diff options
Diffstat (limited to '24931-8.txt')
| -rw-r--r-- | 24931-8.txt | 11701 |
1 files changed, 11701 insertions, 0 deletions
diff --git a/24931-8.txt b/24931-8.txt new file mode 100644 index 0000000..4f2892a --- /dev/null +++ b/24931-8.txt @@ -0,0 +1,11701 @@ +Project Gutenberg's Elements of Agricultural Chemistry, by Thomas Anderson + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Elements of Agricultural Chemistry + +Author: Thomas Anderson + +Release Date: March 28, 2008 [EBook #24931] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK ELEMENTS OF AGRICULTURAL CHEMISTRY *** + + + + +Produced by Steven Giacomelli, Jeannie Howse, Josephine +Paolucci and the Online Distributed Proofreading Team at +http://www.pgdp.net. (This file was produced from images +produced by Core Historical Literature in Agriculture +(CHLA), Cornell University). + + + + + + + + + +ELEMENTS + +OF + +AGRICULTURAL CHEMISTRY + +BY + +THOMAS ANDERSON, M.D. + +F.R.S.E., F.C.S. + +PROFESSOR OF CHEMISTRY IN THE UNIVERSITY OF GLASGOW, AND CHEMIST TO THE +HIGHLAND AND AGRICULTURAL SOCIETY OF SCOTLAND. + +EDINBURGH: + +ADAM AND CHARLES BLACK. + +1860. + + +ERRATUM. + +Page 190, line 11, for "gallon" read "ton." + +PRINTED BY R. AND R. CLARK, EDINBURGH. + + +Transcriber's note: Many of the tables needed to be split to fit space +constraints. Minor typos have been corrected and footnotes moved to the +end of the chapters. A word surrounded by underscores like _this_ +signifies the word is italics in the text. For numbers and equations, +underscores before bracketed numbers in equations denote a subscript. + + + +PREFACE. + + +The object of the present work is to offer to the farmer a concise +outline of the general principles of Agricultural Chemistry. It has no +pretensions to be considered a complete treatise on the subject. On the +contrary, its aim is strictly elementary, and with this view I have +endeavoured, as far as possible, to avoid unnecessary technicalities so +as to make it intelligible to those who are unacquainted with the +details of chemical science, although I have not hesitated to discuss +such points as appeared essential to the proper understanding of any +particular subject. + +The rapid progress of agricultural chemistry, and the numerous +researches prosecuted under the auspices of agricultural societies and +private experimenters in this and other countries, render it by no means +an easy task to make a proper selection from the mass of facts which is +being daily accumulated. In doing this, however, I have been guided by a +pretty intimate knowledge of the wants of the farmer, which has induced +me to enlarge on those departments of the subject which bear more +immediately on the every-day practice of agriculture; and for this +reason the composition and properties of soils, the nature of manures, +and the principles by which their application ought to be governed, have +been somewhat minutely treated. + +In all cases numerical details have been given as fully as is consistent +with the limits of the work; and it may be right to state that a +considerable number of the analyses contained in it have been made in my +own laboratory, and that even when I have preferred to quote the results +of other chemists, they have not unfrequently been confirmed by my own +experiments. + + UNIVERSITY OF GLASGOW, + _1st November 1860._ + + + + +CONTENTS. + + + Page + +INTRODUCTION 1 + + +CHAPTER I. + +THE ORGANIC CONSTITUENTS OF PLANTS. + +Carbon ... Carbonic Acid ... Hydrogen ... Nitrogen ... Nitric Acid ... +Ammonia ... Oxygen ... Sources whence obtained ... The Atmosphere ... +The Soil ... Source of the Inorganic Constituents of Plants ... Manner +in which the Constituents of Plants are absorbed 8 + + +CHAPTER II. + +THE PROXIMATE CONSTITUENTS OF PLANTS. + +The Saccharine and Amylaceous Constituents ... Cellulose ... Incrusting +Matter ... Starch ... Lichen Starch ... Inuline ... Gum ... Dextrine ... +Sugar ... Mucilage ... Pectine and Pectic Acid ... Oily or Fatty Matters +... Margaric, Stearic, and Oleic Acids ... Wax ... Nitrogenous or +Albuminous Constituents of Plants and Animals ... Albumen ... Fibrine +... Casein ... Diastase 40 + + +CHAPTER III. + +THE CHANGES WHICH TAKE PLACE IN THE FOOD OF +PLANTS DURING THEIR GROWTH. + +Changes occurring during Germination ... Changes during the After-Growth +of the Plant ... Decomposition of Carbonic Acid ... Decomposition of +Water ... Decomposition of Ammonia ... Decomposition of Nitric Acid 54 + + +CHAPTER IV. + +THE INORGANIC CONSTITUENTS OF PLANTS. + +The Amount of Inorganic Matters in Different Plants ... The Relative +Proportions of Ash in the Different Parts of Plants ... Influence of the +Nature of the Soil on the Proportion of Mineral Matters in the Plant ... +The Composition of the Ashes of Plants ... Classification of Different +Plants 63 + + +CHAPTER V. + +THE SOIL--ITS CHEMICAL AND PHYSICAL CHARACTERS. + +The Origin of Soils ... Composition of Crystalline and Sedimentary Rocks +... their Disintegration ... Chemical Composition of the Soil ... +Fertile and Barren Soils ... Mechanical Texture of Soils ... Absorbent +Action of Soils ... their Physical Characters ... Relation to Heat and +Moisture ... The Subsoil ... Classification of Soils 83 + + +CHAPTER VI. + +THE IMPROVEMENT OF THE SOIL BY MECHANICAL +PROCESSES. + +Draining ... Its Advantageous Effects ... Subsoil and Deep Ploughing +... Improving the Soil by Paring and Burning ... Warping +... Mixing of Soils ... Chalking 137 + + +CHAPTER VII. + +THE GENERAL PRINCIPLES OF MANURING. + +Fundamental Principles upon which Manures are applied ... _Special_ and +_General_ Manures ... Importance of this distinction ... Views regarding +the Theory of Manures ... Remarks on Special Manures ... Action of +Manures on the Chemical and Physical Properties of a Soil ... Remarks on +the Application of Manures 152 + + +CHAPTER VIII. + +THE COMPOSITION AND PROPERTIES OF FARM-YARD +AND LIQUID MANURES. + +Farm-yard Manure ... Urine ... Composition of ... Dung ... Composition +of ... Farm-yard Manure ... Composition of ... Management of Dung-Heaps +... Box-feeding ... Fermentation and application of Manure ... Liquid +Manure ... Composition and application of ... Sewage Manure ... Its +composition and application 166 + + +CHAPTER IX. + +THE COMPOSITION AND PROPERTIES OF VEGETABLE +MANURES. + +Rape-Dust, Mustard, Cotton and Castor Cake ... Composition of various +Oil-Cakes ... Malt-Dust, Bran, Chaff, etc. ... Straw and Saw-dust ... +Manuring with Fresh Vegetable Matter ... Green Manuring ... Sea-Weed ... +Composition of various Sea-Weeds ... Leaves ... Peat 195 + + +CHAPTER X. + +THE COMPOSITION AND PROPERTIES OF ANIMAL +MANURES. + +Guano, different varieties of ... Average composition of ... Division +into Ammoniacal and Phosphatic ... Characters of ... Adulteration of ... +Application of ... Pigeons' Dung ... Urate and Sulphated Urine ... +Night-Soil and Poudrette ... Hair, Skin, Horn, Wool, etc. ... Blood ... +Fish ... "Fish-Guano"--Bones 204 + + +CHAPTER XI. + +THE COMPOSITION AND PROPERTIES OF MINERAL +MANURES. + +Mineral Manures ... Sulphate and Muriate of Ammonia ... Sulphomuriate +of Ammonia ... Ammoniacal Liquor ... Nitrates of Potash and Soda ... +Muriate and Sulphate of Potash ... Chloride of Sodium, or Common Salt +... Carbonates of Potash and Soda ... Silicates of Potash and Soda ... +Sulphate of Magnesia ... Phosphate of Lime ... Bone-ash ... Coprolites +... Apatite ... Sombrero Guano ... Superphosphates and Dissolved Bones +... Biphosphate of Lime or Soluble Phosphates ... Phospho-Peruvian Guano +... Lime ... Chalk ... Marl ... Application and Action of Lime on Soils +... Sulphate of Lime or Gypsum 226 + + +CHAPTER XII. + +THE VALUATION OF MANURES. + +The Principle on which Manures are valued ... Its application to +different simple and complex Manures ... Method of Calculation ... +General Remarks 255 + + +CHAPTER XIII. + +THE ROTATION OF CROPS. + +Its necessity explained ... Quantity of Mineral Matters in the produce +of an Acre of Different Crops ... The Theory of Rotation 266 + + +CHAPTER XIV. + +THE FEEDING OF FARM STOCK. + +The Principles of Feeding ... The Composition of different Animals in +different stages of Fattening ... The Composition of the Food of Animals +... Milk ... The Principal Varieties of Cattle Food ... General +Observations on Feeding 276 + + + + +AGRICULTURAL CHEMISTRY. + + + + +INTRODUCTION. + + +That the phenomena of vegetation are dependent on certain chemical +changes occurring in the plant, by which the various elements of its +food are elaborated and converted into vegetable matter, was very early +recognised by chemists; and long before the correct principles of that +science were established, Van Helmont maintained that plants derived +their nourishment from water, while Sir Kenelm Digby, Hook, Bradley, and +others, attributed an equally exclusive influence to air, and enlarged +on the practical importance of the conclusions to be deduced from their +views. These opinions, which were little better than hypotheses, and +founded on very imperfect chemical data, are mentioned by Jethro Tull, +the father of modern agriculture, only to deny their accuracy; and he +contended that the plants absorb and digest the finer particles of the +earth, and attributed the success of the particular system of husbandry +he advocated to the comminution of the soil, by which a larger number +of its particles are rendered sufficiently small to permit their ready +absorption by the roots. Popular opinion at that time was in favour of +the mechanical rather than the chemical explanation of agricultural +facts, and Tull's work had the effect of confirming this opinion, and +turning attention away from the application of chemistry to agriculture. +Indeed, no good results could have followed its study at that time, for +chemistry, especially in those departments bearing more immediately on +agriculture, was much too imperfect, and it was only towards the close +of the last century, when Lavoisier established its true principles, +that it became possible to pursue it with any prospect of success. + +Very soon after Lavoisier's system was made known, Lord Dundonald +published his "Treatise on the Intimate Connexion between Chemistry and +Agriculture," in which the important bearings of the recent chemical +discoveries on the practice of agriculture were brought prominently +under the notice of the farmer, and almost at the same time De Saussure +commenced those remarkable researches, which extended over a long series +of years, and laid the foundation of almost all our accurate knowledge +of the chemistry of vegetation. Saussure traced with singular care and +accuracy the whole phenomena of the life of plants, and indicated the +mode in which the facts he established might be taken advantage of in +improving the cultivation of the soil. But neither his researches, nor +Lord Dundonald's more direct appeal to the farmer, excited the attention +they deserved, or produced any immediate effect on the progress of +agriculture. It was not till the year 1812 that the interest of +practical men was fairly awakened by a course of lectures given by Sir +Humphrey Davy, at the instance of Sir John Sinclair, who was at that +time president of the Board of Agriculture. In these lectures, written +with all the clearness and precision which characterised their author's +style, the results of De Saussure's experiments were for the first time +presented to the farmer in a form in which they could be easily +understood by him, the conclusions to which they led were distinctly +indicated, and a number of useful practical suggestions made, many of +which have been adopted into every-day practice, and become so +thoroughly incorporated with it, that their scientific origin has been +altogether forgotten. A lively interest was excited by the publication +of Davy's work, but it soon died out, and the subject lay in almost +complete abeyance for a considerable number of years. Nor could any +other result be well expected, for at that time agriculture was not ripe +for chemistry, nor chemistry ripe for agriculture. The necessities of a +rapidly increasing population had not yet begun to compel the farmer to +use every means adapted to increase the amount of production to its +utmost limit; and though the fundamental principles of chemistry had +been established, its details, especially in that department which +treats of the constituents of plants and animals, were very imperfectly +known. It is not surprising, therefore, that matters should have +remained almost unchanged for the comparatively long period of nearly +thirty years. Indeed, with the exception of the investigation of soils +by Schübler, and some other inquiries of minor importance, and which, in +this country at least, excited no attention on the part of the +agriculturist, nothing was done until the year 1840, when Liebig +published his treatise on _Chemistry, in its application to Agriculture +and Physiology_. + +Saussure's researches formed the main groundwork of Liebig's treatise, +as they had before done for Davy's; but the progress of science had +supplied many new facts which confirmed the opinions of the older +chemists in most respects, and enabled Liebig to generalise with greater +confidence, and illustrate more fully the principles upon which +chemistry ought to be applied to agriculture. Few works have ever +produced a more profound impression. Written in a clear and forcible +style, dealing with scientific truths in a bold and original manner, and +producing a strong impression, as well by its earnestness as by the +importance of its conclusions, it was received by the agricultural +public with the full conviction that the application of its principles +was to be immediately followed by the production of immensely increased +crops, and by a rapid advance in every branch of practical agriculture. +The disappointment of these extravagant expectations, which _chemists_ +themselves foresaw, and for which they vainly attempted to prepare the +agriculturist, was followed by an equally rapid reaction; and those who +had embraced Liebig's views, and lauded them as the commencement of a +new era, but who had absurdly expected an instantaneous effect, changed +their opinion, and contemned, as strongly as they had before supported, +the application of chemistry to agriculture. + +That this effect should have been produced is not unnatural; for +practical men, having at that time little or no knowledge of chemistry, +were necessarily unable to estimate its true position in relation to +agriculture, and forgetting that this department of science was still in +its early youth, and burthened with all the faults and errors of youth, +they treated it as if it were already perfect in all its parts. Neither +could they distinguish between the fully demonstrated scientific truths, +and the uncertain, though probable conclusions deduced from them; and +when the latter, as occasionally happened, proved to be at variance with +practice, it is not surprising: that this should have produced a feeling +of distrust on the part of persons incapable, from an imperfect, and +still oftener from no knowledge of science, of drawing the line of +demarcation, which Liebig frequently omitted to do, between the positive +fact and the hypothetical inference, which, however probable, is, after +all, merely a suggestion requiring to be substantiated by experiment. +This omission, which the scientific reader can supply for himself, +becomes a source of serious misapprehension in a work addressed to +persons unacquainted with science, who adopt indiscriminately both the +facts and the hypotheses of the author. And this is no doubt the cause +of the vary different estimation in which the work of the Giessen +Professor was held by scientific and practical men. + +Liebig's treatise was followed, in the year 1844, by the publication of +Boussingault's _Economic Rurale_, a work winch excited at the time +infinitely less interest than Liebig's, although it is really quite as +important a contribution to scientific agriculture. It is distinguished +by entering more fully into the special details of the application of +chemistry to agriculture, and contains the results of the author's +numerous searches both in the laboratory and the field. Boussingault +possesses the qualification, at present somewhat rare, of combining a +thorough knowledge of practical agriculture with extended scientific +attainments; and his investigations, which have been made with direct +reference to practice, and their results tested in the field, are the +largest and most valuable contribution to the exact data of scientific +agriculture which has yet been made public. + +The year 1844 was also distinguished by the foundation of the +Agricultural Chemistry Association of Scotland, an event of no small +importance in the history of scientific agriculture. That association +was instituted through the exertions of a small number of practical +farmers, for the purpose of pursuing investigations in agricultural +chemistry, and affording to its members assistance in all matters +connected with the cultivation of the soil, and has formed the model of +similar establishments in London, Dublin, and Belfast, as well as in +Germany; and it is peculiarly creditable to the intelligence and energy +of the practical farmers of Scotland, that with them commenced a +movement, which has already found imitators in so many quarters, and +conferred such great benefits on agriculture. Within the last ten or +twelve years, and mainly owing to the establishment of agricultural +laboratories, great progress has been made in accumulating facts on +which to found an accurate knowledge of the principles of agricultural +chemistry, and the number of chemists who have devoted themselves to +this subject has considerably increased, though still greatly less than +its exigencies require. + +Notwithstanding all that has recently been done, it must not be +forgotten that we have scarcely advanced beyond the threshold, and that +it is only by numerous and frequently repeated experiments that it is +possible to arrive at satisfactory results. Agricultural inquiries are +liable to peculiar fallacies due to the perturbing influence of climate, +season, and many other causes, the individual effects of which can only +be eliminated with difficulty, and much error has been introduced, by +hastily generalising from single experiments, in place of awaiting the +results of repeated trials. Hence it is that the progress of scientific +agriculture must necessarily be slow and gradual, and is not likely to +be marked by any great or startling discoveries. Now that the relations +of science to practice are better understood, the extravagant +expectations at one time entertained have been abandoned, and, as a +necessary consequence, the interest in agricultural chemistry has again +increased, and the conviction daily gains ground that no one who wishes +to farm with success, can afford to be without some knowledge of the +scientific principles of his art. + + + + +CHAPTER I. + +THE ORGANIC CONSTITUENTS OF PLANTS. + + +When the water naturally existing in plants is expelled by exposure to +the air or a gentle heat, the residual dry matter is found to be +composed of a considerable number of different substances, which have +been divided into two great classes, called the organic and the +inorganic, or mineral constituents of plants. The former are readily +combustible, and on the application of heat, catch fire, and are +entirely consumed, leaving the inorganic matters in the form of a white +residuum or ash. All plants contain both classes of substances; and +though their relative proportions vary within very wide limits, the +former always greatly exceed the latter, which in many cases form only a +very minute proportion of the whole weight of the plant. Owing to the +great preponderance of the organic or combustible matters, it was at one +time believed that the inorganic substances formed no part of the true +structure of plants, and consisted only of a small portion of the +mineral matters of the soil, which had been absorbed along with their +organic food; but this opinion, which probably was never universally +entertained, is now entirely abandoned, and it is no longer doubted that +both classes of substances are equally essential to their existence. + +Although they form so large a proportion of the plant, its organic +constituents are composed of no more than four elements, viz.:-- + + Carbon. + Hydrogen. + Nitrogen. + Oxygen. + +The inorganic constituents are much more numerous, not less than +thirteen substances, which appear to be essential, having been observed. +These are-- + + Potash. + Soda. + Lime. + Magnesia. + Peroxide of Iron. + Silicic Acid. + Phosphoric Acid. + Sulphuric Acid. + Chlorine. + +And more rarely + + Manganese. + Iodine. + Bromine. + Fluorine. + +Several other substances, among which may be mentioned alumina and +copper, have also been enumerated; but there is every reason to believe +that they are not essential, and the cases in which they have been found +are quite exceptional. + +It is to be especially noticed that none of these substances occur in +plants in the free or uncombined state, but always in the form of +compounds of greater or less complexity, and extremely varied both in +their properties and composition. + +It would be out of place, in a work like the present, to enter into +complete details of the properties of the elements of which plants are +composed, which belongs strictly to pure chemistry, but it is necessary +to premise a few observations regarding the organic elements, and their +more important compounds. + +_Carbon._--When a piece of wood is heated in a close vessel, it is +charred, and converted into charcoal. This charcoal is the most familiar +form of carbon, but it is not absolutely pure, as it necessarily +contains the ash of the wood from which it was made. In its purest form +it occurs in the diamond, which is believed to be produced by the +decomposition of vegetable matters, and it is there crystallized and +remarkably transparent; but when produced by artificial processes, +carbon is always black, more or less porous, and soils the fingers. It +is insoluble in water, burns readily, and is converted into carbonic +acid. Carbon is the largest constituent of plants, and forms, in round +numbers, about 50 per cent of their weight when dry. + +_Carbonic Acid._--This, the most important compound of carbon and +oxygen, is best obtained by pouring a strong acid upon chalk or +limestone, when it escapes with effervescence. It is a colourless gas, +extinguishing flame, incapable of supporting respiration, much heavier +than atmospheric air, and slightly soluble in water, which takes up its +own volume of the gas. It is produced abundantly when vegetable matters +are burnt, as also during respiration, fermentation, and many other +processes. It is likewise formed daring the decay of animal and +vegetable matters, and is consequently evolved from dung and compost +heaps. + +_Hydrogen_ occurs in nature only in combination. Its principal compound +is water, from which it is separated by the simultaneous action of an +acid, such as sulphuric acid and a metal, in the form of a transparent +gas, lighter than any other substance. It is very combustible, burns +with a pale blue flame, and is converted into water. It is found in all +plants, although in comparatively small quantity, for, when dry, they +rarely contain more than four or five per cent. Its most important +compound is water, of which it forms one-ninth, the other eight-ninths +consisting of oxygen. + +_Nitrogen_ exists abundantly in the atmosphere, of which it forms nearly +four-fifths, or, more exactly, 79 per cent. It is there mixed, but not +combined with oxygen; and when the latter gas is removed, by introducing +into a bottle of air some substance for which the former has an +affinity, the nitrogen is left in a state of purity. It is a transparent +gas, which is incombustible and extinguishes flame. It is a singularly +inert substance, and is incapable of directly entering into union with +any other element except oxygen, and with that it combines with the +greatest difficulty, and only by the action of the electric spark--a +peculiarity which has very important bearings on many points we shall +afterwards have to discuss. Nitrogen is found in plants to the extent of +from 1 to 4 per cent. + +_Nitric Acid._--This, the most important compound of nitrogen and +oxygen, can be produced by sending a current of electric sparks through +a mixture of its constituents, but in this way it can be obtained only +in extremely small quantity. It is much more abundantly produced when +organic matters are decomposed with free access of air, in which case +the greater proportion of their nitrogen combines with the atmospheric +oxygen. This process, which is known by the name of nitrification, is +greatly promoted by the presence of lime or some other substance, with +which the nitric acid may combine in proportion as it is formed. It +takes place, to a great extent, in the soil in India and other hot +climates; and our chief supplies of saltpetre, or nitrate of potash, are +derived from the soil in these countries, where it has been formed in +this manner. The same change occurs, though to a much smaller extent, in +the soil in temperate climates. + +_Ammonia_ is a compound of nitrogen and hydrogen, but it cannot be +formed by the direct union of these gases. It is a product of the +decomposition of organic substances containing nitrogen, and is produced +when they are distilled at a high temperature, or allowed to putrefy out +of contact of the air. In its pure state it is a transparent and +colourless gas, having a peculiar pungent smell, and highly soluble in +water. It is an alkali resembling potash and soda, and, like these +substances, unites with the acids and forms salts, of which the sulphate +and muriate are the most familiar. In these salts it is fixed, and does +not escape from them unless they be mixed with lime, or some other +substance possessing a more powerful affinity for the acid with which it +is united. + +_Oxygen_ is one of the most widely distributed of all the elements, and, +owing to its powerful affinities, is the most important agent in almost +all natural changes. It is found in the air, of which it forms 21 per +cent, and in combination with hydrogen, and almost all the other +chemical elements. In the pure state it possesses very remarkable +properties. All substances burn in it with greater brilliancy than they +do in atmospheric air, and its affinity for most of the elements is +extremely powerful. When diluted with nitrogen, it supports the +respiration of animals; but in the pure state it proves fatal after the +lapse of an hour or two. It is found in plants, in quantities varying +from 30 to 36 per cent. + +It is worthy of observation, that of the four organic elements, carbon +only is fixed, and the other three are gases; and likewise, when any two +of them unite, their compound is either a gaseous or a volatile +substance. The charring of organic substances, which is one of their +most characteristic properties, and constantly made use of by chemists +as a distinctive reaction, is due to this peculiarity; for when they are +heated, a simpler arrangement of their particles takes place, the +hydrogen, nitrogen, and oxygen unite among themselves, and carry off a +small quantity of carbon, while the remainder is left behind in the form +of charcoal, and is only consumed when access of the external air is +permitted. + +Now, in order that a plant may grow, its four organic constituents must +be absorbed by it, and that this absorption may take place, it is +essential that they be presented to it in suitable forms. A seed may be +planted in pure carbon, and supplied with unlimited quantities of +hydrogen, nitrogen, oxygen, and inorganic substances, and it will not +germinate; and a plant, when placed in similar circumstances, shows no +disposition to increase, but rapidly languishes and dies. The obvious +inference from these facts is, that these substances cannot be absorbed +when in the _elementary_ state, but that it is only after they have +entered into certain forms of combination that they acquire the property +of being readily taken up, and assimilated by the organs of the plant. + +It was at one time believed that many different compounds of these +elements might be absorbed and elaborated, but later and more accurate +experiments have reduced the number to four--namely, carbonic acid, +water, ammonia, and nitric acid. The first supplies carbon, the second +hydrogen, the two last nitrogen, while all of them, with the exception +of ammonia, may supply the plant with oxygen as well as with that +element of which it is the particular source. + +There are only two sources from which these substances can be obtained +by the plant, viz. the atmosphere and the soil, and it is necessary that +we should here consider the mode in which they may be obtained from +each. + +_The Atmosphere as a source of the Organic Constituents of +Plants._--Atmospheric air consists of a mixture of nitrogen and oxygen +gases, watery vapour, carbonic acid, ammonia, and nitric acid. The two +first are the largest constituents, and the others, though equally +essential, are present in small, and some of them in extremely minute +quantity. When deprived of moisture and its minor constituents, 100 +volumes of air are found to contain 21 of oxygen and 79 of nitrogen. +Although these gases are not chemically combined in the air, but only +mechanically mixed, their proportion is exceedingly uniform, for +analyses completely corresponding with these numbers have been made by +Humboldt, Gay-Lussac, and Dumas at Paris, by Saussure at Geneva, and by +Lewy at Copenhagen; and similar results have also been obtained from air +collected by Gay-Lussac during his ascent in a balloon at the height of +21,430 feet, and by Humboldt on the mountain of Antisano in South +America at a height of 16,640 feet. In short, under all circumstances, +and in all places, the relation subsisting between the oxygen and +nitrogen is constant; and though, no doubt, many local circumstances +exist which may tend to modify their proportions, these are so slow and +partial in their operations, and so counterbalanced by others acting in +an opposite direction, as to retain a uniform proportion between the +main constituents of the atmosphere, and to prevent the undue +accumulation of one or other of them at any one point. + +No such uniformity exists in the proportion of the minor constituents. +The variation in the quantity of watery vapour is a familiar fact, the +difference between a dry and moist atmosphere being known to the most +careless observer, and the proportions of the other constituents are +also liable to considerable variations. + +_Carbonic Acid._--The proportion of carbonic acid in the air has been +investigated by Saussure. From his experiments, made at the village of +Chambeisy, near Geneva, it appears that the quantity is not constant, +but varies from 3·15 to 5·75 volumes in 10,000; the mean being 4·15. +These variations are dependent on different circumstances. It was found +that the carbonic acid was always more abundant during the night than +during the day--the mean quantity in the former case being 4·32, in the +latter 3·38. The largest quantity found during the night was 5·74, +during the day 5·4. Heavy and continued rain diminishes the quantity of +carbonic acid, by dissolving and carrying it down into the soil. +Saussure found that in the month of July 1827, during the time when nine +millimetres of rain fell, the average quantity of carbonic acid amounted +to 5·18 volumes in 10,000; while in September 1829, when 254 millimetres +fell, it was only 3·57. A moist state of the soil, which is favourable +to the absorption of carbonic acid, also diminishes the quantity +contained in the air, while, on the other hand, continued frosts, by +retaining the atmosphere and soil in a dry state, have an opposite +effect. High winds increase the carbonic acid to a small extent. It was +also found to be greater over the cultivated lands than over the lake of +Geneva; at the tops of mountains than at the level of the sea; in towns +than in the country. The differences observed in all these cases, though +small, are quite distinct, and have been confirmed by subsequent +experimenters. + +_Ammonia._--The presence of ammonia in the atmosphere appears to have +been first observed by Saussure, who found that when the sulphate of +alumina is exposed to the air, it is gradually converted into the double +sulphate of alumina and ammonia. Liebig more recently showed that +ammonia can always be detected in rain and snow water, and it could not +be doubted that it had been absorbed from the atmosphere. Experiments +have since been made by different observers with the view of determining +the quantity of atmospheric ammonia, and their results are contained in +the subjoined table, which gives the quantity found in a million parts +of air. + +Kemp 3·6800 + + { 12 feet above the surface 3·5000 +Pierre { 25 feet do. do. 0·5000 + +Graeger 0·3230 + + { By day 0·0980 +Fresenius { By night 0·1690 + + { { Maximum 0·0317 + { In Paris { Minimum 0·0177 + { { Mean 0·0237 +Ville { + { { Maximum 0·0276 + { Environs { Minimum 0·0165 + { of Paris { Mean 0·0210 + +Of these results, the earlier ones of Kemp, Pierre, and Graeger are +undoubtedly erroneous, as they were made without those precautions which +subsequent experience has shown to be necessary. Even those of the other +observers must be taken as giving only a very general idea of the +quantity of ammonia in the air, for a proportion so minute as one +fifty-millionth cannot be accurately determined even by the most +delicate experiments. For this reason, more recent experimenters have +endeavoured to arrive at conclusions bearing more immediately upon +agricultural questions, by determining the quantity of ammonia brought +down by the rain. The first observations on this subject were made by +Barral in 1851, and they have been repeated during the years 1855 and +1856 by Mr. Way. In 1853, Boussingault also made numerous experiments +on the quantity of ammonia in the rain falling at different places, as +well as in dew and the moisture of fogs. He found in the imperial +gallon-- + + Grs. +Rain { Paris 0·2100 + { Liebfrauenberg 0·0350 + + +Dew, Liebfrauenberg { Maximum 0·4340 + { Minimum 0·0714 + + { Liebfrauenberg 0·1790 +Fog { Paris 9·6000 + +It thus appears that in Paris the quantity of ammonia in rain-water is +just six times as great as it is in the country, a result, no doubt, due +to the ammonia evolved during the combustion of fuel, and to animal +exhalations, and to the same cause, the large quantity contained in the +moisture of fogs in Paris may also be attributed. Barral and Way have +made determinations of the quantity of ammonia carried down by the rain +in each month of the year, the former using for this purpose the water +collected in the rain-gauges of the Paris Observatory, and representing, +therefore, a town atmosphere; the latter, that from a large rain-gauge +at Rothamsted, at a distance from any town. According to Barral the +ammonia annually deposited on an acre of land amounts to 12·28 lbs., a +quantity considerably exceeding that obtained by Way, whose experiments +being made at a distance from towns, must be considered as representing +more accurately the normal condition of the air. His results for the +years 1855 and 1856 are given below, along with the quantities of nitric +acid found at the same time. + +_Nitric Acid._--The presence of nitric acid in the air appears to have +been first observed by Priestley at the end of the last century, but +Liebig, in 1825, showed that it was always to be found after +thunder-storms, although he failed to detect it at other times. In 1851 +Barral proved that it is invariably present in rain-water, and stated +the quantity annually carried down to an acre of land at no less than +41·29 lbs. But at the time his experiments were made, the methods of +determining very minute quantities of nitric acid were exceedingly +defective, and Way, by the adoption of an improved process, has shown +that the quantity is very much smaller than Barral supposed, and really +falls short of three pounds. His results for ammonia, as well as nitric +acid, are given in the subjoined table. + +---------------------+----------------+----------------+-----------------+ +| | Nitric Acid in | Ammonia in | Total Nitrogen | +| | Grains. | Grains. | in Grains. | +| +-------+--------+-------+--------+--------+--------+ +| | 1855. | 1856. | 1855. | 1856. | 1855. | 1856. | ++--------------------+-------+--------+-------+--------+--------+--------+ +|January | 230 | 1564 | 1244 | 5,005 | 1084 | 4,526 | +|February | 944 | 544 | 2337 | 4,175 | 2169 | 3,579 | +|March | 1102 | 866 | 4513 | 2,108 | 3995 | 1,945 | +|April | 325 | 1063 | 1141 | 8,614 | 1024 | 7,369 | +|May | 1840 | 3024 | 4206 | 18,313 | 3939 | 15,863 | +|June | 3303 | 2046 | 5574 | 4,870 | 5447 | 4,540 | +|July | 2680 | 1191 | 9620 | 2,869 | 8615 | 2,670 | +|August | 3577 | 2125 | 4769 | 4,214 | 4870 | 4,021 | +|September | 732 | 1756 | 3313 | 5,972 | 2917 | 5,373 | +|October | 4480 | 2075 | 7592 | 3,921 | 7414 | 3,767 | +|November | 1007 | 1371 | 3021 | 2,591 | 2749 | 2,489 | +|December | 664 | 2035 | 2438 | 4,070 | 2180 | 3,352 | ++--------------------+-------+--------+-------+--------+--------+--------+ +|Total in pounds for}| | | | | | | +|the whole year }| 2·98 | ·280 | 7·11 | 9·53 | 6·63 | 8·31 | ++--------------------+-------+--------+----------------+--------+--------+ + +No attempts have been made to determine the proportion of nitric acid in +air, but its quantity is undoubtedly excessively minute, and materially +smaller than that of ammonia. At least this conclusion seems to be a +fair inference from Way's researches, as well as the recent experiments +of Boussingault on the proportion of nitric acid contained in rain, dew, +and fog, made in a manner exactly similar to those on the ammonia, +already quoted. According to his experiments an imperial gallon +contains-- + + Grs. +Rain. {Paris 0·0708 + {Liebfrauenberg 0·0140 + +Dew. {Maximum 0·0785 + {Minimum 0·0030 + +Fog. {Paris 0·7092 + {Liebfrauenberg 0·0718 + +Although it thus appears that Barral's results have been only partially +confirmed, enough has been ascertained to show that the quantity of +ammonia and nitric acid in the air is sufficient to produce a material +influence in the growth of plants. The large amount of these substances +contained in the dew is also particularly worthy of notice, and may +serve to some extent to explain its remarkably invigorating effect on +vegetation. + +_Carburetted Hydrogen._--Gay-Lussac, Humboldt, and Boussingault have +shown, that when the whole of the moisture and carbonic acid have been +removed from the air, it still contains a small quantity of carbon and +hydrogen; and Saussure has rendered it probable that they exist in a +state of combination as carburetted hydrogen gas. No definite proof of +this position has, however, as yet been adduced, and the function of the +compound is entirely unknown. It is possible that the presence of carbon +and hydrogen may be due to a small quantity of organic matter; but, +whatever be its source, its amount is certainly extremely small. + +_Sulphuretted Hydrogen and Phosphuretted Hydrogen._--The proportion of +these substances is almost infinitesimal; but they are pretty general +constituents of the atmosphere, and are apparently derived from the +decomposition of animal and vegetable matters. + +The preceding statements lead to the important conclusion, that the +atmosphere is capable of affording an abundant supply of all the organic +elements of plants, because it not only contains nitrogen and oxygen in +the free state, but also in those forms of combination in which they are +most readily absorbed, as well as a large quantity of carbonic acid, +from which their carbon may be derived. At first sight it may indeed +appear that the quantity of the latter compound, and still more that of +ammonia, is so trifling as to be of little practical importance. But a +very simple calculation serves to show that, though relatively small, +they are absolutely large, for the carbonic acid contained in the whole +atmosphere amounts in round numbers to + + 2,400,000,000,000 tons, + +and the ammonia, assuming it not to exceed one part in fifty millions, +must weigh + + 74,000,000 tons, + +quantities amply sufficient to afford an abundant supply of these +elements to the whole vegetation of our globe. + +_The Soil as a Source of the Organic Constituents of Plants._--When a +portion of soil is subjected to heat, it is found that it, like the +plant, consists of a combustible and an incombustible part; but while in +the plant the incombustible part or ash is small, and the combustible +large, these proportions are reversed in the soil, which consists +chiefly of inorganic or mineral matters, mixed with a quantity of +combustible or organic substances, rarely exceeding 8 or 10 per cent, +and often falling considerably short of this quantity. + +The organic matter exists in the form of a substance called humus, which +must be considered here as a source of the organic constituents of +plants, independently of the general composition of the soil, which will +be afterwards discussed. + +The term _humus_ is generic, and applied by chemists to a rather +numerous group of substances, very closely allied in their properties, +several of which are generally present in all fertile soils. They have +been submitted to examination by various chemists, but by none more +accurately than by Mulder and Herman, to whom, indeed, we owe almost all +the precise information we possess on the subject. The organic matters +of the soil may be divided into three great classes; the first +containing those substances which are soluble in water; the second, +those extracted by means of caustic potash; and the third, those +insoluble in all menstrua. When a soil is boiled with a solution of +caustic potash, a deep brown fluid is obtained, from which acids +precipitate a dark brown flocculent substance, consisting of a mixture +of at least three different acids, to which the names of humic, ulmic, +and geic acids have been applied. The fluid from which they have been +precipitated contains two substances, crenic and apocrenic acids, while +the soil still retains what has been called insoluble humus. + +The acids above named do not differ greatly in chemical characters, but +they have been subdivided into the humic, geic, and crenic groups, which +present some differences in properties and composition. They are +compounds of carbon, hydrogen, and oxygen, and are characterised by so +powerful an affinity for ammonia that they are with difficulty obtained +free from that substance, and generally exist in the soil in combination +with it. They are all products of the decomposition of vegetable +matters in the soil, and are formed during their decay by a succession +of changes, which may be easily traced by observing the course of events +when a piece of wood or any other vegetable substance is exposed for a +length of time to air and moisture. It is then found gradually to +disintegrate with the evolution of carbonic acid, acquiring first a +brown and finally a black colour. At one particular stage of the process +it is converted into one or other of two substances, called humin and +ulmin, both insoluble in alkalies, and apparently identical with the +insoluble humus of the soil; but when the decomposition is more advanced +the products become soluble in alkalies, and then contain humic, ulmic, +and geic acids, and finally, by a still further progress, crenic and +apocrenic acids are formed as the result of an oxidation occurring at +certain periods of the decay. + +The roots and other vegetable debris remaining in the soil undergo a +similar series of changes, and form the humus, which is found only in +the surface soil, that is to say, in the portion which is now or has at +some previous period been occupied by plants, and the quantity of humus +contained in any soil is mainly dependent on the activity of vegetation +on it. Numerous analyses of humus compounds extracted from the soil have +been made, and have served to establish a number of minor differences in +the composition even of those to which the same name has been applied, +due manifestly to the fact that their production is the result of a +gradual decomposition, which renders it impossible to extract from the +soil one pure substance, but only a variable mixture of several, so +similar to one another in properties, that their separation is very +difficult, if not impossible. For this reason great discrepancies exist +in the statements made regarding them by different observers, but this +is a matter of comparatively small importance, as their exact +composition has no very direct bearing on agricultural questions, and it +will suffice to give the names and chemical formulæ of those which have +been analysed and described,-- + +Ulmic acid from long Frisian turf C_{40} H_{18} O_{16} +Humic acid from hard turf C_{40} H_{15} O_{15} +Humic acid from arable soil C_{40} H_{16} O_{16} +Humic acid from a pasture field C_{40} H_{14} O_{14} +Geic acid C_{40} H_{15} O_{17} +Apocrenic acid C_{48} H_{12} O_{24} +Crenic acid C_{24} H_{12} O_{16} + +It is only necessary to observe further, that these formulæ indicate a +close connection with woody fibre, and the continuous diminution of the +hydrogen and increase of oxygen shows that they must have been produced +by a gradually advancing decay. + +The earlier chemists and vegetable physiologists attributed to the humus +of the soil a much more important function than it is now believed to +possess. + +It was formerly considered to be the exclusive, or at least the chief +source of the organic constituents of plants, and by absorption through +the roots to yield to them the greater part of their nutriment. But +though this view has still some supporters, among whom Mulder is the +most distinguished, it is now generally admitted that humus is not a +_direct_ source of the organic constituents of plants, and is not +absorbed as such by their roots, although it is so _indirectly_, in as +far as the decomposition which it is constantly undergoing in the soil +yields carbonic acid, which can be absorbed. The older opinion is +refuted by many well-ascertained facts. As regards the exclusive origin +of the carbon of plants from humus, it is easy to see that this at least +cannot be true, for humus, as already stated, is itself derived solely +from the decomposition of vegetable and animal matters; and if the +plants on the earth's surface were to be supported by it alone, the +whole of their substance would have to return to the soil in the same +form, in order to supply the generation which succeeds them. But this is +very far from being the case, for the respiration of animals, the +combustion of fuel, and many other processes, are annually converting a +large quantity of these matters into carbonic acid; and if there were no +other source of carbon but the humus of the soil, the amount of +vegetable life would gradually diminish, and at length become entirely +extinct. Schleiden, who has discussed this subject very fully, has made +an approximative calculation of the total quantity of humus on the +earth's surface, and of the carbon annually converted into carbonic acid +by the respiration of man and animals, the combustion of wood for fuel, +and other minor processes; and he draws the conclusion that, if there +were no other source of carbon except humus, the quantity of that +substance existing in the soil would only support vegetation for a +period of sixty years. + +The particular phenomena of vegetation also afford abundant evidence +that humus cannot be the only source of carbon. Thus Boussingault has +shown that on the average of years, the crops cultivated on an acre of +land remove from it about one ton more organic matter than they receive +in the manure applied to them, although there is no corresponding +diminution in the quantity of humus contained in the soil. An instance +which leads still more unequivocally to the same conclusion is given by +Humboldt. He states that an acre of land, planted with bananas, yields +annually about 152,000 pounds weight of fruit, containing about 32,000 +pounds, or almost exactly 14 tons of carbon; and as this production goes +on during a period of twenty years, there must be withdrawn in that time +no less than 280 tons of carbon. But the soil on an acre of land weighs, +in round numbers, 1000 tons, and supposing it to contain 4 per cent of +humus, the total weight of carbon in it would amount to little more than +20 tons. + +It is obvious from these and many other analogous facts that humus +cannot be the only or even a considerable source of the carbon of +plants, although it is still contended by some chemists that it may be +absorbed to a small extent. But even this is at variance with many +well-known facts. For if humus were absorbed, it might be expected that +vegetation would be most luxuriant on soils containing abundance of that +substance, especially if it existed in a soluble and readily absorbable +form; but so far from this being the case, nothing is more certain than +that peat, in which these conditions are fulfilled, is positively +injurious to most plants. On the other hand, our daily experience +affords innumerable examples of plants growing luxuriantly in soils and +places where no humus exists. The sands of the sea-shore, and the most +barren rocks, have their vegetation, and the red-hot ashes which are +thrown out by active volcanoes are no sooner cool than a crop of plants +springs up on them. + +The conclusions to be drawn from these considerations have been further +confirmed by the direct experiments of different observers. Boussingault +sowed peas, weighing 15·60 grains, in a soil composed of a mixture of +sand and clay, which had been heated red-hot, and consequently contained +no humus, and after 99 days' growth, during which they had been watered +with distilled water, he found the crop to weigh 68·72 grains, so that +there had been a fourfold increase. Similar experiments have been made +by Prince Salm Horstmar, on oats and rape sown in a soil deprived of +organic matter by ignition, in which they grew readily, and arrived at +complete maturity. One oat straw attained a height of three feet, and +bore 78 grains; another bore 47; and a third 28--in all 153. These when +dried at 212° weighed 46·302 grains, and the straw 45·6 grains. The most +satisfactory experiments, however, are those of Weigman and Polstorf, +these observers having found that it was possible to obtain a +two-hundred-fold produce of barley in an entirely artificial soil, +provided care was taken to give it the _physical_ characters of a +fertile soil. They prepared a mixture of six parts of sand, two of +chalk, one of white bole, and one of wood charcoal; to which was added a +small quantity of felspar, previously fused with marble and some soluble +salts, so as to imitate as closely as possible the inorganic parts of a +soil, and in it they planted twelve barley pickles. The plants grew +luxuriantly, reaching a height of three feet, and each bearing nine +ears, containing 22 pickles. The grain of the twelve plants weighed 2040 +grains. + +These experiments show that plants can grow and produce seed when the +most scrupulous care is taken to deprive them of every trace of humus. +But Saussure has gone further, and shown that even when present, humus +is not absorbed. He allowed plants of the common bean and the Polygonum +Persicaria to grow in solutions of humate of potash, and found a very +trifling diminution in the quantity of humic acid present; but the value +of his experiments is invalidated by his having omitted to ascertain +whether the diminution of humic acid which he observed was really due +to absorption by the plant. This omission has been supplied by Weigman +and Polstorf. They grew plants of mint (Mentha undulata) and of +Polygonum Persicaria in solutions of humate of potash, and placed beside +the glass containing the plant, another perfectly similar, and +containing only the solution of humate of potash. The solution, which +contained in every 100 grains, 0·148 grains of solid matter, consisting +of humate of potash, etc. was found to become gradually paler, and at +the end of a month, during which time the plants had increased by 6-1/2 +inches, the quantity of solid matter in 100 grains had diminished to +0·132. But the solution contained in the other glass, and in which no +plant had grown, had diminished to 0·136, so that the absorption could +not have amounted to more than 0·004 grains for every 100 grains of +solution employed. This quantity is so small as to be within the limits +of error of experiment, and we are consequently entitled to draw the +conclusion that humus, even under the most favourable circumstances, is +not absorbed by plants. + +But though not directly capable of affording nutriment to plants, it +must not, on that account, be supposed that humus is altogether devoid +of importance, for it is constantly undergoing decomposition in the +soil, and thus becomes a source of carbonic acid which can be absorbed, +and, as we shall afterwards more particularly see, it exercises very +important functions in bringing the other constituents of the soil into +readily available forms of combination. + +It has been already observed that carbon, hydrogen, nitrogen, and +oxygen, cannot be absorbed by plants when uncombined, but only in the +forms of water, carbonic acid, ammonia, and nitric acid. It is scarcely +necessary to detail the grounds on which this conclusion has been +arrived at in regard to carbon and hydrogen, for practically it is of +little importance whether they can be absorbed or not, as the former is +rarely, the latter never, found uncombined in nature. Neither can there +be any doubt that water and carbonic acid are the only substances from +which these elements can be obtained. Every-day experience convinces us +that water is essential to vegetation; and Saussure, and other +observers, have shown that plants will not grow if they are deprived of +carbonic acid, and that they actually absorb that substance abundantly +from the atmosphere. The evidence for the non-absorption of oxygen lies +chiefly in the fact that plants obtain, in the form of water and +carbonic acid, a larger quantity of that element than they require, and +in place of absorbing, are constantly exhaling it. The form in which +nitrogen may be absorbed has given rise to much difference of opinion. +In the year 1779, Priestley commenced the examination of this subject, +and drew from his experiments the conclusion, that plants absorb the +nitrogen of the air. Saussure shortly afterwards examined the same +subject, and having found, that when grown in a confined space of air, +and watered with pure water, the nitrogen of the plants underwent no +increase, he inferred that they derived their entire supplies of that +element from ammonia, or the soluble nitrogenous constituents of the +soil or manure. Boussingault has since re-examined this question, and by +a most elaborate series of experiments, in which the utmost care was +taken to avoid every source of fallacy, he was led to the conclusion, +that when haricots, oats, lupins, and cresses were grown in calcined +pumice-stone, mixed with the ash of plants, and supplied with air +deprived of ammonia and nitric acid, their nitrogen underwent no +increase. It has been objected to these experiments, that the plants +being confined in a limited bulk of air, were placed in an unnatural +condition, and Ville has recently repeated them with a current of air +passing through the apparatus, and found a slight increase in the +nitrogen, due, as he thinks, to direct absorption. It is much more +probable, however, that it depends on small quantities of ammonia or +nitric acid which had not been completely removed from the air by the +means employed for that purpose, for nothing is more difficult than the +complete abstraction of these substances, and as the gain of nitrogen +was only 0·8 grains, while 60,000 gallons of air, and 13 of water, were +employed in the experiment, which lasted for a considerable time, it is +reasonable to suppose that a sufficient quantity may have remained to +produce this trifling increase. + +While these experiments show that plants maintain only a languid +existence when grown in air deprived of ammonia and nitric acid, and +hence, that the direct absorption of nitrogen, if it occur at all, must +do so to a very small extent, the addition of a very minute quantity of +the former substance immediately produces an active vegetation and rapid +increase in size of the plants. Among the most striking proofs of this +are the experiments of Wolff, made by growing barley and vetches in a +soil calcined so as to destroy organic matters, and then mixed with +small quantities of different compounds of ammonia. He found that when +the produce from the calcined soil was represented by 100, that from the +different ammoniacal salts was-- + + Barley. Vetches. + +Muriate of Ammonia 257·2 176·4 +Carbonate of Ammonia 123·6 173·8 +Sulphate of Ammonia 203·6 125·2 + +These experiments not only prove that ammonia can be absorbed, but they +also indirectly confirm the statement already made, that humus is not +necessary; for in some instances the produce was higher than that +obtained from the uncalcined soil with the same manures, although it +contained four per cent of humus. + +On such experiments Liebig rests his opinion that ammonia is the +exclusive source of the nitrogen of plants, and although he has recently +admitted that it may be replaced by nitric acid, it is obvious that he +considers this a rare and exceptional occurrence. The evidence, however, +for the absorption of nitric acid appears to rest on as good grounds as +that of ammonia, for experience has shown that nitrate of soda acts +powerfully as a manure, and its effect must be due to the nitric acid, +and not to the soda, for the other compounds of that alkali have no such +effect. Wolff has illustrated this point by a series of experiments on +the sunflower, of which we shall quote one. He took two seeds of that +plant, and sowed them on the 10th May, in a soil composed of calcined +sand, mixed with a small quantity of the ash of plants, and added at +intervals during the progress of the experiment, a quantity of nitrate +of potash, amounting in all to 17·13 grains. The plants were watered +with distilled water, containing carbonic acid in solution, and the pot +in which they grew was protected from rain and dew by a glass cover. On +the 19th August one of the plants had attained a height of above 28 +inches, and had nine fine leaves and a flower-bud; the other was about +20 inches high, and had ten leaves. On the 22d August, one of the plants +having been accidentally injured, the experiment was terminated. The +plants, which contained 103·16 grains of dry matter, were then carefully +analysed, and the quantity of nitrogen contained in the soil after the +experiment and in the seed was determined. + + Grains. +Nitrogen in the dry plants 1·737 } + " remaining in the soil 0·697 } 2·434 + + " in the nitrate of potash 2·370 } + " in the seeds 0·029 } 2·399 + ------ + Difference 0·035 + +Hence, the nitrogen contained in the plants must, in this instance, have +been obtained entirely from the nitrate of potash, for the quantity +contained in it and in the seeds is exactly equal to that in the plants +and the soil, the difference of 0·03 grains being so small that it may +be safely attributed to the errors inseparable from such experiments. +For the sake of comparison, an exactly similar experiment was made on +two seeds grown without nitrate of potash, and in this instance, after +an equally long period of growth, the largest plant had only attained a +height of 7·5 inches, and had three small pale and imperfectly developed +leaves. They contained only 0·033 grains of nitrogen, while the seeds +contained 0·032--indicating that, under these circumstances, there was +no increase in the quantity of that element. + +But, independently of these experimental results, it may be inferred +from general considerations, that nitric acid must be one of the sources +from which plants derive their nitrogen. It has been already stated, +that the humus contained in the soil consists of the remains of decayed +plants, and there is every reason to suppose that the primeval soil +contained no organic matters, and that the first generation of plants +must have derived the whole of their nitrogen from, the atmosphere. If, +therefore, it be assumed that ammonia is the only source of the +nitrogen of plants, it would follow, that as that substance cannot be +produced by the direct union of its elements, the quantity of ammonia in +the air could only remain undiminished in the event of the whole of the +nitrogen of decaying plants returning into that form. But this is +certainly not the case, for every time a vegetable substance is burned, +part of its nitrogen is liberated in the free state, and in certain +conditions of putrefaction, nitric acid is produced. Now, if ammonia be +the only form in which nitrogen is absorbed, there must be a gradual +diminution of the quantity contained in the air; and further, there must +either be some continuous source of supply by which its quantity is +maintained, or there must be some other substance capable of affording +nitrogen in a form fitted for the maintenance of plant life. As regards +the first alternative, it must be stated that we know of no source other +than the decomposition of plants from which ammonia can be derived, and +we are therefore compelled to adopt the second alternative, and to admit +that there must be some other source of nitrogen, and it cannot be +doubted, from what has been already stated, that it is from nitric acid +only that it can be obtained. + +It must be admitted, then, that carbonic acid, ammonia, nitric acid, and +water, are the great organic foods of plants. But while they have +afforded to them an inexhaustible supply of the last, the quantity of +the other three available for food are limited, and insufficient to +sustain their life for a prolonged period. It has been shown by +Chevandrier, that an acre of land under beech wood accumulates annually +about 1650 lb. of carbon. Now, the column of air resting upon an acre of +land contains only about 15,500 lb. of carbon, and the soil may be +estimated to contain 1 per cent., or 22,400 lb. per acre, and the whole +of this carbon would therefore be removed, both from the air and the +soil, in the course of little more than 23 years. But it is a familiar +fact, that plants continue to grow with undiminished luxuriance year +after year in the same soil, and they do so because neither their carbon +nor their nitrogen are permanently absorbed; they are there only for a +period, and when the plant has finished its functions, and dies, they +sooner or later return into their original state. Either the plant +decays, in which case its carbon and nitrogen pass more or less rapidly +into their original state, or it becomes the food of animals, and by the +processes of respiration and secretion, the same change is indirectly +effected. In this way a sort of balance is sustained; the carbon, which +at one moment is absorbed by the plant, passes in the next into the +tissues of the animal, only to be again expired in that state in which +it is fitted to commence again its round of changes. + +But while there is thus a continuous circulation of these constituents +through both plants and animals, there are various changes which tend to +liberate in the free state a certain quantity both of the carbon and +nitrogen of plants, and these being thus removed from the sphere of +organic life, there would be a gradual diminution in the amount of +vegetation at the earth's surface, unless this loss were counterbalanced +by some corresponding source of gain. In regard to carbonic acid the +most important source is volcanic action, but the loss of nitrogen, +which is far more important and considerable, is restored by the direct +combination of its elements. The formation of nitric acid during thunder +storms has been long familiar; but it would appear from the recent +experiments of Clöez, which, should they be confirmed by farther +enquiry, will be of much importance, that this compound is also +produced without electrical action when air is passed over certain +porous substances, saturated with alkaline and earthy compounds. +Fragments of calcined brick and pumice stone were saturated with +solution of carbonate of potash, with carbonates of lime and magnesia +and other mixtures, and a current of air freed from nitric acid and +ammonia passed over them for a long period, at the end of which notable +quantities of nitric acid were detected. + +_Source of the Inorganic Constituents of Plants._--The inorganic +constituents of plants being all fixed substances, it is sufficiently +obvious that they can only be obtained from the soil, which, as we shall +afterwards see, contains all of them in greater or less abundance, and +has always been admitted to be the only substance capable of supplying +them. The older chemists and physiologists, however, attributed no +importance to these substances, and from the small quantities in which +they are found in plants, imagined that they were there merely +accidental impurities absorbed from the soil along with the humus, which +was at that time considered to be their organic food. This opinion, +sufficiently disproved by the constant occurrence of the same substances +in nearly the same proportions, in the ash of each individual plant, has +been further refuted by the experiments of Prince Salm Horstmar, who has +established their importance to vegetation, by experiments upon oats +grown on artificial soils, in each of which one inorganic constituent +was omitted. He found that, without silica, the grain vegetated, but +remained small, pale in colour, and so weak as to be incapable of +supporting itself; without lime, it died when it had produced its second +leaf; without potash and soda, it grew only to the height of three +inches; without magnesia, it was weak and incapable of supporting +itself; without phosphoric acid, weak but upright; and without sulphuric +acid, though normal in form, the plant was feeble, and produced no +fruit. + +_Manner in which the Constituents of Plants are absorbed._--Having +treated of the sources of the elements of plants, it is necessary to +direct attention to the mode in which they enter their system. + +_Water._--The absorption of water by plants takes place in great +abundance, and is connected with many of the most important phenomena of +vegetation. It is principally absorbed by the roots, and passes into the +tissues of the plant, where a part of it is decomposed, and goes to the +formation of certain of its organic compounds; while by far the larger +quantity, in place of remaining in it, is again exhaled by the leaves. +The extent to which this takes place is very large. Hales found that a +sunflower exhaled in twelve hours about 1 lb. 5 oz. of water, but this +quantity was liable to considerable variation, being greater in dry, and +less in wet weather, and much diminished during the night. Saussure made +similar experiments, and observed that the quantity of water exhaled by +a sunflower amounted to about 220 lb. in four months. The exhalation of +plants has recently been examined with great accuracy by Lawes. His +experiments were made by planting single plants of wheat, barley, beans, +peas, and clover, in large glass jars capable of holding about 42 lb. of +soil, and covered with glass plates, furnished with a hole in the centre +for the passage of the stem of the plant. Water was supplied to the soil +at certain intervals, and the jars were carefully weighed. The result of +the experiments, continued during a period of 172 days, is given in the +following table, which shows the total quantity of water exhaled in +grains:-- + +Wheat 113,527 +Barley 120,025 +Beans 112,231 +Peas 109,082 +Clover, cut 28th June 55,093 + +It further appears, that the exhalation is not uniform, but increases +during the active growth of the plant, and diminishes again when that +period is passed. These variations are shown by the subjoined tables, of +which the first gives the total exhalation, and the second the average +daily loss of water during certain periods. + + +TABLE I.--_Showing the Number of Grains of Water given off by the Plants +during stated divisional Periods of their Growth._ + ++-----------+--------+--------+--------+--------+--------+--------+---------+ +|Description|9 Days. |31 Days.|27 Days.|34 Days.|30 Days.|14 Days.| 27 Days.| +| +--------+--------+--------+--------+--------+--------+---------+ +|of Plant. | From |From |From |From |From |From | From | +| | Mar. 19|Mar. 28 |Apr. 28 |May 25 |June 28 |July 28 | Aug. 11 | +| | to |to |to |to |to |to | to | +| |Mar. 28.|Apr. 28.|May 25. |June 28.|July 28.|Aug. 11.| Sept. 7.| ++-----------+--------+--------+--------+--------+--------+--------+---------+ +|Wheat | 129 | 1268 | 4,385 | 40,030 | 46,060 | 15,420 | 6235 | +|Barley | 129 | 1867 | 12,029 | 37,480 | 45,060 | 17,046 | 6414 | +|Beans | 88 | 1854 | 4,846 | 30,110 | 58,950 | 12,626 | 3657 | +|Pease | 101 | 1332 | 2,873 | 36,715 | 62,780 | 5,281 | ... | +|Clover | 400 | 1645 | 2,948 | 50,100 | ... | ... | ... | ++-----------+--------+--------+--------+--------+--------+--------+---------+ + + +TABLE II.--_Showing the average daily Loss of Water (in Grains) by the +Plants, within several stated divisional Periods of their Growth._ + ++------------+--------+--------+--------+--------+--------+--------+--------+ +| Description|9 Days. |31 Days.|27 Days.|34 Days.|30 Days.|14 Days.|27 Days.| +| +--------+--------+--------+--------+--------+--------+--------+ +| of Plant. | From | From | From | From | From | From | From | +| |Mar. 19 |Mar. 28 |Apr. 28 |May 25 |June 28 |July 28 |Aug. 11 | +| | to | to | to | to | to | to | to | +| |Mar. 28.|Apr. 28.|May 25. |June 28.|July 28.|Aug. 11.|Sept. 7.| ++------------+--------+--------+--------+--------+--------+--------+--------+ +| Wheat | 14·3 | 40·9 | 162·4 | 1177·4 | 1535·3 | 1101·4 | 230·9 | +| Barley | 14·3 | 60·2 | 445·5 | 1102·3 | 1502·0 | 1217·6 | 237·5 | +| Beans | 9·7 | 59·8 | 179·5 | 885·6 | 1965·0 | 901·8 | 135·4 | +| Peas | 11·2 | 42·9 | 106·4 | 1079·8 | 2092·7 | 377·2 | ... | +| Clover | 44·4 | 53·0 | 109·2 | 1473·5 | ... | ... | ... | ++------------+--------+--------+--------+--------+--------+--------+--------+ + +Similar experiments were made with the same plants in soils to which +certain manures had been added, and with results generally similar. +Calculating from these experiments, we are led to the apparently +anomalous conclusion that the quantity of water exhaled by the plants +growing on an acre of land greatly exceeds the annual fall of rain; +although it is obvious that of all the rain which falls, only a small +proportion can be absorbed by the plants growing on the soil, for a +large quantity is carried off by the rivers, and never reaches their +roots. It has been calculated, for instance, that the Thames carries off +in this way at least one-third of the annual rain that falls in the +district watered by it, and the Rhine nearly four-fifths. Of course this +large exhalation must depend on the repeated absorption of the same +quantity of water, which, after being exhaled, is again deposited on the +soil in the form of dew, and passes repeatedly through the plant. This +constant percolation of water is of immense importance to the plant, as +it forms the channel through which some of its other constituents are +carried to it. + +_Carbonic Acid._--While the larger part of the water which a plant +requires is absorbed by its roots, the reverse is the case with carbonic +acid. A certain proportion no doubt is carried up through the roots by +the water, which always contains a quantity of that gas in solution, but +by far the larger proportion is directly absorbed from the air by the +leaves. A simple experiment of Boussingault's illustrates this +absorption very strikingly. He took a large glass globe having three +apertures, through one of which he introduced the branch of a vine, with +twenty leaves on it. With one of the side apertures a tube was +connected, by means of which the air could be drawn slowly through the +globe, and into an apparatus in which its carbonic acid was accurately +determined. He found, in this way, that while the air which entered the +globe contained 0·0004 of carbonic acid, that which escaped contained +only 0·0001, so that three-fourths of the carbonic acid had been +absorbed. + +_Ammonia and Nitric Acid._--Little is known regarding the mode in which +these substances enter the plant. It is usually supposed that they are +entirely absorbed by the roots, and no doubt the greater proportion is +taken up in this way, but it is very probable that they may also be +absorbed by the leaves, at least the addition of ammonia to the air in +which plants are grown, materially accelerates vegetation. It is +probable, however, that the rain carries down the ammonia to the roots, +and there is no doubt that that derived from the decomposition of the +nitrogenous matters in the soil is so absorbed. + +_Inorganic Constituents._--The inorganic constituents of course are +entirely absorbed by the roots; and it is as a solvent for them that the +large quantity of water continually passing through the plants is so +important. They exist in the soil in particular states of combination, +in which they are scarcely soluble in water. But their solubility is +increased by the presence of carbonic acid contained in the water, and +which causes it to dissolve, to some extent, substances otherwise +insoluble. It is in this way that lime, which occurs in the soil +principally as the insoluble carbonate, is dissolved and absorbed. And +phosphate of lime is also taken up by water containing carbonic acid, or +even common salt in solution. The amount of solubility produced by these +substances is extremely small; but it is sufficient for the purpose of +supplying to the plant as much of its mineral constituents as are +required, for the quantity of water which, as we have already seen, +passes through a plant is very large when compared with the amount of +inorganic matters absorbed. It has been shown by Lawes and Gilbert, that +about 2000 grains of water pass through a plant for every grain of +mineral matter fixed in it, so that there is no difficulty in +understanding how the absorption takes place. + +It is worthy of notice, however, that the absorption of the elements of +plants takes place even though they may not be in solution in the soil, +the roots apparently possessing the power of directly acting on and +dissolving insoluble matters; but a distinction must be drawn between +this and the view entertained by Jethro Tull, who supposed that they +might be absorbed in the solid state, provided they were reduced to a +state of sufficient comminution. It is now no longer doubted that, +whatever action the roots may exert, the constituents of the plant must +be in solution before they can pass into it--experiment having +distinctly shown that the spongioles or apertures through which this +absorption takes place are too minute to admit even the smallest solid +particle. + + + + +CHAPTER II. + +THE PROXIMATE CONSTITUENTS OF PLANTS. + + +The substances absorbed by the plant, which are of simple composition, +and contain only two elements, are elaborated within it, and converted +into the many complicated compounds of which its mass is composed. Some +of these, as, for example, the colouring matters of madder and indigo, +the narcotic principle of the poppy, &c., are confined to a single +species, or small group of plants, while others are found in all plants, +and form the main bulk of their tissues. The latter are the only +substances which claim notice in a treatise like the present. They have +been divided into three great classes, of widely different properties, +composition, and functions. + +_1st. The Saccharine and Amylaceous Constituents._--These substances are +compounds of carbon, hydrogen, and oxygen, and all possess a certain +degree of similarity in composition, the quantities of hydrogen and +oxygen they contain being always in the proportion required to form +water, so that they may be considered as compounds of carbon and water; +not that it can be asserted that they actually do contain water, as +such, for of that there is no evidence, but only that its elements are +present in the proportion to form it. + +_Cellulose._--This substance forms the fundamental part of all plants. +It is the principal constituent of woody fibre, and is found in a state +of purity in the fibre of cotton and flax, and in the pith of plants; +but in wood it is generally contaminated with another substance, which +has received the name incrusting matter, because it is deposited in and +around the cells of which the plant is in part composed. Cellulose is +insoluble in all menstrua, but, when boiled for a long time with +sulphuric acid, is converted into a substance called dextrine. Cellulose +consists of-- + + From pith of Elder-tree. Spongioles of roots. + +Carbon 43·37 43·00 +Hydrogen 6·04 6·18 +Oxygen 50·59 50·82 + ------- ------- + 100·00 100·00 + +It is represented chemically by the formula, C_{24}H_{21}O_{21}, which +shows it to be a compound of 24 atoms of carbon with 21 of hydrogen and +21 of oxygen. + +_Incrusting matter._--Large quantities of this substance enter into the +composition of all plants. Of its chemical nature little is known, as it +cannot be obtained separate from cellulose, but it is analogous to that +substance in its composition, and probably contains hydrogen and oxygen +in the proportion to form water. + +_Starch._--Starch is one of the most abundant constituents of plants, +and is found in most seeds, as those of the cereals and the leguminous +plants; in the tubers of the potatoe, the bulbs of tulips, &c. &c. It is +obtained by placing a quantity of wheat flour in a bag, and kneading it +under a gentle stream of water. When the water is allowed to stand, it +deposits the starch as a fine white powder, which, when examined by the +microscope, is found to be composed of minute grains, formed of +concentric layers deposited on one another. These grains vary +considerably in size and structure in different plants; but in the same +plant they are generally so much alike as to admit of their recognition +by a practised observer. They were formerly believed to be composed of +an external coating of a substance insoluble in water, and containing in +their interior a soluble kernel; but this opinion has been refuted, and +distinct evidence been brought to show that the exterior and interior of +the globules are identical in chemical properties. Starch is insoluble +in cold water, but by boiling, it dissolves, forming a thick paste. By +long continued boiling with water containing a small quantity of acid, +it is completely dissolved and converted into dextrine, and eventually +into sugar. The same change is produced by the action of fermenting +substances, such as the extract of malt; when heated in the dry state to +a temperature of about 390 Fahr., it becomes soluble in cold water. It +is distinguished by giving a brilliant blue compound with iodine. Starch +contains-- + + Carbon 44·47 + Hydrogen 6·28 + Oxygen 49·25 + ------ + 100·00 + +and its composition is represented by the formula C_{12}H_{10}O_{10}, so +that it differs but little from cellulose in composition, although its +chemical functions in the plant are extremely different. It is connected +with some of the most important changes which occur in the growing +plants, and by a series of remarkable transformations is converted into +sugar and other important compounds. + +_Lichen Starch_ is found in most species of lichens, and is +distinguished from common starch by producing a green colour with +iodine. Its composition is the same as that of ordinary starch. + +_Inuline._--The species of starch to which this name is given is +characterised by its dissolving in boiling water, and giving a white +pulverulent deposit in cooling. It is found in the tuber of the dahlia, +in the dandelion, and some other plants. Its composition is identical +with that of cellulose, and its formula is C_{24}H_{21}O_{21}. + +_Gum_ is excreted from various plants as a thick fluid, which dries up +into transparent masses. Its composition is identical with that of +starch. It dissolves readily in cold water, and is converted into sugar +by long continued boiling with acids. Its properties are best marked in +gum arabic, which is obtained from various species of acacia; that from +other plants differs to some extent, although its chemical composition +is the same. + +_Dextrine._--When starch is exposed to a heat of about 400°, or when +treated with sulphuric acid, or with a substance extracted from malt +called _diastase_, it is converted into dextrine. It may also be +obtained from cellulose by a similar treatment. The dextrine so obtained +has the same composition as the starch from which it is produced, but +its properties more nearly resemble those of gum. It plays a very +important part in the process of germination, and may be converted into +sugar on the one hand, and apparently also into starch on the other. + +_Sugar._--Under this name are included four or five distinct substances, +of which the most important are, cane sugar, grape sugar, and the +uncrystallisable sugar found in many plants. + +_Cane Sugar._--This variety of sugar, as its name implies, is found most +abundantly in the sugar cane, but it occurs also in the maple, +beet-root, and various species of palms, from all of which it is +extracted on the large scale. It is extremely soluble in water, and can +be obtained in large transparent prismatic crystals, as in common +sugar-candy. It swells up, and is converted into a brown substance +called caramel, when heated, and by contact with fermenting substances, +yields alcohol and carbonic acid. It contains-- + + Carbon 42·22 + Hydrogen 6·60 + Oxygen 51·18 + ------ + 100·00 + +and its chemical formula is C_{12}H_{11}O_{11}. + +_Grape Sugar_ is met with in the grape, and most other fruits, as well +as in honey. It is produced artificially when starch is boiled for a +long time with sulphuric acid, or treated with a large quantity of +diastase. It is less soluble in water than cane sugar, and crystallises +in small round grains. Its composition, when dried at 284°, is-- + + Carbon 40·00 + Hydrogen 6·66 + Oxygen 53·34 + ------ + 100·00 + +and its formula is C_{12}H_{12}O_{12}; but when crystallised it contains +two equivalents of water, and is then represented by the formula +C_{12}H_{12}O_{12} + 2H_{2}O. + +The uncrystallisable sugar of plants is closely allied to grape sugar, +and, so far as at present known, has the same composition, although, +from the difficulty of obtaining it quite free from crystallised sugar, +this is still uncertain. + +_Mucilage_ is the name applied to the substance existing in linseed, +and in many other seeds, and which communicates to them the property of +swelling up and becoming gelatinous when treated with water. It is found +in a state of considerable purity in gum tragacanth and some other gums. +Its composition is not known with absolute certainty, but it is either +C_{24}H_{19}O_{19}, or C_{12}H_{10}O_{10}; and in the latter case it +must be identical with starch and gum. + +It will be observed that all the substances belonging to this class are +very closely related in chemical composition, some of them, as starch +and gum, though easily distinguished by their properties, being +identical in constitution, while others only differ in the quantity of +water, or of its elements which they contain. In fact, they may all be +considered as compounds of carbon and water, and their relations are, +perhaps, more distinctly seen when their formulæ are written so as to +show this, as is done in the following table, in the second column of +which those containing twelve equivalents of carbon are doubled, so as +to make them comparable with cellulose:-- + + Water. +Grape sugar, C_{12}H_{12}O_{12} C_{24}H_{24}O_{24} C_{24} + 24 +Cane sugar, C_{12}H_{11}O_{11} C_{24}H_{22}O_{22} C_{24} + 22 +Cellulose, C_{24}H_{21}O_{21} C_{24}H_{21}O_{21} C_{24} + 21 +Inuline, C_{24}H_{21}O_{21} C_{24}H_{21}O_{21} C_{24} + 21 +Starch, C_{12}H_{10}O_{10} C_{24}H_{20}O_{20} C_{24} + 20 +Dextrine, C_{12}H_{10}O_{10} C_{24}H_{20}O_{20} C_{24} + 20 +Gum, C_{12}H_{10}O_{10} C_{24}H_{20}O_{20} C_{24} + 20 +Mucilage, C_{12}H_{10}O_{10} C_{24}H_{20}O_{20} C_{24} + 20 + +The relation between these substances being so close, it is not +difficult to understand how one may be converted into another by the +addition or subtraction of water. Thus, cellulose has only to absorb an +equivalent of water to become grape sugar, or to lose an equivalent in +order to be converted into starch, and we shall afterwards see that +such changes do actually occur in the plant during the process of +germination. + +_Pectine and Pectic Acid._--These substances are met with in many fruits +and roots, as, for instance, in the apple, the carrot, and the turnip. +They differ from the starch group in containing more oxygen than is +required to form water along with their hydrogen; but their exact +composition is still uncertain, and they undergo numerous changes during +the ripening of the fruit. + +_2d. Oily or Fatty Matters._--The oily constituents of plants form a +rather extensive group of substances all closely allied, but +distinguished by minor differences in properties and constitution. Some +of them are very widely distributed throughout the vegetable kingdom, +but others are almost peculiar to individual plants. They are all +compounds of carbon, hydrogen, and oxygen, and are at once distinguished +from the preceding class, by containing much less oxygen than is +required to form water with their hydrogen. The principal constituents +of the fatty matters and oils of plants are three substances, called +stearine, margarine, and oleine, the two former solids, the latter a +fluid; and they rarely, if ever, occur alone, but are mixed together in +variable proportions, and the fluidity of the oils is due principally to +the quantity of the last which they contain. If olive oil be exposed to +cold, it is seen to become partially solid; and if it be then pressed, a +fluid flows out, and a crystalline substance remains; the former is +oleine, though not absolutely pure, and the latter margarine. The +perfect separation of these substances involves a variety of troublesome +chemical processes; and when it has been effected, it is found that each +of them is a compound of a peculiar acid, with another substance having +a sweet taste, and which has received the name of glycerine, or the +sweet principle of oil. Glycerine, as it exists in the fats, appears to +be a compound of C_{3}H_{2}O, and its properties are the same from +whatever source it is obtained. The acids separated from it are known by +the names of margaric, stearic, and oleic acids. + +_Margaric Acid_ is best obtained pure by boiling olive oil with an +alkali until it is saponified, and decomposing the soap with an acid, +expressing the margaric acid, which separates, and crystallising it from +alcohol. It is a white crystalline fusible solid, insoluble in water, +but soluble in alcohol and in solutions of the alkalies. Its composition +is-- + + Carbon 75·56 + Hydrogen 12·59 + Oxygen 11·85 + ------ + 100·00 + +and its formula C_{34}H_{34}O_{4}. + +_Stearic Acid._--Although this acid exists in many plants, it is most +conveniently extracted from lard. It is a crystalline solid less fusible +than margaric acid, but closely resembling it in its other properties. +Its formula is C_{36}H_{36}O_{4}. + +_Oleic Acid._--Under this name two different substances appear to be +included. It has been applied generally to the fluid acids of all oils, +while it would appear that the drying and non-drying oils actually +contain substances of different composition. The acid extracted from +olive oil appears to have the formula C_{36}H_{34}O_{4}, while that from +linseed oil is C_{46}H_{38}O_{6}, but this is still doubtful. + +Other fatty acids have been detected in palm oil, cocoa-nut oil, &c. +&c., which so closely resemble margaric and stearic acids as to be +easily confounded with them. Though presenting many points of interest, +it is unnecessary to describe them in detail here. + +_Wax_ is a substance closely allied to the oils. It consists of two +substances, cerine and myricine, which are separated from one another by +boiling alcohol, in which the former is more soluble. They are extremely +complex in composition, the former consisting principally of an acid +similar to the fatty acids, called cerotic acid, and containing +C_{54}H_{54}O_{4}. The latter has the formula C_{92}H_{92}O_{4}. The wax +found in the leaves of the lilac and other plants appears to consist of +myricine, while that extracted from the sugar-cane is said to be +different, and to have the formula C_{48}H_{50}O_{2}. It is probable +that other plants contain different sorts of wax, but their +investigation is still so incomplete, that nothing definite can be said +regarding them. Wax and fats appear to be produced in the plant from +starch and sugar; at least it is unquestionable that the bee is capable +of producing the former from sugar, and we shall afterwards see that a +similar change is most probably produced in the plant. The fatty matters +contained in animals are identical with those of plants. + +_3d. Nitrogenous or Albuminous Constituents of Plants and Animals._--The +nitrogenous constituents of plants and animals are so closely allied, +both in properties and composition, that they may be most advantageously +considered together. + +_Albumen._--Vegetable albumen is found dissolved in the juices of most +plants, and is abundant in that of the potato, the turnip, and wheat. In +these juices it exists in a soluble state, but when its solution is +heated to about 150°, it coagulates into a flocky insoluble substance. +It is also thrown down by acids and alcohol. Coagulated albumen is +soluble in alkalies and in nitric acid. Animal albumen exists in the +white of eggs, the serum of blood, and the juice of flesh; and from all +these sources is scarcely distinguishable in its properties from +vegetable albumen. + +It is a substance of very complicated composition, and chemists are not +agreed as to the formula by which its constitution is to be expressed, a +difficulty which occurs also with most of the other nitrogenous +compounds. The results of the analyses of albumen from different sources +are however quite identical, as may be seen from those subjoined-- + + From From From From + Wheat. Potatoes. Blood. White of Egg. +Carbon 53·7 53·1 53·4 53·0 +Hydrogen 7·1 7·2 7·0 7·1 +Nitrogen 15·6 ... 15·5 15·6 +Oxygen } { ... 22·1 22·9 +Sulphur } 23·6 { 0·97 1·6 1·1 +Phosphorus } { ... 0·4 0·3 + ----- ----- ----- + 100·0 100·0 100·0 + +Closely allied to vegetable albumen is the substance known by the name +of _glutin_, which is obtained by boiling the gluten of wheat with +alcohol. It appears to be a sort of coagulated albumen, with which its +composition completely agrees. + +_Vegetable Fibrine._--If a quantity of wheat flour be tied up in a piece +of cloth, and kneaded for some time under water, the starch it contains +is gradually washed out, and there remains a quantity of a glutinous +substance called gluten. When this is boiled with alcohol, the _glutin_ +above referred to is extracted, and vegetable fibrine is left. It +dissolves in dilute potash, and on the addition of acetic acid is +deposited in a pure state. Treated with hydrochloric acid, diluted with +ten times its weight of water, it swells up into a jelly-like mass. +When boiled or preserved for a long time under water, it cannot be +distinguished from coagulated albumen. + +_Animal Fibrine_ exists in the blood and the muscles, and agrees in all +its characters and composition with vegetable fibrine, as is shown by +the subjoined analyses-- + + Wheat Flour. Blood. Flesh. +Carbon 53·1 52·5 53·3 +Hydrogen 7·0 6·9 7·1 +Nitrogen 15·6 15·5 15·3 +Oxygen 23·2 24·0 23·1 +Sulphur 1·1 1·1 1·2 + ----- ----- ----- + 100·0 100·0 100·0 + +_Caseine._--Vegetable caseine exists abundantly in most plants, +especially in the seeds, and remains in the juice after albumen has been +precipitated by heat, from which it may be separated in flocks by the +addition of an acid. It has been obtained for chemical examination, +principally from peas and beans, and from the almond and oats. When +prepared from the pea it has been called _legumine,_ from almonds +_emulsine_, and from oats _avenine_; but they are all three identical in +their properties, although formerly believed to be different, and +distinguished by these names. Vegetable caseine is best obtained by +treating peas or beans with hot water, and straining the fluid. On +standing, the starch held in suspension is deposited, and the caseine is +retained in solution in the alkaline fluid; by the addition of an acid +it is precipitated as a thick curd. Caseine is insoluble in water, but +dissolves readily in alkalies; its solution is not coagulated by heat, +but, on evaporation, becomes covered with a thin pellicle, which is +renewed as often as it is removed. + +_Animal Caseine_ is the principal constituent of milk, and is obtained +by the cautious addition of an acid to skimmed milk, by which it is +precipitated as a thick white curd. It is also obtained by the use of +rennet, and the process of curding milk is simply the coagulation of its +caseine. It is soluble in alkalies, and precipitated from its solution +by acids, and in all other respects agrees with vegetable caseine. + +The composition of animal caseine has been well ascertained, but +considerable doubt still exists as to that of vegetable caseine, owing +to the difficulty of obtaining it absolutely pure. The analyses of +different chemists give rather discordant results, but we have given +those which appear most trustworthy-- + + From Peas. + Carbon 50·6 50·7 + Hydrogen 6·8 6·6 + Nitrogen 16·5 15·8 + Oxygen 25·6 23·8 + Sulphur 0·5 0·8 + Phosphorus ... 2·3 + ----- ----- + 100·0 100·0 + +Other results differ considerably from these, and some observers have +even obtained as much as eighteen per cent of nitrogen and fifty-three +of carbon. + +The composition of animal caseine differs from this principally in the +amount of carbon. Its composition is-- + + Carbon 53·6 + Hydrogen 7·1 + Nitrogen 15·8 + Oxygen 22·5 + Sulphur 1·0 + ----- + 100·0 + +The most cursory examination of these analytical numbers is sufficient +to show that a very close relation subsists between the different +substances just described. Indeed, with the exception of vegetable +caseine, they may be said all to present the same composition; and, as +already mentioned, there are analyses of it which would class it +completely with the others. While, however, the quantities of carbon, +hydrogen, nitrogen, and oxygen are the same, differences exist in the +sulphur and phosphorus they contain, and which, though very small in +quantity, are indubitably essential to them. Much importance has been +attributed to these constituents by various chemists, and especially by +Mulder, who has endeavoured to make out that all the albuminous +substances are compounds of a substance to which he has given the name +of _proteine_, with different quantities of sulphur and phosphorus. The +composition of proteine, according to his newest experiments, is-- + + Carbon 54·0 + Hydrogen 7·1 + Nitrogen 16·0 + Oxygen 21·4 + Sulphur 1·5 + ----- + 100·0 + +and is exactly the same from whatever albuminous compound it is +obtained. Although the importance of proteine is probably not so great +as Mulder supposed, it affords an important illustration of the close +similarity of the different substances from which it is obtained, the +more especially as there is every reason to believe that the different +albuminous compounds are capable of changing into one another, just as +starch and sugar are mutually convertible; and the possibility of this +change throws much light on many of the phenomena of nutrition in plants +and animals. Indeed, it would seem probable that these compounds are +formed from their elements by plants only, and are merely assimilated by +animals to produce the nitrogenous constituents they contain. + +_Diastase_ is the name applied to a substance existing in malt, and +obtained by macerating that substance with cold water, and adding a +quantity of alcohol to the fluid, when the diastase is immediately +precipitated in white flocks. It is produced during the malting process, +and is not found in the unmalted barley. Its chemical composition is +unknown, but it is nitrogenous, and is believed to be produced by the +decomposition of gluten. If a very small quantity of diastase be mixed +with starch suspended in hot water, the starch is found gradually to +dissolve, and to pass first into the state of dextrine, then into that +of sugar. The change thus effected takes place also in a precisely +similar manner in the plant, diastase being produced during the process +of germination of all seeds and tubers, for the purpose of effecting +this change, and to fulfil other functions less understood, but no doubt +equally important. Diastase is found in the seeds only during the period +when the starch they contain is passing into sugar; as soon as that +change has taken place, its function is ended, and it disappears. + + + + +CHAPTER III. + +THE CHANGES WHICH TAKE PLACE IN THE FOOD OF PLANTS DURING THEIR GROWTH. + + +The simple compounds which the plant absorbs from the atmosphere and +soil are elaborated within its system, and converted into the various +complex substances of which its tissues are composed, by a series of +changes, the details of which are still in some respects imperfectly +known, although their general nature is sufficiently well understood. +They may be best rendered intelligible by reference, in the first +instance, to the changes occurring during germination, when the young +plant is nourished by a supply of food stored up in the seed, in +sufficient quantity to maintain its existence until the organs by which +it is afterwards to draw its nutriment from the air and soil are +sufficiently developed to serve that purpose. + +_Changes occurring during Germination._--When a seed is placed in the +soil under favourable circumstances, it becomes the seat of an important +and remarkable series of chemical changes, which result in the +production of the young plant. Experiment and observation have shown +that heat, moisture, and air, are necessary to the production of these +changes, and though probably not absolutely essential, the absence of +light is favourable in the early stages. The temperature required for +germination varies greatly in different seeds, some germinating readily +at a few degrees above the freezing point, and others requiring a +tolerably high temperature. The rapidity with which it takes place +appears to increase with the temperature; but this is true only within +very narrow limits, for beyond a certain point heat is injurious, and +when it exceeds 120° or 130° Fahrenheit, entirely prevents the process. +The presence of oxygen is also essential, for it has been shown that if +seeds are placed in a soil exposed to an atmosphere deprived of that +element, or if they be buried so deep that the air does not reach them, +they may lie without change for an unlimited period; but so soon as they +are exposed to the air, germination immediately commences. Illustrations +of this fact are frequently observed where earth from a considerable +depth has been thrown up to the surface, when it often becomes covered +with plants not usually seen in the neighbourhood, which have sprung +from buried seeds. When all the necessary conditions for germination are +fulfilled, the seed absorbs moisture, swells up, and sends out a shoot +which rises to the surface, and a radicle which descends--the one +destined to develop the leaves, the other the roots, by which the plant +is afterwards to derive its nutriment from the air and the soil. But +until these organs are properly developed, the plant is dependent on the +matters contained in the seed itself. These substances are mostly +insoluble, but are brought into solution by the atmospheric oxygen +acting upon the gluten, and converting it into a soluble substance +called diastase, which in its turn reacts upon the starch, converting it +first into dextrine, and then into cellulose, and the latter is finally +deposited in the form of organised cells, and produces the first little +shoot of the plant. At the first moment of germination, the oxygen +absorbed appears simply to oxidize the constituents of the seed, but +this condition exists only for a very limited period, and is soon +followed by the evolution of carbonic acid, water being at the same time +formed from the organic constituents of the seed, which gradually +diminishes in weight. The amount of this diminution is different with +different plants, but always considerable. Boussingault found that the +loss of dry substance in the pea amounted in 26 days to 52 per cent, and +in wheat to 57 per cent in 51 days. Against this, of course, is to be +put the weight of the young plant produced; but this is never sufficient +to counterbalance the diminished weight of the seed, for Saussure found +that a horse bean and the plant produced from it weighed, after 16 days, +less by 29 per cent than the seed before germination. The same +phenomenon is observed in the process of malting, which is in fact the +artificial germination of barley, the malt produced always weighing +considerably less than the grain from which it was obtained. It was +believed by Saussure, and the older investigators, that the carbonic +acid evolved was entirely produced from starch and sugar; and as these +substances may be viewed as compounds of carbon and water, the change +was very simply explained by supposing that the carbon was oxidised and +converted into carbonic acid and its water eliminated. But this +hypothesis is incapable of explaining all the phenomena observed; for +woody fibre, which is one of the chief constituents of the young plant, +contains more carbon than the starch and sugar from which it must have +been produced, and we are, therefore, forced to admit that the action +must be more complicated. There is every reason to believe that the +nitrogenous constituents of the seed are most abundantly oxidized, for +they are remarkably prone to change; but the action of the air is not +confined to them, and it appears most probable that all the substances +take part in the decomposition, and the process of germination may, in +some respects, be compared to decay or putrefaction, which, like it, is +attended by the absorption of oxygen and evolution of carbonic acid; but +while in the latter case the residual substances remain in a useless +state, in the former they at once become part of a new organism. + +_Changes occurring during the After-growth of the Plant._--When the +plant has developed its roots and leaves, and exhausted the store of +materials laid up for it in the seed, it begins to derive its +subsistence from the surrounding air, and to absorb carbonic acid, +water, ammonia, and nitric acid, and to decompose and convert them into +the different constituents of its tissues. These changes take place +slowly at first, and more rapidly as the organs fitted for the +elaboration of its food are developed. The roots and the leaves are +equally active in performing this duty, the former absorbing the mineral +matters along with the carbonic acid, ammonia, nitric acid, and moisture +in the soil, or the manure added to it; the latter gathering the gaseous +substances existing in the air. Each of these undergoes a series of +changes claiming our consideration. + +_Decomposition of Carbonic Acid._--Carbonic acid, which appears to be +absorbed with equal readiness by the roots, leaves, and stems, undergoes +immediate decomposition, its carbon being retained, and its oxygen, in +whole or in part, evolved into the air. This decomposition occurs only +under the action of the sun's rays, and has been found to be +proportionate to the amount of light to which the plant is exposed. It +takes place only in the green parts of plants, for though the roots +absorb carbonic acid, they cannot decompose it, or evolve oxygen; and +the coloured parts, the flowers, fruits, etc., have an entirely opposite +effect, absorbing oxygen and giving off carbonic acid. The absorption of +carbonic acid and escape of oxygen has been proved by numerous direct +experiments by Saussure and others, in which both atmospheric air and +artificial mixtures containing an increased quantity of carbonic acid +have been employed. Saussure allowed seven plants of periwinkle (_Vinca +minor_) to vegetate in an atmosphere containing 7·5 per cent of carbonic +acid for six days, during each of which the apparatus was exposed for +six hours to the sun's rays. The air was analysed both before and after +the experiment, and the results obtained were-- + + Volume Carbonic + of the air. Nitrogen. Oxygen. Acid. +Before the experiment, 5746 4199 1116 431 +After " 5746 4338 1408 0 + ---- ---- ---- ---- +Difference, 0 +139 +292 -431 + +In this experiment the whole of the carbonic acid, amounting to 431 +volumes, was absorbed, but only 292 volumes of oxygen were given off. +Had the carbonic acid been entirely decomposed, and all its oxygen +eliminated, its volume would have been equal to that of the acid, or +431, so that in this instance 139 volumes of the oxygen of the carbonic +acid have been retained to form part of the tissues of the plant. On the +other hand, the nitrogen is found to be increased after the experiment. +It might be supposed that the nitrogen evolved had been derived from the +decomposition of the nitrogenous constituents of the plant, but this +cannot be the true explanation, because in this particular case it +greatly exceeded the whole nitrogen contained in the plants +experimented on. Its source is not well understood, but Boussingault +supposes it to have existed in the interstices of the plant, and to have +escaped during the course of the experiment. Saussure found that the +oak, the horse-chesnut, and other plants, absorb oxygen and give off +carbonic acid in less volumes than the oxygen, while the house-leek and +the cactus absorb oxygen without evolving carbonic acid. The absorption +and decomposition of carbonic acid takes place only during the day, and +matters are entirely reversed during the night, when oxygen is absorbed +and carbonic acid eliminated from all parts of the plants. + +Although the action occurring during the night is the reverse of that +which takes place during the day, it is in no degree to be attributed to +a re-oxidation of the carbon which had been deposited in the tissues of +the plant. It appears, on the contrary, to be a purely mechanical, and +not a chemical process. During the night the sap continues to circulate +through the vessels of the plant, and moisture, carrying with it +carbonic acid in solution, is absorbed by the roots; but when it reaches +the leaves, where the sun's light would have caused its decomposition +during the day, it is again exhaled unchanged. The oxygen absorbed +during the night must, however, take part in some chemical processes, +for if it were merely mechanical, the absorption would not be confined +to that gas alone, but would be participated in by the other +constituents of the air. Moreover, the amount of absorption varies +greatly in different plants--being scarcely appreciable in some, and +very abundant in others. Plants containing volatile oils, which are +readily converted into resins by the action of oxygen, or those +containing tannin or other readily oxidizable substances, take up the +largest quantity. This is remarkably illustrated by an experiment in +which the leaves of the Agave americana, after twenty-four hours' +exposure in the dark, were found to have absorbed only 0·3 of their +volume of oxygen, while those of the fir, in which volatile oil is +abundant, had taken up twice, and those of the oak, containing tannin, +eighteen times as much oxygen. + +In the flowers, both by day and night, there is a constant absorption of +oxygen, and evolution of carbonic acid. In fact, an active oxidation is +going on, attended by the evolution of heat, which, in the _Arum +maculatum_ and some other plants, is so great as to raise the +temperature of the flower 10° or 12° above that of the surrounding air. + +_Decomposition of Water in the Plant._--In addition to the function +which water performs in the plant, as the solvent of the different +substances which form its nutriment, and hence as the medium through +which they pass into its organs, it serves also as a direct food, +undergoing decomposition, and yielding hydrogen to the organic +substances. Its constituents, along with those of the carbonic acid +absorbed, undergo a variety of transformations, and form the principal +part of the non-nitrogenous constituents. It has been already observed +that starch, sugar, and the other allied substances, may be considered +as compounds of carbon with water; and they might be supposed to owe +their origin to the carbonic acid losing the whole of its oxygen, and +direct combination then ensuing between the residual carbon and a +certain proportion of water; but this would imply that the latter +substance undergoes no decomposition, and though undoubtedly the +simplest view of the case, it is by no means the most probable. It is +much more likely that the carbonic acid is only partially decomposed, +half its oxygen being separated, and replaced by hydrogen, produced by +the decomposition of a certain quantity of water into its elements. +Thus, for instance, sugar may be produced from twelve equivalents of +carbonic acid and twelve equivalents of water, twenty-four equivalents +of oxygen being eliminated, as thus represented: + +12 equivalents of carbonic acid, C_{12}O_{12}O_{12} +12 " water, H_{12}O_{12} + 1 " sugar, and 24 of ox. C_{12}H_{12}O_{12} + O_{24} + +It must not be supposed that we are in a condition to assert that sugar +is really produced in the manner here shown, the illustration being +given merely for the purpose of pointing out how it may be supposed to +occur, and on a similar principle it is possible to explain the +formation of most other vegetable compounds; and this subject has been +very fully discussed by the late Dr. Gregory, in his "Handbook of +Organic Chemistry." That water must be decomposed, is evident from the +fact, established by analysis, that the hydrogen of the plant generally +exceeds the quantity required to form water with its oxygen, so that +this excess at least must be produced by the decomposition of water. The +hydrogen of the volatile oils, many of which contain no oxygen, and that +of the fats, which contain only a small quantity, must manifestly be +obtained in a similar manner. + +_Decomposition of Ammonia._--The nitrogenous or albuminous compounds of +vegetables must necessarily obtain their nitrogen from the decomposition +either of ammonia or nitric acid, experiment having distinctly shown +that they are incapable of absorbing it in the free state from the +atmosphere. It has been clearly ascertained that the albuminous +substances do not contain ammonia, and it is hence apparent that a +complete decomposition of that substance must take place in the plant. +No doubt carbonic acid and water take part with it in these changes, +which must be of a very complex character, and in the present state of +our knowledge it seems hopeless to attempt any explanation of them. + +_Decomposition of Nitric Acid._--Chemists are not entirely at one as to +whether nitric acid is directly absorbed by the plant, or is first +converted into ammonia. But there are certain facts connected with the +chemistry of the soil, to be afterwards referred to, which seem to us to +leave no doubt that it may be directly absorbed; and in that case it +must be decomposed, its oxygen being eliminated, and the nitrogen taking +part with carbon and hydrogen in the formation of the organic compounds. +It must be clearly understood that while such changes as those described +manifestly must take place, the explanations of them which have been +attempted by various chemists are not to be accepted as determinately +established _facts_; they are at present no more than hypothetical views +which have been expressed chiefly with the intention of presenting some +definite idea to the mind, and are unsupported by absolute proof; they +are only inferences drawn from the general bearings of known facts, and +not facts themselves. Although, therefore, they are to be received with +caution, they have advantages in so far as they present the matter to us +in a somewhat more tangible form than the vague general statements which +are all that could otherwise be made. + + + + +CHAPTER IV. + +THE INORGANIC CONSTITUENTS OF PLANTS. + + +When treating of the general constituents of plants, it has been already +stated that the older chemists and vegetable physiologists, misled by +the small quantity of ash found in them, entertained the opinion that +mineral matters were purely fortuitous components of vegetables, and +were present merely because they had been dissolved and absorbed along +with the humus, which was then supposed to enter the roots in solution, +and to form the chief food of the plant. This supposition, which could +only be sustained at a time when analysis was imperfect, has been long +since disproved and abandoned, and it has been distinctly shown by +repeated experiment that not only are these inorganic substances +necessary to the plant, but that every one of them, however small its +quantity, must be present if it is to grow luxuriantly and arrive at a +healthy maturity. The experiments of Prince Salm Horstmar, before +alluded to, have established beyond a doubt, that while a seed may +germinate, and even grow, to a certain extent, in absence of one or more +of the constituents of its ash, it remains sickly and stunted, and is +incapable of producing either flower or seed. + +Of late years the analysis of the ash of different plants has formed the +subject of a large number of laborious investigations, by which our +knowledge of this subject has been greatly extended. From these it +appears that the quantity of ash contained in each plant or part of a +plant is tolerably uniform, differing only within comparatively narrow +limits, and that there is a special proportion belonging to each +individual organ of the plant. This fact may be best rendered obvious by +the subjoined table, showing the quantity of ash contained in a hundred +parts of the different substances dried at 212°. Most of these numbers +are the mean of several experiments:-- + + +_Table showing the quantity of inorganic matters in 100 parts of +different plants dried at 212°._ + +SEEDS. + +Wheat 1·97 +Barley 2·48 +Oats (with husk) 3·80 +Oats (without husk) 2·06 +Rye 2·00 +Millet 3·60 +Rice 0·37 +Maize 1·20 +Peas 2·88 +Beans 3·22 +Kidney Beans 4·09 +Lentils 2·51 +Tares 2·60 +Buckwheat 2·13 +Linseed 4·40 +Hemp seed 5·60 +Rape seed 4·35 +Indian Rape-seed[A] 4·06 +Sunflower 3·26 +Cotton seed 5·93 +Guinea Corn 1·99 +Gold of Pleasure 4·10 +White Mustard 4·15 +Black Mustard 4·31 +Poppy 6·56 +Niger seed (_Guizotia oleifera_) 7·00 +Earth nut 3·88 +Sweet Almond 4·90 +Horse-chesnut 2·81 +Grape 2·76 +Clover 6·19 +Turnip 3·98 +Carrot 10·03 +Sainfoin 5·27 +Italian Ryegrass 6·91 +Mangold-Wurzel 6·58 + +STRAWS AND STEMS. + +Wheat 4·54 +Barley 4·99 +Oat 7·24 +Winter Rye 5·15 +Summer Rye 5·78 +Millet 8·32 +Maize 3·60 +Pea 4·81 +Bean 6·59 +Tares 6·00 +Lentil 5·38 +Buckwheat 4·50 +Hops 4·42 +Flax straw 4·25 +Hemp 4·14 +Gold of Pleasure 6·05 +Rape 4·41 +Potato 14·90 +Jerusalem Artichoke 4·40 + +ENTIRE PLANT. + +Potato 17·70 +Spurry 10·06 +Red Clover 8·79 +White Clover 8·72 +Yellow Clover 8·56 +Crimson Clover (_T. incarnatum_) 10·81 +Cow Grass (_T. medium_) 11·31 +Sainfoin 6·51 +Ryegrass 6·42 +Meadow Foxtail (_Alopecurus pratensis_) 7·81 +Sweet-scented Vernal Grass (_Anthoxanthum odoratum_) 6·32 +Downy Oat Grass (_Avena pubescens_) 5·22 +Bromus erectus 5·21 +Bromus mollis 5·82 +Cynosurus cristatus 6·38 +Dactylis glomeratus 5·31 +Festuca duriuscula 5·42 +Holcus lanatus 6·37 +Hordeum pratense 5·67 +Lolium perenne 7·54 +Poa annua 2·83 +Poa pratensis 5·94 +Poa trivialis 8·33 +Phleum pratense 5·29 +Plantago lanceolata 8·68 +Poterium Sanguisorba 7·97 +Yarrow 13·45 +Rape Kale 8·00 +Cow Cabbage 10·00 +Asparagus 6·40 +Parsley 1·10 +Furze 3·11 +Chamomile (_Anthemis arvensis_) 9·66 +Wild Chamomile (_Matricaria Chamomilla_) 9·10 +Corn Cockle (_Agrostemma Githago_) 13·20 +Corn Blue Bottle (_Centaurea Cyanus_) 7·32 +Foxglove 10·89 +Hemlock (_Conium maculatum_) 12·80 +Sweet Rush (_Acorus Calamus_) 6·90 +Common Reed (_Arundo Phragmites_) 1·44 +Celandine (_Chelidonium majus_) 6·85 +Equisetum fluviatile 23·60 +Equisetum hyemale 11·80 + " arvense 13·80 + " linosum 15·50 +Fucus nodosus 19·03 +Fucus vesiculosus 27·63 +Laminaria digitata 39·68 + +LEAVES. + +Turnip 9·37 +Beet 20·30 +Kohl-rabi 18·54 +Carrot 10·95 +Jerusalem Artichoke 28·30 +Hemp 22·00 +Hop 17·25 +Tobacco 22·62 +Spinach 19·76 +Chicory 15·67 +Poplar 23·00 +Red Beech 6·00 +White Beech 10·51 +Oak 9·80 +Elm 16·33 +Horse-chesnut 9·08 +Maple 28·05 +Ash 14·76 +Fir 2·31 +Acacia 18·20 +Olive 6·45 +Orange 13·73 +Potato 15·10 +Tussac Grass 7·15 + +ROOTS AND TUBERS. + +Potato 4·16 +Jerusalem Artichoke 5·38 +Turnip 13·64 +Beet 8·27 +Kohl-rabi 6·08 +Rutabaga 7·34 +Carrot 5·80 +Belgian White Carrot 6·22 +Mangold-Wurzel 8·78 +Parsnip 5·52 +Radish 7·35 +Chicory 5·21 +Madder 8·33 + +WOODS. + +Beech 0·38 +Apple 1·29 +Cherry 0·28 +Birch 1·00 +Oak 2·50 +Walnut 1·57 +Lime 5·00 +Horse-chesnut 1·05 +Olive 0·58 +Mahogany 0·81 +Vine 2·57 +Larch 0·32 +Fir 0·14 +Scotch Fir 0·17 +Filbert 0·50 +Chesnut 3·50 +Poplar 0·80 +Hazel 0·50 +Orange 2·74 +Vine 2·57 + +BARKS. + +Beech 6·62 +Cherry 10·37 +Fir 1·79 +Oak 6·00 +Horse-chesnut 7·85 +Filbert 6·20 +Cork 1·12 + +FRUITS. + +Plum 0·40 +Cherry 0·43 +Strawberry 0·41 +Pear 0·41 +Apple 0·27 +Chesnut 0·99 +Cucumber 0·63 +Vegetable Marrow 5·10 + +On examining this table it may be observed that, notwithstanding the +very great variety in the proportion of ash in different plants, some +general relations may be traced. A certain similarity may be observed +between those belonging to the same natural family, the seeds of all the +cereal grains, for instance, containing in round numbers two per cent of +inorganic matters. Leguminous seeds (peas and beans) contain about three +per cent, while in rape-seed, linseed, and the other oily seeds, it +reaches four per cent. In the stems and straws less uniformity exists, +but with the exception of a few extreme cases, the quantity of ash in +general approaches pretty closely to five per cent. Still more +diversified results are obtained from the entire plants; but this +diversity is probably much more apparent than real, and must be, in part +at least, dependent on the proportion existing between the stem and +leaves, for the leaves are peculiarly rich in ash, and a leafy plant +must necessarily yield a higher total percentage of ash, although, if +stems and leaves were separately examined, they might not show so +conspicuous a difference. + +The leaves surpass all other parts of plants, in the proportion of +inorganic constituents they contain, the table showing that in some +instances, as in the maple and Jerusalem artichoke, they exceed +one-fourth of the whole weight of the dry matter. In other leaves, and +more especially in those of the coniferæ, the proportion is much +smaller. Taking the average of all the analyses hitherto made, it +appears that leaves contain about thirteen per cent of ash, but the +variations on either side are so large that little value is to be +attached to it except as an indication of the general abundance of +mineral matters. + +In roots and tubers the variations are less, and all, except the potato +and the turnip, contain about seven per cent of ash. + +The smallest proportion of mineral matter is found in wood. In one case +only does the proportion reach five per cent, while the average scarcely +exceeds one, and in the fir the quantity amounts to no more than one +six-hundredth of the dry matter. In the bark the quantity is much +larger, and may be stated at seven per cent. + +The general proportion of ash found in different parts of plants is +given in round numbers in the subjoined table:-- + +Wood 1 +Seeds 3 +Stems and straws 5 +Roots and tubers 7 +Bark 7 +Leaves 13 + +The differences in the quantity of ash contained in different parts of +plants are obviously intended to serve a useful purpose, and it is +interesting to observe that the wood which is destined to remain for a +long period, sometimes for several centuries, a part of the plant, +contains the smallest proportion, and it is not improbable that what it +does contain is really due, not to the actual woody matter itself, but +to the sap which permeates its vessels. By this arrangement but a small +proportion of these important mineral matters, which the soil supplies +in very limited quantity, is locked up within the plant, and those which +are absorbed, after circulating through it, and fulfilling their +allotted functions, are accumulated in the leaves, and annually returned +to the soil. + +The different proportions of mineral matters contained in the individual +organs of plants is most strikingly illustrated when parallel +experiments are made on the same species; but the number of instances in +which a sufficiently extensive series of analyses has been made to show +this, is comparatively limited, and is confined to the oat, the +orange-tree, and the horse chesnut--each of which has formed the subject +of a very elaborate investigation. The following table gives the results +obtained on the oat:-- + ++-------------+-----------+---------+-----------+-------+-------+------+ +| | Hopetoun | Hopetoun| Potato | Black | Sandy | | +| | Oats, | Oats, | Oats, | Oats, | Oats, | Mean.| +| | North- | Fife- | North- | Edin- | Fife- | | +| | umberland.| shire. | umberland.| burgh.| shire.| | ++-------------+-----------+---------+-----------+-------+-------+------+ +| Grain | 2·14 | 1·81 | 2·22 | 2·11 | 1·76 | 2·00| +| Husk | 6·47 | 6·03 | 6·99 | 8·24 | 6·03 | 6·75| +| Chaff | 16·53 | 17·23 | 15·59 | 19·19 | 18·97 | 16·06| +| Leaves | 8·44 | 7·19 | 14·59 | 10·29 | 15·92 | 10·88| +| Upper part | | | | | | | +| of straw | 4·95 | 5·44 | 9·22 | 8·25 | 11·0 | 7·77| +| Middle part | | | | | | | +| of straw | 6·11 | 5·23 | 7·41 | 6·53 | 9·01 | 6·66| +| Lower part | | | | | | | +| of straw | 5·33 | 5·18 | 9·76 | 7·11 | 7·30 | 6·93| ++-------------+-----------+---------+-----------+-------+-------+------+ + +The specimens of oats on which these analyses were made were from +different districts of country, grown on soils of different quality, and +were, further, of different varieties; and yet they show, on the whole, +a remarkable similarity in the proportion of ash in each part, and +indicate that there is a normal quantity belonging to it. Such a series +of analyses also affords the most convincing proof that the inorganic +matters cannot be fortuitous, and merely absorbed from the soil along +with their organic food, as the old chemists supposed, because, in that +case, they ought to be uniformly distributed throughout the entire +plant, and not accumulated in particular proportions in each individual +organ. + +Not only does the proportion of ash vary in the different parts of a +plant, but even in the same part it is greatly influenced by its period +of growth. The laws which regulate these variations are very imperfectly +known, but in general it is observed that during the period of active +growth the quantity of ash is largest. Thus, it has been found that in +early spring the wood of the young shoots of the horse-chesnut contains +9·9 per cent of ash. In autumn this has diminished to 3·4, and the last +year's twigs contain only 1·1 per cent, while in the old wood the +quantity does not exceed 0·5. Saussure has also observed that the +quantity of ash diminishes in certain plants when the seed has ripened. +Thus, he found that the percentages of ash, before flowering, and after +seeding, were as follows:-- + + Before flowering. With ripe seed. +Sunflower 14·7 9·3 +Wheat 7·9 3·3 +Maize 12·2 4·6 + +On the other hand, the quantity of ash in the leaves of trees increases +considerably in autumn, as shown by this table:-- + + PER-CENTAGE OF ASH IN + May. September. +Oak leaves 5·3 5·5 +Poplar 6·6 9·3 +Hazel 6·1 7·0 +Horse-chesnut 7·2 8·6 + +In general, the proportion of ash appears to increase as the plant +reaches maturity, and this is particularly seen in the oat, of which +very complete analyses have been made at different periods of its +growth:-- + + +_Proportion of Ash in different parts of the Oat at different periods of +its growth._ + ++--------------+---------+---------+--------+------------+ +| | | | | Grain | +| Date. | Stalks. | Leaves. | Chaff. | with husk. | ++--------------+---------+---------+--------+------------+ +| 2d July | 7·83 | 11·35 | ... | 4·91 | +| 9th July | 7·80 | 12·20 | ... | 4·36 | +| 16th July | 7·94 | 12·61 | 6·00 | 3·38 | +| 23d July | 7·99 | 16·45 | 9·11 | 3·62 | +| 30th July | 7·45 | 16·44 | 12·28 | 4·22 | +| 5th August | 7·63 | 16·05 | 13·75 | 4·31 | +| 13th August | 6·62 | 20·47 | 18·68 | 4·07 | +| 20th August | 6·66 | 21·14 | 21·07 | 3·64 | +| 27th August | 7·71 | 22·13 | 22·46 | 3·51 | +| 3d September | 8·35 | 20·90 | 27·47 | 3·65 | ++--------------+---------+---------+--------+------------+ + +The increase is here principally confined to the leaves and chaff, while +the stalks, which owe their strength to a considerable extent to the +inorganic matters they contain, are equally supplied at all periods of +their growth. In the grain only is there a diminution, but this is +apparent and not real, and is due to the fact that the determination of +the quantity of ash, as made on the grain with its husk, and the former, +which contains only a small quantity of mineral matters, increases much +more rapidly in weight than the latter, when it approaches the period of +ripening, and it is accordingly during the last three weeks of its +growth that this diminution becomes apparent. + +The nature of the soil has also a very important influence on the +proportion of mineral matters, and of this an interesting illustration +is given in the following table, which shows the quantities found in the +grain and straw of the same variety of the pea grown on fourteen +different soils:-- + ++----+-------+--------+ +| | Seed. | Straw. | ++----+-------+--------+ +| 1 | 2·30 | | +| 2 | 3·25 | 3·43 | +| 3 | 4·27 | 3·62 | +| 4 | 3·40 | 3·39 | +| 5 | 2·99 | 3·90 | +| 6 | 3·19 | 6·80 | +| 7 | 2·53 | 3·90 | +| 8 | 2·27 | 6·59 | +| 9 | 2·69 | 3·49 | +| 10 | 1·61 | 3·91 | +| 11 | 3·11 | 5·28 | +| 12 | 3·34 | 7·57 | +| 13 | 2·78 | 3·76 | +| 14 | 3·01 | 3·38 | ++----+-------+--------+ + +Although those differences are very large, especially in the straw, and +must be attributed to the soil, it has hitherto been found impossible to +ascertain the nature of the relation subsisting between it and the crops +it yields; indeed, it must obviously be dependent on very complicated +questions, which cannot at present be solved, for it may be observed +that the increase in the grain does not occur simultaneously with that +in the straw, and in several cases a large proportion of ash in the +former is associated with an unusually small amount in the latter. _A +priori_, it might be expected that those soils which are especially rich +in the more important constituents of the ash should yield a produce +containing more than the average quantity, but this is very far from +being an invariable occurrence, and not unfrequently the very reverse +is the case. In some instances the variations may be traced to the soil, +as in the following analyses of the fruit of the horse-chesnut, grown on +an ordinary forest soil, and on a rich soil, produced by the +disintegration of porphyritic rock, in which the latter yields a much +larger quantity of ash:-- + + Kernel of seed. Green husk. Brown husk. +Forest soil 2·26 4·53 1·70 +Porphyry soil 3·36 7·29 2·20 + +In the majority of instances we fail to establish any connection between +the nature of the soil and the plants it yields, chiefly because we are +still very deficient in analyses of those grown on uncultivated soils; +and on cultivated land it is impossible to draw conclusions, because the +nature of the manure exerts an influence quite as great, if not greater, +than that of the soil itself. + +The relative proportion in which the different mineral matters enter +into the composition of the ash varies within very wide limits, as will +be apparent from the following table, containing a selection of the best +analyses of our common cultivated and a few uncultivated plants. + + +_Table of the Composition of the Ash of different Plants in 100 Parts._ + +_Note._--Alumina and oxide of manganese occur so rarely, that separate +columns have not been introduced for them, but their quantity is stated +in notes at the end of the table. + ++---------------------+--------+------+-----------+---------+------+----------+ +| | Potash.| Soda.| Chloride | Chloride| Lime.| Magnesia.| +| | | | of | of | | | +| | | | Potassium.| Sodium. | | | ++---------------------+--------+------+-----------+---------+------+----------+ +|Wheat, grain | 30·02 | 3·82 | ... | ... | 1·15| 13·39 | +| straw | 17·98 | 2·47 | ... | ... | 7·42| 1·94 | +| chaff | 9·14 | 1·79 | ... | ... | 1·88| 1·27 | +|Barley, grain | 21·14 | ... | 5·65 | 1·01 | 1·65| 7·26 | +| straw | 11·22 | ... | ... | 2·14 | 5·79| 2·70 | +|Oats, grain[B] | 20·63 | ... | 1·03 | ... | 10·28| 7·82 | +| straw | 19·46 | 1·93 | 2·71 | 4·27 | 7·01| 3·79 | +| chaff[C] | 6·33 | 3·93 | ... | 0·24 | 1·95| 0·38 | +|Rye, grain | 33·83 | 0·39 | ... | ... | 2·61| 12·81 | +| straw | 17·20 | ... | 0·30 | 0·60 | 9·10| 2·40 | +|Maize, grain | 28·37 | 1·74 | ... | trace | 0·57| 13·60 | +| stalks and leaves | 35·26 | ... | ... | 2·29 | 10·53| 5·52 | +|Rice, grain | 20·21 | 2·49 | ... | ... | 7·18| 4·26 | +|Buckwheat, straw | 31·71 | ... | 7·42 | 4·55 | 15·71| 1·66 | +|Peas (gray), seed | 41·70 | ... | 3·82 | 1·24 | 4·78| 5·78 | +| straw | 21·30 | 4·22 | ... | ... | 37·17| 7·17 | +|Beans (common field),| | | | | | | +| grain | 51·72 | 0·54 | ... | ... | 5·20| 6·90 | +| straw | 32·85 | 2·77 | ... | 11·54 | 19·85| 2·53 | +|Tare, straw | 32·82 | ... | 3·27 | 4·03 | 20·78| 5·31 | +| straw | 31·72 | ... | 7·41 | 4·55 | 15·71| 1·66 | ++---------------------+--------+------+-----------+---------+------+----------+ + + ++-----------------------+-------+------------+-----------+----------+---------+ +| | Oxide | Phosphoric | Sulphuric | Carbonic | Silica. | +| | of | Acid. | Acid. | Acid. | | +| | Iron. | | | | | ++-----------------------+-------+------------+-----------+----------+---------+ +| Wheat, grain | 0·91 | 46·79 | ... | ... | 3·89 | +| straw | 0·45 | 2·75 | 3·09 | ... | 63·89 | +| chaff | 0·37 | 4·31 | ... | ... | 81·22 | +| Barley, grain | 2·13 | 28·53 | 1·91 | ... | 30·68 | +| straw | 1·36 | 7·20 | 1·09 | ... | 68·50 | +| Oats, grain | 3·85 | 50·44 | ... | ... | 4·40 | +| straw | 1·49 | 5·07 | 3·35 | 1·36 | 49·56 | +| chaff | 1·58 | 1·04 | 9·61 | ... | 72·85 | +| Rye, grain | 1·04 | 39·92 | 0·17 | ... | 9·22 | +| straw | 1·40 | 3·80 | 0·80 | ... | 64·50 | +| Maize, grain | 0·47 | 53·69 | ... | ... | 1·55 | +| stalks and leaves | 2·28 | 8·09 | 5·16 | 2·87 | 27·98 | +| Rice, grain | 2·12 | 62·23 | ... | ... | 1·37 | +| Buckwheat, straw | ... | 10·34 | 4·67 | 20·37 | 3·57 | +| Peas (gray), seed | 0·18 | 36·50 | 4·47 | 0·82 | 0·68 | +| straw | 1·07 | 4·65 | 8·68 | 12·48 | 3·23 | +| Beans (common field), | | | | | | +| grain | ... | 28·72 | 3·05 | 3·42 | 0·42 | +| straw | 0·61 | 0·49 | 1·40 | 25·32 | 2·61 | +| Tare, straw | 0·65 | 10·59 | 2·52 | 18·73 | 1·28 | +| straw | ... | 10·34 | 4·67 | 20·37 | 3·57 | ++-----------------------+-------+------------+-----------+----------+---------+ + ++---------------------+--------+------+-----------+---------+------+----------+ +| | Potash.| Soda.| Chloride | Chloride| Lime.| Magnesia.| +| | | | of | of | | | +| | | | Potassium.| Sodium. | | | ++---------------------+--------+------+-----------+---------+------+----------+ +|Flax, seed | 34·17 | 1·69| ... | 0·36 | 8·40| 13·11 | +| straw | 21·53 | 3·68| ... | 9·21 | 21·20| 4·20 | +|Rape, seed[D] | 16·33 | 0·34| ... | 0·96 | 8·30| 8·80 | +| straw[E] | 16·63 | 10·57| ... | 2·53 | 21·51| 2·92 | +|Spurry | 26·12 | 1·14| ... | 8·90 | 14·46| 8·88 | +|Chicory root | 34·64 | ...| 8·92 | 2·98 | ...| ... | +|Red clover | 25·60 | ...| 9·08 | 6·02 | 21·57| 8·47 | +|Cow grass, | | | | | | | +| _Trifolium medium_ | 22·78 | ...| 12·39 | 1·86 | 24·42| 8·86 | +|Yellow clover | 27·48 | ...| 11·72 | 8·16 | 17·26| 8·39 | +|Alsike clover | 29·72 | ...| 6·29 | 1·05 | 26·83| 4·01 | +|Lucerne | 27·56 | ...| 11·64 | 1·91 | 20·60| 5·22 | +|Anthoxanthum odoratum| 32·03 | ...| 7·03 | 4·90 | 9·21| 2·53 | +|Alopecurus pratensis | 37·03 | ...| 9·50 | ... | 3·90| 1·28 | +|Avena pubescens | 31·21 | ...| 4·05 | 5·66 | 4·72| 3·17 | +|Bromus erectus | 20·33 | ...| 10·63 | 1·38 | 10·38| 4·99 | +|Bromus mollis | 30·09 | 0·33| ... | 3·11 | 6·64| 2·60 | +|Cynosurus cristatus | 24·99 | ...| 11·60 | ... | 10·16| 2·43 | +|Dactylis glomerata | 29·52 | ...| 17·86 | 3·09 | 5·82| 2·22 | +|Festuca duriuscula | 31·84 | ...| 8·17 | 0·62 | 10·31| 2·83 | +|Holcus lanatus | 34·83 | ...| 3·91 | 6·66 | 8·31| 3·41 | +|Lolium perenne | 24·67 | ...| 13·80 | 7·25 | 9·64| 2·85 | +|Annual ryegrass | 28·99 | 0·87| ... | 5·11 | 6·82| 2·59 | +|Poa annua | 41·86 | ...| 0·47 | 3·35 | 11·69| 2·44 | +|Poa pratensis | 31·17 | ...| 11·25 | 1·31 | 5·63| 2·71 | +|Poa trivialis | 29·40 | ...| 6·90 | ... | 8·80| 3·22 | +|Phleum pratense | 31·09 | ...| 0·70 | 3·24 | 14·94| 5·30 | +|Plantago lanceolata | 33·26 | ... | 4·53 | 8·80 | 19·01| 3·51 | +|Poterium Sanguisorba | 30·26 | ... | 3·27 | 1·35 | 24·82| 4·21 | +|Achillea Millefolia | 30·37 | ... | 20·49 | 3·63 | 13·40| 3·01 | +|Potato, tuber | 43·18 | 0·09| ... | 7·92 | 1·80| 3·17 | +| stem | 39·53 | 3·95| ... | 20·43 | 14·85| 4·10 | +| leaves | 17·27 | ... | 4·95 | 11·37 | 27·69| 7·78 | +|Jerusalem Artichoke | 55·89 | ... | 4·88 | ... | 3·34| 1·30 | +| stem | 38·40 | 0·69| ... | 4·68 | 20·31| 1·91 | +| leaves | 6·81 | 3·72| ... | 1·82 | 40·15| 1·95 | +|Turnip, seed | 21·91 | 1·23| ... | ... | 17·40| 8·74 | +| bulb | 23·70 | 14·75| ... | 7·05 | 11·82| 3·28 | +| leaves | 11·56 | 12·43| ... | 12·41 | 28·49| 2·62 | +|Mangold Wurzel, root | 21·68 | 3·13| ... | 49·51 | 1·90| 1·79 | +| leaves | 8·34 | 12·21| ... | 37·66 | 8·72| 9·84 | +|Carrot, root | 42·73 | 12·11| ... | ... | 5·64| 2·29 | +| leaves | 17·10 | 4·85| ... | 3·62 | 24·05| 0·89 | +|Kohl-rabi, bulb | 36·27 | 2·84| ... | 11·90 | 10·20| 2·36 | +| leaves | 9·31 | ... | 5·99 | 6·66 | 30·31| 3·62 | +|Cow cabbage, head | 40·86 | 2·43| ... | ... | 15·01| 2·39 | +| stalk | 40·93 | 4·05| ... | 2·08 | 10·61| 3·85 | +|Poppy seed | 9·10 | ... | 7·15 | 1·94 | 35·36| 9·49 | +| leaves | 36·37 | ... | 2·50 | 2·51 | 30·24| 6·47 | +|Mustard seed (white) | 25·78 | 0·33| ... | ... | 19·10| 5·90 | +|Radish root | 21·16 | ... | 1·29 | 7·07 | 8·78| 3·53 | +|Tobacco leaves | 36·37 | ... | 2·50 | 2·51 | 30·24| 6·47 | +|Fucus nodosus[F] | 20·03 | 4·58| ... | 24·33 | 9·60| 6·65 | +|Fucus vesiculosus[G] | 20·75 | 6·09| ... | 24·81 | 8·92| 5·83 | +|Laminaria digitata[H]| 12·16 | ... | 2·30 | 19·34 | 4·62| 10·94 | ++---------------------+--------+------+-----------+---------+------+----------+ + ++---------------------+-------+------------+-----------+----------+---------+ +| | Oxide | Phosphoric | Sulphuric | Carbonic | Silica. | +| | of | Acid. | Acid. | Acid. | | +| | Iron. | | | | | ++---------------------+-------+------------+-----------+----------+---------+ +|Flax, seed | 0·50 | 38·54 | 1·56 | 0·22 | 1·45 | +| straw | 5·58 | 7·53 | 3·39 | 15·75 | 7·92 | +|Rape, seed | 1·79 | 31·90 | 5·38 | 5·44 | 19·98 | +| straw | 1·30 | 4·68 | 3·90 | 23·04 | 11·80 | +|Spurry | ... | 10·20 | 1·79 | 27·38 | 1·14 | +|Chicory root | ... | ... | ... | ... | ... | +|Red clover | 1·26 | 4·09 | 2·96 | 18·05 | 1·95 | +|Cow grass, | | | | | | +| _Trifolium medium_ | 1·09 | 4·94 | 2·66 | 20·16 | 1·12| +|Yellow clover | 1·40 | ... | 4·82 | 4·31 | 1·76 | +|Alsike clover | 0·71 | 5·64 | 3·25 | 20·74 | 1·73 | +|Lucerne | 2·23 | 6·47 | 4·80 | 15·94 | 2·63 | +|Anthoxanthum odoratum| 1·18 | 10·09 | 3·39 | 1·26 | 28·35 | +|Alopecurus pratensis | 0·47 | 6·25 | 2·16 | 0·65 | 38·75 | +|Avena pubescens | 0·72 | 10·82 | 3·37 | ... | 36·28 | +|Bromus erectus | 0·26 | 7·53 | 5·46 | 0·55 | 38·48 | +|Bromus mollis | 0·28 | 9·62 | 4·91 | 9·07 | 33·34 | +|Cynosurus cristatus | 0·18 | 7·24 | 3·20 | ... | 40·11 | +|Dactylis glomerata | 0·59 | 8·60 | 3·52 | 2·09 | 26·65 | +|Festuca duriuscula | 0·78 | 12·07 | 3·45 | 1·38 | 28·53 | +|Holcus lanatus | 0·31 | 8·02 | 4·41 | 1·82 | 28·31 | +|Lolium perenne | 0·21 | 8·73 | 5·20 | 0·49 | 27·13 | +|Annual ryegrass | 0·28 | 10·07 | 3·45 | ... | 41·79 | +|Poa annua | 1·57 | 9·11 | 10·18 | 3·29 | 16·03 | +|Poa pratensis | 0·28 | 10·02 | 4·26 | 0·40 | 32·93 | +|Poa trivialis | 0·29 | 9·13 | 4·47 | 0·29 | 37·50 | +|Phleum pratense | 0·27 | 11·29 | 4·86 | 4·02 | 31·09 | +|Plantago lanceolata | 0·90 | 7·08 | 6·11 | 14·40 | 2·37 | +|Poterium Sanguisorba | 0·86 | 7·81 | 4·84 | 21·72 | 0·83 | +|Achillea Millefolia | 0·21 | 7·13 | 2·44 | 9·36 | 9·92 | +|Potato, tuber | 0·44 | 8·61 | 15·24 | 18·29 | 1·94 | +| stem | 1·34 | 6·68 | 6·56 | ... | 2·56 | +| leaves | 4·50 | 13·60 | 6·37 | ... | 6·47 | +|Jerusalem Artichoke | 0·45 | 16·99 | 3·77 | 11·80 | 1·52 | +| stem | 0·88 | 2·97 | 3·23 | 25·40 | 1·51 | +| leaves | 1·14 | 6·61 | 2·21 | 24·31 | 17·25 | +|Turnip, seed | 1·95 | 40·17 | 7·10 | 0·82 | 0·67 | +| bulb | 0·47 | 9·31 | 16·13 | 10·74 | 2·69 | +| leaves | 3·02 | 4·85 | 10·36 | 6·18 | 8·04 | +|Mangold Wurzel, root | 0·52 | 1·65 | 3·14 | 15·23 | 1·40 | +| leaves | 1·46 | 5·89 | 6·54 | 6·92 | 2·35 | +|Carrot, root | 0·51 | 12·31 | 4·26 | 18·00 | 1·11 | +| leaves | 3·43 | 6·21 | 5·08 | 23·15 | 11·61 | +|Kohl-rabi, bulb | 0·38 | 13·45 | 11·43 | 10·24 | 0·83 | +| leaves | 5·50 | 9·43 | 10·63 | 8·97 | 9·57 | +|Cow cabbage, head | 0·77 | 12·53 | 7·27 | 16·68 | 1·66 | +| stalk | 0·41 | 19·57 | 11·11 | 6·33 | 1·04 | +|Poppy seed | 0·41 | 31·38 | 1·92 | ... | 3·24 | +| leaves | 2·14 | 3·28 | 5·09 | ... | 11·40 | +|Mustard seed (white) | 0·39 | 44·97 | 2·19 | ... | 1·31 | +|Radish root | 1·19 | 41·09 | 7·71 | ... | 8·17 | +|Tobacco leaves | 2·18 | 3·24 | 5·09 | ... | 11·40 | +|Fucus nodosus | 0·26 | 1·71 | 21·97 | 6·39 | 0·38 | +|Fucus vesiculosus | 0·35 | 2·14 | 28·01 | 2·20 | 0·67 | +|Laminaria digitata | 0·45 | 1·75 | 7·26 | 15·23 | 1·20 | ++---------------------+-------+------------+-----------+----------+---------+ + +A simple inspection of this table leads to various interesting +conclusions. It is particularly to be observed that some of the +constituents of the ash are not invariably present, and two at +least--namely, alumina and manganese--are found so rarely as to justify +the inference that they are not indispensable. Of the other substances, +iodine is restricted exclusively to sea-plants, but to them it appears +to be essential. Oxide of iron, which occurs only in small quantities, +has sometimes been considered fortuitous, but it is almost invariably +present, and the experiments of Prince Salm Horstmar leave no doubt that +it is essential to the plant. Its function is unknown, but it is an +important constituent of the blood of herbivorous animals, and may be +present in the plant, less for its own benefit than for that of the +animal of which it is destined to become the food. + +Soda appears to be a comparatively unimportant constituent of the ash, +of which it generally forms but a small proportion, although the +instances of its entire absence are rare. In the cruciferous plants +(turnip, rape, etc.) it is found abundantly, and to them it appears +indispensable, but in most other plants it admits of replacement by +potash. It seems probable that where the soil is rich in the latter +substance, plants will select that alkali in preference to soda; but as +they must have a certain quantity of alkali, the latter may supply the +place of the former where it is deficient. Cultivation, probably by +enriching the soil in that element, increases the proportion of potash +found in the ash of plants, as is remarkably seen in the asparagus, +which gave the following quantities of alkalies and chlorine:-- + + Wild. Cultivated. + Potash 18·8 50·5 + Soda 16·2 trace. + Chlorine 16·5 8·3 + +The soda having almost entirely disappeared in the cultivated plant, +while a corresponding increase had taken place in the quantity of +potash. + +Potash is one of the most important elements of the ash of all plants, +rarely forming less than 20, and sometimes more than 50 per cent of its +weight. The latter proportion occurs chiefly in the roots and tubers, +but it is also abundant in all seeds and in the grasses. The straw, and +particularly the chaff of the cereals, and the leaves of most plants, +contain it in smaller quantity, although exceptions to this are not +unfrequent, one of the most curious being the case of poppy-seed, which +contains only about 12 per cent, while the leaves yield upwards of 37 +per cent. + +The proportion of lime varies within very wide limits, being sometimes +as low as 1, and in other plants reaching 40 per cent of their ash. The +former proportion occurs in the grains of the cerealia, and the latter +in the leaves of some plants, and more especially in the Jerusalem +artichoke. The turnip and some of the leguminous plants also contain it +abundantly. + +Magnesia is generally found in small quantity. It is largest in the +grains, amounting in them to about 12 or 13 per cent of the ash, but in +other plants it varies from 2 to 4 per cent. Although small in quantity, +it is an important substance, and apparently cannot be dispensed with; +at least there is no instance known of its entire absence. + +_Chlorine_ is by no means an invariable constituent of the ash, although +it is generally present, and sometimes in considerable quantity. It is +most abundant when the proportion of soda is large, and exists in the +ash principally in combination with that base as common salt. The +relation between these two elements may be traced more or less +distinctly throughout the whole table of analyses, and conspicuously in +that of mangold-wurzel, where the common salt amounts to almost exactly +one-half of the whole mineral matter. The analyses of the cultivated and +uncultivated asparagus also show that a diminution in the soda is +accompanied by a reduction in the proportion of chlorine. + +_Sulphuric Acid_ is an essential constituent of the ash. But it is to be +observed that it is in some instances entirely, and in all partially, a +product of the combustion to which the plant has been submitted in order +to obtain the ash. It is partly derived from the sulphur contained in +the albuminous compounds, which is oxidised and converted into sulphuric +acid during the process of burning the organic matter, and remains in +the ash. The quantity of sulphuric acid found in the ash is, however, no +criterion of that existing in the plant, for a considerable quantity of +it escapes during burning. The extent to which this occurs in particular +instances is well illustrated by reference to the case of white mustard, +which yields an ash containing only 2·19 of sulphuric acid, equivalent +to 0·9 of sulphur; and if calculated on the seed itself, this will +amount to no more than 0·039 per cent, while experiments made in another +manner prove it to contain about thirty times as much, or more than 1 +per cent. For the purpose of determining the total quantity of sulphur +which the plants contain in their natural state, it is necessary to +oxidise them by means of nitric acid; and from such experiments the +following table, showing the _total_ amount of sulphur contained in 100 +parts of different plants, dried at 212°, has been constructed:-- + + Poa palustris 0·165 + Lolium perenne 0·310 + Italian Ryegrass 0·329 + Trifolium pratense 0·107 + repens 0·099 + Lucerne 0·336 + Vetch 0·178 + Potato tuber 0·082 + tops 0·206 + Carrot, root 0·092 + tops 0·745 + Mangold-Wurzel, root 0·058 + tops 0·502 + Swede, root 0·435 + tops 0·458 + Rape 0·448 + + Drumhead Cabbage 0·431 + Wheat, grain 0·068 + straw 0·245 + Barley, grain, 0·053 + straw 0·191 + Oats, grain 0·103 + straw 0·289 + Rye, grain 0·051 + Beans 0·056 + Peas 0·127 + Lentils 0·110 + Hops 1·063 + Gold of Pleasure 0·253 + Black Mustard 1·170 + White Mustard 1·050 + +_Phosphoric acid_, which may be looked upon as the most important +mineral constituent of plants, is found to be present in very variable +proportions. The straws, stems, and leaves contain it in comparatively +small quantity, but in the seeds of all plants it is very abundant. In +these of the cereals it constitutes nearly half of their whole mineral +components, and it rarely falls below 30 per cent. + +_Carbonic acid_ occurs in very variable quantities in the ash. It is of +comparatively little importance in itself, and is really produced by the +oxidation of part of the carbonaceous matters of the plant; but it has a +special interest, in so far as it shows that part of the bases contained +in the plant must in its natural state have been in union with organic +acids, or combined in some way with the organic constituents of the +plant. + +_Silica_ is an invariable constituent of the ash, but in most plants +occurs but in small quantity. The cereals and grasses form an exception +to this rule, for in them it is an abundant and important element. It is +not, however, uniformly distributed through them, but is accumulated to +a large extent in the stem, to the strength and rigidity of which it +greatly contributes. The hard shining layer which coats the exterior of +straw, and which is still more remarkably seen on the surface of the +bamboo, consists chiefly of silica; and in the latter plant this element +is sometimes so largely accumulated, that concretions resembling opal, +and composed entirely of it, are found loose within its joints. The +necessity for a large supply of silica in the stems of other plants does +not exist, and in them it rarely exceeds 5 or 6 per cent, but in some +leaves it is more abundant. + +A knowledge of the composition of the ash of plants is of considerable +importance in a practical point of view, and enables us in many +instances to explain why some plants will not grow upon particular soils +on which others flourish. Thus, for instance, a plant which contains a +large quantity of lime, such as the bean or turnip, will not grow in a +soil in which that element is deficient, although wheat or barley, which +require but little lime, may yield excellent crops. Again, if the soil +be deficient in phosphoric acid, those plants only will grow luxuriantly +which require but a small quantity of that element, and hence it follows +that on such a soil plants cultivated for the sake of their stems, +roots, or leaves, in which the quantity of phosphoric acid is small, may +yield a good return; while others, cultivated for the sake of their +seed, in which the great proportion of that constituent of the ash is +accumulated, may yield a very small crop. It is obvious also that even +where a soil contains a proper quantity of all its ingredients, the +repeated cultivation of a plant which removes a large quantity of any +individual element, may, in the course of time, so far reduce the amount +of that substance as to render the soil incapable of any longer +producing that plant, although, if it be replaced by another which +requires but little of the element thus removed, it may again produce an +abundant crop. On this principle also, attempts have been made to +explain the rotation of crops, which has been supposed to depend on the +cultivation in successive years of plants which abstract from the soil +preponderating quantities of different mineral matters. But though this +has unquestionably a certain influence, we shall afterwards see reason +to doubt whether it affords a sufficient explanation of all the observed +phenomena. + +It may be observed, on examining the table of the percentage and +position of the ash, that some plants are especially rich in alkalies, +while in others lime or silica preponderate, and it would therefore be +the object of the farmer to employ, in succession, crops containing +these elements in different proportions. In carrying out this view, +attempts have been made to classify different plants under the heads of +silica plants, lime plants, and potash plants; and the following table, +extracted from Liebig's _Agricultural Chemistry_, in which the +constituents of the ash are grouped under the three heads of salts of +potash and soda, lime and magnesia, and silica, gives such a +classification as far as it is at present possible:-- + +---------------------------------------------------------------------- +| | Salts of | Salts of | Silica. +| | Potash and | Lime and | +| | Soda. | Magnesia. | +|----------------------------------|------------|-----------|--------- +|Silica { Oat straw with seeds | 34·00 | 4·00 | 62·00 +|Plants. { Wheat straw | 22·50 | 7·20 | 61·50 +| { Barley straw with seeds| 19·00 | 25·70 | 55·30 +| { Rye straw | 18·65 | 16·52 | 63·89 +| { Good hay | 6·00 | 34·00 | 60·00 +|Lime { Tobacco | 24·34 | 67·44 | 8·30 +|Plants { Pea straw | 27·82 | 63·74 | 7·81 +| { Potato plant | 4·20 | 59·40 | 36·40 +| { Meadow Clover | 39·20 | 56·00 | 4·90 +|Potash { Maize straw | 72·45 | 6·50 | 18·00 +|Plants. { Turnips | 81·60 | 18·40 | -- +| { Beet root | 88·00 | 12·00 | -- +| { Potatoes | 85·81 | 14·19 | -- +| { Jerusalem Artichoke | 84·30 | 15·70 | -- +---------------------------------------------------------------------- + +The special application of these facts must be reserved till we come to +treat of the rotation of crops. + +It is manifest that, as the crops removed from the soil all contain a +greater or less amount of inorganic matters, they must be continually +undergoing diminution, and at length be completely exhausted unless +their quantity is maintained from some external source. In many cases +the supply of these substances is so large that ages may elapse before +this becomes apparent, but where the quantity is small, a system of +reckless cropping may reduce a soil to a state of absolute sterility. A +remarkable illustration of this fact is found in the virgin soils of +America, from which the early settlers reaped almost unheard-of crops, +but, by injudicious cultivation, they were soon exhausted and abandoned, +new tracts being brought in and cultivated only to be in their turn +abandoned. The knowledge of the composition of the ash of plants assists +us in ascertaining how this exhaustion may be avoided, and indicates the +mode in which such soils may be preserved in a fertile state. + +FOOTNOTES: + +[Footnote A: Apparently a species of Sinapis.] + +[Footnote B: Oxide of Manganese, 0·42.] + +[Footnote C: Oxide of Manganese, 0·92.] + +[Footnote D: Alumina, 1·02.] + +[Footnote E: Alumina, 0·63.] + +[Footnote F: Iodide of Potassium, 0·44; Sulphuret of Sodium, 3·66.] + +[Footnote G: Iodide of Potassium, 0·23.] + +[Footnote H: Iodide of Potassium, 1·68.] + + + + +CHAPTER V. + +THE SOIL--ITS CHEMICAL AND PHYSICAL CHARACTERS. + + +No department of agricultural chemistry is surrounded with greater +difficulties and uncertainties than that relating to the properties of +the soil. When chemistry began to be applied to agriculture, it was not +unnaturally supposed that the examination of the soil would enable us to +ascertain with certainty the mode in which it might be most +advantageously improved and cultivated, and when, as occasionally +happened, analysis revealed the absence of one or more of the essential +constituents of the plant in a barren soil, it indicated at once the +cause and the cure of the defect. But the expectations naturally formed +from the facts then observed have been as yet very partially fulfilled; +for, as our knowledge has advanced, it has become apparent that it is +only in rare instances that it is possible satisfactorily to connect +together the composition and the properties of a soil, and with each +advancement in the accuracy and minuteness of our analysis the +difficulties have been rather increased than diminished. Although it is +occasionally possible to predicate from its composition that a +particular soil will be incapable of supporting vegetation, it not +unfrequently happens that a fruitful and a barren soil are so similar +that it is impossible to distinguish them from one another, and cases +even occur in which the barren appears superior to the fertile soil. The +cause of this apparently anomalous phenomenon lies in the fact that +analysis, however minute, is unable to disclose all the conditions of +fertility, and that it must be supplemented by an examination of its +physical and other chemical properties, which are not indicated by +ordinary experiments. Of late years very considerable progress has been +made in the investigation of the properties of the soil, and many facts +of great importance have been discovered, but we are still unable to +assert that all the conditions of fertility are yet known, and the +practical application of those recently discovered is still very +imperfectly understood. + +It must not be supposed that a careful analysis of a soil is without +value, for very important practical deductions may often be drawn from +it, and when this is not practicable it is not unfrequently due to its +being imperfect or incomplete, for it is so complex that the cases in +which all the necessary details have been eliminated are even now by no +means numerous. In fact, the want of a large number of thorough analyses +of soils of different kinds is a matter of some difficulty, and so soon +as a satisfactory mode of investigation can be determined upon, a full +examination of this subject would be of much importance. + +_Origin of Soils._--The constituents of the soil, like those of the +plant, may be divided into the great classes of organic and inorganic. +The origin of the former has been already discussed: they are derived +from the decay of plants which have already grown upon the soil, and +which, in various stages of decomposition, form the numerous class of +substances grouped together under the name of humus. The organic +substances may therefore be considered as in a manner secondary +constituents of the soil, which have been accumulated in it as the +consequence of the growth and decay of successive generations of plants, +while the primeval soil consisted of inorganic substances only. + +The inorganic constituents of the soil are obtained as the result of a +succession of chemical changes going on in the rocks which protrude +through the surface of the earth. We have only to examine one of these +rocks to observe that it is constantly undergoing a series of important +changes. Under the influence of air and moisture, aided by the powerful +agency of frost, it is seen to become soft, and gradually to +disintegrate, until it is finally converted into an uniform powder, in +which the structure of the original rock is with difficulty, if at all +distinguishable. The rapidity with which these changes take place is +very variable; in the harder rocks, such as granite and mica slate it is +so slow as to be scarcely perceptible, while in others, such as the +shales of the coal formation, a very few years' exposure is sufficient +for the purpose. These actions, operating through a long series of +years, are the source of the inorganic constituents of all soils. + +Geology points to a period at which the earth's surface must have been +altogether devoid of soil, and have consisted entirely of hard +crystalline rocks, such as granite and trap, by the disintegration of +which, slowly proceeding from the creation down to the present time, all +the soils which now cover the surface have been formed. But they have +been produced by a succession of very complicated processes; for these +disintegrated rocks being washed away in the form of fine mud, or at +least of minute particles, and being deposited at the bottom of the +primeval seas, have there hardened into what are called sedimentary +rocks, which being raised above the surface by volcanic action or other +great geological forces, have been again disintegrated to yield +different soils. Thus, then, all soils are directly or indirectly +derived from the crystalline rocks, those overlying them being formed +immediately by their decomposition, while those found above the +sedimentary rocks may be traced back through them to the crystalline +rocks from which they were originally formed. + +Such being the case, the composition of different soils must manifestly +depend on that of the crystalline rocks from which they have been +derived. Their number is by no means large, and they all consist of +mixtures in variable proportions of quartz, felspar, mica, hornblende, +augite, and zeolites. With the exception of quartz and augite, these +names are, however, representatives of different classes of minerals. +There are, for instance, several different minerals commonly classified +under the name of felspar, which have been distinguished by +mineralogists by the names of orthoclase, albite, oligoclase, and +labradorite; and there are at least two sorts of mica, two of +hornblende, and many varieties of zeolites. + +Quartz consists of pure silica, and when in large masses is one of the +most indestructible rocks. It occurs, however, intermixed with other +minerals in small crystals, or irregular fragments, and forms the entire +mass of pure sand. + +The four kinds of felspar which have been already named are compounds of +silica with alumina, and another base which is either potash, soda, or +lime. Their composition is as follows, two examples of each being +given-- + +---------------------------------------------------------------------------- + | Orthoclase. | Albite. | Oligoclase. | Labradorite. | +------------------|--------------|-------------|-------------|--------------| +Silica | 65·72| 65·00| 67·99| 68·23| 62·70| 63·51| 54·66| 54·67| +Alumina | 18·57| 18·64| 19·61| 18·30| 23·80| 23·09| 27·87| 27·89| +Peroxide of iron | traces| 0·83| 0·70| 1·01| 0·62| -- | -- | 0·31| +Oxide of manganese| traces| 0·13| -- | -- | -- | -- | -- | -- | +Lime | 0·34| 1·23| 0·66| 1·26| 4·60| 2·44| 12·01| 10·60| +Magnesia | 0·10| 1·03| -- | 0·51| 0·02| 0·77| -- | 0·18| +Potash | 14·02| 9·12| -- | 2·53| 1·05| 2·19| -- | 0·49| +Soda | 1·25| 3·49| 11·12| 7·99| 8·00| 9·37| 5·46| 5·05| +----------------------------------------------------------------------------| + | 100·00| 99·47|100·08| 99·83|100·79|101·37|100·00| 99·19 | +----------------------------------------------------------------------------- + +It is obvious that soils produced by the disintegration of these +minerals must differ materially in quality. Those yielded by orthoclase +must generally abound in potash, while albite and labradorite, +containing little or none of that element, must produce soils in which +it is deficient. The quality of the soil they yield is not however +entirely dependent on the nature of the particular felspar which yields +it, but is also intimately connected with the extent to which the +decomposition has advanced. It is observed that different felspars +undergo decomposition with different degrees of rapidity but after a +certain time they all begin to lose their peculiar lustre, acquire a +dull and earthy appearance, and at length fall into a more or less white +and soft powder. During this change water is absorbed, and, by the +decomposing action of the air, the alkaline silicate is gradually +rendered soluble, and at length entirely washed away, leaving a +substance which, when mixed with water, becomes plastic, and has all the +characters of common clay. The nature of this change will be best seen +by the following analysis of the clay produced during this composition, +which is employed in the manufacture of porcelain under the name of +kaolin, or china clay-- + + Silica 46·80 + Alumina 36·83 + Peroxide of iron 3·11 + Carbonate of lime 0·55 + Potash 0·27 + Water 12·44 + ---- + 100·00 + +In this instance the decomposition of the felspar had reached its limit, +a mere trace of potash being left, but if taken at different stages of +the process, variable proportions of that alkali are met with. This +decomposition of felspar is the source of the great deposits of clay +which are so abundantly distributed over the globe, and it takes place +with nearly equal rapidity with potash and soda felspar. It is rarely +complete, and the soils produced from it frequently contain a +considerable proportion of the undecomposed mineral, which continues for +a long period to yield a supply of alkalies to the plants which grow on +them. + +Mica is a very widely distributed mineral, and two varieties of it are +distinguished by mineralogists, one of which is characterised by the +large quantity of magnesia it contains. Different specimens are found to +vary very greatly in composition, but the following analyses may +represent their most usual composition: + + MICA. + |----------------| + Potash. Magnesia. + Silica 46·36 42·65 + Alumina 36·80 12·96 + Peroxide of iron 4·53 --- + Protoxide of iron --- 7·11 + Oxide of manganese 0·02 1·06 + Magnesia --- 25·75 + Potash 9·22 6·03 + Hydrofluoric acid 0·70 0·62 + Water 1·84 3·17 + ---- ---- + 99·47 99·35 + +Mica undergoes decomposition with extreme slowness, as is at once +illustrated by the fact that its shining scales may frequently be met +with entirely unchanged in the soil. Its persistence is dependent on the +small quantity of alkaline constituents which it contains; and for this +reason it is observed that the magnesian micas undergo decomposition +less rapidly than those containing the larger quantity of potash. +Eventually, however, both varieties become converted into clay, their +magnesia and potash passing gradually into soluble forms. + +Hornblende and augite are two widely distributed minerals, which are so +similar in composition and properties that they may be considered +together. Of the former two varieties, basaltic and common have been +distinguished, and their composition is given below:-- + + Hornblende. + |----------------| + Common. Basaltic. Augite. + +Silica 41·50 42·24 50·12 +Alumina 15·75 13·92 4·20 +Protoxide of iron 7·75 14·59 11·60 +Oxide of manganese 0·25 0.33 -- +Lime 14·09 12·24 20·55 +Magnesia 19·40 13·74 13·70 +Water 0·50 -- -- + ---- ---- ---- + 99·24 97·05 99·67 + +In these minerals alkalies are entirely absent, and their decomposition +is due to the presence of protoxide of iron, which readily absorbs +oxygen from the air, when the magnesia is separated and a ferruginous +clay left. + +The minerals just referred to, constitute the great bulk of the mountain +masses, but they are associated with many others which take part in the +formation of the soil. Of these the most important are the zeolites +which do not occur in large masses but are disseminated through the +other rocks in small quantity. They form a large class of minerals of +which Thomsonite and natrolite may be selected as examples-- + + Thomsonite. Natrolite. + +Silica 38·73 48·68 +Alumina 30·84 26·36 +Lime 13·43 -- +Potash 0·54 0·23 +Soda 3·85 16·00 +Water 13·09 9·55 + ---- ---- + 100·48 100·83 + +They are chiefly characterized by containing their silica in a soluble +state, and hence may yield that substance to the plants in a condition +particularly favourable for absorption. + +It is obvious from what has been stated that all these minerals are +capable, by their decomposition, of yielding soft porous masses having +the physical properties of soils, but most of them would be devoid of +many essential ingredients, while not one of them would yield either +phosphoric acid, sulphuric acid, or chlorine. It has, however, been +recently ascertained that certain of these minerals, or at least the +rocks formed from them, contain minute, but distinctly appreciable +traces of phosphoric acid, although in too small quantity to be detected +by ordinary analysis; and small quantities of chlorine and sulphuric +acid may also in most instances be found. + +Still it will be observed that most of these minerals would yield a soil +containing only two or three of those substances, which, as we have +already learned, are essential to the plant. Thus, potash felspar, while +it would give abundance of potash, would be but an inefficient source +of lime and magnesia; and labradorite, which contains abundance of lime, +is altogether deficient in magnesia and potash. + +Nature has, however, provided against this difficulty, for she has so +arranged it that these minerals rarely occur alone, the rocks which form +our great mountain masses being composed of intimate mixtures of two or +more of them, and that in such a manner that the deficiencies of the one +compensate those of the other. We shall shortly mention the composition +of these rocks. + +Granite is a mixture of quartz, felspar, and mica in variable +proportions, and the quality of the soil it yields depends on whether +the variety of felspar present be orthoclase or albite. When the former +is the constituent, granite yields soils of tolerable fertility, +provided their climatic conditions be favourable; but it frequently +occurs in high and exposed situations which are unfavourable to the +growth of plants. Gneiss is a similar mixture, but characterised by the +predominance of mica, and by its banded structure. Owing to the small +quantity of felspar which it contains, and the abundance of the +difficulty decomposable mica, the soils formed by its disintegration are +generally inferior. Mica slate is also a mixture of quartz, felspar, and +mica, but consisting almost entirely of the latter ingredient, and +consequently presenting an extreme infertility. The position of the +granite, gneiss, and mica slate soils in this country is such that very +few of them are of much value; but in warm climates they not +unfrequently produce abundant crops of grain. Syenite is a rock similar +in composition to granite, but having the mica replaced by hornblende, +which by its decomposition yields supplies of lime and magnesia more +readily than they can be obtained from the less easily disintegrated +mica. For this reason soils produced from the syenitic rocks are +frequently possessed of considerable fertility. + +The series of rocks of which greenstone and trap are types, and which +are very widely distributed, differ greatly in composition from those +already mentioned. They are divisible into two great classes, which have +received the names of diorite and dolerite, the former a mixture of +albite and hornblende, the latter of augite and labradorite, sometimes +with considerable quantities of a sort of oligoclase containing both +soda and lime, and of different kinds of zeolitic minerals. Generally +speaking, the soils produced from diorite are superior to those from +dolerite. The albite which the former contains undergoes a rapid +decomposition, and yields abundance of soda along with some potash, +which is seldom altogether wanting, while the hornblende supplies both +lime and magnesia. Dolerite, when composed entirely of augite and +labradorite, produces rather inferior soils; but when it contains +oligoclase and zeolites, and comes under the head of basalt, its +disintegration is the source of soils remarkable for their fertility; +for these latter substances undergoing rapid decomposition furnish the +plants with abundant supplies of alkalies and lime, while the more +slowly decomposing hornblende affords the necessary quantity of +magnesia. In addition to these, the basaltic rocks are found to contain +appreciable quantities of phosphoric acid, so that they are in a +condition to yield to the plant almost all its necessary constituents. + +The different rocks now mentioned, with a few others of less general +distribution, constitute the whole of our great mountain masses; and +while their general composition is such as has been stated, they +frequently contain disseminated through them quantities of other +minerals which, though in trifling quantity, nevertheless add their +quota of valuable constituents to the soils. Moreover, the exact +composition of the minerals of which the great masses of rocks are +composed is liable to some variety. Those which we have taken as +illustrations have been selected as typical of the minerals; but it is +not uncommon to find albite containing 2 or 3 per cent of potash, +labradorite with a considerable proportion of soda, and zeolitic +minerals containing several per cent of potash, the presence of which +must of course considerably modify the properties of the soils produced +from them. They are also greatly affected by the mechanical influences +to which the rocks are exposed; and being situated for the most part in +elevated positions, they are no sooner disintegrated than they are +washed down by the rains. A granite, for instance, as the result of +disintegration, has its felspar reduced to an impalpable powder, while +its quartz and mica remain, the former entirely, the latter in great +part, in the crystalline grains which existed originally in the granite. +If such a disintegrated granite remains on the spot, it is easy to see +what its composition must be; but if exposed to the action of running +water, by which it is washed away from its original site, a process of +separation takes place, the heavy grains of quartz are first deposited, +then the lighter mica, and lastly the felspar. Thus there may be +produced from the same granite, soils of very different nature and +composition, from a pure and barren sand to a rich clay formed entirely +of felspathic debris. + +The sedimentary or stratified rocks are formed of particles carried down +by water and deposited at the bottom of the primeval seas from which +they have been upheaved in the course of geological changes. The +process of their formation may be watched at the present day at the +mouths of all great rivers, where a delta composed of the suspended +matters carried down by the waters is slowly formed. The nature of these +rocks must therefore depend entirely on that of the country through +which the river flows. If its course runs through a country in which +lime is abundant, calcareous rocks will be deposited, and if it passes +through districts of different geological characters the deposit must +necessarily consist of a mixture of the disintegrated particles of the +different rocks the river has encountered. For this reason it is +impossible to enter upon a detailed account of their composition. It is +to be observed, however, that the particles of which they are composed, +though originally derived from the crystalline rocks, have generally +undergone a complex series of changes, geology teaching that, after +deposition, they may in their turn undergo disintegration and be carried +away by water, to be again deposited. Their composition must therefore +vary not merely according to the nature of the rock from which they have +been formed, but also according to the extent to which the decomposition +has gone, and the successive changes to which they have been exposed. +They may be reduced to the three great classes of clays, including the +different kinds of clay slates, shales, etc., sandstone and limestone. +It must be added also, that many of them contain carbonaceous matters +produced by the decomposition of early races of plants and animals, and +that mixtures of two or more of the different classes are frequent. + +The purest clays are produced by the decomposition of felspar, but +almost all the crystalline rocks may produce them by the removal of +their alkalies, iron, lime, etc. Where circumstances have been +favourable, the whole of these substances are removed, and the clay +which remains consists almost entirely of silica and alumina, and yields +a soil which is almost barren, not merely on account of the deficiency +of many of the necessary elements of plants, but because it is so stiff +and impenetrable that the roots find their way into it with difficulty. +It rarely happens, however, that decomposition has advanced so far as to +remove the whole of the alkalies, which is exemplified by the following +analyses of the fire clay of the coal formation, and of transition clay +slate:-- + + Transition Fire Clay. + Clay Slate. + +Silica 60·03 54·77 +Alumina 14·91 28·61 +Peroxide of iron 8·94 4·92 +Lime 2·08 0·58 +Magnesia 4·22 1·14 +Potash 3·87 1·00 +Soda -- 0·24 +Carbonic acid } 5·67 8·24 +Water } + ---- ---- + 99·72 99·50 + +The sandstones are derived from the siliceous particles of granite and +other rocks, and consist in many cases of nearly pure silica, in which +case their disintegration produces a barren sand, but they more +frequently contain an admixture of clay and micaceous scales, which +sometimes form a by no means inconsiderable portion of them. Such +sandstones yield soils of better quality, but they are always light and +poor. Where they occur interstratified with clays, still better soils +are produced, the mutual admixture of the disintegrated rocks affording +a substance of intermediate properties, in which the heaviness of the +clay is tempered by the lightness of the sandstone. + +Limestone is one of the most widely distributed of the stratified rocks, +and in different localities occurs of very different composition. +Limestones are divided into two classes, common and magnesian; the +former a nearly pure carbonate of lime, the latter a mixture of that +substance with carbonate of magnesia. But while these are the principal +constituents, it is not uncommon to find small quantities of phosphate +and sulphate of lime, which, however trifling their proportions, are not +unimportant in an agricultural point of view. The following analyses +will serve to illustrate the general composition of these two sorts of +limestone as they occur in the early geological formations:-- + + COMMON. MAGNESIAN. + |-------------------------| |----------------------| + Mid-Lothian. Sutherland. Sutherland. Dumfries. + +Silica 2·00 7·42 6·00 2·31 +Peroxide of iron } 0·45 0·76 1·57 2·00 + and alumina } +Carbonate of lime 93·61 84·11 50·21 58·81 +Carbonate of } 1·62 7·45 41·22 36·41 + magnesia } +Phosphate of lime 0·56 ... ... ... +Sulphate of lime 0·92 ... ... 0·10 +Organic matter 0·20 ... ... ... +Water 0·50 ... 0·69 ... + ---- ---- ---- ---- + 99·86 99·74 99·69 99·63 + +These limestones are hard and possess to a greater or less extent a +crystalline texture. They are replaced in later geological periods by +others which are much softer, and often purer, of which the oolitic +limestones, so called from their resemblance to the roe of a fish, and +chalk are the most important. Other limestones are also known which +contain an admixture of clay. The soils produced by the disintegration +of limestone and chalk are generally light and porous, but when mixed +with clay, possess a very high degree of fertility, and this is +particularly the case with chalk, which yields some of the most valuable +of all soils. But it is true only of the common limestones, for +experience has shown that those which contain magnesia in large quantity +are often prejudicial to vegetation, and sometimes yield barren or +inferior soils. + +Such are the general characters of the three great classes of stratified +rocks; any attempt to particularise the numerous varieties of each would +lead us far beyond the limits of the present work. It is necessary, +however, to remark, that in many instances one variety passes into the +other, or, more correctly speaking, sedimentary rocks occur, which are +mixtures of two or more of the three great classes. In fact, the name +given to each really expresses only the preponderating ingredient, and +many sandstones contain much clay, shales and clay slates abound in +lime, and limestones in sand or clay, so that it may sometimes be a +matter of some difficulty to decide to which class they belong. Such +mixtures usually produce better soils than either of their constituents +separately, and accordingly, in those geological formations in which +they occur, the soils are generally of excellent quality. The same +effect is produced where numerous thin beds of members of the different +classes are interstratified, the disintegrated portions being gradually +intermixed, and valuable soils formed. + +The fertility of the soils formed from the stratified rocks is also +increased by the presence of organic remains which afford a supply of +phosphoric acid, and which are sometimes so abundant as to form a by no +means unimportant part of their mass. They do not occur in the oldest +sedimentary rocks, but as we ascend to the more recent geological +epochs, they increase in abundance, until, in the greensands and other +recent formations, whole beds of coprolites and other organic remains +are met with. Great differences are observed in the quality of the soils +yielded by different rocks. In general, those formed by the +disintegration of clay slates are cold, heavy, and very difficult and +expensive to work; those of sandstone light and poor, and of limestone +often poor and thin. These statements must, however, be considered as +very general; for individual cases occur in which some of these +substances may produce good soils, remarkable exceptions being offered +by the lower chalk and some of the shales of the coal formation. Little +is at present known regarding the peculiar nature of many of these +rocks, or their composition; and the cause of the differences in the +fertility of the soil produced from them is a subject worthy of minute +investigation. + +_Chemical Composition of the Soil._--Reference has been already made to +the division of the constituents of the soil into the two great classes +of organic and inorganic. And when treating of the sources of the +organic constituents of plants, we entered with some degree of +minuteness into the composition and relations of the different members +of the former class, and expressed the opinion that they did not admit +of being directly absorbed by the plant. But though the parts then +stated lead to the inference that, as a direct source of these +substances, humus is unimportant, it has other functions to perform +which render it an essential constituent of all fertile soils. These +functions are dependent partly on the power which it has of absorbing +and entering into chemical composition with ammonia, and with certain of +the soluble inorganic substances, and partly on the effect which the +carbonic acid produced by its decomposition exerts on the mineral +matters of the soil. In the former way, its effects are strikingly seen +in the manner in which ammonia is absorbed by peat; for it suffices +merely to pour upon some dried peat a small quantity of a dilute +solution of ammonia to find its smell immediately disappear. This +peculiar absorptive power extends also to the fixed alkalies, potash and +soda, as well as to lime and magnesia, and has an important effect in +preventing these substances being washed out of the soil--a property +which, as we shall afterwards see, is possessed also by the clay +contained in greater or less quantity in most soils. On the other hand, +the air and moisture which penetrate the soil cause its decomposition, +and the carbonic acid so produced attacks the undecomposed minerals +existing in it, and liberate the valuable substances they contain. + +In considering the composition of a soil, it is important to bear in +mind that it is a substance of great complexity, not merely because it +contains a large number of chemical elements, but also because it is +made up of a mixture of several minerals in a more or less decomposed +state. The most cursory examination shows that it almost invariably +contains sand and scales of mica, and other substances can often be +detected in it. Now it has been already observed that the minerals of +which soils are composed, differ to a remarkable extent in the facility +with which they undergo decomposition, and the bearing of this fact on +its fertility is a matter of the highest importance, for it has been +found that the mere presence of an abundant supply of all the essential +constituents of plants is not always sufficient to constitute a fertile +soil. Two soils, for instance, may be found on analysis to have exactly +the same composition, although in practice one proves barren and the +other fertile. The cause of this difference lies in the particular +state of combination in which the elements are contained in them, and +unless this be such that the plant is capable of absorbing them, it is +immaterial in what quantity they are present, for they are thus locked +up from use, and condemn the soil to hopeless infertility. + +It is admitted that unless the substances be present in a state in which +they can be dissolved, the plant is incapable of absorbing them; but it +is a matter of doubt whether it is necessary that they be actually +dissolved in the water which permeates the soil, or whether the plant is +capable of exercising a directly solvent action. The latter view is the +most probable, but at the same time it cannot be doubted, that if they +are presented to the plant in solution, they will be absorbed in that +state in preference to any other. Hence it has been considered important +in the analysis of a soil, not to rest content with the determination of +the quantity of each element it contains, but to obtain some indication +of the state of combination in which it exists, so as to have some idea +of the ease or difficulty with which they may be absorbed. For this +purpose it is necessary to determine, _1st_, The substances soluble in +water; _2d_, Those insoluble in water, but soluble in acids; _3d_, Those +insoluble both in water and acids; and if to these the organic +constituents be added, there are four separate heads under which the +components of a soil ought to be classified. This classification is +accordingly adopted in the most careful and minute analyses; but the +difficulty and labour attending them has hitherto precluded the +possibility of making them except in a few instances; and, generally +speaking, chemists have been contented with treating the soil with an +acid, and determining in the solution all that is dissolved. Such +analyses are often useful for practical purposes, as for example, when +they show the absence of lime, or any other individual substance, by the +addition of which we may rectify the deficiency of the soil; but they +are of comparatively little scientific value, and throw but little light +on the true constitution of the soil, and the sources of its fertility. +Nor is it likely that much satisfactory information will be obtained +until the number of minute analyses is so far extended as to establish +the fundamental principles on which the various properties of the soil +depends. + +The separation of the constituents of a soil into the four great groups +already mentioned, is effected in the following manner:--A given +quantity of the soil is boiled with three or four successive quantities +of water, which dissolves out all the soluble matters. These generally +amount to about one-half per cent of the whole soil, and consist of +nearly equal proportions of organic and inorganic substances. In very +light and sandy soils, it occasionally happens that not more than one or +two-tenths per cent dissolve in water, and in peaty soils, on the other +hand, the proportion is sometimes considerably increased, principally +owing to the abundance of soluble organic matters. + +When the residue of this operation is treated with dilute hydrochloric +acid, the matters soluble in acids are obtained in the fluid. The +proportion of these substances is liable to very great variations, and +in some soils of excellent quality, and well adapted to the growth of +wheat, it does not exceed 3 per cent; while in calcareous soils, such as +those of the chalk formation, it may reach as much as 50 or 60 per cent. +In general, however, it amounts to about 10 per cent. The organic +constituents are also very variable in amount; ordinary soils of good +quality containing from 2 to 10 per cent, while in peat soils they not +unfrequently reach 30 or even 50 per cent. But these cannot be +considered _fertile_ soils. The insoluble constituents are likewise +subject to great variations, but, in the ordinary clay and sandy soils +of this country, they generally form from 70 to 85 per cent of the +whole. + +The distribution of the constituents under these different heads will be +best illustrated by a few analyses of soils of good quality, and for +this purpose we shall select two, noted for the excellent crops of wheat +they produce, and for their general fertility. The analyses were made +from the upper 10 inches, and a quantity of the 10 inches immediately +subjacent was analysed as subsoil. The first is the ordinary wheat soil +of the county of Mid-Lothian, the other the alluvial soil of the Carse +of Gowrie in Perthshire, so celebrated for the abundance and luxuriance +of the crops it produces. + +|------------------------------------------|------------------- +| | Mid-Lothian. | Perthshire. +|----------------------|-------------------|------------------- +| | Soil. | Subsoil. | Soil. | Subsoil. +|----------------------|--------|----------|---------|--------- +|SUBSTANCES SOLUBLE | | | | +| IN WATER. | | | | +|Silica | 0·0149 | 0·0104 | 0·0072 | 0·0461 +|Lime | 0·0300 | 0·0072 | 0·0184 | 0·0306 +|Magnesia | 0·0097 | 0·0016 | 0·0040 | 0·0034 +|Chlor. of magnesium | -- | -- | -- | 0·0033 +|Potash | 0·0034 | 0·0037 | -- | -- +|Soda | 0·0065 | 0·0049 | -- | -- +|Chloride of potassium | -- | -- | 0·0088 | 0·0080 +|Chloride of sodium | -- | -- | 0·0110 | 0·0166 +|Sulphuric acid | 0·0193 | 0·0124 | 0·0089 | 0·0239 +|Chlorine | trace | trace | -- | -- +|Organic matters | 0·1481 | 0·2228 | 0·0608 | 0·1342 +| | -------|----------|------------------- +| | 0·2319 | 0·2630 | 0·1191 | 0·2661 +|----------------------|--------|----------|---------|--------- +|SOLUBLE IN ACIDS. | | | | +|Silica | 0·1490| 0·0680 | 0·0482 | 0·1697 +|Peroxide of iron | 5·1730| 3·4820 | 4·8700 | 4·6633 +|Alumina | 2·1540| 1·8130 | 2·6900 | 3·9070 +|Lime | 0·4470| 0·3810 | 0·3616 | 0·5050 +|Magnesia | 0·4120| 0·2850 | 0·3960 | 0·9420 +|Potash | 0·0650| 0·1650 | 0·3445 | 0·1670 +|Soda | 0·0050| 0·0560 | 0·1242 | 0·1920 +|Sulphuric acid | 0·0250| 0·0850 | 0·0911 | 0·0160 +|Phosphoric acid | 0·4300| 0·1970 | 0·2400 | 0·2680 +|Carbonic acid | -- | -- | 0·0500 | -- +| |--------|----------|---------|------- +| | 8·8600| 6·5320 | 9·2156 |10·8300 +| |--------|----------|---------|------- +|INSOLUBLE IN ACIDS. | | | | +|Silica | 71·3890| 82·5090 | 63·1400 |61·4200 +|Alumina | 4·7810| 3·5120 | 11·3500 |10·3400 +|Peroxide of iron | trace | trace | -- | 1·5670 +|Lime | 0·7520| 0·5500 | 0·4500 | 0·7400 +|Magnesia | 0·6610| 0·5500 | 0·6200 | 0·4450 +|Potash | 0·2860| -- | 2·4500 | 2·0030 +|Soda | 0·4220| -- | 1·3100 | 0·8440 +| |--------|----------|---------|------- +| | 78·2910| 87·1210 | 79·3200 |77·3590 +| |--------|----------|---------|------- +|ORGANIC MATTERS. | | | | +| | | | | +|Insoluble organic } | | | | +| matter } | 8·8777| 4·2370 | 7·7400 | 6·2910 +|Humine | 0·8850| 0·3450 | 0·0700 | 0·0840 +|Humic acid | 0·1340| 0·0310 | 0·6800 | 0·3600 +|Apocrenic acid | 0·1533| -- | -- | 0·0929 +|Water | 2·6840| 1·7670 | 2·7000 | 4·5750 +| |--------|----------|---------|------- +| | 12·7340| 6·3800 | 11·1900 |11·4020 +| |========|==========|=========|======= +|Sum of all the | | | | +| constituents |100·1169| 100·2960 | 99·8447 |99·8571 +| +| AMOUNT OF CARBON, HYDROGEN, NITROGEN, AND OXYGEN +| CONTAINED IN 100 PARTS OF EACH SOIL. +| +|Carbon | 4·510 | 1·3060 | 2·55 | 2·03 +|Hydrogen | 0·550 | 0·3324 | 0·71 | 0·53 +|Nitrogen | 0·220 | 0·0973 | 0·21 | 0·17 +|Oxygen | 4·918 | 3·1001 | 5·08 | 4·09 +| |--------|----------|---------|------- +| | 10·198 | 4·8358 | 8·55 | 6·82 +--------------------------------------------------------------- + +In examining these analyses, it is particularly worthy of notice that by +far the larger proportion of the substances soluble in water consists of +organic matter, lime, and sulphuric acid, the two last being in +combination as sulphate of lime, while some of those substances which +are usually considered to be the most important mineral constituents of +plants are present in very small quantity--potash, for instance, forming +not more than 1-25,000th of the whole soil, and phosphoric acid being +entirely absent. On the other hand, this portion contains the whole of +the chlorine which exists in the soil, and this might be anticipated +from the ready solubility in water of the compounds of that substance. + +The portion soluble in acids consists of alumina and oxide of iron, both +of which are comparatively unimportant to the plant, but very important, +as we shall afterwards see, in relation to the physical properties of +the soil. The remainder of the substances soluble in acids, amounting to +from 1 and 2 per cent, is composed of some of the most essential +constituents of plants. Lime, magnesia, potash, and soda, appear again +in larger quantity than in the soluble part, and along with them we have +the phosphoric acid to the amount of from 0·2 to 0·4 per cent of the +whole soil, and sulphuric acid in much smaller quantity. + +The insoluble matters differ remarkably in the two soils, that from the +Carse of Gowrie being characterised by a large quantity of potash and +soda, indicating an important difference in the materials from which +they have been formed. In the Perthshire soil it is obvious that the +felspathic element has been abundant, and that its decomposition has +been arrested at a time, when it still contained a large quantity of +alkalies. And this difference is of great practical importance, because +those soils, which contain a large quantity of potash in their insoluble +portion, have within them a source of permanent fertility, the alkali +being gradually liberated by the decomposition which is constantly in +progress, owing to the air and moisture permeating the soil. As regards +the special distribution of the inorganic matters, it is to be observed +that some of them occur in each of the three heads under which they are +arranged, while others are confined to one or two. Silica and the +alkalies occur generally, though not invariably, in all three. Chlorine +is met with only in the part soluble in water, phosphoric acid only in +that soluble in acids, while sulphuric acid occurs in both the +last-named divisions. + +The greater part of the organic matters are insoluble both in water and +acids. At least it is generally believed that any portion dissolved by +strong acids, in the course of analysis, has been entirely decomposed, +and is in a completely different state from that in which it existed +actually in the soil. + +As an example of a calcareous soil, forming a striking contrast to those +given above, we select one from the island of Antigua, from which very +large crops of sugar-cane are obtained. The soil is of great depth, and +analyses of the subsoil at the depth of 18 inches and 5 feet are given. +These last analyses are not so minute as that of the soil itself, the +soluble matters not having been separately determined, but included in +that soluble in acids. + ++-----------------------------+---------+-----------+--------+ +| | Surface | 18 inches | 5 feet | +| | Soil. | deep. | deep. | ++-----------------------------+---------+-----------+--------+ +| SOLUBLE IN WATER. | | | | +| | | | | +| Lime | 0·07 | ... | ... | +| Magnesia | trace | ... | ... | +| Potash | 0·06 | ... | ... | +| Soda | 0·04 | ... | ... | +| Chlorine | 0·05 | ... | ... | +| Organic matter | 0·15 | ... | ... | +| | ---- | | | +| | 0·37 | | | +| SOLUBLE IN ACIDS. | | | | +| | | | | +| Silica | 0·74 | ... | ... | +| Peroxide of iron | 2·22 | 1·67 | 1·87 | +| Protoxide of iron | 0·77 | 9·05 | 3·10 | +| Alumina | 1·90 | 2·52 | 4·21 | +| Lime | 10·43 | 3·04 | 25·75 | +| Magnesia | 0·20 | 0·54 | 0·51 | +| Potash | 0·03 | 0·29 | 0·28 | +| Soda | 0·02 | 0·11 | 0·16 | +| Sulphuric acid | trace | 0·02 | 0·13 | +| Phosphoric acid | 0·14 | trace | 0·04 | +| Carbonic acid | 7·38 | 0·82 | 20·23 | +| | ----- | ----- | ----- | +| | 23·83 | 18·06 | 56·28 | +| | | | | +| INSOLUBLE IN ACIDS. | | | | +| | | | | +| Silica | 41·44 | 51·24 | 27·67 | +| Protoxide of iron | 3·24 | 0·26 | 1·40 | +| Alumina | 9·00 | 1·50 | 1·00 | +| Lime | 0·08 | 0·88 | trace | +| Magnesia | 0·80 | 0·54 | trace | +| Potash | ... | 0·74 | ... | +| Soda | ... | 0·25 | ... | +| | ----- | ----- | ----- | +| | 54·56 | 55·41 | 30·07 | +| ORGANIC MATTERS. | | | | +| | | | | +| Humine | 1·58 }| | | +| Humic acid | 1·15 }| 12·05 | 7·49 | +| Insoluble organic matters | 7·66 }| | | +| Water | 11·13 | 14·69 | 6·06 | +| | ----- | ----- | ----- | +| | 21·52 | 26·74 | 13·55 | +| +---------+-----------+--------+ +| Sum of all the constituents | 100·28 | 100·21 | 99·90 | +| |=========|===========|========| ++-----------------------------+---------+-----------+--------+ + +In this soil there is a general resemblance in the composition of the +portion soluble in water to those of the wheat soils. But the part +soluble in acids is distinguished by the great abundance of carbonate of +lime. + +The subsoil contains also a large quantity of protoxide of iron, a +substance frequently found in subsoils containing much organic matter, +and to which the air has imperfect access. Under these circumstances +peroxide of iron is reduced to protoxide; and when present abundantly in +the soil in that form, iron has been found to exercise a very injurious +influence on vegetation; and it has frequently happened that when +subsoils containing it have been brought up to the surface, they have in +the first instance caused a manifest deterioration of the soil, although +after some time, when it had become peroxidised by the action of the +air, it ceased to be injurious. + +The soil of Holland, from the neighbourhood of the Zuider Zee, which is +an alluvial deposit from the waters of the Rhine, and produces large +crops, gave the results which follow-- + ++-----------------------------+----------+-----------+-----------+ +| | Surface. | 15 inches | 30 inches | +| | | deep. | deep. | ++-----------------------------+----------+-----------+-----------+ +| Insoluble silica | 57·646 | 51·706 | 55·372 | +| Soluble silica | 2·340 | 2·496 | 2·286 | +| Alumina | 1·830 | 2·900 | 2·888 | +| Peroxide of iron | 9·039 | 10·305 | 11·864 | +| Protoxide of iron | 0·350 | 0·563 | 0·200 | +| Oxide of manganese | 0·288 | 0·354 | 0·284 | +| Lime | 4·092 | 5·096 | 2·480 | +| Magnesia | 0·130 | 0·140 | 0·128 | +| Potash | 1·026 | 1·430 | 1·521 | +| Soda | 1·972 | 2·069 | 1·937 | +| Ammonia | 0·060 | 0·078 | 0·075 | +| Phosphoric acid | 0·466 | 0·324 | 0·478 | +| Sulphuric acid | 0·896 | 1·104 | 0·576 | +| Carbonic acid | 6·085 | 6·940 | 4·775 | +| Chlorine | 1·240 | 1·302 | 1·418 | +| Humic acid | 2·798 | 3·991 | 3·428 | +| Crenic acid | 0·771 | 0·731 | 0·037 | +| Apocrenic acid | 0·107 | 0·160 | 0·152 | +| Other organic matters and } | | | | +| Combined water } | 8·324 | 7·700 | 9·348 | +| Loss | 0·540 | 0·611 | 0·753 | +| | ------- | ------- | ------- | +| | 100·000 | 100·000 | 100·000 | +| |==========|===========|===========| ++-----------------------------+----------+-----------+-----------+ + +It is unnecessary to multiply analyses of fertile soils, those now given +being sufficient to show their general composition. They are all +characterised by the presence, in considerable quantity, of all the +essential constituents of plants, in a state in which they may be +readily absorbed. The absence of one or more of these substances +immediately diminishes or altogether destroys the fertility of the soil; +and the extent to which this occurs is illustrated by the following +analysis of a soil from Pumpherston, Mid-Lothian, forming a small patch +in the lower part of a field, and on which nothing would grow. Being +naturally wet, it had been drained and sowed with oats, which died out +about six weeks after sowing, and left a bare soil on which weeds did +not show the slightest disposition to grow. + + SOLUBLE IN ACIDS. + + Soluble silica 0·173 + Peroxide of iron 6·775 + Alumina 1·150 + Oxide of manganese trace + Carbonate of lime 0·856 + Magnesia 0·099 + Potash 0·132 + Soda 0·123 + Phosphoric acid trace + Chlorine trace + ---- 9·308 + Silica 73·096 + Peroxide of iron 1·371 + Alumina 4·263 + Lime 0·858 + Magnesia 0·520 + ---- 80·108 + Organic matter 8·012 + Water 2·391 + ---- 10·403 + ------ + 99·819 + +In this instance the barrenness of the soil is distinctly traceable to +the deficiency of phosphoric acid, sulphuric acid, and chlorine. There +is also a remarkably large quantity of oxide of iron, which, when acted +on by the humic acid, is well known to be highly prejudicial to +vegetation, and that this took place was shown by the fact that the +drains, a couple of months after being laid, were almost stopped up by +humate of iron. Still more striking are the following analyses:-- + ++----------------------+-----------------+------------+-------------+ +| | Moorland soil | Sandy soil | Soil from | +| | near Aurich, | near | near | +| | East Friesland. | Wettingen. | Muhlhausen. | ++----------------------+-----------------+------------+-------------+ +| Silica and sand | 70·576 | 96·000 | 77·490 | +| Alumina | 1·050 | 0·500 | 9·490 | +| Oxide of iron | 0·252 | 2·000 | 5·800 | +| Oxide of manganese } | trace | { trace | 0·105 | +| Lime } | | { 0·001 | 0·866 | +| Magnesia | 0·012 } | | 0·728 | +| Potash } | } | | { trace | +| Soda } | trace } | trace | { | +| Phosphoric acid } | } | | 0·003 | +| Sulphuric acid } | } | | trace | +| Carbonic acid | ... | ... | 0·200 | +| Chlorine | trace | trace | trace | +| Humic acid | 11·910 | 0·200 | 0·732 | +| Insoluble humus | 16·200 | 1·299 | 0·200 | +| Water | ... | ... | 4·096 | +| |-----------------+------------|-------------| +| | 100·000 | 100·000 | 100·000 | ++----------------------+-----------------+------------+-------------+ + +The results contained in these analyses are peculiarly remarkable, for +they indicate the almost total absence of all those substances which the +plant requires. They must, however, be considered as in a great measure +exceptional cases, as it is but rarely that so large a number of +constituents is absent, and it is much more frequent to find the +deficiency restricted to one or two substances. They are illustrations +of barrenness dependent on different circumstances. The first shows the +unimportance of the organic matters of the soil, which are here +unusually abundant, without in any way counteracting the infertility +dependent on the absence of the other constituents. The second is that +of a nearly pure sand; and the third, though it contains a greater +number of the essential ingredients of the ash, is still rendered +unfruitful by the deficiency of alkalies, sulphuric acid, and chlorine. + +An examination of the foregoing analyses indicates pretty clearly some +of the conditions of fertility of the soil, which must obviously +contain all the constituents of the plants destined to grow upon it. But +it by no means exhausts the subject, for numerous instances are known of +soils containing all the essential elements of plants in abundance, but +on which they nevertheless refuse to grow. In these instances the defect +is due either to the presence of some substance injurious to the plant, +or to the state of combination of those it requires being such as to +prevent their absorption. Reference has been already made to the bad +effects of protoxide of iron, and it would appear that organic matter is +sometimes injurious. Even water, by excluding air, and so preventing +those decompositions which play so important a part in liberating the +essential elements from their more permanent compounds, although it +cannot render a soil absolutely barren, not unfrequently materially +diminishes its fertility. + +The state of combination of the soil constituents unquestionably +exercise a most important influence on its fertility. That this must be +the case is an inference which may be easily drawn from the statements +already made regarding the different minerals from which it is directly +or indirectly produced. If, for instance, a soil consist to a large +extent of mica, it would be found on analysis to contain abundance of +potash and some other matters, and yet our knowledge of the difficulty +with which that mineral is decomposed, would enable us to pronounce +unfavourably of the soil; and practical experience here fully confirms +the scientific inference. + +The forms of combination most favourable to fertility is a subject on +which our information is at present comparatively limited. It was at one +time believed that solubility in water was an indispensable requisite, +but recent investigations appear to lead to a directly contrary +conclusion. The analyses of soils already given, show that the part +directly soluble in water embraces only a certain number of the +constituents of the plant, and of those dissolved the quantity is very +small. This becomes still more apparent if we estimate from the analyses +the actual quantities of those substances contained in an acre of soil. +It is generally assumed that the soil on an imperial acre of land 10 +inches deep weighs in round numbers about 1000 tons; and calculating +from this, we find that the quantity of potash soluble in water in the +Mid-Lothian wheat soil, amounts to no more than 70 lb. per acre. But a +crop of hay carries off from the soil about 38 lb. of potash, and one of +turnips, including tops, not less than 200 lb., so that if only the +matters soluble in water could be taken up by the plant, such soils +could not possess the amount of fertility which they are actually found +to have. + +It is to be remembered, also, that in these analyses the experiment is +made under the most favourable circumstances for ascertaining the whole +quantity of matters which are capable of dissolving in water; that +practically dissolved is very different. The recent analysis by Krocker +and Way of the drainage water of soils afford a means of estimating +this. Way found in one gallon of the drainage water from seven different +fields, collected in the end of December-- + ++-------------------+------+------+------+------+------+------+------+ +| | 1 | 2 | 3 | 4 | 5 | 6 | 7 | ++-------------------+------+------+------+------+------+------+------+ +| Potash, |trace |trace | 0·02 | 0·05 |trace | 0·22 |trace | +| Soda, | 1·00 | 2·17 | 2·26 | 0·87 | 1·42 | 1·40 | 3·20 | +| Lime, | 4·85 | 7·19 | 6·05 | 2·26 | 2·52 | 5·82 |13·00 | +| Magnesia, | 0·68 | 2·32 | 2·48 | 0·41 | 0·21 | 0·93 | 2·50 | +| Iron and Alumina, | 0·40 | 0·05 | 0·10 | none | 1·30 | 0·35 | 0·50 | +| Silica, | 0·95 | 0·45 | 0·55 | 1·20 | 1·80 | 0·65 | 0·85 | +| Chlorine, | 0·70 | 1·10 | 1·27 | 0·81 | 1·26 | 1·21 | 2·62 | +| Sulphuric acid, | 1·65 | 5·15 | 4·40 | 1·71 | 1·29 | 3·12 | 9·51 | +| Phosphoric acid, |trace | 0·12 |trace |trace | 0·08 | 0·06 | 0·12 | +| Ammonia, | 0·018| 0·018| 0·018| 0·012| 0·018| 0·006| 0·018| +| Nitric acid, | 7·17 |14·74 |12·72 | 1·95 | 3·45 | 8·05 |11·45 | +| Organic matter, | 7·00 | 7·40 |12·50 | 5·60 | 5·70 | 5·80 | 7·40 | ++-------------------+------+------+------+------+------+------+------+ + +Some of the soils from which these waters were obtained had been manured +with unusually large quantities of nitrogenous matters, which accounts +for the large amount of nitric acid, as well as the lime which that acid +has extracted. Dr. Krocker's analyses were made on soils less highly +manured, and the water was collected in summer. + ++-----------------------+------------------------------------------------+ +| | IN 10,000 PARTS. | +| +-------+-------+-------+-------+-------+--------| +| | 1 | 2 | 3 | 4 | 5 | 6 | ++-----------------------+-------+-------+-------+-------+-------+--------+ +| Organic matter | 0·25 | 0·24 | 0·16 | 0.06 | 0·63 | 0·56 | +| Carbonate of lime | 0·84 | 0·84 | 1·27 | 0·79 | 0·71 | 0·84 | +| Sulphate of lime | 2·08 | 2·10 | 1·14 | 0·17 | 0·77 | 0·72 | +| Nitrate of lime | 0·02 | 0·02 | 0·01 | 0·02 | 0·02 | 0·02 | +| Carbonate of magnesia | 0·70 | 0·69 | 0·47 | 0·27 | 0·27 | 0·16 | +| Carbonate of iron | 0·04 | 0·04 | 0·04 | 0·02 | 0·02 | 0·01 | +| Potash | 0·02 | 0·02 | 0·02 | 0·02 | 0·04 | 0·06 | +| Soda | 0·11 | 0·15 | 0·13 | 0·10 | 0·05 | 0·04 | +| Chloride of sodium | 0·08 | 0·08 | 0·07 | 0·03 | 0·01 | 0·01 | +| Silica | 0·07 | 0·07 | 0.06 | 0·05 | 0·06 | 0·05 | ++-----------------------+-------+-------+-------+-------+-------+--------+ + +In order to obtain from these experiments an estimate of the quantity of +the substances actually dissolved, we shall select the results obtained +by Way. The average rainfall in Kent, where the waters he examined were +obtained, is 25 inches. Now, it appears that about two-fifths of all the +rain which falls escapes through the drains, and the rest is got rid of +by evaporation. An inch of rain falling on an imperial acre weighs +rather more than a hundred tons; hence, in the course of a year, there +must pass off by the drains about 1000 tons of drainage water, carrying +with it, out of the reach of the plants, such substances as it has +dissolved, and 1500 tons must remain to give to the plant all that it +holds in solution. These 1500 tons of water must, if they have the same +composition as that which escapes, contain only two and a half pounds of +potash, and less than a pound of ammonia. It may be alleged that the +water which remains, lying longer in contact with the soil, may contain +a larger quantity of matters in solution; but even admitting this to be +the case, it cannot for a moment be supposed that they can ever amount +to more than a very small fraction of what is required for a single +crop. It may therefore be stated with certainty that solubility in water +is not essential to the absorption of substances by the plant, which +must possess the power of itself directly attacking, acting chemically +on, and dissolving them. The mode in which it does this is entirely +unknown, but it in all probability depends on very feeble chemical +actions, and hence the importance of having the soil constituents, not +in solution, but in such a state that they may be readily made soluble +by the plants. Many of the minerals from which fertile soils are formed +are probably not attackable by plants when in their natural condition, +and even after disintegration the quantity of the essential elements of +their food, which are present in an easily assimilable state, is at no +one time very large. But this is of comparatively little importance, for +the soil is not an inert unchangeable substance; it is the theatre of an +important series of chemical changes effected by the action of air and +moisture, and producing a continued liberation of its constituents. This +decomposition is effected partly by the carbonic acid of the atmosphere, +but to a much larger extent by its oxygen acting upon the organic +matters of the soil, and causing a constant though slow evolution of +that acid, which in its turn attacks the mineral matters. Boussingault +and Levy have illustrated the extent of this action by examining the +composition of the air contained in the pores of different soils, and +have obtained the following results:-- + ++--------------------+------------+---------------+---------------------------+ +| Nature of | Crop. | No. of cubic |100 VOLUMES OF AIR CONTAIN | +| Soil. | | inches of air +--------+--------+---------+ +| | | in 34 cubic |Carbonic| Oxygen.|Nitrogen.| +| | | inches of soil| acid. | | | ++--------------------+------------+---------------+--------+--------+---------+ +|Light sandy soil, | | | | | | +| newly manured | ... | 8·0 | 2·17 | ... | ... | +| Do. manured | | | | | | +| 8 days before | ... | ... | 1·54 | 18·80| 79·66 | +| Do. long |Yellow | | | | | +| after manuring | turnip | 7·9 | 0·93 | 19·50| 79·57 | +|Very sandy |Vineyard | 9·6 | 1·06 | 19·72| 79·22 | +|Sandy, with many | | | | | | +| stones |Forest | 4·0 | 0·87 | 19·61| 79·52 | +|Loamy | ... | 2·4 | 0·46 | ... | ... | +|Sandy, subsoil | | | | | | +| of the last | ... | 3·0 | 0·24 | ... | ... | +|Sandy soil, long | | | | | | +| after manuring |Trefoil | 7·6 | 0·74 | 19·02| 80·24 | +| Do. Recently | | | | | | +| manured | ... | ... | 0·85 | 19·41| 79·74 | +| Do. manured 8 | | | | | | +| days before | ... | ... | 1·54 | 18·80| 79·66 | +|Heavy clay |Jerusalem | 7·0 | 0·66 | 19·99| 79·35 | +| | artichoke | | | | | +|Fertile soil (moist)|Meadow | 5·5 | 1·79 | 19·41| 78·80 | ++--------------------+------------+---------------+--------+--------+---------+ + +From these analyses it appears that the air contained in the pores of +the soil is much richer in carbonic acid than the atmosphere, the +poorest soil containing about 25 times, and a recently manured soil 250 +times as much. This carbonic acid, which is obviously produced by the +decomposition of the vegetable matters and manure, acting partly as gas +and partly dissolved in the soil water, exerts a solvent action on its +constituents. And, though a very feeble acid, its continuous action +produces in the course of time a large effect; while, during the +interval, the constituents of the soil are safely stored up, and +liberated only as the plant requires them, by which bountiful provision +of nature they are exposed to fewer risks of loss than if they had been +all along in a state in which they could be absorbed. Carbonic acid not +only assists in effecting the decomposition of the minerals of the soil, +but its aqueous solution acts as a solvent of many substances, which +are quite insoluble in pure water. It is in this way that much of the +lime contained in natural waters is held in solution, and it has been +ascertained that magnesia, iron, and even phosphate of lime, may also be +dissolved by it. It is probable that when these substances are +dissolved, the plants will take them from solution in place of +themselves attacking the insoluble matters; but of the extent to which +this may occur nothing is yet known--the action of solvents on the soil +being a subject which is as yet scarcely examined. + +Carbonic acid is, however, a most important agent in producing the +chemical changes in the soil, and the particular value of humus lies in +its affording a supply of that substance exactly when it is wanted; but +the carbonic acid of the atmosphere also takes part in these changes, +although with different degrees of rapidity according to the character +of the soil, acting rapidly in light, and slowly in stiff, clay soils. +The solvent action of the carbonic acid is, no doubt, principally +exerted on the substances soluble in acids, but not entirely, for it is +known that the insoluble part is gradually being disintegrated and made +soluble; and hence it is that the composition of that part of the soil +which resists the action of acids, and which at first sight might appear +of no moment, is really important. It is obvious that this circumstance +must at once confer on the soil of the Carse of Gowrie a great +superiority over those of Mid-Lothian and most other districts; for it +contains in its insoluble part a quantity of alkalies which must +necessarily form a source of continued fertility. Accordingly, +experience has all along shown the great superiority of that soil, and +of alluvial soils generally, which are all more or less similar to it. +The facility with which these matters are attackable by carbonic acid is +also an important element of the fertility of a soil, and it is to the +existence of compounds which are readily decomposed by it that we +attribute the high fertility of the trap soils. + +By a further examination of the analyses of fertile soils, it is at once +apparent that the most essential constituents of plants are by no means +very abundant in them. In fact, phosphoric and sulphuric acids, lime, +magnesia, and the alkalies, which in most instances make up nine-tenths +of the ash of plants, form but a small portion of even the most fertile +soils; while silica, which, except in the grasses, occurs in small +quantity, oxide of iron which is a limited, and alumina a rare, +constituent of the ash, constitute by far their larger part. Thus the +total amount of potash, soda, lime, magnesia, phosphoric and sulphuric +acids and chlorine, contained in the Mid-Lothian wheat soil amounts only +to 3·5888 per cent, and in the Perthshire to 6·4385, the entire +remainder being substances which enter into the plant for the most part +in much smaller quantity. And, as these small quantities of the more +important substances are capable of supplying the wants of the plant, it +must be obvious that a very small fraction of the silica, oxide of iron, +and alumina, which the soils contain, would afford to it the whole +quantity of these substances it requires, and that the remainder must +have some other functions to perform. + +The soil must be considered not merely as the source of the inorganic +food of plants, for it has to act also as a support for them while +growing, and to retain a sufficient quantity of moisture to support +their life; and unless it possess the properties which fit it for this +purpose, it may contain all the elements of the food of plants, and yet +be nearly or altogether barren. + +The adaptation of the soil to this function is dependent to a great +extent on its mechanical texture, and on this considerable light is +frequently thrown by a kind of mechanical analysis. + +If a soil be shaken up with water and allowed to stand for a few +minutes, it rapidly deposits a quantity of grains which are at once +recognised as common sand; and if the water be then poured off into +another vessel and allowed to stand for a longer time, a fine soft +powder, having the properties and composition of common clay, is +deposited, while the clear fluid retains the soluble matters. By a more +careful treatment it is possible to distinguish and separate humus, and +in soils lying on chalk or limestone, calcareous matter or carbonate of +lime. + +In this way the components can be classified into four groups, a mixture +of two or more of which in variable proportions is found in all soils. + +The relative proportions in which these substances exist in soils are, +as we shall afterwards see, the foundation of their classification into +the light, heavy, calcareous, and other sub-divisions. But they are also +intimately connected with certain chemical and mechanical peculiarities +which have an important bearing on its fertility. It is a familiar fact, +that particular soils are specially adapted to the growth of certain +crops; and we talk of a wheat or a turnip soil as readily +distinguishable. It is to be observed, however, that in many such +instances the mere analysis may show no difference, or, at least, none +sufficient to account for the peculiarity. A remarkable illustration is +offered by the following analyses of two soils, on one of which red +clover grows luxuriantly, while on the other it invariably fails. + + Clover fails. Clover succeeds. + +Insoluble silicates 83·90 81·34 +Soluble silica 0·08 0·02 +Peroxide of iron 4·45 6·68 +Alumina 2·40 3·00 +Lime 1·23 1·33 +Magnesia 0·45 0·25 +Potash 0·20 0·22 +Soda 0·07 0·09 +Sulphuric acid 0·05 0·08 +Phosphoric acid 0·38 0·07 +Carbonic acid 0·09 0·34 +Chlorine trace trace +Humic acid 0·42 0·43 +Humine ... 0·10 +Insoluble organic matters 3·70 3·61 +Water 2·54 2·52 + ---- ---- + 99·96 100·08 +Nitrogen 0·15 1·15 + +In this instance such difference as exists is rather in favour of the +soil on which clover fails, but it is exceedingly trifling; and it is +necessary to seek an explanation in the special properties of its +mechanical constituents. + +These properties are partly mechanical and partly chemical, and in both +ways exercise an important influence on the fertility of the soil. + +Sand and clay, the most important of the mechanical constituents, confer +on the soil diametrically opposite properties; the former, when present +in large quantity, producing what are designated as light, the latter +stiff or heavy soils. The hard indestructible siliceous grains, of which +sand is composed, form a soil of an open texture, through which water +readily permeates; while clay, from its fine state of division, and +peculiar adhesiveness or plasticity, gives it a close-textured and +retentive character, and their proper intermixture produces a light +fertile loam, each tempering the peculiar properties of the other. +Indeed, their mixture is manifestly essential, for sand alone contains +little or none of the essential ingredients of plants; and if present in +large quantity, the openness of the soil is excessive, water flows +through it with rapidity, manures are rapidly wasted, and on the +accession of drought, the plants growing upon it soon languish and die. +Clay, on the other hand, is by itself equally objectionable; the +closeness of its texture prevents the spreading of the roots of plants, +and the access of carbonic acid, which, as we have already seen, is so +important an agent in the changes occurring in the soil. In fact, a pure +clay, that is to say, a clay unmixed with sand, even though it may +contain all the essential constituents of the plant, is for this reason +unfertile. Practically, of course, these extreme cases rarely occur; the +heaviest clay soils being mixtures of true clay with sand, and the most +sandy containing their proportion of clay; but frequently the +preponderance of the one over the other is so great, as to produce soils +greatly inferior to those in which the mixture is more uniform. + +It is easy to understand how the proportions in which sand and clay are +mixed must affect the suitability of soils to particular crops, and that +an open soil must be favourable to the turnip, and a heavy clay, owing +to the resistance it offers to the expansion of the bulbs, unfavourable. +But these substances also exercise an important chemical action on the +soluble constituents of the food of plants, combining with them, and +converting them into an insoluble, or nearly insoluble state, so as to +prevent their being washed away by the rain or other water which +percolates through the soil. It has long been known to chemists that +clay has a tendency to absorb a small proportion of ammonia, and even +when brought up from a great depth frequently contains that substance. +It is to Mr. Thompson of Moat Hall, however, that we owe the important +observation, that arable soils rapidly remove ammonia from solution, and +Way, who pursued this investigation, showed that not only ammonia, but +potash, and several of the other important elements of the food of +plants, are thus absorbed. The removal of these substances from solution +is easily illustrated by a simple experiment. It suffices to take a tall +cylindrical vessel open at both ends, and filled with the soil to be +operated upon, which is retained by a piece of rag tied over its lower +end. A quantity of a dilute solution of ammonia being then poured upon +the surface of the soil, and allowed to percolate, the first quantity +which flows away is found to have entirely lost its peculiar smell and +taste; and in a similar manner the removal of potash may be illustrated. +This action is by no means confined to those substances when in the free +state, but is equally marked when they are combined with acids in the +form of salts, and in the latter case the absorption is attended with a +true chemical decomposition, the base only being retained, and the acid +escaping most commonly in combination with lime. Thus, if sulphate of +ammonia be employed, the water which flows from the soil contains +sulphate of lime, and if muriate of ammonia be used, it is muriate of +lime which escapes. + +This absorbent action is most remarkably manifested in the case of +ammonia and potash, but it takes place also with magnesia and soda. With +the latter, however, it is incomplete, only a half or a fourth of the +soda being removed from solution, the difference depending to some +extent on the acid with which it is in combination. The extent to which +absorption takes place varies also with the nature of the soil, and the +state of combination of the substance used. Exact experiments have +hitherto been chiefly confined to ammonia, potash, and lime in the free +state, and as bicarbonate; and the following table gives the results +obtained by Way, with solutions containing about 1 per cent of these +substances in solution:-- + +----------------------------------------------------------------------------- +| | Loamy | Red soil,| Pure | Subsoil | +| | soil, | Berkshire.| clay. | clay, | +| |Dorsetshire.| | | Somersetshire.| +------------------------|------------------------|----------|---------------| +|Ammonia, caustic | 0·3438 | 0·1570 | ... | ... | +| " from muriate | 0·3478 | 0·1966 | 0.2847| 0·0818 | +|Potash, caustic | ... | ... | 1·050 | 2·087 | +| " from nitrate | ... | ... | 0·4980| ... | +|Lime, caustic | ... | ... | 1·468 | ... | +| " from bicarbonate | ... | ... | 0·731 | ... | +------------------------|------------|-----------|----------|--------------- + +From these numbers it appears that very great differences exist in the +absorbent power of different soils, the first of those experimented on +being capable of taking more than twice as much ammonia as the second, +and nearly four times as much as the subsoil clay. It appears also, as +far as absorption goes, to be immaterial whether the ammonia is free or +combined. But it is different with potash, which is absorbed from the +nitrate to the extent of about O·6 per cent, and from a caustic solution +of potash to double that amount. + +The circumstances under which absorption takes place modify, in a manner +which cannot well be explained, the amount absorbed by the same soil. It +is found generally to be most complete with very dilute solutions, and +if a soil be agitated with a quantity of ammonia larger than it can +take up, it will absorb only a certain amount of that substance, but by +a further increase of the amount of ammonia a still larger quantity will +be absorbed. + +It is important to observe that when a salt is used, the base only is +absorbed, and the acid escapes in combination with lime; even nitric +acid, notwithstanding its importance as a food of plants, being in this +predicament. From this it may be gathered that lime is not readily +absorbed from solutions of its salts; indeed, it would appear that the +only salt of that substance liable to absorption is the bicarbonate, +from which it is taken to the extent of 1·4 per cent by the soil. The +absorption of lime from this salt, and that of phosphoric acid, which +takes place to a considerable extent, probably occurs, however, quite +independently of the clay present in the soil, and is occasioned by its +_lime_, which forms an insoluble compound with phosphoric acid, and by +removing half the carbonic acid of the bicarbonate of lime converts it +also into an insoluble state. + +In addition to these mineral substances, organic matters are also +removed from solution. This is conspicuously seen in the case of putrid +urine, which not only loses its ammonia, but also its smell and colour, +when allowed to percolate through soil; and an equally marked result was +obtained with flax water, from which the organic matter was entirely +abstracted. + +The cause of this absorptive power is still very imperfectly known. Mr. +Way having observed that sand has no such property, while clay, even +when obtained from a considerable depth, always possesses it, supposed +that the absorption was entirely due to that substance. A difficulty, +however, presents itself in explaining how it should happen that while a +pure clay absorbs only 0·2847 of ammonia, a loamy soil, of which +one-half probably is sand, should absorb a larger quantity. The +inference is, that the effect cannot be due to the clay as a whole, and +Mr. Way has sought to explain it by supposing that there exist in the +soil particular double silicates of alumina and lime. He has shown that +felspar and the other minerals from which the soil is produced have no +absorbent power, but that artificial compounds can be formed which act +upon solutions of ammonia and potash in a manner very similar to the +soil; but there is not the slightest evidence that these compounds exist +in the soil, and in the year 1853[I] I pointed out the probability that +clay is not the only agent at work, but that the organic matters take +part in the process. So powerful indeed is the affinity of these +substances for ammonia, that chemists are at one as to the difficulty of +obtaining humic and other similar acids pure, owing to the obstinacy +with which they retain it; and there cannot be a doubt that in many +soils these substances are in this point of view of much importance. +This is particularly the case in peat soils, which, though naturally +barren, may be made to produce good crops by the application of sand or +gravel; and as neither of these can cause any absorption of the valuable +matters, we must attribute this effect to the organic matter. Referring +to an earlier series of experiments made in 1850, I showed that, if a +quantity of dry peat be taken and ammonia poured on it, its smell +disappears; and this may be continued until upwards of 1·5 per cent of +dry ammonia has been absorbed, and this quantity is _retained_ by the +peat. + +In this case pure ammonia was used, but Way's experiments having shown +that this alkali is not absorbed from its salts by organic matters, I +expressed the opinion that humate of lime (which certainly exists in +most soils) ought on chemical grounds to decompose the salts of ammonia +and cause the retention of their base. The recent researches of +Brustlein have shown that lime does cause the organic matters to absorb +ammonia from its salts. He confirms the fact that pure ammonia is +absorbed by peat, and shows that decayed wood has the same effect, +although both are without action on solutions of its salts. A stiff +clay, on the other hand, containing organic matters and much carbonate +of lime, readily absorbed ammonia, both when pure and combined; but +after extracting the lime by means of a dilute acid, it lost the power +of taking it from its salts, although it retained the free alkali as +completely as before. On the addition of a small quantity of lime, it +again acquired the power of withdrawing ammonia from its compounds. +These experiments may be explained, either on the supposition of the +presence of humate of lime, or by supposing that the carbonate of lime +first decomposed the salts of ammonia, and that the liberated alkali +combined with the organic matter. It must be admitted, however, that it +is very doubtful whether the ammonia and other substances are fixed in +the soil by a true chemical combination. They are certainly retained by +a very feeble attraction, for it appears from Brustlein's experiments +that ammonia may be, to a considerable extent, removed by washing with +abundance of water, and that if the soil which has absorbed ammonia be +allowed to become dry in the air, it loses half its ammonia, and after +four times moistening and drying, three-fourths have disappeared. These +facts are certainly not incompatible with the presence of a true +chemical compound, for the humate of ammonia is not absolutely +insoluble, and many cases occur of actions taking place in the presence +of water, which are entirely reversed when that fluid is removed; and it +is quite possible that when humate of ammonia is dried in contact with +carbonate of lime, it may be decomposed, and carbonate of ammonia +escape. There are other circumstances, however, which render it, on the +whole, most probable that the combination is not wholly chemical, but +rather of a physical character, among which may be more especially +mentioned the fact, that the quantity of the substances retained by the +soil is dependent on the degree of dilution of the fluid from which they +are taken; and that the quantity absorbed never exceeds a very small +fraction of the weight of the soil. + +The practical inferences to be drawn from these facts regarding the +value of soils are of the highest importance. It is obvious that two +soils having exactly the same chemical composition may differ widely in +absorptive power, and that which possesses it most largely must have the +highest agricultural value. The examination of different soils, in this +point of view, is a subject of much importance, and deserves the best +attention of both farmers and chemists, although little has as yet been +done in regard to it, and the results which have been obtained are not +of a very satisfactory character. Liebig states, that in his +experiments, all the arable soils examined possessed the same absorptive +power, whether they contained a large or a small proportion of lime or +alumina. It can scarcely be expected, however, that this should be true +in all cases, and there are many facts which seem to indicate that +differences must exist. It is well known that there are some soils in +which the manure is very rapidly exhausted, and it is more than probable +that this effect is due to deficient absorptive power, which leaves the +soluble matters at the mercy of the weather, and liable at any moment +to be washed out by a heavy fall of rain. + +The more strictly mechanical properties of the soil, such as its +relations to heat and moisture, are not less important than its chemical +composition. It is known that soils differ so greatly in these respects +as sometimes materially to affect their productive capacity. Thus, for +instance, two soils may be identical in composition, but one may be +highly hygrometric, that is, may absorb moisture readily from the air, +while the other may be very deficient in that property. Under ordinary +circumstances no difference will be apparent in their produce, but in a +dry season the crop upon the former may be in a flourishing condition, +while that on the latter is languishing and enfeebled, merely from its +inability to absorb from the air, and supply to the plant the quantity +of water required for its growth. In the same way, a soil which absorbs +much heat from the sun's rays surpasses another which has not that +property; and though in many cases this effect is comparatively +unimportant, in others it may make the difference between successful and +unsuccessful cultivation in soils which lie in an unfavourable climate +or exposure. + +The investigation of the physical characters of soils has attracted +little attention, and we owe all our present knowledge of the subject to +a very elaborate series of researches on this subject, published by +Schübler, nearly thirty years ago. He determined _1st_, The specific +gravity of the soils; _2d_, The quantity of water which they are capable +of imbibing; _3d_, The rapidity with which they give off by evaporation +the water they have imbibed; that is, their tendency to become dry; +_4th_, The extent to which they shrink in drying; _5th_, Their +hygrometric power; _6th_, The extent to which they are heated by the +sun's rays; _7th_, The rapidity with which a heated soil cools down, +which indicates its power of _retaining_ heat; _8th_, Their tenacity, or +the resistance they offer to the passage of agricultural implements; +_9th_, Their power of absorbing oxygen from the air. Each of these +experiments was performed on several different soils, and on their +mechanical constituents. Schübler's experiments are undoubtedly +important, and though the methods employed are some of them not +altogether beyond cavil, they have apparently been performed with great +care. It is nevertheless desirable that they should be repeated, for +such facts ought not to rest on the authority of one experimenter, +however skilful and conscientious, nor on a single series of soils, +which may not give a fair representation of their general physical +properties. In fact, Schübler appears to imagine that having once +determined the extent to which the sand, clay, and other mechanical +constituents of the soil possess these properties, we are in a condition +to predicate the effect of their mixture in variable proportions, +although this is by no means probable. + +In examining these properties, Schübler selected for experiment, pure +siliceous sand, calcareous sand (carbonate of lime in coarse grains), +finely powdered carbonate of lime, pure clay, humus, and powdered +gypsum. He used also a heavy clay consisting of 11 per cent of sand and +89 of pure clay, a somewhat stiff clay containing 24 per cent of sand +and 76 of clay, a light clay with 40 per cent of sand and 60 of pure +clay, a garden soil consisting of 52·4 per cent of clay, 36·5 of +siliceous sand, 1·8 of calcareous sand, 2 per cent of finely divided +carbonate of lime, and 7·2 of humus, and two arable soils, one from +Hoffwyl, and one from a valley in the Jura, the former a somewhat stiff, +the latter a light soil. + + ++-------------------+----------+-----------+-----------+------------+ +| | | | Of 100 | | +| | | | parts of | Diminution | +| | | Water | water | in bulk | +| | | absorbed | absorbed | during | +| | | by 100 | there | drying of | +| | Specific | parts | evaporate | 100 parts | +| | gravity. | per cent. | in four | moist | +| | | | hours | soil | +| | | | at 66° | | ++-------------------+----------+-----------+-----------+------------+ +| Siliceous sand | 2·753 | 25 | 88·4 | 0·0 | +| Calcareous sand | 2·822 | 29 | 75·9 | 0·0 | +| Light clay | 2·701 | 40 | 52·0 | 6·0 | +| Stiff clay | 2·652 | 50 | 45·7 | 8·9 | +| Heavy clay | 2·603 | 61 | 34·9 | 11·4 | +| Pure clay | 2·591 | 70 | 31·3 | 18·3 | +| Carbonate of lime | 2·468 | 85 | 28·0 | 5·0 | +| Humus | 1·225 | 190 | 20·5 | 20·0 | +| Gypsum | 2·358 | 27 | 71·7 | 0·0 | +| Garden soil | 2·332 | 96 | 24·5 | 14·9 | +| Soil from Hoffwyl | 2·401 | 52 | 32·0 | 12·0 | +| Soil from Jura | 2·526 | 47 | 40·1 | 9·5 | ++-------------------+----------+-----------+-----------+------------+ + ++-------------------+-------------------------------------------+------------+ +| | Quantity | Power of | +| | of | retaining | +| | hygrometric water absorbed | heat. | +| | by 77·165 grains of the soil spread on | Calcareous | +| | a surface of 141·48 square inches. | sand, | +--------------------+----------+----------+----------+----------+ 100. | +| | 12 hours.| 24 hours.| 48 hours.| 72 hours.| | +--------------------+----------+----------+----------+----------+------------- +| Siliceous sand | 0 | 0 | 0 | 0 | 95·6 | +| Calcareous sand | 0·154 | 0·231 | 0·231 | 0·231 | 100·0 | +| Light clay | 1·617 | 2·002 | 2·156 | 2·156 | 76·9 | +| Stiff clay | 1·925 | 2·310 | 2·618 | 2·695 | 71·1 | +| Heavy clay | 2·310 | 2·772 | 3·080 | 3·157 | 68·4 | +| Pure clay | 2·849 | 3·234 | 3·696 | 3·773 | 66·7 | +| Carbonate of lime | 2·002 | 2·387 | 2·695 | 2·695 | 61·8 | +| Humus | 6·160 | 7·469 | 8·470 | 9·240 | 49·0 | +| Gypsum | 0·077 | 0·077 | 0·077 | 0·077 | 73·2 | +| Garden soil | 2·695 | 3·465 | 3·850 | 4·004 | 64·8 | +| Soil from Hoffwyl | 1·232 | 1·771 | 1·771 | 1·771 | 70·1 | +| Soil from Jura | 1·078 | 1·463 | 1·540 | 1·540 | 74·3 | +--------------------+----------+----------+----------+----------+------------+ + +|------------------+------------+-----------------| +| | | Quantity of | +| | | oxygen absorbed | +| | | by | +| | | 77·165 grains | +| | | of the moist | +| | | soil in 30 | +| | Tenacity | days, from 15 | +| | of the | cubic inches | +| | soils. | of atmospheric | +| | Pure clay, | air. | +| | 100. | Expressed in | +| | | cubic inches. | ++-----------------+|------------|-----------------| +|Siliceous sand | 0 | 0·24 | +|Calcareous sand | 0 | 0·84 | +|Light clay | 57·3 | 1·39 | +|Stiff clay | 68·8 | 1·65 | +|Heavy clay | 83·3 | 2·04 | +|Pure clay | 100·0 | 2·29 | +|Carbonate of lime | 5·0 | 1·62 | +|Humus | 8·7 | 3·04 | +|Gypsum | 7·3 | 0·40 | +|Garden soil | 7·6 | 2·60 | +|Soil from Hoffwyl | 33·0 | 2·43 | +|Soil from Jura | 22·0 | 2·25 | +--------------------------------------------------- + +The experiments detailed in the preceding table speak in a great measure +for themselves, and scarcely require detailed comment. It may be +remarked, however, that the columns illustrating the relations of the +soil to water are probably more important than the others. The +superiority of a retentive over an open soil is sufficiently familiar in +practice, and though this is no doubt partly due to the former absorbing +and retaining more completely the ammonia and other valuable +constituents of the manures applied to it, it is also dependent to an +equal if not greater extent upon the power it possesses of retaining +moisture. A reference to the table makes it apparent that this power is +presented under three different heads, which are certainly related to +one another, but are not identical. In the second column of the table is +given the quantity of water absorbed by the soil, determined by placing +a given weight of the perfectly dry soil in a funnel, the neck of which +is partially stopped with a small piece of sponge or wool, pouring water +upon it, and weighing it after the water has ceased to drop from it. +This may be considered as representing the quantity of water retained by +these different soils when thoroughly saturated by long continued rains. +The column immediately succeeding gives the quantity of that water which +escapes by evaporation from the same soil after exposure for four hours +to dry air at the temperature of 66°. The fifth, sixth, seventh, and +eighth columns indicate the quantity of moisture absorbed, when the +soil, previously artificially dried, is exposed to moist air for +different periods. These characters are dependent principally, though +not entirely, on the porosity of the soil. The last may also be in some +measure due to the presence of particular salts, such as common salt, +which has a great affinity for moisture, but is chiefly occasioned by +their peculiar structure. It is to be remarked that clay and humus are +two of the most highly hygrometric substances known, and it is +peculiarly interesting to observe, that by a beneficent provision of +nature, they also form a principal part of all fertile soils. The +quantity of water imbibed by the soil is important to its fertility, in +so far as it prevents it becoming rapidly dry after having been +moistened by the rains. It is valuable also in another point of view, +because if the soil be incapable of absorbing much water, it becomes +saturated by a moderate fall of rain, and when a larger quantity falls, +the excess of necessity percolates through the soil, and carries off +with it a certain quantity of the soluble salts. Important as this +property is, however, it must not be possessed in too high a degree, but +must permit the _evaporation_ of the water retained with a certain +degree of rapidity. Soils which do not admit of this taking place are +the cause of much inconvenience and injury in practice. By becoming +thoroughly saturated with moisture during winter, they remain for a long +time in a wet and unworkable condition, in consequence of which they +cannot be prepared and sown until late in the season, and though +chemically unexceptionable, they are always disadvantageous, and in some +seasons greatly disappoint the hopes of the farmer. + +The extent to which the imbibition and evaporation of water takes place +is very variable, but they are obviously related to one another, the +soils which absorb it least abundantly parting with it again with the +greatest, facility; for it appears that siliceous sand absorbs only +one-fourth of its weight of water, and again gives off in the course of +four hours four-fifths of that it had taken up, while humus, which +imbibes nearly twice its weight, retains nine-tenths of that quantity +after four hours' exposure. Long-continued and slow evaporation of the +water absorbed by a soil is injurious in another way, for it makes the +soil "cold"--a term of practical origin, but which very correctly +expresses the peculiarity in question. It is due to the fact, that when +water evaporates it absorbs a very large quantity of heat, which +prevents the soil acquiring a sufficiently high temperature from the +sun's rays. The soils which have absorbed a large quantity of moisture +shrink more or less in the process of drying, and form cracks, which +often break the delicate fibres of the roots of the plants, and cause +considerable injury: the extent of this shrinking is given in the fourth +column. + +The relation of the soils to heat divides itself into two +considerations: the amount of heat absorbed by the soil, and the degree +in which it is retained. Of these the latter only is illustrated in the +table. The former is dependent on so many special considerations, that +the results cannot be tabulated in a satisfactory manner. It is +independent of the chemical nature of the soil, but varies to a great +extent according to its colour, the angle of incidence of the sun's +rays, and its state of moisture. It is, however, an important character, +and has been found by Girardin to exercise a considerable influence on +the rapidity with which the crop ripens. He found in a particular year +that, on the 25th of August, 26 varieties of potatoes were ripe on a +very dark-coloured sandy vegetable mould, 20 on an ordinary sandy soil, +19 on a loamy soil, and only 16 on a nearly white calcareous soil. + +The tenacity of the soil is very variable, and indicates the great +differences in the amount of power which must be expended in working +them. According to Schübler, a soil whose tenacity does not exceed 10, +is easily tilled, but when it reaches 40 it becomes very difficult and +heavy to work. + +On examining the table it becomes manifest, that as far as its +mechanical properties are concerned, humus is a substance of the very +highest importance, for it confers on the soil, in a high degree, the +power of absorbing and retaining water, diminishes its tenacity and +permits its being more easily worked, adds to its hygrometric power and +property of absorbing oxygen from the air, and finally, from its dark +colour, causes the more rapid absorption of heat from the sun's rays. It +will be thus understood, that though it does not directly supply food to +the plant, it ministers indirectly in a most important manner to its +well-being, and that to so great an extent that it must be considered an +indispensable constituent of a fertile soil. But it is important to +observe that it must not be present in too large a quantity, for an +excess does away with all the good effects of a smaller supply, and +produces soils notorious for their infertility. + +Such are the important physical properties of the soil, and it is +greatly to be desired that they should be more extensively examined. The +great labour which this involves has, however, hitherto prevented its +being done, and will, in all probability, render it impossible except in +a limited number of cases. Some of these characters are, however, of +minor importance, and for ordinary purposes it might be sufficient to +determine the specific gravity of the soil in the dry and moist state, +the power of imbibing and retaining water, its hygrometric power, its +tenacity, and its colour. With these data we should be in a condition to +draw probable conclusions regarding the others; for the higher the +specific gravity in the dry state, the greater is the power of the soil +to retain heat, and the darker its colour the more readily does it +absorb it. The greater its tenacity the more difficult is it to work, +and the greater difficulty will the roots of the young plant find in +pushing their way through it. The greater the power of imbibing water, +the more it shrinks in drying; and the more slowly the water evaporates, +the colder is the soil produced. The hygrometric power is so important a +character that Davy and other chemists have even believed it possible to +make it the measure of the fertility of a soil; but though this may be +true within certain limits, it must not be too broadly assumed, the +results of recent experiments by no means confirming the opinion in its +integrity, but indicating only some relation between the two. + +_The Subsoil._--The term soil is strictly confined to that portion of +the surface turned over by the plough working at ordinary depth; which, +as a general rule, may be taken at 10 inches. The portion immediately +subjacent is called the subsoil, and it has considerable agricultural +importance, and requires a short notice. In many instances, soil and +subsoil are separated by a purely imaginary line, and no striking +difference can be observed either in their chemical or physical +characters. In such cases it has been the practice with some persons not +to limit the term soil to the upper portion, but to apply it to the +whole depth, however great it may be, which agrees in characters with +the upper part, and only to call that subsoil which manifestly differs +from it. This principle is perhaps theoretically the more correct, but +great practical advantages are derived from limiting the name of soil to +the depth actually worked in common agricultural operations. The subsoil +is always analogous in its general characters to a soil, but it may be +either identical with that which overlies it or not. Of the former, +striking illustrations are seen in the wheat subsoils, the analyses of +which have been already given. In the latter case great differences may +exist, and a heavy clay is often found lying on an open and porous sand, +or on peat, and _vice versa_. Even where the characters of the subsoil +appear the same as those of the soil, appreciable chemical differences +are generally observed, especially in the quantity of organic matter, +which is increased in the soil by the decay of plants growing upon it +and by the manure added. In general, then, all that we have said +regarding the characters of soils both chemically and physically, will +apply to the subsoils, except that, owing to the difficulty with which +the air reaches the latter, some minor peculiarities are observed. The +most important is the effect of the decay of vegetable matter, without +access of air, which is attended by the reduction of the peroxide of +iron to the state of protoxide, and not unfrequently by the production +of sulphuret of iron, compounds which are extremely prejudicial to +vegetation, and occasionally give rise to some difficulties when the +subsoil is brought to the surface, as we shall afterwards have to +notice. + +The physical characters of the subsoil are often of much importance to +the soil itself. As, for instance, where a light soil lies on a clay +subsoil, in which case its value is much higher than if it reposed on an +open or sandy subsoil. And in many similar modes an important influence +is exerted; but these belong more strictly to the practical department +of agriculture, and need not be mentioned here. + +_Classification of Soils._--Numerous attempts have been made to form a +classification of soils according to their characters and value, but +they have not hitherto proved very successful; and the result of more +recent chemical investigations has not been such as to encourage a +farther attempt. We have not at present data sufficient for the purpose, +nor, if we had, would it be possible to arrange any soil in its class +except after an elaborate chemical examination. The only classification +at present possible must be founded on the general physical characters +of the soil; and the ordinary mode followed in practice of dividing them +into clays, loams, etc. etc., which we need not here particularize, +fulfils all that can be done until we have more minute information +regarding a large number of soils. Those of our readers who desire more +full information on this point are referred to the works of Thaer, +Schübler, and others, where the subject is minutely discussed. + +FOOTNOTES: + +[Footnote I: Transactions of the Highland and Agricultural Society, vol. +vi., p. 317.] + + + + +CHAPTER VI. + +THE IMPROVEMENT OF THE SOIL BY MECHANICAL PROCESSES. + + +Comparatively few uncultivated soils possess the physical properties or +chemical composition required for the production of the most abundant +crops. Either one or more of the substances essential to the growth of +plants are absent, or, if present, they are deficient in quantity, or +exist in some state in which they cannot be absorbed. Such defects, +whether mechanical or chemical, admit of diminution, or even entire +removal, by certain methods of treatment, the adaptation of which to +particular cases is necessarily one of the most important branches of +agricultural practice, as the elucidation of their mode of action is of +its theory. The observations already made with regard to the characters +of fertile soils must have prepared the reader for the statement that +these defects may be removed, either by mechanical or chemical +processes. The former method of improvement may at first sight appear to +fall more strictly under the head of practical agriculture, of which the +mechanical treatment of the soil forms so important a part, and that +their improvement by chemical means should form the sole subject of our +consideration in a treatise on agricultural chemistry. But the line of +demarcation between the mechanical and the chemical, which seems so +marked, disappears on more minute observation, and we find that the +mechanical methods of improvement are frequently dependent on chemical +principles; and those which, at first sight, appear to be entirely +chemical, are also in reality partly mechanical. It will be necessary +for us, therefore, to consider shortly the mechanical methods of +improving the soil. + +_Draining._--By far the most important method of mechanically improving +the soil is by draining--a practice the beneficial action of which is +dependent on a great variety of circumstances. It is unnecessary to +insist on the advantage derived from the rapid removal of moisture, +which enables the soil to be worked at times when this used to be almost +impossible, and other direct practical benefits. Of its more strictly +chemical effects, the most important is probably that which it produces +on the temperature of the soil. It has been already remarked that the +germination of a seed is dependent on the soil in which it is sown +acquiring a certain temperature, and the rapidity of the after-growth of +the plant is, in part at least, dependent on the same circumstance. The +necessary temperature is speedily attained by the heating action of the +sun's rays, when the soil is dry; but when it is wet, the heat is +expended in evaporating the moisture with which it is saturated; and it +is only after this has been effected that it acquires a sufficiently +high temperature to produce the rapid growth of the seeds committed to +it. + +The extent to which this effect occurs may be best illustrated by +reference to some experiments made by Schübler, in which he determined +the temperature attained by different soils, in the wet and dry state, +when exposed to the sun's rays, from 11 till 3 o'clock, in the latter +part of August, when the temperature in the shade varied from 73° to +77°. + ++-----------------------+-------+-------+ +| Description of Soil. | Wet. | Dry. | ++-----------------------+-------+-------+ +| | Degs. | Degs. | +| Siliceous sand | 99·1 | 112·6 | +| Calcareous sand | 99·3 | 112·1 | +| Sandy clay | 98·2 | 111·4 | +| Loamy clay | 99·1 | 112·1 | +| Stiff clay | 99·3 | 112·3 | +| Fine bluish-grey clay | 99·5 | 113·0 | +| Garden mould | 99·5 | 113·5 | +| Arable soil | 97·7 | 111·7 | +| Slaty marl | 101·8 | 115·3 | ++-----------------------+-------+-------+ + +In a soil which is naturally dry or has been drained, the superfluous +moisture escapes by the drains, and only that comparatively small +quantity which is retained by capillary attraction is evaporated, and +hence the soil is more frequently and for a longer period in a condition +to take advantage of the heating effect of the sun's rays, and in this +way the period of germination, and, by consequence also, that of +ripening is advanced. The extent of this influence is necessarily +variable, but it is generally considerable, and in some districts of +Scotland the extensive introduction of draining has made the harvest, on +the average of years, from ten to fourteen days earlier than it was +before. It is unnecessary to insist on the importance of such a change, +which in upland districts may make cultivation successful when it was +previously almost impossible. The removal of moisture by drainage +affects the physical characters of the soil in another manner; it makes +it lighter, more friable, and more easily worked; and this change is +occasioned by the downward flow of the water carrying with it to the +lower part of the soil the finer argillaceous particles, leaving the +coarser and sandy matters above, and in this way a marked improvement is +produced on heavy and retentive clays. The access of air to the soil is +also greatly promoted by draining. In wet soils the pores are filled +with water, and hence the air, which is so important an agent in their +amelioration, is excluded; but so soon as this is removed, the air is +enabled to reach and act upon the organic matters and other decomposable +constituents present. In this way also provision is made for the +frequent change of the air which permeates the soil; for every shower +that falls expels from it a quantity of that which it contains, and as +the moisture flows off by the drains, a new supply enters to take its +place, and thus the important changes which the atmospheric oxygen +produces on the soil are promoted in a high degree. The air which thus +enters acts on the organic matters of the soil, producing carbonic acid, +which we have already seen is so intimately connected with many of its +chemical changes. In its absence the organic matters undergo different +decompositions, and pass into states in which they are slowly acted on, +and are incapable of supplying a sufficient quantity of carbonic acid to +the soil; and they thus exercise an action on the peroxide of iron, +contained in all soils, reduce it to the state of protoxide, or, with +the simultaneous reduction of the sulphuric acid, they produce sulphuret +of iron, forms of combination which are well known to be most injurious +to vegetation. + +The removal of water from the lower part of the soil, and the admission +of air, which is the consequence of draining, submits that part of it to +the same changes which take place in its upper portion, and has the +effect of practically deepening the soil to the extent to which it is +thus laid dry. The roots of the plants growing on the soil, which stop +as soon as they reach the moist part, now descend to a lower level, and +derive from that part of it supplies of nourishment formerly +unavailable. The deepening of the soil has further the effect of making +the plants which grow upon it less liable to be burned up in seasons of +drought, a somewhat unexpected result of making a soil drier, but which +manifestly depends on its permitting the roots to penetrate to a greater +depth, and so to get beyond the surface portion, which is rapidly dried +up, and to which they were formerly confined. + +It may be added also that the abundant escape of water from the drains +acts chemically by removing any noxious matters the soil may contain, +and by diminishing the amount of soluble saline matters, which sometimes +produce injurious effects. It thus prevents the saline incrustation +frequently seen in dry seasons on soils which are naturally wet, and +which is produced by the water rising to the surface by capillary +attraction, and, as it evaporates, depositing the soluble substances it +contained, as a hard crust which prevents the access of air to the +interior of the soil. + +It is thus obvious that the drainage of the soil modifies its properties +both mechanically and chemically. It exerts also various other actions +in particular cases which we cannot here stop to particularize. It +ameliorates the climate of districts in which it is extensively carried +out, and even affects the health of the population in a favourable +manner. The sum of its effects must necessarily differ greatly in +different soils, and in different districts; but a competent +authority[J] has estimated, that, on the average, land which has been +drained produces a quarter more grain per acre than that which is +undrained. But this by no means exhausts the benefits derived from it, +draining being merely the precursor of further improvement. It is only +after it has been carried out that the farmer derives the full benefit +of the manures which he applies. He gains also by the increased facility +of working the soil, and by the rapidity with which it dries after +continued rain, thus enabling him to proceed at their proper season with +agricultural operations, which would otherwise have to be postponed for +a considerable time. + +It would be out of place to enlarge here upon the mode in which draining +ought to be carried out; it may be remarked, however, that much +inconvenience and loss has occasionally been produced by too close +adherence to particular systems. No rules can be laid down as to the +depth or distance between the drains which can be universally +applicable, but the intelligent drainer will seek to modify his practice +according to the circumstances of the case. As a general rule, the +drains ought to be as deep as possible, but in numerous instances it may +be more advantageous to curtail their depth and increase their number. +If, for instance, a thick impervious pan resting on a clay were found at +the depth of three feet below the surface, it would serve no good +purpose to make the drains deeper; but if the pan were thin, and the +subjacent layer readily permeable by water, it might be advantageous to +go down to the depth of four feet, trusting to the possible action of +the air which would thus be admitted, gradually to disintegrate the pan, +and increase the depth of soil above it. It is a common opinion that if +we reach, at a moderate depth, a tenacious and little permeable clay, no +advantage is obtained by sinking the drains into it; but this is an +opinion which should be adopted with caution, both because no clay is +absolutely impermeable, even the most tenacious permitting to a certain +extent the passage of water, and because the clay may have been brought +down by water from the upper part of the soil, and may have stopped +there merely for want of some deeper escape for the water, and which +drains at a lower level might supply. In some cases it may even be +advisable to vary the depth of the drains in different parts of the same +field, and the judicious drainer may sometimes save a considerable sum +by a careful observation of the peculiarities of the different parts of +the ground to be drained. + +_Subsoil and Deep Ploughing._--It frequently happens, when a soil is +drained, that the subsoil is so stiff as to permit the passage of water +imperfectly, and to prevent the tender roots of the plant from +penetrating it, and reaching the new supplies of nourishment which are +laid open to them. In such cases the benefits of subsoil ploughing and +deep ploughing are conspicuous. The mode of action of these two methods +of treatment is similar but not identical. The subsoil plough merely +stirs and opens the subsoil, and permits the more ready passage of water +and the access of air and of the roots of plants--the former to effect +the necessary decompositions, the latter to avail themselves of the +valuable matters set free. But deep ploughing produces more extensive +changes; it raises new soil to the surface, mixes it with the original +soil, and thus not only brings up fresh supplies of valuable matters to +it, but frequently changes its chemical and mechanical characters, +rendering a heavy soil lighter by the admixture of a light subsoil, and +_vice versa_. Both are operations which are useless unless they are +combined with draining, for it must manifestly serve no good purpose to +attempt to open up a soil unless the water which lies in it be +previously removed. In fact, subsoiling is useless unless the subsoil +has been made thoroughly dry; and it has been found by experience that +no good effects are obtained if it be attempted immediately after +draining, but that a sufficient time must elapse, in order to permit the +escape of the accumulated moisture, which often takes place very slowly. +Without this precaution, the subsoil, after being opened by the plough, +soon sinks together, and the good effects anticipated are not realized. +The necessity for allowing some time to elapse between draining and +further operations is still more apparent in deep ploughing, when the +soil is actually brought to the surface. In that case it requires to be +left for a longer period after draining, in order that the air may +produce the necessary changes on the subsoil; for if it be brought up +after having been for a long time saturated with moisture, and +containing its iron as protoxide, and the organic matter in a state in +which it is not readily acted upon by the air, the immediate effect of +the operation is frequently injurious in place of being advantageous. +One of the best methods of treating a soil in this way is to make the +operation a gradual one, and by deepening an inch or two every year +gradually to mix the soil and subsoil; as in this way from a small +quantity being brought up at a time no injurious effects are produced. +Deep ploughing may be said to act in two ways, _firstly_, by again +bringing to the surface the manures which have a tendency to sink to the +lower part of the soil, and, _secondly_, by bringing up a soil which has +not been exhausted by previous cropping--in fact a virgin soil. + +The success which attends the operation of subsoiling or deep ploughing +must manifestly be greatly dependent on the character of the subsoil, +and good effects can only be obtained when its chemical composition is +such as to supply in increased quantity the essential constituents of +the plant; and it is no doubt owing to this that the opinions +entertained by practical men, each of whom speaks from the results of +his own experience, are so varied. The effects produced by deep +ploughing on the estates of the Marquis of Tweeddale, are familiarly +known to most Scottish agriculturists, and they are at once explained by +the analyses of the soil and subsoil here given, which show that the +latter, though poor in some important constituents, contains more than +twice as much potash as the soil. + + Soil. Subsoil. + +Insoluble silicates 87·623 82·72 +Soluble silica 0·393 0·12 +Alumina and peroxide of iron 4·129 8·60 +Lime 0·341 0·18 +Magnesia 0·290 0·24 +Sulphuric acid 0·027 0·03 +Phosphoric acid 0·240 trace +Potash 0·052 0·12 +Soda 0·050 0·04 +Water 1·956 3·26 +Organic matter 5·220 4·02 + ------ ----- + 100·321 99·33 + +In addition to the difference in the amount of potash, something is +probably due to the large proportion of alumina and oxide of iron in the +subsoil, which for this reason must be more tenacious than the soil +itself, which appears to be rather light. In other instances, the use of +the subsoil plough has occasioned much disappointment, and has led to +its being decried by many practical men; but of late years its use +having become better understood, its merits are more generally +admitted. We believe, that in all cases in which the soil is deep, more +or less marked good effects must be produced by its use, but of course +there must be cases in which, from the defective composition of the +subsoil or other causes, it must fail. It may sometimes be possible _a +priori_ to detect these cases, but in a large majority of them our +knowledge is still too limited to admit of satisfactory conclusions +being arrived at. + +_Improving the Soil by Paring and Burning._--It has long been familiarly +known, that a decided improvement has been produced on some soils by +burning. Its advantages have chiefly been observed on two sorts, heavy +clays and peat soils, on both of which it has been practised to a great +extent. The action of heat on the heavy clays appears to be of a twofold +character, depending partly on the change effected in its physical +properties, and partly on a chemical decomposition produced by the heat. +The operation of burning is effected by mixing the clay with brushwood +and vegetable refuse, and allowing it to smoulder in small heaps for +some time. It is a process of some nicety, and its success is greatly +dependent on the care which has been taken to keep the temperature as +low as possible during the whole course of the burning. + +Experience has shown that burning is by no means equally advantageous to +all clays, but is most beneficial on those containing a considerable +quantity of calcareous matter, and of silicates of potash. In such clays +heat operates by causing the lime to decompose the alkaline silicates, +and liberate a quantity of the potash which was previously in an +unavailable state. Its effect may be best illustrated by the following +analyses by Dr. Voelcker of a soil, and the red ash produced in burning +it. + + Soil. Red Ash. +Water 0·93 1·18 +Organic matter 10·67 3·32 +Oxides of iron and alumina 13·40 18·42 +Carbonate of lime 23·90 8·83 +Sulphate of lime trace 1·15 +Carbonate of magnesia 1·10 " +Magnesia " 1·76 +Phosphoric acid trace 0·71 +Potash 0·38 1·08 +Soda 0·13 " +Chloride of sodium " 1·03 +Insoluble matter, chiefly clay 49·66 62·52 + ----- ----- + 100·17 100·00 + +In this instance the quantity of burned soil amounted to about fifteen +tons per acre, and it is obvious that the quantity of potash which had +been liberated from the insoluble clay and the phosphoric acid are equal +to that contained in a considerable manuring. In order to obtain these +results, it is necessary, as has been already observed, to keep the +temperature as low as possible during the process of burning, direct +experiment having shown that when this precaution is not observed +another change occurs, whereby the potash, which at low temperatures +becomes soluble, passes again into an insoluble state. A part of the +beneficial effect is no doubt also due to the change produced in the +physical characters of the clay by burning, which makes it lighter and +more friable, and by mixture with the unburnt clay ameliorates the +whole. This improvement in the physical characters of the clay also +requires that it shall be burnt with as low a heat as possible; for if +it rises too high, the clay coheres into hard masses which cannot again +be reduced to powder, and the success of the operation of burning may +always be judged of by the readiness with which it falls into a uniform +friable powder. + +The improvement of peat by burning has been practised to some extent in +Scotland, though less frequently of late years than formerly; but it is +still the principal method of reclaiming peat soils in many countries, +and particularly in Finland, where large breadths of land have been +brought into profitable cultivation by means of it. The _modus operandi_ +of burning peat is very simple; it acts by diminishing the superabundant +quantity of humus or other organic matters, which, in the previous +section we have seen to be so injurious to the fertility of the soil. It +_may_ act also in the same way as it does on clay, by making part of the +inorganic constituents more really soluble, although it is not probable +that its effect in this way can be very marked. Its chief action is +certainly by destroying the organic matters, and by thus improving the +physical character of the peat, and causing it to absorb and retain a +smaller quantity of water than it naturally does. For this reason it is +that it proves successful only on thin peat bogs, for if they be deep, +the inorganic matters soon sink into the lower part, and the surface +relapses into its old state of infertility. It is probably for this +reason that the practice has been so much abandoned in Scotland, more +especially as other and more economical modes of treating peat soils +have come into use. + +_Warping._--This name has been given to a method of improving soils by +causing the water of rivers to deposit the mud it carries in suspension +upon them, and which has been largely practised in the low lying lands +of Lincoln and Yorkshire, where it was introduced about a century ago. +It is most beneficial on sandy or peaty soil, and by its means large +tracts of worthless land have been brought under profitable cultivation. +It requires that the land to be so treated shall be under the level of +the river at full tide, and it is managed by providing a sluice through +which the river water is allowed to flood the land at high tide, and +again to escape at ebb, leaving a layer of mud generally about a tenth +of an inch in thickness, which it brought along with it. By the +repetition of this process, a layer of several feet in thickness, of an +excellent soil, is accumulated on the surface. Herapath, who has +carefully examined this subject chemically, has shown that in one +experiment where the water used contained 233 grains of mud per gallon, +210 were deposited during the warping. The following analyses will show +the general nature of the matters deposited, and the change which they +produce on the soil:--No. 1 is the mud from the Humber in its natural +state, No. 2 a specimen of warp of average quality artificially dried, +No. 3 a sandy soil before warping, and No. 4, the same fifteen years +after having received a coating of 11 inches of mud. + ++---------------------------------+---------+--------+---------+--------+ +| | 1 | 2 | 3 | 4 | +| +---------+--------+---------+--------+ +| Water | 47·49 | ... | 1·06 | 2·00 | +| Organic matter | 5·94 | 6·93 | 2·20 | 7·61 | +| Chloride of Calcium | ... | ... | } ... | ... | +| Magnesium | } ... | 0·10 | } ... | ... | +| Sodium | } 1·66 | } 0·94 | } 0·14 | 0·16 | +| Potassium | } | } | } | | +| Sulphate of Soda | } ... | 0·31 | } ... | ... | +| Magnesia | } ... | 1·18 | } ... | ... | +| Lime | trace | 1·10 | trace | trace | +| Carbonate of Magnesia | 2·60 | 0·31 | trace | 0·29 | +| Lime | 3·59 | 8·18 | trace | 0·46 | +| Potash and Soda | 0·18 | 0·47 | trace | 0·17 | +| Magnesia | 1·69 | 2·60 | trace | 0·26 | +| Lime | 0·39 | 0·68 | trace | 0·14 | +| Peroxide of Iron | } 6·63 | 5·05 | 0·08 | 1·17 | +| Alumina | } | 8·18 | 0·39 | 0·41 | +| Phosphate of Iron | 0·58 | 1·04 | trace | 0·28 | +| Silica | ... | 9·05 | 0·14 | 2·77 | +| Sand and Stones | 29·15 | 55·87 | 95·91 | 84·97 | +| |---------|--------|---------|--------| +| | 100·00 | 100·00 | 100·00 | 100·00 | ++---------------------------------+---------+--------+---------+--------+ + +It is easy to understand the importance of the effects produced by +adding to any soil large quantities of a mud containing upwards of one +per cent of phosphate of iron; and in point of fact, Herapath has +calculated that in one particular instance the quantity of phosphoric +acid brought by warping upon an acre of land, exceeded seven tons per +acre. As, moreover, the matters are all in a high state of division, +they must exist in a condition peculiarly favourable to the plant. The +overflow of the Nile is only an instance of warping on the large scale, +with this difference, that it is repeated once only in every year, +whereas, in this country, the operation is repeated at every tide until +a deposit sometimes of several feet in thickness is obtained, after +which it is stopped, and the soil brought under ordinary cultivation. + +An operation which is, in some respects, the converse of warping, has +been carried out on Blair-Drummond Moss, where the peat has been +dislodged and carried off by the action of water, leaving the subjacent +soil in a state fitted for cropping. Of course both this and warping are +restricted to special localities, but they are most important means of +ameliorating the soil when circumstances admit of their being carried +out. + +_Mixing of Soils._--When soils possess conspicuous defects in their +physical, and even in their chemical properties, great advantages may, +in some instances, be derived from their proper admixture. A light sandy +soil, for instance, is greatly improved by the addition of clay, and +_vice versa_; so that, when two soils of opposite properties occur near +to one another, both may be improved by mixture. It has been applied to +the improvement of heavy clay soil and of peat, the former being mixed +with sand or marl so as to diminish its tenacity; the latter with clay +or gravel to add to its inorganic matters, and in both instances it has +proved successful. + +The process of chalking, which has been carried out on a large scale in +some parts of England, and which consists in bringing up the chalk from +pits, penetrating through the overlying tenacious clay, and mixing it +with the soil, operates, to some extent, in a similar manner, though no +doubt the lime also exercises a strictly chemical action. It is probable +that the mixing of soils might be advantageously extended, and it merits +more minute study than it has yet obtained. Its use is obviously limited +by the expense, because, of course, where good effects are to be +obtained, it is necessary to remove large quantities of soil, in some +instances as much as 50 or 100 tons per acre, but the expense might be +much diminished if it were carried out methodically, and on a +considerable scale. The admixture of highly fertile soils with others of +inferior quality is also worthy of attention; indeed, it is understood +that this has been done, to some extent, with the rich trap soils of +some parts of Scotland, but the extent of the benefit derived from it +has not been made public. + +FOOTNOTES: + +[Footnote J: Mr. Dudgeon, Spylaw. Transactions of the Highland Society, +vol. cxxix., p. 505.] + + + + +CHAPTER VII. + +THE GENERAL PRINCIPLES OF MANURING. + + +In their natural condition all soils not absolutely barren are capable +of supporting a certain amount of vegetation, and they continue to do so +for an unlimited period, because the whole of the substances extracted +from them are again restored, either directly by the decay of the +plants, or indirectly by the droppings of the wild animals which have +browzed upon them. Under these circumstances, a soil yields what may be +called its normal produce, which varies within comparatively narrow +limits, according to the nature of the season, temperature, and other +climatic conditions. But the case is completely altered if the crop, in +place of being allowed to decay on the soil, is removed from it, for, +though the air will continue to afford an undiminished supply of those +elements of the food of plants which may be derived from it, the fixed +substances, which can only be obtained from the soil, decrease in +quantity, and are at length entirely exhausted. In this way a gradual +diminution of the fertility of the soil takes place, until, after the +lapse of a period, longer or shorter, according to its natural +resources, it will become entirely incapable of maintaining a crop, and +fall into absolute infertility unless the substances removed from it are +restored from some other source in the form of manure. When this is +done, the fertility of the soil may not only be sustained but greatly +increased, and, in point of fact, all cultivated soils, by the use of +manure, are made to yield a much larger crop than they can do in their +natural condition. + +The fundamental principle upon which a manure is employed is that of +adding to the soil an abundant supply of the elements removed from it by +plants in the condition best fitted for absorption by their roots; but +looked at in its broadest point of view, it acts not merely in this way, +but also by promoting the decomposition of the already partially +disintegrated rocks of which the soil is composed, setting free those +substances it already contains, and facilitating their absorption by the +plants. + +In considering the practical applications of the broad general principle +just stated, it might be assumed that a manure ought invariably to +contain all the elements of plants in the quantities in which they are +removed by the crops, and that when this has been accurately ascertained +by analysis, it would only be necessary to use the various substances in +the proportions thus indicated. But this, though a very important, and +no doubt in many cases essential condition, is by no means the only +matter which requires to be taken into consideration in the economical +application of manures. And this becomes sufficiently obvious when the +circumstances attending the exhaustion of the soil are minutely +examined. When a soil is cropped during a succession of years with the +same plant, and at length becomes incapable of longer maintaining it, +the exhaustion is rarely, if ever, due to the simultaneous consumption +of all its different constituents, but generally depends upon that of +one individual substance, which, from its having originally existed in +the soil in comparatively small quantity, is removed in a shorter time +than the others. To restore the fertility of a soil in this condition, +it is by no means necessary to supply all the different substances +required by the plant, for it will suffice to add that which has been +entirely removed. On the other hand, if an ordinary soil be supplied +with a manure containing a very small quantity of one of the elements of +plant food, along with abundance of all the others, the amount of +increase which it yields must obviously be measured, not by those which +are abundant, but by that which is deficient; for the crop which grows +luxuriantly so long as it obtains a supply of all its constituents, is +arrested as effectually by the want of one as of all, as has been proved +by the experiments of Prince Salm Horstmar and others, referred to in a +previous chapter; and hence, in order to obtain a good crop, it would be +necessary to use the manure in such abundance as to supply a sufficiency +of the deficient element for that purpose. If this course were +persevered in for a succession of years, the other substances which +would have been used in much more than the quantity required by the +crops, must either have been entirely lost or have accumulated in the +soil. In the latter case it is sufficiently obvious that the soil must +have been gradually acquiring an amount of resources which must remain +dormant until the system of manuring is changed. To render them +available, it is only necessary to add to it a quantity of the +particular substance in which the manure hitherto employed has been +deficient, so as to restore the lost balance, and enable the plant to +make use of those which have been stored up within it. The substance so +used is called a _special_ manure; that containing all the constituents +of the crop is a _general_ manure. + +The distinction of these two classes of manures is very important in a +practical point of view, because a special manure is not by itself +capable of maintaining the life of plants, but is only a means of +bringing into use the natural and acquired resources of the soil. In +place of preventing or retarding its exhaustion, it rather accelerates +it by causing the increased crops to consume more abundantly, and within +a shorter period of time, those substances which it contains. On the +other hand, a general manure prevents or diminishes the consumption of +the elements of plant-food contained in the soil, and if added in +sufficient abundance, may cause them to accumulate in it, and even +enable an almost absolutely barren soil to yield a tolerable crop. +General manures must therefore always be the most important and +essential, and no others would be used if it were possible to obtain +them of a composition exactly suited to the requirements of the crop to +be raised. Practically, however, this condition cannot be fulfilled, +because all the substances available for the purpose, and particularly +farm-yard manure, are refuse matters, the exact composition of which is +not under our control, and they do not necessarily contain their +constituents either in the most suitable proportions, or the most +available forms, and consequently when they are used during a succession +of years, certain of their constituents may accumulate in the soil, and +it is under such circumstances that special manures are both necessary +and advantageous. + +Several different substances, but more especially farm-yard manure, +fulfil in a very remarkable manner the conditions of a general manure, +and supply abundantly, not merely the mineral, but also the carbonaceous +and nitrogenous matters necessary for building up the organic part of +the plant; and hence its use is governed by principles of comparative +simplicity, and really resolves itself into determining the best mode of +managing it so as effectually to preserve its useful constituents, and, +at the same time, to bring them into those forms of combination in which +they are most available to the plant. But the employment of a special +manure opens up nice questions as to the relative importance of the +different elements of plants which have given rise to much controversy +and difference of opinion. + +In treating of the food of plants, it has been already observed that the +fixed or mineral constituents which are contained in their ash, are +necessarily derived exclusively from the soil, but that the carbon, +hydrogen, nitrogen, and oxygen, of which their organic part is composed, +may be obtained either from that source or from the air. The important +distinction which thus exists between these two classes of substances, +has given rise to two different views regarding the theory of manures. +Basing his views on the presence of the organic elements in the air, +Liebig has maintained that it is unnecessary to supply them in the +manure, while others, among whom Messrs. Lawes and Gilbert have taken a +prominent position, hold that, as a rule, fertile soils, cultivated in +the ordinary manner, contain a sufficient supply of mineral matters for +the production of the largest possible crops, but that the quantity of +ammonia and nitric acid which the plants are capable of extracting from +the air is insufficient, and must be supplemented by manures containing +them. A large number of experiments have been made in support of these +views, but the inferences which can be drawn from them are not +absolutely conclusive on either side, and it is necessary to consider +the matter in a general point of view. + +Setting out from the proposition already so frequently referred to, that +the plant cannot grow unless it receives a supply of all its elements, +it must be obvious that if, to a soil containing a sufficiency of +mineral matters to raise a given number of crops, a supply of ammonia be +added, its total productive capacity cannot be thus increased; and +though it may yield larger crops than it would have done without that +substance, this can only be accomplished by a proportionate diminution +of their number. In either case, the same quantity of vegetable matter +will be produced, but the time within which it is obtained will be +regulated by the supply of ammonia. That substance differs in no respect +from any other element of plant-food, and used in this way is to all +intents and purposes a special manure, and acts merely by bringing into +play those substances which the soil already contains. Its effect may +not be apparent until after the lapse of a very long period of time, but +it ultimately leads to the exhaustion of the soil. If, on the other +hand, a soil be continuously cropped until it ceases to yield any +produce, it is manifest that the exhaustion must in this instance be +entirely due to the removal of its available mineral nutriment, because +the superincumbent air constantly changed by the winds must continue to +afford the same unvarying supply of the organic elements, and the power +of supporting vegetation would be restored to it, by adding the +necessary inorganic matters. Hence when a soil, which in its natural +condition is capable of yielding a certain amount of vegetable matter, +is rendered barren by the removal of the crop, it may be laid down as an +incontrovertible position, that its infertility is due to the loss of +mineral matters, and that it may be restored to its pristine condition +by the use of them, and of them only. + +But the case is materially altered when we come to consider the course +of events in a cultivated soil. The object of agriculture is to cause +the soil, by appropriate treatment, to yield much more than its normal +produce, and the question is, how this can be best and most economically +effected in practice. According to Liebig, it is attained by adding to +the soil a liberal supply of those mineral substances required by the +plant, and that it is unnecessary to use any of the organic elements, +because they are supplied by the air in sufficient quantity to meet the +requirements of the most abundant crops. Other chemists and vegetable +physiologists again hold that though a certain increase may be obtained +in this way, a point is soon reached beyond which mineral matters will +not cause the plant to absorb more ammonia from the air, although a +further increase may be obtained by the addition of nitrogen in that or +some other available form. + +It is admitted on both sides, that all the elements of plant food are +equally essential, and the controversy really lies in determining what +practically limits the crop producible on any soil. The point at issue +may be put in a clear point of view by considering the course of events +on a soil altogether devoid of the elements of plants. If a small +quantity of mineral matters be added to such a soil, it immediately +becomes capable of supporting a certain amount of vegetation, deriving +from the air the organic elements necessary for this purpose, and with +every increase of the former, the air will be laid under a larger +contribution of the latter, to support the increased growth, and this +must proceed until the limit of supply from the atmosphere is reached. +At this point a further supply of mineral matters alone must obviously +be incapable of again increasing the crop, and it would thus be +absolutely necessary to conjoin them with a proportionate quantity of +organic substances. Liebig maintains that this limit is never attained +in practice, but that the air affords ammonia and the other organic +elements in excess of the requirements of the largest crop, while +mineral matters are generally though not invariably present in the soil +in insufficient quantity. Messrs. Lawes and Gilbert, on the other hand, +believe that the soil generally contains an excess of mineral matters, +and that a manure which is to bring out their full effect must contain +ammonia, or some other nitrogenous substance fitted to supplement the +deficient supply afforded by the atmosphere. In short, the question at +issue is, whether there is or is not a sufficiency of atmospheric food +to meet the demands of the largest crop which can practically be +produced. + +An absolutely conclusive reply to this question is by no means easy. The +experiments by which it is to be resolved are complicated by the fact, +that all soils capable of supporting anything like a crop, contain not +only the mineral, but the organic elements of its food in large and +generally in greatly superabundant quantity, and it is impossible +satisfactorily to ascertain how much is derived from this source, and +how much from the atmosphere. There are in fact no experiments in which +the effects of a purely mineral soil have been ascertained. The +important and carefully performed researches of Messrs. Lawes and +Gilbert were made upon a soil which had been long under cultivation, and +contained decaying vegetable matters in sufficient abundance to supply +nitrogen to many successive crops, and it would be most unreasonable to +assert that the produce they did obtain by means of mineral manures, +drew the whole of its nitrogen from the air. On the contrary, it may be +fairly assumed that the soil did yield a certain quantity of its +nitrogenous compounds, but to what extent this occurs, it is impossible +to determine. This difficulty is encountered more or less in all the +other experiments, and precludes absolute conclusions. The same fallacy +also besets the arguments of Liebig when he holds that the crop, +increased by means of mineral manures alone, must derive the whole of +the additional quantity of nitrogen which it contains from the air, as +appears to be tacitly assumed throughout the whole discussion. So far +from this being the case, it is just as likely that the mineral matters +should cause the plants to take it from the soil, if it is there, as +from the atmosphere. + +Taking a general view of the whole question, it is evident that a +certain amount of vegetation may always be produced by means of mineral +manures, and the quantity obtained is generally much beyond the normal +produce of the soil. But it is still open to doubt whether the largest +possible crop can be thus obtained, although the balance of evidence is +against it, and in favour of the addition of ammonia, and other +nitrogenous and organic substances, to the soil. In actual practice +manures containing nitrogen are more important, and more extensively +applied than any others, and the quantity of that element thus used is +very much larger than is generally supposed. Twenty tons of farm-yard +manure, a quantity commonly applied, and often exceeded on well +cultivated land, contain a sufficiency of organic matters to yield about +2-1/2 cwt. of nitrogen. A complete rotation, according to the six-course +shift, contains almost exactly the same quantity of nitrogen, when we +assume average crops throughout the whole, and it is thus made up.[K] + + Lbs. of Nitrogen. +1. Turnips (13-1/2 tons) 60 +2. { Wheat (28 bushels at 60 lbs.) 29 + { Straw 16 +3. Hay (2-1/2 tons) 56 +4. { Oats (34 bushels at 40 lbs.) 27 + { Straw 14 +5. Potatoes (3 tons) 27 +6. Wheat and straw as before 45 + ---- + Total 274 + +The supply is therefore quite sufficient for the requirements of the +crop; and when it is borne in mind that a considerable quantity of +ammonia and nitric acid is annually carried down by the rain, and that +during a long rotation other substances are very generally used in +addition to farm-yard manure, it is obvious that the crop need not +depend to any extent upon what it derives from the air. What is true of +the nitrogenous matters applies with still greater force to the mineral +constituents of the manure. Twenty tons of farm-yard manure contain 32 +cwt. of mineral matters, while the average crops of a six course-shift +contain only 1088 lbs., or less than one-third of this quantity. It is +obvious, therefore, that in well manured land there must be a gradual +increase of all the constituents of plants, but that of the mineral +matters is relatively much greater than that of the nitrogenous. If +therefore from any cause the crop produced on a soil to which farm-yard +manure had been applied were greatly to exceed the average, the amount +of produce, so far as the soil is concerned, would be limited not by +deficiency of mineral, but of nitrogenous food. Hence also when +farm-yard manure is liberally applied, there is a gradual accumulation +of valuable matters, and a progressive improvement of the productive +capacity of the soil. + +It is far otherwise, however, if a special manure is employed, because +in that case the crop is thrown upon the resources of the soil itself +for all its constituents except those contained in the substance +employed, and by persisting in its exclusive use exhaustion is the +inevitable result. It would be wrong, however, to infer from this, that +special manures are to be avoided. On the contrary, great benefits are +derived from their judicious employment, and the circumstances under +which they are admissible may be readily gathered from what has already +been said. They are agents which bring into useful activity the dormant +resources of the soil, they restore the proper balance between its +different constituents, and supply the excessive demand of some +particular elements. Thus, for instance, in a soil containing an +abundant supply of mineral matters, a salt of ammonia or nitric acid +increases the crop, by promoting the absorption of the substances +already present. So likewise a soil on which young cattle and milch cows +have been long pastured has its fertility restored by phosphate of lime, +because that substance is removed in the bones and milk in relatively +much larger proportion than any others. + +The choice of a special manure is necessarily dependent on a great +variety of circumstances, and is governed partly by the nature of the +soil, and partly by that of the crop. It is obvious that cases may occur +in which any individual element of the plant may be deficient, and ought +to be supplied, but experience has shown that, as a rule, nitrogen and +phosphoric acid are the substances which it is most necessary to furnish +in this way, and which in all but exceptional cases produce a marked +effect on the crop. The other substances, such as potash, soda, +magnesia, etc., occasionally act beneficially, but the results obtained +from them are very uncertain, and frequently entirely negative. + +It has been commonly asserted that phosphates are specially adapted to +root crops, and ammonia or nitrates to the cereals, and this statement +is so far true, that the former are used with advantage on the turnip, +while the latter act with great benefit on grain crops and more +especially on oats and barley. The effect of the latter, however, is +more or less apparent in all crops and on all soils, because it promotes +the assimilation of the mineral matters already present. But its +peculiar importance lies in the power which it has of promoting the +rapid development of the young plant, causing it to send its roots out +into the soil, and to spread its leaves into the air, thus enabling it +to take from those two sources, abundance of the useful substances +existing in them. But it ought to be distinctly understood, that the +statement that particular manures are specially suited to particular +crops must be assumed with some reservation, because everything depends +upon the nature of the food contained in the soil. It is well known that +there are many soils in which ammonia acts more favourably on the turnip +than phosphates, and _vice versa_, and the difference is often due to +the previous treatment. In many cases in which ammonia when first used +proved most beneficial, it now begins to lose its effect, and the reason +no doubt is, that by its means the phosphates existing in these soils +have been reduced in amount, while the ammonia has accumulated, so that +a change in the system of manuring becomes necessary. A general manure +may be used year after year in a perfectly routine manner, but where a +special manure is employed, the importance of watching its effects, and +altering it as circumstances indicate, cannot be over-estimated. The +length of time during which special manures have been extensively used +has not been sufficient to bring this prominently before the +agriculturist, but its importance must sooner or later force itself upon +him, and he will then see the necessity for studying the succession of +manures as well as that of crops. + +Hitherto we have considered a manure merely as a source from which +plants derive their food, but it exercises a scarcely less important +action on the chemical and physical properties of the soil. Farm-yard +manure, which, as we shall afterwards see, contains a large amount of +decomposing vegetable and animal matters, yields a supply of carbonic +acid, which operates on the mineral constituents, promotes their further +disintegration, and thus liberates their useful elements. It affects +also their physical properties, for it diminishes the tenacity of heavy +clays; each straw as it decomposes forming a channel through which the +roots of plants, air, and moisture can penetrate more readily than +through the stiff clay itself. On the other hand, it diminishes the +porosity of light sandy soils, causes them to retain moisture, and +generally makes their texture more suitable to the plant. Special +manures probably act to some extent chemically on the soil, but the +nature of the changes they produce is as yet imperfectly understood. +Superphosphates which are highly acid in all probability act powerfully +on the mineral substances, and common salt, which, though of little +importance to the plant, occasionally produces very striking effects, +appears to exercise some decomposing action on the soil. It is +difficult, however, to trace the mode in which they operate on a +substance of such complexity as the soil. Lime, as we shall afterwards +see, acts by promoting the decomposition of the vegetable matters on +the soil, and possibly some other substances may have a similar effect. + +In the application of manures to the soil there are several +circumstances which must be taken into consideration. It is generally +stated that they ought to be distributed as uniformly as possible, but +this is not always necessary nor even advisable, and certainly is not +acted on in practice. Much must depend upon the nature both of crop and +soil. When the former throws out long and widely penetrating roots, the +more uniformly the manure is distributed the better; but if the rootlets +are short, it is clearly more advisable that it should be deposited at +no great distance from the seed. Practically this is observed in the +case of the potato and turnip, which are short rooted, and where the +manure is generally deposited close to the seed. But this course is +never adopted with the long rooted cereals, the manure being usually +applied to the previous crop, so that the repeated ploughings to which +the soil is subjected in the interval may distribute what remains as +widely and uniformly as possible. In soils which are either excessively +tenacious or light, the accumulation of the manure close to the plants +has also the effect of producing an artificial soil in their immediate +neighbourhood, containing abundance of plant-food, and having physical +properties better fitted for the support of the plant. On the other +hand, when a special manure is used alone, and with the view of +promoting the assimilation of substances already existing in the soil, +the more uniform its distribution the better, because it is essential +that the roots which penetrate through it should find at every point +they reach not only the original soil constituents, but also the +substances used to supplement their deficiencies. + +FOOTNOTES: + +[Footnote K: The quantities here taken are the averages deduced from the +agricultural statistics taken in Scotland some years since, with the +exception of hay and straw, which are not included in them. I have +therefore assumed a reasonable quantity in these cases.] + + + + +CHAPTER VIII. + +THE COMPOSITION AND PROPERTIES OF FARM-YARD AND LIQUID MANURES. + + +In the preceding chapter, a general manure has been defined as one +containing all the constituents of the crop to which it is to be +applied, in a state fitted for assimilation. This condition is fulfilled +only by substances derived from the vegetable and animal kingdoms, and +most effectually by a mixture of both. On this account, and also because +its properties are such as enable it to act powerfully on the soil, +farm-yard manure must always be of the highest importance. It is, in +fact, the typical manure, and in proportion as other substances approach +it in properties and composition, is their value for general purposes on +the farm. + +Farm-yard manure is a mixture of the dung and urine of domestic animals, +with the straw used as litter; and its value and composition must +necessarily depend upon that of these substances, as well as on the +proportion in which they are mixed. The dung of animals consists of that +part of their food which passes through the intestinal canal without +undergoing assimilation; the urine containing the portion which has been +assimilated and is again excreted, in consequence of the changes which +are proceeding in the tissues of the animal. Their composition is +naturally very different, and must be separately considered. + +_Urine._--Urine consists of a variety of earthy and alkaline salts, and +of certain organic substances, generally rich in nitrogen, dissolved in +a large quantity of water. That of the different domestic animals has +been frequently examined, but the analyses of Fromberg give the most +complete view of their manurial value:-- + + Horse. Swine. Ox. Goat. Sheep. + +Extractive matter } 2·132 0·142 2·248 0·100 0·340 + soluble in water } +Extractive matter } 2·550 0·387 1·421 0·454 3·330 + soluble in spirit} +Salts soluble in } 2·340 0·909 2·442 0·850 1·957 + water } +Salts insoluble in} 1·880 0·088 0·155 0·080 0·052 + water } +Urea 1·244 0·273 1·976 0·378 1·262 +Hippuric acid 1·260 ... 0·550 0·125 ... +Mucus 0·005 0·005 0·007 0·006 0·025 +Water 88·589 98·196 91·201 98·007 92·897 + ------ ------- ------- ------- ------- + 100·000 100·000 100·000 100·000 99·863 + +_Composition of the Ash of these Urines._ + + Horse. Swine. Ox. Goat. Sheep. +Carbonate of lime 12·50 ... 1·07 trace 0·82 +Carbonate of magnesia 9·46 ... 6·93 7·3 0·46 +Carbonate of potash 46·09 12·10 77·28 trace ... +Carbonate of soda 10·33 ... ... 53·0 42·25 +Sulphate of potash ... ... 13·30 ... 2·98 +Sulphate of soda 13·04 7·00 ... 25·0 7·72 +Phosphate of soda ... 19·00 ... ... ... +Phosphate of lime } +Phosphate of magnesia } ... 8·80 ... ... 0·70 +Chloride of sodium 6·94 53·10 0·30 14·7 32·01 +Chloride of potassium ... trace ... ... 12·00 +Silica 0·55 ... 0·35 ... 1·06 +Oxide of iron and loss 1·09 ... 0·77 ... ... + ------ ------ ------ ------ ------ + 100·00 100·00 100·00 100·00 100·00 + +Human urine has been accurately examined by Berzelius, although his +estimate of the proportion of urea is generally admitted to be above the +average. His analysis gives the following numbers:-- + + Natural. Dry Residue. +Urea 3·010 44·70 +Lactic acid, lactate of ammonia,} 1·714 25·58 + and extractive matter } +Uric acid 0·100 1·49 +Mucus 0·032 0·48 +Sulphate of potash 0·371 5·54 +Sulphate of soda 0·316 4·72 +Phosphate of soda 0·294 4·39 +Biphosphate of ammonia 0·165 2·46 +Chloride of sodium 0·445 6·64 +Muriate of ammonia 0·150 2·46 +Phosphates of magnesia and lime 0·100 1·49 +Silica 0·003 0·05 +Water 93·300 + ------- ------ + 100·000 100·00 + +Among the special organic constituents of the urine are three +substances, urea, uric acid, and hippuric acid, which are of much +importance in a manurial point of view. The first of these is found in +considerable quantity in the urine of all animals, but is especially +abundant in the carnivora. Uric acid is found only in these animals, and +is the most remarkable constituent of the excrement of birds, serpents, +and many of the lower animals. Hippuric acid is most abundant in the +herbivora. These substances are all highly nitrogenous. They contain-- + + Urea. Uric Acid. Hippuric Acid. +Carbon 20·00 36·0 60·7 +Hydrogen 6·60 2·4 5·0 +Nitrogen 46·70 33·4 8·0 +Oxygen 26·70 28·2 26·3 + ------ ----- ----- + 100·00 100·0 100·0 + +They are extremely prone to change, and in presence of animal matters +readily ferment, and are converted into salts of ammonia. Thus human +urine, which, at the time of emission is free from smell of ammonia, and +has a slightly acid reaction, becomes highly ammoniacal if it be kept +for a few days. This is due to the conversion of urea into carbonate of +ammonia; and the same change takes place, though more slowly, with uric +and hippuric acids. + +It is obvious, from the foregoing analyses, that great differences must +exist in the manurial value of the urine of different animals. Not only +do they vary greatly in the proportion of solid matters which they +contain, but also in the kind and quantity of their nitrogenous +constituents. They differ also in regard to their saline ingredients; +and while salts of potash and soda form the principal part of the ash of +the urine of the ox, sheep, goat, and horse, and phosphoric acid and +phosphates are entirely absent, that of the pig contains a considerable +quantity of the latter substances, and in this respect more nearly +resembles the urine of man. Human urine is also much richer in urea and +nitrogenous constituents generally, and has a higher value than any of +the others. + +It is especially worthy of notice that the urine of the purely +herbivorous animals (with the exception of the sheep, which contains a +small quantity), are devoid of phosphates and urea; and consequently, +when employed alone, they are not general manures--a matter of some +importance in relation to the subject of liquid manuring, which will be +afterwards discussed. + +_Dung._--The solid excrement of animals is equally variable in +composition. That of the domestic animals which had the ordinary winter +food was found to have the following composition:-- + + Horse. Cow. Sheep. Swine. +Per-centage of water in the } 77·25 82·45 56·47 77·13 + fresh excrement } +Ash in the dry excrement 13·36 15·23 13·49 37·17 + +100 parts of ash contained-- + + Horse. Cow. Sheep. Swine. +Silica 62·40 62·54 50·11 13·19 +Potash 11·30 2·91 8·32 3·60 +Soda 1·98 0·98 3·28 3·44 +Chloride of sodium 0·03 0·23 0·14 0·89 +Phosphate of iron 2·73 8·93 3·98 10·55 +Lime 4·63 5·71 18·15 2·63 +Magnesia 3·84 11·47 5·45 2·24 +Phosphoric Acid 8·93 4·75 7·52 0·41 +Sulphuric acid 1·83 1·77 2·69 0·90 +Carbonic acid ... trace trace 0·60 +Oxide of manganese 2·13 ... ... ... +Sand ... ... ... 61·37 + ---- ---- ---- ---- + 99·80 99·29 99·64 99·82 + +Human fæces contain about 75 per cent of water; and their dry residue +was found by Way to have the following composition:-- + +Organic matter 88·52 +Insoluble siliceous matters 1·48 +Oxide of iron 0·54 +Lime 1·72 +Magnesia 1·55 +Phosphoric acid 4·27 +Sulphuric acid 0·24 +Potash 1·19 +Soda 0·31 +Chloride of sodium 0·18 + ------ + 100·00 + +In a sample analyzed by myself there were found-- + +Organic matter 86·75 +Phosphates 8·19 +Alkaline salts, containing 1·18 of phosphoric } 2·53 + acid } +Insoluble matters 2·53 + ------ + 100·00 + +Nitrogen 4·59 +Equal to ammonia 5·57 + +It is to be observed that the urine and dung of animals differ +conspicuously in the composition of their ash, the former being +characterized by the abundance of alkaline salts, while the latter +contains these substances in small proportion, but is rich in earthy +matters, and especially in phosphoric acid. Salts of potash, for +example, form nine-tenths of the inorganic part of the urine of the ox, +while less than three per cent of that alkali is found in its dung. +Phosphoric acid, on the other hand, is not met with in the urine, but +forms about ten per cent of the dung. Silica is the most abundant +constituent of the dung, but a large proportion of that found on +analysis has been swallowed in the shape of grains of sand and particles +of soil mechanically mixed with the food, although part is also derived +from the straw and grains, which contain that substance in great +abundance. The difference in the quantity of nitrogen they contain is +also very marked, and is distinctly shown by the following analyses by +Boussingault, which give the quantity of carbon, hydrogen, nitrogen, +oxygen, and ash in the dung and urine of the horse and the cow in their +natural state, and after drying at 212°. + ++---------+--------------------------+--------------------------+ +| | HORSE. | COW. | +| +-------------+------------+-------------+------------+ +| | Natural. | Dry. | Natural. | Dry. | +| +-------------+------------+-------------+------------+ +| |Urine.| Dung.|Urine.|Dung.|Urine.| Dung.|Urine.|Dung.| +| +------+------+------+-----+------+------+------+-----+ +|Carbon | 4·46| 9·56| 36·0| 38·7| 3·18| 4·02| 27·2| 42·8| +|Hydrogen | 0·47| 1·26| 3·8| 5·1| 0·30| 0·49| 2·6| 5·2| +|Nitrogen | 1·55| 0·54| 12·5| 2·2| 0·44| 0·22| 3·8| 2·3| +|Oxygen | 1·40| 9·31| 11·3| 37·7| 3·09| 3·54| 26·4| 37·7| +|Ash | 4·51| 4·02| 36·4| 16·3| 4·68| 1·13| 40·0| 12·0| +|Water | 87·61| 75·31| 0·0| 0·0| 88·31| 90·60| 0·0| 0·0| +| +------+------+------+-----+------+------+------+-----+ +| |100·00|100·00| 100·0|100·0|100·00|100·00| 100·0|100·0| ++---------+------+------+------+-----+------+------+------+-----+ + +Hence, weight for weight, the urine of the horse, in its natural state, +contains three times as much nitrogen as its dung; that of the cow twice +as much; and the difference, especially in the horse, is still more +conspicuous when they are dry. + +It is obvious that the quality of farm-yard manure must depend--1. On +the kind of animal from which it is produced; 2. On the quantity of +straw which has been used as litter; 3. On the nature of the food with +which the animals have been supplied; 4. On the extent to which its +valuable constituents have been rendered available by the treatment to +which it has been subjected; and 5. On the care which has been taken to +prevent the escape of the urine, or of the ammonia produced by its +decomposition. + +The composition of farm-yard manure has engaged the attention of several +chemists; but there are still many points on which our information +regarding it is less complete than might be desired. Its investigation +is surrounded with peculiar difficulties, not merely on account of its +complexity, but because its properties render it exceedingly difficult +to obtain a sample which fairly represents its average composition. In +the case of long dung, these difficulties are so great that it is +scarcely possible to overcome them; and hence, discrepancies are +occasionally to be met with in the analyses of the most careful +experimenters. The most minute and careful analyses yet made are those +of Voelcker, who has compared the composition of fresh and rotten dung, +and studied the changes which the former undergoes when preserved in +different ways. He employed in his experiments both fresh and rotten +dung, and subjected them to different methods of treatment. His analyses +are given in the accompanying table, in which column 1 gives the +composition of fresh long dung, composed of cow and pig dung. 2. Is dung +of the same kind, after having lain in a heap against a wall, but +otherwise unprotected from the weather for three months and eleven days +in winter, during which time little rain fell. 3. The same manure, kept +for the same time under a shed. 4. Well rotten dung, which had been kept +in the manure heap upwards of six months. 5. The same, after having lain +against a wall for two months and nine days longer. + ++-------------------------------+-------------+-------------+--------------+ +| | 1 | 2 | 3 | ++-------------------------------+-------------+-------------+--------------+ +| Water | 66·17 | 69·86 | 67·32 | +| Soluble organic matters | 2·48 | 3·86 | 2·63 | +| Soluble inorganic matters· | | | | +| Silica | 0·237 | 0·279 | 0·239 | +| Phosphate of lime | 0·299 | 0·300 | 0·331 | +| Lime | 0·066 | 0·048 | 0·056 | +| Magnesia | 0·011 | 0·019 | 0·004 | +| Potash | 0·573 | 1·096 | 0·676 | +| Soda | 0·051 | 0·187 | 0·192 | +| Chloride of sodium | 0·030 | 0·106 | 0·058 | +| Sulphuric acid | 0·055 | 0·160 | 0·119 | +| Carbonic acid and loss | 0·218 | 0·775 | 0·445 | +| | ----- 1·54 | ... 2·97 | ----- 2·12 | +| | | | | +| Insoluble organic matters | 25·76 | 18·44 | 20·46 | +| Insoluble inorganic matters-- | | | | +| Soluble silica | 0·967 | 0·712 | 1·893 | +| Insoluble silica | 0·561 | 0·857 | 1·075 | +| Oxide of iron, alumina, and | | | | +| phosphates | 0·596 | 0·810 | 1·135 | ++-------------------------------+-------------+-------------+--------------+ + ++-------------------------------+-------------+-------------+ +| | 4 | 5 | ++-------------------------------+-------------+-------------+ +| Water | 75·42 | 73·90 | +| Soluble organic matters | 3·71 | 2·70 | +| Soluble inorganic matters | | | +| Silica | 0·254 | 0·147 | +| Phosphate of lime | 0·382 | 0·129 | +| Lime | 0·117 | 0·018 | +| Magnesia | 0·047 | 0·018 | +| Potash | 0·446 | 0·960 | +| Soda | 0·023 | 0·082 | +| Chloride of sodium | 0·037 | 0·052 | +| Sulphuric acid | 0·058 | 0·072 | +| Carbonic acid and loss | 0·106 | 0·584 | +| | ----- 1·47 | ----- 2·06 | +| | | | +| Insoluble organic matters | 12·82 | 14·39 | +| Insoluble inorganic matters-- | | | +| Soluble silica | 1·424 | 1·10 | +| Insoluble silica | 1·010 | 1·54 | +| Oxide of iron, alumina, and | | | +| phosphates | 0·947 | 0·37 | ++-------------------------------+-------------+-------------+ + ++-------------------------------+-------------+-------------+--------------+ +| | 1 | 2 | 3 | ++-------------------------------+-------------+-------------+--------------+ +| Containing phosphoric acid |(0·178) |(0·177) |(0·298) | +| Equal to bone earth |(0·386) |(0·277) |(0·646) | +| Lime | 1·120 | 1·291 | 1·868 | +| Magnesia | 0·143 | 1·029 | 0·078 | +| Potash | 0·099 | 0·127 | 0·208 | +| Soda | 0·019 | 0·046 | 0·038 | +| Sulphuric acid | 0·061 | 0·099 | 0·098 | +| Carbonic acid and loss | 0·484 | 0·929 | 1·077 | +| | ----- 4·05 | ----- 4·90 | ----- 7·47 | +| | ----- | ----- | ------ | +| | 100·00 | 100·00 | 100·00 | +| | | | | +| Containing nitrogen | 0·149 | 0·270 | 0·170 | +| Equal to ammonia | 0·181 | 0·320 | 0·206 | +| Containing nitrogen | 0·494 | 0·470 | 0·580 | +| Equal to ammonia | 0·599 | 0·570 | 0·700 | +| Total nitrogen | 0·643 | 0·740 | 0·750 | +| Equal to ammonia | 0·780 | 0·890 | 0·906 | ++-------------------------------+-------------+-------------+--------------+ + ++-------------------------------+-------------+-------------+ +| | 4 | 5 | ++-------------------------------+-------------+-------------+ +| Containing phosphoric acid |(0·274) |(0·06) | +| Equal to bone earth |(0·573) |(0·10) | +| Lime | 1·667 | 2·25 | +| Magnesia | 0·091 | 0·02 | +| Potash | 0·045 | 0·12 | +| Soda | 0·038 | 0·01 | +| Sulphuric acid | 0·063 | 0·10 | +| Carbonic acid and loss | 1·295 | 1·44 | +| |----- 6·58 | ---- 6·95 | +| | ----- | ------ | +| | 100·00 | 100·00 | +| | | | +| Containing nitrogen | 0·297 | 0·149 | +| Equal to ammonia | 0·360 | 0·180 | +| Containing nitrogen | 0·309 | 0·613 | +| Equal to ammonia | 0·375 | 0·744 | +| Total nitrogen | 0·606 | 0·762 | +| Equal to ammonia | 0·735 | 0·924 | ++-------------------------------+-------------+-------------+ + +On examining and comparing these analyses, it appears that the +differences are by no means great, although, on the whole, they tend to +show that, weight for weight, well-rotten dung is superior to fresh, +provided it has been properly treated. Not only is the quantity of +valuable matters existing in the soluble state materially increased, +whereby the dung is enabled to act with greater rapidity, but, owing to +evaporation and the escape of carbonic acid, produced by the +decomposition of the organic substances, the proportion of those +constituents which are most important to the plant is increased. This is +particularly to be noticed, in regard to the nitrogen, which has +distinctly increased in all cases in which the dung has been kept for +some time; and the practical importance of this observation is very +great, because it has been commonly supposed that, during the process of +fermentation, ammonia is liable to escape into the air. It would appear, +however, that there is but little risk of loss in this way, so long as +the dung-heap is left undisturbed; and it is only when it is turned that +any appreciable quantity of ammonia volatilizes. It is different, +however, with the action of rain, which soon removes, by solution, a +considerable quantity of the nitrogen contained in farm-yard manure; and +the deterioration must necessarily be most conspicuous in rotten dung, +which sometimes contains nearly half of its nitrogen in a soluble +condition. The effect produced in this way is conspicuously seen, by the +results of weighings and analyses of small experimental dung-heaps, made +by Dr. Voelcker at different periods. The subjoined table shows the +composition of the heap, lying against a wall, and exposed to the +weather at different periods:-- + ++--------------------------+-------------------------------------------+ +| | WHEN PUT UP. | +| +---------+------------+---------+----------+ +| | Nov 3d | April 30th | Aug 23d | Nov 15th | +| | 1854. | 1855. | 1855. | 1855. | +| +---------+------------+---------+----------+ +| Weight of manure in lbs. | 2838 | 2026 | 1994 | 1974 | +| +---------+------------+---------+----------+ +| Water | 1877·9 | 1336·1 | 1505·3 | 1466·5 | +| Dry Matter | 960·1 | 689·9 | 488·7 | 507·5 | +| +---------+------------+---------+----------| +| Consisting of-- | | | | | +| Soluble organic matter | 70·38 | 86·51 | 58·83 | 54·04 | +| " mineral matter | 43·71 | 57·88 | 39·16 | 36·89 | +| Insoluble organic matter | 731·07 | 389·74 | 243·22 | 214·92 | +| " mineral matter | 114·94 | 155·77 | 147·49 | 201·07 | +| +---------+------------+---------+----------+ +| Total nitrogen | 18·23 | 18·14 | 13·14 | 13·03 | +| Equal to ammonia | 22·14 | 22·02 | 15·96 | 15·75 | ++--------------------------+---------+------------+---------+----------+ + +In this case, during the winter six months, which were very dry, the +manure lost 541·8 lbs. of water and 270·2 lbs. of dry matter, but the +nitrogen remained completely unchanged. But during the succeeding +semi-annual period, when rain fell abundantly, the quantity of nitrogen +is diminished by nearly a third, while the water has increased, and the +loss of dry matter by fermentation, notwithstanding the high temperature +of the summer months, was only 182·4 lbs. The soluble mineral matters +also, which increased during the first period, are again reduced during +the second, until they also fall to about two-thirds of their maximum +quantity. That this effect is to be attributed to the solvent action of +rain is sufficiently obvious, from a comparison of the results afforded +by the other heaps, which had been kept under cover during the same +period, as shown below. + ++--------------------------+----------------------------------------------| +| | WHEN PUT UP. | +| +----------+------------+----------+-----------+ +| | Nov. 3d, | April 30th | Aug. 23d | Nov. 15th | +| | 1854. | 1855. | 1855. | 1855. | +| +----------+------------+----------+-----------+ +| Weight of manure in lbs. | 3258 | 1613 | 1297 | 1235 | +| +----------+------------+----------+-----------| +| Water | 2156·0 | 917·6 | 563·2 | 514·5 | +| Dry Matter | 1102·0 | 695·4 | 733·8 | 720·5 | +| +----------+------------+----------+-----------| +| Consisting of-- | | | | | +| Soluble organic matter | 80·77 | 74·68 | 53·56 | 66·28 | +| " mineral matter | 50·14 | 54·51 | 39·55 | 54·68 | +| Insoluble organic matter | 839·17 | 410·24 | 337·32 | 341·97 | +| " mineral matter | 131·92 | 155·97 | 303·37 | 257·57 | +| +----------+------------+----------+-----------+ +| Total nitrogen | 20·93 | 19·26 | 16·54 | 1·79 | +| Equal to ammonia | 25·40 | 23·33 | 20·08 | 2·81 | ++--------------------------+----------+------------+----------+-----------+ + +The loss of nitrogen is here comparatively trifling, and during the +whole year, but little exceeds two pounds, of which the greater part +escapes during the first six months, and the soluble inorganic matters +are almost unchanged. The total weight of the manure, however, undergoes +a very great reduction, due chiefly to evaporation of water, but in part +also to the loss of organic matters evolved in the form of carbonic acid +during fermentation. + +When the manure is spread out, as it is usually found under cattle in +open yards, the deterioration is very great, a quantity thus treated +having lost, in the course of a year, nearly two-thirds of its nitrogen, +and four-fifths of its soluble inorganic matters. + +The general conclusion deducible from these analyses is that, provided +it be carefully prepared, farm-yard manure does not differ very largely +in value, although the balance is in favour of the well-rotten dung. +This result is in accordance with that obtained by other experimenters, +who have generally found from 0·5 to 0·6 per cent of nitrogen, and 1 or +2 per cent of phosphates. But when carelessly managed, it may fall +greatly short of this standard, as is particularly seen in a sample +examined by Cameron, which had been so effectually washed out by the +rain, as to retain only 0·15 per cent of ammonia. These cases, however, +are exceptional, and well made and well preserved farm-yard manure will +generally be found to differ comparatively little in value; and when +bought at the ordinary price, the purchaser, as we shall afterwards more +particularly see, is pretty sure to get full value for his money, and +the specialities of its management are of comparatively little moment to +him. But the case is very different when the person who uses the manure +has also to manufacture it. The experiments already quoted have shown +that, though the manure made in the ordinary manner may, weight for +weight, be as valuable as at first, the loss during the period of its +preservation is usually very large, and it becomes extremely important +to determine the mode in which it may be reduced to the minimum. + +In the production of farm-yard manure of the highest quality, the object +to be held in view is to retain, as effectually as possible, all the +valuable constituents of the dung and urine. But in considering the +question here, it will be sufficient to refer exclusively to its +nitrogen, both because it is the most important, and also because the +circumstances which favour its preservation are most advantageous to the +other constituents. In the management of the dung-heap, there are three +things to be kept in view:--First, To obtain a manure containing the +largest possible amount of nitrogen; secondly, To convert that nitrogen +more or less completely into ammonia; and thirdly, To retain it +effectually. + +As far as the first of these points is concerned, it must be obvious +that much will depend on the nature and quantity of the food with which +the animals yielding the dung are supplied, and the period of the +fattening process at which it is collected. When lean beasts are put up +to feed, they at first exhaust the food much more completely than they +do when they are nearly fattened, and the manure produced is very +inferior at first, and goes on gradually improving in quality as the +animal becomes fat. + +When the food is rich in nitrogenous compounds, the value of the manure +is considerably increased. It has been ascertained, for instance, that +when oil-cake has been used, not less than seven-eighths of the valuable +matters contained in it reappear in the excrements; and as that +substance is highly nitrogenous, the dung ought, weight for weight, to +contain a larger amount of that element. That it actually does so, I +satisfied myself by experiments, made some years since, when the dung +and urine of animals fed on turnips, with and without oil-cake, were +examined; but unfortunately, no determination of the total quantity of +the excretions could be made, so that it was impossible to estimate the +increased value. It has been commonly supposed that when cattle are fed +with oil-cake, the increased value of the manure is equal to from +one-half to two-thirds the price of the oil-cake; but this is a rather +exaggerated estimate as regards linseed-cake, although it falls short of +the truth in the case of rape, as we shall afterwards more particularly +see. + +Although it may be possible, in this way, to increase the quantity of +nitrogen as a manure, there is a limit to its accumulation, due to the +fact, that it is contained most abundantly in the urine, which can only +be retained by the use of a sufficient supply of litter. Where that is +deficient, the dung-heap becomes too moist, and the fluid and most +valuable part drains off, either to be lost, or to be collected in the +liquid manure-tank. In the well managed manure-heap, the quantity of +litter should be sufficient to retain the greater part of the liquid +manure, and to admit of only a small quantity draining from it, which +should be pumped up at intervals, so as to keep the whole in a proper +state of moisture. Attention to this point is of great moment, and +materially affects the fermentation. When it is too moist or too dry, +that process is equally checked; in the former case by the exclusion of +air, which is essential to it; and in the latter, by the want of water, +without which the air cannot act. The exact mode in which the manure is +to be managed must greatly depend on whether the supply of litter is +large or small. In the latter case the urine escapes, and is collected +in the liquid manure-tank, and must be used by irrigation, and in some +cases this mode of application has advantages, but in general, it is +preferable to avoid it, and have recourse to substances which increase +the bulk of the heap sufficiently to make it retain the whole of the +liquid. For this purpose, clay, or still better, the vegetable refuse of +the farm, such as weeds, ditch cleanings, leaves, and, in short, any +porous matters, may be used. But by far the best substance, when it can +be obtained, is dry peat, which not only absorbs the fluid, but fixes +the ammonia, by converting it more or less completely into humate. +Reference has been already made to the absorbent power of peat in the +section on soils, but it may be mentioned here that accurate experiment +has shown that a good peat will absorb about 2 per cent[L] of ammonia, +and when dry will still retain from 1 to 1·5 per cent, or nearly twice +as much as would be yielded by the whole nitrogen of an equal weight of +farm-yard manure. Peat charcoal has been recommended for the same +purpose, but careful experiment has shown that it _does not absorb +ammonia_, although it removes putrid odour; and though it may be +usefully employed when it is wished to deodorize the manure heap, it +must not be trusted to for fixing the ammonia. + +Much stress has frequently been laid on the advantage to be derived from +the use of substances capable of combining chemically with the ammonia +produced during the fermentation of dung and gypsum, sulphate of iron, +chloride of manganese, sulphate of magnesia, and sulphuric acid, have +been proposed for this purpose, and have been used occasionally, though +not extensively. They all answer the purpose of _fixing_ the ammonia, +that is, of preventing its escaping into the air; but the risk of loss +in this way appears to have been much exaggerated, for a delicate +test-paper, held over a manure-heap, is not affected; and during +fermentation, humic acid is produced in such abundance, as to combine +with the greater part of the ammonia. The real source of deterioration +is the escape of the soluble matters in the drainings from the +manure-heap, which is not prevented by any of these substances; and +where no means are taken to preserve or retain this portion, the loss is +extremely large, and amounts, under ordinary circumstances, to from a +third to a half of the whole value of the manure. Manure, therefore, +cannot be exposed to the weather without losing a proportion of its +valuable matters, depending upon the quantity of rain which falls upon +it. Hence it is obvious that great advantage must be derived, especially +in rainy districts, from covered manure-pits. This plan has been +introduced on some farms with good effect; but the expense and doubts +as to the benefits derived from it, have hitherto prevented the practice +becoming general. The principal difficulty experienced in the use of the +covered dung-pit is, that, where the litter is abundant, the urine does +not supply a sufficiency of moisture to promote the active fermentation +of the dung, and it becomes necessary to pump water over it at +intervals; but when this is properly done, the quality of the manure is +excellent, and its valuable matters are most thoroughly economized. + +Although covered dung-pits have been but little used, their benefits +have been indirectly obtained by the method of box-feeding, one of the +great advantages of which is held to be the production of a manure of +superior quality to that obtained in the old way. In box-feeding none of +the dung or urine is removed from under the animals, but is trampled +down by their feet, and new quantities of litter being constantly added, +the whole is consolidated into a compact mass, by which the urine is +entirely retained. Whatever objection may be taken to this system, so +far as the health of the animals is concerned, there is no doubt as to +the complete economy of the manure, provided the quantity of litter used +be sufficient to retain the whole of the liquid. But its advantage is +entirely dependent on the possibility of fulfilling this condition. + +Whether box manure is really superior to that which can be prepared by +the ordinary method is very questionable, but it undoubtedly surpasses a +large proportion of that actually produced. It is more than probable, +however, that the careful management of the manure-heap would yield an +equally good product. It is manifest that the same number of cattle, fed +in the same way, on the same food, and supplied with the same quantity +of litter, must always excrete the same quantities of valuable matters; +and the only question to be solved is, whether they are more effectually +preserved in the one way than the other? It will be readily seen that +this cannot be done by analysis alone, but that it is necessary to +conjoin with it a determination of the total weight of manure produced; +for though, weight for weight, box manure may be better than ordinary +farm-yard manure, the total quantity obtained by the latter method, from +a given number of cattle, may be so much greater, that the deficiency in +quality may be compensated for. At the present time our knowledge is too +limited to admit of a definite opinion on this subject, but it is highly +deserving of the combined investigation of the farmer and the chemist. + +Supposing the conditions which produce the manure containing the largest +quantity of nitrogen to have been fulfilled, we have now to consider +those which affect its evolution in the form of ammonia. This change is +effected by _fermentation_. When a quantity of manure is left to itself +it becomes hot, and gradually diminishes in bulk, and if it be turned +over after some time, the smell of ammonia may be more or less +distinctly observed. This ammonia is produced, in the first instance, +from the urine, the nitrogenous constituents of which are rapidly +decomposed, and the fermentation thus set up in the mass of manure +extends first to the solid dung, and then to the straw of the litter, +and gradually proceeds until a large quantity of ammonia is produced. + +When fresh manure is deposited in the soil, the same changes occur, but +they then proceed more slowly, and experience has shown that a much +smaller effect is produced on the crop to which it has been applied than +when it has been well fermented in the heap. This effect is consistent +with theory, which would further indicate that well-fermented dung must +be especially advantageous when applied to quick-growing crops, and less +necessary to those which come slowly to maturity. As a rule, well +fermented manure is to be preferred, provided it has been well managed +and carefully prepared; but when this has not been done, and the manure +has been exposed to the weather, or made in open courts or hammels, the +economic advantages are all on the side of the fresh dung. It may be +questioned also whether, now that there are so many other available +sources of ammonia, it may not in many instances be advantageous to use +the dung fresh, conjoined with a sufficient quantity of some salt of +ammonia, or other substance fitted to supply the quantity of that +element necessary for the requirements of the crop. + +After the farm-yard manure has been prepared at the homestead, it is +often necessary to cart it out to the field some time before it is to be +applied, and it is a question of some importance to determine how it may +be best preserved there. The general practice is to store it in heaps in +the corners of the fields, but some difference of opinion exists as to +whether it should be lightly thrown up so as to leave it in a porous +state, and so promote its further fermentation, or whether it should be +consolidated as much as possible by driving the carts on to the top of +the heap during its construction. Considering the risks to which the +manure is exposed on the field, the latter plan would appear to be the +best. It is advisable also to interstratify the dung with dry soil, so +as to absorb any liquid which may tend to escape from it, and it should +also be covered with a well-beaten layer of earth, in order to exclude +the rain. Although these precautions must not be omitted if the manure +is to be stored in heaps, it will probably be often found quite as +advantageous to spread it at once, and leave it lying on the surface +until it is convenient to plough it. The loss of ammonia by +volatilization will, under such circumstances, especially in the cold +season of the year, be very trifling, and the rain which falls will only +serve to incorporate the soluble matters with the soil, where they will +be retained by its absorptive power. + +In the actual application of the manure to the crop, several points +require consideration. It is especially important to determine whether +it ought to be uniformly distributed through the soil, or be kept near +the roots of the plants. Both systems have their advocates, and each has +advantages in particular cases. The choice between the two must greatly +depend upon the nature of the crop and the soil. When the former is of a +kind which spreads its roots wide and deep through the soil, the more +uniformly the manure can be distributed the better; but when it is used +with plants whose roots do not travel far, it is more advantageous to +accumulate it near the seeds. Obvious advantages also attend this +practice in soils which are either too heavy or too light. When, for +example, it is necessary to cultivate turnips in a heavy clay, the +manure put into the drills produces a kind of artificial soil in the +neighbourhood of the plants, in which the bulbs expand more readily than +in the clay itself. On the other hand, when a large quantity of dung, in +a state of active fermentation, comes into immediate contact with the +roots, its effect is not unfrequently injurious. These and many other +points, which will readily suggest themselves to any one who studies the +composition and properties of farm-yard manure, belong more strictly to +the subject of practical agriculture, and need not be enlarged on here. + +In the present state of agriculture, a proper estimate of the money +value of farm-yard manure is of much importance in an economic point of +view, and many matters connected with the profitable management of a +farm must hinge upon it. If an estimate be made upon the principle which +will be explained when we come to treat of artificial manures, it +appears that fresh farm-yard manure of good quality is worth from 12s. +to 15s. per ton, and well-rotted dung rather more. It is questionable, +however, whether the system of valuation which is accurate in the case +of a guano or other rapidly acting substance, is applicable to farm-yard +manure, the effects of which extend over some years. A deduction must be +made for the years during which the manure remains unproductive, and +also for the additional expense incurred in carting and distributing a +substance so much more bulky than the so-called portable manures, and it +would not be safe to estimate its value at more than 7s. or 8s. per ton. + +_Liquid Manure._--This term is applied to the urine of the animals fed +on the farm, and to the drainings from the manure-heap, which, in place +of being returned to it, are allowed to flow away, and collected in +tanks, from which they are distributed by a watering-cart, or according +to the method recently introduced in Ayrshire, and since adopted in +other places, by pipes laid under-ground in the fields, and through +which the manure is either pumped by steam-power, or, where the +necessary inclination can be obtained, is distributed by gravitation. +That liquid manure must necessarily be valuable, is an inference which +maybe at once drawn from the analyses of the urine of different animals +already given, and of which it chiefly consists. In addition to the +urine, however, it contains also the soluble organic and mineral matters +of the dung, as well as a quantity of solid matters in suspension, among +which phosphates are found, and thus it possesses a supply of an +element which would be almost entirely deficient if it were composed of +urine alone. In the following analyses by Professor Johnston, No. 1 is +the drainings of the manure-heap when exposed to rain; and No. 2 the +same, when moistened with cows' urine pumped over it, the results being +expressed in grains per gallon:-- + + No. 1. No. 2. +Ammonia 9·6 21·5 +Organic matter 200·8 77·6 +Ash 268·8 518·4 + ----- ----- +Total solids in a gallon 479·2 617·5 + +The ash contained-- + +Alkaline salts 207·8 420·4 +Phosphates 25·1 44·5 +Carbonate of lime 18·2 31·1 +Carbonate of magnesia, and loss 4·3 3·4 +Silica and alumina 13·4 19·0 + ----- ----- + 268·8 518·4 + +More elaborate analyses of the same fluid have since been made by Dr. +Voelcker, with the subjoined results per gallon:-- + + 1. 2. 3. +Organic matters and ammoniacal } 263·80 250·63 70·121 + salts } +Silica 2·49 9·98 1·154 +Oxide of iron 0·70 0·68 ... +Lime 5·34 25·18 13·011 +Magnesia 2·96 15·33 1·660 +Potash 103·23 112·26 13·411 +Chloride of potassium 72·00 77·38 7·712 +Chloride of sodium 17·18 46·03 17·258 +Phosphoric acid 2·70 9·51 2·304 +Sulphuric acid 22·31 37·60 3·408 +Carbonic acid, and loss 33·90 27·95 14·025 + ------ ------ ------- + Total solids 526·61 612·53 144·064 +Ammonia 114·16 22·31 26·647 + +The differences are here very remarkable, especially in the quantity of +ammonia, which is exceedingly large in the first sample. All of them are +particularly rich in potash, and contain but a small proportion of +phosphoric acid. The general inference to be deduced from them is, that +liquid manure is a most important source of the alkalis and ammonia, and +must be peculiarly valuable on soils in which these substances are +deficient. + +The system of liquid manuring, originally introduced by Mr. Kennedy of +Myremill, Ayrshire, and which has since been adopted in some other +places, differs from liquid manuring in its _strict_ sense, for not only +are the drainings of the manure-heap employed, but the whole solid +excrements are mixed with water in a tank, and rape-dust and other +substances occasionally added, and distributed through the pipes. + +It has been abandoned on Mr. Kennedy's farm, but is in use at Tiptree +Hall, and on the farm of Mr. Ralston, Lagg, where the fluid is +distributed by gravitation. + +The arrangements employed by Mr. Mechi are identical with those formerly +in use at Myremill. The greater part of the stock is kept on boards, and +the liquid and solid excrements are collected together in the tank, and +largely diluted before distribution. The liquid from the tanks has been +recently examined by Dr. Voelcker, who found it to contain per gallon-- + +Organic matter and ammoniacal salts 53·03 +Soluble silica 6·47 +Insoluble siliceous matter (clay) 15·17 +Oxide of iron and alumina 2·36 +Lime 6·60 +Magnesia 1·73 + ----- +Potash 0·35 +Chloride of potassium 1·95 +Chloride of sodium 4·81 +Phosphoric acid 3·72 +Sulphuric acid 1·94 +Carbonic acid, and loss 0·47 + ----- + Total solids 96·60 +Ammonia 8·10 + +The quantity of this liquid distributed per acre is about 50,000 +gallons, at a cost of 2d. per gallon. As this quantity contains about 39 +lbs. of ammonia, it must be nearly equivalent to 2 cwt. of Peruvian +guano, which costs, with the expense of spreading, from 28s. to 30s. per +acre, while the cost of distributing the liquid exceeds £1: 17s. per +acre. On the other hand, the rapidity with which liquid manure produces +its effect must be taken into account. It is on this that its chief +value depends, and especially when applied to grass land in early +spring, it produces an abundant crop just when turnips and other winter +food are exhausted. Mr. Telfer, Cunning Park, who has used this system +for a good many years, has come to the conclusion that it is only in +this way that it can be made profitable; and though pipes are laid all +over his farm, he has latterly restricted the use of the liquid manure +entirely to Italian ryegrass. Its effect on the cereals is much less +marked, and it can scarcely be considered as capable of advantageous +application to the general operations of the farm. Neither can liquid +manure be applied to all soils. It fails entirely on heavy clays, but is +peculiarly adapted to light sandy soils; and even barren sand may by its +repeated application, be made to yield luxuriant crops. It is not likely +that the system of liquid manuring will extend, except in localities +where it is possible to distribute it by gravitation; and even then, it +will probably be found most economical to restrict its use to one +portion of the farm; and for that purpose, the poorest and most sandy +soil ought to be selected. + +_Sewage Manure._--The use of the sewage of towns as a manure is closely +connected with that of the liquid manure produced on the farm. Its +application must take place in a similar manner, and be governed by the +same principles. Although numerous attempts have been made to convert it +into a solid form, or to precipitate its valuable matter, none of them +have succeeded; nor can it be expected that any plan can be devised for +the purpose, because the most important manurial constituents are +chiefly soluble, and cannot be converted into an insoluble state, or +precipitated from their solution. In its liquid form, however, sewage +manure has been employed with the best possible effect in the +cultivation of meadows. The most important instance of its application +is in the neighbourhood of Edinburgh, where 325 acres receive the sewage +of nearly half the town, and have been converted from barren sand into +land which yields from £20 to £30 per acre. The contents of the sewer, +taken just before it flows into the first irrigated meadow, near +Lochend, were found to contain per gallon-- + +Soluble organic matter 21·90 +Insoluble organic matter 21·70 +Peroxide of iron and alumina 2·01 +Lime 10·50 +Magnesia 2·00 +Sulphuric acid 6·09 +Phosphoric acid 6·14 + ----- +Chlorine 12·20 +Potash 2·89 +Soda 13·27 +Silica 6·50 + ------ + 105·20 +Ammonia 14·90 + +It is interesting to notice that this sewage is superior in every +respect to the liquid manure used at Tiptree Hall; and the good effects +obtained from its application, in the large quantities in which it is +used in the Craigentinny meadows, may be well imagined. It operates, not +merely by the substances which it holds in solution, but also by +depositing a large quantity of matters carried along in suspension, and +is in reality warping with a substance greatly superior to river-mud. A +deposit collected in a tank, where the sewage passes through a farm, is +used as a manure, and contains-- + +Peroxide of iron and alumina 4·45 +Lime 1·74 +Magnesia 0·39 +Potash 0·10 +Soda 0·06 +Phosphoric acid 1·08 +Sulphuric acid 0·16 +Organic matter 17·95 +Sand 20·51 +Water 53·56 + ------ + 100·00 +Ammonia 0·93 + +And even, though containing more than half its weight of water and 20 +per cent of sand, this substance has considerable value as a manure. + +The growing evils of the existing system of sewage, and the enormous +waste of a manurial matter, which the experience of the Craigentinny +meadows has shewn to be productive of the most important effects, has +recently directed much attention to the conversion of the contents of +our sewers into a useful manure. Numerous plans for its precipitation +and conversion into a solid manure have been proposed, but most of these +have shewn an entire ignorance of the fundamental principles of +chemistry, and the best only succeed in precipitating a very small +proportion of its valuable matters, and leave almost the whole of the +ammonia, as well as the greater part of the fixed alkalies, in solution. +Nor is it to be expected that any process will be discovered by which +these substances can be precipitated, because solubility is the special +characteristic of their compounds, and no means is known by which it is +possible to convert them into an insoluble form. If sewage is to be used +at all, there seems little doubt that it must be by applying it entire, +and in the liquid state. But here again, the expense of conveying it on +to the land becomes an obstacle which it must frequently be impossible +to overcome. When it can be conveyed by gravitation, as is the case in +the neighbourhood of Edinburgh, it may undoubtedly be used with the +utmost advantage, and with the very best economic results. But when it +requires to be carried to a great distance through pipes, and raised to +a high level by pumping, all these advantages disappear. If the cost of +application amounts to 2d. a gallon, as in Mr. Mechi's case, or even to +half that sum, it may be fairly concluded that it cannot be used with +any great prospect of large economic results, and that, unless under +very exceptional cases, it must be unprofitable. + +The chances of success must also greatly depend upon the kind of soil on +which it is used. Experience has shewn that its effects are most +beneficial on light and deep sandy soils, but that on heavy retentive +clays it is without effect, or even absolutely injurious. In clay soils +it is important to use every means of getting rid of moisture, and any +plan which adds 200 or 300 tons of water to them, only aggravates their +natural defects to an extent which more than counterbalances the +benefits derived from the manurial matter it contains. Whatever the +ultimate result of the use of town sewage in the liquid form may be, it +is unlikely that it will be employed in general agricultural practice. +It is more probable that it will be found necessary to set apart a +certain breadth of land to be treated by it exclusively. Many plans have +been proposed for conveying it through considerable districts, and +selling to the surrounding farmers the quantities which they require, +but wherever large sewage-works are established, it will be impossible +to depend on a precarious demand, and the promoters of such schemes will +be compelled, as part of their speculation, to supply not only the +manure, but the land on which it is to be used. Indeed, the difficulties +attending the whole question are so formidable, that even those who are +most anxious to see a stop put to the waste of manurial matter must +admit that the prospect of a successful economic result is not +encouraging. Nor is it likely that anything will be done until the whole +system of managing town refuse is changed, and in place of deluging it +with water, some plan can be contrived which, while fulfilling sanatory +requirements, shall preserve it in a concentrated form, or convert it +into a dry and inodorous substance. + +FOOTNOTES: + +[Footnote L: Report on the economic uses of peat. Highland Society's +Transactions, N.S., vol. iv. p. 549.] + + + + +CHAPTER IX. + +COMPOSITION AND PROPERTIES OF VEGETABLE MANURES. + + +Many vegetable substances have been employed as manures, either alone or +as auxiliaries to farm-yard manure. Like that substance, they are +general manures, and contain all the constituents of ordinary crops; +but, owing to the absence of animal matter, they in general undergo +decomposition and fermentation much more slowly, although some of them +contain a so largely preponderating proportion of nitrogen, that they +may in some respects be compared to the strictly nitrogenous manures. + +_Rape-dust, Mustard, Cotton and Castor Cake._--Rape-dust has long been +employed as a manure, and the success which has attended its use has led +to the introduction of the refuse cake from some other oil seeds, such +as those of mustard and castor-oil, which cannot be employed for +feeding. Like the seeds of all plants, these substances are rich in +nitrogen, and their ash, containing of course all the constituents of +the plant, supplies the necessary inorganic elements. The following are +analyses of these substances, which, in addition to the amount of +nitrogen and phosphates, shew also that of water and oil, to which +reference will be made in a future chapter, in relation to the feeding +value of some of them. The detailed composition of their ash may be +judged of from that of the seeds from which they are made, and which +have been given under that head. + ++--------------------+------------+-------------+-------------+---------+ +| | Rape-Cake. | Poppy-Cake. | Cotton-seed | Castor- | +| | | | Cake. | Cake. | +| +------------+-------------+-------------+---------+ +| Water | 10·68 | 11·63 | 11·19 | 12·31 | +| Oil | 11·10 | 5·95 | 9·08 | 24·32 | +| Albuminious } | 29·53 | 31·16 | 25·16 | 21·91 | +| compounds } | | | | | +| Ash | 7·79 | 12·98 | 5·64 | 6·08 | +| Other constituents | 40·90 | 38·18 | 48·93 | 35·38 | +| +------------+-------------+-------------+---------+ +| | 100·00 | 100·00 | 100·00 | 100·00 | +| Nitrogen | 4·38 | 4·94 | 3·95 | 3·20 | +| Silica | 1·18 | 3·36 | 1·32 | 1·96 | +| Phosphates | 3·87 | 69·3 | 2·19 | 2·81 | +| Phosphoric acid } | | | | | +| in combination } | 0·39 | 3·27 | 0·15 | 0·64 | +| with alkalies } | | | | | ++--------------------+------------+-------------+-------------+---------+ + +A general similarity may be observed in the composition of all these +substances; they are rich in nitrogen, and contain as much of that +element as is found in six or seven times their weight of farm-yard +manure, and a somewhat similar proportion exists in the amount of +phosphates, and probably of their other constituents. They have all been +employed with success, but the most accurate observations have been made +with rape-dust, which has been longer and more extensively used than any +of the others. It has been employed alone for turnips, or mixed with +farm-yard manure, and also as a top-dressing to cereals. But the most +marked advantage is derived from it when applied in the latter way on +land which has been much exhausted, and its effects are then very +striking. An adequate supply of moisture is essential to the production +of its full effects, and hence it often proves a failure in very dry +seasons, and on dry soils. It must not be applied in too great +abundance, experience having shewn that after a certain point has been +reached, an increase in the quantity produces no benefit, and even +sometimes positively diminishes the crop. The other substances of the +same class, in all probability, act in the same way, but as their +introduction is recent, and their use limited, less is known regarding +their effects. + +_Malt-Dust, Bran, Chaff, etc._--The value of these substances as manures +is chiefly dependent on the nitrogen they contain, though to some extent +also on their inorganic constituents. Malt-dust contains about 4·5 per +cent, and bran 3·2 per cent of nitrogen. But they are little used as +manures, as they can generally be more advantageously employed for +feeding. The value of chaff more nearly resembles that of straw. + +_Straw_ is occasionally employed as a manure, and sometimes even as a +top-dressing for grass land. It is generally admitted, however, that its +application in the dry state, and especially as a top-dressing, is a +practice not to be recommended, as it decomposes too slowly in the soil; +and it is always desirable to ferment it in the manure heap, so as to +facilitate the production of ammonia from its nitrogen. Still +circumstances may occur in which it becomes necessary to employ it in +the dry state, and it will generally prove most valuable on heavy soils, +which it serves to keep open, and so promotes the access of air, and +enables it to act on the soil. On light sandy soils it generally proves +less advantageous, as its tendency of course is to increase the openness +of the soil, and render it less able to retain the essential +constituents of the plant. + +The quantity of nitrogen in straw does not exceed 0·2 per cent, and its +value is mainly due to its inorganic constituents and to its mechanical +effect on the soil. + +_Saw-dust_ has little value as a manure, as it undergoes decomposition +with extreme slowness. It is a good _mechanical_ addition to heavy +soils, and diminishes their tenacity; and though its manurial effects +are small, it sooner or later undergoes decomposition, and yields what +valuable matters it contains. The saw-dust of hard wood is to be +preferred, both because it contains more valuable matters than that of +soft wood, and because the absence of resinous matters permits its more +rapid decomposition. It is a useful absorbent of liquid manure, and may +be advantageously added to the dung-heap for that purpose. + +_Manuring with Fresh Vegetable Matter--Green Manuring._--The term green +manuring is applied to the system of sowing some rapidly growing plant, +and ploughing it in when it has attained a certain size, and the success +attending it, especially on soils poor in organic matters, is very +marked. It is obvious that this mode of manuring can add nothing to the +mineral matters contained in the soil, and its utility must therefore be +due to the plant gathering organic matters from the air, which, by their +decomposition, yield nitrogen and carbonic acid--the former to be +directly made use of by subsequent crops, the latter, in all +probability, acting also on the soil, and setting free its useful +constituents. Hence those plants which obtain the largest quantity of +their organic elements from the air ought to be most advantageous for +green manuring. The plants used for this purpose act also as a means of +bringing up from the lower parts of the soil the valuable matters which +exist in it out of reach of ordinary crops, and mixing them again with +the surface part. Many of the plants found most useful for green +manuring send down their roots to a considerable depth; and when they +are ploughed in, all the substances which they have brought up are of +course deposited in the upper few inches of the soil. Vegetable matter +when ploughed in in the fresh state, also decomposes rapidly, and is +therefore able immediately to improve the subsequent crop; and as this +decomposition takes place in the soil without the loss of ammonia and +other valuable matters, which is liable to occur to a greater or less +extent when they are fermented on the dung-heap, it will be obvious that +in no other mode can equally good results be obtained by its use. + +Many plants have been employed as green manure, and different opinions +have been expressed as to their relative values. In the selection of any +one for the purpose, that should of course be taken which grows most +rapidly, and produces within a given time the largest quantity of +valuable matters, but no general rule can be given for the selection, as +the plant which fulfils those conditions best will differ in different +soils and climates. The plants most commonly employed in this country +are spurry, white mustard, and turnips. Rye, clover, buckwheat, white +lupins, rape, borage, and some others, have been largely employed +abroad. Some of these are obviously unfitted for the climate of the +British Islands; and the others, although they have been tried +occasionally, do not appear to have been very extensively employed. The +turnip is sown broadcast at the end of harvest, and ploughed in after +two months. White mustard and spurry are employed in the same way as a +preparation for winter wheat, and with the best results. The latter is +sometimes sown as a spring crop in March, ploughed in in May, and +another crop sown which is ploughed in in June, and immediately +followed by a third. The effect of this treatment is such that the worst +sands may be made to bear a remunerative crop of rye. + +It is not easy to estimate the addition made by green manuring to the +valuable matters contained in the soil, but it is probably far from +inconsiderable. A crop of turnips, cultivated on the ordinary +agricultural system, after two months' growth, weighs between five and +seven tons per acre, and contains nitrogen equivalent to about 48 lbs. +of ammonia, and half a ton of organic matters; but nothing is known as +to the quantity produced when it is sown broadcast, and is not thinned, +although it must materially exceed this. Neither is it possible to +determine the relative proportions derived from the soil and the air, +although it is, in all probability, dependent on the resources of the +soil itself,--plants grown on a rich soil obtaining their chief supplies +from it, while, on poorer soils, a larger proportion is drawn from the +atmosphere. Hence light and sandy soils are most benefited by green +manuring, partly on this account, and partly also, no doubt, because the +valuable inorganic matters, which are so liable to be washed out of +these soils, are accumulated by the plants and retained in them in a +state in which they are readily available for the subsequent crop. + +_Sea-Weed._--Sea-weeds have been employed from time immemorial as a +manure on the coasts of Scotland and England, in quantities varying from +10 to 20 tons per acre. Their action is necessarily similar to that of +green manure ploughed in, as they contain all the ordinary constituents +of land plants. + +The subjoined analyses of three of the most abundant species will +sufficiently indicate their general composition. + ++----------------+--------+----------+----------------------------+-----------+ +| | | |LAMINARIA DIGITATA. | | +| | | | |Mixed Weeds| +| |Fucus | Fucus +----------------+-----------+in the | +| |nodosus.| vesicu.- | | Stem and |state in | +| | | losus | Collected | Frond |which they | +| | | | in Autumn. | collected |actually | +| | | | | in Spring.|are used | ++----------------+--------+----------+----------------+-----------+-----------+ +|Water | 74·31 | 70·57 | 88·69 | 77·31 | 80·44 | +|Albuminous | | | | | | +| compounds | 1·76 | 2·01 | 0·93 | 3·32 | 2·85 | +|Fibre, etc. | 19·04 | 22·05 | 4·92 | 10·39 | 6·40 | +|Ash | 4·89 | 5·37 | 5·46 | 8·98 | 10·31 | +| +--------+----------+----------------+-----------+-----------+ +| |100·00 | 100·00 | 100·00 | 100·00 | 100·00 | +|Nitrogen | 0·28 | 0·32 | 0·15 | 0·53 | 0·45 | +| | | | | | | +|The ash | | | | | | +| consisted of | | | | | | +| | | | Stem. Frond. | | | +|Peroxide of iron| 0·25 | 0·35 | 0·20 0·50 | 0·45 | 2·35 | +|Lime | 9·60 | 8·92 | 7·21 7·29 | 4·62 | 18·15 | +|Magnesia | 6·65 | 5·83 | 2·73 5·91 | 10·94 | 6·48 | +|Potash | 20·03 | 20·75 | 5·55 11·91 | 12·16 | 12·77 | +|Chloride of | | | | | | +| potassium | ... | ... | 58·42 26·59 | 25·83 | 9·10 | +|Iodide of | | | | | | +| potassium | 0·44 | 0·23 | 1·51 2·09 | 1·22 | 1·68 | +|Soda | 4·58 | 6·09 | ... ... | ... | ... | +|Sulphuret | | | | | | +| of sodium[M]| 3·66 | ... | ... ... | ... | ... | +|Chloride | | | | | | +| of sodium | 24·33 | 24·81 | 15·29 30·77 | 19·34 | 22·08 | +|Phosphoric acid | 1·71 | 2·14 | 2·42 2·66 | 1·75 | 4·59 | +|Sulphuric acid | 21·97 | 28·01 | 2·23 8·80 | 7·26 | 6·22 | +|Carbonic acid | 6·39 | 2·20 | 4·11 2·49 | 15·23 | 13·58 | +|Silicic acid | 0·38 | 0·67 | 0·33 0·99 | 1·20 | 3·00 | +| | ----- | ------ | ------ ------ | ------ | ------ | +| |100·00 | 100·00 | 100·00 100·00 | 100·00 | 100·00 | ++----------------+--------+----------+----------------+-----------+-----------+ + +The first four analyses give the composition of the weeds after they +have been separated from all foreign substances; the last, that of the +mixture taken from the heap just as it is used in Orkney; and its value +is then enhanced by small shells and marine animals adhering to the +plants, which increase the amount of phosphoric acid and nitrogen. + +The ease with which all sea-weeds pass into a state of putrefaction, +adapts them in a peculiar manner to the manurial requirements of a cold +and damp climate. The rapidity of their decomposition is such, that when +spread on the land they are seen to soften and disappear in a short +time. They form therefore a rapid manure, and their effects are said to +be confined to the crop to which they are applied; but this is probably +due to the fact, that they are chiefly used in inferior sandy soils, in +which any manure is rapidly exhausted. In good soils there is no reason +why their effect should not be as lasting as that of farm-yard manure, +which, in many particulars, they considerably resemble. The method of +applying sea-weeds most generally in use, is to spread them on the soil, +and plough them in after putrefaction has commenced, and it is on the +whole the most advantageous. But they are sometimes composted with lime +and earth, or mixed with farm-yard manure, and occasionally, also, they +are used as a top-dressing to grass land. + +On some parts of the western coast of Scotland and in the Hebrides, +sea-weed is the chief manure. It gives excellent crops of potatoes, but +they are said to be of inferior quality, unless marl or shell-sand is +employed at the same time. + +_Leaves_ may be used as a manure, simply by ploughing them in, by +composting them with lime, or by adding them to the manure heap. + +_Peat._--As a source of organic matter, peat may be used with advantage, +especially on soils in which it is naturally deficient. Dry peat of good +quality contains about one per cent of nitrogen, and a quantity of ash +varying from five to twenty per cent. These substances, however, become +available very slowly, owing to the tardy decay of peat in its natural +state; and in order to make it useful, it is necessary to compost it +with lime, or to mix it with farm-yard manure, or some readily +putrescible substance, so that its decomposition may be accelerated. It +may be most advantageously used as an absorbent of liquid manure, and on +this account, forms a useful addition to the manure heap. + +The observations which have been made regarding the use of these +substances, lead directly to the inference that all vegetable matters +possess a certain manurial value, and that they ought to be carefully +collected and preserved. In fact, the careful farmer adds everything of +the sort to his manure heap, where, by undergoing fermentation along +with the manure, their nitrogen becomes immediately available to the +plant; while the seeds of weeds are destroyed during the fermentation, +and the risk of the land being rendered dirty by their springing up when +the manure comes to be used is prevented. + +FOOTNOTES: + +[Footnote M: The presence of sulphuret of sodium in this case is due to +the difficulty of completely burning the ash. It exists in the plant as +sulphate of soda.] + + + + +CHAPTER X. + +COMPOSITION AND PROPERTIES OF ANIMAL MANURES. + + +Manures of animal origin are generally characterized by the large +quantity of nitrogen they contain, which causes them to undergo +decomposition with great rapidity, and to yield the greater part of +their valuable matters to the crop to which they are applied. + +_Guano._--By far the most important animal manure is guano, which is +composed of the solid excrements of carnivorous birds in a more or less +completely decomposed state, and is accumulated in immense quantities on +the coasts of South America and other tropical countries. It has been +used as a manure in Peru from time immemorial, but the accounts given by +the older travellers of its marvellous effects were considered to be +fabulous, until Humboldt, from personal observation, confirmed their +statements. It was first imported into this country in 1840, in which +year a few barrels of it were brought home; and from that time its +importation rapidly increased. Soon after large deposits of it were +found in Ichaboe; and it has since been brought from many other +localities. The quantity of guanos of all kinds imported into this +country and retained for home consumption now exceeds 240,000 tons a +year. + +The value of guano differs greatly according to the extent to which its +decomposition has gone, and this is chiefly dependent on the climate of +the locality from which it is obtained. When deposited in the rainless +districts of Peru it still retains some of the uric acid and the greater +part of the ammonia naturally existing in it, and the quantity which has +escaped by decomposition is unimportant. But that obtained from other +districts has suffered a more or less complete decomposition according +to the humidity of the climate, which reduces the quantity of organic +matters and ammonia, until, in some varieties, they are so small as to +be of little importance. The following are minute analyses of three +specimens of Peruvian guano, shewing all the different constituents it +contains, and the amount of difference which may exist:-- + + I. II. III. +Urate of ammonia 10·70 9·0 3·24 +Oxalate of ammonia 12·38 10·6 13·35 +Oxalate of lime 5·44 7·0 16·36 +Phosphate of ammonia 19·25 6·0 6·45 +Phosphate of magnesia and ammonia ... 2·6 4·20 +Sulphate of potash 4·50 5·5 4·23 +Sulphate of soda 1·95 3·8 1·12 +Sulphate of ammonia 3·36 ... ... +Muriate of ammonia 4·81 4·2 6·50 +Phosphate of soda ... ... 5·29 +Chloride of sodium ... ... 0·10 +Phosphate of lime 15·56 14·3 9·94 +Carbonate of lime 1·80 ... ... +Sand and alumina 1·59 4·7 5·80 +Water 9·14 } + } 32·3 23·42 +Undetermined humus-like organic} 10·00 } +matters } } + ------ ----- ------ + 100·48 100·0 100·00 + +These analyses illustrate two points--_first_, that in some samples the +decomposition has advanced to a greater extent than in others; for we +observe that the quantity of uric acid, or rather of urate of ammonia, +is greatly less in the last analysis than in the other two, and much +smaller than in the fresh dung, which contains from 50 to 70 per cent of +uric acid; and _secondly_, that guano is rich in all the constituents of +the plant, but especially in ammonia, the best form in which nitrogen +can be supplied, in uric acid which by decomposition yields ammonia, and +in phosphoric acid. But such analyses are too elaborate for ordinary +purposes, and much less convenient for comparison and for estimating the +value of the guano than the shorter analysis commonly in use, which +gives the water, the loss by ignition (that is, the sum of the organic +matters and ammoniacal salts), the phosphates, the alkaline salts, and +the quantity of phosphoric acid contained in them, and existing there in +a state similar to that in which it is found in the soluble phosphates +of a superphosphate. In addition to these, the quantities of sand and +other less valuable ingredients are also stated. + +In the subjoined tables the composition of a great variety of different +kinds of guano is given. Most of these are averages deduced from a +considerable number of analyses of good samples. Those of some kinds of +guano, such as Peruvian, which present a considerable amount of +uniformity, afford a sufficiently accurate idea of the general +composition of the variety, but in other cases they are of less value, +because the imports of different seasons, and even of different cargoes, +differ so greatly in composition that no proper average can be made. +Several of these varieties are already exhausted, the importation of +others has ceased, and new varieties are constantly being introduced. + +_Table showing the Average Composition of different varieties of Guano._ + +-------------------+--------+-------+-------------+---------------------------+ + |Angamos.|Peru- | ICHABOE. |Bolivian or Upper | + | | vian. | |Peruvian. | + | | +-------------+------+-----------+--------+ + | | |Old. |New. |Old. |Government.|Inferior| +-------------------+--------+-------+------+------+------+-----------+--------+ +Water | 12·36 | 13·73 |24·21 |18·89 | 12·55| 16·44 | 14·15 | +Organic matter }| | | | | | | | + and ammoniacal }| 59·92 | 53·16 |39·30 |32·49 | 35·89| 12·28 | 26·14 | + salts }| | | | | | | | +Phosphates | 17·01 | 23·48 |30·00 |19·63 | 27·63| 56·09 | 23·13 | +Sulphate of lime | ... | ... | ... | ... | ... | ... | 9·65 | +Carbonate of lime | ... | ... | ... | ... | ... | ... | 12·87 | +Alkaline salts | 7·20 | 7·97 | 4·19 | 8·82 | 15·29| 11·33 | 5·97 | +Sand | 3·51 | 1·66 | 2·30 | 6·72 | 8·64| 2·81 | 8·09 | + +--------+-------+------+------+------+-----------+--------+ + | 100·00 |100·00 |100·00|100·00|100·00|100·00 |100·00 | +Ammonia | 21·10 | 17·00 | 8·50| 10·42| 8·99| 2·57 | 3·26 | +Phosphoric }| | | | | | | | + acid in alkaline}| 1·20 | 2·50 | ... | ... | ... | 3·11 | ... | + salts }| | | | | | | | +-------------------+--------+-------+------+------+------+-----------+--------+ + + +-------------------+---------+-------+--------+-----------+-------------+ + | | | | | | + |Pacquico.|Latham |Saldanha|Australian.|Kooriamooria.| + | |Island.|Bay. | | | + | | | | | | +-------------------+---------+-------+--------+-----------+-------------+ +Water | 8·38 | 24·96 | 21·03 | 13·20 | 8·91 | +Organic matter }| | | | | | + and ammoniacal }| 23·10 | 10·96 | 14·93 | 13·77 | 7·72 | + salts }| | | | | | +Phosphates | 32·36 | 54·47 | 56·40 | 44·47 | 44·15 | +Sulphate of lime | 2·92 | 2·82 | ... | 4·55 | 3·19 | +Carbonate of lime | ... | 2·20 | ... | 8·82 | 3·37 | +Alkaline salts | 25·43 | 4·06 | 6·10 | 7·34 | 11·23 | +Sand | 7·81 | 0·51 | 1·54 | 7·85 | 21·43 | + +---------+-------+--------+-----------+-------------+ + |100·00 |100·00 |100·00 |100·00 |100·00 | +Ammonia | 6·58 | 1·26 | 1·62 | 1·01 | 0·42 | +Phosphoric }| | | | | | + acid in alkaline}| 3·50 | ... | ... | ... | ... | + salts }| | | | | | +-------------------+---------+-------+--------+-----------+-------------+ + +-------------------+-----------+--------+--------+ + | | | | + |Patagonian.|Chilian.|Mexican.| + | | | | + | | | | +-------------------+-----------+--------+--------+ +Water | 20·61 | 14·89 | 18·80 | +Organic matter }| | | | + and ammoniacal }| 19·72 | 16·81 | 12·88 | + salts }| | | | +Phosphates | 30·66 | 36·90 | 18·38 | +Sulphate of lime | 1·30 | ... | 27·79 | +Carbonate of lime | 3·06 | 10·28 | ... | +Alkaline salts | 7·01 | 6·84 | 16·95 | +Sand | 17·04 | 14·26 | 5·20 | + +-----------+--------+--------+ + |100·00 |100·00 |100·00 | +Ammonia | 2·69 | 1·42 | 0·42 | +Phosphoric }| | | | + acid in alkaline}| 3·00 | ... | ... | + salts }| | | | +-------------------+-----------+--------+--------+ + + +_Table shewing the Composition of some of the less common varieties of +Guano._ + +NOTE.--The numbers in this Table are mostly derived only from a single +analysis and have no value as determining the average composition of +these Guanos, but they serve to give a general idea of their value. + +-------------------+--------+---------+---------+-----------+------------+ + | Sea | Indian. | Holme's | Ascension | Possession | + | Bear | | Bird | Island. | Island. | + | Bay. | | Island. | | | +-------------------+--------+---------+---------+-----------+------------+ +Water | 30·82 | 23·62 | 25·00 | 15·97 | 10·92 | +Organic matter }| | | | | | + and ammoniacal }| 31·78 | 60·05 | 32·10 | 23·15 | 15·42 | + salts }| | | | | | +Phosphates | 24·33 | 7·18 | 27·36 | 32·54 | 46·41 | +Sulphate of lime | 3·84 | ... | ... | ... | 7·46 | +Carbonate of lime | 0·58 | 2·79 | ... | ... | ... | +Alkaline salts | 7·38 | 5·58 | 8·82 | 15·92 | 6·15 | +Sand | 1·27 | 0·78 | 6·72 | 12·42 | 13·64 | + +--------+---------+---------+-----------+------------+ + |100·00 | 100·00 | 100·00 | 100·00 | 100·00 | + | | | | | | +Ammonia | 10·45 | 10·27 | 7·75 | 6·06 | 1·34 | +Phosphoric }| | | | | | + acid in alkaline}| ... | ... | ... | 1·82 | ... | + salts }| | | | | | +-------------------+--------+---------+---------+-----------+------------+ + +-------------------+-------+---------+---------+---------+ + | Algoa | New | Bird's | Leone | + | Bay. | Island. | Island. | Island. | +-------------------+-------+---------+---------+---------+ +Water | 30·55 | 28·78 | 16·52 | 23·65 | +Organic matter }| | | | | + and ammoniacal }| 6·85 | 13·78 | 14·84 | 4·27 | + salts }| | | | | +Phosphates | 21·24 | 22·46 | 25·21 | 13·58 | +Sulphate of lime | 36·42 | ... | 40·47 | 29·95 | +Carbonate of lime | ... | 13·78 | ... | ... | +Alkaline salts | 3·32 | 12·62 | 1·16 | 5·40 | +Sand | 1·62 | 11·58 | 1·80 | 23·15 | + +-------+---------+---------+---------+ + |100·00 | 100·00 | 100·00 | 100·00 | + | | | | | +Ammonia | 0·54 | 0·84 | 1·26 | 0·67 | +Phosphoric }| | | | | + acid in alkaline}| ... | ... | ... | ... | + salts }| | | | | +-------------------+-------+---------+---------+---------+ + +On examining the tables given above, it is obvious that guanos may be +divided into two classes, the one characterized by the abundance of +ammonia, the other by that of phosphates; and which, for convenience +sake, may be called ammoniacal and phosphatic guanos. Peruvian and +Angamos are characteristic of the former, and Saldanha Bay and Bolivian +of the latter class. The value of these two classes of guano differs +materially, and they are also applicable under different circumstances, +but to these points reference will afterwards be made. + +Very special precautions are necessary on the part of the farmer in +order to insure his obtaining a guano which is not adulterated, and of +good quality if genuine. In the case of Peruvian guano, which is +tolerably uniform in its qualities, it is possible to form some opinion +by careful examination, and the following points ought to be attended +to: + +1st, The guano should be light coloured. If it is dark, the chances are +that it has been damaged by water. + +2d, It should be dry, and when a handful is well squeezed together it +should cohere very slightly. + +3d, It should not have too powerful an ammoniacal odour. + +4th, It should contain lumps, which, when broken, appear of a paler +colour than the powdery part of the sample. + +5th, When rubbed between the fingers it should not be gritty. + +6th, A bushel of the guano should not weigh more than from 56 to 60 lbs. + +These characters must not, however, be too implicitly relied on, for +they are all imitated with wonderful ingenuity by the skilful +adulterator, and they are applicable only to Peruvian guano; the others +being so variable that no general rules can be given for determining +whether they are genuine. Neither are they so precise as to enable us to +give any opinion regarding the relative values of several samples where +all are genuine. The only way in which adulteration can with certainty +be detected, and the value of different guanos be determined, is by +analysis, and the importance of this can easily be illustrated. + +In the table above, the _average_ composition of the different guanos is +given; but in order to shew how much individual cargos may differ from +the mean, we give here analyses of samples of the highest and lowest +quality of the genuine guanos of most importance: + ++-------------------+-------------------+------------------+------------------+ +| | Angamos. | Peruvian. | Bolivian. | +| +---------+---------+---------+--------+---------+--------+ +| |Highest. |Lowest. |Highest. |Lowest. |Highest. |Lowest. | +| +---------+---------+---------+--------+---------+--------+ +| Water | 12·60 | 7·09 | 10·37 | 21·49 | 11·53 | 16·20 | +| Organic matter } | | | | | | | +| and ammoniacal } | 65·62 | 50·83 | 55·73 | 46·26 | 11·17 | 12·86 | +| salts } | | | | | | | +| Phosphates | 10·83 | 8·70 | 25·20 | 18·93 | 62·99 | 52·95 | +| Alkaline salts | 7·50 | 16·30 | 7·50 | 10·64 | 9·93 | 13·83 | +| Sand | 3·45 | 17·08 | 1·20 | 2·68 | 4·38 | 4·16 | +| +---------+---------+---------+--------+---------+--------+ +| | 100·00 | 100·00 | 100·00 |100·00 | 100·00 | 100·00 | +| | | | | | | | +| Ammonia | 25·33 | 17·15 | 18·95 | 14·65 | 1·89 | 2·23 | ++-------------------+---------+---------+---------+--------+---------+--------+ + +The differences are here exceedingly large; and when the values of the +two Peruvian guanos are calculated according to the method to be +afterwards described, it appears that the highest exceeds the lowest in +value by nearly £3 per ton. Of course, this is an extreme case, but it +is no uncommon occurrence to find a difference of £1 or even £2 per ton +between the values of cargos of Peruvian guano, which are sold at the +same price. + +The adulteration of guano is carried on to a very large extent; and +though perhaps not quite so extensively now as it was some years since, +it is only kept in check by the utmost vigilance on the part of the +purchaser. The chief adulterations are a sort of yellow loam very +similar in appearance to guano, sand, gypsum, common salt, and +occasionally also ground coprolites and inferior guano. These substances +are rarely used singly, but are commonly mixed in such proportions as +most closely to imitate the colour and general appearance of the genuine +article. The extent to which the adulteration is carried may be judged +of from the following analyses taken at random from those of a large +number of guanos, all of which were sold as first-class Peruvian. + +Water 12·85 15·19 12·06 27·86 6·32 +Organic matter and } + ammoniacal salts } 26·84 44·31 34·14 30·41 27·42 +Phosphates 15·54 20·95 22·08 22·17 33·61 +Sulphate of lime ... ... 11·08 ... 22·11 +Alkaline salts 6·07 9·40 12·81 7·92 22·50 +Sand 38·70 10·15 7·83 1·64 10·15 + ------ ------ ------ ------ ------ + 100·00 100·00 100·00 100·00 100·00 + +Ammonia 9·34 13·90 9·77 8·64 9·76 + +In all those cases a very large depreciation in the value has taken +place, and several of them are worth considerably less than half the +price of the genuine guano, while they are generally offered for sale at +about £1 under the usual price. The adulteration is chiefly practised in +London, and cases occasionally occur which can be traced to Liverpool +and other places; but it always takes place in the large towns, because +it is only there that facilities exist for obtaining the necessary +materials and carrying it out without exciting suspicion. The +sophisticated article then passes into the hands of the small country +dealers, to whom it is sold with the assurance that it is genuine, and +analysis quite unnecessary. In other instances, adulterated and inferior +guanos are sold by the analysis of a genuine sample, and sometimes an +analysis is made to do duty for many successive cargos of a guano which, +though all obtained from one deposit, may differ excessively in +composition. In order to insure obtaining a genuine guano, it is above +all things important to deal only with a person of established +character, who will generally, for his own sake, satisfy himself that +the article he vends is genuine and of good quality; and it is always +important that the buyer should examine the analysis, and in all cases +where there is the slightest doubt, should ascertain that the bulk sent +corresponds with it. In the case of a Peruvian guano, a complete +analysis is not necessary for this purpose; but an experienced chemist, +by the application of a few tests, can readily ascertain whether the +sample is genuine. Where the difference in value between different +samples is required, a complete analysis is necessary, and this is +indispensable in the case of the inferior guanos. Many of these are +obtained from deposits of limited extent, and in loading it considerable +quantities of the subjacent soil are taken up, so that very great +differences may exist even in different parts of the same cargo. Nor +must it be forgotten that, except in the case of Peruvian, the name is +no guarantee for the quality of the guano, even if genuine. Peruvian +guano is all obtained from the same deposits, those of the Chincha +Islands, but the guanos which are brought into the market under the name +of Patagonian, Chilian, etc., are obtained from a great variety of +deposits scattered along the coasts of these countries, sometimes at a +distance of several hundred miles from each other, and which have been +accumulated under totally different circumstances. In illustration of +this, it is only necessary to refer to the subjoined analysis of +samples, all of which I believe to be genuine as imported, and which +were sold under the name of Upper Peruvian Guano. + + I. II. III. +Water 7·80 6·65 8·85 +Organic matter and ammoniacal salts 10·85 19·16 10·20 +Phosphates 67·00 20·41 17·10 +Carbonate of lime ... 21·15 ... +Alkaline salts 11·10 5·31 61·30 +Sand 3·25 27·32 2·55 + ------ ------ ------ + 100·00 100·00 100·00 + +Ammonia 2·29 5·73 1·48 +Phosphoric acid in the alkaline salts 2·24 ... 1·70 +Equal to phosphate of lime 4·89 ... 3·70 + +With the exception of Peruvian, the supply of _good_ guanos of uniform +composition is by no means large, and phosphatic guanos of good quality +are now especially rare. The Saldanha Bay, and other similar deposits, +have been exhausted, and few guanos of equally good quality have been +lately discovered. There is no doubt, however, that such guanos are very +useful, and if obtained in large quantity, and of uniform composition, +would be used to a much larger extent than they at present are. + +The value and use of guano are now so well understood, that it is +scarcely necessary to enlarge on the mode of its application. Peruvian +guano owes its chief value to its ammonia and phosphates, but it also +contains potash, soda, and all the other constituents of plants in small +quantity, although in a readily available condition, as is seen in the +detailed analysis given in page 205. + +In other guanos which have undergone more complete decomposition, and +from which the soluble matters have been more or less completely +exhausted by rain, the alkaline salts, or at least the potash they +originally contained, have almost entirely disappeared. Hence an +important difference between Peruvian guano and most other varieties. +The former can be used as a complete substitute for farm-yard manure, +and excellent crops of turnips and potatoes can be raised by means of it +alone, and at a less cost than with ordinary dung. But though this may +be done, and in many cases is attended with great economic advantages, +it is a practice that cannot be recommended for general use, because the +quantity of valuable matters contained in the usual application of guano +is much smaller than in farm-yard manure, and the probability is that it +would not, if used alone during a succession of years, be sufficient to +maintain the soil permanently in a high state of fertility. Five cwt. of +Peruvian guano, which is a liberal application per acre, contains about +95 lbs. of ammonia, and 130 of phosphates, while 20 tons of good +farm-yard manure contain 312 of ammonia, and about the same quantity of +phosphates, and when the other constituents, such as potash and soda, +are compared with those in guano, the difference is still more striking. +On the other hand, guano is a rapidly acting manure; its constituents +are in a condition in which they are more immediately accessible by the +plant, and its immediate effect is far more marked, as it is chiefly +expended on the crop to which it is applied. It has indeed been alleged +that it produces no effects on the subsequent crops, but this opinion +can scarcely be considered as well founded. In no case does the crop +raised by means of it contain the whole of the ammonia or phosphates +present in the manure, and the unappropriated quantity, though it may, +and probably does, escape from the lighter soils, must be retained and +preserved for the use of subsequent crops by heavy and retentive clay +soils. The general inference is, that though guano may at an emergency +be used as an entire substitute for farm-yard manure, the practice is +one to be generally avoided. When, however, as occasionally happens +after a long continued use of farm-yard manure, organic matters have +accumulated in the soil, and passed into an inert condition, then +Peruvian guano may be used alone with very great advantage. In all cases +the rapidity of the action of guano makes it an important auxiliary of +farm-yard manure, and it is in this way that it may be most +advantageously employed. Experience has shewn that one-half the +farm-yard manure may be replaced by guano with the production of a +larger crop than by the former alone in its full quantity. The +proportion of guano usually employed is from three to five cwt., and it +is alleged that a much larger quantity produces prejudicial effects on +the subsequent crops, although it is not very easy to see on what this +depends. + +The variety of guano to be selected must depend to a great extent on the +use to which it is to be put. Peruvian guano is most advantageously +applied as a top-dressing to young corn and particularly to oats. For +the turnip, the ammoniacal guanos were formerly preferred, and on strong +soils, under good cultivation, their effects are excellent, but on +light soils they are less applicable, their soluble salts being more +rapidly washed out, and their effects lost, and in these cases they are +surpassed by the phosphatic guanos. + +No definite rules can be given for determining the soils on which these +different varieties are most applicable, but each individual must +determine by experiment that which best suits his own farm; and the +inquiry is of much importance to him, as, of course, if the phosphatic +guanos will answer as well as the ammoniacal, there is a large saving in +the cost of the manure. A very excellent practice is to employ a mixture +of equal parts of the two sorts of guano. + +_Pigeons' Dung._--The dung of all birds, which more or less closely +resembles guano, may be employed with much advantage as a manure, but +that of the pigeon and the common fowl are the only ones which can be +got in quantity. Pigeons' dung, according to Boussingault, contains 8·3 +per cent of nitrogen, equivalent to 10·0 of ammonia. Its value, +therefore, will be more than half that of guano, but it varies greatly, +and a sample imported from Egypt into this country, and analysed by +Professor Johnston, contained only 5·4 per cent of ammonia. Hens' dung +has not been accurately analysed, but its value must be about the same +as pigeons'. + +_Urate and Sulphated Urine._--We have already discussed the urine of +animals, in reference to farm-yard manure. But human urine, the +composition of which was then stated, is of much higher value than that +of the lower animals, and many attempts have been made to preserve and +convert it into a dry manure. Urate is prepared by adding gypsum to +urine, and collecting and drying the precipitate produced. It contains a +considerable quantity of the phosphoric acid of the urine, but very +little of its ammonia; and as the principal value of urine depends on +the latter, it is necessarily a very inefficient method of turning it to +account. A better method has been proposed by Dr. Stenhouse, who adds +lime-water to the urine, and collects the precipitate, which, when dried +in the air, contains 1·91 per cent of nitrogen, and about 41 per cent of +phosphates. This method is subject to the same objection as that by +which urate is made, namely, that the greater part of the ammonia is not +precipitated. This might probably be got over to some extent by the +addition of sulphate of magnesia, or, still better, of chloride of +magnesium, which would throw down the phosphate of magnesia and ammonia. +By much the best mode of employing urine is in the form of sulphated +urine, which is made by adding to it a sufficient quantity of sulphuric +acid to neutralize its ammonia, and evaporating to dryness. In this form +all the valuable constituents are retained, and excellent results are +obtained from it. Its effects, though mainly attributable to its +ammonia, are also in part dependent on the phosphates and alkaline salts +which it contains; and it is therefore capable of supplying to the plant +a larger number of its constituents than the animal matters already +mentioned. + +_Night-Soil and Poudrette._--The value of night-soil, which is well +known, depends partly on the urine, and partly on the fæces of which it +is formed. Its disagreeable odour has prevented its general use, and +various methods have been contrived both for deodorising and converting +it into a solid and portable form. The same difficulties which beset the +conversion of urine into the solid form occur here, and in most of the +methods employed the loss of ammonia is great. It is sometimes mixed +with lime or gypsum, and dried with heat, and sometimes with animal +charcoal or peat charcoal. The manufacture of a manure from night-soil, +called "poudrette," has long been practised in the neighbourhood of +Paris and other continental towns. The process employed at Montfauçon +and at Bondy is very simple. The contents of the cesspools are conveyed +to the work in large barrels, which are then emptied into tanks capable +of containing the accumulation of several months. When filled they are +allowed to stand for some time, during which the smell diminishes and +the contents become nearly dry. The residue is then dug out and mixed +with ashes, dry loam, charcoal powder, peat, peat-charcoal, saw-dust, +and other matters, so as to deodorize it, and render it sufficiently dry +for transport. Its general composition may be judged of from the +subjoined analyses of samples from different places:-- + + Montfauçon. Bondy. Dresden. American. +Water 28·00 13·60 19·50 39·97 +Organic matters 29·00 24·10 20·80 20·57 +Phosphates 7·65 4·96 5·40 1·88 +Carbonates of lime and } +Magnesia, alkaline } 7·35 14·14 11·30 7·63 +salts, etc. } +Sand 28·00 43·20 43·00 29·95 + ------ ------ ------ ------ + 100·00 100·00 100·00 100·00 + +Ammonia 1·54 1·98 2·60 1·23 + +These analyses shew sufficiently the extent to which the animal matters +have been mixed with valueless driers, the second and third samples +containing considerably more than half their weight of worthless +matters. + +_Hair, Skin, and Horn._--The refuse of manufactories in which these +substances are employed, are frequently used as manures. They are highly +nitrogenous substances, and owe their entire value to the nitrogen they +contain, their inorganic constituents being in too small quantity to be +of any importance, wool and hair having only 2 per cent, and horn 0·7 +per cent of ash. In the pure and dry state, and after subtraction of the +ash, their composition is,-- + + Skin. Human hair. Wool. Horn. +Carbon 50·99 50·65 50·65 51·99 +Hydrogen 7·07 6·36 7·03 6·72 +Nitrogen 18·72 17·14 17·71 17·28 +Oxygen 23·22 20·85 } 24·61 24·01 +Sulphur ... 5·00 } + ------ ------ ------ ------ + 100·00 100·00 100·00 100·00 + +It rarely if ever happens, however, that the refuse offered for sale as +a manure is pure. It always contains water, sand, and other foreign +matters. Woollen rags are mixed with cotton which has no manurial value, +and the skin refuse from tan-works contains much lime. Due allowance +must therefore be made for such impurities which are sometimes present +in very large quantity. + +Refuse horse hair generally contains 11 or 12 per cent of nitrogen. +Woollen rags of good quality contain 12·7 per cent of nitrogen; woollen +cuttings about 14; and what is called shoddy only 5·5 per cent. Horn +shavings are extremely variable in their amount of nitrogen; when pure, +they sometimes contain as much as 12·5 per cent, but a great deal of the +horn shavings from comb manufactories, etc., contain much sand and bone +dust, by which their percentage of nitrogen is greatly diminished, and +it sometimes does not exceed 5 or 6 per cent. + +All these substances are highly valuable as manures, but it must be +borne in mind that they undergo decomposition very slowly in the soil, +and hence are chiefly applicable to slow growing crops, and to those +which require a strong soil. Woollen rags have been largely employed as +a manure for hops, and are believed to surpass every other substance for +that crop. As a manure applicable to the ordinary purposes of the farm +they have scarcely met with that attention which they deserve, probably +because their first action is slow and the farmer is more accustomed to +look to immediate than to future results; but they possess the important +qualification of adding permanently to the fertility of the soil. + +_Blood_ is a most valuable manure, but it is not much employed in this +country, at least in the neighbourhood of large towns, as there is a +demand for it for other purposes, and it can rarely be obtained by the +farmer in large quantity, and at a sufficiently low price. In its +natural state it contains about 3 per cent of nitrogen, and after being +dried up, the residue contains about 15 per cent. It is best used in the +form of a compost with peat or mould, and this forms an excellent manure +for turnips, and is also advantageously applied as a top-dressing to +wheat. + +_Flesh._--The flesh of all animals is useful as a manure, and is +especially distinguished by the rapidity with which it undergoes +decomposition, and yields up its valuable matters to the plant. It is +rarely employed in its natural state, but horse flesh was at one time +converted into a dry and portable manure, although, I understand, this +manufacture is not now prosecuted. The dead animal after being skinned +is cut up and boiled in large cauldrons until the flesh is separated +from the bones. The latter are removed, and the flesh dried upon a flat +stove. The flesh as sold has the following composition:-- + +Water 12·17 +Organic matter 78·44 +Phosphate of lime, etc. 3·82 +Alkaline salts 3·64 +Sand 1·93 + ------ + 100·00 +Nitrogen 9·22 +Ammonia to which the nitrogen is } +equivalent } 11·20 + +The dried flesh and small bones of cattle, from the great slaughtering +establishments of South America, was at one time imported into this +country under the name of flesh manure. Its composition was-- + +Water 9·05 +Fat 11·13 +Animal matter 39·52 +Phosphate of lime 28·74 +Carbonate of lime 3·81 +Alkaline salts 0·57 +Sand 7·18 + ------ + 100·00 +Nitrogen 5·56 +Ammonia to which the nitrogen is } +equivalent } 6·67 + +But owing to the large proportion of phosphates contained in it, it may +be most fairly compared with bones. It is not now imported, the results +obtained from its use being said not to have proved satisfactory, +although this statement appears very paradoxical. + +_Fish_ have been employed in considerable quantity as a manure. That +most extensively employed in this country is the sprat, which is +occasionally caught in enormous quantities on the Norfolk coast, and +used as an application for turnips. They are sold at 8d. per bushel, +and their composition is-- + +Water 64·6 +Organic matter 33·3 +Ash 2·1 + ----- + 100·0 +Nitrogen 1·90 +Phosphoric acid 0·91 + +The refuse of herring and other fish-curing establishments, whales' +blubber, and similar fish refuse, are all useful as manure, and are +employed whenever they can be obtained. They are not usually employed +alone, but are more advantageously made into composts with their own +weight of soil, and allowed to ferment thoroughly before being applied. + +Many attempts have been made to convert the offal of the great +fish-curing establishments, and the inedible fish, of which large +quantities are often caught, into a dry manure, which has received the +name of "fish guano." The processes employed have consisted in boiling +with sulphuric acid and other agents, and then evaporating, or sometimes +by simply drying up the refuse by steam heat. A manure made in this way +proved to have the following composition:-- + +Water 8·00 +Fatty matters 7·20 +Nitrogeneous organic matters 71·46 +Phosphate of lime 8·70 +Alkaline salts 3·80 +Sand 0·84 + ------ + 100·00 + +Nitrogen 11·25 +Equal to ammonia 13·68 +Phosphoric acid in the alkaline salts, } 0·65 + equal to 1·41 phosphate of lime } + +The expense of manufacturing manures of this description has hitherto +acted as a barrier to their introduction. In this country several +manufactories have been established, but either owing to this cause, or +to the difficulty of obtaining sufficiently large and uniform supplies +of the raw material, some of them have not proved successful, but a +manufactory is now in operation in Norway, which exports the manure to +Germany. It is probable that most of the processes used in this country +failed because they were too costly, and it is much to be desired that +the subject should be actively taken up. It is said that the refuse from +the Newfoundland fisheries is capable of yielding about 10,000 tons of +fish guano annually; and the quantity obtainable on our own coasts is +also very considerable. + +_Bones._--Bones have been used as a manure for a long period, but they +first attracted the particular attention of agriculturists from the +remarkable effects produced by their application on the exhausted +pasture lands of Cheshire. During the present century they came into +general use on arable land, and especially as a manure for turnips; and +they are now imported in large quantities from the continent of Europe. +The bones used in agriculture are chiefly those of cattle, but sheep and +horse bones are also employed. They do not differ much in quality when +genuine. The subjoined analysis is that of a good sample. + +Water 6·20 +Organic matter 39·13 +Phosphate of lime 48·95 +Lime 2·57 +Magnesia 0·30 +Sulphuric acid 2·55 +Silica 0·30 + ------ + 100·00 +Ammonia which the organic matter } + is capable of yielding } 4·80 + +In general, bones may be said to contain about half their weight of +phosphate of lime, and 10 or 12 per cent of water. But, in addition to +their natural state, they are met with in other forms in commerce, in +which their organic matter has been extracted either by boiling or +burning. The latter is especially common in the form of the spent animal +charcoal of the sugar refiners, which usually contains from 70 to 80 per +cent of phosphate of lime, but when deprived of their organic matter, +they may be more correctly considered under the head of mineral manures. + +From the analysis given above, it is obvious that the manurial value of +bones is dependent partly on their phosphates and partly on the ammonia +they yield. It has been common to attribute their entire effects to the +former, but this is manifestly erroneous; and although there are no +doubt cases in which the former act most powerfully, the benefit derived +from the ammonia yielded by the organic matter is unequivocal. When the +phosphates only are of use, burnt bones or the spent animal charcoal of +the sugar refiners are to be preferred. + +At their first introduction, bones were applied in large fragments, and +in quantities of from 20 to 30 cwt., or even more, per acre, but as +their use became more general they were gradually employed in smaller +pieces, until at last they were reduced to dust, and it was found that, +in a fine state of division, a few hundredweights produced as great an +effect as the larger quantity of the unground bones. Even the most +complete grinding which can be attained, however, leaves the bones in a +much less minute state of division than guano, and they necessarily act +more slowly than it does, the more especially as they contain no +ready-formed ammonia. They may be still further reduced by fermentation, +which acts by decomposing the organic matter, and causing the production +of ammonia; but not as is frequently, though erroneously supposed, by +converting the phosphates into a soluble condition, for this does not +occur to any extent, and their more rapid action is solely due to the +partial decomposition of the organic matter, by which it is brought into +a condition capable of undergoing a more rapid change in the soil. The +rapidity of action of bones is still more promoted by solution in +sulphuric acid, by which they are converted into the form of dissolved +bones or superphosphate. At the present moment, however, very little of +the superphosphates sold in the market are made exclusively from bones +in their natural state, by far the larger portion being manufactured +from mineral phosphates, or from bones after destruction of their +organic matter, sometimes with the addition of small quantities of +unburnt bones, but more frequently of sulphate of ammonia, to yield the +requisite quantity of ammonia. These substances may therefore be best +considered under the head of mineral manures. + + + + +CHAPTER XI. + +COMPOSITION AND PROPERTIES OF MINERAL MANURES. + + +Mineral manure is a term which is now used with great laxity. In its +strict sense, it means manures which contain only, and owe their +exclusive value to the presence of, those substances which go to make up +the inorganic part or ash of plants. It has, however, been usually taken +to include all saline matters, and especially the compounds of ammonia +and nitric acid, which are indebted for their manurial effects to the +nitrogen they contain; and thus is so far incorrect. It would, however, +be manifestly impossible to arrange these compounds with any degree of +accuracy among either animal or vegetable manures, and hence the +necessity of including them amongst those which are strictly mineral. +The most important practical distinction between them and the substances +discussed in the two preceding chapters is, that the latter generally +contain the whole or the greater part of the constituents of plants. +Even bones yield a certain quantity of alkalies, magnesia, sulphuric +acid, and chlorine, and may in some sense be considered as a general +manure. But those to which the term mineral manure is applied for the +most part contain only one or two of the essential elements of plants, +and hence cannot be applied as substitutes for the substances already +discussed, although they are frequently most important additions to +them. + +_Sulphate and Muriate of Ammonia._--These and other salts of ammonia +have been tried experimentally as manures, and it has been ascertained +that they may all be used with equal success; but as the sulphate is by +much cheaper, it is that which probably will always be employed to the +exclusion of every other. It contains, when pure, 25·7 per cent ammonia. + +It is now manufactured of excellent quality for agricultural use, and +when good, contains from 95 to 97 per cent of actual sulphate, the +remainder consisting chiefly of moisture and a small quantity of fixed +residue; but specimens are occasionally met with containing as much as +10 per cent of impurities, which, as its price is high, makes a material +difference in its value. Inferior descriptions are also occasionally +sold, among which is a variety distinguished by containing a large +quantity of water and fixed salts, although it appears to the eye a good +article. Its composition is-- + + I. II. +Water 9·05 5·77 +Sulphate of ammonia 79·63 85·21 +Fixed salts 11·17 9·02 + ------ ------ + 100·00 100·00 +Ammonia 20·55 21·94 + +An article called sulphomuriate of ammonia is also sold for agricultural +use. It is obtained as a refuse product in the manufacture of magnesia, +and is a mixture of sulphate and muriate of ammonia, with various +alkaline salts. It differs somewhat in quality, and is sold by analysis +at a price dependent on the ammonia it contains. + + I. II. +Water 14·49 25·39 +Sulphate of ammonia 62·55 47·79 +Muriate of ammonia 15·3 ... +Sulphate of soda ... 9·12 +Sulphate of magnesia ... 18·38 +Chloride of potassium 4·75 2·94 +Chloride of sodium 17·35 0·35 + ------ ------ + 100·00 100·00 +Ammonia 16·50 11·28 + +The quality of sulphate of ammonia may generally be judged of from its +dry and uniformly crystalline appearance, and it may be tested by +heating a small quantity on a shovel over a clear fire, when it ought to +volatilize completely, or leave only a trifling residue. Some care, +however, is necessary in applying this test, as in the hands of +inexperienced persons it is sometimes fallacious. The salts of ammonia +may be applied in the same way as guano; but they are most +advantageously employed as a top-dressing, and principally to grass +lands. In this way very remarkable effects are produced, and within a +week after the application, the difference between the dressed and +undressed portions of a field is already conspicuous. Experience has +shewn that success is best insured when the salt is applied during or +immediately before rain, so that it may be at once incorporated with the +soil; as when used in dry weather little or no benefit is derived from +it. It seems also to exert a peculiarly beneficial effect upon clover; +and hence it ought to be employed only on clover-hay, as where ryegrass +or other grasses form the whole of the crop we have better manures. + +_Ammoniacal Liquor of the Gas-Works, and of the Animal Charcoal +Manufacturers._--Both of these are excellent forms in which to apply +ammonia, when they can be obtained. The ammoniacal liquor of the +gas-works is very variable in quality, but contains generally from 4 to +8 ounces of dry ammonia per gallon, which corresponds in round numbers +to from 1 to 2 lb. of sulphate of ammonia. It is best applied with the +watering-cart, but must be diluted before use with three or four times +its bulk of water, as if concentrated it burns up the grass, and it is +also advisable to use it during wet weather. The ammoniacal liquor of +the ivory-black works contains about 12 per cent of ammonia, or about +four or five times as much as gas liquor. It has been used in some parts +of England, made into a compost, and applied to the turnip and other +crops, and, it is said, with good effect. _Bone oil_, which distils over +along with it, has also been used in the form of a compost; it contains +a large quantity of ammonia and of nitrogen in other forms of +combination; the total quantity of nitrogen it contains being 9·04 per +cent, which is equivalent to 10·98 of ammonia. Only part of this +nitrogen is actually in the state of ammonia; and some circumstances +connected with the chemical relations of the other nitrogenous compounds +in this substance render it probable that they may pass very slowly into +ammonia, and may therefore be of inferior value; but the substance +deserves a trial, as it is very cheap. It must be carefully composted +with peat, and turned over several times before being used. + +_Nitrates of Potash and Soda._--Nitrate of potash has long been used as +a manure, but its high price has prevented its general application, and +its place has now been almost entirely taken by nitrate of soda, which +is much cheaper and contains weight for weight a larger quantity of +nitrogen. Both these salts are employed as sources of nitrogen; but +nitrate of potash owes also a certain proportion of its value to the +potash it contains. Nitrate of soda, on the other hand, must be +considered to owe its entire value to its nitric acid, as soda is of +little value to the plant; and, moreover, can be obtained in common salt +at a price so low, as to make it a matter of no moment in the valuation +of the nitrate. In its ordinary state, as imported from Peru, nitrate of +soda contains from 5 to 10 per cent of impurities, and it bears a price +proportionate to the quantity of the pure salt present in it. When of +good quality it contains about 15 per cent of nitrogen, equivalent to 18 +of ammonia, and is, therefore, richer in that constituent of plants than +Peruvian guano. It is essentially a rapidly acting manure, and produces +a marked effect within a very few days after its application; but owing +to the fact that nitric acid cannot be absorbed and retained by the soil +in the same manner as ammonia, it is liable to be lost unless it can be +at once assimilated by the plant. For this reason it acts best when +applied in small quantity as a top-dressing to grass-land, and to young +corn. A large application has no advantages, and there can be no doubt +that the best effect would be produced by several very small quantities, +applied at intervals. In one experiment, Mr. Pusey found 42 lb. per acre +to increase the produce of barley by 7 bushels, and very favourable +results have been obtained by other experimenters. The beneficial +effects of nitrate of soda appear to be almost entirely confined to the +grasses and cereals. At least experience here has shewn that it produces +little or no effect on clover; and one farmer has stated, that having +recently adopted the practice of sowing clover with a very small +proportion of ryegrass only, he has been led to abandon the use of +nitrate of soda, which he formerly employed abundantly, when ryegrass +formed a principal part of his crop. The action of nitrate of soda is +very remarkable, not only in this respect, but also because a given +quantity of nitrogen in it _appears_ to produce a greater effect than +the same quantity in sulphate of ammonia or guano. At the same time this +statement must be taken as very general, definite experiments being +still too few to admit of its being stated as an absolute fact. The +probability is, that the same quantity of nitrogen, in the form either +of ammonia or nitrate of soda, will produce the same effect, although +the conditions necessary for its successful action may not be the same +with the two manures. It is alleged that nitrate of soda is +advantageously conjoined with common salt, which is said to check its +tendency to make the grain crops run to straw, and to prevent their +lodging, as they are apt to do, when it is employed alone. But +considerable difference of opinion exists in this point, many farmers +believing that salt produces no effect. When employed for hay, +especially when mixed with clover, it is advisable to use it along with +an equal quantity of sulphate of ammonia, which gives a better result +than either separately. + +_Salts of Potash and Soda._--The substances just mentioned must be +considered to owe their chief manurial value to nitric acid; but other +salts have been used as manures in which the effect is undoubtedly due +to the alkalies themselves. With the exception of common salt, most of +the alkaline salts have only been used to a limited extent; and it is +remarkable that, so far as our present experience goes, there is no +class of substances from which more uncertain results are obtained. + +_Muriate and Sulphate of Potash_ have both been used, and the former +has in some cases, and in particular seasons, produced a very remarkable +effect in the potato; but in other instances it has proved quite +useless. The cause of this difference has not been ascertained. Sulphate +of soda has also been used to some extent, but apparently without much +benefit; and there is no reason to expect that it should act better than +common salt, which can be obtained at a much lower price. + +_Chloride of Sodium, or Common Salt_, has at different times been +employed as a manure, but its effects are so variable and uncertain, +that its use, in place of increasing, has of late years rather +diminished, it having frequently been found that on soils in all +respects similar, or even on the same soil, in different years, it +sometimes proves advantageous, at others positively injurious. Its use +as an addition to nitrate of soda has been already alluded to, and it is +said that it produces the same effect when mixed with guano and salts of +ammonia. The accuracy of this statement is doubted by many persons, and +the explanation which has been given of the cause of its action is more +than dubious. It is supposed to enable the plant to absorb more silica +from the soil; but this is a speculative explanation of its action, and +has not been supported by definite experiment. Although little effect +has been observed from salt, it deserves a more accurate investigation, +as not withstanding the extent to which it has been employed, we are +singularly deficient in definite experiments with it. + +_Carbonates of Potash and Soda_ have only been tried experimentally, and +that to a small extent, nor is it likely that they will ever come into +use, owing to their high price. The remarks we have made in the section +on the ashes of plants regarding the subordinate value of soda, will +enable the reader to see that greater effects are to be anticipated +from the former than from the latter of these salts. They _may_, +however, exert a chemical action on the soil, altogether independent of +their absorption by the plant, but its nature and amount are still to +determine. + +_Silicates of Potash and Soda_ have been employed with the view of +supplying silica to the plant, but the results have been far from +satisfactory. This may perhaps have been due to the doubtful nature of +the commercial article, but now that silicate of soda can be obtained of +good quality, it is desirable that the experiments should be repeated. +It is said to have produced good effects on the potato. + +_Sulphate of Magnesia_ can be obtained at a low cost, and has been used +as a manure in some instances with very marked success. It has been +chiefly applied as a top-dressing to clover hay, but it seems probable +that it might prove a useful application to the cereals, the ash of +which is peculiarly rich in magnesia. + +Many other saline substances have been tried as manures; but in most +instances on too limited a scale to permit any definite conclusions as +to their value. The experiments have also been too frequently performed +without the precautions necessary to exclude fallacy, so that the +results already arrived at must not be accepted as established facts, +but rather as indications of the direction in which further +investigation would be valuable. There is little doubt that many of +these substances might be usefully employed, if the conditions necessary +for their successful application were eliminated; and no subject is at +present more deserving of elucidation by careful and well-devised field +experiments. + +_Phosphate of Lime._--The use of bones in their natural state as a +manure has been already adverted to, and it was stated, that though +their value depended mainly on the phosphates, the animal matters and +other substances contained in them were not without effect. The action +of phosphates is greatly promoted by solution in sulphuric acid, and the +application of the acid has brought into use many varieties of +phosphates of purely mineral origin, or which have been deprived of +their organic matters by artificial processes. Of these, the spent +animal charcoal of the sugar-refiners, usually containing about 70 per +cent of phosphates, and South American bone ash, are the most important. +The latter is now imported in very large quantity, and has the +composition shewn in the following analyses:-- + + I. II. III. + +Water 6·10 6·28 3·03 +Charcoal 5·05 2·19 2·02 +Phosphates 79·20 71·10 88·55 +Carbonate of lime 4·05 3·55 5·60 +Alkaline salts 0·15 traces ... +Sand 5·45 16·90 0·80 + ------ ------ ------ + 100·00 100·00 100·00 + +Bone ash has hitherto been almost entirely consumed as a raw material +for the manufacture of superphosphates; but as it is sold at from £4: +10s. to £5: 10s. per ton when containing 70 per cent of phosphates, it +is, in reality, a very cheap source of these substances, and merits the +attention of the farmer as an application in its ordinary state. + +Of strictly mineral phosphates, a considerable variety is now in use, +but they are employed exclusively in the manufacture of superphosphates, +as in their natural state they are so hard and insoluble, that the plant +is incapable of availing itself of them. + +_Coprolites._--This name was originally applied by Dr. Buckland to +substances found in many geological strata, and which he believed to be +the dung of fossil animals. It has since been given to phosphatic +concretions found chiefly in the greensand in Suffolk and +Cambridgeshire, which are certainly not the same as those described by +Dr. Buckland, but consist of fragments of bones, ammonites, and other +fossils. Coprolites are now collected in very large quantities, and +about 43,000 tons are annually employed. They are extremely hard, and +require powerful machinery to reduce them to powder, and hence their +price is considerable, being about £2: 10s. per ton. Their composition +varies somewhat according to the care taken in selecting them, and the +locality from which they have been obtained. A general idea of their +composition may be derived from the subjoined analyses:-- + +Water 1·95 1·90 +Organic matter 2·59 6·85 +Phosphate of lime 55·21} 61·15 +Phosphate of iron 3·84} +Carbonate of lime 26·70 16·20 +Sulphate of lime 1·97 " +Alkaline salts 1·85 3·21 +Sand 5·89 11·65 + ------ ------ + 100·00 100·00 + +Within the last two or three years, coprolites have been found in great +abundance in France, but they are of inferior quality, and rarely +contain more than 40 per cent of phosphates. + +_Apatite_, or mineral phosphate of lime, is found in large deposits in +different places. It is particularly abundant in Spain, and occurs also +in America and Norway. From the latter country it has been imported to +some extent; and during the last year considerable quantities have been +brought from Spain, and the importations will undoubtedly increase very +largely as the means of transport improve in that country. Spanish +apatite contains-- + +Water 0·80 +Phosphate of lime 93·30 +Carbonate of lime 0·50 +Chlorine, etc. traces +Sand 4·70 + ----- + 99·30 + +Several other varieties of mineral phosphates have been imported under +the name of guano. The most important is Sombrero Island guano, which is +found on a small island in the Gulf of Mexico, where it occurs in a +layer said to be forty feet thick. It contains-- + +Water 8·96 +Phosphate of lime 37·71 +Phosphates of alumina and iron 44·21 +Phosphate of magnesia 4·20 +Sulphate of lime 0·86 +Carbonate of lime 3·36 +Sand 0·70 + ------ + 100·00 + +A somewhat similar substance, but in hard crusts, has been imported, +under the names of Maracaybo guano, Pyroguanite, etc., which contains-- + +Water 1·03 +Organic matter 6·78 +Phosphates 75·69 +Alkaline salts 4·91 +Sand 11·64 + ------ + 100·00 +Phosphoric acid in the alkaline } 0·78 + salts = 1·68 phosphate of lime } + +These substances are all excellent sources of phosphates, but they are +so hard that the plants cannot extract phosphoric acid from them, and +they are only useful when made soluble by chemical processes. + +_Superphosphate; Dissolved Bones._--These names were at first applied to +bones which had been treated with sulphuric acid; but superphosphates +are now rarely made from bones alone, but bone ash and some of the +mineral phosphates just described are employed, either along with them, +or very frequently alone. The manufacture of superphosphates depends on +the existence of two different compounds of phosphoric acid and lime, +one of which contains three times as much lime as the other. That which +contains the larger quantity of lime is found in the bones and all other +natural phosphates, and is quite insoluble in water; but when two-thirds +of its lime are removed, it is converted into the other compound, which +is exceedingly soluble. This change is effected by the use of sulphuric +acid, which combines with two-thirds of the lime of the ordinary +insoluble phosphate of lime, and converts it into the _biphosphate of +lime_, which is soluble. When, therefore, we add to 100 lbs. of common +phosphate of lime the necessary quantity of sulphuric acid, it yields 64 +lbs. of biphosphate, containing the whole of the phosphoric acid, which +is the valuable constituent, the diminution in weight being due to the +removal of the valueless lime. Hence it follows, also, that as the lime +so removed is converted into sulphate, there must, for every 100 lbs. of +phosphate of lime converted into biphosphate, be produced 87 lbs. of dry +sulphate of lime, or 110 of the ordinary sulphate called gypsum. This is +the minimum quantity which can be present, but in actual practice it is +liable to be greatly exceeded, more especially where coprolites are +used, owing to the large amount of carbonate of lime they contain, which +is also converted into sulphate by the action of the acid, so that it is +far from uncommon to find the gypsum twice as great as it would be if +materials free from carbonates could be obtained. By employing a +sufficiency of sulphuric acid, the whole quantity of phosphoric acid in +the bones may be thus brought into a soluble state, but in actual +practice it is found preferable to leave part of it in the insoluble +condition; as where it is entirely soluble, its effect is too great +during the early part of the season, and deficient at its end. In order +to dissolve bones, bone ash, or mineral phosphates, they are mixed with +from a third to half their weight of sulphuric acid, of specific gravity +1·70 or 140° Twaddell. When mineral phosphates, and particularly +coprolites, are used, the quantity of sulphuric acid must be increased +so as to compensate for the loss of that which is consumed in +decomposing the carbonate of lime they contain. When operating on the +small scale, the materials are put into a vessel of wood, stone, or lead +(iron is to be avoided, as it is rapidly corroded by the acid), and +mixed with from a sixth to a fourth of their weight of water, which may +with advantage be used hot. The sulphuric acid is then added, and mixed +as uniformly as possible with the bones. Considerable effervescence +takes place, and the mass becomes extremely hot. At the end of two or +three days it is turned over with the spade, and after standing for some +days longer, generally becomes pretty dry. Should it still be too moist +to be sown, it must be again turned over, and mixed with some dry +substance to absorb the moisture. For this purpose everything containing +lime or its carbonate must be carefully avoided, as they bring back the +phosphates into the insoluble state, and undo what the sulphuric acid +has done. Peat, saw-dust, sand, decaying leaves, or similar substances, +will answer the purpose, and they should all be made thoroughly dry +before being used. An excellent plan is to sift the bones before +dissolving, to apply the acid to the coarser part, and afterwards to mix +in the fine dust which has passed through the sieve, to dry up the mass; +or a small quantity of bone ash, of good quality, or Peruvian guano, may +be used. On the large scale, mechanical arrangements are employed for +mixing the materials, so as to economise labour, and mineral phosphates, +such as apatite, can then be used with advantage. In such cases, blood, +sulphate of ammonia, soot, and other refuse matters, are occasionally +used to supply the requisite quantity of nitrogenous substances, but +large quantities are also made from bone ash, etc., without these +additions. + +The composition of superphosphates must necessarily vary to a great +extent, and depends not only on the materials, but on the proportion of +acid used for solution. The following analysis illustrates the +composition of good samples made from different substances-- + ++-----------------------------------+------------------+------------------+ +| | | | +| | Bones alone. | Bone-Ash. | +| | | | ++-----------------------------------+------------------+------------------+ +| Water, | 7·74 ... 7·79 | 5·33 ... 10·40 | +| Organic matters and ammoniacal | | | +| salts, | 17·83 ... 21·69 | 6·94 ... 4·92 | +| Biphosphate of lime | 13·18 ... 9·87 | 21·35 ... 23·09 | +| Equivalent to soluble phosphates, |(20·57)...(15·39) |(33·33)...(36·02) | +| Insoluble phosphates | 10·31 ... 21·17 | 5·92 ... 6·08 | +| Sulphate of lime, | 46·00 ... 35·30 | 56·16 ... 47·78 | +| Alkaline salts, | 1·46 ... 0·94 | trace. | +| Sand, | 3·48 ... 3·00 | 4·23 ... 4·30 | +| +------------------+------------------+ +| |100·00 ...100·00 |100·00 ...100·00 | +| Ammonia, | 2·11 ... 3·01 | 0·23 ... 0·31 | ++-----------------------------------+------------------+------------------+ + ++-----------------------------------+-------------------+-------------------+ +| | | Mixtures | +| |Chiefly Coprolites.|containing Salts of| +| | | Ammonia, etc. | ++-----------------------------------+-------------------+-------------------+ +| Water, | 5·90 ... 10·17 | 7·07 ... 15·82 | +| Organic matters and ammoniacal | | | +| salts, | 5·10 ... 4·13 | 9·87 ... 13·96 | +| Biphosphate of lime | 12·24 ... 13·75 | 17·63 ... 12·67 | +| Equivalent to soluble phosphates, |(19·10)...(21·43) |(27·50)...(19·77) | +| Insoluble phosphates | 16·90 ... 0·17 | 12·60 ... 8·40 | +| Sulphate of lime, | 52·39 ... 62·62 | 49·77 ... 45·14 | +| Alkaline salts, | 2·47 ... 0·96 | 0·06 ... 1·07 | +| Sand, | 6·00 ... 8·20 | 3·00 ... 2·94 | +| +-------------------+-------------------+ +| |100·00 ...100·00 |100·00 ...100·00 | +| Ammonia, | 0·11 ... 0·57 | 1·28 ... 1·55 | ++-----------------------------------+-------------------+-------------------+ + +Superphosphates made from bones alone are generally distinguished by a +large quantity of ammonia, and a rather low per centage of biphosphate +of lime. This is owing to the difficulty experienced in making the acid +react in a satisfactory manner on bones, the phosphates being protected +from its action by the large quantity of animal matter which, when +moistened, swells up, fills the pores, and prevents the ready access of +the acid to the interior of the fragments. Superphosphates from +bone-ash, on the other hand, contain a mere trifle of ammonia, and when +well made a very large quantity of biphosphate of lime. Their quality +differs very greatly, and depends, of course, on that of the bone-ash +employed, which can rarely be obtained of quality sufficient to yield +more than 30 or 35 per cent of soluble phosphates. Coprolites are seldom +used alone for the manufacture of superphosphates, but are generally +mixed with bone-ash and bone dust. Mixtures containing salts of ammonia, +flesh, blood, etc., are also largely manufactured, and some are now +produced containing as much as four or five per cent of ammonia, and the +consumption of such articles is largely increasing. + +The analyses above given are all those of good superphosphates, in which +abundance of acid has been used so as to convert a large proportion of +insoluble into soluble phosphates; but there are many samples of very +inferior quality to be met with in the market, in which the proportion +of acid has been reduced, and the quantity of phosphates made soluble is +consequently much lower than it ought to be. The following analyses +illustrate the composition of such manures, which are all very inferior +and generally worth much less than the price asked for them. + +Water 21·60 5·37 7·19 +Organic matter and ammoniacal + salts, 11·62 13·91 8·80 +Biphosphate of lime 2·98 2·02 6·42 +Equivalent to soluble + phosphates (4·65) (3·15) (10·02) +Insoluble phosphates 25·70 15·80 14·03 +Sulphate of lime 23·66 47·52 51·93 +Alkaline salts 10·70 3·73 3·43 +Sand 3·80 11·65 8·20 + ------ ------ ------ + 100·00 100·00 100·00 +Ammonia, 1·32 0·59 0·33 + +The deliberate adulteration of superphosphate, that is, the addition to +it of sand or similar worthless materials, I believe to be but little +practised. The most common fraud consists in selling as pure dissolved +bones, articles made in part, and sometimes almost entirely, from +coprolites. Occasionally refuse matters are used, but less with the +intention of actually diminishing the value of the manure as for the +purpose of acting as driers. It is said that sulphate of lime is +sometimes employed for this purpose, but this is rarely done, because +that substance is always a necessary constituent of superphosphate in +very large quantities; and as farmers look upon it with great suspicion, +all the efforts of the manufacturers are directed towards reducing its +quantity as much as possible. It is very commonly supposed by farmers +that the sulphate of lime found in so large quantity in all +superphosphates, and often amounting to as much as fifty per cent, has +been added to the materials in the process of manufacture, but this is a +mistake; it is a necessary and inevitable product of the chemical action +by which the phosphates are rendered soluble, although its quantity +depends on the materials from which the manure is made. When pure bones +are used its quantity is small, and it does not greatly exceed twice +that of the biphosphate of lime; but in a manure made from coprolites, +or other substances containing a large proportion of carbonate of lime, +which must in the process of manufacture be converted into sulphate, it +may be four or five times as much. + +Although there is no manure which varies more in quality, or requires +greater vigilance on the part of the purchaser, in order to obtain a +good article, there is no doubt that superphosphates, owing to the +process of manufacture being better understood, and to increased +competition, have considerably improved in quality. Six or eight years +since a manure containing thirty per cent of phosphates, of which twelve +or fifteen had been converted into biphosphate, was considered a fair +sample, but now the proportion rendered soluble is greatly increased; +and where bone ash alone is employed, as much as thirty and even forty +per cent of soluble phosphates is occasionally found. This, of course, +is an exceptional case, and great attention and care in the selection of +materials are necessary to obtain so large a proportion. The analyses +already given will shew the farmer what he has to expect in good +superphosphates, but it is very necessary that he should take care to +obtain from the manufacturer a manure equal to the guarantee; and he +ought to bear in mind that, owing to the difficulty of getting materials +of constant composition, variations often take place to a considerable +extent in manures which are supposed to be made in exactly the same +manner. + +_Phospho-Peruvian Guano._--Under this name a kind of superphosphate, +which is understood to be made by dissolving a native "rock guano," has +recently attracted considerable attention, and is used to a large +extent. Its composition is-- + +Water 9·54 +Organic matter 21·38 +Biphosphate of lime, equivalent to 25·22 soluble + phosphates 16·81 +Insoluble phosphates 10·88 +Sulphate of lime 37·21 +Alkaline salts, containing 1·32 of phosphoric acid, + and equivalent to 2·86 soluble phosphates 2·22 +Sand 1·81 + ------ + 100·00 +Ammonia, 3·50 + +It is chiefly distinguished by the large proportion of valuable +ingredients it contains, and the care taken to secure uniformity of +composition. + +A variety of substances are sold under the name of nitrophosphate, +potato manure, cereal manure, etc. etc., which are all superphosphates, +differing only in the proportion of their ingredients, and in the +addition of small quantities of alkaline salts, sulphate of magnesia, +and other substances, but they present little difference from ordinary +superphosphates in their effects. + +The use of superphosphate has greatly extended of late years, and its +consumption has increased in a greatly more rapid ratio than that of +guano or any other manure. Ten or twelve years since it was +comparatively little known, but it has now come to be used in many cases +in which Peruvian guano was formerly employed. It produces a better +effect than that manure on light soils, although in general a mixture of +the two answers better than either separately. When Peruvian guano is +to be applied along with it, the farmer will naturally select a +superphosphate made from bone ash, and containing the largest obtainable +quantity of soluble phosphates; but when it is to be used alone, it is +advisable to take one made from bones, or at all events one containing a +considerable quantity of nitrogenous matter or ammonia. The kind to be +selected must, however, be greatly dependent on the particular soil, and +the situation in which it is to be used. + +_Lime._--Lime is by far the most important of the mineral manures, and +an almost indispensable agent of agricultural improvement. It has been +used as chalk, marl, shell and coral sand, ground limestone, and as +quick and slaked lime, and its action varies according as it is applied +in any of its natural forms, or after being burnt. In all of its native +forms the lime is combined with carbonic acid in the proportion of +fifty-six parts of lime to forty-four of carbonic acid, and the +carbonate is generally mixed with variable quantities of earthy +ingredients, which in some instances are important additions to it, and +affect its utility as a manure. + +_Chalk_ is a very pure form of carbonate of lime, and where it abounds +has been largely employed as an application on the soil. It is dug out +of pits and exposed to the action of the winter's frost, by which it is +thoroughly disintegrated, and in spring it is applied in quantities, +which, in many instances, are only limited by the question of cost. + +_Marl_ is a name given to a mixture of finely-divided carbonate of lime, +with variable proportions of clay and siliceous matters, which is found +at the bottom of valleys and in hollow places in beds often of +considerable extent and thickness, where it is deposited from the waters +of lakes holding lime in solution, fed by streams passing over +limestone, or rocks rich in lime. The composition of marls differs +greatly in different districts, and they have been divided into true +marls, and clay marls, according as the carbonate of lime or clay is the +preponderating ingredient. The following table illustrates the +composition of different varieties:-- + ++---------------------------+------------+-----------+-----------+------------- +| | Barbadoes. | Luneburg. | Ayrshire. | Wesermarsh. ++---------------------------+------------+-----------+-----------+------------- +| Carbonate of lime | 93·2 | 85·4 | 8·4 | 8·2 +| Carbonate of magnesia | ... | 1·3 | ... | 3·0 +| Sulphate of lime | ... | 0·1 | ... | 0·5 +| Phosphate of lime | 0·1 | 2·3 | ... | 1·2 +| Alumina and oxide of iron | 1·6 | 4·6 | 2·2 | 7·2 +| Alkaline salts | ... | 0·1 | ... | 1·0 +| Silica and clay | 4·6 | 5·6 | 84·9 | 78·9 +| Organic matter | 0·5 | 0·6 | 2·8 | ... +| Water | ... | ... | 1·4 | ... ++---------------------------+------------+-----------+-----------+------------- +| | 100·00 | 100·00 | 99·7 | 100·00 ++---------------------------+------------+-----------+-----------+------------- + +The true marls, that is those in which carbonate of lime abounds, are +greatly preferable to clay marls, the latter, indeed, operate chiefly +mechanically, by altering the texture of the soil--the lime they contain +being frequently too small to exercise much appreciable effect. + +Shell and coral sands consist chiefly of fragments of shells and coral +disintegrated by the action of the waves, and mixed with more or less +siliceous sand, and containing small quantities of phosphate of lime. +They occur to a considerable extent both on our own coasts and those of +France, and have been used with good effect on some descriptions of +soil. + +The general composition of limestones has been already adverted to, +when treating of the origin of soils, and a distinction drawn between +the common limestones and dolomite or magnesium limestone. Few +limestones can be considered as even approaching to purity, and they +almost all contain a small quantity of carbonate of magnesia as well as +earthy matters, and occasionally a little phosphate of lime. In good +specimens the quantities of these substances are generally small, and +they usually contain about half their weight of lime. When limestone is +burnt in the kiln, the change which ensues consists in the expulsion of +the carbonic acid, and the consequent conversion of the lime into the +uncombined or quick state. If water be thrown upon it when in this +condition, it becomes hot, swells up, and falls to a fine soft powder, +and has then entered into combination with water. If it be exposed to +the air, the same action takes place, although, of course, more slowly; +and if it be left for a sufficient time, it at length absorbs carbonic +acid, and reverts to its original form of carbonate of lime, although +now in a state of very fine division. + +While lime may be applied in the state of carbonate, either as chalk, +marl, or pounded limestone, and with a certain amount of advantage, much +greater effects are obtained from the use of lime itself in the quick or +slaked state. These advantages are dependent partly on the mechanical +effect of the burning and slaking, which enable us to reduce the lime to +a much more minute state of division, and consequently to incorporate it +more uniformly and thoroughly with the soil, and partly on the more +powerful chemical action which it exists when in the quick or caustic +state. Other minor advantages are also secured, such as the production +of a certain quantity of sulphate of lime, produced by the oxidation of +the sulphur of the coal used in burning, etc., which, though +comparatively trifling, may, under particular circumstances and in some +soils, be of considerable importance. + +The action of lime is of a complicated character. Where the soil is +deficient in lime, it must necessarily act by supplying that substance +to the plants growing in it. But this is manifestly a very subordinate +part of its action,--_1st_, Because no soil exists which does not +contain lime in sufficient quantity to supply that element to the +plants. _2d_, Because its effects are not restricted to those soils in +which it exists naturally in small quantity; and, _3d_, Because it is +found that a small application, such as would suffice for the wants of +the crops, is not sufficient to produce its best effects. + +It is a familiar fact that the quantity of lime applied to the soil for +agricultural purposes is very large, as much as ten, and even twenty +tons per acre having been used, while the smallest application is +exceedingly large when compared with the mere requirements of the crops. +Of late years the very large applications once in use have become less +common, as it has been found preferable to employ smaller doses more +frequently repeated. The quantity used depends, however, to a great +extent, on the nature and condition of the soil, heavy clays, especially +if undrained, and soils of a peaty nature, requiring a large +application; while on well drained and light soils a smaller quantity +suffices. Thin soils also require only a small application. The +geological origin of the soil is also not without its influence, and its +beneficial effect is peculiarly seen on granite, porphyry, and gneiss +soils, both because these are naturally deficient in lime, and because +the decompositions by which their valuable constituents are liberated +take place with extreme slowness. + +The greater part of the action of lime is unquestionably dependent on +its exerting a chemical decomposition on the soil; and it acts equally +on both the great divisions of its constituents, the inorganic and the +organic. On the former, it operates by decomposing the silicates, which +form the main part of the soil, and the alkalies they contain being thus +set free, a larger supply becomes available to the plant. On the organic +constituents its effects are principally expended in promoting the +decomposition which converts their nitrogen into ammonia; and thus a +supply of food, which might remain for a long period locked up, is set +free in a state in which the plant can at once absorb it. But these +chemical decompositions are attended by a corresponding change in the +mechanical characters of the soil. Heavy clays are observed to become +lighter and more open in their texture; and those which are too rich in +organic matter have it rapidly reduced in quantity, and the excessive +lightness which it occasions diminished. + +The effects of an application of lime are not generally observed +immediately, but become apparent in the course of one or two years, when +it has had time to exert its chemical influence on the soil; but from +that time its effects are seen gradually to diminish and finally to +cease entirely. The period within which this occurs necessarily varies +with the amount of the application and the nature of the soil, but it +may be said generally that lime will last from ten to fifteen years. The +cessation of its effects is due to several circumstances, partly of +course to the absorption of lime by the plants, partly to its being +washed out of the soil by the rains, and partly to its tendency to sink +to a lower level, a tendency which most practical men have had +opportunities of observing. In the latter case, deep-ploughing often +produces a marked effect, and sometimes makes it possible to postpone +for a year or two the reapplication of lime. All these circumstances +have their influence in bringing its action to an end, but the most +important is, that after a time it has exhausted its decomposing effect +on the soil, having destroyed all the organic matter, or liberated all +the insoluble mineral substances which the quantity added is competent +to do, and so the soil passes back to its old state. It does even more, +for unless active measures are taken to sustain it by other means, it is +found that the fertility of the soil is apt to become less than it was +before the use of lime. And that it should be so is manifest, if we +consider that the lime added has liberated a quantity of inorganic +matter, which, in the natural state of the soil, would have become +slowly available to the plant, and that it must have acted chiefly in +those very portions which, from having already undergone a partial +decomposition, were ready to pass into a state fitted for absorption, +and thus as it were must have anticipated the supplies of future years. +This effect has been frequently observed by farmers, and is indeed so +common, that it has passed into a proverbial saying, that "lime enriches +the fathers and impoverishes the sons." But this is true only when the +soil is stinted of other manures, for when it is well manured the +exhausting effect of lime is not observed; and it must be laid down as a +practical rule, that its use necessitates a liberal treatment of the +soil in all other respects. But when lime has been once employed it +becomes almost necessary to resort to it again; and generally so soon as +its effects are exhausted a new quantity is applied, not so large as +that which is used when the soil is first limed, but still considerable. +When this is done very frequently, however, bad effects ensue; the soil +gets into a particular state, in which it is so open that the grain +crops become uncertain, and such land is said, in practical language, to +be overlimed. The explanation of this state of matters commonly assumed +by those unacquainted with chemistry is, that the land has become too +full of lime; but a moment's consideration of the very small fraction of +the soil which even the largest application of lime forms, will serve to +shew that this cannot be the cause. Ten tons of lime per acre amounts to +only one per cent of the soil, and as a considerable part of the lime is +carried off by drainage in the course of years, it is obvious that even +very large and frequently repeated doses are not likely to produce any +great accumulation of that substance. In point of fact, analyses of +overlimed soils have proved that the lime does not exceed the ordinary +quantity found in fertile land. The explanation of the phenomenon is +probably to be found in the rapid decomposition of organic matter by the +lime, and its escape as carbonic acid, by which the soil is left in that +curious porous condition so well known in practice. The cure for +overliming is found to be the employment of such means as consolidate +the soil, such as eating off with sheep, rolling, or laying down to +permanent pasture. + +The immediate effect of lime on the vegetation of the land to which it +is applied is very striking. It immediately destroys all sorts of moss, +makes a tender herbage spring up, and eradicates a number of weeds. It +improves the quantity and quality of most crops, and causes them to +arrive more rapidly at maturity. The extent to which it produces these +effects is dependent on the form in which it is applied. When the lime +is used hot, that is, immediately after it has been slaked, they are +produced most rapidly and effectually; but if it has been so long +exposed to the air as to absorb much of the carbonic acid it lost in +burning, and has got into what is commonly called the mild state, it +operates more slowly; and when it is applied as chalk, marl, or pounded +limestone, its action is still more tardy. Various circumstances, which +must depend upon very different considerations, must necessarily +influence the farmer in the selection of one or other of these different +forms of lime; but on the whole, it will be found that the greatest +advantages are on the side of the well-burned and freshly slaked lime. +The consideration of all the minutiæ to be attended to, however, would +carry us far beyond the limits of this work, and trench to some extent +on the subject of practical agriculture. + +Various kinds of refuse matters containing lime have been used in +agriculture, but they are generally inferior to good lime, and not +generally more economical. The most important of these is gas lime, or +lime which has been used for purifying coal gas. In going through this +process it absorbs carbonic acid from the gas, and consequently passes +back, more or less, completely into the form of carbonate of lime. But +it also takes up sulphur, which remains in it in the form of sulphuret +of calcium. It is well known that all sulphurets are prejudicial to +vegetable life, and hence, when fresh gas lime is used, its effects are +often injurious rather than beneficial. But if it be exposed for some +time to the air, oxygen is absorbed, the sulphur is converted into +sulphuric acid, gypsum is produced to the extent of some per cent, and +the lime then becomes innocuous. When composted with dry soil, the +admission of air into the interior of the lime is facilitated, and this +change takes place with greater rapidity. The waste lime from +bleach-works, tanneries, and other manufactories, is occasionally used +by farmers; but unless obtained at a nominal price, it cannot compete +with good quick lime, owing to the large amount of water it contains, +and the consequent increase in the cost of carriage. + +_Sulphate of Lime or Gypsum._--Gypsum has been extensively used as a +manure, and is found to exert a very remarkable influence upon clover, +and leguminous crops generally. It is employed in quantities varying +from two cwt. per acre up to a very large quantity, and almost +invariably with good results, in some instances even with the production +of double crops. Much speculation has taken place as to the cause of +this action which is so specific in its character, and from Sir Humphrey +Davy down to the present time, many chemists and agriculturists have +considered the matter. Sir Humphrey Davy attributed its action to its +supplying sulphur to those plants which, according to him, contain an +unusually large quantity of that element. That opinion has been since +entertained by others, but it can scarcely be considered as well +founded, for the more accurate experiments recently made do not point to +any conspicuous differences between the quantities of sulphur contained +in these and other plants. It is, moreover, to gypsum alone that these +effects are due, and if it were merely as a source of sulphur that it +was employed, there are other salts which could be equally, perhaps more +advantageously, used; such, for instance, as sulphate of soda. Others +have attributed its action to its power of fixing ammonia, but this +explanation is certainly untenable, for the soil itself possesses this +property very powerfully, and it is inconceivable that the addition of a +few hundred weights of gypsum should have any effect in promoting this +action. The experiments which have been made with gypsum leave no doubt +as to its effect, more especially on leguminous plants, but they do not +afford an explanation of its mode of action, for which further +inquiries, directed especially to that object, are required. + +The application of gypsum to the soil appears to have diminished of late +years, and this is probably due to the large consumption of +superphosphates, and other manufactured manures, which contain it in +abundance. In an ordinary application of these substances, there are +contained from one to two hundredweight of gypsum; and it is not likely +that when they have been extensively used, much benefit will be derived +from a further application of it by itself. + + + + +CHAPTER XII. + +THE VALUATION OF MANURES. + + +The determination of the value of a manure is in many respects a +commercial rather than a chemical question, but as it must be founded on +the analysis, and presents some peculiarities dependent on the +complicated nature of the substances to be valued, it has fallen to some +extent into the hands of the chemist. The principle on which the value +of any commercial sample is estimated is very simple. It is only +necessary to know the price of the pure article, and that of the +particular sample to be valued is obtained by making a deduction from +this price proportionate to the per centage of impurities shewn by the +analysis. Thus, for example, if pure sulphate of ammonia sells at £16 +per ton, a sample containing 10 per cent of impurities ought to be +purchased for £14: 8s., and so on for any other quantity. This system +which answers perfectly with sulphate of ammonia, nitrate of soda, or +any other substance whose value depends on one individual element, is +inapplicable in the case of complex manures, such as guano and the like, +in which several factors combine to make up the value. In such cases, +manures of very different composition may have the same value, the +deficiency in one particular element being counterbalanced by the excess +of another. Hence it becomes necessary to obtain an estimate of the +value of each factor, from which that not only of one particular +substance, but of every possible mixture may be determined. + +When we come to inquire minutely into this question, it appears that the +commercial value of any substance is not estimated solely by +considerations of composition, but is dependent to a great extent on +questions of demand and supply, and applicability to particular +purposes. Thus coprolites containing from 55 to 60 per cent of +phosphates sell at about £2: 12s. per ton, while bone-ash containing the +same quantity of that ingredient brings about twice as much; in other +words, phosphates are nearly twice as valuable in bone-ash as in +coprolites, and as a phosphatic guano their price is generally still +higher; and the reason for this is obvious, in bones and guano the +phosphates are in a high state of division, in which they are easily +attacked and disintegrated by the carbonic acid of the soil, and +rendered available to plants; while in coprolites they are in a hard and +compact form, and are of little use unless they have previously +undergone an expensive preparation. In the same way, if the market price +of different kinds of guano be inquired into, very great differences are +found to exist in the rate at which phosphates are sold, and this is +attributable in part to the fact that the price at which any article is +charged commercially, is such as to cover the prime cost, expense of +freight, and other charges, and to leave a profit to the importer; and +partly, also, no doubt, to the carelessness with which manures are often +purchased, and to the want of careful field experiments in which the +effects produced by them are properly compared. It will be readily +understood that the state of division of any substance, the readiness +with which its constituents can be rendered available to the plants, +care of application, and many other circumstances must influence its +price; but making due allowance for these, differences are met with +which appear to some extent to be merely the result of caprice. It is +easy to understand why bone-ash should sell at double the price of +coprolites, but no good reason can be shewn why the phosphates in one +kind of guano should be sold at a much higher price than another, and +the difference would probably disappear if greater attention were paid +to the results of field experiments. + +However great and inexplicable these differences may be, it is not the +business of the valuator of a manure to discuss them. On the contrary, +he is bound to accept them as the basis of his calculation, and to +endeavour to deduce from them a proper system of estimation for each +substance. Strictly speaking, each individual manure ought to be valued +according to a plan special to itself, and deduced from its own standard +market price; but it is obvious that this would lead to innumerable +complications and defeat its own ends, and hence an attempt has been +made to contrive a general system suited to all manures, and which, +though not absolutely correct, is a sufficient approximation for all +practical purposes, and a tolerably accurate guide to the determination +of their relative values. + +The constituents of a manure which are of actual value are ammonia, +insoluble phosphates, biphosphate of lime (soluble phosphates), sulphate +of lime, nitric acid (as nitrate of soda), potash, soda, and organic +matter. These substances differ greatly in value. Ammonia and +phosphates, soluble and insoluble, are costly; and by far the larger +part of the value of all guanos, and the common manufactured manures, +depends on them. Nitric acid and potash are also very valuable +substances, but as they are rarely found in manufactured manures, and +never in sufficient quantity to exert any material influence in their +price, it is not usual to take them into consideration except in +particular cases. The alkali which commonly exists in artificial manures +is soda, and when alkaline salts appear in any analysis, they must be +assumed to consist almost entirely of that substance generally in the +form of common salt, and be valued accordingly. Sulphate of lime and +organic matter though abundant constituents of most manures, add but +little to their value, and it is a moot point whether they ought to be +taken into consideration, although most persons allow a small value for +them. Carbonate of lime, sand, or siliceous matter, and water, of +course, are altogether worthless. + +In order to obtain the value of a manure containing several of these +substances, it is necessary to ascertain the average commercial price of +each individually. This is easily done when they are met with in +commerce separately, or at least mixed only with worthless substances, +but some of them are only found in complex mixtures, and in these cases +it is necessary to arrive at a result by an indirect process, according +to methods which will be immediately explained. The question to be +solved is the price actually paid for a ton of each substance in a pure +state, and we shall proceed to consider them in succession. + +_Insoluble Phosphates._--These are purchased alone, chiefly in the form +of coprolites and bone-ash, or the spent animal charcoal of the sugar +refiners. Ground coprolites, containing about 58 per cent of phosphates, +sell at £2: 12s. per ton, which is at the rate of £4: 8s. for pure +phosphates. Bone-ash varies considerably in price, but of late samples +containing 70 per cent of phosphates have sold as low as £4: 10s. per +ton, and consequently pure phosphates in this form are worth £6: 8s. per +ton. Although these are the only forms in which phosphates are +purchased alone, it is possible to determine the price at which they are +sold in bones and phosphatic guanos, by first deducting the value of the +ammonia they contain, and assuming the remainder to represent the price +paid for the phosphates. In this way we find the following values for +insoluble phosphates:-- + +In Coprolites £4 10 0 + Bone-ash 6 8 0 + Bones 7 5 0 + Phosphatic guanos 10 0 0 + +It is to be observed that these are actual prices, and they are liable +to fluctuate with the state of the market, although they are pretty fair +averages. It is important to notice how much they vary in the different +forms; the farmer who buys a phosphatic guano paying for phosphates a +much higher price than he could have obtained those for in other +substances--a difference which must be attributed to the high state of +division in which they exist in the guano. We do not here enter upon the +question how far this difference in price is justified; we are content +with the fact that it exists, and we are compelled to estimate the value +of phosphates in a phosphatic guano at the price given above, although +in Peruvian guano they are sold at a lower rate. For all other manures, +of which bones and bone-ash form the basis, £7 may be taken as a fair +price, and it is that usually adopted, though £8 and £10 have sometimes +been assumed as the average. + +_Ammonia_ is met with in commerce as muriate and sulphate of ammonia. +The former, owing to its high price, is practically excluded from use as +a manure; the latter sells at present at from £15 to £15: 10s. per ton, +and, making allowance for the usual amount of impurity (5 or 6 per +cent), the actual ammonia is worth about £63 per ton. Calculating from +other substances it appears that ammonia is worth, per ton, in-- + +Sulphate of ammonia £63 0 0 +Bones 61 0 0 +Peruvian guano 57 0 0 + +the average being £60, which is the price usually adopted. + +_Sulphate of Lime_ and _Alkaline Salts_ (consisting chiefly of soda) are +generally estimated at £l per ton; and potash in those cases, in which +it is necessary to take it into account, is usually valued at from £20 +to £30 per ton, the former being its value in kelp, the form in which it +can be most cheaply purchased. + +_Nitrate of Soda_ is usually sold at from £15 to £15: 10s. per ton, and, +making allowance for impurities, £16 may be taken as the value of the +pure salt. + +_Biphosphate of Lime, Soluble Phosphates._--Considerable difficulty is +experienced in estimating the value of these substances, because they +are not met with in commerce alone, or in any form except that of +superphosphate, and the prices at which they are sold in different +samples of that manure differ excessively. The only course by which any +result can be obtained, is to determine the average price of a good +superphosphate, and putting the values already ascertained on all the +other constituents to reckon the difference between that sum and the +market price as the value of soluble phosphates. Throwing out, as +inferior, all samples containing less than 10 per cent of soluble +phosphates, and taking the good only, I find that the average +composition of the phosphates in the market during the present year has +been-- + +Water 10·71 +Organic matter 9·33 +Biphosphate of lime equivalent to 19·43 + "soluble phosphates" 12·45 +Insoluble phosphates 14·78 +Sulphate of lime 45·24 +Alkaline salts 2·11 +Sand 5·38 + ------ + 100·00 +Ammonia 1·71 + +It is more difficult to fix the average price of superphosphate, as in +many cases no information could be obtained on this point; but among +those analyzed were samples at all prices, from £7 up to £10: 10s. per +ton, so that on the whole, £8 may be assumed as an average, and in that +case soluble phosphates are worth £27: 19s. per ton. Had the inferior +samples been included, the price would have been higher, and in fact the +rate at which soluble phosphates have been commonly estimated is £30 per +ton, or £46: 16s. for biphosphate of lime, although sometimes the former +have been reckoned as low as £25, with a corresponding rate for the +latter. It is important that biphosphate of lime and soluble phosphates +should not be confounded with one another in valuing a manure, the +latter having one and a half times the value of the former. + +As manures are liable to considerable fluctuations in price, the value +attached to each of their constituents ought to be varied with the state +of the market; but it is obviously impossible for the farmer to watch +the changes in price with such minuteness as to enable him to do this, +and it is much more convenient, as well as safer, to adopt a fixed +average, which can be used with reasonable accuracy at all times. The +fact is, that this system of valuation is only an approximation to the +truth; and if absolute accuracy were aimed at, it would be necessary to +vary the estimates, not only at different times, but at different +localities at the same time, and to some extent also according to the +kind of manure. The price of soluble phosphates more especially, +fluctuates to a great extent, being practically fixed by each +manufacturer according to the facilities which his position or command +of raw material offer for producing them at a low rate. We thus find +that when made from bones alone, the cost of that substance is not +unfrequently as high as £40 per ton, and when bone-ash alone is used it +is sometimes as low as £20. Such extreme differences, of course, cannot +be taken into account in the system of valuation adopted, where all that +can be done is to take average values, which, when applied to average +samples, ought to bring out their value. + +The data which have already been given regarding the price of the +individual constituents of manures can be applied to the determination +of the value of any mixture in two different ways by means of the +subjoined table:-- + ++----------------------------+-----------------+-------------------+ +| | Price per Ton. | Per cent per Ton. | ++----------------------------+-----------------+-------------------+ +| Ammonia | £60 0 0 | £0 12 0 | +| Insoluble phosphates | 7 0 0 | 0 1 5 | +| Do. in phosphatic guanos | 10 0 0 | 0 2 0 | +| Soluble phosphates | 30 0 0 | 0 6 0 | +| Biphosphate of lime | 46 16 0 | 0 9 4-1/2 | +| Alkaline salts | 1 0 0 | 0 0 2-4/10 | +| Sulphate of lime | 1 0 0 | 0 0 2-4/10 | +| Potash | 20 0 0 | 0 4 0 | +| Nitrate of soda | 16 0 0 | 0 3 2-1/2 | +| Organic matter | 0 10 0 | 0 0 1-1/4 | ++----------------------------+-----------------+-------------------+ + +Supposing it be desired to calculate the value of a manure by the first +column, it is obvious that if we suppose 100 tons to be purchased, the +per centages of the different constituents shewn in the analysis will +give the number of tons of each contained in 100 tons of the mixture, +and, selecting the analysis of the superphosphate given in a previous +page, we proceed in the calculation as follows:-- + +14·11 tons of organic matter at 10s. £7 0 0 +14·86 " soluble phosphates at £30 446 0 0 +15·13 " insoluble phosphates at £7 105 0 0 +39·43 " sulphate of lime at £1 39 0 0 + 3·82 " alkaline salts at £1 4 0 0 + 2·10 " ammonia at £60 126 0 0 + ---------- + Value of 100 tons £727 0 0 +or £7 : 5s. per ton. + +According to the second column, the numbers give the sum by which the +per centages of each ingredient must be multiplied, to give its value +in a ton of manure, and it is used for the same manure in the following +manner:-- + +14·11 organic matter, multiplied by 1-1/4d. £0 1 5 +14·88 soluble phosphates " 6s. 4 9 2 +15·13 insoluble phosphates " 1s. 5d. 1 1 4 +39·43 sulphate of lime " 2-4/10d. O 8 10 + 3·82 alkaline salts " 2-4/10d. O O 9 + 2·10 ammonia " 12s. 1 5 3 + -------- + Value per ton £7 6 9 + +The difference is due to the less minute calculation of fractional +quantities in the latter case. + +The calculation of the value of any other manure is effected in exactly +the same manner, taking care, however, to use the higher value for +phosphates in the case of a phosphatic guano. It will be obvious to +every one who tries the two methods that the first greatly exceeds the +second in convenience and simplicity in the calculations, and it is that +most commonly in use, although some persons prefer the second. + +Although the data just given must always form the basis of the valuation +of any manure, there are a variety of other circumstances which must be +taken into account, and which give great scope for the judgment and +experience of the valuator. Of these the most important is the proper +admixture of the ingredients, and the condition of the manure as regards +dryness, complete reduction to the pulverulent state, and the like. A +certain allowance ought always to be made for careful manufacture; and, +on the other hand, where the manure is damp or ill reduced, a small +deduction (the amount of which must be decided by the experience of the +valuator) ought to be made on account of the risk which the farmer runs +of loss from unequal distribution, and the extra cost of carriage of an +unnecessary quantity of water. + +It is also necessary to take into account the particular element +required by the soil. Thus, a farmer who finds his soil wants +phosphates, will look to the manure containing the largest quantity of +that substance, and possibly not requiring ammonia, will not care to +estimate at its full value any quantity of that substance which he may +be compelled to take along with the former, but will look only to the +source from which he can obtain it most cheaply. It may be well, +therefore, to point out that ammonia is most cheaply purchased in +Peruvian guano; insoluble phosphates in coprolites; and soluble +phosphates in superphosphates, made from bone-ash alone. In general, +however, it will be found most advantageous to select manures in which +the constituents are properly adjusted to one another, so that neither +ammonia, soluble nor insoluble phosphates, preponderate; but, of course, +it must frequently happen that it will prove more economical to buy the +substances separately and to make the mixture, than to take the manure +in which they are ready mixed. + +In judging of the value of any manure, it is also important to make sure +that the analysis which forms the basis of the calculation is that of a +fair sample, which correctly represents the bulk actually delivered to +the purchaser, and not one which has been made to do duty for an +unlimited quantity of manure, which is supposed to be all of equal +quality, as often happens in the hands of careless manufacturers, and +too great attention cannot be devoted to the selection of the sample, +which is very often done in an exceedingly slovenly manner. + + + + +CHAPTER XIII. + +THE ROTATION OF CROPS. + + +Reference has already been more than once made to the fact that a crop +growing in any soil must necessarily exhaust it to a greater or less +extent by withdrawing from it a certain quantity of the elements to +which its fertility is due. That this is the case has been long admitted +in practice, and it has also been established that the exhausting +effects of different species of plants are very different; that while +some rapidly impoverish the soil, others may be cultivated for a number +of years without material injury, and some even _apparently_ improve it. +Thus, it is a notorious fact that white crops exhaust, while grass +improves the soil; but the improvement in the latter case is really +dependent on the fact, that when the land is laid down in pasture, +nothing is removed from it, the cattle which feed on its produce +restoring all but a minute fraction of the mineral matters contained in +their food; and as the plants derive a part, and in some instances a +very large part, of their organic constituents from the air, the +fertility of the soil must manifestly be increased, or at all events +maintained in its previous state. When, however, the plant, or any +portion of it, is removed from the soil, there must be a reduction of +fertility dependent on the quantity of valuable matters withdrawn by it; +and thus it happens that when a plant has grown on any soil, and has +removed from it a large quantity of nutritive matters, it becomes +incapable of producing an equally large crop of the same species; and if +the attempt be made to grow it in successive years, the land becomes +incapable of producing it at all, and is then said to be thoroughly +exhausted. But if the exhausted land be allowed to lie for some time +without a crop, it regains its fertility more or less rapidly according +to circumstances, and again produces the same plant in remunerative +quantity. The observation of this fact led to the introduction of naked +fallows, which, up to a comparatively recent period, were an essential +feature in agriculture. But after a time it was observed that the land +which had been exhausted by successive crops of one species was not +absolutely barren, but was still capable of producing a luxuriant growth +of other plants. Thus peas, beans, clover, or potatoes, could be +cultivated with success on land which would no longer sustain a crop of +grain, and these plants came into use in place of the naked fallow under +the name of fallow crops. On this was founded the rotation of crops; for +it was clear that a judicious interchange of the plants grown might +enable the soil to regain its fertility for one crop at the time when it +was producing another; and when exhausted for the second, it might be +again ready to bear crops of the first. + +The necessity for a rotation of crops has been explained in several +ways. The oldest view is that of Decandolle, who founded his theory on +the fact that the plants excrete certain substances from their roots. He +found that when plants are grown in water, a peculiar matter is thrown +off by the roots; and he believed that this extrementitious substance is +eliminated _because_ it is injurious to the plant, and that, remaining +in the soil, it acts as a poison to those of the same species, and so +prevents the growth of another crop. But this excretion, though +poisonous to the plants from which it is excreted, he believed to be +nutritive to those of another species which is thus enabled to grow +luxuriantly where the others failed. Nothing can be more simple than +this explanation, and it was readily embraced at the time it was +propounded and considered fully satisfactory. But when more minutely +examined, it becomes apparent that the facts on which it is founded are +of a very uncertain character. Decandolle's observations regarding the +radical excretions of plants have not been confirmed by subsequent +observers. On the contrary, it has been shewn that though some plants, +when growing in water, do excrete a particular substance in small +quantity, nothing of the sort appears when they are grown in a siliceous +sand. And hence the inference is, that the peculiar excretion of plants +growing in water is to be viewed as the result of the abnormal method of +their growth rather than as a natural product of vegetation. But even +admitting the existence of these matters, it would be impossible to +accept the explanation founded upon them, because it is a familiar fact +that, on some soils, the repeated growth of particular crops is +perfectly possible, as, for instance, on the virgin soils of America, +from which many successive crops of wheat have been taken; and in these +cases the alleged excretion must have taken place without producing any +deleterious effect on the crop. Besides, it is in the last degree +improbable that these excretions, consisting of soluble organic matters, +should remain in the soil without undergoing decomposition, as all +similar substances do; and even if they did, we cannot, with our present +knowledge of the food of plants, admit the possibility of the direct +absorption of any organic substance whatever. Indeed, the idea of +radical excretions, as an explanation of the rotation of crops, must be +considered as being entirely abandoned. + +The necessity for a rotation of crops is now generally attributed to the +different quantities of valuable matters which different plants remove +from the soil, and more especially to their mineral constituents. It has +been already observed that great differences exist in the composition of +the ash of different plants in the section on that subject; and it was +stated that a distinction has been made between lime, potash, and silica +plants, according as one or other of these elements preponderate in +their ashes. The remarkable difference in the proportion of these +elements has been supposed to afford an explanation of rotation. It is +supposed that if a plant requiring a large quantity of any one element, +potash, for example, be grown during a succession of years on the same +soil, it will sooner or later exhaust all, or nearly all, the potash +that soil contains in an _available_ form, and it will consequently +cease to produce a luxuriant crop. But if this plant be replaced by +another which requires only a small quantity of potash and a large +quantity of lime, it will flourish, because it finds what is necessary +to its growth. In the meantime, the changes which are proceeding in the +soil, are liberating new quantities of the inorganic matters from those +forms of combination in which they are not immediately available, and +when after a time the plant which requires potash is again sown on the +soil, it finds a sufficient quantity to serve its purpose. We have +already, in treating of the ashes of plants, pointed out the extent of +the differences which exist; but these will be made more obvious by the +annexed table, giving the quantity of the different mineral matters +contained in the produce of an imperial acre of the different crops. + +TABLE shewing the quantities of Mineral Matters and Nitrogen in average +Crops of the principal varieties of Farm Produce. + ++---------------+--------------+---------+----------+---------+-------+-------+ +| | Produce per | Total | Total | | | | +| | Imperial | Weight | Mineral | Potash. | Soda. | Lime. | +| | Acre. | in lbs. | Matters. | | | | ++---------------+--------------+---------+----------+---------+-------+-------+ +|Wheat--Grain | 28 bushels | 1,680 | 34·12 | 10·11 | 1·20 | 1.04 | +| | at 60 lbs. | | | | | | +| Straw | 1 ton 3 cwt. | 2,576 | 114·48 | 20·70 | 2·84 | 8·53 | +| Total | ... | ... | 148·60 | 30·81 | 4·04 | 9·57 | +| | | | | | | | +|Barley--Grain | 33 bushels | 1,749 | 44·24 | 9·40 | 0·30 | 0·76 | +| | at 53 lbs. | | | | | | +| Straw | 18 cwt. | 2,106 | 99·14 | 11·24 | 1·14 | 5·81 | +| Total | ... | ... | 143·38 | 20·64 | 1·44 | 6·57 | +| | | | | | | | +|Oats--Grain | 34 bushels | 1,360 | 48.89 | 11·00 | ... | 5·31 | +| | at 40 lbs. | | | | | | +| Straw | 1 ton. | 2,240 | 143·53 | 30·71 | 6·10 | 10·29 | +| Total | ... | ... | 192·42 | 41·71 | 6·10 | 15·60 | +| | | | | | | | +|Beans, Peas-- | 25 bushels | 1,650 | 55·97 | 30·00 | 0·31 | 3·01 | +| Grain | at 60 lbs. | | | | | | +| Straw | 1 ton. | 2,240 | 108·51 | 48·61 | 13·14 | 29·37 | +| Total | ... | ... | 164·48 | 78·61 | 13·45 | 32·38 | +| | | | | | | | +|Turnips--Bulbs | 13-1/2 tons. | 30,240 | 213·75 | 57·35 | 44·71 | 28·60 | +| | | | | | | | +|Potatoes | 3 tons. | 6,720 | 55·58 | 28·92 | 2·85 | 1·20 | +| | | | | | | | +|Hay | 2-1/2 tons. | 5,600 | 391·31 | 129·79 | 4·80 | 35·46 | ++---------------+--------------+---------+----------+---------+-------+-------+ + ++---------------+-----------+--------+-----------+----------+---------+-------+ +| | | | | | | | +| | Magnesia. | Chlor. | Sulphuric | Phosphor | Silica. | Nitro | +| | | -ine | Acid. | -ic Acid.| | -gen. | ++---------------+-----------+--------+-----------+----------+---------+-------+ +|Wheat--Grain | 4.80 | ... | 0.32 | 16.22 | 0.43 | 29.20 | +| | | | | | | | +| Straw | 2·23 | ... | 3·55 | 3·16 | 73·47 | 16·13 | +| Total | 7·03 | ... | 3·87 | 19·38 | 73·90 | 45·33 | +| | | | | | | | +|Barley--Grain | 3·10 | 1·12 | 0·85 | 15·52 | 13·19 | 34·98 | +| | | | | | | | +| Straw | 2·75 | 1·30 | 1·10 | 7·22 | 68·58 | 6·03 | +| Total | 5·85 | 2·42 | 1·95 | 22·74 | 81·77 | 41·01 | +| | | | | | | | +|Oats--Grain | 4·04 | 0·20 | ... | 26·07 | 2·27 | 27·54 | +| | | | | | | | +| Straw | 5·50 | 5·55 | 5·18 | 7·35 | 72·85 | 14·10 | +| Total | 9·54 | 5·75 | 5·18 | 33·42 | 75·12 | 41·64 | +| | | | | | | | +|Beans, Peas-- | 4·00 | ... | 1·76 | 16·65 | 0·24 | 46·10 | +| Grain | | | | | | | +| Straw | 3·74 | 7·00 | 2·07 | 0·74 | 3·84 | 26·88 | +| Total | 7·74 | 7·00 | 3·83 | 17·39 | 4·08 | 72·98 | +| | | | | | | | +|Turnips--Bulbs | 4·65 | 10·35 | 39·02 | 22·57 | 6·50 | 60·48 | +| | | | | | | | +|Potatoes | 2·11 | 3·21 | 10·24 | 5·76 | 1·29 | 26·00 | +| | | | | | | | +|Hay | 9·62 | 39·61 | 16·57 | 21·79 | 133·67 | 56·22 | ++---------------+-----------+--------+-----------+----------+---------+-------+ + +The minor constituents, such as oxide of iron, manganese, etc., have +been omitted as being of little importance; and the quantity of +nitrogen, which is of great moment in estimating the exhaustive effects +of various crops, has been added. + +In examining this table, it becomes apparent that while in regard to +some of the elements, the quantities removed by different crops do not +differ to any marked extent, in others the variation is very great. The +cereals and grasses are especially distinguished by the larger quantity +of silica they contain, and the exhaustive effect consequent upon the +removal of both grain and straw from soils which contain but a limited +supply of that substance in an available condition is obvious. It is +clear that under such circumstances the frequent repetition of a cereal +crop may so far diminish the amount of available silica as to render its +cultivation impossible, although the other substances may be present in +sufficient quantity to produce a plentiful crop of any plant which does +not require that element. Beans and peas, turnips and hay, on the other +hand, require a very large quantity of alkalies, and especially of +potash. + +Looking more minutely, however, into this matter, certain points attract +attention which appear to be at variance with commonly received +opinions. With the exception of silica, for example, the cereals do not +withdraw from the soil so large a quantity of mineral matters as some of +the so-called fallow crops, and if their straw be returned to the soil +they are by far the least exhaustive of all cultivated plants; and we +thus recognise the justice of that practical rule, which lays it down as +an essential point of good husbandry that the straw ought, as far as +possible, to be consumed on the farm on which it is produced. As regards +the general constituents of the ash, it is also to be remarked that +though differences in their proportions exist, they are by no means so +marked as might be expected; thus there are no plants for which a large +quantity of potash, nitrogen, and phosphoric acid is not required; and +it is not very easy to see how the substitution of the one for the other +should be of much importance in this respect. Indeed, the more minutely +the subject is examined, the more do we become convinced of the +insufficiency of that view which attributes the necessity for a rotation +of crops to differences in chemical composition alone. There can be no +doubt that the nature of the plant and the particular mode in which it +gathers its nutriment, have a most important influence. Certain plants +are almost entirely dependent on the soil for their organic +constituents, while others derive a large proportion of them from the +air, and a plant of the latter class will flourish in a soil in which +one of the former is incapable of growing. In other cases, the structure +and distribution of the roots is the cause of the difference. Some +plants have roots distributed near the surface and exhaust the +superficial layer of the soil, others penetrate into the deeper layers, +and not only derive an abundant supply of food from them, but actually +promote the fertility of the surface soil by the refuse portions of them +which are left upon it. Experience has in this respect arrived at +results which tally with theory, and it is for this reason that the +broad-leafed turnip, which obtains a considerable quantity of its +nutriment from the air, alternates with grain crops which are chiefly +dependent on the soil. It is undoubtedly to some such cause that several +remarkable instances of what may be called natural rotations are to be +attributed. It is well known in Sweden that when a pine forest is +felled, a growth, not of pine but of birch, immediately springs up. Now +the difference in composition of the ash of these trees is not +sufficient to explain this fact, and it must clearly be due to some +difference in the distribution of their roots, or the mode in which they +obtain their food. + +Whatever weight may be given to these different explanations of +rotation, there is no doubt about the importance of attending to it, and +there are various practical deductions of much importance to be drawn +from the facts with which we are acquainted. Thus it is to be observed +that the quantities of mineral matters withdrawn by plants of the same +class are generally similar, and hence it may be inferred that crops of +the most opposite class ought as much as possible to alternate with one +another, and each plant should be repeated as seldom as possible, so +that, even when it is necessary to return to the same class, a different +member of it should be employed. Thus, for instance, in place of +immediately repeating wheat, when another grain crop is necessary, it +would theoretically be preferable to employ oats or barley, and to +replace the turnip by mangold-wurzel or some other root. It is obvious, +however, that this system cannot be carried out in practice to its full +extent; for the superior value of individual crops causes the more +frequent repetition of those which make the largest return. But +experience has so far concurred with theory that it has taught the +farmer the advantage of long rotations; and we have seen the successive +introduction of the three, four, five, and six-course shift, and even, +in some instances, of longer periods. + +Such is the theory of rotation, and while it will always be most +advantageous to adhere to it, it is by no means necessary that this +should be done in an absolutely rigid manner. In the practice of +agriculture, plants are placed in artificial circumstances, and instead +of allowing them to depend entirely on the soil, they are supplied with +a quantity of manure containing all the elements they require, and if it +be used in sufficiently large quantity, the same crop may be grown year +after year. And accordingly the order of rotation, which is +theoretically the best, may be, and every day is, violated in practice, +although this must necessarily be done at the expense of a certain +quantity of the valuable matters of the manure added, and is so far a +practice which ought theoretically to be avoided. In actual practice, +however, the matter is to be decided on other grounds. The object then +is, not to produce the largest crops, but those which make the largest +money return, and thus it may be practically economical to grow a crop +of high commercial value more frequently than is theoretically +advantageous. In such cases the farmer must seek to do away as far as +possible with the disadvantages which such a course entails, and this he +will endeavour to accomplish by careful management and a liberal +treatment of the soil. + +But while this system may be adopted to some extent, it must also be +borne in mind that the frequent repetition of some crops cannot be +practised with impunity, for plants are liable to certain diseases which +manifest themselves to the greatest extent when they have been too often +cultivated in the same soil. Clover sickness, which affects the plant +when frequently repeated on light soils, and the potatoe disease and +finger and toe have been attributed to the same cause. Whether this is +the sole origin of these diseases is questionable, but there is no doubt +that they are aggravated by frequent repetition, and hence a strong +argument in favour of rotation. It has been asserted by great +authorities in high farming, that with our present command of manures, +rotations may be done away with; but this is an opinion to which science +gives no countenance, and he would be a rash man who attempted to carry +it out in practice. + + + + +CHAPTER XIV. + +THE FEEDING OF FARM STOCK. + + +The feeding of cattle, once a subordinate part of the operations of the +farm, has now become one of its most important departments, and a large +number of minute and elaborate experiments have been made by chemists +and physiologists with the view of determining the principles on which +its successful and economical practice depends. These investigations, +while they have thrown much light on the matter, have by no means +exhausted it, and it will be readily understood that the complete +elucidation of a subject of such complexity, touching on so many of the +most abstruse and difficult problems of chemistry and physiology, and in +which the experiments are liable to be affected by disturbing causes, +dependent on peculiarities of constitution of different animals, cannot +be otherwise than a slow process. + +In considering the principles of feeding, it is necessary to point out, +in the first instance, that the plant and animal are composed of the +same chemical elements, hence the food supplied to the latter invariably +contains all the substances it requires for the maintenance of its +functions. And not only is this the case, but these elements are to a +great extent combined together in a similar manner,--the fibrine, +caseine, albumen, and fatty matters contained in animals corresponding +in all respects with the compounds extracted from plants under the same +name; and though the starchy and saccharine substances do not form any +part of the animal body, they are represented in the milk, the food +which nature has provided for the young animal. It has been frequently +assumed that the nitrogenous and fatty matters are simply absorbed into +the animal system, and deposited unchanged in its tissues; but it is +probable that the course of events is not quite so simple, although, +doubtless, the decomposition which occurs is comparatively trifling. The +starchy matters, on the other hand, are completely changed, and devoted +to purposes which will be immediately explained. + +It is a matter of familiar experience, that if the food be properly +proportioned to the requirements of the animal, its weight remains +unchanged; and the inference to be drawn from this fact obviously is, +that the food does not remain permanently in the system, but must be +again got rid of. It escapes partly through the lungs, and partly by the +excretions, which do not consist merely of the part which has not been +digested, but also of that portion which has been absorbed, and after +performing its allotted functions within the system, has become effete +and useless. When the weights of the excretions, the carbon contained in +the carbonic acid expired by the lungs and the small quantity of matter +which escapes in the form of perspiration, are added together, they are +found in such a case to be exactly equal to the food. If the animal be +deprived of nutriment, it immediately begins to lose weight, because its +functions must continue--carbon must still be converted into carbonic +acid to maintain respiration--and the excretions be eliminated, although +diminished in quantity, because they no longer contain the undigested +portion of the daily food, and the substances already stored up in the +body are consumed to maintain the functions of life. Universal +experience has shewn that, under such circumstances, the fat which has +accumulated in various parts of the body disappears, and the animal +becomes lean; but it is less generally recognised that the muscular +flesh, that is the lean part of the body, also diminishes, although it +is sufficiently indicated by the fact that nitrogen still continues to +be found in the urine, and that the animal becomes feeble and incapable +of muscular exertion. Respiration and secretion, in fact, proceed quite +irrespective of the food, which is only required to repair the loss they +occasion. When the course of events within the animal body is traced, it +is found to be somewhat as follows: The food consumed is digested and +absorbed into the blood, where it undergoes a series of complicated +changes, as a consequence of which part of it is converted into carbonic +acid, and eliminated by the lungs, and part is deposited in the tissues +as fat and flesh. After the lapse of a certain period, longer or shorter +according to circumstances, a new set of actions comes into play, by +which the complex constituents of the tissues are resolved into simpler +substances, and excreted chiefly by the lungs and kidneys. The changes +thus produced are, to a great extent, identical with those which would +take place if the fat and flesh were consumed in a fire; and the animal +frame may, in a certain sense, be compared to a furnace, in which, by +the daily consumption of a certain quantity of fuel and air inhaled in +the process of respiration, its temperature is maintained above that of +the surrounding atmosphere. If the daily supply of fuel, that is of +food, be properly adjusted to the loss by combustion, the weight of the +animal remains constant; if it be reduced below this quantity, it +diminishes; but if it be increased, the stomach either refuses to +digest and assimilate the excess, or it is absorbed and stored up in the +body, increasing both the fat and flesh. + +When an animal is fed in such a manner that its weight remains constant, +a balance is produced between the supply of nutriment contained in the +food and the waste of the tissues, the gain from the former exactly +counterpoising the loss occasioned by the latter. If in this state of +matters an additional supply of food be given, this balance is deranged, +and the nutriment being in excess of the loss, the animal gains weight, +and it continues to do this for some time, until it reaches a point at +which a new balance is established, and its weight again becomes +constant; and this is due to the fact that the animal becomes subject to +an additional waste, consequent on the increased weight of matter +accumulated in its tissues. If, after the animal has attained its new +constant weight, the food be a second time increased, a further gain is +obtained, and so on, with every addition to the supply of nutriment, +until at length a certain point is reached, beyond which its weight +cannot be forced. In fact, each successive increase of weight is +obtained at a greater expenditure of food. If, for example, a lean +animal is taken, and its food increased by a given quantity, it will +rapidly attain a certain additional weight, but if another extra supply +of food be given, the increase due to it will be much more slowly +attained, and so on until at length an additional increase can only be +secured by the long-continued consumption of a very large quantity of +food. The great object of the feeder is to obtain the greatest possible +increase with the smallest expenditure of food, and to know the point +beyond which it is no longer economical to attempt to force the process +of fattening. To do this it is necessary first to consider the +composition of the animal itself, then that of its food, and lastly, the +mode in which it may be most economically used. + +It has been already observed that the animal tissues are composed of +albuminous or nitrogenous compounds, fat, mineral matters, and water; +but the proportions of these substances have, until lately, been very +imperfectly known. Water is well known to be by far the largest +constituent, and amounts in general to about two-thirds of the entire +weight, and it has been generally supposed that the nitrogenous matters +stood next in point of abundance, but a most important and elaborate +series of experiments by Messrs. Lawes and Gilbert have shewn that they +are greatly exceeded by the fatty matters. The following table contains +a summary of the composition of ten different animals in different +stages of fattening. The first division gives the composition of the +carcass, that is, the portion of the animal usually consumed as human +food; the second that of the offal, consisting of the parts not usually +employed as food; and the third that of the entire animals, including +the contents of the stomach and intestines:-- + +[Transcriber's note: Column titles are printed vertical, which is not +possible to do here. Therefore they are replaced with a 2-3 character +code, explained here] + + Column titles: + MM = Mineral Matter + NC = Nitrogenous Compounds + TDS = Total Dry Substance + CSI = Contents of Stomachs and Intestine in moist state. + Wat = Water + +|--------------------------------------------------------------------------- +| | ||Per cent in Offal, excluding | +| | Per cent in Carcass || contents of Stomachs and | +| | || Intestines. | +| |------------------------||-----------------------------| +| | MM | NC | Fat| TDS| WAT|| MM | NC | Fat | TDS | WAT | +|-------------------|----|----|----|----|----||-----|-----|-----|-----|-----| +|Fat Calf |4·48|16·6|16·6|37·7|62·3|| 3·41| 17·1| 14·6| 35·1| 64·9| +|Half-fat Ox |5·56|17·8|22·6|46·0|54·0|| 4·05| 20·6| 15·7| 40·4| 59·6| +|Fat Ox |4·56|15·0|34·8|54·4|45·6|| 3·40| 17·5| 26·3| 47·2| 52·8| +|Fat Lamb |3·63|10·9|36·9|51·4|48·6|| 2·45| 18·9| 20·1| 41·5| 58·5| +|Store Sheep |4·36|14·5|23·8|42·7|57·3|| 2·19| 18·0| 16·1| 36·3| 63·7| +|Half-fat old Sheep |4·13|14·9|31·3|50·3|49·7|| 2·72| 17·7| 18·5| 38·9| 61·1| +|Fat Sheep |3·45|11·5|45·4|60·3|39·7|| 2·32| 16·1| 26·4| 44·8| 55·2| +|Extra fat Sheep |2·77| 9·1|55·1|67·0|33·0|| 3·64| 16·8| 34·5| 54·9| 45·1| +|Store Pig |2·57|14·0|28·1|44·7|55·3|| 3·07| 14·0| 15·0| 32·1| 67·9| +|Fat Pig |1·40|10·5|49·5|61·4|38·6|| 2·97| 14·8| 22·8| 40·6| 59·4| +|-------------------|----|----|----|----|----||-----|-----|-----|-----|-----| +|Mean of all |3·69|13·5|34·4|51·6|48·4|| 3·02| 17·2| 21·0| 41·2| 58·8| +|-------------------|----|----|----|----|----||-----|-----|-----|-----|-----| +|Mean of 8, viz, the| | | | | || | | | | | +| half-fat, fat, and|3·75|13·3|36·5|53·6|46·4|| 3·12| 17·4| 22·4| 42·9| 57·1| +| very fat animals | | | | | || | | | | | +|-------------------|----|----|----|----|----||-----|-----|-----|-----|-----| +|Mean of 6, viz., | | | | | || | | | | | +| of the fat and |3·38|12·3|39·7|55·4|44·6|| 3·03| 16·9| 24·1| 44·0| 56·0| +| very fat animals| | | | | || | | | | | +|-------------------|----|----|----|----|----||-----|-----|-----|-----|-----| + + + |--------------------------------------------------| + | | | + | | Per cent in Entire Animal.| + | | | + | |------------------------------| + | | MM | NC | Fat| TDS| CSI | WAT| + |-------------------|----|----|----|----|-----|----| + |Fat Calf |3·80|15·2|14·8|33·8| 3·17|63·0| + |Half-fat Ox |4·66|16·6|19·1|40·3| 8·19|51·5| + |Fat Ox |3·92|14·5|30·1|48·5| 5·98|45·5| + |Fat Lamb |2·94|12·3|28·5|43·7| 8·54|47·8| + |Store Sheep |3·16|14·8|18·7|36·7| 6.00|57·3| + |Half-fat old Sheep |3·17|14·0|23·5|40·7| 9·05|50·2| + |Fat Sheep |2·81|12·2|35·6|50·6| 6·02|43·4| + |Extra fat Sheep |2·90|10·9|45·8|59·6| 5·18|35·2| + |Store Pig |2·67|13·7|23·3|39·7| 5·22|55·1| + |Fat Pig |1·65|10·9|42·2|54·7| 3·97|41·3| + |-------------------|----|----|----|----|-----|----| + |Mean of all |3·17|13·9|28·2|44·9| 6·13|49·0| + |-------------------|----|----|----|----|-----|----| + |Mean of 8, viz, the| | | | | | | + | half-fat, fat, and|3·23|13·3|29·9|46·4| 6·26|47·3| + | very fat animals | | | | | | | + |-------------------|----|----|----|----|-----|----| + |Mean of 6, viz., | | | | | | | + | of the fat and |3·00|12·7|32·8|48·5| 5·48|46·0| + | very fat animals| | | | | | | + |-------------------|----|----|----|----|-----|----| + +From this table it appears that, in the carcass, the proportion of fat +is, in general, even in lean animals, much greater than that of +nitrogenous compounds. In one case only, that of the fat calf, are they +equal. But in the lean sheep there is more than one and a half times as +much fat as nitrogenous matters, in the half fat sheep twice, in the fat +sheep four times, and in the very fat sheep about six times as much. As +a general result of the analyses it may be stated, that in the carcass +of an ox in good condition, the quantity of fat will be from two to +nearly three times as great as that of the so called albuminous +compounds; in a sheep three or four times, and in the pig four or five +times as great. In the offal, including the hide, intestines, and other +parts not usually consumed as food, the proportion is very +different,--the quantity of fat being much smaller, and that of +nitrogenous compounds considerably larger. + +Taking a general average of the whole, the following may be assumed as +representing approximately the general composition of a lean and a fat +animal:-- + + Lean. Fat. + + Mineral matters 5 3 + Nitrogenous compounds 15 12·5 + Fat 24 33 + Water 56 48·5 + --- ----- + 100 100·0 + +The data given in the preceding table, coupled with a knowledge of the +relative weights of the lean and fat animals, enable us to ascertain the +composition of the _increase_ during the fattening process. It is +obvious, from the material diminution of the per centage of water, that +the matters deposited in the tissues must contain a much larger +proportion of dry matters than the whole body; and the reduced per +centage of nitrogenous matters shews that the fat must also greatly +preponderate. This is still more distinctly illustrated by the following +table, giving the per centage composition of the increase in fattening +oxen, sheep, and pigs:-- + + ------------------------------------------------ + | Mineral | Nitrogenous | Fat. | Water. | + | Matters. | Compounds. | | | + ------------------------------------------------ + Oxen | 1·47 | 7·69 | 66·2 | 24·6 | + Sheep | 2·34 | 7·13 | 70·4 | 20·1 | + Pigs | 0·06 | 6·44 | 71·5 | 22·0 | + ------------------------------------------------ + +Hence it may be stated in round numbers, that for every pound of +nitrogenous matters added to the weight of a fattening animal, it will +gain ten pounds of fat, and three of water. These are the proportions +over the whole period of fattening, but it is probable that during the +last few weeks of the process the ratio of fat to nitrogenous matters is +still higher. + +In considering the composition of the food of animals, it will be +readily admitted that the milk, the nutriment supplied by nature for the +maintenance of the young animal, must afford special instruction as to +its requirements during the early stages of existence, and indicate, at +least, some of the points to be attended to under the altered conditions +of mature life. The following table gives the average composition of the +milk of the most important farm animals:-- + + Cow. Ewe. Goat. + Caseine 3·4 4·50 4·02 + Butter 3·6 4·20 3·32 + Sugar of milk 6·0 5·00 5·28 + Ash 0·2 0·68 0·58 + Water 86·8 85·62 86·80 + ------ ------ ------ + 100·00 100·00 100·00 + +In examining these, and all other analyses of food, it is necessary to +draw a distinction between the flesh-forming and the respiratory +elements; the former including the nitrogenous compounds which are used +in the production of flesh, the latter, the non-nitrogenous substances +which produce fat and support the process of respiration. The former, +however much they may differ in name, are nearly or altogether identical +in chemical composition, the latter embracing two great classes--the +fats which exist in the body and the saccharine compounds, including the +different kinds of sugar and starch which are not found in the animal +tissues. It was at one time supposed that these substances were entirely +consumed in the respiratory process, and eliminated by the lungs in the +form of carbonic acid and water, but it has been clearly shewn that they +may be and often are converted into fat, and accumulated in the system. +Careful experiments on bees have demonstrated that when fed on sugar +they continue to produce wax, which is a species of fat, and animals +retain their health and become fat, even when their food contains +scarcely any oil. There is, however, an important difference between +these two classes of substances as regards their fat-producing effect. A +pound of fat contained in the food is capable of producing the same +quantity within the animal; but the case is different with starch and +sugar, the most trustworthy experiments shewing that two and a half +pounds of these substances are necessary for that purpose. Hence we talk +of the fat equivalent of sugar, by which is meant the amount of fat it +is capable of producing, and which is obtained by dividing its quantity +by 2·5. Applying this principle to the analyses of the milk, it appears +that the relative proportions of the two great classes of nutritive +substances stand thus:-- + + Flesh Respiratory, expressed in + forming their fat equivalent + + Cow 3·4 6·0 + Ewe 4·5 6·2 + Goat 4·0 5·4 + +Taking the general average, it may be stated, that for every pound of +flesh-forming elements contained in the food of the sucking animal, it +consumes respiratory compounds capable of producing one and a half +pounds of fat, and this does not differ materially from the ratio +subsisting between these substances in the lean animal. When the young +animal is weaned, it obtains a food in which the ratio of nitrogenous to +respiratory elements is maintained nearly unchanged; but the latter, in +place of containing a large amount of fatty matters, is in many cases +nearly devoid of these substances, and consists almost exclusively of +starch and sugar, mixed most commonly with a considerable quantity of +woody fibre. + +A very large number of analyses of different kinds of cattle food have +been made by chemists, but our information regarding them is still in +some respects imperfect. The quantity of nitrogenous compounds and of +oil has been accurately ascertained in almost all, but the amount of +starch, sugar, and woody fibre is still imperfectly determined in many +substances. This is due partly to the fact that the nitrogenous and +fatty matters were formerly believed to be of the highest importance, +and might be used as the measure of the nutritive value of food to the +exclusion of its other constituents, and partly also to the imperfect +nature of the processes in use for obtaining the amounts of woody fibre, +starch, and sugar. These difficulties have now, to a certain extent, +been overcome, and the quantity of fibre and of respiratory elements has +been ascertained, and is introduced, so far as is known, in the +subjoined table:-- + +TABLE giving the Composition of the Principal Varieties of Cattle Food. + +_Note._--Where a blank occurs in the oil column, the quantity of that +substance is so small as to be unimportant. When the respiratory +elements and fibre have not been separated, the sum of the two is given. + ++----------------------------+--------+------+--------+-------+------+-------+ +| |Nitro- | Oil. | Respir-| Fibre.| Ash. | Water.| +| | genous | | tory | | | | +| |Com- | | Com- | | | | +| | pounds.| | pounds.| | | | ++----------------------------+--------+------+--------+-------+------+-------+ +|Decorticated earth-nut cake | 44·00 | 8·86| 19·34 | 5·13 | 14·05| 8·62 | +|Decorticated cotton cake | 41·25 | 16·05| 16·45 | 8·92 | 8·05| 9·28 | +|Poppy cake | 34·03 | 11·04| 23·25 | 11·33 | 13·79| 6·56 | +|Teel or sesamum cake | 31·93 | 12·86| 21·92 | 9·06 | 13·85| 10·38 | +|Rape cake | 29·75 | 8·63| 38·72 | 7·30 | 8·65| 6·95 | +|Dotter cake | 29·00 | 7·99| 27·04 | 16·12 | 12·59| 7·26 | +|Tares, home-grown | 28·57 | 1·30| 58·64 | 2·50| 8·99 | +|Linseed cake | 28·53 | 12·47| 35·78 | 6·32 | 6·11| 10·79 | +|Rübsen cake | 26·87 | 11·00| 31·47 | 16·95 | 8·00| 5·71 | +|Tares, foreign | 26·73 | 1·59| 53·04 | 2·84| 15·80 | +|Earth-nut cake (entire seed)| 26·71 | 12·75| 45·69 | 3·29| 11·56 | +|Niger cake | 25·74 | 6·58| 42·18 | 11·15 | 8·12| 6·23 | +|Beans (65 lbs. per bushel) | 24·70 | 1·59| 54·51 | 3·36| 15·84 | +|Lentils | 24·57 | 1·51| 58·82 | 2·79| 12·31 | +|Linseed | 24·44 | 34·00| 30·73 | 3·33| 7·50 | +|Grey peas | 24·25 | 3·30| 57·99 | 2·52| 11·94 | +|Foreign beans | 23·49 | 1·51| 59·67 | 3·14| 12·21 | +|Cotton cake (with husk) | 22·94 | 6·07| 36·52 | 16·99 | 6·02| 11·46 | +|Pea-nut cake | 22·25 | 7·62| 30·25 | 26·97 | 3·71| 9·20 | +|Sunflower cake | 21·68 | 8·94| 19·05 | 33·00 | 9·33| 8·00 | +|Hempseed cake | 21·47 | 7·90| 22·48 | 25·16 | 15·79| 7·21 | +|Kidney beans | 20·06 | 1·22| 62·16 | 3·56| 13·00 | +|Maple peas | 19·43 | 1·72| 63·18 | 2·04| 13·63 | +|Madia sativa (seed) | 18·41 | 36·55| 34·59 | 4·13| 6·32 | +|Clover hay (mean of | | | | | | | +|different species of clover)| 15·81 | 3·18| 34·42 | 22·47 | 7·59| 16·53 | +|Rye | 14·20 | ...| 81·51 | 2·47 | 1·82| 14·66 | +|Bran | 13·80 | 5·56| 61·67 | 6·11| 12·85 | +|Oats | 11·85 | 5·89| 57·45 | 9·00 | 2·72| 13·09 | +|Fine barley dust | 11·49 | 2·92| 71·41 | 2·67| 11·51 | +|Wheat | 11·48 | ...| 73·52 | 0·68 | 0·82| 13·50 | +|Bere | 10·25 | ...| 62·85 | 10·08 | 2·60| 14·22 | +|Hay (mean of different | | | | | | | +| grasses) | 9·40 | 2·56| 38·54 | 29·14 | 5·84| 14·30 | +|Barley | 8·69 | ...| 64·52 | 9·67 | 2·82| 14·30 | +|Coarse barley dust | 8·46 | 3·47| 69·73 | 7·31| 11·03 | +|Rice dust | 8·08 | 2·95| 69·22 | 8·12| 11·63 | +|Oat dust | 6·92 | 3·21| 72·86 | 7·70| 9·31 | +|Winter bean straw | 5·71 | ...| 67·50 | 6·39| 20·40 | +|Carob bean | 3·11 | 0·41| 62·51 | 18·60 | 2·80| 12·57 | +|Potato | 2·81 | ...| 17·30 | 1·07 | 1·13| 77·69 | +|Carrot | 1·87 | ...| 7·91 | 3·07 | 1·11| 86·04 | +|Wheat straw | 1·79 | ...| 31·06 | 45·45 | 7·47| 14·23 | +|Barley straw | 1·68 | ...| 39·98 | 39·80 | 4·24| 14·30 | +|Oat straw | 1·63 | ...| 37·86 | 43·60 | 4·95| 12·06 | +|Mangold-wurzel | 1·54 | ...| 8·60 | 1·12 | 0·96| 87·78 | +|Cabbage | 1·31 | ...| 4·53 | 1·05| 93·11 | +|Turnips | 1·27 | 0·20| 4·07 | 1·08 | 1·71| 91·47 | ++----------------------------+--------+------+--------+-------+------+-------+ + +It is at once obvious that in many of these descriptions of food the +ratio of the flesh to the fat-forming constituents differ very widely +from that existing in the milk, and this becomes still more apparent +when the latter are represented in their fat equivalent, as is done for +a few of them in the following table:-- + + + Flesh Respiratory, expressed + forming, in their fat equivalent, + + Decorticated earth-nut cake 44·0 16·6 + Linseed cake 28·5 26·7 + Tares 26·73 18·8 + Clover hay 15·81 16·8 + Oats 11·85 28·8 + Hay (mean of grasses) 9·40 17·9 + Potato 2·81 6·9 + Wheat straw 1·79 12·4 + Turnip 1·27 1·8 + +It is especially note-worthy that those varieties of food, which common +experience has shewn to promote the fattening of stock to the greatest +extent, contain in many instances the smallest quantity of respiratory +or fat-forming elements relatively to their nitrogenous compounds. This +is especially the case with the different kinds of oil cake, the +leguminous seeds, clover, hay, and turnips. On the other hand, in the +grains the ratio is nearly that of one to three, or similar to that +found in fat cattle; while in the straw, the excess of the respiratory +elements is extremely great. + +These facts appear at first sight to be completely at variance with the +composition of the increase of fattening animals, as ascertained by +Messrs. Lawes and Gilbert already referred to, and which have shewn that +for every pound of nitrogenous compounds, nearly ten pounds of fat are +stored within the animal; and it might be supposed that those kinds of +food which contain the largest relative amount of respiratory elements +ought to fatten most rapidly, and should be selected by the farmer in +preference to oil-cakes and similar substances. But there are other +matters to be considered, dependent on the complex nature of the changes +attending the absorption and assimilation of the food. It must be +particularly borne in mind that only a small proportion of the food +consumed is stored up within the body, and goes to increase the weight +of the animal. Even in the case of the milk, in which economy in the +supply of nutritive matters has been most clearly attended to by nature, +a considerable proportion escapes assimilation, and in the adult animal +a large amount of the food passes off with the excretions. The justice +of this position is apparent when it is remembered that an ox will go on +day after day consuming from a hundred weight to a hundred weight and a +half of turnips, three or four pounds of bean-meal or oil-cake, and a +considerable quantity of straw, although its daily increase in live +weight may not exceed a couple of pounds. And in this direction a very +fertile field of inquiry lies open to the agricultural experimenter; for +it would be most important to determine whether there are not some +substances from which the nutritive matters may not be more easily +assimilated than from others, and what proportion of each is absorbable +under ordinary circumstances. On this point no information has yet been +obtained applicable to individual feeding substances, but the +experiments of Messrs. Lawes and Gilbert have shewn the quantity of the +total food, and of each of its constituents, stored up in the fattening +animal, and a summary of their results is contained in the following +Table:-- + +TABLE shewing the Amount of each Class of Constituents, stored in the +increase, for 100 consumed in the Food. + + +------+---------+-------------+------+------------+ + | | Mineral | Nitrogenous | | Total Dry | + | | Matters | Compounds. | Fat. | Substance. | + +------+---------+-------------+------+------------+ + |Sheep | 3·27 | 4·41 | 9·4 | 8·06 | + |Pigs | 0·58 | 7·34 | 21·2 | 17·3 | + +------+---------+-------------+------+------------+ + +Hence it appears that the pig makes a better use of its food than the +sheep, retaining twice as much of its solid constituents within the +body, from which may be deduced the important practical conclusion, that +the former must be fattened at a much smaller cost than the latter. +Looking at the individual constituents, it appears that, in the sheep, +less than one-twentieth of the nitrogenous compounds, and one-tenth of +the non-nitrogenous substances contained in the food, remain in the +body; and a knowledge of these facts tends to modify the conclusions +which might be drawn from the composition of the increase in the +fattening animal. Its influence may be best illustrated by a particular +example. If, for instance, the increase in a sheep contained its +nitrogenous and respiratory elements in the ratio of 1 to 10, it would +be totally incorrect to supply these substances in the food in the same +proportions. On the contrary, it would be necessary at the very least to +double the proportion of the former, because one-tenth of the +fat-forming elements are absorbed, and only one-twentieth of the +nitrogenous. + +On further consideration, also, it seems unquestionable that the +quantity of the nutritive elements stored up must depend to a large +extent on the nature of the food and the particular state in which they +exist in it. It is probable, or at least possible, that some kinds of +food may contain their nitrogenous constituents in an easily assimilable +state, and their respiratory elements in a nearly indigestible +condition, or _vice versa_, and under these circumstances their +nutritive value would be below that indicated by analysis; but these +points can only be determined by elaborate and long continued feeding +experiments. It is well known, however, that the mechanical state of the +food has a most important influence on its nutritive value. Thus, for +example, the presence of a large quantity of woody fibre protects the +nutritive substances from assimilation, and seeds with hard husks pass +unchanged through the animal, although, so far as their composition +alone is concerned, they may be highly nutritive; and the loss of a +certain quantity of many varieties of food in this way is familiar to +every one. + +The proper adjustment of the relative quantities of the great groups of +nutritive elements in the food is a matter the importance of which +cannot be over-rated, for it is in fact the foundation of successful and +economical feeding; and this will be readily understood if we consider +what would be the result of giving to an animal a supply of food +containing a large quantity of nitrogenous and a deficiency of +fat-forming compounds. In such circumstances, the animal must either +languish for want of the latter, or it is forced to supply the defect by +an increased consumption of food, in doing which it must take into the +system a larger quantity of nitrogenous compounds than would otherwise +have been requisite, and in this way the other elements, which are +present in abundance, are wasted, and the theoretical and practical +value of a food so constituted may be very different, and it is only +when the proportions of the different groups are properly attended to +that the most economical result can be obtained. It can scarcely be said +that the experiments yet made by feeders enable us to fix the most +suitable proportion in which those substances can be employed, although +experience has led them to the use of mixtures which are in most cases +theoretically correct; thus they combine oil-cakes or turnips with +straw, which is poor nitrogenous, and rich in fat-forming elements; and +in general it will be found that where different kinds of food are +mixed, the deficiencies of the one are counterbalanced by the other, and +though this has hitherto been done empirically, it cannot be doubted +that as our knowledge advances it will more and more be determined by +reference to the composition of the food. + +Although the presence of a sufficient quantity of nutritive compounds in +the food is necessarily the fundamental matter for consideration, its +bulk is scarcely less important. The function of digestion requires that +the food shall properly fill the stomach, and however large the supply +of nutritive matters may be, their effect is imperfectly brought out if +the food is too small in bulk, and it actually may become more valuable +if diluted with woody fibre, or some other inert substance. At first +sight this may appear at variance with the observations already made as +to the effects of woody fibre in protecting the nutritive matters from +absorption; but practically there are two opposite evils to be contended +against, a food having too small a bulk, or one containing so large a +proportion of inert substances as to become disadvantageously +voluminous. The most favourable condition lies between the two extremes, +and the natural food of all herbivorous animals is diluted with a +certain amount of woody fibre. When these are replaced by substances +containing a large quantity of nutritive matters in a small bulk, the +result is that the natural instinct of the animal causes it to continue +feeding until the stomach is properly distended, and it consequently +consumes a much larger quantity of food than it is capable of digesting, +and a more or less considerable quantity passes unchanged through the +intestines, and is lost. On the other hand, if the food be too bulky, +the sense of repletion causes the animal to cease eating long before it +has obtained a sufficient supply of nutritive matter. It is most +necessary, therefore, to study the mixture of different kinds of food, +so as to obtain a proper relation between the bulk and the nutritive +matters contained in the mixture; and on examining the nature of the +mixed foods most in vogue among feeders, it will be found that a very +bulky food is usually conjoined with another of opposite qualities. +Hence it is that turnips, the most voluminous of all foods, are used +along with oil-cake and bean-meal, and if from any circumstances it +becomes necessary to replace a large amount of the former by either of +the latter substances, the deficient bulk must be replaced by hay or +straw. + +It has been already remarked that there are three great purposes to +which the food consumed is appropriated; the increase of weight of the +animal--the object the feeder has in view and desires to promote--the +supplying the waste of the tissues, and the process of respiration, both +of which are sources of loss of food, and which it must necessarily be +his aim to diminish as much as possible. The circumstances which must be +attended to in order to do this are sufficiently well understood. It has +been clearly established that the natural heat of the animal is +sustained by the consumption of a certain quantity of its food in the +respiratory process, during which it undergoes exactly the same changes +as those which occur during combustion. It has further been observed, +that the temperature of the body remains unchanged, whatever be that of +the surrounding air; and it is obvious that if it is to continue the +same in winter as in summer, a larger quantity of fuel (_i. e._ food) +must be consumed for this purpose, just as a room requires more fire to +keep it warm in winter than in summer, and hence it naturally follows, +that if the animal be kept in a warm locality the food is economized. It +may also be inferred that, if it were possible, consistently with the +health of the animal, to keep it in a room artificially heated to the +temperature of its own body, this source of waste of food would be +entirely removed. It is not possible, however, to do this, because a +limit is set to it by physiological laws, which cannot be infringed with +impunity; but the housing of cattle, so as to diminish this waste as far +as possible, is a point in regard to the propriety of which theory and +practice are at one. + +The old feeders kept their cattle in large open courts, where they were +exposed to every vicissitude of the weather, but as intelligence +advanced, we find them substituting, first hammels, and then stalls, in +which the animals are kept during the whole time of fattening at an +equable temperature. The effect of this is necessarily to introduce a +considerable economy of the food required to sustain the animal heat; +but it also produces a saving in another way, for it diminishes the +waste of the tissues. + +It has been ascertained by accurate experiments made chiefly on man, +that muscular exertion is one of the most important causes of the waste +of the tissues, and of increased respiratory activity. We cannot move a +limb without producing a corresponding consumption of matters already +laid up within the body; and it has also been found, that the difference +in the quantity of carbonic acid expired during rest and active +exertion, is very large. The inference to be drawn from this is, that +when it is sought to fatten an animal rapidly, every effort must be made +to restrain muscular motion so far as compatible with health. Hence, the +peculiar advantage of stall-feeding, in which the animal is confined to +one spot, and the more thoroughly it can be kept still, the greater will +be the economy of food. This is gained by darkening the house, and +excluding all persons, except when their presence is indispensable. + +An extension of the same principle has led to the use of food +artificially heated, but it is doubtful whether the advantages derived +from it are commensurate to the increased expense of the process; at +least opinions differ among the best informed practical men on this +subject. + +Many other matters, besides these mentioned, exercise an important +influence on the feeding of stock, such as the general health of the +animal, the breed, etc. These are subjects, however, which bear more +directly on practical agriculture, and need not be discussed here. + +The judicious feeder will not only give due weight to the principles +already discussed in all he does, but he must take into consideration +the extent to which they are liable to be modified in particular cases. +He must also attend to the cost of different kinds of food, and the +value of the manure produced by them, subjects of much importance in a +practical point of view, and which must influence him greatly in choice +of the particular substances he supplies to his cattle. + + + + +INDEX. + + + +Acid, apocrenic, 21. + Carbonic, 10, 15, 20, 37, 57, 115. + Cerotic, 48. + Crenic, 21. + Geic, 21. + Hippuric, 168. + Humic, 21. + Lactic, 168. + Margaric, 47. + Nitric, 11, 17, 30, 33, 38, 62, 112. + Oleic, 47. + Pectic, 46. + Phosphoric, 73, 90. + Stearic, 47. + Sulphuric, 182, 237. + Ulmic, 21. + Uric, 168. + +Adulteration of guano, 211. + +Agricultural Chemistry Association of Scotland, 6. + +Air, influence of, on germination, 55. + In the pores of soils, 115. + +Albite, 86. + +Albumen, 48. + +Albuminous constituents of plants and animals, 48. + +Algoa Bay guano, 208. + +Alkaline salts, value of, 260. + +Alumina, 73, 86, 103. + +Ammonia, absorption of, by plants, 29, 38. + Absorption of, by soils, 123. + Carbonate of, 29. + Composition of, 12. + Decomposition of, by plants, 61. + Presence in dew, 17. + " rain, 17. + Production of, 12. + Properties of, 12. + Proportion of, in air, 16, 20. + Proportion of, in drain water, 112. + Proportion of, in soils, 107. + Sulphate of, 29, 227. + Sulphomuriate of, 227. + Urate of, 205. + Valuation of, 259. + +Ammoniacal liquor, 229. + +Amylaceous constituents of plants, 40. + +Angamos guano, 207, 210. + +Animal charcoal, 224. + Manures, 204. + +Animals, composition of, 281. + Nitrogenous constituents of, 48, 281. + +Apatite, 235. + +Ascension Island guano, 208. + +Augite, 89. + +Australian guano, 207. + +Avenine, 50. + + +Barks, amount of ash in, 66. + +Barley, 286. + +Barrenness of soils, 109. + +Basalt, 92. + +Beans, 286. + +Bere, 286. + +Biphosphate of lime, 237, 260. + +Bird Island guano, 208. + +Blood as a manure, 220. + +Bone ash, 234. + +Bone oil, 229. + +Bones as a manure, 223. + Dissolved, 237. + +Box-feeding, 183. + +Bolivian guano, 207, 210. + +Bran, 197, 286. + +Burning, improvement of soils by, 146. + + +Cabbage, 286. + +Cane sugar, 43. + +Carbon, properties of, 10. + Proportion of, in plants, 10. + +Carbonate of ammonia, 29. + Lime, 96, 247. + Magnesia, 96. + Potash, 232. + Soda, 232. + +Carbonic acid, absorption of, by plants, 37. + Decomposition of, by plants, 57. + Evolution of, by plants, 58. + How obtained, 10. + Properties, 10. + Proportion of, in air, 15, 20. + +Carburetted hydrogen, 19. + +Calcium, sulphuret of, 252. + +Caramel, 44. + +Carrot, 286. + +Caseine, 50, 283. + +Castor cake, 195. + +Cattle food, composition of, 286. + +Cellulose, 40. + +Cerine, 48. + +Cerotic acid, 48. + +Chaff, 197. + +Chalk, 96, 245. + +Charcoal, animal, 224. + +Chilian guano, 207. + +China-clay, 87. + +Chloride of potassium, 73, 102. + Sodium, 73, 232. + Manganese, 182. + +Clay, 87. + Absorbent action of, 121. + Composition of, 95. + Source of, 88, 94. + +Clay-slate, 95. + +Classification of plants, 81. + +Coprolites, 98, 235. + +Coral sand, 246. + +Cotton cake, 195, 286. + +Crenic acid, 21. + +Crops, Mineral matters in, 270. + Nitrogen in different, 270. + Rotation of, 81, 266. + + +Deep Ploughing, effects of, 144. + +Dew, ammonia in, 17. + Nitric acid in, 19. + +Dextrine, 43. + +Diastase, 43, 53, 55. + +Diorite, 92. + +Dissolved bones, 237. + +Dolerite, 92. + +Dotter cake, 286. + +Drainage water, analyses of, 112. + +Draining, 138. + +Dung, composition of, 170. + +Dung heaps, management of, 179. + + +Earth-nut cake, 286. + +Emulsine, 50. + +Exhaustion of soils, 81. + + +Farm stock, feeding of, 276. + +Farm-yard manure, 166, 172. + Application of, 186. + +Fat, amount of, in animals, 281. + +Fatty acids, 47. + Matters, 46. + +Feeding cakes, 286. + +Feeding of farm stock, 276. + +Felspar, 86. + Decomposition of, 88. + +Fermentation of manure, 184. + +Fire-clay, 95. + +Fish manure, 221. + +Flesh as a manure, 220. + +Fog, ammonia in, 17. + Nitric acid in, 19. + +Food, cattle, 286. + +Fruits, amount of ash in, 66. + + +Gas Lime, 252. + +Geic acid, 21. + +Germination, 54. + +Gluten, 49. + +Glutin, 49. + +Glycerine, 47. + +Gneiss, 91. + +Granite, 91. + +Grape sugar, 44. + +Greenstone, 92. + +Green manuring, 198. + +Guano, 204. + Adulteration of, 211. + Application of, 214. + Average composition of, 207. + Fish, 222. + Peruvian, characters of, 209. + Phospho-Peruvian, 243. + Sombrero Island, 236. + + +Hair, 218. + +Hay, 286. + +Heat, evolution of, by plants, 60. + +Hempseed cake, 286. + +Hippuric acid, 168. + +Horn, 218. + +Hornblende, 89. + +Humic acid, 21. + +Humin, 22. + +Humus, 21, 98, 133. + +Hydrogen, 10. + + +Ichaboe Guano, 207. + +Indian guano, 208. + +Inorganic constituents of plants, 9, 34. + +Inorganic constituents; + Absorption by plants, 38. + Proportion in plants, 64. + +Inorganic constituents of soils, 85. + +Inuline, 43. + +Iodine in plants, 76. + +Iron, protoxide of, in soils, 107. + Sulphate of, 182. + Sulphuret of, in subsoils, 135. + + +Kaolin, 87. + +Kooria Mooria guano, 207. + + +Labradorite, 86. + +Lactic acid, 168. + +Latham Island guano, 207. + +Leaves, amount of ash in, 65. + As a manure, 202. + +Legumine, 50. + +Lichen starch, 42. + +Light, influence of, on plants, 57. + +Lime, action of, on soils, 248. + As a manure, 245. + Bicarbonate of, 122. + Carbonate of, 96. + Biphosphate of, 237, 260. + Humate of, 125 + Phosphate of, 96, 233, 258. + Sulphate of, 96, 253, 260. + +Lime-plants, 82. + +Limestone, 96. + +Linseed cake, 195. + +Liquid manure, 166, 187. + + +Madia Sativa, 286. + +Magnesia, carbonate of, 96. + Sulphate of, 182, 233. + +Magnesian limestone, 96. + +Malt-dust, 197. + +Manganese in plants, 73. + Oxide of, 73, 87. + Chloride of, 182. + +Mangold-wurzel, 286. + +Manures, animal, 204. + +Manures, application of, 165, 186. + Fermentation of, 184. + Farm-yard, 166, 172. + Liquid, 166, 187. + Mineral, 226. + Theory of, 156. + Sewage, 191. + Vegetable, 195. + Valuation of, 255. + +Manuring, Green, 198. + Principles of, 152. + +Maple peas, 286. + +Maracaybo guano, 236. + +Margaric acid, 47. + +Margarine, 46. + +Marl, 245. + +Mexican guano, 207. + +Mica, 88. + +Mica slate, 91. + +Milk, composition of, 283. + Curding of, 51. + +Mineral constituents of plants, 9, 63. + +Mineral manures, 226. + +Mineral matters in different crops, 270. + In animals, 281. + +Moisture, influence of, on germination, 55. + +Mucilage, 44. + + +Natrolite, 90. + +New Island guano, 208. + +Niger cake, 286. + +Night-soil, 217. + +Nitrate of potash, 229. + +Nitrate of soda, 229, 260. + +Nitric acid, absorbtion of, by plants, 30, 38. + Decomposition of, by plants, 62. + In drainage water, 112. + In dew, 19. + In air, 17. + In fog, 19. + Production of, 11, 33. + +Nitrification, 11. + +Nitrogen, amount in a six-course rotation, 160. + Amount of, in different crops, 270. + Presence in the atmosphere, 11. + Properties of, 11. + Proportion of, in plants, 11. + +Nitrogenous constituents of plants, 48, 286. + +Nitrogenous constituents of animals, 48, 281. + + +Oats, 286. + Proportion of ash in, 68, 70. + +Oil-cakes, 195, 286. + +Oils, sweet principle of, 47. + +Oily matters, 46. + +Oleic acid, 47. + +Oleine, 46. + +Oligoclase, 86. + +Oolitic limestone, 96. + +Organic constituents of plants, 8. + Sources of the, 13, 20. + +Organic constituents of soils, 103. + +Orthoclase, 86. + +Oxide of iron in rocks and soils, 87, 107. + Of manganese, 87. + +Oxygen, evolution of, by plants, 58. + Influence of, on germination, 55. + Presence in atmosphere, 12. + Properties of, 12. + Proportion of, in plants, 12. + + +Pacquico Guano, 207. + +Paring, improvement of soils by, 146. + +Patagonian guano, 207. + +Pea-nut cake, 286. + +Peas, 286. + +Peat, as a manure, 203. + +Peat, use of, in dung-heaps, 184. + +Pectic acid, 46. + +Pectine, 46. + +Peruvian Guano, 205, 207, 209. + Upper, 207, 213. + +Phosphate of lime, 96, 233. + Value of, 258. + +Phosphates, insoluble, 258. + Soluble, 237, 260. + +Phospho-Peruvian guano, 243. + +Phosphuretted hydrogen in air, 19. + +Pigeons' dung, 216. + +Plants, Albuminous constituents of, 48. + Amylaceous constituents of, 40. + Ash of, 64, 73. + Classification of, 81. + Inorganic constituents of, 9, 34, 38, 63. + Oily constituents of, 46. + Organic constituents of, 8. + Proximate constituents of, 40. + Saccharine constituents of, 40. + +Poppy cake, 196, 286. + +Potash, carbonate of, 232. + Muriate of, 231. + Nitrate of, 229. + Plants, 82. + Salts, 231. + +Potato, 286. + +Poudrette, 217. + +Proximate constituents of plants, 40. + +Pyroguanite, 236. + + +Quartz, 86. + + +Rainwater, 17, 18. + +Rape Cake, 196, 286. + Dust, 195. + +Rocks, crystalline, 85. + Composition of, 91. + Disintegration of, 85. + Sedimentary, 86. + +Roots of plants, amount of ash in, 65. + +Rotation of crops, 81, 266. + +Rübsen cake, 286. + +Rye, 286. + + +Saccharine Constituents of plants, 40. + +Saldanha Bay guano, 207. + +Salt, common, 232. + +Sandstones, 95. + +Schübler's experiments, 127. + +Sea Bear Bay guano, 208. + +Sea weed, 200, 201. + +Seeds, amount of ash in, 64. + +Sesamum cake, 286. + +Sewage manure, 191. + +Shell sand, 246. + +Silica plants, 82. + +Silicate of potash, 233. + Soda, 233. + +Skin, 218. + +Soda, carbonate of, 232. + Nitrate of, 229, 260. + Salts, 231. + Silicate of, 233. + +Sodium, chloride of, 232. + +Soil, the, 20, 83. + Influence on the composition of the ash of plants, 71. + Chemical composition of, 98. + Chemical and physical characters of, 83. + Improvement of, by mechanical means, 137. + +Soil, relation of, to heat and moisture, 127. + +Soils, absorbent action of, 122. + Air in the pores of, 114. + Analysis, 101, 118. + Barrenness of, 109. + Classification of, 135. + Exhaustion of, 81. + Inorganic constituents of, 85. + Mixing of, 150. + Origin of, 84. + Organic matters in, 103. + Physical characters of, 118, 127. + +Sombrero Island guano, 236. + +Starch, 41. + Lichen, 42. + +Stearic acid, 47. + +Stearine, 46. + +Stems of plants, ash in, 64. + +Straw, amount of ash in, 64. + As a manure, 197. + +Sulphate of iron, 182. + Lime, 96, 253, 260. + Magnesia, 182. + Ammonia, 29, 227. + Potash, 231. + +Sulphomuriate of ammonia, 227. + +Sulphur in plants, 78. + +Sulphuret of iron, 135. + Calcium, 252. + +Sulphuretted hydrogen, 19. + +Sugar, 43. + Of milk, 283. + +Subsoil, the, 134. + Ploughing, 143. + +Sunflower cake, 286. + +Syenite, 91. + + +Tares, 286. + +Teelcake, 286. + +Temperature, influence of, on germination, 54. + +Thomsonite, 90. + +Trap rock, 92. + +Tubers, amount of ash in, 65. + + +Ulmic acid, 21. + +Ulmin, 22. + +Upper Peruvian guano, 207, 213. + +Urate, 216. + Of ammonia, 205. + +Urea, 168. + +Uric acid, 168, 205. + +Urine, composition of, 167. + Human, 168. + Sulphated, 216. + + +Valuation of manures, 255. + +Vegetable manures, 195. + +Vegetation, influence of light on, 57. + +Voelcker's analyses of dung, 174. + + +Warping, 148. + +Water, absorption of, by plants, 35. + Decomposition of, by plants, 60. + Exhalation of, by plants, 35. + Rain, 17, 18. + +Wax, 48. + +Wheat, 286. + +Woods, amount of ash in, 65. + +Woody fibre, 41. + +Wool, 219. + + +Zeolites, 90. + + +PRINTED BY R. AND R. CLARK, EDINBURGH. + + + + +A CATALOGUE OF BOOKS + +PUBLISHED BY ADAM & CHARLES BLACK + +EDINBURGH + + +ADAMSON (ROBERT). The Cottage Garden. Second edition fcap. 8vo, cloth, +limp, 1s. + +ALEXANDER (DR. W. L.). Christian Thought and Work; a series of Morning +Meditations on Passages of Scripture. Second edition, fcap. 8vo, price +5s. + +ANDERSON (Professor). Elements of Agricultural Chemistry. Crown 8vo, +price 6s. 6d. + +ANDERSON (REV. WM., LL.D., Glasgow). Discourses. Second series, second +edition, crown 8vo, price 6s. + +---- Regeneration. Second edition, crown 8vo, price 6s. + +ANDERSON (REV. JAMES). Light in Darkness, or Comfort to the Sick and +Afflicted, being a series of Meditations and Prayers, and portions of +Scripture for those visited with bereavement and distress. Second +edition, fcap., cloth, antique, red edges, price 2s. 6d. + +APPERLEY (CHARLES). The Horse and the Hound; their various Uses and +Treatment, including Practical Instructions in Horsemanship and Hunting, +&c., &c. Third edition, with numerous Illustrations on Wood and Steel, +after drawings by Herring, Alken and Harrison Weir. Post 8vo, price 10s. +6d. + +BALFOUR (Professor). A Class-Book of Botany: being an Introduction to +the Study of the Vegetable Kingdom. In one large vol. demy 8vo, with +1800 Illustrations, 31s. 6d. + +Sold also in Two Parts:-- + +Part I. Structural and Morphological Botany, 10s. 6d. + +Part II. Vegetable Physiology, Classification Glossary, &c., 21s. + +BALFOUR (Professor). A Manual of Botany: being an Introduction to the +Study of the Structure, Physiology, and Classification of Plants. Crown +8vo, pp. 700, with 820 Illustrations, price 12s. 6d. + +---- Outlines of Botany. Second edition, revised and enlarged, designed +for Schools and Colleges, illustrated with nearly 600 wood-cuts, pp. +712, fcap. 8vo, cloth, price 8s. 6d. + +---- The Botanist's Companion: or, Directions for the Use of the +Microscope, and for the Collection and Preservation of Plants with a +Glossary of Botanical Terms. Crown 8vo, price 2s. 6d. + +---- Botany and Religion; or, Illustrations of the Works of God in the +Structure, Functions, Arrangement, and General Distribution of Plants. +Third edition, 260 Wood Engravings, 12mo, cloth, price 6s. 6d.; or +cloth, gilt edges, price 7s. + +BEESLY (Rev. E. S.), and REYNOLDS (Rev. S. H.) System of History for the +use of Students. By Rev. E. S. BEESLY M.A., late of Wadham College, +Oxford, Professor of History, University College, London; and REV. S. H. +REYNOLDS, Brazenose College, Oxford. [In preparation.] + +BEGBIE (JAMES, M.D.) Contributions to Practical Medicine. Contents--On +Gout; on Rheumatism and Chorea; on the Connection of Erythema Nodosum +with the Rheumatic Diathesis; on Anæmia and its Consequences; on +Dyspepsia and Nervous Disorder; on Fatty Degeneration of the Heart; on +Erysipelas; on Diphtheria and its Sequels; on the Physiological and +Therapeutical Effects of Arsenic; on the Sedative Powers of the Datura +Stramonii Demy 8vo, price 10s. 6d. + +BENNETT (Professor). Clinical Lectures on the Principles and Practice of +Medicine. New edition (the third), pp. 1005, with five hundred +Illustrations, price 30s. + +---- An Introduction to Clinical Medicine. Six Lectures on the Method of +Examining Patients, &c. Fourth edition, 107 Illustrations, fcap. 8vo, +price 5s. + +---- The Pathology and Treatment of Pulmonary Consumption. Second +edition, with 26 large Illustrations, demy 8vo, price 7s. 6d. + +BLACK'S General Atlas of the World. New edition (1862), containing 56 +maps, and Index of 65,000 names, &c., folio, half-bound morocco, gilt +edges, price 60s. + +---- School Atlas. 40 maps, and Index, 4to or 8vo, price 10s. 6d. + +---- School Atlas for Beginners, 27 maps, oblong 12n price 2s. 6d. + +BLACK'S Atlas of Australia, with all the Gold Regions, 6 maps, royal +4to, price 6s. + +---- New Atlas of Scotland. A series of 12 Maps compiled from the best +sources, on the scale of four miles to the inch. Imp. folio, cloth, +price 30s. + +---- New Large Map of Scotland. Scale, 4 miles to the inch, and +measuring when complete 70 by 56 inches. Price, on rollers varnished, +52s. 6d.; mounted on linen, in case. 42s.; separate sheets coloured, +each, 2s., or in cloth cases, each, 2s. 6d. + +---- Guide Books for Tourists in Great Britain and Ireland, &c. + +---- Guide to London. A Practical Guide to the Metropolis and its +Vicinity. Illustrated by a large and accurate Plan of the City--Map of +the Environs--Plans of the Public Buildings--Views, &c. In a portable +Volume, price 4s. 6d. + +---- New Plan of London. An Accurate Guide to the Streets and Public +Buildings. In a neat Case for the Pocket, price 1s. + +---- Map of Environs of London. Extending from Windsor to Gravesend, +Crystal Palace, Richmond, Hampton Court, Epsom, &c. Price 1s. + +---- Dorset, Devon, and Cornwall. With Maps, Plans, and numerous +Illustrations. Price 5s. + +---- Guide to Yorkshire. New and greatly enlarged Edition, illustrated +with Maps, Plans, and Views. Price 5s. + +---- Guide to Isle of Wight and Hampshire. With Maps, Plans, and Views. +Price 2s. 6d. + +---- Guide to Surrey. Including a full Description of the History, +Antiquities, and Topography of the County. With Map and numerous +Illustrations. Price 5s. + +---- Guide to Kent. With Map and Numerous Illustrations. Price 3s. 6d. + +---- Guide to Scotland. New Edition (the 15th) containing Map, and One +Hundred Illustrations. Price 8s. 6d. + +---- Guide to England. Third Edition, greatly enlarged and improved, +with Maps and Woodcuts. Price 10s. 6d. + +---- Guide to English Lakes. Eleventh Edition, with Maps and +Illustrations. Price 5s. + +---- Guide to Wales, North and South. Eleventh Edition, with Maps and +Charts. Price 5s. + +---- Guide to Ireland. Third Edition, with Maps, Charts, and Views. +Price 5s. + +BLACK'S Guide to Sussex. With Map and Illustrations. Price 2s. 6d. + +---- Where Shall We Go? New Edition. A Guide to the Healthiest and most +Beautiful Watering Places in the British Islands. Illustrated by Maps +and Engravings. Price 2s. 6d. + +---- Map of Australia (size 39-1/2 by 40 inches). Fifth Edition. +Containing the Routes of Stuart and Burke, and the Latest Discoveries. +Price 10s. 6d. in sheets, 14s. in a case folded, and 2 on rollers +varnished. + +"_This is a magnificent addition to geographical science, and must +supersede all other Maps having reference to the Australian +Colonies._"-- GLASGOW DAILY MAIL. + +"_One of the most perfect specimens which toe have ever met with._"-- +AUSTRALIAN AND NEW ZEALAND GAZETTE. + +BROMBY (Rev. C. H.) Church Students' Manual. Contents--Book of Common +Prayer--Collects, Epistles, Collects--Church Catechism--Confirmation +Service--History of the Early Church--History of the English Church. +Fcap 8vo, red edges, price 3s. + +BRUCE (JAMES). Travels and Adventures in Abyssinia. New edition. Edited +by J. M. CLINGAN, M.A. Five page illustrations and portrait on tinted +paper, by C. A. Doyle. Square 12mo, cloth, gilt edges, price 3s. 6d. + +BRYCE (JAMES, M.A., LL.D., Glasgow). A Treatise on Book-keeping by +Double Entry, with an Appendix on Single Entry. Fcap. 8vo, cloth, price +5s. + +---- The Arithmetic of Decimals, adapted to a Decimal Coinage. Second +edition, price 1s. 6d. + +---- A Treatise on Algebra. Third edition. Crown 8vo, cloth, price 6s. + +BUCHAN (A. W., F.E.I.S.) The Advanced Prose and Poetical Reader; being a +collection of select specimens in English, with Explanatory Notes and +Questions on each lesson; to which are appended Lists of Prefixes and +Affixes, with an Etymological Vocabulary. 12mo, cloth, price 3s. + +THE POETICAL READER, separately, price 1s. 6d. + +BURGESS (Rev. HENRY, LL.D., etc.) The Amateur Gardener's Year Book, a +Guide for those who Cultivate their Gardens on the Principles and +Practice of Horticulture. Fcap. cloth, price 3s. 6d. + +CANDLISH (Rev. Dr.) Life in a Risen Saviour. Being Discourses on the +Resurrection. New Edition (the third). [In preparation. + +CARSON (A. R., LL.D.) Exercises in Attic Greek for the use of Schools +and Colleges. 12mo, price 4s. + +CARSON (A.R., LL.D.) Phaedrus' Fables of Æsop in Latin. New edition, +with Vocabulary, edited by Rev. Wm. Veitch, 18mo, bound, price 2s. + +CHRISTISON (Professor). A Dispensatory. New edition in preparation. + +COCKBURN (Lord). Memorials of His Time. With portrait after Raeburn. +Demy 8vo, price 7s. 6d. + +COOK'S (Captain) Voyages and Discoveries. Edited by John Barrow Esq., +F.R.S. Illustrated, square 12mo, gilt edges, price 5s. + +CRAMPTON (Rev. JOSIAH). The Lunar World, its Scenery, Motions, etc. +Principal Contents: Flight through Space--Appearance of the Moon on +approaching her--Lunar Scenery--Wanderings in the Mare +Imbrium--Mountains--Volcanoes--Motions--Utility and Beauty of the +Moon--Habitability of the Moon and Plurality of Worlds, etc. etc. etc. +Fourth Thousand, fcap. 8vo, cloth, price 3s. 6d. + +DAVIDSON (Rev. Dr.) On Biblical Criticism. 8vo, price 18s. + +DEMAUS (Rev. ROBERT, M.A.) Class Book of English Prose, Comprehending +Specimens of the most Distinguished Prose Writers from CHAUCER to the +Present Time, with Biographical Notices, Explanatory Notes, and +Introductory Sketches of the History of English Literature. 12mo, cloth, +price 4s. 6d. + +Or in Two Parts, price 2s. 6d. each. + +---- Introduction to the History of English Literature. 12 mo, price 2s. + +---- Elementary Reading Book. Illustrated, 18mo, cloth, price 1s. + +---- Scripture Class Book. [_In the Press._ + +DENISON (E. B., M.A., Q.C.) Clocks and Locks. Fcap. 8vo, price 3s. 6d. + +DE QUINCEY'S (THOMAS) Works. New Edition. In 15 volumes crown 8vo, price +4s. 6d. each. (See page 14.) + +DE QUINCEY (THOS.) on Style and Conversation. A Series of Essays. Fcap +8vo, cloth, price 5s. + +DICK (WILLIAM). Manual of Veterinary Science. Second Edition. 12 mo, +price 5s. + +DONALDSON (JAMES, M.A.) Latin Reader of Jacobs and Classen. With Notes, +etc., 12mo, price 3s. 6d. + + Or COURSE I., price 1s. 9d. + COURSE II., price 2s. + +---- Modern Greek Grammar, 12 mo, price 2s. + +DRESSER. (Professor). Popular Manual of Botany without technical terms. +Fcap. 8vo, twelve page Wood Illustrations, coloured, price 4s. 6d. + +EDWARDS (A. M.) The Ambulance Surgeon; or, Practical Observations on +Gunshot Wounds. By P. L. APPIA. Edited, with Notes, by T. W. NUNN, +F.R.C.S., Surgeon to the Middlesex Hospital; and A. M. EDWARDS, Lecturer +on Surgery in the Edinburgh Medical School. Fcap. 8vo. Price 6s. + +ENCYCLOPÆDIA BRITANNICA. 21 vols., 4to (each vol. 24s., cloth). +Complete, with Index, £25: 12s. + +---- 21 vols, 4to, half bound, Russia extra, marbled edges, 30s. per +vol., Complete £31: 10s.; with Index £32: 2: 6. + +---- Index to Ditto, 4to, price 8s., cloth; or 12s. 6d. half russia. + +FAIRBAIRN (WILLIAM). Iron: its History, Properties, and Processes of +Manufacture. Crown 8vo, price 6s. + +FARRAR (REV. F. W.) Julian Home: A Tale of College Life. Foolscap 8vo, +second edition, price 5s. + +---- Eric; or Little by Little; a Tale of Roslyn School. Sixth edition, +illustrated, fcap. 8vo, price 5s. + +---- St. Winifred's; or The World of School. Fcap. 8vo, cloth, price 6s. +6d. + +FORBES (Professor J. D.) Occasional Papers on the Theory of Glaciers, +with ten Plates and twenty-nine Wood Engravings. Demy 8vo, price 10s. +6d. + +---- Norway and its Glaciers. Followed by Journals of Excursions in the +High Alps of Dauphiné, Berne, and Savoy. With two Maps, ten Coloured +Lithographic Views, and twenty-two Wood Engravings. Royal 8vo, price +21s. + +FORBES (Professor J. D.) Tour of Mont Blanc and of Monte Rosa. +Illustrated with Map of the Pennine Chain of Alps, fcap. 8vo. price 3s. +6d. + +GRAHAM (G. F.) Musical Composition: its Theory and Practice. With +numerous Engravings, and copious Musical Illustrations. 4to, price 9s. + +GULLIVER'S Travels to Liliput. Illustrated. Fcap. 8vo, gilt edges, price +1s. 6d. + +GUNN (WM. M., LL.D.) Rudiments of the Latin Language. 12mo, price 2s. + +GUTHRIE (Rev. Dr.) Pleas for Ragged Schools. Seventh Thousand. Crown +8vo. Illustrated cover. Price 1s. + +---- The Gospel in Ezekiel. Twenty-seventh thousand. Crown 8vo, price +7s. 6d. + +---- Christ and the Inheritance of the Saints. Sixteenth thousand. Crown +8vo, price 7s. 6d. + +---- The Way to Life. Seventh thousand. Fcap. 8vo, price 5s. + +---- The Christian World Unmasked, by BERRIDGE. Edited by DR. GUTHRIE. +Fcap. 8vo, cloth antique, red edges, price 2s. 6d. + +---- The Street Preacher, being the Autobiography of Robert Flockhart. +Edited by DR. GUTHRIE. Small crown 8vo, cloth limp price 2s. + +HAMPDEN (R. D.) The Fathers of Greek Philosophy. Demy 8vo, price 16s. + +HERSCHEL (Sir J. F. W., Bart.) Physical Geography. Second edition, crown +8vo, price 7s. 6d. + +---- Meteorology. Fcap. 8vo, price 5s. + +---- The Telescope. Fcap. 8vo, price 3s. 6d. + +JEFFREY (Rev. Dr.) Voices from Calvary; or the Seven Last Sayings of Our +Dying Lord. Second edition, fcap. 8vo, cloth antique, price 4s. + +JUKES (J. B.) The Student's Manual of Geology. New and greatly enlarged +Edition, with Lists and Figures of characteristic Fossils, and +containing upwards of Four Hundred Wood Engravings. Crown 8vo, pp. 750, +price 12s. 6d. + +JUKES (J. B.) School Boy's Manual of Geology. [In preparation. + +KELLAND (Professor). Elements of Algebra, for the use of Schools and +Junior Classes in Colleges. Crown 8vo, price 4s. + +---- Algebra--being a Complete and easy Introduction to Analytical +Science. Crown 8vo, pp. 467, price 7s. 6d. + +KEMP (W. S., M.A.) A Course of Exercises in Latin Prose Syntax. Crown +8vo, price 3s. 6d.; or in two Parts,--Part I. Agreement and Government, +2s. Part II. The Syntax of the Subjunctive Mood, 2s. Part III. +Introductory, 10d. + +KITTO (Dr.) New Edition of Kitto's Cyclopædia of Biblical Literature. +Edited by WILLIAM LINDSAY ALEXANDER, D.D., assisted by numerous +Contributors. Now publishing in Monthly Parts, super-royal 8vo, price +2s. 6d. each, illustrated with numerous Engravings on Wood and Steel. + +---- Popular Cyclopædia of Biblical Literature. In one volume, 8vo, +illustrated by 336 Engravings, price 10s. 6d. + +---- History of Palestine; from the Patriarchal Age to the present time. +Numerous Wood Engravings, crown 8vo, price 5s. + +---- School Edition. 12mo, price 4s.; without Map, 3s. 6d. + +LAMARTINE (ALPHONSE DE). Mary Stuart. With Portrait, crown 8vo, price +5s. + +LOCKHART (J.) School Geography for the Use of Junior Pupils in Mixed +Schools. 12mo, price 1s. + +M'CULLOCH (J. R.) Principles of Political Economy. 8vo, price 15s. + +---- A Treatise on Metallic and Paper Money and Banks, written for the +Encyclopædia Britannica. 4to, 5s. + +---- Economical Policy. Second edition, enlarged and improved, 8vo, +price 10s. 6d. + +---- On Taxation. 4to, price 3s. 6d. + +MACAULAY (Lord). Biographies of Atterbury, Bunyan, Goldsmith, Johnson, +and Pitt, contributed to the Encyclopædia Britannica. Eleventh thousand. +Fcap. 8vo, with Portrait by Maull and Polyblank, price 3s. 6d. + +MACAULAY (Dr. ALEXR.) Medical Dictionary, designed for popular use; +containing an account of Diseases and their Treatment, including those +most frequent in warm climates. New edition, greatly enlarged and +improved. By ROBERT WELBANK MACAULAY, M.D., H.E.I.C.S. Demy 8vo, price +10s. 6d. cloth, and 12s. 6d. half-russia. + +MANSEL (H. L., D.C.L.) Metaphysics, or the Philosophy of Consciousness. +Crown 8vo, price 7s. 6d. + +MASSON (GUSTAVE). Introduction to the History of French Literature. +12mo, cloth, 2s. 6d. + +---- Class-Book of French Literature, with Biographical Notices, Notes +and Chronological Tables, crown 8vo, price 4s. 6d. + + MILLER'S (HUGH) Works, crown 8vo, _each_ 7s. 6d. + * MY SCHOOLS AND SCHOOLMASTERS. 11,000. + SCENES AND LEGENDS IN THE NORTH OF SCOTLAND. 6,000. + * FIRST IMPRESSIONS OF ENGLAND AND ITS PEOPLE. 7,000. + THE OLD RED SANDSTONE. 10,000. + TESTIMONY OF THE ROCKS. 29,000. + THE CRUISE OF THE BETSY. 4,000. + SKETCH BOOK OF POPULAR GEOLOGY. 2,000. + FOOT-PRINTS OF THE CREATOR. 7,000. + ESSAYS, HISTORICAL AND CRITICAL. 2,000. + THE HEADSHIP OF CHRIST. 2,000. + ESSAYS, HISTORICAL, BIOGRAPHICAL, AND CRITICAL. 2,000. + TALES AND SKETCHES. + +----* Cheap editions of the above, crown 8vo, cloth, limp, price 2s. 6d. + +MILLER (Professor). Principles and Practice of Surgery. Numerous +Illustrations. New edition. [_In the press._ + +MUNCHAUSEN (Baron). Numerous Illustrations. 18mo, gilt edges, price 1s. +6d. + +MURRAY (ANDREW AND ROBERT). Shipbuilding in Iron and Wood. New Edition. +Illustrated with Plates and Woodcuts, 4to, price 14s. + +NEILL (PATRICK, LL.D.) The Fruit, Flower, and Kitchen Garden. Profusely +Illustrated. Fcap. 8vo, price 3s. 6d. + +NICOL (Professor). Elements of Mineralogy; containing a General +Introduction to the Science, with descriptions of the Species. Fcap. +8vo, price 5s. + +OSWALD (Rev. JOHN). Etymological Dictionary of the English Language. +Seventh edition, 18mo, bound, 5s. + +OWEN (RICHARD, F.R.S.) Palæontology, or a Systematic Summary of Extinct +Animals, and their Geological Relations. 141 Illustrations, second +edition, demy 8vo, price 16s. + +PARK (MUNGO). Travels in Africa. Nine page Illustrations, square 12mo, +gilt edges, price 3s. 6d. + +PATERSON (JAMES, M.A., Barrister at Law). Compendium of English and +Scotch Law. Royal 8vo, price 28s. + +PILLANS (Professor). Eclogæ Ciceronianæ. 18mo, price 3s. 6d. + +---- First Steps in Physical and Classical Geography. Fcap. 8vo, price +1s. 6d. + +PORTEOUS (Bishop). Evidences of the Truth, and Divine Origin of the +Christian Revelation, with Definitions and Analysis by JAMES BOYD, LL.D. +18mo, price 1s. + +POETRY and Poets of Britain. From Chaucer to Tennyson, with Biographical +Sketches, and a rapid View of the Characteristic Attributes of each. By +DANIEL SCRYMGEOUR. Post 8vo, gilt edges, price 7s. 6d. + +POETS and Prose Writers of France, from the Earliest Period to the +Beginning of the Present Century. By GUSTAVE MASSON, B.A., &c., +Assistant Master at Harrow School. Crown 8vo, pp. 517 cloth, gilt edges, +price 7s. 6d. + +PROSE and Prose Writers of Britain. By Rev. ROBERT DEMAUS, M.A. Crown +8vo, gilt edges, price 7s. 6d. + +RAMSAY (ALLAN). The Gentle Shepherd. Illustrated, 16mo, price 2s. 6d.; +gilt edges 3s. + +RICHARDSON (SIR JOHN, LL.D., etc.) The Polar regions. Demy 8vo. With +Map, price 14s. + +ROBINSON CRUSOE. Illustrated by C. A. Doyle. Square 12mo, gilt edges, +price 3s. 6d. + +RUSSELL (SCOTT). The Steam Engine. Illustrated, post 8vo, price 5s. + +RUSSEL (SCOTT). Steam and Steam Navigation. A Treatise on the Nature, +Properties, and Applications of Steam, and on Steam Navigation. +Illustrated, post 8vo, 9s. + +SCHMITZ (Dr.) Elementary Greek Grammar. 12mo, price 3s. 6d. + +SCRYMGEOUR (DANIEL). Class-Book of English Poetry. 12mo, price 4s. 6d. +Or in 2 parts, price 2s. 6d. each. + +SCOTT (Sir WALTER). Complete Works and Life. 98 vols., fcap. 8vo, £14: +14. + +---- Waverley Novels. The latest editions with the Author's Notes-- + +NEW ILLUSTRATED EDITION of 1860, 48 vols., fcap. 8vo, +cloth, 96 Plates, and 1700 Illustrations £10 10 0 + +LIBRARY EDITION, 25 vols. demy 8vo, with 204 Engravings +after Wilkie, Landseer 12 12 0 + +AUTHOR'S FAVOURITE EDITION of 1847, in 48 vols., fcap. +8vo, with Frontispiece and Vignette to each vol. 7 4 0 + +CABINET EDITION, 25 vols., fcap 8vo, each vol. containing +Steel Frontispiece and Woodcut Vignette 3 10 0 + +PEOPLE'S EDITION, 5 vols. royal 8vo, with Illustrations 2 2 0 + +RAILWAY EDITION, 25 vols., fcap. 8vo, Illustrated Covers 1 17 6 + +Separately, 1s. 6d. each, or in cloth, 2s. + +Vol. 1 Waverley, or "'Tis Sixty Years Since." + 2. Guy Mannering, or The Astrologer. + 3. Antiquary + 4. Rob Roy. + 5. Old Mortality. + 6. Black Dwarf, and Legend of Montrose. + 7. Heart of Mid-Lothian. + 8. Bride of Lammermoor. + 9. Ivanhoe. + 10. Monastery. + 11. Abbott. + 12. Kenilworth. + 13. Pirate. + 14. Fortunes of Nigel. + 15. Peveril of the Peak. + 16. Quentin Durward. + 17. St. Ronan's Well. + 18. Redgauntlet. + 19. The Betrothed. + 20. The Talisman. + 21. Woodstock. + 22. Fair Maid of Perth. + 23. Anne of Geierstein, or the Maiden of the Mist. + 24. Count Robert of Paris. + 25. Surgeon's Daughter--Castle Dangerous. + +---- Poetical Works. Various editions, from 5s. to 36s. + +SCOTT (Sir WALTER). Miscellaneous Prose Works. Various editions, from +26s. to 84s. + +---- Life of Napoleon Bonaparte. 5 vols., fcap. 8vo, price 20s. People's +edition, 1 vol., royal 8vo, price 10s. + +---- Tales of a Grandfather. Various editions, 6s. to 15s. + +---- Beauties of. Crown 8vo, gilt edges, price 3s. 6d. + +---- Life of, by J. G. Lockhart. Various editions, 7s. 6d. to 30s. + +SIMPSON (Professor). Obstetric Memoirs and Contributions, including +those on Anaesthesia. Edited by C. W. Priestly, M.D., and H. R. Storer, +M.D. 2 vols. 8vo, profusely Illustrated, 36s. + +---- ON THE DISEASES OF WOMEN. 8vo. [In preparation. + +SMITH (ADAM, LL.D.) The Wealth of Nations: an Inquiry into the Nature +and Causes of the Wealth of Nations. Edited, and with Life of the +Author, by J. R. M'CULLOCH, Esq. Fourth edition, corrected throughout, +and greatly enlarged. 8vo, 16s. + +SPALDING (WM., M.A.) An Introduction to Logical Science. Fcap. 8vo, 4s. +6d. + +STEVENSON (DAVID). Canal and River Engineering. Small 8vo, 4s. 6d. + +STEVENSON (THOMAS). On Harbours. Crown 8vo. [In the Press. + +STEWART (W. C.) The Practical Angler, or the Art of Trout Fishing, more +particularly applied to Clear Water. Fourth edition, 12mo, cloth, price +3s. 6d. + +THOMAS (Dr. ROBERT). The Modern Practice of Physic. Eleventh edition, +edited by Dr. Frampton. 2 vols. 8vo, price 28s. + +THOMSON (Professor). Brewing and Distillation. Post 8vo, price 6s. + +TRAILL (Professor). Medical Jurisprudence. Third Edition, post 8vo, +price 5s. + +TRAIL (Rev. W.) The Literary Characteristics and Achievements of the +Bible. Crown 8vo. + +TYTLER (P. F.) History of Scotland. Enlarged and continued to the +Present Time, by the Rev. JAMES TAYLOR, D.D., and adapted to the +purposes of Tuition by ALEX. REID, LL.D. Sixth edition, 12mo, 3s. 6d. + +---- Outlines of Modern History. Fifth edition, 12mo, 3s. + +---- Outlines of Ancient History. Fourth edition, 12mo, 3s. + +VEITCH (Rev. WM.) Greek Verbs, Irregular and Defective. Post 8vo, price +6s. + +WALPOLE (HORACE). The Castle of Otranto. Fcap. 8vo, Illustrated, gilt +edges, price 2s. 6d. + +WARDLAW (Dr.) Systematic Theology. A Complete System of Polemic +Divinity. In three vols., demy 8vo, price 21s. + +WESTGARTH (WILLIAM). Australia; its Rise, Progress, and Present +Condition; with Map. Fcap. 8vo, price 3s. 6d. + +WHEWELL (Dr.) New Edition of Mackintosh's Ethical Philosophy. Demy 8vo. +Price 10s. 6d. + +WHITE (ROBERT). Madeira; its Climate and Scenery. Second edition by J. +Y. JOHNSON. With numerous Illustrations, and a Map of the Island, crown +8vo, price 7s. 6d. + +WILSON (JOHN). British Farming, a description of the mixed husbandry of +Great Britain. Pp. 569, profusely illustrated. Demy 8vo, price 12s. + +YOUNG (ANDREW). The Angler and Tourist's Guide to the Northern Counties +of Scotland, with Instructions to Young Anglers. 18mo, price 2s. + + + + +DE QUINCEY'S WORKS. + + +AUTHOR'S EDITION. + +_In Fifteen Volumes, price 4s. 6d. each_, + +NEW EDITION OF + +THE WORKS OF THOMAS DE QUINCEY + +"THE ENGLISH OPIUM EATER" + + * * * * * + +Vol. I. CONFESSIONS OF AN ENGLISH OPIUM-EATER. + II. RECOLLECTIONS OF THE LAKE POETS. + III. LAST DAYS OF IMMANUEL KANT. + IV. THE ENGLISH MAIL-COACH. + V. DR. SAMUEL PARR, ETC. + VI. RICHARD BENTLEY, ETC. + VII. PROTESTANTISM AND OTHER ESSAYS. + VIII. LEADERS IN LITERATURE. + IX. THE CÆSARS, AND OTHER WRITINGS. + X. RHETORIC AND STYLE. + XI. COLERIDGE AND OPIUM EATING. + XII. SPECULATIONS, LITERARY AND PHILOSOPHIC. + XIII. CONVERSATION, AND OTHER PAPERS. + XIV. THE AUTOBIOGRAPHIC SKETCHES--1790-1803. + +Volume XIV. concludes the series of Mr. De Quincey's Works, as arranged +by himself; but in order to render this Edition complete, a +SUPPLEMENTARY VOLUME (XV.) will be added, containing the Biographies of +SHAKSPEARE, POPE, GOETHE, and SCHILLER, contributed by Mr. De Quincey to +the "Encyclopædia Britannica," and not included in the last Edition of +his Works, and a paper, hitherto unpublished, on the POLITICAL PARTIES +OF MODERN ENGLAND. Also a Complete GENERAL INDEX to the whole Works. + + * * * * * + +EDINBURGH: ADAM AND CHARLES BLACK + + + + +NEW EDITION OF KITTO'S CYCLOPÆDIA. + +_In royal 8vo, Volume I. (A to E), pp. 884. Price_ £1: 0: 0. + +A THIRD EDITION OF + +KITTO'S + +_Cyclopædia of Biblical Literature._ + +Edited by the Rev. WILLIAM LINDSAY ALEXANDER, D.D., with the assistance +of numerous contributors. + +Illustrated by Numerous Engravings on Wood and Steel. + +In undertaking the New Edition of this work, it was the intention of the +Publishers to complete it in two volumes, but the additions have been so +extensive as to render a third volume necessary. + +Although this change will occasion great extra expense to the +Publishers, there will be no additional charge to Subscribers, who will +receive the complete book at £3, the price to which the Publishers +pledged themselves in their prospectus. + +_List of Contributors._ + +Beard, J. R., D.D. + +Bell, G. M. + +Brown, John, D.D., late Professor of Exegetical Theology to the United +Presbyterian Church of Scotland. + +Browne, Henry, M.A., Vicar of Pevensey. + +Cairns, John, D.D. + +Candlish, James S., M.A. + +Credner, Karl August, D.D., late Professor of Theology at Giessen. + +Davidson, Samuel, D.D., LL.D. + +Denham, Joshua Fred., M.A., F.R.S. + +Deutsch, Emanuel, of the University of Berlin, M. Ger. Or. Soc., etc., +British Museum. + +Doran, John William, LL.D., Rector of Beeston, St. Lawrence, Norfolk. + +Farrar, Frederic W., M.A., late Fellow of Trinity College, Cambridge. + +Geikie, Archibald, F.R.S.E., F.G.S., of the Geological Survey. + +Ginsburg, Christian D. + +Goold, William Henry, D.D., Professor of Theology to the Reformed +Presbyterian Church. + +Gotch, F. W., D.D., President of the Baptist College, Bristol; Examiner +in Hebrew to the London University. + +Gowan, Anthony T., D.D. + +Hävernick, Heinrich August Christ., late Professor of Theology at +Königsberg. + +Holmes, Peter, D.D., F.R.A.S., of Magdalen Hall, Oxford. + +Jamieson, Robert, D.D., Minister of St. Paul's, Glasgow. + +Jennings, Isaac. + +Kitto, John, D.D., F.A.S. + +Leathes, Stanley, M.A. + +Lyon, William P., B.A. + +M'Causland, Dominick, Q.C., LL.D. + +Madden, Fred. W., M.R.S.L., Brit. Museum. + +Michelson, E., Ph. D. of the University of Heidelberg. + +Morren, Nathanael, M.A. + +Newman, Francis W., late Fellow of Balliol College, Oxford; Professor of +Latin in the University of London. + +Newth, Samuel, M.A., Professor, New College, London. + +Nicholson, John, B.A. Oxford; Ph. D. Tübingen. + +Nicholson, W. A., M.D. + +Poole, Reg. Stuart, British Museum. + +Porter, J. Leslie, M.A., Professor of Sacred Literature, Assembly's +College, Belfast. + +Royle, J. F., M.D., F.R.S., F.L.S., F.G.S. + +Ryland, J. E. + +Smith, C. Hamilton, Lieut.-Colonel, K.H. and K.W., F.R.S., F.R.L.S., +etc. + +Smith, John Pye, D.D., F.R.S., F.G.S. + +Stebbing, Henry, D.D. of St. John's College, Cambridge. + +Tholuck, August, D.D., Professor of Theology in the University of Halle. + +Wace, Henry, M.A. + +Wright, William, M.A. and LL.D. of Trinity College, Dublin. + + * * * * * + +EDINBURGH: ADAM AND CHARLES BLACK. + + + + +NEW EDITION, 1862. + +_In folio, half bound morocco, gilt edges, price_ £3, + +_A new edition of_ + +BLACK'S GENERAL ATLAS OF THE WORLD, + +Series of Fifty-six Maps, containing all the Latest Discoveries, +beautifully coloured, and accompanied by an Alphabetical Index of 65,000 +Names, forming a ready Key to the places mentioned in the Maps. + +_List of Maps in the order in which they occur._ + +PHYSICAL GEOGRAPHY, ETC. + + 1. The World in Hemispheres, with Comparative View of Mountains and Rivers. + 2. The World on Mercator's Projection. + 3. Physical and Ethnographical Charts of the World. + 4. Zoological and Botanical Charts of the World. + 5. Isothermal Chart shewing the Temperature of the Earth's Surface. + 6. Northern and Southern Celestial Hemisphere. + 7. Solar System, Theory of the Seasons, etc. + + +EUROPE. + + 8. Europe. + 9. England (North Part). +10. ....... (South Part). +11. Scotland (North Part). +12. ........ (South Part). +13. Ireland. +14. France. +15. Switzerland. +16. Holland and Belgium. +17. Railway Map of Central Europe. +18. Germany. +19. Austria. +20. Prussia. +21. Denmark. +22. Sweden and Norway, with Baltic Sea. +23. Russia in Europe. +24. Spain and Portugal. +25. Italy (North). +26. ..... (South). +27. Turkey in Europe. +28. Greece and Ionian Islands. + + +ASIA. + +29. Asia. +30. Turkey in Asia. +31. Palestine. +32. Persia, Afghanistan, and Beloochistan. +33. India. +34. China. +35. Indian Archipelago, and Further India, + including Burmah, Siam, etc. + + +AFRICA. + +36. Africa, with Barth's, Livingstone's, and Burton's Routes. +37. Egypt. +38. South Africa. + + +AMERICA. + +39. North America, with Enlargement of British Columbia. +40. British America and Arctic Regions. +41. Canada East, New Brunswick, Nova Scotia, etc. +42. Canada West. +43. United States of America (General Map). +44. The Eastern or Principal States. +45. The Western States (California, Oregon, Utah, etc.) +46. Mexico, Central America, etc. +47. West India Islands. +48. South America. +49. Venezuela, New Granada, Equador, and Peru. +50. Chili--Argentine Republic, and Bolivia. +51. Brazil, Uruguay, and Guayana. + + +AUSTRALIA AND ISLANDS OF THE PACIFIC. + +52. Australia. +53. New Zealand, Tasmania, and Western Australia. +54. Polynesia and Pacific Ocean. +55. The World as known to the Ancients. +56. The Principal Countries of the Ancient World, with the + Roman and Persian Empires. + +_Accompanied by Sketch Maps of the Federal and Confederate States, and +of a portion of Mexico._ + + * * * * * + +EDINBURGH: ADAM AND CHARLES BLACK. + + + + + + +End of the Project Gutenberg EBook of Elements of Agricultural Chemistry, by +Thomas Anderson + +*** END OF THIS PROJECT GUTENBERG EBOOK ELEMENTS OF AGRICULTURAL CHEMISTRY *** + +***** This file should be named 24931-8.txt or 24931-8.zip ***** +This and all associated files of various formats will be found in: + http://www.gutenberg.org/2/4/9/3/24931/ + +Produced by Steven Giacomelli, Jeannie Howse, Josephine +Paolucci and the Online Distributed Proofreading Team at +http://www.pgdp.net. (This file was produced from images +produced by Core Historical Literature in Agriculture +(CHLA), Cornell University). + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. Special rules, +set forth in the General Terms of Use part of this license, apply to +copying and distributing Project Gutenberg-tm electronic works to +protect the PROJECT GUTENBERG-tm concept and trademark. Project +Gutenberg is a registered trademark, and may not be used if you +charge for the eBooks, unless you receive specific permission. If you +do not charge anything for copies of this eBook, complying with the +rules is very easy. You may use this eBook for nearly any purpose +such as creation of derivative works, reports, performances and +research. They may be modified and printed and given away--you may do +practically ANYTHING with public domain eBooks. Redistribution is +subject to the trademark license, especially commercial +redistribution. + + + +*** START: FULL LICENSE *** + +THE FULL PROJECT GUTENBERG LICENSE +PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK + +To protect the Project Gutenberg-tm mission of promoting the free +distribution of electronic works, by using or distributing this work +(or any other work associated in any way with the phrase "Project +Gutenberg"), you agree to comply with all the terms of the Full Project +Gutenberg-tm License (available with this file or online at +http://gutenberg.org/license). + + +Section 1. General Terms of Use and Redistributing Project Gutenberg-tm +electronic works + +1.A. By reading or using any part of this Project Gutenberg-tm +electronic work, you indicate that you have read, understand, agree to +and accept all the terms of this license and intellectual property +(trademark/copyright) agreement. If you do not agree to abide by all +the terms of this agreement, you must cease using and return or destroy +all copies of Project Gutenberg-tm electronic works in your possession. +If you paid a fee for obtaining a copy of or access to a Project +Gutenberg-tm electronic work and you do not agree to be bound by the +terms of this agreement, you may obtain a refund from the person or +entity to whom you paid the fee as set forth in paragraph 1.E.8. + +1.B. "Project Gutenberg" is a registered trademark. It may only be +used on or associated in any way with an electronic work by people who +agree to be bound by the terms of this agreement. There are a few +things that you can do with most Project Gutenberg-tm electronic works +even without complying with the full terms of this agreement. See +paragraph 1.C below. There are a lot of things you can do with Project +Gutenberg-tm electronic works if you follow the terms of this agreement +and help preserve free future access to Project Gutenberg-tm electronic +works. See paragraph 1.E below. + +1.C. The Project Gutenberg Literary Archive Foundation ("the Foundation" +or PGLAF), owns a compilation copyright in the collection of Project +Gutenberg-tm electronic works. Nearly all the individual works in the +collection are in the public domain in the United States. If an +individual work is in the public domain in the United States and you are +located in the United States, we do not claim a right to prevent you from +copying, distributing, performing, displaying or creating derivative +works based on the work as long as all references to Project Gutenberg +are removed. Of course, we hope that you will support the Project +Gutenberg-tm mission of promoting free access to electronic works by +freely sharing Project Gutenberg-tm works in compliance with the terms of +this agreement for keeping the Project Gutenberg-tm name associated with +the work. You can easily comply with the terms of this agreement by +keeping this work in the same format with its attached full Project +Gutenberg-tm License when you share it without charge with others. + +1.D. The copyright laws of the place where you are located also govern +what you can do with this work. Copyright laws in most countries are in +a constant state of change. If you are outside the United States, check +the laws of your country in addition to the terms of this agreement +before downloading, copying, displaying, performing, distributing or +creating derivative works based on this work or any other Project +Gutenberg-tm work. The Foundation makes no representations concerning +the copyright status of any work in any country outside the United +States. + +1.E. Unless you have removed all references to Project Gutenberg: + +1.E.1. The following sentence, with active links to, or other immediate +access to, the full Project Gutenberg-tm License must appear prominently +whenever any copy of a Project Gutenberg-tm work (any work on which the +phrase "Project Gutenberg" appears, or with which the phrase "Project +Gutenberg" is associated) is accessed, displayed, performed, viewed, +copied or distributed: + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + +1.E.2. If an individual Project Gutenberg-tm electronic work is derived +from the public domain (does not contain a notice indicating that it is +posted with permission of the copyright holder), the work can be copied +and distributed to anyone in the United States without paying any fees +or charges. If you are redistributing or providing access to a work +with the phrase "Project Gutenberg" associated with or appearing on the +work, you must comply either with the requirements of paragraphs 1.E.1 +through 1.E.7 or obtain permission for the use of the work and the +Project Gutenberg-tm trademark as set forth in paragraphs 1.E.8 or +1.E.9. + +1.E.3. If an individual Project Gutenberg-tm electronic work is posted +with the permission of the copyright holder, your use and distribution +must comply with both paragraphs 1.E.1 through 1.E.7 and any additional +terms imposed by the copyright holder. Additional terms will be linked +to the Project Gutenberg-tm License for all works posted with the +permission of the copyright holder found at the beginning of this work. + +1.E.4. Do not unlink or detach or remove the full Project Gutenberg-tm +License terms from this work, or any files containing a part of this +work or any other work associated with Project Gutenberg-tm. + +1.E.5. Do not copy, display, perform, distribute or redistribute this +electronic work, or any part of this electronic work, without +prominently displaying the sentence set forth in paragraph 1.E.1 with +active links or immediate access to the full terms of the Project +Gutenberg-tm License. + +1.E.6. You may convert to and distribute this work in any binary, +compressed, marked up, nonproprietary or proprietary form, including any +word processing or hypertext form. However, if you provide access to or +distribute copies of a Project Gutenberg-tm work in a format other than +"Plain Vanilla ASCII" or other format used in the official version +posted on the official Project Gutenberg-tm web site (www.gutenberg.org), +you must, at no additional cost, fee or expense to the user, provide a +copy, a means of exporting a copy, or a means of obtaining a copy upon +request, of the work in its original "Plain Vanilla ASCII" or other +form. Any alternate format must include the full Project Gutenberg-tm +License as specified in paragraph 1.E.1. + +1.E.7. Do not charge a fee for access to, viewing, displaying, +performing, copying or distributing any Project Gutenberg-tm works +unless you comply with paragraph 1.E.8 or 1.E.9. + +1.E.8. You may charge a reasonable fee for copies of or providing +access to or distributing Project Gutenberg-tm electronic works provided +that + +- You pay a royalty fee of 20% of the gross profits you derive from + the use of Project Gutenberg-tm works calculated using the method + you already use to calculate your applicable taxes. The fee is + owed to the owner of the Project Gutenberg-tm trademark, but he + has agreed to donate royalties under this paragraph to the + Project Gutenberg Literary Archive Foundation. Royalty payments + must be paid within 60 days following each date on which you + prepare (or are legally required to prepare) your periodic tax + returns. Royalty payments should be clearly marked as such and + sent to the Project Gutenberg Literary Archive Foundation at the + address specified in Section 4, "Information about donations to + the Project Gutenberg Literary Archive Foundation." + +- You provide a full refund of any money paid by a user who notifies + you in writing (or by e-mail) within 30 days of receipt that s/he + does not agree to the terms of the full Project Gutenberg-tm + License. You must require such a user to return or + destroy all copies of the works possessed in a physical medium + and discontinue all use of and all access to other copies of + Project Gutenberg-tm works. + +- You provide, in accordance with paragraph 1.F.3, a full refund of any + money paid for a work or a replacement copy, if a defect in the + electronic work is discovered and reported to you within 90 days + of receipt of the work. + +- You comply with all other terms of this agreement for free + distribution of Project Gutenberg-tm works. + +1.E.9. If you wish to charge a fee or distribute a Project Gutenberg-tm +electronic work or group of works on different terms than are set +forth in this agreement, you must obtain permission in writing from +both the Project Gutenberg Literary Archive Foundation and Michael +Hart, the owner of the Project Gutenberg-tm trademark. Contact the +Foundation as set forth in Section 3 below. + +1.F. + +1.F.1. Project Gutenberg volunteers and employees expend considerable +effort to identify, do copyright research on, transcribe and proofread +public domain works in creating the Project Gutenberg-tm +collection. Despite these efforts, Project Gutenberg-tm electronic +works, and the medium on which they may be stored, may contain +"Defects," such as, but not limited to, incomplete, inaccurate or +corrupt data, transcription errors, a copyright or other intellectual +property infringement, a defective or damaged disk or other medium, a +computer virus, or computer codes that damage or cannot be read by +your equipment. + +1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the "Right +of Replacement or Refund" described in paragraph 1.F.3, the Project +Gutenberg Literary Archive Foundation, the owner of the Project +Gutenberg-tm trademark, and any other party distributing a Project +Gutenberg-tm electronic work under this agreement, disclaim all +liability to you for damages, costs and expenses, including legal +fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT +LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE +PROVIDED IN PARAGRAPH F3. YOU AGREE THAT THE FOUNDATION, THE +TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE +LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR +INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH +DAMAGE. + +1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a +defect in this electronic work within 90 days of receiving it, you can +receive a refund of the money (if any) you paid for it by sending a +written explanation to the person you received the work from. If you +received the work on a physical medium, you must return the medium with +your written explanation. The person or entity that provided you with +the defective work may elect to provide a replacement copy in lieu of a +refund. If you received the work electronically, the person or entity +providing it to you may choose to give you a second opportunity to +receive the work electronically in lieu of a refund. If the second copy +is also defective, you may demand a refund in writing without further +opportunities to fix the problem. + +1.F.4. Except for the limited right of replacement or refund set forth +in paragraph 1.F.3, this work is provided to you 'AS-IS' WITH NO OTHER +WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO +WARRANTIES OF MERCHANTIBILITY OR FITNESS FOR ANY PURPOSE. + +1.F.5. Some states do not allow disclaimers of certain implied +warranties or the exclusion or limitation of certain types of damages. +If any disclaimer or limitation set forth in this agreement violates the +law of the state applicable to this agreement, the agreement shall be +interpreted to make the maximum disclaimer or limitation permitted by +the applicable state law. The invalidity or unenforceability of any +provision of this agreement shall not void the remaining provisions. + +1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the +trademark owner, any agent or employee of the Foundation, anyone +providing copies of Project Gutenberg-tm electronic works in accordance +with this agreement, and any volunteers associated with the production, +promotion and distribution of Project Gutenberg-tm electronic works, +harmless from all liability, costs and expenses, including legal fees, +that arise directly or indirectly from any of the following which you do +or cause to occur: (a) distribution of this or any Project Gutenberg-tm +work, (b) alteration, modification, or additions or deletions to any +Project Gutenberg-tm work, and (c) any Defect you cause. + + +Section 2. Information about the Mission of Project Gutenberg-tm + +Project Gutenberg-tm is synonymous with the free distribution of +electronic works in formats readable by the widest variety of computers +including obsolete, old, middle-aged and new computers. It exists +because of the efforts of hundreds of volunteers and donations from +people in all walks of life. + +Volunteers and financial support to provide volunteers with the +assistance they need, is critical to reaching Project Gutenberg-tm's +goals and ensuring that the Project Gutenberg-tm collection will +remain freely available for generations to come. In 2001, the Project +Gutenberg Literary Archive Foundation was created to provide a secure +and permanent future for Project Gutenberg-tm and future generations. +To learn more about the Project Gutenberg Literary Archive Foundation +and how your efforts and donations can help, see Sections 3 and 4 +and the Foundation web page at http://www.pglaf.org. + + +Section 3. Information about the Project Gutenberg Literary Archive +Foundation + +The Project Gutenberg Literary Archive Foundation is a non profit +501(c)(3) educational corporation organized under the laws of the +state of Mississippi and granted tax exempt status by the Internal +Revenue Service. The Foundation's EIN or federal tax identification +number is 64-6221541. Its 501(c)(3) letter is posted at +http://pglaf.org/fundraising. Contributions to the Project Gutenberg +Literary Archive Foundation are tax deductible to the full extent +permitted by U.S. federal laws and your state's laws. + +The Foundation's principal office is located at 4557 Melan Dr. S. +Fairbanks, AK, 99712., but its volunteers and employees are scattered +throughout numerous locations. Its business office is located at +809 North 1500 West, Salt Lake City, UT 84116, (801) 596-1887, email +business@pglaf.org. Email contact links and up to date contact +information can be found at the Foundation's web site and official +page at http://pglaf.org + +For additional contact information: + Dr. Gregory B. Newby + Chief Executive and Director + gbnewby@pglaf.org + + +Section 4. Information about Donations to the Project Gutenberg +Literary Archive Foundation + +Project Gutenberg-tm depends upon and cannot survive without wide +spread public support and donations to carry out its mission of +increasing the number of public domain and licensed works that can be +freely distributed in machine readable form accessible by the widest +array of equipment including outdated equipment. Many small donations +($1 to $5,000) are particularly important to maintaining tax exempt +status with the IRS. + +The Foundation is committed to complying with the laws regulating +charities and charitable donations in all 50 states of the United +States. Compliance requirements are not uniform and it takes a +considerable effort, much paperwork and many fees to meet and keep up +with these requirements. We do not solicit donations in locations +where we have not received written confirmation of compliance. To +SEND DONATIONS or determine the status of compliance for any +particular state visit http://pglaf.org + +While we cannot and do not solicit contributions from states where we +have not met the solicitation requirements, we know of no prohibition +against accepting unsolicited donations from donors in such states who +approach us with offers to donate. + +International donations are gratefully accepted, but we cannot make +any statements concerning tax treatment of donations received from +outside the United States. U.S. laws alone swamp our small staff. + +Please check the Project Gutenberg Web pages for current donation +methods and addresses. Donations are accepted in a number of other +ways including checks, online payments and credit card donations. +To donate, please visit: http://pglaf.org/donate + + +Section 5. General Information About Project Gutenberg-tm electronic +works. + +Professor Michael S. Hart is the originator of the Project Gutenberg-tm +concept of a library of electronic works that could be freely shared +with anyone. For thirty years, he produced and distributed Project +Gutenberg-tm eBooks with only a loose network of volunteer support. + + +Project Gutenberg-tm eBooks are often created from several printed +editions, all of which are confirmed as Public Domain in the U.S. +unless a copyright notice is included. Thus, we do not necessarily +keep eBooks in compliance with any particular paper edition. + + +Most people start at our Web site which has the main PG search facility: + + http://www.gutenberg.org + +This Web site includes information about Project Gutenberg-tm, +including how to make donations to the Project Gutenberg Literary +Archive Foundation, how to help produce our new eBooks, and how to +subscribe to our email newsletter to hear about new eBooks. |