UNITED STATES OF AMERICA. 
 
 
LETTERS 
 
 ON 
 
 MODERN AamOULTURE, 
 
 BARON VON LIEBIG 
 
 Edited by JOHN BLYTH, M.D., 
 
 PEOFESSOE OF CHEMI8TKT, QUEEN'S COLLEGE, COEK. 
 
 WITH ADDENTDA, 
 
 BY A PRACTICAL AGRICULTURIST. 
 
 EMBRACING YALUABLE SUGGESTIONS, ADAPTED TO THE WANTS OF 
 AMERICAN FARMERS. 
 
 NEW YORK: 
 
 JOHN WILEY, 56 WALKER STREET. 
 
 1859. 
 
Entered, according to Act of Congi-ess, in the year 1859, by 
 
 JOHN WILEY, 
 
 in the Clerk's Office of the District Court of the United States for the Southern 
 District of New York. 
 
 6"^^^ 
 
 K. CRAIGHEAD, 
 
 Stereotyper and Electrotyper, 
 
 (Cavton ISiiiltiing, 
 
 81, 83, and 85 Centre Street. 
 
TO 
 
 HIS MAJESTY MAXIMILIAN II. 
 
 KING OP BAVARIA. 
 
 To the circle of men devoted to Art and Science, whom 
 Your Majesty assembled around you last winter, for the 
 purpose of obtaining from their discourses and their 
 animated interchange of opinions a reflection of the intel- 
 lectual movement of the age, I am in a great measure in- 
 debted for the impulse which led to the researches to which 
 these Letters on Modern Agriculture owe their origin. 
 
 If, therefore, I venture, with the most profound respect, to 
 dedicate to Your Majesty, who takes the same kind and 
 active interest in the practical life of the nation and its wel- 
 fare, as in science and its progress, this Work, which is in- 
 tended to bring about the union of the natural sciences with 
 agriculture, and to effect their beneficial co-operation, I do 
 
IV DEDICATION. 
 
 SO in grateful remembrance of the active and powerful 
 interest which Your Majesty has deigned to take in the 
 labours of 
 
 Your Majesty's 
 
 Most obedient humble Servant, 
 
 JUSTUS VON LIEBIG. 
 
 Munich, April 2, 1859. 
 
EDITOE'S PEEFACE. 
 
 These important and interesting Letters on "Modem 
 Agriculture" are addressed by Baron Liebig, not to agri- 
 culturists alone, but to every one wlio takes an interest in 
 the welfare of bis country. 
 
 The wants of an increasing population, and tbe danger 
 of a possible stoppage, at any moment, of supplies drawn 
 from foreign sources, make all feel a deep interest in tbe 
 "discovery of tbe means of producing more bread and 
 meat on a given surface." Landed proprietors, practical 
 agriculturists, and men of science, bave all of late years 
 devoted tbeir united energies to solve tbis important pro- 
 blem. IVom tbe efforts of so many anxious labourers, as 
 migbt be expected, a corresponding barvest of practical 
 results has been obtained. Tbe autbor, wbo bas for years 
 occupied bimself witb tbe elucidation of tbe laws of tbe 
 nutrition of plants, passes in review, in these Letters, tbe 
 
vi editor's preface. 
 
 mass of practical facts thus acquired, and by the light of 
 science endeavours to give them their true import, and to 
 deduce from them fundamental laws of general application 
 in agriculture. 
 
 It is not long since the humus theory occupied every 
 work on agriculture, and the fertility of our fields was 
 described as entirely dependent on the presence of this 
 supposed valuable substance. The real nature of humus 
 is, however, now understood, as well as the conditions 
 under which alone it can prove valuable in the nutrition 
 of plants. 
 
 It is also now well known, that plants cannot grow and 
 attain complete development, without the simultaneous 
 action of atmospheric food and certain mineral elements, 
 which are absolutely indispensable to their existence. The 
 author has in these Letters shown, that no single element 
 of these indispensable mineral matters possesses superiority 
 over another, but that they are all of equal value to the 
 life of a plant. Hence, if one of them be absent in the 
 soil, a fully developed plant cannot be produced by the 
 others, until the deficient element be supplied. But from 
 the importance of this deficient element in a given case, 
 we are not entitled to infer its equal efiiciency in other 
 cases, where the same conditions may not exist ; — and yet, 
 
vu 
 
 this fallacy lies at the root of many of the practical opera- 
 tions of agriculture. 
 
 The author points out the nature of this fallacy, and in 
 the discussion of this subject, brings forward new and 
 important facts connected with the nutrition of plants, and 
 with the mode of action of some special manures. The 
 mineral food of plants is shown by him to exist in the soil 
 in two different states ; in the one, it is immediately avail- 
 able ; in the other, it is not yet brought by decomposition 
 into a condition for absorption by the roots. In every case 
 the produce of a field and the duration of its fertility bear 
 a fixed relation to the sum of the available food in the 
 soil. Hence, if by mechanical or chemical means applied 
 to the soil, we render the absorption of this food by plants 
 more rapid, we thereby increase the amount of produce in 
 a given time, and thus more quickly exhaust the stock. 
 At the end of this given time the field will, for agricul- 
 tural purposes, be unproductive, if the mineral matters 
 removed by the crops be not restored. 
 
 The author directs attention to the faxjt, that this funda- 
 mental principle has been lost sight of in some of the 
 systems of modern high farming, which have been based 
 on the assumption that the available mineral food of plants 
 in arable soils is inexhaustible. He urgently points out 
 
viii editor's preface. 
 
 that in stimulating the productiveness of our fields by a 
 system of high farming, without at the same time restoring 
 all the mineral matter removed, the present occupiers of 
 the land may rejoice in their abundant crops, but the in- 
 evitable result of this system will be the ultimate exhaus- 
 tion of the soil. 
 
 The editor has endeavoured in this translation to convey 
 to the reader as faithful a transcript as possible of Baron 
 Liebig's views ; and accuracy has been farther insured by 
 the revision of the proofs by the author. In conclusion, 
 the editor begs to acknowledge the kind assistance of his 
 friend Dr. Hofmann, from whom he has received many 
 valuable suggestions whilst the sheets were passing through 
 the press. 
 
 JOHN" BLYTH. 
 
 Queen's College, Cork, 
 April 2, 1859. 
 
PREFACE. 
 
 The state of matters to which the contents of these Let- 
 ters refer, exists in reality in Germany alone ; and I should 
 be taking an erroneous view of the actual position of Bri- 
 tish agriculturists, were I to attribute to them the leading 
 views entertained by Grerman and perhaps French agricul- 
 turists. These letters must therefore be regarded as a mir- 
 ror in which the scientific principles already established, 
 and certain erroneous doctrines prevailing in practice are 
 reflected side by side ; and each individual must be left to 
 draw his own conclusions, on comparing his own acts with 
 the standard thus furnished him. 
 
 Upon the whole, English agriculture, as a rule, is based 
 on the same spoliation system which exists elsewhere ; for 
 though some certainly pursue a rational system, there are 
 but too many who act otherwise. 
 
 The remarks which I have made on writers on agricul- 
 ture and on agricultural training schools, must be received, 
 in like manner, with the same limitation. I am too little 
 acquainted with the English agricultural institutions to 
 pass judgment upon them, and my strictures can only be 
 
X PEEFACE. 
 
 regarded as applying to those of Germany. With respect 
 to the English agricultural chemists, I also readily ac- 
 knowledge that Thos. Way, Professor Hodges, and others, 
 have by their researches rendered the greatest service to 
 agriculture. 
 
 I cannot, however, concur in opinion with those who 
 would base all progress in agriculture upon elementary 
 analysis and on other useless chemical operations ; nor 
 with those who forget that such progress results only from 
 the investigation of scientific laws, and from a correct com- 
 prehension of the facts observed, — things that cannot, like 
 products in a manufactory, be procured wholesale by a 
 mere outlay of capital and by a course of experiments. 
 
 The great progress made in agriculture, since the end of 
 last century, has been essentially confined to improvements 
 in the practical part, by which I here mean to designate 
 the technical operations of farming; but these improve- 
 ments have paved the way for the new and higher develop- 
 ment of the present day. It is in the nature of things, that 
 in all technical pursuits, and more especially in agriculture, 
 the perfecting of the practice should precede the effective 
 application of scientific principles. So long as the man 
 engaged in a technical pursuit finds that there is still ad- 
 vantage to be derived from improvements in the manage- 
 ment of his business, he will not trouble himself with other 
 matters. But by improvements in the practice, or in the 
 management of his business, everything desirable is not 
 attained ; the practical operations in themselves give him 
 
PEEFACE. XI 
 
 no insight into his own acts, nor a reliable standard for the 
 value of his observations and experience : at last he will 
 not permit himself to be swayed by the customary mode 
 of proceeding. It is now that he turns to science to satisfy 
 his requirements. 
 
 As generally happens in the period of transition into a 
 new state of things, a conflict has of late years been carried 
 on between practice and science ; the former was unable 
 to deal properly with the unwonted resources placed at its 
 disposal by the latter ; and it is easy to account for the 
 cause of this conflict. 
 
 If, in fact, a person of the educated classes, who is not 
 an agriculturist, were to peruse the agricultural works and 
 journals that have appeared of late years, he would find 
 that the preponderating majority of agricultural writers 
 are quite agreed on this one point, that the views which I 
 have put forward on agriculture, have no practical value, 
 and must be looked upon as in part refuted. They main- 
 tain that experience, which is older than science, has long 
 since taught the practical man what is needful for him ; 
 that the result proves his system of cultivation to be the 
 best suited to existing circumstances ; and that his abun- 
 dant and increasing crops are irrefragable proofs of the 
 soundness of the views which guide his practice. 
 
 These expressions and opinions are not generally appli- 
 cable and valid ; they are not, however, groundless. The 
 agricultural literature in which these views are put for- 
 ward, exists in reality only for the class of thriving agri- 
 
XU PREFACE. 
 
 culturists who are in a position to buy and possess agricul- 
 tural manuals and journals ; and it is evident, that the 
 literature will reflect the requirements, the wishes, and the 
 practice of these agriculturists to whom it owes its exist- 
 ence. It is not in the nature of things that it should be 
 otherwise. As a rule, an agriculturist of this class is a 
 producer of flesh and corn, and is generally possessed of a 
 good property and plenty of capital ; his fields comprise 
 meadows and arable land ; he keeps a large stock of cattle, 
 produces plenty of farm-yard manure, and is not sparing 
 in its use. If he happens to be short of manure, he has, at 
 all events, money to buy guano. Chili-saltpetre, bone, earth, 
 and rape-dust. He knows the value of farm-yard manure 
 and of the supplementary manures just named, and how 
 to use them to the best advantage. His steward attends to 
 the rotation of crops which has been permanently fixed 
 upon, and to the application of manure at the proper sea- 
 son, — things which do not require the teachings of science ; 
 he has to be guided, he tells you, by other circumstances 
 which give him quite trouble enough. 
 
 The wealthy landed proprietor is an educated man who 
 has certain intellectual wants. Agricultural literature satis- 
 fies these. The writer on agriculture endeavours to prove, 
 by theoretical reasoning, the excellence of empirical prac- 
 tice ; he defends the views of the practical man, and strives 
 to invest them with the authority of science. Even if the 
 explanations are at times in complete opposition to un- 
 doubted truths, they have at all events this much in their 
 
PKEFACE. Xlll 
 
 favour, viz., tliat the agriculturist believes them to be i:i 
 accordance with his own experience ; and, indeed, the ob- 
 ject of the writer does not extend beyond securing the 
 satisfaction of the practical man, by showing what is termed 
 the agreement of the practice of agriculture with the the- 
 ory. Thus, for instance, in the production of corn and 
 flesh, the alkalies in the farm-yard manure remain in the 
 field, and in the progress of cultivation their quantity ra- 
 ther increases than diminishes ; a restoration of these alka- 
 lies is therefore not required, and would often be super- 
 fluous. This circumstance, which arises from the kind of 
 crop grown, the writer explains to the practical man to be 
 the result of the nature of his soil ; he informs him that 
 there is no necessity to restore the alkalies removed, be- 
 cause his soil contains an inexhaustible quantity of them. 
 It is true that this statement is directly opposed to all that 
 Chemistry teaches ; but then it is a matter of indifference 
 whether or not the soil is inexhaustible, if the main point 
 be made out, viz., that there is no compensation of these 
 matters required from without by purchase, &c. 
 
 The writer on agriculture further informs the practical 
 man, why guano and other manures used in aid of farm- 
 yard manure are so beneficial. It is clear, he says, that all 
 these matters contain in the nitrogen a constituent common 
 to all of them ; and as the employment of each is attended 
 by a similar result, viz., by a corresponding increase in the 
 amount of produce, it is obvious that the effect must be 
 attributed to one and the same cause in all. The practical 
 
XIV PKEFACE. 
 
 man is told that in the corn and flesh produced on his land 
 he removes nitrogen ; that the exhaustion of the soil is the 
 consequence of this removal ; and that, of course, by re- 
 placing this nitrogen, the productiveness of his fields is 
 restored. To question the fact of the restoration of fertility 
 to land by guano, bone-dust, or rape-dust, would be an act 
 of great folly, for this fact is borne out by the experience 
 of the practical man ; the latter, therefore, fully accepts the 
 explanation offered, although there be in it only the merest 
 semblance of truth. He is quite satisfied with the belief 
 that his system of cultivation has been shown to rest on a 
 rational and scientific basis; which, in reality, is not the 
 case. 
 
 Practical questions, such as the following : Why the 
 after-effects of the above-mentioned manures are not uni- 
 form with those of farm-yard manure, but differ so much 
 from them : or why clover no longer grows on many 
 fields ; or why peas, again, yield good crops on the same 
 field only after long intervals : such questions as these, of 
 course, do not engage the attention of the agricultural wri- 
 ter. He speaks of such matters as if ordained by Nature ; 
 which cannot be altered ; and for which the agriculturist 
 must therefore make due allowance in his system of hus- 
 bandry. But let the practical man only succeed — which, 
 however, is not likely to be the case — in solving these 
 questions, or in overcoming a difficulty which may have 
 been placed in his way by the writer himself, and the lat- 
 ter will at once proceed with right good will to prove to 
 
PKEFACE. XV 
 
 him by a series of chemical analyses the intimate relation 
 between theory and practice. 
 
 These precepts of agricultural writers do no harm to the 
 agriculturists for whom they are intended. These indi- 
 viduals maintain their fields in a permanent state of fer- 
 tility, by means of farm-yard manure, or by the purchase 
 of guano and other manuring agents ; their simple system 
 of cultivation affords no room for exhaustion of the soil. 
 Whatever constituents they remove from the land in the 
 form of corn and flesh, they replace completely, and even 
 in excess. 
 
 Although scientific doctrines play a very subordinate 
 part in the system of cultivation pursued by these fortu- 
 nate landed proprietors, inasmuch as their entire know- 
 ledge consists in a few recipes which might be written upon 
 a card ; yet it is for them that the most esteemed agricul- 
 tural hand-books and manuals, and the greater number of 
 the articles in agricultural journals are written ; it is for 
 them that books on soils and manures are published, and 
 enriched with stores of scientific learning from the domains 
 of chemistry, physics, botany, and geognosy ; it is for their 
 benefit that so many chemical analyses of corn and straw, 
 hay and turnips, are made. They do not, indeed, read or 
 understand all that is written, because, in fact, there is no 
 intelligible meaning in it ; and they are quite aware that 
 these rows of figures do not advance their business one 
 hair's-breadth ; still they are delighted with all this parade 
 of learning, on account of the seeming deep scientific basis 
 
XVI PREFACE. 
 
 assigned thereby to agriculture, which they follow with so 
 much ardour and profit. 
 
 After the wealthy landed proprietors comes a second 
 class of agriculturists, who possess land, but less capital 
 than the former. They obtain good crops by the simple 
 cultivation of their fields with farm-yard manure; they 
 purchase but a small quantity of guano, or other manuring 
 agents ; and trusting to the theory maintained by writers 
 on agriculture, that their fields are inexhaustible in mineral 
 matters, — which is intended to apply to a different system 
 of cultivation from theirs, — they believe that there are no 
 limits to the fertility of their land. As they have as yet 
 observed no failure in the conditions of its fertility, they 
 are of opinion that it will be time enough to devise means 
 to meet the necessity when it occurs. 
 
 These men also read the agricultural journals, and are 
 quite satisfied in their own mind that the principles of 
 science are not suited to their system of husbandry. They 
 re-echo the opinions of the men of the first class, and are 
 warm supporters of the precepts of the writers on agricul- 
 ture, although the system of cultivation derived from these 
 teachers brings their fields every year nearer that ruin to 
 which they must inevitably come by following such a 
 system. 
 
 The resistance which science has met with on the part 
 of practical men belonging to this class, is partly due to 
 ignorance of its true princij)]es, partly to a wrong concep- 
 tion and interpretation of the same. 
 
PKEFACE. XV 11 
 
 If I have criticised the false views and opposition of 
 these men, in purely chemical questions regarding the soil, 
 manures, and the nutrition of plants, with a severity in- 
 spired by sincere conviction, it must not be overlooked 
 that they were the aggressors in the conflict. An attack 
 of their views on my part would have been inexcusable ; 
 for, with that simplicity which characterises those who pre- 
 sume to j udge of things they do not understand, they have 
 candidly avowed that chemistry and the natural sciences 
 are branches of knowledge unknown to them. They are 
 all, without exception, men deserving the esteem which 
 they enjoy in their social relations, and whose feelings as 
 individuals I could not have the most distant intention of 
 wounding ; but when they step forward as supporters and 
 propagators of precepts, which have nothing to recommend 
 them beyond the fact that people have for half a century 
 pursued a system of cultivation in conformity with them ; 
 which are devoid of all rational basis, and are quite be- 
 neath the present position of chemistry and the natural 
 sciences, — precepts which must in process of time dry up 
 the sources of prosperity of the agricultural population, — I 
 should hold it to be a crime against the public interest 
 were I to be restrained by any consideration for indi- 
 viduals, or the position they may occupy, from laying bare 
 the weakness and flimsiness of their arguments, and from 
 exposing their total ignorance of the first principles of 
 chemistry and the natural sciences. 
 
 From want of a proper insight into their own pursuit, 
 
XVUl PKEFACE. 
 
 these men are in their blindness the worst enemies ol 
 science, the objects of which they do not comprehend. 
 
 The scientific questions connected with agriculture aro, 
 in their consequences, of too great importance for any one 
 to enter upon their discussion, before he has seriously con- 
 sidered whether he really understands the subject. 
 
 One of the most important objects of the practical man 
 is to discover active manures, by the use of which barren 
 fields may be made productive, and the produce of fertile 
 fields be doubled ; but they will never be found, or only 
 accidentally, by seeking them blindfold in an empirical 
 manner. The practical man does not know that for years 
 the study of small and apparently insignificant things must 
 be pursued, before the mind is prepared to grasp questions 
 of importance. 
 
 The method followed by science m seeking out active 
 manures is very different, much more toilsome, but more 
 certain. It is rendered doubly difficult from the fact, that 
 the man of science who adopts it has not only to combat 
 the erroneous notions prevailing in the domain of practice, 
 but also the errors of his own science, which have their 
 influence over him, and may cause him at times to make a 
 false step ; but he knows that the path leading to light is 
 thorny and dark, and the perception of an error is in itself 
 a victory. 
 
 The prevailing agricultural literature has nothing in the 
 shape of aid to offer to the small landed proprietor or far- 
 mer ; or to him who possesses little or no capital, no good 
 
PREFACE. XIX 
 
 arable land, no meadow, an insufficient stock of cattle, and, 
 accordingly, little or no farm-yard manure ; and those who 
 cultivate commercial plants, such as tobacco, hops, flax, 
 hemp, or the vine, find in it no information, no insight 
 into the nature of their pursuit, but only insufficient rules, 
 suited to particular localities. 
 
 Science should, however, be the common property of 
 all ; it should bestow aid on all who require and seek it, 
 and should increase the intellectual store of rich and poor 
 who are sincerely striving after truth. 
 
 From the preceding remarks may be gathered the rea- 
 sons which have induced me to publish these letters on 
 Modern Agriculture. I am desirous to make the educated 
 men of the nation acquainted with the principles which 
 have been established by chemistry in connection with the 
 nutrition of plants, the conditions of the fertility of soils, 
 and the causes of their exhaustion. Should I be fortunate 
 enough to impress upon a wider circle the conviction of 
 the value of these principles, and of their extreme import- 
 ance in a national and economic point of view, I shall look 
 upon one of the tasks of my life as accomplished. With 
 the aid of the educated men to whom I address myself, 
 success is, in my opinion, certain ; but without their assist- 
 ance it appears to me to be impossible. 
 
 As regards those agriculturists who oppose the teaching 
 of science from ignorance of its objects, I hold it of the 
 greatest importance to be unwearied in our efforts in direct- 
 ing their attention to the facts upon which scientific prin- 
 
XX PKEFACE. 
 
 ciples rest ; for if we can but succeed in inducing them to 
 reflect on the proofs of these principles, thej may be con- 
 sidered as converts to the doctrines of science. 
 
 The laws revealed by the study of the natural sciences 
 will determine the future intellectual and material progress 
 of countries and nations ; every individual is personally 
 interested in the questions connected with their application. 
 
 [n conclusion, I have to state that I have been indebted 
 for a number of facts in Letters YI. and YII. to an excel- 
 lent article in " Chambers's Information for the People," 
 written, as I have since been informed, by K. Russell, Esq., 
 Kilwhiss. 
 
CONTENTS 
 
 LETTER I. 
 
 The conflict between Science and Practical Agriculture — The foundation of 
 Agriculture is experience — Progress founded on experience has its limits 
 — The connection of Agriculture with Chemistry and the subsequent 
 reaction — Progress in Agriculture must be based on the Inductive Method 
 — False teachers of Agricultural Science — Practice based on the blind 
 experience of others leads to error — The rejection of scientific teaching by- 
 practical men due to their ignorance of the real object of Science — The 
 solution by mere practical men of questions proposed by Agricultural 
 Societies cannot advance Agriculture — The rejection of all scientific 
 instruction by practical men only leads to self-deception 1 
 
 LETTEK 11. 
 
 Present profit is the leading principle of the prevailing system of Husbandry 
 — This system is one of danger to Agriculture — GTeneral view of the 
 Nutrition of Plants — Atmospheric and Mineral Food — The absolute neces- 
 sity to Plants of aU the Constituents of their Mineral Food — Present 
 views of the Nutrition of Plants erroneous — Rain water does not dissolve 
 out the Mineral matters in the Soil — Remarkable absorbent power of Soils 
 for the soluble Mineral Food of Plants, and particularly for Potash, Ammo- 
 nia, and Phosphoric Acid — This power is limited, and varies with the Soil 
 — Organic matter in the Soil materially modifies this power 19 
 
 LETTER ni. 
 
 Our cultivated plants do not receive their food from Solution — Roots of plants 
 derive their Nourishment only from those portions of Soil absolutely in 
 contact with them — This view supported by the composition of River, 
 Well, and Drainage water — The Roots of plants must themselves exert 
 some peculiar action in Nutrition — The Life of bnd-plants endangered by 
 
XXU CONTENTS. 
 
 food when in Solution — In Water-plants the laws for the absorption of 
 Food must differ from those of Land-plants — The Ash of duck- weed showa 
 that plants have a Power of selecting their Food — Reason why mud from 
 stagnant pools is a good Manure — Remarkable power for absorbiDg Mois- 
 ture possessed by Soils — By absorption and evaporation of Moisture, the 
 Soil is warmed or cooled — Great importance of this fact to Vegetation — 
 The two Sources from which Moisture is absorbed by the Soil — Natural 
 Law deduced from the above facts 30 
 
 LETTER IV. 
 
 The Belief in the value of Humus no longer exists ; its Action now ascertained 
 — Effect of the Salts of Ammonia not dependent on their Nitrogen — The 
 action of Nitrates like that of the Salts of Ammonia — Experiments with 
 Nitrates and Chlorides — Experiments with Salts of Ammonia alone, and 
 with the addition of Common Salt — Solubility of the Earthy Phosphates in 
 solutions of Chlorides of Ammonium and of Sodium, and of Nitrate of Soda 
 — Experiments with these Salts — Their Solvent Action similar to that of 
 Carbonic Acid water — The Salts of Ammonia are decomposed in the soil ; 
 their twofold action — Difference in the Comportment of Salts of Potash and 
 of Soda in the Soil — Potash extracted by Sulphate of Ammonia from silicates 
 — Application of the Action of Chili Saltpetre, Salts of Ammonia, and 
 Chloride of Sodium to explain the increase of fertility in the soil, and the 
 Nutrition of Plants 41 
 
 LETTER Y. 
 
 No free Ammonia in the SoU — The amount of Food obtained from the soil 
 by plants is in proportion to the absorbent Root-surface — The early deve- 
 lopment of Roots due to the accumulation of Nourishment in the surface 
 soil — Estimations of the quantity of Ammonia in our cultivated fields — A 
 deficient crop not due to the Absence of Ammonia in the soil — Experi- 
 ments with salts of Ammonia; the crops only slightly increased thereby — 
 Increase of produce due to accompanying Minerals —Experiments of Lawes 
 and Kuhlmann with salts of Ammonia, &c. — The fertility of a field depend- 
 ent on the sum of the Mineral matters in it — The activity of these Minerals 
 increased within a given time by the Salts of Ammonia — The soil more 
 rapidly exhausted by their use unless there is a restoration to it of the 
 removed Mineral matters 51 
 
 LETTER YL 
 
 The Amount of Carbonic Acid and Ammonia in the Air — ^The Balance of 
 Organic Life — The Absorption and Assimilation of Food differs in Perennial 
 
CONTENTS. XXlll 
 
 and in Annual Plants— The mode of Growth of Perennial, Annual, and 
 Meadow Plants — The quantity of Nitrogen in different Crops — Advantages 
 of Nitrogenous Manures to Cereals is not in consequence of the failure of 
 Nitrogen from Natural Sources — Organic and Nitrogenous Manures useful 
 in Annual Plants with small absorbent Leaf and Root-surface — Effect of 
 Nitrogenous Manures less marked in plants with large Leaf-surface — 
 Supply of Ammonia in Manure not necessary to all Plants — Green Crops 
 condense Ammonia from Natural Sources, and supply it in the excrement 
 of animals to Corn-fields — The Nitrogen of Manures is thus indirectly 
 obtained from the Air — The total quantity of Nitrogen from a manured 
 Corn-field is not greater than from anommauured meadow, but more time 
 is required by the latter to collect it — Explanation of the good effect of 
 Nitrogenised Manures on Annual Plants with small Leaf and Root- 
 surface 69 
 
 LETTER YII. 
 
 Salts of Ammonia increase the number of Roots and Leaves m the first period 
 of the Growth of Plants ; hence the superior action of these salts ui Spring 
 — Circumstances which modify the production of Leaves, Flowers, and Roots 
 — Circumstances under which Nitrogenous and Concentrated Manures are 
 useful — Causes of the failure of plants continuously grown on the same SoQ 
 — Pood of plants when too concentrated often exerts a deleterious Chemical 
 action — Provision in the Soil to prevent this action — Properties of Soils 
 altered in cultivation by the removal of Mineral Matters from them, and by 
 the increase of Organic Matters in them — The increase pf Organic Matter 
 frequently a cause of Disease — Finger and Toe disease ; its cure — Excess 
 of soluble Silica and of hurtful Organic Matter in soils removed by Lime — 
 Noxious Organic Matters arising from the continuous growth of Perennial 
 Plants on Meadows removed by Irrigation 80 
 
 LETTER Vni. 
 
 The food of Land Plants is not absorbed by the roots from Solution, but from 
 the Soil directly in contact with them — Hence the necessity for a uniform 
 distribution of the food of plants in the soil, and for the great Ramification 
 of their Roots — A field with much mineral food may be comparatively 
 unproductive if it is not thoroughly mixed with the Soil — The roots of a 
 crop diminish the mineral food in those portions of the soQ in contact with 
 them — Fertihty is restored to those portions by ploughing and other 
 mechanical means, which mix the soU and allow the roots to ramify freely 
 — Reason of the value of Green Manures — Estimation of amount of mine- 
 ral food in the soil to produce different Remunerative Crops — Law of 
 Exhaustion in soils for different crops — Action of organic remains in the 
 
XXIV CONTENTS. 
 
 soil on the mineral constituents — Progress of diminution in Grain and Straw 
 of cultivated crops, when the Ash Constituents are not restored to the soil, 
 and when those of the straw alone are returned — Relation between the pro- 
 duction of Leaves and of Grain — Relative proportions of mineral food 
 required for Grain and for Root or Leaf-producing crops — The increase of 
 Oi'ganic matter and Nitrogen in the soil by Green Crops, without the 
 addition of mineral food, augments the produce of grain, but hastens the 
 period of Exhaustion of the soil — Progress of the exhaustion of a soil by 
 the cultivation of shallow and of deep rooting plants — The manner in which 
 the Subsoil contributes to the prolongation of the fertility of land — 
 Importance of the formation of large roots after germination — Exliausted 
 fields in an agricultural sense — Fertility restored by manures — The nature 
 of Manures — The part played by the Organic and Inorganic Matter of 
 Manures — Farm-yard Manure 87 
 
 LETTER IX. 
 
 uonstant relation between the Sulphur and Nitrogen of Organic Compounds 
 and the Alkaline Phosphates and Alkaline Earths of Cereals and Legu- 
 minous plants — Mineral substances are as indispensable to the Life of 
 Animals as to that of Plants — The amount of Phosphoric Acid and of 
 Potash ascertained by analysis as existing in Soils is very small — The 
 errors of Practical Teachers proved from the writings of Practical Agri- 
 culturists — Fertility of land cannot be maintained by Nitrogenous and 
 Carbonaceous Manures alone, but by the Restoration of the Ash Constitu- 
 ents of Plants — Critical examination of the views of Walz, a practical 
 teacher, on the Nutrition of Plants — The mineral food of plants in arable 
 soils is not inexhaustible — The volatile and organic matters of Manures 
 are not the most important — The nature of Guano and its active con- 
 stituents 113 
 
 LETTER X. 
 
 The empirical agriculturist is a trader — The duties of the empirical and 
 rational agriculturist — Views of Albrecht Block — Rotation of crops not un- 
 important ; an underground crop is followed by a better cereal — Cropping 
 of land without manure, and the removal of produce, cause exhaustion — 
 The spoliation system of agriculture — Exhaustion of the lands in North 
 America by this system — Exhaustion of the Minas Geraes fields — High 
 farming is a more subtle system of spoliation of the soil — Mutual relation 
 of clover, turnip, and corn crops ; and the results of removing from the 
 lands the mineral constituents of these crops respectively — The German 
 system of farming before the Thirty Years' "War — The German three-field 
 
CONTENTS. XXV 
 
 system of rotation — Introduction of clover cultivation into Germany — 
 Opposition to its introduction — False teaching in connection with the value 
 of manures 138 
 
 LETTER XL 
 
 Ammonia is an element of food indispensable to Plants — Comparison of the 
 action of Water and Ammonia — Ammonia is an element of food and a 
 Solvent of Mineral Matters in the Soil — Ammonia alone, or its Salts, useless 
 to Plants, without Mineral Food — Vast amount of Ammonia in arable Soils 
 — The "Nitrogen" theory of Manures — The error of attributing the chief 
 value of a Manure to its Nitrogen — The reason why the quantity of Nitro- 
 gen in Guano and Excrements may be taken as a standard of their Agri- 
 cultural value — Proper mode of Comparing the relative effects of Guano, 
 Ground Bones, and Chili-saltpetre — The Loss of Fertilising matter in the 
 Flesh and Grain carried to large towns; the constant loss of Phosphates in 
 the Excrements of the inhabitants — The importation of Guano most 
 inadequate to replace this loss — Superiority of Human Excrement over 
 Guano as a Manure for Corn Fields — Tobacco, Potatoes, and Beet-root are 
 more exhausting to a soil than Wheat — Injurious influence of extensive 
 Cultivation of the Vine on the production of Corn and Wheat — Eifect of 
 the Subdivision of the Land 165 
 
 LETTER XIL 
 
 Modern Agriculture has no history — The reason of this — The history of 
 Roman Agriculture shows the existence of the spoliation system at that 
 period — The works of Cato, Virgil, Varro, and Pliny inculcate, two thou- 
 sand years ago, the same precepts that are now taught by many teachers 
 of agriculture — Quotations from these writers, to show their opinions on 
 the exhaustion of the ground ; on the different kinds of soils, and the 
 modes of improving them ; on the selection of plants for the soils which 
 are suitable for them ; on fallowing ; on the cultivation of green crops for 
 manures ; on the different kinds of manure and their relative values, and 
 modes of managing them — The various precepts inculcated of old only 
 hastened the ruin of Roman agriculture 187 
 
 LETTER XIIL 
 
 The true object to be kept in view in establishing Scientific Principles — In 
 scientific agriculture, "Manure," like the term "Phlogiston," has no longer 
 a meaning — The cultivation of Green Crops for the purpose of keeping a 
 stock of Cattle for manure is not necessary in the cultivation of land — The 
 distinction between the Necessity and the Utility of keeping cattle — No 
 
XXVI CONTENTS. 
 
 necessary connection exists between the production of Corn, and that oi 
 JFlesh and Cheese — The fundamental principles of German Agriculture 
 quite unknown in China — Chinese Agriculture — The manures employed 
 by them — Great value set by Chinese on human excrements ; their mode 
 of collecting and using them — Chinese compost — Their mode of sowing 
 and transplanting wheat — Plants cultivated as green manure for rice fields 
 — The lesson taught by the Chinese system of agriculture 196 
 
 LETTER XIY. 
 
 The law of Compensation is of universal application — Elementary information 
 on Chemical subjects connected with Agriculture easily imparted — Im- 
 portance of instructing youth at school in these fundamental truths — Theo- 
 retical instructions should always precede Practical — The proper mode of 
 instructing agriculturists in the Theory and Practice of Agriculture — The 
 present constitution of Agricultural institutions very defective — The false 
 position of Science in practical agriculture is the result of the teachings of 
 these Schools — The demands made by Science on agriculturists are simple, 
 and a knowledge of them cannot prove injurious — Science demands that 
 agriculturists should test the Truths she advances — The truths in these 
 Letters expressed by a Formula — The value of Guano first discovered by 
 Science — The establishment of Reservoirs for animal excreta strongly 
 recommended — Reliance to be placed upon such Excreta rather than on 
 Guano — Chemistry can only help agriculturists after they have exhausted 
 all the means at their disposal — Notes on supply of guano and on the 
 agriculture of Tuscany 2 05 
 
 APPENDIX 221 
 
LETTERS 
 
 THEORETICAL AND PRACTICAL AGRICULTURK 
 
 LETTER I. 
 
 The conflict between Science and Practical Agriculture — The foundation of 
 Agriculture is experience — Progress founded on experience has its limits 
 — The connection of Agriculture with Chemistry and the subsequent 
 reaction — Progress in Agriculture must be based on the Inductive Method 
 — False teachers of Agricultural Science — Practice based on the bhnd 
 experience of others leads to error — The rejection of scientific teaching by 
 practical men due to their ignorance of the real object of Science — The 
 solution by mere practical men of questions proposed by Agricultural 
 Societies cannot advance Agriculture — The rejection of all scientific 
 instruction by practical men only leads to self-deception. 
 
 The present conflict between practical agriculture and 
 scientific Chemistry, carried on by one party with some 
 animosity and passion, perhaps to the ultimate advantage 
 of the question at issue, might justly claim the attention 
 of enlightened statesmen ; for it concerns the weightiest 
 material interests and the fundamental prosperity of the 
 state. The most urgent problem which the present day 
 has to solve, is the discovery of the means of producing 
 more bread and meat^ on a given surface, to supply the 
 wants of a continually increasing population. The most 
 
 Note. — The superior figures in the text refer to the treatment of the sub- 
 jects in the Addenda. 
 
 1 
 
2 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 important social questions are bound up in this problem, 
 whicb science is expected to solve. 
 
 Science has in her own way made the necessary prepara- 
 tions for its solution, but her way does not please practical 
 men. From them she has met with no support, but with 
 opposition in almost eyery thing she has done. 
 
 For the new building, which is to give room and shelter 
 to all who will enter, science has levelled the ground ; she 
 has drained it, and driven piles into the swamp, to insure 
 a firm foundation ; she has indicated the best stone for use, 
 and pointed out the fact that it is not found in all places, 
 though the mortar may be had everywhere in abundance ; 
 she has, finally, given the plan of the house ; but not one 
 mason or carpenter, through whose assistance alone the 
 house can be erected, has raised a hand to help her. 
 Experience, they say, has been for centuries their guide, 
 and must continue to be so for the future. In their eyes 
 no views are admissible or possible, which contradict their 
 views based on this experience. What has been regarded 
 from time immemorial as true, must be true. The new 
 plan is opposed to theirs, which is the best; neither the 
 draining of the swampy ground, nor the driving of the 
 piles, nor even the stones which are to be found every- 
 where, are of any consequence ; only the mortar is wanting, 
 on which every thing depends. 
 
 Agriculture, like every technical pursuit, is based on 
 experience, that is, on the perception by the senses of facts 
 and phenomena ; and it has been enabled by experimental 
 art to reach a certain stage of development. Simple 
 observation shows a certain connection between the condi- 
 tion of the soil and its fertility. Thus, a certain porosity 
 and dark colour bespeak frequently a heavy wheat crop. 
 Bat as all soils do not possess porosity and blackness, 
 experimental art seeks out the means of communicating 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 3 
 
 tliese properties. It endeavours to produce, for a given 
 object, a passing or a permanent connection between two 
 facts ; it seeks to win from the soil a high return by this or 
 that planij manure, or other means. 
 
 Every object attainable by experimental art must be 
 pursued with certain ideas, but it is immaterial whether 
 those ideas be right or wrong. For if we seek an object 
 without knowing the proper way to do so, each path taken 
 by us is, for the time being, the right one. If, then, thou- 
 sands of persons with the same intention strike out 
 thousands of different courses, it will generally happen 
 that something useful is discovered, although not precisely 
 the object sought. In this way trades have been developed. 
 It is almost incredible what can be done, and has, in fact, 
 been accomplished in this way. 
 
 The connection between two objects, such as the soil and 
 manures, is known only through means of a third, viz., the 
 amount of produce. For the practical man, " the matter- 
 of-fact man," there exists no other connecting link. 
 
 The exercise of a trade presupposes no intellectual 
 labour; a knowledge of facts, and of their visible and 
 manifest connection with each other, being quite sufficient 
 for the purpose. The baker knows nothing about flour, 
 leaven, or the influence of fermentation and heat ; the soap- 
 boiler is ignorant of the nature of the alkaline lye, of fat, 
 and of soap ; but both know that by taking certain steps 
 bread or soap is produced. If the articles look well, they are 
 said to have succeeded. In like manner, a few years ago, the 
 agriculturist knew nothing about the soil, the atmosphere, 
 or the action of the plough or of manures ; things with 
 which he was daily occupied. 
 
 The efforts of every tradesman are, as a matter of course, 
 directed to his profits ; every improvement in his business 
 has the increase of his income for its object. Hence the 
 
4: THEORETICAL AND PEACTICAL AGRICULTURE. 
 
 baker regards the highest effort of his art to be the produc- 
 tion of a white and weighty bread from inferior and bad- 
 coloured flour ; and the soap-boiler aims at manufacturing 
 from bad fatty matters a soap with good external aspect. 
 The practical agriculturist, in the same way, endeavours 
 to reap the richest harvest from the poorest soil with the 
 least expenditure of labour and manure. In this petty 
 aim is manifested the paltry principle of the small manu- 
 facturer. 
 
 The progress of every trade by mere empirical experi- 
 ence, and also that of agriculture, has a limit. Every 
 experimental method comes to an end when the senses are 
 no longer sufficient for the perception of facts ; when no 
 new circumstance is presented to the senses for perception ; 
 when, in short, every thing has been tried, and the facts 
 resulting from such trials have been adopted into the par- 
 ticular art or trade. Further progress can then only be 
 looked for, if hidden facts are sought out, the senses are 
 sharpened for their perception, and the means of investiga- 
 tion are improved. But such a course is not possible with- 
 out reflection, without the mind also taking its share in the 
 operation. 
 
 It is long since agriculture has reached this point of its 
 progress. As, however, in following out their own practical 
 mode, agriculturists had never troubled themselves about 
 the way or the means of discovering hidden facts ; it was 
 evident that without the aid of Chemistry, — ^the science 
 which communicates this knowledge, — they could never 
 attain their end. Chemistry most readily responded to the 
 call. In the verj outset the practical agriculturist was 
 informed by the chemist that his conception of the words, 
 azV, soil, manure, was indefinite and ambiguous ; that they 
 had a fixed and definite meaning, and that it was only in 
 this strictly defined form that they could be employed in 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 5 
 
 processes of reasoning. Chemistry thus elevated mere 
 practical notions to the rank of scientific conceptions. 
 
 The newly acquired conception of manure was accepted 
 with enthusiasm by agriculturists, and they set themselves 
 with zeal to work it. It was known that manure was the 
 most important element in increasing a crop. It had been 
 shown that the word " manure" was a collective term; that 
 it consisted of parts, and that its activity depended on its 
 constituents. The practical agriculturist now began to 
 operate with the parts as he had done with the whole 
 manure. But as a part can never replace a whole, so the 
 results, by this mode of proceeding, did not answer his 
 expectations. No progress was made. Enthusiasm began 
 to cool, and reaction commenced. 
 
 " It is utterly absurd," says Mr. Pusey (late President of 
 the Agricultural Society of England), "to put any value on 
 the doubtful precepts of Chemistry. It has done nothing 
 for agriculture, with the exception of giving a receipt for 
 increasing the efficacy of bones by the action of sulphuric 
 acid, and of proposing to employ flax-water instead of 
 liquid manure. We must keep to practice, for it alone is 
 worthy of confidence." Every practical man in England, 
 Germany, and France, quite agreed in this opinion. Che- 
 mistry had done them no good ; it had not increased their 
 crops, nor augmented their incomes. 
 
 As if freed from a frightful night-mare, blind empirical 
 practice again raised her head, and made new and extra- 
 ordinary efforts to refute the conclusions drawn from scien- 
 tific principles. The continued efforts of ten years have, 
 however, shown that practice has only been moving in a 
 circle, like a horse in a mill. More horses have been 
 yoked; but as the beam was not lengthened, the circle 
 has remained the same, only somewhat more trodden than 
 formerly. 
 
6 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 A new movement now occurred in agriculture. Science 
 pointed out that tlie very facts destined to refute her doc- 
 trines, exhibited the fullest proof of their soundness. Agri- 
 culturists had themselves to blame for their want of success, 
 by not taking the right path and by mistaking the nature 
 and essence of science. It is not at all the province of 
 science to seek out the means of increasing produce or 
 augmenting incomes. She inquires not after what is profit- 
 able ; this belongs to experimental art, with which she has 
 been confounded. The business of science is to seek for 
 causes, and like a light, to illuminate the surrounding dark- 
 ness. Science confers poiver^ not money ; and power is the 
 source oi riches and of poverty^ — of riches when it produces^ 
 and of poverty when it destroys ; it is expended by %ise^ and 
 renewed by supply. 
 
 If agriculture is to arrive at results which are to be 
 lasting, she must decide upon entering on that path which 
 science has recognised to be the only trustworthy one to 
 lead to a knowledge of hidden objects and their relations; 
 This could be done without renouncing one of the facts 
 acquired by experience. There is no lack of these, but 
 agriculturists are at fault in their mode of comprehending 
 them. They must, in the first place, desist from drawing 
 hasty conclusions for special purposes from these facts, and 
 only occupy themselves with investigating the proximate 
 conditions of all the facts connected with the life and 
 development of plants, the production of which is their 
 object. From the favourable action of the constituent of a 
 manure in one case, they must not at once infer its equally 
 favourable action in another, in order to derive immediate 
 profit from it ; but they ought, in the first place, to inquire 
 into the reason of its good effects in the special case. 
 
 Such investigations are in an agricultural point of view 
 greatly facilitated by all the conditions of the incidents, or 
 
THEOKETICAL AND PRACTICAL AGRICULTURE. 7 
 
 effects, or their proximate causes, being clearly perceptible 
 by the senses, and palpably manifest if we know the proper 
 way to proceed. 
 
 The favourable action of a manure A is always dependent 
 on certain physical conditions of the soil, and on the pre- 
 sence of a second substance B, of a third C, of a fourth D, 
 and so on. After investigating these different points, our 
 conclusion must then be submitted to proof, which must 
 show whether all the conditions have been considered 
 together, and none overlooked. AYe must endeavour to 
 produce the same effect in another soil, by the combination 
 of all the conditions found. Should the result correspond 
 with our expectations, and be equally favourable as in 
 the first instance, we have made an extraordinary step in 
 advance ; for from this special case we can now in all similar 
 cases predict the like or unlike effect of the manure A. 
 The effects will be like, in every instance in which we 
 know that we have present the same conditions united in 
 the same manner ; and unlike, when one of these is known 
 to be wanting. 
 
 The presence and united action of all the conditions of 
 the effect observed, is designated by the term, a special law; 
 because it refers to a special case, to a certain plant for 
 instance. If this law holds good for superphosphate of 
 lime and " turnips," it does not follow that it is equally true 
 for "wheat." But a similar special law can be estabhshed 
 for each manure, each plant ; and from these again general 
 laws can be deduced, which express the conditions of the 
 growth and development of all varieties of cereals^ all species 
 of turnip and tuberous plants, &c. These connected general 
 laws now receive the name of theory. 
 
 It must be evident, even to the most limited under- 
 standing, that there is nothing hypothetical in this pro- 
 ceeding. It differs from blind experimental art, only in 
 
8 THEOKETICAL AND PEACTICAL AGRICULTUEE. 
 
 being the result of thought and reflection. As the train of 
 thoughts, on which the experiments are based, is carried 
 out in a precise and fixed direction, this mode of proceeding 
 has received the name of the inductive method. 
 
 The world has been metamorphosed by the introduction 
 of this method, which was unknown to antiquity. It is 
 to this method that the present day is indebted for its 
 peculiar characters. The Greeks and Komans possessed 
 metaphysics and the fine arts as we do ; but the natural 
 sciences, the offsprings of the inductive method, were 
 unknown to them. To this method we owe the millions 
 of wilHngand industrious slaves, whose labour costs no 
 tears or groans. It has bestowed on Germany alone what 
 is equivalent to from 700,000 to 800,000 horses, which, 
 with untiring energy, and with the speed of the wind, 
 bring from the most distant lands their various products to 
 satisfy the wants of man ; and they need no hay, no corn 
 to feed them. The fruitful land necessary to produce the 
 food for this number of horses of flesh and blood, remains 
 for the use of five to six millions of men, who can be main- 
 tained on its surface. 
 
 Conclusions deduced from this method of investigation, 
 are evidently but the intellectual expressions for experi- 
 ments and facts. The practical man who adopts this 
 method of solving all useful questions, need entertain no 
 dread of acquiring the reputation of a theorist, which he 
 considers to be of a rather doubtful nature. He may rest 
 assured that by no other means can he solve a single 
 problem. He must first seek after the "why," and the 
 " wherefore " will follow as a matter of course. 
 
 It would be unjust to conceal the fact that, for more than 
 half a century, agriculturists have directed all their efforts 
 to gain an insight into the processes of husbandry. They 
 have endeavoured to connect all its phenomena together by 
 
THEOKETICAL AND PRACTICAL AGRICULTURE. 9 
 
 some intelligible bond, and to ascertain the relation and 
 dependence of its scattered facts. 
 
 Agriculture could not remain unaffected by the extra- 
 ordinary progress of other trades depending on the action 
 of natural forces. The natural sciences were even recog- 
 nised to be the source of this progress. Wise and intelli- 
 gent princes erected schools and institutions, for the express 
 purpose of teaching the doctrines and truths of the natural 
 sciences in connection with the practice of agriculture, of 
 investigating the best modes of cultivation, and of widely 
 spreading the knowledge of them. 
 
 Agriculturists felt the necessity of accounting for their 
 acts ; and the knowledge that they were doing the right thing 
 in the right way, appeared to all indispensable to progress. 
 
 If we open a recent hand-book of practical agriculture, 
 we at once see the zeal with which this task has been per- 
 formed. The effect of soils, manures, irrigation, drainage, 
 and the action of each fertilising agent on individual classes 
 of plants, are all brought into harmony and explained in 
 the most beautiful manner. Everything seems in such 
 works to have been investigated and ascertained ; no pro- 
 cess is involved in obscurity ; and a certain feeling of pride 
 seems to fill the breast of the teachers who have done so 
 much to elevate agriculture to the rank of a science. 
 
 But this is all sham^ without a single law or a single truthf^ 
 " If there is a class of mind in the world which has a native 
 antipathy to improvement, there is another and much more 
 really mischievous, which seems ever destined to caricature 
 it. . . . These are the blundering enthusiasts who dog 
 the path of progressive truth, like distorting shadows, 
 throwing her calm profile against walls, trees, and passing 
 objects, in every variety of burlesque and ridiculous out- 
 
 * The Chronicle of a Clay Farm, by TlaJi^Si.— Agricultural Gazette. 
 1* 
 
10 THEORETICAL AND PRACTICAL AGRICULTURE 
 
 line ; . . . exaggerating every account like street ne"v^ s- 
 vendors ; dressed in the livery of science like a mon.-cey in 
 regimentals, and understanding and appreciatig the lan- 
 guage they talk at second-hand, as much as the organ- 
 grinder does the opera tune that his winch works thread- 
 bare. 
 
 " Agriculture has had enough of this and something to 
 spare. Counterfeits of every sort and shape have crowded 
 at the heels of every improvement, every invention, every 
 good suggestion, every new manure ; till art and science 
 are well nigh ashamed of their own names, and are fain to 
 wear smock-frocks for an incognito. The plague that has 
 reached its height in the present decade, was beginning 
 its infective process in the last of our nineteenth century." 
 
 Agriculturists knew not that the explanation of the most 
 trifling incident or process, or the discovery of the almost 
 self-evident cause of an effect, costs much pains and cir- 
 cumspection ; that in chemistry, for example, the simplest 
 explanation of a single individual fact has been attained, 
 only by persevering labour. They thought that to will^ 
 was to obtain possession ; and they hence gave themselves 
 up to the direction of those caricaturists of science who 
 promised them success without any efforts on their part. 
 They were well pleased with their sham scientific mode of 
 proceeding, with which they were at home, and which cost 
 them but little trouble. The language alone was new, but 
 technical terms were soon learned. Each individual con- 
 sidered himself as fully qualified to institute chemico- 
 agricultural experiments ; and these were undertaken even 
 by men who knew no more about chemistry than the 
 student who considers that the distillation of a fluid is to 
 be attained by simply placing it in the sun, or the other 
 who asked the chemical assistant in a laboratory for a grater 
 to pulverise a mineral. 
 
THEORETICAL AND PEACTICAL AGRICULTURE. 11 
 
 Such men arrived at explanations in the simplest manner 
 possible. If between two facts there existed a certain and 
 unmistakeable connection, — such as for example, between 
 irrigation and the increase of grass on a meadow, — these 
 pseudo-scientific experimenters drew on their imaginations 
 for the explanation of this connection. 
 
 The causes of the effect produced were unknown. There 
 was, however, an effect visible, and it must have a cause. 
 The expounder began first by mystifying with a chemical 
 hocus-pocus of analysis, the good-natured agriculturist 
 thirsting after knowledge ; and when he had sufficiently con- 
 fused the sound common sense of the latter by "unmeaning 
 numbers and calculations, he quietly palmed off on him his 
 explanation which he had ready prepared. 
 
 The connection between two facts was not, however, 
 always so palpable, as between irrigation and production 
 of grass ; but our agricultural expounders were never at a 
 loss. If they wished to show, for example, the connection 
 existing between the exhaustion of the soil and the cultiva- 
 tion of cereals^ they required only to call to their aid certain 
 speculative views derived from experience. For such 
 occasions they had always ready chiefly two famous theo- 
 ries, viz., the ''bone earth" and the "nitrogen" theories. 
 The latter has attained great celebrity in England, and in 
 Grermany. too, it has found ardent supporters. 
 
 There can be only one straight line between two points ; 
 but billions of curved lines may connect them. Thousands 
 of hypotheses may, in like manner, be propounded to 
 explain the connection of two facts ; but there can be only 
 one right theory. Every one will therefore understand 
 that agriculture, by following the method described above, 
 could never arrive at the right way of explaining her 
 various facts. The popularity of this mode of proceeding 
 arose from the circumstance that knowledge was not 
 
12 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 required to practise it. Every agriculturist, in his own 
 estimation, possessed the necessary qualifications for the 
 purpose. He knew the facts, and his own experience was 
 quite sufficient to connect them. But as the individual 
 experience of each necessarily varied in many respects, it 
 followed that each had his own peculiar theory for his pro- 
 ceedings and his mode of viewing things. 
 
 In reality these theories were but little regarded. The 
 practical man kept to what had been tried, and acted upon 
 it. If his neighbour made a successful trial, he imitated 
 his example. This was his mode of making progress ; he 
 knew no other. 
 
 The practical agricultural system of instruction was a 
 mere collection of different receipts suitable to known 
 cases ; it was an olla podrida of facts, with theory as a kind 
 of sauce to it. 
 
 The agriculturist commencing his career became a prac 
 tical man, and acquired reputation and honour somewhat 
 like the so-called "green" Doctor of Offenbach on the 
 Maine, who will perhaps still be recollected by the older 
 inhabitants of this town. He was a Jewish physician of 
 renown who was called in to all dangerous cases of illness 
 in Frankfort, Hanau, and the neighbourhood; and his 
 practice was not without success. Nature had given him 
 a quick eye and fine powers of observation. His know- 
 ledge was obtained in an hospital in which he acted as sick 
 attendant. He used to accompany the physician through 
 the sick wards, looked at the tongues and urine of the 
 patients after him, felt their pulse, and superintended the 
 orders about their diet. He copied the prescriptions regu- 
 larly; marked them with a red cross when the patient 
 recovered, and with a black one when he died. His sheets 
 grew by degrees to the size of a book, and when nothing 
 new presented itself to be added to it, he began in the first 
 
THEOEETICAL AND PEACTICAL AGRICULTUEE. 13 
 
 instance to practise on a small scale, and then started on 
 tbe full career of physician. He was skilled in diagnosis, 
 and had his prescriptions for the various cases. Those 
 with the red crosses came first ; and, if unsuccessful, then 
 followed the black. In this way he acquired his own expe- 
 rience. He was very orthodox, and on the Sabbath day 
 would write no 'prescription, but would then dictate them 
 in the apothecary's shop to the assistant. He commenced 
 with '■'• Rrrrr'^ (this meant Recipe); " Tartemet^ two grains" 
 (^. e. Tartar! emetici grana duo); Syralth {i. e. syrupus 
 altheoe). He could not read his own prescriptions, but his 
 fame as a practical physician was so established, that the 
 regularly educated physicians in Offenbach could not suc- 
 ceed in putting an end to his career, on the ground of his 
 never having received a medical education. 
 
 Agricultural practice is acquired in the present day 
 exactly in the same way as the medical skill of the Offen- 
 bach doctor. The young agriculturists become sick atten- 
 dants in an agricultural hospital ; they copy the prescrip- 
 tions, and when they depart for the purpose of beginning 
 practice, the kindly directors send them on their way, with 
 the substance of two years' earnest devotion to all the aux- 
 iliary sciences summed up in an axiom, "Dung, Guano, 
 and Bone-earth, you must not forget, gentlemen, are, and 
 remain the soul of agriculture."* They knew this very 
 well. They had been taught that no trust was to be put 
 in chemistry or physics ; that food and drink keep body 
 and soul together; and that beer, bread, and meat, are 
 the soul of the handicraftsman. 
 
 Under such circumstances, it cannot excite astonishment, 
 that for more than sixteen years true science found no soil 
 in agriculture for its development. The most exact indue- 
 
 * See G-. Walz. Beleuchtung. p. 128. 
 
14 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 tive conclusions were only regarded as hypotheses. It has 
 ever been the case that when error sat enthroned, truth, 
 like a felon, was kept bound in chains. What arrogance 
 in science to regard practical men like us as blind men, and 
 to attempt to make us see. How can men who know not 
 whether potatoes should be planted in March or April, 
 presume to teach us the properties which land suitable for 
 potatoes ought to possess, — or what is the nature oi fallow? 
 Such scientific explanations are not based on experience ; 
 we can ourselves give much better. Whoever should 
 attempt to depose farmyard manure from its exalted posi- 
 tion deserves to be burnt alive ! 
 
 Agriculturists had not yet acquired the faculty of dis- 
 tinguishing between mere opinions and correct facts. 
 Every fact was acceptable; every opinion was received 
 by them. If science doubted the truth of one of their ex- 
 planations^ they imagined that she ivas disputing their facts. 
 If she asserted that a great progress would be made by 
 substituting for stable manure its active constituents, they 
 believed that in doing so she denied the efficacy of the 
 former. 
 
 About misunderstandings of this kind disputes then arose. 
 The practical man did not yet understand the deductions 
 of science. His dispute was with the bugbear of his own 
 false conceptions, not with science. He did not know that 
 science also has a moral of her own, the foundation of 
 which lies in the precepts of the school and their practice 
 in education. 
 
 As a means of mental training, the study of the natural 
 sciences was quite unknown to the practical man ; and 
 hence the difficulty which existed between him and the 
 scientific man of mutually understanding each other. Had 
 the former turned his attention even in a slight degree to 
 these sciences, he would of himself have acquired all the 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 15 
 
 information wliicli it now costs so mucli trouble to make 
 intelligible to liim. 
 
 In phj^sics and chemistry, disputes of tbis nature occur 
 no longer, tbough the time is not long past since both 
 were at that point of development which agriculture has 
 still to pass. 
 
 A glance at a chemical or physical journal must fill the 
 mind of an agriculturist with astonishment at the mass of 
 problems and their solutions which it contains, and at the 
 immense labour which has been readily and without reward 
 bestowed upon the whole. Each day brings its own pro- 
 gress without strife, for each cultivator of these sciences 
 knows what constitutes a fact, conclusion, rule, law, opinion, 
 and explanation. There are specific tests for all these 
 which every one uses, before he puts each to the test of 
 its own peculiar touchstone, before he circulates the fruits 
 of his labour. Each assiduously seeks to bring to light 
 hidden facts, which are immediately submitted to proof by 
 others, and receive their proper place when they are found 
 to be genuine. One individual possesses the talent for seiz- 
 ing the points of resemblance between two facts ; another 
 has a keen eye for their differences ; in this way they render 
 mutual assistance in the proper elucidation of phenomena. 
 Special pleadings on the part of any one for his own pecu- 
 liar views, without striking facts to support them, or the 
 attempt to palm off on others any unproved facts, is in- 
 stantly rebutted by the moral of science. The earnest desire 
 of a mutual understanding is ever paramount. 
 
 The most intelligent representatives of agriculture have 
 hitherto erred in not discussing their questions in the way 
 which would have led to the attainment of their object. 
 Great agricultural associations, as well as individuals, have 
 proposed questions, and recommended their solution as 
 absolutely necessary for future progress. The majority of 
 
16 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 agiiculturists liave a monomania for propounding such 
 questions, and deceive themselves with the belief that their 
 solution will be attended with sound practical information. 
 Not one of them knows exactly what is wanted, but each is 
 anxious to contribute his suggestions. Such questions pro- 
 pounded by persons who know nothing of the subject are 
 answered by others who understand it as little. Not one, 
 however, really cares about the answer, for they all clearly 
 see that they would not know what to do with it. 
 
 There is a good method of satisfying ourselves of this 
 fact. We have only in our minds to answer these ques- 
 tions with "yes" or "no," or with any negative or positive 
 number we choose, when the answer involves numbers, 
 and we shall at once see that they are thoroughly unprac- 
 tical, or belong to the same stamp as the prize question of a 
 well-known Academy — "The decomposition of Nitrogen," 
 a problem which now seems to us more difficult than the 
 solution of charcoal for the purpose of making diamond. 
 The solvers of such questions (and here I speak only of 
 agriculturo-chemical), are hence always persons who do not 
 possess the necessary knowledge to make the most trifling 
 discovery. About fifteen years ago Hlubeck propounded 
 a series of questions, on the solution of which the very 
 existence of agriculture appeared to him to depend. Since 
 then, neither he nor any other person has troubled himself 
 about the matter ; and the j)resent state of the development 
 of agriculture is a proof, that none of his questions stood 
 in any relation to it, or exercised any influence upon its 
 progress. 
 
 These questions are always tokens of progress. They 
 prove that agriculture has really passed from the state of 
 blind empiricism into the first stage of its scientific develop- 
 ment, viz. into that of its infancy, in which curiosity mani- 
 fests itself by a multitude of questions. In this point of 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 17 
 
 view we may, after all, rejoice that such questions are 
 really put. 
 
 Chemistry and physics have likewise passed through the 
 same stages. Academies and learned societies have in their 
 time proposed an incredible number of absurd prize questions 
 and impossible problems, without having thereby exercised 
 any important influence on the furtherance of science. 
 Those who are not well acquainted with the position in 
 which these problems stand to science, would be easily 
 misled into the belief that they have given origin to many 
 truly substantial works. This is, however, an error, for the 
 problems were proposed by those who knew that their solu- 
 tion was already in progress ; or the questions came acciden- 
 tally in the way of men who had been long previously 
 occupied with them. 
 
 Prizes, sometimes of a very high value, were attached by 
 the Academies to the solution of their questions ; but as our 
 excellent agriculturists regard the answering of their ques- 
 tions as an honour, they may, on that account, calculate the 
 more certainly that nobody will take any notice of them. 
 
 At their great meetings the practical agriculturist com- 
 municates his experience, and expresses his views. The 
 final result is always a mutual agreement between those who 
 differ in opinion ; and each goes home with the proud con- 
 sciousness of having convinced the others that he is a man 
 of progress, and has taken his part in it. Principles are 
 left out of the question ; effective manures and experiments 
 alone are wanted. Poor soils cannot be fertilised by funda- 
 mental truths. 
 
 A few years ago a writer expressed in such a meeting a 
 modest doubt as to the duration of the nitrogen theory so 
 strongly maintained in England, but they unanimously 
 passed to the order of the day, as experience had long since 
 decided the question of its value. 
 
18 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 One of tlie worst points in the character of practical men, 
 is their sensibility to opposition. The total want of founda- 
 tion for their erroneous views is the reason why they regard 
 them with so much affection and tenderness. It makes them 
 blind to their own interest, and deaf to all instruction. 
 They look on every one as an enemy who does not flatter 
 their prejudices, who openly tells them that there yet remains 
 much to be learned, and that the consciousness and confes- 
 sion of our ignorance, and the knowledge of our faults, are 
 the first steps towards improvement. I, who in my heart 
 believe myself to be their most candid and sincere friend, 
 must, therefore, at once make up my mind to bear with 
 resignation the whole weight of their contempt, with which 
 pride in their own experience fills them, if I attempt to 
 prove the assertion, that the prevailing system of agriculture 
 for half a century has been one of spoliation ; and that, if 
 persisted in, the inevitable result will be, at no distant date, 
 the ruin of their fields, and the impoverishment of their 
 children and posterity. 
 
LETTEE II. 
 
 Present prom is the leading principle of the prevailing system of Husbandry 
 — This system is one of danger to Agriculture — Greneral view of the 
 Nutrition of Plants — Atmospheric and Mineral Food — The absolute neces- 
 sity to Plants of all the Constituents of their Mineral Food — Present 
 views of the Nutrition of Plants erroneous — Rain water does not dissolve 
 out the Mineral matters in the Soil — Remarkable absorbent power of Soils 
 for the soluble Mineral Food of Plants, and particularly for Potash, Ammo- 
 nia, and Phosphoric Acid— This power is limited, and varies with the Soil 
 — Organic matter in the Soil materially modifies this power. 
 
 Before proceeding to prove that our present system of 
 agriculture is one of spoliation, I must from the outset 
 remark, that I do not by this mean, that each agriculturist 
 acts contrary to the rules of logic and common sense in 
 tilling his ground in the manner most advantageous to him- 
 self On the contrary, I feel satisfied that, so far as the 
 attainment of this point is concerned, our practical agricul- 
 turist is very reasonable and logical. He knows, in general, 
 the means of rendering barren grounds fertile, and of obtain- 
 ing the best crops from fertile fields ; and he employs these 
 means with reflection and skill, for they have been known 
 and proved for ages. 
 
 A field from which a large crop of corn has been reaped, 
 is again enabled to produce the same crop by mechanical 
 preparation and by manure. Any peasant, who cannot 
 read or write, knows that such a result will follow the 
 employment of these two means. 
 
 It is asserted, that the present system of husbandry 
 yields greater crops, and produces more corn and meat, 
 
20 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 with more profit, on the same area than formerly. I will 
 not, at present, contest this point, and therefore it is not 
 now my object to attack this system^ but rather to discuss 
 the question, whether or not it is a rational one. If the 
 large crops are a consequence of a mode of management 
 by which the ground must gradually lose the conditions of 
 its fertility, by which it must be impoverished and 
 exhausted, then such a system is not rational^ though 
 it enrich the individual who obtains these high returns. 
 
 I am aware that the majority of agriculturists are fully 
 satisfied that their mode of husbandry will insure a con- 
 tinuance of fertihty to their fields. If I can succeed in 
 awaking a doubt in this belief, I shall have gained an 
 important point. The simple perception of their error will 
 sufiice to lead to its correction. 
 
 I hold it, indeed, to be no longer possible to bestow again 
 upon the soil all those conditions of fertility which have 
 been withdrawn by the existing mode of husbandry ; but, 
 by a judicious system of management, so much may be 
 accomplished with the still existing means, as to put in the 
 shade all that has hitherto been done. 
 
 To comprehend clearly the existing system of agricul- 
 ture, we must recall to mind the most general conditions of 
 the Ufe of plants. 
 
 Plants contain combustible and incombustible constitu- 
 ents. The latter, which compose the ash left by all parts 
 of plants on combustion, consist in the case of our culti- 
 vated plants, essentially of phosphoric acid^ potash^ silicic 
 and sulphuric acids, lime, magnesia, iron, chloride of 
 sodium. 
 
 It is now regarded as an undisputed fact, that the consti- 
 tuents of the ash are elements of food, and hence are 
 indispensable to the structure of the different parts of the 
 plant. Its combustible portion is derived from carbonic 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 21 
 
 acw^, water^ and ammonia, which as elements of food are 
 equally indispensable. 
 
 Bj the vital process plants are formed from these 
 materials, when the atmosphere and soil supply them at 
 the same time in suitable quantity, and in the proper pro- 
 portions. The atmospheric elements do not nourish with- 
 out the simultaneous action of the elements of the soil ; and 
 the latter are equally valueless without the former. The 
 presence of both is always required for the growth of the 
 plant. 
 
 It hence follows, as a matter of course, that no single 
 element of the food of plants, named above, .possesses 
 superiority over another : they are all of equal value to the 
 life of the plant. But to the agriculturist, who must pro- 
 vide a suitable supply of all these substances in his land to 
 accomplish his particular object, they are, on the other 
 hand, of unequal value. For should there be a deficiency 
 of one of them, he can calculate on his crop only by sup- 
 plying that particular one to the soil. The deficient or 
 absent element then acquires a superior value, that is, in 
 relation to the other matters (for example, lime in a lime 
 soil), which the soil contains in greater quantity. 
 
 All elements of food of plants belong to the mineral 
 kingdom. The gaseous elements are taken up by the 
 leaves ; the fixed by the roots. The first are frequently 
 constituents of the soil, and, as such, reach the interior of 
 plants by the roots as well as by the leaves. From their 
 nature, these gaseous elements are movable; the incom- 
 bustible ingredients are immovable, and cannot of them- 
 selves leave the spot in which they are found. 
 
 An element of food is ineffective if there be absent a 
 single one of the other elements of food which are condi- 
 tions of its activity. 
 
 Corn plants, and those used for fodder, require for their 
 
22 THEOKETICAL AND PKACTICAL AGRICULTURE. 
 
 development the same constituents, but in very unequal 
 proportions. The successful growth of a green crop on a 
 field, proves that it has found in the air and in the soil the 
 atmospheric and mineral constituents of its food in the pro- 
 portions suitable for its nourishment. The failure of a 
 corn crop on the same field, indicates that in the soil there 
 is something wanting which is necessary for its growth. 
 Hence we must in every case of the failure of a cultivated 
 crop, look to the ground for the cause, and not to any 
 want of atmospheric food; for the same source of atmo- 
 spheric food was available to the corn plant as to the green 
 crop. 
 
 But how does the soil act, and in what manner do its con- 
 stituents take part in vegetation ? This question we shall 
 now consider a little more in detail. 
 
 The process of nutrition consists in the appropriation of 
 food. A plant grows by increasing in bulk ; and its bulk 
 increases by the constituents of its food becoming constituents 
 of its frame. From carbonic acid, for example, sugar is 
 formed ; silicic acid becomes a component part of the stem ; 
 potash of the sap ; phosphoric acid, potash, lime, magnesia 
 of the seed. 
 
 In considering the effect of an element of food, we have 
 to distinguish between the rapidity and the duration of its 
 action. 
 
 In general the result depends on the sum of the active 
 elements available in the soil, in relation to the amount which 
 the plant may altogether absorb, and does absorb, during 
 the period of vegetation. A deficiency diminishes the crop, 
 but an excess does not increase it beyond a certain limit. 
 The excess comes into play in the succeeding period of 
 vegetation. The continuous cultivation of crops is regulated 
 by this excess which remains in the ground after each period 
 of vegetation. If this residue is ten times greater than is 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 23 
 
 necessary for a full crop, then it will suffice for ten full crops 
 during a period of ten years. 
 
 The rapidity with which a substance, such as a piece of 
 sugar, is dissolved by a fluid, is in proportion to its state of 
 division. By pulverization its surface is increased, and con- 
 sequently the number of points augmented, which, in a 
 given time, are brought in contact with the dissolving fluid. 
 In all chemical processes of this kind, the action proceeds 
 from the surface. An element of food in a soil acts by its 
 surface, the portion beneath the surface is inactive, because 
 it cannot be dissolved. Its effect, within a given time, 
 increases with the quantity taken up by the plant during 
 that time. Fifty pounds of bones may in one year produce, 
 according to their state of division, the same effect as one, 
 two, or three hundred pounds coarsely ground. In the 
 latter state it is by no means inefficient ; but to act, that is, 
 to become soluble, it requires a longer time. The effect 
 produced by it is smaller, but it continues longer. 
 
 To understand correctly the effect of the soil and its con- 
 stituents on vegetation, we must keep steadily in view the 
 fact, that the elements of food present in it always possess 
 within themselves active powers, but they are not always in 
 a condition to exert this power. They are ready to enter into 
 circulation, like a maiden to dance, but a partner is necessary. ^. 
 
 The agriculturist requires eight substances in his soil, if j ^f '-♦^ 
 all his plants are to flourish luxuriantly, or his fields to ! |\ -< 
 produce the largest crops. Many of these, though not all, ^ 
 are always present in quantity ; three require to be added 
 to most fields. These eight substances are like eight links 
 of a chain round a wheel. If one is weak, the chain is soon 
 broken, and the missing link is always the most important, 
 without which the machine cannot be put in motion by the 
 wheel. The strength of the chain depends on the weakest 
 of the links. 
 
24 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 We have hitherto believed that plants received their food 
 from a solution, and that the rapidity of its effect was in 
 direct proportion to its solubility. We have supposed the 
 active elements to be carried in solution in rain water and 
 carbonic acid to their roots, and have regarded them in the 
 light of sponges, half in the moist ground and half in the air, 
 continuously absorbing by their roots the water which eva- 
 porated from their leaves. Whatever was in solution passed 
 with the water into the roots, and by the process of nutrition 
 was appropriated by the plant. The soil and the plant were 
 both passive in the operation. 
 
 Vegetable physiology has taught, that an element of food 
 in the soil, at a distance from the rootlets of plants, is avail- 
 able as nourishment, provided there is water between the 
 rootlets and the food to dissolve the latter. In consequence 
 of the evaporation from the leaves, the rootlets suck up the 
 water, which thus, with the substances dissolved in it, 
 receives a movement onwards towards them. We believed 
 that the water was the carrier of the most remote elements 
 of the soil to the immediate presence of the plant. 
 
 If 4000 lbs. of grain and 10,000 lbs. of straw require 100 
 lbs. of potash and 50 lbs. of phosphoric acid for their deve- 
 lopment, and if a hectare of ground contain these quantities 
 in a soluble available form, then there will be sufficient for 
 this crop. If the same field contain double, or a hundred 
 times as much, then we should expect two or a hundred 
 crops. This has been the physiological doctrine. 
 
 But all this has been a great mistake. We have inferred 
 from the effect of water and carbonic acid on rocks, a simi 
 larity of action on soils ; hut this conclusion is false. 
 
 There is not to be found in chemistry a more wonderful 
 phenomenon, one which more confounds all human wisdom, 
 than is presented by the soil of a garden or field. 
 
 By the simplest experiment, any one may satisfy himself. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 25 
 
 that rain water filtered tlirougli field or garden soil, does not 
 dissolve out a trace of potash^ silicic acid^ ammonia^ or phos- 
 phoric acid. The soil does not give up to the water one 
 particle of the food of plants which it contains. The 
 most continuous rain cannot remove from the field, except 
 mechanicallj, any of the essential constituents of its fertility. 
 
 The soil not only retains firmly all the food of plants 
 which is actually in it, but its power to preserve all that may 
 be useful to them, extends much further. If rain or other 
 water, holding in solution ammonia^ potash^ phosphoric and 
 silicic acids^ be brought in contact with the soil, these sub- 
 stances disappear almost immediately from the solution ; the 
 soil withdraws them from the water. Only such substances 
 are completely withdrawn by the soil as are indispensable 
 articles of food for plants ; all others remain wholly or in 
 part in solution. 
 
 If a funnel be filled with soil, and a dilute solution of 
 silicate of potash be poured upon it, there will not be found 
 in the filtered water a trace of potash^ and only under cer- 
 tain circumstances silicic acid. 
 
 If freshly precipitated phosphate of lime, or phosphate of 
 magnesia, be dissolved in water saturated with carbonic acid, 
 and filtered in like manner through soil, there will not be 
 found a trace of phosphoric acid in the filtered water. A 
 solution of phosphate of lime in dilute sulphuric acid, or of 
 phosphate of magnesia and ammonia in carbonic acid water, 
 comports itself in the same manner. The phosphoric acid 
 of the phosphate of lime, and the phosphoric acid and 
 ammonia of the magnesia salt remain in the soil. 
 
 Charcoal re-acts in a similar manner with many soluble 
 salts ; it removes colouring matter and salts from solutions. 
 It is natural to look upon the effect in both cases as pro- 
 ceeding from the same cause. In the case of charcoal, it is 
 a chemical attraction, which proceeds from its surface; 
 
26 THEOKETICAL AND PKACTICAL AGRICULTURE. 
 
 but the constituents of the soil take part in its action, and 
 hence it must in many cases be quite different from that 
 of charcoal. 
 
 Potash and soda are well known to stand to each other 
 in the closest chemical relation, and even their salts have 
 many properties in common. Chloride of potassium, for 
 example, has the same crystalline form as chloride of 
 sodium ; and in taste and solubility they differ but slightly. 
 An unpractised eye can scarcely distinguish them, but the 
 soil can do this in the most perfect manner. 
 
 If we add any soil in powder to a dilute solution of 
 chloride of potassium, in a short time there will not be 
 found any potassium in solution. The same quantity of 
 earth does not withdraw from a solution of chloride of 
 sodium, containing ah equal amount of chlorine, even the 
 half of the sodium. Consequently, a complete decomposition 
 takes place with the potassium, but only in part with the 
 sodium. Potash is found in all our land plants, but soda 
 forms only an exceptional constituent of their ashes. From 
 sulphate and nitrate of soda, the soil withdraws only a part 
 of the soda, but the whole of the potash from the corres- 
 ponding potash salts. Experiments, expressly made for this 
 purpose, have shown that 1 litre = 1000 cubic centimetres 
 (=61 cubic inches Eng.) of garden soil, rich in lime, will 
 take up the potash from 2025 cub. cent. (= 123'6 cub. 
 inches, or 8i pints) of a solution of silicate of potash, which 
 contains in every 1000 cub. cent. 2-78 grammes (:= 43 grs.) 
 of silicic acid, and 1166 grammes {= 18 grs.) of potash. 
 From these data we can calculate that a field of a hectare 
 {= 2i acres) in extent, and having a depth of i of a metre 
 — 10 inches nearly) of soil, of the sanje kind as that used 
 in the experiments, would withdraw from a similar solution 
 more than 100,000 lbs. of potash, and retain them for the 
 use of plants. A similar experiment, made with a solu- 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 27 
 
 tion of phosphate of magnesia and ammonia in carbonic acid 
 water, showed that a 2^ acre field would withdraw 5000 
 lbs. of this salt from such a solution. A loam (poor in 
 lime) produces the same effect. 
 
 These facts give us some conception of the powerful 
 action of soils, and of the strength of their attraction for 
 three of the chief elements of the food of our cultivated 
 plants, which, in consequence of their solubility in pure and 
 carbonic acid water, could not be retained in the soil, did 
 the latter not possess this power of attraction.* 
 
 From stale urine^ liquid manure diluted with much water, 
 or from a solution of guano, soil, when used in sufficient 
 quantity, removes the whole of the ammonia^ potash^ and 
 phosphoric acid which they contain. Not a trace of these 
 substances can be found in the water which flows from the 
 soil. (Thompson, Huxtable, Way.)t 
 
 * These experiments are so simple and so easily performed, that they may 
 be exhibited at lectures. In filtering, care must be taken that the fluid does 
 not form canals, which would prevent the complete contact of the solutions 
 with the soil. Yery dilute solutions of silicate of potash, chloride of potas- 
 sium, &c., must therefore be used, in the proportion, for example, of one part 
 of substance to 500 of water. Saturated solutions of the other substances, such 
 as phosphate of lime in carbonic acid, may be employed. Generally, in the 
 first portions of filtrate from the phosphate of lime, not a trace of phosphoric 
 acid can be detected by molybdate of ammonia. A solution of silicate of 
 potash, which re-acts distinctly alkaline with turmeric paper, instantly loses 
 this re-action by simple mixture with soil. This power of absorption in soils 
 for ammonia was observed by Thompson, and for phosphoric acid and some 
 potash salts by "Way, so long ago as 1850 ; but up to that time neither 
 vegetable physiologists, nor scientific agriculturists, had taken notice of the 
 remarkable discoveries of these English chemists, so pregnant with important 
 results to physiology and agriculture. 
 
 \ I cannot here omit a circumstance communicated to me a few years ago 
 by Dr. Marquart, of Bonn, and which illustrates, in a remarkable enough 
 manner, the power of absorption of clays for ammonia. 
 
 A manufacturer on the Rhine conceived the idea of extracting, by means 
 of ammonia, the oxide of copper, which was found as malachite and azure- 
 
28 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 The power possessed by soils to withdraw ammonia, pot- 
 ash, phosphoric and silicic acid, from solution, is limited. 
 Each soil is endowed with its own peculiar capacity in this 
 respect. When brought in contact with these different 
 solutions, the soil becomes saturated with the dissolved 
 matter, and the excess of soluble substance then remains 
 in solution, and can be detected by the ordinary re-agents. 
 A sandy soil absorbs less than the same volume of a marly 
 soil. And the latter less than a clay soil. The variations 
 in the quantity of matter absorbed are as great as the differ- 
 ences existing among the soils. We know that no two are 
 alike ; and it is not improbable that certain peculiarities in 
 cultivation stand in a certain relation to the unequal power 
 of the different soils for absorbing one of the above sub- 
 stances. It is not impossible, that, by a closer study of 
 this relation, we may arrive at quite new and unexpected 
 
 spar dispersed through shale. The experiment had succeeded with him on a 
 small scale. At a considerable expense he constructed a large extraction 
 apparatus, consisting of two boilers connected by a very wide tube. The 
 fluid ammonia was placed in one boiler ; the tube was filled with the shale ; 
 and the second boiler served as condenser. By this arrangement it was 
 intended that the ammonia and vapour of water should be condensed in the 
 tube, and, after dissolving the oxide of copper, pass over into the second 
 boiler. The tube was then to be filled with fresh shale, the ammonia to be 
 driven by heat from the solution in the second boiler, and made again to 
 extract the copper from the fresh shale. As the whole apparatus was her- 
 metically closed, it was hoped that the same quantity of ammonia would serve 
 without loss to extract large quantities of shale. The boilers were employed 
 alternately as condensers. The first trial was so far successful, that a solution 
 of oxide of copper really collected in one of the boilers. But on passing the 
 ammonia through a second portion of shale, it disappeared in a manner most 
 incomprehensible to the manufacturer. The process had in consequence to 
 be abandoned. The disappearance of the ammonia in this operation was 
 undoubtedly due to the absorbent power of the clay of the shale. This fact 
 may be taken as a proof of the powerful attraction existing between these 
 two substances, which apparently could not be overcome even by the influ- 
 ence of a high temperature. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 29 
 
 means of judging of the agricultural value or fertility of 
 our fields. 
 
 The action of a soil, rich in organic matter, on the solu- 
 tions above mentioned, is worthy of remark. A clay or 
 lime soil, poor in organic matter, withdraws all the potash 
 and silicic acid from a solution of silicate of potash ; 
 whereas one rich in so-called humus extracts the potash, but 
 leaves the silicic acid in solution. This comportment invo- 
 luntarily recalls the action of decaying vegetable remains in 
 the soil on the growth of plants, which, like reeds and 
 horse-tails, require a large quantity of silicic acid. These 
 plants abound in so-called sour moor and meadow lands ; 
 but disappear from them on the application of lime, and 
 give place to others better fitted for fodder. 
 
 Experiment shows, that the same garden and forest soil, 
 rich in humus, which withdraws no silicic acid from a solu- 
 tion of silicate of potash, immediately acquires the power 
 to do so, if it be mixed with a little slaked lime before the 
 silicate is added to it. Both constituents, potash and silicic 
 acid, are then retained by the soil. 
 
LETTER ni. 
 
 Our cultivated plants do not receive their food from Solution — Roots of plants 
 derive their Nourishment only from those portions of Soil absolutely in 
 contact with them — This view supported by the composition of River, 
 Well, and Drainage water — The Roots of plants must themselves exert 
 some peculiar action in Nutrition — The Life of land-plants endangered by 
 food when in Solution — In Water-plants the laws for the absorption of 
 Food must differ from those of Land-plants — The Ash of duck- weed shows 
 that plants have a Power of selecting their Food — Reason why mud from 
 stagnant pools is a good Manure — Remarkable power for absorbing Mois- 
 ture possessed by Soils — By absorption and evaporation of Moisture, the 
 Soil is warmed or cooled — G-reat importance of this fact to Vegetation — 
 The two Sources from which Moisture is absorbed by the Soil — Natural 
 Law deduced from the above facts. 
 
 There can be no doubt, from the action just described 
 of soil on potash, ammonia, and phosphoric acid, that the 
 majority of our cultivated plants cannot receive out of a 
 solution from the soil their essential mineral constituents. 
 For if, after filtering a solution of potash or ammonia 
 through a layer of soil of no greater thickness than usually 
 occurs in a field, these substances are so completely with- 
 drawn from the powerful acids with which they are com- 
 bined, as well as from the watery solution, that chemical 
 analysis can scarcely detect a trace of them in the filtrate, 
 it is not probable that rain-water alone, or even by the aid 
 of a small per-centage of carbonic acid, should possess the 
 power of extracting them from the soil, and forming a solu- 
 tion which should not again be decomposed by passing 
 through the ground. The same fact holds good for phos- 
 phoric acid and its salts. Carbonic acid water will every- 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 31 
 
 where dissolve phosphate of lime when it comes in contact 
 with it ; and the consequence of this solution can only be 
 its distribution through the soil. But such a solution 
 could not pass from the spot in which it was formed with- 
 out being deprived of all the dissolved salt bj such por- 
 tions of the soil as are not already saturated with it. 
 
 These substances are present in the soil in a condition 
 somewhat like colouring matter in charcoal, or iodine in 
 starch, fit for absorption by the rootlets of plants, but 
 not by themselves soluble in rain water, or removable by 
 this solvent until the soil is saturated with them. 
 
 It is more than probable that it is assigned to the 
 majority of our cultivated plants to receive their nourish- 
 ment directly from those portions of soil which are in 
 immediate contact with their rootlets, and that they die 
 when their food is presented to them in solution. The 
 action of concentrated manures, which are said by agricul- 
 turists to hum the young plants, appears to stand in some 
 connection with this supposition. 
 
 The composition of our common river, well, and drain- 
 age water from land, may serve to support these conclusions. 
 
 A number of excellent analyses of river and well 
 waters has been published by Graham, Miller, and Hof- 
 mann (Chem. Soc. Qu. T. iv. 375), from which it appears 
 that 100,000 gallons, or 500 tons of Thames water, taken 
 from five different places, contain : — 
 
 Thames Ditton, Kew. Barnes. Kedhouse, Battersea. Lambeth, 
 Pounds of Potash, 7-3 4-71 3-55 10 7-3 
 
 The following well waters contain, in 100,000 gallons : — 
 
 Witley. Critchmere. Veil wool. Hindhead. Barford. Cosford House. 
 Pounds of Potash, 2-71 25 3 0-7 1-8 6 
 
 Thomas Way found in drainage water — that is, in rain- 
 water (which had naturally percolated through the soil), 
 
82 
 
 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 taken from seven different fields, the following constituents 
 (Journal of the Roy. Ag. Soc, vol. xvii. 133) : 
 
 ' 
 
 Grains in 1 Gallon — 70,000 grains of water. 
 
 1 
 
 2 
 
 3 
 
 4 
 
 5 
 
 6 
 
 7 
 
 Potash 
 
 Trace 
 1-00 
 4-85 
 0-68 
 0-40 
 0-95 
 070 
 1-65 
 
 Trace 
 0018 
 
 Trace 
 2-17 
 7-19 
 2-32 
 0-05 
 0-45 
 1-10 
 5-15 
 012 
 0018 
 
 0-02 
 2-26 
 6-05 
 2-48 
 010 
 0-55 
 1-27 
 4-40 
 Trace 
 0018 
 
 0-05 
 0-87 
 2-26 
 0-41 
 
 1-20 
 0-81 
 1-71 
 Trace 
 0-012 
 
 Trace 
 1-42 
 2-52 
 0-21 
 1-30 
 1-80 
 1-26 
 1-29 
 0-08 
 0-018 
 
 0-22 
 1-40 
 5-82 
 0-93 
 0-35 
 0-65 
 1-21 
 3-12 
 0-06 
 0-018 
 
 Trace 
 3-20 
 
 13-00 
 2 50 
 0-50 
 085 
 262 
 951 
 012 
 0-006 
 
 Soda 
 
 Lime 
 
 Magnesia 
 
 Iron and Alumina. . 
 Silica 
 
 Chlorine 
 
 Sulphuric acid 
 
 Phosphoric acid 
 
 Ammonia 
 
 
 Very similar results were obtained by Dr. Krocker from 
 his analysis of drainage water from Proskau (Lieb. and 
 Kopp's Jahr., £ 1853, p. 742) : - 
 
 
 Drainage Water (in 10,000 parts). 
 
 a 
 
 b 
 
 c 
 
 d 
 
 e 
 
 f* 
 
 Organic matter 
 
 0-25 
 0-84 
 2-08 
 02 
 0-70 
 004 
 002 
 0-11 
 0-08 
 0-07 
 
 0-24 
 0-84 
 210 
 002 
 0-69 
 004 
 0-02 
 015 
 008 
 0-07 
 
 0-16 
 127 
 1-14 
 0-01 
 0-47 
 0-04 
 02 
 013 
 007 
 006 
 
 06 
 0-79 
 017 
 002 
 0-27 
 0-02 
 002 
 010 
 03 
 0-05 
 
 0-63 
 0-71 
 077 
 0-02 
 0-27 
 0-02 
 04 
 005 
 001 
 006 
 
 0-56 
 0-84 
 0-72 
 0-»2 
 0-16 
 001 
 0-06 
 0-04 
 0-01 
 0-05 
 
 Carbonate of lime 
 
 Sulphate of lime. .' 
 
 Nitrate of lime 
 
 Carbonate of magnesia 
 
 Carbonate of iron 
 
 Potash 
 
 Soda 
 
 Chloride of sodium 
 
 Silica 
 
 
 Total solid matter 
 
 4-21 
 
 4-25 
 
 3-37 
 
 1-53 
 
 2-58 
 
 2-47 
 
 * a Drainage water from land A (a clay soil resting on a subsoil of chalky 
 loam), collected 1st of April, 1853. b The same, collected 1st of May, 1853, 
 
THEOKETICAL AND PKACTICAL AGRICULTURE. 33 
 
 These drainage waters contain all the substances which 
 rain-water can dissolve out of the soil, and from their com- 
 position an idea may be formed of the quantity which a 
 plant during the period of its growth can possibly obtain 
 from such a solution. 
 
 Let us assume that on a 2^ acre field 12 million pounds 
 of rain-water fall in a year, and that a third of this quantity 
 dissolves from the soil the same ingredients, in the same 
 proportions, as in the drainage waters analysed by Way. 
 Let us further suppose that these 4 million pounds of water 
 are, during the months of June, July, August, and Septem- 
 ber, completely absorbed by the roots of a crop of potatoes, 
 and again evaporated from the leaves ; then it follows that 
 on four fields of 2^ acres each, the whole crop of potatoes 
 would not receive a single pound of potash ; on two others 
 of the same size they would obtain rather more than a 
 pound ; and on a seventh 2| acre field, two pounds. 
 
 Now, from an average crop of potatoes on a 2^ acre 
 field, there are obtained 408 lbs. of ashes, in which are 
 contained 200 lbs. of potash. 
 
 If, again, we suppose a crop of beet to be grown on the 
 fields, of which Dr. Krocker analysed the drainage water, 
 and also assume that 4 million pounds of rain-water satu- 
 rated with mineral substances from the soil, are absorbed 
 by the crop, then these plants would receive from this 
 source on four difierent fields of 2^ acres each, only 8 lbs. 
 each ; on another, 16 lbs. ; and on a third, 24 lbs. of 
 potash. 
 
 after a heavy fall of rain (218 cub. in. on the square foot), c Drainage water 
 from the same soil, mixed with water from a humus clay soil, with chalky 
 loam as subsoil, collected in October, 1853. d Drainage water from land B 
 (tile-drained, subsoil of chalky loam) collected in October, 1853. e Water 
 passing through the water furrows from a heavy clay soil, collected in the 
 beginning of June, f The same, collected in the middle of August, after 
 heavy rain. 
 
 2* 
 
84 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 Now, an average crop of beet from 2|- acres weiglis, witli 
 leaves, about 1000 cwt., whicli contain 1,144 lbs. of ashes, 
 of which 495 lbs. are potash I 
 
 The quantity of ammonia present in the drainage waters 
 analysed by Way is exceedingly small. It is not very 
 probable that one pound of ammonia in 8^- million pounds 
 of water can exercise any marked influence on vegetation. 
 
 In a gallon (70,000 grs.) of Thames water taken from 
 four different places, the quantity of ammonia could not be 
 estimated. In the portion taken at Eed-house, Battersea, 
 there were found 3 of ammonia, in 7 million parts of 
 water (Lieb. and Kopp's Jahr., f. 1851, p. 658). By irri- 
 gation the Thames water would undoubtedly produce a 
 considerable increase in the crops of hay on many mea- 
 dows, but certainly not by its ammonia, which is present in 
 this, as well as in all river waters in general, in only very 
 minute quantities. 
 
 The amount of phosphoric acid in drain, river, and ordi- 
 nary well-water, is exactly nil. Krocker found in drainage 
 water no phosphoric acid ; Way obtained from three, only 
 traces ; in two others, he found 12 parts of phosphoric acid 
 in 7 million parts of water ; in a third, 8 parts, and in a 
 fourth, 6 parts of phosphoric acid, to the same quantity of 
 water. 
 
 From the action of soils already described, it follows 
 that plants must themselves play some peculiar part in the 
 absorption of their food. As organised living structures, 
 their existence is not quite dependent on external causes. 
 
 Did land plants receive their food from a solution, they 
 should only be able to take up what this solution contains 
 and brings to them in a certain time, and just in proportion 
 to the evaporation of the water from their leaves. It is 
 quite certain that in the process of assimilation, there is a 
 necessary co-operation between the water which soaks 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 35 
 
 through the ground, and the evaporation which takes place 
 from the leaves of plants ; but the ground itself plays the 
 part of a guardian, protecting plants from a hurtful supply. 
 They select from the soil those substances which they re- 
 quire, but which can only pass into the interior of their 
 organisms by the co-operation of a cause which resides 
 within the rootlets. 
 
 We frequently find in meadows smooth lime-stones, 
 with their surfaces covered with a network of small fur- 
 rows. When these stones are newly taken out of the 
 ground, we find that each furrow corresponds to a rootlet, 
 which appears as if it had eaten into the stone. 
 
 It is very difficult to explain in what way plants act in 
 causing the solution of mineral substances. As a matter of 
 course, water is indispensable in the operation. 
 
 The difficulty of explaining the facts ought not at once 
 to deter us from investigating them in all their bearings, 
 and ascertaining the extent of their influence. Exceptions 
 exist in abundance. 
 
 In the case of many water plants whose roots do not 
 come in contact with the ground, there must of course 
 exist other laws for the absorption of their mineral food. 
 As in the case of sea-plants, they must receive it from 
 the surrounding medium ; for, wherever a plant grows, it 
 must find all the conditions necessary to its existence. 
 
 The investigation of duckweed (Lemna trisulca) offers in 
 this respect some points of interest. This plant grows in 
 still waters, in ponds and bogs, floating on the surface, so 
 that its roots are not in contact with the bottom. 
 
 From an artificial piece of bog in the botanic garden of 
 this place (Munich), a quantity of this plant was collected, 
 dried, incinerated, and the amount of ash determined. 
 From 10 to 15 litres (21- to 3^ galls.), of the bog water 
 which was of a slight greenish tint, was at the same time 
 
36 
 
 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 filtered and evaporated to dryness. The ashes, as well as 
 the residue from evaporation of the water, were submitted 
 to analysis. For comparison, the results are here placed 
 together. 
 
 Ash of Duckweed. 
 
 100 parts of dried duckweed, give 
 
 16-6 parts of Ash. In 100 
 
 parts of 
 
 the Ash heated to low redness, are 
 
 contained: — 
 
 
 Lime ... 
 
 16-82 
 
 Magnesia .... 
 
 5 08 
 
 Chloride of sodium . . . 
 
 5-897 
 
 Chloride of potassium . 
 
 1-45 
 
 Potash 
 
 13-16 
 
 Soda 
 
 
 Oxide of iron with traces of 
 
 
 alumina 
 
 . 1-3Q 
 
 Phosphoric acid . . . 
 
 . S-YS 
 
 Sulphuric acid . 
 
 . 6-09 
 
 Silica .... 
 
 12-35 
 
 Evaporated residue from water of the 
 Botanic Gardens. 
 
 1 Litre gives 0-415 grm. salts 
 (heated to low redness). In 100 
 parts of the salts are contained : — 
 
 35-00 
 
 12.264 
 
 10-10 
 
 8-97 
 0-471 
 
 0721 
 2-619 
 8-271 
 3-24 
 
 The amount of mineral constituents of this plant, as well 
 as of the bog water, must strike others with the same as- 
 tonishment as it did the first observer. For we could not 
 presuppose that such a plant should far surpass the ma- 
 jority of land plants in the richness of its mineral con- 
 stituents. These were certainly taken up by the plant from 
 a solution ; but in the process, it is highly deserving of 
 remark, that a power of selection was exercised by the 
 plant. 
 
 The comparison of the composition of the ash with the 
 salts left by the water shows, that all the mineral constitu- 
 ents of the latter, with the exception of the soda, are found 
 in the plant, but in very altered proportions ; the water 
 contains 45 per cent, of lime and magnesia, the plant only 
 21 per cent, of both ; the water contains 0*72 per cent, of 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 87 
 
 oxide of iron, tlie plant ten times this quantity. The dif- 
 ference in the phosphoric acid, potash, &c., is not less strik- 
 ing. The soluble mineral constituents were taken up by 
 the plant in the various degrees required for its vital pro- 
 cesses, and in no way proportional to the amount present 
 in the fluid. 
 
 The amount of mineral water present in this water is 
 remarkable. It is more than ten times greater than in 
 drainage water, and twenty -five to thirty times greater than 
 in well water. It resembles a mineral water in the kind 
 of salts it contains, and except in bogs is not likely to occur 
 in nature. 
 
 The amount of potash, phosphoric, sulphuric, and silicic 
 acids, and oxide of iron, which is found in it, can be easily 
 explained. In such a bog, the remains of dead plants are 
 by degrees collected, the roots of which have received from 
 the soil a quantity of mineral matter. These remains un- 
 dergo decomposition at the bottom of the pool, and their 
 inorganic elements are dissolved by the aid of carbonic 
 acid, and probably of organic acids, and remain in solution 
 in the water after the surrounding mud and earth have 
 been completely saturated with them. An experiment, in 
 fact, showed, that this potash water lost none of its potash 
 on filtration through earth taken at the distance of a foot 
 from the edge of the basin, whilst it was quickly removed 
 by earth taken from other spots. 
 
 In many places the mud from pools, still waters, and 
 many bogs, is highly esteemed as a fertilising agent. It is 
 evident that such mud acts like arable soil which has ab- 
 sorbed as much as it is capable of doing of the soluble 
 elements of food or manure brought in contact with it, 
 and a satisfactory explanation of its effect is found in the 
 quality of the bog water. Finally, it is conceivable that 
 water, in percolating through many field and garden soils, 
 
88 THEOEETICAL AND PRACTICAL AGRICULTURE. 
 
 in which the remains of plants have accumulated, and are 
 undergoing decomposition, will dissolve up many sub- 
 stances not usually found in mineral waters. 
 
 With the chemical properties of soils just described, there 
 is associated a physical quality, not less remarkable in its 
 nature and influence ; viz., the power which they possess 
 of attracting moisture from the air, and condensing it in 
 their pores. It has been long known that earth possesses a 
 strong attraction for watery vapour, but it was to Babo 
 that we were first indebted for the proof that this attrac- 
 tion is only second to that of sulphuric acid, which pos- 
 sesses it in the highest degree. If we fill a flask with air 
 completely saturated with moisture at 20*^ C. (68° Fahr.), 
 the slightest diminution of temperature will cause the 
 moisture to be deposited in the form of dew ; but if a 
 few ounces of earth dried at 85° to 40^ C. (95° to 204° 
 Fahr.), be placed in the flask, the moisture will, in the 
 course of a few minutes, be so completely absorbed by it, 
 that no deposit of dew will take place at a temperature 
 even of 8° to 10° C. below 0° (14° to 18° Fahr.). The ten- 
 sion of the watery vapour has sunk from 17"^^ to less than 
 
 Oram 
 
 In very moist air, soil loses its absorbing power for 
 moisture in proportion as it becomes saturated. When per- 
 fectly saturated it no longer absorbs any moisture from the 
 air. From air of the temperature of 20° C. (68° Fahr.), 
 containing watery vapour with a tension of more than 2""™, 
 dry earth absorbs moisture, until an equilibrium is esta- 
 blished between the tension of the watery vapour in the 
 air, or the force which strives to maintain it in the gaseous 
 state, and the power of attraction in the earth which tends 
 to destroy this state. 
 
 A soil which has been saturated with moisture from the 
 air at a given temperature, gives off a certain portion to 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 89 
 
 drier air, or on an elevation of temperature. On the other 
 hand, it absorbs moisture from air still more moist, until 
 an equilibrium is established. 
 
 The processes of absorption and evaporation are accom- 
 panied by a most important phenomenon. By absorption 
 of moisture the soil is warmed, and by evaporation it is 1 
 cooled. If we suspend in a vessel with moist air, a linen 
 bag full of dry earth, with a thermometer sunk in it, the 
 quicksilver will be observed to rise in a few seconds. In 
 Babo's experiment the temperature rose, in a specimen of 
 soil rich in organic matter, from 20° to 81° C. (68° to 88° 
 Fahr.) ; in a sandy soil to 27° C. (80° Fahr.). In like man- 
 ner, soil which had been partly saturated with moisture 
 from air at 68° Fahr. and 54° dew-point, when placed in 
 air completely saturated with moisture, caused the tempera- 
 ture to rise 8*6° to 54° Fahr. Such phenomena as these 
 must exercise a most decided influence on vegetation ; for 
 though the above extremes in the elevation of temperature 
 are seldom observed, the intermediate points are of frequent 
 occurrence. 
 
 When in a hot summer the surface of the ground is dried, 
 and there is no replacement of moisture by capillary attrac- 
 tion from the deeper strata, the powerful attraction of the 
 soil for the vapours of water in the air provides the means 
 for supporting vegetation. 
 
 The vapour of water which is thus condensed by the soil 
 is derived from two sources. During the night the tempe- 
 rature of the air falls ; the tension of its watery vapour be- 
 comes less ; and then, without the temperature of the air 
 falling to the dew-point, there follows, through the attrac- 
 tion of the soil, absorption of moisture (with ammonia and 
 carbonic acid), accompanied by evolution of heat which 
 moderates the cooling of the ground from radiation. In 
 rainless tropical regions, particularly, this phenomenon 
 
40 THEOEETICAL AND PRACTICAL AGRICULTURE. 
 
 must be of the most palpable influence. If in our tempe- 
 rate climate its effect is not so striking as in these regions, it 
 is nevertheless not to be regarded as altogether inappreci- 
 able. As condensation takes place slowly, the elevation 
 of temperature here cannot amount in many cases to more 
 than fractions of a degree. But it is precisely those frac- 
 tions which promote the better growth of many plants. 
 The soil by means of this property of absorption becomes 
 warmer, and maintains its temperature more equably than 
 it would otherwise do. 
 
 A second source from which the dry soil derives by 
 absorption its moisture, is presented by the deeper lying 
 moist strata. From these a constant distillation of water is 
 taking place towards the surface, accompanied by a corre- 
 sponding evolution of heat in the upper strata on its absorp- 
 tion. By drainage the water, which rises by capillary 
 attraction, being placed at a greater depth, the dry soil now 
 receives from the lower strata a quantity of moisture in the 
 form of vapour, which supplies the wants of plants, and at 
 the same time raises the temperature of the ground. 
 
 In the above facts we recognise one of the most remark- 
 able natural laws. The outermost crust of the earth is destined 
 for the development of organic life^ and its broken particles are 
 endowed^ by the wisest arrangement^ ivith the power of collecting 
 and retaining all the elements of food lohich are essential for the 
 purpose. This power preserves to the productive soil, even 
 in apparently the most unfavourable circumstances, the con- 
 ditions of fertility either contained therein, or bestowed 
 upon it. 
 
LETTER IV. 
 
 The Belief in the value of Humus no longer exists ; its Action now ascertained 
 — Effect of the Salts of Ammonia not dependent on their Nitrogen — The 
 action of Nitrates like that of the Salts of Ammonia — Experiments with 
 Nitrates and Chlorides — Experiments with Salts of Ammonia alone, and 
 with the addition of Common Salt — Solubility of the Earthy Phosphates in 
 solutions of Chlorides of Ammonium and of Sodium, and of Nitrate of Soda 
 — Experiments with these Salts — Their Solvent Action similar to that of 
 Carbonic Acid water — The Salts of Ammonia are decomposed in the soil ; 
 their twofold action — Difference in the Comportment of Salts of Potash and 
 of Soda in the Soil — Potash extracted by Sulphate of Ammonia from silicates 
 — Application of the Action of Chili Saltpetre, Salts of Ammonia, and 
 Chloride of Sodium to explain the increase of fertility in the soil, and the 
 Nutrition of Plants. 
 
 Up to a few years ago, scientific agriculture taught, and all 
 practical men firmly believed, that the productiveness of a 
 soil was dependent on the quantity of humus, or carbonaceous 
 remains of a preceding vegetation, contained in it. Without 
 raising doubts on the efiicacy in certain cases of the organic 
 matter in farm-yard manure, it may be asserted that nobody 
 who possesses any knowledge of the matter, now believes 
 that the produce of a field in carbonaceous substances bears 
 any proportion to the amount of humus in the soil, and that 
 its fertility can in reality be estimated, as was formerly sup- 
 posed, by this humus. 
 
 We have now obtained more exact information on the 
 part played by humus in vegetation, and can predict in what 
 cases its presence will be beneficial or hurtful. We know 
 that it is only useful when the soil contains in sufficient 
 quantity the fixed mineral constituents serviceable to plants ; 
 
42 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 and that it is without action when these are wanting By 
 its decomposition in the soil, humus forms a source of car- 
 bonic acid, by which the fixed elements of food are rendered 
 soluble, and capable of being distributed in all directions. 
 
 In his remarkable experiments on the action of the salts 
 of ammonia, Lawes obtained in twelve years from an acre 
 of the same field, by the use of mineral substances and salts 
 of ammonia, produce in wheat and straw, amounting to 
 51,995 lbs. From a second acre manured in the same way, 
 the return reached 53,182 lbs. By the use of pure mineral 
 manures, there was obtained from these two fields a greater 
 amount of produce, to the extent of 18,525 lbs. in one case, 
 and 19,713 in the other, than from an unmanured field of 
 similar size. It is quite certain that by the employment of 
 farm-yard manure, a similar, if not higher, return would 
 have been obtained from both fields. There can, however, 
 be no doubt that in both cases the salts of ammonia had 
 taken the place, and produced the effect of the decaying 
 organic matter of this manure; and it is not improbable 
 that the same cause was in operation in augmenting the 
 produ(3e. 
 
 It has been abundantly proved by facts, that the action 
 of the salts of ammonia is no way proportional to the amount 
 of nitrogen in them ; hence it is evident that the salts as 
 such, or the acids of the salts, must take part in the efiect 
 produced. The precise nature of this co-operation is, how- 
 ever, not yet distinctly made out ; and from this cause has 
 arisen the great discordance in the views of the peculiar 
 action of the salts of ammonia. Whilst some hold that the 
 action can only be referred to the nitrogen, because the acid 
 can be changed without thereby materially altering the 
 effect ; others assert that the soil already contains so much 
 ammonia, that the increase of produce cannot be attributed 
 to the small quantity of nitrogen added in the salts of 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 43 
 
 ammonia. They maintain tliat an acre of ground which 
 contains in its upper ten inches of soil 10,000 lbs. of 
 ammonia or nitrogen, could not have its fertility increased 
 two-fold by the addition of 30 to 60 lbs. of ammonia. As 
 in such a soil there was no want of nitrogen, the cause of 
 the increased fertility must be sought for in something 
 else. 
 
 The case is much the same with the action of nitrates as 
 with that of the salts of ammonia. Nitrate of soda exer- 
 cises a powerful effect, in certain cases, on the increase of 
 grain and straw, and in others it is valueless. The experi- 
 ments of Kuhlmann have shown that the bases also of these 
 salts play some part in the action. From a meadow ma- 
 nured with 250 kilogrammes (550 lbs.) of nitrate of soda, 
 an increase of crop to the amount of 2053 kilo. (4516 lbs.), 
 per hectare (2-J- acres), was obtained ; whilst from another 
 portion of the same meadow, to which was applied the 
 same quantity of nitrate of lime (containing IJ per cent, 
 more nitric acid), there was an increase of only 693 kilo. 
 (1524 lbs.). Consequently the produce from nitrate of lime 
 was f less than from the soda salt. If we ascribe the 
 increase in the crop to the nitric acid, then the effect of 
 the two salts is quite incomprehensible. 
 
 The action of common salt appears in many cases equally 
 incomprehensible. In 1846, Kuhlmann obtained from 200 
 kilo. (440 lbs.) of sulphate of ammonia an increase of hay, 
 amounting to 2533 kilo. (5572 lbs.) ; a similar quantity of 
 sulphate of ammonia, with the addition of 133 kilo. (292 
 lbs.) of common salt, gave an increase of 3173 kilo. (6980 
 lbs.) of hay. There were consequently 640 kilo. (1408 lbs.) 
 more hay obtained by the addition of the common salt, 
 than from the employment of the sulphate of ammonia 
 alone. 
 
 It might be supposed, that the want of a chlorine com- 
 
44 THEORETICAL AND PRACTICAL AGRICULTUEE. 
 
 pound, whicli is contained in not inconsiderable quantity in 
 meadow plants, was the reason, in the case of the common 
 salt, of the increase of produce ; but a similar difference, as 
 in the above cases, was found in two other experiments, 
 which Kuhlmann made, in 1845 and 1846, with sal-ammo- 
 niac alone, and with sal-ammoniac and common salt. The 
 piece of meadow manured with 200 kilo. (440 lbs.) of sal- 
 ammoniac gave in the two years 3700 kilo. (8140 lbs.) per 
 hectare (2-J acres), more hay than a piece of the same extent 
 which was unman ured. From another portion, to which 
 were applied 200 kilo, of sal-ammoniac and 200 kilo, of 
 common salt, 5687 kilo. (12,511 lbs.) of hay were obtained. 
 Hence, by the use of common salt, there was an increase 
 of 1087 kilo. (2391 lbs.), or a half more than from the sal- 
 ammoniac alone. 200 kilo, of common salt alone, without 
 sal-ammoniac, produced an increase of 1606 kilo, of hay, 
 the difference between the two numbers (1987 and 1606 
 kilo.) is not great enough to exclude the idea, that each 
 salt has acted, just as if the other had not been present, or, 
 in other words, that each salt has a special action of its 
 own. 
 
 In the summer of 1857, the effect of salts of ammonia by 
 themselves, and mixed with common salt, on summer bar- 
 ley, was tried by the General Committee of the Agricul- 
 tural Society of Bavaria, in a series of experiments made 
 at Bogenhausen, in the neighbourhood of Munich. For 
 this purpose, 18 plots, each of 1914 square feet in extent, 
 were marked off in a field which had gone through the 
 usual rotation of crops, having been, three years previously, 
 manured with common farm-yard manure, and having 
 borne rye, and then two crops of oats. Four of these plots 
 were manured with salts of ammonia ; one remained unma- 
 nured ; to four others were applied the same quantity of 
 ammonia salts, and at the same time, to each 3080 grm. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 45 
 
 (6^ lbs.) of common salt. Each plot received tlie same 
 amount ofniirogcn in the ammonia salts. 
 
 In estimating the quantity of manuring matter to be 
 employed, it was assumed that 400 lbs. ( = 440 lbs. Eng.) 
 of guano per English acre, corresponded to the full measure 
 of farm-yard manure usually applied ; this gives twenty 
 pounds of guano for one of the plots. A good sample of 
 guano was selected for the experiments, and on being sub- 
 mitted to analysis, was found to consist of 14-53 water, 
 88*88 ash, and 52*10 organic matter, of which 15*89 was 
 ammonia. Twenty pounds of this guano, therefore, con- 
 tained 8*07 lbs. of ammonia. In the ammonia salts used, 
 analysis gave in 
 
 Carbonate of Ammonia . . . 29-84 per cent. Ammonia. 
 Phosphate " ... 21-96 " " 
 
 Nitrate " ... 19-11 » " 
 
 In correspondence with this percentage of ammonia, 
 there were applied to two of the plots, I. and Y., 10|- Ba- 
 varian pounds ( = 18 lbs. Eng.) of carbonate of ammonia ; 
 to two others, II. and YI., 7^ lbs. ( == 9 lbs. Eng.) of nitrate 
 of ammonia ; to two others, III. and YII., 12 lbs., ( = 14| 
 lbs. Eng.) phosphate of ammonia. Two plots, lY. and 
 YIII., received each 12 lbs. ( — 14| lbs. Eng.) of crystal- 
 lised sulphate of ammonia ; another, 20 lbs. ( = 24-| lbs. 
 Eng.) of the analysed guano. The plots, Y., YI., YIL, 
 YIII., received each at the same time 8080 grm. ( = 6| Ibj. 
 Eng.) of common salt. I will here communicate these ex- 
 periments in full, as they offer other points of interest, in 
 addition to the action which must be ascribed to the com- 
 mon salt. 
 
 Produce of barley (grain and straw), from the four plots 
 manured with ammonia salts alone : — 
 
46 
 
 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 Grain. Straw. 
 
 grm. lbs, Eng. grm. lbs. Eng. 
 L . . . = 6335 = 14-0 16205 = 35-6 
 
 n = 8470 = 18-6 16730 = 36-8 
 
 in. . . . = 7280 = 16-0 17920 = 39-5 
 
 IV. . . . . = 6912 = 15-2 18287 = 40-2 
 
 The umnanured plot gave= 6825 = 150 18375 = 40-4 
 
 Produce of harley (grain and straw) from four plots 
 
 manured with ammonia salts and common salt: — 
 
 V. 
 
 VI. 
 
 VIL 
 
 VIII. 
 
 Grain. 
 
 grm. lbs. Eng. 
 14550 = 320 
 16510 = 36-3 
 
 9887 = 21-7 
 11130 = 24-5 
 
 Straw. 
 grm. lbs. Eng. 
 27020 = 59-5 
 36645 = 80-6 
 24832 = 54-6 
 
 27969 
 
 61-5 
 
 Increase of produce in plots V. to YIII., manured with 
 common salt and salts of ammonia, above that of plots I. 
 to lY., manured with salts of ammonia alone : — 
 
 Grain. Straw. 
 
 grm. lbs. Eng. grm. lbs. Eng. 
 
 V. . . . = 8255 = 18-2 10814 = 23'8 
 
 VI = 7770 = 17-0 19915 = 43-8 
 
 VIL . . . = 2607 = 5-7 6912 = 15-2 
 Vin. . . . . = 4218 = 9-3 9782 = 21-5 
 
 In instituting experiments in practical agriculture with 
 manures, the increase of crop is generally the only object 
 kept in view. If this object be attained, the experiments 
 are said to be successful. In this sense, the above experi- 
 ments, both with and without common salt, are unsuccess- 
 ful; for the returns scarcely reach average crops. The 
 object with which they were made was not, however, to 
 obtain a greater crop than the average, but to investigate 
 the action of the salts of ammonia alone, and with the 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 47 
 
 addition of common salt. In this respect they agree suffi- 
 ciently to banish all doubt as to the physiological import- 
 ance of common salt to the Bogenhausen fields. In every 
 case the crop was increased by the addition of common 
 salt. Common salt when used with carbonate of ammonia, 
 doubled the produce of grain ; and with nitrate of ammonia, 
 it raised the return of corn 90 per cent., — and of straw 120 
 per cent. 
 
 As the mixture of nitrate of ammonia and common salt 
 contains the elements of nitrate of soda, a counter experi- 
 ment with the latter salt on a plot of the same field, made 
 at the same time, is of much interest. The plot manured 
 with 16 lbs. (= 19f lbs. Eng.) of nitrate of soda, gave 
 12320 grm. (= 27 lbs.) grain, and 82480 grm. (= 71i lbs.) 
 straw ; and by the addition of 5^ lbs. (= 6f lbs. Eng.) of 
 common salt, the grain increased to 17920 grm. {= 39|- 
 lbs.), and the straw to 85780 grm. (= 78f lbs.). Common 
 salt had, therefore, also increased the action of Chili salt- 
 petre. A mixture of these two salts produced a still 
 higher yield of grain, than a mixture of common salt 
 and nitrate of ammonia, which contained the same pro- 
 portion of nitrogen. The experiment with 20 lbs. (= 24f 
 lbs.) of guano, on a plot of the same size, gave 17200 
 grm. {= 88 lbs.) grain, and 83820 grm. (= 73^ lbs. 
 straw. 
 
 It is quite certain, that in the action of the guano, which 
 produced the crop next highest after the Chili saltpetre, an 
 unmistakable part was played by the ammonia contained 
 in it. On the other hand, however, the experiments with 
 carbonate and nitrate of ammonia show, that a quantity of 
 ammonia, or nitrogen, equivalent to that in 20 lbs. of 
 guano, and employed under the same conditions, was 
 almost without effect. 
 
 I will not, by further pursuing this subject, weaken the 
 
48 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 significance of the most important fact brought out by 
 these experiments with the salts of ammonia, viz., that 
 common salt, in reality, exercises a favourable action on 
 the growth of straw plants in the Bogenhausen fields, and 
 increases the mass of vegetable matter in them. 
 
 This fact is indeed not new in agriculture ; but in a num- 
 ber of cases, in which common salt has been shown to be a 
 useful addition to other manures, its action has not been 
 sufficiently distinct and decided ; and it is a rule in natural 
 inquiries that a fact must first of all be firmly established, 
 before we proceed to seek its explanation. 
 
 The action of common salt is evidently very similar to 
 that of the salts of ammonia and nitrate of soda ; but if we 
 refer the effect of these last two substances to their nitrogen, 
 because ammonia and nitric acid are food for plants, then 
 this explanation will not hold good for common salt. For 
 neither this salt nor chlorine enters as an element into the 
 structure of plants, and it cannot be asserted that either of 
 them is necessary, although both are frequently met with 
 as constituents of the ashes of plants. 
 
 The most recent observations on the comportment of the 
 soil towards the food of plants show how slight is the 
 knowledge we possess of their mode of nourishment, and 
 of the part which the soil, by its physical condition, plays 
 in it. The comportment of the salts of ammonia, of 
 chloride of sodium, and of nitrate of soda, towards the 
 earthy phosphates in the soil, may perhaps assist us in 
 throwing some light on their action, or on one of their 
 actions, on the growth of plants. 
 
 Like carbonic acid water, the sulphate, as well as other 
 soluble salts of ammonia, possesses the property of render- 
 ing the earthy phosphates soluble in water. 
 
 We know of no other way in which the earthy phos- 
 phates are dispersed through the soil than by means of 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 49 
 
 carbonic acid water. If it is true that one of the chief 
 effects of humus, or the decaying remains of plants in soils 
 or in manures, consists in its forming a source of carbonic 
 acid, with which the air and water in the ground is en- 
 riched ; if it is also true that this carbonic acid water ren- 
 ders the earthy phosphates soluble, and thus contributes to 
 their distribution in the soil, then there can be no doubt 
 that the salts of ammonia, which possess the same solvent 
 property, can in this respect replace the organic matters, 
 and thus exert an equally favourable influence on the 
 growth of plants. 
 
 The same solvent property is also possessed among the 
 salts of soda by Chili saltpetre and common salt. It has 
 been recently shown that these two salts, even in the most 
 dilute solutions, dissolve earthy phosphates to a very appre- 
 ciable extent, and that consequently they must play a part 
 in the process of the nutrition of plants, similar to that 
 which is ascribed to carbonic acid water (to the humus) and 
 to the salts of ammonia. 
 
 From direct experiments it appears, that 100 kilo (= 220 
 lbs.) of sulphate of ammonia in solution in 45,000 litres 
 (= 9,900 galls.) of water can dissolve 8600 grm. (=7*9 lbs.) 
 of bibasic phosphate of lime (POg, 2CaO, aq.) such as 
 exists in bones that have been acted on by sulphuric acid ; 
 or, in other words, 100 lbs. of sulphate of ammonia in 
 4,500 gallons of water — dissolve nearly 4 lbs. of phosphate 
 of lime. In like manner 100 lbs. (=123 lbs. Eng.) of com- 
 mon salt, in 50,000 litres (= 11,000 galls.) of water, dis- 
 solve 3,300 grm. (= 7-J lbs.) of bibasic phosphate of lime ; 
 and 100 kilo. (= 220 lbs.) of nitrate of soda, in 83,400 
 litres (= 7,848 galls.) of water, dissolve 2,630 grm. (= 5f 
 lbs.) of the same phosphate. 
 
 Tribasic phosphate of lime (POg, 8CaO) is much less 
 soluble in these fluids. 
 
 3 
 
60 
 
 THEOEETICAL AND PKACTICAL AGRICULTUKE. 
 
 100 kilo. (220 lbs.) of 
 
 Sulphate of ammonia, 
 
 Common salt 
 
 Nitrate of soda 
 
 In solution in water in 
 
 54,000 litres (=11,880 galls.) 
 50,000 " (=11,000 " ) 
 33,300 " (= 7,326 " ) 
 
 Dissolve of tribasic 
 
 phosphate of lime, 
 
 POs, 3 CaO. 
 
 3400 -grm. ( = 7^ lbs.) 
 1500 " (=3i " ) 
 1200 '' (=2^ " ) 
 
 The seeds of the cereals, particularly wheat, contain 
 phosphate of lime, and in preponderating quantity phos- 
 phate of magnesia. In many kinds of wheat the quantity 
 of phosphate of magnesia is four times, often ten times, 
 greater than that of the phosphate of lime ; and in like 
 manner in the grain of rye, oats, and barley, the magnesia 
 salt exceeds very greatly the phosphate of lime. These 
 proportions are so constant that they cannot be ignored in 
 the cultivation of these plants. The comportment of the 
 salts above-mentioned towards phosphate of magnesia and 
 ammonia, and phosphate of magnesia, appears, therefore, 
 of special interest. 
 
 100 kilo. (220 lbs.) of 
 
 In solution in water, in 
 
 Dissolve of phosphate 
 
 of Magnesia, PCs 
 
 3MgO. 
 
 Nitrate of soda 
 
 Common salt 
 
 33,300 kilo. (= 73,260 lbs.) 
 50,000 " (=110,000 ") 
 
 2160 grm. (=4f lbs.) 
 3790 " (=8^ " ) 
 
 The solubility in the same fluids of phosphate of magne- 
 sia and ammonia is still greater. 
 
 100 kilo. (220 lbs.) of 
 
 In solution in water, in 
 
 Dissolve of phosphate 
 
 of magnesia and 
 
 ammonia, PO5. 2 MgO, 
 
 NH4O. 
 
 Sulphate of ammonia. 
 
 Common salt 
 
 Nitrate of soda 
 
 33,300 litres (= 7326 galls) 
 50,000 " ( = 11,000 " ) 
 33,300 " (= 7326 " ) 
 
 41 13 grm. (= 9 lbs.) 
 6170 '* (=13| " ) 
 4655 " (=10i " ) 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 51 
 
 The quantity of the earthy phosphates taken up by the 
 above fluids does not rise in proportion with the amount 
 of salts in solution, but rather on the contrary with the 
 dilution of these fluids."^ 
 
 It is quite conclusive from these facts, that water con- 
 taining a very small quantity of common salt, nitrate of 
 soda, or a salt of ammonia, acquires thereby the power, 
 (which alone it does not possess, or only in a slight degree) 
 of dissolving phosphoric acid, in the form of earthy phos- 
 phates. These feeble solutions, therefore, react towards 
 earthy phosphates like solutions of carbonic acid in water. 
 100 kilo. (=220 lbs.), for example, of sulphate of ammonia 
 produce the same solvent effect on phosphate of lime as 
 4720 litres {= 1038i galls.) of carbonic acid in solution in 
 water; and 100 kilo, of common salt dissolve as much 
 phosphate of magnesia and ammonia as a watery solution 
 of 3456 litres (= 760J galls.) of carbonic acid. 
 
 Direct experiments prove, that a very dilute solution of 
 the same salts, take up phosphoric acid from a soil which 
 contains earthy phosphates in excess, and that this dissolved 
 acid is again given up by this solution to a similar soil 
 which is not already saturated with phosphoric acid. 
 
 If we submit to a close scrutiny the comportment of the 
 salts of ammonia, nitrate of soda, and common salt towards 
 soils, we find that not one of these salts acts in the same 
 form in which it has been added to the ground. 
 
 *1000C. a of fluid, con- 
 taining at 57° F. 
 
 Dissolve of PCs. 2MgO, 
 NH4O. 
 
 For 1 grm. of salt. 
 
 2-2 grm. NH4OSO3 
 3. u 
 
 10- *' " 
 
 76-7 mLIligrrQ. 
 113-0 " 
 147-0 " 
 
 34-9 milligrm. 
 
 37-6 
 
 14-7 " 
 
52 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 The salts of ammonia are immediately decomposed by 
 the soil ; the ammonia is retained, whilst the acid enters 
 into combination with lime, magnesia, alkalies, or, in short, 
 with any basic substance in immediate contact and capable 
 of combining with it. 
 
 The action of these salts is therefore of a two-fold nature. 
 On the one hand, they enrich the soil with ammonia ; on 
 the other, their acid gives rise to new compounds which 
 come into operation. The alkalies and alkaline earths 
 which combine with the acid acquire thereby a greater 
 degree of solubility, and are more readily diffused through 
 the soil. If the ground is rich in magnesia or lime, the 
 salts of these bases are formed ; but their influence, with 
 the exception of that of gypsum, on certain plants cannot 
 be estimated very high. The use of sal-ammoniac, instead 
 of sulphate of ammonia, gives rise to chloride of magne- 
 sium, and chloride of calcium, which act rather unfavoura- 
 bly than otherwise on vegetation. That salts of these 
 bases are generated by the action of soils on salts of ammo- 
 nia, and that the new salts exert no particularly favourable 
 influence on the increase of produce, are facts on which no 
 doubt can rest. 
 
 If, however, portions of the soil containing in some 
 places phosphate of lime or of magnesia in the form of 
 coarse grain, or powder, or bone earth, come in contact 
 with these ammoniacal fluids, then there follows solution 
 of these earthy phosphates, and their consequent diffusion 
 through the soil. 
 
 Potash salts resemble those of ammonia in the rapidity 
 of their decomposition in contact with soils ; but the com- 
 portment of soda salts is quite different. 
 
 On slowly filtering a solution of nitrate of soda (contain- 
 ing one-fifth per cent, of salt) through an equal volume of 
 Bogenhausen loam, half of the salt passes through unab- 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 53 
 
 sorbed, whilst the other half is converted into nitrate of 
 lime and nitrate of magnesia. Under the same circum- 
 stances three-fourths of a solution of chloride of sodium 
 remain undecomposed. 
 
 If, therefore, a field is manured with nitrate of soda or 
 common salt, and the soil becomes saturated with a dilute 
 solution of these salts formed by rain, a great portion of 
 them will remain unchanged in the ground, and must exer- 
 cise on the moist soil an action which, though in itself 
 feeble, becomes powerful by its continuance. 
 
 Like the salts of ammonia, or a watery solution of car- 
 bonic acid produced by the decay of organic matter in 
 manures, a solution of these salts, wherever they come in 
 contact with spots containing accumulations of earthy phos- 
 phates not fixed by the soil, must become saturated with 
 these phosphates, and thus convert them into a condition 
 in which they can be diffused through the ground. If the 
 earthy phosphates, when thus diffused in solution, come in 
 contact with other portions of soil not yet saturated with 
 these salts, those portions absorb and fix these earthy phos- 
 phates, and the chloride of sodium or nitrate of soda 
 retains, a second time, or more frequently, the power of 
 exercising the same solvent and distributing action over 
 the earthy phosphates until the ultimate and complete con- 
 version of the chloride and nitrate into a lime or magnesia 
 salt. 
 
 When we consider how much the fertilising effect of 
 bone earth is increased by the greater solubility and capabi- 
 lity of distribution in the soil communicated by the action 
 of sulphuric acid, we cannot too highly estimate the signifi- 
 cance of the properties, just described, of the salts of ammo- 
 nia, chloride of sodium, and Chili saltpetre. 
 
 The most abundant application of earthy phosphates in 
 coarse powder, can in its effects bear no comparison with a 
 
54 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 much smaller quantity which, in an infinite state of divi- 
 sion, is dispersed through every portion of soil. A rootlet 
 requires at the spot where it touches the soil a most minute 
 amount of food ; but it is necessary to its functions and its 
 very existence, that this minimum be found exactly at this 
 spot. For if the food of plants be not soluble in water, 
 then is any excess at any other spot as valueless to the func- 
 tion of nutrition of this rootlet as if it did not exist at all 
 in the soil. Now, the salts of which we have been speak- 
 ing, possess the property of conveying these elements of 
 food from the spot in which they exist in superabundance 
 to others in which there is a deficiency ; and even though 
 their elements contributed in no way directly to the pro- 
 cess of nutrition, yet, these salts must nevertheless exercise 
 a marked influence on the increase of produce. 
 
 When the sulphate of ammonia and Chili saltpetre have 
 been completely transformed into lime and magnesia salts, 
 and the chloride of sodium into chloride of calcium and 
 chloride of magnesium, this action then ceases ; and a second 
 dose of these salts is then necessary to reproduce the action. 
 
 If the effect of the salts of ammonia depends on the am- 
 monia, we can scarcely comprehend why, after a large 
 application of them, that portion which has not acted 
 during the first year should not in the second come into 
 operation, since this latter portion is presented in the soil 
 to plants in the same form as the portion which produced 
 its effect during the first year. 
 
 Sulphate of ammonia produces on alkaline silicates a 
 reaction similar to that on earthy phosphates. If this salt, 
 in very dilute solution, is brought in contact with soil satu- 
 rated with silicate of potash, and which does not give up a 
 trace of its potash to water alone, it instantly dissolves a 
 certain quantity of this alkali, which may be easily detected 
 by the ordinary re-agents. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 55 
 
 It is evident that the agriculturist, by the proper appli- 
 cation of the chemical action of common salt, Chili saltpe- 
 tre and ammonia salts, accomplishes the same object as by 
 the mechanical operation of ploughing, and by the action 
 of the atmosphere in fallow. 
 
 We should be committing an error, if, judging from 
 similarity of solvent properties, we concluded that common 
 salt must have the same effect as a corresponding quantity 
 of nitrate of soda. We know that, as a rule, in these cases, 
 the common salt is converted into chloride of calcium, and 
 the Chili saltpetre into nitrate of lime ; and the experi- 
 ments of Kuhlmann have taught us, that chloride of cal- 
 cium by itself is absolutely ineffective, or rather is hurtful 
 in the cultivation of plants, whilst nitrate of lime contri- 
 butes materially to the increase of a hay crop. ISIitrate of 
 soda, consequently, acts favourably in two ways ; chloride 
 of sodium only in one. Further, land plants can bear a 
 considerable quantity of nitrates of soda in the soil, whilst 
 chlorine compounds, beyond a certain very narrow limit, 
 are decidedly hurtful. 
 
 We designate as manures all substances which increase 
 the produce of our fields, without knowing whether many 
 of these may not simply act, by rendering the food already 
 existing in the soil more capable of absorption and assimi- 
 lation. The simple fact of their favourable influence on 
 vegetation, is not yet a proof that they have acted directly 
 as food. We compare the work which the plough performs, 
 to the mastication of food, for which nature has provided 
 animals with a particular instrument ; and, as may be seen 
 from the experiments described above, many substances, 
 such as common salt, nitrate of soda, and ammonia salts, 
 independently of the action which is due to their own ele- 
 ments, play a peculiar part, which may be compared to the 
 digesting action of the stomach, and in which they can 
 
56 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 partly replace eacli other; and inasmucli then as they pre- 
 pare the food existing in the soil for the process of nutri- 
 tion, and render it more fit for assimilation, they must 
 necessarily exert a powerful influence on the growth of 
 plants. 
 
 We can now understand why these salts exercise a 
 favourable action in the cultivation only on certain soils, 
 and why on a second or third application of them, the same 
 effect is only partially, or not at all reproduced. 
 
 An agriculturist in possession of fields containing abund- 
 ance of phosphates, but unequally distributed through them, 
 would, were all other conditions the same, undoubtedly 
 increase the activity of these phosphates, and thereby aug- 
 ment the produce of his fields, if he possessed the means 
 of withdrawing the basic phosphates from the soil and 
 restoring them in the form of superphosphate. These 
 means he actually employs, when he manures his fields 
 with Chili saltpetre, ammonia salts, or chloride of sodium. 
 
LETTEK V. 
 
 No free Ammonia in the Soil — The amount of Food obtained from the soil 
 by plants is in proportion to the absorbent Root-surface — The early deve- 
 lopment of Roots due to the accumulation of Nourishment in the surface 
 soil — Estimations of the quantity of Ammonia in our cultivated fields — A 
 deficient crop not due to the Absence of Ammonia in the soil — Experi- 
 ments with salts of Ammonia; the crops only slightly increased thereby — ■ 
 Increase of produce due to accompanying Minerals —Experiments of Lawes 
 and Kuhlmann with salts of Ammonia, &c. — The fertility of a field depend- 
 ent on the sum of the Mineral matters in it — The activity of these Minerals 
 increased within a given time by the Salts of Ammonia — The soil more 
 rapidly exhausted by their use unless there is a restoration to it of the 
 removed Mineral matters. 
 
 The soil contains a certain quantity of nitrogen in the form 
 of ammonia and of nitrogen compounds derived from plants 
 and animals. 
 
 The observations of Thomson and of Huxtable, and par- 
 ticularly the valuable memoirs of Way, have established 
 the fact, that the carbonate of ammonia of rain water and 
 of manures, and that existing in ammonia salts, are absorbed 
 and so firmly fixed by the soil that no free ammonia can 
 be present in it. As neither pure nor carbonic acid water 
 can withdraw this fixed ammonia from the soil, it is self- 
 evident that, in the nutrition of plants, the rootlets must 
 extract it directly from the soil. 
 
 If we now imagine that plants receive all the nitrogen 
 they require for their development not from the air but 
 from the soil, it is clear that every portion of soil must con- 
 tain the necessary quantity of ammonia or nitrogen for their 
 vital processes; and plants would not attain their maxi- 
 
 3^ 
 
58 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 mum development, if they found in those portions less 
 than the roots could absorb and the plant appropriate. 
 Were all other conditions for the formation of grain pre- 
 sent, they would then produce a smaller quantity, or grain 
 of a lighter weight. 
 
 The productiveness of a field, in so far as it is dependent on 
 nitrogen, would be in proportion to the sum of this element 
 contained in the soil, and to that portion of this sum which 
 is present in each transverse section of the soil from the 
 surface downwards. In whatever spot the rootlets cannot 
 find nitrogen, they would therefore at that spot absorb none. 
 
 From two fields, containing from the surface downwards 
 the same quantity of nitrogen, and supposing all the other 
 conditions of growth to be given, it will be found that two 
 plants will receive unequal quantities of nitrogen, if their 
 absorbent surface of rootlets is unequal in extent. The 
 plant with double extent of absorbing root surface will take 
 up twice as much nitrogen as the other. This proportion 
 holds good for all the elements of food in the soil. 
 
 From a field which contains only half the quantity of 
 food which is present in another, a plant with a double pro- 
 portion of rootlet surface will receive as much nourishment 
 as a plant with only half the rootlet surface obtains from 
 the second field. 
 
 These propositions are self-evident, and may afford an 
 explanation in many cases of one of the leading effects of 
 manures on our fields. For, an accumulation of nourishment 
 in the upper layer of the field enables plants, during the first 
 period of their development, to send out ten-fold, perhaps 
 a hundred-fold more absorbing rootlets than they otherwise 
 would have done, and their later growth will be in propor- 
 tion to the greater number of rootlets thus gained, by which 
 they are enabled to seek and appropriate the food distributed 
 sparingly throughout the deeper layers. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 59 
 
 We possess as yet no investigation of the number of 
 rootlets and the extent of their absorbing surface in our 
 cultivated plants, and cannot therefore with any degree of 
 certainty fix the quantity of ammonia which must neces- 
 sarily be present in each transverse section of soil to satisfy 
 the full requirement of nitrogen in the different classes of 
 plants. 
 
 If we now accept, on the grounds mentioned in the next 
 letter, that each square millimetre of the transverse section 
 of a field must contain -J a milligramme of ammonia, in 
 order to furnish to the rootlets of a wheat plant all the 
 nitrogen which it requires for its full growth, it follows that 
 10,000 lbs. (or 0*12 to 0*13 per cent.) of ammonia must be 
 present in the soil of a hectare (2^ acres) of land within the 
 depth reached by the chief roots. 
 
 If we compare with the above the amount of ammonia 
 or nitrogen, ascertained with certainty by numerous analyses 
 to exist in the soils of different countries, it appears that a 
 depth of even ten inches of the greater number of our cul- 
 tivated fields famishes much more than this quantity. 
 
 As our cultivated plants undoubtedly absorb through 
 the leaves as much nitrogenised food in the form of ammo- 
 nia and nitric acid from the air as well as dissolved in rain 
 and dew, as uncultivated plants which receive no nitrogen- 
 ised manure from the hands of man ; we can therefore 
 conceive that the agriculturist will seldom have to seek the 
 reason of his poor crops in a deficiency of ammonia or 
 nitrogenised food alone, and that he must first of all direct 
 his attention to certain other conditions in order to improve 
 his harvest. 
 
 A knowledge of the quantity of ammonia or nitrogen in 
 a soil is, therefore, not sufiicient to enable us to judge of 
 its facility or capacity for production. For, even though 
 a better crop be obtained from many fields by the applica- 
 
60 THEOKETICAL AND PKACTICAL AGKICULTURE. 
 
 tion of ammonia, on by far tlie great majority of others, the 
 largest quantities of this food produce no effect ; because 
 though the nitrogen must indeed be there, and takes part 
 in the formation of the vegetable mass, yet it produces by 
 itself no effect when the conditions are awanting which 
 render it active. 
 
 The experiments of Schattenmann made in 1843 in 
 Alsace, are in this respect very instructive. Wheat fields 
 manured by him with salts of ammonia gave a smaller return 
 of grain than another portion of the same land which had 
 received none of this manure. In like manner the experi- 
 ments of the General Committee of the Agricultural Soci- 
 ety of Bavaria in 1857 (see p. 46), show that the produce 
 of barley in grain and straw was rather reduced than other- 
 wise in a field to which carbonate of ammonia had been 
 applied; and that the use of sulphate, phosphate, and nitrate 
 of ammonia raised the produce only a few per cents. A 
 quantity of guano containing the same amount of ammonia 
 as these salts gave on the same field three times as much 
 grain, and twice as much straw as the unman ured land. 
 
 It is obvious that the proximate cause of the powerful 
 action of the guano in this case must be sought for in those 
 matters which in it accompany the ammonia ; for, as we 
 have just stated, a quantity of ammonia equal to that of 
 the guano produced no marked effect on the same field, in 
 the same year, and with the same kind of crop. 
 
 It is clear that a field which either originally contained, 
 or has had added to it, a sufficient quantity of the substances 
 that accompany ammonia in guano, would, on the subse- 
 quent application of the salts of ammonia, produce an 
 equally good crop as it would have done with the guano, 
 and better than would have been the case without the 
 aid of the ammonia. In such a case, however, it would be 
 a hasty conclusion to ascribe the higher return to the action 
 
THEOKETICAL AJ^D PRACTICAL AGRICULTURE. 61 
 
 of the ammonia alone, because in tlie years of greater 
 increase ilie salts of ammonia had been exclusively used. 
 
 The experiments of J. B. Lawes, in the years 1844 to 
 1855, give practical proofs of the truth of this view. He 
 manured a wheat field with superphosphate of lime (560 
 lbs. per acre), and with silicate of potash (220 lbs.), and in 
 the eleven following years only with ammonia salts (sul- 
 phate of ammonia and chloride of ammonium) and reaped 
 on an average from it a half more grain and straw than 
 from another piece of unmanured land of the same 
 size which, during the same years, had been sown with 
 wheat. 
 
 These results fully agree with those of Kuhlmann's ex- 
 periments in 1844 to 1846, with salts of ammonia on a 
 meadow. 
 
 From a meadow which had been manured with sal ammo- 
 niac, he obtained an increase of 645 parts of hay for every 
 100 parts of the salt employed. In the same year, from a 
 second meadow, to which sal ammoniac had been also 
 applied, but with the addition of phosphate of lime, he 
 reaped 1666 parts of hay for every 100 parts of sal ammo- 
 niac; consequently the produce was 2l times more than 
 was obtained without phosphate of lime. 
 
 The importance of the addition of fixed mineral food to* 
 the increase of crops, and to the duration of the fertility of 
 our fields, will at once be evident to the most prejudiced i 
 from another series of experiments by Lawes. 
 
 During the period that the experiments already mentioned 
 were in progress, Lawes had applied, on a third field, for 
 three years, fixed mineral matters, and for nine years, salts 
 of ammonia ; in 1846 it remained unmanured. This field 
 had, therefore, received two applications of ammonia salts 
 less, and two of mineral manures more than the second 
 field. 
 
62 THEOEETICAL AND PRACTICAL AGRICULTURE. 
 
 The following was tlje produce per acre of tlie three 
 fields : — 
 
 Grain and Straw. 
 
 I. Unmanured field produced 34,272 lbs. 
 
 II. Field manured 1 year with mineral substances, and ) ^^ 
 
 11 years with salts of ammonia . . . f ' 
 III. Field manured 3 years with mineral substances, 
 and 9 years with salts of ammonia 
 
 55,704 
 
 Although the third plot had received above 700 lbs. of 
 ammonia salts per acre less than the second, its produce 
 had nevertheless increased by half a crop. These facts 
 show in the most undoubted manner, that even on ground 
 so rich in the fixed constituents of food for wheat, as to 
 furnish during twelve continuous years, without any ma- 
 nure, a yearly medium crop of 2856 lbs. of grain and straw, 
 the greatest supply of salts of ammonia, with an insufiicient 
 replacement of the mineral substances removed in the crops, 
 produced a smaller amount of grain and straw than when 
 these minerals were more fully returned to the soil. They 
 show further that the salts of ammonia as manure were 
 rendered unnecessary exactly in proportion to the supply 
 of fixed mineral substances ; for the smaller quantity of 
 ammonia applied to the third field gave, not a correspond- 
 ingly smaller crop, but on the whole a higher return than the 
 larger quantity of this substance on the second field which 
 had received mineral manure only in the first year. 
 
 The effect of mineral substances as manure is apparent 
 by comparing the produce of Plots 11. and III. in the dif- 
 ferent years. 
 
 In the year 1850 Plot III. had been manured for the 
 third time with 300 lbs. of carbonate of potash, 200 lbs. of 
 carbonate of soda, 100 lbs, of sulphate of magnesia, 200 lbs. 
 of bone earth, 150 lbs. of sulphuric acid, and in the five 
 following years had received only salts of ammonia. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 63 
 
 Plot II. had only once (1844) been manured with super- 
 phosphate of lime and silicate of potash, and in the eleven 
 following years with salts of ammonia alone. 
 
 The produce of these plots from the year 1850 was the 
 following : — 
 
 I, Unmanured plot 
 
 Produce of grain and straw In lbs. 
 
 1851 
 
 1852 
 
 1853 
 
 1854 
 
 1855 
 
 2710 
 5036 
 
 4985 
 
 1000 
 1850 
 1800 
 
 2457 
 4107 
 
 4162 
 
 1000 
 1630 
 1690 
 
 1772 
 2691 
 
 3578 
 
 1000 
 1500 
 2010 
 
 3496 
 
 5808 
 
 7003 
 
 1000 
 1690 
 2000 
 
 2860 
 3779 
 
 5074 
 
 1000 
 1520 
 1770 
 
 II. In 1844 received mineral sub- 
 stances, then up to 1855 • 
 
 ammonia salts 
 
 Ill In 1844, 1848, 1850, received ) 
 mineral substances, then >• 
 up to 1855 ammonia salts ) 
 
 I .""^ 
 
 II 
 
 Ill 
 
 
 We see from these numbers that Plot III., after receiving 
 in 1850 a large supply of mineral manure, produced in the 
 two following years no greater crop than Plot II., to which 
 no such excess had been applied. From this absence of 
 any marked effect from the mineral manure, the inexpe- 
 rienced agriculturist might at once believe himself entitled 
 to conclude that the plot already contained a sufficient quan- 
 tity of these substances, and that, therefore, a further supply 
 was unnecessary, and a piece of extravagance. These ex- 
 periments, carried out with so much perseverance, prove, 
 however, the unsoundness of such a conclusion. They 
 show that not one particle has been inefficient, but that 
 their action was only apparent after their distribution in 
 the soil had been effected. They show that these mineral 
 substances by themselves require a longer time to become 
 
64 THEORETICAL AND PRACTICAL AGRICUI PURE. 
 
 active than when applied in the form of farm-yard manure, 
 which supplies in its organic matter a source of carbonic 
 acid as the natural solvent and distributor of its fixed con- 
 stituents. The eftect of the mineral food exhibited in the 
 increase of produce became apparent only in the fourth 
 year (1853), and its continuance was still evident in the 
 most visible manner in the sixth year. 
 
 Whilst the ammonia salts increased the produce of the 
 second plot (which had seven years previously received 
 mineral manure) in the year 1853 one-half more than that 
 of the unmanured plot, the produce of the third plot, with 
 the same quantity of ammonia, was twice as high. In the 
 year 1854, its produce exceeded that of the second plot 
 by 31, and, in 1855, by 45 per cent. 
 
 It is hardly possible to find another cause for the differ- 
 ence between the two wheat fields manured with ammonia 
 salts, than that the one was richer than the other in the 
 mineral food for the wheat plant. Nothing can be more 
 positive than that the produce of both fields bore no pro- 
 portion to the quantity of ammonia applied. 
 
 As the fixed mineral constituents incorporated with the 
 third plot in the year 1850 must be regarded as the proxi- 
 mate cause of its increased produce in the years 1853 to 
 1855, there can be no doubt that the mineral matters (560 
 lbs. superphosphate of lime, and 220 lbs. silicate of potash), 
 applied in 1844 to the second plot, were equally the proxi- 
 mate cause of the greater return obtained from it in the 
 eleven following years than from the unmanured plot. 
 
 With fields under conditions so identical as the experi- 
 mental plots of Lawes, it cannot be supposed that the third 
 plot could possibly have borne a larger crop in 1853, 1854, 
 and 1855, than the second, had it not contained a larger 
 amount of active mineral matters than the latter ; and had 
 the sum of the active mineral substances in the second plot 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 65 
 
 not exceeded that in tlie unmanured, the increase and con- 
 tinuance of the crops from this second plot would also have 
 been impaired. 
 
 It follows, therefore, as a natural consequence, that the 
 crops from the unmanured plot are also proportional to the 
 sum of the active mineral constituents in the soil. Had 
 this sum been smaller, the deficiency would have been evi- 
 dent in the diminution of the crops. With the increase of 
 these mineral matters in the second field, the crops also 
 increased by the aid of the salts of ammonia ; and a fur- 
 ther quantity of these substances, applied to the third plot, 
 was followed by a still larger crop from that plot, not- 
 withstanding that it had received less ammonia than the 
 second plot. 
 
 It is further evident, from the above, that the crops, and 
 the increase in them, were dependent on the sum of the 
 mineral matters in the three plots, and on that portion of 
 this sum, which had been rendered fit for absorption by 
 the action of the salts of ammonia. Without the supply of 
 fixed mineral substances to the second and third plots in 
 Lawes' experiments, they would have been, after the lapse 
 of a few years, precisely in the same condition as those of 
 Schattenmann, from which there was obtained no increase 
 of grain by the application of the salts of ammonia. When 
 by the supply of salts of ammonia, or Chili saltpetre, the 
 produce of corn and straw in a field is increased, the proxi- 
 mate cause of this increase lies in the fact, that an addi- 
 tional portion of the sum of the mineral substances in the 
 field has been thereby rendered capable of assimilation by 
 plants, and therefore become active. Without the presence 
 of such an excess of mineral matter, the salts of ammonia, 
 and Chili saltpetre, would not have been attended with any 
 effect. 
 
 A field, which, by manuring with these last-named salts, 
 
m THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 has produced a larger crop for one or more years is therebj 
 impaired in fertility for f\iture crops : for it could retain the 
 same degree of fertility only when the conditions of fertility 
 remain the same ; just as it can become more fertile only 
 by having those conditions of fertility increased. But, in 
 the rich crops obtained by the use of ammonia salts and 
 Chili saltpetre, the farmer removes from his field in the 
 form of corn and straw, the mineral constituents of the soil, 
 and the field is consequently less rich in these substances 
 after the harvest than it was before. 
 
 Experience teaches, that the produce of fields in the same 
 district is very unequal, even though they contain the same 
 quantity of decaying organic matter and nitrogen. From 
 one meadow is obtained twice or thrice more hay than 
 from a similar extent of another meadow placed in the 
 same external conditions. An acre of clover land yields 
 three or four times as much clover hay as an acre of an- 
 other field. 
 
 The causes of this unequal productiveness, are always 
 and everywhere the same. 
 
 The atmosphere conveys to two fields of equal surface a 
 like quantity of carbonic acid and ammonia ; the more fer- 
 tile field, nevertheless, yields two, three, or four times more 
 carbon and nitrogen, in the form of hay or clover, than the 
 other. It is evident, that in such a case, the cause of the 
 increase lies in the soil, and not in the air. The more fer- 
 tile field has furnished to the plants two, three, or four 
 times more mineral food than the other: it contained a 
 larger absolute quantity, or a larger available proportion of 
 these substances. 
 
 If we take two clover fields or meadows of unequal pro- 
 ductiveness, in one of which there is accordingly present a 
 larger quantity of mineral substances than in the other ; and 
 if we suppose that the atmosphere supplies them in one 
 
THEOKETTCAL AND PEACTICAL AGRICULTUKE. 67 
 
 year with two, three, or four times the amount of ammonia 
 they usually receive, and that their produce is thereby in- 
 creased, — it will be found that the increase of crop in the 
 two fields will be always unequal. The return from the 
 more fertile field will always be greater than that from the 
 less fertile, and this in the same unvarying proportion ; for 
 there has been no change in the sum of the conditions of 
 fertility in the soils of the two fields. 
 
 The increase in the fertility of a field by the application 
 of ammonia, or its salts, necessarily presupposes the pre- 
 sence of the conditions of this increase, and that a greater 
 quantity of mineral matter has in a given time become 
 active and capable of absorption. 
 
 In every case the produce of a field and the duration of 
 its fertility bear a fixed relation to the sum of the mineral 
 substances in the soil. 
 
 The greater or less abundance of the crop is proportional 
 to the rapidity of the action of the mineral matters in a 
 given time ; that is, to that portion of their total quantity 
 which is annually transferred from the soil to the plant. 
 Hence, if a field contains so much mineral matter that, 
 without any supply whatever, it can yield in 100 years ex- 
 actly 100 average (^. e. remunerative) crops of wheat, it 
 may after this time possibly be still rich enough for another 
 kind of crop ; but, in an agricultural sense, it is no longer 
 a wheat field. 
 
 If, by a more thorough mechanical preparation of the 
 ground, or by chemical means, such as Chili-saltpetre, 
 common salt, and salts of ammonia, the action of the avail- 
 able mineral food be accelerated, the field will perhaps 
 yield in 50 years as much grain and straw as it would have 
 done in 100 years without these means, and in half the time 
 it would be exhausted for the cultivation of wheat. 
 
 By the use of such means the total produce of the field 
 
68 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 is not increased, but only the quantity obtained in a given 
 time. 
 
 When the agriculturist loses sight of the conditions which 
 determine the duration of his large crops, and relies on the 
 effect of his labour, and on the application of Chili-salt- 
 petre, salts of ammonia, and common salt, without at the 
 same time taking care to replace the mineral substances 
 removed by his crops, he is then speculating on the wealth 
 of his field, of the extent of which he knows nothing, and 
 can receive no information from others. He seizes before- 
 hand on the produce of his fields, which in after years 
 would undoubtedly have come to him ; and the only 
 difference between him and a railway speculator is in 
 general this : that the punishment for his foolish deeds 
 inevitably overtakes him or his successors, which the specu- 
 lator sometimes escapes by laying on the shoulders of others. 
 The apparently remunerative employment of these means 
 on many fields may last for a long time ere the agriculturist 
 becomes aware of the inj ury he is doing himself by neglect- 
 ing to return the mineral substances removed by his crops ; 
 but the longer he continues by them to obtain these large 
 crops, he is approaching nearer and nearer the limits at 
 which they must cease. 
 
LETTER YI. 
 
 The Amount of Carbonic Acid and Ammonia in the Air — The Balance of 
 Organic Life — The Absorption and Assimilation of Food differs in Perennial 
 and in Annual Plants— The mode of Growth of Perennial, Annual, and 
 Meadow Plants — The quantity of ]S"itrogen in different Crops — Advantages 
 of Nitrogenous Manures to Cereals is not in consequence of the failure of 
 Nitrogen from Natural Sources — Organic and Nitrogenous Manures useful 
 in Annual Plants with small absorbent Leaf and Root-surface — Effect of 
 Nitrogenous Manures less marked in plants with large Leaf-surface — 
 Supply of Ammonia in Manure not necessary to all Plants — G-reen Crops 
 condense Ammonia from Natural Sources, and supply it in the excrement 
 of animals to Corn-fields — The Nitrogen of Manures is thus indirectly 
 obtained from the Air — The total quantity of Nitrogen from a manured 
 Corn-field is not greater than from an unmanured meadow, but more time 
 is required by the latter to collect it — Explanation of the good effect of 
 Nitrogenised Manures on Annual Plants with small Leaf and Root- 
 surface. 
 
 The quantity of nourishment in the air, compared with 
 its mass, is very small. 
 
 If all the carbonic acid and ammonia dispersed through- 
 out the atmosphere were collected in one stratum around 
 the earth, and possessed the same density as at the surface 
 of the sea, the layer of carbonic acid would be a little more 
 than eight feet high, and that of the ammonia less than a 
 quarter of an inch. Both are absorbed by plants, and the 
 quantity of these gases in the atmosphere consequently 
 diminishes. 
 
 Were the whole surface of the earth a continuous mea- 
 dow, from each hectare {2^ acres) of which 100 cwt. of hay 
 was yearly reaped, these meadow plants would in twenty- 
 one to twenty-two years exhaust the whole of the carbonic 
 
70 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 acid in tlie air, and the whole living creation would at the 
 same time come to an end. The air would no longer sup- 
 port plants — that is, would no longer furnish them with an 
 indispensable condition of life. 
 
 We know that careful provision is made for the con- 
 tinuous duration of organic life. Men and animals live on 
 plants. All organised beings have only a passing and 
 comparatively short existence. In the vital processes of 
 animals, the food which nourishes them is transformed into 
 its original form ; and the same change takes place with the 
 bodies of all animals and plants after death : their com- 
 bustible elements reassume the form of carbonic acid and 
 ammonia. Both of these substances are gaseous, and return 
 to the atmospheric sea, to serve once more for the forma- 
 tion and development of a new generation, 
 
 We thas see that the duration of organic life, in reference 
 to the combustible elements forming the frame of plants 
 and animals, is most intimately connected with the return 
 of these conditions. The perpetual round of changes 
 which the Creator has traced out for them, may, to a 
 limited extent, be influenced by man, but it goes on with- 
 out him. 
 
 Wherever food in the form of corn and other produce 
 of the soil abounds, there, men and animals will be found 
 to consume it ; and these, in fulfilling the urgent natural 
 law of self-preservation, continuously reconvert the food 
 that supports them into its original elements. 
 
 The atmosphere is never at rest : even in the absence of 
 every breeze, it is in continual ascending and descending 
 motion. The food which it gives up to plants at one spot 
 is immediately replaced from another — from ever flowing 
 sources. 
 
 There is a marked difference between perennial and 
 annual plants as regards the absorption and assimilation of 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 71 
 
 food. For though different species may possess the same 
 capacity in this respect, yet the quantity necessary in a 
 given time for their vital purposes is very unequal. To 
 attain a maximum of growth in the shorter period of its 
 existence, the annual plant requires more than the biennial, 
 and the latter more than the perennial. 
 
 Everything that tends to promote the growth of plants 
 in general, exerts the same favourable influence on perennial 
 plants as on biennials and annuals, but with this distinc- 
 tion, that the development of the former is not in the same 
 degree dependent on accidental and passing states of wea- 
 ther. If the weather is unfavourable, the growth of the 
 perennial is only retarded for a time : they can await a 
 favourable change. Whilst thus waiting their increase is 
 only for the time being arrested, but the annual plants 
 reach the limit of their existence and die. 
 
 In the first periods of the growth of perennial plants, 
 the most powerful efforts of their vital energy are chiefly 
 directed to the formation of roots. The atmospheric food 
 received by the leaves is destined for the prolongation and 
 ramification of these underground organs of absorption. 
 This fact is most distinctly perceptible in young trees, 
 which appear to grow so slowly in the first periods .of their 
 existence, and afterwards so rapidly. When the roots have 
 acquired a certain compass, their stem or stalk then 
 increases in strength much more rapidly than at first, and 
 the branches, shoots, and leaves, augment in number. 
 
 In the growth of annual plants, the food is expended in 
 two directions at the same time, viz., for the formation of 
 the shoots, as well as of the leaves and roots ; they are, 
 therefore, in reference to the equal supply and the proper 
 proportion of their food, much more dependent than peren- 
 nial plants on the condition of the soil, and on weather. 
 The development of all parts of the annual plant must 
 
72 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 take place within a certain definite, relatively short period 
 of time, and its growth can only be complete when the 
 external conditions are equally favourable with those of 
 the soil. 
 
 The formation of underground suckers appears to be of 
 the greatest importance to vegetation in the case of the 
 perennial grass and meadow plants, because by them vege- 
 tation is maintained. They appear mostly in cases where 
 scarcity of food or external disturbing circumstances would 
 endanger annual plants. Only the smallest portion of the 
 plants on a thickly-covered plot of grass produces stems ; 
 the greater part develops only tufts of leaves ; and a num- 
 ber only underground suckers. A landscape essentially 
 derives its character from perennial plants, which every- 
 where take possession of the ground when not prevented 
 by man. Cleared forest-land produces immediately in the 
 succeeding year plants, many of which (as, for example, the 
 raspberry) flower and bear fruit in the same year, and 
 therefore could not have grown from seed. By continu- 
 ously putting forth underground suckers, plants are kept 
 for a number of years at a low state of growth, till ulti- 
 mately the conditions for their complete development 
 recur. 
 
 The duration of vegetation on our meadows depends 
 on this circumstance. The certainty of their produce 
 under varying conditions of soil and weather, arises from 
 the great number of plants, which are able to maintain 
 themselves at this low stage of development. 
 
 Whilst one species of plants grows, flowers, and bears 
 seed above ground, a second and third collects below it the 
 conditions for a similar future growth. The one seems to 
 disappear, in making room for a second or third, until the 
 conditions for its own growth again recur. By manuring 
 with ashes we cause clover plants to shoot out from the 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 73 
 
 green sward. An abundant crop of French rye-grass 
 showed itself when superphosphate of lime was applied, 
 but not a straw of this grass was to be seen where no 
 superphosphate fell. 
 
 A wonderful provision of nature ensures, by this 
 sequence and change, the continued existence of plants, 
 which clothe the fields with perennial green. The agri- 
 culturist, in adopting the rotation of crops in the cultiva- 
 tion of the annual plants which supply the food of man 
 and animals, but follows in this operation a higher law. 
 
 The circle from which a perennial plant extracts its food 
 enlarges from year to year ; if its roots find but little in 
 one spot, its wants are supplied from another which is 
 richer. Whilst the roots of annual plants die every year, 
 perennial plants preserve theirs in a state of readiness to 
 absorb food at every favourable opportunity. Many retain 
 their stalks or stems, in which are stored up, for the future 
 necessities of leaves and buds, the unconsumed portion of 
 their food. Hence, perennial plants grow with luxuriance 
 on comparatively poor ground, which will not yield annual 
 plants without a supply of food from the hand of man. 
 
 Annual plants cannot follow each other continuously on 
 the same soil without exhausting it ; hence, in the rotation 
 of crops, perennial plants come most advantageously after 
 the annual, and vice versa. 
 
 The nearer an annual plant approaches in its comport- 
 ment to a perennial, the more independent is it of any 
 supply of atmospheric food. So long as a plant puts forth 
 fresh leaves, it exists and maintains its power of absorbing 
 carbonic acid and ammonia from the atmosphere; and, 
 during the continuance of this power, there is so much the 
 less necessity for a supply of these substances from the 
 soil. 
 
 A pea plant which pushes out fresh leaves and blossoms, 
 
 4 
 
74 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 at the same time that its seeds are ripening, receives more 
 combustible elements from the atmosphere, than a corn 
 plant, whose leaves and green stem fade after the appear- 
 ance of the flower, and with the ripening of the seeds, 
 and consequently lose their power to absorb atmospheric 
 food. 
 
 Hence we can understand why organic substances which, 
 in decaying, supply to the roots carbonic acid and ammo- 
 nia, when applied at the proper time cause in one plant an 
 increase of vegetable matter, and in the amount of seed, 
 whilst the produce of another is scarcely increased by 
 them. 
 
 From an equal surface of land we obtain in different cul- 
 tivated plants a very unequal amount of blood and flesh 
 constituents, or nitrogen. If we designate by the number 
 100 the quantity of nitrogen which is yielded by a field of 
 rye in the form of grain and straw, we shall obtain from 
 the same field — 
 
 In Oats 114 
 
 Wheat 118 
 
 Peas 270 
 
 Clover 390 
 
 Turnips 4t0 
 
 Accordingly peas, beans, and green crops in cultivation, 
 yield more nitrogen than the cereals. Peas and beans give 
 more than double, clover and turnips three or four times 
 more flesh and blood constituents than wheat. Clover and 
 turnips can yield on many fields this higher produce with- 
 out receiving any nitrogen in manure. In the case of 
 clover, the yield can be still further augmented by the 
 application of ashes, and in that of turnips by superphos- 
 phate of lime. 
 
 In cultivation, nitrogenous manures prove particularly 
 useful for cereals, though the growth of clover and root- 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 75 
 
 plants on many fields is also greatly promoted by tliem. 
 In general, the luxuriant growth of green crops on fields 
 which have received no nitrogenous manure shows, that the 
 utility or necessity of these manures for cereals does not 
 arise from a deficiency in the supply of nitrogen from 
 natural sources, and cannot be explained by a supposed 
 failure of this supply. The column of air floating above a 
 clover and corn field offers to both plants the same amount 
 of carbonic acid and ammonia, yet from the same soil from 
 which the agriculturist has received a very poor return of 
 nitrogen in the form of grain and straw, he obtains three 
 or four times the quantity of nitrogenous constituents in a 
 crop of a fodder plant. The same source of nitrogen was 
 open to both plants ; there could, therefore, have been no 
 deficient supply to the corn plant, since the clover drew 
 from it its three and fourfold quantity. It is quite certain 
 that a soil, from which a poor crop of corn has been 
 reaped, will not be made to yield a greater quantity, even 
 by the most abundant application of ammonia. 
 
 The failure of the corn crop must therefore be owing to 
 other circumstances, and the proximate causes must be 
 sought for in the condition of the soil. 
 
 On the other hand, it cannot be doubted, that two fields 
 containing equal quantities of the fixed food of plants, are 
 nevertheless unequally productive in cereals, if in one of 
 them there exist more carbonaceous and nitrogenised organic 
 matter than in the other. The field which is richer in 
 organic matter produces a higher crop of com and straw. 
 It is further certain that, if an equal quantity of the fixed 
 constituents of food has been supplied in manure to two 
 fields, but one of them has at the same time received in 
 addition in organic matters a store of carbonic acid and 
 ammonia, in general the latter will produce a larger crop 
 of corn than the other. 
 
76 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 This increase of produce under these circumstances (iu 
 whicli the soil is supposed to be rich enough in mineral 
 food and in carbonaceous and nitrogenous organic matter) 
 takes place in the case of cereals as well as of other annual 
 plants, with a scanty supply of leaves and limited ramifi- 
 cation of roots ; and the reason of the utility, in such cases 
 of organic and nitrogenised substances, is very evident. It 
 lies manifestly in this, that the amount of nitrogenised 
 products, which can be obtained from a given surface of 
 such land, is in fixed proportion to the extent of leaf sur- 
 face, or in general terms, to the organs of absorption, and 
 to the time in which these organs are in a state of 
 activity. 
 
 If one plant possesses twice the extent of surface of 
 leaves which exists in another, it will, during the same 
 period of vegetation, extract double the quantity of nitro- 
 gen from the air. 
 
 Of two plants with equal extent of surface of leaves, and 
 under similar circumstances, but with unequal periods of 
 vegetation, one will yield a larger crop than the other, if 
 with the same supply of food it has longer time for its 
 absorption. By manuring his fields with nitrogenous sub- 
 stances, the agriculturist exercises an immediate influence 
 on the produce ; and the effect of these manures, through 
 the nitrogen they contain, is in inverse proportion to the 
 absorbing leaf and root-surface, and to the period of vegeta- 
 tion of the crop. 
 
 The effect of nitrogenous manures is less marked in 
 plants with a large surface of leaves (as in peas, turnips), or 
 which have a longer period of vegetation (as in meadow 
 plants, clover) than in culmiferous plants. Ammonia is 
 necessary as food to all plants, but a supply of it in 
 manure is, in the agricultural sense, not useful to all culti- 
 vated plants. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 77 
 
 Experience has taught the agriculturist to make a dis- 
 tinction in this respect. As a rule, he does not manure his 
 clover field with nitrogenous matters, because the crop of 
 clover is generally not thereby visibly increased, or only 
 very slightly ; whilst he reaps a decided advantage in the 
 increase of his produce by applying these matters to his 
 corn fields. 
 
 The agriculturist therefore makes use of green crops as a 
 means of increasing the productiveness of his corn fields. 
 
 Green crops, which thrive without nitrogenous manures, 
 collect from the soil and condense from the atmosphere, in 
 the form of blood and flesh constituents, the ammonia sup- 
 plied from these sources. When the agriculturist feeds his 
 cattle, sheep, and horses with these green crops, he obtains 
 in their solid and liquid excrements the nitrogen of the 
 fodder in the form of ammonia and highly nitrogenised 
 products, and thereby a supply of manure for his corn 
 fields. 
 
 The ultimate source of the nitrogen with which the 
 agriculturist manures his corn fields is invariably the air. 
 Each year he carries away from his land a certain quantity 
 of nitrogen in the form of fattened animals, corn, cheese, or 
 milk : but his trading capital of nitrogen is maintained and 
 increased, if he knows how to replace the deficiency by the 
 cultivation of green crops in proper proportions. 
 
 In the temperate zones, it is usually on the annual plants 
 that man depends for his food ; and the problem which the 
 agriculturist has to solve, is to obtain from his land in the 
 form of annual plants as much food for man, as perennial 
 plants furnish to animals from the same extent of surface. 
 Nature takes care of animals which cannot take care of 
 themselves ; whilst for the purpose of ensuring the means 
 of his subsistence, man has been endowed with the power 
 of making the laws of nature minister to his wants. 
 
78 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 The best corn field, whicli has been manured, produces 
 altogether no more blood and flesh constituents than a goc d 
 meadow, which has received no nitrogenous manure. But 
 the corn field without manure would have yielded a smaller 
 amount of these constituents than the meadow. 
 
 Whatever deficiency there is in the quantity of atmo- 
 spheric food, taken up by corn plants within a given time 
 from natural sources, to produce a maximum of corn and 
 straw ; whatever amount of food the scanty supply of leaves 
 has not the power of absorbing from the air during the short 
 period of their existence, that portion the agriculturist sup- 
 plies through the roots. 
 
 The agriculturist thus supplements by manures the dif- 
 ference between the amount of atmospheric food taken up 
 in eight months by meadow plants, and that obtained by 
 cultivated plants from the air during their more limited 
 period of vegetation of four to six months ; and he thereby 
 ensures to corn plants, during their shorter existence, as 
 much nitrogen for assimilation as is furnished to meadow 
 plants from natural sources. 
 
 Hence the explanation which can be offered of the effect 
 of nitrogenised manures and their advantages in certain cases 
 is, that the agriculturist furnishes to certain plants, having a 
 scanty supply of leaves and roots and a short existence, in 
 quantity as manure, the nitrogen which they have not time 
 to absorb from natural sources. 
 
 But the agriculturist does not always apply the nitrogen 
 with which he augments his crops in the form of the 
 ammonia of rotting excrements of man and animals. He 
 also employs frequently for this purpose other nitrogenous 
 substances, as horn, dried blood, fresh bones, rape-dust, &c. 
 
 We know that these substances, as well as all nitrogenous 
 matters derived from man and animals, by degrees decay in 
 the soil, and their nitrogen is gradually transformed into 
 
THEOKETICAL AND PRACTICAL AGRICULTURE. 79 
 
 nitric acid and ammonia, and that the latter is absorbed and 
 retained by the soil. 
 
 In all cases in which ammonia as such produces favourable 
 results on crops, these substances, so far as regards the 
 nitrogen they contain, also act in the same manner. But 
 their effect is more slowly produced, because they require, 
 according to the greater or less facility with which they are 
 decomposed in the soil, a certain time for the transformation 
 of their nitrogen into ammonia. Dried blood and flesh, as 
 well as the nitrogenous constituents of rape-cake, act more 
 quickly than the gelatine of bones, and the latter more 
 quickly than horn. 
 
LETTER YII. 
 
 Salts of Ammonia increase the number of Roots and Leaves in the first period 
 of the Growth of Plants ; hence the superior action of these salts in Spring 
 — Circumstances which modify the production of Leaves, Flowers, and Roots 
 — Circumstances under which Nitrogenous and Concentrated Manures are 
 useful — Causes of the failure of plants continuously grown on the same Soil 
 — Food of plants when too concentrated often exerts a deleterious Cliemical 
 action — Provision in the Soil to prevent this action — Properties of Soils 
 altered in cultivation by the removal of Mineral Matters from them, and by 
 the increase of Organic Matters in them — The increase of Organic Matter 
 frequently a cause of Disease — Finger and Toe disease ; its cure — Excess 
 of soluble Silica and of hurtful Organic Matter in soils removed by Lime — 
 Noxious Organic Matters arising from the continuous growth of Perennial 
 Plants on Meadows removed by Irrigation. 
 
 The experiments of Kuhlmann, Schattenmann, andLawes, 
 agree in showing, that the salts of ammonia exert a most 
 favourable influence on the evolution of straw and leaves ; 
 and if this influence extends in like manner to the under- 
 ground organs, the roots, then it ought to follow that the 
 action of ammonia promotes the development of those 
 organs destined for the absorption of food, and that these 
 salts applied at the proper time increase the number of the 
 leaves and roots. 
 
 This circumstance explains the favourable action exer- 
 cised in spring by ammoniacal manures, whilst in summer 
 their influence under otherwise similar circumstances is 
 trifling. 
 
 If the plant, in fact, has produced during the first period 
 of its growth a sufficient number of leaves and roots, an 
 additional supply of ammonia can be of no great use to its 
 
THEOKETICAL AND PRACTICAL AGRICULTURE. 81 
 
 further development, where the other constituents of food 
 in the soil are not deficient ; for the leaves can now receive 
 from the air the nitrogenous food necessary to the formation 
 of seeds. In summer there is more watery vapour in the 
 air than in the colder spring ; and as the quantity of ammonia 
 in the air, according to the observations of all experimenters, 
 increases with the temperature and moisture, plants must 
 necessarily find more ammonia in the air in summer than in 
 spring. We may as a rule hold, that in the colder seasons 
 of the year, plants are more dependent on a supply of 
 ammonia from the soil, than in the warmer ; or in other 
 words, that the employment of nitrogenous manures in 
 spring is most advantageous to plants. 
 
 In England and Scotland it is the result of general ex- 
 perience, that the earthy phosphates are not always suffi- 
 cient for a good and certain crop of' turnips. When sown 
 in May they require the addition of a nitrogenous manure, 
 whilst, if this take place in the middle of June, they thrive 
 generally as well with phosphates alone, as when combined 
 with ammonia. 
 
 We can hence tolerably well define the cases in which 
 ammonia is hurtful ; for whilst nitrogenous manures pro- 
 mote the growth of the leafy cabbage, they impede that of 
 the roots of turnips. The latter plant is frequently ob- 
 served to shoot out only stem and leaves when growing on 
 spots upon which manure heaps have lain. Mangold-wurzel 
 in a similar case produces the largest roots. The flowering 
 time of these plants is delayed by this manure. 
 
 To produce flower and seeds, it appears to be a necessary 
 condition, in many cases, that the activity of the leaves 
 and roots should reach a certain limit, — a period of rest. 
 It is only from this period that the vegetative activity 
 appears to take a decidedly new direction, and that the 
 sap, when no longer required for the production of new 
 
 4* 
 
82 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 leaves and roots, is applied to the formation of flower and 
 seed. 
 
 With many plants want of rain, and of the consequent 
 supply of food, limits the formation of leaves, and pro- 
 motes the production of flowers. Dry and cool weather 
 hastens the formation of seeds. In warm and moist cli- 
 mates, the cereals when sown in summer bear little or no 
 seed ; and root crops flower and bear seed more readily on 
 a soil poor in ammonia, than on one rich in this substance. 
 
 In the employment of nitrogenous manure, the agricul- 
 turist must consequently have distinctly before him the 
 object which he wishes to attain. He mast act with plants 
 as with animals. When he wishes to fatten the latter, and 
 at the same time to preserve their health, he gives them 
 daily no more food than they can digest. 
 
 Manures must always be of such a nature as to furnish 
 plants with their suitable food at each period of their 
 growth. Plants which have a longer period of vegetation, 
 require consequently no supply, or, at least, a much smaller 
 one of nitrogenous manures than those whose period of ex- 
 istence is short. For such as possess the shortest period 
 of vegetation, and which grow rapidly and with vigour, the 
 concentrated manures are preferable to those which give 
 up their active constituents only slowly. In dry localities, 
 winter wheat thrives after clover without further manuring ; 
 whilst, as a rule, the application of Peruvian guano or 
 Chili-saltpetre (top-dressing) is most beneficial to wheat 
 sown in spring. 
 
 The continuous cultivation of the same plant on the 
 same field, does not necessarily unfit this field for its pro- 
 duction, if it is amply provided with the chemical condi- 
 tions for the growth of the plant, and possesses physical 
 properties of a right kind. If after the third or fourth 
 year, the plant no longer thrives on such a field, the reason 
 
THEOKETICAL AND PRACTICAL AGRICULTURE. 83 
 
 manifestly does not lie in any deficiency of its vital condi- 
 tions (for we have assumed that these are present), but in 
 the accumulation of causes which injure its healthy growth. 
 
 The food of plants consists of chemical compounds, 
 which, in virtue of their chemical properties, produce cer- 
 tain effects on the substance of the cells and the most deli- 
 cate portions of the frame of the leaves and roots, by which 
 plants appropriate their food. Their chemical action in- 
 creases with their quantity ; and if presented to plants be- 
 yond certain limits, they sicken and ultimately die. 
 
 In air in which free ammonia is present in excess, even 
 though it be to only a most minute extent, many plants 
 die as if struck with a poisonous blast. Carbonic acid acts 
 in a similar way, though in a less degree ; and weak solu- 
 tions of free alkalies or alkaline earths and their salts in a 
 soil produce the same effect on other plants. 
 
 In nature we find a wonderful provision exists in the 
 chemical and physical properties inherent in the soil, for 
 completely obviating the chemical action of the nutritive 
 matters on the absorbent rootlets. Free ammonia, the free 
 alkalies, and alkaline earths, are fixed by the soil, and with 
 their loss of solubility they also lose those chemical pro- 
 perties which are hurtful to plants. Plants can then select 
 what is necessary to their existence, without any hindrance 
 from extraneous influences which may endanger their pro- 
 per growth. 
 
 It is evident that the soil must possess such a neutral 
 chemical character as the most important condition of the 
 healthy structure and functions of the roots. The different 
 species of plants require, however, special conditions for 
 the growth of each. One species requires the constituents 
 of fresh spring water; another flourishes only in bogs; 
 others in carbonaceous and sour soils ; others, again, only 
 in ground which abounds in alkaline earths. 
 
84 THEOKETICAL AND PRACTICAL AGRICULTUEE. 
 
 By cultivation the cliaracter of tlie soil is modified, not 
 only by the removal in crops of a portion of its active in- 
 gredients, but also by the addition to it, by means of many 
 plants, of a greater amount of carbon and nitrogen sub- 
 stances, in the form of the remains of roots. The enrich- 
 ment of the soil in organic matter appears to be a cause of 
 disease and death to many plants. Clover and many of 
 the turnip tribe will no longer grow on such a soil, and 
 several species of grass quickly disappear from it. 
 
 It has been frequently found in England that turnips, 
 when grown on the same field at too short intervals, become 
 subject to a peculiar disease, which manifests itself in an 
 unusual development of the roots. Instead of a round, 
 fleshy head, weighing several pounds, from which filament- 
 ous roots spread out into the ground, the tap-root splits into 
 a great number of hard, woody, stem-like roots of the thick- 
 ness of a finger (finger and toe disease). This disease, which 
 is owing to the peculiar character of the ground, is removed 
 by a large dose of quick lime. It is certain, however, that 
 the lime does not act in this case, because there was pre- 
 viously a deficiency of it in the soil, for a supply of it to 
 the field at seed time, like other manures, produces no 
 effect, for the latter is apparent only after one or two years. 
 To produce a favourable change in the quality of the field, 
 the lime must manifestly penetrate to a certain depth, and 
 this requires a considerable time. By the simple applica- 
 tion of superphosphate of lime, to the complete exclusion 
 of organic manures, Lawes succeeded in raising nine suc- 
 cessive crops of turnips on the same land, and in the ninth 
 year obtained 187 cwt. of roots per acre. 
 
 Eain water, in slowly filtering through a soil rich in 
 organic matter, extracts a substance which communicates a 
 brown colour, and at times an acid reaction to the water. 
 An addition of burnt lime to this soil destroys the solubility 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 85 
 
 of the organic matter in water, and its power of diffusion 
 in the soil. Ttie lime decomposes the organic substances, 
 and by its presence converts the process of putrefaction, 
 which is hurtful to plants, into one of decay which is advan- 
 tageous to them. 
 
 The presence of organic matter in a soil rich in silicates, 
 enables water in percolating through the soil to dissolve a 
 much larger quantity of hydrated silicic acid than is con- 
 ducive, in many plants, to the process of absorption taking 
 place in the roots. Lime destroys this property, and, by 
 its direct action on the silicate, potash is ultimately set free, 
 and rendered fit for distribution in the soil. Sainfoin con- 
 tinues to flourish on fields rich in lime. It is certain that 
 the presence of the lime in such a soil is not advantageous to 
 this plant, because it requires more lime for its vital pur- 
 poses than other plants which flourish luxuriantly on land 
 much poorer in lime ; but the canse for the necessity of this 
 excess of lime must be sought for in the fact, that it destroys 
 certain injurious matters which gradually accumulate by 
 the continuous growth of this plant on the same soil. 
 
 As a matter of course we understand, that, in a number 
 of cases in which the same plant will no longer grow on 
 the same soil, the cause just indicated is not alone in opera- 
 tion, but deficiency of food generally, or in the proper pro- 
 portions, must be regarded as the proximate cause of the fail- 
 ure. The necessity for taking into consideration so many 
 causes which impede or promote the growth of plants, 
 makes the practice of agriculture one of the most difficult 
 of pursuits. 
 
 In fields bearing perennial plants, with roots which pene- 
 trate to no great depth, similar injurious matters gradually 
 collect, which are hurtful to the growth of future genera- 
 tions of plants. The irrigation of meadows appears to 
 accomplish the important object among others of removing 
 
86 THEOEETICAL AND PRACTICAL AGRICULTURE. 
 
 these injurious matters by the oxygen and by the carbonic 
 acid dissolved in the water, which penetrates the ground, 
 and brings it into a condition similar to that produced by 
 careful ploughing. An analysis of the water flowing from 
 the meadow would probably show that it removes as much 
 mineral matter and ammonia as it brings to it. We do not, 
 of course, here speak of meadows to which liquid manure 
 has been applied, or which have been irrigated with rich 
 sewerage water from towns ; for in these cases two causes 
 are in operation to augment the produce, one of which (a 
 supply of mineral food and ammonia) is almost excluded 
 in the case of spring and river water. 
 
LETTER Vni. 
 
 The food of Land Plants is not absorbed by the roots from Solution, but from 
 the Soil directly in contact with them — Hence the necessity for a uniform 
 distribution of the food of plants in the soU, and for the great Ramification 
 of their Roots — A field with much mineral food may be comparatively 
 unproductive if it is not thoroughly mixed with the Soil — The roots of a 
 crop diminish the mineral food in those portions of the soil in contact with 
 them — Fertility is restored to those portions by ploughing and other 
 mechanical means, which mix the soil and allow the roots to ramify freely 
 — Reason of the value of Green Manures — Estimation of amount of mine- 
 ral food in the soil to produce different Remunerative Crops — Law of 
 Exhaustion in soils for different crops — Action of organic remains in the 
 soil on the mineral constituents — Progress of diminution in Grain and Straw 
 of cultivated crops, when the Ash Constituents are not restored to the soil, 
 and when those of the straw alone are returned — Relation between the pro- 
 duction of Leaves and of Grain — Relative proportions of mineral food 
 required for Grain and for Root or Leaf-producing crops — The increase of 
 Organic matter and Nitrogen in the soil by Green Crops, without the 
 addition of mineral food, augments the produce of grain, but hastens the 
 period of Exhaustion of the soil — Progress of the exhaustion of a soil by 
 the cultivation of shallow and of deep rooting plants — The manner in which 
 the Subsoil contributes to the prolongation of the fertility of land — 
 Importance of the formation of large roots after germination — Exhausted 
 fields in an agricultural sense — Fertility restored by manures — The nature 
 of Manures — The part played by the Organic and Inorganic Matter of 
 Manures — Farm-yard Manure. 
 
 The culmiferous, turnip, and tuberous plants which the 
 agriculturist cultivates, comport themselves in a most pecu- 
 liar manner in the absorption of their mineral food. Whilst 
 sea-plants receive their whole supply of these substances in 
 a state of solution from the surrounding medium, the water 
 which percolates through cultivated soils, brings to the 
 
88 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 roots of land plants none of the three most important and 
 most essential elements of food, viz., phosphoric acid, pot- 
 ash, and ammonia. Water alone withdraws from the soil 
 none of these substances ; their passing into the organism 
 of plants must therefore be directly effected by the organs 
 of absorption in the ground, with the co-operation of water. 
 The roots extract these substances from those portions of 
 the soil, penetrated with water, which are in direct contact 
 with their absorbent surfaces; and such portions of soil 
 must contain the whole quantity necessary for the complete 
 development of the plant, since the roots can receive none 
 of them, except from the particles of earth with which they 
 are directly in contact. 
 
 If the food of plants in the soil cannot move towards the 
 roots, it is evident that the roots must spread about to look 
 for food. 
 
 Plants cannot obtain from the soil more food than it 
 contains. Further, its fertility is not to be measured by 
 the whole quantity present in it, but only by that portion 
 of the whole quantity which exists in the smallest particles 
 of the soil. For it is only with such portions that the root- 
 lets can come into close contact. 
 
 A piece of bone weighing about 30,000 milligrammes 
 (one ounce) in a cubic foot of earth, produces no marked 
 effect on its fertility. But if these 80,000 milligrammes of 
 phosphate of lime be uniformly distributed throughout the 
 earth, it will suffice for the nourishment of 120 wheat 
 plants. Ten thousand milligrammes of food, having a sur- 
 face extent of 100 square millimetres, are within the same 
 given time not more effective than ten milligrammes having 
 the same surface extent. Of two fields with the same 
 amount of food, one may be very fertile, and the other 
 equally unfruitful, if the food is more uniformly distributed 
 throughout the former than the latter. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 89 
 
 The common plough breaks and turns up the soil with- 
 out mixing it ; it only displaces, to a certain extent, the 
 spots on which plants have already grown. But the spade 
 breaks, turns, and mixes it thoroughly. 
 
 A potato, turnip, or wheat plant cannot thrive on the 
 spot in which the same kind of plant has grown in the pre- 
 ceding year, if the portions of soil with which the rootlets 
 were in contact, contain no more, or only an insufficient 
 residue of food. The roots of the succeeding plants find in 
 all these spots either no food or only a deficient supply. 
 Every other spot contains more. 
 
 As the smallest portions of food cannot of themselves 
 leave the spot in which they are held firmly fixed by the 
 soil, we can understand what immense influence must be 
 exerted on its fertility by its careful mechanical division 
 and thorough intermixture. 
 
 This is the greatest of all the difficulties which the agri- 
 culturist has to overcome. 
 
 If a field is to produce a crop, corresponding to the full 
 amount of food present in it, the first and most important 
 condition for its accomplishment is, that its physical state 
 be such as to permit even the finest rootlets to reach the 
 spots where the food is to be found. The extension of the 
 roots in every direction must not be obstructed by the 
 cohesion of the soil. Plants with thin delicate roots cannot 
 grow on a tenacious heavy soil, even with abundance of 
 mineral food. These facts explain in a very simple manner, 
 one of the many favourable effects of green manures on 
 such soils, and enable us to understand the reasons of the 
 preference given in many cases, by agriculturists, to fresh 
 over rotten farm-yard manure. The mechanical condition 
 of the ground is, in fact, remarkably altered by the plough- 
 ing in of plants and their remains. A tenacious soil loses 
 thereby its cohesion ; it becomes brittle, and more readily 
 
90 THEOEETICAL AND PRACTICAL AGRICULTURE. 
 
 pulverized than by the most careful ploughing ; and, in a 
 sandy soil, a certain coherence is introduced among its 
 shifting particles. Each stem of the green manure plants 
 ploughed in opens up by its decay a road by which the 
 delicate rootlets of the wheat plant ramify in all directions 
 to seek their food. With the exception of their combus- 
 tible elements, the ground receives from the green manure 
 plants nothing which it did not previously contain; and 
 these of themselves would have no effect on the increase of 
 the crop, without the presence in the soil of the necessary 
 mineral food. 
 
 None of the three most important constituents of food 
 exists, by itself, in a soluble form in the ground, and none 
 of the means employed by the agriculturist to make them 
 available to his plants, deprives the soil of its power of 
 retaining them ; or, if dissolved, of withdrawing them from 
 this solution. The principal end gained by the means he 
 employs is only an uniform distribution of the food 
 throughout the soil, so as to put it within the reach of the 
 roots of his plants. 
 
 A 2^ acre field ( = 1 million square decimetres) of good 
 wheat soil produces an average crop of 2000 kilo. ( = 4411 
 lbs.) of grain, and 6000 kilo. ( = 11,028 lbs.) of straw; the 
 two contain together 250 kilo. ( = 551 lbs.) of mineral sub- 
 stances. Each square decimetre ( = 10,000 square milli- 
 metres Or 15*5 square inches) of this field yields 250 milli- 
 grammes ( = 3 "85 grains) of ash constituents to the plants 
 growing upon it. Each square millimetre ( = '00155 
 square inch), from the surface downwards, must contain a 
 quantity of food corresponding to the wants of each indi- 
 vidual rootlet. If the food is wanting in any one particular 
 particle of the soil, then this portion cannot contribute to 
 the nourishment of the plant. The amount of food in each 
 portion of a transverse section of ground^ in each square milli' 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 91 
 
 metre from the surface doivnivards^ is the measure of its capacity 
 for production. Each rootlet absorbs, according to its dia- 
 meter, the food with which it comes in contact on its way 
 downwards. 
 
 If we suppose that the sectional area of the roots of the 
 whole wheat plants which grow on a square decimetre 
 amounts to 100 square millimetres, or that upon the same 
 surface there exists a wheat plant with two or three stems, 
 and with a hundred roots each of a square millimetre sec- 
 tional area, then must each of these rootlets receive 2^ 
 milligrammes of mineral food in order to supply the plant 
 with 250 milligrammes. Each of the 10,000 square milli- 
 metres ( = one square decimetre), from the surface down- 
 wards must contain these 2^ milligrammes ; which would 
 give a total quantity of 25,000 milligrammes ( = 25 
 grammes = 386 grains) to the square decimetre, calculated 
 to a depth of 10 inches ; or 25,000 kilo. (24|- tons), to the 
 hectare (2-J acres), i. e., somewhat more than ^ per cent, of 
 the whole soil. 
 
 A hectare which, from the surface downwards, contains 
 no more than 250 kilo. r:= 550 lbs. of mineral matter (of 
 which 50 kilo. = 110 lbs. are potash, and 25 kilo. = 55 lbs. 
 are phosphoric acid) would, according to this calculation, 
 be completely unsuitable for wheat ; for even though each 
 wheat plant possessed, instead of one hundred, one thou- 
 sand roots, each of the thickness of a hyacinth root, it 
 would nevertheless not be able to receive by these more 
 than a tenth part of its wants from the soil. 
 
 According to our assumption, which probably barely 
 reaches the full amount really present, a hectare must con- 
 tain, from the surface downwards, in order to yield an 
 average crop of wheat, at least 5000 kilo. (= 11,000 lbs.) 
 of potash and 2500 kilo. {= 5500 lbs.) phosphoric acid."^ 
 
 * If the mineral food, so very small in proportion to the whole mass of 
 
92 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 If an average wTieat crop of 2000 kilo. {— 4400 lbs.) of 
 grain and 5000 kilo, of straw, has removed one per cent, of 
 the mineral food from the soil, the latter remains still pro- 
 ductive for new wheat crops in the following years ; but the 
 amount of produce diminishes. 
 
 If the soil has by mechanical means been most carefully 
 mixed, the wheat plants of the second year on the same 
 field will find at each spot one per cent, less food, and the 
 produce in corn and straw must in the same proportion be 
 smaller. Under similar conditions of weather, tempera- 
 ture, and fall of rain, only 1980 kilo. (= 4356 lbs.) of 
 grain, and 4950 kilo. (= 10,890 lbs.) of straw, will be 
 reaped in the second year ; and in each following year the 
 crop must fall off in a fixed ratio. 
 
 If the crop of wheat removed in the first year 250 kilo. 
 (— 550 lbs.) of mineral constituents, and a hectare (2^ acres) 
 of soil to the depth of 12 inches, contained one hundred 
 times this quantity (25,000 kilo., or 24^ tons), there will re- 
 main in the soil at the end of thirty years of cultivation, 
 18,492 kilo. (= 18 tons) of food. 
 
 Whatever then may have been the variations in the 
 amount of produce from this field, in the intervening years 
 caused by different conditions of weather, it is evident, that 
 if there has been no replacement of the mineral matters re- 
 moved, there can be obtained in the thirty-first year, under 
 the most favourable circumstances, only iff = 0*74, or some- 
 what less than J of an average crop. 
 
 soil (2 grains in a cubic inch), were present in chemical combination with it, 
 it is impossible to form an idea how it could be distributed in this state every- 
 where in the soil, so as to be reached by the roots. The comportment of 
 soils of the most different kinds towards solutions of these elements, shows 
 that they are present and fixed in a way somewhat similar to colouring mat- 
 ter in dyed stuffs, or in charcoal which has been used to decolorise a fluid ; 
 in these cases a very small quantity in weight is sufficient to cover an extrac 
 ordinary extent of surface. 
 
THEOKETICAL AND PRACTICAL AGRICULTURE. 93 
 
 If these f of an average crop do not yield to the agri- 
 culturist a sufficient excess of income over expenditure, if 
 they merely cover his expenses, then the crop is no longer 
 remunerative. He considers the field to be now exhausted 
 for wheat crops, although it still contains seventy-four times 
 more food than an average crop yearly requires. The 
 effect of the total quantity of mineral food in the soil has 
 been, that in the first year each root found in those portions 
 of the soil with which it came in contact, the requisite 
 quantity of these substances for its complete development ; 
 and the result of the subsequent continuous crops has been, 
 that in the thirty -first year only f of this quantity is found 
 in these portions. 
 
 A field exhausted for wheat cultivation, will produce 
 remunerative crops of rye. 
 
 An average crop of rye (= 1600 kilo., or 8520 lbs. of 
 grain, and 3800 kilo., or 8360 lbs. of straw) extracts from 
 the ground per hectare only 180 kilo. (= 396 lbs.) of 
 mineral matter. Under similar circumstances, one rye 
 plant takes up only 180 milligrammes (= 2 "77 grains). 
 
 If a soil must contain 25,000 kilo, of mineral matter, in 
 order to produce an average crop of wheat, a soil in which 
 there are only 18,000 kilo, of the same substances, is rich 
 enough for an average crop of rye, and will yield a number 
 of such crops which shall be remunerative. 
 
 According to our calculation a field which is exhausted 
 for the cultivation of wheat, still contains 18,492 kilo, of 
 mineral matter, which in their properties are identical with 
 those required for rye. 
 
 If we now inquire after how many years of continuous 
 rye cultivation will the average crop fall to one of f the 
 amount, we find, — assuming that this amount is no longer 
 remunerative, — that after 28 remunerative crops, the field 
 will be exhausted for the cultivation of rye. The mineral 
 
94 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 matters still remaining in the ground amount, however, to 
 13,869 kilo. (= 13i tons.) 
 
 A field on which rye can no longer be cultivated with 
 profit, is not necessarily unsuitable for oats. 
 
 An average crop of oats (2000 kilo, of grain and 3000 
 kilo, of straw per hectare), withdraws from the soil 310 
 kilo. (= 682 lbs.) of mineral matter, being 60 kilo. (= 132 
 lbs.) more than a wheat crop, and 130 kilo. {— 286 lbs.) 
 more than a rye crop. 
 
 If the absorbent root surface of the oats were the same as 
 that of rye, then oats following rye would not be a remu- 
 nerative crop ; for a soil which furnishes 310 kilo, out of a 
 stock of 13,869 kilo, for a crop of oats, loses thereby 2-23 
 per cent, of its amount of mineral constituents ; whilst by 
 our calculation the roots of the rye extract only one per 
 cent. This can only happen if the root surface of the oats 
 exceeds that of the rye 2-23 times. 
 
 According to the above, the oat crops will exhaust the 
 soil most rapidly. After 121 years the return of produce 
 must sink to I of its original amount. 
 
 None of all the causes which may diminish or increase 
 the amount of a crop, has any influence on this law of 
 exhaustion of the soil by cultivation. When the sum of 
 the food has reached a certain point of diminution, then 
 the soil ceases to be productive, in an agricultural sense, for 
 a cultivated plant. If by incorporating with it atmospheric 
 food, organic materials and salts of ammonia, the produce 
 has been augmented for a number of years, the state of 
 exhaustion will then occur sooner. On the other hand, 
 any obstacle to the free absorption of food diminishes the 
 amount of produce, and the limits of exhaustion are conse- 
 quently reached at a later period. 
 
 For each cultivated plant, there exists a similar law. 
 
 This state of exhaustion inevitably happens, even when there 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 95 
 
 has been withdrawn from the soil by a course of crops only one 
 of all the different mineral substances necessary for the nourish- 
 ment of plants ; for the one which is awaniing, or exists in 
 deficient quantity, renders all the others inefficient^ or deprives 
 them of their activity. 
 
 With each crop, each plant, or portion of a plant, taken 
 away from a field, the soil loses a portion of the conditions 
 of its fertility ; that is, it loses the power of again producing 
 this crop, plant, or portion of a plant, after the expiration 
 of a number of years of cultivation. A thousand grains of 
 corn require from the soil a thousand times as much phos- 
 phoric acid as one grain ; and a thousand straws a thousand 
 times as much silicic acid as one straw ; if, therefore, 'there 
 is a deficiency of a thousandth part of the phosphoric or 
 silicic acid in the soil, then the thousandth grain and straw 
 will not be formed. A single corn straw removed from a 
 corn field, makes this field bear one corn straw less. 
 
 If it is true that the mineral constituents of the culmi- 
 ferous plants are indispensable for their growth, and must 
 be supplied by the soil, if the plants are to flourish ; if it is 
 true that among these mineral matters, potash, phosphoric 
 acid, and silicic acid, are not conveyed to the roots in a state 
 of solution, then it necessarily follows that a hectare ( 2^ 
 acres), containing 25,000 kilo. (= 24^ tons) of the constitu- 
 ents of the ashes of wheat, uniformly distributed through 
 it, and in a state quite fit for assimilation by the roots, can 
 to a certain point yield a series of remunerative crops of 
 different species of straw plants, without any replacement 
 of the minerals removed in the grain and straw, if a uniform 
 state of mixture of the soil has been maintained by careful 
 ploughing and other suitable means. The succession of 
 such crops is determined by this, viz. that the plant culti- 
 vated the second year shall take away from the soil less 
 than that of the first ; or that it contains a greater number 
 
96 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 of roots, or, in general, a greater absorbent root surface 
 than the first. From the average crop of the first year, 
 there would be a diminution of produce from year to year. 
 
 The agriculturist, to whom uniform average crops are 
 exceptions, and varying returns caused by changing states 
 of weather is the rule, would most probably not have noticed 
 this constant diminution, not even though his field had in 
 reality possessed such favourable chemical and physical 
 conditions as to have enabled him to cultivate on it for 
 seventy years successive crops of wheat, rye, and oats, 
 without replacing any of the mineral matters withdrawn 
 from it. 
 
 In* favourable years, good crops approaching nearly to 
 an average one, would have alternated with bad crops in 
 other years, but the proportion of unfavourable to favour- 
 able crops would have constantly increased. 
 
 The greater number of European fields under cultivation 
 does not possess the physical character which has been 
 assumed in the case just under consideration. 
 
 In most fields all the phosphoric acid necessary for plants 
 is not distributed in the state in which it is readily avail- 
 able to the roots. One portion is simply dispersed through- 
 out it in the form of little granules of apatite only (phosphate 
 of lime), so that even though the soil may altogether con- 
 tain more than a sufficient proportion, yet in its various 
 portions there may exist in some too much, in others too 
 little, for the wants of plants. The mechanical preparation 
 of the soil would displace these granules, but would not 
 cause their thorough distribution and incorporation with 
 it. To effect this requires the co-operation of a chemical 
 action. 
 
 After each rye or oat crop there remains in the soil a 
 considerable quantity of roots, which after one or two years 
 entirely disappear. We know that these organic matters 
 
THEOKETICAL AND PRACTICAL AGRICULTURE. 97 
 
 have undergone decay ; tliat tlieir constituents liave united 
 with oxygen; and that the carbon has formed carbonic 
 acid, which has accumulated in the air contained in the 
 porous soil, as analysis shows us. 
 
 When rain falls on this soil, it dissolves the carbonic 
 acid, which thereby acquires the power of taking up phos- 
 phate of lime. This carbonic acid water does not withdraw 
 from the soil the phosphate of lime contained in it, but 
 wherever it meets with the granules of apatite or phospho- 
 rite, it dissolves a certain portion ; for in these granules 
 there exists no cause of resistance to the action of the water; 
 and except the cohesion between its own particles, no other 
 extraneous influence prevents its solubility in water. 
 
 Under these circumstances, a solution of phosphate of 
 lime must consequently be formed, which spreads in all 
 directions around each granule. Wherever this solution 
 comes in contact with soil not already saturated with phos- 
 phate of lime, the soil will take up and retain a certain 
 portion of this salt. The portion of soil now saturated with 
 phosphate will oppose no further obstacle to the wider dif- 
 fasion of the solution. 
 
 The same process is found to take place in the diffusion 
 of the silicic acid and potash in the soil, when the latter 
 contains silicates which can be decomposed by carbonic 
 acid. There is then formed around each particle of silicate 
 a solution of silicate of potash, the constituents of which 
 are always again fixed, in the first place by the nearest 
 lying, and then by the more remote portions of the soil. 
 
 A certain time is required for the distribution through- 
 out the soil of the food in the manner above described. 
 
 If we suppose that our field had contained 25,000 kilo. 
 of the ash-constituents of wheat, distributed in the most 
 uniform manner through it; and in addition to this, but 
 unequally distributed^ five, ten, or more thousand pounds of 
 
 5 
 
98 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 the same food, the phosphoric acid as apatite^ the silicic acid 
 and potash as easily decomposed silicates; — if we further 
 suppose that every two years a certain quantity of the last- 
 named substances had been rendered soluble, and capable 
 of distribution in the soil in the manner above mentioned, 
 and in such proportions that the roots should have found 
 everywhere in the soil these elements of food in the same 
 proportions as in preceding years of cultivation — a suffi- 
 cient amount, therefore, for a full average crop; then 
 should we, under these circumstances, have obtained during 
 a series of years full average crops, if we had interposed a 
 year of fallow between each year of cultivation. Instead of 
 thirty constantly-diminishing crops, we should in this case 
 have obtained, during a period of sixty years, ihirXy full 
 average crops, if the additional portion of minerals in the 
 soil had proved sufficient during that time to replace every- 
 where the phosphoric and silicic acids, and the potash, 
 removed annually by the crops. With the exhaustion of 
 the additional proportion of minerals in our field, the period 
 of diminishing crops would commence ; and the further 
 interposition from this time of fallow years would not then 
 exercise the slightest influence on the increase of produce. 
 
 In the case under consideration, had the supposed addi- 
 tional quantity of phosphoric and silicic acids, and potash, 
 not been unequally but uniformly distributed throughout 
 the field, and everywhere completely accessible to the roots of 
 plants, and in a state fit for absorption, then thirty full cro"^^ 
 would have been reaped in thirty successive years, without 
 the interposition of a year of fallow. 
 
 Let us return to our field, in which we assumed that 
 there were 25,000 kilo, of ash-constituents of wheat, tho- 
 roughly dispersed throughout it, and in a state fit for 
 absorption, and that it was sown each year with wheat; 
 let us now suppose that in each crop the ears only were 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 99 
 
 cut from the straw, and tliat the entire straw was left on 
 the field and imediatelj ploughed in ; then must the loss 
 of minerals be less in this year than before, for all the con- 
 stituents of the straw and the leaves have remained in the 
 ground ; we have only removed from the field the mineral 
 constituents of the grain. 
 
 Among the substances which the straw and leaves have 
 obtained from the soil, are found all the constituents of the 
 seed^ but only in altered proportions. If we express by the 
 number 3, the whole phosphoric acid removed by the grain 
 and straw together, the loss would be represented by the 
 number 2, if the straw remains in the ground. The decrease 
 of produce in a field in a succeeding year bears always a 
 definite proportion to the loss of mineral substances by the 
 preceding crop. The following crop of grain will be a 
 little larger than it would have been, had the straw not 
 been left in the ground. The produce of straw will be 
 nearly the same as in the preceding year, for the conditions 
 for the formation of straw have been but slightly altered. 
 
 By thus taking less from the field than formerly, we 
 thereby increase the number of remunerative crops, or in 
 other words, the total amount of grain produced in the 
 whole series of corn crops. A portion of the straw-consti- 
 tuents is converted into corn-constituents, and in this form 
 is now removed from the soil. The period of exhaustion 
 will always come, but under these circumstances it occurs 
 at a later date. The conditions for the production of grain 
 go on constantly decreasing, for the minerals removed by 
 it have not been replaced. 
 
 This relation would still have remained the same, had 
 the cut straw been carted about the field, or been ploughed 
 in after serving for litter to cattle. What has been sup- 
 plied to the field in this way, had been originally taken 
 from it and cannot therefore enrich it. When we reflect 
 
100 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 tliat the combustible elements of straw are not furnislied 
 bj the ground, it is clear that in leaving the straw in the 
 ground, we really leave only the constituents of its ash. 
 The field was thereby enabled to yield a little more than 
 it otherwise would have done, simply because less had been 
 taken from it. 
 
 Had we also along with the straw ploughed in the grain 
 or its ash-constituents ; or instead of the wheat grain re- 
 turned to the field a corresponding quantity of another 
 seed, rape-dust (that is, rape-seed freed from its fatty oil), 
 which contains the same ash-constituents, the composition 
 of the soil would have remained the same as before, and the 
 same amount of produce would have been obtained as in the 
 preceding year. 
 
 If after each crop, the straw is always returned in this 
 manner to the field, the further result then is, an inequality 
 in the composition of the active constituents of the soil. 
 
 We have assumed that our field contained the mineral 
 matters of the whole wheat plant in the right proportions 
 for the formation of straw, leaves and grain. By leaving 
 the straw-constituents in the soil, whilst those of the grain 
 were constantly removed, an increase of the former took 
 place, when compared with the proportion of grain-consti- 
 tuents still remaining in the field. The field retained its 
 productiveness for straw, but the conditions for the forma- 
 tion of grain decreased. 
 
 The consequence of this inequality is an unequal deve- 
 lopment of the whole plant. So long as the soil contained 
 and supplied, in the proper proportions, all the necessary 
 mineral matters for the uniform growth of all parts of the 
 plant, the quality of the seed and the proportion between 
 straw and grain in the diminishing crops remained uniform 
 and unaltered. But in proportion as the conditions for the 
 formation of straw and leaves became more favourable, so 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 101 
 
 did the quality of the seed deteriorate as its quantity dimi- 
 nish. The sign of this inequaUty in the composition of 
 the soil, as a consequence of cultivation, is the diminution 
 in weight of the bushel of corn. Whilst at first a certain 
 portion of the constituents of the returned straw (phospho- 
 ric acid, potash, magnesia) was expended in the formation 
 of grain, at a later period the reverse of this takes place, 
 and demands are then made on the grain-constituents 
 (phosphoric acid, potash, magnesia) for the formation of 
 straw. We may imagine that when there exists in a field, 
 this inequality in the conditions for the formation of grain 
 and straw, a culmiferous plant may, under conditions of 
 temperature and weather favourable for the production of 
 leaves, yield an enormous crop of straw with empty ears. 
 
 Vine-dressers and gardeners prune trees and vines in 
 order to obtain larger fruit and in greater quantity, by 
 thus limiting the formation of twigs and leaves ; and in 
 many districts, as in lower Bavaria, it is often considered 
 advantageous to cut down or feed off the corn when half 
 grown. It is found that by this proceeding a larger amount 
 and a better quality of grain are obtained. In tropical 
 regions many culmiferous plants bear no seed, or but a 
 small quantity, because the soil does not contain the 
 proper proportion of conditions for the formation of seed 
 and leaf. 
 
 The size of the seed in many plants, is in inverse pro- 
 portion to the development of the leaf. Tobacco, poppy, 
 and clover have proportionably smaller seeds than the 
 culmiferous plants. 
 
 The agriculturist can influence the direction of the vege- 
 tative force only through the soil ; that is, through the 
 proportion of the elements of food which he supplies to it. 
 For the production of the largest crop of grain it is requisite 
 that the soil contain a preponderating proportion of food neces- 
 
102 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 sary for the formation of seeds. For turnips^ ^^(^fy and 
 tuberous plants, this condition is reversed. 
 
 An average crop of turnips with leaves contains five 
 times, a clover or potato crop twice, as much potash as the 
 grain and straw of a wheat crop from an equal surface. A 
 clover and a potato crop together remove from two fields 
 of a hectare each, as much phosphoric acid as the grain of 
 three wheat crops from three fields of the same size. 
 
 It is therefore evident, if we cultivate potatoes and 
 clover on our field which contains 25,000 kilo, of the mine- 
 ral constituents of wheat, and remove the whole produce 
 of tubers and clover, that we withdraw from the soil of 
 these two fields as much phosphoric acid, and three times 
 as much potash, as bj three wheat crops. It is certain, 
 that this removal from the soil, by another plant, of these 
 important mineral substances, produces a great effect on its 
 fertility for wheat ; the yield and the number of the wheat 
 crops diminish. 
 
 If, on the other hand, during a period of two years, we 
 had cultivated on the field, wheat in the first year, and 
 potatoes in the second, and had ploughed in the whole of 
 the potato crop and the wheat straw, and had continued to 
 do this for sixty years, we should not by these means have 
 in the least degree altered or augmented the produce in 
 grain, which the field was capable of yielding. The field 
 has neither acquired nor lost anything by the cultivation of 
 potatoes, for these were always left in the field. When the 
 grain crops taken from the field have diminished the store 
 of mineral matters to I of their original quantity, then this 
 field ceases to furnish a remunerative crop, if 3 of an 
 average return no longer yield any profit to the agricultu- 
 rist. We arrive at the same results, if, instead of potatoes, 
 we had interposed crops of clover, and had in the same 
 way each year ploughed it in. We have assumed that the 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 108 
 
 physical condition of the soil was most favourable, and 
 consequently, could not be improved by incorporating with 
 it the organic matters of the clover and potatoes. Even 
 had we removed the potatoes from the field, mown and 
 dried the clover, and then carted the potatoes and hay back 
 to the field, or made them first pass through the cattle 
 stalls, or made any other use of them ; had we in this way 
 returned to the field the whole sum of mineral matters in 
 both crops, we should not by all these operations have pro- 
 duced from it in thirty, sixty, or seventy years, a single 
 grain more than would have been obtained without all these 
 changes. During this whole period the conditions for the 
 production of grain have not increased, but the cause of 
 decrease in the crops has remained the same. 
 
 The ploughing in of the potatoes and clover could pro- 
 duce a beneficial effect only on those fields, in which a 
 favourable physical state did not exist; or in which the 
 mineral matter was unequally distributed, and was partly 
 inaccessible to the roots of plants. But an action of this 
 kind is just the same as that of green manuring, or of one 
 or more years of fallow. 
 
 By the incorporation with the soil of the clover and 
 organic substances, the amount of decaying matters and of 
 nitrogen in it is increased from year to year. All that these 
 plants received from the atmosphere remained in the 
 ground, but the enriching of the soil with these otherwise 
 useful matters cannot effect the production of more grain 
 than formerly ; for this depends on the proportion of the 
 minerals in the soil, and these have not been increased, but 
 on the contrary, have constantly decreased, in consequence 
 of the removal of the corn. By the increase of nitrogen, 
 and of decaying organic matter in the soil, the produce 
 might possibly be augmented for a number of years, but 
 the period at which such land would no longer produce a 
 
104 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 remunerative crop, occurs in sucli circumstances only so 
 much the more quickly. 
 
 If we cultivate on three different wheat fields respec- 
 tively, wheat, potatoes, and clover, and plough all the 
 potatoes and clover yielded by the other two into the 
 wheat field, from which the grain alone is removed, we 
 shall by these means render the latter more fertile than 
 before, for we have enriched it by the whole amount of 
 minerals which the potatoes and clover had extracted from 
 the other two fields. It has received three times as much 
 phosphoric acid, and twenty times as much potash, as the 
 grain has carried away. 
 
 This wheat field will now be able to produce in three 
 successive years, three full grain crops ; for the conditions 
 for the production of straw have remained unchanged, 
 whilst those for corn have been increased threefold. If 
 the agriculturist in this manner raises in three years as 
 much corn as he would have done in five on the same fields, 
 without the co-operation of the mineral constituents of the 
 clover and potatoes, then has his profit now evidently become 
 greater^ for he has reaped with the seed for three crops as 
 much as he would have done in the other case, with the 
 seed for five. But the other two fields have lost in fertility 
 as much as the wheat field has gained ; and the final result 
 is, that with less cost of cultivation^ and ivith more profit than 
 before, the agriculturist has in his three fields anticipated 
 the period of exhaustion which would inevitably have over- 
 taken them by the continued withdrawal in grain of the 
 mineral constituents of the soil. 
 
 The last case that we have to consider is, when the agri- 
 culturist, instead of potatoes and clover, cultivates turnips 
 and lucerne, which, by means of their long and deep pene- 
 trating roots, extract a large quantity of mineral matter 
 from the subsoil, which is not reached by the greater num- 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 105 
 
 ber of the roots of tlie cereals. Where the fields possess a 
 subsoil, favourable to the growth of these plants, we double, 
 as it were, the extent of surface capable of cultivation. If 
 the roots of these plants received half of their mineral 
 matters from the subsoil, and the other half from the arable 
 soil, the latter will lose by the crops only half so much as 
 they would have done, had the whole of the mineral food 
 for these crops been obtained from the arable soil alone. 
 
 The subsoil considered in the light of a field apart from 
 the arable soil, thus furnishes to the turnip and lucerne 
 crops, a certain quantity of mineral matter. If we sup- 
 pose that in harvest the whole of the turnip and lucerne 
 crops had been ploughed under in the wheat-field, which 
 had yielded an average crop of grain, and in this way as 
 much and more mineral matter had been returned than the 
 grain had removed ; then by these means, this wheat-field 
 can he maintained at the same degree of fertility at the expense 
 of the subsoil^ just so long as the latter continues productive for 
 turnips and lucerne. 
 
 But since turnips and lucerne require for their growth a 
 very large quantity of mineral matter, the subsoil will be 
 the sooner exhausted, in proportion to the smaller quantity 
 of these substances it contains. Now as the subsoil is not 
 in reality separated from the arable soil, but lies beneath it, 
 it can scarcely receive back any of the substances it has lost, 
 because the arable soil retains that portion of them which 
 has been added to it. It is only that part of the potash, 
 ammonia, phosphoric, and silicic acids, which has not been 
 taken up and fixed by the surface soil that can penetrate 
 to the subsoil. 
 
 By the cultivation of these deep-rooting plants, super- 
 abundance of food can consequently be obtained for all 
 those which derive their nourishment chiefly from the sur- 
 face soil. This supply will not, however, be of any dura- 
 
 5* 
 
106 THEORETICAL JlND PRACTICAL AGRICULTURE. 
 
 tion ; for, in a comparatively short time, many fields will 
 cease to produce these plants, because the subsoil is ex- 
 hausted, and its fertility is only restored with difficult}^ 
 In the first place, lucerne no longer grows, and turnips are 
 only now produced in so far as they are able to obtain theii 
 full supply of minerals from the surface soil. Potatoes, 
 which derive their supplies from the upper layers of the 
 surface soil, endure the longest. 
 
 The quantity of food which a plant receives from the 
 ground is not alone dependent on the quantity which is 
 present in the finest particles of the surface soil, but also 
 on the number of organs which extract this food from the 
 ground. Two roots will obtain twice as much as one. 
 
 The crop is partly dependent on the first root forma- 
 tion. 
 
 A grain of wheat or barley contains within itself so large 
 a quantity of food, that it stands in no need of the soil in 
 the first period of its growth. The seeds of these plants 
 when simply moistened, produce ten or more rootlets from 
 six to eight lines in length. The heavier the grain, the 
 stronger and more vigorous is the formation of roots. The 
 seed corn, without receiving anything from the ground, 
 extends in all directions its organs of absorption, by which 
 it procures its food from a comparatively great distance. 
 Hence the agriculturist attaches great importance to the 
 careful selection of seed. 
 
 Small seeds, such as those of tobacco, poppy, and clover, 
 require a richer or more thoroughly prepared surface soil, 
 to prevent the loss of a large proportion ; because the soil 
 in the immediate neighbourhood of the seed must at once 
 supply it with food after germination. Hence, as the agri- 
 culturists say, such plants are more difficult to raise. 
 
 The seeds of the cereals may be compared to a hen's 
 egg, which contains within itself all the necessary elements 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 107 
 
 for the development of the young animal. Husbandry 
 would certainly assume quite another form, if for every 
 single cereal plant, as many seeds should be lost as is the 
 case with poppies, tobacco, and even clover. 
 
 The quantity of food wliich a plant obtains from one and 
 the same soil is in proportion to its absorbent root surface. Of 
 two species of plants^ which require the same quxintity and a 
 similar relation of mineral food^ the one with double extent of 
 root surface takes up double the quantity of food. 
 
 If it is true that the constituents of the ash of plants are 
 indispensable to their life and growth, it is evident that 
 whatever else may exert a favourable influence on their 
 growth, must be subordinate to the law^ that the soil, in 
 order to be fertile in an agricultural sense for a cultivated 
 plant, must contain the constituents of the ash in sufficient 
 quantity, and in a state the most suitable for absorption. 
 
 The agriculturist has to do with the soil alone ; it is only 
 through it that he is able to exercise an immediate influ- 
 ence on plants. The attainment of all his objects in the 
 most complete and profitable manner, pre-supposes the 
 exact knowledge of the effective chemical conditions for 
 the life of plants in the soil ; it further pre-supposes, perfect 
 acquaintance with the food of plants, and the source from 
 which it is derived, as well as with the means for rendering 
 the soil suitable for their nutrition, combined with experi- 
 ence and skill in employing them in the proper way, and 
 at the right time. 
 
 It is evident from the above statement that the cultiva- 
 tion of plants tends to drain or to render a fertile soil un- 
 productive. In the produce of his fields destined for the 
 food of man and beasts, the agriculturist sends away that 
 portion of the active ingredients of his soil which con- 
 tributes to the growth of this very produce. The fertility 
 of his fields continuously diminishes, whatever may be the 
 
108 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 plants he cultivates or the rotation he adopts. The export 
 of his produce is nothing else than a spoliation of his soil 
 of the conditions for its reproduction. 
 
 A field is not exhausted for corn, clover, tobacco, and 
 turnips, so long as it still yields remunerative crops with- 
 out requiring restx)ration of the minerals which are removed. 
 It is exhausted from the moment that the hand of man is 
 needed to restore to it the failing conditions of its fertility. 
 
 The great majority of our cultivated fields are in this sense 
 exhausted. 
 
 The life of men, of animals, and of plants, is connected 
 in the closest manner with the return of all the conditions 
 which promote the vital process. The soil by its constitu- 
 ents contributes to the life of plants ; its continuous fer- 
 tility is inconceivable and impossible without the return of 
 those conditions which have rendered it productive. 
 
 The mightiest stream, which sets in motion thousands of 
 mills and machines, fails, if the streams and brooks run dry 
 which supply it with water ; and these streams and brooks 
 in their turn dry up, if the myriads of little drops of which 
 they consist do not return in the form of rain to those 
 spots from which they have their source. 
 
 A field which has lost its fertility by the successive cul- 
 tivation of different plants, acquires by the application of 
 farm-yard manure^ the power of producing a new series of 
 crops of the same plants. 
 
 But what is farm-yard ma?2wre,^and whence is its origin ? 
 The land of the husbandman is the source of all this 
 manure. Manure consists of the straw which has served 
 for litter, of the remains of plants, and of the fluid and 
 solid excrement of man and animals. The excrement is 
 derived from the food. 
 
 In the bread which a man daily receives, he consumes 
 the ash-constituents of the seeds of the cereals whose flour 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 109 
 
 has served for the preparation of the bread ; in flesh, the 
 ash-constituents of flesh. 
 
 The flesh of herbivorous animals, as well as its ash-con- 
 stituents are derived from plants. These ash constituents 
 are identical with those of the seeds of leguminous plants ; 
 so that if a whole animal were burnt, the residual ash 
 would not differ from that of beans, peas, and lentils. 
 
 In bread and flesh, man consequently consumes the 
 mineral matters of seeds, or of the constituents of seeds, 
 which the agriculturist obtains from his land in the form 
 of flesh. 
 
 But a very small fraction of the large amount of mineral 
 substances received by man in his food during a lifetime re- 
 mains in his body. The body of an adult does not increase 
 in weight from day to day, it therefore follows, that all the 
 constituents of his food have passed again completely out 
 of his body. Chemical analysis demonstrates that the ash 
 of bread and of flesh exists in his excrement very nearly in 
 the same quantity as in his food. The comportment of the 
 food in his body is just the same as if it had been burnt in 
 a furnace. The urine contains the soluble, and the faeces 
 the insoluble mineral matters; the bad smelling ingredi- 
 ents are the smoke and soot of an incomplete combustion. 
 With these are also mingled the undigested and indigesti- 
 ble remains of food. 
 
 The excrement of swine fed on potatoes contains the ash- 
 constituents of potatoes; that of the horse, the mineral 
 matters of hay and oats ; that of cattle, the ash of turnips, 
 clover, &c., which have served for their food. Farm-yard 
 manure consists of a mixture of all these excrements 
 together. 
 
 By farm-yard manure, the fertility of a field which has 
 been exhausted by cultivation, is completely restored. This 
 is a fact which the experience of thousands of years has 
 
110 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 established. In farm-yard manure tlie field receives a cer- 
 tain quantity of organic, that is, combustible matter, and the 
 ash-constituents of the consumed food. We have now to 
 consider what part was played by the organic and inorganic 
 matter in this restoration of fertility. 
 
 The most superficial examination of a cultivated field 
 shows, that all the combustible matter of plants which are 
 reaped from the field are derived /rom the air^ and not from 
 the soil. 
 
 If the carbon of only a portion of the vegetable matter in 
 the crop were derived from the soil, it is perfectly clear, that 
 if the latter contained at first a certain amount of this element 
 before the harvest, this quantity must become smaller after 
 each crop. A soil poor in organic matter would be less 
 productive than one in which it is abundant. 
 
 Observation, however, shows, that a field under continued 
 cultivation does not in consequence become poorer in organic 
 or combustible matter. The soil of a meadow, which during 
 ten years has yielded a thousand cwt. of hay per hectare, is 
 not, after this period, poorer, but richer in organic substances. 
 A clover field, after a crop, retains in the roots remaining in 
 the soil more organic matter, and more nitrogen than it 
 originally possessed; but it has become unproductive for 
 clover, and yields no longer a remunerative crop. 
 
 A wheat or potato field is in like manner, after a crop, 
 not poorer than before in organic matter. In general the soil 
 is enriched hy cultivation with combustible constituents, but its 
 fertility nevertheless steadily diminishes. After a number of 
 consecutive remunerating crops of corn, turnips and clover, 
 these plants are found to flourish no longer on the same soil. 
 
 Since, then, the presence of decaying organic m,atter in a soil^ 
 does not in the slightest degree retard or arrest its exhaustion by 
 cultivation, it is impossible that an increase of these substances 
 can restore the lost capacity for production 
 
THEORETICAL AND PRACTICAL AGRICULTURE. Ill 
 
 111 fact by incorporating with the soil of a field com- 
 pletely exhausted, boiled saw-dust, or salts of ammonia, or 
 both together, we cannot restore to it the power of yielding 
 a second or third time the same series of crops. If these 
 substances improve the physical character of the soil, they 
 will exercise a favourable influence on the produce; but 
 after all, their action still consists in accelerating the exhaus- 
 tion, and rendering it more complete. 
 
 Farm-yard, manure, however, restores thoroughly the 
 power of producing the same series of crops, a second, third, 
 or a hundred times. It arrests fully, according to the 
 quantity employed, the state of exhaustion ; its application 
 may render a field more fertile ; in many cases more so than 
 it has ever been. 
 
 The restoration of fertility by farm-yard manure cannot 
 have been caused by the presence of combustible matters 
 (carbonaceous and nitrogenous substances). If these pro- 
 duced any good effects, they were of a subordinate nature. 
 The action of farm-yard manure depends most undoubtedly on 
 the amount of the incombustible ash-constituents of plants in itj 
 and is determined by these. 
 
 In the farm-yard manure the field received back in fact a 
 certain quantity of all the minerals which had been with- 
 drawn by the crops. The decrease in its fertility stood in 
 exact relation with the removal and the restoration of the 
 fertility with the restitution of these mineral substances. 
 
 The incombustible elements of cultivated plants do Dot 
 of themselves return to the soil like the combustible in the 
 atmospheric sea from which they are derived. By the hand 
 of man alone are the conditions of the life of plants given 
 back to the soil. By farm-yard manure, in which these con- 
 ditions are fulfilled, the agriculturist, as if by a law of nature, 
 restores to his field its lost powers of production. 
 
 A rational practice maintains the circulation of aU the 
 
112 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 conditions of life ; and empirical practice breaks the chain 
 which binds man to his home, by robbing the soil of one 
 condition after another of its fertility. Though the empiric 
 knows that the soil is different to-day from what it was 
 yesterday, he nevertheless believes that it will be to-morrow 
 what it is to-day. Founding on the experience of yesi^rday^ 
 he teaches that the fertile soil is inexhaustible ; but science, 
 guided by laws^ shows that the productiveness even of the 
 most fertile soil, has its end, and that the very soil which 
 appears inexhaustible, is exhausted. Because nature was 
 kind and gave abundantly to the father, the empiric thinks 
 that the son may also take abundantly and without any 
 care for the future. On the fact that man has a home, and 
 that the spot of earth, from which he toils with the sweat 
 of his brow to gam his subsistence, is his home, depends the 
 development of the human race. The continuance of his 
 existence in his home is dependent on the law, that force is 
 expended by use and maintained by supply. 
 
LETTER IX. 
 
 Constant relation between the Sulphur and Nitrogen of Organic Compounds 
 and the Alkaline Phosphates and Alkaline Earths of Cereals and Legu- 
 minous plants — Mineral substances are as indispensable to the Life of 
 Animals as to that of Plants — The amount of Phosphoric Acid and of 
 Potash ascertained by analysis as existing in Soils is very small — The 
 errors of Practical Teachers proved from the writings of Practical Agri- 
 culturists — Fertility of land cannot be maintained by Nitrogenous and 
 Carbonaceous Manures alone, but by the Restoration of the Ash Constitu- 
 ents of Plants — Critical examination of the views o "Walz, a practical 
 teacher, on the Nutrition of Plants — The mineral food of plants in arable 
 soils is not inexhaustible — The volatile and organic matters of Manures 
 are not the most important — The nature of Guano and its active con- 
 stituents. 
 
 The life and development of an organic being cannot be 
 regarded as depending on chance. The assimilation of its 
 food, the transformation of the elements of this food into 
 living forms, and all organic processes, we find are go- 
 verned by laws of necessity and reciprocal dependence, 
 which, like the wheels of a machine, but in an infinitely 
 more perfect manner, play into each other, and give rise to 
 all its vital manifestations, its existence and continuation. 
 
 Chemical analysis has shown that in the seeds of the 
 cereals and of the leguminous plants, those sulphur and 
 nitrogen constituents which, in the process of nutrition of 
 men and animals, are employed in forming the combustible 
 matters of blood, are always accompanied by alkaline phos- 
 phates and alkaline earths, and that between both there ex- 
 ists for each seed a fixed and unchangeable relation. When- 
 ever the percentage of phosphoric acid increases or dimi- 
 
114 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 nishes in any seed, we observe a like increase or diminution 
 in the sanguigenous constituents. 
 
 Chemical analysis has further shown that, in the blood 
 of man who consumes bread, or in that of a warm-blooded 
 animal fed on seeds, there exist the same incombustible 
 matters as are contained in the food. The ash-constituents 
 of the blood of cattle, sheep, swine, correspond to the 
 ash-constituents of the turnips, herbs, or potatoes on which 
 these animals have subsisted. 
 
 The mineral elements of all the different parts of plants 
 are, however, as indispensable to the life of animals, to the 
 formation of their blood, and to its functions, as they are 
 to the life of plants. 
 
 Phosphoric acid is a constituent of the brain and of the 
 nerves ; the alkaline phosphates and alkaline earths exist 
 in the flesh of all animals : and a warm-blooded animal 
 without bones (phosphate of lime), is inconceivable to us. 
 The ash of green crops is rich in alkaline carbonates and 
 common salt; and the blood of herbivorous animals 
 abounds in alkaline carbonates, the chloride of sodium 
 serving for the formation of the carbonate of soda of this 
 fluid. Tea-leaves, of which man makes so much use in in- 
 fusion, contain in their ash 17 per cent, of phosphoric acid ; 
 in mulberry leaves, the food of the silkworm, the amount 
 does not exceed 5 per cent. Each of these numbers has its 
 physiological meaning. 
 
 Were it possible for a plant to grow, flower, and bear 
 seed without the co-operation of mineral matters, it would 
 be utterly valueless to man and animals. A dog will die 
 of hunger in presence of a dish full of raw or boiled white 
 and yolk of eggs, in which is awanting one of the sub- 
 stances most important for the formation of blood. The 
 first trial teaches him that such food is as inefficient as a 
 stone for the purposes of nutrition. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 115 
 
 The constituents of the ashes of turnips and of meadow 
 plants give them their nutritious value. Did they not exist 
 in them, such plants would not be consumed by horses and 
 cows. 
 
 Everywhere in nature prevail those harmonious laws, 
 which attach life to the earth, and maintain it in perpetual 
 freshness and duration. Only there does the earth become 
 old, and the germ of life is extinguished, where man in his 
 narrow-mindedness ignores and denies their existence, when 
 he opposes the circulation of the conditions of life, and de- 
 ranges and obstructs their united action. 
 
 It is certainly one of the most singular, if not one of the 
 most inexplicable circumstances of the present day, that 
 the existence of these natural laws is ignored by a great 
 number of practical agriculturists, — precisely by those men 
 who, in their occupation, are in a position to perceive 
 daily the signs of their existence. Teachers of practical 
 agriculture universally recognised to be the most distin- 
 guished and skilfUl, have for sixteen years, and even up to 
 a recent period, endeavoured to prove that these laws have 
 no value in connection with fertile soils ; that the increase 
 of the fertility of a field hy fallow and hy mechanical opera- 
 tions^ and the removal of the mineral matters of the soil in the 
 cwps, do not diminish the duration of this fertility : that the 
 ground may retain continuously its fertility even when they 
 neglect to supply the minerals which have been withdrawn^ 
 that is, to restore the original composition of the soil. They 
 teach that 2^ fertile field contains an inexhaustible amount of 
 the ash-constituents of plants, and that, consequently, de- 
 ficiency of these can never occur in it ; that the fertility of 
 a soil is in exact proportion to the quantity of combustible 
 matters^ of humus and nitrogen in it ; and that the want of 
 fertility is owing to the want of nitrogen, and that the ex- 
 haustion of the land depends up.on the withdrawal of the 
 
116 THEORETICAL AND PBACTICAL AGRICULTURE. 
 
 latter. Manure, tliej assert, does not produce its beneficial 
 effects by returning to the ground those elements which 
 have been withdrawn from it in corn, clover, turnips, to- 
 bacco, flax, hemp, madder, wine, &c., but it acts by its com- 
 bustible constituents, and its effect is in proportion to the 
 amount of nitrogen it contains. Its incombustible elements 
 only quietly look on to see how the other matters are doing, 
 something in the same way as the moon does when the dew 
 is falling. 
 
 The practical man regards with a smile of contempt the 
 scientific proofs of his errors, but this smile does not arise 
 from the feeling of conscious superiority which knowledge 
 imparts, but it has its origin in a different source. 
 
 Chemical analysis has with its rigorous methods proved, 
 that of thousands of fields there is scarcely one which con- 
 tains more than 1 per cent, of the ash-constituents of plants, 
 of clover, for instance, in a state suitable to the wants of 
 that plant. 
 
 In 1848 the Royal Institute of Rural Economy in Berlin 
 caused the soil from fourteen different places of the king- 
 dom to be submitted to chemical analysis. The specimens 
 were taken from fields which were as much alike as possi- 
 ble, and a portion of each specimen handed to three different 
 chemists for analysis. It resulted from these analyses that 
 the mean quantity of phosphoric acid and potash (the latter 
 in a state probably fit for assimilation) amounted, in five 
 fields to t\ ; in six, to fV ^P to y\ ; and in three, to yV "^^P 
 to y*V per cent. 
 
 These analyses do not teach that a soil which contains y\ 
 per cent, of these mineral substances is in consequence 
 more fertile than another in which there exists only y^^ per 
 cent. ; but they show with tolerable certainty that it con- 
 tains a greater or less proportion of them. 
 
 Practice, on the other hand, asserts that every soil con- 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 117 
 
 tains the ash-constituents of all plants in inexhaustible 
 quantities. 
 
 Chemical analysis points out in the most positive and 
 undoubted manner, that a crop of clover removes from the 
 soil in its ash-constituents a number of the conditions of 
 its fertility for this plant ; it shows that, in the excrement 
 of animals fed on clover, are contained the ash-constituents 
 of clover, and that consequently, by the employment of 
 such a manure, the whole of these ash-constituents which 
 have been removed by the clover are again restored to the 
 land. 
 
 As harmonising with the scientific doctrine, that the 
 exhaustion of a clover field really depends on the removal 
 of the ash-constituenis of the clover, and the renewal of its 
 fertility by farm-yard manure^ on the restoration of these 
 same mineral matters, the writings of the most experienced 
 agriculturists show, that a field which produced no clover^ 
 can be made productive for a series of such crops by manur- 
 ing with wood-ashes^ which contain the same mineral matters 
 as clover ; that in the Netherlands this manure is of the 
 most general application for this purpose; and that in 
 Westphalia there is a proverb that "Ae pays double who 
 buys no ashes.^^ (Schwerz, Anleitung zum prakt. Ackerbau, 
 Bd. ii. S. 323.) It is a well-known fact that on strewing 
 wood-ashes on a meadow, thousands of clover plants make 
 their appearance where they were not visible before. 
 
 Chemical analysis further shows that a similar relation 
 exists between a soil and all plants which are grown upon 
 it ; that a field which will no longer yield grain, but straw, 
 bears a rich crop of the former if it has been manured with 
 the ash-constituents of grain, and in many cases even with 
 phosphate of lime alone. 
 
 In complete opposition to the modern doctrine of our 
 agriculturists, it is proved by indisputable facts that the fer- 
 
118 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 tility of tlie soil is not increased by the amount of organic 
 or combustible matters in it, or by the supply of these 
 alone; that a soil which contains these in the greatest 
 abundance is, as a rule, unproductive ; and that the appli- 
 cation on a wheat field of nitrogenous matters — such as the 
 salts of ammonia — in many cases diminishes rather than 
 increases the crop of grain. It has further been proved 
 that ammonia and nitrogenous manures do not augment 
 the produce of clover, unless accompanied by the ash-con- 
 stituents of the plant ; that by themselves they act favour- 
 ably, only on such fields as are rich in mineral matters ; 
 and that their continued use in such cases only more com- 
 pletely exhausts the land — that is, makes it still more 
 unproductive for future crops than it would have been 
 without their action. 
 
 ""'If our fields really contained so large a quantity of the 
 mineral matters of plants that they could not be exhausted 
 by cultivation ; if the fertility was dependent on the pre- 
 sence and their exhaustion on the absence of ammonia or 
 nitrogenous substances, then an endless series of full crops 
 should be obtained by the supply of these alone, without 
 the addition of any mineral matter. It is, however, an 
 established and indisputable fact, that the maintenance of 
 the fertility of our fields is impossible without replacing the 
 minerals withdrawn by the crops. Hence it follows that 
 farm-yard manure does not act by its combustible elements, 
 and that if the latter in any case produce a favourable effect, 
 it is only when they are accompanied by the ash-constitu- 
 ents of plants which have been removed by previous crops, 
 and which are awanting in the field. 
 
 I believe that among the readers of these letters there 
 will scarcely be found one, at all acquainted with the rules 
 of logic, who could have any doubts of the truth of the 
 conclusions deduced from the chemical analysis of the soiJ^ 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 119 
 
 of plants, and of farm-yard manure. These analyses liave 
 been made in thousands by different chemists in Germany, 
 England, and France, and all agree perfectly in their results. 
 If indeed the existence of a fact can be ascertained by the 
 balance, there is none in the whole domain of chemistry 
 more firmly established than this, that even the most fertile 
 soil contains but an extraordinarily small quantity of the 
 ash-constituents of plants in comparison with its chemically- 
 inactive mass. It will be sufficient to give an idea of this 
 fact when I state that the ablest chemists failed in discover- 
 ing, before 1834, potash as a constituent of soils, of clay, 
 and of limestones, because its amount is so small ; and that 
 before the discovery of new and hitherto unknown re-agents, 
 the simple detection in the soil of phosphoric acid (without 
 any attempt to ascertain its quantity) was attended with 
 the greatest difficulty. In these statements we find a justifi- 
 cation of the views formerly held by philosophers that pot- 
 ash, lime, and phosphoric acid are products of the vital pro- 
 cesses or of the vital force. 
 
 As is well known, there is an infinite variety in the com- 
 position of the rocks and minerals, by the disintegration of 
 which soil is formed. There are minerals which are rich, 
 in potash, and which, like felspar, contain no lime ; in 
 others, silicic acid or magnesia is awanting, or like lime- 
 stones, they contain only traces of alkalies. It is only in 
 exceptional cases, and in those rocks which are not exten- 
 sively distributed, that it has been possible to estimate by- 
 chemical analysis the weight of the phosphoric acid pre- 
 sent. 
 
 Like gold in the gold districts of America and of Australia, 
 arable soil is the residual matter of rocks shattered by 
 mighty mechanical actions, and decomposed by chemical 
 causes. The granite gravel in the neighbourhood of Darm- 
 stadt, in which can be detected felspar, mica, and quartz. 
 
120 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 is as unproductive as pure quartz or pounded marble. A 
 thousand years are perhaps necessary to form from many 
 rocks, from basalt, granite, porphyry, trachyte, &c., a layer 
 of arable soil, a line thick, such as is seen in wide valleys 
 and low grounds, and to give it the physical and chemical 
 properties which render it suitable for the growth of plants. 
 
 Our modern teachers of agriculture inculcate that a fruit- 
 ful soil is inexhaustible in the ash-constituents of plants, 
 which are the essential conditions of their existence ; and 
 the present system of agriculture is, in all its relations, 
 based on this view, and on the further supposition that the 
 increase of the produce of the ground can only be effected, 
 or chiefly so, by the supply of organic matters, the ele- 
 ments of which are obtained, not from the soil, but from 
 the air. 
 
 Practical agriculture asserts, that in such practical ques- 
 tions which refer to soils^ crops, and manures, geology and 
 chemistry have no voice ; experience alone can decide in 
 such cases, and the deductions of science are not confirmed 
 by it. 
 
 We will now examine a little more narrowly the nature 
 of this experience, and the grounds on which she bases her 
 teaching. If founded in truth, it must secure the duration of 
 the fertility of productive soils : it must provide practical 
 agriculturists with the means of restoring to their land the 
 fertility lost by cultivation. If those who follow such 
 teaching are ever in want of these means, then is its con- 
 demnation pronounced. 
 
 Since the commencement of the contest regarding the 
 scientific principles of agriculture, many excellent agricul- 
 turists have communicated to me the most interesting 
 proofs, from their own practice, of the truth of these prin- 
 ciples, which they have hesitated to publish in an agricul- 
 tural journal, through fear of being involved in a discus- 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 121 
 
 sion, whicli, as they very modestly expressed it, they had 
 not sufficient scientific knowledge to carry on. In the po- 
 sition which I occupy, I stand, as may be supposed, 
 towards agriculturists who cultivate their own land, only in 
 social relations of the most instructive and agreeable nature 
 to myself; when, therefore, in these letters, I speak of 
 practical agriculture, or practical agriculturists, as a matter 
 of course only literary practical agriculturists are meant, 
 and those who write and lecture in support of the doctrines 
 of the school to which they belong. Among our agricul- 
 turists are to be found many men of the greatest intelli- 
 gence and information, who, like the gentleman, general, 
 lawgiver, and consul of Home's best age, follow, from in- 
 clination, agriculture as the noblest occupation, and manage 
 their own estates, No one can reasonably expect that 
 such men are to account for views and doctrines which 
 are not theirs, but which they have adopted as they were 
 taught. 
 
 A totally different relation, however, exists between 
 science and the writers on practical agriculture, whose com- 
 petence to pronounce an opinion on the present important 
 questions may not be disputed. From such men it must 
 absolutely be required that they bring to the discussion of 
 such questions, so much of the rudiments at least of che- 
 mistry, physics, and geology, as are usually taught in 
 ordinary schools, so that no doubts may be raised as to their 
 intellectual capacity to comprehend correctly the questions 
 at issue. 
 
 The simple statement of the views and doctrines from his 
 last work, of one of the ablest and most influential teachers 
 of agriculture, as to the composition of the soil, the causes 
 of its fertility and exhaustion, and the action of manures, 
 will be sufficient to enable us to form an opinion on this 
 point. This publication is expressly intended by the 
 
 6 
 
122 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 author to correct scientific teaching, aLcL to bring it into 
 harmony with practical experience.* 
 
 In the application of his theory to practice, the author 
 of this publication puts forward as a fundamental principle 
 that, " the soil (the surface and sub-soil included), may be 
 said to contain an inexhaustible supply of those mineral 
 elements of food which it received at first from nature, and 
 furnishes by disintegration to plants." — (s. 116.) 
 
 The following proposition is propounded by him, " Is 
 the soil of a field of such a nature that it can be completely 
 exhausted in a shorter or longer period of its soluble and 
 insoluble mineral matter, if we do not restore to it the por- 
 tion which is taken away by the crops ?" and it is answered 
 in the following way : — (s. 28.) 
 
 " The soil consists of disintegrated rocks, and either rests 
 upon these same rocks or on others elsewhere ; the trans- 
 ported soil may, nevertheless, have remained the same, 
 and corresponds at least to the rocks from which it has its 
 origin (p. 29, &c.). 
 
 " All rocks undergo disintegration, and the products 
 when not removed remain resting upon these rocks. The 
 disintegration is chiefly effected by atmospheric causes, 
 which extend their action down to the rocks lying deep 
 under the debris. If, then, a soil is fertile for a given class 
 of plants, and contains the mineral food for these plants in 
 sufficient quantity, in proper proportions, and in a state fit 
 for assimilation, and if it still rests upon the original rocks 
 from which it was produced, then these underlying rocks also 
 contain the same mineral food as the soil and subsoil, and in 
 the same proportions. 
 
 * " On the Nutrition of Agricultural Plants. An Examination, in an 
 Agricultural Point of View, of the Fifty Axioms of Baron Liebig," by Gustav 
 Walz, Director of the Agricultural Academy at Hohenheim, Stuttgart. Cotta, 
 1857. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 123 
 
 "If we withdraw from the soil its constituents by crops, 
 its volume diminishes, and the rocks are thereby rendered 
 more accessible to the action of the atmosphere. If the 
 disintegration of the latter proceed in the same ratio as the 
 constituents of the soil above them are withdrawn, then 
 shall we be able to obtain crops from it without restoration 
 of the mineral matters, until the whole quantity in the soil, 
 and in the rocks, be consumed. 
 
 " Suppose the soil of an hectare field (2-| acres), weighs 
 4|- millions kilogrammes, and contains 10 per cent, of the 
 mineral food of wheat plants in the right proportions and 
 in a state fit for assimilation, such a field could, without 
 any further supply, produce 1829 corn-crops. A three- 
 crop rotation could last 2742 years without restoration of 
 the mineral matters ; and were the rocks at the commence- 
 ment of the tillage already disintegrated to the depth of 
 several feet, as is generally the case^ then the three-crop 
 rotation would have the prospect of enduring for each foot 
 depth of earth other 2742 years. After this period, how- 
 ever, the rocks under the subsoil will again undergo further 
 disintegration, and thus there is a prospect of continuing 
 tillage until the rocks forming the soil are entirely disin- 
 tegrated, and the mineral constituents consumed. But 
 there comes then another class of rocks under these, &c., &c. 
 
 " By yearly removing ash-constituents from the soil, its 
 volume is reduced. The agriculturist, however, preserves 
 a soil of the same depth by turning up an equal quantity 
 from the subsoil. If all the mineral food in the soil has 
 been consumed, we have lost 10 per cent., and turned up 
 10 per cent, from the subsoil. The turned up mass of 
 earth, however, only contains 10 per cent, of mineral food. 
 Hence, only yV of the withdrawn matters is replaced, the 
 remaining y^o being waste matter. The second period of 
 the supposed three-crop rotation would therefore not last 
 
124 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 2742 years, but only j\ of this time, viz., 274 years ; it is 
 only after several such periods that the field would be ex- 
 hausted. In the end there would remain nothing but insoluble 
 silica and clay. To maintain the fertility of this soil in 
 mineral matters, the withdrawn ash -constituents must again 
 be supplied to the soil, or the waste matter lying on the 
 subsoil be removed. In this operation nature helps us by 
 yearly washing away the soil, in proportion to its greater 
 or less inclined position. Finally, with respect to the re- 
 placement of mineral matter in the soil, even rain, and 
 wind also, assist in supplying them. 
 
 " Thus, the restoration required, after a shorter or longer 
 time, of the mineral matters removed by crops, in such a 
 soil as we have supposed above, may take place only after 
 thousands of years ; in a soil with 1 per cent, of mineral 
 matters, after hundreds of years; and with j\ per cent., 
 after tens of years. 
 
 " The transported soil comports itself in a similar manner 
 to the untransported ; the rocks lying under it will likewise 
 undergo decomposition, &c., &c." 
 
 Our teacher of practical agriculture concludes his argu- 
 ment with these words : " The two axioms, viz., 
 
 1st, " The increase of the fertility of a field by fal- 
 low and mechanical operations, and the removal of 
 the mineral substances in the crops without replacing 
 them, are followed, after a longer or shorter period, by 
 continued sterility;" and, 
 
 2ndly, ''If the soil is to preserve permanently its 
 
 fertility, the mineral matters withdrawn from it must, 
 
 after a shorter or longer period, be replaced ; that is, 
 
 the composition of the soil must be again restored," 
 
 these two points apply, therefore, in our time, only to soils of 
 
 the very worst description, which required fronn the very com- 
 
 mencement a supply of these substances.'''' (W. S. 34.) 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 125 
 
 The above argument of one of our best teachers of prac- 
 tical agriculture, which professes to harmonise with his 
 agricultural experience, might well awake, in the minds of 
 many of our reflecting agriculturists, just doubts as to the 
 truth of the prevailing system of agricultural teaching. 
 
 Sound common sense demands, in proof of the proposi- 
 tion, that only the very ivorst kinds of soil require for the pro- 
 duction of further crops ^ the restoration of the withdrawn 
 mineral matters — that numerous instances should be adduced 
 from common agricultural experience that a fertile soil, in 
 order to continue productive, stands actually in no need of 
 this supply of these matters ; that for ten, twenty, or a 
 hundred years, it has annually yielded crops without any 
 replacement whatever of the withdrawn minerals ! 
 
 This proof, the only one which the writer from his point 
 of view could adduce for refuting the results of the chemical 
 analysis of soils, he still owes us, as well as the proper defi- 
 nition of his notion of a "fruitful field." It is evident, 
 that if the term "fruitful field" includes only those fields 
 which exist as exceptional cases in Hungary, in many parts 
 of Eussia, in low lands and valleys, and which are used as 
 meadows, and appear to be inexhaustible because they are 
 not yet exhausted, then the soil of ninety-nine oat of every 
 hundred fields that are called fertile in Bavaria, Prussia, 
 and Saxony, belongs to the worst kinds — a view, which no 
 one can support. 
 
 Our teacher of practical agriculture does not pay any 
 attention to these actual facts, but brings forward his proofs 
 in his own peculiar way. Without telling us what he 
 understands by rocks, soil, and subsoil, and what kinds of 
 rock, soil, and subsoil he means, he proceeds to apply these 
 terms as if all soils, rocks, and subsoils were identical ; and 
 leads us to believe that all soils, after their exhaustion by 
 crops, leave, as a residue, quartz and clay. Such an asser- 
 
126 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 tion, however, he would not seriously make, for in that 
 case a great part of Wurtemberg would be w ithout any 
 soil. 
 
 To come to an agreement in a discussion, people must 
 understand each other ; for if the one individual means by 
 a word, sometimes one thing, and sometimes another, it fol- 
 lows that the other cannot understand him ; for, in order 
 to understand, we must have distinct ideas. A scientific 
 definition is nothing but an ordinary one, only definite and 
 unchangeable in its meaning. 
 
 If an agriculturist speaks of his cattle which give him 
 milk and manure, his neighbour agriculturist understands 
 that he means his " cows." The production of milk and 
 manure does not, however, constitute the scientific defini- 
 tion of a "cow," for it does not exclude the idea which 
 might be entertained by a third person that all animals 
 which produce milk and manure are cows, or that a cow 
 which gives only manure and no milk is not a cow. 
 
 The same holds good in chemistry with the notion con- 
 veyed by the word soil^ and also with regard to what is 
 called experience; the word experience in an unscientific 
 sense always recals to mind the man who was seized with 
 sneezing when it thundered, and who always went out 
 with his umbrella in the most beautiful weather, if he had 
 happened to sneeze in the morning, because, according to his 
 experience^ it was sure to be a thunder storm. 
 
 In the argument of our teacher of agriculture, there is, 
 in fact, " no soil " — that is, nothing which an agriculturist 
 from experience knows as such; but it cannot be denied 
 that the argument takes a wide range and view of things. 
 
 The diminution of volume of the soil by the removal of 
 mineral substances is evident ; amounting yearly, if my 
 calculation does not mislead me, in the three-crop rotation 
 to the 4V P^^t ^^ ^^® thickness of a spider's thread. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 127 
 
 Equally clear and intelligible is the way in whicli nature 
 is made to help plants, when the surface soil is exhausted, 
 to obtain their nourishment from the sub-soil. The soil is 
 in this respect made to comport itself to plants somewhat 
 like a mixture of /^ of quartz and j\ of peas to a brood 
 of fowls. When these birds have picked the peas from 
 the soil, then comes the cock, like nature, afterwards, and 
 scratches and scrapes away the useless matters. The saga- 
 city of our teacher will of course also explain what becomes 
 of those four million kilogrammes of waste matter which 
 are yearly washed away in this manner from 1829 
 hectares ; as well as show that the loss of mineral matters 
 is of no importance to those neighbouring fields from which 
 the wind and rain have carried them to our own. 
 
 The experienced teacher of practical agriculture, in order 
 to refute a deduction of exact science which he holds to be 
 false, invents a case which does not exist in nature, and is 
 simply impossible, or at least unknown ; and the conclu- 
 sion to which he had previously carefully prepared his pre- 
 mises to lead, he applies to actual cases. He imagines a 
 fertile field extremely rich in the ash-constituents of plants, 
 and supposes it to gain from below, in the most dexterous 
 manner, what is taken from the surface ; and having in 
 this way made it inexhaustible, he then draws the con- 
 clusion that all fields which are fertile, must comport them- 
 selves exactly like this imaginary field. It follows, then, 
 as a matter of course, that the worst soils, under which can 
 be understood only those which are absolutely sterile, must 
 have required a supply of ash-constituents from the very 
 beginning; for it is impossible to assume that, in the 
 absence of all mineral food, which is taken for granted to 
 be the case, they could have produced crops without these 
 ash-constituents. It is therefore evident that if all fertile 
 soils are inexhaustible in mineral matters, it is only the 
 
128 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 unproductive which require a supply of these substances 
 in order to become productive, and a renewal of the wasted 
 portion in order to remain fertile. 
 
 If an ignorant peasant, who has for thirty years seen 
 crops follow the ploughing and sowing of his land, who 
 knows that his father and grandfather had also reaped for 
 thirty years from the same land after ploughing and sow- 
 ing, believes himself entitled from these facts to conclude 
 that this same land will still yield crops for thirty, sixty, a 
 hundred years, or for an indefinite period, we must hold 
 him excused on account of his ignorance. But when this 
 peasant acknowledges that his grandfather, father, and he 
 himself, have been obliged to manure this land each year, 
 and then asserts that his field has never received ash- 
 constituents in the manure, or that the ash -constituents it 
 received have produced no effect upon the crops, and that 
 their supply has consequently been of no advantage, we 
 turn from him with pity. 
 
 If the peasant had been capable of making a correct 
 observation, he would probably have perceived that his 
 manure heap constantly diminished in activity, and that 
 his grandfather with very little manure obtained much 
 larger corn crops than he now does with all his manure ; 
 he would further have observed that he has now been 
 obliged to include in his rotation plants which were not 
 required by his grandfather, in order to maintain the pro- 
 ductiveness of his fields for corn crops. 
 
 We have believed that the object the agriculturist had in 
 view was the production of grain and flesh, and that the 
 thoughts of the guides and teachers of practical hus- 
 bandry had been directed to ascertain the best means of 
 maintaining the grain and pasture fields in a uniform 
 condition of fertility. We are now taught better by the 
 writings of our modern teachers of agriculture : the pro- 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 129 
 
 duction of flesh and grain is subordinate to that of fcrm- 
 yard manure. 
 
 For cereals, the soil, they tell us, is always fertile if there 
 be only enough of manure. "Above all things let us have 
 fodder enough ; the cereals will then follow of themselves." 
 " Science does not teach agriculturists much when she tries 
 to teach them to force nature," " when she tries to make 
 them do without farm-yard manure." (W. S., 127.) "From 
 the necessity for the rotation of crops agriculture does not 
 wish to be emancipated, for farmers could even now free 
 themselves partly from it if they could only manure more 
 largely." (W. S., 129.) "Most agriculturists would un- 
 doubtedly much rather never cultivate anything but wheat 
 and rapes ; but this would never do, for the soil must have 
 its farm-yard manure, and without a proper rotation farm- 
 yard manure cannot be made." (W. S., 129.) " Farm-yard 
 manure may be termed the raw material, which agricul- 
 tural industry is to convert into marketable articles." (W. 
 S., 124.) " A rich soil is consequently one which produces 
 much manure, and a poor soil one which produces little. 
 Hence, therefore, the division of plants into manure-econo- 
 raising^ manure-exhausting^ and manure-enriching plants. 
 Now, as clover and lucerne are the real manure-producing 
 plants, and manure is the soul of agriculture, everything 
 depends upon them." 
 
 Our practical teachers have reduced, as we see, the most 
 difficult of all trades, which manufactures its products with 
 the most complicated of all machines — organised beings — 
 and the pursuit of which is dependent on influences over 
 which human power has no control, to a most simple fun- 
 damental principle, intelligible to the most stupid peasant- 
 boy, viz., \kiQ j^roduction of manure hy fodder plants. 
 
 To what results then has this excellent teaching, this out- 
 cry after manure, led? Clearly and distinctly mav the 
 
 6* 
 
130 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 present condition of our fields be recognised by tbe follow- 
 ing entreaty and appeal to our sympathy and compassion : 
 
 " Were science only to give us the means to enable us to cul- 
 tivate these 'plants {clover^ lucerne^ esparsette) upon the same 
 ground with uniform su€cess^ more frequently than is the case 
 ivith our present system^ then indeed would the philosopher'' s 
 stone he found for agriculture; for as to the conversion of these 
 plants into the forms adapted to the wants of man, we would 
 look to thaty (W. S., 127.) 
 
 This, then, is the result of the doctrine of these wise, 
 clear-sighted, and skilful men, who assert that fertile soils 
 are inexhaustible in the mineral food of plants. 
 
 To procure farm-yard manure, science is good enough ; 
 they wish to learn nothing from it, but only to obtain a 
 small piece of the philosopher's stone. Then these expe- 
 rienced individuals, who are crammed full of so much in- 
 formation in chemistry, geology, botany, &c., will procure 
 us flesh and bread in abundance : this every simple peasant 
 can do if we only give him manure. Hence, little " Japhet 
 in search of his Father," the poor child called " Mineral 
 Theory," was so ill-used and ridiculed, because he was of 
 opinion that the big purse would at last be emptied, by 
 always taking out money without putting any in. But who 
 could have thought twenty years ago, when there* was 
 plenty of manure, that it would ever occur to these obsti- 
 nate and wilful fodder plants to produce no more manure, 
 and no longer to spare and enrich the ground ? The soil is 
 naturally not the cause of this ; for they teach that it is 
 inexhaustible, and those who have still manure enough 
 believe that the source from which it is derived will always 
 flow. Truly, if this soil could cry out like a cow or a horse 
 which was tormented to give the maximum quantity of milk 
 or work with the smallest expenditure of fodder, the earth 
 would become to these aorriculturists more intolerable than 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 131 
 
 Dante's infernal regions. Hence, the advantageous prose* 
 cution of this system of modern agriculture is only possible 
 on large estates, for the spoliation of a small one would 
 soon come to an end. Instead of stealing the leather, if 
 they had bred the calf, it would have grown to an ox, and 
 then we should have been saved from the fear of going 
 barefooted at last. 
 
 But we need not yet despair : These wise, prudent, and 
 experienced men have found out the means of putting an 
 end to the deficiency of manure. These means, they tell 
 us, consist simply in making use of fresh, instead of rotted 
 farm-yard manure. If short-sighted, careless agriculturists, 
 who do yet not follow this plan, would only put it in practice, 
 many of the complaints about deficiency of manure would 
 cease. 
 
 " Notwithstanding the general outcry about want of manure, 
 and all the trouble taken to increase vegetation ; notwith- 
 standing the great cultivation of fodder plants to produce 
 farm-yard manure, it is allowed, nevertheless, when made, 
 to go to waste on the dung-hill. We may assume that in our 
 system of farming, the manure is carted out on an average 
 at most half-rotted. Before the manure arrives at this state, 
 it loses 25 per cent, of its mass, consisting chiefly oi precious 
 nitrogen ; I will here, however, estimate the loss to he equal in 
 value to what is left. If all agriculturists would employ 
 their manure as fresh as possible, so that at most no more 
 than 5 per cent, be lost, the increase of our cultivated plants 
 would amount to 20 per cent. ISTot only would this 20 per 
 cent, of the whole food employed in increasing the crop be 
 converted into vegetable matter, but by its means a further 
 quantity would also be drawn from the air and the soil," 
 (S. 131.) 
 
 *' An increase of the production of fodder is, howevei, 
 not required, so long as we do not wish to augment vegeta 
 
132 THEORETICAL AND PRACTICAL AGRICULTURE 
 
 tion Still more. Hence, the 20 per cent, of dung capital, 
 could be solely expended on the greater production of grain, 
 which would thus become so much larger, in comparison 
 with that of cattle, which remains the same. The supply 
 of grain would consequently be greater, its price more 
 moderate, and this would put itself more in equilibrium 
 with the production of cattle: producers and consumers 
 would be equally benefited. But greater advantages would 
 also be attained ; for, instead of expending upon the growth 
 of corn the 20 per cent, of manure saved, agriculturists 
 could also diminish their cultivation of fodder by 20 per 
 cent. The production of corn remaining the same, that of 
 cattle would be decreased 20 per cent., and hence the latter 
 would rise in price, whilst that of corn continues the same. 
 Were the 20 per cent, of manure saved, chiefly devoted to 
 the growth of corn, and to a smaller extent to that of fod- 
 der, producers and consumers would derive benefit from 
 this plan ; only on the part of the former it would be greater, 
 and at how small a cost — all by means of the 20 per cent, of 
 volatile matter which careless agricultmnsts lose hy the neglect of 
 the manure on their dunghills^ (S. 132.) 
 
 Had there been any doubt on the point, this proposition 
 would incontestably prove that the modern teacher of 
 practical agriculture puts not the slightest value on the 
 mineral constituents of stable-dung, but ascribes its entire 
 effect to the combustible matters it contains. With the 20 
 per cent, of these matters, which fresh farm-yard manure 
 loses by rotting, the practical man would make us believe 
 that 20 per cent, more corn, clover, or flesh could be 
 produced. 
 
 Because, straw manure had accidentally improved the 
 physical quality of his land, and consequently exerted a 
 more favourable action than short rotted manure, he teaches, 
 in opposition to thousands of well established facts, that 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 183 
 
 fresh manure must produce larger crops on all fields. He 
 would make us believe, that when we simply take away 
 the grain from our fields and plough in the straw, their fer- 
 tility in each succeeding year must receive an additional 
 increase equivalent in amount to what the straw loses, when 
 it has been used as litter, and converted into manure ! 
 
 Now, what is the cause of this great effect of fresh farm- 
 yard manure, and its advantage over that which is well 
 rotted? This, also, the man of practice tells us: ^^ In fresh 
 manure there is more nitrogen than in old ; the latter^ on the 
 other hand^ contains more ash constituents.^'' (W. S. 101.) 
 Hence, fresh manure is more efficacious than old ! Chemi- 
 cal analysis, indeed, proves, that rotted farm-yard manure 
 contains more nitrogen than fresh^ but in such matters 
 practice must decide ; and since, according to its teaching, 
 the larger crops could only have been the result of the greater 
 supply of nitrogen^ it follows that chemical analysis must 
 be in error. 
 
 But, after all, the additional 20 per cent, of manure 
 which the land of our experienced teacher of practical 
 agriculture obtains, appears to him far from sufficient, 
 for he says : " Now, since straw and fodder, the materials 
 for manure, are expensive, and manure must be had at 
 almost any price, and the latter comes tolerably dear in 
 consequence of the low price of cattle produce, agricultu- 
 rists have naturally been seeking for a long time back for 
 a substitute for manure. Such a substitute has been lately 
 found in Guano." 
 
 Now^ what is guano, and in what way is its employment 
 advantageous to the agriculturist? 
 
 Guano consists of the residue of the excrement of fish, 
 that is, flesh eating birds, and contains essentially the ash 
 constituents of the flesh of fish, together with a certain 
 quantity of ammonia salts. 
 
134 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 Comparison shows that the better sorts of guano contain 
 the ash constituents of grain, together with a certain quan- 
 tity of phosphate of lime, which forms an essential element 
 of the ash of our meadow and pasture plants. The effect 
 of guano on our corn fields is therefore palpable. We 
 have for hundreds of years removed from them, by the 
 cultivation of corn, the ash constituents of grain, and by 
 rearing cattle, we have also taken away a large quantity 
 of phosphate of lime (in their bones) without replacing any 
 of these matters ; we have, however, left them the condi- 
 tions for producing straw. 
 
 The increase of the produce of grain, by manuring with 
 guano, is the natural consequence of the restoration of the 
 elements of grain, which we have been at so much pains to 
 drag from our fields. The astonishment of the corn pro- 
 ducer at the powerful effect of guano, after all, arises from 
 the fact that he sees a few handfuls of this substance act- 
 ing more efficaciously than a cart-load of stable-dung ; and 
 because in looking at the smallness of the quantity of 
 the guano, and comparing it with the large increase of grain, 
 his ideas about manure are completely confounded. 
 
 To our experienced teacher of practical agriculture, 
 guano is, as a matter of course, only a means ybr producing 
 manure. Guano, in an agricultural sense, is a "supple- 
 mental manure," which we ought to use so long as the 
 supply lasts, for the purpose of increasing our dung capital. 
 (W.S. 137.) 
 
 That the effect of guano depends on the volatile and 
 combustible materials it contains, caijnot, of course, admit 
 of a question ; let us hear what would be the result of its 
 employment. 
 
 " The general use of guano can only be attended with a 
 result similar to that which would take place if the 20 
 per cent, of manure hitherto lost from the dunghills were 
 
THEOKETICAL AND PRACTICAL AGRICULTURE. 135 
 
 in future to be made use of." " Those agriculturists who 
 still allow their manure to rot, hence clearly act foolishly 
 in buying guano before they derive the fullest advantage 
 from their own manure." (W. S. 136.) No value what- 
 ever is put on the ash constituents of the guano. 
 
 The ideas of our teacher of practical agriculture of the 
 comportment of a soil under cultivation are not less 
 peculiar. 
 
 '''' Notwithstanding that plants are yearly reaped an equal 
 quantity can, on an average, be continuously removed every 
 year from the soil (for example, from an unmanured mea- 
 dow). This is the natural production of tlte soil. The soil 
 remains, and continues to remain at a fixed agricultural point 
 of production. (S. 103.) 
 
 " K during a period of one or more years the plants 
 which grow upon a soil die, and decay, an accumulation 
 of decaying and decomposing products will thus be gradu- 
 ally formed in it. There is thus furnished a further source 
 of both kinds of food, and the development of plants is con- 
 sequently promoted." (S. lOi.) 
 
 " By further new and increased crops more ash constitu- 
 ents than formerly, as well as products of decay, will be 
 removed from the soil." 
 
 " After a series of years, and a corresponding number 
 of crops, the ground sinks again to its original degree of 
 fertility — its fixed point of production. It has again at- 
 tained its original composition, and as nothing else has been 
 changed, this alteration of the soil must be the probable cause 
 ofit& increased and again diminished fertility. ''^ 
 
 " Stable-manure consists of decaying vegetable and ani- 
 mal matter, which also contains a certain quantity of ash 
 constituents, hence the development of plants can be as 
 well promoted by stable-mannre as by plants which decay 
 upon the fields themselves.''^ 
 
186 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 From these propositions which are given as agricultural 
 principles, it would follow that our cultivated fields com- 
 port themselves like unmanured meadows. Whether we 
 cultivate grain, turnips, or clover, on one and the same 
 field, we may fairly expect continuously, and without any 
 application of manure, an average yearly crop of the same 
 amount. This would be the natural production, or the 
 agricultural fixed point of the soil ! 
 
 If we leave meadow plants, corn, and clover, to die and 
 decay on the field, manure accumulates in the soil and ren- 
 ders it more fertile. We obtain larger crops, and withdraw 
 hy these means more ash constitue7its than before^ in consequence 
 of which the ground becomes poorer. 
 
 Having followed this course for some years, the ground, 
 robbed of its ash constituents, sinks back to its fixed point 
 of production. It has again attained its original composi- 
 tion (that is, it contains no more combustible matters than at 
 firsi\ and since nothing further has been changed (as everything 
 depends upon this), then this alteration of the soil — the dimi- 
 nution and increase of combustible matters in if — must be the 
 probable cause of its increased and again diminished fer- 
 tility. 
 
 The views cited above are those of a single man, but 
 with few exceptions belong to the whole class of practical 
 agriculturists. What the author teaches is not an invention 
 of his own, but he retails what he has learned. I have 
 reviewed these doctrines, not for the purpose of exercising 
 indiscriminate criticism, but because, without holding up to 
 view the opinions of practical men, my own peculiar doc- 
 trines might appear to many in the present day incompre- 
 hensible, and perhaps, at no distant date, vain and object- 
 
 I need not add one word more ; the passages just cited 
 give the key to the conflict which has been raised about 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 137 
 
 the recognition and application of scientific principles in 
 practice ; that the latter do not enter into the circle of ideas 
 of practical agriculturists will now be easily understood. 
 
 Many agriculturists are of opinion that in this contest it 
 is a question of words, not of principles, and that an 
 understanding is possible. They think that if they allowed 
 the action of mineral substances, then, injustice, the other 
 party will acknowledge that of combustible substances, and 
 thus the conflict would come to a happy termination. K 
 the contest for the recognition of scientific principles had 
 in fact no higher object than the admission into broth of 
 onions previously forbidden, or the compromise that eggs 
 may be opened at both ends, then they are right. 
 
 They are right so long as they entertain the opinion that 
 the best master brewer of the best Bavarian beer is the fit- 
 test man for a chair of brewing.* I, for my part, do not 
 believe that such a man should be recommended as the 
 proper person for imparting the scientific principles of 
 brewing, even though he had for twenty years conducted 
 the most extensive business of this kind with skill and 
 profit. 
 
 * This sentence refers to the arrangement of many German agricultural 
 institutions. They are in general endowed with a considerable extent of 
 land, which is managed like other government lands. The produce of the 
 soil finds its way into the public coffers. The school and the land are united 
 with each other in the person of the Director, to whom is intrusted the cul- 
 tivation of the ground and the superintendence of the instruction ; in the 
 net proceeds of the farm he has commonly a share. There are men who are 
 endowed with capabilities for both offices, but it usually happens that a good 
 practical man is not the best instructor, and the latter is not generally an 
 individual who sets much value on obtaining great profits fi-om the land. 
 
LETTEK X. 
 
 The empirical agriculturist is a trader — The duties of the empirical and 
 rational agriculturist — Views of Albrecht Block — Rotation of crops not un- 
 important ; an underground crop is followed by a better cereal — Cropping 
 of land without manure, and the removal of produce, cause exhaustion — 
 The spoliation system of agriculture — Exhaustion of the lands in North 
 America by this system — Exhaustion of the Minas Geraes fields — High 
 farming is a more subtle system of spoliation of the soil — Mutual relation 
 of clover, turnip, and corn crops ; and the results of removing from the 
 lands the mineral constituents of these crops respectively — The German 
 system of farming before the Thirty Years' War — The German three-field 
 system of rotation — Introduction of clover cultivation into Germany — 
 Opposition to its introduction — False teaching in connection with the value 
 of manures. 
 
 The empirical agriculturist is a trader who produces 
 meat and corn ; without troubling his mind about collateral 
 matters, he simply seeks to gain from his fields the largest 
 possible crops, and he holds that system of cultivation as 
 the best which will yield him the richest harvest in the 
 cheapest way, and in the shortest time. And why should 
 he not? The same system of husbandry which he pursues 
 has been followed for centuries before his time, and he sim- 
 ply practises the lessons taught him by those who preceded 
 him in the farming of his land. As they never inquired 
 what might ultimately become of the land, and what effect 
 their system of cultivation might have upon it — why should 
 he trouble his mind about it ? If he can succeed in making 
 a living out of his farm, clearing his rent, or the interest 
 on his capital, and acquiring some property besides, this 
 alone is proof positive of the soundness of the systenL 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 189 
 
 When lie happens to remark a falling off in his wieat, 
 clover, turnip, or potato-crops, he tries whether growing 
 some other varieties on his fields will answer better, and 
 attributes the diminished fertility of the soil to any and 
 every event that may have occurred since he first remarked 
 the decrease. Thus he will complain that his fields no 
 longer yield the rich crops of former years, ever since the 
 adjoining wood has been cleared ; or ever since the railway 
 was made ; or the chemical manufactory established in the 
 neighbourhood ; or he will attribute the falling off to the 
 injurious influence of the numerous thunderstorms in the 
 preceding year ; or to any other imaginable or imaginary 
 cause — except always to himself and his system; the idea that 
 the fault might possibly lie with him or his system can find no 
 'place in his mind ; for, has he not pursued the same system 
 for years with the very best results; his dungheap is as 
 large as ever, and the land does not look changed in the 
 least ? 
 
 As a trader he is in the position of a shoemaker who 
 must not devote his attention to investigations into the 
 origin of sole and other varieties of leather, the process of 
 tanning, and the properties which constitute the good qua- 
 lity of the article, and who, were he to do so, would most 
 likely supply the public with boots and shoes, neither cheap 
 nor overwell made. The true shoemaker who thoroughly 
 understands his craft, does not trouble his mind about such 
 matters ; he leaves to others, whose special business it is, 
 the task of studying them ; if he happens to be a man of 
 some education, he studies the anatomy of the foot, and 
 makes shoes that shall delight the female eye, and boots 
 that shall not distort the shape of the foot, nor pro- 
 duce corns. Such a pearl of a shoemaker would never 
 dream of disputing with the man of science about leather, 
 pitch, and thread, as he would have no time for such dis- 
 
1-AO THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 cussions ; lie would, on the contrary, be grateful to the che- 
 mist for teaching him how and by what marks or signs to 
 know and select the sorts of leather for soles and uppers 
 best suited for the purposes for which they are severally 
 intended. 
 
 The scientific farmer and teacher of husbandry has a 
 higher task assigned him. It is for him to rise above the 
 mere routine teachings of empiric observations; to guide 
 and keep the practice of farming in the right path ; to sub- 
 ject to a rigorous and searching investigation the methods 
 of husbandry adopted and pursued by the empirical farmer, 
 in order to point out to him the why and wherefore, and 
 to lead him to a proper sense and rational appreciation 
 of his doings, and their results and consequences. The 
 rational agriculturist has to inquire whether his system ac- 
 cords with established truths and natural laws, or is in 
 opposition to them ; and above all, he must never lose 
 sight of the one great principle, that the aim of true prac- 
 tical husbandry must be directed, not merely to the pre- 
 sent production of the largest crops, but to the securing of 
 a constant return of such crops. 
 
 K the teacher of husbandry, instead of assisting and sup- 
 plementing in this way the practice of agriculture, indulges 
 in views that are simply calculated to vindicate the farmer 
 in his empirical proceedings; — if, whilst clearly seeing that 
 this empirical system of husbandry is opposed to established 
 natural laws, he draws therefrom the conclusion that these 
 natural laws may possibly not apply to practical farming, 
 and that agriculture accordingly may not be subject to 
 natural laws ; — if he asserts that the practice of husbandry 
 and the science of agriculture may be treated as separate 
 and distinct questions, and that a thing may possibly be 
 true in science that is false in practice^ — if such are the doc- 
 trines propounded by him, he stands as an agriculturist far 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 141 
 
 below the practical farmer, who fails to derive instruction 
 from these lessons, simply because he finds in them nothing 
 but a reflex of his own doings in the cultivation of his land, 
 garnished with misconceptions and false views. 
 
 A simple comprehensive natural law governs the greater 
 or less abundance, and the longer or shorter succession and 
 continuance of the crops that can be grown on a field. 
 The greater or less abundance of the yield of a field de- 
 pends upon the aggregate sum of the conditions of fertility 
 therein existing ; the longer or shorter continuance and suc- 
 cession of the crops that may be grown thereon, depend 
 ■upon the unaltered condition of this aggregate sum. 
 
 A practical agriculturist, Albrecht Block, is reported to 
 have said: "J. farmer can afford to sell and permanently 
 alienate only that portion of the produce of his farm which 
 has been supplied by the atmosphere — a field from which no- 
 ting is abstracted can only increase^ not decrease in productive 
 powery If we express the same idea in another form, viz., 
 ^'' A farmer m.ay sell and permanently alienate all that portion 
 of the produce of his farm which has been supplied by the 
 atmosphere — a field from which something is permanently 
 taken away, cannot possibly increase or even continue equal in 
 productive power,'''' the axiom thus enunciated is simply a 
 natural law. In this opinion of this truly experienced man, 
 to whom future agriculture will surely raise a monument, 
 is at once expressed the whole foundation and groundwork 
 of rational farming, and all the knowledge that the science 
 of nature can teach the practical farmer. 
 
 Every act of the farmer which violates the laws of na- 
 ture, must justly be branded as an act of spoliation. 
 
 If a farmer grows in three several fields alternately pota- 
 toes, corn, and vetches or clover, or on one and the same 
 field successively potatoes, corn, and vetches, and sells the 
 produce obtained — the corn, the potatoes, and the vetches, 
 
142 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 and continues to act in this manner for many years^ without 
 manuring his land, the humblest peasant will predict the 
 inevitable end of such a system ; he will tell him that a 
 continuance of this kind of farming is impossible for any 
 length of time. Whatever grass, corn, tuber, or other crop 
 may be selected, and in whatsoever rotation, — the field will 
 ultimately be brought to a state of exhaustion by it ; the 
 corn will only yield an amount equal to the original seed, 
 the potatoes will no longer produce tubers, and the vetches 
 or the clover will die away after barely appearing above 
 ground. 
 
 These facts undeniably demonstrate that there exists no 
 plant that could possibly be said to husband the resources of 
 the soil, and a fortiori^ none that can possibly be had to 
 enrich it. 
 
 Innumerable facts have taught the practical farmer, that, 
 in many cases, the successful cultivation of an after-crop on 
 a field depends upon the nature of the preceding crop, and 
 that it is by no means a matter of indijfference in what suc- 
 cession or rotation he grows his crops. The previous cul- 
 tivation of some underground crop, or some plant with 
 extensive root ramifications, will tend to make the soil 
 more favourable for the subsequent growth of a cereal. 
 The latter will in such cases thrive better, and it will do 
 so without the use (with the sparing application) of manure, 
 and will yield a more abundant crop. But as regards 
 succeeding harvests, there has been in reality no saving of 
 manure, nor has the field increased in the conditions of its 
 fertility. There has been no augmentation in the gross 
 amount of the elements of food in the soil, but simply an 
 increase of the available effective portion of these elements, 
 and an acceleration of the results in a given time. 
 
 The physical and chemical condition of the fields has 
 been improved, but the chemical store has been reduced ; 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 143 
 
 all plants^ without exception^ exhaust the soil, each of them in 
 its own way, of the conditions for their reproduction. 
 
 There are fields that will yield without manuring for six, 
 twelve, fifty, or a hundred years successively, crops of 
 cereals, potatoes, vetches, clover, or any other plants, and 
 the whole produce can be carried away from the land ; but 
 the inevitable result is at last the same, the soil loses its 
 fertility. 
 
 In the produce of his field, the farmer sells. in reality his 
 land ; he sells in his crops certain elements of the atmo- 
 sphere that are constantly being replaced from that inex- 
 haustible store, and certain constituents of the soil that are 
 his property, and which have served to form, out of the 
 atmospheric elements, the body of the- plant, of which they 
 themselves also constitute component parts. In altogether 
 alienating the crops of his fields, he deprives the land of 
 the conditions for their reproduction. A system of farm- 
 ing, based upon such principles, justly deserves to be 
 branded as a system of spoliation. Had all the constituents 
 of the soil, carried off from the field in the produce sold, 
 been, year after year, or rotation after rotation, completely 
 restored to the land, the latter would have preserved its 
 fertility, to the fullest extent ; the gain of the farmer would, 
 indeed, have been reduced by the re-purchase of the alien- 
 ated constituents of the soil, but it would thereby have 
 been rendered permanent. 
 
 The constituents of the soil are the farmer's capital ; the 
 elements of food supplied by the atmosphere, the interest 
 of this capital : by means of the former, he produces the 
 latter. In selling the produce of his farm, he alienates a 
 portion of his capital and the interest ; in returning to the 
 land the constituents of the soil removed in the crops, he 
 simply restores his capital to his field. 
 
 Every system of farming based on the spoliation of the 
 
144 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 land leads to poverty. The countrj in Europe which, in 
 its time, most abounded in gold and silver, was, neverthe- 
 less, the poorest. All the treasures of Mexico and Peru 
 brought to Spain by the richly laden silver fleets, melted 
 away in the hands of the nation, because the Spaniards had 
 forgotten, or no longer practised, the art of making the 
 money return to them, which they had put into circulation 
 in commerce to supply their wants ; because they did not 
 know how to produce articles of exchange required by 
 other nations, who were in possession of their money. 
 There is no other way of maintaining the wealth of a nation. 
 
 It is not the land in itself that constitutes the farmer's 
 wealth, but it is in the constituents of the soil, which serve 
 for the nutrition of .plants, that this wealth truly consists. 
 By means of these constituents alone, he is enabled to pro- 
 duce the conditions indispensable to man for the preserva- 
 tion of the temperature of his body, and of his ability to 
 work. Rational Agriculture^ in contradistinction to the 
 spoliation system of farming, is based upon the principle 
 of restitution ; by giving back to his fields the conditions of 
 their fertility, the farmer insures the permanence of the 
 latter. 
 
 The deplorable effects of the spoliation system of farming 
 are nowhere more strikingly evident than in America,'* where 
 the early colonists in Canada, in the State of New York, in 
 Pennsylvania, Virginia, Maryland, &c., found tracts of 
 land, which for many years, by simply ploughing and sow- 
 ing, yielded a succession of abundant wheat and tobacco 
 harvests ; no falling off in the weight or quality of the 
 crops, reminded the farmer of the necessity of restoring to 
 the land the constituents of the soil carried away in the 
 produce.* 
 
 * New York.— In the debate on the Bill passed by the Lower House of 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 145 
 
 We all know what lias become of these fields. In less 
 than two generations, though originally so teeming with 
 
 Congress, by which a grant of six million acres of Union land is made to the 
 several States, for the establishment and maintenance of agricultural and in- 
 dustrial schools, the mover of the Bill, Mr. Morrill, of Vermont, showed, in a 
 most excellent speech, by means of exact statistical returns, how urgently 
 these schools are required for the better education of our farmers, who at 
 present, it would appear, are guilty of the grossest Vandalism in the manage- 
 ment of their land. The speaker showed that we in America are far behind 
 Europe in agriculture in general, and more especially in the modern scientific 
 system of farming ; and that the sad results of this state of things are even 
 now becoming manifest to an alarming extent. The honourable gentleman 
 said, the general method of husbandry pursued in all parts of the Union was 
 so bad and imperfect, that it must necessarily year after year more and more 
 impoverish the soil ; and the incessant drain on the natural productive power 
 of the soil amounted simply to downright robbery, committed by individuals 
 at the expense of the national property. 
 
 The following table in some measure shows the falling off that has taken 
 place within a period of ten years in the annual yield of agricultural produce 
 in several of the Northern States. The number of bushels of wheat produced 
 was in 
 
 1840 1850 
 
 Connecticut 87,000 41,000 
 
 Massachusetts 15*7,923 31,211 
 
 Rhode Island 3,098 49 
 
 New Hampshire 422,124 185,658 
 
 Maine 848,166 269,259 
 
 Vermont 495,800 585,955 
 
 Sum total . 
 
 . 2,014,111 
 
 1,063,132 
 
 
 Potatoes. 
 
 Connecticut 
 
 . 3,414,238 
 
 2,689,805 
 
 Massachusetts .... 
 
 6,385,652 
 
 3,385,384 
 
 Rhode Island .... 
 
 911,973 
 
 651,029 
 
 New Hampshire 
 
 6,206,606 
 
 4,304,919 
 
 Maine 
 
 10,392,280 
 
 3,436,040 
 
 Vermont 
 
 8,896,751 
 
 4,951,014 
 
 Sum total . . . 35,207,500 19,418,19 
 
146 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 fertility, they were turned into deserts, and in many dis- 
 tricts brought to a state of such absolute exhaustion, that 
 
 In many Southern States this falling off in the produce of the soil is equally 
 significant. The number of bushels of wheat produced was in 
 
 Tennessee . 
 
 Kentucky . 
 Georgia 
 
 Alabama . 
 
 Sum total 
 
 1840 
 
 1850 
 
 4,569,692 
 
 1,616,386 
 
 4,803,162 
 
 2,142,822 
 
 1,801,830 
 
 1,088,534 
 
 838,052 
 
 294,044 
 
 12,012,736 
 
 6,141,186 
 
 These figures show pretty conclusively that in all parts of the Union the 
 land must have been deprived of some of its most essential elements, and that its 
 fertility is constantly on the decrease. In the State of New York there are 
 now 300,000 sheep fewer than thirty years ago. Within a period of five 
 years the decrease in the number of sheep in the State of New York 
 amounted actually to nearly 50 per cent, and in the number of horses, 
 cows, and swine to above 15 per cent. In 1845 the wheat crop in the State 
 of New York amounted to 13,391,770 bushels; it has since then fallen off 
 year after year, and last year it actually did not exceed 6,000,000 bushels. 
 
 The average produce of Indian corn was in 1844, 2475 per acre, in 1854 
 it was only 21-02. The average yield of wheat was in Virginia and North 
 Carolina, in the year 1850, no more than seven bushels per acre, and in Ala- 
 bama five bushels. "While the cotton crops in the new territories of Texas 
 and Arkansas yield annually an average produce of 700 to 750 lbs. per acre, 
 the old fields of South Carolina produce only half as much. The tobacco 
 crop of Virginia was 18 million lbs. less in 1850 than in 1840. No kind of 
 crop has proved so injurious to the fertility of the soil as that of tobacco, and 
 in many of the States whole tracts of land are now lying waste, that for a 
 century had been made to yield, year after year, crops of tobacco, maize, and 
 wheat. There can be no doubt but that three-fourths of the arable soil of 
 the Union are undergoing, to a greater or less degree, this exhaustive pro- 
 cess. Dr. Lee, of Georgia, estimates the decrease in the annual produce of 
 the soil of 100 million acres of land in the United States, at ten cents per 
 acre. This would give a total of 10,000,000 dollars, making the amount lost 
 equal to a capital of 166,666,666 dollars — a larger sum than all our federal 
 and states taxes together. 
 
 In other branches of husbandry also enormous losses are caused by the 
 want of proper information on many essential points — a want which can only 
 be remedied by the establishment of agricultural schools. One of the ablest 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 147 
 
 even now, after having lain fallow more tlian a hundred 
 years, they will not yield a remunerative crop of a cereal 
 plant. 
 
 As every agriculturist in Europe has a notion that his 
 system is an exception and better than that of others, and 
 that, judging from his own experience^ his fertile fields require 
 no restoration of mineral matters to keep them up to the 
 proper degree of productive power, so every early colonist 
 also believes at first that his land, for the crop which he 
 grows on it, forms an exception to other fields. He also 
 trusts to his experience to insure an infinite succession of 
 rich harvests ; but even ere his children are grown up, he 
 finds out his mistake. His farm passes into the hands of 
 another colonist, who continues to despoil the soil in the 
 same way as his predecessor, only with a larger expenditure 
 of capital and labour. When he, in his turn, perceives that 
 the plough will no longer sufiice to keep the yield up to the 
 former height, the land is then finally handed over to the 
 tender mercies of the German colonist, who has been taught 
 to look upon dung as the soul of agriculture, — a maxim of 
 specious wisdom, of which his predecessor knew nothing, 
 and the new owner then sets about despoihng the soil after 
 his own fashion.* 
 
 agriculturists in Massachusetts estimates the annual loss to the States, in 
 cattle of all kinds, and in the produce of the dairy, &c., at several millions. 
 There are about 447,014 horses in the State of New York, on which, from 
 the prevailing ignorance of the veterinary art, there is an annual loss of not 
 less than two million dollars. 
 
 These statistics could not, of course, fail to produce the impression intended, 
 and the House gladly entertained the motion to establish agricultural and 
 industrial schools. It would be a pity if the Senate should not be able to find 
 time before the approaching adjournment to discuss and adopt the measure. 
 — AUgemeine Zeitung, No. 175. Supplement of June 24, 1858. 
 
 * " Agriculture, in so far as I had occasion to inquire into the matter, is in 
 a most primitive and unsatisfactory state in the province of Minas Geraes. It 
 consists simply of a system of downright spoliation, disproportionately large 
 
148 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 The European system of cultivation, called high farming^ 
 is not that open system of robbery of the American farmer, 
 followed by the utter exhaustion of the soil ; but it is a more 
 refined species of spoliation, which at first glance does not 
 look like robbery. It is spoliation accompanied by self- 
 deception, veiled under a system of teaching, the very basis 
 of which is erroneous. 
 
 The simplest peasant has sense enough to see, and all 
 
 quantities of the mineral constituents being constantly taken off, without the 
 restoration of any portion whatever. Thus, for instance, they make a so-called 
 Roca^ i. e., the trees and underwood are cut down on a certain tract, and 
 towards the end of the dry season burnt on the spot ; three or four harvests 
 are then taken from the land so prepared, and it very often occurs that among 
 these there are two Indian-corn crops in immediate succession. After this 
 the field is allowed to lie fallow until it is again sufficiently covered with 
 brushwood, when the same process is repeated ; the interval varying between 
 three and twelve years, according to local conditions and to the wants of the 
 proprietor. It is quite evident, that the soil here has never had restored to it 
 the smallest portion of the mineral constituents removed by the crops. No 
 wonder, then, that there should be universal complaints in the province of the 
 constantly increasing sterihty of the Bocas. One of the more intelligent 
 planters of the province told me that, of all the plants grown there none 
 showed so large a falling off as the sugar cane, and that he at present reaped, 
 on the same Bocas, only a third of the produce obtained by his father 55 to 60 
 years ago ; and yet, he remarked, somewhat naively, he was much better off 
 with his small crop, than his father had been with the larger one, for the 
 latter (his father) had barely been able to realise a milreis for the cask of 
 Cachaza (brandy), whereas he himself had last year received 14 milreis for the 
 same. Now this man was perhaps right in his way ; but how will it fare 
 hereafter with his son, if he continues the same system, and the price of 
 Cachaza happen to fall again ? In the province of Bahia, the falling off in 
 the sugar-cane crops is so great, that about a twelve month since a number of 
 planters combined to send out a ship to bring from several distant ports new 
 sorts of sugar-cane. They attributed the falling off in the produce of their 
 plantations simply and solely to the degeneration of the cane, without reflect- 
 ing that by the incessant cultivation of the plant on a large scale, their land 
 had been most enormously drained of the conditions of its fertility." — J.J. von 
 Tschudi's Journey through the Province of Minos Geraes. — Allgemeine Zeitung, 
 No. 47, May 21, 1858. Supplement. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 149 
 
 agriculturists agree with him, that clover, turnips, hay, &c., 
 cannot be sold off from a farm, without most materially 
 damaging the cultivation of corn. Every one willingly 
 admits that the sale and exportation of clover, turnips, &c., 
 exercise a detrimental influence on the growing of corn. 
 " Above all, let us take care to have plenty of fodder, the 
 corn crop will then take care of itself" But that the exjpor- 
 tation of corn may possibly exercise an injurious influence on 
 the cultivation of clover or turnips, that it is above all 
 indispensable to restore to the soil the mineral constituents 
 of the corn^ to enable the clover or turnip crop in its turn to 
 " take care of itself," — in other words, that in order to grow 
 clover, turnips, &c., we must manure the land — this is a 
 notion utterly incomprehensible, nay absolutely impossible, 
 for most agriculturists. For, is not the clover grown for 
 the sake of the manure ? What advantage, then, would 
 there be if it were necessary to manure again to produce the 
 clover ? This clover the farmer expects to grow for nothing. 
 From this total misapprehension of the very foundation of 
 all true industry, spring all the errors and defects of the 
 prevailing system of cultivation. 
 
 The mutual relations existing in the order of nature 
 between the two classes of plants, are, however, as clear as 
 daylight. The mineral constituents of the clover, turnips, 
 &c., and of the corn, form the conditions for the production 
 of the clover, turnips, &c., and of the corn, and they are in 
 their elements quite identical. The clover, turnips, &c., 
 require for their growth a certain amount of phosphoric 
 acid, potash, lime, magnesia — so does the corn. The mineral 
 constituents contained in the clover are the same as those in 
 the corn, plus a certain excess of potash, lime, and sulphuric 
 acid. The clover draws these constituents from the soil ; 
 the cereal plant receives them — we may so represent it — 
 from the clover. In selling his clover, therefore, the farmer 
 
150 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 removes from his land the conditions for the production of 
 corn ; no mineral constituents are left for the corn. If, on 
 the other hand, he sells his corn, there will be no clover crop 
 in the following year ; for in his corn he has sold some of 
 the most essential conditions for the production of a clover 
 crop. 
 
 The peasant expresses in his own way the part which the 
 cultivation of clover and other fodder plants performs in 
 the economy of his land, when he tells us that he regards, 
 as a self-evident proposition, that a farmer must not sell 
 his stable manure ; that without manure a continued culti- 
 vation of his farm is impossible ; and that a farmer who 
 sells his clover and other fodder plants, does actually sell 
 his manure, and that there is no need of the wisdom of the 
 chemist to make him understand this. This is very true ; 
 for so far as that goes, the common sense of the simplest 
 peasant will guide him. But that a farmer, in selling his 
 corn, is still actually parting with his manure, would, how- 
 ever, appear to be beyond the comprehension of the great 
 majority of the most enlightened agriculturists. The dung 
 contains all the mineral constituents of the clover and 
 other fodder plants, and these consist simply of the mineral 
 constituents of the corn, plus a certain quantity of potash, 
 lime, and sulphuric acid. Now, as the whole dung-heap 
 consists of parts, it is quite evident that the farmer must 
 not sell any part thereof; and that, if it were possible to 
 devise a means of separating the mineral constituents of 
 the corn from the others, those very mineral constituents 
 so separated would have the very highest value for the 
 farmer, as they form the most essential condition for the 
 production of corn. Now, in the cultivation of corn this 
 separation is actually effected, for these mineral constitu- 
 ents of the manure are converted into constituents of corn. 
 In selling the corn produce of his fields the farmer parts, 
 
THEOKETICAL AND PRACTICAL AGRICULTURE. 151 
 
 therefore, with a portion, and, indeec, with the most effi- 
 cient portion of his manure. 
 
 Two dung-heaps of equal appearance, and seemingly 
 equal quality, may have a very dissimilar value for the 
 cultivation of corn ; if one of the heaps contain twice as 
 much mineral constituents of corn as the other, it has 
 double its value. By the exportation of the mineral con- 
 stituents of corn, which the latter had drawn from the 
 manure, the dung of the farm is made to suffer a progres- 
 sive diminution of its efficiency for future corn crops. 
 
 In whatever light, therefore, we may look upon the 
 exportation of corn, or any other produce of the fields, to 
 the farmer who omits to restore to the soil the mineral 
 constituents removed from it, the ultimate result will 
 always be exhaustion of his land. The continued expor- 
 tation of corn renders the soil unproductive for clover, or 
 deprives the dung of its efficacy. Dung, in itself, has an 
 agricultural value only in so far as it contains the conditions 
 necessary for the growth of the saleable produce ; the mere 
 size or extent of a dung-heap does not constitute its value. 
 
 The reader will now understand what a total want of all 
 knowledge there is in the precept, that dung is the raw 
 material to be worked and made into produce by agricultu- 
 ral industry ; and how essentially that axiom and opinion 
 have contributed to blind the eyes of agriculturists to the 
 clear perception of the sole and original source of all 
 agricultural production, and of their own prosperity — viz.^ 
 the soil. 
 
 If our farmers had to till the teeming virgin soil of 
 America, Australia, or New Zealand, a professor of agri- 
 culture, who would try to persuade them that " manure is 
 the soul of agriculture," would simply appear ridiculous in 
 their eyes, as their own experience would show them that 
 the fields yield rich harvests without manure. 
 
152 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 In our exhausted fields tlie roots of the cereal plants 
 find no longer, in the upper layers of the soil, a sufficiency 
 of food for a full crop ; the farmer, therefore, grows on 
 these fields clover, turnips, and other plants, which, with 
 their wide-spreading and deep roots, penetrate through the 
 soil in all directions, and by the great surface of their roots 
 render available, and assimilate to themselves, those con- 
 stituents of the soil which the culmiferous plant requires 
 for the formation of seed. 
 
 In the remains of the roots, stalks, leaves, and tubers of 
 these plants, which the farmer puts in the form of manure 
 on the upper layers of his soil, he returns to it in a concen- 
 trated form the deficient corn constituents required for one 
 or several full crops. These indispensable elements of 
 food, which were before scattered throughout the subsoil, 
 have by the green crops been collected from it and added 
 to the surface soil. In effecting this object, the clover and 
 fodder plants can no more be regarded in the light of 
 creating the conditions necessary for the larger corn crops, 
 than the rag-gatherer, who collects the materials for manu- 
 facturing paper, can be looked upon as the producer of 
 those rags. 
 
 The American farmer despoils his field without the least 
 attempt at method in the process? When it ceases to yield 
 him sufficiently abundant crops, he simply quits it, and 
 with his seeds and plants, betakes himself to a fresh field ; 
 for there is plenty of good land to be had in America ; 
 and it would not be worth his while to work the same field 
 to absolute exhaustion. But our modern system of " high 
 farming" is an organised system of spoliation — ^the last, 
 highest, and most finished degree of the art of wearing out 
 the soil. 
 
 Before the thirty years' war the population of Germany 
 was not smaller than at present. Every individual naturally 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 153 
 
 required at that time for breathing and working, the same 
 supply of oxygen and of the elements of muscular force as 
 people require at present for the same purpose. The agri- 
 culturist of that day pursuing the same spoliation system as 
 the American farmer of our day, produced the same supply 
 of carbonaceous and nitrogenous food as is grown at pre- 
 sent ; only he took m^ore time to do so. There were years of 
 scarcity, the effects of which were more severely felt then 
 than they are now, because they were not mitigated at that 
 time by a supply of the deficiency from America, Hungary, 
 or the great granary of South Eussia; but in ordinary 
 years the land produced plenty. One year. Winter corn 
 was grown ; the next year, Summer corn and turnips {Stop- 
 pelruhen) ; the third, the field was allowed to rest ; there 
 was no other rotation except with pulse. What is now- 
 a-days called stall-feeding, was entirely unknown. The 
 meadow supplied winter fodder for horses ; cattle and 
 sheep found their food on the commons or fallows, and in 
 the woods. The agricultural system of that period might 
 be likened to the system of the man who had an income of 
 one florin a day, and who let the florins of one week accu- 
 mulate in order to spend them in the next week. On 
 Sunday he found himself accordingly with seven florins in 
 his pocket, and could therefore now afford to spend on the 
 Monday following four florins ; on Tuesday, three florins ; 
 and on Wednesday, other three florins, and in this manner 
 was able to buy a number of things which he would have 
 been unable to procure with a daily expenditure of one 
 florin. 
 
 The system of letting the land lie fallow every third / 
 year did not make the soil more fertile, or add to the ele- ' 
 ments and conditions of its productiveness ; but it served ; 
 to render those elements and conditions more available 
 within a certain time. Except by conveying to it a supply \ 
 
 7* 
 
154 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 of fertilising material, it is quite impossil le to make a field 
 richer and permanently more productive. That the field 
 did yield a more abundant crop after having lain fallow 
 was owing simply to the fact that the soil still contained a 
 sufiicient store of effective mineral constituents, only not in 
 a state available or assimilable for the roots. The rest 
 enjoyed by the field during fallow afforded time for part 
 of their store to be made available as food, and in this way 
 a remunerative crop was obtained. The overplus of the 
 more abundant harvest which follows a period of fallow, is 
 not a real addition to the revenue yielded by the field, but 
 simply a saving from the preceding year, when the land 
 was at rest. By means of this system the soil is somewhat 
 more profitably despoiled of its resources, as the work of 
 spoliation proceeds more leisurely. Time, people argued, 
 costs no money, and fallow saves manure, an advantage 
 which was clear to all. This system prevailed till towards 
 the middle of last century. The peasantry, as a body, fell 
 into a state of poverty and wretchedness, and the production 
 of the fields continued decreasing. 
 
 In the seventeenth and the beginning of the eighteenth 
 century, the culture of the vine was still flourishing in 
 countless places in Germany ; fields upon fields were then 
 occupied by vineyards where the grape now no longer 
 grows; the large tithe-cellars alone, which still continue 
 to exist in many places, give evidence of the immense 
 extent of the vine culture in by-gone days. With the 
 vineyards the spoliation system of cultivation sooner pro- 
 duced its results; for vineyards produce no manure, and 
 as the corn growers found that the cultivation of their own 
 fields stood in the utmost need of all their manure, the 
 culture of the vine necessarily died out, like the flame of a 
 lamp for want of a supply of oil. 
 
 "The only winter-food the farmer had for his cattle, 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 155 
 
 besides bad and sour meadow-lierbage, consisted of white 
 turnips, carrots, cabbage and potatoes ; and even of these 
 there was no great store, because the fields had ceased to 
 produce when unmanured. This scanty food was, through- 
 out the whole winter, whilst it lasted, made still scantier by 
 steeping and boiling to eke it out, and when at last it came 
 to an end, the cattle had to starve on barley, oat and pease 
 straw. The milk, butter, and cheese yielded in return were 
 little in quantity and wretched in quality. The coming of 
 spring was anxiously awaited to get a few cuttings of the 
 young wheat shoots, and the cattle were sent to the com- 
 mon to feed on grass barely a couple of inches high, whence 
 the poor beasts returned at night just as famished as when 
 they had left the stable in the morning, looking like the 
 lean kine that Pharaoh saw in his dream." This is the 
 description given of the then state of agriculture in Ger- 
 many by John Christian Schubert, whom the Emperor, 
 Joseph n., created a Knight of the Holy Eoman Empire, 
 bestowing upon him the style and title of Ritter von 
 Kleefeld (Knight of Cloverfield), as a mark of imperial 
 appreciation of the eminent services rendered by him in the 
 introduction of the cultivation of clover into Grermany. 
 
 The new culture introduced by the worthy Knight was 
 hailed with acclamation all over the Empire. The peasants 
 who grew clover received silver "clover-dollars," to wear 
 round the neck. Stercutius^^ the God of Manuring of 
 Ancient Rome, whose worship had been abandoned for 
 2000 years, was replaced on his throne: in Agricultural 
 Educational Institutions altars were raised to him, at which 
 his priests even to this day continue to sacrifice. But the 
 God of the Dunghill proved capricious. He seemed to 
 
 * Stercutius, or Sterquilinus, according to some, one of the names of 
 Saturnus. (See Virgil's "Georgics," by Voss, page 74. 
 
156 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 make some fields the special objects of his bounty, only to 
 forsake them again after a time ; and now, after a hundred 
 years' sway, he has grown altogether stern and unkind. 
 He no longer bestows his former rich gifts even upon his 
 most assiduous worshipper, and from the very fields which he 
 once seemed most to favour, he now withholds the power of 
 producing the poorest crop of manuring plants. Therefore 
 do his priests urgently supplicate for a small piece of the 
 philosopher's stone to be offered as an oblation to the God 
 of Manure, thai he may relent, and make clover for manur- 
 ing grow for the future on fields on which that plant will 
 now no longer thrive. When at a later period the potato 
 and the application of marl and gypsum to the land came 
 to aid the beneficial efforts of the cultivation of clover, 
 people trusted there would now be an end for ever to all 
 want. The old spoliation system, first in its naked form, 
 and then altered by the introduction of fallow, now under- 
 went a further modification, based on the system of a well- 
 known highwayman on the borders of the Ehine. He 
 stripped the rich of their dollars, bestowed at times a 
 penny on the poor, and for sport cut the buttons off their 
 breeches. 
 
 According to his creed the wealth of the rich had been 
 stolen from the poor, and it was but justice therefore to 
 make them disgorge it. 
 
 Our high farmer acts upon a similar principle. In his 
 corn crops he makes the (rich) clover disgorge, as it were 
 the dollars which it has extracted penny by penny from the 
 (poor) field ; and he fancies this system of robbery will last 
 for ever, as his instructors have taught him that his land 
 possesses the property of sweating penny pieces. 
 
 The consequence of this spoliation system upon the 
 principle of the noble robber are clear, patent, and obvious 
 to everybody; never has the want of manure been more 
 
THEORETICAL AND PRACTICAL AGRICULTUJIE. 157 
 
 severely felt than at present. All the ways and means 
 which so marvellously tended towards the end of last cen- 
 tury to increase the productiveness of the land, are at pre 
 sent resorted to in vain ; they fail to produce their former 
 effect. The application of gypsum to the soil now makes 
 the clover only more watery, without increasing the crop ; 
 land treated with marl is more unproductive than before. 
 Were it not for the manure which the trees of the forest 
 yield in many countries, the culture of the cereals would, 
 in many former fertile districts, long since have come to an 
 end, like that of the vine. The agriculturist in these parts 
 now despoils the woods, as he formerly despoiled his fields, 
 and he will continue this new system of depredation as 
 long as it will answer ! "If you will grow clover, and will 
 strictly follow my directions," said the good Schubert to the 
 peasants of his t;me, "you will have ample cause for 
 rejoicing and for praising the Lord out of the fulness of 
 your heart for his rich blessings. But bear in mind one 
 rule, which I charge you now once for all to follow ; never 
 grow clover at the expense of corn, but grow it only in 
 fallow, that it may cost you nothing — in other words, give 
 up the practice of letting a field lie fallow." At that time 
 there was no other system of husbandry known but the so- 
 called " Three-fields-system," or system of triennial rota- 
 tion. In twelve years cereals were grown eight times in a 
 field, and clover four times. Where are those glorious 
 days when the same field yielded in three years two crops 
 of corn and one of clover into the bargain ! Kow-a-days 
 high farming produces in twelve years only six corn crops. 
 In Mecklenburgh good land gives only four com crops in 
 nine years. The original area on which fodder plants 
 were cultivated, and which at the time proved amply suffi- 
 cient to collect and concentrate the food required for the 
 cereals, is therefore no longer large enough to keep up the 
 
158 THEOKETICAL AND PKACTICAL AGRICULTURE. 
 
 supply, and it has become necessary to extend it. The cul- 
 tivation of food for cattle takes up at present as great, and 
 even a greater breadth of land than the raising of food for 
 man ; and men's minds and ideas have become so perverted, 
 that this lamentable fact is actually looked upon in the 
 light of a great improvement ! 
 
 So long as those most interested in the matter, instead 
 of reflecting upon the conditions on which the successful 
 cultivation of all plants depends, and trying to discover 
 these conditions and to understand their application in 
 practice, seek to put agriculture into a healthy condition 
 by " manure," a thing so very indefinite, indefinable, and 
 variable in its nature, no real progress can be expected. 
 For my part, I am quite aware, that science will for a long 
 time to come have to preach to deaf ears. So long as agri- 
 culturists derive from the spoliation of their own lands 
 plentiful crops and a good income, there is no hope of the 
 advent of a more rational system of husbandry. The field 
 is to such men, simply a cow that gives them milk, but 
 which they would feed with its own flesh, taken from its 
 ribs ; and the folly of such a proceeding will strike them 
 only when the light shines through the hollow skeleton of 
 their victim. Man is naturally prone to spoliation, and 
 dreads nothing so much as to have to exert his mental 
 faculties in the acquisition of what he needs ; he is in 
 many respects like a child in whose eyes the school and 
 learning are the greatest of all troubles. ISTecessity is the 
 only compulsory agent that will ever make him move, and 
 this will come soon enough. 
 
 The dangers threatening the state and society from the 
 wanton sjDoliation of our woods, led to the devising of our 
 (German) present most admirable regulations for the 
 management of our woods and forests. If our for'gsts 
 were parcelled out into as many portions and divided 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 159 
 
 among as many foolish hands as our arable land, we should 
 long ago have been without wood. There is the most 
 imminent danger just now, that the rapidly progressing 
 destruction of the Quinine or Peruvian bark-tree will, at 
 no distant period, deprive society of one of the most inva- 
 luable medicinal agents ; and our only consolation is, that 
 when the last tree of the kind shall have fallen, the rational 
 culture of the plant will then begin which after a certain 
 number of years will again provide us with a permanent 
 supply of Bark.* 
 
 The expedients hit upon by certain writers on husbandry 
 to shut the eyes of agriculturists and their own, to the light 
 of science, and to make the comprehension of the laws of 
 the nutrition of plants inaccessible to the mind and under- 
 standing, are truly most remarkable ; and the history of 
 agriculture will surely preserve the memory of them. To 
 this day the farmer of the Wetterau justly regards the sale 
 of his manure, not only as a disadvantage, but as a positive 
 shame: it is an object of ambition with him to raise the 
 largest possible amount of it on his fields. He has been 
 taught that there is in manure a certain inconceivable and 
 
 * It is asserted that our high farmers " know the art of extracting from the 
 same piece of land more grain than could be got from it in the seventeenth 
 century." I doubt the correctness of this assertion, and think it quite within 
 the limits of possibility that accurate statistical researches might prove the 
 very reverse to be the case. Those who can look back a generation will 
 probably remember, as I do, that large tracts of land which now are culti- 
 vated and bear produce, lay formerly waste (an advantage for which we are 
 no doubt indebted to the rotation system). The question arises here wlie- 
 ther, admitting the production to be larger now than formerly, the increase 
 is not rather owing to the simple fact that the extent of producing surface is 
 now considerably greater than it was. A distinguished American Economist, 
 Carey, assures me, that accurate statistical inquiries instituted in 1850 by the 
 '' Times" Commissioner have shown that England at that time produced 
 actually 2,000,000 quarters of corn less than in 1774, according to Arihui 
 Young. I will not venture to guarantee this fact, which, if true, would cer- 
 tainly look very significant. 
 
160 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 indefinable something which is to be met with in manure 
 alone, and in no other matter ; — that ash and gypsum are 
 not food for plants, but serve, like the whip of the carter 
 to his lazy horse, to stimulate the activity of sluggish 
 plants. Even up to the present time, they look upon the 
 mineral constituents in guano and in bone earth, as not in 
 the slightest degree contributing to the nutrition of plants, 
 but simply as auxiliary stimulants applied to the soil for the 
 purpose of promoting the production of stable dung. 
 
 The worshippers of manure act in defence of their notions 
 in a somewhat similar way to the Birkenfeld peasantry of 
 last century, who grievously complained that government 
 wanted to compel them to cultivate a foreign weed (clover). 
 They told the officers in the plainest terms " to stick to 
 their last, and concern themselves about things they had 
 learned. As for husbandry, they (the peasants) were likely 
 to know much more about it than all the margraves and 
 overseers in the world." They did not wish to give the 
 matter a single trial, and when ultimately compelled to 
 sow the clover, they demanded, after a time, a magisterial 
 inspection of their fields, and showed " that not a leaf of 
 the clover had come up ; " and no wonder ; for it turned out 
 at last, that the peasants had boiled the seed before putting 
 it in the ground. In our day scientific principles are treated 
 somewhat in a similar manner ; the professors of modern 
 agriculture boil them in their pot, and it is then openly 
 shown that not a grain has come up. These gentlemen 
 will on no account consent to see farmers freed from the 
 compulsory rotation of crops ; this they must understand 
 much better than anybody does. But their own doctrine 
 is barren, because it has no roots. Whatever good precepts 
 their books contain, the agriculturist knows already, for 
 these teachers derived their information from him ; but 
 such precepts as originate with themselves, inspire the far- 
 
THEOKETICAL AND PKACTICAL AGRICULTURE. 161 
 
 mer with no confidence, lead to no profitable ideas, do not 
 increase his energies nor exalt his faculties. 
 
 If they would confine themselves to simply telling the 
 agriculturist what this or that farmer has at any time done 
 on this or that field ; — that land requires to be well ma- 
 nured; — that guano and bone-earth constitute excellent 
 manures, and that Chili-saltpetre, gypsum, and marl are 
 also not to be despised, — surely no one would blame them 
 for disseminating these truisms. But they have gone much 
 further, and in their blindness and shallowness have laid 
 the axe to the very root of agricultural prosperity — and 
 this can and must no longer be permitted. 
 
 They maintain and teach that in guano. Chili-saltpetre, 
 and bone-earth, nitrogen is the only common constituent 
 that is deserving of consideration, and that it is to this ele- 
 ment alone that increased productiveness is to be attri- 
 buted. 
 
 They teach and wish farmers to believe, that 10 to 12 
 pounds of the urine of cattle, which contains no phosphoric 
 acid, will produce the same effect as 1 pound of guano, 
 which is rich in phosphoric acid, — simply because both sub- 
 stances contain the same quantity of nitrogen. They teach 
 and maintain that the fertilising action of guano and of 
 farm-yard manure depends upon the same cause, viz., their 
 amount of nitrogen, and that guano must produce the same 
 effect as farm-yard manure. 
 
 All this they maintain without adducing a single fact in 
 support of their assertions, or having once sought to show, 
 by some unexceptionable instance, that the application of 
 nitrogen by itself can make an exhausted field yield for a 
 number of years the same crops of corn or other produce 
 that are actually got from it by the application of farm-yard 
 manure, guano, and bone-earth. That nitrogen could really 
 produce such an effect everybody at all acquainted with 
 
162 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 the elementary principles of the nutrition of plants must 
 know to be an actual impossibility. 
 
 But these teachers go even much beyond this. In No. 
 247 of the Swahian Mercury^ of the 15th October, 1856, 
 there is an article on the Chili-saltpetre and its use, written 
 by a Professor at one of the most renowned Agricultural 
 Academies of Germany, in which the reader is told that 
 ''a hundredweight of Chili-saltpetre will produce the same 
 effect as 75 to 80 cwts. of farm-yard manure, whilst a cwt. 
 of guano will only be equivalent to 60 or 70 cwts. of the 
 latter; — that a cwt. of Chili-saltpetre will produce about 
 three cwts. of grain ; that its action, however, is only per- 
 ceptible the first year; that its price is 12 florins (205.) per 
 cwt., and that, accordingly, the corresponding value of a 
 cwt. of farm-yard manure would be 9 krs. (3d)" 
 
 This announcement may be said to be the very culminat- 
 ing point of the theory of our teachers of modern agricul- 
 ture ; it is evidently intended to induce the well-to-do pea- 
 sant, and the small land-owner, who may be in want of 
 manure, to buy Chili-saltpetre — a salt which contains none 
 of the ash constituents of the cereals, but is composed sim- 
 ply of nitric acid and soda; one cwt. of which, we are 
 assured, will produce three cwts. of grain. Its effect, it is 
 true, lasts only one year, but it will, nevertheless, prove 
 equivalent to 75 or 80 cwts. of farm-yard manure, the bene- 
 ficial action of which on a field may still be observed after 
 seven or eight years. The simple comparing of Chili-saltpetre 
 to guano and farm-yard manure is, in itself, an offence against 
 common sense ; and the recommendation of that salt, at the 
 expense of guano and farm-yard manure, is an injury in- 
 flicted on the property of thousands by an unprincipled or 
 ignorant adviser. 
 
 A proceeding of the kind may be excusable in a com- 
 mercial traveller soliciting orders for a speculator in Chili- 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 163 
 
 saltpetre ; but if we find that such notions are disseminated 
 by teachers of agriculture and professors at agricultural 
 institutions ; if we see those teachers intent upon making 
 the farmer believe, by means of a spurious array of figures, 
 entirely inapplicable in the great majority of cases, that 
 nitrogen possesses for him twice the value of phosphoric 
 acid, five times that of potash, and twelve times that of 
 phosphate of lime — it is time for all sensible men to unite 
 and call these teachers to account. We may surely demand 
 of them what is only right and fair, viz., that they simply 
 prove the truth of their theories by a faithful statement of 
 accurately observed and properly guaranteed facts. 
 
 Although it has, in these last years, been most plainly 
 demonstrated to these men that their views and theories are 
 founded in error, this has not brought conviction to the 
 mind of a single individual. One after another has come 
 forward with the vain and impotent attempt — not to adduce 
 new and striking proofs in support of their doctrine — but 
 to suggest doubts against the true import and bearing of the 
 facts brought forward in refutation of their views. Not one 
 of them has ever even dreamt of appealing, in support of 
 the truth of his views, to his own numerous experiments 
 and chemical analyses on which those views are based; 
 because all of them know full well that their labour in this 
 line will not bear the test of a rigorous scientific examina- 
 tion. In their distress they now turn for help to the same 
 agriculturists whom they had, by these analyses, persuaded 
 that nitrogen was the only active agent in guano, bone- 
 earth, and rape-dust, and appeal to them to bear witness 
 that they have given them good advice, and that their 
 theories have been borne out by practical experience ; that 
 a pound of ammonia has a practical value of twelve groschen, 
 a pound of bone-earth of only one groschen. But the prac- 
 tical man, in truth, knows nothing of the action of ammo- 
 
164 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 nia or of nitric acid, or, at all events, nothing but from 
 hearsay ; for he has not been taught by the agricultural 
 chemist that guano, bone-earth, and rape-dust are excellent 
 manures, but the latter has, on the contrary, learned this 
 fact from him, and has simply thrown in his own little 
 hocus-pocus, that a few stray beams of the sunshine of their 
 beneficial action might be reflected on him. 
 
LETTER XL 
 
 Ammonia is an element of food indispensable to Plants — Comparison of the 
 action of Water and Ammonia — Ammonia is an element of food and a 
 Solvent of Mineral Matters in the Soil — Ammonia alone, or its Salts, useless 
 to Plants, without Mineral Food — Vast amount of Ammonia in arable Soils 
 — The " Nitrogen " theory of Manures — The error of attributing the chief 
 value of a Manure to its Nitrogen — The reason v^hy the quantity of Nitro- 
 gen in Guano and Excrements may be taken as a standard of their Agri- 
 cultural value — Proper mode of Comparing the relative effects of Guano, 
 Ground Bones, and Chili-saltpetre — The Loss of Fertilising matter in the 
 Flesh and Grain carried to large towns; the constant loss of Phosphates in 
 the Excrements of the inhabitants — The importation of Guano most 
 inadequate to replace this loss — Superiority of Human Excrement over 
 Guano as a Manure for Corn Fields — Tobacco, Potatoes, and Beet-root are 
 more exhausting to a soil than Wheat — Injurious influence of extensive 
 Cultivation of the Tine on the production of Com and Wheat — Effect of 
 the Subdivision of the Land. 
 
 As an element of food, ammonia is as indispensable to 
 plants as carbonic acid ; a brief consideration of the part 
 which water plays in the nutrition of plants will best enable 
 us to understand the fertilising action of ammonia in 
 manure. 
 
 Water subserves a double purpose in vegetation ; it sup- 
 plies to the plant in one of its constituents an indispensable 
 element, and serves besides to render mineral matter in the 
 soil fit for absorption by the roots. Though the soil be 
 ever so rich in the elements of food for plants, still the latter 
 will not grow in hot weather, if there be a deficiency of 
 moisture in the soil; for the moisture in the soil is the 
 channel through which mineral food has to reach the inte- 
 rior of plants. 
 
166 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 When there is a failure in the supply of mineral food, 
 the leaves absorb neither carbonic acid nor ammonia from 
 the air; and vegetation is brought to a stand-still, although 
 the air contains more moisture in hot days than in cold, — 
 this moisture being of no avail to the plant. With a defi- 
 ciency of water in the ground, sunny and warm days, 
 which under other circumstances would be the most fa- 
 vourable for growth, actually prove the most pernicious, 
 particularly for summer plants, which have not yet had 
 sufficient time to push their roots deep into soil where there 
 still exists a supply of water that might convey food to 
 them. In such cases barley grows barely a hand high and 
 shoots into ear, and potatoes produce no tubers. One good 
 shower at the right time changes this state of matters as if 
 by magic. If the farmer could bring down rain upon his 
 fields at the right time^ as the gardener can water his flower- 
 pots, all plants would give a maximum yield, pre-supposing 
 of course, that there is a sufficient available supply of food ; 
 for if there be a deficiency of the latter in the soil, a corres- 
 ponding diminution in the maximum yield must in conse- 
 
 I quence be expected. Plants therefore absorb carbon and 
 nitrogen in proportion as the water conveys to them more 
 
 , of the mineral constituents of the soil ; their growth is accele- 
 
 1 rated, and the weight of the crop increased. 
 
 It is exactly the same with ammonia. K we increase the 
 quantity of ammonia in the air or in the soil, the plant 
 finds at 2^ favourable juncture a larger supply of this element 
 of food than usual, and the consequence is, that a corres- 
 pondingly larger amount of the mineral elements of food is 
 rendered available. As the leaves of a plant can daily 
 come in contact with only a certain volume of air, they 
 can of course take up from it no more ammonia and car- 
 bonic acid than this volume of air contains ; the absorption 
 of these substances and the increase of the plant consequent 
 
THEOKETICAL AND PRACTICAL AGRICULTURE. 167 
 
 thereon require accordingly a given time. If a plant 
 every day absorb an equal amount of these elements of food, 
 it will receive of course twice as much in two days as in one. 
 
 If a plant on favourable days received twice or four 
 times the usual supply of mineral food, the surplus must 
 remain inactive until the leaves shall have taken up from 
 the air sufficient carbonic acid and ammonia to combine 
 with these mineral elements in the formation of constituent 
 parts of the frame of the plant. None of the elements of 
 food will act without the presence and co-operation of the 
 others. If, accordingly, we increase the amount of ammonia 
 in the soil, or in the air (of carbonic acid, there is generally 
 no deficiency), the development of the plant will, the other 
 conditions of its growth being equal, be considerably 
 quickened; in other words, the plant will grow in bulk 
 and substance much faster than under ordinary circum- 
 stances. Familiar illustrations of this may be seen every 
 day in hot-beds. Had the mineral elements of food not been 
 present in the plant and available for its nutrition^ the ammo- 
 nia would not have had the slightest effect on the increase 
 of the bulk of the plant. 
 
 It need then excite no wonder that the application of 
 guano to a field should so largely increase the yield of 
 corn ; for guano contains not only the mineral elements 
 which a soil must possess to produce corn, but also in the 
 ammonia an indispensable element of food, which serves to 
 quicken their action and to shorten the time required for 
 their assimilation. On many fields the ammonia in the 
 guano may, if the weather prove propitious, possibly effect 
 the assimilation of double the ordinary quantity of these 
 mineral constituents, and thus render the amount of pro- 
 duce yielded in one year equal to what would have been 
 otherwise obtained in two years by these mineral matters 
 alone. 
 
168 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 It is clear also that ammonia used by itself in a soil con- 
 taining a sufficient supply of tlie elements required for the 
 production of a corn crop, must exert a favourable action 
 on the increase of the produce. But as in the large crop 
 reaped, there is now removed from the field a greater pro- 
 portion of the conditions upon the presence of which the 
 efficacy of the ammonia depended, — if the application of 
 ammonia be continued, and no restitution be made to the 
 soil of the mineral elements removed, — then the yield must 
 necessarily diminish, in the years following, in the same 
 proportion as it was higher in the first and second years. 
 
 In one word — ammonia is a most useful manure when it 
 is accompanied by the mineral elements which render it 
 active, or when it finds in the soil those conditions which 
 are necessary to its efficacy ; it is absolutely of no value to 
 the farmer if he neglect to restore or supply these elements. 
 
 In a soil sufficiently rich in nitrogen, but poor in certain 
 mineral elements indispensable to the growth of many 
 plants, the application of ammonia, or of its salts, is at 
 any rate useless, and often absolutely injurious. In such 
 a soil, which simply is deficient in a proper supply of phos- 
 phoric acid, a dose of that substance, unaccompanied by 
 ammonia, will produce the same fertilising effect as guano, 
 only, probably, in a higher degree. The General Commit- 
 tee of the Agricultural Society of Bavaria, at Schleissheim, 
 caused a portion of one of the poorest worn-out fields in the 
 vicinity of Munich to be manured, by way of experiment, 
 with acid phosphate of lime (phosphorite) ; the result was, 
 a crop of summer wheat double in amount to that yielded 
 by an equal portion of the same field unmanured. Had 
 guano been the manure used in this case, the crop would 
 most indubitably have far exceeded that reaped from the 
 unmanured plot, and a supporter of the so-called nitrogen 
 theory would as unquestionably have ascribed the effect to 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 169 
 
 the ammonia contained in the guano, which could not pos- 
 sibly have had anything to do with it, in the foregoing 
 experiment. The same manure, viz., acid phosphate of 
 lime, has been applied with equal success elsewhere, with 
 out any co-operation of ammonia, and frequently larger 
 crops of grain have been obtained than from the use of 
 guano ; it is, therefore, quite evident, that for a field in that 
 condition ammonia is almost quite valueless. The expla- 
 nation also of this fact has been ascertained by chemical 
 examination: it has been found that most fields contain, 
 within a depth of from ten to twelve inches, a hundred, 
 five hundred, often even a thousand times more ammonia 
 in a similar form, than is present in rotten farm-yard 
 manure, in bones, or rape-dust ; it is, then, quite clear, that 
 where the soil happens to be deficient in even one of the 
 indispensable mineral elements of food, the existing great 
 store of ammonia will be of no avail in increasing the pro- 
 ductiveness of the land. 
 
 In the vicinity of Magdeburg, the residue left after the 
 distillation of beetroot-molasses, which contains the soluble 
 salts of the beetroot, (no salts of ammonia) has, of late, been 
 used as a manure, and I have been assured that fields 
 treated with it have yielded, several years in succession, 
 most abundant crops of rape, beet, &c. 
 
 For each field there exists some effective agent of this 
 kind ; but it will never be found, if we rest contented with 
 simply chanting the praises of ammonia. As we have seen, 
 in Letter II., the soil never contains free ammonia ; and in 
 the rotten farm-yard manure the greater proportion of the 
 liberated ammonia enters into chemical combination with 
 the humus-constituents of the dung — being taken up by 
 them directly from the liquid portion, which accounts for 
 the fact that the latter is comparatively so poor in that 
 ingredient. 
 
 8 
 
170 THEORETICAL AND PEACTICAL AGRICULTURE. 
 
 Free ammonia, or an ammoniacal salt, put upon a field, 
 immediately forms with the constituents of the surface soil 
 a combination from which the plant subsequently derives 
 this element of food. In this way, the ammonia conveyed 
 to the soil in rain goes on accumulating ; it would, there- 
 fore, be an act of common sense to expend no money in 
 the purchase of this dearest of all manuring agents, before 
 first making sure that phosphate of lime, either alone, or in 
 conjunction with sulphuric acid, or ash, or the two together, 
 or lime, has failed to stimulate the productiveness of the 
 field, in the first place, for underground plants (turnips, 
 potatoes, &c.), and for the subsequent crop of cereals. It 
 is only after making such trials, that the employment of 
 ammonia can be justified. 
 
 Let it not be thought, however, that the notion of the 
 professors and advocates of the so-called nitrogen theory, 
 which makes the nitrogen, or the ammonia, the principal 
 agent in manures, and the pivot upon which all agricultural 
 production turns, is purely imaginary and absolutely base- 
 less. This notion has, on the contrary, arisen from a very 
 pardonable error, formerly but too common in science, and 
 which is still occasionally met with at the present day. 
 
 It is quite true that the agricultural value, for the produc- 
 tion of grain, of the various sorts of guano, and of all excre- 
 me7its of animals, may be accurately determined by the 
 proportion of nitrogen or ammonia contained in them. 
 The mistake made in the matter essentially lies in this, 
 that, taking their stand upon these facts, which are per- 
 fectly true in themselves, people attributed the action of 
 these manures to the nitrogen, which, indeed, performs a 
 part in this action, but, in most cases, only a suboidinate 
 one. This is the same error which Lavoisier and Davy 
 committed in designating, the one, oxygen, the other, 
 hydrogen, as the acid-generating principle. 
 
THEOEETICAL AND PRACTICAL AGRICULTURE. 171 
 
 To compreliend this fact, we must bear in mind tlie com- 
 position of grain, of flesh, and of those constituent parts of 
 plants which serve to form blood, and which have a com 
 position similar to that of flesh. All these matters contain 
 the combustible and incombustible constituents of the 
 blood. A person living on bread receives into his organ- 
 ism the ash-constituents of the grain which has furnished 
 the flour for the bread; his excrements contain the ash- 
 constituents of the same grain. Out of the elements of the 
 bread flesh is made, and the excrements of men or animals 
 living on flesh are in their elements identical with those of 
 men or animals living on bread or seeds. Bread, flesh, and 
 blood, contain an ingredient rich in nitrogen, which, taken 
 in the food, serves to sustain the vital functions, or the 
 change of matter in the body : the nitrogen of this ingre- 
 dient is again every day eliminated in the urine and fceces, 
 in the same quantity in which it has been partaken of in 
 the food. 
 
 The excrements of men and of animals, therefore, not 
 only contain the ash-constituents of the seeds, the flesh and 
 the component parts of the roots, tubers, herbs, &c., that 
 have served to form blood and flesh in the animal organ- 
 ism, but they also contain the far greater proportion of the 
 nitrogen of these seeds, and of the blood and flesh- forming 
 elements. As we have already had occasion to observe, it 
 has been demonstrated by the most accurate chemical 
 analysis,* that there is a fixed and invariable ratio between 
 the amount of nitrogen in seeds and the quantity of phos- 
 phoric acid or of phosphates contained in them (between 
 the nitrogen and the ash-constituents of the seed) ; so that, 
 if we know the proportion of nitrogen in seeds, we can, 
 
 * See "Results of agricultural and chemico-agricultural experiments con- 
 ducted by the Greneral Committee of the Agricultural Society of Bavaria at 
 Munich; Cotta's Literary and Art Institution, 1857." 
 
172 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 from this, calculate the amount of phosphoric acid, or of 
 phosphates, present in them. 
 
 Kow, in the solid and liquid excrements, these several 
 constituents are naturally contained in the same, or very 
 nearly the same, fixed relative proportions as in the seeds. 
 The solid and fluid excrements together contain the nitro- 
 gen and the ash-constituents of the bread, flesh, &c. of the 
 consumed food ; and we can therefore readily understand 
 how we might, by ascertaining the amount of nitrogen in 
 an excrement, estimate, in an analogous way, in a tolerably 
 exact manner, the quantity of mineral constituents of seeds 
 or of flesh present in it. 
 
 In point of fact, the original relative proportion between 
 the nitrogen and the ash-constituents in excrements is 
 altered. The nitrogen is converted in the putrefactive 
 process into ammonia, a portion of which is lost by evapo- 
 ration ; and even before the process of decomposition has 
 set in, part of the nitrogen present is carried off*, together 
 with the most efficacious soluble salts, in the liquids which 
 ooze awa}^ This latter loss, however, might be guarded 
 against, and ought to be so, by the use of absorbing earths. 
 The proportion of nitrogen in the contents of latrines, or in 
 poudrette, in farm -yard manure, and in guano, affords, 
 therefore, no proper standard of their agricultural value, 
 which depends upon the ash-constituents of seeds contained 
 in them ; but of two sorts of guano analysed, we can, with 
 tolerable certainty, regard that one as the purest in which 
 is found the largest per centage of ammonia ; any adulte- 
 ration of the article lessens that proportion. The same 
 remark applies to poudrette which very often contains as 
 much as fiff;y per cent, of sand (sweepings) and other 
 extraneous matter unfit for the nutrition of plants ; and 
 probably, also, this holds good for farm-yard manure. 
 
 It is therefore by no means absurd, but quite correct, to 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 173 
 
 say, that tlie value of the several sorts of guano, of pou- 
 drette, and of farm-yard manure, bears a certain relation to 
 their amount of nitrogen. But the inference drawn from 
 this fact, that the agricultural value of these manures, and 
 their beneficial action upon the soil, are entirely dependent 
 upon this relative proportion of nitrogen, and that, accord- 
 ingly, ammonia and its salts might be used with equal suc- 
 cess in cultivation, in lieu of them, is over-hasty, and 
 entirely devoid of all foundation. Were a farmer, by the 
 advice of the apostles of this so-called nitrogen theory, mad 
 enough to manure his fields, even for ten years only, con- 
 secutively with salts of ammonia, or with Chili-saltpetre, 
 and were he, confidently relying upon the perfect fitness 
 of these salts to replace farm-yard manure, poudrette, and 
 guano, to sell off from his fields the entire produce, he 
 would assuredly be a beggar at the end of this period. If 
 all agriculturists in Germany were to agree never to return 
 to their fields the mineral constituents of their manure- 
 heaps, because their teachers have assured them that the 
 soil is inexhaustible in these elements, half the population 
 of Germany would be starved to death before the end of 
 ten years. 
 
 It is, altogether, one of the most discouraging signs in 
 agriculture, that frequently the best-informed men will, in 
 judging of the value of a manure, and of its effect, act as 
 if they were devoid of judgment and common sense. 
 
 In comparing the action of guano, bone-earth, and Chili- 
 saltpetre, it will not do to draw a line under the calculation 
 at the time of harvest, or after the expiration of a year, 
 and argue that guano or Chili-saltpetre is a better manure 
 than bone-earth, because so many more pounds of corn have 
 been yielded by the use of the former than by tlie latter. 
 Common sense tells us that the effect of individual manures 
 must he judged ofhy the condition in which they leave the field. 
 
174 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 It is very evident that if after a large crop which, has 
 been obtained bj the use of Chili-saltpetre in one year, the 
 soil has required in the following year a double quantity 
 of manure to yield the same amount of produce, much 
 money has in such a case been laid out to no purpose ; and 
 I greatly fear, if an exact reckoning be kept of the produce 
 of their fields for a series of years, and also of the expendi- 
 ture of manure, in addition to Chili-saltpetre, agriculturists 
 will find that for the money spent in the latter agent, they 
 have received scarcely any other return than a very beau- 
 tiful deep green colour of their crops in the first period of 
 their vegetation. 
 
 A comparison of the action of guano with Chili-saltpetre, 
 and bone-earth (or phosphorite), can be made only after 
 several years. If guano applied to a plot of land very per- 
 ceptibly increases the potato crop in the second, and the 
 clover crop in the fourth year, whilst a dose of Chili-salt- 
 petre of the same pecuniary value is not followed by a 
 similar increase, those after-effects must be taken into ac- 
 count if we would avoid drawing a superficial estimate of 
 the value of the two substances. 
 
 When the agriculturist who makes comparative experi- 
 ments with guano and other manures, and appears to have 
 obtained in the first year from the guano the most favour- 
 able results, points to its greater proportion of nitrogen and 
 draws the conclusion that these greater effects have been 
 directly due to this element, we may well ask him why he 
 has not also made a comparative experiment, upon an equal 
 piece of land, with a similar quantity of ammonia to that 
 which is contained in guano, and in this way obtained 
 a standard by which to measure the effect of ammonia in 
 guano. 
 
 But a proceeding of this kind has never yet been thought 
 of by any one of these experimenters, who also keep from 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 175 
 
 the farmer the fact proved by the most extended and accu- 
 rate experiments of Lawes, Kuhlmann, and others, that a 
 pound of ammonia in guano produces five times the effect of 
 the same quantity applied in the form of a salt of ammonia. 
 (The action of pure ammonia is altogether unknown.) 
 Now it is quite clear that the more powerful effect of the 
 ammonia in the guano is simply owing to the presence and 
 co-operation of other matters ; and when the combined 
 action of these latter and the ammonia is found to be four 
 times greater than that of the ammonia alone, then wher- 
 ever it is thought desirable or requisite to use ammonia it 
 will evidently be a wise step to provide for the presence of 
 these matters, that in such cases likewise the action of the 
 ammonia may be increased five-fold. 
 
 When an agricultural chemist (Dr. Stockhardt) asserts 
 that ''he chiefly owes to guano his positive conviction of 
 the great importance of nitrogen compounds that are easily 
 assimilated, and is thus indirectly indebted to it for the 
 most glorious acquisitions achieved by his labours in the 
 field of agricultural chemistry," the latter alone is true thus 
 far, viz. that if it had not been for guano the world would 
 scarcely have heard of the labour of this individual in the 
 field of agricultural chemistry. A man of science ought 
 not to cling to a cork buoy to enable him to swim ; and 
 if it keeps him afloat he ought to be grateful for this, but 
 not proud of it. Guano requires no cork buoy ; it would 
 assuredly have made its way iis railways have done, as indeed 
 it has done in other countries to a much greater extent than 
 with us, without requiring the least aid at the hands of the 
 chemist. Things which bring in money will always make 
 their own way. 
 
 When agricultural chemists maintain that ammonia or 
 its salts are the universal means for the growth of wheat, 
 or acid phosphate of lime for that of the turnip tribe — they 
 
176 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 simply show thereby that they do not understand the essen- 
 tial principles of the science of agriculture. 
 
 The corn-growing agriculturist removes from a hectare 
 (2^ acres) of his wheat field, in an average crop of corn of 
 2000 kilos, 701bs. of the mineral constituents of the grain ; 
 of which 34 pounds consist of phosphoric acid and 21 pounds 
 of potash, and he supplies these to the consumers in large 
 towns. In an ox of 5501bs weight, the town receives 
 1831bs of bones, containing nearly 1201bs of phosphate of 
 lime ; in the flesh, hide, and other parts of the animal 151bs 
 of phosphates, which are identical with the constituents of 
 the seeds of rye.* 
 
 The annual fluid and solid excrements of a million in- 
 habitants of large cities (men, women, and children), weigh 
 in the dry pulverulent state 45 million pounds; in which are 
 contained 10,300,000 pounds of mineral substances, mostly 
 ash-constituents of bread and meat (not including five mil- 
 lion pounds weight of bones of the slaughtered cattle, &c., 
 nor the mineral substances in the evacuation of horses, &c.). 
 These human excrements alone contain 4,580,000 pounds 
 of phosphates. 
 
 This enormous drain of these matters from the land to 
 towns, has been going on for centuries, and is still going on 
 year after year, without any part of the mineral elements 
 thus removed from the land ever being restored to it ; a 
 very small proportion only is turned to account in the 
 gardens and fields in the more immediate vicinity of 
 towns. 
 
 * In the city of Munich there were slaughtered in the year 1855-56, 
 16,301 heads of cattle, which, at an average of five cwt, weighed 8,150,500 
 lbs.; besides which there were slaughtered 66,186 calves, swine, and sheep, 
 giving, at an average of 70 lbs. each, 5,675,020 lbs. — not reckoning the cattle 
 slaughtered, at the free butcheries, by the keepers of taverns and eating- 
 houses. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 177 
 
 It is perfectly absurd to suppose that the loss of these 
 matters which are so essential to the productiveness of a 
 soil should have had no influence upon the amount of its 
 produce. Indeed, even the most prejudiced agriculturist 
 cannot help feeling some alarm at the enormous extent of 
 the loss, if he reflects upon the amazing increase in the 
 yield of corn and flesh which has taken place since farm- 
 ers began, by the use of guano, to restore to the despoiled 
 fields only a very small fraction of the corn and flesh con- 
 stituents carried away from them. I have already remarked 
 upon the identity of the constituent elements of guano with 
 those of human excrements. In a series of very instructive 
 experiments made expressly for the purpose in six differ- 
 ent parts of Saxony, it was found that a field manured with 
 guano gave in three successive years for every 10 pounds 
 of guano used, 15 pounds of wheat grain, 40 pounds of 
 potatoes, and 28 pounds of clover more than was reaped 
 from an unmanured plot of land of the same kind and 
 extent. According to the condition of the field the surplus 
 thus reaped varies from 10 to 20, and in England up to 22 
 and even 28 pounds of corn, for every 10 pounds of 
 guano used.* 
 
 * "In the United States distances of hundreds and thousands of miles sepa- 
 rate the places where the corn is grown from the markets ; the consequence 
 of this may be seen in the fact that the soil is almost everywhere exhausted, 
 and that the prosperity of the country is declining, instead of increasing. 
 
 " The rate at which this decline is progressing, has lately been shown by a 
 distinguished agriculturist, from whom we learn : ' That the phosphoric acid 
 and the potash taken annually away from the fields, without any compensa- 
 tion worth mentioning being made to them, are at the current price of the 
 market worth twenty miUion dollars; that the ash-constituent of 600,000,000 
 bushels of corn are annually carried away from the land without any mate- 
 rial restoration of them ; that the entire annual waste of the mineral consti- 
 tuents of corn is equal to 1,500,000,000 bushels of corn.' 
 
 " To suppose, says the author of these estimates, that this state of things 
 could last, and we as a nation increase in wealth, is simply ridiculous. It is 
 
 8* 
 
178 THEOKETICAL AND PKACTICAL AGRICULTUEE. 
 
 It may therefore be safely assumed that the importation 
 of a million cwt. of guano is equivalent to an increased 
 production of 2,000,000 cwt. of corn which could not 
 have been raised by the existing stock of home-made 
 manure alone ; this latter performs its own part in increas- 
 ing the produce exactly the same as if the guano had not 
 co-operated with it. 
 
 only a question of time, and time will solve the problem in a way not to be 
 mistaken. What we lose with our system of destroying the soil, and wast- 
 ing its resources, is the very essence of our existence. 
 
 " Our land has not yet grown feeble from this loss of its life-blood ; but the 
 hour is indicated when, should the present system be persisted in, the last 
 throb of the heart of the nation will cease, — when America, Greece, and 
 Rome will stand side by side amidst the ruins of the past. 
 
 " The national economic question is not how much we are able to produce, 
 but how much of our annual produce is returned to the soil. Labour spent 
 in the spoliation of the soil is worse tlian labour thrown away. In the latter 
 case the loss falls upon the present generation, in the former, poverty is the 
 inheritance of posterity. 
 
 " Extravagance, Mr. President, is a crime which finds its punishment in 
 the natural, moral, and political decay to which I have invited your atten- 
 tion. Its eftects may be seen in the fact that in New York, where the ave- 
 rage yield of wheat was from 25 to 30 bushels 80 years ago, it is now only 
 12 bushels; Indian Corn gives only 25 bushels. In Ohio, a State which 80 
 years ago was still a wilderness, the average yield of wheat is under 12 
 bushels, and is decreasing instead of increasing. In Virginia there is an 
 extensive tract of land, once the richest in the State, which now produces 
 only an average yield of wheat of less than seven bushels ; whilst in North 
 Carolina land is cultivated which produces little more than the same yield of 
 Indian corn. 
 
 " In Virginia and Kentucky tobacco was grown until the soil was com- 
 pletely exhausted, and had to be abandoned ; and in the cotton districts we 
 meet with a state of exhaustion unexampled in the world, for the shortness 
 of the time in which it has been brought about. The growers of cotton and 
 tobacco live upon their capital ; in the produce of their fields they sell their 
 fruitful soil at so low a price, that for every dollar they receive they destroy 
 to the value of five dollars." 
 
 (Letters to the President on the Foreign and Domestic Policy of the Union, 
 and the effects as exhibited in the condition of the people and the State. By 
 H.C.Carey. Philadelphia. J. B. Lippmcott & Co. 1858. Tenth letter, p. 54.) 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 179 
 
 In tlie flesh and the produce of the field we have for 
 centuries supplied to the large towns the constituent ele- 
 ments of guano, and have never brought this guano back 
 again ; and we now send vessels to Chili, Peru, and Africa 
 for this substance. For every 45 million pounds of guano 
 we pay the foreigner 3 million florins. By the exporta- 
 tion of these elements our fields have lost in productiveness; 
 were it not so, how could it have been conceivable or pos- 
 sible for us to have been able to raise their fertility by the 
 importation of these elements ? Where a field is truly in 
 prime condition^ no manuring agent can possibly increase its 
 productiveness ; the surplus yield attained by the use of 
 guano is therefore usually much less on well than on ill 
 managed estates. Whilst in the ease of the former it no 
 longer gives a remunerative return so soon as it rises some- 
 what higher in price ; the bad manager will however con- 
 tinue, and justly so, to praise it as a profitable agent. 
 
 In the year 1855-1856 above 10 million cwt. of guano 
 were imported, of which the greater portion remained in 
 England. In the course of half a century above 60 mil- 
 lions cwt. of bones have been imported into that country ; 
 yet all this mass of manure is not worth mentioning when 
 considered in relation to the arable surface of Great Bri- 
 tain, and is but as a drop when compared to the sea of 
 human excrements carried by the rivers to the ocean. 
 
 The loss annually sustained by the land can only be 
 very partially remedied by the purchase of foreign manures. 
 In the year 1852, the consumption of guano in Saxony 
 amounted in the districts of Dresden, Leipzig, Zwickau and 
 Bautzen to 60,000 cwt., which gives 16*9 cwt. for every 
 400 acres of land ( = 55*3 hectares), or 4} pound per acre 
 (3 '82 kilos per hectare). In these 3*82 kilos of guano (of 
 the better sorts) there are contained not above 1^ kilo of 
 the mineral constituents of seeds ; whereas there are annu- 
 
180 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 ally removed from tlie fields 35 kilos per acre in the cc rn 
 crop alone. If therefore Saxony imports in a year 
 1,428,000 cwt. of guano containing 35 per cent, of ash- 
 constituents (for about 5^ million thalers), this is no more 
 than has been taken away from all the Saxon fields in a 
 single corn crop. 
 
 No more importance need be attached to these figures 
 than they deserve. They are sufficiently precise to show 
 that our fields would be incalculably more fertile ; that we 
 might now produce infinitely more food for man upon the 
 same arable area ; that we should not be forced to sacrifice 
 one-half of it to cattle — if our ancestors had only prudently 
 and carefully brought back from the towns and restored 
 to their fields the guano carried away from them in the 
 produce. 
 
 There is not to be found among the industrial classes a 
 set of men more intent upon immediate and temporary gain 
 than the common peasants, and less capable of making cor- 
 rect calculations in an industrial point of view ; although 
 one would suspect the very reverse to be the case. 
 
 The prudent agriculturist who purchases potatoes from 
 the peasants in his neighbourhood, for the purpose of dis- 
 tilling alcohol from them, or rape seed for its oil, knows 
 that every two acre crop of potatoes which the peasant sells 
 to him, will in the residuary matter yield him three crops 
 of rye (seed), or a full crop of rape. He knows that every 
 cwt. of rape in oil-cake is worth two cwt. of wheat grain to 
 him ; — and in establishing a distillery or oil mill, he takes 
 into due account the advantages derived from this addition 
 to the conditions of the fertility of his land. 
 
 The peasant from whom he purchases the potatoes or 
 rape-seed knows that the buyer looks upon this additional 
 supply of fertilising matter from the residues as important^ 
 but he himself considers it of no value to his land. It never 
 
THEOKETICAL AND PEACTICAL AGRICULTURE. 181 
 
 occurs to him that it would be a prudent act to retain the 
 manure constituents for his own fields at the sacrifice of a 
 portion of the money received for his produce. 
 
 The seller, if he is also a farmer, should sell only the oil 
 of his rape seed, and only the starch of his potatoes, — for 
 in this way alone can a proper circulation be maintained. 
 
 But the agriculturist sells not only corn, but also pota- 
 toes, rape-seed, beetroot (to the sugar boiler), tobacco, hemp, 
 flax, madder, poppy, and wine. 
 
 Whilst the corn and flesh growing agriculturist exports 
 m the produce of his fields only phosphoric acid, alkalies, 
 and alkaline earths, he retains on the land the elements of 
 the straw and of the fodder plants which pass in the rota- 
 tion of his crops from one field to another. The deep root- 
 ing clover and the plants of the turnip tribe take them up 
 from the sub-soil, and in the form of farm-yard manure, 
 continually accumulate them in the surface soil. The ma- 
 nure and the surface soil receive every year an additional 
 supply of soluble silicic acid, alkalies, and salts with alka- 
 line bases ; but the proportion of phosphates in them is 
 constantly on the decrease. 
 
 Hence it will be readily understood why the use of these 
 manuring agents — viz. soluble silicic acid, potash, and pot- 
 ash salts — will not have the slightest beneficial effect on the 
 fields of the corn and flesh growing agriculturist ; for his 
 fields contain already an excess of these agents which 
 remain inactive from the want of phosphates. We can 
 further understand why the corn and flesh growing agri- 
 culturist should regard in the most important light the 
 supply of phosphates, of guano and of human excrements ; 
 and hold the other elements of food for plants as almost of no 
 value. 
 
 On such fields, simple manuring with human excrements, 
 with or without the co-operation of farm-yard manure, may 
 
182 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 produce large corn crops for an infinite number of years in 
 succession ; but the continued use of guano exhausts also 
 this land. The excrements of man contain the full comple- 
 ment of mineral elements removed in grain and flesh ; but 
 in guano there is wanting a certain quantity of potash to 
 replace fully these ash constituents. Hence on soils poor 
 in potash (on lime and sandy soils), the action of guano after 
 a certain time perceptibly diminishes, and its efiiciency is 
 then restored by the addition of wood ashes, rich in potash. 
 
 It is a very different matter with the grower of potatoes 
 and beetroot, who sells his produce to the distiller or to the 
 sugar maker. 
 
 In the average produce of three hectares of land, the 
 potato grower sells and takes away from the soil the grain 
 constituents of four wheat crops, and upwards of 600 pounds 
 of potash in addition. 
 
 In the produce of three hectares of land the beetroot 
 grower sells and takes away from the soil the grain consti- 
 tuents of four wheat crops, and 10 civt. of potash besides. 
 The single sugar manufactory at Waghausel supplies to 
 commerce every year 200,000 pounds of salts of potash 
 obtained from the residue of the molasses, and which were 
 originally derived from the beetroot fields of Baden. 
 
 It is evident that, in the cultivation of potatoes and 
 beetroot, two causes of exhaustion operate on the fields : 
 these kinds of produce withdraw from the soil at each 
 harvest, one-third more phosphates than a wheat crop, and 
 in addition to these an immense amount of potash and its 
 salts. Beetroot and potato fields, abounding in potash, may 
 therefore have their produce augmented by simply manuring 
 with guano or super-phosphate of lime ; but as guano and 
 bone manure do not replace the potash removed in the 
 produce, the ultimate result is, that after a certain number 
 of years the land is found to be so much the more thoroughly 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 183 
 
 exhausted. On other potato- and beet-root fields poor in 
 alkahne elements, farm-yard manure, which abounds in 
 alkalies, answers better than guano. 
 
 The growers of marketable plants are in the most unfavour- 
 able position as regards the restoration of the mineral ele- 
 ments annually carried off from their fields by these parts. A 
 tobacco planter takes away in the tobacco leaves an immense 
 amount of mineral elements (in clover-hay, for instance, not 
 above 10 per cent., in tobacco leaves, from 18 to 24 per cent.). 
 If he happens to be in possession of fields for green crops 
 which supply him with manure for the tobacco plants, he 
 is in the same position as the agriculturist who sells and 
 alienates from his land the clover, turnips, &c. grown 
 thereon ; that is to say, in the coarse of a few years he is 
 sure to reach a point when his land will no longer produce 
 tobacco ; and driven to procure elsewhere a supply of the 
 indispensable mineral elements, he now turns to his grain 
 and flesh producing neighbours, and purchases from them 
 at high prices their clover and turnijos in the shape of farm- 
 yard manure. Now, if this neighbour, over estimating the 
 quantity of farm-yard manure in his possession, disposes of 
 a portion of it to the tobacco grower, he generallj^ soon 
 perceives his error, by the diminution of his crops. He is 
 first of all made aware that manure cannot be produced at 
 will, and that the counsel given to him to " grow more pro- 
 vender for his cattle, as corn crops will then be sure to fol- 
 low in due course," is of no use to him ; he finds that it 
 was his manure that for seven or perhaps ten harvests has 
 given him the sixth or seventh grain which constituted his 
 entire profit, and that in parting with his manure he has 
 . actually sold for a song his profits for many years to come. 
 Made wise by experience, he now sells no more farm-yard 
 manure. 
 
 The tobacco planter, finding he can no longer procure 
 
184 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 manure from his neighbour, now applies to grain and flesh 
 producers living farther off, who have yet to find out by 
 experience what the neighbour has already discovered; 
 and thus the sphere of his foraging operations in search of 
 manure grows wider and wider every year, until he finds 
 himself ultimately constrained to procure his manure from 
 towns, and to supply by other means the elements in which 
 the town manure is deficient. 
 
 The same state of matters we find also in countries where 
 the vine is extensively cultivated. Vineyards are generally 
 planted on slopes, and are destitute of arable surface soil ; 
 the soil is, comparatively speaking, infinitely poorer in the 
 elements of food for plants, than is the case with fields 
 situated in plains. Vineyards produce no manure; the 
 wanting mineral elements of food are supplied, within cer- 
 tain limits, from the neighbouring corn and pasture-fields ; 
 and the proprietors of these, if they have an opportunity, 
 in their turn pillage the neighbouring woods. 
 
 By deep digging the vine-dresser seeks to fit his poor 
 soil for the reception of the deep-rooting vine ; and by the 
 occasional cultivation of lucerne and clover, he endeavours 
 to accumulate by their means in the surface soil, the 
 mineral elements in which it is deficient. He conveys to 
 his vineyard arable soil from fields which he has acquired 
 for that special purpose, and also applies as manure the 
 debris of disintegrated rocks abounding in alkaline matter. 
 
 The culture of the vine exercises accordingly on the pro- 
 duction of grain and flesh an adverse influence similar to 
 that caused by the planting of tobacco and other produce 
 grown for sale. 
 
 The producer of corn and flesh, according to the prevail- 
 ing system, robs his own land ; the producer of wine and 
 marketable plants despoils in his turn the corn and flesh 
 producer; and lastly, large towns, like bottomless pits 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 185 
 
 gradually swallow up tlie conditions of fertility of the 
 greatest countries. 
 
 In this way the vine growers and tobacco planters of the 
 Palatinate and of the Bergstrasse exhausted the fields of 
 the Hessian and Badish Odenwald, and completed the ruin 
 of the already impoverished and encumbered peasant who 
 could not resist the tempting sound of the silver offered 
 him for his manure. 
 
 In the same way the sewers of the immense metropolis 
 of the Ancient World, engulfed in the course of centuries, 
 the prosperity of the Eoman peasant ; and when the fields 
 of the latter would no longer yield the means of feeding 
 her population, these same sewers devoured the wealth of 
 Sicily, Sardinia, and the fertile lands on the coast of Africa. 
 
 The fertility of the land has remained unimpaired for 
 centuries, in such parts only where an agricultural popula- 
 tion dwells crowded together on a comparatively small 
 area, and where the tradesman and craftsman inhabiting 
 the small towns thinly scattered over that area, till their 
 own little plots of ground with the assistance of their jour- 
 neymen. 
 
 When there are living on a (German) square mile of land 
 in that position, 2000 to 3000 people, no exportation of 
 grain or flesh is possible, for the produce of the fields is 
 only just sufficient to feed the population; a surplus for 
 exportation either never or very seldom exists. The fer- 
 tility of such a tract of land is kept up unimpaired by the 
 regular circulation of the conditions on which this fertility 
 depends. All the mineral constituents of the produce con- 
 sumed are brought back without diminution to the fields 
 from which they were taken. None of these elements are 
 ever lost; for everybody knows the inevitable consequences, 
 and is therefore careful to do his best to collect and preserve 
 them. 
 
186 THEORETICAL AND PEACTICAL AGRICULTUEE. 
 
 Now, supposing this same land falls into tlie hands of 
 ten great proprietors, the pillage and plunder system then 
 takes the place of the system of restitution and compensa- 
 tion. The petty proprietor almost entirely restores to the 
 field what he takes from it ; the large proprietor, on the 
 other hand, sends his grain and flesh for sale to the great 
 centres of consumption, and accordingly loses the conditions 
 for their reproduction. After a number of years the land 
 placed in this position will be turned into a desert waste 
 like the Koman Campagna. 
 
 This is the natural cause of the impoverishment of lands 
 by cultivation ; there is no other ; the teachers of modern 
 agriculture alone do not recognise this cause, and are with 
 all their power intent upon accelerating the ruin of Ger- 
 man agriculture, and making it irretrievable. Fertile fields 
 ■ — so these teachers tell us — are inexhaustible in the con- 
 ditions of fertility ; they only require the whip to stimu- 
 late them into action. Good fortune kindly sent guano to 
 rescue them in their utmost need, — the result of their own 
 teaching; but in their fatal hands this blessing is actually 
 turned into an instrument for impoverishing the land in 
 the course of time still more completely. But guano will 
 ultimately also come to an end, and what is to be done 
 then? 
 
 "We have not yet come to that pass," we hear those 
 exclaim, whose fields are still fertile and yield abundant 
 crops; "we are not yet come to that pass," said also a 
 certain robber who was admonished to lead a better life, 
 until one fine morning he found the hangman's rope around 
 his neck. "To that pass" it will also assuredly come at 
 last with agriculturists. Their system may -be based on 
 agricultural experience, but it is certainly devoid of all 
 foundation in science. 
 
LETTER XII. 
 
 Modern Agriculture has no history — The reason of this — Tlie history of 
 Roman Agriculture shows the existence of the spoliation system at that 
 period — The works of Cato, Virgil, Yarro, and Pliny inculcate, two thou- 
 sand years ago, the same precepts that are now taught by many teachers 
 of agriculture — Quotations from these writers, to show their opinions on 
 tlie exhaustion of the ground; on the different kinds of soils, and the 
 modes of improving them; on the selection of plants for the soils which 
 are suitable for them ; on fallowing ; on the cultivation of green crops for 
 manures ; on the different kinds of manure and their relative values, and 
 modes of managing them — The various precepts inculcated of old only 
 hastened the ruin of Roman agriculture. 
 
 The history of mankind, says Timer ^ is also tlie liistory 
 of agriculture. No saying can be further from the truth 
 than this. All our departments of industry having any 
 connection with the natural sciences have a history: 
 modern agriculture alone, has none; for it is a thing of 
 to-day, or, at the most, but of yesterday. What occurred 
 a week ago, it knows not ; and if it is acquainted with it, 
 such knowledge does not make the agriculturist any wiser. 
 
 Facts by the million cannot be bequeathed ; but scientific 
 principles which are expressions for these facts, may be so, 
 because they are immutable in their nature. 
 
 Agriculture is, of all industrial pursuits, the richest in 
 facts^ and the poorest in their comprehension. Facts are 
 like grains of sand which are moved by the wind, but 
 principles are these same grains cemented into rocks. A 
 fact simply tells us of its existence, but experience ought to 
 inform us why it exists. 
 
 Science is conservative in her nature, not destructive. 
 She does not reject the truths discovered by practice, but 
 
188 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 receives them ; tliej are never disputed by lier, but are 
 examined and receive from her their proper import and 
 further application. Science, therefore, can produce no 
 revolution in practice ; but she leads the way to a series of 
 progressive developments, which are evolved in natural 
 sequence from each other. 
 
 Modern agriculture has methods and working systems, 
 but it is altogether deficient in fixed principles and positive 
 knowledge. After so many thousand years, even our hest- 
 informed and most experienced agriculturists do not yet 
 hnow what kind of manure will answer best, or under what 
 circumstances /resA manure ought to be used in preference 
 to old, or vice versa! 
 
 Modern agriculture has, up to this time, no connection 
 with the history of the development of man ; that history 
 is the mirror which reflects not only his errors and failures, 
 but also his onward progress. But modern agriculture 
 rejects the idea of ever being in error, and therefore she 
 knows nothing oi p)^ogress. 
 
 If the history of the development and progress of the 
 human race really found a place in the study of modern 
 agriculture, or if teachers of that pursuit would only take 
 the trouble to make themselves acquainted with the pages 
 of that histor}^, our agriculturists would know that, two 
 thousand years ago, the most enlightened and most eminent 
 men of ancient Eome already found the cultivation of the 
 soil beset by the same difiiculties which threaten it to-day ; 
 and that the same S3^stem of "high flirming" which our 
 modern teachers now recommend as the best, was then 
 tried, and found wanting. 
 
 The following statements, taken from the writings of 
 Columella, Cato, Yirgil, Yarro, and Pliny, are calculated to 
 enlighten the agriculturist as to the actual point of " pro- 
 gress" to which he has attained in the practice of his pur 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 189 
 
 suit ; and to show him that his modern teacher, after all, 
 inculcates nothing that was not known to the world equally 
 well, and often even much better, two thousand years ago. 
 Eeading the twelve books of Columella, after a perusal of 
 our modern manuals of practical agriculture, is just like 
 stepping from an arid and barren desert into a beautiful 
 garden — so fresh and charming does everything appear. 
 
 In his preface addressed to Publius Silvinus, Columella 
 says : "The Magnates of the state are in the habit of com- 
 plaining of the sterility of the land, or of the unsettled state 
 of the weather, which has now for a long time exerted an 
 unfavourable influence on the growth of agricultural pro- 
 duce ; others are of opinion that the soil has been exhausted 
 by the over-productiveness of former years. But," he con- 
 tinues, " no one gifted with common sense, will ever permit 
 liimself to be persuaded that our earth has grown old, as 
 man grows old. The sterility of our fields is to be imputed 
 to our own doings, because we hand over the cultivation 
 of them to the unreasoning management of ignorant and 
 unskilful slaves. 
 
 " The agriculturist requires one kind of knowledge, the 
 herdsman another. The former ought to know what pro- 
 duce will answer best for his land ; the latter must under- 
 stand the most remunerative way of breeding cattle. Now, 
 as the two pursuits are most intimately connected with 
 each other, inasmuch as it is much more advantageous to 
 use the provender grown on the field for home consump- 
 tion, than to sell it ; and as manuring mainly contributes 
 to make a field fertile, and cattle are principally kept for 
 the production of manure, therefore every body who owns 
 a farm must not only possess a knowledge of agriculture, 
 but also of pasturage, and of the process of stall-feeding." 
 —(Columella.) 
 
 " Wherein does a good system of agriculture consist? In 
 
190 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 the first place, in thorough ploughing; in the second 
 place, in thorough ploughing; and, in the third place, in 
 manuring." — (Cato). 
 
 " Colour is no reliable sign of the good quality of a soil. 
 For as the strongest cattle exhibit an almost infinite variety 
 of colour, so is also the best land of many and divers 
 colours." — (Columella). 
 
 " There are many different sorts of soil ; such as chalky, 
 sandy, clayey, &c. One soil is moist, another dry, or 
 moderately so; there are rich soils and poor soils, light 
 soils and heavy soils. By the intermixture of these an 
 infinite variety is created. A stiff" clay soil may be 
 improved by the addition of sand or marl ; a sandy soil, 
 by the addition of clay." — (Pliny, Pallad. Col.) 
 
 " Superfluous moisture must be drawn off" by ditches, 
 either open or covered ; in a chalky and stiff" ground open 
 ditches are preferable. Open ditches must be wider at the 
 top than at the bottom; if they are of the same width 
 throughout, the sides are undermined by water, and the 
 falling earth fills up the ditch. Covered ditches are dug to 
 the depth of three feet, half filled with small stones or 
 coarse gravel, and the earth dug out is then thrown over 
 the top and levelled. If neither gravel nor stones are to 
 be got, then as many bundles of brushwood are thrown in 
 as the narrow ditch will hold, and the whole is covered 
 with earth. At the openings of the ditch, two stones are 
 placed upright, as pillars, to support a third, like a small 
 bridge; this keeps the ditch open." — (Col.) 
 
 " A soil to be fertile must, above all things, be light and 
 friable, and this condition we seek to bring about by the 
 operation of ploughing." — (Yirgil). 
 
 " Ploughing the land simply means rendering the earth 
 porous and friable, which most tends to increase its produc- 
 tiveness." — (Cato.) 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 191 
 
 " The ancient Komans held, that a field which required 
 harrowing could not have been well ploughed." — (Colu- 
 mella.) 
 
 " A heavy soil should be turned up in autumn, and 
 ploughed three times, and the furrows be multiplied and 
 drawn so closely together, that it may be barely possible to 
 distinguish from which side the plough has proceeded; 
 for by these means weeds are thoroughly rooted out. 
 Fallow land must be ploughed until it is almost reduced to 
 powder. The owner of a farm should often ascertain for 
 himself whether it is properly ploughed. For this purpose, 
 he need simply thrust a staff through the furrows (the 
 Eomans laid out their fields in broad undulating ridges, as 
 may still be seen at the present day in the neighbourhood of 
 Nuremberg ; only the Koman ridges were much broader) ; 
 if the staff passes through unresisted, it is a sure sign that 
 the soil has been properly ploughed. Care must be taken 
 to break clods of earth. Fields should be ploughed when 
 neither too dry nor too wet ; if the soil is too hard, the 
 plough will not penetrate, or it will simply tear off large 
 clods. Even the best soil is unfruitful in its deeper layers, 
 and the large lumps of earth torn up by the plough bring 
 part of this subsoil to the top, which tends to deteriorate 
 the arable surface soil. Always select for your fields those 
 plants that may be best suited to their positions " (Cato) ; 
 *' for all plants will not thrive equally well in all sorts of 
 soils." — (Yarro). '' Some plants require a dry soil, others 
 thrive best in moist ground." — (Col.) "Katurally moist 
 ground answers best for pasturage." — (Cato). " Hay grown 
 on naturally moist ground is better than where its produc- 
 tion has to be stimulated by irrigation. A meadow plot in 
 a plain must have a slight fall, that rain and other water 
 may not gather on it in pools, but gently flow off." — 
 (CoL). The seeds intended for sowing should be picked 
 
192 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 out bj hand, and pulse be previously soaked in saltpetre 
 water : — 
 
 " Still will the seeds, tho' chos'n with toilsome pains 
 Degenerate, if man's industrious hand 
 Cull not each year the largest and the best. 
 'Tis thus by destiny, all things decay 
 And retrograde, with motion unperceived." 
 
 Kennedy's YirgiVs Georg. 
 
 " Take care to bave your corn weeded twice with the boe, 
 and also by band." — (Cato). 
 
 " On large estates fields are alternately allowed to lie fal- 
 low in order to save manure." — (Pliny). " Where want of 
 space forbids this, green crops are grown alternately with 
 cereals, and the loss of productive energy is restored by 
 manuring." — (Cato, Columella). ^' Some agriculturists grow 
 cereals on their fields two years in succession ; proprietors, 
 however, forbid this to their tenants." — (Festus). " The land 
 must rest every second year, or be sown with lighter kinds 
 of seeds, which prove less exhausting to the soil." — (Yarro). 
 
 " Of the leguminous plants, lupines first deserve our 
 attention, because they require the least labour, are cheap- 
 est, and of all seeds are the most profitable for the land ; 
 they give the best manure for impoverished fields, and will 
 grow on a sterile soil. 
 
 " Some of the leguminous plants manure the soil according 
 to Saserna, and make it fruitful, whilst others exhaust it, and 
 make it barren. Lupines, beans, peas, lentils, vetches are 
 reported to manure the land. Of lupines and vetches I 
 believe this to be truly the case, provided they be cut down 
 green, and ploughed in before they are dry." — (Columella). 
 "Linseed, poppy, and oats exhaust the soil." — (Virgil). 
 " For fields that have suffered from the cultivation of these 
 plants, manuring is the only efficacious means by which the 
 
THEOKETICAL AND PRACTICAL AGRICULTURE. 193 
 
 lost productive energy of the earth is restored." — (Columella). 
 " There are three kinds of manure: the best is the excrement 
 of birds ; then comes that of man ; and lastly, that of cattle. 
 The last also varies in quality. Asses' dung is the best ; 
 then follow sheep's dung, and that of goats, horses, and 
 cattle; the least efficacious of all is the dung of swine. 
 Where an estate consists altogether of corn-fields, there is 
 no need to put on every kind of manure separately; but 
 where there are plantations of trees, arable land, and pas- 
 turage, every kind of manure should be applied separately." 
 — (Columella). " Pigeons' dung (guano) should be spread 
 on meadows and gardens, or over the seeds." — Cato, Yarro, 
 Cassius). " Horse-dung is about the best suited for meadow 
 land, and so in general is that of beasts of burthen fed on 
 barley; for manure produced from this cereal makes the 
 grass grow luxuriantly." — (Yarro). 
 
 '' Ash also is used with advantage on fields ; and on the 
 other side of the Po," says Pliny, "the use of ash is viewed 
 so favourably by farmers, that they actually prefer it to the 
 manure furnished by their cattle. Should there be no kind 
 of manure at hand, the example of my paternal uncle, M. 
 Columella, may be followed with advantage ; he would not 
 manure his vineyard, as he was of opinion that this tended to 
 impair the fine flavour of the wine ; but he applied a layer of 
 artificial mould, or earth brought from the woods, and made 
 sure of obtaining by this means a more abundant vintage. 
 Where no kind of manure is to be had, I think the cultiva- 
 tion of lupines will be found the readiest and best substitute. 
 If they are sown about the middle of September in a poor 
 soil, and then ploughed in, they will answer as well as the 
 best manure." — (Columella). 
 
 " Agriculturists ought to know that a field will indeed 
 lose its productive power when left altogether unmanured ; 
 but that, on the other hand, over-manuring is also very 
 
 9 
 
194 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 prejudicial. Let farmers, therefore, manure ulieir fields 
 often, rather than over much at a time." — (Columella). 
 
 '' I have here one more remark to add, namely ; that 
 manure is best suited for the field when it is a year old. 
 In summer it ought to be turned up and always kept moist, 
 in order that the seeds of noxious weeds in it be rotted, and 
 be not again returned to the land." — (Col.) 
 
 " The best fodder plants are lucerne, fenugreek {Fcenum 
 grcecum), and vetches. Lucerne may be placed in the 
 foremost rank of such plants ; for when it is once sown, it 
 lasts ten years, fattens lean cattle, and has a salutary action 
 on sick cattle. It must be carefully weeded at first, lest 
 the weeds choke the tender lucerne." — (Columbella). 
 
 " A field is not sown entirely for the crop which is to be 
 obtained the same year, but partly for the effect to be pro- 
 duced in the following; because there are many plants 
 which, when cut down and left on the land, improve the 
 soil. Thus, lupines, for instance, are ploughed into a poor 
 soil, in lieu of manure." — (Yarro.) " Mow your hay at the 
 proper season, and take care not to be too late with it ; you 
 must cut it before the seed ripens, and store the best hay 
 separately." — (Cato.) " Mossy meadows may be improved 
 by a fresh sowing, or by manuring ; but neither of these 
 operations will answer so well as frequent strewing with 
 ash, which destroys the moss." — (Columella.) 
 
 All these rules had, as history tells us, only a temporary 
 effect ; they hastened the decay of Eoman agriculture ; and 
 the small farmer ultimately found that he had exhausted all 
 his expedients to keep his fields fruitful, and reap remune- 
 rative crops from them. Even in Columella's time, the 
 produce of the land was only fourfold. The fields fell into 
 the hands of the large landed proprietors, who, by employ- 
 ing a multitude of slaves, were for a time enabled to obtain 
 "the largest crops at the least expenditure of manure." 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 195 
 
 Even by these means the land was in the end not able to 
 bear the heavy taxation ; and, as the history of the first 
 three centuries of our era informs us, there ensued a con- 
 dition of the population, the most calamitous and frightful 
 into which a nation can fall. It is true that many causes 
 co-operated in producing this result, but assuredly one of 
 these was the exhaustion of the soil by the spoliation sys- 
 tem of agriculture then pursued. 
 
LETTER Xin. 
 
 The true object to be kept in view in establishing Scientific Principles — In 
 scientific agriculture, "Manure," like the term '"Phlogiston," has no longer 
 a meaning — The cultivation of Green Crops for the purpose of keeping a 
 stock of Cattle for manure is not necessary in the cultivation of land — The 
 distinction between the Necessity and the Utility of keeping cattle — No 
 necessary connection exists between the production of Corn, and that of 
 Flesh and Cheese — The fundamental principles of German Agriculture 
 quite unknown in China — Chinese Agriculture— The manures employed 
 by them — Great value set by Chinese on human excrements ; their mode 
 of collecting and using them — Chinese compost — Their mode of sowing 
 and transplanting wheat — Plants cultivated as green manure for rice fields 
 — The lesson taught by the Chinese system of agriculture. 
 
 I WILL show the teachers of agriculture another people, 
 who, without the aid of science, of which they know 
 nothing, have found the philosopher's stone, which these 
 very teachers, in their blindness, vainly seek. I will point 
 out to them a land, the fertility of which has for three 
 thousand years never decreased, but, on the contrary, has 
 been ever on the increase ; and where more men are 
 crowded together on a square mile than are to be found on 
 the same space in Holland or England. 
 
 According to the testimony of all reports of our own 
 and former times, made by Davis, Hedde, Fortune, and 
 others, and which have been fully borne out by the 
 special inquiries into the state of Chinese husbandry, insti- 
 tuted on the spot at my request, by the direction of the 
 late Sir Robert Peel, it appears that in China, nothing is 
 known of meadow culture^ or of fodder plants^ which are 
 grown for the sake of cattle. Farm-yard manure is equally 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 197 
 
 unknown ; every field yields produce twice a year^ and is 
 never allowed to lie fallow. 
 
 Wheat often produces one hundred and twenty fold 
 and upwards (Eckeberg) ; and a fifteen-fold crop is con- 
 sidered an average yield (Davis). All those means which 
 the German teacher of agriculture regards as indispensable 
 for increasing the produce of our fields, and instructs his 
 followers to employ, are not only entirely dispensed with by 
 the Chinese farmer, but he actually obtains, without their 
 co-operation, crops which exceed more than two-fold those 
 .of the German high farmers. 
 
 I readily admit that the Chinese are differently circum- 
 stanced from what we are in Europe. Most of them are 
 Buddhists, and eat no beef; we eat more flesh, and must 
 consequently grow fodder for the production of that article 
 of our diet. But that is not the question before us, but one 
 which concerns those principles that are to guide the prac- 
 tice of husbandry. Our teachers of modern agriculture 
 do not tell us to grow fodder that flesh may be produced ; 
 but that we ought to do so for the purpose of forming 
 manure ; which clearly shows that they have no just con- 
 ception of the true nature and aim of agriculture, and that 
 they are altogether ignorant of scientific principles in the 
 matter. 
 
 In laying down a scientific principle, the first point for 
 consideration is not whether the application of it will turn 
 out profitable or not ; but whether it is true ; for if it is a 
 true principle, it must prove advantageous. 
 
 In scientific agriculture "manure" finds no longer a 
 place; for the notions that were formerly attached to the 
 term are completely obsolete ; just as is the case with the 
 word Phlogiston^ which, up to the end of last century, was 
 used to explain chemical phenomena. 
 
 So long as the nature of Phlogiston was unknown, that 
 
198 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 word served as a collective term to connect togetler, in an 
 intelligible form, a number of unknown operating causes ; 
 but when it had once been settled what " Phlogiston" really 
 meant and represented, the term had to give way to more 
 correct ideas ; and interpretations of phenomena became 
 what they had never been before, viz. real and trustworthy. 
 Wood does not, on that account, burn differently now-a- 
 days from what it formerly did ; the air played the same 
 part in its combustion then as now ; and water still possesses 
 the same property of making bodies wet ; but what immense 
 progress has been made by mankind, as the result of sub- 
 stituting for the word " Phlogiston," the proper conceptions 
 of the nature of air, of oxygen, and of the process of com- 
 bustion ! 
 
 A similar progress, but much more important, and infi- 
 nitely more beneficial to man, will spring from a correct 
 apprehension of the process of nutrition in plants and 
 animals. Absurd as would now be the attempt of a teacher 
 of Chemistry to account for any chemical process by having 
 recourse to phlogiston, it is no less inadmissible in a teacher 
 of scientific agriculture to explain a given fact by attribut- 
 ing it to " manure ;" for, in the place of the obsolete notion 
 of " manure," which has no longer any meaning^ we have 
 now for every plant certain positively known elements of 
 food^ to the united action of which we have to look for an 
 explanation of the fact or phenomenon in question. 
 
 The doctrine which inculcates as necessary for the cul- 
 tivation of the land, the production of manure by green 
 crops, and along with this the maintenance of a stock of 
 cattle, is erroneous. 
 
 It is necessary here to distinguish between necessity and 
 utility. A stock of cattle may prove very useful to the 
 farmer, and yield him a remunerative return in butter, 
 cheese, and meat ; but this is quite a distinct affair from the 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 199 
 
 tillage of his fields, and he ought to know, and must be 
 taught, that there is absolutely no compulsion upon him to 
 keep a stock of cattle. 
 
 The keeping of cattle is necessary for the production of 
 manure ; hut the production of manure is hy no means neces- 
 sary for the fertilisation of corn fields. In the system of the 
 rotation of crops, all that is required is that green crops 
 should be grown, and that their constituent parts be incor- 
 porated with the arable surface soil of the field ; and it is 
 quite immaterial for the cereals whether the green crops be 
 previously eaten by the cattle and converted into manure or 
 not. 
 
 If lupines, vetches, clover, turnips, &c., are cut up and 
 ploughed in, in the green state, their action is far more 
 powerful. 
 
 There is no natural connection of mutual dependence 
 between the production of corn and that of flesh and cheese ; 
 on the contrary, they interfere with each other, and must 
 in science be considered as perfectly distinct and separate 
 things ; for the production and sale of flesh is carried on at 
 the expense of grain, and vice versd. We cannot do with- 
 out meat, milk, or cheese ; and if the production of these 
 articles be left entirely to the grazier, who, on his part, ought 
 to meddle as little as possible with the growing of grain, 
 both he and the farmer, as well as the consumer, would 
 profit by it. In England this separation of the two pur- 
 suits is gradually gaining ground ; and when, as is to be 
 hoped, our German farmer shall have succeeded, in the 
 course of time, in mastering the multiplication table, we 
 may expect that the same separation will take place in 
 Germany. Chemical manufactories are not established any- 
 where and everywhere, but only in localities offering cer- 
 tain natural advantages ; and Agriculture, after all, is 
 simply an industrial pursuit, like any other. 
 
200 THEOliETICAL AXU PKACTICAL AGRICULTUEE. 
 
 In CHna they know nothing of the fundamental prin- 
 ciples upon which German agriculture is based. Except 
 green manuring, they neither know nor esteem the applica- 
 tion of any kind of manure beyond the excrements of man. 
 The other matters occasionally employed by them to in- 
 crease their crops, are in quantity and effect utterly in- 
 significant, when compared with the use of human excre- 
 ments. 
 
 It is quite impossible for us in Europe to form an ade- 
 quate conception of the great care which is bestowed in 
 China upon the collection of human excrements. In the 
 eyes of the Chinese, these constitute the true sustenance of 
 the soil (so Davis, Fortune, Hedde, and others tell us), and 
 it is principally to this most energetic agent that they 
 ascribe the activity and fertility of the earth. 
 
 The Chinese, whose house is still, what it most probably 
 has ever been, a tent, only that it is built of stone and 
 wood, knows nothing of privies as we have them in our 
 country ; but, in their stead, there are found in the princi- 
 pal and most comfortable part of his dwelling, earthenware 
 tubs, or cisterns most carefully constructed of stone and 
 lime ; and the notion of utility so completely prevails over 
 the sense of smell, that, as Fortune tells us ("The Tea Dis- 
 tricts of China and India," vol. i., p. 221), " what in every 
 civilised town of Europe would be regarded as a most in- 
 tolerable nuisance, is there looked upon by all classes, rich 
 and poor, with the utmost complacency, and," he continues, 
 " nothing would cause greater surprise to a Chinese than to 
 complain of the stench arising from these receptacles." 
 The Chinese do not disinfect this manure ; but they are 
 perfectly aware that it loses part of its fertilising power by 
 the action of the air ; and they, therefore, take great care 
 to guard against evaporation. 
 
 Except the trade in grain, and in articles of food, gene- 
 
THEOEETICAL AND PRACTICAL AGRICULTURE. 201 
 
 rally, there is none so extensively carried on in China as 
 that in human excrements. Long clumsy boats, which 
 traverse the street canals, collect these matters every day, 
 and distribute them over the country. Every Coolie who 
 has brought his produce to market in the morning, carries 
 home at night two pails full of this manure on a bamboo 
 pole. 
 
 The estimation in which it is held is so great, that every- 
 body knows the amount of excrements voided per man in 
 a day, month, or year ; and a Chinese would regard as a 
 gross breach of manners the departure from his house of a 
 guest who neglects to let him have that advantage to which 
 he deems himself justly entitled in return for his hospitality. 
 The value of the excrements of five people is estimated at 
 two Teu per day, which makes 2000 Cash* per annum, or 
 about twenty hectolitres (440 galls.), at a price of seven 
 florins. 
 
 In the vicinity of large towns, these excrements are con- 
 verted into poudrette, which is then sent to the most distant 
 places, in the shape of square cakes, like bricks. For use, 
 these cakes are soaked in water, and applied in the fluid 
 form. With the exception of his rice fields, the Chinese 
 does not manure the field, but the plant. 
 
 Every substance derived from plants and animals is care- 
 fully collected by the Chinese and converted into manure. 
 Oil cakes, horn, and bones, are highly valued, and so is 
 soot, and more especially ash. To give some notion of the 
 value set by them upon animal ofial, it will be sufficient to 
 mention that the barbers most carefully collect, and sell as 
 an article of trade, the somewhat considerable amount of 
 hair of the beards and heads of the hundreds of millions 
 of custd mers whom they daily shave. The Chinese know 
 
 100 Cash are equal to about 4^d. (Fortune). 
 
202 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 the action of gypsum and lime ; and it often happens that 
 they renew the plastering of the kitchens, for the purpose 
 of making use of the old matter for manure. — (Davis.) 
 
 No Chinese farmer ever sows a seed of corn before it has 
 been soaked in liquid manure diluted with water, and has 
 begun to germinate ; and experience has taught him (so he 
 asserts), that this operation not only tends to promote the 
 growth and development of the plant, but also tc protect 
 the seed from the insects hidden in the ground. — (Davis.) 
 
 During the summer months, all kinds of vegetable refuse 
 are mixed with turf, straw, grass, peat, weeds, and earth, 
 collected into heaps, and when quite dry, set on fire ; after 
 several days of slow combustion, the entire mass is converted 
 into a kind of black earth. This compost is only employed 
 for the manuring of seeds. When seed time arrives, one 
 man makes holes in the ground ; another follows with the 
 seed, which he places in the holes ; and a third adds this 
 black earth. The young seed planted in this manner grows 
 with such extraordinary vigour that it is thereby enabled 
 to push its rootlets through the hard solid soil, and to col- 
 lect its mineral constituents. — (Fortune.) 
 
 " The Chinese farmer sows his wheat, after the grains 
 have been soaked in liquid manure, quite close in seed- 
 beds, and afterwards transplants it. Occasionally, also, the 
 soaked grains are immediately sown in the field properly 
 prepared for their reception, at an interval of four inches 
 from each other. The time of transplanting is towards the 
 month of December. In March the seed sends up from 
 seven to nine stalks with ears, but the straw is shorter than 
 with us. I have been told that wheat yields 120 fold and 
 more, which amply repays the care and labour bestowed 
 upon it." — (Eckeberg, Eeport to the Academy of Sciences 
 at Stockholm, 1765.)* 
 
 * The Dresden Journal, of 16th September, 1856, contains the follow- 
 
THEOEETICAL AND PRACTICAL AGRICULTURE. 203 
 
 In Chusan, and the entire rice districts of Chekiang and 
 Keangsoo, two plants are exclusively cultivated for tlie 
 purpose of serving as green manure for the rice fields ; the 
 one is a species of Coronilla, clover is the other. Broad 
 furrows, similar to those intended for celery, are made, and 
 the seeds are planted on the ridges in patches, at a dis- 
 tance of five inches from each other. In the course of a 
 few days germination begins, and long before the winter is- 
 gone, the entire field is covered with a luxuriant vegeta- 
 tion. In April the plants are ploughed in ; and decompo- 
 sition soon begins, attended with a most disagreeable odour. 
 This method is adopted in all places where rice is grown. — • 
 (Fortune, vol i., p. 238). 
 
 These extracts, which, from want of space, cannot be 
 further extended, will probably suflice to convince the 
 German agriculturist, that his practice, when compared 
 with that of the oldest agricultural nation in the world, 
 stands somewhat in the position of the acts of a child to 
 those of a full grown and experienced man. The Chinese 
 system of husbandry is the more remarkable, if we take 
 
 ing statement: — "As we are informed from Eibenstock, forest-inspector 
 Thiersch, of that place, has for several years past made very successful 
 experiments in transplanting winter corn in the autumn. He transplanted 
 the young plants intended for the purpose in the middle of the month of 
 October, one peck of seed-corn to one hundred square rods of ground, which 
 produced an uncommonly rich crop. There were roots from which sprung 
 as many as fifty-one stalks with ears, and the latter contained as many as 
 one hundred grains." 
 
 I have applied to Mr. F. J. Thiersch for more precise details of his experi- 
 ments ; and from his statement as to the cost of the operation and the 
 return made, there appears to be no doubt that the Chinese mode of hus- 
 bandry might also be resorted to with advantage in Europe, in locahties 
 where the land is rich and labour abundant. One of my friends, who visited 
 M. Thiersch's experimental field, told me that he had counted twenty-one 
 stalks with full ears on a plant pulled up at hazard (not picked out). For 
 poor fields this method of cultivation is entirely unsuited. 
 
204: THEOKETICAL AND PKACTICAL AGRICULTURE. 
 
 into account what they have achieved in other mechanical 
 and chemical pursuits, more incomprehensible, as they owe 
 everything to the purest empiricism. For the Chinese 
 system of instruction has, for thousands of years, so 
 thoroughly excluded every inquiry after an ultimate cause 
 of things, which might possibly have led to the discovery 
 of scientific principles, or to the establishment of a science, 
 that the capability of making further progress, except by 
 imitation, would seem to be destroyed to the very root in 
 that people. The study of the physical laws, which has 
 led European nations to the invention of the steam-engine, 
 and of the electric-telegraph, and has enabled man to con- 
 trol and turn to his account the forces of nature in number- 
 less other instances, is a matter of absolute impossibility to 
 the Chinese scholar. It is the express command of their 
 first and most ancient teacher of religion, Confucius, that 
 the student shall never allow any thought to rise in his 
 mind but such as he finds written in his books. 
 
 It is quite true that what suits one people may not on 
 that account suit all countries and all nations; but one 
 great and incontrovertible truth may, at all events, be 
 learned from Chinese agriculture, viz., that the fields of 
 the Chinese cultivator have preserved their fertility unim- 
 paired, and in continued vigour ever since the days of 
 Abraham, and of the building of the first Pyramid in 
 Egypt.* This result we also learn has been attained solely 
 and simply by the restitution to the soil of the mineral con- 
 stituents removed in the produce ; or what amounts to the 
 same thing, that this has been effected by the aid of a ma- 
 nure, of which the greater portion is lost to the land in the 
 European system of cultivation. 
 
 * Vessels of Chinese porcelain are found in the Pyramids, of the same 
 shape, and with the same characters of writing on them, as are made in 
 China at the present day. 
 
LETTEK Xiy. 
 
 The law of Compensation is of universal application — Elementary information 
 on Chemical subjects connected with Agriculture easily imparted — Im- 
 portance of instructing youth at school in these fundamental truths — Theo- 
 retical instructions should always precede Practical — The proper mode of 
 instructing agriculturists in the Theory and Practice of Agriculture — The 
 present constitution of Agricultural institutions very defective — The false 
 position of Science in practical agriculture is the result of the teachings of 
 these Schools — The demands made by Science on agriculturists are simple, 
 and a knowledge of them cannot prove injurious — Science demands that 
 agriculturists should test the Truths she advances — The truths in these 
 Letters expressed by a Formula — The value of Guano first discovered by 
 Science — The establishment of Reservoirs for animal excreta strongly 
 recommended— Rehance to be placed upon such Excreta rather than on 
 Guano — Chemistry can only help agriculturists after they have exhausted 
 all the means at their disposal — Notes on supply of guano and ou the 
 agriculture of Tuscany. 
 
 The European husbandman has, for centuries past, been 
 in the habit of taking away the produce of his fields, with- 
 out making compensation for the mineral matters removed, 
 and his fields have accordingly been continually diminish- 
 ing in fertility. 
 
 The Chinese husbandman has, for thousands of years 
 past, made it a practice to restore to his fields the mineral 
 constituents removed from them in the produce, and the 
 fertility of his land has accordingly kept pace with the in- 
 crease of the population. 
 
 The law of compensation, which makes the recurrence 
 or permanency of effects dependent upon the recurrence or 
 permanency of the conditions which produce them, is the 
 most universal of the laws of nature ; it governs all natural 
 
206 THEOKETICAL AND PKACTICAL AGRICULTUEE. 
 
 phenomena in their various phases, all organic processes^ 
 all the productions of man's industry. That the agricultu- 
 rist alone should ignore this law, nay, that his teachers and 
 guides should actually deny its operation, shows clearly 
 the condition of the schools in which the sons of our far- 
 mers are taught. 
 
 What Chemistry teaches about air, water, the process of 
 combustion, arable soil, the ash of plants, manure and its 
 constituents, is so easy of comprehension, that every well- 
 informed teacher may, in a dozen lessons, and with the sim- 
 plest means of instruction, impart to the commonest peasant 
 boy an accurate knowledge of these things ; particularly if 
 the teacher strictly confine himself to his subject. The lec- 
 tures occasionally delivered on matters of this nature at the 
 Eoyal Institution of London, by Professor Faraday, before 
 an audience of children, may be adduced in proof that it 
 is quite practicable to do so. 
 
 By command of King Maximilian, a movement in this 
 direction has of late been made in Bavaria. Five years 
 ago, all the teachers of the schools for training schoolmasters 
 were, for this purpose, specially instructed and exercised in 
 Munich. 
 
 The diffusion of this elementary knowledge among the 
 peasantry through the agency of the schoolmaster, will be 
 an immense step in advance, and will prove the very best 
 thing that the state can do in the interest of agriculture. 
 
 The boy who has been taught at school, even though 
 superficially, the conditions on which the fertility of the 
 field depends, and who has been told by his teacher, that 
 he who uselessly wastes these conditions is guilty of an 
 offence against the poor, against himself, and against society, 
 will certainly, when he grows up to man's estate, construct 
 receptacles for human and animal excrements, such as no 
 police regulations could ever compel him to provide. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 207 
 
 A superficial examination of the system prevailing in tlie 
 higher agricultural institutions, is sufficient to convince us, 
 that, such as they are at present, they are totally unsuited 
 for the requirements of our day. 
 
 The combination of the ordinary arrangements of a 
 school, with instructions in the practical work of agricul- 
 ture, does away with the benefits which might be derived 
 from such institutions, which are neither one thing nor an- 
 other; they are neither educational institutions nor good 
 practical workshops ; they possess some of the features of 
 both, but none of the good points of either. 
 
 The technical part of an industrial pursuit can be . 
 learned; principles alone can be taught. To learn the trade \ \ 
 of husbandry, the agriculturist must serve an apprentice- i ; 
 ship to it ; to inform his mind in the principles of the I i 
 science^ he must frequent a school specially devoted to this \i 
 object. 
 
 It is impossible to combine the two ; the only practicable 
 way is to take them up successively. I formerly conducted 
 at Griessen a school for practical chemistry, analysis, and 
 other branches connected therewith, and thirty years' expe- 
 rience has taught me that nothing is to be gained by the 
 combination of theoretical with practical instruction. A 
 student of chemistry who attends the lecture-hall and the 
 laboratory concurrently, positively defeats thereby the 
 object of his stay at the school, and misses the aim of his 
 studies. It is only after having gone through a complete 
 course of theoretical instruction in the lecture-hall that the 
 student can with advantage enter upon the practical part 
 of chemistry ; he must bring with him into the laboratory 
 a thorough knowledge of the principles of the science, or 
 he cannot possibly understand the practical operations. If 
 he is ignorant of these principles, he has no business in the 
 laboratory. ^ 
 
208 THEOKETICAL AND PRACTICAL AGRICULTURE. 
 
 In all industrial pursuits connected with the natural 
 sciences, in fact, in all pursuits not simply dependent on 
 manual dexterity, the development of the intellectual facul- 
 ties, by what may be termed " school learning," constitutes 
 the basis and chief condition of progress and of every im- 
 provement. A young man, with a mind well-stored with 
 solid scientific acquirements, will, without difficulty or 
 effort, master the technical part of an industrial pursuit; 
 whereas, in general, an individual who may be thoroughly 
 master of the technical part, is altogether incapable of seiz- 
 ing upon any new fact that has not previously presented 
 itself to him, or of comprehending a scientific principle 
 and its application. 
 
 I have often found that students coming from good col- 
 leges will speedily leave the pupils of industrial and poly- 
 technic schools far behind them even in the natural sciences^ 
 though the latter, when compared with the former, were at 
 first giants in knowledge. 
 
 I am far from wishing to question in any way the very 
 great utiUty of industrial and technical schools. I consider 
 them just as indispensable as higher schools ; for the same 
 road is not suited to all men, and every one does not pos- 
 sess an aptitude for the study of languages. The minds 
 of youth may be compared to a variety of ores, requiring 
 different furnaces for the smelting and extraction of the 
 metal, and the removal of the slags. But talent is like 
 gold ; wherever it occurs in nature it is found in its pure 
 state, never as an ore, and every furnace is equally suited 
 to it. 
 
 In our agricultural academies the training of the pnpils 
 in the mechanical and technical branches is continually 
 interfering with their proper instruction in principles and 
 theories in the school. Whenever a new sowing machine, 
 or a plough, or some other agricultural implement is to be 
 
THEOEETICAL AND PRACTICAL AGRICULTURE. 209 
 
 tried, the lecture-halls of Chemistry, Physics, &c., are 
 deserted. The greater portion of their teachers of Mathe- 
 matics and the Natural Sciences have received a university 
 education, and are, as may be expected, able scientific men , 
 but their teachings are held of secondary importance to the 
 practical work of husbandry ; they become speedily dis- 
 couraged; and, under sach circumstances, a solid course of 
 instruction in the natural sciences is out of the question. 
 I never yet met with one pupil trained at one of these insti- 
 tutions, who had a correct conception of the theory of dew, 
 or who was able to distinguish the seeds of the meadow 
 grasses, or the grasses themselves. 
 
 The learning of a technical pursuit is a different thing 
 from the acquirement of an art which demands practice. 
 The pupil of an academy of fine arts may see from day to 
 day what progress he has been making ; and this gives him 
 the necessary encouragement, which again tends to stimulate 
 his ardour, and makes him persevere in his efforts. But the 
 pupil at an agricultural academy has no standard by which 
 to measure the progress he has been making in technical 
 knowledge ; the incentive to exertion is wanting, and all 
 emulation ceases. 
 
 The young agriculturist who wishes to acquire a com- 
 petent knowledge, both theoretical and practical, of his pur- 
 suit, ought to visit, in the first place, a university to obtain 
 the necessary knowledge of the natural sciences, and after- 
 wards an agricultural institute, where the principles of 
 agriculture, and, at the same time, its practical operations, 
 are taught on a large scale. 
 
 Kow, if we reflect that the majority of our agricultural 
 academies have, for a generation past, been conducted in a 
 measure by men who have no knowledge whatever of 
 Chemistry, Physics, Botany, Geognosy, &c., the conviction 
 forces itself upon the mind, that they have been much more 
 
210 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 schools of idleness, and of opposition to all progress, than 
 institutions for advancement. 
 
 The conflict at present raging about the principles of 
 science and their application to practical husbandry, is the 
 work of these schools ; and no one need wonder if the prac- 
 tical man should hold science in little respect, nay, if he 
 should regard it with positive contempt. For, whence can 
 this estimation and regard for science proceed, except from 
 a knowledge of its principles ? 
 
 I am ready and willing to retract every word I have 
 uttered against these institutions, if any one will solve, in 
 some other way, the enigma which the antagonism between 
 the precepts of science and the practical lessons of agriculture 
 presents. The former do not simply embrace the principles 
 at which a single individual has arrived ; but they com- 
 prehend the general principles of all science. All chemists 
 and physicists, all students of nature and mathematicians, 
 entertain them, because they are simply expressions of that 
 method to which they all owe their success. 
 
 All practical men are agreed on this one point, that they 
 ought not to alter their practice on account of a doctrine, 
 however probable it may appear ; they demand to be first 
 convinced of its truth, and then, as a matter of course, all 
 opposition on their part will cease. This condition would 
 be reasonable enough, were there anything in this doctrine 
 which might possibly prove injurious to their interests ; but 
 their opposition is not directed against the doctrine, but 
 against common sense, and no science in the world can over- 
 come opposition of such a nature. 
 
 The scientific principles which chemistry wishes to in- 
 troduce into agriculture are so very simple, and the 
 demands made upon the practical husbandman are so much 
 to his own advantage, that, to an unprejudiced person, his 
 opposition is incomprehensible. 
 
THEOEETICAL AND PEACTICAL AGRICULTURE. 211 
 
 Science has taken upon herself to accomplish what was 
 beyond the power of practice, from its very nature, to do. 
 She has thoroughly examined the soil, the air, the excre- 
 ments of man and of animals, the roots and tubers of plants, 
 their leaves, stalks, seeds, and fruits, the blood and flesh of 
 animals ; she has, in short, investigated everything of a 
 combustible and incombustible nature contained in organic 
 bodies, and which is of importance in their production. 
 The results of her researches and analyses she has laid 
 before the practical agriculturist, and has shown him that 
 plants^ manures^ and the soil^ have certain constituent ele- 
 ments in common. From the constant presence of these 
 constituent elements in plants, she has inferred that they 
 are indispensable to the formation of the plant and its parts 
 — an inference which naturally leads to the conclusion that 
 they are equally necessary in the soil in which the plants 
 are to grow, as well as in the manure which is intended to 
 aid their growth. Science has also demonstrated, still with 
 the balance in her hands, that even a soil regarded as 
 abounding in these constituent elements contains in reality 
 only a comparatively very small proportion of them. 
 
 Science demands from the practical agriculturist no more 
 than that he should acquire the very trifling amount of 
 chemical information requisite to enable him to understand 
 the language of chemistry, and to test the correctness of 
 these facts. It would be absurd in the extreme to fancy 
 that this could in any way tend to interfere injuriously 
 with the practical operations of husbandry. She asks the 
 farmer to test the correctness of these facts in his own way ; 
 to prove by actual experiment, whether a field which does 
 not possess these constituent elements, is nevertheless a 
 fruitful soil for the production of cultivated plants ; and if 
 not, whether it may be made fruitful by a proper supply of 
 these matters. She asks him further to try if a field 
 
212 THEORETICAL AND PRACTICAL AGRICULTCJRE. 
 
 abounding in these elements is rendered barren by their 
 removal ffom it. Surely a trial of this kind cannot be said 
 to be of a nature likely to interfere injuriously with the 
 practical operations of husbandry. 
 
 When agriculturists have in this way acquired the con- 
 viction that the facts and inferences of chemistry agree 
 with the facts and results of the agricultural test applied, 
 everything has then been done that can be done by chemistry 
 for agriculture. The instructions given beyond this no 
 longer pertain exclusively to the domain of chemistry, but 
 are common to all sciences. 
 
 When, therefore, the agriculturist has, in the* manner 
 just described, ascertained that the facts and inferences 
 advanced by chemistry are fully borne out by the results 
 of agricultural experience, it can surely only be to his own 
 advantage to shape his practice by her lessons, and to make 
 the necessary changes in those portions of his operations 
 which he finds have been founded in error. It is not che- 
 mistry alone, but common sense, and everything besides 
 connected with these facts, which require him to do this. 
 Common sense tells him that he ought to provide for his 
 fields a proper supply of these constituent elements, and 
 restore them where they have been taken away, if he wishes 
 to make a barren soil produce fruit, or increase the fertility 
 of a fruitful field, or keep a very fertile field constantly at 
 the same high degree of productiveness ; it tells him that 
 the art of the agriculturist cannot simply consist in lower- 
 ing the high productiveness of a field to the level of ordi- 
 nary fertility, and in turning a fruitful into a sterile field. 
 
 It is held as a fundamental principle in science, that 
 every opinion, before it is admitted as true and taught to 
 others, should first be established by proper proofs, which 
 must not in any way run counter to undoubted truths, 
 such as, for instance, that twice two are four, and not five. 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 213 
 
 Inferences and conclusions which are opposed to such 
 truths are rejected by science, and it cannot surely be con- 
 sidered an unreasonable request, to ask agriculturists to 
 adopt the same principle as a guide in drawing their con- 
 clusions. 1^0 w, it is actually upon these points that the 
 conflict turns ; for the opposition is in reality directed, not 
 so much against the facts and teachings of chemistry, as 
 against the deductions drawn from them by common sense. 
 
 The exposition of the scientific principles of agriculture 
 is not a thing of yesterday, but dates so long ago as seven- 
 teen years ; and the system of husbandry as taught in our 
 agricultural institutions (see Letter I.), could certainly not 
 have so long withstood the power of truth and common 
 sense, had it not been separated from them as if by a wall, 
 and defended from their attacks. 
 
 The chemical truths in these Letters may be expressed 
 by a simple formula, which, though bearing a somewhat 
 mathematical appearance, is yet plainly intelligible to every 
 one: 
 
 P = F — E. 
 
 The P in this formula stands for Produce (Corn, Pota- 
 toes, Turnips, &c.); the F. stands for Food (Phosphoric 
 acid, Potash, Lime, Ammonia, &c.) ; the E stands for Ee- 
 sistance. 
 
 Expressed in words the formula stands thus : 
 The amount of produce yielded by a field corresponds 
 with, or is proportionate to the quantity of food in the soil 
 (to the conditions for the production of the crop), minus 
 the sum of the resisting forces which hinder the production 
 of the crop from the elements of food present. Let the 
 letter F stand for six slices of an apple, and the letter E 
 represent three fingers keeping a firm hold on two out of 
 the six slices, there will remain only four slices free, which 
 may be eaten by another person. 
 
214 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 The entire contents of these Letters are simply a develop- 
 ment of this formula. Everything that is said in them 
 about amount and increase of produce, fertility, cultivation 
 of the soil, manure, &c., is comprised in it. It is evident 
 that if the formula be true, its application will embrace 
 millions of receipts for the improvement of millions of 
 fields, and for the continued production of the largest 
 crops; and that the future prospects of our fields, and 
 wealth and income of all agriculturists, will be dependent 
 upon its strict and rational application. No one can then 
 deny, that the development of this formula is of some im- 
 portance to agriculturists, and its discussion of some value 
 to them. 
 
 Whatever progress has been made by practical agricul- 
 ture for some thousands of years past in the knowledge of 
 manures, is clearly referable to those true principles which 
 constitute the basis and conditions for correct conclusions. 
 
 Guided by a careful study of the elements of the food 
 of plants, science, in the year 18-iO, pointed out to the 
 \ agriculturist guano as one of the most infallible means of 
 raising the produce of corn and flesh, and most urgently 
 recommended its application. Before 1840, guano had 
 never been used as manure on a European field. When 
 the first vessel loaded with guano arrived at Liverpool, 
 numerous experiments were made with the new manure, 
 which proved failures ; and agriculturists were not agreed 
 about its utility until they had practically tested its use. 
 Since that time many hundreds of ships have passed to and 
 fro, and have brought to the European Continent guano to 
 the value of above 300,000,000 florins (£26,000,000) ; and 
 within the same period there has been produced a surplus 
 of more than 400,000,000 cwt. of corn, or of its equivalent 
 in flesh. It is true, guano would have found its way to 
 Europe even without the recommendation of science ; for 
 
THEOKETICAL AND PEACTICAL AGRICULTURE. 215 
 
 a kind Providence makes the apple ripen in proper season, 
 and if it drops from the tree and rots, the fault lies with 
 man, or with the soil, if the seeds do not germinate. But 
 guano would probably not have made its way so speedily. 
 In the late seasons of sterility through which we have 
 passed, it has been the means of alleviating the wants of 
 many millions of men. 
 
 The man of theory who predicted the effects of guano 
 had not seen the favourable results of its application, which 
 our "Nitrogen champions" had subsequently occasion to 
 observe in England ; but the predictions of its utihty had 
 been simply based on the results of its chemical analysis, 
 and was only a corollary deduced from the principle, that 
 it is indispensable to resk>re to the jield exhausted by the growth 
 of corn the mineral elements taken away in the crops. 
 
 Not pseudo-chemistry, but science, placed in the hands 
 of the agriculturist the means of making phosphate of lime 
 more readily available for the nutrition of plants, by treat- 
 ment with sulphuric acid ; and the results of the practice in 
 England for the last ten years have shown, that by the use 
 of this means the amount of provender for cattle has been 
 increased to the same extent as if the area of every field for 
 green crops had been doubled. There have been produced 
 since then, on the same area, many million cwt. more flesh 
 than formerly, or its equivalent in corn. 
 
 And the man of theory who advised the use of this 
 means had not seen its effects, as our agricultural chemists 
 in England have seen them ; but he had simply inferred 
 them from the principle, that the action of a manuring agent 
 in a given time m^ust increase in proportion as its surface in- 
 creases. 
 
 Whatever practical agriculturists^ and agricultural socie- 
 ties may do, whatever they may resolve at their annual 
 meetings, every penny spent will be thrown away, and 
 
216 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 every year of experimenting will be in vain, so long as 
 these practical men will not submit to the teachings of true 
 experience, to the rules of logic or of common sense : from 
 the instant they shall so submit, science will be theirs. 
 
 There exists a receipt for insuring the fertility of our 
 fields and the permanence of their crops, and which, if pro- 
 perly and consistently applied, will prove more remunera- 
 tive than all the expedients that have ever before been 
 resorted to by agriculturists. It consists in the following 
 rule: 
 
 Every farmer who takes a sack of corn, or a cwt. of rape, 
 turnips, potatoes, &c., to the town, ought, like the Chinese 
 coolie, to carry back with him from the town an equal (or, 
 if possible, a larger) quantity of the mineral constituents of 
 the produce sold, and restore them to the field from which 
 they have been taken. He should not despise the peel of a 
 potato, nor a straw, but always bear in mind that that peel 
 may be wanting to form one of his potatoes, that straw to 
 form one of his ears of corn. The cost of carrying these 
 matters to his fields is trifling, and the investment is as 
 safe as a savings-bank, and highly productive withal. The 
 fertile area of his field will, in the course of ten years, be as 
 it were doubled ; he will produce more corn, more flesh, 
 and more cheese, without having, on that account, to 
 bestow greater labour and time upon the cultivation of his 
 land ; he will be less anxious about his fields, and need no 
 longer keep his mind constantly on the stretch for some 
 new, unknown, and imaginary expedient to preserve their 
 fertility in some other way. 
 
 All the proprietors of the soil in every great country 
 ought to form a society for the establishment of reservoirs 
 where the excreta of men and animals might be collected, 
 and converted into a portable form. Bones, soot, ashes, 
 lixiviated and unlixiviated, the blood of animals, and offal 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 217 
 
 and refuse of all kinds, ought to be collected together in 
 these establishments, and prepared for transport by the 
 society's own officials. 
 
 To render the execution of a plan of this kind possible, 
 government and the police authorities should take measures 
 to insure the proper construction of latrines and sewers in 
 towns, to guard against the waste of the night-soil, &c.* 
 This must of course be a preliminary arrangement ; but, 
 when once made, an annual subscription of half-a-florin 
 from every farmer, every peasant in the land, will suffice to 
 call into existence establishments of this kind in every 
 town ; and there can be no doubt that these establishments 
 will speedily become self-supporting, if every agriculturist 
 will only make up his mind to act strictly upon the advice 
 here given. 
 
 Agriculturists must not rely upon guano ; its price at the 
 present time, as compared with an earlier period, is already 
 doubled ; and no sensible man would entertain the idea of 
 making the production of an entire country dependent on 
 the supply of a foreign manurcf 
 
 * Judicious arrangements have already been adopted last year in Munich, 
 by the Minister of the Interior, with a view to the improvement of the sani- 
 tary condition of the city. The success of these measures will materially 
 depend upon the manner in which the proprietors of the houses appreciate 
 and aid the wise intentions of government, 
 
 f It is almost to be feared that guano will play a momentous part in his- 
 tory. "When it is considered that one cwt. of that manuring agent contains 
 the effective mineral constituents of between 25 cwt. and 30 cwt. of wheat, 
 or of an equivalent amount of some other produce, and that, when used as 
 manure, it produces, in a succession of crops, a corresponding quantity of 
 elements of food, some conception may be formed of the immense value 
 which the guano beds of America possess, with reference to the production 
 of corn in Europe. From the enormous increase of the population of Lon- 
 don, and other large cities of Great Britain, the loss which the English fields 
 sustain annually in the main conditions of their fertility, is every year becom- 
 ing more and more considerable ; and it would appear that the obstacles 
 
 10 
 
218 THEORETICAL AND PRACTICAL AGRICULTURE. 
 
 Agriculturists must in the first place learn to turn to the 
 best account all the means and resources at their command ; 
 when they have done this, but not till then, will chemistry 
 be able to do them good and useful service. But so long 
 as they expect this science to present them with potent 
 charms for fertility, there is no help for them. They must 
 bear in mind, that wherever success does not attend a good 
 cause, the fault lies in want of energy in using the proper 
 means ; for these are always to be found.* 
 
 which ogpose the collection of the human and animal excrements are alto- 
 getlier insurmountable, at least as regards London. It is evident, therefore, 
 that England, in order to remain permanently a corn-growing country, 
 requires a free and plentiful supply of guano (even now Great Britain con- 
 sumes nearly nine-tenths of all the guano brought to Europe). Fifteen 
 years ago the American agriculturists looked down upon guano with a 
 species of contempt ; but things have greatly altered since then ; and it is 
 said that last year about eight million cwt. of that manuring agent were 
 imported into the United States. In the actual position of English Agricul- 
 ture, America, by her guano-beds, rules the prices of all the corn-markets of 
 Europe, and more especially in England; and should circumstances ever 
 arise to prevent the importation of guano into England, a state of things 
 would ensue in that country of which the consequences might be 
 incalculable. Bloody wars have sometimes sprung from causes of much less 
 importance. 
 
 * If we ask the opinions of different persons on the question of " sewage," 
 we receive contradictory answers. All manufacturers of super-phosphate of 
 lime are quite agreed on the point, that only the fluid portions of sewage, or 
 the matters dissolved in sewage water, are valuable in agriculture. They do 
 not, in giving this opinion, deny the good effect of the solid matters^ but only 
 mean to say that they are not worth the trouble of being collected for 
 manure, because they are ready to deliver fi'om their manufactories these 
 matters to agriculturists. The manufacturers of ammonia salts, and the 
 dealers in guano, take an entirely opposite view. These hold that only the 
 solid sewage matters are to be looked upon as important. There can, how- 
 ever, be no doubt that both the fluid and solid matters are valuable for 
 agriculture. 
 
 " The use of these fertilising matters is not confined to the estates and farms 
 in the immediate vicinity of the centres of population and consumption. Our 
 peasants go long journeys with their wretched carts to seek substitutes for 
 
THEORETICAL AND PRACTICAL AGRICULTURE. 219 
 
 the deficient quantity of their farm-yard manure. The industrious peasant 
 of Lucca is worthy of ranking with the Chinese coolie. Enjoying the bless- 
 ings of irrigation within a circle of twenty-eight miles (English), the former, 
 who has never even heard of the name of guano, manges to reap two crops 
 in the year ; and yet never allows his land to lie fallow. He goes, however, 
 with his cart, not only to the neighbouring town of Lucca, but even as far as 
 Pisa and Leghorn, to collect the contents of the sewers, with the aid of which 
 he produces, by indefatigable labour, marvellous crops, and raises food suffi- 
 cient for the most dense population of the old duchy. The boats of Viarreggio 
 carry from this port the goats' dung of the Maremma, to manure the olive trees 
 of the Apuan coast." 
 
 " From the peculiar circumstances m which our Maremmas are placed, they 
 are debarred from the benefit of a like restitution of the conditions of fertility. 
 Cultivation slowly improves, and the amount of produce reaped increases 
 every year; but the scanty and migratory population of a soil, deserted on 
 account of the miasmatic exhalations, cannot yield an amount of fertilising 
 matter in proportion to the quantity carried off from the land. The gradual 
 introduction of the system of the rotation of crops might slowly lead to the 
 same impoverishment of the soil which has resulted in other places from the 
 'high system of farming.' The apprehension lest this should in reality be the 
 result of it, has by no means escaped the attention of the proprietors and 
 cultivators of the soU in the Grand Duchy, who are so earnestly endeavouring 
 to make agriculture flourish in these parts. The barrenness and desolation 
 which has so long been the fate of the Maremma may, perhaps, be partly 
 attributable to the spoliation system of farming pursued by the ancient Romans 
 and Etruscans." 
 
 " Agriculture in Tuscany, then, is based upon the principle of restoring to 
 the soil those elements which science points out to be the most efficacious for 
 the growth of plants ; and in this respect it is far ahead of the system pursued 
 in other countries," Sec. — {Set nuove ktiere chimiche sulV agricultura di Ckusto 
 Liebig, compendiaie et annotate de Gustavo Dalgas, Dr. Fhilosoph. Firenze^ Felice 
 Paggi, 1858, p. 93.) 
 
APPENDIX. 
 
 TO LETTER VI. 
 
 In the cultivation of grass for a season merely, or in the planting of 
 a particular kind of grass or of several sorts combined, the nature of 
 such grass or grasses is essentially a matter for consideration, but not 
 so in the case of the sward. Just as the beech tree when standing 
 alone covers a broad space, and nearly sweeps the earth with its richly- 
 leaved boughs, while a number of the same trees, standing closely 
 together, tower upwards like columns, and merely clothe themselves 
 with branches and leaves at the very summit, so in the sward of the 
 natural meadow, plant closely clings to plant, altering its very struc- 
 ture in yielding to the law of necessity. 
 
 Those kinds of grasses which do this in a less degree, such as 
 meadow soft-grass {Hblcus lanaius, L.), are on this account less suited 
 for meadow plants, whilst others, though coarse-tufted, such as cocks' 
 foot-grass (Dadylis glomeraia, L.), and even tm-fy hair-grass {Aira 
 caespiiosa, L.\ form large separate tufts only with an inferior sward. 
 
 In the spring of 1857, I examined a patch of quite new grown turf, 
 which was exceedingly fine and close, taken from the ground facing a 
 ditch used for the draining of a large meadow ; I found on an area of 
 11-85 square in. Hess., 265 grasses. On an older piece of turf taken 
 from the irrigated meadow having an area of 14*4 square in., I found 
 210 grasses and 12 other plants ; and on another patch of an area of 
 13*2 square in., 150 grasses and 25 other plants. 
 
222 APPENDIX. 
 
 These high figures sufficed to confirm me in my original supposition, 
 that only a small portion of the store of plants is completely developed 
 in one year, and that a change of plants takes place according to the 
 altered influences of the atmosphere and the soil ; a fact which, ac- 
 cording to Thaer, has been already noticed by others, and, as it ap- 
 pears, was also observed by Schwerz. 
 
 It is well known that many plants, when a condition indispensable 
 to their perfect development ceases to exist, as for instance, where the 
 over-hanging shade of growing timber, or a too great clearance, pre- 
 vents their growth, will for years retain existence by the extension of 
 their roots, remaining as it were at a lower stage of growth, till there 
 is a return of more favourable circumstances for their development. 
 
 Thus we find that cleared ground will frequently become imme- 
 diately covered with plants, many of which, being perennials, such 
 as the raspberry, could not have sprung from seed. I have proved 
 that this state of things is very general and is not confined to cases 
 alone where the impediments to the growth of the plants are so con- 
 siderable, but that it applies also more especially to grasses, and is of 
 the highest importance in the cultivation of meadows. 
 
 Every one knows that ash draws forth clover plants (which, like the 
 grasses, do not flower the first year) ; and likewise that after manuring, 
 other kinds of grasses make their appearance on the meadow. I ob- 
 served on a plot manured with so-called acid-phosphate of hme, the 
 almost exclusive growth of a single kind of grass, French rye-grass 
 (Arrhenaterum avenaceum), which came up in thickly serried blades, 
 whilst on the unmanured ground but a few stalks presented them- 
 selves. 
 
 I have examined the stock of plants on meadows at the time of the 
 development of the culms. I had pieces of turf carefully cut out, 
 measured, and the soil washed away, which left a dense mat of closely 
 interwoven roots. There were found on one square foot, Hess. in. : 
 
 1. Irrigated meadow near Zerby: dry patch. Predominant: — Bromus 
 mollis, L,, ei Arrhenaterum avenaceum P.B. Size of sod, 22 square inches ; 
 containing 472 plants; in stalk, 36. 
 
APPENDIX. 223 
 
 2. Irrigated meadow, same place: wet patch. Predominant: — Glyceria 
 fluitans. Size of sod, 20 square inches ; containing 1230 plants; in stalk, 20. 
 
 3. Dry unirrigated meadow, near Fehlheim : manured with compost. Pre- 
 dominant: — Agrostis alba et vulgaris. Size of sod, 56 square inches; con- 
 taining 668 plants, of which there were 601 grasses and 67 other plants; in 
 stalk, 66. 
 
 The other plants consisted of Lysimachia nummularia, BeUis jperen- 
 7iiSj L., Veronica chamcedris, Ranunculus , Rumex. 
 
 4. Irrigated meadow, near Fehlheim, somewhat mossy. Predominant: — 
 Poa irivialis, Festuca jpratensis^ Avena jiavescens, Fesiuca rubra, Agroslis vul- 
 garis. Size of sod, 55'25 square inches; containing 730 plants, of which 
 there were 584 grasses, 182 other plants; in stalk, 125. 
 
 The other plants consisted of Plantago, Daucus, Veronica, Rumex, 
 Ranunculus, Chrysanthemum, Trifolium repens, Lathyrus. 
 
 5. Meadow near Balsbach, in the Hessian Odenwald (counted by Peter 
 Kreuz, of that place). Predominant : — Agrostis siohnifera and Anthoxanthum 
 odoratum. Size of sod, 1 square foot; containing 1176 plants, of which there 
 were 1070 grasses, 56 clover, and 80 other plants; in stalk, 38. 
 
 6. Meadow near Balsbach, in the Hessian Odenwald (counted by Peter 
 Kreuz, of that place). Predominant: — Lolium perenne, Festuca pratensis, 
 Dactylis glomeraia. Size of sod, 1 square foot; containing 790 plants, of 
 which there were 710 grasses, 80 other plants (before the second cutting, 
 without stalks). 
 
 7. Meadow near Balsbach, in the Hessian Odenwald (counted by Peter 
 Kreuz, of that place). Predominant: — Festuca rubra, Agrostis stolonifera, 
 Anthoxanthum odoratum, Cynosurus cristatus. Size of sod, 1 square foot; 
 containing 920 plants, of which there were 800 grasses, 120 other plants ; in 
 stalk, 14. 
 
 In numbers 5, 6, and 7, an entire square foot of sod was examined, 
 which must have been a most arduous and laborious undertaking. 
 The examiner (Mr. Peter Kreuz) says : " We have carefully separated 
 the single plants, and to guard against mistakes, collected them in little 
 heaps of 10, and afterwards in heaps of 100 plants, by putting 10 of 
 the small heaps together." 
 
224 APPENDIX. 
 
 8. Unirrigated meadow in the parsonage garden of Hohenstein : not irri- 
 gated, mossy, with tolerably dry soil (counted by the Rev. Mr Snell, of that 
 place). Predominant : — Alopecums, Badylis, Arrhenaterum avenaceum. Size 
 of sod, 1 square foot, Nassau measure; containing 1040 plants, of which 
 there were 832 grasses, 80 clover, 128 other plants; in stalk, 208. 
 
 The other plants consisted of Planiago, Leontodon, Veronica, Lysi- 
 machia nummularia. 
 
 9. Dry unmanured meadow, near Fehlheim : weedy (counted by the author). 
 Size of sod, 60 square inches; containing 379 plants to the square foot 
 (Hessian), of which there were 276 grasses, 103 other plants; in stalk, 0. 
 
 The other plants were Planiago, Prunella vulgaris, BeJlis, Ranuncu- 
 lus, HieraciuTn, Veronica, Carex. 
 
 Sinclair found on one English square foot, equal to about 1^ square 
 foot, Hessian in : 
 
 Yery rich natural meadow, 
 
 at Endsleigh, . 
 Rich old meadow, at Croft' 
 
 church. 
 Old meadow at Woburn, 
 Old meadow at "Woburn, soil 
 
 moist, surface mossy, 
 Irrigated meadow. 
 
 If we place the figures given by me by the side of those of Sinclair, 
 properly reduced, we find that they agree as closely as can well be ex- 
 pected : 
 
 Hanstetn. Sinclair. 
 
 1230 1200 
 
 1176 — 
 
 920 — 
 
 790 726 
 
 730 — ■ 
 
 668 666 
 
 472 606 
 
 379 423 
 
 :\ 
 
 Plants. 
 
 Grasses. 
 
 other plante. 
 
 1000 
 
 940 
 
 60 
 
 1090 
 
 1032 
 
 58 
 
 910 
 
 880 
 
 30 
 
 634 
 
 510 
 
 124 
 
 1798 
 
 1702 
 
 96 
 
APPENDIX. 225 
 
 This comportment of the grasses is of the highest importance; 
 it explains the fact of the permanent duration of natural meadows, 
 and the certainty of their yield; it is this property that causes " the 
 sward, which in the temperate zone neither heat nor cold can destroy, 
 to be clothed with perpetual verdure." 
 
 The large number of plants which are in a low stage of develop- 
 ment, await, as if in a slumbering state, the coming of the time for 
 their perfect development ; the more important plant is in such case 
 replaced by the plant of lesser pretension, until the conditions of per- 
 fect growth have again returned for the former. — H. Hdnstein — Jour- 
 nal for Agriculture, IX. year, p. 270. 
 
ADDENDA. 
 
 SHOULD THE FARMER BE EDUCATED? 
 
 Although it has been said that every farmer should not 
 try to be a geologist, meteorologist, chemist, etc., or study 
 medicine to be his own doctor, or law to make it unneces- 
 sary to employ a lawyer, or theology with the sole view of 
 doing his own preaching, still there is little doubt that all 
 general information, and the more exact the better, has a 
 great tendency, if well applied, to be useful to the farmer's 
 best interests. Every cultivator desires to gather from the 
 soil, at small expense, large crops, with as little injury as 
 possible to the source of production. He cannot do this 
 without being familiar with general principles in the 
 various departments of his profession, and understanding 
 most thoroughly the art of agriculture. The man who 
 grows crops well must understand the nature of soils, 
 which certainly includes more research than would enable 
 him to arrive at the sage conclusion that one is sandy and 
 another clayey, etc. Then what should be the extent of 
 the farmer's education ? Who will answer the question ? 
 One person is found fault with for being " too scientific ;" 
 another, for not being enough so. Now, suppose all 
 
228 ADDENDA. 
 
 should practise with science, cast away prejudice, and seek 
 to apply knowledge for its own dear sake, we might hope 
 for rapid progress in mental acquisition, national wealth, 
 and prosperity. If the farmer was not placed in such 
 close relation with almost every department of science — in 
 a word, with Nature's endlessly beautiful and diversified 
 works — it would not be difficult to define what should be 
 the extent of his education. Let us apply truths as fast as 
 we discover them, and not find fault with the man of 
 science because he cannot supplant the Divine Architect. 
 It would be impossible for any agriculturist, during his 
 whole life, to study any one department bearing on his 
 calling to its fullest extent ; and, therefore, who will ven- 
 ture to advise when he shall cease to explore and grieve 
 over the exhaustion of the realms of knowledge ? 
 
 ' SCIENCE AND COMMON SENSE.— P. 215. 
 
 Liebig truly says, " Whatever practical agriculturists and 
 agricultural societies may do, whatever they may resolve 
 at their annual meetings, every penny spent will be thrown 
 away, and every year of experimenting will be in vain, so 
 long as these practical men will not submit to the teachings 
 of true experience, to the rules of logic or of common 
 sense ; from the instant they shall so submit, science will be 
 theirs." 
 
 How very different is the meaning of the expression 
 ** common sense " when unfolded in the light of science as 
 
ADDENDA. 229 
 
 compared with its ordinary acceptation. The words, as in 
 everj-day use, are of little value, but how telling is their 
 effect when under the control of science, as used by Baron 
 Von Liebig. Some agricultural writers speak of " common 
 sense unaided by science ;" which seems to be a desire to cater 
 to the prejudices of an uneducated class of farmers. This 
 is beneath the dignity of a man, who should be guided by 
 truth alone. The expression common sense, as some people 
 use it, is exceedingly indefinite; for every person, from 
 the fool to the philosopher, has a common sense standard 
 of his own, differing from that of every other man ; and 
 as no two minds are exactly alike, the varieties of common 
 sense are in proportion to the number of persons who ad- 
 mit such faulty expressions. Science has to do with the 
 observation and classification of the truths or laws of 
 nature. Common sense, as in every-day use long ago, 
 said the world was flat ; science has proved it to be round. 
 She has resolved the once mysterious soil into the constitu- 
 ents or elements of plants, and told us of their qualities 
 and quantities. Common sense, as used by the crowd, 
 never said a word on the subject. Why should any one 
 say, as we find in some of the books, that " the roots of 
 plants themselves go out in quest of that food," which com- 
 mon sense, unaided by science, tells us is " by them communi- 
 cated to the plant?" To follow this style of argument 
 would be very uncommon sense. Agricultural writers 
 should not draw lines of distinction between the practical 
 intelligent farmer and scientific man. Science and practice 
 should come together ; for in exact proportion to the union 
 between them will agriculture prosper. Why repudiate 
 
280 ADDENDA. 
 
 science, and in the same breath say, " If you wish to make 
 a youth a shoemaker, you must first send him to school in 
 order that his mind may be expanded and prepared to re- 
 ceive the seeds of practical instruction." If the farmer is 
 to depend so much on " common sense," and so little on 
 science, why does not the shoemaker, feeling that there is 
 nothing like leather, graduate with the wax-end in his 
 hand ? which would be carrying out the maxim, " Ne sutor 
 ultra crepidamy Even tinkers claim that their collabora- 
 teurs should be men of common sense, but it is their busi- 
 ness to bottom kettles. A tinker need not trouble his mind 
 with the science of mining or the manufacture of the useful 
 metal which he hammers. The farmer who is averse to 
 scientific education, is but an agricultural tinker. Let the 
 cultivator of the soil arouse to the dignity of his calling. 
 
 Let it not be forgotten that science has made the rough 
 places smooth, and interlaced the face of Christendom with 
 railroads, over which the commerce of nations is sent to 
 and fro for the use of busy man. She has prepared the 
 way for, and sent the steam-engine through, the trackless 
 forest, disturbing the haunts of the red man and wild beast 
 with the sound of civilization, and, like Prometheus, 
 brought the fire from heaven to be the errand-boy of the 
 human race. 
 
ADDENDA. 231 
 
 AaRICULTURAL MACHIKES. 
 
 If necessity be the motlier of invention, it will not be 
 denied that she possesses to some extent parental protection 
 over discovery. Invention and Discovery are members of 
 one family. In an agricultural point of view, necessity, in 
 this country, and indeed many others, has not caused the 
 gathering of knowledge for general application to the cul- 
 ture of the soil. New land is so easily got and so produc- 
 tive, except in a few places, that the necessity for modes of 
 culture other than those of the most common kind has not 
 been generally felt by landed proprietors. Let us think 
 of the growing want for soil on which to operate, by the 
 rapidly increasing home population, immigrants, and the 
 general introduction of labor-saving machinery. Necessity 
 has been, in this case, of great value to the nation in 
 developing its resources. The demand for labor-saving 
 machinery has called into action the intellect of the land, 
 which has invented and constructed for agricultural pur- 
 poses, reaping, mowing, and threshing machines, etc., all 
 suited for well cultivated soil, free from stumps, and equally 
 so to all other parts of the country, as fast as they become 
 so. The mowing machine lays a basis for more animal 
 food, for by it the material necessary for its production may 
 be gathered more easily. The fact that the agricultural 
 machinery of to-day — should there be no more inventions 
 — applies to soil all over the globe, may assist us in form- 
 ing a correct estimate of the future vastness of agricultural 
 operations. 
 
232 ADDENDA. 
 
 At a great national exhibition, as for instance, like that 
 of the Fair of our American Institute, it is exceedingly in- 
 teresting to examine the labor-saving contrivances that 
 come from the mind, and to see visitors looking at the life- 
 like things, whose muscles of iron and steel perform so 
 important a part in the development of national wealth and 
 prosperity. Here may be seen the labors of the brain- 
 wearied inventor, of whom it has well been said : 
 
 "In the great scale of being which with God began, 
 there is no created intelligence which approaches him in 
 dignity. Next to the eternal Architect, at whose bidding 
 the vast machine of the universe came into being — whose 
 cunning hand moulded the wondrous mechanism of our 
 frames — he stands ; creating out of the airy fabric of the 
 brain the magic forms which never die. Look back upon 
 the track of time, and what survives its wreck ? Here- and 
 there upon the strand a solitary monument of literature, 
 of marvellous beauty — out of the millions of books which 
 have delighted their millions of men — survives to tell us 
 that the rest have perished ; but every creation of the 
 inventor, from the first dawn of time to the present hour, 
 exists among us. As time rolls on it but widens the circle 
 and adds glory to the memory of those whose works sur- 
 vive them. The names of millions have perished, but the 
 thoughts they thought will never die. Their blessings, 
 like the air and light, are now our daily life ; but when we 
 reflect, we know there was a time when they did not exist, 
 and that the art of the engineer produced them all. Civi- 
 lized men have reared their monuments and worship at 
 their shrine. The splendid temple whose lofty arches 
 
ADDENDA. 233 
 
 sprang into tlie skies, above the trees of tlie forest, and the 
 palaces of kings erected by a great nation and devoted to 
 them, is the world's tribute to genius — the acknowledg- 
 ment of the mastery of the mind. As I stood within its 
 crystal walls, and gazed into its gorgeous dome, the 
 shadows of the mighty dead in solemn pomp passed by. 
 Archimedes, and Bacon, and Watt, and Fulton, Gutten- 
 berg, Gralvani, Franklin, and Torricelli, and a host of other 
 immortal ones; and in shadowy outlines their mighty 
 works — the printing-press, the steam engine, the electric 
 wire, the foaming steamer, the unerring compass, the 
 roaring cannon. The powers of the earth attend their foot- 
 steps — the lightnings of heaven obey their commands. 
 My soul drank in the inspiration of the fairy scene, and I 
 felt the dignity of his calling." 
 
 Stop the machinery of the world for a day, and a blank 
 would be left in its history that would throw a gloom over 
 coming ages. Even the plough and less respected plough- 
 boy should they forget their labors, fields of golden grain 
 would be things of the past. The labor saved by machinery 
 is applied to new purposes either mental or manual ; and 
 the consequence is new development. The inventor of a 
 machine to do the work of many men and oxen is a useful 
 laborer. 
 
234 ADDENDA. 
 
 " MORE BREAD AND MEAT.— P. 1. 
 
 " The most urgent problem wliich the present day has 
 to solve," says Liebig, "is the discovery of the means 
 of producing more bread and meat on a given surface, to 
 supply the wants of a continually increasing population. 
 The most important social questions are bound up in this 
 problem, which science is expected to solve." The problem 
 spoken of by the great Liebig has a world-wide significance. 
 Let us look at some of its facts in their relation to our 
 own country with a view to showing the necessity for a 
 rational system of agriculture. The production of more 
 bread and meat is of daily increasing importance. We 
 want more in time of war and peace to sell to other people. 
 The increase of animal food is not keeping pace with the 
 increase of population. We have no figures of more recent 
 date than those given below, which, if not exact^ come near 
 enough to the truth for general purposes. There is every 
 reason to suppose that the next census would show more 
 strongly the necessity for growing more meat. The follow- 
 ing table gives the number and increase of cattle in the United 
 States. 
 
 
 1840. 
 
 1850. 
 
 Horses and mules, 
 
 . 4,385,399 
 
 4,896,050 
 
 Neat cattle, 
 
 . 14,971,586 
 
 18,378,907 
 
 Swine, 
 
 . 26,201,293 
 
 30,854,213 
 
 Sheep, 
 
 . 19,111,374 
 
 21,723,290 
 
 The increase of 'population has been S5 per cent.j while that 
 of cattle has been only 20 per cent. 
 
ADDENDA. 235 
 
 In New England, New York, New Jersey, Delaware, 
 Maryland, and Virginia, tlie three principal meat-producing 
 animals, cattle, slieep, and swine, have been rapidly de- 
 creasing, as is shown by the following tables : 
 
 DOMESTIC ANIMALS IN THE OLD STATES. 
 
 
 1840. 
 
 1850. 
 
 Decrease. 
 
 Horses and Mules, 
 
 1,612,883 
 
 1,529,189 
 
 83,694 
 
 Neat Cattle, 
 
 6,172,569 
 
 6,033,841 
 
 138,728 
 
 Swine, 
 
 6,897,396 
 
 4,909,334 
 
 1,988,062 
 
 Sheep, 
 
 11,872,622 
 
 5,450,678 
 
 6,421,950 
 
 The population has been increasing in the Old States, 
 while the meat-producing animals have been decreasing. 
 
 It is now quite natural to look to some of the New States 
 for a supply. The following table will apply to the States 
 of Indiana, Ohio, Kentucky, Illinois, Tennessee, and Mis- 
 souri : — 
 
 DOMESTIC ANIMALS IN THE NEW STATES. 
 
 
 1840. 
 
 1850. 
 
 Increase. 
 
 Horses and Mules, 
 
 1,804,092 
 
 2,116,160 
 
 312,068 
 
 Neat Cattle, 
 
 4,307,952 
 
 5,280,433 
 
 972,481 
 
 Swine, 
 
 11,726,209 
 
 13,843,041 
 
 2,116,832 
 
 Sheep, 
 
 5,197,906 
 
 8,435,658 
 
 3,237,752 
 
 The increase of animals in these States for the ten years 
 ending 1850, is shown in the above table. 
 
 Our exports of breadstuffs and animal products were as 
 follow : — 
 
236 ADDENDA. 
 
 1836— '40 inclusive, $63,050,000 
 
 1842— '46 " ..... 110,521,000 
 
 1847— '51 " 194,330,000 
 
 1852 — '56 " 233,697,000 
 
 From the foregoing it will be seen that our exports 
 during the periods named were gradually increasing, nor 
 is there any reason to suppose that the markets abroad are 
 falling off in their demand. These, of course, have their 
 influence on the money value of bread and meat. Every 
 pound of salted meat sent to other countries will affect the 
 price of animals in the most distant parts of the United 
 States. This puts money in the pockets of producers, while 
 it increases the cost to less productive consumers who live 
 in the towns and cities. By looking at the first table, which 
 refers to the numl:jer and increase of cattle in the whole of 
 the United States, it will be seen that the increase has been 
 only about twenty per cent., whereas the increase in the 
 population has been thirty-five per cent. These are strange 
 facts to be true of the cattle raised on the soil of the United 
 States. And we are beginning to feel their result, for we 
 have had to pay more and more for meat — the price has 
 been gradually increasing for a long time. 
 
 Many farmers near large towns and cities cannot afford 
 to make butter and cheese from their milk, on account of 
 the demand for it, and the facility of getting it to market 
 by railroads. This milk business is destructive to cattle ; 
 the calves as well as the milk are sent to market; and 
 these facts, of course, have their influence on supply and 
 demand. 
 
ADDENDA. 237 
 
 It is impossible that the prices of meat should long 
 continue high in any town or city of importance ; for, if 
 the supply is abundant, the prices soon become equalized 
 all over the country, less the cost of transportation, the 
 means of getting it to market are so easy. The increase 
 in prices has hardly caused us to eat less meat ; and as the 
 quality is improving with our appreciation, we do not break 
 up habits already formed — those of a meat-eating people. 
 
 These facts and figures do not show that the cost of 
 meat is owing to an unusually short supply of animals for 
 any one or two seasons, short crops, increase of foreign 
 demand (although this has had its influence), fluctuations 
 of trade, or to causes of much importance besides the 
 disproportion between the number of animals and our 
 rapidly-increasing population — that is to say, the results 
 have been subject to the invariable law of demand and 
 supply. The principle in this question is easily under- 
 stood. If a family of six persons have a given quantity 
 of meat which is equally divided, each person will have 
 twice as much for his share as would the individuals of a 
 family of twelve persons from the same quantity. The 
 same facts are true of a nation, which is nothing more 
 than a big family. Although animals are increasing in 
 the great North- West, there is a want on the part of the 
 increasing population of all ike States^ not being supplied 
 at the prices of by-gone days ; nor is there any likelihood 
 of an immediate remedy. That meat will cost less under 
 this state of things, for a long time to come, is impossible. 
 We take it for granted that this increase in price for many 
 years past, as figures show to be true, puts this subject 
 
238 ADDENDA. 
 
 entirely beyond speculation, excepting, perhaps, the sud- 
 den rise and fall of ordinary transactions of commercial 
 life, the details of which cannot be reasoned upon ; but 
 they are hardly necessary to throw light on the future 
 operations of the meat-grower and cattle-breeder, in mak- 
 ing their calculations, with a view of finding a remunera- 
 tive market. . It is for these reasons, in part at least, that 
 we ought to regard what Liebig has to say on soil culture, 
 and be on the look-out for the best machines in the shape 
 of animals, as well as for all facts connected with breed- 
 ing, feeding, and caring generally, with the view to pro- 
 duce the largest possible amount of meat, of the best qua- 
 lity, at the smallest expense. It becomes a self-evident 
 fact that we must pay more for meat, use less of it, or 
 increase the supplies. This is at least encouraging to in- 
 telligent farmers. More attention must be paid to produc- 
 tion. This may be done in part, not only by increasing 
 the proportion of the industrious over the idle consumers, 
 but by exciting the best efforts of those engaged in agri- 
 culture in favor of the most rational system of practice. 
 
 It is pleasing to see every little while, statements in Eng- 
 lish journals relative to the purchase of choice animals for 
 the United States. The gentlemen who make the selec- 
 tions are invariably spoken of by the British press as spar- 
 ing neither expense nor trouble to obtain the choicest ani- 
 mals of the respective breeds considered worthy of special 
 attention. 
 
 But let the day soon come when the rich prairies will 
 grow cultivated grasses to support the best kinds of stock, 
 and to be no more consumed by fire. 
 
ADDENDA. 239 
 
 The finer grasses should take the place of inferior ones, 
 and green crops should be more grown. The culture and 
 fertilization necessary for them are sure to prepare the way 
 for other crops. 
 
 The improvement in the quality of animal food in Great 
 Britain and Ireland, since the general cultivation of turnips 
 and other roots, is too well known to be spoken of more 
 fully. The same facts will be true with us wherever the 
 root crops receive proper attention. Before their introduc- 
 tion into England the fattening of animals to perfection in 
 that country was unknown. A slight increase in our ani- 
 mals and crops would amount to more than the total 
 expenses of the general government. In these days of steam 
 cars, steam ships, electric telegraphs, arctic expeditions, and 
 voyages round the world, too little attention is paid to the 
 grand source of human subsistence for a thousand million 
 of men, and it is a matter of some importance to every human 
 being to know that he will get his daily bread. It is the 
 first petition in the prayer which our Master left us as an 
 example. " Give us this day our daily bread " means much 
 in the domestic economy of a nation — how much more so 
 among nations when ships freighted with bread are passing 
 every ocean across the track of ships of war, one on its mis- 
 sion of peace and plenty — the other on its mission of war- 
 fare and death. At such a moment this question of more 
 bread and more meat from the same number of acres, with- 
 out exhaustion, and with better directed labor, is a question 
 of life, of power, and prosperity to our continent. 
 
 "The increase of population on the Eastern Continent 
 (says Mr. Jay in his Statistical Yiew of American Agricul- 
 
240 ADDENDA. 
 
 ture), beyond the capacity of production, is investing the 
 question of food in this age with a significance that never 
 belonged to it before, and the growing demands for bread 
 that come to us from Western Europe, give a world-wide 
 interest to the statistics of American agriculture, far beyond 
 that which they could derive simply from the wants of our 
 own countrymen. 
 
 *' Consumption has there overtaken production, and 
 henceforth in England, France, Belgium, Holland, and a 
 great part of Germany, the yboc? question will be the question 
 that must take precedence of all others, as the regulator of 
 commerce, and entitled to the first attention and the wisest 
 treatment on the part of Grovernment." 
 
 John Stuart Mill, the well known political economist, 
 says : " Suppose, then, that the population of Great Britain 
 goes on increasing at its present rate, and demands every 
 year a supply of imported food considerably beyond that 
 of the year preceding. This annual increase in the food 
 demanded from the exporting countries, can only be ob- 
 tained either by great improvements in their agriculture, 
 or by the application of a great capital to the growth of 
 food. The former is likely to be a very slow process from 
 the rudeness and ignorance of the agricultural classes in 
 the food-exporting countries of Europe, while the British 
 colonies and the United States are already in possession of 
 most of the improvements yet made, so far as suitable to 
 their circumstances. There remains as a resource the ex- 
 tension of cultivation, and on this it is to be remarked that 
 the capital by which any such extension can take place is 
 mostly still to be created. In America it is rapid, but not 
 
ADDENDA. 241 
 
 more rapid than the population. The principal fund at 
 present available for supplying the country with a yearly im- 
 portaiion of food is that portion of the annual savings of 
 Araerica which has hitherto been applied to increasing the 
 manufacturing establishments of the United States^ and which 
 may now possibly be diverted from that purpose to growing 
 food for our market. This limited source of supply, unless 
 great improvements take place in agriculture, cannot be 
 expected to keep pace with the growing demands of so 
 rapidly increasing a population as that of Great Britain — 
 and if our population and capital continue to increase with 
 tJieir present rapidity^ the only mode in which food can con- 
 tinue to be supplied cheaply to the one is by sending the other 
 abroad to produce ity 
 
 " One fact," says the Mark Lane Express, " is clear, that 
 it is to Western America that we must in future look for 
 the largest amount of cereal produce." 
 
 All these facts show the necessity for the production of 
 more bread and meat. We shall be compelled to look into 
 this subject with great care, and consider well the prepara- 
 tion, fertilization, and cultivation of the soil, also the best 
 varieties of seed, their preparation, time of sowing, changing 
 of seed, quantity to be sown per acre, the habits of insects 
 and modes of preventing them from injuring crops, etc. ; but 
 above all when elements of fertility are taken from the soil 
 to be sure to put them back again. 
 
 Our field crops, such as wheat, rye, barley, oats, Indian 
 corn, potatoes, the hay crop, etc., and stock are a necessity, 
 and there is no thanks for us to grow them as well as we know 
 how, for without them we should starve. But the vegetable 
 
 11 
 
242 ADDENDA. 
 
 garden is more of a luxury, though it will soon be a neces- 
 sity. A farmer once knowing the value of good vegetables 
 could not think of living without them. Why should not 
 farmers generally, as well as citizens, eat cauliflowers, 
 cabbages, pease, beans, lettuce, spinach, etc. ? But through- 
 out the interior of this vast country, how few gi ve attention 
 to these commonplace but useful products of our gardens. 
 
 Many citizens pay extravagant prices for fruits, grown 
 here, and imported from foreign countries. Some of the 
 choice pears grown by a few persons in this country are 
 sold now and then at the enormous price of a couple of 
 shillings apiece. What harm would it be for farmers to 
 grow the finest pears, apples, peaches, plums, apricots, 
 nectarines, strawberries, and to eat them too, and when 
 they have too much for themselves give the rest to their 
 animals ? And while we supply our bodily wants with the 
 necessaries of life let us not forget the charms of a flower- 
 garden, and to render our homes as comfortable as intel- 
 ligence and industry can make them. 
 
 4 EXHAUSTION OF THE SOIL.*— P. 144. 
 
 Our pilgrim fathers, a couple of centuries ago, began to 
 till a somewhat stubborn but productive soil. They and 
 their children took all they could get, but put little back 
 again into the soil. This cannot be denied, while with all 
 honor we must regard them as the pioneers of American 
 
 * See pages 94, 108, 144, and 152. 
 
ADDENDA. 243 
 
 agriculture. In the early history of this country our 
 fathers found an immense expanse, and their urgent neces- 
 sities calling for immediate action, they selected the most 
 prolific spots and began to grow crops. Here were the 
 washings of the highlands gathered, and localities like the 
 Miami Yalley, the receptacles of vegetable decaying 
 matter for centuries, were interspersed through the whole 
 Atlantic slope. As men began to till the soil, and as fast 
 as they exhausted one locality of such elements of God's 
 bounty as were in a condition, from their solubility, to act 
 as food for plants, they moved to new places rather than to 
 properly work or fertilize old ones. They were not the 
 servitors of their grandchildren, but with a vast country 
 before them they chose to skim it, and as they drove the 
 Eed Men westward, they found new fields for planting, 
 and they " skimmed" the land. Here the great mistake was 
 made, that of overrunning the soil to reap a few good 
 crops that ended in impoverishing it, and this bad 
 example has followed to the present day. Thus the 
 Atlantic slope became a depleted expanse, and unprofitable 
 with the modes of culture in practice. 
 
 " A writer in the ' Year Book of Agriculture for 1855,' 
 on the 'Alarming Deterioration of the Soil,' referred to 
 various statistics of great significance in connexion with 
 this subject. Some of them regarded Massachusetts, where 
 the hay crop declined twelve per cent, from 1840 to 1850, 
 notwithstanding the addition of 90,000 acres to its mowing 
 lands, and the grain crop absolutely depreciated 6,000 bush- 
 els, although the tillage lands had been increased by the 
 addition of 60,000 acres. 
 
244: ADDENDA. 
 
 "In Indiana the river bottoms, which used to produce 
 an average crop of 60 bushels of corn to the acre, now pro- 
 duce but 40. In Wisconsin, which is younger still, it is 
 estimated that only one-half the bushels of wheat are now 
 raised to the acre that were raised twelve years ago ; and 
 the writer declares as the conclusion of the whole matter 
 that the soils of New England, after all the admonitions we 
 have received, are annually growing poorer, and that even 
 the virgin lands of the Great West are rapidly becoming 
 exhausted of their fertility." * 
 
 The reader will find very interesting notes on the exhaus- 
 tion of American soil on pages 179, 180, 181, 220. and 221, 
 of this work. 
 
 We choose rather to give the researches of others, as 
 being most likely to convince the reader than the gleanings 
 of one mind. In examining the foregoing facts in relation 
 to short crops in some of the old states it will be well to 
 consider that the ravages of insects doubtless deterred many 
 from devoting the same area to the cultivation of wheat, but 
 this fact could hardly be true of potatoes and some other 
 crops ; still it would be well to bear in mind the probable area 
 devoted to the crops referred to. There is no doubt that 
 in the main the bad principle of exhaustion is too true. 
 Liebig, in his " Familiar Letters on Chemistry," says : " Is it 
 possible, after so many decisive investigations into the ori- 
 gin of the elements of animals and vegetables, the use of the 
 alkalies, of lime, and the phosphates, any doubt can exist as 
 to the principles upon which a rational agriculture depends? 
 
 * Jay's Statistical View of American Agriculture. 
 
ADDENDA. 245 
 
 Can the art of agriculture be based upon anything but the 
 restitution of a disturbed equilibrium ? Can it be imagined 
 that any country, however rich and fertile, with a flourish- 
 ing commerce, which for centuries exports its produce in 
 the shape of grain and cattle, will maintain its fertility, if 
 the same commerce does not restore, in some form of 
 manure, those elements which have been removed from the 
 soil, and which cannot be replaced by the atmosphere? 
 Must not the same fate await every such country which has 
 actually befallen the once prolific soil of Virginia, now in 
 many parts no longer able to grow its staple productions 
 — wheat and tobacco ?" 
 
 Again he says, in the present work (p. 152), *' Let it be 
 remembered that in Virginia there are vast tracts of land 
 which at one time gave full crops of tobacco, Indian corn, 
 and wheat, now lying waste. In 1850 the tobacco crop 
 was eighteen million pounds less than in 1840. In 1850 
 the average yield of wheat per acre was only seven bushels ! 
 The American farmer despoils his field luithout the hast 
 attempt at method in the process. When it ceases to yield 
 him sufficiently abundant crops, he simply quits it, and, 
 with his seeds and plants, betakes himself to a fresh field ; 
 for there is plenty of good land to be had in America ; and 
 it would not be worth his while to work the same field to 
 absolute exhaustion." 
 
 Thus it will be seen our agriculture is a system of con- 
 stant depletion — it should be one of enriching and multi- 
 plying resources, involving all the elements of the soil for 
 the production of its fruits. 
 
 Some few enlightened agriculturists of the Atlantic 
 
246 ADDENDA. 
 
 border have restored worn out lands, and made them 
 produce so bountifully, that in proportion to the capital 
 and labor bestowed they make more money, acre per acre, 
 than most farmers do from the unexhausted virgin soils of 
 the West. 
 
 Our wants are rapidly increasing. Whole districts, 
 which thirty years ago gave an average of thirty bushels 
 of wheat per acre, do not give ten bushels now. Until we 
 stop eating bread this subject will not lose its interest. 
 Why should we not grow as large crops, and of as good a 
 quality as can be grown ? Does any one think good wheat 
 can be grown on had soil ? Can the land give that which 
 it has not ? 
 
 If soil be too poor to pay for labor, the more of it the 
 wheat grower tills without renovation, the poorer that 
 land and himself will grow. 
 
 The common opinion, that the soil of the West cannot 
 be exhausted, is a great mistake. See how the crops have 
 fallen off, as shown by the tables already given. Grain is 
 carried to the cities, and the substances that made it are far 
 away from their original source. The wheat crop of 1858 
 robbed the soil of more than thirty million pounds of pot- 
 ash, and sixty million pounds of phosphoric acid. But a 
 small proportion of these elements is sent back to the 
 soil. In Nature's economy nothing is lost ; but when man 
 displaces things he should put them back again in their 
 own places. A wise nation looks well to its agriculture, 
 the great source of wealth. England dug the fields of 
 Waterloo for human bones to enrich her soil. She sent 
 her ships to foreign nations to bring home fertilizers. In 
 
ADDENDA. 247 
 
 our agriculture we are a wasteful and soil-exhausting 
 people. We are tenants of it but for life ; others will come 
 after us. 
 
 These are a few of the reasons, based on the had jprinciple 
 of EXHAUSTION, why our crops in many districts are falling 
 off. 
 
 In some places land is so much exhausted that crops to 
 pay for the labor cannot be grown. Again, we find soils 
 that are very rich, but not in balance ; others are all that 
 can be desired, but they are the fewest, excepting those 
 we take from the hunting grounds of the red man, which 
 are as new to us as the Garden of Eden was to our First 
 Parents. 
 
 MANURES.^ 
 
 The much agitated subject of farm fertilizers continues 
 to be of intense interest to every agriculturist, whether 
 he be the mere laborer or the intelligent working farmer, 
 whose motto is, " Practice with science." 
 
 The investigations that are being made in the laboratory 
 of the chemist, the farm-yard, and in the field of nature, 
 operate to increase new interest in behalf of the superlative 
 importance not only of the ordinary facts that attract 
 attention, but also of the abstract truths that guide uner- 
 ringly to the goal of perfection. 
 
 The proper manipulation and fertilization of the soil 
 furnish a great basis for national wealth and prosperity. 
 
 * See pages 82, 108, 113, and 183. 
 
248 ADDENDA. 
 
 It is only by means of manure that the equilibrium of 
 the soil is restored. 
 
 Like the farmers of England and other nations, we, too, 
 have our strenuous and prejudiced advocates of the nume- 
 rous modes of practice detailed by agricultural lecturers, 
 manufacturers of agricultural books, as well as the novel- 
 ties presented by the motley groups who constitute those 
 assemblages denominated Farmers' Clubs. There is every 
 shade of intelligence, from him who simply knows that a 
 cabbage grows, and that he eats it, to the man of sound 
 mind and sound body, who interrogates the silent opera- 
 tions of nature to reveal to him structures of animal and 
 vegetable life which are infinitely more beautiful and 
 grand than the most ponderous artistic and imposing edifice 
 that has ever been raised on the surface of our globe by the 
 hands of man. 
 
 Many men of as many minds, and a much larger number 
 of theories, herald forth detailed accounts of faulty experi- 
 ments, both orally and in printed periodicals ; the latter 
 too often furnishing space which might remain unoccupied 
 unless the greasy leaves of cookerj^ books were explored 
 to grace the columns of the agricultural press, thus giving 
 opportunity to laudation or abuse, either of which is far 
 easier than the discovery of new truths. Some of the 
 experimenters give good sense and the laws of nature as 
 wide a berth as possible ; and their ill-directed labors furnish 
 results more remote from truth than those of the most 
 careless operator who tills the soil in the sweat of his brow. 
 
 What vast amounts of labor and capital have been 
 wasted in testing the value of fertilizers ! Farmers often 
 
ADDENDA. 249 
 
 repeat tlie same experiments a hundred times, without its 
 being known to one another that they do so ; but few of 
 the results of their labor and capital are recorded. Experi- 
 ments in the field, to be of value, must be exact ; if not, 
 the tendency is to confuse rather than instruct. The writer 
 once saw a neighboring farmer, when planting potatoes, 
 use as fertilizers, farm-yard manure, guano, bone-dust, 
 phosphate of lime, wood-ashes, plaster of Paris, salt, caustic 
 lime, oyster-shell lime, water-slaked lime, the salt and lime 
 mixture, and muck treated with salt and lime. Each was 
 used separately, and in different parts of a field, having the 
 same quality of soil throughout, and all done with the 
 view of ascertaining what kind of manure was best for the 
 potato! No attention was paid to the chemical or me- 
 chanical qualities of the soil, its requirements, or those of 
 the crop about to be grown. Men who thus blindly grope 
 in the dark are the first to advocate, dogmatically, some 
 extreme notion in relation to long or short manures, their 
 treatment and modes of application. We freely admit that 
 among the more intelligent of our profession may be found 
 the advocates of long and short manures, the deep drainers, 
 and the shallow drainers, as well as those who are favorable 
 to the many intermediate shades of difference, without any 
 modes in particular, being supported by the unanimous 
 voice of agriculturists. The explorer should not be guided 
 by the dupes of any theory in particular, but rather seek 
 from every source that which seems most rational, and in 
 best obedience to the unerring laws of nature. 
 
 Chemical science has searched into the nature of the soil, 
 the plant, and the air, and has shown that the word soil 
 
 11* 
 
250 ADDENDA. 
 
 means several substances rather than one, and that this is 
 also true of the word plant^ and the word air. The soil 
 and the air are the sources whence the material necessary 
 for the building of the plant is obtained. 
 
 Let it be remembered that the plant is not a single or 
 simple substance, but is made up of several. If a piece of 
 wood is burned, ashes will be the result. During the burn- 
 ing some parts of the wood pass into the air. The house- 
 keeper is in the habit of leaching the ashes to get Ije for 
 making soft-soap ; a large per centage of this lye is potash, 
 which came from the ashes, which came from the plant, 
 which came from the soil on which the plant grew. This 
 substance, potash, is one of the several which compose the 
 ashes, such as lime, soda, and so forth. If, then, researches 
 have shown that the absence of particular substances in the 
 soil prevents some plants from growing successfully, and 
 that supplying them in a proper manner restores fertility, 
 we get at a simple and truthful explanation of a principle 
 which must govern the action of all fertilizers. The word 
 manure^ like the word soil^ means more substances than 
 one ; and different manures must vary in action as they 
 vary in composition, even if all other things are equal. 
 These principles have their home in nature ; nor do we 
 lay any claim to their discovery. The honor of this is due 
 to greater minds. We are but the errand-boy giving the 
 message to our readers. 
 
 What is a manure ? It is that substance, whether simple 
 or compound, solid or fluid, which yields to a plant food 
 essentially necessary to its structure and development. 
 According to this definition, water is a fertilizer, and such 
 
ADDENDA. 251 
 
 constituents of tlie air and soil as go to support plant 
 life. 
 
 The farmer should consider what food is essentially- 
 necessary to the plant about to be grown. 
 
 What food is essentially necessary to the plant about to 
 be grown ? 
 
 From what source of advancement should the food be 
 supplied ? 
 
 What should be its mechanical and chemical condition 
 in the soil ? 
 
 These are a few of the important questions that relate to 
 vegetable growth. 
 
 Practice has fully satisfied experimenters that if any of 
 the elements of which plants are composed be absent from 
 the soil, they will not grow to perfection, and that the 
 most perfect result can only be obtained from soils in exact 
 balance. Qualitative and quantitative analyses of plants 
 and soils have cast much light on these important features 
 of the subject. The old notion that plants can create food 
 is now abandoned by every intelligent mind. 
 
 An animal fed on hay and oats will not furnish in its 
 excreta the precise constituents, in the same relative pro- 
 portions to each other, as they exist in the food. 
 
 All the most valuable, most needed, and ready-to-he easily 
 assimilated portions, such as are in an advanced condition, 
 go to increase the size or bulk of the animal, or to make 
 up for the wastage of the system. All that part of the food 
 known as starch and gluten, or a very large portion of it, 
 is not to be found in the excreta, unless the animal be 
 over fed. The elements of farm-yard manure are not in 
 
252 ADDENDA. 
 
 as advanced a condition as many of the crops to whicli 
 they are applied, but many of them are on the very next 
 plane of existence in the scale of progression, and must, 
 therefore, be particularly suited for the production of the 
 same plants as those from which they arise, and for all 
 others of an analogous newness of creation. 
 
 This principle must be clearly understood, and admitted, 
 before the reader will be prepared to comprehend the ra- 
 tionale or method of treating manures. Every vine-grower 
 knows that the inorganic substances of the soil that go to 
 make the wood of this year will be rendered fit pabulum 
 for the fruit of next year, if made soluble by natural pro- 
 cesses. Thus, the vigneron cuts the trimmings of his 
 grape-vines, with an ordinary straw-cutter, and after hav- 
 ing buried them in damp soil during winter applies them 
 in the spring around the roots of the growin gvines, and 
 increases the amount of fruit by doing so. 
 
 Now, it must be evident, that when these cuttings are 
 applied to the root of the same vine from which they were 
 removed, no new inorganic matter is added to the soil, 
 but it is simply that the same inorganic substances are 
 replaced in the soil after having been progressed, by once 
 assuming the form of wood, and that, therefore, without 
 any increase of quantity, but only from superior condition, 
 that the increased amount of fruit occurs. If this principle 
 be correct, a hay crop undergoing decay beneath a soil 
 where hay is intended to be raised for its seed, the 
 quantity would be greater than from a less advanced 
 manure, and simply because the constituents of the hay 
 were ready for re-assimilation ; and it is to this fact that 
 
ADDENDA. 253 
 
 stable manure, in no small degree, owes much of its 
 value. 
 
 Liebig, on a strictly cbemical basis, truly says, that 
 "The solid and liquid excrements of an animal 
 aee of the highest value as manure for those 
 plants which furnished food to the animal." 
 
 For a full understanding of the value of farm-yard 
 manure, it will be necessary to consider its source and 
 composition, and causes for the changes it undergoes, as 
 compared with the integrants of the materials from which 
 it arises. 
 
 Plants receive support from the soil ; they nourish 
 animals ; but certain portions, not appropriated, are known 
 as liquid and solid excrements. 
 
 The analysis of any specimen of farm-yard manure 
 cannot be viewed as a universal standard of comparison. 
 
 The peculiarities of animals as mere machines, the 
 quantity and kinds of food consumed by them, their age, 
 amount of exercise, climate, season of the year, the bear- 
 ing of young, the giving of milk, and a variety of other 
 circumstances, have a great influence on the composition 
 of manures. The drainage of some compost heaps is 
 exposed to rains, evaporation, or permitted to flow away 
 to creeks. 
 
 Others are carefully protected, but parts of them may 
 abound in straw. Occasionally, farmers permit their cattle to 
 roam and feed in the farm-yard, and they often waste as much 
 food as they consume. How difficult, then, is it to select a 
 sample for chemical examination, the analysis of which will 
 be an exact representation of farm-yard manures in general. 
 
254 ADDENDA. 
 
 The loss of ammonia during the preparation of farm- 
 yard manures has been and is attracting much attention. 
 
 The pungency of the odor given off from fermenting 
 substances is no indication of the quantity of ammonia 
 liberated. Many agricultural writers give Dr. Yoelcker 
 the credit of having made this discovery. The value of 
 the Doctor's experiment consists chiefly in following out 
 the detail of a principle, the credit of which is entirely 
 due to Baron von Liebig. It is no new information to 
 the agricultural world to be told that decaying animal 
 substances, in addition to eliminating ammonia, also give 
 off " sulphuretted and phosphurett£d hydrogen^ and a great 
 variety of gaseous matter s^''^ to which the pungency of odor 
 referred to is due to a very considerable extent. But it is 
 quite novel that agricultural writers should deduce from 
 Dr. Voelcker's researches that manures may be exposed on 
 the surface of a soil without loss, and especially because 
 his analyses show with great clearness the loss that must 
 necessarily arise from drainage by water, on account of the 
 great solubility of some of the compounds. In comment- 
 ing on the analysis of drainings from a dung-heap, he says : 
 
 " It will be seen that these drainings contain a good deal 
 of ammonia, which should not be allowed to run to waste. 
 
 "They also contain phosphate of lime. The fermenta- 
 tion of the dung-heap brings a portion of the phosphates 
 contained in manure into a soluble state, and enables them 
 to be washed out by any watery fluid that comes in contact 
 with them. 
 
 "Drainings of dung-heaps are rich in alkaline salts, 
 especially in the more valuable salts of potash. 
 
ADDENDA. 255 
 
 "By allowing tlie washings of dung-heaps to run to 
 waste not only ammonia is lost, but also much soluble or- 
 ganic matter, salts of potash, and other inorganic sub- 
 stances, which enter into the composition of our crops, 
 and which are necessary to their growth." 
 
 The Mark Lane Express^ of London, republished an 
 article, by an American writer, containing the following 
 language : — 
 
 '' * Those who imagine,' says the editor of the Working 
 Farmer^ 'they find good results from spreading of the 
 manure on the surface, and leaving it for days, weeks, or 
 months, before it is ploughed under, mistake the action of 
 the litter or longer portions of the manure as a mulch for 
 the action of the manure on the soil.' We so far differ from 
 this and kindred opinions on the subject that we think 
 manuring on the surface, for ninety-nine farmers in a hun- 
 dred, the best general method of application." 
 
 The author quoted, edifies his readers by saying, " we 
 think manuring on the surface, for ninety-nine farmers in a 
 hundred, the best general method of application." Nor 
 does he favor us with any other rationale than his sage 
 thought ! 
 
 One very serious error has been caused by the recent 
 discussions on " Farm-yard Fertilizers." Impressions have 
 been made on the minds of many farmers that science at 
 last has discovered that the ordinary system of treating 
 farm-yard manure is correct, whereas the experiments of 
 Dr. Yoelcker, which gave rise to the excitement both on 
 the other and this side of the Atlantic, do not go to prove 
 any such result. Many of the agricultural journals of 
 
256 ADDENDA. 
 
 Europe and America, wliose editors desire to cater to pre- 
 judices, were higbly pleased to liave an opportunity of fur- 
 nishing such material as would delight a certain class of 
 readers, and be the cause of exciting the advocates of oppo- 
 site views to action. 
 
 There is no doubt that portions of manure spread on the 
 surface of a soil are washed into it. The quantity carried 
 into the soil by the soluble and mechanical action of water, 
 will be governed by its composition (whether clayey or 
 sandy) and its mechanical condition. It is also admitted 
 by the wisest advocates of the foregoing, that many and 
 large amounts of the elements essential as food for plants, 
 are carried to the lowlands in obedience to the same laws 
 that cause alluvial deposits. 
 
 In direct opposition to these well known truths, a writer 
 in the Edinburgh Journal of Agriculture furnishes the ex- 
 tract given below, which has been published in almost 
 every agricultural paper in the United States. Care has 
 been taken to say that the "striking experiments" were 
 made by a scientific man, and by certain explanatory quali- 
 fications to give more importance to the man than to the 
 subject. 
 
 If the experiments be striking, it is because they appear 
 very unceremoniously to strike Dame Truth in the face. 
 The writer in the Edinburgh journal says : 
 
 " There being a difference of opinion among scientific 
 men regarding the advantage of spreading dung upon the 
 surface, and leaving it exposed for some time before cover- 
 ing it in, Professor Legnitz, of Eldena, had recourse to ex- 
 periment for the solving of the question. For this purpose 
 
ADDENDA. 257 
 
 lie selected two and a half roods, which he divided into four 
 equal parts. To No. 1 no manure was given, No. 2 re- 
 ceived about two tons of farm-yard dung, which was spread 
 immediately and covered in by means of the plough. No. 3 
 was treated in the same manner, with this difference, that 
 the hoe was used instead of the plough. 
 
 " The same quantity of dung was carried to No. 4, and 
 allowed to remain spread for three weeks on the soil before 
 being covered in by the hoe. On the 10th of October the 
 four lots subjected to experiment, were sown with about 
 ninety -five pints of rye-seed each. The following are the 
 total results of the crop of each lot, grain and straw included : 
 
 No. 1 produced . . . 583 lbs. 
 
 No. 2 produced . . . 770 " 
 
 No. 3 produced . . . 818 " 
 
 No. 4 produced . . . 935 "» 
 
 The author of the above has well said, that one experi- 
 ment should not be considered conclusive, and we will 
 suggest that he might have added, especially because the 
 full conditions for a useful experiment were not present, and 
 such as were, not recorded in a manner to be of value. 
 
 In the first experiment no manure was used, nor does it 
 appear that the soil was ploughed, and as might be expected, 
 it gave the smallest crop. 
 
 In the second experiment, manure was used, and the soil 
 was ploughed in the act of covering it, and, as was reason- 
 able to expect, the crop was larger than in the first-named 
 instance. 
 
 In the third experiment an equal quantity of manure 
 was given to the same surface of soil, but instead of 
 
258 ADDENDA. 
 
 ploughing it under, a hoe was used to cover it, which gave 
 the soil more mechanical disturbance than the plough ; the 
 latter turns the soil over in masses, whereas the former acts 
 with greater intensity, and on small quantities of soil during 
 its vigorous action, thus abrading the surfaces of particles 
 more fully than could be accomplished by one ploughing, 
 for which reason there was a greater amount of plant food 
 liberated, and as might be anticipated, the crop was larger 
 than in the case of the second experiment. 
 
 In the fourth experiment, and to which the others are 
 merely introductory, the result is such as clearly indicates 
 unusual conditions, such as the manure, perhaps, being so 
 fermented before its use as to present a large proportion in a 
 soluble condition, its application followed in all probability 
 by heavy rains and dews, while the long undecomposed por- 
 tion remaining on the surface of the ground for three weeks, 
 acted as a mulch, and probably during such a state of the 
 atmosphere as to produce its greatest action as su(3h, and 
 when evenly ploughed in, the same ploughing that turned 
 under the mulch, mixed the soil through which the fluid or 
 manurial portions had previously been well disseminated. 
 The chemical conditions of the soil may have been more 
 favorable than in either of the other three experiments. 
 
 No account is given of the condition of this soil as com- 
 pared with the others, for a second crop, nor of the kind 
 of weather occurring during the three weeks referred to. 
 If the experiments were made during a season of drought, 
 the effects would not have been such as are stated; or during 
 a season of excessive rain on soil not previously disturbed, 
 no such result would have been produced. It is quite com- 
 
ADDENDA. 259 
 
 mon to see tall grass wliere an old plank or rail has covered 
 it for a time, whicli, acting as a mulch, causes the growth 
 of better grass than would have been produced by an ordi- 
 nary quantity of manure, but to no small extent evidently 
 at the expense adjacent of grass. The portion so mulched 
 receives and fixes a larger quantity of fertilizing gases from 
 the atmosphere. We are not told whether the soil used for 
 the fourth experiment was or not on a lower level than 
 the surrounding soil on which the others were made, and 
 thus benefited by water flowing from No. 2 and No. 3, said 
 water carrying elements of their fertilizers and soil to No. 4. 
 Nor is it stated that the manure in each case was alike in 
 quality. Indeed, the account is altogether too inaccurate 
 to be reliable, and therefore should not have been published 
 without comment in the most important agricultural jour- 
 nals in England and America. 
 
 Let it not be forgotten that the fluid portions of manure 
 are highly valuable ; the various salts they contain are in 
 a state of solution, and are capable of extreme division, in 
 addition to assisting by their presence all the sui generis 
 actions of a chemical character which take place in a soil ; 
 for just as yeast multiplies itself in a brewery by its action 
 on vegetable matter, so do the constituents in solution in 
 the urine of animals induce chemical changes which cause 
 the integrants in the soil to be rendered suitable jmbulum 
 for plants. 
 
 From the foregoing it must be evident that the excre- 
 ments of all animals should be well cared ; and their mani- 
 pulation should be such as not only to secure their con- 
 stituents for the use of plants, but to change the condition 
 
260 ADDENDA. 
 
 of such of them as plants cannot avail themselves of, by the 
 usual treatment of the manure before it reaches the field. 
 In addition to the inorganic matter, are many proximates, 
 known as organic compounds, which plants may use, and in 
 a condition which renders them active in the further decom- 
 position of a soil for the use of plants. Among these are 
 the bile and chyle of the animal, and the different vegetable 
 proximates not appropriated ; and we are sorry to say that 
 most farmers, by the injudicious management of manures, 
 lose them by evaporation, washing, etc., and also much of 
 the more valuable and most soluble of the inorganic consti- 
 tuents. These occur in open farmyard practice, and in the 
 washes and streams that pass away, sometimes crossing 
 roads, on their way to creeks and rivers, while from the 
 exposed surface ammoniacal and other gases, hurtful to the 
 health of animals, pass into the atmosphere. 
 
 Some of the losses that arise from improper exposure 
 are as follows : 
 
 The most soluble elements, and consequently the most 
 readily available constituents to plants, are washed out by 
 rains. If the manures permeate the farm-yard, a larger 
 amount of surface is exposed to evaporation than if 
 gathered into a heap. 
 
 The amount of surface exposed to evaporation is a great 
 number of times increased if cattle are permitted to roam 
 promiscuously through the yard. Every step taken by an 
 animal exposes a new surface to the action of sun and air. 
 Every spear of hay or straw projecting from the surface of 
 manure, by capillary attraction, gives an increased amount 
 of surface for evaporation. 
 
ADDENDA. 261 
 
 The proper composting of fertilizers is, to American far- 
 mers, of more importance than to the English cultivators of 
 the soil : because gases from any decomposing substance, 
 whether animal or vegetable, cannot so readily pass into an 
 atmosphere like that of England, Ireland, or Scotland, as 
 they will into that of America, owing to the sudden changes 
 of temperature of the latter. 
 
 Any vegetable matter that can be decomposed in a com- 
 post, should not be burned. It is not proper, therefore, to 
 subject witch or couch grass, clippings of hedges, or live 
 fences, leaves, or other similar materials, to the action of 
 fire. They ought rather to find their way to compost 
 heaps, and receive such treatment as will secure full de- 
 composition. Let everything of a manurial character find 
 its way to the compost. Remember the Scotch adage: 
 " A stone is the only mote in a muck heap." 
 
 Such adages, now being published in so many of the 
 agricultural papers, that " No one should have a farm-yard 
 bigger than the body of his ox-cart," are mere words with- 
 out meaning. It would be well for the authors of such 
 sayings to give accompanying explanations. One-sided, 
 prejudiced views never lead to truth ; writers should not, 
 Paganini-like, play on a single string. 
 
 LAND DRAlKAaE. 
 
 There can be little doubt that thorough drainage is one 
 of the surest means of preparing the soil for the applica- 
 
262 ADDENDA. 
 
 tion of the principles so ably set forth by Baron von 
 Liebig. 
 
 We have no space to devote to the history of this impor- 
 tant subject ; there is, however, little doubt that improve- 
 ments in the art of drainage, extending over a long series 
 of years, show conclusively, the applicability of thorough 
 land drainage to a large proportion of our continent. Its 
 advantages are very numerous, a few of which may be 
 briefly stated. Its object is not merely, as many suppose, 
 to rid the land of stagnant water. The action of the air on 
 the soil, and the absorption of moisture from it by the 
 driest lands that are under-drained and deeply cultivated, 
 are advantages that are now well considered by the intelli- 
 gent practical farmer. Soils, especially such as are full of 
 stagnant water, treated in this way, are easily worked, 
 when the water is carried away by under drains ; and this 
 is particularly true of them when sufficient time has 
 elapsed to permit those important influences of the air 
 which liberate pent up food, and thus improve its physical 
 condition, thereby lessening the labor necessary for their 
 successful culture. Under-draining, even without the appli- 
 cation of manure, has been known to double the crop in 
 many soils. Let it not be forgotten, however, that in this 
 point of view, it aids the "rapid system of spoliation," 
 unless the farmer restore to the soil the elements taken 
 away by crops. In under-drained soils, when the drains 
 are at full depth, the roots of plants can strike deeply in 
 search of food ; thus they are invigorated and not likely to be 
 thrown out or "winter-killed" by frequent freezings and 
 thawings, or summer-killed by not having a deep soil 
 
ADDENDA. 263 
 
 in which to luxuriate and absorb the moisture which is 
 sure, in the hottest weather, to be deposited on the 
 cool particles. It is also well known that under-drained 
 soils are warmer than those full of cold stagnant water. 
 They are earlier in spring and not frozen till later in the 
 fall, thus giving the farmer a longer season in which to do 
 his work. What can be more uninviting than a cold, wet, 
 unproductive soil? "Can the rush grow without mire? 
 Can the flag grow without water ?" After thorough drain- 
 age, the rush and the flag disappear, and instead of coarse 
 grasses, alders, skunk cabbages, mosses, and other rubbish, 
 fine plants may at once be grown. 
 
 Into low, wet places much of the fertility of the higher 
 lands is washed by the soluble and mechanical action of 
 water, which is made available by thorough drainage, and 
 a basis is thus laid for all possible improvements of the 
 soil. 
 
 Although the farmer who can buy new and rich soil at 
 a very low price, is not likely to under-drain it, because he 
 can buy more land at little cost, which, although studded 
 with stumps, that will yield him full crops of cereals ; still 
 few will doubt that thorough drainage is applicable to 
 extensive tracts of land near large cities, used for agri- 
 cultural purposes. Indeed that the farmer must drain 
 all such lands that are wet, or do without crops, few will 
 doubt. 
 
 George W. P. Custis, Esq., at the meeting of the United 
 States Agricultural Society, in 1857, asked attention to 
 100,000 acres of rich land, on the banks of the lower Poto- 
 mac, now lying waste, but which if thoroughly drained, 
 
264 ADDENDA. 
 
 might at once be rendered available for tlie production of 
 the jfinest crops. This is only one case among many 
 beyond number which must yet yield to the almost magic 
 influences of thorough drainage as the agricultural resources 
 of our country are developed. A wide field for opera- 
 tion offers itself in the fifty million acres of swamp land 
 granted by Congress to different states during the past ten 
 years, with the hope that their governments will reclaim 
 them. Many a farm, by the drainage of low places, would 
 add quite a number of acres which have received the wash 
 of the highlands for ages, capable of immediate cultiva- 
 tion and profit. 
 
 The drainage of the Central Park, under the direction of 
 George E. Waring, Jr., Esq., is probably the most thorough 
 work, on a large scale, that has yet been done in this coun- 
 try. Enough of this is already done to see to some 
 extent its efficacy ; although the drains have not yet been 
 long enough made to act in the best manner, still the water, 
 clear as crystal, may be seen gushing from the almost 
 magical pipes. On the land appropriated for the park, 
 there were many offensive pools, half full of decaying 
 vegetable matter, whose value, as a manure, to other parts 
 of the grounds, would more than pay the cost of drainage. 
 As the park consists of a great variety of soil, among 
 which may be named both blue and yellow clay of the 
 most tenacious kind, there is a fine opportunity for seeing 
 the effect of tile drainage by farmers who may visit the 
 grounds. 
 
 The first thing to be done in the laying out of drains is 
 to understand the natural lay of the ground, selecting the 
 
ADDENDA. 265 
 
 lowest part, having the best outlet, as the line for the main 
 drain. The lateral drains should connect with the main at 
 the same angle as the slope of the ground to the line of the 
 main. Where the slope is not sufficient to give a self-evi- 
 dent fall it will be necessary to have the ground levelled by 
 an engineer, as any inaccuracy in this respect would be 
 fatal to the efficient working of the drains. The engineer 
 proceeds by driving stakes, of two or two and a half feet in 
 length, in the ground at given intervals along one of the 
 intended sides of each drain, and they are lettered and 
 numbered for easy reference. Beside each of these stakes, 
 a shorter one is driven, the top of which should be a little 
 above the ground, so as to be easily seen. On the shorter 
 stakes the engineer's rod is placed as occasion may require, 
 when observations are made to ascertain levels. After the 
 calculation of the grades, the depth of the intended excava- 
 tion, from the top of the shorter stake, is marked in feet 
 and tenths on the longer one. 
 
 It is wel] to sound the lines of the drains with a sound- 
 ing-bar, to ascertain whether rocks, separate stones, boul- 
 ders, etc., will much interfere with the cutting of them ; in 
 which case new lines would have to be found. The obser- 
 vance of this precaution will save a great deal of labor and 
 expense. A sounding-bar is a round iron rod about an 
 inch thick and five or six feet long, tapering towards the 
 point and enlarged at the head to about two inches in dia- 
 meter; having a cross-bar about eighteen inches long through 
 an eye in the head. Sounding-bars three-quarters of an 
 inch thick, and seven or eight feet long, are sometimes used; 
 
 but they have to be worked into the ground by a swinging 
 
 12 
 
266 ADDENDA. 
 
 motion of the hand. This is a very slow process, compared 
 with the speed with which the larger sounding-bar may be 
 driven into the ground by a sledge. Twenty soundings 
 may be made with the larger bar, while one is effected with 
 the smaller one. 
 
 The main drain and laterals being located, commence 
 digging at the outlet of the main, and so proceed to the 
 head of the drain — that is its most distant part from the 
 outlet. Care must be taken to give them a regular and 
 sufficient fall, which should not, if possible, be less than one 
 foot in 100. A uniform grade on the bottom of the drain 
 is very desirable ; and it is for this reason that levelling-rods 
 are used. A levelling-rod is shaped like the letter T and is 
 made of board about one inch thick, five or six inches wide, 
 with a piece of board of same width about eighteen inches 
 long nailed across the top, and square to, that is at right 
 angles with, the perpendicular. All the rods must be the 
 same length ; otherwise a uniform grade cannot be obtained. 
 Levelling-rods are usually made six or seven feet long. 
 
 Having got the drain as nearly as possible to the required 
 depth, place the rods on the bottom of it in an upright posi- 
 tion about forty feet apart;, then hold another rod, which 
 may be lighter, on the bottom of the drain, and if its grade 
 be correct, the top will lie in a line with the tops of the 
 other two. Great care must be taken not to go below the 
 proper grade, as in that case the bottom of the drain will 
 have to be filled, and cannot be made as compact as the 
 natural bed. Where it is necessary to have the land lev- 
 elled by an engineer, and the fall is only sufficient, the rods 
 must be placed very accurately at the depths- — calculated 
 
ADDENDA. 267 
 
 from the " levels" — which are generally marked on stakes 
 at proper distances along the lines of the drains. Beside 
 each stake, so marked, is the grade stake, the top of which 
 is a fixed point from which to measure the depth of the 
 drain. In order to find the exact depths of points along 
 the bottom of the drain corresponding to the depths marked 
 on the stakes, a sliding measure is used having a plumb- 
 line attached. First ascertain the required depth from the 
 top of the grade stake to the bottom of the drain ; then 
 apply the sliding measure, the arm set to the proper height. 
 K the bottom of the drain be soft, place a flat stone under 
 the end of the sliding measure, making due allowance for it 
 when removing the soil from the point where the levelling 
 rod is about to be set. The sliding arm of the measure 
 must rest on the top of the grade stake. When the proper 
 depth is thus ascertained, remove the measure and place 
 the levelling-rod upright on the stone, it being held in its 
 position by a board reaching across the drain having a slit 
 in its centre into which the levelling-rod is wedged. 
 
 The main drain dug and graded, then proceed with the 
 laterals, commencing with those nearest the head of the main 
 and proceeding on to those nearest the outlet. Commence 
 to lay the tiles first in the main drain, and continue a little 
 beyond the point where the highest lateral connects. Pro- 
 ceed in the same way with the rest of the laterals, laying 
 the tiles connecting with the main, and then place inverted 
 sods, if the soil be silty, and cover with soil to the depth of 
 a foot and a half, and use a pounder to compact. Every 
 foot of soil put in afterwards should be pounded. These 
 precautions will prevent water in case of a rain storm from 
 
268 ADDENDA. 
 
 rushing rapidly through, before the soil has become settled ; 
 on the contrary it will pass gradually without carrying any 
 silt into the tiles. Continue to dig laterals and lay tiles in 
 the main and in them as fast as dug until the outlet of the 
 main is reached. 
 
INDEX. 
 
 PAGE 
 
 Absorbent power of soils varies 28 
 Agricultural Colleges system of 
 instruction in, 
 defective. . 209 
 
 — — the cause of the 
 
 present conflict 
 about princi- 
 ples . . 210 
 
 — instruction, how ac- 
 
 quired . .12 
 
 — prize questions . 16 
 
 — teachers, errors of . 161 
 Agriculture, based on expe- 
 rience . . 2 
 
 — connection with 
 
 chemistry . . 4 
 
 — false teachers of . 11 
 
 — modern, deficient in 
 
 principles . .187 
 
 — present system of, 
 
 not rational . 20 
 
 — spoliation system of 144 
 
 — spoliation system 
 
 of, in America . 144 
 Agriculturist, the empirical, a 
 
 trader . .138 
 
 — the scientific du- 
 
 ties of . . 140 
 Air, carbonic acid and ammonia 
 
 in 69 
 
 America, exhaustion of soil 
 
 in ... . 144, ni 
 A.mmonia, action of, compared 
 
 with that of water 165 
 
 — amount of, in air . 69 
 
 PAOB 
 
 Ammonia, combbaation of, with 
 
 soils . .110 
 
 — effect of salts of, 
 
 attributed to the 
 nitrogen . , 43 
 
 — effect of salts of, 
 
 on production of 
 straw and leaves 80 
 
 — exhaustive action 
 
 of salts of . .67 
 
 — experiments with 
 
 salts of, at Bogen- 
 hausen . . 44 
 
 — in a soil, not a sign 
 
 of its fertility . 59 
 
 — quantity of, in 
 
 soils . 59, 169 
 
 — quantity of, no cri- 
 
 terion of produc- 
 tiveness . . 59 
 
 — salts of; double ac- 
 
 tion of, in soils 52, 16*7 
 
 — solvent action of, 
 
 on earthy phos- 
 phates . . 48 
 
 — without mineral 
 
 matters, of no use 
 to plants . . 88 
 Aramoniacal manures, when 
 
 useful .... 98 
 
 Annuals, absorption of food by 71 
 
 Apatite 96 
 
 Appendix . . . .221 
 
 Arable soils, how formed . 119 
 
 Ash constituents . . .116 
 
270 
 
 INDEX. 
 
 B. 
 
 Bavaria — experiments of agri- 
 cultural society of) with am- 
 monia . . . .60 
 Beet — minerals removed by .182 
 Birkenfeld peasant, his opinion 
 
 of clover . . . .160 
 Block, Albrecht, opinions of . 141 
 Bogenhausen experiments with 
 
 salts of ammonia, &c. 44 
 — experiments with 
 
 nitrate of soda, 41 
 Bog-water, analysis of . .36 
 Bone earth, comparison with 
 Chih-saltpetre . . .173 
 
 C. 
 
 Carbonic acid, amount of, in air 69 
 
 — — source of . .70 
 Cato, opinions of, on agriculture 190 
 Cattle, stock of, not necessary . 198 
 Cereals, amount of nitrogen in 74 
 Chemistry, connection of, with 
 
 agriculture . . 4 
 
 — elementary instruc- 
 
 tions in . .206 
 
 — reaction against . 5 
 Chili-saltpetre, effects of, . . 47 
 
 — — solvent action of, 
 
 on earthy phos- 
 phates . . 48 
 
 — — comparison of, with 
 
 guano and farm- 
 yard manure . 162 
 
 — — exhaustive effects of 67 
 China, continued fertility of 
 
 land in . . . .204 
 
 Chinese, agriculture of . . 200 
 
 — mode of collecthig 
 
 human excrements ib. 
 
 — mode of sowing wheat 202 
 
 — valuation of human 
 
 excrement . . 201 
 Clover, introduction of into 
 
 Germany . . 155 
 
 — and corn, relation of, to 
 
 each other . . 149 
 
 Clover, and potatoes, phosphoric 
 acid and 
 potash re- 
 moved by 103 
 Columella, opinions of, on agri- 
 culture . . . .189 
 Combustible matter of plants 
 
 derived from air . . .110 
 Common salt, effects of . 43 
 
 — — experiments with, 
 
 at Bogenhausen . 44 
 
 — — solvent action of, on 
 
 earthy phosphates 48 
 Compensation, the law of . 205 
 Corn, mineral matters of, lost 
 
 to the land . .150 
 
 — and flesh, mutual rela- 
 
 tion of the production 
 of . . . .199 
 Crops, rotation of . . . 142 
 
 D. 
 
 Deep rooting plants, effects of 105 
 Disintegration of rocks . .122 
 Distilleries, residues from 169, 180 
 Drainage water, ammonia in . 34 
 — — analysis of .31 
 
 E. 
 
 Earth, outer crust of, conden- 
 ses and retains the food of 
 plants 40 
 
 Earthy phosphates rendered 
 soluble by salts of ammonia, 
 common salt, and Chili-salt- 
 petre 48 
 
 Excrements of man, amount of, 
 in large towns . . .176 
 
 Exhaustion of soils, law of . 94 
 — — — real nature of 108 
 
 Experience of practical men as 
 a guide .... 120 
 
 Fallow, effect of 
 False reasoning 
 
 98 
 121 
 
INDEX. 
 
 271 
 
 PAGE 
 
 False teachers . . . .11 
 Farm-yard manure . . .109 
 — — value of . Ill 
 
 Fertility, duration of. propor- 
 tional to amount of 
 mineral matters in 
 soils . . .61 
 
 — how maintained . . Ill 
 
 — not restored by or- 
 
 ganic matters . .110 
 
 Finger and toe disease . . 84 
 
 — — removed by lime 84 
 
 Food of plants absorbed in 
 
 proportion to 
 
 root surface . 10 V 
 
 — — — atmospheric 
 
 and mineral . 21 
 
 — — — not in solution 
 
 in soils . 30 
 
 — — — not received 
 
 from a solution 87 
 
 — — — rapidity and 
 
 duration of ac- 
 tion of . 22 
 
 — - — — relation of 
 
 phosphates 
 and nitrogen 
 compounds in 170 
 Formula for the chemical truths 
 in the agricultural letters . 264 
 
 G. 
 
 German agriculture before the 
 
 Thirty Years' War . .153 
 Graham — analysis of waters by 31 
 Grain, conditions for producing 
 
 largest crops of . . 101 
 
 — decrease in the condi- 
 
 tions for its growth . 101 
 
 — increase of, by means of 
 
 straw constituents . 99 
 
 — and straw unequal de- 
 
 velopment of . .100 
 Grasses, underground growth of 
 
 71, 224 
 Green crops, effects of . .77 
 
 — — thrive without ni- 
 
 trogenous ma- 
 nures . . 77 
 
 Green manures, effects of 
 
 PAGE 
 
 89 
 
 Guano, comparison of, with hu- 
 
 
 man excrements 
 
 177 
 
 — effects of^ not due to its 
 
 
 ammonia alone . 
 
 168 
 
 — experiments with . 
 
 60 
 
 — nature of . . . 
 
 133 
 
 — not a complete substi- 
 
 
 tute for human ex- 
 
 
 crements . 
 
 182 
 
 — quantity of, imported . 
 
 179 
 
 H. 
 
 High farming, a rapid system 
 
 of spoliation . . . 148 
 
 Highwayman, on the Ehine, 
 
 system of .... 156 
 Hofmann, analysis of water by. 31 
 Hoskyns, opinion of . . 9 
 
 Human excrements, collection 
 
 of from towns . . .217 
 Humus, when useful . . 42 
 
 — former belief in the 
 
 value of . . .41 
 Huxtable, observations of .57 
 
 Inductive method applied to 
 
 agriculture . 8 
 — — triumphs of 8 
 
 Irrigation, effect of, on injurious 
 organic matter . . .85 
 
 K. 
 
 Krocker, analysis of drainage 
 water by . . . .32 
 
 Kuhlmann, experiments with 
 salts of ammonia by . .61 
 
 L. 
 
 Land, cause of unequal pro- 
 ductiveness of . . .66 
 
272. 
 
 INDEX. 
 
 PAGE 
 
 Lawes, experiments of, with 
 ammonia and mineral 
 matters . . .42, 61 
 
 Leaf-surface, effect of on 
 amount of nitrogen absorp- 
 tion .... 16 
 
 Leguminous plants, amount of 
 nitrogen in . . . . H 
 
 Lemna trisulca, analysis of ash 
 of 36 
 
 Lime, a cure for injurious 
 organic matter . . .85 
 
 M. 
 
 Manures, effect of, on land, 
 how properly es- - 
 timated . .1*13 
 
 — failure of supply of 183 
 
 — nature of . .108 
 
 — nitrogen of, derived 
 
 from air . .7*7 
 
 — not always food for 
 
 plants . .55 
 
 — proper supply of . 82 
 
 — proportion of phos- 
 
 phates to nitro- 
 gen in . . 172 
 
 — value of, estimated 
 
 by nitrogen pre- 
 sent . . .170 
 Maremma . . . .271 
 Meadows, vegetation of, depen- 
 dent on underground suckers 72 
 Mecklenburgh, agriculture of .157 
 isniler, analysis of waters by . 31 
 Minas Geraes, agriculture of . 148 
 jMiueral food, all elements of, 
 
 possess equal value . . 20 
 Mineral matters, activity of, in- 
 creased hy salts 
 of ammonia, Chili- 
 saltpetre, &c. . 65 
 
 — — importance of, in 
 
 Lawes' experi- 
 ments . . .61 
 
 — — necessary to ani- 
 
 mals . . .114 
 
 — — in soils not inex- 
 
 haustible . 116, 130 
 
 PA6B 
 
 Mineral matters, restoration of 124 
 Moisture, attraction of soils for 38 
 
 — condensation of, in 
 
 soils attended by 
 evolution of heat . 39 
 
 — supply of . . .40 
 Molasses, residue from, used as 
 
 manure .... 169 
 Mud from pools, &c., a fertilis- 
 ing agent . . 37 
 _ _ _ effects of . .165 
 
 N. 
 
 Nitrate of ammonia and 
 common salt, experiments 
 
 with 47 
 
 Nitrates, effects of, on ci'ops . 43 
 Nitrogen absorbed in propor- 
 tion to root surface 58 
 
 — compounds and phos- 
 
 phates, relation be- 
 tween . . . 113 
 
 — in different crops . . 74 
 
 — supposed loss of, in 
 
 rotten manure . .131 
 
 — the supposed active 
 
 ingredient in salts 
 
 of ammonia . . 42 
 
 — theory of manures 
 
 115, 170 
 Nitrogenised products in plants 
 
 proportional to leaf surface . 76 
 Nitrogenous manures for cereals 74 
 
 — manures when use- 
 
 ful . . . 81 
 
 — manures, effect of, 
 
 on plants with 
 large leaves . 76 
 Nutrition of plants, present view 
 of 24 
 
 0. 
 
 Oats, remunerative crop of . 94 
 Offenbach, Green Doctor of .12 
 Oil mills, residue from . .180 
 Organic matter, not a source of 
 fertility in itself . . .118 
 
INDEX. 
 
 273 
 
 PAGE 
 
 Organic substances destroyed 
 
 by irrigation . 85 
 
 — — destroyed by lime 85 
 
 — — in soils frequently 
 
 a cause of dis- 
 ease . . 84 
 
 — — not exhausted by 
 
 cultivation . 110 
 
 — — when useful in 
 
 soils . . 74, 16 
 
 P. 
 
 Perennials, absorption of food 
 by 11 
 
 Phlogiston . . . .197 
 Phosphoric acid, in what forms 
 
 present in soil 96 
 
 — — not present in 
 
 drain, river, or 
 well water . 34 
 
 — — quantity removed 
 
 by clover and 
 potatoes . 102 
 
 Phosphate of lime, action of soil 
 
 on . . .25 
 
 — — — how distributed 
 
 through soils . 97 
 Phosphate of magnesia, action 
 
 of soQ on . . . .25 
 Phosphates, loss of, by the 
 
 soil . . .176 
 
 — removed by potatoes 102 
 
 — and nitrogen in 
 food . . .171 
 
 Plants, amount of nitrogen 
 
 in . . . .74 
 
 — conditions of the life of 21 
 
 — general constituents of 
 
 ash of . . .20 
 
 — deep and shallow root- 
 
 ing, object in cultivat- 
 ing . . 104, 152 
 
 — mineral constituents of, 
 
 not received out of a 
 solution . . 30 
 
 — nutrition of . .22 
 
 — origin of combustible 
 
 portion of . .20 
 
 PAGB 
 
 Plants, possess a power of se- 
 lecting food . 35 
 — present view of mode 
 of nutrition of, 
 erroneous . . 24 
 Pliny, opinions of, on agricul- 
 ture 193 
 
 Potash in plants and drain water 
 
 compared . . 33 
 
 — removed by beet and 
 
 potatoes . . 182 
 
 — salts rapidly decom- 
 
 posed by soils . 52 
 
 — and soda salts diflfer- 
 
 ently acted on by 
 soils . . .52 
 
 Potassium, chloride of, action of 
 soil on .... 26 
 
 Potatoes, minerals removed by 182 
 — phosphoric acid re- 
 moved by . . 102 
 
 Poudrette, relation of phos- 
 phates to nitrogen in . .172 
 
 Practical agriculturists, their 
 sensibility to opposition . 18 
 
 Practical instructions, to be 
 always preceded by theoreti- 
 cal 207 
 
 Practical teachers, false reason- 
 ing of 127 
 
 Prize questions in agriculture 
 valueless . . . .17 
 
 Progress based on experience, 
 limited .... 4 
 
 Pusey, opinions of . . .5 
 
 R. 
 
 Remunerative crops, how de- 
 termined . . . .93 
 River water, analysis of . .31 
 Rocks, disintegration of . .122 
 Rome, the cause of the exhaus- 
 tion of the lands of the 
 ancient world . . .185 
 Roots, absorbent surface of . 58 
 
 — action of, on stones . 35 
 
 — protected by the action 
 
 of the soil ... 83 
 
274 
 
 INDEX. 
 
 Rotation of crops, without re- 
 storation of minerals, 
 ultimate effects of . 143 
 — value of . . . 143 
 Rye, remunerative crop of .93 
 
 S. 
 
 ScHATTENMANN, experiments 
 
 with ammonia . . .60 
 Schubert, Knight of Cloverfield 155 
 Science confers power . . 6 
 
 — the objects o^ in agri- 
 
 culture . . .211 
 
 — the results already ob- 
 
 tained by . . . 215 
 
 — true province of . .6 
 
 — value of, recognised . 9 
 Scientific research, true mode of 15 
 
 — teaching, rejection of 14 
 Silicates, how distributed 
 
 through soils . . .97 
 Soda, nitrate of, effects of 52, 55 
 
 — — — experiments with 47 
 Soda salts only partially de- 
 composed by soils . . .53 
 
 Sodium, chloride of, action of 
 
 soils on . 26 
 
 — — effects of, on 
 
 crops . . 43 
 Soils, action of, on solution of 
 
 chloride of.potassium . 26 
 
 — action of, on eolution of 
 
 chloride of sodium . 26 
 
 — analysis of, in Prussia . 116 
 " — attraction of, for moisture 38 
 
 — cooled by evaporation . 39 
 effects of, on solutions "of 
 
 ammonia, potash, phos- 
 phoric, and silicic acids 
 limited . . .28 
 
 — effects of, on solutions of 
 
 salts indispensable to 
 plants ... 25, 26 
 
 — effects of, on solutions of 
 
 salts not indispensable 
 
 to plants . . .25 
 
 — eight elements required 
 
 by plants iu . . 23 
 
 Soils, exhaustion of, by removal 
 of minerals without re- 
 storation . . .67 
 
 — fertility of, dependent on 
 
 quantity of soluble 
 mineral matters present 65 
 
 — fertility of, not dependent 
 
 on nitrogen or organic 
 matter . . .118 
 
 — mechanical division of . 89 
 
 — mineral matters of, in- 
 
 soluble in water . . 25 
 
 — productiveness of, how 
 
 estimated . . .90 
 
 — progressive exhaustion of 103 
 
 — rich in organic matter, 
 
 effect of . . .29 
 
 — warmed by absorbing 
 
 moisture , . .39 
 Special law .... 7 
 Stercutius, god of manure . 155 
 Subsoil, food derived from . 104 
 Suckers, underground, import- 
 ance of .... 72 
 Sulphur compounds and phos- 
 phates, relation between . 114 
 Sulphur and nitrogen organic 
 compounds . . . .113 
 
 T. 
 
 Temperatuke of soils, elevation 
 of, by condensation of mois- 
 ture 40 
 
 Thames water . . . .31 
 
 Theory 7 
 
 Theoretical and practical teach- 
 ing, not useful together . 207 
 Thomson, observations of. . 57 
 Tobacco, minerals removed by 183 
 Trader, the objects of a . . 3 
 Turnip, finger and toe disease 
 in 84 
 
 Varro, opinions of, on agricul- 
 ture 192 
 
INDEX. 
 
 275 
 
 Yine-dresser, his mode of im- 
 proving his soil . . .184 
 Yines, exhausting to land . 154 
 Yirgil, opinions of, on agricul- 
 ture 192 
 
 W. 
 
 Walz on the causes of fertility 
 
 in a soil . . . 135 
 
 diminution of volume 
 
 of soils . . . 126 
 
 disintegration of rocks 122 
 
 exhaustion of soils . 123 
 
 guano .... 134 
 
 the loss of nitrogen in 
 
 manure heaps . .131 
 
 PAGK 
 
 Walz on the nature of manure . 135 
 the necessity for pro- 
 ducing manure . 129 
 
 — opinions of, on arable soils 122 
 
 — on the restoration of 
 
 minerals . . .124 
 
 — on the value of fresh manure 133 
 "Water plants receive food from 
 
 solution . . . .35 
 Waters, river and well, analysis 
 
 of 31 
 
 Way, analysis of drainage water 
 
 by .... 32 
 
 — observations of . . .57 
 Wetterau, farmer . . .159 
 Wheat-field, when exhausted . 93 
 Writers on practical agriculture 121 
 
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