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diff --git a/24931-h/24931-h.htm b/24931-h/24931-h.htm new file mode 100644 index 0000000..dd52d4e --- /dev/null +++ b/24931-h/24931-h.htm @@ -0,0 +1,12029 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> + +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" /> + <title> + The Project Gutenberg eBook of Elements of Agricultural Chemistry, by Thomas Anderson, M.D. + </title> + <style type="text/css"> +/*<![CDATA[ XML blockout */ +<!-- + p { margin-top: .75em; + text-align: justify; + margin-bottom: .75em; + } + h1,h2,h3,h4,h5,h6 { + text-align: center; /* all headings centered */ + clear: both; + } + hr { width: 33%; + margin-top: 2em; + margin-bottom: 2em; + margin-left: auto; + margin-right: auto; + clear: both; + } + + table {margin-left: auto; margin-right: auto;} + + body{margin-left: 10%; + margin-right: 10%; + } + + .linenum {position: absolute; top: auto; right: 4%;} + .pagenum { /* uncomment the next line for invisible page numbers */ + /* visibility: hidden; */ + position: absolute; + left: 92%; + font-size: smaller; + text-align: right; + } /* page numbers */ + .notes {background-color: #eeeeee; color: #000; padding: .5em; margin-left: 10%; margin-right: 10%;} + + .blockquot{margin-left: 5%; margin-right: 10%;} + + .center {text-align: center;} + .right {text-align: right;} + .smcap {font-variant: small-caps;} + .caption {font-weight: bold;} + + .figcenter {margin: auto; text-align: center;} + + .figleft {float: left; clear: left; margin-left: 0; margin-bottom: 1em; margin-top: + 1em; margin-right: 1em; padding: 0; text-align: center;} + + .figright {float: right; clear: right; margin-left: 1em; margin-bottom: 1em; + margin-top: 1em; margin-right: 0; padding: 0; text-align: center;} + + .footnotes {border: dashed 1px;} + .footnote {margin-left: 10%; margin-right: 10%; font-size: 0.9em;} + .footnote .label {position: absolute; right: 84%; text-align: right;} + .fnanchor {vertical-align: super; font-size: .8em; text-decoration: none;} + + .poem {margin-left:10%; margin-right:10%; text-align: left;} + .poem br {display: none;} + .poem .stanza {margin: 1em 0em 1em 0em;} + .poem span.i0 {display: block; margin-left: 0em; padding-left: 3em; text-indent: -3em;} + .poem span.i2 {display: block; margin-left: 2em; padding-left: 3em; text-indent: -3em;} + .poem span.i4 {display: block; margin-left: 4em; padding-left: 3em; text-indent: -3em;} + // --> + /* XML end ]]>*/ + </style> + </head> +<body> + + +<pre> + +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). + + + + + + +</pre> + + + + + +<h2>ELEMENTS</h2> + +<h4>OF</h4> + +<h1>AGRICULTURAL CHEMISTRY</h1> + +<h3>BY</h3> + +<h2>THOMAS ANDERSON, M.D.</h2> + +<h4>F.R.S.E., F.C.S.</h4> + +<p class="center">PROFESSOR OF CHEMISTRY IN THE UNIVERSITY OF GLASGOW, AND CHEMIST TO THE +HIGHLAND AND AGRICULTURAL SOCIETY OF SCOTLAND.<br /><br /> + +EDINBURGH:<br /><br /> + +ADAM AND CHARLES BLACK.<br /><br /> + +1860.</p> + + +<p>ERRATUM.</p> + +<p>Page 190, line 11, for "gallon" read "ton."</p> + +<p>PRINTED BY R. AND R. CLARK, EDINBURGH.</p> + + +<p class="notes">Transcriber's note: Many of the tables needed to be split to fit space +constraints.</p> + + + +<h2>PREFACE.</h2> + + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_iv" id="Page_iv">[Pg iv]</a></span> 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.</p> + +<p>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.</p> + +<p> +<span style="margin-left: 2.5em;"><span class="smcap">University of Glasgow</span>,</span><br /> +<span style="margin-left: 2.5em;"><i>1st November 1860.</i></span><br /> +</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_v" id="Page_v">[Pg v]</a></span></p> +<h2>CONTENTS.</h2> + +<p> +<span class="linenum">Page</span><br /> +<br /> +<span class="smcap">Introduction</span> <span class="linenum"><a href="#Page_1">1</a></span><br /> +<br /> +<br /> +CHAPTER I.<br /> +<br /> +<span class="smcap">The Organic Constituents of Plants.</span><br /> +<br /> +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 <span class="linenum"><a href="#Page_8">8</a></span><br /> +<br /> +<br /> +CHAPTER II.<br /> +<br /> +<span class="smcap">The Proximate Constituents of Plants.</span><br /> +<br /> +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 <span class="linenum"><a href="#Page_40">40</a></span><br /> +<br /> +<br /> +CHAPTER III.<br /> +<br /> +<span class="smcap">The Changes which take place in the Food of +Plants during their Growth.</span><br /> +<br /> +Changes occurring during Germination ... Changes during the After-Growth<span class='pagenum'><a name="Page_vi" id="Page_vi">[Pg vi]</a></span> +of the Plant ... Decomposition of Carbonic Acid ... Decomposition of +Water ... Decomposition of Ammonia ... Decomposition of Nitric Acid <span class="linenum"><a href="#Page_54">54</a></span><br /> +<br /> +<br /> +CHAPTER IV.<br /> +<br /> +<span class="smcap">The Inorganic Constituents of Plants.</span><br /> +<br /> +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 <span class="linenum"><a href="#Page_63">63</a></span><br /> +<br /> +<br /> +CHAPTER V.<br /> +<br /> +<span class="smcap">The Soil—Its Chemical and Physical Characters.</span><br /> +<br /> +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 <span class="linenum"><a href="#Page_83">83</a></span><br /> +<br /> +<br /> +CHAPTER VI.<br /> +<br /> +<span class="smcap">The Improvement of the Soil by Mechanical +Processes.</span><br /> +<br /> +Draining ... Its Advantageous Effects ... Subsoil and Deep Ploughing +... Improving the Soil by Paring and Burning ... Warping +... Mixing of Soils ... Chalking <span class="linenum"><a href="#Page_137">137</a></span><br /> +<br /> +<br /> +CHAPTER VII.<br /> +<br /> +<span class="smcap">The General Principles of Manuring.</span><br /> +<br /> +Fundamental Principles upon which Manures are applied ... <i>Special</i> and +<i>General</i> Manures ... Importance of this distinction ... Views regarding<span class='pagenum'><a name="Page_vii" id="Page_vii">[Pg vii]</a></span> +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<span class="linenum"><a href="#Page_152">152</a></span><br /> +<br /> +<br /> +CHAPTER VIII.<br /> +<br /> +<span class="smcap">The Composition and Properties of Farm-yard +and Liquid Manures.</span><br /> +<br /> +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 <span class="linenum"><a href="#Page_166">166</a></span><br /> +<br /> +<br /> +CHAPTER IX.<br /> +<br /> +<span class="smcap">The Composition and Properties of Vegetable +Manures.</span><br /> +<br /> +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 <span class="linenum"><a href="#Page_195">195</a></span><br /> +<br /> +<br /> +CHAPTER X.<br /> +<br /> +<span class="smcap">The Composition and Properties of Animal +Manures.</span><br /> +<br /> +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 <span class="linenum"><a href="#Page_204">204</a></span><br /> +<br /> +<br /> +CHAPTER XI.<br /> +<br /> +<span class="smcap">The Composition and Properties of Mineral +Manures.</span><br /> +<br /> +Mineral Manures ... Sulphate and Muriate of Ammonia ... Sulphomuriate +<span class='pagenum'><a name="Page_viii" id="Page_viii">[Pg viii]</a></span>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 <span class="linenum"><a href="#Page_226">226</a></span><br /> +<br /> +<br /> +CHAPTER XII.<br /> +<br /> +<span class="smcap">The Valuation of Manures.</span><br /> +<br /> +The Principle on which Manures are valued ... Its application to +different simple and complex Manures ... Method of Calculation ... +General Remarks <span class="linenum"><a href="#Page_255">255</a></span><br /> +<br /> +<br /> +CHAPTER XIII.<br /> +<br /> +<span class="smcap">The Rotation of Crops.</span><br /> +<br /> +Its necessity explained ... Quantity of Mineral Matters in the produce +of an Acre of Different Crops ... The Theory of Rotation<span class="linenum"><a href="#Page_266">266</a></span><br /> +<br /> +<br /> +CHAPTER XIV.<br /> +<br /> +<span class="smcap">The Feeding of Farm Stock.</span><br /> +<br /> +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 <span class="linenum"><a href="#Page_276">276</a></span><br /></p> + + + + +<hr style="width: 65%;" /> +<h2>AGRICULTURAL CHEMISTRY.</h2> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_1" id="Page_1">[Pg 1]</a></span></p> +<h2>INTRODUCTION.</h2> + + +<p>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,<span class='pagenum'><a name="Page_2" id="Page_2">[Pg 2]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_3" id="Page_3">[Pg 3]</a></span> 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<span class='pagenum'><a name="Page_4" id="Page_4">[Pg 4]</a></span> 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 <i>Chemistry, in its application to Agriculture +and Physiology</i>.</p> + +<p>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 <i>chemists</i> +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<span class='pagenum'><a name="Page_5" id="Page_5">[Pg 5]</a></span> as they had before supported, +the application of chemistry to agriculture.</p> + +<p>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.</p> + +<p>Liebig's treatise was followed, in the year 1844, by<span class='pagenum'><a name="Page_6" id="Page_6">[Pg 6]</a></span> the publication of +Boussingault's <i>Economic Rurale</i>, 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.</p> + +<p>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<span class='pagenum'><a name="Page_7" id="Page_7">[Pg 7]</a></span> 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.</p> + +<p>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.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_8" id="Page_8">[Pg 8]</a></span></p> +<h2>CHAPTER I.</h2> + +<h3>THE ORGANIC CONSTITUENTS OF PLANTS.</h3> + + +<p>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.</p> + +<p>Although they form so large a proportion of the plant,<span class='pagenum'><a name="Page_9" id="Page_9">[Pg 9]</a></span> its organic +constituents are composed of no more than four elements, viz.:—</p> + +<p> +<span style="margin-left: 2.5em;">Carbon.</span><br /> +<span style="margin-left: 2.5em;">Hydrogen.</span><br /> +<span style="margin-left: 2.5em;">Nitrogen.</span><br /> +<span style="margin-left: 2.5em;">Oxygen.</span><br /> +</p> + +<p>The inorganic constituents are much more numerous, not less than +thirteen substances, which appear to be essential, having been observed. +These are—</p> + +<p> +<span style="margin-left: 2.5em;">Potash.</span><br /> +<span style="margin-left: 2.5em;">Soda.</span><br /> +<span style="margin-left: 2.5em;">Lime.</span><br /> +<span style="margin-left: 2.5em;">Magnesia.</span><br /> +<span style="margin-left: 2.5em;">Peroxide of Iron.</span><br /> +<span style="margin-left: 2.5em;">Silicic Acid.</span><br /> +<span style="margin-left: 2.5em;">Phosphoric Acid.</span><br /> +<span style="margin-left: 2.5em;">Sulphuric Acid.</span><br /> +<span style="margin-left: 2.5em;">Chlorine.</span><br /> +</p> + +<p>And more rarely</p> + +<p> +<span style="margin-left: 2.5em;">Manganese.</span><br /> +<span style="margin-left: 2.5em;">Iodine.</span><br /> +<span style="margin-left: 2.5em;">Bromine.</span><br /> +<span style="margin-left: 2.5em;">Fluorine.</span><br /> +</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.<span class='pagenum'><a name="Page_10" id="Page_10">[Pg 10]</a></span></p> + +<p><i>Carbon.</i>—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.</p> + +<p><i>Carbonic Acid.</i>—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.</p> + +<p><i>Hydrogen</i> 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<span class='pagenum'><a name="Page_11" id="Page_11">[Pg 11]</a></span> cent. Its most important +compound is water, of which it forms one-ninth, the other eight-ninths +consisting of oxygen.</p> + +<p><i>Nitrogen</i> 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.</p> + +<p><i>Nitric Acid.</i>—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.<span class='pagenum'><a name="Page_12" id="Page_12">[Pg 12]</a></span></p> + +<p><i>Ammonia</i> 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.</p> + +<p><i>Oxygen</i> 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.</p> + +<p>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<span class='pagenum'><a name="Page_13" id="Page_13">[Pg 13]</a></span> 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.</p> + +<p>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 <i>elementary</i> 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.</p> + +<p>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.</p> + +<p>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.<span class='pagenum'><a name="Page_14" id="Page_14">[Pg 14]</a></span></p> + +<p><i>The Atmosphere as a source of the Organic Constituents of +Plants.</i>—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.</p> + +<p>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.<span class='pagenum'><a name="Page_15" id="Page_15">[Pg 15]</a></span></p> + +<p><i>Carbonic Acid.</i>—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.</p> + +<p><i>Ammonia.</i>—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<span class='pagenum'><a name="Page_16" id="Page_16">[Pg 16]</a></span> 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.</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Kemp</td><td align='left'></td><td align='left'></td><td align='left'>3·6800</td></tr> +<tr><td rowspan="2">Pierre</td><td align='left'>{12 feet above the surface</td><td align='left'></td><td align='left'>3·5000</td></tr> +<tr><td align='left'>{25 feet do. do.</td><td align='left'></td><td align='left'>0·5000</td></tr> +<tr><td align='left'>Graeger</td><td align='left'></td><td align='left'></td><td align='left'>0·3230</td></tr> +<tr><td rowspan="2">Fresenius</td><td align='left'>{By day</td><td align='left'></td><td align='left'>0·0980</td></tr> +<tr><td align='left'>{By night</td><td align='left'></td><td align='left'>0·1690</td></tr> +<tr><td rowspan="6">Ville</td><td align='left'>{</td><td align='left'>{Maximum</td><td align='left'>0·0317</td></tr> +<tr><td align='left'>{ In Paris</td><td align='left'>{Minimum</td><td align='left'>0·0177</td></tr> +<tr><td align='left'>{</td><td align='left'>{Mean</td><td align='left'>0·0237</td></tr> +<tr><td align='left'>{</td><td align='left'>{Maximum</td><td align='left'>0·0276</td></tr> +<tr><td align='left'>{ Environs</td><td align='left'>{Minimum</td><td align='left'>0·0165</td></tr> +<tr><td align='left'>{ of Paris</td><td align='left'>{Mean</td><td align='left'>0·0210</td></tr> +</table></div> + +<p>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,<span class='pagenum'><a name="Page_17" id="Page_17">[Pg 17]</a></span> 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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='left'></td><td align='left'></td><td align='left'>Grs.</td></tr> +<tr><td align='left'>Rain</td><td align='left'>{ Paris</td><td align='left'></td><td align='left'>0·2100</td></tr> +<tr><td align='left'></td><td align='left'>{ Liebfrauenberg</td><td align='left'></td><td align='left'>0·0350</td></tr> +<tr><td align='left'>Dew,</td><td align='left'>Liebfrauenberg</td><td align='left'>{ Maximum</td><td align='left'>0·4340</td></tr> +<tr><td align='left'></td><td align='left'></td><td align='left'>{ Minimum</td><td align='left'>0·0714</td></tr> +<tr><td align='left'></td><td align='left'>{ Liebfrauenberg</td><td align='left'></td><td align='left'>0·1790</td></tr> +<tr><td align='left'>Fog</td><td align='left'>{ Paris</td><td align='left'></td><td align='left'>9·6000</td></tr> +</table></div> + + +<p>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.</p> + +<p><i>Nitric Acid.</i>—The presence of nitric acid in the air appears to have +been first observed by Priestley at the<span class='pagenum'><a name="Page_18" id="Page_18">[Pg 18]</a></span> 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.</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td colspan="2"> Nitric Acid in Grains.</td><td colspan="2"> Ammonia in Grains.</td><td colspan="2"> Total Nitrogen in Grains.</td></tr> +<tr><td align='left'> </td><td align='left'> 1855.</td><td align='left'> 1856.</td><td align='left'> 1855.</td><td align='left'> 1856.</td><td align='left'> 1855.</td><td align='left'> 1856.</td></tr> +<tr><td align='left'>January</td><td align='left'> 230</td><td align='left'> 1564</td><td align='left'> 1244</td><td align='left'> 5,005</td><td align='left'> 1084</td><td align='left'> 4,526</td></tr> +<tr><td align='left'>February</td><td align='left'> 944</td><td align='left'> 544</td><td align='left'> 2337</td><td align='left'> 4,175</td><td align='left'> 2169</td><td align='left'> 3,579</td></tr> +<tr><td align='left'>March</td><td align='left'> 1102</td><td align='left'> 866</td><td align='left'> 4513</td><td align='left'> 2,108</td><td align='left'> 3995</td><td align='left'> 1,945</td></tr> +<tr><td align='left'>April</td><td align='left'> 325</td><td align='left'> 1063</td><td align='left'> 1141</td><td align='left'> 8,614</td><td align='left'> 1024</td><td align='left'> 7,369</td></tr> +<tr><td align='left'>May</td><td align='left'> 1840</td><td align='left'> 3024</td><td align='left'> 4206</td><td align='left'> 18,313</td><td align='left'> 3939</td><td align='left'> 15,863</td></tr> +<tr><td align='left'>June</td><td align='left'> 3303</td><td align='left'> 2046</td><td align='left'> 5574</td><td align='left'> 4,870</td><td align='left'> 5447</td><td align='left'> 4,540</td></tr> +<tr><td align='left'>July</td><td align='left'> 2680</td><td align='left'> 1191</td><td align='left'> 9620</td><td align='left'> 2,869</td><td align='left'> 8615</td><td align='left'> 2,670</td></tr> +<tr><td align='left'>August</td><td align='left'> 3577</td><td align='left'> 2125</td><td align='left'> 4769</td><td align='left'> 4,214</td><td align='left'> 4870</td><td align='left'> 4,021</td></tr> +<tr><td align='left'>September</td><td align='left'> 732</td><td align='left'> 1756</td><td align='left'> 3313</td><td align='left'> 5,972</td><td align='left'> 2917</td><td align='left'> 5,373</td></tr> +<tr><td align='left'>October</td><td align='left'> 4480</td><td align='left'> 2075</td><td align='left'> 7592</td><td align='left'> 3,921</td><td align='left'> 7414</td><td align='left'> 3,767</td></tr> +<tr><td align='left'>November</td><td align='left'> 1007</td><td align='left'> 1371</td><td align='left'> 3021</td><td align='left'> 2,591</td><td align='left'> 2749</td><td align='left'> 2,489</td></tr> +<tr><td align='left'>December</td><td align='left'> 664</td><td align='left'> 2035</td><td align='left'> 2438</td><td align='left'> 4,070</td><td align='left'> 2180</td><td align='left'> 3,352</td></tr> +<tr><td align='left'>Total in pounds for the whole year</td><td align='left'> 2·98</td><td align='left'> ·280</td><td align='left'> 7·11</td><td align='left'> 9·53</td><td align='left'> 6·63</td><td align='left'> 8·31</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_19" id="Page_19">[Pg 19]</a></span> 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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='left'></td><td align='left'>Grs.</td></tr> +<tr><td align='left'>Rain.</td><td align='left'>{Paris</td><td align='left'>0·0708</td></tr> +<tr><td align='left'></td><td align='left'>{Liebfrauenberg</td><td align='left'>0·0140</td></tr> +<tr><td align='left'>Dew.</td><td align='left'>{Maximum</td><td align='left'>0·0785</td></tr> +<tr><td align='left'></td><td align='left'>{Minimum</td><td align='left'>0·0030</td></tr> +<tr><td align='left'>Fog.</td><td align='left'>{Paris</td><td align='left'>0·7092</td></tr> +<tr><td align='left'></td><td align='left'>{Liebfrauenberg</td><td align='left'>0·0718</td></tr> +</table></div> + + +<p>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.</p> + +<p><i>Carburetted Hydrogen.</i>—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.</p> + +<p><i>Sulphuretted Hydrogen and Phosphuretted Hydrogen.</i>—The proportion of +these substances is almost infinitesimal;<span class='pagenum'><a name="Page_20" id="Page_20">[Pg 20]</a></span> but they are pretty general +constituents of the atmosphere, and are apparently derived from the +decomposition of animal and vegetable matters.</p> + +<p>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</p> + +<p> +<span style="margin-left: 2.5em;">2,400,000,000,000 tons,</span><br /> +</p> + +<p>and the ammonia, assuming it not to exceed one part in fifty millions, +must weigh</p> + +<p> +<span style="margin-left: 2.5em;">74,000,000 tons,</span><br /> +</p> + +<p>quantities amply sufficient to afford an abundant supply of these +elements to the whole vegetation of our globe.</p> + +<p><i>The Soil as a Source of the Organic Constituents of Plants.</i>—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.<span class='pagenum'><a name="Page_21" id="Page_21">[Pg 21]</a></span></p> + +<p>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.</p> + +<p>The term <i>humus</i> 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.</p> + +<p>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<span class='pagenum'><a name="Page_22" id="Page_22">[Pg 22]</a></span> 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.</p> + +<p>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,<span class='pagenum'><a name="Page_23" id="Page_23">[Pg 23]</a></span> 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,—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Ulmic acid from long Frisian turf</td><td align='left'>C<sub>40</sub></td><td align='left'>H<sub>18</sub></td><td align='left'>O<sub>16</sub></td></tr> +<tr><td align='left'>Humic acid from hard turf</td><td align='left'>C<sub>40</sub></td><td align='left'>H<sub>15</sub></td><td align='left'>O<sub>15</sub></td></tr> +<tr><td align='left'>Humic acid from arable soil</td><td align='left'>C<sub>40</sub></td><td align='left'>H<sub>16</sub></td><td align='left'>O<sub>16</sub></td></tr> +<tr><td align='left'>Humic acid from a pasture field</td><td align='left'>C<sub>40</sub></td><td align='left'>H<sub>14</sub></td><td align='left'>O<sub>14</sub></td></tr> +<tr><td align='left'>Geic acid</td><td align='left'>C<sub>40</sub></td><td align='left'>H<sub>15</sub></td><td align='left'>O<sub>17</sub></td></tr> +<tr><td align='left'>Apocrenic acid</td><td align='left'>C<sub>48</sub></td><td align='left'>H<sub>12</sub></td><td align='left'>O<sub>24</sub></td></tr> +<tr><td align='left'>Crenic acid</td><td align='left'>C<sub>24</sub></td><td align='left'>H<sub>12</sub></td><td align='left'>O<sub>16</sub></td></tr> +</table></div> + + +<p>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.</p> + +<p>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.</p> + +<p>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 +<i>direct</i> source of the organic constituents of plants, and is not +absorbed as such by their roots, although it is so <i>indirectly</i>, 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<span class='pagenum'><a name="Page_24" id="Page_24">[Pg 24]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_25" id="Page_25">[Pg 25]</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_26" id="Page_26">[Pg 26]</a></span> 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 <i>physical</i> 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.</p> + +<p>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<span class='pagenum'><a name="Page_27" id="Page_27">[Pg 27]</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_28" id="Page_28">[Pg 28]</a></span> 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<span class='pagenum'><a name="Page_29" id="Page_29">[Pg 29]</a></span> 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.</p> + +<p>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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Barley.</td><td align='right'>Vetches.</td></tr> +<tr><td align='left'>Muriate of Ammonia</td><td align='right'>257·2</td><td align='right'>176·4</td></tr> +<tr><td align='left'>Carbonate of Ammonia</td><td align='right'>123·6</td><td align='right'>173·8</td></tr> +<tr><td align='left'>Sulphate of Ammonia</td><td align='right'>203·6</td><td align='right'>125·2</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_30" id="Page_30">[Pg 30]</a></span></p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_31" id="Page_31">[Pg 31]</a></span> in the soil after the +experiment and in the seed was determined.</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='center'></td><td align='right'>Grains.</td></tr> +<tr><td align='center'>Nitrogen</td><td align='left'>in the dry plants</td><td align='right'>1·737</td><td align='right'>}</td></tr> +<tr><td align='center'>"</td><td align='left'>remaining in the soil</td><td align='right'>0·697</td><td align='right'>}</td><td align='right'>2·434</td></tr> +<tr><td align='center'>"</td><td align='left'>in the nitrate of potash</td><td align='right'>2·370</td><td align='right'>}</td></tr> +<tr><td align='center'>"</td><td align='left'>in the seeds</td><td align='right'>0·029</td><td align='right'>}</td><td align='right'>2·399</td></tr> +<tr><td align='center'></td><td align='center'></td><td align='center'></td><td align='center'></td><td align='right'>———</td></tr> +<tr><td align='center'></td><td colspan="2">Difference</td><td align='center'></td><td align='right'>0·035</td></tr> +</table></div> + + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_32" id="Page_32">[Pg 32]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_33" id="Page_33">[Pg 33]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_34" id="Page_34">[Pg 34]</a></span> 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.</p> + +<p><i>Source of the Inorganic Constituents of Plants.</i>—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<span class='pagenum'><a name="Page_35" id="Page_35">[Pg 35]</a></span> +itself; without phosphoric acid, weak but upright; and without sulphuric +acid, though normal in form, the plant was feeble, and produced no +fruit.</p> + +<p><i>Manner in which the Constituents of Plants are absorbed.</i>—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.</p> + +<p><i>Water.</i>—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:<span class='pagenum'><a name="Page_36" id="Page_36">[Pg 36]</a></span>—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Wheat</td><td align='right'>113,527</td></tr> +<tr><td align='left'>Barley</td><td align='right'>120,025</td></tr> +<tr><td align='left'>Beans</td><td align='right'>112,231</td></tr> +<tr><td align='left'>Peas</td><td align='right'>109,082</td></tr> +<tr><td align='left'>Clover, cut 28th June</td><td align='right'>55,093</td></tr> +</table></div> + +<p>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.</p> + + +<h4><span class="smcap">Table I.</span>—<i>Showing the Number of Grains of Water given off by the Plants +during stated divisional Periods of their Growth.</i></h4> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td rowspan="2">Description of Plant.</td><td align='left'>9 Days.</td><td align='left'>31 Days.</td><td align='left'>27 Days.</td><td align='left'>34 Days.</td><td align='left'>30 Days.</td><td align='left'>14 Days.</td><td align='left'> 27 Days.</td></tr> +<tr><td align='left'> From Mar. 19 to Mar. 28.</td><td align='left'>From Mar. 28 to Apr. 28.</td><td align='left'>From Apr. 28 to May 25.</td><td align='left'>From May 25 to June 28.</td><td align='left'>From June 28 to July 28.</td><td align='left'>From July 28 to Aug. 11.</td><td align='left'> From Aug. 11 to Sept. 7.</td></tr> +<tr><td align='left'>Wheat</td><td align='left'> 129</td><td align='left'> 1268</td><td align='left'> 4,385</td><td align='left'> 40,030</td><td align='left'> 46,060</td><td align='left'> 15,420</td><td align='left'> 6235</td></tr> +<tr><td align='left'>Barley</td><td align='left'> 129</td><td align='left'> 1867</td><td align='left'> 12,029</td><td align='left'> 37,480</td><td align='left'> 45,060</td><td align='left'> 17,046</td><td align='left'> 6414</td></tr> +<tr><td align='left'>Beans</td><td align='left'> 88</td><td align='left'> 1854</td><td align='left'> 4,846</td><td align='left'> 30,110</td><td align='left'> 58,950</td><td align='left'> 12,626</td><td align='left'> 3657</td></tr> +<tr><td align='left'>Pease</td><td align='left'> 101</td><td align='left'> 1332</td><td align='left'> 2,873</td><td align='left'> 36,715</td><td align='left'> 62,780</td><td align='left'> 5,281</td><td align='left'> ...</td></tr> +<tr><td align='left'>Clover</td><td align='left'> 400</td><td align='left'> 1645</td><td align='left'> 2,948</td><td align='left'> 50,100</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td></tr> +</table></div> + + +<h4><span class="smcap">Table II.</span>—<i>Showing the average daily Loss of Water (in Grains) by the +Plants, within several stated divisional Periods of their Growth.</i></h4> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td rowspan="2">Description of Plant.</td><td align='left'>9 Days.</td><td align='left'>31 Days.</td><td align='left'>27 Days.</td><td align='left'>34 Days.</td><td align='left'>30 Days.</td><td align='left'>14 Days.</td><td align='left'> 27 Days.</td></tr> +<tr><td align='left'> From Mar. 19 to Mar. 28.</td><td align='left'>From Mar. 28 to Apr. 28.</td><td align='left'>From Apr. 28 to May 25.</td><td align='left'>From May 25 to June 28.</td><td align='left'>From June 28 to July 28.</td><td align='left'>From July 28 to Aug. 11.</td><td align='left'> From Aug. 11 to Sept. 7.</td></tr> +<tr><td align='left'>Wheat</td><td align='left'> 14·3</td><td align='left'> 40·9</td><td align='left'> 162·4</td><td align='left'> 1177·4</td><td align='left'> 1535·3</td><td align='left'> 1101·4</td><td align='left'> 230·9</td></tr> +<tr><td align='left'>Barley</td><td align='left'> 14·3</td><td align='left'> 60·2</td><td align='left'> 445·5</td><td align='left'> 1102·3</td><td align='left'> 1502·0</td><td align='left'> 1217·6</td><td align='left'> 237·5</td></tr> +<tr><td align='left'>Beans</td><td align='left'> 9·7</td><td align='left'> 59·8</td><td align='left'> 179·5</td><td align='left'> 885·6</td><td align='left'> 1965·0</td><td align='left'> 901·8</td><td align='left'> 135·4</td></tr> +<tr><td align='left'>Peas</td><td align='left'> 11·2</td><td align='left'> 42·9</td><td align='left'> 106·4</td><td align='left'> 1079·8</td><td align='left'> 2092·7</td><td align='left'> 377·2</td><td align='left'> ...</td></tr> +<tr><td align='left'>Clover</td><td align='left'> 44·4</td><td align='left'> 53·0</td><td align='left'> 109·2</td><td align='left'> 1473·5</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td></tr> +</table></div> +<p><span class='pagenum'><a name="Page_37" id="Page_37">[Pg 37]</a></span></p> + +<p>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.</p> + +<p><i>Carbonic Acid.</i>—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,<span class='pagenum'><a name="Page_38" id="Page_38">[Pg 38]</a></span> 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.</p> + +<p><i>Ammonia and Nitric Acid.</i>—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.</p> + +<p><i>Inorganic Constituents.</i>—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<span class='pagenum'><a name="Page_39" id="Page_39">[Pg 39]</a></span> 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.</p> + +<p>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.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_40" id="Page_40">[Pg 40]</a></span></p> +<h2>CHAPTER II.</h2> + +<h3>THE PROXIMATE CONSTITUENTS OF PLANTS.</h3> + + +<p>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.</p> + +<p><i>1st. The Saccharine and Amylaceous Constituents.</i>—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.</p> + +<p><i>Cellulose.</i>—This substance forms the fundamental part<span class='pagenum'><a name="Page_41" id="Page_41">[Pg 41]</a></span> 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—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>From pith of Elder-tree.</td><td align='right'>Spongioles of roots.</td></tr> +<tr><td align='left'>Carbon</td><td align='right'>43·37</td><td align='right'>43·00</td></tr> +<tr><td align='left'>Hydrogen</td><td align='right'>6·04</td><td align='right'>6·18</td></tr> +<tr><td align='left'>Oxygen</td><td align='right'>50·59</td><td align='right'>50·82</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td><td align='right'>100·00</td></tr> +</table></div> + +<p>It is represented chemically by the formula, C<sub>24</sub>H<sub>21</sub>O<sub>21</sub>, which +shows it to be a compound of 24 atoms of carbon with 21 of hydrogen and +21 of oxygen.</p> + +<p><i>Incrusting matter.</i>—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.</p> + +<p><i>Starch.</i>—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<span class='pagenum'><a name="Page_42" id="Page_42">[Pg 42]</a></span> 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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Carbon</td><td align='right'>44·47</td></tr> +<tr><td align='left'>Hydrogen</td><td align='right'>6·28</td></tr> +<tr><td align='left'>Oxygen</td><td align='right'>49·25</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +</table></div> + + +<p>and its composition is represented by the formula C<sub>12</sub>H<sub>10</sub>O<sub>10</sub>, 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.</p> + +<p><i>Lichen Starch</i> is found in most species of lichens, and is +distinguished from common starch by producing a green<span class='pagenum'><a name="Page_43" id="Page_43">[Pg 43]</a></span> colour with +iodine. Its composition is the same as that of ordinary starch.</p> + +<p><i>Inuline.</i>—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<sub>24</sub>H<sub>21</sub>O<sub>21</sub>.</p> + +<p><i>Gum</i> 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.</p> + +<p><i>Dextrine.</i>—When starch is exposed to a heat of about 400°, or when +treated with sulphuric acid, or with a substance extracted from malt +called <i>diastase</i>, 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.</p> + +<p><i>Sugar.</i>—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.</p> + +<p><i>Cane Sugar.</i>—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,<span class='pagenum'><a name="Page_44" id="Page_44">[Pg 44]</a></span> 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—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Carbon</td><td align='right'>42·22</td></tr> +<tr><td align='left'>Hydrogen</td><td align='right'>6·60</td></tr> +<tr><td align='left'>Oxygen</td><td align='right'>51·18</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +</table></div> + +<p>and its chemical formula is C<sub>12</sub>H<sub>11</sub>O<sub>11</sub>.</p> + +<p><i>Grape Sugar</i> 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—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Carbon</td><td align='right'>40·00</td></tr> +<tr><td align='left'>Hydrogen</td><td align='right'>6·66</td></tr> +<tr><td align='left'>Oxygen</td><td align='right'>53·34</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +</table></div> + + +<p>and its formula is C<sub>12</sub>H<sub>12</sub>O<sub>12</sub>; but when crystallised it contains +two equivalents of water, and is then represented by the formula +C<sub>12</sub>H<sub>12</sub>O<sub>12</sub> + 2H<sub>2</sub>O.</p> + +<p>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.</p> + +<p><i>Mucilage</i> is the name applied to the substance existing<span class='pagenum'><a name="Page_45" id="Page_45">[Pg 45]</a></span> 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<sub>24</sub>H<sub>19</sub>O<sub>19</sub>, or C<sub>12</sub>H<sub>10</sub>O<sub>10</sub>; and in the latter case it +must be identical with starch and gum.</p> + +<p>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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='left'></td><td align='left'></td><td align='left'>Water.</td></tr> +<tr><td align='left'>Grape sugar,</td><td align='left'>C<sub>12</sub>H<sub>12</sub>O<sub>12</sub></td><td align='left'>C<sub>24</sub>H<sub>24</sub>O<sub>24</sub></td><td align='left'>C<sub>24</sub> + 24</td></tr> +<tr><td align='left'>Cane sugar,</td><td align='left'>C<sub>12</sub>H<sub>11</sub>O<sub>11</sub></td><td align='left'>C<sub>24</sub>H<sub>22</sub>O<sub>22</sub></td><td align='left'>C<sub>24</sub> + 22</td></tr> +<tr><td align='left'>Cellulose,</td><td align='left'>C<sub>24</sub>H<sub>21</sub>O<sub>21</sub></td><td align='left'>C<sub>24</sub>H<sub>21</sub>O<sub>21</sub></td><td align='left'>C<sub>24</sub> + 21</td></tr> +<tr><td align='left'>Inuline,</td><td align='left'>C<sub>24</sub>H<sub>21</sub>O<sub>21</sub></td><td align='left'>C<sub>24</sub>H<sub>21</sub>O<sub>21</sub></td><td align='left'>C<sub>24</sub> + 21</td></tr> +<tr><td align='left'>Starch,</td><td align='left'>C<sub>12</sub>H<sub>10</sub>O<sub>10</sub></td><td align='left'>C<sub>24</sub>H<sub>20</sub>O<sub>20</sub></td><td align='left'>C<sub>24</sub> + 20</td></tr> +<tr><td align='left'>Dextrine,</td><td align='left'>C<sub>12</sub>H<sub>10</sub>O<sub>10</sub></td><td align='left'>C<sub>24</sub>H<sub>20</sub>O<sub>20</sub></td><td align='left'>C<sub>24</sub> + 20</td></tr> +<tr><td align='left'>Gum,</td><td align='left'>C<sub>12</sub>H<sub>10</sub>O<sub>10</sub></td><td align='left'>C<sub>24</sub>H<sub>20</sub>O<sub>20</sub></td><td align='left'>C<sub>24</sub> + 20</td></tr> +<tr><td align='left'>Mucilage,</td><td align='left'>C<sub>12</sub>H<sub>10</sub>O<sub>10</sub></td><td align='left'>C<sub>24</sub>H<sub>20</sub>O<sub>20</sub></td><td align='left'>C<sub>24</sub> + 20</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_46" id="Page_46">[Pg 46]</a></span> to be converted into starch, and we shall afterwards see that +such changes do actually occur in the plant during the process of +germination.</p> + +<p><i>Pectine and Pectic Acid.</i>—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.</p> + +<p><i>2d. Oily or Fatty Matters.</i>—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<span class='pagenum'><a name="Page_47" id="Page_47">[Pg 47]</a></span> 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<sub>3</sub>H<sub>2</sub>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.</p> + +<p><i>Margaric Acid</i> 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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Carbon</td><td align='right'>75·56</td></tr> +<tr><td align='left'>Hydrogen</td><td align='right'>12·59</td></tr> +<tr><td align='left'>Oxygen</td><td align='right'>11·85</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +</table></div> + +<p>and its formula C<sub>34</sub>H<sub>34</sub>O<sub>4</sub>.</p> + +<p><i>Stearic Acid.</i>—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<sub>36</sub>H<sub>36</sub>O<sub>4</sub>.</p> + +<p><i>Oleic Acid.</i>—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<sub>36</sub>H<sub>34</sub>O<sub>4</sub>, while that from +linseed oil is C<sub>46</sub>H<sub>38</sub>O<sub>6</sub>, but this is still doubtful.</p> + +<p>Other fatty acids have been detected in palm oil, cocoa-nut oil, &c. +&c., which so closely resemble margaric<span class='pagenum'><a name="Page_48" id="Page_48">[Pg 48]</a></span> 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.</p> + +<p><i>Wax</i> 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<sub>54</sub>H<sub>54</sub>O<sub>4</sub>. The latter has the formula C<sub>92</sub>H<sub>92</sub>O<sub>4</sub>. 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<sub>48</sub>H<sub>50</sub>O<sub>2</sub>. 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.</p> + +<p><i>3d. Nitrogenous or Albuminous Constituents of Plants and Animals.</i>—The +nitrogenous constituents of plants and animals are so closely allied, +both in properties and composition, that they may be most advantageously +considered together.</p> + +<p><i>Albumen.</i>—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<span class='pagenum'><a name="Page_49" id="Page_49">[Pg 49]</a></span> 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.</p> + +<p>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—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>From Wheat.</td><td align='right'>From Potatoes.</td><td align='right'>From Blood.</td><td align='right'>From White of Egg.</td></tr> +<tr><td align='left'>Carbon</td><td align='right'>53·7</td><td align='right'>53·1</td><td align='right'>53·4</td><td align='right'>53·0</td></tr> +<tr><td align='left'>Hydrogen</td><td align='right'>7·1</td><td align='right'>7·2</td><td align='right'>7·0</td><td align='right'>7·1</td></tr> +<tr><td align='left'>Nitrogen</td><td align='right'>15·6</td><td align='right'>...</td><td align='right'>15·5</td><td align='right'>15·6</td></tr> +<tr><td align='left'>Oxygen</td><td align='right'>} {</td><td align='right'>...</td><td align='right'>22·1</td><td align='right'>22·9</td></tr> +<tr><td align='left'>Sulphur</td><td align='right'>}23·6{</td><td align='right'>0·97</td><td align='right'>1·6</td><td align='right'>1·1</td></tr> +<tr><td align='left'>Phosphorus</td><td align='right'>} {</td><td align='right'>...</td><td align='right'>0·4</td><td align='right'>0·3</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='left'></td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>100·0</td><td align='left'></td><td align='right'>100·0</td><td align='right'>100·0</td></tr> +</table></div> + +<p>Closely allied to vegetable albumen is the substance known by the name +of <i>glutin</i>, 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.</p> + +<p><i>Vegetable Fibrine.</i>—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 <i>glutin</i> +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<span class='pagenum'><a name="Page_50" id="Page_50">[Pg 50]</a></span> 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.</p> + +<p><i>Animal Fibrine</i> 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—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Wheat Flour.</td><td align='right'>Blood.</td><td align='right'>Flesh.</td></tr> +<tr><td align='left'>Carbon</td><td align='right'>53·1</td><td align='right'>52·5</td><td align='right'>53·3</td></tr> +<tr><td align='left'>Hydrogen</td><td align='right'>7·0</td><td align='right'>6·9</td><td align='right'>7·1</td></tr> +<tr><td align='left'>Nitrogen</td><td align='right'>15·6</td><td align='right'>15·5</td><td align='right'>15·3</td></tr> +<tr><td align='left'>Oxygen</td><td align='right'>23·2</td><td align='right'>24·0</td><td align='right'>23·1</td></tr> +<tr><td align='left'>Sulphur</td><td align='right'>1·1</td><td align='right'>1·1</td><td align='right'>1·2</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>100·0</td><td align='right'>100·0</td><td align='right'>100·0</td></tr> +</table></div> + + +<p><i>Caseine.</i>—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 <i>legumine,</i> from almonds +<i>emulsine</i>, and from oats <i>avenine</i>; 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.<span class='pagenum'><a name="Page_51" id="Page_51">[Pg 51]</a></span></p> + +<p><i>Animal Caseine</i> 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.</p> + +<p>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—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td colspan="2">From Peas.</td></tr> +<tr><td align='left'>Carbon</td><td align='left'>50·6</td><td align='left'>50·7</td></tr> +<tr><td align='left'>Hydrogen</td><td align='left'>6·8</td><td align='left'>6·6</td></tr> +<tr><td align='left'>Nitrogen</td><td align='left'>16·5</td><td align='left'>15·8</td></tr> +<tr><td align='left'>Oxygen</td><td align='left'>25·6</td><td align='left'>23·8</td></tr> +<tr><td align='left'>Sulphur</td><td align='left'>0·5</td><td align='left'>0·8</td></tr> +<tr><td align='left'>Phosphorus</td><td align='left'>...</td><td align='left'>2·3</td></tr> +<tr><td align='left'></td><td align='left'>——</td><td align='left'>——</td></tr> +<tr><td align='left'></td><td align='left'>100·0</td><td align='left'>100·0</td></tr> +</table></div> + +<p>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.</p> + +<p>The composition of animal caseine differs from this principally in the +amount of carbon. Its composition is—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Carbon</td><td align='right'>53·6</td></tr> +<tr><td align='left'>Hydrogen</td><td align='right'>7·1</td></tr> +<tr><td align='left'>Nitrogen</td><td align='right'>15·8</td></tr> +<tr><td align='left'>Oxygen</td><td align='right'>22·5</td></tr> +<tr><td align='left'>Sulphur</td><td align='right'>1·0</td></tr> +<tr><td align='left'></td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>100·0</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_52" id="Page_52">[Pg 52]</a></span></p> + +<p>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 <i>proteine</i>, with different quantities of sulphur and phosphorus. The +composition of proteine, according to his newest experiments, is—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Carbon</td><td align='right'>54·0</td></tr> +<tr><td align='left'>Hydrogen</td><td align='right'>7·1</td></tr> +<tr><td align='left'>Nitrogen</td><td align='right'>16·0</td></tr> +<tr><td align='left'>Oxygen</td><td align='right'>21·4</td></tr> +<tr><td align='left'>Sulphur</td><td align='right'>1·5</td></tr> +<tr><td align='left'></td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>100·0</td></tr> +</table></div> + + +<p>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;<span class='pagenum'><a name="Page_53" id="Page_53">[Pg 53]</a></span> 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.</p> + +<p><i>Diastase</i> 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.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_54" id="Page_54">[Pg 54]</a></span></p> +<h2>CHAPTER III.</h2> + +<h3>THE CHANGES WHICH TAKE PLACE IN THE FOOD OF PLANTS DURING THEIR GROWTH.</h3> + + +<p>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.</p> + +<p><i>Changes occurring during Germination.</i>—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<span class='pagenum'><a name="Page_55" id="Page_55">[Pg 55]</a></span> 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<span class='pagenum'><a name="Page_56" id="Page_56">[Pg 56]</a></span> +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<span class='pagenum'><a name="Page_57" id="Page_57">[Pg 57]</a></span> 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.</p> + +<p><i>Changes occurring during the After-growth of the Plant.</i>—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.</p> + +<p><i>Decomposition of Carbonic Acid.</i>—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,<span class='pagenum'><a name="Page_58" id="Page_58">[Pg 58]</a></span> 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 (<i>Vinca +minor</i>) 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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Volume of the air.</td><td align='right'>Nitrogen.</td><td align='right'>Oxygen.</td><td align='right'>Carbonic Acid.</td></tr> +<tr><td align='left'>Before the experiment,</td><td align='right'>5746</td><td align='right'>4199</td><td align='right'>1116</td><td align='right'>431</td></tr> +<tr><td align='left'>After "</td><td align='right'>5746</td><td align='right'>4338</td><td align='right'>1408</td><td align='right'>0</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>——</td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'>Difference,</td><td align='right'>0</td><td align='right'>+139</td><td align='right'>+292</td><td align='right'>-431</td></tr> +</table></div> + + +<p>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<span class='pagenum'><a name="Page_59" id="Page_59">[Pg 59]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_60" id="Page_60">[Pg 60]</a></span> 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.</p> + +<p>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 <i>Arum +maculatum</i> and some other plants, is so great as to raise the +temperature of the flower 10° or 12° above that of the surrounding air.</p> + +<p><i>Decomposition of Water in the Plant.</i>—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<span class='pagenum'><a name="Page_61" id="Page_61">[Pg 61]</a></span> 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:</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>12</td><td align='left'>equivalents of</td><td align='left'>carbonic acid,</td><td align='left'>C<sub>12</sub>O<sub>12</sub>O<sub>12</sub></td></tr> +<tr><td align='left'>12</td><td align='center'>"</td><td align='left'>water,</td><td align='left'>H<sub>12</sub>O<sub>12</sub></td></tr> +<tr><td align='left'>1</td><td align='center'>"</td><td align='left'>sugar, and 24 of ox.</td><td align='left'>C<sub>12</sub>H<sub>12</sub>O<sub>12</sub> + O<sub>24</sub></td></tr> +</table></div> + + +<p>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.</p> + +<p><i>Decomposition of Ammonia.</i>—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<span class='pagenum'><a name="Page_62" id="Page_62">[Pg 62]</a></span> 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.</p> + +<p><i>Decomposition of Nitric Acid.</i>—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 <i>facts</i>; 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.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_63" id="Page_63">[Pg 63]</a></span></p> +<h2>CHAPTER IV.</h2> + +<h3>THE INORGANIC CONSTITUENTS OF PLANTS.</h3> + + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_64" id="Page_64">[Pg 64]</a></span> 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:—</p> + + +<p><i>Table showing the quantity of inorganic matters in 100 parts of +different plants dried at 212°.</i></p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>SEEDS.</td></tr> +<tr><td align='left'>Wheat</td><td align='right'>1·97</td></tr> +<tr><td align='left'>Barley</td><td align='right'>2·48</td></tr> +<tr><td align='left'>Oats (with husk)</td><td align='right'>3·80</td></tr> +<tr><td align='left'>Oats (without husk)</td><td align='right'>2·06</td></tr> +<tr><td align='left'>Rye</td><td align='right'>2·00</td></tr> +<tr><td align='left'>Millet</td><td align='right'>3·60</td></tr> +<tr><td align='left'>Rice</td><td align='right'>0·37</td></tr> +<tr><td align='left'>Maize</td><td align='right'>1·20</td></tr> +<tr><td align='left'>Peas</td><td align='right'>2·88</td></tr> +<tr><td align='left'>Beans</td><td align='right'>3·22</td></tr> +<tr><td align='left'>Kidney Beans</td><td align='right'>4·09</td></tr> +<tr><td align='left'>Lentils</td><td align='right'>2·51</td></tr> +<tr><td align='left'>Tares</td><td align='right'>2·60</td></tr> +<tr><td align='left'>Buckwheat</td><td align='right'>2·13</td></tr> +<tr><td align='left'>Linseed</td><td align='right'>4·40</td></tr> +<tr><td align='left'>Hemp seed</td><td align='right'>5·60</td></tr> +<tr><td align='left'>Rape seed</td><td align='right'>4·35</td></tr> +<tr><td align='left'>Indian Rape-seed<a name="FNanchor_A_1" id="FNanchor_A_1"></a><a href="#Footnote_A_1" class="fnanchor">[A]</a></td><td align='right'>4·06</td></tr> +<tr><td align='left'>Sunflower</td><td align='right'>3·26</td></tr> +<tr><td align='left'>Cotton seed</td><td align='right'>5·93</td></tr> +<tr><td align='left'>Guinea Corn</td><td align='right'>1·99</td></tr> +<tr><td align='left'>Gold of Pleasure</td><td align='right'>4·10</td></tr> +<tr><td align='left'>White Mustard</td><td align='right'>4·15</td></tr> +<tr><td align='left'>Black Mustard</td><td align='right'>4·31</td></tr> +<tr><td align='left'>Poppy</td><td align='right'>6·56</td></tr> +<tr><td align='left'>Niger seed (<i>Guizotia oleifera</i>)</td><td align='right'>7·00</td></tr> +<tr><td align='left'>Earth nut</td><td align='right'>3·88</td></tr> +<tr><td align='left'>Sweet Almond</td><td align='right'>4·90</td></tr> +<tr><td align='left'>Horse-chesnut</td><td align='right'>2·81</td></tr> +<tr><td align='left'>Grape</td><td align='right'>2·76</td></tr> +<tr><td align='left'>Clover</td><td align='right'>6·19</td></tr> +<tr><td align='left'>Turnip</td><td align='right'>3·98</td></tr> +<tr><td align='left'>Carrot</td><td align='right'>10·03</td></tr> +<tr><td align='left'>Sainfoin</td><td align='right'>5·27</td></tr> +<tr><td align='left'>Italian Ryegrass</td><td align='right'>6·91</td></tr> +<tr><td align='left'>Mangold-Wurzel</td><td align='right'>6·58</td></tr> +<tr><td align='left'>STRAWS AND STEMS.</td></tr> +<tr><td align='left'>Wheat</td><td align='right'>4·54</td></tr> +<tr><td align='left'>Barley</td><td align='right'>4·99</td></tr> +<tr><td align='left'>Oat</td><td align='right'>7·24</td></tr> +<tr><td align='left'>Winter Rye</td><td align='right'>5·15</td></tr> +<tr><td align='left'>Summer Rye</td><td align='right'>5·78</td></tr> +<tr><td align='left'>Millet</td><td align='right'>8·32</td></tr> +<tr><td align='left'>Maize</td><td align='right'>3·60</td></tr> +<tr><td align='left'>Pea</td><td align='right'>4·81</td></tr> +<tr><td align='left'>Bean</td><td align='right'>6·59</td></tr> +<tr><td align='left'>Tares</td><td align='right'>6·00</td></tr> +<tr><td align='left'>Lentil</td><td align='right'>5·38</td></tr> +<tr><td align='left'>Buckwheat</td><td align='right'>4·50</td></tr> +<tr><td align='left'>Hops</td><td align='right'>4·42</td></tr> +<tr><td align='left'>Flax straw</td><td align='right'>4·25</td></tr> +<tr><td align='left'>Hemp</td><td align='right'>4·14</td></tr> +<tr><td align='left'>Gold of Pleasure</td><td align='right'>6·05</td></tr> +<tr><td align='left'>Rape</td><td align='right'>4·41</td></tr> +<tr><td align='left'>Potato</td><td align='right'>14·90</td></tr> +<tr><td align='left'>Jerusalem Artichoke</td><td align='right'>4·40</td></tr> +<tr><td align='left'>ENTIRE PLANT.</td></tr> +<tr><td align='left'>Potato</td><td align='right'>17·70</td></tr> +<tr><td align='left'>Spurry</td><td align='right'>10·06</td></tr> +<tr><td align='left'><span class='pagenum'><a name="Page_65" id="Page_65">[Pg 65]</a></span></td></tr> +<tr><td align='left'>Red Clover</td><td align='right'>8·79</td></tr> +<tr><td align='left'>White Clover</td><td align='right'>8·72</td></tr> +<tr><td align='left'>Yellow Clover</td><td align='right'>8·56</td></tr> +<tr><td align='left'>Crimson Clover (<i>T. incarnatum</i>)</td><td align='right'>10·81</td></tr> +<tr><td align='left'>Cow Grass (<i>T. medium</i>)</td><td align='right'>11·31</td></tr> +<tr><td align='left'>Sainfoin</td><td align='right'>6·51</td></tr> +<tr><td align='left'>Ryegrass</td><td align='right'>6·42</td></tr> +<tr><td align='left'>Meadow Foxtail (<i>Alopecurus pratensis</i>)</td><td align='right'>7·81</td></tr> +<tr><td align='left'>Sweet-scented Vernal Grass (<i>Anthoxanthum odoratum</i>)</td><td align='right'>6·32</td></tr> +<tr><td align='left'>Downy Oat Grass (<i>Avena pubescens</i>)</td><td align='right'>5·22</td></tr> +<tr><td align='left'>Bromus erectus</td><td align='right'>5·21</td></tr> +<tr><td align='left'>Bromus mollis</td><td align='right'>5·82</td></tr> +<tr><td align='left'>Cynosurus cristatus</td><td align='right'>6·38</td></tr> +<tr><td align='left'>Dactylis glomeratus</td><td align='right'>5·31</td></tr> +<tr><td align='left'>Festuca duriuscula</td><td align='right'>5·42</td></tr> +<tr><td align='left'>Holcus lanatus</td><td align='right'>6·37</td></tr> +<tr><td align='left'>Hordeum pratense</td><td align='right'>5·67</td></tr> +<tr><td align='left'>Lolium perenne</td><td align='right'>7·54</td></tr> +<tr><td align='left'>Poa annua</td><td align='right'>2·83</td></tr> +<tr><td align='left'>Poa pratensis</td><td align='right'>5·94</td></tr> +<tr><td align='left'>Poa trivialis</td><td align='right'>8·33</td></tr> +<tr><td align='left'>Phleum pratense</td><td align='right'>5·29</td></tr> +<tr><td align='left'>Plantago lanceolata</td><td align='right'>8·68</td></tr> +<tr><td align='left'>Poterium Sanguisorba</td><td align='right'>7·97</td></tr> +<tr><td align='left'>Yarrow</td><td align='right'>13·45</td></tr> +<tr><td align='left'>Rape Kale</td><td align='right'>8·00</td></tr> +<tr><td align='left'>Cow Cabbage</td><td align='right'>10·00</td></tr> +<tr><td align='left'>Asparagus</td><td align='right'>6·40</td></tr> +<tr><td align='left'>Parsley</td><td align='right'>1·10</td></tr> +<tr><td align='left'>Furze</td><td align='right'>3·11</td></tr> +<tr><td align='left'>Chamomile (<i>Anthemis arvensis</i>)</td><td align='right'>9·66</td></tr> +<tr><td align='left'>Wild Chamomile (<i>Matricaria Chamomilla</i>)</td><td align='right'>9·10</td></tr> +<tr><td align='left'>Corn Cockle (<i>Agrostemma Githago</i>)</td><td align='right'>13·20</td></tr> +<tr><td align='left'>Corn Blue Bottle (<i>Centaurea Cyanus</i>)</td><td align='right'>7·32</td></tr> +<tr><td align='left'>Foxglove</td><td align='right'>10·89</td></tr> +<tr><td align='left'>Hemlock (<i>Conium maculatum</i>)</td><td align='right'>12·80</td></tr> +<tr><td align='left'>Sweet Rush (<i>Acorus Calamus</i>)</td><td align='right'>6·90</td></tr> +<tr><td align='left'>Common Reed (<i>Arundo Phragmites</i>)</td><td align='right'>1·44</td></tr> +<tr><td align='left'>Celandine (<i>Chelidonium majus</i>)</td><td align='right'>6·85</td></tr> +<tr><td align='left'>Equisetum fluviatile</td><td align='right'>23·60</td></tr> +<tr><td align='left'>Equisetum hyemale</td><td align='right'>11·80</td></tr> +<tr><td align='left'> " arvense</td><td align='right'>13·80</td></tr> +<tr><td align='left'> " linosum</td><td align='right'>15·50</td></tr> +<tr><td align='left'>Fucus nodosus</td><td align='right'>19·03</td></tr> +<tr><td align='left'>Fucus vesiculosus</td><td align='right'>27·63</td></tr> +<tr><td align='left'>Laminaria digitata</td><td align='right'>39·68</td></tr> +<tr><td align='left'>LEAVES.</td></tr> +<tr><td align='left'>Turnip</td><td align='right'>9·37</td></tr> +<tr><td align='left'>Beet</td><td align='right'>20·30</td></tr> +<tr><td align='left'>Kohl-rabi</td><td align='right'>18·54</td></tr> +<tr><td align='left'>Carrot</td><td align='right'>10·95</td></tr> +<tr><td align='left'>Jerusalem Artichoke</td><td align='right'>28·30</td></tr> +<tr><td align='left'>Hemp</td><td align='right'>22·00</td></tr> +<tr><td align='left'>Hop</td><td align='right'>17·25</td></tr> +<tr><td align='left'>Tobacco</td><td align='right'>22·62</td></tr> +<tr><td align='left'>Spinach</td><td align='right'>19·76</td></tr> +<tr><td align='left'>Chicory</td><td align='right'>15·67</td></tr> +<tr><td align='left'>Poplar</td><td align='right'>23·00</td></tr> +<tr><td align='left'>Red Beech</td><td align='right'>6·00</td></tr> +<tr><td align='left'>White Beech</td><td align='right'>10·51</td></tr> +<tr><td align='left'>Oak</td><td align='right'>9·80</td></tr> +<tr><td align='left'>Elm</td><td align='right'>16·33</td></tr> +<tr><td align='left'>Horse-chesnut</td><td align='right'>9·08</td></tr> +<tr><td align='left'>Maple</td><td align='right'>28·05</td></tr> +<tr><td align='left'>Ash</td><td align='right'>14·76</td></tr> +<tr><td align='left'>Fir</td><td align='right'>2·31</td></tr> +<tr><td align='left'>Acacia</td><td align='right'>18·20</td></tr> +<tr><td align='left'>Olive</td><td align='right'>6·45</td></tr> +<tr><td align='left'>Orange</td><td align='right'>13·73</td></tr> +<tr><td align='left'>Potato</td><td align='right'>15·10</td></tr> +<tr><td align='left'>Tussac Grass</td><td align='right'>7·15</td></tr> +<tr><td align='left'>ROOTS AND TUBERS.</td></tr> +<tr><td align='left'>Potato</td><td align='right'>4·16</td></tr> +<tr><td align='left'>Jerusalem Artichoke</td><td align='right'>5·38</td></tr> +<tr><td align='left'>Turnip</td><td align='right'>13·64</td></tr> +<tr><td align='left'>Beet</td><td align='right'>8·27</td></tr> +<tr><td align='left'>Kohl-rabi</td><td align='right'>6·08</td></tr> +<tr><td align='left'>Rutabaga</td><td align='right'>7·34</td></tr> +<tr><td align='left'>Carrot</td><td align='right'>5·80</td></tr> +<tr><td align='left'>Belgian White Carrot</td><td align='right'>6·22</td></tr> +<tr><td align='left'>Mangold-Wurzel</td><td align='right'>8·78</td></tr> +<tr><td align='left'>Parsnip</td><td align='right'>5·52</td></tr> +<tr><td align='left'>Radish</td><td align='right'>7·35</td></tr> +<tr><td align='left'>Chicory</td><td align='right'>5·21</td></tr> +<tr><td align='left'>Madder</td><td align='right'>8·33</td></tr> +<tr><td align='left'>WOODS.</td></tr> +<tr><td align='left'>Beech</td><td align='right'>0·38</td></tr> +<tr><td align='left'><span class='pagenum'><a name="Page_66" id="Page_66">[Pg 66]</a></span></td></tr> +<tr><td align='left'>Apple</td><td align='right'>1·29</td></tr> +<tr><td align='left'>Cherry</td><td align='right'>0·28</td></tr> +<tr><td align='left'>Birch</td><td align='right'>1·00</td></tr> +<tr><td align='left'>Oak</td><td align='right'>2·50</td></tr> +<tr><td align='left'>Walnut</td><td align='right'>1·57</td></tr> +<tr><td align='left'>Lime</td><td align='right'>5·00</td></tr> +<tr><td align='left'>Horse-chesnut</td><td align='right'>1·05</td></tr> +<tr><td align='left'>Olive</td><td align='right'>0·58</td></tr> +<tr><td align='left'>Mahogany</td><td align='right'>0·81</td></tr> +<tr><td align='left'>Vine</td><td align='right'>2·57</td></tr> +<tr><td align='left'>Larch</td><td align='right'>0·32</td></tr> +<tr><td align='left'>Fir</td><td align='right'>0·14</td></tr> +<tr><td align='left'>Scotch Fir</td><td align='right'>0·17</td></tr> +<tr><td align='left'>Filbert</td><td align='right'>0·50</td></tr> +<tr><td align='left'>Chesnut</td><td align='right'>3·50</td></tr> +<tr><td align='left'>Poplar</td><td align='right'>0·80</td></tr> +<tr><td align='left'>Hazel</td><td align='right'>0·50</td></tr> +<tr><td align='left'>Orange</td><td align='right'>2·74</td></tr> +<tr><td align='left'>Vine</td><td align='right'>2·57</td></tr> +<tr><td align='left'>BARKS.</td></tr> +<tr><td align='left'>Beech</td><td align='right'>6·62</td></tr> +<tr><td align='left'>Cherry</td><td align='right'>10·37</td></tr> +<tr><td align='left'>Fir</td><td align='right'>1·79</td></tr> +<tr><td align='left'>Oak</td><td align='right'>6·00</td></tr> +<tr><td align='left'>Horse-chesnut</td><td align='right'>7·85</td></tr> +<tr><td align='left'>Filbert</td><td align='right'>6·20</td></tr> +<tr><td align='left'>Cork</td><td align='right'>1·12</td></tr> +<tr><td align='left'>FRUITS.</td></tr> +<tr><td align='left'>Plum</td><td align='right'>0·40</td></tr> +<tr><td align='left'>Cherry</td><td align='right'>0·43</td></tr> +<tr><td align='left'>Strawberry</td><td align='right'>0·41</td></tr> +<tr><td align='left'>Pear</td><td align='right'>0·41</td></tr> +<tr><td align='left'>Apple</td><td align='right'>0·27</td></tr> +<tr><td align='left'>Chesnut</td><td align='right'>0·99</td></tr> +<tr><td align='left'>Cucumber</td><td align='right'>0·63</td></tr> +<tr><td align='left'>Vegetable Marrow</td><td align='right'>5·10</td></tr> +</table></div> + +<p>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.<span class='pagenum'><a name="Page_67" id="Page_67">[Pg 67]</a></span></p> + +<p>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.</p> + +<p>In roots and tubers the variations are less, and all, except the potato +and the turnip, contain about seven per cent of ash.</p> + +<p>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.</p> + +<p>The general proportion of ash found in different parts of plants is +given in round numbers in the subjoined table:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Wood</td><td align='right'>1</td></tr> +<tr><td align='left'>Seeds</td><td align='right'>3</td></tr> +<tr><td align='left'>Stems and straws</td><td align='right'>5</td></tr> +<tr><td align='left'>Roots and tubers</td><td align='right'>7</td></tr> +<tr><td align='left'>Bark</td><td align='right'>7</td></tr> +<tr><td align='left'>Leaves</td><td align='right'>13</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_68" id="Page_68">[Pg 68]</a></span> 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.</p> + +<p>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:—</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Hopetoun Oats, Northumberland.</td><td align='left'> Hopetoun Oats, Fifeshire.</td><td align='left'> Potato Oats, Northumberland.</td><td align='left'> Black Oats, Edinburgh.</td><td align='left'> Sandy Oats, Fifeshire.</td><td align='left'> Mean.</td></tr> +<tr><td align='left'>Grain</td><td align='left'> 2·14</td><td align='left'> 1·81</td><td align='left'> 2·22</td><td align='left'> 2·11</td><td align='left'> 1·76</td><td align='left'> 2·00</td></tr> +<tr><td align='left'>Husk</td><td align='left'> 6·47</td><td align='left'> 6·03</td><td align='left'> 6·99</td><td align='left'> 8·24</td><td align='left'> 6·03</td><td align='left'> 6·75</td></tr> +<tr><td align='left'>Chaff</td><td align='left'> 16·53</td><td align='left'> 17·23</td><td align='left'> 15·59</td><td align='left'> 19·19</td><td align='left'> 18·97</td><td align='left'> 16·06</td></tr> +<tr><td align='left'>Leaves</td><td align='left'> 8·44</td><td align='left'> 7·19</td><td align='left'> 14·59</td><td align='left'> 10·29</td><td align='left'> 15·92</td><td align='left'> 10·88</td></tr> +<tr><td align='left'>Upper part of straw</td><td align='left'> 4·95</td><td align='left'> 5·44</td><td align='left'> 9·22</td><td align='left'> 8·25</td><td align='left'> 11·0</td><td align='left'> 7·77</td></tr> +<tr><td align='left'>Middle part of straw</td><td align='left'> 6·11</td><td align='left'> 5·23</td><td align='left'> 7·41</td><td align='left'> 6·53</td><td align='left'> 9·01</td><td align='left'> 6·66</td></tr> +<tr><td align='left'>Lower part of straw</td><td align='left'> 5·33</td><td align='left'> 5·18</td><td align='left'> 9·76</td><td align='left'> 7·11</td><td align='left'> 7·30</td><td align='left'> 6·93</td></tr> +</table></div> +<p><span class='pagenum'><a name="Page_69" id="Page_69">[Pg 69]</a></span></p> + +<p>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.</p> + +<p>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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Before flowering.</td><td align='right'>With ripe seed.</td></tr> +<tr><td align='left'>Sunflower</td><td align='right'>14·7</td><td align='right'>9·3</td></tr> +<tr><td align='left'>Wheat</td><td align='right'>7·9</td><td align='right'>3·3</td></tr> +<tr><td align='left'>Maize</td><td align='right'>12·2</td><td align='right'>4·6</td></tr> +</table></div> + +<p>On the other hand, the quantity of ash in the leaves<span class='pagenum'><a name="Page_70" id="Page_70">[Pg 70]</a></span> of trees increases +considerably in autumn, as shown by this table:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td colspan="2">Per-centage of ash in</td></tr> +<tr><td align='left'></td><td align='right'>May.</td><td align='right'>September.</td></tr> +<tr><td align='left'>Oak leaves</td><td align='right'>5·3</td><td align='right'>5·5</td></tr> +<tr><td align='left'>Poplar</td><td align='right'>6·6</td><td align='right'>9·3</td></tr> +<tr><td align='left'>Hazel</td><td align='right'>6·1</td><td align='right'>7·0</td></tr> +<tr><td align='left'>Horse-chesnut</td><td align='right'>7·2</td><td align='right'>8·6</td></tr> +</table></div> + +<p>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:—</p> + + +<h4><i>Proportion of Ash in different parts of the Oat at different periods of +its growth.</i></h4> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="6" summary=""> +<tr><td align='left'>Date.</td><td align='right'> Stalks.</td><td align='right'> Leaves.</td><td align='right'> Chaff.</td><td align='right'>Grain with husk.</td></tr> +<tr><td align='left'>2d July</td><td align='right'> 7·83</td><td align='right'> 11·35</td><td align='right'> ...</td><td align='right'> 4·91</td></tr> +<tr><td align='left'>9th July</td><td align='right'> 7·80</td><td align='right'> 12·20</td><td align='right'> ...</td><td align='right'> 4·36</td></tr> +<tr><td align='left'>16th July</td><td align='right'> 7·94</td><td align='right'> 12·61</td><td align='right'> 6·00</td><td align='right'> 3·38</td></tr> +<tr><td align='left'>23d July</td><td align='right'> 7·99</td><td align='right'> 16·45</td><td align='right'> 9·11</td><td align='right'> 3·62</td></tr> +<tr><td align='left'>30th July</td><td align='right'> 7·45</td><td align='right'> 16·44</td><td align='right'> 12·28</td><td align='right'> 4·22</td></tr> +<tr><td align='left'>5th August</td><td align='right'> 7·63</td><td align='right'> 16·05</td><td align='right'> 13·75</td><td align='right'> 4·31</td></tr> +<tr><td align='left'>13th August</td><td align='right'> 6·62</td><td align='right'> 20·47</td><td align='right'> 18·68</td><td align='right'> 4·07</td></tr> +<tr><td align='left'>20th August</td><td align='right'> 6·66</td><td align='right'> 21·14</td><td align='right'> 21·07</td><td align='right'> 3·64</td></tr> +<tr><td align='left'>27th August</td><td align='right'> 7·71</td><td align='right'> 22·13</td><td align='right'> 22·46</td><td align='right'> 3·51</td></tr> +<tr><td align='left'>3d September</td><td align='right'> 8·35</td><td align='right'> 20·90</td><td align='right'> 27·47</td><td align='right'> 3·65</td></tr> +</table></div> + + +<p>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<span class='pagenum'><a name="Page_71" id="Page_71">[Pg 71]</a></span> 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.</p> + +<p>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:—</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Seed.</td><td align='left'> Straw.</td></tr> +<tr><td align='left'>1</td><td align='left'> 2·30</td><td align='left'> </td></tr> +<tr><td align='left'>2</td><td align='left'> 3·25</td><td align='left'> 3·43</td></tr> +<tr><td align='left'>3</td><td align='left'> 4·27</td><td align='left'> 3·62</td></tr> +<tr><td align='left'>4</td><td align='left'> 3·40</td><td align='left'> 3·39</td></tr> +<tr><td align='left'>5</td><td align='left'> 2·99</td><td align='left'> 3·90</td></tr> +<tr><td align='left'>6</td><td align='left'> 3·19</td><td align='left'> 6·80</td></tr> +<tr><td align='left'>7</td><td align='left'> 2·53</td><td align='left'> 3·90</td></tr> +<tr><td align='left'>8</td><td align='left'> 2·27</td><td align='left'> 6·59</td></tr> +<tr><td align='left'>9</td><td align='left'> 2·69</td><td align='left'> 3·49</td></tr> +<tr><td align='left'>10</td><td align='left'> 1·61</td><td align='left'> 3·91</td></tr> +<tr><td align='left'>11</td><td align='left'> 3·11</td><td align='left'> 5·28</td></tr> +<tr><td align='left'>12</td><td align='left'> 3·34</td><td align='left'> 7·57</td></tr> +<tr><td align='left'>13</td><td align='left'> 2·78</td><td align='left'> 3·76</td></tr> +<tr><td align='left'>14</td><td align='left'> 3·01</td><td align='left'> 3·38</td></tr> +</table></div> + +<p>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. <i>A +priori</i>, 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<span class='pagenum'><a name="Page_72" id="Page_72">[Pg 72]</a></span> 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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Kernel of seed.</td><td align='right'>Green husk.</td><td align='right'>Brown husk.</td></tr> +<tr><td align='left'>Forest soil</td><td align='right'>2·26</td><td align='right'>4·53</td><td align='right'>1·70</td></tr> +<tr><td align='left'>Porphyry soil</td><td align='right'>3·36</td><td align='right'>7·29</td><td align='right'>2·20</td></tr> +</table></div> + +<p>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.</p> + +<p>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.<span class='pagenum'><a name="Page_73" id="Page_73">[Pg 73]</a></span></p> + + +<h4><i>Table of the Composition of the Ash of different Plants in 100 Parts.</i></h4> + +<p><i>Note.</i>—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.</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Potash.</td><td align='left'> Soda.</td><td align='left'> Chloride of Potassium.</td><td align='left'> Chloride of Sodium.</td><td align='left'> Lime.</td><td align='left'> Magnesia.</td></tr> +<tr><td align='left'>Wheat, grain</td><td align='left'> 30·02</td><td align='left'> 3·82</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 1·15</td><td align='left'> 13·39</td></tr> +<tr><td align='left'> straw</td><td align='left'> 17·98</td><td align='left'> 2·47</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 7·42</td><td align='left'> 1·94</td></tr> +<tr><td align='left'> chaff</td><td align='left'> 9·14</td><td align='left'> 1·79</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 1·88</td><td align='left'> 1·27</td></tr> +<tr><td align='left'>Barley, grain</td><td align='left'> 21·14</td><td align='left'> ...</td><td align='left'> 5·65</td><td align='left'> 1·01</td><td align='left'> 1·65</td><td align='left'> 7·26</td></tr> +<tr><td align='left'> straw</td><td align='left'> 11·22</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 2·14</td><td align='left'> 5·79</td><td align='left'> 2·70</td></tr> +<tr><td align='left'>Oats, grain<a name="FNanchor_B_2" id="FNanchor_B_2"></a><a href="#Footnote_B_2" class="fnanchor">[B]</a></td><td align='left'> 20·63</td><td align='left'> ...</td><td align='left'> 1·03</td><td align='left'> ...</td><td align='left'> 10·28</td><td align='left'> 7·82</td></tr> +<tr><td align='left'> straw</td><td align='left'> 19·46</td><td align='left'> 1·93</td><td align='left'> 2·71</td><td align='left'> 4·27</td><td align='left'> 7·01</td><td align='left'> 3·79</td></tr> +<tr><td align='left'> chaff<a name="FNanchor_C_3" id="FNanchor_C_3"></a><a href="#Footnote_C_3" class="fnanchor">[C]</a></td><td align='left'> 6·33</td><td align='left'> 3·93</td><td align='left'> ...</td><td align='left'> 0·24</td><td align='left'> 1·95</td><td align='left'> 0·38</td></tr> +<tr><td align='left'>Rye, grain</td><td align='left'> 33·83</td><td align='left'> 0·39</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 2·61</td><td align='left'> 12·81</td></tr> +<tr><td align='left'> straw</td><td align='left'> 17·20</td><td align='left'> ...</td><td align='left'> 0·30</td><td align='left'> 0·60</td><td align='left'> 9·10</td><td align='left'> 2·40</td></tr> +<tr><td align='left'>Maize, grain</td><td align='left'> 28·37</td><td align='left'> 1·74</td><td align='left'> ...</td><td align='left'> trace</td><td align='left'> 0·57</td><td align='left'> 13·60</td></tr> +<tr><td align='left'> stalks and leaves</td><td align='left'> 35·26</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 2·29</td><td align='left'> 10·53</td><td align='left'> 5·52</td></tr> +<tr><td align='left'>Rice, grain</td><td align='left'> 20·21</td><td align='left'> 2·49</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 7·18</td><td align='left'> 4·26</td></tr> +<tr><td align='left'>Buckwheat, straw</td><td align='left'> 31·71</td><td align='left'> ...</td><td align='left'> 7·42</td><td align='left'> 4·55</td><td align='left'> 15·71</td><td align='left'> 1·66</td></tr> +<tr><td align='left'>Peas (gray), seed</td><td align='left'> 41·70</td><td align='left'> ...</td><td align='left'> 3·82</td><td align='left'> 1·24</td><td align='left'> 4·78</td><td align='left'> 5·78</td></tr> +<tr><td align='left'> straw</td><td align='left'> 21·30</td><td align='left'> 4·22</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 37·17</td><td align='left'> 7·17</td></tr> +<tr><td align='left'>Beans (common field),</td><td align='left'> </td><td align='left'> </td><td align='left'> </td><td align='left'> </td><td align='left'> </td><td align='left'> </td></tr> +<tr><td align='left'> grain</td><td align='left'> 51·72</td><td align='left'> 0·54</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 5·20</td><td align='left'> 6·90</td></tr> +<tr><td align='left'> straw</td><td align='left'> 32·85</td><td align='left'> 2·77</td><td align='left'> ...</td><td align='left'> 11·54</td><td align='left'> 19·85</td><td align='left'> 2·53</td></tr> +<tr><td align='left'>Tare, straw</td><td align='left'> 32·82</td><td align='left'> ...</td><td align='left'> 3·27</td><td align='left'> 4·03</td><td align='left'> 20·78</td><td align='left'> 5·31</td></tr> +<tr><td align='left'> straw</td><td align='left'> 31·72</td><td align='left'> ...</td><td align='left'> 7·41</td><td align='left'> 4·55</td><td align='left'> 15·71</td><td align='left'> 1·66</td></tr> +<tr><td align='left'>Flax, seed</td><td align='left'> 34·17</td><td align='left'> 1·69</td><td align='left'> ...</td><td align='left'> 0·36</td><td align='left'> 8·40</td><td align='left'> 13·11</td></tr> +<tr><td align='left'> straw</td><td align='left'> 21·53</td><td align='left'> 3·68</td><td align='left'> ...</td><td align='left'> 9·21</td><td align='left'> 21·20</td><td align='left'> 4·20</td></tr> +<tr><td align='left'>Rape, seed<a name="FNanchor_D_4" id="FNanchor_D_4"></a><a href="#Footnote_D_4" class="fnanchor">[D]</a></td><td align='left'> 16·33</td><td align='left'> 0·34</td><td align='left'> ...</td><td align='left'> 0·96</td><td align='left'> 8·30</td><td align='left'> 8·80</td></tr> +<tr><td align='left'> straw<a name="FNanchor_E_5" id="FNanchor_E_5"></a><a href="#Footnote_E_5" class="fnanchor">[E]</a></td><td align='left'> 16·63</td><td align='left'> 10·57</td><td align='left'> ...</td><td align='left'> 2·53</td><td align='left'> 21·51</td><td align='left'> 2·92</td></tr> +<tr><td align='left'>Spurry</td><td align='left'> 26·12</td><td align='left'> 1·14</td><td align='left'> ...</td><td align='left'> 8·90</td><td align='left'> 14·46</td><td align='left'> 8·88</td></tr> +<tr><td align='left'>Chicory root</td><td align='left'> 34·64</td><td align='left'> ...</td><td align='left'> 8·92</td><td align='left'> 2·98</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Red clover</td><td align='left'> 25·60</td><td align='left'> ...</td><td align='left'> 9·08</td><td align='left'> 6·02</td><td align='left'> 21·57</td><td align='left'> 8·47</td></tr> +<tr><td align='left'>Cow grass, <i>Trifolium medium</i></td><td align='left'> 22·78</td><td align='left'> ...</td><td align='left'> 12·39</td><td align='left'> 1·86</td><td align='left'> 24·42</td><td align='left'> 8·86</td></tr> +<tr><td align='left'>Yellow clover</td><td align='left'> 27·48</td><td align='left'> ...</td><td align='left'> 11·72</td><td align='left'> 8·16</td><td align='left'> 17·26</td><td align='left'> 8·39</td></tr> +<tr><td align='left'>Alsike clover</td><td align='left'> 29·72</td><td align='left'> ...</td><td align='left'> 6·29</td><td align='left'> 1·05</td><td align='left'> 26·83</td><td align='left'> 4·01</td></tr> +<tr><td align='left'>Lucerne</td><td align='left'> 27·56</td><td align='left'> ...</td><td align='left'> 11·64</td><td align='left'> 1·91</td><td align='left'> 20·60</td><td align='left'> 5·22</td></tr> +<tr><td align='left'>Anthoxanthum odoratum</td><td align='left'> 32·03</td><td align='left'> ...</td><td align='left'> 7·03</td><td align='left'> 4·90</td><td align='left'> 9·21</td><td align='left'> 2·53</td></tr> +<tr><td align='left'>Alopecurus pratensis</td><td align='left'> 37·03</td><td align='left'> ...</td><td align='left'> 9·50</td><td align='left'> ...</td><td align='left'> 3·90</td><td align='left'> 1·28</td></tr> +<tr><td align='left'>Avena pubescens</td><td align='left'> 31·21</td><td align='left'> ...</td><td align='left'> 4·05</td><td align='left'> 5·66</td><td align='left'> 4·72</td><td align='left'> 3·17</td></tr> +<tr><td align='left'>Bromus erectus</td><td align='left'> 20·33</td><td align='left'> ...</td><td align='left'> 10·63</td><td align='left'> 1·38</td><td align='left'> 10·38</td><td align='left'> 4·99</td></tr> +<tr><td align='left'>Bromus mollis</td><td align='left'> 30·09</td><td align='left'> 0·33</td><td align='left'> ...</td><td align='left'> 3·11</td><td align='left'> 6·64</td><td align='left'> 2·60</td></tr> +<tr><td align='left'>Cynosurus cristatus</td><td align='left'> 24·99</td><td align='left'> ...</td><td align='left'> 11·60</td><td align='left'> ...</td><td align='left'> 10·16</td><td align='left'> 2·43</td></tr> +<tr><td align='left'>Dactylis glomerata</td><td align='left'> 29·52</td><td align='left'> ...</td><td align='left'> 17·86</td><td align='left'> 3·09</td><td align='left'> 5·82</td><td align='left'> 2·22</td></tr> +<tr><td align='left'>Festuca duriuscula</td><td align='left'> 31·84</td><td align='left'> ...</td><td align='left'> 8·17</td><td align='left'> 0·62</td><td align='left'> 10·31</td><td align='left'> 2·83</td></tr> +<tr><td align='left'>Holcus lanatus</td><td align='left'> 34·83</td><td align='left'> ...</td><td align='left'> 3·91</td><td align='left'> 6·66</td><td align='left'> 8·31</td><td align='left'> 3·41</td></tr> +<tr><td align='left'>Lolium perenne</td><td align='left'> 24·67</td><td align='left'> ...</td><td align='left'> 13·80</td><td align='left'> 7·25</td><td align='left'> 9·64</td><td align='left'> 2·85</td></tr> +<tr><td align='left'>Annual ryegrass</td><td align='left'> 28·99</td><td align='left'> 0·87</td><td align='left'> ...</td><td align='left'> 5·11</td><td align='left'> 6·82</td><td align='left'> 2·59</td></tr> +<tr><td align='left'>Poa annua</td><td align='left'> 41·86</td><td align='left'> ...</td><td align='left'> 0·47</td><td align='left'> 3·35</td><td align='left'> 11·69</td><td align='left'> 2·44</td></tr> +<tr><td align='left'>Poa pratensis</td><td align='left'> 31·17</td><td align='left'> ...</td><td align='left'> 11·25</td><td align='left'> 1·31</td><td align='left'> 5·63</td><td align='left'> 2·71</td></tr> +<tr><td align='left'>Poa trivialis</td><td align='left'> 29·40</td><td align='left'> ...</td><td align='left'> 6·90</td><td align='left'> ...</td><td align='left'> 8·80</td><td align='left'> 3·22</td></tr> +<tr><td align='left'>Phleum pratense</td><td align='left'> 31·09</td><td align='left'> ...</td><td align='left'> 0·70</td><td align='left'> 3·24</td><td align='left'> 14·94</td><td align='left'> 5·30</td></tr> +<tr><td align='left'>Plantago lanceolata</td><td align='left'> 33·26</td><td align='left'> ...</td><td align='left'> 4·53</td><td align='left'> 8·80</td><td align='left'> 19·01</td><td align='left'> 3·51</td></tr> +<tr><td align='left'>Poterium Sanguisorba</td><td align='left'> 30·26</td><td align='left'> ...</td><td align='left'> 3·27</td><td align='left'> 1·35</td><td align='left'> 24·82</td><td align='left'> 4·21</td></tr> +<tr><td align='left'>Achillea Millefolia</td><td align='left'> 30·37</td><td align='left'> ...</td><td align='left'> 20·49</td><td align='left'> 3·63</td><td align='left'> 13·40</td><td align='left'> 3·01</td></tr> +<tr><td align='left'>Potato, tuber</td><td align='left'> 43·18</td><td align='left'> 0·09</td><td align='left'> ...</td><td align='left'> 7·92</td><td align='left'> 1·80</td><td align='left'> 3·17</td></tr> +<tr><td align='left'><span class='pagenum'><a name="Page_74" id="Page_74">[Pg 74]</a></span></td></tr> +<tr><td align='left'> stem</td><td align='left'> 39·53</td><td align='left'> 3·95</td><td align='left'> ...</td><td align='left'> 20·43</td><td align='left'> 14·85</td><td align='left'> 4·10</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 17·27</td><td align='left'> ...</td><td align='left'> 4·95</td><td align='left'> 11·37</td><td align='left'> 27·69</td><td align='left'> 7·78</td></tr> +<tr><td align='left'>Jerusalem Artichoke</td><td align='left'> 55·89</td><td align='left'> ...</td><td align='left'> 4·88</td><td align='left'> ...</td><td align='left'> 3·34</td><td align='left'> 1·30</td></tr> +<tr><td align='left'> stem</td><td align='left'> 38·40</td><td align='left'> 0·69</td><td align='left'> ...</td><td align='left'> 4·68</td><td align='left'> 20·31</td><td align='left'> 1·91</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 6·81</td><td align='left'> 3·72</td><td align='left'> ...</td><td align='left'> 1·82</td><td align='left'> 40·15</td><td align='left'> 1·95</td></tr> +<tr><td align='left'>Turnip, seed</td><td align='left'> 21·91</td><td align='left'> 1·23</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 17·40</td><td align='left'> 8·74</td></tr> +<tr><td align='left'> bulb</td><td align='left'> 23·70</td><td align='left'> 14·75</td><td align='left'> ...</td><td align='left'> 7·05</td><td align='left'> 11·82</td><td align='left'> 3·28</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 11·56</td><td align='left'> 12·43</td><td align='left'> ...</td><td align='left'> 12·41</td><td align='left'> 28·49</td><td align='left'> 2·62</td></tr> +<tr><td align='left'>Mangold Wurzel, root</td><td align='left'> 21·68</td><td align='left'> 3·13</td><td align='left'> ...</td><td align='left'> 49·51</td><td align='left'> 1·90</td><td align='left'> 1·79</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 8·34</td><td align='left'> 12·21</td><td align='left'> ...</td><td align='left'> 37·66</td><td align='left'> 8·72</td><td align='left'> 9·84</td></tr> +<tr><td align='left'>Carrot, root</td><td align='left'> 42·73</td><td align='left'> 12·11</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 5·64</td><td align='left'> 2·29</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 17·10</td><td align='left'> 4·85</td><td align='left'> ...</td><td align='left'> 3·62</td><td align='left'> 24·05</td><td align='left'> 0·89</td></tr> +<tr><td align='left'>Kohl-rabi, bulb</td><td align='left'> 36·27</td><td align='left'> 2·84</td><td align='left'> ...</td><td align='left'> 11·90</td><td align='left'> 10·20</td><td align='left'> 2·36</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 9·31</td><td align='left'> ...</td><td align='left'> 5·99</td><td align='left'> 6·66</td><td align='left'> 30·31</td><td align='left'> 3·62</td></tr> +<tr><td align='left'>Cow cabbage, head</td><td align='left'> 40·86</td><td align='left'> 2·43</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 15·01</td><td align='left'> 2·39</td></tr> +<tr><td align='left'> stalk</td><td align='left'> 40·93</td><td align='left'> 4·05</td><td align='left'> ...</td><td align='left'> 2·08</td><td align='left'> 10·61</td><td align='left'> 3·85</td></tr> +<tr><td align='left'>Poppy seed</td><td align='left'> 9·10</td><td align='left'> ...</td><td align='left'> 7·15</td><td align='left'> 1·94</td><td align='left'> 35·36</td><td align='left'> 9·49</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 36·37</td><td align='left'> ...</td><td align='left'> 2·50</td><td align='left'> 2·51</td><td align='left'> 30·24</td><td align='left'> 6·47</td></tr> +<tr><td align='left'>Mustard seed (white)</td><td align='left'> 25·78</td><td align='left'> 0·33</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 19·10</td><td align='left'> 5·90</td></tr> +<tr><td align='left'>Radish root</td><td align='left'> 21·16</td><td align='left'> ...</td><td align='left'> 1·29</td><td align='left'> 7·07</td><td align='left'> 8·78</td><td align='left'> 3·53</td></tr> +<tr><td align='left'>Tobacco leaves</td><td align='left'> 36·37</td><td align='left'> ...</td><td align='left'> 2·50</td><td align='left'> 2·51</td><td align='left'> 30·24</td><td align='left'> 6·47</td></tr> +<tr><td align='left'>Fucus nodosus<a name="FNanchor_F_6" id="FNanchor_F_6"></a><a href="#Footnote_F_6" class="fnanchor">[F]</a></td><td align='left'> 20·03</td><td align='left'> 4·58</td><td align='left'> ...</td><td align='left'> 24·33</td><td align='left'> 9·60</td><td align='left'> 6·65</td></tr> +<tr><td align='left'>Fucus vesiculosus<a name="FNanchor_G_7" id="FNanchor_G_7"></a><a href="#Footnote_G_7" class="fnanchor">[G]</a></td><td align='left'> 20·75</td><td align='left'> 6·09</td><td align='left'> ...</td><td align='left'> 24·81</td><td align='left'> 8·92</td><td align='left'> 5·83</td></tr> +<tr><td align='left'>Laminaria digitata<a name="FNanchor_H_8" id="FNanchor_H_8"></a><a href="#Footnote_H_8" class="fnanchor">[H]</a></td><td align='left'> 12·16</td><td align='left'> ...</td><td align='left'> 2·30</td><td align='left'> 19·34</td><td align='left'> 4·62</td><td align='left'> 10·94</td></tr> +</table></div> + +<p><br /><br /><br /></p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Oxide of Iron.</td><td align='left'> Phosphoric Acid.</td><td align='left'> Sulphuric Acid.</td><td align='left'> Carbonic Acid.</td><td align='left'> Silica.</td></tr> +<tr><td align='left'>Wheat, grain</td><td align='left'> 0·91</td><td align='left'> 46·79</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 3·89</td></tr> +<tr><td align='left'> straw</td><td align='left'> 0·45</td><td align='left'> 2·75</td><td align='left'> 3·09</td><td align='left'> ...</td><td align='left'> 63·89</td></tr> +<tr><td align='left'> chaff</td><td align='left'> 0·37</td><td align='left'> 4·31</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 81·22</td></tr> +<tr><td align='left'>Barley, grain</td><td align='left'> 2·13</td><td align='left'> 28·53</td><td align='left'> 1·91</td><td align='left'> ...</td><td align='left'> 30·68</td></tr> +<tr><td align='left'> straw</td><td align='left'> 1·36</td><td align='left'> 7·20</td><td align='left'> 1·09</td><td align='left'> ...</td><td align='left'> 68·50</td></tr> +<tr><td align='left'>Oats, grain</td><td align='left'> 3·85</td><td align='left'> 50·44</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 4·40</td></tr> +<tr><td align='left'> straw</td><td align='left'> 1·49</td><td align='left'> 5·07</td><td align='left'> 3·35</td><td align='left'> 1·36</td><td align='left'> 49·56</td></tr> +<tr><td align='left'> chaff</td><td align='left'> 1·58</td><td align='left'> 1·04</td><td align='left'> 9·61</td><td align='left'> ...</td><td align='left'> 72·85</td></tr> +<tr><td align='left'>Rye, grain</td><td align='left'> 1·04</td><td align='left'> 39·92</td><td align='left'> 0·17</td><td align='left'> ...</td><td align='left'> 9·22</td></tr> +<tr><td align='left'> straw</td><td align='left'> 1·40</td><td align='left'> 3·80</td><td align='left'> 0·80</td><td align='left'> ...</td><td align='left'> 64·50</td></tr> +<tr><td align='left'>Maize, grain</td><td align='left'> 0·47</td><td align='left'> 53·69</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 1·55</td></tr> +<tr><td align='left'> stalks and leaves</td><td align='left'> 2·28</td><td align='left'> 8·09</td><td align='left'> 5·16</td><td align='left'> 2·87</td><td align='left'> 27·98</td></tr> +<tr><td align='left'>Rice, grain</td><td align='left'> 2·12</td><td align='left'> 62·23</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 1·37</td></tr> +<tr><td align='left'>Buckwheat, straw</td><td align='left'> ...</td><td align='left'> 10·34</td><td align='left'> 4·67</td><td align='left'> 20·37</td><td align='left'> 3·57</td></tr> +<tr><td align='left'>Peas (gray), seed</td><td align='left'> 0·18</td><td align='left'> 36·50</td><td align='left'> 4·47</td><td align='left'> 0·82</td><td align='left'> 0·68</td></tr> +<tr><td align='left'> straw</td><td align='left'> 1·07</td><td align='left'> 4·65</td><td align='left'> 8·68</td><td align='left'> 12·48</td><td align='left'> 3·23</td></tr> +<tr><td align='left'>Beans (common field),</td><td align='left'> </td><td align='left'> </td><td align='left'> </td><td align='left'> </td><td align='left'> </td></tr> +<tr><td align='left'> grain</td><td align='left'> ...</td><td align='left'> 28·72</td><td align='left'> 3·05</td><td align='left'> 3·42</td><td align='left'> 0·42</td></tr> +<tr><td align='left'> straw</td><td align='left'> 0·61</td><td align='left'> 0·49</td><td align='left'> 1·40</td><td align='left'> 25·32</td><td align='left'> 2·61</td></tr> +<tr><td align='left'>Tare, straw</td><td align='left'> 0·65</td><td align='left'> 10·59</td><td align='left'> 2·52</td><td align='left'> 18·73</td><td align='left'> 1·28</td></tr> +<tr><td align='left'> straw</td><td align='left'> ...</td><td align='left'> 10·34</td><td align='left'> 4·67</td><td align='left'> 20·37</td><td align='left'> 3·57</td></tr> +<tr><td align='left'><span class='pagenum'><a name="Page_75" id="Page_75">[Pg 75]</a></span></td></tr> +<tr><td align='left'>Flax, seed</td><td align='left'> 0·50</td><td align='left'> 38·54</td><td align='left'> 1·56</td><td align='left'> 0·22</td><td align='left'> 1·45</td></tr> +<tr><td align='left'> straw</td><td align='left'> 5·58</td><td align='left'> 7·53</td><td align='left'> 3·39</td><td align='left'> 15·75</td><td align='left'> 7·92</td></tr> +<tr><td align='left'>Rape, seed</td><td align='left'> 1·79</td><td align='left'> 31·90</td><td align='left'> 5·38</td><td align='left'> 5·44</td><td align='left'> 19·98</td></tr> +<tr><td align='left'> straw</td><td align='left'> 1·30</td><td align='left'> 4·68</td><td align='left'> 3·90</td><td align='left'> 23·04</td><td align='left'> 11·80</td></tr> +<tr><td align='left'>Spurry</td><td align='left'> ...</td><td align='left'> 10·20</td><td align='left'> 1·79</td><td align='left'> 27·38</td><td align='left'> 1·14</td></tr> +<tr><td align='left'>Chicory root</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Red clover</td><td align='left'> 1·26</td><td align='left'> 4·09</td><td align='left'> 2·96</td><td align='left'> 18·05</td><td align='left'> 1·95</td></tr> +<tr><td align='left'>Cow grass, <i>Trifolium medium</i></td><td align='left'> 1·09</td><td align='left'> 4·94</td><td align='left'> 2·66</td><td align='left'> 20·16</td><td align='left'> 1·12</td></tr> +<tr><td align='left'>Yellow clover</td><td align='left'> 1·40</td><td align='left'> ...</td><td align='left'> 4·82</td><td align='left'> 4·31</td><td align='left'> 1·76</td></tr> +<tr><td align='left'>Alsike clover</td><td align='left'> 0·71</td><td align='left'> 5·64</td><td align='left'> 3·25</td><td align='left'> 20·74</td><td align='left'> 1·73</td></tr> +<tr><td align='left'>Lucerne</td><td align='left'> 2·23</td><td align='left'> 6·47</td><td align='left'> 4·80</td><td align='left'> 15·94</td><td align='left'> 2·63</td></tr> +<tr><td align='left'>Anthoxanthum odoratum</td><td align='left'> 1·18</td><td align='left'> 10·09</td><td align='left'> 3·39</td><td align='left'> 1·26</td><td align='left'> 28·35</td></tr> +<tr><td align='left'>Alopecurus pratensis</td><td align='left'> 0·47</td><td align='left'> 6·25</td><td align='left'> 2·16</td><td align='left'> 0·65</td><td align='left'> 38·75</td></tr> +<tr><td align='left'>Avena pubescens</td><td align='left'> 0·72</td><td align='left'> 10·82</td><td align='left'> 3·37</td><td align='left'> ...</td><td align='left'> 36·28</td></tr> +<tr><td align='left'>Bromus erectus</td><td align='left'> 0·26</td><td align='left'> 7·53</td><td align='left'> 5·46</td><td align='left'> 0·55</td><td align='left'> 38·48</td></tr> +<tr><td align='left'>Bromus mollis</td><td align='left'> 0·28</td><td align='left'> 9·62</td><td align='left'> 4·91</td><td align='left'> 9·07</td><td align='left'> 33·34</td></tr> +<tr><td align='left'>Cynosurus cristatus</td><td align='left'> 0·18</td><td align='left'> 7·24</td><td align='left'> 3·20</td><td align='left'> ...</td><td align='left'> 40·11</td></tr> +<tr><td align='left'>Dactylis glomerata</td><td align='left'> 0·59</td><td align='left'> 8·60</td><td align='left'> 3·52</td><td align='left'> 2·09</td><td align='left'> 26·65</td></tr> +<tr><td align='left'>Festuca duriuscula</td><td align='left'> 0·78</td><td align='left'> 12·07</td><td align='left'> 3·45</td><td align='left'> 1·38</td><td align='left'> 28·53</td></tr> +<tr><td align='left'>Holcus lanatus</td><td align='left'> 0·31</td><td align='left'> 8·02</td><td align='left'> 4·41</td><td align='left'> 1·82</td><td align='left'> 28·31</td></tr> +<tr><td align='left'>Lolium perenne</td><td align='left'> 0·21</td><td align='left'> 8·73</td><td align='left'> 5·20</td><td align='left'> 0·49</td><td align='left'> 27·13</td></tr> +<tr><td align='left'>Annual ryegrass</td><td align='left'>0·28</td><td align='left'>10·07</td><td align='left'>3·45</td><td align='left'>...</td><td align='left'>41·79</td></tr> +<tr><td align='left'>Poa annua</td><td align='left'> 1·57</td><td align='left'> 9·11</td><td align='left'> 10·18</td><td align='left'> 3·29</td><td align='left'> 16·03</td></tr> +<tr><td align='left'>Poa pratensis</td><td align='left'> 0·28</td><td align='left'> 10·02</td><td align='left'> 4·26</td><td align='left'> 0·40</td><td align='left'> 32·93</td></tr> +<tr><td align='left'>Poa trivialis</td><td align='left'> 0·29</td><td align='left'> 9·13</td><td align='left'> 4·47</td><td align='left'> 0·29</td><td align='left'> 37·50</td></tr> +<tr><td align='left'>Phleum pratense</td><td align='left'> 0·27</td><td align='left'> 11·29</td><td align='left'> 4·86</td><td align='left'> 4·02</td><td align='left'> 31·09</td></tr> +<tr><td align='left'>Plantago lanceolata</td><td align='left'> 0·90</td><td align='left'> 7·08</td><td align='left'> 6·11</td><td align='left'> 14·40</td><td align='left'> 2·37</td></tr> +<tr><td align='left'>Poterium Sanguisorba</td><td align='left'> 0·86</td><td align='left'> 7·81</td><td align='left'> 4·84</td><td align='left'> 21·72</td><td align='left'> 0·83</td></tr> +<tr><td align='left'>Achillea Millefolia</td><td align='left'> 0·21</td><td align='left'> 7·13</td><td align='left'> 2·44</td><td align='left'> 9·36</td><td align='left'> 9·92</td></tr> +<tr><td align='left'>Potato, tuber</td><td align='left'> 0·44</td><td align='left'> 8·61</td><td align='left'> 15·24</td><td align='left'> 18·29</td><td align='left'> 1·94</td></tr> +<tr><td align='left'> stem</td><td align='left'> 1·34</td><td align='left'> 6·68</td><td align='left'> 6·56</td><td align='left'> ...</td><td align='left'> 2·56</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 4·50</td><td align='left'> 13·60</td><td align='left'> 6·37</td><td align='left'> ...</td><td align='left'> 6·47</td></tr> +<tr><td align='left'>Jerusalem Artichoke</td><td align='left'> 0·45</td><td align='left'> 16·99</td><td align='left'> 3·77</td><td align='left'> 11·80</td><td align='left'> 1·52</td></tr> +<tr><td align='left'> stem</td><td align='left'> 0·88</td><td align='left'> 2·97</td><td align='left'> 3·23</td><td align='left'> 25·40</td><td align='left'> 1·51</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 1·14</td><td align='left'> 6·61</td><td align='left'> 2·21</td><td align='left'> 24·31</td><td align='left'> 17·25</td></tr> +<tr><td align='left'>Turnip, seed</td><td align='left'> 1·95</td><td align='left'> 40·17</td><td align='left'> 7·10</td><td align='left'> 0·82</td><td align='left'> 0·67</td></tr> +<tr><td align='left'> bulb</td><td align='left'> 0·47</td><td align='left'> 9·31</td><td align='left'> 16·13</td><td align='left'> 10·74</td><td align='left'> 2·69</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 3·02</td><td align='left'> 4·85</td><td align='left'> 10·36</td><td align='left'> 6·18</td><td align='left'> 8·04</td></tr> +<tr><td align='left'>Mangold Wurzel, root</td><td align='left'> 0·52</td><td align='left'> 1·65</td><td align='left'> 3·14</td><td align='left'> 15·23</td><td align='left'> 1·40</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 1·46</td><td align='left'> 5·89</td><td align='left'> 6·54</td><td align='left'> 6·92</td><td align='left'> 2·35</td></tr> +<tr><td align='left'>Carrot, root</td><td align='left'> 0·51</td><td align='left'> 12·31</td><td align='left'> 4·26</td><td align='left'> 18·00</td><td align='left'> 1·11</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 3·43</td><td align='left'> 6·21</td><td align='left'> 5·08</td><td align='left'> 23·15</td><td align='left'> 11·61</td></tr> +<tr><td align='left'>Kohl-rabi, bulb</td><td align='left'> 0·38</td><td align='left'> 13·45</td><td align='left'> 11·43</td><td align='left'> 10·24</td><td align='left'> 0·83</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 5·50</td><td align='left'> 9·43</td><td align='left'> 10·63</td><td align='left'> 8·97</td><td align='left'> 9·57</td></tr> +<tr><td align='left'>Cow cabbage, head</td><td align='left'> 0·77</td><td align='left'> 12·53</td><td align='left'> 7·27</td><td align='left'> 16·68</td><td align='left'> 1·66</td></tr> +<tr><td align='left'> stalk</td><td align='left'> 0·41</td><td align='left'> 19·57</td><td align='left'> 11·11</td><td align='left'> 6·33</td><td align='left'> 1·04</td></tr> +<tr><td align='left'>Poppy seed</td><td align='left'> 0·41</td><td align='left'> 31·38</td><td align='left'> 1·92</td><td align='left'> ...</td><td align='left'> 3·24</td></tr> +<tr><td align='left'> leaves</td><td align='left'> 2·14</td><td align='left'> 3·28</td><td align='left'> 5·09</td><td align='left'> ...</td><td align='left'> 11·40</td></tr> +<tr><td align='left'>Mustard seed (white)</td><td align='left'> 0·39</td><td align='left'> 44·97</td><td align='left'> 2·19</td><td align='left'> ...</td><td align='left'> 1·31</td></tr> +<tr><td align='left'>Radish root</td><td align='left'> 1·19</td><td align='left'> 41·09</td><td align='left'> 7·71</td><td align='left'> ...</td><td align='left'> 8·17</td></tr> +<tr><td align='left'>Tobacco leaves</td><td align='left'> 2·18</td><td align='left'> 3·24</td><td align='left'> 5·09</td><td align='left'> ...</td><td align='left'> 11·40</td></tr> +<tr><td align='left'>Fucus nodosus</td><td align='left'> 0·26</td><td align='left'> 1·71</td><td align='left'> 21·97</td><td align='left'> 6·39</td><td align='left'> 0·38</td></tr> +<tr><td align='left'>Fucus vesiculosus</td><td align='left'> 0·35</td><td align='left'> 2·14</td><td align='left'> 28·01</td><td align='left'> 2·20</td><td align='left'> 0·67</td></tr> +<tr><td align='left'>Laminaria digitata</td><td align='left'> 0·45</td><td align='left'> 1·75</td><td align='left'> 7·26</td><td align='left'> 15·23</td><td align='left'> 1·20</td></tr> +</table></div> +<p><span class='pagenum'><a name="Page_76" id="Page_76">[Pg 76]</a></span></p><p>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.</p> + +<p>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:<span class='pagenum'><a name="Page_77" id="Page_77">[Pg 77]</a></span>—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Wild.</td><td align='right'>Cultivated.</td></tr> +<tr><td align='left'>Potash</td><td align='right'>18·8</td><td align='right'>50·5</td></tr> +<tr><td align='left'>Soda</td><td align='right'>16·2</td><td align='right'>trace.</td></tr> +<tr><td align='left'>Chlorine</td><td align='right'>16·5</td><td align='right'>8·3</td></tr> +</table></div> + +<p>The soda having almost entirely disappeared in the cultivated plant, +while a corresponding increase had taken place in the quantity of +potash.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.<span class='pagenum'><a name="Page_78" id="Page_78">[Pg 78]</a></span></p> + +<p><i>Chlorine</i> 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.</p> + +<p><i>Sulphuric Acid</i> 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<span class='pagenum'><a name="Page_79" id="Page_79">[Pg 79]</a></span> 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 <i>total</i> amount of sulphur contained in 100 +parts of different plants, dried at 212°, has been constructed:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Poa palustris</td><td align='right'>0·165</td></tr> +<tr><td align='left'>Lolium perenne</td><td align='right'>0·310</td></tr> +<tr><td align='left'>Italian Ryegrass</td><td align='right'>0·329</td></tr> +<tr><td align='left'>Trifolium pratense</td><td align='right'>0·107</td></tr> +<tr><td align='left'> repens</td><td align='right'>0·099</td></tr> +<tr><td align='left'>Lucerne</td><td align='right'>0·336</td></tr> +<tr><td align='left'>Vetch</td><td align='right'>0·178</td></tr> +<tr><td align='left'>Potato tuber</td><td align='right'>0·082</td></tr> +<tr><td align='left'> tops</td><td align='right'>0·206</td></tr> +<tr><td align='left'>Carrot, root</td><td align='right'>0·092</td></tr> +<tr><td align='left'> tops</td><td align='right'>0·745</td></tr> +<tr><td align='left'>Mangold-Wurzel, root</td><td align='right'>0·058</td></tr> +<tr><td align='left'> tops</td><td align='right'>0·502</td></tr> +<tr><td align='left'>Swede, root</td><td align='right'>0·435</td></tr> +<tr><td align='left'> tops</td><td align='right'>0·458</td></tr> +<tr><td align='left'>Rape</td><td align='right'>0·448</td></tr> +<tr><td align='left'>Drumhead Cabbage</td><td align='right'>0·431</td></tr> +<tr><td align='left'>Wheat, grain</td><td align='right'>0·068</td></tr> +<tr><td align='left'> straw</td><td align='right'>0·245</td></tr> +<tr><td align='left'>Barley, grain,</td><td align='right'>0·053</td></tr> +<tr><td align='left'> straw</td><td align='right'>0·191</td></tr> +<tr><td align='left'>Oats, grain</td><td align='right'>0·103</td></tr> +<tr><td align='left'> straw</td><td align='right'>0·289</td></tr> +<tr><td align='left'>Rye, grain</td><td align='right'>0·051</td></tr> +<tr><td align='left'>Beans</td><td align='right'>0·056</td></tr> +<tr><td align='left'>Peas</td><td align='right'>0·127</td></tr> +<tr><td align='left'>Lentils</td><td align='right'>0·110</td></tr> +<tr><td align='left'>Hops</td><td align='right'>1·063</td></tr> +<tr><td align='left'>Gold of Pleasure</td><td align='right'>0·253</td></tr> +<tr><td align='left'>Black Mustard</td><td align='right'>1·170</td></tr> +<tr><td align='left'>White Mustard</td><td align='right'>1·050</td></tr> +</table></div> + +<p><i>Phosphoric acid</i>, 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.</p> + +<p><i>Carbonic acid</i> 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<span class='pagenum'><a name="Page_80" id="Page_80">[Pg 80]</a></span> union with organic +acids, or combined in some way with the organic constituents of the +plant.</p> + +<p><i>Silica</i> 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.</p> + +<p>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<span class='pagenum'><a name="Page_81" id="Page_81">[Pg 81]</a></span> 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.</p> + +<p>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 <i>Agricultural Chemistry</i>, 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:<span class='pagenum'><a name="Page_82" id="Page_82">[Pg 82]</a></span>—</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> </td><td align='left'> Salts of Potash and Soda.</td><td align='left'> Salts of Lime and Magnesia.</td><td align='left'> Silica.</td></tr> +<tr><td rowspan="5">Silica Plants. </td><td align='left'>Oat straw with seeds</td><td align='left'> 34·00</td><td align='left'> 4·00</td><td align='left'> 62·00</td></tr> +<tr><td align='left'> Wheat straw</td><td align='left'> 22·50</td><td align='left'> 7·20</td><td align='left'> 61·50</td></tr> +<tr><td align='left'> Barley straw with seeds</td><td align='left'> 19·00</td><td align='left'> 25·70</td><td align='left'> 55·30</td></tr> +<tr><td align='left'> Rye straw</td><td align='left'> 18·65</td><td align='left'> 16·52</td><td align='left'> 63·89</td></tr> +<tr><td align='left'> Good hay</td><td align='left'> 6·00</td><td align='left'> 34·00</td><td align='left'> 60·00</td></tr> +<tr><td rowspan="4">Lime Plants</td><td align='left'>Tobacco</td><td align='left'> 24·34</td><td align='left'> 67·44</td><td align='left'> 8·30</td></tr> +<tr><td align='left'> Pea straw</td><td align='left'> 27·82</td><td align='left'> 63·74</td><td align='left'> 7·81</td></tr> +<tr><td align='left'> Potato plant</td><td align='left'> 4·20</td><td align='left'> 59·40</td><td align='left'> 36·40</td></tr> +<tr><td align='left'> Meadow Clover</td><td align='left'> 39·20</td><td align='left'> 56·00</td><td align='left'> 4·90</td></tr> +<tr><td rowspan="5">Potash Plants.</td><td align='left'>Maize straw</td><td align='left'> 72·45</td><td align='left'> 6·50</td><td align='left'> 18·00</td></tr> +<tr><td align='left'> Turnips</td><td align='left'> 81·60</td><td align='left'> 18·40</td><td align='left'> —</td></tr> +<tr><td align='left'> Beet root</td><td align='left'> 88·00</td><td align='left'> 12·00</td><td align='left'> —</td></tr> +<tr><td align='left'> Potatoes</td><td align='left'> 85·81</td><td align='left'> 14·19</td><td align='left'> —</td></tr> +<tr><td align='left'> Jerusalem Artichoke</td><td align='left'> 84·30</td><td align='left'> 15·70</td><td align='left'> —</td></tr> +</table></div> + + +<p>The special application of these facts must be reserved till we come to +treat of the rotation of crops.</p> + +<p>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.</p> + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_A_1" id="Footnote_A_1"></a><a href="#FNanchor_A_1"><span class="label">[A]</span></a> Apparently a species of Sinapis.</p></div> + +<div class="footnote"><p><a name="Footnote_B_2" id="Footnote_B_2"></a><a href="#FNanchor_B_2"><span class="label">[B]</span></a> Oxide of Manganese, 0·42.</p></div> + +<div class="footnote"><p><a name="Footnote_C_3" id="Footnote_C_3"></a><a href="#FNanchor_C_3"><span class="label">[C]</span></a> Oxide of Manganese, 0·92.</p></div> + +<div class="footnote"><p><a name="Footnote_D_4" id="Footnote_D_4"></a><a href="#FNanchor_D_4"><span class="label">[D]</span></a> Alumina, 1·02.</p></div> + +<div class="footnote"><p><a name="Footnote_E_5" id="Footnote_E_5"></a><a href="#FNanchor_E_5"><span class="label">[E]</span></a> Alumina, 0·63.</p></div> + +<div class="footnote"><p><a name="Footnote_F_6" id="Footnote_F_6"></a><a href="#FNanchor_F_6"><span class="label">[F]</span></a> Iodide of Potassium, 0·44; Sulphuret of Sodium, 3·66.</p></div> + +<div class="footnote"><p><a name="Footnote_G_7" id="Footnote_G_7"></a><a href="#FNanchor_G_7"><span class="label">[G]</span></a> Iodide of Potassium, 0·23.</p></div> + +<div class="footnote"><p><a name="Footnote_H_8" id="Footnote_H_8"></a><a href="#FNanchor_H_8"><span class="label">[H]</span></a> Iodide of Potassium, 1·68.</p></div> +</div> + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_83" id="Page_83">[Pg 83]</a></span></p> +<h2>CHAPTER V.</h2> + +<h3>THE SOIL—ITS CHEMICAL AND PHYSICAL CHARACTERS.</h3> + + +<p>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<span class='pagenum'><a name="Page_84" id="Page_84">[Pg 84]</a></span> 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.</p> + +<p>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.</p> + +<p><i>Origin of Soils.</i>—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<span class='pagenum'><a name="Page_85" id="Page_85">[Pg 85]</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_86" id="Page_86">[Pg 86]</a></span> +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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_87" id="Page_87">[Pg 87]</a></span>—</p> + + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td colspan="2"> Orthoclase.</td><td colspan="2"> Albite.</td><td colspan="2"> Oligoclase.</td><td colspan="2"> Labradorite.</td></tr> +<tr><td align='left'>Silica</td><td align='left'> 65·72</td><td align='left'> 65·00</td><td align='left'> 67·99</td><td align='left'> 68·23</td><td align='left'> 62·70</td><td align='left'> 63·51</td><td align='left'> 54·66</td><td align='left'> 54·67</td></tr> +<tr><td align='left'>Alumina</td><td align='left'> 18·57</td><td align='left'> 18·64</td><td align='left'> 19·61</td><td align='left'> 18·30</td><td align='left'> 23·80</td><td align='left'> 23·09</td><td align='left'> 27·87</td><td align='left'> 27·89</td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='left'> traces</td><td align='left'> 0·83</td><td align='left'> 0·70</td><td align='left'> 1·01</td><td align='left'> 0·62</td><td align='left'> —</td><td align='left'> —</td><td align='left'> 0·31</td></tr> +<tr><td align='left'>Oxide of manganese</td><td align='left'> traces</td><td align='left'> 0·13</td><td align='left'> —</td><td align='left'> —</td><td align='left'> —</td><td align='left'> —</td><td align='left'> —</td><td align='left'> —</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 0·34</td><td align='left'> 1·23</td><td align='left'> 0·66</td><td align='left'> 1·26</td><td align='left'> 4·60</td><td align='left'> 2·44</td><td align='left'> 12·01</td><td align='left'> 10·60</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·10</td><td align='left'> 1·03</td><td align='left'> —</td><td align='left'> 0·51</td><td align='left'> 0·02</td><td align='left'> 0·77</td><td align='left'> —</td><td align='left'> 0·18</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 14·02</td><td align='left'> 9·12</td><td align='left'> —</td><td align='left'> 2·53</td><td align='left'> 1·05</td><td align='left'> 2·19</td><td align='left'> —</td><td align='left'> 0·49</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 1·25</td><td align='left'> 3·49</td><td align='left'> 11·12</td><td align='left'> 7·99</td><td align='left'> 8·00</td><td align='left'> 9·37</td><td align='left'> 5·46</td><td align='left'> 5·05</td></tr> +<tr><td align='left'> </td><td align='left'> 100·00</td><td align='left'> 99·47</td><td align='left'>100·08</td><td align='left'> 99·83</td><td align='left'>100·79</td><td align='left'>101·37</td><td align='left'>100·00</td><td align='left'> 99·19</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_88" id="Page_88">[Pg 88]</a></span>—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Silica</td><td align='right'>46·80</td></tr> +<tr><td align='left'>Alumina</td><td align='right'>36·83</td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='right'>3·11</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>0·55</td></tr> +<tr><td align='left'>Potash</td><td align='right'>0·27</td></tr> +<tr><td align='left'>Water</td><td align='right'>12·44</td></tr> +<tr><td align='left'></td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +</table></div> + +<p>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.</p> + +<p>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:</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td colspan="2">Mica.</td></tr> +<tr><td align='left'></td><td align='right'>Potash.</td><td align='right'>Magnesia.</td></tr> +<tr><td align='left'>Silica</td><td align='right'>46·36</td><td align='right'>42·65</td></tr> +<tr><td align='left'>Alumina</td><td align='right'>36·80</td><td align='right'>12·96</td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='right'>4·53</td><td align='right'>—</td></tr> +<tr><td align='left'>Protoxide of iron</td><td align='right'>—</td><td align='right'>7·11</td></tr> +<tr><td align='left'>Oxide of manganese</td><td align='right'>0·02</td><td align='right'>1·06</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>—</td><td align='right'>25·75</td></tr> +<tr><td align='left'>Potash</td><td align='right'>9·22</td><td align='right'>6·03</td></tr> +<tr><td align='left'>Hydrofluoric acid</td><td align='right'>0·70</td><td align='right'>0·62</td></tr> +<tr><td align='left'>Water</td><td align='right'>1·84</td><td align='right'>3·17</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>99·47</td><td align='right'>99·35</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_89" id="Page_89">[Pg 89]</a></span></p> + +<p>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.</p> + +<p>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:—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td colspan="3">Hornblende.</td></tr> +<tr><td align='left'></td><td align='right'>Common.</td><td align='right'>Basaltic.</td><td align='right'>Augite.</td></tr> +<tr><td align='left'>Silica</td><td align='right'>41·50</td><td align='right'>42·24</td><td align='right'>50·12</td></tr> +<tr><td align='left'>Alumina</td><td align='right'>15·75</td><td align='right'>13·92</td><td align='right'>4·20</td></tr> +<tr><td align='left'>Protoxide of iron</td><td align='right'>7·75</td><td align='right'>14·59</td><td align='right'>11·60</td></tr> +<tr><td align='left'>Oxide of manganese</td><td align='right'>0·25</td><td align='right'>0.33</td><td align='right'>—</td></tr> +<tr><td align='left'>Lime</td><td align='right'>14·09</td><td align='right'>12·24</td><td align='right'>20·55</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>19·40</td><td align='right'>13·74</td><td align='right'>13·70</td></tr> +<tr><td align='left'>Water</td><td align='right'>0·50</td><td align='right'>—</td><td align='right'>—</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>99·24</td><td align='right'>97·05</td><td align='right'>99·67</td></tr> +</table></div> + +<p>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.</p> + +<p>The minerals just referred to, constitute the great bulk of the mountain +masses, but they are associated with<span class='pagenum'><a name="Page_90" id="Page_90">[Pg 90]</a></span> 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—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Thomsonite.</td><td align='right'>Natrolite.</td></tr> +<tr><td align='left'>Silica</td><td align='right'>38·73</td><td align='right'>48·68</td></tr> +<tr><td align='left'>Alumina</td><td align='right'>30·84</td><td align='right'>26·36</td></tr> +<tr><td align='left'>Lime</td><td align='right'>13·43</td><td align='right'>—</td></tr> +<tr><td align='left'>Potash</td><td align='right'>0·54</td><td align='right'>0·23</td></tr> +<tr><td align='left'>Soda</td><td align='right'>3·85</td><td align='right'>16·00</td></tr> +<tr><td align='left'>Water</td><td align='right'>13·09</td><td align='right'>9·55</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>100·48</td><td align='right'>100·83</td></tr> +</table></div> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_91" id="Page_91">[Pg 91]</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_92" id="Page_92">[Pg 92]</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_93" id="Page_93">[Pg 93]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_94" id="Page_94">[Pg 94]</a></span> +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.</p> + +<p>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<span class='pagenum'><a name="Page_95" id="Page_95">[Pg 95]</a></span> 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:—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Transition Clay Slate.</td><td align='right'>Fire Clay.</td></tr> +<tr><td align='left'>Silica</td><td align='right'>60·03</td><td align='right'>54·77</td></tr> +<tr><td align='left'>Alumina</td><td align='right'>14·91</td><td align='right'>28·61</td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='right'>8·94</td><td align='right'>4·92</td></tr> +<tr><td align='left'>Lime</td><td align='right'>2·08</td><td align='right'>0·58</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>4·22</td><td align='right'>1·14</td></tr> +<tr><td align='left'>Potash</td><td align='right'>3·87</td><td align='right'>1·00</td></tr> +<tr><td align='left'>Soda</td><td align='right'>—</td><td align='right'>0·24</td></tr> +<tr><td align='left'>Carbonic acid {</td><td align='right'>5·67</td><td align='right'>8·24</td></tr> +<tr><td align='left'>Water {</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>99·72</td><td align='right'>99·50</td></tr> +</table></div> + +<p>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.<span class='pagenum'><a name="Page_96" id="Page_96">[Pg 96]</a></span></p> + +<p>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:—</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td colspan="2">Common.</td><td colspan="2">Magnesian.</td></tr> +<tr><td align='left'></td><td align='left'>Mid-Lothian.</td><td align='left'>Sutherland.</td><td align='left'>Sutherland.</td><td align='left'>Dumfries.</td></tr> +<tr><td align='left'>Silica</td><td align='left'>2·00</td><td align='left'>7·42</td><td align='left'>6·00</td><td align='left'>2·31</td></tr> +<tr><td align='left'>Peroxide of iron and alumina</td><td align='left'>0·45</td><td align='left'>0·76</td><td align='left'>1·57</td><td align='left'>2·00</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='left'>93·61</td><td align='left'>84·11</td><td align='left'>50·21</td><td align='left'>58·81</td></tr> +<tr><td align='left'>Carbonate of magnesia</td><td align='left'>1·62</td><td align='left'>7·45</td><td align='left'>41·22</td><td align='left'>36·41</td></tr> +<tr><td align='left'>Phosphate of lime</td><td align='left'>0·56</td><td align='left'>...</td><td align='left'>...</td><td align='left'>...</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='left'>0·92</td><td align='left'>...</td><td align='left'>...</td><td align='left'>0·10</td></tr> +<tr><td align='left'>Organic matter</td><td align='left'>0·20</td><td align='left'>...</td><td align='left'>...</td><td align='left'>...</td></tr> +<tr><td align='left'>Water</td><td align='left'>0·50</td><td align='left'>...</td><td align='left'>0·69</td><td align='left'>...</td></tr> +<tr><td align='left'> </td><td align='left'>——</td><td align='left'>——</td><td align='left'>——</td><td align='left'>——</td></tr> +<tr><td align='left'> </td><td align='left'>99·86</td><td align='left'>99·74</td><td align='left'>99·69</td><td align='left'>99·63</td></tr> +</table></div> + + +<p>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<span class='pagenum'><a name="Page_97" id="Page_97">[Pg 97]</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_98" id="Page_98">[Pg 98]</a></span> 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.</p> + +<p><i>Chemical Composition of the Soil.</i>—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<span class='pagenum'><a name="Page_99" id="Page_99">[Pg 99]</a></span> 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.</p> + +<p>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.<span class='pagenum'><a name="Page_100" id="Page_100">[Pg 100]</a></span> 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.</p> + +<p>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, <i>1st</i>, The substances soluble in +water; <i>2d</i>, Those insoluble in water, but soluble in acids; <i>3d</i>, 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<span class='pagenum'><a name="Page_101" id="Page_101">[Pg 101]</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_102" id="Page_102">[Pg 102]</a></span> 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 <i>fertile</i> 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.</p> + +<p>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.</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td colspan="2"> Mid-Lothian.</td><td colspan="2"> Perthshire.</td></tr> +<tr><td align='left'> </td><td align='left'> Soil.</td><td align='left'> Subsoil.</td><td align='left'> Soil.</td><td align='left'> Subsoil.</td></tr> +<tr><td colspan="5">SUBSTANCES SOLUBLE IN WATER.</td></tr> +<tr><td align='left'>Silica</td><td align='left'> 0·0149</td><td align='left'> 0·0104</td><td align='left'> 0·0072</td><td align='left'> 0·0461</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 0·0300</td><td align='left'> 0·0072</td><td align='left'> 0·0184</td><td align='left'> 0·0306</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·0097</td><td align='left'> 0·0016</td><td align='left'> 0·0040</td><td align='left'> 0·0034</td></tr> +<tr><td align='left'>Chlor. of magnesium</td><td align='left'> —</td><td align='left'> —</td><td align='left'> —</td><td align='left'> 0·0033</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 0·0034</td><td align='left'> 0·0037</td><td align='left'> —</td><td align='left'> —</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 0·0065</td><td align='left'> 0·0049</td><td align='left'> —</td><td align='left'> —</td></tr> +<tr><td align='left'>Chloride of potassium</td><td align='left'> —</td><td align='left'> —</td><td align='left'> 0·0088</td><td align='left'> 0·0080</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='left'> —</td><td align='left'> —</td><td align='left'> 0·0110</td><td align='left'> 0·0166</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='left'> 0·0193</td><td align='left'> 0·0124</td><td align='left'> 0·0089</td><td align='left'> 0·0239</td></tr> +<tr><td align='left'>Chlorine</td><td align='left'> trace</td><td align='left'> trace</td><td align='left'> —</td><td align='left'> —</td></tr> +<tr><td align='left'>Organic matters</td><td align='left'> 0·1481</td><td align='left'> 0·2228</td><td align='left'> 0·0608</td><td align='left'> 0·1342</td></tr> +<tr><td align='left'> </td><td align='left'> 0·2319</td><td align='left'> 0·2630</td><td align='left'> 0·1191</td><td align='left'> 0·2661</td></tr> +<tr><td align='left'><span class='pagenum'><a name="Page_103" id="Page_103">[Pg 103]</a></span></td></tr> +<tr><td colspan="5">SOLUBLE IN ACIDS.</td></tr> +<tr><td align='left'>Silica</td><td align='left'> 0·1490</td><td align='left'> 0·0680</td><td align='left'> 0·0482</td><td align='left'> 0·1697</td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='left'> 5·1730</td><td align='left'> 3·4820</td><td align='left'> 4·8700</td><td align='left'> 4·6633</td></tr> +<tr><td align='left'>Alumina</td><td align='left'> 2·1540</td><td align='left'> 1·8130</td><td align='left'> 2·6900</td><td align='left'> 3·9070</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 0·4470</td><td align='left'> 0·3810</td><td align='left'> 0·3616</td><td align='left'> 0·5050</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·4120</td><td align='left'> 0·2850</td><td align='left'> 0·3960</td><td align='left'> 0·9420</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 0·0650</td><td align='left'> 0·1650</td><td align='left'> 0·3445</td><td align='left'> 0·1670</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 0·0050</td><td align='left'> 0·0560</td><td align='left'> 0·1242</td><td align='left'> 0·1920</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='left'> 0·0250</td><td align='left'> 0·0850</td><td align='left'> 0·0911</td><td align='left'> 0·0160</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='left'> 0·4300</td><td align='left'> 0·1970</td><td align='left'> 0·2400</td><td align='left'> 0·2680</td></tr> +<tr><td align='left'>Carbonic acid</td><td align='left'> —</td><td align='left'> —</td><td align='left'> 0·0500</td><td align='left'> —</td></tr> +<tr><td align='left'> </td><td align='left'> 8·8600</td><td align='left'> 6·5320</td><td align='left'> 9·2156</td><td align='left'>10·8300</td></tr> +<tr><td colspan="5">INSOLUBLE IN ACIDS.</td></tr> +<tr><td align='left'>Silica</td><td align='left'> 71·3890</td><td align='left'> 82·5090</td><td align='left'> 63·1400</td><td align='left'>61·4200</td></tr> +<tr><td align='left'>Alumina</td><td align='left'> 4·7810</td><td align='left'> 3·5120</td><td align='left'> 11·3500</td><td align='left'>10·3400</td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='left'> trace</td><td align='left'> trace</td><td align='left'> —</td><td align='left'> 1·5670</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 0·7520</td><td align='left'> 0·5500</td><td align='left'> 0·4500</td><td align='left'> 0·7400</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·6610</td><td align='left'> 0·5500</td><td align='left'> 0·6200</td><td align='left'> 0·4450</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 0·2860</td><td align='left'> —</td><td align='left'> 2·4500</td><td align='left'> 2·0030</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 0·4220</td><td align='left'> —</td><td align='left'> 1·3100</td><td align='left'> 0·8440</td></tr> +<tr><td align='left'> </td><td align='left'> 78·2910</td><td align='left'> 87·1210</td><td align='left'> 79·3200</td><td align='left'>77·3590</td></tr> +<tr><td colspan="5">ORGANIC MATTERS.</td></tr> +<tr><td align='left'>Insoluble organic matter</td><td align='left'> 8·8777</td><td align='left'> 4·2370</td><td align='left'> 7·7400</td><td align='left'> 6·2910</td></tr> +<tr><td align='left'>Humine</td><td align='left'> 0·8850</td><td align='left'> 0·3450</td><td align='left'> 0·0700</td><td align='left'> 0·0840</td></tr> +<tr><td align='left'>Humic acid</td><td align='left'> 0·1340</td><td align='left'> 0·0310</td><td align='left'> 0·6800</td><td align='left'> 0·3600</td></tr> +<tr><td align='left'>Apocrenic acid</td><td align='left'> 0·1533</td><td align='left'> —</td><td align='left'> —</td><td align='left'> 0·0929</td></tr> +<tr><td align='left'>Water</td><td align='left'> 2·6840</td><td align='left'> 1·7670</td><td align='left'> 2·7000</td><td align='left'> 4·5750</td></tr> +<tr><td align='left'> </td><td align='left'> 12·7340</td><td align='left'> 6·3800</td><td align='left'> 11·1900</td><td align='left'>11·4020</td></tr> +<tr><td align='left'>Sum of all the constituents</td><td align='left'>100·1169</td><td align='left'> 100·2960</td><td align='left'> 99·8447</td><td align='left'>99·8571</td></tr> +<tr><td colspan="5">AMOUNT OF CARBON, HYDROGEN, NITROGEN, AND OXYGEN CONTAINED IN 100 PARTS OF EACH SOIL.</td></tr> +<tr><td align='left'>Carbon</td><td align='left'> 4·510</td><td align='left'> 1·3060</td><td align='left'> 2·55</td><td align='left'> 2·03</td></tr> +<tr><td align='left'>Hydrogen</td><td align='left'> 0·550</td><td align='left'> 0·3324</td><td align='left'> 0·71</td><td align='left'> 0·53</td></tr> +<tr><td align='left'>Nitrogen</td><td align='left'> 0·220</td><td align='left'> 0·0973</td><td align='left'> 0·21</td><td align='left'> 0·17</td></tr> +<tr><td align='left'>Oxygen</td><td align='left'> 4·918</td><td align='left'> 3·1001</td><td align='left'> 5·08</td><td align='left'> 4·09</td></tr> +<tr><td align='left'> </td><td align='left'> 10·198</td><td align='left'> 4·8358</td><td align='left'> 8·55</td><td align='left'> 6·82</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_104" id="Page_104">[Pg 104]</a></span></p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_105" id="Page_105">[Pg 105]</a></span> 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.</p> + +<p>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.</p> + +<p>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.<span class='pagenum'><a name="Page_106" id="Page_106">[Pg 106]</a></span></p> + + + +<div class='center'> +<table border="" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Surface Soil.</td><td align='left'> 18 inches deep.</td><td align='left'> 5 feet deep.</td></tr> +<tr><td colspan="4">SOLUBLE IN WATER.</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 0·07</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> trace</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 0·06</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 0·04</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Chlorine</td><td align='left'> 0·05</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Organic matter</td><td align='left'> 0·15</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'> </td><td align='left'> ——</td><td align='left'> </td><td align='left'> </td></tr> +<tr><td align='left'> </td><td align='left'> 0·37</td><td align='left'> </td><td align='left'> </td></tr> +<tr><td colspan="4">SOLUBLE IN ACIDS.</td></tr> +<tr><td align='left'>Silica</td><td align='left'> 0·74</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='left'> 2·22</td><td align='left'> 1·67</td><td align='left'> 1·87</td></tr> +<tr><td align='left'>Protoxide of iron</td><td align='left'> 0·77</td><td align='left'> 9·05</td><td align='left'> 3·10</td></tr> +<tr><td align='left'>Alumina</td><td align='left'> 1·90</td><td align='left'> 2·52</td><td align='left'> 4·21</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 10·43</td><td align='left'> 3·04</td><td align='left'> 25·75</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·20</td><td align='left'> 0·54</td><td align='left'> 0·51</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 0·03</td><td align='left'> 0·29</td><td align='left'> 0·28</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 0·02</td><td align='left'> 0·11</td><td align='left'> 0·16</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='left'> trace</td><td align='left'> 0·02</td><td align='left'> 0·13</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='left'> 0·14</td><td align='left'> trace</td><td align='left'> 0·04</td></tr> +<tr><td align='left'>Carbonic acid</td><td align='left'> 7·38</td><td align='left'> 0·82</td><td align='left'> 20·23</td></tr> +<tr><td align='left'> </td><td align='left'> ——</td><td align='left'> ——</td><td align='left'> ——</td></tr> +<tr><td align='left'> </td><td align='left'> 23·83</td><td align='left'> 18·06</td><td align='left'> 56·28</td></tr> +<tr><td colspan="4">INSOLUBLE IN ACIDS.</td></tr> +<tr><td align='left'>Silica</td><td align='left'> 41·44</td><td align='left'> 51·24</td><td align='left'> 27·67</td></tr> +<tr><td align='left'>Protoxide of iron</td><td align='left'> 3·24</td><td align='left'> 0·26</td><td align='left'> 1·40</td></tr> +<tr><td align='left'>Alumina</td><td align='left'> 9·00</td><td align='left'> 1·50</td><td align='left'> 1·00</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 0·08</td><td align='left'> 0·88</td><td align='left'> trace</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·80</td><td align='left'> 0·54</td><td align='left'> trace</td></tr> +<tr><td align='left'>Potash</td><td align='left'> ...</td><td align='left'> 0·74</td><td align='left'> ...</td></tr> +<tr><td align='left'>Soda</td><td align='left'> ...</td><td align='left'> 0·25</td><td align='left'> ...</td></tr> +<tr><td align='left'> </td><td align='left'> ——</td><td align='left'> ——</td><td align='left'> ——</td></tr> +<tr><td align='left'> </td><td align='left'> 54·56</td><td align='left'> 55·41</td><td align='left'> 30·07</td></tr> +<tr><td colspan="4">ORGANIC MATTERS.</td></tr> +<tr><td align='left'>Humine</td><td align='left'> 1·58 }</td><td align='left'> </td><td align='left'> </td></tr> +<tr><td align='left'>Humic acid</td><td align='left'> 1·15 }</td><td align='left'> 12·05</td><td align='left'> 7·49</td></tr> +<tr><td align='left'>Insoluble organic matters</td><td align='left'> 7·66 }</td><td align='left'> </td><td align='left'> </td></tr> +<tr><td align='left'>Water</td><td align='left'> 11·13</td><td align='left'> 14·69</td><td align='left'> 6·06</td></tr> +<tr><td align='left'> </td><td align='left'> ——</td><td align='left'> ——</td><td align='left'> ——</td></tr> +<tr><td align='left'> </td><td align='left'> 21·52</td><td align='left'> 26·74</td><td align='left'> 13·55</td></tr> +<tr><td align='left'>Sum of all the constituents</td><td align='left'> 100·28</td><td align='left'> 100·21</td><td align='left'> 99·90</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_107" id="Page_107">[Pg 107]</a></span></p> + +<p>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.</p> + +<p>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.</p> + +<p>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—</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Surface.</td><td align='left'> 15 inches deep.</td><td align='left'> 30 inches deep.</td></tr> +<tr><td align='left'>Insoluble silica</td><td align='left'> 57·646</td><td align='left'> 51·706</td><td align='left'> 55·372</td></tr> +<tr><td align='left'>Soluble silica</td><td align='left'> 2·340</td><td align='left'> 2·496</td><td align='left'> 2·286</td></tr> +<tr><td align='left'>Alumina</td><td align='left'> 1·830</td><td align='left'> 2·900</td><td align='left'> 2·888</td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='left'> 9·039</td><td align='left'> 10·305</td><td align='left'> 11·864</td></tr> +<tr><td align='left'>Protoxide of iron</td><td align='left'> 0·350</td><td align='left'> 0·563</td><td align='left'> 0·200</td></tr> +<tr><td align='left'>Oxide of manganese</td><td align='left'> 0·288</td><td align='left'> 0·354</td><td align='left'> 0·284</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 4·092</td><td align='left'> 5·096</td><td align='left'> 2·480</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·130</td><td align='left'> 0·140</td><td align='left'> 0·128</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 1·026</td><td align='left'> 1·430</td><td align='left'> 1·521</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 1·972</td><td align='left'> 2·069</td><td align='left'> 1·937</td></tr> +<tr><td align='left'>Ammonia</td><td align='left'> 0·060</td><td align='left'> 0·078</td><td align='left'> 0·075</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='left'> 0·466</td><td align='left'> 0·324</td><td align='left'> 0·478</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='left'> 0·896</td><td align='left'> 1·104</td><td align='left'> 0·576</td></tr> +<tr><td align='left'>Carbonic acid</td><td align='left'> 6·085</td><td align='left'> 6·940</td><td align='left'> 4·775</td></tr> +<tr><td align='left'>Chlorine</td><td align='left'> 1·240</td><td align='left'> 1·302</td><td align='left'> 1·418</td></tr> +<tr><td align='left'>Humic acid</td><td align='left'> 2·798</td><td align='left'> 3·991</td><td align='left'> 3·428</td></tr> +<tr><td align='left'>Crenic acid</td><td align='left'> 0·771</td><td align='left'> 0·731</td><td align='left'> 0·037</td></tr> +<tr><td align='left'>Apocrenic acid</td><td align='left'> 0·107</td><td align='left'> 0·160</td><td align='left'> 0·152</td></tr> +<tr><td align='left'>Other organic matters and Combined water</td><td align='left'> 8·324</td><td align='left'> 7·700</td><td align='left'> 9·348</td></tr> +<tr><td align='left'>Loss</td><td align='left'> 0·540</td><td align='left'> 0·611</td><td align='left'> 0·753</td></tr> +<tr><td align='left'> </td><td align='left'> ———</td><td align='left'> ———</td><td align='left'> ———</td></tr> +<tr><td align='left'> </td><td align='left'> 100·000</td><td align='left'> 100·000</td><td align='left'> 100·000</td></tr> +</table></div> + +<p>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.</p> + + +<h4>SOLUBLE IN ACIDS.</h4> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Soluble silica</td><td align='right'>0·173</td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='right'>6·775</td></tr> +<tr><td align='left'><span class='pagenum'><a name="Page_109" id="Page_109">[Pg 109]</a></span></td></tr> +<tr><td align='left'>Alumina</td><td align='right'>1·150</td></tr> +<tr><td align='left'>Oxide of manganese</td><td align='right'>trace</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>0·856</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>0·099</td></tr> +<tr><td align='left'>Potash</td><td align='right'>0·132</td></tr> +<tr><td align='left'>Soda</td><td align='right'>0·123</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='right'>trace</td></tr> +<tr><td align='left'>Chlorine</td><td align='right'>trace</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>9·308</td></tr> +<tr><td align='left'>Silica</td><td align='right'>73·096</td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='right'>1·371</td></tr> +<tr><td align='left'>Alumina</td><td align='right'>4·263</td></tr> +<tr><td align='left'>Lime</td><td align='right'>0·858</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>0·520</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>80·108</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>8·012</td></tr> +<tr><td align='left'>Water</td><td align='right'>2·391</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>10·403</td></tr> +<tr><td align='left'></td><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='left'></td><td align='right'>99·819</td></tr> +</table></div> + +<p>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:<span class='pagenum'><a name="Page_110" id="Page_110">[Pg 110]</a></span>—</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Moorland soil near Aurich, East Friesland.</td><td align='left'> Sandy soil near Wettingen.</td><td align='left'> Soil from near Muhlhausen.</td></tr> +<tr><td align='left'>Silica and sand</td><td align='left'> 70·576</td><td align='left'> 96·000</td><td align='left'> 77·490</td></tr> +<tr><td align='left'>Alumina</td><td align='left'> 1·050</td><td align='left'> 0·500</td><td align='left'> 9·490</td></tr> +<tr><td align='left'>Oxide of iron</td><td align='left'> 0·252</td><td align='left'> 2·000</td><td align='left'> 5·800</td></tr> +<tr><td align='left'>Oxide of manganese }</td><td rowspan="2"> trace</td><td align='left'> { trace</td><td align='left'> 0·105</td></tr> +<tr><td align='left'>Lime }</td><td align='left'> { 0·001</td><td align='left'> 0·866</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·012 </td><td rowspan="5"> trace</td><td align='left'> 0·728</td></tr> +<tr><td align='left'>Potash }</td><td rowspan="4"> trace </td><td rowspan="2">trace</td></tr> +<tr><td align='left'>Soda }</td></tr> +<tr><td align='left'>Phosphoric acid }</td><td align='left'> 0·003</td></tr> +<tr><td align='left'>Sulphuric acid }</td><td align='left'> trace</td></tr> +<tr><td align='left'>Carbonic acid</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 0·200</td></tr> +<tr><td align='left'>Chlorine</td><td align='left'> trace</td><td align='left'> trace</td><td align='left'> trace</td></tr> +<tr><td align='left'>Humic acid</td><td align='left'> 11·910</td><td align='left'> 0·200</td><td align='left'> 0·732</td></tr> +<tr><td align='left'>Insoluble humus</td><td align='left'> 16·200</td><td align='left'> 1·299</td><td align='left'> 0·200</td></tr> +<tr><td align='left'>Water</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 4·096</td></tr> +<tr><td align='left'> </td><td align='left'> 100·000</td><td align='left'> 100·000</td><td align='left'> 100·000</td></tr> +</table></div> + +<p>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.</p> + +<p>An examination of the foregoing analyses indicates pretty clearly some +of the conditions of fertility of the<span class='pagenum'><a name="Page_111" id="Page_111">[Pg 111]</a></span> 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.</p> + +<p>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.</p> + +<p>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.<span class='pagenum'><a name="Page_112" id="Page_112">[Pg 112]</a></span> 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.</p> + +<p>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—</p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> 1</td><td align='left'> 2</td><td align='left'> 3</td><td align='left'> 4</td><td align='left'> 5</td><td align='left'> 6</td><td align='left'> 7</td></tr> +<tr><td align='left'>Potash,</td><td align='left'>trace</td><td align='left'>trace</td><td align='left'> 0·02</td><td align='left'> 0·05</td><td align='left'>trace</td><td align='left'> 0·22</td><td align='left'>trace</td></tr> +<tr><td align='left'>Soda,</td><td align='left'> 1·00</td><td align='left'> 2·17</td><td align='left'> 2·26</td><td align='left'> 0·87</td><td align='left'> 1·42</td><td align='left'> 1·40</td><td align='left'> 3·20</td></tr> +<tr><td align='left'>Lime,</td><td align='left'> 4·85</td><td align='left'> 7·19</td><td align='left'> 6·05</td><td align='left'> 2·26</td><td align='left'> 2·52</td><td align='left'> 5·82</td><td align='left'>13·00</td></tr> +<tr><td align='left'>Magnesia,</td><td align='left'> 0·68</td><td align='left'> 2·32</td><td align='left'> 2·48</td><td align='left'> 0·41</td><td align='left'> 0·21</td><td align='left'> 0·93</td><td align='left'> 2·50</td></tr> +<tr><td align='left'>Iron and Alumina,</td><td align='left'> 0·40</td><td align='left'> 0·05</td><td align='left'> 0·10</td><td align='left'> none</td><td align='left'> 1·30</td><td align='left'> 0·35</td><td align='left'> 0·50</td></tr> +<tr><td align='left'>Silica,</td><td align='left'> 0·95</td><td align='left'> 0·45</td><td align='left'> 0·55</td><td align='left'> 1·20</td><td align='left'> 1·80</td><td align='left'> 0·65</td><td align='left'> 0·85</td></tr> +<tr><td align='left'>Chlorine,</td><td align='left'> 0·70</td><td align='left'> 1·10</td><td align='left'> 1·27</td><td align='left'> 0·81</td><td align='left'> 1·26</td><td align='left'> 1·21</td><td align='left'> 2·62</td></tr> +<tr><td align='left'>Sulphuric acid,</td><td align='left'> 1·65</td><td align='left'> 5·15</td><td align='left'> 4·40</td><td align='left'> 1·71</td><td align='left'> 1·29</td><td align='left'> 3·12</td><td align='left'> 9·51</td></tr> +<tr><td align='left'>Phosphoric acid,</td><td align='left'>trace</td><td align='left'> 0·12</td><td align='left'>trace</td><td align='left'>trace</td><td align='left'> 0·08</td><td align='left'> 0·06</td><td align='left'> 0·12</td></tr> +<tr><td align='left'>Ammonia,</td><td align='left'> 0·018</td><td align='left'> 0·018</td><td align='left'> 0·018</td><td align='left'> 0·012</td><td align='left'> 0·018</td><td align='left'> 0·006</td><td align='left'> 0·018</td></tr> +<tr><td align='left'>Nitric acid,</td><td align='left'> 7·17</td><td align='left'>14·74</td><td align='left'>12·72</td><td align='left'> 1·95</td><td align='left'> 3·45</td><td align='left'> 8·05</td><td align='left'>11·45</td></tr> +<tr><td align='left'>Organic matter,</td><td align='left'> 7·00</td><td align='left'> 7·40</td><td align='left'>12·50</td><td align='left'> 5·60</td><td align='left'> 5·70</td><td align='left'> 5·80</td><td align='left'> 7·40</td></tr> +</table></div> +<p><span class='pagenum'><a name="Page_113" id="Page_113">[Pg 113]</a></span></p> + +<p>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.</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td colspan="7">IN 10,000 PARTS.</td></tr> +<tr><td align='left'> </td><td align='left'> 1</td><td align='left'> 2</td><td align='left'> 3</td><td align='left'> 4</td><td align='left'> 5</td><td align='left'> 6</td></tr> +<tr><td align='left'>Organic matter</td><td align='left'> 0·25</td><td align='left'> 0·24</td><td align='left'> 0·16</td><td align='left'> 0.06</td><td align='left'> 0·63</td><td align='left'> 0·56</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='left'> 0·84</td><td align='left'> 0·84</td><td align='left'> 1·27</td><td align='left'> 0·79</td><td align='left'> 0·71</td><td align='left'> 0·84</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='left'> 2·08</td><td align='left'> 2·10</td><td align='left'> 1·14</td><td align='left'> 0·17</td><td align='left'> 0·77</td><td align='left'> 0·72</td></tr> +<tr><td align='left'>Nitrate of lime</td><td align='left'> 0·02</td><td align='left'> 0·02</td><td align='left'> 0·01</td><td align='left'> 0·02</td><td align='left'> 0·02</td><td align='left'> 0·02</td></tr> +<tr><td align='left'>Carbonate of magnesia</td><td align='left'> 0·70</td><td align='left'> 0·69</td><td align='left'> 0·47</td><td align='left'> 0·27</td><td align='left'> 0·27</td><td align='left'> 0·16</td></tr> +<tr><td align='left'>Carbonate of iron</td><td align='left'> 0·04</td><td align='left'> 0·04</td><td align='left'> 0·04</td><td align='left'> 0·02</td><td align='left'> 0·02</td><td align='left'> 0·01</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 0·02</td><td align='left'> 0·02</td><td align='left'> 0·02</td><td align='left'> 0·02</td><td align='left'> 0·04</td><td align='left'> 0·06</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 0·11</td><td align='left'> 0·15</td><td align='left'> 0·13</td><td align='left'> 0·10</td><td align='left'> 0·05</td><td align='left'> 0·04</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='left'> 0·08</td><td align='left'> 0·08</td><td align='left'> 0·07</td><td align='left'> 0·03</td><td align='left'> 0·01</td><td align='left'> 0·01</td></tr> +<tr><td align='left'>Silica</td><td align='left'> 0·07</td><td align='left'> 0·07</td><td align='left'> 0.06</td><td align='left'> 0·05</td><td align='left'> 0·06</td><td align='left'> 0·05</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_114" id="Page_114">[Pg 114]</a></span> 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:<span class='pagenum'><a name="Page_115" id="Page_115">[Pg 115]</a></span>—</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td rowspan="2">Nature of Soil.</td><td rowspan="2"> Crop.</td><td rowspan="2"> No. of cubic inches of air in 34 cubic inches of soil</td><td colspan="3">100 VOLUMES OF AIR CONTAIN</td></tr> +<tr><td align='left'>Carbonic acid.</td><td align='left'> Oxygen.</td><td align='left'>Nitrogen.</td></tr> +<tr><td align='left'>Light sandy soil, newly manured</td><td align='left'> ...</td><td align='left'> 8·0</td><td align='left'> 2·17</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'> Do. manured 8 days before</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 1·54</td><td align='left'> 18·80</td><td align='left'> 79·66</td></tr> +<tr><td align='left'> Do. long after manuring</td><td align='left'>Yellow turnip</td><td align='left'> 7·9</td><td align='left'> 0·93</td><td align='left'> 19·50</td><td align='left'> 79·57</td></tr> +<tr><td align='left'>Very sandy</td><td align='left'>Vineyard</td><td align='left'> 9·6</td><td align='left'> 1·06</td><td align='left'> 19·72</td><td align='left'> 79·22</td></tr> +<tr><td align='left'>Sandy, with many stones</td><td align='left'>Forest</td><td align='left'> 4·0</td><td align='left'> 0·87</td><td align='left'> 19·61</td><td align='left'> 79·52</td></tr> +<tr><td align='left'>Loamy</td><td align='left'> ...</td><td align='left'> 2·4</td><td align='left'> 0·46</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Sandy, subsoil of the last</td><td align='left'> ...</td><td align='left'> 3·0</td><td align='left'> 0·24</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Sandy soil, long after manuring</td><td align='left'>Trefoil</td><td align='left'> 7·6</td><td align='left'> 0·74</td><td align='left'> 19·02</td><td align='left'> 80·24</td></tr> +<tr><td align='left'> Do. Recently manured</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 0·85</td><td align='left'> 19·41</td><td align='left'> 79·74</td></tr> +<tr><td align='left'> Do. manured 8 days before</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 1·54</td><td align='left'> 18·80</td><td align='left'> 79·66</td></tr> +<tr><td align='left'>Heavy clay</td><td align='left'>Jerusalem artichoke</td><td align='left'> 7·0</td><td align='left'> 0·66</td><td align='left'> 19·99</td><td align='left'> 79·35</td></tr> +<tr><td align='left'>Fertile soil (moist)</td><td align='left'>Meadow</td><td align='left'> 5·5</td><td align='left'> 1·79</td><td align='left'> 19·41</td><td align='left'> 78·80</td></tr> +</table></div> +<p>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,<span class='pagenum'><a name="Page_116" id="Page_116">[Pg 116]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_117" id="Page_117">[Pg 117]</a></span> 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.</p> + +<p>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.</p> + +<p>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.<span class='pagenum'><a name="Page_118" id="Page_118">[Pg 118]</a></span></p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.<span class='pagenum'><a name="Page_119" id="Page_119">[Pg 119]</a></span></p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Clover fails.</td><td align='right'>Clover succeeds.</td></tr> +<tr><td align='left'>Insoluble silicates</td><td align='right'>83·90</td><td align='right'>81·34</td></tr> +<tr><td align='left'>Soluble silica</td><td align='right'>0·08</td><td align='right'>0·02</td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='right'>4·45</td><td align='right'>6·68</td></tr> +<tr><td align='left'>Alumina</td><td align='right'>2·40</td><td align='right'>3·00</td></tr> +<tr><td align='left'>Lime</td><td align='right'>1·23</td><td align='right'>1·33</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>0·45</td><td align='right'>0·25</td></tr> +<tr><td align='left'>Potash</td><td align='right'>0·20</td><td align='right'>0·22</td></tr> +<tr><td align='left'>Soda</td><td align='right'>0·07</td><td align='right'>0·09</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='right'>0·05</td><td align='right'>0·08</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='right'>0·38</td><td align='right'>0·07</td></tr> +<tr><td align='left'>Carbonic acid</td><td align='right'>0·09</td><td align='right'>0·34</td></tr> +<tr><td align='left'>Chlorine</td><td align='right'>trace</td><td align='right'>trace</td></tr> +<tr><td align='left'>Humic acid</td><td align='right'>0·42</td><td align='right'>0·43</td></tr> +<tr><td align='left'>Humine</td><td align='right'>...</td><td align='right'>0·10</td></tr> +<tr><td align='left'>Insoluble organic matters</td><td align='right'>3·70</td><td align='right'>3·61</td></tr> +<tr><td align='left'>Water</td><td align='right'>2·54</td><td align='right'>2·52</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>99·96</td><td align='right'>100·08</td></tr> +<tr><td align='left'>Nitrogen</td><td align='right'>0·15</td><td align='right'>1·15</td></tr> +</table></div> + +<p>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.</p> + +<p>These properties are partly mechanical and partly chemical, and in both +ways exercise an important influence on the fertility of the soil.</p> + +<p>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,<span class='pagenum'><a name="Page_120" id="Page_120">[Pg 120]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_121" id="Page_121">[Pg 121]</a></span> +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.</p> + +<p>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<span class='pagenum'><a name="Page_122" id="Page_122">[Pg 122]</a></span> 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:—</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Loamy soil,<br /> Dorsetshire.</td><td align='left'> Red soil,<br /> Berkshire.</td><td align='left'> Pure clay.</td><td align='left'> Subsoil clay,<br /> Somersetshire.</td></tr> +<tr><td align='left'>Ammonia, caustic</td><td align='left'> 0·3438</td><td align='left'> 0·1570</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'> " from muriate</td><td align='left'> 0·3478</td><td align='left'> 0·1966</td><td align='left'> 0.2847</td><td align='left'> 0·0818</td></tr> +<tr><td align='left'>Potash, caustic</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 1·050</td><td align='left'> 2·087</td></tr> +<tr><td align='left'> " from nitrate</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 0·4980</td><td align='left'> ...</td></tr> +<tr><td align='left'>Lime, caustic</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 1·468</td><td align='left'> ...</td></tr> +<tr><td align='left'> " from bicarbonate</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 0·731</td><td align='left'> ...</td></tr> +</table></div> + + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_123" id="Page_123">[Pg 123]</a></span> 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.</p> + +<p>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 +<i>lime</i>, 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_124" id="Page_124">[Pg 124]</a></span> 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<a name="FNanchor_I_9" id="FNanchor_I_9"></a><a href="#Footnote_I_9" class="fnanchor">[I]</a> 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 <i>retained</i> by the +peat.</p> + +<p>In this case pure ammonia was used, but Way's experiments having shown +that this alkali is not absorbed<span class='pagenum'><a name="Page_125" id="Page_125">[Pg 125]</a></span> 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<span class='pagenum'><a name="Page_126" id="Page_126">[Pg 126]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_127" id="Page_127">[Pg 127]</a></span> matters at the mercy of the weather, and liable at any moment +to be washed out by a heavy fall of rain.</p> + +<p>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.</p> + +<p>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 <i>1st</i>, The specific +gravity of the soils; <i>2d</i>, The quantity of water which they are capable +of imbibing; <i>3d</i>, The rapidity with which they give off by evaporation +the water they have imbibed; that is, their tendency to become dry; +<i>4th</i>, The extent to which they shrink in drying; <i>5th</i>, Their +hygrometric power; <i>6th</i>, The extent to which they are heated by the +sun's rays;<span class='pagenum'><a name="Page_128" id="Page_128">[Pg 128]</a></span> <i>7th</i>, The rapidity with which a heated soil cools down, +which indicates its power of <i>retaining</i> heat; <i>8th</i>, Their tenacity, or +the resistance they offer to the passage of agricultural implements; +<i>9th</i>, 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.</p> + +<p>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.<span class='pagenum'><a name="Page_129" id="Page_129">[Pg 129]</a></span></p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='left'> Specific gravity.</td><td align='left'>Water absorbed by 100 parts per cent.</td><td align='left'>Of 100 parts of water absorbed there evaporate in four hours at 66°</td><td align='left'> Diminution in bulk during drying of 100 parts moist soil.</td></tr> +<tr><td align='left'>Siliceous sand</td><td align='left'> 2·753</td><td align='left'> 25</td><td align='left'> 88·4</td><td align='left'> 0·0</td></tr> +<tr><td align='left'>Calcareous sand</td><td align='left'> 2·822</td><td align='left'> 29</td><td align='left'> 75·9</td><td align='left'> 0·0</td></tr> +<tr><td align='left'>Light clay</td><td align='left'> 2·701</td><td align='left'> 40</td><td align='left'> 52·0</td><td align='left'> 6·0</td></tr> +<tr><td align='left'>Stiff clay</td><td align='left'> 2·652</td><td align='left'> 50</td><td align='left'> 45·7</td><td align='left'> 8·9</td></tr> +<tr><td align='left'>Heavy clay</td><td align='left'> 2·603</td><td align='left'> 61</td><td align='left'> 34·9</td><td align='left'> 11·4</td></tr> +<tr><td align='left'>Pure clay</td><td align='left'> 2·591</td><td align='left'> 70</td><td align='left'> 31·3</td><td align='left'> 18·3</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='left'> 2·468</td><td align='left'> 85</td><td align='left'> 28·0</td><td align='left'> 5·0</td></tr> +<tr><td align='left'>Humus</td><td align='left'> 1·225</td><td align='left'> 190</td><td align='left'> 20·5</td><td align='left'> 20·0</td></tr> +<tr><td align='left'>Gypsum</td><td align='left'> 2·358</td><td align='left'> 27</td><td align='left'> 71·7</td><td align='left'> 0·0</td></tr> +<tr><td align='left'>Garden soil</td><td align='left'> 2·332</td><td align='left'> 96</td><td align='left'> 24·5</td><td align='left'> 14·9</td></tr> +<tr><td align='left'>Soil from Hoffwyl</td><td align='left'> 2·401</td><td align='left'> 52</td><td align='left'> 32·0</td><td align='left'> 12·0</td></tr> +<tr><td align='left'>Soil from Jura</td><td align='left'> 2·526</td><td align='left'> 47</td><td align='left'> 40·1</td><td align='left'> 9·5</td></tr> +</table></div> +<p><br /><br /></p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td colspan="4"> Quantity of hygrometric water absorbed by 77·165 grains of the soil spread on a surface of 141·48 square inches.</td><td align='left'> Power of retaining heat. Calcareous sand, 100.</td></tr> +<tr><td align='left'> </td><td align='left'> 12 hours.</td><td align='left'> 24 hours.</td><td align='left'> 48 hours.</td><td align='left'> 72 hours.</td><td align='left'> </td></tr> +<tr><td align='left'>Siliceous sand</td><td align='left'> 0</td><td align='left'> 0</td><td align='left'> 0</td><td align='left'> 0</td><td align='left'> 95·6</td></tr> +<tr><td align='left'>Calcareous sand</td><td align='left'> 0·154</td><td align='left'> 0·231</td><td align='left'> 0·231</td><td align='left'> 0·231</td><td align='left'> 100·0</td></tr> +<tr><td align='left'>Light clay</td><td align='left'> 1·617</td><td align='left'> 2·002</td><td align='left'> 2·156</td><td align='left'> 2·156</td><td align='left'> 76·9</td></tr> +<tr><td align='left'>Stiff clay</td><td align='left'> 1·925</td><td align='left'> 2·310</td><td align='left'> 2·618</td><td align='left'> 2·695</td><td align='left'> 71·1</td></tr> +<tr><td align='left'>Heavy clay</td><td align='left'> 2·310</td><td align='left'> 2·772</td><td align='left'> 3·080</td><td align='left'> 3·157</td><td align='left'> 68·4</td></tr> +<tr><td align='left'>Pure clay</td><td align='left'> 2·849</td><td align='left'> 3·234</td><td align='left'> 3·696</td><td align='left'> 3·773</td><td align='left'> 66·7</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='left'> 2·002</td><td align='left'> 2·387</td><td align='left'> 2·695</td><td align='left'> 2·695</td><td align='left'> 61·8</td></tr> +<tr><td align='left'>Humus</td><td align='left'> 6·160</td><td align='left'> 7·469</td><td align='left'> 8·470</td><td align='left'> 9·240</td><td align='left'> 49·0</td></tr> +<tr><td align='left'>Gypsum</td><td align='left'> 0·077</td><td align='left'> 0·077</td><td align='left'> 0·077</td><td align='left'> 0·077</td><td align='left'> 73·2</td></tr> +<tr><td align='left'>Garden soil</td><td align='left'> 2·695</td><td align='left'> 3·465</td><td align='left'> 3·850</td><td align='left'> 4·004</td><td align='left'> 64·8</td></tr> +<tr><td align='left'>Soil from Hoffwyl</td><td align='left'> 1·232</td><td align='left'> 1·771</td><td align='left'> 1·771</td><td align='left'> 1·771</td><td align='left'> 70·1</td></tr> +<tr><td align='left'>Soil from Jura</td><td align='left'> 1·078</td><td align='left'> 1·463</td><td align='left'> 1·540</td><td align='left'> 1·540</td><td align='left'> 74·3</td></tr> +</table></div> +<p><br /><br /></p> +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Tenacity of the soils. Pure clay, 100.</td><td align='left'> Quantity of oxygen absorbed by 77·165 grains f the moist soil in 30 days, from 15 cubic inches of atmospheric air. Expressed in cubic inches.</td></tr> +<tr><td align='left'>Siliceous sand</td><td align='left'> 0</td><td align='left'> 0·24</td></tr> +<tr><td align='left'>Calcareous sand</td><td align='left'> 0</td><td align='left'> 0·84</td></tr> +<tr><td align='left'>Light clay</td><td align='left'> 57·3</td><td align='left'> 1·39</td></tr> +<tr><td align='left'>Stiff clay</td><td align='left'> 68·8</td><td align='left'> 1·65</td></tr> +<tr><td align='left'>Heavy clay</td><td align='left'> 83·3</td><td align='left'> 2·04</td></tr> +<tr><td align='left'>Pure clay</td><td align='left'> 100·0</td><td align='left'> 2·29</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='left'> 5·0</td><td align='left'> 1·62</td></tr> +<tr><td align='left'>Humus</td><td align='left'> 8·7</td><td align='left'> 3·04</td></tr> +<tr><td align='left'>Gypsum</td><td align='left'> 7·3</td><td align='left'> 0·40</td></tr> +<tr><td align='left'>Garden soil</td><td align='left'> 7·6</td><td align='left'> 2·60</td></tr> +<tr><td align='left'>Soil from Hoffwyl</td><td align='left'> 33·0</td><td align='left'> 2·43</td></tr> +<tr><td align='left'>Soil from Jura</td><td align='left'> 22·0</td><td align='left'> 2·25</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_130" id="Page_130">[Pg 130]</a></span></p> + +<p>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<span class='pagenum'><a name="Page_131" id="Page_131">[Pg 131]</a></span> 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 <i>evaporation</i> 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.</p> + +<p>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,<span class='pagenum'><a name="Page_132" id="Page_132">[Pg 132]</a></span> 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.</p> + +<p>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.</p> + +<p>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,<span class='pagenum'><a name="Page_133" id="Page_133">[Pg 133]</a></span> but when it reaches 40 it becomes very difficult and +heavy to work.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_134" id="Page_134">[Pg 134]</a></span> 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.</p> + +<p><i>The Subsoil.</i>—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<span class='pagenum'><a name="Page_135" id="Page_135">[Pg 135]</a></span> 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 <i>vice versa</i>. 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.</p> + +<p>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.</p> + +<p><i>Classification of Soils.</i>—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<span class='pagenum'><a name="Page_136" id="Page_136">[Pg 136]</a></span> 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.</p> + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_I_9" id="Footnote_I_9"></a><a href="#FNanchor_I_9"><span class="label">[I]</span></a> Transactions of the Highland and Agricultural Society, vol. +vi., p. 317.</p></div> +</div> + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_137" id="Page_137">[Pg 137]</a></span></p> +<h2>CHAPTER VI.</h2> + +<h3>THE IMPROVEMENT OF THE SOIL BY MECHANICAL PROCESSES.</h3> + + +<p>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,<span class='pagenum'><a name="Page_138" id="Page_138">[Pg 138]</a></span> 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.</p> + +<p><i>Draining.</i>—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.</p> + +<p>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°.<span class='pagenum'><a name="Page_139" id="Page_139">[Pg 139]</a></span></p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Description of Soil.</td><td align='left'> Wet. Degs.</td><td align='left'> Dry. Degs.</td></tr> +<tr><td align='left'>Siliceous sand</td><td align='left'> 99·1</td><td align='left'> 112·6</td></tr> +<tr><td align='left'>Calcareous sand</td><td align='left'> 99·3</td><td align='left'> 112·1</td></tr> +<tr><td align='left'>Sandy clay</td><td align='left'> 98·2</td><td align='left'> 111·4</td></tr> +<tr><td align='left'>Loamy clay</td><td align='left'> 99·1</td><td align='left'> 112·1</td></tr> +<tr><td align='left'>Stiff clay</td><td align='left'> 99·3</td><td align='left'> 112·3</td></tr> +<tr><td align='left'>Fine bluish-grey clay</td><td align='left'> 99·5</td><td align='left'> 113·0</td></tr> +<tr><td align='left'>Garden mould</td><td align='left'> 99·5</td><td align='left'> 113·5</td></tr> +<tr><td align='left'>Arable soil</td><td align='left'> 97·7</td><td align='left'> 111·7</td></tr> +<tr><td align='left'>Slaty marl</td><td align='left'> 101·8</td><td align='left'> 115·3</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_140" id="Page_140">[Pg 140]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_141" id="Page_141">[Pg 141]</a></span> 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.</p> + +<p>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.</p> + +<p>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<a name="FNanchor_J_10" id="FNanchor_J_10"></a><a href="#Footnote_J_10" class="fnanchor">[J]</a> has estimated, that, on the<span class='pagenum'><a name="Page_142" id="Page_142">[Pg 142]</a></span> 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.</p> + +<p>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;<span class='pagenum'><a name="Page_143" id="Page_143">[Pg 143]</a></span> 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.</p> + +<p><i>Subsoil and Deep Ploughing.</i>—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 +<i>vice versa</i>. Both are operations which are useless unless they are +combined with draining, for it must<span class='pagenum'><a name="Page_144" id="Page_144">[Pg 144]</a></span> 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, <i>firstly</i>, by again +bringing to the surface the manures which have a tendency to sink to the +lower part of the soil, and, <i>secondly</i>, by bringing up a soil which has +not been exhausted by previous cropping—in fact a virgin soil.</p> + +<p>The success which attends the operation of subsoiling or deep ploughing +must manifestly be greatly dependent<span class='pagenum'><a name="Page_145" id="Page_145">[Pg 145]</a></span> 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.</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Soil.</td><td align='right'>Subsoil.</td></tr> +<tr><td align='left'>Insoluble silicates</td><td align='right'>87·623</td><td align='right'>82·72</td></tr> +<tr><td align='left'>Soluble silica</td><td align='right'>0·393</td><td align='right'>0·12</td></tr> +<tr><td align='left'>Alumina and peroxide of iron</td><td align='right'>4·129</td><td align='right'>8·60</td></tr> +<tr><td align='left'>Lime</td><td align='right'>0·341</td><td align='right'>0·18</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>0·290</td><td align='right'>0·24</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='right'>0·027</td><td align='right'>0·03</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='right'>0·240</td><td align='right'>trace</td></tr> +<tr><td align='left'>Potash</td><td align='right'>0·052</td><td align='right'>0·12</td></tr> +<tr><td align='left'>Soda</td><td align='right'>0·050</td><td align='right'>0·04</td></tr> +<tr><td align='left'>Water</td><td align='right'>1·956</td><td align='right'>3·26</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>5·220</td><td align='right'>4·02</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>100·321</td><td align='right'>99·33</td></tr> +</table></div> +<p>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<span class='pagenum'><a name="Page_146" id="Page_146">[Pg 146]</a></span> 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 <i>a +priori</i> 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.</p> + +<p><i>Improving the Soil by Paring and Burning.</i>—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.</p> + +<p>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.<span class='pagenum'><a name="Page_147" id="Page_147">[Pg 147]</a></span></p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Soil.</td><td align='right'>Red Ash.</td></tr> +<tr><td align='left'>Water</td><td align='right'>0·93</td><td align='right'>1·18</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>10·67</td><td align='right'>3·32</td></tr> +<tr><td align='left'>Oxides of iron and alumina</td><td align='right'>13·40</td><td align='right'>18·42</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>23·90</td><td align='right'>8·83</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='right'>trace</td><td align='right'>1·15</td></tr> +<tr><td align='left'>Carbonate of magnesia</td><td align='right'>1·10</td><td align='right'>"</td></tr> +<tr><td align='left'>Magnesia</td><td align='center'>"</td><td align='right'>1·76</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='right'>trace</td><td align='right'>0·71</td></tr> +<tr><td align='left'>Potash</td><td align='right'>0·38</td><td align='right'>1·08</td></tr> +<tr><td align='left'>Soda</td><td align='right'>0·13</td><td align='right'>"</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='center'>"</td><td align='right'>1·03</td></tr> +<tr><td align='left'>Insoluble matter, chiefly clay</td><td align='right'>49·66</td><td align='right'>62·52</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>100·17</td><td align='right'>100·00</td></tr> +</table></div> + +<p>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.<span class='pagenum'><a name="Page_148" id="Page_148">[Pg 148]</a></span></p> + +<p>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 <i>modus operandi</i> +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 +<i>may</i> 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.</p> + +<p><i>Warping.</i>—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<span class='pagenum'><a name="Page_149" id="Page_149">[Pg 149]</a></span> +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.</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> 1</td><td align='left'> 2</td><td align='left'> 3</td><td align='left'> 4</td></tr> +<tr><td align='left'>Water</td><td align='left'> 47·49</td><td align='left'> ...</td><td align='left'> 1·06</td><td align='left'> 2·00</td></tr> +<tr><td align='left'>Organic matter</td><td align='left'> 5·94</td><td align='left'> 6·93</td><td align='left'> 2·20</td><td align='left'> 7·61</td></tr> +<tr><td align='left'>Chloride of Calcium</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> } ...</td><td align='left'> ...</td></tr> +<tr><td align='left'> Magnesium</td><td align='left'> } ...</td><td align='left'> 0·10</td><td align='left'> } ...</td><td align='left'> ...</td></tr> +<tr><td align='left'> Sodium</td><td align='left'> } 1·66</td><td align='left'> } 0·94</td><td align='left'> } 0·14</td><td align='left'> 0·16</td></tr> +<tr><td align='left'> Potassium</td><td align='left'> }</td><td align='left'> }</td><td align='left'> }</td><td align='left'></td></tr> +<tr><td align='left'>Sulphate of Soda</td><td align='left'> } ...</td><td align='left'> 0·31</td><td align='left'> } ...</td><td align='left'> ...</td></tr> +<tr><td align='left'> Magnesia</td><td align='left'> } ...</td><td align='left'> 1·18</td><td align='left'> } ...</td><td align='left'> ...</td></tr> +<tr><td align='left'> Lime</td><td align='left'> trace</td><td align='left'> 1·10</td><td align='left'> trace</td><td align='left'> trace</td></tr> +<tr><td align='left'>Carbonate of Magnesia</td><td align='left'> 2·60</td><td align='left'> 0·31</td><td align='left'> trace</td><td align='left'> 0·29</td></tr> +<tr><td align='left'> Lime</td><td align='left'> 3·59</td><td align='left'> 8·18</td><td align='left'> trace</td><td align='left'> 0·46</td></tr> +<tr><td align='left'>Potash and Soda</td><td align='left'> 0·18</td><td align='left'> 0·47</td><td align='left'> trace</td><td align='left'> 0·17</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 1·69</td><td align='left'> 2·60</td><td align='left'> trace</td><td align='left'> 0·26</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 0·39</td><td align='left'> 0·68</td><td align='left'> trace</td><td align='left'> 0·14</td></tr> +<tr><td align='left'>Peroxide of Iron</td><td align='left'> } 6·63</td><td align='left'> 5·05</td><td align='left'> 0·08</td><td align='left'> 1·17</td></tr> +<tr><td align='left'>Alumina</td><td align='left'> }</td><td align='left'> 8·18</td><td align='left'> 0·39</td><td align='left'> 0·41</td></tr> +<tr><td align='left'>Phosphate of Iron</td><td align='left'> 0·58</td><td align='left'> 1·04</td><td align='left'> trace</td><td align='left'> 0·28</td></tr> +<tr><td align='left'>Silica</td><td align='left'> ...</td><td align='left'> 9·05</td><td align='left'> 0·14</td><td align='left'> 2·77</td></tr> +<tr><td align='left'>Sand and Stones</td><td align='left'> 29·15</td><td align='left'> 55·87</td><td align='left'> 95·91</td><td align='left'> 84·97</td></tr> +<tr><td align='left'></td><td align='left'>————</td><td align='left'>————</td><td align='left'>————</td><td align='left'>————</td></tr> +<tr><td align='left'></td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_150" id="Page_150">[Pg 150]</a></span></p> + +<p>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.</p> + +<p>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.</p> + +<p><i>Mixing of Soils.</i>—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 +<i>vice versa</i>; 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<span class='pagenum'><a name="Page_151" id="Page_151">[Pg 151]</a></span> with clay +or gravel to add to its inorganic matters, and in both instances it has +proved successful.</p> + +<p>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.</p> + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_J_10" id="Footnote_J_10"></a><a href="#FNanchor_J_10"><span class="label">[J]</span></a> Mr. Dudgeon, Spylaw. Transactions of the Highland Society, +vol. cxxix., p. 505.</p></div> +</div> + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_152" id="Page_152">[Pg 152]</a></span></p> +<h2>CHAPTER VII.</h2> + +<h3>THE GENERAL PRINCIPLES OF MANURING.</h3> + + +<p>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.<span class='pagenum'><a name="Page_153" id="Page_153">[Pg 153]</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_154" id="Page_154">[Pg 154]</a></span> 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 <i>special</i> manure; that containing all the constituents +of the crop is a <i>general</i> manure.</p> + +<p>The distinction of these two classes of manures is very important in a +practical point of view, because a special<span class='pagenum'><a name="Page_155" id="Page_155">[Pg 155]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_156" id="Page_156">[Pg 156]</a></span> 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.</p> + +<p>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.</p> + +<p>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,<span class='pagenum'><a name="Page_157" id="Page_157">[Pg 157]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_158" id="Page_158">[Pg 158]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_159" id="Page_159">[Pg 159]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_160" id="Page_160">[Pg 160]</a></span> 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.</p> + +<p>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.<a name="FNanchor_K_11" id="FNanchor_K_11"></a><a href="#Footnote_K_11" class="fnanchor">[K]</a></p> +<p><span class='pagenum'><a name="Page_161" id="Page_161">[Pg 161]</a></span></p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='left'></td><td align='right'>Lbs. of Nitrogen.</td></tr> +<tr><td align='left'>1.</td><td align='left'>Turnips (13-1/2 tons)</td><td align='right'>60</td></tr> +<tr><td align='left'>2.</td><td align='left'>{ Wheat (28 bushels at 60 lbs.)</td><td align='right'>29</td></tr> +<tr><td align='left'></td><td align='left'>{ Straw</td><td align='right'>16</td></tr> +<tr><td align='left'>3.</td><td align='left'>Hay (2-1/2 tons)</td><td align='right'>56</td></tr> +<tr><td align='left'>4.</td><td align='left'>{ Oats (34 bushels at 40 lbs.)</td><td align='right'>27</td></tr> +<tr><td align='left'></td><td align='left'>{ Straw</td><td align='right'>14</td></tr> +<tr><td align='left'>5.</td><td align='left'>Potatoes (3 tons)</td><td align='right'>27</td></tr> +<tr><td align='left'>6.</td><td align='left'>Wheat and straw as before</td><td align='right'>45</td></tr> +<tr><td align='left'></td><td align='left'></td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='left'>Total</td><td align='right'>274</td></tr> +</table></div> + + +<p>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<span class='pagenum'><a name="Page_162" id="Page_162">[Pg 162]</a></span> accumulation +of valuable matters, and a progressive improvement of the productive +capacity of the soil.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_163" id="Page_163">[Pg 163]</a></span> substances, such as potash, soda, +magnesia, etc., occasionally act beneficially, but the results obtained +from them are very uncertain, and frequently entirely negative.</p> + +<p>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 <i>vice versa</i>, 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<span class='pagenum'><a name="Page_164" id="Page_164">[Pg 164]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_165" id="Page_165">[Pg 165]</a></span> decomposition of the vegetable matters on +the soil, and possibly some other substances may have a similar effect.</p> + +<p>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.</p> + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_K_11" id="Footnote_K_11"></a><a href="#FNanchor_K_11"><span class="label">[K]</span></a> 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.</p></div> +</div> + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_166" id="Page_166">[Pg 166]</a></span></p> +<h2>CHAPTER VIII.</h2> + +<h3>THE COMPOSITION AND PROPERTIES OF FARM-YARD AND LIQUID MANURES.</h3> + + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_167" id="Page_167">[Pg 167]</a></span> is +naturally very different, and must be separately considered.</p> + +<p><i>Urine.</i>—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:—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Horse.</td><td align='right'>Swine.</td><td align='right'>Ox.</td><td align='right'>Goat.</td><td align='right'>Sheep.</td></tr> +<tr><td align='left'>Extractive matter soluble in water</td><td align='right'>2·132</td><td align='right'>0·142</td><td align='right'>2·248</td><td align='right'>0·100</td><td align='right'>0·340</td></tr> +<tr><td align='left'>Extractive matter soluble in spirit</td><td align='right'>2·550</td><td align='right'>0·387</td><td align='right'>1·421</td><td align='right'>0·454</td><td align='right'>3·330</td></tr> +<tr><td align='left'>Salts soluble in water</td><td align='right'>2·340</td><td align='right'>0·909</td><td align='right'>2·442</td><td align='right'>0·850</td><td align='right'>1·957</td></tr> +<tr><td align='left'>Salts insoluble in water</td><td align='right'>1·880</td><td align='right'>0·088</td><td align='right'>0·155</td><td align='right'>0·080</td><td align='right'>0·052</td></tr> +<tr><td align='left'>Urea</td><td align='right'>1·244</td><td align='right'>0·273</td><td align='right'>1·976</td><td align='right'>0·378</td><td align='right'>1·262</td></tr> +<tr><td align='left'>Hippuric acid</td><td align='right'>1·260</td><td align='right'>...</td><td align='right'>0·550</td><td align='right'>0·125</td><td align='right'>...</td></tr> +<tr><td align='left'>Mucus</td><td align='right'>0·005</td><td align='right'>0·005</td><td align='right'>0·007</td><td align='right'>0·006</td><td align='right'>0·025</td></tr> +<tr><td align='left'>Water</td><td align='right'>88·589</td><td align='right'>98·196</td><td align='right'>91·201</td><td align='right'>98·007</td><td align='right'>92·897</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·000</td><td align='right'>100·000</td><td align='right'>100·000</td><td align='right'>100·000</td><td align='right'>99·863</td></tr> +</table></div> + +<h4><i>Composition of the Ash of these Urines.</i></h4> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Horse.</td><td align='right'>Swine.</td><td align='right'>Ox.</td><td align='right'>Goat.</td><td align='right'>Sheep.</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>12·50</td><td align='right'>...</td><td align='right'>1·07</td><td align='right'>trace</td><td align='right'>0·82</td></tr> +<tr><td align='left'>Carbonate of magnesia</td><td align='right'>9·46</td><td align='right'>...</td><td align='right'>6·93</td><td align='right'>7·3</td><td align='right'>0·46</td></tr> +<tr><td align='left'>Carbonate of potash</td><td align='right'>46·09</td><td align='right'>12·10</td><td align='right'>77·28</td><td align='right'>trace</td><td align='right'>...</td></tr> +<tr><td align='left'>Carbonate of soda</td><td align='right'>10·33</td><td align='right'>...</td><td align='right'>...</td><td align='right'>53·0</td><td align='right'>42·25</td></tr> +<tr><td align='left'>Sulphate of potash</td><td align='right'>...</td><td align='right'>...</td><td align='right'>13·30</td><td align='right'>...</td><td align='right'>2·98</td></tr> +<tr><td align='left'>Sulphate of soda</td><td align='right'>13·04</td><td align='right'>7·00</td><td align='right'>...</td><td align='right'>25·0</td><td align='right'>7·72</td></tr> +<tr><td align='left'>Phosphate of soda</td><td align='right'>...</td><td align='right'>19·00</td><td align='right'>...</td><td align='right'>...</td><td align='right'>...</td></tr> +<tr><td align='left'>Phosphate of lime }</td></tr> +<tr><td align='left'>Phosphate of magnesia }</td><td align='right'> ...</td><td align='right'>8·80</td><td align='right'>...</td><td align='right'>...</td><td align='right'>0·70</td></tr> +<tr><td align='left'><span class='pagenum'><a name="Page_168" id="Page_168">[Pg 168]</a></span></td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='right'>6·94</td><td align='right'>53·10</td><td align='right'>0·30</td><td align='right'>14·7</td><td align='right'>32·01</td></tr> +<tr><td align='left'>Chloride of potassium</td><td align='right'>...</td><td align='right'>trace</td><td align='right'>...</td><td align='right'>...</td><td align='right'>12·00</td></tr> +<tr><td align='left'>Silica</td><td align='right'>0·55</td><td align='right'>...</td><td align='right'>0·35</td><td align='right'>...</td><td align='right'>1·06</td></tr> +<tr><td align='left'>Oxide of iron and loss</td><td align='right'>1·09</td><td align='right'>...</td><td align='right'>0·77</td><td align='right'>...</td><td align='right'>...</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td><td align='right'>100·00</td><td align='right'>100·00</td><td align='right'>100·00</td><td align='right'>100·00</td></tr> +</table></div> + +<p>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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Natural.</td><td align='right'>Dry Residue.</td></tr> +<tr><td align='left'>Urea</td><td align='right'>3·010</td><td align='right'>44·70</td></tr> +<tr><td align='left'>Lactic acid, lactate of ammonia, and extractive matter</td><td align='right'>1·714</td><td align='right'>25·58</td></tr> +<tr><td align='left'>Uric acid</td><td align='right'>0·100</td><td align='right'>1·49</td></tr> +<tr><td align='left'>Mucus</td><td align='right'>0·032</td><td align='right'>0·48</td></tr> +<tr><td align='left'>Sulphate of potash</td><td align='right'>0·371</td><td align='right'>5·54</td></tr> +<tr><td align='left'>Sulphate of soda</td><td align='right'>0·316</td><td align='right'>4·72</td></tr> +<tr><td align='left'>Phosphate of soda</td><td align='right'>0·294</td><td align='right'>4·39</td></tr> +<tr><td align='left'>Biphosphate of ammonia</td><td align='right'>0·165</td><td align='right'>2·46</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='right'>0·445</td><td align='right'>6·64</td></tr> +<tr><td align='left'>Muriate of ammonia</td><td align='right'>0·150</td><td align='right'>2·46</td></tr> +<tr><td align='left'>Phosphates of magnesia and lime</td><td align='right'>0·100</td><td align='right'>1·49</td></tr> +<tr><td align='left'>Silica</td><td align='right'>0·003</td><td align='right'>0·05</td></tr> +<tr><td align='left'>Water</td><td align='right'>93·300</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·000</td><td align='right'>100·00</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_169" id="Page_169">[Pg 169]</a></span> 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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Urea.</td><td align='right'>Uric Acid.</td><td align='right'>Hippuric Acid.</td></tr> +<tr><td align='left'>Carbon</td><td align='right'>20·00</td><td align='right'>36·0</td><td align='right'>60·7</td></tr> +<tr><td align='left'>Hydrogen</td><td align='right'>6·60</td><td align='right'>2·4</td><td align='right'>5·0</td></tr> +<tr><td align='left'>Nitrogen</td><td align='right'>46·70</td><td align='right'>33·4</td><td align='right'>8·0</td></tr> +<tr><td align='left'>Oxygen</td><td align='right'>26·70</td><td align='right'>28·2</td><td align='right'>26·3</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td><td align='right'>100·0</td><td align='right'>100·0</td></tr> +</table></div> + + +<p>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.</p> + +<p>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.<span class='pagenum'><a name="Page_170" id="Page_170">[Pg 170]</a></span></p> + +<p>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.</p> + +<p><i>Dung.</i>—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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Horse.</td><td align='right'>Cow.</td><td align='right'>Sheep.</td><td align='right'>Swine.</td></tr> +<tr><td align='left'>Per-centage of water in the fresh excrement</td><td align='right'>77·25</td><td align='right'>82·45</td><td align='right'>56·47</td><td align='right'>77·13</td></tr> +<tr><td align='left'>Ash in the dry excrement</td><td align='right'>13·36</td><td align='right'>15·23</td><td align='right'>13·49</td><td align='right'>37·17</td></tr> +</table></div> + + +<p>100 parts of ash contained—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Horse.</td><td align='right'>Cow.</td><td align='right'>Sheep.</td><td align='right'>Swine.</td></tr> +<tr><td align='left'>Silica</td><td align='right'>62·40</td><td align='right'>62·54</td><td align='right'>50·11</td><td align='right'>13·19</td></tr> +<tr><td align='left'>Potash</td><td align='right'>11·30</td><td align='right'>2·91</td><td align='right'>8·32</td><td align='right'>3·60</td></tr> +<tr><td align='left'>Soda</td><td align='right'>1·98</td><td align='right'>0·98</td><td align='right'>3·28</td><td align='right'>3·44</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='right'>0·03</td><td align='right'>0·23</td><td align='right'>0·14</td><td align='right'>0·89</td></tr> +<tr><td align='left'>Phosphate of iron</td><td align='right'>2·73</td><td align='right'>8·93</td><td align='right'>3·98</td><td align='right'>10·55</td></tr> +<tr><td align='left'>Lime</td><td align='right'>4·63</td><td align='right'>5·71</td><td align='right'>18·15</td><td align='right'>2·63</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>3·84</td><td align='right'>11·47</td><td align='right'>5·45</td><td align='right'>2·24</td></tr> +<tr><td align='left'>Phosphoric Acid</td><td align='right'>8·93</td><td align='right'>4·75</td><td align='right'>7·52</td><td align='right'>0·41</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='right'>1·83</td><td align='right'>1·77</td><td align='right'>2·69</td><td align='right'>0·90</td></tr> +<tr><td align='left'>Carbonic acid</td><td align='right'>...</td><td align='right'>trace</td><td align='right'>trace</td><td align='right'>0·60</td></tr> +<tr><td align='left'>Oxide of manganese</td><td align='right'>2·13</td><td align='right'>...</td><td align='right'>...</td><td align='right'>...</td></tr> +<tr><td align='left'>Sand</td><td align='right'>...</td><td align='right'>...</td><td align='right'>...</td><td align='right'>61·37</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>——</td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>99·80</td><td align='right'>99·29</td><td align='right'>99·64</td><td align='right'>99·82</td></tr> +</table></div> +<p>Human fæces contain about 75 per cent of water; and their dry residue +was found by Way to have the following composition:<span class='pagenum'><a name="Page_171" id="Page_171">[Pg 171]</a></span>—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Organic matter</td><td align='right'>88·52</td></tr> +<tr><td align='left'>Insoluble siliceous matters</td><td align='right'>1·48</td></tr> +<tr><td align='left'>Oxide of iron</td><td align='right'>0·54</td></tr> +<tr><td align='left'>Lime</td><td align='right'>1·72</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>1·55</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='right'>4·27</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='right'>0·24</td></tr> +<tr><td align='left'>Potash</td><td align='right'>1·19</td></tr> +<tr><td align='left'>Soda</td><td align='right'>0·31</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='right'>0·18</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +</table></div> + +<p>In a sample analyzed by myself there were found—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Organic matter</td><td align='right'>86·75</td></tr> +<tr><td align='left'>Phosphates</td><td align='right'>8·19</td></tr> +<tr><td align='left'>Alkaline salts, containing 1·18 of phosphoric acid</td><td align='right'>2·53</td></tr> +<tr><td align='left'>Insoluble matters</td><td align='right'>2·53</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +<tr><td align='left'>Nitrogen</td><td align='right'>4·59</td></tr> +<tr><td align='left'>Equal to ammonia</td><td align='right'>5·57</td></tr> +</table></div> + + +<p>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<span class='pagenum'><a name="Page_172" id="Page_172">[Pg 172]</a></span> 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°.</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td colspan="4"> HORSE.</td><td colspan="4"> COW.</td></tr> +<tr><td align='left'> </td><td colspan="2"> Natural.</td><td colspan="2"> Dry.</td><td colspan="2"> Natural.</td><td colspan="2"> Dry.</td></tr> +<tr><td align='left'> </td><td align='left'>Urine.</td><td align='left'> Dung.</td><td align='left'>Urine.</td><td align='left'>Dung.</td><td align='left'>Urine.</td><td align='left'> Dung.</td><td align='left'>Urine.</td><td align='left'>Dung.</td></tr> +<tr><td align='left'>Carbon</td><td align='left'> 4·46</td><td align='left'> 9·56</td><td align='left'> 36·0</td><td align='left'> 38·7</td><td align='left'> 3·18</td><td align='left'> 4·02</td><td align='left'> 27·2</td><td align='left'> 42·8</td></tr> +<tr><td align='left'>Hydrogen</td><td align='left'> 0·47</td><td align='left'> 1·26</td><td align='left'> 3·8</td><td align='left'> 5·1</td><td align='left'> 0·30</td><td align='left'> 0·49</td><td align='left'> 2·6</td><td align='left'> 5·2</td></tr> +<tr><td align='left'>Nitrogen</td><td align='left'> 1·55</td><td align='left'> 0·54</td><td align='left'> 12·5</td><td align='left'> 2·2</td><td align='left'> 0·44</td><td align='left'> 0·22</td><td align='left'> 3·8</td><td align='left'> 2·3</td></tr> +<tr><td align='left'>Oxygen</td><td align='left'> 1·40</td><td align='left'> 9·31</td><td align='left'> 11·3</td><td align='left'> 37·7</td><td align='left'> 3·09</td><td align='left'> 3·54</td><td align='left'> 26·4</td><td align='left'> 37·7</td></tr> +<tr><td align='left'>Ash</td><td align='left'> 4·51</td><td align='left'> 4·02</td><td align='left'> 36·4</td><td align='left'> 16·3</td><td align='left'> 4·68</td><td align='left'> 1·13</td><td align='left'> 40·0</td><td align='left'> 12·0</td></tr> +<tr><td align='left'>Water</td><td align='left'> 87·61</td><td align='left'> 75·31</td><td align='left'> 0·0</td><td align='left'> 0·0</td><td align='left'> 88·31</td><td align='left'> 90·60</td><td align='left'> 0·0</td><td align='left'> 0·0</td></tr> +<tr><td align='left'> </td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'> 100·0</td><td align='left'>100·0</td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'> 100·0</td><td align='left'>100·0</td></tr> +</table></div> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_173" id="Page_173">[Pg 173]</a></span> 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.</p> + +<p>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.<span class='pagenum'><a name="Page_174" id="Page_174">[Pg 174]</a></span></p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> 1</td><td align='left'> 2</td><td align='left'> 3</td></tr> +<tr><td align='left'>Water</td><td align='left'> 66·17</td><td align='left'> 69·86</td><td align='left'> 67·32</td></tr> +<tr><td align='left'>Soluble organic matters</td><td align='left'> 2·48</td><td align='left'> 3·86</td><td align='left'> 2·63</td></tr> +<tr><td align='left'>Soluble inorganic matters·</td><td colspan="3"> </td></tr> +<tr><td align='left'>Silica</td><td align='left'> 0·237</td><td align='left'> 0·279</td><td align='left'> 0·239</td></tr> +<tr><td align='left'>Phosphate of lime</td><td align='left'> 0·299</td><td align='left'> 0·300</td><td align='left'> 0·331</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 0·066</td><td align='left'> 0·048</td><td align='left'> 0·056</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·011</td><td align='left'> 0·019</td><td align='left'> 0·004</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 0·573</td><td align='left'> 1·096</td><td align='left'> 0·676</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 0·051</td><td align='left'> 0·187</td><td align='left'> 0·192</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='left'> 0·030</td><td align='left'> 0·106</td><td align='left'> 0·058</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='left'> 0·055</td><td align='left'> 0·160</td><td align='left'> 0·119</td></tr> +<tr><td align='left'>Carbonic acid and loss</td><td align='left'> 0·218</td><td align='left'> 0·775</td><td align='left'> 0·445</td></tr> +<tr><td align='left'> </td><td align='left'> —— 1·54</td><td align='left'> ... 2·97</td><td align='left'> —— 2·12</td></tr> +<tr><td align='left'>Insoluble organic matters</td><td align='right'> 25·76</td><td align='right'> 18·44</td><td align='right'> 20·46</td></tr> +<tr><td align='left'>Insoluble inorganic matters—</td><td colspan="3"> </td></tr> +<tr><td align='left'> Soluble silica</td><td align='left'> 0·967</td><td align='left'> 0·712</td><td align='left'> 1·893</td></tr> +<tr><td align='left'> Insoluble silica</td><td align='left'> 0·561</td><td align='left'> 0·857</td><td align='left'> 1·075</td></tr> +<tr><td align='left'> Oxide of iron, alumina, and phosphates</td><td align='left'> 0·596</td><td align='left'> 0·810</td><td align='left'> 1·135</td></tr> +</table></div> +<p><br /><br /></p> +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> 4</td><td align='left'> 5</td></tr> +<tr><td align='left'>Water</td><td align='left'> 75·42</td><td align='left'> 73·90</td></tr> +<tr><td align='left'>Soluble organic matters</td><td align='left'> 3·71</td><td align='left'> 2·70</td></tr> +<tr><td align='left'>Soluble inorganic matters</td><td colspan="2"> </td></tr> +<tr><td align='left'>Silica</td><td align='left'> 0·254</td><td align='left'> 0·147</td></tr> +<tr><td align='left'>Phosphate of lime</td><td align='left'> 0·382</td><td align='left'> 0·129</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 0·117</td><td align='left'> 0·018</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·047</td><td align='left'> 0·018</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 0·446</td><td align='left'> 0·960</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 0·023</td><td align='left'> 0·082</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='left'> 0·037</td><td align='left'> 0·052</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='left'> 0·058</td><td align='left'> 0·072</td></tr> +<tr><td align='left'>Carbonic acid and loss</td><td align='left'> 0·106</td><td align='left'> 0·584</td></tr> +<tr><td align='left'> </td><td align='left'> —— 1·47</td><td align='left'> —— 2·06</td></tr> +<tr><td align='left'>Insoluble organic matters</td><td align='right'> 12·82</td><td align='right'> 14·39</td></tr> +<tr><td align='left'>Insoluble inorganic matters—</td><td colspan="2"> </td></tr> +<tr><td align='left'> Soluble silica</td><td align='left'> 1·424</td><td align='left'> 1·10</td></tr> +<tr><td align='left'> Insoluble silica</td><td align='left'> 1·010</td><td align='left'> 1·54</td></tr> +<tr><td align='left'> Oxide of iron, alumina, and phosphates</td><td align='left'> 0·947</td><td align='left'> 0·37</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_175" id="Page_175">[Pg 175]</a></span></p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> 1</td><td align='left'> 2</td><td align='left'> 3</td></tr> +<tr><td align='left'>Containing phosphoric acid</td><td align='left'>(0·178)</td><td align='left'>(0·177)</td><td align='left'>(0·298)</td></tr> +<tr><td align='left'>Equal to bone earth</td><td align='left'>(0·386)</td><td align='left'>(0·277)</td><td align='left'>(0·646)</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 1·120</td><td align='left'> 1·291</td><td align='left'> 1·868</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·143</td><td align='left'> 1·029</td><td align='left'> 0·078</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 0·099</td><td align='left'> 0·127</td><td align='left'> 0·208</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 0·019</td><td align='left'> 0·046</td><td align='left'> 0·038</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='left'> 0·061</td><td align='left'> 0·099</td><td align='left'> 0·098</td></tr> +<tr><td align='left'>Carbonic acid and loss</td><td align='left'> 0·484</td><td align='left'> 0·929</td><td align='left'> 1·077</td></tr> +<tr><td align='left'> </td><td align='left'> —— 4·05</td><td align='left'> —— 4·90</td><td align='left'> —— 7·47</td></tr> +<tr><td align='left'> </td><td align='right'> ——</td><td align='right'> ——</td><td align='right'> ———</td></tr> +<tr><td align='left'> </td><td align='right'> 100·00</td><td align='right'> 100·00</td><td align='right'> 100·00</td></tr> +<tr><td align='left'>Containing nitrogen</td><td align='left'> 0·149</td><td align='left'> 0·270</td><td align='left'> 0·170</td></tr> +<tr><td align='left'>Equal to ammonia</td><td align='left'> 0·181</td><td align='left'> 0·320</td><td align='left'> 0·206</td></tr> +<tr><td align='left'>Containing nitrogen</td><td align='left'> 0·494</td><td align='left'> 0·470</td><td align='left'> 0·580</td></tr> +<tr><td align='left'>Equal to ammonia</td><td align='left'> 0·599</td><td align='left'> 0·570</td><td align='left'> 0·700</td></tr> +<tr><td align='left'>Total nitrogen</td><td align='left'> 0·643</td><td align='left'> 0·740</td><td align='left'> 0·750</td></tr> +<tr><td align='left'>Equal to ammonia</td><td align='left'> 0·780</td><td align='left'> 0·890</td><td align='left'> 0·906</td></tr> +</table></div> +<p><br /><br /></p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> 4</td><td align='left'> 5</td></tr> +<tr><td align='left'>Containing phosphoric acid</td><td align='left'>(0·274)</td><td align='left'>(0·06)</td></tr> +<tr><td align='left'>Equal to bone earth</td><td align='left'>(0·573)</td><td align='left'>(0·10)</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 1·667</td><td align='left'> 2·25</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 0·091</td><td align='left'> 0·02</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 0·045</td><td align='left'> 0·12</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 0·038</td><td align='left'> 0·01</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='left'> 0·063</td><td align='left'> 0·10</td></tr> +<tr><td align='left'>Carbonic acid and loss</td><td align='left'> 1·295</td><td align='left'> 1·44</td></tr> +<tr><td align='left'> </td><td align='left'>—— 6·58</td><td align='left'> —— 6·95</td></tr> +<tr><td align='left'> </td><td align='right'> ——</td><td align='right'> ———</td></tr> +<tr><td align='left'> </td><td align='right'> 100·00</td><td align='right'> 100·00</td></tr> +<tr><td align='left'>Containing nitrogen</td><td align='left'> 0·297</td><td align='left'> 0·149</td></tr> +<tr><td align='left'>Equal to ammonia</td><td align='left'> 0·360</td><td align='left'> 0·180</td></tr> +<tr><td align='left'>Containing nitrogen</td><td align='left'> 0·309</td><td align='left'> 0·613</td></tr> +<tr><td align='left'>Equal to ammonia</td><td align='left'> 0·375</td><td align='left'> 0·744</td></tr> +<tr><td align='left'>Total nitrogen</td><td align='left'> 0·606</td><td align='left'> 0·762</td></tr> +<tr><td align='left'>Equal to ammonia</td><td align='left'> 0·735</td><td align='left'> 0·924</td></tr> +</table></div> +<p><span class='pagenum'><a name="Page_176" id="Page_176">[Pg 176]</a></span></p> + +<p>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:<span class='pagenum'><a name="Page_177" id="Page_177">[Pg 177]</a></span>—</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td colspan="4"> When Put up.</td></tr> +<tr><td align='left'> </td><td align='left'> Nov 3d 1854.</td><td align='left'> April 30th 1855.</td><td align='left'> Aug 23d 1855.</td><td align='left'> Nov 15th 1855.</td></tr> +<tr><td align='left'>Weight of manure in lbs.</td><td align='left'> 2838</td><td align='left'> 2026</td><td align='left'> 1994</td><td align='left'> 1974</td></tr> +<tr><td align='left'>Water</td><td align='left'> 1877·9</td><td align='left'> 1336·1</td><td align='left'> 1505·3</td><td align='left'> 1466·5</td></tr> +<tr><td align='left'>Dry Matter</td><td align='left'> 960·1</td><td align='left'> 689·9</td><td align='left'> 488·7</td><td align='left'> 507·5</td></tr> +<tr><td align='left'> Consisting of—</td><td colspan="4"> </td></tr> +<tr><td align='left'>Soluble organic matter</td><td align='left'> 70·38</td><td align='left'> 86·51</td><td align='left'> 58·83</td><td align='left'> 54·04</td></tr> +<tr><td align='left'> " mineral matter</td><td align='left'> 43·71</td><td align='left'> 57·88</td><td align='left'> 39·16</td><td align='left'> 36·89</td></tr> +<tr><td align='left'>Insoluble organic matter</td><td align='left'> 731·07</td><td align='left'> 389·74</td><td align='left'> 243·22</td><td align='left'> 214·92</td></tr> +<tr><td align='left'> " mineral matter</td><td align='left'> 114·94</td><td align='left'> 155·77</td><td align='left'> 147·49</td><td align='left'> 201·07</td></tr> +<tr><td align='left'>Total nitrogen</td><td align='left'> 18·23</td><td align='left'> 18·14</td><td align='left'> 13·14</td><td align='left'> 13·03</td></tr> +<tr><td align='left'>Equal to ammonia</td><td align='left'> 22·14</td><td align='left'> 22·02</td><td align='left'> 15·96</td><td align='left'> 15·75</td></tr> +</table></div> + +<p>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.<span class='pagenum'><a name="Page_178" id="Page_178">[Pg 178]</a></span></p> + + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td colspan="4"> When Put up.</td></tr> +<tr><td align='left'> </td><td align='left'> Nov 3d 1854.</td><td align='left'> April 30th 1855.</td><td align='left'> Aug 23d 1855.</td><td align='left'> Nov 15th 1855.</td></tr> +<tr><td align='left'>Weight of manure in lbs.</td><td align='left'> 3258</td><td align='left'> 1613</td><td align='left'> 1297</td><td align='left'> 1235</td></tr> +<tr><td align='left'>Water</td><td align='left'> 2156·0</td><td align='left'> 917·6</td><td align='left'> 563·2</td><td align='left'> 514·5</td></tr> +<tr><td align='left'>Dry Matter</td><td align='left'> 1102·0</td><td align='left'> 695·4</td><td align='left'> 733·8</td><td align='left'> 720·5</td></tr> +<tr><td align='left'> Consisting of—</td><td colspan="4"> </td></tr> +<tr><td align='left'>Soluble organic matter</td><td align='left'> 80·77</td><td align='left'> 74·68</td><td align='left'> 53·56</td><td align='left'> 66·28</td></tr> +<tr><td align='left'> " mineral matter</td><td align='left'> 50·14</td><td align='left'> 54·51</td><td align='left'> 39·55</td><td align='left'> 54·68</td></tr> +<tr><td align='left'>Insoluble organic matter</td><td align='left'> 839·17</td><td align='left'> 410·24</td><td align='left'> 337·32</td><td align='left'> 341·97</td></tr> +<tr><td align='left'> " mineral matter</td><td align='left'> 131·92</td><td align='left'> 155·97</td><td align='left'> 303·37</td><td align='left'> 257·57</td></tr> +<tr><td align='left'>Total nitrogen</td><td align='left'> 20·93</td><td align='left'> 19·26</td><td align='left'> 16·54</td><td align='left'> 1·79</td></tr> +<tr><td align='left'>Equal to ammonia</td><td align='left'> 25·40</td><td align='left'> 23·33</td><td align='left'> 20·08</td><td align='left'> 2·81</td></tr> +</table></div> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_179" id="Page_179">[Pg 179]</a></span> 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.</p> + +<p>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.</p> + +<p>As far as the first of these points is concerned, it must<span class='pagenum'><a name="Page_180" id="Page_180">[Pg 180]</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_181" id="Page_181">[Pg 181]</a></span> +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<a name="FNanchor_L_12" id="FNanchor_L_12"></a><a href="#Footnote_L_12" class="fnanchor">[L]</a> of ammonia, +and when dry will still retain from 1 to 1·5 per cent, or nearly twice +as<span class='pagenum'><a name="Page_182" id="Page_182">[Pg 182]</a></span> 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 <i>does not absorb +ammonia</i>, 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.</p> + +<p>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 <i>fixing</i> 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<span class='pagenum'><a name="Page_183" id="Page_183">[Pg 183]</a></span> +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.</p> + +<p>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.</p> + +<p>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;<span class='pagenum'><a name="Page_184" id="Page_184">[Pg 184]</a></span> +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.</p> + +<p>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 <i>fermentation</i>. 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.</p> + +<p>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<span class='pagenum'><a name="Page_185" id="Page_185">[Pg 185]</a></span> 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.</p> + +<p>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,<span class='pagenum'><a name="Page_186" id="Page_186">[Pg 186]</a></span> 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.</p> + +<p>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.</p> + +<p>In the present state of agriculture, a proper estimate of the money +value of farm-yard manure is of much importance<span class='pagenum'><a name="Page_187" id="Page_187">[Pg 187]</a></span> 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.</p> + +<p><i>Liquid Manure.</i>—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<span class='pagenum'><a name="Page_188" id="Page_188">[Pg 188]</a></span> +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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>No. 1.</td><td align='right'>No. 2.</td></tr> +<tr><td align='left'>Ammonia</td><td align='right'>9·6</td><td align='right'>21·5</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>200·8</td><td align='right'>77·6</td></tr> +<tr><td align='left'>Ash</td><td align='right'>268·8</td><td align='right'>518·4</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'>Total solids in a gallon</td><td align='right'>479·2</td><td align='right'>617·5</td></tr> +</table></div> + +<p>The ash contained—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Alkaline salts</td><td align='right'>207·8</td><td align='right'>420·4</td></tr> +<tr><td align='left'>Phosphates</td><td align='right'>25·1</td><td align='right'>44·5</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>18·2</td><td align='right'>31·1</td></tr> +<tr><td align='left'>Carbonate of magnesia, and loss</td><td align='right'>4·3</td><td align='right'>3·4</td></tr> +<tr><td align='left'>Silica and alumina</td><td align='right'>13·4</td><td align='right'>19·0</td></tr> +<tr><td align='left'></td><td align='right'>——</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>268·8</td><td align='right'>518·4</td></tr> +</table></div> + +<p>More elaborate analyses of the same fluid have since been made by Dr. +Voelcker, with the subjoined results per gallon:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>1.</td><td align='right'>2.</td><td align='right'>3.</td></tr> +<tr><td align='left'>Organic matters and ammoniacal salts</td><td align='right'>263·80</td><td align='right'>250·63</td><td align='right'>70·121</td></tr> +<tr><td align='left'>Silica</td><td align='right'>2·49</td><td align='right'>9·98</td><td align='right'>1·154</td></tr> +<tr><td align='left'>Oxide of iron</td><td align='right'>0·70</td><td align='right'>0·68</td><td align='right'>...</td></tr> +<tr><td align='left'>Lime</td><td align='right'>5·34</td><td align='right'>25·18</td><td align='right'>13·011</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>2·96</td><td align='right'>15·33</td><td align='right'>1·660</td></tr> +<tr><td align='left'>Potash</td><td align='right'>103·23</td><td align='right'>112·26</td><td align='right'>13·411</td></tr> +<tr><td align='left'>Chloride of potassium</td><td align='right'>72·00</td><td align='right'>77·38</td><td align='right'>7·712</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='right'>17·18</td><td align='right'>46·03</td><td align='right'>17·258</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='right'>2·70</td><td align='right'>9·51</td><td align='right'>2·304</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='right'>22·31</td><td align='right'>37·60</td><td align='right'>3·408</td></tr> +<tr><td align='left'>Carbonic acid, and loss</td><td align='right'>33·90</td><td align='right'>27·95</td><td align='right'>14·025</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'> Total solids</td><td align='right'>526·61</td><td align='left'>612·53</td><td align='right'>144·064</td></tr> +<tr><td align='left'>Ammonia</td><td align='right'>114·16</td><td align='right'>22·31</td><td align='right'>26·647</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_189" id="Page_189">[Pg 189]</a></span></p> + +<p>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.</p> + +<p>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 <i>strict</i> 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.</p> + +<p>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.</p> + +<p>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—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Organic matter and ammoniacal salts</td><td align='right'>53·03</td></tr> +<tr><td align='left'>Soluble silica</td><td align='right'>6·47</td></tr> +<tr><td align='left'>Insoluble siliceous matter (clay)</td><td align='right'>15·17</td></tr> +<tr><td align='left'>Oxide of iron and alumina</td><td align='right'>2·36</td></tr> +<tr><td align='left'>Lime</td><td align='right'>6·60</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>1·73</td></tr> +<tr><td align='left'></td><td align='right'>——</td></tr> +<tr><td align='left'>Potash</td><td align='right'>0·35</td></tr> +<tr><td align='left'>Chloride of potassium</td><td align='right'>1·95</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='right'>4·81</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='right'>3·72</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='right'>1·94</td></tr> +<tr><td align='left'>Carbonic acid, and loss</td><td align='right'>0·47</td></tr> +<tr><td align='left'></td><td align='right'>——</td></tr> +<tr><td align='left'> Total solids</td><td align='right'>96·60</td></tr> +<tr><td align='left'>Ammonia</td><td align='right'>8·10</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_191" id="Page_191">[Pg 191]</a></span> 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.</p> + +<p><i>Sewage Manure.</i>—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—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Soluble organic matter</td><td align='right'>21·90</td></tr> +<tr><td align='left'>Insoluble organic matter</td><td align='right'>21·70</td></tr> +<tr><td align='left'>Peroxide of iron and alumina</td><td align='right'>2·01</td></tr> +<tr><td align='left'>Lime</td><td align='right'>10·50</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>2·00</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='right'>6·09</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='right'>6·14</td></tr> +<tr><td align='left'></td><td align='right'>——</td></tr> +<tr><td align='left'>Chlorine</td><td align='right'>12·20</td></tr> +<tr><td align='left'>Potash</td><td align='right'>2·89</td></tr> +<tr><td align='left'>Soda</td><td align='right'>13·27</td></tr> +<tr><td align='left'>Silica</td><td align='right'>6·50</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>105·20</td></tr> +<tr><td align='left'>Ammonia</td><td align='right'>14·90</td></tr> +</table></div> + + +<p>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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Peroxide of iron and alumina</td><td align='right'>4·45</td></tr> +<tr><td align='left'>Lime</td><td align='right'>1·74</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>0·39</td></tr> +<tr><td align='left'>Potash</td><td align='right'>0·10</td></tr> +<tr><td align='left'>Soda</td><td align='right'>0·06</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='right'>1·08</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='right'>0·16</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>17·95</td></tr> +<tr><td align='left'>Sand</td><td align='right'>20·51</td></tr> +<tr><td align='left'>Water</td><td align='right'>53·56</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='right'>0·93</td></tr> +</table></div> + +<p>And even, though containing more than half its weight of<span class='pagenum'><a name="Page_193" id="Page_193">[Pg 193]</a></span> water and 20 +per cent of sand, this substance has considerable value as a manure.</p> + +<p>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.<span class='pagenum'><a name="Page_194" id="Page_194">[Pg 194]</a></span></p> + +<p>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.</p> + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_L_12" id="Footnote_L_12"></a><a href="#FNanchor_L_12"><span class="label">[L]</span></a> Report on the economic uses of peat. Highland Society's +Transactions, N.S., vol. iv. p. 549.</p></div> +</div> + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_195" id="Page_195">[Pg 195]</a></span></p> +<h2>CHAPTER IX.</h2> + +<h3>COMPOSITION AND PROPERTIES OF VEGETABLE MANURES.</h3> + + +<p>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.</p> + +<p><i>Rape-dust, Mustard, Cotton and Castor Cake.</i>—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<span class='pagenum'><a name="Page_196" id="Page_196">[Pg 196]</a></span> that of the seeds from which they are made, and which +have been given under that head.</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Rape-Cake.</td><td align='left'> Poppy-Cake.</td><td align='left'> Cotton-seed Cake.</td><td align='left'> Castor-Cake.</td></tr> +<tr><td align='left'>Water</td><td align='left'> 10·68</td><td align='left'> 11·63</td><td align='left'> 11·19</td><td align='left'> 12·31</td></tr> +<tr><td align='left'>Oil</td><td align='left'> 11·10</td><td align='left'> 5·95</td><td align='left'> 9·08</td><td align='left'> 24·32</td></tr> +<tr><td align='left'>Albuminious compounds</td><td align='left'> 29·53</td><td align='left'> 31·16</td><td align='left'> 25·16</td><td align='left'> 21·91</td></tr> +<tr><td align='left'>Ash</td><td align='left'> 7·79</td><td align='left'> 12·98</td><td align='left'> 5·64</td><td align='left'> 6·08</td></tr> +<tr><td align='left'>Other constituents</td><td align='left'> 40·90</td><td align='left'> 38·18</td><td align='left'> 48·93</td><td align='left'> 35·38</td></tr> +<tr><td align='left'> </td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td></tr> +<tr><td align='left'>Nitrogen</td><td align='left'> 4·38</td><td align='left'> 4·94</td><td align='left'> 3·95</td><td align='left'> 3·20</td></tr> +<tr><td align='left'>Silica</td><td align='left'> 1·18</td><td align='left'> 3·36</td><td align='left'> 1·32</td><td align='left'> 1·96</td></tr> +<tr><td align='left'>Phosphates</td><td align='left'> 3·87</td><td align='left'> 69·3</td><td align='left'> 2·19</td><td align='left'> 2·81</td></tr> +<tr><td align='left'>Phosphoric acid in combination with alkalies</td><td align='left'> 0·39</td><td align='left'> 3·27</td><td align='left'> 0·15</td><td align='left'> 0·64</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_197" id="Page_197">[Pg 197]</a></span> 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.</p> + +<p><i>Malt-Dust, Bran, Chaff, etc.</i>—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.</p> + +<p><i>Straw</i> 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.</p> + +<p>The quantity of nitrogen in straw does not exceed 0·2<span class='pagenum'><a name="Page_198" id="Page_198">[Pg 198]</a></span> per cent, and its +value is mainly due to its inorganic constituents and to its mechanical +effect on the soil.</p> + +<p><i>Saw-dust</i> has little value as a manure, as it undergoes decomposition +with extreme slowness. It is a good <i>mechanical</i> 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.</p> + +<p><i>Manuring with Fresh Vegetable Matter—Green Manuring.</i>—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.<span class='pagenum'><a name="Page_199" id="Page_199">[Pg 199]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_200" id="Page_200">[Pg 200]</a></span> 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.</p> + +<p>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.</p> + +<p><i>Sea-Weed.</i>—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.</p> + +<p>The subjoined analyses of three of the most abundant species will +sufficiently indicate their general composition.<span class='pagenum'><a name="Page_201" id="Page_201">[Pg 201]</a></span></p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> </td><td align='left'> </td><td colspan="2"><span class="smcap">Laminaria Digitata.</span></td><td align='left'> </td></tr> +<tr><td align='left'></td><td align='left'> Fucus nodosus.</td><td align='left'>Fucus vesiculosus.</td><td align='left'>Collected in Autumn.</td><td align='left'> Stem and Frond collected in Spring.</td><td align='left'>Mixed Weeds state in<br /> which they actually<br /> are used.</td></tr> +<tr><td align='left'>Water</td><td align='left'> 74·31</td><td align='left'> 70·57</td><td align='left'> 88·69</td><td align='left'> 77·31</td><td align='left'> 80·44</td></tr> +<tr><td align='left'>Albuminous compounds</td><td align='left'> 1·76</td><td align='left'> 2·01</td><td align='left'> 0·93</td><td align='left'> 3·32</td><td align='left'> 2·85</td></tr> +<tr><td align='left'>Fibre, etc.</td><td align='left'> 19·04</td><td align='left'> 22·05</td><td align='left'> 4·92</td><td align='left'> 10·39</td><td align='left'> 6·40</td></tr> +<tr><td align='left'>Ash</td><td align='left'> 4·89</td><td align='left'> 5·37</td><td align='left'> 5·46</td><td align='left'> 8·98</td><td align='left'> 10·31</td></tr> +<tr><td align='left'> </td><td align='left'>100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td></tr> +<tr><td align='left'>Nitrogen</td><td align='left'> 0·28</td><td align='left'> 0·32</td><td align='left'> 0·15</td><td align='left'> 0·53</td><td align='left'> 0·45</td></tr> +<tr><td align='left'> The ash consisted of</td><td colspan="5"> </td></tr> +<tr><td align='left'> </td><td align='left'> </td><td align='left'> </td><td align='left'> Stem. Frond.</td><td align='left'> </td><td align='left'> </td></tr> +<tr><td align='left'>Peroxide of iron</td><td align='left'> 0·25</td><td align='left'> 0·35</td><td align='left'> 0·20 0·50</td><td align='left'> 0·45</td><td align='left'> 2·35</td></tr> +<tr><td align='left'>Lime</td><td align='left'> 9·60</td><td align='left'> 8·92</td><td align='left'> 7·21 7·29</td><td align='left'> 4·62</td><td align='left'> 18·15</td></tr> +<tr><td align='left'>Magnesia</td><td align='left'> 6·65</td><td align='left'> 5·83</td><td align='left'> 2·73 5·91</td><td align='left'> 10·94</td><td align='left'> 6·48</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 20·03</td><td align='left'> 20·75</td><td align='left'> 5·55 11·91</td><td align='left'> 12·16</td><td align='left'> 12·77</td></tr> +<tr><td align='left'>Chloride of potassium</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 58·42 26·59</td><td align='left'> 25·83</td><td align='left'> 9·10</td></tr> +<tr><td align='left'>Iodide of potassium</td><td align='left'> 0·44</td><td align='left'> 0·23</td><td align='left'> 1·51 2·09</td><td align='left'> 1·22</td><td align='left'> 1·68</td></tr> +<tr><td align='left'>Soda</td><td align='left'> 4·58</td><td align='left'> 6·09</td><td align='left'> ... ...</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Sulphuret of sodium<a name="FNanchor_M_13" id="FNanchor_M_13"></a><a href="#Footnote_M_13" class="fnanchor">[M]</a></td><td align='left'> 3·66</td><td align='left'> ...</td><td align='left'> ... ...</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='left'> 24·33</td><td align='left'> 24·81</td><td align='left'> 15·29 30·77</td><td align='left'> 19·34</td><td align='left'> 22·08</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='left'> 1·71</td><td align='left'> 2·14</td><td align='left'> 2·42 2·66</td><td align='left'> 1·75</td><td align='left'> 4·59</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='left'> 21·97</td><td align='left'> 28·01</td><td align='left'> 2·23 8·80</td><td align='left'> 7·26</td><td align='left'> 6·22</td></tr> +<tr><td align='left'>Carbonic acid</td><td align='left'> 6·39</td><td align='left'> 2·20</td><td align='left'> 4·11 2·49</td><td align='left'> 15·23</td><td align='left'> 13·58</td></tr> +<tr><td align='left'>Silicic acid</td><td align='left'> 0·38</td><td align='left'> 0·67</td><td align='left'> 0·33 0·99</td><td align='left'> 1·20</td><td align='left'> 3·00</td></tr> +<tr><td align='left'> </td><td align='left'> ——</td><td align='left'> ———</td><td align='left'> ——— ———</td><td align='left'> ———</td><td align='left'> ———</td></tr> +<tr><td align='left'> </td><td align='left'>100·00</td><td align='left'> 100·00</td><td align='left'> 100·00 100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_202" id="Page_202">[Pg 202]</a></span></p> +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + +<p><i>Leaves</i> may be used as a manure, simply by ploughing<span class='pagenum'><a name="Page_203" id="Page_203">[Pg 203]</a></span> them in, by +composting them with lime, or by adding them to the manure heap.</p> + +<p><i>Peat.</i>—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.</p> + +<p>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.</p> + +<div class="footnotes"><h3>FOOTNOTES:</h3> + +<div class="footnote"><p><a name="Footnote_M_13" id="Footnote_M_13"></a><a href="#FNanchor_M_13"><span class="label">[M]</span></a> 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.</p></div> +</div> + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_204" id="Page_204">[Pg 204]</a></span></p> +<h2>CHAPTER X.</h2> + +<h3>COMPOSITION AND PROPERTIES OF ANIMAL MANURES.</h3> + + +<p>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.</p> + +<p><i>Guano.</i>—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.</p> + +<p>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<span class='pagenum'><a name="Page_205" id="Page_205">[Pg 205]</a></span> 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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>I.</td><td align='right'>II.</td><td align='right'>III.</td></tr> +<tr><td align='left'>Urate of ammonia</td><td align='right'>10·70</td><td align='right'>9·0</td><td align='right'>3·24</td></tr> +<tr><td align='left'>Oxalate of ammonia</td><td align='right'>12·38</td><td align='right'>10·6</td><td align='right'>13·35</td></tr> +<tr><td align='left'>Oxalate of lime</td><td align='right'>5·44</td><td align='right'>7·0</td><td align='right'>16·36</td></tr> +<tr><td align='left'>Phosphate of ammonia</td><td align='right'>19·25</td><td align='right'>6·0</td><td align='right'>6·45</td></tr> +<tr><td align='left'>Phosphate of magnesia and ammonia</td><td align='right'>...</td><td align='right'>2·6</td><td align='right'>4·20</td></tr> +<tr><td align='left'>Sulphate of potash</td><td align='right'>4·50</td><td align='right'>5·5</td><td align='right'>4·23</td></tr> +<tr><td align='left'>Sulphate of soda</td><td align='right'>1·95</td><td align='right'>3·8</td><td align='right'>1·12</td></tr> +<tr><td align='left'>Sulphate of ammonia</td><td align='right'>3·36</td><td align='right'>...</td><td align='right'>...</td></tr> +<tr><td align='left'>Muriate of ammonia</td><td align='right'>4·81</td><td align='right'>4·2</td><td align='right'>6·50</td></tr> +<tr><td align='left'>Phosphate of soda</td><td align='right'>...</td><td align='right'>...</td><td align='right'>5·29</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='right'>...</td><td align='right'>...</td><td align='right'>0·10</td></tr> +<tr><td align='left'>Phosphate of lime</td><td align='right'>15·56</td><td align='right'>14·3</td><td align='right'>9·94</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>1·80</td><td align='right'>...</td><td align='right'>...</td></tr> +<tr><td align='left'>Sand and alumina</td><td align='right'>1·59</td><td align='right'>4·7</td><td align='right'>5·80</td></tr> +<tr><td align='left'>Water</td><td align='right'>9·14 }</td></tr> +<tr><td align='left'></td><td align='right'>}</td><td align='right'>32·3</td><td align='right'>23·42</td></tr> +<tr><td align='left'>Undetermined humus-like organic matters</td><td align='right'>10·00 }</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>——</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·48</td><td align='right'>100·0</td><td align='right'>100·00</td></tr> +</table></div> + +<p>These analyses illustrate two points—<i>first</i>, that in some samples the +decomposition has advanced to a greater extent than in others; for we +observe that the quantity of<span class='pagenum'><a name="Page_206" id="Page_206">[Pg 206]</a></span> 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 <i>secondly</i>, 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.</p> + +<p>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.<span class='pagenum'><a name="Page_207" id="Page_207">[Pg 207]</a></span></p> + + +<h4><i>Table showing the Average Composition of different varieties of Guano.</i></h4> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'>Angamos.</td><td align='left'>Peruvian.</td><td colspan="2"> ICHABOE.</td><td colspan="3">Bolivian or Upper Peruvian.</td></tr> +<tr><td align='left'> </td><td align='left'> </td><td align='left'> </td><td align='left'>Old.</td><td align='left'>New.</td><td align='left'>Old.</td><td align='left'>Government.</td><td align='left'>Inferior</td></tr> +<tr><td align='left'>Water</td><td align='left'> 12·36</td><td align='left'> 13·73</td><td align='left'>24·21</td><td align='left'>18·89</td><td align='left'> 12·55</td><td align='left'> 16·44</td><td align='left'> 14·15</td></tr> +<tr><td align='left'>Organic matter and ammoniacal salts</td><td align='left'> 59·92</td><td align='left'> 53·16</td><td align='left'>39·30</td><td align='left'>32·49</td><td align='left'> 35·89</td><td align='left'> 12·28</td><td align='left'> 26·14</td></tr> +<tr><td align='left'>Phosphates</td><td align='left'> 17·01</td><td align='left'> 23·48</td><td align='left'>30·00</td><td align='left'>19·63</td><td align='left'> 27·63</td><td align='left'> 56·09</td><td align='left'> 23·13</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 9·65</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 12·87</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='left'> 7·20</td><td align='left'> 7·97</td><td align='left'> 4·19</td><td align='left'> 8·82</td><td align='left'> 15·29</td><td align='left'> 11·33</td><td align='left'> 5·97</td></tr> +<tr><td align='left'>Sand</td><td align='left'> 3·51</td><td align='left'> 1·66</td><td align='left'> 2·30</td><td align='left'> 6·72</td><td align='left'> 8·64</td><td align='left'> 2·81</td><td align='left'> 8·09</td></tr> +<tr><td align='left'> </td><td align='left'> 100·00</td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'>100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='left'> 21·10</td><td align='left'> 17·00</td><td align='left'> 8·50</td><td align='left'> 10·42</td><td align='left'> 8·99</td><td align='left'> 2·57</td><td align='left'> 3·26</td></tr> +<tr><td align='left'>Phosphoric acid in alkaline salts</td><td align='left'> 1·20</td><td align='left'> 2·50</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 3·11</td><td align='left'> ...</td></tr> +</table></div> +<p><br /><br /></p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'>Pacquico Island.</td><td align='left'>Latham Bay.</td><td align='left'>Saldanha.</td><td align='left'>Australian.</td><td align='left'>Kooriamooria.</td></tr> +<tr><td align='left'>Water</td><td align='left'> 8·38</td><td align='left'> 24·96</td><td align='left'> 21·03</td><td align='left'> 13·20</td><td align='left'> 8·91</td></tr> +<tr><td align='left'>Organic matter and ammoniacal salts</td><td align='left'> 23·10</td><td align='left'> 10·96</td><td align='left'> 14·93</td><td align='left'> 13·77</td><td align='left'> 7·72</td></tr> +<tr><td align='left'>Phosphates</td><td align='left'> 32·36</td><td align='left'> 54·47</td><td align='left'> 56·40</td><td align='left'> 44·47</td><td align='left'> 44·15</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='left'> 2·92</td><td align='left'> 2·82</td><td align='left'> ...</td><td align='left'> 4·55</td><td align='left'> 3·19</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='left'> ...</td><td align='left'> 2·20</td><td align='left'> ...</td><td align='left'> 8·82</td><td align='left'> 3·37</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='left'> 25·43</td><td align='left'> 4·06</td><td align='left'> 6·10</td><td align='left'> 7·34</td><td align='left'> 11·23</td></tr> +<tr><td align='left'>Sand</td><td align='left'> 7·81</td><td align='left'> 0·51</td><td align='left'> 1·54</td><td align='left'> 7·85</td><td align='left'> 21·43</td></tr> +<tr><td align='left'> </td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'>100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='left'> 6·58</td><td align='left'> 1·26</td><td align='left'> 1·62</td><td align='left'> 1·01</td><td align='left'> 0·42</td></tr> +<tr><td align='left'>Phosphoric acid in alkaline salts</td><td align='left'> 3·50</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td></tr> +</table></div> + +<p><br /><br /></p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'>Patagonian.</td><td align='left'>Chilian.</td><td align='left'>Mexican.</td></tr> +<tr><td align='left'>Water</td><td align='left'> 20·61</td><td align='left'> 14·89</td><td align='left'> 18·80</td></tr> +<tr><td align='left'>Organic matter and ammoniacal salts</td><td align='left'> 19·72</td><td align='left'> 16·81</td><td align='left'> 12·88</td></tr> +<tr><td align='left'>Phosphates</td><td align='left'> 30·66</td><td align='left'> 36·90</td><td align='left'> 18·38</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='left'> 1·30</td><td align='left'> ...</td><td align='left'> 27·79</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='left'> 3·06</td><td align='left'> 10·28</td><td align='left'> ...</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='left'> 7·01</td><td align='left'> 6·84</td><td align='left'> 16·95</td></tr> +<tr><td align='left'>Sand</td><td align='left'> 17·04</td><td align='left'> 14·26</td><td align='left'> 5·20</td></tr> +<tr><td align='left'> </td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'>100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='left'> 2·69</td><td align='left'> 1·42</td><td align='left'> 0·42</td></tr> +<tr><td align='left'>Phosphoric acid in alkaline salts</td><td align='left'> 3·00</td><td align='left'> ...</td><td align='left'> ...</td></tr> +</table></div> + + +<p><span class='pagenum'><a name="Page_208" id="Page_208">[Pg 208]</a></span></p> + + +<h4><i>Table shewing the Composition of some of the less common varieties of +Guano.</i></h4> + +<p><span class="smcap">Note</span>.—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.</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Sea Bear Bay.</td><td align='left'> Indian.</td><td align='left'> Holme's Bird Island.</td><td align='left'> Ascension Island.</td><td align='left'> Possession Island.</td></tr> +<tr><td align='left'>Water</td><td align='left'> 30·82</td><td align='left'> 23·62</td><td align='left'> 25·00</td><td align='left'> 15·97</td><td align='left'> 10·92</td></tr> +<tr><td align='left'>Organic matter and ammoniacal salts</td><td align='left'> 31·78</td><td align='left'> 60·05</td><td align='left'> 32·10</td><td align='left'> 23·15</td><td align='left'> 15·42</td></tr> +<tr><td align='left'>Phosphates</td><td align='left'> 24·33</td><td align='left'> 7·18</td><td align='left'> 27·36</td><td align='left'> 32·54</td><td align='left'> 46·41</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='left'> 3·84</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 7·46</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='left'> 0·58</td><td align='left'> 2·79</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='left'> 7·38</td><td align='left'> 5·58</td><td align='left'> 8·82</td><td align='left'> 15·92</td><td align='left'> 6·15</td></tr> +<tr><td align='left'>Sand</td><td align='left'> 1·27</td><td align='left'> 0·78</td><td align='left'> 6·72</td><td align='left'> 12·42</td><td align='left'> 13·64</td></tr> +<tr><td align='left'> </td><td align='left'>100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='left'> 10·45</td><td align='left'> 10·27</td><td align='left'> 7·75</td><td align='left'> 6·06</td><td align='left'> 1·34</td></tr> +<tr><td align='left'>Phosphoric acid in alkaline salts</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 1·82</td><td align='left'> ...</td></tr> +</table></div> + +<p><br /><br /></p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Algoa Bay.</td><td align='left'> New Island.</td><td align='left'> Bird's Island.</td><td align='left'> Leone Island.</td></tr> +<tr><td align='left'>Water</td><td align='left'> 30·55</td><td align='left'> 28·78</td><td align='left'> 16·52</td><td align='left'> 23·65</td></tr> +<tr><td align='left'>Organic matter and ammoniacal salts</td><td align='left'> 6·85</td><td align='left'> 13·78</td><td align='left'> 14·84</td><td align='left'> 4·27</td></tr> +<tr><td align='left'>Phosphates</td><td align='left'> 21·24</td><td align='left'> 22·46</td><td align='left'> 25·21</td><td align='left'> 13·58</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='left'> 36·42</td><td align='left'> ...</td><td align='left'> 40·47</td><td align='left'> 29·95</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='left'> ...</td><td align='left'> 13·78</td><td align='left'> ...</td><td align='left'> ...</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='left'> 3·32</td><td align='left'> 12·62</td><td align='left'> 1·16</td><td align='left'> 5·40</td></tr> +<tr><td align='left'>Sand</td><td align='left'> 1·62</td><td align='left'> 11·58</td><td align='left'> 1·80</td><td align='left'> 23·15</td></tr> +<tr><td align='left'> </td><td align='left'>100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='left'> 0·54</td><td align='left'> 0·84</td><td align='left'> 1·26</td><td align='left'> 0·67</td></tr> +<tr><td align='left'>Phosphoric acid in alkaline salts</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> ...</td></tr> +</table></div> + + +<p><span class='pagenum'><a name="Page_209" id="Page_209">[Pg 209]</a></span></p> + +<p>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.</p> + +<p>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:</p> + +<p>1st, The guano should be light coloured. If it is dark, the chances are +that it has been damaged by water.</p> + +<p>2d, It should be dry, and when a handful is well squeezed together it +should cohere very slightly.</p> + +<p>3d, It should not have too powerful an ammoniacal odour.</p> + +<p>4th, It should contain lumps, which, when broken, appear of a paler +colour than the powdery part of the sample.</p> + +<p>5th, When rubbed between the fingers it should not be gritty.</p> + +<p>6th, A bushel of the guano should not weigh more than from 56 to 60 lbs.</p> + +<p>These characters must not, however, be too implicitly relied on, for +they are all imitated with wonderful ingenuity<span class='pagenum'><a name="Page_210" id="Page_210">[Pg 210]</a></span> 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.</p> + +<p>In the table above, the <i>average</i> 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:</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td colspan="2"> Angamos.</td><td colspan="2"> Peruvian.</td><td colspan="2"> Bolivian.</td></tr> +<tr><td align='left'> </td><td align='left'>Highest.</td><td align='left'>Lowest.</td><td align='left'>Highest.</td><td align='left'>Lowest.</td><td align='left'>Highest.</td><td align='left'>Lowest.</td></tr> +<tr><td align='left'>Water</td><td align='left'> 12·60</td><td align='left'> 7·09</td><td align='left'> 10·37</td><td align='left'> 21·49</td><td align='left'> 11·53</td><td align='left'> 16·20</td></tr> +<tr><td align='left'>Organic matter and ammoniacal salts</td><td align='left'> 65·62</td><td align='left'> 50·83</td><td align='left'> 55·73</td><td align='left'> 46·26</td><td align='left'> 11·17</td><td align='left'> 12·86</td></tr> +<tr><td align='left'>Phosphates</td><td align='left'> 10·83</td><td align='left'> 8·70</td><td align='left'> 25·20</td><td align='left'> 18·93</td><td align='left'> 62·99</td><td align='left'> 52·95</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='left'> 7·50</td><td align='left'> 16·30</td><td align='left'> 7·50</td><td align='left'> 10·64</td><td align='left'> 9·93</td><td align='left'> 13·83</td></tr> +<tr><td align='left'>Sand</td><td align='left'> 3·45</td><td align='left'> 17·08</td><td align='left'> 1·20</td><td align='left'> 2·68</td><td align='left'> 4·38</td><td align='left'> 4·16</td></tr> +<tr><td align='left'> </td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'>100·00</td><td align='left'> 100·00</td><td align='left'> 100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='left'> 25·33</td><td align='left'> 17·15</td><td align='left'> 18·95</td><td align='left'> 14·65</td><td align='left'> 1·89</td><td align='left'> 2·23</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_211" id="Page_211">[Pg 211]</a></span> of £1 or even £2 per ton +between the values of cargos of Peruvian guano, which are sold at the +same price.</p> + +<p>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.</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='left'>12·85</td><td align='left'>15·19</td><td align='left'>12·06</td><td align='left'>27·86</td><td align='left'>6·32</td></tr> +<tr><td align='left'>Organic matter and ammoniacal salts</td><td align='left'>26·84</td><td align='left'>44·31</td><td align='left'>34·14</td><td align='left'>30·41</td><td align='left'>27·42</td></tr> +<tr><td align='left'>Phosphates</td><td align='left'>15·54</td><td align='left'>20·95</td><td align='left'>22·08</td><td align='left'>22·17</td><td align='left'>33·61</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='left'>...</td><td align='left'>...</td><td align='left'>11·08</td><td align='left'>...</td><td align='left'>22·11</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='left'>6·07</td><td align='left'>9·40</td><td align='left'>12·81</td><td align='left'>7·92</td><td align='left'>22·50</td></tr> +<tr><td align='left'>Sand</td><td align='left'>38·70</td><td align='left'>10·15</td><td align='left'>7·83</td><td align='left'>1·64</td><td align='left'>10·15</td></tr> +<tr><td align='left'> </td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'>100·00</td><td align='left'>100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='left'>9·34</td><td align='left'>13·90</td><td align='left'>9·77</td><td align='left'>8·64</td><td align='left'>9·76</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_212" id="Page_212">[Pg 212]</a></span> 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<span class='pagenum'><a name="Page_213" id="Page_213">[Pg 213]</a></span> 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.</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>I.</td><td align='right'>II.</td><td align='right'>III.</td></tr> +<tr><td align='left'>Water</td><td align='right'>7·80</td><td align='right'>6·65</td><td align='right'>8·85</td></tr> +<tr><td align='left'>Organic matter and ammoniacal salts</td><td align='right'>10·85</td><td align='right'>19·16</td><td align='right'>10·20</td></tr> +<tr><td align='left'>Phosphates</td><td align='right'>67·00</td><td align='right'>20·41</td><td align='right'>17·10</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>...</td><td align='right'>21·15</td><td align='right'>...</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='right'>11·10</td><td align='right'>5·31</td><td align='right'>61·30</td></tr> +<tr><td align='left'>Sand</td><td align='right'>3·25</td><td align='right'>27·32</td><td align='right'>2·55</td></tr> +<tr><td align='left'></td><td align='left'>———</td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='left'>100·00</td><td align='right'>100·00</td><td align='right'>100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='right'>2·29</td><td align='right'>5·73</td><td align='right'>1·48</td></tr> +<tr><td align='left'>Phosphoric acid in the alkaline salts</td><td align='right'>2·24</td><td align='right'>...</td><td align='right'>1·70</td></tr> +<tr><td align='left'>Equal to phosphate of lime</td><td align='right'>4·89</td><td align='right'>...</td><td align='right'>3·70</td></tr> +</table></div> + + +<p>With the exception of Peruvian, the supply of <i>good</i> 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.</p> + +<p>The value and use of guano are now so well understood,<span class='pagenum'><a name="Page_214" id="Page_214">[Pg 214]</a></span> 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.</p> + +<p>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,<span class='pagenum'><a name="Page_215" id="Page_215">[Pg 215]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_216" id="Page_216">[Pg 216]</a></span> 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.</p> + +<p>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.</p> + +<p><i>Pigeons' Dung.</i>—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'.</p> + +<p><i>Urate and Sulphated Urine.</i>—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<span class='pagenum'><a name="Page_217" id="Page_217">[Pg 217]</a></span> +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.</p> + +<p><i>Night-Soil and Poudrette.</i>—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<span class='pagenum'><a name="Page_218" id="Page_218">[Pg 218]</a></span> 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:—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Montfauçon.</td><td align='right'>Bondy.</td><td align='right'>Dresden.</td><td align='right'>American.</td></tr> +<tr><td align='left'>Water</td><td align='right'>28·00</td><td align='right'>13·60</td><td align='right'>19·50</td><td align='right'>39·97</td></tr> +<tr><td align='left'>Organic matters</td><td align='right'>29·00</td><td align='right'>24·10</td><td align='right'>20·80</td><td align='right'>20·57</td></tr> +<tr><td align='left'>Phosphates</td><td align='right'>7·65</td><td align='right'>4·96</td><td align='right'>5·40</td><td align='right'>1·88</td></tr> +<tr><td align='left'>Carbonates of lime and Magnesia, alkaline salts, etc.</td><td align='right'>7·35</td><td align='right'>14·14</td><td align='right'>11·30</td><td align='right'>7·63</td></tr> +<tr><td align='left'>Sand</td><td align='right'>28·00</td><td align='right'>43·20</td><td align='right'>43·00</td><td align='right'>29·95</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td><td align='right'>100·00</td><td align='right'>100·00</td><td align='right'>100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='right'>1·54</td><td align='right'>1·98</td><td align='right'>2·60</td><td align='right'>1·23</td></tr> +</table></div> + + +<p>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.</p> + +<p><i>Hair, Skin, and Horn.</i>—The refuse of manufactories in which these +substances are employed, are frequently used as manures. They are highly +nitrogenous substances,<span class='pagenum'><a name="Page_219" id="Page_219">[Pg 219]</a></span> 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,—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Skin.</td><td align='right'>Human hair.</td><td align='right'>Wool.</td><td align='right'>Horn.</td></tr> +<tr><td align='left'>Carbon</td><td align='right'>50·99</td><td align='right'>50·65</td><td align='right'>50·65</td><td align='right'>51·99</td></tr> +<tr><td align='left'>Hydrogen</td><td align='right'>7·07</td><td align='right'>6·36</td><td align='right'>7·03</td><td align='right'>6·72</td></tr> +<tr><td align='left'>Nitrogen</td><td align='right'>18·72</td><td align='right'>17·14</td><td align='right'>17·71</td><td align='right'>17·28</td></tr> +<tr><td align='left'>Oxygen</td><td align='right'>23·22</td><td align='right'>20·85 }</td><td align='right'>24·61</td><td align='right'>24·01</td></tr> +<tr><td align='left'>Sulphur</td><td align='right'>...</td><td align='right'>5·00}</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td><td align='right'>100·00</td><td align='right'>100·00</td><td align='right'>100·00</td></tr> +</table></div> + +<p>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.</p> + +<p>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.</p> + +<p>All these substances are highly valuable as manures, but it must be +borne in mind that they undergo decomposition<span class='pagenum'><a name="Page_220" id="Page_220">[Pg 220]</a></span> 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.</p> + +<p><i>Blood</i> 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.</p> + +<p><i>Flesh.</i>—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:<span class='pagenum'><a name="Page_221" id="Page_221">[Pg 221]</a></span>—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>12·17</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>78·44</td></tr> +<tr><td align='left'>Phosphate of lime, etc.</td><td align='right'>3·82</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='right'>3·64</td></tr> +<tr><td align='left'>Sand</td><td align='right'>1·93</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +<tr><td align='left'>Nitrogen</td><td align='right'>9·22</td></tr> +<tr><td align='left'>Ammonia to which the nitrogen is equivalent</td><td align='right'>11·20</td></tr> +</table></div> + +<p>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—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>9·05</td></tr> +<tr><td align='left'>Fat</td><td align='right'>11·13</td></tr> +<tr><td align='left'>Animal matter</td><td align='right'>39·52</td></tr> +<tr><td align='left'>Phosphate of lime</td><td align='right'>28·74</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>3·81</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='right'>0·57</td></tr> +<tr><td align='left'>Sand</td><td align='right'>7·18</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +<tr><td align='left'>Nitrogen</td><td align='right'>5·56</td></tr> +<tr><td align='left'>Ammonia to which the nitrogen is equivalent</td><td align='right'>6·67</td></tr> +</table></div> + +<p>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.</p> + +<p><i>Fish</i> 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<span class='pagenum'><a name="Page_222" id="Page_222">[Pg 222]</a></span> for turnips. They are sold at 8d. per bushel, +and their composition is—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>64·6</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>33·3</td></tr> +<tr><td align='left'>Ash</td><td align='right'>2·1</td></tr> +<tr><td align='left'></td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>100·0</td></tr> +<tr><td align='left'>Nitrogen</td><td align='right'>1·90</td></tr> +<tr><td align='left'>Phosphoric acid</td><td align='right'>0·91</td></tr> +</table></div> + +<p>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.</p> + +<p>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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>8·00</td></tr> +<tr><td align='left'>Fatty matters</td><td align='right'>7·20</td></tr> +<tr><td align='left'>Nitrogeneous organic matters</td><td align='right'>71·46</td></tr> +<tr><td align='left'>Phosphate of lime</td><td align='right'>8·70</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='right'>3·80</td></tr> +<tr><td align='left'>Sand</td><td align='right'>0·84</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> + +<tr><td align='left'><span class='pagenum'><a name="Page_223" id="Page_223">[Pg 223]</a></span></td></tr> + + +<tr><td align='left'>Nitrogen</td><td align='right'>11·25</td></tr> +<tr><td align='left'>Equal to ammonia</td><td align='right'>13·68</td></tr> +<tr><td align='left'>Phosphoric acid in the alkaline salts, equal to 1·41 phosphate of lime</td><td align='right'>0·65</td></tr> +</table></div> + + +<p>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.</p> + +<p><i>Bones.</i>—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.</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>6·20</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>39·13</td></tr> +<tr><td align='left'>Phosphate of lime</td><td align='right'>48·95</td></tr> +<tr><td align='left'><span class='pagenum'><a name="Page_224" id="Page_224">[Pg 224]</a></span></td></tr> +<tr><td align='left'>Lime</td><td align='right'>2·57</td></tr> +<tr><td align='left'>Magnesia</td><td align='right'>0·30</td></tr> +<tr><td align='left'>Sulphuric acid</td><td align='right'>2·55</td></tr> +<tr><td align='left'>Silica</td><td align='right'>0·30</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +<tr><td align='left'>Ammonia which the organic matter is capable of yielding</td><td align='right'>4·80</td></tr> +</table></div> + + + +<p>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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_225" id="Page_225">[Pg 225]</a></span> 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.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_226" id="Page_226">[Pg 226]</a></span></p> +<h2>CHAPTER XI.</h2> + +<h3>COMPOSITION AND PROPERTIES OF MINERAL MANURES.</h3> + + +<p>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.<span class='pagenum'><a name="Page_227" id="Page_227">[Pg 227]</a></span></p> + +<p><i>Sulphate and Muriate of Ammonia.</i>—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.</p> + +<p>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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>I.</td><td align='right'>II.</td></tr> +<tr><td align='left'>Water</td><td align='right'>9·05</td><td align='right'>5·77</td></tr> +<tr><td align='left'>Sulphate of ammonia</td><td align='right'>79·63</td><td align='right'>85·21</td></tr> +<tr><td align='left'>Fixed salts</td><td align='right'>11·17</td><td align='right'>9·02</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td><td align='right'>100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='right'>20·55</td><td align='right'>21·94</td></tr> +</table></div> + +<p>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.<span class='pagenum'><a name="Page_228" id="Page_228">[Pg 228]</a></span></p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>I.</td><td align='right'>II.</td></tr> +<tr><td align='left'>Water</td><td align='right'>14·49</td><td align='right'>25·39</td></tr> +<tr><td align='left'>Sulphate of ammonia</td><td align='right'>62·55</td><td align='right'>47·79</td></tr> +<tr><td align='left'>Muriate of ammonia</td><td align='right'>15·3</td><td align='right'>...</td></tr> +<tr><td align='left'>Sulphate of soda</td><td align='right'>...</td><td align='right'>9·12</td></tr> +<tr><td align='left'>Sulphate of magnesia</td><td align='right'>...</td><td align='right'>18·38</td></tr> +<tr><td align='left'>Chloride of potassium</td><td align='right'>4·75</td><td align='right'>2·94</td></tr> +<tr><td align='left'>Chloride of sodium</td><td align='right'>17·35</td><td align='right'>0·35</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td><td align='right'>100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='right'>16·50</td><td align='right'>11·28</td></tr> +</table></div> + +<p>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.<span class='pagenum'><a name="Page_229" id="Page_229">[Pg 229]</a></span></p> + +<p><i>Ammoniacal Liquor of the Gas-Works, and of the Animal Charcoal +Manufacturers.</i>—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. <i>Bone oil</i>, 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.</p> + +<p><i>Nitrates of Potash and Soda.</i>—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<span class='pagenum'><a name="Page_230" id="Page_230">[Pg 230]</a></span> 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<span class='pagenum'><a name="Page_231" id="Page_231">[Pg 231]</a></span> 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 <i>appears</i> 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.</p> + +<p><i>Salts of Potash and Soda.</i>—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.</p> + +<p><i>Muriate and Sulphate of Potash</i> have both been used,<span class='pagenum'><a name="Page_232" id="Page_232">[Pg 232]</a></span> 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.</p> + +<p><i>Chloride of Sodium, or Common Salt</i>, 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.</p> + +<p><i>Carbonates of Potash and Soda</i> 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<span class='pagenum'><a name="Page_233" id="Page_233">[Pg 233]</a></span> anticipated +from the former than from the latter of these salts. They <i>may</i>, +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.</p> + +<p><i>Silicates of Potash and Soda</i> 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.</p> + +<p><i>Sulphate of Magnesia</i> 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.</p> + +<p>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.</p> + +<p><i>Phosphate of Lime.</i>—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<span class='pagenum'><a name="Page_234" id="Page_234">[Pg 234]</a></span> 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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>I.</td><td align='right'>II.</td><td align='right'>III.</td></tr> +<tr><td align='left'>Water</td><td align='right'>6·10</td><td align='right'>6·28</td><td align='right'>3·03</td></tr> +<tr><td align='left'>Charcoal</td><td align='right'>5·05</td><td align='right'>2·19</td><td align='right'>2·02</td></tr> +<tr><td align='left'>Phosphates</td><td align='right'>79·20</td><td align='right'>71·10</td><td align='right'>88·55</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>4·05</td><td align='right'>3·55</td><td align='right'>5·60</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='right'>0·15</td><td align='right'>traces</td><td align='right'>...</td></tr> +<tr><td align='left'>Sand</td><td align='right'>5·45</td><td align='right'>16·90</td><td align='right'>0·80</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td><td align='right'>100·00</td><td align='right'>100·00</td></tr> +</table></div> + +<p>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.</p> + +<p>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.<span class='pagenum'><a name="Page_235" id="Page_235">[Pg 235]</a></span></p> + +<p><i>Coprolites.</i>—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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>1·95</td><td align='right'>1·90</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>2·59</td><td align='right'>6·85</td></tr> +<tr><td align='left'>Phosphate of lime</td><td align='right'>55·21}</td><td align='right'>61·15</td></tr> +<tr><td align='left'>Phosphate of iron</td><td align='right'>3·84}</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>26·70</td><td align='right'>16·20</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='right'>1·97</td><td align='right'>"</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='right'>1·85</td><td align='right'>3·21</td></tr> +<tr><td align='left'>Sand</td><td align='right'>5·89</td><td align='right'>11·65</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td><td align='right'>100·00</td></tr> +</table></div> + +<p>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.</p> + +<p><i>Apatite</i>, or mineral phosphate of lime, is found in<span class='pagenum'><a name="Page_236" id="Page_236">[Pg 236]</a></span> 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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>0·80</td></tr> +<tr><td align='left'>Phosphate of lime</td><td align='right'>93·30</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>0·50</td></tr> +<tr><td align='left'>Chlorine, etc.</td><td align='right'>traces</td></tr> +<tr><td align='left'>Sand</td><td align='right'>4·70</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>99·30</td></tr> +</table></div> +<p>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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>8·96</td></tr> +<tr><td align='left'>Phosphate of lime</td><td align='right'>37·71</td></tr> +<tr><td align='left'>Phosphates of alumina and iron</td><td align='right'>44·21</td></tr> +<tr><td align='left'>Phosphate of magnesia</td><td align='right'>4·20</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='right'>0·86</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='right'>3·36</td></tr> +<tr><td align='left'>Sand</td><td align='right'>0·70</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +</table></div> +<p>A somewhat similar substance, but in hard crusts,<span class='pagenum'><a name="Page_237" id="Page_237">[Pg 237]</a></span> has been imported, +under the names of Maracaybo guano, Pyroguanite, etc., which contains—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>1·03</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>6·78</td></tr> +<tr><td align='left'>Phosphates</td><td align='right'>75·69</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='right'>4·91</td></tr> +<tr><td align='left'>Sand</td><td align='right'>11·64</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +<tr><td align='left'>Phosphoric acid in the alkaline salts = 1·68 phosphate of lime</td><td align='right'>0·78</td></tr> +</table></div> + + + +<p>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.</p> + +<p><i>Superphosphate; Dissolved Bones.</i>—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 <i>biphosphate of +lime</i>, which is soluble.<span class='pagenum'><a name="Page_238" id="Page_238">[Pg 238]</a></span> 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<span class='pagenum'><a name="Page_239" id="Page_239">[Pg 239]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_240" id="Page_240">[Pg 240]</a></span>—</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Bones alone.</td><td align='left'> Bone-Ash.</td></tr> +<tr><td align='left'>Water,</td><td align='left'> 7·74 ... 7·79</td><td align='left'> 5·33 ... 10·40</td></tr> +<tr><td align='left'>Organic matters and ammoniacal salts,</td><td align='left'> 17·83 ... 21·69</td><td align='left'> 6·94 ... 4·92</td></tr> +<tr><td align='left'>Biphosphate of lime</td><td align='left'> 13·18 ... 9·87</td><td align='left'> 21·35 ... 23·09</td></tr> +<tr><td align='left'>Equivalent to soluble phosphates,</td><td align='left'>(20·57)...(15·39)</td><td align='left'>(33·33)...(36·02)</td></tr> +<tr><td align='left'>Insoluble phosphates</td><td align='left'> 10·31 ... 21·17</td><td align='left'> 5·92 ... 6·08</td></tr> +<tr><td align='left'>Sulphate of lime,</td><td align='left'> 46·00 ... 35·30</td><td align='left'> 56·16 ... 47·78</td></tr> +<tr><td align='left'>Alkaline salts,</td><td align='left'> 1·46 ... 0·94</td><td align='left'> trace.</td></tr> +<tr><td align='left'>Sand,</td><td align='left'> 3·48 ... 3·00</td><td align='left'> 4·23 ... 4·30</td></tr> +<tr><td align='left'> </td><td align='left'>100·00 ...100·00</td><td align='left'>100·00 ...100·00</td></tr> +<tr><td align='left'>Ammonia,</td><td align='left'> 2·11 ... 3·01</td><td align='left'> 0·23 ... 0·31</td></tr> +</table></div> +<p><br /><br /></p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'>Chiefly Coprolites.</td><td align='left'>Mixtures containing Salts of Ammonia, etc.</td></tr> +<tr><td align='left'>Water,</td><td align='left'> 5·90 ... 10·17</td><td align='left'> 7·07 ... 15·82</td></tr> +<tr><td align='left'>Organic matters and ammoniacal salts,</td><td align='left'> 5·10 ... 4·13</td><td align='left'> 9·87 ... 13·96</td></tr> +<tr><td align='left'>Biphosphate of lime</td><td align='left'> 12·24 ... 13·75</td><td align='left'> 17·63 ... 12·67</td></tr> +<tr><td align='left'>Equivalent to soluble phosphates,</td><td align='left'>(19·10)...(21·43)</td><td align='left'>(27·50)...(19·77)</td></tr> +<tr><td align='left'>Insoluble phosphates</td><td align='left'> 16·90 ... 0·17</td><td align='left'> 12·60 ... 8·40</td></tr> +<tr><td align='left'>Sulphate of lime,</td><td align='left'> 52·39 ... 62·62</td><td align='left'> 49·77 ... 45·14</td></tr> +<tr><td align='left'>Alkaline salts,</td><td align='left'> 2·47 ... 0·96</td><td align='left'> 0·06 ... 1·07</td></tr> +<tr><td align='left'>Sand,</td><td align='left'> 6·00 ... 8·20</td><td align='left'> 3·00 ... 2·94</td></tr> +<tr><td align='left'> </td><td align='left'>100·00 ...100·00</td><td align='left'>100·00 ...100·00</td></tr> +<tr><td align='left'>Ammonia,</td><td align='left'> 0·11 ... 0·57</td><td align='left'> 1·28 ... 1·55</td></tr> +</table></div> +<p><span class='pagenum'><a name="Page_241" id="Page_241">[Pg 241]</a></span></p> + +<p>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.</p> + +<p>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.<span class='pagenum'><a name="Page_242" id="Page_242">[Pg 242]</a></span></p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>21·60</td><td align='right'>5·37</td><td align='right'>7·19</td></tr> +<tr><td align='left'>Organic matter and ammoniacal salts,</td><td align='right'>11·62</td><td align='right'>13·91</td><td align='right'>8·80</td></tr> +<tr><td align='left'>Biphosphate of lime</td><td align='right'>2·98</td><td align='right'>2·02</td><td align='right'>6·42</td></tr> +<tr><td align='left'>Equivalent to soluble phosphates</td><td align='right'>(4·65)</td><td align='right'>(3·15)</td><td align='right'>(10·02)</td></tr> +<tr><td align='left'>Insoluble phosphates</td><td align='right'>25·70</td><td align='right'>15·80</td><td align='right'>14·03</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='right'>23·66</td><td align='right'>47·52</td><td align='right'>51·93</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='right'>10·70</td><td align='right'>3·73</td><td align='right'>3·43</td></tr> +<tr><td align='left'>Sand</td><td align='right'>3·80</td><td align='right'>11·65</td><td align='right'>8·20</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td><td align='right'>100·00</td><td align='right'>100·00</td></tr> +<tr><td align='left'>Ammonia,</td><td align='right'>1·32</td><td align='right'>0·59</td><td align='right'>0·33</td></tr> +</table></div> + +<p>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<span class='pagenum'><a name="Page_243" id="Page_243">[Pg 243]</a></span> 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.</p> + +<p>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.</p> + +<p><i>Phospho-Peruvian Guano.</i>—Under this name a kind of superphosphate, +which is understood to be made by<span class='pagenum'><a name="Page_244" id="Page_244">[Pg 244]</a></span> dissolving a native "rock guano," has +recently attracted considerable attention, and is used to a large +extent. Its composition is—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>9·54</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>21·38</td></tr> +<tr><td align='left'>Biphosphate of lime, equivalent to 25·22 soluble phosphates</td><td align='right'>16·81</td></tr> +<tr><td align='left'>Insoluble phosphates</td><td align='right'>10·88</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='right'>37·21</td></tr> +<tr><td align='left'>Alkaline salts, containing 1·32 of phosphoric acid, and equivalent to 2·86 soluble phosphates</td><td align='right'>2·22</td></tr> +<tr><td align='left'>Sand</td><td align='right'>1·81</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +<tr><td align='left'>Ammonia,</td><td align='right'>3·50</td></tr> +</table></div> + +<p>It is chiefly distinguished by the large proportion of valuable +ingredients it contains, and the care taken to secure uniformity of +composition.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_245" id="Page_245">[Pg 245]</a></span> 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.</p> + +<p><i>Lime.</i>—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.</p> + +<p><i>Chalk</i> 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.</p> + +<p><i>Marl</i> 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<span class='pagenum'><a name="Page_246" id="Page_246">[Pg 246]</a></span> 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:—</p> + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Barbadoes.</td><td align='left'> Luneburg.</td><td align='left'> Ayrshire.</td><td align='left'> Wesermarsh.</td></tr> +<tr><td align='left'>Carbonate of lime</td><td align='left'> 93·2</td><td align='left'> 85·4</td><td align='left'> 8·4</td><td align='left'> 8·2</td></tr> +<tr><td align='left'>Carbonate of magnesia</td><td align='left'> ...</td><td align='left'> 1·3</td><td align='left'> ...</td><td align='left'> 3·0</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='left'> ...</td><td align='left'> 0·1</td><td align='left'> ...</td><td align='left'> 0·5</td></tr> +<tr><td align='left'>Phosphate of lime</td><td align='left'> 0·1</td><td align='left'> 2·3</td><td align='left'> ...</td><td align='left'> 1·2</td></tr> +<tr><td align='left'>Alumina and oxide of iron</td><td align='left'> 1·6</td><td align='left'> 4·6</td><td align='left'> 2·2</td><td align='left'> 7·2</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='left'> ...</td><td align='left'> 0·1</td><td align='left'> ...</td><td align='left'> 1·0</td></tr> +<tr><td align='left'>Silica and clay</td><td align='left'> 4·6</td><td align='left'> 5·6</td><td align='left'> 84·9</td><td align='left'> 78·9</td></tr> +<tr><td align='left'>Organic matter</td><td align='left'> 0·5</td><td align='left'> 0·6</td><td align='left'> 2·8</td><td align='left'> ...</td></tr> +<tr><td align='left'>Water</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 1·4</td><td align='left'> ...</td></tr> +<tr><td align='left'> </td><td align='left'> 100·00</td><td align='left'> 100·00</td><td align='left'> 99·7</td><td align='left'> 100·00</td></tr> +</table></div> + + + +<p>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.</p> + +<p>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.</p> + +<p>The general composition of limestones has been already<span class='pagenum'><a name="Page_247" id="Page_247">[Pg 247]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_248" id="Page_248">[Pg 248]</a></span> of the coal used in burning, etc., which, though +comparatively trifling, may, under particular circumstances and in some +soils, be of considerable importance.</p> + +<p>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,—<i>1st</i>, Because no soil exists which does not +contain lime in sufficient quantity to supply that element to the +plants. <i>2d</i>, Because its effects are not restricted to those soils in +which it exists naturally in small quantity; and, <i>3d</i>, 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.</p> + +<p>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.<span class='pagenum'><a name="Page_249" id="Page_249">[Pg 249]</a></span></p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_250" id="Page_250">[Pg 250]</a></span> 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<span class='pagenum'><a name="Page_251" id="Page_251">[Pg 251]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_252" id="Page_252">[Pg 252]</a></span> 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.</p> + +<p>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,<span class='pagenum'><a name="Page_253" id="Page_253">[Pg 253]</a></span> 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.</p> + +<p><i>Sulphate of Lime or Gypsum.</i>—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<span class='pagenum'><a name="Page_254" id="Page_254">[Pg 254]</a></span> 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.</p> + +<p>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.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_255" id="Page_255">[Pg 255]</a></span></p> +<h2>CHAPTER XII.</h2> + +<h3>THE VALUATION OF MANURES.</h3> + + +<p>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<span class='pagenum'><a name="Page_256" id="Page_256">[Pg 256]</a></span> of the +value of each factor, from which that not only of one particular +substance, but of every possible mixture may be determined.</p> + +<p>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<span class='pagenum'><a name="Page_257" id="Page_257">[Pg 257]</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_258" id="Page_258">[Pg 258]</a></span> 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.</p> + +<p>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.</p> + +<p><i>Insoluble Phosphates.</i>—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<span class='pagenum'><a name="Page_259" id="Page_259">[Pg 259]</a></span> 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:—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="8" summary=""> +<tr><td align='left'>In Coprolites</td><td align='right'>£4</td><td align='right'>10</td><td align='right'>0</td></tr> +<tr><td align='left'>Bone-ash</td><td align='right'>6</td><td align='right'>8</td><td align='right'>0</td></tr> +<tr><td align='left'>Bones</td><td align='right'>7</td><td align='right'>5</td><td align='right'>0</td></tr> +<tr><td align='left'>Phosphatic guanos</td><td align='right'>10</td><td align='right'>0</td><td align='right'>0</td></tr> +</table></div> + +<p>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.</p> + +<p><i>Ammonia</i> is met with in commerce as muriate and<span class='pagenum'><a name="Page_260" id="Page_260">[Pg 260]</a></span> 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—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="8" summary=""> +<tr><td align='left'>Sulphate of ammonia</td><td align='right'>£63</td><td align='right'>0</td><td align='right'>0</td></tr> +<tr><td align='left'>Bones</td><td align='right'>61</td><td align='right'>0</td><td align='right'>0</td></tr> +<tr><td align='left'>Peruvian guano</td><td align='right'>57</td><td align='right'>0</td><td align='right'>0</td></tr> +</table></div> + + +<p>the average being £60, which is the price usually adopted.</p> + +<p><i>Sulphate of Lime</i> and <i>Alkaline Salts</i> (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.</p> + +<p><i>Nitrate of Soda</i> 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.</p> + +<p><i>Biphosphate of Lime, Soluble Phosphates.</i>—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<span class='pagenum'><a name="Page_261" id="Page_261">[Pg 261]</a></span> 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—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>Water</td><td align='right'>10·71</td></tr> +<tr><td align='left'>Organic matter</td><td align='right'>9·33</td></tr> +<tr><td align='left'>Biphosphate of lime equivalent to 19·43 "soluble phosphates"</td><td align='right'>12·45</td></tr> +<tr><td align='left'>Insoluble phosphates</td><td align='right'>14·78</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='right'>45·24</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='right'>2·11</td></tr> +<tr><td align='left'>Sand</td><td align='right'>5·38</td></tr> +<tr><td align='left'></td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td></tr> +<tr><td align='left'>Ammonia</td><td align='right'>1·71</td></tr> +</table></div> + + +<p>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<span class='pagenum'><a name="Page_262" id="Page_262">[Pg 262]</a></span> another in valuing a manure, the +latter having one and a half times the value of the former.</p> + +<p>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.</p> + +<p>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:<span class='pagenum'><a name="Page_263" id="Page_263">[Pg 263]</a></span>—</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Price per Ton.</td><td align='left'> Per cent per Ton.</td></tr> +<tr><td align='left'>Ammonia</td><td align='left'> £60 0 0</td><td align='left'> £0 12 0</td></tr> +<tr><td align='left'>Insoluble phosphates</td><td align='left'> 7 0 0</td><td align='left'> 0 1 5</td></tr> +<tr><td align='left'> Do. in phosphatic guanos</td><td align='left'> 10 0 0</td><td align='left'> 0 2 0</td></tr> +<tr><td align='left'>Soluble phosphates</td><td align='left'> 30 0 0</td><td align='left'> 0 6 0</td></tr> +<tr><td align='left'>Biphosphate of lime</td><td align='left'> 46 16 0</td><td align='left'> 0 9 4-1/2</td></tr> +<tr><td align='left'>Alkaline salts</td><td align='left'> 1 0 0</td><td align='left'> 0 0 2-4/10</td></tr> +<tr><td align='left'>Sulphate of lime</td><td align='left'> 1 0 0</td><td align='left'> 0 0 2-4/10</td></tr> +<tr><td align='left'>Potash</td><td align='left'> 20 0 0</td><td align='left'> 0 4 0</td></tr> +<tr><td align='left'>Nitrate of soda</td><td align='left'> 16 0 0</td><td align='left'> 0 3 2-1/2</td></tr> +<tr><td align='left'>Organic matter</td><td align='left'> 0 10 0</td><td align='left'> 0 0 1-1/4</td></tr> +</table></div> + + +<p>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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>14·11 tons of organic matter at 10s.</td><td align='right'>£7 0 0</td></tr> +<tr><td align='left'>14·86 " soluble phosphates at £30</td><td align='right'>446 0 0</td></tr> +<tr><td align='left'>15·13 " insoluble phosphates at £7</td><td align='right'>105 0 0</td></tr> +<tr><td align='left'>39·43 " sulphate of lime at £1</td><td align='right'>39 0 0</td></tr> +<tr><td align='left'> 3·82 " alkaline salts at £1</td><td align='right'>4 0 0</td></tr> +<tr><td align='left'> 2·10 " ammonia at £60</td><td align='right'>126 0 0</td></tr> +<tr><td align='left'></td><td align='right'>—————</td></tr> +<tr><td align='left'> Value of 100 tons</td><td align='right'>£727 0 0</td></tr> +<tr><td align='left'>or £7 : 5s. per ton.</td></tr> +</table></div> + +<p>According to the second column, the numbers give the sum by which the +per centages of each ingredient must be<span class='pagenum'><a name="Page_264" id="Page_264">[Pg 264]</a></span> multiplied, to give its value +in a ton of manure, and it is used for the same manure in the following +manner:—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'>14·11 organic matter, multiplied by</td><td align='left'>1-1/4d.</td><td align='left'>£0</td><td align='left'>1</td><td align='left'>5</td></tr> +<tr><td align='left'>14·88 soluble phosphates "</td><td align='left'>6s.</td><td align='left'>4</td><td align='left'>9</td><td align='left'>2</td></tr> +<tr><td align='left'>15·13 insoluble phosphates "</td><td align='left'>1s. 5d.</td><td align='left'>1</td><td align='left'>1</td><td align='left'>4</td></tr> +<tr><td align='left'>39·43 sulphate of lime "</td><td align='left'>2-4/10d.</td><td align='left'>0</td><td align='left'>8</td><td align='left'>10</td></tr> +<tr><td align='left'>3·82 alkaline salts "</td><td align='left'>2-4/10d.</td><td align='left'>0</td><td align='left'>0</td><td align='left'>9</td></tr> +<tr><td align='left'>2·10 ammonia "</td><td align='left'>12s.</td><td align='left'>1</td><td align='left'>5</td><td align='left'>3</td></tr> +<tr><td align='left'></td><td align='left'></td><td colspan="3">————</td></tr> +<tr><td align='left'> Value per ton</td><td align='left'></td><td align='left'>£7</td><td align='left'>6</td><td align='left'>9</td></tr> +</table></div> + + +<p>The difference is due to the less minute calculation of fractional +quantities in the latter case.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_265" id="Page_265">[Pg 265]</a></span> 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.</p> + +<p>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.</p> + +<p>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.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_266" id="Page_266">[Pg 266]</a></span></p> +<h2>CHAPTER XIII.</h2> + +<h3>THE ROTATION OF CROPS.</h3> + + +<p>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 <i>apparently</i> 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<span class='pagenum'><a name="Page_267" id="Page_267">[Pg 267]</a></span> 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.</p> + +<p>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 <i>because</i> 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<span class='pagenum'><a name="Page_268" id="Page_268">[Pg 268]</a></span> 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<span class='pagenum'><a name="Page_269" id="Page_269">[Pg 269]</a></span> explanation of the rotation of crops, must be +considered as being entirely abandoned.</p> + +<p>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 <i>available</i> 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.<span class='pagenum'><a name="Page_270" id="Page_270">[Pg 270]</a></span></p> + +<h4><span class="smcap">Table</span> shewing the quantities of Mineral Matters and Nitrogen in average +Crops of the principal varieties of Farm Produce.</h4> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Produce per Imperial Acre.</td><td align='left'>Total Weight in lbs.</td><td align='left'>Total Mineral Matters.</td><td align='left'> Potash.</td><td align='left'> Soda.</td><td align='left'> Lime.</td></tr> +<tr><td align='left'>Wheat—Grain</td><td align='left'> 28 bushels at 60 lbs.</td><td align='left'> 1,680</td><td align='left'> 34·12</td><td align='left'> 10·11</td><td align='left'> 1·20</td><td align='left'> 1.04</td></tr> +<tr><td align='left'> Straw</td><td align='left'> 1 ton 3 cwt.</td><td align='left'> 2,576</td><td align='left'> 114·48</td><td align='left'> 20·70</td><td align='left'> 2·84</td><td align='left'> 8·53</td></tr> +<tr><td align='left'> Total</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 148·60</td><td align='left'> 30·81</td><td align='left'> 4·04</td><td align='left'> 9·57</td></tr> +<tr><td align='left'>Barley—Grain</td><td align='left'> 33 bushels at 53 lbs.</td><td align='left'> 1,749</td><td align='left'> 44·24</td><td align='left'> 9·40</td><td align='left'> 0·30</td><td align='left'> 0·76</td></tr> +<tr><td align='left'> Straw</td><td align='left'> 18 cwt.</td><td align='left'> 2,106</td><td align='left'> 99·14</td><td align='left'> 11·24</td><td align='left'> 1·14</td><td align='left'> 5·81</td></tr> +<tr><td align='left'> Total</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 143·38</td><td align='left'> 20·64</td><td align='left'> 1·44</td><td align='left'> 6·57</td></tr> +<tr><td align='left'>Oats—Grain</td><td align='left'> 34 bushels at 40 lbs.</td><td align='left'> 1,360</td><td align='left'> 48.89</td><td align='left'> 11·00</td><td align='left'> ...</td><td align='left'> 5·31</td></tr> +<tr><td align='left'> Straw</td><td align='left'> 1 ton.</td><td align='left'> 2,240</td><td align='left'> 143·53</td><td align='left'> 30·71</td><td align='left'> 6·10</td><td align='left'> 10·29</td></tr> +<tr><td align='left'> Total</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 192·42</td><td align='left'> 41·71</td><td align='left'> 6·10</td><td align='left'> 15·60</td></tr> +<tr><td align='left'>Beans, Peas—Grain</td><td align='left'> 25 bushels at 60 lbs</td><td align='left'> 1,650</td><td align='left'> 55·97</td><td align='left'> 30·00</td><td align='left'> 0·31</td><td align='left'> 3·01</td></tr> +<tr><td align='left'> Straw</td><td align='left'> 1 ton.</td><td align='left'> 2,240</td><td align='left'> 108·51</td><td align='left'> 48·61</td><td align='left'> 13·14</td><td align='left'> 29·37</td></tr> +<tr><td align='left'> Total</td><td align='left'> ...</td><td align='left'> ...</td><td align='left'> 164·48</td><td align='left'> 78·61</td><td align='left'> 13·45</td><td align='left'> 32·38</td></tr> +<tr><td align='left'>Turnips—Bulbs</td><td align='left'> 13-1/2 tons.</td><td align='left'> 30,240</td><td align='left'> 213·75</td><td align='left'> 57·35</td><td align='left'> 44·71</td><td align='left'> 28·60</td></tr> +<tr><td align='left'>Potatoes</td><td align='left'> 3 tons.</td><td align='left'> 6,720</td><td align='left'> 55·58</td><td align='left'> 28·92</td><td align='left'> 2·85</td><td align='left'> 1·20</td></tr> +<tr><td align='left'>Hay</td><td align='left'> 2-1/2 tons.</td><td align='left'> 5,600</td><td align='left'> 391·31</td><td align='left'> 129·79</td><td align='left'> 4·80</td><td align='left'> 35·46</td></tr> +</table></div> +<p><br /><br /></p> +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Magnesia.</td><td align='left'> Chlorine.</td><td align='left'> Sulphuric Acid.</td><td align='left'> Phosphoric Acid.</td><td align='left'> Silica.</td><td align='left'> Nitrogen.</td></tr> +<tr><td align='left'>Wheat—Grain</td><td align='left'> 4.80</td><td align='left'> ...</td><td align='left'> 0.32</td><td align='left'> 16.22</td><td align='left'> 0.43</td><td align='left'> 29.20</td></tr> +<tr><td align='left'> Straw</td><td align='left'> 2·23</td><td align='left'> ...</td><td align='left'> 3·55</td><td align='left'> 3·16</td><td align='left'> 73·47</td><td align='left'> 16·13</td></tr> +<tr><td align='left'> Total</td><td align='left'> 7·03</td><td align='left'> ...</td><td align='left'> 3·87</td><td align='left'> 19·38</td><td align='left'> 73·90</td><td align='left'> 45·33</td></tr> +<tr><td align='left'>Barley—Grain</td><td align='left'> 3·10</td><td align='left'> 1·12</td><td align='left'> 0·85</td><td align='left'> 15·52</td><td align='left'> 13·19</td><td align='left'> 34·98</td></tr> +<tr><td align='left'> Straw</td><td align='left'> 2·75</td><td align='left'> 1·30</td><td align='left'> 1·10</td><td align='left'> 7·22</td><td align='left'> 68·58</td><td align='left'> 6·03</td></tr> +<tr><td align='left'> Total</td><td align='left'> 5·85</td><td align='left'> 2·42</td><td align='left'> 1·95</td><td align='left'> 22·74</td><td align='left'> 81·77</td><td align='left'> 41·01</td></tr> +<tr><td align='left'>Oats—Grain</td><td align='left'> 4·04</td><td align='left'> 0·20</td><td align='left'> ...</td><td align='left'> 26·07</td><td align='left'> 2·27</td><td align='left'> 27·54</td></tr> +<tr><td align='left'> Straw</td><td align='left'> 5·50</td><td align='left'> 5·55</td><td align='left'> 5·18</td><td align='left'> 7·35</td><td align='left'> 72·85</td><td align='left'> 14·10</td></tr> +<tr><td align='left'> Total</td><td align='left'> 9·54</td><td align='left'> 5·75</td><td align='left'> 5·18</td><td align='left'> 33·42</td><td align='left'> 75·12</td><td align='left'> 41·64</td></tr> +<tr><td align='left'>Beans, Peas—Grain</td><td align='left'> 4·00</td><td align='left'> ...</td><td align='left'> 1·76</td><td align='left'> 16·65</td><td align='left'> 0·24</td><td align='left'> 46·10</td></tr> +<tr><td align='left'> Straw</td><td align='left'> 3·74</td><td align='left'> 7·00</td><td align='left'> 2·07</td><td align='left'> 0·74</td><td align='left'> 3·84</td><td align='left'> 26·88</td></tr> +<tr><td align='left'> Total</td><td align='left'> 7·74</td><td align='left'> 7·00</td><td align='left'> 3·83</td><td align='left'> 17·39</td><td align='left'> 4·08</td><td align='left'> 72·98</td></tr> +<tr><td align='left'>Turnips—Bulbs</td><td align='left'> 4·65</td><td align='left'> 10·35</td><td align='left'> 39·02</td><td align='left'> 22·57</td><td align='left'> 6·50</td><td align='left'> 60·48</td></tr> +<tr><td align='left'>Potatoes</td><td align='left'> 2·11</td><td align='left'> 3·21</td><td align='left'> 10·24</td><td align='left'> 5·76</td><td align='left'> 1·29</td><td align='left'> 26·00</td></tr> +<tr><td align='left'>Hay</td><td align='left'> 9·62</td><td align='left'> 39·61</td><td align='left'> 16·57</td><td align='left'> 21·79</td><td align='left'> 133·67</td><td align='left'> 56·22</td></tr> +</table></div> +<p><span class='pagenum'><a name="Page_271" id="Page_271">[Pg 271]</a></span></p> + +<p>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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_272" id="Page_272">[Pg 272]</a></span> 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<span class='pagenum'><a name="Page_273" id="Page_273">[Pg 273]</a></span> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_274" id="Page_274">[Pg 274]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_275" id="Page_275">[Pg 275]</a></span> 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.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_276" id="Page_276">[Pg 276]</a></span></p> +<h2>CHAPTER XIV.</h2> + +<h3>THE FEEDING OF FARM STOCK.</h3> + + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_277" id="Page_277">[Pg 277]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_278" id="Page_278">[Pg 278]</a></span> 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,<span class='pagenum'><a name="Page_279" id="Page_279">[Pg 279]</a></span> 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.</p> + +<p>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.<span class='pagenum'><a name="Page_280" id="Page_280">[Pg 280]</a></span> 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.</p> + +<p>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:<span class='pagenum'><a name="Page_281" id="Page_281">[Pg 281]</a></span>—</p> + +<p class="notes">[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]</p> + +<p><span style="margin-left: 2.5em;">Column titles:</span><br /> +<span style="margin-left: 2.5em;">MM = Mineral Matter</span><br /> +<span style="margin-left: 2.5em;">NC = Nitrogenous Compounds</span><br /> +<span style="margin-left: 2.5em;">TDS = Total Dry Substance</span><br /> +<span style="margin-left: 2.5em;">CSI = Contents of Stomachs and Intestine in moist state.</span><br /> +<span style="margin-left: 2.5em;">Wat = Water</span><br /></p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td colspan="5"> Per cent in Carcass</td><td align='left'> </td><td colspan="5">Per cent in Offal, excluding contents of Stomachs and Intestines.</td></tr> +<tr><td align='left'> </td><td align='left'> MM</td><td align='left'> NC</td><td align='left'> Fat</td><td align='left'> TDS</td><td align='left'> WAT</td><td align='left'> </td><td align='left'> MM</td><td align='left'> NC</td><td align='left'> Fat</td><td align='left'> TDS</td><td align='left'> WAT</td></tr> +<tr><td align='left'>Fat Calf</td><td align='left'>4·48</td><td align='left'>16·6</td><td align='left'>16·6</td><td align='left'>37·7</td><td align='left'>62·3</td><td align='left'> </td><td align='left'> 3·41</td><td align='left'> 17·1</td><td align='left'> 14·6</td><td align='left'> 35·1</td><td align='left'> 64·9</td></tr> +<tr><td align='left'>Half-fat Ox</td><td align='left'>5·56</td><td align='left'>17·8</td><td align='left'>22·6</td><td align='left'>46·0</td><td align='left'>54·0</td><td align='left'> </td><td align='left'> 4·05</td><td align='left'> 20·6</td><td align='left'> 15·7</td><td align='left'> 40·4</td><td align='left'> 59·6</td></tr> +<tr><td align='left'>Fat Ox</td><td align='left'>4·56</td><td align='left'>15·0</td><td align='left'>34·8</td><td align='left'>54·4</td><td align='left'>45·6</td><td align='left'> </td><td align='left'> 3·40</td><td align='left'> 17·5</td><td align='left'> 26·3</td><td align='left'> 47·2</td><td align='left'> 52·8</td></tr> +<tr><td align='left'>Fat Lamb</td><td align='left'>3·63</td><td align='left'>10·9</td><td align='left'>36·9</td><td align='left'>51·4</td><td align='left'>48·6</td><td align='left'> </td><td align='left'> 2·45</td><td align='left'> 18·9</td><td align='left'> 20·1</td><td align='left'> 41·5</td><td align='left'> 58·5</td></tr> +<tr><td align='left'>Store Sheep</td><td align='left'>4·36</td><td align='left'>14·5</td><td align='left'>23·8</td><td align='left'>42·7</td><td align='left'>57·3</td><td align='left'> </td><td align='left'> 2·19</td><td align='left'> 18·0</td><td align='left'> 16·1</td><td align='left'> 36·3</td><td align='left'> 63·7</td></tr> +<tr><td align='left'>Half-fat old Sheep</td><td align='left'>4·13</td><td align='left'>14·9</td><td align='left'>31·3</td><td align='left'>50·3</td><td align='left'>49·7</td><td align='left'> </td><td align='left'> 2·72</td><td align='left'> 17·7</td><td align='left'> 18·5</td><td align='left'> 38·9</td><td align='left'> 61·1</td></tr> +<tr><td align='left'>Fat Sheep</td><td align='left'>3·45</td><td align='left'>11·5</td><td align='left'>45·4</td><td align='left'>60·3</td><td align='left'>39·7</td><td align='left'> </td><td align='left'> 2·32</td><td align='left'> 16·1</td><td align='left'> 26·4</td><td align='left'> 44·8</td><td align='left'> 55·2</td></tr> +<tr><td align='left'>Extra fat Sheep</td><td align='left'>2·77</td><td align='left'> 9·1</td><td align='left'>55·1</td><td align='left'>67·0</td><td align='left'>33·0</td><td align='left'> </td><td align='left'> 3·64</td><td align='left'> 16·8</td><td align='left'> 34·5</td><td align='left'> 54·9</td><td align='left'> 45·1</td></tr> +<tr><td align='left'>Store Pig</td><td align='left'>2·57</td><td align='left'>14·0</td><td align='left'>28·1</td><td align='left'>44·7</td><td align='left'>55·3</td><td align='left'> </td><td align='left'> 3·07</td><td align='left'> 14·0</td><td align='left'> 15·0</td><td align='left'> 32·1</td><td align='left'> 67·9</td></tr> +<tr><td align='left'>Fat Pig</td><td align='left'>1·40</td><td align='left'>10·5</td><td align='left'>49·5</td><td align='left'>61·4</td><td align='left'>38·6</td><td align='left'> </td><td align='left'> 2·97</td><td align='left'> 14·8</td><td align='left'> 22·8</td><td align='left'> 40·6</td><td align='left'> 59·4</td></tr> +<tr><td align='left'>Mean of all</td><td align='left'>3·69</td><td align='left'>13·5</td><td align='left'>34·4</td><td align='left'>51·6</td><td align='left'>48·4</td><td align='left'> </td><td align='left'> 3·02</td><td align='left'> 17·2</td><td align='left'> 21·0</td><td align='left'> 41·2</td><td align='left'> 58·8</td></tr> +<tr><td align='left'>Mean of 8, viz., the half-fat, fat, and very fat animals</td><td align='left'>3·75</td><td align='left'>13·3</td><td align='left'>36·5</td><td align='left'>53·6</td><td align='left'>46·4</td><td align='left'> </td><td align='left'> 3·12</td><td align='left'> 17·4</td><td align='left'> 22·4</td><td align='left'> 42·9</td><td align='left'> 57·1</td></tr> +<tr><td align='left'>Mean of 6, viz., of the fat and very fat animals</td><td align='left'>3·38</td><td align='left'>12·3</td><td align='left'>39·7</td><td align='left'>55·4</td><td align='left'>44·6</td><td align='left'> </td><td align='left'> 3·03</td><td align='left'> 16·9</td><td align='left'> 24·1</td><td align='left'> 44·0</td><td align='left'> 56·0</td></tr> +</table></div> +<p><br /><br /></p> + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td colspan="6"> Per cent in Entire Animal.</td></tr> +<tr><td align='left'> </td><td align='left'> MM</td><td align='left'> NC</td><td align='left'> Fat</td><td align='left'> TDS</td><td align='left'> CSI</td><td align='left'> WAT</td></tr> +<tr><td align='left'>Fat Calf</td><td align='left'>3·80</td><td align='left'>15·2</td><td align='left'>14·8</td><td align='left'>33·8</td><td align='left'> 3·17</td><td align='left'>63·0</td></tr> +<tr><td align='left'>Half-fat Ox</td><td align='left'>4·66</td><td align='left'>16·6</td><td align='left'>19·1</td><td align='left'>40·3</td><td align='left'> 8·19</td><td align='left'>51·5</td></tr> +<tr><td align='left'>Fat Ox</td><td align='left'>3·92</td><td align='left'>14·5</td><td align='left'>30·1</td><td align='left'>48·5</td><td align='left'> 5·98</td><td align='left'>45·5</td></tr> +<tr><td align='left'>Fat Lamb</td><td align='left'>2·94</td><td align='left'>12·3</td><td align='left'>28·5</td><td align='left'>43·7</td><td align='left'> 8·54</td><td align='left'>47·8</td></tr> +<tr><td align='left'>Store Sheep</td><td align='left'>3·16</td><td align='left'>14·8</td><td align='left'>18·7</td><td align='left'>36·7</td><td align='left'> 6.00</td><td align='left'>57·3</td></tr> +<tr><td align='left'>Half-fat old Sheep</td><td align='left'>3·17</td><td align='left'>14·0</td><td align='left'>23·5</td><td align='left'>40·7</td><td align='left'> 9·05</td><td align='left'>50·2</td></tr> +<tr><td align='left'>Fat Sheep</td><td align='left'>2·81</td><td align='left'>12·2</td><td align='left'>35·6</td><td align='left'>50·6</td><td align='left'> 6·02</td><td align='left'>43·4</td></tr> +<tr><td align='left'>Extra fat Sheep</td><td align='left'>2·90</td><td align='left'>10·9</td><td align='left'>45·8</td><td align='left'>59·6</td><td align='left'> 5·18</td><td align='left'>35·2</td></tr> +<tr><td align='left'>Store Pig</td><td align='left'>2·67</td><td align='left'>13·7</td><td align='left'>23·3</td><td align='left'>39·7</td><td align='left'> 5·22</td><td align='left'>55·1</td></tr> +<tr><td align='left'>Fat Pig</td><td align='left'>1·65</td><td align='left'>10·9</td><td align='left'>42·2</td><td align='left'>54·7</td><td align='left'> 3·97</td><td align='left'>41·3</td></tr> +<tr><td align='left'>Mean of all</td><td align='left'>3·17</td><td align='left'>13·9</td><td align='left'>28·2</td><td align='left'>44·9</td><td align='left'> 6·13</td><td align='left'>49·0</td></tr> +<tr><td align='left'>Mean of 8, viz., the half-fat, fat, and very fat animals</td><td align='left'>3·23</td><td align='left'>13·3</td><td align='left'>29·9</td><td align='left'>46·4</td><td align='left'> 6·26</td><td align='left'>47·3</td></tr> +<tr><td align='left'>Mean of 6, viz., of the fat and very fat animals</td><td align='left'>3·00</td><td align='left'>12·7</td><td align='left'>32·8</td><td align='left'>48·5</td><td align='left'> 5·48</td><td align='left'>46·0</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_282" id="Page_282">[Pg 282]</a></span></p> + +<p>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.</p> + +<p>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:—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Lean.</td><td align='right'>Fat.</td></tr> +<tr><td align='left'>Mineral matters</td><td align='right'>5</td><td align='right'>3</td></tr> +<tr><td align='left'>Nitrogenous compounds</td><td align='right'>15</td><td align='right'>12·5</td></tr> +<tr><td align='left'>Fat</td><td align='right'>24</td><td align='right'>33</td></tr> +<tr><td align='left'>Water</td><td align='right'>56</td><td align='right'>48·5</td></tr> +<tr><td align='left'></td><td align='right'>—</td><td align='right'>——</td></tr> +<tr><td align='left'></td><td align='right'>100</td><td align='right'>100·0</td></tr> +</table></div> + + +<p>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 <i>increase</i> 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<span class='pagenum'><a name="Page_283" id="Page_283">[Pg 283]</a></span> 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:—</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Mineral Matters.</td><td align='left'> Nitrogenous Compounds.</td><td align='left'> Fat.</td><td align='left'> Water.</td></tr> +<tr><td align='left'>Oxen</td><td align='left'> 1·47</td><td align='left'> 7·69</td><td align='left'> 66·2</td><td align='left'> 24·6</td></tr> +<tr><td align='left'>Sheep</td><td align='left'> 2·34</td><td align='left'> 7·13</td><td align='left'> 70·4</td><td align='left'> 20·1</td></tr> +<tr><td align='left'>Pigs</td><td align='left'> 0·06</td><td align='left'> 6·44</td><td align='left'> 71·5</td><td align='left'> 22·0</td></tr> +</table></div> + + +<p>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.</p> + +<p>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:—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'></td><td align='right'>Cow.</td><td align='right'>Ewe.</td><td align='right'>Goat.</td></tr> +<tr><td align='left'>Caseine</td><td align='right'>3·4</td><td align='right'>4·50</td><td align='right'>4·02</td></tr> +<tr><td align='left'>Butter</td><td align='right'>3·6</td><td align='right'>4·20</td><td align='right'>3·32</td></tr> +<tr><td align='left'>Sugar of milk</td><td align='right'>6·0</td><td align='right'>5·00</td><td align='right'>5·28</td></tr> +<tr><td align='left'>Ash</td><td align='right'>0·2</td><td align='right'>0·68</td><td align='right'>0·58</td></tr> +<tr><td align='left'>Water</td><td align='right'>86·8</td><td align='right'>85·62</td><td align='right'>86·80</td></tr> +<tr><td align='left'></td><td align='right'>———</td><td align='right'>———</td><td align='right'>———</td></tr> +<tr><td align='left'></td><td align='right'>100·00</td><td align='right'>100·00</td><td align='right'>100·00</td></tr> +</table></div> + +<p><span class='pagenum'><a name="Page_284" id="Page_284">[Pg 284]</a></span></p> + +<p>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:<span class='pagenum'><a name="Page_285" id="Page_285">[Pg 285]</a></span>—</p> + + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="8" summary=""> +<tr><td align='left'></td><td align='right'>Flesh forming</td><td align='right'>Respiratory, expressed in their fat equivalent</td></tr> +<tr><td align='left'>Cow</td><td align='right'>3·4</td><td align='right'>6·0</td></tr> +<tr><td align='left'>Ewe</td><td align='right'>4·5</td><td align='right'>6·2</td></tr> +<tr><td align='left'>Goat</td><td align='right'>4·0</td><td align='right'>5·4</td></tr> +</table></div> + +<p>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.</p> + +<p>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:<span class='pagenum'><a name="Page_286" id="Page_286">[Pg 286]</a></span>—</p> + +<h4><span class="smcap">Table</span> giving the Composition of the Principal Varieties of Cattle Food.</h4> + +<p><i>Note.</i>—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.</p> + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'>Nitrogenous Compounds.</td><td align='left'> Oil.</td><td align='left'> Respiratory Compounds.</td><td align='left'> Fibre.</td><td align='left'> Ash.</td><td align='left'> Water.</td></tr> +<tr><td align='left'>Decorticated earth-nut cake</td><td align='left'> 44·00</td><td align='left'> 8·86</td><td align='left'> 19·34</td><td align='left'> 5·13</td><td align='left'> 14·05</td><td align='left'> 8·62</td></tr> +<tr><td align='left'>Decorticated cotton cake</td><td align='left'> 41·25</td><td align='left'> 16·05</td><td align='left'> 16·45</td><td align='left'> 8·92</td><td align='left'> 8·05</td><td align='left'> 9·28</td></tr> +<tr><td align='left'>Poppy cake</td><td align='left'> 34·03</td><td align='left'> 11·04</td><td align='left'> 23·25</td><td align='left'> 11·33</td><td align='left'> 13·79</td><td align='left'> 6·56</td></tr> +<tr><td align='left'>Teel or sesamum cake</td><td align='left'> 31·93</td><td align='left'> 12·86</td><td align='left'> 21·92</td><td align='left'> 9·06</td><td align='left'> 13·85</td><td align='left'> 10·38</td></tr> +<tr><td align='left'>Rape cake</td><td align='left'> 29·75</td><td align='left'> 8·63</td><td align='left'> 38·72</td><td align='left'> 7·30</td><td align='left'> 8·65</td><td align='left'> 6·95</td></tr> +<tr><td align='left'>Dotter cake</td><td align='left'> 29·00</td><td align='left'> 7·99</td><td align='left'> 27·04</td><td align='left'> 16·12</td><td align='left'> 12·59</td><td align='left'> 7·26</td></tr> +<tr><td align='left'>Tares, home-grown</td><td align='left'> 28·57</td><td align='left'> 1·30</td><td align='left'> 58·64</td><td align='left'> 2·50</td><td align='left'> 8·99</td></tr> +<tr><td align='left'>Linseed cake</td><td align='left'> 28·53</td><td align='left'> 12·47</td><td align='left'> 35·78</td><td align='left'> 6·32</td><td align='left'> 6·11</td><td align='left'> 10·79</td></tr> +<tr><td align='left'>Rübsen cake</td><td align='left'> 26·87</td><td align='left'> 11·00</td><td align='left'> 31·47</td><td align='left'> 16·95</td><td align='left'> 8·00</td><td align='left'> 5·71</td></tr> +<tr><td align='left'>Tares, foreign</td><td align='left'> 26·73</td><td align='left'> 1·59</td><td align='left'> 53·04</td><td align='left'> 2·84</td><td align='left'> 15·80</td></tr> +<tr><td align='left'>Earth-nut cake (entire seed)</td><td align='left'> 26·71</td><td align='left'> 12·75</td><td align='left'> 45·69</td><td align='left'> 3·29</td><td align='left'> 11·56</td></tr> +<tr><td align='left'>Niger cake</td><td align='left'> 25·74</td><td align='left'> 6·58</td><td align='left'> 42·18</td><td align='left'> 11·15</td><td align='left'> 8·12</td><td align='left'> 6·23</td></tr> +<tr><td align='left'>Beans (65 lbs. per bushel)</td><td align='left'> 24·70</td><td align='left'> 1·59</td><td align='left'> 54·51</td><td align='left'> 3·36</td><td align='left'> 15·84</td></tr> +<tr><td align='left'>Lentils</td><td align='left'> 24·57</td><td align='left'> 1·51</td><td align='left'> 58·82</td><td align='left'> 2·79</td><td align='left'> 12·31</td></tr> +<tr><td align='left'>Linseed</td><td align='left'> 24·44</td><td align='left'> 34·00</td><td align='left'> 30·73</td><td align='left'> 3·33</td><td align='left'> 7·50</td></tr> +<tr><td align='left'>Grey peas</td><td align='left'> 24·25</td><td align='left'> 3·30</td><td align='left'> 57·99</td><td align='left'> 2·52</td><td align='left'> 11·94</td></tr> +<tr><td align='left'>Foreign beans</td><td align='left'> 23·49</td><td align='left'> 1·51</td><td align='left'> 59·67</td><td align='left'> 3·14</td><td align='left'> 12·21</td></tr> +<tr><td align='left'>Cotton cake (with husk)</td><td align='left'> 22·94</td><td align='left'> 6·07</td><td align='left'> 36·52</td><td align='left'> 16·99</td><td align='left'> 6·02</td><td align='left'> 11·46</td></tr> +<tr><td align='left'>Pea-nut cake</td><td align='left'> 22·25</td><td align='left'> 7·62</td><td align='left'> 30·25</td><td align='left'> 26·97</td><td align='left'> 3·71</td><td align='left'> 9·20</td></tr> +<tr><td align='left'>Sunflower cake</td><td align='left'> 21·68</td><td align='left'> 8·94</td><td align='left'> 19·05</td><td align='left'> 33·00</td><td align='left'> 9·33</td><td align='left'> 8·00</td></tr> +<tr><td align='left'>Hempseed cake</td><td align='left'> 21·47</td><td align='left'> 7·90</td><td align='left'> 22·48</td><td align='left'> 25·16</td><td align='left'> 15·79</td><td align='left'> 7·21</td></tr> +<tr><td align='left'>Kidney beans</td><td align='left'> 20·06</td><td align='left'> 1·22</td><td align='left'> 62·16</td><td align='left'> 3·56</td><td align='left'> 13·00</td></tr> +<tr><td align='left'>Maple peas</td><td align='left'> 19·43</td><td align='left'> 1·72</td><td align='left'> 63·18</td><td align='left'> 2·04</td><td align='left'> 13·63</td></tr> +<tr><td align='left'>Madia sativa (seed)</td><td align='left'> 18·41</td><td align='left'> 36·55</td><td align='left'> 34·59</td><td align='left'> 4·13</td><td align='left'> 6·32</td></tr> +<tr><td align='left'>Clover hay (mean of different species of clover)</td><td align='left'> 15·81</td><td align='left'> 3·18</td><td align='left'> 34·42</td><td align='left'> 22·47</td><td align='left'> 7·59</td><td align='left'> 16·53</td></tr> +<tr><td align='left'>Rye</td><td align='left'> 14·20</td><td align='left'> ...</td><td align='left'> 81·51</td><td align='left'> 2·47</td><td align='left'> 1·82</td><td align='left'> 14·66</td></tr> +<tr><td align='left'>Bran</td><td align='left'> 13·80</td><td align='left'> 5·56</td><td align='left'> 61·67</td><td align='left'> 6·11</td><td align='left'> 12·85</td></tr> +<tr><td align='left'>Oats</td><td align='left'> 11·85</td><td align='left'> 5·89</td><td align='left'> 57·45</td><td align='left'> 9·00</td><td align='left'> 2·72</td><td align='left'> 13·09</td></tr> +<tr><td align='left'>Fine barley dust</td><td align='left'> 11·49</td><td align='left'> 2·92</td><td align='left'> 71·41</td><td align='left'> 2·67</td><td align='left'> 11·51</td></tr> +<tr><td align='left'>Wheat</td><td align='left'> 11·48</td><td align='left'> ...</td><td align='left'> 73·52</td><td align='left'> 0·68</td><td align='left'> 0·82</td><td align='left'> 13·50</td></tr> +<tr><td align='left'>Bere</td><td align='left'> 10·25</td><td align='left'> ...</td><td align='left'> 62·85</td><td align='left'> 10·08</td><td align='left'> 2·60</td><td align='left'> 14·22</td></tr> +<tr><td align='left'>Hay (mean of different grasses)</td><td align='left'> 9·40</td><td align='left'> 2·56</td><td align='left'> 38·54</td><td align='left'> 29·14</td><td align='left'> 5·84</td><td align='left'> 14·30</td></tr> +<tr><td align='left'>Barley</td><td align='left'> 8·69</td><td align='left'> ...</td><td align='left'> 64·52</td><td align='left'> 9·67</td><td align='left'> 2·82</td><td align='left'> 14·30</td></tr> +<tr><td align='left'>Coarse barley dust</td><td align='left'> 8·46</td><td align='left'> 3·47</td><td align='left'> 69·73</td><td align='left'> 7·31</td><td align='left'> 11·03</td></tr> +<tr><td align='left'>Rice dust</td><td align='left'> 8·08</td><td align='left'> 2·95</td><td align='left'> 69·22</td><td align='left'> 8·12</td><td align='left'> 11·63</td></tr> +<tr><td align='left'>Oat dust</td><td align='left'> 6·92</td><td align='left'> 3·21</td><td align='left'> 72·86</td><td align='left'> 7·70</td><td align='left'> 9·31</td></tr> +<tr><td align='left'>Winter bean straw</td><td align='left'> 5·71</td><td align='left'> ...</td><td align='left'> 67·50</td><td align='left'> 6·39</td><td align='left'> 20·40</td></tr> +<tr><td align='left'>Carob bean</td><td align='left'> 3·11</td><td align='left'> 0·41</td><td align='left'> 62·51</td><td align='left'> 18·60</td><td align='left'> 2·80</td><td align='left'> 12·57</td></tr> +<tr><td align='left'>Potato</td><td align='left'> 2·81</td><td align='left'> ...</td><td align='left'> 17·30</td><td align='left'> 1·07</td><td align='left'> 1·13</td><td align='left'> 77·69</td></tr> +<tr><td align='left'>Carrot</td><td align='left'> 1·87</td><td align='left'> ...</td><td align='left'> 7·91</td><td align='left'> 3·07</td><td align='left'> 1·11</td><td align='left'> 86·04</td></tr> +<tr><td align='left'>Wheat straw</td><td align='left'> 1·79</td><td align='left'> ...</td><td align='left'> 31·06</td><td align='left'> 45·45</td><td align='left'> 7·47</td><td align='left'> 14·23</td></tr> +<tr><td align='left'>Barley straw</td><td align='left'> 1·68</td><td align='left'> ...</td><td align='left'> 39·98</td><td align='left'> 39·80</td><td align='left'> 4·24</td><td align='left'> 14·30</td></tr> +<tr><td align='left'>Oat straw</td><td align='left'> 1·63</td><td align='left'> ...</td><td align='left'> 37·86</td><td align='left'> 43·60</td><td align='left'> 4·95</td><td align='left'> 12·06</td></tr> +<tr><td align='left'>Mangold-wurzel</td><td align='left'> 1·54</td><td align='left'> ...</td><td align='left'> 8·60</td><td align='left'> 1·12</td><td align='left'> 0·96</td><td align='left'> 87·78</td></tr> +<tr><td align='left'>Cabbage</td><td align='left'> 1·31</td><td align='left'> ...</td><td align='left'> 4·53</td><td align='left'> 1·05</td><td align='left'> 93·11</td></tr> +<tr><td align='left'>Turnips</td><td align='left'> 1·27</td><td align='left'> 0·20</td><td align='left'> 4·07</td><td align='left'> 1·08</td><td align='left'> 1·71</td><td align='left'> 91·47</td></tr> +</table></div> +<p><span class='pagenum'><a name="Page_287" id="Page_287">[Pg 287]</a></span></p> + +<p>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:—</p> + + +<div class='center'> +<table border="0" cellpadding="4" cellspacing="10" summary=""> +<tr><td align='left'></td><td align='right'>Flesh forming,</td><td align='right'>Respiratory, expressed in their fat equivalent,</td></tr> +<tr><td align='left'>Decorticated earth-nut cake</td><td align='right'>44·0</td><td align='right'>16·6</td></tr> +<tr><td align='left'>Linseed cake</td><td align='right'>28·5</td><td align='right'>26·7</td></tr> +<tr><td align='left'>Tares</td><td align='right'>26·73</td><td align='right'>18·8</td></tr> +<tr><td align='left'>Clover hay</td><td align='right'>15·81</td><td align='right'>16·8</td></tr> +<tr><td align='left'>Oats</td><td align='right'>11·85</td><td align='right'>28·8</td></tr> +<tr><td align='left'>Hay (mean of grasses)</td><td align='right'>9·40</td><td align='right'>17·9</td></tr> +<tr><td align='left'>Potato</td><td align='right'>2·81</td><td align='right'>6·9</td></tr> +<tr><td align='left'>Wheat straw</td><td align='right'>1·79</td><td align='right'>12·4</td></tr> +<tr><td align='left'>Turnip</td><td align='right'>1·27</td><td align='right'>1·8</td></tr> +</table></div> + + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_288" id="Page_288">[Pg 288]</a></span> 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:<span class='pagenum'><a name="Page_289" id="Page_289">[Pg 289]</a></span>—</p> + +<h4>TABLE shewing the Amount of each Class of Constituents, stored in the +increase, for 100 consumed in the Food.</h4> + + + + +<div class='center'> +<table border="1" cellpadding="4" cellspacing="0" summary=""> +<tr><td align='left'> </td><td align='left'> Mineral Matters</td><td align='left'>Nitrogenous Compounds.</td><td align='left'> Fat.</td><td align='left'>Total Dry Substance.</td></tr> +<tr><td align='left'>Sheep</td><td align='left'> 3·27</td><td align='left'> 4·41</td><td align='left'> 9·4</td><td align='left'> 8·06</td></tr> +<tr><td align='left'>Pigs</td><td align='left'> 0·58</td><td align='left'> 7·34</td><td align='left'> 21·2</td><td align='left'> 17·3</td></tr> +</table></div> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_290" id="Page_290">[Pg 290]</a></span> 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 <i>vice versa</i>, 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.</p> + +<p>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<span class='pagenum'><a name="Page_291" id="Page_291">[Pg 291]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_292" id="Page_292">[Pg 292]</a></span> 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.</p> + +<p>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<span class='pagenum'><a name="Page_293" id="Page_293">[Pg 293]</a></span> +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>i. e.</i> 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.</p> + +<p>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.</p> + +<p>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<span class='pagenum'><a name="Page_294" id="Page_294">[Pg 294]</a></span> 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.</p> + +<p>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.</p> + +<p>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.</p> + +<p>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.</p> + + + +<hr style="width: 65%;" /> +<p><span class='pagenum'><a name="Page_295" id="Page_295">[Pg 295]</a></span></p> +<h2>INDEX.</h2> + + +<p> +<br /> +Acid, apocrenic, <a href='#Page_21'>21</a>.<br /> +<span style="margin-left: 1em;">Carbonic, <a href='#Page_10'>10</a>, <a href='#Page_15'>15</a>, <a href='#Page_20'>20</a>, <a href='#Page_37'>37</a>, <a href='#Page_57'>57</a>, <a href='#Page_115'>115</a>.</span><br /> +<span style="margin-left: 1em;">Cerotic, <a href='#Page_48'>48</a>.</span><br /> +<span style="margin-left: 1em;">Crenic, <a href='#Page_21'>21</a>.</span><br /> +<span style="margin-left: 1em;">Geic, <a href='#Page_21'>21</a>.</span><br /> +<span style="margin-left: 1em;">Hippuric, <a href='#Page_168'>168</a>.</span><br /> +<span style="margin-left: 1em;">Humic, <a href='#Page_21'>21</a>.</span><br /> +<span style="margin-left: 1em;">Lactic, <a href='#Page_168'>168</a>.</span><br /> +<span style="margin-left: 1em;">Margaric, <a href='#Page_47'>47</a>.</span><br /> +<span style="margin-left: 1em;">Nitric, <a href='#Page_11'>11</a>, <a href='#Page_17'>17</a>, <a href='#Page_30'>30</a>, <a href='#Page_33'>33</a>, <a href='#Page_38'>38</a>, <a href='#Page_62'>62</a>, <a href='#Page_112'>112</a>.</span><br /> +<span style="margin-left: 1em;">Oleic, <a href='#Page_47'>47</a>.</span><br /> +<span style="margin-left: 1em;">Pectic, <a href='#Page_46'>46</a>.</span><br /> +<span style="margin-left: 1em;">Phosphoric, <a href='#Page_73'>73</a>, <a href='#Page_90'>90</a>.</span><br /> +<span style="margin-left: 1em;">Stearic, <a href='#Page_47'>47</a>.</span><br /> +<span style="margin-left: 1em;">Sulphuric, <a href='#Page_182'>182</a>, <a href='#Page_237'>237</a>.</span><br /> +<span style="margin-left: 1em;">Ulmic, <a href='#Page_21'>21</a>.</span><br /> +<span style="margin-left: 1em;">Uric, <a href='#Page_168'>168</a>.</span><br /> +<br /> +Adulteration of guano, <a href='#Page_211'>211</a>.<br /> +<br /> +Agricultural Chemistry Association of Scotland, <a href='#Page_6'>6</a>.<br /> +<br /> +Air, influence of, on germination, <a href='#Page_55'>55</a>.<br /> +<span style="margin-left: 1em;">In the pores of soils, <a href='#Page_115'>115</a>.</span><br /> +<br /> +Albite, <a href='#Page_86'>86</a>.<br /> +<br /> +Albumen, <a href='#Page_48'>48</a>.<br /> +<br /> +Albuminous constituents of plants and animals, <a href='#Page_48'>48</a>.<br /> +<br /> +Algoa Bay guano, <a href='#Page_208'>208</a>.<br /> +<br /> +Alkaline salts, value of, <a href='#Page_260'>260</a>.<br /> +<br /> +Alumina, <a href='#Page_73'>73</a>, <a href='#Page_86'>86</a>, <a href='#Page_103'>103</a>.<br /> +<br /> +Ammonia, absorption of, by plants, <a href='#Page_29'>29</a>, <a href='#Page_38'>38</a>.<br /> +<span style="margin-left: 1em;">Absorption of, by soils, <a href='#Page_123'>123</a>.</span><br /> +<span style="margin-left: 1em;">Carbonate of, <a href='#Page_29'>29</a>.</span><br /> +<span style="margin-left: 1em;">Composition of, <a href='#Page_12'>12</a>.</span><br /> +<span style="margin-left: 1em;">Decomposition of, by plants, <a href='#Page_61'>61</a>.</span><br /> +<span style="margin-left: 1em;">Presence in dew, <a href='#Page_17'>17</a>.</span><br /> +<span style="margin-left: 2em;">" rain, <a href='#Page_17'>17</a>.</span><br /> +<span style="margin-left: 1em;">Production of, <a href='#Page_12'>12</a>.</span><br /> +<span style="margin-left: 1em;">Properties of, <a href='#Page_12'>12</a>.</span><br /> +<span style="margin-left: 1em;">Proportion of, in air, <a href='#Page_16'>16</a>, <a href='#Page_20'>20</a>.</span><br /> +<span style="margin-left: 1em;">Proportion of, in drain water, <a href='#Page_112'>112</a>.</span><br /> +<span style="margin-left: 1em;">Proportion of, in soils, <a href='#Page_107'>107</a>.</span><br /> +<span style="margin-left: 1em;">Sulphate of, <a href='#Page_29'>29</a>, <a href='#Page_227'>227</a>.</span><br /> +<span style="margin-left: 1em;">Sulphomuriate of, <a href='#Page_227'>227</a>.</span><br /> +<span style="margin-left: 1em;">Urate of, <a href='#Page_205'>205</a>.</span><br /> +<span style="margin-left: 1em;">Valuation of, <a href='#Page_259'>259</a>.</span><br /> +<br /> +Ammoniacal liquor, <a href='#Page_229'>229</a>.<br /> +<br /> +Amylaceous constituents of plants, <a href='#Page_40'>40</a>.<br /> +<br /> +Angamos guano, <a href='#Page_207'>207</a>, <a href='#Page_210'>210</a>.<br /> +<br /> +Animal charcoal, <a href='#Page_224'>224</a>.<br /> +<span style="margin-left: 1em;">Manures, <a href='#Page_204'>204</a>.</span><br /> +<br /> +Animals, composition of, <a href='#Page_281'>281</a>.<br /> +<span style="margin-left: 1em;">Nitrogenous constituents of, <a href='#Page_48'>48</a>, <a href='#Page_281'>281</a>.</span><br /> +<br /> +Apatite, <a href='#Page_235'>235</a>.<br /> +<br /> +Ascension Island guano, <a href='#Page_208'>208</a>.<br /> +<br /> +Augite, <a href='#Page_89'>89</a>.<br /> +<br /> +Australian guano, <a href='#Page_207'>207</a>.<br /> +<br /> +Avenine, <a href='#Page_50'>50</a>.<br /> +<br /> +<br /> +Barks, amount of ash in, <a href='#Page_66'>66</a>.<br /> +<br /> +Barley, <a href='#Page_286'>286</a>.<br /> +<br /> +Barrenness of soils, <a href='#Page_109'>109</a>.<br /> +<br /> +Basalt, <a href='#Page_92'>92</a>.<br /> +<br /> +Beans, <a href='#Page_286'>286</a>.<br /> +<br /> +Bere, <a href='#Page_286'>286</a>.<br /> +<br /> +Biphosphate of lime, <a href='#Page_237'>237</a>, <a href='#Page_260'>260</a>.<br /> +<br /> +Bird Island guano, <a href='#Page_208'>208</a>.<br /> +<br /> +Blood as a manure, <a href='#Page_220'>220</a>.<br /> +<br /> +Bone ash, <a href='#Page_234'>234</a>.<br /> +<br /> +Bone oil, <a href='#Page_229'>229</a>.<br /> +<br /> +Bones as a manure, <a href='#Page_223'>223</a>.<br /> +<span style="margin-left: 1em;">Dissolved, <a href='#Page_237'>237</a>.</span><br /> +<br /> +Box-feeding, <a href='#Page_183'>183</a>.<br /> +<br /> +Bolivian guano, <a href='#Page_207'>207</a>, <a href='#Page_210'>210</a>.<br /> +<br /> +Bran, <a href='#Page_197'>197</a>, <a href='#Page_286'>286</a>.<br /> +<br /> +<span class='pagenum'><a name="Page_296" id="Page_296">[Pg 296]</a></span>Burning, improvement of soils by, <a href='#Page_146'>146</a>.<br /> +<br /> +<br /> +Cabbage, <a href='#Page_286'>286</a>.<br /> +<br /> +Cane sugar, <a href='#Page_43'>43</a>.<br /> +<br /> +Carbon, properties of, <a href='#Page_10'>10</a>.<br /> +<span style="margin-left: 1em;">Proportion of, in plants, <a href='#Page_10'>10</a>.</span><br /> +<br /> +Carbonate of ammonia, <a href='#Page_29'>29</a>.<br /> +<span style="margin-left: 1em;">Lime, <a href='#Page_96'>96</a>, <a href='#Page_247'>247</a>.</span><br /> +<span style="margin-left: 1em;">Magnesia, <a href='#Page_96'>96</a>.</span><br /> +<span style="margin-left: 1em;">Potash, <a href='#Page_232'>232</a>.</span><br /> +<span style="margin-left: 1em;">Soda, <a href='#Page_232'>232</a>.</span><br /> +<br /> +Carbonic acid, absorption of, by plants, <a href='#Page_37'>37</a>.<br /> +<span style="margin-left: 1em;">Decomposition of, by plants, <a href='#Page_57'>57</a>.</span><br /> +<span style="margin-left: 1em;">Evolution of, by plants, <a href='#Page_58'>58</a>.</span><br /> +<span style="margin-left: 1em;">How obtained, <a href='#Page_10'>10</a>.</span><br /> +<span style="margin-left: 1em;">Properties, <a href='#Page_10'>10</a>.</span><br /> +<span style="margin-left: 1em;">Proportion of, in air, <a href='#Page_15'>15</a>, <a href='#Page_20'>20</a>.</span><br /> +<br /> +Carburetted hydrogen, <a href='#Page_19'>19</a>.<br /> +<br /> +Calcium, sulphuret of, <a href='#Page_252'>252</a>.<br /> +<br /> +Caramel, <a href='#Page_44'>44</a>.<br /> +<br /> +Carrot, <a href='#Page_286'>286</a>.<br /> +<br /> +Caseine, <a href='#Page_50'>50</a>, <a href='#Page_283'>283</a>.<br /> +<br /> +Castor cake, <a href='#Page_195'>195</a>.<br /> +<br /> +Cattle food, composition of, <a href='#Page_286'>286</a>.<br /> +<br /> +Cellulose, <a href='#Page_40'>40</a>.<br /> +<br /> +Cerine, <a href='#Page_48'>48</a>.<br /> +<br /> +Cerotic acid, <a href='#Page_48'>48</a>.<br /> +<br /> +Chaff, <a href='#Page_197'>197</a>.<br /> +<br /> +Chalk, <a href='#Page_96'>96</a>, <a href='#Page_245'>245</a>.<br /> +<br /> +Charcoal, animal, <a href='#Page_224'>224</a>.<br /> +<br /> +Chilian guano, <a href='#Page_207'>207</a>.<br /> +<br /> +China-clay, <a href='#Page_87'>87</a>.<br /> +<br /> +Chloride of potassium, <a href='#Page_73'>73</a>, <a href='#Page_102'>102</a>.<br /> +<span style="margin-left: 1em;">Sodium, <a href='#Page_73'>73</a>, <a href='#Page_232'>232</a>.</span><br /> +<span style="margin-left: 1em;">Manganese, <a href='#Page_182'>182</a>.</span><br /> +<br /> +Clay, <a href='#Page_87'>87</a>.<br /> +<span style="margin-left: 1em;">Absorbent action of, <a href='#Page_121'>121</a>.</span><br /> +<span style="margin-left: 1em;">Composition of, <a href='#Page_95'>95</a>.</span><br /> +<span style="margin-left: 1em;">Source of, <a href='#Page_88'>88</a>, <a href='#Page_94'>94</a>.</span><br /> +<br /> +Clay-slate, <a href='#Page_95'>95</a>.<br /> +<br /> +Classification of plants, <a href='#Page_81'>81</a>.<br /> +<br /> +Coprolites, <a href='#Page_98'>98</a>, <a href='#Page_235'>235</a>.<br /> +<br /> +Coral sand, <a href='#Page_246'>246</a>.<br /> +<br /> +Cotton cake, <a href='#Page_195'>195</a>, <a href='#Page_286'>286</a>.<br /> +<br /> +Crenic acid, <a href='#Page_21'>21</a>.<br /> +<br /> +Crops, Mineral matters in, <a href='#Page_270'>270</a>.<br /> +<span style="margin-left: 1em;">Nitrogen in different, <a href='#Page_270'>270</a>.</span><br /> +<span style="margin-left: 1em;">Rotation of, <a href='#Page_81'>81</a>, <a href='#Page_266'>266</a>.</span><br /> +<br /> +<br /> +Deep Ploughing, effects of, <a href='#Page_144'>144</a>.<br /> +<br /> +Dew, ammonia in, <a href='#Page_17'>17</a>.<br /> +<span style="margin-left: 1em;">Nitric acid in, <a href='#Page_19'>19</a>.</span><br /> +<br /> +Dextrine, <a href='#Page_43'>43</a>.<br /> +<br /> +Diastase, <a href='#Page_43'>43</a>, <a href='#Page_53'>53</a>, <a href='#Page_55'>55</a>.<br /> +<br /> +Diorite, <a href='#Page_92'>92</a>.<br /> +<br /> +Dissolved bones, <a href='#Page_237'>237</a>.<br /> +<br /> +Dolerite, <a href='#Page_92'>92</a>.<br /> +<br /> +Dotter cake, <a href='#Page_286'>286</a>.<br /> +<br /> +Drainage water, analyses of, <a href='#Page_112'>112</a>.<br /> +<br /> +Draining, <a href='#Page_138'>138</a>.<br /> +<br /> +Dung, composition of, <a href='#Page_170'>170</a>.<br /> +<br /> +Dung heaps, management of, <a href='#Page_179'>179</a>.<br /> +<br /> +<br /> +Earth-nut cake, <a href='#Page_286'>286</a>.<br /> +<br /> +Emulsine, <a href='#Page_50'>50</a>.<br /> +<br /> +Exhaustion of soils, <a href='#Page_81'>81</a>.<br /> +<br /> +<br /> +Farm stock, feeding of, <a href='#Page_276'>276</a>.<br /> +<br /> +Farm-yard manure, <a href='#Page_166'>166</a>, <a href='#Page_172'>172</a>.<br /> +<span style="margin-left: 1em;">Application of, <a href='#Page_186'>186</a>.</span><br /> +<br /> +Fat, amount of, in animals, <a href='#Page_281'>281</a>.<br /> +<br /> +Fatty acids, <a href='#Page_47'>47</a>.<br /> +<span style="margin-left: 1em;">Matters, <a href='#Page_46'>46</a>.</span><br /> +<br /> +Feeding cakes, <a href='#Page_286'>286</a>.<br /> +<br /> +Feeding of farm stock, <a href='#Page_276'>276</a>.<br /> +<br /> +Felspar, <a href='#Page_86'>86</a>.<br /> +<span style="margin-left: 1em;">Decomposition of, <a href='#Page_88'>88</a>.</span><br /> +<br /> +Fermentation of manure, <a href='#Page_184'>184</a>.<br /> +<br /> +Fire-clay, <a href='#Page_95'>95</a>.<br /> +<br /> +Fish manure, <a href='#Page_221'>221</a>.<br /> +<br /> +Flesh as a manure, <a href='#Page_220'>220</a>.<br /> +<br /> +Fog, ammonia in, <a href='#Page_17'>17</a>.<br /> +<span style="margin-left: 1em;">Nitric acid in, <a href='#Page_19'>19</a>.</span><br /> +<br /> +Food, cattle, <a href='#Page_286'>286</a>.<br /> +<br /> +Fruits, amount of ash in, <a href='#Page_66'>66</a>.<br /> +<br /> +<br /> +Gas Lime, <a href='#Page_252'>252</a>.<br /> +<br /> +Geic acid, <a href='#Page_21'>21</a>.<br /> +<br /> +Germination, <a href='#Page_54'>54</a>.<br /> +<br /> +Gluten, <a href='#Page_49'>49</a>.<br /> +<br /> +Glutin, <a href='#Page_49'>49</a>.<br /> +<br /> +Glycerine, <a href='#Page_47'>47</a>.<br /> +<br /> +Gneiss, <a href='#Page_91'>91</a>.<br /> +<br /> +Granite, <a href='#Page_91'>91</a>.<br /> +<br /> +Grape sugar, <a href='#Page_44'>44</a>.<br /> +<br /> +Greenstone, <a href='#Page_92'>92</a>.<br /> +<br /> +Green manuring, <a href='#Page_198'>198</a>.<br /> +<br /> +Guano, <a href='#Page_204'>204</a>.<br /> +<span style="margin-left: 1em;">Adulteration of, <a href='#Page_211'>211</a>.</span><br /> +<span style="margin-left: 1em;">Application of, <a href='#Page_214'>214</a>.</span><br /> +<span style="margin-left: 1em;">Average composition of, <a href='#Page_207'>207</a>.</span><br /> +<span style="margin-left: 1em;">Fish, <a href='#Page_222'>222</a>.</span><br /> +<span style="margin-left: 1em;">Peruvian, characters of, <a href='#Page_209'>209</a>.</span><br /> +<span style="margin-left: 1em;">Phospho-Peruvian, <a href='#Page_243'>243</a>.</span><br /> +<span style="margin-left: 1em;">Sombrero Island, <a href='#Page_236'>236</a>.</span><br /> +<br /> +<br /> +Hair, <a href='#Page_218'>218</a>.<br /> +<br /> +Hay, <a href='#Page_286'>286</a>.<br /> +<br /> +Heat, evolution of, by plants, <a href='#Page_60'>60</a>.<br /> +<br /> +Hempseed cake, <a href='#Page_286'>286</a>.<br /> +<br /> +<span class='pagenum'><a name="Page_297" id="Page_297">[Pg 297]</a></span>Hippuric acid, <a href='#Page_168'>168</a>.<br /> +<br /> +Horn, <a href='#Page_218'>218</a>.<br /> +<br /> +Hornblende, <a href='#Page_89'>89</a>.<br /> +<br /> +Humic acid, <a href='#Page_21'>21</a>.<br /> +<br /> +Humin, <a href='#Page_22'>22</a>.<br /> +<br /> +Humus, <a href='#Page_21'>21</a>, <a href='#Page_98'>98</a>, <a href='#Page_133'>133</a>.<br /> +<br /> +Hydrogen, <a href='#Page_10'>10</a>.<br /> +<br /> +<br /> +Ichaboe Guano, <a href='#Page_207'>207</a>.<br /> +<br /> +Indian guano, <a href='#Page_208'>208</a>.<br /> +<br /> +Inorganic constituents of plants, <a href='#Page_9'>9</a>, <a href='#Page_34'>34</a>.<br /> +<br /> +Inorganic constituents;<br /> +<span style="margin-left: 1em;">Absorption by plants, <a href='#Page_38'>38</a>.</span><br /> +<span style="margin-left: 1em;">Proportion in plants, <a href='#Page_64'>64</a>.</span><br /> +<br /> +Inorganic constituents of soils, <a href='#Page_85'>85</a>.<br /> +<br /> +Inuline, <a href='#Page_43'>43</a>.<br /> +<br /> +Iodine in plants, <a href='#Page_76'>76</a>.<br /> +<br /> +Iron, protoxide of, in soils, <a href='#Page_107'>107</a>.<br /> +<span style="margin-left: 1em;">Sulphate of, <a href='#Page_182'>182</a>.</span><br /> +<span style="margin-left: 1em;">Sulphuret of, in subsoils, <a href='#Page_135'>135</a>.</span><br /> +<br /> +<br /> +Kaolin, <a href='#Page_87'>87</a>.<br /> +<br /> +Kooria Mooria guano, <a href='#Page_207'>207</a>.<br /> +<br /> +<br /> +Labradorite, <a href='#Page_86'>86</a>.<br /> +<br /> +Lactic acid, <a href='#Page_168'>168</a>.<br /> +<br /> +Latham Island guano, <a href='#Page_207'>207</a>.<br /> +<br /> +Leaves, amount of ash in, <a href='#Page_65'>65</a>.<br /> +<span style="margin-left: 1em;">As a manure, <a href='#Page_202'>202</a>.</span><br /> +<br /> +Legumine, <a href='#Page_50'>50</a>.<br /> +<br /> +Lichen starch, <a href='#Page_42'>42</a>.<br /> +<br /> +Light, influence of, on plants, <a href='#Page_57'>57</a>.<br /> +<br /> +Lime, action of, on soils, <a href='#Page_248'>248</a>.<br /> +<span style="margin-left: 1em;">As a manure, <a href='#Page_245'>245</a>.</span><br /> +<span style="margin-left: 1em;">Bicarbonate of, <a href='#Page_122'>122</a>.</span><br /> +<span style="margin-left: 1em;">Carbonate of, <a href='#Page_96'>96</a>.</span><br /> +<span style="margin-left: 1em;">Biphosphate of, <a href='#Page_237'>237</a>, <a href='#Page_260'>260</a>.</span><br /> +<span style="margin-left: 1em;">Humate of, <a href='#Page_125'>125</a></span><br /> +<span style="margin-left: 1em;">Phosphate of, <a href='#Page_96'>96</a>, <a href='#Page_233'>233</a>, <a href='#Page_258'>258</a>.</span><br /> +<span style="margin-left: 1em;">Sulphate of, <a href='#Page_96'>96</a>, <a href='#Page_253'>253</a>, <a href='#Page_260'>260</a>.</span><br /> +<br /> +Lime-plants, <a href='#Page_82'>82</a>.<br /> +<br /> +Limestone, <a href='#Page_96'>96</a>.<br /> +<br /> +Linseed cake, <a href='#Page_195'>195</a>.<br /> +<br /> +Liquid manure, <a href='#Page_166'>166</a>, <a href='#Page_187'>187</a>.<br /> +<br /> +<br /> +Madia Sativa, <a href='#Page_286'>286</a>.<br /> +<br /> +Magnesia, carbonate of, <a href='#Page_96'>96</a>.<br /> +<span style="margin-left: 1em;">Sulphate of, <a href='#Page_182'>182</a>, <a href='#Page_233'>233</a>.</span><br /> +<br /> +Magnesian limestone, <a href='#Page_96'>96</a>.<br /> +<br /> +Malt-dust, <a href='#Page_197'>197</a>.<br /> +<br /> +Manganese in plants, <a href='#Page_73'>73</a>.<br /> +<span style="margin-left: 1em;">Oxide of, <a href='#Page_73'>73</a>, <a href='#Page_87'>87</a>.</span><br /> +<span style="margin-left: 1em;">Chloride of, <a href='#Page_182'>182</a>.</span><br /> +<br /> +Mangold-wurzel, <a href='#Page_286'>286</a>.<br /> +<br /> +Manures, animal, <a href='#Page_204'>204</a>.<br /> +<br /> +Manures, application of, <a href='#Page_165'>165</a>, <a href='#Page_186'>186</a>.<br /> +<span style="margin-left: 1em;">Fermentation of, <a href='#Page_184'>184</a>.</span><br /> +<span style="margin-left: 1em;">Farm-yard, <a href='#Page_166'>166</a>, <a href='#Page_172'>172</a>.</span><br /> +<span style="margin-left: 1em;">Liquid, <a href='#Page_166'>166</a>, <a href='#Page_187'>187</a>.</span><br /> +<span style="margin-left: 1em;">Mineral, <a href='#Page_226'>226</a>.</span><br /> +<span style="margin-left: 1em;">Theory of, <a href='#Page_156'>156</a>.</span><br /> +<span style="margin-left: 1em;">Sewage, <a href='#Page_191'>191</a>.</span><br /> +<span style="margin-left: 1em;">Vegetable, <a href='#Page_195'>195</a>.</span><br /> +<span style="margin-left: 1em;">Valuation of, <a href='#Page_255'>255</a>.</span><br /> +<br /> +Manuring, Green, <a href='#Page_198'>198</a>.<br /> +<span style="margin-left: 1em;">Principles of, <a href='#Page_152'>152</a>.</span><br /> +<br /> +Maple peas, <a href='#Page_286'>286</a>.<br /> +<br /> +Maracaybo guano, <a href='#Page_236'>236</a>.<br /> +<br /> +Margaric acid, <a href='#Page_47'>47</a>.<br /> +<br /> +Margarine, <a href='#Page_46'>46</a>.<br /> +<br /> +Marl, <a href='#Page_245'>245</a>.<br /> +<br /> +Mexican guano, <a href='#Page_207'>207</a>.<br /> +<br /> +Mica, <a href='#Page_88'>88</a>.<br /> +<br /> +Mica slate, <a href='#Page_91'>91</a>.<br /> +<br /> +Milk, composition of, <a href='#Page_283'>283</a>.<br /> +<span style="margin-left: 1em;">Curding of, <a href='#Page_51'>51</a>.</span><br /> +<br /> +Mineral constituents of plants, <a href='#Page_9'>9</a>, <a href='#Page_63'>63</a>.<br /> +<br /> +Mineral manures, <a href='#Page_226'>226</a>.<br /> +<br /> +Mineral matters in different crops, <a href='#Page_270'>270</a>.<br /> +<span style="margin-left: 1em;">In animals, <a href='#Page_281'>281</a>.</span><br /> +<br /> +Moisture, influence of, on germination, <a href='#Page_55'>55</a>.<br /> +<br /> +Mucilage, <a href='#Page_44'>44</a>.<br /> +<br /> +<br /> +Natrolite, <a href='#Page_90'>90</a>.<br /> +<br /> +New Island guano, <a href='#Page_208'>208</a>.<br /> +<br /> +Niger cake, <a href='#Page_286'>286</a>.<br /> +<br /> +Night-soil, <a href='#Page_217'>217</a>.<br /> +<br /> +Nitrate of potash, <a href='#Page_229'>229</a>.<br /> +<br /> +Nitrate of soda, <a href='#Page_229'>229</a>, <a href='#Page_260'>260</a>.<br /> +<br /> +Nitric acid, absorbtion of, by plants, <a href='#Page_30'>30</a>, <a href='#Page_38'>38</a>.<br /> +<span style="margin-left: 1em;">Decomposition of, by plants, <a href='#Page_62'>62</a>.</span><br /> +<span style="margin-left: 1em;">In drainage water, <a href='#Page_112'>112</a>.</span><br /> +<span style="margin-left: 1em;">In dew, <a href='#Page_19'>19</a>.</span><br /> +<span style="margin-left: 1em;">In air, <a href='#Page_17'>17</a>.</span><br /> +<span style="margin-left: 1em;">In fog, <a href='#Page_19'>19</a>.</span><br /> +<span style="margin-left: 1em;">Production of, <a href='#Page_11'>11</a>, <a href='#Page_33'>33</a>.</span><br /> +<br /> +Nitrification, <a href='#Page_11'>11</a>.<br /> +<br /> +Nitrogen, amount in a six-course rotation, <a href='#Page_160'>160</a>.<br /> +<span style="margin-left: 1em;">Amount of, in different crops, <a href='#Page_270'>270</a>.</span><br /> +<span style="margin-left: 1em;">Presence in the atmosphere, <a href='#Page_11'>11</a>.</span><br /> +<span style="margin-left: 1em;">Properties of, <a href='#Page_11'>11</a>.</span><br /> +<span style="margin-left: 1em;">Proportion of, in plants, <a href='#Page_11'>11</a>.</span><br /> +<br /> +<span class='pagenum'><a name="Page_298" id="Page_298">[Pg 298]</a></span>Nitrogenous constituents of plants, <a href='#Page_48'>48</a>, <a href='#Page_286'>286</a>.<br /> +<br /> +Nitrogenous constituents of animals, <a href='#Page_48'>48</a>, <a href='#Page_281'>281</a>.<br /> +<br /> +<br /> +Oats, <a href='#Page_286'>286</a>.<br /> +<span style="margin-left: 1em;">Proportion of ash in, <a href='#Page_68'>68</a>, <a href='#Page_70'>70</a>.</span><br /> +<br /> +Oil-cakes, <a href='#Page_195'>195</a>, <a href='#Page_286'>286</a>.<br /> +<br /> +Oils, sweet principle of, <a href='#Page_47'>47</a>.<br /> +<br /> +Oily matters, <a href='#Page_46'>46</a>.<br /> +<br /> +Oleic acid, <a href='#Page_47'>47</a>.<br /> +<br /> +Oleine, <a href='#Page_46'>46</a>.<br /> +<br /> +Oligoclase, <a href='#Page_86'>86</a>.<br /> +<br /> +Oolitic limestone, <a href='#Page_96'>96</a>.<br /> +<br /> +Organic constituents of plants, <a href='#Page_8'>8</a>.<br /> +<span style="margin-left: 1em;">Sources of the, <a href='#Page_13'>13</a>, <a href='#Page_20'>20</a>.</span><br /> +<br /> +Organic constituents of soils, <a href='#Page_103'>103</a>.<br /> +<br /> +Orthoclase, <a href='#Page_86'>86</a>.<br /> +<br /> +Oxide of iron in rocks and soils, <a href='#Page_87'>87</a>, <a href='#Page_107'>107</a>.<br /> +<span style="margin-left: 1em;">Of manganese, <a href='#Page_87'>87</a>.</span><br /> +<br /> +Oxygen, evolution of, by plants, <a href='#Page_58'>58</a>.<br /> +<span style="margin-left: 1em;">Influence of, on germination, <a href='#Page_55'>55</a>.</span><br /> +<span style="margin-left: 1em;">Presence in atmosphere, <a href='#Page_12'>12</a>.</span><br /> +<span style="margin-left: 1em;">Properties of, <a href='#Page_12'>12</a>.</span><br /> +<span style="margin-left: 1em;">Proportion of, in plants, <a href='#Page_12'>12</a>.</span><br /> +<br /> +<br /> +Pacquico Guano, <a href='#Page_207'>207</a>.<br /> +<br /> +Paring, improvement of soils by, <a href='#Page_146'>146</a>.<br /> +<br /> +Patagonian guano, <a href='#Page_207'>207</a>.<br /> +<br /> +Pea-nut cake, <a href='#Page_286'>286</a>.<br /> +<br /> +Peas, <a href='#Page_286'>286</a>.<br /> +<br /> +Peat, as a manure, <a href='#Page_203'>203</a>.<br /> +<br /> +Peat, use of, in dung-heaps, <a href='#Page_184'>184</a>.<br /> +<br /> +Pectic acid, <a href='#Page_46'>46</a>.<br /> +<br /> +Pectine, <a href='#Page_46'>46</a>.<br /> +<br /> +Peruvian Guano, <a href='#Page_205'>205</a>, <a href='#Page_207'>207</a>, <a href='#Page_209'>209</a>.<br /> +<span style="margin-left: 1em;">Upper, <a href='#Page_207'>207</a>, <a href='#Page_213'>213</a>.</span><br /> +<br /> +Phosphate of lime, <a href='#Page_96'>96</a>, <a href='#Page_233'>233</a>.<br /> +<span style="margin-left: 1em;">Value of, <a href='#Page_258'>258</a>.</span><br /> +<br /> +Phosphates, insoluble, <a href='#Page_258'>258</a>.<br /> +<span style="margin-left: 1em;">Soluble, <a href='#Page_237'>237</a>, <a href='#Page_260'>260</a>.</span><br /> +<br /> +Phospho-Peruvian guano, <a href='#Page_243'>243</a>.<br /> +<br /> +Phosphuretted hydrogen in air, <a href='#Page_19'>19</a>.<br /> +<br /> +Pigeons' dung, <a href='#Page_216'>216</a>.<br /> +<br /> +Plants, Albuminous constituents of, <a href='#Page_48'>48</a>.<br /> +<span style="margin-left: 1em;">Amylaceous constituents of, <a href='#Page_40'>40</a>.</span><br /> +<span style="margin-left: 1em;">Ash of, <a href='#Page_64'>64</a>, <a href='#Page_73'>73</a>.</span><br /> +<span style="margin-left: 1em;">Classification of, <a href='#Page_81'>81</a>.</span><br /> +<span style="margin-left: 1em;">Inorganic constituents of, <a href='#Page_9'>9</a>, <a href='#Page_34'>34</a>, <a href='#Page_38'>38</a>, <a href='#Page_63'>63</a>.</span><br /> +<span style="margin-left: 1em;">Oily constituents of, <a href='#Page_46'>46</a>.</span><br /> +<span style="margin-left: 1em;">Organic constituents of, <a href='#Page_8'>8</a>.</span><br /> +<span style="margin-left: 1em;">Proximate constituents of, <a href='#Page_40'>40</a>.</span><br /> +<span style="margin-left: 1em;">Saccharine constituents of, <a href='#Page_40'>40</a>.</span><br /> +<br /> +Poppy cake, <a href='#Page_196'>196</a>, <a href='#Page_286'>286</a>.<br /> +<br /> +Potash, carbonate of, <a href='#Page_232'>232</a>.<br /> +<span style="margin-left: 1em;">Muriate of, <a href='#Page_231'>231</a>.</span><br /> +<span style="margin-left: 1em;">Nitrate of, <a href='#Page_229'>229</a>.</span><br /> +<span style="margin-left: 1em;">Plants, <a href='#Page_82'>82</a>.</span><br /> +<span style="margin-left: 1em;">Salts, <a href='#Page_231'>231</a>.</span><br /> +<br /> +Potato, <a href='#Page_286'>286</a>.<br /> +<br /> +Poudrette, <a href='#Page_217'>217</a>.<br /> +<br /> +Proximate constituents of plants, <a href='#Page_40'>40</a>.<br /> +<br /> +Pyroguanite, <a href='#Page_236'>236</a>.<br /> +<br /> +<br /> +Quartz, <a href='#Page_86'>86</a>.<br /> +<br /> +<br /> +Rainwater, <a href='#Page_17'>17</a>, <a href='#Page_18'>18</a>.<br /> +<br /> +Rape Cake, <a href='#Page_196'>196</a>, <a href='#Page_286'>286</a>.<br /> +<span style="margin-left: 1em;">Dust, <a href='#Page_195'>195</a>.</span><br /> +<br /> +Rocks, crystalline, <a href='#Page_85'>85</a>.<br /> +<span style="margin-left: 1em;">Composition of, <a href='#Page_91'>91</a>.</span><br /> +<span style="margin-left: 1em;">Disintegration of, <a href='#Page_85'>85</a>.</span><br /> +<span style="margin-left: 1em;">Sedimentary, <a href='#Page_86'>86</a>.</span><br /> +<br /> +Roots of plants, amount of ash in, <a href='#Page_65'>65</a>.<br /> +<br /> +Rotation of crops, <a href='#Page_81'>81</a>, <a href='#Page_266'>266</a>.<br /> +<br /> +Rübsen cake, <a href='#Page_286'>286</a>.<br /> +<br /> +Rye, <a href='#Page_286'>286</a>.<br /> +<br /> +<br /> +Saccharine Constituents of plants, <a href='#Page_40'>40</a>.<br /> +<br /> +Saldanha Bay guano, <a href='#Page_207'>207</a>.<br /> +<br /> +Salt, common, <a href='#Page_232'>232</a>.<br /> +<br /> +Sandstones, <a href='#Page_95'>95</a>.<br /> +<br /> +Schübler's experiments, <a href='#Page_127'>127</a>.<br /> +<br /> +Sea Bear Bay guano, <a href='#Page_208'>208</a>.<br /> +<br /> +Sea weed, <a href='#Page_200'>200</a>, <a href='#Page_201'>201</a>.<br /> +<br /> +Seeds, amount of ash in, <a href='#Page_64'>64</a>.<br /> +<br /> +Sesamum cake, <a href='#Page_286'>286</a>.<br /> +<br /> +Sewage manure, <a href='#Page_191'>191</a>.<br /> +<br /> +Shell sand, <a href='#Page_246'>246</a>.<br /> +<br /> +Silica plants, <a href='#Page_82'>82</a>.<br /> +<br /> +Silicate of potash, <a href='#Page_233'>233</a>.<br /> +<span style="margin-left: 1em;">Soda, <a href='#Page_233'>233</a>.</span><br /> +<br /> +Skin, <a href='#Page_218'>218</a>.<br /> +<br /> +Soda, carbonate of, <a href='#Page_232'>232</a>.<br /> +<span style="margin-left: 1em;">Nitrate of, <a href='#Page_229'>229</a>, <a href='#Page_260'>260</a>.</span><br /> +<span style="margin-left: 1em;">Salts, <a href='#Page_231'>231</a>.</span><br /> +<span style="margin-left: 1em;">Silicate of, <a href='#Page_233'>233</a>.</span><br /> +<br /> +Sodium, chloride of, <a href='#Page_232'>232</a>.<br /> +<br /> +Soil, the, <a href='#Page_20'>20</a>, <a href='#Page_83'>83</a>.<br /> +<span style="margin-left: 1em;">Influence on the composition of the ash of plants, <a href='#Page_71'>71</a>.</span><br /> +<span style="margin-left: 1em;">Chemical composition of, <a href='#Page_98'>98</a>.</span><br /> +<span style="margin-left: 1em;">Chemical and physical characters of, <a href='#Page_83'>83</a>.</span><br /> +<span class='pagenum'><a name="Page_299" id="Page_299">[Pg 299]</a></span><span style="margin-left: 1em;">Improvement of, by mechanical means, <a href='#Page_137'>137</a>.</span><br /> +<br /> +Soil, relation of, to heat and moisture, <a href='#Page_127'>127</a>.<br /> +<br /> +Soils, absorbent action of, <a href='#Page_122'>122</a>.<br /> +<span style="margin-left: 1em;">Air in the pores of, <a href='#Page_114'>114</a>.</span><br /> +<span style="margin-left: 1em;">Analysis, <a href='#Page_101'>101</a>, <a href='#Page_118'>118</a>.</span><br /> +<span style="margin-left: 1em;">Barrenness of, <a href='#Page_109'>109</a>.</span><br /> +<span style="margin-left: 1em;">Classification of, <a href='#Page_135'>135</a>.</span><br /> +<span style="margin-left: 1em;">Exhaustion of, <a href='#Page_81'>81</a>.</span><br /> +<span style="margin-left: 1em;">Inorganic constituents of, <a href='#Page_85'>85</a>.</span><br /> +<span style="margin-left: 1em;">Mixing of, <a href='#Page_150'>150</a>.</span><br /> +<span style="margin-left: 1em;">Origin of, <a href='#Page_84'>84</a>.</span><br /> +<span style="margin-left: 1em;">Organic matters in, <a href='#Page_103'>103</a>.</span><br /> +<span style="margin-left: 1em;">Physical characters of, <a href='#Page_118'>118</a>, <a href='#Page_127'>127</a>.</span><br /> +<br /> +Sombrero Island guano, <a href='#Page_236'>236</a>.<br /> +<br /> +Starch, <a href='#Page_41'>41</a>.<br /> +<span style="margin-left: 1em;">Lichen, <a href='#Page_42'>42</a>.</span><br /> +<br /> +Stearic acid, <a href='#Page_47'>47</a>.<br /> +<br /> +Stearine, <a href='#Page_46'>46</a>.<br /> +<br /> +Stems of plants, ash in, <a href='#Page_64'>64</a>.<br /> +<br /> +Straw, amount of ash in, <a href='#Page_64'>64</a>.<br /> +<span style="margin-left: 1em;">As a manure, <a href='#Page_197'>197</a>.</span><br /> +<br /> +Sulphate of iron, <a href='#Page_182'>182</a>.<br /> +<span style="margin-left: 1em;">Lime, <a href='#Page_96'>96</a>, <a href='#Page_253'>253</a>, <a href='#Page_260'>260</a>.</span><br /> +<span style="margin-left: 1em;">Magnesia, <a href='#Page_182'>182</a>.</span><br /> +<span style="margin-left: 1em;">Ammonia, <a href='#Page_29'>29</a>, <a href='#Page_227'>227</a>.</span><br /> +<span style="margin-left: 1em;">Potash, <a href='#Page_231'>231</a>.</span><br /> +<br /> +Sulphomuriate of ammonia, <a href='#Page_227'>227</a>.<br /> +<br /> +Sulphur in plants, <a href='#Page_78'>78</a>.<br /> +<br /> +Sulphuret of iron, <a href='#Page_135'>135</a>.<br /> +<span style="margin-left: 1em;">Calcium, <a href='#Page_252'>252</a>.</span><br /> +<br /> +Sulphuretted hydrogen, <a href='#Page_19'>19</a>.<br /> +<br /> +Sugar, <a href='#Page_43'>43</a>.<br /> +<span style="margin-left: 1em;">Of milk, <a href='#Page_283'>283</a>.</span><br /> +<br /> +Subsoil, the, <a href='#Page_134'>134</a>.<br /> +<span style="margin-left: 1em;">Ploughing, <a href='#Page_143'>143</a>.</span><br /> +<br /> +Sunflower cake, <a href='#Page_286'>286</a>.<br /> +<br /> +Syenite, <a href='#Page_91'>91</a>.<br /> +<br /> +<br /> +Tares, <a href='#Page_286'>286</a>.<br /> +<br /> +Teelcake, <a href='#Page_286'>286</a>.<br /> +<br /> +Temperature, influence of, on germination, <a href='#Page_54'>54</a>.<br /> +<br /> +Thomsonite, <a href='#Page_90'>90</a>.<br /> +<br /> +Trap rock, <a href='#Page_92'>92</a>.<br /> +<br /> +Tubers, amount of ash in, <a href='#Page_65'>65</a>.<br /> +<br /> +<br /> +Ulmic acid, <a href='#Page_21'>21</a>.<br /> +<br /> +Ulmin, <a href='#Page_22'>22</a>.<br /> +<br /> +Upper Peruvian guano, <a href='#Page_207'>207</a>, <a href='#Page_213'>213</a>.<br /> +<br /> +Urate, <a href='#Page_216'>216</a>.<br /> +<span style="margin-left: 1em;">Of ammonia, <a href='#Page_205'>205</a>.</span><br /> +<br /> +Urea, <a href='#Page_168'>168</a>.<br /> +<br /> +Uric acid, <a href='#Page_168'>168</a>, <a href='#Page_205'>205</a>.<br /> +<br /> +Urine, composition of, <a href='#Page_167'>167</a>.<br /> +<span style="margin-left: 1em;">Human, <a href='#Page_168'>168</a>.</span><br /> +<span style="margin-left: 1em;">Sulphated, <a href='#Page_216'>216</a>.</span><br /> +<br /> +<br /> +Valuation of manures, <a href='#Page_255'>255</a>.<br /> +<br /> +Vegetable manures, <a href='#Page_195'>195</a>.<br /> +<br /> +Vegetation, influence of light on, <a href='#Page_57'>57</a>.<br /> +<br /> +Voelcker's analyses of dung, <a href='#Page_174'>174</a>.<br /> +<br /> +<br /> +Warping, <a href='#Page_148'>148</a>.<br /> +<br /> +Water, absorption of, by plants, <a href='#Page_35'>35</a>.<br /> +<span style="margin-left: 1em;">Decomposition of, by plants, <a href='#Page_60'>60</a>.</span><br /> +<span style="margin-left: 1em;">Exhalation of, by plants, <a href='#Page_35'>35</a>.</span><br /> +<span style="margin-left: 1em;">Rain, <a href='#Page_17'>17</a>, <a href='#Page_18'>18</a>.</span><br /> +<br /> +Wax, <a href='#Page_48'>48</a>.<br /> +<br /> +Wheat, <a href='#Page_286'>286</a>.<br /> +<br /> +Woods, amount of ash in, <a href='#Page_65'>65</a>.<br /> +<br /> +Woody fibre, <a href='#Page_41'>41</a>.<br /> +<br /> +Wool, <a href='#Page_219'>219</a>.<br /> +<br /> +<br /> +Zeolites, <a href='#Page_90'>90</a>.<br /> +</p> + + +<p>PRINTED BY R. AND R. CLARK, EDINBURGH.</p> + + + +<hr style="width: 65%;" /> +<h2>A CATALOGUE OF BOOKS</h2> + +<h3>PUBLISHED BY ADAM & CHARLES BLACK</h3> + +<h4>EDINBURGH</h4> + + +<p>ADAMSON (<span class="smcap">Robert</span>). The Cottage Garden. Second edition fcap. 8vo, cloth, +limp, 1s.</p> + +<p>ALEXANDER (<span class="smcap">Dr. W. L.</span>). Christian Thought and Work; a series of Morning +Meditations on Passages of Scripture. Second edition, fcap. 8vo, price +5s.</p> + +<p>ANDERSON (Professor). Elements of Agricultural Chemistry. Crown 8vo, +price 6s. 6d.</p> + +<p>ANDERSON (<span class="smcap">Rev. Wm., LL.D</span>., Glasgow). Discourses. Second series, second +edition, crown 8vo, price 6s.</p> + +<p>---- Regeneration. Second edition, crown 8vo, price 6s.</p> + +<p>ANDERSON (<span class="smcap">Rev. James</span>). 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.</p> + +<p>APPERLEY (<span class="smcap">Charles</span>). 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.</p> + +<p>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.</p> + +<p>Sold also in Two Parts:—</p> + +<p>Part I. Structural and Morphological Botany, 10s. 6d.</p> + +<p>Part II. Vegetable Physiology, Classification Glossary, &c., 21s.</p> + +<p>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.</p> + +<p>---- 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.</p> + +<p>---- 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.</p> + +<p>---- 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.</p> + +<p>BEESLY (Rev. E. S.), and REYNOLDS (Rev. S. H.) System of History for the +use of Students. By Rev. <span class="smcap">E. S. Beesly</span> M.A., late of Wadham College, +Oxford, Professor of History, University College, London; and <span class="smcap">Rev. S. H. +Reynolds</span>, Brazenose College, Oxford. [In preparation.]</p> + +<p>BEGBIE (<span class="smcap">James</span>, 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.</p> + +<p>BENNETT (Professor). Clinical Lectures on the Principles and Practice of +Medicine. New edition (the third), pp. 1005, with five hundred +Illustrations, price 30s.</p> + +<p>---- An Introduction to Clinical Medicine. Six Lectures on the Method of +Examining Patients, &c. Fourth edition, 107 Illustrations, fcap. 8vo, +price 5s.</p> + +<p>---- The Pathology and Treatment of Pulmonary Consumption. 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Guy Mannering, or The Astrologer.</span><br /> +<span style="margin-left: 3em;">3. Antiquary</span><br /> +<span style="margin-left: 3em;">4. Rob Roy.</span><br /> +<span style="margin-left: 3em;">5. Old Mortality.</span><br /> +<span style="margin-left: 3em;">6. Black Dwarf, and Legend of Montrose.</span><br /> +<span style="margin-left: 3em;">7. Heart of Mid-Lothian.</span><br /> +<span style="margin-left: 3em;">8. Bride of Lammermoor.</span><br /> +<span style="margin-left: 3em;">9. Ivanhoe.</span><br /> +<span style="margin-left: 2.5em;">10. Monastery.</span><br /> +<span style="margin-left: 2.5em;">11. Abbott.</span><br /> +<span style="margin-left: 2.5em;">12. Kenilworth.</span><br /> +<span style="margin-left: 2.5em;">13. Pirate.</span><br /> +<span style="margin-left: 2.5em;">14. Fortunes of Nigel.</span><br /> +<span style="margin-left: 2.5em;">15. Peveril of the Peak.</span><br /> +<span style="margin-left: 2.5em;">16. Quentin Durward.</span><br /> +<span style="margin-left: 2.5em;">17. St. Ronan's Well.</span><br /> +<span style="margin-left: 2.5em;">18. Redgauntlet.</span><br /> +<span style="margin-left: 2.5em;">19. The Betrothed.</span><br /> +<span style="margin-left: 2.5em;">20. The Talisman.</span><br /> +<span style="margin-left: 2.5em;">21. Woodstock.</span><br /> +<span style="margin-left: 2.5em;">22. Fair Maid of Perth.</span><br /> +<span style="margin-left: 2.5em;">23. Anne of Geierstein, or the Maiden of the Mist.</span><br /> +<span style="margin-left: 2.5em;">24. Count Robert of Paris.</span><br /> +<span style="margin-left: 2.5em;">25. Surgeon's Daughter—Castle Dangerous.</span><br /> +</p> + +<p>---- Poetical Works. Various editions, from 5s. to 36s.</p> + +<p>SCOTT (Sir <span class="smcap">Walter</span>). Miscellaneous Prose Works. Various editions, from +26s. to 84s.</p> + +<p>---- Life of Napoleon Bonaparte. 5 vols., fcap. 8vo, price 20s. People's +edition, 1 vol., royal 8vo, price 10s.</p> + +<p>---- Tales of a Grandfather. Various editions, 6s. to 15s.</p> + +<p>---- Beauties of. Crown 8vo, gilt edges, price 3s. 6d.</p> + +<p>---- Life of, by J. G. Lockhart. Various editions, 7s. 6d. to 30s.</p> + +<p>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.</p> + +<p>---- ON THE DISEASES OF WOMEN. 8vo. [In preparation.</p> + +<p>SMITH (<span class="smcap">Adam</span>, 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 <span class="smcap">J. R. M'Culloch</span>, Esq. Fourth edition, corrected throughout, +and greatly enlarged. 8vo, 16s.</p> + +<p>SPALDING (<span class="smcap">Wm.</span>, M.A.) An Introduction to Logical Science. Fcap. 8vo, 4s. +6d.</p> + +<p>STEVENSON (<span class="smcap">David</span>). Canal and River Engineering. Small 8vo, 4s. 6d.</p> + +<p>STEVENSON (<span class="smcap">Thomas</span>). On Harbours. Crown 8vo. [In the Press.</p> + +<p>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.</p> + +<p>THOMAS (Dr. <span class="smcap">Robert</span>). The Modern Practice of Physic. Eleventh edition, +edited by Dr. Frampton. 2 vols. 8vo, price 28s.</p> + +<p>THOMSON (Professor). Brewing and Distillation. Post 8vo, price 6s.</p> + +<p>TRAILL (Professor). Medical Jurisprudence. Third Edition, post 8vo, +price 5s.</p> + +<p>TRAIL (Rev. W.) The Literary Characteristics and Achievements of the +Bible. Crown 8vo.</p> + +<p>TYTLER (P. F.) History of Scotland. Enlarged and continued to the +Present Time, by the Rev. <span class="smcap">James Taylor</span>, D.D., and adapted to the +purposes of Tuition by <span class="smcap">Alex. Reid</span>, LL.D. Sixth edition, 12mo, 3s. 6d.</p> + +<p>---- Outlines of Modern History. Fifth edition, 12mo, 3s.</p> + +<p>---- Outlines of Ancient History. Fourth edition, 12mo, 3s.</p> + +<p>VEITCH (Rev. <span class="smcap">Wm.</span>) Greek Verbs, Irregular and Defective. Post 8vo, price +6s.</p> + +<p>WALPOLE (<span class="smcap">Horace</span>). The Castle of Otranto. Fcap. 8vo, Illustrated, gilt +edges, price 2s. 6d.</p> + +<p>WARDLAW (Dr.) Systematic Theology. A Complete System of Polemic +Divinity. In three vols., demy 8vo, price 21s.</p> + +<p>WESTGARTH (<span class="smcap">William</span>). Australia; its Rise, Progress, and Present +Condition; with Map. Fcap. 8vo, price 3s. 6d.</p> + +<p>WHEWELL (Dr.) New Edition of Mackintosh's Ethical Philosophy. Demy 8vo. +Price 10s. 6d.</p> + +<p>WHITE (<span class="smcap">Robert</span>). Madeira; its Climate and Scenery. Second edition by <span class="smcap">J. +Y. Johnson</span>. With numerous Illustrations, and a Map of the Island, crown +8vo, price 7s. 6d.</p> + +<p>WILSON (<span class="smcap">John</span>). British Farming, a description of the mixed husbandry of +Great Britain. Pp. 569, profusely illustrated. Demy 8vo, price 12s.</p> + +<p>YOUNG (<span class="smcap">Andrew</span>). The Angler and Tourist's Guide to the Northern Counties +of Scotland, with Instructions to Young Anglers. 18mo, price 2s.</p> + + + +<hr style="width: 65%;" /> +<h2><b>DE QUINCEY'S WORKS</b>.</h2> + + +<h3>AUTHOR'S EDITION.</h3> + +<h4><i>In Fifteen Volumes, price 4s. 6d. each</i>,</h4> + +<h5>NEW EDITION OF</h5> + +<h3><b>THE WORKS OF THOMAS DE QUINCEY</b></h3> + +<h4>"THE ENGLISH OPIUM EATER"</h4> + +<hr style='width: 45%;' /> + +<p> +Vol. I. <span class="smcap">Confessions of an English Opium-Eater</span>.<br /> +<span style="margin-left: 2em;">II. <span class="smcap">Recollections of the Lake Poets</span>.</span><br /> +<span style="margin-left: 1.5em;">III. <span class="smcap">Last Days of Immanuel Kant</span>.</span><br /> +<span style="margin-left: 2em;">IV. <span class="smcap">The English Mail-Coach</span>.</span><br /> +<span style="margin-left: 2.5em;">V. <span class="smcap">Dr. Samuel Parr, etc.</span></span><br /> +<span style="margin-left: 2em;">VI. <span class="smcap">Richard Bentley, etc.</span></span><br /> +<span style="margin-left: 1.5em;">VII. <span class="smcap">Protestantism and other Essays</span>.</span><br /> +<span style="margin-left: 1em;">VIII. <span class="smcap">Leaders in Literature</span>.</span><br /> +<span style="margin-left: 2em;">IX. <span class="smcap">The Cæsars, and other Writings</span>.</span><br /> +<span style="margin-left: 2.5em;">X. <span class="smcap">Rhetoric and Style</span>.</span><br /> +<span style="margin-left: 2em;">XI. <span class="smcap">Coleridge and Opium Eating</span>.</span><br /> +<span style="margin-left: 1.5em;">XII. <span class="smcap"> Speculations, Literary and Philosophic</span>.</span><br /> +<span style="margin-left: 1em;">XIII. <span class="smcap">Conversation, and other Papers</span>.</span><br /> +<span style="margin-left: 1.5em;">XIV. <span class="smcap">The Autobiographic Sketches</span>—1790-1803.</span><br /> +</p> + +<p>Volume XIV. concludes the series of Mr. De Quincey's Works, as arranged +by himself; but in order to render this Edition complete, a +<span class="smcap">Supplementary Volume</span> (XV.) will be added, containing the Biographies of +<span class="smcap">Shakspeare</span>, <span class="smcap">Pope</span>, <span class="smcap">Goethe</span>, and <span class="smcap">Schiller</span>, 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 <span class="smcap">Political Parties +of Modern England</span>. Also a Complete <span class="smcap">General Index</span> to the whole Works.</p> + +<hr style='width: 45%;' /> + +<p><b>EDINBURGH: ADAM AND CHARLES BLACK</b></p> + + + +<hr style="width: 65%;" /> +<h2>NEW EDITION OF KITTO'S CYCLOPÆDIA.</h2> + +<h4><i>In royal 8vo, Volume I. (A to E), pp. 884. Price</i> £1: 0: 0.</h4> + +<h3>A THIRD EDITION OF</h3> + +<h2>KITTO'S</h2> + +<h2><i>Cyclopædia of Biblical Literature.</i></h2> + +<h4>Edited by the Rev. WILLIAM LINDSAY ALEXANDER, D.D., with the assistance +of numerous contributors.</h4> + +<p>Illustrated by Numerous Engravings on Wood and Steel.</p> + +<p>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.</p> + +<p>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.</p> + +<p><i>List of Contributors.</i></p> + +<p> +Beard, J. R., D.D.<br /> +<br /> +Bell, G. M.<br /> +<br /> +Brown, John, D.D., late Professor of<br /> +Exegetical Theology to the United Presbyterian<br /> +Church of Scotland.<br /> +<br /> +Browne, Henry, M.A., Vicar of Pevensey.<br /> +<br /> +Cairns, John, D.D.<br /> +<br /> +Candlish, James S., M.A.<br /> +<br /> +Credner, Karl August, D.D., late Professor<br /> +of Theology at Giessen.<br /> +<br /> +Davidson, Samuel, D.D., LL.D.<br /> +<br /> +Denham, Joshua Fred., M.A., F.R.S.<br /> +<br /> +Deutsch, Emanuel, of the University of<br /> +Berlin, M. Ger. Or. Soc., etc., British<br /> +Museum.<br /> +<br /> +Doran, John William, LL.D., Rector of<br /> +Beeston, St. Lawrence, Norfolk.<br /> +<br /> +Farrar, Frederic W., M.A., late Fellow of<br /> +Trinity College, Cambridge.<br /> +<br /> +Geikie, Archibald, F.R.S.E., F.G.S., of the<br /> +Geological Survey.<br /> +<br /> +Ginsburg, Christian D.<br /> +<br /> +Goold, William Henry, D.D., Professor of<br /> +Theology to the Reformed Presbyterian<br /> +Church.<br /> +<br /> +Gotch, F. W., D.D., President of the Baptist<br /> +College, Bristol; Examiner in Hebrew<br /> +to the London University.<br /> +<br /> +Gowan, Anthony T., D.D.<br /> +<br /> +Hävernick, Heinrich August Christ., late<br /> +Professor of Theology at Königsberg.<br /> +<br /> +Holmes, Peter, D.D., F.R.A.S., of Magdalen<br /> +Hall, Oxford.<br /> +<br /> +Jamieson, Robert, D.D., Minister of St.<br /> +Paul's, Glasgow.<br /> +<br /> +Jennings, Isaac.<br /> +<br /> +Kitto, John, D.D., F.A.S.<br /> +<br /> +Leathes, Stanley, M.A.<br /> +<br /> +Lyon, William P., B.A.<br /> +<br /> +M'Causland, Dominick, Q.C., LL.D.<br /> +<br /> +Madden, Fred. W., M.R.S.L., Brit. Museum.<br /> +<br /> +Michelson, E., Ph. D. of the University of<br /> +Heidelberg.<br /> +<br /> +Morren, Nathanael, M.A.<br /> +<br /> +Newman, Francis W., late Fellow of Balliol<br /> +College, Oxford; Professor of Latin in<br /> +the University of London.<br /> +<br /> +Newth, Samuel, M.A., Professor, New<br /> +College, London.<br /> +<br /> +Nicholson, John, B.A. Oxford; Ph. D.<br /> +Tübingen.<br /> +<br /> +Nicholson, W. A., M.D.<br /> +<br /> +Poole, Reg. Stuart, British Museum.<br /> +<br /> +Porter, J. Leslie, M.A., Professor of Sacred<br /> +Literature, Assembly's College, Belfast.<br /> +<br /> +Royle, J. F., M.D., F.R.S., F.L.S., F.G.S.<br /> +<br /> +Ryland, J. E.<br /> +<br /> +Smith, C. Hamilton, Lieut.-Colonel, K.H.<br /> +and K.W., F.R.S., F.R.L.S., etc.<br /> +<br /> +Smith, John Pye, D.D., F.R.S., F.G.S.<br /> +<br /> +Stebbing, Henry, D.D. of St. John's College,<br /> +Cambridge.<br /> +<br /> +Tholuck, August, D.D., Professor of Theology<br /> +in the University of Halle.<br /> +<br /> +Wace, Henry, M.A.<br /> +<br /> +Wright, William, M.A. and LL.D. of Trinity<br /> +College, Dublin.<br /> +</p> + +<hr style='width: 45%;' /> + +<p>EDINBURGH: ADAM AND CHARLES BLACK.</p> + + + +<hr style="width: 65%;" /> +<h2>NEW EDITION, 1862.</h2> + +<h4><i>In folio, half bound morocco, gilt edges, price</i> £3,</h4> + +<h4><i>A new edition of</i></h4> + +<h3><b>BLACK'S GENERAL ATLAS OF THE WORLD</b>,</h3> + +<p>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.</p> + +<p><i>List of Maps in the order in which they occur.</i></p> + +<p> +PHYSICAL GEOGRAPHY, <span class="smcap">Etc.</span><br /> +<br /> +<span style="margin-left: 0.5em;">1. The World in Hemispheres, with Comparative View of Mountains and Rivers.</span><br /> +<span style="margin-left: 0.5em;">2. The World on Mercator's Projection.</span><br /> +<span style="margin-left: 0.5em;">3. Physical and Ethnographical Charts of the World.</span><br /> +<span style="margin-left: 0.5em;">4. Zoological and Botanical Charts of the World.</span><br /> +<span style="margin-left: 0.5em;">5. Isothermal Chart shewing the Temperature of the Earth's Surface.</span><br /> +<span style="margin-left: 0.5em;">6. Northern and Southern Celestial Hemisphere.</span><br /> +<span style="margin-left: 0.5em;">7. Solar System, Theory of the Seasons, etc.</span><br /> +<br /> +<br /> +EUROPE.<br /> +<br /> +<span style="margin-left: 0.5em;">8. Europe.</span><br /> +<span style="margin-left: 0.5em;">9. England (North Part).</span><br /> +10. ....... (South Part).<br /> +11. Scotland (North Part).<br /> +12. ........ (South Part).<br /> +13. Ireland.<br /> +14. France.<br /> +15. Switzerland.<br /> +16. Holland and Belgium.<br /> +17. Railway Map of Central Europe.<br /> +18. Germany.<br /> +19. Austria.<br /> +20. Prussia.<br /> +21. Denmark.<br /> +22. Sweden and Norway, with Baltic Sea.<br /> +23. Russia in Europe.<br /> +24. Spain and Portugal.<br /> +25. Italy (North).<br /> +26. ..... (South).<br /> +27. Turkey in Europe.<br /> +28. Greece and Ionian Islands.<br /> +<br /> +<br /> +ASIA.<br /> +<br /> +29. Asia.<br /> +30. Turkey in Asia.<br /> +31. Palestine.<br /> +32. Persia, Afghanistan, and Beloochistan.<br /> +33. India.<br /> +34. China.<br /> +35. Indian Archipelago, and Further India,<br /> +<span style="margin-left: 2em;">including Burmah, Siam, etc.</span><br /> +<br /> +<br /> +AFRICA.<br /> +<br /> +36. Africa, with Barth's, Livingstone's, and Burton's Routes.<br /> +37. Egypt.<br /> +38. South Africa.<br /> +<br /> +<br /> +AMERICA.<br /> +<br /> +39. North America, with Enlargement of British Columbia.<br /> +40. British America and Arctic Regions.<br /> +41. Canada East, New Brunswick, Nova Scotia, etc.<br /> +42. Canada West.<br /> +43. United States of America (General Map).<br /> +44. The Eastern or Principal States.<br /> +45. The Western States (California, Oregon, Utah, etc.)<br /> +46. Mexico, Central America, etc.<br /> +47. West India Islands.<br /> +48. South America.<br /> +49. Venezuela, New Granada, Equador, and Peru.<br /> +50. Chili—Argentine Republic, and Bolivia.<br /> +51. Brazil, Uruguay, and Guayana.<br /> +<br /> +<br /> +AUSTRALIA AND ISLANDS OF THE PACIFIC.<br /> +<br /> +52. Australia.<br /> +53. New Zealand, Tasmania, and Western Australia.<br /> +54. Polynesia and Pacific Ocean.<br /> +55. The World as known to the Ancients.<br /> +56. The Principal Countries of the Ancient<br /> +<span style="margin-left: 2em;">World, with the Roman and Persian</span><br /> +<span style="margin-left: 2em;">Empires.</span><br /> +</p> + +<p><i>Accompanied by Sketch Maps of the Federal and Confederate States, and +of a portion of Mexico.</i></p> + +<hr style='width: 45%;' /> + +<p>EDINBURGH: ADAM AND CHARLES BLACK.</p> + + + + + + + + + +<pre> + + + + + +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-h.htm or 24931-h.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. 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