts — of which discordance mention 
 has been made as likely to awaken doubt and dis- 
 trust in the mind of the less instructed student 
 in regard to the predictions of agricultural geo- 
 logy. There are several circumstances, however, 
 by which the careful observer is materially aided 
 in endeavouring to understand what the nature of 
 the soils is likely to be, 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 mate- 
 rials 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 on other spots from the decay of these 
 rocks alone. 
 
112 HOW OBVIATED. 
 
 2. Where the formation is extensive, or covers 
 a large area, as the new red sandstones and coal 
 measures do in this country, — the mountain lime- 
 stones 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 ano- 
 ther part of the same formation, 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 constitution of these rocks. 
 
 3. Or if not from the rocks of the same forma- 
 tion, they have most frequently been derived from 
 those of a neighbouring formation — from rocks 
 which are to be found at no great distance^ and 
 generally on higher ground. Thus the ruins of 
 the mill-stone grit rocks^ tir€ often spread over 
 the surface of the coal measures — of these, again, 
 over the magnesian limestone, — of the latter, over 
 the new red sandstone, and so on. The effect of 
 this kind of transport upon 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 drift- 
 ed materials are known to have come. 
 
 It appears, therefore, that the occurrence on 
 certain spots, or tracts of country, of soils that 
 
USE OF GEOLOGICAL MAPS. 113 
 
 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 conclu- 
 sions drawn from the more general facts and prin- 
 ciples 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 
 the agricultural geologist a more careful study of 
 the structure of each district, before he pronoun- 
 ces a dicided opinion as to the degree of fertility 
 it either naturally possesses, or by skilful cultiva- 
 tion may be made to attain. 
 
 Geological maps point out with more or less 
 precision the extent of country over which the 
 chalk, the red sandstone, the granites, &;c., are 
 found immediately beneath the loose materials on 
 the surface ; and these maps are of great value 
 in indicating also the general quality of the soils 
 over the same districts. It may be true, that here 
 and there the 7iatural 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 capi- 
 talist judge in what part of it he is likely to meet 
 
 with an agreeable investment — and the practical 
 10* 
 
114 RELATIVE DENSITY OF SOILS. 
 
 farmer in what country he may expect to find 
 land that will best reward his labours — that will 
 admit of the kind of culture to which he is most 
 accustomed, or, by the application of better me- 
 thods, will manifest the greatest agricultural im- 
 provement. 
 
 SECTION m. — OF THE PHYSICAL CHARACTERS OF SOILS. 
 
 The influence of climate on the fertility of a 
 soil is often very great. This influence depends 
 very much upon what are called the physical pro- 
 perties of soils. 
 
 1. Some soils are heavier and denser than others, 
 sand and marls being the heaviest, and peaty soils 
 the lightest. In reclaiming peat lands, it is found 
 to be highly beneficial to increase their density by 
 a covering of clay, sand, or limestone gravel. 
 
 2. 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 re- 
 tain nearly three times as much water as sandy 
 soils do, while peaty soils absorb a still larger 
 proportion. Hence the more frequent necessity 
 for draining clayey than sandy soils ; hence also 
 the reason why, in peaty lands, the drains must be 
 kept carefully open, in order that the access of 
 
THEIR RELATIONS TO WATER. 115 
 
 springs and of other water from beneath, may be 
 as much as possible prevented. 
 
 3. When dry weather comes, soils lose water by 
 evaporation with different degrees of rapidity. In 
 this way a siliceous sand will give off the same 
 weight of water in the form of vapour, 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 sustain a luxuriant vegetation, when plants will 
 perish on clay lands from excess of moisture. 
 
 4. In drying under the influence of the sun, soils 
 contract and diminish in bulk in proportion to the 
 quantity of clay or of peaty matter they contain. 
 Sand does not at all diminish in bulk in drying, 
 but peat shrinks in one-fifth, and agricultural clay 
 nearly as much. The roots are thus compressed, 
 and air is excluded, especially from the hardened 
 clays, and thus the plant is placed in a condition 
 unfavourable to its growth. Hence the value of 
 proper admixtures of sand and clay. By the lat- 
 
 .\ 
 
116 THEIE POWER OF ABSORBING MOISTURE. 
 
 ter (the clay), a sufficient quantity of moisture is 
 retained, and for a sufficient length of time ; while, 
 by the former, the roots are preserved from com- 
 pression, and a free access of air is permitted. 
 
 5. In the hottest and most drying weather, the 
 soil has seasons of respite from the scorching in- 
 fluence 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 clay, on the other hand, 
 will in a single night absorb sometimes as much 
 as a 30th part of its own weight, and a dry peat 
 as much as a 12th of its weight ; and, generally, the 
 quantity thus drunk in by soils of various quali- 
 ties, is dependent upon the proportions of clay 
 and vegetable matter they severally contain. We 
 cannot fail to perceive from these facts, how much 
 of the productive capabilities of a soil is dependent 
 upon the proportions in which its different earthy 
 and veoretable constituents are mixed together, 
 
 6. The temperature of a soil, or the degree of 
 warmth it is capable of attaining under the in- 
 fluence of the sun's rays, materially affects the 
 progress of vegetation. Every gardener knows 
 
/A^ 
 
 <*^ /* /cU 
 
 GRANITE SOILS. 117 
 
 Granite generally forms hills and sometimes 
 entire ridges of mountains. When it decays, the 
 rains and streams wash out and carry down the 
 jfine felspar clay, and leave the (quartz) sand on 
 the sides of the hills. Hence the soil in the bot- 
 toms and flats of granite countries consists of a 
 cold, stiff, wet, more or less impervious clay, 
 which often bears only heath, bog, or a poor and 
 unnutritive pasture. The hill sides are either 
 bare or covered with a thin, sandy, and ungrate- 
 ful soil, of which little can be made by the aid 
 even of skill and industry. Yet the opposite 
 sides of the same mountains often present a re- 
 markable 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 barren. 
 
 2. The traj) rocks, comprising the greenstones 
 and basalts, 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 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 
 
 * The reader is referred for more precise information to 
 the author's " Lectures," pp. 377 to 390, 
 
118 SIMILAR PROPERTIES OF PEAT AND CLAY. 
 
 all. It is probable, therefore, that the presence 
 of dark-coloured vegetable matter renders the soil 
 more absorbent of heat from the sun, while the 
 colour 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 practi- 
 cal reader can hardly fail to have been struck 
 with the remarkable similarity in physical proper- 
 ties between stiff clay and peaty soils. Both re- 
 tain much of the water that falls in rain, and both 
 part with it slowly by evaporation. Both con- 
 tract 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 aids 
 to, or elements of, fertility — of which they are 
 alike possessed. 
 
 SECTION IV. OF THE CHEMICAL CONSTITUTION OF SOILS. 
 
 Soils perform at least three functions, in refer- 
 ^enee to vegetation. They serve as a basis in 
 
CONSTITUTION OF SOILS. 119 
 
 which plants may fix their roots and sustain them- 
 selves in their erect position, — they supply inor- 
 ganic 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 or- 
 ganic substances in smaller and variable propor- 
 tions. But the study of the ash of plants (see 
 chap, iv.) shews us, that a fertile soil must of ne- 
 cessity contain an appreciable quantity of at least 
 eleven different 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 pre- 
 cisely the same conclusion. We have seen that 
 the soils formed from the unstratified rocks, — the 
 granites and the traps, — while they each contain 
 certain earthy substances in proportions peculiar 
 to themselves, yet contain also in general a trace 
 of most of those different kinds of matter which 
 are found in the ash of plants. And when to 
 this fact is added the other, that the stratified 
 
120 IWDICATKI) in (;1IE31ICAL ANALYSIS. 
 
 rocks appear to bo only tlio long accumnlating 
 fragments and ruins of m(>rc anciont unstratificd 
 masses — wliicli, under various agencies, have gra- 
 dually crumbled to dust, been strewed over tbc 
 surface in alternate layers, and afterwards again 
 consolidated, — the reader will readily grant, that 
 in all rocks, and consequently in all soils, traces of 
 every one of these substances may generally bo 
 presumed to exist. 
 
 Actual chemical analysis confirms these deduc- 
 tions in regard to the constitution of soils. It 
 shews that, in most soils, the presence of the seve- 
 ral constituents of the ash of plants may be de- 
 tected, though in very variable proportions. And 
 following up its investigations, in regard to the 
 cflcct of this diiferencc in the proportion of the 
 generally less abundant constituents of the soil, 
 it establishes certain other points of the greatest 
 possible importance to agricultural practice. Thus, 
 it has found, for example, 
 
 1. 'I'hat as a proper adjustment of the propor- 
 tions of clay and sand is necessary, in order that 
 a soil may possess the most favourable physical 
 properties — so that the mere presence of the vari- 
 ous kinds of inorganic food in a soil is not suffi- 
 cient to make it productive of a given crop, but 
 that they must be so adjusted in quantity that 
 
GENERAL DEDUCTIONS FROM ANALYSES. 121 
 
 the plant shall bo able readily and at the proper 
 time to obtain an adequate supply of each. 
 
 2. That when a soil is particularly poor in cer- 
 tain of these substances, the valuable, cultivated 
 corn crops, grasses, and trees, refuse to grow upon 
 them in a healthy manner, and to yield remune- 
 ratihg returns. And, 
 
 3. That when certain other substances are pre- 
 sent in too great abundance, the soil is rendered 
 equally unpropitious to the most important crops. 
 
 In these facts the intelligent reader will per- 
 ceive the foundation of the varied applications to 
 the soil which are everywhere made under the 
 direction of a skilful practice, and of the difficul- 
 ties which, in so 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 object of artifi- 
 cial culture easily and abundantly to raise. 
 
 Chemical analysis is a difficult art, — one which 
 demands much chemical knowledge, and skill in 
 chemical practice (manipulation, as it is called), 
 and calls for both time and perseverance — if valu- 
 able, 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 
 11 
 
122 AGRICULTURE AND CHEMISTRY* 
 
 properties of those soils which, while they possess 
 much general similarity in composition and in 
 physical properties, are yet found in practice to 
 possess very different agricultural capabilities. 
 Many such cases occur in every country, and they 
 are the kind of difficulties in regard to which 
 agriculture has a right to say to chemistry — 
 " These are matters which I hope and expect you 
 will satisfactorily clear up." But while agricul- 
 ture 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 che- 
 mical theory to agricultural practice, and in an- 
 other to ask the sacrifice of time and labour in 
 doing her chemical work. Chemistry is a wide 
 field, and many zealous lives may be 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 humour or 
 natural bias of some one chemist to apply his 
 knowledge to this most important art ; but hitherto 
 the appreciation of such efforts has, in general, 
 been so small — ^the reception of scientific results 
 and suggestions by the agricultural body so un- 
 gracious — that little wonder can exist that so 
 many have quitted the field in disgust — that the 
 majority of capable men should studiously avoid it. 
 
 'a 
 
ACCURATE ANALYSIS OF SOILS RARE. 128 
 
 Hence it has happened that, in England, the 
 analysis of soils has rarely been undertaken, ex- 
 cept as a matter of professional business, where 
 so much time was, by a fair calculation, given for 
 so much money, and an analysis made, of that 
 degree of accuracy only which the time allotted 
 to it permitted the analyst to attain. 
 
 In order, therefore, to illustrate the deductions 
 which, as above stated, may be drawn from an 
 accurate chemical analysis, I shall exhibit the 
 constitution of three different soils as determined 
 by Sprengel, a German chemist, now at the head 
 of the Prussian Agricultural school, and whose 
 own taste, as well as his professional function, 
 have long directed his attention, and with much 
 success, to scientific agriculture. 
 
 No. 1 is a very fertile alluvial soil from East 
 Friesland, formerly overflowed by the sea, but 
 for 60 years cultivated with corn and pulse crops 
 without manure. 
 
 No. 2 is a fertile soil near Gottingen, which 
 produces excellent 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 Lunenburg. 
 
 When washed with water in the manner des- 
 
 ;>)«*'. 
 
124 coMrosiTioN of certain soils. 
 
 cribed in pages 70 to 73, they gave, respectively, 
 from 1000 parts of soil — 
 
 No. 1. No. 2. No. 3. 
 
 Soluble saline matter, . . 18 1 1 
 
 Fine earthy and organic matter (clay), 937 839 599 
 
 Siliceous sand, . , , 45 160 400 
 
 1000 1000 1000 
 
 The most striking distinction presented by these 
 numbers is the large quantity of saline matter in 
 No. 1. This soluble matter consisted of common 
 salt, chloride of potassium, sulphate of potash and 
 gypsum, with a trace of sulphate of magnesia, 
 sulphate of iron, and phosphate of soda. The 
 presence of this comparatively large quantity of 
 these different saline substances, — originally de- 
 rived, no doubt, in great part from the sea, — was 
 probably one reason why it could be so long 
 cropped without manure. 
 
 The unfruitful soil is much the lightest of the 
 three, containing 40 per cent, of sand ; but this is 
 not enough to account for its barrenness — many 
 light soils containing a larger proportion of sand, 
 and yet being sufficiently fertile. 
 
 The finer portions separated from the sand, and 
 soluble matter, consisted in 1000 parts of 
 
COMPOSITION OF CERTAIN SOILS. 
 
 125 
 
 
 No. 1. 
 
 No. 2. 
 
 No. 3. 
 
 Organic matter, 
 
 97 
 
 50 
 
 40 
 
 Silica, 
 
 . 648 
 
 833 
 
 778 
 
 Alumina, 
 
 57 
 
 51 
 
 91 
 
 Lime, 
 
 . 59 
 
 18 
 
 4 
 
 Magnesia, 
 
 8i 
 
 8 
 
 1 
 
 Oxide of iron, 
 
 . 61 
 
 30 
 
 81 
 
 Oxide of manganese, 
 
 1 
 
 3 
 
 i 
 
 Potash, . 
 
 2 
 
 trace. 
 
 trace. 
 
 Soda, 
 
 4 
 
 do. 
 
 do. 
 
 Ammonia, 
 
 trace. 
 
 do. 
 
 do. 
 
 Chlorine, 
 
 2 
 
 do. 
 
 do. 
 
 Sulphuric acid, 
 
 2 
 
 1 
 
 do. 
 
 Phosphoric acid, . 
 
 41 
 
 If 
 
 do. 
 
 Carbonic acid, 
 
 40 
 
 ^ 
 
 do. 
 
 Loss, 
 
 14 
 
 — 
 
 4i 
 
 1000 1000 1000 
 
 1. The composition of No. 1 illustrates the first 
 of those general deductions above stated, that a 
 considerable supply of all the species of inorganic 
 food is necessary to render a soil eminently fer- 
 tile. Not only does this soil contain a compara- 
 tively large quantity of soluble saline matter, but 
 it contains also nearly 10 per cent, of organic mat- 
 ter, and, what in connection with this is of great 
 importance, 6 per cent, of lime. The potash and 
 soda, and the several acids, are also present in suf- 
 ficient abundance. 
 11* 
 
126 PRACTICAL DEDUCTIONS 
 
 2. In the second, — a fertile soil, but one which 
 cannot dispense with manure, — there is little soluble 
 saline matter, and in the insoluble portion we see 
 that there are mere traces of potash, soda, and the 
 important acids. It contains also 5 per cent, only 
 of organic matter, and about 2 per cent, of lime, 
 which smaller proportions, together with the de- 
 ficiencies above stated, remove this soil from the 
 most naturally fertile class to that class which is 
 susceptible, in hands of ordinary skill, of being 
 brought to, and ke^H in, a very productive condi- 
 tion. 
 
 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 ap- 
 parently to 4 per cent., and there seems to be 
 nearly half a per cent, of lime. But it will be re- 
 collected, that this soil contains 40 per cent, of 
 sand, so that in every hundred of soil there are 
 only 60 of the fine matter, of which the composi- 
 tion is presented in the table, or 100 lbs. of the 
 native soil contain only 2^ lbs. of organic matter 
 and I lb. of lime. 
 
 But all these wants would not condemn the soil 
 to hopeless barrenness, because in favourable cir- 
 cumstances, and where it was worth the cost, they 
 might all be supplied. But the oxide of iron 
 
FROM THESE ANALYSES. 127 
 
 amounts to 8 per cent, of this fine matter, a pro- 
 portion of this substance which, in a soil contain- 
 ing so Uttle organic matter, appears, from practi- 
 cal experience, to be incompatible with the healthy 
 growth of cultivated crops. To this soil, there- 
 fore, there requires to be added not only those 
 substances of which it is destitute, but such other 
 substances also as shall prevent the injurious ef- 
 fect of the large proportion of oxide of iron. 
 
 In these three soils, then, we have examples, 
 first, of one which contains within itself all the 
 elements of fertility ; second, of a soil which is des- 
 titute, or nearly so, of certain substances, — which, 
 however, can be readily added by the ordinary 
 manures in general use, — and to which the ele- 
 ments of gypsum are especially useful, in aid- 
 ing it to feed the potato and the turnip ; and, 
 thirdf of a soil not only poor in many of the ne- 
 cessary species of the inorganic food of plants, 
 but too rich in one which, when present in excess, 
 is 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 capa- 
 bilities of soils, and to direct agricultural prac- 
 tice. 
 
128 PLANTS SELECT THE SOILS 
 
 SECTION V. — OF THE RELATION THAT EXISTS BETWEEN THE 
 CHARACTER OF THE SOIL AND THE KIND OP PLANTS THAT 
 GROW UPON IT. 
 
 The importance of this study of the chemical 
 constitution 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. 
 
 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 nourish- 
 ing pasture, and are deaf to the often repeated so- 
 licitations of the diligent husbandman. There 
 exists, therefore, a universally understood connec- 
 tion between the kind of soil and the kind of plants 
 that naturally grow upon it. It is interesting to 
 observe how close this relation in many cases is. 
 
 1. The sands of the sea-shore, and the margins of 
 salt-lakes, are distinguished by their peculiar tribes 
 of salt-loving plants; — the drifted sands more re- 
 mote from the beach produce their own long wav- 
 ing coarser grass, — while further inland again, 
 other vegetable races appear. 
 
 2. Peaty soils laid down to grass, or existing as 
 natural meadows, produce one woolly soft grass 
 
ON WHICH THEY CHOOSE TO GROW. 129 
 
 almost exclusively (the Holcus lanatus) ; when 
 limed, again, these same soils become propitious to 
 green crops and produce much straw, but refuse 
 to fill the ear. 
 
 3. On the margins of water-courses, in which sili- 
 ca abounds, the mare's-tail (Equisetum) springs up 
 in abundance ; while, if the stream contain much 
 carbonate of lime, the water-cress appears and 
 lines its sides, and the bottom of its shallow bed, 
 sometimes for many miles from its source. 
 
 4. The Cornish heath {Erica vagans) shews itself 
 only above the serpentine rocks ; the red clover 
 and the vetch delight in the presence of gypsum ; 
 and white clover, of alkaline matter in the soil. 
 
 5. 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 cen- 
 turies old, — gradually giving place to a natural 
 growth of beech ; and others where the pine is suc- 
 ceeding to both. In the Palatinate, the ancient oak 
 woods are followed by natural pines ; and in the 
 Jura, the Tyrol, and Bohemia, the pine alternates 
 with the beech. 
 
ISO ON SOME SOILS A PLANT WILL THRIVE, 
 
 These and other similar differences depend upon 
 the chemical constitution of the soil. The slug 
 may live well, and therefore infest a field almost de- 
 ficient in lime ; the common land snail will abound 
 at the roots of the hedges only where lime is plen- 
 tiful, and can easily be obtained for the construc- 
 tion 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 the constitution of the soil 
 as to fit it for ministering to their most important 
 v/ants. 
 
 And such changes do naturally come over the 
 soil. The oak, after thriving for long generations 
 on a particular spot, gradually sickens ; its entire 
 race dies out, — and other races succeed it. The 
 operation of natural causes has gradually removed 
 from the soil that which favoured the oak, and has 
 introduced or given the predominance to those sub- 
 stances which favour the beech or the pine. 
 
 In the hands of the farmer the land grows sick 
 of this crop, — it becomes tired of that. These facts 
 are generally indications of a change in the che- 
 mical constitution of the soil. This alteration 
 
ON OTHERS IT WILL SICKEN. 1^1 
 
 may proceed slowly and for many years, and the 
 same crops may still grow upon it for a succes- 
 sion of rotations. At length the change is too 
 great for the plant to bear ; it sickens, yields an 
 unhealthy crop, and becomes ultimately extinct. 
 
 The plants we raise for food have similar Hkes 
 and dislikes with those that are naturally pro- 
 duced. 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 follow 
 nature. One 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 crop carries off in preference a 
 larger quantity of those substances which the for- 
 mer had left ; and thus it is clearly seen, both why an 
 abundant manuring may so alter the constitution 
 of the soil, as to enable it to grow almost any crop ; 
 and why, at the same time, this soil may in suc- 
 cession yield more abundant crops and in greater 
 number, if the kinds of plant 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. 
 
 The management and tilling of the soil, in fact. 
 
132 AGRICULTURE A CHEMICAL ART. 
 
 is a branch of practical chemistry, wliich, Hkc the 
 art of dyeing or of lead smelting, may advance to 
 a certain degree of perfection, without the aid of 
 pure science ; but which can only have its pro- 
 cesses explained, and be led on to shorter, — more 
 simple, — more economical, — and more perfect pro- 
 cesses, by the aid of scientific principles. 
 
CHAPTER VIII. 
 
 Of the Improvement of the Soil— Mechanical and Chemical 
 Methods — Draining — Subsoiling — Ploughing, and Mix- 
 ing of Soils — Use of Lime, Marl, and Shell-sand — Ma- 
 nures — Vegetable, Animal, and Mineral Manures. 
 
 The soil is possessed of certain existing and ob- 
 vious qualities, and of certain other dormant ca- 
 pabilities ; how are these qualities to be improved, 
 "^these dormant capabilities to be awakened 1 
 
 There are two distinct methods by which these 
 ends may be, in some measure, attained, — by the 
 use of mechanical, and by the application of che- 
 mical, means. Mechanical operations produce 
 changes chiefly in the physical properties of the 
 soil, — chemical means alter its elementary consti- 
 tution. Ploughing, draining, mixing, &;c. belong 
 to the former class of operations ; manuring and 
 irrigation belong to the latter. It will be proper 
 
 to consider these methods separately. 
 12 
 
134 IMPllOVEMENT BY DRAINING, 
 
 SECTION I. — OF MlOOHANICAr- MKTIIOUS OF IMPROVINtJ 
 THE SOIL. 
 
 1. Drainidg. — Ti^ie first step to be taken, in or- 
 der to increase the fertility of nearly all the 'im- 
 provcablo lands of (Jreat Britain, is to drain them. 
 So long as they remain wet, they will conlinnc to 
 be cold. Tlie lieat of the sun's rays, which is in- 
 tended by natare to warm the soil, will be ex- 
 pended in evaporating the water from its surface; 
 and thus the plants will never receive that ge- 
 nial warmth about thcii- roots wliich so much 
 favours their rapid growth. Where too much wa- 
 ter is present in the soil also, that food of the 
 plant which the soil supplies is so much diluted, 
 that either a nmcli greater quantity of fluid must 
 be tak(Mi in by the roots, — much more work done, 
 — or tlie plant will be scantily nourished. The 
 presence of so much water in the siem and leaf 
 keeps down ihcir temperature likewise, when the 
 sun-shine appears ; an increased evaporation takes 
 place from their surfaces, a lower natiwal heat, in 
 consequence, prevails in the interior of the plant, 
 and the chemical changes on which its growth de- 
 pends proceed with less rapidity. 
 
 By the removal of the water, the physical pro- 
 
EFFECT OF DRAINING. 135 
 
 perties 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. The soil ex- 
 pands, becomes close and adhesive, and excludes 
 the air from the roots of the growing plant, — the 
 access of which air appears to be almost an essen- 
 tial element in the healthy growth of the most im- 
 portant vegetable productions. 
 
 Open an outlet for the water below, and as it 
 trickles away, the air from above will follow it 
 and take its place among the pores of the soil, car- 
 rying to every root the salutary influences it is 
 appointed to bear with it wherever it penetrates. 
 When freed from water also, the stiff" soil becomes 
 more mellow ; and when once stirred up to a con- 
 siderable depth, more universally porous, — ^so that 
 air can make its way everywhere, and the roots 
 can find their easy way in every direction. The 
 presence of vegetable matter, — whether existing 
 naturally in a soil thus physically altered, or ar- 
 tificially added to it, — becomes of double value. 
 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 
 
130 I)UA1NA(JK OF I.ICUT KOir^S. 
 
 tho oiirlhy juhI .snIiiKi (oiiHlidK^jls of Uk; soil. In 
 tho prosonco of air, on (Ik; coiilnny, HiIh vofroliiblo 
 ijmtl(!r <l(;(()iii|)o,s(\s rjipidly, i)ro(lucos carbonic acid 
 ill ljii-^<! <|uaii(iiy, as well as <»(li(5r cornponnds ill 
 lor food, and (!V(!ii mmmNms (Ik; iiK)r<^anic coiiHlitii- 
 cnts of the soil jiioro 11 tied to (Uilcr tlio roots, and 
 llms to siij)j)ly iiioro rapidly what (ho several parts 
 oi' the plaiil r<M|iiir(;. 
 
 Nor is it only still" and clayev .soils to whicdi 
 draining can wilh a(lva.nta<>-<; \n) a|>plied. It will 
 Ik; <»l)vious to every one, that w hen s|)rin<»a rise to 
 the; siirlaiM; in sandy soils, adrain niiisl he niach; to 
 carry oil' (lu; vva(<;r, — it will als<> r(;a(lily occiir, 
 that where a sandy soil rests upon a hard or clayey 
 bottom, drains may also lui n(!C(;ssary ; but it is 
 not mirre((iiently suppos(;(l, that when tlic subsoil 
 is sand or gravel, (hat drains can only in Hpccial 
 cas(;s b(^ iK;eessary. 
 
 I'iVery one, h<>W(;ver, is lainiliar with tla; Iju^t, 
 that wlK;n wa((>r is applied to the bottom of a 
 llowor-pot lull of soil, it will «;ra(luallv find ils 
 way to tla; surface, how<;ver li<;ht the soil may be. 
 So it is in sandy soils or subsoils in the op(;n field. 
 Tf waler abound at the de[)th of u iow feet, or if 
 it so abound a( certain seasons of the year, that 
 waler will rise (o the; surface; aial as tho sun's 
 heat dries it oil' by evaporation, more water will 
 
CLAV HUHHOILS (;HADUALLY SOFTKN. 137 
 
 follow U) Hij|)|)ly its j)lacc. This jiltraction IVorn 
 beneath will always {j^o on wlion llx; :iir indiy iiiid 
 warm, and thuH a douMo (;vil will oMHue — llie soil 
 will 1x5 kept rnoi.st and (M>ld, Jirid instead of ji, con- 
 stant circulation of air downwards, thore will l>e 
 a constant curr<!nt of water upwards. 'I'lius 
 will (Ix! roots, the under soil, ;i.nd the orn;i.ni(i 
 matter it contains, hr; all <l«;prived of the henfjtits 
 which the access of ilie ;i.ir is tilted (o eotiler. 'I'he 
 remedy lor these evils is (o he found in ;i,n (dli- 
 cicnt system of draina/^c. 
 
 On I his suhj(!ct I shull add one important prac- 
 tical rerrjark, which will readily HU<»gest itself to 
 the geolo«»;is( who has studi(;d the action of air and 
 wat(;r on tin; various cd;iy IxmIs that occur lM;r(; 
 and there as mcmhers of the series of str.-iti/ied 
 rocks. Thara arc, no clays which do not, fj^raduaUy 
 soften under the united injlucncc of air and of run- 
 nin^ umlcr. Il is false economy^ ihercfore^ to lay 
 dovm tiles w/dhout soles — however hard and sti fT 
 the clay suhsoil fnay appear to h(;. Jn the course 
 often (n- (ifteen years the stiffest clays will soften, 
 «o as to allow the tih; to sink ; ;i.nd many very 
 much sooner. 'J'he j)assage for I lie water is Ihus 
 gradually narrowed ; and when the tile has sunk 
 a cou[)le of inches, the whole must he taken up. 
 Thousands of miles of drains liavc been thus laid 
 
138 TILES SHOULD NOT BE LAID WITHOUT SOLES. 
 
 down, both in the low country of Scotland and in 
 the southern counties of England, which have now 
 become nearly useless ; and yet the system still 
 goes on. It would appear even as if the farmers 
 and proprietors of each district — unwilling to be- 
 lieve in or to be benefitted by the experience of 
 others — were determined to prove the matter in 
 their own case also, before they will consent to 
 adopt that surer system which, though demand- 
 ing a slightly greater outlay at first, will return 
 upon the drainer with no after-calls for either 
 time or capital. If my reader live in a district 
 where this practice is now exploded, and if he be 
 inclined to doubt if other counties be farther be- 
 hind the advance of knowledge than his own, I 
 would invite him to spend a week in crossing the 
 county of Durham, where he may find opportuni- 
 ties not only of satisfying his own doubts, but of 
 scattering here and there a few words of useful 
 advice among the more intelligent of our prac- 
 tical farmers. 
 
 2. Suhsoiling. — The subsoil plough is an auxil-. 
 iary to the drain. Though there are few subsoils 
 through which the water will not at length make 
 its way, yet there are some so stiff either naturally 
 or from long consolidation, that the good effect of 
 a well-arranged line of drains is lessened by the 
 
USE OF THE SUBSOIL PLOUGH. 139 
 
 slowness with which they allow the superfluous 
 rains to pass through them. In such cases, the 
 use of the subsoil plough is most advantageous in 
 loosening the under layers of clay, and allowing 
 the water to find a ready escape downwards and 
 to either side until it reach the drains. 
 
 It is well known that if a piece of stiff clay be 
 cut into the shape of a brick, and then allowed to 
 dry, it will contract and harden — it will form an 
 air-dried brick, almost impervious to any kind of 
 gas — 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. 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 sub- 
 soil being very retentive, the subsoil plough is 
 used to open it up — to let out the water and to let 
 in the air. If this is not done, the stiif under- 
 clay will contract and bake as it dries, but it will 
 neither sufficiently admit the air nor open a free 
 passage for the roots. But let this operation be 
 performed when the clay is still too wet, a good 
 
140 AFTKR rill': LAND IS DllY. 
 
 oflcct will follow, in (he lirsj; instanco ; bill nflcr 
 a wliiKi, IIk; cut cJjiy will ii<»ain cohere, and llic 
 former will |)i-oiioiiiic(! siibsoiliMjr to \n\ n hhv.W.mh 
 expense on his land. Defer (In; iis(! of tlm Hiih- 
 Hoil |)loii«!;li till I lie clay is dry — il will then tear 
 and break iiKstcjid of riiUhi<r, iiiid its openness will 
 remnin. Oikm; ^ive the air free accciss, and it, 
 jift(!r !i lime, so modifies the drained ciny, Ihnt it 
 no lon«>;er has ;in ('(lual Icndency to cohere. 
 
 Mr. Smilliof l)c;ms((»n v(!ry jiKliciously recom- 
 mends lli:il lli(> subsoil |>lou<i,li should never be 
 used till ill Iciisl ii yc'ir aflcr (he liind h:is been iho- 
 rou^hly dr;iin(>d. This in many cjises will Ix; a 
 sulfK'ient safc^^ujird — will Jillow n siidicient (iin(; 
 for the clay iu dry ; in otln^r cases two years nniy 
 not be too much. I»ut this precaution has by 
 some bc(Mi n(;}Tl(U't(Ml, Jind subsoilin<>" being with 
 tluMii a failure, they lijiv(! sou<;lit, in souk; sup- 
 posed chemical or oilier cpiality of their soil, for 
 the cause; of a wan! of siie<^ess which is to be found 
 in their own n(;«;lect of a, most necessary precau- 
 tion. Let not the practical man be (oo hasf// in 
 d(\sirino; to attain those; l)(;ne(its which attend the 
 adoption of improved mod(;s of culture; let him 
 give ev(;ry method a fair trial ; and ahime all^ let 
 him make his trial in the way and with the pre- 
 
KPFECT or DKEP rLOtTOIIINO. I'll 
 
 cautions recommended hy the author of the methodf 
 before ho pronounce its condemnation. 
 
 3. Deep-plou^hingf lik(5 .sulxsoilin*^, nids <lio ef- 
 fect ^A' tli(; (IniinH, and so fjir, and when; it f^oes 
 nearly as i\v.v.\}, more eomj)l(5t(;ly eflects tin; ssirno 
 ol>j(!ot. JJut ind('[)(;nd(!nt of tliis, it has other usos 
 an<l merits, and whore it lias been suceesslully ap- 
 |)hed, lias improved the land by the operation of 
 other causes. 
 
 Snhsoiling ordy lets out i\\(\ wator, and allows 
 access to tlio air and a frc^o passjiof; to the roots. 
 D(^ep-plou<;hin^, in addition to tll(^s(^, hririf^s new 
 earth to the surface, forms tims a d(;(!por soil, and 
 more or h^ss alt(;rs both its [)hysic;d qualities and 
 its chemical constitution. 
 
 If the ploiif^h be mad(^ to bring up two inches 
 of clay or sand, it will stilh^n or loosen the soil, 
 as the case may be, or it iriay allnct its colour or 
 density. It is cle.'ir and simple enouf^h, there- 
 fore, that by <leoi)-])Ioughing the physical proper- 
 ties of tlie soil m;iy 1x5 all(!red. 
 
 IJnt th(!re are certain substniuM^s contjiiiKul in 
 every soil, whetlusr in pasture or utkNt the plou«^li, 
 which frradually niMko their way down towards 
 the subsoil. Thoy sink till they reach at last 
 that [>oint beyond whicdi the [)lou«;h does not 
 
142 LIME, CLAY, AND MAEL SINK. 
 
 usually penetrate. Every farmer kuows that lime 
 thus sinks. In peat-soils top-dressed with clay, 
 the clay thus sinks. In sandy soils also which 
 have been clayed, the clay sinks ; and in all these 
 cases, I believe, the sinking takes place more ra- 
 pidly 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 fertilizing virtue to the under chalk- 
 soils (see page 88), and render necessary a new 
 application from beneath, to renovate its produc- 
 tive powers. 
 
 If this be the case with earthy substances such 
 as those now mentioned, which are insoluble in 
 water, it will be readily believed that those saline 
 ingredients of the soil which are readily 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. Bring 
 up a portion of this subsoil by deep-ploughing, 
 and you restore to the land a portion of what it 
 has lost — substances, perhaps, which may render 
 it much more fruitful than before. Such is an 
 outline of the theory of deep-ploughing, and it 
 is entirely unexceptionable. 
 
 But suppose the land to have originally con- 
 
BRINGING SUBSOILS TO THE SURFACE. 143 
 
 tained something noxious to vegetation, which in 
 process of time has been washed down into the 
 subsoil, then to bring this again to the surface 
 would be materially to injure the land. This 
 also is true, and a sound discretion must no doubt 
 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 a full and 
 fair exposure to a winter's frost will not in a great 
 degree deprive 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 Yester, and give a calm consideration to 
 the efforts produced by the use of deep-ploughing 
 on the home-farm of the Marquis of Tweeddale. 
 
 In many cases the farmer fears, as he does in 
 the county of Durham, to bring up a single inch 
 of the yellow clay that lies beneath his 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 consider- 
 able quantity. Till it is exposed to the air, this 
 iron is hurtful to vegetation, and one of the bene- 
 fits of a winter's exposure of such subsoils to the 
 air, is the effect produced upon the iron it con- 
 tains. 
 
144 EFFECT OF ORDINARY PLOUGHING. 
 
 It is the want of drainage, however, and of thd 
 free access of air, that most frequently renders 
 subsoils for a time injurious to vegetation. Let 
 the lands be well drained — let the subsoils bo 
 washed for a few years by the rain-water passing 
 through them, — and there are few of those which 
 are clayey in their nature that may not ultimately 
 be brought to the surface, not only with safety, but 
 with advantage to the soil. 
 
 4. Ploughing* — Other benefits, again, attend 
 upon the ordinary ploughings, hocings, and work- 
 ings of the land. Its parts are more minutely di- 
 vided — the air gets access to every particle — it is 
 rendered lighter, more open, more permeable to 
 the roots. The vegetable matter it contains de- 
 composes 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 pro- 
 duction of ammonia and of nitric acid also (see 
 pages .33 to 36), and the absorption of one or both 
 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 af the atmosphere. 
 The general advantage, indeed, to be derived from 
 the constant working of the soil, may be inferred 
 
MIXING THE SOIL. 145 
 
 from the fact, that TuU reaped twelve successive 
 crops of wheat from the same land by the repeated 
 use of the plough and the horse-hoe. There are 
 few soils so stubborn as not to shew themselves 
 grateful in proportion to the amount of this kind 
 of labour that may be bestowed upon them. 
 
 5. Mixing. — It has been shewn (page 114), 
 that the physical properties of the soil have an im- 
 portant influence upon its average fertility. The 
 admixture of pure sand with clay soils produces 
 an alteration which is often beneficial, and which 
 is wholly physical. The sand merely 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 
 alteration. 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 suffi- 
 cient abundance. It thus alters its chemical con- 
 stitution, 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 consol- 
 idate the sands and open the clays, and thus im- 
 13 
 
146 USES OP Marl and siiell-sano. 
 
 prove the mechanical texture of both kinds of 
 soil, but their main operation is chemical ; and the 
 almost universal benefit they produce depends upon 
 the new chemical element they introduce into the 
 constitution of the soil. 
 
 It is a matter of almost universal remark, that 
 in our climate soils are fertile — clayey or loamy 
 soils, that is — only when they contain an appre- 
 ciable quantity of lime. In whatever 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 agriculture pro- 
 duce are usually obtained. Some of the chemical 
 effects of the lime upon the soil will be explained 
 in a subsequent section. (See page Wp.) 
 
 SECTION 11. — OP THE CHEMICAL METHOD OF IMPROVING ThE 
 SOIL BY THE USE OF MANURES. 
 
 None of the above methods of improving the 
 soil are mechanical only — they all involve some 
 chemical alterations also, which are readily to be 
 explained by a knowledge of elementary chemical 
 principles. But the manuring of the land is more 
 strictly a chemical operation, and may therefore 
 
AIM OF THE FARMER IN TILLING HIS LAND. 147 
 
 with propriety be separated from those methods 
 of improving its quality which involve at the same 
 time important and expensive mechanical opera- 
 tions. 
 
 In commencing the tillage of a piece of land, 
 the conscientious farmer may have three objects 
 in view in regard to it. 
 
 1. He may wish to reclaim a waste, or to re- 
 store 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 develope all 
 its capabilities, and to increase its permanent pro- 
 ductiveness ^li the greatest 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 friend. The highest 
 farming, skilfully and prudently conducted, is also 
 the most remunerating. 
 
 But whichever of these three ends he aims at, 
 he will be unable to attain it without a due know- 
 ledge 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 spe- 
 cial purposes they are each intended to serve — 
 
14y WHAT AUl] MANUUKR. 
 
 which arc the nioat dhictivo lor this or that crop 
 — how tlioy aro to hcohtainod in tlio greatest al)ini- 
 (lanco, and at tlic least cost — how their streii«;(li 
 may he econoiui/iul, — and in vvlial static and at what 
 seasons lli<^y may 1)C most henelicially nppliiid to 
 tli(^ land. Sncli an; a lew of tlx; (jia^stions which 
 lli<; skillhl farmer should hv. r(;a(ly (o ask hiniself, 
 and should Uc ahh; to answer. 
 
 |{y a manure is to he understood whatever is 
 capahle of fe(Mlin»>; or of supplying food to the 
 plant. And as plants reipiire earlliy and saline 
 as W(;ll as vegiitahlo food, gypsum and nitrate oi" 
 soda aro as properly calh^l manures as larm-yard 
 dung, hon(i-dusl, or night-soil. 
 
 IVIa,mu-es naturally divide themselves into such 
 as ar(; t)f vcgclahlc^ of ani/iKtl, and ol' mineral ori- 
 gin. 
 
 1. OK VlUJK'rAlU.K MANIIKKS. 
 
 There are two purposes which vegetahle mamu'C 
 is generally supposiMl to serve wlien added to the 
 soil. It hjosens the land, opens its j>ores, and 
 makes it light(U- ; and it also serves to supply or- 
 ganic food (o (Ik; roots of the growing plant. It 
 serves, how(<ver, a lliird purpose : it yields to the 
 roots those; saline antl earthy matters wliich it is 
 their duty to lind in tlu; soil, and which exist in 
 
DECAYED VEGETABLE MATTER. 149 
 
 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 enrich, 
 ing the land must vary considerably 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 and kind of inorganic matter present in 
 different vegetable substances, as indicated by the 
 ash they leave (see pages 52 to 62). Thus if 1000 
 lbs. of the saw-dust of the willow be fermented, 
 and added to the soil, they will enrich it by the 
 addition of only 4^ lb. of saline and earthy mat- 
 ter, while 1000 lbs. of the dry leaves of the same 
 tree fermented, and laid on, will add 82 lbs. of in- 
 organic matter. Thus, independent of the effect 
 of the vegetable matter in each, the one will pro- 
 duce a very much greater effect upon the soil than 
 the other.* 
 
 There are three states in which vegetable mat- 
 ter is collected by the husbandman for the purpose 
 
 * It is owing to this large quantity of saline and othe 
 inorganic mattfir that fermented leaves form too strong a 
 dressing for flower borders, aiad that geirdeners therefore ge- 
 nerally mix them up into a eompost. 
 13* 
 
150 GREEN MANURING. 
 
 of being applied to the land — the green state ; the 
 dry state ; and that state of imperfect decay in 
 which it forms peat, 
 
 1. Green Manuring. — When grass is mown in 
 the field, and laid in heaps, it speedily heats, fer- 
 ments, 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 green plant begins very soon to ferment in the 
 interior of the stem and leaves, and speedily com- 
 municates 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 tend- 
 ency to decay, and thus admits of long preserva- 
 tion. 
 
 The same rapid decay of green vegetable mat- 
 ter takes place when it is buried in the soil. Thus 
 the cleanings and scourings of the ditches and 
 hedge-sides form a compost of mixed earth and 
 fresh vegetable matter, which soon becomes capa- 
 ble 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 
 
UNIVERSALITY OF THE PRACTICE. 151 
 
 jciatter in a short time decays into a light, black 
 mould, and enriches in a remarkable degree and 
 fertihzes the soil. 
 
 Hence the practice of green manuring has been 
 in use from very early periods. The second or 
 third crop of lucerne was ploughed in by the an- 
 cient Romans — as it still is by the modern Italians. 
 In Tuscany, the white lupin is ploughed in, in 
 preference — in Germany, borage. In French 
 Flanders, two crops of clover are cut, and the third 
 is ploughed in. In Sussex, turnip seed has been 
 sown at the end of harvest, and after two months 
 again ploughed in, with great benefit to the land. 
 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 econo- 
 my, therefore, 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 cuttings of the 
 vine stocks at the roots of the vines themselves ; 
 and many vineyards flourish for a succession of 
 years without any other manuring. 
 
 Buckwheat, winter tares, clover, and rape, are 
 all occasionally sown for the purpose of being 
 ploughed in. This should be done when the flower 
 
152 HFKK(!T OF (JI;i;|.;n l>lAIVl/KIN(i. 
 
 has just h('f(un to open, niid if jxissiUld at a season 
 when tho warmdi of Hw :iir nrul (lui dryness of the 
 soil Jirci siicli ;i.s lo Ijicilitato decomposition. 
 
 TIimI iUr. soil should hcc.onio richer in vegetable 
 matter by Ibis burinl of n croj) tlian it was before 
 the seed of <hiit crop vvjis sown, and shouhl also 
 be otherwise ben(^litt(Ml, will be undtustood l)y re- 
 collecting^ (see pjvgcj 42) that perhaps three-fourths 
 of the whol(^ or<»anic nuitter w(^ bury h;is been 
 derived from lh(^ air — that by liiis process of 
 ploughin<^ in, Iho v(><:;(!tnble matler is more (Mpially 
 dillViS(Ml lhrou«;h (h(i whoK; soil Ihaii it (Mudd ever 
 be by any miMcly mechanical means ; — and that by 
 the natural decay of this ve<jjetjd)le matter, anuno- 
 nia. and nilric acid are, to a j^rcatcr extent (pa^c's 
 IVA and :M), i)rodueed in the soil, and its agri- 
 cultural capahilities in consequence materially 
 increasiMl. 
 
 Tliese considerations, whiU^ they explain tho 
 effect and illustral(^ the value of green manuring, 
 will also satisfy the; intelligent agriculturist that 
 there ar(5 methods of improving his land without 
 the aid either of town or of foreign manures — and 
 that he overlooks an imj)orlant natural means of 
 wealtii w lio neglects the green sods and crops of 
 weeds that llourish by his hedgerows and ditches, 
 licft to themselves, they ripen their seeds and sow 
 
USE OF SEA WEE I). 153 
 
 ihcm annually in his iiclds — colh^clcd in compost 
 heaps thoy wouhl niatorinlly a<i(l lo his yearly 
 crops of corn. 
 
 Sca-nuxds, — Amon^ «;n.(;n manures, (lu^ us<' of 
 fr(!sh s(!a-wji.r(? (l(!S(;rvos (!S|)()cial mcfulion, IVom lh(i 
 r(!inarka.l)ly Icrlilizinfr properties it is known (o 
 possess, us well as Irom lh(5^reat exlciiit to which it 
 is cnjployod on all our (joasts. 'Vho produrj; of the 
 islo ol'Th.-iiict in Kent is said to have heendoiihird 
 or triphsd hy th(5 iis<i of this manure; Iho laniis 
 on the Lolhian coasts ar(! said to Ix; l(!t lor !2()s. or 
 'M)h. more rent when they have a riyht of way (o 
 the s(Mi, where the w(!(!d is thrown on slior(! ; and 
 in th(5 W(!sl(!rn Isles th(! s(!a-war<^, th(^ sliell-marl, 
 and tl'ie peat-ash, are the tincse ^reat jiatural ler- 
 tilizcrs to which the agriculture of the district 
 is indehted lor tin; comparative ()rosp(Mily to 
 which it iias in some of tlu; islands already at- 
 tained. 
 
 Sea-w(;odH dccomposo with great onso when col- 
 lected in h<!aps or spniad upon the land. Dining 
 tlniir ileeay, th(;y yicsid not only orga,iii<: food to 
 the [)lant hut saline matters also, to wiiich much 
 of their (!tnca,cy hoth on the grass and tiie corn 
 crops is no douht to Im; ascrilxid. 
 
 2. Manuring vnl.li, dry VefrrJ.ahIr Mailer. — Al- 
 most every one knows that the saw-du.st of most 
 
154 FERMENTATION OF DRY STRAW. 
 
 common woods decays very slowly — so slowly, that 
 it is rare to meet with a practical farmer who con- 
 siders it worth the trouble of mixing with his 
 composts. This property of slow decay is pos- 
 sessed in a certain degree by all dry vegetable 
 matter. Heaps of dry straw alone, or even 
 mixed with earth, will ferment with comparative 
 difficulty and with great slowness. It is neces- 
 sary, therefore, to mix it, as is usually done, with 
 some substance that ferments more readily, and 
 which will impart its own condition to the straw. 
 Animal 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 farm-yard is made 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 mi- 
 nute 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 ex- 
 posure to the air, and other agencies, as to be fitted 
 to yield both organic and inorganic food to the 
 roots of the plants it is intended to nourish. 
 
 We have seen that this decomposition takes 
 place very speedily, and of its own accord, when 
 the vegetable matter is green, but that it can l:^ 
 
tONG AND SHORT DUNG. 155 
 
 induced or brought on in the case of dry straw by 
 the agency of animal matter. The same means will 
 cause the fermentation of any other vegetable sub- 
 stance which is in a minute state of division. Even 
 saw-dust made into a compost heap with soil or 
 sods, and watered regularly and copiously with the 
 liquid manure of the farm -yards, may be thug con- 
 verted into a fertilizing vegetable mould. 
 
 Differences of opinion have prevailed, and dis^ 
 eussions 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 solely for the 
 purpose of yielding food to the plant, or of pre- 
 paring food for it, the case is very simple. The 
 more complete the state of fermentation — if not 
 carried too far — the more immediate will be the 
 agency of the manure ; hence the propriety of the 
 application of short dung to turnips and othef 
 plants it is desirable to bring rapidly forward ; 
 but if the manure be only half decayed, it will re- 
 quire time in the soil to complete the decomposi- 
 tion, so that its action will be more gradual and 
 prolonged. 
 
 Though in the latter case the immediate action 
 is not so perceptible, yet the ultimate benefit to 
 the soil, and to the*crops, may be even greater, 
 supposing them to be such as require no special 
 
150 SLOW EFFECTS OF SAW-DUST. 
 
 forcing at one period of the year. With a view 
 to this slow amcUoration, vegetable matter of any 
 kind may be added with benefit, if in a suflicient 
 state of division, to the soil. JCven saw-dust ap- 
 plied larg(>ly to tlio land, has been found to im- 
 prove it, though little at first, yet 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 matter, therefore, does not produce 
 an immediate eifect, ought not to induce the prac- 
 tical farmer to despise tiie application to his land — 
 either alone, or in the form of a compost — of every 
 thing of the kind he can readily obtain. If his 
 fields are not already very rich in vegetable mat- 
 ter, both he and tlu^y are likely to bo ultimately 
 benefitted by sucli additions to the soil. 
 
 Rape Dust, — It is from tlic straw of the corn- 
 bearing plants, or from the stems and leaves of 
 the grasses, that the largest portion of the strictly 
 vegetable manures apj)rKMl to the soil is generally 
 obtained or prepared. ]{ut the seeds of all plants 
 are much more enriching than the substance of 
 their leaves and stems. These seeds, however, 
 are in general too valuable for food to admit of 
 their ap[>lication as a manure. Still the refuse of 
 some, as that of diflferent kinds of rape-seed after 
 
RAPE AND MALT DUST. 157 
 
 the oil is expressed, and which is unpalatahle to 
 cattle, is applied with great henefit to the land. 
 Drilled in with spring wheat, or scattered as a 
 top-dressing in spring at the rate of 5 cwt. to iln 
 acre, it gives a largely increased and remunerat- 
 ing return. It is applied with equal success to 
 the cultivation of potatoes, and generally it may 
 be substituted for farm-yard manure at the rate 
 of about 1 cwt. of rape-dust for each ton of ma- 
 nure. 
 
 Malt Dust consists of the dried sprouts of bar- 
 ley, 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 fertilizing power. 
 
 Charcoal Powder possesses the remarkable pro- 
 perty of absorbing noxious vapours from the air 
 and soil, and unpleasant impurities from water. 
 It also sucks into its pores much oxygen from the 
 air. Owing to these and other properties, it is a 
 valuable substance for mixing with liquid manure, 
 night-soil, farm-yard manure, ammoniacal liquor, 
 or other rich applications to the soil. It is even 
 capable by itself of yielding slow supplies of nour- 
 ishment to living plants, and is said, in many cases, 
 without any admixture, to have been used with ad- 
 vantage in practical agriculture. In moist charcoal 
 14 
 
158 SOOT AND CIIAUCOAL POWDER. 
 
 the seeds of the gardener are found to sprout with 
 remarkable quickness and certainty. 
 
 Soot, whether from the burning of wood or of 
 coal, is of vegetable origin, and consists chiefly of 
 a finely-divided charcoal, possessing the properties 
 above nuuitioneil. It contains, liovv(>ver, ammonia 
 and certain other substances in small quantity, to 
 wliich its well known, and especially its immediate, 
 effects upon vegetation are in part to be ascribed. 
 3. The use of Peat. — In many parts of the 
 world, and in none more abundantly, perhaps, 
 than in Gt. Britain, is vegetable nuitter collected 
 in the form of peat. This ought to supply an 
 inexhaustible store of organic matter for the ame- 
 lioration of the adjacent soils. We know that by 
 draining off the sour and unwholesomt water, 
 and afterwards applying lime and clay, the sur- 
 face of peat bogs may be gradually converted into 
 rich corn-bearing lands. It nuist, therefore, be 
 possible to convert peat iiscW by a similnr process 
 into a compost litted to improve the condition of 
 other soils. 
 
 The late Lord Meadowbank, who made many 
 important experiments on this subject, found, that 
 after being partially dried by exposure to the air, 
 peat might be readily fermented, and brought into 
 the state of a rich fertilizing compost by the same 
 
USE OF PEAT IN COMPOSTS. 159 
 
 means which arc adopted in the ordinary ferment- 
 ing of straw. lie mixed with it a portion of ani- 
 mal matter, which soon communicated its own 
 fermenting qurdity to the surrounrhng peat, and 
 hroiight it n;adily in to a proper Ijeat. Jle found 
 tliat one ton of hot fermenting manure, mixed 
 in alternate layers with two of half dry peat, and 
 covered hy the same, was sufTicient to ferment the 
 whole ; and Hul).se(juently that tlie vapours wliich 
 rise from naturally fermenting farm-yard manure 
 or animal matters, would alone j)roduce the same 
 effect upon peat, placed so as readily to r(;ccive 
 and ahsorh them. 
 
 Ah ammonia is one oi' the compounds specially 
 given of!* by putrifying animal substances, it is 
 not unlikely that a watering with anirnoniacal li- 
 quor would materially prej)are the peat for un- 
 dergoing fermentation. At all events it seems 
 possible to pre[)are any quantity of valuable peat 
 compost by mixing the peat with a still less (juan- 
 tity of f(;rm(;nt<;<l manure than was emphjyed by 
 Lord Meadowhank, provided the liquid manure 
 of the farm-yard be collected in a cistern, and he 
 thrown at intervals by means of a pump over the 
 prepared heaps. 
 
 One important use also to which I think peat 
 may be applied is, after it is partly dried, to 
 
160 RELATIVE VALUE 
 
 build it into covered heaps, and half burn or char 
 it till it become readily reducible into a fine pow- 
 der. In this state it would be of great value as 
 a mixture to preserve the virtues of liquid ma- 
 nures of all kinds, of night-soil, and of ammonia- 
 cal hquor. 
 
 SECTION III. — RELATIVE VALUE OF DIFFERENT VEGETABLE 
 
 MANURES. 
 
 There are two principles on which the relative 
 value of different vegetable substances, as ma- 
 nures, may be stated to depend— ^rst, on the rela- 
 tive quantity and kind of inorganic matter they 
 contain ; and second, on the relative proportions 
 of nitrogen present in each, 
 
 1. Valued according to the quantity of inorga- 
 nic matter they contain^ — the worth of the several 
 kinds of straw and hay would be represented by 
 the following numbers : — 
 
 Wheat straw, 
 
 70 to 360 
 
 Oat straw, 
 
 . 100 to 180 
 
 Hay, .... 
 
 . 100 to 200 
 
 Barley straw, 
 
 . 100 to 120 
 
 Pea straw, . 
 
 . 100 
 
 Bean straw, 
 
 60 to 80 
 
 Rye straw, . 
 
 50 to 70 
 
OF DIFFERENT VEGETABLE MANURES. 161 
 
 Dry potato tops, • . . 100 
 
 Dry turnip tops, . . . 260 
 
 Rape, cake .... 120 
 
 that is, a ton weight of each of these substances, 
 
 when made into manure — provided nothing is 
 
 washed out by the rains — will return to the soil 
 
 the above quantities of inorganic matter in pounds. 
 
 Generally, perhaps, these numbers will give the 
 
 reader an idea of the relative permanent effect oi 
 
 these different kinds of vegetable matter when 
 
 laid upon the soil. But, by a reference to the facts 
 
 stated in pp. 58 to 64, in regard to the quality of 
 
 the inorganic matter contained in plants, he will 
 
 satisfy himself, that the effect of these manures o:i 
 
 particular crops is not to be judged of solely by 
 
 the absolute quantity of earthy and saline mattei 
 
 they contain ; — that which the turnip-top, foi 
 
 example, or the bean-stalk, returns to the soil, may 
 
 not be exactly what will best promote the growth 
 
 of wheat. 
 
 2. On the other hand, if the fertiUzing value ot' 
 
 vegetable substances is to be calculated by the re ■ 
 
 lative quantities of nitrogen they severally contain, 
 
 we should place them in the following order : — 
 
 the number opposite to each substance representin-^ 
 
 that weight of it in pounds, which would producQ 
 14* 
 
102 RELATIVE QTTANTITIER OF NITROGEN. 
 
 the same ofloct as 100 pounds of farm-yard ma- 
 nure, consisting of the mixed droppings and litter 
 of cattle. 
 
 Equivalont qiiantitioB 
 
 in i»f)uii(lH. 
 
 Farm-yard manure, . . . 1(K) 
 
 Wheat straw 80 to 170 
 
 Oat Hlmw, 150 
 
 RarU'y Hlruw, IHO 
 
 Buckwheat, 85 
 
 Pea straw, 45 
 
 Wheat chair, 50 
 
 Gretm y;rass, HO 
 
 Potato tops, . • . . • 75 
 
 Fresh sea-weed, .... 80 
 
 Rape (kist, 8 
 
 Fir saw-dust, .... 250 
 
 Oak snw-(U>st, .... 180 
 
 Cool soot, 30 
 
 This tahlo again presents the same substances 
 in a sonuiwhat diircront order of value ; shewing, 
 for example, nol only that such substances as rape- 
 dust and soot should prodtice a much more re- 
 markable cilbct ui)on vegetation, than the same 
 W(^ight even of farm-yard manure, but also that 
 certain dry vegetables, such as chalfand pea-straw, 
 will yield, when not uiuliily fermented, a more 
 enriching manure than barley, oat, or wheat straw. 
 It agrees, also, witii the known ellect of green 
 
KFFECT OF THIS NITROGEN. 163 
 
 manuring upon the land, since 80 pounds of mea- 
 dow-grass ploughed in, will be equal in virtue to 
 100 of farm-yard manure. 
 
 Some writers ascribe the entire action of theso 
 measures to the nitrogen they contain. This, how- 
 ever, is taking a one-side view of their real natu- 
 ral operation. The nitrogen, during their decay, 
 is liberated chiefly in the form of ammonia — an 
 evanescent substance, producing an immediate ef- 
 fect in hastening or carrying further forward the 
 growth of the plant, but not remaining perma- 
 nently in the soil. The reader, therefore, will 
 form an opinion consistent alike with theory and 
 with practice, if he conclude — 
 
 1. That the immediate effect of a vegetable 
 manure, in hastening the growth of plants, is de- 
 pendent, in a great degree, upon the quantity of 
 nitrogen it contains and gives off during its decay 
 in the soil. 
 
 2. That the permanent effect and value of man- 
 ures 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 ex- 
 pended in a single season — that of the earthy and 
 saline matter may not be exhausted for several 
 years. 
 
164 USE OF THEIR OTHER INGREDIENTS. 
 
 Nor is the carbon of vegetable substances with- 
 out its important uses to vegetaHon. From the 
 statements contained in the earlier chapters of the 
 present work, 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 of these im- 
 portant natural operations is that which considers 
 each element present in decaying plants to be ca- 
 pable of ministering food to such as are still alive, 
 — though we may not be able as yet, either to 
 estimate the precise importance of each element 
 to any particular kind of crop, or exactly to adjust 
 their relative quantities in our manures, so as to 
 promote the growth of such a crop in the greatest 
 possible degree. 
 
CHAPTER IX. 
 
 Animal Manures — Their relative value and mode of Action 
 — Difference between Animal and Vegetable Manures — 
 Cause of this difference — Mineral Manures — Nitrates of 
 Potash and Soda — Sulphate of Soda, Gypsum, Chalk, and 
 Ctuicklime — Chemical action of these Manures — Artifi- 
 cial Manures — Burning and Irrigation of the Soil — Plant- 
 ing and laying down to grass. 
 
 The" animal substances employed as manure 
 consist chiefly of the flesh, blood, bones, horns, and 
 hair of animals, of fish — which in some places are 
 found in sufficient quantity to be laid upon the 
 land — and of the solid and liquid excrements of 
 animals and birds. 
 
 SECTION I. — OF UNDIGESTED ANIMAL MANURES. 
 
 Animal substances, in general, act more power- 
 fully as manures than vegetable substances — it is 
 only the seeds of plants which can at all compare 
 with them in efficacy. 
 
 The Jlesh of animals is rarely used as a manure, 
 
166 FLESH, FISH, AND THE BODIES OF INSECTS. 
 
 except in the case of dead horses, or cattle which 
 cannot be used for food. Fish is chiefly apphed 
 in the form of the refuse of the herring and pilchard 
 fisheries, though occasionally such shoals of sprats, 
 herrings, and even mackerel, have been caught on 
 our shores, as to make it necessary to employ them 
 as manure. These recent animal substances are 
 found to be too strong when applied directly to the 
 land ; they are generally, therefore, made 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. The refuse 
 of fish oils, — of the fat of animals that has been 
 melted for the extraction of the tallow — of skins 
 that have been boiled for the manufacture of glue 
 — horns, hair, wool (woollen rags), and all simi- 
 lar substances, when made into composts, exercise, 
 in proportion to their weight, a much greater in- 
 fluence upon vegetation than any of the more 
 abundant forms of vegetable matter. 
 
 Even the bodies of insects are in many parts of 
 the world important manures of the soil. In 
 warm climates, a handful of soil sometimes seems 
 almost half made up of the wings and skeletons of 
 dead insects — the peasant in Hungary and Carin- 
 thia occasionally collects as many as thirty cart- 
 loads of dead marsh flies in a single year ; — and in 
 
BLOOD, HORN, HAIR, AND WOOL. 167 
 
 the richer soils of France and England, where 
 worms and other insects abound, the presence of 
 their remains in the soil must also aid its natural 
 productiveness. 
 
 Blood is rarely applied to the land directly — 
 though, like the other parts of animals, it makes 
 an excellent compost. As it comes from the sugar 
 refineries, however, in which, with lime water and 
 animal charcoal, it is employed for the refining 
 of sugar, it has obtained a very extensive employ- 
 ment, especially in the south of France. This 
 animal black, or animalized charcoal, as it is some- 
 times called, contains about twenty 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 
 animalized charcoal. The only disadvantage at- 
 tending these artificial preparations is, that they 
 are liable to be adulterated, or, for cheapness, pre- 
 pared in a less efficient manner. 
 
 Horn, hair, and wool, depend for their efficacy 
 precisely on the same principles as the blood and 
 flesh of animals. They differ chiefly in this, that 
 they are dry, while blood and flesh contain 80 to 
 
168 
 
 COMPOSITION OF BONES. 
 
 90 per cent, of their weight of water. Hence, a 
 ton of horn shavings, of hair, or of dry woollen 
 rags, ought to enrich the soil as much as ten 
 tons of Wood. 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, 
 that of hard and dry substances less visible, but 
 continuing for a much longer period of time. 
 
 Bones, again, while they resemble horn in being 
 dry, differ from it in containing, besides the ani- 
 mal matter, a large quantity of earthy matter also, 
 and hence they introduce a new agent to aid their 
 effect upon the soil. Thus, the bones of the cow 
 consist of 100 lbs. of 
 
 Phosphate of lime, 
 Phosphate of magnesia, 
 Soda and common salt, 
 Carbonate of lime, 
 Fluoride of calcium, . 
 Grelatine (the substance oflwrn), 
 
 55i 
 3 
 3i 
 3f 
 1 
 
 33i 
 
 100 
 
 While 100 lbs. of bone-dust, therefore, add to 
 the soil as much organic animal matter as 33 lbs. 
 of horn, or as 300 or 400 lbs. of blood or flesh, 
 they add, at the same time, much inorganic matter 
 — lime, magnesia, soda, common salt, and phos- 
 
GENERAL CONCLUSIONS. 160 
 
 phoric 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 sub- 
 stances, like the inorganic matter of plants, may 
 remain in the soil, and may exert a beneficial action 
 upon vegetation after all the organic or gelatinous 
 matter has decayed and disappeared. 
 
 From what is above stated, therefore, the reader 
 will gather these general conclusions : 
 
 1. That animal substances which, like flesh and 
 blood, contain much water, decay rapidly, and are 
 fitted to operate immediately and powerfully upon 
 vegetation, but are only temporary or evanescent 
 in their action. 
 
 2. That when dry, as in horn, hair, and wool, 
 they decompose, and consequently act more slow- 
 ly, and continue to manifest an influence, it may 
 be, for several seasons. 
 
 3. That bones, acting hke horn, in so far as their 
 animal matter is concerned, and, like it, for a 
 number of seasons, more or less, according as they 
 have been more or less finely crushed — may ame- 
 liorate the soil by their earthy matter for a still 
 longer period — permanently improving the con- 
 dition and adding to the natural capabiUties of 
 
 the land. 
 
 15 
 
170 LIQUID MANURES. 
 
 SECTION II. — OF DIGESTED ANIMAL MANURES. 
 
 Practical men have long been of opinion that 
 the digestion of food, either animal or vegetable, 
 — the passing of it through the bodies of animals, 
 — enriches its fertihzing power, weight for weight, 
 wlien added to the land. II(;nce, in causing ani- 
 mals to out up as much of tlie vegetable produc- 
 tions of the larm as possible, it is suppostul that 
 not only is so much food saved, but that the value 
 of the remainder in fertilizing the land is greatly 
 increased. Jii a subsequent section we shall see 
 how far theory serves to throw light upon these 
 opinions. (See Section IV., p. 182 to 186.) 
 
 I. I.KIVW EXCUICTIONS. 
 
 The digested animal substances usually em- 
 ployed as manures are, the urine of the cow and 
 the sheep, the solid excrements of the horse, the 
 cow, th(5 h1i(!0I), and the pig, the droppings of 
 pigeons and other birds, and night-soil. The li- 
 ([uid manures act chielly through the saline sub- 
 stances they hold in solution, whih; the solid 
 manures contain also insohd)le matters, which 
 decay slowly in the soil, and thtsre become useful 
 only after a time. The former, therefore, will 
 iiiduence vegetation more powerfully at first ; the 
 
coiviroHiTroN or TiniNr:. 171 
 
 arliori of iUo hdUr will bo Iohh cvidoril, hiij will 
 cuiiliiiiK; to o|)(;riil(! lor ;i. itiiu^h UtUfrcj period. 
 Urine. — Ihun.-i.n iirinncoiiHiHtH, in 1000 parlH, of 
 
 WaUir, .... IK{2 
 
 Urea, and oIIkt on^iuur. rniillcr.s conlMinin'.;- inUotjv.u, -1!) 
 Pkonyhaka of anunonin, lirn*^, «(»(!«, and rnn;'U(;;iin, 
 SulphaUm of soda and ttrrirnoriia, . . 7 
 
 Sal arnrifioniuc iukI r.onimon Hidt,, . . (I 
 
 1000 
 
 A thoufland jioundH of urino thoroforo conUiin 
 flH ll).s. of dry lorlili/iii*; malior of the riclnjHt 
 (junlily, worUi, al. (he, prr.snd rafc of selling arlijl' 
 cud tnaimrcN in ili.ls anmtri/j at KsaHt 20h. a <;wt. 
 Ah cacli prirwon voids ulitioHt 1000 II). of urino in 
 a, yojir, tlio national wnsto iii(iirr(;d in tiiis loriri 
 aniountH, ;it tin; al)<)V<; vji-luation, to I2h. a Iio.'id. 
 And if livo ton.s of farm-yard rnanuro por arjo, 
 add«!d year by y(;ar, will ki)<'\> ;i fnrfri in j^ood 
 lio.'irt, four owt. of tlio Holid matter of urino would 
 j)rol)al>ly liavo an ctpisil olfoot ; or tlu; urin(5 alono 
 di.srli;ir«^c;d iido tin; rivorH by a population of 
 10,000 iidiabitants would supply manure; to a farm 
 of ir)00 acroH, yioldin;; .'i. return of A^tiH) (piartor« 
 of corn or an (Kpiiv.'ilont produce of otber cropH. 
 
 Tho urine of the <;ow is wiid to eontoin Iohh 
 water tluiri tbat of man, tliou^b of courHO much 
 must depend upon the kind of food witb wbicb it 
 
172 VALUE OF URINE AS A MANURE. 
 
 is fed. R(3ckoning, then, the largo quantity of 
 liquid manure that is yielded by the cow (2000 or 
 3000 gallons a year), we may safely estimate the solid 
 matter given off by a healthy animal in tliis form 
 in twcilve months at 1200 to 1500 pounds weight, 
 wortli, if itwv/rr. in Ihc, dry sUde^ from XIO to X12 
 st(;rling. In the liquid state, the urine of one cow 
 collected and preserved as it is in Flanders, is valued 
 in that country at about j£2 a year. Any practical 
 farmer may calculate for himself, therefore, how 
 much real wealth, taking it even at the Flemish va- 
 lue, is lost in his own farm-yard — iiow much of the 
 natural means of reproductive industry passes into 
 his drains or evaporates into the air. 
 
 This liquid manure is invaluable, when collected 
 in tanks, for watering the manure and compost 
 heaps, and thus hastening their decomposition ; 
 but great part of it may also be sprinkled directly 
 upon the fields of grass and upon the young corn, 
 with the best cHecls. It nuist, however, be permit- 
 ted to stand till fermentntion commences, and af- 
 terwards diluted with a considerable quantity of 
 water, b(;fore it will be in the best condition for 
 laying on the land. 
 
 Urate, — In order to obtain the virtues of ani- 
 mal urine in a concentrated form, the custom has 
 been adopted of mixing burnt gypsum with it, 
 
DRIED URINE URATE. 173 
 
 in the proportion of 10 lbs. to every 7 gallons, allow- 
 ing the mixture, occasionally stirred, to stand some 
 time, pouring off tlic liquid, and drying and crush- 
 ing the gypsum. This is sold by manure manu- 
 facturers 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 lbs. of urate con- 
 tain no greater weight of saline and organic matter 
 than 10 gallons of urine. If it bo true, then, as 
 the manufacturers state, that 3 or 4 cwt. of urate 
 are sufficient manure for an acre, the practical 
 farmer will, I hope, draw the conclusion, — not that 
 it is well worth his while to venture his money in 
 trying a portion of it upon a piece of his land, — but 
 that a far more promising adventure will be to go 
 to some expense in saving his own liquid manure, 
 and, after mixing it with burned gypsum, to lay it 
 abundantly upon all his fields. 
 
 II. SOLID EXCRKTIONS. 
 
 Cow and Horse Dung. — So much of the saline, 
 
 nutritive, and soluble organic matters from the cow 
 
 pass off'in the li([uid form, that cow dung is correctly 
 
 called cold, since it does not readily heat and run into 
 15* 
 
174 HORSE AND COW DUNG NIGHT-SOIL. 
 
 fermentation. Mixed with other manures, however, 
 or well diffused through the soil, it aids materially 
 in promoting vegetation. The horse heing fed 
 generally on less liquid food, and discharging less 
 urine, yields a hotter and richer dung, which, how- 
 ever, answers hest also when mixed with other 
 varieties. The dung of the swine is soft and cold, 
 like that of the cow, containing, like it, at least 75 
 per cent, of water. As this animal lives on more 
 varied food than any other reared for the use of 
 man, the manure ohtaincd from it is also very 
 variahic in quality. Ap])licd alone, as a manure 
 to roots, it is said to give them an unpleasant 
 taste, and even to injure the flavour of tohacco. 
 It answers best for hemp, and, it is said, also for 
 hops ; but, mixed with other manures, it may be 
 applied to any crop. 
 
 Night-soil is probably the most valuable, and 
 yet, in I'Airope at least, the most disliked and ne- 
 glected of all the solid animal manures. It varies 
 no doubt in richness with the food of the inhabi- 
 tants of each district, — chiefly with tlic quantity 
 of animal food they consume, — but when dry, no 
 other solid manure, weight for weight, can proba- 
 bly be compared with it in general eflicacy. It 
 contains nmch soluble and saline matter, and as it 
 is made up from the constituents of the food wo 
 
POUDRETTE AND ANIMALIZRD CHARCOAL. 175 
 
 eat, of course it contains most of those elementary 
 substances which arc necessary to the growth of 
 the plants on which we principally live. 
 
 Attempts have been made to dry this manure 
 also, so as to render it more portable, — to destroy 
 its unplc.isant smell, so as to reconcile practical 
 men to a more general use of it, — and by certain 
 chemical additions, to prevent the waste of ammo- 
 nia and other volatile substances, which are apt to 
 escape and be lost when this and other powerful 
 animal manures begin to putrify through decay. 
 In Paris, Berlin, and other large cities, the night- 
 soil, dried first in the air with or without a mix 
 ture of gypsum or lime, then upon drying plates, 
 and finally in stoves, is sold under the name of 
 poudrelte, and is extensively exported in casks to 
 various parts of the country. In London also it 
 is dried with various mixtures, while in others of 
 our large towns an animalized charcoal is prepared 
 by mixing and drying night-soil with gypsum and 
 ordinary wood charcoal in fine powder. 
 
 The lialf-burned peat above described (p. 80,) 
 would answer well for such a purpose, while few 
 simple and easily attainable substances would 
 make a better compost with niglit-soil, and more 
 thoroughly preserve its virtues, than half-dry peat 
 or rich vegetable soil, mixed with more or less 
 
176 
 
 marl or gypsum. It is impossible to estimate the 
 proportion of waste which this valuable manure 
 undergoes by being allowed to ferment, without 
 mixture, in the open air. 
 
 Taffo. — In China it 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. 
 
 Pigeons^ Dung. — The dung of all birds is found 
 to possess eminent fertilizing virtues. Some va- 
 rieties are stronger than others, or more imme- 
 d iate 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 worth 20s. a 
 year for agricultural purposes. 
 
 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 nu- 
 merous shipping of modern times has disturbed 
 and driven away many of the sea-fowl, so that 
 comparatively little of their recent droppings is 
 now preserved or collected. Ancient heaps of it, 
 however, still exist in many places, more or less 
 covered up with drifted sand, and also more or less 
 decomposed. These are now largely excavated for 
 
USES OF THE DROPPINGS OF BIRDS. 177 
 
 exportation, 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 espe- 
 cially to England. It is at present sold at 20s. a 
 cwt. in this country, and is capable of entirely re- 
 placing farm-yard dung, — that is to say, turnips 
 may be manured successfully with guano alone ; — 
 but it has not yet been satisfactorily determined 
 that the English farmer can afford to use it in this 
 way to any extent, at the price now asked for it. 
 The dung of birds possesses the 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 absolutely ne- 
 cessary for the support and for the right discharge 
 of the functions of its own body. It is thus fitted, 
 therefore, 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 nourishing to 
 vegetable growth. 
 
 SECTION III. OF THE RELATIVE GROWTH OF THE 
 
 DIFFERENT ANIMAL MANURES. 
 
 The fertilizing power of animal manures, in ge- 
 neral, is dependent, like that of the soil itself, 
 
 
 
178 
 
 EELATIVE VALUES OF 
 
 upon the happy admixture they contain of a great 
 number, if not of all, those substances which are 
 required by plants in the universal vegetation of 
 the globe. Nothing they contain, therefore, is 
 without its share of influence upon their general 
 effects, yet the amount of nitrogen present in 
 each affords the readiest and most simple cri- 
 terion by which their agricultural value, com- 
 pared with that of vegetable matters and with that 
 of each other, can be pretty nearly estimated. 
 
 In reference to their relative quantities of ni- 
 trogen, therefore, they have been arranged in the 
 following order, the number opposite to each re- 
 presenting the weight in pounds which is equiva- 
 lent to or would produce the same sensible effect 
 upon the soil as 100 lbs. of farm-yard manure. 
 
 Farm-yard manure, 
 
 100 
 
 Solid excrements of the cow 
 
 135 
 
 (( (C 
 
 " horse, 
 
 73 
 
 Liquid ditto of the 
 
 cow, 
 
 91 
 
 <( l( (C 
 
 horse, . 
 
 16 
 
 Mixed ditto of the 
 
 cow. 
 
 98 
 
 (( (( a 
 
 horse, 
 
 54 
 
 (f (C (( 
 
 sheep . 
 
 36 
 
 C( 11 (I 
 
 pig. • 
 
 64 
 
 Dry flesh, 
 
 . 
 
 3 
 
 Pigeons' dung, 
 
 . 
 
 5 
 
 Flemish liquid manure, 
 
 200 
 
DIFFERENT ANIMAL MANURES 
 
 Liquid blood, 
 Dry blood, 
 Feathers, 
 Cow hair, . 
 Horn shavings. 
 Dry woollen rags, 
 
 iTg* 
 
 15 
 4 
 3 
 3 
 3 
 2i 
 
 It is probable that the numbers in this table do 
 not err very widely from the true relative value 
 of these different manures, in so far as the organic 
 matter they severally contain is concerned. The 
 reader will bear in mind, however, 
 
 1. That the most powerful substances in this 
 table, woollen rags, for example, — 2\ lbs. of which 
 arc equal in virtue to 100 lbs. of farm-yard manure, 
 — may yet shew less immediate sensible effect upon 
 the crop than an equal weight of sheep's dung, or 
 even of urine. Such dry substances are long in 
 dissolving and decomposing, and continue to evolve 
 fertilizing matter, after the softer and more fluid 
 manures have spent their force. Thus, while farm- 
 yard manure or rape dust will immediately hasten 
 the growth of turnips, woollen rags will come into 
 operation at a later period, and prolong their 
 growth into the autumn. 
 
 2. That besides their general relative value, as 
 represented in the above table, each of these sub- 
 
180 OREATER VALUE OF MIXED MANURES. 
 
 stances has a further special value not here exhibited, 
 dependent upon the kind and quantity of saline and 
 other inorganic matter which they severally contain. 
 Thus three of dry Ilesh are equal to live 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 scarcely present 
 at all in the former. Hence pigeons' dung will be- 
 nefit vegetation in circumstances where dry flesh 
 would in some degree fail. So the liquid excre- 
 tions contain much important saline matter not 
 present in the solid excretions, — not present either 
 in such substances as horn, wool, and hair, — and, 
 therefore, each must be capable of exercising an 
 influence upon vegetation peculiar to itself. 
 
 Hence the practical farmer sees the reason why 
 no one smple manure can long answer on the 
 same land ; and why in all ages and countries the 
 habit of employing mixed manures and artilicial 
 composts has been universally difluscd. 
 
 SECTION IV. — NATURAL DISTINCTION OR PIFFEKENCE BE- 
 TWEEN ANIMAL AND VEUETABLE MANURES, AND TlIK 
 CAUSE OF THIS DIFFERENCE. 
 
 In what do animal manures difler from vege- 
 table manures, — what is the cause of this dillor- 
 
ANIMAL DIFFER FROM VEGETABLE MANURES. 181 
 
 encc, — how docs the digestion of vegetable matter 
 improve its value as a manure ? 
 
 1. The characteristic distinction between 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 compar- 
 ing together the tables given in the two preced- 
 ing sections, in which the numbers represent the 
 relative agricultural values of certain animal and 
 vegetable substances compared with farm-yard ma- 
 nure. 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 containing so much nitro- 
 gen, animal substances are further distinguished 
 by the rapidity with which, when moist, they pu- 
 trify or run to decay. During this decay the ni- 
 trogen they contain gradually assumes the form 
 of ammonia, which is perceptible by the smell, and 
 which, when proper precautions are not taken, is 
 apt in great part to escape into the air. Hence 
 the loss by fermenting manure too completely, — or 
 without proper precautions to prevent the escape 
 of volatile substances. And as animal manure, 
 when thus over-fermented, or permitted to lose its 
 
 ammonia into the air, is. found much less active 
 16 
 
182 IN WHAT THEt DIFFER. 
 
 upon vegetation than before ; it is reasonably con- 
 cluded, that to this ammonia, chiefly, their pecu- 
 liar virtue, when rightly prepared, is in a great 
 measure to be ascribed. 
 
 Vegetable substances do not decay so rapidly, — • 
 do not emit the odour of ammonia when ferment- 
 ing, — nor, when prepared in the most careful way, 
 does vegetable manure exhibit the same remark- 
 able action upon vegetable life as is displayed by 
 almost every substance of animal origin. 
 
 3. Whence do animal substances derive all this 
 nitrogen ? Animals live only upon vegetable pro- 
 ductions containing little nitrogen ; can they then 
 procure all they require from this source alone ? 
 Again, does the act of digestion produce any che- 
 mical alteration upon the food of animals, that 
 their e:^cretions should be a better manure, — 
 should be 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 na- 
 tural principle. 
 
 Animals have two necessary vital functions to 
 perform, — to breathe and to digest. Both are of 
 equal importance to the health and general wel- 
 
EFFECTS OF ANIMAL DIGESTION. 183 
 
 fare of the animal. The digester (the stomach) 
 receives the food, melts it down, extracts from it 
 what is best suited to its purposes, and conveys 
 it 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 carbon, 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 in- 
 tended 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, every thing that enters the body 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 quantity varies in different in^ 
 dividuals — chiefly according to the quantity of 
 exercise they take. From 5 to 9 ounces a day is 
 the average quantity, though in periods of violent 
 bodily exertion 13 to 15 ounces of carbon are 
 breathed out in the form of carbonic acid. 
 
184 HOW THE PROPORTION OF THE NITROGEN 
 
 Suppose a man to cat a pound and a half of 
 
 bread and a pound of beef in 24 hours, and that 
 
 he gives off* by respiration 8 ounces of carbon 
 
 (3500 grains) during the same time. Then he 
 has 
 
 Carbon. Nitrogen. 
 
 Talccn, in his food, about 4500 grains, and 500 grs. while 
 
 He lias given oft' in > .j^nrk ;i i%.i 
 
 .. > o500 and httle or no nitrogen, 
 
 respiration, • . > 
 
 Leaving to be convert- ^ 
 ed into food, or to > 1000 grs. and 500 grs. 
 be rejected, . . ) 
 
 Our two conclusions, therefore, are clear. The 
 vegetable food, by respiration, is freed from a 
 large portion of its carbon, which is discharged in- 
 to the air, — nearly the whole of the nitrogen re- 
 maining behind. In the food consumed the car- 
 bon was to the nitrogen as 9 to 1 ; in that which 
 remains, 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 in 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 themselves rich 
 in the same element. 
 
BECOMES GREATER IN THE EXCRETIONS. 185 
 
 It is this same residue also which, after it has 
 performed its functions within the body, is dis- 
 charged again in the form of solid and liquid ex- 
 cretions. Hence the greater richness in nitrogen, 
 —the greater fertilizing power of the dung of ani- 
 mals than of the food on which they live. 
 
 Two other remarks I shall add for the benefit of 
 the practical man. 
 
 1. The manure of the cow, taking it mixed, is 
 not so rich in nitrogen as that of man, — because 
 the cow in the stall, large though it be, and great 
 the bulk of food it consumes, does not give off 
 much more carbon by respiration than an active 
 full grown man. Hence the proportion of carbon 
 in the excretions of this animal is greater than in 
 those of man. The dry manure is richer than the 
 dry food, weight for weight, but not in the same 
 proportion as if the cow respired a quantity of 
 carbon more nearly corresponding to its bulk, 
 when compared with the weight of carbon thrown 
 off from the lungs of man. 
 
 2. Since the parts of animals — their blood, mus- 
 cles, tendons, and the gelatinous portion of the 
 bones— contain much nitrogen, young beasts which 
 are growing, must appropriate to their own use, 
 and work up into flesh and bone, a portion of the 
 
 nitrogen contained in the non-respired part of their 
 16* 
 
186 MINERAL MANURES. * 
 
 food. But the more they thus appropriate, the 
 less will 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, will not be so rich as that 
 which is yielded by full-grown animals. I am 
 not aware how far this deterioration has been 
 observed in practice, but it may with some degree 
 of certainty be expected to take place, — unless by 
 giving a richer food to the young cattle, the dif- 
 ference to the farm-yard be made up.* 
 
 SECTION V. — OF MINERAL WATERS. 
 
 The general nature and mode of operation of 
 such mineral substances as are capable of act- 
 ing as manures, ^ill be in some measure un- 
 derstood from what has already been so fully 
 stated in regard to the necessity of inorganic 
 food to living plants, and to the kinds of such 
 food which they specially require. A slight no- 
 
 * Though I have dwelt as long upon these interesting 
 and, I believe, novel considerations, as the limits of this lit- 
 tle work will permit, yet I must refer the reader for fuller de- 
 tails, and to perhaps a clearer exposition of the principles 
 above advanced than I have here been able to give, to my 
 " Lectures 07i Agricultural Chemistnj and Geology" 
 
NITRATES AND SULPIIATES, 187 
 
 ticc, therefore, of the more important of theso 
 manures now in use will here be sufficient. 
 
 1. N'drales of Potash and Soda. — Saltpetre and 
 nitrate of soda have been deservedly commended 
 for their beneficial action, especially upon young 
 vegetation. They are distinguished by imparting 
 to the leaves a beautiful dark green colour, and 
 are applied with advantage to grass and young 
 corn, at the rate of 1 cwt. to li cwt. per acre. 
 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 bene 
 ficial purposes. 
 
 Sulphate of Soda, or Glauber's salt, has lately 
 been recommended in this country for clovers, 
 grasses, and green crops. Mixed with nitrate of 
 soda it produces remarkable crop.s of potatoes.* 
 
 Sulphate of Magnesia, or Epsom salts, might 
 also be beneficially applied in agriculture, i)roba- 
 bly to clovers and corn crops. As it can be had 
 in pure crystals at 10s. a cwt., and in an impure 
 state at a much less price, from the alum works, 
 it might readily be submitted to trial. 
 
 Sulphate of Lime, or Gypsum, is in Germany 
 applied to grass lands with great success, over 
 
 * See the author's " Suggcstiims for Experiments in Practi' 
 col Agriculture," Nos. 1 & 3 
 
188 GYPSUM AND COMMON SALT. 
 
 large tracts of country. In the United States it 
 is used for every kind of crop. It is especially 
 adapted to clovers and looiimes. 
 
 Tliese three sid)stances all adord sulphur to the 
 growing plant, while the lime, soda, and magnesia 
 are themselves in part directly appropriated by it, 
 and in part employed in preparing other kinds of 
 food, and in conveying them into the ascending sap. 
 
 Though there can be no (juestion that these and 
 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 benefitting the land in this 
 or that district. If he has already bricl^ enough 
 at hand, you must carry the builder mortar, or he 
 will be unable to go on with his work : so, if 
 the soil contain gypsum or sulphate of magnesia 
 in sufficient natural abundance, it is .it once a 
 needless and a foolisii waste to attempt to improve 
 the land by adding more ; it is still more foolish 
 to conclude that these same saline compounds are 
 unlikely to reward the j)atient experimenter in 
 other localities. 
 
 Common Salt has undoubtedly, in very many 
 districts, a fertilizing influence upon the soil. The 
 theoretical agricultiuist knows that a small quan- 
 tity of it is absolutely necessary to the healthy 
 
USE OF KKLP. 189 
 
 growth of all our cultivated crops, and he will 
 therefore, early try by a preliminary experiment 
 upon one of his fields, whether or not they re- 
 quire the addition of this species of vegetable food. 
 It is in inland and sheltered situations, and on 
 high lands often washed by the rains, that the ef- 
 fect of common salt is likely to be most appreci- 
 able. The spray of the sea, borne to great dis- 
 tances by the winds, is in many districts, where 
 prevailing sea winds are known, sufficient to sup- 
 ply an ample annual dressing of common salt to 
 the land. 
 
 Kelp, — Among mineral substances kelp ought 
 not properly to be included, since it is the ash left 
 by the burning of sea- weed. It, however, par- 
 takes of the nature of mineral substances, and 
 may, therefore, be properly considered in this 
 place. It contains potash, soda, silica, sulphur, 
 chlorine, and several other of the inorganic con- 
 stituents of plants 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 bene- 
 ficial efiects upon the soil. In the Western Isles 
 a method is practised of half burning or charring 
 sea-weed, by wiiich it is prevented from melting 
 together, and is readily obtained in the form of 
 
190 WOOD AND DUTCH ASHES, 
 
 a fine black powder. The use of this variety 
 ought to ccmbine the beneficial action of the or- 
 dinary saline constituents of kelp, with the re. 
 markable properties observed in animal and ve- 
 getable charcoals. 
 
 Wood-ash, among other compounds, contains a 
 portion of common pearl-ash in an impure form, 
 with sulphate also, and silicate of potash. These 
 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. 
 
 Dutch ashes are the ashes of peat burned for the 
 purpose of being applied to the land. They vary 
 in constitution with the kind of peat from which 
 they have been prepared. They often contain 
 traces of potash and soda, and generally a quan- 
 tity of gypsum and carbonate of lime, a trace of 
 phosphate of lime, and much siliceous matter. 
 In almost every country where peat abounds, the 
 yalue of peat ashes as a manure has been more or 
 Jess generally recognised. 
 
 SECTION VI. USE OF LIME, SHELL-SAND, ANT) MARL. 
 
 The use of lime is of the greatest importance in 
 practical agriculture. It has been employed, ia 
 
LIMESTONE AND aUICKLIME* 19l 
 
 Eur6pe at least, in one or other of its forms of 
 shells, shell-sand, marl, chalk, limestone, and 
 quicklime, from the most remote periods. 
 
 Native limestone, and all the unburned varieties 
 of chalk, shells, &;c. consist of carbonate of lime 
 (p. 51), more or less pure. When burned in the 
 kiln, the carbonic acid is driven off, and lime, 
 burned lime, or quicklime remains. 
 
 Quicklime, when exposed to the air, gradually 
 falls into the state of an exceedingly fine white 
 powder. It will do so more rapidly if water be 
 thrown upon it, when it also heats much, swells, 
 and becomes about one-third heavier than before. 
 After being exposed to the air for some time in 
 this white powdery state, it is found to have again 
 absorbed from the air a portion of carbonic acid, 
 though a very long period generally elapses be- 
 fore it is all re-converted into carbonate. In com- 
 post heaps, where much carbonic acid is formed 
 during the fermentation, the conversion of any 
 quicklime that may be mixed with them into car- 
 bonate of lime, is much more rapid and complete 
 than in the open air. 
 
 Lime, therefore, is laid on the land in two 
 states. 
 
 \st^ In the mild state — that of carbonate — in 
 marls, in chalk, in shell-sand, &;c. 
 
192 DIFFEEENT QUALITIES OF LIME. 
 
 2d, In the caustic, or quick state, as it comes 
 hot from the kiln, or after it is simply slaked. 
 
 Limes are laid on also in a more or less pure form. 
 Marl contains only from 5 to 20 per cent, of car- 
 bonate of lime, generally in the state of a very fine 
 powder. Shell-sand consists of a mixture of mi- 
 nute fragments of shells with from 20 to 50 per 
 cent, of siliceous sand. The limestones which are 
 burned are also more or less impure, though, 
 when the impurity is very great, they do not burn 
 well, and are therefore usually rejected. 
 
 Some limestones contain much magnesia, by 
 which their agricultural qualities are materially 
 affected. These are known by the name of mag- 
 nesian limestones. There are few limestones in 
 which a small quantity of magnesia may not be 
 detected, and this minute proportion is likely to 
 be beneficial rather than otherwise ; but when it 
 is present to the amount of 10 per cent, or up 
 wards, it appears to have for some time a poison- 
 ous influence upon vegetation, if added in the 
 same large doses in which other lime may be 
 safely spread upon the land. 
 
 The quantity of lime laid on at a single dress] 
 ing, and the frequency with which it may be re- 
 peated, must depend upon the kind of land, upon 
 the depth of the soil, and upon the species of culture 
 
DOSES IN WHICH LIME MAY BE APPLIED. 193 
 
 to which it is subjected. If land be wet, or badly 
 drained, a larger application is necessary to pro- 
 duce the same effect, and it must be more fre- 
 quently repeated. When the soil is thin, again, 
 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 two or 
 three inches of soil only, a feebler dressing, more 
 frequently repeated, appears to be the more rea- 
 sonable practice, though in reclaiming and laying 
 down lands to grass, a heavy first liming is often 
 indispensable. .,^^1^ 
 
 In arable culture larger doses are admissible, 
 both because the soil through which the roots pe- 
 netrate 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 vegetable 
 matter abounds, much lime may be usefully add- 
 ed, and on stiff clay lands after draining, its good 
 effect is most remarkable. On light land, chiefly 
 because there is neither moisture nor vegetable 
 matter present in equal quantity, very large ap- 
 plications of lime are not so usual, and some pre- 
 fer adding it to such lands in the shape of com- 
 
 osts only. 
 
 17 
 
194 VISIBLE EFFECTS OF LIME. 
 
 The largest doses, however, which are applied 
 in practice, alter in a very immaterial degree the 
 chemical constitution of the soil. We have seen 
 that the best soils generally contain a natural pro- 
 portion 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 requires 
 about 300 bushels 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. 
 
 The most remarkable visible alterations pro- 
 duced by liming are — n^on pastures, the greater 
 jfineness, closeness, and nutritive character of the 
 grasses — on arable lands, the improvement in the 
 texture and mellowness of stiff clays, the more 
 productive crops and the earlier period at which 
 they ripen. 
 
 But these effects gradually diminish year by 
 year, till the land returns again nearly to its ori- 
 ginal condition. On analyzing the soil, the lime 
 originally added is found to be in great mea- 
 sure, or altogether, gone. In this condition the 
 land must either be limed again, or must be left 
 to produce sickly and un-remunerating crops. 
 
 This removal arises from two causes. The rain 
 
HOW THE LIME IS GHADUALLY REMOVED. 195 
 
 water that descends upon the land holds in solu- 
 tion 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 slowly remove as they 
 sink to the drains, or run over the surface, a por- 
 tion of the lime which the soil contains. Acid 
 substances are also formed naturally in the land, 
 by which another portion of the lime is rendered 
 easily soluble in water, and, therefore, readil)^ re- 
 movable by every shower that falls. 
 
 The chemical effects of lime upon the soil are 
 chiefly the following ; — 
 
 1. When laid upon the land in the caustic state, 
 the first action of the lime is to combine imme- 
 diately with every portion of acid matter it may 
 contain, and thus to sweeten the soil. Some of 
 the compounds it thus forms being soluble in 
 water, either enter into the roots and feed the 
 plant, — supplying it at once with lime and with 
 organic matter, — -or are washed out by the springs 
 and rains, while other compounds, which are in- 
 soluble, remain more permanently in the soil. 
 
 2. Another portion decomposes certain saline 
 compounds of iron, manganese, and alumina, 
 which naturally form themselves in the soil, and 
 thus renders them unhurtful to vegetation. A 
 
196 CHEMICAL EFFECTS OF CAUSTIC LIME. 
 
 similar action is exerted upon certain compounds 
 of potash and soda, and of ammonia, — if any such 
 are present, — by which these substances are set 
 and placed within the reach of the plant. 
 
 3. Its presence in the caustic state further dis- 
 poses the organic matter of the soil to undergo 
 more rapid decomposition — it being observed, that 
 where lime is present in readiness to combine 
 with the substances produced during the decay of 
 organic matter, that decay, if other circumstances 
 be favourable, will proceed with much greater ra- 
 pidity. The reader will not fail to recollect, that 
 during this decay many compounds are formed 
 which are of importance in promoting vegetation, 
 
 4. Further, quicklime has the advantage of 
 being soluble in cold water, and thus the com? 
 plete diffusion of it through the soil is aided by 
 the power of water to carry it in solution in every 
 direction. 
 
 5. When it has absorbed carbonic acid, and be- 
 come reconverted into carbonate, the original 
 caustic lime has no cliemical virtue over chalk, 
 rich shell-sand or marl, or crushed limestone. It 
 has, however, the important mechanical advantage 
 of being in the form of a far finer powder, than any 
 to which we could reduce the limestone by art — 
 in consequence of which it can be more uniformly 
 
CHEMICAL EFFECTS OF THE CARBONATE. 197 
 
 ^iiffused 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 pur- 
 poses which, in this state of carbonate, lime serves 
 upon the land. 
 
 1. It directly affords food to the plant, which, 
 as we have seen, languishes where lime is not at- 
 tainable. It serves also to convey other food to 
 the roots in a state in which it can be made avail- 
 able to vegetable growth. 
 
 2. It neutralizes (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 lands — and this effect it produces in com- 
 mon with wood-ashes, and many similar sub- 
 stances. 
 
 3. During the decay of organic matter in the 
 soil, it aids and promotes the production of nitric 
 acid, — so influential, as I believe, in the general 
 vegetation of the globe (see page 35). With this 
 acid it combines and forms nitrate of lime — a sub- 
 stance very soluble in water — entering readily, 
 therefore, into the roots of plants, and producing 
 
 upon their growth effects precisely similar to those 
 17* 
 
X98 IMPROVEMENT BY IRRIGATION. 
 
 of the now well known nitrate of soda. The sue. 
 cess of frequent ploughings, harrowings, hoeings, 
 and other modes of stirring the land, is partly 
 owing to the facilities which these operations af- 
 ford to the production of this and other natural 
 pitrates. 
 
 SECTION VII. OF THE IRRIGATION OF THE LAND. 
 
 The irrigation of the land is, in general, only a 
 rnore refined method of manuring it. The nature 
 of the process itself, however, is different in differ- 
 ent countries, as are also the kind and degree of 
 effect it produces, and the theory by which these 
 effects are to be explained. 
 
 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 opera- 
 tion. In such cases, as in the irrigations practised 
 so extensively in eastern countries, and without 
 which, whole provinces in Africa and Southern 
 America would lie waste, it is unnecessary to sup- 
 pose any other virtue in irrigation than the mere 
 supply of water it affords to the parched and 
 cracking sti!. 
 
 But in climates such as our own, there are two 
 other beneficial purposes in reference to the soil, 
 
now IRRIGATION ACT3. 199 
 
 which irrigation may, and one at least of which it 
 always does, serve. 
 
 2. The occasional flow of pure water over the 
 surface, as in our irrigated meadows, and its de- 
 scent into the drains, where the drainage is perfect, 
 washes out acid and other noxious substances na- 
 turally generated in the soil, and thus purifies and 
 sweetens it. The beneficial effect of such washing 
 will be readily understood in the case of peat 
 lands laid down to water meadow, since, as every 
 one knows, peat soils abound in matters unfavour- 
 able to general vegetation, and which are usually 
 in part drawn off by drainage, and in part destroyed 
 by lime and by exposure to the air, before boggy 
 lands can be brought into profitable cultivation. 
 
 2. But it seldom happens that 'pure water is 
 employed for the purposes of irrigation. The 
 water of rivers, more generally, is diverted from 
 its course, more or less loaded with mud and 
 other finer particles of matter, which are either 
 gradually filtered from it as it passes 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 
 waters from common sewers, or from the little 
 streams enriched by them, are turned with benefit 
 upon the favoured fields. These are evidently cases 
 
^00 IT MANURES THE LAND. 
 
 of gradual and uniform manuring. And even 
 where the water employed is clear and apparently 
 undisturhed l>y mud, it alwayH contains saline 
 suhstanccs grateful to the plant in its search for 
 food, and which it always contrives to extract 
 more or less copiously as the water passes over its 
 lf;aves or along its roots. Mvery fresh access of 
 water affords the grass in reality another liquid 
 manuring. 
 
 In the refreshment continually afforded to the 
 plant by a plentiful siip[)ly of water, in the removal 
 of noxious substances from the soil, or in the fro- 
 <juent additions of enriching food to the land — the 
 eflici<;ncy of irrigation, therefore, seems entirely 
 to consist. 
 
 BECTION vni. — OK I'ARINO AND BURNINO, AND OF 
 7JUKNKU CLAY. 
 
 A mode of improvement often resorted to is the 
 paring and burning of poor land. The eflicacy of 
 !>iirned clay, also, even in superseding manure on 
 good lands, has been highly extolled by some prac- 
 tical men. 
 
 1. The effect of paring and burning is easily 
 understood. The matted sods consist of a mixture 
 of much vegetable with a comparatively small 
 
OF PAKINC; AND JJUKNING. 201 
 
 quantity of earthy matter. When these are burned 
 the ash of the plants only is left, intimately mixed 
 with the caleined earth. To strew this mixture 
 over the soil is much the same as to dress it with 
 peat or wood ashes, the beneficial effect of which 
 upon vegetation is 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 ellect which 
 the potash and soda it contains exercise either in 
 pr(!paring organic food in the soil, or in assisting 
 its diiiostion and assimilation in the interior of the 
 plant. 
 
 Another part of this process is, that the roots 
 of the weeds and |)oorer grasses are materially 
 injured hy the paring, and tliat the subsequent 
 dressing of ashes is unfavourahle to their further 
 growth. 
 
 2. Much greater uncertainty hangs over the al- 
 leged virtues of burned clay. That benefits are 
 supposed to have been derived from its use there 
 can be no doubt, though in many cases the better 
 tillage of the land generally prescribed along with 
 the use of burned clay, may have had some share 
 in producing the good results actually experienced 
 during its use. 
 
 By the burning, in kilns or otherwise, any or- 
 
202 EFFECT OF BURNING UPON CLAY. 
 
 ganic matter the clay may contain will be con- 
 sumed, and the texture of the clay itself will be 
 mechanically altered. It will crumble down like 
 a burned brick into a hard friable powder, and 
 will never again cohere into a paste as before the 
 burning. It will, therefore, render clay soils more 
 open, and may thus, when mixed in large quan- 
 tity, produce a permanent amelioration in the 
 mechanical texture of many stiff wheat soils. It 
 cannot itself undergo any chemical change that is 
 likely so to alter its constitution as to make it a 
 more useful chemical constituent of the soil than 
 before. Any saline matter we may suppose to be 
 set free could be far more cheaply added in the 
 form of a top-dressing to the soil. 
 
 Bricks, however, are generally more porous 
 than the clay from which they are formed ; burned 
 clay is so also. And all porous substances suck 
 in and condense much air and many vapours in 
 large quantities into their pores. In consequence 
 of this property, porous substances, like charcoal 
 and burned clay, are supposed, when mixed with 
 the soil, to be continually yielding air to decaying 
 vegetable matter on the one hand, and as continu- 
 ally re-absorbing it from the atmosphere on the 
 other, and by this means to be of singular service in 
 supplying the wants of plants in the earlier seasons 
 
HOW BURNED CLAY ACTS. 203 
 
 of their growth. The vapours of nitric acid and 
 of ammonia, which float in the air, they are also 
 supposed to imbibe, and by the beneficial action of 
 the substances believed to be thus conveyed by 
 burned clay into the soil, the fertilizing virtues 
 ascribed to it are attempted to be explained. 
 
 It must be confessed, however, that on this point 
 considerable obscurity still rests. It is in some 
 measure doubtful what the true action of charcoal 
 and of burned clay is, both in kind and in quantity. 
 It is the part of science, therefore, to decline offer- 
 ing more than a mere conjecture till the facts to 
 be explained are more fully and satisfactorily de- 
 monstrated. 
 
 SECTION IX. PLANTING AND LAYING DOWN TO GRASS, 
 
 1, Planting, — 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 planta- 
 tions, and of being greatly increased in permanent 
 value by the prolonged growth of wood. Not 
 only, however, do all trees not thrive ahke 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 
 
204 IMPROVEMKNT OF THrO SOIL }{Y PLA1MTIN(;. 
 
 is not worth Gd. more per acre than before it was 
 plant(3tl — under the beech and spruce, it is worth 
 oven less than before, though the spruce affords ex- 
 cellent shelter ; — under ash, it gradually acquires 
 an increased value of 2s. or lis. per acre. In oak 
 copses, it becomes worth 5s. or Gs., but only dur- 
 ing the last eight years (of the twenty-four), be- 
 fore it is cut down. But under the larch, after 
 the first thirty years, when the tliinnings are all 
 cut, land not worth originally more than Is. per 
 acre, becomes worth 8s. to 10s. per acre for per- 
 manent pasture.* 
 
 The cause of this improvement is to be found in 
 the nature of the soil, which gradually accumu- 
 lates beneath the trees by the shedding of their 
 leaves. The shelter from the sun and rain which 
 the foliage affords, prevents the vegetable matter 
 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 exists. The more 
 complete the slielter, therefore, the more rapid 
 will the accumulation of soil be in so far as it de- 
 pends upon this cause. 
 
 But the quantity of leaves which annually falls 
 
 * The result of trials made on the rnica slate and gneiss 
 soils (see page 100) of the Duke of Atholl. 
 
CAUSE OF THIS IMPKOVKMENT. 205 
 
 has also much influence upon the extent to which 
 the soil is capable of being innproved by any given 
 species of tree, as well as the degree of rapidity 
 with which those leaves, under ordinary circum- 
 stances, undergo decay. The broad membranous 
 leaf of the beech and oak decay more quickly than 
 tlie needle-shaped leaves of the pine tribes, and 
 this circumstance may assist in rendering the larch 
 more valuable as a permanent improver. 
 
 We should expect likewise that the quantity and 
 quality of the inorganic matter contained in the 
 leaves, — brought up year by year from the roots, 
 and strewed afterwards uniformly over the sur- 
 face where the leaves are shed, — would materially 
 affect the value of the soil they form. The leaves 
 of the oak contain about 5 per cent, of saline and 
 earthy matter, and those of the Scotch fir less than 
 2 per cent. ; so that, supposing the actual weight 
 of leaves wliich falls from each kind of tree to be 
 ecpial, we should expect a greater depth of soil to 
 be formed in the same time by the oak than by 
 the Scotch fir. I am not aware of any experi- 
 ments on the quantity of ash left by the leaves of 
 the larch. 
 
 The improvement of the land, therefore, by the 
 planting of trees, depends in part upon the quan- 
 tity of organic food which the trees can extract 
 18 
 
206 LAYING DOWN TO GRASS. 
 
 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 quantity and quality of 
 the latter will, in a great measure, determine the 
 kind of grasses which will spring up, and the con- 
 sequent value of the pasture in the feeding of stock. 
 In the larch districts of the Duke of Athol, 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.) 
 
 2. Laying down to grass. — On this point two 
 facts seem to be pretty generally acknowledged : 
 
 Firstf that land laid down to artificial grasses 
 for one, two, three, or more years, is in some de- 
 gree rested or recruited, and is fitted for the better 
 production of after-corn crops. Letting it lie a 
 year or two longer in grass, therefore, is one of the 
 received modes of bringing back to a sound condi- 
 tion a soil that has been exhausted by injudicious 
 cropping. 
 
 Second, that land thus laid down with artificial 
 grasses deteriorates more or less after two or three 
 years, and only by slow degrees acquires a thick 
 sward of rich and nourishing herbage. Hence the 
 opinion, that grass-land improves in quality the 
 
IMPOBTANT GENERAL OBSERVATIONS. 207 
 
 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 lands are known to yield. 
 
 Granting that grass lands do 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 an 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^ how- 
 ever long it may lie. The extensive 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 herbage as to 
 have been considered unworthy of being enclosed 
 as a permanent pasture. 
 
 2. Some grass lands will retain the good con- 
 dition they thus slowly acquire for a very long 
 period, and without manuring^ in the same way, 
 and upon the same principle, that some rich corn 
 lands have yielded successive crops for 100 years 
 
208 SOME REQUIRE MANURING. 
 
 without manure. The rich grass lands of Eng- 
 land, and especially of Ireland, many of which 
 have been in pasture from time immemorial, with- 
 out, it is said, receiving any return for all they 
 have yielded, are illustrations of this fact. 
 
 3. But that others, if grazed, cropped with 
 sheep or meadowed, will gradually deteriorate, 
 unless some proper supply of manure be given to 
 them, — which required supply must vary with the 
 nature of the soil, and with the kind of treat- 
 ment to which it has been subjected. 
 
 In regard to the acknowled<^ed benefit of lay- 
 ing down to grass, then, two points require con- 
 sideration, — what form does it assume ? — and how 
 is it effected ? 
 
 1. The improvement takes place by the gradual 
 accumulation of a dark-brown soil on the surface, 
 rich in vegetable matter : and which soil thickens 
 or deepens in proportion to the time which elapses 
 from its being first laid down to grass. 
 
 If the soil be very light and sandy, the thicken- 
 ing is sooner arrested ; if it be moderately heavy 
 land, the improvement continues for a longer pe- 
 riod ; and some of the heaviest clays in England 
 are known to bear the richest permanent pastures. 
 On analyzing the soils of the richest of these pas- 
 tures, whatever be the degree of tenacity of the 
 
UNIFORMITY OF OLD PASTURE SOILS. 209 
 
 clays or loams (the subsoils) on which they rest, 
 or their deficiency in vegetable matter, — they are 
 found to be generally characterized by containing 
 from 8 to 12 per cent, of organic, chiefly vegeta- 
 ble matter, from 5 to 10 only of alumina, and from 
 1 to 6 per cent, of lime. 
 
 Thus the soil formed on the surface of all rich 
 old pasture lands is possessed of a remarkable de- 
 gree of uniformity, — both in physical character 
 and in chemical composition. This uniformity 
 they gradually acquire, even upon the stiff clays of 
 the Lias and of the Oxford clay, which originally, 
 no doubt, have been, — as many clay lands still are, 
 — left to natural pasture from the difficulty and 
 expense of submitting them to arable culture. 
 
 2. But how do they acquire this new character, 
 and why is it the work of so much time ? 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 mat- 
 ter. It is not known what average proportion 
 the roots of the natural grasses bear to the leaves ; 
 
 no doubt it varies much, both with the kind of 
 
 18* 
 
210 now THE SOIL ON GRASS LANDS 
 
 grass and with the kind of soil. When wheat is 
 cut down, the quantity of straw left in the field, 
 in the form of stuhble and roots, is sometimes 
 greater than the quantity carried off in the sheaf. 
 Upon a grass field two or three tons of hay may 
 be r(!apo(l from an acre ; and if we suppose only 
 a tenth part of lliis quantity to die every year in 
 the form of roots or parts of roots, or of excre- 
 tions from roots, we can easily understand how 
 the vegetable matter in the soil thus gradually 
 accumulating, should at length become very con- 
 siderable in quantity. In ara])le land this accu- 
 mulation is prevented by the constant turning up 
 of the soil, by whi(;h tiie vegetable fd)res being 
 exposed to the free access of air and moisture, are 
 made to undergo a more rapid decomposition. 
 
 Hut the roots and leaves of the grasses contain 
 inorganic earthy and saline matter also. Dry 
 hay leaves from an eighth to a tenth part of ita 
 weight of ash when burned. Along wilii the 
 dead vegetable matter of the soil, this inorganic 
 matter accumulates also on tlie surface, in the 
 form of an exceedingly line eartliy powder ; hence 
 one cause of the universal fineness of the surfacei 
 mould of old grass fields. And the earthy por-, 
 tion of this inorganic matter consists chielly of 
 silica and lime, with scarcely a trace of alumina, 
 
BECOMES GRADUALLY CIIANOED. 211 
 
 eo that, even on the stiffcst clays, a surface soil 
 may be ultimately formed, in which the quantity 
 of alumina will be comparatively small. 
 
 But there are still other agencies at work by 
 which the surface of stiff soils is made to undergo 
 a change. As the roots 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 observed, 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 soil, by removing 
 a portion of its clay. They constitute one of 
 those natural agencies by which, as elsewhere ex- 
 plained, important differences are ultimately es- 
 tablished, almost everywhere, between the surface 
 crop-bearing soil and the subsoil on which it rests. 
 
 But further, the heats of summer and the frosts 
 of winter aid this slow alteration. In the ex- 
 tremes of heat and of cold, the soil contracts more 
 than the roots of the grasses do ; and similar 
 though less striking differences take place during 
 the changes of temperature experienced in our 
 climate in a single day. When the rain falls on 
 
212 EFFECT OF THE WINTEr's FEOST. 
 
 the parched field, or when a thaw comes on, 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 has witnessed in winter how, on a 
 field or a by-way side, the earth rises above the 
 stones, and appears inclined to cover them ; he 
 may even have seen in a deserted and undisturbed 
 highway, the stones gradually sinking and disap- 
 pearing altogether, when the repetition of this 
 alternate contraction and expansion of the soil for 
 a succession of winters has increased in a great 
 degree the effects which follow from a single ac- 
 cession 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 because this loosening 
 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. 
 
 Such movements as these act in opening up 
 the surface-soil, in mixing it with the decaying ve- 
 getable matter, and in allowing the slow action of 
 
EFFECT OF INSECTS. 213 
 
 the rains gradually to give its earthy portion a 
 lighter character. But with these, among other 
 causes, conspire also the action of living animals. 
 Few persons have followed the plough without 
 occasionally observing 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 burden of fine fertilizing 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 labours of these insect 
 tribes must both materially improve its quality 
 and increase its depth ? 
 
 There are natural causes, then, which we know 
 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 lands 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 
 
214 GRASS ON LIGHT AND HEAVY SOILS. 
 
 the aid of manure. Let them, however, be defi- 
 cient, or let them gradually become exhausted of 
 any one kind of this food, and the grass lands will 
 either gradually deteriorate after they have reached 
 a certain degree of excellence — or they must be sup- 
 plied with that ingredient — that manure of which 
 they stand in need. It is doubtful if any pasture- 
 lands are so naturally rich as to bear to be crop^ 
 ped for centuries without the addition of manure, 
 and at the same time without deterioration.* 
 
 On soils that are light, again, which naturally 
 contain little clay, the grasses will thrive more 
 rapidly, a thick sward will be sooner formed, but 
 the tendency of the rains to wash out the clay 
 may prevent them from ever attaining that luxu- 
 riance which is observed upon the old pastures of 
 the clay -lands. 
 
 On undrained heaths and commons, and gene- 
 rally on any soil which is deficient in some fer- 
 tilizing 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. 
 
 • See pages 240 and 241. 
 
PLOUGHIHG UP OLD PASTURES. 215 
 
 Finally, plough up the old pastures, on the sur- 
 face of which this light and most favourable soil has 
 been long accumulating — and the heavy soil from 
 beneath will be again mixed up with it — the vege- 
 table matter will disappear rapidly by exposure to 
 the air, — 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 of again 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 sward may at once be 
 obtained — and on light loamy lands, rich in vege- 
 table matter, this method may, to a certain extent, 
 succeed — but on heavy lands, in which vegetable 
 matter is defective, disappointment will often fol- 
 low the sowing of the most carefully selected 
 seeds. By the agency of the causes above ad- 
 verted 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 natur- 
 ally and luxuriantly grow upon it. 
 
CHAPTER X. 
 
 The Products of Vegetation — Importance of Chemical qual- 
 ity as well as quantity of Produce — Influence of diflferent 
 Manures on the quantity and quality of the Crop — Influ- 
 ence of the time of Cutting — Absolute quantity of Food 
 yielded by different Crops — Principles on which the Feed- 
 ing of Animals depends — Theoretical and experimental 
 value of different kinds of Food for Feeding Stock — Con- 
 cluding Observations. 
 
 The first object of the practical farmer is, to 
 reap from his land the largest possible return of 
 the most valuable crops, without permanently ex-- 
 hausting the soil. With this view he adopts one 
 or other of the methods of treatment above ad- 
 verted to, by which either the physical condition 
 or the chemical constitution of the soil is altered 
 for the better. It may be useful to shew how 
 very much both the quantity and the quahty of a 
 crop is dependent upon the mode in which it is 
 
INFLUENCE OF DIFFERENT MANURES. 217 
 
 cultivated and reaped, and how much control, 
 therefore, the skilful agriculturist really possesses 
 over the ordinary productions 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 
 otherwise, for the reception of the seed. The fol- 
 lowing table shews the effect produced upon the 
 quantity of the crop hy equal quantities oi different 
 manures applied to the same soil, sown with an 
 equal quantity of the same seed. 
 
 Manure applied. 
 
 Blood, 
 Night soil, 
 Sheep's dung, 
 Horse dung, 
 Pigeon's dung, . 
 Cow dung, 
 Vegetable matter, 
 Without manure, 
 19* 
 
 Return in bushels from each } 
 bushel of seed. 
 Wheat. Barley. Oats. Rye. 
 
 14 
 
 16 
 
 12i 
 
 14 
 
 — 
 
 13 
 
 141 
 
 13i 
 
 12 
 
 16 
 
 14 
 
 13 
 
 10 
 
 13 
 
 14 
 
 11 
 
 — 
 
 10 
 
 12 
 
 9 
 
 7 
 
 11 
 
 16 
 
 9 
 
 3 
 
 7 
 
 13 
 
 6 
 
 — 
 
 4 
 
 5 
 
 4 
 
218 OW THE aUANTlTY OF THE CROP. 
 
 It is probable that on different soils the returns 
 obtained by the use of these several manures may 
 not be always in the same order, yet, generally 
 speaking, it will always be found that blood, night- 
 soil, and sheep, horse, and pigeon's dung, are 
 among the most enriching manures that can bo 
 employed. 
 
 We have already seen a theoretical reason for 
 believing that night-soil should be among the 
 most enriching manures, and the result of actual 
 trial here shews that it is one of the most practi- 
 cally valuable which the farmer can employ. 
 
 Two other facts will strike the practical man on 
 looking at the above table. 
 
 1. That exclusive of blood, sheep's dung gave 
 the greatest increase in the barley crop. The fa- 
 vourite Norfolk system of eating off turnips with 
 sheep previous to barley, besides other benefits 
 which are known to attend the practice, may owe 
 part of its acknowledged utility to this powerful 
 action of sheep's dung upon the barley crop. 
 
 2. The action of cow-dung upon oats is equally 
 striking, and the large return obtained by the 
 use of vegetable manure alone ■ — thirteen fold- 
 may perhaps explain why in poorly farmed dis- 
 tricts oats should be a favourite and comparatively 
 profitable crop, and why they may be cultivated 
 
INFLUENCE OF THE KIND OF MANURE. 219 
 
 with a certain degree of success on lands to which 
 no rich manure is ever added. 
 
 SECTION II. — INFLUENCE OF THE KIND OF MANURE ON THE 
 CHEMICAL QUALITY OF THE GRAIN. 
 
 But the quaUty of the grain also, as well as its 
 quantity, is materially affected by the kind of ma- 
 nure by which its growth is assisted. The appa- 
 rent quality of wheat and oats is very various ; 
 but in samples apparently equal in quality, im- 
 portant chemical differences may exist, by which 
 it is believed that the nourishing properties of the 
 grain are materially affected. 
 
 It has been stated in a previous chapter (p. 43), 
 that when flour is made into dough, and this 
 dough is washed upon a linen cloth with water as 
 long as the latter passes through milky, — the flour 
 is separated into starch, which subsides from the 
 water, and gluten, which remains behind. The 
 quantity of gluten thus left varies more or less 
 with almost every sample of flour, and the nutri- 
 tive properties of each sample are supposed to de- 
 pend very much upon the quantity of gluten it 
 contains. So far it seems to be pretty well as- 
 certained, that those varieties of grain which 
 contain the largest amount of gluten yield also 
 
220 ON THE QUALITY OF WHEAT, 
 
 the greatest return of flour, and the heaviest weight 
 of bread. 
 
 The weight of gUiten contained in 100 lbs. of 
 dry wheat has been found to vary from 8 to 34 lbs., 
 and this proportion is affected in a very remark- 
 able manner by the kind of manure which has 
 been applied to the land. Thus the proportions 
 of starch and gluten in 100 lbs. of the grain of the 
 same wheat, grown on the same land, differently 
 manured, was as follows : — 
 
 Manure. 
 
 Starch. 
 
 Gluten. 
 
 Blood, 
 
 41 lbs. 
 
 34 lbs. 
 
 Sheep's dung, . 
 
 42 — 
 
 33 — 
 
 Horse dung, 
 
 62 — 
 
 14 — 
 
 Cow dung, 
 
 62 — 
 
 12 — 
 
 Vegetable manure, . 
 
 66 — 
 
 10 — 
 
 Potato-flour, which consists entirely of starch, 
 makes a fine light bread, easily raised. Wheaten- 
 flour, which contains little gluten, approaches in 
 this respect to potato-flour. When the quantity 
 of gluten is large, greater care is required to 
 make a good light bread ; but the bread from such 
 flour is generally found to be more nutritive in its 
 quality. A dough peculiarly rich in gluten is re- 
 quired for the manufacture of macaroni and ver- 
 micelli ; such is said to be the flour naturally pro- 
 duced in southern Italy. By the above table it 
 
AND OF BARLEY AND OATS. 
 
 221 
 
 appears, that the use of richer animal, or poorer 
 vegetable manures, would enable the farmer to 
 raise, at his pleasure, either a rich macaroni wheat, 
 or one poor in gluten suited for the makers of 
 fancy bread. 
 
 An equally striking effect is not produced upon 
 other kinds of grain by varying the manure. Thus 
 the proportions of starch and gluten in the dry 
 grain of barley and oats, differently manured, were 
 found to be as follows : — 
 
 
 BARLEY. 
 
 Oi 
 
 TS. 
 
 
 starch. 
 
 Gluten. 
 
 Starch. 
 
 Gluten. 
 
 Blood, 
 
 66i 
 
 . 6i 
 
 60 
 
 5i 
 
 Night-soil, 
 
 66 
 
 . 6h 
 
 60 
 
 5 
 
 Sheep dung, 
 
 66i 
 
 . 6i 
 
 61 
 
 4i 
 
 Horse dung, . 
 
 66 
 
 . 6h 
 
 6li 
 
 4i 
 
 Cow dung, 
 
 69 
 
 . 3i 
 
 62 
 
 3i 
 
 Vegetable manure, 
 
 69 
 
 . 3 
 
 66i 
 
 . 2i 
 
 Unmanured, . 
 
 69^ 
 
 . 3 
 
 66h 
 
 . 2i 
 
 Though a variation in the proportion of gluten 
 can be observed in both of these kinds of grain, 
 according as one or other of the above kinds of 
 manure was employed, yet neither the average 
 quantity of gluten present in them, nor the varia- 
 tions to which the quantity is liable, are at all 
 equal in amount to what are observed in the case 
 of wheat. 
 
 The malting of barley is known to be affected 
 19* 
 
222 THE MALTING OF BARLEY. 
 
 by a variety of circumstances. It should be so 
 uniform in ripeness as to sprout uniformly, so that 
 no part of it should be beginning to shoot when 
 the rest has already germinated sufficiently for 
 the maker's purpose. On this perfect sprouting 
 of the whole depends in some degree the swell- 
 ing of the malt, which is of considerable conse- 
 quence to the manufacturer. 
 
 But the melting quality of the grain, which is of 
 more consequence to the brewer and distiller, is 
 modified chiefly by the proportion of gluten which 
 the barley contains. That which contains the least 
 gluten, and therefore the most starch, will melt 
 the most easily and the most completely, and will 
 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-board of the county 
 of Durham will not purchase the barley of their 
 own neighbourhood, while Norfolk grain can be 
 had at a moderate increase of price. But that 
 which refuses to melt 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 brewer and 
 distiller reject. 
 
COW-DUNG RAISES MUCH BARLEY. 223 
 
 So far as a practical deduction can be drawn 
 from the effects of different manures on the pro- 
 portion of gluten in barley, it would appear that 
 the larger the quantity of cow-dung contained in 
 the manure applied to barley land — in other 
 words, the greater the numbers of stock folded 
 about the farm-yard^ the more likely is the barley to 
 be such as will bring a high price from the brewer* 
 
 The folding of sheep produces a larger return 
 (p. 206), from the barley crop — while the folding 
 of cattle gives grain of a better malting quality. 
 
 SECTION III. INFLUENCE OF THE TIME OF CUTTING, ON THE 
 
 QUANTITY AND QUALITY OF THE PRODUCE. 
 
 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 tur- 
 nippy 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, which, as they grow up, is 
 
224 INFLUENCE OF THE TIME OF CUTTING. 
 
 gradually changed, first into starch, and then into 
 woody fibre (pages 44 and 45.) The more com- 
 pletely the latter change is effected — that is, the 
 riper the plant becomes — the less sugar and starch, 
 both readily soluble substances, they contain. 
 And though it has been ascertained that woody 
 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 hay or 
 straw reaped, is actually less when allowed to be- 
 come fully ripe ; and therefore, by cutting soon 
 after the plant has attained its greatest height, a 
 larger quantity, as well as a better quality of hay, 
 will be obtained, while the land also will be less 
 exhausted. 
 
 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 nour- 
 ishing 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. 
 
ON THE QUANTITY AND QUALITY. 225 
 
 On the other hand, the ear which is sweet and 
 milky a month before it is ripe, gradually con- 
 solidates, the sugar changing into starch, and the 
 milk thickening into the gluten and the albumen* of 
 the flour. As soon as this change is nearly com- 
 pleted, or about a fortnight before ripening, the 
 grain contains the largest proportion of starch and 
 gluten ; if reaped at this time, the bushel will be 
 heavier, 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 ripen- 
 ing 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 ; hence 
 the diminished yield of flour, and the increased 
 produce of bran. 
 
 Theory and experience, therefore, indicate about 
 
 * Albumen is the name given by chemists to the white of 
 the egg. A small quantity of this substance is present in 
 every kind of grain. It is closely related to gluten. 
 
226 PROPER TIME OF CUTTING. 
 
 a fortnight before full ripening as the most proper 
 time for cutting corn. The skin is then thinner, 
 the grain fuller, the bushel heavier, the yield of 
 flour greater, 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 un- 
 til it is considered to be fully ripe.* 
 
 SECTION IV. — ON THE ABSOLUTE QUANTITY OF FOOD YIELDED 
 BY DIFFERENT CROPS. 
 
 The quantity of food capable of yielding nour- 
 ishment to man, which can be grown from an acre 
 of land of average quality, depends very much 
 upon the kind of crop we raise. 
 
 In seeds, 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 nutri- 
 tive 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 
 
 * On this subject the reader will consult with advantage 
 an excellent practical paper in the Quarterhj Journal of Agri- 
 culture for June 1841, by Mr. Hannam of North Deighton, 
 Yorkshire, to whom I have to express my obligations for in- 
 formation regarding the results of some further experiments 
 made by him during the last autumn (1841). 
 
AVERAGE PRODUCE OP DIFFERENT CROPS. 227 
 
 in which these roots are consumed, and this is es- 
 pecially the case with the turnip. These substan- 
 ces, therefore, must be included among the nutri- 
 tive ingredients of such kinds of food. 
 
 If we suppose an acre of land to yield the fol- 
 lowing quantities of the usually cultivated cropsy 
 namely — 
 
 Of wheat, 
 
 25 bushels, 
 
 or 15001b 
 
 Of barley, 
 
 38 " 
 
 or 2000 " 
 
 Of oats, . 
 
 50 " 
 
 or 2250 " 
 
 Of peas, 
 
 15 " 
 
 or 1000 " 
 
 Of beans. 
 
 25 " 
 
 or 1600 " 
 
 Of Indian corn, 
 
 60 " 
 
 or 3120 " 
 
 Of potatoes. 
 
 10 tons, 
 
 or 22400 " 
 
 Of turnips. 
 
 25 " 
 
 or 56000 " 
 
 The weight of dry starch, gluten, sugar, and gum, 
 reaped in each crop, will be represented very 
 nearly by the following numbers : — 
 
 
 Starch. 
 
 Wheat, . 
 
 . 825 lbs. 
 
 Barley, . 
 
 . 1200 " 
 
 Oats, 
 
 . 1215 " 
 
 f eas, 
 
 . 420 " 
 
 Beans, 
 
 . 670 '' 
 
 Indian com, 
 
 . 2100 " 
 
 Potatoes, . 
 
 . 2688 " 
 
 Turnips, . 
 
 3090 
 
 Gluten and 
 Albumen. 
 
 Sugar and 
 Gum. 
 
 Woody 
 Fibre. 
 
 315 lbs. 
 
 60 
 
 — 
 
 120 " 
 
 160 
 
 — 
 
 o 
 o 
 
 1— ( 
 
 250 
 
 — 
 
 260 " 
 
 20 
 
 . — 
 
 370 '' 
 
 — 
 
 — 
 
 280 « 
 
 90 
 
 — 
 
 224 " 
 
 — 
 
 1253 
 
 1400 
 
 5000 — 
 
228 RELATIVE PKOPORTIONS OF STARCH, 
 
 «f it be granted that the crops above stated are 
 fair average returns from the same quality of 
 land — that the acre, for example, which produces 
 25 bushels of wheat, will also produce 10 tons of 
 potatoes, and so on — then it appears that the land 
 which, by cropping with wheat, would yield a given 
 weight of starch, would, when cropped with barley 
 or oats, yield one-half more, with Indian corn or 
 potatoes about three times as much, and with 
 turnips five 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 half if sown with barley or oats, three with 
 Indian corn or potatoes, and five with turnips — 
 in so far as the nutritive power of these crops de- 
 pends upon the starch and sugar they contain. 
 
 Again, if we compare the relative quantities of 
 gluten, we see that wheat, beans, and Indian corn 
 yield, from the same breadth of land, nearly an 
 equal quantity of this kind of nourishment — pota- 
 toes one-third less, and barley and oats only one- 
 third of the quantity — while turnips yield four 
 times as much as either wheat, beans, or Indian 
 CO n. 
 
 On whichever of these two substances, therefore, 
 the starch or the gluten, we consider the nutritive 
 property of the above kind of food to depend, it 
 
GLUTEN, SUGAR, AND GU3I. 229 
 
 appears that the turnip is by far the most nutri- 
 tive crop we can raise. It is by no means the most 
 nutritive weight for weight, but the largeness of 
 the crop (25 tons) aflbrds us from the same field a 
 much greater weight of food than can be reaped 
 in the form of any of the other crops here men- 
 tioned. 
 
 In this the practical farmer will sec the peculiar 
 adaptation of the turnip husbandry to the rearing 
 and fattening of stock. Could the turnip be made 
 an agreeable article of general human consump- 
 tion, the produce of the land might be made to 
 sustain a much larger population than under any 
 other of the above kinds of cropping. 
 
 The relative nourishing power or value as food 
 of different vegetable substances, is supposed by 
 some to depend entirely upon the relative propor- 
 tions of gluten they contain. According to this 
 view, the pea and the bean are much more nourish- 
 ing, weight for weight, even than wheat, and this 
 latter grain, than any of the other substances 
 mentioned in the above table. Thus, 56 Ibsr of 
 beans would afford as much sustenance to an ani- 
 mal as 07 of pease, 100 of wheat-flour, or 117 of 
 
 rice. 
 
 In order to understand the value of this opi- 
 
 20 
 
230 RELATIVE NUTRITIVE PROPERTIES. 
 
 nion, it will be proper to consider the several pur- 
 poses which the food is destined to serve in the 
 animal economy — what the animal must derive 
 from its food to maintain its existing condition, 
 or to admit of a healthy increase of bulk. 
 
 SECTION V. OP THE FEEDING OF ANIMALS, AND THE PUR- 
 POSES SERVED BY THE FOOD THEY CONSUME. 
 
 The food of plants we have seen to consist es- 
 sentially of two kinds, the organic and the inor- 
 ganiCf both of which we have insisted upon as 
 equally necessary to the living vegetable — equally 
 indispensable to its healthy growth. A brief 
 glance at the purposes served by plants in the 
 feeding of animals, will not only confirm this view, 
 but will also throw some additional light upon 
 the kind of inorganic food which the plants must 
 be able to procure, in order that they may be 
 fitted to fulfil their assigned purpose in the eco- 
 nomy of nature. 
 
 Man, and all domestic animals, may be sup- 
 ported, 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 attendant upon the performance of the ne- 
 
THE FOOD MUST SUPPLY CARBON. 231 
 
 cessary functions of animal life. Let us consider 
 what these substances are, and in what quantities 
 they must be supplied to the human body. 
 
 1. The food must supply carbon for respiration* 
 
 A man of sedentary habits, or whose occupa- 
 tion requires little bodily exertion, may respire 
 about 5 ounces of carbon in twenty-four hours 
 — one who takes moderate exercise, about 8 ounces 
 — and one who has to undergo violent bodily exer- 
 tion, from 12 to 15 ounces. 
 
 If we take the mean quantity of 8 ounces, then 
 to supply this alone, a man must eat 18 ounces of 
 starch or sugar every day. If he take it in the form 
 of wheaten bread, he will require If lbs, of bread, 
 if in the form of potatoes, about 7i lbs. of raw po- 
 tatoes, to supply the waste caused by his respira- 
 tory organs alone. 
 
 When the habits are sedentary, 5 lbs. of pota- 
 toes may be sufficient, when violent and continued 
 exercise is taken, 12 to 15 lbs. may be too little. 
 At the same time, it must be observed, that where 
 the supply is less, the quantity of carbonic acid 
 given off will either be less also, or the deficiency 
 will be supplied at the expense of the body itself. 
 In either case the strength will be impaired, and 
 fresh food will be required to recruit the exhaust- 
 ed frame. 
 
232 THE FOOD MUST REPAIR THE DAILY WASTE. 
 
 2. The food must repair the daily waste of the 
 muscular parts of the body. 
 
 When the body is full grown, a portion from 
 every part of it is daily abstracted by natural pro- 
 cesses , and rejected either in the perspiration or 
 in the solid and fluid excrements. This portion 
 must be supplied by the food, or the strength will 
 diminish — the frame will gradually waste away. 
 
 The muscles of animals, of which lean beef and 
 mutton are examples, are generally coloured by 
 blood, but when well washed with water, they be- 
 come 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 chemists. The clot of the blood consists 
 of the same substance ; while skin, hair, horn, and 
 the organic part of the bones, are composed of va- 
 rieties oi gelatine. This latter substance is fami- 
 liarly known in the form of glue^ and though it 
 differs in its sensible properties, it is remarkably 
 analogous to fibrin in its elementary constitution, 
 as both of these substances are to the white of the 
 Qgg {albumen), to the curd of milk (casein), and 
 to the gluten of flour. They all contain nitrogen, 
 and all consist of the four elementary bodies (or- 
 ganic elements), very nearly in the following pro- 
 portions : — 
 
OF NITROGEN IN THE EXCRETIONS. 233 
 
 Carbon, . . . .55 
 
 Hydrogen, . • . .7 
 
 Nitrogen, . . . .18 
 
 Oxygen, . . . .20 
 
 100 
 
 They all contain, likewise, a small proportion 
 of sulphur and of phosphorous. 
 
 The quantity of one or other of these removed 
 from the body in 24 hours, either in the perspira- 
 tion or in the excretions, amounts to ahout jive 
 ounces, containing 350 grains of nitrogen, and this 
 waste at least must be made up by the gluten or 
 fibrin of the food. 
 
 In the If lb. of wheaten bread we have sup- 
 posed to be eaten to supply carbon for respira- 
 tion, there will be contained also about 3 ounces 
 of gluten. Let the other 2 ounces be made up in 
 beef, of which half a pound contains 2 ounces of 
 dry fibrin, and we have 
 
 r-^^ ^^cr^s—f.-^.. For waste of 
 
 For respiration. muscle, &c. 
 
 If lbs. of bread yielding 18 oz, starch and 3 oz, of gluten. 
 
 8 oz. of beef yielding . , 2 oz. of fibrin. 
 
 Total consumed by res- ) ) gluten or 
 
 piration, and the or- > 18 oz. starch and5oz. ) fibrin, 
 dinary waste, ) 
 
 If, again, the 1\ lbs. of potatoes be eaten, thea 
 20* 
 
234 QUANTITY OF FOOD KEaUIRED 
 
 in these are contained about 2^ ounces of gluten 
 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 mixture of vegetable and 
 animal food. It is not merely that such a mix- 
 ture is more agreeable to the palate, or even that 
 it is absolutely necessary, — for, as already observed, 
 the strength may be fully maintained by vegetable 
 food alone ; — it is, that without animal food in one 
 form or another, so large a bulk of vegetable food 
 must be consumed in order to supply the requi- 
 site quantity of nitrogen in the form of gluten. 
 Of ordinary wheaten bread alone, about 3 lbs. 
 daily must be eaten to supply the nitrogen,* and 
 there would then be a considerable waste of 
 carbon in the form of starch, by which the 
 stomach would be overloaded, and which, not 
 being worked up by respiration, would pass off in 
 the excretions. The wants of the body would be 
 equally supphed, and with more ease, by If lbs. 
 of bread and 4 ounces of cheese. 
 
 Of rice, again, no less than 4 lbs. daily would 
 
 * The flour being supposed to contain 15 per cent, of 
 dry gluten, on which supposition nil the above calcula- 
 tions are made. 
 
TO SUPPLY TUIS CARBON AND NITROGEN. 235 
 
 bo required to impart to the system the required 
 proportion of gluten ; and it is a famihar obser- 
 vation of those who have been in India and other 
 countries, where rice is the usual food of the 
 people, that the degree to which the natives dis- 
 tend, and apparently overload their stomachs with 
 this grain, is quite extraordinary. 
 
 The stomachs and other digestive apparatus of 
 our domestic animals are of larger dimensions, 
 and they are able, therefore, to contain with case 
 as much vegetable food, of almost any wholesome 
 variety, as will supply them with the quantity of 
 nitrogen they may require. Yet every feeder of 
 stock knows that the addition of a small portion 
 of oil-cake, a substance rich in nitrogen, will not 
 only fatten an animal more speedily, but will also 
 save a large hulk of other kinds of food. 
 
 .3. But the blood and other fluids of the body 
 contain much saline matter of various kinds, sul- 
 phates, muriates, phosphates, and other saline 
 compounds of potash, soda, lime, and magnesia. 
 All these have their special functions to perform 
 in the animal economy, and of each of them an 
 undetermined quantity daily escapes from the 
 body in the perspiration, in the urine, or in the 
 solid excretions. This quantity, therefore, must 
 be daily restored by the food. 
 
236 THE FOOD MUST ALSO YIELD 
 
 No precise experiments have yet been made 
 with the view of determining how much saUne 
 matter is daily excreted from the body of a healthy 
 man, or in what proportions the different inor- 
 ganic substances are present in it ; but it is satis- 
 factorily ascertained, that without a certain suffi- 
 cient supply, 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, there- 
 fore, that plants are so organized as to refuse to 
 grow in a soil from which they cannot readily ob- 
 tain a 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 existences, — the plant is 
 the connecting bond by which they are tied to- 
 gether on the one hand, — the decaying animal 
 matter which returns to the soil, connects them on 
 the other. 
 
 4. The solid bones of the animal are supplied 
 from the same original source, — the vegetable food 
 on which they live. The bones of the cow con- 
 tain 55 per cent, of phosphate of lime, of the sheep 
 
SALINE AND EARTHY MATTER. 237 
 
 70, of the horse 67, of the calf 54, and of the pig 
 52 lbs., in every hundred of dry bone. All this must 
 come from the vegetable food. Of the bone-earth 
 also, a portion, — perhaps a variable portion, — is 
 every day rejected from the animal ; the food, 
 therefore, must contain a daily supply, or that 
 which passes off will be taken from the substance 
 of the bones, and the animal will become feeble. 
 
 It is kindly provided by nature, that a certain 
 proportion 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, in using any of 
 these latter along with his vegetable food, obtains 
 from them, with comparative ease, the quantity of 
 the earth of bones which is necessary to keep his 
 system in repair ; while those animals which live 
 upon vegetables alone, extract all they require 
 along with the gluten of the plants on which they 
 feed. 
 
 The provision is very beautiful by which the 
 young animal, — the muscle and bones of which 
 are rapidly growing, — is supplied with a larger 
 portion of nitrogenous food and of bone-earth, 
 than are necessary to maintain the healthy condi- 
 tion of the full grown animal. The milk of the 
 mother is the natural food from which its supplies 
 
238 HOW THESE SUBSTANCES ARE SUPPLIED TO 
 
 are drawn. The sugar of the milk supplies the 
 comparatively 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 
 growing muscles, and of the animal part of the 
 bones, — while dissolved along with the curd 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 constitution of milk will shew us 
 how copious the supply of all these substances is, 
 — how beautifully the constitution of the mother's 
 milk is adapted to the wants of her infant off- 
 spring. Cow's milk consists in 1000 parts by 
 weight of — 
 
 Butter, 27 to 35 
 
 Cheesy matter (casein), . . 45 to 90 
 
 Milk sugar, . . . . 36 to 50 
 Chloride of potassium, and a little 
 
 chloride of sodium, . . . ^2 ^ in 
 
 Phosphates, chiefly of lime, . . 2| > 
 
 Other salts, .... 6 
 
 Water, • . . . . 882|to815 
 
 1000 1000 
 
 The quality of the milk, and, consequently, the 
 proportions of the several constituents above men- 
 
YOUNG ANIMALS IN THEIR MOTHER's MILK. 239 
 
 tioncd, vary with the breed of the cow, — 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 diflicrent quantities. 
 
 Milk of the quality above analyzed contains, in 
 every ten gallons, 4| lbs. of casein, equal to the 
 formation of 18 lbs. of ordinary muscle, and 3^ 
 ounces of phosphate of Ume (bone-earth), equal to 
 the production of 7 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 contained also a minute portion 
 of the bone-earth. A portion of all the ingredi- 
 ents of the milk likewise passes ofl* in the ordinary 
 excretions, and yet every one knows how rapidly 
 young animals thrive, when allowed to consuniQ 
 the whole of the milk which nature has provided 
 as their most suitable nourishment. 
 
 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 
 
 * In warm weather the milk contains more butter, in cold 
 weather more cheese and sugar. 
 
240 WHENCE DERIVED BY THE MOTHER. 
 
 to yield so large a supply of nourishing milk ? 
 She must extract them from the vegetables on 
 which she lives, and they 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 gal- 
 lons in a year — every 10 gallons of which contain 
 bone-earth enough to form about 7 ounces of dry 
 bone — then the milking of the cow alone exhausts 
 her of the earthy ingredients of 33 lbs. of dry bone. 
 And this she draws necessarily from the soil ! 
 
 If this milk be consumed on the spot, then all 
 returns again to the soil in the annual manuring 
 of the land. Let it be carried for sale to a dis- 
 tance, or let it be converted into cheese and butter, 
 and in this form exported, there will then be a 
 yearly drain upon the land of the materials of 
 bones, from this cause alone, equal to 30 lbs. of 
 bone-dust. After the lapse of centuries, it is con- 
 ceivable that old pasture lands in cheese and dairy 
 countries should become poor in the materials 
 of ibones — and that in such districts, as now in 
 Cheshire, the application of bone-dust should en- 
 tirely alter the character of the grasses, and reno- 
 vate the old pastures. 
 
 Thus, as was stated at the commencement of 
 
CAN THIS EFFECT THE QUALITY OF SOIL ? 241 
 
 the present section the study of the nature, and 
 functions of the food of animals throws additional 
 light upon the nature also and final uses of the 
 food of plants. It even teaches us what to look 
 for in the soil — what a fertile soil must contain 
 that it may grow nourishing food — what we must 
 add to the soil when chemical analysis fails to 
 detect its actual presence, or when the food it pro- 
 duces is unable to supply all that the animal 
 requires. , 
 
 The principles above explained, therefore, shew 
 that the value of any vegetable production, con- 
 sidered as the sole food of an animal, is not to be 
 judged of — cannot, in short, be accurately deter- 
 mined — ^by the amount it may contain of any one 
 of those substances, all of which together are ne- 
 cessary 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 feed- 
 ing them upon pure starch or sugar alone. These 
 substances would supply carbon for respiration, 
 but all the natural waste of nitrogen, of saline 
 matter, and of earthy phosphates, must have been 
 
 drawn from the existing solids and fluids of their 
 21 
 
242 CONSTITUENTS OF NUTRITIVE FOOD. 
 
 living bodies. The animals in consequence pined 
 away, and sooner or later died. 
 
 Some have expressed surprise that animals have 
 refused to thrive, and have ultimately died, when 
 fed upon animal jelly or gelatine (from bones) 
 alone, nourishing though that substance as part of 
 the food undoubtedly is. When given in sufficient 
 quantity, gelatine might indeed supply carbon 
 enough for respiration, with a great waste of ni- 
 trogen, but it is deficient in the saline ingredients 
 which a naturally nourishing food contains. 
 
 Even on the natural mixture of starch and 
 gluten in fine white bread, dogs have been unable 
 to live beyond 50 days, though others fed on 
 household bread, containing a portion of the bran 
 — in which earthy matter more largely resides—^ 
 continued to thrive long after. It is immaterial 
 whether the general quantity of the whole food be 
 reduced too low, or whether one of its necessary 
 ingredients only be too much diminished or en- 
 tirely withdrawn. In either case, the effect will 
 be the same — the animal will pine away, and 
 sooner or later die. 
 
VALUE OF DIFFERENT KINDS OF FOOD. 243 
 
 SECTION VII. — OP THE PRACTICAL AND THEORETICAL VALUE 
 OF DIFFERENT KINDS OF FOOD. 
 
 From what has been stated in the preceding 
 section, it appears, that, for various reasons, differ- 
 ent kinds of food are not equally nourishing. 
 This fact is of great importance, not only in the 
 preparation of human food, bnt also in the feed- 
 ing of stock. It has, therefore, been made the 
 subject of experiment by many practical agricul- 
 turists, with the following general results. 
 
 If common hay be taken as the standard of com- 
 parison, then to yield the same amount of nourish- 
 ment with 10 lbs. of hay, 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, 
 
 Clover hay, 
 Green clover, 
 Wheat straw. 
 Barley straw, 
 Oat straw, 
 Pea straw, 
 Potatoes, 
 Old potatoes, 
 
 10 
 
 8 to 10 
 45 to 50 
 40 to 50 
 20 to 40 
 20 to 40 
 10 to 15 
 20 
 407 
 
 Carrots, 
 
 Turnips, 
 
 Cabbage, 
 
 Pease and Beans, 
 
 Wheat, . 
 
 Barley, 
 
 Oats, 
 
 Indian corn, 
 
 Oil cake, 
 
 25 to 30 
 
 50 
 
 20 to 30 
 
 3 to 5 
 5 to 
 5 to 
 
 4 to 
 5 
 2 to 
 
244 EXPERIMENTAL AND THEORETICAL VALUE. 
 
 It is found in practice, as the above table shews, 
 that twenty stones of potatoes or three of oil-cake 
 will nourish an animal as much as ten stones of 
 hay, and five stones of oats as much as either. 
 Something, however, will depend upon the qual- 
 ity of each kind of food, and upon the age and 
 constitution of the animal. The skilful feeder of 
 stock knows also the value of a change of food, or 
 of a mixture of the different kinds of vegetable 
 food ho may have at his command. 
 
 The nutritive value of different kinds of food 
 has also been represented theoretically, by sup- 
 posing it to be very nearly in proportion to the 
 quantity of nitrogen, or of gluten, which vege- 
 tables contain. Though this cannot be considered 
 as a correct principle, yet as the ordinary kind 
 of food on which stock is fed contains in general 
 an ample supply of carbon for respiration, with a 
 comparatively small proportion of nitrogen, these 
 theoretical determinations are by no means with- 
 out 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 lbs. of hay yield a certain amount of nourish- 
 ment, then of the other vegetable substances it 
 will be necessary, according to theory, to give -the 
 
COMPARED WITH THAT OF HAY. 
 
 245 
 
 following quantities, in order to produce the same 
 effect : 
 
 Hay, . 
 
 10 
 
 Turnips, 
 
 60 
 
 Clover hay. 
 
 8 
 
 Carrots, 
 
 35 
 
 Vetch hay,* 
 
 4 
 
 Cabbage, 
 
 30 to 40 
 
 Wheat straw, 
 
 52 
 
 Pease and Beans, 
 
 2 to 3 
 
 Barley straw, 
 
 52 
 
 Wheat, 
 
 5 
 
 Oat straw,^ 
 
 55 
 
 Barley, 
 
 6 
 
 Pea straw, 
 
 6 
 
 Oats, 
 
 5 
 
 Potatoes, 
 
 28 
 
 Indian corn, . 
 
 6 
 
 Old potatoes, 
 
 40 
 
 Oil cake, 
 
 3 
 
 If the feeder be careful to supply his stock with 
 a mixture or occasional change of food, he may 
 very safely regulate the quantity of any one he 
 ought to substitute for a given weight of any of 
 the others, by the numbers in the above tables — 
 since the theoretical and practical results do not 
 in general very greatly differ. 
 
 As has been already stated, it is not strictly 
 correct that this or that kind of vegetable is more 
 fitted to sustain animal life, simply because of the 
 larger proportion of nitrogen it contains ; but it 
 is wisely provided, that along with this nitrogen 
 in all plants, a certain proportion of starch or 
 
 * Both cut in flower. 
 21* 
 
246 A MIXTURE OR CHANGE OF FOOD 
 
 sugar and of saline and earthy matter are always 
 associated— so that the quantity of nitrogen may 
 be considered as a rough practical index of the 
 proportion of some of the important saline and 
 earthy ingredients also. 
 
 An important practical lesson on this subject 
 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 un- 
 hatched bird — -but in rich natural pastures the 
 same mixture uniformly occurs. Hence, in crop- 
 ping the mixed herbage, the animal introduces 
 into its stomach portions of various plants — ^some 
 abounding more in starch or sugar, some more ii^ 
 gluten or albumen, some naturally richer in 
 saline, others in earthy constituents ; and out of 
 these varied materials the digestive organs select 
 a due proportion 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 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 
 
BEST FITTED TO NOURISH ALL ANIMALS. 247 
 
 kind of vegetable only, there is a waste of one or 
 other of the necessary elements of animal food, 
 and that the great lesson on this subject taught 
 us by nature is, that, by a judicious admixture, 
 not only is food economised, but the labour im- 
 posed upon the digestive organs is also materially 
 diminished. 
 
 SECTION VIII. — CONCLUDING OBSERVATIONS. 
 
 In this little work, now brought to a close, I 
 have presented the reader with a slight, and I 
 hope plain and familiar, sketch of the various 
 topics connected with practical agriculture, on 
 which the sciences of chemistry and geology 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 which are of the greatest im- 
 portance in the vegetable kingdom. We have 
 examined the nature of the seed, — seen by what 
 beautiful provision it is fed during its early ger- 
 mination — in what form the elements by which it 
 is nourished are introduced into the circulation 
 of the young plant when the functions of the seed 
 
248 CONCLUDING OBSERVATIONS. 
 
 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, dur- 
 ing the formation of its woody stem, the blossom- 
 ing of its flower, and the ripening of its seed or 
 fruit, — and have traced the further changes it un- 
 dergoes, when, the functions of its short life being 
 discharged, it hastens to serve other purposes, by 
 mingling 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 natu- 
 ral productiveness, have each occupied a share of 
 our attention — while the various means of im- 
 proving their agricultural value by manuring or 
 otherwise, have been practically considered, and 
 theoretically explained. Lastly, we have glanced 
 at the comparative worth of the various products 
 of the land, as food for man or other animals, 
 and have briefly illustrated the principles upon 
 which the feeding of animals and the relative nu- 
 tritive powers of the vegetables on which they 
 live are known to depend. 
 
 In this short and familiar treatise I have not 
 sought so much to satisfy the demands of the phi- 
 
OBJECT OF THIS LITTLE WORK. 249 
 
 losophical agriculturist, as to awaken the curiosity 
 of my less instructed reader, to shew him how 
 much interesting as well as practically useful in- 
 formation chemistry and geology are able and will- 
 ing to impart to him, and thus to allure him in 
 quest of further knowledge and more accurate de- 
 tails to my larger work,* of which the present ex- 
 hibits only a brief outline. 
 
 * Lectures (m AgricvUural Chemistry and Geology. 
 
 J. p. Wright, Printer, 18 New street, N. Y- 
 
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